97 results on '"Meyer LC"'
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2. One disease, two lives: exploring the treatment of breast cancer during pregnancy.
- Author
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Visco AG, Meyer LC, Xi S, and Brown CG
- Abstract
Because breast cancer risk increases with age and women in the United States continue to delay childbirth, the incidence of breast cancer during pregnancy will rise. About 10% of patients younger than age 40 diagnosed with breast cancer are pregnant. Historically, labor-delivery and oncology, the two spheres of clinical care, rarely overlapped. However, breast cancer occurs in about 1 in 3,000 pregnancies. Case studies suggest that the administration of chemotherapeutic agents during the second and third trimesters may be safe for the mother and fetus. Three specific case studies of pregnant women with cancer who received treatment are presented to identify the issues of cancer during pregnancy. Outcomes of infants who received chemotherapy in utero and associated nursing implications also are explored. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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3. Prosthetic management of children with unilateral congenital below-elbow deficiency.
- Author
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Davids JR, Wagner LV, Meyer LC, Blackhurst DW, Davids, Jon R, Wagner, Lisa V, Meyer, Leslie C, and Blackhurst, Dawn W
- Abstract
Background: There is substantial controversy concerning the prosthetic management of children with unilateral congenital below-elbow deficiency. The optimal age at the time of the initial fitting, the value of intensive prosthetic training, and the preferred prosthetic design for these children have not been established.Methods: The outcomes of prosthetic management for 260 children with unilateral congenital below-elbow deficiency, treated between 1954 and 2004, were analyzed with respect to ongoing clinic attendance and self-reported prosthetic use. A successful prosthetic outcome was defined as a child and parents who continued to attend the limb-deficiency clinic and claimed at the time of the most recent follow-up that the prosthesis had been worn for any period of time. An unsuccessful prosthetic outcome was defined as a child and parents who were lost to follow-up or who claimed at the time of the most recent follow-up that the child never wore the prosthesis. Survival analysis was performed.Results: An unsuccessful prosthetic outcome was noted for 127 children (49%). Initial fitting prior to the age of three years was associated with improved prosthetic outcome (p < 0.001). With the numbers studied, there was no additional benefit noted for fitting before one year of age (p = 0.60). Improved prosthetic outcomes were noted in children who had received intensive training at the time of fitting with an active terminal device (p = 0.005). Provision of a variety of prosthetic designs over the growing years was also associated with improved prosthetic outcome (p < 0.001).Conclusions: This study supports the initial prosthetic fitting for a child with unilateral congenital below-elbow deficiency prior to the age of three years, the provision of intensive training under the direction of an occupational therapist when an active terminal device is applied, and utilization of a variety of prosthetic designs over the child's years of growth. Further analysis of outcomes for the prosthetic management of these children will require more precise definitions of outcome in multiple domains and the development and validation of specific outcome instruments. [ABSTRACT FROM AUTHOR]- Published
- 2006
4. Coordination and diffusion in glyoxal-based electrolytes for potassium-ion batteries.
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Meyer LC, Johansson P, and Balducci A
- Abstract
Glyoxal-based electrolytes have been identified as promising for potassium-ion batteries (PIBs). Here we investigate the properties of electrolytes containing bis(fluorosulfonyl)imide (KFSI) in 1,1,2,2-tetra-ethoxy-ethane (tetra-ethyl-glyoxal, TEG) using density functional theory (DFT) calculations, Raman spectroscopy, and impedance spectroscopy. The coordination and configuration of the complexes possible to arise from coordination of the K+ ions by FSI and TEG were investigated both from an energetic point of view as well as qualitatively determined via comparing experimental and artificial Raman spectra. Overall, the K+ coordination depends heavily on the electrolyte composition with contributions both from FSI and TEG. Energetically the coordination by both the trans FSI anion conformer and the TEG solvent with four z-chain conformation is preferrable. From the spectroscopy we find that at lower concentrations, the predominant coordination is by TEG, whereas at higher concentrations, K+ is coordinated mostly by FSI. Concerning the diffusion of ions, investigated by impedance spectroscopy, show that the diffusion of the potassium salt is faster as compared to lithium and sodium salts in comparable electrolytes., (© 2024 Wiley‐VCH GmbH.)
- Published
- 2024
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5. The role of extracorporeal life support and timing of repair in infants with congenital diaphragmatic hernia.
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Gehle DB, Meyer LC, and Jancelewicz T
- Abstract
Extracorporeal life support (ECLS) serves as a rescue therapy for patients with congenital diaphragmatic hernia (CDH) and severe cardiopulmonary failure, and only half of these patients survive to discharge. This costly intervention has a significant complication risk and is reserved for patients with the most severe disease physiology refractory to maximal cardiopulmonary support. Some contraindications to ECLS do exist such as coagulopathy, lethal chromosomal or congenital anomaly, very preterm birth, or very low birth weight, but many of these limits are being evaluated through further research. Consensus guidelines from the past decade vary in recommendations for ECLS use in patients with CDH but this therapy appears to have a survival benefit in the most severe subset of patients. Improved outcomes have been observed for patients treated at high-volume centers. This review details the evolving literature surrounding management paradigms for timing of CDH repair for patients receiving preoperative ECLS. Most recent data support early repair following cannulation to avoid non-repair which is uniformly fatal in this population. Longer ECLS runs are associated with decreased survival, and patient physiology should guide ECLS weaning and eventual decannulation rather than limiting patients to arbitrary run lengths. Standardization of care across centers is a major focus to limit unnecessary costs and improve short-term and long-term outcomes for these complex patients., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)
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- 2024
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6. Efficacy and safety of three different opioid-based immobilisation combinations in blesbok ( Damaliscus pygargus phillipsi ).
- Author
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Roug A, Smith C, Raath JP, Meyer LC, and Laubscher LL
- Abstract
African wildlife species are increasingly being immobilised with combinations of a low dose of potent opioids combined with medetomidine and azaperone. The physiological effects of these combinations in comparison to conventional potent opioidazaperone combinations have scarcely been evaluated. In this cross-over study conducted on eight captive blesbok, we compared the physiological variables of blesbok immobilised with 2 mg of thiafentanil + 10 mg of azaperone (TA); 0.5 mg thiafentanil + 1.5 mg medetomidine (TM), and 0.5 mg thiafentanil + 1.5. mg medetomidine + 10 mg azaperone (TMA). Thiafentanil's effects were antagonised with naltrexone at 10 mg naltrexone per mg thiafentanil, and the medetomidine effects with atipamezole at 5 mg atipamezole per mg medetomidine. The physiological variables were compared between treatment groups using descriptive statistics and repeated measures ANOVA. The TA combination resulted in the shortest induction and recovery times, higher heart rates, respiratory rates, PaO
2 , SpO2 , and lower MAP and A-a gradients, but with less muscle relaxation. The TM and TMA combinations caused marked bradycardia and hypoxaemia. The hypoxaemia was most severe in animals immobilised with TMA, and four of eight blesbok immobilised had a PaO2 < 35 mmHg at the 10- or 15-minute sampling point. These blesbok were provided supplementary oxygen, which corrected the hypoxaemia. The TA combinations caused the lowest degree of physiological compromise. All three combinations were effective for the immobilisation of blesbok, but as the low-dose thiafentanil and high-dose medetomidine combinations caused marked hypoxaemia, supplementary oxygen is recommended when using these combinations.- Published
- 2023
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7. Reliability of pulse oximetry at four different attachment sites in immobilized white rhinoceros (Ceratotherium simum).
- Author
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Mtetwa TK, Snelling EP, Buss P, Zeiler GE, and Meyer LC
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- Male, Animals, Cross-Over Studies, Reproducibility of Results, Perissodactyla, Oxygen, Hemoglobins, Etorphine, Oximetry veterinary, Oximetry methods
- Abstract
Objectives: To determine the reliability of peripheral oxygen haemoglobin saturation (SpO
2 ), measured by a Nonin PalmSAT 2500A pulse oximeter with 2000T transflectance probes at four attachment sites (third eyelid, cheek, rectum and tail), by comparing these measurements to arterial oxygen haemoglobin saturation (SaO2 ), measured by an AVOXimeter 4000 co-oximeter reference method in immobilized white rhinoceros (Ceratotherium simum)., Study Design: Randomized crossover study., Animals: A convenience sample of eight wild-caught male white rhinoceros., Methods: White rhinoceros were immobilized with etorphine (0.0026 ± 0.0002 mg kg-1 , mean ± standard deviation) intramuscularly, after which the pinna was aseptically prepared for arterial blood sample collection, and four pulse oximeters with transflectance probes were fixed securely to their attachment sites (third eyelid, cheek, rectum and tail). At 30 minutes following recumbency resulting from etorphine administration, the animals were given either butorphanol (0.026 ± 0.0001 mg kg-1 ) or an equivalent volume of saline intravenously. At 60 minutes following recumbency, insufflated oxygen (15 L minute-1 flow rate) was provided intranasally. In total, the SpO2 paired measurements from the third eyelid (n = 80), cheek (n = 67), rectum (n = 59) and tail (n = 76) were compared with near-simultaneous SaO2 measurements using Bland-Altman to assess bias (accuracy), precision, and the area root mean squares (ARMS) method., Results: Compared with SaO2 , SpO2 measurements from the third eyelid were reliable (i.e., accurate and precise) above an SaO2 range of 70% (bias = 1, precision = 3, ARMS = 3). However, SpO2 measurements from the cheek, rectum and tail were unreliable (i.e., inaccurate or imprecise)., Conclusions and Clinical Relevance: A Nonin PalmSAT pulse oximeter with a transflectance probe inserted into the space between the third eyelid and the sclera provided reliable SpO2 measurements when SaO2 was > 70%, in immobilized white rhinoceros., (Copyright © 2022 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)- Published
- 2022
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8. Hydrogen Bonding Enhances the Electrochemical Hydrogenation of Benzaldehyde in the Aqueous Phase.
- Author
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Sanyal U, Yuk SF, Koh K, Lee MS, Stoerzinger K, Zhang D, Meyer LC, Lopez-Ruiz JA, Karkamkar A, Holladay JD, Camaioni DM, Nguyen MT, Glezakou VA, Rousseau R, Gutiérrez OY, and Lercher JA
- Abstract
The hydrogenation of benzaldehyde to benzyl alcohol on carbon-supported metals in water, enabled by an external potential, is markedly promoted by polarization of the functional groups. The presence of polar co-adsorbates, such as substituted phenols, enhances the hydrogenation rate of the aldehyde by two effects, that is, polarizing the carbonyl group and increasing the probability of forming a transition state for H addition. These two effects enable a hydrogenation route, in which phenol acts as a conduit for proton addition, with a higher rate than the direct proton transfer from hydronium ions. The fast hydrogenation enabled by the presence of phenol and applied potential overcompensates for the decrease in coverage of benzaldehyde caused by competitive adsorption. A higher acid strength of the co-adsorbate increases the intensity of interactions and the rates of selective carbonyl reduction., (© 2020 The Authors. Published by Wiley-VCH GmbH.)
- Published
- 2021
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9. Endogenous opioid peptides and brain development: Endomorphin-1 and Nociceptin play a sex-specific role in the control of oligodendrocyte maturation and brain myelination.
- Author
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Mohamed E, Paisley CE, Meyer LC, Bigbee JW, and Sato-Bigbee C
- Subjects
- Analgesics, Opioid metabolism, Analgesics, Opioid pharmacology, Animals, Brain growth & development, Rats, Sprague-Dawley, Receptors, Opioid metabolism, Receptors, Opioid, mu metabolism, Brain metabolism, Oligodendroglia metabolism, Opioid Peptides metabolism, Sex Factors
- Abstract
The generation of fully functional oligodendrocytes, the myelinating cells of the central nervous system, is preceded by a complex maturational process. We previously showed that the timing of oligodendrocyte differentiation and rat brain myelination were altered by perinatal exposure to buprenorphine and methadone, opioid analogs used for the management of pregnant addicts. Those observations suggested the involvement of the μ-opioid receptor (MOR) and the nociceptin/orphanin FQ receptor (NOR). However, it remained to be determined if these receptors and their endogenous ligands could indeed control the timing of myelination under normal physiological conditions of brain development. We now found that the endogenous MOR ligand endomorphin-1 (EM-1) exerts a striking stimulatory action on cellular and morphological maturation of rat pre-oligodendrocytes, but unexpectedly, these effects appear to be restricted to the cells from the female pups. Critically, this stimulation is abolished by coincubation with the endogenous NOR ligand nociceptin. Furthermore, NOR antagonist treatment of 9-day-old female pups results in accelerated brain myelination. Interestingly, the lack of sex-dependent differences in developmental brain levels of EM-1 and nociceptin, or oligodendroglial expression of MOR and NOR, suggests that the observed sex-specific responses may be highly dependent on important intrinsic differences between the male and female oligodendrocytes. The discovery of a significant effect of EM-1 and nociceptin in the developing female oligodendrocytes and brain myelination, underscores the need for further studies investigating brain sex-related differences and their implications in opioid use and abuse, pain control, and susceptibility and remyelinating capacity in demyelinating disease as multiple sclerosis., (© 2020 Wiley Periodicals, Inc.)
- Published
- 2020
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10. Potential Neurodevelopmental Effects of Pediatric Intensive Care Sedation and Analgesia: Repetitive Benzodiazepine and Opioid Exposure Alters Expression of Glial and Synaptic Proteins in Juvenile Rats.
- Author
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Iqbal O'Meara AM, Miller Ferguson N, Zven SE, Karam OL, Meyer LC, Bigbee JW, and Sato-Bigbee C
- Abstract
Sedatives are suspected contributors to neurologic dysfunction in PICU patients, to whom they are administered during sensitive neurodevelopment. Relevant preclinical modeling has largely used comparatively brief anesthesia in infant age-approximate animals, with insufficient study of repetitive combined drug administration during childhood. We hypothesized that childhood neurodevelopment is selectively vulnerable to repeated treatment with benzodiazepine and opioid. We report a preclinical model of combined midazolam and morphine in early childhood age-approximate rats., Design: Animal model., Setting: Basic science laboratory., Subjects: Male and female Long-Evans rats., Interventions: Injections of morphine + midazolam were administered twice daily from postnatal days 18-22, tapering on postnatal days 23 and 24. Control groups included saline, morphine, or midazolam. To screen for acute neurodevelopmental effects, brain homogenates were analyzed by western blot for synaptophysin, drebrin, glial fibrillary acidic protein, S100 calcium-binding protein B, ionized calcium-binding adaptor molecule 1, and myelin basic proteins. Data analysis used Kruskal-Wallis with Dunn posttest, with a p value of less than 0.05 significance., Measurements and Main Results: Morphine + midazolam and morphine animals gained less weight than saline or midazolam ( p ≤ 0.01). Compared with saline, morphine + midazolam expressed significantly higher drebrin levels ( p = 0.01), with numerically but not statistically decreased glial fibrillary acidic protein. Similarly, morphine animals exhibited less glial fibrillary acidic protein and more S100 calcium-binding protein B and synaptophysin. Midazolam animals expressed significantly more S100 calcium-binding protein B ( p < 0.001) and 17-18.5 kDa myelin basic protein splicing isoform ( p = 0.01), with numerically increased synaptophysin, ionized calcium-binding adaptor molecule 1, and 21.5 kDa myelin basic protein, and decreased glial fibrillary acidic protein., Conclusions: Analysis of brain tissue in this novel rodent model of repetitive morphine and midazolam administration showed effects on synaptic, astrocytic, microglial, and myelin proteins. These findings warrant further investigation because they may have implications for critically ill children requiring sedation and analgesia., Competing Interests: The authors have disclosed that they do not have any potential conflicts of interest., (Copyright © 2020 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the Society of Critical Care Medicine.)
- Published
- 2020
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11. Compared to etorphine-azaperone, the ketamine-butorphanol-medetomidine combination is also effective at immobilizing zebra (Equus zebra).
- Author
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Stemmet GP, Meyer LC, Bruns A, Buss P, Zimmerman D, Koeppel K, and Zeiler GE
- Subjects
- Analgesics, Opioid administration & dosage, Analgesics, Opioid adverse effects, Anesthetics, Dissociative administration & dosage, Animals, Animals, Wild, Azaperone administration & dosage, Azaperone adverse effects, Azaperone pharmacology, Blood Pressure drug effects, Butorphanol administration & dosage, Butorphanol pharmacology, Cross-Over Studies, Drug Combinations, Etorphine administration & dosage, Etorphine adverse effects, Etorphine pharmacology, Female, Hypertension chemically induced, Hypertension veterinary, Hypnotics and Sedatives administration & dosage, Hypnotics and Sedatives adverse effects, Hypoxia chemically induced, Hypoxia veterinary, Ketamine administration & dosage, Ketamine adverse effects, Ketamine pharmacology, Male, Medetomidine administration & dosage, Medetomidine adverse effects, Medetomidine pharmacology, Oxygen administration & dosage, Random Allocation, Analgesics, Opioid pharmacology, Anesthetics, Dissociative pharmacology, Equidae, Hypnotics and Sedatives pharmacology, Immobilization veterinary
- Abstract
Objective: To compare immobilization efficacy of a nonpotent opioid drug combination, ketamine-butorphanol-medetomidine (KBM) to the preferred etorphine-azaperone (EA) combination in zebras., Study Design: Randomized crossover trial., Animals: A group of ten adult zebra (six females and four male)., Methods: KBM and EA were administered once to the zebras in random order by dart, 3 weeks apart. Once a zebra was recumbent and instrumented, physiological parameters were measured and recorded at 5-minute intervals until 20 minutes. Antagonist drugs were administered at 25 minutes. KBM was antagonised using atipamezole (7.5 mg mg
-1 medetomidine dose) and naltrexone (2 mg mg-1 butorphanol dose). EA was antagonized using naltrexone (20 mg mg-1 etorphine dose). Induction and recovery (following antagonist administration) times were recorded. Physiological parameters, including invasive blood pressure and blood gas analysis, were compared between combinations using a general linear mixed model. Data are reported as mean ± standard deviation or median (interquartile range)., Results: The doses of KBM and EA administered were 3.30 ± 0.18, 0.40 ± 0.02 and 0.16 ± 0.01 mg kg-1 ; and 0.02 ± 0.001 and 0.20 ± 0.01 mg kg-1 , respectively. KBM and EA induction times were 420 (282-564) and 240 (204-294) seconds, respectively (p = 0.03). Zebras remained recumbent throughout the study procedures. Systolic blood pressure (226 ± 42 and 167 ± 42 mmHg) and oxygen partial pressure (64 ± 12 and 47 ± 13 mmHg) were higher for KBM compared to EA (p < 0.01). Recovery time, after administering antagonists, was 92 (34-1337) and 26 (22-32) seconds for KBM and EA, respectively (p = 0.03)., Conclusions and Clinical Relevance: Compared to EA, KBM also immobilized zebras effectively. Systemic hypertension and moderate hypoxaemia are clinical concerns of KBM and severe hypoxaemia is a concern of EA. This occurrence of hypoxaemia highlights the importance of oxygen administration during immobilization., (Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)- Published
- 2019
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12. Nanoplatelet cryoaerogels with potential application in photoelectrochemical sensing.
- Author
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Schlosser A, Meyer LC, Lübkemann F, Miethe JF, and Bigall NC
- Abstract
Semiconductor nanoparticle based porous 3D assemblies are interesting materials for various applications in the fields of photovoltaics, catalysis, or optical sensing. For use as photoelectrodes in photoelectrochemical sensors they need to be characterised by a high porosity, a good photostability, and a high charge carrier mobility. Our work reports on the preparation of cryoaerogel photoelectrodes based on CdSe nanoplatelets and their photoelectrochemical characterisation by means of linear sweep voltammetry (LSV) and intensity modulated photocurrent spectroscopy (IMPS). The obtained open-pored cryoaerogel films were observed to produce much higher photocurrents than comparable drop-cast films. By means of IMPS, the performance differences could be linked to the occurrence of charge carrier movement, which could solely be proven for the cryoaerogels. In a proof-of-principle experiment, the potential of the prepared photoelectrodes for application in photoelectrochemical sensing was moreover demonstrated.
- Published
- 2019
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13. Novel role of the nociceptin system as a regulator of glutamate transporter expression in developing astrocytes.
- Author
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Meyer LC, Paisley CE, Mohamed E, Bigbee JW, Kordula T, Richard H, Lutfy K, and Sato-Bigbee C
- Subjects
- Aldehyde Dehydrogenase 1 Family, Animals, Animals, Newborn, Astrocytes drug effects, Cells, Cultured, Enzyme Inhibitors pharmacology, Fetus cytology, Glial Fibrillary Acidic Protein metabolism, Glutamic Acid metabolism, Humans, Hydroxylamines pharmacology, Mice, Knockout, Neurons drug effects, Neurons metabolism, Opioid Peptides pharmacology, Rats, Rats, Sprague-Dawley, Receptors, Opioid genetics, Retinal Dehydrogenase metabolism, Signal Transduction drug effects, Signal Transduction physiology, Nociceptin Receptor, Nociceptin, Amino Acid Transport System X-AG metabolism, Astrocytes metabolism, Gene Expression Regulation, Developmental genetics, Opioid Peptides metabolism, Receptors, Opioid deficiency
- Abstract
Our previous results showed that oligodendrocyte development is regulated by both nociceptin and its G-protein coupled receptor, the nociceptin/orphanin FQ receptor (NOR). The present in vitro and in vivo findings show that nociceptin plays a crucial conserved role regulating the levels of the glutamate/aspartate transporter GLAST/EAAT1 in both human and rodent brain astrocytes. This nociceptin-mediated response takes place during a critical developmental window that coincides with the early stages of astrocyte maturation. GLAST/EAAT1 upregulation by nociceptin is mediated by NOR and the downstream participation of a complex signaling cascade that involves the interaction of several kinase systems, including PI-3K/AKT, mTOR, and JAK. Because GLAST is the main glutamate transporter during brain maturation, these novel findings suggest that nociceptin plays a crucial role in regulating the function of early astrocytes and their capacity to support glutamate homeostasis in the developing brain., (© 2017 Wiley Periodicals, Inc.)
- Published
- 2017
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14. Deregulated Ca 2+ cycling underlies the development of arrhythmia and heart disease due to mutant obscurin.
- Author
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Hu LR, Ackermann MA, Hecker PA, Prosser BL, King B, O'Connell KA, Grogan A, Meyer LC, Berndsen CE, Wright NT, Jonathan Lederer W, and Kontrogianni-Konstantopoulos A
- Subjects
- Animals, Arrhythmias, Cardiac diagnosis, Disease Models, Animal, Echocardiography, Electrocardiography, Heart Diseases diagnosis, Magnetic Resonance Spectroscopy, Mice, Mice, Transgenic, Protein Serine-Threonine Kinases, Rho Guanine Nucleotide Exchange Factors, Arrhythmias, Cardiac genetics, Arrhythmias, Cardiac metabolism, Calcium metabolism, Calcium Signaling, Guanine Nucleotide Exchange Factors genetics, Heart Diseases genetics, Heart Diseases metabolism, Muscle Proteins genetics, Mutation
- Abstract
Obscurins are cytoskeletal proteins with structural and regulatory roles encoded by OBSCN . Mutations in OBSCN are associated with the development of hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Specifically, the R4344Q mutation present in immunoglobulin domain 58 (Ig58) was the first to be linked with the development of HCM. To assess the effects of R4344Q in vivo, we generated the respective knock-in mouse model. Mutant obscurins are expressed and incorporated normally into sarcomeres. The expression patterns of sarcomeric and Ca
2+ -cycling proteins are unaltered in sedentary 1-year-old knock-in myocardia, with the exception of sarco/endoplasmic reticulum Ca2+ adenosine triphosphatase 2 (SERCA2) and pentameric phospholamban whose levels are significantly increased and decreased, respectively. Isolated cardiomyocytes from 1-year-old knock-in hearts exhibit increased Ca2+ -transients and Ca2+ -load in the sarcoplasmic reticulum and faster contractility kinetics. Moreover, sedentary 1-year-old knock-in animals develop tachycardia accompanied by premature ventricular contractions, whereas 2-month-old knock-in animals subjected to pressure overload develop a DCM-like phenotype. Structural analysis revealed that the R4344Q mutation alters the distribution of electrostatic charges over the Ig58 surface, thus interfering with its binding capabilities. Consistent with this, wild-type Ig58 interacts with phospholamban modestly, and this interaction is markedly enhanced in the presence of R4344Q. Together, our studies demonstrate that under sedentary conditions, the R4344Q mutation results in Ca2+ deregulation and spontaneous arrhythmia, whereas in the presence of chronic, pathological stress, it leads to cardiac remodeling and dilation. We postulate that enhanced binding between mutant obscurins and phospholamban leads to SERCA2 disinhibition, which may underlie the observed pathological alterations.- Published
- 2017
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15. CONTINUOUS INTRAVENOUS INFUSION ANESTHESIA WITH MEDETOMIDINE, KETAMINE, AND MIDAZOLAM AFTER INDUCTION WITH A COMBINATION OF ETORPHINE, MEDETOMIDINE, AND MIDAZOLAM OR WITH MEDETOMIDINE, KETAMINE, AND BUTORPHANOL IN IMPALA (AEPYCEROS MELAMPUS).
- Author
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Gerlach CA, Kummrow MS, Meyer LC, Zeiler GE, Stegmann GF, Buck RK, Fosgate GT, and Kästner SB
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- Analgesics administration & dosage, Anesthesia Recovery Period, Anesthetics, Intravenous administration & dosage, Animals, Butorphanol administration & dosage, Butorphanol pharmacology, Drug Administration Schedule, Drug Therapy, Combination, Etorphine administration & dosage, Etorphine pharmacology, Female, Hypnotics and Sedatives administration & dosage, Ketamine administration & dosage, Ketamine pharmacology, Medetomidine administration & dosage, Medetomidine pharmacology, Midazolam administration & dosage, Midazolam pharmacology, Analgesics pharmacology, Anesthetics, Intravenous pharmacology, Antelopes, Hypnotics and Sedatives pharmacology
- Abstract
In order to develop a long-term anesthesia for flighty antelope species in field situations, two different protocols for induction and maintenance with an intravenous infusion were evaluated in wild-caught impala ( Aepyceros melampus ). Ten adult female impala were induced with two induction protocols: one consisted of 0.2 mg/kg medetomidine, 4 mg/kg ketamine, and 0.15 mg/kg butorphanol (MKB) and one consisted of 0.375 mg/kg etorphine, 0.2 mg/kg medetomidine, and 0.2 mg/kg midazolam (EMM). In both treatments, anesthesia was maintained with a continuous intravenous infusion (CII) at an initial dose rate of 1.2 μg/kg per hr medetomidine, 2.4 mg/kg per hr ketaminen and 36 μg/kg per hr midazolam. Partial reversal was achieved with naltrexone (2 : 1 mg butorphanol; 20 : 1 mg etorphine) and atipamezole (5 : 1 mg medetomidine). Evaluation of anesthesia included respiratory rate, heart rate, rectal temperature, arterial blood pressure, oxygen saturation, end tidal carbon dioxide tension, and tidal volume at 5-min intervals, palpebral reflex and response to painful stimuli at 15-min intervals, and arterial blood gases at 30-min intervals. Plasma cortisol concentration was determined after induction and before reversal. Duration and quality of induction and recovery were evaluated. EMM caused a faster induction of 9.5 ± 2.9 min compared to 11.0 ± 6.4 min in MKB. Recovery was also quicker in EMM (EMM: 6.3 ± 5.4 min; MKB: 9.8 ± 6.0 min). However, EMM also produced more cardiopulmonary side effects, including hypoxemia and hypercapnia, and calculated oxygenation indices (PaCO
2 -PETCO2 ) were worse than in MKB. One animal died after induction with EMM. The CII provided surgical anesthesia in 7 of 10 animals in MKB and in 9 of 9 animals in EMM for 120 min. In conclusion, the MKB induction protocol had advantages for prolonged anesthesia in impala with significantly less cardiopulmonary depression compared to EMM. The comparably decreased anesthetic depth could easily be adjusted by an increase of the CII.- Published
- 2017
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16. Tremors in white rhinoceroses ( Ceratotherium simum ) during etorphine-azaperone immobilisation.
- Author
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De Lange SS, Fuller A, Haw A, Hofmeyr M, Buss P, Miller M, and Meyer LC
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- Analysis of Variance, Animals, Butorphanol therapeutic use, Epinephrine blood, Hypoxia chemically induced, Hypoxia physiopathology, Immobilization methods, Immobilization veterinary, Male, Monitoring, Physiologic, Narcotic Antagonists therapeutic use, Random Allocation, South Africa, Tremor chemically induced, Tremor drug therapy, Azaperone adverse effects, Etorphine adverse effects, Hypnotics and Sedatives adverse effects, Hypoxia veterinary, Perissodactyla blood, Perissodactyla physiology, Tremor veterinary
- Abstract
Little is known about the mechanisms causing tremors during immobilisation of rhinoceros and whether cardiorespiratory supportive interventions alter their intensity. Therefore, we set out to determine the possible mechanisms that lead to muscle tremors and ascertain whether cardiorespiratory supportive interventions affect tremor intensity. We studied tremors and physiological responses during etorphine-azaperone immobilisation in eight boma-held and 14 free-living white rhinoceroses. Repeated measures analysis of variance and a Friedman test were used to determine differences in variables over time and between interventions. Spearman and Pearson correlations were used to test for associations between variables. Tremor intensity measured objectively by activity loggers correlated well (p < 0.0001; r2 = 0.9) with visual observations. Tremor intensity was greatest when animals were severely hypoxaemic and acidaemic. Tremor intensity correlated strongly and negatively with partial pressure of oxygen (PaO2 ) (p = 0.0003; r2 = 0.9995) and potential of hydrogen (pH) (p = 0.02, r2 = 0.97). It correlated strongly and positively with adrenaline concentrations (p = 0.003; r2 = 0.96), and adrenaline correlated strongly and negatively with PaO2 (p = 0.03; r2 = 0.95) and pH (p = 0.03; r2 = 0.94). Therefore, hypoxaemia and acidaemia were likely associated with the intensity of tremors through their activation of the release of tremorgenic levels of adrenaline. Tremors can be reduced if circulating adrenaline is reduced, and this can be achieved by the administration of butorphanol plus oxygen insufflation. Furthermore, to assist with reducing the risks associated with rhinoceros immobilisation, tremor intensity could be used as a clinical indicator of respiratory and metabolic compromise.
- Published
- 2017
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17. A structure-function analysis of the left ventricle.
- Author
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Snelling EP, Seymour RS, Green JE, Meyer LC, Fuller A, Haw A, Mitchell D, Farrell AP, Costello MA, Izwan A, Badenhorst M, and Maloney SK
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- Animals, Blood Pressure physiology, Computer Simulation, Female, Goats, Male, Models, Anatomic, Organ Size physiology, Oxygen metabolism, Sheep, Cardiac Output physiology, Heart Ventricles anatomy & histology, Mitochondria, Heart physiology, Models, Cardiovascular, Oxygen Consumption physiology, Ventricular Function, Left physiology
- Abstract
This study presents a structure-function analysis of the mammalian left ventricle and examines the performance of the cardiac capillary network, mitochondria, and myofibrils at rest and during simulated heavy exercise. Left ventricular external mechanical work rate was calculated from cardiac output and systemic mean arterial blood pressure in resting sheep (Ovis aries; n = 4) and goats (Capra hircus; n = 4) under mild sedation, followed by perfusion-fixation of the left ventricle and quantification of the cardiac capillary-tissue geometry and cardiomyocyte ultrastructure. The investigation was then extended to heavy exercise by increasing cardiac work according to published hemodynamics of sheep and goats performing sustained treadmill exercise. Left ventricular work rate averaged 0.017 W/cm
3 of tissue at rest and was estimated to increase to ∼0.060 W/cm3 during heavy exercise. According to an oxygen transport model we applied to the left ventricular tissue, we predicted that oxygen consumption increases from 195 nmol O2 ·s-1 ·cm-3 of tissue at rest to ∼600 nmol O2 ·s-1 ·cm-3 during heavy exercise, which is within 90% of the oxygen demand rate and consistent with work remaining predominantly aerobic. Mitochondria represent 21-22% of cardiomyocyte volume and consume oxygen at a rate of 1,150 nmol O2 ·s-1 ·cm-3 of mitochondria at rest and ∼3,600 nmol O2 ·s-1 ·cm-3 during heavy exercise, which is within 80% of maximum in vitro rates and consistent with mitochondria operating near their functional limits. Myofibrils represent 65-66% of cardiomyocyte volume, and according to a Laplacian model of the left ventricular chamber, generate peak fiber tensions in the range of 50 to 70 kPa at rest and during heavy exercise, which is less than maximum tension of isolated cardiac tissue (120-140 kPa) and is explained by an apparent reserve capacity for tension development built into the left ventricle., (Copyright © 2016 the American Physiological Society.)- Published
- 2016
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18. Ampakine CX1942 attenuates opioid-induced respiratory depression and corrects the hypoxaemic effects of etorphine in immobilized goats (Capra hircus).
- Author
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Haw AJ, Meyer LC, Greer JJ, and Fuller A
- Subjects
- Animals, Doxapram pharmacology, Female, Goats, Hypoxia drug therapy, Immobilization, Naltrexone administration & dosage, Narcotic Antagonists pharmacology, Respiratory Insufficiency chemically induced, Respiratory System Agents pharmacology, Analgesics, Opioid pharmacology, Etorphine pharmacology, Hypoxia chemically induced, Receptors, AMPA agonists, Respiratory Insufficiency drug therapy
- Abstract
Objectives: To determine whether CX1942 reverses respiratory depression in etorphine-immobilized goats, and to compare its effects with those of doxapram hydrochloride., Study Design: A prospective, crossover experimental trial conducted at 1753 m.a.s.l., Animals: Eight adult female Boer goats (Capra hircus) with a mean ± standard deviation mass of 27.1 ± 1.6 kg., Methods: Following immobilization with 0.1 mg kg(-1) etorphine, goats received one of doxapram, CX1942 or sterile water intravenously, in random order in three trials. Respiratory rate, ventilation and tidal volume were measured continuously. Arterial blood samples for the determination of PaO2 , PaCO2 , pH and SaO2 were taken 2 minutes before and then at 5 minute intervals after drug administration for 25 minutes., Results: Doxapram corrected etorphine-induced respiratory depression but also led to arousal and hyperventilation at 2 minutes after its administration, as indicated by the low PaCO2 (27.8 ± 4.5 mmHg) and ventilation of 5.32 ± 5.24 L minute(-1) above pre-immobilization values. CX1942 improved respiratory parameters and corrected etorphine's hypoxaemic effects more gradually than did doxapram, with a more sustained improvement in PaO2 and SaO2 in comparison with the control trial., Conclusions: CX1942 attenuated opioid-induced respiratory depression and corrected the hypoxaemic effects of etorphine in immobilized goats., Clinical Relevance: Ampakines potentially offer advantages over doxapram, a conventional treatment, in reversing etorphine-induced respiratory depression without causing unwanted side effects, particularly arousal, in immobilized animals., (© 2016 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.)
- Published
- 2016
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19. Nalbuphine and butorphanol reverse opioid-induced respiratory depression but increase arousal in etorphine-immobilized goats (Capra hircus).
- Author
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Haw AJ, Meyer LC, and Fuller A
- Subjects
- Animals, Cross-Over Studies, Female, Goats, Immobilization, Prospective Studies, Respiratory Insufficiency chemically induced, Respiratory Insufficiency drug therapy, Analgesics, Opioid pharmacology, Butorphanol pharmacology, Etorphine pharmacology, Nalbuphine pharmacology, Narcotic Antagonists pharmacology
- Abstract
Objectives: To evaluate and compare the efficacy of two opioid agonist-antagonists, nalbuphine and butorphanol, in reversing etorphine-induced respiratory depression in immobilized goats., Study Design: Prospective, crossover, experimental trial conducted at 1753 m.a.s.l., Animals: Eight adult female Boer goats (Capra hircus)., Methods: Eight minutes following immobilization with an intramuscular injection of 0.1 mg kg(-1) etorphine, goats were given one of nalbuphine (0.8 mg kg(-1) ), butorphanol (0.1 mg kg(-1) ) or sterile water intravenously, in random order in three trials. Respiratory rate (fR ), ventilation, tidal volume, oxygen consumption (V˙O2 ) and carbon dioxide production (V˙CO2 ) were measured continuously. Arterial blood samples to determine PaO2 and PaCO2 were taken 2 minutes before and at 5 minute intervals after etorphine administration for 25 minutes., Results: Both nalbuphine and butorphanol increased mean PaO2 from 44 mmHg (5.9 kPa) to 63 mmHg (8.4 kPa) after etorphine administration. Butorphanol, but not nalbuphine, also corrected hypopnea and hypoventilation such that fR increased from 13 ± 4 to 21 ± 7 breaths minute(-1) (compared with 16 ± 6 breaths minute(-1) following nalbuphine) and ventilation increased from 4.69 ± 3.04 to 6.91 ± 4.42 L minute(-1) following butorphanol administration. Despite decreases in PaCO2 following nalbuphine and butorphanol, PaCO2 remained elevated compared with pre-immobilization values [nalbuphine: 34 ± 3 mmHg (4.5 ± 0.3 kPa); butorphanol: 34 ± 2 mmHg (4.5 ± 0.3 kPa)] throughout the immobilization. Both agents also decreased the level of immobilization, and increased V˙O2 and V˙CO2 ., Conclusions: Nalbuphine and butorphanol significantly improved respiratory function in immobilized goats, with butorphanol eliciting a greater positive response than nalbuphine. However, both opioid agonist-antagonists partly reversed etorphine-induced immobilization., Clinical Relevance: Butorphanol and nalbuphine can be used to improve respiratory parameters in etorphine-immobilized wildlife, with butorphanol being more effective, but unwanted arousal can occur., (© 2016 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.)
- Published
- 2016
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20. Three African antelope species with varying water dependencies exhibit similar selective brain cooling.
- Author
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Strauss WM, Hetem RS, Mitchell D, Maloney SK, Meyer LC, and Fuller A
- Subjects
- Animals, Body Temperature physiology, Body Water physiology, Carotid Arteries anatomy & histology, Carotid Arteries physiology, Female, South Africa, Species Specificity, Antelopes physiology, Body Temperature Regulation physiology, Brain physiology
- Abstract
The use of selective brain cooling, where warm arterial blood destined for the brain is cooled in the carotid rete via counter-current heat exchange when in close proximity to cooler venous blood, contributes to the conservation of body water. We simultaneously measured carotid blood and hypothalamic temperature in four gemsbok, five red hartebeest and six blue wildebeest to assess the extent to which these free-living animals, with varying water dependency, routinely rely on selective brain cooling. We investigated the hypothesis that innate differences in selective brain cooling exist in large, sympatric artiodactyls with varying water dependency. All three species used selective brain cooling, without any discernible differences in three selective brain cooling indices. GLMMs revealed no species differences in the threshold temperature for selective brain cooling (z = 0.79, P = 0.43), the magnitude (z = -0.51, P = 0.61), or the frequency of selective brain cooling use (z = -0.47, P = 0.64), after controlling for carotid blood temperature and black globe temperature. Comparison of anatomical attributes of the carotid retes of the three species revealed that the volume (F 2,9 = 5.54, P = 0.03) and height (F 2,9 = 5.43, P = 0.03) of the carotid rete, per kilogram body mass, were greater in the red hartebeest than in the blue wildebeest. Nevertheless, intraspecific variability in the magnitude, the frequency of use, and the threshold temperature for selective brain cooling exceeded any interspecific variability in the three indices of selective brain cooling. We conclude that the three species have similar underlying ability to make use of selective brain cooling in an environment with freely available water. It remains to be seen to what extent these three species would rely on selective brain cooling, as a water conservation mechanism, when challenged by aridity, a condition likely to become prevalent throughout much of southern Africa under future climate change scenarios.
- Published
- 2016
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21. ETORPHINE-KETAMINE-MEDETOMIDINE TOTAL INTRAVENOUS ANESTHESIA IN WILD IMPALA (AEPYCEROS MELAMPUS) OF 120-MINUTE DURATION.
- Author
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Zeiler GE, Stegmann GF, Fosgate G, Buck RK, Kästner SB, Kummrow M, Gerlach C, and Meyer LC
- Subjects
- Analgesics, Non-Narcotic administration & dosage, Analgesics, Non-Narcotic pharmacology, Analgesics, Opioid administration & dosage, Analgesics, Opioid pharmacology, Anesthetics, Dissociative administration & dosage, Anesthetics, Dissociative pharmacology, Animals, Animals, Wild, Drug Administration Schedule, Etorphine administration & dosage, Ketamine administration & dosage, Medetomidine administration & dosage, Anesthesia, Intravenous veterinary, Antelopes, Etorphine pharmacology, Ketamine pharmacology, Medetomidine pharmacology
- Abstract
There is a growing necessity to perform long-term anesthesia in wildlife, especially antelope. The costs and logistics of transporting wildlife to veterinary practices make surgical intervention a high-stakes operation. Thus there is a need for a field-ready total intravenous anesthesia (TIVA) infusion to maintain anesthesia in antelope. This study explored the feasibility of an etorphine-ketamine-medetomidine TIVA for field anesthesia. Ten wild-caught, adult impala ( Aepyceros melampus ) were enrolled in the study. Impala were immobilized with a standardized combination of etorphine (2 mg) and medetomidine (2.2 mg), which equated to a median (interquartile range [IQR]) etorphine and medetomidine dose of 50.1 (46.2-50.3) and 55.1 (50.8-55.4) μg/kg, respectively. Recumbency was attained in a median (IQR) time of 13.9 (12.0-16.5) min. Respiratory gas tensions, spirometry, and arterial blood gas were analyzed over a 120-min infusion. Once instrumented, the TIVA was infused as follows: etorphine at a variable rate initiated at 40 μg/kg per hour (adjusted according to intermittent deep-pain testing); ketamine and medetomidine at a fixed rate of 1.5 mg/kg per hour and 5 μg/kg per hour, respectively. The etorphine had an erratic titration to clinical effect in four impala. Arterial blood pressure and respiratory and heart rates were all within normal physiological ranges. However, arterial blood gas analysis revealed severe hypoxemia, hypercapnia, and acidosis. Oxygenation and ventilation indices were calculated and highlighted possible co-etiologies to the suspected etorphine-induced respiratory depression as the cause of the blood gas derangements. Impala recovered in the boma post atipamezole (13 mg) and naltrexone (42 mg) antagonism of medetomidine and etorphine, respectively. The etorphine-ketamine-medetomidine TIVA protocol for impala may be sufficient for field procedures of up to 120-min duration. However, hypoxemia and hypercapnia are of paramount concern and thus oxygen supplementation should be considered mandatory. Other TIVA combinations may be superior and warrant further investigation.
- Published
- 2015
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22. Selective brain cooling reduces water turnover in dehydrated sheep.
- Author
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Strauss WM, Hetem RS, Mitchell D, Maloney SK, Meyer LC, and Fuller A
- Subjects
- Animals, Body Temperature, Carotid Arteries, Cavernous Sinus, Osmolar Concentration, Temperature, Body Temperature Regulation, Body Water metabolism, Brain, Dehydration, Sheep
- Abstract
In artiodactyls, arterial blood destined for the brain can be cooled through counter-current heat exchange within the cavernous sinus via a process called selective brain cooling. We test the hypothesis that selective brain cooling, which results in lowered hypothalamic temperature, contributes to water conservation in sheep. Nine Dorper sheep, instrumented to provide measurements of carotid blood and brain temperature, were dosed with deuterium oxide (D2O), exposed to heat for 8 days (40 ◦C for 6-h per day) and deprived of water for the last five days (days 3 to 8). Plasma osmolality increased and the body water fraction decreased over the five days of water deprivation, with the sheep losing 16.7% of their body mass. Following water deprivation, both the mean 24h carotid blood temperature and the mean 24h brain temperature increased, but carotid blood temperature increased more than did brain temperature resulting in increased selective brain cooling. There was considerable inter-individual variation in the degree to which individual sheep used selective brain cooling. In general, sheep spent more time using selective brain cooling, and it was of greater magnitude, when dehydrated compared to when they were euhydrated. We found a significant positive correlation between selective brain cooling magnitude and osmolality (an index of hydration state). Both the magnitude of selective brain cooling and the proportion of time that sheep spent selective brain cooling were negatively correlated with water turnover. Sheep that used selective brain cooling more frequently, and with greater magnitude, lost less water than did conspecifics using selective brain cooling less efficiently. Our results show that a 50 kg sheep can save 2.6L of water per day (~60% of daily water intake) when it employs selective brain cooling for 50% of the day during heat exposure. We conclude that selective brain cooling has a water conservation function in artiodactyls.
- Published
- 2015
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23. Hypoxia following etorphine administration in goats (Capra hircus) results more from pulmonary hypertension than from hypoventilation.
- Author
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Meyer LC, Hetem RS, Mitchell D, and Fuller A
- Subjects
- Analgesics, Opioid adverse effects, Animals, Female, Goat Diseases pathology, Goats, Hypertension, Pulmonary chemically induced, Hypoventilation chemically induced, Hypoxia chemically induced, Etorphine adverse effects, Goat Diseases chemically induced, Hypertension, Pulmonary veterinary, Hypoventilation veterinary, Hypoxia veterinary
- Abstract
Background: Etorphine, a potent opioid agonist, causes pulmonary hypertension and respiratory depression. Whether etorphine-induced pulmonary hypertension negatively influences pulmonary gas exchange and exacerbates the effects of ventilator depression and the resultant hypoxemia is unknown. To determine if these effects occurred we instrumented twelve goats with peripheral and pulmonary arterial catheters to measure systemic and pulmonary pressures before and after etorphine administration. Concurrent cardiopulmonary and arterial blood gas variables were also measured., Results: Etorphine induced hypoventilation (55% reduction to 7.6 ± 2.7 L.min(-1), F(11,44) = 15.2 P < 0.0001), hypoxia (<45 mmHg, F(11,44) = 8.6 P < 0.0001), hypercapnia (>40 mmHg, F(11,44) = 5.6 P < 0.0001) and pulmonary hypertension (mean 23 ± 6 mmHg, F(11,44) = 8.2 P < 0.0001). Within 6 min of etorphine administration hypoxia was twice (F(11,22) = 3.0 P < 0.05) as poor than that expected from etorphine-induced hypoventilation alone. This disparity appeared to result from a decrease in the movement of oxygen (gas exchange) across the alveoli membrane, as revealed by an increase in the P(A-a)O2 gradient (F(11,44) = 7.9 P < 0.0001). The P(A-a)O2 gradient was not correlated with global changes in the ventilation perfusion ratio (P = 0.28) but was correlated positively with the mean pulmonary artery pressure (P = 0.017, r(2) = 0.97), indicating that pulmonary pressure played a significant role in altering pulmonary gas exchange., Conclusion: Attempts to alleviate etorphine-induced hypoxia therefore should focus not only on reversing the opioid-induced respiratory depression, but also on improving gas exchange by preventing etorphine-induced pulmonary hypertension.
- Published
- 2015
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24. In vivo evaluation of a mucoadhesive polymeric caplet for intravaginal anti-HIV-1 delivery and development of a molecular mechanistic model for thermochemical characterization.
- Author
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Ndesendo VM, Choonara YE, Meyer LC, Kumar P, Tomar LK, Tyagi C, du Toit LC, and Pillay V
- Subjects
- Adhesiveness drug effects, Administration, Intravaginal, Animals, Anti-HIV Agents administration & dosage, Drug Evaluation, Preclinical methods, Female, HIV Infections pathology, Molecular Structure, Polymers administration & dosage, Swine, Tissue Adhesives administration & dosage, Anti-HIV Agents chemistry, Drug Delivery Systems methods, HIV Infections drug therapy, HIV-1 drug effects, Polymers chemistry, Tissue Adhesives chemistry
- Abstract
Context and Objective: The aim of this study was to develop, characterize and evaluate a mucoadhesive caplet resulting from a polymeric blend (polymeric caplet) for intravaginal anti-HIV-1 delivery., Materials and Methods: Poly(lactic-co-glycolic) acid, ethylcellulose, poly(vinylalcohol), polyacrylic acid and modified polyamide 6, 10 polymers were blended and compressed to a caplet-shaped device, with and without two model drugs 3'-azido-3'-deoxythymidine (AZT) and polystyrene sulfonate (PSS). Thermal analysis, infrared spectroscopy and microscopic analysis were carried out on the caplets employing temperature-modulated DSC (TMDSC), Fourier transform infra-red (FTIR) spectrometer and scanning electron microscope, respectively. In vitro and in vivo drug release analyses as well as the histopathological toxicity studies were carried out on the drug-loaded caplets. Furthermore, molecular mechanics (MM) simulations were carried out on the drug-loaded caplets to corroborate the experimental findings., Results and Discussion: There was a big deviation between the Tg of the polymeric caplet from the Tg's of the constituent polymers indicating a strong interaction between constituent polymers. FTIR spectroscopy confirmed the presence of specific ionic and non-ionic interactions within the caplet. A controlled near zero-order drug release was obtained for AZT (20 d) and PSS (28 d). In vivo results, i.e. the drug concentration in plasma ranged between 0.012-0.332 mg/mL and 0.009-0.256 mg/mL for AZT and PSS over 1-28 d., Conclusion: The obtained results, which were corroborated by MM simulations, attested that the developed system has the potential for effective delivery of anti-HIV-agents.
- Published
- 2015
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25. Chemical immobilization and anesthesia of free-living aardvarks (Orycteropus afer) with ketamine-medetomidine-midazolam and isoflurane.
- Author
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Rey B, Costello MA, Fuller A, Haw A, Hetem RS, Mitchell D, and Meyer LC
- Subjects
- Anesthesia, General veterinary, Anesthesia, Inhalation veterinary, Anesthetics, Inhalation administration & dosage, Anesthetics, Inhalation pharmacology, Animals, Animals, Wild, Hypnotics and Sedatives administration & dosage, Hypnotics and Sedatives pharmacology, Isoflurane administration & dosage, Ketamine administration & dosage, Medetomidine administration & dosage, Midazolam administration & dosage, Isoflurane pharmacology, Ketamine pharmacology, Medetomidine pharmacology, Midazolam pharmacology, Xenarthra
- Abstract
Abstract We evaluated the effectiveness of a ketamine-medetomidine-midazolam drug combination administered intramuscularly by remote injection followed by isoflurane anesthesia in free-living aardvarks (Orycteropus afer). Seven aardvarks weighing 33-45 kg were immobilized to perform surgical implantation of temperature loggers using 3.8 mg/kg ketamine, 0.1 mg/kg medetomidine, and 0.25 mg/kg midazolam. Immobilized aardvarks were transported to a surgical theater and received 0.5-1% isoflurane in oxygen after tracheal intubation. After surgery, medetomidine was antagonized with 0.5 mg/kg atipamezole, and aardvarks were released at the site of capture. We recorded induction and recovery times, clinical and physiologic parameters, and conducted blood gas analyses before and during isoflurane administration. Aardvarks showed initial effects within 3 min and reached lateral recumbency within 7 min after drug administration. Heart rate (50-67 beats/min), respiratory rate (10-15 breaths/min), oxygen hemoglobin saturation (SaO2; 90-97%), and rectal temperature (34.0-37.5 C) were within acceptable physiologic ranges. Mean arterial blood pressure was initially high (146 ± 12 mmHg), but the hypertension resolved over time. Rectal temperature dropped significantly during anesthesia. Four animals had to be treated to relieve apnea. Blood gas analyses revealed mild to moderate hypercapnia but no hypoxaemia. The ketamine-medetomidine-midazolam combination provided effective immobilization. Combined with a low concentration of isoflurane, it can be used for prolonged surgical procedures in wild aardvarks. However, caution is needed, and monitoring of clinical parameters is required.
- Published
- 2014
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26. Thermoregulatory plasticity in free-ranging vervet monkeys, Chlorocebus pygerythrus.
- Author
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Lubbe A, Hetem RS, McFarland R, Barrett L, Henzi PS, Mitchell D, Meyer LC, Maloney SK, and Fuller A
- Subjects
- Animals, Body Temperature physiology, Linear Models, Photoperiod, Rain, South Africa, Statistics, Nonparametric, Telemetry, Acclimatization physiology, Body Temperature Regulation physiology, Cercopithecinae physiology, Circadian Rhythm physiology, Seasons
- Abstract
We used implanted miniature data loggers to obtain the first measurements of body temperature from a free-ranging anthropoid primate. Vervet monkeys (Chlorocebus pygerythrus) living in a highly seasonal, semi-arid environment maintained a lower mean 24-h body temperature in winter (34.6 ± 0.5 °C) than in summer (36.2 ± 0.1 °C), and demonstrated increased heterothermy (as indexed by the 24-h amplitude of their body temperature rhythm) in response to proximal environmental stressors. The mean 24-h amplitude of the body temperature rhythm in summer (2.5 ± 0.1 °C) was lower than that in winter (3.2 ± 0.4 °C), with the highest amplitude for an individual monkey (5.6 °C) recorded in winter. The higher amplitude of the body temperature rhythm in winter was a consequence primarily of lower 24-h minimum body temperatures during the nocturnal phase, when monkeys were inactive. These low minimum body temperatures were associated with low black globe temperature (GLMM, β = 0.046, P < 0.001), short photoperiod (β = 0.010, P < 0.001) and low rainfall over the previous 2 months, which we used as a proxy for food availability (β = 0.001, P < 0.001). Despite the lower average winter minimum body temperatures, there was no change in the lower modal body temperature between winter and summer. Therefore, unlike the regulated physiological adjustments proposed for torpor or hibernation, these minimum winter body temperatures did not appear to reflect a regulated reduction in body temperature. The thermoregulatory plasticity nevertheless may have fitness benefits for vervet monkeys.
- Published
- 2014
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27. Structure of giant muscle proteins.
- Author
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Meyer LC and Wright NT
- Abstract
Giant muscle proteins (e.g., titin, nebulin, and obscurin) play a seminal role in muscle elasticity, stretch response, and sarcomeric organization. Each giant protein consists of multiple tandem structural domains, usually arranged in a modular fashion spanning 500 kDa to 4 MDa. Although many of the domains are similar in structure, subtle differences create a unique function of each domain. Recent high and low resolution structural and dynamic studies now suggest more nuanced overall protein structures than previously realized. These findings show that atomic structure, interactions between tandem domains, and intrasarcomeric environment all influence the shape, motion, and therefore function of giant proteins. In this article we will review the current understanding of titin, obscurin, and nebulin structure, from the atomic level through the molecular level.
- Published
- 2013
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28. Energy intake and the circadian rhythm of core body temperature in sheep.
- Author
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Maloney SK, Meyer LC, Blache D, and Fuller A
- Abstract
We tested the hypothesis that different levels of energy intake would alter the circadian rhythm of core body temperature (Tc) in ovariectomized sheep. We measured arterial blood temperature every 5 min while ten sheep were offered a maintenance diet, 70% of maintenance requirements, or 150% of maintenance requirements, for 12 days, and later fasted for 2 days. The rhythmicity of Tc was analyzed for its dominant period and then a least-squares cosine wave was fitted to the data that generated a mesor, amplitude, and acrophase for the rhythm. When energy intake was less than maintenance requirements we observed a significant decrease in the mesor and minimum, and a significant increase in the amplitude and goodness of fit, of the body temperature rhythm. Fasting also resulted in a decrease in the maximum of the body temperature rhythm. Feeding the sheep to excess did not affect the mesor or maximum of the rhythm, but did result in a decrease in the goodness of fit of the rhythm in those sheep that consumed more energy than when they were on the maintenance diet, indicating that circadian rhythmicity was decreased when energy intake increased. Our data indicate that modulation of the circadian rhythm of body temperature, characterized by inactive-phase hypothermia, occurs when energy intake is reduced. The response may be an adaptation to energy imbalance in large mammals.
- Published
- 2013
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29. Cheetah do not abandon hunts because they overheat.
- Author
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Hetem RS, Mitchell D, de Witt BA, Fick LG, Meyer LC, Maloney SK, and Fuller A
- Subjects
- Animals, Body Temperature, Acinonyx physiology, Fever, Predatory Behavior
- Abstract
Hunting cheetah reportedly store metabolic heat during the chase and abandon chases because they overheat. Using biologging to remotely measure the body temperature (every minute) and locomotor activity (every 5 min) of four free-living cheetah, hunting spontaneously, we found that cheetah abandoned hunts, but not because they overheated. Body temperature averaged 38.4°C when the chase was terminated. Storage of metabolic heat did not compromise hunts. The increase in body temperature following a successful hunt was double that of an unsuccessful hunt (1.3°C ± 0.2°C versus 0.5°C ± 0.1°C), even though the level of activity during the hunts was similar. We propose that the increase in body temperature following a successful hunt is a stress hyperthermia, rather than an exercise-induced hyperthermia.
- Published
- 2013
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30. A novel stimuli-synchronized alloy-treated matrix for space-defined gastrointestinal delivery of mesalamine in the Large White pig model.
- Author
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Bawa P, Choonara YE, du Toit LC, Kumar P, Ndesendo VM, Meyer LC, and Pillay V
- Subjects
- Administration, Oral, Animals, Anti-Inflammatory Agents, Non-Steroidal blood, Anti-Inflammatory Agents, Non-Steroidal chemistry, Barium Sulfate chemistry, Carboxymethylcellulose Sodium chemistry, Chemistry, Pharmaceutical, Chitosan chemistry, Cross-Linking Reagents chemistry, Mesalamine blood, Mesalamine chemistry, Microscopy, Electron, Scanning, Molecular Docking Simulation, Pectins chemistry, Polygalacturonase metabolism, Polyphosphates chemistry, Polysaccharides, Bacterial chemistry, Solubility, Spectroscopy, Fourier Transform Infrared, Surface Properties, Swine, beta-Glucosidase metabolism, Anti-Inflammatory Agents, Non-Steroidal administration & dosage, Colon enzymology, Colon metabolism, Drug Carriers chemistry, Mesalamine administration & dosage
- Abstract
The study focussed on designing a Stimuli-Synchronized Matrix (SSM) for space-defined colonic delivery of the anti-inflammatory drug mesalamine. The configured matrix provided time-independent delivery and stimuli targeting. Formulations were optimized according to a Box-Behnken experimental design that constituted mesalamine-loaded BaSO4-crosslinked chitosan dispersed within a pectin, carboxymethylcellulose and xanthan gum complex. The complex was compressed into matrices and subsequently alloy-treated with pectin and ethylcellulose. In vitro drug release was determined in the presence and absence of colonic enzymes and the mean dissolution time was used for formulation optimization. To mechanistically elucidate the synchronous catalytic action of the enzymes pectinase and glucosidase on the matrix, computer-aided 3D modelling of active fractions of the enzyme-substrate complexes was generated to predict the orientation of residues affecting the substrate domain. Drug release profiles revealed distinct colonic enzyme responsiveness with fractions of 0.402 and 0.152 of mesalamine released in the presence and absence of enzymes, respectively after 24h. The commercial comparator product showed irreproducible release profiles over the same period (SD=0.550) compared to the SSM formulation (SD=0.037). FTIR spectra of alloy-treated matrices showed no peaks from 1589 to 1512cm(-1) after colonic enzyme exposure. With increasing enzyme exposure there were also no peaks between 1646 and 1132cm(-1). This indicated polymeric enzyme cleavage for controlled and space-defined release of mesalamine. Plasma concentration profiles in the Large White pig model produced a Cmax of 3.77±1.375μg/mL compared to 10.604±2.846μg/mL for the comparator formulation. The SSM formulation proved superior over the comparator product by providing superiorly controlled enzyme-responsive colonic drug delivery., (Copyright © 2012 Elsevier B.V. All rights reserved.)
- Published
- 2013
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31. Body temperature and physical activity correlates of the menstrual cycle in Chacma Baboons (Papio hamadryas ursinus).
- Author
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Nyakudya TT, Fuller A, Meyer LC, Maloney SK, and Mitchell D
- Subjects
- Animals, Estradiol urine, Female, Perineum physiology, Progesterone urine, Body Temperature, Menstrual Cycle, Motor Activity, Ovulation, Papio ursinus physiology
- Abstract
We investigated the temporal relationship between abdominal temperature, physical activity, perineal swelling, and urinary progesterone and estradiol concentrations over the menstrual cycle in unrestrained captive baboons. Using a miniature temperature-sensitive data logger surgically implanted in the abdominal cavity and an activity data logger implanted subcutaneously on the trunk, we measured, continuously over 6 months at 10-min intervals, abdominal temperature and physical activity patterns in four female adult baboons Papio hamadryas ursinus (12.9-19.9 kg), in cages in an indoor animal facility (22-25°C). We monitored menstrual bleeding and perineal swelling changes, and measured urinary progesterone and estradiol concentrations, daily for up to 6 months, to ascertain the stage and length of the menstrual cycle. The menstrual cycle was 36 ± 2 days (mean ± SD) long and the baboons exhibited cyclic changes in perineal swellings, abdominal temperature, physical activity, urinary progesterone, and estradiol concentrations over the cycle. Mean 24-hr abdominal temperature during the luteal phase was significantly higher than during the periovulatory phase (ANOVA, F((2, 9)) = 4.7; P = 0.04), but not different to that during the proliferative phase. Physical activity followed a similar pattern, with mean 24-hr physical activity almost twice as high in the luteal than in the periovulatory phase (ANOVA, P = 0.58; F((2, 12)) = 5.8). We have characterized correlates of the menstrual cycle in baboons and shown, for the first time, a rhythm of physical activity and abdominal temperature over the menstrual cycle, with a nadir of temperature and activity at ovulation., (© 2012 Wiley Periodicals, Inc.)
- Published
- 2012
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32. Activity re-assignment and microclimate selection of free-living Arabian oryx: responses that could minimise the effects of climate change on homeostasis?
- Author
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Hetem RS, Strauss WM, Fick LG, Maloney SK, Meyer LC, Shobrak M, Fuller A, and Mitchell D
- Subjects
- Animals, Climate Change, Female, Homeostasis, Male, Microclimate, Behavior, Animal, Hot Temperature, Motor Activity, Ruminants psychology
- Abstract
Predicting whether behaviour could buffer the effects of climate change on long-lived mammals requires a better understanding of the long-term behavioural responses of mammals to environmental stress. Using biologging, we measured locomotor activity and microclimate selection, over eight months, in five Arabian oryx (Oryx leucoryx) living free in a Saudi Arabian desert. The oryx displayed seasonal flexibility in activity patterns, shifting from a continuous 24-h activity pattern with crepuscular peaks in cooler months to a predominantly nocturnal activity pattern during the hottest months, without reducing the total 24-h activity level. The proportion of total 24-h activity that occurred during daylight hours was just 29±8% during the hottest months, versus 53±8% (mean±SD, n=5 oryx) in the other months. The attenuation in diurnal activity levels during the hot months was accompanied by the selection of cooler microclimates, presumably via shade seeking, during the heat of the day. Analysis of miniature black globe (miniglobe) temperature from a remote sensor on the collar of two female animals revealed that oryx selected microclimates cooler than the microclimates in direct sun at higher environmental heat loads across all periods, but with enhanced efficiency during the dry periods. We have quantified activity re-assignment and microclimate selection as responses to hot arid conditions in a free-living artiodactyl. Such flexible behavioural processes may act to buffer the adverse effects of the progressively hotter and drier conditions predicted to occur with climate change., (Copyright © 2012 Elsevier GmbH. All rights reserved.)
- Published
- 2012
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33. Selective brain cooling in Arabian oryx (Oryx leucoryx): a physiological mechanism for coping with aridity?
- Author
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Hetem RS, Strauss WM, Fick LG, Maloney SK, Meyer LC, Fuller A, Shobrak M, and Mitchell D
- Subjects
- Air, Animals, Carotid Arteries physiology, Circadian Rhythm physiology, Conservation of Natural Resources, Female, Linear Models, Male, Organ Specificity, Saudi Arabia, Antelopes physiology, Body Temperature Regulation physiology, Brain physiology, Desert Climate
- Abstract
Selective brain cooling is a thermoregulatory effector proposed to conserve body water and, as such, may help artiodactyls cope with aridity. We measured brain and carotid blood temperature, using implanted data loggers, in five Arabian oryx (Oryx leucoryx) in the desert of Saudi Arabia. On average, brain temperature was 0.24±0.05°C lower than carotid blood temperature for four oryx in April. Selective brain cooling was enhanced in our Arabian oryx compared with another species from the same genus (gemsbok Oryx gazella gazella) exposed to similar ambient temperatures but less aridity. Arabian oryx displayed a lower threshold (37.8±0.1°C vs 39.8±0.4°C), a higher frequency (87±6% vs 15±15%) and a higher maximum magnitude (1.2±0.2°C vs 0.5±0.3°C) of selective brain cooling than did gemsbok. The dominant male oryx displayed less selective brain cooling than did any of the other oryx, but selective brain cooling was enhanced in this oryx as conditions became hotter and drier. Enhanced selective brain cooling in Arabian oryx supports the hypothesis that selective brain cooling would bestow survival advantages for artiodactyl species inhabiting hot hyper-arid environments.
- Published
- 2012
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34. Optimization of a polymer composite employing molecular mechanic simulations and artificial neural networks for a novel intravaginal bioadhesive drug delivery device.
- Author
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Ndesendo VM, Pillay V, Choonara YE, du Toit LC, Kumar P, Buchmann E, Meyer LC, and Khan RA
- Subjects
- Adhesiveness, Adhesives metabolism, Administration, Intravaginal, Amino Acid Sequence, Antigens, Surface chemistry, Antigens, Surface metabolism, Computer Simulation, Female, Glycoproteins chemistry, Glycoproteins metabolism, HIV Infections drug therapy, Humans, Models, Chemical, Models, Molecular, Molecular Sequence Data, Neural Networks, Computer, Polymers metabolism, Vagina metabolism, Adhesives chemistry, Anti-HIV Agents administration & dosage, Drug Delivery Systems instrumentation, Polymers chemistry, Zidovudine administration & dosage
- Abstract
This study aimed at elucidating an optimal synergistic polymer composite for achieving a desirable molecular bioadhesivity and Matrix Erosion of a bioactive-loaded Intravaginal Bioadhesive Polymeric Device (IBPD) employing Molecular Mechanic Simulations and Artificial Neural Networks (ANN). Fifteen lead caplet-shaped devices were formulated by direct compression with the model bioactives zidovudine and polystyrene sulfonate. The Matrix Erosion was analyzed in simulated vaginal fluid to assess the critical integrity. Blueprinting the molecular mechanics of bioadhesion between vaginal epithelial glycoprotein (EGP), mucin (MUC) and the IBPD were performed on HyperChem 8.0.8 software (MM+ and AMBER force fields) for the quantification and characterization of correlative molecular interactions during molecular bioadhesion. Results proved that the IBPD bioadhesivity was pivoted on the conformation, orientation, and poly(acrylic acid) (PAA) composition that interacted with EGP and MUC present on the vaginal epithelium due to heterogeneous surface residue distributions (free energy= -46.33 kcalmol(-1)). ANN sensitivity testing as a connectionist model enabled strategic polymer selection for developing an IBPD with an optimally prolonged Matrix Erosion and superior molecular bioadhesivity (ME = 1.21-7.68%; BHN = 2.687-4.981 N/mm(2)). Molecular modeling aptly supported the EGP-MUC-PAA molecular interaction at the vaginal epithelium confirming the role of PAA in bioadhesion of the IBPD once inserted into the posterior fornix of the vagina.
- Published
- 2012
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35. Does size matter? Comparison of body temperature and activity of free-living Arabian oryx (Oryx leucoryx) and the smaller Arabian sand gazelle (Gazella subgutturosa marica) in the Saudi desert.
- Author
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Hetem RS, Strauss WM, Fick LG, Maloney SK, Meyer LC, Shobrak M, Fuller A, and Mitchell D
- Subjects
- Analysis of Variance, Animals, Humidity, Saudi Arabia, Species Specificity, Telemetry, Temperature, Adaptation, Biological physiology, Antelopes physiology, Body Size physiology, Body Temperature physiology, Circadian Rhythm physiology, Motor Activity physiology
- Abstract
Heterothermy, a variability in body temperature beyond the normal limits of homeothermy, is widely viewed as a key adaptation of arid-adapted ungulates. However, desert ungulates with a small body mass, i.e. a relatively large surface area-to-volume ratio and a small thermal inertia, are theoretically less likely to employ adaptive heterothermy than are larger ungulates. We measured body temperature and activity patterns, using implanted data loggers, in free-ranging Arabian oryx (Oryx leucoryx, ±70 kg) and the smaller Arabian sand gazelle (Gazella subgutturosa marica, ±15 kg) inhabiting the same Arabian desert environment, at the same time. Compared to oryx, sand gazelle had higher mean daily body temperatures (F(1,6) = 47.3, P = 0.0005), higher minimum daily body temperatures (F(1,6) = 42.6, P = 0.0006) and higher maximum daily body temperatures (F(1,6) = 11.0, P = 0.02). Despite these differences, both species responded similarly to changes in environmental conditions. As predicted for adaptive heterothermy, maximum daily body temperature increased (F(1,6) = 84.0, P < 0.0001), minimum daily body temperature decreased (F(1,6) = 92.2, P < 0.0001), and daily body temperature amplitude increased (F(1,6) = 97.6, P < 0.0001) as conditions got progressively hotter and drier. There were no species differences in activity levels, however, both gazelle and oryx showed a biphasic or crepuscular rhythm during the warm wet season but shifted to a more nocturnal rhythm during the hot dry season. Activity was attenuated during the heat of the day at times when both species selected cool microclimates. These two species of Arabian ungulates employ heterothermy, cathemerality and shade seeking very similarly to survive the extreme, arid conditions of Arabian deserts, despite their size difference.
- Published
- 2012
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36. Advanced preformulation investigations for the development of a lead intravaginal bioadhesive polymeric device.
- Author
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Ndesendo VM, Pillay V, Choonara YE, du Toit LC, Buchmann E, Kumar P, Khan RA, and Meyer LC
- Subjects
- Administration, Intravaginal, Animals, Biocompatible Materials chemistry, Delayed-Action Preparations, Drug Design, Female, Humans, Hydrophobic and Hydrophilic Interactions, Materials Testing methods, Models, Biological, Polylactic Acid-Polyglycolic Acid Copolymer, Tissue Adhesives, Drug Delivery Systems, Lactic Acid chemistry, Nylons chemistry, Polyglycolic Acid chemistry, Polymers chemistry
- Abstract
Context and Objective: To screen various polymers through extensive preformulation investigations to ultimately obtain a lead polymer combination for designing a desirable Intravaginal Bioadhesive Polymeric Device (IBPD)., Materials and Methods: Hydrophilic and hydrophobic polymers (18) at different combinations were blended and compressed into 62 caplet-shaped devices at 5 tons, one of the hydrophilic polymers being a modified synthetic product of polyamide 6,10 ((m)PA 6,10). Two sets of crosslinked PAA-based caplets comprising either allyl-sucrose (AS-PAA) or allyl-penta-erythritol (APE-PAA) were explored. The devices were subjected to in-process validation tests and thereafter to preformulation investigational screening {equilibrium swelling ratio (ESR) being a screening parameter}, using a One Variable at a Time (OVAT) approach. Molecular mechanics force field simulations in both vacuum and solvated systems were conducted to investigate the influence of addition and subsequent replacement of a polymer(s) on the spatial disposition and energetic profile of the sterically constrained and geometrically optimized multi-polymeric complex, IBPD., Results and Discussion: The developed devices were sufficiently strong (longitudinal crushing force:286 ± 0.01 N; mean weight:600 ± 0.48 mg; mean friability:0.31 ± 0.04%). Through OVAT approach, 15 lead formulations with minimal swelling tendencies (ESRs ranging from 0.011 to 0.084) were obtained out of 62 formulations. F62 {i.e. (m)PA 6,10, (150 mg), PLGA (400 mg), EC (200 mg), PVA (25 mg) and PAA (25 mg)} displayed minimal swelling tendency and therefore the highest stability. The highly stabilized conformation of the final in silico IBPD polymeric assembly PLGA-(m)PA6,10-PVA-PAA-EC corroborated the experimental results in terms of preformulation investigational screening using the OVAT approach., Conclusion: The results obtained suggest that (m)PA 6,10, PLGA, EC, PVA and PAA at an appropriate weight ratio may be suitable for development of an IBPD.
- Published
- 2012
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37. [Severe laryngomalacia in children can be treated with laser assisted surgery].
- Author
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Meyer LC and Godballe C
- Subjects
- Glottis surgery, Humans, Infant, Infant, Newborn, Laryngomalacia diagnosis, Laryngoscopy, Treatment Outcome, Laryngomalacia surgery, Laser Therapy methods
- Abstract
Laryngomalacia is the most common cause for congenital stridor. The stridor is caused by collapse of supraglottic structures during inspiration. Two severe cases treated with laser-assisted supraglottoplasty are presented. Our cases as well as the literature describe good effect of the treatment with only few complications. However since laryngomalacia usually it is a benign condition, which in most cases resolves spontaneously within the first two years of the patients life, this treatment should only be used in severe cases, where the alternative treatment would be tracheotomia.
- Published
- 2012
38. Uterine torsion in a Sprague Dawley rat (Rattus norvegicus).
- Author
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Erlwanger KH, Costello MA, and Meyer LC
- Subjects
- Animals, Fatal Outcome, Female, Pregnancy, Pregnancy Complications diagnosis, Rats, Torsion Abnormality diagnosis, Fallopian Tubes pathology, Pregnancy Complications veterinary, Rats, Sprague-Dawley abnormalities, Rodent Diseases diagnosis, Torsion Abnormality veterinary
- Abstract
Uterine torsion is a twisting of the uterus or uterine horn perpendicular to its long axis. We report a case of uterine torsion in an adult breeding Sprague Dawley rat. The rat died a month after her last recorded delivery. Post mortem examination of the rat revealed 270 degrees torsion of the right uterine horn. The uterus contained a single foetus. The liver was pale and enlarged. The rest of the viscera appeared normal. Histopathological examination showed acute hepatic necrosis and pulmonary congestion with mild lymphocytic infiltrates peribronchially. The acute hepatic necrosis may have been associated with septicaemia due to compromised blood vessels following the uterine torsion. The presence of a single foetus could have resulted in foeto-maternal disproportion with resultant uterine torsion. Torsion of the uterus can be accompanied by haemostatic and metabolic complications, which could have caused the death of the rat. Although uterine torsion is a rare condition in rats, it should be considered as a potential complication of gestation in animal breeding units.
- Published
- 2011
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39. Angularis oculi vein blood flow modulates the magnitude but not the control of selective brain cooling in sheep.
- Author
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Fuller A, Hetem RS, Meyer LC, and Maloney SK
- Subjects
- Animals, Body Temperature physiology, Brain blood supply, Carotid Arteries physiology, Cavernous Sinus physiology, Dehydration, Female, Ligation, Veins surgery, Body Temperature Regulation physiology, Brain physiology, Nose blood supply, Regional Blood Flow physiology, Sheep, Domestic physiology, Veins physiology
- Abstract
To investigate the role of the angularis oculi vein (AOV) in selective brain cooling (SBC), we measured brain and carotid blood temperatures in six adult female Dorper sheep. Halfway through the study, a section of the AOV, just caudal to its junction with the dorsal nasal vein, was extirpated on both sides. Before and after AOV surgery, the sheep were housed outdoors at 21-22°C and were exposed in a climatic chamber to daytime heat (40°C) and water deprivation for 5 days. In sheep outdoors, SBC was significantly lower after the AOV had been cut, with its 24-h mean reduced from 0.25 to 0.01°C (t(5) = 3.06, P = 0.03). Carotid blood temperature also was lower (by 0.28°C) at all times of day (t(5) = 3.68, P = 0.01), but the pattern of brain temperature was unchanged. The mean threshold temperature for SBC was not different before (38.85 ± 0.28°C) and after (38.85 ± 0.39°C) AOV surgery (t(5) =0.00, P = 1.00), but above the threshold, SBC magnitude was about twofold less after surgery. SBC after AOV surgery also was less during heat exposure and water deprivation. However, SBC increased progressively by the same magnitude (0.4°C) over the period of water deprivation, and return of drinking water led to rapid cessation of SBC in sheep before and after AOV surgery. We conclude that the AOV is not the only conduit for venous drainage contributing to SBC in sheep and that, contrary to widely held opinion, control of SBC does not involve changes in the vasomotor state of the AOV.
- Published
- 2011
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40. Minimum daily core body temperature in western grey kangaroos decreases as summer advances: a seasonal pattern, or a direct response to water, heat or energy supply?
- Author
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Maloney SK, Fuller A, Meyer LC, Kamerman PR, Mitchell G, and Mitchell D
- Subjects
- Animals, Body Temperature, Hot Temperature, Seasons, Body Temperature Regulation, Macropodidae physiology, Water metabolism
- Abstract
Using implanted temperature loggers, we measured core body temperature in nine western grey kangaroos every 5 min for 24 to 98 days in spring and summer. Body temperature was highest at night and decreased rapidly early in the morning, reaching a nadir at 10:00 h, after ambient temperature and solar radiation had begun to increase. On hotter days, the minimum morning body temperature was lower than on cooler days, decreasing from a mean of 36.2°C in the spring to 34.0°C in the summer. This effect correlated better with the time of the year than with proximate thermal stressors, suggesting that either season itself or some factor correlated with season, such as food availability, caused the change. Water saving has been proposed as a selective advantage of heterothermy in other large mammals, but in kangaroos the water savings would have been small and not required in a reserve with permanent standing water. We calculate that the lower core temperature could provide energy savings of nearly 7%. It is likely that the heterothermy that we observed on hot days results either from decreased energy intake during the dry season or from a seasonal pattern entrained in the kangaroos that presumably has been selected for because of decreased energy availability during the dry season.
- Published
- 2011
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41. In vivo evaluation of a biodegradable donut-shaped minitablet for prolonged posterior segment drug delivery in the rabbit eye model.
- Author
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Choonara YE, Pillay V, Danckwerts MP, Carmichael TR, Meyer LC, Du Toit LC, Naylor S, and Wanblad C
- Subjects
- Absorbable Implants, Animals, Delayed-Action Preparations chemistry, Equipment Design, Hydrogen-Ion Concentration, Male, Polylactic Acid-Polyglycolic Acid Copolymer, Posterior Eye Segment ultrastructure, Rabbits, Antiviral Agents administration & dosage, Drug Delivery Systems instrumentation, Ganciclovir administration & dosage, Lactic Acid chemistry, Polyglycolic Acid chemistry, Posterior Eye Segment drug effects
- Abstract
This study focused on the in vivo evaluation of a biodegradable ganciclovir-loaded donut-shaped minitablet (DSMT) for controlled drug delivery in the New Zealand white albino rabbit eye model. Specialized tablet tooling was used to manufacture a poly(lactic-co-glycolic acid) DSMT device that was implanted into 18 rabbits through the pars plana/peripheral retina of the right eyes of each rabbit. The left eyes were used as controls. Possible adverse effects on ocular tissues were assessed by histomorphology, slit-lamp biomicroscopy, intraocular pressure (IOP) measurements, and indirect ophthalmoscopy. The ex vivo microenvironmental vitreous pH was also monitored. Rabbits were euthanized at predetermined intervals and the residual devices, vitreous humor, and ocular tissue were retrieved and stored appropriately until further analysis. The DSMT was well tolerated up to 72 days and was still visible in the superotemporal quadrant of the eye. The mean IOP range (6-8 mmHg; N = 18) and changes in vitreous pH (7.25 ± 0.01; N = 3) correlated with baseline measurements. The DSMT displayed constant ganciclovir release at a rate of 2.02 μ g/h maintained within the 50% effective dose for human cytomegalovirus retinitis (N = 3). The design simplicity and application of the biodegradable DSMT device may provide a superior alternative for prolonged rate-controlled intraocular drug delivery., (Copyright © 2010 Wiley-Liss, Inc.)
- Published
- 2011
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42. In vivo evaluation of the release of zidovudine and polystyrene sulfonate from a dual intravaginal bioadhesive polymeric device in the pig model.
- Author
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Ndesendo VM, Pillay V, Choonara YE, Du Toit LC, Meyer LC, Buchmann E, Kumar P, and Khan RA
- Subjects
- Adhesiveness, Administration, Intravaginal, Animals, Anti-HIV Agents blood, Anti-HIV Agents pharmacokinetics, Biocompatible Materials chemistry, Chelating Agents pharmacokinetics, Female, Polymers chemistry, Polystyrenes blood, Polystyrenes pharmacokinetics, Swine, Zidovudine blood, Zidovudine pharmacokinetics, Anti-HIV Agents administration & dosage, Chelating Agents administration & dosage, Drug Delivery Systems instrumentation, Polystyrenes administration & dosage, Vagina metabolism, Zidovudine administration & dosage
- Abstract
This study focused on determining the concentration of zidovudine (AZT) and polystyrene sulfonate (PSS) in the plasma and vaginal tissue of the large white pig from an intravaginal bioadhesive polymeric device (IBPD). Biocompatible polymers were compressed with AZT and PSS into caplet-shaped devices for insertion into the posterior fornix of the pig vagina. A total of 25 pigs were used in this study. Plasma was sampled from the jugular vein at various time points after insertion of the IBPD reaching 28 days. At day 28, the pigs were euthanized and vaginal tissue was removed and digested with subtilisin for AZT and PSS extraction. The mean concentration detected in vaginal tissue at day 28 was 1.214 ± 0.062 mg/mL for AZT and 1.400 ± 0.071 mg/mL for PSS. Plasma concentration was significantly lower for AZT (0.332 ± 0.014 mg/mL) and PSS (0.256 ± 0.013 mg/mL). This indicated higher retention of AZT and PSS within the vaginal tissue. Molecular mechanics simulations blueprinted polymer-drug-mucin force-field interactions and energies that explicated the spatial preference of AZT and PSS for the vaginal tissue. Histopathotoxicity studies revealed negative-to-mild foreign body events and results strongly suggest that the IBPD may be suitable for prolonged intravaginal drug delivery in preventing the transmission of sexually transmitted infections and HIV/AIDS., (Copyright © 2010 Wiley-Liss, Inc.)
- Published
- 2011
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43. Assessment of the use of temperature-sensitive microchips to determine core body temperature in goats.
- Author
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Torrao NA, Hetem RS, Meyer LC, and Fick LG
- Subjects
- Animals, Female, Rectum physiology, Reproducibility of Results, Retroperitoneal Space physiology, Sensitivity and Specificity, Body Temperature physiology, Goats physiology, Microchip Analytical Procedures veterinary
- Abstract
Body temperature was measured at five different body sites (retroperitoneum, groin, semimembranosus muscle, flank and shoulder) using temperature-sensitive microchips implanted in five female goats, and compared with the core body and rectal temperatures. Body temperature was measured while the goats were kept in different ambient temperatures, with and without radiant heat, as well as during a fever induced experimentally by injection of bacterial lipopolysaccharide. Bland-Altman limit of agreement analysis was used to compare the temperature measurements at the different body sites during the different interventions. Temperatures measured by the microchip implanted in the retroperitoneum showed the closest agreement (mean 0.2 °C lower) with core and rectal temperatures during all interventions, whereas temperatures measured by the microchips implanted in the groin, muscle, flank and shoulder differed from core body temperature by up to 3.5 °C during the various interventions.
- Published
- 2011
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44. Necessity prompts strategic adaptation.
- Author
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Meyer LC
- Subjects
- Financial Management, Hospital, Humans, Organizational Policy, Outcome and Process Assessment, Health Care, Planning Techniques, Primary Health Care organization & administration, United States, Chief Executive Officers, Hospital organization & administration, Hospital Administration, Prospective Payment System organization & administration, Quality Assurance, Health Care organization & administration
- Published
- 2011
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45. Ostriches sleep like platypuses.
- Author
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Lesku JA, Meyer LC, Fuller A, Maloney SK, Dell'Omo G, Vyssotski AL, and Rattenborg NC
- Subjects
- Animals, Conservation of Natural Resources, Electroencephalography, Sleep, REM physiology, South Africa, Time Factors, Wakefulness physiology, Platypus physiology, Sleep physiology, Struthioniformes physiology
- Abstract
Mammals and birds engage in two distinct states of sleep, slow wave sleep (SWS) and rapid eye movement (REM) sleep. SWS is characterized by slow, high amplitude brain waves, while REM sleep is characterized by fast, low amplitude waves, known as activation, occurring with rapid eye movements and reduced muscle tone. However, monotremes (platypuses and echidnas), the most basal (or 'ancient') group of living mammals, show only a single sleep state that combines elements of SWS and REM sleep, suggesting that these states became temporally segregated in the common ancestor to marsupial and eutherian mammals. Whether sleep in basal birds resembles that of monotremes or other mammals and birds is unknown. Here, we provide the first description of brain activity during sleep in ostriches (Struthio camelus), a member of the most basal group of living birds. We found that the brain activity of sleeping ostriches is unique. Episodes of REM sleep were delineated by rapid eye movements, reduced muscle tone, and head movements, similar to those observed in other birds and mammals engaged in REM sleep; however, during REM sleep in ostriches, forebrain activity would flip between REM sleep-like activation and SWS-like slow waves, the latter reminiscent of sleep in the platypus. Moreover, the amount of REM sleep in ostriches is greater than in any other bird, just as in platypuses, which have more REM sleep than other mammals. These findings reveal a recurring sequence of steps in the evolution of sleep in which SWS and REM sleep arose from a single heterogeneous state that became temporally segregated into two distinct states. This common trajectory suggests that forebrain activation during REM sleep is an evolutionarily new feature, presumably involved in performing new sleep functions not found in more basal animals.
- Published
- 2011
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46. Variation in the daily rhythm of body temperature of free-living Arabian oryx (Oryx leucoryx): does water limitation drive heterothermy?
- Author
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Hetem RS, Strauss WM, Fick LG, Maloney SK, Meyer LC, Shobrak M, Fuller A, and Mitchell D
- Subjects
- Animals, Dehydration physiopathology, Desert Climate, Female, Hot Temperature adverse effects, Male, Photoperiod, Saudi Arabia, Seasons, Acclimatization, Antelopes physiology, Body Temperature Regulation, Circadian Rhythm, Drinking
- Abstract
Heterothermy, a variability in body temperature beyond the limits of homeothermy, has been advanced as a key adaptation of Arabian oryx (Oryx leucoryx) to their arid-zone life. We measured body temperature using implanted data loggers, for a 1-year period, in five oryx free-living in the deserts of Saudi Arabia. As predicted for adaptive heterothermy, during hot months compared to cooler months, not only were maximum daily body temperatures higher (41.1 ± 0.3 vs. 39.7 ± 0.1°C, P = 0.0002) but minimum daily body temperatures also were lower (36.1 ± 0.3 vs. 36.8 ± 0.2°C, P = 0.04), resulting in a larger daily amplitude of the body temperature rhythm (5.0 ± 0.5 vs. 2.9 ± 0.2°C, P = 0.0007), while mean daily body temperature rose by only 0.4°C. The maximum daily amplitude of the body temperature rhythm reached 7.7°C for two of our oryx during the hot-dry period, the largest amplitude ever recorded for a large mammal. Body temperature variability was influenced not only by ambient temperature but also water availability, with oryx displaying larger daily amplitudes of the body temperature rhythm during warm-dry months compared to warm-wet months (3.6 ± 0.6 vs. 2.3 ± 0.3°C, P = 0.005), even though ambient temperatures were the same. Free-living Arabian oryx therefore employ heterothermy greater than that recorded in any other large mammal, but water limitation, rather than high ambient temperature, seems to be the primary driver of this heterothermy.
- Published
- 2010
- Full Text
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47. Investigation of the physicochemical and physicomechanical properties of a novel intravaginal bioadhesive polymeric device in the pig model.
- Author
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Ndesendo VM, Pillay V, Choonara YE, du Toit LC, Buchmann E, Meyer LC, Khan RA, and Rosin U
- Subjects
- Adhesiveness, Animals, Anti-HIV Agents administration & dosage, Anti-HIV Agents chemistry, Diffusion, Drug Compounding methods, Female, Surface Properties, Swine, Tensile Strength, Delayed-Action Preparations chemical synthesis, Tissue Adhesives chemical synthesis, Vagina chemistry, Zidovudine administration & dosage, Zidovudine chemistry
- Abstract
The purpose of this study was to develop and evaluate the bioadhesivity, in vitro drug release, and permeation of an intravaginal bioadhesive polymeric device (IBPD) loaded with 3'-azido-3'-deoxythymidine (AZT) and polystyrene sulfonate (PSS). Modified polyamide 6,10, poly(lactic-coglycolic acid), polyacrylic acid, polyvinyl alcohol, and ethylcellulose were blended with model drugs AZT and PSS as well as radio-opaque barium sulfate (BaSO4) and then compressed into caplet devices on a tableting press. One set of devices was coated with 2% w/v pentaerythritol polyacrylic acid (APE-PAA) while another remained uncoated. Thermal analysis was performed on the constituent polymers as well the IBPD. The changes in micro-environmental pH within the simulated human vaginal fluid due to the presence of the IBPD were assessed over a period of 30 days. Textural profile analysis indicated that the bioadhesivity of the APE-PAA-coated devices (3.699 +/- 0.464 N; 0.0098 +/- 0.0004 J) was higher than that of the uncoated devices (1.198 +/- 0.150 N; 0.0019 +/- 0.0001 J). In addition, BaSO4-facilitated X-ray imaging revealed that the IBPD adhered to pig vaginal tissue over the experimental period of 30 days. Controlled drug release kinetics was obtained over 72 days. During a 24-h permeation study, an increase in drug flux for both AZT (0.84 mg cm(-2) h(-1)) and PSS (0.72 mg cm(-2) h(-1)) was realized up to 12 h and thereafter a steady-state was achieved. The diffusion and dissolution dynamics were mechanistically deduced based on a chemometric and molecular structure modeling approach. Overall, results suggested that the IBPD may be sufficiently bioadhesive with desirable physicochemical and physicomechanical stability for use as a prolonged intravaginal drug delivery device.
- Published
- 2010
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48. Effects of serotonin agonists and doxapram on respiratory depression and hypoxemia in etorphine-immobilized impala (Aepyceros melampus).
- Author
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Meyer LC, Hetem RS, Fick LG, Mitchell D, and Fuller A
- Subjects
- Analgesics, Opioid administration & dosage, Analgesics, Opioid adverse effects, Animals, Animals, Wild, Carbon Dioxide analysis, Etorphine administration & dosage, Hypoxia chemically induced, Immobilization methods, Immobilization physiology, Immobilization veterinary, Oxygen analysis, Oxygen Consumption, Partial Pressure, Respiratory Insufficiency chemically induced, Respiratory Rate drug effects, Tidal Volume drug effects, Ventilation-Perfusion Ratio drug effects, Antelopes physiology, Doxapram pharmacology, Etorphine adverse effects, Hypoxia veterinary, Respiratory Insufficiency veterinary, Serotonin Receptor Agonists pharmacology
- Abstract
Respiratory depression is a common side effect when opioids are used to immobilize wildlife. Serotonergic ligands have the potential to reverse opioid-induced respiratory depression. We examined whether any of three serotonergic ligands could reverse this depression in etorphine-immobilized (0.07 mg/kg) impala (Aepyceros melampus). The study took place in September-December 2007. Impala received intravenous injections of metoclopramide (10 mg/kg, n=6), buspirone (0.05 mg/kg, n=8), pimozide (1 mg/kg, n=8), doxapram (1 mg/kg, n=6), and control solutions on separate occasions. During the immobilization, partial pressures of oxygen (PaO(2), mmHg) and carbon dioxide (PaCO(2), mmHg), respiratory rate (breaths/min), ventilation (l/min), peripheral O(2) saturation (%), tidal volume (l), and respiratory exchange ratio were measured before and after injection of the experimental drugs. Etorphine immobilization caused respiratory depression and hypoxia (mean+/-SD, PaCO(2)=51+/-2 mmHg, PaO(2)=40+/-3 mmHg). Metoclopramide and buspirone, but not pimozide, attenuated the hypoxic effects of etorphine; 3 min after injection, metoclopramide increased the PaO(2) by 7.5+/-6.3 mmHg and buspirone by 6+/-6.6 mmHg (F=3.9, P=0.02). These effects were similar to those of doxapram (8+/-7 mmHg, F=3.9; P>0.05). Neither metoclopramide nor buspirone significantly increased ventilation, but they increased PaO(2) by significantly improving the alveolar-arterial oxygen partial pressure gradient (A-a gradient, F=1.4, P<0.05), indicating improved oxygen diffusion. Metoclopramide and buspirone transiently improved blood oxygenation of opioid-immobilized impala, probably by improving ventilation-perfusion ratios, without reversing catatonic immobilization.
- Published
- 2010
- Full Text
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49. Hepatic capillariasis in a Cape ground squirrel (Xerus inaurus).
- Author
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Erlwanger KH, De Witt BA, Fick LG, Hetem RS, Meyer LC, Mitchell D, Wilson WA, and Mitchell B
- Subjects
- Animals, Disease Reservoirs parasitology, Disease Reservoirs veterinary, Enoplida Infections diagnosis, Fatal Outcome, Female, Parasite Egg Count veterinary, Capillaria isolation & purification, Enoplida Infections veterinary, Rodent Diseases diagnosis, Sciuridae parasitology
- Abstract
We report, for the first time, an incidental finding of Calodium hepaticum infestation in a sub-adult female Cape ground squirrel (Xerus inaurus). Post mortem examination of the squirrel revealed severe haemoperitoneum, splenomegaly and hepatomegaly with miliary white spots distributed diffusely throughout the hepatic parenchyma. Histologically the portal tracts in the liver showed granulomatous inflammation with fibrosis and numerous giant cells. Occasional adult worms were identified and there were multiple C. hepaticum eggs distributed diffusely throughout the portal tracts and the parenchyma. The spleen also contained C. hepaticum eggs. The genus Rattus is the primary host and reservoir of C. hepaticum, but C. hepaticum infections have been reported previously in other Sciuridae. Based on our findings, people should be cautious of the zoonotic potential of C. hepaticum, when they come into contact with the Cape ground squirrel.
- Published
- 2009
- Full Text
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50. Shearing at the end of summer affects body temperature of free-living Angora goats ( Capra aegagrus) more than does shearing at the end of winter.
- Author
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Hetem RS, de Witt BA, Fick LG, Fuller A, Kerley GI, Maloney SK, Meyer LC, and Mitchell D
- Abstract
Angora goats are known to be vulnerable to cold stress, especially after shearing, but their thermoregulatory responses to shearing have not been measured. We recorded activity, and abdominal and subcutaneous temperatures, for 10 days pre-shearing and post-shearing, in 10 Angora goats inhabiting the succulent thicket of the Eastern Cape, South Africa, in both March (late summer) and September (late winter). Within each season, environmental conditions were similar pre-shearing and post-shearing, but September was an average 5°C colder than March. Shearing resulted in a decreased mean (P < 0.0001), minimum (P < 0.0001) and maximum daily abdominal temperature (P < 0.0001). Paradoxically, the decrease in daily mean (P = 0.03) and maximum (P = 0.01) abdominal temperatures, from pre-shearing to post-shearing, was greater in March than in September. Daily amplitude of body temperature rhythm (P < 0.0001) and the maximum rate of abdominal temperature rise (P < 0.0001) increased from pre-shearing to post-shearing, resulting in an earlier diurnal peak in abdominal temperature (P = 0.001) post-shearing. These changes in amplitude, rate of abdominal temperature rise and time of diurnal peak in abdominal temperature suggest that the goats' thermoregulatory system was more labile after shearing. Mean daily subcutaneous temperatures also decreased post-shearing (P < 0.0001), despite our index goat selecting more stable microclimates after shearing in March (P = 0.03). Following shearing, there was an increased difference between abdominal and subcutaneous temperatures (P < 0.0001) at night, suggesting that the goats used peripheral vasoconstriction to limit heat loss. In addition to these temperature changes, mean daily activity increased nearly two-fold after March shearing, but not September shearing. This increased activity after March shearing was likely the result of an increased foraging time, food intake and metabolic rate, as suggested by the increased water influx (P = 0.0008). Thus, Angora goats entered a heat conservation mode after shearing in both March and September. That the transition from the fleeced to the shorn state had greater thermoregulatory consequences in March than in September may provide a mechanistic explanation for Angora goats' vulnerability to cold in summer.
- Published
- 2009
- Full Text
- View/download PDF
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