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Urine expulsion from the upper urinary tract is a necessary process that eliminates waste, promotes renal filtration and prevents nephron damage. To facilitate the movement of urine boluses throughout the upper urinary tract, smooth muscle cells that line the renal pelvis contract in a coordinated effort to form peristaltic waves. Resident pacemaker cells in the renal pelvis are critical to this process and spontaneously evoke transient depolarizations that initiate each peristaltic wave and establish rhythmic contractions. Renal pacemakers have been termed atypical smooth muscle cells due to their low expression of smooth muscle myosin and poor organization of myofilaments compared to typical (or contractile) smooth muscle cells that perform peristalsis. Recent findings discovered that pacemaker cells also express the tyrosine kinase receptor PDGFRα, enabling their identification and purification amongst other renal pelvis cell types. Improved identification methods have determined that the calcium-activated chloride channel, ANO1, is expressed by pacemaker cells and may contribute to spontaneous depolarization. A greater understanding of pacemaker and peristaltic mechanisms is warranted since aberrant contractile function may underlie diseases such as hydronephrosis, a deleterious condition that can cause significant and irreversible nephron injury., (© 2024 The Authors. The Journal of Physiology © 2024 The Physiological Society.)

Introduction: Developmental and epileptic encephalopathies (DEEs) are rare epilepsy conditions that collectively impact 1 in 2000 children. They are highly genetically heterogeneous, resulting in significant barriers to accurate and adequate information for caregivers. This can lead to increased distress and dissatisfaction with the healthcare system. To address this gap, we developed 'GenE Compass' to provide caregivers with the highest-quality possible, understandable and relevant information in response to specific questions about their child's DEE. Using a mixed-method design, we will now pilot GenE Compass to evaluate the acceptability to caregivers and clinicians, feasibility and impact to caregivers., Methods and Analysis: We will recruit 88 caregivers (estimated final sample of 50 at follow-up) who have a child under 18 years of age with a suspected or confirmed DEE diagnosis. Following consent and a baseline questionnaire (questionnaire 1 (Q1)), participants will be able to submit questions to GenE Compass over a 3-month period. After 3 months, participants will complete a follow-up questionnaire (Q2) and an optional telephone interview to answer the research questions. Primary outcomes are acceptability of GenE Compass and feasibility of delivering the intervention (eg, cost of the intervention, number of questions submitted and time taken to respond to questions). Secondary outcomes include the impact of GenE Compass on caregivers' quality of life, information searching behaviours, perceptions of their child's illness and activation., Ethics and Discussion: The study protocol (V.2, dated 16 September 2021) has been approved by the Sydney Children's Hospitals Network Human Research Ethics Committee (ETH11277). The results will be disseminated in peer-reviewed journals and at scientific conferences. A lay summary will be disseminated to all participants., Trial Registration Number: ACTRN12621001544864., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

The sinoatrial node (SAN), the leading pacemaker region, generates electrical impulses that propagate throughout the heart. SAN dysfunction with bradyarrhythmia is well documented in heart failure (HF). However, the underlying mechanisms are not completely understood. Mitochondria are critical to cellular processes that determine the life or death of the cell. The release of Ca 2+ from the ryanodine receptors 2 (RyR2) on the sarcoplasmic reticulum (SR) at mitochondria-SR microdomains serves as the critical communication to match energy production to meet metabolic demands. Therefore, we tested the hypothesis that alterations in the mitochondria-SR connectomics contribute to SAN dysfunction in HF. We took advantage of a mouse model of chronic pressure overload-induced HF by transverse aortic constriction (TAC) and a SAN-specific CRISPR-Cas9-mediated knockdown of mitofusin-2 ( Mfn2 ), the mitochondria-SR tethering GTPase protein. TAC mice exhibited impaired cardiac function with HF, cardiac fibrosis, and profound SAN dysfunction. Ultrastructural imaging using electron microscope (EM) tomography revealed abnormal mitochondrial structure with increased mitochondria-SR distance. The expression of Mfn2 was significantly down-regulated and showed reduced colocalization with RyR2 in HF SAN cells. Indeed, SAN-specific Mfn2 knockdown led to alterations in the mitochondria-SR microdomains and SAN dysfunction. Finally, disruptions in the mitochondria-SR microdomains resulted in abnormal mitochondrial Ca 2+ handling, alterations in localized protein kinase A (PKA) activity, and impaired mitochondrial function in HF SAN cells. The current study provides insights into the role of mitochondria-SR microdomains in SAN automaticity and possible therapeutic targets for SAN dysfunction in HF patients.

The process of urine removal from the kidney occurs via the renal pelvis (RP). The RP demarcates the beginning of the upper urinary tract and is endowed with smooth muscle cells. Along the RP, organized contraction of smooth muscle cells generates the force required to move urine boluses toward the ureters and bladder. This process is mediated by specialized pacemaker cells that are highly expressed in the proximal RP that generate spontaneous rhythmic electrical activity to drive smooth muscle depolarization. The mechanisms by which peristaltic contractions propagate from the proximal to distal RP are not fully understood. In this study, we utilized a transgenic mouse that expresses the genetically encoded Ca 2+ indicator, GCaMP3, under a myosin heavy chain promotor to visualize spreading peristaltic contractions in high spatial detail. Using this approach, we discovered variable effects of L-type Ca 2+ channel antagonists on contraction parameters. Inhibition of T-type Ca 2+ channels reduced the frequency and propagation distance of contractions. Similarly, antagonizing Ca 2+ -activated Cl - channels or altering the transmembrane Cl - gradient decreased contractile frequency and significantly inhibited peristaltic propagation. These data suggest that voltage-gated Ca 2+ channels are important determinants of contraction initiation and maintain the fidelity of peristalsis as the spreading contraction moves further toward the ureter. Recruitment of Ca 2+ -activated Cl - channels, likely Anoctamin-1, and T-type Ca 2+ channels are required for efficiently conducting the depolarizing current throughout the length of the RP. These mechanisms are necessary for the efficient removal of urine from the kidney., (© The Author(s) 2022. Published by Oxford University Press on behalf of American Physiological Society.)

Monogenic rare disorders contribute significantly to paediatric morbidity and mortality, and elucidation of the underlying genetic cause may have benefits for patients, families and clinicians. Advances in genomic technology have enabled diagnostic yields of up to 50% in some paediatric cohorts. This has led to an increase in the uptake of genetic testing across paediatric disciplines. This can place an increased burden on paediatricians, who may now be responsible for interpreting and explaining test results to patients. However, genomic results can be complex, and sometimes inconclusive for the ordering paediatrician. Results may also cause uncertainty and anxiety for patients and their families. The paediatrician's genetic literacy and knowledge of genetic principles are therefore critical to inform discussions with families and guide ongoing patient care. Here, we present four hypothetical case vignettes where genomic testing is undertaken, and discuss possible results and their implications for paediatricians and families. We also provide a list of key terms for paediatricians., (© 2021 The Authors Journal of Paedisatrics and Child Health published by John Wiley & Sons Australia, Ltd on behalf of Paediatrics and Child Health Division (The Royal Australasian College of Physicians).)

The cardiac cycle starts when an action potential is produced by pacemaking cells in the sinoatrial node. This cycle is repeated approximately 100 000 times in humans and 1 million times in mice per day, imposing a monumental metabolic demand on the heart, requiring efficient blood supply via the coronary vasculature to maintain cardiac function. Although the ventricular coronary circulation has been extensively studied, the relationship between vascularization and cellular pacemaking modalities in the sinoatrial node is poorly understood. Here, we tested the hypothesis that the organization of the sinoatrial node microvasculature varies regionally, reflecting local myocyte firing properties. We show that vessel densities are higher in the superior versus inferior sinoatrial node. Accordingly, sinoatrial node myocytes are closer to vessels in the superior versus inferior regions. Superior and inferior sinoatrial node myocytes produce stochastic subthreshold voltage fluctuations and action potentials. However, the intrinsic action potential firing rate of sinoatrial node myocytes is higher in the superior versus inferior node. Our data support a model in which the microvascular densities vary regionally within the sinoatrial node to match the electrical and Ca 2+ dynamics of nearby myocytes, effectively determining the dominant pacemaking site within the node. In this model, the high vascular density in the superior sinoatrial node places myocytes with metabolically demanding, high-frequency action potentials near vessels. The lower vascularization and electrical activity of inferior sinoatrial node myocytes could limit these cells to function to support sinoatrial node periodicity with sporadic voltage fluctuations via a stochastic resonance mechanism., (© The Author(s) 2021. Published by Oxford University Press on behalf of American Physiological Society.)

The renal pelvis (RP) is a funnel-shaped, smooth muscle structure that facilitates normal urine transport from the kidney to the ureter by regular, propulsive contractions. Regular RP contractions rely on pacemaker activity, which originates from the most proximal region of the RP at the pelvis-kidney junction (PKJ). Due to the difficulty in accessing and preserving intact preparations of the PKJ, most investigations on RP pacemaking have focused on single-cell electrophysiology and Ca 2+ imaging experiments. Although important revelations on RP pacemaking have emerged from such work, these experiments have several intrinsic limitations, including the inability to accurately determine cellular identity in mixed suspensions and the lack of in situ imaging of RP pacemaker activity. These factors have resulted in a limited understanding of the mechanisms that underlie normal rhythmic RP contractions. In this paper, a protocol is described to prepare intact segments of mouse PKJ using a vibratome sectioning technique. By combining this approach with mice expressing cell-specific reporters and genetically encoded Ca 2+ indicators, investigators may be able to more accurately study the specific cell types and mechanisms responsible for peristaltic RP contractions that are vital for normal urine transport.

Genomic testing for a genetic diagnosis is becoming standard of care for many children, especially those with a syndromal intellectual disability. While previously this type of specialised testing was performed mainly by clinical genetics teams, it is increasingly being 'mainstreamed' into standard paediatric care. With the introduction of a new Medicare rebate for genomic testing in May 2020, this type of testing is now available for paediatricians to order, in consultation with clinical genetics. Children must be aged less than 10 years with facial dysmorphism and multiple congenital abnormalities or have global developmental delay or moderate to severe intellectual disability. This rebate should increase the likelihood of a genetic diagnosis, with accompanying benefits for patient management, reproductive planning and diagnostic certainty. Similar to the introduction of chromosomal microarray into mainstream paediatrics, this genomic testing will increase the number of genetic diagnoses, however, will also yield more variants of uncertain significance, incidental findings, and negative results. This paper aims to guide paediatricians through the process of genomic testing, and represents the combined expertise of educators, clinical geneticists, paediatricians and genomic pathologists around Australia. Its purpose is to help paediatricians navigate choosing the right genomic test, consenting patients and understanding the possible outcomes of testing., (© 2021 The Authors Journal of Paediatrics and Child Health published by John Wiley & Sons Australia, Ltd on behalf of Paediatrics and Child Health Division (The Royal Australasian College of Physicians).)

Key Points: Platelet-derived growth factor receptor-α (PDGFRα) is a novel biomarker along with smooth myosin heavy chain for the pacemaker cells (previously termed 'atypical' smooth muscle cells) in the murine and cynomolgus monkey pelvis-kidney junction. PDGFRα + cells present in adventitial and urothelial layers of murine renal pelvis do not express smooth muscle myosin heavy chain (smMHC) but are in close apposition to nerve fibres. Most c-Kit + cells in the renal pelvis are mast cells. Mast cells (CD117 + /CD45 + ) are more abundant in the proximal renal pelvis and pelvis-kidney junction regions whereas c-Kit + interstitial cells (CD117 + /CD45 - ) are found predominantly in the distal renal pelvis and ureteropelvic junction. PDGFRα + cells are distinct from c-Kit + interstitial cells. A subset of PDGFRα + cells express the Ca 2+ -activated Cl - channel, anoctamin-1, across the entire renal pelvis. Spontaneous Ca 2+ transients were observed in c-Kit + interstitial cells, smMHC + PDGFRα cells and smMHC - PDGFRα cells using mice expressing genetically encoded Ca 2+ sensors., Abstract: Rhythmic contractions of the renal pelvis transport urine from the kidneys into the ureter. Specialized pacemaker cells, termed atypical smooth muscle cells (ASMCs), are thought to drive the peristaltic contractions of typical smooth muscle cells (TSMCs) in the renal pelvis. Interstitial cells (ICs) in close proximity to ASMCs and TSMCs have been described, but the role of these cells is poorly understood. The presence and distributions of platelet-derived growth factor receptor-α + (PDGFRα + ) ICs in the pelvis-kidney junction (PKJ) and distal renal pelvis were evaluated. We found PDGFRα + ICs in the adventitial layers of the pelvis, the muscle layer of the PKJ and the adventitia of the distal pelvis. PDGFRα + ICs were distinct from c-Kit + ICs in the renal pelvis. c-Kit + ICs are a minor population of ICs in murine renal pelvis. The majority of c-Kit + cells were mast cells. PDGFRα + cells in the PKJ co-expressed smooth muscle myosin heavy chain (smMHC) and several other smooth muscle gene transcripts, indicating these cells are ASMCs, and PDGFRα is a novel biomarker for ASMCs. PDGFRα + cells also express Ano1, which encodes a Ca 2+ -activated Cl - conductance that serves as a primary pacemaker conductance in ICs of the GI tract. Spontaneous Ca 2+ transients were observed in c-Kit + ICs, smMHC + PDGFRα cells and smMHC - PDGFRα cells using genetically encoded Ca 2+ sensors. A reporter strain of mice with enhanced green fluorescent protein driven by the endogenous promotor for Pdgfra was shown to be a powerful new tool for isolating and characterizing the phenotype and functions of these cells in the renal pelvis., (© 2020 The Authors. The Journal of Physiology © 2020 The Physiological Society.)

Background: Front-of-neck airway rescue in a cannot intubate, cannot oxygenate (CICO) scenario with impalpable anatomy is particularly challenging. Several techniques have been described based on a midline vertical neck incision with subsequent finger dissection, followed by either a cannula or scalpel puncture of the now palpated airway. We explored whether the speed of rescue oxygenation differs between these techniques., Methods: In a high-fidelity simulation of a CICO scenario in anaesthetised Merino sheep with impalpable front-of-neck anatomy, 35 consecutive eligible participants undergoing airway training performed scalpel-finger-cannula and scalpel-finger-bougie in a random order. The primary outcome was time from airway palpation to first oxygen delivery. Data, were analysed with Cox proportional hazards., Results: Scalpel-finger-cannula was associated with shorter time to first oxygen delivery on univariate (hazard ratio [HR]=11.37; 95% confidence interval [CI], 5.14-25.13; P<0.001) and multivariate (HR=8.87; 95% CI, 4.31-18.18; P<0.001) analyses. In the multivariable model, consultant grade was also associated with quicker first oxygen delivery compared with registrar grade (HR=3.28; 95% CI, 1.36-7.95; P=0.008). With scalpel-finger-cannula, successful oxygen delivery within 3 min of CICO declaration and ≤2 attempts was more frequent; 97% vs 63%, P<0.001. In analyses of successful cases only, scalpel-finger-cannula resulted in earlier improvement in arterial oxygen saturations (-25 s; 95% CI, -35 to -15; P<0.001), but a longer time to first capnography reading (+89 s; 95% CI, 69 to 110; P<0.001). No major complications occurred in either arm., Conclusions: The scalpel-finger-cannula technique was associated with superior oxygen delivery performance during a simulated CICO scenario in sheep with impalpable front-of-neck anatomy., (Copyright © 2020 British Journal of Anaesthesia. All rights reserved.)

Competing Interests: The authors declare no competing interest.

Excitation-contraction (EC) coupling is the coordinated process by which an action potential triggers cardiac myocyte contraction. EC coupling is initiated in dyads where the junctional sarcoplasmic reticulum (jSR) is in tight proximity to the sarcolemma of cardiac myocytes. Existing models of EC coupling critically depend on dyad stability to ensure the fidelity and strength of EC coupling, where even small variations in ryanodine receptor channel and voltage-gated calcium channel-α 1.2 subunit separation dramatically alter EC coupling. However, dyadic motility has never been studied. Here, we developed a novel strategy to track specific jSR units in dissociated adult ventricular myocytes using photoactivatable fluorescent proteins. We found that the jSR is not static. Instead, we observed dynamic formation and dissolution of multiple dyadic junctions regulated by the microtubule-associated molecular motors kinesin-1 and dynein. Our data support a model where reproducibility of EC coupling results from the activation of a temporally averaged number of SR Ca 2+ release units forming and dissolving SR-sarcolemmal junctions. These findings challenge the long-held view that the jSR is an immobile structure and provide insights into the mechanisms underlying its motility.

Key Points: Electrical pacemaking in gastrointestinal muscles is generated by specialized interstitial cells of Cajal that produce the patterns of contractions required for peristalsis and segmentation in the gut. The calcium-activated chloride conductance anoctamin-1 (Ano1) has been shown to be responsible for the generation of pacemaker activity in GI muscles, but this conclusion is established from studies of juvenile animals in which effects of reduced Ano1 on gastric emptying and motor patterns could not be evaluated. Knocking down Ano1 expression using Cre/LoxP technology caused dramatic changes in in gastric motor activity, with disrupted slow waves, abnormal phasic contractions and delayed gastric emptying; modest changes were noted in the small intestine. Comparison of the effects of Ano1 antagonists on muscles from juvenile and adult small intestinal muscles suggests that conductances in addition to Ano1 may develop with age and contribute to pacemaker activity., Abstract: Interstitial cells of Cajal (ICC) generate slow waves and transduce neurotransmitter signals in the gastrointestinal (GI) tract, facilitating normal motility patterns. ICC express a Ca 2+ -activated Cl - conductance (CaCC), and constitutive knockout of the channel protein anoctamin-1 leads to loss of slow waves in gastric and intestinal muscles. These knockout experiments were performed on juvenile mice. However, additional experiments demonstrated significant differences in the sensitivity of gastric and intestinal muscles to antagonists of anoctamin-1 channels. Furthermore, the significance of anoctamin-1 and the electrical and mechanical behaviours facilitated by this conductance have not been evaluated on the motor behaviours of adult animals. Cre/loxP technology was used to generate cell-specific knockdowns of anoctamin-1 in ICC (Kit CreERT2/+ ;Ano1 tm2jrr/+ ) in GI muscles. The recombination efficiency of Kit CreERT was evaluated with an eGFP reporter, molecular techniques and immunohistochemistry. Electrical and contractile experiments were used to examine the consequences of anoctamin-1 knockdown on pacemaker activity, mechanical responses, gastric motility patterns, gastric emptying and GI transit. Reduced anoctamin-1 caused loss of gastric, but not intestinal slow waves. Irregular spike complexes developed in gastric muscles, leading to uncoordinated antral contractions, delayed gastric emptying and increased total GI transit time. Slow waves in intestinal muscles of juvenile mice were more sensitive to anoctamin-1 antagonists than slow waves in adult muscles. The low susceptibility to anoctamin-1 knockdown and weak efficacy of anoctamin-1 antagonists in inhibiting slow waves in adult small intestinal muscles suggest that a conductance in addition to anoctamin-1 may develop in small intestinal ICC with ageing and contribute to pacemaker activity., (© 2019 The Authors. The Journal of Physiology © 2019 The Physiological Society.)

Key Points: Activation of focal adhesion kinase (FAK) by integrin signalling facilitates smooth muscle contraction by transmitting the force generated by myofilament activation to the extracellular matrix and throughout the smooth muscle tissue. Here we report that electrical field stimulation (EFS) of cholinergic motor neurons activates FAK in gastric fundus smooth muscles, and that FAK activation by EFS is atropine-sensitive but nicardipine-insensitive. PDBu and calyculin A contracted gastric fundus muscles Ca 2+ -independently and also activated FAK. Inhibition of FAK activation inhibits the contractile responses evoked by EFS, and inhibits CPI-17 phosphorylation at T38. This study indicates that mechanical force or tension is sufficient to activate FAK, and that FAK appears to be involved in the activation of the protein kinase C-CPI-17 Ca 2+ sensitization pathway in gastric fundus smooth muscles. These results reveal a novel role for FAK in gastric fundus smooth muscle contraction by facilitating CPI-17 phosphorylation., Abstract: Smooth muscle contraction involves regulating myosin light chain phosphorylation and dephosphorylation by myosin light chain kinase and myosin light chain phosphatase. C-kinase potentiated protein phosphatase-1 inhibitor of 17 kDa (CPI-17) and myosin phosphatase targeting subunit of myosin light-chain phosphatase (MYPT1) are crucial for regulating gastrointestinal smooth muscle contraction by inhibiting myosin light chain phosphatase. Integrin signalling involves the dynamic recruitment of several proteins, including focal adhesion kinase (FAK), to focal adhesions. FAK tyrosine kinase activation is involved in cell adhesion to the extracellular matrix via integrin signalling. FAK participates in linking the force generated by myofilament activation to the extracellular matrix and throughout the smooth muscle tissue. Here, we show that cholinergic stimulation activates FAK in gastric fundus smooth muscles. Electrical field stimulation in the presence of N ω -nitro-l-arginine methyl ester and MRS2500 contracted gastric fundus smooth muscle strips and increased FAK Y397 phosphorylation (pY397). Atropine blocked the contractions and prevented the increase in pY397. The FAK inhibitor PF-431396 inhibited the contractions and the increase in pY397. PF-431396 also inhibited the electrical field stimulation-induced increase in CPI-17 T38 phosphorylation, and reduced MYPT1 T696 and T853, and myosin light chain S19 phosphorylation. Ca 2+ influx was unaffected by PF-431396. Nicardipine inhibited the contractions but had no effect on the increase in pY397. Phorbol 12,13-dibutyrate or calyculin A contracted gastric fundus smooth muscle strips Ca 2+ independently and increased pY397. Our findings suggest that FAK is activated by mechanical forces during contraction and reveal a novel role of FAK in the regulation of CPI-17 phosphorylation., (© 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society.)

Serum response factor (SRF) transcriptionally regulates expression of contractile genes in smooth muscle cells (SMC). Lack or decrease of SRF is directly linked to a phenotypic change of SMC, leading to hypomotility of smooth muscle in the gastrointestinal (GI) tract. However, the molecular mechanism behind SRF-induced hypomotility in GI smooth muscle is largely unknown. We describe here how SRF plays a functional role in the regulation of the SMC contractility via myotonic dystrophy protein kinase (DMPK) and L-type calcium channel CACNA1C. GI SMC expressed Dmpk and Cacna1c genes into multiple alternative transcriptional isoforms. Deficiency of SRF in SMC of Srf knockout (KO) mice led to reduction of SRF-dependent DMPK, which down-regulated the expression of CACNA1C. Reduction of CACNA1C in KO SMC not only decreased intracellular Ca2+ spikes but also disrupted their coupling between cells resulting in decreased contractility. The role of SRF in the regulation of SMC phenotype and function provides new insight into how SMC lose their contractility leading to hypomotility in pathophysiological conditions within the GI tract., Competing Interests: The authors have declared that no competing interests exist.

Objectives: Obtaining a diagnosis of an Autism Spectrum Disorder (ASD) for a child is a pivotal point in developing the treatment plan for the child but can also be regarded as highly stressful by parents. The current study examined the impact of different aspects of the diagnosis process on the self-reported mental health of mothers of children undergoing a diagnosis for ASD in a cross-sectional cohort design., Methods: One-hundred-fifty-eight mothers of consequently diagnosed children with ASD participated. The severity of the children's ASD and their intellectual functioning was assessed within twelve months of the diagnosis, and the mothers completed a psychometric assessment battery including the Hospital Anxiety and Depression Scale, General Health Questionnaire, and Questionnaire on Resources and Stress., Results: The actual time from first reporting a problem to obtaining a diagnosis, and the speed of the diagnostic process from first to last appointment, were both negatively related to patenting stress. In contrast, mothers' perceptions of the speed and helpfulness of the process were negatively related to levels of anxiety and depression. The number of professionals involved in the process and the perceived coherence of the diagnosis were also negatively related to aspects of mothers' functioning., Conclusions: Care is needed to help mothers through the diagnostic process with regard to their own functioning. Providing information and help sources throughout the process, while keeping the number of professionals involved to a minimum, may improve the parent perception of the process and reduce the negative impacts of the diagnosis on the family as a whole., Competing Interests: The authors declare no conflict of interest.

Following the use of rotenone to eradicate invasive pest fish, a dynamic first-order kinetic model is usually used to determine the half-life and rate at which rotenone dissipated from the treated waterbody. In this study, we investigate the use of a stochastic gamma model for determining the half-life and rate at which rotenone dissipates from waterbodies. The first-order kinetic and gamma models produced similar values for the half-life (4.45 days and 5.33 days respectively) and days to complete dissipation (51.2 days and 52.48 days respectively). However, the gamma model fitted the data better and was more flexible than the first-order kinetic model, allowing us to use covariates and to predict a possible range for the half-life of rotenone. These benefits are particularly important when examining the influence that different environmental factors have on rotenone dissipation and when trying to predict the rate at which rotenone will dissipate during future operations. We therefore recommend that in future the gamma distribution model is used when calculating the half-life of rotenone in preference to the dynamic first-order kinetics model., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Background: The reduced availability of human cadavers and their associated high costs, coupled with an increasing requirement for meeting continuing professional development targets, has accentuated the need for alternative training models that meet current ethical standards. The aim of this study is to identify suitable substitutes that are accessible and cost effective for use as training models for meniscal repairs and small joint arthroscopy., Method: Ovine, bovine and porcine stifles were analysed for comparable anatomy to the human knee, arthroscopic access, arthroscopic view and ease of meniscal repair., Results: The bovine stifle joint was found to be too large and offered limited access due to a large anterior fat pad and thick surrounding soft tissue. The ovine and bovine stifles were both easily available and had comparable anatomy to the human knee. Advantages of the porcine stifle include better availability and easier accessibility, comparable anatomy to the human knee and its relatively larger size that made it easier to arthroscope., Conclusion: Porcine stifles are cost effective, accessible, allow for meniscal repair and are suitable for arthroscopic access and view. Our view is that they are an ideal training model for arthroscopic meniscal repair, small joint arthroscopy and anterior cruciate ligament reconstruction., (© 2015 Royal Australasian College of Surgeons.)

Background: 5-Hydroxytryptamine (5-HT, serotonin) is an important regulator of colonic motility and secretion; yet the role of serotonergic neurons in the colon is controversial., Methods: We used immunohistochemical techniques to examine their projections throughout the enteric nervous system and interstitial cells of Cajal (ICC) networks in the murine proximal to mid colon., Key Results: Serotonergic neurons, which were mainly calbindin positive, occurred only in myenteric ganglia (1 per 3 ganglia). They were larger than nNOS neurons but similar in size to Dogiel Type II (AH) neurons. 5-HT neurons, appeared to make numerous varicose contacts with each other, most nNOS neurons, Dogiel Type II/AH neurons and glial cells. 5-HT, calbindin and nNOS nerve fibers also formed a thin perimuscular nerve plexus that was associated with ganglia, which contained both nNOS positive and negative neurons, which lay directly upon the submucosal pacemaker ICC network. Neurons in perimuscular ganglia were surrounded by 5-HT varicosities. Submucous ganglia contained nNOS positive and negative neurons, and calbindin positive neurons, which also appeared richly supplied by serotonergic nerve varicosities. Serotonergic nerve fibers ran along submucosal arterioles, but not veins. Varicosities of serotonergic nerve fibers were closely associated with pacemaker ICC networks and with intramuscular ICC (ICC-IM). 5-HT2B receptors were found on a subpopulation of non-5-HT containing myenteric neurons and their varicosities, pacemaker ICC-MY and ICC-IM., Conclusions & Inferences: Myenteric serotonergic neurons, whose axons exhibit considerable divergence, regulate the entire enteric nervous system and are important in coordinating motility with secretion. They are not just interneurons, as regularly assumed, but possibly also motor neurons to ICC and blood vessels, and some may even be sensory neurons., (© 2014 John Wiley & Sons Ltd.)

Background: Currently, there is a lack of cheap and effective training models to allow orthopaedic surgery trainees to learn the basics of anterior cruciate ligament reconstruction. The aim of this paper was to investigate the viability of using various animal joints as models for the training of anterior cruciate ligament reconstruction., Method: Equine stifles, bovine stifles and carpal joints, sheep stifles and porcine stifles, were sourced from a local abattoir. Each joint was assessed for the following criteria: suitable tendons for harvesting, ease of arthroscopy access, adequacy of arthroscopy view and suitable joint surfaces. Tendon harvesting, preparation, joint arthroscopy and tendon tunnelling were performed on the most suitable joint., Results: Equine, bovine, sheep and porcine stifles were found to be unsuitable. The bovine carpal joint was similar to a human wrist joint with two rows of carpal bones and fused metacarpal bones, but with deeper flexion - similar to a human knee joint. The distal joint space was found to provide a greater range of flexion and space than the narrower proximal joint space. The joint capsule provided sufficient integrity during saline irrigation to allow adequate visualization of joint structures. Tendons surrounding the joint were found to be of similar diameter to human hamstring tendons and easily accessible. Tendon tunnelling was successfully performed in a manner similar to human anterior cruciate ligament repair., Conclusion: The use of bovine carpal joints is a cost-effective, safe and easily reproducible model for education on basic anterior cruciate ligament repair skills and technique prior to patient contact., (© 2013 Royal Australasian College of Surgeons.)

The mechanisms underlying slow-transit constipation (STC) are unclear. In 50% of patients with STC, some form of outlet obstruction has been reported; also an elongated colon has been linked to patients with STC. Our aims were 1) to develop a murine model of STC induced by partial outlet obstruction and 2) to determine whether this leads to colonic elongation and, consequently, activation of the inhibitory "occult reflex," which may contribute to STC in humans. Using a purse-string suture, we physically reduced the maximal anal sphincter opening in C57BL/6 mice. After 4 days, the mice were euthanized (acutely obstructed), the suture was removed (relieved), or the suture was removed and replaced repeatedly (chronically obstructed, over 24-31 days). In partially obstructed mice, we observed increased cyclooxygenase (COX)-2 levels in muscularis and mucosa, an elongated impacted large bowel, slowed transit, nonpropagating colonic migrating motor complexes (CMMCs), a lack of mucosal reflexes, a depolarized circular muscle with slow-wave activity due to a lack of spontaneous inhibitory junction potentials, muscle hypertrophy, and CMMCs in mucosa-free preparations. Elongation of the empty obstructed colon produced a pronounced occult reflex. Removal of the obstruction or addition of a COX-2 antagonist (in vitro and in vivo) restored membrane potential, spontaneous inhibitory junction potentials, CMMC propagation, and mucosal reflexes. We conclude that partial outlet obstruction increases COX-2 leading to a hyperexcitable colon. This hyperexcitability is largely due to suppression of only descending inhibitory nerve pathways by prostaglandins. The upregulation of motility is suppressed by the occult reflex activated by colonic elongation.

Background and Aim of the Study: The English literature on replacement heart valves up to the end of 1994 was reviewed to establish normal ranges for forward function and patterns of regurgitation., Methods: A total of 48 papers were collected, but 16 were excluded leaving normative data for 14 different designs on a total of 1595 valves in the aortic and 1127 valves in the mitral position. Values for velocity, derived pressure drop, effective orifice area and pressure half-time were tabulated by annulus diameter for each class of valve., Results: Comparison between valve designs was difficult as a result of differences in methodology. For the aortic position, differences in velocity and derived pressure drop within one valve type were similar to those between all valve designs. The homograft and Labcor-Santiago valves appeared the least obstructive although using flow-corrected effective orifice area, there were no material differences between the valve designs. For the mitral position, there was a narrow range in mean pressure drop of 2.0 mmHg to 7.8 mmHg. Little data for the tricuspid position were available. Patterns of normal transvalvar regurgitation varied widely between the valves, but obvious transvalvar regurgitation was a feature of most mechanical valves., Conclusion: Much work using standardized protocols and with appropriate hemodynamic formulae needs to be done to improve our knowledge of replacement valve function.

We have studied the responses to a brief interruption of a train of steady state beats, namely: (1) a single prolonged depolarisation within the train; (2) a single short interval within the train; (3) a single long interval within the train. These responses are predicted by a two compartment model of intracellular calcium handling. They are characterised by the following phenomena. (1) Prolongation of one depolarisation/action potential in the steady state train causes potentiation of the following beat. We postulate on the basis of the published evidence that this may be due to "reversed" sodium/calcium exchange during late systole leading to extra calcium entry during the prolonged depolarisation. (2) Postextrasystole potentiation is postulated to share this mechanism when a depolarisation (extrasystole) is introduced immediately after one of the steady state depolarisations (single short interval). The postextrasystolic beat is then potentiated. (3) A single short interval during the steady state train also leads to attenuation of contractile force on the beat immediately after the short interval, that is, the extrasystole. Mechanical restitution is the term applied to the recovery of this force with increasing interval. This consists of two phases. The initial rapid phase is ryanodine and caffeine insensitive, indicating possible independence of sarcoplasmic reticular function. We postulate that a "membrane compartment" of internal calcium may be responsible. The second, slower, phase of mechanical restitution is ryanodine and caffeine sensitive, indicating that it is likely to be a property of the sarcoplasmic reticulum.(ABSTRACT TRUNCATED AT 250 WORDS)