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An imbalance between proinflammatory and regulatory processes underlies autoimmune disease pathogenesis. We have shown that acute relapses of multiple sclerosis are characterized by a deficit in the immune suppressive ability of CD8+ T cells. These cells play an important immune regulatory role, mediated in part through cytotoxicity (perforin [PRF]/granzyme [GZM]) and IFNγ secretion. In this study, we further investigated the importance of IFNγ-, GZMB-, PRF1-, and LYST-associated pathways in CD8+ T cell-mediated suppression. Using the CRISPR-Cas9 ribonucleoprotein transfection system, we first optimized efficient gene knockout while maintaining high viability in primary bulk human CD8+ T cells. Knockout was confirmed through quantitative real-time PCR assays in all cases, combined with flow cytometry where appropriate, as well as confirmation of insertions and/or deletions at genomic target sites. We observed that the knockout of IFNγ, GZMB, PRF1, or LYST, but not the knockout of IL4 or IL5, resulted in significantly diminished in vitro suppressive ability in these cells. Collectively, these results reveal a pivotal role for these pathways in CD8+ T cell-mediated immune suppression and provide important insights into the biology of human CD8+ T cell-mediated suppression that could be targeted for immunotherapeutic intervention., (Copyright © 2024 by The American Association of Immunologists, Inc.)

Background: The Pre-Operative Window of Endocrine Therapy to Inform Radiation Therapy Decisions (POWER, NCT04272801) trial aims to determine whether 3 months of preoperative endocrine therapy (pre-ET) informs adjuvant radiation therapy decisions among older women with early stage, ER-positive breast cancer. We propose the POWER Pathologic Assessment and Ki-67 (POWER-PAK) scoring system to characterize the histologic effects of pre-ET., Methods: Histologic evaluation was performed on core biopsy and lumpectomy specimens from 37 POWER trial participants who completed pre-ET and surgery. The POWER-PAK score consists of tumor regression, decrease in Ki-67 expression, and ER expression, each ranging from 0 to 2. Scores were aggregated to create the POWER-PAK score with a range from 0 to 6. Participants with no residual tumor were labelled 6-NRT., Results: ER expression did not decrease after pre-ET. Ki-67 decreased from 13% in biopsy specimens to 5% in the lumpectomy specimens (p < 0.001). Cellularity decreased from 40% to 23% (p < 0.001). There was heterogeneity of POWER-PAK scores ranging from 2 to 6-NRT: score of 2, n = 2 (5.4%); 4, n = 8 (21.6%); 5, n = 4 (10.8%); 6, n = 16 (43.2%); and 6-NRT, n = 7 (18.9%). Participants with a score ≥ 5 were more likely to have smaller tumors after pre-ET compared with those with a score < 5 (p = 0.04)., Conclusions: The tumor responses following treatment with pre-ET are heterogenous. We propose that the POWER-PAK scoring system can be used to quantify response to pre-ET. Future studies will explore the use of POWER-PAK to support informed decision-making for adjuvant therapy options for older women with early stage breast cancer., (© 2023. Society of Surgical Oncology.)

CD4+ T-helper 17 (Th17) T cells are a key population in protective immunity during infection and in self-tolerance/autoimmunity. Through the secretion of IL-17, Th17 cells act in promotion of inflammation and are thus a major potential therapeutic target in autoimmune disorders. Recent reports have brought to light that the IL-17 family cytokines, IL-17A, IL-17F and IL-17AF, can directly act on CD4+ T-cells, both in murine and human systems, inducing functional changes in these cells. Here we show that this action is preferentially targeted toward naïve, but not memory, CD4+ T-cells. Naïve cells showed transcriptome changes as early as 48 hours post-IL-17 exposure, whereas memory cells remained unaffected as late as 7 days. These functional differences occurred despite similar IL-17 receptor expression on these subsets and were maintained in co-culture/transwell systems, with each subset maintaining its functional response to IL-17. Importantly, there were differences in downstream transcriptional signaling by the three IL-17 cytokines, with the IL-17AF heterodimer conferring both the greatest transcriptional change and most altered functional consequences. Detailed transcriptome analysis provides important insights into the genes and pathways that are modulated as a result of IL-17-mediated signaling and may serve as targets of future therapies., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Competing Interests: The authors have no relevant financial interest in the products or companies described in this article.

Autoimmune diseases are characterized by regulatory deficit in both the CD4+ and CD8+ T-cell compartments. We have shown that CD8+ T-cells associated with acute relapse of multiple sclerosis are significantly deficient in their immune suppressive ability. We hypothesized that distinct CD8+ cytotoxic T-cell (Tc) lineages, determined by cytokine milieu during naïve T-cell differentiation, may harbor differential ability to suppress effector CD4+ T-cells. We differentiated purified human naïve CD8+ T-cells in vitro toward Tc0 (media control), Tc1 and Tc17 lineages. Using in vitro flow cytometric suppression assays, we observed that Tc0 and Tc17 cells had similar suppressive ability. In contrast, Tc1 cells showed significant loss of suppressive ability against ex vivo CD4+ T-cells and in vitro -differentiated Th0, Th1 and Th17 cells. Of note, Tc1 cells were also suboptimal in suppressing CD4-induced acute xenogeneic graft versus host disease (xGVHD) in vivo . Tc subtypes derived under various cytokine combinations revealed that IL-12-containing conditions resulted in less suppressive cells exhibiting dysregulated cytotoxic degranulation. RNA sequencing transcriptome analyses indicated differential regulation of inflammatory genes and enrichment in GM-CSF-associated pathways. These studies provide insights into the role of T-cell differentiation in CD8 suppressive biology and may reveal therapeutically targetable pathways to reverse suppressive deficit during immune-mediated disease., (Copyright © 2020 Renavikar, Sinha, Brate, Borcherding, Crawford, Steward-Tharp and Karandikar.)

Factors regulating self-antigen directed immune-responses in autoimmunity are poorly understood. Signal regulatory protein gamma (SIRPγ) is a human T-cell specific protein with genetic variants associated with type 1 diabetes (T1D). SIRPγ's function in the immune system remains unclear. We show that T1D and relapsing remitting multiple sclerosis (RRMS) subjects have significantly greater frequency of rs2281808 T genetic variant, that correlates with reduced SIRPγ-expression in T-cells. Importantly, reduced SIRPγ-expression in RRMS and T1D subjects was not restricted to T variant, suggesting SIRPγ-expression is also regulated by disease specific factors in autoimmunity. Interestingly, increased frequencies of SIRPγlow T-cells in RRMS and T1D positively correlated with proinflammatory molecules from T-cells. Finally, we show that SIRPγlow T-cells have enhanced pathogenecity in vivo in a GVHD model. These findings suggest that decreased-SIRPγ expression, either determined by genetic variants or through peripherally acquired processes, may have a mechanistic link to autoimmunity through induction of hyperactive T-cells., Competing Interests: The authors have declared that no competing interests exist.

Untoward effector CD4+ T cell responses are kept in check by immune regulatory mechanisms mediated by CD4+ and CD8+ T cells. CD4+ T helper 17 (Th17) cells, characterized by IL-17 production, play important roles in the pathogenesis of autoimmune diseases (such as arthritis, multiple sclerosis, psoriasis, inflammatory bowel disease, among others) and in the host response to infection and cancer. Here, we demonstrate that human CD4+ T cells cells exposed to a Th17-differentiating milieu are significantly more resistant to immune suppression by CD8+ T cells compared to control Th0 cells. This resistance is mediated, in part, through the action of IL-17A, IL-17F, and IL-17AF heterodimer through their receptors (IL-17RA and IL-17RC) on CD4+ T cells themselves, but not through their action on CD8+ T cells or APC. We further show that IL-17 can directly act on non-Th17 effector CD4+ T cells to induce suppressive resistance, and this resistance can be reversed by blockade of IL-1β, IL-6, or STAT3. These studies reveal a role for IL-17 cytokines in mediating CD4-intrinsic immune resistance. The pathways induced in this process may serve as a critical target for future investigation and immunotherapeutic intervention., Competing Interests: The authors declare no competing interest.

Background: We report a case of prosthetic hip joint infection in a heart transplant recipient due to Anaerobiospirillum succiniciproducens, a genus of spiral-shaped curved anaerobic gram-negative rod which colonizes the gastrointestinal tract of cats and dogs. Invasive infections in humans are rare and typically occur in immunocompromised hosts., Case Presentation: A 65-year-old male dog breeder with a history of rheumatoid arthritis, bilateral hip arthroplasties, and non-ischemic cardiomyopathy with a heart transplant 10 years ago presented with a three month history of progressive left hip pain and frank purulence on hip aspiration. He underwent irrigation and debridement of the left hip and one-stage revision with hardware exchange. Although gram stain and culture from synovial fluid and intraoperative cultures were initially negative, anaerobic cultures from tissue specimens later grew a spiral-shaped gram-negative rod, identified as Anaerobiospirillum spp. by 16S rRNA gene sequencing. The patient was treated with ceftriaxone 2 g daily for 6 weeks with a good response to treatment. A similar organism was unable to be isolated from culture of 2 of the patient's dogs, however, they were thought to be the most likely source of his infection., Conclusion: Anaerobiospirillum spp. should be considered in immunocompromised patients with exposure to dogs or cats who present with bacteremia, gastrointestinal infection, pyomyositis, or prosthetic joint infections, especially in cases of culture-negative or with anaerobic culture growth.

Multiple genome-wide association studies have shown that the single-nucleotide polymorphism (SNP) rs2281808 TT variant, present within the signal regulatory protein gamma (SIRPG) gene, is associated with autoimmune diseases, such as type 1 diabetes. SIRPγ is the only SIRP expressed on T cells. The role of SIRPγ in human T-cells or the effect of the TT variant are poorly understood. In this short report, we demonstrate the rather unusual finding that this intronic SNP is associated with a reduction of SIRPγ expression on T cells, both in healthy subjects as well as patients with type 1 diabetes. Using this information, we propose that a simple flow cytometric detection of SIRPγ could be a potential diagnostic testing approach for the presence of SNP in the appropriate clinical context., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Multiple GWAS studies have shown that the SNP rs2281808 TT variant, present within the SIRPG gene, is associated with autoimmune diseases, such as type 1 diabetes. However, the role of SIRPγ in human T-cells is not known, neither is the functional significance of TT variant. Here we investigated SIRPG genotypes and their effects on the fate and function of human T-cells. We found that the presence of T variant resulted in reduction of SIRPγ expression on T-cells. Functionally, SIRPγ low CD8 T-cells in CT and TT individuals existed in a heightened effector state with lower activation threshold and had greater expression of genes and molecules associated with migratory and cytotoxic potential. Further, SIRPγ low CD8 T-cells were deficient in transcription factors associated with long-term functional memory formation. Our study reveals biological consequences of the SNP rs2281808 and provides novel insights into the potential mechanisms by which SIRPγ might regulate human immune responses.

Regulatory T-cells (Tregs) are vital for maintaining immunological self-tolerance, and the transcription factor FOXP3 is considered critical for their development and function. Peripheral Treg induction may significantly contribute to the total Treg pool in healthy adults, and this pathway may be enhanced in thymic-deficient conditions like multiple sclerosis (MS). Here, we evaluated iTreg formation from memory versus naïve CD4(+)CD25(-) T-cell precursors. We report the novel finding that memory T-cells readily expressed CD25 and FOXP3, and demonstrated significantly greater suppressive function. Additionally, the CD25(-)FOXP3(-) fraction of stimulated memory T-cells also displayed robust suppression not observed in naïve counterparts or ex vivo resting (CD25(-)) T-cells. This regulatory population was present in both healthy subjects and clinically-quiescent MS patients, but was specifically deficient during disease exacerbation. These studies indicate that iTreg development and function are precursor dependent. Furthermore, MS quiescence appears to correlate with restoration of suppressive function in memory-derived CD4(+)CD25(-)FOXP3(-) iTregs., (Published by Elsevier Inc.)

The vast majority of studies regarding the immune basis of MS (and its animal model, EAE) have largely focused on CD4(+) T-cells as mediators and regulators of disease. Interestingly, CD8(+) T-cells represent the predominant T-cell population in human MS lesions and are oligoclonally expanded at the site of pathology. However, their role in the autoimmune pathologic process has been both understudied and controversial. Several animal models and MS patient studies support a pathogenic role for CNS-specific CD8(+) T-cells, whereas we and others have demonstrated a regulatory role for these cells in disease. In this review, we describe studies that have investigated the role of CD8(+) T-cells in MS and EAE, presenting evidence for both pathogenic and regulatory functions. In our studies, we have shown that cytotoxic/suppressor CD8(+) T-cells are CNS antigen-specific, MHC class I-restricted, IFNγ- and perforin-dependent, and are able to inhibit disease. The clinical relevance for CD8(+) T-cell suppressive function is best described by a lack of their function during MS relapse, and importantly, restoration of their suppressive function during quiescence. Furthermore, CD8(+) T-cells with immunosuppressive functions can be therapeutically induced in MS patients by glatiramer acetate (GA) treatment. Unlike CNS-specific CD8(+) T-cells, these immunosuppressive GA-induced CD8(+) T-cells appear to be HLA-E restricted. These studies have provided greater fundamental insight into the role of autoreactive as well as therapeutically induced CD8(+) T-cells in disease amelioration. The clinical implications for these findings are immense and we propose that this natural process can be harnessed toward the development of an effective immunotherapeutic strategy.

The immune system plays a major pathological and regulatory role in multiple sclerosis (MS) and, therefore, is a focus of extensive research. Animal models of MS have been crucial in understanding the pathological processes in MS and developing certain treatments, however, all crucial aspects of the human disease may not be appropriately modeled. With the exception of detecting oligoclonal bands and IgG synthesis in cerebrospinal fluids of MS patients, there has not been major progress in the development of immunologic tests that can be used for diagnosis of MS. Further, due to the lack of validated immune assays, routine monitoring of the immune system following therapy initiation is not a part of standard patient care in MS. This is critical since immunomodulatory therapies used for MS treatment are not benign and, more importantly, there is a considerable variation in clinical responses in MS patients initiating such therapies. Flow cytometry is a powerful tool that can be used for studying both the phenotype and function of immune cells. The studies described here will demonstrate how flow cytometry can be used to apply current knowledge about the MS immune system to develop a diagnostic laboratory test for the immunologic monitoring of this disease. Importantly, we will also show that the multiparameter flow cytometry based assay developed by us can also be implemented for the immunologic evaluation of therapeutic success in MS patients.

Background: Epstein-Barr virus (EBV) is associated with MS, but it is not clear whether EBV plays a role in the pathogenesis of MS., Hypothesis: We hypothesized that the immune control of EBV might be defective in MS, and that reactivation of EBV might drive the immune response in MS., Methods: We collected blood from controls and patients with MS, and measured the amounts of EBV DNA and RNA using quantitative PCR., Results: We found that EBV DNA and RNA were frequently detectable in peripheral blood leukocytes from both patients with MS and normal controls. There was no significant difference between patients with MS or controls. Paired samples from a small number of subjects suggest that EBV DNA may increase before and during clinical relapse., Conclusions: We conclude that the immune control of EBV infection is similar in MS and controls, and that reactivation of EBV may correlate with MS disease activity.

Objective: To determine whether the presence of Nogo-A protein in CSF is a useful biomarker for multiple sclerosis (MS)., Methods: We performed Western blots on CSF from patients with MS and controls with the commercially available Nogo-A antibody and secondary antibody used in a prior report. We used densitometry to measure band density on Western blot. Controls included blots without primary antibody, samples without dithiothreitol (DTT), CSF passed through a protein G column, and Western blots with anti-Ig-light chain antibody. IgG concentration in CSF was measured by ELISA., Results: A band at about 25 kD band was detectable in almost all CSF specimens, but was darker in samples from patients with MS. The density relative to a reference sample (mean +/- SD) was 0.84 +/- 0.67 for relapsing MS (n = 17), 1.16 +/- 0.74 for primary progressive MS (n = 11), and 0.49 +/- 0.22 in controls (n = 12). This band was still present when the primary antibody was omitted, but was absent if the sample buffer did not include DTT or if the CSF was first adsorbed with protein G. IgG concentration was higher in MS CSF and correlated closely with the 25 kD band density (r = 0.78)., Conclusions: A 25 kD band is detectable on Western blots stained with Nogo-A antibody in almost all CSF specimens, but is darker in MS specimens. Our results suggest this band is immunoglobulin light chains rather than Nogo-A. It is not likely to be a useful biomarker for multiple sclerosis.

A 36-year-old multiparous woman with fetus in the breech position applied ice to the fundus of the uterus and achieved successful cephalic version. No other reports of using ice to induce cephalic version are found with MEDLINE search; however, it has been used as a folk remedy. Further research to evaluate the efficacy and safety of ice is needed to determine whether it increases cephalic vaginal birth.

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system (CNS) with features suggestive of T-cell-mediated pathology. Most prior reports have focused on CD4(+) T cells with the underlying assumption that MS is predominantly a CD4(+) T helper 1 (Th1)-mediated disease. In this report, we used a novel flow cytometric approach to evaluate autoreactive T-cell responses against a large variety of neuroantigenic targets. We found that both CD4(+) and CD8(+) T cells targeted against several CNS autoantigens were widely prevalent in patients with MS and healthy individuals. Whereas the distribution of CD4(+) responses was similar in different groups, patients with relapsing-remitting MS showed a higher proportion of CNS-specific CD8(+) responses. Autoreactive CD4(+) T cells from patients with MS exhibited a more differentiated Th1 phenotype compared with healthy subjects. Similarly, CNS-specific CD8(+) T-cell responses from patients with MS were functionally distinct from those in healthy individuals. Collectively, these studies reveal the high prevalence of class I-restricted autoreactive CD8(+) T-cell responses in MS that has been underappreciated thus far. The results emphasize the need to evaluate both CD4(+) and CD8(+) T-cell responses in MS and to make both subsets a consideration in the development of novel therapeutic strategies.

Glatiramer acetate (GA; Copaxone) is a random copolymer of glutamic acid, lysine, alanine, and tyrosine that is used therapeutically in patients with multiple sclerosis (MS). To investigate the mechanism of the drug's immunomodulatory effect, we used immunophenotypic approaches to characterize the precise nature of GA-induced T cell responses. We demonstrate here that healthy individuals and untreated MS patients exhibit prominent T cell proliferative responses to GA. However, these responses are different in distinct subsets of T cells. Whereas GA-induced CD4(+) T cell responses are comparable in healthy individuals and MS patients, CD8(+) T cell responses are significantly lower in untreated MS patients. Treatment with GA results in upregulation of these CD8(+) responses with restoration to levels observed in healthy individuals. Both CD4(+) and CD8(+) GA-specific responses are HLA-restricted. GA therapy also induces a change in the cytokine profile of GA-specific CD4(+) and CD8(+) T cells. This study provides the first direct immunophenotypic evidence, to our knowledge, of GA-specific CD8(+) T cell responses and their upregulation during the course of therapy, which may suggest a role for these responses in the immunomodulatory effects of the drug.

This investigation was designed to examine the interactive effects of blood flow (Q) and oxygen delivery (QO2) on peak oxygen consumption (VO2peak) and fatigue in the gastrocnemius-plantaris dog muscle in situ. Arterial oxygen content (CaO2) was manipulated by varying the fraction of inspired O2 to create a high- and a low-QO2 treatment at each of three levels of Q (approximately/=800, 1100 and 1500 ml x kg(-1) x min(-1)). Isometric contraction was achieved by stimulation with one tetanic contraction per second (200 ms at 70 Hz) at supramaximal voltage for 10 min to achieve VO2peak under each condition. Arterial and venous blood were sampled, and Q and tension development (TD) were measured at 1, 5 and 10 min into the contractions. Fatigue was calculated as the percentage (%) change in TD from min 1 to min 10. While VO2peak was highly correlated to QO2 (R = 0.97) in both the moderate- and high-Q conditions, both low-Q conditions had a significantly (P < 0.05) higher VO2peak than predicted by the QO2-VO2 relationship. In addition, VO2 peak was significantly greater in the low-Q versus the high-Q condition. Fatigue (% decrease in TD) was significantly different between the two low-Q conditions [Low-QO2=38.4 (6.9); Norm QO2=27.9 (1.8)] and the two moderate-Q conditions [low-QO2=31.1 (7.3); high-QO2 = 20.9 (4.1)] but not between the two high-Q conditions [normal-QO2 = 10.4 (6.9); high-QO2 = 11.9 (4.5)]. In the two conditions of equal QO2, fatigue was significantly less in the high-Q condition (10.4%) compared to the low (27.9%). Thus, it seems that there is a unique interaction between Q and QO2 which determine the VO2peak and rate of fatigue in contracting muscle.

The objective of this study was to determine if intraarticular pressure, elastance of the soft tissue forming the dorsal pouch, and range of motion in flexion measurements are significantly different in Thoroughbred metacarpophalangeal joints with clinical evidence of idiopathic synovitis, primary synovitis, synovitis/capsulitis, or osteoarthritis relative to clinically normal joints. Forty-two metacarpophalangeal joints, in 25 active or retired Thoroughbred racehorses, were categorised by palpation and visual inspection of the palmar pouch into one of 4 increasing grades of distention. Intra-articular pressures were then measured using 2 pressure transducers attached to 22-gauge needles from both the dorsal and palmar pouches simultaneously while the horses stood squarely under mild sedation. After obtaining baseline pressure measurements, a third needle was inserted into the dorsal pouch, and 0.5 ml increments of saline solution were added every 10 s to perform a pressure/volume (elastance) study of the dorsal pouch. The elastance study for each joint ended when leakage into the palmar pouch was detected by the pressure transducer placed in that region. A lateral radiographic view was taken of each metacarpophalangeal joint in maximal flexion. The maximum angle of flexion was measured from the radiograph, and this angle was subtracted from 180 degrees to acquire the range of motion in flexion. In this study, all Thoroughbreds with clinical evidence of lameness and/or sensitivity to flexion, referable to the metacarpophalangeal joint region, had fluid distention of the palmar pouch (grade 2 or 3 distention). The 16 metacarpophalangeal joints with no clinical abnormalities had a mean palmar pouch pressure of -1.25 mmHg. Joints afflicted with synovitis/capsulitis had the highest intraarticular pressures (mean +51.00 mmHg); however, joints with idiopathic synovitis (mean +15.71 mmHg), primary synovitis (mean +28.33 mmHg) and osteoarthritis (mean +26.20 mmHg) also had significantly elevated intraarticular pressures relative to the clinically normal group. Thoroughbred metacarpophalangeal joints diagnosed with synovitis/capsulitis, or osteoarthritis, had significantly increased elastance (stiffness) of the soft tissue forming the dorsal pouch relative to the normal group and, probably, as a result significantly decreased range of motion in flexion. The presence of primary synovitis alone did not have a significant immediate effect on elastance of the dorsal pouch and range of motion in flexion. The 16 Thoroughbred metacarpophalangeal joints assessed as having no clinical abnormalities had a mean range of motion in flexion of 60.81 degrees. The mean range of motion in flexion of Thoroughbred metacarpophalangeal joints with a clinical diagnosis of primary synovitis was 53.67 degrees; idiopathic synovitis 52.14 degrees; synovitis/capsulitis 44.20 degrees; and those with radiographic evidence of moderate to marked osteoarthritis 30.80 degrees. This study demonstrated that, as the severity of the clinical evidence of metacarpophalangeal joint injury/disease increased, the range of motion in flexion decreased.

The sedative and analgesic effects of medetomidine were evaluated in heartworm-infected (HW+) and uninfected (HW-) beagle dogs by intravenous (IV) and intramuscular (IM) administration of 30 micrograms/kg and 40 micrograms/kg doses, respectively. Posture, response to noise and the pedal reflex were monitored. A procedure for mock radiographic positioning was performed to evaluate its overall clinical use. Observation times were 0, 15, 30, 60, 90, 120 and 180 min. In addition, the times from injection until the dog could not stand on its feet (down time), from lateral to sternal recumbency (sternal recumbency time), and from sternal recumbency to rising again (rising time) were also noted. Medetomidine produced rapid sedation and analgesia by both routes. Down times for the IM and IV routes were similar, which verified the manufacturer's recommended doses. The HW+ dogs had shorter down times, probably owing to increased blood flow to the brain caused by adrenergic alpha-2 activity. Sternal recumbency and rising times did not differ between the groups, suggesting a similar metabolism. Sedation and analgesia were adequate for performing the procedure in all dogs. HW- dogs showed less resistance to handling during the procedure than HW+ dogs. Overall, medetomidine seems to be a suitable agent for short-term chemical restraint in dogs, even with subclinical heartworm infestation.

A study was done to determine whether intra-articular pressure is increased in equine metacarpophalangeal joints with increasing degrees of synovial distention, and to correlate elastance of the soft tissue forming the dorsal pouch of the metacarpophalangeal joint to maximal range of motion in flexion. Sixty seven metacarpophalangeal joints in 36 horses were categorized by palpation and visual inspection of the palmar pouch into 1 of 4 increasing grades of distention. Intra-articular pressures were then measured, using 2 pressure transducers attached to 22 gauge needles, from the dorsal and palmar pouches simultaneously while horses stood squarely under mild sedation. Intra-articular pressure ranged from -13 to +78 mm of Hg. Mean (+/- SEM) palmar pouch pressure was subatmospheric (-2.53 +/- 2.78 mm of Hg) in joints in which the palmar pouch was not discernible (grade 0), and was markedly increased (+37.13 +/- 2.775 mm of Hg) in joints in which the palmar pouch was distended laterally beyond the lateral branch of the suspensory ligament (grade 3). Grade of distention was positively correlated with intra articular pressure (r = 0.758; P < 0.001). Significant compartmentation (P < 0.002) was observed between the dorsal and palmar pouches in all horses. In 25 of the aforementioned horses, (42 joints), which were active or retired Thoroughbred racehorses with variable degree of metacarpophalangeal joint injury/disease, a third needle was inserted into the dorsal pouch, and 0.5-ml increments of saline solution were added every 10 seconds to perform a pressure/volume (elastance) study of the dorsal pouch. The elastance study for each joint ended when leakage into the palmar pouch was detected by the pressure transducer placed in that region. A flexed lateral radio graphic view was taken of each metacarpophalangeal joint in maximal flexion. The maximal angle of flexion was measured from the radiograph, and this angle was subtracted from 180 degrees to acquire the range of motion in flexion. Range of motion in flexion has strong negative correlation (r= -0.68; P < 0.0001) with elastance (stiffness) of the dorsal pouch, and moderate pouches (r= -0.48; P < 0.0001). To adjust for the possible correlations resulting from repeated measures on limbs within horses, a normal linear mixed model was used to assess the effect of limb (right vs left), range of motion in flexion, and volume of saline solution added on the dependent variable (delta mm of Hg) in the elastance study. There was no significant limb effect, but a highly significant effect regarding volume of saline solution added (P < 0.00001) and range of motion in flexion (P < 0.00001). Loss of range of motion in flexion of this joint is associated with shortening or loss of the initial low elastance (flat) phase of the elastance profile. Measuring the elastance of the dorsal pouch or measuring maximal range of motion in flexion provides an objective measure of the degree of metacarpophalangeal joint stiffness secondary to joint disease.

Medetomidine, an investigational drug indicated for clinical use as a short-term chemical restraint in dogs, was evaluated for its cardiopulmonary effects, in 10 naturally heartworm-infected (HW+) and 10 noninfected (HW-) Beagles. The drug was randomly administered i.v. (30 micrograms/kg of body weight) and i.m. (40 micrograms/kg) in single injections to all dogs. Heart rate, respiratory rate, ECG, blood gas tensions, blood pH, central venous and arterial pressures were measured at 0, 15, 30, 60, 90, 120, and 180 minutes. Medetomidine induced an immediate significant (P < or = 0.001) increase in mean arterial blood pressure followed by decreased blood pressure that remained below normal throughout the study in both groups, irrespective of route of administration. Medetomidine increased central venous pressure, over time, for both groups and both routes of administration. Heart and respiratory rates were significantly (P < or = 0.001) decreased after medetomidine administration and remained reduced for the duration of the study in all dogs. The ECG variables were not significantly different between groups or between routes of administration. The HW+ dogs tended to have higher mean PaO2 than did HW- dogs at several postinjection determination times, particularly when the drug was administered i.m. The PaO2 decreased during the first 30 minutes in both groups and tended to increase gradually thereafter. The pH decreased over time for both groups and both routes. A significant (P < or = 0.05) decrease in pH was seen in the HW- dogs, compared with HW+ dogs at each measuring time for both routes.(ABSTRACT TRUNCATED AT 250 WORDS)

Ten canine gastrocnemius-plantaris muscle preparations were stimulated in situ to determine the interaction between tension development and the duty cycle in determining Qpeak and VO2peak. The muscle was stimulated with supramaximal voltage using four different stimulation protocols: 1) 5 twitches.s-1 (Tw), 2) 1 train.s-1-200 ms (1-200), 3) 1 train.s-1-300 ms (1-300), and 4) 2 trains.s-1-100 ms (2-100). Arterial and venous blood were sampled and Qpeak measured for determination of VO2peak. The total tension developed per second was integrated and averaged over 1 s (TDa) and used as an index of work of the muscle for each condition. The Qpeak and VO2peak were greater (P < 0.05) in the 1-200 condition compared to all other conditions. Further, Qpeak and VO2peak were greater (P < 0.05) in both the 1-300 and 2-100 conditions than during Tw: Qpeak (ml.kg-1.min-1) (mean +/- SE) for (Tw) = 928 +/- 65; (1-200) = 1368 +/- 102; (1-300) = 1150 +/- 96; (2-100) = 1189 +/- 89; VO2peak (ml.kg-1.min-1) for (Tw) = 108 +/- 8; (1-200) = 159 +/- 9; (1-300) = 135 +/- 11; (2-100) = 137 +/- 8. The TDa was significantly different among all conditions: TDa (N.kg-1) for (Tw) = 443 +/- 56; (1-200) = 606 +/- 81; (1-300) = 722 +/- 79; (2-100) = 522 +/- 41. We interpret these findings as an indication that the interaction of the duty cycle and tension development is a prime determinant of blood flow during muscle contractions.

Esophagotomies were performed on 36 dogs and closed with 3-0 polydioxanone in double-layer simple interrupted, single-layer simple interrupted, or single-layer simple continuous patterns. The operative time was shortest for single-layer simple continuous closure, followed by single-layer simple interrupted and double-layer simple interrupted, respectively. Three dogs with each suture pattern were euthanatized at hours 0 and 1, and days 4 and 28 after surgery. The esophagotomy incisions were subjected to bursting strength testing and examined microscopically. The bursting wall tension was higher for all three suture pattern groups at 28 days than at 0 and 1 hour. The double-layer closure had higher bursting wall tension than the single-layer closures at 0 hour and 4 days. Single-layer simple continuous closure had the lowest bursting wall tension for each time period. Single-layer simple interrupted closure had the highest bursting wall tension at 28 days. Microscopic examination revealed close approximation of tissue planes for the double-layer closure and mucosal eversion for the simple interrupted and simple continuous single-layer closures. Healing was superior histologically with the double-layer closure.

This investigation was designed to describe alterations in O2 uptake (VO2) and tension development in a contracting in situ gastrocnemious-plantaris muscle preparation during three conditions of reduced O2 delivery [arterial O2 concentration X blood flow (Q)]. The three conditions, hypoxemia (H), ischemia (I), and anemia (A), were matched for O2 delivery. A normoxic normal flow condition was also utilized for comparison. H was produced by respiring the animals with 9% O2 in N2; I was produced by lowering Q, and A was produced by hemodilution with 6% dextran. The stimulation pattern for the isometric tetanic contractions used was 1 train/s, and each train was 200 ms, 70 Hz, and 6 V. The muscle was maximally contracted during each of the experimental conditions, and the conditions were administered in random order. In each bout the contractions continued for 5 min with 30 min of rest between bouts. Samples of arterial and muscle venous blood were obtained during the last 30 s of each bout. VO2 during I (125 ml.kg-1.min-1) was less than during N (145 ml.kg-1.min-1; P < 0.05) and greater than during H or A (104 and 101 ml.kg-1.min-1, respectively; P < 0.05). Venous PO2 (PVO2) was significantly lower during H (17.1 Torr) compared with the other conditions; no differences existed between N, I, and A (26.8, 26.0, and 28.1 Torr, respectively). Tension development was reduced by the reduction of O2 delivery during I, H, and A compared with N. Tension developed among the reduced O2 delivery groups was not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary artery strips from control and Dirofilaria immitis-infected dogs were tested for isometric contractile response to histamine, carbamylcholine, and norepinephrine. The strips from D immitis-positive dogs showed diminished response to histamine; a smaller percentage of the strips contracted, and the magnitude of the contraction was less than the response of the control strips to the highest concentration used. Carbamylcholine caused virtually no contractile effect in either group. Norepinephrine contracted all strips, even those not responding to histamine. A role for histamine in the pathogenesis of the pulmonary arterial lesions associated with dirofilariasis is presented.

Several problems exist when dextrans are used as plasma substitutes. High molecular weight dextrans can cause red cell aggregation and increased blood viscosity. Low molecular weight dextrans, although shown to improve circulation and promote flow, are removed rather rapidly from the circulation due to high premeation rates across capillary walls. In the present study, a small anionic charge is introduced onto the dextran to make it electrostatically negative. Since capillary walls have been shown to retain negatively charged solutes in preference to neutral solutes, the anionic dextran should retain its effectiveness for longer periods of time compared to similar sized neutral dextran. Studies were done on eight unanaesthetized dogs to compare the relative disappearance rates of dextran and anionic dextran (carboxymethyl dextran) from the circulation. It was shown that anionic dextrans do remain in the circulation over a longer period of time compared to neutral dextrans.

Bronchial spirals and pulmonary parenchymal strips from control (noninfected) and Dirofilaria immitis-infected dogs were tested for isometric contractile response to histamine and carbamylcholine. Responses of bronchial spirals from control dogs and from D immitis-positive groups did not differ in responses to histamine or carbamylcholine. Parenchymal strips from D immitis-positive dogs showed greater response to histamine than did those from controls; responses to carbamylcholine did not differ.

Colonic anastomoses were performed on two groups of 13 dogs each. Epidural anesthesia and general anesthesia were performed in one group and general anesthesia only in the other. Intraoperatively, the epidural-general anesthesia dogs tended to bleed less, making the anastomosis less difficult. Histologic comparisons showed healing to be more advanced in the epidural-general anesthesia dogs compared to the general anesthesia dogs 24 hours and 7 days postoperatively. Differences were not noticed 14 and 28 days postoperatively. Bursting pressures were determined 24 hours after surgery. Differences between the groups were not noticed. Leakage occurred at 72% of the pressure determined to cause leakage in normal colons.