No description available.

No description available.

Recurrent airway obstruction (RAO) and Rhodococcus equi (R. equi) pneumonia are two equine respiratory diseases. RAO is an allergic asthma like disease of the middle-aged horses while the R. equi pneumonia affects only young foals. Respiratory disease is considered among the major causes of economic loss to the equine industry and tops the priority list for research that will focus on preventative and diagnostic facets of such disease. The objective of this research was to investigate the effect of antigen exposure and remission (via allergen avoidance and/or drug) on chronically affected RAO horses. Additionally, we also wanted to understand the changes in equine neonatal immune system due to R. equi exposure and identify molecular biomarkers for early disease screening. Various biological samples (lung tissue for the RAO study and blood leukocytes and nasal epithelial cells for the R. equi study) were used to extract ribonucleic acid (RNA). Complimentary deoxyribonucleic acid (cDNA) obtained from RNA was used to perform microarray hybridization experiments. Our findings suggest that compared to control horses allergen exposure leads to an elevated protein synthesis and inflammation that contributes to aggravation of symptoms and airway changes. We found that allergen avoidance controls inflammation and causes an improvement in lung function and other chronic features of RAO. The drug administration led to an accelerated remission in the chronic RAO features; a complete remission could however not be achieved. Hence it appears that although not a complete resolution, but allergen avoidance and drugs will help in a better management of chronic RAO symptoms. Our results suggest that the neonatal immune system is capable of initiating a protective immune response through birth up to 8 weeks of age. However there are also processes present that may be counter-productive to the host. Induction of such suppressive mechanisms may be a result of bacterial modulation of the host immune response or a result of immature host immune system. We also identified molecular biomarkers that will have the potential to screen foals for R. equi pneumonia soon after birth and before the onset of clinical symptoms. The research findings of this study will improve the current understanding of the two equine diseases.

Although progress has been made in the last decade in understanding the causes of colitis in horses, perhaps 60% of cases of fatal colitis in horses have no known cause. The role of type A Clostridium perfringens strains was evaluated in this study. Fecal samples from 55 horses (43 adults, 12 foals) with colitis were cultured for Clostridium difficile, Salmonella, and C. perfringens. Feces were also tested for C. difficile toxins A/B and C. perfringens toxins (alpha [CPA], beta2 [CPB2], enterotoxin [CPE]) using enzyme-linked immunosorbent assays (EIA). All fecal samples were negative for Salmonella. Clostridium perfringens and C. difficile were isolated from 40% and 5.4% of samples, respectively. No CPE was detected but 36.4% and 18.2% of animals were positive for CPA and CPB2 toxin, respectively. Subsequently, five C. perfringens isolates per fecal sample were genotyped and the supernatants of each of these isolates were evaluated for toxicity. None of the isolates were cpe, netB or tpeL positive, but atypical cpb2 and consensus cpb2 were identified in 13.6% and 3.6% isolates, respectively. All equine C. perfringens isolates showed mild toxicity effects compared to CPB producing C. perfringens positive control. Based on this study population, there was no evidence that C. perfringens had an important role in equine colitis. / Equine Guelph and Natural Sciences and Engineering Research Council

No description available.

No description available.

Chondrocytes in growth cartilage undergo proliferation, hypertrophy, and then die by a mechanism that has not been characterised. The aims of the current study were to document the morphology of dying hypertrophic chondrocytes in equine growth cartilage and to establish a culture system in which the isolated chondrocytes can be induced to undergo the same modes of hypertrophy and physiological death seen in growth cartilage in vivo. Growth cartilage from foetal and growing postnatal horses was examined by electron microscopy. Ultrastructural studies of the tissue specimens suggested that the two types of hypertrophic chondrocytes that have previously been described as dark and light cells were dying by different non-apoptotic forms of cell death. Dying hypertrophic dark chondrocytes were characterised by a dark nucleus, and their cytoplasm appeared to undergo extrusion into the extracellular matrix, whereas light chondrocytes appeared to disintegrate within the cell membrane.

Thesis (Ph.D.)--Murdoch University, 2008. / Thesis submitted to the Faculty of Health Sciences. Includes bibliographical references (leaves 197-242).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1957. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 48-51).

Antisera were raised in rabbits against serum samples taken from pregnant and non-pregnant mares. Using these antisera in two-dimensional crossed immunoelectrophoresis, a protein (beta2-hors.PP) was found to be pregnancy specific and first detectable in the maternal circulation 6 days after mating. beta2-hors.PP detection as a pregnancy test during the first 21 days after mating was found to be significant at the 10% level. Levels of the protein were also found to increase during this period. The protein, of possible uterine origin, may have a biological activity associated with implantation (day 37) as levels of beta2-hors.PP were elevated from around days 21 to 83. For the remainder of gestation, the concentration of beta2-hors.PP in the serum decreased. It is possible that beta2-hors.PP detection may be a means of monitoring foetal well being. Equine epitheliochorial placental extracts, taken from 2 mares 60 days and 80 days after mating, were found to induce a dose-dependent inhibition of lymphocyte proliferation in the mixed lymphocyte reaction (MLR) and mitogen stimulated assay (MSA), MLR supernatant reversed the inhibition and the addition of foetal tissue extracts to previously activated lymphocytes suppressed lymphocyte proliferation. This suggests suppression at the IL-1/IL-2 level of the immune response. Commercially available eCG inhibited lymphocyte proliferation. The presence of endometrial cup secretion containing high levels of eCG had no additive effect on the inhibitory activity of an extract of allantochorion (day 80), previously shown to induce less than 100% inhibition. This suggests that the commercially available eCG may contain an immunosuppressive contaminant.Equine and bovine epitheliochorial placental extracts (allantochorion) inhibited collagen and ADP-induced platelet aggregation respectively. The mode of action of the anti-aggregatory factors may be related to the vascularity of the placentae. Overall, it appears that local immunomodulatory and haemostatic mechanisms are important in the maintenance of pregnancy in species with epitheliochorial placentation.