2006 merck/merial - School of Veterinary Medicine - Louisiana State ...

the concept that the greater detoxication of OPs in the adult is an important factor in the greater tolerance of organophosphateacute toxicity in adults, as well as the fact that detoxication is more effective for CPS than MPS.The Safety of Tulathromycin Administration in GoatsKathryn L. Cass*, Kevin E. Washburn, Wesley Bissett, Virginia Fajt, Fred Club, Mitzi Libal, Geoffrey Fosgate,Katie E. SmyreCollege of Veterinary Medicine, Texas A&M University, College Station, TXThe objective of our study was to determine if the administration of tulathromycin to goats at ten times the labeldose for cattle and swine results in adverse effects. Ten mixed breed, male goats were enrolled in the study and randomlyassigned to treatment or control groups with five animals each. Tulathromycin or an equivalent volume of saline wasadministered subcutaneously to treatment and control groups, respectively. Blood, urine, and fecal samples were obtainedfrom both groups prior to and following treatment for hematology, serum chemistry, urinalysis, and fecal floatation. Goatswere observed daily for evidence of adverse effects following treatment. Clinical parameters assessed included feed intake,injection site swelling, temperature, pulse and respiratory rate. Although all treated goats experienced periods of transientpain following administration of tulathromycin, laboratory data collected in addition to clinical observations indicated nosignificant differences in diagnostic parameters between treatment and control goats. All goats survived to the end of thestudy period. Seven days following treatment, a complete post-mortem examination was performed. No gross lesions wereobserved in either group. The results of this study suggest that administration of tulathromycin to goats at ten times thelabeled therapeutic dose for cattle and swine results in clinically mild and transient effects. Pharmacokinetic studies areneeded to determine a therapeutic dose for goats. If in vitro studies of caprine respiratory pathogens display susceptibility totulathromycin, this drug may be an effective tool in the treatment of caprine respiratory disease.Kisspeptin and the equine hypothalamic-pituitary axisCharity Corning, Christianne Magee, Todd Farmerie, Patrick McCue, Collin ClayColorado State UniversitySeasonal reproduction in horses limits lifetime fecundity of mares. Thus, development of efficacious methods toshorten seasonal anestrous remains an important goal in equine reproduction. Pituitary hormones LH and FSH drivereproductive function. Released into the circulation, they bind specific ovarian receptors to stimulate follicular developmentand ovulation. GnRH is a hypothalamic decapeptide which binds specific receptors on pituitary gonadotropes, stimulatingsynthesis and release of LH and FSH. Recently, the peptide Kisspeptin (KiSS) has been found to play a key role in this axis.KiSS is made in the hypothalamus by neurons in close proximity to GnRH neurons. Proteolytic processing of the KiSSprepropeptide yields a family of biologically active peptides. KiSS binds a G-protein coupled receptor, GPR-54, on GnRHneurons, leading to GnRH production and release. The goal of these studies is to determine if in horses the genes encodingKiSS and GPR-54 are present and if exogenous KiSS treatment leads to LH release. To clone KiSS and GPR-54, we alignedsequences from several species and designed oligonucleotide primers to highly conserved regions. PCR amplification fromequine genomic DNA resulted in products of appropriate lengths. These will be sequenced. For the in vivo study, 6 lutealphase mares received indwelling IV catheters. KiSS (decapeptide) was administered IV (1.0 mg or 10.0 mg) and bloodsamples were collected at varying intervals from 120 before to 240 min after injection. Mares then were given 25 ìg GnRH asa positive control for pituitary responsiveness. Serum concentrations of LH were determined by radioimmunoassay. Two of 3mares in both 1.0 and 10 mg groups displayed an average 4.5 and 2-fold increase in LH respectively at 30 min followingKiSS administration. Thus, KiSS stimulates LH secretion in horses and may represent a target to develop pharmacologicalapproaches to stimulate pituitary and ovarian activity in seasonally anestrous mares.Age and Gender Influence Ventilatory Responses in Awake, Behaving RatsCaitlin Cotter*, Julie Wenninger, E. Burt Olson, Mary BehanSchool of Veterinary Medicine, University of Wisconsin- MadisonThere is a growing body of evidence suggesting that sex hormones are not exclusively involved in sexual behaviorsand reproduction, but also influence other aspects of brain function, including the respiratory control system and respiratoryplasticity. The effects of sex hormones on the neural control of breathing across the life cycle of male and female rats areimportant to our understanding of normal and pathological aging processes associated with respiration. Previous work hasdemonstrated that the magnitude of responses to hypoxic and hypercapnic events decreases with age. While responses maydiffer between males and females, the data are somewhat conflicting and no studies evaluate hormone levels. Studies ofhumans have indicated that ventilatory responses in females vary throughout the estrus cycle and pregnancy, suggestinghormonal modulation. We hypothesize that: (1) sex hormones are critically involved in adaptations in the neural control ofbreathing throughout the life cycle of both males and females, and (2) adequate levels of sex hormones, especially in aging,are required to maintain the capacity of the respiratory control system to respond to challenges. This project presents asystematic study of age-associated changes in the ventilation of male and female rats. Rats of three different age groups (4-6months, 12-14 months, >20 months) are being studied (24 males, 48 females- 24 estrus, 24 proestrus). Telemetry134