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Brown, J. L., Wasser, S. K., Wildt, D. E., & Graham, L. H. (1994). Comparative Aspects of Steroid Hormone Metabolism and Ovarian Activity in Felids, Measured Noninvasively in Feces. Biol Reprod, 51(4), 776–786.
Abstract: Noninvasive fecal assays were used to study steroid metabolism and ovarian activity in several felid species. Using the domestic cat (Felis catus) as model, the excretory products of injected [14C]estradiol (E2) and [14C]progesterone (P4) were determined. Within 2 days, 97.0 +/- 0.6% and 96.7 +/- 0.5% of recovered E2 and P4 radioactivity, respectively, was found in feces. E2 was excreted as unconjugated estradiol and estrone (40%) and as a non-enzyme- hydrolyzable conjugate (60%). P4 was excreted primarily as non-enzyme- hydrolyzable, conjugated metabolites (78%) and as unconjugated pregnenolone epimers. A simple method for extracting fecal steroid metabolites optimized extraction efficiencies of the E2 and P4 excretion products (90.1 +/- 0.8% and 87.2 +/- 1.4%, respectively). Analysis of HPLC fractions of extracted fecal samples from the radiolabel-injected domestic cats revealed that E2 immunoreactivity coincided primarily with the unconjugated metabolized [14C]E2 peak, whereas progestogen immunoreactivity coincided with a single conjugated epimer and multiple unconjugated pregnenolone epimers. After HPLC separation, similar immunoreactive E2 and P4 metabolite profiles were observed in the leopard cat (F. bengalensis), cheetah (Acinonyx jubatus), clouded leopard (Neofelis nebulosa), and snow leopard (Panthera uncia). Longitudinal analyses demonstrated that changes in fecal E2 and P4 metabolite concentrations reflected natural or artificially induced ovarian activity. For example, severalfold increases in E2 excretion were associated with overt estrus or exogenous gonadotropin treatment, and elevated fecal P4 metabolite concentrations occurred during pregnant and nonpregnant (pseudopregnant) luteal phases. Although overall concentrations were similar, the duration of elevated fecal P4 metabolites during pseudopregnancy was approximately half that observed during pregnancy. In summary, steroid metabolism mechanisms appear to be conserved among these physically diverse, taxonomically related species. Results indicate that this hormone-monitoring approach will be extremely useful for elucidating the hormonal regulatory mechanism associated with the reproductive cycle, pregnancy, and parturition of intractable and endangered felid species.
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Kazensky, C. A., Munson, L., & Seal, U. S. (1998). The effects of melengestrol acetate on the ovaries of captive wild felids. Journal-of-Zoo-and-Wildlife-Medicine, 29(1), 1–5.
Abstract: Melengestrol acetate (MGA) is the most widely used contraceptive in zoo felids, but the mechanism of contraception and the pathologic effects have not been investigated. For this study, the effects of MGA on folliculogenesis were assessed, and the association of MGA with ovarian lesions was evaluated. Comparisons were made among the histopathologic findings in the ovaries from 88 captive wild felids (representing 15 species) divided into three groups: 37 currently contracepted with MGA, eight previously exposed to MGA, and 43 never contracepted. Ninety-one percent of the felids evaluated had tertiary follicles, and no differences were noted between contracepted and uncontracepted cats. Some MGA-contracepted cats also had corpora lutea indicating recent ovulation. These results indicate that folliculogenesis is not suppressed by current doses of MGA and ovulation occurred in some cats. Therefore, the contraceptive actions of MGA do not occur by suppressing folliculogenesis, and MGA-contracepted felids likely have endogenous estrogens that may confound progestin effects on the uterus. Cystic rete ovarii was the most common pathologic finding, but they were not more prevalent in MGA-contracepted cats. These findings indicate that MGA is not associated with ovarian disease, including ovarian cancer, in contrast to the uterine lesions noted in MGA-treated cats.
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Roth, T. L., Armstrong, D. L., Barrie, M. T., & Wildt, D. E. (1997). Seasonal effects on ovarian responsiveness to exogenous gonadotrophins and successful artificial insemination in the snow leopard (Uncia uncia). Reprod Fertil Dev, 9(3), 285–295.
Abstract: Ovaries of the seasonally-breeding snow leopard (Uncia uncia) were examined to determine whether they were responsive to exogenous gonadotrophins throughout the year. The potential of laparoscopic artificial insemination (AI) also was assessed for producing offspring. During the non-breeding, pre-breeding, breeding and post-breeding seasons, females (n = 20) were treated with a standardized, dual- hormone regimen given intramuscularly (600 I.U. of equine chorionic gonadotrophin followed 80-84 h later with 300 I.U. of human chorionic gonadotrophin (hCG)). Laparoscopy was performed 45-50 h after administration of hCG, and all ovarian structures were described. Females with fresh corpora lutea (CL) were inseminated, and anovulatory females were subjected to follicular aspiration to examine oocyte quality. Snow leopards responded to exogenous gonadotrophins throughout the year. Mean number of total ovarian structures (distinct follicles mature in appearance plus CL) did not differ (P > or = 0.05) with season, but the proportion of CL: total ovarian structures was greater (P < 0.01) for the breeding season compared with all other seasons. The proportion of females ovulating was greater (P < 0.05) during the breeding and post-breeding seasons than during the pre-breeding and non- breeding seasons respectively. No Grade-1 quality oocytes were recovered from follicles of anovulatory females. Serum concentrations of oestradiol-17 beta appeared elevated in all females, and neither oestradiol-17 beta concentrations nor progesterone concentrations differed (P > or = 0.05) among seasons. Of 15 females artificially inseminated, the only one that was inseminated in the non-breeding season became pregnant and delivered a single cub. This is the first successful pregnancy resulting from AI in this endangered species.
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