Persistent free-running circannual reproductive cycles during prolonged exposure to a constant 12L:12D photoperiod in laboratory woodchucks (Marmota monax).

Serum levels of gonadal steroid were assayed at approximately 3-month intervals in groups of 5 to 8 male or female woodchucks which were exposed to a natural photoperiod for 1 year as yearlings or 3 years as adults (Study 1), or a constant photoperiod of 12L:12D from birth for 4.5 years (Study 2). After 4.5 years of 12L:12D, food intake was measured in November and compared with that in natural photoperiod animals (Study 3). Other groups of 11 males and 3 females were housed in 12L:12D for 2.5 years after capture at 2 months of age, and gonadal structure and serum steroid levels in November were compared with those of animals at selected times in the normal annual cycle (Study 4). All animals were provided food and water ad libitum and were not induced to hibernate. In Study 1, normal circannual breeding season elevations in testosterone in males and in progesterone in females were detected in most animals maintained in natural photoperiod. In Study 2, similar cycles persisted for 4.5 years in animals exposed to 12L:12D. However, based on quarterly blood samples, obvious asynchrony relative to natural light animals appeared to develop after 2, 3, or 4 years, with apparent free-running intervals of about 10 to 11 months. In Study 3, mean daily food consumption in late autumn for woodchucks in the 12L:12D group was 72% greater than animals in the natural photoperiod. In Study 4, some woodchucks exposed to 12L:12D for only 2.5 years had prematurely increased spermatogenic activity, Leydig tissue development, and elevated serum testosterone levels in November. They were similar in November to those in natural photoperiod animals in March, and significantly greater than those in natural photoperiod animals in November when normal regression and repair of the testis was complete. Likewise, females in the 12L:12D group had luteinized follicles and elevated progesterone in November which were not noted in natural photoperiod animals and which were similar to those observed during the spring in unbred females under normal conditions. The results suggest that circannual cycles of metabolic and reproductive activity in woodchucks persist in the absence of normal changes in photoperiod, are entrained to seasonal changes in the natural photoperiod, and can recede to a periodicity of less than 12 months within 2.5 to 4 years of laboratory maintenance in 12L:12D.     

Pregnancy-specific elevations in fecal concentrations of estradiol, testosterone and progesterone in the domestic dog (Canis familiaris)

Estradiol (E2), testosterone (T) and progesterone (P4) concentrations were determined by enzyme-immunoassay in aqueous extracts of fecal samples obtained during anestrus, proestrus, estrus and metestrus of 11 nonpregnant and 11 pregnant bitches. Fecal hormone concentrations (ng/g) changed in relation to stage of cycle. Mean fecal steroid concentrations in 22 anestrous bitches and 3 ovariectomized bitches were low and similar for E2 (53 +/- 5 and 27 +/- 2), T (60 +/- 7 and 36 +/- 6), and P4 (62 +/- 6 and 86 +/- 15). Within 0 to 3 d of the ovulatory LH surge fecal E2 reached peak concentrations (301 +/- 38). The T peaks (281 +/- 41) were coincident or 1 to 3 d later. Fecal P4 was then elevated for approximately 2 m.o. Between Days 26 and 45 after ovulation, mean fecal P4 concentrations were higher (P < 0.05) in pregnant (401 +/- 60) than in nonpregnant bitches (164 +/- 23) and peak fecal P4 concentrations in individual animals were higher (P < 0.01) in pregnant (812 +/- 121) than in nonpregnant bitches (425 +/- 97). In the same period mean concentrations of E2 (117 +/- 13 vs 61 +/- 5) and T (102 +/- 10 vs 70 +/- 6) were also higher (P < or = 0.05) in pregnant than in nonpregnant bitches. Serum E2, T and P4 concentration were positively correlated (P = 0.1) with concentration in fecal samples obtained one day after serum collection. Although serial fecal ovarian steroid concentrations demonstrate the time course of ovulatory cycles, the diagnostic value of individual fecal samples appears limited. The ratios of peak to basal values were approximately 6, 5 and 7 for E2, T and P4, respectively, and were considerably lower than ratios of 12 to 50 previously reported for serum or plasma concentrations. The results demonstrate that there are pregnancy-specific increases in P4, E2 and T production reflected in fecal concentrations. While such increases are reflected in fecal samples, they are generally not evident in serum or plasma concentrations because of increased hemodilution, metabolism and clearance in pregnant bitches. The physiological stimulus for these increases, presumably ovarian in origin, or the potential role of prolactin is not known.     

Dinucleotide repeat polymorphism at 11q23

A highly polymorphic CA repeat sequence was identified near the NCAM gene on chromosome 11q23. It should be a useful marker in the localization of genes responsible for neurological disorders that are known to map to this region.