Gonadotropic activity of the pituitary gland in relation to the seasonal sexual cycle of the cottontail rabbit (Sylvilagus floridanus Mearnsi)

Elder, Wm. H.; Finerty, John C.

doi:10.1002/ar.1090850102

Cited by 23 publications

(11 citation statements)

References 15 publications

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“…The shape of the weight curve for the testes found in this study of the muskrat agrees quite well with that found by Elder and Finerty (1943) for the cottontail rabbit. These both contrast with that found by Wells (1935) in the thirteenlined ground squirrel, as the peak testes weights for the muskrat and cottontail rabbit I1re maintained for a considerable period of time, while the peak testes weights for the thirteen-lined ground squirrel are held for a very short period.…”

Section: Adsupporting

confidence: 89%

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Seasonal Changes in the Endocrine Organs and Behavior Patterns of the Muskrat

Beer

Meyer

1951

Journal of Mammalogy

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Behavior patterns combine with the physical environmental conditions to control the population density and distribution of the muskrat, Ondatra zibethica zibethica (Linn.). Many of these behavior patterns are seasonal or at least seasonal in the intensity with which they are manifest and seem to be correlated with and probably controlled by the seasonal physiological changes which occur in the animal.In this study we attempt to correlate the seasonal behavior patterns with the physiological cycles, and suggest how they may affect the composition and density of the population in the Wisconsin marshes. The investigation includes anatomical data from 237 muskrats, from every month of the year, and field observations on seasonal behavior patterns. The number of animals examined was limited by the difficulty of obtaining them. Most of the muskrats were captured alive, while a few were freshly skinned carcasses obtained from trappers. The live muskrats were obtained from the Horicon Marsh Wildlife Area in Dodge County, Wisconsin, and from the University of Wisconsin Arboretum, with the carcasses coming from nearby areas. This is a contribution from the Department of Wildlife Management and the Department of Zoology, University of Wisconsin. The study was made possible through the co-operation of the Pittman-Robertson Division of the Wisconsin Conservation Department, and was supported in part by a grant from the Wisconsin Alumni Research Foundation.Live muskrats were brought into the laboratory where they were killed within a few hours and the pituitary, testes, epididymides, prostate, preputial glands, ovaries, uteri, adrenals, and thyroids were removed and weighed immediately on a torsion balance. The coagulating glands were separated from the prostate since there seems to be some disagreement as to whether these lobes are morphologically and physiologically different (Walker, 1910a and 191Ob;Price, 1936). All organs, except the uteri, were weighed with their fluids and the combined weights of paired organs were recorded. The uteri were nicked with a razor blade and any fluids that were present were removed. The uteri from pregnant females were not used as it was nearly impossible to separate the maternal from the embryonic tissues. Smears were made from one epididymis to determine the presence or absence of sperm.The animals were divided into four classes: adult males, adult females, im-

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Section: Adsupporting

confidence: 89%

“…This was also found in the cottontail rabbit by Elder and Finerty (1943). The activity of the immature female muskrat was quite irregular while the immature males show an even, low activity.…”

Section: Adsupporting

confidence: 54%

Seasonal Changes in the Endocrine Organs and Behavior Patterns of the Muskrat

Beer

Meyer

1951

Journal of Mammalogy

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“…Seasonal changes in concentration of testosterone and gonadotrophin, testicular size and fec¬ undity have been well documented in wild rabbits (Elder & Finerty, 1943;Davis & Meyer, 1973a;Lincoln, 1976;Boyd & Myhill, 1987). Gonadotrophin concentrations increase with testicular weight during the spring and summer and decline during the autumn, reaching minimum values at about the winter solstice.…”

Section: Introductionmentioning

confidence: 99%

Influences of castration and testosterone on spring to summer changes in release of luteinizing-hormone-releasing hormone in rabbits

Lin¹,

Ramírez²

1992

Reproduction

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Push-pull cannulae were implanted toward the tuberal region of the hypothalamus in ten intact New Zealand male rabbits. In the first experiment, rabbits were perfused at different times after castration: 5-10 days (n = 10), 22-31 days (n = 9) and 50-64 days (n = 8). The release, mean amplitude and mean frequency of luteinizing-hormone-releasing hormone (LHRH) signals from 37 perfusions in ten animals were analysed in intact rabbits and at different times after castration. No significant changes in release of LHRH and in amplitude were observed, but the frequency was significantly higher 22-31 days after castration than in intact rabbits (intact: 0.86 +/- 0.12; castrated: 1.20 +/- 0.13 pulses h-1, P < 0.035; n = 9). In Expt 2, testosterone and placebo Silastic capsules were implanted in the castrated rabbits. Perfusions were performed in the following four periods, defined by season and time after testosterone and placebo implants: (i) spring; before implants, (ii) late spring; 0-2 weeks after implants, (iii) summer solstice; 2-4 weeks after implants and (iv) summer; 4-6 weeks after implants. Castrated rabbits were perfused during spring; castrated rabbits with testosterone capsule implants were perfused during late spring, around summer solstice and in summer and castrated rabbits with placebo implants were perfused during periods (iii) and (iv). Castrated animals with placebo implants showed no significant changes in mean LHRH release and amplitude, although the frequency was significantly higher around the summer solstice period than in castrated rabbits perfused in the spring. In castrated rabbits with testosterone implants LHRH release was significantly higher in late spring than around the summer solstice and in the summer. In addition, the concentrations of LHRH in late spring were significantly higher than those of intact and castrated animals. In contrast, mean LHRH amplitude and frequency did not change. Mean amount of LHRH released and amplitude in castrated rabbits with testosterone implants were significantly lower around the summer solstice than in late spring or summer and compared with intact animals around summer solstice and in castrated rabbits in early spring. These data demonstrate that there were no significant changes in the mean amplitude and release of LHRH after castration from 5 and up to 64 days in rabbits with hypothalamic push-pull cannulae, in contrast to the well established dramatic effect of castration on gonadotrophin concentrations. However, there was a small, but significant, increase in the mean frequency of LHRH pulses 22-31 days after castration compared with values from intact rabbits.(ABSTRACT TRUNCATED AT 400 WORDS)

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“…At the onset of the main breeding season in the autumn there is a great increase in the size and activity of the prostate which averages a sixfold increase in weight (Gilmore, 1968). The size of the testes does not alter significantly during the year, but there is a marked stimulation of the interstitial tissue in the autumn.Changes in the pituitary gonadotrophin content in seasonal breeding animals have been observed (see Elder & Finerty, 1943;Swift & Pickford, 1965). In contrast Hutchinson & Robertson (1960) found no changes in the ewe.…”

mentioning

confidence: 99%

“…Changes in the pituitary gonadotrophin content in seasonal breeding animals have been observed (see Elder & Finerty, 1943;Swift & Pickford, 1965). In contrast Hutchinson & Robertson (1960) found no changes in the ewe.…”

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confidence: 99%

Gonadotrophins in the Pituitary of the Male Possum Trichosurus Vulpecula During the Seasonal Breeding Cycle

Gilmore¹,

Sirett²,

Purves³

1968

Journal of Endocrinology

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Throughout the year spermatogenesis in the adult male possum (Trichosurus vulpecula) is continuous, but the weight of the prostate gland varies with breeding activity. At the onset of the main breeding season in the autumn there is a great increase in the size and activity of the prostate which averages a sixfold increase in weight (Gilmore, 1968). The size of the testes does not alter significantly during the year, but there is a marked stimulation of the interstitial tissue in the autumn.Changes in the pituitary gonadotrophin content in seasonal breeding animals have been observed (see Elder & Finerty, 1943;Swift & Pickford, 1965). In contrast Hutchinson & Robertson (1960) found no changes in the ewe.The gonads of immature hypophysectomized rats are known to respond to injections of extracts of wallaby pituitaries (Purves & Sirett, 1959) and the gonadotrophin content of male possum pituitaries at the 'breeding' and 'non-breeding' seasons has been investigated. Pituitaries were removed from freshly killed possums and placed in dry acetone. The mean prostate weight of the 'non-breeding' males was 6-1 g. and that of 'breeding' males was 34-4 g. The pituitaries were acetonedried, the anterior lobes ground into a fine powder and a saline suspension (0-5 mg./ml.) prepared. Butanol (0-05 %) was added to inhibit bacterial growth. The extract was injected s.c. in three equal daily doses into immature hypophysectomized male or female rats beginning on the third day after the operation. The total dose was 0-15 or 0-75 mg. Control hypophysectomized rats were injected with 0-9 % NaCl solution (0-5 ml.). Each rat was weighed daily from 2 days before the operation. The rats were killed the day after the last injection, the gonads placed in formol-saline, trimmed free of fat and weighed. No rats were included that failed to pass our previous criteria for complete hypophysectomy (Purves, Sirett & Griesbach, 1965). The potency ratios of the extracts were calculated according to Gaddum (1953).The results of the bioassays are shown in Table 1 and indicate that there was no significant difference in the pituitary gonadotrophin concentration between ' breeding ' and 'non-breeding' male possums. Both extracts stimulated the ventral prostate,

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Gonadotropic activity of the pituitary gland in relation to the seasonal sexual cycle of the cottontail rabbit (Sylvilagus floridanus Mearnsi)

Cited by 23 publications

References 15 publications

Seasonal Changes in the Endocrine Organs and Behavior Patterns of the Muskrat

Seasonal Changes in the Endocrine Organs and Behavior Patterns of the Muskrat

Influences of castration and testosterone on spring to summer changes in release of luteinizing-hormone-releasing hormone in rabbits

Gonadotrophins in the Pituitary of the Male Possum Trichosurus Vulpecula During the Seasonal Breeding Cycle

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