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  • Author: J. G. Vandenbergh x
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J. G. Vandenbergh

Summary.

In comparison to controls reared in isolation, female rats reared in the presence of an adult male from weaning attained puberty 5 days earlier when living in groups or almost 9 days earlier when living singly with a male. Accelerated sexual development occurred in the absence of accelerated physical growth.

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J. G. VANDENBERGH

Summary.

Albino male mice were reared from weaning in the presence of an adult female, in the presence of an adult male, or in the absence of an adult. At 36, 48, 60 and 78 days of age, males in samples from each rearing condition were killed to assess their reproductive state. The testicular development of young males was most rapid when they were reared in the presence of an adult female. By 78 days of age, this advantage was lost when the males were compared to those reared without an adult present. In contrast to the effect of an adult female, the presence of an adult male had an inhibitory effect on testicular and accessory gland development. The inhibition was most pronounced at 78 days of age.

The inhibition of sexual maturation found in this experiment contrasts with an earlier finding that the presence of males accelerates female development. This dual rôle of the male may be an important factor in the dynamics of rodent populations by increasing the availability of mature females and reducing the reproductive capabilities of potential competitors for these females.

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C. Bielert and J. G. Vandenbergh

Summary. The annual distribution of births of rhesus monkeys in zoos in the southern hemisphere and changes in sex skin coloration in one colony were examined. Most (79%) of the births occurred between October and January and the sex skin reached its greatest development during spring and early summer (i.e. at the time of mating). These results demonstrate a 6-month reversal from the breeding activity of rhesus monkeys in the northern hemisphere.

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D. M. Coppola and J. G. Vandenbergh

Summary. The ability of urine from female mice to delay puberty in test females was directly related to the density and duration of grouping of females. When females were removed from group housing their urine lost its ability to delay puberty within 10 days. No interactive effects were observed between duration and density of grouping on the onset of pheromone release after grouping or on the persistence of pheromone release after re-isolation. Urine from grouped females lost its ability to delay puberty in test females after 7 days of exposure to air.

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M. K. Izard and J. G. Vandenbergh

Summary. Post-pubertal Holstein heifers with palpable corpora lutea were injected i.m. with 25 mg PGF-2α to bring all animals to the follicular phase of the oestrous cycle. After 3 oronasal treatments with secretions from oestrous cows or water, heifers were observed for oestrus and inseminated about 12 h after the onset of oestrus. In Exp. I, heifers were treated with water or a mixture of urine and cervical mucus from oestrous cows at 6, 30 and 56 h after the PGF-2α injection. The percentage of heifers in oestrus within 72 h after PGF-2α was 86% for urine + cervical mucus-treated heifers and 60% for water-treated heifers (P > 0·05). Days to oestrus and conception rate after A.I. did not differ between the treatments. The degree of synchrony of oestrus after PGF-2α was significantly greater (P < 0·05) in the animals receiving urine + mucus treatment.

In Exp. II, urine and cervical mucus from oestrous cows were separately tested in comparison to water. Test substances were applied at the time of PGF-2α injection, and 6 and 30 h later. The percentage of heifers in oestrus within 72 h after PGF-2α (100%) was highest (P < 0·05) in the cervical mucus-treated heifers but the conception rate (24%) was the lowest. The days to oestrus did not differ amongst groups but the degree of synchrony of oestrus after PGF-2α was greatest (P < 0·05) in animals treated with cervical mucus. These data indicate that a priming pheromone in the cervical mucus of oestrous cows can affect the ovarian function of herdmates and thereby improve synchrony of oestrus after PGF-2α injection.

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J. G. VANDENBERGH, L. C. DRICKAMER and D. R. COLBY

Summary.

At 21 days of age, 144 female albino mice were individually isolated and reared on either 8%, 16% or 24% protein diets. Within each protein level, mice were exposed to the presence of an adult male, or to male odour, or were reared in isolation. Each female was examined daily for vaginal opening and signs of first oestrus. Body weight and food consumption measures confirmed that body growth was equal in each cell of the design and that mice on low protein diets were not compensating for a low protein diet by consuming more food.

The results showed that, although both dietary protein and the presence of males (or their odour) were significant factors in regulating sexual maturation, social factors contributed 47·3% and dietary protein levels 4·8% of the total variance. Accelerated sexual development was not accompanied by accelerated body growth. Thus, the hypothesis that puberty occurs at a critical body weight was not supported by these data. That social stimulation was more effective than protein intake may have relevance to the phenomenon of accelerated sexual maturation in human females.

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JOHN G. VANDENBERGH, J. M. WHITSETT and JOSEPH R. LOMBARDI

Summary.

The sexual development of female mice is accelerated by exposure to an adult male or to male urine. The component of the urine responsible for this effect is androgen-dependent, heat labile, nondialysable, precipitatable with ammonium sulphate, and is not extractable in ether. These results indicate that the pheromone causing accelerated sexual development is associated with a protein component of male urine. Tests of the active fraction after digestion with proteolytic enzymes suggest that the pheromone may be a portion of a protein or a substance bound to a protein.