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Biomedical subjects

C Desjardins

Publications and source records attributed to C Desjardins.

At least 73 records · Page 4Linked to original sources
PubMed1977

Dominant-subordinate relationships in castrated male mice bearing testosterone implants.

This study tested the hypothesis that subordination in male mice is directly related to reduced levels of circulating testosterone. Several measures of aggressiveness and submissiveness were quantified during or after daily encounters between pairs of intact males, castrated males, or castrated males bearing testosterone implants that were designed to maintain plasma testosterone titers at levels slightly above those of intact males. Behavioral measures included the total amount of fighting that resulted from daily pairing, the tendency for subordinates to fight back, and the relative frequency of urine marking. In all these regards, pairs of testosterone-implanted, castrated males formed dominant-subordinate relationships that involved apparently normal submissive behavior (compared to intact control pairs). Thus we found no evidence that submissive behavior was directly related to a reduction in circulating testosterone titers.

Animals↗
PubMed1977

Reproductive failure in aged CBF1 male mice: interrelationships between pituitary gonadotropic hormones, testicular function, and mating success.

Circulating pituitary gonadotropins and testicular function were examined in aged CBF1 male mice using two experimental designs: a) a longitudinal analysis of 2 to 30-month-old males, and b) a direct comparison of weight-matched, sexually-active vs. sexually-inactive 24-month-old males, all of whom were relatively robust. Measurements included serum concentrations of testosterone, follicle stimulating hormone, and luteinizing hormone, gonadotropic responsiveness to castration, success in a 4-day mating test, testicular sperm content, and reproductive organ weights. The longitudinal analysis showed progressive losses in mating success and sperm production between 18 and 30 months, changes which were correlated with decreased levels of serum LH and testosterone but not with FSH. The direct comparison of robust, sexually-active vs.-inactive males provided a better design for identifying reproductive-specific effects of aging, as opposed to debilitative changes that are general to several supporting systems. Such comparisons in 24-month-old CBF1 males suggest the existence of a subpopulation of mice in which reproductive failure is specifically correlated with a loss in the episodic release of LH.

Aging↗
PubMed1977

Response of plasma corticosteroids and circulating leukocytes in cattle following intravenous injection of different doses of adrenocorticotropin.

The relationships among exogenous adrenocorticotropin (ACTH), plasma corticosteroids, and circulating leukocytes were studied in 7 lactating cows. Blood samples were obtained from jugular cannulas at -2, -1, and 0 hours before ACTH was injected (base line) and 0.25, 0.50, 1, 2, 3, 6, and 24 hours after injection. Plasma corticosteroids were increased progressively by injecting doses of ACTH between 1 and 200 IU. Plasma corticosteroids reached peak concentrations between 15 and 30 minutes and returned to base line within 1 to 3 hours after 1, 5, and 10 IU doses of ACTH were injected, but required as long as 6 hours after injection of 100 and 200 IU. Base line counts of circulating leukocytes averaged 7.3 X 10(3) cells/mm3 and remained unchanged after injecting 0 and 1 IU of ACTH (P less than 0.05). Significant dose-dependent increases in circulating leukocytes were detected within 2 hours after administering 5, 10, and 100 IU of ACTH. Responses to 100 and 200 IU were similar. The average concentration of leukocytes increased up to 6 hours after ACTH administration and returned to base line values within 12 to 24 hours in cows injected with 5 and 10 IU, but not until 48 hours in cows injected with 100 and 200 IU of ACTH. In contrast to the delayed and sustained responses observed for leukocytes, corticosteroid responses were rapid and transient. Moreover, the administration of 200 IU of ACTH was considered to increase circulating corticosteroids and leukocytes beyond that found in dairy cattle exposed to stress associated with overmilking, acute coliform mastitis, or parturition.

Adrenal Cortex Hormones↗
PubMed1976

Melatonin-induced inhibition of testicular function in adult golden hamsters.

Melatonin (12-100 mug/day) administered via subcutaneous Silastic implants prevented or suppressed light-induced testicular recrudescence in adult golden hamsters. In addition, melatonin (150 mug/day) induced marked testicular regression in sexually mature hamsters maintained on photostimulatory long days. These results clearly establish that exogenous melatonin can inhibit gonodal function in adult male hamsters.

Animals↗
PubMed1975

Melatonin: antigonadal and progonadal effects in male golden hamsters.

Melatonin induced marked testicular regression in hamsters maintained on photostimulatory long days (light-dark 14 : 10). In animals maintained on nonstimulatory short days (light-dark 6 : 18), small amounts of melatonin (50 micrograms per day; 100 millimeters capsule length) prevented testicular regression; but testicular atrophy occurred in hamsters that received larger amounts of melatonin (75 to 100 micrograms per day; 150 to 200 millimeters capsule length) and in control hamsters that received none. The results demonstrate that melatonin can exert either pro- or antigonadal effects and emphasize that the effects of melatonin on the testis cannot be properly assessed unless account is taken of the dosage and mode of melatonin administration and the photoperiod on which experimental animals are maintained.

Animals↗
PubMed1975

The inheritance of the Aarskog facial-digital-genital syndrome.

Prominent physical features of the Aarskog syndrome are short stature, telecanthus, ptosis, short broad nose, long philtrum, thin upper vermilion border and pouty lower lip, low-set jug-handle ears, short broad hands with clawlike positioning of the fingers, broad feet with bulbous toes, ventral scrotal folds, cryptorchidism, and hernias. Four families with 20 affected males are reported. Pedigree analysis is compatible with X-linked recessive inheritance with occasional partial expression in heterozygote females. The fact that seven sons, all unaffected, have been born to affected males argues against the alternative hypothesis of autosomal sex-influenced inheritance.

Abnormalities, Multiple↗
PubMed1975

Adpatations for urinary marking in rodents: prepuce length and morphology.

Urine marking was examined in house mice, deermice, gerbils and hamsters. The frequency of urine deposition varied with the species, and a correlation is suggested between the propensity of males to mark in this fashion and prepuce length and morphology. We postulate an adaptational advantage for a long penis sheath and for a particular configuration of the prepuce; i.e. to act as a wick for the deposition of urinary pheromones.

Adaptation, Biological↗