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Biomedical subjects

C Jean

Publications and source records attributed to C Jean.

At least 109 records · Page 6Linked to original sources
PubMed1981

Pituitary luteinizing hormone and follicle-stimulating hormone from birth to adulthood in male rabbit. Changes in the pituitary responsiveness to LHRH injection.

Pituitary content and concentration of LH and FSH were measured by radioimmunoassay from birth to adulthood. The pituitary contents and concentrations of both gonadotropins increased from birth to 70-90 days, then reaching adult levels. 1 microgram/100 g body weight of synthetic LHRH was administered to immature (25 and 55 days of age) and adult male rabbits. LH and FSH were measured in plasma samples taken just before and 30 min after LHRH injection. At all stages studied, LHRH significantly increased circulating LH and FSH. The FSH response at 55 days and at adult age was lower than that of LH. There was a peripubertal increase of the mobilizable pituitary reserve of LH while the FSH reserve slightly but not significantly increased. This change in the pituitary responsiveness to LHRH could play a role in pubertal processes.

Aging↗
PubMed1981

Effects of dense housing on the growth of reproductive organs, plasma testosterone levels and fertility of male mice.

Male mice were raised in populations of two different sizes from birth to adulthood: six animals (three of each sex) or 30 animals (15 of each sex) being maintained in cages of the same dimensions. Animals were killed every 10 days from weaning to 60 days and at 90 days. Increased population size induced decreased body and seminal vesicle weights; testicular, pituitary and adrenal weights were little affected. Plasma testosterone levels were lowered by increasing population size over the period from weaning to 50 days but they were increased at 60 and 90 days. The age at which first fertile matings occurred was not affected. These results indicate that the endocrine function of the testis, as determined by the measures used here, was specifically affected by this differential housing.

Animals↗
PubMed1981

The influence of the parental environment on sexual maturation in male mice.

Experiments were designed to examine the influence of either one or both parents on the sexual maturation of male mice. A pregnant female and an adult vasectomized male were housed together and, at delivery, the litter was reduced to 6 pups, 3 of each sex. After weaning, mother, foster-father or both, stayed in cohabitation with their pups until sacrifice. The results showed that: (1) the permanent presence of one or both parents did not affect either testicular growth or the age at first fertile matings. (2) in maturing males (30-40 days), seminal vesicle growth was accelerated by the presence of the mother, inhibited by the presence of the foster-father. (3) in maturing males, the presence of one or both parents lowered plasma testosterone levels. On the opposite, in 90-day-old males, the same conditions increased testosterone levels. These results indicate that only the endocrine function of the testis is affected by the parental environment. The effects are age-dependent.

Animals↗
PubMed1980

Ontogeny of pituitary gonadotrophin hormone activity and of testicular responsiveness to gonadotrophins in foetal rabbit.

Synthesis and secretion of T and DHT by 18, 19 and 20 day old foetal rabbit testes were measured (RIA) in an organ culture system (M199). It was demonstrated that synthesis and secretion in vitro of T and DHT were greater at 19 and 20 days than at 18 days. The T and DHT production could be stimulated by ovine LH at 19 and 20 days but not at 18 days. The pituitaries of 19 and 20 day old male and female foetuses (but not those of foetuses aged 18 days) stimulate synthesis and secretion of T by 20 day old testis. A gonadotrophic factor, active on testicular T production, is present in the pituitary gland of 19 day old foetuses of both sexes. These findings indicate that the testicular responsiveness to LH and to the pituitary appears concomitantly with the pituitary gonadotrophic activity, between 19 and 20 days, just prior to the beginning of male sexual differentiation (20-25 days).

Animals↗
PubMed1980

[Effects of social deprivation from birth or weaning on the development of the genital tract, on plasma testosterone, and on fertility in the male mouse].

Male mice were placed in one of the following 5 types of rearing conditions: group I: 3 males and 3 females in cohabitation from birth to sacrifice; group II: without littermates from birth to sacrifice; group III: isolated from weaning to sacrifice; groups IV, V: males of groups II, III placed in cohabitation with 5 mature females, from 40 to 90 days. All animals were weaned at 20 days and sacrificed from 20 to 90 days. Plasma testosterone was radioimmunologically determined. Male mice reared in various types of social deprivation showed transient or definitive modifications in body, testicular and seminal vesicle weights as well as in plasma testosterone. Fertility was not affected. Mechanisms of these modifications are unknown.

Aging↗
PubMed1980

[Effects of the absence of females on the sexual maturation of male mice].

Male mice were assigned to two groups. Group I: 3 males and 3 females in cohabitation from birth to sacrifice. Group II: litters of 6 males placed, after weaning, in a female-free room. 15-20 animals of each group were sacrificed from 30 to 90 days. Sexual maturation, characterized by testicular and seminal vesicle growth and by plasma testosterone levels, followed a similar pattern in both groups. Only minor difference were observed. These findngs suggest that female stimuli are not a necessary factor of sexual maturation in male mouse.

Animals↗
PubMed1980

[Sexual organogenesis and circulating androgens in the rabbit fetus. Study after active immunization of mothers against testosterone (author's transl)].

The circulating level of free androgens (testosterone and dihydrotestosterone) in fetal rabbit was reduced by active immunization of mothers against testosterone. The level of testosterone and dihydrotestosterone binding to circulating proteins was about 100% in immunized fetuses and newborns. The testosterone and dihydrotestosterone binding capacities were higher than their circulating concentrations. Macroscopically, all newborns exhibited feminine external genitalia. Histological examinations showed the presence of complete wolffian ducts differentiated in epididymis, deferent ducts and seminal vesicles with normal structure. Prostatic development was strongly inhibited; anterior prostates were present but lateral and posterior prostates were frequently absent. In most animals the masculinization of the genital tubercle was prevented: 60% of males exhibited feminine external genitalia, 40% severe hypospadias. These results suggest: 1 degrees that fetal free circulating androgens (testosterone and/or dihydrotestosterone) induced masculinization of urogenital sinus and genital tubercle; 2 degrees that testicular testosterone was responsible for stabilization and differentiation of the wolffian duct.

Androgens↗
PubMed1979

Percentage binding of testosterone and dihydrotestosterone and unbound testosterone and dihydrotestosterone in rabbit maternal and fetal plasma during sexual organogenesis.

The percentages of bound testosterone (17 beta-hydroxy-4-androsten-3-one; T) and dihydrotestosterone (17 beta-hydroxy-5 alpha-androstan-3-one; DHT) and their unbound concentrations were determined in pregnant rabbits and their fetuses from the 18th day of gestation to birth. T and DHT were also measured in fetal testes. In the testis, the total T/total DHT ratio, very high at 22 days (73.7 +/- 15.2), decreased until birth (6.7 +/- 0.8). In male fetuses the concentrations of total and unbound circulating T and DHT were always low and did not show any peak during sexual organogenesis. The percent binding of T (from 73.0 +/- 0.5 to 77.6 +/- 0.6) and DHT (from 76.5 to 83.7 +/- 1.1) in fetuses were similar in both sexes and significantly lower than those measured in mothers (T: from 87.2 +/- 0.6 to 91.6 +/- 0.9; DHT: from 87.3 +/- 0.9 to 93.8 +/- 0.9).

Animals↗
PubMed1979

Effect of luteinizing hormone-releasing hormone on plasma testosterone in immature and adult male rabbits.

1 microgram/100 g body weight of synthetic luteinizing hormone-releasing hormone (LHRH) was administered to immature (25, 35 and 55 days of age) and adult (180 days) male rabbits. Testosterone was measured by radioimmunoassay in plasma samples taken just before and 30 min after LHRH injection. At all stages studied, LHRH significantly increased plasma testosterone. Expressed as a percent of over basal levels, the plasma testosterone was increased by 2,695% at 25 days, 3,955% at 35 days, 6,032% at 55 days and 3,766% at 180 days. Expressed in absolute amounts, the plasma testosterone levels showed an increase of 520 pg/ml at 25 days, 604 pg/ml at 35 days, 1,189 pg/ml at 55 days and 7,596 pg/ml at 180 days. The exact interpretation of the data was difficult since it is dependent on the mode of expression used. Nevertheless, the results support the observation that the hypophyso-testicular axis is functional in immature rabbits.

Age Factors↗
PubMed1979

Changes in the testosterone to dihydrotestosterone ratio in plasma and testes of maturing rabbits.

Testosterone (T) and dihydrostestosterone (DHT) were radioimmunologically assayed in the testes and plasma of rabbits at 1, 10, 20, 40, and 60 days of age and at 3, 4, 5, and 8 months. In the testis (nanograms per 100 mg testis) and plasma (picograms per ml), both hormones are low at birth, reach their maxima between 60--90 days, and then decline and remain low after 120 days. In the testes, the T:DHT ratio is very high from birth (4.2 +/- 0.4) to 60 days (8.8 +/- 1.1). A significant decrease (P less than 0.001) occurs between 60 (8.8 +/- 1.1) and 90 (1.2 +/- 0.1) days. The T:DHT ratio is always less than or equal to unity after 90 days. From 1--60 days, T is the dominant testicular hormone, while the levels of DHT are greater than or equal to those of T after 60 days. The mean value of the plasma T:DHT ratio is always greater than unity from birth (1.7 +/- 0.4) to adulthood (2.6 +/- 0.7). The dominant circulating hormone, at all ages, is T. Our results show that sexual maturation in rabbits is characterized by an inversion of the T:DHT ratio in the testes but not in the plasma.

Aging↗
PubMed1979

Developmental patterns of the testicular response to experimental modifications of circulating androgen levels in the fetal rabbit.

The circulating level of free androgens in fetal and newborn rabbits was reduced by active immunization of mothers against testosterone (T) or was increased by injecting dihydrotestosterone (DHT) into the mothers. After immunization, about 100% of the circulating T and DHT in fetuses was bound. After maternal injection of DHT, the circulating level of this hormone in fetuses was increased 2- to 120-fold. The effects of these treatments were evaluated by determining testicular levels of T, a physiological index of circulating gonadotropin. From 20--23 days of gestation, testicular T content was modified neither by circulating antibodies nor by an increase of blood DHT. The same overloads of circulating DHT, which were ineffective between 20--23 days, significantly reduced testicular T content between 25--29 days. Testicular T content was significantly increased in newborns from immunized mothers. These results suggest that the appearance of the negative feedback action of circulating androgens takes place relatively late, at 24 or 25 days, after differentiation of the genital tract.

Animals↗
PubMed1978

Developmental patterns of plasma and testicular testosterone in mice from birth to adulthood.

Male mice were raised in cohabitation with females from birth to 90 days. Testosterone was measured every 10 days in plasma and testes. Sex difference in body weight was related to the pre-pubertal increase of testosterone levels in males. The weight of the seminal vesicle was positively correlated with circulating testosterone levels between 1 and 40 days but not between 50 and 90 days. Testosterone concentrations in the plasma and testes were high at birth: 630 pg/ml and 58.0 +/- 17.7 ng/100 mg; they subsequently decreased during the first days of life and remained low until day 20:240 +/- 110 pg/ml and 0.1 +/- 0.03 ng/100 mg. The testosterone levels then increased rapidly between days 20 and 30 and especially between 30 and 40 reaching their maxima: 5770 +/- 1720 pg/ml and 123.7 +/- 18.3 ng/100 mg testis. This increase was transitory and testosterone levels fell after day 40. By 90 days, the testosterone levels, 440 +/- 65 pg/ml and 43.2 +/- 5.5 ng/100 mg testis, were comparable to those measured at birth. Plasma testosterone and age were positively correlated between 1 and 40 days, and negatively between 50 and 90 days. The first fertile matings occurred at age 40 days.

Age Factors↗
PubMed1978

The effect of unilateral castration on plasma and testicular testosterone in rabbits from birth to 60 days.

Male rabbits were hemigonadectomized every 10 days from 1 to 50 days of age and were sacrificed 10 days after the operation. Non-operated controls were sacrificed at the same stages. Plasma and testicular testosterone were quantified by radioimmunoassay. Compensatory testicular hypertrophy was not observed in hemicastrated rabbits. Hemicastration has variable effects on testicular and plasma testosterone levels as a function of age. When it is performed at birth, there is a significant increase in testicular and plasma concentrations of testosterone. Similar results are obtained if the operation is performed at 30 days. Unilateral castration performed at 10, 20 and 50 days reduces testicular and plasma testosterone levels. When hemicastration is performed at 40 days or at the adult age, testicular and plasma testosterone levels are not modified.

Age Factors↗
PubMed1978

[Binding of testosterone and dihydrotestosterone to plasma proteins in rabbits under different physiological conditions].

Percent binding and unbound levels of T and DHT were determined in rabbits of both sexes at the end of intra-uterine life, ten days of age and adulthood. For both hormones, the lowest percent binding were observed in fetus, the highest in immature animals. The percent binding of T and DHT were significantly higher in adult females than in age-paired males. In pregnant mothers the percent binding of T and DHT were lowered.

Animals↗
PubMed1977

Effect of luteinizing hormone (LH) and LH-releasing hormone (LHRH) on testosterone production in vivo, in fetal rabbit testis in late gestation.

Plasma and tesicular testosterone were measured by radioimmunoassay in the 29-day-old rabbit fetus receiving an injection of saline solution, LH or LHRH. 30 min following the injection of 5 microgram LH into the umbilical vein, testosterone levels were significantly increased by 287% in the plasma and 293% in the testis, compared with controls receiving saline solution. The injection of 2 microgram of LHRH under the same conditions significantly increased testicular testosterone by 256% and plasma testosterone by 746%. The results show that the fetal rabbit testis, at the end of gestation, is capable of responding to LH stimulation. The hypophysio-testicular axis is apparently functional at this stage of gestation, as shown by the response to LHRH.

Animals↗