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C Jean-Faucher

Publications and source records attributed to C Jean-Faucher.

15 recordsLinked to original sources
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↗
PubMed1976

Levels of testosterone in the plasma, gonads, and adrenals during fetal development of the rabbit.

Testerone (T) concentrations in the plasma, gonads, and adrenals were measured by radioimmunoassay in 188 male and 160 female rabbit fetuses. Determinations were performed daily from the 20th to the 31st day of gestation and were correlated with the maternal plasma concentration of T. The T content of both testes remained relatively constant from the 20th (3040 pg) to the 26th day (3940 pg), and subsequently decreased until the 31st day (1630pg). the concentration of testicular T fluctuated only slightly from the 20th (1040 pg/mg) to the 23rd day (783 pg/mg), and thereafter decreased until the 31st day (138 pg/mg). The T levels in plasma of males (132-361 pg/ml) were significantly higher than those of females (21-116 pg/ml). Plasma T levels in males were relatively constant and did not exhibit any rise, which is similar to observations of the testis during differentiation of the genital tract. Testosterone concentrations were low in the adrenals (3.5-12.3 pg/mg) of both sexes and in the ovaries (1.5-20.4 pg/mg) of fetuses. These data provide the first evidence for testicular T secretion at the time of genital differentiation in the rabbit.

Adrenal Glands↗
PubMed1976

[Effect of neonatal injections of estradiol, testosterone and cryproterone acetate on plasma and testicular testosterone and on the genital system in adult male mice].

On day old male mice received a single injection of oestradiol benzoate, testosterone propionate or cyproterone acetate in order to study their action on testicular development, particularly testosterone secretion. Oestrogenization of newborn males leads, when the animals mature, to a high proportion or cryptorchidism, to atrophy of testes and seminal vesicles, and inhibition of spermatogenesis. Testosterone levels were reduced in the plasma. Testosterone propionate produced moderate reduction of testicular weight but spermatogenesis was not impaired. Plasma testosterone level was reduced. Cyproterone acetate increased significantly testicular testosterone level.

Animals↗