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Biomedical subjects

G Grizard

Publications and source records attributed to G Grizard.

52 records · Page 3Linked to original sources
PubMed1981

Effect of foetal pinealectomy on the pituitary gonadal axis in male rats.

Pinealectomy was performed on rat foetuses aged 16.5 days +/- 8 h. Sham-pinealectomized animals were bred under the same conditions. Animals were killed when 50 or 64-days old. Plasma LH response to Gn-RH (100 ng via carotid artery) was studied in undisturbed adult male rats. 1. Body weight at birth was higher in pinealectomized rats than in sham-pinealectomized animals but, in 50 or 64-day-old body weights were not different. 2. In 50-day-old pinealectomized rats, absolute weights of testis and epididymis were higher than in sham-pinealectomized animals. When organ weights were compared to body weight by analysis of covariance, only the epididymis weight was enhanced by pinealectomy. 3. In 64-day-old animals, foetal pinealectomy did not increase reproductive organ weights. In contrast, prostate weight was decreased after pineal removal. 4. Plasma and pituitary gonadotropins were not modified by foetal pinealectomy. In undisturbed adult male rats, the plasma LH response to Gn-RH administration was identical in pinealectomized rats and in sham-pinealectomized animals. These findings may suggest an inhibitory effect of the pineal and foetal growth, but foetal pinealectomy exerts no gonadal stimulation in the adult male rats.

Animals↗
PubMed1980

[Developmental changes in plasma gonadotropins and testosterone and in testicular lutropin receptors in normal and cryptorchid rats].

Testis weight, ventral prostate weight, plasma gonadotropins and testosterone and testicular LH receptors were assessed throughout sexual maturation in the 23 to 84 day old rat. Intact, sham-operated and cryptorchid rats (operated at day 21) were studied. In the intact rats, plasma FSH rose to a peak at day 33, and fell to a plateau from day 50 throughout adult life. Plasma LH showed a sharp peak at day 42. Testis LH receptor content increased continually with age, reaching a plateau at day 49, but there was no change in the affinity constant (Ka = 2.4 +/- 0.5 X 10(10) M-1) measured at four time intervals. These observations suggested that the peak of FSH initiated an increase in testicular LH receptors, and that the LH peak enhanced it. In the cryptorchid rats, FSH showed a maximum between days 30 and 40. After day 33, FSH was higher in the cryptorchid rats than in the controls. The pattern of plasma LH was different in controls and cryptorchids; in the latter group, LH was often higher than in the controls. Testicular LH receptors increased continually between days 23 and 84, but Ka remained constant (Ka = 2.2 +/- 0.9 X 10(10) M-1) during that period. When compared with the control rats, the cryptorchid animals showed an increased concentration of testicular LH receptors at day 84, but this concentration decreased at days 35, 49 and 84; plasma testosterone also declined at days 23 and 49. These data suggested that the Leydig cell function of the cryptorchid rats was altered.

Animals↗
PubMed1979

[Purification of pineal antigonadotropic factor (author's transl)].

Pineal activity on hypothalamo-hypophyso genital axis is well established. The mechanism is not simple, since progonadotropic or/an antigonadotropic activity were described. The biochemical isolation of the potent factor has been assayed. Several substances: melatonin, AVT, peptides have antigonadotropic properties. In this paper, we report many experiments concerning isolation and purification by several chromatographies of the factor (probably peptidic), that we believe to be responsible of antigonadotropic activity. Biological activity of the substance is proved by "in vitro" methods and radio immunoassays. This component is quite pure because electrophoresis on gel polyacrylamid reveals only one strip. Gel Sephadex G10 chromatography indicates a probable MW is between 500 and 1,000. This component causes an important inhibition of pituitary LH discharge (in vitro methods).

Animals↗
PubMed1978

Circadian variations of ovarian ascorbic acid depletion in response to luteinising hormone in the rat.

The ovarian ascorbic acid (OAA) was titrated, three hours after an I.V. injection of either saline or LH, administered to 46 day-old Sprague Dawley female rats pretreated with P.M.S., H.C.G., and estradiol benzoate (and undecylate). The rats were killed at specific times along the 24-hour scale (L.D. 12:12; L 06(00) to 18(00); Ambient temperature 24 degrees C +/- 2 degrees C). The OAA content varied with a statistically significant circadian rhythm in the controls. The minimum dose of LH effecting OAA depletion varied systematically with the circadian system phase. OAA depletion increases with the dose of LH, and also depends on the circadian time that the animal is killed; it is maximum at the same time that the OAA peak is found in the controls. The slope of the linear regression (quantity of OAA as a function of the logarithm of the LH doses administered) is always significant, but varies over the 24-hour span; in consequence the LH biological titration must be carried out rapidly, the optimal circadian time for killing the animals is about 16(30).

Animals↗
PubMed1975

[Biological assay of hypophyseal gonadotropins in the male rat (statistical study)].

The reproductibility, the experimental and statistical procedures of FSH and LH bioassays are studied. The estrogen pretreatment of animals increases, considerably the responsiveness and reliability of the LH bioassays. FSH levels have been determined, by the methods for parallel line assays, in the pituitary gland of normal rats and three days or seventeen days orchiectomized rats.

Animals↗
PubMed1975

[Interrelationship between adrenal cortex and genital apparatus of the male rat].

Interactions between gonadal hormones and adrenocortical function have been studied in the male rat. After injection (im) of testosterone, the accessory reproductive organs are more stimulated in the castrated rats than in the castrated adrenalectomized rats. Gonadectomy increases lipids, cholesterol and corticosterone in adrenal glands and plasma corticosterone levels. Testosterone reverses these effects.

17-Ketosteroids↗
PubMedDate not supplied

Pituitary gonadal function in infertile men with varicocele.

Infertile men with varicocele or idiopathic infertility were compared with a control group. Spermocytograms were taken and the following radioimmunological plasma analyses carried out: testosterone, FSH and LH before and after 50 micrograms LRH, Prolactin (PRL) before and after 200 micrograms TRH; in addition, 8 patients with varicoceles and 3 controls received LRH intravenously (0.4 microgram/min.) for 4 hours. The binding of [125I] human chorionic gonadotrophin (hCG) to testicular tissue obtained by biopsy from 10 infertile men was also investigated. Of the parameters studied, no differences were found between the unilateral or bilateral varicoceles. In the two groups of infertile men, sperm motility and percentage normal forms were similar and significantly lower than in controls. As compared to the controls, in the groups of infertile men, basal LH and testosterone levels were no different but basal FSH levels was increased, basal PRL was higher (p less than 0.05) in the varicocele group. Responses of the LH, FSH and PRL to LRH and TRH stimulations were generally higher in infertile men than in controls. As compared to the idiopathic infertile men, testosterone levels and responses of plasma FSH to LRH injection were lower in varicocele group. Moreover, in infertile men with varicocele, age was correlated negatively with sperm motility and testosterone level and it was correlated positively with LH response to LRH injection. For each patient, testicular tissue was able to specifically bind [125I]hCG, but in some cases of varicoceles, hCG binding capacity was different in the two testes and seemed higher than that observed in men with obstructive azoospermia. These results suggest: 1) dysfunction in both spermatogenesis and Leydig cells with a compensatory hyperfunction of the pituitary gland in infertile men with varicocele; 2) worsening in Leydig cells and tubular lesions with longer duration of varicocele; and 3) absence of any gross abnormality in hCG binding to its specific receptors in the testis of men with varicocele. These data suggest varicoceles may play a causal role in infertility.

Adult↗
PubMedDate not supplied

Bromocriptine, a dopamine agonist, directly inhibits testosterone production by rat Leydig cells.

We investigated the direct effects of bromocriptine (BR) on both basal and hCG-stimulated testosterone production by rat collagenase-dispersed Leydig cells. In a final volume of 2.2 ml, 2.10(6) Leydig cells were incubated at 33 degrees C for 3 h either alone or with various amounts of hCG (1. 10. 10(2). 10(3). 10(4) mUI/vial) and BR (1.5 10(-9), 1.5 10(-7), 1.5 10(-5) M); BR was dissolved in 20 microliters of ethanol. BR (1.5 10(-5) M) decreased significantly both basal and hCG-stimulated testosterone production whereas at lower doses, BR had no effect. These results suggest that the dopamine itself may regulate rat Leydig cell function and that there is room for criticism of BR-induced hypoprolactinemia as an experimental model to study the effect of prolactin on the androgenic function.

Animals↗
PubMedDate not supplied

Modulation of Leydig cell testosterone production by secretory products of macrophages.

Unstimulated macrophages from testes inhibited the production of testosterone by Leydig cells from adult, but not immature, Sprague-Dawley rats (significant after 48 h). Similar results were observed with unstimulated macrophage-conditioned media, suggesting that the observed effect was mediated by one or more secretory products. None of these substances was interleukin-1, since macrophage supernatants tested negative in an interleukin-1 alpha and interleukin-1 beta sensitive, thymocyte assay. Interleukin-6 was detected by a B cell proliferation assay. After stimulation by LPS, testicular macrophages enhanced testosterone production by Leydig cells from adult and immature rats. This enhancement was dose-dependent and required low concentrations (but over 2.5%) of conditioned media. Interleukin-1 and interleukin-6 activities were detected in LPS-stimulated macrophage supernatants. Supernatants of LPS-stimulated, human monocytes had similar effects on Leydig cells. They were rich in interleukin-1, interleukin-1 receptor antagonist and interleukin-6. The present study suggests that, in adult rats, testicular macrophages modulate Leydig cell steroidogenesis by secretory products whose secretion depends on the physiological state of macrophages. The factor or factors responsible for stimulation are not species-specific. The effect cannot be accounted for by variations in the concentration of the above mentioned interleukins in macrophage supernatants.

Animals↗
PubMedDate not supplied

Effect of short-term starvation on Leydig cell function in adult rats.

An experiment was carried out to analyze the effect of 3 days of starvation on the Leydig cell function in adult rats. Starvation markedly decreased plasma insulin and testosterone levels (p < .05). The weight of testes was maintained, whereas the testicular interstitial fluid volume decreased (p < .05). The level of testosterone decreased in this fluid (60%), whereas insulin levels showed no significant change. Purified Leydig cells showed normal LH/hCG binding in fasted rats but low insulin binding. The ability of these cells to produce testosterone in vitro was normal under both basal conditions and hCG stimulation in the absence and presence of insulin in the incubation medium. These data suggest that there is no gross impediment in the Leydig cell capacity to produce testosterone that might explain the starvation-associated decrease in plasma testosterone.

Animals↗
PubMedDate not supplied

Insulin binding sites in solubilized membranes from rat testis. Effect of age.

The effect of aging on the binding of insulin to testicular solubilized microsomal membranes was studied in rats. The insulin receptor was solubilized in triton x-100 and its properties compared with those of solubilized membranes of rat liver. At the three life stages studied (21, 38-40 and 75-80 days) binding specificity in testicular solubilized membranes showed the following order of competition relative to porcine insulin (100): proinsulin (7), guinea-pig insulin and IGF-I (less than 1). Scatchard analysis of the binding data always gave curvilinear plots with a high affinity of about 0.9 10(9) M-1. With aging, high affinity binding expressed as fmol per mg protein did not vary in the testis whereas it decreased in the liver. Where expressed as fmol bound per testis, the binding of insulin increased 14-fold between the age of 21 days and adult age. It is concluded that the characteristics of solubilized membranes receptors for insulin are roughly similar in the testis and liver but the effect of age on the number of high affinity binding sites is quite different in the two tissues.

Aging↗