Biomedical subjects

C Monet-Kuntz

Publications and source records attributed to C Monet-Kuntz.

17 recordsLinked to original sources

PubMed1997

Metalloelastase expression in a mouse macrophage cell line--regulation by 4beta-phorbol 12-myristate 13-acetate, lipopolysaccharide and dexamethasone.

The regulation of the expression of mouse macrophage elastase (MME) was investigated using the murine tumor cell line P388D1. The effects of three factors were studied: a phorbol ester (4beta-phorbol 12-myristate 13-acetate, PMA), an endotoxin (lipopolysaccharide, LPS) and a corticosteroid (dexamethasone). Both in situ hybridization and northern blot analysis showed that P388D1 cells constitutively express the MME gene. Quantification of the MME mRNA by northern blot analysis showed that only PMA and dexamethasone significantly regulate MME gene expression in a time-dependent and dose-dependent manner. After PMA treatment, the MME mRNA level was maximal between 4 h and 9 h (medium-term response), and the mean amplitude of the response to a concentration of 100 nM was 2.5-fold (P<0.01). LPS did not induce any significant change in MME mRNA level even when 1% serum was added to the cultures. Following dexamethasone treatment, the MME mRNA level was minimal between 21 h and 33 h (long-term response), and the mean amplitude of the response to a concentration of 100 nM was 0.49-fold (P < 0.05). Using actinomycin D, it appeared that the inhibition of RNA synthesis reduces the ulterior stimulating effect of PMA from 184% to 121%, and that MME mRNA has a half-life longer than 8 h, which is not diminished by dexamethasone. These results strongly suggest that the two factors modify MME mRNA level by stimulating (PMA) or inhibiting (dexamethasone) the transcription of the gene, rather than by modifying the transcript stability. Analysis of the cell-conditioned media by elastin zymography showed the MME as a lysis band in the 22-kDa region, the intensity of which varied with the treatments. The MME secretion is stimulated by PMA, inhibited by dexamethasone and does not show any variation after LPS treatment.

Animals↗

PubMed1993

Secretion of transferrin in ovine seminiferous tubule cell cultures in response to FSH: influence of breed, season of birth and age of lambs.

The response of lamb Sertoli cells to follicle stimulating hormone (FSH) was investigated by measuring transferrin secretion in seminiferous tubule cell cultures throughout the non-pubertal and the prepubertal periods. Cells could be cultured from birth until they attained a testicular weight of 19 g. The characteristics of individual dose-response curves were compared according to the breed, season of birth and testicular weight of the lambs. At the same season of birth and within a given testis weight range, dose-response curves of Romanov and Ile-de-France lambs were similar. Within a given testis weight range, spring-born animals exhibited a higher maximal transferrin secretion than autumn-born lambs, but the ED50 was similar. The main factor of variation of the dose-response curve parameters was the testicular weight of the lambs: the amplitude of FSH response increased 3-fold from a testicular weight of 6 g onwards, i.e. from the appearance of spermatogonia in seminiferous tubules. The ED50 increased 5-fold from 11 g onwards, i.e. from the beginning of the prepubertal period. Thus, Sertoli cells become less sensitive to FSH as spermatogenesis develops in seminiferous tubules. This phenomenon is largely the result of higher phosphodiesterase activity and is greatly reduced by 1-methyl-3-isobutyl-xanthine (MIX).

1-Methyl-3-isobutylxanthine↗

PubMed1992

Purification of ovine transferrin and study of the hormonal control of its secretion in enriched cultures of ovine Sertoli cells.

Ovine transferrin (o-transferrin) was purified from sheep serum by fractionated precipitation with ammonium sulphate, ion-exchange chromatography on DEAE trisacryl and finally by affinity chromatography on Affigel blue to remove albumin. Ovine transferrin was identified by its apparent molecular weight in sodium dodecyl sulphate polyacrylamide gel electrophoresis and by its N-terminal amino-acid sequence. The procedure presented in this report permits the preparation of highly purified o-transferrin with a good recovery (52% of initial total immunoactivity). An antiserum against o-transferrin was then raised in rabbits, using this highly purified preparation. A specific radioimmunoassay was set up using 125I-labelled o-transferrin. Its detection threshold (4 ng/ml) was low enough to measure o-transferrin in spent culture media of ovine Sertoli cells, which ranged between 15 and 600 ng/ml. Sheep seminiferous tubule cells, containing approximately 80% Sertoli cells, were cultured at a high density (1.5 x 10(6) cells/cm2) on a thin layer of reconstituted basement membrane. Kinetic studies showed that basal daily secretion of o-transferrin was reduced by half (-49%) between Day 1 and Day 2 of culture, and progressively decreased thereafter. Under FIRT (500 ng ovine follicle-stimulating hormone (FSH)/ml + 10 micrograms insulin/ml + 500 ng retinol/ml + 5 x 10(-7) mol/l testosterone) stimulation, the ratio of stimulated to basal secretions increased 11-fold between Day 1 (1.1) and Day 6 (12). When 10% fetal calf serum was added, mean o-transferrin secretion was a third of that in serum-free medium, suggesting that fetal calf serum contains factors that inhibit secretion of ovine Sertoli cell transferrin. In the presence of serum, the ratio of FIRT-stimulated to basal secretions doubled between Day 1 (1.0) and Day 4-6 (2.0). Between Days 2 and 4 of culture, insulin had a slight stimulatory effect on o-transferrin secretion (128% of control at 10 micrograms insulin/ml), as well as epidermal growth factor (124% of control at 50 ng/ml). Testosterone at up to 5 x 10(-7) mol/l had no effect; 500 ng retinol/ml doubled o-transferrin secretion (218% of control) as did 500 ng FSH/ml (220% of control). A combination of retinol and FSH increased the secretion 4-fold, indicating that maximal stimulation of o-transferrin secretion by ovine Sertoli cells requires the combined actions of mechanisms dependent and independent of cAMP.

Animals↗

PubMed1991

Equine follicle-stimulating hormone action in cultured Sertoli cells from rat, sheep and pig.

Using a suspension of seminiferous tubule cells, we had previously shown that equine FSH is superactive in the male rat, i.e. that it exhibits a higher biological potency than expected from its binding activity. In this work we investigated equine FSH superactivity in rat, pig and sheep, by comparing in each species the equine FSH with the homologous FSH, both for their binding activities (in a radioreceptor assay using a testicular membrane fraction) and for their in vitro biological potencies (in a plasminogen activator assay using a Sertoli cell-enriched population cultured on plastic). In the rat, the binding activity of equine FSH was identical to that of rat FSH, and the biological potency of equine FSH was 47 times higher than that of rat FSH. Hence, superactivity of equine FSH was confirmed in the rat. In the pig, equine FSH was not superactive, since it exhibited binding activity and biological potency identical to those of porcine FSH. In the sheep, the binding activity of equine FSH was 6 times higher than that of ovine FSH, and its biological potency was also higher (14 times). Therefore, equine FSH cannot be considered superactive in this species. In conclusion, equine FSH superactivity is closely related to the species from which Sertoli cells are isolated.

Animals↗

PubMed1990

Expression of fetal-type intermediate filaments by 17-day-old rat Sertoli cells cultured on reconstituted basement membrane.

The expression of cytokeratin- and vimentin-type intermediate filaments was studied by means of immunohistochemistry in Sertoli cells cultured on two types of reconstituted basement membrane in two-compartment culture chambers. In situ, the Sertoli cells of 17-day-old rats contained only vimentin intermediate filaments. During culture, a gradual reorganization of intermediate filaments accompanied by an increased cytokeratin immunoreactivity was observed. After 6 days, Sertoli cells contained both cytokeratin and vimentin, and the same cytokeratin type as in fetal and newborn testis was revealed by electrophoresis and immunoblotting. The present study shows that the isolation and culture of Sertoli cells causes, even in an improved culture system, qualitative changes in the expression of intermediate filament proteins.

Animals↗

PubMed1990

Comparisons of endocrinological and testis parameters in 18-month-old Ile de France and Romanov rams.

Endocrinological and testis parameters of adult 18-month-old Ile de France (IF) and Romanov (Ro) rams were compared during sexual season. Testis weights, total volumes of intertubular tissue, and of blood and lymph vessels, total seminiferous tubule length, rete testis flow rate and daily production of germ cells were significantly higher in IF than in Ro rams. These variations originated from differences in Sertoli cell numbers, which were established before puberty. When daily productions of germ cells, of ABP or of RTF were expressed per Sertoli cell, they were higher in Ro than in IF rams. Quality of spermatids, as measured by their cellular size prior to elongation, was lower in Ro than in IF. The number of FSH-binding sites per Sertoli did not differ between the two breeds but FSH plasma levels were higher in Ro than in IF rams. Total numbers of Leydig cells per testis, their individual size or their LH-binding capacity did not differ significantly between the two breeds. However, the ratio of mean testosterone upon mean LH plasma levels were greater in Ro than in IF rams while both breeds had identical LH mean plasma levels.

Animals↗

PubMed1989

Age-dependent changes in the in-vitro response of a pig Sertoli cell-enriched population to FSH.

The response of pig Sertoli cell-enriched cultures to FSH was investigated by measuring plasminogen activator (PA) secretion in culture, throughout the nonpubertal and prepubertal periods. Sertoli cell-enriched populations could be isolated from birth until a testicular weight of 56 g. FSH elicited a dose-dependent increase in PA secretion by pig Sertoli cell-enriched cultures. The ED50 was minimal for cells coming from testes weighing 10-22 g, and increased more than 2-fold for cells from heavier testes. This suggests that, at the end of the non-pubertal period, an increased FSH sensitivity is important for initiation of spermatogenesis in this species, and that during the prepubertal period Sertoli cells become less sensitive to FSH. The FSH-stimulated PA secretion increased about 10-fold from a testicular weight of 25 g onwards, i.e. when primary spermatocytes appear in seminiferous tubules.

Animals↗

PubMed1987

Testicular growth and hormonal parameters in the male Snell dwarf mouse.

Dwarf mice show delayed testicular growth and their adult testis weights are half the normal value. The aims of the present work were firstly, to compare the developmental profiles of plasma gonadotropins and of testicular cell multiplication and differentiation in dwarf vs normal mice and secondly, to determine the effect of hMG supplementation on dwarf mice. In the dwarf mice no pubertal rise in plasma FSH was observed, and the adult values remained very low when compared with those of normal mice; plasma LH decreased after 40 days of age and remained equal to half the normal values. In adults, testicular testosterone content was greatly increased in dwarf mice compared with normal mice, whereas plasma testosterone and accessory gland weights were reduced. At 24 days of age, the total numbers per testis of Leydig and Sertoli cells were reduced in dwarf vs normal mice, whereas in adult mice their differentiation, but not their total numbers, was reduced. This resulted in lower daily production of leptotene primary spermatocytes and of round spermatids in dwarf than in normal mice. hMG supplementation promoted Leydig and Sertoli cell multiplication, but did not produce full differentiation, resulting in increased daily production of round spermatids. In conclusion, in adult dwarf mice a deficiency in plasma gonadotropins prevents full differentiation of Leydig and Sertoli cells without affecting the number of these cells.

Animals↗

PubMed1987

Spermatogenesis and Sertoli cell numbers and function in rams and bulls.

The two main types of cellular associations (type I, 2 generations of spermatocytes + 1 of spermatids; type II, 1 of spermatocytes and 2 of spermatids) occupy, respectively, more than half and about a third of the seminiferous epithelium cycle in rams and bulls. However, the duration of the cycle of the seminiferous epithelium and that of spermatogenesis differ between the species. A1 spermatogonia and Sertoli cell total numbers are highly correlated in adult rams and bulls. Mitosis in Sertoli cells occurs mostly in utero but may still occur for a short period after birth. Between birth and puberty there is about a 5-fold increase in the number of Sertoli cells. After that there are no seasonal- or age-related increases in the number of adult Sertoli cells. Some factors (season of birth; nutrition; genetics; hormones) affect mitosis of Sertoli cells in prepubertal animals. Sertoli cells differentiate after cessation of mitosis. Their differentiation is affected by cryptorchidism, nutrition, genetics and hormones. Their adult function is only poorly known. ABP and rete testis fluid secretions and nuclear Sertoli volume fluctuate under the influence of the same factors, but they are not always linked together. This reinforces the need for more knowledge of Sertoli cell secretions and function.

Animals↗

PubMed1985

Changes in intratesticular testosterone, cytoplasmic androgen receptors and ABP content of the ram testis after a single endogenous pulse of LH.

The effects of an endogenous LH pulse on the testicular concentration of testosterone, cytoplasmic androgen receptor content and androgen binding protein (ABP) content was studied in rams. Blood was collected from 36 rams for at least 14 h and their testes then removed. Animals were then grouped according to the interval from their last LH pulse and the time of slaughter. The concentration of testosterone in the testis was highest during the first h following the LH pulse and returned to its baseline within 5 h. There was a 60% reduction in the testicular content of cytoplasmic androgen receptors at 3 h after the LH pulse, followed by slow replenishment. The testicular content of ABP was highest at 4 h after the LH pulse. It is in the testis concluded that the pulsatility of LH and testosterone induces a pulsatile translocation of cytoplasmic androgen receptors.

Androgen-Binding Protein↗

PubMed1984

Variations in testicular androgen receptors and histology of the lamb testis from birth to puberty.

Changes in testicular androgen receptor numbers were studied in lambs from 25 to 100 days of age. During this period, cytoplasmic receptors increased from 5 to 80 pmol/testis and nuclear receptors from 1 to 12 pmol/testis, while the total volume of Leydig cells increased 7-fold. The total number of Sertoli cells doubled between 25 and 40 days of age. From 40 days onward their number remained constant while their cellular and nuclear sizes increased by a factor of 3 and 1.5 respectively. Cytoplasmic receptor concentration was positively correlated with the number of Sertoli cells per section of seminiferous tubule, and negatively correlated with the number of germinal cells per cross section. One explanation for these results could be that Sertoli cells are the main androgen target cells in lamb seminiferous tubules.

Animals↗

PubMed1983

Nuclear testosterone receptors in the ovine testis.

Nuclear [3H] testosterone-receptor complexes were demonstrated in hypophysectomized ram testis after in vitro direct labelling. The nuclear binding was maximal after a 45 min incubation of the tissue. The receptors are extractable by 0.4 M KC1 or NaSCN with a 25-30% efficiency. They migrate towards the anodic region during electrophoresis on agar gel. Nuclear androgen receptors were characterized in intact lamb testis by a testosterone exchange assay. After precipitation by protamine sulphate, the receptors were labelled with [3H]testosterone during a 12 h incubation at 4 degrees C. The exchange activity was linear between 0.1 and 0.9 mg of DNA per ml of incubation buffer. The receptors bind testosterone with a limited capacity (40-180 fmoles per mg DNA) and a dissociation constant Kd of 2 x 10(-9) M. Their relative affinities for steroids are dihydrotestosterone greater than testosterone greater than estradiol greater than progesterone greater than 5 alpha-androstanediol greater than cyproterone acute greater than R5020.

Animals↗

PubMed1979

Characterization of a cytoplasmic androgen receptor in the ram testis.

An androgen receptor has been characterized in the cytosol fraction of testes from hypophysectomized adult rams after in vitro labelling with [3H]testosterone. It can be distinguished from the testicular androgen-binding protein (ABP) and from the plasma 5 alpha-dihydrotestosterone-binding protein by electrophoresis on 3.25% acrylamide gels (Rx = 0.5) and on agar gels (anodic migration). It sediments in the 4S region in sucrose gradient containing 0.4 M KCl. Its complex with testosterone dissociates very slowly (t 1/2 = 29 h at 0 degrees C), and is destroyed by heating at 50 degrees C for 30 min and by pronase. Its relative affinities for steroids are 5 alpha-DHT greater than T greater than 5 alpha-androstanediols greater than cyproterone acetate greater than estradiol greater than progesterone. The number of binding sites is limited (about 20 fmoles/mg protein) and the apparent equilibrium dissociation constant (KD) is 5 x 10(-9) M.

Adsorption↗

PubMed1979

Endocrinology of spermatogenesis in the hypophysectomized ram.

Adult rams were hypophysectomized and treated for 20 days with testosterone (2 X 0.25 g/day), PMSG (2 X 300 i.u./day) or hCG (2 X 250 i.u./day), or for 40 days with testosterone (2 X 0.25 g/day). All treatments maintained a normal concentration of testosterone within the seminiferous tubules. Quantitative histological analysis showed that (1) the differentiation from A0 to A1 spermatogonia was maintained by PMSG or hCG but not completely by testosterone; (2) the transition from intermediate spermatogonia to primary spermatocytes was maintained only by PMSG but not by testosterone or hCG; (3) meiotic prophase and spermiogenesis were maintained by the three hormones but there were qualitative abnormalities in the spermatids. These results suggest that in the ram, the differentiation of renewing stem spermatogonia is under LH control and that the last stages of spermatogonial multiplication, from intermediate to B spermatogonia and to primary spermatocytes, are under the control of the FSH-like activity of PMSG.

Animals↗

PubMed1976

[Spermatogenesis after testosterone supplementation in the hypophysectomized ram].

Six adult rams were hypophysectomized and immediately injected with 0,5 g (group A) or 2 g (group B) of testosterone per day for 2 weeks. Three normal rams (group C) received the solvent only. The testosterone concentrations in the testis (ng/g) were the same in groups A (23 +/- 7) and C (22 +/- 4) and 3 times higher in group B (72 +/- 18). There was an uptake of testosterone by the testis of the two supplemented groups. In the Rete Testis Fluid, the testosterone concentration was normal with 0,5 g/day (29 +/- 0.6 ng/ml). The testicular weight was maintained by the two treatments. However, spermatogenesis was abnormal in both supplemented groups; meiosis and spermiogenesis occurred normally, but the efficiency of spermatogonial divisions, as shown by the number of leptotene and zygotene primary spermatocytes, was greatly reduced (85%). The results indicate that testosterone alone in the Ram is unable to support complete spermatogenesis, which is contrary to that found in the Rat.

Animals↗

PubMedDate not supplied

Endocrine parameters, hormone receptors, and functions of the testicular interstitium and seminiferous epithelium in estradiol-immunized Ile-de-France rams.

The testicular response of Ile-de-France rams actively immunized against estradiol (E2) was evaluated during both the ovine nonbreeding season (spring) and breeding season (autumn). Plasma concentrations of LH, FSH and testosterone were elevated in E2-immunized rams during both spring and autumn when compared with BSA-immunized controls. Testis weights were significantly elevated by E2 immunization and were characterized by greater interstitial cell volume, including Leydig cells, blood and lymph vessels, greater seminiferous tubule length, and greater numbers of leptotene spermatocytes and round spermatids. Neither Sertoli cell number, Sertoli cell nuclear volume nor testicular FSH receptor number were affected by E2 immunization, but testis weight, Sertoli cell nuclear area, FSH receptor number and LH receptor number were significantly greater in autumn than in spring. A positive effect of E2 immunization on testicular LH receptors was evident in spring but not in autumn. Testicular androgen receptors were suppressed by E2 immunization but were not affected by season. It was concluded that E2 immunization results in moderate stimulation of the ovine testis to increase testosterone secretion and to enhance total daily spermatid production. This effect appears to result from a change in E2 negative feedback and increased pituitary gonadotropin secretion.

Androgen-Binding Protein↗

PubMedDate not supplied

Effects of experimental cryptorchidism and subsequent orchidopexy on seminiferous tubule functions in the lamb.

The reversibility of damage caused by cryptorchidism to the seminiferous tubules of the lamb was investigated at various ages. Lambs were made bilaterally cryptorchid either at birth or at 2 months of age. Then orchidopexy was performed at either 2 or 4 months of age. In permanently cryptorchid lambs, spermatogenesis stopped completely, and Sertoli cell function, as measured by FSH receptors, androgen receptors and ABP, was much reduced (-96%, -86% and -81%, respectively). Orchidopexy allowed the cryptorchid seminiferous epithelium to grow again, but the more differentiated the germ cells, the less they were capable of restoration. Even in 0- to 2- and 0- to 4-month-old temporarily cryptorchid lambs that had recovered normal Sertoli cell function, 16 to 49% of the tubules still were empty. It was concluded that cryptorchidism irreversibly damages the seminiferous tubules at a level other than the hormone receptors.

Age Factors↗