PubMed Health⌕ Search

Biomedical subjects

J Reventos

Publications and source records attributed to J Reventos.

36 records · Page 2Linked to original sources
PubMed1984

Interactions between immature porcine Leydig and Sertoli cells in vitro. An ultrastructural and biochemical study.

Interactions between Leydig and Sertoli cells, as well as a stimulatory effect of FSH on Leydig cell activity, have been reported in many studies. In order to investigate these interactions, the ultrastructure of immature pig Leydig cells under different culture conditions has been studied. When cultured alone in a chemically defined medium, there is a marked regression of the Leydig cell smooth endoplasmic reticulum and a swelling of the mitochondria. Addition of FSH or hCG does not prevent these phenomena. Co-culturing of Leydig cells with Sertoli cells from the same animal maintains the smooth endoplasmic reticulum at the level seen in vivo and in freshly isolated Leydig cells. The addition of FSH to the co-culture stimulates its development and increases Leydig cell activity, as assessed by an increase in hCG binding sites and an increased steroidogenic response to hCG. These results suggest that Sertoli cells exert a trophic effect on Leydig cells, and that the stimulatory effect of FSH on Leydig cell function is mediated via the Sertoli cells. These results reinforce the concept of a local regulatory control of Leydig cell steroidogenesis.

Animals↗
PubMed1983

[Modulation of Leydig cell activity by Sertoli cell: an in vitro study].

In vivo studies indicate that FSH can modulate Leydig cells steroidogenic activity. However, in the testis only Sertoli cells contain specific FSH receptors. In order to clarify the mechanism by which FSH exerts this effect on testicular steroidogenesis, purified Pig Leydig and Sertoli cells were cultured alone or in co-culture. Leydig cell activity has been evaluated by two parameters: 1. hCG-stimulated testosterone secretion. 2. LH/hCG binding sites. FSH does not stimulate these two parameters of purified Leydig cells when cultured alone. On the other hand, when Leydig cells are co-cultured with Sertoli cells, FSH significantly increases these two parameters of Leydig cell function. These results suggest that the effect of FSH on Leydig cells is not direct but mediated by Sertoli cells.

Animals↗
PubMed1983

Steroidogenesis of cultured purified pig Leydig cells: effects of lipoproteins and human chorionic gonadotropin.

Dispersed Leydig cells were prepared from pig testes and purified in a discontinuous Percoll gradient. About 95% of these cells stained for 3 beta-hydroxysteroid dehydrogenase. The cells were cultured in a chemically defined medium. Testosterone production was low (2 +/- 0.4 ng/10(6) cells/day) under basal conditions, but increased by 8- to 10-fold on the third day of daily human CG (hCG) treatment. Addition to the medium of both human and pig low density lipoprotein (LDL) produced a dramatic increase in both basal (8-fold) and acute hCG-stimulated (5-fold) testosterone production, whereas both human and pig high density lipoprotein were far less effective. Furthermore the effect of lipoproteins was synergistic with that of hCG. The effects of human LDL on both basal and hCG-stimulated testosterone productions were dose-dependent. Maximum effect was achieved at a protein concentration of 10-40 micrograms/ml with an ED50 of about 4 micrograms/ml. Three days of pretreatment with hCG or (Bu)2cAMP alone induced Leydig cell steroidogenic refractoriness to both hCG and (Bu)2cAMP stimulation. Concomitant treatment with LDL restored the steroidogenic capacity, but only partially. Production of pregnenolone and testosterone of desensitized cells was significantly higher than that of control cells under basal conditions, but was 60% and 40% lower, respectively, after acute hCG stimulation. Moreover, the conversion of exogenous pregnenolone to testosterone by desensitized cells was only 60% of that of control cells. These results show that the de novo synthesis of cholesterol is able to account for only 25% of the maximal steroidogenic capacity of pig Leydig cells and that hCG-induced steroidogenic desensitization is only partially due to cholesterol depletion.

Animals↗
PubMed1983

Hormonal regulation of pig Leydig cells in culture.

Using a primary culture of purified immature pig Leydig cells, the hormonal and non hormonal regulation of steroidogenic activity have been studied. The effects of LH/hCG, FSH, LHRH, o-prolactin, estradiol, epidermal growth factor (EGF), human low density lipoprotein (hLDL) and human high density lipoprotein (hHDL) on 125I-hCG binding and basal and hCG-stimulated cAMP and steroids (testosterone and dehydroepiandrosterone sulfate) production were evaluated. These data on the regulation of pig Leydig cell activity are compared with other published results, mainly in the rat model, obtained either in vivo and in vitro.

Animals↗
PubMed1975

Evolution of spirographic patterns in pulmonary bilaterally denervated dogs.

One stage total bilateral pulmonary denervation produced in a group of 23 dogs an increase breathing frequency, an increase in the amplitude of respiration and a characteristic morphology of the spirographic pattern. Later in the evolution, these alterations returned to normal with the exeption of the amplitude of respiration which remained increased. This normalization was not accompanied by the reappearance of the Hering-Breuer reflux. Administration of an aerosol of acetylcholine after normalization of the spirographic pattern produced a temporary reappearance of the immediate postdenervation spirographic pattern. We postulate that in denervated lung a nervous plexus localized in the bronchi not related to the vagus might assume an important role in the regulation of respiration. One cannot exclude, however, the possibility that the reappearance of postdenervation pattern is due to stimulation of airways vagal receptors located in areas proximal to the level of the nervous section.

Acetylcholine↗
PubMedDate not supplied

Leydig cell and extracellular matrix effects on Sertoli cell function: biochemical and morphologic studies.

The reciprocal influence between Leydig and Sertoli cells prepared from pig testis were studied by coculture of both types of cells in either plastic dishes or dishes coated with basement membrane matrix. After 2-3 days in plastic dishes, Sertoli cells produced an increase in the steroidogenic response of Leydig cells to hCG. Pretreatment of the coculture with pFSH enhanced the steroidogenic capacity of Leydig cells and increased the number of hCG receptors. Similarly, the number of FSH binding sites and the FSH-induced plasminogen activator activity secretion of Sertoli cells cocultured with Leydig cells were increased. Pretreatment of the coculture with hCG further enhanced both parameters. The positive reciprocal tropic effects between Leydig cells and Sertoli cells were significantly enhanced when the coculture was carried out on the top of extracellular matrix. In addition, when cells were cocultured under these conditions, but not on plastic dishes, they were organized in cell clusters or island structures, with most of the Leydig cells located in the outer area, whereas Sertoli cells were located inside the islands.

Animals↗
PubMedDate not supplied

Clinical relevance of molecular markers in neuroblastoma: results from a single institution.

Neuroblastomas, the most common extracranial solid tumors in children, present an extremely heterogeneous behaviour that can be explained in part by their genetic abnormalities. Thirty-four patients treated at the Pediatric Oncology Unit, Hospital Vall d'Hebron from 1993 to 1997 were prospectively studied to determine the relative prognostic impact of a number of clinical and molecular factors. The factors studied were: ploidy, MYCN and 1p status, and TRK-A expression, in addition to age, stage and histology. Their impact on prognosis was analyzed. In univariate analysis, advanced stage, unfavorable histology, diploidy, MYCN amplification, and 1p deletion were identified as adverse prognostic factors; TRK-A expression was associated with favorable prognosis. After multivariate analysis, only MYCN amplification proved to be an independent adverse prognostic factor (p=0.03), whereas TRK-A expression identified a subset of good-prognosis patients (p=0.003).

Age Factors↗
PubMedDate not supplied

Advances in the molecular genetics of endometrial cancer (Review).

Recent studies have identified some of the genetic alterations involved in endometrial carcinoma development. Transforming genes, including K-ras and c-erbB2/neu oncogenes and the p53, PTEN and hMLH1 tumor suppressor genes, are the most frequently altered. In addition, endometrial carcinomas express high levels of chemoresistance markers, including the MDR-1 or the MRP genes. The genetic background of an endometrial cancer patient may include high-penetrance genes such as the DNA mismatch repair genes causing microsatellite instability, and low-penetrance genes such as those involved in estrogen-metabolism. The spectrum of several molecular lesions suggest a model for endometrial tumorigenesis through two divergent pathways, and which may improve the design of more rational therapeutic agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

[Role of plasma lipoproteins in the function of steroidogenic tissues].

Steroidogenic cells (adrenal, gonads and placenta) utilize cholesterol as a substrate for hormonal biosynthesis. Cholesterol can be synthetized de novo acetate or can enter the cell as a component of plasma lipoproteins, particularly LDL (low density lipoprotein) and HDL (high density lipoprotein). Steroidogenic cells utilize predominantly lipoproteins. Lipoprotein-cholesterol enters the cell by a specific pathway: binding of lipoproteins, particularly LDL to a membrane specific receptor and internalization of the complex receptor-lipoprotein, followed by dissociation of the complex; the receptor is reutilized, while LDL is hydrolyzed by lysosomal enzymes in amino-acids and free cholesterol. The liberated cholesterol is available for utilization by the cell. In addition, lipoproteins modulate intra-cellular cholesterol metabolism via two enzymatic activities; inhibition of hydroxymethyl-glutaryl coenzyme A reductase activity (HMG CoA reductase) which controls the rate limiting step of cholesterol biosynthesis, and stimulation of acyl CoA cholesterol acyltransferase (ACAT) activity which controls the esterification of cholesterol, before its translocation to lipids droplets. Peptide hormones LH/hCG and ACTH regulate lipoproteins metabolism in their target tissues by increasing LDL receptors number, a way which allow more cholesterol to enter the cell. The role of lipoproteins on steroidogenesis has been studied predominantly in adrenal and to a lesser extent in ovary and placenta and poorly in testis. Using a model of cultured porcine Leydig cells, we have demonstrated that de novo synthesis of cholesterol accounts for only 25% of the maximal steroidogenic capacity of these cells. Moreover the effects of lipoprotein LDL was synergistic with that of gonadotropins.

Adrenal Cortex↗
PubMedDate not supplied

Differential polymerase chain reaction with serial dilutions for quantification of MYCN gene amplification in neuroblastoma.

BACKGROUND: MYCN amplification is a powerful prognostic marker in neuroblastoma. Since MYCN status guides therapy results should be available promptly after diagnosis. MATERIAL AND METHODS: We used a differential PCR assay to analyze neuroblastoma samples obtained from 25 patients diagnosed and treated at our Institution. Serial dilutions of test DNA in control DNA were performed prior to differential PCR in order to quantitate the MYCN copy number. RESULTS: MYCN amplification was identified by differential PCR in five samples out of twenty five. The serial dilutions of amplified DNAs performed before the PCR reaction allowed a precise estimation of the copy number in the 5 samples with amplification. CONCLUSIONS: The present results confirm differential PCR assay as an easy, sensitive and rapid technique to evaluate the MYCN gene amplification in neuroblastoma. Serial dilutions accurately estimate the gene copy number allowing the early onset of the appropriate treatment.

Blotting, Southern↗