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Biomedical subjects

V Papadopoulos

Publications and source records attributed to V Papadopoulos.

125 records · Page 7Linked to original sources
PubMed1987

Adult rat Sertoli cells secrete a factor or factors which modulate Leydig cell function.

Production of testosterone and oestradiol-17 beta by Leydig cells from adult rats was stimulated by LH or dibutyryl cyclic AMP (10 and 2.5-fold respectively). The addition of spent medium from normal, hemicastrated or gamma-irradiated rat seminiferous tubule cultures, as well as from Sertoli cell cultures, to purified Leydig cells further enhanced both basal (44 and 53% for testosterone and oestradiol-17 beta respectively) and LH-stimulated (56 and 18%) steroid output. Simultaneously, a decrease (20-30%) in intracellular cyclic AMP levels was observed. This stimulating factor (or factors) secreted by the Sertoli cells is different from LHRH, is of proteinic nature and has a molecular weight ranging between 10,000 and 50,000; its synthesis is not controlled by FSH nor by testosterone. This factor(s) involved in rat Leydig cell steroidogenesis, at a step beyond the adenylate cyclase, does not require protein synthesis for testosterone formation whereas it does for oestradiol-17 beta production. It should be noted that a germ cell-Sertoli cell interaction modulates the synthesis of this factor(s).

Animals↗
PubMed1986

Effects of seminiferous tubule secreted factor(s) on Leydig cell cyclic AMP production in mature rat.

The effects of spent media from seminiferous tubules (STM) on Percoll-purified rat Leydig cells were investigated. Intracellular and extracellular cyclic AMP (cAMP) accumulation and testosterone production were measured. After a 5 h incubation period, STM reduces both the basal and LH-dependent cAMP levels (38 and 20%, respectively for intra- and extracellular cAMP) while, simultaneously, a stimulation of testosterone production is observed (47 to 50%, respectively in the absence or presence of LH). The reduction of cAMP levels observed after 5 h is likely to be due to the potentiating effect of the STM factor on the LH-dependent initial rise of the cAMP level which, in turn, induces a desensitization of the Leydig cell adenylate cyclase. This substance is a thermolabile protein (Mr greater than 50 000) produced by the Sertoli cell, independent of FSH and testosterone controls, and different from the LHRH-like substance.

Animals↗
PubMed1986

Rat testis 17 beta-estradiol: identification by gas chromatography-mass spectrometry and age related cellular distribution.

The aromatization of testosterone into 17 beta-estradiol (E2) was assessed in purified Leydig and Sertoli cells from rats aged 10-80 days. E2 was identified by gas chromatography-mass spectrometry (GC-MS) and measured both by radioimmunoassay (RIA) and GC-MS associated with stable isotope dilution. A potent competitive inhibitor of the aromatase activity, 4-hydroxyandrostenedione (4-OH-A) was used to test the enzymatic specificity. The basal aromatase activity was present in both cell types whatever the age of the animals. The basal E2 levels did not vary in Sertoli cells while a gradual increase was noted in Leydig cells until day 40, followed by a slight decrease in mature rats. In 10-day old animals, the aromatase activity was localized in Sertoli cells and highly stimulated by FSH; on day 20, both Sertoli and Leydig cells synthesized E2 although E2 from Sertoli cell origin was still predominant. Starting on day 20 until adulthood, the aromatase activity was under LH control in Leydig cells with a maximum around 40 days. The FSH and LH effects were mediated by cyclic AMP.

Aging↗
PubMed1985

Effect of phorbol ester and phospholipase C on LH-stimulated steroidogenesis in purified rat Leydig cells.

When the phorbol ester, 4 beta-phorbol-12-myristate-13-acetate (PMA) or bacterial phospholipase C (PL-C) is added to a preparation of purified adult rat Leydig cells, containing 2 mM CaCl2, a time- and dose-dependent decreases of LH-stimulated testosterone production is observed. After a 3 h stimulation with oLH (100 ng/ml), PMA (100 ng/ml) and PL-C (1.6 U/ml) do not affect the cell viability or the hCG specific binding, while cAMP accumulation is significantly reduced; cAMP-stimulated steroidogenesis is diminished only in the presence of PL-C. These observations suggest that in vitro: (i) activated Ca2+- and phospholipid-dependent protein kinase is implicated in the regulation of rat Leydig cell steroidogenesis by LH at a step before the adenylate cyclase; (ii) phospholipids play an important role in cAMP-stimulated testosterone synthesis.

Animals↗
PubMedDate not supplied

Dual compartment (bicameral) culture: role of basement membrane in epithelial differentiation.

A number of years ago we reported that tight junctions between adjacent Sertoli cells subdivide the seminiferous epithelium into two compartments, basal and adluminal, thus forming the morphological basis of the blood-testis barrier. It is now generally believed that the special milieu created by the Sertoli cells in the adluminal compartment is essential for germ cell differentiation. In order to duplicate the compartmentalization that occurs in vivo, Sertoli cells were cultured in bicameral chambers on Millipore filters impregnated with a reconstituted basement membrane. Confluent monolayers of these cells were tall columnar (40-60 microns in height) and highly polarized. These Sertoli cell monolayers established electrical resistance that peaked when the Sertoli-Sertoli tight junctions developed in culture. In addition, the monolayers formed a permeability barrier to 3H-inulin and lanthanum nitrate. The bicameral chambers were utilized in a number of studies on protein secretion, and it was revealed that numerous proteins are secreted in a polarized manner. In another study, hormone-stimulated aromatase activity was measured in Sertoli cells grown on plastic culture dishes, plastic dishes coated with laminin or Matrigel, and in the bicameral chambers. Cell culture on basement membrane substrates decreased the FSH-dependent estrogen production. No estrogen production was observed when the Sertoli cells were cultured in the bicameral chambers. These results are in accord with the hypothesis that differentiated Sertoli cells lose their ability to metabolize androgen to estrogen in an hormone-dependent manner, whereas undifferentiated cells in culture, or in vivo, have a very active FSH-dependent aromatase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Effect of mono-ethylhexyl phthalate on MA-10 Leydig tumor cells.

We examined the effect of mono-ethylhexyl phthalate (MEHP) on MA-10 Leydig tumor cell structure and function. Cells were exposed to various concentrations of MEHP for 24 h and then stimulated with saturating concentrations of hCG for 2.5 h. Progesterone production, cell viability, and protein content were moderately inhibited by low concentrations and severely inhibited by high concentrations of MEHP. Electron microscopy showed a variety of alterations in the MEHP-treated cells, increasing in severity with increasing concentrations of MEHP. Lipid droplets were profoundly affected in the cells treated with MEHP and morphologic evidence that metabolism of lipid storage droplets ceases at approximately the same time progesterone synthesis stops was seen. Morphometric studies indicated that the number of lipid droplets appeared to be increased 2.5-fold over control levels at MEHP concentrations of 10(-6) to 10(-3) M whereas mitochondrial volume fraction decreased. These results suggest that MEHP in Leydig cells may act as a mitochondrial toxicant and lipid metabolism disrupter.

Animals↗
PubMedDate not supplied

In vitro studies on the role of the peripheral-type benzodiazepine receptor in steroidogenesis.

In vitro studies using isolated cells, mitochondria and submitochondrial fractions demonstrated that in steroid synthesizing cells, the peripheral-type benzodiazepine receptor (PBR) is an outer mitochondrial membrane protein, preferentially located in the outer/inner membrane contact sites, involved in the regulation of cholesterol transport from the outer to the inner mitochondrial membrane, the rate-determining step in steroid biosynthesis. Mitochondrial PBR ligand binding characteristics and topography are sensitive to hormone treatment suggesting a role of PBR in the regulation of hormone-mediated steroidogenesis. Targeted disruption of the PBR gene in Leydig cells in vitro resulted in the arrest of cholesterol transport into mitochondria and steroid formation; transfection of the mutant cells with a PBR cDNA rescued steroidogenesis demonstrating an obligatory role for PBR in cholesterol transport. Molecular modeling of PBR suggested that it might function as a channel for cholesterol. This hypothesis was tested in a bacterial system devoid of PBR and cholesterol. Cholesterol uptake and transport by these cells was induced upon PBR expression. Amino acid deletion followed by site-directed mutagenesis studies and expression of mutant PBRs demonstrated the presence in the cytoplasmic carboxy-terminus of the receptor of a cholesterol recognition/interaction amino acid consensus sequence. This amino acid sequence may help for recruiting the cholesterol coming from intracellular sites to the mitochondria.

Animals↗
PubMedDate not supplied

In vitro effects of prolactin and dexamethasone on rat Leydig cell aromatase activity.

In Percoll purified adult rat Leydig cells, the estradiol secretion, in presence of exogenous testosterone (200 ng/ml) is stimulated 2-fold by either LH (100 ng/ml) or dbcAMP (1 mM). The addition of prolactin (1 microgram/ml) or dexamethasone (10(-7) M) to the Leydig cell incubation medium induces a 20% increase of the basal estradiol production, whereas, under LH or dbcAMP stimulations, 46 and 41% decreases are noted; moreover, a synergistic effect between prolactin and dexamethasone was observed in presence of dbcAMP leading to a 53% diminution of the estradiol synthesis. There results suggest that either hyperprolactinemia or high doses of glucocorticoids might inhibit the Leydig cell aromatase activity in presence of LH.

Animals↗
PubMedDate not supplied

Predictive value of risk factors in patients with obstructive jaundice.

Clinical and laboratory parameters that may affect post-operative mortality and morbidity were studied in 215 patients operated on for obstructive jaundice. The cause of the bile duct obstruction was benign disease in 56.7% of patients and malignant disease in 43.3%. Overall postoperative mortality and morbidity rates were 21.9% and 33.5%, respectively. Eight risk factors were shown to be associated with increased mortality: age > 70 years; malignancy; leucocytosis > 15 000 cells/microl and fever > 38.5 degrees C; haematocrit < or = 30%; creatinine > 1.3 mg/dl; albumin < or = 3 g/dl; bilirubin > 20 mg/dl; and serum alkaline phosphatase > 100 IU/l. The simultaneous presence of less than three risk factors was always associated with post-operative survival, but concomitant existence of seven or more risk factors indicated 100% mortality. Understanding the factors related to post-operative morbidity and mortality in patients with obstructive jaundice will better guide appropriate surgical or non-surgical management and lead to improved survival.

Adult↗
PubMedDate not supplied

In vivo studies on the role of the peripheral benzodiazepine receptor (PBR) in steroidogenesis.

In various steroidogenic cell models, mitochondrial preparations and submitochondrial fractions, the expression of the mitochondrial 18 kDa peripheral-type benzodiazepine receptor (PBR) protein confers the ability to take up and release, upon ligand activation, cholesterol. Thus, cholesterol becomes available to P450scc on the inner mitochondrial membrane. These in vitro studies were validated by in vivo experiments. Treatment of rats with ginkgolide B (GKB), specifically reduced the ligand binding capacity, protein, and mRNA expression of the adrenocortical PBR and circulating glucocorticoid levels. Treatment with GKB also resulted in inhibition of PBR protein synthesis and corticosterone production by isolated adrenocortical cells in response to ACTH. The ontogeny of both PBR binding capacity and protein directly paralleled that of ACTH-inducible steroidogenesis in rat adrenal cells and in rats injected with ACTH. In addition, the previously described suppression of luteal progesterone synthesis in the pregnant rat by continuous in vivo administration of a gonadotropin-releasing hormone agonist may be due to decreased luteal PBR ligand binding and mRNA. These results suggest that (i) PBR is an absolute prerequisite for adrenocortical and luteal steroidogenesis, (ii) regulation of adrenal PBR expression may be used as a tool to control circulating glucocorticoid levels and (iii) the stress hypo-responsive period of neonatal rats may result from decreased adrenal cortical PBR expression.

Adrenal Cortex Hormones↗
PubMedDate not supplied

Adamantinoma of tibia: a case of late local recurrence along with lung metastases.

Adamantinomas of long bones are rare primary low-grade malignant tumours composed of cells with epithelial and fibrous characteristics. Local recurrence, though scarce, occurs 5-15 years after the onset of diagnosis. We report a case of local recurrence of an adamantinoma localised in tibia, along with the presence of two lung metastases, 24 years after diagnosis and surgical therapy of the primary tumour. The local recurrence and the lung metastases were removed surgically. The patient remains free of the disease for 3 years.

Adult↗
PubMedDate not supplied

Drug-induced inhibition of the peripheral-type benzodiazepine receptor expression and cell proliferation in human breast cancer cells.

The peripheral-type benzodiazepine receptor (PBR) expression and localization correlate with human breast cancer cell proliferation and aggressive phenotype expression. The standardized extract of Ginkgo biloba leaves (EGb 761) and isolated ginkgolide B (GKB) were shown to decrease PBR mRNA expression in adrenal cells. We examined the effect of EGb 761 and GKB on PBR expression and cell proliferation in human breast cancer cells. EGb 761 and GKB decreased in a time- and dose-dependent manner PBR expression and cell proliferation in the highly aggressive, rich in PBR, human breast cancer cell line MDA-231 whereas they did not affect the proliferation of the non-aggressive human breast cancer cell line MCF-7, which contains very low PBR levels. This effect was reversible and not due to the antioxidant properties of the compounds tested. Using a human cDNA expression array we determined that EGb 761 treatment altered, in addition to PBR, the expression of 36 gene products involved in various pathways regulating cell proliferation. These in vitro data were further validated in an in vivo model where EGb 761 and GKB significantly inhibited the nuclear PBR expression and growth of MDA-231 cell xenografts in nude mice. Taken together, these data suggest that the manipulation of PBR expression could be used to control tumor growth and that EGb 761 and GKB, under the conditions used, exert cytostatic properties.

Animals↗
PubMedDate not supplied

Structure, function and regulation of the mitochondrial peripheral-type benzodiazepine receptor.

Steroid biosynthesis begins with the transfer of cholesterol from intracellular stores into mitochondria. Through in vitro and in vivo studies using various steroidogenic cell models and with the help of pharmacological, biochemical, morphological and molecular approaches we demonstrated that the peripheral-type benzodiazepine receptor (PBR) is an 18 kDa mitochondrial protein that interacts with other proteins in the outer mitochondrial membrane to form a multimeric complex. PBR is required for the binding, uptake and release, upon ligand activation, of the substrate cholesterol. Thus, cholesterol becomes available to the inner mitochondrial membrane P450scc where steroid biosynthesis begins. The presence of mitochondrial PBR is also critical in maintaining outer mitochondrial membrane stability and in preventing apoptosis. Considering these functions of PBR and the fact that PBR is a ubiquitous protein, it is suggested that this drug receptor may serve as a target to control various mitochondrial and cell functions and to protect against experimentally or pathologically induced mitochondrial and cell toxicity.

Animals↗
PubMedDate not supplied

Primary biliary cirrhosis complicated by transverse myelitis in a patient without Sjögren's syndrome.

Transverse myelitis is an acute inflammatory process, affecting one or more segments of the spinal cord. Its association with primary biliary cirrhosis has been documented in only four cases--all along with Sjögren's syndrome. Herein, we report for the first time, a patient who developed recurrent acute transverse myelitis in association with primary biliary cirrhosis without any clinical or histological indication of Sjögren's syndrome. A 42-year-old woman with primary biliary cirrhosis developed acute onset quadriparesis and urinary retention. Diagnostic evaluation excluded the presence of Sjögren's syndrome, other autoimmune syndromes, infections and multiple sclerosis. Magnetic resonance imaging of the spinal cord disclosed signal intensity abnormalities from C1 to T2 after gadolinium enhancement. As diagnosis of acute transverse myelitis was prominent, the patient was treated with intravenous methylprednisolone. The patient had a fair outcome despite an early recurrence of the symptoms after treatment withdrawal.

Adult↗
PubMedDate not supplied

The Crithidia luciliae and Farr assays for the detection of systemic lupus erythematosus.

The specificity and sensitivity of two commercial systems for the detection of anti-native deoxyribonucleic acid (DNA) antibodies in the diagnosis of active systemic lupus erythematosus were evaluated. Sera containing antinuclear antibodies from 64 patients were tested by an indirect immunofluorescent antibody technique employing the protozoan Crithidia luciliae as substrate and immunoradioassay based on the Farr technique. Twenty one patients had active systemic lupus erythematosus, 21 had other collagen vascular diseases, and 22 had miscellaneous non-collagen vascular diseases. The immunofluorescence test was 100 percent specific and 66.7 percent sensitive for systemic lupus erythematosus, whereas the radioimmunoassay was 90.7 percent specific and 80.9 percent sensitive. There was agreement between methods in 57 of the 64 (89.1 percent) sera tested.

Antibodies↗