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S Vidal

Publications and source records attributed to S Vidal.

At least 127 records · Page 7Linked to original sources
PubMed1987

The use of a tyrosine-hydroxylase cDNA probe to study the neurotransmitter plasticity of rat sympathetic neurons in culture.

We have compared quantitatively the effects of muscle-conditioned medium (CM) and elevated K+ concentration (40 mM) on the enzymatic activity of tyrosine hydroxylase (TH) and on TH-mRNA levels in primary cultures of rat sympathetic neurons. Northern blot analysis of RNA from cultured neurons with a 32P-labeled rat TH-cDNA probe was performed. The probe hybridized strongly with a single RNA species of 1.9 kb, similar in size to the TH-mRNA from PC12 pheochromocytoma cells. In agreement with earlier data both CM and a partially purified factor from CM increased choline acetyltransferase activity up to 200-fold and depressed TH activity by 2- to 7-fold in cultured sympathetic neurons. These effects were accompanied by a decrease in TH-mRNA level, which correlated with the decrease in TH activity. On the other hand, a culture medium supplemented with 40 mM KCl caused a 1.5- to 5-fold increase in TH activity, which was accompanied by an increase in TH-mRNA level of the same order of magnitude. As a working hypothesis, we suggest that CM and neuronal depolarization control the transcription of the TH gene in an antagonistic manner.

Animals↗
PubMed1987

Comparison of the effects of elevated K+ ions and muscle-conditioned medium on the neurotransmitter phenotype of cultured sympathetic neurons.

Neuronal depolarization and culture media conditioned by certain nonneuronal cells (CM) are known to exert opposite effects on the expression of cholinergic and noradrenergic traits in cultured rat sympathetic neurons. We have compared their effects on the developments of choline acetyltransferase (CAT), tyrosine hydroxylase (TOH), dopa decarboxylase (AADC) and acetylcholinesterase (AcChE) in these cultures. A macromolecular factor which was partially purified from CM increased CAT development in a dose-dependent manner and depressed the development of TOH and AADC by 5- to 10-fold. In the presence of intermediate concentrations of this partially purified factor, both CAT and catecholamine synthesizing enzymes developed to high levels, whereas high concentrations caused a long-lasting, but not total, impairment of TOH development. The effects of CM on both CAT and AADC activities resulted from variations in the number of immunotitratable enzyme molecules. Conversely, K+ ions (30-40 mM) depressed the development of CAT by 90% and stimulated TOH development 2.5-fold. Cultures grown with CM in high K+ medium had similar CAT and TOH activities as compared to those cultures grown without CM in low K+ medium suggesting that CM and K+ ions had antagonistic effects on the expression of these enzymes. However, K+ ions did not affect the development of AADC in these cultures. CM suppressed in a reversible manner the development of the 16 S form of AcChE. In the presence of 40 mM K+, the rate of development of AcChE was reduced. In particular, the development of 16 S AcChE was strikingly impaired, although not totally suppressed. The effect of elevated K+ ions on the percentage of 16 S AcChE was rapidly reversible. It is concluded that CM and elevated K+ ions have antagonistic effects on CAT and TOH, but not on AADC development; AcChE, in particular its asymmetric 16 S form, is regulated independently of the cholinergic/noradrenergic status of sympathetic neurons.

Acetylcholinesterase↗
PubMed1986

Effects of a very low dose rate of chronic ionizing radiation on the division potential of human embryonic lung fibroblasts in vitro.

Among the various parameters that are supposed to play a role in aging at the cellular level, the "free radical theory" involves biochemical modifications that can be induced by radiation. Human embryonic lung fibroblasts were serially subcultivated at low density under chronic low dose rate irradiation (40 mrad/day) and in a normal environment. Irradiation increases cell attachment and the population doubling/day throughout their entire in vitro lifespan. Consequently, the doubling potential reached by irradiated cells was higher than that of control cultures. Finally, the total number of cells produced under chronic irradiation was 8-14 times higher than in a normal environment. These results are discussed with respect to the increased enzymatic activities (superoxidismutase, catalase, glutathion-reductase, G6PD) found in some irradiated organisms.

Cell Adhesion↗
PubMed1985

Studies on catalase, glutathione peroxidase and superoxidismutase activities in aging cells of Paramecium tetraurelia.

The nature of the aging process has been the subject of considerable speculation. Now, some data indicate that free radical reactions going on continuously in the cells contribute to aging. Considering these data, we have investigated the activity of enzymes (catalase, glutathione peroxidase, superoxidismutase) present physiologically in the cell to limit to tolerable levels, the rate of free radicals or H2O2. These enzymes activities were assayed in Paramecium tetraurelia as clonal age increased. Catalase activity increases slightly during aging of paramecia, i.e. during maturity and senescence phases (20-150 fissions). No significant changes in glutathione peroxidase and superoxidismutase is found. Catalase activity was also assayed as a function of culture conditions. As the cells begin starving and the percentage of autogamous cells increases, catalase activity decreases. After autogamy, a large increase of catalase activity occurs during the sexual immaturity phase, i.e. during the first 20 fissions. By another way, H2O2 added in the culture medium (from 0 to 15 X 10(-5)M) causes an important increase of catalase activity (from 100 U.I. to 250 U.I.). The possible role of O-.2, OH. and H2O2 in aging is discussed.

Animals↗
PubMed1984

Effects of polyamines on platelet aggregation.

Polyamines, spermine and spermidine in the micromolar range (1-100 mumol/l) increase ADP and epinephrine-induced platelet aggregation in vitro. The possible rôle of polyamines as regulating factors of platelet aggregation in physiological and pathological states is discussed.

Adenosine Diphosphate↗
PubMed1982

Cellular content and biosynthesis of polyamines during rooster spermatogenesis.

The natural polyamines spermine and spermidine, and the diamine putrescine, were extracted from rooster testis cells separated by sedimentation at unit gravity, and from vas-deferens spermatozoa. The ratios spermine/DNA and spermidine/DNA were kept relatively constant throughout spermatogenesis, whereas the ratio putrescine/DNA rose in elongated spermatids. The cellular content of spermine, spermidine and putrescine decreased markedly in mature spermatozoa. Two rate-limiting enzymes in the biosynthetic pathway of polyamines, ornithine decarboxylase and S-adenosyl-L-methionine decarboxylase, showed their highest activities at the end of spermiogenesis and were not detectable in vas-deferens spermatozoa. A marked reduction in cell volume during spermiogenesis without a parallel decrease in the cellular content of polyamines suggests the possibility that the marked changes in chromatin composition and structure occurring in rooster late spermatids could take place in an ambience of high polyamine concentration.

Adenosylmethionine Decarboxylase↗
PubMed1982

Effect of high mobility group nonhistone proteins HMG-20 (ubiquitin) and HMG-17 on histone deacetylase activity assayed in vitro.

We have used a method previously described by Reeves and Candido (1) to partially release histone deacetylase from cell nuclei together with putative regulators of the enzyme. Histone deacetylase released from testis cell nuclei and its putative regulators were separated by gel filtration in Sepharose 6B. A peak of low molecular weight contains a heat-stable factor that stimulate histone deacetylase in vitro. Many of the properties of the activator coincide with those of the protein HMG-20 (ubiquitin). Ubiquitin isolated from testis cell nuclei stimulated histone deacetylase in vitro. It has been suggested that HMG-17 partially inhibits histone deacetylase in Fried cell nuclei (2). In our system, HMG-17 shows no inhibitory effect on histone deacetylase activity

Amidohydrolases↗
PubMed1982

Proliferation kinetics of paramecium tetraurelia in balloon-borne experiments.

Experiments were carried out to demonstrate the effect of cosmic radiation, at a balloon-flight ceiling of about 36,500 m (120,000 ft) on single-cell organism proliferation. Paramecium tetraurelia were placed in air-tight containers and maintained at 25 degrees +/- 0.1 degrees C. Cellular growth was determined by cell count, either after recovery or during the flight, by means of an automatic fixation device. Dosimetry was performed by a tissue equivalent proportional counter and was of about 0.5 mrad/h. Flight ceiling duration ranged from 48 min - 22 h. A secondary stimulating effect of growth rate, preceded by a temporary decrease, was observed after recovery. Because of the high bacterial concentration in the trans-Mediterranean flight culture medium, the temporary drop of the growth rate, due to the radiolysis products, disappears. We consider that the stimulating effect can be the result of enzymatic intracellular scavenging of radiolysis products generated in the cell.

Altitude↗
PubMedDate not supplied

Molecular diagnosis of the fragile X and FRAXE syndromes in patients with mental retardation of unknown cause in Mexico.

The fragile X syndrome (Fra-X) is the most common cause of inherited mental retardation with X-linked semi-dominant inheritance. The prevalence of Fra-X in the Mexican population is unknown. The aim of this population screening study was to determine if Fra-X or FRAXE mutations are the cause of a number of cases of mental retardation in a sample of Mexican children with mental retardation of unknown cause (MRUC) and to stress the importance of performing molecular analysis of the FMR-1 gene in all patients with MRUC. We report here the direct analysis of CGG and GCC repeats within the FMR-1 and FMR-2 genes, respectively, in 62 unrelated patients with MRUC. Two male index cases had the CGG expansion, although they did not express the Xq27.3 fragile site cytogenetically. Fra-X diagnosis was highly suspected on a clinical basis in one of the patients, but not in the other. Both mothers were found to be premutation carriers. The molecular studies of FMR-1 showed that the proportion of MRUC patients with Fra-X is 3.2%. This frequency was not significantly different to that reported in most populations. As reported in other series, no patients with FRAXE were found in our sample. Our findings confirm that the molecular analysis of the FMR-1 gene is necessary in MRUC patients to achieve unequivocal diagnosis of fragile X syndrome, carrier premutation detection and for accurate genetic counseling.

Child↗
PubMedDate not supplied

Leptin and leptin receptor in anterior pituitary function.

Leptin is a 16 kDa protein that exerts important effects on the regulation of food intake and energy expenditure by interacting with the leptin receptor in the brain and in many other tissues. Although leptin is produced mainly by white adipose tissue, several laboratories have shown low levels of leptin production by a growing number of tissues including the anterior pituitary gland. Many studies have implicated leptin in anterior pituitary function including the observation that homozygous mutations of the leptin receptor gene led to morbid obesity, lack of pubertal development and decreased GH and TSH secretion. In addition, leptin functions as a neuroendocrine hormone and regulates many metabolic activities. Leptin also interacts with and regulates the hypothalamic-pituitary-adrenal, the hypothalamic-pituitary-thyroid and the hypothalamic-pituitary-gonadal axes. All of the anterior pituitary cell types express the leptin receptor. However, leptin has been localized in specific subtypes of anterior pituitary cells indicating cell type-specific production of leptin in the anterior pituitary. Subcellular localization of leptin indicates co-storage with secretory granules and implicates hypothalamic releasing hormones in leptin secretion from anterior pituitary hormone cells. Leptin signal transduction in the anterior pituitary has been shown to involve the janus protein-tyrosine kinase (JAK)/signal transducer and activation of transcription (STAT) as well as suppressor of cytokine signalling (SOCS). These proteins are activated by tyrosine-phosphorylation in anterior pituitary cells. The various steps in pituitary leptin signal transduction remain to be elucidated.

Aging↗
PubMedDate not supplied

Ultrastructural features of apoptosis in human pituitary adenomas.

Although several recent studies deal with various molecular aspects of apoptosis, or programmed cell death, very little information is available on the ultrastructural changes associated with apoptosis in the adenohypophysis and its role in the regulation of pituitary adenoma growth and progression. This paper describes the distinct ultrastructural sequences that develop during the various phases of the apoptotic process. The study is based on the ultrastructural investigation of more than 8,000 surgically removed pituitary biopsies, which were examined by histology and immunocytochemistry for diagnostic purposes. No apoptosis was found in normal adenohypophysis and it is also a rare event in pituitary adenomas. When present, adenomatous adenohypophysial cells exhibit common and characteristic apoptotic changes. The ultrastructural alterations of membraneous organelles associated with apoptosis are similar to those previously reported in other tissues. It is noteworthy that apoptosis is clearly distinguishable from the ubiquitous dark cells denoting the common way of cell death. The findings suggest that apoptosis in pituitary adenomas is not a random event. Practically every specimen containing multiple apoptotic cells represents corticotroph adenoma. Occasional examples occur in lactotroph or gonadotroph adenomas. Although electron microscopic specimens are admittedly small, the large number of investigated cases gives credence to the observations.

Adenoma↗
PubMedDate not supplied

Pituitary adenoma in Carney complex: an immunohistochemical, ultrastructural, and immunoelectron microscopic study.

First described in 1985, Carney complex is a rare, heritable disorder featuring abnormal skin pigmentation, cardiac and cutaneous myxoma, melanotic schwannoma of psammomatous type, and endocrine abnormalities, including pituitary adenomas. Patients with the latter present with elevated growth hormone (GH) levels and acromegaly or gigantism. Prolactin (PRL) elevation may also be seen. The authors have investigated 2 resected pituitary adenomas from patients with Carney complex. One, a 19-year-old female acromegalic with elevated GH, IgF-1, and PRL levels, had a mammosomatotroph adenoma immunoreactive for GH and PRL. Ultrastructurally, GH and PRL were present in the same secretory granules. The second patient, a 27-year-old acromegalic, had a sparsely granulated GH cell adenoma that by immuno-electron microscopy revealed GH immunoreactivity only. The lack of morphologic similarity between the 2 adenomas indicatesthat pituitary tumors in patients with Carney complex may not exhibit the same phenotype.

Abnormalities, Multiple↗
PubMedDate not supplied

Ultrastructural and immunoelectron microscopic study of three unusual plurihormonal pituitary adenomas.

Monomorphous pituitary adenomas expressing several hormones by immunocytochemistry are common, whereas adenomas displaying multiple immunoreactivities and consisting of more than one morphologic cell types are rare. Three such unusual pituitary adenomas, surgically removed from two patients with acromegaly and one patient with hyperprolactinemia, were investigated by histology, immunocytochemistry, transmission electron microscopy, as well as immunoelectron microscopy using double immunogold labeling. Immunocytochemistry revealed variable degrees of immunoreactivities for growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (beta-TSH), and alpha-subunit of glycoprotein hormones in all three tumors. The three adenomas consisted of phenotypically diverse cell populations as documented by transmission electron microscopy. In addition to monohormonal GH cells, immunoelectron microscopy demonstrated numerous cells colocalizing GH and PRL or GH and beta-TSH, and rarely PRL and beta-TSH in tumors of acromegalics. The adenoma causing hyperprolactinemia consisted chiefly of mammosomatotrophs colocalizing PRL and GH, whereas beta-TSH labeling was scant. The three tumors in the study were selected from a cluster of five plurimorphous plurihormonal adenomas received from the same locale where they accounted for an unprecedented 21% of adenomas producing GH and/or PRL. The enhanced susceptibility to develop plurimorphous adenomas of the acidophil cell line may have a genetic basis in the stable population the patients came from.

Acromegaly↗