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Biomedical subjects

R Goberna

Publications and source records attributed to R Goberna.

At least 55 records · Page 3Linked to original sources
PubMed1990

Nucleotide regulation of vasoactive intestinal peptide binding to bovine thyroid plasma membranes.

The specific binding of vasoactive intestinal peptide (VIP) to bovine thyroid plasma membranes is inhibited by guanine nucleotides. Guanosine 5'-triphosphate (GTP) and the non-hydrolyzable GTP analogs guanosine 5'-beta,gamma-imidotriphosphate (Gpp(NH)p) and guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S) inhibited markedly the binding of VIP to its receptors. This inhibition was higher with GTP than with Gpp(NH)p and GTP-gamma-S and was due to an increase of the rate of dissociation of peptide bound to membranes. Other nucleotides did not show any effect.

Animals↗
PubMed1990

Glycogenolytic effect of pancreastatin in the rat.

Pancreastatin is a novel 49-amino acid peptide with a C-terminal glycine amide. The peptide was isolated from porcine pancreatic extracts and shows a structural similarity to chromogranin A. The effect of synthetic porcine pancreastatin on blood glucose levels and hepatic glycogen content was investigated in rats in vivo. Pancreastatin (300 pmol/kg) produced a time-dependent decrease in glycogen content of liver and a slight hyperglycemia. Basal plasma insulin and glucagon levels were not modified by pancreastatin. We suggest that pancreastatin could play a biological role in the glucose metabolism through a glycogenolytic effect.

Animals↗
PubMed1990

Ontogeny of type II thyroxine 5'-deiodinase, N-acetyltransferase, and hydroxyindole-O-methyltransferase activities in the rat Harderian gland.

The ontogeny and regulation by isoproterenol of type II thyroxine 5'-deiodinase, N-acetyltransferase, and hydroxyindole-O-methyltransferase activities were studied in the rat Harderian gland. Both 5'-deiodinase and N-acetyltransferase activities exhibited maximal values at the first week of age. These activities gradually decreased till the fourth week. However, hydroxyindole-O-methyltransferase activity did not change during the period of time studied. Neither the different killing times (1600 or 0200 h) nor the photoperiod regimens (darkness or light exposure at night) modified the enzyme activities. On the other hand, isoproterenol, a beta-adrenergic agonist, could not to stimulate 5'-deiodinase at first week of life. Nevertheless, while basal 5'-deiodinase activity was diminishing during development, the enzyme was becoming sensitive to the action of isoproterenol. Thus, isoproterenol elicited increases in Harderian gland 5'-deiodinase activity in rats older than two weeks. However, both N-acetyltransferase and hydroxyindole-O-methyltransferase activities were not affected by isoproterenol treatment in either week studied.

Acetylserotonin O-Methyltransferase↗
PubMed1990

Effects of high-carbohydrate or high-fat diet on carbohydrate metabolism and insulin secretion in the normal rat.

The effects of changes in the content of dietary carbohydrate, protein and fat on glucose metabolism and insulin secretion were examined in normal male rats. The animals were fed for 10 days with three types of diet: (a) standard diet, (b) glucose diet and (c) high fat/protein diet. The weight of the rats fed with the glucose diet decreased when compared to the standard diet fed rats. The glucose diet decreased insulin secretion in response to glucose in vivo and in vitro and slightly improved glucose tolerance. The hepatic glycogen content was approximately three times higher in animals fed with the glucose diet than in the control group. When compared to the standard diet, the high fat/protein diet induced an increase of the weight gain. This type of diet caused an increase of the fasting plasma glucose, a decrease of hepatic glycogen and a marked glucose intolerance to an intravenous load as demonstrated by lower rates of glucose disappearance. Plasma insulin levels were increased both in basal and glucose stimulated states. These results indicate that the glucose diet leads to an enhanced insulin sensitivity of the target tissues. By contrast, the high fat/protein diet induces an obesity-like state and an in vivo insulin resistance.

Animals↗
PubMed1989

Decreased binding of vasoactive intestinal peptide to intestinal epithelial cells from hypothyroid rats.

The binding of vasoactive intestinal peptide (VIP) and stimulation of adenylate cyclase by VIP were studied in intestinal epithelial cells during hypothyroidism. Experimental hypothyroidism was induced in rats by the administration of KC10(4). The binding capacity, but not the affinity, of VIP receptors decreased in the hypothyroid rats. Besides, the stimulation of cyclic AMP production by VIP was also diminished in cells from hypothyroid rats. These observations indicate a decrease of the responsiveness of intestinal epithelial cells to VIP in the hypothyroid status, suggesting a role of the peptide in the pathophysiologic mechanism of intestinal manifestations during hypothyroidism.

Animals↗
PubMed1989

Effect of chronic intake of ethanol on the binding of vasoactive intestinal peptide to rat spleen lymphoid cells.

1. The effect of chronic intake of ethanol on the binding of vasoactive intestinal peptide (VIP) to rat spleen lymphoid cells was investigated. 2. The intake chronic of ethanol elicited an increase in specific VIP binding. 3. This increase was due to an increase in binding capacity of both the high and the low affinity binding sites. 4. There was a decrease in the affinities of both classes of VIP binding sites.

Alcoholism↗
PubMed1989

Interaction of thymic peptide thymosin alpha 1 with VIP receptors in rat intestinal epithelial cells: comparison with PHI and secretin.

1. Thymic peptide thymosin alpha 1 (10(-10)-10(-7) M) is shown to inhibit the specific binding of 125I-labelled VIP. 2. Thymosin alpha 1 was 1500 times less potent than VIP at inhibiting 125I-labelled VIP binding. 3. Thymosin alpha 1 (10(-10)-10(-7) M) was weak in stimulating cyclic AMP production. 4. Interaction of thymosin alpha 1 with VIP receptors is compared with PHI and secretin. 5. The order of affinity of different peptides is VIP greater than PHI greater than secretin greater than thymosin alpha 1.

Animals↗
PubMed1988

Evaluation of maternal serum alpha-foetoprotein assay using dry blood spot samples.

The quantification of alpha-foetoprotein in dry blood spots from pregnant women was evaluated, using a conventional radioimmunoassay (RIA) with a monospecific antibody. The stability of alpha-foetoprotein in dry blood spots on filter paper was evaluated with respect to mailing, distances travelled, and the existence of high summer temperatures in our region. The results obtained show that the blood alpha-foetoprotein is stable on dry filter spots sent by mail and is stable for up to four weeks at 4, 25 and 37 degrees C. The analytical method used has a minimal detectable concentration of 10 +/- 1.9 international kilo-units/l. Both inter- and intra-assay variabilities are smaller than 10% and this method can provide results comparable with those of conventional serum assays. Results from dry blood spots and serum samples (the latter analysed by both RIA and two-site enzyme immunoassay) exhibited a good correlation (r = 0.98 and r = 0.97, p less than 0.001). The design of the assay and the nature of the samples make this method suitable for a screening programmes for the antenatal detection of open neural tube defects.

Female↗
PubMed1987

Effects of fasting and refeeding on vasoactive intestinal peptide binding to rat blood mononuclear cells.

The effect of acute and chronic starvation on vasoactive intestinal peptide (VIP) binding to rat blood mononuclear cells was studied. A short-term (1 day) fasting period did not induce significant changes in VIP binding. Longer periods of fasting (3 and 5 days) elicited an increase in VIP binding. This increase was due to an increase in affinity of both the high and the low affinity binding sites rather than to changes in binding capacity. Refeeding of fasted animals resulted in a decrease in VIP binding, reaching similar values to those of the control groups.

Animals↗
PubMed1986

Interaction of a bovine thymic peptide extract with vasoactive intestinal peptide (VIP) receptors.

Bovine thymic peptide extract (1-100 micrograms/ml) is shown to completely inhibit the binding of [125I]VIP to rat blood mononuclear cells, lymphoid cells of spleen, and liver plasma membranes. In the three models, the bovine thymic peptide extract inhibits [125I]VIP binding with a potency that is 4000-7000 times lower than that of the native VIP, on a weight basis. In rat liver plasma membranes, the bovine thymic peptide extract stimulates adenylate cyclase with a maximal efficiency that is similar to that of VIP. At maximal doses, VIP and thymic peptide extract do not exert an additive effect on adenylate cyclase, suggesting that the activation of the enzyme by the bovine thymic peptide extract occurs through VIP receptors. Finally, no VIP-like immunoreactivity was detected in the thymic peptide extract using an antiserum raised against mammalian VIP. All these data suggest the presence in the bovine thymic peptide extract of a new substance which behaves as a VIP agonist in rat.

Adenylyl Cyclases↗
PubMed1986

Interaction of thymic peptide thymosin alpha 1 with vasoactive intestinal peptide (VIP) receptors.

Thymic peptide thymosin alpha 1 (10(-9) to 3 X 10(-7) M) is shown to inhibit the specific binding of [125I]VIP to rat blood mononuclear cells and liver plasma membranes. Thymosin alpha 1 was 160 and 6250 times less potent that VIP at inhibiting [125I]VIP binding to blood mononuclear cells and liver plasma membranes, respectively. Thymosin alpha 1 (10(-10) to 10(-7) M) was weak in stimulating adenylate cyclase activity. Its efficacy is about 25% and 27% that of native VIP in blood mononuclear cells and liver plasma membranes, respectively. Thymosin alpha 1 may behave as a partial VIP agonist in rat.

Adenylyl Cyclases↗
PubMed1986

Vasoactive intestinal peptide (VIP) binding to solubilized material from rat liver plasma membranes.

A non-ionic detergent such as Lubrol-PX extracts in soluble form the VIP-binding structures of rat liver plasma membranes. Detergent-solubilized proteins bind specifically [125I]VIP and the complex tracer-protein is identified by the use of Sepharose 6B columns. The interaction is only possible in the absence of detergent (below 0.001%) and is inhibited by native peptide. A molecular weight of about 80,000 was estimated for VIP-binding proteins by reference to a series of globular markers of proteins. Binding to VIP soluble proteins is specific and dependent on time as studied by the Hummel and Dreyer (Biochim. Biophys. Acta 63:530-532, 1962) assay.

Absorption↗
PubMed1986

Interaction of vasoactive intestinal peptide (VIP) with human peripheral blood lymphocytes: specific binding and cyclic AMP production.

VIP binding sites and cyclic AMP production by the peptide have been studied in human blood mononuclear cells before and after selective depletion of or enrichment for T-lymphocytes, B-lymphocytes-K-NK cells and monocytes. The specifically bound 125I-labelled VIP correlated significantly with the presence of B-lymphocytes and/or cells of K-NK system. The stoichiometric data were compatible with the existence of two classes of binding sites. T-lymphocytes and monocytes did not show binding of the tracer. The cyclic AMP production stimulated by VIP correlated significantly with the presence of B-lymphocytes and/or K-NK cells.

Adult↗
PubMed1986

Involvement of cyclic AMP-dependent protein kinase on the phosphorylase kinase inhibition by glucose-6-phosphate in adipose tissue extracts.

In order to achieve further clarification of the regulation of glycogenolysis in adipose tissue, we studied the effect of glucose-6-phosphate on phosphorylase activation in Sephadex G-25 filtrate of adipose tissue. The activity of phosphorylase kinase was decreased by 50% and by 75% in the presence of 0.5 mM and 2 mM of glucose-6-phosphate, respectively. This inhibition could be partially prevented by 0.5 mM AMP. Furthermore, we investigated the influence of glucose-6-phosphate on the effect of cyclic-AMP-dependent protein kinase on the activation of phosphorylase. The addition of cyclic-AMP and cyclic-AMP-dependent protein kinase caused a decrease in the inhibition of the phosphorylase activation by glucose-6-phosphate. Also, the glucose-6-phosphate at physiological concentration, decreased adipose tissue cyclic-AMP-dependent protein kinase activity.

Adenosine Monophosphate↗
PubMed1985

The interaction of vasoactive intestinal peptide (VIP) with isolated bovine thyroid plasma membranes.

The binding of vasoactive intestinal peptide (VIP) and stimulation of adenylate cyclase were studied in bovine thyroid plasma membranes. The binding depended on time, temperature and was saturable and specific. Binding studies suggested the presence of two classes of binding sites: a class with high affinity (Kd = 13 nM) and low capacity (6411 sites/pg), and a class with low affinity (Kd = 480 nm) and high capacity (105,300 sites/pg) at 15 degrees C. Secretin, glucagon, insulin and somatostatin did not displace the tracer from the membranes. VIP stimulated cyclic AMP production. Maximal cyclic AMP production (2-fold above basal values) was observed with 100 nM VIP and half-maximal response was obtained at 5 nM VIP at 15 degrees C.

Adenylyl Cyclases↗
PubMed1984

Histamine release by pharmacological agents in the absence of external free Ca2+.

The involvement of extracellular free Ca2+ in histamine release was investigated in rat peritoneal mast cells. Incubation of non-antigenized cells in a media with high extracellular potassium did not increase histamine release. Secretion induced by A23187 and compound 48/80 in the presence of Ca2+ requires metabolic energy. In the absence of external free Ca2+ (2.5 microM) histamine release induced by A23187 is reduced but not abolished. Secretion induced by compound 48/80 is independent of extracellular Ca2+. These results lead us to suggest that mast cell plasma membranes probably lack voltage-gated Ca2+ channels and that external Ca2+ may not be an absolute requisite for histamine secretion.

Animals↗