Biomedical subjects

J C Prieto

Publications and source records attributed to J C Prieto.

At least 91 records · Page 5Linked to original sources

PubMed1991

Up-modulation of phorbol dibutyrate receptors by carbachol and arachidonic acid in rat prostatic epithelial cells.

Phorbol dibutyrate (PDBu) binding to rat prostatic epithelial cells has been measured as an indirect determination of protein kinase C in this cell system. Analysis of [3H]PDBu binding using competitive displacement demonstrated a single class of PDBu receptors with a Kd = 141 nM and a binding capacity of 4.8 pmol PDBu bound/mg cell protein. Raising cytosolic Ca2+ levels by redistribution of intracellular Ca2+ after cell treatment with carbachol or arachidonic acid (which also affects the bulk biophysical properties of the cell membrane) resulted in up-regulation of the available number of PDBu receptors. These results appear to be a consequence of PKC translocation from the cytosolic compartment to the plasma membrane after a cytosolic Ca2+ increase, confirming previous results in other cell systems.

Animals↗

PubMed1991

Effect of lindane upon the beta-adrenergic stimulation of cyclic AMP accumulation in rat renal cortical tubules caused by alterations in membrane fluidity.

The influence of lindane (gamma-hexachlorocyclohexane) on fluidity and lipid composition in rat renal cortical tubules has been investigated. Lindane increased membrane fluidity as measured by a fluorescence polarization technique using the probe diphenylhexatriene. This effect was dose-dependent and was accompanied by a 70% inhibition of the beta-adrenergic stimulatory activity upon cyclic AMP accumulation after 30 min of preincubation with lindane at 25 degrees C. Experiments with increasing concentrations of isoproterenol indicated that the efficacy, but not the potency, of the beta-adrenergic effect upon cyclic AMP accumulation was affected by lindane. Lindane toxicity could also be associated with variations in the incorporation of acetate into various lipid classes. Lindane increased acetate incorporation into phospholipids and decreased that into cholesterol.

Acetates↗

PubMed1991

Characterization of vasoactive intestinal peptide receptors in rat seminal vesicle.

Receptors for vasoactive intestinal peptide (VIP) in membranes from rat seminal vesicle were examined using 125I-labeled VIP as ligand. The receptor binding was rapid, reversible, saturable, specific, and dependent on temperature and membrane concentration. At 15 degrees C, the stoichiometric data suggested the presence of two classes of VIP receptors with Kd values of 0.54 and 44.4 nM and binding capacities of 73 and 1,065 fmol VIP/mg membrane protein, respectively. The interaction showed a high degree of specificity, as suggested by competition experiments with various peptides structurally related to VIP as follows: helodermin was 10 times, secretin 30 times, and rat growth hormone-releasing factor 300 times less potent than VIP, whereas glucagon did not recognize VIP receptors in concentrations of up to 10 microM. The binding of 125I-VIP to membranes was sensitive to the presence of GTP in the incubation medium in a dose-dependent manner. To characterize the molecular weight of these VIP receptors, 125I-VIP was covalently bound to membranes from rat seminal vesicle using dithiobis(succinimidyl propionate); sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the solubilized receptor revealed the presence of a specific component with a molecular mass of 47,000 Da as estimated in denaturing conditions. These findings, together with the known presence of VIP-containing nerves in the seminal vesicle, suggest a direct physiological role for this peptide in this accessory gland of the male genital tract.

Animals↗

PubMed1990

Beta-adrenergic stimulation of cyclic AMP accumulation in rat prostatic epithelial cells during sexual maturation.

The effect of age, castration and androgen-replacement therapy upon the stimulatory activity of the beta-adrenergic agonist isoproterenol on cyclic AMP accumulation was determined in rat prostatic epithelial cells. The potency of isoproterenol was similar in all the experimental models (ED50 = 0.3-0.4 microM). Mature animals showed a lower efficiency of isoproterenol than that of pubertal rats. Pubertal rats (which are absolutely dependent on androgens) exhibited an increase of the responsiveness of prostatic cyclic AMP to isoproterenol after castration, normalization being reached after subsequent testosterone treatment; this feature could be reproduced by in vitro incubation of the corresponding cells with testosterone or dihydrotestosterone. Mature rats (which are relatively dependent on androgens) maintained the efficiency of isoproterenol upon prostatic cyclic AMP after castration, and testosterone therapy elicited an increase of this activity. The present study contributes original observations mainly in the puberty period and supports the importance of the androgenic status not only for direct actions of androgens but also for the regulation of many other hormone/neurotransmitter/growth factor receptor-effector systems.

Adrenergic beta-Agonists↗

PubMed1990

Effect of bilateral adrenalectomy on VIP receptor/effector system in rat intestinal epithelial cells.

The number of vasoactive intestinal peptide (VIP) receptors and the efficiency of VIP in the stimulation of cyclic AMP accumulation in rat jejunal epithelial cells increased after bilateral adrenalectomy. However, this condition increased neither receptor affinity nor VIP potency. In addition, jejunal VIP levels followed a parallel increase. These changes reversed to control conditions after glucocorticoid replacement with dexamethasone indicating that adrenalectomy modifies the intestinal VIP receptor/effector system and suggest a relationship between corticosteroids and VIP in the functions of intestinal epithelium.

Adrenalectomy↗

PubMed1990

Effect of morphine and acetylcholine on contractile activity and cyclic AMP in guinea-pig ileum.

Neither acute nor prolonged exposure to morphine altered cAMP content or spontaneous movements of longitudinal muscle-myenteric plexus strips of the guinea-pig ileum. By contrast, exogenous acetylcholine or electrical stimulation of the strips elicited both a decrease of cAMP concentration and a twitch response. Atropine blocked the effects of stimulation on these parameters. Addition of morphine to electrically stimulated strips inhibited the twitch response but did not affect cAMP levels. Incubation with morphine led to the development of tolerance to the inhibitory effect on twitch activity and prevented the fall in cAMP normally elicited by electrical stimulation. These results suggest that muscarinic activation is associated with a reduction of cAMP content, an effect which would be impaired in opiate-tolerant tissues.

Acetylcholine↗

PubMed1990

Somatostatin inhibition of VIP- and isoproterenol-stimulated cyclic AMP accumulation in dissociated cells from rat cerebral cortex.

Freshly dissociated cerebral cortex cells from adult rats have been used in the present study to determine if dual regulation of cyclic AMP levels by inhibitory and stimulatory agents can be expressed in the mature brain. Somatostatin, an inhibitory agent, barely affected the basal cyclic AMP metabolism while vasoactive intestinal peptide (VIP) and isoproterenol, two stimulatory agents enhanced cyclic AMP production. However, this increase was depressed by somatostatin, which decreased the efficiency, but not the potency, of the effects of the two stimulatory agents on cyclic AMP accumulation.

Animals↗

PubMed1990

Modulation of the beta-adrenergic stimulation of cyclic AMP accumulation in rat prostatic epithelial cells by membrane fluidity.

1. The influence of membrane lipid composition on the beta-adrenergic stimulation of cyclic AMP accumulation in rat prostatic epithelial cells was assessed after treating the cells with cholesteryl hemisuccinate (ChH). 2. ChH treatment resulted in a 40% inhibition of the beta-adrenergic response after 30 min of lipid preincubation at 37 degrees C. 3. The inhibitory effect of ChH was dose-dependent and was accompanied by an increase of microviscosity as measured by a fluorescence polarization technique with the probe diphenylhexatriene. 4. Experiments with increasing concentrations of isoproterenol indicated that the efficiency, but not the potency, of the beta-adrenergic response was affected by the increasing of the cholesterol content in the cell membrane.

Animals↗

PubMed1990

[Antitubercular agents: pharmacogenetic factors in the development of adverse effects].

We studied the distribution of the acetylator phenotype in 47 patients aged 15 to 77 years receiving isonyazid as antituberculous therapy. 62% were fast and 32% slow acetylators. Ethnical, socio-economic and biologic factors were not related to acetylator type. The incidence of liver alterations, mainly elevated transaminase levels, was higher than reported in the literature and was not shown to be influenced by acetylator type. Adverse reactions to isonyacid were not related to drug serum levels.

Acetylation↗

PubMed1989

Effects of insulin-induced hypoglycemia on somatostatin level and binding in rat cerebral cortex and hippocampus.

The effects of severe insulin-induced hypoglycemia on somatostatin level and specific binding in the cerebral cortex and hippocampus were examined using 125I-Tyr11-somatostatin as a ligand. Severe insulin-induced hypoglycemia did not affect the level of somatostatin-like immunoreactivity in the brain areas studied. However, the number (but not the affinity) of specific somatostatin receptors was significantly decreased in membrane preparation from the hippocampus but not in the cerebral cortex at the onset of hypoglycemic coma (5-10 min). Administration of glucose at the onset of hypoglycemic coma brought about extensive recovery of hippocampal somatostatin receptor number. These results suggest that glucose modulates the somatostatin receptor in the rat hippocampus. The physiological significance of these findings remains to be clarified.

Animals↗

PubMed1989

Lindane effect upon the vasoactive intestinal peptide receptor/effector system in rat enterocytes.

Isolated rat enterocytes exposed to the insecticide lindane (the gamma-isomer of hexachlorocyclohexane, HCCH) showed an important decrease in the efficiency of the neuropeptide vasoactive intestinal peptide (VIP) upon the stimulation of cyclic AMP accumulation. The effect of lindane was time- and dose-dependent, optimal conditions being reached after 5 min incubation of cells at 25 degrees C with 0.5 mM of this organochlorine compound. Lindane action exhibited an important degree of specificity since the isomer alpha-HCCH and endrin reproduced the same inhibitory pattern but beta-HCCH and dieldrin were inactive. The inhibition of VIP-induced cyclic AMP accumulation could not be explained by a lindane-dependent reduction in the binding of VIP to its specific receptors. Among various possibilities, the results suggest the modification of membrane fluidity by lindane and/or the activation of Ca2+-dependent protein kinase C by this compound leading to phosphorylation of Gs/adenylate cyclase.

Animals↗

PubMed1989

The effects of experimental uremia in rats on duodenal VIP levels and the interaction of VIP with duodenal epithelial cells.

The effects of experimental uremia on the concentration of vasoactive intestinal peptide (VIP) in duodenum as well as on the interaction of this neuropeptide with the corresponding epithelial cells were studied in rats. Duodenal VIP concentration was significantly decreased in uremic rats as compared to control animals. The specific binding of VIP to duodenal epithelial cells increased in rats with uremia due to an increase in the number of VIP receptors rather than a change in the binding affinity or in the extent of VIP degradation. On the other hand, the efficacy but not the potency of VIP upon cyclic AMP generation varied in parallel to that observed at the receptor level.

Animals↗

PubMed1989

Effect of intestinal ischaemia on intestinal VIP levels and VIP interaction with intestinal epithelial cells from rat.

1. The number (but not the affinity) of vasoactive intestinal peptide (VIP) receptors in small intestinal epithelial cells decreased following intestinal ischaemia in rats as compared to sham-operated animals. 2. There was a parallel decrease of the efficiency (but not the potency) of the neuropeptide upon cyclic AMP formation at the same level after intestinal ischaemia. 3. The surgical manipulation did not modify the level of VIP immunoreactivity in the gut segment studied. 4. These results suggest that the VIPergic system is not directly involved in the high loss of water and electrolytes that appears following intestinal ischaemia.

Animals↗

PubMed1989

[Genetic polymorphism of isoniazid acetylation in Chilean patients with tuberculosis].

We studied genetic polymorphism of isoniazid acetylation in 47 tuberculous patients treated with 4 drugs between Aug 1987 and Dec 1988. Inactivation of isoniazid was estimated from urine samples after administration of the drug (10 mg/kg). There were 18 slow and 29 fast acetylators. The frequency of the slow mutant gene was estimated at 0.612, which is intermediate between values found in american natives (0.46) and western europeans (0.73). No associations of the presence of slow gene with sex, ABO group, ancestors, socioeconomic level, undernutrition, alcoholism or tobacco consumption were found.

Acetylation↗

PubMed1989

Identification of specific binding sites for vasoactive intestinal peptide in rat testis Leydig cells and study of developmental changes.

The interaction of vasoactive intestinal peptide (VIP) with isolated Leydig cells from rat testis was time- and temperature-dependent, as well as saturable and specific. Scatchard analysis suggested the presence of both high- and low-affinity binding sites with KD values of 1.7 and 43 nM, respectively, and receptor concentrations of 35 and 1394 fmol VIP bound/mg protein in mature (3- to 6-month old) rats. When considering pubertal (45-day old) rats, the affinities were similar but the binding capacities showed considerably lower values (25 and 193 fmol VIP bound/mg protein) indicating that VIP receptors are subject to developmental changes during animal maturation.

Animals↗

PubMed1988

Influence of castration and testosterone treatment on the vasoactive intestinal peptide receptor/effector system in rat prostatic epithelial cells.

The interaction of vasoactive intestinal peptide (VIP) with prostatic epithelial cells was studied after castration and testosterone replacement in pubertal and mature rats. The number of VIP receptors (but not the affinity) decreased 2 days after castration and returned to normal when subsequently treated with testosterone for 4 days. However, the stimulatory effect of VIP upon cyclic AMP accumulation was unaffected by the androgen withdrawal elicited by the surgical procedure. The results suggest the importance of androgens in the biosynthesis of VIP receptors and also in their coupling to adenylate cyclase by affecting the membrane fluidity.

Age Factors↗

PubMed1988

Effects of alloxan-induced diabetes on somatostatin binding to cytosolic components of rabbit gastric fundic mucosa.

Diabetes was induced by administration of alloxan (150 mg/Kg) to 24 h-fasted rabbits. Somatostatin-like immunoreactivity (SLI) and cytosolic binding sites for somatostatin in gastric fundic mucosa were studied using radiolabelled Tyr11-somatostatin. Three months after the onset of the disease, the specific binding of somatostatin to these sites was seen to be significantly lower, due to a reduction in the number (but not the affinity) of specific somatostatin binding sites of high-affinity and a disappearance of the specific somatostatin binding sites of low-affinity. These changes were associated with an increase in the SLI concentration in both gastric fundic mucosa and plasma.

Animals↗

PubMed1988

Partial enterectomy decreases somatostatin-binding sites in residual intestine of rabbits.

1. Three weeks after partial enterectomy in the rabbit there was an increased somatostatin concentration and a decreased number of somatostatin-binding sites (without changes in the corresponding affinity values) in the cytosol of the residual intestinal tissue, except in the terminal ileum and the colon. 2. Five weeks after surgery both the somatostatin concentration and the number of somatostatin-binding sites returned towards control values. 3. These results suggest that an increase in bowel somatostatin content could lead to down-regulation of somatostatin-binding sites in the intestinal mucosa.

Animals↗