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Biomedical subjects

A Sierra

Publications and source records attributed to A Sierra.

At least 91 records · Page 5Linked to original sources
PubMed1991

L-dopa stimulates the release of [3H]gamma-aminobutyric acid in the basal ganglia of 6-hydroxydopamine lesioned rats.

L-DOPA stimulated the K(+)-induced [3H]GABA (gamma-aminobutyric acid) release from slices of substantia nigra pars reticulata, entopeduncular nucleus, globus pallidus and caudate-putamen isolated from the ipsilateral side of 6-hydroxydopamine-lesioned rats, but the release from ipsilateral subthalamic slices was not affected. In substantia nigra, L-DOPA stimulation (EC50 = 1 microM) of [3H]GABA release was dose-dependently blocked (IC50 = 0.1 microM for the stimulation caused by 10 microM L-DOPA) by the D1 antagonist SCH 23390, but was not affected by (-)-sulpiride, a D2 antagonist. SCH 23390 also blocked the stimulation in the other nuclei. The DOPA decarboxylase inhibitor NSD-1015 (500 microM) did not prevent the stimulation induced by L-DOPA in all of the studied nuclei. The results suggest that L-DOPA is able to activate D1 receptors located on the terminals of striatal projections via the dopamine formed by a decarboxylation mediated by an NSD-1015-resistant enzyme. Activation of the presynaptic D1 receptors results in stimulation of GABA release.

Animals↗
PubMed1991

Blood lymphocytes are sensitized to branchial plexus nerves in patients with neuralgic amyotrophy.

The percentage of lymphocytic subsets in the blood of cases with neuralgic amyotrophy (NA), and the proliferative response of blood lymphocytes cultured with different nerve extracts, obtained from normal subjects at postmortem, were examined in 6 patients with NA and in 18 age-matched controls with shoulder pain not related to NA. Most (5/6) NA patients had decreased CD3 values and increased CD4/CD8 ratios due to a decreased of the CD8 subset. Lymphocytes of NA patients increased their blastogenic activity in cultures with nerve extracts from different brachial plexus nerves and its branches, but not in cultures with extracts of sacral plexus nerves. Cultures did not respond to nerve extracts in any of the control cases, although mitogenic activity was similarly elicited in cultured lymphocytes stimulated with phytohemagglutinin in both control cases and NA patients. These results suggest that NA is probably an immune mediated disease.

Adolescent↗
PubMed1991

Suicide in the Canary Islands, 1977-1983.

We studied suicide in the Canary Islands between 1977 and 1983 and found 775 cases, twice the official number of 381. This indicates the lack of validity and reliability of official figures for suicide in Spain today. The figures reveal an upward trend in the Canary Islands, with the annual rate of 6.81 per 100,000 in 1977 having increased to 10.64 per 100,000 in 1983. There were no significant differences in the frequency of suicide according to season, month or day of the week.

Atlantic Islands↗
PubMed1990

Bombesin microinjected into the dorsal vagal complex inhibits TRH-stimulated gastric contractility in rats.

The effects of centrally injected bombesin on central and peripheral stimulated gastric contractility were investigated in fasted urethane-anesthetized rats. Miniature strain gauge force transducers were acutely implanted on the corpus of the stomach and gastric contractility was analyzed by computer. Intracisternal injection of the stable thyrotropin-releasing hormone (TRH)-analog RX 77368 (77 pmol) induced a stimulation of gastric contractility for 40 min. Intracisternal injection of bombesin (62-620 pmol) followed 30 min later by that of RX 77368 resulted in a dose-related inhibition of the TRH-analog-induced gastric contractility. Intracisternal injection of bombesin (620 pmol) did not modify gastric contractility stimulated by intravenous carbachol. Stimulation of gastric contractility induced by TRH-analog microinjected into the dorsal vagal complex (DVC) was dose-related suppressed by concomitant injections of bombesin (6.2-620 pmol). Neither bombesin alone (6.2 pmol) nor vehicle modified basal gastric contractility. These results demonstrate that bombesin acts within the brain to inhibit vagally stimulated gastric contractility and that the DVC is a sensitive site for bombesin inhibitory action. These findings suggest a possible interaction between TRH and bombesin in the central vagal regulation of gastric contractility.

Animals↗
PubMed1990

Activation of D1 dopamine receptors stimulates the release of GABA in the basal ganglia of the rat.

Here we have explored whether dopamine is able to modulate the release of gamma-aminobutyric acid (GABA) from striatal terminals to substantia nigra pars reticulata, entopeduncular nucleus, globus pallidus and caudate-putamen. The type of dopamine receptors involved was assessed by the blocking effect of either SCH 23390 (D1 antagonist) or (-)-sulpiride (D2 antagonist) of the dopamine effect. Dopamine stimulated (EC50 3.2 microM) the depolarization-induced release of [3H]GABA from slices isolated from all of the above mentioned nuclei. SCH 23390 dose-dependently blocked the dopamine stimulation, but (-)-sulpiride did not show any blocking effect. The results suggest that dopamine via D1 receptors modulates the release of GABA from striatal GABAergic terminals.

Animals↗
PubMed1989

The role of calcium in the repetitive firing of neostriatal neurons.

The Ca++ -dependence of the repetitive firing of neostriatal neurons was studied in an in vitro slice preparation of the rat neostriatum. Neuronal firing was evoked by injecting depolarizing currents of 100-200 ms duration. In normal conditions, the mode of firing was tonic and showed very little adaptation. The frequency-current relation was linear over a wide range of frequencies. The repetitive firing was first enhanced and later suppressed by Co++, Mn++ and Cd++. These effects on the repetitive firing by the Ca++ -channel blockers paralleled the suppression of the slow afterhyperpolarizing potential. The lowering (0.2 mM) of Ca++ had similar effects. In the presence of TEA (up to 10 mM), the cell fired both Na+ and Ca+ action potentials. The results suggest that, as in other CNS neurons of the vertebrate, in neostriatal neurons the slow afterhyperpolarizing potential (AHP) is due to a Ca++ -activated K+ -conductance, and that the AHP plays a crucial role in the repetitive firing of these neurons.

Action Potentials↗
PubMed1989

Medullary sites for TRH analogue stimulation of gastric contractility in the rat.

Medullary sites at which the stable thyrotropin-releasing hormone (TRH) analogue, RX 77368 (p-Glu-His-[3,3'-dimethyl]-Pro-NH2), stimulates gastric contractility were investigated in rats under urethan anesthesia. The peptide analogue was microinjected in 50-100 nl of volume unilaterally into various brain stem nuclei using glass micropipettes (50 microns). Gastric contractility was recorded continuously with acutely implanted strain-gauge force transducers and traces analyzed by computer. RX 77368 (2.6-77 pmol) microinjected into the dorsal vagal complex (DVC) dose dependently stimulated gastric contractility. Peptide action (77 pmol) had a rapid onset with a peak response at 15 min, continued for 45 min after the microinjection, and was blocked by vagotomy. TRH microinjected into the DVC had a shorter duration of action. RX 77368 (0.7-77 pmol) microinjected into the nucleus ambiguus also dose dependently stimulated gastric contractions. In contrast, microinjection of RX 77368 (77 pmol) into the hypoglossal nucleus had no effect. These findings demonstrate that the DVC and nucleus ambiguus are sites of action for TRH-induced stimulation of gastric contractility in the rat. The effect is dose dependent, long lasting, site specific, and vagally mediated. These results are consistent with a possible physiological role for medullary TRH in the vagal regulation of gastric contractility.

Animals↗
PubMed1988

Physostigmine stimulates phosphoinositide breakdown in the rat neostriatum.

The reversible acetylcholinesterase inhibitor, physostigmine, stimulated in a dose-dependent manner the accumulation of [3H]inositol monophosphate ([3H]IP1) in lithium-treated neostriatal slices. The muscarinic agonists, carbachol and oxotremorine, also stimulated [3H]IP1 accumulation. Atropine completely blocked the physostigmine-induced accumulation but had no effect on the basal accumulation. Tetrodotoxin partially inhibited the physostigmine-induced [3H]IP1 accumulation but had no effect on the carbachol-induced accumulation. 4-Aminopyridine stimulated the basal [3H]IP1 accumulation and potentiated the physostigmine-induced accumulation. This potentiation was blocked by tetrodotoxin. The physostigmine dose-response curve for the stimulation of [3H]IP1 accumulation was similar to its dose-response curve to inhibit acetylcholinesterase activity in the neostriatum. The results suggest that, under our experimental conditions, the acetylcholine released spontaneously from intrinsic cholinergic neurons does not activate the striatal muscarinic receptors coupled to phosphoinositide breakdown unless the intrinsic acetylcholinesterases are inhibited.

4-Aminopyridine↗
PubMed1988

Corticotropin-releasing factor acts centrally to suppress stimulated gastric contractility in the rat.

The effects of intracisternal (i.c.) and intravenous (i.v.) administration of corticotropin-releasing factor (CRF) on gastric contractility stimulated by i.c. injection of the TRH analog RX77368 [p-Glu-His-(3,3'-dimethyl)-Pro-NH2], 2-deoxy-D-glucose (2DG) and i.v. infusion of carbachol were evaluated in rats under urethane anesthesia. Gastric contractility was monitored using acutely implanted extraluminal force transducers sutured to the corpus of the stomach. I.c. injection of CRF (6.3-210 pmol) resulted in a dose dependent suppression of gastric contractility stimulated by RX77368 (260 pmol) and 2DG (6 mg). Gastric inhibitory response to i.c. CRF was rapid in onset and lasted at least 45 min. Carbachol (200 mg/kg/h)-induced stimulation of gastric contractility was not modified by i.c. injection of CRF. The stimulation of contractility caused by both i.v. carbachol and i.c. 2DG were completely inhibited by atropine (1 mg/kg, i.v.). CRF (210 pmol) given i.v. suppressed RX77368-stimulated gastric contractions, but was less than 1/10 as potent as administered i.c. I.v. CRF (210 pmol) did not alter 2DG- or carbachol-induced gastric contractions. These results demonstrate that the i.c. administration of CRF acts within the brain to inhibit gastric contractility elicited by vagus-dependent mechanisms.

Animals↗
PubMed1986

High-field magnetic resonance imaging of paranasal sinus inflammatory disease.

Magnetic resonance imaging using a 1.5 tesla magnet and a spin echo technique has revealed a remarkably intense signal from abnormal tissue in the human paranasal sinuses. Inflammatory disease in the maxillary, sphenoid, ethmoid, and frontal sinuses has been detected and demonstrated with greater clarity than any other available technique. The pathophysiologic basis for the intense signal has not been defined. These observations do, however, provide an opportunity to discover, clarify, and study paranasal sinus disease. Acute upper respiratory disease, allergic episodes, and the effect of drug treatment based on the MR signal and pathology can now be investigated with this technique. In addition, this may form a basis for assessing the epidemiology of paranasal sinus pathology.

Humans↗
PubMed1982

Analysis of antigenic variation in cysticerci of Taenia solium.

By studying the reactions and cross-reactions of antigen extracts from different collections of Taenia solium with their respective hyperimmune antisera, and by using numerical taxonomy to analyze the results, a measure of antigenic diversification within T. solium was established. Results varied somewhat depending on the immunological method employed. Double immunodiffusion and immunoelectrophoresis agreed in that all cysticerci were not identical, but shared approximately one third of their antigens. Double immunodiffusion recognized two groups of identical cysticerci: one included 50% of the cysticerci and the other, 21%. Immunoelectrophoresis was more discriminatory in that it recognized few extracts as identical. Electrophoretic data revealed that the most frequently shared antigen among cysticerci corresponded to that most frequently detected by immunologically responsive humans with cerebral cysticercosis. Antigen diversification of T. solium may provide a possible explanation of the pleomorphic immune response of man to this parasite.U

Animals↗