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Biomedical subjects

C Arias

Publications and source records attributed to C Arias.

At least 73 records · Page 4Linked to original sources
PubMed1985

Binding of lanthanum ions and ruthenium red to synaptosomes and its effects on neurotransmitter release.

A technique for studying the binding of La3+ to synaptosomes in a double-beam spectrophotometer, using murexide as indicator, is described. The binding of La3+ was very rapid and Scatchard plots revealed two components, with KD values of 0.6 and 27 microM in a Na+-free medium (sucrose medium) and 2.3 and 63 microM in an ionic medium containing 135 mM Na+. The binding of the cationic dye ruthenium red (RuR) showed only one site, with a KD of 3.7 microM. La3+ binding was partially inhibited by RuR and vice versa, and La3+ was also capable of partially displacing RuR previously bound to the synaptosomes, particularly in the sucrose medium. The release of labeled gamma-aminobutyric acid (GABA) stimulated by K+ depolarization was inhibited by La3+ concentrations at or above 1 microM, in the ionic medium, whereas in the sucrose medium 2.5 microM or higher La3+ concentrations notably stimulated the spontaneous release of both GABA and glutamic acid. It is concluded that La3+ and RuR share at least one type of binding site, which is probably the high-affinity La3+ site. Since both La3+ and RuR at low concentrations have been shown to block the depolarization-induced Ca2+ entry in synaptosomes, this site might be related to the voltage-dependent Ca2+ entry involved in neurotransmitter release.

Animals↗
PubMed1984

Stimulation of [3H]gamma-aminobutyric acid release by calcium chelators in synaptosomes.

The effect of EGTA on the release of labeled gamma-aminobutyric acid (GABA), glutamate, acetylcholine, and dopamine was studied in superfused synaptosomes from mouse brain. In the absence of both Ca2+ and Mg2+, EGTA and also EDTA at 50 microM or higher concentrations induced a 2.5-5-fold stimulation of [3H]GABA release, similar to that produced by potassium depolarization, whereas only a slight effect, or no effect at all, was observed on the release of the other transmitters studied. The GABA-releasing action of EGTA was practically abolished in the presence of Mg2+. In contrast, the effect of EDTA was also observed when the medium contained Mg2+. Studies on the ionic dependence showed that the stimulation of GABA release by EGTA was abolished in a Na+-free medium. Li+ did not substitute Na+ for the EGTA effect, which was also independent of chloride. This Na+ dependence does not seem to involve voltage-sensitive channels, since tetrodotoxin did not affect the GABA-releasing action of EGTA, whereas in parallel superfusion chambers it blocked over 80% the stimulation of GABA release by veratridine. In contrast, two calcium channel blockers in synaptosomes, La3+ and the cationic dye ruthenium red, greatly inhibited the GABA-releasing effect of EGTA. L-2,4-Diaminobutyric acid, an inhibitor of the Na+-dependent GABA carrier, did not affect the releasing action of EGTA, whereas in a parallel experiment this drug inhibited by more than 90% the exchange of labeled GABA with unlabeled GABA.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1983

Sequence analysis of two mutants of Sindbis virus defective in the intracellular transport of their glycoproteins.

We have sequenced the complementary DNA corresponding to the genes encoding the viral glycoproteins of ts10 and ts23, mutants of Sindbis virus defective in the intracellular transport of their glycoproteins, and of revertants of these mutants. These studies have been augmented by direct amino acid sequencing of the amino-terminal regions of the glycoproteins of several virus strains. By comparing the deduced amino acid sequence with that of Sindbis HR virus, the parental strain of these mutants, and with the sequence of the revertants, we found ts23 to have a double mutation in glycoprotein E1, while ts10 was a single mutant in the same glycoprotein. In each case reversion to temperature insensitivity occurred by changes at the same site as the mutation, in two cases restoring the original amino acid and in the third case substituting an homologous amino acid (arginine in place of lysine). The three mutations were far apart from each other in the protein, suggesting that the three-dimensional conformation is very important for the correct migration of the glycoproteins from the rough endoplasmic reticulum to the plasma membrane. The sequence data also reveal that a number of other changes have occurred in the various virus strains during mutagenesis or passage.

Amino Acid Sequence↗
PubMed1982

Selective stimulation of neurotransmitter release from chick retina by kainic and glutamic acids.

The excitatory action of kainic and glutamic acids in chick whole retina was demonstrated as an immediate stimulation of the release of labeled gamma-aminobutyric acid (GABA) and glycine in a superfusion system. This stimulatory effect was 3-10 times greater than that produced by a depolarizing K+ concentration; in addition, it was independent of Ca2+ in the medium, but notably inhibited when Na+ was omitted from the medium. Under identical experimental conditions, neither kainic nor glutamic acid had any effect on the release of labeled dopamine or alpha-aminoisobutyric acid, thus indicating that their effect is not unspecific or due to cell damage. Similar although less marked stimulation of labeled GABA and glycine release by kainic acid was obtained in subcellular retinal fractions, particularly in fraction P1, which contained photoreceptor terminals and outer segments. This stimulation was also Ca2+ independent and greatly reduced when Na+ was omitted from the medium. It is suggested that the stimulation of GABA release by kainic and glutamic acids is probably due to a Na+-dependent, carrier-mediated mechanism that responds to the entry of Na+ produced by the interaction of glutamic and kainic acids with retinal membranes. In cortical or striatal slices from mouse brain, these acids had a negligible stimulatory effect on GABA and dopamine release.

Animals↗
PubMed1981

Structural polypeptides of simian rotavirus SA11 and the effect of trypsin.

Analysis of purified simian rotavirus has shown that it contains fewer structural polypeptide classes than previously reported. Two polypeptides (molecular weights, 62,000 and 28,000) commonly found in purified rotaviruses were, in fact, produced by cleavage of a larger structural polypeptide (molecular weight, about 88,000) by trypsin, which is usually employed to increase the yield of rotaviruses in tissue culture. Trypsin-uncleaved, double-shelled rotaviruses are probably composed of only five polypeptide classes; three in the inner layer, and two in the outer layer.

Electrophoresis, Polyacrylamide Gel↗
PubMedDate not supplied

Changes in the flow properties of phospholipid dispersions induced by procaine hydrochloride. Effect of pH and temperature.

Since local anaesthetics are known to interact with membrane lipids, we have examined the changes taken place by procaine hydrochloride in lipid matrices as a function of pH. Rheological methods might give useful information on the association of this anaesthetic with soybean lecithin. The procaine interacted with negatively charged phospholipid polar head groups at pH 4. This system exhibits a loosening in the tight arrangement of phospholipid molecules caused by the addition of procaine as a function of this anaesthetic's concentration. The flow enthalpy values as a function of procaine-lipid ratio shows biphasic behaviour and suggests a phase transition when the anaesthetic concentration goes from 10 to 14 mM and temperatures dip below 10 degrees C.

Chemical Phenomena↗
PubMedDate not supplied

Mucopolysaccharides in aqueous solutions: effect of ionic strength on titration curves.

We study the changes taking place in hyaluronic acid, chondroitin 4-sulfate (C4-S) and condroitin 6-sulfate (C6-S), at ionic strengths of 0.10, 0.15, and 0.20 in NaCl, in a neutralization process in aqueous solution. We apply the equation of Henderson Hasselbalch modified for polyelectrolytes and evaluate the changes in the electrostatic free energy starting from the pK curves as a function of the dissociation degree. For a dissociation degree next to 0.4 corresponding to the -COOH group of the hyaluronic acid, we observed a change in the conformation of the three glycosaminoglycans studied. This conformational change takes place as a consequence of the break of intramolecular links and the beginning of the ionization process. The macromolecules in solution show a structure of random coil sufficiently expanded so that the interaction among the close ionizable groups is negligible.

Algorithms↗
PubMedDate not supplied

Follow-up study in head and neck cancer: cure rate according to tumor location and stage.

The purpose of this clinical study was to analyze a long-term follow-up of all the patients with head and neck cancer in our institution. Between 1973 and 1993, 1,355 consecutive cases of head and neck cancerwere diagnosed, treated and followed up regularly. All were subjected to a multidisciplinary approach, and followed up until death or for 10 years with no event of disease. The local relapse rate was 20% and the node-regional relapse rate 15%. Distant metastases were observed in 6% of the patients mainly arising from the nasopharynx (23%) followed by the hypopharynx (11%). The main organ involved was the lung (50%). Median follow-up of the group was 10 years (range 4 months to 15 years). Cancer cure was observed after 5 years in glottic and supraglottic laryngeal carcinoma, oral and nasopharyngeal cancer and after 2.5 years in patients with cancer of the oropharynx and hypopharynx. The highest cure rate was 80% in the glottis, followed by 70% in the supraglottic area, 45% in the mouth, 30% in the nasopharynx, 25% in the oropharynx, and 20% in the hypopharynx. A second primary tumor was observed in 7% of the patients and a third primary in 0.6% of the patients. Only in 7 patients, the second or third primary was seen after 5 years of follow-up. Curability should be observed after 5 years from definitive therapy of glottic, supraglottic, oral and nasopharyngeal and earlier in oropharyngeal and hypopharyngeal cancer. Further follow-up should be discontinued. Second and third neoplasias are the main problems after 5 years of follow-up but their incidence is low.

Adult↗
PubMedDate not supplied

Radiotherapy in the maxillary hemangioma.

We present the case of a large maxillary hemangioma treated by radiotherapy. Only 4 cases managed by radiotherapy have been reported in the literature, and most authors negate the radiosensitivity of the tumor. In our patient, the outcome was excellent; by 6 months tumor reduction was more than 50%. This is the first case referred to in the literature whose radiotherapy response was evaluated by magnetic resonance imaging. We describe the clinical and imaging findings of this very rare tumor and its evolution. We also comment on the literature reviewed.

Adult↗