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Biomedical subjects

E García

Publications and source records attributed to E García.

At least 199 records · Page 11Linked to original sources
PubMed1991

Potassium current kinetics in bursting secretory neurons: effects of intracellular calcium.

1. The kinetics of delayed rectifier (IK) and transient potassium (IA) currents and their modification by intracellular calcium ions in bursting X-organ neurons of the crayfish were studied with whole-cell patch-clamp technique. Activation and inactivation kinetics were analyzed according to Hodgkin and Huxley-type equations. 2. IK activates with sigmoidal time course at membrane potentials more positive than -38.4 +/- 3.5 (SD) mV (n = 5), and does not inactivate. The conductance through delayed rectifier channels (gK) is described by the equation gK = GKn2. 3. IA activates at membrane potentials close to the resting potential (-52.2 +/- 4.3 mV, n = 5) and, after a peak, inactivates completely. The conductance through A-channels (gA) can be described by the product of independent activation and inactivation parameters: gA = GAa4b. Both activation and inactivation processes are voltage and time dependent. 4. Steady-state activation of IK and IA as well as inactivation of IA can be described by Boltzmann distributions for single particles with valencies of 2.55 +/- 0.01 (n = 5), 1.60 +/- 0.25 (n = 5), and 3.87 +/- 0.39 (n = 3), respectively. 5. Increasing [Ca2+]i, we observed the following: 1) a considerable inactivation of IK during test pulses, 2) an increase of maximal conductance for IA, 3) a reduction of the valency of IA inactivation gating particle (from 3.87 to 2.27), 4) a reduction of the inactivation time constants of IA, and 5) a shift of the inactivation steady-state curve to more positive membrane potentials.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effect of different MCT/LCT ratios on protein synthesis in injured rats fed parenterally.

The effect of the lipidic composition of the diet on the proteic synthesis of the male Sprague-Dawley rats fed parenterally for four days has been studied. All animals received identical nitrogen and caloric intake, but the ratio of medium to long-chain triglycerides (MCT/LCT) varied: group 1, control (0/100); group 2 (30/70); group 3 (50/50) and group 4 (70/30). Hepatic and jejunal protein synthesis were determined with L-(1-14C)-leucine. In groups 1, 3 and 4 muscle protein synthesis was measured with L-(3,4-3H)-phenylalanine. In liver, there were no significant differences in the fractional synthesis rate among the groups. In jejunum, the control group showed a higher fractional synthesis rate with statistically significant differences among the groups. In muscle, group 3 presented the highest fractional synthesis rate with statistically significant differences (p less than 0.05).

Animals↗
PubMed1991

[Adult celiac disease and hepatopathy].

A retrospective study was performed in order to evaluate the prevalence of significant hepatic disease in patients with coeliac disease and its outcome after a gluten-free diet. Out of 46 patients with coeliac disease, 28 (60.87%) presented abnormal liver function test. These tests were normal after a gluten-free diet in 20 patients; one patient presented an acute B-virus hepatitis and in the remaining 7 patients a chronic liver disease was diagnosed (2 chronic persistent hepatitis, 1 chronic active hepatitis, 1 steatosis, 2 cirrhosis and 1 primary biliary cirrhosis). In conclusion, the high prevalence of significant hepatic disease in our patients with coeliac disease (15%) suggests an association between both disorders. Gluten-free diet does not modify the course of hepatic disease.

Adolescent↗
PubMed1990

Cloning and expression of gene fragments encoding the choline-binding domain of pneumococcal murein hydrolases.

The cloning in Escherichia coli of the 3' moieties of the lytA and cpl-1 genes is described, coding for the C-terminal regions of the lytic amidase of Streptococcus pneumoniae and the phage Cp-1 lysozyme, respectively. The truncated genes were overexpressed in E. coli and the purified polypeptides showed a great affinity for choline, although they were devoid of cell wall-degrading activity. Biochemical and circular dichroism analyses indicated that these are the domains responsible for the specific recognition of the choline-containing pneumococcal cell walls by the lytic enzymes. The data presented here suggested that these choline-binding domains can function independently of their catalytic domains.

Amidohydrolases↗
PubMed1990

Modular organization of the lytic enzymes of Streptococcus pneumoniae and its bacteriophages.

The nucleotide sequences of genes cpl7 and cpl9 of the Streptococcus pneumoniae bacteriophages Cp-7 and Cp-9, encoding the muramidases CPL-7 and CPL-9, respectively, have been determined. The N-terminal domains of CPL-7 and CPL-9 were virtually identical to that previously reported for the CPL-1 muramidase. The C-terminal domain of the CPL-7 muramidase, however, was different from those of the host amidase and the phage Cp-1 and Cp-9 lysozymes. Whereas all enzymes studied are characterized by repeated sequences at their C termini, the repeat-unit lengths are 20 amino acids (aa) in CPL-1, CPL-9 and in the host amidase, but 48 aa in CPL-7. Six repeated sequences represent the C-terminal domains of CPL-1, CPL-9 and the host amidase, and 2.8 perfect tandem repetitions that of CPL-7. The peculiar characteristics of the structure of CPL-7 muramidase correlate with its biochemical and biological properties. Whereas CPL-1, CPL-9 and the pneumococcal amidase strictly depend on the presence of choline-containing cell walls for activity, CPL-7 is able to degrade cell walls containing either choline or ethanolamine. These results support the previously postulated role for the C-terminal domain of these lytic enzymes in substrate recognition and provide further experimental evidence supporting the notion that the proteins have evolved by an exchange of modular units.

Amino Acid Sequence↗
PubMed1990

Mutagenic evaluation of some triazino indoles using the Salmonella/mammalian microsome assay.

The mutagenicity of ethyl 1,2,3-triazino[5,4-b]indole-4-carboxylate N(3)-oxide (D3) and 2-chloroethyl 1,2,3-triazino-[5,4-b]indole-4-carboxylate N(3)-oxide (D4), heads of series of new products with considerable platelet antiaggregating and hypotensive activity, and their precursors 2-ethoxy-carbonylmethyl-1-methylindole-3-carboxylic acid (A3) and 2-(2-chloroethoxycarbonylmethyl)-1-methylindole-3-carboxylic acid (A4) were tested in four strains of Salmonella typhimurium (TA98, TA100, TA97 and TA102) using the standard plate incorporation technique. A3 and A4 were not mutagenic whereas D3 was mutagenic to all the strains and D4 was mutagenic to TA97, TA98 and TA100. The addition of 4 or 10% of S9 mix decreased the mutagenic activity of both compounds. This effect was independent of the concentration of S9 in the S9 mix.

Animals↗
PubMed1990

Influence of fat emulsions in parenteral nutrition on visceral protein synthesis: study in hepatectomized rats.

The aim of this study was to evaluate the effect of total parenteral nutrition (TPN) with 100% long-chain triglyceride (LCT) (group A) and 50/50% medium/long-chain triglyceride (MCT/LCT) (group B) fat emulsions on visceral protein synthesis in 70% hepatectomized rats. The rats were fed TPN continuously for 7 days posthepatectomy. Protein synthesis was measured in the liver and jejunal mucosa with the flooding dose method. All rats received the same caloric and nitrogen intake, without statistically significant differences. The only difference between the two groups was the proportion of MCT to LCT in the diets. Hepatic and jejunal mucosa protein synthesis were significantly higher in group B, fed 50/50% MCT/LCT. These results suggest that fat emulsions with 50/50% MCT/LCT significantly enhance visceral protein synthesis after partial hepatectomy.

Animals↗
PubMed1989

Purification and characterization of the autolytic glycosidase of Streptococcus pneumoniae.

A new lytic enzyme isolated from Streptococcus pneumoniae has been purified to electrophoretical homogeneity. The enzyme, showing a Mr of 64000, has been characterized as an endo-beta-1,4-N-acetylglucosaminidase that requires choline in the teichoic acid of the cell wall substrate for catalytic activity. In vivo experiments demonstrate that the glucosaminidase behaves as an autolytic enzyme.

Acetylglucosaminidase↗
PubMed1989

Subcellular localization of the major pneumococcal autolysin: a peculiar mechanism of secretion in Escherichia coli.

The major pneumococcal autolysin (N-acetylmuramoyl-L-alanine amidase) has been localized in the cellular envelope of Streptococcus pneumoniae and Escherichia coli by using immunocytochemical labeling on ultrathin sections and whole-mounted cells. Cell fractionation experiments in E. coli confirmed the peripheral localization of the pneumococcal amidase and suggested that this enzyme is weakly bound to the outer face of the cytoplasmic membrane. This interaction does not depend on the presence of choline but represents an intrinsic property of the amidase. The autolysin, that is synthesized without any N-terminal signal sequence (García, P., García, J. L., García, E., and López, R. (1986) Gene (Amst.) 43, 265-272) was not processed during translocation. A new regulatory mechanism that might be specific for bacterial autolysins is discussed.

Amidohydrolases↗
PubMed1989

Intracranial cavernous angioma in the dura.

Cavernous malformations located in the dura are rare. We present a case of a large cavernous malformation located in the anterior fossa and implanted in the dura of a pregnant woman. It showed great vascularization on an angiogram, and resembled a meningioma on computed tomographic scan. The operation was difficult because of the tumor's great vascularity and profuse bleeding.

Adult↗
PubMed1988

Sex-related severity of inflammation in parenchymal brain cysticercosis.

To determine sex-related differences in the severity of host inflammatory reaction to cysticercosis, we studied computed tomographic findings in 100 patients with parenchymal neurocysticercosis and cerebrospinal fluid results in 239 patients with subarachnoid neurocysticercosis. Computed tomographic and cerebrospinal fluid data in male subjects were compared with those obtained in female subjects. We found that when cysticerci are found in brain parenchyma, women develop a greater degree of inflammation; such differences disappear when cysticerci are found in the subarachnoid space. Our results point out the possibility of a factor located within brain parenchyma that accounts for the observed sex-related differences in the severity of immune response to the parasite; this factor could also play a role in the pathogenesis of other immunologically mediated diseases of the brain that may occur more frequently in women. To our knowledge, this study is the first in demonstrating that sex is a risk factor for the severity of inflammatory response within brain parenchyma to a parasitic disease.

Cysticercosis↗
PubMed1988

Unique HLA-DR/DQ associations revealed by family studies in Warao Amerindians. Haplotype and homozygosity frequencies.

HLA-A, Cw, B and A, Cw, B, DR genotypes have been assigned, respectively, to 318 and 175 Warao Amerindians belonging to 73 sibships, who were tested with International Histocompatibility Workshop reagents. Only 33% of the theoretically possible three-loci and 7% of the possible four-loci haplotypes were found, with 10 and 6 of them accounting, respectively, for 75% of the total observed. This limited haplotype variability, expected in an inbred population, was not accompanied by either an increased or a decreased frequency of homozygous individuals, as demonstrated by population and family analysis. Inheritance of five HLA loci haplotypes in 20 families showed the expected distribution of parental haplotypes in sibling pairs. The study revealed DR2sh (DRw16), DR4 and DRw6 in association with DQw7, and DRw8 with DQw4, and significant positive linkage disequilibria between Bw62 CW1, B51 DRw16, B39 DR4, Bw62 DRw6, and DRw8 DQw4. The DR2-DQw7 and DRw6-DQw7 associations and the first three paired loci disequilibria mentioned are described for the first time in Amerindians and have not yet been found among Japanese, Negroid, or Caucasoid populations.

Gene Frequency↗
PubMed1988

Molecular evolution of lytic enzymes of Streptococcus pneumoniae and its bacteriophages.

A 2.9-kilobase Acc I fragment of the DNA of the pneumococcal bacteriophage Cp-1, containing the cpl gene, hybridizes with the lytA gene encoding the pneumococcal amidase. The nucleotide sequence of the cpl gene of Cp-1, encoding a muramidase (CPL), has been determined. The 3' regions of the cpl and lytA coding sequences show considerable nucleotide sequence homology and the carboxyl-terminal domains of the deduced amino acid sequences of these lysins are quite similar: 73 of the carboxyl-terminal 142 amino acid residues are identical, and of the 69 substitutions, 55 are conservative. Comparisons between CPL, the pneumococcal amidase, and the muramidase of the fungus Chalaropsis sp. (an enzyme that also degrades the pneumococcal cell wall) strongly suggest that the carboxyl-terminal domains of CPL and of the amidase might be responsible for the specific recognition of choline-containing cell walls, as well as for the noncompetitive inhibition of the catalytic activity of these enzymes by the pneumococcal lipoteichoic acid or by high concentrations of choline. In addition, the active center of these enzymes should be located in their amino-terminal domains. Our results suggest an evolutionary relationship between phage and host lysins.

Amidohydrolases↗