PubMed Health⌕ Search

Biomedical subjects

M Ramírez

Publications and source records attributed to M Ramírez.

At least 127 records · Page 7Linked to original sources
PubMed1990

Mn2(+)-activated aspartate aminopeptidase activity, subcellular localization in young and adult rat brain.

The levels of soluble and membrane-bound aminopeptidase activities were assayed in subcellular fractions from young (4 weeks old) and adult (20 weeks old) rat brains, using Asp-2-naphthylamide as substrate. The young rats showed the highest soluble and membrane-bound levels of activity in the microsomal fraction but no differences among fractions were found at 20 weeks of age. The membrane-bound activity was significantly higher than the soluble one in all subcellular fractions of young rats. Soluble activity of the homogenate and the mitochondrial fraction was significantly increased in adult animals when compared to that of younger ones.

Aging↗
PubMed1990

Soluble and membrane-bound leucyl- and arginyl-aminopeptidase activities in subcellular fractions of young and adult rat brains.

The subcellular distribution of soluble and membrane-bound leucyl- and arginyl-aminopeptidase activities were analyzed in one and five month old rat brains using Leu- and Arg-2-naphthylamide as substrates. Both soluble leucyl- and arginyl-aminopeptidase activities showed the highest levels in the synaptosomal fraction in the two groups of rats. The highest levels of membrane-bound leucyl- and arginyl-aminopeptidase activities were found in the microsomal fraction in the two ages studied. There were no differences between the two ages in soluble leucyl- and arginyl-aminopeptidase activities. However, a significant decrease in both membrane-bound enzymatic activities was evidenced in the synaptosomal fraction of older rats. Developmental changes of these aminopeptidase activities in a determined subcellular localization, may reflect modifications in their effect on neuropeptides susceptible to be hydrolyzed in this particular location.

Aminopeptidases↗
PubMed1989

The major yeast exoglucanase: an extracellular glycoprotein lacking the carbohydrate outer chain.

The major exoglucanase (1,3-beta-D-glucan glucanohydrolase, EC 3.2.1.39) secreted by Saccharomyces cerevisiae contains protein, mannose and phosphate in a molar ratio of 1:27:1. When digested with endo-beta-N-acetylglucosaminidase H (EC 3.2.1.96) it sequentially released two asparagine-linked oligosaccharide chains. Oligosaccharides were fractionated into a neutral and acidic component, each one accounting for 50% of the total carbohydrate. The neutral oligosaccharide consisted of a mixture of three homologues ranging from GlcNAc-(Man)12 to GlcNAc-(Man)14. The acidic carbohydrate was, in turn, split into two components. The major one (45% of the initial material) contained a phosphodiester bond and released only mannose when subjected to mild acid hydrolysis. From the filtration pattern, it was shown to be a mixture of oligosaccharides ranging from GlcNAc-(Man)11-P to GlcNAC-(Man)13-P. The minor phosphorylated component, which represented the residual carbohydrate (5%), contained a phosphomonoester bond. It was also heterogeneous in size, the several homologues having one mannose less than their counterparts from the phosphodiester oligosaccharide. These results clearly indicate that the addition of an outer chain of carbohydrate is not a requirement for the externalization of yeast glycoproteins.

Carbohydrates↗
PubMed1989

A similar protein portion for two exoglucanases secreted by Saccharomyces cerevisiae.

Exoglucanase (exo-1,3-beta-D-glucan glycohydrolase, EC 3.2.1.56) activity secreted by Saccharomyces cerevisiae into the culture medium was separated by ion exchange chromatography into two glycoprotein isoenzymes which contributed 10% (exoglucanase I) and 90% (exoglucanase II) towards the total activity. Analysis of the "in vitro" deglycosylated products by polyacrylamide gel electrophoresis under native or denaturing conditions indicated that the protein portions of both exoglucanases exhibited identical mobility, each one consisting of two polypeptides with Mr of 47,000 and 48,000. The same profile was shown by the exoglucanase secreted in the presence of tunicamycin. Antibodies raised against the protein portion of exoglucanase II did react with both native exoglucanases and their deglycosylated products with a pattern indicative of immunological identity. Digestion of the "in vitro" deglycosylated products of both exoglucanases with Staphylococcus aureus V-8 protease or trypsin generated the same proteolytic fragments in each case. Only exoglucanase II was secreted by protoplasts. These and previously reported results indicate that the protein portions of both isoenzymes may be the product of the same gene (or a family of related genes), and that exoglucanase I is a product of enzyme II, modified by a process occurring beyond the permeability barrier of the cell.

Chromatography, Gel↗
PubMed1989

Postnatal development of aminopeptidase (arylamidase) activity in rat brain.

Changes in the activities of Leu- and Arg-arylamidase in rat frontal and parietal cortices and the subcortical area (including thalamus, hypothalamus, and striatum) were examined in the 2nd, 4th, 8th, 12th, and 24th weeks of life. Average levels found in the subcortical region were greater than those in the cortical areas. The most marked changes in enzymatic activity in the course of brain development were found in the subcortical structure. Leu-arylamidase activity increased from the 2nd week up to the 8th week, returning to the 2nd week level at the 12th and 24th weeks. The maximum levels of Arg-arylamidase activity were found at the 4th and 8th weeks. These data suggest that proteolytic activity is involved in the postnatal development of rat brain.

Aminopeptidases↗
PubMed1989

Lys- and Tyr-arylamidase activities in serum and brain during the estrous cycle of the rat.

Peptidase enzymes are involved in neuropeptide processing or degradation. In order to analyse a possible functional participation of these enzymes, arylamidase activity of several rat brain regions and serum was assayed in the soluble fraction during the estrous cycle using L-Lys- and L-Tyr-beta-naphthylamide as substrates. Significant differences were present in the hypothalamus, the pituitary and serum when both substrates were used. However, there were no differences in cortical areas. These results suggest a role for arylamidase activity in the hormonal changes that happen during the estrous cycle of the rat.

Aminopeptidases↗
PubMed1989

[Aging and cerebral aminopeptidase activity].

A comparative study of brain aminopeptidase activity between 18 month old male rats and young adults of 3 months has been carried out utilizing the arylamides Leu-, Arg-, Lys-, Tyr- and Asp-beta-naphthylamide as substrates. Statistical analysis of results showed no significant differences either in areas studied or for enzymatic activities detected when both ages were compared. Two different patterns of regional distribution of enzymatic activity were observed: One came to be as a result of the use of Lys-, Arg-, Leu- or Tyr-beta-naphthylamide and the other as a result of the use of Asp-beta-naphthylamide.

Aging↗
PubMed1988

Two ionic forms of exoglucanase in yeast secretory mutants.

Analysis of exoglucanase activity accumulated by sec mutants from Saccharomyces cerevisiae revealed the presence of two ionic forms of the major exoglucanase (exo II) secreted into the culture medium. From the accumulation pattern of representative sec mutants and the carbohydrate composition it appears that the less acidic form is converted into the more acidic one by addition of one phosphate to one of the oligosaccharide cores as the enzyme progresses through the secretory pathway. Exoglucanase I, the heavier isoenzyme, was not accumulated by the mutants. Accordingly, it should arise from exoglucanase II after the execution point of sec1 mutation.

Glucan 1,3-beta-Glucosidase↗
PubMed1988

IgE pyroglobulinemia in multiple myeloma.

A new case of IgE/K myeloma in a 38-year-old male is described. The clinical course, bone marrow picture and serum electrophoretic pattern were typical of multiple myeloma. Heating of the serum at 56 degrees C induced an irreversible gel formation or pyroglobulin that was isolated and proved to be identical to the IgE paraprotein, by biochemical and immunochemical methods. The thermoprecipitability was abolished by treatment with urea, sodium dodecyl sulphate and neutral salts and not inhibited by sugars, alcohols, 2-beta-mercaptoethanol and guanidine HCl. The association of an IgE myeloma protein with a pyroglobulin is a finding not previously reported in a myeloma of this class.

Adult↗
PubMed1987

Purification of two exoglucanases secreted by Saccharomyces cerevisiae and partial characterization of their protein moieties.

Growth of Saccharomyces cerevisiae cells in a synthetic buffered culture medium resulted in the secretion of high levels of two soluble exoglucanases which were purified by a procedure involving one (exglucanase II) and two (exoglucanase I) steps, respectively. Once treated with endoglucosaminidase H (Endo H) both enzymes behaved indistinguishably when analyzed by SDS-PAGE, high pressure liquid chromatography (HPLC) and ionic exchange chromatography. Exoglucanase I, the isoenzyme with higher carbohydrate content, exhibited a higher Km against laminarin and a higher thermal stability than exoglucanase II. However, once the enzymes were deglycosylated in vitro these parameters turned out to be identical. These results suggest that both exoglucanases share a very similar, if not identical protein portion and accordingly may be product of either the same gene or a family of related genes.

Glucan 1,3-beta-Glucosidase↗
PubMed1986

Accumulation of exoglucanase activity in yeast secretory mutants blocked at the endoplasmic reticulum level.

Saccharomyces cerevisiae HMSF-176 (sec 18), a thermosensitive secretory mutant blocked at the endoplasmic reticulum (ER) level, drastically increased its osmotic sensitivity when grown at the restrictive temperature of 37 degrees C in high glucose concentration. This fact led to the erroneous interpretation that glucanases were inactive when localized in the ER. The development of a suitable osmotic stabilizer now indicates that sec 18 accumulates exoglucanase activity. Another ER-blocked mutant behaved in a similar way. All the accumulated exoglucanase was found in a soluble form. By contrast, a significant portion of the accumulated invertase remained in a membrane-bound form.

Endoplasmic Reticulum↗
PubMed1986

Accumulation and secretion of exoglucanase activity in yeast secretory mutants.

Representative conditional yeast secretory mutants, blocked in transport of secretory and plasma membrane proteins from the endoplasmic reticulum (sec 18), from the Golgi body (sec 7) and in transport of secretory vesicles (sec 1), accumulated exoglucanase, a constitutive yeast activity, when incubated at the restrictive temperature (37 degrees C). Different proportions of the accumulated activity were released by mutant cells under permissive conditions. The presence or absence of cycloheximide during the secretion period made no differences in the results. More than 90% of the internal activity was bound to membrane in wild type cells. However, only the soluble pool underwent changes during the accumulation or secretion periods. The bulk of secretory invertase accumulated by sec 1 was also soluble. By contrast sec 7 and sec 18 accumulated membrane-bound as well as soluble invertase forms and both were secreted in similar proportions in each mutant. More than 90% of the accumulated invertase was secreted at the permissive temperature in sec 18 cells. That percentage was significantly lower for exoglucanase (less than 65%). Concomitantly, invertase accumulated by this mutant exited from the cells with a lower half time (t1/2 = 24 min) than accumulated exoglucanase (t1/2 = 150 min). These results may be interpreted assuming that exoglucanase is exported by a passive flow of the soluble pool.

Cycloheximide↗
PubMed1984

An unusual case of Waldenström macroglobulinemia with half molecules of IgG in serum and urine.

Immunochemical studies are described in an unusual case of Waldenström's macroglobulinemia. Two monoclonal Igs (whole IgG1/kappa and IgG1/kappa half molecules) occurred in the serum in addition to the IgM monoclonal protein. Protein electrophoresis of the serum showed a monoclonal component in the gamma region, and the immunoelectrophoresis allowed detection of a monoclonal IgM/kappa and another abnormality represented by a double precipitin line in serum and urine, observed when antiserum anti IgG was used. The abnormal proteins were purified and further analyzed. The IgG-related proteins were whole four chains IgG monoclonal molecules, 1/2 IgG monoclonal molecules, composed of one heavy and one light chain, and residual polyclonal IgG. The half molecules were antigenically deficient with respect to normal IgG. The idiotypic analysis showed that the three monoclonal proteins shared idiotypic determinants. This patient had clinical and morphological findings of Waldenström's macroglobulinemia and, as observed in other cases, the formation of half molecules was not associated with a distinct clinical syndrome.

Blood Protein Electrophoresis↗
PubMed1984

Two cases of alpha heavy chain disease in Venezuelans.

Two cases of alpha chain disease are described. The clinicopathological features of the two patients were very similar, and similar to the numerous cases described in the literature, presenting the gastrointestinal form of the disease. In both patients the pathological protein was not noticeable in the electrophoretic pattern. The diagnosis was established by immunoselection with electrophoresis. The alpha-HCD proteins belonged to the alpha 1 subclass and in no case was it found in the urine. The patients were young Venezuelan mestizos and seem to be the first cases reported in Venezuela.

Adult↗