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Biomedical subjects

M Ramírez

Publications and source records attributed to M Ramírez.

At least 109 records · Page 6Linked to original sources
PubMed1995

Unusual cases of hyperparathyroidism.

The history, physical and radiologic findings, treatment and pathology in five unusual cases of hyperparathyroidism is presented. The hyperparathyroidism was caused by a large (113 grams) mediastinal adenoma in the first patient, who is alive 25 years after surgery. A parathyroid carcinoma with compression of the esophagus was documented in the second patient. This patient is alive and normocalcemic 23 years after surgical treatment. A third patient with hyperplasia returned with hypercalcemia 20 years postsurgery requiring reoperation. A fourth patient with advanced bone findings was found to have a parathyroid adenoma. The fifth case is a patient with tertiary hyperparathyroidism secondary to hypophosphatemic rickets.

Adenoma↗
PubMed1995

Subcellular distribution of soluble and membrane-bound Arg-beta-naphthylamide hydrolyzing activities in the developing and aged rat brain.

The subcellular distribution of soluble and membrane-bound Arg-beta-naphthylamide-hydrolyzing activities was studied in the left and right rat brain during development and aging. During development, the soluble activity was heterogeneous, whereas adult animals showed the highest activity in the synaptosomal fraction. However, except in fetuses, membrane-bound activity was greatest in the microsomal fraction. Except in microsomal and myelin fractions, soluble and membrane-bound activities showed a decrease in 1-wk-old rats compared with fetuses and a subsequent increase to adult levels in 1-mo-old rats. This profile differed in the microsomal fraction, which increased steadily throughout development. In the synaptosomal fraction, both activities were lower in 24-mo-old rats than in 5-mo-old animals. No differences between the hemispheres were observed in soluble or membrane-bound fractions at any age tested.

Aging↗
PubMed1994

Multistep carcinogenesis and genital papillomavirus infection. Implications for diagnosis and vaccines.

Activated cellular oncogenes (myc and ras, for example) and inactivated anti-oncogenes (p53 or Rb) participate in multistep carcinogenesis. In addition, some high risk human papillomaviruses (HPV) are also involved in uterine cervix carcinomas. Typification of HPV is important for clinical diagnosis. Unravelling the complexities of the immune system and understanding the biochemistry and molecular genetics of cellular oncogenes and tumor viruses have opened up new possibilities for vaccination.

Cocarcinogenesis↗
PubMed1993

Developmental and ageing changes in aminopeptidase activities in selected tissues of the rat.

Aminopeptidase activities, assayed as arylamidase activities, were investigated in selected tissues of 1, 6, 12 and 24-month-old rats. The enzyme activities were found to have a heterogeneous distribution and age-related changes were observed. The highest levels of soluble arginyl-aminopeptidase activity were detected in brain homogenate at all the studied ages, whereas membrane-bound activity presented the highest levels in brain and kidney in the four ages tested. Aspartyl-aminopeptidase activity was detected mainly in the particulate fraction of kidney at all four ages. In 1, 6 and 12-month-old animals, soluble aspartyl-aminopeptidase activity was also higher in the kidney than in the rest of the tissues, whereas in the group of 2-year-old rats, the highest levels were found in both kidney and liver. Age-related changes were observed in all the studied tissues and for all the assayed enzymatic activities. In general, the maximal levels were detected in both the youngest and the oldest animals, and the minimal ones in 6 and 12-month-old rats. However, in the adrenals, the soluble and membrane-bound arginyl-aminopeptidase activity was higher in 6-month and 2-year-old rats than in 1-month and 12-month-old rats. These changes may reflect the functional status of the susceptible endogenous substrates of aminopeptidases.

Aging↗
PubMed1993

Relationship between oxygen consumption and oxygen delivery during anesthesia in high-risk surgical patients.

OBJECTIVE: To identify critical oxygen delivery (DO2) and oxygen extraction ratio in high-risk surgical patients studied preoperatively and intraoperatively. DESIGN: Prospective study. Consecutive series of intraoperatively monitored patients. SETTING: The surgical ICU in a tertiary care center. PATIENTS: High-risk surgical patients undergoing major noncardiac surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Twenty high-risk patients were studied during the preoperative and intraoperative periods. All patients were monitored with triple-lumen thermodilution catheters. Hemodynamic profiles consisted of determinations of intravascular pressures, cardiac output, and arterial and venous pulmonary gases. Oxygen transport variables were calculated by standard formulas. Multiple determinations were carried out during the perioperative period in each patient. The critical levels of DO2, determined by a polynomial regression method, were 375 and 390 mL/min/m2 in the preoperative and intraoperative periods, respectively. Oxygen extraction reached at the critical level of DO2 was significantly (p < .01) lower during the intraoperative period (31 +/- 4.5% vs. 18 +/- 2.3%). Critical mixed venous oxygen tension was significantly (p < .01) higher in the intraoperative period (36 +/- 5 vs. 46 +/- 4 torr [4.8 +/- 0.7 vs. 6.1 +/- 0.5 kPa]). CONCLUSIONS: Our data show that the intraoperative period might be associated with a reduction in tissue ability to extract oxygen. If this reduction in oxygen extraction is proportionately higher than the reduction in metabolic oxygen demand produced by anesthetic agents and hypothermia, then the critical value for DO2 may be similar to, or higher than, that value in the preoperative period. Thus, the intraoperative period represents, for this patient population, a high-risk condition for the development of a tissue oxygenation debt in the presence of a limitation in DO2. Cautious dosing of inhaled agents, maintenance of normothermia, and early optimization of the oxygen delivery/oxygen consumption relationship seem to constitute reasonable measures in the intraoperative handling of these patients in order to reduce perioperative morbidity and mortality.

Adult↗
PubMed1992

Neutralization of myotoxic phospholipases A2 from the venom of the snake Bothrops asper by monoclonal antibodies.

The neutralization of two myotoxic phospholipases A2 from the venom of Bothrops asper, myotoxins I and II, by two murine monoclonal antibodies is reported. The monoclonal antibodies, MAb-3 and Mab-4, recognize different epitopes of the toxin. Both antibodies completely neutralized myotoxic activity of myotoxin I and crude venom. MAb-3 also completely neutralized myotoxic activity of myotoxin II, a lysine-49 phospholipase A2 isoform, whereas MAb-4 neutralized this toxin only partially. MAb-3 neutralized myotoxin II at a molar ratio of 1:1, showing a higher efficiency than affinity-purified polyclonal antibodies. A dissociation of myotoxic and enzymatic activities of myotoxin I was observed with both monoclonal antibodies.

Animals↗
PubMed1992

Plasma polyunsaturated fatty acid pattern in active inflammatory bowel disease.

Plasma fatty acid patterns were assessed by gas liquid chromatography in 73 patients with active inflammatory bowel disease and 107 healthy controls. The influence of the disease activity on fatty acid profile was also investigated. Plasma fatty acid patterns in patients with ulcerative colitis and Crohn's disease were similar. Plasma C18:3n3 and C22:6n3 were significantly higher in active ulcerative colitis (p = 0.0143 and p < 0.00001 respectively) and in Crohn's disease (p < 0.00001 for both) than in controls, whereas C20:3n6 was significantly lower in patients than in controls, both in ulcerative colitis (p = 0.0001) and in Crohn's disease (p = 0.0041). In more severe disease, plasma polyunsaturated fatty acid concentrations fell with a significant stepwise decrease in the desaturation index (p = 0.0031 in ulcerative colitis and p = 0.0355 in Crohn's disease). Even in patients with severe disease, however, plasma n3 fatty acids (C18:3n3 and C22:6n3) never fell below those of healthy controls. These findings suggest that in active inflammatory bowel disease, an increased biosynthesis might coexist with an increased consumption of polyunsaturated fatty acids. These observations may be of relevance in the pathogenesis of the disease as polyunsaturated fatty acids are involved in tissue eicosanoid synthesis and cellular membrane function, including that of immunocompetent cells. These results also question the rationale of using n3 polyunsaturated fatty acids in the treatment of inflammatory bowel disease.

Adolescent↗
PubMed1992

Daily rhythm of aspartate aminopeptidase activity in the retina, pineal gland and occipital cortex of the rat.

The levels of specific soluble aspartyl aminopeptidase activity were assayed in retina, occipital cortex, anterior pituitary, posterior pituitary, pineal gland and serum of adult male rats, using Asp-2-naphthylamide as substrate, in a 12:12 h light:dark cycle (7-19 h light). Significant diurnal variations appeared in retina, pineal gland, occipital cortex and serum. In addition, different patterns of diurnal variation of the enzymatic activity were observed in the tissues analyzed. A regular increase of the activity was noticed at the end of the dark period in all the tissues as a common feature, except in serum, in which the enzymatic activity reached a peak in the middle of the light period, decreasing progressively during the dark hours. After the last hours of darkness, the pattern of variation in the activity differed in each tissue. These diurnal variations in aspartyl aminopeptidase activity could reflect the functional status of its putative endogenous substrates, such as angiotensin II, and it may also suggest the existence of differential regulatory mechanisms associated with each location.

Aminopeptidases↗
PubMed1992

[Regional distribution of brain aminopeptidases in the rat].

Soluble and membrane-bound aminopeptidase activities in eleven regions of the rat brain were assayed using L-leucine-2-naphthylamide as a substrate. In addition, two metabolic enzymatic activities were compared: lactate dehydrogenase and aspartate aminotransferase. All enzymatic activities showed significant regional differences when the data were analyzed statistically. Soluble aminopeptidase and aspartate aminotransferase activities were significantly lower in cortical than in subcortical areas. Membrane-bound aminopeptidase activity levels were higher in cortical areas. Lactate dehydrogenase activities did no differ between cortical areas and the rest of the zones studied. However, while no wide regional differences were found for the other enzymatic activities, membrane-bound aminopeptidase varied markedly across brain regions: a 5-fold difference was observed between zones. The differential distribution of this enzymatic activity is consistent with the hypothesis that it is responsible for the enzymatic inactivation of some neuroactive peptides.

Aminopeptidases↗
PubMed1991

Effect of dietary nucleotides and orotate on the blood levels of prostacyclin (PGI2) and thromboxane (TXA2) in the weanling rat.

Dietary nucleotides affect the maintenance of immune responses, tissue repair and polyunsaturated fatty acid metabolism. Orotate, a pyrimidine nucleotide precursor, induces fatty livers by impairing VLDL hepatic secretion. The aim of this study was to evaluate the changes in the blood levels of fatty acids and prostacyclin (PGI2) and thromboxane (TXA2) in the weanling rat caused by the dietary intake of nucleotides and orotate. Three groups of rats at weaning were fed a control diet, an orotate supplemented diet (O-50) and a nucleotide supplemented diet (N-50) during 4 weeks, respectively. Absolute values of plasma polyunsaturated fatty acids greater than 18 carbon atoms of the n-6 and n-3 series were increased in the N-50 group and decreased in O-50 with regard to the control. However, the relative fatty acid composition of plasma lipid fractions was mostly unaffected. Plasma 6-keto-PGF1 alpha showed a trend to be increased in N-50 and serum TXB2 was significantly increased in that group. Both eicosanoids were unchanged by dietary orotate intake. These results may be explained because of the increased plasma 20:4n-6 found in rats fed a supplemented nucleotide diet. Thus, nucleotides present in foods appear to modulate PUFA conversion and eicosanoids synthesis in early life.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Circadian rhythm in Leu-beta-naphthylamide hydrolysing activity in selected photoneuroendocrine areas of adult male rats.

Soluble Leu-beta-naphthylamide hydrolysing activity (arylamidase activity) was assayed in retina, superior cervical ganglia, several brain areas and serum of adult male rats, at different time points of a 12:12h light:dark cycle (from 7h to 19h light). The results demonstrated a left or right biased asymmetrical distribution of this activity depending on the time point studied: While the levels of activity were significantly higher in the left retina than in the right one at 10h of the light period, these were predominant in the right side, at 01h of the dark period. In addition, this activity was higher in the left hypothalamus at 13h of the light period. No asymmetries were disclosed in the rest of time points and structures studied. On the other hand, this activity demonstrated a diurnal variation in the left anterior hypothalamus and total posterior hypothalamus but no periodic variation was evidenced in right anterior hypothalamus or the rest of zones studied. These results may reflect the role of this activity regulating the functional status of its susceptible endogenous substrates.

Animals↗
PubMed1990

Two glycosylation patterns for a single protein (exoglucanase) in Saccharomyces cerevisiae.

Exoglucanases (beta-glucosidases) I and II secreted into the culture medium by Saccharomyces cerevisiae were purified from cell cultures harvested at the early exponential phase of growth in order to avoid contamination of the second by a new immunologically-related material. The amino acid composition of the purified enzymes was roughly the same. In addition, both exoglucanases exhibited an identical NH2-terminal sequence (50 residues). These results confirm our previous results about the identity of the protein moieties of both enzymes. Exoglucanase I appears to arise by elongation of one or both short oligosaccharides present in enzyme II.

Amino Acid Sequence↗