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Biomedical subjects

M Torres

Publications and source records attributed to M Torres.

At least 127 records · Page 7Linked to original sources
PubMed1998

Heavy metal uptake by polyphosphate bodies in living and killed cells of Plectonema boryanum (cyanophycae).

The study was conducted to determine whether living or killed cell polyphosphate bodies (PPB) would sequester more of several heavy metals. Living and heat- or glutaraldehyde-killed cells were exposed to 20 ppm of Zn, Pb, Mn and Al. Air-dried cells on Formvar-coated grids were first observed in the transmission electron microscope. The unit was then switched to the scanning transmission mode of operation with the spot setting. X-rays were collected on an energy dispersive X-ray spectrometer and mass fractions of the metals were determined. In all cases live cells sequestered a larger amount of the metal than cells killed by boiling or with glutaraldehyde. In all cases the cells killed by glutaraldehyde sequestered more of the heavy metals than cells killed by boiling. The results of the investigation show that PPB in living cells with active uptake systems take up and sequester more of the metals Zn, Pb, Mn and Al than killed cells.

Absorption↗
PubMed1998

Molecular, genetic and physiological analysis of Cladosporium resistance gene function in tomato.

Characterization of the DNA sequence of 4 tomato leaf mould disease resistance genes (Cf-2, Cf-4, Cf-5 and Cf-9) leads to the prediction that they encode C-terminally membrane anchored glycopeptides with many extracytoplasmic leucine rich repeats (LRRs). The N terminal LRRs are variable between the Cf-genes, suggesting a role in specificity, and the C terminal LRRs are more conserved, suggesting a role in signal transduction. Genetic analysis has revealed several Rcr genes that are required for Cf-gene function; their isolation will help us understand how Cf-genes work. Cf-9 confers responsiveness to pathogen-encoded Avr9 peptide on introduction to tobacco. Tobacco suspension cultures carrying the Cf-9 gene produce reactive oxygen species in response to Avr9 peptide, whereas untransformed cultures do not. The significance of these observations is discussed.

Cladosporium↗
PubMed1998

[Radionuclide bone scanning in patients with breast carcinoma. Study of lesions by stages, locations and diagnostic assessment].

The aim of this study was to evaluate the diagnostic role of bone scan in patients with breast carcinoma. With this purpose, we have studied 591 patients (4 males). In 261 of them, we were able to establish the stage of disease: 33 in stage I, 137 in stage II, 71 in stage III y 20 in stage IV. Metastatic lesions were detected in 6% of patients in stage I, 8.8% in stage II, 12.7% in stage III y 50% in stage IV. Altogether, 71 from 591 patients (12%) had metastatic lesions. In 4 patients (5.3%) we obtained a false positive result. The bone lesions found in the scintigraphic studies were classified as not metastatic lesions in 236 patients (39.9%) but 26 of them were malignant (11%). Another 193 patients (32.6%) presented scintigraphic studies considered as equivocal for metastasis and 33 of them were also malignant (17%). In 150 patients scintigraphic studies did not present lesions during the follow up. In other 156 patients isolated lesions were detected and 24 of them (15.4%) were malignant. Only 4 < > lesions were detected and not any < > image was observed in this study.

Adult↗
PubMed1997

Evidence for the stochastic integration of gene trap vectors into the mouse germline.

A large scale insertional mutagenesis experiment was performed in embryonic stem (ES) cells by introducing two types of gene trap vectors into the genome. These cell lines carrying mutations were introduced into the mouse germline. In order to assess the feasibility of a large scale cloning of the targeted genes from these lines, we have isolated and characterized 55 trapped exons from the corresponding ES cells. Analysis of the data has revealed that vectors containing or lacking an internal ribosome entry site (IRES) can integrate into the ES cell genome stochastically. The targeted genes comprise 30% known genes, 20% expressed sequence tags (ESTs) and 50% novel or unknown genes. The known genes belong to several major classes and represent complete or partial knockouts. Using currently available methods or modifications of them, it should be feasible to do a large scale cloning of trapped genes from the mouse ES cell lines.

Animals↗
PubMed1997

[Diagnosis of renovascular disease by heart catheterization].

Atherosclerotic renovascular disease is a common entity, particularly in persons older than 50 years of age and especially in those patients with other evidence of atherosclerotic vascular disease. The illness clearly progresses in some patients, and progression rate appears to be highly variable. Taken into account the apparent high prevalence of renovascular disease in older persons, it is possible that this disorder be the cause of end stage renal disease in 5% to 15% of patients currently entering the dialysis program each year. Surgery and percutaneous angioplasty can both improve renal function in patients with renal artery stenosis. We describe a patient in whom the detection of renovascular disease was made accidentally at the time of coronary arteriography. He presented an acute renal failure after use of angiotensin-converting enzyme inhibitors and/or contrast media associated nephrotoxicity, and was treated with percutaneous transluminal balloon angioplasty and had a successful outcome.

Acute Kidney Injury↗
PubMed1997

The Pax4 gene is essential for differentiation of insulin-producing beta cells in the mammalian pancreas.

The mammalian pancreas contains two distinct cell populations: endocrine cells which secrete hormones into the bloodstream, and exocrine cells, which secrete enzymes into the digestive tract. The four endocrine cell types found in the adult pancreas-(alpha, beta, delta and PP-synthesize glucagon, insulin, somatostatin and pancreatic polypeptide, respectively. All of these endocrine cells arise from common multipotent precursors, which coexpress several hormones when they start to differentiate. Expression of some homeobox genes in the early developing pancreas has been reported. The Pax4 gene is expressed in the early pancreas, but is later restricted to beta cells. Inactivation of Pax4 by homologous recombination results in the absence of mature insulin- and somatostatin-producing cells (beta and delta, respectively) in the pancreas of Pax4 homozygous mutant mice, but glucagon-producing alpha cells are present in considerably higher numbers. We propose that the early expression of Pax4 in a subset of endocrine progenitors is essential for the differentiation of the beta and delta cell lineages. A default pathway would explain the elevated number of alpha cells in the absence of Pax4.

Animals↗
PubMed1997

Establishment of the dorso-ventral axis in Xenopus embryos is presaged by early asymmetries in beta-catenin that are modulated by the Wnt signaling pathway.

Eggs of Xenopus laevis undergo a postfertilization cortical rotation that specifies the position of the dorso-ventral axis and activates a transplantable dorsal-determining activity in dorsal blastomeres by the 32-cell stage. There have heretofore been no reported dorso-ventral asymmetries in endogenous signaling proteins that may be involved in this dorsal-determining activity during early cleavage stages. We focused on beta-catenin as a candidate for an asymmetrically localized dorsal-determining factor since it is both necessary and sufficient for dorsal axis formation. We report that beta-catenin displays greater cytoplasmic accumulation on the future dorsal side of the Xenopus embryo by the two-cell stage. This asymmetry persists and increases through early cleavage stages, with beta-catenin accumulating in dorsal but not ventral nuclei by the 16- to 32-cell stages. We then investigated which potential signaling factors and pathways are capable of modulating the steady-state levels of endogenous beta-catenin. Steady-state levels and nuclear accumulation of beta-catenin increased in response to ectopic Xenopus Wnt-8 (Xwnt-8) and to the inhibition of glycogen synthase kinase-3, whereas neither Xwnt-5A, BVg1, nor noggin increased beta-catenin levels before the mid-blastula stage. As greater levels and nuclear accumulation of beta-catenin on the future dorsal side of the embryo correlate with the induction of specific dorsal genes, our data suggest that early asymmetries in beta-catenin presage and may specify dorso-ventral differences in gene expression and cell fate. Our data further support the hypothesis that these dorso-ventral differences in beta-catenin arise in response to the postfertilization activation of a signaling pathway that involves Xenopus glycogen synthase kinase-3.

Animals↗
PubMed1997

An alpha-E-catenin gene trap mutation defines its function in preimplantation development.

Catenins are proteins associated with the cytoplasmic domain of cadherins, a family of transmembrane cell adhesion molecules. The cadherin-catenin adhesion system is involved in morphogenesis during development and in the maintenance of the integrity of different tissue types. Using a gene trap strategy, we have isolated a mouse mutation for the gene encoding the alpha-E-catenin. This form of the alpha-catenin appears frequently coexpressed with E-cadherin in epithelial cell types. The mutation obtained eliminates the carboxyl-terminal third of the protein but nevertheless provokes a complete loss-of-function phenotype. Homozygous mutants show disruption of the trophoblast epithelium (the first differentiated embryonic tissue), and development is consequently blocked at the blastocyst stage. This phenotype parallels the defects observed in E-cadherin mutant embryos. Our results show the requirement of the alpha-E-catenin carboxy terminus for its function and represent evidence of the role of the alpha-E-catenin in vivo, identifying this molecule as the natural partner of the E-cadherin in trophoblast epithelium.

Animals↗
PubMed1997

WNTs modulate cell fate and behavior during vertebrate development.

Wnt genes encode a family of secreted glycoproteins that modulate cell fate and behavior in embryos through activation of receptor-mediated signaling pathways. Wnt sequences, patterns of expression and activities are highly conserved in evolution, so it has been possible to gain insights into the functions, and mechanisms of action, of the Wnt genes through a synthesis of genetic and cell biological approaches in different organisms. These studies suggest that there are functionally distinct WNT proteins as assayed by the ability to transform cells and by differences in embryonic responses to ectopic WNT signals. Moreover, gain-of-function and loss-of-function studies both support the involvement of Wnt proteins in modulating cell fate and cell behavior during vertebrate development, often through combinatorial interactions with other signaling pathways to regulate gene expression.

Animals↗
PubMed1997

Distribution of [3H]diadenosine tetraphosphate binding sites in rat brain.

The distribution of the diadenosine tetraphosphate high-affinity binding sites has been studied in rat brain by an autoradiographic method using [3H]diadenosine tetraphosphate as the ligand. The binding characteristics are comparable to those described in studies performed on rat brain synaptosomes. White matter is devoid of specific binding. The range of binding site densities in gray matter varies from 3 to 15 fmol/mg of tissue, exhibiting a widespread but heterogeneous distribution. The highest densities correspond to the seventh cranial nerve, medial superior olive, pontine nuclei, glomerular and external plexiform layers of the olfactory bulb, and the granule cell layer of the cerebellar cortex. Intermediate density levels of binding correspond to different cortical areas, several nuclei of the amygdala, and the oriens and pyramidal layers of the hippocampal formation. The localization of diadenosine tetraphosphate binding sites in the brain may provide information on the places where diadenosine polyphosphate compounds can be expected to function in the central nervous system.

Animals↗
PubMed1997

Identification of the vertebrate Iroquois homeobox gene family with overlapping expression during early development of the nervous system.

In Drosophila the decision processes between the neural and epidermal fate for equipotent ectodermal cells depend on the activity of proneural genes. Members of the Drosophila Iroquois-Complex (Iro-C) positively regulate the activity of certain proneural AS-C genes during the formation of external sensory organs. We have identified and characterized three mouse Iroquois-related genes: Irx1, -2 and -3, which have a homeodomain very similar to that of the Drosophila Iro-C genes. The sequence similarity implies that these three genes represent a separate homeobox family. All three genes are expressed with distinct spatio/temporal patterns during early mouse embryogenesis. These patterns implicate them in a number of embryonic developmental processes: the A/P and D/V patterning of specific regions of the central nervous system (CNS), and regionalization of the otic vesicle, branchial epithelium and limbs.

Amino Acid Sequence↗
PubMed1997

Prostanoids and free radicals in Cl4C-induced hepatotoxicity in rats: effect of astilbin.

A beneficial effect of flavonoids in Cl(4)C-induced hepatoxicity in rats has been reported. In this communication we have evaluated the protective effect of astilbin, an active flavonoid isolated from a crude extract of Hymenaea martiana, as well as its action on liver arachidonate metabolism in Cl(4)C-treated rats. The following groups of rats were studied: Group I = controls; Group II = Astilbine-treated animals (40 mg/Kg); Group III = Cl(4)C-treated at 1 ml/kg; Group IV = Astilbine + ClC4 and Group V = Vitamine E (50 mg/Kg) + Cl(4)C-treated animals. Histological findings, superoxide dismutase activity, lipoperoxides and prostanoid profiling studies revealed that the hepatoprotective effect of astilbine was higher than that of vitamin E. Astilbine was capable to restore lipoperoxides and tissue prostanoids to basal values.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

Simulation by a diagnostic CT for the early vocal cord carcinoma.

The CT-based simulation with a 3D planning system permits the optimization of radiotherapy treatments. The goal is to obtain an increase in the local control and survival with a reduction of the treatment related toxicity. In our hospital, we do not have a CT simulator and our 3D planning system is not yet working, therefore, we have developed a system to simulate radiotherapy treatments using a diagnostic CT. We began by simulating an early vocal cord carcinoma. The rules of this simulation are presented using a clinical case as an example.

Humans↗