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Biomedical subjects

J M Alvarez

Publications and source records attributed to J M Alvarez.

72 records · Page 4Linked to original sources
PubMed1992

Technical improvements in the repair of acute postinfarction ventricular septal rupture.

Postinfarction ventricular septal rupture (VSR) is a high-risk complication following myocardial infarction (MI). Surgical treatment has evolved to improve an otherwise poor prognosis. Certain subsets of patients remain a formidable challenge. The presence of cardiogenic shock has consistently been found to have the highest risk. Over a 10-year period, our technique of repair has evolved from established procedures to one we believe confers superior results. Endocardial patching to viable myocardium reinforced with an epicardial patch not only corrects the shunt but maintains ventricular geometry and avoids tension on friable muscle. We report on a series of nine consecutive patients in cardiogenic shock. The operative mortality was 22%, none due to low cardiac output syndrome, shunt recurrence, or bleeding. All patients have been followed with transesophageal echocardiography at a mean period of 14 months (range 3-31 months). One patient is in New York Heart Association (NYHA) Class I, four are in NYHA Class II, and two in NYHA Class III.

Aged↗
PubMed1992

Resistance of Trypanosoma cruzi to blood clearance induced by acute-phase immune mouse serum.

To investigate functional changes in Trypanosoma cruzi parasites induced during their interaction with the vertebrate host, we compared the blood clearance profiles of blood forms isolated from infected normal mice (Reg-Tc) or from infected mice immunodepressed after treatment with cyclophosphamide (Cy-Tc). Parasite blood numbers were measured at various time intervals in animals injected intravenously (i.v.) with 1-2 x 10(6) T. cruzi of either isolate. In the absence of added immune sera (spontaneous clearance), Reg-Tc and Cy-Tc were cleared from blood at similar rates. However, when acute immune mouse serum (Ac-IMS) was injected i.v. 2 min after inoculation of parasites, a significant proportion of Cy-Tc only was cleared from the blood an hour later, whereas Reg-Tc were not, their clearance profile being identical to that observed in mice injected with normal mouse serum. Cy-Tc susceptibility to Ac-IMS was not the result of a toxic effect of cyclophosphamide over T. cruzi as parasites recovered from animals immunodepressed by irradiation before infection were cleared similarly by acute serum. Contrary to Ac-IMS, chronic immune mouse serum induced similar rates of disappearance of Reg-Tc and Cy-Tc from blood. Our results suggest the occurrence of T. cruzi selection or modification during the acute phase, which leads to an increased parasite resistance to the clearance properties of acute-phase antibodies.

Acute-Phase Reaction↗
PubMed1990

High performance liquid chromatographic separation of cisplatin and its hydrolysis products on alumina and application to studies of their interaction with cysteine.

An alumina stationary phase has been assessed in the study of the retention behaviour of the anticancer drug cisplatin and its major hydrolysis products. Parameters such as buffer concentration in the mobile phase, pH, organic modifier and competing ion have been investigated in order to optimize chromatographic separation with ultraviolet detection. The separation scheme developed has been used to monitor the hydrolysis of cisplatin in aqueous and saline media, and to monitor the interaction of hydrolysed solutions of cisplatin with the amino acid cysteine. A new peak was observed in the chromatograms of such mixtures when they had been allowed to stand for periods of greater than 16 h and, from analysis of the data obtained, it was concluded that this new peak was due to a complex formed between the mono-aquo hydrolysis product of cisplatin and the amino acid.

Aluminum↗
PubMed1989

Determination of microscopic dissociation constants of 3-hydroxy-alpha-(methylamino)methyl-benzenemethanol by a spectral deconvolution method.

Microscopic dissociation constants of 3-hydroxy-alpha-(methylamino)methyl-benzenemethanol have been calculated from the titration spectrophotomeric data (c = 3.8 x 10(-4) M. Ionic strength = 0.16; buffer system: H3BO3/KOH) by application of a spectral deconvolution method. The results found (pKa = 9.48; pKb = 9.71; pKc = 10.12 and pKd = 9.88) are in good concordance with those obtained from the conventional regression linear method (pKa = 9.45; pKb = 9.77; pKc = 10.14 and pKd = 9.81).

Chemical Phenomena↗
PubMed1985

Specific binding of 3H-estradiol to rat prostate nuclear matrix.

Specific estradiol binding activities can be demonstrated in nuclear matrix preparations obtained from intact rat prostate nuclei. Some of the characteristics of these in vitro binding activities to intranuclear components are presented and compared to those exhibited by purified nuclear fractions. Examination of the effects of exposure to castration and testosterone on the number of nuclear matrix binding sites revealed that the quantity and quality (Type) of receptors was modified. Furthermore, these changes are prevented when protein synthesis was inhibited.

Animals↗
PubMed1984

Insulin regulation of insulin-like growth factor action in rat hepatoma cells.

We have reported previously that insulin causes a complete but reversible desensitization to insulin action in rat hepatoma HTC cells in tissue culture, and that this insulin resistance is mediated by postbinding mechanisms rather than receptor down-regulation (Heaton, J. H., and Gelehrter, T. D. (1981) J. Biol. Chem. 256, 12257-12262). We report here that insulin causes a similar desensitization to the induction of tyrosine aminotransferase by the insulin-like growth factors IGF-I and IGF-II isolated from human plasma, and by multiplication-stimulating activity, the rat homologue of IGF-II. The results of both competition-binding studies and affinity cross-linking experiments indicate that insulin-like growth factors (IGFs) bind primarily to IGF receptors rather than to insulin receptors. The low concentrations at which these factors induce transaminase is consistent with their acting primarily via IGF receptors. This is confirmed by experiments utilizing anti-insulin receptor antibody which both inhibits 125I-insulin binding and shifts the concentration dependence of insulin induction of tyrosine aminotransferase to the right. This same immunoglobulin does not inhibit 125I-multiplication-stimulating activity binding and only minimally inhibits 125I-IGF-I binding. Anti-insulin receptor antibody also does not significantly shift the concentration dependence for the IGFs, suggesting that IGFs induce transaminase by acting via IGF receptors. Although insulin down regulates insulin receptors, it does not decrease IGF-I or IGF-II binding. We conclude that insulin causes desensitization of HTC cells to IGFs by affecting a postbinding step in IGF action, which may be common to the actions of both insulin and insulin-like growth factors.

Animals↗
PubMed1981

Human interleukin 2: production by both TG cells and other T cells.

We have investigated the production of interleukin 2 (IL-2) by human T cells after their stimulation by phytohaemagglutinin (PHA). T cells isolated by rosetting with sheep erythrocytes produced high levels of IL-2. Further separation of rosette-forming cells, according to the expression of Fc receptors for IgG, showed that TG and non-TG cells are equally able to produce IL-2. The release of IL-2 by TG cells did not require DNA synthesis or functional Rc gamma receptors, since positively selected TH cells produced IL-2, even though they lacked lymphoproliferative responses to PHA and antibody-dependent cell-mediated cytotoxicity.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1978

Cytotoxic activities of normal cultured human T cells.

Normal human T cells grown in continued cultures in medium containing conditioned medium (CM) from PHA-stimulated lymphocytes were studied for their ability to manifest three known forms of cell-mediated cytotoxicity: lectin-induced cellular cytotoxicity (LICC), natural killer cell (NK) activity, and antibody-dependent cellular cytotoxicity (ADCC). The cultured T cells (CTC) were very effective mediators of LICC, being cytotoxic even at very low attacker-target cell ratios in the presence of different lectins, and against different types of targets. When tested without the addition of lectin, the CTC demonstrated a low degree of spontaneous cytotoxicity. This spontaneous cytotoxicity might not be due to conventional NK cells however, since the CTC failed to show significant numbers of cells with Fc receptors (FcR) for IgG, and had no detectable ADCC activity. CTC could represent a population enriched in polyclonal activated T cells with low spontaneous cytotoxicity against a variety of allogeneic target cells, which is greatly enhanced by the addition of lectins dur ing the 51Cr release assay.

Animals↗
PubMedDate not supplied

Trait understanding or evaluative reasoning? An analysis of children's behavioral predictions.

This study tested the hypothesis that in predicting the future behavior of an actor, older children rely on trait inferences, whereas younger children rely on global, evaluative inferences. Vignettes depicting actors engaging in trait-relevant behaviors were presented to 5- and 6-year-olds (N = 67) and 9- and 10-year-olds (N = 71). For each actor, children made predictions of future behavior, evaluated the goodness and badness of the actor, and rated each actor on a relevant trait. A mediational analysis found that the behavioral predictions of older children were mediated solely by trait ratings, whereas those of younger children were mediated by evaluative ratings. Furthermore, unlike older children, younger children made trait-like predictions only when they made an evaluation of the actor. These results suggest that young children utilize evaluative reasoning when making behavioral predictions, and therefore rely on an inferential process that is distinct from that of older children.

Age Factors↗
PubMedDate not supplied

Evolution of subpatent parasitaemia in Trypanosoma cruzi chronically infected mice with the help of a cyclophosphamide amplification transfer assay.

We have evaluated the sensitivity of the classical blood subinoculation method, modified through cyclophosphamide treatment of transferred mice, for the detection of occult parasitaemias in Trypanosoma cruzi chronically infected mice. Besides its simplicity, the method was shown to be highly sensitive for both the "chronic" phase parasites (99% of chronic cases were shown to harbour occult parasitaemias) and for the acute phase parasites (T. cruzi could be detected in 53.8% of animals transferred with one Y strain parasite and in 20% of animals transferred with one CL strain parasite). Using acute phase bloodforms, the assay proved to be more sensitive than conventional subinoculation when dealing with the CL, but not the Y strain of the parasite. With the help of this parasite detection tool, we have studied during a one year period, the evolution of subpatent parasitaemias in a group of mice which survived through chemotherapy from lethal acute phase of T. cruzi infection. Cyclophosphamide transfer assay revealed occult parasitaemias in 100% of the chronic animals, nevertheless, continuous and discontinuous patterns of positivity were observed.

Acute Disease↗