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Biomedical subjects

A Rivas

Publications and source records attributed to A Rivas.

At least 55 records · Page 3Linked to original sources
PubMed1994

Nosocomial septicaemias in a cardiologic ward. A case-control study.

Nosocomial septicaemias were studied in a cardiologic ward at the University Hospital of Antwerp, Belgium. The incidence of nosocomial infections was found to be 2.7 per 1,000 admissions per year. A case-control study suggested that in contrast with coronarography and pacemaker implantation, percutaneous transluminal coronary angioplasty may be a risk factor for nosocomial septicaemia (OR 4.5, 95% confidence interval 0.7-33.4).

Aged↗
PubMed1994

Left ventricular function determined by Doppler echocardiography in adolescents with type I (insulin-dependent) diabetes mellitus.

Sixty-one children with insulin-dependent diabetes mellitus and twenty-three healthy subjects were investigated. The patients with diabetes mellitus aged 4 to 20 years (13.4 +/- 4.0) had had diabetes for 1 to 16 years (6.4 +/- 3.5). There were no cardiovascular risk factor other than diabetes. Patients received no medication other than insulin. The following echocardiographic and Doppler parameters of the left ventricle were analyzed in both groups: systolic and diastolic dimensions, systolic time intervals, fractional shortening, mean velocity of circumferential fiber shortening, percent relaxation of the left ventricular posterior wall at 50% of diastole, peak velocity of early (E) and late atrial (A) mitral flow. E/A ratio, deceleration of the E-wave, and the isovolumetric relaxation time. None of the parameters were significantly different between the groups. There was no relation observed between duration of diabetes and any of the parameters analyzed. It is concluded that there is not echocardiographic data to support the concept of diabetic cardiomyopathy in adolescents with type I (insulin-dependent) diabetes mellitus.

Adolescent↗
PubMed1992

The VLA-4/VCAM-1 molecules participate in gamma delta cell interaction with endothelial cells.

The accumulation of T lymphocytes at the site of chronic inflammation depends on a number of factors including adherence of T cells to vascular endothelial cells (EC) and endothelial permeability. We examined the effects of human gamma delta + T lymphocytes on the permeability of EC to macromolecules and characterized the cell surface molecules that are involved in these interactions. In this model, the flux of [125I]albumin was measured across the EC monolayer after a short-term culture with cloned gamma delta cells. Our results show that coculture of activated, but not resting, gamma delta cells with EC enhances endothelial permeability by a cytolytic process. Pretreating gamma delta cells with monoclonal antibodies directed at either LFA-1 or VLA-4 molecules or pretreating EC with monoclonal antibodies directed against either ICAM-1 or VCAM-1 molecules significantly inhibited gamma delta cell-mediated enhancement in endothelial permeability. This indicated that VLA-4/VCAM-1 and LFA-1/ICAM-1 adhesion pathways participate in gamma delta cell-EC interaction.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1990

Alloantigen-specific cytotoxic clones bearing the alpha,beta T cell antigen receptor but not CD4 or CD8 molecules.

The vast majority of circulating lymphocytes that express the alpha,beta TCR in association with CD3 also express either CD4 or CD8 molecules, which are thought to act as important accessory structures in HLA class II- and I-restricted T cell functions, respectively. In the current study alpha,beta TCR+ clones devoid of detectable CD4 or CD8 were generated by repeated stimulation of fresh CD3+,CD4-,CD8- cells with an allogeneic lymphoblastoid cell line in the presence of conditioned medium containing IL-2. Except for the absence of CD4 and CD8, which was associated with undetectable levels of CD4 and CD8 mRNA, the clones were phenotypically indistinguishable from classical CD3+,alpha,beta TCR+ cells. Furthermore, they mediated potent cytolysis of their specific stimulator line but did not kill irrelevant LCL or NK-sensitive targets. mAb to CD3 and the alpha,beta TCR inhibited cytolysis, suggesting that the clones use the TCR/CD3 complex to recognize and respond to their targets. mAbs to CD2 and CD11a also inhibited cytolysis, indicating that the clones use these accessory molecules to interact with their targets. Finally, cytolysis was inhibited by an HLA-A,B,C framework-specific mAb (W6/32) as well as a mAb (MA2.1) specific for an HLA-A2 epitope. These results demonstrate that CD3+,alpha,beta TCR+,CD4-,CD8- cytotoxic clones can be generated from the peripheral blood of healthy adults, and use their TCR/CD3 complexes to function in an HLA class I-restricted manner.

Antigens, CD↗
PubMed1990

A method for removal of toxic chromium using dialysis-sac cultures of a chromate-reducing strain of Enterobacter cloacae.

A method for removal of toxic hexavalent chromium (chromate: CrO2-4) was developed by use of dialysis-sac cultures of a chromate-reducing strain of Enterobacter cloacae (HO1). E. cloacae strain HO1 cells were put in dialysis (semipermeable membrane) sacs, and the sacs were submerged in water containing toxic CrO2-4. The dialysis sacs allowed CrO2-4 to diffuse into the culture, and CrO2-4 was reduced anaerobically in the dialysis sacs by the E. cloacae cells. Because reduced chromium readily formed insoluble chromium hydroxides in the dialysis sacs, the greater part of reduced chromium was unable to diffuse out through the semipermeable membrane. Thus the dialysis culture of E. cloacae strain HO1 could successfully remove toxic chromium from the surrounding water. If the initial concentration of CrO2-4 was less than 4 mM (208 ppm as chromium), about 90% of the total chromium could be removed from water by the described method.

Bacteriological Techniques↗
PubMed1990

Peptides derived from the CDR3-homologous domain of the CD4 molecule are specific inhibitors of HIV-1 and SIV infection, virus-induced cell fusion, and postinfection viral transmission in vitro. Implications for the design of small peptide anti-HIV therapeutic agents.

Peptides 12-25 amino acids in length from the V1J1 region of the CD4 molecule (residues 1-120) were synthesized as randomly derivatized, deliberately derivatized, or pure peptide products, and tested for their ability to inhibit HIV-1-induced cell fusion, HIV-1 and SIV infection of CD4-positive human cells, HIV-1 envelope glycoprotein binding to the CD4 molecule, CD4-neutralizing antibody binding to the CD4 holoreceptor, and CD4-dependent cellular immune function in the mixed lymphocyte and cytotoxic T-cell bioassays. Only peptides derived from the complementarity-determining region 3 (CDR3)-homologous domain of CD4, in particular CD4(81-92) and CD4(81-101), were effective antiviral agents. Within the CD4(81-92) series, R-group derivatization of selective amino acid residues was an absolute requirement for biological activity. The prototype compound T1C4E5-tribenzyl-K10-acetyl-TYICEVEDQKEE inhibited HIV-1-induced cell fusion at 32 microM, HIV-1 infection of CEM-SS cells at 10 microM, SIV infection of CEM-174 cells at less than 125 microM, gp120/CD4 binding at 60 microM, and postinfection cell-mediated viral transmission at 10-15 microM. Compounds of identical structure and derivatization, but of altered primary sequence, were substantially less active, or without activity, in these assays. These data indicate that the effect of amino acid derivatization of the CD4(81-92) peptide was most likely restriction of the flexible underivatized peptide backbone to a conformation closely approximating that of the CDR3-homologous gp120 binding site of the native CD4 molecule. Peptide antiviral activity was specific, as judged by lack of cytotoxicity, lack of inhibition of HTLV-1-induced cell fusion, and lack of inhibition of CD4-dependent cellular immune function in vitro. Further derivatization of the prototype compound involving the production of cyclic congeners yielded peptides with submicromolar potency to block HIV-1 infection, strengthening the hypothesis that previous peptide derivations accomplished partial restriction of the conformation of CD4(81-92) to one favorable for interaction with gp120. Concentrations of the original prototype compound T1C4E5-tribenzyl-CD4(81-92) that inhibited infection in vitro more than 50% could be achieved for several hours by intravenous infusion in primates and were well-tolerated at these levels. The peptide was not efficacious to inhibit establishment of viral infection at these doses; however, peptide treatment did lower average viral antigenemia and delay the cumulative time to morbidity relative to the control group.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Natural killer (NK)-like cytotoxic activity of allospecific T cell receptor-gamma,delta+ T cell clones. Distinct receptor-ligand interactions mediate NK-like and allospecific cytotoxicity.

We recently generated a series of human alloantigen-specific, CD3+,TCR-gamma,delta+ clones by stimulating CD3+,CD4-,CD8- T cells from normal individuals with allogeneic lymphoblastoid cell lines (LCL). As reported previously, these clones display cytotoxic activity against their specific stimulators but not against irrelevant LCL. Further studies of these and other TCR-gamma,delta+ clones, described in this report, indicate that most but not all of these clones express the NK cell associated marker, NKH-1 or Leu-19, and kill NK-sensitive targets such as the K562 and Molt 4 lines, but not an irrelevant LCL or NK-resistant line, Raji. TCR-gamma,delta+ clones which lacked expression of Leu-19 lysed their allospecific targets but had no detectable NK activity. The allospecific cytotoxicity of Leu-19+ and Leu-19- clones was inhibited by mAb to CD3 or the TCR delta-chain. In contrast, the NK-like activity of the Leu-19+ clones was enhanced by these antibodies over a wide range of antibody concentration. Although mAb to LFA-1 markedly inhibited both the allospecific and NK-like activity of these clones, an HLA class I framework specific mAb (W6/32) had no effect on NK-like cytolysis but did inhibit allospecific killing, suggesting that the target structures on the surface of allospecific and NK-sensitive cells are distinct. The receptors utilized by the TCR-gamma,delta+ clones to recognize NK-sensitive and allospecific targets are also distinct, since killing of NK-sensitive targets was blocked by the presence of cold (unlabeled) NK-sensitive cells but not by cold allospecific targets, whereas allospecific cytolysis was inhibited by cold allospecific targets but not by NK-sensitive cells. We conclude that some CD3+,TCR-gamma,delta+ clones exhibit NK-like as well as allospecific killing and that these two activities are mediated by distinct receptor-ligand interactions.

Adult↗
PubMed1989

Evidence for involvement of the gamma, delta T cell antigen receptor in cytotoxicity mediated by human alloantigen-specific T cell clones.

The vast majority of mature T cells express the alpha, beta TCR and use this receptor to recognize Ag in association with MHC determinants. Recent reports indicate that a small subpopulation of CD3+ T cells does not express alpha, beta TCR and lacks CD4 and CD8 molecules, but expresses another TCR heterodimer designated gamma, delta. To date, however, there are very few examples of gamma, delta TCR-bearing T cells which have Ag-specific functions and the precise role of the gamma, delta TCR remains unknown. In an attempt to explore the function of the gamma, delta TCR in man, we generated a panel of CD3+, CD4-, CD8- T cell clones from cultures of normal T cells stimulated with allogeneic lymphoblastoid cell line (LCL). All of the clones stained with mAb to gamma, delta TCR determinants, and Northern blot analysis of total cellular RNA revealed mature gamma- and delta-chain transcripts and immature beta-chain transcript. The clones displayed cytolytic activity against their specific stimulating LCL, but not irrelevant LCL, and killing was inhibited by a mAb to HLA class I (HLA-A,B,C) determinants, suggesting that these cells recognized class I MHC antigenic determinants on specific stimulator/target cells. Cytolysis by these clones was markedly inhibited by low concentrations (0.00001 to 0.001 microgram/ml) of mAb to CD3 or TCR delta-chain, but high concentrations (0.1 to 20 micrograms/ml) of the same antibodies enhanced cytotoxicity. When absorbed to plastic tissue culture wells, anti-CD3 mAb stimulated the clones to proliferate. These results indicate that alloantigen specific, gamma, delta TCR+, CD4-, CD8- T cell clones can be reproducibly generated in vitro, and that the gamma, delta TCR plays a direct role in the specific recognition and cytolysis displayed by these clones.

Adult↗
PubMed1989

Morphological types of Taenia solium cysticerci.

In human brain cysticercosis, there are three morphological types of cysticercus. Teresa Robielo, Angelica Rivas and Ana Flisser describe the appearance and possible taxonomic position of these forms, and discuss their relation to the various pathologies of neurocysticercosis.

Journal Article↗
PubMed1988

CD4 molecules are associated with the antigen receptor complex on activated but not resting T cells.

To explore the relationship between CD4 and CD3/Ti on the T cell surface, we have studied a panel of Ag-specific Th cell lines and clones, as well as resting and mitogen-activated CD4+ cells. Our results show that exposure of Th cells to their specific antigenic stimuli, but not to irrelevant stimuli, induced the rapid disappearance of approximately 20 to 35% of CD3 and CD4 molecules. The modulation of these molecules was detected in less than 1 h, became maximal at 12 h, and recovered thereafter in parallel. Treatment of Th cells with anti-CD4 antibody prevented Ag-induced modulation of CD3, and treatment with anti-CD3 blocked modulation of CD4. In the absence of Ag, treatment of these cells with an antibody (WT-31) directed at a conformational determinant within CD3/Ti or with the combination of anti-CD3 antibody and goat anti-mouse Ig, also resulted in significant modulation of CD4. Similar treatment of PHA-activated CD4+ T cells with anti-CD3/Ti antibodies also induced CD4 modulation; however, the same antibodies failed to affect CD4 expression on fresh resting T cells. These results indicate that on activated, but not resting T cells, CD4 molecules can be physically associated with CD3/Ti. We postulate that this association is essential for efficient Th cell activation, and further that the ability of anti-CD4 antibodies to inhibit helper functions is due to their prevention of CD4-CD3/Ti interaction on the T cell surface.

Antigen-Antibody Reactions↗
PubMed1986

Proliferative response in solid culture of T cells from patients with extrinsic bronchial asthma.

T cells proliferative response in both liquid and solid culture conditions (the later prevents direct cell to cell contact) was investigated in nineteen Extrinsic Bronchial Asthma patients (EBA). Tetradecanoyl-phorbol-13-acetate (TPA), a T cell mitogen was used as mitogenic stimulus in both liquid and solid conditions. While the response to phytohemaglutinin (used in liquid culture as reference) was intact, the EBA group showed a significant reduction in the proliferative response to TPA in both culture conditions. Furthermore, when adherent cells were removed prior to TPA stimulation, while the control group showed a significant decrease in proliferation, the already depressed low proliferation of the EBA group remained unchanged. These results suggest the prevalence of suppressor signals in EBA and may indicate heterogeneity of the suppressor cells pool since high levels of total serum IgE were also present in the same patients.

Adolescent↗
PubMed1986

The QS2/QT ratio as an index of appropriate left ventricular response to autonomic and inotropic stimuli.

Dissociation between duration of electrical and mechanical systole has been seen with increase of myocardial shortening velocity or adrenergic activity. We found a decrease of the QS2/QT ratio after exercise in 10 pts with semisitting bicycle maximal exercise test and a normal radionuclide angiogram. No change was seen in 9 patients with a normal study with beta blockade, and in pts with a abnormal radionuclide test, without beta blockade (11 pts). In 19 normal active individuals, a significant QS2/QT decrease (p less than 0.001) was seen after a submaximal exercise treadmill test, which was inhibited by beta blockade. We believe that QS2/QT diminution is suggestive of an increase of the inotropic state of the left ventricle with exercise, produced through adrenergic stimulation. It is not seen either when an ischemic left ventricle cannot adequately respond to exercise or after beta blockade.

Adult↗
PubMed1982

Cell-mediated effector mechanisms in aging humans.

Specific and nonspecific cell-mediated effector mechanisms have been simultaneously assayed in 15 aged humans. 8 were female and 7 male, including a 114-year-old male in remarkably good health. Proliferative response to alloantigens, the generation of T killer cells and the ability to express cell-mediated lympholysis as well as the presence of natural cell-mediated cytotoxicity against K562 tumor cell line and the capacity to mount an ADCC response to RhD+ human red blood cell sensitized with anti-D antisera, revealed that in the human aged, while T function significantly declines, nonspecific cell-mediated effector mechanisms are operative.

Aged↗