PubMed Health⌕ Search

Biomedical subjects

J Quintáns

Publications and source records attributed to J Quintáns.

At least 19 recordsLinked to original sources
PubMed1999

[Combined perioperative ultrafiltration in pediatric cardiac surgery. The preliminary results].

INTRODUCTION AND OBJECTIVES: Recently, ultrafiltration techniques are used more and more as a treatment for the inflammatory response of cardiopulmonary bypass. It also provides fine control of fluids. The purpose of this study is to present a technique which combines conventional and modified ultrafiltration and to analyze the obtained results. PATIENTS AND METHODS: 22 patients (mean weight 13.1 +/- 8.4 kg) operated on cardiopulmonary bypass. Combined ultrafiltration was performed during cardiopulmonary bypass (conventional) and after pump (modified ultrafiltration). We analyzed cardiopulmonary bypass variables, the first 24-hour hemodynamics, biological variables (arterial blood gases, cell counts, IL-6, adhesion molecules ICAM-1 and VCAM-1, and coagulation profiles). RESULTS: A total amount of 1,399 +/- 680 ml/m2 of mean combined ultrafiltrate volume was obtained (657 +/- 386 ml/m2 during cardiopulmonary bypass and 845 +/- 358 ml/m2 post-cardiopulmonary bypass). After modified ultrafiltration, hematocrit rose from 23 +/- 2.3 to 32 +/- 4.1, arterial systolic blood pressure rose from 74 +/- 13 to 98 +/- 20 mmHg, heart rate decreased from 133 +/- 22 to 126 +/- 23 bpm, and central versus pressure did not change. A statistically significant relationship (multivariable), was shown between modified ultrafiltration time and VCAM-1 post-ultrafiltration levels. Platelet count was lower and diuresis rose related to cardiopulmonary bypass ultrafiltration volume and diuresis increased. CONCLUSIONS: Perioperative combined ultrafiltration is feasible without undue morbidity and provides adequate hemoconcentration and excellent postoperative hemodynamic results. More studies with control groups are necessary to better define the therapeutic influence in antiinflammatory properties of this technique.

Cardiac Surgical Procedures↗
PubMed1997

Anti-immunoglobulin-induced apoptosis in WEHI 231 cells involves the slow formation of ceramide from sphingomyelin and is blocked by bcl-XL.

Prolonged (>24 h) exposure to anti-IgM (an antigen surrogate that induces membrane cross-linking and apoptosis) induced a 3-fold increase in the mass of endogenous ceramide measured by 32P labeling by diacylglycerol kinase and a 4-fold increase in ceramide as measured by metabolic labeling with [3H]palmitate in a B-lymphocyte cell line, WEHI 231. This correlated with the induction of apoptosis. Shorter exposure times to anti-IgM (up to 8 h) failed to elicit apoptosis and did not elicit increased ceramide formation. After 8 h, apoptosis occurs concomitantly with ceramide formation over the next 40 h. Further, we showed that exogenous ceramide mimicked anti-IgM-induced apoptosis and that apoptosis was potentiated in serum-free media. Treatment of cells with an inhibitor of ceramide catabolism, N-oleoylethanolamine, increased both ceramide formation and apoptosis and accelerated apoptosis induced by anti-IgM. To examine further how ceramide metabolism is involved in apoptosis, we derived cell lines from a small population of cells resistant to N-oleoylethanolamine. These cell lines were selected based on an altered ceramide metabolic pathway, were resistant to apoptosis induced by anti-IgM, and showed no significant increase in ceramide when challenged with anti-IgM. The basis of this resistance was shown to be the failure to activate neutral sphingomyelinase activity following 24-h treatment with anti-IgM, in contrast to the 2-fold increase in neutral sphingomyelinase activity observed in wild type cells. We have shown previously that transfection of WEHI cells with bcl-xL conferred resistance to anti-IgM-induced apoptosis, whereas transfection with bcl-2 did not (Gottschalk, A., Boise, L., Thompson, C., and Quintans, J. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 7350-7354). In this study, these bcl-xL transfectants also displayed increased resistance to exogenous N-acetylsphingosine (C2-ceramide) or N-hexanoylsphingosine (C6-ceramide). However, when challenged with anti-IgM the bcl-xL transfectants produced levels of ceramide similar to wild type cells, suggesting that ceramide formation is upstream of bcl-xL and that it is a major determinant of B-cell death.

Amidohydrolases↗
PubMed1996

The ability of Bcl-x(L) and Bcl-2 to prevent apoptosis can be differentially regulated.

Although expression of Bcl-2 has been shown to prevent apoptosis under many circumstances, there are several systems in which Bcl-2 fails to promote cell survival. We have previously reported that Bcl-2 and Bcl-x(L) display differential ability to protect WEHI-231 cells from multiple inducers of apoptosis. A possible explanation for this paradox was provided by the discovery of Bax. Bax is a Bcl-2-related protein which can inhibit the ability of Bcl-2 to enhance the survival of growth factor-dependent cell lines in the absence of growth factor. Consistent with the possibility that Bcl-2 function in WEHI-231 cells is inhibited by Bax, WEHI-231 cells were found to express a high level of Bax. To directly test the effects of Bax expression on Bcl-x(L) function, FL5.12 cells were transfected with both genes. Although Bax overexpression can inhibit Bcl-2 from prolonging cell survival upon growth factor withdrawal, Bax overexpression did not inhibit Bcl-x(L) from preventing apoptosis in this cell line. Although Bcl-2 and Bcl-x(L) were both found to be able to form heterodimers with Bax, the majority of Bax in both cases was not complexed to a partner. Our data suggest that Bcl-x(L) does not function by simply preventing the formation of Bax homodimers which promote cell death. Instead Bax appears to display selectivity in its ability to inhibit Bcl-2 but not Bcl-x(L) from prolonging survival. Furthermore, our data suggest that the abilities of Bcl-2 and Bcl-x(L) to promote cell survival are not identical and can be independently regulated within a cell. Regulation of a cell's apoptotic threshold is likely to result from a complex set of interactions among Bcl-2 family members and other, as yet uncharacterised, regulators of apoptosis.

Journal Article↗
PubMed1995

Resistance to anti-IgM-induced apoptosis in a WEHI-231 subline is due to insufficient production of ceramide.

We describe the properties of a physiological cell death (PCD)-resistant subline of WEHI-231 generated from the PCD-susceptible WEHI-231.7 JM cell line maintained in our laboratory. The PCD-resistant WEHI-231.7 JMRE subline was uniquely resistant to anti-immunoglobulin (Ig)M-induced PCD but not to irradiation and etoposide. In these sublines, we compared the expression of genes implicated in regulating PCD. Northern analysis of c-myc, c-fos, egr-1, Fas, p53 and retinoblastoma revealed similar basal levels of expression in all sublines tested and comparable responses to anti-IgM treatment. Similarly, the expression of bcl-2, bcl-x, bax and IL-1 beta converting enzyme did not correlate with susceptibility to anti-IgM-induced PCD. Next, we systematically studied signal transduction events including: tyrosine phosphorylation, Ca++ flux, and ceramide production in the Jm and JMRE sublines. The tyrosine phosphorylation patterns and the Ca++ influx generated following sIgM engagement were very similar in the JM and JMRE sublines. In contrast, the generation of ceramide differed in the PCD-resistant and PCD-susceptible sublines. Ceramide is produced following cross-linking sIgM on WEHI-231.7 JM cells and causes PCD. Ceramide levels in anti-IgM-treated WEHI-231.7 JMRE cells are low and appear to be insufficient to induce PCD.

Apoptosis↗
PubMed1995

Bcl-2 and Bcl-2-related proteins in apoptosis regulation.

In this review we have discussed the importance of Bcl-2 and related proteins in the regulation of apoptotic cell death in mammalian systems. It is clear that Bcl-2 plays a critical role in controlling many forms of PCD. Bcl-2 seems to have particular significance in lymphocyte development and the function of the immune system. We have also discussed the increasing size of the newly identified Bcl-2 family. There are a number of Bcl-2 homologues in human, murine, avian, nematode, and viral systems. The evolutionary conservation of the function of the Bcl-2 homologues, reinforces the importance of PCD in all complex organisms. Some of these bcl-2-like genes function as agonists and others as antagonists. Despite the seemingly universal importance of Bcl-2, it is unable to prevent PCD in all systems. In addition, we have described a role for other Bcl-2 family members in systems in which Bcl-2 is ineffective and supplied a potential rationale for the large number of genes involved in the regulation of PCD. Identification and functional analysis of the Bcl-2 family members reveals the complex nature of cell death regulation. As we begin to appreciate the significance of PCD in the control of development and homeostasis, its regulation at the molecular level is becoming better understood. Bcl-2 has long been the only known intracellular regulator of the PCD pathway(s), although its ability to prevent apoptosis is not universal. We now know that bcl-2 is only one member of an evolutionary conserved family of genes which display different patterns of expression as well as function. At least two family members, Bcl-xs and Bax, act in opposition to Bcl-2. The discovery of these new family members, including those with Bcl-2-like function and antagonists, should help clear up the discrepancies seen in Bcl-2's ability to protect cells from PCD. In doing so, we will be able to further define the pathways associated with cell death signaling. The study of these family members, as well as the non-related genes of the PCD pathways (ced-3, ced-4, ice) should lead us to understanding of how cells of multicellular organisms make decisions to die.

Animals↗
PubMed1995

Apoptosis in B lymphocytes: the WEHI-231 perspective.

In this review we summarize recent work on the molecular basis of apoptosis in the murine B cell lymphoma WEHI-231. WEHI-231 cells undergo apoptosis in response to antigen receptor cross-linking with anti-Ig reagents. Death is specifically triggered via surface IgM (sIgM); cross-linking sIgD, Ia or FcR has no effect. Apoptosis is preceded by growth arrest in the G0/G1 phase of the cell cycle and may not occur in all currently available WEHI-231 sublines. The continuous passage of WEHI-231 cells in different laboratories has yielded variants that differ greatly in their response to anti-Ig treatment because apoptotic cells tend to be negatively selected in culture. Resistant and susceptible variants undergo growth arrest in response to anti-Ig but only susceptible cells go on to die by apoptosis. Cells resistant to anti-Ig have intact apoptotic machinery as indicated by their susceptibility to dexamethasone, irradiation and other treatments. However, anti-Ig-resistant cells are also resistant to apoptosis induced by the immunosuppressants cyclosporin A, FK-506 and rapamycin. We discuss the experimental evidence indicating that the apoptotic machinery in WEHI-231 cells is pre-activated but under constant negative regulation by short-lived protein inhibitors. Inhibition is removed by a mediator released in response to anti-Ig treatment in susceptible sublines. The mediator of death is the sphingosine derivative, ceramide, presumably produced by membrane sphingomyelinases activated by anti-Ig. A hypothetical model on how ceramide kills WEHI-231 is presented.

Animals↗
PubMed1994

Identification of immunosuppressant-induced apoptosis in a murine B-cell line and its prevention by bcl-x but not bcl-2.

Cyclosporin A, FK-506, and rapamycin are immunosuppressants often used as pharmacological probes to study lymphocyte activation and physiological cell death (PCD). Because cyclosporin A and FK-506 are known to prevent PCD in T-cell hybridomas and thymocytes, we used these reagents, as well as rapamycin, to determine whether they alter the pathway leading to apoptosis in murine WEHI-231 cells following surface IgM cross-linking. We observed that the immunosuppressants themselves induced PCD in WEHI-231 cells, but only in sublines susceptible to anti-IgM-mediated apoptosis. PCD was preceded by growth arrest and characterized by the DNA fragmentation pattern typical of apoptosis. In B-cell lines resistant to anti-immunoglobulin- and immunosuppressant-induced PCD, cyclosporin A, FK-506, and rapamycin caused growth arrest. PCD was also induced by inhibitors of protein synthesis in WEHI-231 cells but not in the mature B-cell line BAL-17. Immunosuppressant-induced and protein synthesis inhibitor-induced PCD, but not growth arrest, could be prevented by the overexpression of bcl-xL, while transfection with bcl-2 did not affect PCD or cell cycle arrest. These results suggest that bcl-2 and bcl-xL may control partially independent systems to inhibit PCD in lymphoid cells and that PCD in B and T cells may be differentially regulated.

Animals↗
PubMed1994

Fc gamma RII cross-linking inhibits anti-Ig-induced erg-1 and erg-2 expression in BCL1.

Activation of B cells through their Ag receptor is known to be negatively regulated by Fc gamma RII engagement. To explore the molecular and biochemical mechanisms of Fc gamma RII-mediated inhibition, we investigated the effect of Fc gamma RII engagement on the expression of two immediate-early genes, egr-1 and egr-2, and tyrosine phosphorylation events following the activation of the murine B cell line, BCL1. Egr-1 and egr-2 were expressed in BCL1 after slg cross-linking. The induction of egr-1 and egr-2 expression was prevented when the Fc gamma RII was co-cross-linked with slg in BCL1, but not in WEHI-231. The inhibitory effects of Fc gamma RII engagement on egr-1 and egr-2 expression occurred when the Fc gamma RII was cross-linked with either slgM or slgD. Treatment with cyclosporin A prevented the expression of egr-2 induced by slg cross-linking, but did not inhibit egr-1 expression. In addition, cyclosporin A did not prevent the negative-regulatory effects of Fc gamma RII engagement on egr-1 expression, suggesting that the Fc gamma RII works upstream from the site of action of cyclosporin A. To investigate activation signals more proximal to the plasma membrane, we compared tyrosine phosphorylation patterns of several effector molecules known to play a role in B cell activation. Cross-linking of slg induced tyrosine phosphorylation of the p62 GAP-associated protein. The p62 protein became hyperphosphorylated in response to co-cross-linking of slg with Fc gamma RII. Our results identify egr-1 and egr-2 as targets of Fc gamma RII-mediated inhibition of anti-Ig-induced B cell activation. In addition, they show that negative regulation by Fc gamma RII is effective in both cyclosporin A-sensitive and insensitive pathways. Further, we suggest a possible Fc gamma RII signaling pathway leading to the inhibition of egr-1 and egr-2 expression.

Animals↗
PubMed1994

Immunity and inflammation: the cosmic view.

This paper presents an overview of the evolution of defence reactions in multicellular animal life. The co-evolution of hosts and pathogens provides the context to describe the major features of defence reactions and the countermeasures they evoke in their targets. Three major types of solutions to the riddle of self-non-self discrimination are discussed briefly: non-clonal recognition mediated by lectins, the preferential accumulation of C3 in microbial surfaces and vertebrate clonal immunity. Vertebrate immunity is described as a specialized type of inflammation against infectious agents that evolved in response to countermeasures successfully used by intracellular pathogens against non-specific defences.

Animals↗
PubMed1994

Physiological cell death in B lymphocytes: I. Differential susceptibility of WEHI-231 sublines to anti-Ig induced physiological cell death and lack of correlation with bcl-2 expression.

WEHI-231 is a murine lymphoma generally considered to represent an immature B cell. Cross-linking of slg on WEHI-231 leads to growth arrest and eventually physiological cell death (PCD). We characterized three sublines of WEHI-231 by flow cytometry and compared their responses with slg cross-linking. All sublines had identical expression of a series of common B cell surface markers (IgM, IgD, Fc gamma R, ICAM-1, and CD45), but one was I-A-. Despite the phenotypic similarities between these sublines, anti-IgM caused aptotosis in only two sublines, although it inhibited growth in all three. The growth arrest induced by anti-IgM was reversible by lipopolysaccharide and Th2 clones and independent of Fc gamma R engagement. Anti-IgD, unlike anti-IgM, induced neither growth arrest nor apoptosis. To further compare the sublines' susceptibility to PCD, we investigated their responses to anti-IgM by ultrastructural morphology, [3H]thymidine release, propidium iodide exclusion, and incorporation into DNA. By all these experimental criteria, two of the WEHI-231 sublines were susceptible to PCD while the third demonstrated remarkable resistance to anti-IgM, but not irradiation or Th1-induced PCD. This differential susceptibility to PCD did not correlate with either bcl-2 levels in the resting cells or to the decrease in bcl-2 expression following slg engagement. We discuss the implications of these findings for our understanding of PCD in B cells.

Animals↗
PubMed1993

Differential induction of Egr-1 expression in WEHI-231 sublines does not correlate with apoptosis.

To determine whether the absence of inducible Egr-1 expression correlates with apoptosis and growth arrest, we compared the inducible expression of two Egr family members (Egr-1 and Egr-2) in three sublines of WEHI-231. Expression of Egr-2 is induced in all sublines of WEHI-231 following surface immunoglobulin (sIg) cross-linking, but Egr-1 expression is induced in only two. We find that the lack of inducible Egr-1 expression corresponded to an increase in the methylation pattern of the Egr-1 gene. In spite of these differences in Egr-1 expression, all the sublines demonstrate similar inhibition of [3H] thymidine incorporation following anti-Ig treatment. Growth arrest leads to apoptosis in only two of the sublines, but apoptosis does not correlate with the absence of inducible Egr-1 expression. Demethylation, by treatment with 5-azacytidine, in the Egr-1 non-expressing subline allows for induction of Egr-1 expression by anti-Ig, but fails to prevent growth arrest and apoptosis. Therefore, we conclude that the lack of Egr-1 expression is not responsible for either the apoptotic response or growth arrest induced by anti-Ig in WEHI-231.

Animals↗
PubMed1989

Direct activation of murine resting T cells by con A or anti-CD3 Ig.

The induction of antigen-specific T cell activation is highly dependent on accessory cells (AC) which present processed antigenic fragments associated with MHC molecules and provide costimulatory signals for T cells. Antigen-specific T cell activation requires cross-linking of the TCR and the reception of one or more nonantigen-specific signals which eventually lead to T cell activation and proliferation. This sequence of events can be mimicked by lectins, bacterial enterotoxins, and anti-TCR antibodies in conjunction with APC or the combination of phorbol esters and Ca ionophores. Although the combination of PMA + Ca ionophore and certain types of T-T interactions result in APC independent T cell activation, it is generally assumed that physiologic T cell activation requires APC. The seemingly direct activation of T cells by other T cells is rather surprising in view of the known APC dependence of antigen, lectin and anti-TCR mediated T cell activation. It is conceivable that T cell mediated T cell activation is due to "cryptic" APC contamination because the total absence of APC is difficult to disprove. In reality, neither total depletion nor residual contamination with APC can be proven or disproven experimentally. Thus it can be legitimately argued that both APC dependent and independent T cell activation occur, albeit under different experimental conditions. For instance, it is possible that APC independent activation of T cells by lectins and anti-TCR antibodies would require high concentrations of activators to overide their dependence on APC. It is also conceivable and, in our opinion quite likely, that once activated, T cells could propagate T cell activation through T-T interactions. In this report we test two hypotheses: (1) The triggering of resting T cells leading to autocrine cell proliferation depends entirely on cross-linking TCR molecules, and (2) The presence of activated T cells facilitates TCR mediated activation of resting T cells without the participation of conventional APC. We present evidence that highly purified, small resting T cells can be reproducibly activated with high doses of ConA, plastic bound anti-CD3 mab and its F(ab')2 fragments. This APC independent response results in blastic transformation, expression of the IL2 Receptor, the secretion of IL2 and significant proliferation of both CD4+ and CD8+ murine T cells. These observations demonstrate that vigorous cross-linking of TCRs by anti-CD3 mab and, presumably ConA, is sufficient to induce T cell activation and autocrine (IL2 driven) proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Cellular pathways for rejection of class-I-MHC--disparate skin and tumor allografts.

We have investigated the relative roles of the Lyt-2+ and L3T4+ T lymphocyte subsets in rejection of class-I-MHC-antigen-disparate skin and tumor allografts. To deplete T cells in vivo, rat anti-Lyt-2 or anti-L3T4 monoclonal antibodies (mAb) were administered to adult-thymectomized (ATX) recipient mice prior to transplantation. BALB/c (H-2d) recipient mice rejected the Ia- Sarcoma I (Sa1) (H-2a) tissue culture-derived tumor after depletion of the L3T4+ T cell subset in vivo. In contrast, depletion of the Lyt-2+ T cell subset permitted lethal tumor growth in all recipient mice. To determine the role of particular T cell subsets in rejection of Ld class-I-MHC-antigen-disparate allografts, BALB/c skin was transplanted to BALB/c-H-2dm2 recipient mice. Skin grafts were rejected by control mice with a mean survival time (MST) of 14.5 days. The MST of skin grafts for mice treated with anti-L3T4 mAb was 16.6 days. In contrast, administration of anti-Lyt-2 mAb alone (MST = greater than 47 days) or together with anti-L3T4 mAb (MST = greater than 50 days) caused prolonged or indefinite graft survival in all recipient mice. Depletion of specific T cell subsets was confirmed by flow cytometric analysis and by analysis of T cell function in vitro. These results suggest that Lyt-2+ T lymphocytes are essential for rejection of class-I-MHC-disparate allografts; indirect presentation of alloantigen to L3T4+ T cells may not be necessary for rejection.

Animals↗
PubMed1986

T15 idiotype expression in the murine response to phosphorylcholine is actively regulated by genes linked to the Igh-C locus.

In this report, we demonstrate the existence of a regulatory system that can determine the relative expression of individual clones (idiotypes) within the total immune response to PC. Studies of Igh-C-congenic mice and backcross analysis demonstrate that this regulation is controlled by genes linked to the immunoglobulin heavy chain locus. The regulation acts in a trans fashion. The regulatory genes of one parental allele can control the expression of idiotopes coded for by both parental alleles. This regulation does not appear to affect the quantity of the response, but could affect the quality of the response, depending on the potential repertoire and avidity of the individual clones available to respond to a given antigenic challenge.

Animals↗
PubMed1986

Immunoregulation by T cells. I. Characterization of the IEk-specific Lbd self-reactive T cell clone that helps, suppresses and contrasupresses B cell responses.

This paper describes an L3T4+, Lyt-2- cloned T cell line of CBA/N origin that is specific for IEk-encoded products. Splenic dendritic cells are the predominant stimulatory populations for Lbd cells, being approximately 100 times more effective than large activated B cells. Small B cells and T cells are nonstimulatory. Lbd cells help large B cells to make polyclonal antibody responses, but are unable to activate small B cells and to replace antigen-specific helper T cells in T cell-dependent responses to phosphorylcholine or sheep red blood cells. In the presence of antigen-specific helper T cells, Lbd can amplify, suppress, or contrasuppress T cell function, depending on the type and relative ratios of antigen-reactive cells. We explain our findings as a consequence of the self reactivity among helper T cells.

Animals↗
PubMed1986

Functional studies of pluripotential hemopoietic stem cells in mouse brain.

The report of pluripotential hemopoietic stem cells (PHSC) in the murine brain, as detected in the colony-forming unit (CFUs) assay (Bartlett 1982), prompted us to investigate the functional significance of these cells. Although we confirmed that the transfer of brain cells into irradiated hosts produced CFUs, they did not reconstitute erythropoietic or immune functions. Failure to reconstitute immune function was corroborated by FACS analysis. To test whether the injection of brain cells stimulates self-reconstitution, the effect of host irradiation on CFUs production was studied. CFUs frequencies resulting from the transfer of brain or irradiated brain cells were similar and significantly higher in 800 R vs. 1200 R recipients at 10 days. Our experiments do not support the existence of PHSC in the brain, and suggest that colony formation after brain cell transfer may be the result of an adjuvant effect.

Anemia↗