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Biomedical subjects

J Rojo

Publications and source records attributed to J Rojo.

15 recordsLinked to original sources
PubMed1992

Effects of dimethyl sulfone (DMSO2) on early gametogenesis in Caenorhabditis elegans: ultrastructural aberrations and loss of synaptonemal complexes from pachytene nuclei.

The free-living nematode Caenorhabditis elegans has been used extensively for studies in developmental and reproductive genetics. Recently, toxicologic studies have been initiated using specific sex chromosome mutations. In the present study, high incidence of male (him) mutants, him-5 and him-8, were treated with dimethyl sulfone (DMSO2), the primary metabolite of dimethyl sulfoxide (DMSO). In addition to differential effects on X-chromosome nondisjunction, loss of viability and fertility were observed. Much lower concentrations of DMSO2 were required to elicit the same aberrational effects characteristic of DMSO (1); thus, the toxicity of the former was significantly more potent. The observed decrease in life span was associated with senescent morphology of meiotic prophase nuclei, such that nuclei from young and old specimens could not be differentiated. Aging in oocytes at pachytene is characterized by nucleo-cytoplasmic aberrations, increased density of the nucleoplasm and cytoplasm, and decrease in numbers of mitochondria. Increasing concentrations of DMSO2 resulted in a corresponding decrease in fertility and increased production of abnormal gametes. At DMSO2 concentrations higher than 1.0%, synaptonemal complexes (SC) were absent from pachytene nuclei; thus, effective pairing and segregation of homologous chromosomes was prohibited. Since the SC is essential for regulating pairing and subsequent separation of bivalents, the lack of an SC explains the loss of fertility, due to the production of unbalanced gametes, observed in DMSO2-treated specimens.

Animals↗
PubMed1990

Molecular associations on the T cell surface correlate with immunological memory.

Different isoforms of CD45 are expressed on naive and memory CD4 T cells in the mouse, as revealed by an antibody to a set of isoforms of CD45 that utilize exon B, called CD45RB. Cloned TH1 and TH2 lines also differ for expression of isoforms detected by this antibody. Differential expression of CD45 isoforms correlates with different behavior of cell surface molecules involved in transmembrane signal transduction. On naive T cells, CD4, CD45 and the CD3/T cell receptor complex behave as independent entities. On memory T cells, these three molecules are stably associated on the T cell surface. Furthermore, on TH2 cells, which express intermediate levels of CD45RB, CD4 is stably associated with CD45 isoforms other than CD45RB, but this complex is not associated with the CD3/T cell receptor. These results lead us to propose that immunological memory in CD4 T cells consists of an altered structure of the T cell's specific signal transduction apparatus controlled by low-molecular weight CD45 isoforms. This altered receptor structure would allow the more sensitive triggering of the T cell characteristic of memory cells. The organization of multimolecular signal transduction systems may be a general means by which cells alter their physiological behavior, allowing the acquisition of new phenotypic characteristics.

Animals↗
PubMed1989

Monoclonal antibodies to murine CD3 epsilon define distinct epitopes, one of which may interact with CD4 during T cell activation.

The TCR is comprised of two variable chains that confer specificity, called alpha:beta or gamma:delta, physically associated with five different molecules that comprise the complex known as CD3. Antibodies to this complex are very useful, as they react with all T lymphocytes. A rat mAb to mouse CD3 has been prepared. It reacts with 100% of T cells in all mouse strains tested but with no other cell type. It binds to the CD3 epsilon chain. This antibody activates cloned T cell lines and normal T cells, provided suitable accessory cells and signals are present. This antibody detects a determinant similar to but not identical with those detected by two previously reported hamster anti-CD3 epsilon antibodies. This antibody fixes C efficiently, and it is thus useful for depletion of T cells from bulk populations. Activation of T cells by one of the three different anti-CD3 epsilon antibodies was inhibited by the Fab fragment of anti-CD4, similar to the effects of anti-CD4 Fab on two previously reported anti-TCR V region antibodies that bind a CD3 epsilon-associated epitope. This further defines a site involving TCR V regions and CD3 epsilon with which CD4 appears to associate during T cell activation.

Animals↗
PubMed1989

Cross-linking and conformational change in T-cell receptors: role in activation and in repertoire selection.

TCRs undergo a series of interactions with ligands during development. We have characterized the interaction of a TCR with its ligand and the attendant co-receptor and co-ligand structures. This characterization has led to the model in which the TCR not only binds to class II MHC, but also binds to CD4 co-receptors and co-ligands such as Mls. We have shown that both cross-linking and conformational change in the TCR are required for optimal T-cell activation. Finally, we have used the observation that a particular self-peptide found abundantly associated with class II MHC in the periphery is essentially lacking from thymic cortical epithelium to argue that positive selection for self-MHC recognition may occur by a novel process in the thymic cortex. A TCR recognizing class II MHC with low affinity could either be multiply cross-linked in the absence of conformational change, which here would be driven by a unique peptide, or could be conformationally changed without cross-linking due to the rarity of the individual high-affinity peptide on thymic cortical epithelial cells. Either proposal leads to a partial signal one delivered via the TCR, which we refer to as signal one-half. This signal one-half would induce the cell to repress its other co-receptor molecule and to undergo maturation events such as up-regulation in TCR expression. Such cells are then rigorously screened for activating interactions with autologous structures, such as Mls. The threshold for clonal deletion is set very low to avoid autoreactivity. By this combination of signaling events, a mature TCR repertoire is generated that has the functional characteristics observed in immune systems.

Animals↗
PubMed1988

Immune recognition and effector function in subsets of CD4 T cells.

T cells expressing the cell surface differentiation antigen CD4 are involved in most immune responses. Our studies address two issues about CD4 T cell responses to antigen: first, how does the T cell receptor come together with its ligand to generate an immune response, and what is the role of the CD4 molecule in this response? Second, are all CD4 T cells identical in their functional activity, and how does the activating signal determine the functional outcome of a response? Our studies outlined below suggest that the T cell receptor and its peptide: class II major histocompatibility complex (MHC) molecule ligand come together in a defined orientation determined in part by the binding of CD4 to both the T cell receptor and its ligand. Our studies suggest that the V beta chain is involved directly in MHC antigen recognition, binding self MHC with low affinity and non-self MHC with high affinity. The selective effect of the Mls locus on V beta expression is believed to reflect the binding of the Mls protein directly to the V beta region. CD4 is described as a co-receptor, forming an inducible part of the T cell receptor and binding to the same class II MHC molecule as that receptor. Studies with both cloned lines and normal CD4 T cell populations suggest the existence of two separable subsets with definable function. One set appears to be specialized for the activation of the humoral immune response, while the other drives the cell-mediated immune responses, particularly those involving the activation of macrophages. These two subsets of CD4 T cells have differential activation requirements, seen particularly in the requirement for interleukin 1 (IL-1) in the activation and clonal expansion of CD4 T cells involved in humoral immunity. This requirement for IL-1 may also be observed in the priming of this subset of CD4 T cells. These studies demonstrate that the optimal activation of CD4+ T cells involves recognition of peptide fragments presented by class II MHC molecules and accessory signals derived from the antigen presenting cells.

Animals↗
PubMed1987

The influence of valence on the functional activities of monoclonal anti-L3T4 antibodies. Discrimination of signaling from other effects.

Anti-L3T4 antibodies have different functional effects on different ligands that activate a cloned, L3T4+ helper T cell line. It is reported here that some of these effects involve positive or negative signaling induced by cross-linking L3T4 molecules, because such effects are not observed using the Fab fragment of anti-L3T4. However, the Fab fragment does inhibit responses to antigen:self class II major histocompatibility complex (MHC) and to anti-T cell receptor monoclonal antibodies directed at a particular V region epitope. The finding that the Fab fragment of anti-L3T4, which does not block binding of anti-T cell receptor V region antibodies and does not negative signal can still block activation by such antibodies suggests an intimate association of L3T4 with the T3: alpha: beta T cell receptor complex. This association may normally be induced by interaction of both structures with antigen:self class II MHC complexes. The data also support the hypothesis that cross-linking the L3T4 molecule in the absence of engagement of the T3: alpha: beta complex generates negative or inhibitory signals. Thus, L3T4 plays a central role in the process of class II MHC-restricted T cell antigen recognition and activation.

Animals↗
PubMedDate not supplied

Evidence for a physical association of CD4 and the CD3:alpha:beta T-cell receptor.

CD4 is a molecule expressed on the surface of T lymphocytes which recognize foreign protein antigens in the context of class II major histocompatibility complex (MHC) molecules. Recognition of antigen:class II MHC complexes by CD4+ T cells can be inhibited by anti-CD4 (ref. 3). Nevertheless, specific recognition of the antigen:Ia complex is clearly a function of the T-cell receptor, which is composed of CD3 and the variable polypeptides alpha and beta. Thus, it has been proposed that CD4 serves an accessory function in the interaction of CD4+ T cells and Ia-bearing antigen-presenting cells by binding to non-polymorphic portions of class II MHC molecules and stabilizing the cell interaction. Based on our observation that anti-CD4 could inhibit activation of a cloned line of CD4+ T cells by antibodies directed at a particular epitope on the variable region of the T-cell receptor, we have recently proposed that CD4 is actually part of the T-cell antigen recognition complex, physically associated with CD3:alpha:beta. But numerous studies showing that CD3 and CD4 are not stably associated on the T-cell surface would appear to contradict this model. Here we show that anti-T-cell-receptor antibodies can co-modulate expression of the T-cell receptor and CD4, and that the monovalent Fab fragment of such an anti-T-cell-receptor antibody can, in conjunction with bivalent anti-CD4 antibody, generate an activating signal for the T cell. These findings provide further evidence for a physical association of the T-cell receptor complex and CD4.

Antibodies, Monoclonal↗
PubMedDate not supplied

Chronic granulocytic leukemia in blastic crisis. Prognostic factors.

Thirty-nine patients with chronic granulocytic leukemia (CGL) in blastic crisis (BC) were studied from 1981 to 1988 at the Hematology Service of the General Hospital of Mexico. The patients were from 18 to 80 years old. Twenty-one patients (54%) were in lymphatic BC and 18 patients (46%) corresponded to BC myeloid. All the patients were treated with different chemotherapy schedules. Only three patients in lymphoid BC and two in myeloid BC achieved complete remission. The longest remission time was 24 weeks and the longest survival 36 weeks. The clinical and laboratory features, such as age, anemia, bleeding, fever, bone pain, adenopathy, splenomegaly, hepatomegaly, extramedullary infiltration, leukocyte count, hemoglobin, platelets, blast cells, in peripheral blood and bone marrow, basophils, and morphology and cytochemistry stains characteristic in bone marrow, were compared between the two groups of patients. None of the clinical and laboratory findings studied were significantly different between the two types of BC, except the evolution time from the diagnosis to the BC, which was more than than two years for most of the patients in lymphoid BC. We also studied the prognosis factors related to survival time. There were no clinical or laboratory differences among the patients who survived more than or less than 14 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Non-Hodgkin's lymphoma (NHL) of the testicle. A clinicopathologic study of 19 patients.

To investigate the frequency, clinical and anatomopathologic characteristics of non-Hodgkin's Lymphoma (NHL) present in the testicle as primary or secondary disease, we reviewed the files of the Hematology and Pathology Services of the General Hospital of Mexico, from January 1975 to December 1988. We found 681 cases of NHL in the Hematology Service; of these, 388 (57%) were male and 8 (2%) of them presented testicle involvement. Two were considered as primary disease, 4 as systemic disease and 2 as secondary or late complications. The overall mean age was 49 years. According to the New Working Formulation (NWF), 7 cases corresponded to the intermediate grade of malignancy and one to a plasmacytoma. The mean survival time of the whole group was 3.9 months. In the Pathology Department, the files of 203 autopsies of patients with NHL were reviewed; 124 (61%) were male and 11 (8.9%) of them presented testicle infiltration. In two, the testicular involvement was known before death and in 9 it was found at autopsy. In one case the infiltration was located in the epididimus and in other in the spermatic cords. The mean age of these patients was 50.7 years. In 6 cases there was extranodal infiltration other than in the testicle: 1 in the nose, and 1 in the central nervous system. According to the NWF, 1 was classified as of low malignancy grade, 7 were of the intermediate malignancy, and 3 of high malignancy grade.

Humans↗