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Biomedical subjects

A Altman

Publications and source records attributed to A Altman.

At least 163 records · Page 9Linked to original sources
PubMed1982

Growth and metabolic activity of lemon juice vesicle explants in vitro.

Actively growing juice-vesicle explants, established from small lemon (Citrus limon L. Burm. f. var. ;Eureka') fruits, were cultured in vitro on defined media. The juice vesicles continued to enlarge in culture for several months, without callus proliferation, and their initial growth was promoted by indoleacetic acid, gibberellic acid, and N(6)-benzyladenine.The metabolic competence of the explants, and its relevance to whole fruit development, was further investigated. Juice vesicles continued to accumulate protein on all media, for at least 16 days, but sugars did not change much during culture. Acid invertase increased dramatically during the first days of culture, and its specific activity was markedly promoted by indoleacetic acid, and to a lesser degree by gibberellic acid. Total peroxidase of juice vesicles increased progressively up to the 11th day of culture, and its specific activity was promoted by all three hormones, especially by N(6)-benzyladenine. Explant growth was accompanied by appearance of several cathodic and anodic isoperoxidases.The results suggest that the study of this unique juice vesicle system may contribute to a better understanding of fruit development.

Journal Article↗
PubMed1982

Arginine and ornithine decarboxylases, the polyamine biosynthetic enzymes of mung bean seedlings.

General properties and relative activities of l-arginine decarboxylase (ADC) (EC 4.1.1.19) and l-ornithine decarboxylase (ODC) (EC 4.1.1.17), two important enzymes in putrescine and polyamine biosynthesis, were investigated in mung bean (Vigna radiata L.) tissues. Both activities increase linearly with increasing concentrations of crude enzyme, but the increase in ADC activity is considerably greater. The decarboxylation reaction is linear for up to 30 to 60 minutes, and both enzymes have a pH optimum of 7.2. alpha-Difluoromethyl-ornithine inhibits ODC activity of excised roots, while increasing ADC activity.High specific activity of both enzymes is detected in terminal buds and leaves, while root and hypocotyl activity is low. Different ADC-to-ODC activity ratios are found in various tissues of mung bean plants. Substantial increase in the activity of both enzymes is detected in incubated sections as compared with intact plants. A comparison of several plant species indicates a wide range of ADC-to-ODC activity ratio.It is suggested that both ADC and ODC are active in plant tissues and that their relative contribution to putrescine biosynthesis is dependent upon the type of tissue and growth process.

Journal Article↗
PubMed1982

Polyamines and root formation in mung bean hypocotyl cuttings : I. Effects of exogenous compounds and changes in endogenous polyamine content.

The effect of several polyamines (putrescine, spermidine, and spermine), their precursors (l-arginine and l-ornithine), and some analogs and metabolic inhibitors (l-canavanine, l-canaline, and methylglyoxal-bis [guanylhydrazone]) on root formation have been studied in mung bean (Vigna radiata [L.] Wilczek) hypocotyl cuttings.Exogenously applied polyamines did not promote adventitious root formation. Rooting was inhibited by l-canavanine and l-canaline, and this inhibition was reversed by the corresponding amino acids l-arginine and l-ornithine. Methylglyoxal-bis (guanylhydrazone), an inhibitor of S-adenosylmethionine decarboxylase and polyamine biosynthesis, was also found to inhibit root formation. All compounds at concentrations of >10(-4) molarity completely inhibited natural root formation, whereas at <10(-5) molarity only the indole-butyric acid-induced root formation was inhibited.Indole-butyric acid-induced root formation was accompanied by a considerable increase in polyamine levels, more than 2-fold of the control. Whereas senescing (unrooted) cuttings evinced a rapid decline in polyamine content during 48 hours, indole-butyric acid treatment resulted in elevated levels of putrescine and increased putrescine to spermidine ratio. The changes in polyamines were dependent on indole-butyric acid concentration and were organ specific.

Journal Article↗
PubMed1982

Constitutive and mitogen-induced production of T cell growth factor by stable T cell hybridoma lines.

Stable T cell growth factor- (TCGF; IL 2) producing cloned T cell hybridoma lines were constructed by fusing murine alloantigen-activated T cells with the 8-azaguanine-resistant lymphoma line, BW5147. Many, but not all, clones of one of these hybridomas, i.e., hybridoma 24, secreted TCGF constitutively, but production was markedly enhanced by stimulation with T cell mitogens. Large numbers of TCGF-secreting hybridoma cells in a stable functional state could be obtained from histocompatible mice inoculated with cloned T cell hybridomas. Moreover, such in vivo-derived hybridoma cells could be stimulated sequentially with mitogen at least twice to secrete their biologically-active product, resulting in larger TCGF yields from the same cells. The secreted product of these T cell hybridoma lines resembled TCGF isolated from other cellular sources in that it: a) supported the growth of a TCGF-dependent T cell line; b) provided help for the induction of alloantigen-reactive cytotoxic T lymphocytes from thymocyte precursors; c) facilitated concanavalin A-induced mitogenic responses of low thymocyte numbers; d) had an apparent m.w. of 30,000 to 40,000 by gel filtration chromatography; and e) was eluted from DEAE-Sephacel ion-exchange chromatography columns by salt concentrations of 30 to 150 mM NaCl. The ability of these T cell hybridomas to grow in vivo and retain their functional characteristics in a stable form should prove useful in terms of providing large numbers of TCGF-secreting cells and studying in vivo aspects of the production of TCGF as well as other immunoregulatory mediators.

Animals↗
PubMed1982

Helper factor production in murine secondary syngeneic mixed leukocyte reactions.

Culture supernatants of murine thymocytes or spleen cells responding in a secondary syngeneic mixed leukocyte reaction (SMLR) were studied for their biologic effects on cell-mediated immune responses in vitro. Such supernatants contained helper factor(s) that facilitated the development of alloantigen-specific cytotoxic T lymphocyte (CTL) responses from thymocyte precursors. Thymocytes, but not spleen cells, required activation by allogeneic effect factor (AEF) in primary culture in order to proliferate and produce biologically active mediator(s) during a secondary SMLR. The same culture supernatants possessed, in some instances, weak T cell growth factor (TCGF; IL 2) activity. However, TCGF activity could be dissociated from helper factor(s) active in the CTL induction assay because some culture supernatants that had potent helper activity were devoid of TCGF activity. This lack of TCGF activity was not due to a lower degree of sensitivity of the TCGF assay or to the presence of a selective TCGF inhibitor in the SMLR-derived supernatants, indicating that the helper factor(s) studied is distinct from TCGF. Production of immunoregulatory lymphokines during the SMLR may serve as a physiologically relevant model for studying the role of T cell-derived lymphokines in immunoregulation.

Animals↗
PubMed1982

Adenosine deaminase positive, E receptor negative lymphoma.

The measurement of enzymatic activity in the blast cell is a recent investigational technique which seems to complement immunologic measurement of cell membrane receptors in childhood lymphoproliferative malignancies. We have identified a patient with non-Hodgkin's lymphoma, not readily classifiable on the basis of either morphology or cell surface markers, i.e., E rosette and SIg negative, EAC positive. Analysis of enzymatic function, however, revealed markedly elevated ADA activity and essentially normal TdT activity. ADA positive lymphoma can arise from a primitive T-cell line. It is, thus, apparent that the morphological description of malignant lymphoid lines must be accompanied by surface marker and enzymatic data in order to properly classify cell lineage and identify appropriate therapeutic modalities.

Adenosine Deaminase↗
PubMed1981

Analysis of T cell function in autoimmune murine strains. Defects in production and responsiveness to interleukin 2.

In the studies reported here, we have analyzed the production and consumption of T cell growth factor, more recently termed interleukin 2 (IL-2), as well as some cell-mediated immune functions, in murine strains [MRL, BXSB, NZB, and (NZB x NZWF1] manifesting systemic lupus erythematosus (SLE)-like syndromes. Young (4-6 wk) or old (4-8 mo) autoimmune or normal mice were studied and compared with regard to the following T cell functions in vitro after stimulation with concanavalin A (Con A): (a) mitogenic response; (b) IL-2 levels in culture supernates; and (c) the ability to respond to and adsorb IL-2. In addition, proliferative activity in the allogeneic mixed leukocyte culture and frequency of alloreactive cytotoxic T lymphocyte precursors (CTLp) were analyzed in some of these strains. Reduced Con A-induced mitogenic responses and IL-2 production appeared at 3-6 wk of age in the early, severe SLE developing strains MRL-Mp-lpr/lpr (MRL/l) and male BXSB and progressed thereafter. Similar defects appeared at a later stage in MRL/Mp-+/+ and (NZB x NZW)F1 hybrid mice, which develop late disease. Detailed analysis of cells from the enlarged lymph nodes and spleens of older MRL/l mice demonstrated that such cells: (a) responded poorly to Con A or allogeneic stimulator cells, even in the presence of exogenous IL-2; (b) did not suppress IL-2 production by normal spleen cells; (c) were relatively incapable of adsorbing or inactivating IL-2; and (d) had a markedly reduced anti-H-2b CTLp frequency in the mesenteric lymph nodes but a normal one in spleen. These results indicate that the proliferating Thy-1.2+, Lyt-1+ T cells in MRL/l mice are defective in their responses to mitogenic stimuli, in IL-2 production, and in expression of acceptor sites for IL-2. The relevance of these defects to the MRL/l disease as well as to the role of IL-2 in autoimmunity in general remains to be determined.

Age Factors↗
PubMed1981

Differentiation of murine bone marrow stem cells in vitro: long-term growth promoted by a lymphocyte-derived mediator.

In attempts to induce differentiation of lymphoid cells from hematopoietic stem cells in vitro, the effects of allogeneic effect factor on the growth of murine bone marrow cultures were studied. Allogeneic effect factor is a soluble mediator derived from mixed secondary murine leukocyte cultures. For several weeks it supported the growth of bone marrow cultures, as indicated by the maintenance of stem cell activity, cellular proliferation, and heterogeneity. Another lymphokine, T cell growth factor, did not, Pre-T lymphocytes could be detected in these cultures for several weeks.

Animals↗
PubMed1981

Molecular analysis of the beta-thalassemia phenotype associated with inheritance of hemoglobin E (alpha 2 beta2(26)Glu leads to Lys).

Inheritance of the gene for betaE-globin is associated with hypochromia and microcytosis, reminiscent of typical heterozygous beta-thalassemia. Patients with hemoglobin (Hb)E-beta-thalassemia exhibit clinical phenotypes of severe beta-thalassemia, a circumstance not encountered in other compound heterozygous states for structural beta-chain mutations and beta-thalassemia. We have analyzed the kinetics of globin synthesis and the levels of globin messenger (m) RNA accumulation in patients with Hb E-beta-thalassemia and Hb E trait. The initial rate of beta-globin synthesis (betaE/alpha=0.20-0.34) was less than expected on the basis of gene dosage, or comparable studies of other compound heterozygous states for beta-thalassemia and structurally abnormal beta-chains. betaE-globin synthesis was not only reduced during short-term incubations (1-5 min), but also remained relatively unchanged during long-term pulse or chase incubations up to 5h. Analysis of globin mRNA by cell-free translation and molecular hybridization confirmed that the unexpectedly low levels of betaE-globin synthesis were associated with comparable reduction in the levels of beta-globin mRNA. In Hb E-beta-thalassemia the betaA + betaE (alpha globin nRNA ratio observed were substantially lower than those obtained from reticulocytes of patients with heterozygous beta-thalassemia, or Hb S-betaO-thalassemia, while in Hb E trait, the betaA + betaE/alpha mRNA ratio was in the ranged observed for beta-thalassemia trait. The betaE-globin gene specifies reduced accumulation of betaE-globin mRNA, a property characteristic of other forms of beta-thalassemia. The beta-thalassemia phenotype associated with inheritance of Hb E is thus determined at the level of beta-globin mRNA metabolism.

Globins↗
PubMed1980

Construction of T cell hybridomas secreting allogeneic effect factor.

T cell hybridoma lines were constructed by fusion of DBA/2 alloantigen-activated T cell blasts with the AKR thymoma line BW5147. Certain of the hybridomas prepared in this manner secreted spontaneously into their culture supernates biologically active molecules that displayed B cell- and T cell-activating properties characteristic of allogeneic effect factor (AEF). Cell surface phenotype analysis documented that the hybridomas were, indeed, somatic cell hybrids between the two respective partner cells used for fusion. The B cell-activating properties of these hybridoma supernates was demonstrated by their capacity to stimulate T cell-depleted spleen cells to respond in vitro to T-dependent antigens. The T cell-activating properties of these hybridoma supernates was verified by their capacity to stimulate autonomous development of self-specific cytotoxic T lymphocytes and by their capacity to exert mitogenic effects on unprimed T cells. The biologically active molecules secreted by these hybridomas were, like conventional AEF, inhibitable by specific anti-Ia antibodies thus indicating the presence of Ia determinants on the relevant hybridoma products. Finally, these AEF-secreting hybridomas could be stimulated to proliferate and to secrete increased quantities of AEF when exposed to the specific alloantigen-bearing target cells to which the T cell blasts had been originally sensitized.

Animals↗
PubMed1980

Promotion of hematopoietic stem cell differentiation in vitro by a soluble mediator, allogeneic effect factor.

This study was designed to investigate the effects of allogenic effect factor (AEF), a soluble mediator derived from short-term mixed lymphocyte cultures (MLC) of in vitro alloantigen-primed T cells, on cultures of murine bone marrow cells. Cultures established under suboptimal conditions namely, in the absence of a pre-established adherent cell layer as required in conventional Dexter-type cultures--declined and lost their stem cell activity rapidly. In contrast, supplementation of these cultures, at initiation and thereafter, with AEF, but not with T cell growth factor (TCGF), induced cell growth and proliferation for several weeks. Such AEF-supplemented cultures exhibited cellular heterogeneity and stem cell activity for significantly longer periods than the control cultures. Even in conventional Dexter cultures, established under optimal conditions, AEF had a beneficial effect on cellular growth and proliferation and myeloid progenitor cell (CFU-C) activity. Furthermore, cell capable of synergizing with suboptimal numbers of mature T cells in con A-induced mitogenic responses, shown by others to be pre-T cells, were detected in the AEF-supplemented cultures for several weeks.

Animals↗
PubMed1980

Existence of T cells manifesting self-reactivity indistinguishable from alloreactivity.

The studies reported here were designed to analyze the phenotypic characteristics of self-reactive T lymphocytes induced in culture by allogeneic effect factor (AEF), as well as the control of their functional activities by the major histocompatibility complex (MHC). Unprimed T cells cultured with AEF in the absence of exogenous stimulating target cells become activated against self-antigens, as evidenced by their ability to manifest two distinct activities. First, such cells could lyse syngeneic target cells. This cytolytic activity was directed against H-2K antigens and was mediated by Lyt-2+ T cells. Second, the AEF-activated T cells could be stimulated in a secondary culture to high levels of proliferative activity by irradiated syngeneic spleen cells. The stimulator cells in this syngeneic mixed lymphocyte reaction (MLR) were found to be Thy-1-negative, Ia-positive splenic adherent cells. Stimulation in the secondary syngeneic MLR was provided by I-region specificities, and the majority of the proliferating cells were Lyt-1+ cells. Finally, AEF-induced T cells were effective in serving as effectors of graft-vs-host reactions in vivo in syngeneic recipients. These results prove that, under appropriate conditions, murine T lymphocytes can display aggressive patterns of self-reactivity that are similar in both quantity and quality to the classical patterns of alloreactivity and may have great significance for our understanding of MHC recognition processes.

Animals↗