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Biomedical subjects

B Singh

Publications and source records attributed to B Singh.

At least 721 records · Page 40Linked to original sources
PubMed1986

Alloantigenic sites on class I major histocompatibility complex antigens: 61-69 region in the first domain of the H-2Kb molecule induces specific antibody and T cell responses.

The most polymorphic residues in the first domain of class I major histocompatibility complex (MHC) molecules are in the 61-69 region. We have chosen the H-2Kb molecule for determining the role of this region in the induction of alloimmune responses. A synthetic peptide, Glu-Arg-Glu-Thr-Gln-Lys-Ala-Lys-Gly corresponding to this region was synthesized. T cells enriched from the lymph nodes of allostrain mice that were previously primed with H-2Kb containing cells or with the synthetic peptide in complete Freund's adjuvant undergo extensive in vitro proliferation in response to the synthetic (61-69)H-2Kb peptide. The response was dependent on the presentation of the (61-69)H-2Kb peptide by the syngeneic antigen-presenting cells and was blocked by anti-class II MHC monoclonal antibodies. This peptide fragment of class I MHC molecule activates only helper/inducer type T cells that are involved in the primary responses but not the effector cytotoxic T cells. When coupled to a carrier protein, (61-69)H-2Kb peptide induced antibodies in allostrain mice that bind to intact H-2Kb molecule. No antibodies or T cell responses could be induced in syngeneic H-2b mice. The antigenic site on the H-2Kb molecule recognized by two H-2Kb-specific monoclonal antibodies B8 X 3 X 24 and Y-25 was also mapped in the 61-69 region by direct binding to the synthetic peptide. Therefore the 61-69 region on the H-2Kb molecule represents the first defined sequence on a class I molecule that is directly involved in the induction of alloimmune responses.

Animals↗
PubMed1986

Moloney murine sarcoma virus encoded p37mos expressed in yeast has protein kinase activity.

We describe the expression of the Moloney murine sarcoma virus env-mos protein (p37mos) in yeast under the control of the yeast GAL1 promoter. Consistent with our previous results concerning the p37mos protein kinase made in virus infected mouse cells, p37mos produced in yeast possesses autophosphorylation activity in an immune complex kinase assay using anti-mos (37-35) serum.

Gene Expression Regulation↗
PubMed1986

A requirement for physical linkage between determinants recognized by helper molecules and cytotoxic T cell precursors in the induction of cytotoxic T cell responses.

It has long been understood that both antibody and delayed-type hypersensitivity responses are induced through collaborative events in which the determinants recognized by the precursor cells must be physically linked to the determinants recognized by the helper. Although it is clear that the generation of memory cytotoxic T lymphocyte precursors (CTLp) involves linked recognition of determinants, the induction of CTL responses has been viewed as being dependent upon interleukin 2 (IL 2), which could be provided by a helper cell, but independent of requirements for antigen bridging. In this work, we have designed a system that lacks exogenous IL 2 by using as our source of help, antigen-specific helper molecules derived from helper T cells. These soluble helper molecules are uncontaminated by IL 2 and unlike a helper cell, are unable to produce IL 2. Helper molecules specific for chicken red blood cells (Crbc) and for a synthetic polypeptide, poly 18, were tested. Thymocyte responders require a source of help to respond to alloantigens intrinsically expressed on the surface of adherent stimulator cells. To analyze the mechanism whereby the helper molecules acted, we used a system involving recognition of haptenic and carrier determinants that were physically linked by virtue of being located on the same cell surface (intra-structural linkage). Adherent stimulator cells were pulsed with Crbc or poly 18 so that the alloantigens recognized by the thymocyte CTLp (intrinsically expressed class I) were either linked or unlinked to the carrier determinants (Crbc or poly 18) presented by the adherent cells and recognized by the helper molecules. Both types of helper molecule were shown to be antigen-specific in crisscross experiments. The helper molecules specific for Crbc were able to induce the thymocyte CTLp only when both hapten and carrier were present on the same stimulator cell surface. Because we were not able to detect a requirement for H-2-restricted recognition of carrier antigen, this inductive event must be viewed as requiring linked associative recognition of determinants, but being noncognate. In contrast, the helper molecules recognizing poly 18 showed a requirement for both physical linkage of determinants and for H-2 restricted recognition, indicating that the mechanism of induction was cognate in nature. Therefore, we have shown that interactions between CTLp and soluble, antigen-specific, helper cell-derived inductive molecules are similar in nature to those of other T cell precursors and of B cells in the stringent requirement for close physical proximity achieved by linked or cognate recognition of determinants across an antigen bridge.

Animals↗
PubMed1986

A new "marker" protein for astrocytes.

A monoclonal antibody (Mab J1-31) has been produced by using human brain homogenate as immunogen in mouse. Double-label immunofluorescence microscopy on cryostat sections of human, rabbit and rat brain, reveals staining of cells that are also stained with antiserum to glial fibrillary acidic protein (GFAP, a commonly used marker protein for astrocytes). However, there is no decrease in staining due to Mab J1-31 in sections incubated in antiserum to GFAP prior to incubation with the J1-31 ascites fluid. Immunoprecipitation of aqueous and detergent extracts of brain homogenate gives a single band at 30K by SDS-PAGE followed by autoradiography. Immunoelectron microscopy shows that the J1-31 antigen is associated with the cytoskeleton. Thus, the Mab J1-31 recognizes a new protein present in GFAP positive cells (astrocytes) in the brain.

Animals↗
PubMed1986

Fine-specificity analysis of antibodies directed to the C-terminal peptides of cytochrome c recognized by T-lymphocytes.

Recognition of cytochrome c by T-lymphocytes seems to involve the amino acid residues in the C-terminal region of the molecule. Lys-99 has particularly been identified as one of the critical residues in the recognition process. We have now raised antibodies against the C-terminal region of the cytochrome c molecule to map the residues that may be recognized by B-lymphocytes. These antibodies were generated in high-responder B10.A mice against either the 81-104 CNBr fragment of pigeon cytochrome c or against the synthetic spliced fragment (86-90)-(94-103) of the tobacco hornworm moth cytochrome c. A good antibody response was obtained for both fragments as measured by solid-phase radioimmunoassay. A series of peptides related to these fragments were synthesized for competitive inhibition to assess the antigenic sites on these molecules. In spite of substantial homology between the moth (86-90)-(94-103) and pigeon (81-104) fragments, the antibody populations raised against each fragment differed in their recognition patterns. Residues 99 (Lys), 103 (Ala) and 104 (Lys) were found to be crucial for binding of the anti-pigeon antibody to the pigeon 81-104 fragment. The fine specificity mapping of the antigenic sites on the moth (86-90)-(94-103) fragment indicated that along with some of the residues in the N-terminus (86-90), residue 99 (Lys) was involved in recognition of the moth (86-90)-(94-103) fragment by its antibody. This residue (Lys-99) also acts as a T-cell receptor contact site for both pigeon and moth cytochrome c. We therefore conclude that common patterns of recognition must exist between T and B-cells that recognize the C-terminal region of cytochrome c. Since Lys-99 is also present in mouse cytochrome c, the antigenic site must involve both self and non-self residues.

Amino Acid Sequence↗
PubMed1986

Temperature-dependent cytocidal effects of Moloney murine sarcoma virus.

Infection of L6E9 rat myoblasts with Moloney murine sarcoma virus (Mo-MuSV) at 37 degrees C resulted in the killing of target cells in less than one week. However, cells infected at 37 degrees C and shifted to 40 degrees C were not killed but underwent morphological transformation and had reduced levels of virus-specific RNA. A marked decrease in a cellular 55 kDa protein, as judged by immunoblotting, correlated with increased expression of Mo-MuSV RNA in infected cells.

Animals↗
PubMed1986

Comparison of rostro-caudal brain stem influence on preoptic neurons and cortical EEG.

The changes in activity of preoptic area (POA) neurons, and cortical EEG, upon stimulation of the caudal brain stem reticular formation (CBS) and the rostral brain stem reticular formation (RBS) are compared in this study. Low frequency (LF) stimulation of the CBS (which induced EEG synchronization) and the RBS (which generally did not affect the EEG) had an excitatory influence on a majority of the affected neurons of the POA. In contrast, high frequency (HF) stimulation of the CBS (which produced EEG desynchronization in many instances) and the RBS (which induced EEG desynchronization in all instances) resulted in inhibition of a majority of the affected POA neurons. A larger number of neurons responded to HF stimulation of both brain stem regions, as compared to LF stimulation. The changes induced in the POA neurons, upon stimulation of the two brain stem reticular structures, were not dependent on simultaneous changes in the cortical EEG, except during some cases of stimulation-induced EEG desynchronization.

Animals↗
PubMed1986

Alpha adrenergic system in medial preoptic area involved in sleep-wakefulness in rats.

The study is aimed at investigating the possible involvement of adrenergic mechanisms in the medial preoptic area (mPOA) for modulation of sleep-wakefulness in rats. In this study, saline, norepinephrine (NE), phenoxybenzamine (PBZ) and propranolol (PROP) were injected in the mPOA in different groups of male rats during the day and night. NE and PBZ were injected, during the day and the night respectively, in some control areas adjoining the mPOA in two other groups of animals. Arousal was produced by NE, and sleep by PBZ when they were applied in the mPOA. All other procedures, including application of NE and PBZ in the control areas and beta blocker (PROP) in the mPOA, did not produce alterations in sleep-wakefulness. These findings provide support for a physiological role played by the alpha adrenergic system in the mPOA for arousal, and area specificity of action of this system.

Animals↗
PubMed1986

Influence of preoptico-anterior and posterior hypothalamus on midline thalamic neurons.

The present study was aimed at understanding the influence of the posterior hypothalamus (PH) and the preoptico-anterior hypothalamus (PO-AH) on the neurons of the midline thalamus (MTh) in encéphale isolé cats. A majority of the influenced neurons of the MTh showed increased firing on stimulation of the PH. Although the number of neurons showing increased or decreased firing on PO-AH stimulation were nearly equal, stimulus bound increased firing in many neurons was followed by a prolonged decreased firing. It is likely that the hypothalamo-thalamic circuit constitutes a parallel pathway to the reticulo-thalamic circuit for alteration of the cortical EEG.

Action Potentials↗
PubMed1986

Expression of the v-mos gene alters a Mr 55,000 protein during acute infection by Moloney murine sarcoma virus.

Infection of the rat myoblast cell line, L6E9, with Moloney murine sarcoma virus (Mo-MuSV) clone 124, altered a cellular protein of Mr 55,000 (P55) within 2 days of infection. The alteration of P55 was observed as a reduction in its steady-state level in cell extracts. The reduction of P55 correlated with the appearance of p37mos in infected cells. Except for P55 and one other protein, no change was detected in the total protein pattern of infected cells compared to uninfected cells, as judged by either immunoblots of one-dimensional NaDodSO4 gels or direct two-dimensional gel analysis. P55 levels were unchanged when L6E9 cells were infected with Moloney murine leukemia virus or several different transforming retroviruses. To determine the specificity of this v-mos-induced effect on P55, L6E9 cells were acutely infected with a temperature-sensitive variant (ts110) of Mo-MuSV. When these cells were shifted from 39 degrees C to 33 degrees C, which activates the gag-mos gene product, the P55 level dropped by greater than 50% within 2-3 hr. Conversely, with a shift in temperature from 33 degrees C to 39 degrees C, the cells' P55 level returned to normal within 5 hr, starting at 30 min after shift. These results clearly show that v-mos expression in acutely infected L6E9 cells alters the cellular protein, P55.

Animals↗