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V Kumar

Publications and source records attributed to V Kumar.

At least 343 records · Page 19Linked to original sources
PubMed1995

Human oligosaccharyltransferase: isolation, characterization, and the complete amino acid sequence of 50-kDa subunit.

Oligosaccharyltransferase (OT) catalyzes the glycosylation of asparagine residues in nascent polypeptides in the endoplasmic reticulum. In a previous communication we reported the purification and characterization of this enzyme from chicken oviduct. Here we describe the purification and sequence analysis of OT from human liver microsomes. Oligosaccharyltransferase copurified with three proteins designated 50-kDa, 65-I and 65-II based on their molecular weights by gel electrophoresis. The N-terminal sequence of the 50-kDa component was homologous to the 50-kDa subunit of avian OT. The N-terminal sequences of 65-I and 65-II were identical to the primary structures of human ribophorins I and II, respectively, predicted by cDNA sequencing. The complete amino acid sequence of the 50-kDa subunit of human OT was determined by chemical sequencing of peptides isolated from chemical and enzymatic digests. The 50-kDa subunit of human OT is 98% identical to its canine homolog, 93% identical to its avian homolog, and 25% identical to the beta subunit of yeast OT. These data indicate that structural features of oligosaccharyltransferase are conserved in all eukaryotes.

Amino Acid Sequence↗
PubMed1995

T cell determinants from autoantibodies to DNA can upregulate autoimmunity in murine systemic lupus erythematosus.

(NZB x NZW) F1 (BWF1) mice develop spontaneous T cell autoimmunity to VH region determinants of syngeneic anti-DNA before the onset of clinical disease. In this study, we characterized the immunogenicity, MHC binding, and lymphokine secretion patterns induced by T cell determinants from the VH region of one such anti-DNA mAb (A6.1) and examined their role in the regulation of autoimmunity. Determinants were identified by proliferation of syngeneic splenic T cells from young, unprimed BWF1 mice in response to overlapping 12-mer peptides representing the entire VH region sequence. Immunization of young BWF1 mice with any of three determinants (A6H 34-45 [p34], A6H 58-69 [p58], and A6H 84-95 [p84]) elicited proliferative responses upon in vitro recall. Upon immunization with the whole A6.1 molecule, however, proliferative responses could be recalled only to the p58 peptide, defining this as immunodominant. The other two peptides (p34 and p84) elicited minimal or no proliferation and could be termed cryptic. Proliferative responses elicited by the cryptic determinants were restricted by a single class II (I-Ed for p34 and I-Au for p84), whereas the immunodominant p58 determinant was restricted by both I-Ed and I-Eu. The cryptic p34 and p84 bound strongly to I-Ed and I-Au, respectively, whereas the immunodominant p58 peptide bound poorly to I-Ed. A6H p84 elicited T cells that secreted lymphokines in a pattern consistent with a Th1-like phenotype, whereas p58 induced a Th2-like cytokine pattern. Immunization with p34 or p84, or adoptive transfer of a p84-reactive T cell line to young BWF1 mice significantly increased IgG anti-DNA levels, accelerated nephritis, and decreased survival. In conclusion, in BWF1 mice, autoreactive T cells recognizing both cryptic and dominant self-determinants on anti-DNA autoantibodies escape deletion or anergy induction. Furthermore, since these cells are spontaneously activated before the onset of clinical disease, they may be involved in the development of the autoimmune process.

Animals↗
PubMed1995

Bone marrow cell transplants involving donors and hosts with haplotypes derived from spretus mice.

Intra-H2 recombinant inbred mice derived from matings between B10 (H2b) and B10.SP2 (H2sp2) mice, with an H2 haplotype derived from Mus spretus, have been used to map genes at H2. Recombinants 10115, 10484, R40, 9347, and 9950 were used as donors or hosts in bone marrow cell (BMC) transplants in irradiated mice. From previous studies of Mus musculus mice, the antigens (Ag) on BMC appear to be inherited recessively. The mechanisms offered include codominant inheritance of transacting genes that regulate expression of BMC Ag (Hh hypothesis) and codominant inheritance of class I Ag motifs capable of sending "negative signals" to effector natural killer (NK) cells (missing self hypothesis). Our results indicate that stem cell donors that express the same class I Ag, but differ at genes between Bat2 and Tnfa in the H2-S/D interval, can differ in immunogenicity of transplanted stem cells. The structural gene for the H2sp2 Ag appears to map telomeric of Bat2 and is codominantly inherited. An H2b gene capable of inhibiting expression of the H2sp2 Ag (or contributing to class I motifs capable of inhibiting NK cell mediated lysis of H2sp2 BMC) maps in the Bat2/Tnfa gene segment, but requires homozygosity for this function and may require the H2-Db gene as well. Although H2sp2 hosts reject H2b BMC, hosts (10115, 10484, R40, and 9347 strain) that are H2b in the centromeric, and H2sp2 in the telomeric, portion of H2 accept H2b BMC grafts. These two observations have not been made with haplotypes entirely of Mus musculus origin. The data do not support the Hh hypothesis, and are consistent with the missing self hypothesis only if the gene (requiring homozygozity for function) in the Bat2/Tnfa region codes for a particular protein or peptide that associates with Db to generate a "protective motif."

Animals↗
PubMed1995

Novel NMDA antagonists: replacement of the pyridinium ring of 6,11-ethanobenzo[b]quinolizinium cations with heteroisoquinolinium cations.

Replacement of the pyridinium ring of 6,11-ethanobenzo[b]quinolizinium cations with thiazolium (4a and 4b) and N-methylimidazolium (4c and 4d) resulted in equipotent compounds in the [3H]TCP binding assay. The corresponding N-methyl-1,2,4-triazolium analogs were less potent in this assay. The thiazolium derivative 4b, with a Ki = 2.9 nM, is being evaluated as a possible neuroprotective N-methyl-D-aspartic acid (NMDA) antagonist.

Animals↗
PubMed1995

Hybrid and allogeneic resistance to T cell grafts mediated by murine NK and CD8+ T cells.

Lethally irradiated mice can reject H-2 allogeneic or parental strain stem cells in bone marrow cell (BMC) grafts within 48 h after transplantation. This rapid rejection of BMC grafts occurs without prior sensitization and is mediated by NK1.1+ NK cells. One hypothesis to account for the ability of host NK cells to mediate acute rejection of allogenic and parental stem cells is that these effector cells recognize hemopoietic histocompatibility (Hh-1) Ags on the donor stem cells. T cells present in the donor BMC can prevent NK cell-mediated rejection. However, lethally irradiated mice can also reject T cells present in lymph node cell preparations that respond to alloantigens of the host. T cell grafts from H-2k/Hh-1k, H-2r/Hh-1null, and H-2ia1/Hh-1null donors were rejected by CD8+ NK1.1- T cells. Ags other than Hh-1 Ags appeared to be recognized by these CD8+ T cells. In contrast, host NK cells rejected H-2d/Hh-1d T cell grafts, whereas both NK cells and CD8+ TCR-alpha beta + T cells rejected H-2b/Hh-1b T cell grafts. Therefore, both CD8+ TCR-alpha beta T cells and NK cells mediate allogeneic and hybrid resistance to T cell grafts.

Animals↗
PubMed1995

Transplantable NK cell progenitors in murine bone marrow.

Differentiation of NK cells from pluripotent hematopoietic stem cells is a poorly understood process. Although it is known that NK cells are bone marrow derived and dependent upon an intact bone marrow microenvironment for complete maturation, it is not known if they arise from an intermediate lymphoid stem cell or from progenitors exclusively committed to the NK lineage. To determine whether phenotypically distinct committed NK progenitor cells exist in murine bone marrow, we sorted cells capable of repopulating recipient mice with mature NK cells upon i.v. transfer. We identified a rare population of bone marrow cells with the phenotype Ly6+ Lin- c-kit+ CD43high Fall-3high TSA-1- AA4.1low Rh123high that is highly enriched for the ability to generate NK cells after transplantation. Although these cells are relatively depleted of Rh123low pluripotent stem cells, they are highly enriched for both lymphoid and myeloid repopulating ability. Thus, we have found no evidence to support the existence of a phenotypically distinct transplantable progenitor population in mouse bone marrow that is either exclusively committed to the NK cell lineage or exhibits the functional characteristics of a common lymphoid stem cell.

Animals↗
PubMed1995

Immunodominant framework region 3 peptide from TCR V beta 8.2 chain controls murine experimental autoimmune encephalomyelitis.

Previous work has demonstrated the existence of regulatory circuitry that controls response to the dominant determinant Ac1-9 of myelin basic protein (MBP) which is highly restricted in TCR V gene usage to V beta 8.2 and V alpha 2.3. In particular, a CD4+ V beta 14+ regulatory T cell was shown to be a vital component of this circuit. In our work presented here, the peptide specificity of the response to V beta 8.2 peptides was examined. Five overlapping peptides, B1 through B5, were studied for their ability to induce a proliferative response: B2 (21-50), B4 (61-90), and B5 (76-101) each had this capacity in the B10.PL or (SJL x B10.PL)F1 mice. The determinant within the TCR peptide B5 appears dominant, whereas determinants within the B2 and B4 peptides are physiologically cryptic. Furthermore, only B5 could down-regulate the response to MBP Ac1-9 and significantly protect mice from MBP- or Ac1-9-induced EAE, whereas B2 or B4 treatment had no significant effect. Treatment of mice with B5 did not result in generalized deletion or inactivation of V beta 8.2+ T cells. The core residues of the B5 determinant lie within framework region 3 of the V beta 8.2 chain and do not include residues from the joining CDR3 region. Response to B5 was restricted by the I-Au MHC molecule. Furthermore, B5 only induced responses in mice with certain MHC alleles. It is evident that by specifically down-regulating the initial dominant response to Ac1-9, Ag-induced disease can be prevented. These data have implications for understanding induction of TCR-based regulation, as well as relevance to possible therapeutic approaches for oligoclonal responses in human autoimmune diseases.

Amino Acid Sequence↗
PubMed1995

ERF-2, the human homologue of the murine Tis11d early response gene.

A human cDNA specifying a member of the Tis11 early response gene family was cloned and sequenced. The human gene differs from its mouse homologue by encoding an additional 97 amino acids at its C-terminal end. The sequence has transactivation-like motifs, an unusual Cys-Ser-Ala-rich motif and displays sequence similarity at the extreme C-terminal end with another Tis11 family member, ERF-1.

Amino Acid Sequence↗
PubMed1995

Discovery of 6,11-ethano-12,12-diaryl-6,11-dihydrobenzo[b]quinolizinium cations, a novel class of N-methyl-D-aspartate antagonists.

6,11-Ethano-12,12-diaryl-6,11-dihydrobenzo[b]quinolizinium cations 8, a novel class of N-methyl-D-aspartate (NMDA) antagonists acting at the phencyclidine site, have been identified. Structure-activity relationship studies around the lead compound 8a led to the identification of 12g (WIN 67870-2), one of the most potent compounds in this series. Compound 12g has a Ki = 1.8 +/- 0.2 nM vs [3H]TCP binding, has 700-fold selectivity for binding to the open state of the NMDA receptor-ionophore, and was devoid of MK-801- and PCP-like behavioral effects in rats. Compound 12g was neuroprotective in cultured mouse cortical neurons and exhibited antiischemic activity in a rat middle cerebral artery occlusion/reperfusion model of focal ischemia.

Animals↗
PubMed1995

Activation of murine epidermal gamma delta T cells through surface 2B4.

Dendritic epidermal T cells (DETC) are gamma delta T cells that normally reside in murine skin. They express on their surface the 2B4 molecule, a 66-kDa glycoprotein of the immunoglobulin gene superfamily thought to be associated with anti-tumor cytotoxicity by natural killer and lymphokine-activated killer cells. Here, we show that ligation of surface 2B4 transduces cell activation signals in DETC. Treatment with anti-2B4 monoclonal antibodies triggers the secretion of interferon-gamma and interleukin-2 by DETC lines, induces proliferation of resting DETC lines, amplifies anti-CD3-dependent proliferation of DETC freshly isolated from mouse skin; and up-regulates egr-1 and c-fos mRNA expression. These results indicate a unique pathway for DETC activation.

Animals↗
PubMed1995

Isolation and characterization of two major degradation products of dyclonine hydrochloride.

Dyclonine hydrochloride, a local anesthetic, is known to degrade in aqueous media. In this paper, the isolation and characterization of two major degradation products, formed by heating of an aqueous solution of dyclonine hydrochloride for 2 weeks at 50 degrees C, are presented. The proton and carbon-13 nuclear magnetic resonance, infrared, and mass spectral data reported conclusively show the two products to be 1-(4-butoxyphenyl)-2-propen-1-one and 1-(4-butoxyphenyl)-3-hydroxy-1-propanone. The proton and carbon-13 nuclear magnetic resonance spectral data of the free dyclonine base are also included.

Anesthetics, Local↗
PubMed1995

Transforming growth factor alpha.

Transforming growth factor alpha (TGF alpha) is a close relative of epidermal growth factor (EGF), the first polypeptide mitogen discovered in 1962 (Cohen, 1962). TGF alpha, like EGF, exerts its effect on cells through binding to the EGF-Receptor (EGF-R). Here we review the molecular and cell biology of TGF alpha before proceeding to describe our own work on signaling molecules induced in response to activation of the EGF-R.

Amino Acid Sequence↗
PubMed1995

Two genes encoding midgut-specific maltase-like polypeptides from Anopheles gambiae.

Full-length cDNA clones of two genes have been isolated from the African malaria vector mosquito, Anopheles gambiae. These genes, designated Agm1 and Agm2, encode maltase-like polypeptides of 498 and 599 residues, respectively. Deduced amino acid sequences contain a putative signal peptide sequence and four potential glycosylation sites. Agm1 and Agm2 show highest similarities to the Mal1 gene from Aedes aegypti and three clustered maltase genes from Drosophila melanogaster. Both genes are located at position 46D, in the terminal division of the left arm of the third chromosome. Agm2 has very strict tissue and temporal specificity, being expressed exclusively in the adult midgut. The specificity of Agm1 is similar but appears slightly broader; transcripts of this gene are detected at a low level in the pupae, and occasionally in the adult carcass after removal of the midgut.

Amino Acid Sequence↗
PubMed1995

Hybrid resistance: 'negative' and 'positive' signaling of murine natural killer cells.

Murine NK cells can reject allogenic or parental-strain bone marrow cells (BMC) in vivo and can lyse T lymphoblasts in vitro. The 'missing self' hypothesis states that absence or presence of 'negative signals' from target cell class I antigens (Ag) to NK receptors determines whether or not lysis occurs. Indeed, lysis of parental-strain blasts by purified F1 NK cell subsets occurred only in the presence of anti-receptor antibodies. Evidence for 'positive signaling' to NK cells by class I Ag includes rejection of D8 (Dd) transgene to B6) BMC by B6 hosts. The outcome of other BMC transplants contradict the missing self idea, because donors with identical class I Ag differ in compatibility with certain hosts. Perhaps class I Ag-NK cell receptor interactions dominate over other target-NK cell interactions. These interactions are usually 'negative' but can be 'positive'.

Animals↗
PubMed1995

Failure of experimental infection of baboons (Papio hamadryas) with the eggs of Asian Taenia.

The infectivity of the eggs of Asian Taenia sp. for humans is not known. Using baboons (Papio hamadryas) as a model to extrapolate the findings, three animals were exposed per os with 1000, 10,000 and 50,000 infective eggs of the Asian Taenia sp. The serological, biochemical, haematological and parasitological (based on necropsy) results show that baboons are refractory to the infection. It is concluded that the Asian taeniid eggs may fail to develop in man.

Animals↗