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Biomedical subjects

H Tang

Publications and source records attributed to H Tang.

At least 217 records · Page 12Linked to original sources
PubMed1996

Melatonin attenuates L-cysteine-induced seizures and lipid peroxidation in the brain of mice.

The effect of melatonin, a potent free radical scavenger, on L-cysteine-induced seizures and lipid peroxidation was investigated in mice. When L-cysteine (1.25, or 5.0 mumol/animal) was injected intracerebroventricularly (i.c.v.) into mice, severe tonic seizures were observed for over 20 sec in 75% and 100% of the treated mice, respectively. However, when melatonin (20 or 100 mg/kg) was injected subcutaneously (sc) into mice 15 min before L-cysteine injection (1.25 mumol/animal, i.c.v.), the incidence of seizures was observed in only 35% and 20% of the treated mice, respectively. Furthermore, when L-cysteine (1.25 or 5.0 mumol/animal, i.c.v.) was injected into mice, lipid peroxidation in whole brain 20 min after injection was significantly increased by 56% or 67% as compared to that of the control. However, when the seizures induced by L-cysteine (1.25 mumol/animal) were abolished by preadministration of melatonin, the increased lipid peroxidation induced by L-cysteine was prevented. These results suggest that there may be a positive correlation between free radical formation and seizures induced by L-cysteine and that melatonin affords protection against the seizures as well as against the associated lipid peroxidation.

Animals↗
PubMed1996

Torque generation in the flagellar motor of Escherichia coli: evidence of a direct role for FliG but not for FliM or FliN.

Among the many proteins needed for assembly and function of bacterial flagella, FliG, FliM, and FliN have attracted special attention because mutant phenotypes suggest that they are needed not only for flagellar assembly but also for torque generation and for controlling the direction of motor rotation. A role for these proteins in torque generation is suggested by the existence of mutations in each of them that produce the Mot- (or paralyzed) phenotype, in which flagella are assembled and appear normal but do not rotate. The presumption is that Mot- defects cause paralysis by specifically disrupting functions essential for torque generation, while preserving the features of a protein needed for flagellar assembly. Here, we present evidence that the reported mot mutations in fliM and fliN do not disrupt torque-generating functions specifically but, instead, affect the incorporation of proteins into the flagellum. The fliM and fliN mutants are immotile at normal expression levels but become motile when the mutant proteins and/or other, evidently interacting flagellar proteins are overexpressed. In contrast, many of the reported fliG mot mutations abolish motility at all expression levels, while permitting flagellar assembly, and thus appear to disrupt torque generation specifically. These mutations are clustered in a segment of about 100 residues at the carboxyl terminus of FliG. A slightly larger carboxyl-terminal segment of 126 residues accumulates in the cells when expressed alone and thus probably constitutes a stable, independently folded domain. We suggest that the carboxyl-terminal domain of FliG functions specifically in torque generation, forming the rotor portion of the site of energy transduction in the flagellar motor.

Bacterial Proteins↗
PubMed1996

The role of alpha 4 integrin and intercellular adhesion molecule-1 (ICAM-1) in murine experimental autoimmune thyroiditis.

Mouse-thyroglobulin (MTg)-sensitized spleen cells activated in vitro with MTg induce a lymphocytic form of experimental autoimmune thyroiditis (EAT) whereas activation of the same cell population with MTg in the presence of anti-interleukin 2 receptor antibody (M7/20) induces a granulomatous form of EAT. The thyroid infiltrate in both lymphocytic and granulomatous EAT includes both CD4+ and CD8+ T cells and CD4+ T cells are the primary effector cells for both forms of EAT. This investigation was undertaken to begin to define the roles of alpha 4 integrin, and intercellular adhesion molecule-1 (ICAM-1) in the migration of CD4+ and CD8+ T cells to the thyroid in EAT. The studies presented here demonstrate the expression of alpha 4 integrin and ICAM-1 on CD4+ and CD8+ T cells infiltrating the thyroid and the expression of vascular cell adhesion molecule (VCAM) and ICAM-1 on thyroid cells of mice with EAT. The effects of anti-alpha 4 and anti-ICAM mAb administration on EAT severity in recipient mice was also determined. Anti-alpha 4 administration reduced or abolished lymphocyte infiltration in the thyroid resulting in reduced severity of both lymphocytic and granulomatous EAT. In contrast, anti-ICAM mAb had little effect on EAT severity. These results suggest that these two adhesion molecules exhibit differential functional roles in the modulation of EAT disease severity and that alpha 4-VCAM interactions may be of particular importance in trafficking of effector cells to the thyroid.

Animals↗
PubMed1996

Discordant phenotype in siblings with X-linked agammaglobulinemia.

X-linked agammaglobulinemia (XLA) is a congenital humoral immunodeficiency caused by a defect in a B-cell-specific signaling molecule, Btk. There has been little concordance of phenotype with genotype in this disorder, and defects in Btk cause immunodeficiencies that range from mild impairment to complete inability to produce antibodies. The factors modifying the phenotype of XLA are not understood. The current study is the first description of two male siblings with identical T134 --> C mutations in the translation initiation ATG of Btk who have different clinical phenotypes. The proband lacks immunoglobulins and B cells and has recurrent infections, while the elder, affected brother has normal levels of IgG and IgM and very few infections. Both have undetectable levels of Btk kinase activity in circulating mononuclear cells. Complete sequencing of Btk gene transcripts in both brothers revealed no additional mutations to account for the discordant phenotypes. This description provides unequivocal evidence that the phenotype of XLA is influenced by factors additional to the Btk gene.

Adolescent↗
PubMed1996

A novel mutation (Cys145-->Stop) in Bruton's tyrosine kinase is associated with newly diagnosed X-linked agammaglobulinemia in a 51-year-old male.

BACKGROUND: X-linked agammaglobulinemia (XLA) is a severe, life-threatening disease characterized by failure of B cell differentiation and antibody production and is associated with mutations in Bruton's tyrosine kinase (Btk). The proband in this study is a 51-year-old male presenting with chronic nasal congestion, recurrent sinusitis, sporadic pneumonia, and pronounced B cell deficiency. A family history suggestive of an X-linked immunodeficiency disease was noted. MATERIALS AND METHODS: cDNA was synthesized from mRNA prepared from peripheral blood mononuclear leukocytes. Btk cDNA amplified by polymerase chain reaction (PCR) was subjected to both manual and automated DNA sequencing. A DNA sequence corresponding to exons 6 and 7 of Btk was amplified from genomic DNA. Western blot analysis employed both polyclonal and monoclonal antibodies to Btk and reaction patterns were obtained both by chemiluminescence and an in vitro kinase assay. RESULTS: A mutation (Cys145-->Stop) was identified in Btk cDNA and was confirmed in amplified exon 6 of genomic DNA from both the proband and an affected nephew. Neither Btk nor a truncated peptide was detected in Western blot analyses of peripheral blood mononuclear cell lysates. CONCLUSIONS: The C145A mutation reported here is novel. This family study is extraordinary in that affected male members who did not undergo aggressive medical management either succumbed to complications in early life or survived into later life. The proband is the oldest de novo diagnosed patient with XLA reported to date.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1996

[Effect of acupuncture combined with peridural anesthesia on SCE and RNA/DNA of lymphocytes].

In the present paper, three anesthetic methods including acupuncture combined with peridural anesthesia of small dose of anesthics used in subtotal gastrectomy are introduced. Changes in SCE (sister chromatid exchange) contents of RNA and DNA and RNA/DNA before, during and after operation are measured in 14 patients. Results suggest that acupuncture combined with peridual anesthesia, acupunctrue anesthesia and peridual anesthesia all have no any effect in inducing mutation, carcinoma and aberration.

Acupuncture Analgesia↗
PubMed1995

Rapid RNA polymerase genetics: one-day, no-column preparation of reconstituted recombinant Escherichia coli RNA polymerase.

We present a simple, rapid procedure for reconstitution of Escherichia coli RNA polymerase holoenzyme (RNAP) from individual recombinant alpha, beta, beta', and sigma 70 subunits. Hexahistidine-tagged recombinant alpha subunit purified by batch-mode metal-ion-affinity chromatography is incubated with crude recombinant beta, beta', and sigma 70 subunits from inclusion bodies, and the resulting reconstituted recombinant RNAP is purified by batch-mode metal-ion-affinity chromatography. RNAP prepared by this procedure is indistinguishable from RNAP prepared by conventional methods with respect to subunit stoichiometry, alpha-DNA interaction, catabolite gene activator protein (CAP)-independent transcription, and CAP-dependent transcription. Experiments with alpha (1-235), an alpha subunit C-terminal deletion mutant, establish that the procedure is suitable for biochemical screening of subunit lethal mutants.

Base Sequence↗
PubMed1995

Expression of biologically active human factor IX in human hematopoietic cells after retroviral vector-mediated gene transduction.

Gene therapy is a potential treatment for hemophilia, wherein cells transduced with a normal factor IX gene could provide a continuous in vivo source of circulating factor IX. In this study, we examined the potential use of hematopoietic cells as a target for factor IX gene therapy. Human myeloid leukemia cells (HL-60) were transduced by retroviral vectors carrying a normal human factor IX cDNA under control of either the Moloney murine leukemia virus long terminal repeat (MoMuLV LTR) (LIXSN), the SV40 promoter (LNSVIX), or a cytomegalovirus (CMV) promoter (LNCIX). Factor IX production was measured in the transduced cells both in the uninduced state and after induction of granulocytic differentiation [with dimethylsulfoxide (DMSO)] or monocytoid differentiation [with phorbol myristic acetate (PMA)]. Transcription of factor IX from the MoMuLV LTR was seen in all cells, with a two-fold increase upon differentiation. Induction with PMA led to an 8- to 15-fold increase in factor IX transcripts from an internal CMV promoter. No factor IX transcripts from the internal SV40 promoter were detected. Immunoreactive factor IX protein was identified by Western blot from induced HL-60 cells transduced by either LIXSN or LNCIX. Factor IX production by HL-60 cells transduced by LNCIX ranged from 38-93 ng/10(6) cells/24 hr following induction of monocytic differentiation. The factor IX antigen titer was directly related to factor IX coagulant titer (r = 0.98; p < 0.001). These data indicate that human myelomonocytic cells are capable of performing the necessary post-translational modifications to produce functional factor IX.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Northern↗
PubMed1995

Neuropeptide regulation of cytokine expression: effects of VIP and Ro 25-1553.

The neuropeptide VIP is present in high concentrations in normal lung, where it acts as a potent bronchodilator. VIP also downregulates T lymphocyte proliferation, possibly through its effect on cytokine expression. Although deficiencies in VIP levels are associated with asthma, VIP replacement therapy is impaired by its rapid degradation in the pulmonary microenvironment. A metabolically stable VIP peptide analog Ro 25-1553 has been developed and shown to act as a potent smooth muscle relaxant and suppressant of inflammatory cell accumulation. Proinflammatory cytokines play essential roles in inflammatory reactions. Here we compare the effects of VIP and Ro 25-1553 on IL-2, IL-4, and IFN-gamma production. Both VIP and Ro 25-1553 inhibit IL-2 and IL-4 but not IFN-gamma production and induce intracellular cAMP. Similar to VIP, Ro 25-1553 downregulates the IL-2 message and affects IL-4 production posttranscriptionally. Cytokines play important roles in allergic reactions, and increased cytokine levels are present in allergic asthmatic subjects. Therefore, downregulation of IL-2 and IL-4 production by Ro 25-1553 could play a significant role in the antiinflammatory activity of this peptide within the pulmonary microenvironment.

Animals↗
PubMed1995

Evidence that plant K+ channel proteins have two different types of subunits.

Plant K+ channel proteins have been previously characterized as tetramers of membrane-spanning alpha subunit polypeptides. Recent studies have identified a 39-kD, hydrophilic polypeptide that is a structural component of purified animal K+ channel proteins. We have cloned and sequenced an Arabidopsis thaliana cDNA encoding a 38.4-kD polypeptide that has a sequence homologous to the animal K+ channel beta subunit. Southern and northern analyses indicate the presence of a gene encoding this cDNA in the Arabidopsis genome and that its transcription product is present in Arabidopsis cells. To our knowledge, this is the first report to document the presence of K+ channel beta subunits in plants.

Amino Acid Sequence↗
PubMed1995

Role of Pseudomonas aeruginosa pili in acute pulmonary infection.

The role of piliation in the development and course of acute pulmonary infection was examined using infant BALB/cByJ mice inoculated by intranasal instillation of isogenic Pil+ and Pil- mutants of Pseudomonas aeruginosa PA1244, PAK, and PAO1. The piliated strains caused more cases of pneumonia, bacteremia, and mortality than the nonpiliated strains (chi-square analysis, alpha = 0.001). The piliated strains were more often associated with severe diffuse pneumonias, while the nonpiliated organisms resulted in less severe, focal pneumonias, although these differences did not achieve statistical significance. Purified pilin protein used to inoculate the mice resulted in local inflammatory changes. The nonpiliated strain PA1244-NP was as virulent as the piliated strain PAO1, suggesting that expression of other virulence factors are also important in the development of acute pneumonia. This infant mouse model of pulmonary infection appears to be a useful system for the analysis of P. aeruginosa virulence factors involved in the pathogenesis of pneumonia.

Animals↗
PubMed1995

Regulated underexpression of the FliM protein of Escherichia coli and evidence for a location in the flagellar motor distinct from the MotA/MotB torque generators.

The FliM protein of Escherichia coli is essential for the assembly and function of flagella. Here, we report the effects of controlled low-level expression of FliM in a fliM null strain. Disruption of the fliM gene abolishes flagellation. Underexpression of FliM causes cells to produce comparatively few flagella, and most flagella built are defective, producing subnormal average torque and fluctuating rapidly in speed. The results imply that in a normal flagellar motor, multiple molecules of FliM are present and can function independently to some degree. The speed fluctuations indicate that stable operation requires most, possibly all, of the normal complement of FliM. Thus, the FliM subunits are not as fully independent as the motility proteins MotA and MotB characterized in earlier work, suggesting that FliM occupies a location in the motor distinct from the MotA/MotB torque generators. Several mutations in fliM previously reported to cause flagellar paralysis in Salmonella typhimurium (H. Sockett, S. Yamaguchi, M. Kihara, V.M. Irikura, and R. M. Macnab, J. Bacteriol. 174:793-806, 1992) were made and characterized in E. coli. These mutations did not cause flagellar paralysis in E. coli; their phenotypes were more complex and suggest that FliM is not directly involved in torque generation.

Bacterial Proteins↗
PubMed1995

Regulated underexpression and overexpression of the FliN protein of Escherichia coli and evidence for an interaction between FliN and FliM in the flagellar motor.

The FliN protein of Escherichia coli is essential for the assembly and function of flagella. Here, we report the effects of regulated underexpression and overexpression of FliN in a fliN null strain. Cells that lack the FliN protein do not make flagella. When FliN is underexpressed, cells produce relatively few flagella and those made are defective, rotating at subnormal, rapidly varying speeds. These results are similar to what was seen previously when the flagellar protein FliM was underexpressed and unlike what was seen when the motility proteins MotA and MotB were underexpressed. Overexpression of FliN impairs motility and flagellation, as has been reported previously for FliM, but when FliN and FliM are co-overexpressed, motility is much less impaired. This and additional evidence presented indicate that FliM and FliN are associated in the flagellar motor, in a structure distinct from the MotA/MotB torque generators. A recent study showed that FliN might be involved in the export of flagellar components during assembly (A. P. Vogler, M. Homma, V. M. Irikura, and R. M. Macnab, J. Bacteriol. 173:3564-3572, 1991). We show here that approximately 50 amino acid residues from the amino terminus of FliN are dispensable for function and that the remaining, essential part of FliN has sequence similarity to a part of Spa33, a protein that functions in transmembrane export in Shigella flexneri. Thus, FliN might function primarily in flagellar export, rather than in torque generation, as has sometimes been supposed.

Amino Acid Sequence↗
PubMed1995

Inhibition of protein kinase C prevents rapid desensitization of type 1B angiotensin II receptor.

The type 1B angiotensin II (AT1B) receptor cloned from rat kidney was stably expressed in Chinese hamster ovary cells. The stably expressed receptor was characterized by radioligand binding studies and functional coupling to inositol 1,4,5-triphosphate (IP3) formation. Exposure of cells expressing the AT1B receptor to angiotensin II (Ang II) resulted in a rapid and dose-dependent homologous desensitization of receptor-mediated production of IP3, with an essentially complete desensitization at an agonist concentration > 10 nmol/L. Binding studies revealed no significant change in the number of AT1B receptors in transfected cells exposed to 1 nmol/L Ang II, whereas exposure to 100 nmol/L Ang II caused a rapid decrease of cell surface receptors, with a 75% loss of receptor number seen at 1 hour. Rapid desensitization occurred in the absence of receptor internalization. Blockade of receptor internalization with concanavalin A had at most only a slight effect on the agonist-induced desensitization. This indicates that factors other than internalization are chiefly responsible for the rapid agonist-induced desensitization. Phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, caused rapid desensitization of the receptor-mediated IP3 response. Neither tyrosine kinase inhibitors nor a protein kinase A activator affected the receptor-mediated IP3 response. The specific PKC inhibitor GF109203X or PKC depletion by prolonged treatment with 1 mumol/L PMA completely blocked the PMA-dependent desensitization. Desensitization evoked by a low Ang II agonist concentration (1 nmol/L) was reversed by the PKC-specific inhibitor GF109203X or PKC depletion, whereas the desensitizing effect at a high agonist concentration (100 nmol/L) is only partially prevented by PKC inhibitory treatment. These results demonstrate that PKC plays a crucial role in the desensitization of the AT1B receptor. They also suggest that receptor internalization and an additional PKC-independent pathway also contribute to desensitization of the AT1B receptor in transfected cells.

Analysis of Variance↗