Biomedical subjects

H Tang

Publications and source records attributed to H Tang.

At least 163 records · Page 9Linked to original sources

PubMed1998

New core promoter element in RNA polymerase II-dependent transcription: sequence-specific DNA binding by transcription factor IIB.

A sequence element located immediately upstream of the TATA element, and having the consensus sequence 5'-G/C-G/C-G/A-C-G-C-C-3', affects the ability of transcription factor IIB to enter transcription complexes and support transcription initiation. The sequence element is recognized directly by the transcription factor IIB. Recognition involves alpha-helices 4' and 5' of IIB, which comprise a helix-turn-helix DNA-binding motif. These observations establish that transcription initiation involves a fourth core promoter element, the IIB recognition element (BRE), in addition to the TATA element, the initiator element, and the downstream promoter element, and involves a second sequence-specific general transcription factor, IIB, in addition to transcription factor IID.

Amino Acid Sequence↗

PubMed1998

Induction of granulomatous experimental autoimmune thyroiditis in IL-4 gene-disrupted mice.

To study the role of IL-4 in development of granulomatous experimental autoimmune thyroiditis (EAT), IL-4 gene-disrupted mice expressing the EAT-susceptible H-2k haplotype were generated and used for EAT induction. Spleen cells from mouse thyroglobulin (MTg) and LPS-primed IL-4(+/+) and IL-4(-/-) donors could induce severe granulomatous EAT when spleen cells were activated with MTg and anti-IL-2R mAb in the presence of IL-12. Thyroid lesions had extensive follicular cell proliferation, large numbers of histiocytes, polymorphonuclear leukocytes, and multinucleated giant cells, in addition to lymphocytes and other mononuclear cells. Expression of IFN-gamma gene mRNA and production of IFN-gamma by effector spleen cells stimulated with MTg and IL-12 were similar for both IL-4(+/+) and IL-4(-/-) mice. Although IL-4 was undetectable in IL-4(-/-) mice, expression of mRNA for IL-5, IL-10, and IL-13 and production of IL-5 by both MTg-activated spleen cells and anti-CD3-activated CD4+ T cells were comparable for cells from IL-4(+/+) and IL-4(-/-) mice, indicating that the absence of IL-4 did not prevent production of other Th2 cytokines. Production of MTg-specific IgG1 was very low or undetectable in IL-4(-/-) mice. IL-4 gene mRNA and MTg-specific IgG1 could be detected in IL-4(+/+) or IL-4(-/-) recipients only when they received effector cells from IL-4(+/+) donor mice, indicating that IL-4- and IgG1-secreting cells are of donor origin. These results demonstrate that IL-4 is not essential for development of granulomatous EAT.

Animals↗

PubMed1998

Acetylcholinesterase immunolesioning: regional vulnerability of preganglionic sympathetic neurons in rat spinal cord.

Rats given antibodies against acetylcholinesterase (AChE) develop sympathetic dysfunction stemming from losses of preganglionic neurons in spinal cord. Central effects of AChE antibodies are surprising since IgG does not readily cross the blood-brain barrier, and lesions of peripheral terminals should not cause cell death. This study was designed to explore the distribution of central neural damage and to investigate features that might account for vulnerability. Rat spinal cord and brainstem were stained for choline acetyltransferase (ChAT) and nitric oxide synthase (NOS) immunoreactivity. Four months after administration of AChE antibodies, ChAT-positive neurons in the intermediolateral nucleus (IML) were 61-66% fewer throughout the thoracolumbar cord (T1, T2, T8, T12, L1). NOS-positive neurons in these loci were affected to the same extent by antibody-treatment, although they were only two-thirds as numerous. By contrast, neurons in the central autonomic nucleus of the thoracolumbar cord were scarcely affected. These results point to immunochemical differences in the central autonomic outflow, which may partially explain the puzzling selectivity of neural damage in AChE immunolesioning. Different results were obtained after guanethidine sympathectomy, which ablated nearly all neurons in the superior cervical ganglion without any effect on preganglionic neurons in the IML. Therefore, if the central effects of antibodies are indirectly mediated by loss of trophic support from the periphery, this support cannot arise from adrenergic neurons but must come from other ganglionic cells.

Acetylcholinesterase↗

PubMed1998

The kinetics of cytokine gene expression in the thyroids of mice developing granulomatous experimental autoimmune thyroiditis.

To study the potential roles of cytokines in development and resolution of granulomatous experimental autoimmune thyroiditis (EAT), the kinetics of in vivo expression of cytokine genes in thyroid infiltrates was analysed using reverse transcriptase-PCR (RT-PCR). Both Th1 (IL-2 and IFN-gamma) and Th2 (IL-4 and IL-10) cytokines as well as TGF-betaTNF-alphaIL-12 and IL-1beta were detected in thyroids during both the initial phase and peak of granulomatous EAT. Maximal expression of cytokine genes generally occurred 11-14 days after cell transfer, prior to maximal EAT severity, which occurred 19-21 days after cell transfer. The relative ratios of Th1:Th2 cytokines and mouse thyroglobulin-(MTg)-specific IgG1 and IgG2a autoantibody levels were similar during both the initial phase and peak of EAT. Depletion of CD8(+) T cells did not decrease the severity of EAT but delayed resolution of lesions. Cytokine gene expression in thyroids was not decreased by anti-CD8 treatment. Together, these data indicate that both Th1 and Th2 cytokines produced by CD4(+) T cells are involved in induction and development of granulomatous EAT, and CD8-dependent resolution of granulomatous EAT is apparently not mediated by these cytokines.

Animals↗

PubMed1998

A proportion of proteinase 3 (PR3)-specific anti-neutrophil cytoplasmic antibodies (ANCA) only react with PR3 after cleavage of its N-terminal activation dipeptide.

ANCA directed against PR3 are highly specific for Wegener's granulomatosis and microscopic polyangiitis, and have been implicated in the pathogenesis of small vessel vasculitis. Most PR3-ANCA are directed against conformational epitopes on PR3. This study was designed to determine whether the cleavage of the N-terminal activation dipeptide of PR3 is required for the binding of PR3-ANCA. Recombinant PR3 (rPR3) variants were expressed in the epithelial cell line, 293. As confirmed by radiosequencing, the rPR3 secreted into the 293 cell culture supernatant is N-terminally unprocessed. Two enzymatically inactive rPR3 mutants were expressed in 293 cells: rPR3-S176A and delta-rPR3-S176A. rPR3-S176A contains the N-propetide Ala-2-Glu-1, delta-rPR3-S176A does not. Culture supernatants of rPR3-S176A and delta-rPR3-S176A expressing 293 cells were used as sources of target antigen for PR3-ANCA testing by capture ELISA. Forty unselected consecutive PR3-ANCA+ sera were tested. With delta-rPR3-S176A as antigen all 40 were recognized, compared with only 34 of 40 when rPR3-S176A served as target antigen. The majority of the serum samples contained a mixture of antibodies reacting with epitopes accessible on the mature and on the proform of PR3. In conclusion, the cleavage of the N-terminal activation dipeptide of PR3 is not an absolute requirement for recognition by all PR3-ANCA. However, a substantial proportion of PR3-ANCA recognize (a) target antigen(s) exposed only after the conformational change of PR3 associated with the N-terminal processing. In 15% of sera this PR3-ANCA subset occurred exclusively. PR3-ANCA subtypes can be differentiated using specifically designed rPR3 variants as target antigens, and non-haematopoietic mammalian cells without regulated secretory pathway can be used for their expression.

Antibodies, Antineutrophil Cytoplasmic↗

PubMed1998

A microfabricated electrostatic haptic display for persons with visual impairments.

An electrostatic haptic display with three 7 x 7 electrode arrays of three different sizes was fabricated on a 4-in wafer using lithographic microfabrication techniques. The display utilizes electrostatic stimulation to generate a tactile sensation of texture on a scanning finger. The tactile sensation appeared to be a result of increased friction and vibration due to the electrostatic forces between the finger skin and the electrodes. Various spatial tactile patterns (lines, circles, squares, and triangles, etc.) can be presented on the display. Experiments of threshold, line separation, and pattern recognition were performed on subjects with visual impairments to study the spatial resolution and information transmission on arrays of variant electrode size and spacing. Two columns with two-column spacing can be resolved with 80% accuracy on the small array, for a spatial resolution of 5.8 mm in terms of edge-to-edge electrode distance. The overall percentages of correct recognition for the patterns were 68.3, 72.1, and 71.3% on the small, medium, and large arrays, respectively. While subject is an important factor for both threshold and pattern recognition, electrode size was statistically significant for threshold only. Frequency and duty cycle of the stimulation waveform did not show statistical significance.

Adult↗

PubMed1998

Role of flagella in pathogenesis of Pseudomonas aeruginosa pulmonary infection.

Pseudomonas aeruginosa strains are opportunistic pathogens associated with infections in immunocompromised hosts and patients with cystic fibrosis. Like many other mucosal pathogens, P. aeruginosa cells express flagella which provide motility and chemotaxis toward preferred substrates but also provide a ligand for clearance by phagocytic cells. We tested the role of flagella in the initial stages of respiratory tract infection by comparing the virulence of fliC mutants in a neonatal mouse model of pneumonia. In the absence of fliC, there was no mortality, compared with 30% mortality attributed to the parental strain PAK or 15% mortality associated with infection due to a pilA mutant PAK/NP (P < 0.0001). The fliC mutants caused pneumonia in only 25% of the mice inoculated, regardless of whether there was expression of the pilus, whereas the parental strain was associated with an 80% rate of pneumonia. Histopathological studies demonstrated that the fliC mutants caused very focal inflammation and that the organisms did not spread through the lungs as seen in infection due to either PAK or PAK/NP. Purified flagellin elicited an intense inflammatory response in the mouse lung. 125I-labeled flagellin bound to the glycolipids GM1 and GD1a and to asialoGM1 in an in vitro binding assay. However, flagellin-mediated binding to epithelial gangliosides was a relatively unusual event, as quantified by binding assays of wild-type or fliC mutant organisms to CHO Lec-2 cells with membrane-incorporated GM1. Fla+ organisms but not fliC mutants were efficiently taken up by murine macrophages. P. aeruginosa flagella are important in the establishment of respiratory tract infection and may act as a tether in initial interactions with epithelial membranes. This function is offset by the contribution of flagella to host clearance mechanisms facilitating phagocytic clearance and the role of flagellar genes in mucin binding and clearance.

Animals↗

PubMed1998

Patterns of alcohol consumption after liver transplantation.

BACKGROUND: Uncertainty exists about the extent and consequences of a return to alcohol consumption after liver transplantation for alcoholic liver disease (ALD). AIMS: To determine the prevalence and consequences of alcohol consumption in patients transplanted for ALD. METHODS: A retrospective case controlled study of all patients transplanted for ALD at the Queen Elizabeth Hospital, Birmingham, between 1987 and 1996. RESULTS: Seventy patients with ALD were transplanted, of which 59 survived more than three months; 56 were interviewed. Twenty eight had consumed some alcohol after transplantation; for the nine "heavy drinkers" (HD), the median time to resumption of alcohol intake was six months and for the 19 "moderate drinkers" (MD) it was eight months. There was no significant difference in episodes of acute rejection or compliance with medication between those who were abstinent, MD, or HD. Histological evidence of liver injury was common in ALD patients who had returned to drink. Mild fatty change was found in 1/11 biopsy specimens from abstinent patients but moderate to severe fatty change and ballooned hepatocytes were seen in 3/5 MD and 2/5 HD specimens. Two HD patients had early fibrosis. One HD patient had died of alcohol related complications. CONCLUSIONS: Moderate to heavy alcohol consumption occurs in patients transplanted for ALD. Patient recall of abstinence advice is unreliable, and patients return to alcohol mainly within the first year after liver transplantation. Return to alcohol consumption after liver transplantation is associated with rapid development of histological liver injury including fibrosis.

Adult↗

PubMed1998

Over-expression of c-fos mRNA in the hippocampal neurons in Alzheimer's disease.

OBJECTIVE: To analyze the relationship between the proto-oncogene c-fos change and neuronal degeneration in the hippocampus of the patients with Alzheimer's disease. METHODS: The post mortem human hippocampal tissues were divided into three groups, namely, the aged, the young and Alzheimer's disease (AD) groups. Each group consisted of 10 patients. The diagnosis of AD was made by clinical manifestation and argentatine (Bodían) staining. Patients of both the young and the aged groups had no neurological disorders. The proto-oncogene c-fos mRNA was investigated in the hippocampal neurons using the method of in situ hybridization. RESULTS: The optical density of stained area and the integral within proto-oncogene c-fos mRNA revealed a significant increase in the hippocampal neurons in cases of Alzheimer's disease as compared with the controls. CONCLUSIONS: The over-expression of the proto-oncogene c-fos might play a role in the pathological process of Alzheimer's disease. These changes might result from a suffering stage of the hippocampal neurons or from a compensatory mechanism in the surviving neurons which are not yet affected-by the pathological process.

Adult↗

PubMed1998

Research on nucleolar organizer regions of hippocampal neuron in Alzheimer's disease.

OBJECTIVE: To understand the cellular genetic expression of the cell's population by studying the nucleolar organizer regions (NORs) of hippocampal neuron of Alzheimer's disease (AD). METHODS: The postmortem human hippocampal tissues were divided into three groups, namely, the young, the elderly and the AD groups. Each group contained tissues from 10 patients. The study was conducted using image pattern analysis of the nucleoli-nucleoplasms ratio of the neurons of Nissl's stained pathological cerebral hippocampal tissues, the area of stain, and the integrating absorption of nucleoli of silver-stained NORs. RESULTS: The nucleoli-nucleoplasms ratio of the neurons of Nissl's stained cerebral hippocampal tissues, the area of stain, and the integrating absorption of the nucleoli of hippocampal neuron were decreased in the elderly and the AD groups as compared with the young group. However, the area of stain and the integrating absorption of the nucleoli of the hippocampal neurons were relatively increased in the AD group in comparison with the elderly group. CONCLUSION: Nissl's stain demonstrates the hypofunction of the hippocampal neurons in the elderly and the AD patients. The Silver stain of NORs shows the decline of rDNA transcription activity of the nucleoli of the hippocampal neurons in the elderly and the AD patients. However, the transcription activity of the nucleoli of the hippocampal neurons of AD patients was relatively improved, and the cellular genetic expression of the cell's population was relatively strengthened. These cellular morphological changes have probably reflected the cellular defensive system.

Adult↗

PubMed1998

[Analysis of molecular karyotype of Leishmania isolates from hilly foci and plain foci of China].

AIM: To analyse the molecular karyotypes of Leishmania isolates from hilly and plain foci of China. METHODS: Pulsed field gel electrophoresis(PFGE) was performed in 1% agarose at 6 V/cm in 0.5 x TBE at 14 degrees C with a pulse time of 60 s for 15 h and a pulse time 90 s for 9 h. RESULTS: Each isolate was resolved into 15 different EtBr-staining bands ranging in size from 200 to 2,200 kb, in which the karyotypes of 6 isolates from hilly foci were similar (including karyotypes of canine isolates similar with those of human isolates), and they were partly similar with those of L. infantum. The karyotypes of the two isolates from plain foci were similar, but the isolates from the two topographically different foci were different from each other. CONCLUSION: Homology exists between L. d. isolates from hilly foci and plain foci respectively, and exists in part between L. d. isolates from hilly foci and L. infantum; while heterogeneity exists between L. d. isolates from hilly foci and plain foci. The reservoir host, domestic dog, plays an important role as the infection source of leishmaniasis in the hilly foci of China.

Animals↗

PubMed1998

[Interactive 2D/3D image processing, registration and display system].

This paper presents an integrated system for interactive 2D/3D image processing, registration and display. The main image processing algorithm in the system is image filtering, enhancement, adaptive B-snake model, image registration, pseudo color representation and 3D volume rendering. The system provides good visulization interface and image tool.

Humans↗

PubMed1998

[Analysis of higher basidiomycetous mitochondrial DNA with four-GC-cutter restriction enzymes].

The mitochondrial DNA band patterns emerged from basidiomycetous genomic DNA digested with four-GC-cutter restriction enzymes, HaeIII, CfoI and MspI, were reported in this paper. It was demonstrated that mtDNAs of higher basidiomycetes had abundant diversity after comparison of their band patterns, summated sizes, the number of fragments and homology among 12 strains of Agaricales, Aphyllophorales. The results also showed that the technique, displaying fungal mtDNA bands directly from their total DNA, would be more efficient and sensitive for analyses of fungal mtDNA RFLP if several four-GC-cutter restriction enzymes, instead of one, were used.

Agaricales↗

PubMed1998

Interleukin-12 promotes activation of effector cells that induce a severe destructive granulomatous form of murine experimental autoimmune thyroiditis.

Granulomatous inflammatory lesions are a major histopathological feature of a wide spectrum of human infectious and autoimmune diseases. Experimental autoimmune thyroiditis (EAT) with granulomatous histopathological features can be induced by mouse thyroglobulin (MTg)-sensitized spleen cells activated in vitro with MTg and anti-interleukin-2 receptor (anti-IL-2R), anti-IL-2, or anti-interferon-gamma (anti-IFN-gamma) monoclonal antibody (MAb). These studies suggested that IFN-gamma-producing T cells requiring IL-2 for growth may negatively regulate activation of granulomatous EAT effector cells. As IL-12 promotes activation of IFN-gamma-producing Th1 cells, the present study was undertaken to determine the role of IL-12 in activation of effector cells for granulomatous EAT. MTg-sensitized cells activated in vitro with MTg, anti-IL2R MAb, and IL-12 induced severe, destructive granulomatous thyroiditis with neutrophil inflammation, fibrin deposition, and necrosis. Many glands ultimately underwent atrophy and became fibrotic; some also showed fibrinoid necrosis and a mixed inflammatory cell infiltration of blood vessel walls indicative of a necrotizing vasculitis. Induction of severe granulomatous EAT by IL-12 required MTg in vitro and was unrelated to the IL-12-induced increase in IFN-gamma production. IL-12 markedly increased IFN-gamma production but did not induce a shift to a Th1-dominant phenotype, as other Th1 and Th2 cytokines were generally unaffected and both Th1 and Th2 cytokines were expressed in recipient thyroids. Addition of IL-12 or neutralization by anti-IL-12 at various times indicated that IL-12 exerted its primary effects in the final 24 hours of the 72-hour culture and was not required in recipient mice. Cells cultured with anti-IL-12, MTg, and anti-IL2R MAb transferred mild lymphocytic EAT but little or no granulomatous EAT. Thus, IL-12 profoundly regulates the in vitro activation of effector cells that induce histologically distinct autoimmune inflammatory lesions in the thyroid.

Animals↗

PubMed1998

Effect of antiphospholipid antibodies on beta(2) glycoprotein I-phospholipid Interaction.

PROBLEM: Beta(2)glycoprotein I (beta(2)GPI) physiologically binds to negatively charged phospholipids (PLs) and is a natural regulator of the coagulation cascade. Thrombotic clinical complications and recurrent fetal loss associated with autoimmune antiphospholipid (aPL) antibodies are thought to be related to their binding to Beta(2)GPI-PL complex and interference with the physiological function of Beta(2)GPI. METHOD OF STUDY: To investigate the effect of aPL on beta(2)GPI-PL interaction, we studied the binding of biotinylated Beta(2)GPI to cardiolipin (CL) by enzyme-linked immunosorbent assay (ELISA) in the presence and absence of purified aPL immunoglobulin G (IgG) antibodies. RESULTS: Adding five different aPL IgG antibodies with different levels of aPL activity isolated from the sera of five patients with aPL-associated recurrent fetal death greatly increased the binding of biotinylated beta(2)GPI to CL-coated plates. The optical densities (ODs) were 0.635, 0.890, and 1.265 in the presence of three aPL IgG antibodies, compared to 0.425 in the absence of aPL IgG. In contrast, normal human IgG had no enhancing effect. The OD was 0.480 and 0.425, respectively. The enhancement of beta(2)GPI binding to CL by aPL IgG correlated with the titers of aPL antibodies. The use of phosphate-buffered saline with increasing salt concentrations as a washing buffer for the ELISA resulted in more stable binding of beta(2)GPI to PL in the presence of aPL IgG. CONCLUSIONS: These findings suggest that the binding of autoimmune aPL antibodies to beta(2)GPI-PL complex results in abnormally tighter interaction between beta(2)GPI and PLs, which may lead to physiological dysfunction of beta(2)GPI as a regulator of coagulation.

Antibodies, Antiphospholipid↗

PubMed1998

[Expression regulation of purine biosynthetic genes in Salmonella typhimurium. VI. Isolation and characterization of super-repressor mutants].

Starting from strain of Salmonella typhimurium purD::lac, 86 exponential cultures were mutagenized with NTG and white or light blue clones on E + ado + Xgal plate were selected as candidates of purRs mutant. Total 66 independent candidate strains were obtained. By assaying their beta-galactosidase activity under the repressed and derepressed conditions, determining their frequency of revertional mutation, Conducting transductional analysis of mutational site and dorminance test, 11 candidates strains were proved to be super-repressor mutants. These mutants are useful for studying the expression of purine biosynthetic gene and relationship between protein structure and function in general.

Bacterial Proteins↗

PubMed1997

The transactivation and p53-interacting functions of hepatitis B virus X protein are mutually interfering but distinct.

Transactivation of viral and host genes expression by hepatitis B virus X protein (HBx) is believed to be involved in hepatocarcinogenesis. The interaction of HBx with the tumor suppressor p53 and its inhibitory effect on p53 functions have been reported recently. However, the question of whether p53 is directly involved in HBx transactivation has not yet been addressed. In this study, we delineated the interaction sites of HBx and p53 using far-Western blotting and glutathione S-transferase-resin pull-down assays. The results indicate that the HBx-binding sites are located within the oligomerization and specific DNA-binding domains of p53 and that the p53-binding site was confined to a small region in the HBx transactivation domain. Mutual interference of the transactivations by HBx and p53 was detected by CAT assays in a transient transfection system. Strikingly, transactivation by HBx was observed in the p53-negative cells, Saos-2 and Hep3B, indicating that the transactivation and the p53-inhibiting functions of HBx are mutually interfering but distinct.

Binding Sites↗

PubMed1997

Spatial and temporal patterns of acidity and heavy metals in predicting the potential for ecological impact on the Le An river polluted by acid mine drainage.

Integration and comparison of metal contamination from acid mine drainage and an assessment of the potential for ecological impact was conducted in the aquatic ecosystems of the Le An river. The results indicated low acidity, high levels of suspended solids containing a high content of copper in river water and sediment in the upstream region of the Le An river due to the pollution from the Dexing copper mine, and high concentrations of zinc and copper in surface water and sediments, high release potential and ready bioavailability of heavy metals in sediments downstream (after site A07) due to the pollution from the Jishui river. The pollution from acid mine drainage in the Le An river potentially effects an ecological impact on the aquatic ecosystem, mainly between sites A04 and A08. The management strategy should, therefore be mainly applied to acid mine drainage from the Dexing copper mine and heavy metal discharges from the Jishui river.

Acids↗