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H Tian

Publications and source records attributed to H Tian.

At least 91 records · Page 5Linked to original sources
PubMed1998

Flexibility of the neck region of the rieske iron-sulfur protein is functionally important in the cytochrome bc1 complex.

The crystal structure of the mitochondrial cytochrome bc1 complex suggests that movement of the extramembrane (head) domain of the Rieske iron-sulfur protein (ISP) is involved in electron transfer. Such movement requires flexibility in the neck region of ISP. To test this hypothesis, Rhodobacter sphaeroides mutants expressing His-tagged cytochrome bc1 complexes with altered ISP necks (residues 39-48) were generated and characterized. Mutants with increased rigidity of the neck, generated by a double-proline substitution at Ala-46 and Ala-48 (ALA-PLP) or by a triple-proline substitution of ADV at residues 42-44 (ADV-PPP), have retarded (50%) or no photosynthetic growth, respectively. However, the mutant with a shortened neck, generated by deleting ADV (DeltaADV), has a photosynthetic growth rate comparable to that of complement cells, indicating that the length of the ISP neck is less critical than its flexibility in support of photosynthetic growth. The DeltaADV and ALA-PLP mutant membranes have 10 and 30% of the cytochrome bc1 complex activity found in the complement membrane, respectively, whereas the ADV-PPP mutant membrane contains no cytochrome bc1 complex activity. The loss of cytochrome bc1 complex activity in the DeltaADV membrane is attributed to improper docking of the head domain of ISP on cytochrome b, as indicated by a drastic change in the EPR characteristics of the Rieske iron-sulfur cluster. The loss of cytochrome bc1 complex activity in the ALA-PLP and ADV-PPP mutant membranes results from the decreased mobility of the ISP head domain due to the increased rigidity of the ISP neck. The ALA-PLP mutant complex has a larger activation energy than the wild-type complex, suggesting that movement of the head domain decreases the activation energy barrier of the cytochrome bc1 complex. Using the conditions developed for the isolation of the His-tagged complement cytochrome bc1 complex, a two-subunit complex (cytochromes b and c1) was obtained from the DeltaADV and ADV-PPP mutants, indicating that mutations at the neck region of ISP weaken the interactions among cytochrome b, ISP, and subunit IV.

Amino Acid Sequence↗
PubMed1998

BRCA1 physically associates with p53 and stimulates its transcriptional activity.

Mutations of the BRCA1 tumor suppressor gene are the most commonly detected alterations in familial breast and ovarian cancer. Although BRCA1 is required for normal mouse development, the molecular basis for its tumor suppressive function remains poorly understood. We show here that BRCA1 increases p53-dependent transcription from the p21WAF1/CIP1 and bax promoters. We also show that BRCA1 and p53 proteins interact both in vitro and in vivo. The interacting regions map, in vitro, to aa 224-500 of BRCA1 and the C-terminal domain of p53. Tumor-derived transactivation-deficient BRCA1 mutants are defective in co-activation of p53-dependent transcription and a truncation mutant of BRCA1 that retains the p53-interacting region acts as a dominant inhibitor of p53-dependent transcription. BRCA1 and p53 cooperatively induce apoptosis of cancer cells. The results indicate that BRCA1 and p53 may coordinately regulate gene expression in their role as tumor suppressors.

Animals↗
PubMed1998

ATM mutations in patients with ataxia telangiectasia screened by a hierarchical strategy.

ATM has been identified as a gene that is responsible for ataxia telangiectasia (AT), a pleiotropic disorder of autosomal recessive inheritance. While many mutations of this gene in AT patients of various ethnicities have been reported, data on Japanese patients are scarce. In this report, we present the results of a thorough survey of ATM mutations in 14 unrelated AT patients, with an emphasis on Japanese subjects. We used a hierarchical strategy in which we extensively analyzed the entire coding region of the cDNA. In the first stage, point mutations were sought by PCR-SSCP in short patches. In the second and third stages, the products of medium- and long-patch PCR, each covering the entire region, were examined by agarose gel electrophoresis to search for length changes. We found a total of 15 mutations (including 12 new) and 4 polymorphisms. Abnormal splicing of ATM was frequent among Japanese, and no hotspot was obvious, suggesting no strong founder effects in this ethnic group. Eleven patients carried either one homozygous or two compound heterozygous mutations, one patient carried only one detectable heterozygous mutation, and no mutation was found in two patients. Overall, mutations were found in at least 75% of the different ATM alleles examined. Possible reasons for the inability to detect mutations in some patients are discussed.

Ataxia Telangiectasia↗
PubMed1998

Osteoarthrosis of the temporomandibular joint induced by intra-articular injection of lactate dehydrogenase: an experimental study in adult rabbits.

OBJECTIVE: The purpose of this study was to establish an animal model of osteoarthrosis in the temporomandibular joint (TMJOA) by injecting lactate dehydrogenase (LDH) into the maxillary compartments of TMJs in adult rabbits. METHODS: Adult New Zealand white rabbits were randomly divided into four groups (A through D) of five animals each. The A and B groups were used as a control. The maxillary compartments of the C and D group (TMJs) were injected with 0.1 mL of LDH in two different concentrations. The TMJ samples were analyzed histologically and with a scanning electron microscope four different times after injection. RESULTS: The animals that had been injected with LDH at two different concentrations showed similar results. The TMJs had changes typical of OA in early to moderate stages. No pathologic changes could be found in the TMJs of the control groups. CONCLUSIONS: The results suggest that LDH may be of use in establishing an animal model of TMJOA.

Animals↗
PubMed1998

[Respiratory muscle function and serum enzymology in hyperthyroidism before and after treatment].

To investigate the effect of hyperthyroidism on respiratory muscle function and its possible mechanism, the thyroid function, serum enzymology, serum potassium, pulmonary function and respiratory muscle function were examined in 60 patients with Grave's disease before treatment and 26 patients among them after treatment, and 20 normal subjects as control. T3, T4, and FT4 increased while FVC and PImax, which reflect the respiratory muscle strength, and Pi/PImax, which reflects the reserve capacity of inspiratory muscle, decreased significantly in the 60 patients with Grave's disease, compared with the ones of normal subjects. The comparison of above measurements in the 26 patients between before- and after-treatment showed that respiratory muscle strength increased obviously along with the improvement of throid function. The serum enzymology, potassium and TSH, however, were not abnormal and not changed after treatment. The thyroid functions in 10 patients with hyperthyroid heart disease were not different, compared with the ones of other 50 patients without hyperthyroid heart disease, but their respiratory muscle strength was significantly lower than the ones of latter. The above results suggested that hyperthyroidism could lead to significant decrease of respiratory muscle strength and its reserve capacity, whereas treatment for hyperthyroidism would improve respiratory muscle function, so the measurement of respiratory muscle function in hyperthyroidism cases might be useful in prediction of hyperthyroid heart disease.

Adult↗
PubMed1998

[Preparation of acyclovir-polybutylcyanoacrylate-nanoparticles by emulsion polymerization method].

The aim of this study was to optimize the conditions and technology of preparing acyclovir-polybutylcyanoacrylate-nanoparticles (ACV-PBCA-NP) which has the diameter of about 100 nm and the shape of a sphere. The influential factors on sphericization were observed by single factor optimization. The preparation conditions and technology were optimized by the even design method. The contents of acyclovirin in acyclovir polybutyloganoacrylate nanoparticles were determined by HPLC. The optimum conditions and technology of preparing acyclovir polybutylcyanoacrylate nanoparticles were decided and put into use. The average diameter of the ACV-PBCA-NP thus prepared was 108.5 +/- 94.8 (n = 588). Its embedding ratio was 71.8%, and drug loading was 18.5%. The results suggest that the conditions and technology of preparing ACV-PBCA-NP presented in this paper are stable and practical.

Acyclovir↗
PubMed1998

[Effects of ligustrazine on myocardium and coronary artery].

OBJECTIVE: To study the effects of ligustrazine on mechanical electricity in guinea pig ventricular papillary muscles and on contraction of pig coronary artery. METHOD: Standard glass microelectrode technology; electrophysiological method; and blood vessel perfusion were used. RESULT: 1. ligustrazine(3-100 mumol/L) suppressed the action potential duration (APD) and the force of contraction (FC) of the fast action potentials (FAP), as well as the action potential amplitude (APA), APD, FC and the maximal upstroke velocity(Vmax) of the slow action potentials (SAP). 2. ligustrazine (3.0 mmol/L) induced SAP and contraction, but failed in beta-adrenoreceptor blocked muscles. Elevation of[Ca2+]o increased the action potential amplitude (APA). 3. ligustrazine(10(-5)-5 x 10(-3) mol/L) decreased the contractile response to high KCl in pig coronary artery. CONCLUSION: Ligustrazine might affect the inward current of myocardial cells through beta-adrenoreceptor, and the diastolizing effect of ligustrazine on coronary artery might have nothing to do with the exciting beta-adrenoreceptor.

Action Potentials↗
PubMed1998

[Effect of TNF-alpha monoclonal antibody on tissue lipopolysaccharide-binding protein mRNA expression in rats after thermal injury].

OBJECTIVE: To explore the effects of tumor necrosis factor-alpha (TNF-alpha) monoclonal antibody (MAb) on tissue TNF-alpha and lipopolysaccharide-binding protein (LBP) mRNA expression, and multiple organ dysfunction in rats after thermal injury. METHOD: 24 male Wistar rats were subjected to a 35% total body surface area full-thickness thermal injury. RESULT: The tissue TNF-alpha and LBP mRNA expressions of liver, lung, intestine, and kidney were markedly increased (P < 0.05 approximately equal 0.01) after thermal injury. Treatment with TNF-alpha MAb could significantly lower TNF-alpha mRNA expression of lung, intestine and kidney, but had no effect on liver TNF-alpha mRNA expression (P > 0.05). Similarly, the tissue LBP mRNA expression also decreased significantly (36.0% - 72.9%), and returned to normal in lung, intestine and kidney. In addition, biochemical parameters including GPT, TBiL, BUN, CK-MB, and LDH were markedly elevated after thermal injury, and decreased significantly after treatment with TNF-alpha MAb. CONCLUSION: The increase of tissue TNF-alpha gene expression caused by thermal injury might be associated with a marked elevation of tissue LBP mRNA expression, which could contribute to the development of multiple organ dysfunction. The early use of TNF-alpha MAb seems to be effective in inhibiting significant LBP mRNA expression in various tissues and ameliorating multiple organ damage after major thermal injury.

Acute-Phase Proteins↗
PubMed1998

[Study on the NIR-Raman spectra and NIR-SERS spectra of amsacrine].

The near infrared surface-enhanced Raman spectra (NIR-SERS) of amsacrine,an anticancer agent, on silver collids were recored with high quality. The NIR-SERS enhancement factor is up to 10(4) magnitude. In comparison with the near infrared Raman (NIR-Raman) spectra of solid amsacrine, more information of vibrational structures of amsacrine molecules at low concentration and almost in its practical application envi ronment, can be given by the NIR-SERS. The enhancement mechanism is associated with the adsorption of acridyl ring and sulfonyl on silver surface.

Amsacrine↗
PubMed1997

Molecular Transport and SAPO-11 Crystal Growth in an i-Pr2NH-AlPO4-H3PO4-SiO2-H2O System

The crystal growth of SAPO-11 molecular sieve synthesized with i-Pr2NH as a novel template from mixtures of Si, Al, and P sources were studied by XRD, MAS-NMR, IR, and AAS techniques. It was found that the crystallization was improved partially by the desorption of i-Pr2NH from the crystallite products at high temperatures. The growth on (010) face was enhanced by stepwise adding external silica sol to the reaction mixtures during the synthesis process. The molecular transport and mechanism of the crystallization were discussed. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

The involvement of serine 175 and alanine 185 of cytochrome b of Rhodobacter sphaeroides cytochrome bc1 complex in interaction with iron-sulfur protein.

An approach involving cysteine replacement of potentially noncritical amino acid residues, followed by chemical modification studies, was used to investigate structure-function of the "cd helix" of cytochrome b from Rhodobacter sphaeroides. Three amino acid residues, Ser-155, Ser-175, and Ala-185, which span this region of cytochrome b, were selected for this study. The S155C substitution yields cells unable to support photosynthetic growth, indicating that Ser-155 is a critical amino acid residue. Further mutational studies of Ser-155 indicate that the size of the amino acid side chain at this position is critical for photosynthetic growth of R. sphaeroides. On the other hand, the S175C and A185C substitutions yield cells with photosynthetic growth rates and enzyme kinetics of the bc1 complexes very similar to those of the unmutated complex, indicating that Ser-175 and Ala-185 are noncritical residues. Thus, engineered cysteines at these two positions of cytochrome b are suitable for membrane topology and domain/subunit interaction studies. Cys-175 does not react with a sulfhydryl-modifying reagent, N-ethylmaleimide (NEM), either in sealed, inside-out chromatophores or in detergent-disrupted chromatophores, indicating that position 175 of cytochrome b is inaccessible from both sides of the membrane and is probably buried within the protein complex. Cys-185 reacts with NEM only after detergent disruption of the sealed, inside-out chromatophores, indicating that this position of cytochrome b is accessible on the outer (periplasmic) surface of the membrane. These results place the cd helix of cytochrome b on the periplasmic side of the chromatophore membrane. When purified A185C-substituted bc1 complex was treated with NEM, about 87% of the activity was abolished due to NEM modification of Cys-185. The signature of the Rieske iron-sulfur center is broadened upon NEM modification of A185C, with the gx signal shifting from g = 1.80 to g = 1.75, suggesting that Ala-185 of cytochrome b interacts with the iron-sulfur protein. When purified S175C-substituted bc1 complex is treated with NEM, no change in the activity is observed, since Cys-175 is inaccessible to NEM. However, when the iron-sulfur protein is removed from the S175C-substituted bc1 complex, Cys-175 becomes accessible to NEM, indicating that Ser-175 of cytochrome b is shielded by the iron-sulfur protein in the bc1 complex.

Alanine↗
PubMed1997

Molecular characterization of two mammalian bHLH-PAS domain proteins selectively expressed in the central nervous system.

Here we describe two mammalian transcription factors selectively expressed in the central nervous system. Both proteins, neuronal PAS domain protein (NPAS) 1 and NPAS2, are members of the basic helix-loop-helix-PAS family of transcription factors. cDNAs encoding mouse and human forms of NPAS1 and NPAS2 have been isolated and sequenced. RNA blotting assays demonstrated the selective presence of NPAS1 and NPAS2 mRNAs in brain and spinal cord tissues of adult mice. NPAS1 mRNA was first detected at embryonic day 15 of mouse development, shortly after early organogenesis of the brain. NPAS2 mRNA was first detected during early postnatal development of the mouse brain. In situ hybridization assays using brain tissue of postnatal mice revealed an exclusively neuronal pattern of expression for NPAS1 and NPAS2 mRNAs. The human NPAS1 gene was mapped to chromosome 19q13.2-q13.3, and the mouse Npas1 gene to chromosome 7 at 2 centimorgans. Similarly, the human NPAS2 gene was assigned to chromosome 2p11.2-2q13, and the mouse Npas2 gene to chromosome 1 at 21-22 centimorgans. The chromosomal regions to which human NPAS1 and NPAS2 map are syntenic with those containing the mouse Npas1 and Npas2 genes, indicating that the mouse and human genes are true homologs.

Amino Acid Sequence↗
PubMed1997

Endothelial PAS domain protein 1 (EPAS1), a transcription factor selectively expressed in endothelial cells.

Here we describe the cloning and characterization of a PAS domain transcription factor termed endothelial PAS-1 (EPAS1). This protein shares 48% sequence identity with hypoxia inducible factor (HIF-1alpha) and lesser similarity with other members of the basic helix-loop-helix/PAS domain family of transcription factors. Like HIF-1alpha, EPAS1 binds to and activates transcription from a DNA element originally isolated from the erythropoietin gene and containing the sequence 5'-GCCCTACGTGCTGTCTCA-3'. Activation by both HIF-1alpha and EPAS1 is stimulated by hypoxic conditions. EPAS1 forms a heterodimeric complex with the aryl hydrocarbon nuclear transporter prior to transcriptional activation of target genes. EPAS1 expression is limited to the endothelium of mouse embryos and, in agreement with its cell type-specific expression pattern, is capable of specifically activating the transcription of the endothelial tyrosine kinase gene Tie-2. These observations raise the possibility that EPAS1 may represent an important regulator of vascularization, perhaps involving the regulation of endothelial cell gene expression in response to hypoxia.

Amino Acid Sequence↗
PubMed1997

Expression and regulation of steroid 5 alpha-reductase in the genital tubercle of the fetal rat.

The genital tubercle is a bipotential anlage that can develop into a penis or a clitoris. Formation of the penis requires synthesis within the tubercle of the androgen dihydrotestosterone by steroid 5 alpha-reductase isozymes. Isozyme 1 mRNA and protein were present in epithelial cells, whereas isozyme 2 transcripts were present in mesenchymal cells of developing genital tubercles from day 17, 19, and 21 rat embryos. These expression patterns were observed in both uncommitted anlagen and in committed male or female structures. Androgens did not significantly influence levels of 5 alpha-reductase mRNAs or affect their cellular distributions. Together with genetic data, the results implicate the mesenchyme as the crucial cell type in formation of the male external genitalia.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1997

Modulation of multidrug resistance by three bisbenzyl-isoquinolines in comparison with verapamil.

AIM: To compare cycleanine (Cyc), insularine (Insr), insulanoline (Insn) and verapamil (Ver) in modulation of multidrug resistance (MDR) in vitro. METHODS: The cytotoxic effect was determined by 3-[4, 5-dimethylthiazol-2-yl], 5-diphenyl tetarzolium bromide (MTT) assay. The intracellular doxorubincin (Dox) accumulation was assayed by spectrofluorometer. RESULTS: Cyc, Insr, Insn, and Ver showed significant activities in modulating Dox and vincristine resistances in acquired resistant MCF-7/Adr and KBv200 cell lines in a dose-dependent manner. Cyc, Insr, Insn, and Ver increased intracellular Dox accumulation in MCF-7/Adr cells. Cyc and Insr had greater activities than Ver in modulating MDR, while Insn had similar activity to that of Ver. CONCLUSION: MDR was modulated by Cyc, Insr, and Insn, due to the increase of intracellular Dox accumulation.

Alkaloids↗
PubMed1997

[Water vapor permeability measurement of the materials used as a wound covering].

This paper introduces a new apparatus and method that suits to measuring the water vapor transmission rate (WVTR) of wound covering materials. WVTR of synthetic materials, amniotic membrane, porcine and cadaveric skin was measured under different conditions of four temperatures, three mediums, and "water cup" or "inverted water cup". The temperature was in close relationship with the WVTR except Omiderm, amniotic membrane, and cadaveric skin between 30 degrees C and 37 degrees C groups. The medium did not affect the WVTR (P > 0.05). There was significant difference between the "water cup" and "inverted water cup" groups(P < 0.01). This study suggests that the apparatus is easy-to-operate, reliable and suitable for the measurement of WVTR of burn wound coverings and other membranous materials.

Bandages↗
PubMed1997

[A comparative study on effect of two bisbenzylisoquinolines, tetrandrine and berbamine, on reversal of multidrug resistance].

A comparative study on the effect of two bisbenzylisoquinolines, tetrandrine (TTD) and berbamine (BBM), and verapamil (VRP) on reversing multidrug resistance was reported. TTD, BBM and VRP showed significant activity in reversing adriamycin (ADR) and vincristine (VCR) resistance in acquired resistant MCF-7/Adr and KBv200 cell lines, and the effect was shown to be dose-dependent. TTD, at the concentration of 10 mumol.L-1, completely reversed ADR resistance in MCF-7/adr cells. TTD, BBM and VRP increased intracellular ADR accumulation in MCF-7/adr cells. There is minor difference in structure between TTD and BBM. TTD showed greater activity than VRP in reversing MDR, while BBM showed similar activity to that of VRP. TTD also showed significant activity in vivo in reversing ADR resistance in MDR MCF-7/Adr solid tumor in nude mice.

Alkaloids↗