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Biomedical subjects

H Zhu

Publications and source records attributed to H Zhu.

At least 505 records · Page 28Linked to original sources
PubMed1993

Cloning of a xylanase gene from the ruminal fungus Neocallimastix patriciarum 27 and its expression in Escherichia coli.

An endo-beta-1,4-xylanase gene was cloned from Neocallimastix patriciarum 27 in the bacteriophage vector lambda gtWES lambda B and was subcloned into the plasmid vectors pUC18 and pUC19 in which xylanase activity was expressed in both orientations. The xylanase was located in the periplasmic space of the host, Escherichia coli HB101. The pH and temperature optima for periplasmic xylanase activity were 6.2 and 40 degrees C, respectively, and the Km for oat spelt xylan hydrolysis was 0.89 mg.mL-1. It also exhibited hydrolytic activity on carboxymethyl cellulose that was equivalent to 28% of the activity exhibited by the enzyme on xylan. It bound to crystalline cellulose, but lacked hydrolytic activity on amorphous cellulose. SDS-PAGE followed by zymogram analysis showed active bands of 68, 58, and 51 kDa. Isoelectric focusing in gels combined with zymogram analysis showed one band of xylanase activity with a pI of 3.6.

Animals↗
PubMed1993

Targeting gene expression to specific cardiovascular cell types in transgenic mice.

Transgenic techniques, which allow the introduction of exogenous genes into the genome of experimental animals, promise to bridge the gap between the in vitro observations made by molecular and cellular biologists on cardiac and vascular cells in tissue culture and the physiology and pathology of the whole organ system. One such application of these techniques is tissue targeting: by genetic manipulation to direct expression of a protein--such as a signaling peptide, a growth factor receptor, or an oncogene involved in cell growth--to a tissue where it normally would not be expressed (or where expression is tightly controlled) by fusing it to the transcriptional control sequences of another gene normally expressed in that tissue. In the cardiovascular system, regulatory sequences for cardiomyocyte-specific proteins, vascular endothelium-specific proteins, and smooth muscle-specific proteins can be used to target heterologous genes to their respective tissues in transgenic animals. The effects that such perturbations have on organ physiology and intracellular and intercellular communication can be observed by applying established physiological and molecular approaches. In this review, we highlight some tissue-specific genes from cardiac and vascular cell types whose regulatory sequences may be used to target heterologous proteins; we discuss neutral "reporter" proteins and signal transduction components as paradigms for the application of this technique; and we briefly touch on the potentials and pitfalls of transgenic approaches to molecular physiology.

Animals↗
PubMed1993

Features of symptomatic gastroesophageal reflux in elderly patients.

Scarce information is available on gastroesophageal reflux disease in elderly patients. In this study we investigated patterns of gastroesophageal reflux and esophageal lesions in 24 elderly patients with typical gastroesophageal reflux symptoms and a mean age of 69 years (range, 65-76 years), as compared with 147 symptomatic younger patients with a mean age of 45 years (range, 21-64 years). The results of 24-h pH-monitoring and endoscopy showed that the elderly patients had pathologic reflux and reflux esophagitis more frequently than the young patients. The percentage time with pH < 4 in elderly patients with reflux esophagitis was 32.5% in 24 h, as compared with 12.9% in the younger patients with reflux esophagitis (P < 0.05). The elderly patients with reflux esophagitis had more prolonged periods of acid reflux in both the upright and supine positions than the younger patients. Endoscopy showed that 20.8% of elderly patients had grade III/IV esophagitis, whereas only 3.4% of younger patients had grade III/IV esophagitis (p < 0.002). The percentages of grade I/II esophagitis in the two groups were 12.5% and 26.5%, respectively (p < 0.002). We concluded that, compared with younger subjects, elderly patients have more severe gastroesophageal reflux and esophageal lesions.

Adult↗
PubMed1993

Gastric acid secretion and pattern of gastroesophageal reflux in patients with esophagitis and concomitant duodenal ulcer. A multivariate analysis of pathogenetic factors.

This study was designed to assess the relationship between gastric acid output (GAO) and both pattern of gastroesophageal reflux (GER) and severity of esophageal lesions. Gastric acid secretory testing and 24-h intraesophageal pH-monitoring were performed in 31 patients with esophagitis and concomitant duodenal ulcer (E+DU) and compared with those of 72 patients with esophagitis (E). The second aim of this study was to evaluate the role of GAO and other potential pathogenetic factors in the development of esophagitis. The results of the study showed that GAO in patients with E+DU was significantly higher than in patients with E (p < 0.05). There was no significant difference between the two groups of patients with regard to endoscopic findings or GER variables (p < 0.05). Multiple regression analysis with stepwise deletion showed that the presence of hiatal hernia, GER in the upright position and age appear to correlate significantly with the presence of esophagitis. We conclude that no parallel relationship exists between GAO and severity of GER or esophageal lesions in patients with E+DU and that GAO is not a major pathogenetic factor in GER disease.

Adult↗
PubMed1993

Excellent population research prize to be awarded.

In order to promote the development of population science in China, mobilize the initiativeness of demographers and more effectively serve the purpose of controlling population growth and improving the quality of human resources, the Population Association of China has sponsored an Excellent Population Research Award to encourage the demographers with outstanding achievements within the term (January 1991-June 30, 1993) of the Association. All the research staff and family planning workers with the membership of the Population Association of China as well as research institutes with notable achievements are eligible to the application for the award. The research achievements include monographs (or teaching materials), papers, survey reports, translated works, dictionaries or reference books, and softwares. For each category, 2 classes of prizes have been set, and winners are to be awarded with diplomas and money. The evaluation work will be started in September and October and concluded by the end of November 1993.

Asia↗
PubMed1993

Treatment of stomatological complications in 31 cases of acute leukemia with Chinese herbal drugs.

The authors treated 31 cases of stomatological complications of acute leukemia with Chinese herbal drugs. It was found that the prevalence of oral mucosal ulcers was the highest (80%) in acute lymphocytic leukemia, and the prevalence of gingival swelling was the highest (44%) in acute monocytic leukemia. In accordance with symptom differentiation, Qing Wei San (Powder for Clearing Stomach-heat) with modifications was administered in cases of exuberance and Yü Nü Jian (Gypsum Decoction) with modifications was administered in cases of deficiency, plus gargling solution and hemostatic powder for external use. As a result, 7 cases (22.6%) were markedly effective, and 19 cases (61.3%) effective, the total effective rate being 83.9%. The authors believed that stomatological complications of leukemia were due to insufficiency of yin and blood in the body or to the toxicity and heat of anti-neoplastic medication, and the Chinese herbal drugs were to replenish yin and clear the heat.

Adolescent↗
PubMed1993

[Analysis of fatty acid composition of spotted fever group rickettsiae isolated in China by gas chromatography].

In present paper, fatty acid composition of seven Chinese isolates of SFG rickettsiae and six prototype strains of SFG rickettsiae were analyzed by GC-MS. Tested prototype strains of SFG rickettsiae were R. sibirica (strains 232 and 246), R. conorii (Simko), R. rickettsi (R), R. akari (Kaplan), R. australis (W58); Chinese isolates were An-84, Se-85, W-88 (human strain), MT-84, FT-84 (D. nuttalli strain), TO-85 (ova of nuttalli) and Chinese reference strain -JH-74 (D. nuttalli). They were propagated in yolk sacs of embryonated hen eggs and purified by centrifugation in a 30%-36%-42% discontinuous renografin density gradient. The fatty acid composition of selected strains of SFG rickettsiae was analyzed by gas chromatography, and then comparison being carried out by single linkage on mini-computer. Identification of the strains was performed based on the results obtained from GC-MS. Results showed that the fatty acid profiles of all the isolates from China were quantitatively similar to that of R. sibirica and quite different from other prototype strains of SFG rickettsiae.

China↗
PubMed1993

[A voltage-clamp study on voltage-gated calcium channels translated in Xenopus oocytes by rat brain mRNA].

Voltage-gated calcium channels, expressed in Xenopus oocytes after injection of rat brain mRNA, were studied by using voltage-clamp technique. The properties of the calcium channels were characterized by barium current (IBa) passed through the channels. All oocytes used in this study were taken from five identified donors. Endogenous voltage--activated barium current measured in most oocytes from these donors were not detectable, or smaller than 15 nA, mRNA was extracted from the whole brains of 10 day postnatal rats and microinjected into the oocytes. IBa increased gradually during five days after mRNA injection. The maximum amplitude of the expressed voltage-activated barium current was usually larger than one hundred of nA on the third day after mRNA injection. In comparison, the expression of voltage-activated barium current was hardly detectable in oocytes injected by mRNA extracted from brains of embryonic rats. The voltage-dependence of activation and inactivation pharmacology of IBa were studied. It was found that IBa was inhibited potently by lanthanide cations (La+3,Nd+3,Sm+3,Eu+3,Gd+3,Dy+3,Er+3) at mumol/L concentration level. L-type calcium channel ligands, nifedipine and Bay K 8644 inhibited IBa at 100 mumol/L, while another dihydropyridine ligand (+/-) nimodipine enhanced IBa at the same concentration.

Animals↗
PubMed1993

Hepatocyte growth factor/scatter factor is an autocrine factor for human normal bronchial epithelial and lung carcinoma cells.

Hepatocyte growth factor (HGF) or scatter factor (SF) has been considered primarily as an endocrine/paracrine factor. We report here that HGF/SF mRNA was expressed by cultured human normal bronchial epithelial cells and many non-small cell lung carcinoma cell lines. Scatter activity was detected in the culture media of these cells, and this activity was inhibited by a neutralizing anti-recombinant human HGF antiserum. Immunostaining confirmed the presence of immunoreactive human HGF-like protein in the cytoplasm of these cultured cells, and in ciliated columnar epithelium of normal human bronchus/bronchioles. The met/HGF/SF receptor of these cultured cells was constitutively phosphorylated on tyrosine residues. A neutralizing anti-recombinant human HGF antiserum decreased the phosphorylation of the receptor, inhibited the proliferation of 45% of the non-small cell lung carcinoma cell lines studied, and stimulated the proliferation of normal bronchial epithelial cells. Altogether, the data demonstrate that HGF/SF and/or HGF-like protein is an autocrine factor for normal and neoplastic human bronchial epithelial cells in culture.

Base Sequence↗
PubMed1993

[Effect of gamma-irradiation on infectivity of Clonorchis sinensis metacercariae].

The purpose of the present study was to observe the survival and development of Clonorchis sinensis metacercariae in their final hosts after Co-60 gamma irradiation exerting on both metacercariae isolated or in fish. Guinea pigs or albino rats were orally infected by gavage. Bio-assay, fecal examination for ova and dissection of infected animals were used for the estimation of minimum effective dose of gamma irradiation to control infectivity of Clonorchis sinensis metacercariae. Results showed that the minimum effective irradiation dose for isolated metacercariae was 0.05 kGy. The LD50 of the irradiation dose for metacercariae in fish was 0.05 kGy, and the minimum effective dose was 0.15 kGy. No significant difference in radiation susceptibility to Co-60 gamma irradiation was found among Clonorchis sinensis metacercariae in fishes collected at different localities in the northern, middle or southern parts of China. The present finding suggests that irradiation of the fish at a dose of 0.15 kGy could control the infectivity of Clonorchis sinensis metacercariae and thus be adopted as a control measure in preventive medicine.

Animals↗
PubMed1992

Protein conformational perturbations affect the photoreduction of native cytochrome c peroxidase (III) at alkaline pH.

Ferric cytochrome c peroxidase (CCP) undergoes a ligation-state transition from a pentacoordinate, high-spin (5c/hs) heme to a hexacoordinate, low-spin (6c/1s) heme when titrated over a pH range of 7.30-9.70. This behavior is similar to that exhibited by the ferrous form of the enzyme. However, the photodissociation of the low-spin, axial ligand, exhibited by ferrous CCP at alkaline pH, is not observed for ferric CCP. Instead, a photoinduced reduction of the ferric heme is apparent in the pH range 7.90-9.70. In the absence of O2 and redox mediators such as methyl viologen (MV2+), the reoxidation of the photoreduced enzyme is very slow (tau 1/2 approximately 3 min). F(-)-bound CCP(III) (6c/hs) displays similar pH-dependent photoreduction. Horseradish peroxidase, however, does not. The formation of 6c/1s heme coincides with the onset of appreciable photoreduction (between laser pulses, > 60 ms) of CCP (III) at alkaline pH, suggesting a global protein conformational rearrangement within or around its heme pocket. Photoreduction of alkaline CCP(III) most likely involves intramolecular electron transfer (ET) from the aromatic residue in the proximal heme pocket to the photoexcited heme. We speculate that the kinetics of electron transfer are affected by changes in the orientation of Trp-191.

Cytochrome-c Peroxidase↗
PubMed1992

Priority among air pollution factors for preventing chronic obstructive pulmonary disease in Shanghai.

The problems that city environmental protection planners face are how important the air pollution exposures are in relation to chronic obstructive pulmonary disease (COPD) in local residents and which factor should be controlled most urgently. The purpose of our study is to determine the control priority among ambient sulphur dioxide (SO2) inhalable particulates (IP) and indoor use of coal to prevent COPD in residents of the city. Ambient air pollution is mainly from SO2 and IP(< 10 nm). Indoor air pollution is mainly from the use of coal for heating and/or cooking. Distribution of ambient SO2, and IP concentrations were described using a quartic trend surface simulation. When stratified by two extreme levels of ambient SO2 and IP and types of fuel used indoors, eight local area populations in four communities with different combinations of exposure levels were selected. In each community a local area population mostly using coal and one mostly burning gas was chosen. Chronic obstructive pulmonary diseases (COPD, ICD 490-493) including chronic bronchitis, asthma and emphysema, are a major cause of death in residents of Shanghai. The relationship between the three air pollution factors and their health effects were analyzed at the level of mortality (1978-1987, 232,459 person-years), prevalence of symptoms (12,037 persons) of COPD, lung function and non-specific immunologic function (514 women). The results show that indoor use of coal has stronger associations with health than estimated exposure to ambient SO2 or IP.

Adult↗
PubMed1992

Wild-type p53 activates transcription in vitro.

The p53 protein is an important determinant in human cancer and regulates the growth of cells in culture. It is known to be a sequence-specific DNA-binding protein with a powerful activation domain, but it has not been established whether it regulates transcription directly. Here we show that intact purified wild-type human and murine p53 proteins strongly activate transcription in vitro. This activation depends on the ability of p53 to bind to a template bearing a p53-binding sequence. By contrast, tumour-derived mutant p53 proteins cannot activate transcription from the template at all, and when complexed to wild-type p53, these mutants block transcriptional activation by the wild-type protein. Moreover, the simian virus 40 large T antigen inhibits wild-type p53 from activating transcription. Our results support a model in which p53 directly activates transcription but this activity can be inhibited by mutant p53 and SV40 large T antigen through interaction with wild-type p53.

Animals↗
PubMed1992

Identification of a coactivator that increases activation of transcription by serum response factor and GAL4-VP16 in vitro.

We have identified an activity in HeLa cell nuclear extracts that increases activation of transcription in vitro by serum response factor (SRF). This coactivator activity, termed CoS, did not affect basal (TATA only) transcription. CoS initially fractionated with transcription factors TFIIE and -F but was further purified to separate it from both TFIIE and -F as well as any other general transcription factor activity. We found that CoS was not specific for SRF activation, since it also increased transcriptional activation by the chimeric GAL4-VP16 activator. Differences among CoS and recently identified coactivators are discussed.

Cell Nucleus↗
PubMed1992

Yeast flavohemoglobin is an ancient protein related to globins and a reductase family.

The hemoglobin of yeast is a two-domain protein with both heme and flavin prosthetic groups. The nucleotide sequences of the cDNA and genomic DNA encoding the protein from Saccharomyces cerevisiae show that introns are absent and that both domains are homologous with a flavoheme protein from Escherichia coli. The heme domains are also homologous with those of O2-binding heme proteins from several other distantly related bacteria, plants, and animals; all appear to be members of the same globin superfamily. Although the homologous hemoglobin of the bacterium Vitreoscilla sp. is a single-domain protein, several bacteria have related O2-binding heme proteins whose second domains have different structures and enzymatic activities: dihydropteridine reductase (E. coli), cytochrome c reductase (Alcaligenes eutrophus), and kinase in the O2 sensor of Rhizobium meliloti. This indicates that one evolutionary pathway of hemoglobin is that of a multipurpose domain attached to a variety of unrelated proteins to form molecules with different functions. The flavin domain of yeast hemoglobin is homologous with members of a flavoprotein family that includes ferredoxin reductase, nitric oxide synthase, and cytochrome P-450 reductase. The correspondence of yeast and E. coli flavohemoglobins indicates that the two-domain protein has been conserved intact for as long as 1.8 billion years, the estimated time of divergence of prokaryotes and eukaryotes provided that cross-species gene transfer has not occurred.

Alcaligenes↗
PubMed1992

In vitro squelching of activated transcription by serum response factor: evidence for a common coactivator used by multiple transcriptional activators.

Low amounts of serum response factor (SRF) activate transcription in vitro from a fos promoter construct containing an SRF binding site. Using this human HeLa cell-derived in vitro transcription system, we have found that high amounts of SRF inhibited, or 'squelched', transcription from this construct. Transcription from several other promoters activated by different gene-specific factors, including CREB and the acidic activator VP16, was also inhibited by high amounts of SRF. Basal transcription, from TATA-only promoters, however, was not inhibited. These results suggest that SRF binds to a common factor(s) (termed coactivator) required for activated transcription by a diverse group of transcriptional activators. Inhibition of transcription by SRF could be blocked by a double stranded oligonucleotide containing an SRF binding site. Mutations in SRF which abolished its DNA binding activity also reduced its ability to inhibit transcription. In addition, a C-terminal truncation of SRF which reduced its ability to activate transcription also reduced SRF's ability to inhibit transcription. These results suggest that activation and inhibition of transcription may be mediated by SRF binding to the same factor and that SRF can only bind to this factor when SRF is bound to plasmid DNA.

Base Sequence↗