Biomedical subjects

H Zhu

Publications and source records attributed to H Zhu.

At least 469 records · Page 26Linked to original sources

PubMed1995

[Histomorphology research of keloid in different regions].

In order to explore the mechanism of keloid and provide scientific basis for clinical treatment, we carried out a study on histomorphologic comparison of keloids of different tissues. Based on the histomorphologic features, a keloid was divided into three different parts: invasive, proliferative and aged parts. Its pathologic process was described as invasive period, proliferative period, stable period and aging period, to provide scientific basis for treatment.

Adolescent↗

PubMed1995

[Clinical trial of oral etoposide in the treatment of malignancies].

From June 1993 to April 1994, a multi-centre prospective clinical trial was conducted to evaluate efficacy of domestic oral etoposide in the treatment of malignancies. One hundred and ten evaluable patients were assessed for both response and toxicity. Oral etoposide was given as single agent in 50 patients, including 18 patients with small cell lung cancer (SCLC), 18 with malignant lymphoma (ML), 8 with gastric cancer and 6 with ovarian cancer. The response rate was 50% in SCLC, 83.3% in ML, 16.7% in ovarian cancer and 0 in gastric cancer. Sixty patients were treated with combination chemotherapy containing oral etoposide. There were 45 patients in the control group. The response rates in the treated and control groups were 57.1% and 55.6% in SCLC, 95% and 87.5% in ML, 20% and 0 in gastric cancer, respectively. Oral etoposide was well tolerated by the majority of patients. In conclusion, oral etoposide has definite antitumor activity in SCLC, ML and ovarian cancer.

Administration, Oral↗

PubMed1995

[Effects of dynorphin A (1-8) on cell cycle and total cellular protein during neuronal aging in vitro].

Serum-free culture of mouse neuroblastoma cells was used as the experimental model for the study of neuronal aging, with flow cytometry of cell cycle, DNA and total cellular protein as the indices of neuronal aging. After addition of dynorphin A (1-8) 10(-7) mol.L-1 into the culture medium, the following general tendencies were obtained: (1) The number of S and G2 + M phase cells was increased and the number of G1 phase cells decreased. (2) The total cellular protein in aged experimental neural cells decreased. The results implies that Dyn A (1-8) Produced effects on cell cycle, DNA and total cellular protein in the direction of delaying neuronal aging. The relation between Dyn A (1-8) and neuronal aging merits further investigation.

Animals↗

PubMed1995

[Application of the polymerase chain reaction to the epidemiological study of amoebiasis].

The polymerase chain reaction (PCR) has been used in studying the pathogenicity of Entamoeba histolytica in a rural community in Shandong province. Formalin-fixed stool samples were used for extraction of DNA. The PCR amplifications were performed using two sets of primer that discriminate between pathogenic and nonpathogenic E. histolytica. All of the 32 cases of cyst carrier diagnosed microscopically were identified as positive. Three groups were defined through PCR analysis: 6 cases (18.8%) were positive for pathogenic but negative for nonpathogenic, 25 cases (78.1%) were negative for pathogenic but positive for nonpathogenic, and only one case (3.1%) was positive for both pathogenic and nonpathogenic. The cases found to be pathogenic by PCR were also closely correlated with their clinical manifestations (diarrhea) (OR = 31.5, P < 0.005). All of the control cases showed negative reaction to PCR. PCR has also been used to study the epidemiology of amoebiasis in a small population group with 40 persons in the same province. Both positive rates by PCR on pathogenic and nonpathogenic were 10%. The results showed that this new technique can be applied in the field for the epidemiological studies of pathogenic and nonpathogenic E. histolytica.

Animals↗

PubMed1995

[An analysis of complications after implantation of saline-filled silicone prosthesis for augmentation mammaplasty in 294 cases].

Complications after implantation of saline-filled silicone prosthesis for augmentation mammaplasty were analyzed in 294 patients after being followed for 3-5 years. The complications included hematoma, infection, capsular contraction, rupture of the implant, exposure of the implant, psychataxia and poor contour etc. Conditions in which these complications occurred, causes, clinical malifestations, prevention and treatment are discussed.

Breast Diseases↗

PubMed1994

Phospholipase A2 engineering. Structural and functional roles of the highly conserved active site residue aspartate-49.

Site-directed mutagenesis and high-resolution two-dimensional (2D) proton nuclear magnetic resonance (NMR) were used to probe the structural and functional roles of a highly conserved residue, Asp-49, in the interfacial catalysis by bovine pancreatic phospholipase A2 (PLA2, overexpressed in Escherichia coli). According to crystal structures, the side chain carboxylate of Asp-49, along with the carbonyl oxygens of Tyr-28, Gly-30, and Gly-32, and two water molecules, provides the necessary ligands for Ca2+ which is essential for the enzymatic activity. The Asp-49 of PLA2 was changed to Asn, Glu, Gln, Lys, and Ala; the resulting mutants are named D49N, D49E, D49Q, D49K, and D49A, respectively. The conformational stabilities of all five mutants are similar to that of WT as judged by guanidine hydrochloride-induced denaturation. The structural analyses by NMR indicated no global perturbations upon substitutions, although localized conformational perturbations can be observed for less conserved replacements. Direct Ca2+ binding studies showed no specific binding for D49A, D49N, D49Q, and D49K; however, D49E retains a 12-fold weaker calcium binding affinity (Kd,Ca = 23 mM). The specific activities of all five mutant enzymes decrease significantly, ranging from 5.4 x 10(2)- to 5.8 x 10(5)-fold in comparison with that of the wild-type enzyme. The observed activities of mutants require the presence of Ca2+. This demonstrates the functional importance of Asp-49 in the catalytic mechanism of PLA2, presumably by helping to bind and properly orient Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Tyrosine 1356 in the carboxyl-terminal tail of the HGF/SF receptor is essential for the transduction of signals for cell motility and morphogenesis.

The met proto-oncogene is a receptor tyrosine kinase for hepatocyte growth factor/scatter factor (HGF/SF). HGF/SF is a multifunctional cytokine that stimulates mitogenesis, motility, invasion, and tubulogenesis of a spectrum of epithelial and endothelial cells in culture. Using a chimeric receptor (CSF-MET), containing the extracellular domain of the colony stimulating factor-1 (CSF-1) receptor fused to the transmembrane and intracellular domain of the Met receptor, we have previously demonstrated that activation of the Met kinase domain is sufficient to mediate the motility, invasion and morphogenic signals of HGF/SF in Madin-Darby canine kidney epithelial cells (MDCK). In this study we have analyzed the role of tyrosine phosphorylation of the Met receptor in the transmission of these signals by site-directed mutagenesis of specific tyrosine residues. Mutation of two tyrosine residues (tyrosine 1234 and tyrosine 1235), involved in activation of the catalytic activity of the kinase, abrogates the biological activity of the chimera. In addition, we have identified a single noncatalytic tyrosine residue (tyrosine 1356) in the carboxyl terminus of the Met receptor, that is essential for the biological activity of the chimeric receptor. Mutation of tyrosine 1356 to a nonphosphorylatable phenylalanine residue does not affect the exogenous kinase activity of the receptor toward enolase, but it impairs the ability of the mutant protein to associate with the adaptor protein Grb2, and MDCK cells expressing this mutant fail to scatter, invade, and form branching tubules in response to CSF-1. These results support a crucial role for tyrosine 1356 in activation of signaling pathways involved in the biological activity of the Met receptor in response to HGF/SF.

Animals↗

PubMed1994

Synthesis and biochemical evaluation of a series of aminoflavones as potential inhibitors of protein-tyrosine kinases p56lck, EGFr, and p60v-src.

A series of nitroflavones, 8a-p, and their corresponding aminoflavone hydrochloride salts, 10a-p, was synthesized. The preparation of nitroflavones 8b-i,o,p began with commercially available o-hydroxyacetophenones 2b-f which were converted to o-hydroxynitroacetophenones 3a-h via a variety of nitration methods, followed by condensation with nitrobenzoyl chlorides and cyclization under acidic condition. The nitroflavones 8aj-n were prepared by nitration of the corresponding flavones 7a-e. These new compounds were evaluated for their abilities to inhibit the in vitro protein-tyrosine kinase activities of p56lck, EGFr, and p60v-src, and all of the active compounds were amino-substituted flavones. None of the nitroflavones inhibited the enzymes. The most active substance in this series against p56lck was compound 10j, which had an IC50 of 18 microM. When tested versus EGFr, compounds 10a,m displayed IC50's of 8.7 and 7.8 microM, respectively. Against p60v-src, 10a,m showed IC50 values of 28.8 and 38.4 microM, respectively.

Adenosine Triphosphate↗

PubMed1994

Ich-1, an Ice/ced-3-related gene, encodes both positive and negative regulators of programmed cell death.

We report here the isolation and characterization of Ich-1, a gene related to the C. elegans cell death gene ced-3 and the mammalian homolog of ced-3, interleukin-1 beta-converting enzyme (ICE). Alternative splicing results in two distinct Ich-1 mRNA species. One mRNA species encodes a protein product of 435 amino acids (ICH-1L) that is homologous to both the P20 and P10 subunits of ICE (27% identity) and the entire CED-3 protein (28% identity). The other mRNA encodes a 312 amino acid truncated version of ICH-1L protein (ICH-1S). Overexpression of IchL induces programmed cell death, suggesting that Ich-1 is also a mammalian programmed cell death gene. More interestingly, overexpression of the Ich-1S suppresses Rat-1 cell death induced by serum deprivation. These observations suggest that Ich-1 plays an important role in both positive and negative regulation of programmed cell death in vertebrate animals.

Alternative Splicing↗

PubMed1994

High-sensitivity capillary electrophoresis of double-stranded DNA fragments using monomeric and dimeric fluorescent intercalating dyes.

Fluorescence-detected capillary electrophoresis separations of phi X174/HaeIII DNA restriction fragments have been performed using monomeric and dimeric intercalating dyes. Replaceable hydroxyethyl cellulose solutions were used as the separation medium. Confocal fluorescence detection was performed following 488-nm laser excitation. The limits of DNA detection for on-column staining with monomeric dyes (ethidium bromide, two propidium dye derivatives, oxazole yellow, thiazole orange, and a polycationic thiazole orange derivative) were determined. The thiazole orange dyes provide the most sensitive detection with limiting sensitivities of 2-4 amol of DNA base pairs per band, and detection of the 603-bp fragment was successful, injecting from phi X174/HaeIII samples containing only 1-2 fg of this fragment per microliter. Separations of preformed DNA-dimeric dye complexes were also performed. The breadth of the bands observed in separations of preformed DNA-dimeric dye complexes is due to the presence of DNA fragments with different numbers of bound dye molecules that can be resolved as closely spaced subbands in many of our separations. The quality of these DNA-dye complex separations can be dramatically improved by performing the electrophoresis with 9-aminoacridine (9AA) in the column and running buffers. The optimum concentrations of 9AA for the separation of complexes preformed with the dimeric dyes TOTO, EthD, TOTAB, and YOYO were determined to be 100, 1, 1, and 0.5 microM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA↗

PubMed1994

Physiologically based pharmacokinetic model for specific and nonspecific monoclonal antibodies and fragments in normal tissues and human tumor xenografts in nude mice.

A physiologically based pharmacokinetic model to describe the biodistribution of a specific monoclonal antibody IgG1 (ZCE025) and its fragments (F(ab')2 and Fab) and of a nonspecific IgG1 (MOPC21) in normal tissues and a human colon carcinoma xenograft (T380) in nude mice is developed. The model simulates the experimental data on the concentration of these four macromolecules in plasma, urine, heart, lung, liver, kidney, spleen, bone, muscle, skin, GI tract, and tumor. This is the first such model for macromolecules with specific binding. A two-pore formalism for transcapillary solute exchange is used which avoids the oversimplifications of unidirectional transport or a single effective permeability coefficient. Comparison of the model with our biodistribution data shows that: (a) a physiologically based pharmacokinetic model for specific and nonspecific antibodies is able to explain experimental data using as few adjustable parameters as possible; (b) for antibodies and fragments, the tumor itself has no significant influence on the pharmacokinetics in normal tissues; and (c) the two-pore formalism for transcapillary exchange describes the data better than a single-pore model without introducing extra adjustable parameters. Sensitivity analysis shows that the lymph flow rate and transvascular fluid recirculation rate are important parameters for the uptake of antibodies, while for the retention of specific antibodies, extravascular binding is the key parameter. A single-pore model could also obtain a good fit between model and data by adjusting two parameters; however, the estimated permeability was 1000 times higher than with the two-pore model, and the binding affinity was such that approximately five times more material was bound than free in the extravascular space for nonspecific antibody. Setting the binding affinity to zero or reducing the value of the permeability-surface area product did not allow a good fit, even when the lymph flow rate was varied. The present model may be useful in scaling up antibody pharmacokinetics from mouse to man.

Animals↗

PubMed1994

Role of transcription factor TFIIF in serum response factor-activated transcription.

We have found that the general transcription factor TFIIF has an important role in serum response factor (SRF)-activated transcription in vitro. A low amount of TFIIF was sufficient for basal transcription, whereas higher amounts were required for SRF, but not Sp1, activation. High TFIIF levels also increased activation by GAL4-VP16, whereas none of the other general transcription factors had these properties. TFIIF could also relieve squelching by SRF in vitro, suggesting that SRF may directly bind TFIIF. We found more direct evidence for SRF-TFIIF interaction by DNA binding assays where the RAP74 subunit of TFIIF bound DNA in conjunction with SRF, but not alone. RAP74 also bound DNA with GAL4-VP16, but not with Sp1 or the DNA binding domain of GAL4. These results suggest that the mechanism of transcriptional activation by SRF, and perhaps some other activators, involves their interaction with TFIIF.

Cell Nucleus↗

PubMed1994

Structure and function of the catalytic site mutant Asp 99 Asn of phospholipase A2: absence of the conserved structural water.

To probe the role of the Asp-99 ... His-48 pair in phospholipase A2 (PLA2) catalysis, the X-ray structure and kinetic characterization of the mutant Asp-99-->Asn-99 (D99N) of bovine pancreatic PLA2 was undertaken. Crystals of D99N belong to the trigonal space group P3(1)21 and were isomorphous to the wild type (WT) (Noel JP et al., 1991, Biochemistry 30:11801-11811). The 1.9-A X-ray structure of the mutant showed that the carbonyl group of Asn-99 side chain is hydrogen bonded to His-48 in the same way as that of Asp-99 in the WT, thus retaining the tautomeric form of His-48 and the function of the enzyme. The NH2 group of Asn-99 points away from His-48. In contrast, in the D102N mutant of the protease enzyme trypsin, the NH2 group of Asn-102 is hydrogen bonded to His-57 resulting in the inactive tautomeric form and hence the loss of enzymatic activity. Although the geometry of the catalytic triad in the PLA2 mutant remains the same as in the WT, we were surprised that the conserved structural water, linking the catalytic site with the ammonium group of Ala-1 of the interfacial site, was ejected by the proximity of the NH2 group of Asn-99. The NH2 group now forms a direct hydrogen bond with the carbonyl group of Ala-1.

Animals↗

PubMed1994

Oxidation pathways for the intracellular probe 2',7'-dichlorofluorescein.

The oxidation of 2',7'-dichlorofluorescin (DCFH) to a fluorescent product is currently used to evaluate oxidant stress in cells. However, there is considerable uncertainty as to the enzymatic and nonenzymatic pathways that may result in DCFH oxidation. Iron/hydrogen peroxide-induced DCFH oxidation was inhibited by catalase or by the hydroxyl radical scavenger dimethylsulfoxide; however, superoxide dismutase (SOD) had no effect on DCFH oxidation. The formation of hydroxyl radical (indicated by the oxidation of salicylic acid to 2,3-dihydroxybenzoic acid) was proportional to DCFH oxidation, suggesting that the hydroxyl radical is responsible for the iron/peroxide-mediated oxidation of DCFH. Utilizing a superoxide generating system consisting of hypoxanthine/xanthine oxidase, oxidation of DCFH was unaffected by SOD, catalase or desferoxamine, and stimulated by removing hypoxanthine from the reaction mixture. In contrast, SOD or elimination of hypoxanthine abolished superoxide formation. In addition, potassium superoxide did not support the oxidation of DCFH. Thus, superoxide is not involved in DCFH oxidation. Boiling xanthine oxidase eliminated its concentration-dependent oxidation of 1 microM DCFH, indicating that xanthine oxidase can enzymatically utilize DCFH as a high affinity substrate. Kinetic studies of the oxidation of DCFH by xanthine oxidase indicated a Km(app) of 0.62 microM. Hypoxanthine competed with DCFH with a Ki(app) of 1.03 mM. These studies suggest that DCFH oxidation may be a useful indicator of oxidative stress. However, other types of cellular damage may produce DCFH oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluoresceins↗

PubMed1994

Regulation of [Ah] gene battery enzymes and glutathione levels by 5,10-dihydroindeno[1,2-b]indole in mouse hepatoma cell lines.

The murine aromatic hydrocarbon ([Ah]) gene battery consists of at least six genes that code for two functionalizing (Phase I) enzymes and four non-functionalizing (Phase II) enzymes. These enzymes are induced by compounds such as aromatic hydrocarbons and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) that bind to the cytosolic Ah receptor protein. Studies in rodents indicate that certain enzymes of this battery, namely cytochrome P4501A1 (CYP1A1), UDP-glucuronosyltransferase (UGT1*06) and NAD(P)H: quinone acceptor oxidoreductase (NMO1) are induced by the synthetic antioxidant 5,10-dihydroindeno[1,2-b]indole (DHII). The induction of [Ah] gene battery enzymes and the levels of reduced glutathione (GSH) were examined in mouse Hepa-1c1c7 hepatoma wild-type cells (wt), a CYP1A1 metabolism-deficient mutant (c37) and an Ah receptor nuclear translocation-defective mutant (c4). DHII and TCDD increased the activities of ethoxyresorufin O-deethylase, an indicator of CYP1A1 activity, as well as NMO1, UGT1*06, cytosolic aldehyde dehydrogenase class 3 and glutathione S-transferase form A1 in wt cells, but had little or no induction effect in c37 or c4 cells. DHII and TCDD differed in their effects on GSH levels; while DHII increased GSH levels 3-fold in wt, but not at all in c37 or c4 cells, TCDD had no effect on GSH levels in any cell type. However, GSH levels were enhanced in both wt and c4 cells by tert-butyl hydroquinone (TBHQ). L-Buthionine S,R-sulfoximine, an inhibitor of gamma-glutamylcysteine synthetase, prevented DHII-induced increases in wt cell GSH. The increase in GSH levels occurred after 8 h, while the induction of enzymes occurred within 4 h. The induction of the higher GSH levels in wt cells by DHII and TBHQ correlated with increases in intracellular levels of the GSH precursor thiol cysteine, as well as with increased activities of gamma-glutamylcysteine synthetase, the rate-limiting enzyme of GSH synthesis. However, TBHQ-mediated GSH increases in c4 cells were accompanied by increased gamma-glutamylcysteine synthetase activity with no change in intracellular cysteine concentration. The results suggest that DHII induction of [Ah] gene battery enzymes requires a functional Ah receptor, but not the functional gene product CYP1A1. Furthermore, metabolism, possibly via CYP1A1, appears to be required for DHII to enhance intracellular levels of cysteine and GCS activity that result in higher GSH levels.

Aldehyde Dehydrogenase↗

PubMed1994

Enzymatic specificities and modes of action of the two catalytic domains of the XynC xylanase from Fibrobacter succinogenes S85.

The xylanase XynC of Fibrobacter succinogenes S85 was recently shown to contain three distinct domains, A, B, and C (F. W. Paradis, H. Zhu, P. J. Krell, J. P. Phillips, and C. W. Forsberg, J. Bacteriol. 175:7666-7672, 1993). Domains A and B each bear an active site capable of hydrolyzing xylan, while domain C has no enzymatic activity. Two truncated proteins, each containing a single catalytic domain, named XynC-A and XynC-B were purified to homogeneity. The catalytic domains A and B had similar pH and temperature parameters of 6.0 and 50 degrees C for maximum hydrolytic activity and extensively degraded birch wood xylan to xylose and xylobiose. The Km and Vmax values, respectively, were 2.0 mg ml-1 and 6.1 U mg-1 for the intact enzyme, 1.83 mg ml-1 and 689 U mg-1 for domain A, and 2.38 mg ml-1 and 91.8 U mg-1 for domain B. Although domain A had a higher specific activity than domain B, domain B exhibited a broader substrate specificity and hydrolyzed rye arabinoxylan to a greater extent than domain A. Furthermore, domain B, but not domain A, was able to release xylose at the initial stage of the hydrolysis. Both catalytic domains cleaved xylotriose, xylotetraose, and xylopentaose but had no activity on xylobiose. Bond cleavage frequencies obtained from hydrolysis of xylo-alditol substrates suggest that while both domains have a strong preference for internal linkages of the xylan backbone, domain B has fewer subsites for substrate binding than domain A and cleaves arabinoxylan more efficiently. Chemical modification with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide methiodide and N-bromosuccinimide inactivated both XynC-A and XynC-B in the absence of xylan, indicating that carboxyl groups and tryptophan residues in the catalytic site of each domain have essential roles.

Amino Acid Sequence↗

PubMed1994

Positive regulatory elements (HF-1a and HF-1b) and a novel negative regulatory element (HF-3) mediate ventricular muscle-specific expression of myosin light-chain 2-luciferase fusion genes in transgenic mice.

The cardiac myosin light-chain 2v (MLC-2v) gene has served as a model system to identify the pathways which restrict the expression of cardiac muscle genes to particular chambers of the heart during cardiogenesis. To identify the critical cis regulatory elements which mediate ventricular chamber-specific expression of the MLC-2v gene in the in vivo context, a series of transgenic mice which harbor mutations in putative MLC-2 cis regulatory elements in a 250-bp MLC-2-luciferase fusion gene which is expressed in a ventricular chamber-specific fashion in transgenic mice were generated. These studies demonstrate that both components of HF-1 (HF-1a and HF-1b/MEF-2) are required to maintain ventricular chamber-specific expression and function as positive regulatory elements. Mutations in another conserved element (HF-2) are without statistically significant effect on ventricular chamber expression. Transgenics harboring mutations in the E-box site also displayed significant upregulation of reporter activity in the soleus, gastrocnemius, and uterus, with a borderline effect on expression in liver. Mutations in another conserved element (HF-3) result in a marked (> 75-fold) upregulation of the luciferase reporter activity in the soleus muscle of multiple independent or transgenic founders. Since the HF-3 mutations appeared to have only a marginal effect on luciferase reporter activity in liver tissue, HF-3 appears to function as a novel negative regulatory element to primarily suppress expression in muscle tissues. Thus, a combination of positive (HF-1a/HF-1b) and negative (E-box and HF-3) regulatory elements appear to be required to maintain ventricular chamber-specific expression in the in vivo context.

Animals↗

PubMed1994

[Crystalloids in salivary gland pleomorphic adenoma].

We examined crystalloids in salivary gland pleomorphic adenomas. The crystalloids were detected in 4 of 34 pleomorphic adenomas (11.7%). In three cases they were found in the minor salivary gland and in one case in the major salivary gland. Light microscopy revealed that all the crystalloids were in parenchyma. They were composed of eosinphilic structure and radially arranged clusters of needle-shape fibers. The central parts sometimes contained clear space. They were usually closely surrounded by neoplastic myoepithelial cells. All 4 cases containing crystalloids were million reaction-negative and positive to van Gieson, Mallory and Reticulin Silver Impregnation stains. Therefore all the crystalloids in our 4 cases were considered as collagen-rich.

Adenoma, Pleomorphic↗