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Biomedical subjects

H Zhu

Publications and source records attributed to H Zhu.

At least 433 records · Page 24Linked to original sources
PubMed1996

Comparison of ligand binding affinities at human I1-imidazoline binding sites and the high affinity state of alpha-2 adrenoceptor subtypes.

To identify selective compounds for nonadrenergic I1-imidazoline receptors (I1), the affinities of 22 ligands for [125I]p-iodoclonidine binding have been compared at human platelet I1-imidazoline binding sites (analyzed under norepinephrine mask of alpha-2 AR) and at human alpha-2A, alpha-2B and alpha-2C adrenoceptors stably expressed on transfected Chinese hamster ovary cells. Competition curves at the platelet I1-imidazoline binding site were biphasic for most compounds. Only tizanidine and BDF,6143 displayed monophasic I1 competition curves. Agmatine, an endogenous neurotransmitter candidate for the I1-imidazoline receptor, was identified as the most selective agent for a subcomponent of platelet I1 sites. The affinity of agmatine at the high affinity component of platelet I1 sites was 1400-fold selective over alpha-2A adrenoceptors, 5000-fold selective over alpha-2B adrenoceptors and 800-fold selective over alpha-2C adrenoceptors. Moxonidine and tizanidine also displayed selectivities for a high affinity component of the platelet I1 binding sites over alpha-2 adrenoceptors. Naphazoline was the most selective compound for the high affinity state of the alpha-2A adrenoceptor, displaying 7-, 23- and 9-fold higher affinity than alpha-2B, alpha-2C and platelet I1-midazoline binding sites, respectively. No single selective compound was identified for the alpha-2B adrenoceptor. Norepinephrine displayed, respectively, 18- and 31-fold selectivity for the high affinity state of the alpha-2C adrenoceptor as compared to alpha-2A- or alpha-2B adrenoceptors, and was > 100,000- fold selective over platelet I1-imidazoline sites. Thus, human alpha-2 adrenoceptors and the platelet I1-imidazoline binding site can be clearly discriminated based on their affinities for certain compounds.

Animals↗
PubMed1996

[The influence of hypoxia/reoxygenation on production and release of nitric oxide from cultured newborn rat cardiomyocytes].

OBJECTIVE: To study the influence of hypoxia/reoxygenation on the production and release of nitric oxide (NO), lactate dehydrogenase (LDH) and creatine kinase (CPK) from cultured newborn rat cardiomyocytes. METHODS: The rats were divided into four groups: control, hypoxia/reoxy-genation, heat shock pretreated, dexamethasone pretreated. RESULTS: After 3 hours of hypoxia and 30 minutes of reoxygenation, the content of NO in the supernatent of cardiomyocytes increased significantly (P < 0.05), which was accompanied by an increase in the release of LDH and CPK (P < 0.001, P < 0.001 respectively). When pretreated by the heat shock (exposed to 42 degrees C for 1 hour and then allowed to recover for 24 hours) or by applying dexamethasone at the onset of hypoxia, the production and release of NO, LDH, CPK decreased markedly (P < 0.05). CONCLUSIONS: Excessive release of NO may play an important role in the reperfusion injury of cardiomyocytes. Heat shock seems to provide protection for cardiomyocytes from hypoxia/reoxygenation injury. The mechanism may be related to the inhibition of excessive release of No from the cardiomyocytes.

Animals↗
PubMed1996

Application of polymerase chain reaction for diagnosing amebic liver abscess.

Polymerase chain reaction (PCR) has been applied in diagnosing amebic liver infection by detecting pathogenic Entamoeba histolytica DNA in liver aspirates. Oligonucleotide primers found to be specific for the gene encoding the 30 kDa molecule of this pathogenic ameba were used in the test. Liver aspirates obtained from 23 patients with amebic liver abscess substantiated by typical clinical manifastation or with very high titres of anti-E histolytica antibodies by ELISA were found to be positive by PCR. Fourteen control samples (3 cases of bacterial liver abscess, 1 of liver cancer and 10 of other abscess) were all found to be negative to this reaction. The results suggested PCR to be a specific and sensitive tool for diagnosing amebic liver abscess infections.

Animals↗
PubMed1996

[Effect of IGF-II on progesterone production by cultured rat luteal cells in vitro].

It has been reported recently that IGF-II plays an important role in the regulation of ovarian function. The aim of this study is to investigate whether IGF-II can affect progesterone production by cultured rat luteal cells. The results showed that IGF-II could significantly stimulate basal progesterone production in a dose-dependent manner without altering the cAMP content. IGF-II could enhance 3H-leu incorporation into protein and 3H-TdR incorporation into DNA of the luteal cells, but these effects could be inhibited by CYX and Act D. The above results suggest that stimulating effect of IGF-II on progesterone production by rat luteal cells may be related to enhanced protein and DNA synthesis.

Animals↗
PubMed1996

[Expression of ras P21 oncoprotein in Syrian golden hamster embryo cells transformation induced by water pollutants].

Carcinogenic activities of organic pollutants in freshwater collected from Taihu Lake, Chaohu Lake and Dianshanhu Lake in Jiangsu Province were analyzed by in vitro Syrian hamster embryo (SHE) cell transformation and immunohistochemical methods. Results revealed organic pollutants in the originally collected water could, to the different extent, induce morphological changes of SHE cells, with a certain dose-response relationship. Expression of ras P21 oncoprotein increased in typical transformation cells of type I, which showed a positive immunohistochemical stain. And, ras P21 oncoprotein expressed to a certain extent in types I and II transformation cells during transition stage. It suggests water pollutants in the above-mentioned lakes had certain carcinogenic activities, and activation of ras oncogene may be one of the mechanisms to induce malignant transformation of SHE cells.

Animals↗
PubMed1996

[Measurement of serum apoA I and apoA II in 438 male healthy subjects aged 40-70 in Chengdu area].

Using the method of immunoturbidimetric assay (INA) for apoA 1 and the method of radial immunodiffusion assay (RID) for apoA II developed by ourselves, we measured the serum apoA I and apoA II concentrations in 438 male healthy subjects aged 40-70 in Chengdu area. The contents of serum apoA I and apoA II for male aged 40-70 were 130.1 +/- 22.0 mg/dl (n = 438) and 29.9 +/- 4.90 mg/dl (n = 437) respectively. The serum apoA I and A II levels showed no significant increase with age and had a normal distribution.

Adult↗
PubMed1996

[Repression of voltage gated K+ channel expressed in Xenopus oocytes after injection total RNA from carp retina by an antisense oligonucleotide].

Injection of total RNA from carp retina induced the formation of a membrane K+ channel in Xenopus oocytes. We found an oligonucleotide complementary to the mRNA coding for a peptide fragment in the K+ channel of drosophila and mice could suppress the K+ channel current in a very specific manner. This provides important information for the cloning of this gene and for studying it's function.

Animals↗
PubMed1996

[Studies on glutamate and GABA receptor expressed in amphibian oocytes after injection of carp retina mRNA].

Using voltage clamp and perfusion technique, the types and characteristics of amino acid receptors of carp (Carassius carassius) retinas were studied by expressed response of amphibian oocytes previous injected with the retinal mRNA. The results were as follows: (1) Glu receptor: Diazoxide could potentiated KA induced depolarization, suggesting that some of the retinal Glu receptors may be AMPA-preferring subtype. (2) GABA receptor: Bicuculine could greatly suppress the GABA induced inward rapid current, while GABAB agonist baclofen was without effect. This suggests that the most of retinal GABA receptors may be GABAA type.

Animals↗
PubMed1996

[Valve replacement in children].

We report 27 children aged 2-14 years underwent valve replacement. Twelve patients underwent mitral valve replacement, 11 tricuspid valve replacement, and 4 aortic valve replacement. Of them, 16(59.3%) were associated with cardiac malformation, 23 were in NYHA functional class III and IV in preoperation. 13 patients required additional procedures. There were 3 hospital deaths (11.1%), 4 late deaths (16.6%), and 2 reoperation. Our experiment suggested that the greater type of mechanical valve be essential for valve replacement in children, but suture technique be modified for the children with small valvular ring. After replacement of mechanical valve, low concentration anticoagulation therapy is considered as a safe and reliable method.

Adolescent↗
PubMed1995

The Y-box motif mediates redox-dependent transcriptional activation in mouse cells.

We show here that the OxyR response element (ORE) in the bacterial oxyR promoter can also function as a redox-dependent enhancer in mammalian cells. Fusion of ORE to an SV40 basal promoter driving chloramphenicol acetyltransferase (CAT) expression confers H2O2 inducibility to expression of the cat gene in mouse Hepa-1 hepatoma cells. Nuclear extracts from these cells contain DNA-binding proteins that specifically interact with ORE DNA, cannot be completed by cognate oligonucleotides to AP-1 or NF kappa B, and are constitutively expressed, since treatment with H2O2 causes no detectable changes in binding activity or DNA-protein interaction. Recombinant cDNA clones that express ORE-binding proteins were isolated from a mouse hepatoma expression library and found to be representatives of two different members of the murine Y-box family of transcription factors. Canonical Y-box and ORE oligonucleotides compete with each other for binding to Y-box proteins in gel shift assays and antibodies to FRGY2, a Xenopus Y-box protein, supershift both Y-box and ORE DNA-protein complexes. In addition, antisense oligonucleotides to mouse YB-1 mRNA abolish induction of ORE-mediated cat expression by H2O2, and luciferase reporter constructs containing ORE, or the Y-box from the human MHC class II HLA-DQ gene, exhibit identical dose-dependent H2O2 inducibilities, which can be abolished by addition of 2-mercaptoethanol to the culture medium. These results suggest that the Y-box proteins may be an integral component of a eukaryotic redox signaling pathway.

3T3 Cells↗
PubMed1995

Involvement of natural killer cells in nitric oxide production by spleen cells after stimulation with Mycobacterium bovis BCG. Study of the mechanism of the different abilities of viable and killed BCG.

Viable and killed BCG were compared for the ability to induce nitric oxide (NO) production in normal spleen cells and peritoneal exudate macrophages. Stimulation of spleen cells with viable BCG resulted in a strong expression of inducible NO synthase followed by an enhanced production of nitrite. However, those responses were not induced after stimulation with killed BCG or when macrophages were stimulated with killed and viable BCG. The same level of TNF-alpha mRNA expression was observed in reverse transcription-PCR after stimulation of spleen cells with viable and killed BCG. However, IFN-gamma production was induced only when spleen cells were stimulated with viable BCG. Concurrent stimulation of rIFN-gamma with either viable or killed BCG resulted in a strong nitrite production by macrophages. Neutralization of IFN-gamma and TNF-alpha caused a complete inhibition of nitrite production. Furthermore, anti-asialo GM1 Ab plus complement treatment abolished IFN-gamma production after stimulation with viable BCG, indicating that the NK cell was the major source of IFN-gamma, and its production was triggered only by stimulation with viable BCG. The present study showed that the ability of viable BCG to induce NO production is superior to that of killed BCG, and both IFN-gamma and TNF-alpha are essential for BCG-induced NO production by spleen cells. NK cells appeared to be important as a source of IFN-gamma, and the insufficient NO induction by killed BCG was due to the inability to induce IFN-gamma from NK cells.

Animals↗
PubMed1995

Phospholipase A2 engineering. The roles of disulfide bonds in structure, conformational stability, and catalytic function.

Site-directed mutagenesis was used to probe the contribution of each of the seven disulfide bonds of bovine pancreatic phospholipase A2 (PLA2, overexpressed in Escherichia coli) to the structure, conformational stability, and catalytic function of the enzyme. Each of the seven disulfide bonds, C11-C77, C27-C123, C29-C45, C44-C105, C51-C98, C61-C91, and C84-C96, was deleted separately by changing both cysteine (C) residues to alanine (A). The structural properties of the mutants were analyzed by 1D and 2D proton NMR, the conformational stability by guanidine hydrochloride-induced denaturation, and the catalytic property by measuring kinetic parameters toward DC8PC (1,2-dioctanoyl-sn-glycero-3-phosphocholine) micelles. The results led to the following significant findings: (i) All but one (C84A-C96A) mutants have been refolded and purified by use of the same procedure for wild-type PLA2. Thus, the disulfide bonds are generally not important to the folding pathway of PLA2. (ii) The disulfide bond C11-C77 is most important to the conformation and conformational stability of the enzyme since deletion of this disulfide bond resulted in greatly perturbed NMR properties and in a decrease of 6.2 kcal/mol in conformational stability. However, the C11A-C77A mutant displayed little change in catalytic function. (iii) The effects of deleting disulfide bonds on the catalytic function of PLA2 are small, except the disulfide bond C29-C45 which connects the calcium binding loop with the helix C. However, the conformation and conformational stability of the C29A-C45A mutant was found to decrease by a factor of 10 or greater. (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

An ICE-like protease is a common mediator of apoptosis induced by diverse stimuli in human monocytic THP.1 cells.

Apoptosis was induced in THP.1 cells, a human monocytic tumour cell line, by diverse stimuli including cycloheximide, thapsigargin, etoposide and staurosporine. Induction of apoptosis by all these stimuli, except etoposide, was enhanced in the presence of the trypsin-like protease inhibitor, N alpha-tosyl-L-lysinyl chloromethyl ketone (TLCK). Induction of apoptosis, assessed by morphological, flow cytometric and biochemical criteria, including proteolysis of poly(ADP-ribose) polymerase and cleavage of DNA to large kilobasepair fragments, was completely abrogated when cells were pretreated with an ICE-like protease inhibitor, Z-Val-Ala-Asp.fluoromethylketone. This suggested that an ICE homologue was a common mediator of apoptosis in THP.1 cells.

Amino Acid Chloromethyl Ketones↗
PubMed1995

Biodistribution of monoclonal antibodies: scale-up from mouse to human using a physiologically based pharmacokinetic model.

The efficacy of a novel diagnostic or therapeutic agent depends on its selective localization in a target tissue. Biodistribution studies are expensive and difficult to carry out in humans, but such data can be obtained easily in rodents. We have developed a physiologically based pharmacokinetic model for scaling up data from mice to humans, the first such model for genetically engineered macromolecules that bind to their targets in vivo, such as mAbs. The mathematical model uses physiological parameters including organ volumes, blood flow rates, and vascular permeabilities; the compartments (organs) are connected anatomically. This allows the use of scale-up techniques to predict antibody distribution in humans. The model was tested with data obtained in human patients for the biodistribution of a mAb against carcinoembryonic antigen. The model was further tested for a two-step protocol: bifunctional antibodies and radiolabeled hapten, which compared favorably with data in both mice and humans. The model was useful for optimization of treatment parameters, such as dose and time interval of injections, binding affinities, and choice of molecular carrier. This framework may be applicable to other genetically engineered molecules (e.g., growth factors, antisense oligonucleotides, and gene-carrying vectors).

Animals↗
PubMed1995

Glu-96 of basic fibroblast growth factor is essential for high affinity receptor binding. Identification by structure-based site-directed mutagenesis.

The importance of basic fibroblast growth factor (bFGF) in several pathophysiological processes has stimulated interest in the design of receptor antagonists to mitigate such effects. Of key importance in this connection is the characterization of the functional binding epitopes of the growth factor for its receptor. Based on peptide mapping and molecular dynamics calculations of the three-dimensional structure of basic fibroblast growth factor, we employed site-directed mutagenesis to investigate the effect of altering residues at positions 107, 109-114, and 96 on bFGF on receptor binding affinity. All muteins were cloned and expressed in Escherichia coli, purified to homogeneity employing heparin-Sepharose columns, and evaluated for receptor binding affinity. We found that replacement of residues at positions 107 and 109-114 by alanine or phenylalanine had little effect on receptor binding affinities compared with wild type bFGF, in agreement with previous evidence that bFGF residues 109-114 comprise a low affinity binding site. By contrast, substitution of Glu-96 with alanine yielded a molecule having about 0.1% of the affinity of the wild type bFGF. The affinity of the corresponding lysine and glutamine muteins was 0.3 and 10%, respectively, emphasizing the importance of a negative charge at this position. Our findings are consistent with the view that residues 106-115 on bFGF represent a low affinity binding site on bFGF. In addition, we identify Glu-96 as a crucial residue for binding to fibroblast growth factor receptor-1.

Amino Acid Sequence↗
PubMed1995

Structure of a frequently rearranged rRNA-encoding chromosome in Giardia lamblia.

It has been shown previously that the rRNA encoding chromosomes in Giardia lamblia undergo frequent rearrangements with an estimated rate of approximately 1% per cell per division (Le Blancq et al., 1992, Nucleic Acids Res., 17, 4539-4545). Following these observations, we searched for highly recombinogenic regions in one of the frequently rearranged rRNA encoding chromosomes, that is chromosome 1, a small, 1.1 Mb chromosome. Chromosome 1 undergoes frequent rearrangements that result in size variation of 5-20%. We analyzed the structure of chromosome 1 in clonal lineages from the WB strain. The two ends of chromosome 1 comprise telomere repeat [TAGGG] arrays joined to a truncated rRNA gene and a sequence referred to as '4e', respectively. Comparison of the structure of four polymorphic versions of chromosome 1, resulting from independent rearrangement events in four cloned lines, located a single polymorphic region to the variable rDNA-telomere domain. Chromosome 1 is organized into two domains: a core region spanning approximately 850 kb that does not exhibit size heterogeneity among different chromosome 1 and a variable region that spans 185-450 kb and includes the telomeric rRNA genes, referred to as the variable rDNA-telomere domain. The core region contains a conserved region, spanning approximately 550 kb adjacent to the telomeric 4e sequence, which is only present in the 4e containing chromosomes and a 300 kb region of repetitive sequences that are also components of other chromosomes as well. Changes in the number of rDNA repeats accounted for some, but not all, of the size variation. Since there are four chromosomes that share the core region of chromosome 1, we suggest that the genome is tetraploid for this chromosome.

Animals↗
PubMed1995

Phospholipase A2 engineering. Probing the structural and functional roles of N-terminal residues with site-directed mutagenesis, X-ray, and NMR.

The N-terminal residues of phospholipase A2 (PLA2) are believed to be involved in the hydrogen-bonding network, the interfacial binding site, or the hydrophobic channel. Site-directed mutants of bovine pancreatic PLA2 with substitutions at positions 2, 3, 4, 5, 6, and 9 were constructed to test the roles of these residues in the structure and function of PLA2. Nonconservative mutations of Phe-5 and Ile-9, which are located inside the hydrophobic channel, led to significant perturbations in the conformation and conformational stability. Kinetic studies also indicated that mutations at Ile-9 and Phe-5 caused significant decreases in the rate of hydrolysis toward micellar and vesicle substrates. Scooting mode kinetic analysis showed that the binding step of the mutant enzymes to the DC14PM (1,2-dimyristoyl-sn-glycero-3-phosphomethanol) vesicle interface is not significantly affected and that the perturbations in catalysis occur mainly in kcat at the interface. The results taken together suggest that the residues Ile-9 and Phe-5 are important for both structure and catalysis. The mutant W3A (Trp-3 to Ala) also showed decreased rates of hydrolysis but to a lesser extent than Ile-9 and Phe-5 mutants. In addition, the binding affinity of W3A to the surface of the vesicles (i.e., the E to E* step) has been perturbed to the extent that hopping between anionic vesicles has been observed. On the other hand, the mutants of Gln-4 and Asn-6, which are located at or near the surface, displayed structural and kinetic properties similar to those of the wild-type PLA2 with the exception of the highly hydrophilic lysine mutant. The X-ray structure of the Q4E mutant indicates that the overall structure, the catalytic triad, and the link between residue 4 and Asp-99 via hydrogen bonding through Ala-1 and the structural water remain the same as in the WT. Substitutions for Leu at position 2 showed an acyl chain length discrimination toward different substrates, which may reflect the contacting position(s) of the substrate acyl chain with Leu-2.

Amino Acid Sequence↗