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H Zhang

Publications and source records attributed to H Zhang.

At least 325 records · Page 18Linked to original sources
PubMed2001

Co-culture with astrocytes or microglia protects metabolically impaired neurons.

Thiamine deficiency (TD) is a model of chronic impairment of oxidative metabolism that leads to neurodegeneration. TD induces oxidative stress and death in neurons, but does not kill astrocytes, microglia or brain endothelial cells. TD primary hippocampal neurons were either cultured alone, or co-cultured with primary astrocytes or microglia. After 7 days of TD, 50% of the neurons died, and the processes of many of the surviving neurons were severely truncated. When TD neurons were co-cultured with astrocytes or microglia, neurons did not die nor show decreased neurite outgrowth. Thus, neuronal-glial interactions are critical for maintaining neuronal homeostasis during chronic metabolic impairment.

Animals↗
PubMed2001

Differential display analysis of gene expression altered by ras oncogene.

The goal of the signal transduction pathways, such as those controlled by Ras, is in large part to ensure highly stringent regulation of the target genes in the nucleus, which are collectively responsible for the signal output, or phenotypes, of the cell. Understanding of the Ras effect ultimately requires the identification of these downstream target genes. Reverse genetic approaches would trace back the pathways by which they are regulated by Ras. While newer methods such as DNA microarray are emerging, differential display has allowed the identification of a greater number of differentially expressed genes than have been cloned by all the other methods combined, based on Medline search. Much of this success has been attributed to its simplicity (RT-PCR and DNA-sequencing gel) and versatility (compare more than two RNAs for both up- and downregulated genes). It has become obvious that finding the genes by either differential display or DNA microarray is only the first step toward the understanding of biological problems under investigation. It is hoped that finding the right genes through careful experimental designs, such as outlined here, will narrow down the number of relevant genes and increase the odds for solving the puzzles of nature, such as ras.

Animals↗
PubMed2001

In vitro degradation of chitosan by a commercial enzyme preparation: effect of molecular weight and degree of deacetylation.

A commercially available almond emulsin beta-glucosidase preparation has been reported to have chitobiose activity, and can hydrolyze chitin substrates due to a chitinase present in the enzyme preparation. This beta-glucosidase preparation was used to investigate hydrolytic activity on five chitosan samples with different molecular weight and degree of deacetylation. The degree of deacetylation and molecular weight of the chitosan samples were determined using a circular dichroism and a viscometric method, respectively. The hydrolytic activity of this beta-glucosidase preparation on chitosan was monitored viscometrically as the most convenient means of screening. Solutions of chitosan in pH 5.0 acetate buffer were prepared using the different viscosity grades of chitosan. The specific viscosity, measured after addition of beta-glucosidase to the above solutions, decreased dramatically over time in comparison to that of the respective control mixture without enzyme. Eadie-Hofstee plots established that hydrolysis of chitosan by this enzyme preparation obeyed Michaelis-Menten kinetics. Apparent Michaelis-Menten parameters and initial degradation rates were calculated and compared to determine the influences of the degree of deacetylation and molecular weight on the hydrolysis. The results show that higher molecular weight and higher degree of deacetylation chitosans possessed a lower affinity for the enzyme and a slower degradation rate. Faster degradation rates, then, are expected with lower molecular weight and low degree of deacetylation chitosans. Hydrolysis of these chitosan samples confirms the existence of a chitinase in the almond emulsin beta-glucosidase preparation, and further studies are warranted.

Chitin↗
PubMed2001

Nitric oxide production by coelomocytes of Asterias forbesi.

Vertebrate mononuclear phagocytes produce a plethora of molecules involved in host defense. Among the most potent are the reactive oxygen and nitrogen intermediates. Coelomocytes from invertebrates subserve many of the same functions. In order to determine whether invertebrate phagocytes employ reactive nitrogen intermediates, we investigated the effect of various nonspecific stimulators and invertebrate interleukin (IL)-1alpha- and beta-like molecules on nitric oxide (NO) production. Elevated NO release by stimulated coelomocytes was seen after 24 h. Incubation of stimulated coelomocytes in the presence of arginine analogs inhibited NO release. When invertebrate IL-1-like molecules were added to the coelomocytes, they stimulated the release of NO. Western blot analysis using a polyclonal rabbit antiserum to murine NO synthase detected a band at approximately 125 kDa. These data indicate that coelomocytes are capable of producing and releasing NO and that NO is a chemical mediator that has been conserved as a host defense weapon of phagocytes through evolutionary time.

Animals↗
PubMed2001

Cloning, characterization and genomic structure of the natural killer cell enhancement factor (NKEF)-like gene from homozygous clones of rainbow trout (Oncorhynchus mykiss).

Natural killer cell enhancement factor (NKEF) belongs to the antioxidant protein family. In the human, NKEF has the ability to enhance natural killer cell cytotoxic activity in vitro. In the present work, the cDNAs of NKEF from three strains of homozygous clones of rainbow trout were cloned from the splenic cDNA library of one of the strains, OSU142, and then by RT-PCR for the Hot Creek (HC) and Arlee (AR) strains. The HC sequence has 99% sequence identity with both OSU142 and AR. OSU142 and AR have only one nucleotide difference in the cDNA sequence. All three sequences have the same deduced NKEF peptide, which contains 199 amino acids. The 6. 5 kb genomic DNA of OSU142 containing NKEF was sequenced and contains six exons and five introns. Tissue specific expression of NKEF was studied by RT-PCR in eight different tissues of OSU142 and revealed that all tissues expressed NKEF. A southern blot revealed that the gene for NKEF is present in a single copy. The cDNA and amino acid sequences of trout NKEF have high similarity with human, rat, mouse and carp sequences, therefore, indicating that NKEF is a very conserved gene.

Amino Acid Sequence↗
PubMed2001

Amplification and cloning of the full-length genome of Japanese encephalitis virus by a novel long RT-PCR protocol in a cosmid vector.

A novel and rapid full-length long RT-PCR technique was established to produce genome-length cDNA from Japanese encephalitis virus. In vitro positive strand RNA transcripts from the full-length RT-PCR amplicon including T7 promoter sequences at the 5' end were proved to be infectious upon transfection. The full-length amplicon without the T7 promoter was cloned into a cosmid vector under the SP6 promoter. This stable clone, designated as pJEV-1, was characterised further and used as a genetic resource for generation of infectious RNA transcripts, gene manipulation and expression. The 'run-off' transcript from pJEV-1 with vector sequences at the either end of the insert was not infectious, but transcripts of the full-length PCR amplicon from pJEV-1 produced infectious virus upon transfection. A transcript with an engineered Xho I site from two ligated PCR fragments amplified from pJEV-1 was also infectious. Furthermore, the coding region for premembrane and envelope proteins (preM-E) from pJEV-1 was subcloned and expressed in the Drosophila Expression System. The expressed protein showed correct molecular size and was immunoreactive with a Japanese encephalitis virus E protein-specific antibody. The derivation of genome-size cDNA from Japanese encephalitis virus and the stable clone will facilitate investigation of this virus and elucidation of its pathogenesis at the molecular level.

Animals↗
PubMed2001

Cholinergic neurons expressing neuromedin K receptor (NK3) in the basal forebrain of the rat: a double immunofluorescence study.

By using a double immunofluorescence method we have examined the distribution of cholinergic neurons expressing neuromedin K receptor (NK3) in the rat brain and spinal cord. The distribution of neuromedin K receptor-like immunoreactive neurons completely overlapped with that of choline acetyltransferase-positive neurons in certain regions of the basal forebrain, e.g. the medial septal nucleus, nucleus of the diagonal band of Broca, magnocellular preoptic nucleus and substantia innominata. Partially overlapping distributions of neuromedin K receptor-like immunoreactive and choline acetyltransferase-positive neurons were found in the basal nucleus of Meynert, globus pallidus, ventral pallidum of the forebrain, tegmental nuclei of the pons and dorsal motor nucleus of the vagus. Neurons showing both neuromedin K receptor-like and choline acetyltransferase immunoreactivities, however, were found predominantly in the medial septal nucleus, nucleus of the diagonal band of Broca and magnocellular preoptic nucleus of the basal forebrain: 66-80% of these choline acetyltransferase-positive neurons displayed neuromedin K receptor-like immunoreactivity. Neurons showing both neuromedin K receptor-like and choline acetyltransferase immunoreactivities were hardly detected in other aforementioned regions of the forebrain, brainstem and spinal cord. The present study has provided morphological evidence for direct physiological modulation or regulation of cholinergic neurons by tachykinins through the neuromedin K receptor in the basal forebrain of rats.

Animals↗
PubMed2001

Cerebrospinal fluid and plasma testosterone levels in post-traumatic stress disorder and tobacco dependence.

BACKGROUND: Little is known about the relationship between endogenous central nervous system (CNS) testosterone and any psychiatric syndrome. The goal of this study was to screen for potential abnormalities in CNS testosterone levels in patients with post-traumatic stress disorder (PTSD) and/or tobacco dependence. METHODS: We sampled cerebrospinal fluid (CSF) via a subarachnoid catheter over six hours and determined hourly basal CSF concentrations of testosterone in 11 combat veterans with PTSD and 12 normal volunteers. Smokers were abstinent for 11-17 h. Testosterone in CSF and matching plasma samples was assayed by radioimmunoassay. RESULTS: A factor analysis for effects of PTSD status, smoking status and sample time revealed significant effects of PTSD or smoking status, but not time, on CSF testosterone. CSF testosterone levels were lower in individuals with PTSD as compared with normal volunteers. When divided by smoking status, abstinent smokers had mean CSF testosterone levels higher than those of non-smokers. A similar analysis of plasma testosterone revealed no significant effects of any factor on plasma testosterone. CONCLUSIONS: These results indicate that CSF testosterone is significantly influenced by PTSD and smoking status. The exposure of the brain to altered levels of testosterone in smokers and patients with PTSD may have pathophysiologic significance in these conditions.

Adult↗
PubMed2001

Evaluation of a fluorogenic derivatization method for the reversed-phase HPLC analysis of 2'-beta-fluoro-2',3'-dideoxyadenosine, a new anti-AIDS drug.

High sensitivity (10(-7) to 10(-9) M) reversed-phase high-performance liquid chromatography (HPLC) analysis of adenine nucleosides and nucleotides, especially in a biological matrix, is difficult using only ultraviolet detection. Derivatization coupled with fluorescence detection has been investigated as a means of enhancing sensitivity for the reversed-phase HPLC analysis of 2'-beta-fluoro-2',3'-dideoxyadenosine (F-ddA), an experimental, acid-stable, anti-AIDS drug. The reaction of chloroacetaldehyde with the adenine base has been employed to form fluorescent 1,N(6)-etheno derivatives of F-ddA and 5'-deoxyadenosine, which is used as an internal standard. These derivatives give an analytically useful fluorescence emission at 416 nm after excitation at 230, 265, or 275 nm. Derivatization, fluorescence detection and reversed-phase chromatography have been optimized for the analysis of nanomolar concentrations of F-ddA in human plasma. This method has potential for the measurement of F-ddA at low concentration and in limited volume samples from in vivo biological studies.

Anti-HIV Agents↗
PubMed2001

Synthesis and characterization of a tetranucleotide analogue containing alternating phosphonate-amide backbone linkages.

Described herein is the synthesis and characterization of a tetranucleotide, 5'-dC-phosphonate-T-amide-T-ophosphonate-dC (III), in which the C-T and T-C steps contain a phosphonate backbone bond and T-T is a peptide nucleic acid dimer unit (neutral backbone). The 5'- and 3'-OH groups of the tetramer can be further derivatized and, thus, the compound is a potential building block for longer oligonucleotides which will contain alternating backbone modifications at designated positions. The synthesis involved first the preparation of two hybrid peptide-deoxyribose dinucleotides, CT-CO (I) and N-CT (II) (C and T are nucleobases; CO and N are carboxylic and amino terminal, respectively); each is linked through a phosphonate linkage. A condensation reaction between the two dimers, followed by deprotection, resulted in the formation of a peptide linkage to give the desired tetramer III. The reaction conditions used are mild to afford products in moderate to excellent yields. The DNA-PNA-DNA tetramer, d(CTTC), is a substrate for T4 kinase but fails to give a ligation product, even though NMR shows weak interactions between the tetramer III with its complementary sequence, d(GAAG).

Amides↗
PubMed2001

Association of ErbB2 Ser1113 phosphorylation with epidermal growth factor receptor co-expression and poor prognosis in human breast cancer.

The carboxyterminal domain of the epidermal growth factor receptor (EGFR)--a putative binding site for the ubiquitin ligase Cbl--is the site of serine phosphorylation events which are essential for ligand-dependent EGFR desensitization and degradation. Using a monoclonal antibody (aPS1113) which selectively recognizes the homologous phosphorylated domain in the ErbB2 oncoprotein, we show here that wild-type ErbB2 becomes Ser1113-phosphorylated following treatment of 3T3 cells with growth factors or tyrosine phosphatase inhibitors. In EGFR-overexpressing A431 cells, ligand-inducible aPS1113 immunoreactivity declines more rapidly than other detectable phosphorylation events and is followed by EGFR downregulation. Analysis of 65 ErbB2-expressing primary breast cancers reveals a highly significant relationship between Ser1113 phosphorylation and EGFR overexpression (p < 0.0001) as well as an association with poor prognosis (p = 0.005). We submit that ErbB2 Ser1113 phosphorylation status represents a novel and informative biomarker of cancer cell biology and tumor behavior.

Animals↗
PubMed2001

BAPTA blocks DNA fragmentation and chromatin condensation downstream of caspase-3 and DFF activation in HT-induced apoptosis in HL-60 cells.

DFF ((DNA Fragmentation Factor) is a heterodimer composed of 40 kDa (DFF40, CAD) and 45 kDa (DFF45, ICAD) subunits. During apoptosis, activated caspase-3 cleaves DFF45 and activates DFF40, a DNase that targets nucleosomal linker region and cleaves chromatin DNA into nucleosomal fragments. We have previously reported that HT induced apoptosis in HL-60 cells, and intracellular Ca(2+) chelator BAPTA blocked apoptosis-associated DNA fragmentation induced by HT. We report here that HT also induced activation of caspase-3 and cleavage of DFF45. BAPTA prevented neither the caspase-3 activation nor the cleavage of DFF45. Mitochondrial membrane potential was disrupted in BAPTA-AM treated cells. However, BAPTA did prevent DNA fragmentation and chromatin condensation in HT-treated cells. These data suggest a novel role for intracellular calcium in regulating apoptotic nuclease that causes DNA fragmentation and chromatin condensation.

Antineoplastic Agents↗
PubMed2001

Prevalence and correlates of antisocial behaviors among three ethnic groups.

Using data from the MECA Study, this report examines the prevalence of Conduct Disorder (CD), Oppositional Defiant Disorder (ODD), and various levels of antisocial behavior and their correlates among three ethnic groups: Hispanics, subdivided into Island Puerto Ricans and Mainland Hispanics; African Americans; and Mainland Non-Hispanic, Non-African Americans. Correlates considered include stressful life events, birth defects, low birth weight, learning difficulties, teen mothers, family environment, marital adjustment, social competence, parental monitoring, and family relationships. Logistic regression was used to determine the association of outcomes with individual correlates and of interaction terms with ethnicity. Differences between adjusted rates and observed rates of disorders and levels of antisocial behaviors are compared to estimate the extent to which each correlate explains the group differences in rates. Island Puerto Ricans had a lower prevalence of CD, ODD, and various levels of antisocial behavior than mainland Hispanics, African Americans, and non-Hispanic Whites. The lower prevalence appears to be associated with differences in the extent to which a number of these correlates are found on the island, the most salient being better family relations between the target children and their parents and siblings.

Adolescent↗
PubMed2001

Rowed to recovery: the use of phonological and orthographic information in reading Chinese and English.

To examine how readers of Chinese and English take advantage of orthographic and phonological features in reading, the authors investigated the effects of spelling errors on reading text in Chinese and English using the error disruption paradigm of M. Daneman and E. Reingold (1993). Skilled readers in China and the United States read passages in their native language that contained occasional spelling errors. Results showed that under some circumstances very early phonological activation can be identified in English, but no evidence for early phonology was found in Chinese. In both languages, homophone errors showed a benefit in measures of later processing, suggesting that phonology helps readers recover from the disruptive effects of errors. These results suggest that skilled readers take advantage of the special features of particular orthographies but that these orthographic effects may be most pronounced in the early stages of lexical access.

Adult↗
PubMed2001

Tumoricidal activity of a novel anti-human DR5 monoclonal antibody without hepatocyte cytotoxicity.

A novel anti-human DR5 monoclonal antibody, TRA-8, induces apoptosis of most tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-sensitive tumor cells both in vitro and in vivo. In contrast to both the membrane-bound form of human TRAIL, which induced severe hepatitis in mice, and the soluble form of human TRAIL, which induced apoptosis of normal human hepatocytes in vitro, TRA-8 did not induce significant cell death of normal human hepatocytes. However, both primary hepatocellular carcinoma cells and an established liver cancer cell line were highly susceptible to the killing mediated by TRA-8. We show here that elevated levels of cell-surface expression of DR5 and increased susceptibility to DR5-mediated apoptosis are characteristics of malignant tumor cells. In contrast, DR5 alone is not sufficient to trigger apoptosis of normal hepatocytes. Therefore, selective, specific targeting of DR5 with an agonistic antibody might be a safe and effective strategy for cancer therapy.

Animals↗
PubMed2001

HAL1 mediate salt adaptation in Arabidopsis thaliana.

The yeast HAL1 gene was introduced into Arabidopsis thaliana by Agrobacterium tumefaciens-mediated transformation with vacuum infiltration under the control of CaMV 35S promoter. Thirty-three individual kanamycin resistant plants were obtained from 75,000 seeds. Southern blotting analysis indicated that HAL1 gene had been integrated into all of the transgenic plants' genomes. The copy number of HAL1 gene in transgenic plants was mostly 1 to 3 by Southern analysis. Phenotypes of transgenic plants have no differences with wild type plants. Several samples of transformants were self-pollinated, and progenies from transformed and non-transformed plants (controls) were evaluated for salt tolerance and gene expression. Measurement of concentrations of intracellular K+ and Na+ showed that transgenic lines were able to retain less Na+ than that of the control under salt stress. Results from different tests indicated the expression of HAL1 gene promotes a higher level of salt tolerance in vivo in the transgenic Arabidopsis plants.

Adaptation, Physiological↗
PubMed2001

The influence of fish, meat and polyunsaturated fat intakes on platelet phospholipid polyunsaturated fatty acids in male Melbourne Chinese and Caucasian.

OBJECTIVE: The aims of this study were to investigate (1) platelet phospholipid (PL) polyunsaturated fatty acid (PUFA) composition in subjects who were the Melbourne Chinese migrants, compared with those who were the Melbourne Caucasians and (2) the relationship between platelet PL PUFA and intake of fish, meat and PUFA. DESIGN: Cross-sectional comparison of the Melbourne Chinese and Caucasians. SETTING: Free-living male subjects. SUBJECTS: Ninety-seven Melbourne Chinese migrants and 78 Melbourne Caucasians who were recruited in Melbourne. OUTCOME MEASURES: Dietary intake was assessed using a semi-quantitative food frequency questionnaire. The platelet PUFA was measured by gas-liquid chromatography. RESULTS: The Melbourne Chinese had significantly higher proportions of platelet PL 20:5n-3 (P=0.006), 22:6n-3 (P<0.0001), total n-3 (P=0.027) and 22:5n-6 (P=0.0002), and a significantly higher intake of fish (P=0.012) and white meat (P=0.0045) compared with the Melbourne Caucasians. In addition, the Melbourne Chinese had significantly lower proportions of 20:3n-6 (P=0.023), 20:4n-6 (P<0.002), 22:4n-6 (P<0.0001), total n-6 (P=0.037), 22:5n-3 (P<0.0001) and ratio of n-6/n-3 (P=0.011), and a significantly lower intake of red and total meat (P<0.0001) than the Melbourne Caucasians. Fish consumption was significantly positively correlated with platelet PL 20:5n-3 and 22:6n-3, and significantly negatively correlated with 22:5n-3 (P<0.05). Meat consumption was significantly positively correlated with 22:5n-3 and significantly negatively correlated with 22:5n-6, 20:5n-3 and 22:6n-3 (P<0.05). Dietary PUFA intake was significantly positively correlated with 20:3n-6, 22:4n-6 and 22:5n-3, and significantly negatively correlated with 22:5n-6, 20:5n-3 and 22:6n-3 (P<0.05). CONCLUSIONS: Compared with Caucasians, the Melbourne Chinese had a significantly higher level of platelet PL n-3 PUFA, which might contribute to the low CVD mortality in this population. Platelet PL 20:5n-3 and 22:6n-3 were significantly positively correlated with fish intake, and negatively significantly correlated with dietary intake of meat and PUFA, while 22:5n-3 was significantly positively correlated with dietary meat and PUFA intake, and significantly negatively correlated with fish intake. Dietary intake of PUFA and fish are potential confounding factors for assessing the effects of meat consumption on platelet PL individual PUFA. Dietary intake of PUFA and meat did not influence the incorporation of fish long chain n-3 PUFA to platelet PL in this study population. SPONSORSHIP: Palm Oil Research Institute of Malaysia, Meat Research Corporation Australia.

Adult↗