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Biomedical subjects

J Zhang

Publications and source records attributed to J Zhang.

At least 307 records · Page 17Linked to original sources
PubMed2001

Mitochondrial nitric oxide synthase is constitutively active and is functionally upregulated in hypoxia.

Nitric oxide is a potent modulator of mitochondrial respiration, ATP synthesis, and K(ATP) channel activity. Recent studies show the presence of a potentionally new isoform of the nitric oxide synthase (NOS) enzyme in mitochondria, although doubts have emerged regarding the physiological relevance of mitochondrial NOS (mtNOS). The aim of the present study were to: (i) examine the existence and distribution of mtNOS in mouse tissues using three independent methods, (ii) characterize the cross-reaction of mtNOS with antibodies against the known isoforms of NOS, and (iii) investigate the effect of hypoxia on mtNOS activity. Nitric oxide synthase activity was measured in isolated brain and liver mitochondria using the arginine to citrulline conversion assay. Mitochondrial NOS activity in the brain was significantly higher than in the liver. The calmodulin inhibitor calmidazolium completely inhibited mtNOS activity. In animals previously subjected to hypoxia, mtNOS activity was significantly higher than in the normoxic controls. Antibodies against the endothelial (eNOS), but not the neuronal or inducible isoform of NOS, showed positive immunoblotting. Immunogold labeling of eNOS located the enzyme in the matrix and the inner membrane using electron microscopy. We conclude that mtNOS is a constitutively active eNOS-like isoform and is involved in altered mitochondrial regulation during hypoxia.

Animals↗
PubMed2001

Simultaneous inhibition of glioma angiogenesis, cell proliferation, and invasion by a naturally occurring fragment of human metalloproteinase-2.

Angiogenesis, tumor cell proliferation, and migration are the hallmarks of solid tumors, such as gliomas. This study demonstrates that a fragment derived from the autocatalytic digestion of matrix metalloproteinase (MMP)-2, called PEX, acts simultaneously as an inhibitor of glioma angiogenesis, cell proliferation, and migration. PEX is detected in the cultured medium of various human glioma, endothelial, breast, and prostate carcinoma cell lines. PEX is purified from the medium of glioma cell lines by chromatography, where PEX is constitutively expressed as a free and a TIMP-2-bound form. In human glioma tissue, PEX expression correlates with histological subtype and grade and with alpha v beta 3 integrin expression to which it is bound. Systemic administration of PEX to s.c. and intracranial human glioma xenografts results in a 99% suppression of tumor growth with no signs of toxicity. Thus, PEX is a very promising candidate for the treatment of human malignant gliomas.

Adult↗
PubMed2001

[Relationship between serum CA125 level and prognosis in the patients with uterine endometrial carcinoma].

OBJECTIVE: To study the relationship between serum CA125 level and prognosis of uterine endometrial carcinoma. METHODS: The serum CA125 levels in 71 patients with uterine endometrial carcinoma were measured by using microparticle enzyme immunoassay. The relationship between preoperative CA125 levels and surgical pathologic staging, histologic classification, and other prognostic factors was investigated. RESULTS: (1) The positive rate of serum CA125 in postmenopausal patients was significantly higher than in premenopausal patients. (2) The positive rate of serum CA125 was related to surgical pathologic staging. (3) Serum CA125 level was correlated not only with histological classification but also with other prognosis factors. (4) Increase of serum CA125 after operation predicted the possibility of relapse. CONCLUSION: CA125 is a useful marker in predicting the prognosis of uterine endometrial carcinoma.

Adolescent↗
PubMed2001

Linkage analysis of schizophrenia to chromosome 15.

We have mapped a sample of 68 families consisting of one or more affected sibling pairs with schizophrenia or schizoaffective disorder with 20 markers spanning all of chromosome 15 to investigate whether there is a locus on chromosome 15 that confers an increased susceptibility to schizophrenia using parametric and nonparametric linkage analyses. Allele sharing identical by descent and multipoint maximum likelihood score (MLS) statistics were employed. Results show excess allele sharing for multiple markers in 15q11.2-q25, a chromosomal region previously found linked to a decrease in the normal inhibition of the P50 auditory-evoked response to the second of paired stimuli, a decrease associated with schizophrenia. Excess allele sharing was found for markers spanning about 48 cM in 15q11.2-q25 (D15S1002-D15S1023). The greatest single point allele sharing was found at D15S659 (62.6%). The multipoint MLS scores were greater than 1.0 in the 30-52 cM interval delimited by ACTC and D15S150, with a maximum value of 2.0 with GENEHUNTER PLUS near D15S1039.

Alleles↗
PubMed2001

Further characterization and population data for the pentanucleotide STR polymorphism D10S2325.

Pentanucleotide tandem repeat markers are interesting for forensic sciences, because they may present less stutter on the electrophoretic pattern. We focused on the analysis of the DNA sequence for each allele at the pentanucleotide STR locus D10S2325 in order to understand their structures in the human genome and to construct human allelic ladder, which is necessary for forensic DNA typing. In order to evaluate the forensic applicability of D10S2325 and to construct a preliminary database, the genotype distributions and allele frequencies in three major ethnic groups were investigated. The population samples included Caucasians (Germans), Africans (African Americans), and Asians (Chinese). A total of 520 samples from unrelated individuals was analyzed by Amp-FLP. An example of each allele and new alleles were sequenced. Allele determination was carried out by comparison with a sequenced human allelic ladder made in-house. This pentanucleotide STR provided easily interpretable results. A total of 15 alleles was found in our population samples. Three new alleles were observed and named as alleles 19 and 21 based on the number of repeat motifs, while allele 19 can be divided further into two alleles, 19a and 19 according to analysis of the sequence. No evidence of deviation from Hardy-Weinberg equilibrium was observed. In 64 confirmed father/mother/child triplets no mutation event was observed. Using a maximum likelihood method, the mutation rate was indirectly estimated as 2.5 x 10(-5). These results suggest that D10S2325 is a useful marker for forensic casework and paternity analysis.

Black or African American↗
PubMed2001

Interaction between krit1 and icap1alpha infers perturbation of integrin beta1-mediated angiogenesis in the pathogenesis of cerebral cavernous malformation.

Cerebral cavernous malformation (CCM) is a common autosomal dominant disorder characterized by venous sinusoids that predispose to intracranial hemorrhage. CCM is genetically heterogeneous, with loci at 7q, 7p and 3q. Mutations in KRIT1 account for all cases linked to 7q (CCM1), but the pathogenesis of CCM is not understood. Krev Interaction Trapped 1 (krit1) was originally identified through its interaction with the Ras-family GTPase krev1/rap1a in a two-hybrid screen, inferring a role in GTPase signaling cascades. We demonstrated additional 5'-coding exons for krit1, extending the N-terminus by 207 amino acids compared to the previously reported protein. Remarkably, by two-hybrid analysis and co-immunoprecipitation, full-length krit1 fails to interact with krev1/rap1a but shows strong interaction with integrin cytoplasmic domain-associated protein-1 (icap1). Icap1 binds to a NPXY motif in the cytoplasmic domain of beta1 integrin and participates in beta1-mediated cell adhesion and migration. The novel N-terminus of krit1 contains a NPXY motif that it is required for icap1 interaction. Like beta1 integrin, krit1 interacts with the 200 amino acid isoform of icap1 (icap1alpha), but not a 150 amino acid form that results from alternative splicing (icap1beta). In a competition assay, induced expression of krit1 diminishes the interaction between icap1alpha and beta1 integrin. Taken together, these data suggest that beta1 integrin and krit1 compete for the same site on icap1alpha, perhaps constituting a regulatory mechanism. Loss-of-function KRIT1 mutations, as observed in CCM1, would shift the balance with predicted consequences for endothelial cell performance during integrin beta1-dependent angiogenesis.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Directed evolution of alpha-aspartyl dipeptidase from Salmonella typhimurium.

Model-free approaches (error-prone PCR to introduce random mutations, DNA shuffling to combine positive mutations, and screening of the resultant mutant libraries) have been used to enhance the catalytic activity and thermostability of alpha-aspartyl dipeptidase from Salmonella typhimurium, which is uniquely able to hydrolyze Asp-X dipeptides (where X is any amino acid) and one tripeptide (Asp-Gly-Gly). Under double selective pressures of activity and thermostability, through two rounds of error-prone PCR and three sequential generations of DNA shuffling, coupled with screening, a mutant pepEM3074 with approximately 47-fold increased enzyme activity compared with its wild-type parent was obtained. Moreover, the stability of pepEM3074 is increased significantly. Three amino acid substitutions (Asn89His, Gln153Glu, and Leu205Arg), two of them are near the active site and substrate binding pocket, were identified by sequencing the genes encoding this evolved enzyme. The mechanism of the enhancement of activity and stability was analyzed in this paper.

Amino Acid Substitution↗
PubMed2001

Platelet-derived growth factor promotes the expression of peroxisome proliferator-activated receptor gamma in vascular smooth muscle cells by a phosphatidylinositol 3-kinase/Akt signaling pathway.

Vascular diseases such as atherosclerosis are characterized by abnormal accumulation of vascular smooth muscle cells (VSMCs) within the intimal lining. The intimal VSMCs exhibit an increased expression of peroxisome proliferator-activated receptor gamma (PPARgamma), and the administration of pharmacological PPARgamma agonists attenuates vascular lesion formation. The factors that regulate PPARgamma expression in the vasculature are poorly defined. Here we report that platelet-derived growth factor (PDGF) upregulates PPARgamma by the phosphatidylinositol 3-kinase (PI3-kinase)/Akt signaling pathway. Using Northern-blotting and Western-blotting analyses, we observed that the levels of PPARgamma mRNA and protein were increased by 2- to 3.5-fold in human aortic smooth muscle cells (HASMCs) treated with PDGF (20 ng/mL). This was abolished by preincubation of HASMCs with a PI3-kinase inhibitor (LY294002, 50 micromol/L), and partially inhibited by a MEK1 inhibitor (U0126, 10 micromol/L), but not affected by a p38 kinase inhibitor (SB202190, 10 micromol/L). In addition, overexpression of the dominant-negative p85 subunit of PI3-kinase or Akt proteins blocked the PDGF-induced PPARgamma expression. Taken together, our results suggest that PDGF induces PPARgamma expression in VSMCs by a PI3-kinase/Akt signaling pathway. The characterization of factors and signaling pathways that modulate PPARgamma expression in VSMCs may have important implications for understanding the pathogenesis of vascular diseases.

Aorta↗
PubMed2001

Synthesis of an L-rhamnose tetrasaccharide, the common and major structure of the repeating unit of the O-antigenic polysaccharide of a strain of Klebsiella pneumoniae and Pseudomonas holci.

A tetrasaccharide, alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->2)-alpha-L-Rhap-(1-->2)-L-Rhap, the common and major structure of the repeating unit of the O-antigenic polysaccharide of a strain of Klebsiella pneumoniae and Pseudomonas holci was synthesized as its methyl and octyl glycosides. Selective 3-O-glycosylation of allyl alpha-L-rhamnopyranoside with 2,3,4-tri-O-acetyl-alpha-L-rhamnopyranosyl trichloroacetimidate gave allyl 2,3,4-tri-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-alpha-L-rhamnopyranoside (3). Benzoylation, deallylation, and trichloroacetimidation afforded 2,3,4-tri-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl trichloroacetimidate (6). Self condensation of 3,4-di-O-benzoyl-beta-L-rhamnopyranose 1,2-methyl orthoester or 1,2-octyl orthoester gave methyl or octyl 2-O-acetyl-3,4-di-O-benzoyl-alpha-L-rhamnopyranosyl-(1-->2)-3,4-di-O-benzoyl-alpha-L-rhamnopyranoside (16 or 17), and subsequent selective deacetylation gave the disaccharide acceptor (18 or 19). Coupling of 6 with 18 (or 19), followed by deacylation in ammonia-saturated methanol, produced the target tetrasacharide.

Klebsiella pneumoniae↗
PubMed2001

[Analysis of cDNA and protein structure of tree shrew cholesterol ester transfer protein].

OBJECTIVE: To obtain the nucleotide sequence and deduced amino acid sequence of cholesteryl ester transfer protein (CETP) cDNA of tree shrew, mammalian insusceptible to atherosclerosis. METHODS: The first strand of cDNA of tree shrew was obtained from its liver. The sequence of tree shrew CETP cDNA was obtained by using techniques of switching mechanism at 5' end of RNA transcript (SMART) and rapid amplification of cDNA end (RACE), The CETP amino acid sequence was deduced from this cDNA and its primary and secondary structures were predicted by using DNAMAN, a software of molecular biology. Results The tree shrew CETP cDNA sequence covers 1636 bp, including a 178 bp fragment at the 3' of untranslated region and a 1458 bp fragment in the coding region, coding the complete sequence of mature tree shrew CETP except the initiator methionine. There are 477 amino acids in its mature protein, one amino acid more than that in human beings, with an extra Gly318. The homology of tree shrew CETP and human CETP and rabbit CETP is 88% and 82% respectively judged by comparing the amino acid sequence of tree shrew CETP and those of human beings and rabbit. The regions concerning the CETP function of binding and transferring neutral lipids in tree shrew CETP amino acid sequence are highly conservative. However, there is a deletion of N-linked glycosylation site at Asn342 in tree shrew protein that may increase the ability of removing peripheral cholesterol and cholesteryl ester. CONCLUSION: The glycosylation in tree shrew CETP may be one of the mechanisms of insusceptibility to atherosis of tree shrew.

Amino Acid Sequence↗
PubMed2001

Synthesis of an extremely crowded naphthalene via a stable norbornadienone.

Computational studies at the HF/3-21G and B3LYP/6-31G(d) levels suggest that 5,6,8-tri(tert-butyl)-1,2,3,4-tetraphenylnaphthalene (2) is perhaps the most crowded naphthalene derivative that will show normal stability; more highly congested naphthalenes will prefer to exist as the corresponding Dewar isomers. Initial attempts to prepare 2 by reacting 3,4,5,6-tetraphenylbenzyne with 2,3,5-tri(tert-butyl)cyclopentadienone at 83 degrees C gave instead a stable norbornadienone, 1,2,4-tri(tert-butyl)-5,6,7,8-tetraphenyl-9-oxo-1,4-dihydro-1,4-methanonaphthalene (3), which was characterized by X-ray crystallography. The experimental and calculated (HF/3-21G) activation energies (E(a)) for the decarbonylation of 3 were quite high: 39 and 46 kcal/mol, respectively, a manifestation of the substantially increased strain in the transition state as the tert-butyl groups are forced together. The naphthalene 2 was obtained in good yield by heating 3 in refluxing toluene, and its X-ray structure showed exceptional distortions from a normal naphthalene geometry. However, 2 is not completely stable, and it decomposes upon prolonged heating in xylenes.

Journal Article↗
PubMed2001

Effects of laser polarization on jet emission of fast electrons in femtosecond-laser plasmas.

Effects of laser polarization on fast electron emission are studied from an aluminum target irradiated by ultrashort laser pulses at 2 x 10(16) W/cm(2). Jet emission of outgoing fast electrons collimated in the polarization direction is observed for s-polarized laser irradiation, whereas for p-polarized irradiation highly directional emission of outgoing fast electrons is found in the direction close to the normal of the target. The behavior of ingoing fast electrons into the target for s- and p-polarized irradiation is also investigated by observing x-ray bremsstrahlung radiation at the backside of the target.

Journal Article↗
PubMed2001

Sry promoters from domesticus (Tirano) and C57BL/6 mice function similarly in embryos and adult animals.

Introduction of the Y chromosome from a Mus musculus domesticus (Tirano) subspecies into the Mus musculus musculus C57BL/6 (B6) inbred strain background results in sex reversal in XY offspring. It has been hypothesized that the domesticus testis-determining Y (Tdy) locus is misregulated in B6 genome, thereby impairing sex determination in B6.Y(Dom) animals. The identification of a gene in the sex-determining region on the Y chromosome (Sry) as the Tdy has provided a means to experimentally examine this hypothesis. We have generated several lines of B6 transgenic mice harboring a green fluorescent protein gene directed by a Sry promoter from the domesticus (Tirano) Y chromosome. Detailed analysis of the transgene expression was conducted in both fetal and adult tissues of the transgenic mice. The domesticus Sry promoter was capable of directing the expression of the green fluorescent protein gene in a pattern similar, if not identical, to that of the endogenous B6 Sry gene. These observations suggest that the domesticus Sry promoter is not involved in the postulated misregulation of the domesticus (Tirano) Sry gene in the B6 genomic background. These results are discussed with reference to a second hypothesis invoking incompatible protein interaction(s) as a mechanism of aberrant sex determination in B6.Y(Dom) animals.

Animals↗
PubMed2001

The vasorelaxant effect of H(2)S as a novel endogenous gaseous K(ATP) channel opener.

Hydrogen sulfide (H(2)S) has been traditionally viewed as a toxic gas. It is also, however, endogenously generated from cysteine metabolism. We attempted to assess the physiological role of H(2)S in the regulation of vascular contractility, the modulation of H(2)S production in vascular tissues, and the underlying mechanisms. Intravenous bolus injection of H(2)S transiently decreased blood pressure of rats by 12- 30 mmHg, which was antagonized by prior blockade of K(ATP) channels. H(2)S relaxed rat aortic tissues in vitro in a K(ATP) channel-dependent manner. In isolated vascular smooth muscle cells (SMCs), H(2)S directly increased K(ATP) channel currents and hyperpolarized membrane. The expression of H(2)S-generating enzyme was identified in vascular SMCs, but not in endothelium. The endogenous production of H(2)S from different vascular tissues was also directly measured with the abundant level in the order of tail artery, aorta and mesenteric artery. Most importantly, H(2)S production from vascular tissues was enhanced by nitric oxide. Our results demonstrate that H(2)S is an important endogenous vasoactive factor and the first identified gaseous opener of K(ATP) channels in vascular SMCs.

Animals↗
PubMed2001

Efficacy of 3'-azido 3'deoxythymidine (AZT) in preventing HTLV-1 transmission to human cord blood mononuclear cells.

The present study investigated the effect of 3'-azido 3'deoxythymidine (AZT) treatment on in vitro infection of human cord blood mononuclear cells (CBMCs) exposed to HTLV-1 by cocultivation with the MT-2 cell line. Cultures of CBMCs were grown in IL-2 and were either left untreated or were treated with concentrations of AZT ranging from 0.0078 to 32 microM. HTLV-1-infected cultures were monitored at different times of culture by evaluating proliferation activity, cell growth and the presence and expression of HTLV-1 genes. Results showed that untreated cultures infected with HTLV-1 were able to grow for several weeks, while those treated with AZT at 0.03 microM or higher concentrations were limited in their growth capacity. Moreover, the addition of AZT at the moment of infection significantly inhibited cell proliferation in a dose-dependent fashion. In the presence of AZT, detection of proviral DNA and, more remarkably, viral RNA expression were clearly reduced. In addition, treatment with AZT resulted in a noticeable decrease in Tax protein expression. Using treatment with relatively low doses of AZT, effective in exerting an antiviral action, cytotoxicity on CBMCs was not observed, whereas higher doses induced apoptosis in uninfected CBMCs. These data show that CBMCs are protected by AZT against HTLV-1 transmission even at low, non-toxic doses.

Apoptosis↗