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W Wang

Publications and source records attributed to W Wang.

At least 793 records · Page 44Linked to original sources
PubMed1998

Dissociation of GLUT4 translocation and insulin-stimulated glucose transport in transgenic mice overexpressing GLUT1 in skeletal muscle.

Overexpression of the human GLUT1 glucose transporter protein in skeletal muscle of transgenic mice results in large increases in basal glucose transport and metabolism, but impaired stimulation of glucose transport by insulin, contractions, or hypoxia (Gulve, E. A., Ren, J.-M., Marshall, B. A., Gao, J., Hansen, P. A., Holloszy, J. O. , and Mueckler, M. (1994) J. Biol. Chem. 269, 18366-18370). This study examined the relationship between glucose transport and cell-surface glucose transporter content in isolated skeletal muscle from wild-type and GLUT1-overexpressing mice using 2-deoxyglucose, 3-O-methylglucose, and the 2-N-[4-(1-azi-2,2, 2-trifluoroethyl)benzoyl]-1,3-bis(D-mannos-4-yloxy)-2-propyl amine exofacial photolabeling technique. Insulin (2 milliunits/ml) stimulated a 3-fold increase in 2-deoxyglucose uptake in extensor digitorum longus muscles of control mice (0.47 +/- 0.07 micromol/ml/20 min in basal muscle versus 1.44 micromol/ml/20 min in insulin-stimulated muscle; mean +/- S.E.). Insulin failed to increase 2-deoxyglucose uptake above basal rates in muscles overexpressing GLUT1 (4.00 +/- 0.40 micromol/ml/20 min in basal muscle versus 3.96 +/- 0.37 micromol/ml/20 min in insulin-stimulated muscle). A similar lack of insulin stimulation in muscles overexpressing GLUT1 was observed using 3-O-methylglucose. However, the magnitude of the insulin-stimulated increase in cell-surface GLUT4 photolabeling was nearly identical (approximately 3-fold) in wild-type and GLUT1-overexpressing muscles. This apparently normal insulin-stimulated translocation of GLUT4 in GLUT1-overexpressing muscle was confirmed by immunoelectron microscopy. Our findings suggest that GLUT4 activity at the plasma membrane can be dissociated from the plasma membrane content of GLUT4 molecules and thus suggest that the intrinsic activity of GLUT4 is subject to regulation.

3-O-Methylglucose↗
PubMed1998

Induction of NADPH:quinone reductase by dietary phytoestrogens in colonic Colo205 cells.

Phytoestrogens are a group of naturally occurring diphenolic compounds present in legumes, whole grains, fruits, and vegetables. High consumption of phytoestrogen-rich foods has been linked to a reduced incidence of cancers at many sites. A potential mechanism of dietary anticarcinogenesis involves the induction of detoxifying phase II enzymes such as NADPH:quinone reductase (QR). This study, therefore, examined the ability of six prominent phytoestrogens to affect cellular expression of QR in colonic cells. Colo205 cells were cocultured with various concentrations (0.001 to 10.0 microM) of each phytoestrogen, and then were assessed for cytosolic QR activity, cell growth, and QR mRNA expression. A maximum of 6- to 8-fold induction of QR activity was observed for both enterolactone and genistein, although at high concentrations they showed an adverse effect upon cell growth. The concentrations required to double the specific activity of QR for enterolactone and genistein were about 0.04 and 0.14 microM, respectively. A 2- to 3-fold increase of QR specific activity was found with either biochanin A (1.1 microM) or coumestrol (12.0 microM) treatments. No significant effects were found for daidzein or formononetin treatments. QR induction was further confirmed by using reverse transcription-polymerase chain reaction (RT-PCR) techniques to measure mRNA expression. A significant correlation between the expression of QR mRNA and the corresponding QR activity was observed (r = 0.76, P < 0.001). The results demonstrated that certain dietary phytoestrogens are capable of QR induction in Colo205 cells by promoting QR mRNA expression, and suggest a novel mechanism by which dietary phytoestrogens may be implicated in colorectal cancer chemoprevention.

Base Sequence↗
PubMed1998

The CC chemokine 6Ckine binds the CXC chemokine receptor CXCR3.

We cloned the mouse homologue of the chemokine receptor CXCR3, which is located in mouse chromosome X. We screened a large panel of chemokines for their ability to induce a calcium flux in mouse CXCR3-transfected cells and identified a new ligand for this receptor, the recently reported CC chemokine 6Ckine. This represents an example of a CC chemokine, which binds to a CXC chemokine receptor. Like other ligands of this receptor, 6Ckine has angiostatic properties. 6Ckine is known to chemoattract T cells. In line with this, CXCR3 is expressed preferentially in Th1 cells and in lymphoid organs of the IL-10(-/-) mouse that develops chronic colitis. Its ability to attract T cells as well as its angiostatic properties suggest that 6Ckine may be an effective anti-tumor agent.

Amino Acid Sequence↗
PubMed1998

Cyclic peptides as probes of the substrate binding site of the cytosolic tyrosine kinase, pp60c-src.

A series of 48 cyclic peptides based on the amino acid sequence surrounding the autophosphorylation site of pp60(c-src) was synthesized and each was tested as both a substrate and an inhibitor of this protein tyrosine kinase. Starting with cyclo(Asp1-Asn2-Gln3-Tyr4-Ala5-Ala6-Arg7-Gln8-d- Phe9-Pro10) a six-amino-acid survey was performed at positions 1 through 8 to determine which positions were critical for affinity and phosphorylation and which amino acids produced the greatest activity. Our survey found that Arg7 was detrimental for binding and phosphorylation and that aromatic residues were preferred at this position. Further increases in affinity were obtained with hydrophobic residues at position 6 with the optimum for both affinity and phosphorylation being Phe. Changes on the "amino-terminal" side of Tyr4 resulted in reduced Vmax values, illustrating the requirement for acidic residues in peptidic tyrosine kinase substrates. The result of the survey was cyclo(Asp1-Asn2-Gln3-Tyr4-Ala5-Phe6-Phe7-Gln8-d-Phe 9-Pro10). The change of residues 6 and 7 resulted in a 42-fold increase in affinity and no increase in Vmax. As a substrate, this peptide displayed Michaelis-Menten kinetics at saturating ATP conditions. As an inhibitor, mixed inhibition was observed. A linear version of this peptide was 13-fold less potent an inhibitor than the cyclic peptide.

Amino Acid Sequence↗
PubMed1998

Five SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin (SMARC) genes are dispersed in the human genome.

The SWI/SNF-related, matrix-associated, actin-dependent regulators of chromatin (SMARC), also called BRG1-associated factors, are components of human SWI/SNF-like chromatin-remodeling protein complexes. We mapped five human SMARC genes toregions on four different human chromosomes, SMARCC1 to 3p23-p21, SMARCC2 to 12q13-q14, SMARCD1 to 12q13-q14, SMARCD2 to 17q23-q24, and SMARCD3 to 7q35-q36. SMARCC1, SMARCC2, and SMARCD1 are assigned to chromosomal regions that are frequently involved in somatic rearrangements in human cancers. SMARCD1 was mapped to the critical region of Allgrove syndrome; however, no mutation was identified in one Allgrove syndrome family studied.

Abnormalities, Multiple↗
PubMed1998

Ambiguities in mapping the active site of a conformationally dynamic enzyme by directed mutation. Role of dynamics in structure-function correlations in Escherichia coli adenylosuccinate synthetase.

On the basis of ligated crystal structures, Asn21, Asn38, Thr42, and Arg419 are not involved in the chemical mechanism of adenylosuccinate synthetase from Escherichia coli, yet these residues are well conserved across species. Purified mutants (Asp21 --> Ala, Asn38 --> Ala, Asn38 --> Asp, Asn38 --> Glu, Thr42 --> Ala, and Arg419 --> Leu) were studied by kinetics, circular dichroism spectroscopy, and equilibrium ultracentrifugation. Asp21 and Arg419 are not part of the active site, yet mutations at positions 21 and 419 lower kcat 20- and 10-fold, respectively. Thr42 interacts only through its backbone amide with the guanine nucleotide, yet its mutation to alanine significantly increases Km for all substrates. Asn38 hydrogen-bonds directly to the 5'-phosphoryl group of IMP, yet its mutation to alanine and glutamate has no effect on Km values, but reduces kcat by 100-fold. The mutation Asn38 --> Asp causes 10-57-fold increases in Km for all substrates along with a 30-fold decrease in kcat. At pH 5.6, however, the Asn38 --> Asp mutant is more active, yet binds IMP 100-fold more weakly, than the wild-type enzyme. Proposed mechanisms of ligand-induced conformational change and subunit aggregation can account for the properties of mutant enzymes reported here. The results underscore the difficulty of using directed mutations alone as a means of mapping the active site of an enzyme.

Adenylosuccinate Synthase↗
PubMed1998

[A technique of constructing human chromosomal band-specific probe pools using degenerate oligonucleotide primer].

OBJECTIVE: To establish a rapid and efficient technique of constructing human chromosomal band specific probe pools and their libraries. METHODS: A modified method of combining chromosome microdissection with degenerate oligonucleotide primed PCR(DOP-PCR) was used. 3p23-p26, 3q21-q22 and 4p12- p16 band from human chromosomes were microdissected and amplified as probe pools. The origins of the PCR products were determined by chromosome fluorescence in situ hybridization. The PCR products and pUC19 were digested by Xho I and Sal I respectively, and linke up. The DH5alpha were transformed by the recombinated vectors as the specific band libraries. The inserts were digested by EcoR I and Hind III, then measured by electrophoretic analysis. And the copies of inserts were identified by in situ bacterial colony hybridization with genomic DNA. RESULTS: All the three probe pools showed the special yellow-green signals in their microdissection responsible bands. The sizes of DOP-PCR products ranged from 300bp to 1800bp. 3q21-q22 probe pool generated about 1.2 x 10(4) clones. The average size of inserts was about 420bp by analysis of 30 positive clones. The rate of single-copy and low-repeated sequences was about 81%(178/220), while the rate of middle-repeated and high- repeated sequences was about 19%(42/220). CONCLUSION: The results proved that the modified microdissection combining DOP-PCR technique provided a simple and efficient method to construct the human chromosome band-specific probe pools and might contribute to gene cloning and complete sequencing of human genome.

Chromosome Banding↗
PubMed1998

All-cause mortality and cardiovascular disease mortality in three American Indian populations, aged 45-74 years, 1984-1988. The Strong Heart Study.

Community mortality surveillance for 1984-1988 was conducted by researchers of the Strong Heart Study, which examined the incidence, prevalence, and risk factors of cardiovascular disease in three American Indian populations, aged 45-74 years, in Arizona, Oklahoma, and South/North Dakota. All-cause and cardiovascular disease mortality rates were determined through the use of death certificate data. Cardiovascular disease deaths were confirmed by independent systematic review of medical records. In all three populations, men had higher all-cause and cardiovascular disease mortality rates than did women. Oklahoma exhibited slightly lower 5-year, age-adjusted, all-cause mortality (96/1,000) than did Arizona (107/1,000) and South/North Dakota (114/1,000). The leading cause of death among both sexes in Oklahoma and in South/North Dakota was cardiovascular disease. Diabetes mellitus led among Arizona women. The other major causes of death were cancer, liver disease including cirrhosis, and injury. When compared with the rates in each state, average annual all-cause mortality rates were higher for the American Indian populations in almost every age group. The all-cause annual mortality rates in the three Indian populations were close to rates in the US black population and higher than the rates of the entire US population and of US whites. This trend was amplified in the 45- to 64-year age group. Only in the 65- to 74-year age group did mortality rates in the Indian population approach those of the US population. Cardiovascular disease mortality rates were close to the US averages in Arizona and Oklahoma, but they were more than two times higher in South/North Dakota among those between 45 and 64 years of age. Thus, American Indians in Arizona, Oklahoma, and South/North Dakota exhibit high all-cause mortality rates. In particular, the South/North Dakota population cardiovascular disease death rate appears to present a potential target for community-based programs to intervene on known risk factors to promote healthy lifestyles.

Aged↗
PubMed1998

U/Pb zircon geochronology and tempo of the end-permian mass extinction

The mass extinction at the end of the Permian was the most profound in the history of life. Fundamental to understanding its cause is determining the tempo and duration of the extinction. Uranium/lead zircon data from Late Permian and Early Triassic rocks from south China place the Permian-Triassic boundary at 251.4 +/- 0.3 million years ago. Biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the Changhsingian pulse of the end-Permian extinction, corresponding to the disappearance of about 85 percent of marine species, lasted less than 1 million years. At Meishan, a negative excursion in delta13C at the boundary had a duration of 165,000 years or less, suggesting a catastrophic addition of light carbon.

Journal Article↗
PubMed1998

Glutathione S-conjugate formation and metabolism in HepG2 cells: a cell model of mercapturic acid biosynthesis.

Mercapturic acid biosynthesis is mediated by a series of at least four enzymatic steps and three cell membrane transport events, and is believed to require the interorgan shuttling of the various metabolic intermediates. To identify a single cell type that can carry out all of these metabolic and transport steps, the present study examined whether HepG2 cells, a human hepatoma-derived cell line, can convert an electrophilic chemical (1-chloro-2,4-dinitrobenzene, CDNB) to its corresponding mercapturic acid (S-dinitrophenyl-N-acetylcysteine, DNP-NAC). The results demonstrate that HepG2 cells are able to convert CDNB to DNP-NAC in a dose- and time-dependent fashion. Intracellular conjugation with glutathione occurred rapidly, and the resulting glutathione S-conjugate was promptly transported into the culture medium, where it was sequentially degraded to the cysteinylglycine and cysteine S-conjugates. The cysteine conjugate was then presumably reabsorbed, and N-acetylated intracellularly to form the mercapturic acid. The mercapturic acid was found to accumulate slowly in the culture medium, such that after 4 h of incubation, 4-10% of the CDNB dose was recovered as the mercapturic acid. These data provide the first demonstration that a single cell type can carry out all of the transport and enzymatic steps required for mercapturic acid biosynthesis. HepG2 cells may provide a useful model system for studying this important detoxification pathway.

Acetylcysteine↗
PubMed1998

Association of prostate cancer with vitamin D receptor haplotypes in African-Americans.

In previous studies, allelic variation in the 3' end of the vitamin D receptor gene was associated with increased risk of prostate cancer in white men. Several polymorphisms, including a BsmI restriction site and a poly(A) microsatellite, can be used interchangeably to mark the unidentified locus in whites. In African-Americans, however, these markers are not interchangeable, due to weaker linkage disequilibrium in this genomic region in this population. Here, we genotyped both the BsmI and poly(A) markers for 151 African-American prostate cancer cases (102 localized and 49 advanced) and 174 African-American male controls from a large epidemiological cohort. A direct haplotyping procedure was devised to determine BsmI/poly(A) haplotypes for double heterozygotes so that haplotypes could be used as allelic markers in standard logistic regression analyses. Using BsmI alone, b alleles were associated with a 2-fold decrease in risk of advanced prostate cancer. The association was, however, confined to haplotypes carrying a long (L) allele of the poly(A) microsatellite. BL and bL haplotypes were associated with increased and decreased risk, respectively, whereas neither BS nor bS haplotypes were associated with prostate cancer risk. An allelic variant that confers increased risk of advanced prostate cancer appears to be associated with the BsmI/poly(A) BL haplotype in African-Americans.

Aged↗
PubMed1998

[Association between angiotensin II type I receptor gene and human essential hypertension].

OBJECTIVE: To determine whether the angiotensin II type I receptor gene might be implicated in human essential hypertension. METHODS: This was a case-control study on hypertension and normal blood pressure in Chinese DNA abstracted samples from 51 cases of essential hypertension and 74 normal controls were analysed by polymerase chain reaction,digestion of restriction enzyme and electrophesis. RESULTS: The genotype frequency of 1166A/1166C was 0. 196 (10/51) in the essential hypertension group, 0.081 (6/74) in the control group. The genotype frequency of 1166C/1166C was 0 in both groups. The gene frequency of 1166C was 0.098 in the essential hypertension group, 0.041 in the controls. There was a significant increase in allelic frequency of 1166C in hypertension. CONCLUSION: The results indicate that the increase in allelic frequency of 1166C is a risk factor and hence suggest that the change in the angiotensin II type I receptor gene is associated with essential hypertension.

Adolescent↗
PubMed1998

Regulation of Ca2+ signaling in transgenic mouse cardiac myocytes overexpressing calsequestrin.

To probe the physiological role of calsequestrin in excitation-contraction coupling, transgenic mice overexpressing cardiac calsequestrin were developed. Transgenic mice exhibited 10-fold higher levels of calsequestrin in myocardium and survived into adulthood, but had severe cardiac hypertrophy, with a twofold increase in heart mass and cell size. In whole cell-clamped transgenic myocytes, Ca2+ channel- gated Ca2+ release from the sarcoplasmic reticulum was strongly suppressed, the frequency of occurrence of spontaneous or Ca2+ current-triggered "Ca2+ sparks" was reduced, and the spark perimeter was less defined. In sharp contrast, caffeine-induced Ca2+ transients and the resultant Na+-Ca2+ exchanger currents were increased 10-fold in transgenic myocytes, directly implicating calsequestrin as the source of the contractile-dependent pool of Ca2+. Interestingly, the proteins involved in the Ca2+-release cascade (ryanodine receptor, junctin, and triadin) were downregulated, whereas Ca2+-uptake proteins (Ca2+-ATPase and phospholamban) were unchanged or slightly increased. The parallel increase in the pool of releasable Ca2+ with overexpression of calsequestrin and subsequent impairment of physiological Ca2+ release mechanism show for the first time that calsequestrin is both a storage and a regulatory protein in the cardiac muscle Ca2+-signaling cascade. Cardiac hypertrophy in these mice may provide a novel model to investigate the molecular determinants of heart failure.

Animals↗
PubMed1998

EH domain-dependent interactions between Eps15 and clathrin-coated vesicle protein p95.

The endocytic protein Eps15 contains three copies of the EH domain, a protein module thought to function in protein-protein interactions. Using overlay assays with an Eps15 EH domain fusion protein, we have now identified a protein of 95 kDa (p95) as a major EH domain-binding partner in a wide variety of tissues. The amino acids asparagine-proline-phenylalanine (NPF) form the core of an EH domain-binding motif and three NPF repeats are found in the endocytic protein synaptojanin-170. We have confirmed previous studies indicating that synaptojanin-170 is an EH domain-binding protein, and have used peptide blocking experiments to demonstrate that the interaction is mediated through the NPF repeats. Interestingly, the same peptide also blocks EH domain-binding to p95. Finally, we have shown that p95 is enriched on clathrin-coated vesicles, suggesting an endocytic role for the protein. These data support an important role for EH domain-NPF motif interactions in endocytosis.

Amino Acid Sequence↗
PubMed1998

Design and synthesis of monocyclic beta-lactams as mechanism-based inhibitors of human cytomegalovirus protease.

Mechanism based inhibitors of HCMV protease have been designed based on the monocyclic beta-lactam nucleus, which have been shown to acylate the viral enzyme in a time dependent manner. SAR in a series of monocyclic beta-lactam N-ureas, has defined the size and relative stereochemistry of the C-3 substituent producing a low micromolar inhibitor 17b with good aqueous stability and selectivity over the mammalian serine proteases.

Drug Stability↗
PubMed1998

Pentoxifylline inhibits Ig kappa gene transcription and rearrangements in pre-B cells.

Pentoxifylline (PF) has been used in a wide variety of clinical situations; however, the molecular consequences of this drug are not well characterized. In this paper we assayed the effects of PF in two models of pre-B differentiation. In 70Z pre-B cells, transcriptional induction of rearranged Ig kappa-chain gene in response to LPS was suppressed by PF, without affecting the induction of Rel family proteins. In contrast, kappa induction by IFN-gamma was not suppressed by PF, indicating that the drug inhibited certain activation pathways. We also found that LPS-induced activation of germline kappa transcription and V kappa to J kappa recombination were inhibited by PF in the pre-B cell line 38B9. These observations suggest that PF may adversely affect B lymphopoiesis during chronic administration.

Animals↗
PubMed1998

The minor histocompatibility antigen HA-1: a diallelic gene with a single amino acid polymorphism.

The minor histocompatibility antigen (mHag) HA-1 is the only known mHag for which mismatching is correlated with the development of severe graft versus host disease (GvHD) after human leukocyte antigen-identical bone marrow transplantation. HA-1 was found to be a nonapeptide derived from an allele of the KIAA0223 gene. The HA-1-negative allelic counterpart encoded by KIAA0223 had one amino acid difference from HA-1. Family analysis with HA-1 allele-specific polymerase chain reaction showed an exact correlation between this allelic polymorphism and the HA-1 phenotype. HA-1 allele typing of donor and recipient should improve donor selection and allow the determination of bone marrow transplantation recipients with high risk for HA-1-induced GvHD development.

Alleles↗