Biomedical subjects

X Xin

Publications and source records attributed to X Xin.

At least 37 records · Page 2Linked to original sources

PubMed2000

Receptor-selective variants of human vascular endothelial growth factor. Generation and characterization.

Vascular endothelial growth factor (VEGF) is a pleiotropic factor that exerts a multitude of biological effects through its interaction with two receptor tyrosine kinases, fms-like tyrosine kinase (Flt-1) or VEGF receptor 1 and kinase insert domain-containing receptor (KDR) or VEGF receptor 2. Whereas it is commonly accepted that KDR is responsible for the proliferative activities of VEGF, considerable controversy and uncertainty exist about the role of the individual receptors in eliciting many of the other effects. Based on a comprehensive mutational analysis of the receptor-binding site of VEGF, an Flt-1-selective variant was created containing four substitutions from the wild-type protein. This variant bound with wild-type affinity to Flt-1, was at least 470-fold reduced in binding to KDR, and had no activity in cell-based assays measuring autophosphorylation of KDR or proliferation of primary human vascular endothelial cells. Using a competitive phage display strategy, two KDR-selective variants were discovered with three and four changes from wild-type, respectively. Both variants had approximately wild-type affinity for KDR, were about 2000-fold reduced in binding to Flt-1, and showed activity comparable with the wild-type protein in KDR autophosphorylation and endothelial cell proliferation assays. These variants will serve as useful reagents in elucidating the roles of Flt-1 and KDR.

Endothelial Growth Factors↗

PubMed2000

Hypothalamic c-fos-like immunoreactivity in high-fat diet-induced obese and resistant mice.

Some C57Bl/6 mice become obese, whereas others remain lean when raised on a high-fat diet. The mechanisms underlying this interindividual susceptibility to diet-induced obesity remain unknown. Because hypothalamus plays a major role in the regulation of body weight, this study was conducted to identify the differences of hypothalamic neuronal activity between diet-induced obese and diet-resistant mice. Using c-fos as a marker, this study showed that diet-induced obese mice significantly increased c-fos-like immunoreactive neurons in the dorsal part of lateral hypothalamus (+183%) and dorsomedial hypothalamic nucleus (+87.5%) compared with diet-resistant mice. Furthermore, switching from high fat to low fat, or high n-3 polyunsaturated fatty acid diet, significantly decreased body weight gain (-35.7% and -31.0%), overall fat storage (-63.4% and -59.6%), and c-fos-like immunoreactive neurons in the dorsal part of lateral hypothalamus (-76.5% and -64.7%) and dorsomedial hypothalamic nucleus (-73.3% and -56.7%) in diet-induced obese mice, respectively. The present study also showed that the ratio of serum leptin/fat mass was threefold higher in the diet-resistant mice than in the diet-induced obese mice, which may be responsible for the less fat storage in the diet-resistant mice. The current data further confirm that the increased neuronal activity in the key autonomic regulatory centers may contribute to the excessive fat storage in diet-induced obese mice. Moreover, both high-fat diet-induced excessive fat storage and the altered hypothalamic neuronal activity may be largely corrected by reducing dietary fat content or replacing it with non-obesogenic fat.

Animals↗

PubMed2000

Gene expression profiling in an in vitro model of angiogenesis.

In the present study we have used a novel, comprehensive mRNA profiling technique (GeneCalling) for determining differential gene expression profiles of human endothelial cells undergoing differentiation into tubelike structures. One hundred fifteen cDNA fragments were identified and shown to represent 90 distinct genes. Although some of the genes identified have previously been implicated in angiogenesis, potential roles for many new genes, including OX-40, white protein homolog, KIAA0188, a homolog of angiopoietin-2, ADAMTS-4 (aggrecanase-1), and stanniocalcin were revealed. Support for the biological significance was confirmed by the abrogation of the changes in the expression of angiogenesis inhibitors and in situ hybridization studies. This study has significantly extends the molecular fingerprint of the changes in gene expression that occur during endothelial differentiation and provides new insights into the potential role of a number of new molecules in angiogenesis.

Cells, Cultured↗

PubMed2000

Polymorphism in the interleukin-4 promoter affects acquisition of human immunodeficiency virus type 1 syncytium-inducing phenotype.

The emergence of syncytium-inducing (SI) variants of human immunodeficiency virus type 1 (HIV-1) in infected individuals is an indicator of poor prognosis and is often correlated with faster CD4(+) cell depletion and rapid disease progression. Interleukin-4 (IL-4) is a pleiotropic cytokine with various immune-modulating functions including induction of immunoglobulin E (IgE) production in B cells, down-regulation of CCR5 (a coreceptor for HIV-1 non-SI [NSI] strains), and up-regulation of CXCR4 (a coreceptor for HIV-1 SI variants). Here we show that homozygosity of a polymorphism in the IL-4 promoter region, IL-4 -589T, is correlated with increased rates of SI variant acquisition in HIV-1-infected individuals in Japan. This mutation was also shown to be associated with elevated serum IgE levels in HIV-1-infected individuals, especially in those at advanced stages of disease. In contrast, neither a triallele polymorphism in IL-10, another Th2 cytokine, nor a biallele polymorphism in the RANTES promoter affected acquisition of the SI phenotype. This finding suggested that IL-4-589T increases IL-4 production in the human body and thus accelerates the phenotypic switch of HIV-1 from NSI to SI and possibly disease progression of AIDS.

Alleles↗

PubMed2000

[Effect of cadmium on soil animal community structure].

A indoor simulating test showed that there existed a close relationship between the community structure of soil animal and the concentration of soil Cd. When the concentration of soil Cd was high (99.48 mg.kg-1), the species, quantity, diversity index, homogeneous index, and abundance of soil animal were low. With the concentration going down, all indexes above increased gradually. When the concentration of soil Cd was 2.27 mg.kg-1, all the indexes were the same as control. The species and individuals of soil animal were negatively related with the natural logarithm of Cd concentration in soil.

Animal Population Groups↗

PubMed2000

[Seed growth characteristics of Ginkgo biloba and its physiological change].

The length, width, volume and weight of Ginkgo biloba seed were measured, and the concentrations of water, sugars, fatty acids and amino acids in seed growth process were analyzed. A typical "S" seed growth curve was found, and the length, width, volume, weight and absolute water content all showed the similar changes during growing period. With the growing of ssed, the concentrations of physiological substances in seeds showed regular changes and had their own characteristics. The total amount of sugars appeared to be an increasing trend at the later stage of seed growth, indicating that sugars are the main nutrition substance accumulated in seeds. The concentrations of various substances in matured seeds were starch 8.4%, glucose 6.7%, fructose 4.2%, polysaccharide 0.02%, disaccharide 0.01%, myristic acid 10.6%, palmitic acid 4.1%, flax acid 2.4%, stearic acid 1.9%, oleic acid 1.1%, and linoleic acid 0.4%. Fifteen types of free amino acids were detected in matured seeds, with total content of 1.56 g.100 g-1FW. Among them, lysine aspartic acid, alanine, arginine, histidine, glutamic acid, and isoleucine were dominant, and their concentrations were 0.287%, 0.163%, 0.136%, 0.133%, 0.123%, 0.115%, 0.095%, respectively.

Amino Acids↗

PubMed2000

[Hostility behavior as risk factor of coronary heart disease].

OBJECTIVE: To explore the relationships between hostility, and the risks of coronary-prone behavior and the clusters of unhealthy behaviors in individuals with different levels of hostility. METHODS: A cross-sectional study was carried out among 1 010 male employees from two factories in Beijing Capital Steel and Iron Company in 1997. Data on major risks of cardiovascular, other social-demographic factors and levels of hostility by Cook-Medley Scales were collected. RESULTS: Body mass index, amounts of cigarette smoking and alcohol drinking were significantly increased (P < 0.01) with a characteristic of reduced social support from one's colleagues, when individual's level of hostility increased. In addition, less years of education, higher prevalence of other chronic diseases (P < 0.05) and clustering of various unhealthy behaviors were found related to the increase of individual's hostility. The odds ratio in the group with highest hostility was 2.37 times higher than in the lowest one, after confounding effects from age, blood pressure, education level, status of chronic disease and social support being adjusted. No significant differences on both systolic and diastolic blood pressures among groups with different levels of hostility were discovered. CONCLUSION: The association between hostility, coronary-prone risk behavior and cluster of unhealthy behaviors suggested that hostility might increase the risk of coronary heart diseases through affecting individual's behavior.

Adolescent↗

PubMed1999

Enhanced anti-HIV-1 activity of CC-chemokine LD78beta, a non-allelic variant of MIP-1alpha/LD78alpha.

We compared the anti-HIV-1 activity of CC-chemokine LD78beta with that of MIP-1alpha, another CC-chemokine which shows 94% sequence homology with LD78beta. Despite its close similarity to MIP-1alpha, the anti-HIV-1 activity of LD78beta appeared to be nearly 10 times higher than that of MIP-1alpha. Mutagenesis of MIP-1alpha showed that the N-terminal additional tetrapeptide, which was present in LD78beta and absent in MIP-1alpha, is responsible for enhanced anti-HIV-1 activity. The N-terminal structure-function relationship of LD78beta described here will be of value in understanding the chemokine-receptor interactions and designing anti-HIV-1 compounds based on LD78beta.

Animals↗

PubMed1999

Polymorphism in RANTES chemokine promoter affects HIV-1 disease progression.

RANTES (regulated on activation normal T cell expressed and secreted) is one of the natural ligands for the chemokine receptor CCR5 and potently suppresses in vitro replication of the R5 strains of HIV-1, which use CCR5 as a coreceptor. Previous studies showed that peripheral blood mononuclear cells or CD4(+) lymphocytes obtained from different individuals had wide variations in their ability to secrete RANTES. These findings prompted us to analyze the upstream noncoding region of the RANTES gene, which contains cis-acting elements involved in RANTES promoter activity, in 272 HIV-1-infected and 193 non-HIV-1-infected individuals in Japan. Our results showed that there were two polymorphic positions, one of which was associated with reduced CD4(+) lymphocyte depletion rates during untreated periods in HIV-1-infected individuals. This mutation, RANTES-28G, occurred at an allele frequency of approximately 17% in the non-HIV-1-infected Japanese population and exerted no influence on the incidence of HIV-1 infection. Functional analyses of RANTES promoter activity indicated that the RANTES-28G mutation increases transcription of the RANTES gene. Taken together, these data suggest that the RANTES-28G mutation increases RANTES expression in HIV-1-infected individuals and thus delays the progression of the HIV-1 disease.

Base Sequence↗

PubMed1999

Peroxisome proliferator-activated receptor gamma ligands are potent inhibitors of angiogenesis in vitro and in vivo.

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor that functions as a transcription factor to mediate ligand-dependent transcriptional regulation. Activation of PPARgamma by the naturally occurring ligand, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), or members of a new class of oral antidiabetic agents, e.g. BRL49653 and ciglitizone, has been linked to adipocyte differentiation, regulation of glucose homeostasis, inhibition of macrophage and monocyte activation, and inhibition of tumor cell proliferation. Here we report that human umbilical vein endothelial cells (HUVEC) express PPARgamma mRNA and protein. Activation of PPARgamma by the specific ligands 15d-PGJ2, BRL49653, or ciglitizone, dose dependently suppresses HUVEC differentiation into tube-like structures in three-dimensional collagen gels. In contrast, specific PPARalpha and -beta ligands do not affect tube formation although mRNA for these receptors are expressed in HUVEC. PPARgamma ligands also inhibit the proliferative response of HUVEC to exogenous growth factors. Treatment of HUVEC with 15d-PGJ2 also reduced mRNA levels of vascular endothelial cell growth factor receptors 1 (Flt-1) and 2 (Flk/KDR) and urokinase plasminogen activator and increased plasminogen activator inhibitor-1 (PAI-1) mRNA. Finally, administration of 15d-PGJ2 inhibited vascular endothelial cell growth factor-induced angiogenesis in the rat cornea. These observations demonstrate that PPARgamma ligands are potent inhibitors of angiogenesis in vitro and in vivo, and suggest that PPARgamma may be an important molecular target for the development of small-molecule inhibitors of angiogenesis.

Animals↗

PubMed1999

The developmental fate of green fluorescent mouse embryonic germ cells in chimeric embryos.

Primordial germ cells (PGCs), as precursors of mammalian germ lineage, have been gaining more attention as a new resource of pluripotent stem cells, which bring a great possibility to study developmental events of germ cell in vitro and at animal level. EG4 cells derived from 10.5 days post coitum (dpc) PGCs of 129/svJ strain mouse were established and maintained in an undifferentiated state. With an attempt to study the differentiation capability of EG4 cells with a reporter protein: green fluorescence protein, and the possible application of EG4 cells in the research of germ cell development, we have generated several EG4-GFP cell lines expressing enhanced green fluorescence protein (EGFP) and still maintaining typical characteristics of pluripotent stem cells. Then, the differentiation of EG4-GFP cells in vitro as well as their developmental fate in chimeric embryos which were produced by aggregating EG4-GFP cells to 8-cell stage embryos were studied. The results showed that EG4 cells carrying green fluorescence have a potential use in the research of germ cell development and other related studies.

Animals↗

PubMed1999

Identification of mouse CPX-1, a novel member of the metallocarboxypeptidase gene family with highest similarity to CPX-2.

The recent finding that Cpe(fat)/Cpe(fat) mice, which lack carboxypeptidase E (CPE) activity because of a point mutation, are still capable of a reduced amount of neuroendocrine peptide processing suggested that additional carboxypeptidases (CPs) participate in this processing reaction. Searches for novel members of the CPE gene family led to the discovery of CPD, CPZ, AEBP1, and CPX-2. In the present report, we describe mouse CPX-1, another novel member of this gene family. Like AEBP1 and CPX-2, CPX-1 contains an N-terminal region of 160 amino acids with sequence similarity to the discoidin domain of a variety of proteins. The 410-residue CP-like domain of CPX-1 has 54% to 62% amino acid sequence identity with AEBP1 and CPX-2 and 33% to 49% amino acid identity with other members of the CPE subfamily. However, several active-site residues that are important for catalytic activity of other CPs are not conserved in CPX-1. Furthermore, CPX-1 expressed in either the baculovirus system or the mouse AtT-20 cell line does not cleave standard CP substrates. Northern blot analysis showed the highest levels of CPX-1 mRNA in testis and spleen and lower levels in salivary gland, brain, heart, lung, and kidney. In situ hybridization of CPX-1 mRNA in embryonic and fetal mouse tissue showed expression throughout the head and thorax, with abundance in primordial cartilage and skeletal structures. In the head, high levels of CPX-1 mRNA were associated with the nasal mesenchyme, primordial cartilage structures in the ear, and the meninges. In the thorax, CPX-1 mRNA was expressed in multiple developing skeletal structures, including chondrocytes and perichondrial cells of the rib, vertebral, and long-bone primordia. Taken together, these findings suggest that it is unlikely that CPX-1 functions in the processing of neuroendocrine peptides. Instead, CPX-1 may have a role in development, possibly mediating cell interactions via its discoidin domain.

Amino Acid Sequence↗

PubMed1999

Platelet-derived growth factor inhibits alpha1D-adrenergic receptor expression in vascular smooth muscle cells in vitro and ex vivo.

Indirect evidence suggests that stimulation of alpha1-adrenergic receptors (ARs) increases smooth muscle cell (SMC) growth in the growing and adult artery and worsens atherosclerosis and restenosis after balloon injury. In support of a direct adrenergic effect, we have previously shown that alpha1D-AR stimulation induces SMC hypertrophy in cell and vessel organ culture. Because interactions between alpha1-ARs and peptide growth factors may be important in normal and pathological SMC growth, herein we examined regulation of alpha1D-AR expression by growth factors. Platelet-derived growth factor (PDGF)-BB dose- and time-dependently lowered alpha1D mRNA in cultured quiescent SMCs (e.g., 58% inhibition at 20 ng/ml, 24 h, p <.05), whereas other alpha1-AR transcripts were unaffected. This same selective effect was seen in the medial layer of aorta in ex vivo organ culture. However, PDGF-AA, insulin-like growth factor-1, insulin, epidermal growth factor, endothelin, histamine, and serotonin had no effect, whereas thrombin induced a modest (1.8-fold) increase. PDGF-BB inhibition of alpha1D-AR mRNA was accompanied by a 42% reduction in total alpha1-AR density (p <.05) and a functional decrease in norepinephrine-mediated protein synthesis. alpha1D mRNA half-life was not significantly affected by PDGF-BB (3.8 versus 3.2 h). However, transcriptional activity of the alpha1D promoter was inhibited. Reduction in alpha1D-AR mRNA depended partly on new protein synthesis, and was abolished by protein kinase C inhibition, whereas phosphatidylinositol 3 kinase and mitogen-activated protein kinase kinase inhibition had no effect. These data demonstrate that PDGF-beta receptor stimulation (because PDGF-AA had no effect) induces a selective inhibition of alpha1D-AR expression and hence norepinephrine-mediated SMC growth. This down-regulation may lessen additive or synergistic growth effects of catecholamines with other growth factors in vascular hypertrophic diseases.

Adrenergic alpha-Agonists↗

PubMed1999

Platelet-derived growth factor-BB inhibits rat alpha1D-adrenergic receptor gene expression in vascular smooth muscle cells by inducing AP-2-like protein binding to alpha1D proximal promoter region.

We have previously found that, in addition to mediating contraction of vascular smooth muscle, activation of alpha1D-adrenergic receptors (AR) induces smooth muscle cell (SMC) hypertrophy. Despite their importance, little is known about how alpha1D-AR expression is regulated. Recently, we demonstrated that platelet-derived growth factor (PDGF)-beta receptor stimulation, but not various other growth factors, inhibits transcription of alpha1D-, but not alpha1A- or alpha1B-ARs, resulting in reduced norepinephrine-mediated SMC growth. To investigate this inhibitory mechanism, herein we cloned and characterized 1.6 kb of the 5'-flanking region of the rat alpha1D-AR gene. Reporter gene transfection assays in rat aorta and vena cava SMCs showed that this 5'-flanking region, which lacks a TATA-box, possesses strong promoter activity. Two transcription initiation sites and their flanking promotor regions were identified, wherein the proximal promotor mediated PDGF-BB inhibition of transcription. Gel mobility shift assays suggested that Sp1 binds constitutively at two consensus sites within the -399 base pair (bp)/-349-bp region of the proximal promotor. This constitutive binding was unaffected by PDGF-BB. In contrast, a flanking motif (-384 bp/-349 bp), possessing putative Sp1/activator protein-2 (AP-2) overlapping binding sites and located upstream of the proximal transcription initiation site, was required for PDGF-BB inhibition of alpha1D transcription. PDGF-BB increased AP-2 binding to the distal AP-2 site in this region in the context of SMCs. Furthermore, overexpression of AP-2 protein, by transgene transfection, dose-dependently inhibited alpha1D-AR activity driven by this motif. Thus, PDGF-BB may increase AP-2 binding within the proximal promoter to cause down-regulation of alpha1D-AR expression in SMCs when PDGF is elevated, such as in the postnatal growing vascular wall and in vascular hypertrophic diseases.

Animals↗

PubMed1998

Importance of the N-glycan in the V3 loop of HIV-1 envelope protein for CXCR-4- but not CCR-5-dependent fusion.

The V3 region of HIV-1 envelope protein possesses a single N-linked sugar chain, which is conserved in most HIV-1 strains. We studied its role in the life cycle of HIV-1 strains with different co-receptor usage. Removal of the glycan appeared to cause a marked reduction of CXCR-4- but not CCR-5-dependent virus entry. A basic amino acid substitution at the 11th position of V3 markedly compensated for the removal of the N-glycan. These results indicate that the N-glycan plays an important role for CXCR-4-dependent virus entry and that this role is exerted in a particular context of the peptide backbone.

Amino Acid Sequence↗

PubMed1998

Large quantity production with extreme convenience of human SDF-1alpha and SDF-1beta by a Sendai virus vector.

We describe a robust expression of human stromal cell-derived factor-1alpha (SDF-1alpha) and SDF-1beta, the members of CXC-chemokine family, with a novel vector system based upon Sendai virus, a non-segmented negative strand RNA virus. Recombinant SDF-1alpha and SDF-1beta were detected as a major protein species in culture supernatants, reached as high as 10 microg/ ml. This remarkable enrichment of the products allowed us to use even the crude supernatants as the source for biological and antiviral assays without further concentration nor purification and will thus greatly facilitate to screen their genetically engineered derivatives.

Anti-HIV Agents↗

PubMed1998

Facilitation of HIV-1 isolation from patients by neuraminidase.

We previously reported that infectivities of human and other non-human lentiviruses including human immunodeficiency virus type 1 (HIV-1) are activated by desialylation of the virion surface [H. Hu et al., J Virol 70: 7,462-7,470 (1996)]. The present study was designed to determine whether neuraminidase (NA) is useful for isolation of HIV-1 from patients. Peripheral blood mononuclear cells (PBMC) or CD4+ cells isolated from the PBMC of infected individuals were cocultured with PBMC or CD4+ cells from uninfected healthy donors, and the efficiency and frequency of virus isolation in the presence of NA were compared with those by a routine conventional procedure. In a total of 41 isolation trials from 28 individuals, the presence of NA markedly increased the frequency of isolation. Furthermore, both the day when virus was first detected and the day when the virus titer was the highest in the cultures were significantly earlier in the presence of NA than in the absence of NA. The deduced amino acid sequences of the V2 and V3 regions of gp120 were identical or very similar between the isolates obtained in the presence or absence of NA, suggesting that both isolation procedures selected a similar population. NA was thus found to facilitate HIV-1 isolation and its use is recommended particularly when isolation is negative by the conventional procedures.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Cloning, sequence analysis, and distribution of rat metallocarboxypeptidase Z.

A cDNA encoding human carboxypeptidase Z (CPZ), a novel metallocarboxypeptidase, was recently cloned (Song and Fricker, J. Biol. Chem., 272, 1054, 1997). In the present study, a cDNA encoding the rat homolog of CPZ was identified. As with the human form, rat CPZ contains an N-terminal domain of 120 amino acids that has 20% to 30% amino acid identity with the "frizzled" domain found on proteins that interact with Wnt, a protein involved in tissue polarity in early embryogenesis. Sequence analysis showed rat and human CPZ to be highly conserved within the frizzled domain (77% amino acid identity), the carboxypeptidase domain (91%), and the C-terminal 28 residues (78%). The entire rat CPZ protein has high sequence similarity with human CPZ (81% amino acid identity), moderate sequence similarity to human carboxypeptidase N (45%), human carboxypeptidase E (41%), and human carboxypeptidase M (33%), and less sequence similarity with other metallocarboxypeptidases. Northern blot analysis showed rat CPZ mRNA to be abundant in the placenta, with low to moderate levels in the brain, lung, thymus, and kidney. The BRL3A rat liver cell line and the PC12 rat adrenal cell line express high levels of CPZ mRNA. In situ hybridization analysis indicated that CPZ is expressed only in specific cell types. For example, in the brain, CPZ mRNA is present in leptomeningeal cells, but not in the majority of other cell types. This distribution in leptomeningeal cells is shared by AEBP1, a recently reported member of the metallocarboxypeptidase gene family. However, the distribution of CPZ and AEBP1 differ in pituitary and thyroid. Taken together, these studies suggest that CPZ functions in a range of cell types.

Amino Acid Sequence↗