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Hong Yu

Publications and source records attributed to Hong Yu.

At least 145 records · Page 8Linked to original sources
PubMed2002

Drac1 and Crumbs participate in amnioserosa morphogenesis during dorsal closure in Drosophila.

Dorsal closure of the Drosophila embryo involves morphological changes in two epithelia, the epidermis and the amnioserosa, and is a popular system for studying the regulation of epithelial morphogenesis. We previously implicated the small GTPase Drac1 in the assembly of an actomyosin contractile apparatus, contributing to cell shape change in the epidermis during dorsal closure. We now present evidence that Drac1 and Crumbs, a determinant of epithelial polarity, are involved in setting up an actomyosin contractile apparatus that drives amnioserosa morphogenesis by inducing apical cell constriction. Expression of constitutively active Drac1 causes excessive constriction of amnioserosa cells and contraction of the tissue, whereas expression of dominant-negative Drac1 impairs amnioserosa morphogenesis. These Drac1 transgenes may be acting through their effects on the amnioserosa cytoskeleton, as constitutively active Drac1 causes increased staining for F-actin and myosin, whereas dominant-negative Drac1 reduces F-actin levels. Overexpression of Crumbs causes premature cell constriction in the amnioserosa, and dorsal closure defects are seen in embryos homozygous for hypomorphic crumbs alleles. The ability of constitutively active Drac1 to cause contraction of the amnioserosa is impaired in a crumbs mutant background. We propose that amnioserosa morphogenesis is a useful system for studying the regulation of epithelial morphogenesis by Drac1.

Actins↗
PubMed2002

Plasminogen activator inhibitor type 2: a regulator of monocyte proliferation and differentiation.

We have explored the role of plasminogen activator inhibitor type 2 (PAI-2) in THP-1 monocyte-like cells. These cells possess a mutation in the PAI-2 gene and do not produce an active PAI-2 protein. Transfection of THP-1 cells with plasmids expressing active PAI-2 reduced the cells' inherent adhesive properties and decreased the rate of cell proliferation. THP-1 cells expressing active PAI-2 also displayed an altered phenotype in response to phorbol ester-induced differentiation that was concomitant with a reduction in CD14 expression. THP-1 cells transfected with a variant PAI-2 containing a mutation in the reactive center (PAI-2(Ala380)) displayed no noticeable change in any of these parameters, suggesting the involvement of a PAI-2-sensitive serine protease(s). The antiproliferative effect of PAI-2 was attenuated by treating the PAI-2-expressing THP-1 cells with recombinant urokinase (u-PA), suggesting that PAI-2 was disruptive of a u-PA/u-PA receptor signaling pathway initiated on the cell surface. Consistent with this, treatment of wild-type THP-1 cells with recombinant PAI-2 also caused a reduction in cellular proliferation. These results implicate endogenous PAI-2 as a modulator of monocyte adhesion, proliferation, and differentiation.

Amino Acid Substitution↗
PubMed2002

Melanin-concentrating hormone 1 receptor-deficient mice are lean, hyperactive, and hyperphagic and have altered metabolism.

Melanin-concentrating hormone (MCH) is a cyclic 19-aa hypothalamic neuropeptide derived from a larger prohormone precursor of MCH (Pmch), which also encodes neuropeptide EI (NEI) and neuropeptide GE (NGE). Pmch-deficient (Pmch-/-) mice are lean, hypophagic, and have an increased metabolic rate. Transgenic mice overexpressing Pmch are hyperphagic and develop mild obesity. Consequently, MCH has been implicated in the regulation of energy homeostasis. The MCH 1 receptor (MCH1R) is one of two recently identified G protein-coupled receptors believed to be responsible for the actions of MCH. We evaluated the physiological role of MCH1R by generating MCH1R-deficient (Mch1r-/-) mice. Mch1r-/- mice have normal body weights, yet are lean and have reduced fat mass. Surprisingly, Mch1r-/- mice are hyperphagic when maintained on regular chow, and their leanness is a consequence of hyperactivity and altered metabolism. Consistent with the hyperactivity, Mch1r-/- mice are less susceptible to diet-induced obesity. Importantly, chronic central infusions of MCH induce hyperphagia and mild obesity in wild-type mice, but not in Mch1r-/- mice. We conclude that MCH1R is a physiologically relevant MCH receptor in mice that plays a role in energy homeostasis through multiple actions on locomotor activity, metabolism, appetite, and neuroendocrine function.

Agouti-Related Protein↗
PubMed2002

Isolation and characterization of a bioactive mannose-binding protein from the Chinese chive Allium tuberosum.

A mannose-binding protein was isolated from two different cultivars of the Chinese chive Allium tuberosum by extraction with 0.2 M NaCl, ammonium sulfate precipitation, and affinity chromatography on mannose agarose and fetuin agarose. It exhibited hemagglutinating activity toward rabbit erythrocytes. The lectin (agglutinin) was adsorbed on the mannose-agarose column, but not on the fetuin-agarose column. This A. tuberosum lectin (ATL) is unglycosylated, and not sialic acid binding. Lectins isolated from the two cultivars exhibited the same molecular mass of 25 kDa on gel filtration (Superose 12) and 12.5 kDa on SDS-polyacrylamide gel electrophoresis, indicating that they might be a dimeric protein composed of two identical subunits. The N-terminal amino acid sequence analysis of the lectin of various cultivars of A. tuberosum revealed that they were identical and showed 50%, or more, homology to the lectins from Galanthus nivalis (family Amaryllidaceae), Narcissus tazetta (family Amaryllidaceae), and Aloe arborescenes (family Liliaceae).

Allium↗
PubMed2002

Melanin-concentrating hormone receptor subtypes 1 and 2: species-specific gene expression.

To assess the contribution of potential central nervous system pathways implicated in the control of appetite regulation and energy metabolism, it is essential to first identify appropriate animal models. Melanin-concentrating hormone (MCH), a conserved cyclic neuropeptide implicated in the modulation of food intake, has been shown to bind and activate two G-protein-coupled receptors, called GPR24 and MCHR2, expressed in human brain and other tissues. Here we show that several non-human species (rat, mouse, hamster, guinea pig, and rabbit) do not have functional MCHR2 receptors, or encode a nonfunctional MCHR2 pseudogene while retaining GPR24 expression. We identified three species for further evaluation that express both MCH receptor subtypes. We cloned and functionally characterized dog, ferret, and rhesus GPR24 and MCHR2 in mammalian cells and studied their brain distribution patterns by in situ hybridization. The homology, expression profile, and functional similarity of the receptors in the dog, ferret, and rhesus to that of human support the potential use of these species as preclinical animal models in the development of therapeutic agents for obesity or other MCH-mediated disorders.

Amino Acid Sequence↗
PubMed2002

Injury induced neointima formation and its inhibition by retrovirus-mediated transfer of nitride oxide synthase gene in an in-vitro human saphenous vein culture model.

Human saphenous veins were cultured to characterize neointima formation and feasibility of gene transfer to inhibit the intimal proliferative response to injury. Mechanical injury was introduced by abrading the luminal surface of the vein patch with a sterile cotton bud. Both injured and non-injured vein patches were cultured and transduced with retroviral vectors carrying marker or therapeutic genes. After a 14-day culture, the thickness of the intimal layer of non-injured vein patches reached 90+/-28 microm at the edge and 61+/-22 microm at the center (n=29) from the original 22+/-12 microm at harvest (n=6, P=0.02). Mechanical injury to the intimal surface prior to culture resulted in an exaggerated proliferative response. The intimal thickness of injured vein patches increased from 3.4+/-1 microm right after injury to 128+/-23 microm (n=12, P<0.001) at the edge after 14-day culture. Genes were transduced efficiently into a luminal layer of cultured veins using a pseudotyped murine leukemia viral vector. Transduction of gene encoding nitric oxide synthase resulted in reduction of neointima formation to 33+/-7 microm (n=12) at the edge after 14-day culture compared to 90 microm (P<0.01) seen in untransduced non-injured vein patches. Marker gene transduction did not alter intimal proliferative response or its immunohistochemical profile. The data suggest that cultured vein can be used as a model for studying the effects of injury to blood vessels and to evaluate the effects of candidate therapeutic genes.

Cells, Cultured↗
PubMed2002

An integrative pharmacokinetic and pharmacodynamic study of the 5-HT1A receptor antagonist (S)-UH-301 in the rat.

(S)-UH-301 ((-)-(S)-5-fluoro-8-hydroxy-2-(di-n-propylamino)tetralin hydrochloride) is a well known 5-HT(1A) receptor antagonist. The present study describes the pharmacokinetic properties of (S)-UH-301 after subcutaneous administration in rats, using a newly developed HPLC-UV bioanalytical method. The relationships between (S)-UH-301 concentrations and some pharmacodynamic effects were also studied. The AUC of (S)-UH-301 in brain, but not in plasma, increased in proportion to dose (1-100 mumol/kg). However, at doses above 32 mumol/kg, peak concentrations of the drug did not increase in proportion to dose, and there was a doubling of its apparent half-life. There was a good correspondence between the time courses for the antagonism of 8-OH-DPAT-induced motor behaviours and hypothermia and the tissue concentrations of (S)-UH-301. Doses of (S)-UH-301 above 10 mumol/kg decreased 5-HT and dopamine synthesis. Therefore, a selective 5-HT(1A) antagonistic dose range of (S)-UH-301 should be 0.1-10 mumol/kg s.c., corresponding to concentrations below approximately 10 nmol/g in brain and approximately 1 nmol/ml in plasma.

5-Hydroxytryptophan↗
PubMed2002

Arginase expression in mouse embryonic development.

We are using the model of the developing mouse embryo to elucidate the pattern of arginase expression in mammalian cells in normal animals and in arginase I (AI) deficiency during development by digoxigenin-labeled RNA in situ hybridization. Our goal is to understand the regulation of these isozymes, with the expectation that this knowledge will help patients suffering from AI deficiency. We found that AI mRNA was widely and strongly expressed in the normal developing mouse embryo; in contrast, a relatively strong AII mRNA signal was found only in the intestine. In the AI knockout mouse embryo, no AII overexpression was found. These results indicated that arginases are needed in mouse embryonic development and AI is the principal form required. The strong AI expression in the peripheral nervous system suggests that the pathogenesis of the neurological retardation in AI deficiency may be conditioned by AI deficiency in the nervous system during embryonic development.

Animals↗
PubMed2002

Expression of the liver form of arginase in erythrocytes.

Arginase I (AI) has a critical function in mammalian liver as the final enzyme in the urea cycle responsible for the disposal of ammonia from protein catabolism. AI is also expressed in various extrahepatic tissues and may play a role in regulating arginine levels and in providing ornithine for biosynthetic reactions that generate various critical intermediary metabolites such as glutamate, glutamine, GABA, agmatine, polyamines, creatine, proline, and nitric oxide. AI is expressed in red blood cells (RBCs) only in humans and certain higher primates. Macaca fascicularis has been identified as an evolutionary transition species in which RBC-AI expression is co-dominantly regulated. The M. fascicularis AI gene was analyzed to understand AI expression in erythrocytes. Erythroid progenitor cells [nucleated red blood cells (nRBCs)] isolated from cord blood were utilized to demonstrate AI expression by immunocytochemical staining using anti-AI antibody. Introduction of EGFP reporter vectors into nRBC showed that the proximal 1.2 kbp upstream of the AI gene is sufficient for AI expression. Expression of a second arginase isoform, AII, in nRBCs was discovered by cDNA profiling. This contrasts with mature fetal or adult RBCs which contain only the AI protein. In addition, an alternatively spliced AI (AI(')) variant was observed from erythroid mRNA analysis with an alternative splice acceptor site located within intron 2, causing the insertion of eight additional amino acids yet retaining significant enzymatic activity.

Alternative Splicing↗
PubMed2002

Syntheses of two cytotoxic sinapyl alcohol derivatives and isolation of four new related compounds from Ligularia nelumbifolia.

Phytochemical reinvestigation on Ligularia nelumbifolia afforded four novel sinapyl alcohol analogues named nelumols B-E (1-4) and three known sinapyl alcohol derivatives (5-7). Their structures were elucidated by NMR techniques. Total syntheses of cytotoxic geranyloxy sinapyl alcohol (6) and geranyloxy sinapyl aldehyde (7) were carried out via two different paths. The 4-O-benzyl-substituted analogues (20 and 27) as well as the 4-O-(2-methylbutenyl) derivatives (34 and 35) were also synthesized. The cytotoxicities of 6 and 7 were measured using A-549, HL-60, and KB cancer cell lines.

Alcohols↗
PubMed2002

Hid, Rpr and Grim negatively regulate DIAP1 levels through distinct mechanisms.

Inhibitor of apoptosis (IAP) proteins suppress apoptosis and inhibit caspases. Several IAPs also function as ubiquitin-protein ligases. Regulators of IAP auto-ubiquitination, and thus IAP levels, have yet to be identified. Here we show that Head involution defective (Hid), Reaper (Rpr) and Grim downregulate Drosophila melanogaster IAP1 (DIAP) protein levels. Hid stimulates DIAP1 polyubiquitination and degradation. In contrast to Hid, Rpr and Grim can downregulate DIAP1 through mechanisms that do not require DIAP1 function as a ubiquitin-protein ligase. Observations with Grim suggest that one mechanism by which these proteins produce a relative decrease in DIAP1 levels is to promote a general suppression of protein translation. These observations define two mechanisms through which DIAP1 ubiquitination controls cell death: first, increased ubiquitination promotes degradation directly; second, a decrease in global protein synthesis results in a differential loss of short-lived proteins such as DIAP1. Because loss of DIAP1 is sufficient to promote caspase activation, these mechanisms should promote apoptosis.

Animals↗
PubMed2002

CordyMax Cs-4 improves glucose metabolism and increases insulin sensitivity in normal rats.

OBJECTIVE: To evaluate effects of CordyMax trade mark Cs-4, a mycelial fermentation product of Cordyceps sinensis, on improving glucose metabolism and insulin sensitivity. DESIGN: An in vivo pharmacology study. Subjects and Study Interventions: Adult Wistar rats, male and female, were given CordyMax 250 or 500 mg/kg per day or placebo for 17 days by gavage. OUTCOME MEASUREMENTS: Fasting blood glucose, fasting plasma insulin, glucose-insulin index, and oral glucose tolerance. RESULTS: Rats fed Cs-4 at either 250 or 500 mg/kg showed significantly reduced fasting blood glucose after the 17-day treatment, by 27% and 24% from baselines respectively (both p < 0.001). Examination of fasting plasma insulin demonstrated a 37% decrease in the high dose treatment groups (p = 0.012). Glucose-insulin index, an index of insulin sensitivity, increased by 10% and 17% in both 250 and 500 mg/kg groups (p = 0.008 and p = 0.0001, respectively). Oral glucose tolerance tests showed significantly improved glucose tolerance at 0.5, 1.0, and 2.0 hours after oral administration of a bolus of glucose (the area under the glucose curve: p = 0.05-0.006), but no change at 5 hours. CONCLUSION: CordyMax Cs-4 is effective in lowering basal blood glucose and plasma insulin, improving glucose metabolism by enhancing insulin sensitivity, and improving oral glucose tolerance.

Administration, Oral↗
PubMed2002

Human immunodeficiency virus type 1 recombination: rate, fidelity, and putative hot spots.

Previously, we reported that human immunodeficiency virus type 1 (HIV-1) recombines approximately two to three times per genome per replication cycle, an extremely high rate of recombination given the relatively small genome size of HIV-1. However, a recombination hot spot involving sequence of nonretroviral origin was identified in the vector system utilized, raising the possibility that this hot spot skewed the rate of recombination, and the rate of recombination observed was an overestimation. To address this issue, an HIV-1-derived vector system was used to examine the rate of recombination between autologous HIV-1 sequences after restricting replication to a single cycle in the absence of this hot spot. Viral DNA and RNA were analyzed by a combination of the heteroduplex tracking assay, restriction enzyme analysis, DNA sequencing, and reverse transcription-PCR. The results indicate that HIV-1 undergoes recombination at a minimum rate of 2.8 crossovers per genome per cycle. Again, this is a very high rate given the small size of the HIV-1 genome. The results also suggested that there might be local hot spots of recombination at different locations throughout the genome since 13 of the 33 strand transfers identified by DNA sequencing shared the same site of recombination with one or two other clones. Furthermore, identification of crossover segments also allowed examination of mutations at the point of recombination, since it has been predicted from some studies of cell-free systems that mutations may occur with a frequency of 30 to 50% at crossover junctions. However, DNA sequence analysis of crossover junctions indicated that homologous recombination during viral replication was not particularly mutagenic, indicating that there are other factors or conditions not yet reproduced in cell-free systems which contribute to fidelity during retroviral recombination.

Cell Line↗
PubMed2002

Mouse model for human arginase deficiency.

Deficiency of liver arginase (AI) causes hyperargininemia (OMIM 207800), a disorder characterized by progressive mental impairment, growth retardation, and spasticity and punctuated by sometimes fatal episodes of hyperammonemia. We constructed a knockout mouse strain carrying a nonfunctional AI gene by homologous recombination. Arginase AI knockout mice completely lacked liver arginase (AI) activity, exhibited severe symptoms of hyperammonemia, and died between postnatal days 10 and 14. During hyperammonemic crisis, plasma ammonia levels of these mice increased >10-fold compared to those for normal animals. Livers of AI-deficient animals showed hepatocyte abnormalities, including cell swelling and inclusions. Plasma amino acid analysis showed the mean arginine level in knockouts to be approximately fourfold greater than that for the wild type and threefold greater than that for heterozygotes; the mean proline level was approximately one-third and the ornithine level was one-half of the proline and ornithine levels, respectively, for wild-type or heterozygote mice--understandable biochemical consequences of arginase deficiency. Glutamic acid, citrulline, and histidine levels were about 1.5-fold higher than those seen in the phenotypically normal animals. Concentrations of the branched-chain amino acids valine, isoleucine, and leucine were 0.4 to 0.5 times the concentrations seen in phenotypically normal animals. In summary, the AI-deficient mouse duplicates several pathobiological aspects of the human condition and should prove to be a useful model for further study of the disease mechanism(s) and to explore treatment options, such as pharmaceutical administration of sodium phenylbutyrate and/or ornithine and development of gene therapy protocols.

Animals↗
PubMed2002

Neither agouti-related protein nor neuropeptide Y is critically required for the regulation of energy homeostasis in mice.

Agouti-related protein (AgRP), a neuropeptide abundantly expressed in the arcuate nucleus of the hypothalamus, potently stimulates feeding and body weight gain in rodents. AgRP is believed to exert its effects through the blockade of signaling by alpha-melanocyte-stimulating hormone at central nervous system (CNS) melanocortin-3 receptor (Mc3r) and Mc4r. We generated AgRP-deficient (Agrp(-/-)) mice to examine the physiological role of AgRP. Agrp(-/-) mice are viable and exhibit normal locomotor activity, growth rates, body composition, and food intake. Additionally, Agrp(-/-) mice display normal responses to starvation, diet-induced obesity, and the administration of exogenous leptin or neuropeptide Y (NPY). In situ hybridization failed to detect altered CNS expression levels for proopiomelanocortin, Mc3r, Mc4r, or NPY mRNAs in Agrp(-/-) mice. As AgRP and the orexigenic peptide NPY are coexpressed in neurons of the arcuate nucleus, we generated AgRP and NPY double-knockout (Agrp(-/-);Npy(-/-)) mice to determine whether NPY or AgRP plays a compensatory role in Agrp(-/-) or NPY-deficient (Npy(-/-)) mice, respectively. Similarly to mice deficient in either AgRP or NPY, Agrp(-/-);Npy(-/-) mice suffer no obvious feeding or body weight deficits and maintain a normal response to starvation. Our results demonstrate that neither AgRP nor NPY is a critically required orexigenic factor, suggesting that other pathways capable of regulating energy homeostasis can compensate for the loss of both AgRP and NPY.

Agouti-Related Protein↗
PubMed2002

[Inhibition of K562 cell growth and tumor angiogenesis in nude mice by antisense VEGF(121) cDNA transfection].

OBJECTIVE: To investigate the effect of antisense vascular endothelial growth factor (VEGF)(121) cDNA transfection on the growth of K562 cells in nude mice. METHODS: K562 cells transfected with the antisense (AS) or sense (S) VEGF(121) cDNA, and the vector (V, pcDNA3) alone were transplanted subcutaneously into nude mice and the growth of the transfected cells in vivo was investigated. The effects of transfected K562 cells on human bone marrow endothelial cells (BMEC) were analyzed by MTT assay, the microvessel density (MVD) in tumor mass by vWF immunohistochemistry stain. RESULTS: K562/V tumor grew more slowly [(207.5 +/- 192.9) mm(3) vs (445.0 +/- 150.9) mm(3), P < 0.05] and K562/S tumor more rapidly than K562/V tumor did [(1 174.6 +/- 508.7)/mm(3) vs (445.0 +/- 150.9) mm(3), P < 0.01]. K562/S cell culture supernatant was more strongly in promoting the proliferation of BMEC than K562/V supernatant did, but K562/AS supernatant resulted in a marked decrease of the promoting effect as compared with K562/V's. The MVDs in K562/AS, K562/S, and K562/V tumors were [(11.0 +/- 7.6)/0.72 mm(2) vs (50.8 +/- 11.7)/0.72 mm(2) vs (18.9 +/- 7.0)/0.72 mm(2)], respectively. CONCLUSIONS: Antisense VEGF(121) cDNA transfected K562 cells show growth retardation in transplanted nude mice, decrease of tumor MVD, and decrease of promoting BMEC proliferation capacity.

Animals↗
PubMed2002

Using point of service clinical documentation to reduce variability in charge capture.

Data collected at bedside to document patient care can also be used to generate an itemized summary of charges including activity-based clinician charges. This approach becomes advantageous when the charge capture operation is transparent to the clinician who would otherwise have to review the care documentation, recall the appropriate charging rules, and exercise discretion in capturing charges. Documented procedures and supplies convert directly into patient charge rules. Documented patient care is more difficult to translate into activity-based charges because nursing care can vary in intensity and duration depending on the patient's needs. The problem can be overcome by embedding time or data-driven logic into the charging rules. Using this approach in the labor and delivery units of 7 IHC hospitals (114 beds), we generated consistent charge summaries. We improved the accuracy of patient charges from 65% to over 98% of our charge summaries having no missed charges.

Algorithms↗