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Biomedical subjects

Y Huang

Publications and source records attributed to Y Huang.

At least 343 records · Page 19Linked to original sources
PubMed2000

Petrochemical exposure and menstrual disturbances.

BACKGROUND: An exploratory, cross-sectional retrospective study was conducted to examine the effects of benzene exposure on menstrual problems. METHODS: The study was based on a survey administered to over 3,000 women who worked in a large petrochemical company in Beijing, China. An abnormal menstrual cycle length (AMCL), defined as an average menstrual cycle length of greater than 35 days or less than 21 days, is the major outcome of interest. RESULTS: After 7 years of benzene exposure, the adjusted odds ratio of having AMCL for each additional 5 years of exposure was 1.71 (95% CI 1.27-2.31). Feeling stressed at work was also an important predictor. CONCLUSIONS: This study suggests a significant association of benzene exposure and perceived stress with menstrual disturbance. A prospective study is needed to confirm this finding.

Adult↗
PubMed2000

Proper developmental control of human globin genes reproduced by transgenic mice containing a 160-kb BAC carrying the human beta-globin locus.

Four independent bacterial artificial chromosome (BAC) clones containing the human Beta-globin gene locus were obtained from a human genomic BAC library. A 160-kb clone (186D7) carrying the entire human Beta-globin locus including the Beta-globin gene family, locus control region (LCR), and 3' regulatory elements was used to transform mice. Four transgenic lines were generated by microinjecting the purified BAC DNA into the fertilized eggs. RNase protection analysis showed that the expression of human Beta-globin genes is tissue- and developmental stage-specific and the expression level is similar among the three independent transgenic lines which carry the entire human Beta-globin locus; however, no Beta-globin gene expression was detected in the transgenic mice lacking the LCR region. The results suggest that the transgenic mouse model system that we have produced and that uses BAC to study the complex human Beta-globin gene cluster is stable and reproducible. Our results also indicate that some newly characterized HSs upstream from the LCR appear not to play an important role in globin gene expression and switching, while the traditional LCR can ensure correct human Beta-globin gene expression in transgenic mice. The BAC-mediated transgenic system can be used for further studies to determine which kinds of cis-acting elements are included in regulating the developmental timing and the level of human Beta-globin gene expression.

Animals↗
PubMed2000

Uptake and interconversion of fluorescent lipid analogs in the protozoan parasite, Perkinsus marinus, of the oyster, Crassostrea virginica.

Uptake, distribution, and interconversion of fluorescent lipid analogs (phosphatidylcholine, PC; cholesteryl ester, CHE; phosphatidylethanolamine, PE; palmitic acid, C16; sphingomyelin, SM) by the two life stages, meront and prezoosporangium, of the oyster protozoan parasite, Perkinsus marinus, were investigated. Class composition of these two life stages and lipid contents in meront cells were also examined. Both meronts and prezoosporangia incorporated and modified fluorescent lipids from the medium, but their metabolic modes differ to some extent. Results revealed that among the tested analogs, neutral lipid components (CHE and C16) were incorporated to a greater degree than the phospholipids (PC, PE, and SM). HPLC analysis of meront lipids showed that while the majority of the incorporated PC, CHE, and PE remained as parent compounds, most of the incorporated C16 was in triacylglycerol (TAG) and SM was in ceramide and free fatty acids. The cellular distribution of fluorescent labels varied with lipid analogs and the extent of their metabolism by the parasite. Fluorescence distribution was primarily in cytoplasmic lipid droplets of both life stages after 24 h incubation with PC. After 24 h incubation with SM, fluorescence appeared in the membrane and cytosol. Total lipid contents in meront cultures increased during proliferation and TAG accounted for most of the increased total lipids. Since total lipid content per meront cell did not increase until the day of culture termination, the lipid increase in the meront culture was mainly a result of increased cell numbers. Both life stages contain relatively high levels of phospholipids, 53.8% in 8-day-old meronts and 39.4% in prezoosporangia. PC was the predominant phospholipid.

Animals↗
PubMed2000

Cross-regulation of intracellular cGMP and cAMP in cultured human corpus cavernosum smooth muscle cells.

The goal of this study was to assess the potential cross-regulation of cyclic nucleotides in human corpus cavernosum (HCC). Incubation of primary cultures of HCC smooth muscle cells with either the NO donor sodium nitroprusside (SNP, 10 microM) or the phosphodiesterase type 5 (PDE 5) inhibitor sildenafil (50 nM) produced little or no changes in the intracellular cGMP levels. Incubation with both SNP and sildenafil produced marked increases in cGMP. Interestingly, incubation of cells with 10 microM of forskolin or PGE(1) produced significant enhancement of cGMP accumulation. These increases were not further enhanced by the addition of SNP and sildenafil. Kinetic analyses of cGMP hydrolysis by PDE 5 showed that high concentrations of cAMP reversibly inhibited the enzyme with a K(i) of 258 +/- 54 microM. The increase in cGMP levels in response to cAMP generating agents is not due to assay artifact since cAMP did not cross-react with cGMP antibody. Our data suggest that cAMP up-regulates intracellular levels of cGMP, in part, by inhibition of PDE 5. We also noted that cGMP down-regulates cAMP synthesis via a mechanism requiring G-protein coupling of adenylyl cyclase. These observations may have important implications in the utility of pharmacotherapeutic agents targeting cyclic nucleotide metabolism for the treatment of erectile dysfunction.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2000

Phylogenetic relationships of north American field crickets inferred from mitochondrial DNA data.

A well-supported molecular phylogeny for North American Gryllus species based on a combined data set of mitochondrial (mt) DNA is presented. A total of 26 individuals representing 13 populations of 11 species of the genus Gryllus and 4 individuals of two outgroup species, Teleogryllus oceanicus and Acheta domestica, were sampled in this study. The complete cytochrome b gene (1036 bp) and a 500-bp fragment of the 16S rRNA gene were sequenced for each individual. Since results from separate analyses of the cytochrome b and 16S data sets, as well as a previously published mtDNA restriction-site data set, were not conflicting, all data were combined for phylogenetic analyses. The clade of European Gryllus was clearly separated from the North American clade. The amount of sequence divergence between these clades was significantly greater than within the clades, suggesting a basal drift-vicariant event in the genus. This is the first phylogenetic analysis of North American Gryllus that includes western species. Four well-supported groups were identified but their relationships showed no clear east-west structure. Our phylogeny supports the recent reassignment of G. integer Scudder 1901 from Texas to G. texensis Cade and Otte 2000. The evolution of cricket song and life cycle is discussed using the new phylogenetic framework.

Animals↗
PubMed2000

Rejection of disseminated metastases of colon carcinoma by synergism of IL-12 gene therapy and 4-1BB costimulation.

In an orthotopic model of metastatic colon carcinoma established in the liver of mice, we have previously shown that the natural killer (NK) cells were the major effectors after intratumoral delivery of a recombinant adenovirus expressing the murine IL-12 gene. However, tumor cure and long-term survival were achieved only in a minority of animals. In the present study, we generated an effective antitumoral CD8(+ ) T-cell response by the combination of IL-12 gene therapy and systemic delivery of an agonistic monoclonal antibody against 4-1BB, a costimulatory molecule expressed on activated T cells. In the IL-12 plus anti-4-1BB combination treatment, the effective dose of IL-12 could even be reduced even up to 18-fold and still achieved a better efficacy than the maximal dose of either treatment alone. We further demonstrate that the innate and the adaptive antitumoral immune responses were synergistic, as animals bearing hepatic as well as multiple pulmonary metastases were quantitatively cured of their diseases after IL-12 gene therapy + anti-4-1BB combination treatment. Both NK and CD8(+) T cells were necessary in maintaining the long-term antitumor immunity, as depletion of either cell type in the cured animals abolished their abilities to reject tumor cells implanted at distal sites. These results indicate that synergism between innate and adaptive immune responses may be effectively exploited to treat patients with metastatic diseases.

4-1BB Ligand↗
PubMed2000

Endogenous apolipoprotein E modulates cholesterol efflux and cholesteryl ester hydrolysis mediated by high-density lipoprotein-3 and lipid-free apolipoproteins in mouse peritoneal macrophages.

We investigated the effect of endogenous apolipoprotein (apo) E synthesis in mouse peritoneal macrophages on cholesterol efflux and intracellular cholesteryl ester hydrolysis mediated by high-density lipoprotein-3 (HDL3) and lipid-free apolipoproteins (apo). After loading with acetylated LDL (acLDL) peritoneal macrophages from wild-type (apoE(+/+)) and apoE-deficient (apoE(-/-)) mice were incubated with medium alone or with liposomes, HDL3, lipid-free apoA-I, or lipid-free apoE3. Cholesterol and cholesteryl esters in the cells and culture media were quantified by HPLC. Incubation of apoE(+/+) or apoE(-/-) macrophages for 18 h with medium alone or with liposomes did not cause significant changes in cellular cholesterol. Addition of HDL3, apoA-I, or apoE3 to the medium led to significant cholesterol efflux, which was less efficient in apoE(-/-) macrophages than in apoE(+/+) macrophages. HDL and lipid-free apolipoproteins were more effective in reducing the cellular content of cholesteryl esters of apoE(+/+) macrophages than of apoE(-/-) macrophages, suggesting that endogenous apoE stimulates cholesteryl ester hydrolysis. The difference in the mass of cholesteryl esters was more pronounced for cholesteryl arachidonate and linoleate than for cholesteryl oleate or palmitate. Furthermore, in [(14)C]arachidonate labeling experiments cholesterol arachidonate hydrolysis was higher in apoE(+/+) macrophages than in apoE(-/-) macrophages in the presence of cholesterol efflux mediated by HDL3 or apoA-I. In contrast, in the absence of cholesterol efflux cholesterol arachidonate synthesis was higher in apoE(+/+) macrophages than in apoE-/- macrophages. Taken together, our data suggest that endogenous apoE stimulates cholesterol efflux and intracellular cholesteryl ester hydrolysis mediated by HDL3 and lipid-free apolipoproteins in mouse peritoneal macrophages. This may contribute to the antiatherogenic effect of apoE.

Animals↗
PubMed2000

Abolition of endothelium-dependent relaxation in the rat aorta by tetraoctylammonium ions.

Quaternary ammonium ions are common pharmacological probes used to study the kinetic properties of K+ channels in smooth muscle cells. On the other hand, some ammonium compounds cause vasorelaxation through unknown mechanisms. The main aim of this study was to examine a unique role of endothelium in the vascular response to tetraoctylammonium ions (TOA+) in the isolated rat aorta. Changes in contractile force were measured by force transducers and total tissue content of cGMP was measured by radioimmunoassay. Endothelial cytosolic Ca2+ ([Ca2+]i) was assessed by laser scanning confocal microscopy.

Acetylcholine↗
PubMed2000

A flow injection chemiluminescence system for the determination of isoniazid.

A chemiluminescence (CL) flow system is described for the determination of isoniazid based on its enhancement on the chemiluminescence (CL) emission produced upon mixing a hexacyanoferrate(III) solution with an alkaline luminol solution. The system responds linearly to isoniazid concentration in the range 0-1 mg/L with a detection limit (3sigma) of 0.03 microg/L, relative standard deviation (RSD) of 1.2% for 0.1 mg/L isoniazid (n = 11). The system has been successfully applied to the determination of isoniazid in pharmaceutical preparations.

Antitubercular Agents↗
PubMed2000

Ventricular remodeling after cardiomyoplasty in heart failure sheep: passive and dynamic effects.

BACKGROUND: Recent reports claim that cardiomyoplasty (CMP) has a girdling effect on the left ventricle, to prevent dilatation and functional deterioration, but the mechanism of its long-term effects on the native heart is not known. We compared the relative role of CMP's active squeezing and passive girdling in chronically failing hearts. METHODS: After induction of stable heart failure (left ventricular ejection fraction = 27% +/- 7%) by staged coronary microembolization, CMP was performed in 11 of 18 sheep. After 8 weeks pacing training of the latissimus dorsi muscle (LDM), cardiac assist was begun with 1:2 synchronous bursts in 6 sheep (d-CMP, n = 6), and the LDM in the passive group (p-CMP, n = 5) remained unstimulated. Four (base line) and 30 weeks after induction of heart failure, the pressure-volume relationship was derived. RESULTS: After 30 weeks in d-CMP the slope (Emax) of the end-systolic pressure-volume relationship increased by 66% +/- 55% (p < 0.05) and external work efficiency by 48% +/- 41% (p < 0.01). In the passive CMP and control groups, slope and external work efficiency were unchanged. Conversely, left ventricular end-diastolic volume decreased (-14% +/- 12%, p < 0.05) in the dynamic CMP group compared with a static course in the passive CMP group (3% +/- 10%, p > 0.05) and an increase (18% +/- 15%, p < 0.05) in controls. CONCLUSIONS: Dynamic CMP improved native heart's contractility and external work efficiency. In addition, whereas passive CMP has simply a girdling effect, dynamic CMP also induces reverse left ventricular chamber remodeling.

Animals↗
PubMed2000

Differential analysis of human leukocytes by dielectrophoretic field-flow-fractionation.

The differential analysis of human leukocytes has many important biological and medical applications. In this work, dielectrophoretic field-flow-fractionation (DEP-FFF), a cell-separation technique that exploits the differences in the density and dielectric properties of cells, was used to separate the mixtures of the major human leukocyte subpopulations (T- and B-lymphocytes, monocytes, and granulocytes). The separation was conducted in a thin chamber equipped with an array of microfabricated interdigitated electrodes on the bottom surface, and the separation performance was characterized by on-line flow cytometry. To investigate optimal separation conditions for different leukocyte mixtures, elution fractograms at various DEP field frequencies were obtained for each leukocyte subtype. With appropriately chosen conditions, high separation performance was achieved in separating T- (or B-) lymphocytes from monocytes, T- (or B-) lymphocytes from granulocytes, and monocytes from granulocytes. DEP-FFF does not involve cell-labeling or cell-modification step, and provides a new approach to hematological analysis.

B-Lymphocytes↗
PubMed2000

Nitric oxide mediated endothelium-dependent relaxation induced by glibenclamide in rat isolated aorta.

OBJECTIVES: Glibenclamide was found to act as both a selective ATP-sensitive K(+) channel blocker and a vasorelaxant. The exact mechanisms underlying the relaxant effect of glibenclamide are unknown. The present study was designed to examine the role of endothelium/nitric oxide in glibenclamide-induced relaxation in rat isolated aortic rings. METHODS: A combination of experimental approaches including isometric force measurement, cell culture, Ca(2+) fluorescence measurement and radioimmunoassay were used to examine the vascular effect of glibenclamide. RESULTS: Glibenclamide induced a concentration-dependent relaxation more effectively in rings with endothelium (IC(50) of 32+/-4 microM) than those without endothelium (IC(50) of 365+/-29 microM). Incubation with N(G)-nitro-L-arginine methyl ester (L-NAME) or methylene blue significantly reduced and L-arginine (3 mM) potentiated the glibenclamide-induced relaxation. L-Arginine (3 mM) partially antagonized the effect of L-NAME. Glibenclamide (100 microM) increased the cyclic GMP content of endothelium-intact tissues. Pretreatment with N(G)-nitro-L-arginine (100 microM) or removal of endothelium significantly suppressed the effect of glibenclamide on cyclic GMP production. Glibenclamide elevated the intracellular Ca(2+) levels in cultured rat aortic endothelial cells. Glibenclamide also inhibited the endothelium-independent contractile response to 60 mM K(+) (IC(50) of 137+/-21 microM) and caused a rightward shift in the concentration-contraction curve for CaCl(2). Besides, glibenclamide inhibited phorbol-12,13-diacetate (1 microM)-induced contraction in Ca(2+)-free Krebs solution. CONCLUSION: These results indicate that glibenclamide-induced endothelium-dependent relaxation involves nitric oxide release and this effect may be related to its stimulatory effect on endothelial Ca(2+) levels. However, the glibenclamide-induced endothelium-independent relaxation may be associated with its inhibitory effect on Ca(2+) influx through Ca(2+) channels and on the protein kinase C-mediated contractile mechanism.

Animals↗
PubMed2000

Endothelium-dependent relaxation by tetraoctylammonium ions in rat isolated aortic rings.

Quaternary ammonium ions are common pharmacological blockers of K+ channels. This study examined the vasorelaxant effect of tetraoctylammonium ions (TOA+) in rat isolated aortic rings. TOA+ caused a concentration-dependent transient relaxation of endothelium-intact tissues. Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME, 3x10(-5) M) or methylene blue (3 x 10(-6) M) or removal of the endothelium abolished the TOA+-induced relaxation. L-arginine (10(-3) M ) partially antagonized the effect of L-NAME. Glibenclamide (3x10(-6) M), charybdotoxin (CTX, 10(-7) M), indomethacin (10(-5) M), or atropine (3x10(-6) M) had no effect. Both TOA+ (10(-5) M)- and acetylcholine (ACh, 10(-5) M)-induced increase in tissue content of cyclic GMP was significantly attenuated by NG-nitro-L-arginine (L-NNA, 10(-4) M) and abolished in endothelium-denuded arteries. These results indicate that TOA+ induced endothelium-dependent relaxation which is likely mediated through nitric oxide but not other endothelium-derived factors. This relaxant action seems unique for TOA+ since other quaternary ammonium ions did not cause nitric oxide-dependent relaxation.

Animals↗
PubMed2000

Deletion of 3'-CBFB gene in association with an inversion (16)(p13q22) and a loss of the Y chromosome in a 2-year-Old child with acute myelogenous leukemia-M4.

Inversion 16(p13q22) is most commonly associated with acute myelomonocytic leukemia with abnormal eosinophils (M4). In association with this inversion, a proximal deletion at the 16p13 primary arm breakpoint occurs in 20% of cases. We report on a first case of inversion 16 with a distal deletion at the primary arm breakpoint 16q22, detected by using the fluorescent-labeled dual-color probe CBFB.

Child, Preschool↗
PubMed2000

Studies on anti-complementary activity of extracts and isolated flavones from Ligustrum vulgare and Phillyrea latifolia leaves (Oleaceae).

Polar fractions and flavones isolated from methanolic extracts of the leaves of Ligustrum vulgare and Phillyrea latifolia (Oleaceae), whose popular use as an anti-inflammatory is well-known in Mediterranean historical medicine and ethnobotany, showed significant in vitro complement inhibiting effect on the classical pathway of the complement system. Among the isolated flavonoidic structures, apigenin-7-O-glucoside, apigenin-7-O-rutinoside, luteolin-4'-O-glucoside, luteolin-7-O-glucoside and ligustroflavone presented remarkable activity.

Apigenin↗
PubMed2000

Chin-Shan Community Cardiovascular Cohort in Taiwan-baseline data and five-year follow-up morbidity and mortality.

A cohort consisting of 3602 residents (82.8% of the target population) aged 35 years and older was established in 1990 in the Chin-Shan Community, a suburb 20 miles outside of metropolitan Taipei, Taiwan. The long-term objective was to investigate the prospective impact on cardiovascular health in a society undergoing transition from a developing to a developed nation. This article presents the study design, selected baseline risk factors of cardiovascular diseases (CVD), and CVD events at the 5-year follow-up evaluation with an emphasis on sociodemographic differences. The multivariate logistic regression analyses revealed that white-collar individuals were more likely than blue-collar workers to have dyslipidemia including high-density lipoprotein cholesterol (HDL-C) levels <35 mg/dl [odds ratio (OR) = 1.7, 95% confidence interval (CI) = 1.2-2.4] and low-density lipoprotein cholesterol (LDL-C) levels >/=160 mg/dl (OR = 1.3, 95% CI = 1.0-1.7). However, they were at slightly lower risk for stroke and CVD/sudden death, and at moderately higher risk for coronary artery disease and diabetes, although both these trends were not significant. Men were more likely than women to have HDL-C levels <35 mg/dl (OR = 1.8, 95% CI = 1.4-2.2), but they were less likely to have LDL-C levels >/=160 mg/dl (OR = 0.7, 95% CI = 0.6-0.8). The risk of CVD/sudden death was higher for men than for women during the follow-up period (OR = 1.9, 95% CI = 1.3-2.9). This could be due to risk factors such as a much higher prevalence of tobacco (61.9% vs. 4.5%) and alcohol (43.7% vs. 6.4%) use in men. In conclusion, individuals of higher socioeconomic status have a higher prevalence of dyslipidemia but slightly lower 5-year incidence of CVD events.

Adult↗
PubMed2000

Interaction between flavonoids and alpha-tocopherol in human low density lipoprotein.

Oxidative modification of low density lipoprotein (LDL) may play an important role in the development of atherosclerosis. Alpha-tocopherol functions as a major antioxidant in human LDL. The present study was to test whether four natural flavonoids (kempferol, morin, myricetin, and quercetin) would protect or regenerate alpha-tocopherol in human LDL. The oxidation of LDL incubated in sodium phosphate buffer (pH 7.4, 10 mM) was initiated by addition of either 5.0 mM CuSO(4) at 37 degrees C or 1.0 mM of 2,2'-azo-bis (2-amidinopropane) dihydrochloride (AAPH) at 40 degrees C. It was found that alpha-tocopherol was completely depleted within 1 hour. Under the same experimental conditions, all four flavonoids demonstrated a dose-dependent protecting activity to alpha-tocopherol in LDL at the concentration ranging from 1 to 20microM. All flavonoids showed a varying protective activity against depletion of alpha-tocopherol in LDL, with kempherol and morin being less effective than myricetin and quercetin. The addition of flavonoids to the incubation mixture after 5 minutes demonstrated a significant regeneration of alpha-tocopherol in human LDL. The protective activity of four flavonoids to LDL is related to the number and location of hydroxyl groups in the B ring as well as the stability in sodium phosphate buffer.

Journal Article↗