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Biomedical subjects

N Huang

Publications and source records attributed to N Huang.

At least 73 records · Page 4Linked to original sources
PubMed1998

Reduced noradrenergic tone to the hypothalamic paraventricular nucleus contributes to the stress hyporesponsiveness of lactation.

Lactation in mammals is accompanied by a marked decrease in stress responsiveness that we previously attributed, in part, to a reduction in noradrenergic (NA) innervation of hypothalamic paraventricular nucleus (PVN) neurons controlling neuroendocrine stress responses. In the present study, we compared in-vivo PVN catecholamine secretion by microdialysis between nonlactating and lactating females and tested the effects of NA alpha-1 and alpha-2 receptor antagonists (corynanthine and idazoxan, respectively) on the acute stress response of lactating and virgin female rats. To determine if PVN alpha-adrenoreceptor density, affinity, or synthesis, changes as a function of lactation, we performed receptor autoradiography, Scatchard analysis and in situ hybridization of alpha-adrenoreceptors. Densitometric analysis of the alpha-adrenoreceptors in the supraoptic nucleus (SON) was used to evaluate changes in magnocellular neurons. Endogenous PVN norepinephrine release under basal conditions was lower in lactating females than in females who had their pups removed for 2 days, and microdialysate concentrations of adrenaline and MHPG were attenuated in lactating females. Alpha-2 adrenoreceptor density in the PVN showed a significant decrease from lactation day 3 to lactation days 10-12 and a reduction to 40% of virgin controls on days 10-20 of lactation. A similar pattern was observed for the SON. The affinity of hypothalamic alpha-2 adrenoreceptors was reduced as a function of lactation. Alpha-1 adrenoreceptor density in the PVN and in the hypothalamus rose as a function of lactation, although the affinity of these receptors was not altered. In contrast, alpha-1D adrenoreceptor subtype mRNA expression in the PVN decreased in middle lactating females (day 10) compared to virgins. Intracerebroventricular (i.c.v.) application of idazoxan, significantly increased the ACTH response to swim stress in virgin females, but had the opposite effect in lactating females. In contrast, i.c.v. corynanthine treatment significantly decreased the ACTH response in virgins, but not in lactating females. Overall, these data suggest that the secretion of NA in the PVN is reduced during lactation, and that the ability of PVN parvocellular neurons to respond to changes in synaptic NA levels (i.e. after stress) is also altered.

Adrenergic alpha-Antagonists↗
PubMed1998

A high-density rice genetic linkage map with 2275 markers using a single F2 population.

A 2275-marker genetic map of rice (Oryza sativa L.) covering 1521.6 cM in the Kosambi function has been constructed using 186 F2 plants from a single cross between the japonica variety Nipponbare and the indica variety Kasalath. The map provides the most detailed and informative genetic map of any plant. Centromere locations on 12 linkage groups were determined by dosage analysis of secondary and telotrisomics using > 130 DNA markers located on respective chromosome arms. A limited influence on meiotic recombination inhibition by the centromere in the genetic map was discussed. The main sources of the markers in this map were expressed sequence tag (EST) clones from Nipponbare callus, root, and shoot libraries. We mapped 1455 loci using ESTs; 615 of these loci showed significant similarities to known genes, including single-copy genes, family genes, and isozyme genes. The high-resolution genetic map permitted us to characterize meiotic recombinations in the whole genome. Positive interference of meiotic recombination was detected both by the distribution of recombination number per each chromosome and by the distribution of double crossover interval lengths.

Chromosome Mapping↗
PubMed1998

Development, validation, and interlaboratory comparison of an HMG-CoA reductase inhibition assay for quantitation of atorvastatin in plasma matrices.

An HMG-CoA reductase inhibition assay was developed and validated for quantitation of atorvastatin in human, dog, rat, and mouse plasma. Atorvastatin was isolated from plasma by protein precipitation. Rat-liver microsomes were used to provide the reductase enzyme. The method was validated by assaying calibration standards and quality controls in triplicate on each of the 3 days. A customized computer program was used for data calculation. Quantitation of the assay ranged from 0.36 to 16 ng/ml of atorvastatin in different plasma matrices. Assay precision and accuracy, based on the coefficient of variation and percent relative error, respectively, of quality controls were 10.4% to 14.5% and within +/- 6.25% in human; 4.89% to 10.6% (+/- 8.13%) in dog; 2.68% to 8.62% (+/- 5.00%) in rat; and 3.68% to 8.96% (+/- 5.38%) in mouse plasma. The method has been applied to pharmacokinetic studies of atorvastatin in human and toxicokinetic studies in dog, rat, and mouse after atorvastatin administration. Atorvastatin equivalent concentrations in a set of plasma samples from subjects receiving single and multiple doses of atorvastatin were determined by validated HMG-CoA reductase inhibition assays at four different laboratories. Results were compared using linear regression and concordance correlation statistical procedures. Good agreements among these data indicated that results from different laboratories with the same validated method can be used interchangeably.

Animals↗
PubMed1998

[Isolation of antibacterial polypeptides of human cervical mucus].

The acid-soluble extract of human cervical mucus was obtained by solving mucus with 5% acetic acid in the presence of protease inhibitor. The antibacterial activity of the acid-soluble extract was analyzed by gel overlay technique. The result showed that two protein bands which were designated human cervical protein-1 (Hcp-1), human cervical protein-2(Hcp-2) were potently antibacterial against E. coli 25922 and S. aureus 25923. Tricine-SDS-PAGE analysis indicated that Hcp-1, Hcp-2 actually contained three and four protein bands respectively. The molecular weights of Hcp-1 were 6.7 kd, 10 kd, 15.4 kd; these of Hcp-2 were 4.4 kd, 6.7 kd, 9 kd, 15.4 kd. Our studies suggested that human cervical mucosa might secrete some currently-unknown antibacterial polypeptides which play an important role in the cervical defense against infection.

Anti-Bacterial Agents↗
PubMed1998

[Partially purified antibacterial polypeptides from granules of human large granular lymphocytes].

This was a study on the antibacterial activity of human large granular lymphocytes (LGL). In our previous work, three antibacterial fractions named HLP-1, HLP-2 and HLP-3 had been identified from the acid-soluble extracts of the granules of LGL by using the gel overlay technique. The present study demonstrated that HLP-1, HLP-2 and HLP-3 separated by preparative acid-urea polyacrylamide gel electrophoresis were potently bactericidal against E. coli MI-35P, S. aureus ATCC 25923, P. aeruginosa ATCC 27853 when tested for their antibacteiral activities by using both agarose radial diffusion assay and gel overlay technique. SDS-PAGE analysis showed that the HLP-3 was almost purified with the molecular weight of 7 kd. The HLP-1 and HLP-2 were more complex, and the ranges of molecular weight were 5.6-13 kd and 5.6-8.8 kd respectively. Our study suggests that the granules of human LGL might contain some low molecular weight antibiotic peptides which play an important role in human innate immunity.

Anti-Bacterial Agents↗
PubMed1998

[Effect of turmeric volatile oil on the respiratory tract].

OBJECTIVE: Researching the effect of turmeric volatile oil on functions of the respiratory tract. METHOD: The action of turmeric volatile oil on sputum removing, cough and asthma relieving was observed by vapour inhaling. RESULT: The volatile oil is significantly active in removing sputum, relieving cough and preventing asthma. CONCLUSION: Turmeric volatile oil may be an efficacious drug for the treatment of respiratory diseases.

Animals↗
PubMed1998

[Studies on the structure-activity relationship of retinoids--Hansch analysis and 3D-OSAR studies on specific ligands of retinoid x receptor].

Retinoids (Vitamin A, its metabolites and synthetic analogues) play important roles in a variety of biological processes, including cellular differentiation, proliferation and apoptosis. The many diverse actions of retinoids attribute to the ability of regulating transcription of different target genes through activation of multiple retinoid nuclear receptors (RAR of RXR). So, retinoids with selective binding ability to specific receptor may not only have improved therapeutic indices, but may also be invaluable for elucidating the molecular mechanism of retinoidal transcriptional activation. Based on the two dimensional and three dimensional quantitative structure-activity relationships of specific ligands of RXR, we carried out mimesis of environment of ligands interacting with their receptor and, to some extent, mapping the topological and physico-chemical characteristics of receptor. The knowledge of the QSAR study will offer detailed molecular information for design, synthesis and biological evaluation in drug research and development.

Alitretinoin↗
PubMed1997

Comparative molecular field analysis of a series of paclitaxel analogues.

A series of 94 paclitaxel analogues exhibiting antitumor activity by promoting the assembly of microtubules and inhibiting the disassembly process of microtubules to tubulin were investigated using the comparative molecular field analysis (CoMFA) method. These compounds belonging to 10 structural classes were randomly divided into a training set of 80 compounds and a test set of 14 compounds. Since the three-dimension structure of ligand--receptor complex is unknown, from X-ray and NMR data we rationally selected the three-dimension structure of paclitaxel in a polar solution as the active conformation and starting structure for molecule modeling, the other molecules were aligned using this molecule model as the template. The most optimal CoMFA yielded a two-components model, with significant cross-validation r2cv of 0.640 and conventional r2 of 0.868. The predictive ability of training set model was tested on the test set of 14 compounds. The tests not only revealed the robustness of the CoMFA model but demonstrated that for our model r2pred based on the mean activity of test set compounds can accurately estimate external predictivity but r2pred based on the mean activity of training set compounds overestimated the model. The CoMFA model explained why the activity of taxoid is sensitive to the stereochemistry of the atoms at C-2' and C-3' positions and the presence of hydroxyl group at C-2' position. The other factors affecting activity were also elucidated according to standard coefficient contour maps of steric and electrostatic fields derived from the CoMFA model.

Antineoplastic Agents↗
PubMed1997

Chromosomal regions associated with segregation distortion of molecular markers in F2, backcross, doubled haploid, and recombinant inbred populations in rice (Oryza sativa L.).

Chromosomal regions associated with marker segregation distortion in rice were compared based on six molecular linkage maps. Mapping populations were derived from one interspecific backcross and five inter-subspecific (indica/japonica) crosses, including two F2 populations, two doubled haploid (DH) populations, and one recombinant inbred (RI) population. Mapping data for each population consisted of 129-629 markers. Segregation distortion was determined based on chi-square analysis (P < 0.01) and was observed at 6.8-31.8%, of the mapped marker loci. Marker loci associated with skewed allele frequencies were distributed on all 12 chromosomes. Distortion in eight chromosomal regions bracketed previously identified gametophyte (ga) or sterility genes (S). Distortion in three other chromosomal regions was found only in DH populations, where japonica alleles were over-represented, suggesting that loci in these regions may be associated with preferential regeneration of japonica genotypes during anther culture. Three additional clusters of skewed markers were observed in more than one population in regions where no gametophytic or sterility loci have previously been reported. A total of 17 segregation distortion loci may be postulated based on this study and their locations in the rice genome were estimated.

Alleles↗
PubMed1997

Oct-1 and CCAAT/enhancer-binding protein (C/EBP) bind to overlapping elements within the interleukin-8 promoter. The role of Oct-1 as a transcriptional repressor.

Interleukin-8 (IL-8), a potent neutrophil chemoattractant, can be expressed at high levels by many different cell types after immune stimulation. In contrast, expression of IL-8 in these same cells is virtually absent in the unstimulated state, demonstrating the tight regulation of the IL-8 gene. Although much is known about how this gene is transcriptionally activated after immune stimulation, little is known about the regulation of the IL-8 promoter in the absence of immune activation. In this study we examine how the IL-8 promoter is transcriptionally regulated in the uninduced state and how these mechanisms are altered in response to immune stimulation by IL-1beta. Electrophoretic mobility shift assay and transfection studies show that the IL-8 promoter is transcriptionally regulated by both positive and negative elements. Although the nuclear factor-kappaB (NFkappaB) element regulates only inducible activity of the IL-8 promoter in response to stimulation with IL-1beta, the AP-1 and CCAAT/Enhancer-binding Protein (C/EBP) elements influence both basal and inducible activities. In contrast to these three positive regulatory elements, the binding of the ubiquitously expressed POU-homeodomain transcription factor, Oct-1, strongly represses transcriptional activity of the IL-8 promoter by binding independently to an element overlapping that of C/EBP.

Base Sequence↗
PubMed1997

Inhibition of IL-8 gene expression in Caco-2 cells by compounds which induce histone hyperacetylation.

Ulcerative colitis, an idiopathic inflammatory disease of the colonic mucosa, can be effectively treated by enemas containing short chain fatty acids (SCFA) such as butyrate, propionate, and acetate. The molecular mechanisms that lead to this response have not been well characterized. It is well known that intestinal inflammation leads to an alteration in patterns of epithelial differentiation with an increase in epithelial proliferation and an expansion of cell populations in an undifferentiated state. SCFAs such as butyrate are capable of inhibiting cell proliferation and inducing a differentiated phenotype in vitro. The Caco-2 colon cancer cell line was used to study the effect of SCFAs and the process of cellular differentiation on the expression of the pro-inflammatory cytokine, interleukin 8 (IL-8). SCFAs and trichostatin A, structurally unrelated compounds which both induce histone hyperacetylation, both led to a dose-dependent inhibition of IL-8 gene expression. Furthermore, spontaneous differentiation of Caco-2 cells by growth to a post-confluent state also inhibited the expression of IL-8. A possible mechanism by which SCFAs may be effective in the treatment of ulcerative colitis may be through their ability to increase histone acetylation states and inhibit the production of pro-inflammatory substances by the intestinal epithelium.

Acetylation↗
PubMed1997

Mapping QTLs for submergence tolerance in rice by AFLP analysis and selective genotyping.

By combining the amplified fragment length polymorphism (AFLP) technique with selective genotyping, we constructed a linkage map for rice and assigned each linkage group to a corresponding chromosome. The AFLP map, consisting of 202 AFLP markers, was generated from 74 recombinant inbred lines (RIL) which were selected from both extremes of the population (250 lines) with respect to the response to complete submergence. Map length was 1756 cM, with an average interval size of 8.5 cM. To assign linkage groups to chromosomes, we used 50 previously mapped AFLP markers as anchor markers distributed over the 12 chromosomes. Other AFLP markers were then assigned to specific chromosomes based on their linkage to anchor markers. This AFLP map is equivalent to the RFLP/AFLP map constructed previously as the anchors were in the same order in both maps. Furthermore, tests with two restriction fragment length polymorphism (RFLP) markers and two sequence-tagged site (STS) markers showed that they mapped in the expected positions. Using this AFLP map, a major gene for submergence tolerance was localized on chromosome 9. Quantitative trait loci (QTL) associated with submergence tolerance were detected on chromosomes 6, 7, 11, and 12. We conclude that the combination of AFLP mapping and selective genotyping provides a much faster and easier approach to QTL identification than the use of RFLP markers.

Chromosome Mapping↗
PubMed1997

Effects of chronic neuroleptic treatments on dopamine D1 and D2 receptors: homogenate binding and autoradiographic studies.

The antipsychotic effects of neuroleptics are believed to be mediated via dopamine D2 receptor blockade; however, the anatomical and pharmacological targets of these drugs remain somewhat controversial. The purpose of this study was to examine the effects of chronic clozapine (CLZ) and haloperidol (HAL) treatments on the densities of DA D1 and D2 receptors. Adult male Sprague-Dawley rats (300-350 g) were treated for 21 days with either HAL (1 mg/kg/day, i.p.), CLZ (20 mg/kg/day, i.p.) or saline. Three days after ending the treatments, the brains were removed and used for biochemical assays of tissue DA and metabolites as well as for receptor studies. DA D1 and D2 receptors were labelled with [3H]SCH23390 and [3H]raclopride, respectively, and measured in the neostriatum by binding studies, and in autoradiograms of forebrain sections by quantitative densitometry. The autoradiographic measurements revealed significant increases in the densities of D2 receptors in nucleus accumbens, in the medio-ventral, latero-dorsal and latero-ventral quadrants of the rostral neostriatum, in caudal neostriatum and in globus pallidus of both HAL-(28-44%) and CLZ-treated (15-85%) animals. The HAL-induced up-regulation of D2 receptors in rostral and caudal neostriatum was homogenous, but CLZ produced a more uneven increase, with the highest absolute densities measured in latero-dorsal neostriatum, as well as with changes in the medio-dorsal rostral neostriatum. For D1 receptors, only CLZ and not HAL, produced significant increases in five regions, namely nucleus accumbens (43%) latero-dorsal rostral neostriatum (16%), caudal neostriatum (30%), globus pallidus (67%) and substantia nigra (12%). The observation that CLZ, contrary to HAL, also has an effect on D1 receptor densities may explain the greater therapeutic and selective efficacy with fewer side-effects of this agent, in comparison to other neuroleptics.

Animals↗
PubMed1997

Binding of L-branched-chain amino acids causes a conformational change in BkdR.

BkdR is the positive transcriptional activator of the inducible bkd operon of Pseudomonas putida. Evidence is accumulating that L-branched-chain amino acids are the inducers of the operon, and the data obtained in this study show that they induce a conformational change in BkdR. Addition of L-branched-chain amino acids increased the susceptibility of BkdR to trypsin with the cleavage between Arg-51 and Gln-52 on the C-terminal side of the DNA-binding domain. L-Valine also caused an increased fluorescence emission intensity and produced significant changes in the circular dichroism spectrum of BkdR. Analytical ultracentrifugation confirmed earlier data obtained from gel filtration that BkdR was a tetramer with a Stokes radius of 32 +/- 3 A and an axial ratio of 2:1.

Amino Acids↗
PubMed1997

[Study on the structure-activity relationships of retinoids. II. 3D-QSAR of retinoids and receptor interaction].

Precise prediction of the binding constant of ligand to receptor is an important aspect of structure-based drug design. Almost all methods including de novo design and 3D database search are over concentrated on structure generation rather than quantitative evaluation of the binding properties of the newly produced molecule. Using epididymal retinoic acid binding protein (ERABP) as a model, we simulated the interaction between retinoids and their receptor with DOCK program and obtained an equation for predicting the binding constants. According to the docking conformers of the ligands, CoMFA was also used to deduce a pharmacophoric model of this series of compound.

Receptors, Retinoic Acid↗
PubMed1997

Microsatellite marker development, mapping and applications in rice genetics and breeding.

Microsatellites are simple, tandemly repeated di- to tetra-nucleotide sequence motifs flanked by unique sequences. They are valuable as genetic markers because they are co-dominant, detect high levels of allelic diversity, and are easily and economically assayed by the polymerase chain reaction (PCR). Results from screening a rice genomic library suggest that there are an estimated 5700-10,000 microsatellites in rice, with the relative frequency of different repeats decreasing with increasing size of the motif. A map consisting of 120 microsatellite markers demonstrates that they are well distributed throughout the 12 chromosomes of rice. Five multiple copy primer sequences have been identified that could be mapped to independent chromosomal locations. The current level of genome coverage provided by these simple sequence length polymorphisms (SSLPs) in rice is sufficient to be useful for genotype identification, gene and quantitative trail locus (QTL) analysis, screening of large insert libraries, and marker-assisted selection in breeding. Studies of allelic diversity have documented up to 25 alleles at a single locus in cultivated rice germplasm and provide evidence that amplification in wild relatives of Oryza sativa is generally reliable. The availability of increasing numbers of mapped SSLP markers can be expected to complement existing RFLP and AFLP maps, increasing the power and resolution of genome analysis in rice.

Breeding↗
PubMed1996

Stoichiometry of BkdR to substrate DNA in Pseudomonas putida.

BkdR is the transcriptional activator of the bkd operon of Pseudomonas putida, which encodes branched chain keto acid dehydrogenase. BkdR binds to a large region of DNA between its own structural gene and the first gene of the bkd operon. The object of the present studies was to determine the stoichiometry of binding as part of an effort to understand the action of BkdR in regulation of the bkd operon. [35S]BkdR was prepared and found to be essentially 100% active in the gel shift assay. Only one complex was formed under all the conditions used. The stoichiometry of BkdR binding to its specific substrate DNA was three tetramers per mold substrate DNA. L-valine did not affect the stoichiometry although this ligand was previously shown to affect the DNase I protection pattern. The addition of nonspecific DNA to the incubation mixture also did not affect this stoichiometry.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗