PubMed Health⌕ Search

Biomedical subjects

H Fang

Publications and source records attributed to H Fang.

At least 37 records · Page 2Linked to original sources
PubMed2001

Threshold analysis of selected dose-response data for endocrine active chemicals.

Using a biologically relevant mathematical model, the Michaelis-Menten equation, we examined published data from endocrine active chemicals for evidence of no-threshold dose-response curves. Data were fit to a modified Michaelis-Menten equation which accounted for total background response. Subsequently, the data sets were analyzed using non-linear regression in order to estimate the four parameters of interest (non-hormone controlled background (Bnh), maximum response (Rmax), endogenous hormone level (D0), and the dose at which a half-maximal response was observed (ED50)) and to determine the fit to the fully modified Michaelis-Menten equation. Subsequently, response data were adjusted to account for Bnh and then normalized to Rmax, while dose data were adjusted to account for D0 and then normalized to the ED50. This data set was combined into a single, composite data set and fit to the fully modified Michaelis-Menten equation. We examined 31 data sets (24 endpoints) from studies on 9 different chemical/hormone treatments. Twenty-six of the data sets fit the modified Michaelis-Menten equation with high multiple correlation coefficients (r>0.90). The normalized data demonstrated a good fit to the modified Michaelis-Menten equation. These results indicate that a variety of biological responses fit the modified Michaelis-Menten equation, which does not have a threshold dose term.

Dose-Response Relationship, Drug↗
PubMed2001

Surface acoustic waves propagating over a rotating piezoelectric half-space.

Surface acoustic waves (SAW) propagating over a piezoelectric half-space rotating at a constant angular rate about a fixed axis are analyzed using the linear theory of piezoelectricity, including Coriolis and centrifugal forces. Rotation sensitivity, the rotation induced change of wave speed, is studied. The dependence of the rotation sensitivity on the orientation of the rotation axis and the orientation of the material is examined. Numerical results for polarized ceramics PZT-5H are presented to show the detailed characteristics of the rotation sensitivity. The implications of the numerical results are discussed for different applications.

Journal Article↗
PubMed2001

One-dimensional equations for a piezoelectric ring and applications in a gyroscope.

One-dimensional equations for coupled in-plane extensional and flexural vibrations of a piezoelectric ring are derived. The equations are used to analyze a ring piezoelectric gyroscope. Free and forced vibration solutions are obtained. Resonant frequencies and voltage sensitivity as well as their dependence on rotation rate and other parameters are examined.

Journal Article↗
PubMed2001

Quaternary ammonium salt derivative of haloperidol inhibits KCl-induced calcium increase in rat aortic smooth muscle cells.

AIM: To study the effect of quaternary ammonium salt derivative of haloperidol (F3) on intracellular calcium (Ca2+) dynamic change in vascular smooth muscle cells (VSMC). METHODS: Using laser confocal scanning microscopy (LCSM), to observe the effect of F3 (0.01 - 10 micromol/L) on increase of intracellular Ca2+ fluorescent intensity induced by KCl (30 mmol/L) in VSMC. RESULTS: KCl induced a rapid increase of intracellular Ca2+ fluorescent intensity. F3 inhibited the rapid increase of that in both concentration-dependent manner (KCl: 67 +/- 24; F3 0.01 micromol/L: 57 +/- 13; 0.1 micromol/L: 40 +/- 13; 1 micromol/L: 29 +/- 9; 10 micromol/L: 20 +/- 6) and time-dependent manner; during 0 - 30 s after F3 was added, the change of fluorescent intensity was more rapid. CONCLUSION: The inhibitory effect of F3 on Ca2+ concentration in VSMC was mainly due to the blocking of the Ca2+ influx, and might partially attributed to opening of the potassium (K+) channel.

Alkanes↗
PubMed2001

[The identification of flos magnoliae by TLC].

OBJECTIVE: To establish a TLC identification method for Flos Magnoliae. METHOD: Selecting optimum TLC conditions. RESULTS: A TLC identification method of Flos Magnoliae has been established. CONCLUSION: The method is simple, accurate and reliable.

Chromatography, Thin Layer↗
PubMed2001

[Cloning of promelittin cDNA and its expression in Escherichia coli].

The cDNA encoding promelittin was obtained from the total RNA of bee poison gland by RT-PCR and was cloned to pT7Blu-T vector. The expression vector of promelittin fused with partial sequence of beta-galactosidase was constructed by ligating the fragment inserted to pUC118. Moreover, it was expressed in the strain DH5 alpha of Escherichia coli. The result of DNA sequence analysis demonstrated that the obtained cDNA sequence was same with the published one and the reading frame of fusion gene was correct.

Animals↗
PubMed2001

[Determination of Se, Fe, Si in electrolytic manganese metal by ICP-AES].

The method was established for the simultaneous determination of Se, Fe and Si in electrolytic manganese metal by inductively coupled plasma atomic emission spectrometry (ICP-AES). The sample was dissolved by light sulphuric acid. The analysis conditions were obtained by studying dissolved acid, Mn matrix and background. The recommended method not only proved to be simple and rapid but showed satisfying precision and accuracy as well. The relative standard deviation is less than 2.68% and the recovery is 98%-105%. The t-test showed that no conspicuous difference with typical methods was found.

Electrolysis↗
PubMed2000

Signal peptidase and oligosaccharyltransferase interact in a sequential and dependent manner within the endoplasmic reticulum.

We demonstrate that the signal peptides of prepro-alpha-factor and preinvertase must be cleaved before Asn-X-Ser/Thr acceptor tripeptides located near the signal peptides of these precursors can be efficiently glycosylated within the endoplasmic reticulum of the yeast Saccharomyces cerevisiae. The data support a model whereby the interaction of a signal peptide with the membrane prevents an acceptor tripeptide juxtaposed to the signal peptide from accessing the oligosaccharyltransferase active site until the signal peptide is cleaved.

Amino Acid Sequence↗
PubMed2000

IL-13-mediated worm expulsion is B7 independent and IFN-gamma sensitive.

B7 costimulation is a required component of many type 2 immune responses, including allergy and protective immunity to many nematode parasites. This response includes elevations in Th2 cytokines and associated effector functions including elevations in serum IgG1 and IgE and parasite expulsion. In studies of mice infected with Trichuris muris, blocking B7 ligand interactions inhibited protective immunity, suppressed IL-4 production, and enhanced IFN-gamma production, but unexpectedly did not inhibit production of the Th2 cytokine, IL-13. Blocking both IFN-gamma and B7 restored protective immunity, which was IL-13 dependent, but did not restore IL-4 or associated IgE responses. Although IL-13 was required for worm expulsion in mice in which both IFN-gamma and B7 were blocked, IL-4 could mediate expulsion in the absence of both IL-13 and IFN-gamma. These studies demonstrate that 1) B7 costimulation is required to induce IL-4, but not IL-13 responses; 2) IL-13 is elevated in association with the IFN-gamma response that occurs following inhibition of B7 interactions, but can only mediate IL-4-independent protection when IFN-gamma is also inhibited; and 3) increased IL-13 production, in the absence of increased IL-4 production, is not associated with an IgE response, even in the absence of IFN-gamma.

Abatacept↗
PubMed2000

Ectopic expression of Xenopus noggin RNA induces complete secondary body axes in embryos of the direct developing frog Eleutherodactylus coqui.

We tested the effects of noggin RNA from Xenopus laevis on axis induction in embryos of a direct developing frog, Eleutherodactylus coqui. We microinjected noggin RNA into one blastomere of 4-cell embryos at the site close to the animal pole, and found that overexpression of noggin RNA is not only sufficient to induce additional axes but also induces heads with eyes. We also injected noggin RNA into 8-cell or 16-cell embryos in various sites, including the marginal zone, above the marginal zone, and the vegetal pole, and found the formation of a complete secondary axis in all three types of injection. These effects of X. laevis noggin RNA on the E. coqui embryo are remarkably different from those found in the X. laevis embryo itself. It has been shown previously that overexpression of noggin RNA on the ventral side of the normal X. laevis embryo induces only a partial axis, with no head structures. We show here that the failure of noggin induction of a complete axis when overexpressed on the ventral side of the X. laevis embryos is not due to an insufficient amount of RNA injected. Also, the failure is unlikely due to inhibition from the primary axis since noggin RNA can induce duplicated head structures on opposite sides of UV-irradiated X. laevis embryos. There appear to be fundamental differences in the responses of E. coqui and X. laevis embryos to exogenous noggin RNA. We propose that these differences stem from an alteration in cytoplasmic arrangements that occurred during evolution of this large egg.

Animals↗
PubMed2000

The estrogen receptor relative binding affinities of 188 natural and xenochemicals: structural diversity of ligands.

We have utilized a validated (standardized) estrogen receptor (ER) competitive-binding assay to determine the ER affinity for a large, structurally diverse group of chemicals. Uteri from ovariectomized Sprague-Dawley rats were the ER source for the competitive-binding assay. Initially, test chemicals were screened at high concentrations to determine whether a chemical competed with [3H]-estradiol for the ER. Test chemicals that exhibited affinity for the ER in the first tier were subsequently assayed using a wide range of concentrations to characterize the binding curve and to determine each chemical's IC50 and relative binding affinity (RBA) values. Overall, we assayed 188 chemicals, covering a 1 x 10(6)-fold range of RBAs from several different chemical or use categories, including steroidal estrogens, synthetic estrogens, antiestrogens, other miscellaneous steroids, alkylphenols, diphenyl derivatives, organochlorines, pesticides, alkylhydroxybenzoate preservatives (parabens), phthalates, benzophenone compounds, and a number of other miscellaneous chemicals. Of the 188 chemicals tested, 100 bound to the ER while 88 were non-binders. Included in the 100 chemicals that bound to the ER were 4-benzyloxyphenol, 2,4-dihydroxybenzophenone, and 2,2'-methylenebis(4-chlorophenol), compounds that have not been shown previously to bind the ER. It was also evident that certain structural features, such as an overall ring structure, were important for ER binding. The current study provides the most structurally diverse ER RBA data set with the widest range of RBA values published to date.

Animals↗
PubMed2000

Global exponential stability and periodic solutions of cellular neural networks with delay.

In this paper, some sufficient conditions for the global exponential stability and the existence of periodic solutions of cellular neural networks with delay (DCNN) model are obtained by means of a Lyapunov functional approach. These conditions can be used to design globally stable DCNN's and periodic oscillatory DCNN's and thus have important significance in both theory and applications.

Animals↗
PubMed2000

Simulation of field-induced structural formation and transition in electromagnetorheological suspensions.

A computer simulation method has been used to study the three-dimensional structural formation and transition of electromagnetorheological (EMR) suspensions under compatible electric and magnetic fields. When the fields are applied simultaneously and perpendicularly to each other, the particles rapidly arrange into single layer structures parallel to both fields. In each layer, there is a two-dimensional hexagonal lattice. The single layers then combine together to form thicker sheetlike structures. With the help of the thermal fluctuations, the thicker structures relax into three-dimensional close-packed structures, which may be face-centered cubic (fcc), hexagonal close-packed (hcp) lattices, or, more probably, the mixture of them, depending on the initial configurations and the thermal fluctuations. On the other hand, if the electric field is applied first to induce the body-centered tetragonal (bct) columns in the system, and then the magnetic field is applied in the perpendicular direction, the bct to fcc structure transition is observed in a very short time. Following that, the structure keeps on evolving due to the demagnetization effect and finally forms close-packed structures with fcc and hcp lattice character. The simulation results are in agreement with the theoretical and experimental results.

Journal Article↗
PubMed2000

Modulation of humoral immune response through probiotic intake.

Thirty healthy volunteers were randomised into three different treatment groups and consumed Lactobacillus GG, Lactococcus lactis or placebo (ethyl cellulose) for 7 days. On days 1, 3 and 5, an attenuated Salmonella typhi Ty21a oral vaccine was given to all subjects to mimic an enteropathogenic infection. All subjects responded well to the vaccine, but no significant differences were observed in numbers of IgA-, IgG- and IgM-secreting cells among the different groups. There was a trend towards a greater increase in specific IgA among the subjects receiving the vaccine in combination with Lactobacillus GG. Those receiving L. lactis with their vaccine evinced significantly higher CR3 receptor expression on neutrophils than those receiving either the placebo or Lactobacillus GG. These results indicate that probiotics may influence differently the immune response to oral S. typhi vaccine and that the immunomodulatory effect of probiotics is strain-dependent.

Adult↗
PubMed2000

Quantitative comparisons of in vitro assays for estrogenic activities.

Substances that may act as estrogens show a broad chemical structural diversity. To thoroughly address the question of possible adverse estrogenic effects, reliable methods are needed to detect and identify the chemicals of these diverse structural classes. We compared three assays--in vitro estrogen receptor competitive binding assays (ER binding assays), yeast-based reporter gene assays (yeast assays), and the MCF-7 cell proliferation assay (E-SCREEN assay)--to determine their quantitative agreement in identifying structurally diverse estrogens. We examined assay performance for relative sensitivity, detection of active/inactive chemicals, and estrogen/antiestrogen activities. In this examination, we combined individual data sets in a specific, quantitative data mining exercise. Data sets for at least 29 chemicals from five laboratories were analyzed pair-wise by X-Y plots. The ER binding assay was a good predictor for the other two assay results when the antiestrogens were excluded (r(2) is 0.78 for the yeast assays and 0.85 for the E-SCREEN assays). Additionally, the examination strongly suggests that biologic information that is not apparent from any of the individual assays can be discovered by quantitative pair-wise comparisons among assays. Antiestrogens are identified as outliers in the ER binding/yeast assay, while complete antagonists are identified in the ER binding and E-SCREEN assays. Furthermore, the presence of outliers may be explained by different mechanisms that induce an endocrine response, different impurities in different batches of chemicals, different species sensitivity, or limitations of the assay techniques. Although these assays involve different levels of biologic complexity, the major conclusion is that they generally provided consistent information in quantitatively determining estrogenic activity for the five data sets examined. The results should provide guidance for expanded data mining examinations and the selection of appropriate assays to screen estrogenic endocrine disruptors.

Binding, Competitive↗
PubMed2000

[The influence of some factors on DNA cycle sequencing].

OBJECTIVE: To study the influence of some factors on DNA cycle sequencing. METHODS: The effects of DNA templates, primers, cycle sequencing reaction conditions as well as purification methods were comparatively analyzed. RESULTS: When the DNA concentration was low, the nucleotide curve showed low ratio of signal to noise, even there were no fluorescent signal. While DNA concentration was too high, the readable length of nucleotides was short. Ions in the DNA template could result in bad sequencing reaction. The Tm value, length and G+C content of primers had no obvious influences on sequencing reaction. The alteration of the denaturing, annealing and extension temperature, or the addition of dimethl sulfoxide or glycerin facilitated sequencing some DNA templates. The fluorescent residues in the purified products of the sequence reaction could interfere the automatic reading of the sequencer, but did not influence the manually proofreading of the sequence. CONCLUSION: The purity and concentration of DNA templates are closely related to sequence data quality. The modification of reaction parameters and usage of additives can help to obtain good result of sequencing some DNA with certain structure. The use of 70% ethanol is recommended to precipitate the extension product.

Sequence Analysis, DNA↗
PubMed2000

[A study on membrane fluidity of thyroid gland in rats with iodine deficiency or iodine excess].

OBJECTIVES: To explore the effect of iodine deficiency and excess on thyroid membrane fluidity and its pathogenesis. METHODS: Wistar rats were fed different levels of iodine in the diet (normal iodine as control, low iodine and excess iodine). Serum T4 and T3 levels, thyroid superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities and malondialdehyde (MDA) content were determined, and two parameters of polarization (Pr) and micro-viscosity (eta) using DPH as a florescence probe were tested. RESULTS: Serum T4 and T3 levels in the low iodine (LI) group were markedly decreased, and the thyroid SOD and GPx activities and MDA content were significantly increased compared with the other two groups. However no changes were found in the high iodine (HI) group. There were no differences in Pr and eta values among three groups at 12th week of experiment, but at 24th week, both Pr and eta values in LI group were increased significantly compared to the other two groups. But the effect of iodine excess as expected was not found in this study. CONCLUSIONS: Long-term iodine deficiency caused a marked increase of membrane micro-viscosity and decrease of membrane fluidity in rat thyroid gland. Oxidative damage of thyroid by free radicals and retardation of lipid metabolism are considered as two important pathogenesis factors.

Animals↗