Biomedical subjects

M Wang

Publications and source records attributed to M Wang.

At least 163 records · Page 9Linked to original sources

PubMed2001

Identification of estrogen-responsive genes in chick liver.

Identification of targets of estrogen is an important step in understanding the mechanisms of estrogen action. A two-step strategy was developed to identify estrogen-responsive genes (ERGs) in chick liver. Initially, differential-display, reverse transcription polymerase chain reaction (DDRT-PCR) was introduced to isolate ERGs. Isolated ERGs were then analyzed using Northern blot hybridization. A number of differentially expressed cDNA fragments were isolated following estrogen exposure. Four cDNA fragments that displayed dramatic change after estrogen administration were identified as liver adenylosuccinate lyase (ADL), phenobarbital-inducible cytochrome P-450 (CYP450), ovoinhibitor, and glutathione-dependent prostaglandin D2 synthase (PGDS). Time sequence analysis showed that estrogen-induced alteration occurred as early as 0.5 h and peaked between 1 and 4 h after estrogen exposure. Nuclear runoff assay indicated that estrogen significantly increased the transcription rate of these genes. To determine whether the observed alteration was due to the direct effect of estrogen, protein synthesis was inhibited by cycloheximide (CHX) during stimulation by estradiol, Estrogen-mediated upregulation of PGDS was completely abolished by a concurrent treatment with CHX, suggesting that its activation requires the participation of some newly synthesized factor(s). In contrast, CHX did not affect the expression of other genes, indicating the alteration is a direct response to estrogen. In conclusion, ADL, CYP450, ovoinhibitor, and PGDS represent the novel targets of estrogen, which regulates the transcriptional activity of these genes.

Adenosine Monophosphate↗

PubMed2001

Speeds of invasion in a model with strong or weak Allee effects.

We study an invasion model based on a reaction-diffusion equation with an Allee effect. We use a special, piecewise-linear, population growth rate. This function allows us to obtain traveling wave solutions and to compute wave speeds for a full range of Allee effects, including weak Allee effects. Some investigators claim that linearization fails to give the correct speed of invasion if there is an Allee effect. We show that the minimum speed for a sufficiently weak Allee may, in fact, be the same as that derived by means of linearization.

Models, Biological↗

PubMed2001

Pattern formation during C. elegans vulval induction.

Studies of C. elegans vulval development provide insights into the process of pattern formation during animal development. The invariant pattern of vulval precursor cell fates is specified by the integration of at least two signaling systems. Recent findings suggest that multiple, partially redundant mechanisms are involved in patterning the vulval precursor cells. The inductive signal activates the LET-60/RAS signaling pathway and induces the 1 degree fate, whereas the lateral signal mediated by LIN-12/Notch is required for specification of the 2 degrees fate. Several regulatory pathways antagonize the RAS signaling pathway and specify the non-vulval 3 degrees fate in the absence of induction. The temporal and spatial regulation of VPC competence and production of the inductive and the lateral signal are precisely coordinated to ensure the wild-type vulval pattern.

Animals↗

PubMed2001

Neuroactive steroids and central nervous system disorders.

Steroid hormones are vital for the cell life and affect a number of neuroendocrine and behavioral functions. In contrast to their endocrine actions, certain steroids have been shown to rapidly alter brain excitability and to produce behavioral effects within seconds to minutes. In this article we direct attention to this issue of neuroactive steroids by outlining several aspects of current interest in the field of steroid research. Recent advances in the neurobiology of neuroactive are described along with the impact of advances on drug design for central nervous system (CNS) disorders provoked by neuroactive steriods. The theme was selected in association with the clinical aspects and therapeutical potentials of the neuroactive steroids in CNS disorders. A wide range of topics relating to the neuroactive steroids are outlined, including steroid concentrations in the brain, premenstrual syndrome, estrogen and Alzheimer's disease, side effects of oral contraceptives, mental disorder in menopause, hormone replacement therapy, Catamenial epilepsy, and neuractive steroids in epilepsy treatment.

Alzheimer Disease↗

PubMed2001

Chemically coupled hydroxyapatite-polyethylene composites: structure and properties.

Silanation of hydroxyapatite and acrylic acid grafting of polyethylene were employed to improve bonding between hydroxyapatite and polyethylene. The structure and properties of chemically coupled hydroxyapatite reinforced high-density polyethylene (HA/HDPE) composites were subsequently investigated using various techniques. It was shown that there existed a silicon-containing interphase between the hydroxyapatite particle and the polyethylene matrix. The silane coupling agent used promoted chemical adhesion between hydroxyapatite particles and the polymer. The use of the silane coupling agent also facilitated the penetration of polymer into cavities in individual ceramic particles, which resulted in enhanced mechanical interlocking at the matrix-reinforcement interface. With a strong bond (both mechanical and chemical) being formed between hydroxyapatite and polyethylene, chemically coupled HA/HDPE composites possessed improved mechanical properties and fracture behaviour.

Durapatite↗

PubMed2001

Functionally graded calcium phosphate coatings produced by ion beam sputtering/mixing deposition.

Ar+ ion beam sputtering/mixing deposition was used to produce thin calcium phosphate coatings on titanium substrate from hydroxyl-poly-calcium sodium phosphate (HPPA) and HPPA + Ti targets. Three types of coatings (one type of monolayer coating and two types of functionally graded coating) were manufactured. It was found that as-sputtered coatings were amorphous. No distinct hydroxyl band was observed in the FTIR spectra, but new absorption bands were determined for CO3(2-), which resulted during the deposition process. Compositional gradients from the surface to the interior (i.e. adjacent to the substrate) were achieved for the functionally graded coatings. Post-deposition heat treatment indicated that the bonding strength between the coating and the substrate was improved by the use of functionally graded structures.

Argon↗

PubMed2001

Prednisolone suppresses ischemia-reperfusion injury of the rat liver by reducing cytokine production and calpain mu activation.

BACKGROUND: We investigated the effects of prednisolone on cytokine production and calpain mu activation during hepatic ischemia-reperfusion (IR) injury. METHODS: The hilar area of the left lateral and median lobes of rat liver was clamped for 60 min. Prednisolone was administered at 1.0, 3.0, or 10 mg/kg at 30 min before ischemia. In addition to biochemical and microscopic analyses, IL-beta and TNF-alpha production was evaluated by RT-PCR. Calpain mu activation and talin degradation were determined by Western blotting, using specific antibodies. RESULTS: In the control and prednisolone (1.0 mg/kg) groups, serum AST and ALT levels were elevated, and cell membrane bleb formation was observed after 2 h of reperfusion. Moreover, calpain mu activation, talin degradation, and overexpression of IL-beta and TNF-alpha mRNAs were detected. Infusion of prednisolone at 3.0 or 10 mg/kg significantly suppressed biochemical and microscopic changes. At 10 mg/kg, prednisolone markedly suppressed IL-beta and TNF-alpha transcription and calpain mu activation and talin degradation, consistent with the improved 7-day survival after total hepatic ischemia (75% vs. 25% in control group, P = 0.039). CONCLUSIONS: Cytoprotective effect of prednisolone in hepatic IR injury was closely associated with suppression of IL-beta/TNF-alpha production and calpain mu activation.

Alanine Transaminase↗

PubMed2001

Gender differences in the attenuation of salt-induced hypertension by angiotensin (1-7).

Chronic infusion of angiotensin (1-7) [Ang-(1-7)] lowers blood pressure in spontaneously hypertensive rats (SHR). To assess the role of Ang-(1-7) in salt-induced hypertension, Ang-(1-7) (24 microg/kg/hr) or saline was administered chronically via osmotic minipump into the jugular vein of 5-6 wk-old male (M) and female (F) Dahl salt-sensitive rats placed on a high-salt (8% NaCl) diet for 2 weeks. Blood pressure (BP) and heart rate were measured prior to the start of the diet and weekly thereafter. Ang-(1-7) significantly attenuated the BP increase after 1 wk on the diet in both M and F rats, but after 2 weeks only in F rats. Enhanced release of prostacyclin, (6-keto PGF1 alpha), following Ang-(1-7) treatment was observed in both M and F rats. In addition, significant increases in aortic blood flow and plasma levels of nitric oxide were observed in the F rats following Ang-(1-7) treatment. These findings demonstrate that the reduction in BP is due to both prostacyclin and NO and that there is a gender difference in the attenuation of salt-induced hypertension by Ang-(1-7).

6-Ketoprostaglandin F1 alpha↗

PubMed2001

mRNA expression for insulin-like growth factor 1, receptors of growth hormone and IGF-1 and transforming growth factor-beta in the kidney and liver of Zucker rats.

Kidney dysfunction and mesangial enlargement are consequences of obesity found in Zucker rats. This study examines some of the early mechanisms by which the kidneys of Zucker rats undergo these changes. Our study shows that the glomerular planar area in the genetically obese Zucker rat undergo enlargement as early as 12 weeks of life, compared to the lean controls. This suggests mesangial proliferation is already occurring at this time, earlier than previously shown. The mRNA expression for IGF-I, and GHR in the kidney and liver of the obese Zucker rats were significantly reduced compared to the lean controls. However, the mRNA of the IGF-IR was significantly elevated in the kidney of the obese Zucker rats. The increase in kidney IGF-1R mRNA in the obese Zucker rat may suggest an increase in IGF-1 binding leading to the kidney hypertrophy observed in these rats.

Journal Article↗

PubMed2001

Effects of Fe(2+) on ion channels: Na(+) channel, delayed rectified and transient outward K(+) channels.

The effects of Fe(2+) on the properties of three types of ion channels were studied in acutely dissociated rat hippocampal pyramidal neurons from area CA1 at postnatal ages of 7-14 days using the whole cell patch clamp technique. The results indicated that: (1) in the existence of Fe(2+), the activation voltage threshold of transient outward K(+) currents (I(A)) was decreased. The normalized current-voltage curves of activation were well fitted with a single Boltzmann function, and the V(1/2) was 2.44+/-1.14 mV (n=15) in control, whereas 1.79+/-1.53 (n=15), -2.96+/-0.92 (n=14), -5.11+/-1.31 (n=13), -9.05+/-1.64 mV (n=12) in 1, 10, 100 and 1000 microM Fe(2+), respectively. Differences between two groups were significant (P<0.05, n=12-15), except for that between the control and 1 microM (P>0.05, n=15). (2) Fe(2+) caused a left shift of the current-voltage curves of steady-state inactivation of I(A) in a concentration-dependent manner. The curves were well fitted with a single Boltzmann function with similar slope (P>0.05, n=10-13). The V(1/2) were -70.71+/-1.23 (n=13), -71.14+/-1.37 (n=13), -78.21+/-1.17 (n=11), -84.61+/-1.34 (n=12), and -89.68+/-2.59 mV (n=10) in control, 1, 10, 100 and 1000 microM Fe(2+), respectively. Fe(2+) also shifted the current-voltage curves of Na(+) channel steady-state inactivation to more negative depolarization potentials in parallel, with V(1/2), -67.37+/-1.33 mV (n=12) in control, and -67.52+/-1.28 mV (n=12), -68.24+/-1.61 mV (n=10), -71.58+/-1.45 mV (n=10), -76.65+/-1.76 mV (n=9) in 1, 10, 100 and 1000 microM Fe(2+) solutions, respectively. (3) In Fe(2+) solutions, the recovery from inactivation of I(A) was slowed. (4) With application of different concentrations of Fe(2+), the voltage threshold of activation of delayed rectified outward K(+) currents (I(K)) was decreased, while Fe(2+) showed a little inhibition at more positive depolarization. Briefly, the results demonstrated that Fe(2+) is a dose- and voltage-dependent, reversible modulator of I(A), I(K) and Na(+) channels. The results will be helpful to explain the mechanism of Fe(2+) physiological function and Fe(2+) intoxication in the central nervous system.

Animals↗

PubMed2001

Prevalence and phenotypes of erythromycin-resistant Streptococcus pneumoniae in Shanghai, China.

Bacterial resistance of Streptococcus pneumoniae against erythromycin and clindamycin and resistance phenotypes of erythromycin-resistant Streptococcus pneumoniae were investigated. The MICs of erythromycin and clindamycin against 345 strains of Streptococcus pneumoniae were tested with agar dilution method; the phenotypes of erythromycin-resistant Streptococcus pneumoniae were detected by double-disk test. One hundred and eighty-three and 171 of 345 (53.0% and 49.6%) of isolates had MICs > or =1 microg/ml for erythromycin and for clindamycin. Among erythromycin-resistant Streptococcus pneumoniae, the percentage of cMLS, iMLS and M phenotype was 90.3% (159/176), 5.7% (10/176) and 4.0% (7/176), respectively. The incidence of erythromycin-resistant Streptococcus pneumoniae is very high in Shanghai. The main phenotype is cMLS.

Child↗

PubMed2001

Application of concentrated TiO2 sols for gamma-ray radiation dosimetry.

Upon exposure to gamma-radiation, a concentrated TiO2 sol changes from colorless to deep blue with an absorption maximum at 540 nm. The absorption has been assigned to trapped electrons or Ti3+ states in the solid matrix based on its spectroscopic similarity to the samples irradiated with UV light. Unlike the conduction-band electrons generated from direct excitation by UV radiation, the origin of the trapped electrons during gamma-ray irradiation may be traced to a series of reducing species produced by the high energy electrons, which in turn, are the direct result of gamma-irradiation. As the absorption intensity is linearly related to the duration of exposure to gamma-radiation, it may have an application in gamma-ray dosimetry. The sensitivity of its dosage response has been found to be influenced by the semiconductor particle concentration and the dispersing solvent.

Journal Article↗

PubMed2001

Identification of glycogen phosphorylase and creatine kinase as calpain substrates in skeletal muscle.

The goal of this study was to identify calpain substrates in muscle cells. Our hypothesis was that the yeast two-hybrid method could be used to identify novel calpain substrates. To accomplish this, native mu- and m-calpains, as well as a variety of calpain DNA fragments, were expressed in yeast cells and used to screen for binding proteins in a human skeletal muscle cDNA library. Calpain constructs that were used in the screening process included native mu- and m-calpains, a dominant negative (DN) m-calpain (i.e. active site modified), N-terminal truncated DN m-calpain (i.e. autolyzed DN-m-calpain) and, finally, an N- and C-terminal truncated m-calpain (i.e. autolyzed DN-m-calpain lacking a calcium-binding domain). Yeast cells were transformed using yeast two-hybrid expression vectors containing the different calpain constructs as "baits". Beta-galactosidase activity was assayed as an index of interaction between calpain and its potential target proteins. From this analysis, four clones (Ca2+-ATPase, novel nebulin-related protein (N-RAP), creatine kinase and glycogen phosphorylase) were recovered. Two of these, creatine kinase and glycogen phosphorylase, were selected for further study. In in-vitro assays, calpain was able to partially digest both proteins, suggesting that both creatine kinase and glycogen phosphorylase are natural calpain substrates.

Calpain↗

PubMed2001

Silyl ether-coupled poly(epsilon-caprolactone)s with stepwise hydrolytic degradation profiles.

Silyl ether-coupled poly(epsilon-caprolactone)s (PCLs) with stepwise degradation profiles were synthesized via the cross-dehydrocoupling polymerizations between 1,4-bis(dimethylsilyl)benzene (BDSB) and telechelic, diol-terminated PCL macromonomers. With the presence of 10 wt % palladium on activated carbon as the catalyst, the condensations between BDSB and diol-terminated PCL macromonomers having molecular weights of 1200, 2010, and 5500 g/mol were performed in toluene at 100 degrees C under argon. Hydrogen was eliminated as the condensate upon the formation of silyl ether bonds linking the PCL blocks, yielding within 24 h, silyl ether-coupled PCLs of molecular mass 7590, 29,900, and 29,500 g/mol, respectively. The characterization of each polymer included (1)H NMR, (13)C NMR, and (29)Si NMR spectroscopies, size exclusion chromatography (SEC), and differential scanning calorimetry. The hydrolytic degradation properties of the polymers in solution were studied, and the molecular weight reductions over time were monitored by SEC. The silyl ether linkages of the polymers underwent hydrolysis in the presence of mineral acids, whereas the PCL segments released from the cleavage of the labile silyl ether coupling unit did not undergo detectable molecular weight reduction over 15 days. In the presence of acetic acid, the silyl ether functionalities were cleaved with a half-life of 3 days; however, the PCL chain required reaction with trifluoroacetic acid to give a number-average molecular weight loss half-life of 4 days. The silyl ether-coupled PCLs underwent degradation in a gradient fashion, therefore, by a protocol that involved the addition of acetic acid for cleavage of the silyl ether functionalities, followed by further addition of trifluoroacetic acid to bring the hydrolysis of the silyl ether functionalities to completion and to trigger the degradation of PCL segments.

Biodegradation, Environmental↗

PubMed2001

Five new insecticidal sesquiterpenoids from Celastrus angulatus.

Five new sesquiterpene polyol esters were isolated from the root bark of Celastrus angulatus by bioassay-guided fractionation. Their structures were determined by spectral data interpretation as 1alpha,2alpha,6beta,8beta,13-pentaacetoxy-9beta-benzoyloxy-4beta-hydroxy-beta-dihydroagarofuran (1), 1alpha,2alpha,6beta-triacetoxy-8alpha-(beta-furancarbonyloxy)-9beta-benzoyloxy-13-isobutanoyloxy-4beta-hydroxy-beta-dihydroagarofuran (2), 1alpha,2alpha,6beta-triacetoxy-8beta-isobutanoyloxy-9beta-(beta-furancarbonyloxy)-13-(alpha-methyl)butanoyloxy-4beta-hydroxy-beta-dihydroagarofuran (3), 1alpha,2alpha,6beta-triacetoxy-8alpha,13-diisobutanoyloxy-9beta-benzoyloxy-4beta-hydroxy-beta-dihydroagarofuran (4), and 1alpha,2alpha,6beta-triacetoxy-8alpha-isobutanoyloxy-9beta-benzoyloxy-13-(alpha-methyl)butanoyloxy-4beta-hydroxy-beta-dihydroagarofuran (5). Compounds 1-5 exhibited insecticidal activity against the larval of Mythimna separata.

Animals↗

PubMed2001

Cycloartane triterpene saponins from the roots of Cimicifuga foetida.

The structures of two new cycloartane-type saponin constituents of the roots of Cimicifuga foetida were established by the interpretation of spectroscopic data as 2'-O-acetylactein (1) and 2'-O-acetyl-27-deoxyactein (2), respectively. Also isolated were the known compounds actein, 27-deoxyactein, cimicifugoside H-1, and 15alpha-hydroxycimicidol 3-O-beta-D-xyloside.

Magnetic Resonance Spectroscopy↗

PubMed2001

Iridoid glycosides from the leaves of Morinda citrifolia.

A new iridoid glucoside (1), named citrifolinoside A, was isolated from the leaves of Morinda citrifolia along with the known iridoids asperuloside and asperulosidic acid. The structure of 1 was established by interpretation and full assignments of NMR spectroscopic data.

Glucosides↗

PubMed2001

Furanosesquiterpenoids of Commiphora myrrha.

An investigation on the gum exudates of Commiphora myrrha has led to the isolation of six sesquiterpenoids. On the basis of spectroscopic data interpretation, they were determined as two new furanosesquiterpenoids, rel-1S,2S-epoxy-4R-furanogermacr-10(15)-en-6-one (1) and rel-2R-methyl-5S-acetoxy-4R-furanogermacr-1(10)Z-en-6-one (2), and four known furanosesquiterpenoids, rel-3R-methoxy-4S-furanogermacra-1E,10(15)-dien-6-one (3), rel-2R-methoxy-4R-furanogermacr-1(10)E-en-6-one (4), furanogermacra-1(10)Z,4Z-dien-6-one, and curzerenone [6,7-dihydro-5beta-isopropenyl-3,6beta-dimethyl-6-vinylbenzofuran-4(5H)-one]. This is the first report of the relative stereochemistry for the known compounds 3 and 4. Compound 1 exhibited weak cytotoxic activity against a MCF-7 breast tumor cell line in a clonogenic assay, while the other five compounds were inactive in this assay.

Antineoplastic Agents, Phytogenic↗