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Biomedical subjects

W Feng

Publications and source records attributed to W Feng.

At least 55 records · Page 3Linked to original sources
PubMed1999

Site-selective modification of hyperreactive cysteines of ryanodine receptor complex by quinones.

Quinones undergo redox cycling and/or arylation reactions with key biomolecules involved with cellular Ca2+ regulation. The present study utilizes nanomolar quantities of the fluorogenic maleimide 7-diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin (CPM) to measure the reactivity of hyperreactive sulfhydryl moieties on sarcoplasmic reticulum (SR) membranes in the presence and absence of quinones by analyzing the kinetics of forming CPM-thioether adducts and localization of fluorescence by SDS-polyacrylamide gel electrophoresis. Doxorubicin, 1,4-naphthoquinone (NQ), and 1, 4-benzoquinone (BQ) are found to selectively and dose-dependently interact with a class of hyperreactive sulfhydryl groups localized on ryanodine-sensitive Ca2+ channels [ryanodine receptor (RyR)], and its associated protein, triadin, of skeletal type channels. NQ and BQ are the most potent compounds tested for reducing the rate of CPM labeling of hyperreactive SR thiols (IC50 = 0.3 and 1.8 microM, respectively) localized on RyR and associated protein. The reduced forms of quinone, tert-butylhydroquinone, and 5-imino-daunorubicin do not alter significantly the pattern or kinetics of CPM labeling up to 100 microM, demonstrating that the quinone group is essential for modulating the state of hyperreactive SR thiols. Nanomolar NQ is shown to enhance the association of [3H]ryanodine for its high-affinity binding site and directly enhance channel-open probability in bilayer lipid membrane in a reversible manner. By contrast, micromolar NQ produces a time-dependent biphasic action on channel function, leading to irreversible channel inactivation. These results provide evidence that nanomolar quinone selectively and reversibly alters the redox state of hyperreactive sulfhydryls localized in the RyR/Ca2+ channel complex, resulting in enhanced channel activation. The Ca2+-dependent cytotoxicities observed with reactive quinones formed at the microsomal surface by oxidative metabolism may be related to their ability to selectively modify hyperreactive thiols regulating normal functioning of microsomal Ca2+ release channels.

Animals↗
PubMed1999

[An experimental study of anti-angiogenesis with a cartilage-derived inhibitor].

OBJECTIVE: To evaluate the efficacy of a cartilage-derived inhibitor for the treatment of corneal neovascularization in vivo. METHODS: A cartilage-derived inhibitor (CDI) from bovine scapula was purified to homogeneity. By rabbit corneal neovascularization (CNV) model, the effect of inhibition of CDI under various conditions was determined in corneal micropocket analysis. RESULTS: The purified CDI could inhibit strongly the growing speed and area of rabbit CNV compared to control (P < 0.001). CONCLUSION: It is demonstrated that CDI is a potent dose-dependent inhibitor of angiogenesis.

Angiogenesis Inhibitors↗
PubMed1999

[The selection of tympanoplastic type in treating chronic suppurative otitis media].

OBJECTIVE: To investigate the effect of different type of tympanoplasty on chronic suppurative otitis media (CSOM). METHOD: Myringoplasty, focuses clearance and myringoplasty, focuses clearance and ossiculoplasty and myringoplasty were performed in 189 cases of CSOM. RESULT: The cure rate of perforation of tympanic membrane with myringoplasty was above 99% accompanied by the varying improvement in acoustic sensibility. CONCLUSION: Different types of tympanoplasty should be used according to the CSOM. The slighter the pathological changes of CSOM, the more the hearing improve. The better effects was in tympanoplasty of simple type. The tympanic exploration is necessary to be included in tympanoplasty.

Adolescent↗
PubMed1999

[Determination of 14 elements in chromium-rich brewer's yeast by ICP-AES].

An ICP-AES method was established for the determination of 14 elements in chromium-rich and normal brewer's yeast. The RSDs of two standard reference materials were 0. 5%-3.2% and 0.4%-3.4%, respectively. The results showed that chromium contents could affect the concentrations of other elements in chromium-rich brewer's yeast. The concentrations of K, Mn, P, V, Mg and Ca in chromium-rich brewer's yeast were significantly lower than those in normal brewer's yeast.

Chromium↗
PubMed1999

[Ultra trace determination of platinum, palladium, gold and rhodium in minerals].

Our work studied the minerals dissolved in aqua regia. The trace Pt(II), Pd(II) Au (III) and Rh(I) complexes were loaded by the mixed carbon powder which carried diphenyl thiourea when aqua regia or hydrochloric acid media as well as stannous chloride were present. We added some carbon powder in ashen loader and determined the elements with atomic emission spectrometry. The determination sensitivity counted with 10 grams of samples is 1 x 10(-9). The RSD for 0.05 x 10(-6) standard Pt, Pd, Au and Rh solutions are 6.0%, 5.1%, 8.5% and 11.4%, respectively. The method is simple and operation is easy. The results satisfy our requirement.

English Abstract↗
PubMed1998

The Kaiser Permanente/USC Patient Consultation Study: change in use and cost of health care services.

The impacts of three alternative models of pharmacist consultation on the use and cost of health care services were studied. Two studies were conducted concurrently in an HMO over two years. In one, 6000 patients were randomly assigned to one of three consultation models; in the other, the three models were implemented in six geographic regions of California (4600 patients). The models were (1) consultation about new or changed prescriptions as mandated by state law (state model), (2) consultation focused on selected high-risk ambulatory care patients (Kaiser Permanente [KP] model), and (3) a control model. The patients were surveyed three times about their health status and satisfaction, and computerized data on health care use and cost were collected. The effect of the consultation models on the use and cost of health care services was examined across five risk groups that were based on drug-use profiles. An additional 37,750 patients (10% of the patients residing in the areawide study sites) were included in a supplemental analysis of the use and cost of health care services. There was no indication in the random-assignment study that pharmacist consultations affected either drug costs or the cost of office visits. Similar results were found in the areawide study, with the exception that the KP model was associated with lower drug costs than the control model. In the 10% sample, the KP model appeared to be associated with lower office visit costs but higher drug costs. Both models were associated with a lower likelihood of a hospital admission and with lower total health care costs for some high-risk patients compared with the control model. Counseling patients about their medications may be unlikely to reduce medication costs or the cost of office visits but may reduce the likelihood of hospital admissions and the overall costs of health care services; a combination of counseling patients at high risk for drug-related problems and counseling all patients about any new or changed prescription should be considered.

Adult↗
PubMed1998

Solution NMR structure and backbone dynamics of the major cold-shock protein (CspA) from Escherichia coli: evidence for conformational dynamics in the single-stranded RNA-binding site.

The major cold-shock protein (CspA) from Escherichia coli is a single-stranded nucleic acid-binding protein that is produced in response to cold stress. We have previously reported its overall chain fold as determined by NMR spectroscopy [Newkirk, K., Feng, W., Jiang, W., Tejero, R., Emerson, S. D., Inouye, M., and Montelione, G. T. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 5114-5118]. Here we describe the complete analysis of 1H, 13C, and 15N resonance assignments for CspA, together with a refined solution NMR structure based on 699 conformational constraints and an analysis of backbone dynamics based on 15N relaxation rate measurements. An extensive set of triple-resonance NMR experiments for obtaining the backbone and side chain resonance assignments were carried out on uniformly 13C- and 15N-enriched CspA. Using a subset of these triple-resonance experiments, the computer program AUTOASSIGN provided automatic analysis of sequence-specific backbone N, Calpha, C', HN, Halpha, and side chain Cbeta resonance assignments. The remaining 1H, 13C, and 15N resonance assignments for CspA were then obtained by manual analysis of additional NMR spectra. Dihedral angle constraints and stereospecific methylene Hbeta resonance assignments were determined using a new conformational grid search program, HYPER, and used together with longer-range constraints as input for three-dimensional structure calculations. The resulting solution NMR structure of CspA is a well-defined five-stranded beta-barrel with surface-exposed aromatic groups that form a single-stranded nucleic acid-binding site. Backbone dynamics of CspA have also been characterized by 15N T1, T2, and heteronuclear 15N-1H NOE measurements and analyzed using the extended Lipari-Szabo formalism. These dynamic measurements indicate a molecular rotational correlation time taum of 4.88 +/- 0.04 ns and provide evidence for fast time scale (taue < 500 ps) dynamics in surface loops and motions on the microsecond to millisecond time scale within the proposed nucleic acid-binding epitope.

Amides↗
PubMed1998

Hormone-dependent coactivator binding to a hydrophobic cleft on nuclear receptors.

The ligand-binding domain of nuclear receptors contains a transcriptional activation function (AF-2) that mediates hormone-dependent binding of coactivator proteins. Scanning surface mutagenesis on the human thyroid hormone receptor was performed to define the site that binds the coactivators, glucocorticoid receptor-interacting protein 1 (GRIP1) and steroid receptor coactivator 1 (SRC-1). The residues involved encircle a small surface that contains a hydrophobic cleft. Ligand activation of transcription involves formation of this surface by folding the carboxyl-terminal alpha helix against a scaffold of three other helices. These features may represent general ones for nuclear receptors.

HeLa Cells↗
PubMed1998

Activation of NF-kappaB via a Src-dependent Ras-MAPK-pp90rsk pathway is required for Pseudomonas aeruginosa-induced mucin overproduction in epithelial cells.

Cystic fibrosis (CF) is an autosomal recessive disorder, the most common lethal genetic disease in Caucasians. Respiratory disease is the major cause of morbidity and mortality. Indeed, 95% of CF patients die of respiratory failure. Pseudomonas aeruginosa, an opportunistic pathogen, chronically infects the lungs of over 85% of CF patients. It is ineradicable by antibiotics and responsible for airway mucus overproduction that contributes to airway obstruction and death. The molecular mechanisms underlying this pathology are unknown. Here we show that P. aeruginosa activates a c-Src-Ras-MEK1/2-MAPK-pp90rsk signaling pathway that leads to activation of nuclear factor NF-kappaB (p65/p50). Activated NF-kappaB binds to a kappaB site in the 5'-flanking region of the MUC2 gene and activates MUC2 mucin transcription. These studies bring new insight into bacterial-epithelial interactions and more specifically into the molecular pathogenesis of cystic fibrosis. Understanding these signaling and gene regulatory mechanisms opens up new therapeutic targets for cystic fibrosis.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1998

Dicyclohexylcarbodiimide interaction with the voltage-dependent anion channel from sarcoplasmic reticulum.

In a recent study [Shoshan-Barmatz, V., Orr, I., Weil, S., Meyer, H., Varsanyi, M. & Heilmeyer, L. M. G. (1996) FEBS Lett. 386, 205-210] we have demonstrated the presence of the voltage-dependent anion channel (VDAC) in skeletal muscle sarcoplasmic reticulum (SR) as supported here by co-localization of VDAC and (Ca2+ + Mg2+)ATPase in the SR using double-immunogold labeling. The interaction of the carboxyl-modifying reagent dicyclohexylcarbodiimide with the SR-VDAC is characterized by labeling with [14C]dicyclohexylcarbodiimide and by dicyclohexylcarbodiimide modification of the reconstituted-purified VDAC channel activity. In both SR and mitochondrial membranes, [14C]dicyclohexylcarbodiimide most specifically labeled a 35-kDa protein, identified as VDAC by specific anti-VDAC Ig. Labeling of the SR-VDAC was about twofold higher than that of the mitochondrial VDAC, which could result either form higher labeling of the SR protein or from relatively higher amounts of VDAC/mg total protein in the SR membranes. [14C]Dicyclohexylcarbodiimide labeling of the SR, but not the mitochondrial VDAC, was biphasic with respect to time and concentration of [14C]dicyclohexylcarbodiimide. Partial digestion of [14C]dicyclohexylcarbodiimide-labeled SR-VDAC with chymotrypsin yielded five proteolytic fragments which were recognized by the anti-VDAC Ig, and the dicyclohexylcarbodiimide-binding site was localized in the 19-kDa fragment. VDAC was purified from SR and mitochondrial membranes by spermine-agarose column. The interaction of dicyclohexylcarbodiimide with functional carboxyl residue(s) in the purified VDAC is demonstrated by recording its channel activity, following its reconstitution into planar lipid bilayer (PLB). Dicyclohexylcarbodiimide inhibited the channel activity in a voltage-dependent manner, requiring incubation with dicyclohexylcarbodiimide at high (negative or positive) potentials. Dicyclohexylcarbodiimide slowed down the transition from the high-conducting to a long-lived low-conducting states of the channel (approximately 20% of its maximal conductance), by stabilizing the intermediate states. Similar results were also obtained with purified-reconstituted mitochondrial VDAC. Hydrophilic carboxyl reagents [[1-ethyl-3-(3-dimethylamino)propyl] carbodiimide, N-ethyl-phenylisoxazolium-3'-sulfonate] neither modified the channel activity nor prevented [14C]dicyclohexylcarbodiimide labeling. These results indicate that dicyclohexylcarbodiimide interacts with a carboxyl group located in a hydrophobic region of the protein which is involved in the channel gating.

Animals↗
PubMed1998

Identification, characterization and partial purification of a thiol-protease which cleaves specifically the skeletal muscle ryanodine receptor/Ca2+ release channel.

A 94 kDa large subunit thiol-protease, as identified by anti-calpain antibodies, has been isolated from skeletal muscle junctional sarcoplasmic reticulum (SR). This protease cleaves specifically the skeletal muscle ryanodine receptor (RyR)/Ca2+ release channel at one site resulting in the 375 kDa and 150 kDa fragments. The 94 kDa thiol-protease degrades neither other SR proteins nor the ryanodine receptor of cardiac nor brain membranes. The partially purified 94 kDa protease, like the SR associated protease, had an optimal pH of about 7.0, was absolutely dependent on the presence of thiol reducing reagents, and was completely inhibited by HgCl2, leupeptin and the specific calpain I inhibitor. However, while the SR membrane-associated protease requires Ca2+ at a submicromolar concentration, the isolated thiol-protease has lost the Ca2+ requirement. The 94 kDa thiol-protease had no effect on ryanodine binding but modified the channel activity of RyR reconstituted into planar lipid bilayer: in a time-dependent manner, the channel activity decreases and within several minutes the channel is converted into a subconducting state. The protease-modified channel activity is still Ca2+-dependent and ryanodine sensitive. This 94 kDa thiol-protease cross react with anti-calpain antibodies thus, may represent the novel large subunit of the skeletal muscle specific calpain p94.

Animals↗
PubMed1998

Correlation of mercury with selenium in human hair at a typical mercury-polluted area in China.

The levels of mercury (Hg) and selenium (Se) and their correlation in human scalp hair of 29 pairs of pregnant women and their newborns living at a high-Hg and low-Se area, the Second Song-Hua-Jiang River System, have been studied by instrumental neutron activation analysis. Our results indicate that the Hg level in infant hair samples are roughly close to that in their mothers, whereas the Se level in infants is much higher. Furthermore, the molar ratios of Se/Hg in newborns are also 40% higher than those in mothers. It demonstrates that infants are able to absorb more selenium from their mothers' bodies to protect against or alleviate the intoxication of Hg. This "autoprotective mechanism" likely plays a critical role during fetal development. The possible chemical species of Hg and Se in hair is also discussed.

China↗
PubMed1998

Use of the enriched stable isotope Cr-50 as a tracer to study the metabolism of chromium (III) in normal and diabetic rats.

The activable enriched stable isotope Cr-50 compound Cr2O3 was used as a tracer to study the metabolism of chromium(III) [CR(III)] intragastrically administered in normal and diabetic rats. The comparison of absorption, distribution, and excretion in organs and tissues of the two groups do not show much alteration, but some differences exist indeed. The contents of 51Cr radioactivity of the diabetic rats appear to be of higher retention than in most studied organisms. The urinary 51Cr excretion of diabetics is significantly higher than that of normal rats. Therefore, a conclusion can be drawn that the insulin-dependent rats generally absorb and excrete more chromium (Cr) than the normal rats.

Absorption↗
PubMed1998

Serum and urine chromium concentrations in elderly diabetics.

The serum and urine chromium concentrations of 57 diabetics and 55 normal fasting subjects were determined by atomic absorption spectrometry (AAS). Our results indicate that the chromium concentration ranges of serum and urine for diabetics are 0.22-0.36 and 4.54-5.90 microg/L, respectively, significantly lower than 0.66-0.84 7.80-9.68 microg/L for the normal (P<0.001), which implies that the elderly diabetics probably lack chromium. Further, it was found that the urine chromium level of the female diabetics was substantially higher than that of the male in the same age group (P<0.01), whereas the serum chromium level was almost the same. However, the urine chromium concentration increases with aging, no matter who the diabetics or the controls are. The serum chromium concentrations of the 24 cases patients with 2-h oral glucose tolerance test (OGTT) were significantly lower than that of those with empty stomach, whereas the urine chromium exhibits a contrary tendency. Our data indicate that the chromium lost and excreted from human body increases with aging and is related to the diabetics. Thus, it is recommended to supplement a certain amount of chromium to the elderly diabetics according to their nutritional level.

Aged↗
PubMed1998

X-ray crystallographic and functional studies of thyroid hormone receptor.

We have solved several X-ray crystallographic structures of TR ligand-binding domains (LBDs), including the rat (r) TR alpha and the human (h) TR beta bound to diverse ligands. The TR-LBD folding, comprised mostly of alpha-helices, is likely to be general for the superfamily. The ligand, buried in the receptor, forms part of its hydrophobic core. Tight fitting of ligand into the receptor explains its high affinity for the TR, although the structure suggests that ligands with even higher affinities might be generated. The kinetics of 3,5,3'-triiodo-L-thyronine (T3) and 3,5,3',5'-tetraiodo-L-thyronine (T4) binding suggest that folding around the ligand, rather than receptor opening, is rate-limiting for high affinity binding. TR beta mutations in patients with resistance to T3 cluster around the ligand; these different locations could differentially affect on other receptor functions and explain the syndrome's clinical diversity. Guided by the structure, mutations have been placed on the TR surface to define interactions with other proteins. They suggest that a similar surface in the LBD is utilized for homo- or heterodimerization on direct repeats and inverted palindromes but not on palindromes. Coactivator proteins that mediate TR transcriptional activation bind to a small surface comprised of residues on four helices with a well-defined hydrophobic cleft, which may be a target for pharmaceuticals. The coactivator-binding surface appears to form upon ligand-binding by the folding of helix 12 into the scaffold formed by helices 3, 4 and 5. The analysis of most currently used antagonists suggest that although they probably fit into the ligand-binding pocket, they possess a group that may alter proper folding of the receptor, with disruption of the coactivator-binding surface (the 'extension model').

Animals↗
PubMed1998

Voltage-dependent anion channel proteins in synaptosomes of the torpedo electric organ: immunolocalization, purification, and characterization.

In this study, we purified and characterized the voltage-dependent anion channel (VDAC) from the Torpedo electric organ. Using immunogold labeling, VDAC was colocalized with the voltage-gated Ca2+ channel in the synaptic plasma membrane. By immunoblot analysis, five protein bands in synaptosomes isolated from the Torpedo electric organ cross reacted with two monoclonal anti-VDAC antibody. No more than about 7 to 10% mitochondrial contains could be detected in any synaptosomal membrane preparation tested. This was estimated by comparing the specific activity in mitochondria and synaptosomes of succinate-cytochrome-c oxidoreductase and antimycin-insensitive NADH-cytochrome-c oxidoreductase activities; mitochondrial inner and outer membrane marker enzymes, respectively. [14C]DCCD (dicyclohexylcarbodiimide), which specifically label mitochondrial VDAC, labeled four 30-35 kDa protein bands that were found to interact with the anti-VDAC antibody. The distribution of the Torpedo VDAC protein bands was different among membranes isolated from various tissues. VDAC was purified from synaptosomes and a separation between two of the proteins was obtained. The two purified proteins were characterized by their single channel activity and partial amino acid sequences. Upon reconstitution into a planar lipid bilayer, the purified VDACs showed voltage-dependent channel activity with properties similar to those of purified mitochondrial VDAC. Amino acid sequence of four peptides, derived from VDAC band II, exhibited high homology to sequences present in human VDACI (98%), VDAC2 (91.8%), and VDAC3 (90%), while another peptide, derived from VDAC band III, showed lower homology to either VDAC1 (88.4%) or VDAC2 (79%). Two more peptides show high homology to the sequence present in mouse brain VDAC3 (100 and 78%). In addition, we demonstrate the translocation of ATP into synaptosomes, which is inhibited by DCCD and by the anion transport inhibitor DIDS. The possible function of VDAC in the synaptic plasma membrane is discussed.

Amino Acid Sequence↗
PubMed1998

Differential expression of Borrelia burgdorferi genes during erythema migrans and Lyme arthritis.

Borrelia burgdorferi, the agent of Lyme disease, selectively expresses genes in the arthropod vector and mammalian host. Specific B. burgdorferi gene expression during human infection was examined in tissue specimens, using RNA-polymerase chain reaction, from 3 patients with Lyme disease. ospA was investigated because OspA is down-regulated by B. burgdorferi in ticks during engorgement and is a vaccine candidate in phase III clinical trials. p35 and p37 were also assessed because these genes are induced by spirochetes during murine Lyme borreliosis and play roles in protective immunity. p35 and p37 mRNA were detected in erythema migrans biopsy specimens from 2 patients and in the synovium of 1 patient with Lyme arthritis. ospA mRNA was not identified in any of these tissues. These data show that ospA is repressed while p35 and p37 are induced in human infection; these results are the first direct demonstration of differential B. burgdorferi gene expression during Lyme disease.

Adolescent↗