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Biomedical subjects

Fei Wang

Publications and source records attributed to Fei Wang.

143 records · Page 8Linked to original sources
PubMed2002

The distribution characteristics of bacterial beta-glucosidase activity in Taiwan strait.

Twenty stations were established in the near-shore regions of South Fujian Shoal (116 degrees 10'-119 degrees 00' E, 21 degrees 20'-24 degrees 10' N) on summer and winter cruises during the period from August 1997 and February to March 1998. The distribution pattern of marine bacterial beta-glucosidase activity (beta-GlcA) has been investigated by using fluorogenic model substrate (FMS) technique in order to have better understanding of the beta-GlcA, as well as its relation to marine bacterial biomass, productivity and environmental factors in Taiwan strait. The results showed that: (1) In summer, the average of beta-GlcA at the Southern stations of Taiwan strait was 1.94 nmol/l h. While in winter, the average of beta-GlcA at the Northern stations was 0.86 nmol/l h and the range of variation (0.34-1.89 nmol/l h) was much more narrow than that in summer (0.31-8.1 nmol/l h). (2) According to the carbon conversion factor, the beta-GlcA was 0.14 and 0.062 ugc/l h in summer and winter respectively. These beta-GlcA values were higher than the bacterial production of the two seasons respectively. (3) The beta-GlcA gradually rises from offshore water to near-shore water. (4) The correlation between the beta-GlcA and the bacterial secondary production was not so obvious. (5) The correlation between the section distributions, daily varying of the beta-GlcA and the bacterial production was not obvious. (6) In the surface water, the distribution character of free-state beta-GlcA from bacteria was equal to that of the total beta-GlcA in the whole sea area.

Bacteria↗
PubMed2002

Overexpression of DsbC and DsbG markedly improves soluble and functional expression of single-chain Fv antibodies in Escherichia coli.

Single-chain Fv antibodies (scFv), a group of reconstructed molecules with several disulfide bonds, are prone to aggregate as inclusion bodies, the insoluble species of natural proteins, when expressed in Escherichia coli, especially at high level. Recovery of functionally active products from inclusion bodies is onerous and ineffective. We have increased the soluble and functional scFv yields by fusing either DsbC or DsbG, two E. coli disulfide isomerases with general chaperone function, to scFvs. Compared to the totally insoluble inclusion bodies of scFvs expressed separately, more than half of each fusion protein DsbC-scFv or DsbG-scFv was soluble, according to SDS-PAGE analysis. The more effective solubility was obtained when the fused protein DsbG-scFv was co-expressed simultaneously with DsbC under the same promoter. Under this condition, the soluble portion of DsbG-scFv increased from about 50% to 90% measured by scanning SDS-PAGE gel. Co-expression of DsbC can change fusion protein CBD-scFv from totally insoluble when expressed in E. coli separately to a considerable portion of soluble CBD-scFv. Antigen-binding activity assay showed that scFvs retained full affinity to specific antigens. We also determined that general molecular chaperones GroEL and GroES had no effects on the solubility of scFvs when co-expressed with scFv in E. coli. We propose that the correct formation of disulfide bonds in scFvs is the crucial factor responsible for solubility of scFvs.

Base Sequence↗
PubMed2002

The gated gait of the processive molecular motor, myosin V.

Class V myosins are actin-based molecular motors involved in vesicular and organellar transport. Single myosin V molecules move processively along F-actin, taking several 36-nm steps for each diffusional encounter. Here we have measured the mechanical interactions between mouse brain myosin V and rabbit skeletal F-actin. The working stroke produced by a myosin V head is approximately 25 nm, consisting of two separate mechanical phases (20 + 5 nm). We show that there are preferred myosin binding positions (target zones) every 36 nm along the actin filament, and propose that the 36-nm steps of the double-headed motor are a combination of the working stroke (25 nm) of the bound head and a biased, thermally driven diffusive movement (11 nm) of the free head onto the next target zone. The second phase of the working stroke (5 nm) acts as a gate - like an escapement in a clock, coordinating the ATPase cycles of the two myosin V heads. This mechanism increases processivity and enables a single myosin V molecule to travel distances of several hundred nanometres along the actin filament.

Actins↗
PubMed2002

Identification of an organelle receptor for myosin-Va.

Little is known about how molecular motors bind to their vesicular cargo. Here we show that myosin-Va, an actin-based vesicle motor, binds to one of its cargoes, the melanosome, by interacting with a receptor-protein complex containing Rab27a and melanophilin, a postulated Rab27a effector. Rab27a binds to the melanosome first and then recruits melanophilin, which in turn recruits myosin-Va. Melanophilin creates this link by binding to Rab27a in a GTP-dependent fashion through its amino terminus, and to myosin-Va through its carboxy terminus. Moreover, this latter interaction, similar to the ability of myosin-Va to colocalize with melanosomes and influence their distribution in vivo, is absolutely dependent on the presence of exon-F, an alternatively spliced exon in the myosin-Va tail. These results provide the first molecular description of an organelle receptor for an actin-based motor, illustrate how alternate exon usage can be used to specify cargo, and further expand the functional repertoire of Rab GTPases and their effectors.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Lipid products of PI(3)Ks maintain persistent cell polarity and directed motility in neutrophils.

In gradients of external chemo-attractant, mammalian neutrophilic leukocytes (neutrophils) and Dictyostelium discoideum amoebae adopt a polarized morphology and selectively accumulate lipid products of phosphatidylinositol-3-OH kinases (PI(3)Ks), including PtdIns(3,4,5)P(3), at their up-gradient edges; the internal PtdIns(3,4,5)P(3) gradient substantially exceeds that of the external attractant. An accompanying report presents evidence for a positive feedback loop that amplifies the gradient of internal signal: PtdIns(3,4,5)P(3) at the leading edge stimulates its own accumulation by inducing activation of one or more Rho GTPases (Rac, Cdc42, and/or Rho), which in turn increase PtdIns(3,4,5)P(3) accumulation. Here we show that interruption of this feedback by treatment with PI(3)K inhibitors reduces the size and stability of pseudopods and causes cells to migrate in jerky trajectories that deviate more from the up-gradient direction than do those of controls. Moreover, amplification of the internal PtdIns(3,4,5)P(3) gradient is markedly impaired by latrunculin or jasplakinolide, toxins that inhibit polymerization or depolymerization of actin, respectively. Thus reciprocal interplay between PtdIns(3,4,5)P(3) and polymerized actin initiates and maintains the asymmetry of intracellular signals responsible for cell polarity and directed motility.

Animals↗
PubMed2002

Management of rosiglitazone-induced edema: two case reports and a review of the literature.

The thiazolidinediones are an important class of insulin-sensitizing agents used for the treatment of type 2 diabetes. Similar to other antidiabetic agents, use of the thiazolidinediones is limited by adverse drug reactions. Specifically, use of the thiazolidinediones is associated with a triad of fluid retention, edema, and weight gain. In premarketing clinical trials, edema was reported to occur infrequently with minimal severity. However, several published cases from postmarketing data demonstrate that thiazolidinedione-induced fluid retention, exhibited by the initial onset of peripheral edema and weight gain, can progress to a more severe form of pulmonary edema that is refractory to diuretic therapy with resolution of symptoms only through discontinuation of the offending thiazolidinedione. In clinical practice, the occurrence of edema secondary to a thiazolidinedione drug may occur more frequently than reported. Two cases presented in this report illustrate a different outpatient management approach that enables both desired glycemic control and minimal fluid retention while using the thiazolidinediones.

Body Weight↗
PubMed2002

Rab27a is an essential component of melanosome receptor for myosin Va.

Melanocytes that lack the GTPase Rab27a (ashen) are disabled in myosin Va-dependent melanosome capture because the association of the myosin with the melanosome surface depends on the presence of this resident melanosomal membrane protein. One interpretation of these observations is that Rab27a functions wholly or in part as the melanosome receptor for myosin Va (Myo5a). Herein, we show that the ability of the myosin Va tail domain to localize to the melanosome and generate a myosin Va null (dilute) phenotype in wild-type melanocytes is absolutely dependent on the presence of exon F, one of two alternatively spliced exons present in the tail of the melanocyte-spliced isoform of myosin Va but not the brain-spliced isoform. Exon D, the other melanocyte-specific tail exon, is not required. Similarly, the ability of full-length myosin Va to colocalize with melanosomes and to rescue their distribution in dilute melanocytes requires exon F but not exon D. These results predict that an interaction between myosin Va and Rab27a should be exon F dependent. Consistent with this, Rab27a present in detergent lysates of melanocytes binds to beads coated with purified, full-length melanocyte myosin Va and melanocyte myosin Va lacking exon D, but not to beads coated with melanocyte myosin Va lacking exon F or brain myosin Va. Moreover, the preparation of melanocyte lysates in the presence of GDP rather than guanosine-5'-O-(3-thio)triphosphate reduces the amount of Rab27a bound to melanocyte myosin Va-coated beads by approximately fourfold. Finally, pure Rab27a does not bind to myosin Va-coated beads, suggesting that these two proteins interact indirectly. Together, these results argue that Rab27a is an essential component of a protein complex that serves as the melanosome receptor for myosin Va, suggest that this complex contains at least one additional protein capable of bridging the indirect interaction between Rab27a and myosin Va, and imply that the recruitment of myosin Va to the melanosome surface in vivo should be regulated by factors controlling the nucleotide state of Rab27a.

Alternative Splicing↗
PubMed2002

[Isolation, purification and analysis of polysaccharides from Adenophora potaninii Korsh].

Polysaccharides, AP-1 and AP-3, were obtained through extraction of the roots of Adenophora potaninii Korsh by hot water, followed by the isolation and purification by DEAE-cellulose and Sephadex G-200 column chromatography. It was proved to be homogeneous by gel filtration chromatography and their average MW was estimated to be 8.3 x 10(4) and 6.3 x 10(4) respectively. Analysis of sugar composition showed that AP-1 is D-glucan, while AP-3 is composed of glucose, rhamnose, arabinose and glucronic acid in the molar ratio of 5:1:1:3.

Campanulaceae↗
PubMedDate not supplied

Disparities in diabetes care: impact of mental illness.

BACKGROUND: Emerging evidence indicates that patients with mental health conditions (MHCs) may receive less intensive medical care. Diabetes serves as a useful condition in which to test for MHC-related disparities in care. We examined whether quality measures for diabetes care are worse for patients with or without MHCs. METHODS: This national, cross-sectional study included 313 586 noninstitutionalized Veterans Health Administration patients with diabetes (identified from diagnostic codes and prescriptions) whose Veterans Health Administration facility transmitted laboratory data to a central database; 76 799 (25%) had MHCs (based on diagnostic codes for depressed mood, anxiety, psychosis, manic symptoms, substance use disorders, personality disorders, and other categories). National data from Veterans Health Administration records, Medicare claims, and a national survey were linked to characterize 1999 diabetes care. RESULTS: Failure to meet diabetes performance measures was more common in patients with MHCs: unadjusted odds ratio (95% confidence interval) was 1.24 (1.22-1.27) for no hemoglobin A(1c) testing, 1.25 (1.23-1.28) for no low-density lipoprotein cholesterol testing, 1.05 (1.03-1.07) for no eye examination, 1.32 (1.30-1.35) for poor glycemic control, and 1.17 (1.15-1.20) for poor lipemic control. Disparities persisted after case mix adjustment and were more pronounced with specific MHCs (psychotic, manic, substance use, and personality disorders). The percentage not meeting diabetes care standards increased with increasing number of MHCs. CONCLUSION: Patients with mental illness merit special attention in national diabetes quality improvement efforts.

Age Factors↗
PubMedDate not supplied

Study on the interaction between protein and Eu(III)-chlorotetracycline complex and the determination of protein using the fluorimetric method.

Chlorotetracycline (CTC) can react with europium ions Eu3+, and the complex emits the intrinsic fluorescence of Eu3+. The intensity is greatly enhanced by proteins and this forms the basis of a new fluorimetric method for determination of protein. Further research indicates that under optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of proteins, in the range 2.0 x 10(-7)-1.0 x 10(-5) g/mL for bovine serum albumin (BSA) (linear equation, I(f) = 34.35933 + 11.54467 x 10(6)C)(r = 0.99895) and 8.0 x 10(-7)-1.0 x 10(-5) g/mL for human serum albumin (HSA) (linear equation, I(f) = 76.58881 + 5.3569 x 10(6)C) (r = 0.99283). Detection limits (S/N = 3) were 8.9 x 10(-9) g/mL for BSA and 3.3 x 10(-8) g/mL for HSA. In an assay for BSA in calf serum, this method gave a value close to that determined by the UV spectrophotometric method.

Buffers↗
PubMedDate not supplied

Fluorescence enhancement effect of the morin-Al3+ -sodium dodecyl benzene sulphonate-protein system and the determination of proteins.

The fluorescence intensity of the morin-Al(3+) complex was greatly enhanced by proteins in the presence of sodium dodecyl benzene sulphonate (SDBS). Based on this, a new fluorimetric method for the determination of protein was developed. Under optimum conditions, the enhanced intensity of fluorescence was in proportion to the concentration of proteins in the range 1.0 x 10(-8)-1.3 x 10(-5) g/mL for bovine serum albumin (BSA), 4.0 x 10(-8)-1.2 x 10(-5) g/mL for egg albumin (EA) and 5.0 x 10(-8)-1.2 x 10(-5) g/mL for human serum albumin (HSA). Their detection limits (S:N = 3) were 5.0 x 10(-9), 1.8 x 10(-8) and 1.6 x 10(-8) g/mL, respectively. The interaction mechanism was also studied.

Aluminum↗
PubMedDate not supplied

Improvement of the acridine orange-protein-surfactant system for protein estimation based on aromatic ring stacking effect of sodium dodecyl benzene sulphonate.

The fluorescence of acridine orange (AO) is greatly quenched by the anionic surfactant sodium dodecyl benzene sulphonate (SDBS), but when protein is added into the AO-SDBS system, the fluorescence intensity of the latter is enhanced again. Based on this, a new fluorimetric method of determination of protein was developed. Under optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of protein, such as bovine serum albumin (BSA), human serum albumin (HSA) and egg albumin (EA), over a wide range with detection limits at the 10(-9) g/mL level. This method has been satisfactorily used for the determination of protein in samples. We compared results using 280 nm and 490 nm excitation wavelengths and the mechanism of the assay.

Acridine Orange↗
PubMedDate not supplied

The sensitive determination of nucleic acids using a fluorescence-quenching method.

Experiments indicated that nucleic acids can quench the fluorescence of the Eu3+ -2-thenoyltrifluoroacetone (TTA)-1,10-phenanthroline (Phen) system. Based on this, a sensitive method for the determination of nucleic acids was proposed. The experiments indicated that under the optimum conditions, the quenched fluorescence intensity was in proportion to the concentration of nucleic acids in the range 1.0 x 10(-11)-1.0 x 10(-6) g/mL for yeast RNA (yRNA), 5.0 x 10(-11)-5.0 x 10(-7) g/mL for fish sperm (fsDNA) and 1.0 x 10(-10)-1.5 x 10(-6) g/mL for calf thymus DNA (ctDNA). Their detection limits were 3.0 x 10(-12), 4.0 x 10(-12) and 5.0 x 10(-11) g/mL, respectively. Therefore, the proposed method is one of the most sensitive methods available. The interaction between nucleic acids and Eu3+ -TTA-Phen is also discussed.

Europium↗
PubMedDate not supplied

Up-regulation of the expression of cocaine and amphetamine-regulated transcript peptide by electroacupuncture in the arcuate nucleus of diet-induced obese rats.

It was reported that acupuncture or electro-acupuncture (EA) is effective in reducing the body weight for obese patients, although the mechanisms remain obscure. In a previous study, we have found that rats fed with high-fat (HIF) diet developed diet-induced obesity (DIO) with a concomitant decrease in the hypothalamic content of the cocaine and amphetamine-regulated transcript (CART) peptide, a peptide with anorexiogenic effect. To assess the central effect of EA on DIO rat, we revealed that EA up-regulated the expression of CART peptide in the arcuate nucleus (ARC) of the DIO rats. After feeding with HIF diet for 14 weeks, the DIO rats received EA stimulation three times per week for 4 weeks. The expression of CART peptide in ARC was measured using immunohistochemistry. The plasma ACTH was measured with ELISA. EA caused a reduction of both body weight and energy intake in DIO rats and increased the expression of CART peptide in ARC. The plasma ACTH was increased in response to restraint stress, but EA produced no further increase in ACTH levels. The results suggest that EA can up-regulate the expression of CART peptide to approach normal level, resulting in an inhibition of food intake and a reduction of body weight in DIO rats.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Modeling the isolated cardiac myocyte.

Computer modeling of cardiac myocytes has flourished in recent years. Models have evolved from mathematical descriptions of ionic channels alone to more sophisticated formulations that include calcium transport mechanisms, ATP production and metabolic pathways. The increased complexity is fueled by the new data available in the field. The continuous production of experimental data has led to the evolution of increasingly refined descriptions of the phenomena by modelers. Integrating the numerous systems involved in cardiac myocyte homeostasis makes the use of computer models necessary due to the unreliability of intuitive approaches. However the complexity of the model should not imply a cumbersome operation of the program. As with any tool, computer models have to be easy to operate or their strength will be diminished and potential users will not benefit fully from them. The contribution of the computer modeler to their respective biological fields will be more successful and enduring if modelers devote sufficient time to implement their equations into a model with user-friendly characteristics.

Action Potentials↗
PubMedDate not supplied

Synthesis and evaluation of a star amphiphilic block copolymer from poly(epsilon-caprolactone) and poly(ethylene glycol) as a potential drug delivery carrier.

A star polymer composed of amphiphilic block copolymer arms has been synthesized and characterized. The core of the star polymer is polyamidoamine (PAMAM) dendrimer, the inner block in the arm is lipophilic poly(epsilon-caprolactone) (PCL), and the outer block in the arm is hydrophilic poly(ethylene glycol) (PEG). The star-PCL polymer was synthesized first by ring-opening polymerization of epsilon-caprolactone with a PAMAM-OH dendrimer as initiator. The PEG polymer was then attached to the PCL terminus by an ester-forming reaction. Characterization with SEC, (1)H NMR, FTIR, TGA, and DSC confirmed the star structure of the polymers. The micelle formation of the star copolymer (star-PCL-PEG) was studied by fluorescence spectroscopy. Hydrophobic dyes and drugs can be encapsulated in the micelles. A loading capacity of up to 22% (w/w) was achieved with etoposide, a hydrophobic anticancer drug. A cytotoxicity assay demonstrated that the star-PCL-PEG copolymer is nontoxic in cell culture. This type of block copolymer can be used as a drug delivery carrier.

Animals↗