Biomedical subjects

Fei Wang

Publications and source records attributed to Fei Wang.

At least 73 records · Page 4Linked to original sources

PubMed2005

The predicted coiled-coil domain of myosin 10 forms a novel elongated domain that lengthens the head.

Myosin 10 contains a region of predicted coiled coil 120 residues long. However, the highly charged nature and pattern of charges in the proximal 36 residues appear incompatible with coiled-coil formation. Circular dichroism, NMR, and analytical ultracentrifugation show that a synthesized peptide containing this region forms a stable single alpha-helix (SAH) domain in solution and does not dimerize to form a coiled coil even at millimolar concentrations. Additionally, electron microscopy of a recombinant myosin 10 containing the motor, the three calmodulin binding domains, and the full-length predicted coiled coil showed that it was mostly monomeric at physiological protein concentration. In dimers the molecules were joined only at their extreme distal ends, and no coiled-coil tail was visible. Furthermore, the neck lengths of both monomers and dimers were much longer than expected from the number of calmodulin binding domains. In contrast, micrographs of myosin 5 heavy meromyosin obtained under the same conditions clearly showed a coiled-coil tail, and the necks were the predicted length. Thus the predicted coiled coil of myosin 10 forms a novel elongated structure in which the proximal region is a SAH domain and the distal region is a SAH domain (or has an unknown extended structure) that dimerizes only at its end. Sequence comparisons show that similar structures may exist in the predicted coiled-coil domains of myosins 6 and 7a and MyoM and could function to increase the size of the working stroke.

Amino Acid Sequence↗

PubMed2005

Myosin V from Drosophila reveals diversity of motor mechanisms within the myosin V family.

Myosin V is the best characterized vesicle transporter in vertebrates, but it has been unknown as to whether all members of the myosin V family share a common, evolutionarily conserved mechanism of action. Here we show that myosin V from Drosophila has a strikingly different motor mechanism from that of vertebrate myosin Va, and it is a nonprocessive, ensemble motor. Our steady-state and transient kinetic measurements on single-headed constructs reveal that a single Drosophila myosin V molecule spends most of its mechanochemical cycle time detached from actin, therefore it has to function in processive units that comprise several molecules. Accordingly, in in vitro motility assays, double-headed Drosophila myosin V requires high surface concentrations to exhibit a continuous translocation of actin filaments. Our comparison between vertebrate and fly myosin V demonstrates that the well preserved function of myosin V motors in cytoplasmic transport can be accomplished by markedly different underlying mechanisms.

Actins↗

PubMed2005

Neutrophil microtubules suppress polarity and enhance directional migration.

How do microtubules, which maintain and direct polarity of many eukaryotic cells, regulate polarity of blood neutrophils? In sharp contrast to most cells, disrupting a neutrophil's microtubule network with nocodazole causes it to polarize and migrate [Niggli, V. (2003) J. Cell Sci. 116, 813-822]. Nocodazole induces the same responses in differentiated HL-60 cells, a model neutrophil cell line, and reduces their chemotactic prowess by causing them to pursue abnormally circuitous paths in migrating toward a stationary point source of an attractant, f-Met-Leu-Phe (fMLP). The chemotactic defect stems from dramatic nocodazole-induced imbalance between the divergent, opposed fMLP-induced "backness" and "frontness" signals responsible for neutrophil polarity. Nocodazole (i) stimulates backness by increasing Rho- and actomyosin-dependent contractility, as reported by Niggli, and also (ii) impairs fMLP-dependent frontness: pseudopods are flatter, contain less F-actin, and show decreased membrane translocation of PH-Akt-GFP, a fluorescent marker for 3'-phosphoinositide lipids. Inhibiting backness with a pharmacologic inhibitor of a Rho-dependent kinase substantially reverses nocodazole's effects on chemotaxis, straightness of migration paths, morphology, and PH-Akt-GFP translocation. Thus, microtubules normally balance backness vs. frontness signals, preventing backness from reducing the strength of pseudopods and from impairing directional migration.

Antineoplastic Agents↗

PubMed2005

Unfolding and refolding of bovine serum albumin induced by cetylpyridinium bromide.

The interaction of bovine serum albumin (BSA) with cationic surfactant cetylpyridinium bromide (CPB) in aqueous solution (pH 7.00) was studied quantitatively with ultraviolet (UV)-visible, far-UV, and near-UV circular dichroism, fluorescence, small angle x-ray scattering, and nuclear magnetic resonance measurement. It was found that CPB at low and high concentrations could induce the unfolding and refolding of BSA, respectively. We suggest that in the unfolding process, there existed BSA-CPB complex with the "necklace and bead" structure in which the unfolded BSA wrapped around CPB micelles, and that the hydrophobic interaction between the complexes led to the formation of large aggregates. The aromatic headgroup of CPB interacted with the tryptophan residues of BSA, resulting in the aromatic ring stacking between BSA and CPB. During the refolding process, the BSA molecule was penetrated into the rod micelle of CPB and the hydrophobic moiety of the BSA molecule was exposed outside while its hydrophilic part was hidden inside, thereby disrupting the aromatic ring stacking.

Animals↗

PubMed2005

Mechanism of action of myosin X, a membrane-associated molecular motor.

We have performed a detailed biochemical kinetic and spectroscopic study on a recombinant myosin X head construct to establish a quantitative model of the enzymatic mechanism of this membrane-bound myosin. Our model shows that during steady-state ATP hydrolysis, myosin X exhibits a duty ratio (i.e. the fraction of the cycle time spent strongly bound to actin) of around 16%, but most of the remaining myosin heads are also actin-attached even at moderate actin concentrations in the so-called "weak" actin-binding states. Contrary to the high duty ratio motors myosin V and VI, the ADP release rate constant from actomyosin X is around five times greater than the maximal steady-state ATPase activity, and the kinetic partitioning between different weak actin-binding states is a major contributor to the rate limitation of the enzymatic cycle. Two different ADP states of myosin X are populated in the absence of actin, one of which shows very similar kinetic properties to actomyosin.ADP. The nucleotide-free complex of myosin X with actin shows unique spectral and biochemical characteristics, indicating a special mode of actomyosin interaction.

Actins↗

PubMed2005

Impedance analysis of an electrode-separated piezoelectric sensor as a surface-monitoring technique for gelatin adsorption on quartz surface.

The early events pertaining to gelatin adsorption and desorption onto quartz surfaces were studied, employing an electrode-separated piezoelectric sensor (ESPS). The adsorption of gelatin on a quartz crystal surface corresponds to a mass increase, which can be monitored in real time by the changes in the impedance parameters of the ESPS. It was shown that the adsorption of gelatin on a quartz surface is partly irreversible with respect to the dilution of the bulk phase. The observed adsorption kinetics is compatible with a mechanism that involves adsorption, desorption, and transformation from a reversible adsorption state to irreversible one. A progressive approach method was established to simulate the adsorption process. The adsorption densities and kinetic parameters in the early adsorption process were obtained from the responses of the ESPS in the adsorption process. The influence of pH and ionic strength was tested. A comparison with the Langmuir adsorption model was made.

Adsorption↗

PubMed2005

SIRT3, a mitochondrial sirtuin deacetylase, regulates mitochondrial function and thermogenesis in brown adipocytes.

SIRT3 is one of the seven mammalian sirtuin homologs of the yeast Sir2 gene, which mediates the effect of caloric restriction on life span extension in yeast and Caenorhabditis elegans. Because adipose tissue is essential in energy homeostasis and also plays a role in life span determination, we decided to investigate the function of sirtuin members in fat. We report here that murine SIRT3 is expressed in brown adipose tissue and is localized on the mitochondria inner membrane. Caloric restriction activates SIRT3 expression in both white and brown adipose. Additionally, cold exposure up-regulates SIRT3 expression in brown fat, whereas elevated climate temperature reduces the expression. Enforced expression of SIRT3 in the HIB1B brown adipocytes enhances the expression of the uncoupling protein PGC-1alpha, UCP1, and a series of mitochondria-related genes. Both ADP-ribosyltransferase and deacetylase activities of SIRT3 are required for this action. Furthermore, the SIRT3 deacetylase mutant exhibits a dominant negative effect by inhibiting UCP1 expression. This inhibitive effect can be abolished by the coexpression of PGC-1alpha, indicating a major role of PGC-1alpha in the SIRT3 action. In addition, SIRT3 stimulates CREB phosphorylation, which reportedly activates PGC-1alpha promoter directly. Functionally, sustained expression of SIRT3 decreases membrane potential and reactive oxygen species production while increasing cellular respiration. Finally, SIRT3, along with genes related to mitochondrial function, is down-regulated in the brown adipose tissue of several genetically obese mice. In summary, our results demonstrate that SIRT3 activates mitochondria functions and plays an important role in adaptive thermogenesis in brown adipose.

ADP Ribose Transferases↗

PubMed2005

Asymmetry analysis of cingulum based on scale-invariant parameterization by diffusion tensor imaging.

Current analysis of diffusion tensor imaging (DTI) is based mostly on a region of interest (ROI) in an image dataset, which is specified by users. This method is not always reliable, however, because of the uncertainty of manual specification. We introduce an improved fiber-based scheme rather than an ROI-based analysis to study in DTI datasets of 31 normal subjects the asymmetry of the cingulum, which is one of the most prominent white matter fiber tracts of the limbic system. The present method can automatically extract the quantitative anisotropy properties along the cingulum bundles from tractography. Moreover, statistical analysis was carried out after anatomic correspondence specific to the cingulum across subjects was established, rather than the traditional whole-brain registration. The main merit of our method compared to existing counterparts is that to find such anatomic correspondence in cingulum, a scale-invariant parameterization method by arc-angle was proposed. It can give a continuous and exact description on any segment of cingulum. More interestingly, a significant left-greater-than-right asymmetry pattern was obtained in most segments of cingulum bundle (-50-25 degrees), except in the most posterior portion of cingulum (25-50 degrees).

Adult↗

PubMed2005

Simultaneous registration and segmentation of anatomical structures from brain MRI.

In this paper, we present a novel variational formulation of the registration assisted image segmentation problem which leads to solving a coupled set of nonlinear PDEs that are solved using efficient numerical schemes. Our work is a departure from earlier methods in that we have a unified variational principle wherein non-rigid registration and segmentation are simultaneously achieved; unlike previous methods of solution for this problem, our algorithm can accommodate for image pairs having very distinct intensity distributions. We present examples of performance of our algorithm on synthetic and real data sets along with quantitative accuracy estimates of the registration.

Algorithms↗

PubMed2005

A new cytotoxic lanostane triterpenoid from the basidiomycete Hebeloma versipelle.

A new cytotoxic lanostane triterpenoid, 24(E)-3beta-hydroxylanosta-8,24-dien-26-al-21-oic acid (1), was isolated from the fruiting bodies of the mushroom Hebeloma versipelle. The structure was elucidated on the basis of spectroscopic studies including 2D NMR experiments. Compound 1 moderately inhibited the growth of several tumor cell lines (IC50 10-25.0 microg/ml).

Antibiotics, Antineoplastic↗

PubMed2005

Aurovertin E, a new polyene pyrone from the basidiomycete Albatrellus confluens.

A new polyene pyrone, aurovertin E (2), was isolated along with aurovertin B (1) from the culture mycelia of the basidiomycete Albatrellus confluens. Their structures were elucidated on the basis of spectroscopic studies including 2D NMR experiments. This is the first example of the occurrence of aurovertins in basidiomycetes.

Aurovertins↗

PubMed2005

Rufuslactone, a new antifungal sesquiterpene from the fruiting bodies of the basidiomycete Lactarius rufus.

A new lactarane sesquiterpene, rufuslactone (1), was isolated from the fruiting bodies of the basidiomycete Lactarius rufus. Rufuslactone (1) is an isomer of a previously described lactarane 3,8-oxa-13-hydroxylactar-6-en-5-oic acid gamma-lactone (2) from Lactarius necatar. Its structure,was elucidated on the basis of spectroscopic data. Rufuslactone (1) showed antifungal properties against plant pathogenic fungi.

Antifungal Agents↗

PubMed2005

Preliminary evidence for persistent abnormalities in amygdala volumes in adolescents and young adults with bipolar disorder.

OBJECTIVES: Abnormalities in volumes of the amygdala have been reported previously in adolescents and adults with bipolar disorder (BD). Several studies have reported reduced volumes in adolescents with BD; however, both decreases and increases in volumes have been reported in adults with BD. Understanding of potential developmental contributions to these disturbances in morphology of the amygdala has been limited by the absence of longitudinal data in persons with BD. Here we use a within-subject longitudinal design to investigate whether amygdala volume abnormalities persist in adolescents and young adults with BD over a time interval of approximately 2 years. METHODS: Participants included 18 adolescents and young adults: 10 participants with BD I and 8 healthy comparison participants. Amygdala volumes were measured on high-resolution magnetic resonance imaging scans acquired twice for each subject over intervals of approximately 2 years. Amygdala volumes were the dependent measures in a mixed-model statistical analysis to compare amygdala volumes between groups over time while covarying for total brain volume. RESULTS: Amygdala volumes were significantly smaller in adolescents and young adults with BD compared with healthy participants (p = 0.018). The effect of time was not significant. CONCLUSIONS: Although the sample size is modest, this study provides preliminary evidence to support the presence of decreased amygdala volumes in adolescents and young adults with BD that persist during this developmental epoch.

Adolescent↗

PubMed2005

Purchasing or providing nursing home care: can quality of care data provide guidance.

OBJECTIVES: To examine whether quality of care differed for veterans in Department of Veterans Affairs (VA) nursing homes and those on contract in community nursing homes, and whether the VA was contracting with nursing homes providing better quality of care than other nursing homes. DESIGN: Observational study using administrative databases from 1997 to 1999. SETTING: Ten VA and 650 community nursing homes in New York state. PARTICIPANTS: Four thousand seven hundred sixty-three veteran and 195,438 nonveteran residents of these nursing homes. MEASUREMENTS: Risk-adjusted rates of pressure ulcer development, functional decline, behavioral decline, and mortality. RESULTS: Veterans in VA nursing homes were significantly (P< .05) less likely to develop a pressure ulcer (odds ratio (OR)=0.63) but more likely to experience functional decline (OR=1.6) than veterans in community nursing homes. Residents of community nursing homes with VA contracts were significantly (P< .05) less likely to develop a pressure ulcer (OR=0.91) but more likely to die than residents in noncontract homes. Few nursing homes were consistently among the best or worst performers on all measures; only seven of 650 nursing homes were in the top or bottom decile and 34 in the top or bottom quartile for each measure. CONCLUSION: Large purchasers and providers of nursing home care such as the VA are unlikely to find information on quality of care useful in making decisions on whether they should "make" or "buy" care. Nursing homes performing well on one quality measure may perform poorly on another, and it is difficult to identify nursing homes that are consistently among the best or worst. Other consumers may encounter similar difficulties when using data on nursing home quality.

Aged↗

PubMed2005

[Natural history of small hepatocellular carcinoma: studied by MRI].

OBJECTIVE: To study natural history of small hepatocellular carcinoma (sHCC) and value of MRI in this research. METHODS: From 1999 to 2002, serial MR imagings were performed in 192 patients with cirrhosis no less than twice in order to detect sHCC focus. Characteristic MRI findings of focus were analysed. Diameters of focus (D) were measured. Tumorigenesis detected time (T) was counted; T and D were analysed by statistics and tumor volume doubling time (T(d)) was calculated. RESULTS: Fifty-eight new tumor foci in 33 patients were found, including 31 foci in 23 patients developed on the basis of cirrhosis, with a 12.0% cumulative tumorigenic rate of three years. The tumorigenesis detected time (T) was 386.9 +/- 256.4 days and the maximum diameter (D) was 2.258 +/- 1.074 cm. T was statistical correlated with D(3) (P < 0.01) and regressive formulas were established: D(3) = -2.69 + 0.058T (P = 0.0007), D(3) = -72.13 + 16.04lnT (P = 0.0064). Tumor volume doubling time was 20 approximately 279 days (mean: 104 days). CONCLUSION: The percentage of tumorigenesis is high in patients with cirrhosis. Regular MRI examinations are necessary to detect sHCC early. The optimal interval time is 3 approximately 6 months.

Adult↗

PubMed2005

Mechanism of L-arginine-induced sebaceous gland hyperplasia in rats.

OBJECTIVE: To study the effect of L-arginine (L-arg) on the sebaceous gland of SD rat. METHODS: The SD rats of different sexes and ages were subjected to intragastric administration of L-arg at 10 mg.kg(-1).d(-1) (L-arg group) or saline (saline group) for 14 days. Blood samples were obtained from these rats for serum androgen determination and the pathological changes of the skin were observed. RESULTS: After L-arg treatment for 7 days, the dorsal hair of all the adult male rats appeared damp, greasy and yellow, while that of the adult and 5-week-old female rats looked normal. When the treatment was prolonged to 14 days, the same changes occurred in most of the adult female rats and all the 5-week-old female rats. The sebaceous glands of the abnormal skin showed hyperplasia in pathologic examination. The serum levels of androgen in rats with sebaceous gland hyperplasia were significantly higher than those in the control rats. CONCLUSION: L-arg can promote sebaceous gland hyperplasia in rats in relation to increased androgen secretion induced by L-arg and NO.

Androgens↗

PubMed2005

[Karyotype analysis of Lonicera japonica and L. maackii].

OBJECTIVE: To study Lonicera japonica Thunb. and Lonicera maackii (Rupr. ) Maxim. chromosome number, karyotype, volume. METHODS: Sections combined with micrograph were used to analyse chromosome. RESULTS: Lonicera japonica Thunb. normal diploid 2n = 18; the relative length was 2n = 18 = 2L +8M, + 6M1 + 2S; karyotpye formula was K(2n) = 2X = 18 = 10 sm + 6 m + 2st, which belong to "2A" type; the AS. K% was 66.65%. Lonicera maackii (Rupr.) Maxim. normal diploid 2n = 18; the relative length was 2n = 18 = 4L + 4M, + 10M1; karyotype formula was K(2n) = 2X = 18 = 10 sm + 8m, which belong to"2A" type; the AS. K% was 63.28%. CONCLUSION: The chromosome number, karyotype, and chromosome volume of Lonicera japonica Thunb. and Lonicera maackii (Rupr.) Maxim. were showed clear.

Chromosomes, Plant↗

PubMed2005

[Establishment of the transfected cell line expressing the mouse OX40 gene and its potency to induce differentiation of B cells].

AIM: To establish HUVECs line expressing mouse OX40(CD134) and to study its promotive effect on proliferation of B cells. METHODS: The cDNA fragment encoding mouse OX40 was obtained from the total RNA of ConA-activated lymphocytes of thymus by using RT-PCR and cloned into pUCm-T vector. The cDNA was then inserted into the eukaryotic expression vector pIRES2-EGFP. The recombinant vector was transfected into HUVECs with lipofectin reagent, and the positive cellular clones were selected by G418. Expression of mouse OX40 in the transfected cells was analyzed by FCM. The differentiation of B cells in vitro induced by OX40 signal was studied by means of (3)H-TdR method. RESULTS: The cDNA fragment in the recombinant plasmid was consistent with the reported mouse OX40 cDNA in GenBank, which was confirmed by DNA sequencing, PCR and enzyme digestion. The HUVECs stably expressing the mouse OX40 were successfully cloned. The transfected cells promoted the differentiation of B cells in vitro and there existed a synergic effect between OX40/OX40L and CD40/CD40L signals. CONCLUSION: Transfected cell line expressing the mouse OX40 gene is established successfully. OX40 enhances the proliferation of B cells.

Animals↗