Biomedical subjects

Wei Hua

Publications and source records attributed to Wei Hua.

28 records · Page 2Linked to original sources

PubMed2004

Source identification of PM10, collected at a heavy-traffic roadside, by analyzing individual particles using synchrotron radiation.

Synchrotron radiation microbeam X-ray fluorescence (micro-SXRF) was used to analyze individual aerosol particles collected at a height of 2 m above a heavy-traffic roadside in a heavy-industrial area of Shanghai. A pattern recognition technique, which took micro-SXRF spectra of single aerosol particles as its fingerprint, was used to identify the origins of the particles. The particles collected from the environmental monitoring site are mainly from metallurgic industry (26%), unleaded gasoline automobile exhaust (15%), coal combustion (10%), cement dust (10%) and motorcycle exhaust (8%).

Aerosols↗

PubMed2004

A tobacco calcium/calmodulin-binding protein kinase functions as a negative regulator of flowering.

A tobacco calcium/calmodulin-binding protein kinase (NtCBK1) was isolated and identified. The predicted NtCBK1 protein has 599 amino acids, an N-terminal kinase domain, and shares high homology with other calmodulin (CaM)-related kinases. Whereas NtCBK1 phosphorylates itself and substrates such as histone IIIS and syntide-2 in the absence of CaM, its kinase activity can be stimulated by tobacco CaMs. However, unlike another tobacco protein kinase designated NtCBK2, NtCBK1 was not differentially regulated by the different CaM isoforms tested. The CaM-binding domain of NtCBK1 was located between amino acids 436 and 455, and this domain was shown to be necessary for CaM modulation of kinase activity. RNA in situ hybridization showed that NtCBK1 was highly regulated in the transition to flowering. Whereas NtCBK1 mRNA was accumulated in the shoot apical meristem during vegetative growth, its expression was dramatically decreased in the shoot apical meristem after floral determination, and in young flower primordia. The expression of NtCBK1 was up-regulated to high levels in floral organ primordia. Fluctuations in NtCBK1 expression were verified by analysis of tobacco plants expressing green fluorescent protein under the control of the NtCBK1 promoter, suggesting a role of NtCBK1 in the transition to flowering. This conclusion was confirmed by overexpressing NtCBK1 in transgenic tobacco plants, where maintenance of high levels of NtCBK1 in the shoot apical meristem delayed the switch to flowering and extended the vegetative phase of growth. Further work indicated that overexpression of NtCBK1 in transgenic tobacco did not affect the expression of NFL, a tobacco homologue of the LFY gene that controls meristem initiation and floral structure in tobacco. In addition, the promotion of tobacco flowering time by DNA demethylation cannot be blocked by the overexpression of NtCBK1.

Amino Acid Sequence↗

PubMed2004

Social network correlates of self-reported non-fatal overdose.

The leading cause of death among heroin users is drug overdose. The present study examined the relationship between history of self-reported drug overdoses and social network characteristics among cocaine and opiate users. Data were from cross-sectional surveys administered from March 2001 through February 2003 as part of follow-up of an experimental network oriented HIV prevention intervention. A total of 838 participants with histories of cocaine and opiate use completed the survey. Several social network variables were found to be significantly associated with drug overdose in the prior 2 years, including larger number of network members who were injection drug users and a larger number of conflictual ties among the network members. Even after controlling for age, gender, frequency of injection drug and alcohol use, and health status, network variables continued to have a strong association with history of recent overdose. These data suggest that large drug networks should be targeted for drug overdose prevention interventions.

Adult↗

PubMed2004

Social support among HIV positive injection drug users: implications to integrated intervention for HIV positives.

The study compared social support networks of HIV seropositive versus seronegative injection drug users (IDUs). Participants were 635 low income African Americans; 47% were HIV seropositive (of whom 17% had AIDS), 45% female, and 45% current drug users. A social network methodology elicited structural, functional, and relational network components. After controlling for confounders, HIV seropositive compared with HIV seronegative IDUs had larger support networks, including more females, kin and sources of instrumental assistance, and marginally more sources of emotional support, though they were less likely to have a sex partner. There was no difference between HIV status and number of active drug users in support networks. Results suggest that HIV seropositive IDUs had mobilized a range of network support but that they also relied on drug using social influences. Findings may have implications to the development of integrated HIV prevention and care intervention that builds on HIV seropositives' natural support structures.

Adult↗

PubMed2004

Factors associated with peer HIV prevention outreach in drug-using communities.

Peer education is a critical approach to HIV prevention. The current study evaluated 156 peer outreach educators 6 months after their 10-session training. Specifically, we examined factors associated with talking to network members about HIV-related topics as well as distributing risk reduction materials. Overall, current drug users were less likely to report engaging in HIV-related conversations in the prior month but were more likely to provide bleach to drug-using network members. Older participants (aged 41 and older) were more likely to report HIV prevention conversations, and women were marginally more likely to report providing condoms to network members. HIV-seropositive participants were significantly more likely to report talking to sex partners and family members about HIV. These data suggest that demographic characteristics, drug use, and HIV status are associated with HIV prevention conversations among network members. These characteristics should be considered when designing peer outreach HIV prevention programs.

Adult↗

PubMed2004

Effects of right atrial and ventricular DDD pacing on cardiac function and ventricular contraction synchrony.

BACKGROUND: Right ventricular apical pacing has been reported to reduce cardiac performance. But there are few reports on the effects of dual chamber (DDD) pacing on cardiac function compared to sinus rhythm. In this study, we evaluated the effects of right atrial and ventricular DDD pacing on cardiac function and ventricular contraction synchrony using equilibrium radionuclide angiography. METHODS: Ten patients implanted with a right atrial and ventricular DDD pacemaker underwent equilibrium radionuclide angiography. The scintigraphic data were obtained during sinus rhythm and pacing rhythm. Cardiac function parameters were obtained semimanually. Phase analysis was used to study the ventricular activation sequence and ventricular synchrony. RESULTS: The left ventricular 1/3 ejection fraction decreased significantly during pacing compared with that during sinus rhythm [(23.4 +/- 6.1)% vs (27.7 +/- 4.5)%, P = 0.01]. Regional ejection fraction also decreased during pacing, although the difference was not statistically significant. Phase analysis showed that the right ventricle was activated earlier than the left ventricle during pacing, and that the phase shift was significantly greater during pacing than that during sinus rhythm [64.13 degrees +/- 16.80 degrees vs 52.88 degrees +/- 9.26 degrees, P = 0.007]. The activation of both ventricles occurred simultaneously during sinus rhythm, with the activation sequence from proximal septum or base of left ventricle to apex. The earliest activation during pacing occurred at the right ventricular apex, and subsequently spread to the base and left ventricle. CONCLUSION: Right atrial and ventricular DDD pacing impairs left ventricular systolic function and ventricular synchrony.

Cardiac Pacing, Artificial↗

PubMed2004

[Design and field calculation of coil array for functional magnetic stimulation].

OBJECTIVE: To locate the activation point in functional magnetic stimulation (FMS). METHOD: Coil arrays were applied to establish the magnetic field distribution with ideal focusing capability. Models of hemispherical and plane coil arrays were established. Then an improved adaptive genetic algorithm (GA) was applied in the optimization of value and phase of the electric current infused into each coil. RESULT: Based on the calculated results of the optimized current configurations, ideal focusing capability was drawn as contour lines and 3-D mesh charts of the magnitude of magnetic and electric field within the calculated area. CONCLUSION: It was shown that the coil arrays have good capability to establish the magnetic distribution in focused shape. In addition, it was also shown that the coil arrays have the capability of focusing on two or more targets simultaneously.

Electricity↗

PubMed2003

A tobacco (Nicotiana tabaccum) calmodulin-binding protein kinase, NtCBK2, is regulated differentially by calmodulin isoforms.

A calcium (Ca2+)/calmodulin (CaM)-binding protein kinase (CBK) from tobacco (Nicotiana tabaccum ), NtCBK2, has been characterized molecularly and biochemically. NtCBK2 has all 11 conserved subdomains of the kinase-catalytic domain and a CaM-binding site as shown by other kinases, including Ca2+-dependent protein kinase and chimaeric Ca2+/CaM-dependent protein kinases. However, this kinase does not contain an EF-hand motif for Ca2+ binding, and its activity was not regulated by Ca2+. Whereas NtCBK2 phosphorylated both itself and other substrates, such as histone IIIS and syntide-2, in a Ca2+/CaM-independent manner, as also shown by OsCBK, a CaM-binding protein kinase from rice (Oryza sativa ), the kinase activity of NtCBK2 was greatly stimulated by Ca2+/CaM, whereas that of OsCBK was not. By molecular dissection analyses, the CaM-binding domain of NtCBK2 has been localized in a stretch of 30 amino acid residues at residue positions 431-460 as a 1-5-10 protein motif. Three tobacco CaM isoforms (NtCaM1, NtCaM3 and NtCaM13) used in the present study have been shown to bind to NtCBK2, but with different dissociation constants ( K(d)s), as follows: NtCaM1, 55.7 nM; NtCaM3, 25.4 nM; and NtCaM13, 19.8 nM, indicating that NtCBK2 has a higher affinity for NtCaM3 and NtCaM13 than for NtCaM1. The enzymic activity of NtCBK2 was also modulated differently by various CaM isoforms. Whereas the phosphorylation activity of NtCBK2 was shown by assay to be enhanced only approximately 2-3-fold by the presence of NtCaM1, the activity could be amplified up to 8-9-fold by NtCaM3 or 10-11-fold by NtCaM13, suggesting that NtCaM3 and NtCaM13 are better activators than NtCaM1 for NtCBK2.

Amino Acid Sequence↗

PubMed2002

Distinguishing inchworm and hand-over-hand processive kinesin movement by neck rotation measurements.

The motor enzyme kinesin makes hundreds of unidirectional 8-nanometer steps without detaching from or freely sliding along the microtubule on which it moves. We investigated the kinesin stepping mechanism by immobilizing a Drosophila kinesin derivative through the carboxyl-terminal end of the neck coiled-coil domain and measuring orientations of microtubules moved by single enzyme molecules at submicromolar adenosine triphosphate concentrations. The kinesin-mediated microtubule-surface linkage was sufficiently torsionally stiff (>/=2.0 +/- 0.9 x 10(-20) Newton meters per radian2) that stepping by the hypothesized symmetric hand-over-hand mechanism would produce 180 degree rotations of the microtubule relative to the immobilized kinesin neck. In fact, there were no rotations, a finding that is inconsistent with symmetric hand-over-hand movement. An alternative "inchworm" mechanism is consistent with our experimental results.

Adenosine Triphosphate↗

PubMedDate not supplied

GFFD: Generalized free-form deformation with scalar fields.

The novel free-form deformation(FFD) technique presented in the paper uses scalar fields defined by skeletons with arbitrary topology. The technique embeds objects into the scalar field by assigning a field value to each point of the objects. When the space of the skeleton is changed, the distribution of the scalar field changes accordingly, which implicitly defines a deformation of the space. The generality of skeletons assures that the technique can freely define deformable regions to produce a broader range of shape deformations.

Computer Graphics↗