Biomedical subjects

K Wang

Publications and source records attributed to K Wang.

At least 181 records · Page 10Linked to original sources

PubMed2000

Heteroduplex mobility assay detects DNA mutations for differentiation of closely related phytoplasma strains.

We present the first use of DNA heteroduplex mobility assay (HMA) to detect the point mutations including substitutions and deletions/insertions in 16S rDNA of aster yellows phytoplasma (AY27) and to differentiate phytoplasmas collected from field samples of clover proliferation (CP) and alfalfa witches'-broom (AWB). The phytoplasmal 16S rDNA fragment was amplified from AY27 by polymerase chain reaction (PCR) and cloned into a plasmid vector. The cloned DNA fragment was subjected to in vitro mutation to produce 1- to 4-base substitutions and 1- to 3-base deletions. The mutated 16S rDNA fragments were analyzed by HMA. The results showed that a single two-base substitution or a single-base deletion/insertion in the 529 bp DNA fragment was directly detected and that a DNA divergence at a level of as low as 0.2% was detectable by HMA. Heteroduplex mobilities were affected by the number and composition of the phytoplasma DNA bases in mismatches or gaps and were proportional to the degree of DNA divergences. Gaps caused greater retardation in heteroduplex mobility than mismatches did. HMA was highly sensitive in detecting the mixed infections of phytoplasmas. In analyses of CP and AWB field samples collected in Alberta, two CP and one AWB phytoplasma isolates were differentiated from others by HMA but not by restriction fragment length polymorphism (RFLP). Therefore, HMA provides a simple, rapid, highly sensitive and analytical method to detect and estimate the genetic divergence of phytoplasmas when other methods such as RFLP are not readily applicable.

DNA Mutational Analysis↗

PubMed2000

False positive head-up tilt: hemodynamic and neurohumoral profile.

OBJECTIVES: This study examined differences in mechanisms of head-up tilt (HUT)-induced syncope between normal controls and patients with neurocardiogenic syncope. BACKGROUND: A variable proportion of normal individuals experience syncope during HUT. Differences in the mechanisms of HUT-mediated syncope between this group and patients with neurocardiogenic syncope have not been elucidated. METHODS: A 30-min 80 degrees HUT was performed in eight HUT-negative volunteers (Group I), eight HUT-positive volunteers (Group II) and 15 patients with neurocardiogenic syncope. Heart rate and blood pressure (BP) were monitored continuously. Epinephrine and norepinephrine plasma levels, as well as left ventricular dimensions and contractility determined by echocardiography, were measured at baseline and at regular intervals during the test. RESULTS: The main findings of this study were the following: 1) All parameters were similar at baseline in the three groups; and 2) During tilt: a) the time to syncope was shorter in Group III than in group II (9.5 +/- 3 vs. 17 +/- 3 min p < 0.05); b) there was an immediate, persisting drop in mean BP in Group III; c) the decrease rate of left ventricular end-diastolic dimensions was greater in Group III than in Group II or Group I (-1.76 +/- 0.42 vs. -0.87 +/- 0.35 and -0.67 +/- 0.29 mm/min, respectively, p < 0.05); d) the leftventricular shortening fraction was greater in Group III than in the other two groups (39 +/- 1 vs. 34 +/- 1 and 32 +/- 1%, respectively, p < 0.05); and e) although the norepinephrine level remained comparable among the groups, there was a significantly higher peak epinephrine level in Group III than in Group II and Group I (112.3 +/- 34 vs. 77.6 +/- 10 and 65 +/- 12 pg/ml, p < 0.05). CONCLUSIONS: Mechanisms of syncope during HUT appeared to be different in normal volunteers and patients with neurocardiogenic syncope. In the latter, there was evidence of an impaired vascular resistance response from the beginning of the orthostatic challenge. Furthermore, in the patients there was more rapid peripheral blood pooling, as indicated by the echocardiographic measurements of left ventricular end-diastolic changes, leading to more precocious symptoms. In syncopal patients, the higher level of plasma epinephrine probably mediated the increased cardiac contractility and possibly contributed to the impaired vasoconstrictive response.

Adult↗

PubMed2000

Architecture of the thin filament-Z-line junction: lessons from nebulette and nebulin homologies.

Nebulette and nebulin are homologous proteins associated with the Z-lines of cardiac and skeletal muscle sarcomeres. Although these proteins share 70% sequence homology and an identical domain layout, nebulette is one-tenth the size of nebulin. To define structurally important features of these proteins in terms of the Z-line architecture, we have analyzed the primary structure of nebulette and nebulin from a variety of species and developmental stages. Alignment of the 35 residue nebulin-like modules from both proteins demonstrates that the individual modules share 30-90% homology across the six proteins analyzed. In addition, this analysis demonstrates a number of areas in which the identity across the six proteins is as high as 75%. These areas may be important signals for Z-line assembly and function in the striated muscles. Significantly, most of the areas of high identity also coincide with consensus phosphorylation sites. To evaluate if nebulette, like nebulin, exhibits tissue-specific and developmental specific polymorphism, a series of immunoblot assays were performed. These data demonstrate that nebulettes from different portions of the heart are the same size. Comparison of nebulette from embryonic and adult cardiac muscle also demonstrates that this protein does not appear to vary in size with developmental stage. Consistent with the large number of consensus phosphorylation sites identified in the nebulette primary structure, we find that nebulette is phosphorylated in the cardiac muscle at serine and threonine residues. These data and sequence analyses are discussed in terms of current models for Z-line architecture.

Actin Cytoskeleton↗

PubMed2000

Evaluation of fluorinated polymers as coronary stent coating.

In this report, some fluorinated polyphosphazenes and polymethacrylates were selected for evaluation as coronary stent coating. After applying the polymer film by dipcoating, the stents were implanted in porcine coronary arteries. No acute thrombotic occlusions were observed. The neointimal proliferation was studied by a 6 week follow-up of the minimal lumen stented diameter, using quantitative coronary analysis. All polymers demonstrated a slight hyperplasia, resulting in a 10-20% lumen narrowing at follow-up. Only for one fluorinated polymethacrylate, PFM-P75, a minimal neointimal response (3% lumen narrowing) was found.

Journal Article↗

PubMed2000

Trilinear modeling of event-related potentials.

This paper describes a method for estimating a set of spatial components (brain maps) and temporal components (waveforms) of brain potentials. These components play the role of bases of a coordinate system, in the sense that the brain potentials of any subject can be represented as superpositions of these components. The representation is unique given the spatial and temporal components, and this decomposition is particularly appealing for comparing the brain potentials of different subjects (say alcoholics and controls). It can also be used for single trial modeling, clinical classification of patients, and data filtering. The method is based on the topographic component model (TCM, Möcks 1988) which models brain potentials in a trilinear form. We extend the TCM in two aspects. First, the diagonal amplitude matrix is replaced by a general loading matrix based on some neurophysiological considerations. Secondly, the number of spatial components and the number of temporal components can be different. The spatial components and temporal components are obtained respectively by performing singular value decomposition (SVD). This method is illustrated with visual P3 data.

Alcoholism↗

PubMed2000

The seven-transmembrane receptor smoothened cell-autonomously induces multiple ventral cell types.

Sonic Hedgehog (Shh) is a secreted protein that controls cell fate and mitogenesis in the developing nervous system. Here we show that a constitutively active form of Smoothened (Smo-M2) mimics concentration-dependent actions of Shh in the developing neural tube, including activation of ventral marker genes (HNF3beta, patched, Nkx2.2, netrin-1), suppression of dorsal markers (Pax-3, Gli-3, Ephrin A5) and induction of ventral neurons (dopaminergic, serotonergic) and ventrolateral motor neurons (Islet-1+, Islet-2+, HB9+) and interneurons (Engrailed-1+, CHX10+). Furthermore, Smo-M2's patterning activities were cell autonomous, occurring exclusively in cells expressing Smo-M2. These findings suggest that Smo is a key signaling component in the Hh receptor and that Shh patterns the vertebrate nervous system as a morphogen, rather than through secondary relay signals.

Amino Acid Substitution↗

PubMed2000

Mutations of PKD1 in ADPKD2 cysts suggest a pathogenic effect of trans-heterozygous mutations.

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 and PKD2. The products of these genes associate to form heteromeric complexes. Several models have been proposed to explain the mechanism of cyst formation. Here we find somatic mutations of PKD2 in 71% of ADPKD2 cysts analysed. Clonal somatic mutations of PKD1 were identified in a subset of cysts that lacked PKD2 mutations.

Base Sequence↗

PubMed2000

EMG-force relationships are influenced by experimental jaw-muscle pain.

The bite force at different levels and the corresponding electromyographic (EMG) activity of the masseter and anterior temporalis muscles were recorded in 12 healthy subjects in order to evaluate the modulation of EMG-force curves by a standardized painful stimulus. Hypertonic saline (5%) was infused into the right masseter muscle for up to 15 min to induce pain. The pain intensity was scored continuously by the subjects on a 10-cm visual analogue scale (VAS). Subjects were asked to bite on a force transducer at the maximum voluntary bite force (MVBF). They were then asked to bite at submaximum levels of 12, 25, 37, 50, 67, 75 and 87% of MVBF. The biting was performed in three different positions (right first molar, left first molar and incisor) before, during and after infusion. Hypertonic saline caused moderate pain during infusion (mean VAS +/- s.e.m. = 6.5+/-0.5 cm). Both the MVBF and the maximum EMG activity in the right masseter and the left anterior temporalis muscles were significantly decreased during muscle pain when the subjects bit on the painful side. The EMG-force curves could be fit by linear relationships. The slope of the curve became less steep in the right masseter muscle during and after painful biting in every position. The results suggest that tonic saline-induced jaw-muscle pain is able to modulate the motor unit recruitment pattern of the jaw-closing muscles on the painful side. The main effect of pain in this experiment was an inhibition of static EMG activity.

Adult↗

PubMed2000

alpha-crystallin prevents irreversible protein denaturation and acts cooperatively with other heat-shock proteins to renature the stabilized partially denatured protein in an ATP-dependent manner.

alpha-Crystallin, a major lens protein of approximately 800 kDa with subunits of approximately 20 kDa has previously been shown to act as a chaperone protecting other proteins from stress-induced aggregation. Here it is demonstrated that alpha-crystallin can bind to partially denatured enzymes at 42-43 degrees C and prevent their irreversible aggregation, but cannot prevent loss of enzyme activity. However, the alpha-crystallin-bound enzymes regain activity on interaction with other chaperones. The data indicate that the re-activated enzymes are no longer associated with the alpha-crystallin, and ATP is required for re-activation. When inactive luciferase bound to alpha-crystallin was treated with reticulocyte lysate, a rich source of chaperones, up to 60% of the original luciferase activity could be recovered. Somewhat less re-activation was observed when the alpha-crystallin-bound enzyme was treated with heat-shock protein (HSP)70, HSP40, HSP60 and an ATP-generating system. Similar results were also obtained with citrate synthase. The overall results suggest that alpha-crystallin acts to stabilize denaturing proteins so that they can later be re-activated by other chaperones.

Adenosine Triphosphate↗

PubMed2000

The consistency of the posterior probability of linkage.

When searching for trait loci along the genome, properly incorporating prior genomic information into the analysis will almost certainly increase the chance of success. Recently, we devised a method that utilizes such prior information in the mapping of trait genes for complex disorders (Vieland, 1998; Wang el al. 1999; Vieland et al. 2000). This method uses the posterior probability of linkage (PPL) based on the admixture model as a measure of linkage information. In this paper, we study the consistency of the PPL. It is shown that, as the number of pedigrees increases, the PPL converges in probability to 1 when there is linkage between the marker and a trait locus, and converges to 0 otherwise. This conclusion is shown to be true for general pedigrees and trait models, even, when the likelihood functions are based on misspecified trait models. As part of the effort to prove this conclusion, it is shown that when there is no linkage, the maximum likelihood estimator of the recombination fraction in the admixture model is asymptotically 0.5, even when the admixture model misrepresents the true model.

Computer Simulation↗

PubMed2000

Tubed latissimus dorsi musculocutaneous flaps for esophageal replacement in puppies: long-term follow-up.

PURPOSE: The aim of this study was to show that a tubed latissimus dorsi musculocutaneous flap (tubed LDMCF) may be useful for treating circumferential esophageal defects. METHODS: A segment of esophagus 3 vertebrae long was excised through a right thoracotomy in each of 6 puppies, and a tubed LDMCF was interposed between the cut ends of esophagus. The puppies were sacrificed after a mean follow-up period of 6.6 years. The tubed LDMCF was examined histologically. Functional integrity was assessed using barium meal and endoscopy before sacrifice. RESULTS: All puppies survived and grew normally on a normal diet, although 4 vomited occasionally. There was smooth passage of barium through the tubed LDMCF without stenosis, although endoscopy showed regrowth of hair. Histologically, no metaplasia, dysplasia, or malignancy was observed in any tubed LDMCF. CONCLUSIONS: The tubed LDMCF is technically safe, obviates the necessity for laparotomy, and long-term follow-up would suggest that it is histologically stable. Thus, it could become an alternative procedure for bridging esophageal defects.

Animals↗

PubMed2000

Breast cancer education program based in Asian grocery stores.

Culturally and linguistically compatible university students were trained as community health educators to provide breast cancer education and screening information to shoppers at Asian grocery stores. Information about early detection of breast cancer was shared with 8,877 women, who reported speaking 40 different languages. Baseline surveys were completed by 1,202 women; 779 took part in the follow-up survey. The survey questions assessed baseline knowledge, attitudes, and screening behaviors regarding breast cancer, tested the efficacy of the intervention, and sought barriers to accessing screening services. Screening adherence at baseline was low, but reported screening compliance had increased by follow-up. This study confirms the cost-effectiveness of student health educators and Asian grocery store sites as venues to reach the diverse age, ethnic, and socioeconomic segments of the Asian community, while demonstrating the community's receptiveness to the dissemination of health information and introducing bilingual students to health education and research careers.

Asian↗

PubMed2000

A method for individual identification of echolocation signals in free-ranging finless porpoises carrying data loggers.

Echolocation click events of a free-ranging juvenile and an adult finless porpoise (Neophocaena phocaenoides) were recorded with an acoustic data logger. Additionally, dive depth and swim speed of the juvenile were recorded with a behavior data logger. Echoes of echolocation signals from the water surface were clearly detected in shallow dives approximately less than 2 m. The delay time between a surface echo and a direct signal corresponded with the two-way transmission time for the animal's depth, indicating that the signals originated from the animal wearing the data loggers. The finless porpoises produced echolocation signals frequently and were thought to be able to detect their depth by listening to echoes from the water surface.

Animals↗

PubMed2000

Regulation of adenovirus membrane penetration by the cytoplasmic tail of integrin beta5.

Adenovirus (Ad) cell entry involves sequential interactions with host cell receptors that mediate attachment (CAR), internalization (alphavbeta3 and alphavbeta5), and penetration (alphavbeta5) of the endosomal membrane. These events allow the virus to deliver its genome to the nucleus. While integrins alphavbeta3 and alphavbeta5 both promote Ad internalization into cells, integrin alphavbeta5 selectively facilitates Ad-mediated membrane permeabilization and endosome rupture. In the experiments reported herein, we demonstrate that the intracellular domain of the integrin beta5 subunit specifically regulates Ad-mediated membrane permeabilization and gene delivery. CS-1 melanoma cells expressing a truncated integrin beta5 or a chimeric (beta5-beta3) cytoplasmic tail (CT) supported normal levels of Ad endocytosis but had reduced Ad-mediated gene delivery and membrane permeabilization relative to cells expressing a wild-type integrin beta5. Thin-section electron microscopy revealed that virion particles were capable of being endocytosed into cells expressing a truncated beta5CT, but they failed to escape cytoplasmic vesicles and translocate to the nucleus. Site-specific mutagenesis studies suggest that a C-terminal TVD motif in the beta5CT plays a major role in Ad membrane penetration.

Adenoviruses, Human↗

PubMed2000

Frequency modulation within electrocardiograms during ventricular fibrillation.

Periods of reentrant activation and effective refractory periods are correlated with dominant frequency or reciprocal of cycle periods during ventricular fibrillation (VF). In the present study, we used an analysis technique based on Wigner transforms to quantify time-varying dominant frequencies in electrocardiograms (ECGs) during VF. We estimated dominant frequencies within orthogonal ECGs recorded in 10 dogs during trials of 10 s of VF and in 9 dogs during trials of 30 s of VF. In four additional dogs, we compared dominant frequencies during 10 s of VF before and after administration of amiodarone. Our results showed the following. 1) There was substantial frequency variation or modulation within the ECGs during 10 and 30 s of VF, the average variation being +/-15% from the mean frequency. Amiodarone decreased mean frequencies (P < 0.05) as expected; however, amiodarone also decreased the variation in frequencies (P < 0.05). 2) During 30 s of VF, the dominant frequencies increased continuously from 7.3 to 8.1 Hz (P < 0.05). The increase in frequency was almost linear with a rate of 0.022 Hz/s (r(2) = 0.93, P < 0.0005). 3) Modulation of frequencies during the first and the last one-half of 30 s of VF was not different. Average (in time) mean frequencies and modulation of frequencies were similar in all three ECGs. 4) Although the averages were similar, during any VF episode, dominant frequencies in ECGs recorded from different locations on the body surface were similar to each other at some times and markedly different from each other at other times. We conclude that during VF, 1) frequencies in ECGs vary considerably and continuously, and amiodarone decreases this variation; 2) mean frequencies increase linearly during first 30 s; 3) the variability in frequency does not change during 30 s; and 4) at any given time, the frequencies within spatially different body surface ECGs can be either similar or markedly different.

Amiodarone↗

PubMed2000

Seasonal variations in mood and behavior among Chinese medical students.

OBJECTIVE: The goal of this study was to estimate the frequency of seasonal variations in mood and behavior among Chinese medical students. METHOD: A total of 1,358 medical students were surveyed with Chinese versions of the Seasonal Pattern Assessment Questionnaire and the Beck Depression Inventory in Jining, China. RESULTS: The mean global seasonality score was 8.3 (SD=3.6) out of a possible 24; 81.7% (N=1,110) of the subjects reported some trouble adapting to changing seasons. Summer difficulties were more common than winter difficulties by a ratio of 3:2; estimated rates of summer seasonal affective disorder and subsyndromal seasonal affective disorder were 4.4% and 8.0%, respectively, compared with corresponding winter rates of 2.4% and 5.7%. CONCLUSIONS: These results suggest that seasonal variations in mood and behavior are common in China. The predominance of summer difficulties stands in contrast to that in most Western studies and is consistent with the only other published study performed in Asia.

Adolescent↗

PubMed2000

Lanthanides enhance pulmonary absorption of insulin.

In an effort to investigate the enhancement effect of lanthanide ions (Ln3+) on the absorption of larger molecules from the pulmonary pathway, insulin (mol. wt. = 5730) was chosen as a model peptide. The absorption of insulin preadministered or coadministered with Ln3+ from the lung was investigated by means of an in situ pulmonary absorption experiment. The enhancement absorption of insulin by Ln3+ ions was evaluated by calculating the various bioavailabilities (Fr) of insulin from pulmonary absorption. Moreover, the temporal change of Gd content in serum was also investigated. Results showed that the promoting effect of Ln3+ on the bioavailability of insulin is closely related to its species, concentration, and delivery order. The effect of the median Ln3+ series was remarkably greater than that of light and heavy Ln3+. The anionic form of Gadolinium (Fr = 68.4%) seemed to be more effective compared with its cationic form (Fr = 59.5%). Coadministration of Gd3+ with insulin (Fr = 80.1%) was the most effective in increasing insulin absorption from the lung. Gd3+ was rapidly absorbed and metabolized to a normal level after 4 h. It was suggested that lanthanides in a very low concentration might become potent absorption enhancers to improve absorption of larger molecules via the pulmonary pathway.

Absorption↗

PubMed2000

A SXRF method for determining the relative concentration of trace elements in plasma protein affected by cisplatin.

This article presents an analytical method for the determination of the relative concentrations of trace elements in plasma protein by gel chromatography combined with SXRF (synchrotron radiation X-ray fluorescence). The fraction of plasma protein of male Kunming mice (body weight 24.2 +/- 0.3 g), treated with a cisplatin i.p. injection at a dose of 10 mg/kg, was obtained by the separation of a Sephadex G-50 column (buffered with ammonium acetate, pH 5.7). The SXRF experiments were performed at the Beijing Electron Positron Collider synchrotron radiation facility. The elements (Pt, S, Ca, Fe, Ni, Cu, Zn, Se, Br, and Sr) in the fraction of the plasma proteins (>22 kDa) were assayed using highly sensitive SXRF. The relative concentrations of elements were calculated by a normalization of Compton scattering intensity around 22 keV, after the normalization for the collection time of the X-ray spectrum and the counting of the ion chamber, and subtracting the contribution of the polycarbonate film for the supporting sample. The determination could prove that the element Pt in plasma was bound with macromolecular protein. Cu and S were present in the fraction of the protein in mice treated with cisplatin increase, and their ratios of treated/control were 1.66 +/- 0.06 and 1.78 +/- 0.33, respectively; Zn decreased to a ratio of 0.78 +/- 0.09. Our results are in agreement with others that cisplatin exposure leads to a marked loss of kidney copper and a moderate rise in kidney zinc. However, this article primarily describes one of the analytical methods used; it does not emphasize the results of the effect of cisplatin on trace elements in plasma protein.

Animals↗