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Biomedical subjects

D J Wu

Publications and source records attributed to D J Wu.

At least 19 recordsLinked to original sources
PubMed2003

Model of nonlinear kinetic Alfvén waves with dissipation and acceleration of energetic electrons.

The acceleration of energetic electrons has long been one of the most outstanding problems in astrophysics and space physics, and some recent observations from space satellites show that low-frequency electromagnetic fluctuations in the auroral ionosphere and magnetosphere can often be identified as the kinetic Alfvén modes. A model of nonlinear kinetic Alfvén waves is presented here, in which the effect of electron collisional dissipation has been taken into account. The result is a dissipative solitary kinetic Alfvén wave (DSKAW), which can produce a local shocklike structure with a net electric potential drop and which can thereby accelerate efficiently the electrons to the order of the local Alfvén velocity. Since Alfvénic fluctuation is the most common electromagnetic activity in extensive cosmic plasma environments, the present result suggests that the DSKAW could play an important role in the acceleration and energization of cosmic plasmas.

Journal Article↗
PubMed2001

Occurrence of butyltin compounds in the waters of selected lakes, rivers and coastal environments from China.

The presence of butyltin compounds was investigated for the first time in selected lakes, rivers and coastal environments of China. Aqueous samples were pretreated by the technique of headspace solid phase micro-extraction after hydride generation with sodium tetrahydroborate (NaBH4). Quantitative measurement of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) concentrations were accomplished by capillary gas chromatography with flame photometric detector using quartz surface-induced luminescence. Experimental data demonstrated the widespread occurrence of butyltin compounds in the Chinese aquatic environment. In some locations, the concentrations of TBT were higher than the acute and chronic toxicity threshold of sensitive fresh water or marine organisms. Although DBT and MBT (which mainly come from the degradation of TBT), are less toxic, their occurrence can still affect the ecosystem over a long time frame.

China↗
PubMed2001

Acute and long-term effects of atrioventricular junction ablation and VVIR pacemaker in symptomatic patients with chronic lone atrial fibrillation and normal ventricular response.

INTRODUCTION: The precise role of irregular ventricular response in atrial fibrillation (AF) has not been fully elucidated. This study examined the independent effects of rhythm regularity in patients with chronic AF. METHODS AND RESULTS: This study included 50 patients who had chronic lone AF and a normal ventricular rate. Among these patients, 21 who underwent AV junction ablation and implantation of a VVIR pacemaker constituted the ablation group; the other 29 patients were the medical group. Acute hemodynamic findings were measured in 21 ablation patients before ablation (during AF, baseline) and 15 minutes after ablation (during right ventricular pacing). Compared with baseline data, ablation and pacing therapy increased cardiac output (4.7 +/- 0.8 vs 5.2 +/- 0.9 L/min; P = 0.05), decreased pulmonary capillary wedge pressure (16 +/- 5 vs 13 +/- 4 mmHg; P = 0.001), and decreased left ventricular end-diastolic pressure (14 +/- 4 vs 11 +/- 3 mmHg; P < 0.05). After 12 months, the ablation group patients showed lower scores in general quality of life (-20%; P < 0.001), overall symptoms (-24%; P < 0.001), overall activity scale (-23%; P = 0.004), and significant increase of left ventricular ejection fraction (44% +/- 6% vs 49% +/- 5%; P = 0.02) by echocardiographic examination. CONCLUSION: AV junction ablation and pacing in patients with chronic AF and normal ventricular response may confer acute and long-term benefits beyond rate control by eliminating rhythm irregularity.

Aged↗
PubMed2001

Combination of N-methyl-1-deoxynojirimycin and ischemic preconditioning markedly reduces the size of myocardial infarcts in rabbits.

N-methyl-1-deoxynojirimycin (NMDN), an a-glucosidase inhibitor, reduces myocardial infarct size by reducing the glycogenolytic rate through inhibition of the alpha-1,6-glucosidase of glycogen-debranching enzyme in the heart, in addition to possessing an antihyperglycemic action by blocking alpha-1,4-glucosidase in the intestine. Ischemic preconditioning (PC), which markedly reduces the size of the myocardial infarct, is known to reduce the activity of phosphorylase and reduce the glycogenolytic rate. Therefore, it was hypothesized that a combination of pharmacological inhibition of glycogenolysis by an alpha-1,6-glucosidase inhibitor, NMDN, and PC could markedly reduce myocardial infarct size more than NMDN or PC alone. Japanese white rabbits without collateral circulation were subjected to a 30-min coronary occlusion followed by 48-h reperfusion. The infarct sizes as a percentage of area at risk were significantly reduced by pre-ischemic treatment with either 100mg/kg of NMDN or PC of 5 min ischemia and 5 min reperfusion alone (15.9+/-2.0%, n=8, and 10.3+/-1.2%, n=8, respectively) as compared with the control (43.9+/-2.2%, n=8). However, the combination of 100mg/kg of NMDN and PC significantly reduced the infarct size (4.9+/-1.2, n=8) compared with NMDN or PC alone. Another 40 rabbits, also given 100mg of NMDN, PC, NMDN+PC or saline before ischemia (n=10 in each group), were killed for biochemical analysis after 30 min of ischemia. NMDN and PC preserved the glycogen content and attenuated the lactate accumulation, respectively, as compared with the control. However, the combination of NMDN and PC preserved significantly more glycogen and significantly reduced lactate accumulation than either NMDN or PC alone. The combination of NMDN and PC markedly reduced the myocardial infarct size more than either process alone. The marked preservation of glycogen and marked attenuation of lactate accumulation by the combination of NMDN and PC suggest that the mechanism for this effect of NMDN+PC is related to the inhibition of glycogenolysis.

1-Deoxynojirimycin↗
PubMed2000

Radiofrequency catheter modification of atrioventricular junction in patients with COPD and medically refractory multifocal atrial tachycardia.

BACKGROUND: Multifocal atrial tachycardia (MAT) is a difficult clinical problem generally associated with acute cardiorespiratory illness. The purpose of this study was to assess the feasibility and clinical usefulness of atrioventricular (AV) junction modification as a nonpharmacologic therapy for medically refractory MAT. METHODS AND RESULTS: Thirteen patients with COPD and medically refractory MAT underwent AV junction modification. Complications and outcome of this procedure were monitored. Subjective perceptions of quality of life assessed by a semiquantitative questionnaire and cardiac performance study were obtained before ablation (baseline) and 1 and 6 months after ablation. Radiofrequency energy was applied until the average ventricular rate fell to < 100 beats/min. Ablation procedures controlled the ventricular response in 11 of 13 patients (84%). One patient had unsuccessful modification. Another patient developed delayed complete AV block on the second day after ablation. In these 13 patients, average ventricular rate was reduced from a mean of 145 +/- 11 to 89 +/- 22 beats/min immediately after the ablation (p < 0.01). One patient had recurrent symptomatic MAT at 1 month after ablation; this patient underwent a second procedure without late recurrence. All patients were followed up for at least 6 months (mean, 11 +/- 5 months; range, 6 to 18 months). General quality of life and frequency of significant symptoms improved significantly in patients with successful modification at 1 and 6 months. The left ventricular ejection fraction increased significantly after ablation (44.5 +/- 7.3% at baseline, 49.4 +/- 4. 2% at 1 month, and 50.0 +/- 4.9% at 6 months; all p < 0.05). However, right ventricular ejection fraction remained unchanged (34.7 +/- 6. 2% at baseline, 35.7 +/- 4.4% at 1 month, and 34.3 +/- 4.6% at 6 months; all p > 0.05). The consumption of health-care resources (including frequency of hospital admission and emergency department attendance, antiarrhythmic drug trials) decreased significantly 6 months after AV junction modification. Pulmonary function and theophylline level remained unchanged during follow-up. CONCLUSIONS: AV junction modification offers an effective therapy for controlling ventricular rate in medically refractory MAT. This procedure improves the quality of life and left ventricular function in selected patients with symptomatic and medically refractory MAT.

Aged↗
PubMed1999

Optimization of throughput and desorbent consumption in simulated moving-bed chromatography for paclitaxel purification.

In simulated moving-bed (SMB) applications, throughput and desorbent consumption are two key factors that control process cost. For a given adsorbent volume and product purity requirements, throughput and desorbent consumption depend on desorbent composition, column configuration, column length to diameter ratio, and adsorbent particle size. In this study, these design parameters are systematically examined for paclitaxel purification. The results show that if adsorbent particle size, column dimensions and column configuration are fixed, the higher the product purity required, the lower the throughput. If product purity and yield are fixed, the larger the solute migration speed ratio, the higher the throughput, and the lower the desorbent consumption. If total bed volume and product purities are fixed, the longer the separation zones, the higher the throughput, but the higher the desorbent flow-rate. An intermediate configuration gives the minimum desorbent consumption. If there are no limits on pressure drop or zone flow-rate, the larger the column length to diameter ratio, the smaller the adsorbent particle size, the higher the throughput, and the lower the desorbent consumption. If the maximum zone flow-rate is controlled by the pressure drop limit and not by the standing waves requirement, the longer the columns, the lower the zone flow-rates and the lower the throughput. For 150 microns adsorbent particles and a maximum zone flow-rate of 300 ml/min, a design with optimal throughput and desorbent consumption is found for paclitaxel purification.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Single nucleotide polymorphic discrimination by an electronic dot blot assay on semiconductor microchips.

We have developed a rapid assay for single nucleotide polymorphism (SNP) detection that utilizes electronic circuitry on silicon microchips. The method was validated by the accurate discrimination of blinded DNA samples for the complex quadra-allelic SNP of mannose binding protein. The microchip directed the transport, concentration, and attachment of amplified patient DNA to selected electrodes (test sites) creating an array of DNA samples. Through control of the electric field, the microchip enabled accurate genetic identification of these samples using fluorescently labeled DNA reporter probes. The accuracy of this approach was established by internal controls of dual labeled reporters and by using mismatched sequences in addition to the wild-type and variant reporter sequences to validate the SNP-genotype. The ability to customize this assay for multiple genes has advantages over other existing approaches.

Base Sequence↗
PubMed1999

Effect of correlation between additive and multiplicative noises on the activation from a double well.

We study the thermal activation problem of a bistable system driven by correlated additive and multiplicative noises by means of numerical simulation. We find that in the colored noise case the suppression effect of the positive correlation decreases and finally is released as the autocorrelation time tau of the colored noise grows. When tau is large enough, negative correlation becomes more suppressive than the positive correlation. Such phenomena are ascribed to the collaboration between noises as well as the memory effect of the multiplicative colored noise.

Journal Article↗
PubMed1997

Electric field directed nucleic acid hybridization on microchips.

Selection and adjustment of proper physical parameters enables rapid DNA transport, site selective concentration, and accelerated hybridization reactions to be carried out on active microelectronic arrays. These physical parameters include DC current, voltage, solution conductivity and buffer species. Generally, at any given current and voltage level, the transport or mobility of DNA is inversely proportional to electrolyte or buffer conductivity. However, only a subset of buffer species produce both rapid transport, site specific concentration and accelerated hybridization. These buffers include zwitterionic and low conductivity species such as: d- and l-histidine; 1- and 3-methylhistidines; carnosine; imidazole; pyridine; and collidine. In contrast, buffers such as glycine, beta-alanine and gamma-amino-butyric acid (GABA) produce rapid transport and site selective concentration but do not facilitate hybridization. Our results suggest that the ability of these buffers (histidine, etc.) to facilitate hybridization appears linked to their ability to provide electric field concentration of DNA; to buffer acidic conditions present at the anode; and in this process acquire a net positive charge which then shields or diminishes repulsion between the DNA strands, thus promoting hybridization.

Buffers↗
PubMed1997

Trace elements burden in geriatric hemodialysis patients: a prospective multicenter collaborative study.

INTRODUCTION: Hemodialysis therapy and the aging process have been reported to interfere with the trace element (TE) status in the body. This multicenter collaborative study on blood levels of TE in geriatric hemodialysis (HD) patients was carried out with an aim to clarify the impact of the aging process and HD therapy on the TE status in such patients. METHODS: One hundred and fifty-one HD patients (65 male, 86 female), all aged over 60 (68.2+/-3.86 y), and 112 elderly controls (58 male, 54 female) with a mean age of 67.5+/-3.03 were enrolled. All patients underwent standard HD for at least 6 months. The artificial kidneys used were hollow-fiber dialyzers of cellulose membranes. Water used for HD was prepared by reverse osmosis. Blood was collected in the morning prior to dialysis and after fasting. Atomic absorption spectrophotometry was applied to measure blood levels of Pb, Cd and Hg as well as plasma levels of Cu, Zn and Al. Data are presented as mean +/- SEM. Student's t-test and linear regression were applied for statistics. RESULTS: Our geriatric chronic HD patients showed a marked elevation of blood Al and decreased plasma Zn concentrations. The blood levels of Cu, Cd, Pb and Hg were within normal limits. The blood concentrations of Al, Cu and Pb were significantly higher in HD patients than in the normal elderly controls, whereas Cd and Hg were similar in both groups, and Zn were lower in HD patients. Plasma Zn value decreased as dialysis duration increased, however there was a reversely linear correlation between plasma Zn and age. CONCLUSIONS: This data reported can be regarded as a starting point and may serve as an insight to further studies on TE imbalances in geriatric and chronic HD populations.

Aged↗
PubMed1995

Intrafamilial transmission of hepatitis C virus in hemodialysis patients.

The prevalence of hepatitis C virus (HCV) infection in chronic hemodialysis patients ranges from 20 to 50% and these patients may serve as a reservoir of infection for their household contacts. The aim of this study was to investigate the prevalence of anti-HCV in hemodialysis patients and their families, and to evaluate possible routes of infection. One hundred eighty-six family members of 84 hemodialysis patients and 529 healthy adults were enrolled. The family members consisted of 50 spouses, 96 children, 11 parents, 29 siblings, and other relatives living together with the patients. Serum samples were collected for testing anti-HCV. Exposure to risk factors was obtained by a questionnaire and an interview. The results showed that prevalence of anti-HCV in hemodialysis patients was 44%, whereas in family members it was 5.4%, not significantly different from that of age-matched healthy adults (standardized morbidity rate = 1.51, P = 0.390). The anti-HCV rate in family members tended to increase with age, and a spouse of an infected hemodialysis patient had a higher risk of HCV infection than other family members (15% vs. 2.6%, odds ratio 6.6, P = 0.058). Except for the age factor, no difference was found between seropositive and seronegative family members with respect to risk factors such as blood transfusion, surgery, frequent injections, dental procedures, or acupuncture. It was concluded that, although the anti-HCV positivity of hemodialysis patients is high, the risk of HCV infection for their family members is not higher than that of the general population. Among family members, spouses of seropositive hemodialysis patients have the highest risk of HCV infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Deletions of the cyclin-dependent kinase-4 inhibitor gene in multiple human cancers.

Cytogenetic abnormalities of chromosome 9p21 are characteristic of malignant melanomas, gliomas, lung cancers and leukaemias. From a panel of 46 human malignant cell lines, we localized by positional cloning the most frequently deleted region on 9p21. Sequence analysis of the isolated fragment reveals two open reading frames identical to the recently described complementary DNA for the inhibitor of cyclin-dependent kinase 4 (CDK4). Polymerase chain reaction and Southern blot analysis confirmed the frequent deletion or rearrangement of the CDK4-inhibitor gene in melanomas, gliomas, lung cancers and leukaemias, and the absence of detectable gene transcripts. One carcinoma had a deletion entirely within the CDK4-inhibitor gene. The CDK4-inhibitor gene from a patient with dysplastic nevus syndrome had a germ-line nonsense mutation. The CDK4 inhibitor is thought to be a physiological suppressor of proliferation. Cells unable to produce the inhibitor may be prone to neoplastic transformation.

Base Sequence↗
PubMed1993

Acute myocardial infarction caused by transnasal inhalation of amphetamine.

A 42-year-old man developed acute myocardial infarction 20 minutes following transnasal inhalation of amphetamine. To our knowledge, no cases of amphetamine-induced myocardial infarction by transnasal inhalation have ever been reported. Consequently its pharmacological effects on the cardiovascular system are discussed.

Administration, Inhalation↗
PubMed1993

Chronic active myocarditis simulating constrictive pericarditis-like findings: report of a case.

A 34-year-old female with rhythm disturbance and characteristic hemodynamic features of constrictive pericarditis is presented. A left ventricular wall open needle biopsy revealed mild mononuclear cell infiltration suggestive of myocarditis. The patient died of intractable heart failure seven years later. The autopsy revealed left and right ventricular dilatation, multiple foci of mononuclear cell infiltration, and diffuse replacement fibrosis in 31%, 13% and 14% of the areas of the left ventricular free wall, ventricular septum, and right ventricular wall, respectively, predominantly in the inner layers (68%). The pericardium was intact. These clinically constrictive pericarditis-like findings are considered to be secondary to chronic active myocarditis.

Adult↗
PubMed1992

Effects of age and posture on plasma active renin and plasma inactive renin in normal subjects.

To investigate the effects of age and posture on plasma active and inactive renin, we measured the plasma active renin concentration (ARC) and inactive renin concentration (IRC) in 81 healthy subjects. The subjects were divided into five groups according to age and body position at the time the blood was taken. Group I included 15 five-day-old newborns in a supine position. Group H included 18 adults, aged from 20 to 50 years, who were in a supine position. Group III included 21 adults, over 50 years old, who were in a supine position. Group IV included 20 adults, aged from 20 to 50 years, who were in an upright position. Group V included 19 adults, over 50 years old, who were in an upright position. Twelve subjects were included in Groups II and IV. Plasma active renin was measured by the amount of angiotensin I general when an exogenous renin substrate was added. Plasma inactive renin was activated by trypsin. The results showed that, in a supine position, both ARC and IRC were significantly higher in newborns (Group I) than in the two adult groups (Groups II and III). The mean of the ARC/TPRC (total plasma renin concentration) ratio was lower in adults over 50 years old (Group III) than in those from 20 to 50 years old (Group II), but the difference was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The clinicopathological implication of myocytes with contraction bands in autopsy hearts. Quantitative analysis of myocytes with contraction bands in autopsy hearts.

To define the normal extent of myocytes with contraction bands, 51 adult autopsied hearts including 30 normal and 21 common hypertrophic hearts were studied. Based on the histologic features, contraction bands were divided into mild and severe types. They were found in 48 and 32 of the total 51 cases, respectively. However, in five hearts, myocytes with contraction bands were more diffused or localized in one part of the ventricular wall. There were no special different treatments before death among the five cases or others. They seemed however to correlate with sudden death or acute cerebral damages. Therefore, reperfusion injury and metabolic cell injuries were considered. If these 5 cases were excluded, the normal extend of myocytes with contraction bands was considered as less than a 1.7% area in the mild type and a 0.5% area in the severe type found in the ventricular wall. These mild and severe contraction bands were considered related to autolysis or events occurring before death.

Adult↗