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Biomedical subjects

W L Zhu

Publications and source records attributed to W L Zhu.

At least 19 recordsLinked to original sources
PubMed2006

A time-temperature rheological study of konjac glucomannan hydrocolloid.

Konjac glucomannan (KGM) is one of the most versatile soluble biomaterials having wide-ranging applications. The shear storage, G', and loss, G", moduli of this hydrocolloid were recorded as functions of angular frequency varying from 0.1 to 100.0 rad/s and temperature from 5 to 50 degrees C. It was found that both G' and G" mainly increase with angular frequency in the range from 0.1 to 100 rad/s. As the temperature increases from 5 to 95 degrees C, the values of G' and G" decrease. A novel criterion for the thermorheologically simple material, and a procedure to calculate the shift factor from the angular frequency sweep and temperature ramp data were presented. By these methods, the KGM hydrocolloid is found to obey the TTS principle as log G" and log G' are less than 1.529 and 1.436, respectively. The Williams-Landel-Ferry equation can describe the shift factor of the KGM hydrocolloid.

Colloids↗
PubMed2001

Engineering principles applied to implantable otologic devices.

The engineering principles of possible actuators and sensors for totally implantable mid-ear or cochlear hearing devices are summarized. The selection considerations are discussed. The frequency response, and the needed force and displacement at the ossicular chain sites were measured on fresh temporal bones to determine approximately the middle ear device requirements and design considerations. A design example of the actuator and sensor is outlined with laboratory and acute animal evaluation results.

Acoustics↗
PubMed2001

[Evaluation of clinical application of intravascular ultrasound image].

OBJECTIVE: To prospectively evaluate the clinical applications of intravascular ultrasound (IVUS). METHODS: Four hundred and thirty seven patients with coronary artery disease (CAD) or suspect CAD were imaged with CAD and IVUS, including (1) assessment IVUS in 135 cases with normal coronary angiography (CAG) (2) comparison IVUS with CAG pre and after angioplasty in 52 patients with CAD (3) assessment of detecting calcification lesions with CAG and IVUS in 150 patients (4) predicting the cardiac events after stent implantation guided by IVUS (n = 47) and CAG (N = 53). RESULTS: IVUS may detect coronary atherosclerosis lesions with normal by CAG. CAG overestimated effect of angioplasty. IVUS was more accurate to determine effect and complications of PTCA compared with CAG. IVUS interpreted the mechanism of vessel dilatation in PTCA. The cardiac events after stent implantation were significantly reduced after IVUS examination as compared with CAG. CONCLUSIONS: IVUS represents a radically different approach to vascular anatomy. Unlike angiography, which displays the coronary artery as a silhouette of the contrast-filled lumen, IVUS generates a cross-sectional tomographic image of the lumen and vessel wall. IVUS plays an important role as a guidance in cardiac intervention.

Adult↗
PubMed1999

Molecular modeling on kappa opioid receptor and its interaction with nonpeptide kappa opioid agonists.

AIM: To study the interaction between kappa-opioid receptor and its nonpeptide agonists. METHODS: The "conservation patterns" for G-protein coupled receptors (GPCR) were used to determine 7 transmembrane (TM) regions. Taking the crystallographic coordinates of bacteriorhodopsin (BR) as the template, the 3D structural model was constructed for 7 TM of kappa-opioid subtype with molecular mechanics (MM) method. Five highly active nonpeptide kappa-opioid agonists were docked into the 7 helices of kappa-opioid receptor to study the ligand-receptor interaction. RESULTS: Four important interactions between U-50488-like agonists and kappa-opioid receptors were drawn according to our modeling study: (1) the protonated pyrrolidine nitrogen of the ligands formed a hydrogen-bond with the carboxyl of Asp138; (2) the carbonyl oxygen of ligands forms a hydrogen bond to the hydroxyl of Ser187; (3) the aryl groups connected to acylamide of the agonists inserted into a hydrophobic cavity enclosed by residues Val239, Val236, Phe235, Val232, Leu186, and Trp183; (4) the pyrrolidine of the ligands in the complexes was surrounded by Ile290, Asp138, Ile194, Ile135, and Cys131. CONCLUSION: The proposed interaction mechanism is helpful for further mutant experiments and designing novel potent kappa-opioid agonists.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1998

A 3D-QSAR study on ginkgolides and their analogues with comparative molecular field analysis.

Comparative molecular field analysis (CoMFA), a three-dimensional quantitative structure-activity relationship (3D-QSAR) paradigm was used to study the correlation between the physicochemical properties and the in vitro bioactivities of ginkgolide analogues. The correlation derived from CoMFA analysis has a good predictive capability. Based on the result of CoMFA analysis, we designed some compounds. Pharmacological assay indicated that three of these new designed compounds are 2 and 4 times more potent than that of ginkgolides.

Diterpenes↗
PubMed1995

Contactless semi-implantable electromagnetic middle ear device for the treatment of sensorineural hearing loss. Short-term and long-term animal experiments.

A contactless electromagnetic hearing device has been designed following basic science experiments, improvement of electronics, and precision micromechanics. Different prototypes have been developed and tested in the laboratory, fresh human temporal bones, and acute and chronic animal experimentation. A conductive hearing loss model was first developed in the cat using samarium cobalt as the target magnet. Later, a highly efficient electromagnetic air-core coil was selected to vibrate a neodymium iron boron magnet cemented to the body of the incus and tested in acute and chronic experiments using the cat as the model. In this group of animals, the ossicular chain was left intact. There was no failure of the target magnet, driving coil, or implanted electronics. The only problem encountered in this evaluation was a malfunction of the receiving antenna that had to be redesigned and retrofitted into the implanted units. This system would be suitable for the treatment of moderate to severe sensorineural hearing loss. Planning to begin human clinical trials is ongoing.

Animals↗
PubMed1995

Engineering principles of mechanical stimulation of the middle ear.

This article presents the transducer principles of possible middle ear hearing devices with their characteristics and selection considerations summarized. The frequency response and the needed force and displacement at the ossicular chain sites were measured to determine approximately the system requirements and design considerations. The power required to vibrate the ossicular chain is estimated to be of the order of 0.1 watt, which is three orders of magnitude smaller than the power consumption of devices being developed in various laboratories. Careful engineering design and evaluation is needed. A design example of the transducer used with a partially implantable, noncontact electromagnetic hearing device is presented in this article with laboratory evaluation results.

Biomedical Engineering↗
PubMed1994

[Analysis of risk factors in postinfarction angina].

The clinical and echocardiographic variables related to postinfarction angina were evaluated in 54 patients with acute myocardial infarction. All patients underwent 2D echocardiography at 2-3 weeks after infarction. Wall motion analysis was quantified with a wall motion score index (WMSI) based on 16 left ventricular wall segments. Among the 54 patients with acute myocardial infarction 23 (42.6%) had early postinfarction angina. Multiple regression analysis demonstrated no significant difference between the patients with and without postinfarction angina in age, sex, location of infarction, Killip classification, previous angina, hypertension, hyperlipidemia, diabetes mellitus, creatine kinase level and left ventricular ejection fraction. In comparison with patients without postinfarction angina, patients with postinfarction angina had higher WMSI. It indicates that postinfarction angina appears to be related more to myocardial ischemia rather than to the infarct of myocardium.

Adult↗
PubMed1994

A contactless electromagnetic implantable middle ear device for sensorineural hearing loss.

Following basic science experiments, improvement of precision micromechanics and electronics design, and development of different prototypes, a contactless electromagnetic hearing device has been successfully implanted in cats (acute experiments). Chronic animal experiments using the cat as well as the rabbit are ongoing to test the components of the device. A highly efficient air core coil is used to vibrate a neodymium-iron-boron magnet cemented to the body of the incus. The parts of the system, including implanted electronics (hybrid circuit, solid state), are laser welded and hermetically sealed. The system allows for the generation of enough force which vibrates the magnet implanted on the incus. It would be suitable for the treatment of moderate to severe sensorineural hearing loss.

Animals↗
PubMed1992

[Prognosis and factors predicting the long-term prognosis of myocardial infarction].

200 cases of consecutively admitted acute myocardial infarction (AMI), who had survived for at least 2 weeks, were studied prospectively. 193 cases were followed-up for 0.5-27 (average 15) months; 41 of them (21.2%) had cardiac events, including 3 sudden cardiac death (1.6%) and 35 obvious cardiac failure (18.1%). 11 patients died of heart failure and 4 of reinfarction. Before discharge, noninvasive tests were done: LVEF < or = 40%, age > or = 60, maximum value of creatinine-phosphokinase > or = 1000 IU/dl and positive ventricular late potential were the 4 factors of high risk. Patients with 3 or 4 positive risk factors had poorer prognosis, if they were compared with those with one or none.

Age Factors↗
PubMed1990

[Hemochromatosis: a review of 22 Chinese cases].

22 cases of hemochromatosis were analysed. 19 cases were collected from Chinese medical journals and 3 from our hospital. We showed the similarities and differences between Chinese and western patients. The diagnosis, mode of heredity, possible pathogenesis and management of idiopathic hemochromatosis were also briefly discussed.

Adult↗
PubMed1989

[Clinical study of fetal echocardiography].

92 fetuses from 52 women who were about to undergo midtrimester termination of pregnancy and 40 fetuses at high risk were studied by M-mode, 2D and pulsed Doppler echocardiography. One fetus of 24 weeks gestation was found to have a cardiac tumor. The pathological diagnosis was rhabdomyoma. The right ventricular tumor was located between the tricuspid and septum. It obstructed the tricuspid valve and caused tricuspid regurgitation and bradycardia. The measurement of atrial and ventricular dimensions by fetal echocardiography in 91 normal fetuses showed an average RV/LV ratio of 1.11. Doppler velocities of mitral and tricuspid valves showed a Peak A/peakE ratio of 1.

Blood Flow Velocity↗
PubMed1989

[Identification of congenital cardiac malformation and in utero arrhythmia by fetal echocardiography].

UNLABELLED: M-mode, 2D and Pulsed Doppler Echocardiography were performed on 111 fetuses of high-risk pregnancies. Fetal gestation ages ranged 16-41 weeks. Six congenital cardiac diseases were detected in utero and confirmed at autopsy in 4 cases, and one by Pulsed Doppler Echocardiography after delivery. These included a rhabdomyoma, an endocardial fibroelastosis with hydrops, a pulmonary stenosis with tricuspid regurgitation, a VSD, a VSD with descending aortic stenosis, an AV canal defect with single atrium and single AV valve with regurgitation. Arrhythmia was diagnosed in 23 fetuses, 9 had transient sinus bradycardia, 8 had premature atrial contraction, 2 had premature ventricular contraction which disappeared after birth, 4 had sustained sinus bradycardia, one of them combined PVC occurring in bigeminy and trigeminy, which continued after birth. These 4 fetuses had congenital heart disease. CONCLUSION: (1) 2 DE and PDE are the most valuable non-invasive technique for detection of fetal structural cardiac abnormalities. (2) M-mode and PDE make correct rhythm diagnosis in fetus. (3) The fetus with transient sinus bradycardia or PAC usually has a favorable prognosis. Sustained bradycardia has a more ominous prognosis, particularly if associated with heart abnormalities. (4) Fetal hydrops may associate with congestive cardiac failure in uterus. The incidence of cardiac disease is high in hydrops.

Adult↗
PubMed1989

[Quantitative evaluation of aortic stenosis using continuous wave Doppler].

Thirteen patients with suspected aortic stenosis were studied with left-heart catheterization and 2 D, Doppler echocardiography. Thickness and abnormal motion of aortic valve was detected by 2 D Echo in 12 cases. One case had thick aortic valve with normal motion. The causes of lesions included rheumatic heart disease in one patient, bicuspid aortic valve in one, and senile calcific aortic valves in eleven. The left ventricular and aortic pressure were recorded simultaneously with left-heart catheterization. Peak-to-peak, instant peak and mean pressure gradients were measured. The aortic velocity was obtained with Continuous Wave (CW) Doppler. Instant peak and mean pressure gradients were calculated from Bernoulli equation. Both catheterization and Doppler demonstrated significant pressure gradient between LV and aorta in twelve patients. The instant peak and mean pressure gradients calculated from CW Doppler were compared with catheterization data. Doppler pressure gradients correlated well with that measured at catheterization: Doppler instant peak pressure gradient compared with that by catheterization, r = 0.89, P less than 0.001, Doppler instant peak pressure gradient compared with peak-to-peak pressure gradient by catheterization, r = 0.79, P less than 0.001, Doppler mean pressure gradient compared with that by catheterization, r = 0.75, P = 0.002. This study demonstrates that CW Doppler provides a valuable method for assessment of the severity of aortic stenosis.

Adult↗