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Biomedical subjects

W L Chen

Publications and source records attributed to W L Chen.

At least 73 records · Page 4Linked to original sources
PubMed1994

Atrial demand pacing in patients with symptomatic sick sinus syndrome.

Atrial demand pacing provides a physiological, simply implemented, and less costly alternative of cardiac stimulation in symptomatic sick sinus syndrome (SSS) patients. Hindrance from widespread use stems mainly from the potential development of high degree AV block and persistent atrial fibrillation. A reappraisal of atrial pacing is now justified as we gain more clinical information. In this study we examined retrospectively the clinical course of 22 well-selected SSS patients paced in AAI mode for 30 +/- 29 months. Two patients had infrequent short-run atrial tachyrhythmia before implantation. There was an early lead dislodgement which required repositioning later. Three acute threshold increments were noted which necessitated a change in atrial pacing site in one and short-term steroid use in the other two. No other sensing, pacing or operative complication occurred and all pacing systems performed well. AII patients survived during follow-up and no patient developed congestive heart failure, though depressed left ventricular function was found in three preoperatively. No high degree AV block was encountered. Four patients presented paroxysmal atrial fibrillation (PAF) 25 +/- 16 months after the procedure, of whom one developed chronic atrial fibrillation. No single factor predicted the development of PAF. Resumption of normal pacemaker function always occurred immediately in the pause following cessation of PAF and no revision of pacing mode was required in the patient with chronic AF. Symptomatic relief was obtained in all patients. In summary, single chamber, single rate atrial pacing remains a physiologic, reliable, economic and easily implemented pacing modality affordable to a number of sick sinus patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Significance of acceleration period in a dynamic strength testing study.

The acceleration period that occurs during isokinetic tests may provide valuable information regarding neuromuscular readiness to produce maximal contraction. The purpose of this study was to collect the normative data of acceleration time during isokinetic knee testing, to calculate the acceleration work (Wacc), and to determine the errors (ERexp, ERwork, ERpower) due to ignoring Wacc during explosiveness, total work, and average power measurements. Seven male and 13 female subjects attended the test by using the Cybex 325 system and electronic stroboscope machine for 10 testing speeds (30-300 degrees/sec). A three-way ANOVA was used to assess gender, direction, and speed factors on acceleration time, Wacc, and errors. The results indicated that acceleration time was significantly affected by speed and direction; Wacc and ERexp by speed, direction, and gender; and ERwork and ERpower by speed and gender. The errors appeared to increase when testing the female subjects, during the knee flexion test, or when speed increased. To increase validity in clinical testing, it is important to consider the acceleration phase effect, especially in higher velocity isokinetic testing or for weaker muscle groups.

Acceleration↗
PubMed1994

Therapeutic drug monitoring can avoid iatrogenic alterations caused by 99mTc-methylene diphosphonate (MDP)-gentamicin interaction.

Gentamicin is an aminoglycoside antibiotic used to treat a wide variety of infections caused by gram-negative organisms, but it is potentially toxic to the kidneys. Due to its nephrotoxicity, gentamicin may cause abnormal renal uptake to be seen on 99mTc-MDP bone scintigraphy. The presence of the radiopharmaceutical in the kidneys, along with an increase in renal retention, tend to produce scintigraphic results that falsely identify characteristics related to diseases such as renal vascular, or urinary tract obstruction, and even renal cancer. An altered biodistribution may provide misleading information that can either mask or mimic certain disease symptoms. A method to maximize the therapeutic benefit of gentamicin while minimizing the risk of nephrotoxicity and the appearance of a hot kidney on scintigraphy is desirable. Serial pharmacokinetic dosing has been proposed as a method to accomplish this goal. Therapeutic drug monitoring (TDM) of gentamicin therapy, and bone scintigraphy employing 99mTc-MDP as the radiopharmaceutical was carried out in 22 patients. The data presented here demonstrate that with serial pharmacokinetic dosing of gentamicin, the iatrogenic alteration caused by gentamicin therapy can be avoided.

Bone and Bones↗
PubMed1993

The development of a radioimmunoassay for reverse triiodothyronine sulfate in human serum and amniotic fluid.

Sulfated iodothyronines including T4-sulfate (T4S) and T3-sulfate (T3S) have been identified in human serum and amniotic fluid. Little is known, however, about the existence of sulfate conjugation of reverse T3 (rT3S) in man. In this report, we employed a novel, sensitive, and specific rT3S RIA to address this question. The rabbit antiserum to rT3S was highly specific; T4, T3, rT3, and 3,3'-T2 showed less than 0.002% cross-reaction with the antiserum. Only T4S and T3S cross-reacted significantly (0.3% and 0.01%, respectively); other analogs cross-reacted less than 0.0001%. The detection threshold of the RIA was 14 pmol/L (1.0 ng/dL). The mean serum rT3S concentration (pmol/L) was 40 in euthyroid subjects. Values were similar in hypothyroid patients (38) and pregnant women (52) but significantly (P < 0.01) elevated to 176 in hyperthyroid patient, 74 in patients with nonthyroid illnesses, and 684 in cord sera of newborns. Serum rT3S increased significantly in hyperthyroid patients 1 day after administration of 1 g sodium ipodate orally. Reverse T3S was detected consistently in amniotic fluid at 14 to 22 weeks of gestation and showed a marked rise 1-3 weeks after intraamniotic administration of 500-1000 micrograms T4. The various data suggest that: (1) rT3S is a normal component of human serum and amniotic fluid; (2) it is derived from metabolism of T4 or rT3; (3) circulating rT3S increases in hyperthyroidism and in circumstances where type I 5'-monodeiodinating activity is low, e.g. nonthyroid illnesses, fetal life, and after administration of ipodate.

Amniotic Fluid↗
PubMed1993

[Study of the location of mandibular mental foremen in modern and neolithic adult]

37 cases of mandible of Neolithic adult that both sexes without missing teeth,alveolar bone were studied.The result showed that the location of the mental foramen below the apex of the lower second premolar was the most common(67.97%) in the modern adult,and the location of the mental foramen below between the apex of the lower second premolar and the first molar was the most common (64.86%) in the neolithic adult.

Journal Article↗
PubMed1993

Radioiodine I-131 therapy in the management of differentiated thyroid carcinoma: a review of 202 patients.

During the 13-year period from 1978 to 1991, 202 patients with differentiated thyroid carcinoma were treated with radioactive iodine-131 (I-131) post-operatively. The therapeutic response and survival rates were studied. Of these patients, 172 (85%) patients were shown to be totally disease-free; others showed a partial response or persistence of disease. A total of 134 patients (66%) achieved total thyroid ablation with only one therapeutic dose of I-131, ranging from 100-200 mCi. Patients over the age of 40 years at the time of diagnosis had a lower survival rate than those under 40 years old (98.6% vs 68.9%; p < 0.001). However, patients over the age of 50 years and follicular patients had a lower recurrence rate than patients under the age of 50 years and those with papillary carcinoma. Eight of the 32 patients (25%) with lung metastases were detected by a therapeutic I-131 whole body scan (WBS), in which the diagnostic I-131 WBS was negative. In six of the 16 patients (37.5%) with bony metastases, the I-131 WBS showed more obvious positive results than the Tc-99m methylene diphosphonate (MDP) bone scanning. Most of the remaining patients exhibited the same findings for the two methods. Therefore, I-131 WBS is superior to Tc-99m MDP bone scanning in the detection of bony metastases from thyroid carcinoma. The mortality rate of patients with bony metastases was four times that of patients with lung metastases (40% vs 10%). Patients with follicular carcinoma had higher rates of distant metastases than those with papillary carcinoma (13% vs 4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma, Follicular↗
PubMed1993

[Studies on longevity tea].

This paper reports the preparation, physical and chemical identification and content determination of Longevity Tea. The preparation process is advanced, the content determination is simple and accurate and thus can be taken as standards for the quality control of Longevity Tea.

Drugs, Chinese Herbal↗
PubMed1993

[The investigation of the correlations between left ventricular end diastolic pressure and pulmonary function parameters].

Left ventricular end diastolic pressure (LVEDP) in 24 patients with coronary heart, hypertension or rheumatic heart disease (mainly aortic valve pathologic change, exclude mitral stenosis), who had unobvious clinical heart failure. Before left heart catheterization pulmonary function were tested by plethysmogram, results revealed: when LVEDP > 15 mmHg in the patients, pulmonary function parameter expectancy value percentage including FEF25-75%, V25, V50, V75, FVC, VC, FEV1.0 were obviously decreased. RV/TLC expectancy value percentage was obviously increased. Pulmonary function parameter expectancy value percentage including FEF25-75%, V25, V50, V75, FEV1.0, FVC, etc. had significant negative correlation with LVEDP (r = -0.715, P < 0.001; r = -0.699, P < 0.001; r = -0.678, P < 0.001; r = -0.671, P < 0.001; r = -0.648, P < 0.001; r = -0.516, P < 0.01; respectively). RV/TLC expectancy value percentage had significant positive correlation with LVEDP (r = 0.515, P < 0.05). The results indicate that testing pulmonary function parameter helps to evaluate left ventricular function and diagnose early (mesenchymal) pulmonary edema.

Blood Pressure↗
PubMed1992

Site-directed mutagenesis and chemical modification of cysteine residues of rat glutathione S-transferase 3-3.

Rat liver glutathione S-transferase (GST) 3-3 is composed of two identical subunits, each containing three cysteine residues, Cys-86, Cys-114 and Cys-173. We have shown previously that Cys-86 is not involved in the enzymic activity of GST 3-3 [Hsieh, Huang, Chen, Lai & Tam (1991) Biochem, J. 278, 293-297]. At 50 degrees C, iodoacetamide can inactivate the enzyme by modifying Cys-86 and Cys-114. Cys-114 can be protected against iodoacetamide inhibition by S-(dinitrophenyl)glutathione. Site-directed mutagenesis was used to construct mutants in which serine replaced one (C114S and C173S) or all three (CallS) cysteine residues. These mutants were over-expressed in Spodoptera frugiperda cells in a baculovirus system and were found to be fully active. Replacing Cys-86 or Cys-114 with alanine (C86A and C114A) does not diminish the activity of the protein. The results suggest that cysteines are not involved in the enzymic mechanism, and Cys-114 is possibly located at the active site of GST 3-3.

Amino Acid Sequence↗
PubMed1992

Localization and therapy of human cervical tumor xenografts with radiolabeled monoclonal antibody 1H10.

Murine IgG3 monoclonal antibody (Mab) 1H10, which recognizes a tumor-associated antigen expressed on the surface of more than 40% of human cervical carcinoma tissues, was used for in vivo localization and therapy of cervical tumor xenografts. A human cervical carcinoma cell line, CaSki, was used as our experimental tumor system. Mab 1H10 antigen expression on the surface of CaSki cells was found to be cell-cycle independent. The ability of Mab 1H10 F(ab')2 to bind to CaSki tumor xenografts was verified by direct immunohistochemical staining of thin tumor sections with a Mab 1H10-peroxidase conjugate. Radioimmunoscintigraphy of nude mice bearing CaSki tumors after iv administration of [131I]1H10 F(ab')2 showed clear tumor images 48 hr after Mab injection. Radiolabeled Mab 1H10 F(ab')2 was found to specifically localize in solid CaSki tumors 96 hr after antibody injection. Radioactivity in tumor tissue was 4 times higher than that in kidney tissue and over 6 times higher than that in liver tissue. Mab 1H10 F(ab')2 binding to xenografted CaSki tumors was 17 times greater than a control IgG3 F(ab')2 after 96 hr. Therapy of athymic mice bearing established CaSki tumors with three iv injections of 100 microCi [131I]1H10 F(ab')2 resulted in extensive tumor necrosis and significant suppression (p < 0.05) of tumor growth compared to that in control mice. These results indicate that Mab 1H10 F(ab')2 may be clinically useful for detection or treatment of cervical cancer.

Animals↗
PubMed1992

Percutaneous absorption of nicotinic acid, phenol, benzoic acid and triclopyr butoxyethyl ester through rat and human skin in vitro: further validation of an in vitro model by comparison with in vivo data.

The in vitro percutaneous absorption of three model compounds, nicotinic acid, phenol and benzoic acid, and the herbicide triclopyr butoxyethyl ester (triclopyr BEE) has been investigated in flow-through diffusion cells using skin from male Fischer 344 rats and humans. After the application of the four chemicals to the epidermal surface of unoccluded full-thickness rat skin, the absorption of each compound across the skin and into the receptor fluid at 72 hr reached 3.7 +/- 0.3, 5.7 +/- 0.6, 26.7 +/- 3.7 and 48.3 +/- 1.2% (mean +/- SD, n = 2-7) of the applied dose for triclopyr BEE, nicotinic acid, phenol and benzoic acid, respectively. After the application of the four chemicals to the epidermal surface of unoccluded full-thickness human skin, the absorption of each compound across the skin and into the receptor fluid at 72 hr was significantly (P < 0.05) less than through rat skin, reaching 0.7 +/- 0.1, 0.7 +/- 0.2, 18.8 +/- 1.3 and 37.8 +/- 6.9% (mean +/- SD, n = 2-7) of the applied dose for triclopyr BEE, nicotinic acid, phenol and benzoic acid, respectively. Occlusion of the skin surface with teflon caps often significantly (P < 0.05) enhanced the percutaneous absorption of the model compounds, although this effect was not uniform, varying with the compound under study and the skin (rat or human) used. When rat skin was occluded with teflon caps, the extent of absorption at 72 hr reached 8.6 +/- 0.8, 36.2 +/- 1.7 and 51.8 +/- 3.3% (mean +/- SD, n = 3-4) for nicotinic acid, phenol and benzoic acid, respectively. Corresponding values for human skin occluded with teflon caps were 3.3 +/- 1.6, 47.1 +/- 0.5 and 65.5 +/- 7.1% (mean +/- SD, n = 3-4). The experiments on the absorption of each model compound through rat and human skin were repeated and there was generally good agreement between the results from the two sets of experiments. The in vitro data reported compare favourably with data obtained by other workers using both in vitro and in vivo methodologies. The in vitro: in vivo correlation supports the use of the flow-through diffusion cell system as a model for the prediction of percutaneous absorption in vivo in the rat and in humans.

Absorption↗
PubMed1992

Ultracytochemical studies on Trichomonas hominis.

The results of ultracytochemical studies on Trichomonas hominis showed that ACPase and CMPase were mainly located in the mature face sacs of the primary lysosomes, digestive vacuoles, as well as in the parabasal body. TPPase and NADPase were found in the saccules at the mature face and the intermediate saccules of parabasal body respectively. This study revealed that T. hominis had well-developed parabasal bodies. Negative COase and catalase reactions indicated that T. hominis lacked both mitochondria and microbody. Hydrogenosome was stained well with the Ur-Pb-Cu impregnation technique.

Acid Phosphatase↗
PubMed1992

[Bioavailability of a controlled-release suspension of phenylpropanolamine in healthy volunteers].

A high-performance liquid chromatographic analysis of phenylpropanolamine (PPA) in human plasma is presented. Using direct UV detection the method is sufficiently sensitive to 25 ng/ml for PPA. Single-dose pharmacokinetics of PPA in 10 healthy volunteers taking controlled release suspension (C) or tablet (T), each containing 150 mg PPA was compared. The study described here has shown that the (C) AUC(0-infinity)/(T) AUC(0-infinity) = 1.02 (P greater than 0.4). The controlled-release product of PPA is equivalent to PPA tablet.

Adult↗
PubMed1991

Cysteine-86 is not needed for the enzymic activity of glutathione S-transferase 3-3.

Recombinant glutathione S-transferase 3-3 expressed in Spodoptera frugiperda (SF9) cells with the use of a baculovirus expression system was modified with 1 mM-iodoacetamide. Amino acid analysis indicated that 0.79 +/- 0.15 cysteine residue was modified per enzyme subunit. The S-carbaminomethylated protein retains the GSH-conjugating activity. Glutathione S-transferase 3-3 modified with iodo[14C]acetamide was digested with Achromobacter proteinase I and the resulting peptides were separated by h.p.l.c. The modified peptides were pooled and further digested with Staphylococcus aureus V8 proteinase. Isotope-labelled peptides were isolated and collected for N-terminal sequence analysis. By this procedure, cysteine-86 was identified as the major S-carbaminomethylated residue. Verification of this findings came from the use of site-directed mutagenesis in which this cysteine was replaced by serine (C86S mutant). The C86S mutant is enzymically active. Therefore cysteine-86 is not needed for the conjugation of GSH with electrophilic compounds on glutathione S-transferase 3-3.

Amino Acid Sequence↗
PubMed1991

Near-infrared Fourier transform Raman and conventional Raman studies of calf gamma-crystallins in the lyophilized state and in solution.

We present in this report a detailed structural study of calf gamma-crystallins both in the solid state and in solution by the newly developed technique of near-infrared (IR) Fourier transform (FT)-Raman spectroscopy as well as by the conventional Raman method. In comparison with conventional laser Raman spectroscopy, the near-IR FT-Raman approach exhibits several attractive features such as fluorescence rejection capability, frequency accuracy, and the FT's multiplex and throughput advantages. These distinct characteristics combined form the basis for the particular suitability of FT-Raman in crystallin structural analysis and elucidation. We have thus obtained evidence in support of the view that native calf gamma-II crystallin does not contain a disulfide bond either in the lyophilized state or in solution. In addition, conventional Raman spectra are examined for all four gamma-crystallin fractions. gamma-S, gamma-II, gamma-III, and gamma-IV, and the results indicate a high degree of structural similarities among them. It is also found that the sulfhydryl groups in all four gamma-crystallins are highly resistant to air oxidation and are capable of maintaining their reduced state during isolation in the absence of added reductants or such chelating agents as EDTA.

Animals↗
PubMed1991

Congenital complete atrioventricular block--two cases report.

We encountered two cases of congenital complete atrioventricular block out of 23,400 deliveries during the past 3 years. Two-dimensional and M-mode fetal echocardiography revealed complete atrioventricular block without structural abnormality. Anti-Ro (SS-A) antibodies were present in both the mother and infant of these two cases. The ventricular rates of these two infants were 31 and 80 beats/min respectively. Pacemaker implantation was performed for the first infant.

Adult↗
PubMed1991

Perfusion scan in pulmonary tumor microembolism: report of a case.

A 76-year-old male patient was admitted to our hospital with the chief complaint of dyspnea. A chest CT scan showed pericardial effusion, mediastinal lymphadenopathy and a tumor in the right ventricle with invasion to the main trunk of the pulmonary artery. A 99mTc MAA perfusion lung scan revealed multiple small subsegmental peripheral defects and a "fissure sign", while the 133Xe ventilation scan was normal. After the chest CT scan and scans of both lungs, tumor microembolism was highly suspected. Open chest surgery was performed. A huge tumor in the right ventricle involving the main trunk of the pulmonary artery was found. In addition, multiple tumor thrombi in the pulmonary arteries and veins were also noted. The pathology was metastatic squamous cell carcinoma. Thereafter, the primary lesion was found by bronchoscopy. The final diagnosis was squamous cell carcinoma of the right lower lobe bronchus with metastases to the right ventricle and pulmonary vessels, and in association with pulmonary tumor microembolism. We present this uncommon case and describe the pulmonary perfusion pattern of the tumor microembolism.

Aged↗