Search PubMed⌕ Search

Biomedical subjects

S F Chang

Publications and source records attributed to S F Chang.

At least 127 records · Page 7Linked to original sources
PubMed1983

Analysis of theophylline by automated multidimensional high-performance liquid chromatography involving direct plasma injection.

A procedure of direct injection of whole plasma for the analysis of theophylline by an automated multidimensional high-performance liquid chromatographic (HPLC) technique is described. The procedure requires as little as 30 microliters of plasma sample and has a linear range of 0.25-30 micrograms/ml. Unknown plasma samples, after the addition of internal standard, are directly injected into the HPLC system. The chromatographic procedure is fully automated, thus the attention and time required from the analyst is reduced to a minimum. About 70 samples can be analyzed per day with approximately 3 hr of analyst time.

Biological Availability↗
PubMed1983

Measurement of flecainide acetate in human plasma by an extraction spectrophotofluorometric method.

A fluorometric method for the quantitation of 2,5-bis-(2,2,2-trifluoroethoxy)-N-(2-piperidylmethyl)benzamide acetate (R-818, flecainide acetate) in human plasma has been developed. The minimum quantifiable concentration of flecainide acetate by this method is 25 ng/ml with a 2 ml plasma sample; a slightly modified procedure which also requires the use of a microcell in the spectrophotofluorometer further increases the maximum sensitivity to 12.5 ng/ml. The precision, expressed as relative standard deviation is 2.9, 0.7, 5.6, 3.5, and 4.3% for 75, 150, 250, 500, and 700 ng flecainide acetate/ml, respectively. The accuracy, expressed as relative error, is -6.7, -3.3, -0.4, +4.4, and -0.4%, respectively, for the corresponding concentrations specified above. The relative standard deviations for the inter-day variation are 19, 7, 9, 9, 8, 10, 13, 12, and 9% for the 25, 50, 100, 200, 300, 400, 600, 800, and 1000 ng/ml standards, respectively. Preliminary data indicate that propranolol and quinidine interfere with this method while procainamide, disopyramide, hydralazine, methyldopa, diazepam, hydrochlorothiazide, and sulfinpyrazone exhibit little or no interference. The results of the analyses of clinical samples by the fluorometric method agree well with an established GLC method. Thus, the quality of the fluorometric method is considered adequate for estimating plasma flecainide acetate levels during drug therapy in most non-research settings, if careful consideration is given to possible interference by other drugs.

Chromatography, Gas↗
PubMed1981

Quantitative determination of nefopam in human plasma, saliva and cerebrospinal fluid by gas-liquid chromatography using a nitrogen-selective detector.

A sensitive and selective gas-liquid chromatographic method for the determination of nefopam in human plasma, saliva and cerebrospinal fluid has been developed. The method includes the selective extraction of nefopam and the internal standard, orphenadrine, from biological fluids by a double extraction procedure. The extracted nefopam and internal standard are analyzed by a gas chromatograph equipped with a 3% OV-17 glass column and a nitrogen-phosphorus flame ionization detector (NPFID) operated in the nitrogen mode. The detector provides the needed high sensitivity and also selectivity due to the inherent characteristics of NPFID to discriminate against non-nitrogen containing materials. Five nanograms nefopam per ml plasma or saliva are routinely quantitated with a 1-ml sample or as little as 2 ng per ml cerebrospinal fluid with a 3-ml sample. The intra-day reproducibilities, expressed as the relative standard deviation, are 5, 2 and 3% at 10, 35 and 75 ng/ml plasma levels, respectively. The accuracies expressed by relative error at these levels are 12, -4 and -2%, respectively. The inter-day reproducibility is demonstrated by the small relative standard, deviation, 2%, of the slopes from ten plasma standard curves run on ten different days. In various clinical studies in humans the method has been successfully applied to the study of single-dose pharmacokinetics of nefopam and the monitoring of nefopam concentrations in saliva and cerebrospinal fluids.

Gas Chromatography-Mass Spectrometry↗
PubMed1981

Oral flecainide acetate for the treatment of ventricular arrhythmias.

The antiarrhythmic efficacy and safety of oral flecainide acetate were assessed during a controlled, short-term dosage-maintenance study. Thirteen patients with chronic ventricular ectopy entered a placebo control period, and 11 with persistent, frequent (greater than 600 per 12 hours) premature ventricular complexes (PVCs) advanced to drug therapy. Of 10 patients completing a trial of different doses, nine responded completely, with a mean PVC suppression of 98,3 per cent. Repetitive PVCs were eliminated. The mean effective dose was 189 mg per 12 hours, and the effective plasma concentration before administration of a dose averaged 635 ng per milliliter. One patient responded partially (68 per cent of PVCs suppressed). Flecainide continued to be effective and well tolerated at the end of a two-week outpatient trial in the nine complete responders, maintaining an average PVC suppression of 94.6 per cent. The PR and QRS intervals were mildly prolonged. The echocardiographic ejection fraction was unchanged during treatment. The elimination half-life was long - 18.8 +/- 3.8 hours. Flecainide thus appears to be a highly effective and well-tolerated antiarrhythmic agent with favorable pharmacokinetics.

Administration, Oral↗
PubMed1981

Comparative absorption of theophylline from theophylline-guaifenesin tablets and liquid and from a reference theophylline liquid.

This single-dose, three-way crossover study in 18 healthy adults compared the oral absorption of theophylline from a theophylline-guaifenesin tablet and from a theophylline-guaifenesin liquid with absorption from a theophylline liquid. Each dose form contained 500 mg theophylline and, when indicated, 400 mg guaifenesin. The extents of theophylline absorption from the formulations were within 10% of each other. The absolute differences in the areas under the curve among the formulations were small and, although significantly higher statistically for the theophylline-guaifenesin tablet, are without therapeutic consequence. The theophylline plasma level curves from each of the three formulations were similar. Comparable theophylline absorption and elimination characteristics were seen.

Adult↗
PubMed1978

Borderlands in the diagnosis of regional enteritis: trends in overdiagnosis and value of therapeutic trial.

Our regional experience in the state of Connecticut indicates that Crohn's disease is being overdiagnosed. Six patients with disorders mimicking regional enteritis are presented, one of whom had an atypical clinical course and the remainder had atypical therapeutic responses. The radiologist should be aware of clinical responses and make reassessments if necessary, in order not to overlook surgically treatable conditions.

Adolescent↗
PubMed1978

The protean gastrointestinal manifestations of metastatic breast carcinoma.

Metastatic breast carcinoma commonly remains silent for many years following initial diagnosis and mastectomy, and then appears as metastases at various locations. Gastrointestinal involvement is not uncommon and includes any site along the whole length of the gut, the liver, and the biliary tree; it occasionally simulates other diseases and causes difficulty in diagnosis. The radiographic features and differential diagnoses are discussed.

Adult↗
PubMed1977

Determination of an anti-inflammatory methanesulfonanilide in plasma by high-speed liquid chromatography.

A sensitive and chemically specific high-speed liquid chromatographic method was developed for the determination of 4-nitro 2-phenoxymethanesulfonanilide in plasma. The method includes selective extraction of the anti-inflammatory drug and an internal standard, 2-(4'-chlorophenoxy)-4-nitromethanesulfonanilide, into benzene from acidified plasma followed by reextraction into 0.2 N NaOH. The aqueous layer is acidified, and the drug is reextracted into benzene. The benzene is evaporated, and the residue is dissolved in a small volume of acetonitrile. A 10-microliter aliquot is analyzed on a reversed-phase column. The mean overall extraction recovery, after correction for aliquot factors, is 99%. The accuracy, expressed as the relative error, is 4, 0.3, and -3% at 0.60, 1.50, and 3.00 microgram/ml, respectively. Repeated analysis of reference standards indicates that the precision, expressed as the relative standard deviation, is 3% or less. The lower sensitivity limit is 0.2 microgram/ml with a 2-ml plasma sample. The method was applied successfully to the determination of plasma levels of 4-nitro-2-phenoxymethanesulfonanilide in humans and rats in metabolic experiments at pharmacological doses.

Animals↗
PubMed1976

Loss of colonic haustration in progressive systemic sclerosis.

Complete loss of colonic haustration was observed in six cases of progressive systemic sclerosis. Varying degrees of haustral loss or sacculation were noted in twelve others. An increase in colonic length was characteristic and, occasionally, there was slight to moderate generalized dilatation. Correlation of these findings with the microscopic appearance of the colon showed that muscular atrophy and fibrous replacement were consistent findings, varying in degree. Although the data are insufficient to permit definite conclusions, it is suggested that these changes may be responsible for colonic lengthening and loss of haustration. Attention is drawn to the importance of not confusing this appearance with other conditions, particularly chronic ulcerative colitis.

Adult↗
PubMed1976

Studies on shigella isolated in southern Taiwan.

During 1969, a total of 1,476 fecal and rectal swab specimens was collected from children with diarrhea and 249 strains of shigella were isolated. The incidence was 16.9%. The serotypes of 249 strains were: Shigella dysenteriae, 1.6% (4 strains); S. flexneri, 73.1% (182 strains); S. boydii, 3.2 (8 strains) and S. sonnei, 22.1% (55 strains). There was no marked difference of the isolation rate throughout the whole year. The susceptibility of shigella isolates to chemotherapeutic agents were also investigated. The percentage of the strains susceptible to gentamicin was 97.2%; to cephaloridine, 93.2%; to kanamycin, 91.9%; to colistin, 91.6%; to hetacillin, 88.4%; to ampicillin, 82.4% and to nalidixic acid, 79.9%. The other tested chemotherapeutic agents were less effective.

Anti-Bacterial Agents↗
PubMed1975

The wandering gallbladder.

An unusual case of a hypermobile gallbladder and liver is presented. The liver and gallbladder, supported only by a long midline falciform ligament, rotated freely from the right to the left upper quadrant. Because of a long gastrohepatic ligament and mesocolon, intermittent volvulus of the stomach and colon were associated findings.

Adult↗
PubMedDate not supplied

Surveillance of noise-induced hearing loss in Taiwan, ROC: a report of the PRESS-NHL results.

BACKGROUND: To understand the extent of noise-induced hearing loss (NIHL) among noise-exposed workers, an ongoing public health surveillance system (Program to Reduce Exposure by Surveillance System or PRESS-NIHL) was established in Taiwan in 1995 to monitor the prevalence of NIHL. METHODS: A total of 9,535 noise-exposed (> 85 dBA) workers were recruited into PRESS-NIHL from January to June 1995. Each received a periodic annual audiometric examination at 1 of 73 well-qualified audiometric examination rooms in accredited hospitals. Among those examined, 9,463 audiograms were acceptable for evaluation to determine the severity of NIHL at 4K Hz. RESULTS: The mean hearing threshold at 4K Hz was 36.8 dB among male workers and 29.7 dB among female workers. The mean hearing loss at 4K Hz of male workers was higher than that of female workers. Among both men and women, hearing ability was found to decrease with increasing age. A total of 3,216 (34.0%) workers were found to have NIHL, with a hearing threshold higher than 40 dB (NIHL) in either one or both ears. Among these workers, 1,886 (19.9%) had mild NIHL (hearing threshold between 40 and 55 dB) and 1,330 (14.1%) had severe NIHL (hearing threshold above 55 dB) in either one or both ears. The proportion of severe NIHL was higher in certain industries, including construction (38.6%), ship building/repairing (19.2%), and weapon manufacturing (13.6%). CONCLUSION: This surveillance system for NIHL is on of the first surveillance systems in the world established to monitor and control NIHL in the setting of industrial hygiene and occupational disease prevention. Our finding of a high prevalence of NIHL in certain industries will trigger immediate actions to control noise hazard, which in turn will provide better protection for noise-exposed workers.

Adult↗
PubMedDate not supplied

Rapid detection of hog cholera virus in tissues by the polymerase chain reaction.

A rapid method for the detection of hog cholera virus (HCV) in infected tissues, using polymerase chain reaction (PCR) was developed. Total RNA isolated from HCV-infected tissues was reverse transcribed with AMV reverse transcriptase and the resulting complementary DNA was amplified by Taq DNA polymerase in the presence of two HCV-specific primers. The amplified DNA fragment was detected by agarose gel electrophoresis. The sensitivity of this method was at 10(4) TCID50 of HCV. The sensitivity increased approximately 1000-fold when the DNA was reamplified with a set of nested primers. DNA sequencing analysis of the PCR products revealed that the HCV sequence amplified from a local field isolate was highly homologous to the HCV Alfort strain. This method may be useful for pathological and epidemiological studies of HCV in pigs.

Animals↗
PubMedDate not supplied

The pathology of systemic iridoviral disease in fish.

Iridoviruses have been associated with severe disease and economic loss in farmed food fish and ornamental fish, with mortality often reported to reach 50% or more. In the present study, three tropical marine food fish species and four tropical freshwater ornamental fish species with systemic iridovirus infections were examined histopathologically and ultrastructurally. Light microscopy consistently revealed pale to intensely basophilic hypertrophied virus-infected cells in spleen, kidney and intestine from all seven species. Ultrastructural examination showed changes in the vascular endothelium overlying hypertrophied virus-infected cells suggestive of pressure necrosis. Viral isolation was improved by the use of fibroblastic cell lines. This, together with the sub-endothelial location of infected cells in all infected species examined, suggests that systemic iridoviruses are mesotheliotropic.

Animals↗