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Biomedical subjects

W H Chang

Publications and source records attributed to W H Chang.

At least 145 records · Page 8Linked to original sources
PubMed1990

Serological classification by monoclonal antibodies of Rickettsia tsutsugamushi isolated in Korea.

Antigenic types of 113 strains of Rickettsia tsutsugamushi isolated from Korean patients were analyzed by using murine polyclonal and monoclonal antibodies. The isolates can be classified in six groups according to their reaction to a panel of monoclonal antibodies. Nine isolates of group I were identified as the Gilliam serotype, and 13 isolates of groups II and III were identified as the Karp serotype. There were two groups that were considered to be a mixture of groups I and II or groups I and III, respectively. The remaining 88 strains of group IV had a unique antigenic determinant that was not present in the prototype strains (Karp, Kato, Gilliam), in addition to sharing common antigens with the prototype strains. Therefore these strains, which are more prevalent in Korea, seem to belong to a new serotype closely related to the Karp serotype.

Animals↗
PubMed1990

A case of laboratory-acquired murine typhus.

We encountered a 32-year-old Korean woman who developed murine typhus in a laboratory. She worked as a technician in a laboratory for rickettsial disease. Immunofluorescence test with rickettsial antigen (R. typhi) was positive at 1: 320 on admission and 1: 1280 after 4 weeks. A dose of 200 mg of doxycycline for 7 days proved to be effective for her condition.

Adult↗
PubMed1989

Chronic haloperidol treatment with low doses may enhance the increase of homovanillic acid in rat brain.

Homovanillic acid (HVA) levels were determined by high performance liquid chromatography with electrochemical detection in the striatum and prefrontal cortex of rats that had received single or repeated injections of various doses of haloperidol. Haloperidol increased the HVA concentrations in both brain regions after both acute and chronic treatment with doses of 0.01-1 mg/kg. The increase in the HVA concentrations in the striatum was blunted after repeated haloperidol injections with doses of 0.5-1 mg/kg, suggesting that haloperidol pretreatment results in a decreased responsiveness to the drug at high doses (tolerance). Tolerance also developed to the effect of long-term haloperidol treatment on the HVA concentrations in the prefrontal cortex at the highest dose used (1 mg/kg). This suggests that the differences in the development of tolerance between the striatum and prefrontal cortex are not qualitative but quantitative. However, repeated haloperidol injections at doses of 0.01-0.05 mg/kg enhanced the increase in HVA concentrations. This suggests that tolerance does not develop after chronic haloperidol treatment with low doses. Decreased HVA concentrations were also found after withdrawal from chronic haloperidol treatment (rebound decrease). However, this rebound decrease was much smaller than the decrease in response of the HVA concentrations to repeated haloperidol injections, suggesting that different mechanisms are involved.

Animals↗
PubMed1989

Pharmacodynamics and pharmacokinetics of haloperidol and reduced haloperidol in schizophrenic patients.

Twelve male chronic schizophrenic inpatients, neuroleptic-free for at least 4 weeks, were given an oral test dose of 10 mg haloperidol (HAL) and reduced HAL (RHAL) in a random order, with a 2-week interval. Two weeks after the last test dose, the patients were given HAL, 5 mg orally twice daily for 7 days. Blood samples were drawn at baseline and between 0.5 and 24 hr after the test doses, and during HAL treatment as well. Plasma drug concentrations and homovanillic acid (HVA) levels were measured with high-performance liquid chromatography using electrochemical detection. HAL, but not RHAL, produced increments in plasma HVA (pHVA) levels at 24 hr after a test dose. pHVA levels remained higher than baseline during HAL treatment. Detectable interconversion between HAL and RHAL was observed in eight patients. The capacity of the reductive drug-metabolizing enzyme system, however, was greater than that of the oxidative processes. The plasma RHAL:HAL ratios on days 6 and 7 were higher than and positively correlated with those at Tmax after a single dose of HAL and were negatively correlated with the HAL:RHAL ratios at Tmax after a single dose of RHAL. Thus, both reductive and oxidative drug-metabolizing systems probably contribute to individual differences in plasma RHAL:HAL ratios in HAL-treated schizophrenic patients.

Adult↗
PubMed1989

Haloperidol and reduced haloperidol plasma levels in Chinese vs. non-Chinese psychiatric patients.

Haloperidol and reduced haloperidol plasma concentrations were measured in age-matched Chinese and non-Chinese patients (n = 32). Steady-state plasma concentrations were obtained 10-12 hours after the bedtime dose. Haloperidol and reduced haloperidol concentrations were measured by liquid chromatography and radioimmunoassay. Haloperidol plasma concentrations did not significantly differ between the populations, but reduced haloperidol levels were 3 times greater in non-Chinese patients than in Chinese patients. The incidence of extrapyramidal side effects was higher in Chinese patients (18 vs. 10), while non-Chinese patients with extrapyramidal symptoms had higher reduced haloperidol plasma levels. Logistic regression analysis revealed that ethnicity and reduced haloperidol/haloperidol ratios were important variables in predicting extrapyramidal symptoms. These results suggest that the metabolism and disposition of haloperidol and reduced haloperidol could differ among ethnic populations.

Adult↗
PubMed1989

QRS feature extraction using linear prediction.

This communication proposes a method called linear prediction (a high performant technique in digital speech processing) for analyzing digital ECG signals. There are several significant properties indicating that ECG signals have an important feature in the residual error signal obtained after processing by Durbin's linear prediction algorithm. This communication also indicates that the prediction order need not be more than two for fast arrhythmia detection. The ECG signal classification puts an emphasis on the residual error signal. For each ECG's QRS complex, the feature for recognition is obtained from a nonlinear transformation which transforms every residual error signal to a set of three states pulse-code train relative to the original ECG signal. The pulse-code train has the advantage of easy implementation in digital hardware circuits to achieve automated ECG diagnosis. The algorithm performs very well in feature extraction in arrhythmia detection. Using this method, our studies indicate that the PVC (premature ventricular contraction) detection has at least a 92 percent sensitivity for MIT/BIH arrhythmia database.

Algorithms↗
PubMed1989

Leptospirosis of the lung: radiographic findings in 58 patients.

Leptospirosis is the disease produced by any of the group of spirochetes of the genus Leptospira. The main organs involved are the liver, central nervous system, kidneys, skeletal muscle, and lungs. Thirty-seven (64%) of 58 patients with leptospirosis, proved by positive serology, had pulmonary radiographic findings. Three radiographic patterns were evident: (1) 21 (57%) of the 37 patients had small nodular densities, (2) six (16%) had large confluent areas of consolidation, and (3) 10 (27%) had diffuse, ill-defined, ground-glass density. Serial radiographs showed a tendency for the nodular pattern to be followed by confluent consolidation and/or ground-glass density. Abnormalities were bilateral, nonlobar in all cases, and had a marked tendency toward peripheral predominance. Pulmonary abnormalities resolved within 15 days, except in eight patients who died because of respiratory failure (six patients) or other causes (two patients). In order to correlate pathology with the radiographic findings, Leptospira, isolated from a patient, was injected intraperitoneally into 20 guinea pigs. All lungs from the guinea pigs showed petecheal hemorrhage, which progressed to large confluent areas of hemorrhage. The typical pulmonary radiographic findings of leptospirosis are compatible with the multifocal pulmonary hemorrhage seen in the guinea pigs.

Adult↗
PubMed1989

Plasma homovanillic acid in schizophrenics: supportive evidence for the two-subtype hypothesis.

Plasma levels of homovanillic acid (pHVA), a major metabolite of dopamine (DA), were measured in a group of 51 schizophrenic inpatients before and during 6 weeks of neuroleptic treatment. Steady-state plasma drug concentrations were monitored in parallel with pHVA. Good responders (n = 22) had higher pretreatment pHVA levels as compared to poor responders (n = 22). Differential pHVA changes during neuroleptic treatment were also found between each group. The two groups did not differ significantly in terms of age, duration of illness, severity of presenting symptoms, neuroleptic, dose, or plasma drug concentration. Two hypothetical subtypes in the group of schizophrenics were proposed.

Adult↗
PubMed1989

Leptospirosis in Chonbuk Province of Korea in 1987: a study of 93 patients.

Leptospirosis is a zoonosis with protean clinical manifestation. Diagnosis requires a high index of suspicion and is confirmed by isolation of the organism or, more commonly, by serologic studies. In the fall of 1987, after severe flooding, we saw 93 patients with leptospirosis, confirmed by a microagglutination test. Thirteen percent of the patients had no clinical or laboratory findings except fever and headache, but the rest had mild to severe manifestations. Jaundice, renal failure, and aseptic meningitis were not common, but pulmonary symptoms, when present, were striking. The mortality rate was 5%. The main cause of death was asphyxiation due to massive hemoptysis from pulmonary hemorrhage and acute respiratory failure.

Agglutination Tests↗
PubMed1988

Dose-response curves of homovanillic acid in pre-frontal cortex and caudate following antipsychotic drugs: relation to clinical potencies.

Dose-response curves for the elevation of homovanillic acid (HVA) levels, determined by high performance liquid chromatography using electrochemical detection, in the pre-frontal cortex and caudate of rats after acute treatment with 12 antipsychotic drugs are presented. The order of potency in both brain regions was: haloperidol greater than or equal to fluphenazine greater than loxapine greater than trifluoperazine greater than thiothixene greater than molindone greater than clopenthixol greater than chlorpromazine greater than metoclopramide greater than thioridazine greater than clozapine greater than sulpiride. This ranking is roughly correlated with that based on clinical potencies. The relative elevation of the content of HVA was weaker in the pre-frontal cortex than in the caudate for all drugs tested, except clozapine at a high dose.

Animals↗
PubMed1988

Pharmacodynamics and pharmacokinetics of haloperidol and reduced haloperidol in guinea pigs.

Striatal homovanillic acid (HVA) levels and drug concentrations in striatum and plasma were examined in guinea pigs after acute and subchronic administrations of haloperidol (HAL) and reduced HAL (RHAL). HVA and drug levels were measured by high performance liquid chromatography with electrochemical detection. HAL and RHAL were interconverted in 10 min. Both maximal HVA responses and peak levels of HAL and RHAL in the striatum were reached at 2 h after injections of both HAL and RHAL. The potency of RHAL in HVA elevation was about one-half that of HAL, consistent with the HAL levels after RHAL and HAL administration. The higher the dose of HAL or RHAL injected, or after repeated injections, the greater the RHAL to HAL ratio produced. In addition, the RHAL to HAL ratios after RHAL were higher than those after HAL. These results suggest that the oxidative drug metabolizing systems are weaker than the reductive processes.

Animals↗
PubMed1988

Plasma homovanillic acid levels and subtyping of schizophrenia.

Plasma levels of homovanillic acid (HVA), a major metabolite of dopamine, were measured in a group of 24 schizophrenic inpatients before and during 6 weeks of haloperidol (HAL) treatment. Steady-state plasma HAL levels were measured in parallel with plasma HVA. Differential plasma HVA responses to HAL treatment were found between good and poor outcome patients. The two groups did not differ significantly in plasma HAL levels. Two hypothetical subtypes of schizophrenia are proposed.

Adolescent↗
PubMed1988

In vitro activities of eight antibiotics against methicillin-resistant S. aureus and S. epidermidis strains isolated in Korea.

Staphylococcus aureus and Staphylococcus epidermidis strains isolated at eight large medical centers in Korea were examined for methicillin resistance and resistance to eight other antibiotics; cefazolin, cefamandole, cefuroxime, cefoxitin, cefotaxime, moxalactam, penicillin G and vancomycin. Methicillin resistance was found in 296 of 1225 strains (24.2%) of S. aureus and 126 of 348 strains (36.2%) of S. epidermidis. Methicillinresistant strains were isolated from all sources with the frequency of isolation ranging from 11% to 60%. From pleural effusion, throat swab and blood, methicillin-resistant strains of S. aureus were more frequently isolated with statistical significance (Chi-squared test, 95% confidence). Almost all of Methicillin-resistant S. aureus (MRSA) and S. epidermidis (MRSE) strains were multiply resistant to one or more tested eight antibiotics. However only 7(2.4%) of 296 MRSA strains and 2(1.6%) of 126 MRSE strains were resistant to vancomycin. Vancomycin was the most effective antibiotic against staphylococcal isolates as well as MRSA and MRSE.

Anti-Bacterial Agents↗
PubMed1987

Reduced haloperidol and haloperidol: effects on homovanillic acid in caudate and prefrontal cortex.

The effects of acute administration of reduced haloperidol (RHAL) on homovanillic acid (HVA) in the caudate and prefrontal cortex were examined in rats. Haloperidol (HAL) was used as a reference compound. Concentrations of HVA and HAL were measured by HPLC/ECD. The maximal HVA response time was 3 hr after the injection, in both caudate and prefrontal cortex, for both RHAL and HAL. The potency of RHAL in the elevations of HVA in the caudate and prefrontal cortex was only about one-third to one-fifth that of HAL. The concentrations of HAL in the prefrontal cortex and caudate after RHAL administration were just about one-third to one-fifth those after HAL administration. These results suggest that less antidopaminergic activity of RHAL in this neuroleptic test might be explained by the lesser conversion of RHAL to HAL.

Animals↗