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Biomedical subjects

M C Wu

Publications and source records attributed to M C Wu.

176 records · Page 10Linked to original sources
PubMed1973

Isolation and characterization of lipopolysaccharide protein from Escherichia coli.

Extraction of the cell envelope of E. coli with 1% sodium dodecyl sulfate yielded a lipopolysaccharide protein that was purified to homogeneity by conventional techniques. Analysis of the pure protein indicated that it is a complex lipopolysaccharide protein with the following molar ratios of constitutents: 3-deoxyoctulosonate, 1.0; glucosamine, 1.3; neutral sugar (glucose + heptose), 1.0; organic phosphate, 2.3; and amino acid, 21. On a quantitative basis, all of the 3-deoxyoctulosonate present in the cell envelope preparation was solubilized in hot sodium dodecyl sulfate and subsequently accounted for in its entirely in the isolated protein component. After incubation of the cell-wall particulate fraction of cells grown on [(3)H]glucosamine with UDP-[(14)C]galactose under conditions designed to measure galactosyl transferase activity, the isolated lipopolysaccharide protein contained all of the [(14)C]galactose that was incorporated during the incubation. We concluded that the lipopolysaccharide of this organism occurs in the outer cellenvelope membrane exclusively in the form of lipopolysaccharide protein.

Autoradiography↗
PubMedDate not supplied

Analysing changes in the presence of informative right censoring caused by death and withdrawal.

Several approaches for estimating and comparing the rates of change of a continuous variable in two treatment groups in the presence of informative right censoring are reviewed and compared. The comparisons are made under different models for the censoring probabilities and various types of treatment effects. Some recommendations are discussed regarding the application of these approaches to the different settings.

Clinical Trials as Topic↗
PubMedDate not supplied

Testing for differences in changes in the presence of censoring: parametric and non-parametric methods.

Some commonly used parametric and non-parametric methods for analysing repeated measures with incomplete observations are briefly reviewed. The performances of these methods in the presence of completely random, as well as informative censoring are compared in simulated experiments generated under the linear random effects model with parameter values derived from realistic examples. The effects of some moderate model deviations are also compared. The results indicate that in the presence of informative censoring, the usual parametric and nonparametric methods derived under the assumption of random censoring could either suffer severe loss of power or provide false positive results. The conditional linear model for informative censoring when used in conjunction with the bootstrap variance estimation procedure performed well under both random and informative censoring mechanisms. The non-parametric procedure obtained by ranking the individual summary statistics, although not as efficient as the conditional linear model with robust variance, also performed relatively well in most situations. Therefore, in situations in which informative censoring is likely to occur it is important to select the proper method of analysis to test for the informativeness of censoring and to account for its effects.

Bias↗
PubMedDate not supplied

Studying the relationship between change and initial value in longitudinal studies.

Blomqvist's problem of studying the relationship between change and initial value in a linear growth curve setting is reformulated from a random effects model perspective. First, a maximum likelihood estimate of the between-individual covariance matrix for a simple linear regression model with stochastic parameters is obtained via an EM algorithm as discussed by Laird and Ware. Second, the regression coefficient of the individual-specific slopes on the individual-specific intercepts is estimated as a ratio of elements of the between-individual covariance matrix as discussed by Zucker et al. Then a Fieller's type confidence interval for this ratio is proposed. Discussion is facilitated by recognizing the Laird-Ware model as a special case of a more general model discussed by Hocking.

Algorithms↗
PubMedDate not supplied

Rehepatectomy of primary liver cancer.

From January 1960 to July 1991, 72 patients underwent reoperation for recurrence of liver cancer. Hepatectomy was performed twice in 59 cases, three and four times each in nine and three cases. The 1, 3, and 5-year survival rates after the first operation were 98.6%, 69.9%, and 49.5%, respectively, while after the second operation these rates were 90.8%, 53.5%, and 36.1%, respectively. The 1,2, and 3-year survival rates after the third operation were 100%, 85.6%, and 36.7%, respectively. The preliminary results of rehepatectomy are thus encouraging. The indications for reintervention, types of operation, prophylactic measures against tumor recurrence and metastases, and evaluation of rehepatectomy are discussed.

Adolescent↗
PubMedDate not supplied

Operational design and quality control in the CATCH multicenter Trial.

BACKGROUND: The Child and Adolescent Trial for Cardiovascular Health (CATCH) was the first multicenter school-based research study to employ the fundamentals of clinical trials including the standardized protocol and Manuals of Operation, a steering committee for study governance, a distributed data system, an extensive quality control system, and a Data and Safety Monitoring Board. METHOD: CATCH tested the effectiveness of changes in school lunches, physical education, smoking policy, curricula, and family activities. Ninety-six elementary schools in four states were randomized to intervention or control conditions. The baseline cohort comprised 5, 106 ethnically diverse third graders followed through fifth grade. RESULTS: The percentages of calories from fat and saturated fat were reduced significantly more in the intervention school lunches than among the controls. Significant increases in moderate to vigorous activity levels in existing physical education classes were made as well. Changes in self-reported dietary, physical activity, and psychosocial measures were significant. There were no significant differences in the physiological measures. Measurement error was generally low for all physiologic measures except skinfolds, indicating a high level of reliability. Across all sites, the coefficients of variation for lipids, height, and weight were less than 3%, whereas for skinfolds, they were considerably higher, ranging from 6 to 8%. Intraclass correlations for lipid studies were also uniformly high at 0.99. Interobserver agreement scores for SOFIT were greater than 90% for 9 of the 11 activities observed. Data entry error rates were low with less than five errors per 1,000 fields for all forms. CONCLUSIONS: The CATCH results provided more scientific evidence on the importance of schools in the population approach to health promotion. Many of the strategies used in this complex multicenter trial in the areas of design and analysis, measurement, training, data management, and quality control protocols might be appropriate for adoption in other studies.

Adolescent↗
PubMedDate not supplied

Phenacetin O-deethylation in extrahepatic tissues of rats.

Phenacetin O-deethylation is a marker reaction of CYP450 1A2 activity. The drug-metabolizing enzyme is constitutively expressed in liver. In this study, an in vivo rat model for assessment of extrahepatic metabolism was used to investigate phenacetin O-deethylation and the alterations in the disposition of phenacetin due to the loss of liver function. Rats were divided into the model and normal control groups. The model was established according to our previously described method. The concentrations of phenacetin and its major metabolites acetaminophen, glucuronate-acetaminophen and sulfate-acetaminophen in plasma and urine were determined by HPLC. 30 min after intravenous administration of 0.16% phenacetin 10 mg x kg(-1), plasma acetaminophen in the model group was only 3.6% of that in the control group (0.09+/-0.04 microg x mL(-1) vs 2.49+/-0.85 microg x mL(-1), n = 8). 30 min after intragastric injection of 0.4% phenacetin 30 mg x kg(-1), plasma acetaminophen formation was very slight, about 8.6% of plasma phenacetin in the model group (0.74+/-0.43 microg x mL(-1) acetaminophen vs 8.57+/-8.42 microg x mL(-1) phenacetin) and 6.8% in the control group (1.06+/-0.59 microg x mL(-1) acetaminophen vs 15.47+/-7.21 microg x mL(-1) phenacetin, n = 8); no significant differences were observed in plasma phenacetin, total acetaminophen and the ratio of acetaminophen to phenacetin between control and model groups. In the urine collected for 3 h after intravenous administration of 0.16% phenacetin 10 mg x kg(-1), the total recovery of acetaminophen (as free, glucuronate- and sulfate-acetaminophen ) in the model group was 4.6% of that in the control group (4.47+/-4.27 microg vs 96.63+/-8.50 microg, n = 6), but phenacetin recovery in the model group was 9 times higher than that in the control group (15.03+/-17.72 microg vs 1.66+/-0.50 microg). The results indicate that phenacetin O-deethylation in the extrahepatic tissues and the first-pass metabolism of the probe compound seem to be negligible in rats, but the renal excretion of phenacetin, as a compensation, dramatically increases in model rats.

Acetaminophen↗
PubMedDate not supplied

Carrier detection of Duchenne/Becker muscular dystrophy by using fluorescent linkage analysis in Taiwan.

The mutation analysis of Duchenne/Becker muscular dystrophy (DMD/BMD) is made difficult by the size and structure of the gene. The dystrophin gene deletion is responsible for 45-58% of DMD/BMD cases in Taiwan. For the others, who have no deletions, carrier detection was performed by DNA linkage analysis. To determine frequencies of each allele and heterozygosity of each short tandem repeats (STR) marker, we analyzed 50 unrelated Taiwanese males and 50 unrelated Taiwanese females unaffected by DMD/BMD using ten fluorescently labeled intragenic markers (these ten being located in 5' terminus, intron 1, 44, 45, 48, 49, 50, 55-57 and 3' untranslated region of the human dystrophin gene). The predicted heterozygosity frequency is 46.7-88.3% in our study population and these STR markers are quite informative for linkage analysis. Using these ten intragenic STR markers, we analyzed 14 DMD/BMD families with 62 family members for carrier detection. Our retrospective study of DMD/BMD families highlights the informative power of STR haplotyping. In summary, STR analysis using (CA)n repeats within the human dystrophin gene is well suited for routine use in clinical laboratories engaged in linkage studies for carrier detection and prenatal diagnosis in DMD/BMD families.

Alleles↗
PubMedDate not supplied

Mutation analysis of type II Gaucher disease in five Taiwanese children: identification of two novel mutations.

Gaucher disease (GD), one of the most prevalent lysosomal storage diseases, is caused by deficiency of lysosomal acid beta-glucosidase (GBA). It is divided into three types according to the presence and progression of neurologic symptoms. Of those, type II is relatively rare and most severe; patients usually die before the age of two years. Using polymerase chain reaction (PCR) and direct sequencing of GBA gene in five Taiwanese type II GD patients, we identified two novel mutations: G355D and three-nucleotide insertion in exon 7 of GBA. The latter resulted in an in-frame insertion of a methionine residue between Leu241 and Ser242. L444P, the second most common GD allele among non-Jewish Caucasian population, was found in all five type II GD patients (50%). Overall, 9 out of 10 GD alleles were identified in this study. Direct sequencing of all PCR products led to high detection rate of GD alleles and identification of the RecNci 1 alleles. In the future, high throughput sequencing will make it possible identifying more rare mutations in type II GD patients.

Base Sequence↗