Biomedical subjects
Publications and source records attributed to C H Cheng.
Complementation analysis with independently isolated plA and adk (adenylate kinase) mutants of Escherichia coli showed that all the mutants belong to the same complementation group. The results suggest that the adk (plsA) locus is the structural gene for adenylate kinase.
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Membranous lipodystrophy apparently is a new disease, first reported and named by Nasu and associates 31 in 1971. We have collected six cases of this disease. The initial manifestation was articular pain at adolescence. Symmetrical changes in the bones of the extremities then appeared and the disease seemed to progress slowly with age. The younger patients exhibited only skeletal pain or fractures, while the older patients had some neuropsychiatric changes. Three of the patients died in middle age. The cystic bone lesions contained a yellow, lipid-like substance which histologically showed a characteristic membranocystic appearance. Electron microscopic study showed unique features, but biochemical analysis of the substance did not reveal a definable abnormality.
The purpose of this study was to evaluate the possibility of using leukocyte transketolase activity (TKA) as an index of thiamin status. It was shown previously that hepatic TKA in rats is altered by changes in the type and amounts of carbohydrate, protein, and fat in the diet. It was, therefore, essential to determine whether leukocyte TKA in rats is affected by dietary factors other than thiamin intake. Hepatic TKA and leukocyte TKA both varied with dietary thiamin intake; maximum activity was attained when the diet contained 3 to 4 mg thiamin/kg diet. Administration of oxythiamin resulted in decreases in TKA in both liver and leukocytes. The changes in leukocyte and hepatic TKA induced by varying degrees of thiamin deficiency were closely correlated. The responses of thiamin content were also closely correlated in liver and leukocytes. However, only hepatic TKA was altered by increasing the fat or protein content of the diet or by substituting fructose for glucose. None of the dietary manipulations studied except the production of thiamin deficiency had any effect on leukocyte TKA. We conclude from our results that leukocyte TKA is a sensitive and specific indicator of thiamin nutriture in rats.
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Patients on hemodialysis therapy are at a relatively high risk of exposure to hepatitis B virus (HBV) infection. The prevalence of hepatitis C virus (HCV) infection is even higher and was reported as 33.2% in Taiwan. Although the efficacy of hepatitis B vaccine was well documented, the vaccination schedule in hemodialysis patients is not clearly defined. And under such a high prevalence of HCV infection, little is known about the influence of HCV imposing on HBV vaccination. We studied 50 chronic hemodialysis patients who were serologically negative for the hepatitis B surface antigen (HBsAg), the antibody to the hepatitis B surface antigen (anti-HBs) and the antibody to the hepatitis B core antigen (anti-HBc); 26 of them were positive for the antibody to hepatitis C virus (anti-HCV) test. Recombinant hepatitis B vaccine (Engerix-B) 40 micrograms per dose was administered by the intramuscular route at deltoid region at 0, 1, 2, 6 and 12 months respectively to all the patients. Forty-six patients had completed the study. The effective seroconversion rate (serum anti-HBs titer > 10 mIU ml-1) at 1 month after the final vaccine was 76.1% (35/46). The effective conversion rates of the anti-HCV(+) group to the anti-HCV(-) were 75% versus 77.3% (P = 0.857). Geometric mean anti-HBs titers were 177.67 mIU ml-1 versus 189.28 mIU ml-1 (P = 0.867). Our results showed that five-dose injections of HBV vaccine do not present a superior outcome to the four-dose regimen comparing to published data. The status of positivity of anti-HCV do not pose an suboptimal effect on HBV vaccination of hemodialysis patients.
OBJECTIVES: The objective of this study was to use a three-dimensional (3-D) finite element model to investigate normal stress distribution to substantiate the tooth flexure mechanism. The study also compared the changes in the stresses by different occlusal loading sites and directions. METHODS: The 3-D finite element analysis was used. A maxillary premolar was selected to construct the simulation model. The model was constructed step-by-step for convergence and validity. Seven load conditions for various load sites and different directions were simulated to the model. RESULTS: The maximal principal stress and minimal principal stress distributions developed within the structures of seven load conditions were output and their stress distributions on z-plane at the vertical midline were shown. The peak tensile stress of the cervical area for various load conditions were compared and listed. CONCLUSIONS: This study has shown that the presence of tensile stresses in the cervical region of a maxillary premolar by various loading sites and different directions. The results coincided with the stress-induced theory, hence sustaining it. The relationship of the affected factors of leverage to the development of cervical abfraction lesions, was explored.
Concentrations of airborne culturable fungi were measured in the kitchen of a bakery in Boston, Mass., to evaluate variabilities associated with common worker activities, outdoor aerosol distributions, and season. Activities were categorized as early morning preparation, cornmeal sifting and tossing, flour dumping and mixing, sweeping, and low activity. Sets of measurements were taken over 1 day in spring and 1 day in summer. Fungal concentrations were measured using a one-stage culture plate impactor, and bulk samples were taken from suspected fungal reservoirs within the bakery and subsequently cultured. Compared with the low activity category, elevated levels of total culturable fungi were found during all other activities, with the amount of increase closely related to individual worker activity as well as outdoor concentrations and initial bakery conditions. In the spring, Penicillium was the dominant genus showing activity-related elevations in concentrations, while Cladosporium was the dominant genus during the summer. Clearly, due to variabilities in worker activities and ambient fungal concentrations, a standardized sampling protocol involving a large sample size over multiple days is needed to estimate accurately exposure to either total airborne fungi or specific fungal taxa.