Biomedical subjects

L H Chen

Publications and source records attributed to L H Chen.

150 records · Page 9Linked to original sources

PubMedDate not supplied

Interaction of vitamin E and ascorbic acid (review).

Ascorbic acid appears to have two opposite roles in animal tissues: to act as an antioxidant or to act as a prooxidant. The effects of ascorbic acid supplementation on the tissue antioxidant status seem to be dependent on the dose of ascorbic acid and the vitamin E status. Adequate doses of ascorbic acid supplementation to vitamin E-deficient subjects or animals help to partially maintain vitamin E levels, probably through sparing the degradative metabolism of vitamin E, and thus increase the antioxidant effectiveness. The sparing effect of ascorbic acid on vitamin E metabolism is also shown in the partial reversal of the manifestation of vitamin E deficiency. On the other hand, when the animals are marginally adequate in vitamin E status, ascorbic acid supplementation in large doses appears to promote lipid peroxidation and significantly decreases the antioxidant potential of animals. An increase of the level of vitamin E supplementation overcomes the prooxidant effect of large doses of ascorbic acid. This observation suggests that vitamin E requirement may be increased with a large dose of ascorbic acid supplementation.

Animals↗

PubMedDate not supplied

Induction of glutathione-S-transferase activity by antioxidants in hepatocyte culture.

Twelve male Sprague-Dawley rats were used for the study. Six rats were injected with benzo(a)pyrene (BP); the other six rats served as the control. Twenty-four hours after injection, hepatocytes were isolated and cultured. The cultured plates were divided into 5 groups and treated with absolute ethanol (control), butylated hydroxytoluene, vitamin E, ascorbic acid or vitamin Elascorbic acid. After 48 hours, the hepatocytes were harvested for enzyme activation determination. With both control and BP-injected rats, each antioxidant treatment significantly increased glutathione-S-transferase activity. The results suggest that antioxidants may have a detoxifying effect against BP-induced carcinogenesis.

Animals↗

PubMedDate not supplied

Vitamin C, vitamin E and cancer (review).

The influences of vitamin C and vitamin E on cancer reported in the literature are reviewed. Several correlational studies and case-control studies suggest that the consumption of vitamin C-containing foods is associated with lower risk for certain cancers, particularly gastric and esophageal cancer. No definite links between dietary vitamin E and human cancer have been demonstrated. Animal and in vitro studies have shown that vitamins C and E can effectively inhibit the formation of carcinogenic nitrosamines. However, animal studies examining the effects of these two vitamins on other chemically-induced cancers are not conclusive. Vitamin C supplementation has been reported to inhibit skin, nerve, lung and kidney carcinogenesis. Vitamin E has been shown to inhibit skin, liver, oral, ear duct, and forestomach carcinogenesis; and to enhance, to have no effect on, or to inhibit mammary gland or colon carcinogenesis, depending upon the method of administration, the level of dietary selenium or fat, and the species and strain of animals used. Both vitamin C and vitamin E can inhibit mutagenesis and carcinogenesis in vitro. Each of the vitamins has been shown to inhibit tumor cell growth and carcinogen-induced DNA damage. The mechanism of action of the two vitamins against carcinogens is not clearly understood. Several suggested mechanisms of action include modification of the metabolism of polycyclic hydrocarbons, reduction of mutagenic activity and reaction with genotoxic free radicals. It is concluded that the potential usefulness of vitamin C and vitamin E in the prevention and treatment of cancer should not be ignored because under certain experimental conditions these two vitamins exert inhibitory effects on chemical carcinogenesis. More carefully standardized and controlled experiments are required to adequately evaluate this potential.

Animals↗

PubMedDate not supplied

A rapid three-dimensional measurement system for facial morphology by laser multi-slits.

A laser light-sectioning technique for measuring the three-dimensional shape of the face has been developed. Multi-slit lasers were used to minimize the recording time, and the accumulating technique of multiple images was used to reduce the memory size. The system can scan the entire human face within 6 seconds and develop a three-dimensional image in approximately 4 minutes. The accuracy of this system was found to be within a 0.4% relative error. The method has the advantages of being contact-free, rapid, automatic, and useful for three dimensional clinical assessment.

Cephalometry↗

PubMedDate not supplied

Developmental stages of Chinese children's concepts of health and illness in Taiwan.

This research showed that conceptual development of health and illness of Chinese children in Taiwan follows the general pattern of Piaget's levels of development. But Reichenbach's hypotheses of social influence explained the incongruencies in the data. Questionnaire and unstructured interview were used to explore the conceptual development of 468 children who were grouped according to their educational level: kindergarten, first and second grades, third and fourth grades, as well as fifth and sixth grades. Results showed that children in general defined illness and health based on physiological dysfunction. The older school children attributed "inappropriate behaviors" as the cause of illness more than young school children did. Nearly a quarter of the kindergarten group appeared to be at Piaget's level of "phenomenism" when asked to explain the cause of illness. Children also relied on "external resources" as the method to treat illness; younger school children emphasized "medicine treatment". In addition, all children believed "appropriate behaviors" can promote health, but awareness of psychological health did not appear until third and fourth grades.

Attitude to Health↗

PubMedDate not supplied

A CAD/CAM technique for fabricating facial prostheses: a preliminary report.

A computer-aided designing and manufacturing (CAD/CAM) technique for clinical fabrication of facial prostheses was developed. Laser surface scanning was applied to acquire three-dimensional imaging data of the patient's facial defect. The three-dimensional imaging data was then transferred to a CAD/CAM interactive program for image processing, which then mathematically designed and produced a model for fabrication of the facial prosthesis. This CAD/CAM technique has the potential to simplify the procedure and decrease the laboratory work required compared to that required for the conventional plaster-cast method. This new technique also provides a novel approach to the fabrication of prostheses for the reconstruction of facial defects. Two alternative three-dimensional modeling processes, laser lithographic modeling and numerically controlled milling modeling, were integrated in this study. The possibilities and current limitations of the techniques are also discussed.

Computer-Aided Design↗