Search PubMed⌕ Search

Biomedical subjects

W L Chen

Publications and source records attributed to W L Chen.

At least 109 records · Page 6Linked to original sources
PubMed1984

Assessing safety of agricultural chemicals.

The objective of occupational health and safety programs in the chemical industry is to protect human health and the environment. Through studies in laboratory animals, bacteria, insects, and cultured cells, toxicologists collect data which allow them to predict which chemicals are likely to be hazardous to humans. The effects of acute (single high level exposures), subchronic (up to 6 months duration to sublethal levels), and chronic (lifetime to low level) exposures are studied. Toxicity involving all organ systems is evaluated. Specific end points such as skin sensitization, birth defects, mutations, accumulation in tissues, carcinogenesis, and other toxic effects are evaluated. The data collected are used to provide information for forming guidelines regarding the safe manufacture, handling, use, and disposal of agricultural and other chemicals. The results of toxicology studies are also used to support the registration of products with government agencies in Canada and other countries.

Agricultural Workers' Diseases↗
PubMed1982

Determination of the active marrow dose distribution within the paediatric pelvis and spine.

The active marrow dose distributions have been determined inside the pelvis and the spine of two heterogeneous phantoms representing children aged one and five years. Both theoretical calculation and experimental measurement were used to simulate radiographic examinations typical for those ages. Twelve typical radiographic examinations were performed on these phantoms to represent common paediatric diagnostic procedures. The calculated and measured tissue-air ratios were compared for the pelvis and the spine. Uncertainty associated with the measured dose was estimated to be +/- 7%. The results show that most calculated absorbed doses agreed with those measured within twice the coefficient of variation of the calculated value.

Bone Marrow↗
PubMed1975

The orientation of cytochrome c oxidase in coupled phospholipid membrane vesicles--a spin-label study.

Cytochrome oxidase, an enzyme containing six different subunits, has been shown to span the inner mitochrondrial membrane. The arrangement of the subunits within the membrane is unknown. Wh have specifically labeled the 25 000 molecular weight subunit with a spin-label derivative of N-ethylmaleimide, 3-maleimido-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (NEM-SL(5)). NEM-SL(5)-lebeled cytochrome oxidase can be incorporated into phospholipid membranes to form coupled vesicles of the Hinkle, Kim & Racker ((1972) Jriol. Chem; 247, 1338-1399) type. The resonance spectrum of NEM-SL(5) is similar in both soluble and vesicular cytochrome oxidase. Since ascorbate has been shown to reduce only spin label that is exposed to the exterior surface of a closed vesicle, we have used ascorbate to determine the NEM-SL(5)-binding site in the coupled vesicles; NEM-SL(5)-labeled cytochrome oxidase vesicles are reduced by 10 mM ascorbate with tau 1/2 of 1 min at 22 degrees C; The rate of reduction is relatively independent of temperature. We conclude that (1) cytochrome oxidase is unidirectionally or preferentially oriented in the vesicle membrane, and (2) the NEM-SL(5)-binding site on the 25 000 molecular weight subunit is exposed to the external aqueous medium.

Animals↗