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Biomedical subjects

T C Shen

Publications and source records attributed to T C Shen.

25 records · Page 2Linked to original sources
PubMed1972

Nitrate reductase of rice seedlings and its induction by organic nitro-compounds.

Nitrate simultaneously induced NADH- and NADPH-nitrate reductase activities in rice seedlings. Chloramphenicol, other organic nitro-compounds such as o-nitroaniline and 2,4-dinitrophenol and nitrite also induced nitrate reductase in rice seedlings. The nitrate- or nitrite-induced nitrate reductase could accept electrons more efficiently from NADH than NADPH. However, when this enzyme was induced by organic nitro-compounds, it could accept electrons more efficiently from NADPH than NADH.

Journal Article↗
PubMed1969

The induction of nitrate reductase and the preferential assimilation of ammonium in germinating rice seedlings.

Nitrate reduotase is induced by nitrate in excised embryos and germinating intact seedlings of rice (Oryza sativa L.). The enzyme is induced 24 hr after imbibition. The rate of enzyme formation increases with the age of seedlings. There is a lag period of 30 to 40 min between the addition of substrate and the formation of nitrate reductase. Formation of the enzyme is promoted by the presence of ammonium. Chloramphenicol, actinomycin D and cycloheximide effectively inhibit the formation of nitrate reductase.Rice seedlings can assimilate nitrate from the beginning of germination. However, the utilization of nitrate is completely suppressed by the presence of ammonium. As soon as ammonium is depleted from the medium, nitrate utilization is resumed. Ammonium inhibits the first step of nitrate reduction, i.e., NO(-) (3) --> NO(-) (2), but does not inhibit the assimilation of nitrite. This provides an example of feedback inhibition in higher plants.

Journal Article↗
PubMedDate not supplied

A new method for the preparation of polymeric porous layer open tubular columns for GC application.

A new method to prepare polymeric PLOT columns by using in situ polymerization technology is described. The method involves a straightforward in situ polymerization of the monomer. The polymer produced is directly coated on the metal tubing. This eliminates many of the steps needed in conventional polymeric PLOT column preparation. Our method is easy to operate and produces very reproducible columns, as shown previously (T. C. Shen. J. Chromatogr. Sci. 30, 239, 1992). The effects of solvents, tubing pretreatments, initiators and reaction temperatures in the preparation of PLOT columns are studied. Several columns have been developed to separate (1) highly polar compounds, such as water and ammonia or water and HCN, and (2) hydrocarbons and inert gases. A recent improvement has allowed us to produce bonded polymeric PLOT columns. These were studied, and the results are included also.

Chromatography, Gas↗
PubMedDate not supplied

Partial embolization of the spleen in patients with thalassemia.

PURPOSE: The role of partial splenic embolization in alleviating hyperslenism was evaluated in children with thalassemia. PATIENTS AND METHODS: Five children with thalassemia (three with alpha-thalassemia, two with beta-thalassemia) underwent embolization with polyvinyl alcohol particles. In two patients, a second splenic embolization was required. RESULTS: Of the four patients who were transfusion dependent before embolization, two no longer needed transfusion after embolization and two had decreased requirements. In fifth patient who was not transfusion dependent, the hemoglobin level increased from 7.5 g/dL to 8.2 g/dL (75 to 82 g/L) after embolization. The mean platelet count also increased after embolization in all five patients from 266 x 10(9)/L to 480 x 10(9)/L, and the mean leukocyte count increased in four of the five patients from 7.29 x 10(9)/L to 10.1 x 10(9)/L. In the fifth patient, it was unchanged. In all five patients, there was a decrease in spleen size. All patients experienced abdominal pain, but no other severe complications were noted. CONCLUSION: In these five patients, partial splenic embolization was a safe procedure that may be an acceptable alternative to partial or total surgical splenectomy. Transfusion requirements and the spleen size were reduced and the leukocyte and platelet counts increased.

Abdominal Pain↗