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Biomedical subjects

L Tan

Publications and source records attributed to L Tan.

At least 217 records · Page 12Linked to original sources
PubMed1982

Formation of 6 beta-hydroperoxyprogesterone in rat liver microsomes.

To verify the concept that molecular oxygen can be enzymically introduced as such into the steroid nucleus, radioactive progesterone and also 5-pregnene-3,20-dione were incubated with microsomal preparations of rat liver. In both cases, a significant amount of radioactive 6 beta-hydroperoxyprogesterone was isolated, together with 6 beta-hydroxyprogesterone and 6-oxoprogesterone. Addition of p-hydroxymercuribenzoate and mercurichloride significantly inhibited the formation of the hydroperoxide, whereas potassium cyanide and carbon monoxide were only partially inhibitory. Addition of 6 beta-hydroperoxyprogesterone to cytochrome P-450 containing fractions of hepatic microsomes induced a Type I difference spectrum characterized by an absorption maximum at 392 nm, a minimum at 420 nm, and an isosbestic point at 407 nm. At 4 degrees C, its apparent dissociation constant was found to be in the same order of magnitude as that of 6 beta-hydroxyprogesterone, namely 1.33 microM. A new pathway in rat liver for the formation of both 6 beta-hydroxyprogesterone and 6-oxoprogesterone via the 6 beta-hydroperoxide as a common precursor, is proposed.

Animals↗
PubMed1980

Prognostic indicators in ocular hypertension.

Decreased pupil size and lens opacity, rather than high intraocular pressure, have been cited as reasons for the concentric constriction of the visual field occurring in eyes with suspected glaucoma. We studied a group of eyes showing ocular hypertension and found increased concentric constriction of the visual field when compared with that of healthy control eyes. While the degree of constriction and patient age tended to predict the transition to glaucoma, we found the absence of hypermetropia to be a strong prognostic indicator.

Adult↗
PubMed1978

3-Hydroxy-3-methylglutaryl coenzyme A reductase activity in beef adrenal cortex.

3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) activity (mevalonate:NADP+ oxidoreductase )CoA-acylating) EC 1.1.1.34) was demonstrated in beef adrenal cortex. Most of the HMG-CoA reductase activity is in the microsomal fraction while a small percentage of the activity is associated with the mitochondria, Mitochondria purified on a linear sucrose gradient are enriched in HMG-CoA reductase and cytochrome c oxidase activities. The reductase present in microsomal preparations from the whole adrenal cortex has an apparent Km of 5.6 X 10(-5) M for (R,S)-HMG-CoA. Reductase activities found in the microsomal fractions from the zona glomerulosa, the zona fasciculata, and the zona reticularis were 1.32, 7.37, and 9.74 nmol mevalonate formed per milligram protein in 30 min respectively.

Adrenal Cortex↗
PubMed1977

Atrial myxoma.

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Adult↗