5 p-CHOLESTANE · 3 a , 27-DIOL : NAD + OXIDOREDUCTASE AND 3 a-HYDROXY-5 p-CHOLESTAN-27-AL : NAD + OXIDOREDUCT ASE IN RAT LIVER EXTRACT * )
Using rat liver alcohol:NAD+ oxidoreductase and aldehyde:NAD+ oxidoreductase, the following facts were found: 1) 3a-hydroxy-5~-cholestan-27-al was reduced to 5fi -cholestane-3a, 27-diol by liver alcohol: NAD+ oxidoreductase. 2) The optimum pH was pH 7. 0 with potassium phosphate buffer and pH 8. 5 with Tris buffer. 3) The Km value of the substrate to the enzyme was 14. 3 μM. 4) 3a-Hydroxy5fi-cholestan-27al was oxidized to 3a-hydroxy5fi-cholestan27-oic acid by liver aldehyde: NAD+ oxidoreductase. 5) The optimum pH was pH 8. 5 with Tris buffer. 6) The Km value of the substrate to the enzyme was 26. 3 μM.
The formation of lithocholic acid, chenodeoxycholic acid and other bile acids from 3 beta-hydroxychol-5-enoic acid in vitro and in vivo.
Abstract Previous work has shown that 3β-hydroxycholenoic acid and several naturally occurring C 24 bile acids are formed from cholesterol incubated with rat-liver mitochondria. It is now shown that [ 3 H]3β-hydroxycholenoic acid is converted into lithocholic, chenodeoxycholic, 3α,6β-dihydroxycholanoic and β-muricholic acids in vitro . This suggests that 3β-hydroxycholenoic acid is an intermediate in the formation of C 24 bile acids from cholesterol in vitro . When [ 3 H]3β-hydroxycholenoic acid is injected intravenously into rats, 80% of the radioactivity is recovered in the bile within 2 h, mainly as lithocholic, chenodeoxycholic, 3α,6β-dihydroxycholanoic and β-muricholic acids. This raises the possibility that 3β-hydroxycholenoic acid lies on one of the pathways by which chenodeoxycholic acid is formed in vivo .
THE IRON-ACETOCARMINE METHOD OF FIXING AND STAINING CHROMOSOMES
A short description of this procedure was given in Vol. 55 of the American Naturalist, pp. 573â€”574. The method has now been used almost daily for five years, and certain improvements have suggested themselves. The solution can be prepared by mixing about equal volumes of glacial acetic acid and water. To this is added powdered carmine in excess. The liquid is then â€ ? just brought to boil, cooled, and decanted. To the red solution there are then added a few drops of a solution of ferric hydrate in 50 per cent. acetic acid, to act as a mordant. The amount of iron varies with different objects. Too much produces a precipitate in a short time. The more