15-Acetoxycostunolide from Magnolia sieboldii

A new germacranolide isolated from M. sieboldii was shown to be 15-acetoxycostunolide by spectroscopic and chemical methods. ¹H NMR spin decoupling and NOE experiments in the presence of a lanthanide shift reagent were used for structure elucidation.     

Isolation and identification of 25-hydroxy-24-oxocholecalciferol: A metabolite of 25-hydroxycholecalciferol

A metabolite of 25-hydroxycholecalciferol has been isolated in pure form from chicken kidney homogenates. It has been identified as 25-hydroxy-24-oxocholecalciferol by means of ultraviolet absorption spectrophotometry, mass spectrometry, infrared spectrometry, nuclear magnetic resonance spectrometry, and specific chemical reactions.     

High concentration of a gastrin releasing peptide-like immunoreactive substance in pregnant human milk

The level of a gastrin releasing peptide-like immunoreactive substance (GRP-IS) in human milk and plasma during late pregnancy and after delivery was measured. GRP-IS in milk increased during late pregnancy (1.3 nM at 39 weeks) and decreased after delivery (100 pM). GRP-IS in plasma during late pregnancy and after delivery was much lower (below 2 pM). By using HPLC and gel-filtration chromatography, two peaks of GRP-IS were purified. The one was coeluted with GRP (18-27) and the other was a prohormone. The GRP-IS in milk during pregnancy was mostly composed of proGRP. These results suggest that GRP may be produced and secreted in mammary glands.     

Topographic examination of sister chromatid differential staining by nomarski interference microscopy and scanning electron microscopy

BrdU-substituted Chinese hamster chromosomes were treated with a hot Na₂HPO₄ solution and stained with Giemsa to produce sister chromatid differential staining (SCD). The process of SCD was examined with the Nomarski differential interference microscope and the scanning electron microscope. After the Na₂HPO₄ treatment alone, unifilarly BrdU-substituted (TB) chromatids appeared somewhat more severely collapsed than the bifilarly substituted (BB) chromatids. Subsequent Giemsa staining, however, brought about pronounced piling up of the Giemsa dye on the TB-chromatids but not on the BB-ones, causing highly distinct differential Giemsa staining as well as a marked differentiation in surface topography between the sister chromatids. Removal of the Giemsa dye from the differentially Giemsa stained chromosomes resulted in a disappearance of such a pronounced topographic differentiation.     

Two opposite types of sister chromatid differential staining in BUdR-substituted chromosomes using tetrasodium salt of EDTA

The direct staining of BUdR-substituted Chinese hamster chromosomes in a 4Na-EDTA-Giemsa solution resulted in a B-dark type of sister chromatid differential staining (SCD) in which bifilarly substituted chromatids stained dark. On the other hand, when BUdR-substituted chromosomes were pretreated with a 4Na-EDTA solution and then stained with Giemsa, a B-light type SCD was obtained in which bifilarly substituted chromatids stained light.     

Alpha reduced nicotinamide adenine dinucleotide-dependent reductase reactions of rat liver microsomes.

The kinetics of alpha-NADH-dichlorophenolindophenol (DCPIP) and alpha-NADH-cytochrome c reductase reactions of rat liver microsomes showed that the reactio ns proceeded by a ping-pong mechanism, and that the oxidation of alpha-NADH was the rate-determining reaction. The DCPIP-reducing activity with alpha-NADH in the presence of ADP was about 1% of that with beta-NADH. ADP inhibited the alpha-NADH-DCPIP reductase reaction in a competitive manner with respect to alpha-NADH and a value of 1.2 mM for the inhibition constant was obtained. ADP also inhibited cytochrome b5 reduction with alpha-NADH. More than 90% of cytochrome b5 was reduced under conditions where 90% of the alpha-NADH-DCPIP reductase activity was suppressed with ADP. The reduction of DCPIP with alpha-NADH preceded that of cytochrome b5, but the reductions partly overlapped. From these results, a diversed electron flow from alpha-NADH to cytochrome b5 and electron sharing between cytochrome b5 and DCPIP were indicated. alpha-NAD+ also inhibited the alpha-NADH-DCPIP reductase reaction. Analyses of the inhibition indicated that two types of alpha-NADH-DCPIP reductase reaction existed, one of which was resistant to alpha-NAD+ inhibition. In contrast to the reoxidation of beta-NADH-reduced cytochrome b5, the process was largely monophasic when cytochrome b5 was reduced with alpha-NADH.