Ceramide metabolism in brain

Summary Ceramide is the fundamental structure and key intermediate of all sphingolipids. Biosynthesis and catabolism of brain ceramide, especially their relationship to the metabolism of more complex sphingolipids in brain, are reviewed. Human genetic diseases which involve altered ceramide metabolism are also discussed.     

Fatty acid α-hydroxylation and its relation to myelination

Summary -Hydroxylation is an enzymatic reaction by which long-chain fatty acids are converted to their -hydroxy derivatives. This reaction, in animals, can be detected only in developing brain and is the rate-determining step in the synthesis of hydroxycerebroside, which is an indispensable and abundant myelin lipid. In addition to a particulate fraction from brain, two cytoplasmic factors, one heat-stable and the other heat-labile, are required for -hydroxylation. During the past eight years we have been investigating -hydroxylation. Our progress is summarized and discussed here.     

Adenylate regulation of photosynthetic electron transport and the coupling sites of phosphorylation in spinach chloroplasts

The regulation by adenylates of activities of various partial electron transport systems in spinach chloroplasts was studied using systems from H₂O to 2,5-dimethyl-p-benzoquinone, H₂O to 2,6-dichlorophenolindophenol, reduced 2,6-dichlorophenolindophenol to methyl viologen, and H₂O to methyl viologen or ferricyanide. Adenylates regulated all of them. The ratio of the amount of esterified Pi (P) to that of electrons transported (e) in coupling with phosphorylation manifested that there are two phosphorylation sites: one between H₂O and 2,5-dimethyl-p-benzoquinone or 2,6-dichlorophenolindophenol and another between reduced 2,6-dichlorophenolindophenol and methyl viologen, under the proposed stoichiometries,i.e., P/H⁺=0.5 and H⁺/e=1, where H⁺ is the amount of protons pumped by electron transport (= those translocated during phosphorylation), when the basal electron transport (the part not regulated by adenylates) was excluded. The effects of pH, phlorizin, and methylamine on the adenylate regulation of electron transport, and the stimulation profile of electron transport coupled with quasiarsenylation suggested no distinction between the two phosphorylation sites.     

Biochemical evidence of DNA transport from the silk gland to the fat body of the silkworm, Bombyx mori

β-DNA, a component of DNA found in the pupal fat body of the silkworm, Bombyx mori, has the same GC content but a smaller molecular weight than typical silkworm DNA (α-DNA). Its origin and time of synthesis were studied by MAK column chromatography of phenol extracts after labelling with radioactive precursors.The DNA components of the fat body changed greatly during the early pupal stage, the β-DNA showing a striking increase relative to α-DNA. Thymidine-6-³H and phosphoric acid-³²P injected into the animals 1 day before analysis caused labelling of α-DNA, but not of β-DNA of the fat body, indicating that β-DNA was not synthesized during the stage of its appearance in the fat body.On the other hand, injection of thymidine-6-³H into 2-day-old fifth instar larvae, when DNA of the silk gland was being actively synthesized, gave high incorporation of the isotope into β-DNA of the pupal fat body. The sudden appearance of highly labelled β-DNA in the fat body during the early pupal stage as well as the occurrence of β-DNA in both the silk gland and fat body suggested that DNA might move from the silk gland to the fat body.It is possible that the fat body stores DNA as a nutrient from the degenerating silk gland.     

Inhibition and uncoupling of the ADP-regulated electron transport in isolated chloroplasts

The effects of energy transfer inhibitors, electron transport inhibitors and uncouplers on the ADP-regulated and ADP-independent activity of ferricyanide reduction in isolated spinach chloroplasts were studied. Phlorizin and sulfate did not affect the ADP-independent ferricyanide reduction. In the ADP-regulated reduction, these reagents did not affect the ADP inhibition process but inhibited the activity restoration process due to phosphorylation. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea and linolenic acid depressed both ADP-regulated and ADP-independent activity of ferricyanide reduction. Gramicidin S and 2-amino-1-butanol depressed ADP-regulated activity and stimulated ADP-independent activity. The decrease in the ADP-regulated ferricyanide-reducing activity (restoration) due to (incomplete) uncoupling paralleled the decrease in phosphorylation activity (P/Δe=1).     

Isolation and Characterization of a Filamentous Phage,Vf33, Specific for Vibrio parahaemolyticus

Phage Vf33, a filamentous phage about 1,400 nm long and 7 nm wide, specific for Vibrio parahaemolyticus, was isolated and characterized. The buoyant density of Vf33 in CsCl was 1.292 g/cm³. As with other filamentous phages, the lytic activity of Vf33 was resistant to heating below 80 C and to treatment with diethylether, acetone or methanol but sensitive to chloroform. The nucleic acid of this phage is single-stranded circular DNA 8.4 kb in size. The viral genome was converted to a double-stranded replicative form in the host cell. Among the strains tested, only V. parahaemolyticus strains possessing K38 antigen was sensitive to the phage.