Phlegmacins and anhydrophlegmacinquinones: Dimeric hydroanthracenes from seedlings of Cassia torosa

From seedlings of Cassia torosa four dimeric hydroanthracenes have been isolated. Two, a pair of atropisomeric dimers consisting of two molecules o     

Two new coumarins in Boenninghausenia albiflora

Two new isomeric coumarins were isolated from leaves of Boenninghausenia albiflora Reichb. Their structures were elucidated as (E)-7-hydroxy-6-(3-hydroxy-3-methyl-1-butenyl)-2(H)-1-benzpyran-2-one and (Z)-7-hydorxy-6-(3-hydroxy-3-methyl-1-butenyl)-2(H)-1-benzopyran-2-one.     

Flash reactivation of Tris-inactivated chloroplasts

The light conditions required for reactivation of the oxygen-evolvingsystem in Tris-treated chloroplasts were studied by means ofrepetitive flashes. Inactive Tristreated chloroplasts were washedwith reduced 2,6-dichlorophenolindophenol, suspended in a reactivationmedium containing Mn²⁺⁺ and Ca²⁺⁺ ions, then illuminated withflashes. Flashes at dark intervals of 2 sec were most effectivefor reactivation, while those at shorter or longer intervalswere less effective. It was deduced that more than two sequentiallight reactions with dark reactions in between were involvedin the reactivation. (Received December 28, 1977; )     

Localization of laminin in nephritic glomeruli as revealed by a quick-freezing and deep-etching method with immunohistochemistry

Summary The three-dimensional localization of laminin in rat glomeruli at the chronic phase of Masugi nephritis was investigated by a quick-freezing and deep-etching method combined with immunohistochemistry. Light-microscopically, laminin was localized in increased mesangial matrix and thickened glomerular basement membrane. The quick-freezing and deep-etching method revealed that the increased mesangial matrix, which was newly formed in axial portions and areas of mesangial interposition, was composed of fine fibrillar networks. They were revealed with the 3,3-diaminobenzidine tetrahydrochloride (DAB) reaction products of peroxidase-labelled secondary antibody following anti-laminin antibody. However, these reaction products were not uniformly distributed in the newly formed matrix. Although the fibrils organizing lamina densa were also immunostained with anti-laminin antibody, the fibrils connected to mesangial cells, podocytes and endothelial cells had smaller amounts of DAB reaction products for laminin. These results indicate that one of the components of fibrils in the mesangial matrix and lamina densa is laminin, which is heterogeneously distributed in the newly formed matrix.     

Calphobindins (placental annexins) inhibit protein kinase C.

Calphobindins (CPBs, placental annexins) are intracellular Ca(2+)- and phospholipid-dependent proteins like protein kinase C [EC 2.7.1.37]. We investigated the inhibitory effects of calphobindins on the protein kinase C activity in vitro. CPB I inhibited the protein kinase C activity for both histone phosphorylation and lipocortin phosphorylation, but CPB II and CPB III inhibited only the protein kinase C activity for histone phosphorylation. In the case of histone phosphorylation, all CPBs inhibited the protein kinase C activity in a concentration-dependent manner, and the IC50 (concentration required for 50% inhibition) value of CPB I was 70 nM. The inhibition of protein kinase C by CPB I was Ca(2+)-dependent, and did not disappear upon increasing the concentration of phosphatidyl-serine. Kinetic analysis by double-reciprocal plots indicated that CPB I interacted not only with phosphatidylserine but also with protein kinase C. Although CPB I partially interacts with phospholipid, it is conceivable that the inhibitory action of CPB I on protein kinase C results from direct interaction of CPB I with protein kinase C. Since CPBs are mainly present under the plasma membrane, it is presumed that CPB I is an endogenous inhibitor of protein kinase C, and according to intracellular circumstances, CPB II and CPB III may also be endogenous inhibitors.     

Adenovirus E1A proteins stimulate inositol phospholipid metabolism in PC12 cells.

To study the influence of nuclear oncogenes on inositol phospholipid metabolism, we examined the various parameters of inositol phospholipid metabolism in PC12 cells expressing adenovirus type 12 or adenovirus type 5 E1A. Although the inositol 1,4,5-trisphosphate content was increased only slightly, the diacylglycerol content was 2.4-fold higher in E1A-expressing PC12 cells. Furthermore, we found that the activity of phospholipase C, one of the key enzymes in inositol phospholipid metabolism, was increased at least five- to eightfold. Diacylglycerol kinase activity in the membrane fraction was 10 to 15% of that in parental PC12 cells. Overall protein kinase C activities in E1A-expressing PC12 cells were decreased, but the activity of membrane-bound protein kinase C was significantly increased. These observations clearly indicate that inositol phospholipid metabolism is stimulated in cells producing E1A and suggest that nuclear oncogene E1A has the ability to stimulate inositol phospholipid metabolism.     

Appearance of new lipoxygenases in soybean cotyledons after germination and evidence for expression of a major new lipoxygenase gene

The appearance and subsequent disappearance of lipoxygenase activity at pH 6.8 in germinated cotyledons of soybean (Glycine max [L.]) was shown using a variant soybean cultivar (Kanto 101) that lacks the two lipoxygenase isozymes, L-2 and L-3, that are present in dry seeds of a normal soybean cultivar (Enrei). Three new lipoxygenases, designated lipoxygenase L-4, L-5, and L-6, were purified using anionic or cationic ion exchange chromatography. The major lipoxygenase in 5-day-old cotyledons of the variant soybean was lipoxygenase L-4. Lipoxygenases L-5 and L-6 preferentially produced 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoic acid (13S-HPOD) as a reaction product of linoleic acid, whereas lipoxygenase L-4 produced both 13S-HPOD and 9(S)-hydroperoxy-10(E), 12(Z)-octadecadienoic acid. All three isozymes have pH optima of 6.5, no activity at pH 9.0, and preferred linolenic acid to linoleic acid as a substrate. Partial amino acid sequencing of lipoxygenase L-4 showed that this isozyme shares amino acid sequence homology with lipoxygenases L-1, L-2, and L-3 but is not identical to any of them. This indicates that a new lipoxygenase, L-4, is expressed in cotyledons.