Effect of glucose on protein phosphorylation in rat pancreatic islets

Isolated rat pancreatic islets, incubated in the presence of extracellular ³²Pi to steady state ³²P incorporation into cellular phosphopeptides, were exposed to glucose for 10 min. Glucose (16.7 mM) significantly stimulated the phosphorylation of six phosphoproteins with molecular weights of 15,000, 35,000, 49,000, 64,000, 93,000 and 138,000. Mannoheptulose (16.7 mM) markedly inhibited glucose-stimulated phosphorylation of these six phosphoproteins. This protein phosphorylation might be important in mediating glucose-stimulated insulin release.     

Biological effects of anti-idiotypic antibodies on lymphocyte function: I. Analysis of the effects on B lymphocytes of combining site and framework-directed anti-T-15 idiotypic antibodies

Anti-idiotypic antibodies against TEPC-15 myeloma protein (BALB/c origin) were raised in allogeneic animals by immunization of A/J mice with the myeloma protein. The antibody activities were fractionated into two specificities by TEPC-15 immunoadsorbent affinity columns by elution with free hapten (phosphorylcholine, PC), followed by elution with acidic buffer (glycine- HCl, pH 2.3). Idiotype binding analysis indicated that the fraction eluted with hapten could be inhibited in its binding to TEPC-15 by free hapten (i.e., binding site-directed anti-idiotypic antibody), whereas the acid-eluted fraction could not (i.e., framework-directed anti-idiotypic antibody). When analyzed for their biological activities on PC-specific B lymphocytes producing T-15 idiotype-bearing antibodies, both anti-idiotypic antibody fractions had similar suppressive effects on the in vitro production of antiphosphorylcholine antibody in culture.     

Inhibitory effects of condiments and herbal drugs on the growth and toxin production of toxigenic fungi

The effects of thirteen kinds of powdered herbal drugs and seven kinds of commercial dry condiments on the growth and toxin production ofAspergillus parasiticus, A. flavus,A. ochraceus, andA. versicolor were observed by introducing these substances into culture media for mycotoxin production.Of the twenty samples tested, cinnamon bark completely inhibited the fungal growth, while the others only inhibited the toxin production.The inhibitors were easily extracted from the samples with solvents such as hot water, chloroform, or ethanol.The extracts from coptis, philodendron bark, mustard, green tea leaves, and zanthoxylum completely inhibited the aflatoxin production ofA. parasiticus, however, they had little or no inhibitory effect againstA. flavus.     

Pumpkin (Cucurbita sp.) seed globulin I. Purification, characterization, and subunit structure

A heat stable globulin present in the cotyledons of pumpkinseeds was prepared as crystals which were soluble in a dilutesaline solution below pH 4.5 or in a solution with a high ionicstrength at neutral pHs. The protein was nearly homogeneousby ultracentrifuge analysis, and had a molecular weight of about112,000 daltons. Sodium dodecyl sulfate-polyacrylamide gel electrophoresisseparated the globulin into two subunits, and ß,corresponding to molecular weights of about 63,000 and 56,000daltons, respectively. By reduction of disulfide bonds, thetwo subunits were each separated into two polypeptide chainswith molecular weights of around 36,000 and 22,000 daltons,judged by gel electrophoresis. The amino acid composition ofwhole globulin indicated high contents of arginine, glutamicacid and aspartic acid. The total number of half-cystine residuewas nine and only one residue was shown to be free. The subunitstructure of the globulin is discussed. The protein has beenshown to have oxaloacetate decarboxylase activity, and thisfact was confirmed. However, the activity decreased markedlyat pH 4.5 in a fairly short period. It did not require Mn⁺⁺,and the K_m for oxaloacetate was determined to be 4.1 mM. (Received April 9, 1976; )     

Kinetic study of isomerization of ferricytochrome c at alkaline pH

Kinetic studies of the isomerization reaction of horse heart ferricytochrome c between pH 8.5 and pH 12.1 have been carried out by using stopped-flow and rapid scanning stopped-flow techniques. Below pH 10, our results were in good agreement with the scheme proposed earlier (Davis, L. A., Schejter, A. and Hess, G. P. (1974) J. Biol. Chem. 249, 2624–2632). Above pH 10, another faster first-order process was observed, which suggested the existence of a transient species in the isomerization reaction between the species with and without a 695 nm band. The probable scheme of the isomerization reaction is considered to be

where H denotes a proton, the colored forms are the species predominant at neutral pH with a 695 nm band and the noncolored forms are the species without a 695 nm band. The transient species has a small 695 nm absorbance which suggests that the sixth ligand is still Met-80, although the protein conformation might be different from that at neutral pH.     

Changes in serum lipoproteins during metamorphosis of the bullfrog,Rana catesbeiana

Serum lipoproteins of the bullfrog, Rana catesbeiana, were studied during metamorphosis. Adult bullfrog has essentially one lipoprotein, designated β-lipoprotein. This β-lipoprotein migrates during electrophoresis to β-globulin region and it has a low hydrated density such that it exhibits floatation in a solvent of density 1.063. On the other hand, tadpole serum has one more lipoprotein, designated as α-lipoprotein, in addition to the β-lipoprotein. The α-lipoprotein migrates to the α-globulin region in zone electrophoresis and corresponds to the so called high density lipoprotein judging from ultracentrifugal behavior. Serum α-lipoprotein disappears and β-lipoprotein content decreases during metamorphosis.     

Two new iridoid glucosides from Ixora chinensis

From leaves and twigs of Ixora chinensis, two new iridoid glucosides, ixoroside (1) and ixoside (7,8-dehydroforsythide) (2) along with known geniposidic acid (3) have been isolated and their structures have been established.     

Procedure for the efficient acquisition of progeny seeds from crossed potato plants grafted onto tomato

Potato, Solanum tuberosum L. is an important crop. However, it is difficult to breed potato cultivars by applying conventional crossing methods because potato has a tetraploid genome and is vegetatively propagated. Flower formation and tuber development occur simultaneously. Many potato cultivars hardly produce any fruits after crossing and fail to produce seeds. We report an improved procedure for obtaining progeny seeds by grafting potatoes onto tomatoes. The rate of fruit formation was more than 19% when the grafted potatoes were used for the crossing experiments, whereas crossing using the ungrafted plants showed a rate of 1.1%. This result suggests that our procedure results in the easy acquisition of null-segregant progenies by crossing mutant lines. It is also expected to improve conventional potato breeding.