Occurrence of glycosphingolipids in chicken egg yolk.

Chicken egg yolk was found to contain a unique glycosphingolipid pattern not seen in other types of tissue or cell. These glycosphingolipids were isolated in pure form and their structures established by sequential enzymic hydrolysis and permethylation analysis. The major gangliosides in chicken egg yolk are N-acetylneuraminosylgalactosylceramide, N-acetylneuraminosyl-lactosylceramide and di-N-acetylneuraminosyl-lactosylceramide. The only neutral glycosphingolipid found in chicken egg yolk is galactosylceramide.     

The pathways of assimilation of 13NH4+ by the cyanobacterium, Anabaena cylindrica.

The principal initial product of metabolism of 13N-labeled ammonium by Anabaena cylindrica grown with either NH4+ or N2 as nitrogen source is amide-labeled glutamine. The specific activity of glutamine synthetase is approximately half as great in NH4+-grown as in N2-grown filaments. After 1.5 min of exposure to 13NH4+, the ratio of 13N in glutamate to 13N in glutamine reaches a value of approximately 0.1 for N2- and 0.15 for NH4+-grown filaments, whereas after the same period of exposure to [13N]N2, that ratio has reached a value close to unity and is rising rapidly. During pulse-chase experiments, 13N is transferred from the amide group to glutamine into glutamate, and then apparently into the alpha-amino group of glutamine. Methionine sulfoximine, an inhibitor of glutamine synthetase, inhibits the formation of glutamine. In the presence of the inhibitor, direct formation of glutamate takes place, but accounts for only a few per cent of the normal rate of formation of that amino acid; and alanine is formed about as rapidly as glutamate. Azaserine reduces formation of [13N]glutamate approximately 100-fold, with relatively little effect on the formation of [13N]glutamine. Aminooxyacetate, an inhibitor of transaminase reactions blocks transfer of 13N to aspartate, citrulline, and arginine. We conclude, on the basis of these results and others in the literature, that the glutamine synthetase/glutamate synthase pathway mediates most of the initial metabolism of ammonium in A. cylindrica, and that glutamic acid dehydrogenase and alanine dehydrogenase have only a very minor role.     

Preferential assignment of allotype a1 globulin for the production of early IgM anti-para-azobenzenearsonate antibodies in heterozygous a1a3 rabbits.

Rabbits of allotype a1a3 were injected on days 0, 2, and 4 with mixtures containing equal amounts of pigeon erythrocytes (Prbc) coupled to para-azobenzenearsonate (AA) and to para-azobenzene-N-trimethylammonium (TMA). On day 6, the allotypes of antibody from plaque-forming cells (PFC) of the blood were determined by observing the inhibition of plaque formation by anti-allotype sera. Anti-AA PFC appeared to consist for the most part of cells making antibody of allotype a1 since 65% of them were inhibited by anti-a1 serum and only 8% by anti-a3. Anti-TMA PFC, on the other hand, appeared to consist mostly of cells making antibody of allotype a3, since less than 1% of them were inhibited by anti-a1 but 47% by anti-a3. Antibody allotype for spleen PFC was also determined on day 6 and was similar to that found for blood PFC. Anti-AA PFC were inhibited 74% by anti-a1 serum and 15% by anti-a3 whereas anti-TMA PFC were inhibited 19% by anti-a1 and 43% by anti-a3. Serum hemolysin specific for AA hapten from a1a3 animals was also strongly inhibited by anti-a1 serum but not by anti-a3 whereas the converse was true for hemolysin against TMA hapten. The a1a3 rabbits, in whcih the anti-AA was restricted to allotype a1, were mated to produced homozygous a3a3 animals. When the PFC and serum antibodies of these a3a3 offspring were examined by specific inhibition, the anti-AA activity was found to be of allotype a3 rather than being a-negative. The number of anti-AA PFC in the blood of a3a3 rabbits was lower than that in blood of a1a3 or a1a1 animals. In addition, the TMA hapten appeared to inhibit the response to the AA hapten. Thus a1a3 rabbits immunized with AA-Prbc alone had 14-fold more anti-AA PFC or 18-fold higher anti-AA hemolysin titer than a3a3 animals immunized with both AA-Prbc and TMA-Prbc. Our results are discussed in relation to various explanations which have been offered for an imbalance of allotypes in a given antibody.     

Heteroduplex analysis of the RNA of clone 3 Moloney murine sarcoma virus.

Heteroduplex analysis of the RNA isolated from purified virions of clone 3 Moloney murine sarcoma virus (M-MSV) hybridized to cDNA's from Moloney murine leukemia virus (M-MLV) and clone 124 M-MSV shows that the main physical component of clone 3 RNA is missing all or most of the 1.5-kilobase (kb) clone 124 M-MSV specific sequence denoted beta s (S. Hu et al. Cell 10:469--477, 1977). This sequence is either deleted in clone 3 RNA or substituted by a very short (0.3-kilobase) sequence. In other respects, clone 3 and clone 124 RNAs show the same heteroduplex structure relative to M-MLV. Since beta s is believed to contain the src gene(s) of clone 124 RNA, this result leaves as an unresolved question the nature of the src gene(s) of the clone 3 M-MSV RNA complex.     

Effects of two free radical scavengers and intermittent warming on chilling injury and polar lipid composition of cucumber and sweet pepper fruits

Cucumber (Cucumis sativus L.) and sweet pepper (Capsicum annuumL.) fruits were chilled at 2.5?C for different periods and thentransferred to 20?C and subsequently evaluated for chillinginjury. Sodium benzoate at 10 nw or ethoxyquin at 9.2 mM, appliedas a 5-min dip before chilling, increased the degree of unsaturationof 18-carbon fatty acids in the polar lipids and reduced theseverity of chilling injury. Intermittent warming to 20?C for24 hr at 3-day intervals also alleviated the chilling symptomsand increased fatty acid unsaturation of the polar lipids incucumber and pepper fruits. (Received August 22, 1978; )     

Baseline and sodium arsenite-induced sister chromatid exchanges in cultured lymphocytes from patients with Blackfoot disease and healthy persons

Summary A significantly higher frequency of baseline sister chromatid exchange (SCE) was found in the cultured lymphocytes of 13 Blackfoot disease patients (BFP) in comparison with that of healthy persons (HP). Twelve of these BFP consumed well water containing a high concentration of arsenic for 15 years or longer and had switched to drinking tap water 12 years before the time of this study. Sodium arsenite was found to be effective in increasing the SCE frequency and delaying the cell growth of the lymphocytes from both BFP and HP. However, the SCE increment induced by sodium arsenite as well as the progression of the cell divisions in the cultured lymphocytes showed no significant difference between BFP and HP.     

Histochemical localization of zinc in the feline tapetum

Summary High resolution electron microscopy of ultrathin sections confirms the presence of a membrane surrounding the tapetal rods in the cat. Cats depleted of taurine exhibit disruption and disorganization of this membrane, probably the first stage of more severe tapetal degeneration. Histochemical localization of zinc shows it to be present on the periphery of the tapetal rods. The amount of zinc present on the periphery of the tapetal rods of taurine depleted cats was greatly reduced. Taurine in feline tapetum, confirmed by autoradiography and direct measurement, was also greatly reduced in taurine-depleted cats. We conclude that both taurine and zinc are localized on the periphery of the tapetal rods and that they contribute to the stability of the membrane. We have also confirmed earlier reports that the cat tapetal rods contain riboflavin and no detectable cysteine.Presented in part at the International Symposium Taurine-Questions and Answers Mexico City, November 16–19, 1980     

Characterization of gangliosides from bovine erythrocyte membranes

Two glucosamine-containing gangliosides, sialosylhexaglycosylceramides, were isolated from bovine erythrocyte membranes. Both gangliosides were hydrolyzed by neuraminidase isolated from Clostridium perfringens to become neutral hexaglycosylceramides. Based on the results of sequential enzymatic hydrolysis and gas chromatography-mass spectrometric analyses of the methylated sugars, the structures of these two gangliosides were shown to be NeuAcalpha2 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4Glc-ceramide and NeuGcalpha2 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4Glc-ceramide, respectively. In addition, N-acetyl- and N-glycolylneuraminosyllacto-N-neotetraosylceramides, and N-acetyl- and N-glycolylneuraminosyllactosylceramides were also found in bovine erythrocytes. The predominant fatty acids in these two gangliosides were C 22:0 and C 24:0. C-18 sphingosine was the major base detected.