Effects of cholinergic stimulation on levels and fatty acid composition of diacylglycerols in mouse pancreas.

1. During 15 min after intraperitoneal injection of 1 mg pilocarpine in vivo in the mouse, the level of diacylglycerol in the pancreas rose from 0.47 to 0.80 mumol per g wet weight. There were increase in the levels of all of the individual fatty acids which were measured in the diacylglycerol pool. The major increases were in palmitic and linoleic acids. These accounted for 65% o the total increase. 2. After in vitro incubation of mouse pancreas for 80 min, the levels of diacylglycerol (expressed in mumol/g wet weight) in unstimulated tissue and in tissue incubated with 10 micrometer or 100 micrometers acetylcholine (plus 100 micrometers eserine) were, respectively, 0.51 1.30 and 3.73. Increases in palmitic, oleic and linoleic acids in the diacylglycerol pool accounted for 75% of the total increase. With 100 micrometers acetylcholine, the proportions of individual fatty acids in diacylglycerol showed a significant enrichment of stearic and arachidonic acid at 40 min and of linoleic and arachidonic acids at 80 min. With the exception of an enrichment of stearic and arachidonic acids, the fatty acid composition of the new diacylglycerol resembled that of the triacylglycerol pool more closely than that of other classes of lipid in the pancreas. 3. After addition of atropine to acetylcholine-stimulated tissue, the level of diacylglycerol fell so that, after 40 min, the levels and proportions of all individual fatty acids in the diacylglycerol were not significantly different from those in unstimulated tissue. 4. In both the in vivo and in vitro experiments, the changes in levels of stearic and arachidonic acids in diacylglycerol indicated that only a small proportion of the total increase in diacylglycerol level could have been derived from the breakdown of stearoyl, arachidonoyl phosphatidylinositol which occurs in response to cholinergic stimulation in the pancreas. The major effect of acetylcholine in diacylglycerol metabolism in mouse pancreas in separate, therefore, from the effect on phosphatidylinositol metabolism.

Effect of excess dietary L-histidine on plasma cholesterol levels in weanling rats.

Supplementation of a closed formula, cereal based stock diet with excess L-histidine at a 5% or 8% level for 4 days reduced growth and induced hepatomegaly and an increase in plasma cholesterole levels in weanling rats. The enlargement of the liver was in part due to glycogen accumulation; plasma glucose concentration was unchanged. Feeding four different amino acids (L-phenylalanine, L-glutamic acid, glycine and L-tryptophan), at levels which caused reduction of growth comparable to the 5% and 8% L-histidine supplementation, did not effect liver weight or plasma cholesterol levels. L-Threonine added, at a 2% level, to the 8% L-histidine diet did not alleviate any of the histidine effects. Rats fed a diet containing 5% urocanic acid, the first metabolite of the histidine degradative pathway, grew at a normal rate but had higher plasma cholesterol levels compared to rats fed stock diet. When rats fed L-histidine-or urocanic acid-supplemented diets were returned to stock diet, a normal growth rate was resumed immediately and plasma cholesterol levels returned to normal within 6 days. These results suggest that L-histidine and/or urocanic acid induce a hypercholesterolemia which disappears several days after the supplementation ceases.

Sibship with histidinemia and an unrelated encephalopathy. Clinical and biochemical studies.

Histidinemia was found in 3 of 4 siblings in one family, while a fatal encephalopathy with mental retardation was present in two of them and in the fourth child who did not have histidinemia. Biochemical studies of the histidinemic subjects showed elevated histidine levels in urine, CSF, and brain, while in a few urine samples histidine related imidazole compounds were found. Plasma levels of other amino acids were positively correlated with plasma histidine levels. Obesity and heart abnormalities appeared to be associated with the encephalopathy, which is probably of a new type. The histidinemia appears to be unrelated to the mental retardation or the encephalopathy in this family.

Tolerance of protein and lipid synthesis to mild hyperphenylalaninemia in developing rat brain.

Chronic injection of low levels (1.5-2.5 mg/g body wt./day for 6-8 days) of L-phenylalanine which did not significantly affect body weight or brain to body weight ratios also did not significantly affect myelin accumulation or synthesis in developing rat brain. A single injection of L-phenylalanine (1 mg/g body wt.) significantly reduced in vivo protein synthesis by 10% in cerebral cortex of 7-day-old rats. Although transient reductions in protein synthesis are produced during low level daily injections, cumulative effects are not expressed in significant reductions in brain to body growth ratios. It is concluded that myelination is significantly inhibited in hyperphenylalaninemia only when other parameters of brain growth and development are affected.

Urinary organic acid analysis in non-ketotic hyperglycinemia: non-specific occurrence of free benzoic acid, due to a beta-streptococcus infection.

The presence of free benzoic acid in the urine of a patient with non-ketotic hyperglycinemia was demonstrated to be due to a urinary tract infection with beta-streptococci (group B), and was eliminated by treatment with Penicillin G. In addition, the continuous excretion of p-hydroxyphenylacetic acid was observed. The patient was also found to excrete small and variable amounts of tiglic acid during the period of observation. Except for benzoic acid, large excesses of any specific organic acid were not observed.

Incorporation of (2-3H)glycerol into rat brain 1,2-diacyl-sn-glycero-3-phosphorylcholine and 1,2-diacyl-sn-glycerol molecular species in vivo.

Rat brain 1,2-diacyl-sn-glycerols (diglycerides) and 1,2-diacyl-sn-glycerols obtained from 1,2-diacyl-sn-glycero-3-phosphorylcholine after treatment with phospholipase C differ markedly in carbon number distribution. 70% of the 1,2-diacyl-sn-glycerols had a total of 38 fatty acid carbon atoms, and there was no detectable change in the 1,2-diacyl-sn-glycerol mass pattern between 7 and 23 days of age. In contrast, 1,2-diacyl-sn-glycero-3-phosphorylcholine contained at most 10% of this molecular species in the brains of rats of comparable age. A small increase in the C(36) species of 1,2-diacyl-sn-glycero-3-phosphorylcholine, which is associated with myelination, was noted between 10 and 17 days. The incorporation of intracranially injected [2-(3)H]glycerol into 1,2-diacyl-sn-glycero-3-phosphoryl-choline species with polyunsaturated fatty acids containing 20 or 22 carbon atoms was greater than into the species containing only saturated and/or monoenoic fatty acids between 30 min and 24 hr. The 1,2-diacyl-sn-glycerol fractions containing polyunsaturated fatty acids had the lowest specific activity at 30 min. The specific activity of the particular 1,2-diacyl-sn-glycerol fraction containing the stearate-arachidonate pair is the lowest for 4 hr after intracranial injection of the isotope. Thus, molecular species of 1,2-diacyl-sn-glycerol and 1,2-diacyl-sn-glycero-3-phosphorylcholine differed considerably in their labeling patterns, and a direct precursor-product relationship could not be demonstrated during the time period studied.