Evidence for the existence of two phenotypes of piglets born to experimental herds was obtained based on the susceptibility of intestinal brush borders to adhesion of K99-positive Escherichia cofi. The enterocytes of the K99-receptive piglets displayed a characteristic sialoglycolipid pattern, with a higher content of the monosialoglycolipids I13NeuGc-LacCer (GM~Gc), IV3NeuGc-nLcOse4Cer (SPGGc) and IV3NeuAc-nLcOse4Cer (SPG) and the oligosialogangliosides IV3NeuAc,I13NeuAc-GgOse,Cer (GDla), I13(NeuAc),-GgOse,Cer (GD2), I13(NeuAc)z-GgOse4Cer (GD1 b) and IV3NeuAc,I13(NeuAc)2-GgOse4Cer (GTlb) when compared to the gangliosides of non-receptive piglets. The gangliosides from enterocytes of the non-receptive piglets were mainly the monosialogangliosides 113 NeuAc-GgOse,Cer (GM2) and I13NeuAc-LacCer (GM3), only traces of the other sialoglycolipids being detected. Adhesion of 4C-labelled K99-positive E. cofi cells to the piglet small intestinal sialoglycolipids, as tested by the thin-layer chromatogram overlay assay, revealed that the receptive enterocyte membrane was richer in glycolipids containing K99 receptor structures than the non-receptive enterocyte.Adhesion of K99-positive E. cofi correlated with the degree of sialylation of the brush border glycolipids.

Leucyl-tRNA and arginyl-tRNA synthetases were purified from wheat embryos by the following purification steps : ammonium sulfate precipitation, gel filtration on Sephadex G-75, chromatographies on DEAE-cellulose and hydroxyapatite, and finally gel electrophoresis.The molecular weights of these enzymes were found to be about 110000 for leucyl-tRNA synthetase and 70 000 for arginyl-tRNA synthetase.Their structures, deduced by dodecylsulfate electrophoresis after reducing treatment, were found to be dimeric for the former and monomeric for the latter. Leucyl-tRNA synthetase exhibits an equilibrium between an active dimeric form and an inactive monomeric form. The number of subunits was determined at dissociation equilibrium by relations deduced from the law of mass action and modified for oligomeric enzymes.When the instantaneous modifications of the activity of these two synthetases are studied in the presence of ribosomes, both activities are slightly stimulated. In addition, when ribosomes (or bovine serum albumin) are preincubated together with the two synthetases, they reduce both the inactivation by dissociation of leucyl-tRNA synthetase and the inactivation (probably by isomerization) of arginyl-tRNA synthetase.Although the ribosomes and bovine serum albumin have apparently similar effects, the great difference in effective concentration between the two, % 1 nM for ribosomes and 30 pM for bovine serum albumin, suggest that the ribosomes have a certain specificity of action; this may involve the maintenance of the synthetases in their conformationally active state.Dimeric aniinoacyl-tRNA synthetases, such as bovine pancreatic tryptophanyl-tRNA synthetase [l], Escherichiu coli prolyl-tRNA synthetase [2] and wheat germ methionyl-tRNA synthetase [3], may dissociate at certain protein concentrations and undergo a partial loss of enzymatic activity. Recent studies, especially with eukaryotic systems, have shown that these enzymes are not free in the intracellular medium, but are associated as multimolecular complexes, occasionally attaining a relatively large size [4-91. They are probably localized on the membranes of the endoplasmic reticulum, in proximity to ribosomes. It is thus probable that synthetases participate in translation processes in the form of integrated sysAbhrrvicrtions. Albumin, bovine serum albumin ; Hepes, 4-(2-hydroxyethy1)-2-piperazineethane sulfonic acid; eEF-1, elongation factor 1 ; eEF-2, elongation factor 2.Definition. A260 unit, quantity of material contained in 1 ml of a solution having an absorbance of 1.0 for 1-cm path length.

Quantitative determination of total fatty acids in rabbit blood serum is achieved using the infrared absorption band, associated with the C = O stretching vibration at 1713 cm−1 (5.84 μm). Different tests are described to show the validity of this method for a wide range of variation in total concentration and in individual percentages of any one fatty acid. The results are treated by statistical methods, and it is found that infrared analysis is five times more sensitive than methods described previously. This accurate technique, which can be applied to other serums has, for example, been applied to disclose a systematic error in the preparation of total fatty acid samples when nitrogen flushing is not used.

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SummaryCellular distribution of elongation factors (EFl) from imbibed then redessicated wheat embryos is determined after purification and analytical gel electTophoresis of soluble and ribosome-bound factors.Two heavy forms (EFlR, mol. wt, 250 000) are found in cytosol while ribosome-bound factors contain a light form (EFlL, mol. wt, 45 000) with the greatest activity and a heavy form (mol. wt, 160 000) which might well be an intermediary in the recycling of ribosomal factor EFIL to soluble factor EF~J.J.