Structures and fatty acid compositions of neutral glycosphingolipids of human plasma

Major neutral glycosphingolipids were isolated from human plasma and their structures and fatty acid compositions studied. The four neutral glycosphingolipids of plasma were characterized as Glc beta(1 leads to 1)ceramide, Gal beta(1 leads to 1)- ceramide, Gal beta(1 leads to 4) Glc beta (1 leads to 1)ceramide, Gal alpha(1 leads to 4) Gal beta(1 leads to 4) Glc beta(1 leads to 1)ceramide and GalNAc beta(1 leads to 3) Gal (1 leads to 4) Gal (1 leads to 4) Glc beta(1 leads to 1)-ceramide. The glycosphingolipids contained mostly short chain fatty acids of which most prominent was C16. Erythrocyte glucosylceramide and lactosylceramide exhibited similar fatty acid compositions as their plasma counterparts. Triglycosylceramide and globoside of erythrocytes contained almost exclusively long-chain fatty acids. In lactosylceramide obtained from "p" erythrocytes, an accumulation of long-chain fatty acids was found; this accumulation was not observed, however, in lactosylceramide isolated from "p" plasma. It was concluded that plasma and erythrocyte glycosphingolipids are synthesized at separate sites where short- and long-chain fatty acids, respectively, are available. Plasma and erythrocyte glucosylceramide, and probably a fraction of lactosylceramide, exchange between plasma and erythrocyte pools. The latter conclusion is discussed in the light of the relative roles of carbohydrate and lipid moieties of the glycosphingolipids in maintaining their association with erythrocyte membranes.     

Heme sulfuric anhydrides as soybean leghemoglobin structure probes

Mesoheme monosulfuric anhydride reacts at three distinct sites in soybean apoleghemoglobin a, at lysine-6, lysine-19 and lysine-57, the last one being the major site of reaction. The heme peptides obtained from thermolytic and pronase hydrolysates of the anhydride-leghemoglobin a were purified and correlated with the known amino acid sequence of the protein. Mesoheme bissulfuric anhydride also reacts with soybean apoleghemoglobin a giving a complex mixture of hemepeptides after hydrolysis with pronase. The visible spectrum of anhydride leghemoglobin is that of low spin heme. This suggests that anhydride leghemoglobin has a conformation with a covalent attachment via propionic acid side chain to lysine-57 and the sixth coordination position of the heme iron occupied by the distal histidine at position 61. Native leghemoglobin is assumed to exist in a similar type of configuration at low temperature, but with the heme propionate side chain being involved in a salt bridge with lysine-57.     

Morphometric investigations on endocrine glands. III. The effect of turisynchron and suisynchron on the thyroid gland of the Wistar rats

Karyometric and morphometric investigations on the thyroids of Wistar rats had the following results: complexing of methallibure (Turisynchron) with zinc lowers the inhibiting action of the parent substance on the thyroid in a short time test period.     

The glucose tolerance, insulin response and pancreatic exocrine function in patients after acute pancreatitis

In 25 patients having a history of acute pancreatitis (AP) in anamnesis one year ago and in 12 control subjects the insulin response to oral glucose was investigated and in some cases the exocrine function of pancreas was evaluated. The disturbances in glucose tolerance occurred in about 30% of the patients and were associated with impairment of insulin response and deterioration of exocrine pancreatic function. The double cortisone and glucose load did not influence the glucose tolerance in the patients. In persons investigated during AP and one year later only slight improvement of insulin response was noted. The results support the significance of follow-up studies of carbohydrate tolerance and insulin response in patients after AP for the evaluation of the diabetic risk in such cases.     

Dual interference of hygromycin B with ribosomal translocation and with aminoacyl-tRNA recognition.

RNA-dependent DNA polymerases from Rous-associated virus-O and avian myeloblastosis virus were partially purified by affinity chromatography and compared to each other. The enzymes are indistinguishable in the immunoglobulin inhibition test and by several enzymological criteria, such as optimum curves for the concentrations of Mg2+, K+, H+; monophasic Lineweaver-Burk plot for dTTP and biphasic Lineweaver-Burk plot for dGTP. In thermal inactivation studies a small difference can be observed, suggesting a minor difference in the physical structures of the enzymes. Our findings are consistent with the idea that the RNA-dpendent DNA polymerases of endogenous and exogenous avian leukosis viruses are very closely related to each other and therefore may be regarded as one group of polymerases.     

The effects of tiamulin, a semisynthetic pleuromutilin derivative, on bacterial polypeptide chain initiation.

Tiamulin, a water-soluble and highly effective semisynthetic derivative of pleuromutilin leads to the formation of physiologically inactive polypeptide chain initiation complexes which readily decompose and do not enter the phase of peptide chain elongation. Once elongation has begun it continues even in the presence of tiamulin as has been shown by measuring the formation of N-acetylphenylalanine-poly(phenylalanine). The formation of abortive initiation complexes was observed regardless of whether AcPhe-tRNA of fMet-tRNA was used as an initiator or whether artificial messengers or a natural messenger, like R17 bacteriophage RNA, was used. When this drug was acting on whole cells, it led to the disappearance of polysomes. The only structures which could be detected were of the monosome size. Therefore, polysomes seem to elongate the polypeptide chains in whole cells in the presence of this antibiotic, but since effective reinitiation is blocked, the polysome pool of the cell soon becomes depleted.     

Superoxide-independent platelet response to xanthine oxidase.

Xanthine oxidase (1--5 microgram/ml) from cow's milk induces shape change, aggregation, and the release reaction of human washed platelets. Xanthine oxidase plus xanthine produce superoxide radicals, which reduce nitro blue tetrazolium. Superoxide dismutase, allopurinol, or ommission of xanthine inhibits the reduction of nitro blue tetrazolium but has no influence on the platelet response to xanthine oxidase. In contrast, small amounts of plasma or apyrase from potatoes abolish the effect on platelets, but not the enzyme activity of xanthine oxidase. Comparison of two xanthine oxidase preparations shows that higher specific enzyme activity corresponds to a lesser effect on platelets. The results suggest that platelet and enzyme activities reside in different components of xanthine oxidase preparations.