Whole body hyperthermia of rats decreases insulin binding to erythrocytes

125I-insulin binding to rat erythrocytes was studied to investigate the effect of whole body hyperthermia on the insulin receptor. Heat treatment of rats at 42 degrees C for 15 min caused a significant decrease (48.7% of control) in 125I-insulin binding to rat erythrocytes. Scatchard analysis showed that the decreased binding resulted from a decrease in the number of the insulin receptors rather than from a decrease in receptor affinity. The decreased receptor number for insulin showed no evidence of recovery, 2 h and 8 h after the hyperthermia. Plasma insulin levels remained lower than the control, up to 8 h after the hyperthermia, whereas plasma glucose, which decreased immediately after the hyperthermia, increased higher than the control, 8 h after the hyperthermia. The low plasma insulin level and decreased number of insulin receptor are believed to be possible factors for the elevation of plasma glucose.     

Mutagenic nucleoside analog N4-aminocytidine: metabolism, incorporation into DNA, and mutagenesis in Escherichia coli.

N4-Aminocytidine, a nucleoside analog, is strongly mutagenic to various organisms including Escherichia coli. Using E. coli WP2 (trp), we measured the incorporation of [5-3H]N4-aminocytidine into DNA and at the same time measured the frequency of reversion of the wild type, thereby attempting to correlate the incorporation with mutation induction. First, we observed that N4-aminocytidine uptake by the E. coli cells was as efficient as cytidine uptake. High-pressure liquid chromatographic analysis of nucleoside mixtures obtained by enzymatic digestion of isolated cellular DNA showed that the DNA contained [3H]N4-aminodeoxycytidine, corresponding to 0.01 to 0.07% of the total nucleoside; the content was dependent on the dose of N4-aminocytidine. There was a linear relationship between the N4-aminocytosine content in DNA and the mutation frequency observed. These results constitute strong evidence for the view that the N4-aminocytidine-induced mutation in E. coli is caused by the incorporation of this agent into DNA as N4-aminodeoxycytidine. We also found that the major portion of radioactivity in DNA of cells that had been treated with [5-3H]N4-aminocytidine was in the deoxycytidine fraction. We propose a metabolic pathway for N4-aminocytidine in cells of E. coli. This pathway involves the formation of both N4-aminodeoxycytidine 5'-triphosphate and deoxycytidine 5'-triphosphate; the deoxycytidine 5'-triphosphate formation is initiated by conversion of N4-aminocytidine into uridine. In support of this proposed scheme, a cytidine deaminase preparation obtained from E. coli catalyzed the decomposition of N4-aminocytidine into uridine and hydrazine.     

Primary structure of a ribonuclease from bovine brain

The primary structure of a pyrimidine base-specific ribonuclease from bovine brain was determined. The sequence determined is (sequence; see text). Although the sequence homology of this RNase with bovine pancreatic RNase A is 78.2%, it consists of 140 amino acid residues, and it is 16 amino acid residues longer than RNase A at the carboxyl-terminal. In addition to an N-glycosylated long carbohydrate chain, the bovine brain RNase has two short O-glycosylated carbohydrate chains at the 129th and the 133rd serine residues. The additional C-terminal tail of the bovine brain RNase has a unique composition: 6 proline, 5 hydrophobic amino acids, and two basic amino acids, arginine and histidine.     

Polymorphism of human liver alcohol dehydrogenase: Identification of ADH2 2-1 and ADH2 2-2 phenotypes in the Japanese by isoelectric focusing

Liver homogenate-supernatants from most Japanese exhibit an atypical pH optimum for ethanol oxidation at pH 8.8 instead of 10.5, the typical pH-activity optimum. It has been proposed that atypical livers contain alcohol dehydrogenase isozymes with ₂ subunits while typical livers contain isozymes with ₁ subunits, both produced by the ADH ₂ gene. Because it is difficult to differentiate the atypical ADH₂ 2-2 phenotype from the ADH₂ 2-1 phenotype by starch gel electrophoresis, an agarose isoelectric focusing procedure was developed that clearly separated the atypical Japanese livers into two groups, A1 and A2. The isozymes in A1 and A2 livers were purified. Type A1 livers contained a single isozyme with an atypical pH-rate profile; it was designated ₂₂. Three isozymes were isolated from A2 livers, two of which corresponded to ₁₁ and ₂₂. A third, absent from the typical and the atypical A1 livers, had an intermediate mobility; it was designated ₂₁. Type A1 livers are, therefore, the homozygous ADH₂ 2-2 phenotype, and type A2 livers, the heterozygous ADH₂ 2-1 phenotype. The ADH₂ 2-2 phenotype was found in 53% of 194 Japanese livers, and the ADH₂ 2-1 phenotype, in 31%. Accordingly, the frequency of ADH ₂ ² was 0.68.This study was supported by U.S. Public Health Service Grant AA 02342.     

Mechanism of the Mg-facilitated specific cleavage of the terminal phosphoryl group of adenosine 5′-triphosphate

The exchange rate constant between free Mg²⁺ and Mg²⁺ bound to adenosine 5′-triphosphate (ATP) was determined at various temperatures from the ³¹P-NMR spectra of ATP in the absence and presence of Mg²⁺. The activation free energy of this exchange reaction showed that Mg²⁺ binds asymmetrically to the β- and γ-phosphoryl groups and that it coordinates with the β-phosphoryl group more tightly than with the γ-phosphoryl group of ATP. On binding, Mg²⁺ becomes located closer to the β-phosphoryl group. This asymmetric location of Mg²⁺ weakens the chemical bond of the terminal bridged phosphoryl group, thus causing specific cleavage of this group. This mechanism was confirmed by an ab initio molecular orbital calculation, and by experiments on the stability of ATP in aqueous solution.     

Isolation and structures of glycoprotein-derived free sialooligosaccharides from the unfertilized eggs of Tribolodon hakonensis, a dace. Intracellular accumulation of a novel class of biantennary disialooligosaccharides

Novel acidic oligosaccharides were isolated in abnormally large amounts (about 200 ng/egg) from the unfertilized eggs of Tribolodon hakonensis (a dace, "ugui" in Japanese). The free oligosaccharides were found to consist of a mixture of disialylated species most of which end with beta-mannosyl N-acetylglucosamine structure at their reducing termini, i.e. greater than Man beta 1-4GlcNAc. A minute portion of the sialooligosaccharides was found to have the reducing terminal structure, di-N-acetylchitobiose, i.e. greater than Man beta 1-4GlcNAc beta 1-4GlcNAc. From the structural analysis of these free sialooligosaccharides, the following structures are proposed: (sequence; see text) Occurrence of such a symmetrically or dissymmetrically branched form of the biantennary nonreducing periphery as revealed here is novel. Although it is unknown why and how such high amounts of free oligosaccharides are accumulated in unfertilized eggs, these were presumably protein-linked components and must be released at certain stages of oogenesis.     

Variations with age in the topographic distribution of coronary atherosclerotic lesions as assessed by image analysis

The localization of macroscopic coronary atherosclerotic lesions was investigated for 184 cases by image analysis. Atherosclerotic lesions were classified into 2 types: fatty streaks and raised lesions. The overall distribution of fatty streaks in arteries involved only by fatty streaks and the distribution of raised lesions in those arteries having raised lesions were demonstrated at similar sites in 3 coronary vessels. If the localization of lesions was examined within age groups, those sites involved with fatty streaks in one age group were replaced with raised lesions in the next older age group; fatty streaks in this older group were located distally to the raised lesions. Subsequently the areas occupied with fatty streaks were replaced with raised lesions in the next older age group. Furthermore, raised lesions seldom appeared at the site where fatty streaks had not existed in the preceding age group. Similar changes in topographic distribution were present if such changes were analyzed according to extent of atherosclerosis. Data from cases with myocardial bridges show that both fatty streaks and raised lesions are seldom observed in the region distal to myocardial bridge. We conclude, thus, that fatty streaks are the precursors of raised lesions in the coronary artery.     

Characterization of very low density lipoprotein from Watanabe heritable hyperlipidemic rabbits

We investigated the properties of very low density lipoprotein (VLDL) from two types of Watanabe heritable hyperlipidemic (WHHL) rabbits: one with a high incidence of coronary atherosclerosis (type 1), and the other with a low incidence (type 2). When incubated with mouse peritoneal macrophages, VLDL from type 1 WHHL rabbit (type 1-VLDL) stimulated cholesteryl ester synthesis 10.5-fold more than VLDL from the type 2 WHHL rabbit (type 2-VLDL) did. Moreover, a similar difference was seen in the stimulation of cholesteryl ester synthesis in peritoneal macrophages isolated from the WHHL rabbits. The mass ratios of cholesterol to protein in type 1- and type 2-VLDL were 5.69 and 2.05, respectively. Agarose gel electrophoresis of type 1-VLDL showed beta mobility, and that of type 2-VLDL showed pre-beta mobility. No difference was seen between the sizes of VLDL particles of the two types. The amount of apolipoprotein E in type 1-VLDL was greater than that in type 2-VLDL. In conclusion, the difference between type 1 and type 2 WHHL rabbits is at least partly due to the presence in type 1 animals of VLDL particles rich in cholesteryl esters and apolipoprotein E, particles which are very similar to beta-VLDL in conformation.     

Cell wall cementing materials of grass leaves

Treatment of grass leaves with either a purified pectin lyase of Aspergillus japonicus or a purified xylanase of Trichoderma viride could lead to the isolation of some single leaf cells. However, a mixture of pectin lyase and xylanase brought about more rapid isolation of single cells than did either of the two enzymes alone, indicating a synergistic effect. Analysis of the components released from oat cell walls by the enzymes indicated that both homogalacturonans with a high degree of esterification and a kind of glucuronoarabinoxylan with ferulic acid ester may play a role in cell wall cementing in grass leaves.