G6PD Ube, a glucose-6-phosphate dehydrogenase variant found in four unrelated Japanese families.

A total of 6,120 Japanese males were screened for glucose-6-phosphate dehydrogenase deficiency (G6PD). Five cases with the deficiency were discovered. Two of them and an additional two cases have the same variant, G6PD Ube, characterized by moderate enzyme deficiency, fast moving enzyme activity on electrophoresis, high Ki Nadph, utilization of substrate analogues, kinetics, pH optima, and stability. This variant was distinguished for G6PD A- and from other Oriental variants by biochemical parameters. Differences in the frequency and type of the variants between southern Asia and Japan, suggest that the Japanese who have been isolated on islands where malaria is not endemic, may have developed their own variant traits.     

Application of jackknife procedures to inter-experiment comparisons of parameter estimates for the Michaelis-Menten equation.

The jackknife procedure is introduced as a means of making comparisons among Michaelis-Menten parameter estimates for six different experimental conditions. In addition to providing a solution to the general inter-experimental comparison problem, the jackknife procedure will provide valid parameter estimates even when some of the assumptions usually required for statistical analysis are violated, e.g., the random errors are not normally distributed and the variances are not homogeneous. Other recent variations of the jackknife have also been introduced and briefly investigated: (i) the linear jackknife, which is more efficient computationally, and (ii) the weighted jackknife, which reduces the influence of design points (substrate concentrations) that have an excessive influence on the precision of parameter estimates.     

Drug residue formation from ronidazole, a 5-nitroimidazole. III. Studies on the mechanism of protein alkylation in vitro

Ronidazole (1-methyl-5-nitroimidazole-2-methanol carbamate) is reductively metabolized by liver microsomal and purified NADPH-cytochrome P-450 reductase preparations to reactive metabolites that covalently bind to tissue proteins. Kinetic experiments and studies employing immobilized cysteine or blocked cysteine thiols have shown that the principal targets of protein alkylation ara cysteine thiols. Furthermore, ronidazole specifically radiolabelled with 14C in the 4,5-ring, N-methyl or 2-methylene positions give rise to equivalent apparent covalent binding suggesting that the imidazole nucleus is retained in the bound residue. In contrast, the carbonyl-14C-labeled ronidazole gives approx. 6--15-fold less apparent covalent binding indicating that the carbamoyl group is lost during the reaction leading to the covalently bound metabolite. The conversion of ronidazole to reactive metabolite(s) is quantitative and reflects the amazing efficiency by which this compound is activated by microsomal enzymes. However, only about 5% of this metabolite can be accounted for as protein-bound products under the conditions employed in these studies. Consequently, approx. 95% of the reactive ronidazole metabolite(s) can react with other constituents in the reaction media such as other thiols or water. Based on these results, a mechanism is proposed for the metabolic activation of ronidazole.     

Effects of nitrogen dioxide exposure on prostacyclin synthesis in lung and thromboxane A2 synthesis in platelets in rats

Effects of nitrogen dioxide (NO₂) exposure on prostacyclin (PGIP₂) synthesis in the rat lung and thromboxane A₂ (TXA₂) synthesis in the platelets were studied. Male Wistar rats were exposed to 10 ppm NO₂ for 1, 3, 5, 7 and 14 days. PGI₂ synthesizing activity of homogenized lung decreased. The damage of PGI₂ synthesizing activity reaches its maximum at 3 days. At 14 days, PGI₂ synthesizing activity returned to the normal level. The activity of PGI₂ synthetase decreased significantly. The formation of lipid peroxides due to NO₂ exposure may cause the depression of PGI₂ synthesizing activity of lung. On the other hand, platelet TXA₂ synthesizing activity increased. This increased TXA₂ synthesizing activity lasted at least till 3 days. Then, it returned to the normal level. The counts of platelet were decreased significantly by 1, 3, 5 and 7 days NO₂ exposure. Then the decreased counts of platelet returned to the normal level at 14 days NO₂ exposure. These results indicate that the depression of PGI₂ synthesizing activity lung by NO₂ exposure cause an increase in TXA₂ synthesizing activity of platelets. It may contribute to induce platelet aggregation and to the observed decrease in the number of platelets during NO₂ exposure.     

Release of newly synthesized platelet-activating factor (PAF) from human polymorphonuclear leukocytes under in vivo conditions. Contribution of PAF-releasing factor in serum.

The behavior of platelet-activating factor (PAF) produced in stimulated human polymorphonuclear leukocytes (PMN) was investigated in the presence of serum under conditions close to those existing in vivo. When the cells were stimulated in the presence of the serum obtained from a PAF acetylhydrolase (PAF-AH)-deficient Japanese subject, over 60% of synthesized PAF was detected in the extracellular medium by bioassay, scintillation proximity RIA and selected ion monitoring/gas chromatography/mass spectrography analysis. The release of PAF from PMN after stimulation with FMLP and A23187 was also observed in the presence of normal serum treated with acid to inactivate PAF-AH. The heterogeneity of the molecular species of extracellular PAF was similar to that of intracellular PAF produced in stimulated PMN in the presence of PAF-AH-deficient serum, ruling out the possibility that a specific molecular species of PAF was preferentially released from the cells in the presence of the serum. As these data suggested the occurrence of PAF-releasing factor(s) in the serum, an attempt was made to partially purify this factor from PAF-AH-deficient serum and acid-treated normal serum by ammonium sulfate fractionation and column chromatography with DEAE-Cellulofine and Sepharose CL-6B. The molecular mass of PAF-releasing factor revealed on a TSK gel G3000 SW HPLC column was 240 kDa, which was different from that of albumin. The binding assay, newly developed for this study, revealed that the PAF-binding activity of PAF-releasing factor is stronger than that of albumin, and that the PAF-releasing factor forms a complex with PAF at low concentration (10(-9) M). PAF bound to this factor was difficult to be hydrolyzed by serum PAF-AH. On the other hand, the PAF/PAF-releasing factor complex had aggregatory activity toward washed rabbit platelets. These observations suggest that certain protein(s) releases and carries the PAF newly synthesized by PMN in blood plasma/serum. Thus it appears that PAF functions as an autacoid in vivo, along with other mediators.     

L-dopa administration enhances exocytotic dopamine release in vivo in the rat striatum.

Peripheral administration of L-3,4-dihydroxyphenylalanine (L-DOPA) methylester increased extracellular levels of DOPA and dopamine (DA) in the rat striatum monitored by in vivo brain microdialysis. The increase in DA levels persisted after inhibition of DA reuptake by nomifensine. Administration of blockers of voltage-dependent Na+ (tetrodotoxin) or Ca2+ (NKY-722) channels through the dialysis membrane completely eliminated the increase in DA levels. These results demonstrate that the L-DOPA-induced DA release is exocytotic in nature and hence, derived from neurons in the striatum.     

A CHO strain producing high-level human IL-6 with the 3' deletion construct.

A Chinese Hamster Ovary (CHO) strain producing high-level human interleukin 6 (IL-6) was obtained, by introduction of the IL-6 cDNA from which the 3' AU-rich region was deleted. The IL-6 mRNA of this strain was stable. The productivity was more than 15 times higher than the previously obtained clone, which has intact IL-6 cDNA in the same expression vector. This strain produced IL-6 at a high level of 30 micrograms ml-1 in batch culture, or a continuous 20 micrograms per 10(6) cells per day in microcarrier cultivation.     

Evidence for WT1 as a Wilms tumor (WT) gene: intragenic germinal deletion in bilateral WT.

The inactivation of two alleles at a locus on the short arm of chromosome 11 (band 11p13) has been suggested to be critical steps in the development of Wilms tumor (WT), a childhood kidney tumor. Two similar candidate WT cDNA clones (WT33 and LK15) have recently been identified on the basis of both their expression in fetal kidney and their location within the smallest region of overlap of somatic 11p13 deletions in some tumors. These homozygous deletions, however, are large and potentially affect more than one gene. Using a cDNA probe to the candidate gene, we have analyzed DNA from both normal and tumor tissue from WT patients, in an effort to detect rearrangements at this locus. We report here a patient with bilateral WT who is heterozygous for a small (less than 11 kb) germinal deletion within this candidate gene. DNA from both tumors is homozygous for this intragenic deletion allele, which, by RNA-PRC sequence analysis, is predicted to encode a protein truncated by 180 amino acids. These data support the identification of this locus as an 11p13 WT gene (WT1) and provide direct molecular data supporting the two-hit mutational model for WT.     

Anomeric preference of glucose utilization in human erythrocytes loaded with glucokinase

Human erythrocytes were loaded with homogeneous rat liver glucokinase by an encapsulation method based on hypotonic hemolysis and isotonic resealing. As assayed at 10 mM glucose, glucokinase and hexokinase activities in glucokinase-loaded erythrocytes were 218 and 384 nmol/min/gHb, respectively; whereas hexokinase activity in both intact and unloaded red cells, which contain no glucokinase activity, was about 400 nmol/min/gHb. No difference in the rate of lactate production from glucose anomers between intact and unloaded erythrocytes suggested that the encapsulation procedure itself did not affect glucose utilization in red cells. Alpha-anomeric preference in lactate production from glucose was observed in glucokinase-loaded erythrocytes, whereas the beta anomer of glucose was more rapidly utilized than the alpha anomer in intact and unloaded erythrocytes. The results indicate that the step of glucose phosphorylation determines the anomeric preference in glucose utilization by human erythrocytes, since glucokinase and hexokinase are alpha- and beta-preferential, respectively, in glucose phosphorylation.