Effect of selenium and protein deficiency on selenium and glutathione peroxidase in rats

Twenty-four weanling male Wistar rats were divided into four groups fed diets containing adequate or deficient levels of selenium (0.5 ppm [+ Se] or <0.02 ppm [−Se] and protein (15% [+Pro] or 5% [−Pro]), but adequate levels of all other nutrients for 4 wk to determine the effects of Se deficiency and protein deficiency on tissue Se and glutathione peroxidase (GSHPx) activity in rats. Plasma, heart, liver, and kidney Se and GSHPx were significantly lower in Se-deficient groups in relation to Se-sufficient groups. In Se-deficient groups, Se and GSHPx were significantly higher in −Se−Pro rats in heart, liver, and kidney. Data analysis showed that there were significant interaction effects between dietary Se and protein on Se and GSHPx of rats. It is assumed that under the condition of Se deficiency. a low level of protein may decrease Se and GSHPx utilization, increase GSHPx synthesis, and result in Se redistribution. This could account for high levels of Se and GSHPx in the −Se−Pro rats compared to −Se+Pro rats.     

Presynaptic α2 Adrenoceptors Inhibit Glutamate Release from Rat Spinal Cord Synaptosomes

Abstract: The presynaptic regulation of amino acid release from nerve terminals was investigated using synaptosomes prepared from the rat spinal cord. The basal releases of endogenous glutamate (Glu), aspartate (Asp), and γ-amino-butyric acid (GABA) were 34.6, 21.5, and 10.0 pmol/min/mg of protein, respectively. Exposure to a depolarizing concentration of KCl (30 m M ) evoked 2.7-, 1.5-, and 2.9-fold increases in Glu, Asp, and GABA release, respectively. Clonidine reduced the K⁺-evoked overflow of Glu to 56% of the control overflow with a potency (IC₅₀) of 17 n M , but it did not affect K⁺-evoked overflow of Asp, GABA, and their basal releases. Similarly, noradrenaline inhibited the K⁺-evoked overflow of Glu, although phenylephrine and isoproterenol showed no effect. The inhibitory effect of clonidine was counteracted by α₂-adrenoceptor antagonists, rauwolscine, yohimbine, and idazoxan, regardless of the imidazoline structures. Because Glu is considered a neurotransmitter of primary afferents that transmit both nociceptive and nonnociceptive stimuli in the spinal cord, these data suggest that part of Glu release may be regulated by the noradrenergic system through α₂ adrenoceptors localized on the primary afferent terminals.     

Structural characterization of the dihydroflavonol 4-reductase B (DFR-B) gene in the sweet potato.

A genomic fragment containing the dihydroflavonol 4-reductase B (DFR-B) gene was cloned from the sweet potato (Ipomoea batatas) and its nucleotide sequence was analyzed. The exons and flanking regions were highly homologous to those of previously reported DFR-B genes of the Japanese morning glory, whereas the introns and the intergenic region were less conserved. In addition to the sequences of three miniature inverted-repeat transposable elements (MITEs) and one direct repeat previously reported in the DFR-B gene of Japanese morning glory, two mobile element-like sequences were newly identified in the sweet potato DFR-B gene. At least four allelic sequences were found to exist by amplification of the DFR-B gene from various sweet potato cultivars. One of these allelic sequences had a 2-kb deletion in the intergenic region and was observed in the cultivars with high anthocyanin content in their storage roots.     

PLD activation in Chinese hamster ovary (CHO) cells transfected with PGF2α receptor cDNA

Pertussis toxin-insensitive GTP-binding protein was observed to be involved in prostaglandin F2α(PGF2α)-induced phosphoinositide metabolism in Chinese hamster ovary (CHO) cells transfected with PGF2α receptor cDNA (CHO-PGF2α·R cells) (Ito, S. et al. Biochem. Biophys. Res. Commun. 200: 756, 1994). In the present study, we investigated PGF2α-induced PLD activation in CHO-PGF2α·R cells. PLD activation was examined by measuring the production of [³H]phosphatidylbutanol ([³H]PBut), a specific product of the PLD-catalyzed transphosphatidylation reaction. PGF2α-induced [³H]PBut formation was concentration-dependent with the maximal level obtained at 1 μM PGF2α. The maximal [³H]PBut formation was observed at 2 min after addition of PGF2α. Depletion of extracellular Ca²⁺ with EGTA suppressed PGF2α-induced PLD activation by 50%. PKC inhibitors Ro31–8425 and calphostin C inhibited PGF2α-induced [³H]PBut formation by 50%. PTK inhibitors genistein and herbimycin A failed to inhibit PGF2α-induced PLD activation. A combination of maximal effective concentrations of PGF2α (1 μM) and PMA (100 nM) enhanced PLD activation in an additive manner. Pretreatment of the cells with PMA for 2 h down-regulated PKCα and decreased PGF2α-induced PLD activation. These results suggest that PLD activation by PGF2α is mediated by both PKC-dependent and -independent pathways and that PKCα is involved in the former pathway.     

Iodothyronine deiodinase activity in methionine-deficient rats fed selenium-deficient or selenium-sufficient diets

We examined the effect of methionine deficiency on iodothyronine 5’-deiodinase activity in selenium-deficient rats or selenium-sufficient rats fed sodium selenate or selenomethionine. Forty-two weanling male Wistar rats were divided into six groups and pair fed the respective purifiedl-amino acid-based diets for 4 wk.l-methionine concentrations in the diet were 8.0 g/kg for sufficient rats, and 2.0 g/kg for deficient rats. Selenium concentrations in the diet were 0.5 mg/kg (as sodium selenate or selenomethionine) for selenium-sufficient rats and less than 0.005 mg/kg for selenium-deficient rats. Type I 5’-deiodinase activities were significantly lower in liver and higher in kidney of methionine-deficient rats than in those of methionine-sufficient rats fed either the selenium-sufficient or the selenium-deficient diets. The type I 5’-deiodinase activity in brain was significantly lower in the methionine-deficient rats than in the methionine-sufficient rats fed the selenium-deficient diet. Type II 5’-deiodinase activity in brain was significantly higher in the methionine-deficient rats than in the methionine-sufficient rats fed selenium-sufficient diet as sodium selenate. Both thyroxine and 3,3’,5-triiodothyronine concentrations in plasma were significantly higher in the methionine-deficient rats than in the methionine-sufficient rats. It is suggested that the methionine deficiency affects the 5’-deiodinase activity and thyroid hormones level in the rats.     

Physical effects of negative air ions in a wet sauna

 The physical effects of negative air ions on humans were determined in an experimental sauna room equipped with an ionizer. Thirteen healthy persons took a wet sauna bath (dry bulb temperature 42° C, relative humidity 100%, 10 min exposure) with or without negative air ions. The subjects were not told when they were being exposed to negative air ions. There were no differences in the moods of these persons or changes in their blood pressures between the two saunas. The surface temperatures of the foreheads, hands, and legs in the sauna with negative ions were significantly higher than those in the sauna without ions. The pulse rates and sweat produced in the sauna with ions were singificantly higher than those in the sauna without ions. The results suggest that negative ions may amplify the effects on humans of the sauna. Received: 31 March 1995 / Revised: 25 July 1995 / Accepted: 26 July 1996     

Lethality of the covalent linkage between mislocalized major outer membrane lipoprotein and the peptidoglycan of Escherichia coli.

The major outer membrane lipoprotein (Lpp) of Escherichia coli possesses serine at position 2, which is thought to function as the outer membrane sorting signal, and lysine at the C terminus, through which Lpp covalently associates with peptidoglycan. Arginine (R) is present before the C-terminal lysine in the wild-type Lpp (LppSK). By replacing serine (S) at position 2 with aspartate (D), the putative inner membrane sorting signal, and by deleting lysine (K) at the C terminus, Lpp mutants with a different residue at either position 2 (LppDK) or the C terminus (LppSR) or both (LppDR) were constructed. Expression of LppSR and LppDR little affected the growth of E. coli. In contrast, the number of viable cells immediately decreased when LppDK was expressed. Prolonged expression of LppDK inhibited separation of the inner and outer membranes by sucrose density gradient centrifugation, whereas short-term expression did not. Pulse-labeled LppDK and LppDR were localized in the inner membrane, indicating that the amino acid residue at position 2 functions as a sorting signal for the membrane localization of Lpp. LppDK accumulated in the inner membrane covalently associated with the peptidoglycan and thus prevented the separation of the two membranes. Globomycin, an inhibitor of lipoprotein-specific signal peptidase II, was lethal for E. coli only when Lpp possessed the C-terminal lysine. Taken together, these results indicate that the inner membrane accumulation of Lpp per se is not lethal for E. coli. Instead, a covalent linkage between the inner membrane Lpp having the C-terminal lysine and the peptidoglycan is lethal for E. coli, presumably due to the disruption of the cell surface integrity.     

Mucopolysaccharidosis IVA: structural gene alterations identified by Southern blot analysis and identification of racial differences

Ninety-six alleles (36 alleles of Japanese and 60 of Caucasian origin) from forty-eight patients with mucopolysaccharidosis IVA were investigated for structural gene alterations using Southern blot analysis. All patients had a previously demonstrated deficiency of N-acetylgalactosamine-6-sulfate-sulfatase and exhibited a wide spectrum of clinical severity. Initially, using the fulllength cDNA as a probe, five of 36 chromosomes from the Japanese patients revealed similar rearrangements with respect to DNA digested with BamHI, SacI, and XhoI. Subsequent analysis using seven genomic fragments, covering the entire gene, enhanced the detection of aberrant fragments produced by the above restriction enzymes. Conversely, the 60 chromosomes of Caucasian origin revealed no evidence of large structural rearrangements when analyzed by these methods. There was a statistically significant difference between the two populations (P < 0.01). A severely affected Japanese patient showed structural rearrangements on both chromosomes by means of BamHI blots. An 8.0-kb fragment and a highly polymorphic 7.0-kb to 11.0-kb fragment present in normal individuals disappeared and two aberrant fragments of 11.5 kb and 12.0 kb were observed. Three other Japanese patients also showed these two aberrant fragments, in addition to the normal fragment pattern, and were thus heterozygous for this rearrangement. Interpretation of Southern blots was difficult because of the complexity of polymorphic bands resulting from variable number of tandem repeat elements. However, by utilizing these aberrant fragments or polymorphic bands, carrier detection was effective, even in families with poorly characterized mutations. Hybridization with probe MG-A (5end genomic probe in intron 1) showed a 8.4-kb fragment in BamHI blots of one Japanese and one Caucasian patient; XhoI, SacI, and EcoRI blots were normal. Since this BamHI alteration was also observed in one normal control, it appears to be a rare nonpathological polymorphism.