Effect of pyridoxine-deficiency on the turnover of aspartate aminotransferase isozymes in rat liver

DL-[14C]Leucine or L-[3H]leucine was injected intraperitoneally into pyridoxine-deficient and control rats, and the subsequent incorporation of the radioactivities into aspartate aminotransferase (AspAT) isozymes and the total soluble protein in the liver was measured. AspAT in the cytosol (AspATc) was separated into 3 subfractions with different characteristics on chromatofocusing. The results showed that in the liver of pyridoxine-deficient rats, the syntheses of all 3 subfractions of AspATc and degradation of AspATc (total) were increased, but that the syntheses and degradation of the total soluble protein and mitochondrial AspAT (AspATm) were not much different from those in control rats. The half-lives of soluble protein and AspATm were calculated to be 3.26-3.72 and 5.02-6.67 days, respectively, in both groups, and that of AspATc in control liver was found to be 4.78 days. The rate of degradation of AspATc in pyridoxine-deficient rat liver could not be calculated, because its kinetics were very complicated; there were apparently at least 2 components with different rates of degradation. Thus pyridoxal 5'-phosphate (PLP) apparently affects both the synthesis and degradation of AspATc, but does not affect the turnover of AspATm in rat liver.     

Effects of Suanzaorentang on behavior changes and central monoamines

Previously, it was found that the ancient Chinese remedy of Suanzaorentang could be a promising anxiolytic drug (Chen and Hsieh, 1985a, Chen and Hsieh, 1985b). To understand the mechanism of the action of Suanzaorentang, the effects of Suanzaorentang on behavior changes and central monoamines and their metabolites were studied in rats. It was found that Suanzaorentang significantly (1) prolonged the period from the onset of clonic to tonic convulsions induced by pentylenetetrazol or picrotoxin, (2) prolonged the sleep duration induced by hexobarbital, (3) reduced locomotor activity, (4) enhanced the hypomotility induced by alpha-MT, (5) reduced the locomotor stimulation produced by levodopa plus benserazide, and (6) reduced central HVA, VMA, and 5-HIAA, but had no significant effects on central DA, NA, and 5-HT. These facts implied that Suanzaorentang decreased the turnover rate of central monoamines and central catecholaminergic activity.     

Morphological and electrophysiological characteristics of the epipharyngeal sensilla of the silkworm, Bombyx mori

One pair of gustatory sensilla was found on the epipharynx ofBombyx mori larvae, and some morphological and electrophysiological characteristics of the epipharyngeal sensilla were investigated. They are sensilla coeloconica composed of a small papilla with a pore at the tip and a swelling of cuticle encircling the papilla. Three bipolar neurons innervate each sensillum. One neuron is an inositol receptor which responds to inositol only. Another cell responds with action potentials of relatively large amplitude to some feeding deterrent substances, such as strychnine nitrate. The thresholds of these cells for inositol and strychnine nitrate are approximately 10⁻⁴ M and 10⁻⁷ M, respectively. At least two kinds of spikes can be observed when these sensilla are stimulated with some salts and acids. Dose-response relationships and time courses of responses to inositol and strychnine nitrate were also examined in this study.     

Effects of Temperature on Bud-Sprouting and Early Growth of Cyperus esculentus in the Dark

Cyperus esculentus tubers and early growth of their sprouts. Percent sprouting increased with increasing temperature within the range of 12 to 38 C, while no sprouting occurred at 10 C and few tubers sprouted at 42 C. The rate of sprouting also increased with temperature up to 35 C. A base temperature of 11.4 C was determined for bud-sprouting of tubers in this species. Higher temperatures led to larger sprouts and greater survival rate. In particular, increased temperature favored root growth, and hence resulted in high root: shoot ratio of the sprouts. Larger tubers produced larger sprouts as a consequence of mobilizing a greater amount of their reserves, but they tended to utilize a smaller proportion of their reserves. The efficiency of reserve utilization significantly differed among the incubation temperatures, and its relation with temperature followed a quadratic pattern. This pattern is different from that documented for the bud-sprouting of rhizomes and stolons of other perennials. Our results demonstrate that temperature is crucial to the successful establishment of C. esculentus. Received 24 June 1999/ Accepted in revised form 14 December 1999     

Geographical variations in the concentration of biliary free fatty acids with anti-mutagenic action.

The concentrations and compositions of free fatty acids (FFAs) in human bile, especially of inhibitory free fatty acids (IFFAs), were analyzed in terms of anti-mutagenic effects in relation to the mutagenic activity of bile. Bile samples were collected from patients with cholelithiasis residing in either Niigata or Kochi prefectures of Japan, regions characterized as the highest and lowest risk areas for gallbladder cancer (GBC), respectively. Biliary FFAs and IFFAs were analyzed by high-performance liquid chromatography and mutagenicity was examined in by the Ames test (TA98+S9mix) after blue rayon treatment. There was a tendency for higher biliary FFA and IFFA concentrations in the Kochi subjects, but the proportion of IFFA to the total FFA concentration did not differ between the two areas. There was an inverse correlation between the concentrations of IFFAs and the numbers of revertant colonies in both Niigata and Kochi subjects. However, at a dose of 591 micromol/l, (calculated based on the average amount of IFFAs absorbed in blue rayon) IFFAs did not exhibit anti-mutagenic actions in the blue rayon extracts. Within this range, more positive samples were seen in Niigata than in Kochi, suggesting the presence of more active mutagen(s) in Niigata samples.     

Identification of S-acyl glutathione conjugates of bile acids in human bile by means of LC/ESI-MS

Previous work from this laboratory has reported the biotransformation of bile acids (BA) into the thioester-linked glutathione (GSH) conjugates via the intermediary metabolites formed by BA:CoA ligase and shown that such GSH conjugates are excreted into the bile in healthy rats as well as rats dosed with lithocholic acid or ursodeoxycholic acid. To examine whether such novel BA-GSH conjugates are present in human bile, we determined the concentration of the GSH conjugates of the five BA that predominate in human bile. Bile was obtained from three infants (age 4, 10, and 13 months) and the BA-GSH conjugates quantified by means of liquid chromatography (LC)/electrospray ionization (ESI)-linear ion trap mass spectrometry (MS) in negative-ion scan mode, monitoring characteristic transitions of the analytes. By LC/ESI-MS, only primary BA were present in biliary BA, indicating that the dehydroxylating flora had not yet developed. GSH conjugates of chenodeoxycholic and lithocholic acid were present in concentrations ranging from 27 to 1120 pmol/ml, several orders of magnitude less than those of natural BA N-acylamidates. GSH conjugates were not present, however, in the ductal bile obtained from 10 adults (nine choledocholithiasis, one bile duct cancer). Our results indicate that BA-GSH conjugates are formed and excreted in human bile, at least in infants, although this novel mode of conjugation is a very minor pathway.     

Hydrogen sulfide protects the retina from light-induced degeneration by the modulation of Ca2+ influx

Hydrogen sulfide (H(2)S) has recently been recognized as a signaling molecule as well as a cytoprotectant. Cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) are well-known as H(2)S-producing enzymes. We recently demonstrated that 3-mercaptopyruvate sulfurtransferase (3MST) along with cysteine aminotransferase (CAT) produces H(2)S in the brain and in vascular endothelium. However, the cellular distribution and regulation of these enzymes are not well understood. Here we show that 3MST and CAT are localized to retinal neurons and that the production of H(2)S is regulated by Ca(2+); H(2)S, in turn, regulates Ca(2+) influx into photoreceptor cells by activating vacuolar type H(+)-ATPase (V-ATPase). We also show that H(2)S protects retinal neurons from light-induced degeneration. The excessive levels of light exposure deteriorated photoreceptor cells and increased the number of TUNEL- and 8-hydroxy-2'-deoxyguanosine (8-OHdG)-positive cells. Degeneration was greatly suppressed in the retina of mice administered with NaHS, a donor of H(2)S. The present study provides a new insight into the regulation of H(2)S production and the modulation of the retinal transmission by H(2)S. It also shows a cytoprotective effect of H(2)S on retinal neurons and provides a basis for the therapeutic target for retinal degeneration.     

Synthesis and anti-influenza evaluation of orally active bicyclic ether derivatives related to zanamivir

We synthesized bicyclic ether sialidase inhibitors such as tetrahydro-furan-2-yl, tetrahydro-pyran-2-yl, and oxepan-2-yl derivatives related to zanamivir. These compounds substituted by diol at the C-3' and C-4' positions resulted in the retention of low nanomolar inhibitory activities against not only influenza A virus sialidase but also influenza A virus in cell culture. Compound 11a in particular showed comparable efficacy in vivo relative to that of oseltamivir phosphate.     

Accumulation of 8-oxoguanine in the cellular DNA and the alteration of the OGG1 expression during ischemia-reperfusion injury in the rat kidney

During ischemia-reperfusion (I/R) injury in the rat kidney, apoptosis was observed in the distal tubules of the cortico-medullary region and outer medulla (OM) while severe necrosis was seen in the proximal straight tubules of the OM. The majority of these changes disappeared within 2 weeks. We examined the contents of 8-oxo-2'-deoxyguanosine (8-oxo-dG), which is a major type of oxidative damage in DNA, in the rat kidney during I/R injury, and also investigated the expression level of the OGG1 gene encoding the 8-oxoguanine DNA glycosylase. High-performance liquid chromatography with an MS/MS analysis of the nuclear DNA revealed an immediate accumulation of 8-oxo-dG in the nuclear DNA prepared from the cortex and OM of the kidney 1h after I/R, and an immunohistochemical analysis demonstrated the immediate accumulation of 8-oxo-dG in the nuclei of renal tubular cells both in the cortex and OM. A delayed increase of cytoplasmic staining with anti-8-oxo-dG was observed only in the cortico-medulla and OM, where the cytoplasmic staining in the proximal tubular cells is higher than in the distal tubular cells. The level of cytoplasmic staining representing 8-oxo-dG in mitochondrial DNA, peaked at 6h after I/R and preceded the necrosis of proximal tubular cells in the OM. An RNase protection assay showed a high level of OGG1 mRNA in the normal kidney, and the level decreased within 3h only in the OM, and increased thereafter 1-7 days of I/R both in the cortex and OM. In situ hybridization showed higher levels of OGG1 mRNA expression in the renal tubules in the OM than in the cortex of the normal kidney, which decreased rapidly within 3h of I/R. Thus, the accumulation of 8-oxo-dG in the mitochondrial DNA rather than in nuclear DNA is likely to be involved in the pathogenic responses such as necrosis of renal tubular cells during I/R injury of the kidney, together with an altered level of OGG1 expression.