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Biomedical subjects

S Ikegami

Publications and source records attributed to S Ikegami.

At least 73 records · Page 4Linked to original sources
PubMed1994

Beta-carotene prevents x-ray induction of micronuclei in human lymphocytes.

The effects of beta-carotene and ascorbic acid on spontaneous and x-ray-induced appearance of micronuclei (MNs) in human lymphocytes were studied. For 12 d, three groups of healthy volunteers were given beta-carotene-deficient meals containing 100 mg ascorbic acid. There was no supplementation in the first 6 d but, in the last 6 d, the respective groups were given beta-carotene (30 mg), ascorbic acid (300 mg), or placebo. Blood samples were drawn on days 7 and 13 before breakfast, exposed either to x-ray irradiation or left unexposed and were cultured. Lymphocytes containing MNs were then counted. On day 7 the three groups showed comparable MN frequencies. On day 13 lymphocytes containing x-ray-induced MNs became less frequent in the beta-carotene but not the ascorbic acid group. Both before and after the supplementation, the MN frequency of irradiated lymphocytes showed a significant inverse correlation with plasma beta-carotene. These results strongly suggest that beta-carotene protects human lymphocytes from x-ray-induced genetic damage.

Adult↗
PubMed1994

Viscous indigestible polysaccharides reduce accumulation of pentachlorobenzene in rats.

To investigate an effect of indigestible polysaccharides (cellulose as control, sodium alginate, guar gum or lambda-carrageenan) on the accumulation of pentachlorobenzene, male Sprague Dawley rats were fed experimental diets containing 5 g/100 g of these polysaccharides for 2 wk. They were then given orally 80 mumol (20 mg) of pentachlorobenzene along with their respective diets and the residual pentachlorobenzene was determined after 7 d. The ingestion of the viscous indigestible polysaccharides resulted in significantly lower accumulation of pentachlorobenzene in adipose tissue, liver and kidney than that found in rats fed a cellulose diet. Soon (5 h) after pentachlorobenzene administration, its concentration in the blood of rats fed sodium alginate and guar gum was higher than that of rats fed cellulose, but lower in the groups fed all three viscous polysaccharides after d 3. These results indicate that pentachlorobenzene excretion was increased by the ingestion of viscous indigestible polysaccharides. Lower relative weight of adipose tissue, a storage tissue for pentachlorobenzene, was found in the rats fed sodium alginate and guar gum. The lower adipose tissue mass was likely the main contributor to the enhancement of pentachlorobenzene excretion.

Administration, Oral↗
PubMed1994

Marine natural products. XXXIII. Theonellapeptolide IId, a new tridecapeptide lactone from the Okinawan marine sponge Theonella swinhoei.

Following the characterization of theonellapeptolides Ia-Ie (2-6), another new tridecapeptide lactone named theonellapeptolide IId (1) was isolated from the Okinawan marine sponge Theonella swinhoei. The structure of 1 has been determined on the bases of chemical and physicochemical examinations which included an HPLC-CD combined analysis of the amino acid composition. Theonellapeptolide IId (1) prevented fertilization of the sea urchin Hemicentrotus pulcherrimus at the concentration of 25 micrograms/ml or greater but did not affect early embryonic development of fertilized eggs up to the gastrula stage.

Amino Acid Sequence↗
PubMed1994

Anti-bacillus substance in the marine sponge, Hyatella species, produced by an associated Vibrio species bacterium.

The bacterial isolate, M22-1, belonging to the genus Vibrio was obtained from an homogenate of the sponge, Hyatella sp. The bacterium was cultured in marine agar and was found to produce an anti-Bacillus compound. The substance was chemically identified as a peptide antibiotic, an andrimid. The same substance was found in the sponge extract, suggesting that the active component was synthesized by the associated microorganism.

Animals↗
PubMed1993

Synthesis and evaluation of (piperidinomethylene)bis(phosphonic acid) derivatives as anti-osteoporosis agents.

Some (piperidinomethylene)bis(phosphonic acid) derivatives were prepared and their activity to inhibit a rise in serum calcium induced by parathyroid hormone in thyroparathyroidectomised rats was evaluated. Several (4-alkylidene-, 4,4-dialkyl-, or 4-alkyl-4-halopiperidinomethylene)bis(phosphonic acid) derivatives showed considerable inhibitory activity. But compounds having aromatic and polar substituents such as azido, hydroxy, amino and amido on the piperidine ring were generally inactive. In this study, two 4-alkylidene compounds (8a and 8b) and a 4,4-cyclic dialkyl compound (61) showed potent activity when administered either intravenously or perorally.

Animals↗
PubMed1993

Effects of restricted feeding on the absorption, metabolism, and accumulation of pentachlorobenzene in rats.

To investigate the effect of restricted feeding (RF) on the absorption, metabolism, and accumulation of pentachlorobenzene (PECB), rats were fed either ad libitum (AD) or a restricted diet (at 25 or 50% of AD) for 15 days. On the 7th day (day 0), PECB (15 mg/rat) was orally administered. Daily fecal weight and the total amount of PECB excreted into feces were decreased by RF, indicating an increase in PECB absorption due to its prolonged retention in the gastrointestinal tract. However, the amount of PECB excreted was only 4.8% of the dose given to the AD group, and 2.1 and 2.4% of that given to the 50 and 25% restricted diet groups, respectively. The concentrations of PECB and pentachlorophenol, and major metabolite, in blood of the restricted diet groups were higher on day 2 and day 4, while lower on day 6 and day 8 than those of the AD group. On day 8, PECB in liver, kidney, brain, and fat tissue were also lower in the restricted diet groups; the PECB levels in such tissue in the 25 and 50% restricted diet groups were 10-40 and 5-11% of that in the AD group, respectively. These results indicate that PECB metabolism was increased by RF. As PECB is lipophilic, it is most likely that the fat tissue mass, which was markedly decreased by RF, contributed to the enhancement of PECB metabolism. The mechanism seemed to be as follows: as fat tissue mass accumulating PECB decreased, the concentration of PECB in the liver increased, thus the amount of PECB metabolites formed was increased.

Absorption↗
PubMed1993

Influence of dietary vitamin E on the 8-hydroxydeoxyguanosine levels in rat liver DNA.

Rats were fed either a low vitamin E (VE) diet (-VE), a basal VE diet (+VE, 4.5 mg%), or a high VE diet (+VE, 45 mg%) for 7 weeks. VE content, oxidative DNA damage and lipid peroxide levels in their livers were measured. When purified lard was used as a dietary fat, VE content decreased in the low VE group to one-thirtieth of that in the basal VE group; in the high VE group it increased to 4.5-fold that in the basal VE group. Corresponding to the VE levels, lipid peroxide levels increased to 2.7-fold in the low VE group and decreased to two-thirds in the high VE group. The level of 8-hydroxydeoxyguanosine (8-OHdG) in DNA, a marker of oxidative DNA damage, was about 0.6 per 10(5) deoxyguanosine in the basal VE group and comparable values were found in the low VE and the high VE groups. When either soybean oil or safflower oil was used as a dietary fat, VE content and lipid peroxide levels in the liver were also markedly changed in both the low VE group and the high VE group. 8-OHdG levels in DNA of the low VE with safflower oil group tended to be higher than that of the basal and high VE groups. However, no significant difference was observed among them. These results suggest that the change in VE has little influence on the level of oxidative DNA damage in the liver.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1992

Age-related changes in radial-arm maze learning and basal forebrain cholinergic systems in senescence accelerated mice (SAM).

Age-related changes in learning performance and the brain cholinergic system were studied in a senescence accelerated mice-prone series (SAM-P/8) and a senescence accelerated mice-resistant series (SAM-R/1, control) bred under specific pathogen-free conditions. In a radial-arm maze task, SAM-P/8 mice at 4 and 12 months of age showed virtually no significant impairment in working memory or reference memory compared with SAM-R/1 mice at the same age, although they needed more time to complete a trial than SAM-R/1. In contrast, in a passive avoidance task, SAM-P/8 showed a marked age-accelerated deficit in acquisition performance relative to SAM-R/1. Also, SAM-P/8 showed an age-accelerated decrease in locomotion and rearing in an open-field box. At the end of these behavioral tasks, neurochemical analyses showed that there were no differences in the concentrations of acetylcholine (ACh) in the cortex, hippocampus, striatum, midbrain, or cerebellum between SAM-P/8 and SAM-R/1. Although SAM-P/8 mice did not demonstrate any age-accelerated decline in radial-arm maze performance, they showed a normal age-related decline particularly in working memory, equal to that observed in SAM-R/1. Also, ACh levels in the aged groups of SAM-P/8 showed a significant decrease related to normal aging in the hippocampus and striatum, and a slight decrease in the cortex compared to the young group of the same strain. Thus, we found that SAM-P/8 show dissociative effects of aging in spatial learning and passive avoidance performance.

Aging↗
PubMed1992

Selective inhibition of membrane fusion events in echinoderm gametes and embryos by halenaquinol sulfate.

Halenaquinol sulfate, a hydroquinone sulfate obtained from the sponge Xestospongia sapra, prevented cell membrane fusion events of echinaderm gametes but did not affect early embryonic development of fertilized eggs up to the gastrula stage. However, halenaquinol sulfate inhibited secretion of hatching enzyme, resulting in the formation of gastrulae that were surrounded by the fertilization envelope. Therefore, the use of halenaquinol sulfate offers a unique opportunity to analyze the role of secretory events in complex populations of cells without affecting other cellular functions.

Animals↗
PubMed1992

Intercellular transport through a partially denuded arterial endothelial monolayer. Effect of platelets and PGI2.

Fluorescein Dextran (FD) was shown to be transported at increased rates through partially denuded endothelial monolayer. Platelet binding to the partially denuded monolayer lowered transport rates to those comparable with intact endothelium. Inhibition of transport by platelet binding was not affected by the addition of isocarbacyclin (a stable derivative of PGI2). This result suggests that adherent platelets at the partial denudation site are sufficient to suppress transport of FD.

Animals↗
PubMed1991

Transplantation of ventral forebrain cholinergic neurons to the hippocampus ameliorates impairment of radial-arm maze learning in rats with AF64A treatment.

Two types of cholinergic neurons were transplanted into the hippoccampus of adult rats chemically damaged by lateral ventricular administration of AF64A, a cholinergic neurotoxin, and the effects were compared with respect to their ability to reinnervate the hippocampus and to repair behavioral deficit. Pieces of brain tissue containing the nucleus basalis magnocellularis (NBM) or the striatum were taken for grafting from 17-day rat fetuses. About 3 months after transplantation, the rats with bilateral NBM grafts showed significant amelioration in radial-arm maze performance and habituation to a novel environment in an open field box, although they had not recovered to the control level. In rats with NBM grafts that showed a good performance, there were surviving grafts and many ingrowths of AChE-positive fibers in the hippocampus. By contrast, rats with striatal grafts showed hardly any significant improvement in these behavioral measures. The AChE staining revealed poor outgrowth of the striatal grafts into the hippocampus. These results indicate that grafting of NBM cholinergic neurons, which are anatomically similar to septal neurons, into the hippocampus produces a partial restorative effect on the cognitive impairment associated with hypofunction of the septohippocampal system.

Analysis of Variance↗
PubMed1991

Expression of murine dihydrofolate reductase complementary DNA in oocytes of Xenopus laevis.

1. Murine dihydrofolate reductase was produced efficiently in a Xenopus laevis oocyte that received microinjection of the dihydrofolate reductase mRNA. 2. Murine dihydrofolate reductase was produced under the direction of the plasmid pAdD26SVpA, which contains adenovirus major late promoter and the simian virus 40 T antigen gene for transcription initiation and murine dehydrofolate reductase complementary DNA fragment. 3. Injection of the plasmid pDHFR26, which contains murine dihydrofolate reductase complementary DNA and normal transcription initiation site segment in the 5' untranslational region, failed to produce proper translational products due to improper transcription.

Animals↗
PubMed1990

Effect of viscous indigestible polysaccharides on pancreatic-biliary secretion and digestive organs in rats.

Effects of viscous indigestible polysaccharides on the pancreas exocrine function were investigated in growing rats. Rats were fed a nonfiber diet or a diet containing approximately 5% of one of the following fibers: apple pectin, lambda-carrageenan, locust bean gum, gum xanthan, guar gum or sodium (Na) alginate. Pancreatic-bile secretion was found to be elevated in rats fed for 2 wk the highly viscous polysaccharides, sodium alginate, locust bean gum, gum xanthan and guar gum. The polysaccharides may have interfered with the digestion and absorption of nutrients, resulting in a decreased digestibility and an enlargement of digestive organs. When alginic acid and calcium alginate, insoluble polysaccharides that did not contribute to viscosity, were given to rats, they had no effect on pancreatic and biliary secretion compared with sodium alginate. The results demonstrate that consumption of viscous indigestible polysaccharides leads to changes in the exocrine pancreatic-biliary function and may depress the process of digestion and absorption. Rats may compensate for the inefficiency of digestion and absorption with a hyperplasia/hypertrophy of digestive organs and an increased secretion of digestive juice.

Alginates↗
PubMed1990

Influence of vitamin B2 deficiency on polychlorinated biphenyls-induced liver lipid peroxides formation in rats.

The present study is carried out to explore whether the liver microsomal drug-metabolizing enzymes induced by PCB are associated with the PCB-induced liver lipid peroxide formation in rats. For this purpose, variations of the drug-metabolizing enzyme activities mediated by vitamin B2 deficiency were utilized. The administration of PCB to rats induced the liver microsomal cytochrome P-450 and vitamin B2 deficiency promoted the induction. The cytochrome b5 was also induced by PCB but no further induction by vitamin B2 deficiency was observed. The flavoenzyme, NADPH-cytochrome c reductase, was induced by PCB when the vitamin B2-supplemented PCB diet was fed to rats, but the activity of the enzyme was decreased by vitamin B2 deficiency and PCB further decreased the activity. The liver lipid peroxide levels increased in PCB groups with and without vitamin B2 compared with each PCB-free group, but the lipid peroxide level in vitamin B2-deficient PCB group was significantly lower than in vitamin B2-supplemented PCB group. From these results, the PCB-induced liver lipid peroxide formation was not necessarily related to the variations of the liver microsomal drug-metabolizing enzymes.

Animals↗
PubMed1989

Transplantation of septal cholinergic neurons to the hippocampus improves memory impairments of spatial learning in rats treated with AF64A.

Embryonic septal neurons were transplanted into damaged hippocampus in adult rats which had received lateral ventricular administration of AF64A, a cholinergic neurotoxin. About 3 months after transplantation, the rats with bilateral septal grafts showed significant improvement in the radial maze and T-maze tasks. Many ingrowths of acetylcholinesterase (AChE)-positive fibers originating from the grafts were observed in the hippocampus of the rats which showed good performance in these learning tasks. These results indicate that transplantation of septal cholinergic neurons into the AF64A-treated hippocampus may induce at least partial recovery in learning tasks believed to involve the hippocampus.

Animals↗