Biomedical subjects

Hiroyuki Sakakibara

Publications and source records attributed to Hiroyuki Sakakibara.

9 recordsLinked to original sources

PubMed2006

Antidepressant effect of extracts from Ginkgo biloba leaves in behavioral models.

Extracts of Ginkgo biloba (EGB) are a complex product prepared from green leaves of the Ginkgo biloba tree. In the present study, the antidepressant effect of EGB was examined using two behavioral models, the forced swimming test (FST) in rats and tail suspension test (TST) in mice. EGB significantly reduced immobility time in the FST at a dosage of 10 and 50 mg/kg body weight after repeated oral treatment for 14 d, although no change of motor dysfunction was observed with the same dosage in the open field test. These results indicate that EGB might possess an antidepressant activity. In addition, EGB markedly shortened immobility time in the TST after acute inter-peritoneal treatment at a dosage of 50 and 100 mg/kg body weight. The present study clearly demonstrated that EGB exerts an antidepressant effect in these two behavioral models.

Animals↗

PubMed2006

Effects of combined administration of quercetin, rutin, and extract of white radish sprout rich in kaempferol glycosides on the metabolism in rats.

Quercetin, rutin, the extract of white radish sprout rich in kaempferol glycosides, and their combination were intragastrically administered to Wistar rats to investigate the interactive metabolism of these flavonoids. The combined administration of these flavonoids changed the concentrations of the metabolites in plasma as compared with the concentrations after the administration of a single compound.

Animals↗

PubMed2005

Effects of forced swimming stress on rat brain function.

Chronic stress has been reported to be an essential factor for depression. In this study, the effect of forced swimming stress on neurotransmitters and cellular signaling pathway contributing to brain functions was investigated using the forced swimming test (FST) in order to understanding of mechanisms to regulate stress signals in brain. Antidepressant drug, imipramine, significantly reduced the immobility time of male rats in the FST by 85% at a dose of 15 mg/kg for 2 weeks. This result indicated that the swimming stress caused a depressed state in the rats without administration of imipramine. Swimming stress significantly lowered the serotonergic ratio and also markedly enhanced the phosphorylation of ERK1/2 in the hypothalamus region compared to the rats without FST. These phenomena may be included in key mechanisms of the development of depression.

Animals↗

PubMed2005

Effects of Japanese kelp (kombu) on life span of benzo[a]pyrene-fed mice.

The prolonging effect of Japanese kelp (kombu) on life span was investigated in mice fed a diet containing the carcinogen benzo[a]pyrene (BaP). Three groups of six mice each were fed a normal diet with 0, 2 and 5%, kombu powder, while another three groups were fed those diets with 4 ppm BaP loading. The 2 and 5% kombu diets did not affect life span compared to the control group given 0%, kombu. BaP significantly reduced the life span. Addition of 2 or 5%, kombu to the BaP diet remarkably recovered the life span to a level similar to that of the control. The feces of the 2 and 5% kombu groups contained 6.9+/-1.2 and 16.8+/-1.8% of the ingested BaP, respectively, mainly in forms adsorbed on kombu fibers. The BaP-alone group given cellulose as dietary fiber instead of kombu, did not show any such effects. Humans are exposed to various environmental carcinogens such as BaP, and kombu fibers probably contribute to longevity by removing them.

Animals↗

PubMed2004

Anti-obesity actions of green tea: possible involvements in modulation of the glucose uptake system and suppression of the adipogenesis-related transcription factors.

To investigate mechanisms of the anti-obesity actions of green tea in vivo, rats were given green tea instead of drinking water for 3 weeks. It was confirmed that green tea reduced adipose tissue weight without any change in body weight, other tissue weights, and food and water intakes. Green tea also significantly reduced the plasma levels of cholesterols and free fatty acids. Certain catechins existed in the plasma at 0.24 microM under our experimental conditions, though most of them existed as conjugated forms. For mechanisms of the anti-obesity actions, green tea significantly reduced glucose uptake accompanied by a decrease in translocation of glucose transporter 4 (GLUT4) in adipose tissue, while it significantly stimulated the glucose uptake with GLUT4 translocation in skeletal muscle. Moreover, green tea suppressed the expression of peroxisome proliferator-activated receptor gamma and the activation of sterol regulatory element binding protein-1 in adipose tissue. In conclusion, green tea modulates the glucose uptake system in adipose tissue and skeletal muscle and suppresses the expression and/or activation of adipogenesis-related transcription factors, as the possible mechanisms of its anti-obesity actions.

Adipose Tissue↗

PubMed2004

Isoflavones in several clover species and in milk from goats fed clovers.

Isoflavones that exist in forages such as clover can move in milk, and may have beneficial effects on human health. We measured the isoflavones in subterranean (cv Yarloop, Geraldton, Dinninup and Dwalganup) and red (cv Merviot and Hamua) clovers, grown in a mountain environment, and in the milk of two goats fed a fresh mixture of the four subterranean clovers gathered at flowering stage. Isoflavone glycosides were hydrolysed with an improved beta glycosidase method. Free aglycones (FA) and the hydrolysed glycosides + free aglycones fraction (HF) were analysed by HPLC. In milk, the methanol extracted compounds were deconjugated and similarly analysed. Total HF was highest in Yarloop (19 g kg(-1) dry matter) and was three times lower in Merviot. Formononetin was the major compound (46-64% of total HF). FA varied from 30 to 73% of HF. Milk contained formononetin (50 microg L(-1)), similar amounts of equol and p ethylphenol (about 250 microg L(-1)), and equol like compounds (1120 microg L(-1)). Equol, which has estrogenic activity, and p ethylphenol were produced by biotransformation of formononetin, and biochanin A or genistein, respectively. The modulation of isoflavone amounts in milk and the estimation of their interests for human health warrant further investigation.

Animal Feed↗

PubMed2003

Simultaneous determination of all polyphenols in vegetables, fruits, and teas.

Polyphenols, which have beneficial effects on health and occur ubiquitously in plant foods, are extremely diverse. We developed a method for simultaneously determining all the polyphenols in foodstuffs, using HPLC and a photodiode array to construct a library comprising retention times, spectra of aglycons, and respective calibration curves for 100 standard chemicals. The food was homogenized in liquid nitrogen, lyophilized, extracted with 90% methanol, and subjected to HPLC without hydrolysis. The recovery was 68-92%, and the variation in reproducibility ranged between 1 and 9%. The HPLC eluted polyphenols with good resolution within 95 min in the following order: simple polyphenols, catechins, anthocyanins, glycosides of flavones, flavonols, isoflavones and flavanones, their aglycons, anthraquinones, chalcones, and theaflavins. All the polyphenols in 63 vegetables, fruits, and teas were then examined in terms of content and class. The present method offers accuracy by avoiding the decomposition of polyphenols during hydrolysis, the ability to determine aglycons separately from glycosides, and information on simple polyphenol levels simultaneously.

Chromatography, High Pressure Liquid↗

PubMed2002

Preparation and properties of alginate lyase modified with poly(ethylene glycol).

Modification of the enzyme alginate lyase (AL) with poly(ethylene glycol) (PEG) was attempted for the degradation and removal of alginate biofilms in infectious diseases. The modification of AL with PEG was attempted with three kinds of N-succinimidyl succinate PEG (SS-PEG), which differed in molecular weight (i.e., 2000, 5000 and 12,000 Da). The conjugation of PEG to free amino groups on AL was confirmed by gel permeation chromatography. Quantification of residual free amino groups revealed that PEG modification progressed further with a higher pH and a larger molar ratio of SS-PEG to AL. The reproducibility of the reaction was fairly good. The enzyme activity decreased with increasing PEG modification but the immunoreactivity toward anti-AL antibodies, as evaluated by an ELISA method, was much more remarkably reduced. The immunoreactivity was more reduced by the conjugated PEG with the larger molecular weight. In the reaction with PEG of molecular weight 12,000 Da, we obtained PEG-modified AL retaining approximately 40% enzyme activity but only 0.5% of the immunoreactivity of native AL.

Animals↗

PubMed2002

A novel method using 8-hydroperoxy-2'-deoxyguanosine formation for evaluating antioxidative potency.

Degenerative diseases such as cancer are induced by oxidative genetic damage. Antioxidants can scavenge reactive oxygen species, but to prevent disease, they must do so quickly, before the DNA bases are damaged. In the present study, a novel method was established for evaluating the potency of antioxidants employing 2'-deoxyguanosine as a target and 2,2'-azobis(2-amidino-propane) dihydrochloride as a reactive oxygen generator. The reaction formed one product linearly with time. This product was a novel 8-hydroperoxy-2'-deoxyguanosine (8-OOHdG). Using this system, 81 antioxidants occurring in our diet were assayed for activity to suppress the formation of 8-OOHdG by high-performance liquid chromatography (HPLC). The system was useful for the evaluation of antioxidative potency, compared to another method utilizing 1,1-diphenyl-2-picrylhydrazyl (DPPH). Further, it was enabled to examine the synergism of antioxidants. The formation of 8-OOHdG started only after the antioxidants had been consumed. Ascorbic acid, quercetin, and epigallocatechin gallate together delayed the formation by the sum total of the delay times of each factor alone. The proposed method is simple and easy, and can evaluate which dietary antioxidants inhibit reactive oxygen species more quickly than the DNA bases are damaged.

8-Hydroxy-2'-Deoxyguanosine↗