Keiichi Abe

Effects of leptomycin B on the cell cycle of fibroblasts and fission yeast cells

An antifungal antibiotic, leptomycin B (LMB), which induced cell elongation of fission yeast, Schizosaccharomyces pombe, was found to be a unique inhibitor of the cell cycle of mammalian and fission yeast cells. Proliferation of rat 3Y1 fibroblasts was reversibly blocked by LMB in both the G1 and G2 phases and the treated cells were presumably introduced into the resting state (GO). After removal of LMB, proliferative tetraploid cells were produced from the cells which had been arrested by LMB at the G2 phase, as a result of DNA replication without passage through the M phase. LMB also inhibited the proliferation of S. pombe in both the G1 and G2 phases. These results suggest that the molecular target of LMB is one of the components necessary for progression of both G1 and G2 in the eukaryotic cell cycle.

Highly synchronous culture of fibroblasts from G2 block caused by staurosporine, a potent inhibitor of protein kinases

The effect of staurosporine, a potent microbial inhibitor of protein kinases, on the cell cycle of cultured fibroblast cells was investigated. A low concentration of staurosporine (1-10 ng/ml) blocked the cell cycle of rat 3Y1 fibroblasts at the early G1 phase within 2 h after serum stimulation. On the other hand, a higher concentration of the drug (100 ng/ml) caused the specific G2 block. Both of these blocks were reversible. After release from the G2 block, highly synchronous transition to M phase was observed and both nuclear and cell divisions were completed within 180 min. This reversible G2 block showed a clear contrast to those by the other G2 arresters, trichostatin A and leptomycin B, which formed proliferative tetraploid cells after release by entering the cells into a new S phase without passage through M phase. The presence of trichostatin A or leptomycin B did not interfere with this synchronous progression through G2/M phases, suggesting that the arrest point of staurosporine was present in late G2 phase following those of trichostatin A and leptomycin B.

Effects of chicken essence on recovery from mental fatigue in healthy males

Background Fatigue is a common symptom in modern society. There has been a recent resurgence of interest in traditional remedies for fatigue. Chicken essence, which is rich in anserine and carnosine, has been widely taken in Asian countries as a traditional remedy with various aims, including attenuation of physical and mental fatigue. However, the evidence for its efficacy specifically for mental fatigue remains unclear. We examined the effect of essence of chicken on mental fatigue in humans, using our established fatigue-inducing task and evaluation methods. Material/Methods In this placebo-controlled crossover study, 20 healthy male volunteers were randomized to receive daily oral administration of essence of chicken or placebo drink provided by Cerebos Pacific Ltd. via Suntory holdings Ltd. for 4 weeks. The participants performed 2-back test trials as a fatigue-inducing mental task and then had a rest session. Just before and after each session, they completed cognitive task trials focusing on selective attention to evaluate the level of mental fatigue. Results After essence of chicken intake for 1 and 4 weeks, the reaction times on the cognitive task trials after the rest session were significantly shorter than those at baseline, and significant changes were not observed with placebo intake. The reaction times before and after the fatigue-inducing session were not altered by either essence of chicken or placebo intake. Conclusions We showed that daily intake of essence of chicken could be effective for the recovery from mental fatigue and is a promising candidate for use as an anti-fatigue food.

Effects of Essence of Chicken on Cognitive Brain Function: A Near-Infrared Spectroscopy Study

The aim of this study was to investigate the effects of the essence of chicken on brain function by near-infrared spectroscopy. Twelve healthy elderly subjects took the essence of chicken or a placebo for 7 d in a double-blind cross-over design study. Changes in oxy-hemoglobin concentrations in the bilateral prefrontal areas of the brain were measured while the subjects performed the simple reaction task, the Groton Maze Learning Test, and the working memory task. In the latter case, there were significant interactions in the changes in oxy-hemoglobin concentrations between treatment and period of intake according to two-way repeated ANOVA. The changes in oxy-hemoglobin concentrations significantly increased in several regions of the prefrontal areas of the brain in those taking essence of chicken for 7 d. These results suggest that essence of chicken is useful as a nutritional supplement to enhance or maintain brain function in the elderly.

LEPTOLSTATIN FROM Streptomyces sp. SAM 1595, A NEW GAP PHASE-SPECIFIC INHIBITOR OF THE MAMMALIAN CELL CYCLE

Leptolstatin, a new inhibitor of the progression of G1 and G2 phases of the mammalian cell cycle, was discovered through a unique screening system, in which effects of microbial metabolites on the cell cycle progression of the cultured rat fibroblasts were monitored by flow cytometry. The new inhibitor was extracted from the fermentation broth of Streptomyces sp. SAM1595 with ethyl acetate, and purified by silica gel column chromatography and HPLC. Leptolstatin showed a strong cytostatic effect on rat normal fibroblasts 3Y1 with an IC50 value of 0.4 ng/ml, but its antimicrobial activity was very weak. A 24-hour treatment of the fibroblast cells with 10 ng/ml of leptolstatin caused an arrest at G1 or G2 phase, as determined by flow cytometry. When the G2-arrested cells were freed from leptolstatin, those containing 4C DNA entered a new S phase without intervening M phase, resulting in the formation of proliferative tetraploid cells.