A brief local application of bradykinin (BK) induced an immediate outward current, followed by a sustained inward current. BK produced an increase of inositol 1, 4, 5-trisphosphate and diacylglycerol. These two intermediates can duplicate the outward and inward current, suggesting that they play as intracellular second messegers.

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It is considered that the actin regulatory protein plays key roles in the dynamic behaviors of the actin cytoskeleton in non muscle cells. Many protein factors have been isolated from the cells and the properties of the protein factors have been identified in vitro. They could be classified to 1) the regulatory protein of the actin polymerization, 2) the F-actin severing protein, and 3) the F-actin gelation or/and F-actin bundling protein. The methods of extraction, purification, and identification of these proteins are briefly described.

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Crickets and other small insects detect delicate movement of air by filamentous sensory hairs. They utilize the sensory cue for behavioral decision making. The sense of medium flow is unorthodox in large animals. Biological and physical constraints which evolve the sensory capacity for medium flow are described.

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Various mutations in Drosophila are now known to lead to substantial decrease in the rhodopsin content of the photoreceptors. One is a mutation on the gene that encodes for opsin. Others recently provided unexpected evidence for the involvement of cytoskeletal proteins and an immunosuppressant-binding protein, cyclophilin.

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A peculiar cellular pattern resembling a checkerboard was observed on the luminal surface of the oviduct epithelium of an adult Japanese quail. The epithelium was a monolayer cell sheet and consisted of two types of columnar cells, ciliated cells and gland cells assembled in alternating blocks. An assumption that adhesion was stronger between unlike cells than between like cells formed a checherboard pattern, because all cell boundries in it were edges along which unlike cells meeted. This consideration accompanying with cell boundary contraction of an epithelium enabled us to estimate an energy ratio between cell adhesions of unlike cells and like cells¹¹⁾

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Membrane fluidity, rate of responses to a hypotonic environment, and membrane elasticity of cultured dorsal root ganglion neurons from different age groups of mice decrease with aging. These results show that the neuronal cell membrane becomes rigid with aging. This change might play an essential role in the decrease of the regenerative capacity and plasticity of neurons.

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Exposure of mammalian cells to hyperthermic temperature results in both cytotoxicity and radiosensitization; the molecular mechanisms are still obscure. We have investigated the effect of hyperthermia on DNA repair after exposure of UV irradiation which produces simple DNA damage, namely pyrimidine dimers, as compared with ionizing radiation which induces various DNA lesions. We have utilized Dictyostelium discoideum which is a lower eukaryote for which several DNA repair-deficient mutants are available. Though the optimum temperature for cell growth of the amoebae was 23°C, the critical temperature for effective enhancement of cell killng was ca. 30°C. In a wild-type strain (NC4), an increased temperature immediately after UV irradiation resulted in an increase in cell killing, since heat treatment did not inhibit the nicking of DNA strand, but did inhibit removal of pyrimidine dimers and the rejoining of the strand breaks. On the other hand, a radiationsensitive mutant (TW8) defective in an incision step of excision repair did not show an increase in cell killing in response to heat treatment administered after UV irradiation. Similar effects on NC4 as UV irradiation were observed in the case of heat treatment after treatment with 4-nitroquinoline 1-oxide, cis-platinum (II) diamminedichloride or 8-methoxypsoralen photo-addition, which produces excision repairable DNA lesions, not but N-methyl-N'-nitro-N-nitrosoguanidine or methylmethanesulphonate, which produces methylated DNA lesions independent of excision repair. Therefore, it is suggested that the sensitization of heat treatment might be dependent on the depression of excision repair mechanism.

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Mathematical models making use of linear diffusion systems are constructed to investigate effects of a spatial or temporal variation of environment on population persistence. Both cases of an isolated patchy environment and a multi-patchy one are dealt with. The results demonstrate the importance of taking these environmental heterogeneities into consideration to analyze the population persistence.

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