Inhibitory effects of calcium antagonists on mitochondrial swelling induced by lipid peroxidation or amchidonic acid in the rat brain in vitro

Inhibitory effects of calcium antagonists, efonidipine (NZ-105), nicardipine, nifedipine, nimodipine and flunarizine, on mitochondrial swelling induced by lipid peroxidation or arachidonic acid in the rat brain in vitro were investigated. Mitochondrial swelling and lipid peroxidation induced by FeSO₄ and ascorbic acid system showed a close and significant relationship. Mitochondrial swelling and lipid peroxidation induced by FeSO₄ and ascorbic acid were inhibited by all of calcium antagonists tested. The order of inhibition was: flunarizine>nicardipine>efonidipine>nimodipine>nifedipine. This result suggests that calcium antagonists tested have antiperoxidant activities resulting in protection of mitochondrial membrane damage and that each moiety of these structures would play an important role in appearance of anti-peroxidant activities. Furthermore, flunarizine and efonidipine inhibited mitochondrial swelling induced by arachidonic acid, which is not associated with lipid peroxidation. In contrast, nicardipine, nifedipine, and nimodipine did not inhibited this swelling. It is possible that flunarizine and efonidipine could directly interact with mitochondrial membrane. In conclusion, it is capable that calcium antagonists tested may protect from the membrane damage induced by lipid peroxidation and that flunarizine and efonidipine could stabilize the membrane, which is attributed to a direct interaction with the membrane.     

Evolutionary character changes and population responses in an insect host-parasitoid experimental system

In an insect host (the cowpea weevilCallosobruchus maculatus)- parasitoidHeterospilus prosopidis) experimental system, the population densities of the component species oscillated for the first 20 generations and then abruptly stabilized as the parasitoid density decreased. Examination of the host and parasitoid after the 40th generation in the long-term experiment showed that (1) host larvae exhibited contest-type competition (killing other larvae inhabiting the same bean), in contrast to the founder population being scramble-type competitors and (2) the parasitoid attack rate on the host did not change. There was also an evolutionary trade-off between body size and the rates of larval survival and development, suggesting a cost of contest competition on larval survivorship and development. I tested model predictions (Tuda and Iwasa 1998) that (1) host equilibrium population size should gradually decrease as the proportion of the contest type increases and that (2) random attacks of the parasitoid on the host should reduce the rate of increase in proportion of the contest type, and the effect should become manifest especially during the first 20 generations. Two of three host-only replicates showed significant decrease in population sizes. Although the density of emerging adults per bean did not differ between replicates of the host-only and host-parasitoid systems, comparison of the host body size between them on day 270 (at the 13th generation) showed that the host was more contest-type in the host-only system than in the host-parasitoid system, as the model predicted, and later on day 650 the effect of the parasitoid had disappeared.     

Purification and some properties of Monilinia fructicola DNase

DNase was extracted and purified about 1,000-fold from the myceliaof a phyto-pathogenic fungus, Monilinia fructicola. The DNasewas an endonucleolytic enzyme and digested both native and heat-denaturedDNA’s into oligonucleotides having 5'-phosphoryl and 3'-hydroxyltermini. The DNase required Mg ions for full activity. The isoelectricpoint of this enzyme was 9.0, and the molecular weight was about36,000 daltons. (Received January 18, 1980; )     

Characterization of fucosyl glycopeptides from cell surface and cellular material of rat fibroblasts

Approximately 70% of fucose-labeled glycopeptides from the cell surface and cellular material of rat fibroblasts (3Y1B cells) were hydrolyzed by endo-β-N-acetylglucosaminidase D in the presence of neuraminidase, β-glactosidase and β-N-acetylglucosaminidase. Structure of the suspceptible glycopeptides were found to be very similar to non-membrane glycopeptides of the complex heteropolysaccharide unit, such as the sialylated glycopeptides of thyroglobulin. On the other hand, the resistant glycopeptides were also refractory toward endo-β-N-acethylglucosaminidase H and α-mannosidase, and appeared to be a mixture of glycopeptides with unique structures.     

Acceleration of the electrogenic Na+ pump by adrenaline in frog skeletal muscle fibres

The effect of adrenaline on the K⁺-activated hyperpolarization of frog skeletal muscle fibres was studied. The amplitude of K⁺-activated hyperpolarization, which was produced when the external K⁺ concentration was changed from 0 to 2 mM, was markedly increased in the presence of adrenaline. In the presence of ouabain (1 × 10^?5 M), which completely and reversibly eliminated the K⁺-activated hyperpolarization, adrenaline caused no significant changes in both the membrane potential and conductance under the condition where the K⁺-activated hyperpolarization was supposed to be produced. These results suggested that adrenaline accelerated the electrogenic Na⁺ pump which produced the K⁺-activated hyperpolarization.