Using our newly developed freezing system, we have succeeded in analyzing the 'instantaneous' electron microscopic images of sarcoplasmic reticulum obtained at each step of the excitation-contraction (E-C) coupling process in skeletal muscle. The results have led us to conclude that E-C coupling is accompanied by the remarkable structural changes of the sarcoplasmic reticulum.
When a gel undergoes an extensive swelling, a beautiful, regular pattern appears on the gel surface. At the beginning the pattern is extremely fine and has a texture similar to a frosted glass. As time goes on, the pattern units coalesce, doubling their characteristic length. When the unit size becomes comparable to the size of the gel, the pattern gradually disappears. Finally the entire gel regains a homoneneous shape. The pattern formation and evolution can be understood in terms of mechanlical instability of the swollenl layer on the gel surface induced by a large lateral compression.
Protein folding- and unfolding-tmnsitions were studied by computer simulation based on a lattice model of proteins in the case of absence of hydrophobic interactions. Two amino acid substituted models were investigated. Dynamic behavior of the protein folding was discussed from the temperature dependence of the relaxation time and the rate constants.
Based upon characteristic behavior appearing in the ripple phase of phospholipid membranes, the molecular configuration, the fluid-like character in the ripple phase and the periodic zonal structure in phospholipid-cholesterol systems are discussed.
A gene highly homologous to the Escherichia coli dnaA gene, essential for initiation of chromosomal replication, is conserved in evolutionarily diverged bacteria, Bacillus subtilis, Pseudomonas putida and Micrococcus luteus. In addition, a unique repeating sequence, DnaA-box, present in E. coli oriC and recognized by DnaA protein, is clustered in noncoding regions flanking these putative dnaA genes. These results suggests that interaction between DnaA protein and DnaA- box is key step in the initiation of bacterial chromosomal replication in common. Some preliminary results concerning evolution of regulation of chromosomal replication are also discussed.
Using nucleotide sequence data of AIDS virus strains isolated from patients at various locations of the world, we examined the phylogenetic relationships among AIDS virus strains. In particular, a phylogenetic tree for AIDS virus strains was constructed using the estimated numbers of nucleotide substitutions. The phylogenetic tree constructed shows that AIDS viruses can be classified into the two major groups; "HIV-1 group" and "HIV-2 group". Evolutionary features of these virus groups were discussed from the viewpoint of molecular epidemiology.
Mechano-, thermo- and photo-stimulation of Paramecium cell elicits changes in the membrane potential called receptor potentials. The receptor potentials are caused by modulating ionic conductances of specific channels localized on the cell surface.
Method for spectral analysis of heart rate variability (HRV), and physiological characteristics of their spectral components are discussed. Respiratory component has a liner relationship with cardiac parasympathetic activity. Other component ranging around 0.1Hz is related to Mayer wave of arterial blood pressure. They provide a quantitative index of autonomic nervous function.
The History of the evolutionary study of eusociality in Hymenoptera are briefly reviewed, and simultaneous evolution of sex ratio and worker behavior is studied. The importance of haplodiploid sex determination is corroborated by computer Simulation. It is also found that the sex ratio of the first brood is biassed by their mother towards the sex which has more worker than another sex. This fact suggests that mother control of sex ratio in first brood is important factor responsible for Hymenopteran society having no male worker.