P elements and P-M characteristics in natural populations of Drosophila melanogaster in the southernmost islands of Japan and in Taiwan.

In order to study P element dynamics in natural populations of Drosophila melanogaster, 126 isofemale lines were examined from seven of the southernmost islands of Japan (the Sakishima Islands) and from Taiwan. Gonadal dysgenesis (GD) tests showed large divergences in the P-M phenotypes (P inducing and P repressing abilities) between the island populations. The P-M characteristics of each population, however, had not greatly changed in the past 15 years. Their genomic P element profiles are highly similar, consisting mostly of full-size P and of KP elements. We found no clear relationship between phenotype and genomic P element composition.

Further genetic studies on the Katsunuma population of Drosophila melanogaster.

Changes in the genetic structure of the Katsunuma natural population of Drosophila melanogaster have been examined during the past 35 years. The frequency of recessive lethal genes on the second chromosome once increased from 15% to 30% in the early 1970s, then decreased to about 24% in the late 1970s, and thereafter showed no significant changes. Sterility genes, the frequency of which is always less than the lethals, showed a similar tendency. The SD (segregation distorter) mutant gene disappeared but some others such as rbl (reduced bristle) and bw (brown) persisted in the population. The frequency of inversion-carrying chromosomes gradually decreased in the period, such that the standard chromosome frequency in the second and third chromosomes increased from about 40% to more than 80%. Coincident with these frequency changes is the invasion of a transposable element P into the Katsunuma population. The P element should have invaded into Katsunuma in the late 1960s. It spread over the population apparently inducing deleterious mutations, causing the decrease in the allelism rate, and hence increasing the effective population size. Soon, however, most flies became resistant to the P element-mediated transposition as they began to harbor defective P elements. During the course of spreading, the P element must also have induced deleterious mutations on the polymorphic inversions, breaking up the heterotic gene complexes along the chromosomes, which probably caused the reduction in the frequency of inversion chromosomes. Temporal invasion of D. simulans, a sibling species of D. melanogaster, into Katsunuma occurred several times after 1978, and the species seems to have been settled since 1990. This, however, did not have any effect on the genetic structure of D. melanogaster population.

Genetic divergence and evolutionary relationships of the old and new world emberizidae.

Genetic differentiation and evolutionary relationships were surveyed on 12 species of the Old and seven species of the New World Emberizidae by allozyme electrophoresis of 20 loci. Genetic variability of the Emberizidae is similar to those of the other Passeriformes. The degree of genetic differentiation in the family were large among species of the genus Emberiza of the Old World, and also among genera of the New World Emberizidae. Evolutionary relationships of the Emberizidae based on these genetic distances differed considerably from those of previous publications on some points: (1) Emberiza tristrami, E. elegans, E. bruniceps and E. schoeniclus were genetically much diverged from the other Emberiza as a species of the same genus. (2) Some genetic distances between Emberiza were larger than distances between subfamilies of the New World Emberizidae. (3) Species of the Cardinarinae examined genetically, belonged to the Emberizinae of the New World. Genetic data did not support the current classification that the Old World buntings arose from the New World forms by recent colonization. Discussion was made on the evolution of the Old and New World Emberizidae from the genetic view point.

Effect of trapidil on prostacyclin generation of arterial wall.

Prostacyclin (PGI2) has been reported to be a labile but potent inhibitor of platelet aggregation and a powerful vasodilator. This paper reports the effect of trapidil on PGI2 generation in rat aorta by means of bioassay system. The aortic ring was incubated in 0.05 M Tris HCl buffer (pH 7.5) for 10 min. This incubation medium was added into human PRP, and then incubated at 37 degrees C for 2 min., and ADP was added. PGI2 activity was assayed by the inhibitory percentage of ADP induced platelet aggregation. When the aortic ring was incubated in a medium containing trapidil, PGI2 generation was accelerated. This acceleration was inhibited by pretreatment with indomethacin. Moreover, the aortas of rats intravenously injected with 30 mg/kg of trapidil were incubated in the same way, and PGI2 activity in the medium was estimated. More potent PGI2 activity was observed in the aortas of rat treated with trapidil compared with the controls. These results indicate that acceleration of PGI2 generation from aorta by trapidil is involved in the mode of action of this drug of thrombus formation.