Mitosis in Beating Cardiac Muscle Cells from Newt Embryos In Vitro

Cardiac muscle cells from newt embryos were cultured at relatively low cell density. Within 10 days in culture, 2 cell types (spindle and flat type) were distinguished both among beating and non-beating cells. Mitosis in single beating cells was frequently observed both in spindle and flat cells. Some cells maintained almost constant contractile activities throughout the mitotic stages, while the others transiently stopped beating during mitosis, which accords well to the case in chick embryos (1). Ultra-thin section shows the presence of myofibril's structure in a dividing cell, as shown in newborn rats (2, 3, 4), chick embryos (1, 5, 6, 7) and adult newts (8, 9). As a consequence of mitosis, 3 types (spindle, flat and mixed type) of beating colonies developed after 34 weeks in culture. Cell proliferation was accompanied with pulsation and could be directly pursued till the 4th division, suggesting that differentiated myocardiac cells with myofibrils proliferate by their mitoses in vivo , maintaining rhythmic contraction.     

First records of Microptila Ris (Trichoptera: Hydroptilidae) from Japan, with description of a new species

Microptila orienthula , sp. n. from Japan is described and illustrated based on adults of both sexes. The new species represents the first finding of Microptila in the Eastern Palaearctic Region, and it appears to be more closely related to Oriental species of Microptila than to the two Western Palaearctic species. The finding of a new species with affinities to the Oriental species as far northeast as Japan is noteworthy but fits well with general zoogeographical affinities of the Japanese fauna to the Oriental Region. The type locality indicates a hygropetric habitat for the larva, in agreement with the known larval habitat of the European type species Microptila minutissima Ris, 1897.     

Seemingly maladaptive refraining from infanticidal probing at the third parasitism attack by the semi-solitary parasitoid Echthrodelphax fairchildii （Hymenoptera： Dryinidae）

We assessed the adaptiveness of refraining from infanticidal probing at the third attack under triple parasitism in the parasitoid Echthrodelphaxfairchildii Perkins, by comparing fitness returns from the third attack with and without probing. Fitness returns were assessed in terms of the survival rate, mean developmental time, and mean adult head width of the progenies. Not probing was maladaptive under triple parasitism with oviposition intervals of 1/24 and 24/24 hours （where the numbers before and after the slash refer to the first-to-second and second-to-third oviposition intervals, respectively）, although no significant difference was detected in fitness returns for oviposition intervals of 24/1 hours. We suggest that the cost of probing （especially the decrease in the chance of future ovipositions） is a reason for the seemingly maladaptive absence of probing.     

Dysplastic Melanocytic Nevi Contain High Levels of Pheomelanin: Quantitative Comparison of Pheomelanin/Eumelanin Levels Between Normal Skin,Common Nevi,and Dysplastic Nevi

The degree and type of melanogenesis, i.e., either eumelanin of pheomelanin, has been shown to be a reliable marker for the differentiation of the melanocyte. If exposed to UV light, these two melanins were reported to behave differently; eumelanin was photoprotective whereas pheomelanin was phototoxic to cultured tumor cells. Our previous study indicated that dysplastic melanocytic nevus (DMN) undergoes altered melanogenesis, forming pheomelanosome-like granules. The present study examined chemically the type and degree of melanin synthesized in 31 melanocytic nevi excised from 27 patients as compared with that occurring in the surrounding normal skin. The tissue content of eumelanin and pheomelanin was expressed by the amounts of pyrrole-2,3,5-tricarboxylic acid (PTCA) and aminohydroxyphenylalanine (AHP), respectively. We found that DMN lesions contain significantly higher amounts of pheomelanin than either common melanocytic nevus (CMN) or normal skin. Differences in pheomelanin content between DMN and CMN could not be accounted for by inherently higher levels of pheomelanin within the skin in general from DMN patients. Our present finding substantiates our previous claim that epidermal melanocytes in DMN undergo deranged melanogenesis.