No increase in sister-chromatid exchange frequency in lymphocytes of chromium platers

To detect mutagenic effects of hexavalent chromium (Cr) in vivo, sister-chromatid exchange (SCE) frequency was analyzed in lymphocytes of 24 Cr platers occupationally exposed to hexavalent Cr and 24 matched controls. There were no significant differences in SCE frequency between the two groups. Smokers, both Cr platers and controls, had a significantly higher SCE frequency than non-smokers.     

Comparative leaf morphology of young sporophytes of rheophyticOsmunda lancea and drylandO. japonica

Field and morphological observations were made of the young sporophytes of rheophyticOsmunda lancea and its related drylandO. japonica, and the rheophyte's adaptation in the early sporophytic stages was discussed. Mature plants ofO. lancea andO. japonica do not occur in dryland and rheophytic habitats, respectively, but their very young sporophytes rarely grow there. The young sporophytes ofO. lancea differ considerably from those ofO. japonica in having the relatively short petioles with thin-walled epidermal cells, early lamina partition, cuneate leaf- and pinna-base, oblique (not horizontal) lamina disposition, a fine network of spongy tissue in the 4th and older leaves, and dense epicuticular wax deposits on leaf epidermis. They seem to relate to the flexibility of petioles and the toughness and flood-tolerance of blades, and make the young sporophytes adapted to the rheophytic habitat.Osmunda japonica lacking those characteristics disappears from the rheophytic habitat during the early ontogenetic stages.     

Endosymbionts in paramecium

Paramecium species are extremely valuable organisms to enable experiments for the reestablishment of endosymbiosis. This is investigated in two different systems, the first with Paramecium caudatum and the endonuclear symbiotic bacterium Holospora species. Although most endosymbiotic bacteria cannot grow outside the host cell as a result of their reduced genome size, Holospora species can maintain their infectivity for a limited time. We found that an 89-kDa periplasmic protein has an important function for Holospora's invasion into the target nucleus, and that Holospora alters the host gene expression; the host thereby acquires resistance against various stresses. The second system is the symbiosis between P. bursaria and symbiotic Chlorella. Alga-free P. bursaria and the algae retain the ability to grow without a partner. Consequently, endosymbiosis between the aposymbiotic host cells and the symbiotic algae can be reestablished easily by mixing them. We now found four checkpoints for the reestablishment of the endosymbiosis between P. bursaria and the algae. The findings in the two systems provide excellent opportunities for us to elucidate not only infection processes but also to assess the associations leading to eukaryotic cell evolution. This paper summarizes recent progresses on reestablishment of the primary and the secondary endosymbiosis in Paramecium.     

The presence of cytokine (IL-8, IL-1alpha,IL-1beta)-producing cells in inflamed gingival tissue from a patient manifesting Papillon-Lefevre syndrome(PLS)

The point of this study was to examine the presence or absence of cytokine-positive cells by means of immunohistochemical methods in the samples of inflamed gingival tissues obtained from an 11-year-old girl with Papillon-Lefevre syndrome (PLS). Interleukin-8 (IL-8)-positive cells were found to be present. In addition, IL-1alpha-and IL-1beta-positive cells were detected. No dysfunction in the phagocytosis and the bacterial killing of peripheral blood polymorphonuclear neutrophils (PMNs) was observed in this patient. Our findings suggest that these cytokines may be members responsible for modulating the process of rapidly progressive periodontitis for patient with PLS.     

Ontogenetic changes of habitat selection and thyroid hormone levels in black rockfish (Sebastes schlegelii) reared in captivity

This study examined the ontogenetic change in vertical distribution associated with algae and the thyroid hormone profiles of black rockfish (Sebastes schlegelii) under rearing conditions. Experimental observations on distribution were carried on black rockfish from the newly born larval stage to juveniles 75 days after birth (DAB). Position was categorized by vertical location [upper layer, mid layer and lower layer (LL)] and by association with artificial algae (floating algae, bottom algae and no association). Position of fish was observed four times a day, at 0400 (dawn), 1200 (noon), 1800 (dusk) and 2400 (midnight) hours. The majority of fish (>80%) reached transforming larval stage [17.8 ± 0.7 mm total length (TL)] at 25 DAB and juvenile stage (24.3 ± 0.6 mm TL) at 35 DAB. Newly born larvae were mainly distributed at surface and middle layers, the shift of vertical distribution to the LL occurred between 10 and 25 DAB, and over 98% of the individuals were distributed near the bottom after 35 DAB. Association behavior with algae was first observed from 20 to 30 DAB depending on the time of day. Percentage of fish associated with bottom algae increased from 25 to 40 DAB and reached 50–70% thereafter. Thyroid hormone (T₄) showed two surges at 30 and 50 DAB. The first surge corresponded to the transforming larval stage and the occurrence of association behavior with algae. The results indicate that pelagic larvae settle to the bottom layer before metamorphosis, and association behavior with algae appears at the transforming larval stage. A high T₄ concentration at 30 DAB indicates a close relationship with these morphological and behavioral developments.