Difference in the stable nitrogen isotope ratio of Sargassum piluliferum (Phaeophyceae: Fucales) associated with fish and pearl oyster aquaculture facilities

In order to estimate the nitrogen loading from fish aquaculture facilities, we studied the nitrogen and carbon stable isotope ratios (δ¹⁵N and δ¹³C, respectively) in the brown macroalga Sargassum piluliferum and small amphipod crustaceans Caprella spp., both of which are lower trophic level biota found at fish and pearl oyster aquaculture facilities situated along the eastern coast of the Uwa Sea, Japan. This coastal region is one of the least populated areas along the Japanese coast. The mean concentrations of chlorophyll a, dissolved inorganic nitrogen, dissolved inorganic phosphate, and dissolved silicate-Si were 1.5- to 2-fold higher in samples from the fish aquaculture facilities than in those from the pearl oyster aquaculture facilities, indicating that the fish aquaculture facilities were associated with nitrogen loading. The δ¹⁵N abundance level in S. piluliferum collected from the fish aquaculture facilities was significantly higher (1.3‰) than that in macroalga collected at the pearl oyster aquaculture facilities, whereas that in Caprella spp., primary consumers, was only slightly higher (0.3‰). The feeding style of Caprella spp., which depends on suspended particulate organic matter and attached microalgae, is considered to the primary causal factor for the lack of a significant difference in δ¹⁵N abundance level between the two types of aquaculture facilities. Based on these results, we conclude that S. piluliferum found in close proximity of aquaculture facilities is a suitable organism for monitoring nitrogen loading from fish aquaculture facilities, through the analysis of δ¹⁵N.     

The effects of selective logging on stand structure and the regeneration of subboreal forests in Hokkaido, northern Japan

We investigated the effects of selective logging on stand structure and regeneration in selectively logged subboreal forests in Taisetsuzan National Park in Hokkaido in northern Japan. The basal area decreased and the size structure of trees altered in the stands studied due to repeated, intense selective logging, in which larger trees were cut down as a priority. Sapling density in the stands was much lower than that in primary forests. In the simple and multiple regression analyses that were used to estimate the effects of selective logging on sapling density, sapling density had a significant positive correlation with tree density and had little correlation with the density of logged stumps or the height ofSasa (dwarf bamboo) growing on the forest floor. These results suggest that the establishment sites around canopy trees influenced the establishment of saplings, rather than the gaps caused by selective logging. However, both the coefficient of determination and the standardized partial regression coefficient of multiple regression analysis were higher for the stand with a dense cover ofSasa than for the stand with a sparse cover ofSasa. Thus, the success of regenerating forests with selective logging depends on both the site of advanced regeneration and the light conditions that regulate growth.     

Changes in nitrogen metabolism in rice seedlings infected with Piricularia oryzae cavara

Blast disease is one of the biggest diseases of rice plant in Japan. For example, in 1953, the total area of damage by blast disease was about 160 × 10⁴ hectare and the decreased yield of rice Was about 67.5 × 10⁴ ton in Japan. There have been many studies on blast disease for a long time. Tanaka and Katsuki (7)studied the relation between environmental conditions and blast disease. They always used adult healthy rice plants as plant materials and have not analysed the plants damaged by blast fungus directly. They suggested the presence of growth-promoting factors of blast funngus especially in susceptible rice varieties. Tamari and Kaji (5, 6) suggested that the blast fungus produced some effective toxic substances which might cause the disease. Suzuki, Doi and Toyoda (4) continued to study the mechanism of rice blast resistance and they have proposed 3 phases of resistance. They are (a) resistance and environtmental factors, (b) resistance and host camponents and (c) relation of host variety to fungus race.     

Quantitative structure-activity studies of substituted benzyl chrysanthemates: 2. Physicochemical substituent effects and neurophysiological and symptomatic activities against American cockroaches

The substituent effects on the symptomatic and neurophysiological activities of a number of substituted benzyl (1R)-trans-chrysanthemates against American cockroaches were quantitatively analyzed using electronic, hydrophobic, and steric parameters. The effects were shown to be highly specific to substituent positions except for those on the neuroblocking activity. Steric effect of substituents represented by van der Waals volume was found to play the most significant role in determining the variation in each activity. Peculiar substituent effects depending upon the bulkiness and position of substituents, which had been observed in the toxicity of this class of compounds, can be rationalized by the present analysis indicating that the optimum van der Waals volume of substituents is largest at the ortho and smallest at the para position.     

Changes in the Expression Patterns of the Genes Involved in the Segregation and Function of Inner Cell Mass and Trophectoderm Lineages During Porcine Preimplantation Development

In mouse embryos, segregation of the inner cell mass (ICM) and trophectoderm (TE) lineages is regulated by genes, such as OCT-4, CDX2 and TEAD4. However, the molecular mechanisms that regulate the segregation of the ICM and TE lineages in porcine embryos remain unknown. To obtain insights regarding the segregation of the ICM and TE lineages in porcine embryos, we examined the mRNA expression patterns of candidate genes, OCT-4, CDX2, TEAD4, GATA3, NANOG, FGF4, FGFR1-IIIc and FGFR2-IIIc, in blastocyst and elongated stage embryos. In blastocyst embryos, the expression levels of OCT-4, FGF4 and FGFR1-IIIc were significantly higher in the ICM than in the TE, while the CDX2, TEAD4 and GATA3 levels did not differ between the ICM and TE. The expression ratio of CDX2 to OCT-4 (CDX2/OCT-4) also did not differ between the ICM and TE at the blastocyst stage. In elongated embryos, OCT-4, NANOG, FGF4 and FGFR1-IIIc were abundantly expressed in the embryo disc (ED; ICM lineage), but their expression levels were very low in the TE. In contrast, the CDX2, TEAD4 and GATA3 levels were significantly higher in the TE than in the ED. In addition, the CDX2/OCT-4 ratio was markedly higher in the TE than in the ED. We demonstrated that differences in the expression levels of OCT-4, CDX2, TEAD4, GATA3, NANOG, FGF4, FGFR1-IIIc and FGFR2-IIIc genes between ICM and TE lineages cells become more clear during development from porcine blastocyst to elongated embryos, which indicates the possibility that in porcine embryos, functions of ICM and TE lineage cells depend on these gene expressions proceed as transition from blastocyst to elongated stage.