Phylogenetic Relationships Among Microsporidia Based on rDNA Sequence Data, With Particular Reference to Fish-Infecting Microsporidium Balbiani 1884 Species.

Recently, large discrepancies have been identified between microsporidian systematics based on molecular and traditional characteristics. In the current study the 530f-580r region of the rRNA gene of eight microsporidian species was cloned and sequenced. Included were two unclassified species of Microsporidium Balbiani, 1884 and an unidentified microsporidian that infects the musculature of different sea bream species. Sequence identities in excess of 98% indicated that these three species almost certainly are members of the same genus. Phylogenetic analyses of all microsporidian sequence data available for this region of the gene (20 species) and for partial small subunit sequences (51 species of 21 genera) revealed these species to be distinct from the family Pleistophoridae Doflein, 1901 and closely related them to the genus Sproguea Weissenberg, 1976. This clade was found to comprise a sister taxon to that containing the vast majority of fish-infecting species. Broad cladistic divisions were found between terrestrial insect-infecting and fish-infecting species, which together are distant from the aquatic insect-infecting microsporidia. The rRNA gene of certain fish-infecting genera was found to be more highly conserved than previously reported. This has implications for its utility in diagnostic assays and phylogenetic studies at, or close to, the species level.     

Six polymorphic microsatellite loci in the Japanese Spanish mackerel,Scomberomorus niphonius

Six polymorphic microsatellite loci were isolated for genetic structure studies of the Japanese Spanish mackerel, Scomberomorus niphonius, a severely exploited marine fish species. The number of observed alleles for each locus ranged from seven to 41, and the values of expected and observed heterozygosities were 0.546–0.946 and 0.602–1.000, respectively. These microsatellite markers should prove to be a useful tool for estimating the population genetic structure and genetic variability of Japanese Spanish mackerel.     

DEFORMATION MOVEMENT INDUCED BY DIVALENT IONOPHORE A23187 IN THE TUBIFEX EGG

Deformation movement (groove-forming activity of the equatorial surface) was induced in the spherical Tubifex egg by treatment with ionophore A23187 (5–10 μg/ml). The degree of induced movement was maximal when the treatment was commenced at the beginning of the round stages, i.e. , immediately after disappearance of the grooves formed in the preceding normal deformation movement; it gradually decreased as the onset of the treatment was delayed. This induction was independent of either external Ca²⁺ or Mg²+. Ultrastructural examination of eggs undergoing the induced movement revealed the presence of organized microfilaments in the cortical layer of the grooving regions. It is assumed that the absence of contractile activity during the round stages of the Tubifex egg is attributed basically to the low availability of intracellularly stored Ca²⁺. The results also suggest that the distribution and/or the amount of the contractile elements change during these stages.     

Morphological responses of Daphnia ambigua to different concentrations of a chemical extract from Chaoborus flavicans

1. Daphnia ambigua were reared individually with eight different concentrations of a chemical extract from larvae of Chaohorus flavicans, and the frequency of appearance of helmeted individuals and the helmet sizes were determined in the instars 1–6. 2. The animals developed most marked helmets in the second instar in response to the extract. The frequency of the helmeted individuals and helmet size in the second instar increased with increasing chemical concentration, although their dose-response curves differed between them. 3. The results may explain the cyclomorphosis of Daphnia, which develop the highest helmets in summer, when the predators are abundant and active, and the concentrations of the predator-released chemicals would presumably be high. 4. The extract became toxic to Daphnia at the highest concentration prepared.     

Assessment of the methane mitigation potentials of alternative water regimes in rice fields using a process‐based biogeochemistry model

Rice production is a substantial source of atmospheric CH₄, which is second only to CO₂ as a contributor to global warming. Since CH₄ is produced in anaerobic soil environments, water management is expected to be a practical measure to mitigate CH₄ emissions. In this study, we used a process‐based biogeochemistry model (DNDC‐Rice) to assess the CH₄ mitigation potentials of alternative water regimes (AWR) for rice fields at a regional scale. Before regional application, we tested DNDC‐Rice using site‐scale data from three rice fields in Japan with different water regimes. The observed CH₄ emissions were reduced by drainage of the fields, but were enhanced by organic amendments. DNDC‐Rice gave acceptable predictions of variation in daily CH₄ fluxes and seasonal CH₄ emissions due to changes in the water regime. For regional application, we constructed a GIS database at a 1 × 1 km mesh scale that contained data on rice field area, soil properties, daily weather, and farming management of each cell in the mesh, covering 3.2% of the rice fields in Japan's Hokkaido region. We ran DNDC‐Rice to simulate CH₄ emissions under five simulated water regimes: the conventional water regime and four AWR scenarios with gradually increasing drainage. We found that AWR can reduce CH₄ emission by up to 41% compared with the emission under conventional water regime. Including the changes in CO₂ and nitrous oxide emissions, potential mitigation of greenhouse gas (GHG) was 2.6 Mg CO₂ Eq. ha^?1 yr^?1. If this estimate is expanded to Japan's total rice fields, expected GHG mitigation is 4.3 Tg CO₂ Eq. yr^?1, which accounts for 0.32% of total GHG emissions from Japan. For a reliable national‐scale assessment, however, databases on soil, weather, and farming management must be constructed at a national scale, as these factors are widely variable between regions in Japan.     

Movements of Mitochondria Associated with Isolated Egg Cortex

Cortical tragments of Tubifex eggs undergoing ooplasmic segregation were isolated in plastic dishes with an oil droplet separating part of them from the dish. Except at the edges of fragments and at the base of the oil droplet, the nearly entire area of the cortex was firmly attached to the plastic surface. Many mitochondria were associated with the cortical actin lattice. On addition of ATP to the preparations, only nonadhering portions of the cortex exhibited contractions. At the base of oil droplets, some mitochondria moved in the same direction concurrently with cortical contractions. Contractile activities of isolated cortices were completely inhibited by their preincubation with N-ethylmaleimide-modified heavy meromyosin, suggesting the involvement of an actomyosin force-generating mechanism in the cortical contractions during ooplasmic segregation.     

Maternal and paternal effects on the germination time of non‐dormant seeds of a monocarpic perennial species,Aster kantoensis (Compositae)

In plant species producing non‐dormant seeds, the germination time (from the start of imbibition to radicle emergence) is the main factor determining the timing of seedling emergence. We investigated maternal and paternal genetic effects on the germination time of non‐dormant seeds of a monocarpic perennial, Aster kantoensis Kitamura (Compositae). Three sets of reciprocal diallel crosses among five plants were conducted to produce genetic variation in seeds, and the germination time of the progeny of each parent was determined. The effects of the maternal parent and the interaction of maternal and paternal parents on the germination time of progeny were significant in all sets, and the effect of the paternal parent was significant in two of the three sets. This result means that the germination time of the progeny of a maternal or paternal parent can vary with the genotype of its mating partners. Because variation in the emergence time of seedlings contributes to avoiding seedling loss owing to unpredictable environmental changes, genetic variation in the germination time among the progeny of each parent mating with multiple partners could contribute to the establishment of the parent's seedlings in species producing non‐dormant seeds in the field.     

Detection of Enterotoxin in Faeces and Anti-enterotoxin in Serum after Clostridium perfringens Food-poisoning

Two outbreaks of Clostridium perfringens food-poisoning involving the same person were investigated. In the first, typical symptoms with diarrhoea and abdominal pain were observed. In the second, there were no classical signs of food-poisoning; the victim felt some flatulence and the faeces had a pasty appearance and an unpleasant smell. Counterimmunoelectrophoresis and the reversed passive haemagglutination test were rapid and reliable assay methods for enterotoxin in faeces. In the first outbreak, 13–16 μg enterotoxin/g faeces were detected, and 3–4 μg/g in the second. The detection of enterotoxin in faeces indicates the potential use of enterotoxin tests on diarrhoeal samples for diagnosing C. perfringens food-poisoning. No enterotoxin was detected in serum during the acute stage of the illness, but the antibody titre showed a considerable rise in the first two months after the food-poisoning outbreak.     

β-Lactoglobulin Suppresses Melanogenesis in Cultured Human Melanocytes

The effects of whey proteins from bovine milk on melanogenesis in cultured human melanocytes were examined. Among the major protein components of milk whey including β-lactoglobulin (BLG), α-lactalbumin, serum albumin, and IgG, only BLG exhibited the depigmenting effect at a concentration of 1 mg/ml. Also, BLG suppressed the activity of tyrosinase in these cells. Retinol, to which BLG is known to bind, slightly increased the pigmentation of the cells at concentrations in the range of 1–100 nM, and retinoic acid, a metabolite of retinol, exhibited a strong pigmentation-promoting effect within the same concentration range. Treatment of the cells with 1 mg/ml BLG completely abrogated the pigmentation induced by these A vitamins. These results demonstrate a novel biological activity of BLG and suggest that this activity is dependent on its ability to bind retinol.