Complex constitutive nature of Japanese upland rice, Oryza sativa L.

Two rice ecotypes, the so-called lowland and upland populations, which carry different isozyme genotypes mostly at a single locus, are cultivated in Japan. The aim of this study was to examine the origin and the mechanism for keeping these genetic differences. The upland population is cultivated in upland fields and carries a different allele for a particular isozyme gene, Pgd-1, which has never been found in the lowland population. RFLP markers showed a weak trend for genetic differentiation between the two ecotypes. On the other hand, morphological, and physiological traits showed marked differences between the two ecotypes. Furthermore, based on the genotypic difference, two Japonica subgroups are defined in the upland population. Subgroup I is the minor group and carries key lowland characters, including the genotype for PGD. Subgroup II carries different traits and the genotype for PGD of the alternative subgroup. As an allelic difference for Pgd-1 is known to occur between the two ecospecies, Tropical (Tr) and Temperate (Tm) Japonicas, upland cultivars can be classified by diagnostic characters which distinguish a variety into Tr or Tm type. The upland population consists of three types of cultivars, Tr-, Tm- and intermediate-type. In contrast, the lowland population consists of a uniform Tm type Japonicas. As Japanese upland cultivars still have an isozyme allele specific to the Tr type, the upland population has a rather complex constitution which is presumably now being introgressed by lowland genetic material, but still represents a major difference at some genetic levels. Upland rice carries several stress-resistant genes which would be useful for lowland rice breeding. The genetic difference would be efficient for tagging upland specific traits by upland specific genetic markers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Human hypertension caused by mutations in WNK kinases

Hypertension is a major public health problem of largely unknown cause. Here, we identify two genes causing pseudohypoaldosteronism type II, a Mendelian trait featuring hypertension, increased renal salt reabsorption, and impaired K+ and H+ excretion. Both genes encode members of the WNK family of serine-threonine kinases. Disease-causing mutations in WNK1 are large intronic deletions that increase WNK1 expression. The mutations in WNK4 are missense, which cluster in a short, highly conserved segment of the encoded protein. Both proteins localize to the distal nephron, a kidney segment involved in salt, K+, and pH homeostasis. WNK1 is cytoplasmic, whereas WNK4 localizes to tight junctions. The WNK kinases and their associated signaling pathway(s) may offer new targets for the development of antihypertensive drugs.     

Gigantic photoresponse in 1/4-filled-band organic salt (EDO-TTF)2PF6

We report that the organic salt (EDO-TTF)2PF6 with 3/4-filled-band (1/4-filled in terms of holes), which forms an organic metal with strong electron and lattice correlation, shows a highly sensitive response to photoexcitation. An ultrafast, photoinduced phase transition from the insulator phase to the metal phase can be induced with very weak excitation intensity at near room temperature. This response makes the material attractive for applications in switching devices with room-temperature operation. The observed photo-induced spectroscopic change shows that this photoinduced phase transition process is caused by the cooperative melting of charge ordering assisted by coherent phonon generation.     

Effects of stratification and misspecification of covariates on species distribution models for abundance estimation from virtual line transect survey data

The aim of this study was to examine the effects of stratification of the survey region on the performance of species distribution models (SDMs) described by generalized linear models or generalized additive models when estimating school abundance by using a line transect survey. True covariates that define spatial school distribution are not always obtainable explanatory variables. When the true covariates differ from explanatory variables in the model, the explanatory variables are determined to be misspecified. We evaluated the performance of SDMs in abundance estimation with misspecified covariates by using dummy datasets for which the true abundance was known. Simulated replicates of spatial distributions of a whale school and sighting data were generated from possible scenarios motivated by the spatial school distribution of Antarctic minke whales Balaenoptera bonaerensis. This distribution was obtained from the Japanese Whale Research Program under Special Permit in the Antarctic. Our results showed that the relative bias of the abundance estimators was large when covariates were misspecified and a survey region was stratified. Although stratification of the survey region is intended to produce a conventional line transect estimator with a smaller variance than that of non-stratified survey region, it also acts to increase the bias of the abundance estimate obtained from SDMs.     

Behavior of histamine-producing bacteria in shimesaba, raw mackerel salted and marinated in vinegar during processing and storage at various temperatures

To study the behavior of histamine-producing bacteria during the processing and storage of shimesaba, we inoculated histamine-producing bacteria into raw mackerel and then evaluated bacterial counts and histamine content at each shimesaba processing step. Six histamine-producing bacteria—Morganella morganii, Enterobacter aerogenes, Raoultella planticola, Photobacterium damselae (2 strains), and Photobacterium phosphoreum—were inoculated onto the surface of mackerel fillets at various cell densities (no inoculation, 10⁴, and 10⁷ cfu ml^?1). The fillets were then treated according to the common procedure used for processing shimesaba. The concentration of NaCl in brine during the salting procedure was 10 % (w/v), and the main ingredients of the marinade broth were 27 % vinegar, 3.8 % sucrose, 0.3 % sodium glutamate, and 0.1 % sodium succinate. The level of histamine-producing bacteria and of histamine did not increase during the salting and marinating procedures. However, during the storage tests, histamine content increased remarkably in the shimesaba products stored at 10 °C for 3 days, and organoleptical degradation was also observed. However, significant deterioration, based on bacterial count, histamine content, and organoleptic evaluation, was not observed in samples stored at 5 °C. These results indicate that the use of traditional marinade broth during the processing of shimesaba and storage below 5 °C are effective methods for preventing histamine accumulation.     

Nutritional evaluation of live food organisms and commercial dry feeds used for seed production of amberjack Seriola dumerili

To improve the nutritional quality of live foods and dry feeds ordinarily used for the seed production of amberjack Seriola dumerili, the nutrient contents of rotifers, Artemia nauplii and commercial feeds used in two larval production stations were evaluated. For comparison of the nutrient contents, artificially produced larvae, wild-caught juveniles and wild zooplankton samples were also analyzed. The proportions of 22∶6n-3 in the polar lipid of the cultured larvae increased by feeding the dry feeds. The taurine contents of the cultured larvae reflected the contents of their foods (rotifers<dry feed<Artemia nauplii). The taurine content and the proportion of 22∶6n-3 in Acartia spp. were higher than in foods fed to the larvae. These parameters in the wild juveniles were higher than the cultured ones. The A/E ratios [(each essential amino acid/total essential amino acids)×1000] of the total amino acids of the live foods and dry feeds were similar to those of the cultured larvae, except for the lower ratios of histidine, arginine, threonine and lysine in the live foods. The mucosal folds of the intestine of the cultured larvae did not show typical signs of dietary phospholipid deficiency. These results suggest that requirements of nutrients such as 22∶6n-3 and taurine should be determined for mass production of amberjack seeds.     

Role of small-scale fishing in Kompong Thom Province, Cambodia

ABSTRACT:   Household surveys of small-scale fishing were conducted in Svay Ear and Srey Rangit villages in Kompong Thom Province, Cambodia. Data were collected from 104 of 183 households and 105 of 140 households in Svay Ear and Srey Rangit, respectively. In both villages, almost all households conducted rice cultivation and approximately 75% of them also conducted fishing. Three fishing groups: (i) inside lake; (ii) around lake; and (iii) around village were observed in both villages, according to their main fishing grounds. The inside lake group conduct fishing only in Tonle Sap Lake which is located 30 km away from the villages. The around lake group fish in lakes, marshes and flooded forests adjacent to Tonle Sap Lake, which are more than 5 km from the villages. The around village group collects fish from rice fields and ponds located inside the villages and also in some streams, rivers and lakes adjacent to the villages. The distance to the fishing grounds is less than 5 km from the villages. Most fishing groups were the inside and around lake groups, which occupied 76.0 and 65.7% of Svay Ear and Srey Rangit, respectively. These two groups produced 80.6 and 69.7% of the respective village annual total fish catches. These two groups sold a large portion of their fish catches. Although previous reports indicated that small-scale fishing is for subsistence, present results indicated that small-scale fishing was commercially conducted and fishing was important as an income source.     

Bacterial community composition shifts in sediments influenced by fish feeds

This study investigated the influence of fish feed deposition on the microbial community of sediments in a coastal lake. Microcosms were designed to simulate the addition of fish feeds to the sediment, and physicochemical factors as well as composition of microbial assemblages were analysed. Although total organic carbon and total organic nitrogen did not significantly increase, redox potential and total sulphides showed a transition of sediment environments into anaerobic condition due to the addition of fish feeds. The bacterial community composition shifted with fish feed deposition as revealed by the band profiles of denaturing gradient gel electrophoresis, Sørensen's similarity indices and cell numbers of sulphate‐reducing bacteria. Occurrence of anaerobic bacteria (sulphate and nitrate reducers) and disappearance of strictly aerobic bacteria were observed with fish feed inputs. The results clarify the succession of the microbial flora and suggest negative impact of uneaten fish feeds on the microbial community in sediment and resultant environmental deterioration of fish‐farming areas.