Influence of saltwater wedges on irrigation water near a river estuary

Paddy and Water Environment - Paddy fields irrigated using water from the Shinkawa River in Niigata, Japan, are subject to adverse effects associated with the occurrence of saltwater wedges in the...     

Effects of epilactose on calcium absorption and serum lipid metabolism in rats

Epilactose (4-O-beta-galactopyranosyl-D-mannnose) is a rare disaccharide in cow milk that can be synthesized from lactose by the cellobiose 2-epimerase of Ruminococcus albus. In this study, we examined the biological activities of epilactose using male Wistar-ST rats. The apparent rates of calcium and magnesium absorption of rats fed epilactose and fructooligosaccharide diets were greater than those fed control and lactose diets, accompanied by greater weight gain of the cecal wall and higher levels of short-chain fatty acids and other organic acids. Epilactose also increased the calcium absorption in everted small intestinal sacs. In addition, the levels of plasma total cholesterol and nonhigh-density lipoprotein cholesterol were lower in epilactose-fed rats. These results indicate that epilactose promotes calcium absorption in the small intestine and possibly lowers the risk of arteriosclerosis. Cecal microbes may efficiently utilize epilactose and contribute to these biological activities.     

Mortality of the short-neck clam <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis> induced by the toxic dinoflagellate <Emphasis Type="Italic">Heterocapsa circularisquama</Emphasis>

Mortality of the short-neck clam Ruditapes philippinarum exposed to the toxic dinoflagellate Heterocapsa circularisquama was studied under controlled conditions to clarify the mechanisms of recurrent mass deaths of clams occurring in western Japanese coastal areas. One-week mortality tests, involving three water temperatures, six H. circularisquama concentrations, and two clam body sizes, showed a significant increase in mortality with increasing temperature, H. circularisquama concentration, exposure duration, and body size (ANOVA, P < 0.01). Clam death was observed at concentrations as low as 50 cells/ml and temperatures as low as 15°C. Prior to death, clams showed an extreme retraction of their mantle edge and siphon, along with recurrent vomiting behavior before initiating a closure reaction followed by paralysis then death. Gills of paralyzed clams showed an important uptake of dye, implying gill damage. This study is the first laboratory evidence of bivalve mortality induced by H. circularisquama at low concentrations and low temperature, and the first report of differential effects according to the body size of bivalves.     

Spatial variation of quantitative color traits in green and black types of sea cucumber <Emphasis Type="Italic">Apostichopus japonicus</Emphasis> (Stichopodidae) using image processing

It has been suggested that the Japanese sea cucumber, Apostichopus japonicus, has three color types (red, green, and black), although the qualitative difference between the color types, particularly between the green and black types, is unclear because of continuous color variation among color types. This study elucidated the color variation between green and black types using image processing (RGB, red–green–blue system) and multivariate analysis to demonstrate whether or not the black and green types can be quantitatively classified. Moreover, spatial variation of the RGB value among various local sites was clarified to estimate potential environmental factors that may affect the color variation. The series of analyses revealed that a quantitative boundary between green and black types could be provisionally established, and also that spatial variability in the intermediate (continuous) color trait between green and black types was significant. Potential environmental factors (depth and industrial activity index) were correlated with the color traits in both color types. These results suggest that the green and black types cannot be regarded as independent color traits and that the color variation between green and black types may be influenced by local environmental factors.     

Amylopectin Staling of Cooked Milled Rices and Properties of Amylopectin and Amylose

Starches of waxy rices that showed varietal differences in hardness testing of cooked rice after amylopectin staling and high-amylose content (AC) rices differing in gel consistency (GC) and starch gelatinization temperature (GT) were studied to determine the factors related to varietal differences in amylopectin staling of cooked rice. Intermediate- and high-GT starches showed greater amylopectin staling of gelatinized rice by hardness testing values or differential scanning calorimetry (DSC) endotherm than did low-GT starches in both waxy and nonwaxy rices. Isoamylase-debranched amylopectins of waxy rices differed in the ratio of weight-average degree of polymerization (DP_w) fractions, but these fraction ratios were not simply related to differences in amylopectin staling of cooked rice. Among high-AC rices, amylopectin from low-GT starch was confirmed to have higher iodine affinity (2.3–2.5%) than amylopectin from intermediate-GT starches (1.7–1.8%), regardless of GC. Within high-AC starch of the same GT type, soft-GC rice corresponded with more A + B₁ DP_w 16–18 and less B₃ DP_w 150–200 fractions of debranched amylopectin and low DP_w of amylose. Amylopectin of amylose extender mutant of IR36 was confirmed to have a longer chain length than ordinary rice amylopectin: the debranched amylopectin has more B₂ DP_w 47–51 fraction, less A + B₁ DP_w fraction, but no B₄ fraction with DP_w > 200. Only high-AC amylopectin had debranched fraction with DP_w >120.     

Development of late-bolting F<Subscript>1</Subscript> hybrids of Chinese cabbage (<Emphasis Type="Italic">Brassica rapa</Emphasis> L.) allowing early spring cultivation without heating

We developed new F₁ hybrids of Chinese cabbage (Brassica rapa L. ssp. pekinensis) that allow cultivation earlier in spring without heating by introducing extremely late-bolting alleles at two homologs of the flowering repressor Flowering Locus C (BrFLC2 and BrFLC3) from non-heading ‘Leafy Green Parental Line No. 2’. These new F₁ hybrids were produced by the following four steps. First, the extremely late bolting selected lines were developed. These selected lines headed in spring after overwintering cultivation, whereas the conventional F₁ cultivars flowered. Secondly, an investigation of the three plantings showed that our F₁ hybrids formed heads when seeds were sown from mid-February to early March, whereas the conventional F₁ cultivar did not form heads because of premature bolting. Thirdly, we identified some F₁ hybrids with extremely late bolting during early spring cultivation in an investigation of many F₁ hybrids. Finally, based on an investigation across four cold regions for 2 years, we compared the commercialization rate, defined as the proportion of plants greater than 2000 g in weight and with a flowering stalk less than 10 cm long. Then we identified a F₁ of MS02 × 12-04 which had a high commercialization rate on average (92%), whereas the rates of three conventional F₁ cultivars were only 0–2%. In the near future, these F₁ hybrids will be valuable late-bolting cultivars despite climate change, permitting stable cultivation and harvest over wide regions.     

Influence of Water Temperature on Morphological Deformities in Cultured Larvae of Japanese Eel,Anguilla japonica,at Completion of Yolk Resorption

The occurrence of morphological deformities under different rearing water temperatures (18, 20, 22, 24, 26, 28, and 30 C) was examined in Japanese eel larvae. The rates of hatching and survival until yolk resorption at 22–26 C were higher than those at other water temperatures. Fertilized eggs never hatched at 18 and 30 C. The rates of occurrence of abnormal larvae reared at the water temperatures 24–28 C were lower than those at 20 or 22 C. Pericardial edema and lower jaw deformities occurred most frequently at lower temperatures (20 and 22 C). In contrast, the incubation temperature did not significantly affect the relative frequency of some neurocranial deformities and of spinal curvature. These results imply that the optimal temperatures for rearing Japanese eel eggs and embryos are 24–26 C from the viewpoints of survival and deformity.     

Multiplication of low and high cell culture passaged strains of transmissible gastroenteritis virus in organs of newborn piglets

Distribution and persistence of four different strains of transmissible gastroenteritis (TGE) virus in newborn piglets were compared.The piglets inoculated with high-passaged TO-163 strain did not show any clinical signs of TGE on any days postinoculation (DPI), but the piglets inoculated with one of the other three strains, SH-14, SH-164 or TO-16, had soft feces or diarrhea. In the latter cases, the virus was isolated mainly from respiratory organs, lymph nodes, and digestive tract on any DPI, but was rarely detected in the digestive tract of piglets inoculated with the TO-163 strain. The frequency of virus recovery from the tissues was the highest till 4 DPI in all of the piglets inoculated with one of the four virus strains, and it was markedly reduced thereafter in the piglets inoculated with high-passaged strains.The TO-163 strain was subjected to serial passage in newborn piglets for seven passages. There was no evidence of regained pathogenicity with advance in passage, and detection of virus was restricted to lymph nodes and lung of these piglets.In gnotobiotic piglets inoculated with the TO-163 strain, frequent virus recovery and high titers of virus from the tissues were obtained on up to the 4th DPI. The viruses in high titer were found in the digestive tract of some of the piglets; however, none of them showed any clinical signs of TGE.     

Abundance and composition of ammonia oxidizers in response to degradation of root cap cells of rice in soil microcosms

Purpose

Nitrification is a key process in the global nitrogen cycle, of which the first and rate-limiting step is catalyzed by ammonia monooxygenase. Root cap cells are one of substrates for microorganisms that thrive in the rhizosphere. The degradation of root cap cells brings about nitrification following ammonification of organic nitrogen derived from the root cap cells. This study was designed to gain insights into the response of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) to mineralized N from root cap cells and the composition of active bacterial and archaeal ammonia oxidizers in rice soil.

Materials and methods

Rice callus cells were used as a model for root cap cells, and unlabelled (¹²C) and ¹³C-labelled callus cells were allowed to decompose in aerobic soil microcosms. Real-time quantitative polymerase chain reaction (PCR), DNA-based stable isotope probing (SIP), and denaturing gradient gel electrophoresis (DGGE) were applied to determine the copy number of bacterial and archaeal amoA genes and the composition of active AOB and AOA.

Results and discussion

The growth of AOB was significantly stimulated by the addition of callus cells compared with the growth of AOA with a much lesser extent. AOB communities assimilated ¹³C derived from the callus cells, whereas no AOA communities grew on ¹³C-callus. Sequencing of the DGGE bands in the SIP experiments revealed that the AOB communities belonging to Nitrosospira spp. dominated microbial ammonia oxidation with rice callus amendment in soil.

Conclusions

The present study suggests that root cap cells of rice significantly stimulated the growth of AOB, and the active members dominating microbial ammonia oxidation belonged to Nitrosospira spp. in rice rhizosphere.