Plasma amino acid profiles at various reproductive stages in female rats

We measured the plasma levels of amino acids at various reproductive stages in female rats, including the estrous cycle, pregnancy and lactation, and compared the resulting amino acid profiles using two- or three-dimensional figures. These figures revealed that the amino acid profiles of pregnant and lactating dams differed considerably from those during the estrous cycle or in male rats. The plasma levels of individual amino acids were almost the same between proestrus, estrus, metestrus and diestrus, and their profiles did not differ significantly. However, the amino acid profiles changed during pregnancy and lactation in dams. The plasma Ser level decreased significantly in mid and late pregnancy, whereas Tyr, Gly and His decreased significantly in the late and end stages of pregnancy, and Trp and Lys significantly decreased and increased at the end of pregnancy, respectively. Much larger changes in amino acid profiles were observed during lactation, when the levels of many amino acids increased significantly, and none showed a significant decrease. Plasma Pro, Ser and Gly levels increased continuously from day 1 until day 15 of lactation, whereas Asn and Met increased significantly from days 1 and 5 respectively until the end of lactation. These results suggest that the profiles of plasma amino acids show characteristic changes according to reproductive stage and that it may be necessary to consider such differences when performing amino acid-based diagnosis.     

Nursery soil cover influences germination of Thujopsis dolabrata var. hondai seeds

We examined the influence of nursery soil cover on germination of Thujopsis dolabrata var. hondai. Seeds were sown under seeding bed conditions: (1) nursery soil (andosol) without soil cover, (2) Kanuma pumice without soil cover, (3) nursery soil with nursery soil cover, and (4) nursery soil with sterilized sand cover. Germination percentages were compared between these conditions. The germination percentage (8.8%) at 10 weeks after sowing under condition 3 was significantly lower than under conditions 1, 2, and 4 (56.8%, 52.0%, and 47.2%, respectively). Of the nongerminated seeds under condition 3, 75.0% were decayed and several fungi were isolated from decayed seeds. An inoculation test of isolated fungi Cylindrocarpon tenue, Cylindrocarpon sp., Fusarium oxysporum, and Botrytis sp. to seeds showed that these fungi caused seed decay. Our results indicated that nursery soil cover may not be suitable for T. dolabrata var. hondai seeds sown in nursery soil because of seed decay by pathogens.     

Comparison of morphological and DNA-based techniques for stomach content analyses in juvenile chum salmon <Emphasis Type="Italic">Oncorhynchus keta</Emphasis>: a case study on diet richness of juvenile fishes

To identify the stomach contents of marine organisms, morphological observations are commonly conducted. However, the results obtained by this traditional method are frequently biased, as it is difficult to detect partially digested, soft-bodied organisms. To resolve this, recent studies have used DNA-based (DNA barcoding) analyses to examine the diet breadth of marine organisms. Here, we compared the prey richness of juvenile fishes using morphological observations and DNA-based analyses, with a focus on juvenile chum salmon Oncorhynchus keta. A higher number of prey taxa were successfully identified using DNA-based analyses than morphological observations. However, we also noticed several shortcomings of the DNA-based analyses, as reported in other diet-analysis studies that used molecular techniques. For example, the degree of digestion among prey taxa might have resulted in differential sensitivity to DNA detection. Additionally, several prey taxa could not be precisely identified, as the sequence data for some of the targeted organismal groups are unavailable in public gene databases. Remarkably, it is also possible that DNA-based analyses detected secondary prey, and therefore, the richness of prey taxa was likely overestimated. Thus, dietary analyses of juvenile fishes need to be carefully conducted, considering the respective advantages and disadvantages of DNA-based and morphological techniques.     

Seasonal Changes in Rigor Development and Flesh Texture of Wild Japanese Sea Bass (Lateolabrax japonicus)

The season for finding the firmest sashimi made from wild Japanese sea bass was investigated. Flesh rigor tension and contraction were measured by a “new” device with isometric (muscle length kept constant) and isotonic (balance beam moves freely) transducers. Both flesh rigor tension and contraction peaks appeared at the same postmortem times, with attainment of ultimate pH and adenosine triphosphate/inosine monophosphate ratio in four seasons. Seasonal seawater temperature correlated negatively to seasonal maximum rigor contraction and positively to seasonal flesh breaking strength at 72 h postmortem. After rigor peak tension attainment, the tension relaxation was much lower than that of other wild fish species, especially in summer. The sea bass muscle resisted structure disruption in rigor isometric tension generation. Wild sea bass sashimi was firmest in breaking strength in summer.     

The genetic diversities of 4 species of subg. Lithocerasus (Prunus, Rosaceae) revealed by RAPD analysis

RAPD analysis was applied to reveal the genetic diversities of 4 speciesof subg. Lithocerasus within the genus Prunus using 40accessions representing the subgenera Prunophora, Amygdalus,Lithocerasus and Cerasus. The accession of subg. Lithocerasus are phenotypically similar to members of subgenus Cerasus but different with them in interspecific crossing tests and isozymeprofiles. Two major clusters, `Prunophora and Amygdalus group' and `Cerasus group' were constructed in the phenogram. We revealthat the examined 4 species of subg. Lithocerasus species; P.tomentosa Thunb., P. japonica Thunb., P. glandulosa Thunb.and P. besseyi Bailey, were genetically closer to the members ofsubgenera Prunophora and Amygdalus than to subg. Cerasus.     

Antioxidant activity of peptides obtained from porcine myofibrillar proteins by protease treatment

Hydrolysates obtained from porcine myofibrillar proteins by protease treatment (papain or actinase E) exhibited high antioxidant activity in a linolenic acid peroxidation system induced by Fe(2+). Hydrolysates produced by both papain and actinase E showed higher activities at pH 7.1 than at pH 5.4. The antioxidant activity of the papain hydrolysate was almost the same as that of vitamin E at pH 7.0. These hydrolysates possessed 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and chelating activity toward metal ions. Antioxidant peptides were separated from the papain hydrolysate by ion exchange chromatography. The acidic fraction obtained by this method exhibited higher activity than the neutral or basic fractions. Antioxidant peptides in the acidic fraction were isolated by high-performance liquid chromatography on an ODS column and shown to possess the structures DSGVT, IEAEGE, DAQEKLE, EELDNALN, and VPSIDDQEELM. The DAQEKLE peptide showed the highest activity among these peptides.     

Combination of lipids and emulsifiers enhances the absorption of orally administered quercetin in rats

The effects of lipids, emulsifiers, and ethanol on the absorption of orally administered quercetin in rats were investigated for its efficient intestinal absorption. Rats were administered 150 micromol/kg quercetin in water supplemented with lipids and/or emulsifiers, or ethanol, and blood was collected from the tail for 6 h after administration. Co-administration of lipids such as lecithin and soybean oil or emulsifiers including sucrose fatty acid ester, polyglycerol fatty acid ester, and sodium taurocholate had no statistically significant effects on quercetin absorption, although these constituents rather increased the accumulation of conjugated forms of quercetin and those of isorhamnetin in rat plasma. However, the combination of lipids and emulsifiers enhanced the absorption of quercetin significantly. Thirty and fifty percent (v/v) of the ethanol in the vehicle raised the efficiency of quercetin absorption in a concentration-dependent manner. Quercetin absorption-enhancing effects of these constituents seemed to be affected by quercetin's solubility in respective vehicles used for the administration. Ethanol is not helpful for the effective absorption of quercetin, as a high concentration is required. In conclusion, a combination of lipids and emulsifiers is necessary for enhancing quercetin absorption.     

Differentiation-inducing effects of small fruit juices on HL-60 leukemic cells

Epidemiological studies indicate that high intakes of fruits and vegetables are associated with a reduced risk of cancer, and several plant-derived drugs have been developed in medical oncology. Since only a small part of the flora has been tested for any kind of bioactivity, we chose small fruits as sources of differentiation-inducing activity against HL-60 leukemic cells. We have prepared juices from various small fruits that grow mainly in the northern part of Japan. Screening of 43 samples indicated that juices of Actinidia polygama Maxim., Rosa rugosa Thunb., Vaccinium smallii A. Gray, and Sorbus sambucifolia Roem. strongly induced differentiation of HL-60 cells to monocyte/macrophage characteristics in a concentration-dependent manner as indicated by histochemical and biochemical examinations.     

Effect of intermittent drainage in reduction of methane emission from paddy soils in Hokkaido,northern Japan

ABSTRACT

Emission of methane (CH₄), a major greenhouse gas, from submerged paddy soils is generally reduced by introducing intermittent drainage in summer, which is a common water management in Japan. However, such a practice is not widely conducted in Hokkaido, a northern region in Japan, to prevent a possible reduction in rice grain yield caused by cold weather. Therefore, the effects of intermittent drainage on CH₄ emission and rice grain yield have not been investigated comprehensively in Hokkaido. In this study, we conducted a three-year field experiment in Hokkaido and measured CH₄ and nitrous oxide (N₂O) fluxes and rice grain yield to elucidate whether the reduction in CH₄ emission can be achieved in Hokkaido as well as other regions in Japan. Four experimental treatments, namely, two soil types [soils of light clay (LiC) and heavy clay (HC) textures] and two water management [continuous flood irrigation (CF), and intermittent drainage (ID)], were used, and CH₄ and N₂O fluxes were measured throughout the rice cultivation periods from 2016 to 2018. Cumulative CH₄ emissions in 2016 were markedly low, suggesting an initially low population of methanogens in the soils presumably due to no soil submergence or crop cultivation in the preceding years, which indicates a possible reduction in CH₄ emission by introducing paddy-upland crop rotation. Cumulative CH₄ emissions in the ID-LiC and ID-HC plots were 21–91% lower than those in the CF-LiC and CF-HC plots, respectively, whereas the cumulative N₂O emissions did not significantly differ between the different water managements. The amount of CH₄ emission reduction by the intermittent drainage was largest in 2018, with a comparatively long period of the first drainage for 12 days in summer. Rice grain yields did not significantly differ between the different water managements for the entire 3 years, although the percentage of well-formed rice grains was reduced by the intermittent drainage in 2018. These results suggest that CH₄ emission from paddy fields can be reduced with no decrease in rice grain yield by the intermittent drainage in Hokkaido. In particular, the first drainage for a long period in summer is expected to reduce CH₄ emission markedly.