Seasonal change in N<Subscript>2</Subscript>O flux from forest soils in a forest catchment in Japan

Temperate forest soils are one source of nitrous oxide (N₂O), which is an important greenhouse gas and the most important ozone-depleting substance. To clarify N₂O flux mechanisms in relation to soil temperature, moisture, and nitrification activity, we measured N₂O fluxes and net nitrification rates over 3 years at the lower (Japanese cedar) and upper (deciduous broad-leaved trees) parts of a hill slope in a small forest catchment in the northern Kanto region of Japan. The N₂O flux was measured by the closed-chamber technique every month, along with soil temperature and water-filled pore space (WFPS). At the lower slope, the N₂O flux increased with increasing soil temperature (r ² = 0.383, P < 0.01) owing to an increase in the nitrification rate. At the upper slope, no positive linear correlation of N₂O flux with soil temperature, WFPS, or nitrification rate was observed. The low N₂O flux at the upper slope during summer was caused by the low summertime WFPS there. We attributed the higher mean N₂O fluxes observed at the lower slope (median 2.36 μg N m⁻² h⁻¹) than at the upper slope (median 1.10 μg N m⁻² h⁻¹) to a high soil moisture during summer season in the surface soil of the lower slope.     

Daily age and food habits of Lateolabrax latus larvae and juveniles occurring in the innermost shallow waters of Uwajima Bay, Japan

ABSTRACT:   Daily age and food habits of Lateolabrax latus larvae and juveniles were investigated at two different habitats in Uwajima Bay, western Shikoku, Japan. In the shallow zone at Miura, which contained eelgrass beds, larvae occurred from January and were collected abundantly in March. The size, age, and hatch-date distributions suggested that late-hatched specimens stay longer than early-hatched specimens at this station. On the contrary, in the intertidal flats of the Kunomura River mouth larvae were rarely collected, but juveniles were collected in relative abundance from April. The distributions in the intertidal flats station suggested that specimens had migrated from another location and then resided in the intertidal flats. Spatial and temporal trophic variations increased remarkably with metamorphosis, and thus, the spatial differences in growth rate were considered in relation to the trophic diversity of prey items. Our results suggest that the nursery environment, nursery utilization pattern, and food habits of early life stages of L. latus show remarkable flexibility. From the similarity of these ecological aspects with L. japonicus , which is a closely related species, we suggest the important role of the interspecific competition to the realized niche difference between Lateolabrax congeners.     

3-(4-Hydroxyphenyl)propionic acid is involved in the biosynthesis of myricanol in Myrica rubra

There is little evidence concerning the biosynthetic pathways for cyclic diarylheptanoids. We previously demonstrated that the cyclic diarylheptanoids myricanol and myricanone were biologically synthesized from two molecules of 4-coumaric acid by the feeding of 4-[8,9-¹³C₂]coumaric acid to young shoots of Myrica rubra. In the present study, using a ¹³C-labeled compound, we revealed that two molecules of 3-(4-hydroxyphenyl)propionic acid could also be a biosynthetic precursor of myricanol in M. rubra. These results indicated that both 4-coumaric acid and its dihydro-derivative were incorporated into myricanol. Competitive feeding experiments with 4-[8,9-¹³C₂]coumaric acid and 3-(4-hydroxyphenyl)-[1-¹³C]propionic acid were performed in M. rubra to determine the preferential incorporation of these two precursors. ¹³C-NMR studies indicated that 3-(4-hydroxyphenyl)-[1-¹³C]propionic acid was preferentially incorporated into myricanol. The data provided evidence for a biosynthetic sequence originating from 4-coumaric acid and leading to myricanol, through 3-(4-hydroxyphenyl)propionic acid, in M. rubra.     

A radio transmission pH measurement system for continuous evaluation of fluid pH in the rumen of cows

We developed a novel wireless radio transmission pH measurement system to continuously monitor ruminal bottom pH in cows, and compared these measurements to pH values determined by a spot-sample method. The wireless system consists of a pH sensor, data measurement receiver, relay unit, and personal computer with special software. The bullet-shaped sensor can be easily administered orally via a catheter into the rumen, without surgery. The glass electrode, using a temperature compensation system, can detect the rumen fluid pH with high accuracy. The ruminal bottom pH in healthy rumen-fistulated cows was measured as 6.52 ± 0.18 by the wireless system and as 6.62 ± 0.20 by the spot-sample method; with a correlation between pH measurements using these different methods (n = 8, 24 samples, r = 0.952, P < 0.01). When measured serially in a cow fed a diet evoking rumen acidosis, the ruminal bottom pH decreased markedly following the morning feeding and then increased gradually by the next morning feeding. This wireless system is a ready-to-use tool for estimating circadian changes in ruminal bottom pH.     

3-Methylthiopropionic acid ethyl ester, isolated from Katsura-uri (Japanese pickling melon, Cucumis melo var. conomon), enhanced differentiation in human colon cancer cells

The fully ripened fruit of Katsura-uri Japanese pickling melon ( Cucumis melo var. conomon) has rarely been used for food because the midripened fruit is utilized for making pickles, but the fully ripened fruit is no longer valuable for pickles due to the fruit body being too soft. We have considered the utilization of the fully ripened Katsura-uri fruit that may be used for nonpickling products, particularly if the fully ripened fruit demonstrated health benefits such as anticarcinogenic properties. The phytochemical extract from the fully ripened fruit of Katsura-uri Japanese pickling melon was purified via a bioassay-guided fractionation scheme, which was based on the induction of differentiation in a RCM-1 human colon cancer cell line. On the criteria of two differentiation markers (duct formation and alkaline phosphatase activity), the most potent fraction contained a compound identified as 3-methylthiopropionic acid ethyl ester, based on GC retention time, EI-MS, (1)H NMR, and (13)C NMR spectra. Previously, the role of 3-methylthiopropionic acid ethyl ester was considered as an odor producing compound in many fruits, but this study indicates potential medical benefits of this compound.     

Molecular epidemiology of VapA-positive Rhodococcus equi in thoroughbred horses in Kagoshima,Japan

The prevalence of virulent R. equi having 15- to 17-kDa antigens (VapA) in fecal isolates from 13 thoroughbred foals and their dams on 5 farms in Kagoshima, Japan, and the plasmid profiles of VapA-positive isolates by restriction fragment digestion patterns were investigated to compare the genotypic variation among virulence plasmids of R. equi isolates from Japan. In total, 218 (24.6%) of 886 isolates from the feces of the 13 foals and 13 (12.5%) of 104 isolates from the feces of their dams demonstrated VapA-positive R. equi. Plasmid DNA preparations of 231 virulent isolates from foals and dams were analyzed by restriction enzyme digestion with endonucleases EcoRI, EcoT22I and HindIII and were divided into 3 types: 172 isolates contained a 90-kb type I plasmid, 57 contained a 90-kb type III plasmid and 2 contained a 90-kb type IV plasmid. This study demonstrates a geographic character in the distribution of virulence plasmids found in VapA-positive isolates from thoroughbred foals in Kagoshima.