Comparison of the color vision and spectral sensitivity of three flatfish species of different ecotypes,and application to selective fishing methods

In this study, we determined the color vision and spectral sensitivity of pointhead flounder, slime flounder, and red halibut by recording electrophysiological S-potentials from isolated retinas; this basic data was collected to aid the selection of appropriate colors and effective wavelengths for selective fishing gear for sustainable fisheries. Four kinds of L-response and one C-response were recorded in the pointhead flounder and red halibut. Two kinds of L-response were recorded in the slime flounder. The occurrence of a C-response indicates the possession of color vision. The C-responses show that the pointhead flounder has superior distinction from blue to yellow, and red halibut has superior distinction from blue and green to red. The most frequently recorded L-responses indicate high spectral sensitivity at 544 nm in pointhead flounder and 518 nm in slime flounder and red halibut. All recorded L- and C-responses indicate sensitivity to ultraviolet wavelengths.     

Symbiotic efficiency and compatibility of native rhizobia in northern Thailand with different soybean cultivars

Symbiotic efficiency and compatibility of 81 isolates of native bradyrhizobia from irrigated areas in northern Thailand with four soybean cultivars and one cowpea cultivar were evaluated under laboratory conditions. Effectiveness and / or compatibility of the tested isolates were compared with those of a standard strain (Bradyrhizobium japonicum CB 1809) by using plants grown on plastic seed bags. Effectiveness of the isolates was also estimated using uninoculated control plants grown in a nitrogen-free solution. Nodulation of a wide range of host plants by the majority of the tested isolates was observed, which agreed well with the results of our previous field experiment (Shutsrirung et al. 2002: Soil Sci. Plant Nutr., 48, 491–499). Up to 75% of the tested isolates induced a higher growth efficiency than that of the uninoculated control in association with one of the tested cultivars, Black soybean. Comparision with uninoculated control plants, enable to estimate the proportion of the tested isolates leading to effective growth promotion (E + e) of each cultivar, namely, Black soybean (local Thai cultivar), 75%; Cowpea, 82%; SJ5 (commercial Thai cultivar), 33%; Bragg (US cultivar), 33%; and Improved Pelican (US cultivar), 9%. These results indicated that although isolates with a high infectiveness with both “Asian-type” and “US-type” soybeans could be found, a high frequency of isolates leading to inefficient nodules was observed in the US cultivar, suggesting the presence of genetic differences in the soybean cultivars that express high-preference (efficient nodules) or low-preference (inefficient nodules) for a certain group of tested isolates. Based on the results of this laboratory experiment together with our previous field experiment, native rhizobial populations in the irrigated area of northern Thailand could be separated into three groups; Group 1: rhizobium strains showing a high effectiveness with only Asian cultivars, Group 2: strains showing a high effectiveness with only US origin cultivars, and Group 3: strains showing a high effectiveness with both Asian and US origin cultivars. The majority of the native rhizobial populations belonged to Group 1. The isolates in Group 3 may display a high potential for manipulating useful rhizobial inoculant.     

Community structure of bacteria on different types of mineral particles in a sandy soil

Various types of mineral particles in a soil probably provide different microenvironments for microorganisms. The purpose of this study is to investigate whether different types of mineral in a soil harbor different bacterial populations. DNA was extracted from five types (quartz, feldspar, pyroxene, magnetite, iron-coated reddish brown particles) of sand-size mineral particles separated from a sandy soil, and was amplified for partial 16 S rRNA gene by polymerase chain reaction (PCR). Twenty-nine to 69 amplicons per each type of mineral were cloned and sequenced, followed by phylogenetic affiliation of the sequences. As a result, some types of bacteria were detected on all of the types of mineral including the orders Rhizobiales, Bacillales, and Acidobacteriales. In the case of Acidobacteriales, higher percentages were found on magnetite and quartz. Some taxa were restricted to specific types of mineral; the class Actinobacteria was found on pyroxene but not on quartz, and rarely on magnetite and feldspar. Bacterial diversity at the order level estimated by Chao1 value was higher in feldspar and pyroxene than the other three types of mineral. The UniFrac Significance test indicated that the differences in bacterial communitiy structures among the particles were suggestive except that between feldspar and pyroxene. These results support the idea that different communities of bacteria were associated with each of the mineral types.     

Decreased expression of p63, a regulator of epidermal stem cells, in the chronic laminitic equine hoof

Reasons for performing study: Abnormal epidermal stem cell regulation may contribute to the pathogenesis of equine chronic laminitis. Objective: To analyse the involvement of p63, a regulator of epidermal stem cell proliferative potential, in chronic laminitis. Methods: Epidermal tissues from skin, coronet and lamellae of the dorsal foot were harvested from 5 horses with chronic laminitis and 5 control horses. Tissues were analysed using histopathology, immunofluorescence microscopy and quantitative immunoblotting Results: Hoof lamellae of laminitic horses had a lower frequency of p63 positive cells than control lamellae, particularly in the distal region. Quantitative immunoblotting confirmed reduced p63 expression in the laminitic distal lamellar region. The decreased p63 expression in laminitic epidermal lamellae was most apparent in the abaxial region adjacent to the hoof wall and highly associated with the formation of terminally differentiated, dysplastic and hyperkeratotic epidermis in this region, whereas lamellae from control horses maintained high p63 expression throughout the axial‐abaxial axis. Conclusions: Expression of p63 in equine skin resembles that reported in other species, including man and rodents, suggesting that p63 can serve as a marker for the proliferative potential of equine epidermal stem cells. p63 expression was significantly lower in the chronic laminitic hoof than in that of control horses, suggesting laminitic hoof epithelium has more limited proliferative potential with a shift towards differentiation. This may reflect reduced activity of epidermal stem cells in laminitic hoof. It is proposed that p63 contributes to the maintenance of hoof lamellae and that misregulation of p63 expression may lead to epidermal dysplasia during lamellar wedge formation. Potential relevance: This study suggests that loss of epidermal stem cells contributes to the pathogenesis of equine laminitis. Autologous transplantation of p63‐positive epidermal stem cells from unaffected regions may have regenerative therapeutic potential for laminitic horses.     

Glucose uptake activity in murine red blood cells infected with Babesia microti and Babesia rodhaini

The glucose uptake activity in Babesia rodhaini and B. microti - infected red blood cell (IRBC) was investigated in mice using 2-deoxy-D-glucose (2DOG) and L-glucose (L-Glc), a non-metabolizable analogue of D-glucose and non-incorporative glucose to non-infected RBC (NRBC), respectively. The uptake activities of both DOG and L-Glc were higher in IRBCs than those in NRBC. The concentration dependent uptake of 2DOG and L-Glc in both IRBC revealed a linear curve, indicating non-transporter mediated uptake. In addition, B. microti IRBC showed higher 2DOG uptake than B. rodhaini IRBC, whereas no difference was observed in L-Glc uptake. These results indicated that some new glucose uptake system, at least two systems, developed in both IRBC. The new systems were sodium independent, non-competitive to L-Glc, and sensitive to temperature. One of two systems had no kinetical difference between B. rodhaini and B. microti IRBC, however another one might have higher uptake activity in B. microti IRBC compared to that in B. rodhaini IRBC.     

Temporal shifts in diversity and quantity of nirS and nirK in a rice paddy field soil

Denitrification is an important part of the nitrogen cycle in the environment, and diverse bacteria, archaea, and fungi are known to have denitrifying ability. Rice paddy field soils have been known to have strong denitrifying activity, but the microbes responsible for denitrification in rice paddy field soils are not well known. Present study analyzed the diversity and quantity of the nitrite reductase genes (nirS and nirK) in a rice paddy field soil, sampled four times in one rice-growing season. Clone library analyses suggested that the denitrifier community composition varied over sampling time. Although many clones were distantly related to the known NirS or NirK, some clones were related to the NirS from Burkholderiales and Rhodocyclales bacteria, and some were related to the NirK from Rhizobiales bacteria. These denitrifiers may play an important role in denitrification in the rice paddy field soil. The quantitative PCR results showed that nirK was more abundant than nirS in all soil samples, but the nirK/nirS ratio decreased after water logging. These results suggest that both diversity and quantity changed over time in the rice paddy field soil, in response to the soil condition.     

Nitrification and nitrifying microbial communities in forest soils

How nitrogen (N) cycling is regulated and how environmental change affects it are major study questions in forest ecology, because N availability often limits the primary production of plants in many forest ecosystems. These are being extensively highlighted because of growing concerns regarding chronic and elevated N deposition in forest ecosystems on a global scale. Until now, N cycling has been mainly documented in association with various environmental factors other than microbial communities. However, with the recent rapid development in culture-independent molecular-based techniques, microbial ecologists have discovered that alterations in N cycling are highly associated with alternations in microbial communities through changes in either resource supplies or processing rates. In this review, we describe nitrification as a key N cycling process and present general approaches to associate the nitrification process with the nitrifying community in forest soils. Furthermore, we briefly summarize currently available information about the relationship between the process and nitrifying community dynamics in soil. We suppose that linking N cycling processes with microbial community dynamics provides a deeper insight into the mechanisms regulating N cycling in forest ecosystems.     

Difference in light perception capability and spectral response between juveniles and sub-adults of the whiteleg shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> as determined by electroretinogram

In this study, we determined light perception capability in juveniles and sub-adults of L. vannamei by means of electroretinogram (ERG) measurements. Eyes were assumed to be dark-adapted when the response magnitude had stabilized after 70–80 min under dark conditions. ERG responses elicited by mono-wavelength (336–694 nm) stimuli of equal intensity were determined in individual dark-adapted specimens. Relative spectral response curves determined from the amplitudes of on and off relative responses were found to be significantly different in juveniles and sub-adults. Both maximum on relative spectral response magnitudes were observed at 544 nm, but the on relative spectral response magnitudes of sub-adults to 518 nm were higher than for juveniles, and the on relative spectral response magnitudes of sub-adults to 568 nm were lower than for juveniles. The on and off relative spectral response curves of juveniles were steeper than those of sub-adults, while the on relative spectral response magnitude of juveniles was lower than that of sub-adults from 336 to 544 nm. The off relative spectral response magnitude of juveniles was higher than that of sub-adults from 518 to 597 nm.