Nationwide surveillance of salmonella in the faeces of pigs in Japan

The prevalence of faecal carriage of salmonella in 5393 pigs reared on 218 pig farms located in 31 of 47 prefectures in Japan over the period July 2003 to June 2005 was investigated. We isolated 172 strains belonging to 20 serovars and one untypable Salmonella enterica from 169 pig faecal samples (3.1%) collected from 48 farms (22.0%). The most prevalent type of S. enterica was untypable O4,12:d:- which lacks phase 2 flagellar antigen, representing 29.1% (50/172) of all isolates. Of 26 S. enterica serovar Typhimurium isolates, 16 strains appeared to be definitive phage type 104 (DT104) by polymerase chain reaction.     

Detection of Ehrlichia muris DNA from sika deer (Cervus nippon yesoensis) in Hokkaido, Japan

Ehrlichia muris DNA was detected in the blood of sika deer (Cervus nippon yesoensis) by species-specific PCR based on the citrate synthase gene, which was shown to be more sensitive than species-specific PCR based on the 16S rRNA gene. Among 102 deer examined, one deer was positive. Deer may be a possible mammalian reservoir of E. muris.     

Changes in soil chemical and physical characteristics in Japanese cypress (Chamaecyparis obtusa Endl.) stands by mixture of deciduous broad-leaved trees in the northern Kanto region of Japan

In order to clarify the effects of a mixture of deciduous broad-leaved trees on soil fertility, we investigated litter biomass accumulation, mineral soil chemical and physical characteristics, characteristics of nitrogen mineralization, and the mutual relationships between them in Japanese cypress (Chamaecyparis obtusa) stands mixed with deciduous broad-leaved trees at different ratios (mixture ratio; MR = 0, 16, 33, 43, 100% by basal area) in the northern Kanto region of Japan. Litter biomass in the forest floor and mineral soil was 19.1 Mg ha⁻¹ in MR 0% and decreased approximately 60 % in MR 33%, MR 43% and MR100%. The permeability at 0–5 cm soil depth in MR100% was twice as much as that in MR 0%. Increases in soil permeability were likely due to larger soil pores in the higher MR with much accumulated deciduous broad-leaves. At 0–5 cm soil depth, the differences in carbon concentration among the plots were not clear. On the other hand, carbon concentrations at 5–10 cm depth increased from 90 g kg⁻¹ to 147 g kg⁻¹ with increases in MR from 0% to 100%. Concentrations of exchangeable bases increased two to four times with increases in MR from 0 to 100% at 0–10 cm depth. Soil pH (H₂O) generally increased with increases in MR at each depth. The rates of net nitrogen mineralization at 0–5 cm depthin vitro increased from 25 to 87 mg kg⁻¹ 2 weeks⁻¹ with increases in MR from 0 to 100%. However, increases in nitrification with increases in MR were not clear compared with nitrogen mineralization. These results indicated that a mixture of deciduous broad-leaved trees in a Japanese cypress stand was effective in preventing soil fertility decline. This study was supported by a grant from the Showa Shell Sekiyu Fundation for Promotion of Environmental Research. A part of this study was presented at the 7th International Congress of Ecology (1998).     

Comparison of organic matter dynamics in soil between Japanese cedar (Cryptomeria japonica) forest and adjacent Japanese red pine (Pinus densiflora) forest established on flatland

In order to clarify the effects of tree species on organic matter dynamics in soil, we investigated the amount of forest floor material, leaf litter decomposition rate, soil chemical characteristics, soil respiration rate and cellulose decomposition rate in a Japanese cedar forest (cedar plot) and an adjacent Japanese red pine forest (pine plot) established on a flatland. The amount of forest floor material in the cedar plot was 34.5 Mg ha⁻¹ which was greater than that in the pine plot. Because the leaf litter decomposition rate was higher in the pine plot than in the cedar plot, it is likely that the difference in the amount of forest floor material between the plots is caused by the difference in the leaf litter decomposition rate. The C concentrations of soil in the cedar plot were 1.2–2.1 times higher than those in the pine plot. Soil pH(H₂O)s in the cedar plot were significantly higher than those in the pine plot. The soil respiration rates and the rates of mineralized C in the cedar plot byin vitro incubation were higher than those in the pine plot. From this result, it is assumed that soil organic matter in the cedar plot was decomposed relatively faster compared with the pine plot. Furthermore, microbial activities, which were reflected as cellulose decomposition rates in the cedar plot, were higher than those in the pine plot. A part of this paper was presented at the 109th Annual Meeting of the Japanese Forestry Society (1998).     

Kidney leucocytes of rainbow trout, Oncorhynchus mykiss, are activated by intraperitoneal injection of beta-endorphin.

The immunomodulatory effects of beta-endorphin were studied by measurements of the production of superoxide anion, phagocytosis and chemotaxis of kidney phagocytic cells in rainbow trout, Oncorhynchus mykiss. The production of superoxide anion in phagocytic cells increased significantly in rainbow trout injected with chum salmon beta-endorphin. The responses were dose-dependent. The phagocytosis and chemotaxis also significantly increased in kidney phagocytic cells of rainbow trout injected with alpha-endorphin. These results show that beta-endorphin in rainbow trout activates the function of phagocytic cells in vivo.     

In vitro fertilization and cortical granule distribution of bovine oocytes having heterogeneous ooplasm with dark clusters.

In vitro maturation, fertilization and subsequent development of oocytes with homogeneous (category 1), or heterogeneous ooplasm (category 2) were investigated. No significant differences were observed in the nuclear maturation and total fertilization rates between the two categories. However, category 2 oocytes showed a higher normal fertilization rate due to their lower incidence of polyspermy as compared to category 1 oocytes. Electron microscopic study revealed that all category 2 oocytes had cortical granules lined up next to the plasma membrane, and that some category 1 oocytes still had small clusters of cortical granules after maturation. Although the proportion of cleaved zygotes was higher in category 2, the percentages of cleaved zygotes that developed to the blastocyst stage did not differ between the two categories. These results demonstrate that oocytes with heterogeneous ooplasm have a higher capacity for normal fertilization due to the reduction in polyspermy. This can be attributed to the normal distribution of cortical granules in category 2 oocytes after maturation.     

Effects of feed restriction and cold exposure on glucose metabolism in response to feeding and insulin in sheep.

The effects of feed restriction, cold exposure, and the initiation of feeding on blood glucose metabolism, other blood metabolites, hormones, and tissue responsiveness and sensitivity to insulin were measured in sheep. The sheep consumed orchardgrass hay ad libitum (AL) or were restricted to 82% of the ME requirement for maintenance (RE) and were exposed to a thermoneutral (20 degrees C) or a cold environment (2 degrees C). An isotope dilution method and a glucose clamp approach were applied to determine blood glucose metabolism and insulin action, respectively. Plasma NEFA and insulin concentrations were influenced by feed restriction. Concentrations of plasma glucose, NEFA, insulin, and glucagon were influenced by cold exposure. Plasma NEFA concentration for RE decreased after the initiation of feeding and plasma insulin concentration increased transiently for all treatments. [U-13C]Glucose was continuously infused for 8 or 7 h after a priming injection starting 3 h before the initiation of either feeding or insulin infusion, respectively. When responses to feeding were studied, blood glucose turnover rate was less (P < .001) for RE than for AL, and it was greater (P < .001) during cold exposure than in the thermoneutral environment. The rate changed little after the initiation of feeding. For the glucose clamp approach, insulin was infused over four sequential 1-h periods at rates from .64 to 10 mU x kg BW(-1) x min(-1), with concomitant glucose infusion to maintain preinfusion plasma glucose concentrations. The rates of glucose infusion and blood glucose turnover increased (P < .001) dose-dependently with insulin infusion rate. The maximal glucose infusion rate was greater (P < .05) for RE than for AL and was greater (P < .001) during cold exposure than in the thermoneutral environment. The plasma insulin concentration at half-maximal glucose infusion rate was lower (P < .1) during cold exposure. Blood glucose turnover rate tended to be greater (P = .10) for RE than for AL, and it was greater (P < .001) during cold exposure than in the thermoneutral environment. The ratio of endogenous production to utilization of glucose was suppressed by insulin infusion. In sheep fed a roughage diet, blood glucose turnover rate seems to be influenced by both intake level and environmental temperature, but not by the act of feeding. Moreover, the action of insulin on glucose metabolism is enhanced during cold exposure, and the effect of feed restriction is somewhat enhanced.     

Wireless monitoring of blood glucose levels in flatfish with a needle biosensor

A wireless biosensor system was developed for the continuous measurement of blood glucose levels in flatfish. The biosensor was implanted in the interstitial fluid under the scleral surface of the eyeball (EISF) to investigate the relationship between EISF and blood glucose levels. EISF glucose levels were found to be correlated with those in the blood and to be approximately the same as blood glucose levels in the range of 7–25 mg dl⁻¹. A needle-type biosensor was prepared for the continuous EISF glucose monitoring in flatfish. A working electrode was constructed using platinum iridium wire, and glucose oxidase was immobilized to the electrode. The biosensor was inserted into the EISF of flatfish for sensor implantation. A 650-mV potential (vs. Ag/AgCl) was applied by a wireless potentiostat to the working electrode for the amperometric glucose measurement. We investigated whether glucose in the EISF can be determined in vivo. The estimated glucose levels using a one-point calibration method were correlated with actual blood glucose levels. In conclusion, using a wireless biosensor system, we were able to monitor blood glucose levels in flatfish under free-swimming conditions for 16 h.     

Photosensitivity in mice caused by pyropheophorbide in the midgut gland of the scallop <Emphasis Type="Italic">Patinopecten yessoensis</Emphasis> observed in diarrhetic shellfish poisoning mouse bioassays

Photosensitivity was observed in the mice used in bioassays of diarrhetic shellfish poisoning. The mice were intraperitoneally injected with the extracts from the midgut glands of cultured scallops Patinopecten yessoensis gathered in early spring in Funka Bay, Hokkaido, Japan. The injections induced atypical symptoms in the mice within 24 h. The symptoms included piloerection, substantial eye discharge, swelling of the ears and head, and ear scratching. They were similar to those reported in studies of photosensitivity caused by pyropheophorbide in the midgut glands of abalones, which are herbivorous gastropods. The problematic scallops also accumulated a large amount of pyropheophorbide-a. The amount determined with high-performance liquid chromatography was 300–530 μg per 1 g of the homogenate of the midgut glands. The dose of pyropheophorbide sufficient to cause photosensitivity in a mouse is estimated to be 0.99–2.3 mg per mouse with 20-g body weight. Moreover, comparative tests in mice showed that the onset of the symptoms required light and a substantial amount of pyropheophorbide. Therefore, we determined that the observed symptoms were photosensitivity caused by pyropheophorbide. Scallops, which are suspension-feeding bivalves, can accumulate a large amount of pyropheophorbide in the midgut glands depending on the habitat environment.