A 90-day Feeding Toxicity Study of l-Serine in Male and Female Fischer 344 Rats

A subchronic feeding study of l-serine (l-Ser) was conducted with groups of 10 male and 10 female Fischer 344 rats fed a powder diet containing 0, 0.06, 0.5, 1.5 or 5.0% concentrations of l-Ser for 90 days. There were no toxicologically significant, treatment-related changes with regards to body weight, food intake, water intake or urinalysis data. In several of the hematology, serum biochemistry and organ weight parameters, significant changes were observed between some of the treated groups and the controls. All these changes, however, were subtle and lacked any corresponding pathological findings. In addition, the increased or decreased values remained within the range of the historical control values. In fact, histopathological assessment revealed only sporadic and/or spontaneous lesions. In conclusion, the no-observed-adverse-effect-level (NOAEL) for l-Ser was, therefore, determined to be at least a dietary dose of 5.0% (2765.0 mg/kg body weight/day for males and 2905.1 mg/kg body weight/day for females) under the present experimental conditions.     

Effect of soil solarization on subsequent nitrification activity at elevated temperatures

Soil solarization is a nonchemical method of soil disinfection achieved by covering the soil surface with sheets of vinyl plastic to generate elevated soil temperature, generally over 45°C. Such elevated temperatures may be detrimental to some nitrifying microorganisms and favorable to others. However, little information exists to indicate how nitrification activity in soil is affected after solarization. We performed several experiments to investigate the effects of soil solarization on nitrification activity. We found that: (1) if a soil was subjected to pretreatment of 45 or 50°C for as little as 1 d, nitrification activity in a subsequent incubation at 30°C was less than that of a soil that did not receive any high-temperature pretreatment. However, if a soil received pretreatments of 45 or 50°C for more than 7 d, nitrification activity in a subsequent incubation at 45 or 50°C was greater than that of soil that did not receive high temperature pretreatment. (2) Nitrification activity in three kinds of soil taken from 0–5 cm depth after solarization treatment was greater at 45°C than 30°C. (3) Nitrification activity at 45°C in soil that had received solarization in the preceding year was greater than that in soil that had not been subjected to solarization. This was consistent with the fact that the population densities of ammonia oxidizers were greater in soils that had been subjected to solarization. These results suggest that soil solarization induces nitrifying microorganisms that are more active at 45–50°C than they are at 30°C, and that the effect of solarization on nitrification persists until the next crop season.     

Colonization of Pythium oligandrum in the tomato rhizosphere for biological control of bacterial wilt disease analyzed by real-time PCR and confocal laser-scanning microscopy

It recently has been reported that the non-plant-pathogenic oomycete Pythium oligandrum suppresses bacterial wilt caused by Ralstonia solanacearum in tomato. As one approach to determine disease-suppressive mechanisms of action, we analyzed the colonization of P. oligandrum in rhizospheres of tomato using real-time polymerase chain reaction (PCR) and confocal laser-scanning microscopy. The real-time PCR specifically quantified P. oligandrum in the tomato rhizosphere that is reliable over a range of 0.1 pg to 1 ng of P. oligandrum DNA from 25 mg dry weight of soil. Rhizosphere populations of P. oligandrum from tomato grown for 3 weeks in both unsterilized and sterilized field soils similarly increased with the initial application of at least 5 x 10(5) oospores per plant. Confocal microscopic observation also showed that hyphal development was frequent on the root surface and some hyphae penetrated into root epidermis. However, rhizosphere population dynamics after transplanting into sterilized soil showed that the P. oligandrum population decreased with time after transplanting, particularly at the root tips, indicating that this biocontrol fungus is rhizosphere competent but does not actively spread along roots. Protection over the long term from root-infecting pathogens does not seem to involve direct competition. However, sparse rhizosphere colonization of P. oligandrum reduced the bacterial wilt as well as more extensive colonization, which did not reduce the rhizosphere population of R. solanacearum. These results suggest that competition for infection sites and nutrients in rhizosphere is not the primary biocontrol mechanism of bacterial wilt by P. oligandrum.     

Serotypes and antimicrobial susceptibility of Pseudomonas aeruginosa strains isolated from diseased dogs

Strains of Pseudomonas aeruginosa isolated from diseased dogs in Tokyo area during 1983 through 1986 were serotyped and assayed for antimicrobial susceptibility to obtain an epizootiological aspect of canine P. aeruginosa infection. Major sources of specimens were ear and nasal discharges and urine. The results of O-antigen typing using a monoclonal antibody kit showed that the most predominant serotype was type M. Types G and B were also major serotypes. In a yearly distribution of serotypes, type I was almost limited in 1986, and was isolated mainly from surgical wounds, which showed an episode of nosocomial infection, whereas that of type M or B was dispersed during 4 years from 1983 to 1986. As a result of antimicrobial susceptibility test, most canine strains were considered to be susceptible to 4 drugs, which were commonly used in both human and veterinary clinics, in contrast to human isolates.     

Annual changes in macrobenthos abundance in Funka Bay,Japan

The temporal variation in macrobenthos abundance was studied in Funka Bay in the periods 2001–2004 and 2007–2010. Dissolved oxygen just above the sea floor of the basin was lower and ignition loss at the level of the sea floor was higher in 2007–2010 than in 2001–2004. Macrobenthic species were categorized into three groups: long-lived species, sedental polychaeta Notomastus latericeus, and short-lived species. Ignition loss was the most influential factor affecting macrobenthos abundance as this variable restricts the recruitment of macrobenthos. The abundance of both long-lived species and N. latericeus was lower between 2007 and 2010 than between 2001 and 2004. Supplementation of oxygen from outside the bay by the Tsugaru Warm Current may be an important factor impacting the increase in the abundance of long-lived species. The abundance of N. latericeus barely increased between 2007 and 2010, possibly because dissolved organic matter, which is their food item, may have become limited due to a narrow chink between sediments with eutrophication. The abundances of short-lived species did not differ between the periods 2001–2004 and 2007–2010 due to the organisms having a low tolerance to hypoxia. The current conditions in Funka Bay are on the verge of turning the bay into an azoic zone.     

Low-fidelity homing behaviour of Biwa salmon <Emphasis Type="Italic">Oncorhynchus</Emphasis> sp. landlocked in Lake Biwa as inferred from otolith elemental and Sr isotopic compositions

Biwa salmon Oncorhynchus sp. is endemic to Lake Biwa, Japan, where it is an important commercial and recreational fisheries species. However, no information is currently available on its population structure and migration ecology. Therefore, here we evaluated whether otolith Sr/Ca, Ba/Ca and ⁸⁷Sr/⁸⁶Sr ratios can be used as natural signatures in Biwa salmon and then used these to determine the natal origins of lake-migration-phase individuals and spawning adults, and the homing ability of spawning adults in the Lake Biwa water system. Quadratic discriminant function analysis demonstrated that the lake-migration school comprised individuals with multiple origins, including rivers to the east, west and north of Lake Biwa, and that the homing rate of spawning adults was low (18 out of 80 individuals), with ca. 78% of fish straying into non-natal rivers. However, this straying behaviour was not spatially random, with fish tending to migrate upstream in rivers neighbouring their natal rivers. The high rate of straying in spawning adults is considered important for establishing and maintaining this species, which is highly adapted to life in the Lake Biwa water system where environmental disturbances often occur.     

Identification of a resistant protein from scallop shell extract and its bile acid-binding activity

In this study, we showed that feeding rats the organic extract of scallop shells (scallop shell extract) caused a decrease in the weights of white adipose tissues in rats fed a high-fat diet. In addition, the cholesterol concentration in the serum of rats that received a diet containing scallop shell extract was significantly lower than that in the serum of rats on the control diet. Feeding this scallop shell extract to rats increased the fecal weight as well as the fecal excretion of bile acids. The amino acid composition of the feces from rats fed the scallop shell extract was different from that of feces from rats fed the control diet, and treatment of the extract with pepsin and pancreatin identified a protein with a molecular weight of 90 kDa (90-kDa protein) as one of the indigestible proteins. Interestingly the 90-kDa protein was found to be identical to a free radical-scavenging protein we previously identified and showed the ability to bind bile acids. These results suggest that indigestible proteins (resistant proteins) in the scallop shell extract, including the 90-kDa protein, inhibit the absorption of bile acid by binding to it and cause increased excretion of fecal bile acid, which subsequently may decrease the serum cholesterol level.