重金属复合污染对灯心草的生态毒性效应及重金属积累特性的影响

以现行土壤环境质量标准为浓度设置依据并结合实际污染土壤,通过盆栽试验研究了Cu、Cd、Pb、Zn、As5种重金属复合污染对灯心草的联合生理毒性效应及各重金属在灯心草植株内的积累和分布情况。结果表明,5种重金属复合污染对灯心草地上部生长有一定程度的抑制作用,当污染达土壤环境质量二级标准上限值,灯心草地上部生物量减产9.15%,但地下部生物量减产趋势不明显,灯心草分蘖数、株高与地上部干重呈显著正相关。生长在矿毒水和铅锌尾矿污染土壤中的灯心草,地上部生物量分别减产28.23%和37.1%,但POD、SOD和CAT3种酶活性均高于对照。在Cd、Pb、Cu、Zn、As复合污染条件下,各重金属在灯心草茎叶和根系中的积累和分布存在差异,且与土壤中重金属含量间存在一定的相关性。应用综合生态环境效益法,以灯心草为指示植物,可以将土壤环境质量二级标准上限值设定为土壤中5种重金属的临界毒性效应值。     

Molecular cloning, tissue expression, and subcellular localization of porcine peptidoglycan recognition proteins 3 and 4

Peptidoglycan recognition proteins (PGRPs) are innate immune molecules that are present in most invertebrates and vertebrates. Mammals have four PGRPs, PGLYRP1-4. In the present study, we cloned the cDNAs encoding porcine PGLYRP3 and 4 from the esophagus of adult swine. The length of the complete open reading frames of porcine PGLYRP3 and 4 are identical and contain 1125bp encoding 374 amino acid residues. The amino acid sequences of these two proteins were more similar to their human orthologs (78.9% [PGLYRP3] and 73.9% [PGLYRP4]) than to their mouse orthologs (71.3% [PGLYRP3] and 67.9% [PGLYRP4]). Expression analysis revealed that both PGLYRP3 and 4 were more strongly expressed in digestive tract, especially the esophagus, than in immune organs such as spleen or mesenteric lymph nodes in both newborn and adult swine. To analyze the subcellular distribution of porcine PGLYRP1-4, we constructed transfectant cell lines. Western blot and flow cytometric analyses revealed that porcine PGLYRP3 and 4 are not only secreted, but also expressed on the cell surface, unlike PGLYRP1 and 2. These results should help contribute to the understanding of PGLYRP3- and 4-mediated immune responses via their recognition of intestinal microorganisms in newborn and adult swine.     

<Emphasis Type="Italic">Verticillium tricorpus</Emphasis> causing lettuce wilt in Japan differs genetically from California lettuce isolates

In January 2002, Verticillium wilt of lettuce (Lactuca sativa L.) caused by Verticillium tricorpus occurred in upland paddy fields in Hyogo Prefecture for the first time in Japan. This fungal species was first isolated from lettuce in California, USA. In the present study, the genetic relationships between the American and Japanese isolates of V. tricorpus from lettuce were analyzed to determine whether the pathogen could have migrated to Japan from the USA, the major lettuce-seed supplier for Japan. Nucleotide sequences of the rDNA internal transcribed spacer regions, as well as the genes coding for translation elongation factor 1-alpha and RNA polymerase II were compared among American and Japanese V. tricorpus isolates from lettuce. The Japanese isolates of V. tricorpus were distinct from the American. Random amplified polymorphic DNA analyses also supported this conclusion. These results demonstrated that Verticillium wilt on lettuce caused by V. tricorpus in Japan was not related to the isolates causing the disease in California.     

Large-scale molecular dynamics simulations of self-assembling systems

Relentless increases in the size and performance of multiprocessor computers, coupled with new algorithms and methods, have led to novel applications of simulations across chemistry. This Perspective focuses on the use of classical molecular dynamics and so-called coarse-grain models to explore phenomena involving self-assembly in complex fluids and biological systems.     

Factors Affecting Microbial Biomass and Dehydrogenasc Activity in Apple Orchard Soils with Heavy Metal Accumulation

The size of the microbial biomass and dehydrogenase activity were measured in air-dried and rewetted apple orchard surface soils with accumulation of Cu, Pb, and As due to the application of Bordeaux mixtures and lead arsenate. The largest amounts of total Cu, Pb, and As found in the soils used were 1,108, 1,271, and 209 mg kg^-1 soil, respectively. The amounts of 0.1 M HCl-extractable heavy metals were strongly correlated with the total amounts, while those of 0.1 M CaCl₂-extractable heavy metals, except for As, increased significantly with decreasing soil pH. The amounts of microbial biomass C and N, expressed on a soil organic C and total N basis, respectively, were each negatively correlated with the amounts of total and 0.1 M HCl-extractable Cu. On the other hand, the dehydrogenase activity was not affected by the amounts of total and 0.1 M HCl-extractable heavy metals, and was negatively correlated with the amount of 0.1 M CaCl₂-extractable Cu and positively with the soil pH. Higher significant correlations were observed when the dehydrogenase activity was calculated per unit of soil organic C. Thus the microbial biomass was adversely affected by the slightly soluble fractions of Cu accumulated in apple orchard soils, whereas the dehydrogenase activity was affected by the water-soluble and exchangeable Cu of which amount depended on the soil pH. It is suggested that the microbial biomass and dehydrogenase activity expressed on a soil organic matter basis could become useful indicators for assessing the effects of heavy metals on the size and activity of the microbial biomass in soils differing in organic matter contents.     

Quantitative and qualitative changes of organic matter in an Ando soil induced by mineral fertilizer and cattle manure applications for 20 years

The effects of continuous application of cattle manure on the quantity and quality of soil organic matter (OM) were investigated in an Ando soil (Melanudand). Surface soil samples were periodically taken from NPK and NPK+ manure (80, 160, and 320 Mg ha^-1 y^-1) plots over a period of 20 y. Particulate (>53 µm) and mineral-associated <53 µm) OM fractions were separated from the soil samples by sieving after:mechanical dispersion. For the NPK treatment, both the organic C and total N concentrations of the whole soil continued to decrease, the reduction reaching about 10% after 20 y. Manure application at the rate of 80 Mg ha^-1 y^-1 did not lead to an increase in the amounts of organic C and total N in the whole soil. In contrast, both the organic C and total N concentrations increased by the application of 160 and 320 Mg ha^-1 y^-1 manure. Manure application at the rate of 320 Mg ha^-1 y^-1 increased the organic C concentration by 30% and total N concentration by 48% after 20 y. The decrease in the organic C and total N concentrations in soil with NPK fertilization was attributed to a decrease in the amount of mineralassociated OM. Manure application increased significantly the amount of particulate OM, while it did not affect the amount of mineral-associated OM. It also resulted in a decrease in the C/N ratio of soil OM, especially of the particulate OM. The analysis of humic acids showed that manure application induced a decrease in the degree of humification and an accumulation of high molecular weight components. The quantitative'and qualitative changes of OM in the Ando soil upon manure application were mainly due to the accumulation of manure-derived particulate OM.     

Correlation between skeletal muscle fiber type and responses of a taste sensing system in various beef samples

The difference of muscle fiber type composition affects several parameters related to meat quality; however, the relationship between muscle fiber types and meat taste is unclear. To elucidate this relationship, we determined the taste of various beef samples using a taste sensor (INSENT SA402B) and analyzed its correlation with different muscle fiber type composition. We used 22 kinds of beef samples and measured nine tastes, including the relative and change of membrane potential caused by adsorption (CPA) values, using six sensors (GL1, CT0, CA0, AAE, C00, and AE1). The taste sensor analysis indicated positive value outputs for the relative C00, AAE, and GL1 values as well as for the CPA value of AAE, which corresponded to bitterness, umami, sweetness, and richness, respectively. We found significant positive correlations of the myosin heavy chain 1 (MyHC1) composition with umami taste, and with richness. This result suggests that high levels of slow MyHC1 can induce strong umami taste and richness in beef. We expect that our results will contribute to the elucidation of the relationship between muscle fiber types and meat palatability.     

Metabolic process of the C-sugars on the translocation pathways of cucumber plants

Studies on the metabolic process of photoassimilates and enhancement of sugar accumulation into fruit are important in fruit crop production. The metabolic process of the ¹⁴C-photoassimilates in cucumber plants was analyzed with respect to the vascular system. At 4 h after the start of ¹⁴CO₂ feeding, the ¹⁴C-photoassimilates synthesized in a selected leaf on the main shoot were translocated to the vascular bundles of the internode just below the ¹⁴CO₂-fed leaf. The radioactivity of ¹⁴C-stachyose was as high as that of ¹⁴C-sucrose in the vascular bundles of petiole and internode just below the ¹⁴CO₂-fed leaf as well as in the midrib, while the radioactivity of ¹⁴C-stachyose was lower than that of ¹⁴C-sucrose in the mesophyll. The ¹⁴C-photoassimilates appeared to have been translocated without any metabolic change in the translocation pathways between the petiole and internode just below the ¹⁴CO₂-fed leaf, because the ratio of ¹⁴C-stachyose radioactivity in the two parts was similar. At 8 h after the start of ¹⁴CO₂ feeding, the ¹⁴C-photoassimilates were translocated to the fruit. In the vascular bundles of the peduncle, the ratios of the radioactivity of ¹⁴C-stachyose and ¹⁴C-raffinose were lower, and the ratio of the radioactivity of ¹⁴C-sucrose was higher, than that at the petiole and internode just below the ¹⁴CO₂-fed leaf at 8 h after the start of ¹⁴CO₂ feeding. Therefore, it seemed that ¹⁴C-stachyose and ¹⁴C-raffinose were hydrolyzed to ¹⁴C-sucrose in the peduncle.     

Evidence of niche segregation between freshwater eels and conger eels in Kojima Bay, Japan

The aim of this study was to examine the possible interspecific interactions between the freshwater eel Anguilla japonica and the marine conger eel Conger myriaster. Spatial distribution, foraging time, and diet were compared between 380 A. japonica and 221 C. myriaster juveniles in a large brackish water bay and a tributary river estuary. Almost no C. myriaster were caught in the estuary, but both species coexisted in the bay at similar densities. For both species, percentages of eels with stomach contents were greater in the morning than in the afternoon, indicating they forage at night. Both species mainly fed on benthic crustaceans in the bay, but the size of the main prey species, mud shrimp Upogebia major, was significantly larger in A. japonica. The difference in prey size appears to be related to the eel body size (A. japonica: 559.5 ± 88.0 mm, C. myriaster: 356.4 ± 56.0 mm), which probably reflects the differences in the life history-related movements of these eels, with A. japonica using the bay at large sizes and C. myriaster using the bay as a nursery area before moving to deeper water. The differences in their migratory and movement patterns may result in niche segregation in the brackish bay where both species coexist.     

cDNA cloning and expression analysis of two heat shock protein genes,Hsp90 and Hsp60, from a sterile Ulva pertusa (Ulvales,Chlorophyta)

Molecular chaperones are synthesized and accumulated under a variety of unfavorable conditions in all organisms. Heat shock protein 90 (Hsp90) and Hsp60, which are classified into the major classes of molecular chaperones, play important roles in cellular stress responses. In this study, we characterized sterile Ulva pertusa Hsp90 (UpHsp90) and UpHsp60 genes which may be involved in tolerance to thermal and heavy metal stresses in this alga. The UpHsp90 cDNA consisting of 2,118 nucleotides encoded a polypeptide of 705 amino acids (AA). On the other hand, the UpHsp60 cDNA consisting of 1,722 nucleotides encoded a protein whose predicted length was 573 AA. The AA sequence alignment and phylogenetic analyses showed that the UpHsp90 and UpHsp60 proteins were more similar to cytoplasmic Hsp90s and mitochondrial Hsp60s, respectively, than to other types of the respective Hsps. Southern blot analysis indicated that the sterile U. pertusa genome had at least two cytoplasmic Hsp90-encoding genes and two mitochondrial Hsp60-encoding genes. The UpHsp90 and UpHsp60 mRNA levels were significantly affected by diurnal and temperature changes, and slightly affected by exposure to heavy metals. These results suggest that UpHsp90 and UpHsp60 genes play particularly important roles in adaptation to diurnal and temperature changes.