Molecular characterization of three Rana grylio virus (RGV) isolates and Paralichthys olivaceus lymphocystis disease virus (LCDV-C) in iridoviruses

Three Rana grylio virus (RGV) isolates and lymphocystis disease virus (LCDV-C) were molecularly characterized by antigenicity comparison, Western blot detection of viral polypeptides, restriction fragment length polymorphism analysis of viral genomes, and MCP sequence analysis. Significant antigenicity differences existed among the three RGV isolates and LCDV-C. Western blot detection indicated that the viral polypeptides of three RGV isolates could be recognized by the anti-RGV9807 serum, whereas no bands were observed in the LCDV-C, and significant differences exist among the band patterns of three RGV isolates. Restriction fragment length polymorphism (RFLP) analysis was performed by digesting genomic DNA of the four iridovirus isolates with restriction endonucleases HindIII, KpnI, XbaI and BamHI. On the whole, obvious discrepancies existed between LCDV-C and RGV isolates, and some significant band pattern differences were also revealed between RGV9808 and RGV9506 (or RGV9807) in the profiles of restriction endonucleases Xbal, Kpn I and BamHI. PCR amplification and sequence analysis of MCP gene sequence further revealed their phylogenetic relationship among the three RGV isolates, LCDV-C and other iridoviruses. RGV9506, RGV9807 and RGV9808 are clustered together with other ranaviruses, such as FV3, BIV, TFV and ENHV, although the RGV9808 is more close to EHNV than to other ranaviruses. Additionally, LCDV-C is clustered with LCDV-1, the type species of genus Lymphocystisvirus. The current study provides clear evidence that significant genetic difference exists among the three RGV isolates. Therefore, further work on comparative genomic studies will contribute significantly to understanding of their taxonomic position and pathological mechanism. (C) 2005 Elsevier B.V. All rights reserved.

Physiological and biochemical microcystin-RR toxicity to the Synechococcus elongatus

Freshwater Microcystis may form dense blooms in eutrophic lakes. It is known to produce a family of related cyclic hepatopeptides (microcystins, MC) that constitute a threat to aquatic ecosystems. Most toxicological studies of microcystins have focused on aquatic animals and plants, with few examining the possible effects of microcystins on phytoplankton. In this study we chose the unicellular Synechococcus elongatus (one of the most studied and geographically most widely distributed cyanobacteria in the picoplankton) as the test material and investigated the biological parameters: growth, pigment (chlorophyll-a, phycocyanin), photosynthetic activity, nitrate reductase activity, and protein and carbohydrate content. The results revealed that microcystin-RR concentrations above 100 mug (.) L-1 significantly inhibited the growth of Synechococcus elongatus. In addition, a change in color of the toxin-treated algae (chlorosis) was observed in the experiments. Furthermore, MC-RR markedly inhibited the synthesis of the pigments chlorophyll-a and phycocyanin. A drastic reduction in photochemical efficiency of PSII (F-v/F-m) was found after a 96-h incubation. Changes in protein and carbohydrate concentrations and in nitrate reductase activity also were observed during the exposure period. This study aimed to evaluate the mechanisms of microcystin toxicity on a cyanobacterium, according to the physiological and biochemical responses of Synechococcus elongatus to different doses of microcystin-RR. The ecological role of microcystins as an allelopathic substance also is discussed in the article. (C) 2004 Wiley Periodicals, Inc.

Rickettsia-like organism infection in a freshwater cultured fish Ophiocephalus argus C. in China

From 2001 to 2002, a new and emergent infectious disease of Ophiocephalus argus occurred in a fishery in Hubei Province, China, with an incidence of 60% similar to 70% and a mortality as high as 100 %. The diseased fish showed an enlarged abdomen, the millet-like nodules in internal organs, and the swollen kidney which was composed of 5 similar to 10 sarcoma-like bodies in cream or gray-white colour or ulcerated into beandregs-like substance. Light microscopic observation revealed the basophilic or acidphilic inclusions in cytoplasm of the cells and the granulomas, a diffusive chronic inflammation in internal organs. Further analysis under an electron microscope indicated that the intracytoplasmic inclusions were rickettsia-like organisms (RLOs) that are either spherical or coccoid, with variable size, ranging from 0.5 similar to 1.5 mum in diameter, and enclosed within membrane-bound cytoplasmic vacuoles. RLO had a central nucleoid region with some fine filamentous structures and an electron-dense granule. Its cytoplasm contained abundant ribosomal bodies. Occasionally, RLO appeared to be divided by binary fission. RLOs were also observed in the homogenized tissue of infected fish. The results suggested that the death of cultured O. argus was caused by RLO infection.

A C-type lectin associated and translocated with cortical granules during oocyte maturation and egg fertilization in fish

Oocyte maturation and egg fertilization in both vertebrates and invertebrates are marked by orchestrated cytoplasmic translocation of secretory vesicles known as cortical granules. It is thought that such redistribution of cellular content is critical for asymmetrical cell division during early development, but the mechanism and regulation of the process is poorly understood. Here we report the identification, purification and cDNA cloning of a C-type lectin from oocytes of a freshwater fish species gibel carp (Carassius auratus gibelio). The purified protein has been demonstrated to have lectin activity and to be a Ca2+-dependent C-type lectin by hemagglutination activity assay. Immunocytochemistry revealed that the lectin is associated with cortical granules, gradually translocated to the cell surface during oocyte maturation, and discharged to the egg envelope upon fertilization. Interestingly, the lectin becomes phosphorylated on threonine residues upon induction of exocytosis by fertilization and returns to its original state after morula stage of embryonic development, suggesting that this posttranslational modification may represent a critical molecular switch for early embryonic development. (C) 2003 Elsevier Inc. All rights reserved.

a-Si:H/a-C:H超晶格的研究

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

Si-C系材料的生长及其性能研究

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

C 波段无线宽带收发芯片中直流漂移、 多模基带的研究

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z