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81.
82.
To examine whether the pathogenic bacterium, Erwinia carotovora subsp. carotovora, causal agent of soft rot of Chinese cabbage (Brassica campestris L., pekinensis group), can overwinter in plant debris and soil and serve as inoculum the following year, we monitored field populations of rifampicin-resistant, phage-sensitive strains of the bacterium. Chinese cabbage (cv. Matsushima Kohai W1116) were planted in field soil in pots that were sunk into the field on Aug. 2, 1996 and eventually reduced to one plant per pot. Outer petioles of the plants were inoculated with mixture of 13 bacterial strains of E. carotovora subsp. carotovora on Sept.5, 1996. After the soft rot spread throughout the plant, the diseased plant was buried in the potted soil. New seeds were sown in the pots on April 30, 1997, and the disease was observed in June and July. The bacterial strains were re-isolated from the potted soil, diseased tissue and rhizosphere soil by the dilution plating method on modified Drigalski's medium containing 100 ppm rifampicin and by the enrichment technique. In addition to rifampicin resistance, phage sensitivities of some of the re-isolated strains were identical to those of the strains buried in the soil with the diseased plant in the previous year. From these results, some of the 13 strains overwintered in the soil and infested plant tissue and acted as primary inoculum the following year. The frequency of re-isolation varied among the strains, perhaps because of competition among the strains, differences in epidemiological behavior and stabilizing selection among the strains, and the presence of different ecotypes of the organism. Received 21 July 2000/ Accepted in revised form 19 September 2000  相似文献   
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Carbon tetrachloride (CCl(4)) -induced hepatotoxicity is a commonly used model for investigating lipid peroxidation-related tissue injury. In the present study, the effect of flaxseed extract was observed on histological sections, glutathione-content and DNA strand breaks. Lignan-containing flaxseed extract (1.6 g/kg body weight/day) was daily administered with intragastric injection to rats for three days, on the fourth day, CCl(4) (2 g/kg) was intraperitoneally injected. Liver tissue was sampled at 24 hr after administering CCl(4). Liver-necrosis was observed in CCl(4)-injected rats without pretreatment of flaxseed extract. Pretreatment of flaxseed extract reduced extent of the necrosis found 24 hr after the intraperitoneal administration of CCl(4). Pretreatment of flaxseed extract protect against CCl(4)-induced decrease of reduced glutathione-content measured from reactions with 5,5'-dithiobis-(2-nitrobenzoic acid) and also protect against the elevation of DNA strand breaks in the liver cells measured by comet assay. Flaxseed-extract appears to protect liver cells against CCl(4)-induced necrosis.  相似文献   
85.
Immunohistochemical localization of TGF-alpha and cell proliferation kinetics during liver regeneration after two-thirds partial hepatectomy (PH) were investigated. Twenty-four to 72 hr after PH, appreciable increase in the number of TGF-alpha-positive hepatocytes was observed in zones 1 and 2. At the peak at 36 hr, almost all positive cells were stained in their nuclei. Considerable increase in the BrdU labeling index was observed 24-36 hr after PH with a peak at 24 hr in zones 1 and 2. These results indicated an association between TGF-alpha expression and hepatocyte regeneration. It is suggested that immunohistochemical localization of TGF-alpha may be a useful marker of cell proliferation activity in rat liver.  相似文献   
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Nicotiana benthamiana was transformed with a green fluorescent protein (GFP) gene driven by cauliflower mosaic virus 35S promoter. A GFP-silenced line and a nonsilenced line were selected after ultraviolet irradiation. GFP short-interfering RNAs (siRNAs) were detected in the silenced line but not in the nonsilenced line. T1 progeny of the silenced line varied in GFP suppression patterns and were grouped into three types (I, II, III) based on the GFP suppression pattern. With Northern blot analysis, different levels of GFP mRNA accumulated, from a very low level in type I and II to an intermediate level in type III, in contrast to a much higher level in the nonsilenced line. Plants were also inoculated with Potato virus X engineered to contain the GFP sequence to evaluate the levels of virus resistance. None to a few GFP spots were observed on inoculated leaves in types I and II, whereas numerous spots and systemic infection appeared in type III. These results showed that virus resistance was inversely correlated with the levels of mRNA, suggesting that the strength of RNA silencing determines the extent of virus resistance.  相似文献   
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ABSTRACT When Ipomoea nil was coinfected with Sweet potato feathery mottle virus (SPFMV), a member of the genus Potyvirus, and Potato virus X (PVX) typical symptoms caused by PVX were observed on those by SPFMV on the first upper true leaves at 14 days postinoculation (dpi). On the other hand, no PVX-induced symptoms were observed on the first upper true leaves at 14 dpi when plants were infected with PVX alone. In the case of coinfection with PVX and SPFMV, PVX RNA was detected not only in the inoculated cotyledonary leaves but also in the first upper true leaves at 14 dpi. In the case of single infection with PVX, PVX RNA was detected in the inoculated cotyledonary leaves but not in the first upper true leaves at 14 dpi. The accumulation of SPFMV remained unchanged, regardless of whether the inoculum consisted of SPFMV alone or a mixture of SPFMV and PVX. Although recombinant PVX engineered to express the helper component-proteinase (HC-Pro) of SPFMV (PVX.HC) enhanced symptoms severity in Nicotiana benthamiana, PVX.HC induced the synergism characterized by an enhanced viral movement in Ipomoea nil. Immunofluorescence microscopic examination revealed that the HC-Pro was present in phloem of SPFMV-infected I. nil. These results suggest that SPFMV HC-Pro acts as an enhancer of long distance movement for PVX in I. nil.  相似文献   
90.
Hantaviruses are causative agents of some severe human illnesses, including hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). The viruses are maintained by rodent hosts, and humans acquire infection by inhaling virus-contaminated excreta from infected animals. To examine the epidemiology of hantavirus infections in Japan and Far East Russia, we conducted epidemiological surveys in these regions. In Japan, anti-hantavirus antibodies were found in four rodent species, Clethrionomys rufocanus, Rattus norvegicus, R. rattus, and Apodemus speciosus. Although no new HFRS cases have been officially reported over the past 20 years in Japan, one member of the Japan Ground Self-Defense Force did test positive for hantavirus antibody. Repeated surveys in Far East Russia have revealed that two distinct hantavirus types cause severe HFRS in this region. Hantavirus sequences identified from A. peninsulae, fetal HFRS cases in Vladivostok, and Amur virus are highly similar to each other (> 92% identity), but they are less similar (approximately 84% identity) to the prototypical Hantaan virus, which is carried by A. agrarius. Phylogenetic analysis also indicates that Amur and A. peninsulae-associated viruses are distinct from Hantaan virus, suggesting that A. peninsulae is the reservoir animal for Amur virus, which causes severe HFRS. From HFRS patients in the Khabarovsk region, we identified viruses with nucleotide sequences that are more similar to Far East virus (> 96%identity) than to the Hantaan (88-89% identity) or Amur (81-83% identity) viruses. Phylogenetic analysis also indicates that the viruses from Khabarovsk HFRS patients are closely related to the Far East virus, and distinct from Amur virus.  相似文献   
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