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We have constructed a physical map of the human genome by using a panel of 90 whole-genome radiation hybrids (the TNG panel) in conjunction with 40,322 sequence-tagged sites (STSs) derived from random genomic sequences as well as expressed sequences. Of 36,678 STSs on the TNG radiation hybrid map, only 3604 (9.8%) were absent from the unassembled draft sequence of the human genome. Of 20,030 STSs ordered on the TNG map as well as the assembled human genome draft sequence and the Celera assembled human genome sequence, 36% of the STSs had a discrepant order between the working draft sequence and the Celera sequence. The TNG map order was identical to one of the two sequence orders in 60% of these discrepant cases.  相似文献   
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Experimental infections with Piscirickettsia salmonis via intraperitoneal (IP), oral (PO) and gill (GS) routes were compared, and the importance of physical contact in the horizontal transmission of this organism was investigated. Atlantic salmon, Salmo salar L., under-yearling parr raised in fresh water were used in this study. Samples of liver, kidney, spleen, gill and brain were collected weekly for 5 weeks after challenge, and were examined using the indirect fluorescent-antibody technique (IFAT). The pathogen was transmitted horizontally to fish with and without physical contact. However, transmission of P. salmonis occurred significantly more rapidly among fish with physical contact. Mortalities occurred in 50% of fish experimentally challenged with P. salmonis and their cohabitants. The estimates of the relative risk of dying demonstrated that fish challenged by the IP and GS routes had a significantly higher probability of dying than fish challenged by the PO route ( P < 0.005). Contact cohabitants with infected fish had a higher probability of death than non-contact cohabitants ( P < 0.005). The sequential studying using IFAT indicated that a haematogenous pattern of infection occurred among fish infected by oral and gill routes, or by cohabitation. This was different from the capsular (serosal) infection pattern observed in intraperitoneally inoculated fish. Piscirickettsia salmonis was observed within the cytoplasm of leucocytes and renal tubules, the latter indicating that elimination of this pathogen through the urine may be possible. Aeromonas salmonicida was also detected (by IFAT) in some of the fish exposed to P. salmonis , suggesting that P. salmonis may cause immunosuppression, and thus, increase the susceptibility of the host to other pathogens.  相似文献   
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Piscirickettsia salmonis, the etiologic agent of salmonid rickettsial septicemia (SRS), or piscirickettsiosis, causes substantial economic losses to the salmon industry. The pathogenesis of the disease has not been fully characterized. The aim of this study is to describe the hepatic lesions associated with experimental P. salmonis infection in Atlantic salmon juveniles. Fish were maintained in fresh water and inoculated intraperitoneally (IP), orally, or on the gill surface with P. salmonis. A group of uninfected fish was kept as control. Liver samples from 5 fish in each inoculated group and 3 controls were collected weekly and processed for histological and immunohistochemical examination. Thickening of the liver capsule by inflammatory cells was a characteristic histologic feature of IP inoculated fish. Three weeks post-IP inoculation, 8 fish had died and 2 fish were sampled. Histological changes at this time consisted of vasculitis, presence of fibrin thrombi, vacuolated hepatocytes and focal areas of necrosis. Leukocytes containing intracytoplasmic basophilic microorganisms were seen within hepatic sinusoids. Vasculitis and intracytoplasmic vacuoles were prominent features in fish inoculated orally and on the gill surface. The presence of P. salmonis within hepatocellular vacuoles, endothelial cells, and leucocytes was confirmed by immunohistochemistry. The intracellular location of P. salmonis and the vascular damage seen in infected fish are characteristic of rickettsial infections. Histological lesions induced by experimental infection with P. salmonis using the oral and gill surface routes were similar to those observed in natural outbreaks of piscirickettsiosis. The tropism of P. salmonis for endothelial cells explains the vascular lesions observed in SRS, whereas hepatic lesions are due to ischemic necrosis and direct injury by intracytoplasmic organisms.  相似文献   
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Piscirickettsia salmonis, the etiologic agent of salmonid rickettsial septicemia (SRS), affects several species of salmonids. Previous reports using the appearance of cytopathic effect (CPE) as the criterion for susceptibility, showed that Piscirickettsia salmonis (ATCC strain) can be grown in vitro in some cells lines derived from salmonid fish, but not in BB cells from brown bullhead (Ictalurus nebulosus) and BF-2 cells from bluegill (Lepomis macrochirus). In this study we describe growth of P. salmonis (ATCC strain VR 1361) in a cell line previously believed to be nonpermissive for this organism. CPE was first detected in chinook salmon embryo (CHSE-214) and epithelioma papulosum ciprini (EPC) cell lines at 6 d postinfection (dpi). In contrast, using BB cell line, CPE was first detected 45 dpi and the monolayer completed CPE by 78 dpi. Electron microscopic examination of BB cells 78 dpi revealed free, intracytoplasmic and extracellular localization of the agent. P. salmonis was also observed within membrane-bounded vacuoles in BB cells, similar to that described in CHSE 214 cells. Contrary to earlier reports, results from the present study show that the BB cell line, is susceptible to Piscirickettsia salmonis infection. The delayed onset of CPE in BB cells in comparison to other permissive cell lines suggests that BB cells are not ideal hosts for P. salmonis. Interestingly, however, these results demonstrate that P. salmonis can infect non-salmonid cell lines, and raises the possibility that non-salmonid fish may play a role in the persistence and transmission of SRS in the natural environment.  相似文献   
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Females of Siganus guttatus reared to sexual maturity in canvas tanks were induced to spawn by using human chorionic gonadotropin (HCG, Ayerst) at 500 IU/fish or about 2 IU/g body weight. The amount of HCG used depended on the initial mean egg diameter; the smaller the diameter, the more HCG was used. Fish with oocytes characterized by germinal vesicle migration (mean egg diameter ≥ 0.47 mm) spawned without HCG injection. Fertilization and hatching rates for both treated and untreated fish were more than 90%. The larvae were reared to metamorphosis using rotifers from day 2–17, rotifers + newly hatched Artemia nauplii from day 18–20 and rotifers + newly hatched Artemia nauplii + artificial feed from day 21–35. In addition, Isochrysis galbana was introduced to the rearing tanks from day 1–10 and Chlorella sp. and/or Tetraselmis sp. from day 1–35. Survival rates of larvae tended to be lower as the broodstock became older.  相似文献   
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