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The use of a new single long-terminal-repeat retroviral shuttle vector has allowed us to obtain copies of the Ld gene with the first seven exons spliced correctly, as well as many other partially spliced or aberrantly recombined copies. Nucleotide sequencing performed on double-stranded DNA with primers specific for the vector and for the coding region of the gene, allowed rapid screening of the recovered plasmids. Synthetic oligodeoxyribonucleotides were then used to link the 5 nt of the last exon, and the functionality of the cDNA copy was verified by expression in transfected L(TK-) cells. Cells that produced the Ld antigen were detected by immunofluorescence and were shown to synthesize an immunoprecipitable molecule of the expected size. In addition, Ld-producing cells were susceptible to killing by Ld-restricted cytotoxic T-lymphocytes. This material should prove useful for mutagenesis and for expression in cell types in which expression of the genes of the major histocompatibility complex appears to be highly regulated. 相似文献
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To assess risk factors associated with the contamination of the domestic environment by legionellae, 211 houses in the Quebec City area were randomly selected and water samples were collected from the hot water tank, the shower heads, and the most frequently used faucet. After centrifugation, concentrated samples were seeded in triplicate on BCYE and GPV media. Data on the characteristics of the hot water system and plumbing in the house and on the personal habits of the occupants were collected for each house. Among these 211 houses, hot water was provided by either an oil or gas heater in 33 and by an electric heater in 178. Legionellae were isolated from none of the samples from houses with oil or gas heaters and from 39% (69 of 178) of those with electric water heaters (P less than 0.0001). This association remained highly significant after control for water temperature and other variables in a stratified analysis. In the 178 houses with an electric heater, 12% of the faucets, 15% of the shower heads, and 37% of the water heaters were contaminated. Legionella pneumophila serogroups 2 and 4 were the most frequently isolated strains. Logistic regression showed that factors associated with electric water heater contamination were (i) location of the house in older districts of the city (P less than 0.0001), (ii) old age of the water heater (P = 0.003), and (iii) low water temperature (P = 0.05). Contamination of the water heater was the only factor significantly associated with the contamination of peripheral outlets (P less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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The existence of precipitin reactions between some molecules in egg jellies (oviduct secretions) of tailed amphibians (Amphibia caudata) has been demonstrated by double diffusion on agarose plates. These reactions do not exist in frogs and toads (Amphibia salientia). One precipitin reaction was related to compounds with a common molecular site of interaction for all A. caudata: all cross-species reactions were possible; a common antigenic rate has been shown. Another precipitin reaction, positively demonstrated in Pleurodeles waltl, probably exists in other A. caudata. The putative influence of these reactions on egg jelly-spermatozoon interactions has been discussed. An homology between these intra-egg jelly reactions and cortical granule content-egg jelly reactions in A. salientia has been suggested. 相似文献
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