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161.
Transfer of purified herpes virus thymidine kinase gene to cultured mouse cells. 总被引:342,自引:0,他引:342
Treatment of Ltk?, mouse L cells deficient in thymidine kinase (tk), with Bam I restriction endonuclease cleaved DNA from herpes simplex virus-1 (HSV-1) produced tk+ clones with a frequency of 10?6/2 μg of HSV-1 DNA. Untreated cells or cells treated with Eco RI restriction endonuclease fragments produced no tk+ clones under the same conditions. The thymidine kinase activities of four independently derived clones were characterized by biochemical and serological techniques. By these criteria, the tk activities were found to be identical to HSV-1 tk and different from host wildtype tk. The tk+ phenotype was stable over several hundred cell generations, although the rate of reversion to the tk? phenotype, as judged by cloning efficiency in the presence of bromodeoxyuridine, was high (1–5 × 10?3). HSV-1 DNA Bam restriction fragments were separated by gel electrophoresis, and virtually all activity, as assayed by transfection, was found to reside in a 3.4 kb fragment. Transformation efficiency with the isolated fragment is 20 fold higher per gene equivalent than with the unfractionated total Bam digest. These results prove the usefulness of transfection assays as a means for the bioassay and isolation of restriction fragments carrying specific genetic information. Cells expressing HSV-1 tk may also provide a useful model system for the detailed analysis of eucaryotic and viral gene regulation. 相似文献
162.
Incorporation of [14C]-phenylalanine and [14C]-methionine into cinnamon cuttings suggests that synthesis of eugenol from phenylalanine involves exchange of the terminal carbon in the side chain with that from a donor molecule such as methionine whereas synthesis of cinnamic aldehyde incorporates phenylalanine in toto. 相似文献
163.
164.
Specific adhesion of rat hepatocytes to beta-galactosides linked to polyacrylamide gels 总被引:6,自引:0,他引:6
Rat hepatocytes, isolated by a collagenase perfusion technique, specifically bind to polyacrylamide gel containing covalently immobilized 6-aminohexyl beta-D-galactopyranosyl groups. Less than 5% of these cells bind to polyacrylamide or to gels with the following covalently linked ligands: 6-aminohexanol, or the 6-aminohexyl D-pyranosides of alpha-mannose, beta-glucose, beta-2-acetamido-2-deoxyglucose, beta-cellobiose, beta-maltose, or beta-melibiose. Cell binding to beta-D-galactoside gels occurs after a lag period at 37 degrees and 65 to 100% (depending on the cell preparation) of the cells adhere. The duration of the lag period is inversely related to the beta-D-galactoside content of the gel but preincubation of the cells at 37 degrees reduces the lag period. Cell-gel binding is a threshold phenomenon. Adhesion of cells to gels does not occur when the glycoside concentration is less than about 900 nmol per cm2 x 0.25 mm thick gel piece. Above this critical concentration, cell-gel binding occurs and becomes maximal when the concentration is increased by only 20%. If these in vitro results apply to cellular interactions in vivo, they suggest that slight changes in the levels of cell surface or extracellular matrix carbohydrates may profoundly influence the behavior of neighboring cells. 相似文献
165.
166.
A method for the culture of spiral-shaped bacteria associated with the intestinal mucosa of rodents is described. The appearance in culture of a spiral organism from rat ceca and a spirochete from mouse ceca is illustrated; these organisms are morphologically similar to the major inhabitants of the cecal mucosa in each animal species. 相似文献
167.
Kinetic studies of enzymatic hydrolysis of insoluble cellulose: analysis of the initial rates 总被引:1,自引:0,他引:1
A study was conducted on the kinetics of enzymatic hydrolysis of pure insoluble cellulose using unpurified culture filtrate Trichoderma reesei, with the emphasis on the initial reaction period. The initial hydrolysis rate and extent of enzyme (soluble protein)adsorption, either apparent or initial, were evaluated under various experimental conditions. It has been found that the various mass-transfer steps do not control the overall hydrolysis rate and that the hydrolysis rate is mainly controlled by the surface reaction step promoted by the adsorbed enzyme. It has also been found that the initial hydrolysis rate strongly depends on the initial extent of soluble protein adsorption and the effectiveness of the adsorbed soluble protein to promote the hydrolysis. The initial extent of soluble protein adsorption, in turn, is related to the initial cellulose concentration, enzyme concentration, and specific surface area of cellulose, whereas the effectiveness of the initially adsorbed soluble protein to promote the derived to interrelate these parameters without resorting to the Michaelis-Menten kinetics. The present result appear to imply that the role of enzyme-substrate complex formation should not be ignored in deriving a mechanistic kinetic model for enzymatic hydrolysis of cellulose. 相似文献
168.
A numerical taxonomic study of species of Vibrio isolated from the aquatic environment and birds in Kent, England 总被引:4,自引:3,他引:1
A numerical taxonomic study has been carried out to confirm the identity of strains of the family Vibrionaceae isolated during an ecological study. A total of 237 strains were studied including 148 from the aquatic environment, 6 from estuarine birds, 1 from sheep faeces, and 61 control cultures. Duplicates of 21 of the strains were randomly selected and included to estimate test and operator error. Taxonomic resemblance was estimated on the basis of 148 characters using Euclidean distance. The taxonomic position of some strains was reevaluated using the pattern difference coefficient. Strains were clustered by three methods, all of which gave similar results. The estimated average probability of test error was 1.5%. Strains previously identified as Vibrio anguillarum fell into four distinct phenons corresponding to V. anguillarum biovar I, ' V. anguillarum biovar II', V. diazotrophicus , and strains pathogenic to oyster larvae. The latter group characteristically degraded xanthine and probably represents a new species. The phenon corresponding to V. cholerae included the type strain, strains of human origin, and strains isolated in the United Kingdom from birds and the aquatic environment. Some strains of V. cholerae were luminous. Other phenons were identified as V. metschnikovii, V. fluvialis , and Aeromonas spp. 相似文献
169.
R. M. Lee R. D. Mcdowall 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1983,273(2):335-345
Two high-performance liquid chromatographic methods for the assay of oxmetidine are described: both utilize the same liquid extraction from plasma, urine and bile samples. A normal-phase technique is considered most suitable for the analysis of plasma extracts and a reversed-phase method is preferred for the assay of excretory fluids such as urine and bile which will contain polar metabolites in detectable quantity as well as unchanged oxmetidine.The methods are sensitive enough to follow the kinetic changes in concentration for up to 8 h after the administration of recommended therapeutic doses. Both methods can be automated in respect of the high-performance liquid chromatograph and the samples can be stored for several weeks at −20°C without prejudicing the accuracy of the analysis. 相似文献
170.
R K Clark E V Lee S LoCastro P Bhatnagar K Esser W Prichett D Dunnington 《The journal of histochemistry and cytochemistry》1991,39(10):1409-1413
A synthetic peptide corresponding to a novel protein sequence isolated from bovine kidney was used to immunize rabbits. When applied to Western blots of bovine kidney extracts, antiserum to this peptide recognizes proteins with molecular weights of 23 and 18 KD. Immunohistochemical examination of a variety of bovine and rat tissues with this antiserum revealed a unique distribution of immunoreactivity with the intermediate layers of a variety of stratified epithelia, in addition to renal glomeruli. The pattern of reactivity differed from previously described epithelial markers such as cytokeratins. These results indicate that this antiserum may be useful as a tool for the identification of cells of the intermediate layer of stratified epithelia and, as such, may aid in the study of this differentiating/proliferating tissue compartment. 相似文献