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排序方式: 共有498条查询结果,搜索用时 15 毫秒
1.
2.
Heat resistance of Listeria: strain differences and effects of meat type and curing salts 总被引:3,自引:1,他引:2
The heat resistances of 27 strains of Listeria monocytogenes and two strains of L. innocua were compared in broth heated at 57°C. No strain was exceptionally resistant. The heat resistance of a representative isolate of L. monocytogenes was compared in fresh and cured beef and chicken, and an equation was derived to predict the time necessary to achieve a '7D' inactivation at temperatures between 50 and 70°C. 相似文献
3.
The survival of Salmonella typhimurium after a standard heat challenge at 55°C for 25 min increased by several orders of magnitude when cells grown at 37°C were pre-incubated at 42°, 45° or 48°C before heating at the higher temperature. Heat resistance increased rapidly after the temperature shift, reaching near maximum levels within 30 min. Elevated heat resistance persisted for at least 10 h. Preincubation of cells at 48°C for 30 min increased their resistance to subsequent heating at 50°, 52°, 55°, 57° or 59°C. Survival curves of resistant cells were curvilinear. Estimated times for a '7D' inactivation increased by 2.6- to 20-fold compared with cells not pre-incubated before heat challenge. 相似文献
4.
Determinants of time-dependent membrane conductance. The nonrole of classical ion-membrane molecule interactions
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We have examined the steady-state and time-dependent electrical properties of a model membrane system. The model assumes that the directed velocity and energy of ions moving through the membrane are determined by the applied electric field, ionic diffusion forces, and central elastic collisions between ions and membrane molecules. A simple analysis of the steady-state electrical properties of the model yields results identical with ones obtained previously using a more complex analysis procedure. The time-dependent conductance changes of the model in response to a step change in electric field strength when there is solution symmetry display three qualitative patterns dependent on the nature of the ion-membrane molecule interaction. One of the patterns of conductance change is quite similar to that observed in the sodium conductance system of a number of excitable tissues: an initial conductance rise to a maximum (activation) followed by a decay to a final steady-state value (inactivation). However, the correspondence between the time-dependent model behavior and known experimental behavior of excitable systems is only qualitative. We conclude that the classical ion-membrane molecule interactions we consider are not involved in determining time-dependent conductance processes in the excitable systems for which comparison is possible. 相似文献
5.
6.
The effect of high hydrostatic pressure on Salmonella thompson and Listeria monocytogenes examined by electron microscopy 总被引:3,自引:0,他引:3
B.M. Mackey K. Forestière N.S. Isaacs R. Stenning B. Brooker 《Letters in applied microbiology》1994,19(6):429-432
Cells of Listeria monocytogenes that had been exposed to pressure contained vacuolar regions in the cytoplasm. Pressure-treated cells of Salmonella thompson contained no vacuoles but had fewer ribosomes than untreated cells and their appearance suggested that some cell lysis had occurred. In both organisms changes in the appearance of the nuclear material were observed. 相似文献
7.
Thermal denaturation and loss of viability in Escherichia coli and Bacillus stearothermophilus 总被引:1,自引:0,他引:1
B. M. Mackey C. A. Miles D. A. Seymour S. E. Parsons 《Letters in applied microbiology》1993,16(2):56-58
When Escherichia coli was heated at 10°C/min in a differential scanning calorimeter, the onset of irreversible thermal denaturation occurred at 51°C, about 5°C above the maximum growth temperature. The temperature at which death rate was maximal (63°C) coincided with the thermogram peak caused by denaturation of the 30S ribosomal subunit. The maximum death rate in vegetative cells of Bacillus stearothermophilus occurred at the higher temperature of 71°C which also coincided with the leading edge of the main thermogram peak. 相似文献
8.
P Deberghes A M Betbeder F Boisard R Blanc J F Delaby S Krivobok R Steiman F Seigle-Murandi EE Creppy 《Mycotoxin Research》1995,11(1):37-47
The toxicity of ochratoxin A (OTA), a mycotoxin produced by fungi ofAspergillus orPenicillium genera is now well documented. Its nephrotoxicity, immunosuppression, teratogenicity, and carcinogenicity have been widely studied. Physical and biochemical methods have been studied to prevent these toxinogenicAspergillus andPenicillium from producing OTA, and/or to destroy the mycotoxin when already produced in a liquid or a solid medium. Repeated freezing at ? 20?C and thawing at + 26?C aleatory reduce OTA production in a liquid medium. Exposure to UV B for different periods of time is efficient in preventing OTA production in a liquid medium. Gamma-irradiation from 2 to 5 kGy gives good results in preventing the production of OTA or destroying it when already produced. Carboxypeptidase is very efficient at 5 units/50 ml in a liquid medium for cleaving the OTA already produced. 相似文献
9.
Mammalian DNA ligase III: molecular cloning, chromosomal localization, and expression in spermatocytes undergoing meiotic recombination. 总被引:14,自引:4,他引:10
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10.
Multiple Copies of Human Adenovirus 12 Genomes Are Integrated in Virus-Induced Hamster Tumors 总被引:4,自引:2,他引:2
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Tumors induced in hamsters by highly oncogenic human adenovirus 12 contain multiple copies of 90 to 100% of the viral genome in an integrated form. 相似文献