ISSN:
1432-8798
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The experimental conditions suitable forS→L mutation rate determination in ECHO virus 19 were investigated. Selection curves ofL mutants during multicycle growth andS→L mutation rate determinations in single cycle growth of clonalS virus populations were performed on monkey kidney cultures with and without human embryo extract and, respectively, calf serum added as well as on human embryo cultures. The mutation rate values obtained varied for the sameS clone with the selective effect of the host cell-medium system used even in single cycle growth experiments. On human embryo cultures (selectively favouringL particles) mutation-rate values were the highest, while on monkey kidney cells in the presence of human embryo extracts (with stabilizing effect onS virus) these values were lowest. Finally on unsupplemented monkey kidney cultures intermediate mutation rate values were recorded. It thus seems impossible to establish the exact role of mutation and that of favouring or limiting effects of selection in theS→L shift of ECHO virus 19 populations during in vitro passages. These findings also suggest that actualS→L mutation rate values could be obtained only on host cell systems selectively “neutral” for parentalS and mutantL particles. The impossibility to resolve this vicious cycle —i.e. necessity to know the rate of a mutational event prior to its determination — imposes specification of the host cell medium system in studies in which mutation rate determinations are performed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01242127
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