ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
A strain of diploid fibroblasts, obtained from the skin of a male infant, was cultured in vitro and cells were tested throughout their lifespan for the appearance of altered glucose-6-phosphate dehydrogenase (G-6-PD) detected either by thermostability studies or by immunotitration. No significant difference was found in the proportion of thermolabile enzyme in 31 young cultures (4.8 ± 1%, S.E.), in comparison with that in 19 old cultures (4.9 ± 1%, S.E.). Old cultures had ceased active cell division (49-60 doublings); DNA replication, measured by [3H] thymidine uptake over a period of 24 hours, was limited to less than 5% of these cells. Young cells (5-22 doublings) had a [3H] thymidine labeling index of 75-85%. Titration of G-6-PD activity in extracts of young and old cells with neutralizing antibody directed specifically against G-6-PD failed to detect an increment of enzymatically defective G-6-PD in old cells. The thermostability studies were capable of detecting altered G-6-PD in skin fibroblasts from a female heterozygous for a thermolabile mutant of G-6-PD, and in fibroblasts treated with a proline analogue, azetidine carboxylic acid. The immunotitration technique was also capable of detecting catalytically altered G-6-PD from the thermolabile mutant and G-6-PD inactivated with N-ethylmaleimide. These findings argue against a protein error catastrophe as the cause of in vitro clonal senescence.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1040870103
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