Human Diploid Skin Fibroblasts Research Articles

Regulation of alkaline phosphatase in human skin fibroblasts.

SummaryThe specific activity of alkaline phosphatase in human diploid skin fibroblasts in tissue culture increased following addition of prednisolone, hydrocortisone, and cortisone. Estradiol-17β, testosterone, and progesterone had no significant effect on induction of alkaline phosphatase in the same tissue culture system. Using prednisolone-21-phosphate (10–5 to 10–8M), we have shown that the phase of rapid increase in enzyme activity is linear with respect to time and that the rate of increase is dependent on concentration of the hormone. Maximal rate of induction occurred at a 10–6M concentration of prednisolone-21-phosphate. Evidence from our in vitro system indicates that the activity of alkaline phosphatase in regenerating connective tissue may be effectively regulated by physiological levels of adrenal glucocorticoids present in plasma.We sincerely thank Miss M. Gail Hawkins and Mr. Boyd R. Switzer for assistance in this work.

EVIDENCE THAT XERODERMA PIGMENTOSUM CELLS DO NOT PERFORM THE FIRST STEP IN THE REPAIR OF ULTRAVIOLET DAMAGE TO THEIR DNA

Xeroderma pigmentosum (XP) is a recessively transmitted disorder of man characterized by increased sensitivity to ultraviolet light. Homozygous, affected individuals, upon exposure to sunlight, sustain severe damage to the skin; this damage is characteristically followed by multiple basal and squamous cell carcinomas and not uncommonly by other malignant neoplasia. A tissue culture cell line was derived from the skin of a man with XP. Our measurements of ultraviolet-induced pyrimidine dimers in cellular DNA show that normal diploid human skin fibroblasts excise up to 70 per cent of the dimers in 24 hours, but that fibroblasts derived from the individual with XP excise less than 20 per cent in 48 hours. Alkaline gradient sedimentation experiments show that during the 24 hours after irradiation of normal cells a large number of single-strand breaks appear and then disappear. Such changes are not observed in XP cells. XP cells apparently fail to start the excision process because they lack the required function of an ultraviolet-specific endonuclease. These findings, plus earlier ones of Cleaver on the lack of repair replication in XP cells, raise the possibility that unexcised pyrimidine dimers can be implicated in the oncogenicity of ultraviolet radiation.

Establishment of Human Skin Fibroblast Cultures with an Automatic Wedge Biopsy Instrument

Establishment of Human Skin Fibroblast Cultures with an Automatic Wedge Biopsy Instrument