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Biomedical subjects

L Hayflick

Publications and source records attributed to L Hayflick.

At least 109 records · Page 6Linked to original sources
PubMed1967

Growth inhibition test for identification of Mycoplasma species utilizing dried antiserum-impregnated paper discs.

The growth inhibition test for identifying Mycoplasma species has been modified by drying antibody-impregnated paper discs at 5 C. When stored at -20 C, these discs have been found to retain their inhibitory activity for longer than 7 months. Since these discs can be stored for long period of time, significant advantages over present methods result. When, for example, discs are arranged on a ring, a single test can be used for the identification of an unknown human species. Valuable antisera can be distributed to other laboratories on paper discs in much less volume than can fluid antiserum. Considerable savings of time result from prior preparation of many discs that can then be stored and used over a long period of time. The growth-inhibiting antibody is stable, and the activity is not enhanced by a heat-labile accessory factor from fresh guinea pig serum which increases the antibody titer in the metabolic inhibition test.

Animals↗
PubMedDate not supplied

Comparison by autoradiography of macromolecular biosynthesis in "young" and "old" human diploid fibroblast cultures. A brief note.

The biosynthetic abilities of WI-38 fibroblasts from early and late population-doubling-level cultures were compared by autoradiography of cells grown with labeled precursors of DNA, RNA, protein and lipids. Incorporation of radioactive thymidine, uridine, protein-hydrolysate, acetate, oleic acid and cholesterol, as measured by the number of grains per cell surface, decreased with the progressive aging of the culture. However, the decrease in the incorporation of acetate, oleic acid and cholesterol was much smaller than that of the other precursors, indicating that lipid synthesis is affected to a lesser degree than protein and nucleic acid synthesis on aging. This result is in accord with the higher lipid content and proliferation of intracellular membranes in cells of "old" WI-38 cultures reported by others.

Acetates↗
PubMedDate not supplied

Recent advances in the cell biology of aging.

Cultured normal human and animal cells are predestined to undergo irreversible functional decrements that mimic age changes in the whole organism. When normal human embryonic fibroblasts are cultured in vitro, 50 +/- 10 population doublings occur. This maximum potential is diminished in cells derived from older donors and appears to be inversely proportional to their age. The 50 population doubling limit can account for all cells produced during a lifetime. The limitation on doubling potential of cultured normal cells is also expressed in vivo when serial transplants are made. There may be a direct correlation between the mean maximum life spans of several species and the population doubling potential of their cultured cells. A plethora of functional decrements occurs in cultured normal cells as they approach their maximum division capability. Many of these decrements are similar to those occurring in intact animals as they age. We have concluded that these functional decrements expressed in vitro, rather than cessation of cell division, are the essential contributors to age changes in intact animals. Thus, the study of events leading to functional losses in cultured normal cells may provide useful insights into the biology of aging.

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