Normal human diploid cells, TIG-1, ceased to proliferate at about the 62 population doubling level (PDL). Transformed clones isolated from TIG-1 cells infected with wtSV40 and those with tsA900 SV40 cultured at 34 degrees C were subcultured up to about 80 PDL. When the culture temperature of tsA SV40-transformed cells was shifted from 34 to 39.5 degrees C at 51 PDL, the growth curve of these transformed cells changed to that of normal young cells.
An extension of the mathematical model of immunological tolerance including two categories of B and T helper cells, each having a different lifespan, is presented. The simulated recovery from tolerance is compared with experimental data on B and T helper cell tolerance to human gamma globulin (HGG) induced in adult mice. The performed simulation runs suggest the conclusion that in this case it seems impossible to incorporate a high ratio of both, long-lived B cells and/or short-lived T helper cells, if good agreement with the available experimental data should be preserved.
International Journal of Cancer. Journal International Du Cancer
Dermal fibroblasts from patients with the autosomal dominant cancer-prone disease Basal Cell Nevus Syndrome (BCNS) exhibit a serum dependence, anchorage dependence and in vitro lifespan (about 20 population doublings or less) similar to those of fibroblasts from normal age-, race- and sex-matched controls.
Tumor-promoting phorbol esters, like growth factors, elicit pleiotropic responses involving biochemical pathways that lead to different biological responses. Genetic variant cell lines that are resistant to mitogenic, differentiation, or transformation responses to tumor promoters have been valuable tools for understanding the molecular bases of these responses.
In Vitro Cellular & Developmental Biology: Journal of the Tissue Culture Association
Human microvascular endothelial cells (HMVEC) from adult adipose tissue were cultured in MCDB 131 medium supplemented with 10% fetal bovine serum. Under these conditions, HMVEC from seven different donors had finite proliferative life spans ranging from 14.5 to 23.5 population doublings (PD), with a mean life span of 19 PD. Addition of 10% conditioned medium from activated human leukocyte cultures (BM Condimed) extended the life span of HMVEC to 31 to 41 PD, with a mean life span of 37 PD.
The idea that putrefaction of the stools causes disease, i.e., intestinal autointoxication, originated with physicians in ancient Egypt. They believed that a putrefactive principle associated with feces was absorbed in to the general circulation, where it acted to produce fever and pus. This description of the materia peccans represented the earliest forerunner of our present notion of endotoxin and its effect.
The desire for the extension of life is not one out of many desire in life, but a form of the fundamental desire for life itself. This so called 'categorical desire' is a necessary condition for the many desires in life. The question why we desire for life (and for its extension), is the question for the meaning of life. The searching for a 'natural lifespan' is meaningless when it wants to find in nature a given norm for the duration of life. It can only have meaning when it tries to formulate the conditions for the experience of life as successful and meaningful.
Abortion, primarily as a measure of population control, certainly continues to be an emotional, frustrating and stressful event. In continuation of our work on stressful situations in the female life span and biochemical parameters, serum lipid peroxide levels in terms of malondialdehyde (nmol/ml) have been determined in females undergoing abortion [suction curettage (n = 30), Emcredil-induced abortion (n = 30) and spontaneous abortion (n = 40)] and were compared with appropriate gestational controls.
Human diploid fibroblasts, strain MRC-5, were sequentially irradiated with 60Co gamma rays at intervals during their in vitro lifespan. The results indicate that 3 or 6 doses of 1 Gy can increase lifespan, and the same was true for cells treated with 3 doses of 3 Gy. Higher doses (5 x 3 Gy) did reduce growth potential, suggesting either that mid-late passage cells become more sensitive to radiation, or that doses beyond a given threshold reduce population lifespan by multiple cellular hits. The life extension induced by gamma rays might be due to an induced hypermethylation of DNA.