Doubling time

Abstract: We describe the isolation of a nonhematopoietic (CD45-, CD34-, SH2+, SH3+, Thy-1+, CD44+) human umbilical cord perivascular (HUCPV) cell population. Each HUCPV cell harvest (2-5 x 10(6), depending on the length of cord available) gave rise to a morphologically homogeneous fibroblastic cell population, which expressed alpha-actin, desmin, vimentin, and 3G5 (a pericyte marker) in culture. We determined the colony-forming unit-fibro-blast (CFU-F) frequency of primary HUCPV cells to be 1:333 and the doubling time, which was 60 hours at passage 0 (P0), decreased to 20 hours at P2. This resulted in a significant cell expansion, producing over 10(10) HUCPV cells within 30 days of culture. Furthermore, HUCPV cells cultured in nonosteogenic conditions contained a subpopulation that exhibited a functional osteogenic phenotype and elaborated bone nodules. The frequency of this CFU-osteogenic subpopulation at P1 was 2.6/10(5) CFU-F, which increased to 7.5/10(5) CFU-F at P2. Addition of osteogenic supplements to the culture medium resulted in these frequencies increasing to 1.2/10(4) and 1.3/10(4) CFU-F, respectively, for P1 and P2. CFU-O were not seen at P0 in either osteogenic or non-osteogenic culture conditions, but P0 HUCPV cells did contain a 20% subpopulation that presented neither class I nor class II cell-surface major histocompatibility complexes (MHC-/-). This population increased to 95% following passage and cryopreservation (P5). We conclude that, due to their rapid doubling time, high frequencies of CFU-F and CFU-O, and high MHC-/- phenotype, HUCPV cells represent a significant source of cells for allogeneic mesenchymal cell-based therapies.

Abstract: Radiation survival curves were generated for V79 Chinese hamster and two human lung cancer cell lines (NCI-H460 and NCI-H249) with doubling times of 10, 20, and 85 h, respectively, using a standard clonogenic assay, a dye exclusion assay, and a semiautomated colorimetric assay utilizing a tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylformazan bromide. Comparable results for D0 and extrapolation number (n) were observed for all assays in the lines with doubling times of 10 and 20 h. In these instances the tumor cell lines had undergone seven or more doublings after radiation. For the tumor line (H249) with an 80-h doubling time the D0S were comparable between the assays while the extrapolation number was increased in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylformazan bromide assay, a result probably related to the lower number of doublings (less than 4) after radiation. We then tested the ability of the assays to detect radiation protection and sensitization using known agents. We found that cysteamine treatment resulted in radioprotection (by a factor of 8 at 8 Gy) while 5-bromo-2-deoxyuridine incorporation caused enhancement of radiation sensitivity in all three assays. We conclude that, while optimal conditions for each cell line (cell number plated and doubling time) must be established, using characterized tumor cell lines, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylformazan bromide assay could be automated and thus be of great value in screening large numbers of potential radiosensitizers or protectors.

Abstract: This review begins by briefly presenting the history of research on the chemical composition and other parameters of cells of E. coli and S. enterica at different exponential growth rates. Studies have allowed us to determine the in vivo strength of promoters and have allowed us to distinguish between factor-dependent transcriptional control of the promoter and changes in promoter activity due to changes in the concentration of free functional RNA polymerase associated with different growth conditions. The total, or bulk, amounts of RNA and protein are linked to the growth rate, because most bacterial RNA is ribosomal RNA (rRNA). Since ribosomes are required for protein synthesis, their number and their rate of function determine the rate of protein synthesis and cytoplasmic mass accumulation. Many mRNAs made in the presence of amino acids have strong ribosome binding sites whose presence reduces the expression of all other active genes. This implies that there can be profound differences in the spectrum of gene activities in cultures grown in different media that produce the same growth rate. Five classes of growth-related parameters that are generally useful in describing or establishing the macromolecular composition of bacterial cultures are described in detail in this review. A number of equations have been reported that describe the macromolecular composition of an average cell in an exponential culture as a function of the culture doubling time and five additional parameters: the C- and D-periods, protein per origin (PO), ribosome activity, and peptide chain elongation rate.

Abstract: An epithelioid cell line, started from a human pancreatic carcinoma of ductal cell origin, has been maintained in culture for over 2 years and has been subcultured more than 40 times. The PANC-1 cell line has a doubling time of 52 h and G6PD activity of the slow mobility of B type. Chromosome studies show a modal number of 63 with three distinct marker chromosomes and a small ring chromosome. The malignant nature of the PANC-1 cell line was verified by: (1) the ready growth of PANC-1 cells in soft agar and on top of a fibroblast monolayer; and (2) the formation of a progressively growing anaplastic carcinoma after injection of a nude-athymic mouse with PANC-1 cells.