Population Doubling Time

I don t want to grow young again. I just want to keep on growing old. 

Population doubling time is an important measure of the recovery time for a threatened species. Population doubling time (l2 , in years) has been given by Calder (2000) for mammals as 

Each of these equations is based on a different sample of mammals. Calder (2000) gives doubling times for birds of 

Therefore, bird populations take roughly three times as long to double as do mammalian populations. 

The goal of an endangered species recovery plan is to increase numbers to sustainable levels (Calder, 2000). This requires an adequate area of suitable habitat and protection from the historic causes of decline. 

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A method of assessing the toxicity of implants has been proposed based on the effects on cell ultrastructure in organ cultures, on cell surface characteristics, and cell population doubling times. The effects have been correlated with hemorrhage, fibrosis, and necrosis, respectively (103). Poly-e-caprolactone was stated to give minimal tissue reaction and could not be scored in these tests. 

Based on the results from those cell calibration assays, the routine incubation period was set at 3 days. During that interval, some of the cells will proliferate, some will be quiescent but metabolically active, and some will die, which is the case for most primary cell cultures. Because these cells are cultured for periods far shorter than their typical population doubling time (about 6 to 7 days), these cells should not fully adapt to the tissue culture conditions and, therefore, maintain their primary cell phenotype. 

The use of an immobilized biofilm system is recommended, since the oxidation products often are only slowly biodegradable. Biomass, especially slow growing microorganisms, can efficiently be kept in the system using support material. This is especially important in continuously operated systems where the liquid phase is completely mixed. In such a system suspended biomass would be washed out when the hydraulic retention time is less than or equal to the population doubling time (i. e. the reciprocal of the specific growth rate Grady, 1985). In several studies materials such as polyurethane foams (Moerman et al., 1994 Jochimsen, 1997) or quartz sand particles (Stem etal., 1995 and 1996 Heinzle et al, 1995 Saupe and Wiesmann, 1998) have been used for immobilization. 

Cell generation time The interval between consecutive divisions of a cell. This interval can best be determined, at present, with the aid of cmephotomicrography. This term is not synonymous with population doubling time . 

Population doubling time The interval calculated during the logarithmic phase of growth in which, for example, 1.0 x 10 cells increase to 2.0 x 10 cells. This term is not synonymous with the term cell generation time. 

Several differences distinguish human from mouse ES cells [32]. The hES cells have a slightly different morphology and form flatter colonies. The stage-specific embryonic antigen-3 and -4 as well as TRA-1-60 and TRA-1-81 are expressed by the human, but not by mouse, ES cells [32]. Moreover, hES cells grow more slowly than mouse ES cells the population doubling time of mouse ES cells is -12 hours, whereas that of hES cells is about 36 hours. 

Fig. 3.7 Typical adaptation profiles for two different antibody-producing PER.C5 cell lines (A and B). Cells cultured in the presence of 10% FBS are transferred directly to serum-free media in Erlenmeyer shake flasks. Cells are passaged and population doubling time is calculated.

Fig. 3.9 Overview of the seven antibody-producing cell lines yielding more than 500 mg in batch culture (A), specific productivity ranging from 12 to 22 pg per cell per day (B), and population doubling time ranging from 24 to 34 hours (C).

These results were the first investigation regarding the relationship between the cytotoxicity of silica and the population doubling time of different cell lines as well as the benefits of using chitosan to prepare composite silica nanoparticles. They would be relevant for future applications of silica nanoparticles in drug delivery and controlled release applications. 

The population doubling time has been given in Equation 7.6.8c as... 

From Table A.1, the mass of a male bison is found to be 1000 kg. The population doubling time is calculated as... 

Cell Culture. Chinese hamster ovary (CHO) cells were used for mutagenetic studies. These cells were grown in Eagle s minimum essential medium with 10% fetal calf serum, in which they had a population doubling time of 10 h. 

P388 and B16 population doubling time by the acyclic monoterpene geraniol. Cancer Res., 51 37-42. 

The term X, describes the age distribution of the population, it is a term which varies slowly with population doubling time with a minimiun value of 0.693 in steady state tissues and a maximum value of 1.38 if the S phase cxrcupied the complete cell cycle. In tumours a value of 0.8-1 is common. The volmne doubling time represents the time interval in which a tumour doubles its volmne and will be subject to cell loss and the growth fraction, as well as the influence of any host cells contained within the tumour mass, and is related to Tp by the equation ... 

Cells were isolated and cultured in serum - free medium, the keratinocytes commenced to form cell clusters in the third or the fourth day. Then, these clusters became more and more big and associated to form a single cell layer onto culture dish surface (the seventh day). The population double time is 36h. 

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