Cell maintenance

Cells are stored In liquid nitrogen for longer shelf life. The freezing and thawing protocols are as follows  

For thawing cells from a frozen vial Requirements  

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A plot of the specific respiration rate ( 02 versus the specific growth rate coefficient [L is linear, with the intercept on the ordinate equal to the oxygen uptake rate for cell maintenance. A formulation of this is ... 

True Growing and dividing cells need to use substrate to provide energy and materials for growth, maintenance and product formation. In immobilised (non-growing) systems the energy and materials are only required for cell maintenance and product formation. 

CSF-I is thus one major bioactive factor released by MSS cells which can stimulate Myl-D7. However, it should be noted that stimulation of lineage negative Myl-D7 cells by E.coli-derived recombinant-CSF-1 at equivalent CSF-i concentrations was by far less efficient than CM from MSS cells. Furthermore, the stimulation of lineage negative cells by MSS supernatants was far better than that of L929 supernatants having similar concentrations of CSF-I (data not shown). Thus it is likely that MSS stromal cells produce additional factors that are required for Myl-D7 cell maintenance. 

Carmell MA, Xuan Z, Zhang MQ et al (2002) The argonaute family tentacles that reach into RNAi, developmental control, stem cell maintenance, and tumorigenesis. Genes Dev 16 2733-2742... 

Li Z, Rich JN (2010) Hypoxia and hypoxia inducible factors in cancer stem cell maintenance. Curr Top Microbiol Immunol 345 21-30... 

A number of procedures used to determine protein quality involve bioassays. Bioassays require feeding live animals protein ingredients for a specified period of time, and then estimating the nutritive value of the protein. Two such assays are the rat-based protein efficiency ratio (PER) bioassay and the human nitrogen balance assay (Dimes et al., 1994). Animal feeding experiments require chemical analyses of both the dietary inputs and then the metabolic output of the animal (e.g., body composition analysis, fecal sample analysis, collection, and assay for urine) from which the efficiency of protein metabolism can be predicted as well as how the protein supports animal growth and cell maintenance. 

PER is a method to metabolize or determine the quality of protein in foods. Quality is measured by the amount of usable protein and the growth resulting from it through an animal assay. Formerly, this method was used as the standard method for all protein quality analysis. However, there is some question as to whether or not it is a valid measurement. This is because PER does not account for the differences in amino acid requirements between humans and rats (Seligson and Mackey, 1984), nor does PER account for the protein needed for cell maintenance. Therefore, PER results often overestimate the requirements for some amino acids and underestimate others. Specifically, PER tends to underestimate the protein quality of lysine-deficient proteins such as wheat gluten (Hackler, 1977). 

Net protein ratio (NPR) is used to correct PER values for the amount of protein required for cell maintenance. NPR is often run in conjunction with a PER. The experiment requires that one additional set of animals be added as a treatment group. This group of animals is fed a basal diet with no protein (zero protein or basal diet). Results from RNPR are similar to net protein utilization (NPU) and biological value (BV methods, see Alternate Protocol 4). A 2-week RNPR is thought to be the most appropriate rat test for routine assessment of protein quality. 

PER zero-protein diet formula. For determination of net protein ratio, a test diet that contains no protein is run as one of the test diets. This zero protein diet is used to derive a correction to account for the amount of protein required for cell maintenance. 

High protein digestibility does not necessarily mean high protein quality. Protein quality measures the balance between the amino acids in the protein necessary for growth and cell maintenance. 

Kitsos, C. M., Sankar, U., Illario, M., Colomer-Font, J. M., Duncan, A. W., Ribar, T. J., Reya, T. and Means, A. R., 2005, Calmodulin-dependent protein kinase IV regulates hematopoietic stem cell maintenance, J Biol Chem, 280, pp 33101-8. 

Once the nutrients enter the bloodstream, they are transported to various parts of the body for vital body functions. Nutrients are used to maintain essential functions such as breathing, circulation of blood and muscle movement, replacement of worn-out cells (maintenance), growth, reproduction and egg production. 

The classical studies of Monod (1942) demonstrated a carbon flux partition between catabolism and anabolism, and suggested that a small amount of the carbon uptake is used for maintenance purposes. However, at that time it was impossible to determine the consumption needed for cell maintenance, because the methodologies lacked precision. 

Later, it was observed that substrate to cell yield factors (YX/s) could vary as a function of specific growth rate. Pirt (1966) described a linear relationship between growth and substrate consumption, as well as the statement of a term for cell maintenance (Equation 26). 

Several of the terms above have been discussed in Sec. 7 rg and r are the specific rates (per broth volume) for cell growth and death, respectively rsm is the specific rate of substrate consumed for cell maintenance, and are the stoichiometric yield coefficient of species i relative to biomass x. The maintenance term in Eq. (19-81) can result... 

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