Viability test

Binder, W.D., Mitchell, G.M. Ballantyne, D.J. (1974). Pollen viability testing, storage and related physiology. Canada Forestry Service, Pacific Forest Research Centre, Victoria, B.C. Report BC-X-105, pp. 1-37. 

The knowledge gathered so far consists of data based on a nonstandardized CNT material thus, all the studies reviewed in Table 7.1 have to be considered as isolated and not directly comparable experiments. In particular, from the divergent interpretation of the WST-1 assay output in two different studies, it is clear that a standardized CNT reference material used by all toxicologists is needed. It is also important to keep in mind that the employment of viability tests based on the... 

ATP is an ideal indicator of cell viability. Blood or blood cell concentrates prepared for transfusion are stored for periods of a few days to several weeks in the blood bank. Viability checking of the blood cells is necessary to avoid posttransfusional reactions [94], This quality control of the conserved red blood cells and platelets can easily be performed by measuring the ATP concentration as an expression of their integrity. By the same measurement it was possible to confirm the diagnosis and monitor the treatment effects in various cases of platelet disease [97], The possibility of determining cells viability can be exploited to examine more free cells or tissue, as in the spermatozoa viability test, based on the correlation between ATP content and mobility. 

Because these different viability tests all reflect different aspects of cell viability, the choice of test depends on the aim of the study. For toxicity studies where biotransformation is an important bioactivation or detoxification step, metabolic function tests should be included to judge the validity of the method, whereas viability tests are needed to assess toxic effects. Both positive and negative controls should be included in such studies. When human liver is used, the characterization of metabolic activity is especially important because of the large inter-individual variability associated with this property [75]. 

However, another large meta-analysis study found no difference between different viability testing methods for predicting survival after revascularization, suggesting that decisions driven by viability studies are clinically equivalent and have similar outcomes, irrespective of the technique used [88]. While improved LV function is a major factor affecting... 

Allman KC, Shaw LJ, Hachamovitch R, Udelson JE. Myocardial viability testing and impact of revascularization on prognosis in patients with coronary artery disease and left ventricular dysfunction a meta-analysis. J Am Coll Cardiol 2002 39 1151-1158... 

Wash cells twice with labeling buffer by centrifugating at 300g and proceed to determine cell concentration using a particle counter. Also, perform a viability test using a Trypan blue exclusion method. Keep cells in cold storage (4°C) until used. 

Prolonged and unnecessary enzymatic treatment, i.e., trypsinization of tumor cells, can also alter their survival and metastatic behavior in vivo. Moreover, viability tests (trypan blue exclusion) and even plating efficiency in vitro do not predict or correlate with the in vivo biological behavior of trypsinized cells. 

Samples for cell viability tests were taken three times during the different batch and fed-batch fermentations. A sample of 1 mL was diluted 104-105 times and 0.1 mL of diluted sample was applied to an agar plate. Five to six plates were prepared for every sample, and the plates were incubated for 24 h at 30°C. The total cell concentration in the reactor sample was determined with microscopy using a Biirker counting chamber. The viability, expressed as the fraction of cells able to form colonies, was calculated by dividing the concentration of colony-forming cells by the total cell concentration. 

On the other hand, electrical impedance measurement of bacterial suspensions (.Listeria innocua) was carried out on a Si-glass chip. This method was used to perform a cell viability test. This is because the metabolic products produced from viable cells modify the ionic strength of a low-conductivity medium, significantly altering its electrical characteristics. Later work also involved the detection of the presence of small numbers of bacterial cells in a Si chip 100 L. innocua cells, 200 L. monocytogenes cells, and 40 E. coli cells [93,885], In another report, impedance spectroscopy has been used for analysis of erythrocytes in a glass-polyimide chip [886]. 

Some cytotoxicity assays, such as dye incorporation by dead cells or 51Cr or fluorescein release by labeled cells, offer instantaneous results and are named viability tests. These tests are adequate for the identification of dead cells, but can overestimate cell survival over longer periods. Most of them cause membrane rupture and cell death. 

Before use, frozen aliquots should be allowed to thaw overnight at 4°C and may then be killed by heating at 60°C for 30 40 min with regular mixing during this time. It is recommended that viability tests be performed after this heat treatment to ensure adequate killing. 

Prior to immunizations, viability tests are conducted on the vaccines by inoculating different tubes containing 10 mL of sterile Todd-Hewitt broth with 0.1,0.2, and 0.5 mL of vaccine. A tube with a sample of viable streptococcal cells is also prepared. The tubes are incubated at 37°C and growth is monitored by measuring the absorbance at 600 nm after 12, 24, and 48 h of incubation. Growth should be observed in the control, but not in the formaldehyde-treated sample. 

Nonviable cells of S. faecalis strain N were used for the immunization of rabbits to activate the immune system to synthesize antibodies. To prepare the vaccine, the cells from 500 mL of freshly grown culture were collected by centrifugation at 10,000 rpm and then shaken in 100 mL of 0.2% formaldehyde in saline for 48 h. After removal of the formaldehyde by washing the cells with 0.01 M phosphate buffer of pH 7.2 in saline, the cells were suspended in 80 mL of sterile saline. Viability tests showed that the cells were made nonviable by this treatment. This suspension exhibited high absorbance at 600 nm and was used for immunizing rabbits. 

Another and more convincing explanation for this discrepancy of previous and recent studies related to the inactivation of Cryptosporidium refers to the methods of viability testing. So, it seems that in vitro viability assays (chemical excystation and vital stains) that have been used previously may have significantly underestimated the inactivation efficacy of UV-C irradiation of the parasites compared with in vivo infectivity assays applied in recent studies using neonatal mouse models (Craik et al, 2001). This was also demonstrated by UV inactivation of Giardia muris cysts using MP Hg lamps (Craik et al., 2000). 

Fig. 3.13 Investigation of the response of murine fibroblast cells incubated with different concentrations of NS. (a) Cell viability test conducted with the Cell-Titer-Blue assay over 4 days incubation of cells with a range of NS concentrations between 0 and 300 fM (0-1,800 NS/cell). (b) Assays of apoptosis and necrosis markers at two selected NS concentrations (10 and 300 fM), results show no difference to untreated cell controls...

Before performing a product bacteria challenge test, it has to be assured that the liquid product does not have any detrimental, bactericidal or bacteriostatic, effects on the challenge organisms. This is done utilizing viability tests. The organism is inoculated into the product to be filtered at a certain bioburden level. At specified times, the log value of this bioburden is tested. If the bioburden is reduced due to the fluid properties, a different bacteria challenge test mode becomes applicable. ... 

Use In germination and viability tests. Viable parts of seed are stained red by deposition of red insoluble triphenyl formazan. 

Seeds. Witchweed seeds were collected from plants in experimental field of the USDA Methods Development Laboratory, Whiteville, N.C., USA and stored for three years at room temperature. Viability of these seeds was more than 95% according to a tetrazolium chloride viability test. 

Cell Proliferation and Viability Tests 7.10.3.1 Alkaline Phosphatase (ALP) Activity... 

Cellular Labeling with Chelates Relevance of In Vitro and In Vivo Viability Testing... 

For evaluation the function of labeled RBC, in vitro and in vivo viability testing have been used. No evidence of morphological alteration of RBC (histological and/or electron microscopic examinations (Fig. 8.5) after Tc-labeling was seen. 

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