Appropriate Number Of Cells Research Articles

68] Procedures for the isolation and characterization of cell lines resistant to interferon

Publisher Summary This chapter describes the procedures for the isolation and characterization of cell lines resistant to interferon. The method of isolating resistant cell lines from an interferon-sensitive cell population is in principle identical with that of isolating cells resistant to growth-inhibiting drugs. As a model system human transformed cell lines RSa and RSb is used. These cell lines are characterized by their high sensitivity to the anticellular action of human interferon. Effects of interferon on the growth of cells are influenced by the density of cells and units of interferon applied. Interferon-resistant cell clones are isolated from cell colonies by inoculating an appropriate number of cells in soft agar or agarose medium, in which interferon is incorporated. Two strains of interferon-resistant cells, mouse L1210 R and human IF, have been maintained and their characteristics are analyzed. Therefore, the characterization of interferon-resistant cell lines is described by referring to these cells. Sensitivities of isolated cell strains to antiviral and cell growth-inhibiting action of interferon must be estimated quantitatively.

Evaluation of estimation method of X-ray spectral distribution by attenuation data (author's transl)

This paper describes a method for estimating spectral distributions from X-ray attenuation data obtained by inserting metal filters in the beam. First, the principle of the estimation method is briefly outlined. the spectral distribution is approximated by a histogram with an appropriate number of cells whose heights are estimated by recursive algorithm. The algorithm is based on a gradient method that seeks the minimum of a least-square criterion function. Next, the following two problems to which special attention should be paid in practical applications are discussed: 1) appearance of discontinuity in estimated distribution; and 2) termination criterion of iterative computation. The problem 1) is investigated theoretically and the improved algorithm is devised. Computer simulation is performed for the problem 2), and a proper termination criterion based on the decreasing curve of the least-square criterion function is given. The validity of estimation results is illustrated about the spectral distribution of 140 kV constant potential X-ray source.

The Interaction of Clostridium perfringens and Its Toxins in the Production of Necrotic Enteritis of Chickens

The intraduodenal administration of large numbers of Clostridium perfringens cells harvested from broth cultures and resuspended in PBS or fresh sterile thioglycollate broth produced a very mild form of necrotic enteritis. Administering an appropriate number of cells in culture supernatant, however, produced typical field-type disease. Alpha toxin was shown to be the significant toxin recoverable from broth-culture supernatant fluids. Requirements to produce the disease are minor intestinal damage and sufficient numbers of toxigenic C. perfringens in the intestine.

A new method for the study of cell division and cell extension with some preliminary observations on the effect of temperature and of nutrients

A novel technique for determining the total and the meristematic number of cells in a root meristem is described; it involves macerating the tissue in a known volume of fluid, and subsequently determining the appropriate number of cells in an aliquot on a haemacytometer slide. Root tips are cultured in batches on sintered glass disks with different nutrient media and at four temperatures. Samples of four roots are taken from each culture at intervals of 12 hr., and with each sample the average total number, the average meristematic number of cells, and the average length of each root are determined. From these primary data rates of division and indices of extension are calculated. It is shown that no division occurs in the absence of sugar, and the rate of division is increased by providing inorganic salts with the sugar, and still further increased by supplying yeast extract. With each nutrient the rate of division is higher at 15° than at 25°C, but lower at 5° than at 15°C. No extension occurs in the absence of sugar, and the greatest extension is given with sugar and inorganic salts. Yeast extract in the form and concentration used in these experiments tends to depress extension. The results of the main body of experiments are discussed along with others showing the effects of single mineral deficiencies. It is suggested tentatively that in these experiments the level in the cells of certain products of carbohydrate degradation determine the rate of cell division, and that in cell extension the process depends to some extent on a synthesis of protein which requires a supply of sugar and of certain inorganic salts.