Comparison Of Growth Curves Research Articles

Transplantation of Nuclei in Neurospora crassa

Wilson, James F. (Hartnell Coll., Salinas, Calif.) Transplantation of nuclei in Neurospora crassa. Amer. Jour. Bot. 50(8): 780–786. Illus. 1963.—Heterocaryons of N. crassa were produced artificially by cell-to-cell transfer of protoplasm of genetically marked strains. The injected hyphal sections were excised and cultured separately. The criteria of prototrophic growth and recovery of conidia of the donor genotype were used to prove that functional nuclei had been transplanted. Reciprocal injections were made with 2 pairs of macroconidial and 3 pairs of microconidial strains. Growth curves and conidial ratios of these artificial heterocaryons were compared to the corresponding natural heterocaryons. In each pair of heterocaryons produced by reciprocal injection, the growth curve of only one was equivalent to the naturally formed heterocaryon of that pair. The growth curve of the other artificial heterocaryon differed either in rate or in the lag period before growth occurred. There was no apparent relation between conidial ratios of the natural heterocaryons and the artificial heterocaryons with comparable growth curves. Injection of normal nuclei into a morphological temperature-sensitive mutant produced an apparent heterocaryon which grew with normal morphology at 34 C. The apparent stability of Neurospora nuclei may make in vitro studies possible.

TRANSPLANTATION OF NUCLEI IN NEUROSPORA CRASSA

Wilson, James F. (Hartnell Coll., Salinas, Calif.) Transplantation of nuclei in Neurospora crassa. Amer. Jour. Bot. 50(8): 780–786. Illus. 1963.—Heterocaryons of N. crassa were produced artificially by cell‐to‐cell transfer of protoplasm of genetically marked strains. The injected hyphal sections were excised and cultured separately. The criteria of prototrophic growth and recovery of conidia of the donor genotype were used to prove that functional nuclei had been transplanted. Reciprocal injections were made with 2 pairs of macroconidial and 3 pairs of microconidial strains. Growth curves and conidial ratios of these artificial heterocaryons were compared to the corresponding natural heterocaryons. In each pair of heterocaryons produced by reciprocal injection, the growth curve of only one was equivalent to the naturally formed heterocaryon of that pair. The growth curve of the other artificial heterocaryon differed either in rate or in the lag period before growth occurred. There was no apparent relation between conidial ratios of the natural heterocaryons and the artificial heterocaryons with comparable growth curves. Injection of normal nuclei into a morphological temperature‐sensitive mutant produced an apparent heterocaryon which grew with normal morphology at 34 C. The apparent stability of Neurospora nuclei may make in vitro studies possible.

The effect of pH on growth, protein synthesis, and lipid-rich particles of cultured mammalian cells.

A simple procedure has been established for controlling and measuring the pH of media in which the bicarbonate-carbonic acid system is the predominant buffer. The HCO(-) (3) concentration was maintained at 22.5 mM and the H(2)CO(3) concentration was varied by equilibrating the media with 0.5 to 40 per cent CO(2) in air. The curve relating extracellular pH to 3 day cell growth was similar for glass-attached HeLa and Chang liver cells. Maximum growth occurred over a pH range of 7.38 to 7.87. Cell growth declined precipitously on the alkaline side and more gradually on the acid side of the optimal pH range. Comparable pH growth curves were also obtained with newly isolated cells from rat liver and skeletal muscle. It was shown that the effect of pH on growth was independent of the CO(2) concentration and that the essential nutrients in the medium were stable over the pH range studied. Although alkalosis depressed the 3 day cell population, cells exposed to a pH of 8.0 to 8.2 grew at the maximal rate for the first 12 to 24 hours. Growth then ceased abruptly and the cells entered a steady state with respect to net protein synthesis. This was followed by cytoplasmic retraction and cell death. Increasing the concentrations of calcium or magnesium in the medium failed to prevent the effects of alkalosis. Moreover, the increase in CO(-) (3) concentration of the media and the concomitant decrease in Ca(++) ion concentration that occur at high pH were eliminated as determining factors in the growth failure and death. While acidosis had a less pronounced effect on the 3 day cell population, its effect on the growth rate was immediate. The increase in cell generation time was proportional to the H(+) ion concentration. In each of the cell lines studied, acidosis was accompanied by a striking increase in the number of cytoplasmic perinuclear granules. These granules which stain supravitally with Janus green are extracted from fixed cells with lipid solvents. They maintain their identity in cell homogenates and may be isolated from the other subcellular structures by differential centrifugation; at 100,000 g they form a distinct layer at the top of the supernatant fraction. On the basis of their physical and chemical properties, these granules have been called lipid-rich particles. The accumulation of lipid-rich particles in acidosis was independent of the growth rate and the CO(2) concentration.

Note on a Method of Comparing Diets for the Pale Western Cutworm, Agrotis orthogonia Morr. (Lepidoptera: Noctuidae)

The pale western cutworm, Agrotis orthogonia Morr., has been successfully reared in the laboratory on a number of different foods (Jacobson and Blakeley, 1958; McGinnis and Kasting, 1959). Initial evaluation of the nutritional adequacy of diets for the cutworm has been achieved by comparing growth curves based on mean weights of the groups of larvae on test (McGinnis and Kasting, 1959). This note shows that the relative value of diets for the larvae of the pale western cutworm can be established more simply by comparing growth curves based on mean weights recorded two days after each moult.

A Comparison of Growth Curves of Man and Other Animals

A Comparison of Growth Curves of Man and Other Animals