Effects of inhibitors of nucleic acid and protein synthesis on growth and aggregation of the cellular slime mold Dictyostelium discoideum.

Precursor--Product Relationships between Nucleotides and RNA during Differentiation in Dictyostelium discoideum

“…In fact, bacterial contamination significantly contributed to the results of incorporation studies only when the level of bacteria reached I x 107/ml in the incubation suspension. This is the same level of bacteria for measurable incorporation of uridine into RNA as that found by Hirschberg et al (1968).…”

“…The rate of RNA turnover in Dictyostelium discoideum has been estimated previously by several different methods (Hirschberg et al 1968;Inselburg & Sussman, 1967;Pannbacker, 1967). However, the percentage of the RNA pool which is undergoing turnover at a particular stage of differentiation has not been accurately determined, primarily because of the lack of an appropriate method for determining this parameter.…”

“…Too often these parameters have been calculated from simplified models which represent the flow of radioactivity from precursor to product as would occur in an in vitro system, rather than fully considering the complexities in vivo. In some cases, it is assumed that the rate of incorporation of exogenous radioactive precursors into a macromolecule truly reflects the absolute rate of synthesis (Hirschberg, Ceccarini, Osnos & Carchman, 1968), but this rate of incorporation rarely reflects synthesis alone and degradation must be considered. Likewise, the macromolecule may be synthesized from only a portion of the soluble precursor pool (Cowie & Bolton, 1957;Plagemann, 1971Plagemann, , 1972.…”

Aggregation and Differentiation in the Cellular Slime Molds

“…This means that either the DNA fragments can manufacture normal messenger RNA or all the messages have been prefabricated before the irradiation. The former possibility seems more promising, although Hirschberg et al (48) suggest, because of the greater sensitivity of dividing cells to RNA synthesis inhibi tors as compared to cells in later stages of development, that all the mes sages could conceivably be manufactured before the beginning of the aggre gation stage.…”

Growth of Dictyostelium discoideum in the Presence of Antibiotics

“…A few antibiotics have been used with Dictyostelium di8coideum to lower the level of contamination of stock cultures (1) and growing cultures (2) and as inhibitors of macromolecular synthesis during differentiation (3)(4)(5). Penicillin and streptomycin are frequently used and are known to have no effect on amoeba growth.…”