Rates of RNA synthesis during early embryogenesis in Drosophila melanogaster

We determined the absolute rates of RNA synthesis during embryogenesis in Drosophila melanogaster by measuring the incorporation of ³H-5-orotic acid into RNA, and the specific activity of the UTP pool. Initially (preblastoderm) the rate of RNA synthesis is relatively high, but declines to a lower level by gastrulation. The data suggest that RNA synthesis is initiated during very early embryogenesis.     

OBSERVATIONS ON THE RELATIONSHIP OF THE GOLGI APPARATUS TO WALL FORMATION IN THE MARINE CHRYSOPHYCEAN ALGA, PLEUROCHRYSIS SCHERFFELII PRINGSHEIM

The role of the Golgi apparatus in wall formation of vegetative cells of a marine chrysophyte, Pleurochrysis scherffelii, is described. Wall fragments are synthesized within the cisternae of the Golgi apparatus. A single Golgi apparatus is always located at the cell periphery, and the distended cisternae are oriented toward the cell surface. A highly-ordered body found near the inflated cisternae is associated with spherical, membrane-bounded bodies which may be involved in the progressive degeneration of cisternal membranes which release wall fragments. Protoplast movement has been detected by time-lapse cinephotomicrography and is correlated at the ultrastructural level with change in positions of the Golgi cisternae. Wall-synthesizing capacity is greatest during transverse wall formation. Senescent cells lack a Golgi apparatus with inflated cisternae. In addition, wall fragments are not present in the Golgi cisternae at this stage. Zoosporogenesis results in a temporary loss of the wall-forming capacity of the Golgi apparatus; this activity then resumes with the formation of a different morphological entity, the scale. Preliminary quantitative measurements of the turnover capacity of the Golgi apparatus have been made. From these data it has been determined that between 41 and 82 Golgi generations are required to synthesize the cell wall of an actively growing cell; this estimate indicates that approximately one cisterna is produced every 2 min, provided the cell generation time is 3 days. The time-lapse cinephotomicrographic data confirm that the rate of production of Golgi cisternae is at least one cisterna every 2 min.     

Effect of Gibberellic Acid on the Elongation Rate of Agrostis alba Root Hairs

The influence of gibberellic acid over a wide range of concentrations on the rate of elongation of root hairs of redtop grass was investigated. The rate of root hair elongation was increased by GA over the concentration range of 10^?7 to 10^?12 M inclusive, with peak stimulation occurring at 10^?6 M. Although root hair growth was slightly accelerated by 10^?6 M GA, this concentration damaged many root hairs and caused some to stop growing altogether. Rate of root hair elongation was reduced to less than 84% of the control by 10^?5 M GA.     

Effect of actinomycin D and guanidine on the formation of a ribonucleic acid polymerase induced by foot-and-mouth-disease virus and on the replication of virus and viral ribonucleic acid

The RNA-dependent RNA polymerase induced in baby-hamster kidney cells by infection with foot-and-mouth-disease virus can be detected as early as 60min. after infection, which is 60min. before viral RNA synthesis commences. The time at which the polymerase can first be detected coincides with the latest time at which actinomycin D (50mug./10(7) cells) or guanidine (1mg./10(7) cells) inhibits virus replication. However, by increasing the concentration of guanidine, viral replication can be inhibited later in the growth cycle, casting doubt on the validity of the hypothesis that guanidine acts specifically on the formation of the viral RNA polymerase.     

A comparative study of three hypnotics: methyprylon,glutethimide and chloral hydrate

A controlled study designed to evaluate the hypnotic potentiality of methyprylon (300 mg.), glutethimide (500 mg.) and chloral hydrate (1000 mg.) was carried out on 50 in-patients experiencing long-standing insomina. The patients ranged in age from 21 to 60 years, the sexes were equally represented and the clinical diagnoses were psychoneurosis, reactive depression, or anxiety reaction. An interesting feature of the experimental design allowed for the exclusion of placebo reactors before the initiation of the main trials. No difference in effectiveness of maintaining sleep could be established among the three hypnotic agents, indicating that at the usual levels of statistical significance, all three agents were equally effective as hypnotics. However, a significant trend (P = .05) was found for methyprylon (Noludar) to be the most effective and chloral hydrate to be the least effective of the three drugs in maintaining sleep. Methyprylon was found statistically (P = .05) to be the fastest sleep-inducing agent, whereas glutethimide (Doriden) proved to be the slowest of the three hypnotics with respect to sleep induction time.