THE ACCELERATING EFFECT OF MANGANOUS IONS ON PHAGE ACTION

Dilute solutions of MnCl₂ or MnSO₄ accelerate the lytic effect of phage upon susceptible staphylococci. Under the conditions of our experiments the manganese-containing mixtures lysed regularly 0.5 hour sooner than the controls. The effect is shown to be due to a lowering of the lytic threshold, i.e. the quantity of phage/bacterium requisite for lysis; Mn⁺⁺ reduces the ratio from 54 to about 12. In the presence of Mn⁺⁺ phage distribution is altered and in growing phage-bacteria mixtures the extracellular phage concentration is increased by manganese to approximately 4 times that occurring in the absence of manganese. There appears to be no enhancement of phage formation nor any affect on the rate of bacterial growth. As would be anticipated, for any given initial phage concentration the end titre after completion of lysis is less in the presence of manganese than in its absence. This is due to the reduced lytic threshold produced by Mn⁺⁺, there consequently being less phage needed to bring about lytic destruction of the bacteria.     

FURTHER OBSERVATIONS ON THE STRUCTURE OF SELAGINELLITES CRASSICINCTUS

Leisman , Gilbert A. (Kansas State Teachers Coll., Emporia.) Further observations on the structure of Selaginellites crassicinctus. Amer. Jour. Bot. 48(3): 224–229. Illus. 1961.—Specimens of Selaginellites crassicinctus Hoskins and Abbott in coal balls from southeastern Kansas have yielded new information concerning the anatomy of this strobilus. The axis contains an exarch protostele apparently suspended in an air-cavity by endodermal trabeculae. Sporophylls are attached in alternating whorls of 4 each. The strobilus is compared with modern Selaginella and a related compression fossil species.     

STUDIES ON THE MECHANISM OF ACTION OF PEDERINE

Pederine, a drug extracted from the coleopter Paederus fuscipes, inhibits the growth of in vitro cultured cell lines at concentrations of the order of 1.5 nanogram/ml. Cytological examination shows a generalized cytotoxic effect. Analysis of macromolecular syntheses by the use of radioactive precursors shows that pederine causes an almost immediate block of protein and DNA synthesis, without affecting RNA synthesis. The effects on the synthesis of the two types of macromolecules remain nearly simultaneous even at the lowest active concentrations of pederine. Studies with cell-free systems show that the drug inhibits protein synthesis, whereas it is ineffective on the DNA-polymerizing activity. It seems, therefore, that the drug acts primarily on the amino acid-polymerizing system, and that the effect on DNA is secondary. This idea is strengthened by the observation that puromycin, a specific inhibitor of protein synthesis, also affects promptly DNA synthesis of in vitro cultured cells. Other authors have shown the same phenomenon with a number of inhibitors of protein synthesis; the properties of pederine support, therefore, the view that continuous protein synthesis is necessary for the maintenance of DNA replication in higher organisms.     

FURTHER OBSERVATIONS ON THE FINE STRUCTURE OF THE PARIETAL EYE OF LIZARDS

An electron microscopical study of the third eye of the Western Fence Lizard, Sceloporus occidentalis, fixed with 1 per cent osmium tetroxide, pH 7.4–7.6, for 16 to 20 hours at 0°C., revealed the following new facts. The fibrillar system of the retinal photoreceptor consists of nine double fibrils enclosed in a sheath. Pigment cells and lens cells possess similar systems. Two short cylindrical centrioles are associated with the fibrillar apparatus: one, from which striated rootlets extend inward, lies at the base of the fibrils, with the other at an oblique angle to the axis of the system. A Golgi complex, whorls of endoplasmic reticulum, lipid (?) droplets, and other organelles and inclusions in the photoreceptors are described. An axon leads from the base of the photoreceptor into the nervous layer of the retina which consists of many nerve fibers and large ganglion cells. Although the pattern of neural connections has not yet been determined, some synapses were found. The parietal nerve consists of about 250 non-medullated fibers. The capsule of the eye usually has a layer of iridocytes, which contain rows of guanine (?) rods. A few parietal eyes of the Granite Night Lizard, Xantusia henshawi, were also examined. Large lipid (?) droplets occur in the bases of their receptoral processes.     

FURTHER OBSERVATIONS ON THE FINE STRUCTURE OF THE MACRONUCLEUS IN TOKOPHRYA INFUSIONUM

In a previous paper (8) an organized structure was described in the macronuclei of certain old organisms of Tokophrya infusionum. It was found that the same honeycomb structure appears in great abundance in the macronuclei of overfed organisms. This permitted a better three-dimensional reconstruction of the described structure. Since the defined structure may be experimentally induced, it offers an opportunity for further more detailed studies as to its nature and meaning.