The differential effect of 2-deoxyguanosine on concanavalin A-induced suppressor and cytotoxic activity

The effect of 2-deoxyguanosine (dGuo) on the generation in vitro of nonspecific suppressor cells in murine spleen cell cultures by concanavalin A (Con A) is examined. The experiments indicate that dGuo abrogates the generation of nonspecific suppressor activity by lectin stimulation of murine spleen cells. When comparisons were made between the effect of this nucleoside on the generation of suppressor and cytotoxic cells by Con A stimulation of murine spleen cells, it was found that dGuo only affected the generation of suppressor cells. The development of lectin-stimulated cytotoxicity was not affected by dGuo. In addition it was found that dGuo does not affect the NK activity of murine spleens.     

Stimulation of cholesterol side-chain cleavage by a luteinizing-hormone-releasing hormone (luliberin) agonist (ICI 118630) in rat Leydig cells.

The action of a luliberin (luteinizing-hormone-releasing hormone) agonist (ICI 118630) and lutropin (luteinizing hormone) on the activity of the cytochrome P-450 cholesterol side-chain cleavage enzyme in rat Leydig cells has been investigated. This has been carried out by studying the metabolism of exogenous (22R)-22- and 25-hydroxycholesterol to testosterone. It was found that both hydroxycholesterols increased testosterone production to higher levels than achieved by lutropin alone. Addition of luliberin agonist but not lutropin was found to increase further the metabolism of the hydroxycholesterol to testosterone; this occurred in the presence of saturating and subsaturating levels of the hydroxycholesterols. This effect of luliberin agonist was potentiated in the presence of lutropin. The protein synthesis inhibitor, cycloheximide, inhibited the luliberin agonist-induced stimulation of the hydroxycholesterol metabolism. At low calcium levels (1.1 microM), testosterone production was increased by addition of (22R)-22-hydroxycholesterol but the luliberin agonist effect was negated. The calmodulin inhibitor trifluoperazine inhibited (22R)-22-hydroxycholesterol-stimulated steroidogenesis and negated the luliberin agonist effect. These results indicate that luliberin agonist specifically increases the synthesis of the cytochrome P-450 cholesterol side-chain cleavage enzyme in rat testis Leydig cells.     

Analysis of a model of a vertically transmitted disease

A model is presented of a disease that can be transmitted directly from parent to offspring (vertical transmission) as well as through contact with infectives. A global stability analysis is given for the basic model and the epidemiological effects of vertical transmission are discussed. The effects of the addition of maturation and incubation delays as well as spatial diffusion are analyzed in some special cases.     

Effects of alkali ions on myosin conformation

We have used two probes to study the effects of alkali ions on the conformation of myosin. One was paramagnetic, the “spin label” N-(1-oxyl-2,2,6,6-tetramethyl-4-piperidinyl)-maleimide, which binds primarily to SH groups; and the other was fluorescent, l-anilino-8-naphthalenesulfonate, which binds to an apolar niche. The bonding of the spin label to myosin was carried out in 0.6M LiCl, 0.6M NaCl, or 0.6M KCl, and the resulting labeled myosin was studied in the same medium in which the myosin was labeled as well as in other alkali chlorides. The electron paramagnetic resonance spectra of the spin label showed that the structure of myosin in the vicinity of the labeled groups differed in the various salts. The protein surface in the region of the labeled groups restricted the rotational freedom of the spin label more in KCl than in any of the other salts. Although ions are known to influence the properties of myosin, our results show that these ions also effect the molecular structure. The fluorescence of l-anilino-8-naphthalenesulfonate, noncovalently attached to myosin in the presence of alkali chlorides, decreased progressively with increasing size of the cations, again showing the protein structure near the probe attachment to be a function of the cation, in the solvent. Ca²⁺ quenched the fluorescence of the bound probe, indicating an interaction between Ca²⁺ and the myosin molecule. The effect of Ca²⁺ on the fluorescence was greatest in KCl.     

The action of α-amanitin in vivo on the synthesis and maturation of mouse liver ribonucleic acids

α-Amanitin acts in vitro and in vivo as a selective inhibitor of nucleoplasmic RNA polymerases. Treatment of mice with low doses of α-amanitin causes the following changes in the synthesis, maturation and nucleocytoplasmic transfer of liver RNA species. 1. The synthesis of the nuclear precursor of mRNA is strongly inhibited and all electrophoretic components are randomly affected. The labelling of cytoplasmic mRNA is blocked. These effects may be correlated with the rapid and lasting inhibition of nucleoplasmic RNA polymerase. 2. The synthesis and maturation of the nuclear precursor of rRNA is inhibited within 30min. (a) The initial effect is a strong (about 80%) inhibition of the early steps of 45S precursor rRNA maturation. (b) The synthesis of 45S precursor rRNA is also inhibited and the effect increases from about 30% at 30min to more than 70% at 150min. (c) The labelling of nuclear and cytoplasmic 28S and 18S rRNA is almost completely blocked. The labelling of nuclear 5S rRNA is inhibited by about 50%, but that of cytoplasmic 5S rRNA is blocked. (d) The action of α-amanitin on the synthesis of precursor rRNA cannot be correlated with the slight gradual decrease of nucleolar RNA polymerase activity (only 10–20% inhibition at 150min). (e) The inhibition of precursor rRNA maturation and synthesis precedes the ultrastructural lesions of the nucleolus detected by standard electron microscopy. 3. The synthesis of nuclear 4.6S precursor of tRNA is not affected by α-amanitin. However, the labelling of nuclear and cytoplasmic tRNA is decreased by about 50%, which indicates an inhibition of precursor tRNA maturation. The results of this study suggest that the synthesis and maturation of the precursor of rRNA and the maturation of the precursor of tRNA are under the control of nucleoplasmic gene products. The regulator molecules may be either RNA or proteins with exceedingly fast turnover.     

MORPHOLOGY OF CHAETOMIUM ERRATICUM

Development of perithecia from single, uninucleate ascospores disclosed a homothallic condition for Chaetomium erraticum. This species was found to produce sessile ascogonial coil initials from uninucleate vegetative cells that become enveloped by hyphae formed at the base of the ascogonium. The ascogonium consists of several cells that are uninucleate or binucleate. A perithecium forms from numerous divisions and enlargement of the surrounding uninucleate cells. Differentiation of the perithecial cells results in the formation of a carbonaceous wall, perithecial hairs, and an ostiole lined with periphyses. A convex hymenial cluster of ascogenous cells forms in the lower half of the centrum from which typical croziers develop. Asci push up into the pseudoparenchyma cells of the centrum. The growth of the ascogenous system is in part responsible for increase in perithecial size. The breakdown of the pseudoparenchyma cells around the developing asci results in the formation of a central cavity in which ascospores are released when the asci deliquesce. No paraphyses are present. The type of development and features of the centrum of C. erraticum and other species of Chaetomium indicate a distinct Xylaria-type centrum.     

The occurrence of fungi in activated sludge

The population of a biological system in a sewage treatment plant is formed of a fortuitous assemblage of microorganisms, members of which are continually dropped out while additional members are recruited. Many of these organisms are active throughout the year. Fewer yeasts than filamentous fungi are found by the plating technique. The population is about evenly divided between species producing their spores in dry states and in wet states. The fungus population includes species which under certain circumstances are able to use a wide variety of substrates from simple sugars to complex carbohydrates and hydrocarbons.

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Zusammenfassung Die Population eines biologischen Systems in einem Kloakenwasser-Behandlungs-werk ist durch ein zufälliges Zusammentreffen von Mikroorganismen geformt, deren Mitglieder fortwährend ausfallen, während andere hinzukommen. Viele dieser Mikroorganismen sind während des ganzen Jahres aktiv. Weniger Hefen denn Fadenpilze sind mit der Plattentechnique gefunden. Die Population ist ungefähr gleichmäßig unter den Arten verteilt, die die Sporen in trockenem wie in feuchtem Zustand produzieren. Die Pilzpopulation umfaßt Arten, die unter gewissen Umständen fähig sind, eine große Varietät von Nährmaterial, von einfachen wie auch komplexen Kohlenstoffhydraten und Kohlenstoffhydraten zu benutzen.

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Much of the material included here was Presented at the 23rd Industrial Waste Conference Purdue University, Lafayette, Indiana May 7–9, 1968