The reaction of alkylating agents with bacteriophage R17. Biological effects of phosphotriester formation

The extent of biological inactivation and of the degradation of the RNA after reaction of bacteriophage R17 with ethyl methanesulphonate, isopropyl methanesulphonate and N-ethyl-N-nitrosourea was studied. Formation of breaks in the RNA chain probably results from hydrolysis of phosphotriesters formed in the alkylation reactions. Near neutral pH the ethyl and isopropyl phosphotriesters are sufficiently stable for the kinetics of the hydrolysis reaction to be followed. Results indicate that the rate of hydrolysis increases rapidly as the pH is raised. The evidence shows that a phosphotriester group does not itself constitute a lethal lesion. The extent of phosphotriester formation by the different agents is discussed in terms of reaction mechanism.     

Further observations on the effect of ethionine on the synthesis of β-galactosidase inEscherichia coli: Formation of an immunologically cross-reacting protein

It was found that ethionine partially inhibits the transport of the inducer (TMG) of β-galactosidase into the cells ofEscherichia coli ML-30. The synthesis of β-galactosidase-specific messenger RNA is not inhibited. Ethionine appears to be incorporated into proteins synthesized by the strains used. The incorporation of ethionine into the molecule of β-galactosidase results in the synthesis of an enzymically inactive, immunologically cross-reacting protein.     

The metabolism of d-glyceraldehyde by the lens

1. The metabolism of d-glyceraldehyde by the lens was examined. 2. When low concentrations of d-[U-(14)C]glyceraldehyde were incubated with lens extracts there was no incorporation of the label into protein; more than two-thirds of the labelled metabolites consisted of glyceric acid and glycerol, their relative proportions depending on the species. Lactic acid, a phosphate, glutathione-glyceraldehyde compounds and a neutral compound were also formed. 3. When high concentrations of d-[U-(14)C]glyceraldehyde were incubated with lens, extensive incorporation of the label into protein occurred and the protein became yellow-brown. This coloured protein did not exhibit the fluorescent properties shown by the brown proteins of human cataractous senile lens, or of naphthaquinone-treated lens. 4. Evidence that d-glyceraldehyde is formed by the lens was sought but not found.     

Dämpfung der Gewebeatmung (QO2) von Mäuseleber durch künstliche Impulsstrahlung

Zusammenfassung In einem gegen die natürliche Langwellenstrahlung abgeschirmten Versuchsraum wurde die Atmung von Mäuselebergewebe in künstlich erzeugten elektromagnetischen Feldern gemessen. Unter der Einwirkung von zyklonale Wetterlagen simulierenden Programmen (30–100 pulses sec^–1, > 100 mV m^–1, 10–100 kHz) ergab sich im Vergleich zu den Kontroll-QO₂-Werten eine signifikante Dämpfung der Gewebeatmung um 42% ± 2,8% (p<0,001). Die Applikation eines H-Feld-Programms blieb ohne Wirkung. Programme mit Simulierung antizyklonaler Wetterlagen(1–3 pulses sec^–1, <10 mV m^–1, 10 kHz) hatten ebenfalls keinen Einfluss auf die Atmungsgeschwindigkeit der Mäuseleber.

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In a room completely shielded against long wave radiation, liver tissue of mice in a Warburg apparatus was exposed to artificial electromagnetic radiation simulating cyclonic and anticyclonic weather. Under the influence of simulated cyclonic weather programs (30–100 pulses sec^–1, > 100 mV m^–1 10–100 kHz) a significant decrease (42% ± 2,8%) of the respiration rate of the liver tissue was found, compared with the control QO₂ (p < 0,001). The application of a cyclonic weather H-field program had no effect. Simulated anticyclonic weather (1–3 pulses sec^–1, < 10 mV m^–1, 10 kHz) also failed to produce a demonstrable effect on the respiration rate of mouse liver tissue.

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Resume Dans un local absolument protégé contre l'irradiation naturelle par ondes longues, des tissus de foie de souris ont été exposés, dans un appareil de Warburg, à des impulsions électromagnétiques artificielles, correspondant à celles de temps cyclonal et anticyclonal. Sous l'influence des programmes artificiels simulant le temps cyclonal(30–100 pulses sec^–1, > 100 mV m^–1, 10–100 kHz), il a été constaté une inhibitation significative de la respiration tissulaire de 42% ± 2,8% comparée aux valeurs du QO₂ de contrôle (p < 0.001). L'application d'un temps cyclonal-"H-field"-programme séparé, est demeuré sans effet. De même. les signaux de temps anticyclonal(1–3 pulses sec^–1, < 10 mV m^–1, 10 kHz), n'ont eu aucune influence démonstrable sur la vitesse de respiration du fois de souris.

     

Deoxyribonucleic Acid Base Compositions of Selected Mycoplasmas and L-Phase Variants

Deoxyribonucleic acid base compositions were determined for 25 Mycoplasma strains and 6 L-phase variant strains. Values obtained correlated well with the results of other investigators.     

The effect of nucleosides on the induced synthesis of β-galactosidase in non-growing cells ofEscherichia coli

The induced synthesis of β-galactosidase in non-growing cells ofEscherichia coli starving for exogenous carbon and nitrogen sources was stimulated markedly by the addition of any of four nucleosides tested: adenosine, guanosine, cytidine, and uridine. Adenosine was used as a representative of this group of compounds in most experiments. The decrease of ability of the cells to synthesize β-galactosidase, resulting from a prolonged starvation for exogenous carbon and nitrogen, was removed by adenosine. This compound also considerably reduced the inhibitory effect of metabolic poisons on the induced synthesis of β-galactosidase. The blockade of induced β-galactosidase synthesis evoked in aerobically grown cells by anaerobic starvation for exogenous sources of carbon and nitrogen was also significantly reduced by adenosine. The weak transient catabolic repression of induced synthesis of β-galactosidase evoked by glucose in non-growing cells ofEscherichia coli deprived of exogenous carbon and nitrogen sources was prevented by adenosine. The total repression caused by higher glucose concentrations was not influenced by this compound. The results are discussed from the point of view of the role of the energy state ofEscherichia coli cells in the regulation of β-galactosidase synthesis.