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There are two general classes of reversible events or states that must be distinguished. There are radiation-induced biological events that may be reversible; and there are reversible radiation-induced events that lead to these reversible biological events or, perhaps, to irreversible ones. We should expect that the processes of reversal will be different in the two general categories. For instance, the repair of a broken chromosome should depend upon factors and show characteristics that are different from those exhibited by reversal or removal of the radiation-induced chemical species that precede in time and would lead to the chromosome break if allowed to remain in the cell. Both are examples of reversible radiation effects. One is a %o-chemical" or "enzymatic" type of reversibility; the other is chemical or physicochemical. The purpose of this paper is to examine in bacterial spores radiation effects that probably are physico-chemical in nature, with the particular purpose of separating the reversible from the irreversible (or those that are reversed with greater difficulty), and of noting the effect on the measured response of the cell to the varying degrees of rcversibility that we can observe.The end-points we shall examine are biological in nature-the ability of an irradiated spore to germinate and develop into a cell that can then go through approximately 10 fissions. The radiation effects that we shall manipulate are physicochemical, not biological, in nature. It is important to appreciate that, in this way, we may gain an understanding of the relationship between physical and chemical effects of radiation in cells and the biological consequences of these effects. This understanding is impossible, or nearly so, if one examines only one or the other.The system that we use is particularly suitable for this kind of analysis, for in this almost dry cell no metabolic activity occurs before, during, or after irradiation. The varying biological effects we see can certainly be ascribed to antecedent physical and chemical effects; and the use of the biological end-point of colony formation measures directly, in one respect, the biological importance of these physico-chemical events. We should expect to recognize precise behavior on the psrt of the reversal processes if we can isolate them for measurement. We should expect to be able to predict the consequences of the rules that we recognize, even though the interrelations among them may be complex. This paper will present the results of an examination of the radiation response in terms of subunits that are experimentally recognizable and measurable. It will demonstrate their characteristics and behavior and will show that understanding of these elements of the over-all radiation response must be realized before an understanding of complex responses to radiation is possible.
There are two general classes of reversible events or states that must be distinguished. There are radiation-induced biological events that may be reversible; and there are reversible radiation-induced events that lead to these reversible biological events or, perhaps, to irreversible ones. We should expect that the processes of reversal will be different in the two general categories. For instance, the repair of a broken chromosome should depend upon factors and show characteristics that are different from those exhibited by reversal or removal of the radiation-induced chemical species that precede in time and would lead to the chromosome break if allowed to remain in the cell. Both are examples of reversible radiation effects. One is a %o-chemical" or "enzymatic" type of reversibility; the other is chemical or physicochemical. The purpose of this paper is to examine in bacterial spores radiation effects that probably are physico-chemical in nature, with the particular purpose of separating the reversible from the irreversible (or those that are reversed with greater difficulty), and of noting the effect on the measured response of the cell to the varying degrees of rcversibility that we can observe.The end-points we shall examine are biological in nature-the ability of an irradiated spore to germinate and develop into a cell that can then go through approximately 10 fissions. The radiation effects that we shall manipulate are physicochemical, not biological, in nature. It is important to appreciate that, in this way, we may gain an understanding of the relationship between physical and chemical effects of radiation in cells and the biological consequences of these effects. This understanding is impossible, or nearly so, if one examines only one or the other.The system that we use is particularly suitable for this kind of analysis, for in this almost dry cell no metabolic activity occurs before, during, or after irradiation. The varying biological effects we see can certainly be ascribed to antecedent physical and chemical effects; and the use of the biological end-point of colony formation measures directly, in one respect, the biological importance of these physico-chemical events. We should expect to recognize precise behavior on the psrt of the reversal processes if we can isolate them for measurement. We should expect to be able to predict the consequences of the rules that we recognize, even though the interrelations among them may be complex. This paper will present the results of an examination of the radiation response in terms of subunits that are experimentally recognizable and measurable. It will demonstrate their characteristics and behavior and will show that understanding of these elements of the over-all radiation response must be realized before an understanding of complex responses to radiation is possible.
Es wird eine Methode zur Synchronsporulation von Bacillus stearothermophilus in einem belufteten Trypton-Hefeextrakt-Mineralmedium beschrieben. Die Sporogenese war auf 2,5 Std. begrenzt. Die Kultur wurde durch mehrere Passagen a m der fruhen logarithmischen Wachstumsphase aktiviert. Der fortlaufende Anstieg der optischen Dichte diente als NaO der Sporulationssynchronisation.Die Sporen des Sporulationsstadiums VI waren nicht in der Lage, sich aus ihren Sporangien zu befreien. Die Sporangien wurden unmittelbar nach der Synchronsporulation unter endotrophen Bedingungen in Tris-Puffer (pH 8,4/23 "C) bei 60 "C lysiert. Die Enzymreaktion konnte durch Zufiigen von M Calcium, M Magnesium und M Mangan beschleunigt werden.
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