X-Ray Survival Response of the Mouse L Cells

Terasima, Toyozo; Fujiwara, Yoshisada; Yasukawa, Mieko; Tanaka, Sachiko

doi:10.1269/jrr.12.61

Cited by 5 publications

(6 citation statements)

References 15 publications

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“…Our hypothesis makes the kinetics of synchronized cultures predictable and increases their usefulness. Methods for synchronizing cells in culture have been extensively used in the study of biochemical changes through the cycle (25 (9). The value of P = 0.18 hr-was obtained from the distribution of intermitotic times (see Fig.…”

Section: ]*mentioning

confidence: 99%

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Do Cells Cycle?

Smith

Martin

1973

Proc. Natl. Acad. Sci. U.S.A.

820

416

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We propose that a cell's life is divided into two fundamentally different parts. Some time after mitosis all cells enter a state (A) in which their activity is not directed towards replication. A cell may remain in the A-state for any length of time, throughout which its probability of leaving A-state remains constant. On leaving A-state, cells enter B-phase in which their activities are deterministic, and directed towards replication. Initiation of cell replication processes is thus random, in the sense that radioactive decay is random. Cell population growth rates are determined by the probability with which cells leave the A-state, the duration of the B-phase, and the rate of cell death. Knowledge of these parameters permits precise calculation of the distribution of intermitotic times within populations, the behavior of synchronized cell cultures, and the shape of labeled mitosis curves.

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Section: ]*mentioning

confidence: 99%

“…TB is then the time between the beginning of the first and second peaks of labeled mitoses. Then P may be computed from the cell production rate constant (Kp) (13) [9] From [8] NAt-TB = 2Nt-TB -Nt-TB exp(KpTB) [a] Nt = Nt-TB exp(KpTB) [b] Substituting a and b in [9] and dispensing with subscripts to N Ktrans = Kp exp(KpTB)/2 -exp(KpTB) […”

mentioning

confidence: 99%

Do Cells Cycle?

Smith

Martin

1973

Proc. Natl. Acad. Sci. U.S.A.

820

416

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“…Thus mitotic delay is minimal for cells irradiated in G1 and increases as they pass through S and G2. 8 It must be kept in mind that the populations of cells which have been used in the study of phase-dependent radiosensitivity, as well as dosedependent division delay, are relatively homogeneous with respect to the duration of the generation cycle and, correspondingly, its several subdivisions or phases. In marked contrast to this is the situation in a neoplastic cell population, particularly as found in a spontaneous animal tumor by Mendelsohn.…”

Section: Discussionmentioning

confidence: 99%

“…In other words, a state of refractoriness relative to the sensitivity of the unirradiated population would have been induced. (8) It is attractive to assume that because cells are, in a sense, synchronized by radiation insofar as they are blocked at a common stage, Gz, they may also be then synchronized in their escape from the block. This is entirely consistent with the sequence of events outlined in (3), above: Cells irradiated close to the block point in Gz experience longer delays than their younger counterparts and thus, in effect, "wait" for these younger survivors to reach the same stage.…”

Section: Discussionmentioning

confidence: 99%

Some Observations and an Hypothesis Concerning the Early Stages of Radiation Recovery*

Kallman

Silini

1964

Annals of the New York Academy of Sciences

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In recent years, biological systems of diverse types have been studied under somewhat different conditions in order to elucidate the course of recuperation following radiation injury. These investigations have yielded results which appear to agree qualitatively, if not quantitatively. The present report will present some new data for one system and an hypothesis to correlate these findings with others in the literature.Elkind' has compared the survival of hamster cells, irradiated in vilro, after single acute radiation exposures with that following doses given in two fractions. Varying lengths of time were allowed to intervene between the first, or conditioning dose, and the second, or test dose. Essentially, the net effect of a given dose delivered in two fractions was never as great as when it was delivered singly. The effect on surviving cells of the first of two fractions disappeared completely by approximately 20 hours, .i.e, recuperation was complete. Elkind has subdivided this 20-hour period into two phases: recovery, meaning changes in survival response after a n initial exposure, which changes occur during the period of division delay, and repair, meaning changes in per cent survival that involve repopulation by viable cells. A characteristic and well-defined fine structure was described for the recuperation kinetics during the first few hours following initial irradiation, i.e., the recovery period : the fraction of cells surviving was higher when the second dose was given at about two hours, fell to a minimum at about six hours, and then rose progressively until complete recovery occurred at roughly 20 hours.The kind of recuperation kinetics described has been observed in whole body lethality experiments, using the LD00/30 as the criterion of effect. Mole2 and Storer and Sanders3 have found that radiation sensitivity decreases shortly after conditioning irradiation of mice, to rise again before falling progressively and continuously until recuperation is complete. The likelihood that the shape of this injury decay curve is attributable to changes in the probability of survival per unit-radiationdose in bone-marrow cells after conditioning irradiation is supported by the recent findings

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“…One is a continuously downward-bending curve when plotted semilogarithmically, the slope of which increases with increase in dose (Oliver andShepstone 1964, Terasima, Fujiwara, Yusukawa andTanaka 1971) . The other response consists either of a simple exponential correlation between survival and radiation dose, or an initial shoulder followed by an apparently exponential decrease in survival with increase in dose (Hewitt, Chan andBlake 1967, Todd 1968) .…”

Section: Introductionmentioning

confidence: 99%