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Effects of Ionizing Radiation on Mammalian Cells

John B. Little, Jerry R. Williams

10.1002/cphy.cp090108

Source: Supplement 26: Handbook of Physiology, Reactions to Environmental Agents

Originally published: 1977

Published online: January 2011

Full Article on Wiley Online Library



Abstract

The sections in this article are:

1 Physical and Chemical Events
1.1 Development of Radiation Injury
1.2 The Target Theory
1.3 Direct and Indirect Effects, Radiation Chemistry
2 Effects on Cell Division
2.1 Division Delay
2.2 Mitotic Inhibition (Reproductive Failure)
2.3 Radiation Sensitivity in Different Phases of the Life Cycle
2.4 Chromosomal Damage
2.5 Interphase Death
2.6 Nonlethal Heritable Changes
2.7 Biological Variation in Radiation Sensitivity
2.8 Mechanisms
3 Modification of Radiation Effects
3.1 Physical Factors
3.2 Chemical Radiation Protection and Sensitization
3.3 Oxygen Effect
3.4 Intracellular Recovery Processes
3.5 Repair of Potentially Lethal Damage
3.6 Repair of Sublethal Damage (Split‐Dose Recovery)
4 Molecular Repair Processes
4.1 Damage Observed in DNA
4.2 Cellular Repair Systems for DNA Damage
4.3 Repair Activities in Mammalian Cells
4.4 Correlation of DNA Repair with Biological Effects
5 Concluding Remarks
6 Addendum
Figure 1. Figure 1.

Development of radiation injury in cells.
Figure 2. Figure 2.

Hypothetical dose‐response curves for radiation‐induced reproductive failure in cells. Curve 1 is often referred to as a single‐event and curve 2 a multiple‐event survival curve. The latter is the type associated with the killing of mammalian cells by gamma or X‐irradiation, and its shape can be described by two parameters: the extrapolation number ñ, which indicates the magnitude of the shoulder on the curve, and the D0 or dose necessary to reduce survival to 37% on the linear portion of the curve, which determines its slope. Mathematically the D0 is the inverse of the slope.
Figure 3. Figure 3.

Stages of interphase during life cycle of a typical mammalian cell. DNA synthesis (S phase) occurs during a discrete period when genetic material is reduplicated. The phases before and after S are called G1 and G2 (gaps). The time periods shown for each stage are typical for cells with a 20‐h generation time, although generation time and length of the three stages of interphase vary among different cell types.
Figure 4. Figure 4.

Pedigrees of X‐irradiated mouse L cells obtained by time‐lapse cinematography. Both cells were irradiated with 216 rads. Numbers are generation times in hours. PYK, pyknosis (staining abnormality indicating cell death); arrows, nondividing cells. A: Expression of damage delayed until after the 4th division. Injury manifest primarily in the 6th and 7th divisions in a variety of ways including pyknosis, nondivision, giant cell formation, abnormal mitosis such as fusion and multipolar division, and prolonged generation times. Some progeny will probably survive. B: Abortive clone with extensive cell death in several generations. It is unlikely that any of the progeny survived to proliferate indefinitely.

From Thompson & Suit 196
Figure 5. Figure 5.

X‐ray survival curves for synchronized cultures of Chinese hamster cells irradiated during various stages of the cell cycle.

From Sinclair & Morton 190
Figure 6. Figure 6.

Repair of potentially lethal damage in a line of human liver cells (LICH). Cells were irradiated while in the density‐inhibited phase of growth. They were then subcultured to assay for survival either immediately or 6 h later. The enhanced survival found in cells allowed to remain under conditions of growth inhibition for 6 h after a single dose of radiation is due to a change in the slope of the survival curve.

From Little et al. 136
Figure 7. Figure 7.

Split‐dose recovery in human LICH cells. The curve on the left is the single‐dose survival curve. The shoulder is interpreted as representing the accumulation of sublethal damage by the cells at low radiation doses. The survival curve on the right was obtained with cells that had survived a single dose of 600 rads given 6 h before. The return of the shoulder is interpreted as indicating that the sublethal damage incurred during the first exposure was repaired between doses. Net survival following 1,000 rads, for example, was about three times greater when the dose was split for two fractions. Note there was no change in the slope of the survival curve. PE, plating efficiency; D0, inverse of slope; ñ, extrapolation number.
Figure 8. Figure 8.

Variation of the mean fraction number of the DNA sedimentation peak against minutes of repair incubation at 37°C after 10 kilorads of gamma irradiation. Cells were labeled with tritiated thymidine for 24–50 h, irradiated, placed in repair media at 37°C for specified times, then suspended, lysed, and centrifuged using the technique of McGrath & Williams 143. On the ordinate, fractions 16–18 would correspond to DNA molecules of 2 to 5 × 108 daltons, fractions 7 −9 would correspond to DNA molecules of 2 to 7 × 107 daltons. ○, diploid fibroblasts from a patient with precocious aging; □, diploid fibroblasts from a normal adult; Δ, diploid fibroblasts from a normal human fetus; ⋄ aneuploid human cells (LICH).

From Epstein et al. 70
Figure 9. Figure 9.

Alternate rejoining and incision of DNA molecules after gamma irradiation in aneuploid human cells (LICH). Conditions are similar to those described in the legend of Figure 8.
Figure 10. Figure 10.

Survival of a hybrid cell line αRST (○—○), and its parent cell lines, Cl‐1D (x—x) and GH12Cl (○‐○) after graded doses of X‐radiation.

From Little et al. 137


Figure 1.

Development of radiation injury in cells.



Figure 2.

Hypothetical dose‐response curves for radiation‐induced reproductive failure in cells. Curve 1 is often referred to as a single‐event and curve 2 a multiple‐event survival curve. The latter is the type associated with the killing of mammalian cells by gamma or X‐irradiation, and its shape can be described by two parameters: the extrapolation number ñ, which indicates the magnitude of the shoulder on the curve, and the D0 or dose necessary to reduce survival to 37% on the linear portion of the curve, which determines its slope. Mathematically the D0 is the inverse of the slope.



Figure 3.

Stages of interphase during life cycle of a typical mammalian cell. DNA synthesis (S phase) occurs during a discrete period when genetic material is reduplicated. The phases before and after S are called G1 and G2 (gaps). The time periods shown for each stage are typical for cells with a 20‐h generation time, although generation time and length of the three stages of interphase vary among different cell types.



Figure 4.

Pedigrees of X‐irradiated mouse L cells obtained by time‐lapse cinematography. Both cells were irradiated with 216 rads. Numbers are generation times in hours. PYK, pyknosis (staining abnormality indicating cell death); arrows, nondividing cells. A: Expression of damage delayed until after the 4th division. Injury manifest primarily in the 6th and 7th divisions in a variety of ways including pyknosis, nondivision, giant cell formation, abnormal mitosis such as fusion and multipolar division, and prolonged generation times. Some progeny will probably survive. B: Abortive clone with extensive cell death in several generations. It is unlikely that any of the progeny survived to proliferate indefinitely.

From Thompson & Suit 196


Figure 5.

X‐ray survival curves for synchronized cultures of Chinese hamster cells irradiated during various stages of the cell cycle.

From Sinclair & Morton 190


Figure 6.

Repair of potentially lethal damage in a line of human liver cells (LICH). Cells were irradiated while in the density‐inhibited phase of growth. They were then subcultured to assay for survival either immediately or 6 h later. The enhanced survival found in cells allowed to remain under conditions of growth inhibition for 6 h after a single dose of radiation is due to a change in the slope of the survival curve.

From Little et al. 136


Figure 7.

Split‐dose recovery in human LICH cells. The curve on the left is the single‐dose survival curve. The shoulder is interpreted as representing the accumulation of sublethal damage by the cells at low radiation doses. The survival curve on the right was obtained with cells that had survived a single dose of 600 rads given 6 h before. The return of the shoulder is interpreted as indicating that the sublethal damage incurred during the first exposure was repaired between doses. Net survival following 1,000 rads, for example, was about three times greater when the dose was split for two fractions. Note there was no change in the slope of the survival curve. PE, plating efficiency; D0, inverse of slope; ñ, extrapolation number.



Figure 8.

Variation of the mean fraction number of the DNA sedimentation peak against minutes of repair incubation at 37°C after 10 kilorads of gamma irradiation. Cells were labeled with tritiated thymidine for 24–50 h, irradiated, placed in repair media at 37°C for specified times, then suspended, lysed, and centrifuged using the technique of McGrath & Williams 143. On the ordinate, fractions 16–18 would correspond to DNA molecules of 2 to 5 × 108 daltons, fractions 7 −9 would correspond to DNA molecules of 2 to 7 × 107 daltons. ○, diploid fibroblasts from a patient with precocious aging; □, diploid fibroblasts from a normal adult; Δ, diploid fibroblasts from a normal human fetus; ⋄ aneuploid human cells (LICH).

From Epstein et al. 70


Figure 9.

Alternate rejoining and incision of DNA molecules after gamma irradiation in aneuploid human cells (LICH). Conditions are similar to those described in the legend of Figure 8.



Figure 10.

Survival of a hybrid cell line αRST (○—○), and its parent cell lines, Cl‐1D (x—x) and GH12Cl (○‐○) after graded doses of X‐radiation.

From Little et al. 137
References
 1. Adelstein, S. J. Radiation‐induced changes in biologically active macromoles. Radiol. Clin. N. Amer. 3: 181–195, 1965.
 2. Agnew, D. A., and L. D. Skarsgard. Sensitization of anoxic mammalian cells to radiation by triacetoneamine‐N‐Oxyl. Effect of Pre‐ and Postirradiation treatment. Radiation Res. 51: 97–109, 1972.
 3. Albert, M. D., and N. L. R. Bucher. Latent injury and repair in rat liver induced to regenerate at intervals after X‐radiation. Cancer Res. 20: 1512–1522, 1960.
 4. Arlett, C. F. The influence of post‐irradiation conditions on the survival of Chinese hamster cells after gamma‐irradiation. Intern. J. Radiation Biol. 17: 515–526, 1970.
 5. Ashby, R. R., F. J. Bonte, and J. A. Belli. A study of some metabolic requirements for repair of sublethal irradiation damage. Radiology 93: 895–899, 1969.
 6. Bachetti, S., and W. K. Sinclair. The relation of protein synthesis to radiation‐induced division delay in Chinese hamster cells. Radiation Res. 44: 788–806, 1970.
 7. Bacq, Z. M. Chemical Protection Against Ionizing Radiation: with an Introduction by Shields Warren. (American Lectures in Living Chemistry.). Springfield, Ill.: Thomas, 1965.
 8. Barendsen, G. W. Modification of radiation damage by fractionation of the dose, anoxia and chemical protectors in relation to LET. Ann. NY Acad. Sci. 114: 96–114, 1964.
 9. Barendsen, G. W., C. J. Koot, G. R. vanKersen, D. K. Bewley, S. B. Field, and C. J. Parnell. Effect of oxygen on impairment of proliferative capacity of human cells in culture by ionizing radiations of different LET. Intern. J. Radiation Biol. 10: 317–327, 1966.
 10. Barendsen, G. W., H. M. D. Walter, J. F. Fowler, and D. K. Bewley. Effects of different ionizing radiations on human cells in tissue culture. III. Experiments with cyclotron‐accelerated alpha‐particles and deuterons. Radiation Res. 18: 106–119, 1963.
 11. Bedford, J. S., and E. J. Hall. Survival of HeLa cells cultured in vitro and exposed to protracted gamma irradiation. Intern. J. Radiation Biol. 7: 377–383, 1963.
 12. Bedford, J. S., and E. J. Hall. Threshold hypoxia. Its effect on the survival of mammalian cells irradiated at high and low dose‐rates. Brit. J. Radiol. 39: 896–900, 1966.
 13. Bedford, J. S., and E. J. Hall. Chromosome constitution and gamma ray sensitivity: a possible correlation in hamster cells cultured in vitro. Radiation Res. 31: 679–692, 1967.
 14. Bedford, J. S., and J. B. Mitchell. Dose‐rate effects in synchronous mammalian cells in culture. Radiation Res. 54: 316–327, 1973.
 15. Beer, J. Z., J. T. Lett, and P. Alexander. Influence of temperatures and medium on the X‐ray sensitivities of leukemic cells in vitro. Nature 199: 193–194, 1963.
 16. Belli, J. A., and M. Shelton. Potentially lethal radiation damage: repair by mammalian cells in culture. Science 165: 490–492, 1969.
 17. Berry, R. J. Quantitative studies of relationships between tumor cell ploidy and dose response to ionizing radiation in vivo Radiation Res. 18: 236–245, 1963.
 18. Berry, R. J. Effects of some metabolic inhibitors on X‐ray dose‐response curves for survival of mammalian cells in vitro, and on early recovery between fractionated X‐ray doses. Brit. J. Radiol. 39: 458–463, 1966.
 19. Berry, R. J. On use of arbitrary minimum clone size to define survival of cell reproductive capacity. Radiation Res. 30: 237–247, 1967.
 20. Berry, R. J., J. Cavanagh, R. Oliver, and B. M. Winston. Variation of relative biological effectiveness with dose rate for different radiation qualities. Health Phys. 24: 369–374, 1973.
 21. Berry, R. J., E. J. Hall, D. W. Forster, T. H. Storr, and M. J. Goodman. Survival of mammalian cells exposed to X rays at ultra‐high dose‐rates. Brit. J. Radiol. 42: 102–107, 1969.
 22. Berry, R. J., and J. B. H. Stedeford. Reproductive survival of mammalian cells after irradiation at ultra‐high dose‐rates: further observations and their importance of radiotherapy. Brit. J. Radiol. 45: 171–177, 1972.
 23. Blood, A. D., and J. H. Tijo. In vivo effects of diagnostic X‐irradiation on human chromosomes. New Engl. J. Med. 270: 1341–1344, 1964.
 24. Blum, E., and T. Alper. Radiation‐target molecular weights of urease and of L‐glutamate dehydrogenase, and their relevance to the size of the functional subunits. Biochem. J. 122: 677–680, 1971.
 25. Bootsma, D., L. Budke, and O. Vos. Studies on synchronous division of tissue culture cells initiated by excess thymidine. Exptl. Cell Res. 33: 301–309, 1964.
 26. Brent, T. R. A human endonuclease activity for gamma‐irradiated DNA. Biophys. J. 13: 399–401, 1973.
 27. Broerse, J. J., G. W. Barendsen, and G. R. vanKersen. Survival of cultured human cells after irradiation with fast neutrons of different energies in hypoxic and oxygenated conditions. Intern. J. Radiation Biol. 13: 559–572, 1967.
 28. Brues, A. M., and L. Rietz. Effects of external and internal radiation on cell division. Ann. NY Acad. Sci. 51: 1497–1507, 1951.
 29. Buhl, S. N., R. B. Setlow, and J. D. Regan. Steps in DNA chain elongation and joining after ultra‐violet irradiation of human cells. Intern. J. Radiation Biol. 22: 417–424, 1972.
 30. Carrano, A. V. Chromosome aberrations and radiation‐induced cell death. I. Transmission and survival parameters of aberrations. Mutat. Res. 17: 341–353, 1973.
 31. Carrano, A. V. Chromosome aberrations and radiation‐induced cell death. II. Predicted and observed cell survival. Mutat. Res. 17: 355–366, 1973.
 32. Chapman, J. D., C. L. Greenstock, A. P. Reuvers, E. McDonald, and I. Dunlop. Radiation chemical studies with nitrofurazone as related to its mechanism of radiosensitization. Radiation Res. 53: 190–203, 1973.
 33. Chapman, J. D., J. A. Raleigh, J. Borsa, R. G. Webb, and R. Whitehouse. Radiosensitization of mammalian cells by p‐Nitroacetophenone. II. Effectiveness of analogues. Intern. J. Radiation Biol. 21: 475–482, 1972.
 34. Chapman, J. D., A. P. Reuvers, J. Borsa, and C. L. Greenstock. Chemical radioprotection and radiosensitization of mammalian cells growing in vitro. Radiation Res. 56: 291–306, 1973.
 35. Chapman, J. D., A. P. Reuvers, J. Borsa, A. Petkau, and D. R. McCalla. Nitrofuransradiosensitizers of hypoxic mammalian cells. Cancer Res. 32: 2616–2624, 1972.
 36. Chapman, J. D., R. G. Webb, and J. Borsa. Radiosensitization of mammalian cells by p‐nitroacetophenone. I. Characterization in asynchronous and synchronous populations. Intern. J. Radiation Biol. 19: 561–573, 1971.
 37. Chu, E. H. Y. Effects of ultra violet radiation on mammalian cells. II. Differential UV and X‐ray sensitivity of chromosomes to breakage in 5‐aminouracil synchronized cell populations. Genetics 52: 1279–1294, 1965.
 38. Cleaver, J. E. Excision repair: our current knowledge based on human (Xeroderma pigmentosum) and cattle cells. In: Molecular and Cellular Repair Processes, Johns Hopkins Med. J. Suppl. 1: 195–211, 1972.
 39. Cleaver, J. E., and R. B. Painter. Evidence for repair replication of HeLa cell DNA damaged by ultraviolet light. Biochim. Biophys. Acta 161: 552–554, 1968.
 40. Cook, J. S. Photoenzymatic repair in animal cells. Johns Hopkins Med. J. Suppl. 1: 79–103, 1972.
 41. Coquerelle, T., L. Bohno, and U. Hagen. Radiation sensitivity of bacteriophage DNA. I. Breaks and crosslinks after irradiation in vitro. Z. Naturforsch [B] 24b: 885–893, 1969.
 42. Crowther, J. A. Actions of X‐rays on tissue cells. Proc. Roy. Soc., London, Ser B 96: 207–211, 1924.
 43. Dale, W. M. Effect of X‐rays on enzymes. Biochem. J. 34: 1367–1373, 1940.
 44. Davis, M. A., J. B. Little, K. M. M. S. Ayyanger, and A. R. Reddy. Relative biological effectiveness of the 10B (n, α)7Li reaction in HeLa cells. Radiation Res. 43: 534–553, 1970.
 45. Dertinger, H., and H. Jung. Molecular Radiation Biology. The action of Ionizing Radiation on Elementary Biological Objects, translated by R. P. O. Huber and P. A. Gresham. New York, Heidelberg, Berlin: Springer‐Verlag, 1970.
 46. Dettor, C. M., W. C. Dewey, L. F. Winans, and J. S. Noel. Enhancement of X‐ray damage in synchronous Chinese hamster cells by hypertonic treatments. Radiation Res. 52: 352–372, 1972.
 47. Dewey, W. C. Confirmation of lesions having the potential for forming chromosomal aberrations. Intern. J. Radiation Biol. 22: 95–97, 1972.
 48. Dewey, W. C., and R. M. Humphrey. Restitution of radiation‐induced chromosomal damage in Chinese hamster cells related to cells' life cycle. Exptl. Cell Res. 35: 262–276, 1964.
 49. Dewey, W. C., and H. H. Miller. Effect of temperature on X‐ray induced cell lethality and chromosomal aberrations. Intern. J. Radiation Biol. 18: 91–93, 1970.
 50. Dewey, W. C., H. H. Miller, and D. B. Leeper. Chromosomal aberrations and mortality of X‐irradiated mammalian cells: emphasis on repair. Proc. Natl. Acad. Sci. 68: 667–671, 1971.
 51. Dewey, W. C., J. S. Noel, and C. M. Dettor. Changes in radiosensitivity and dispersion of chromatin during the cell cycle of synchronous Chinese hamster cells. Radiation Res. 52: 373–394, 1972.
 52. Dewey, W. C., L. E. Stone, H. H. Miller, and R. E. Giblak. Radiosensitization with 5‐bromodeoxyuridine of Chinese hamster cells X‐irradiated during different phases of the cell cycle. Radiation Res. 47: 672–688, 1971.
 53. Djordjevic, B., L. L. Anderson, and S. H. Kim. Oxygen enhancement ratios in HeLa cells irradiated with californium and radium sources. Radiology 107: 429–434, 1973.
 54. Djordjevic, B., and J. H. Kim. Modification of radiation response in synchronized HeLa cells by metabolic inhibitors: effects of inhibitors of DNA and protein synthesis. Radiation Res. 37: 435–450, 1969.
 55. Djordjevic, B., and W. Szybalski. Genetics of human cell lines. III. Incorporation of 5‐bromo‐ and 5‐indodeoxyuridine into deoxyribonucleic acid of human cells and its effect on radiation sensitivity. J. Exptl. Med. 112: 509–531, 1960.
 56. Doida, Y., and S. Okada. Radiation‐induced mitotic delay in cultured mammalian cells (L5178Y). Radiation Res. 38: 513–529, 1969.
 57. Doull, J., V. Plzak, and S. J. Brois. A survey of compounds for radiation protection. US Air Force Sch. Aerospace Med. 62: 29, 1962.
 58. Drewinko, B., and R. M. Humphrey. The radiation response of a long‐term culture of human lymphoid cells. II. Synchronized populations. Intern. J. Radiation Biol. 23: 1–9, 1973.
 59. Drewinko, B., R. M. Humphrey, and J. M. Trujillo. The radiation response of a long‐term culture of human lymphoid cells. I. Asynchronous populations. Intern. J. Radiation Biol. 21: 361–373, 1972.
 60. Eker, P., and A. Pihl. Studies on growth‐inhibiting and radio‐protective effect of cystamine, cysteamine, and AET on mammalian cells in tissue culture. Radiation Res. 21: 165–179, 1964.
 61. Elkind, M. M., A. Han, and K. Volz. Radiation response of mammalian cells grown in culture. IV. Dose dependence of division delay and post‐irradiation growth of surviving and non‐surviving Chinese hamster cells. J. Natl. Cancer Inst. 30: 705–721, 1963.
 62. Elkind, M. M., and C. Kamper. Two forms of repair of DNA in mammalian cells following irradiation. Biophys. J. 10: 237–244, 1970.
 63. Elkind, M. M., and E. Kano. Radiation‐induced age‐response changes in Chinese‐hamster cells. Evidence for a new form of damage and its repair. Intern. J. Radiation Biol. 19: 547–560, 1971.
 64. Elkind, M. M., W. B. Moses, and G. H. Sutton. Radiation response of mammalian cells grown in culture. VI. Protein. DNA and RNA inhibition during repair of X ray damage. Radiation Res. 31: 156–173, 1967.
 65. Elkind, M. M., and H. Sutton. X‐ray damage and recovery in mammalian cells in culture. Nature, London 184: 1293–1295, 1959.
 66. Elkind, M. M., H. Sutton‐Gilbert, W. B. Moses, T. Alescio, and R. W. Swain. Radiation response of mammalian cells grown in culture. V. Temperature dependence of the repair of X‐ray damage in surviving cells (Aerobic and Hypoxic). Radiation Res. 25: 359–376, 1965.
 67. Elkind, M. M., R. W. Swain, T. Alescio, H. Sutton, and W. B. Moses. Oxygen, nitrogen, recovery and radiation therapy. Symposium on Fundamental Cancer Research. 18th, Anderson Hospital and Tumor Institute, 1964. Cellular Radiation Biology: a symposium considering radiation effects in the cell and possible implications for cancer therapy, a collection of papers. Baltimore: Williams & Wilkins, 1965, p. 442–466.
 68. Elkind, M. M., G. F. Whitmore, and T. Alescio. Actinomycin‐D: suppression of recovery in X‐irradiated mammalian cells. Science 143: 1454–1457, 1964.
 69. Epp, E. R., H. Weiss, B. Djordjevic, and A. Santomasso. The radiosensitivity of cultured mammalian cells exposed to single high intensity pulses of electrons in various concentrations of oxygen. Radiation Res. 52: 324–332, 1972.
 70. Epstein, J., J. R. Williams, and J. B. Little. Deficient DNA repair in human progeroid cells. Proc. Natl. Acad. Sci. 70: 977–981, 1973.
 71. Evans, H. L. Repair and recovery from chromosome damage induced by fractionated X‐ray exposures. In: Radiation Research, edited by G. Silini. Amsterdam: North‐Holland, 1967, p. 482–501.
 72. Evans, R. G., M. A. Bagshaw, L. Gordon, and G. M. Hahn. Inhibition of the capacity of plateau phase Chinese hamster cells to recover from X‐ray damage (Abstr.). Radiation Res. 51: 522–523, 1972.
 73. Fetner, R. H. A comparison of radiation‐induced reproductive death and chromosome exchanges in Chinese hamster cells at room temperature and in liquid nitrogen. Intern. J. Radiation Biol. 17: 467–478, 1970.
 74. Firket, H., and P. Mahieu. Irradiation et protection de cultures synchrones de cellules HeLa. I. Effet sur le premier cycle cellulaire. Intern. J. Radiation Biol. 11: 245–253, 1966.
 75. Fox, M. The effects of halogenated nucleosides on the sensitivity of a mouse lymphoma P338F to X‐rays and methyl methanesulphonate. Intern. J. Cancer 3: 382–389, 1968.
 76. Frindee, E., and M. Tubiana. Radiobiology and the cell cycle. In: The Cell Cycle and Cancer, edited by R. Baserga New York: Dekker, 1971.
 77. Froese, G. Division delay in HeLa cells and Chinese hamster cells: time‐lapse study. Intern. J. Radiat. Biol. 10: 353–367, 1966.
 78. Goldstein, R., and S. Okada. Further studies of radiation‐induced interphase death of cultured mammalian cells. Radiation Res. 51: 685–695, 1972.
 79. Gray, L. H. Radiobiologic basis of oxygen as modifying factor in radiation therapy. Am. J. Roentgenol. Radium Therapy Nucl. Med. 85: 803–815, 1961.
 80. Hahn, G. M. Failure of Chinese hamster cells to repair sublethal damage when X‐irradiated in the plateau phase of growth. Nature 217: 741–742, 1968.
 81. Hahn, G. M., and M. A. Bagshaw. Serum concentration: effects on cycle and X‐ray sensitivity of mammalian cells. Science 151: 459–461, 1966.
 82. Hahn, G. M., M. A. Bagshaw, R. G. Evans, and L. F. Gordon. Repair of potentially lethal lesions in X‐irradiated, density inhibited Chinese hamster cells; metabolic effects and hypoxia. Radiation Res. 55: 280–290, 1973.
 83. Hahn, G. M., and J. B. Little. Plateau‐phase cultures of mammalian cells: An in vitro model for human cancer. Current Topics Radiation Res. 8: 39–83, 1972.
 84. Hahn, G. M., S. C. Rockwell, R. F. Kallman, L. F. Gordon, and E. Frindel. Repair of potentially lethal damage in vivo in solid tumor cells after X‐irradiation. Cancer Res. 34: 351–356, 1974.
 85. Hall, E. J. Radiation dose‐rate: a factor of importance in radiobiology and radiotherapy. Brit. J. Radiol. 45: 81–97, 1972.
 86. Hall, E. J. The effect of hypoxia on the repair of sublethal radiation damage in cultured mammalian cells. Radiation Res. 49: 405–415, 1972.
 87. Hall, E. J., and J. S. Bedford. Dose‐rate: its effect on the survival of HeLa cells irradiated with gamma‐rays. Radiation Res. 22: 305–315, 1964.
 88. Hall, E. J., J. S. Bedford, and R. Oliver. Extreme hypoxia; its effect on the survival of mammalian cells irradiated at high and low dose‐rates. Brit. J. Radiol. 39: 302–307, 1966.
 89. Hall, E. J., W. Gross, R. F. Dvorak, A. M. Kellerer, and H. M. Rossi. Survival curves and age response functions for Chinese hamster cells exposed to X‐rays or high LET alpha‐particles. Radiation Res. 52: 88–98, 1972.
 90. Hariharan, P. V., and P. A. Cerutti. Formation and repair of X‐ray induced thymine damage in Micrococcus radiodurans. J. Mol. Biol. 66: 65–81, 1972.
 91. Harm, W., C. S. Rupert, and H. Harm. Photoenzymatic repair of DNA. I. Investigation of the reaction by flash illumination. Johns Hopkins Med. J. Suppl. 1: 53–78, 1972.
 92. Harris, J. W., R. B. Painter, and G. M. Hahn. Endogenous non‐protein sulfhydryl and cellular radiosensitivity. Intern. J. Radiation Biol. 15: 289–292, 1969.
 93. Harris, J. W., and J. A. Power. Diamide: a new radiosensitizer for anoxic cells. Radiation Res. 56: 97–109, 1973.
 94. Harris, J. W., and S. S. Teng. Sulfhydryl groups during the S phase: comparison of cells from G1, plateau‐phase G1, and G0. J. Cell. Physiol. 81: 91–96, 1973.
 95. Haynes, R. H. Interpretation of microbial inactivation and recovery phenomena. Radiation Res. Suppl. 6: 1–29, 1966.
 96. Hems, G. Chemical effects of ionizing radiation on deoxyribonucleic acid in dilute aqueous solution. Nature 186: 710–712, 1960.
 97. Hewitt, H. B., and C. W. Wilson. Survival curve for mammalian leukemia cells irradiated in vivo. Brit. J. Cancer 13: 69–75, 1959.
 98. Hill, R. F. A radiation‐sensitive mutant of E. coli. Biochim. Biophys. Acta 30: 636–642, 1958.
 99. Hopwood, L. E., and L. J. Tolmach. Deficient DNA synthesis and mitotic death in X‐irradiated HeLa cells. Radiation Res. 46: 70–84, 1971.
 100. Howard‐Flanders, P., and D. Moore. Time interval after pulsed irradiation within which injury to bacteria can be modified by dissolved oxygen. Radiation Res. 9: 422–437, 1958.
 101. Howard‐Flanders, P., and W. D. Rupp. Recombinational repair in UV‐irradiated Escherichia coli. Johns Hopkins Med. J. Suppl. 1: 212–225, 1972.
 102. Hsu, T. C., W. C. Dewey, and R. M. Humphrey. Radiosensitivity of cells of Chinese hamster in vitro in relation to the cell cycle. Exptl. Cell. Res. 27: 441–452, 1962.
 103. Humphrey, R. M., W. C. Dewey, and A. Cork. Effect of oxygen on mammalian cells sensitized to radiation by incorporation of 5‐bromodeoxyuridine into DNA. Nature, London 198: 268, 1963.
 104. Hurwitz, C., and L. J. Tolmach. Time‐lapse cinematographic studies of X‐irradiated HeLa cells. I. Cell progression and cell disintegration. Biophys. J. 9: 607–633, 1969.
 105. Hurwitz, C., and L. J. Tolmach. Time‐lapse cinemicrographic studies of X‐irradiated HeLa S3 cells. II. Cell fusion. Biophys. J. 9: 1131–1143, 1969.
 106. Hutchinson, F. Molecular basis for radiation effects on cells. Cancer Res. 26: 2045–2052, 1966.
 107. Jacobs, A., A. Bopp, and U. Hagen. In vitro repair of single‐strand breaks in γ‐irradiated DNA by polynucleotide ligase. Intern. J. Radiation Biol. 22: 431–435, 1972.
 108. Jacobson, B. S. Evidence for recovery from X‐ray damage in chlamydomonas. Radiation Res. 7: 394–406, 1957.
 109. Jacobson, B. S. Factors affecting the response of chlamydomonas to fractionation of X‐ray doses. Radiation Res. 9: 134, 1958.
 110. Kember, N. F. Cell survival and radiation damage in growth cartilage. Brit. J. Radiol. 40: 496–505, 1967.
 111. Kim, J. H., M. L. Eidinoff, and J. S. Laughlin. Recovery from sublethal X‐ray damage of mammalian cells during inhibition of synthesis of deoxyribonucleic acid. Nature, London 204: 598, 1964.
 112. Kim, J. H., M. L. Eidinoff, and J. S. Laughlin. Recovery from sublethal X‐ray damage of synchronized HeLa cells during inhibition of protein synthesis. Intern. J. Radiation Biol. 11: 509–511, 1966.
 113. Kitayama, S., and A. Matsuyama. Possibility of the repair of double strand scission in M. radiodurans DNA caused by gamma‐rays. Biochem. Biophys. Res. Commun. 33: 418, 1968.
 114. Koch, C. J., and J. Kruuv. The effect of extreme hypoxia on recovery after radiation by synchronized mammalian cells. Radiation Res. 48: 74–85, 1971.
 115. Koch, C. J., J. Kruuv, and H. E. Frey. Variation in radiation response of mammalian cells as a function of oxygen tension. Radiation Res. 53: 33–42, 1973.
 116. Kriss, J. P., Y. Maruyama, L. A. Tung, S. B. Bond, and L. Révész. Fate of 5‐bromodeoxyuridine, 5‐bromodeoxycyti‐dine, and 5‐iododeoxycytidine in man. Cancer Res. 23: 260–268, 1963.
 117. Lange, C. S. On the relative importance of repair and progression in Elkind recovery as measured in synchronous HeLa cells. Intern. J. Radiation Biol. 17: 61–79, 1970.
 118. Lea, D. E. Actions of Radiations on Living Cells. New York: Macmillan, 1947.
 119. Leeper, D. B., and R. F. Hagemann. Repair kinetics of radiation‐induced mitotic delay. Biophys. J. 13: 179–185, 1973.
 120. Leeper, D. B., M. H. Schneiderman, and W. C. Dewey. Radiation‐induced cycle delay in synchronized Chinese hamster cells: comparison between DNA synthesis and division. Radiation Res. 53: 326–337, 1973.
 121. Lehmann, A. R. Postreplication repair of DNA in ultraviolet‐irradiated mammalian cells. J. Mol. Biol. 66: 319–337, 1972.
 122. Lett, J. T., I. Caldwell, C. J. Dean, and P. Alexander. Rejoining of X‐ray induced breaks in DNA of leukemia cells. Nature 214: 790–792, 1967.
 123. Lett, J. T., I. Caldwell, and J. G. Little. Repair of X‐ray damage to the DNA in M. radiodurans: the effect of 5‐bromodeoxyuridine. J. Mol. Biol. 48: 395–408, 1970.
 124. Lett, J. T., and C. Sun. The production of strand breaks in mammalian DNA by X‐rays: at different stages in the cell cycle. Radiation Res. 44: 771–787, 1970.
 125. Lett, J. T., C. Sun, and K. T. Wheeler. Restoration of the DNA structure in X‐irradiated eucaryotic cells: in vitro and in vivo. In: Molecular and Cellular Repair Processes. Johns Hopkins Med. J. Suppl. 1: 147–158, 1972.
 126. Lindahl, T. Excision‐repair enzymes from calf thymus (Abstr.). 1974. ICN‐UCLA Winter Conferences on Molecular Biology.
 127. Littbrand, B., and L. Révész. Recovery from X‐ray injury and effect of oxygen. Nature, London 203: 889–891, 1964.
 128. Littbrand, B., and L. Revesz. The effect of oxygen on cellular survival and recovery after irradiation. Brit. J. Radiol. 42: 914–924, 1969.
 129. Little, J. B. Cellular effects of ionizing radiation. New Engl. J. Med. 278: 308–315, 369–376, 1968.
 130. Little, J. B. Repair of sub‐lethal and potentially lethal radiation damage in plateau phase cultures of human cells. Nature, London 224: 804–806, 1969.
 131. Little, J. B. Differential response of rapidly and slowly proliferating human cells to X irradiation. Radiology 93: 307–313, 1969.
 132. Little, J. B. Irradiation of primary human amnion cell cultures: effects on DNA synthesis and progression through the cell cycle. Radiation Res. 44: 674–699, 1970.
 133. Little, J. B. Factors influencing exogenous nucleoside utilization in DNA synthesis by irradiated human cells. Exptl. Cell Res. 62: 368–374, 1970.
 134. Little, J. B. Factors influencing the repair of potentially lethal radiation damage in growth‐inhibited human cells. Radiation Res. 56: 320–333, 1973.
 135. Little, J. B., and G. M. Hahn. Life cycle dependence of repair of potentially lethal radiation damage. Intern. J. Radiation Biol. 23: 401–407, 1973.
 136. Little, J. B., G. M. Hahn, E. Frindel, and M. Tubiana. Repair of potentially lethal radiation damage in vitro and in vivo. Radiology 106: 689–694, 1973.
 137. Little, J. B., U. I. Richardson, and A. H. Tashjian, Jr. Unexpected resistance to X‐irradiation in a strain of hybrid mammalian cells. Proc. Natl. Acad. Sci. 69: 1363–1365, 1972.
 138. Little, J. B., U. I. Richardson, and A. H. Tashjian, Jr. Irradiation of hybrid mammalian cells. Radiation Res. 51: 513, 1972.
 139. Malone, J. F., C. J. Foster, J. S. Orr, and E. Solomonides. The effects on the survival of HeLa S‐3 cells of independent variations in the sizes of the first and the second X‐ray doses in split dose experiments. Intern. J. Radiation Biol. 20: 225–231, 1971.
 140. Malone, J. F., L. A. Hooper, J. S. Orr, and W. R. Greig. Repair of radiation damage to rat thyroid cells in vivo: a highly‐differentiated system. Intern. J. Radiation Biol. 21: 503–510, 1972.
 141. Marin, G., and M. A. Bender. Radiation‐induced mammalian cell death: lapse‐time cinematographic observations. Exptl. Cell Res. 43: 413–423, 1966.
 142. McBurney, N. W., F. L. Graham, and G. F. Whitmore. Sedimentation analysis of DNA from irradiated and unirradiated L‐cells. Biophys. J. 12: 369–383, 1972.
 143. McGrath, R. A., and R. W. Williams. Reconstruction in vivo of irradiated E. coli deoxyribonucleic acid: the rejoining of broken pieces. Nature 212: 534–535, 1966.
 144. Miller, D. R., W. C. Dewey, and H. H. Miller. X‐ray‐induced delay in the Chinese hamster cell‐cycle: dependence on phase irradiated under different culturing conditions, BUdR incorporation, and hypertonic treatment. Intern. J. Radiation Biol. 23: 591–602, 1973.
 145. Milvy, P. Control of free radical mechanisms in nucleic acid systems: studies in radioprotection and radiosensitization. Federation Proc. 32: 1895–1902, 1973.
 146. Mishra, K. P., B. B. Singh, and A. R. Gopal‐Ayengar. E.s.r. studies on gamma‐irradiated TAN (triacetoneamine n‐oxyl) radicals. Intern. J. Radiation Biol. 24: 417–420, 1973.
 147. Modig, H. G., M. Edgren, and L. Révész. Release of thiols from cellular mixed disulphides and its possible role in radiation protection. Intern. J. Radiation Biol. 22: 257–268, 1971.
 148. Munro, T. R. The site of the target region for radiation‐induced mitotic delay in cultured mammalian cells. Radiation Res. 44: 748–757, 1970.
 149. Myers L. S., Jr. Free radical damage of nucleic acids and their components by ionizing radiation. Federation Proc. 32: 1882–1894, 1973.
 150. Nagle, W. A., and R. M. Humphrey. X‐irradiation of mitotic Chinese hamster cells. I. Damage expression and recovery in surviving daughter cells. Intern. J. Radiation Biol. 23: 611–625, 1973.
 151. Neary, G. J., V. J. Horgan, D. A. Bance, and A. Stretch. Further data on DNA strand breakage by various radiation qualities. Intern. J. Radiation Biol. 22: 525–537, 1972.
 152. Nias, A. H. W., D. Greene, M. Fox, and R. L. Thomas. Effect of 14 MeV monoenergetic neutrons on HeLa and P388F cells in vitro. Intern. J. Radiation Biol. 13: 449–456, 1967.
 153. Nias, A. H. W., A. J. Swallow, J. P. Keene, and B. W. Hodgson. Absence of a fractionation effect in irradiated HeLa cells. Intern. J. Radiation Biol. 23: 559–569, 1973.
 154. Ohara, H., and T. Terasima. Variations of cellular sulfhydryl content during cell cycle of HeLa cells and its correlation to cyclic change of X‐ray sensitivity. Exptl. Cell Res. 58: 182–185, 1969.
 155. Olivera, B. M., and I. R. Lehman. Linkage of polynucleotides through phosphodiester bonds by an enzyme from Escherichia coli. Proc. Natl. Acad. Sci. 57: 1426, 1967.
 156. Omerod, M. G., and U. Stevens. The rejoining of X‐ray induced strand breaks in the DNA of a murine lymphoma cell. Biochim. Biophys. Acta 232: 72–82, 1971.
 157. Painter, R. B. The importance of repair replication for mammalian cells. Johns Hopkins Med. J. Suppl. 1: 140–146, 1972.
 158. Painter, R. B., and J. E. Cleaver. Repair replication in HeLa cells after large doses of X‐irradiation. Nature 216: 369–370, 1967.
 159. Pettersen, E. O., R. Oftebro, and T. Brustad. X‐ray inactivation of human cells in tissue culture under aerobic and extremely hypoxic conditions in the presence and absence of TMPN. Intern. J. Radiation Biol. 24: 285–296, 1973.
 160. Phillips, R. A., and L. J. Tolmach. Repair of potentially lethal damage in X‐irradiated HeLa cells. Radiation Res. 29: 413–432, 1966.
 161. Pollard, E. C., W. R. Guild, F. Hutchinson, and R. B. Setlow. Direct action of ionizing radiation on enzymes and antigens. Progress in Biophys. 5: 72–108, 1955.
 162. Pryor, W. A. Free radical reactions and their importance in biochemical systems. Federation Proc. 32: 1862–1869, 1973.
 163. Puck, T. T., and P. I. Marcus. Action of X‐rays on mammalian cells. J. Exptl. Med. 103: 653–666, 1956.
 164. Puck, T. T., P. I. Marcus, and S. J. Cieciura. Clonal growth of mammalian cells in vitro. J. Exptl. Med. 103: 273–284, 1956.
 165. Puck, T. T., and J. Steepen. Life cycle analysis of mammalian cells. I. Method for localizing metabolic events within life cycle, and its application to action of colcemide and sublethal doses of X‐irradiation. Biophys. J. 3: 379–397, 1963.
 166. Racni, G., and W. Szybalski. Molecular radiobiology of human cell lines. II. Effects of thymidine replacement by halogenated analogues on cell inactivation by decay of incorporated radiophosphorus. J. Mol. Biol. 4: 338–346, 1962.
 167. Raleigh, J. A., J. D. Chapman, J. Borsa, W. Kremers, and A. P. Reuvers. Radiosensitization of mammalian cells by p‐nitroacetophenone. III. Effectiveness of nitrobenzene analogues. Intern. J. Radiation Biol. 23: 377–387, 1973.
 168. Rasmussen, R. E., and R. B. Painter. Evidence for the repair of ultraviolet damaged DNA in cultured mammalian cells. Nature 203: 1360–1362, 1964.
 169. Rasmussen, R. E., and R. B. Painter. Radiation‐stimulated DNA synthesis in cultured mammalian cells. J. Cell Biol. 29: 11–19, 1966.
 170. Rauth, A. M. Evidence for dark‐reactivation of ultraviolet light damage in mouse L cells. Radiation Res. 31: 121–138, 1967.
 171. Regan, J. D., J. E. Trosko, and W. L. Carrier. Evidence for excision of ultraviolet‐induced pyrimidine dimers from the DNA of human cells in vitro. Biophys. J. 8: 319–325, 1968.
 172. Reinhold, H. S. Quantitative evaluation of the radiosensitivity of cells of a transplantable rhabdomyosarcoma in the rat. European J. Cancer 2: 33–42, 1966.
 173. Reuvers, A. P., C. L. Greenstock, J. Borsa, and J. D. Chapman. Studies on the mechanism of chemical radioprotection by dimethyl sulphoxide. Intern. J. Radiation Biol. 24: 533–536, 1973.
 174. Revesz, L., and B. Littbrand. Variation of relative sensitivity of closely related neoplastic cell lines irradiated in culture in presence or absence of oxygen. Nature, London 203: 742–744, 1964.
 175. Roots, R., and S. Okada. Protection of DNA molecules of cultured mammalian cells from radiation‐induced single‐strand scissions by various alcohols and SH compounds. Intern. J. Radiation Biol. 21: 329–342, 1972.
 176. Rupert, C. S., W. Harm, and H. Harm. Photoenzymatic repair of DNA. II. Physical/chemical characterization of the process. In: Molecular and Cellular Repair Processes. Fifth International Symposium on Molecular Biology, edited by Roland F. Beers, Jr., Roger M. Herriott and R. Carmichael Tilghman, 1972, p. 64–78.
 177. Sawada, S., and S. Okada. Effects of BUdR‐labelling on radiation‐induced DNA breakage and subsequent rejoining in cultured mammalian cells. Intern. J. Radiation Biol. 21: 599–602, 1972.
 178. Schaer, J. C., and L. Ramseier. Studies on the division cycle of mammalian cells VII. X‐ray sensitivity and repair capacity of synchronously dividing murine mastocytoma cells. Radiation Res. 56: 258–270, 1973.
 179. Schrek, R. In vitro sensitivity of normal human lymphocytes of X‐rays and radiomimetic agents. J. Lab. Clin. Med. 51: 904–915, 1958.
 180. Schrek, R., and S. Stefani. Radioresistance of phytohemagglutinin‐treated normal and leukemic lymphocytes. J. Natl. Cancer Inst. 32: 507–517, 1964.
 181. Schulman, S. G. Fundamentals of interaction of ionizing radiations with chemical, biochemical, and pharmaceutical systems. J. Pharm. Sci. 62: 1745–1757, 1973.
 182. Shaeffer, J., R. A. Vincent, Jr., and T. Merz. Chromosomal rejoining in the absence of unscheduled DNA synthesis. Mutat. Res. 11: 256–257, 1971.
 183. Shipley, W. U., M. M. Elkind, and W. B. Prather. Potentiation of X‐ray killing by 5‐bromodeoxyuridine in Chinese hamster cells: a reduction in capacity for sublethal damage accumulation. Radiation Res. 47: 437–449, 1971.
 184. Silini, C. T., and S. Hornsey. Studies on cell‐survival of irradiated Erlich ascites tumor. III. A comparison of the X‐ray survival curves obtained with a diploid and a tetraploid strain. Intern. J. Radiation Biol. 5: 147–153, 1962.
 185. Simic, M., and E. Hayon. Radical reactions of N‐ethyl maleimide in radiation sensitization. Intern. J. Radiation Biol. 20: 589–592, 1971.
 186. Sinclair, W. K. X‐ray‐induced heritable damage (small‐colony formation) in cultured mammalian cells. Radiation Res. 21: 584–611, 1964.
 187. Sinclair, W. K. Hydroxyurea: effects on Chinese hamster cells grown in culture. Cancer Res. 27: 297–308, 1967.
 188. Sinclair, W. K. Protection by cysteamine against lethal X‐ray damage during the cell cycle of Chinese hamster cells. Radiation Res. 39: 135–154, 1969.
 189. Sinclair, W. K. N‐ethylmaleimide and the cyclic response to X‐rays of synchronous Chinese hamster cells. Radiation Res. 55: 41–57, 1973.
 190. Sinclair, W. K., and R. A. Morton. X‐ray sensitivity during cell generation cycle of cultured Chinese hamster cells. Radiation Res. 29: 450–474, 1966.
 191. Stroud, A., and D. Resh. Characteristics of mutant clones of pig‐kidney cells several years after X‐irradiation. Radiation Res. (Abstr.) 31: 580–581, 1967.
 192. Suit, H. D., and R. J. Shalek. Response of anoxic C3H mouse mammary carcinoma isotransplants (1‐25 mm3) to X‐irradiation. J. Natl. Cancer Inst. 31: 479–495, 1963.
 193. Terasima, T., and L. J. Tolmach. Variations in several responses of HeLa cells to X‐irradiation during division cycle. Biophys. J. 3: 11–33, 1963.
 194. Thomlinson, R. H. The oxygen effect and radiotherapy with fast neutrons. European J. Cancer 7: 139–144, 1971.
 195. Thompson, L. H., and R. M. Humphrey. Proliferation kinetics of mouse L‐P59 cells irradiated with ultraviolet light: a time‐lapse photographic study. Radiation Res. 41: 183–201, 1970.
 196. Thompson, L. H., and H. D. Suit. Proliferation kinetics of X‐irradiated mouse L cells studied with time‐lapse photography. II. Intern. J. Radiation Biol. 15: 347–362, 1969.
 197. Till, J. E. Radiosensitivity and chromosome numbers in strain L mouse cells in tissue culture. Radiation Res. 15: 400–409, 1961.
 198. Till, J. E., and E. A. McCulloch. Direct measurement of radiation sensitivity of normal mouse bone marrow cells. Radiation Res. 14: 213–222, 1961.
 199. Todd, P. Defective mammalian cells isolated from X‐irradiated cultures. Mutat. Res. 5: 173–183, 1968.
 200. Todd, P., T. P. Coohill, A. B. Hellewell, and J. A. Mahoney. Postirradiation properties of cultured Chinese hamster cells exposed to ultraviolet light. Radiation Res. 38: 321–339, 1969.
 201. Todd, P., P. Coohill, and J. A. Mahoney. Responses of cultured Chinese hamster cells to ultraviolet light of different wave‐lengths. Radiation Res. 35: 390–400, 1968.
 202. Tolmach, L. J., and P. I. Marcus. Development of X‐ray induced giant HeLa cells. Exptl. Cell Res. 20: 350–360, 1960.
 203. Tolmach, L. J., B. G. Weiss, and L. E. Hopwood. Ionizing radiations and the cell cycle. Federation Proc. 30: 1742–1751, 1971.
 204. Trosko, J. E., E. H. Y. Chu, and W. L. Carrier. The induction of thymine dimers in ultraviolet‐irradiated mammalian cells. Radiation Res. 24: 667–672, 1965.
 205. Trott, K.‐R., and O. Hug. Intraclonal recovery of division probability in pedigrees of single X‐irradiated mammalian cells. Intern. J. Radiation Biol. 17: 483–486, 1970.
 206. Vos, O., L. Budke, and A. J. Vergroesen. Protection of tissue‐culture cells against ionizing radiation. I. Effect of biological amines, disulphide compounds and thiols. Intern. J. Radiation Biol. 5: 543–557, 1962.
 207. Vulpis, N. Chromosome aberrations induced in human peripheral blood lymphocytes using heavy particles from 10B (n, α) 7Li reaction. Mutat. Res. 18: 103–111, 1973.
 208. Watanabe, I., and S. Okada. Study of mechanisms of radiation‐induced reproductive death of mammalian cells in culture: estimation of stage at death and biological description of processes leading to cell death. Radiation Res. 27: 290–306, 1966.
 209. Weiss, B., and C. C. Richardson. Enzymatic breakage and joining of deoxyribonucleic acid. I. Repair of single‐strand breaks in DNA by an enzyme system of Escherichia coli infected with T4 bacteriophage. Proc. Natl. Acad. Sci. 57: 1021, 1967.
 210. Weiss, B. G. Perturbations in precursor incorporation into DNA of X‐irradiated HeLa S3 cells. Radiation Res. 48: 128–145, 1971.
 211. Weiss, B. G., and L. J. Tolmach. Modification of X‐ray induced killing of HeLa S3 cells by inhibitors of DNA synthesis. Biophys. J. 7: 779–795, 1967.
 212. Whitmore, G. F., and S. Gulyas. Synchronization of mammalian cells with tritiated thymidine. Science 151: 691–694, 1966.
 213. Whitmore, G. F., and S. Gulyas. Studies on recovery processes in mouse L cells. Natl. Cancer Inst. Monogr. 24: 141–156, 1967.
 214. Whitmore, G. F., S. Gulyas, and J. Botond. Radiation sensitivity through‐out cell cycle and its relationship to recovery. In: Cellular Radiation Biology: 18th Symposium on Fundamental Cancer Research, M. D. Anderson Hospital and Tumor Institute. Baltimore: Williams & Wilkins, 1965, p. 423–441.
 215. Whitmore, G. F., and J. E. Till. Quantitation of cellular radiobiological responses. Ann. Rev. Nucl. Sci. 14: 347–374, 1964.
 216. Whitmore, G. F., J. E. Till, and S. Gulyas. Radiation‐induced mitotic delay in L cells. Radiation Res. 30: 155–171, 1967.
 217. Whitmore, G. F., J. E. Till, R. B. L. Gwatkin, L. Siminovitch, and A. F. Graham. Increase of cellular consitiuents in X‐irradiated mammalian cells. Biochem. Biophys. Acta 30: 583–590, 1958.
 218. Wilkins, R. J. Alpha‐ray induced breaks in the DNA of Escherichia colis. Intern. J. Radiation Biol. 20: 497–500, 1971.
 219. Winans, L. F., W. C. Dewey, and C. M. Dettor. Repair of sublethal and potentially lethal X‐ray damage in synchronous Chinese hamster cells. Radiation Res. 52: 333–351, 1972.
 220. Withers, H. R. Dose‐survival relationship for irradiation of epithelial cells of mouse skin. Brit. J. Radiol. 40: 187–194, 1967.
 221. Wolff, S. Some postirradiation phenomena that affect induction of chromosome aberrations. J. Cellular Comp. Physiol. 58 (3): 151–162, Part 2, 1961.
 222. Wolff, S. Chromosome aberrations and the cell cycle. Radiation Res. 33: 609–619, 1968.
 223. Wolff, S., and K. C. Atwood. Independent X‐ray effects on chromosome beakage and reunion. Proc. Natl. Acad. Sci. 40: 187–192, 1954.
 224. Wolff, S., and D. Scott. Repair of radiation‐induced damage to chromosomes. Exptl. Cell Res. 55: 9–16, 1969.
 225. Yu, C. K., and W. K. Sinclair. Division delay and chromosomal aberrations induced by X Rays in synchronized Chinese hamster cells in vitro. J. Natl. Cancer Inst. 39: 619–632, 1967.
 226. Zirkle, R. E., and W. Bloom. Irradiation of parts of individual cells. Science 117: 487–493, 1953.
References in Addendum
 1. Cleaver, J. E. Repair processes for photochemical damage in mammalian cells. In: Advances in Radiation Biology, vol. 4, edited by J. T. Lett, M. R. Zelle, and H. Adler. New York: Academic, 1974, p. 1–69.
 2. Grossman, L. Enzymes involved in the repair of DNA. In: Advances in Radiation Biology, vol. 4, edited by J. T. Lett, M. R. Zelle, and H. Adler. New York: Academic, 1974, p. 77–126.
 3. Grossman, L., A. Braun, R. Feldberg, and I. Mahler Enzymatic repair of DNA. Ann. Rev. Biochem., 1976. In press.
 4. Williams, J. R. The rate of DNA repair in cell inactivation, aging and transformation: a selected review, a speculative model. In: Advances in Radiation Biology, vol. 6, edited by J. T. Lett, M. R. Zelle, and H. Adler. New York: Academic, 1976. In press.
 5. Williams, J. R., and J. B. Little. DNA repair in cultured mammalian cells. In: Growth, Nutrition and Metabolism of Cells in Culture, vol. III, edited by V. Cristofalo and G. Rothblatt. New York: Academic. In press.

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Article Title: Effects of Ionizing Radiation on Mammalian Cells
 

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John B. Little, Jerry R. Williams. Effects of Ionizing Radiation on Mammalian Cells. Compr Physiol 2011, Supplement 26: Handbook of Physiology, Reactions to Environmental Agents: 127-155. First published in print 1977. doi: 10.1002/cphy.cp090108