THE PRODUCTION OF PERSISTENT ALOPECIA IN RABBITS BY ROENTGEN RADIATION; A STUDY OF THE MINIMUM DOSE REQUIRED AND THE CONSISTENCY OF THE REACTION

THE SKIN REACTIONS PRODUCED BY ALTERNATIONS OF HEAT AND X-RAY AT VARIOUS TIME INTERVALS

Areas on the abdomen of the same guinea pig were exposed to suberythemal doses of soft X-rays, to heat of an intensity below the critical dose for the production of burns, and to both radiations in sequence with various time intervals between the exposures. The only effect of exposure to X-ray or heat alone was a slight scaling of the skin. The areas exposed to heat and X-radiation developed well-marked and persistent burns when the exposure to one agent was made within 3 hours of the other. Scaling of the skin developed when the exposure to one agent was made 1 day after the other. This scaling was more marked and lasted longer than the scaling produced by either agent alone. The results were the same no matter in which sequence the agents were applied.

THE INACTIVATION OF TRYPSIN BY X-RAYS

1. The inactivating effect of soft x-rays on trypsin in solutions of various degrees of concentration has been studied. 2. It has been found to run parallel with spontaneous heat inactivation. It is almost, if not entirely, confined to the free or active trypsin. 3. Under radiation of constant intensity, the inactivation follows the simple exponential law which indicates a monomolecular reaction. 4. Estimates have been made of the amount of ionization required to inactivate trypsin to half value in these experiments and in those of Hussey and Thompson, who employed the beta rays from Radium B and C. The close agreement corroborates the idea that the effect is a function of ionization only. 5. The nature of the process of inactivation is discussed; inactivation seems to result from electrical neutralization of the trypsin ion.

SKIN REACTIONS TO ALTERNATE HEAT AND X-RAY EXPOSURES

Different areas on the abdomen of the same guinea pigs have been exposed to suberythema doses of soft x-rays, to heat of an intensity below the critical dose for the production of burns, and to both radiations in sequence. The only effect of exposure to x-ray or heat alone was a slight scaling of the skin. The areas exposed to heat and x-radiation developed well marked and persistent burns. The results were the same no matter in which sequence the agents were applied.

THE PRODUCTION OF PERSISTENT ALOPECIA IN RABBITS BY X-RAYS OF VARIOUS DEGREES OF HARDNESS

1. The minimum dose of x-ray, of each of three degrees of hardness, required to produce persistent alopecia of the abdominal skin of normal white rabbits has been studied. 40 kilovolt rays filtered by 0.5 mm., 50 kilovolt rays filtered by 1 mm., and 70 kilovolt rays filtered by 1.5 mm. of aluminium were employed. The 70 kilovolt work is unfinished. 2. Under constant conditions of treatment, the animals were found to react with a high degree of consistency. 3. The values of the critical minimum doses expressed in terms of air ionization (pair of ions per gm. of air divided by 10¹⁵), for rays produced at 30, 40, 50, and 70 kilovolt peak, are 2.04, 3.7, 4.5, and over 5.1 respectively. The 30 kilovolt value is taken from a previous paper. 4. It is shown that the alopecia reaction does not run parallel to the erythema and pigmentation reactions.

SKIN REACTIONS TO SIMULTANEOUS TREATMENTS WITH RADIANT HEAT AND SOFT X-RAYS

Guinea pigs have been exposed to suberythema doses of soft x-rays, to radiant heat of intensity about critical for producing slight burns, and to both radiations simultaneously. No erythema was produced in the skin of the animals exposed to x-rays alone and only slight burns resulted in 50 per cent of the animals exposed to heat radiation alone. The animals exposed to heat and x-radiation simultaneously developed well marked burns which healed much more slowly than those produced by heat alone.