A. Maggiora

De I’hyperpigmentation par rayons X chez le cobaye

Doses of x rays of 50 to 800 r were delivered to an area of guinea pig skin 3 cm in diameter to determine the threshold radiation dose to induce hyperpigmentation of skin. Hyperpigmentation was noted after 100-r but not 50-r doses, indicating that the threshold lies between 50 and 100 r. Hyperpigmentation appeared to be intensified at doses above 300 or 400 r. It appeared between the 8th and 11th day after irradiation and reached max. development after 24 hr, after which its intensity remained constant for 15 to 30 days. Normal skin color returned in 40 to 60 days; by then the skin color could not be distinguished from that of nonirradiated skin. The time of appearance and intensity of hyperpigmentation showed no relation to the quality of x rays used, over the range of 10 to 70 kv. When the min. effective dose, 100 r, was given in two 50-r doses 1 day apart, no hyperpigmentation of skin resulted, indicating that fractional doses are not as effective as a single dose in inducing this condition.

Effet protecteur de la cystéamine envers les rayons X appliqués localement sur la peau du cobaye

The protective action of cysteamine against local application of x rays to the skin of gunea pigs was investigated. The temporary epilation and acanthosis tests were used. For the epi1ation test, both sides of the animal were shaven and a 3-cm/sup 2/ area on one side was exposed to an 800 r dose of 50 kv x rays for 2 hours 32 minutes, which was followed by an intraperitoneal injection of 40 mg of cysteamine base, and, 5 minutes later, by identical x ray exposure of the other side. Results showed that only when cysteamine was injected before irradiation did it prevent temporary epilation, which always occurred in animals receiving 800 r and no medication. For the second test, the same procedure was followed, but radiation consisted in 1600 r given for 5 hours. When skin excision took place 27 days postirradiation, acanthosis was found to be far less pronounced on the protected side, this being a farther demonstration of the protective action of cysteamine against x rays. Acanthosis, as measured by thickness of the epidermis, was about 50% greater in the animals injected with cystesanine after, as compared with before, irradiation. (BBB)The protective action of cysteamine against local application of x rays to the skin of gunea pigs was investigated. The temporary epilation and acanthosis tests were used. For the epi1ation test, both sides of the animal were shaven and a 3-cm/sup 2/ area on one side was exposed to an 800 r dose of 50 kv x rays for 2 hours 32 minutes, which was followed by an intraperitoneal injection of 40 mg of cysteamine base, and, 5 minutes later, by identical x ray exposure of the other side. Results showed that only when cysteamine was injected before irradiation did it prevent temporary epilation, which always occurred in animals receiving 800 r and no medication. For the second test, the same procedure was followed, but radiation consisted in 1600 r given for 5 hours. When skin excision took place 27 days postirradiation, acanthosis was found to be far less pronounced on the protected side, this being a farther demonstration of the protective action of cysteamine against x rays. Acanthosis, as measured by thickness of the epidermis, was about 50% greater in the animals injected with cystesanine after, as compared with before, irradiation. (BBB)

L’épilation par rayons X chez le cobaye (doses fractionnées avec intervalles de 6, 12 et 24 h)

A single dose of 800 r delivered to an area of guinea pig skin 3 cm in diameter regularly caused epilation. However, no epilation followed four 200-r doses given at intervals of 24 hr. or even after eight 200-r doses. In contrast, either of these fractional doses given at 12-hr intervals produced epilation. The same fractional doses at 6-hr intervals were also effective. A single 1600- r dose caused persistent alopecia compared with the transient (1- to 2month) hair loss caused by 800 r. However, if the 1600-r dose was given fractionally the duration of alopecia was diminished. These results in guinea pigs differ from results on fractional doses necessary to induce erythema in man. which showed that the effect diminished as the interval was decreased below 24 hr. The threshold epilatory dose is higher in guinea pigs than man. (H.H.D.)