Pathological aspects of photodynamic lesions of the skin

Oxygen Dependence of Hypericin‐induced Phototoxicity to Emt6 Mouse Mammary Carcinoma Cells

“…Photoactivated hypericin also exhibits biological activity in vitro, disrupting enzyme activity, membrane integrity, viral infectivity, and mediating the photodynamic killing of ciliate cells (Knox and Dodge, 1985;Yang et al, 1986;Carpenter and Kraus, 1991;Thomas et al, 1992). The photodynamic activity of hypericin apparently requires oxygen, but few reports demonstrate this oxygen dependence (Castellani and Torlone, 1956). Most evidence suggests that, after excitation by visible light and intersystem conversion (Reaction l), hypericin undergoes a type I1 oxygendependent mechanism in which energy transfer from excited triplet state hypericin to ground state molecular oxygen generates singlet oxygen as the pri- (Jardon et al, 1987;Racinet el al., 1988).…”

Photodynamic effect of haematoporphyrin on blood microcirculation

“…Histologically the most evident alteration is shown by the dermis (Levy, 1929). Histochemically under photodynamic conditions there is loss of the chromotropic property of the ground-substance of the connective tissue of the skin (Castellani and Torlone, 1956). The blood vessels of the corium appear dilated and full of a dense mass of red cells, suggesting a profound alteration of the blood circulation.In order to have direct experimental evidence of the modifications brought about in the capillary network by the photodynamic effect, living photosensitised tissue particularly rich in blood vessels was observed under the microscope in viva The tissues used were the tongue of the frog (Runa esculentu) and the mesentery of the white rat.…”

“…Histologically the most evident alteration is shown by the dermis (Levy, 1929). Histochemically under photodynamic conditions there is loss of the chromotropic property of the ground-substance of the connective tissue of the skin (Castellani and Torlone, 1956). The blood vessels of the corium appear dilated and full of a dense mass of red cells, suggesting a profound alteration of the blood circulation.…”

Effect of Ultraviolet Irradiation on Hyaluronic Acid in Vitro.

“…1959). CASTELLANI (1954) and CASTELLANI & TORLONE (1956) demonstrated reduction in the viscosity of hyaluronic acid by irradiation with light of a wave-length about 4460 A, which is within the range of visible light. The effect they observed depended on addition of photosensitising substances as well as on the presence of oxygen.…”

“…Thus ultrasonic waves (HUNZINGER et al 1949), ionising rays (RAGAN et al 1947;HEINRICHS et al 1956) and ultraviolet light (MOGILEVSKIJ & LAUFER 1951;HVIDBERG et al 1958) can each reduce the viscosity of hyaluronic acid. CASTELLANI (1954) and CASTELLANI & TORLONE (1956) showed that by adding substances producing an abnormal photosensitivity in man and animals, such as haematoporphyrin, hypericin and phyllo-erythrin, the viscosity of hyaluronic acid was reduced by exposure to visible rays, though only in presence of oxygen.…”