A photosynergistic lethal effect in the irradiation of yeasts with long-wave ultraviolet and visible light

A lethal synergistic effect which is expressed as the nonadditive summing of the damaging effect of each irradiation separately has been found during the investigation of combined action of longwave ultraviolet (UV) rays (337 nm or 365 nm) and visible light (400-600 nm) on the yeast cells. Based on the data on different mechanisms of lethal effect of longwave UV and visible light, it has been suggested that the basis of the photosynergistic effect is the mutual intensification of the photo-destructive processes occurring in different intracellular structures and processes induced by different endogenous sensitizers.     

Effect of serotonin on the yield of UV-induced thymine dimers in DNA

Using a fluorescence method the interaction between serotonin and DNA has been investigated and the association constant Kc = 4.2 X 10(4) M-1 was determined. Bound serotonin is shown to reduce the yield of UV-induced thymine dimers in DNA. It is calculated that the value of the effective distance over which each protector acts is a segment of the DNA helix about four base pairs long.     

The age-related characteristics of the contractile function and of the calcium-transport system of the rat myocardium under conditions of restricted coronary perfusion

In experiments on isolated rat heart, it has been shown that in old animals the sensitivity to restriction of the coronary perfusion increases whereas the resistance of the heart to this restriction decreases. It was established that incomplete reversible ischaemia causes significant changes in different steps of Ca2(+)-transporting system of the myocardium which are more evident in older animals and which presumably account for the increased sensitivity of cardiac muscle to ischaemia.     

Photogeneration of the superoxide anion oxygen radical and its role in the inactivation of yeast cells by long-wave UV light

Long-wave (320-400 nm) UV-induced oxygen superoxide anion radical (O2-) formation was found in yeast cells. This radical plays an important part in initiation of photodestruction reactions in DNA which serves as a main target of UV irradiation in yeast. The observed cell photoinactivation spectrum at the wavelengths 320-400 nm suggests that NADH can serve as an endogenous sensitizer of O2- formation.