Influence of pH on the UV sensitivity of peritoneal macrophage plasma membrane

Lowering the extracellular pH (from 7.2 to 6.3) or intracellular acidification in isolated murine peritoneal macrophages before UV-irradiating them to 9 J/cm² (λ_max = 306 nm) diminish the percentage of cells with damaged membranes. Extracellular pH 8.4 or intracellular alkalization have an opposite effect. After transient hypoosmotic swelling, the UV-induced membrane damage is fully pronounced regardless of external pH. In cells that survive UV-irradiation to 8 and 10 J/cm² (λ_max = 297 nm), the intracellular pH is 0.2 and 0.25 unit lower than in nonirradiated cells.     

The effect of periovulatory imbalance of prolactin on the expression of prolactin receptors in rat ovary cells

Using the technique of immunohistochemistry in combination with cytophotometry, we have studied the effect of periovulatory hyper- and hypoprolactinemia on the expression of prolactin receptors in various cell types of rat ovaries during early estrus. It has been shown that intense specific staining of oocytes is positively controlled by prolactin. The maximal intensity of specific staining was found in cells of the cumulus and the inner layer of granulosa cells in mature follicles; staining intensity gradually diminished towards the outer boundary cell layer. Postovulatory follicles are distinct from those mature follicles in which there was no ovulation in their more intense manifestation of prolactin receptors in cells of the inner layer and cumulus, as well as in increased positive staining (after prolactin administration) only in the granulosa layer cells closest to theca. In follicles which did not ovulate by the time of the early estrus, prolactin administration leads to a proportional growth of specific immunoreactivity in all cell layers of the granulosa. The administration of bromocryptin, an inhibitor of prolactin secretion, leading to a 10-fold decrease in the prolactin level in the blood, results in a twofold decrease in the intensity of specific staining of all cell layers of the granulosa in either type of follicle. Corpora lutea of the previous cycle have irregularly positioned luteocytes with weak and strong specific staining, the intensity of which is not changed in response to prolactin and diminishes slightly after the administration of bromocryptin. We conclude that the most intense changes in the content of prolactin receptors under the conditions of imbalance of this hormone during the periovulatory period are observed in those follicles where the oocyte did not ovulate by the time of early estrus.     

Photodynamic Damage to Yeast Subcellular Organelles Induced by Elevated Levels of Endogenous Protoporphyrin IX

The 2,2"-dipyridyl-induced accumulation of protoporphyrin IX in Saccharomyces cerevisiae cells was shown to be accompanied by the photoinhibition of cell respiration and the enhancement of the photoinduced permeability of plasma membranes to the fluorescent dye primuline. The visible-light illumination (at 400–600 nm) of the mitochondria and plasma membranes isolated from yeast cells with a high level of endogenous protoporphyrin IX intensified lipid peroxidation in these subcellular organelles. Comparative studies showed that the rad 52 mutant cells, which are deficient in the postreplicative recombinational DNA repair system, are considerably more sensitive to the inactivating action of visible light than are the wild-type cells and the rad 3 mutant cells, which are deficient in the excision DNA repair system. The contribution of photodynamic damage to the yeast subcellular organelles to the lethal photodynamic effect is discussed.     

Damage to plasmatic membranes of mice peritoneal macrophages under the influence of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

Using the microfluorescent method of identification of damaged plasmatic membranes, the influence of hydrogen peroxide on mice peritoneal macrophages was determined. H₂O₂ in vitro produced a destructive effect on the cells depending on the temperature, time of incubation, and concentration of the agent. The damage increases after the incubation medium is replaced with Hanks solution containing no H₂O₂.