[Quantitative determination and reversible modification of sulfhydryl groups in low and high molecular weight compounds using a biradical spin marker]. / Kolichestvennoe opredelenie i obratimaia modifikatsiia sul'fgidril'nykhgrupp nizko- i vysokomolekuliarnykh soedinenii s ispol'zovaniem biradikal'noi spinovoi metki.

A new method for quantitation of sulfhydryl groups of low and high molecular weight compounds is proposed. The method is based on the use of a biradical spin label carrying a disulfide bond, RS-SR, where R is the imidazoline radical. It was found that this biradical is involved in the reaction of thiol-disulfide exchange with thiols; the EPR spectra of the original biradical and monoradical products differ essentially. This circumstance made it possible to determine the bimolecular rate constant for the biradical interaction with cysteamine, cysteine, glutathione and human serum albumin. The method was used for measuring glutathione and cysteine levels in murine and rat blood and for assaying the insect acetylcholine esterase activity and reversible inhibition of NADPH-cytochrome P-450 reductase. The method is marked for a high sensitivity (10(-6)-10(-7) M) towards sulfhydryl groups and allows the determination of thiol groups in coloured and nontransparent solutions.

[Effect of cyclic 3',5'-adenosine monophosphate on hyaluronate hydrolase activity in the renal papilla]. / Vliianie tsiklicheskogo 3',5'-adenozinmonofosfata na aktivnost' gialuronatgidrolaz sosochka pochki.

The relationships between cAMP and hyaluronate hydrolases (HH) activity were studied in the renal tissue. Both the urine osmolality and the HH activity were increased in the papilla tissue of rats treated with cAMP. Incubation of mild homogenized cells prepared from kidney papilla with cAMP, resulted in a significant increase in the total HH activity and that of beta-glucuronidase and N-acetyl-beta-D-hexosaminidase, whereas the activity of hyaluronidase remained unchanged. The data obtained suggest that ADH effect on the HH activity is mediated by adenylate cyclase mechanism.

[Effect of vasopressin, aldosterone and angiotensin on the permeability of the choroid plexus to water]. / Vliianie vazopressina, al'dosterona i angiotenzina na pronitsaemost' khoroidal'nogo spleteniia dlia vody.

In anesthetized dogs with cannulae implanted in the lateral cerebral ventricle, the water transfer from the CSF to the blood was studied using determination of drainage of tritiated water injected into the ventricle. Vasopressin and aldosterone accelerated the transfer of tritiated water into veins whereas angiotensin decelerated it. The data obtained suggest that the above hormones regulate volume and osmolality of the CSF.