[Comparative analysis of Ca(2+)-signalling in brown preadipocytes of ground squirrel Spermophillus undulatus and mouse].

Analysis of the slow Ca(2+)-responses of brown preadipocytes of ground squirrel Spermophillus undulatus and mouse was carried out. The mouse brown preadipocytes demonstrated low but prominent responses to noradrenalin with the maximum at 3 and 10 microM being the less effective. The ground squirrel brown preadipocytes practically did not practically respond to 10 nM-10 microM, whereas 30-600 microM noradrenalin was able to raise intracellular [Ca2+]i up to 600 nM with 300 microM agonist being the most effective. Stimulation of the plasma membrane Ca(2+)-channels with thimerosal showed considerable reduction of the calcium entry system in the cell precursors of both species comparing with their mature adipocytes. Intracellular calcium stores liberated in preadipocytes of both species by tapsigargin and ionomycin in Ca(2+)-free medium were insignificant, and capacitative Ca(2+)-entry in response to the cellular Ca(2+)-stores depletion was completely absent in Ca(2+)-containing medium. The Ca(2+)-responses of the ground squirrel brown preadipocytes were independent on physiological state of the animals and annual seasons. Preadipocytes of both species showed the same dose-response curves for the Ca(2+)-raise under thimerosal, and the mouse had two-fold higher kinetic constants for the Ca2+ ions entry. The ground squirrel brown adipocytes responded to ionomycin with approximately 25% higher increase in [Ca2+]i and the entry of the ions had 7-10-fold higher kinetic constants for this process. Kinetic constants for the [Ca2+]i raise in mouse preadipocytes were independent of ionomycin concentration, whereas in the ground squirrel brown preadipocytes the constant linearly increased with the ionophore concentration. It is suggested that the found difference in the function of Ca(2+)-signalling in preadipocytes of two species, which becomes apparent in the presence of ionomycin, might be responsible for the observed difference in the noradrenalin induced cellular Ca(2+)-responses as well.

[Increase in access to SH-groups of membrane proteins in Ehrlich ascites carcinoma cells upon purinergic receptor activation]. / Uvelichenie dostupnosti SH-grupp membrannykh belkov v kletkakh astsitnoi kartsinomy Ehrlikha pri aktivatsii purinoretseptora.

The effect of ATP on SH-groups accessibility of the surface membrane proteins in Ehrlich ascites tumor cells has been studied using a fluorescent nonpenetrating reagent Thiolyte MQ. No accessible protein SH-groups in plasma membrane of unstimulated cells have been found. The accessibility of SH-groups in proteins with molecular masses 82 and 23 kDa was increased in 10 s after the ATP addition. The data are interpreted as a result of the conformational transition or vertical translocation of certain thiol-bearing membrane proteins at purinoreceptor activation. The effect may apparently be coupled to the changes in the membrane potential and calcium concentration in the cytoplasm occurring in the same time interval.

[Use of the principle of reverse problems for detecting processes, occurring in cells suspended in culture. II. Distribution of glutathione, SH groups, and optical density in the E. coli cell cycle]. / Primenenie printsipa obratnykh zadach dliia vyiavleniia protsessov, proiskhodiashchikh v kletkakh pri ikh suspenzionnom kul'tirovanii. II. Opredelenie glutationa, SH-grupp i opticheskoi plotnosti v kletochnom tsikle E. coli.

A method was proposed for calculating the content of intracellular components during the cell cycle of an individual cell. The principle of reverse problems was used in the mathematical model proposed. The model allowed us to calculate changes of intracellular parameters of an individual cell from corresponding parameters measured in the whole culture. Optical density, total SH-group and glutathione content in synchronous culture of E. coli were the parameters studied. The proposed method may be applied for both synchronous and asynchronous cell cultures.

[Metabolite level from energy metabolism in Escherichia coli cells during growth on various substrates]. / Soderzhanie metabolitov énergeticheskogo obmena v kletkakh Escherichia coli pri roste na raznykh substratakh.

In the present work, an attempt has been made to analyse some parameters of the intracellular energy metabolism and to determine whether they are related to the cell growth rate. The authors measured intracellular concentrations of adenine nucleotides, the content of glycogen, an energy "depot" of glucose, the rate of its synthesis, and the content of glutathione which specifies the redox state in the cytoplasm of E. coli cells upon continuous cultivation on a minimal nutrient medium containing various carbon sources (glucose, glycerol, lactate, and acetate). It was found that the specific contents of adenine nucleotides and reduced glutathione were independent of the cell growth rate. Based on the results obtained, it is assumed that a possible reason for changes in the duration of the sell cycle of the bacteria cultured on different substrates is an alteration in the content of reserve carbohydrates.

[The role of glutathione in the interphase death of dividing cells]. / Izuchenie roli glutationa v interfaznoi gibeli deliashchikhsia kletok.

A study was made of a change in the content of reduced glutathione (GSH) in Ehrlich ascites tumor (EAT) cells after irradiation with doses evoking their interphase death (ID). GSH content was determined in a suspension of EAT cells fixed by hot ethanol. The postirradiation decrease in the GSH content of the suspension was due to its oxidation by hydrogen peroxide resulting from radiochemical reactions after releasing thereof from cells upon fixation. In the absence of an irradiated medium no changes occurred in the GSH content of EAT cells. It is concluded that ID of EAT cells is not associated with the radiation-induced decrease in the content of GSH, an endogenous antioxidant.

[Synchronous conformational oscillations in the titer of sulfhydryl groups in protein solutions. Reversible oxidation as a possible cause of this phenomenon]. / Sinkhronnye konformatsionnye kolebaniia titra sul'fgidril'nykh grupp v rastvorakh belkov. Obratimoe okislenie kak vozmozhnaia prichina étogo iavleniia.

In solutions of creatine kinase, actin and lactic dehydrogenase oscillations of SH-groups are revealed by three independent methods using three different reagents AgNO3, PCMB, DTNB. The variations of the SH-group titre remain after denaturation of the individual protein solution portions. In the solutions of predenaturated proteins no titre oscillations are observed. Possible cause of the observed oscillations of SH-groups titre may be reversible SH--SS transformation.

[The content and types of sulfhydryl groups in muscle creatine kinase detected by their accessibility to different reagents]. / Soderzhanie i tipy sul'fgidril'nykh grupp kreatinkinazy, otlichaiushchikhsia po ikh dostupnosti dlia razlichnykh reagentov.

Using three independent methods tte amperometric titration, Boyer's method and the method of Ellman it is shown that rabbit muscle creatine kinase contains 11-12 SH-groups, 3-6 of which are easily oxidized by atmospheric oxygen to form S-S-bonds. It is found that creatine kinase has four types of SH-groups distinguished by their accessibility to different SH-reagents. The first type related to the enzymatic activity is detected by the Ellman method (2 SH-groups), the first and the second ones taken together--by the Boyer method (4 SH-groups), the first, second and third ones--by the method of amperometric titration (6 SH-groups), all the 4 types together--when detecting SH-groups after protein denaturation--by any of the above methods (8-12 SH-groups).