Light scattering at a temporal boundary in a Lorentz medium.

Temporal discontinuity in the permittivity of a nondispersive dielectric (temporal boundary) is a conventional model for considering electromagnetic phenomena in dynamic materials and metamaterials. Here we apply a more general model of a Lorentz medium with the rapidly changing density of its structural elements (oscillators) or their resonant frequency to determine the realms of applicability of the conventional temporal boundary model. We demonstrate the dependence of the continuity conditions and the energy relations at a temporal boundary on the nonstationarity mechanism and the ratio between the rate of nonstationarity and the characteristic frequencies in the system.

[Regulatory volume increase (RVI) and apoptotic volume decrease (AVD) in U937 cells placed into hyperosmotic medium].

Time course of changes in intracellular water, K+ and Na+ of U937 cells incubated in hyperosmolar medium with addition of 200 mM sucrose was studied. Ouabain-sensitive and ouabain-resistant Rb+ (K+) influxes were measured during regulatory cell volume increase (RVI) and apoptotic volume decrease (AVD). Microscopy of cells stained by Acrydine orange, Ethydium bromide, APOPercenrage Dye and polycaspase marker FLICA was performed. We found that initial osmotic cell shrinkage induced both RVI and AVD responses. RVI dominated at the early stage whereas AVD prevailed at the later stage. In view of the data obtained in U937 cells the current opinion that RVI "dysfunction" is a prerequisite for apoptosis and AVD (Subramanyam et al., 2010) should be revised. U937 cells are capable to trigger of apoptosis and AVD in spite of the unimpaired RVI response. It is concluded that AVD plays a significant role in preventing osmotic lysis of apoptotic cells rather than in the initiation of apoptosis.

Effect of magnetic fields on antioxidant system enzymes in mice with Ehrlich ascites carcinoma.

The combination of weak steady-state and weak low-frequency alternating magnetic fields activates SOD in Ehrlich ascites carcinoma cells and catalase in liver cells by 3.7 and 1.3 times, respectively (p<0.05), which can result from enhanced production of ROS induced by combined exposure to magnetic fields with the specified parameters.

[Changes in K+, Na+ and Cl- contents and K+ and Cl- fluxes during apoptosis of U937 cells by staurosporine. On the mechanism of cell dehydration in apoptosis].

K+, Na+ and Cl- balance and K+ (Rb+) and 36Cl fluxes in during apoptosis of U937 cells caused by 0.2 or 1 microM staurosporine were studied by flame emission and radiotracer techniques. It is found that monovalent ion redistribution accounts for 2/3 of all decrease in the amount of intracellular osmolytes in apoptotic cells while 1/3 is due to the loss of other intracellular osmolytes. Na+ gain in apoptotic cells hampers dehydration is caused by K+ and Cl- loss. It is found that the rate of equilibration of 36Cl, Rb+ (K+) and 22Na+ between cells and the medium exceeds significantly the rate of alteration of cell ion content associated with apoptosis. It is concluded that apoptotic changes should be considered as a drift of the balanced ion distribution. Alteration of the ion balance in apoptosis, caused by 0.2 microM staurosporine, is associated with an increase in the uabain-resistant Rb+ (K+) "channel" influx and insignificant alteration of the uabain-sensitive "pump" influx. Stronger apoptosis, induced by 1 microM staurosporine, is associated with a decrease in the pump fluxes and insignificant changes in the "channel" Rb+ (K+) fluxes. Decreasing of the Cl- level in apoptotic cells by a factor 1.4-1.8 is accompanied with a decrease in the flux, by a factor 1.2-1.6.

[Verbena canadensis Britt mutants with altered development of flowers and inflorescences generated by chemical mutagenesis].

Rose vervain is a little-known ornamental annual plant. The adaptive properties (drought and cold resistance) and long period of flowering make this species promising for growing in flower gardens and containers. Chemical mutagenesis widely used for various plant species was applied to induce character variation in Rose vervain. The properties of development of flowers and inflorescences in lines descending from the M3--M5 mutants generated by the seed exposure to chemical mutagens diethyl sulfate and nitrosomethylurea were considered.

[Apoptosis. Signaling network and changes of cell ion and water balance].

The review focuses on the shift of the monovalent ion balance, pH, and the membrane potential during apoptosis with respect to the ionic mechanism of apoptotic cell shrinkage. As an introduction the current views on the main signaling network, involved in the induction of apoptosis, i. e. receptor and mitochondrial pathways of caspase cascade activation and a caspase-independent induction of apoptosis are considered. The review summarizes the recent data on alteration of ion transporters and channels of the plasma membrane during apoptosis.

[Cell shrinkage during apoptosis is not obligatory. Apoptosis of U937 cells induced by staurosporine and etoposide]. / Degidratsionnoe sokrashchenie ob"ema kletok pri apoptoze--fakul'tativnyi priznak. Apoptoz kletok U937, vyzvannyi staurosporinom i étopozidom.

A study was made of apoptotic cell shrinkage, which is generally believed to be a hallmark of apoptosis. The two conventional models of apoptosis were used for examination of changes in cell water balance--one is apoptosis caused in human lymphoma cell line U937 by staurosporine, and the other by etoposide. Intracellular water was determined by measuring buoyant density of cells in continuous Percoll gradient. Apoptosis was recognized by microscopy and flow cytometry. Apoptosis caused by staurosporine (1 microM, 4 h) was found to be associated with a decrease in cell water content by almost 24%. In contrast, no decrease in cell water content was observed in U937 cells incubated with etoposide (50 microM, 4 h), in spite of the number of features suggesting the presence of apoptosis, such as the appearance of apoptotic bodies, chromatin condensation and fragmentation and disappearance of S-phase cells in DNA histogram. It is concluded that definition of apoptosis as "shrinkage-necrosis" (Kerr, 1971) needs correcting: the distinction of apoptotic cells involves the absence of swelling, rather than cell shrinkage.

[Water and ion balance in rat thymocytes under apoptosis induced with dexamethasone or etoposide. Ion-osmotic model of cell volume decrease]. / Vodnyi i ionnyi balans timotsitov krysy pri apoptoze, vyzvannom deksametazonom i étopozidom. Iono-osmoticheskaia model' umen'sheniia ob'ema kletki.

Cell ion and water balance was studied with respect to analysis of the osmotic model of apoptotic volume decrease (AVD) in rat thymocytes under dexamethasone (1 microM, 4-6 h) or etoposide (50 microM, 5 h) treatment. Intracellular water content was determined by measurement of cell buoyant density in continuous Percoll gradient, while intracellular potassium and sodium contents were determined by flame emission analysis. Apoptosis was verified by an increase in cell buoyant density, fluorescence of cells stained with Acridine orange and Ethidium bromide (flow cytometry), by changes in the cell cycle and the appearance of sub-diploid peak in the DNA histogram (flow cytometry), and by a decrease in cell size examined with light microscope. A separate fraction of dense cells with reduced size was found to appear after dexamethasone or etoposide treatment. This fraction was considered as apoptotic. An increase in buoyant density of apoptotic cells corresponded to a decrease in cell water content. In apoptotic cells vs. cells with normal buoyant density, the intracellular potassium content was lower, but sodium content was higher. The sum of potassium and sodium contents was lower in apoptotic cells. Taken into account the loss of anions, associated with the loss of cations, the bulk decrease in ions content has been sufficient to be accounted for cell volume decrease on the basis of the ion-osmotic model.