Interaction of the fluorescent probe diS-C3-(5) with lecithin-cholesterol membranes

Behaviour of fluorescent carbocyanine probe disS-C3(5) in the egg lecithin-cholesterol membrane suspension was studied in relation to the lecithin/cholesterol ratio. The partition coefficient of the probe between aqueous and lipid phases decreases unlinearly with increase of cholesterol molar part in a bilayer. This parameter over molar part units was estimated to be (2.4 +/- 0.1) X 10(6) for egg lecithin membranes and (1.8 +/- 0.2) X 10(6) for 10 mol% cholesterol, (1.2 +/- 0.1) X 10(6) for 20, (0.8 +/- 0.1) X 10(6) for 30, and (0.48 +/- 0.02) X 10(6) for 50 mol% cholesterol. It is suggested that the probe partition coefficient value consists of two components: one caused by pure lecithin bilayer regions and another by local lecithin concentration fluctuations in the mixed lecithin-cholesterol regions.     

A method for recording the motor activity of the cilia of ciliated epithelium

The article deals with the television system which registers the lash movements on the screen of TV monitor. The natural moving activity (frequency of whipping) and lashes' activity after the action of different concentration of surface-active substance Triton-H-305 and potassium chloride were investigated on the example of the epithelium of two-folding molluscum. It observes the following type of lashes reaction: unbroken (continuous) whipping, mechanically induced stopping of whipping ("stop effect"), spontaneous "stop effect", starting of whipping due to mechanic action-specific "sorting" lashes (the last are described for the first time).     

Individual optimization: Mechanisms shaping the optimal reaction norm

In general, optimal reaction norms in heterogeneous populations can be obtained only by iterative numerical procedures (McNamara, 1991; Kawecki and Stearns, 1993). We consider two particular, but biologically plausible and analytically tractable cases of individual optimization to gain insight into the mechanisms which shape the optimal reaction norm of fecundity in relation to an environmental variable or an individual trait. In the first case, we assume that the quality of the environment (e.g. food abundance) or the quality of the individual (e.g. body size) is fixed during its entire life; it may also be a heritable individual trait. In the second case, individual quality is assumed to change randomly such that the probability distribution of quality in the next year is the same for the parent and for her offspring. For these two cases, we obtain analytical expressions for the shape of the optimal reaction norm, which are heuristically interpretable in terms of underlying selective mechanisms. It is shown that better quality may reduce the optimal fecundity. This outcome is particularly likely if better quality increases a fecundity-independent factor of parental survival in a long-lived species with fixed quality. This revised version was published online in July 2006 with corrections to the Cover Date.     

The patterns of colchicine-induced death of lymphoid cells

It is shown that colchicine injection at doses higher than 1 mg/kg of animal weight induces cell death in thymus, spleen, bone marrow and intestine mucosa. The cell death is accompanied by a regular internucleosomal cleavage of nuclear DNA and by the elimination of the formed fragments from cells. Both the processes begin after a 1.5 hour lag-period and proceed before the outer membrane permeability for supravital dyes increases. DNA degradation is prevented by the inhibitor of protein synthesis cycloheximide. Cytochalasin B does not induce chromatin degradation or cell death and has no effect on radiation death of lymphocytes. A possible role of microtubule destruction as a switch-on mechanism of DNA degradation and cell death is discussed.     

Analysis of DNA degradation in the thymocytes of irradiated rats by flow cytometry

The method of flow cytofluorometry of cells treated with probes specifically bound to AT- or GC-pairs of DNA was used to study DNA degradation in thymocytes of irradiated and hydrocortisone-treated rats. Death of thymocytes was shown to be accompanied by the decrease in the DNA content. The main regularities in the formation and accumulation of cells, the DNA content of which being lower than that of diploid cells, were the same as those of the internucleosome DNA fragmentation.     

General similarities and differences in the postradiation death of various animal species and of man

It was found in various animal species and man that an ordered internucleosome fragmentation of DNA is characteristic of lymphoid cells dying in the interphase. Both in vivo and in vitro, the postirradiation DNA degradation in thymocytes of rodents and piglets preceded the increase in the permeability of their plasma membrane. The in vivo kinetics of death of lymphoid cells from the thymus and spleen is similar in rodents and piglets. Rat thymocytes died in vitro earlier than thymocytes of piglets, calves and man which was evidently associated with a worse adaptive capacity of the latter to cultivation conditions.     

Flow cytometry and biochemical analysis of DNA degradation characteristic of two types of cell death

Interactions of tuftsin (Thr-Lys-Pro-Arg) with bovine serum albumin (BSA) were analysed by fluorescence spectroscopy and circular dichroism. The data show that tuftsin interacts weakly with BSA, but this interaction is considerably enhanced by introducing an apolar substituent at the C-terminus of the tetrapeptide. It is suggested that strong binding of tuftsin to albumin in blood may enhance its macrophage-stimulating activity in vivo.     

The effect of electromagnetic radiation on the membranes of the sarcoplasmic reticulum

On the sarcoplasmic reticulum membranes has been shown that at temperature of Ca2(+)-ATPase activity change of dependence in the Arrhenius plot the microwaves (2450 MHz, specific absorption rate 12 w/kg) inhibit the ATP-hydrolase and Ca2(+)-transporting activity of Ca2(+)-ATPase. The effect of radiation exhibits within the narrow temperature range (approximately 1 degree C) and quantitatively corresponds to the decrease of Ca2(+)-ATPase activity caused by the decrease of temperature by 1.6 degrees C from 18 degrees C. The fluorescence intensity of naphthalene sulfonic probes reduces under the influence of microwaves at 18 degrees C.