Cis- and trans-acting influences on telomeric position effect in Drosophila melanogaster detected with a subterminal transgene

One model of telomeric position effect (TPE) in Drosophila melanogaster proposes that reporter genes in the vicinity of telomeres are repressed by subterminal telomere-associated sequences (TAS) and that variegation of these genes is the result of competition between the repressive effects of TAS and the stimulating effects of promoters in the terminal HeT-A transposon array. The data presented here support this model, but also suggest that TPE is more complex. Activity of a telomeric white reporter gene increases in response to deletion of some or all of the TAS on the homolog. Only transgenes next to fairly long HeT-A arrays respond to this trans-interaction. HeT-A arrays of 6-18 kb respond by increasing the number of dark spots on the eye, while longer arrays increase the background eye color or increase the number of spots sufficiently to cause them to merge. Thus, expression of a subtelomeric reporter gene is influenced by the telomere structure in cis and trans. We propose that the forces involved in telomere length regulation in Drosophila are the underlying forces that manifest themselves as TPE. In the wild-type telomere TAS may play an important role in controlling telomere elongation by repressing HeT-A promoter activity. Modulation of this repression by the homolog may thus regulate telomere elongation.     

cGMP-binding centers in photoreceptor membranes

The binding of cGMP by structural components of bovine rod outer segments was studied. The discs and plasma membranes were shown to contain two types of the specific binding sites for cGMP which are distinct from cyclic GMP phosphodiesterase. The sites have a "high" and "low" (Kd = 0.1 divided by 0.35 and 1.5 divided by 2.0 X 10(-6) M respectively) affinity for cGMP. They belong to membraneous integral proteins presumably associated with phospholipids. Their affinity for cGMP is controlled by GTP and calmodulin.     

Photoreactivation of the cytochrome oxidase complex with cyanide: the reaction of heme a3 photoreduction.

Electron transfer activity of isolated cytochrome oxidase inhibited by low concentrations of cyanide by 93-95% was shown to rise no less than three times under exposure to visible light. Irradiation with visible light was found to increase the rate of reduction of cytochrome oxidase heme groups in the presence of sodium dithionite. Based on these results, it is suggested that the modification of the catalytic and spectral characteristic of the cytochrome oxidase-cyanide complex is due to the photostimulation of the intramolecular electron transport at the interheme (heme a heme a3) transfer stage, i.e., is caused by photoreduction of the enzyme's heme a3-CN complex.     

Inactivation of muscarinic acetylcholine receptors in brain synaptic membranes by free fatty acids. Evaluation of the role of lipid phase

Arachidonic, linolenic and linoleic acids decreased the binding of the m-cholinergic antagonist [3H] QNB and did not affect the ratio of high to low affinity binding sites to the agonist carbamoylcholine in rat brain synaptic membranes. In the presence of arachidonic acid, SH-reagent N-ethylmaleimide acquired the ability to block QNB binding to receptor. Lipids in the bilayer and annular regions were probed by fluorescence of 1,6-diphenyl-1, 3, 5-hexatriene and pyrene. A microviscosity drop induced by increasing temperature from 10 to 37 degrees C did not affect the level of QNB equilibrium binding, whereas arachidonic acid strongly inhibited the binding at concentrations inducing the same drop in microviscosity as that induced by heating. For various unsaturated fatty acids an equal extent of receptor blocking was reached at quite different degrees of bilayer fluidization, the state of annular lipid being not changed under these conditions. It is suggested that the effect of unsaturated acids is reached through their direct interaction with the receptor, which undergoes a conformational change, rather than by an alteration of the physical state of the lipid phase of the membrane.     

Influence of UV-light on erythrocyte membrane structure and catalytic behaviour of membrane acetylcholine esterase]

UV-light is shown to induce the structural transitions in the erythrocyte membrane described by S-shape curves in plots of the structural response versus the irradiation dose. In contrast to the free acetylcholine esterase (AChE) UV-light acts on the membrane enzyme as a mixed inhibitor (simultaneous change in Vmax and Km). The modification of the environment structure of residual enzyme is suggested to be the main reason of this phenomenon. The effect is under the control of membrane integrity and disappears after its desintegration. Membrane AChE treated ultrasonically both prior to and after irradiation is inactivated without a Km change. The data obtained show the influence of erythrocyte membrane structure on the catalytic behaviour of membrane-bound AChE.     

Detection of endotoxins of Gram-negative bacteria on the basis of electromagnetic radiation frequency spectrum

Method of Gram-negative bacteria endotoxins detection on the basis of their own spectrum of electromagnetic radiation frequency was developed. Frequency spectrum typical for chemotype Re glycolipid, which is a part of lypopolysaccharides in the majority of Gram-negative bacteria, was used. Two devices--"Mini- Expert-DT" (manufactured by IMEDIS, Moscow) and "Bicom" (manufactured by Regumed, Germany)--were used as generators of electromagnetic radiation. Detection of endotoxin using these devices was performed by electropuncture vegetative resonance test. Immunoenzyme reaction with antibodies to chemotype Re glycolipid was used during analysis of preparations for assessment of resonance-frequency method specificity. The study showed that resonance-frequency method can detect lypopolysaccharides of different enterobacteria in quantities up to 0.1 pg as well as bacteria which contain lypopolysaccharides. At the same time, this method does not detect such bacteria as Staphylococcus aureus, Bifidobacterium spp., Lactobacillus spp., and Candida albicans. The method does not require preliminary processing of blood samples and can be used for diagnostics of endotoxinemia, and detection of endotoxins in blood samples or injection solutions.     

Effect of chlorpromazine on the relation between temperature and the binding of ANS by human erythrocytes

It has been shown that under the effect of chlorpromazin (concentration to 2.10(-5) M) breaks observed on Arrhenius graphs of the rate constant of ANS binding with erythrocytes (k) at 28 and 36 degrees C are shifted to the region of low temperatures approximately to a similar interval (14-15 degrees C). The value k measured at 22 degrees C is not changed within the pH range of 5-7. It is concluded that breaks characterised the initial and final stages of temperature transition initiated in the zone of acid phospholipid of membranes.