Role of electrostatics in the binding of charged metallophthalocyanines to neutral and charged phospholipid membranes

Binding of the cationic tetra(tributylammoniomethyl)-substituted hydroxoaluminum phthalocyanine (AlPcN₄) to bilayer lipid membranes was studied by fluorescence correlation spectroscopy (FCS) and intramembrane field compensation (IFC) methods. With neutral phosphatidylcholine membranes, AlPcN₄ appeared to bind more effectively than the negatively charged tetrasulfonated aluminum phthalocyanine (AlPcS₄), which was attributed to the enhancement of the coordination interaction of aluminum with the phosphate moiety of phosphatidylcholine by the electric field created by positively charged groups of AlPcN₄. The inhibitory effect of fluoride ions on the membrane binding of both AlPcN₄ and AlPcS₄ supported the essential role of aluminum-phosphate coordination in the interaction of these phthalocyanines with phospholipids. The presence of negative or positive charges on the surface of lipid membranes modulated the binding of AlPcN₄ and AlPcS₄ in accord with the character (attraction or repulsion) of the electrostatic interaction, thus showing the significant contribution of the latter to the phthalocyanine adsorption on lipid bilayers. The data on the photodynamic activity of AlPcN₄ and AlPcS₄ as measured by sensitized photoinactivation of gramicidin channels in bilayer lipid membranes correlated well with the binding data obtained by FCS and IFC techniques. The reduced photodynamic activity of AlPcN₄ with neutral membranes violating this correlation was attributed to the concentration quenching of singlet excited states as proved by the data on the AlPcN₄ fluorescence quenching.     

Characteristics of the range of mutations in nystatin resistance induced in yeasts by 6-N-hydroxylaminopurine

A simple procedure for induction of nistatin-resistant mutants in yeasts under the action of 6-N-hydroxylaminopurine (HAP) is proposed. Some differences between the spectra of mutations induced by HAP and UV-light are observed: HAP induces dominant and double recessive mutants more frequently.     

Comparative analysis of background activity of ventrolateral thalamic neurons in patients with parkinsonism and torsion muscle dystonia

In the course of neurosurgical interventions in 40 patients with parkinsonism and torsion muscle dystonia, the background activity (BA) was recorded from 124 neurons of the ventrolateral nucleus (VL) of the thalamus with the aid of microelectrodes during demarcation of boundaries between nuclear structures, and identification of zones within a nucleus. The following characteristic features of the BA in patients with parkinsonism were found: a relatively large proportion (71%) of cells with a burst pattern of activity; a great diversity of burst duration in the activity (short or prolonged bursts); a large proportion (67%) of cells with cyclic changes in the BA frequency; diverse patterns of cyclic modulation, where periods varied from fractions of a second (0.2–0.8 sec) to seconds (2–10 sec) or to tens of seconds (20–40 sec); cyclic successions of spike bursts with the rhythm typical of the peripheral tremor (3–7/sec) in a substantial proportion (40%) of the units.The background spike trains recorded in patients with torsion muscle dystonia consisted of separated spikes in the majority (69%) of units. Only short high-frequency discharges were found in the burst activity in this group; a cyclic BA pattern occurred much less frequently (in 23% of neurons); burst discharges at a 3–4/sec frequency were found only in 4% of the examined cells.The possible nature of motor disorders in patients with parkinsonism and torsion muscle dystonia and the mechanisms of the curing effects of cryodestruction of theVL of the thalamus in the treatment of the disease are discussed.Neirofiziologiya/Neurophysiology, Vol. 25, No. 4, pp. 246–253, July–August, 1993.     

Characteristics of the immunosuppressive activity of lymphoid organ cells in the process of sensitization with ram erythrocytes and exposure to antilymphocyte serum

In the adoptive transfer of cells obtained from the thymus, lymph nodes and the spleen to intact syngeneic animals the suppression of immune response was induced by lymph node cells. If the donors were previously sensitized, the cells of the thymus and lymph nodes showed suppressive activity in the adoptive transfer test. A single injection of antilymphocytic serum to the donors of lymphoid cells, previously sensitized with sheep red blood cells, enhanced the immunosuppressing action of thymocytes and lymph node cells.     

Characteristics of mRNA and cDNA of fructose-1,6-diphosphate aldolase

Problems concerning synthesis of fructose-1,6-diphosphataldolase A (EC 4.1.2.13) in vitro, and localization in a cell and sizes of mRNA of this enzyme are considered in the review. The following items are described: methods for production and properties of individual mRNA and cDNA of the aldolase isoenzymes; making of the amino acid sequence of the aldolase isoenzyme forms according to the nucleotide sequence of mRNA and cDNA and peculiarities of isoform structure in different tissues of animals; structure of mRNA and cDNA of FDP-aldolase in the norm and under pathology and mechanisms of the appearance of nonspecific enzyme isoforms. Regulation of protein biosynthesis under pathology is considered as exemplified by mRNA and cDNA of FDP-aldolase.     

Effect of Metalaxyl on the incidence and severity of Pearl millet downy mildew disease in Northern Nigeria

Pearl millet downy mildew (DM) incidence, severity and yield losses of two pearl millet varieties (local and improved) due to the disease were determined in the field. Significant differences in the disease incidence and severity were recorded in the plots sown with metalaxyl-treated seeds and those sown with non-treated seeds, indicating the efficacy of the fungicide on the fungus. Yield losses due to non-treatment of seeds with metalaxyl was 40.88 and 45.39% in a local variety and 43.00 and 18.60% in an improved variety in the 2000 and 2001 cropping seasons respectively. Significant differences between plots sown with metalaxyl-treated and those sown with non-treated seeds were obtained for other yield components such as 1000-grains weight, panicle length and weight.     

Gene expression and the evolution of phenotypic diversity in social wasps

Background  

Organisms are capable of developing different phenotypes by altering the genes they express. This phenotypic plasticity provides a means for species to respond effectively to environmental conditions. One of the most dramatic examples of phenotypic plasticity occurs in the highly social hymenopteran insects (ants, social bees, and social wasps), where distinct castes and sexes all arise from the same genes. To elucidate how variation in patterns of gene expression affects phenotypic variation, we conducted a study to simultaneously address the influence of developmental stage, sex, and caste on patterns of gene expression in Vespula wasps. Furthermore, we compared the patterns found in this species to those found in other taxa in order to investigate how variation in gene expression leads to phenotypic evolution.     

Situation of brucellosis in the regions of Stavropol Territory affected by the flood of 2002

The emergency situation caused by inundations and high floods on the rivers in the affected regions exerts no direct influence on brucellosis morbidity among humans. Still the urgent evacuation of agricultural animals in connection with the natural calamity, their displacement and regrouping give grounds to prognosticate the deterioration of the epizootic situation in this infection in a number of regions of the territory where no sufficient veterinary surveillance has been ensured.     

Response of the MGE 412 pattern to truncation selection of a quantitative trait in an isogenic line of drosophila after severe heat shock (SHS)

Positive and negative selection on the total length of two fragments of an interrupted longitudinal wing vein in an isogenic line of Drosophila melanogaster was accompanied by changes in the genomic localization pattern of MGE 412. Strong truncation selection was conducted in the population of effective size Ne = 160 for 50 generations. Twenty-six out of 35 polymorphic HHS-induced segments of MGE localization behaved as independent copies and markers, whereas 9 segments proved to be selective. The second group included "hot" segments of HHS transposition induction (43B, 97E, etc.). Thus, final consensus patterns of induced MGE transpositions have a random and an adaptive component in generation 50 of positive and negative selection. Selective patterns probably include modifier MGEs, which generate induced genetic regulatory variation of polygenes controlling the selected quantitative trait in the isogenic line after HHS.     

Stabilization of O-pyromellitylgramicidin channels in bilayer lipid membranes through electrostatic interaction with polylysines of different chain lengths

Functioning of membrane proteins, in particular ionic channels, can be modulated by alteration of their arrangement in membranes. We addressed this issue by studying the effect of different chain length polylysines on the kinetics of ionic channels formed in a bilayer lipid membrane (BLM) by O-pyromellitylgramicidin carrying three negative charges at the C-terminus. The method of sensitized photoinactivation was applied to the analysis of the channel association-dissociation kinetics (characterized by the exponential factor of the curve describing the time course of the flash-induced decrease in the transmembrane current, tau). Addition of polylysine to the bathing solutions of BLM led to the deceleration of the photoinactivation kinetics, i.e. to the increase in tau. It was shown here that for a series of polylysines differing in their chain lengths, the value of tau grew as their concentration increased above a threshold level until at a certain concentration of each polylysine tau reached maximum. At higher polylysine concentrations tau began to decrease and finally became close to the control level observed in the absence of polylysine. With lengthening of the polylysine chain the maximum value of tau increased, the concentration dependence became steeper, and the threshold concentration decreased. The increase in the ionic strength of the medium shifted the concentration dependence of tau to higher polylysine concentrations and decreased the maximum value of tau. It was concluded that the increase in tau was caused by the formation of domains of O-pyromellitylgramicidin molecules induced by binding of polylysines. This can be related to functional aspects of polycation-induced sequestering of negatively charged transmembrane peptides in neutral membranes.