Calcium permeability of synaptosomes induced by alpha-latrotoxin

The paper deals with characteristics of ionic alpha-latrotoxin-induced permeability of rat brain synaptosomes. It has been shown that the addition of alpha-latrotoxin to synaptosomes in the Ca2+-containing media resulted in an extensive and rapid uptake of 45Ca2+ in synaptosomes. alpha -Latrotoxin was not able to enhance the 22Na+ and 86Rb+ uptake or efflux in the Ca2+-containing and Ca2+- and Mg2+-free media. The dye di-O-C3 was used to monitor the membrane potential changes as a consequence of alpha-latrotoxin treatment of synaptosomes. It has been found that alpha-latrotoxin increased synaptosomal fluorescence in the Ca2+-containing media, but failed to induce any increase of fluorescence in Ca2+- and Mg2+-free media. It has been also shown that the calcium uptake induced by alpha-latrotoxin depends on free calcium concentration in synaptosomes. Toxin-induced calcium flows are shown to be of the vector character.     

Latrotoxin-induced fusion of liposomes with bilayer phospholipid membranes

Liposomes containing amphotericin B as ionophoric marker were used to investigate the fusion of bilayer phospholipid membranes with liposomes. It was found that latrotoxin isolated from black widow spider venom induced the fusion of liposomes with planar bilayer when liposomes and latrotoxin were administered at opposite sides of the membrane.     

Antigenic similarity between cytoplasmic tetrodotoxin-sensitive protein and neuronal membrane proteins

Membrane proteins with a molecular weight of 290, 180, and 55 kDa were isolated using immunosorbent attached to sepharose and rabbit antibodies to cytoplasmic tetrodotoxin-sensitive protein from beef brain gray matter. A technique used for research into voltage-dependent sodium channels was applied to reconstruction of these proteins and investigation of toxin-dependent sodium flows through the lipoprotein membrane. Findings are interpreted as evidence of the similarity between cytoplasmic tetrodotoxin-sensitive protein and that of sodium channels at the cell membrane.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev; A. V. Palladin Institute of Biochemistry, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 485–489, July–August, 1989.     

Resistance of liposomes with different physico-chemical characteristics to the effect of plasma

The chemical composition, liquid content sign and value of charge as well as structure and size of lipid vesicles are studied for the effect they exert on the liposome permeability for 22Na+ in the presence of human blood plasma. The rate of the isotope outlet from the electroneutral lecithin liposomes is determined by the size of vesicles and the quantity of phospholipid bilayers in their membrane. The presence either of a negative or a positive charge on the surface of the liposome membrane has no essential effect on the outlet rate of the radioactive marker. Introduction of different amounts of cholesterol or sphingomyelin into the liposome composition decreases considerably the lipid vesicle permeability and an increase in the liquid content of their membranes due to the temperature elevation is accompanied by a sharp rise in the isotope outlet rate. A conclusion is drawn on the possibility to control the outlet rate of the liposome content in the presence of blood plasma.     

Transport of Rb+ via activated sodium channels of clone N 18 phi 1 neuroblastoma cells

A study was made of the Rb+ transport via activated sodium channels of clone N 18 phi 1 neuroblastoma cells cultured in the Eagle medium with 10% bovine serum. The time of population doubling was about 10 h. The cell differentiation was induced by adding bromdeoxyuridine in a concentration of 1-4 10(-5) M. The cells contained 172 +/- 12 and 340 +/- 35 micrograms of protein per 10(6) cells at the logarithmic growth phase and in differentiated state, respectively. It is shown that veratrin produced a 1.3-fold increase in the rate of 86Rb+ removal from undifferentiated cells and 2.5-fold increase in that from differentiated cells. Tetrodotoxin removed completely the effect of veratrin. A conclusion is made on the presence of a new clone of fast sodium channels in cell membranes.     

Relation between the functional characteristics of fast sodium channels and lipid composition of neuroblastoma C1300 cells

The paper deals with functional characteristics of fast sodium channels modified by liposomes of differentiated neuroblastoma cells. Cells with a 60% increased total cholesterol content were used. The cells were found to contain lysolecithin. In lecithin the amount of polyunsaturated fatty acids was enhanced. It is established that veratrin added to the culture medium of cholesterol-enriched cells increased the rate of 86Rb release to a greater extent than in the control cells. When studying the temperature dependence of veratrin-activated transport of Rb+ in the intact and lecithin-cholesterol-lyposomes-modified cells it was shown that the veratrin-activated Rb+ release is more sensitive to temperature fluctuations than nonactivated one. In this case it is higher in lecithin-cholesterol-lyposomes-modified cells than in intact ones.     

A microsatellite-based consensus linkage map for species of Eucalyptus and a novel set of 230 microsatellite markers for the genus

Background  

Eucalypts are the most widely planted hardwood trees in the world occupying globally more than 18 million hectares as an important source of carbon neutral renewable energy and raw material for pulp, paper and solid wood. Quantitative Trait Loci (QTLs) in Eucalyptus have been localized on pedigree-specific RAPD or AFLP maps seriously limiting the value of such QTL mapping efforts for molecular breeding. The availability of a genus-wide genetic map with transferable microsatellite markers has become a must for the effective advancement of genomic undertakings. This report describes the development of a novel set of 230 EMBRA microsatellites, the construction of the first comprehensive microsatellite-based consensus linkage map for Eucalyptus and the consolidation of existing linkage information for other microsatellites and candidate genes mapped in other species of the genus.     

Structural analyses of the ankyrin repeat domain of TRPV6 and related TRPV ion channels

Transient receptor potential (TRP) proteins are cation channels composed of a transmembrane domain flanked by large N- and C-terminal cytoplasmic domains. All members of the vanilloid family of TRP channels (TRPV) possess an N-terminal ankyrin repeat domain (ARD). The ARD of mammalian TRPV6, an important regulator of calcium uptake and homeostasis, is essential for channel assembly and regulation. The 1.7 A crystal structure of the TRPV6-ARD reveals conserved structural elements unique to the ARDs of TRPV proteins. First, a large twist between the fourth and fifth repeats is induced by residues conserved in all TRPV ARDs. Second, the third finger loop is the most variable region in sequence, length and conformation. In TRPV6, a number of putative regulatory phosphorylation sites map to the base of this third finger. Size exclusion chromatography and crystal packing indicate that the TRPV6-ARD does not assemble as a tetramer and is monomeric in solution. Adenosine triphosphate-agarose and calmodulin-agarose pull-down assays show that the TRPV6-ARD does not interact with either ligand, indicating a different functional role for the TRPV6-ARD than in the paralogous thermosensitive TRPV1 channel. Similar biochemical findings are also presented for the highly homologous mammalian TRPV5-ARD. The implications of the structural and biochemical data on the role of the ankyrin repeats in different TRPV channels are discussed.