Paroxysmal itching in multiple sclerosis

In three women with multiple sclerosis, paroxysmal attacks of itching occurred. There were several similarities between these attacks and other types of paroxysmal phenomena previously described in multiple sclerosis. The attacks were brief, but usually lasted several minutes, they started and ended abruptly, and recurred several times a day. The were controlled effectively by carbamazepine. It is suggested that paroxysmal itching is caused by transversely spreading ephaptic activation of axons within a partially demyelinated lesion in pain-conducting fibre tracts in the central nervous system.     

Theory of cooperative transition of DNA complexes with multimodal ligands

The theory of the cooperative transition of DNA.ligand complexes have been developed, in which a model was implied where the multimodal ligands simultaneously interacted with DNA. Obtained formula express the dependence of the experimentally estimated values of the changes of transition point and width of transition on the concentration of the ligands. These expressions make possible to obtain the thermodynamic parameters of the interaction of the multimodal ligands with DNA (binding constants, number of base pairs corresponding to one binding site of DNA etc.) by comparing the theoretical and the experimental data.     

Constitutive nitric oxide synthase is expressed and nitric oxide-mediated relaxation is preserved in retrieved human aortocoronary vein grafts

Although little is known about the endothelial cell function of human saphenous vein coronary artery bypass grafts, there is evidence to suggest that receptor-activated, endothelial-dependent relaxation mediated by nitric oxide is impaired. This study examines the expression and function of endothelial cell constitutive nitric oxide synthase (cNOS) of aortocoronary vein bypass grafts and human saphenous veins obtained from 10 patients undergoing repeat coronary artery bypass grafting for recurrent ischemic symptoms. Following precontraction with norepinephrine (10(-5) M), responses to acetylcholine (receptor-mediated, endothelium-dependent), calcium ionophore (A23187; receptor-independent, endothelium-dependent), and sodium nitroprusside (endothelium-independent) were assessed. Following total RNA extraction using phenol/guanidinium isothiocyanate from specimens of human saphenous vein and vein graft, a quantitative RNase Protection Assay (RPA) was performed using a cRNA riboprobe corresponding to a fragment of the human endothelial cell cNOS gene. Histologically, the vein grafts showed both intimal hyperplasia development and focal atherosclerosis formation compared to the saphenous veins. Scanning electron microscopy of the saphenous veins and the vein grafts showed an intact endothelium. Precontracted vein grafts did not relax in response to acetylcholine; in contrast, the saphenous vein relaxed in a dose-dependent manner to reach a maximal relaxation of 19 +/- 4% precontracted tension. Saphenous veins and vein grafts relaxed in response to A23187 with maximal relaxation of 92 +/- 5 and 73 +/- 13%, respectively. Both vessels relaxed in a dose dependent manner to sodium nitroprusside. RPA normalized to beta-actin showed similar levels of expression of endothelial cell cNOS equivalent to 1 pg of sense RNA in both the saphenous vein and vein graft.(ABSTRACT TRUNCATED AT 250 WORDS)     

The attachment and penetration of T7 DNA/phage in Syrian hamster embryonic cells

Bacteriophage T7 DNA can penetrate Syrian hamster embryonic cells after a mandatory initial pretreatment with DEAE-dextran. In 3 h an extracellular complex between T7DNA and the cell monolayer is formed which is equivalent to 105 T7 genomes per cell. During the ensuing 24-48 h of cell growth, an average of 102-103 T7 genomes are transported to the nucleus in 90% of the cells of the culture.     

Monoclonal antibodies against human immunodeficiency virus type 1 integrase: epitope mapping and differential effects on integrase activities in vitro

Human immunodeficiency virus type 1 (HIV-1) integrase (IN) catalyzes the integration of viral DNA into the host chromosome, an essential step in retroviral replication. As a tool to study the structure and function of this enzyme, monoclonal antibodies (MAbs) against HIV-1 IN were produced. Epitope mapping demonstrated that the 17 MAbs obtained could be divided into seven different groups, and the selection of MAbs representing these groups were tested for their effect on in vitro activities of IN. Four groups of MAbs recognized epitopes within the region of amino acids (aa) 1 to 16, 17 to 38, or 42 to 55 in and around the conserved HHCC motif near the N terminus of IN. MAbs binding to these epitopes inhibited end processing and DNA joining and either stimulated or had little effect on disintegration and reintegration activities of IN. Two MAbs binding to epitopes within the region of aa 56 to 102 in the central core or aa 186 to 250 in the C-terminal half of the protein showed only minor effects on the in vitro activities of IN. Three Mabs which recognized on epitope within the region of aa262 to 271 of HIV-1 IN cross-reacted with HIV-2 IN. MAbs binding to this epitope clearly inhibited end processing and DNA joining and stimulated or had little effect on disintegration. In contrast to the N-terminal-specific MAbs, these C-terminal-specific MAbs abolished reintegration activity of IN.     

Dependence of hepatocytic autophagy on intracellularly sequestered calcium

Autophagic sequestration of endogenous lactate dehydrogenase or electroinjected [3H]raffinose in isolated rat hepatocytes was strongly suppressed by the Ca2+ chelator EGTA, unless the cells had previously been electroloaded in the presence of high concentrations of Ca2+ (1.2 mM). The extracellular Ca2+ chelator bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA) and the intracellular Ca2+ chelator BAPTA/tetra(acetoxymethyl)-ester (BAPTA/AM) both inhibited autophagy to the same extent as did EGTA. Inhibitors of Ca(2+)-activated protein kinases (KN-62, H-7, W-7) had little or no effect on autophagy, indicating that the Ca2+ requirement of autophagy was not mediated by such kinases. Agents that elevate cytosolic Ca2+ by releasing Ca2+ from intracellular stores, like thapsigargin, 2,5-di-(tert-butyl)-1,4-benzohydroquinone (tBuBHQ) and the ionophores A23187 and ionomycin, inhibited autophagy strongly, implicating depletion of sequestered rather than of cytosolic intracellular Ca2+ as a common mechanism of inhibition. Lysosomal (propylamine-sensitive) protein degradation, known to be largely autophagy-dependent, was inhibited by thapsigargin and tBuBHQ. Thapsigargin had no effect on cellular ATP levels, but all agents tested (thapsigargin, tBuBHQ, ionophores) inhibited protein synthesis. Our results suggest that autophagy, like protein synthesis, is dependent on the presence of Ca2+ in some intracellular storage compartment.     

Insulin exocytosis and glucose-mediated increase in cytoplasmic free Ca2+ concentration in the pancreatic beta-cell are independent of cyclic ADP-ribose

Stimulation of pancreatic beta-cells by glucose gives rise to an increase in the cytoplasmic free calcium concentration ([Ca2+]i) and exocytosis of insulin. Cyclic adenosine 5'-diphosphate ribose (cADPR), a metabolite of beta-NAD+, has been reported to increase [Ca2+]i in pancreatic beta-cells by releasing Ca2+ from inositol 1,4,5-trisphosphate-insensitive intracellular stores. In the present study, we have examined the role of cADPR in glucose-mediated increases in [Ca2+]i and insulin exocytosis. Dispersed ob/ob mouse beta-cell aggregates were either pressure microinjected with fura-2 salt or loaded with fura-2 acetoxymethyl ester, and [Ca2+]i was monitored by microfluorimetry. Microinjection of beta-NAD+ into fura-2-loaded beta-cells did not increase [Ca2+]i nor did it alter the cells' subsequent [Ca2+]i response to glucose. Cells microinjected with the cADPR antagonist 8NH2-cADPR increased [Ca2+]i in response to glucose equally well as those injected with cADPR. Finally, the ability of cADPR to promote exocytosis of insulin in electropermeabilized beta-cells was investigated. cADPR on its own did not increase insulin secretion nor did it potentiate Ca2+-induced insulin secretion. We conclude that cADPR neither plays a significant role in glucose-mediated increases in [Ca2+]i nor interacts directly with the molecular mechanisms regulating exocytosis of insulin in normal pancreatic beta-cells.