Membrane cholesterol modulates the cytolytic mechanism of myotoxin II, a Lys49 phospholipase A2 homologue from the venom of Bothrops asper

19-04-2081 Embargo por política editorialLys49 phospholipase A2 (PLA2) homologues present in crotalid snake venoms lack enzymatic activity, yet they induce skeletal muscle necrosis by a membrane permeabilizing mechanism whose details are only partially understood. The present study evaluated the effect of altering the membrane cholesterol content on the cytolytic activity of myotoxin II, a Lys49 PLA2 isolated from the venom of Bothrops asper, using the myogenic cell line C2C12 as a model target. Cell membrane cholesterol depletion by methyl-β-cyclodextrin (MβCD) treatment enhanced the cytolytic action of myotoxin II, as well as of its bioactive C-terminal synthetic peptide p(115-129) . Conversely, cell membrane cholesterol enrichment by preformed cholesterol-MβCD complexes reduced the cytolytic effect of myotoxin II. The toxic actions of myotoxin I, a catalytically active PLA2 from the same venom, as well as of the cytolytic peptide melittin from bee venom, also increased in cholesterol-depleted cells. Although physical and functional changes resulting from variations in membrane cholesterol are complex, these findings suggest that membrane fluidity could be a relevant parameter to explain the observed modulation of the cytolytic mechanism of myotoxin II, possibly influencing bilayer penetration. In concordance, the cytolytic effect of myotoxin II decreased in direct proportion to lower temperature, a physical factor that affects membrane fluidity. In conclusion, physicochemical properties that depend on membrane cholesterol content significantly influence the cytolytic mechanism of myotoxin II, reinforcing the concept that the primary site of action of Lys49 PLA2 myotoxins is the plasma membrane.Universidad de Costa Rica/[741‐A9‐513]/UCR/Costa Ricainternational Centre for Genetic Engeneering and Biotechnology - Collaborative Research Programme/[COS‐ 08‐03)]/ICGEB‐CRP/ItaliaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP

Functionality and stability data of detergent purified nAChR from Torpedo using lipidic matrixes and macroscopic electrophysiology

The presented data provides additional information about the assessment of affinity purified nicotinic acetylcholine receptor (nAChR) rich membrane solubilized with long chain (16 saturated carbons) lysophospholipid with glycerol headgroup (LFG-16). The assessment of stability and functionality of solubilized membrane protein is a critical step prior to further crystallization trails. One of the key factors for this task is the appropriate choice of a detergent that can support nAChR activity and stability comparable to the crude membranes. The stability of the nAChR-LFG-16 complex incorporated into lipid cubic phase (LCP) was monitored for a period of 30 days by means of fluorescence recovery after photobleaching (FRAP) and the functionality was evaluated after its incorporation into Xenopus oocyte by means of the two electrode voltage clamp technique. Keywords: Detergents, Fluorescence recovery after photobleaching, Lipidic Cubic Phase, nAChR, Planar lipid bilayer, Two-electrode voltage clam

Resultados de la cirugía mayor ambulatoria en el Hospital Clinicoquirúrgico Docente "Comandante Manuel Fajardo

Se presentan los resultados de 521 enfermos atendidos en el Hospital Clinicoquirúrgico Docente "Comandante Manuel Fajardo", por el sistema de cirugía mayor ambulatoria, en el período comprendido entre enero de 1995 y agosto de 1997. Predominó el sexo masculino con el 59,5 % y dicha cirugía se realizó con mayor frecuencia entre los 30 y 49 años de edad. El mayor número de pacientes intervenidos fueron los diagnosticados con hernias abdominales y nódulos de mama, y los procederes quirúrgico y anestésico fueron satisfactorios, con escasas complicaciones posoperatorias no inherentes a éstos. El ahorro por concepto días/cama fue de 82 820 pesos en moneda nacional, lo que da una medida de lo necesario de incrementar esta modalidad en nuestra instituciónThe results of 521 patients served at the "Comandante Manuel Fajardo" Clinical and Surgical Teaching Hospital by the system of ambulatory major surgery from January, 1995, to August, 1997, were presented. Males prevailed with 59.5 %. Such surgery was more frequently performed among those aged 30-49. Most of the patients that were operated on had diagnoses of abdominal hernias and breast nodules. Surgical and anesthetic procedures were satisfactory with a few postoperative complications that were not inherent to them. The saving by days/bed was 82 820 Cuban pesos, which showed the need to increase this modality in our institutio