Structure and permeability of Low-Methoxyl Pectin (LMP)-Sodium alginates (NaAlg) films

Alginate and pectin form synergistic mixed gels that lead to a microstructure totally different from that of pure biopolymers. Synergistic mixed gels are of particular interest as makers of films with new improved characteristics. The objectives of the present work were, (a) to develop composite biodegradable films based on sodium alginate (NaAlg) and low-methoxyl pectin (LMP), (b) to evaluate the water vapor (WVP) and oxygen permeability, and (c) to characterize film microstructure by electron microscopy. A film-forming solution was prepared by adding 2% w/w of NaAlg, LMP or their mixtures, in a constantly stirred solution of NaCl (0,1M), during 4 h and then poured into Petri glass plates and allowed to dry at ambient, resulting in about 40 jam films. WVTR was determined gravimetrically using a modified ASTM Method E 96-95, and oxygen permeability of the prepared films was measured according to ASTM D3985. Films structure was characterized using both transmission (TEM) and scanning (SEM) electron microscopy. Results indicated that water vapor permeation follows Henry's law after two weeks of assay. Water permeability reduced in mixed biopolymer films, indicating NaAlg/LMP synergism. Pure pectin films resulted a better water vapor barrier, indicating the molecular weight has not effect on permeability. On the other hand, the reduction in permeability by alginate adding was assumed to be a result of the filling of pectin net. Permeability to oxygen was irrelevant. Confirming permeability assays, SEM micrographs of 1:1 alginate/pectin films show surface with lower porosity than pure (pectin or alginate) films. Moreover, TEM studies at the higher magnification (140,000X) also show a closer and denser nature in the case of mixed networks.Fil: Pérez Lambrech, María V.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Sorrivas, Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Villar, Marcelo Armando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Lozano, Jorge Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin

Changes of myoid and endothelial cells in the peritubular wall during contraction of the seminiferous tubule

The wall of the seminiferous tubule in rodents consists of an inner layer of myoid cells covered by an outer layer of endothelial cells. Myoid cells are a type of smooth muscle cell containing α-actin filaments arranged in two independent layers that contract when stimulated by endothelin-1. The irregular surface relief of the tubular wall is often considered a hallmark of contraction induced by a variety of stimuli. We examine morphological changes of the rat seminiferous tubule wall during contraction by a combination of light, confocal, transmission and scanning electron microscopy. During ET-1-induced contraction, myoid cells changed from a flat to a conical shape, but their actin filaments remained in independent layers. As a consequence of myoid cell contraction, the basement membrane became wavy, orientation of collagen fibers in the extracellular matrix was altered and the endothelial cell layer became folded. To observe the basement of the myoid cell cone, the endothelial cell monolayer was removed by collagenase digestion prior to SEM study. In contracted tubules, it is possible to distinguish cell relief: myoid cells have large folds on the external surface oriented parallel to the tubular axis, whereas endothelial cells have numerous cytoplasmic projections facing the interstitium. The myoid cell cytoskeleton is unusual in that the actin filaments are arranged in two orthogonal layers, which adopt differing shapes during contraction with myoid cells becoming cone-shaped. This arrangement impacts on other components of the seminiferous tubule wall and affects the propulsion of the tubular contents to the rete testis.Fil: Losinno, Antonella Denise. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Sorrivas, Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; ArgentinaFil: Ezquer, Eduardo Marcelo. Universidad del Desarrollo; ChileFil: Ezquer, Fernando. Universidad del Desarrollo; ChileFil: Lopez, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Morales, Alfonsina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; Argentin