Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2018 ( 12 )

2017 ( 8 )

2016 ( 7 )

2015 ( 138 )

Custom range...

Search Results: 1 - 10 of 4678 matches for " Santiago Ituarte "
All listed articles are free for downloading (OA Articles)
Page 1 /4678
Display every page Item
Agglutinating Activity and Structural Characterization of Scalarin, the Major Egg Protein of the Snail Pomacea scalaris (d’Orbigny, 1832)
Santiago Ituarte, Marcos Sebastián Dreon, Marcelo Ceolin, Horacio Heras
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0050115
Abstract: Apple snail perivitellins are emerging as ecologically important reproductive proteins. To elucidate if the protective functions of the egg proteins of Pomacea canaliculata (Caenogastropoda, Ampullariidae), involved in embryo defenses, are present in other Pomacea species we studied scalarin (PsSC), the major perivitellin of Pomacea scalaris. Using small angle X-ray scattering, fluorescence and absorption spectroscopy and biochemical methods, we analyzed PsSC structural stability, agglutinating activity, sugar specificity and protease resistance. PsSC aggluttinated rabbit, and, to a lesser extent, human B and A erythrocytes independently of divalent metals Ca2+ and Mg2+ were strongly inhibited by galactosamine and glucosamine. The protein was structurally stable between pH 2.0 to 10.0, though agglutination occurred only between pH 4.0 to 8.0 (maximum activity at pH 7.0). The agglutinating activity was conserved up to 60°C and completely lost above 80°C, in agreement with the structural thermal stability of the protein (up to 60°C). PsSC was able to withstand in vitro gastrointestinal digestion, and showed no trypsin inhibition activity. The presence of lectin activity has been reported in eggs of other Pomacea snails, but here we link for the first time, this activity to an apple snail multifunctional perivitellin. This novel role for a snail egg storage protein is different from closely related P.canaliculata defensive proteins.
The Role of the Proteinase Inhibitor Ovorubin in Apple Snail Eggs Resembles Plant Embryo Defense against Predation
Marcos Sebastián Dreon,Santiago Ituarte,Horacio Heras
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015059
Abstract: Fieldwork has thoroughly established that most eggs are intensely predated. Among the few exceptions are the aerial egg clutches from the aquatic snail Pomacea canaliculata which have virtually no predators. Its defenses are advertised by the pigmented ovorubin perivitellin providing a conspicuous reddish coloration. The nature of the defense however, was not clear, except for a screening for defenses that identified a neurotoxic perivitellin with lethal effect on rodents.
Novel Animal Defenses against Predation: A Snail Egg Neurotoxin Combining Lectin and Pore-Forming Chains That Resembles Plant Defense and Bacteria Attack Toxins
Marcos Sebastián Dreon, María Victoria Frassa, Marcelo Ceolín, Santiago Ituarte, Jian-Wen Qiu, Jin Sun, Patricia E. Fernández, Horacio Heras
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0063782
Abstract: Although most eggs are intensely predated, the aerial egg clutches from the aquatic snail Pomacea canaliculata have only one reported predator due to unparalleled biochemical defenses. These include two storage-proteins: ovorubin that provides a conspicuous (presumably warning) coloration and has antinutritive and antidigestive properties, and PcPV2 a neurotoxin with lethal effect on rodents. We sequenced PcPV2 and studied whether it was able to withstand the gastrointestinal environment and reach circulation of a potential predator. Capacity to resist digestion was assayed using small-angle X-ray scattering (SAXS), fluorescence spectroscopy and simulated gastrointestinal proteolysis. PcPV2 oligomer is antinutritive, withstanding proteinase digestion and displaying structural stability between pH 4.0–10.0. cDNA sequencing and protein domain search showed that its two subunits share homology with membrane attack complex/perforin (MACPF)-like toxins and tachylectin-like lectins, a previously unknown structure that resembles plant Type-2 ribosome-inactivating proteins and bacterial botulinum toxins. The protomer has therefore a novel AB toxin combination of a MACPF-like chain linked by disulfide bonds to a lectin-like chain, indicating a delivery system for the former. This was further supported by observing PcPV2 binding to glycocalix of enterocytes in vivo and in culture, and by its hemaggutinating, but not hemolytic activity, which suggested an interaction with surface oligosaccharides. PcPV2 is able to get into predator’s body as evidenced in rats and mice by the presence of circulating antibodies in response to sublethal oral doses. To our knowledge, a lectin-pore-forming toxin has not been reported before, providing the first evidence of a neurotoxic lectin in animals, and a novel function for ancient and widely distributed proteins. The acquisition of this unique neurotoxic/antinutritive/storage protein may confer the eggs a survival advantage, opening new perspectives in the study of the evolution of animal defensive strategies.
Modeling Agricultural Change through Logistic Regression and Cellular Automata: A Case Study on Shifting Cultivation  [PDF]
Santiago Lopez
Journal of Geographic Information System (JGIS) , 2014, DOI: 10.4236/jgis.2014.63021

Agricultural expansion is one of the prime driving forces of global land cover change. Despite the increasing attention to the factors that cause it, the patterns and processes associated with indigenous cultivation systems are not well understood. This study analyzes agricultural change associated with subsistence-based indigenous production systems in the lower Pastaza River Basin in the Ecuadorian Amazon through a spatially explicit dynamic model. The model integrates multiple logistic regression and cellular automata to simulate agricultural expansion at a resolution consistent with small scale agriculture and deal with inherently spatial processes. Data on land use and cultivation practices were collected through remote sensing and field visits, and processed within a geographic information system framework. Results show that the probability of an area of becoming agriculture increases with population pressure, in the vicinity of existing cultivation plots, and proximity to the center of human settlements. The positive association between proximity to cultivation areas and the probability of the presence of agriculture clearly shows the spillover effect and spatial inertia carried by shifting cultivation practices. The model depicts an ideal shifting cultivation system, with a complete cropping-fallow-cropping cycle that shows how agricultural areas expand and contract across space and over time. The model produced relatively accurate spatial outputs, as shown by the results of a spatial comparison between the simulated landscapes and the actual one. The study helped understand local landscape dynamics associated with shifting cultivation systems and their implications for land management.

Efecto del estrés térmico en la supervivencia y el retraso de la metamorfosis en larvas del erizo morado Strongylocentrotus purpuratus
Díaz-Pérez, L;Carpizo-Ituarte, E;
Ciencias marinas , 2011,
Abstract: the effect of thermal stress (heat shock) on survival was evaluated for advanced larval stages and the possible effect on delay of metamorphosis in competent larvae was also evaluated in the purple sea urchin strongylocentrotus purpuratus under laboratory conditions. eight-arm precompetent and competent larvae were kept at 15, 19, 23, 28, and 31 °c during 24 h to estímate their thermal tolerance and measure their survival in each treatment. delay of metamorphosis was evaluated in competent larvae exposed to heat shock treatments of 15, 20, 24, 28, and 32 °c for 30 min. after this, larvae were induced to metamorphose in the presence of biofilms and kcl. our results indicated that the thermal tolerance limit for precompetent and competent larvae was 27 °c; temperatures equal or above this value are lethal for both stages of development, where we observed 100% mortality in a period of 24 h for the treatment at 27 °c and of 2 h at 31 °c. competent larvae subjected to a heat shock treatment of 28 °c for 30 min delayed the onset of metamorphosis (<40%) and showed high percentage of larvae with incomplete metamorphosis (55%). these results indicate the sensitivity of late larval stages to temperatures above 27 °c for short periods of time, and that this sensitivity may compromise the onset of metamorphosis. this could have some effect on the settlement and recruitment patterns of the purple sea urchin, particularly in intertidal sites exposed to high temperatures during the summer.
Comprehensible Technique in Solving Consecutive Number Problems in Algebra  [PDF]
Gener Santiago Subia
Journal of Applied Mathematics and Physics (JAMP) , 2018, DOI: 10.4236/jamp.2018.63041
Abstract: This research paper evaluated and investigated the effectiveness of the comprehensible technique (CT) introduced by the researcher as an alternative solution to Algebra’s linear equations in solving consecutive number problems. The CT is a proposed easy and efficient way of solving number problems which aimed to help the learners reduce their difficulties in using variables since the technique only uses basic arithmetic and mental Mathematics. Evaluation research was utilized in this study where 20 people, from various ages and professions, were chosen purposively as respondents of the study. The study found out that CT was very effective for the respondents especially in unlocking difficulties in solving consecutive number problems. Moreover, according to them, the CT is easy to use, it is engaging and enjoyable, direct and simple and can be utilized as shortcut way of solving consecutive number problems when competing in Math quiz bees or taking board examinations where time is of the essence.
Respuesta al incremento abrupto de temperatura (shock térmico) en el coral Pocillopora verrucosa en condiciones de laboratorio
Rodríguez-Troncoso, AP;Carpizo-Ituarte, E;Cupul-Maga?a, A;
Ciencias marinas , 2010,
Abstract: coral bleaching is an increasing worldwide phenomenon associated with climate change. bleaching results from the interaction of biotic and abiotic variables including sudden changes in temperature. to evaluate the response to sudden changes in temperature (thermal shock) prior to bleaching, fragments of pocillopora verrucosa were subjected to experimental thermal stress. the fragments were acclimatized at 27°c during eight days and then exposed to thermal shock at two temperatures (28.5°c and 30.5°c) for 72 h. the stress response was evaluated quantifying the total lipid content, symbiont density, and tissue damage. changes in the evaluated estimators were evident at 30.5°c when an initial increase in the amount of lipids was detected, followed by a decrease after 30 h; symbiont density diminished up to 84% at the end of the experiment relative to the initial density estimated. the control and 28.5°c treatments presented no differences. damage to the polyp tissue was mainly observed as a thinning of the mesenteries and the gastrodermal layer. the study area is strongly influenced by internal waves that cause sudden changes in temperature, so understanding how corals respond to these daily fluctuations will allow us to estimate their survival potential and help future management and conservation efforts in this region.
Reporte histopatológico de vesículas biliares
Gustavo E. Beauregard-Ponce,Yolanda Ituarte-Izquierdo,Elías Balcázar-Peralta
Salud en Tabasco , 2002,
Abstract: Las enfermedades de la vesícula biliar, son un problema de salud pública en la República Mexicana, se ha calculado que el 9% de la población adulta padece de algún proceso patológico de la vesícula. Los principales signos y síntomas son el dolor tipo cólico agudo, Con las siguientes características: dolor intenso en la parte superior derecha del abdomen, el cual frecuentemente irradia hacia la parte baja de la escapula derecha, con movimientos involuntarios del músculo abdominal derecho, se presenta intolerancia a los alimentos con nausea y vomito. El método diagnóstico más importante, menos caro y más eficaz es el clínico. Material y Métodos: se realizó una revisión retrospectiva de los registros anatomopatológicos de vesícula biliar, analizados por el servicio de patología del hospital Dr. Juan Graham Casasús. en un periodo de cinco a os (01/ 01/94 - 01/01/99). Las variables en estudio fueron: fecha del estudio, edad del paciente, sexo y diagnóstico histopatológico. Resultados: se obtuvo un total de 986 reportes anatomopatológicos, de éstos, los principales fueron: 613 con diagnóstico de colecistitis crónica litiásica y 334 con diagnóstico de colecistitis crónica alitiásica. Conclusión: las personas que acudieron a atención a este hospital, se enfermaron a más temprana edad, predominando en el sexo femenino.
Single-channel response of hamster oocytes to ertilization with homologous spermatozoa
Leonor M.E. Ituarte,Teresa B. Viera,Teobaldo A. Salde?a,Juan C. De Rosas
Biocell , 2006,
Abstract: Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration . Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved. Oocyte diameter was 70.2 ± 2.2 μm; their resting parameters were: membrane potential 23.8 ± 0.8 mV; total membrane specific resistance 519.1 ± 94.6 Ω.cm2, and specific capacity 0.99 ± 0.03 μF.cm-2. Total membrane current was decreased by 42 % by 4-aminopyridine. Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in control oocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ entry.
Bego?a Martínez Domínguez,Amaia Mendizábal Ituarte,Virginia P. Sostoa Gaztelu-Urrutia
Abstract: En este artículo se presenta un resumen de la investigación realizada por un equipo de la Universidad del País Vasco (UPV) sobre la experiencia que están realizando los Centros de Iniciación Profesional (CIP) en la Comunidad Autónoma Vasca (CAV). En dichos centros y través dos programas, Los Programas de Escolarización Complementaria (PEC) y los Programa de Iniciación Profesional (PIP), se atiende compartiendo los mismos fines, profesorado e infraestructura a jóvenes que por distintos motivos fracasan en la escuela, ofreciéndoles una oportunidad para evitar que se instalen en la zona de riesgo de exclusión.
Page 1 /4678
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.