Expression of Cementitious Pore Solution and the Analysis of Its Chemical Composition and Resistivity Using X-ray Fluorescence.

The goal of this method is to determine the chemical composition and electrical resistivity of cementitious pore solution expressed from a fresh paste sample. The pore solution is expressed from a fresh paste sample using a pressurized nitrogen gas system. The pore solution is then immediately transferred to a syringe to minimize evaporation and carbonation. After that, assembled testing containers are used for the X-ray fluorescence (XRF) measurement. These containers consist of two concentric plastic cylinders and a polypropylene film which seals one of the two open sides. The pore solution is added into the container immediately prior to the XRF measurement. The XRF is calibrated to detect the main ionic species in the pore solution, in particular, sodium (Na+), potassium (K+), calcium (Ca2+), and sulfide (S2-), to calculate sulfate (SO42-) using stoichiometry. The hydroxides (OH-) can be calculated from a charge balance. To calculate the electrical resistivity of the solution, the concentrations of the main ionic species and a model by Snyder et al. are used. The electrical resistivity of the pore solution can be used, along with the electrical resistivity of concrete, to determine the formation factor of concrete. XRF is a potential alternative to current methods to determine the composition of pore solution, which can provide benefits in terms of reduction in time and costs.

In vivo analysis of intestinal permeability following hemorrhagic shock.

AIM: To determine the time course of intestinal permeability changes to proteolytically-derived bowel peptides in experimental hemorrhagic shock. METHODS: We injected fluorescently-conjugated casein protein into the small bowel of anesthetized Wistar rats prior to induction of experimental hemorrhagic shock. These molecules, which fluoresce when proteolytically cleaved, were used as markers for the ability of proteolytically cleaved intestinal products to access the central circulation. Blood was serially sampled to quantify the relative change in concentration of proteolytically-cleaved particles in the systemic circulation. To provide spatial resolution of their location, particles in the mesenteric microvasculature were imaged using in vivo intravital fluorescent microscopy. The experiments were then repeated using an alternate measurement technique, fluorescein isothiocyanate (FITC)-labeled dextrans 20, to semi-quantitatively verify the ability of bowel-derived low-molecular weight molecules (< 20 kD) to access the central circulation. RESULTS: Results demonstrate a significant increase in systemic permeability to gut-derived peptides within 20 min after induction of hemorrhage (1.11 ± 0.19 vs 0.86 ± 0.07, P < 0.05) compared to control animals. Reperfusion resulted in a second, sustained increase in systemic permeability to gut-derived peptides in hemorrhaged animals compared to controls (1.2 ± 0.18 vs 0.97 ± 0.1, P < 0.05). Intravital microscopy of the mesentery also showed marked accumulation of fluorescent particles in the microcirculation of hemorrhaged animals compared to controls. These results were replicated using FITC dextrans 20 [10.85 ± 6.52 vs 3.38 ± 1.11 fluorescent intensity units (× 10(5), P < 0.05, hemorrhagic shock vs controls)], confirming that small bowel ischemia in response to experimental hemorrhagic shock results in marked and early increases in gut membrane permeability. CONCLUSION: Increased small bowel permeability in hemorrhagic shock may allow for systemic absorption of otherwise retained proteolytically-generated peptides, with consequent hemodynamic instability and remote organ failure.

Protective role of hemeoxygenase-1 in gastrointestinal diseases.

Disorders and diseases of the gastrointestinal system encompass a wide array of pathogenic mechanisms as a result of genetic, infectious, neoplastic, and inflammatory conditions. Inflammatory diseases in general are rising in incidence and are emerging clinical problems in gastroenterology and hepatology. Hemeoxygenase-1 (HO-1) is a stress-inducible enzyme that has been shown to confer protection in various organ-system models. Its downstream effectors, carbon monoxide and biliverdin have also been shown to offer these beneficial effects. Many studies suggest that induction of HO-1 expression in gastrointestinal tissues and cells plays a critical role in cytoprotection and resolving inflammation as well as tissue injury. In this review, we examine the protective role of HO-1 and its downstream effectors in modulating inflammatory diseases of the upper (esophagus and stomach) and lower (small and large intestine) gastrointestinal tract, the liver, and the pancreas. Cytoprotective, anti-inflammatory, anti-proliferative, antioxidant, and anti-apoptotic activities of HO-1 make it a promising if not ideal therapeutic target for inflammatory diseases of the gastrointestinal system.

The autodigestion hypothesis for shock and multi-organ failure.

An important medical problem with high mortality is shock, sepsis and multi-organ failure. They have currently no treatments other than alleviation of symptoms. Shock is accompanied by strong markers for inflammation and involves a cascade of events that leads to failure in organs even if they are not involved in the initial insult. Recent evidence indicates that pancreatic digestive enzymes carried in the small intestine after mixing with ingested food are a major cause for multi-organ failure. These concentrated and relatively non-specific enzymes are usually compartmentalized inside the intestinal lumen as requirement for normal digestion. But after breakdown of the mucosal barrier they leak into the wall of the intestine and start an autodigestion process that includes destruction of villi in the intestine. Digestive enzymes also generate cytotoxic mediators, which together are transported into the systemic circulation via the portal venous system, the intestinal lymphatics and via the peritoneum. They cause various degrees of cell and organ dysfunction that can reach the point of complete organ failure. Blockade of digestive enzymes in the lumen of the intestine in experimental forms of shock serves to reduce breakdown of the mucosal barrier and autodigestion of the intestine, organ dysfunctions and mortality.

Breakdown of mucin as barrier to digestive enzymes in the ischemic rat small intestine.

Loss of integrity of the epithelial/mucosal barrier in the small intestine has been associated with different pathologies that originate and/or develop in the gastrointestinal tract. We showed recently that mucin, the main protein in the mucus layer, is disrupted during early periods of intestinal ischemia. This event is accompanied by entry of pancreatic digestive enzymes into the intestinal wall. We hypothesize that the mucin-containing mucus layer is the main barrier preventing digestive enzymes from contacting the epithelium. Mucin breakdown may render the epithelium accessible to pancreatic enzymes, causing its disruption and increased permeability. The objective of this study was to investigate the role of mucin as a protection for epithelial integrity and function. A rat model of 30 min splanchnic arterial occlusion (SAO) was used to study the degradation of two mucin isoforms (mucin 2 and 13) and two epithelial membrane proteins (E-cadherin and toll-like receptor 4, TLR4). In addition, the role of digestive enzymes in mucin breakdown was assessed in this model by luminal inhibition with acarbose, tranexamic acid, or nafamostat mesilate. Furthermore, the protective effect of the mucin layer against trypsin-mediated disruption of the intestinal epithelium was studied in vitro. Rats after SAO showed degradation of mucin 2 and fragmentation of mucin 13, which was not prevented by protease inhibition. Mucin breakdown was accompanied by increased intestinal permeability to FITC-dextran as well as degradation of E-cadherin and TLR4. Addition of mucin to intestinal epithelial cells in vitro protected against trypsin-mediated degradation of E-cadherin and TLR4 and reduced permeability of FITC-dextran across the monolayer. These results indicate that mucin plays an important role in the preservation of the mucosal barrier and that ischemia but not digestive enzymes disturbs mucin integrity, while digestive enzymes actively mediate epithelial cell disruption.

Impaired small-bowel barrier integrity in the presence of lumenal pancreatic digestive enzymes leads to circulatory shock.

In bowel ischemia, impaired mucosal integrity may allow intestinal pancreatic enzyme products to become systemic and precipitate irreversible shock and death. This can be attenuated by pancreatic enzyme inhibition in the small-bowel lumen. It is unresolved, however, whether ischemically mediated mucosal disruption is the key event allowing pancreatic enzyme products systemic access and whether intestinal digestive enzyme activity in concert with increased mucosal permeability leads to shock in the absence of ischemia. To test this possibility, the small intestinal lumen of nonischemic rats was perfused for 2 h with either digestive enzymes, a mucin disruption strategy (i.e., mucolytics) designed to increase mucosal permeability, or both, and animals were observed for shock. Digestive enzymes perfused included trypsin, chymotrypsin, elastase, amylase, and lipase. Control (n = 6) and experimental animals perfused with pancreatic enzymes only (n = 6) or single enzymes (n = 3 for each of the five enzyme groups) maintained stable hemodynamics. After mucin disruption using a combination of enteral N-acetylcysteine, atropine, and increased flow rates, rats (n = 6) developed mild hypotension (P < 0.001 compared with groups perfused with pancreatic enzymes only after 90 min) and increased intestinal permeability to intralumenally perfused fluorescein isothiocyanate-dextran 20 kd (P < 0.05) compared with control and enzyme-only groups, but there were no deaths. All animals perfused with both digestive enzymes and subjected to mucin disruption (n = 6) developed hypotension and increased intestinal permeability (P < 0.001 after 90 min). Pancreatic enzymes were measured in the intestinal wall of both groups subjected to mucin disruption, but not in the enzyme-only or control groups. Depletion of plasma protease inhibitors was found only in animals perfused with pancreatic enzymes plus mucin disruption, implicating increased permeability and intralumenal pancreatic enzyme egress in this group. These experiments demonstrate that increased bowel permeability via mucin disruption in the presence of pancreatic enzymes can induce shock and increase systemic protease activation in the absence of ischemia, implicating bowel mucin disruption as a key event in early ischemia. Digestive enzymes and their products, if allowed to penetrate the gut wall, may trigger multiorgan failure and death.

Disruption of the mucosal barrier during gut ischemia allows entry of digestive enzymes into the intestinal wall.

Intestinal ischemia is associated with high morbidity and mortality, but the underlying mechanisms are uncertain. We hypothesize that during ischemia the intestinal mucosal barrier becomes disrupted, allowing digestive enzymes access into the intestinal wall initiating autodigestion. We used a rat model of splanchnic ischemia by occlusion of the superior mesenteric and celiac arteries up to 30 min with and without luminal injection of tranexamic acid as a trypsin inhibitor. We determined the location and activity of digestive proteases on intestinal sections with in situ zymography, and we examined the disruption of two components of the mucosal barrier: mucin isoforms and the extracellular and intracellular domains of E cadherin with immunohistochemistry and Western blot techniques. The results indicate that nonischemic intestine has low levels of protease activity in its wall. After 15-min ischemia, protease activity was visible at the tip of the villi, and after 30 min, enhanced activity was seen across the full thickness of the intestinal wall. This activity was accompanied by disruption of the mucin layer and loss of both intracellular and extracellular domains of E cadherin. Digestive protease inhibition in the intestinal lumen with tranexamic acid reduced morphological damage and entry of digestive enzymes into the intestinal wall. This study demonstrates that disruption of the mucosal epithelial barrier within minutes of intestinal ischemia allows entry of fully activated pancreatic digestive proteases across the intestinal barrier triggering autodigestion.

Nivel de motivación en los estudiantes de licenciatura en enfermería. Primer año del nuevo modelo pedagógico. Curso 2006-2007 / Level of Motivation in Nursing Students. First Year of the New Pedagogical Model. Course 2006-2007

La enseñanza de la enfermería en Cuba se inicia antes de 1959. En aquella época se disponía de escasos recursos materiales y humanos, estando los existentes muy mal distribuidos y no eran accesibles a la mayoría de la población. Con el triunfo de la Revolución se crean nuevos programas y se da una mayor prioridad a la formación de recursos humanos en enfermería. Teniendo en cuenta que el trabajo pedagógico tiene entre sus objetivos brindar a los alumnos una adecuada formación y reafirmación vocacional, siendo la educación el proceso de modificación del comportamiento primario, es natural que constituya un punto de partida en la formación de estos profesionales. Por tal motivo en este trabajo pretendemos valorar el nivel de motivación de los estudiantes de primer año de Licenciatura en Enfermería por la carrera, para ello se realizó un estudio retrospectivo y longitudinal seleccionando al azar una muestra de 93 estudiantes de un universo de 156 a los cuales se les aplicó una encuesta. La información fue procesada a través del método porcentual aritmético y fue reflejada en tablas cuyos resultados fueron, la solicitud de la carrera en primera opción por la mayoría de los estudiantes y la expresión de que la solicitaron por vocación, siendo la asignatura Fundamentos de Enfermería lo que ha ayudado a fomentar esta vocación.

Teaching in Nursing in Cuba starts before 1959, and at that time scarce material and human resources were available, these being wrongly distributed and were not accessible to most of the population. With the Triumph of the Revolution new programs are designed and the formation of human resources in Nursing are more prioritized. Considering that the pedagogical work has as one of its objectives providing the students with an appropriate formation and vocational reaffirmation, being education the process of modification and primary behavior, it's natural for it to be starting point in the formation of these professionals. That is why, in this paper we aim at assessing the level of motivation of first-year Nursing students for their major. To that end, a retrospective, longitudinal study was carried out, randomly choosing a 93-student small sample out of the whole sample of 156, who were surveyed. The information was processed through the arithmetic percentage method and tabled whose results were that most students applied for their major as a first choice and stated that they applied for it out of vocation, being the subject of Nursing Guidelines which most helped to encourage this vocation.

Nivel de motivación en los estudiantes de Licenciatura en Enfermería: primer año del Nuevo Modelo Pedagógico, curso 2006-2007 / Level of Motivation in Nursing Students: first year of the New Pedagogical Model, course 2006-2007

La enseñanza de la enfermería en Cuba se inicia antes de 1959. En aquella época se disponía de escasos recursos materiales y humanos, estando los existentes muy mal distribuidos y no eran accesibles a la mayoría de la población. Con el triunfo de la Revolución se crean nuevos programas y se da una mayor prioridad a la formación de recursos humanos en enfermería. Teniendo en cuenta que el trabajo pedagógico tiene entre sus objetivos brindar a los alumnos una adecuada formación y reafirmación vocacional, siendo la educación el proceso de modificación del comportamiento primario, es natural que constituya un punto de partida en la formación de estos profesionales. Por tal motivo en este trabajo pretendemos valorar el nivel de motivación de los estudiantes de primer año de Licenciatura en Enfermería por la carrera, para ello se realizó un estudio retrospectivo y longitudinal seleccionando al azar una muestra de 93 estudiantes de un universo de 156 a los cuales se les aplicó una encuesta. La información fue procesada a través del método porcentual aritmético y fue reflejada en tablas cuyos resultados fueron, la solicitud de la carrera en primera opción por la mayoría de los estudiantes y la expresión de que la solicitaron por vocación, siendo la asignatura Fundamentos de Enfermería lo que ha ayudado a fomentar esta vocación (AU)

Teaching in Nursing in Cuba starts before 1959, and at that time scarce material and human resources were available, these being wrongly distributed and were not accessible to most of the population. With the Triumph of the Revolution new programs are designed and the formation of human resources in Nursing are more prioritized. Considering that the pedagogical work has as one of its objectives providing the students with an appropriate formation and vocational reaffirmation, being education the process of modification and primary behavior, its natural for it to be starting point in the formation of these professionals. That is why, in this paper we aim at assessing the level of motivation of first-year Nursing students for their major. To that end, a retrospective, longitudinal study was carried out, randomly choosing a 93-student small sample out of the whole sample of 156, who were surveyed. The information was processed through the arithmetic percentage method and tabled whose results were that most students applied for their major as a first choice and stated that they applied for it out of vocation, being the subject of Nursing Guidelines which most helped to encourage this vocation (AU)