Dynamics of a linearly perturbed May-Leonard competition model.

The May-Leonard model was introduced to examine the behavior of three competing populations where rich dynamics, such as limit cycles and nonperiodic cyclic solutions, arise. In this work, we perturb the system by adding the capability of global mutations, allowing one species to evolve to the other two in a linear manner. We find that for small mutation rates, the perturbed system not only retains some of the dynamics seen in the classical model, such as the three-species equal-population equilibrium bifurcating to a limit cycle, but also exhibits new behavior. For instance, we capture curves of fold bifurcations where pairs of equilibria emerge and then coalesce. As a result, we uncover parameter regimes with new types of stable fixed points that are distinct from the single- and dual-population equilibria characteristic of the original model. On the contrary, the linearly perturbed system fails to maintain heteroclinic connections that exist in the original system. In short, a linear perturbation proves to be significant enough to substantially influence the dynamics, even with small mutation rates.

In vitro mineral apposition analysis of two Colombian plant extracts on Amelogenesis imperfecta teeth.

OBJECTIVE: To determine if native Colombian Piper marginatum Jacq. and Ilex guayusa Loes plant extracts have a remineralizing effect on teeth with Amelogenesis imperfecta in comparison with the commercial products Clinpro-3M and Recaldent™. MATERIAL AND METHODS: An in vitro study was carried out with 128 human teeth slices (64 healthy and 64 with Amelogenesis imperfecta) on which an initial Raman spectroscopy was performed followed by Raman spectroscopies at 0, 24, 48, and 72 h to determine possible remineralization by observing mineral increase or decrease as a result of P. marginatum Jacq. and I. guayusa Loes extract application in comparison to control substance (Clinpro and Recaldent™) application. Obtained data were analyzed using a bivariate method with a t unidirectional test. Significant differences among groups were determined by an ANOVA with Dunnett post hoc tests. RESULTS: Native I. guayusa Loes and P. marginatum Jacq. Colombian plants extracts exhibited phosphate and orthophosphate mineral apposition, where P. marginatum Jacq. presented better results. CONCLUSIONS: Native Colombian I. guayusa Loes and P. marginatum Jacq plant extract might in the future be useful for dental tissue remineralization, as they induced phosphate and orthophosphate mineral apposition, main components of tooth enamel. These types of natural compounds can become an alternative to fluorine, whose ingestion is harmful to the human body.

Frecuencia del cierre de herida por segunda intención en cirugías abdominales contaminadas y sucias / Frequency of wound closure by second intention in surgeries contaminated and dirty

El cierre por segunda intención se caracteriza por la sutura de la herida quirúrgica hasta la aponeurosis, dejando abierta la piel y el tejido celular subcutáneo. La cicatrización por segunda intención puede planifcarse, por ejemplo, cuando las heridas están contaminadas o corren un alto riesgo de infección. Esto ocurre cuando la cirugía incluye cavidades corporales que contienen tejido infectado, necrótico o contaminado. El cierre por segunda intención sigue siendo un tema de controversia, debido a que la mayoría de las heridas quirúrgicas cicatrizan por primera intención; además, el cierre por segunda intención prolonga la estancia hospitalaria y requiere de curaciones diarias, condicionando un mayor gasto en atención e incluso puede afectar la psicología del paciente [1, 2]. Este trabajo se realizó con el objetivo de determinar la frecuencia de empleo del cierre por segunda intención en pacientes del Hospital Carlos Andrade Marín que tuvieron cirugías abdominales contaminadas y sucias.

The closure by second intention is characterized by the suture of the surgical wound to the aponeurosis, leaving the skin and subcutaneous cell tissue open. Healing by second intention can be planned, for example, when the wounds are contaminated or at high risk of infection. This occurs when surgery It includes body cavities that contain infected, necrotic or contaminated tissue. The closure by second intention remains a matter of controversy, due to that most surgical wounds heal by first intention; also the Closing by second intention prolongs the hospital stay and requires daily cures, conditioning a higher cost of care and may even affect the patient psychology [1,2]. This work was carried out with the objective of determining the frequency of use of the closure by second intention in patients of the Hospital Carlos Andrade Marín who had contaminated and dirty abdominal surgeries.

Composición corporal en pacientes en hemodiálisis: relación con la modalidad de hemodiálisis, parámetros inflamatorios y nutricionales / Body composition in patients on haemodialysis: relationship between the type of haemodialysis and inflammatory and nutritional parameters

Introducción: El sobrepeso y la obesidad se asocian a un mayor riesgo cardiovascular y mayor mortalidad en la población general, y existen datos controvertidos en la población en diálisis. Las adipoquinas (leptina, adiponectina) producidas en los adipocitos podrían jugar un papel en dicho proceso, así como los parámetros inflamatorios (proteína C reactiva [PCR], interleuquina 6 (..) (AU)

Introduction: Overweight and obesity are associated to a higher cardiovascular risk and mortality in the general population and conflicting findings exist in the dialysis population. Adipokines (Leptin, adiponectin) produced in adipocytes may play a role in that process, and inflammatory parameters ((..) (AU)

Body composition in patients on haemodialysis: relationship between the type of haemodialysis and inflammatory and nutritional parameters.

INTRODUCTION: Overweight and obesity are associated to a higher cardiovascular risk and mortality in the general population and conflicting findings exist in the dialysis population. Adipokines (Leptin, adiponectin) produced in adipocytes may play a role in that process, and inflammatory parameters (CRP, IL-6) may be markers for it. Nevertheless, obtaining dry weight is today one of the main aims of adequacy in dialysis because overhydration is a clear mortality predictor. OBJECTIVES: The aim of this study was to analyse body composition using an impedance spectroscopy technique in patients on haemodialysis (HD): and evaluate overweight and overhydration prevalence and its possible relation with adipokines, inflammatory and nutritional parameters, HD technique (Conventional [CHD], on-line haemodiafiltration [OL-HFD]) and erythropoietin needs. METHODS: In a cross-sectional observational study, a pre-HD multifrequency bioimpedance spectroscopy (BIS) was performed in the middle of the week on 77 HD outpatients: 56 CHD and 21 OL-HFD. Patients were considered overweight when Body Mass Index (BMI) was ≥25kg/m² and overhydrated when overhydration normalised for extracellular water was higher than 0.15l. Clinical and biochemical parameters were analysed and IL-6, leptin and adiponectin levels were determined. This information was analysed in overweight and non-overweight, regular and overhydrated patients and both HD techniques. RESULTS: 50% of patients fulfilled overweight criteria and 21% were pre-HD overhydrated. Overweight patients had a superior fat and extracellular water content (P<.001). Leptin (P=.001) and CRP (P=.036) levels were higher and adiponectin levels were lower (P=.003). An inverse correlation did exist between BMI and lean mass (P=.01). Nutritional markers (prealbumin, albumin, total proteins, creatinine and transferrin) were related to lean mass (P=.05). Comparing both HD techniques, a lower fat content was observed in OL-HFD (P=.049) without overhydration differences. In the univariate analysis, age, fat, extracellular/intracellular water ratio, leptin, hipoadiponectinaemia, lower lean mass and CHD technique were predictors of overweight. In the multivariate analysis, hipoadiponectinaemia (OR: 0.86; IC: 0.76-0.98), lean mass (OR: 0.89; IC: 0.84-0.94) and OL-HFD technique (OR: 0.200; IC: 0.04-0.99) predicted the absence of overweight. CONCLUSION: This observational study emphasises the high prevalence of overweight in the outpatient haemodialysis population, as long as overweight is related with fat and extracellular water. Furthermore, it is accompanied by higher inflammation and leptin levels and lower levels of adiponectin. The use of the OL-HFD technique is associated to less overweight and fat content. Bioimpedance may prove to be a valuable ally for decisions regarding weight changes in dialysis patients.

Polimorfismos genéticos del proto-oncogén RET asociados con la enfermedad de Hirschsprung en niños ecuatorianos / Genetic polymorphisms in the RET proto-oncogene associated with Hirschsprung's disease in Ecuadorian children

Contexto La enfermedad de Hirschsprung es un desorden congénito caracterizado por la ausencia de células ganglionares en una porción variable del tracto gastrointestinal. Está causada por defectos en la migración de las células del sistema nervioso entérico durante el desarrollo embrionario. Actualmente se sabe el proto-oncogén RET es el principal gen involucrado en la patogénesis de Hirschsprung. Objetivo Determinar la asociación entre los polimorfismos de nucleótido simple (SNP) presentes en los exones 2, 7 y 15 e intrón 1 del gen RET y la enfermedad de Hirschsprung en niños ecuatorianos. Diseño Estudio caso-control. Lugar y sujetos 41 casos con enfermedad de Hirschsprung y 41 controles procedentes del Hospital Pediátrico Baca Ortiz de la ciudad de Quito y del Hospital de Machachi (Área de Salud N° 16). Mediciones principales Análisis de los polimorfismos de nucleótido simple en los exones 2, 7, 15 e intrón 1 del gen RET, mediante las técnicas PCR-RFLP y secuenciación directa. Resultados El polimorfismo A45A (c135 G>A, exón 2) se asoció significativamente con la enfermedad de Hirschsprung (OR=11.2; IC95%=1.61­78.5; p=0.02). Los polimorfismos A432A (c1296G>A, exón 7) y S904S (c2712C>G, exón 15) mostraron tendencias sugestivas de un papel protector en la patogénesis de la enfermedad (OR=0.05; IC95%=0.01­0.25 y OR=0.13; IC95%=0.01­1.28, respectivamente). No se observó una asociación con el polimorfismo IVS1+1813 C>T (OR=4.16; IC95%=0.88­19.5). Conclusión Los polimorfismos estudiados del proto-oncogén RET desempeñan un papel importante en la etiología de la enfermedad de Hirschsprung en la población ecuatoriana.

Context Hirschsprung's disease is a congenital disorder characterized by the absence of ganglion cells in a variable portion of the gastrointestinal tract. It´s caused by defects in the migration of cells of the enteric nervous system during embryonic development. Nowadays the RET proto-oncogene is recognized as a major gene involved in the pathogenesis of Hirschsprung. Objective To determine the association between single nucleotide polymorphisms of the RET gene and Hirschsprung's disease in Ecuadorian children. Design Case control study. Subjects and setting 41 cases with Hirschsprung's disease and 41 controls from Children's Hospital "Baca Ortiz" and Hospital Machachi. Main measurements Analysis of single nucleotide polymorphisms in exons 2, 7, 15 and intron 1 of the RET gene by PCR-RFLP techniques and direct sequencing. Results A45A polymorphism (C135 G> A, exon 2) was significantly associated with Hirschsprung´s disease (OR=11.2; 95%CI=1.61­78.5; p=0.02). Polymorphism A432A (c1296G>A, exon 7) and S904S (c2712C>G, exon 15) showed trends of a protective role in the pathogenesis of the disease (OR= 0.05; 95%CI=0.01­0.25 and OR=0.13; 95%CI=0.01­1.28, respectively). There was no association with polymorphism IVS1 +1813 C>T (OR=4.16; 95%CI=0.88­19.5). Conclusion The studied polymorphisms confirm that the RET proto-oncogene plays an important role in the etiology of Hirschsprung in the Ecuadorian population.

Mycobacterium tuberculosis antigens specifically modulate CCR2 and MCP-1/CCL2 on lymphoid cells from human pulmonary hilar lymph nodes.

Macrophages and dendritic cells are involved in the immune response to Mycobacterium tuberculosis (Mtb). Such a response, although extensively studied using animal models and cells from human blood, has not been characterized in cells from pulmonary hilar lymph nodes (PHLN). We characterized populations of myeloid APC from PHLN and determined their expression of CCR2, CCR5, CCR7, CD40, CD54, CD80, and CD86 as well as the cytokine/chemokine microenvironment before and after purified protein derivative (PPD) and mannosilated lipoarabinomannan (ManLAM) stimulation. Results show that there are at least three APC populations in PHLN, defined as CD14highHLA-DRlow/-, CD14dimHLA-DRdim, and CD14-HLA-DRhigh/dendritic cells (DC), with the largest number represented by CD14dimHLA-DRdim cells (where dim indicates intermediate levels). CD14-HLA-DRhigh/DC expressed higher levels of costimulatory molecules and lower levels of CCR2 and CCR5, but all cell populations showed similar CCR7 levels. PPD and ManLAM specifically down-regulated CCR2 expression but not that of CCR5 and CCR7, and such down-regulation was observed on all APC populations. Mtb Ag did not affect the expression of costimulatory molecules. PPD but not ManLAM specifically induced MCP-1/CCL2 production, which was likely associated with the induction of IFN-gamma because this cytokine was highly induced by PPD. We characterized, for the first time, different APC from human PHLN and show that Mtb Ag exert fine and specific regulation of molecules closely associated with the immune response to Mtb infection. Because knowledge of this response in secondary lymphoid tissues is still poorly understood in humans, such studies are necessary and important for a better understanding of lymphoid cell microenvironment and migrating capacities and their role in the immunopathogenesis of tuberculosis.

Chemokine/cytokine production by mononuclear cells from human lymphoid tissues and their modulation by Mycobacterium tuberculosis antigens.

The majority of knowledge about the role of cytokines and chemokines in controlling Mycobacterium tuberculosis infection mainly derives from animal models. In humans, this knowledge is still mainly limited to the blood compartment or accessible lymphoid organs, such as tonsils. Here, we studied cytokine and chemokine production and their modulation by M. tuberculosis antigens in mononuclear cells from human blood, spleen and hilar lung lymph nodes. Results show that the kinetics and magnitude of cytokine and chemokine production varied according to the tissue of cell origin. Mycobacterium tuberculosis antigens enhanced cytokine and chemokine production in blood, but the enhancement was restricted in spleen and hilar lung lymph node cells. We show, for the first time in humans, differences in cytokine and chemokine microenvironments according to lymphoid tissues, and suggest that these differences may affect the way cells respond to M. tuberculosis infection.

Genetic variability of Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) populations from Latin America is associated with variations in susceptibility to Bacillus thuringiensis cry toxins.

Bacillus thuringiensis strains isolated from Latin American soil samples that showed toxicity against three Spodoptera frugiperda populations from different geographical areas (Mexico, Colombia, and Brazil) were characterized on the basis of their insecticidal activity, crystal morphology, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of parasporal crystals, plasmid profiles, and cry gene content. We found that the different S. frugiperda populations display different susceptibilities to the selected B. thuringiensis strains and also to pure preparations of Cry1B, Cry1C, and Cry1D toxins. Binding assays performed with pure toxin demonstrated that the differences in the toxin binding capacities of these insect populations correlated with the observed differences in susceptibility to the three Cry toxins analyzed. Finally, the genetic variability of the three insect populations was analyzed by random amplification of polymorphic DNA-PCR, which showed significant genetic diversity among the three S. frugiperda populations analyzed. The data presented here show that the genetic variability of S. frugiperda populations should be carefully considered in the development of insect pest control strategies, including the deployment of genetically modified maize in different geographical regions.

Chemokine receptor expression and modulation by Mycobacterium tuberculosis antigens on mononuclear cells from human lymphoid tissues.

Chemokine receptor switching on lymphoid cells is an important factor regulating migration and homing, but little is known about the expression of such molecules during Mycobacterium tuberculosis infection in humans. We describe CCR2, CCR5 and CCR7 expression on human cells from blood, spleen and pulmonary hilar lymph nodes (PHLN) stimulated by M. tuberculosis antigens. CCR2 was not expressed by CD3+ cells regardless of the presence of antigen, but was highly expressed on CD14+ CD63+ monocytes/macrophages. CCR2 decreased on splenic monocytes/macrophages by nearly 50% in culture, independent of antigen, but remained high in blood and PHLN. CCR5 was low in CD3+ cells and was down-regulated by M. tuberculosis antigens on blood and splenic cells but not in PHLN. CCR5 was highly expressed on monocytes/macrophages and was down-regulated by M. tuberculosis antigens at 48 hr only in blood. Less than 15% of CD3+ cells from spleen and PHLN were CCR7+, whereas nearly 40% from blood expressed this receptor on primary isolation. However, CCR7 in PHLN increased in culture, independent of antigen. Monocytes/macrophages did not express CCR7. Thus, we characterize, for the first time, chemokine receptor expression and differential modulation by M. tuberculosis antigens on human mononuclear cells from spleen, blood and PHLN. Knowledge of chemokine receptor switching in human lymphoid tissue provides novel insight into mechanisms of the immune response to M. tuberculosis with potential effects on directing cell trafficking.