Isohydricity and hydraulic isolation explain reduced hydraulic failure risk in an experimental tree species mixture.

Species mixture is promoted as a crucial management option to adapt forests to climate change. However, there is little consensus on how tree diversity affects tree water stress, and the underlying mechanisms remain elusive. By using a greenhouse experiment and a soil-plant-atmosphere hydraulic model, we explored whether and why mixing the isohydric Aleppo pine (Pinus halepensis, drought avoidant) and the anisohydric holm oak (Quercus ilex, drought tolerant) affects tree water stress during extreme drought. Our experiment showed that the intimate mixture strongly alleviated Q. ilex water stress while it marginally impacted P. halepensis water stress. Three mechanistic explanations for this pattern are supported by our modelling analysis. First, the difference in stomatal regulation between species allowed Q. ilex trees to benefit from additional soil water in mixture, thereby maintaining higher water potentials and sustaining gas exchange. By contrast, P. halepensis exhibited earlier water stress and stomatal regulation. Second, P. halepensis trees showed stable water potential during drought, although soil water potential strongly decreased, even when grown in a mixture. Model simulations suggested that hydraulic isolation of the root from the soil associated with decreased leaf cuticular conductance was a plausible explanation for this pattern. Third, the higher predawn water potentials for a given soil water potential observed for Q. ilex in mixture can - according to model simulations - be explained by increased soil-to-root conductance, resulting from higher fine root length. This study brings insights into the mechanisms involved in improved drought resistance of mixed species forests.

Distinct excitability of thalamocortical neurons correlates with the presence of cerebellar afferents.

Thalamocortical (TC) neurons within the ventrolateral thalamus (VL) receive projections from the cerebellum and the basal ganglia (BG) to facilitate motor and non-motor functions. Tonic and rebound firing patterns in response to excitatory cerebellar and inhibitory BG inputs, respectively, are a canonical feature of TC neurons and plays a key role in signal processing. The intrinsic excitability of TC neurons has a strong influence on how they respond to synaptic inputs, however, it is unknown whether their afferents influence their firing properties. Understanding the input-specific firing patterns could shed light into movement disorders with cerebellar or BG involvement. Here, we used whole-cell electrophysiology in brain slices from C57BL/6 mice to investigate the firing of TC neurons with optogenetic confirmation of cerebellar or BG afferents. TC neurons with cerebellar afferents exhibited higher tonic and rebound firing rates than those with BG afferents. This increased firing was associated with faster action potential depolarization kinetics and a smaller afterhyperpolarization potential. We also found differences in the passive membrane properties and sag currents during hyperpolarization. Despite higher rebound firing in TC neurons with cerebellar afferents, there were no differences in T-type calcium channel function compared to those with BG inputs. These data suggest input-specific differences in sodium and SK, but not T-type calcium channels, impact firing properties in TC populations. Altogether, we showed that the pronounced divergence observed in TC neuron firing properties correlate with its heterogeneous anatomical connectivity, which could signify a distinct signal integration and processing by these neurons. Keypoints: Thalamocortical neurons in the VL with cerebellar afferents have higher intrinsic tonic and rebound firing properties than those with basal ganglia afferents.Membrane resistance and action potential depolarization slope were different based on the presence of cerebellar afferents.Despite elevated rebound burst firing, T-type mediated currents did not correlate with increased firing in neurons with cerebellar afferents.

Plant hydraulic modelling of leaf and canopy fuel moisture content reveals increasing vulnerability of a Mediterranean forest to wildfires under extreme drought.

Fuel moisture content (FMC) is a crucial driver of forest fires in many regions world-wide. Yet, the dynamics of FMC in forest canopies as well as their physiological and environmental determinants remain poorly understood, especially under extreme drought. We embedded a FMC module in the trait-based, plant-hydraulic SurEau-Ecos model to provide innovative process-based predictions of leaf live fuel moisture content (LFMC) and canopy fuel moisture content (CFMC) based on leaf water potential ( ψ Leaf ). SurEau-Ecos-FMC relies on pressure-volume (p-v) curves to simulate LFMC and vulnerability curves to cavitation to simulate foliage mortality. SurEau-Ecos-FMC accurately reproduced ψ Leaf and LFMC dynamics as well as the occurrence of foliage mortality in a Mediterranean Quercus ilex forest. Several traits related to water use (leaf area index, available soil water, and transpiration regulation), vulnerability to cavitation, and p-v curves (full turgor osmotic potential) had the greatest influence on LFMC and CFMC dynamics. As the climate gets drier, our results showed that drought-induced foliage mortality is expected to increase, thereby significantly decreasing CFMC. Our results represent an important advance in our capacity to understand and predict the sensitivity of forests to wildfires.

Drought acclimation of Quercus ilex leaves improves tolerance to moderate drought but not resistance to severe water stress.

Increasing temperature and drought can result in leaf dehydration and defoliation even in drought-adapted tree species such as the Mediterranean evergreen Quercus ilex L. The stomatal regulation of leaf water potential plays a central role in avoiding this phenomenon and is constrained by a suite of leaf traits including hydraulic conductance and vulnerability, hydraulic capacitance, minimum conductance to water vapour, osmotic potential and cell wall elasticity. We investigated whether the plasticity in these traits may improve leaf tolerance to drought in two long-term rainfall exclusion experiments in Mediterranean forests. Osmotic adjustment was observed to lower the water potential at turgor loss in the rainfall-exclusion treatments, thus suggesting a stomatal closure at more negative water potentials and a more anisohydric behaviour in drier conditions. Conversely, leaf hydraulic conductance and vulnerability did not exhibit any plasticity between treatments so the hydraulic safety margins were narrower in the rainfall-exclusion treatments. The sequence of leaf responses to seasonal drought and dehydration was conserved among treatments and sites but trees were more likely to suffer losses of turgor and hydraulic functioning in the rainfall-exclusion treatments. We conclude that leaf plasticity might help the trees to tolerate moderate drought but not to resist severe water stress.

Differences in hippocampal plasticity and memory outcomes in anterior versus posterior cerebellar stroke.

Neurological symptoms following cerebellar stroke can range from motor to cognitive-affective impairments. Topographic imaging studies from patients with lesions confined to the cerebellum have shown evidence linking anterior cerebellar lobules with motor function and posterior lobules with cognitive function. Damage to the cerebellum can disrupt functional connectivity in cerebellar stroke patients, as it is highly interconnected with forebrain motor and cognitive areas. The hippocampus plays a key role in memory acquisition, a cognitive domain that is negatively impacted by posterior cerebellar stroke, and there is increasing evidence that the cerebellum can affect hippocampal function in health and disease. To study these topographical dissociations, we developed a mouse photo-thrombosis model to produce unilateral strokes in anterior (lobules III-V) or posterior (lobules VI-VIII) cerebellar cortex to examine hippocampal plasticity and behavior. Histological and MRI data demonstrate reproducible injury that is confined to the targeted lobules. We then measured hippocampal long-term potentiation (LTP) ex-vivo with extracellular field recording experiments in acute brain slices obtained from mice 7 days post-cerebellar stroke. Interestingly, we found that a unilateral posterior stroke resulted in a contralateral hippocampal impairment, matching the cerebellothalamic pathway trajectory, while LTP was intact in both hippocampi of mice with anterior strokes. We also assessed motor coordination and memory function at 7 days post-stroke using a balance beam, contextual and delay fear conditioning (CFC and DFC), and novel object recognition (NOR) tasks. Mice with anterior strokes showed lack of coordination evaluated as an increased number of missteps, while mice with posterior strokes did not. Mice with anterior or posterior cerebellar strokes demonstrated similar freezing behavior to shams in CFC and DFC, while only posterior stroke mice displayed a reduced discrimination index in the NOR task. These data suggest that a unilateral LTP impairment observed in mice with posterior strokes produces a mild memory impairment. Our results demonstrate that our model recapitulates aspects of clinical lesion-symptom mapping, with anterior cerebellar strokes producing impaired motor coordination and posterior cerebellar strokes producing an object-recognition memory impairment. Further studies are warranted to interrogate other motor and cognitive-affective behaviors and brain region specific alterations following focal cerebellar stroke. The novel model presented herein will allow for future preclinical translational studies to improve neurological deficits after cerebellar stroke.

Two ectomycorrhizal truffles, Tuber melanosporum and T. aestivum, endophytically colonise roots of non-ectomycorrhizal plants in natural environments.

Serendipitous findings and studies on Tuber species suggest that some ectomycorrhizal fungi, beyond their complex interaction with ectomycorrhizal hosts, also colonise roots of nonectomycorrhizal plants in a loose way called endophytism. Here, we investigate endophytism of T. melanosporum and T. aestivum. We visualised endophytic T. melanosporum hyphae by fluorescent in situ hybridisation on nonectomycorrhizal plants. For the two Tuber species, microsatellite genotyping investigated the endophytic presence of the individuals whose mating produced nearby ascocarps. We quantified the expression of four T. aestivum genes in roots of endophyted, non-ectomycorrhizal plants. Tuber melanosporum hyphae colonised the apoplast of healthy roots, confirming endophytism. Endophytic Tuber melanosporum and T. aestivum contributed to nearby ascocarps, but only as maternal parents (forming the flesh). Paternal individuals (giving only genes found in meiotic spores of ascocarps) were not detected. Gene expression of T. aestivum in non-ectomycorrhizal plants confirmed a living status. Tuber species, and likely other ectomycorrhizal fungi found in nonectomycorrhizal plant roots in this study, can be root endophytes. This is relevant for the ecology (brûlé formation) and commercial production of truffles. Evolutionarily speaking, endophytism may be an ancestral trait in some ectomycorrhizal fungi that evolved from root endophytes.

Delayed inhibition of tonic inhibition enhances functional recovery following experimental ischemic stroke.

The current study focuses on the ability to improve cognitive function after stroke with interventions administered at delayed/chronic time points. In light of recent studies demonstrating delayed GABA antagonists improve motor function, we utilized electrophysiology, biochemistry and neurobehavioral methods to investigate the role of α5 GABAA receptors on hippocampal plasticity and functional recovery following ischemic stroke. Male C57Bl/6 mice were exposed to 45 min transient middle cerebral artery occlusion and analysis of synaptic and functional deficits performed 7 or 30 days after recovery. Our findings indicate that hippocampal long-term potentiation (LTP) is impaired 7 days after stroke and remain impaired for at least 30 days. We demonstrate that ex vivo administration of L655,708 reversed ischemia-induced plasticity deficits and importantly, in vivo administration at delayed time-points reversed stroke-induced memory deficits. Western blot analysis of hippocampal tissue reveals proteins responsible for GABA synthesis are upregulated (GAD65/67 and MAOB), increasing GABA in hippocampal interneurons 30 days after stroke. Thus, our data indicate that both synaptic plasticity and memory impairments observed after stroke are caused by excessive tonic GABA activity, making inhibition of specific GABA activity at delayed timepoints a potential therapeutic approach to improve functional recovery and reverse cognitive impairments after stroke.

FoxO6 regulates Hippo signaling and growth of the craniofacial complex.

The mechanisms that regulate post-natal growth of the craniofacial complex and that ultimately determine the size and shape of our faces are not well understood. Hippo signaling is a general mechanism to control tissue growth and organ size, and although it is known that Hippo signaling functions in neural crest specification and patterning during embryogenesis and before birth, its specific role in postnatal craniofacial growth remains elusive. We have identified the transcription factor FoxO6 as an activator of Hippo signaling regulating neonatal growth of the face. During late stages of mouse development, FoxO6 is expressed specifically in craniofacial tissues and FoxO6-/- mice undergo expansion of the face, frontal cortex, olfactory component and skull. Enlargement of the mandible and maxilla and lengthening of the incisors in FoxO6-/- mice are associated with increases in cell proliferation. In vitro and in vivo studies demonstrated that FoxO6 activates Lats1 expression, thereby increasing Yap phosphorylation and activation of Hippo signaling. FoxO6-/- mice have significantly reduced Hippo Signaling caused by a decrease in Lats1 expression and decreases in Shh and Runx2 expression, suggesting that Shh and Runx2 are also linked to Hippo signaling. In vitro, FoxO6 activates Hippo reporter constructs and regulates cell proliferation. Furthermore PITX2, a regulator of Hippo signaling is associated with Axenfeld-Rieger Syndrome causing a flattened midface and we show that PITX2 activates FoxO6 expression. Craniofacial specific expression of FoxO6 postnatally regulates Hippo signaling and cell proliferation. Together, these results identify a FoxO6-Hippo regulatory pathway that controls skull growth, odontogenesis and face morphology.

Cardiac Arrest Induces Ischemic Long-Term Potentiation of Hippocampal CA1 Neurons That Occludes Physiological Long-Term Potentiation.

Ischemic long-term potentiation (iLTP) is a form of synaptic plasticity that occurs in acute brain slices following oxygen-glucose deprivation. In vitro, iLTP can occlude physiological LTP (pLTP) through saturation of plasticity mechanisms. We used our murine cardiac arrest and cardiopulmonary resuscitation (CA/CPR) model to produce global brain ischemia and assess whether iLTP is induced in vivo, contributing to the functionally relevant impairment of pLTP. Adult male mice were subjected to CA/CPR, and slice electrophysiology was performed in the hippocampal CA1 region 7 or 30 days later. We observed increased miniature excitatory postsynaptic current amplitudes, suggesting a potentiation of postsynaptic AMPA receptor function after CA/CPR. We also observed increased phosphorylated GluR1 in the postsynaptic density of hippocampi after CA/CPR. These data support the in vivo induction of ischemia-induced plasticity. Application of a low-frequency stimulus (LFS) to CA1 inputs reduced excitatory postsynaptic potentials in slices from mice subjected to CA/CPR, while having no effects in sham controls. These results are consistent with a reversal, or depotentiation, of iLTP. Further, depotentiation with LFS partially restored induction of pLTP with theta burst stimulation. These data provide evidence for iLTP following in vivo ischemia, which occludes pLTP and likely contributes to network disruptions that underlie memory impairments.

Sox2 and Lef-1 interact with Pitx2 to regulate incisor development and stem cell renewal.

Sox2 marks dental epithelial stem cells (DESCs) in both mammals and reptiles, and in this article we demonstrate several Sox2 transcriptional mechanisms that regulate dental stem cell fate and incisor growth. Conditional Sox2 deletion in the oral and dental epithelium results in severe craniofacial defects, including impaired dental stem cell proliferation, arrested incisor development and abnormal molar development. The murine incisor develops initially but is absorbed independently of apoptosis owing to a lack of progenitor cell proliferation and differentiation. Tamoxifen-induced inactivation of Sox2 demonstrates the requirement of Sox2 for maintenance of the DESCs in adult mice. Conditional overexpression of Lef-1 in mice increases DESC proliferation and creates a new labial cervical loop stem cell compartment, which produces rapidly growing long tusk-like incisors, and Lef-1 epithelial overexpression partially rescues the tooth arrest in Sox2 conditional knockout mice. Mechanistically, Pitx2 and Sox2 interact physically and regulate Lef-1, Pitx2 and Sox2 expression during development. Thus, we have uncovered a Pitx2-Sox2-Lef-1 transcriptional mechanism that regulates DESC homeostasis and dental development.

Extended therapeutic window of a novel peptide inhibitor of TRPM2 channels following focal cerebral ischemia.

INTRODUCTION: TRPM2 channels have been suggested to play a role in ischemic neuronal injury, specifically in males. A major hindrance to TRPM2 research has been the lack of specific TRPM2 inhibitors. The current study characterized the specificity and neuroprotective efficacy of a novel TRPM2 inhibitor. METHODS: Fluorescent calcium imaging (Fluo5F) was used to determine inhibitor efficacy of the TRPM2 peptide inhibitor (tat-M2NX) in HEK293 cells stably expressing hTRPM2. Adult (2-3months) and aged (18-20months) mice were subjected to 60min middle cerebral artery occlusion (MCAO) and injected with tat-M2NX, control scrambled peptide (tat-SCR) or clotrimazole (CTZ) either 20min prior or 3h after reperfusion. Infarct size was assessed using TTC staining. RESULTS: TRPM2 inhibition by tat-M2NX was observed by decreased Ca(2+) influx following H2O2 exposure human TRPM2 expressing cells. Male mice pre-treated with tat-M2NX had smaller infarct volume compared to tat-SCR. No effect of tat-M2NX on infarct size was observed in female mice. Importantly, male TRPM2(-/-) mice were not further protected by tat-M2NX, demonstrating selectivity of tat-M2NX. Administration of tat-M2NX 3h after reperfusion provided significant protection to males when analyzed at 24h or 4days after MCAO. Finally, we observed that tat-M2NX reduced ischemic injury in aged male mice. CONCLUSIONS: These data demonstrate the development of a new peptide inhibitor of TRPM2 channels that provides protection from ischemic stroke in young adult and aged male animals with a clinically relevant therapeutic window.

Estimation of seasonal risk caused by the intake of lead, mercury and cadmium through freshwater fish consumption from urban water reservoirs in arid areas of northern Mexico.

Bioavailability and hence bioaccumulation of heavy metals in fish species depends on seasonal conditions causing different risks levels to human health during the lifetime. Mercury, cadmium and lead contents in fish from Chihuahua (Mexico) water reservoirs have been investigated to assess contamination levels and safety for consumers. Muscle samples of fish were collected across the seasons. Lead and cadmium were analyzed by inductively coupled plasma-optical emission spectrometry, and mercury by cold-vapor atomic absorption spectrometry. The highest concentrations of cadmium (0.235 mg/kg), mercury (0.744 mg/kg) and lead (4.298 mg/kg) exceeded the maximum levels set by European regulations and Codex Alimentarius. Lead concentrations found in fish from three water reservoirs also surpassed the limit of 1 mg/kg established by Mexican regulations. The provisional tolerable weekly intake (PTWI) suggested by the World Health Organization for methyl mercury (1.6 µg/kg bw per week) was exceeded in the spring season (1.94 µg/kg bw per week). This might put consumers at risk of mercury poisoning.

TBX1 protein interactions and microRNA-96-5p regulation controls cell proliferation during craniofacial and dental development: implications for 22q11.2 deletion syndrome.

T-box transcription factor TBX1 is the major candidate gene for 22q11.2 deletion syndrome (22q11.2DS, DiGeorge syndrome/Velo-cardio-facial syndrome), whose phenotypes include craniofacial malformations such as dental defects and cleft palate. In this study, Tbx1 was conditionally deleted or over-expressed in the oral and dental epithelium to establish its role in odontogenesis and craniofacial developmental. Tbx1 lineage tracing experiments demonstrated a specific region of Tbx1-positive cells in the labial cervical loop (LaCL, stem cell niche). We found that Tbx1 conditional knockout (Tbx1(cKO)) mice featured microdontia, which coincides with decreased stem cell proliferation in the LaCL of Tbx1(cKO) mice. In contrast, Tbx1 over-expression increased dental epithelial progenitor cells in the LaCL. Furthermore, microRNA-96 (miR-96) repressed Tbx1 expression and Tbx1 repressed miR-96 expression, suggesting that miR-96 and Tbx1 work in a regulatory loop to maintain the correct levels of Tbx1. Cleft palate was observed in both conditional knockout and over-expression mice, consistent with the craniofacial/tooth defects associated with TBX1 deletion and the gene duplication that leads to 22q11.2DS. The biochemical analyses of TBX1 human mutations demonstrate functional differences in their transcriptional regulation of miR-96 and co-regulation of PITX2 activity. TBX1 interacts with PITX2 to negatively regulate PITX2 transcriptional activity and the TBX1 N-terminus is required for its repressive activity. Overall, our results indicate that Tbx1 regulates the proliferation of dental progenitor cells and craniofacial development through miR-96-5p and PITX2. Together, these data suggest a new molecular mechanism controlling pathogenesis of dental anomalies in human 22q11.2DS.

A pituitary homeobox 2 (Pitx2):microRNA-200a-3p:ß-catenin pathway converts mesenchymal cells to amelogenin-expressing dental epithelial cells.

Pitx2, Wnt/ß-catenin signaling, and microRNAs (miRs) play a critical role in the regulation of dental stem cells during embryonic development. In this report, we have identified a Pitx2:ß-catenin regulatory pathway involved in epithelial cell differentiation and conversion of mesenchymal cells to amelogenin expressing epithelial cells via miR-200a. Pitx2 and ß-catenin are expressed in the labial incisor cervical loop or epithelial stem cell niche, with decreased expression in the differentiating ameloblast cells of the mouse lower incisor. Bioinformatics analyses reveal that miR-200a-3p expression is activated in the pre-ameloblast cells to enhance epithelial cell differentiation. We demonstrate that Pitx2 activates miR-200a-3p expression and miR-200a-3p reciprocally represses Pitx2 and ß-catenin expression. Pitx2 and ß-catenin interact to synergistically activate gene expression during odontogenesis and miR-200a-3p attenuates their expression and directs differentiation. To understand how this mechanism controls cell differentiation and cell fate, oral epithelial and odontoblast mesenchymal cells were reprogrammed by a two-step induction method using Pitx2 and miR-200a-3p. Conversion to amelogenin expressing dental epithelial cells involved an up-regulation of the stem cell marker Sox2 and proliferation genes and decreased expression of mesenchymal markers. E-cadherin expression was increased as well as ameloblast specific factors. The combination of Pitx2, a regulator of dental stem cells and miR-200a converts mesenchymal cells to a fully differentiated dental epithelial cell type. This pathway and reprogramming can be used to reprogram mesenchymal or oral epithelial cells to dental epithelial (ameloblast) cells, which can be used in tissue repair and regeneration studies.

MicroRNA-26b represses colon cancer cell proliferation by inhibiting lymphoid enhancer factor 1 expression.

microRNAs (miR) can act as oncogenes and tumor suppressors and several miRs are associated with cancer development and progression through the modulation of multiple cellular processes. miR26b is downregulated in several cancers and tumors and miR26b directly targets the lymphoid enhancer factor 1 (Lef1)3'UTR and inhibits endogenous Lef1 expression. We report that miR26b expression is associated with human colon cancer through the regulation of LEF1 expression in colon cancer cells. Analyses of multiple colon cancer cell lines revealed an inverse correlation between miR26b and LEF1 expression. Normal human colon cells express low levels of LEF1 and high levels of miR26b; however, human colon cancer cells have decreased miR26b expression and increased LEF1 expression. We demonstrate that miR26b expression is a potent inhibitor of colon cancer cell proliferation and significantly decreases LEF1 expression. The LEF1-regulated genes cyclin D1 and c-Myc were indirectly repressed by miR26b and this was consistent with decreased proliferation. miR26b overexpression in SW480 colon cancer cells also inhibited tumor growth in nude mice and this was due to decreased tumor growth and not apoptosis. Analyses of human colon cancer databases also demonstrated a link between miR26b and LEF1 expression. c-Myc expression is associated with multiple cancers and we propose that miR26b may act as a potential therapeutic agent in reducing cancer cell proliferation through repressing LEF1 activation of c-Myc and cyclin D1 expression.

Arsenic in freshwater fish in the Chihuahua County water reservoirs (Mexico).

Water reservoirs in Chihuahua County, Mexico, are affected by some punctual and non-punctual geogenic and anthropogenic pollution sources; fish are located at the top of the food chain and are good indicators for the ecosystems pollution. The study goal was to: (i) determine arsenic concentration in fish collected from the Chuviscar, Chihuahua, San Marcos and El Rejon water reservoirs; (ii) to assess if the fishes are suitable for human consumption and (iii) link the arsenic contents in fish with those in sediment and water reported in studies made the same year for these water reservoirs. Sampling was done in summer, fall and winter. The highest arsenic concentration in the species varied through the sampling periods: Channel catfish (Ictalurus punctatus) with 0.22 ± 0.15 mg/kg dw in winter and Green sunfish (Lepomis cyanellus) with 2.00 ± 0.15 mg/kg dw in summer in El Rejon water reservoir. A positive correlation of arsenic contents was found through all sampling seasons in fish samples and the samples of sediment and water. The contribution of the weekly intake of inorganic arsenic, based on the consumption of 0.245 kg fish muscles/body weight/week was found lower than the acceptable weekly intake of 0.015 mg/kg/body weight for inorganic arsenic suggested by FAO/WHO.

Mercury levels in locally manufactured Mexican skin-lightening creams.

Mercury is considered one of the most toxic elements for plants and animals. Nevertheless, in the Middle East, Asia and Latin America, whitening creams containing mercury are being manufactured and purchased, despite their obvious health risks. Due to the mass distribution of these products, this can be considered a global public health issue. In Mexico, these products are widely available in pharmacies, beauty aid and health stores. They are used for their skin lightening effects. The aim of this work was to analyze the mercury content in some cosmetic whitening creams using the cold vapor technique coupled with atomic absorption spectrometry (CV-AAS). A total of 16 skin-lightening creams from the local market were investigated. No warning information was noted on the packaging. In 10 of the samples, no mercury was detected. The mercury content in six of the samples varied between 878 and 36,000 ppm, despite the fact that the U.S. Food and Drug Administration (FDA) has determined that the limit for mercury in creams should be less than 1 ppm. Skin creams containing mercury are still available and commonly used in Mexico and many developing countries, and their contents are poorly controlled.

Modelo de enseñanza de las habilidades psicomotoras básicas en anestesia para estudiantes de ciencias de la salud: sistematización de una experiencia / Teaching model of basic psychomotor skills in anesthesia for students of health sciences: systematization of an experience

Esta investigación, de tipo cualitativo, propone un modelo pedagógico orientado a facilitar los procesos de enseñanza y aprendizaje de las siguientes habilidades psicomotoras básicas en anestesia: intubación oro-traqueal, colocación de máscara laríngea y canalización venosa en niños y adultos. El modelo se elaboró mediante la adopción de algunas teorías y diseños propuestos en la literatura, la recuperación de la experiencia docente y pruebas piloto de los modelos de instrucción con estudiantes que realizan prácticas hospitalarias. Los objetivos generales fueron: primero, sistematizar la experiencia de construcción de un modelo pedagógico orientado a facilitar los procesos de enseñanza y aprendizaje de las habilidades psicomotoras básicas en anestesia; segundo, aportar a la cualificación de la práctica del anestesiólogo y del educador en anestesia, a partir del reconocimiento del saber de un equipo de expertos anestesiólogos y docentes en el área. resultados de la sistematización fueron: primero, la descripción de los supuestos teóricos más relevantes para el diseño de un modelo de instrucción de enseñanza de las competencias psicomotoras; segundo, la propuesta de un método para la enseñanza de estas competencias y la elaboración de un instrumento de evaluación de las competencias psicomotoras del estudiante. Las conclusiones de la sistematización fueron: primero, que la enseñanza de las competencias psicomotoras se puede fundamentar en supuestos, teorías y modelos definidos en la literatura en forma sinérgica; segundo, que la enseñanza de las competencias psicomotoras exige planificación y estructuración coherentes y pertinentes, dado que estas competencias se consideran como "capacidades productoras"; y tercero, que los modelos de instrucción de evaluación deben considerar tanto el proceso como los resultados, para lograr una mayor retroalimentación de los procesos de aprendizaje y una mejor interacción entre el aprendiz y el maestro.

This type of qualitative research, proposes a pedagogical model designed to facilitate teaching and lear-ning processes of the following basic psychomotor skills in anesthesia: orotracheal intubation, placement of laryngeal mask and channeling vein in children and adults. The model was designed through the adoption of some theories and designs proposed in the literature, the systematization of teaching experience, and leading tests of the instructions to students who perform hospital practices. The general objectives set for the systematization were: first, systematize the experience of building a pe-dagogical model aimed at facilitating the process of teaching and learning of psychomotor skills in basic anesthesia. Second, help improve the qualifcation of the practice of anesthesiologists and educators in anes-thesia, upon recognition of knowledge of an expert team of anesthesiologists and teachers in the area. The results of the systematization were: first, the description of the more relevant assumptions used for the design of an instructive teaching tool of psychomotor skills. Second, proposing a method for teaching these skills and developing a tool for evaluating the students’ psychomotor skills. The conclusion of the systematization was: first, the teaching of psychomotor skills can be based on as-sumptions, theories and models defned in the literature in a synergistic manner. Second, the teaching of psychomotor skills requires coherent planning and structuring, given that these competencies are considered as "producing capabilities." And third, instructional evaluation should consider both the processes and results, to achieve greater input from the processes of learning and better interaction between master and apprentice.

Impacto y beneficio de la simulación clínica en el desarrollo de las competencias psicomotoras en anestesia: un ensayo clínico aleatorio doble ciego / Impact and benefit of clinical simulation in the development of psychomotor skills in anesthesia: a randomized double-blind clinical trial

Introducción. La atención médica apropiada de pacientes en condiciones de urgencia, requiere de competencias cognitivas y psicomotoras relacionadas con el manejo de la vía aérea y de la canalización venosa. La simulación surge en las últimas décadas como una herramienta pedagógica que complementa la formación tradicional. Objetivo. Comparar la eficacia, la curva de aprendizaje y las complicaciones en la realización de la intubación orotraqueal, la aplicación de máscara laríngea y la canalización venosa hecha por estudiantes que basan su aprendizaje en la simulación, y estudiantes cuyo proceso se centra en la práctica clínica. metodología. Ensayo clínico aleatorio, doble ciego; 29 estudiantes de cuarto año de medicina recibieron instrucción teórica apoyada en una multimedia sobre los procedimientos estudiados; posteriormente, en forma aleatoria, fueron distribuidos en dos grupos, un grupo de simulación que recibió entrenamiento en maniquíes hasta completar la competencia, y un grupo control que procedió al manejo clínico. Se utilizó un instrumento de evaluación con puntaje máximo de 200; se compararon los promedios de ambos grupos en cuanto a eficacia, curva de aprendizaje y complicaciones. Resultados. No se encontraron diferencias significativas en las evaluaciones en la intubación orotraqueal, pero sí en la fase de preparación para la misma; el grupo de simulación obtuvo mejores califcaciones que el grupo control en la colocación de una máscara laríngea; no se observaron diferencias signifcativas entre los grupos en la canalización venosa. El porcentaje de complicaciones no mostró diferencias entre los grupos. Conclusiones. La instrucción basada en la simulación obtuvo mejores calificaciones que la instrucción basada en la clínica para la colocación de la máscara laríngea, pero no para la intubación traqueal ni la canalización venosa.

Introduction. Proper medical care for patients in emergency conditions, requires cognitive and psychomotor skills related to the management of the airway and vein channeling. Simulations surge in recent decades as a pedagogical tool that complements traditional training. Objectives: to compare the effectiveness, learning curve and complications in conducting orotracheal intu-bation, insertion of laryngeal mask and vein channeling done by students who base their learning in the simulation, and students whose process focuses on clinical practice. methodology: randomized double-blind, 29 fourth year medicine students received a process of theoretical instruction supported by multimedia on the procedures studied thereafter at random. Students were divided into two groups. A frst group that received training in simulation mannequins until the complete jurisdiction and a second group of control which proceeded to clinical management. An assessment tool with maximum score of 200 was used by the evaluators; averages were compared among the two groups in terms of effec-tiveness, learning curve, and complications. Results: here were no signifcant differences in the orotracheal intubation assessments, however, signifcant differences were revealed while preparing the same, where the simulation group got better grades than the control group, in the insertion of a laryngeal mask. No signifcant differences were found between groups, in vein channeling procedures. The rate of complications did not differ between groups either. Conclusions: the group instruction based on simulation got better grades that instruction based on just clinical knowledge for the insertion of laryngeal mask study, but not for tracheal intubation or vein channeling studies.