The photosynthetic capacity in 35 ferns and fern allies: mesophyll CO2 diffusion as a key trait.

Ferns and fern allies have low photosynthetic rates compared with seed plants. Their photosynthesis is thought to be limited principally by physical CO2 diffusion from the atmosphere to chloroplasts. The aim of this study was to understand the reasons for low photosynthesis in species of ferns and fern allies (Lycopodiopsida and Polypodiopsida). We performed a comprehensive assessment of the foliar gas-exchange and mesophyll structural traits involved in photosynthetic function for 35 species of ferns and fern allies. Additionally, the leaf economics spectrum (the interrelationships between photosynthetic capacity and leaf/frond traits such as leaf dry mass per unit area or nitrogen content) was tested. Low mesophyll conductance to CO2 was the main cause for low photosynthesis in ferns and fern allies, which, in turn, was associated with thick cell walls and reduced chloroplast distribution towards intercellular mesophyll air spaces. Generally, the leaf economics spectrum in ferns follows a trend similar to that in seed plants. Nevertheless, ferns and allies had less nitrogen per unit DW than seed plants (i.e. the same slope but a different intercept) and lower photosynthesis rates per leaf mass area and per unit of nitrogen.

Photosynthesis limitations in three fern species.

Maximum photosynthesis rates in ferns are generally lower than those of seed plants, but little is known about the limiting factors, which are crucial to understand the evolution of photosynthesis in land plants. To address this issue, a gas exchange/chlorophyll fluorescence analysis was performed in three fern species spanning high phylogenetic range within Polypodiopsida (Osmunda regalis, Blechnum gibbum and Nephrolepis exaltata) to determine their maximum net photosynthesis (AN ), stomatal (gs ) and mesophyll (gm ) conductances to CO2 , and the maximum velocity of carboxylation (Vc,max ). The in vitro Rubisco specificity factor (SC /O ) was also determined. All three species had values for SC /O similar to those typical of seed plants, but values of AN , gs , gm and Vc,max were within the lowest range of those observed in seed plants. In addition, gs was unresponsive to light and CO2 , as already described in other fern species. On the contrary, gm varied with changes CO2 . A quantitative photosynthesis limitation analysis suggested that early land plants (ferns) presented not only stomatal limitations-which were less adjustable to the environment-but also restricted gm and Vc,max , resulting in limited maximum photosynthesis rates.

Variability of water relations and photosynthesis in Eucryphia cordifolia Cav. (Cunoniaceae) over the range of its latitudinal and altitudinal distribution in Chile.

The aim of this study was to investigate, during the summer of the year 2008, the variation in leaf water and photosynthetic characteristics of Eucryphia cordifolia Cav. (Cunoniaceae) along its broad latitudinal distribution in central south Chile (36 degrees to 42 degrees S). The latitudinal variation in water potential (Psi(w)), water potential at saturation (Psipi(sat)), water potential at the turgor lost point (Psipi(tlp)), stomatal density of the leaves, leaf nitrogen concentrations and photosynthetic light response were studied in eight populations. The populations located in the northern region of the distribution of E. cordifolia had the lowest leaf water potential. Osmotic potential at full turgor was highest in the two southernmost populations and gradually decreased towards the northernmost points. Similarly, osmotic potential at zero turgor was the lowest in the northern population. On the contrary, the symplastic water content was lower in the two southernmost populations. The highest net photosynthesis rate was recorded for plants in the populations of intermediate distributions, and it was dependent on the precipitation and temperature gradient. The northern populations, which are subject to the lowest precipitations, showed the lowest stomatal densities, which were tightly linked with stomatal conductance variation. Therefore, the variability of A(max) was independent of stomatal density and conductance, so that the northern populations, subject to environments with less water availability, presented higher photosynthetic water use efficiency. Photosynthesis variations were also not associated with changes in leaf water potential or in nitrogen content in E. cordifolia leaves, which did not show any consistent latitudinal or altitudinal trend. In conclusion, the results support our hypothesis that the leaf water relations, stomatal characteristics and photosynthetic rates of the leaf would vary along its latitudinal gradient, helping to explain the ability of E. cordifolia trees to inhabit a broad latitudinal and altitudinal range throughout the central south Chile.

Changes during early development in photosynthetic light acclimation capacity explain the shade to sun transition in Nothofagus nitida.

Nothofagus nitida (Phil.) Krasser, an emergent tree of the Chilean evergreen forest, regenerates under the canopy. Nonetheless, it is common to find older saplings in clear areas. We hypothesized that this transition from shade to sun during the early developmental stages is made possible by an ontogenetic increase in the light acclimation capacity of photosynthesis. To test our hypothesis, we studied photosynthetic performance and photoprotection in N. nitida saplings at different developmental stages corresponding with three different height classes (short: 16.2 cm; medium-height: 48.0 cm; and tall: 73.7 cm) grown under contrasting light conditions (photosynthetic photon flux (PPF) of 20, 300 or 600 micromol m(-2) s(-1)) until newly expanded leaves had developed. Light-saturated CO(2) assimilation rate and light compensation and saturation points increased with increasing PPF. Medium-height and tall saplings acclimated to high light had higher electron transport rates and higher proportions of open Photosystem II reaction centers than shorter plants acclimated to high light. Short saplings showed higher thermal dissipation and contents of xanthophylls than taller saplings. Only medium-height and tall saplings acclimated to high light recovered after photoinhibition. State transitions were higher in short plants growing in low light, and decreased with plant height and growth irradiance. Thus, during development, N. nitida changes the balance of light energy utilization and photoprotective mechanisms, supporting a phenotypic transition from shade to sun during its early ontogeny.

Acclimation of leaf cohorts expanded under light and water stresses: an adaptive mechanism of Eucryphia cordifolia to face changes in climatic conditions?

Eucryphia cordifolia Cav. is a long-lived evergreen tree species, commonly found as a canopy emergent tree in the Chilean temperate rain forest. This species displays successive leaf cohorts throughout the entire growing season. Thus, full leaf expansion occurs under different environmental conditions during growing such as air temperature, vapor pressure deficit and the progress of moderate water stress (WS). These climate variations can be reflected as differences in anatomical and physiological characteristics among leaf cohorts. Thus, we investigated the potential adaptive role of different co-existing leaf cohorts in seedlings grown under shade, drought stress or a combination of the two. Photosynthetic and anatomical traits were measured in the first displayed leaf cohort and in a subsequent leaf cohort generated during the mid-season. Although most anatomical and photosynthetic pigments did not vary between cohorts, photosynthetic acclimation did occur in the leaf cohort and was mainly driven by biochemical processes such as leaf nitrogen content, Rubisco carboxylation capacity and maximal Photosystem II electron transport rather than CO2 diffusion conductance. Cohort acclimation could be relevant in the context of climate change, as this temperate rainforest will likely face some degree of summer WS even under low light conditions. We suggest that the acclimation of the photosynthetic capacity among current leaf cohorts represents a well-tuned mechanism helping E. cordifolia seedlings to face a single stress like shade or drought stress, but is insufficient to cope with simultaneous stresses.

Mesophyll diffusion conductance to CO2: an unappreciated central player in photosynthesis.

Mesophyll diffusion conductance to CO(2) is a key photosynthetic trait that has been studied intensively in the past years. The intention of the present review is to update knowledge of g(m), and highlight the important unknown and controversial aspects that require future work. The photosynthetic limitation imposed by mesophyll conductance is large, and under certain conditions can be the most significant photosynthetic limitation. New evidence shows that anatomical traits, such as cell wall thickness and chloroplast distribution are amongst the stronger determinants of mesophyll conductance, although rapid variations in response to environmental changes might be regulated by other factors such as aquaporin conductance. Gaps in knowledge that should be research priorities for the near future include: how different is mesophyll conductance among phylogenetically distant groups and how has it evolved? Can mesophyll conductance be uncoupled from regulation of the water path? What are the main drivers of mesophyll conductance? The need for mechanistic and phenomenological models of mesophyll conductance and its incorporation in process-based photosynthesis models is also highlighted.

Causas de abandono, cambio o fallo terapéutico de la anticoncepción hormonal en mujeres universitarias / Causes of dropout, change or therapeutic failure to hormonal contraception in university women

Introducción: los anticonceptivos hormonales son determinantes para el control de la natalidad. Pese a su uso, pueden aparecer embarazos no deseados, asociados al cambio o abandono terapéutico. Las causas de estos eventos deben ser identificadas para su intervención. Objetivo: medir la frecuencia de posibles causas asociadas al cambio y abandono terapéutico, que puedan desencadenar embarazos no deseados en mujeres universitarias entre los 17 y 30 años de edad, que usan o han usado anticonceptivos hormonales como método de planificación familiar. Materiales y métodos: Estudio de corte en mujeres matriculadas en alguno de los programas de la Universidad de Antioquia, que usan o usaron anticonceptivos hormonales como método de planificación familiar. Muestreo no aleatorio estratificado. Se diseñó e implementó una encuesta para recolectar los datos. Se analizó la estadística descriptiva de las variables. Resultados: se incluyeron 353 mujeres (edad promedio de 21,3 años). El 22,5% de las usuarias actuales y el 24,7% de las usuarias en el pasado del método anticonceptivo hormonal lo toman o tomaron por autoprescripción. Aunque la mayoría de ellas recibieron información sobre uso adecuado de la medicación, entre el 26,2 % y el 41,4 %, consideraron que la capacitación fue insuficiente. La causa más importante de abandono de la terapia fue los eventos adversos (48,6 %); de los cuales el dolor de cabeza y aumento de peso fueron los más relevantes. Las condiciones de acceso fueron la segunda causa de abandono terapéutico (23,6 %). Por su parte, el cambio de terapia se atribuyó a los eventos adversos y la incomodidad del uso. En total se reportaron siete fallos terapéuticos (2 %), sin causas destacables. Conclusiones: la alta incidencia de eventos adversos asociados a los anticonceptivos hormonales, puede ser una de las causas más importantes de cambio y abandono de la terapia. Otras causas, en orden de importancia, son la falta de acceso a los medicamentos ...

Hormonal contraceptives are decisive for birth control. Despite the use of these, undesired pregnancies could appear, associated with therapeutic change or dropout. The causes of these events must be measured to plan further interventions. Objectives: To measure the prevalence of possible causes associated with hormonal contraceptive change or dropout that can trigger therapeutic failure in university women between 17 and 30 years old. Women who use or have used some hormonal contraceptive for birth prevent. Materials and methods: A cross-sectional study was made. The target population was women enrolled in any of the programs of the University of Antioquia. Women included in this study use or have used hormonal contraceptives as a method of birth control. A non-randomized and stratified sampling was made. A poll to collect data was designed and implemented. The descriptive statistics of the variables was evaluated. Results: 353 women (average age of 21,3 years) were included. A 22,5 % of current users and 24,7 % of past users, take or took hormonal method for self-prescription. Although most of the women had received information of proper use of medication, between 26.2 % and 41.4 % believed that training was insufficient. The most important cause of dropout of therapy was adverse events (48,6% of total cases). Headache and weight gain were the most relevant. Access and economic issues were the second cause of dropout (23.6 % of total cases). Meanwhile, therapy change was attributed to adverse events and discomfort in use. In total there were 7 pregnancies (2 %) without any remarkable cause. Conclusions: The high incidence of adverse events associated to hormonal contraceptives, may be one of the most important causes of change and dropout therapy. Access problems and economic issues are other causes, in order of importance. With these findings, we can highlight the need for vigilance and education in hormonal contraceptive use.

Segunda medición de las metas regionales de recursos humanos para la salud Perú 2007 - 2015 / Second measurement of regional objectives of human resources for health Peru 2007 - 2015

La publicación diseña una metodología centrada en el trabajo coordinado con las instituciones prestadoras de salud, universidades y colegios profesionales, la cual obtiene información precisa, procesada, analizada y consensuada permitiendo optimizar la medición de los indicadores de cada una de las 20 metas regionales

Aneurismas arteriales cerebrales múltiples de origen postraumático / Cerebral arterial aneurisms manifold of postraumático origin

Exponemos el caso de una paciente con aneurismas arteriales cerebrales múltiples localizados en las arterias pericallosa y calloso marginal izquierdas, secundarios a heridas craneales por proyectil de arma de fuego; fueron diagnosticados mediante arteriografía cerebral, la cual fue realizada frente a un cuadro clínico y tomográfico sugestivo de una lesión vascular. Comentamos su forma de presentación, los estudios de imagen y el tratamiento de esta rara complicación del trauma craneal.

Indicadores antropométricos en los estudios de prevalencia de desnutrición infantil / Anthropometric indicators in the studies of prevalence of child malnutrition

Se presenta una metodología de evaluación de la prevalencia de DEP infantil en comunidades basada en la clasificación de los valores de peso/edad, talla/edad y peso/talla en intervalores de 1 DS y utilizando los patrones de crecimiento del USNCHS como población de referencia. Los valores se clasifican en: "bajo severo", si es menor que la mediana -3 DS del patrón; "bajo moderado", si es igual o mayor que la mediana -3DS pero menor que la mediana -2 DS; "bajo leve", si es igual o mayor que la mediana -2 DS pero menor que la mediana -1 DS "normal bajo", si es igual o mayor que la mediana -1 DS pero menor que la mediana; "normal alto", si igual o mayor que la mediana pero menor que la mediana + 1 DS y "alto" si es igual o mayor que la mediana + 1 DS. Ella ha sido aplicada en la evaluación nutricional de 155 niños menores de 05 años del P.J. "Mi Perú", de Ventanilla. Se concluye que esta clasificación posee ventajas sobre la de Gómez porque permite diferenciar entre prevalencia del DEP crónica y DEP aguda mediante un simple análisis estadístico y que en la población estudiada, la prevalencia de DEP crónica es del 24.17%, mientras que la prevalencia de DEP aguda es discutible

Los costos de las altas méedicas no efectivizadas en un Hospital de Lima, años 2001 y 2002 / Costs for non executed discharges in a Lima Hospital Between 2001 and 2002

Objetivo: Cuantificar los costos de las altas médicas no efectivizadas por falta de pago en el Hospital Nacional Cayetano Heredia (HNCH), Lima, Perú, de los años 2001 y 2002. Materiales y método: Se obtuvieron los montos totales, pagados y exonerados de las cuentas de los pacientes con alta médica no efectivizada por falta de pago, y los costos del día cama de cada servicio hospitalario. Resultados: En el HNCH los años 2001 y 2002 respectivamente, los pacientes con alta médica no efectivizada por falta de pago fueron 2 120 y 1 102 y estuvieron 6 871 y 3 017 días hospitalizados posteriores al alta médica, la cuenta total al momento del alta médica fue USD 538 692,57 y USD 298 081,51, la cuenta pagada fue USD 179 224,69 y USD 144 740,47 y la cuenta exonerada fue USD 359 467,88 y USD 153 341,04; la cuenta exonerada a los pacientes con alta médica no efectivizada por falta de pago fue 66,73 por ciento y 51,44 por ciento del total de la cuenta, el monto promedio de la cuenta exonerada por paciente fue USD 169,56 y USD 139,15 y los costos por día cama originados por los días que permanecieron luego del alta médica fueron USD 202 422,34 y USD 100 483,56. Conclusiones: La permanencia innecesaria del paciente en el hospital luego del alta medica genera una mayor pérdida económica que la exoneración parcial o total en dicho momento

Tratamiento de quistes de cisticerco por punción, mediante métodos estereotáxicos y tomografía computada / Cysticer cyst treatment by stereotaxic TC punction

Presentamos siete pacientes con quistes de cisticerco cuyo diagnóstico fue efectuado en base al cuadro clínico, a pruebas de inmunofluorescencia en el suero y al estudio tomográfico axial. Mediante pequeños agujeros de trépano y con control de tomografía computada (TC) succionamos el contenido quístico. El líquido se sometió a estudio citoquímico y examen microscópico posterior al secado del mismo; estableciendo comparación con muestras similares de quistes localizados en otros órganos. Controles posteriores de TC demostraron la desaparición completa de los quistes, en cinco pacienets pese a que en dos la extracción del líquido no fue total. En un enfermo, con un quiste pequeño, no se consiguió absorver el líquido y en otro, de un quiste grande, puncionando directamente vía transcutánea y transósea, se produjo contaminación por bacterias de la epidermis y se presentó un absceso, el mismo que fue drenado quirúrgicamente.

Epilepsia post-traumática

Es bien conocido, que incluso traumatismosencéfalo-craneanos (TCE) catalogos como triviales, pueden estar implicados en la génesis de crisis convulsivas únicas o cronicamente recurrentes y tempranas o tardías. Sin embargo, no todos los pacientes con TEC graves, desarrollando postraumaticas de esta enfermedad, permiten determinar las posibilidades de aparición de CPT y estar atentos para su tratamiento, que en determinadas ocaciones es dificil. La incidencia global de convulsiones despúes de un TCE no penetrante está generalmente aceptada como del 5 por ciento, después de TEC con heridas penetrantes está cifra aumenta entre 20-40 por ciento, según las diferentes series. El valor clínico de estas estimaciones es limitado por la gran variabilidad de los grupos de pacientes.