Nutrient scarcity as a selective pressure for mast seeding.

Mast seeding is one of the most intriguing reproductive traits in nature. Despite its potential drawbacks in terms of fitness, the widespread existence of this phenomenon suggests that it should have evolutionary advantages under certain circumstances. Using a global dataset of seed production time series for 219 plant species from all of the continents, we tested whether masting behaviour appears predominantly in species with low foliar nitrogen and phosphorus concentrations when controlling for local climate and productivity. Here, we show that masting intensity is higher in species with low foliar N and P concentrations, and especially in those with imbalanced N/P ratios, and that the evolutionary history of masting behaviour has been linked to that of nutrient economy. Our results support the hypothesis that masting is stronger in species growing under limiting conditions and suggest that this reproductive behaviour might have evolved as an adaptation to nutrient limitations and imbalances.

Global patterns of phosphatase activity in natural soils.

Soil phosphatase levels strongly control the biotic pathways of phosphorus (P), an essential element for life, which is often limiting in terrestrial ecosystems. We investigated the influence of climatic and soil traits on phosphatase activity in terrestrial systems using metadata analysis from published studies. This is the first analysis of global measurements of phosphatase in natural soils. Our results suggest that organic P (Porg), rather than available P, is the most important P fraction in predicting phosphatase activity. Structural equation modeling using soil total nitrogen (TN), mean annual precipitation, mean annual temperature, thermal amplitude and total soil carbon as most available predictor variables explained up to 50% of the spatial variance in phosphatase activity. In this analysis, Porg could not be tested and among the rest of available variables, TN was the most important factor explaining the observed spatial gradients in phosphatase activity. On the other hand, phosphatase activity was also found to be associated with climatic conditions and soil type across different biomes worldwide. The close association among different predictors like Porg, TN and precipitation suggest that P recycling is driven by a broad scale pattern of ecosystem productivity capacity.

[A study using positron emission tomography of a case of vascular dementia due to left thalamic haematoma, an example of the diaschisis phenomenon]. / Estudio con tomografia por emision de positrones de un caso de demencia vascular por hematoma talamico izquierdo, ejemplo del fenomeno de diasquisis.

INTRODUCTION: Thalamic vascular lesions as strategic strokes can cause amnesia, executive dysfunctions or dysphasia and behavioral or psychological symptoms causing vascular dementia. CASE REPORT: A 58 years-old woman with hypertension and dyslipemia, who after a left thalamic hemorrhage with good radiological evolution, presents a severe amnesic syndrome as well as other subtle changes in orientation and in language, difficulties in managing money and depressive symptoms requiring anxiolytic and antidepressive treatment. All this joined to limitations in the normal course of her work. Followed by neurology service, a positron emission tomography with 18F-2-fluoro-2-deoxy-D-glucose integrated with computed tomography was performed, which showed a hypometabolism in left thalamic area and also in ipsilateral inferior frontal region, explained by the diaschisis phenomenon. CONCLUSIONS: Diaschisis phenomenon is a neuroimaging and pathophysiological finding whereby thalamic or basal ganglia strokes cause hypoperfusion/hypometabolism in the ipsilateral or contralateral cortex and could explain cortical distal symptoms. This case report demonstrates the presence of thalamocortical connections, which helps to understand the circuitry of memory and help to explain the association of other cortical symptoms as dysphasia or executive dysfunction.

TITLE: Estudio con tomografia por emision de positrones de un caso de demencia vascular por hematoma talamico izquierdo, ejemplo del fenomeno de diasquisis.Introduccion. Las lesiones vasculares talamicas que se comportan como ictus estrategicos pueden causar amnesia, disfunciones ejecutivas o disfasia, asi como sintomas comportamentales o psicologicos, y causar una demencia vascular. Caso clinico. Mujer de 58 años, hipertensa y dislipidemica, que, tras una hemorragia talamica izquierda que evoluciono radiologicamente de manera favorable, presento un sindrome amnesico grave y otras alteraciones sutiles en la orientacion y el lenguaje, dificultades en el manejo del dinero y sintomas depresivos que precisaron tratamiento ansiolitico y antidepresivo, todo lo cual fue causa de limitaciones para el normal desempeño de su trabajo. Seguida en la consulta de neurologia, se le practico una tomografia por emision de positrones/tomografia axial computarizada con 18F-2-fluoro-2-desoxi-D-glucosa, donde se aprecio un hipometabolismo en el talamo izquierdo y, ademas, en la region frontal inferior ipsilateral, que se explicaria mediante el fenomeno de diasquisis. Conclusiones. El fenomeno de diasquisis es un hallazgo de neuroimagen y fisiopatologico por el cual los ictus talamicos o de los ganglios basales causan hipoperfusion/hipometabolismo en la corteza ipsilateral o contralateral, y que puede explicar sintomas a distancia corticales. El presente caso evidencia la presencia de conexiones talamocorticales, lo cual ayuda a comprender los circuitos de la memoria y a explicar la asociacion en el de otros sintomas corticales, como la disfasia o las alteraciones ejecutivas.

A randomised clinical trial to evaluate the effects of Plantago ovata husk in Parkinson patients: changes in levodopa pharmacokinetics and biochemical parameters.

BACKGROUND: Plantago ovata husk therapy could be used in patients with Parkinson disease to reduce the symptoms of gastrointestinal disorders, but it is important to know whether this compound modifies levodopa pharmacokinetics. The maintenance of constant plasma concentrations of levodopa abolishes the clinical fluctuations in parkinsonian patients. The aim of this randomised clinical trial was to establish the influence of the fiber Plantago ovata husk in the pharmacokinetics of levodopa when administered to Parkinson patients well controlled by their oral medication. METHODS: To evaluate the effects of this fiber on several biochemical parameters. 18 volunteers participated in the study and received alternatively two treatments (Plantago ovata husk or placebo) with their usual levodopa/carbidopa oral dose. On days 0 (initial situation), 14 and 35 of the study, blood samples were taken to assess levodopa pharmacokinetics and to determine biochemical parameters. RESULTS: Levodopa Cmax was very similar in the initial situation (603.2 ng/ml) and after placebo administration (612.0 ng/ml), being slightly lower (547.8 ng/ml) when Plantago ovata husk was given. AUC was very similar in the three groups: initial situation.- 62.87 µg.min/ml, fiber treatment.- 64.47 µg.min/ml and placebo treatment.- 65.10 µg.min/ml. Fiber reduced significantly the number of peaks observed in the levodopa concentrations, maintaining concentrations more stable. No significant differences were found in total cholesterol, LDL-cholesterol and triglycerides with the administration of Plantago ovata husk. CONCLUSIONS: Plantago ovata husk administration caused a smoothing and homogenization of levodopa absorption, providing more stable concentrations and final higher levels, resulting in a great benefit for patients. TRIAL REGISTRATION: EudraCT2006-000491-33.