Distribuição das frações do carbono orgânico nos solos de florestas maduras na bacia Amazônica: o papel das propriedades do solo, da qualidade da liteira e do clima

Soil organic carbon (SOC) stability is a function of environmental and biological conditions such as edaphic factors, climate and organic matter quality. Considering that a wide variation occurs in all these parameters across Amazonia, one could expect that there should be systematic variations in SOC fractions across the area. Understand the processes involved in carbon stabilization in tropical pristine forests is very important to improve our understanding of ecosystem function and to allow the preparation of better and more accurate models of soil carbon dynamics. We used soil carbon fractionation techniques to answer the following questions: (i) How the different soil carbon fractions are distributed among the different soil types, at varying depths (ii) How they are inter-related and (iii) What is the role of soil properties, climate and litter quality in modulating SOC fractions across the Amazon Basin. This study was carried out on 30 1 hectare pristine rainforest plots located at Brazil, Peru, Colombia and French Guyana. Our results show that SOC concentration in the different fractions vary following a soil weathering gradient, where soil carbon on young, more fertile soils is predominantly associated to relatively stable pools (silt+clay fraction) while highly weathered soils such as Ferralsols and Acrisols have large proportion of their soil carbon associated with stable aggregates. Very sandy and infertile soils have organic matter mainly associated with the maintenance of particulate organic matter on soil surface, which is clearly associated to poor organic matter quality and low decomposability. Concentration of SOC on most fractions was found to be mainly associated to edaphic properties, with the exception of the light fraction which is related to litter quality. We have found little evidence of climate influence on SOC fractions.A estabilidade do carbono orgânico no solo (SOC) é dependente das condições do ambiente, como o clima, fatores edáficos e qualidade da matéria orgânica. Assim, considerando-se que existe uma ampla variação destas condições na Bacia Amazônica, espera-se que a concentração de SOC em frações lábeis e estáveis varie também. Investigar esses processos em sistemas florestais naturais é importante para compreender os mecanismos de funcionamento do ecossistema e produzir modelos ecológicos de dinâmica do carbono com um grau maior de precisão. Neste estudo foram respondidas as seguintes questões: (i) como estão distribuídas as frações do SOC em diferentes tipos de solos e profundidades? (ii) como as frações do SOC estão inter-relacionadas? (iii) qual é o papel das propriedades do solo, da qualidade das folhas da liteira e das variáveis climáticas sobre a distribuição das frações do SOC ao longo da Bacia Amazônica? O estudo foi realizado em 30 parcelas de 1h de florestas maduras no Brasil, Peru, Colômbia e Guiana Francesa. Foram utilizadas técnicas de fracionamento da matéria orgânica do solo e análises químicas e físicas padronizadas do solo e liteira. Os resultados mostraram uma variação na concentração de SOC nas frações ao longo do gradiente de intemperismo do solo. Os solos mais jovens e férteis tenderam a apresentar maiores concentrações de SOC associada às frações minerais estáveis (silte+argila), enquanto os solos altamente intemperizados como Ferralsols e Acrisols apresentaram maiores concentrações de SOC nos agregados do solo. Os solos arenosos e altamente inférteis tenderam a apresentar maiores concentrações de SOC nas frações leve, entretanto a labilidade dessa fração da MOS pode variar dependendo da qualidade da matéria orgânica. A concentração de SOC nas frações do solo demonstrou ser principalmente controlada pelos fatores edáficos, com exceção da fração leve que apresentou relação forte com a qualidade da liteira. Nós encontramos poucas evidências do efeito direto do clima sobre as frações de SOC

Efeitos de diferentes espécies pioneiras sobre a colonização de Podocarpus lambertii em uma área em restauração

Biotic interactions between pioneer and late-successional species may affect the spatial arrangement of the individuals in plant communities resulting in positive or negative patterns of association. Studies that analyze the plant colonization patterns in areas of natural forest regeneration are important to ecological restoration projects. The aim of this work is to investigate the population structure and the spatial distribution of Podocarpus lambertii (Podocarpaceae) in a restoration area, verifying the effect of pioneer plant species on P. lambertii recruitment. The work was performed in a 1 ha degraded area in the National Forest of São Francisco de Paula, RS, Brazil. In contiguous plots of 10 x 10 m all individuals of P. lambertii and adult individuals of the pioneer species Baccharis uncinella and Vernonia discolor were mapped and measured. The P. lambertii population maintained itself stable during the study period, with the number of individuals in each size class reasonably constant. Juveniles of P. lambertii were negatively associated with the pioneer B. uncinella indicating a competitive interaction, and were positively associated with V. discolor individuals, indicating facilitation. These results may contribute to the development of management techniques for the restoration of degraded areas in southern Brazil. Key words: spatial associations, competition, facilitation, Araucaria Forest, forest regeneration.Interações ecológicas entre espécies pioneiras e tardias influenciam o arranjo espacial de indivíduos em comunidades vegetais, resultando em associações espaciais positivas ou negativas. Estudos que analisam esses padrões espaciais em áreas em processos de regeneração são importantes para projetos de restauração florestal. O objetivo deste trabalho foi investigar a estrutura populacional e a distribuição espacial de Podocarpus lambertii Klotsch (Podocarpaceae) em uma área em processo de regeneração, verificando o efeito das espécies pioneiras nativas sobre os regenerantes dessa espécie. O trabalho foi realizado em uma área degradada de 1 ha em estágio inicial de sucessão na Floresta Nacional (FLONA) de São Francisco de Paula, RS, Brasil. Em parcelas contíguas de 10 x 10 m, foram medidos e mapeados todos os indivíduos de P. lambertii e os indivíduos das pioneiras nativas Baccharis uncinella e Vernonia discolor. A população de P. lambertii manteve-se estável ao longo do estudo, sendo que o número de indivíduos nas classes de tamanho manteve-se razoalvelmente constante. Os regenerantes de P. lambertii apresentaram-se negativamente associados à pioneira B. uncinella, indicando competição, e positivamente associados à pioneira V. discolor, indicando facilitação. Esses resultados podem contribuir com o desenvolvimento de técnicas de manejo para a restauração de áreas degradadas no sul do Brasil. Palavras-chave: associações espaciais, competição, facilitação, Floresta Ombrófila Mista, regeneração florestal

Fertilidade de sêmen suíno avaliada pelo teste de ligação dos espermatozóides a um substrato sintético

The objective of this work was to evaluate boar semen fertility by a sperm-binding assay to a synthetic substrate. Motility (MOT) and percentage of bound sperm (PSB) were evaluated after 5, 24, 48 and 72 hours of storage at 17°C. PSB was analyzed in solutions containing 6.25 or 12.5 million of spermatozoa/mL, with or without bovine serum albumin (BSA), processed from two to five ejaculates of four boars. Fifty eight gilts were inseminated, a single time, 24 hours after the beginning of estrus. There was a positive correlation (P = 0.0001; r = 0.33) between MOT and PSB. Higher percentages of PSB were observed with 12.5 million of spermatozoa/mL and in the presence of BSA (P < 0.05). After 72 hours, boar 3 showed lower PSB (P < 0.05) than the other boars. The cleavage (TC) and normal embryo rates did not differ among boars, but boar 3 showed less than 70.0% of TC belonging to the superior quartile while boars 1, 2 and 4 had more than 75.0%. After 24 hours of sperm storage, boars differ in their sperm binding to the synthetic substrate. Binding of swine spermatozoa to the synthetic substrate is higher in the presence of BSA and with the increase of spermatic concentration.O objetivo deste trabalho foi avaliar a fertilidade de sêmen suíno pelo teste de ligação de espermatozóides a um substrato sintético. A motilidade (MOT) e o porcentual de espermatozóides ligados (PEL) foram avaliados após 5, 24, 48 e 72 horas de armazenamento a 17ºC. O PEL foi determinado em soluções contendo 6,25 ou 12,5 milhões de espermatozóides/mL, com ou sem albumina sérica bovina (BSA), preparadas a partir de dois a cinco ejaculados de cada um dos quatro machos. Cinqüenta e oito leitoas foram inseminadas, uma vez, 24 horas após o início do estro. Houve correlação positiva (P = 0,0001; r = 0,33) entre a MOT e o PEL. O PEL foi maior com 12,5 milhões de  espermatozóides/mL e na presença de BSA (P < 0,05). Após 72 horas, o macho 3 apresentou PEL inferior ao dos outros três (P < 0,05). As taxas de clivagem (TC) e de embriões morfologicamente normais não diferiram entre indivíduos, mas o macho 3 apresentou menos de 70,0% de TC no quartil superior, enquanto os outros tiveram mais de 75,0%. Os machos diferem quanto à capacidade de ligação de seus espermatozóides ao substrato sintético, a partir de 24 horas de armazenamento do sêmen. A ligação dos espermatozóides ao substrato sintético é maior com a inclusão de BSA e com o aumento da concentração espermática

Longitudinal changes of SARA scale in Friedreich ataxia: Strong influence of baseline score and age at onset

BACKGROUND: The Scale for Assessment and Rating of Ataxia (SARA) is widely used in different types of ataxias and has been chosen as the primary outcome measure in the European natural history study for Friedreich ataxia (FA). METHODS: To assess distribution and longitudinal changes of SARA scores and its single items, we analyzed SARA scores of 502 patients with typical-onset FA (<25 years) participating in the 4-year prospective European FA Consortium for Translational Studies (EFACTS). Pattern of disease progression was determined using linear mixed-effects regression models. The chosen statistical model was re-fitted in order to estimate parameters and predict disease progression. Median time-to-change and rate of score progression were estimated using the Kaplan-Meier method and weighted linear regression models, respectively. RESULTS: SARA score at study enrollment and age at onset were the major predictive factors of total score progression during the 4-year follow-up. To a less extent, age at evaluation also influenced the speed of SARA progression, while disease duration did not improve the prediction of the statistical model. Temporal dynamics of total SARA and items showed a great variability in the speed of score increase during disease progression. Gait item had the highest annual progression rate, with median time for one-point score increase of 1 to 2 years. INTERPRETATION: Analyses of statistical properties of SARA suggest a variable sensitivity of the scale at different disease stages, and provide important information for population selection and result interpretation in future clinical trials

Common genetic variation and susceptibility to partial epilepsies: a genome-wide association study

Partial epilepsies have a substantial heritability. However, the actual genetic causes are largely unknown. In contrast to many other common diseases for which genetic association-studies have successfully revealed common variants associated with disease risk, the role of common variation in partial epilepsies has not yet been explored in a well-powered study. We undertook a genome-wide association-study to identify common variants which influence risk for epilepsy shared amongst partial epilepsy syndromes, in 3445 patients and 6935 controls of European ancestry. We did not identify any genome-wide significant association. A few single nucleotide polymorphisms may warrant further investigation. We exclude common genetic variants with effect sizes above a modest 1.3 odds ratio for a single variant as contributors to genetic susceptibility shared across the partial epilepsies. We show that, at best, common genetic variation can only have a modest role in predisposition to the partial epilepsies when considered across syndromes in Europeans. The genetic architecture of the partial epilepsies is likely to be very complex, reflecting genotypic and phenotypic heterogeneity. Larger meta-analyses are required to identify variants of smaller effect sizes (odds ratio <1.3) or syndrome-specific variants. Further, our results suggest research efforts should also be directed towards identifying the multiple rare variants likely to account for at least part of the heritability of the partial epilepsies. Data emerging from genome-wide association-studies will be valuable during the next serious challenge of interpreting all the genetic variation emerging from whole-genome sequencing studie

Epilepsy, hippocampal sclerosis and febrile seizures linked by common genetic variation around SCN1A

Epilepsy comprises several syndromes, amongst the most common being mesial temporal lobe epilepsy with hippocampal sclerosis. Seizures in mesial temporal lobe epilepsy with hippocampal sclerosis are typically drug-resistant, and mesial temporal lobe epilepsy with hippocampal sclerosis is frequently associated with important co-morbidities, mandating the search for better understanding and treatment. The cause of mesial temporal lobe epilepsy with hippocampal sclerosis is unknown, but there is an association with childhood febrile seizures. Several rarer epilepsies featuring febrile seizures are caused by mutations in SCN1A, which encodes a brain-expressed sodium channel subunit targeted by many anti-epileptic drugs. We undertook a genome-wide association study in 1018 people with mesial temporal lobe epilepsy with hippocampal sclerosis and 7552 control subjects, with validation in an independent sample set comprising 959 people with mesial temporal lobe epilepsy with hippocampal sclerosis and 3591 control subjects. To dissect out variants related to a history of febrile seizures, we tested cases with mesial temporal lobe epilepsy with hippocampal sclerosis with (overall n = 757) and without (overall n = 803) a history of febrile seizures. Meta-analysis revealed a genome-wide significant association for mesial temporal lobe epilepsy with hippocampal sclerosis with febrile seizures at the sodium channel gene cluster on chromosome 2q24.3 [rs7587026, within an intron of the SCN1A gene, P = 3.36 × 10−9, odds ratio (A) = 1.42, 95% confidence interval: 1.26-1.59]. In a cohort of 172 individuals with febrile seizures, who did not develop epilepsy during prospective follow-up to age 13 years, and 6456 controls, no association was found for rs7587026 and febrile seizures. These findings suggest SCN1A involvement in a common epilepsy syndrome, give new direction to biological understanding of mesial temporal lobe epilepsy with hippocampal sclerosis with febrile seizures, and open avenues for investigation of prognostic factors and possible prevention of epilepsy in some children with febrile seizure

Common genetic variation and susceptibility to partial epilepsies: a genome-wide association study

Partial epilepsies have a substantial heritability. However, the actual genetic causes are largely unknown. In contrast to many other common diseases for which genetic association-studies have successfully revealed common variants associated with disease risk, the role of common variation in partial epilepsies has not yet been explored in a well-powered study. We undertook a genome-wide association-study to identify common variants which influence risk for epilepsy shared amongst partial epilepsy syndromes, in 3445 patients and 6935 controls of European ancestry. We did not identify any genome-wide significant association. A few single nucleotide polymorphisms may warrant further investigation. We exclude common genetic variants with effect sizes above a modest 1.3 odds ratio for a single variant as contributors to genetic susceptibility shared across the partial epilepsies. We show that, at best, common genetic variation can only have a modest role in predisposition to the partial epilepsies when considered across syndromes in Europeans. The genetic architecture of the partial epilepsies is likely to be very complex, reflecting genotypic and phenotypic heterogeneity. Larger meta-analyses are required to identify variants of smaller effect sizes (odds ratio <1.3) or syndrome-specific variants. Further, our results suggest research efforts should also be directed towards identifying the multiple rare variants likely to account for at least part of the heritability of the partial epilepsies. Data emerging from genome-wide association-studies will be valuable during the next serious challenge of interpreting all the genetic variation emerging from whole-genome sequencing studies