Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Avaliação dos níveis de peroxidação lipídica em células da mucosa cólica após aplicação de enemas com peróxido de hidrogênio: estudo experimental em ratos Evaluation of lipid peroxidation levels on mucosa colonic cells afther application of hydrogen peroxide in enemas: experimental study in rats

A aplicação de clisteres contendo peróxido de hidrogênio (H2O2) determina o aparecimento de quadros graves de colite, algumas vezes de evolução fatal. É possível que a colite induzida por H2O2 possa ocorrer pela quebra da barreira funcional do epitélio cólico por estresse oxidativo. Objetivo: Avaliar os níveis de peroxidação lipídica em células da mucosa cólica após instilação de H2O2 no reto excluso de trânsito fecal. Método: Vinte seis ratos Wistar machos foram submetidos a colostomia proximal terminal no cólon descendente e fístula mucosa distal. Os animais foram randomizados em dois grupos segundo o sacrifício ter sido realizado duas ou quatro semanas após a derivação intestinal. Cada grupo experimental foi dividido e dois subgrupos segundo aplicação de clisteres, em dias alternados, contendo solução fisiológica a 0,9% ou H2O2 a 3%. O diagnóstico de colite foi estabelecido por estudo histopatológico e os níveis de dano oxidativo tecidual pela dosagem de malondialdeído por espectrofotometria. Os resultados foram analisados com os testes de Mann-Whitney e Kruskal-Wallis, estabelecendo-se nível de significância de 5% (p<0,05). Resultados: Os níveis de malondialdeído nos irrigados com SF nos cólons com e sem trânsito fecal após duas e quatro semanas de irrigação foram de: 0,05 ± 0,006; 0,06 ± 0,006 e 0,05 ± 0,03, 0,08 ± 0,02, respectivamente. Os níveis de malondialdeído nos irrigados com H2O2, nos cólons com e sem trânsito, após duas e quatro semanas de irrigação foram de 0,070 ± 0,006; 0,077 ± 0,01 e 0,052 ± 0,01, 0,08 ± 0,04, respectivamente. Após duas semanas os níveis de malondialdeído foram maiores nos animais irrigados com H2O2 em relação ao grupo controle (p= 0,007 e p= 0,01, respectivamente). Após quatro semanas não houve diferenças significantes Não ocorreu variação nos níveis de malondialdeído com o decorrer tempo de irrigação. Conclusão: Clisteres com H2O2, podem determinar o aparecimento de colite por ocasionarem estresse oxidativo nas células epiteliais da mucosa intestinal.<br>The use of rectal enemas with hydrogen peroxide (H2O2) determines the onset of severe colitis, sometimes with fatal evolution. It is possible that H2O2-induced colitis can occur by damage to the functional epithelial barrier of the colon by oxidative stress. Objective: The aim of present study was evaluate the levels of lipid peroxidation in cells of the colonic mucosa after instillation of H2O2 into the rectum excluded from fecal transit. Method: Twenty six male Wistar rats were undergone to proximal terminal colostomy in the descending colon and distal mucous fistula. The animals were randomized in two experimental groups according to the sacrifice was made two or four weeks after diversion of the fecal stream. Each experimental group was divided into two subgroups second application of enemas containing saline solution 0.9% or 3% H2O2 on alternate days. The diagnosis of colitis was established by histopathology study and the oxidative damage by tissue levels of malondialdehyde quantified by spectrophotometry. The results were analyzed with the Mann-Whitney and Kruskal-Wallis test, adopting a significance level of 5% (p <0.05). Results: The levels of malondialdehyde in colon segments irrigated with saline, with and without fecal stream after two and four weeks of irrigation were: 0.05 ± 0.006, 0.06 ± 0.006 and 0.05 ± 0.03, 0.08 ± 0.02, respectively. The levels of malondialdehyde in colon segments irrigated with H2O2, in the colon with and without fecal stream, after two and four weeks of irrigation were 0.070 ± 0.006, 0.077 and 0.052 ± 0.01 ± 0.01, 0.08 ± 0.04, respectively . After two weeks the levels of malondialdehyde were higher on animals irrigated with H2O2 than control group (p = 0.007 and p = 0.01, respectively). After four weeks there were no significant differences in malondialdehyde levels related with the time of irrigation. Conclusion: Rectal enemas with H2O2, may determine the onset of colitis by oxidative stress on epithelial cells of intestinal mucosa

Three-dimensional and stereological characterization of the human substantia nigra during aging

The human brain undergoes non-uniform changes during aging. The substantia nigra (SN), the source of major dopaminergic pathways in the brain, is particularly vulnerable to changes in the progression of several age-related neurodegenerative diseases. To establish normative data for high-resolution imaging, and to further clinical and anatomical studies we analyzed SNs from fifteen subjects aged 50–91 cognitively normal human subjects without signs of parkinsonism. Complete brains or brainstems with substantia nigra were formalin fixed, celloidin-mounted, serially cut and Nissl-stained. The shapes of all SNs investigated were reconstructed using fast, high-resolution computer-assisted 3D reconstruction software. We found a negative correlation between age and SN volume (p=0.04 rho=−0.53), with great variability in neuronal numbers and density across participants. The 3D reconstructions revealed SN inter- and intra-individual variability. Furthermore, we observed that human SN is a neuronal reticulum, rather than a group of isolated neuronal islands. Caution is required when using SN volume as a surrogate for SN status in individual subjects. The use of multimodal sequences including those for fiber tracts may enhance the value of imaging as a diagnostic tool to assess SN in vivo. Further studies with a larger sample size are needed for understanding the structure-function interaction of human SN

Water table depth modulates productivity and biomass across Amazonian forests

Aim: Water availability is the major driver of tropical forest structure and dynamics. Most research has focused on the impacts of climatic water availability, whereas remarkably little is known about the influence of water table depth and excess soil water on forest processes. Nevertheless, given that plants take up water from the soil, the impacts of climatic water supply on plants are likely to be modulated by soil water conditions. Location: Lowland Amazonian forests. Time period: 1971–2019. Methods: We used 344 long-term inventory plots distributed across Amazonia to analyse the effects of long-term climatic and edaphic water supply on forest functioning. We modelled forest structure and dynamics as a function of climatic, soil-water and edaphic properties. Results: Water supplied by both precipitation and groundwater affects forest structure and dynamics, but in different ways. Forests with a shallow water table (depth <5 m) had 18% less above-ground woody productivity and 23% less biomass stock than forests with a deep water table. Forests in drier climates (maximum cumulative water deficit < −160 mm) had 21% less productivity and 24% less biomass than those in wetter climates. Productivity was affected by the interaction between climatic water deficit and water table depth. On average, in drier climates the forests with a shallow water table had lower productivity than those with a deep water table, with this difference decreasing within wet climates, where lower productivity was confined to a very shallow water table. Main conclusions: We show that the two extremes of water availability (excess and deficit) both reduce productivity in Amazon upland (terra-firme) forests. Biomass and productivity across Amazonia respond not simply to regional climate, but rather to its interaction with water table conditions, exhibiting high local differentiation. Our study disentangles the relative contribution of those factors, helping to improve understanding of the functioning of tropical ecosystems and how they are likely to respond to climate change