What Factors Affect Diversity and Species Composition of Endangered Tumbesian Dry Forests in Southern Ecuador?

This paper reports a study on species richness and composition of Tumbesian dry forest communities. We tested two alternative hypotheses about species assemblage processes in tropical dry forests: (1) species assemblage is determined by the filtering effect of environmental conditions and (2) species assemblage is determined by facilitative processes along the gradient of water availability, and thus, species richness and evenness increase as water becomes limited. In addition, we also explored the effect of climate and soil conditions on species composition in tropical dry forests. Species composition was sampled in 109 plots in terms of cover and tree diameter at breast height. Climatic, edaphic, topographic and anthropogenic degradation variables were obtained for each plot. We used generalized linear models and canonical correspondence analyses to evaluate the effect of environmental variables on species composition, richness and evenness. Water availability negatively affected richness and significantly determined the species assemblage. Species richness increased from ridges to valleys and evenness increased at higher altitudes. Soil characteristics showed no effect on richness and evenness but soil moisture, nitrogen concentration and soil temperature explained significant fractions of species composition. Although timber extraction and livestock in our study area were of low intensity, it negatively affected richness but had only a minor effect on species composition. Our results suggest that species composition in these endangered tropical dry forests may be at least partially explained by the stress‐gradient hypothesis, with higher species richness at drier conditions probably induced by facilitation processes.     

What do we know about the secretion and degradation of incretin hormones?

The incretin hormones, glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1) are secreted from endocrine cells located in the intestinal mucosa, and act to enhance meal-induced insulin secretion. GIP and GLP-1 concentrations in the plasma rise rapidly after food ingestion, and the presence of unabsorbed nutrients in the intestinal lumen is a strong stimulus for their secretion. Nutrients can stimulate release of both hormones by direct contact with the K-cell (GIP) and L-cell (GLP-1), and this may be the most important signal. However, nutrients also stimulate GLP-1 and GIP secretion indirectly via other mechanisms. Incretin hormone secretion can be modulated neurally, with cholinergic muscarinic, beta-adrenergic and peptidergic (gastrin-releasing peptide, GRP) fibres generally having positive effects, while secretion is restrained by alpha-adrenergic and somatostatinergic fibres. Hormonal factors may also influence incretin hormone secretion. Somatostatin exerts a local inhibitory effect on the activity of both K- and L-cells via a paracrine mechanism, while, in rodents at least, GIP from the proximal intestine has a stimulatory effect on GLP-1 secretion, possibly mediated via a neural loop involving GRP. Once they have been released, both GLP-1 and GIP are subject to rapid degradation. The ubiquitous enzyme, dipeptidyl peptidase IV (DPP IV) cleaves N-terminally, removing a dipeptide and thereby inactivating both peptides, because the N-terminus is crucial for receptor binding. Subsequently, the peptides may be degraded by other enzymes and extracted in an organ-specific manner. The intact peptides are inactivated during passage across the hepatic bed and further metabolised by the peripheral tissues, while the kidney is important for the final elimination of the metabolites.     

What are we talking about when we talk about education and Chagas? A systematic review of the issue

More than 110 years has passed since the first publications on Chagas disease, and it still urges the necessity of understanding it as a complex socioenvironmental issue in which components of diverse nature converge and interact beyond the biomedical and epidemiological aspects. The current scenarios of the issue, both rural and Latin American as urban and global, demand that the education on Chagas disease include all possible contexts: where there are insect vectors and where there are not; inside and outside Latin America; in rural, periurban, and urban areas; in formal and non-formal educational environments. We consider essential the requirement of both an integral approach that overcomes the biomedical aspect to include the multidimensionality of the issue and a dialogical educational perspective that allows individuals and communities to analyze, decide, and lead contextualized prevention and promotion actions regarding their health. In this study, we surveyed, described, and critically analyzed studies approaching the link education-Chagas disease in scientific publications from the last 15 years. We aimed at contributing methodological-theoretical elements to (re)think the development of educational research and experiences that truly help facing this issue. From the electronic search of scientific literature in 6 databases, we found 426 articles, out of which we selected 25. We incorporated 10 articles from other sources to this initial corpus and performed both qualitative and quantitative analyses over the total number [35] to characterize the studied works in general, focusing on the conceptions on the Chagas disease issue and the underlying health education approaches.     

What have we learned about the kallikrein-kinin and renin-angiotensin systems in neurological disorders?

The kallikrein-kinin system(KKS) is an intricate endogenous pathway involved in several physiological and pathological cascades in the brain. Due to the pathological effects of kinins in blood vessels and tissues, their formation and degradation are tightly controlled. Their components have been related to several central nervous system diseases such as stroke, Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy and others. Bradykinin and its receptors(B1R and B2R) may have a role in the pathophysiology of certain central nervous system diseases. It has been suggested that kinin B1R is up-regulated in pathological conditions and has a neurodegenerative pattern, while kinin B2R is constitutive and can act as a neuroprotective factor in many neurological conditions. The renin angiotensin system(RAS) is an important blood pressure regulator and controls both sodium and water intake. AngⅡ is a potent vasoconstrictor molecule and angiotensin converting enzyme is the major enzyme responsible for its release. AngⅡ acts mainly on the AT1 receptor, with involvement in several systemic and neurological disorders. Brain RAS has been associated with physiological pathways, but is also associated with brain disorders. This review describes topics relating to the involvement of both systems in several forms of brain dysfunction and indicates components of the KKS and RAS that have been used as targets in several pharmacological approaches.     

What can we learn about the behaviour of red and grey squirrels from YouTube?

Citizen science has emerged as an important tool in biology, ecology, and conservation studies. In this paper, we examined YouTube (YT) videos featuring the behaviour of red (Sciurus vulgaris) and grey (Sciurus carolinensis) squirrels in Europe, in both urban and forest habitats. Our study shows that specific behaviours of these squirrels, such as aggression, grooming and calling, have frequently been recorded on YT videos. The present paper uses this open data for the first time to compare differences between the frequency of some types of behaviour in two habitats. Based on detrended correspondence analysis, we show a significant difference in sets of behaviours between two squirrel species. Our investigation show that YT can be a source for monitoring the behaviour of wild species, especially in urban habitats, thus affording insights into the species plasticity of urban individuals. YT, as part of citizen science, is a potential source of information in behavioural ecology.     

What do we know about the non-uniform perception of a phototropic stimulus in Phycomyces?

For a comprehensive study of phototropism in sporangiophores of the fungus Phycomyces, quantitative treatment of spatial aspects is necessary. The first step in quantifying spatial factors of phototropic signal processing is the elucidation of the non-uniform light profile, predominantly caused by a lens effect in the cylindrical body of the sporangiophore. Herein we compare recently presented theoretical and experimental studies of light profiles. Errors and ambiguities arising from instrumental limitations and arbitrary assumptions are revealed. On the other hand, by combining theoretical and experimental results we have been able to select out the reliable information, which can now be applied in phototropic studies.Dedicated to Professor Hans Mohr on the occasion of his 60th birthday     

What do we know about the mechanisms of aromatase inhibitor resistance?

Clinical trials have demonstrated the importance of aromatase inhibitor (AI) therapy in the effective treatment of hormone-dependent breast cancers. Yet, as with all prolonged drug therapy, resistance to aromatase inhibitors does develop. To date, the precise mechanism responsible for resistance to aromatase inhibitors is not completely understood. In this paper, several mechanisms of de novo/intrinsic resistance and acquired resistance to AIs are discussed. These mechanisms are hypothesized based on important findings from a number of laboratories.

To better understand this question, our lab has generated, in vitro, breast cancer cell lines that are resistant to aromatase inhibitors. Resistant cell lines were generated over a prolonged period of time using the MCF-7aro (aromatase overexpressed) breast cancer line. These cell lines are resistant to the aromatase inhibitors letrozole, anastrozole and exemestane and the anti-estrogen tamoxifen, for comparison. Two types of resistant cell lines have been generated, those that grow in the presence of testosterone (T) which is needed for cell growth, and resistant lines that are cultured in the presence of inhibitor only (no T). In addition to functional characterization of aromatase and ER in these resistant cell lines, microarray analysis has been employed in order to determine differential gene expression within the aromatase inhibitor resistant cell lines versus tamoxifen, in order to better understand the mechanism responsible for AI resistance on a genome-wide scale. We anticipate that our studies will generate important information on the mechanisms of AI resistance. Such information can be valuable for the development of treatment strategies against AI-resistant breast cancers.     

What can we learn from Einstein and Arrhenius about the optimal flow of our blood?

Background

The oxygen flow in humans and other higher animals depends on the erythrocyte-to-blood volume ratio, the hematocrit. Since it is physiologically favourable when the flow of oxygen transport is maximum it can be assumed that this situation has been achieved during evolution. If the hematocrit was too low, too few erythrocytes could transport oxygen. If it was too high, the blood would be very viscous, so that oxygen supply would again be reduced.

Methods

The theoretical optimal hematocrit can be calculated by considering the dependence of blood viscosity on the hematocrit. Different approaches to expressing this dependence have been proposed in the literature. Here, we discuss early approaches in hydrodynamics proposed by Einstein and Arrhenius and show that especially the Arrhenius equation is very appropriate for this purpose.

Results & conclusions

We show that despite considerable simplifications such as neglecting the deformation, orientation and aggregation of erythrocytes, realistic hematocrit values of about 40% can be derived based on optimality considerations. Also the prediction that the ratio between the viscosities of the blood and blood plasma at high shear rates nearly equals Euler's constant (2.718) is in good agreement with observed values. Finally, we discuss possible extensions of the theory. For example, we derive the theoretical optimal hematocrit for persevering divers among marine mammals to be 65%, in excellent agreement with the values observed in several species.

General significance

These considerations are very important for human and animal physiology since oxygen transport is an important factor for medicine and physical performance.     

What can we learn about ecology and evolution from the fossil record?

The increased application of abundance data embedded within a more detailed and precise environmental context is enabling paleontologists to explore more rigorously the dynamics and underlying processes of ecological and evolutionary change in deep time. Several recent findings are of special theoretical interest. Community membership is commonly more stable and persistent than expected by chance, even in the face of the extreme environmental changes of the Ice Ages, and major evolutionary novelties commonly lie dormant for tens of millions of years before the ecological explosions of the clades that possess them. As we discuss here, questions such as these cannot be adequately addressed without the use of the fossil record.     

What do we know about parasitic plants and the leaf economic spectrum?

对于寄生植物和叶经济谱,我们了解多少？ 叶经济谱(leaf economic spectrum, LES)对维管植物中的关键性叶片性状间的相关性进行了量化,并且将这些性状的大量变异信息提炼为一根单轴。叶经济谱的显著优势是其近乎完美的普适性,且已在诸多领域得到了广泛的研究。然而,对于寄生植物与叶经济谱框架间关系的研究仍相对缺乏。由于叶经济谱的部分驱动力是碳获取中的生理性权衡,因此从理论上而言,寄生植物中的异养性(其取代了叶片的一些基本功能)可能导致对叶经济谱的偏离。利用从TRY数据库中获得的全局叶片性状数据,本研究评价了TRY数据库对寄生植物的整体代表性情况,然后将寄生植物叶片性状的叶经济谱组与非寄生的对应植物进行了比较。尽管寄生植物有着独特的生理特征,但它们并未显著偏离叶经济谱,不过还是有一些例子可以表明存在着叶经济谱上位置和性状间的差异。尤为重要的是,TRY数据库未能很好地代表寄生植物,因而就此得出的任何结论都还是不成熟的。     

What Do We Really Know about Cellulose Biosynthesis in Higher Plants?

Cellulose biosynthesis is one of the most important biochemical processes in plant biology. Despite the considerable progress made during the last decade, numerous fundamental questions related to this key process in plant development are outstanding. Numerous models have been proposed through the years to explain the detailed molecular events of cellulose biosynthesis. Almost all models integrate solid experimental data with hypotheses on several of the steps involved in the process. Speculative models are...     

What do we know about salt stress in bryophytes?

Bryophytes are among the first plants that faced the terrestrial way of life. They settled almost all terrestrial habitats, but no extant seawater representatives are known. It is not widely documented how bryophytes cope with salt stress, but there are species inhabiting salty environments. Here, we present the current state of knowledge on salt stress biology in bryophytes.     

What do we know about Hawaiian ferns and lycophytes?

The Hawaiian Islands are home to one of the most distinctive fern and lycophyte floras in the world. Of the 144 native fern species, 76% are endemic and, including subspecies and varieties, 84% of the 167 native fern taxa are endemic. There are 15 native lycophyte species, 47% of which are endemic, and 16 taxa, 50% of which are endemic. I review here most of the available literature on Hawaiian ferns and lycophytes. Few species of ferns or lycophytes have been studied in any kind of detail and, for most, we only know basic classification and general ecological information. Although the total number of studies reviewed here is not large, research has been conducted on a wide range of topics including systematics, floristics, dispersal, phylogeny, biogeography, ecology, form and function, population genetics, microevolution, fern-animal and fern-fungi associations, reproductive biology, demography, ethnobotany, and conservation.