The limits to population density in birds and mammals

We address two fundamental ecological questions: what are the limits to animal population density and what determines those limits? We develop simple alternative models to predict population limits in relation to body mass. A model assuming that within‐species area use increases with the square of daily travel distance broadly predicts the scaling of empirical extremes of minimum density across birds and mammals. Consistent with model predictions, the estimated density range for a given mass, ‘population scope’, is greater for birds than for mammals. However, unlike mammals and carnivorous birds, expected broad relationships between body mass and density extremes are not supported by data on herbivorous and omnivorous birds. Our results suggest that simple constraints on mobility and energy use/supply are major determinants of the scaling of density limits, but further understanding of interactions between dietary constraints and density limits are needed to predict future wildlife population responses to anthropogenic threats.     

Stress distribution of three-unit fixed partial prostheses (conventional and pontic) supported by three or two implants: 3D finite element analysis of ductile materials

In implantology, when financial or biological feasibility limitations appear, it is necessary to use prostheses with geometries that deviate from the conventional, with a pontic in the absence of an intermediate implant. The aim of this study was analyze and understand the general differences in the stresses generated in implants, components and infrastructures according to the configuration of the prosthesis over three or two implants. Thus, this paper analyzes the von Mises equivalent stresses (VMES) of ductile materials on their external surfaces. The experimental groups: Regular Splinted Conventional Group (RCG), which had conventional infrastructures on 3 regular-length Morse taper implants (4x11?mm); Regular Splinted Pontic Group (RPG), which had infrastructures with intermediate pontics on 2 regular-length Morse taper implants (4x11?mm). The simulations of the groups were created with Ansys Workbench 10.0 software. The results revealed that the RPG presented greater areas of possible fragility due to higher stress concentrations, for example, in the cervical area of the union between the implant and component the top platform of the abutment, as well as greater coverage of the stress by the cervical implant threads. The RPG infrastructure was also more affected by stresses in the connection areas between the prostheses and on the occlusal surface. There is an advantage to using prostheses supported by a greater number of implants (RCG) because this decreases the stress in the analyzed structures and consequently improves stress dissipation to the supporting bone, which would preserve the system.     

Oxygen tension modulates extracellular vesicles and its miRNA contents in bovine embryo culture medium

The biotechnology for in vitro embryo production is becoming increasingly popular, being applied to humans and domestic animals. Embryo development can be achieved with either 20% or 5% oxygen tension. The extracellular vesicles (EVs) are secreted by different cell types and carry bioactive materials. Our objective was to determine the secretion pattern and micro RNA (miRNA) contents of EVs released in the bovine embryo culture environment—embryo and cumulus cell monolayer—on Days 3 and 7 of in vitro culture under two different oxygen tensions: High (20%) and low (5%). The EVs were isolated from the medium and analyzed to determine size, concentration, and miRNA levels. EVs concentration in low oxygen tension increased on Day 3 and decreased on Day 7. Additionally, altered EV miRNAs derived from the embryo‐cumulus culture medium were predicted to regulate survival and proliferation‐related pathways on Days 3 and 7. Moreover, miR‐210 levels decreased in EVs isolated from the culture medium under high oxygen tension suggesting that this miRNA can be used as a marker for normoxia since it is associated with low oxygen tension. In summary, this study provides knowledge of the oxygen tension effects on EVs release and content, and potentially, on cell‐to‐cell communication during in vitro bovine embryo production.     

Comparative polytene chromosome maps of <Emphasis Type="Italic">D. montana</Emphasis> and <Emphasis Type="Italic">D. virilis</Emphasis>

Chromosomal inversion polymorphism was characterized in Finnish Drosophila montana populations. A total of 14 polymorphic inversions were observed in Finnish D. montana of which nine had not been described before. The number of polymorphic inversions in each chromosome was not significantly different from that expected, assuming equal chance of occurrence in the euchromatic genome. There was, however, no correlation between the number of polymorphic inversions and that of fixed inversions in each chromosome. Therefore, a simple neutral model does not explain the evolutionary dynamics of inversions. Furthermore, in contrast to results obtained by others, no significant correlation was found between the two transposable elements (TEs) Penelope and Ulysses and inversion breakpoints in D. montana. This result suggests that these TEs were not involved in the creation of the polymorphic inversions seen in D. montana. A comparative analysis of D. montana and Drosophila virilis polytene chromosomes 4 and 5 was performed with D. virilis bacteriophage P1 clones, thus completing the comparative studies of the two species.     

Sting_RDB: a relational database of structural parameters for protein analysis with support for data warehousing and data mining

An effective strategy for managing protein databases is to provide mechanisms to transform raw data into consistent, accurate and reliable information. Such mechanisms will greatly reduce operational inefficiencies and improve one's ability to better handle scientific objectives and interpret the research results. To achieve this challenging goal for the STING project, we introduce Sting_RDB, a relational database of structural parameters for protein analysis with support for data warehousing and data mining. In this article, we highlight the main features of Sting_RDB and show how a user can explore it for efficient and biologically relevant queries. Considering its importance for molecular biologists, effort has been made to advance Sting_RDB toward data quality assessment. To the best of our knowledge, Sting_RDB is one of the most comprehensive data repositories for protein analysis, now also capable of providing its users with a data quality indicator. This paper differs from our previous study in many aspects. First, we introduce Sting_RDB, a relational database with mechanisms for efficient and relevant queries using SQL. Sting_rdb evolved from the earlier, text (flat file)-based database, in which data consistency and integrity was not guaranteed. Second, we provide support for data warehousing and mining. Third, the data quality indicator was introduced. Finally and probably most importantly, complex queries that could not be posed on a text-based database, are now easily implemented. Further details are accessible at the Sting_RDB demo web page: http://www.cbi.cnptia.embrapa.br/StingRDB.     

Leaf functional traits and monodominance in Southern Amazonia tropical forests

Tropical monodominant forests are rare communities with low tree species diversity. Species monodominance is not the product of a single mechanism, but the result of a set of not yet fully understood integrated ecological factors acting together. We compared populations of Brosimum rubescens in monodominant and mixed forests in Southern Amazonia to test whether leaf functional traits are ecological factors related to monodominance. Individuals of B. rubescens in the mixed forest invest in conservative strategies, while those in the monodominant forest invest in acquisitive strategies. Leaf functional traits, such as petiole length and adaxial cuticle thickness, could be associated with the monodominance of B. rubescens. Our study highlights for the first time the power of integrating leaf functional traits as a component of the set of ecological conditions to explain species monodominance. B. rubescens showed different functional strategies to establish and maintain its population in different forests, which makes it a strong competitor for resources, such as water and light, through variation in its leaf functional traits. We also suggest that such high plasticity can be an important condition for the persistence of the species over time.

     

Epiphytic cyanobacterial strains in the roots of Salvinia auriculata and the effect of light and nutrients on the production of heterocyst,akinete and hormogonia

Aquatic Ecology - In epiphytic associations, cyanobacteria form the periphyton with phytoplanktonic algae and with aquatic macrophytes. In this study, we found homocytous and heterocytous...     

Electrophysiological characterization of Tityus obscurus β toxin 1 (To1) on Na+-channel isoforms

To1, previously named Tc49b, is a peptide neurotoxin isolated from venom of the scorpion Tityus obscurus that is responsible for lethal human poisoning cases in the Brazilian Amazonian region. Previously, To1 was shown to be lethal to mice and to change Na⁺ permeation in cerebellum granular neurons from rat brain. In addition, To1 did not affect Shaker B K⁺ channels. Based on sequence similarities, To1 was described as a β-toxin. In the present work, To1 was purified from T. obscurus venom and submitted to an electrophysiological characterization in human and invertebrate Na_V channels. The analysis of the electrophysiological experiments reveal that To1 enhances the open probability at more negative potentials of human Na_V 1.3 and 1.6, of the insect channel BgNa_V1 and of arachnid VdNa_V1 channel. In addition, To1 reduces the peak of Na⁺ currents in some of the Na_Vs tested. These results support the classification of the To1 as a β-toxin. A structure and functional comparison to other β-toxins that share sequence similarity to To1 is also presented.     

Atlantic Forest topsoil nutrients can be resistant to disturbance and forest clearing

Human impacts can affect the soil properties through erosion and leaching, the ecosystem functions and, consequently, the capacity of a forest to regenerate. Here, we determine the effects of forest disturbance and succession on selected soil chemical properties using two different approaches, before‐after‐control‐impact (BACI) and space‐for‐time (SFT) substitution, and the threatened Atlantic Forest biome as model. We assessed with BACI the long‐term (37‐year) effects of clear cutting on soil properties by comparing data from two topsoil surveys (1978–2017) divided into two treatments: a preserved old growth forest (control) and an adjacent forest that was experimentally cleared with full tree removal (clear‐cut). We examined with SFT the relationship between stand age and soil properties using soil data from three old growth and 13 s growth forests ranging from 7 to 33 years. We found no significant differences between treatments for any soil property or significant changes in phosphorus, potassium, and calcium + magnesium over time. In contrast, pH increased and aluminum decreased in both areas. No relation was found between forest age and most of soil properties, with the exception of potassium which returned to old growth forest levels after 20 years of natural succession, and pH. BACI indicated that deforestation of old growth forest caused no significant effects on soil chemical properties after 37 years of regeneration. SFT demonstrated that soil properties did not change significantly during forest regeneration on formerly disturbed lands. Our findings indicate that natural nutrient‐depleted lowland forests were overall resistant to deforestation followed by passive regeneration at landscape scale. Abstract in Portuguese is available with online material.