Habitat fragmentation,EFN‐bearing trees and ant communities: Ecological cascades in Atlantic Forest of northeastern Brazil

Habitat fragmentation has a marked impact on the functional composition of tropical forest tree assemblages, and such change is likely to cascade through other trophic levels. Here, we investigate how habitat fragmentation affects extrafloral nectary (EFN)‐bearing plants and ant functional groups known to attend EFNs in a fragmented landscape of the Atlantic Forest. Extrafloral nectary‐bearing trees were identified in 50 0.1‐ha plots located in forest fragments, edge and interior patches. Ants were surveyed in 30 1‐m² litter samples in each of 17 forest fragments and in forest interior. Extrafloral nectary‐bearing plants accounted for 19.9% of individuals and 10.5% of species and included both pioneer and shade‐tolerant species similarly rich in the three habitat types. However, shade‐tolerant individuals accounted for >80% of EFN‐bearing plants in forest interior, compared with 2% in forest edge and 29% in fragments. Forest edge and fragment plots had a third fewer EFN‐bearing individuals and species compared with forest interior. This appeared to have important implications for local ant communities as the density of EFN‐bearing trees was the most important variable explaining the species richness of arboreal dominant ants. Our results show that plant loser–winner replacements promoted by forest fragmentation can cascade through higher trophic levels, with implications for forest dynamics and biodiversity conservation.     

Passive Restoration of Atlantic Forest Following Pinus taeda Harvesting in Southern Brazil

The understory of exotic tree plantations can have non‐negligible native species richness. Ecological restoration of these sites may include the harvest of trees, depending on the tradeoff between timber income and harvest impacts on biodiversity. This study aimed to investigate how a site can recover from harvest disturbance, by comparing the regeneration of woody species in the understory of two types of 37‐year‐old Pinus taeda plantation (P1 and P2, high and low relative density of pine seedlings in the understory, respectively), with stands that were similar to P2 but subjected to harvest and then abandoned for 15 years (R sites). Secondary forests (SF) were used as references. We sampled three different sites for each stand condition; soil chemical properties, estimations of litter mass, and canopy cover were measured. P1 had low species diversity, and P2 and R had 50 and 46% of SF richness, respectively. The R site contained few pine saplings and was floristically similar to P2; this indicated that 15 years was sufficient for the recovery of plant diversity to near pre‐harvesting levels. Soil fertility was highest in SF and lowest in P1. Thus old plantations of P. taeda with low relative density of pine juveniles can be cost‐effective starting points for restoration. Despite the destructive effects of pine harvest, recovery of native species can occur rapidly. In situations in which clearcutting of pine stands is not planned or possible, modest thinning of P. taeda adults and/or intensive thinning of juveniles could expedite restoration.     

Modulation of Mouse Embryonic Stem Cell Proliferation and Neural Differentiation by the P2X7 Receptor

Background

Novel developmental functions have been attributed to the P2X7 receptor (P2X7R) including proliferation stimulation and neural differentiation. Mouse embryonic stem cells (ESC), induced with retinoic acid to neural differentiation, closely assemble processes occurring during neuroectodermal development of the early embryo.

Principal Findings

P2X7R expression together with the pluripotency marker Oct-4 was highest in undifferentiated ESC. In undifferentiated cells, the P2X7R agonist Bz-ATP accelerated cell cycle entry, which was blocked by the specific P2X7R inhibitor KN-62. ESC induced to neural differentiation with retinoic acid, reduced Oct-4 and P2X7R expression. P2X7R receptor-promoted intracellular calcium fluxes were obtained at lower Bz-ATP ligand concentrations in undifferentiated and in neural-differentiated cells compared to other studies. The presence of KN-62 led to increased number of cells expressing SSEA-1, Dcx and β3-tubulin, as well as the number of SSEA-1 and β3-tubulin-double-positive cells confirming that onset of neuroectodermal differentiation and neuronal fate determination depends on suppression of P2X7R activity. Moreover, an increase in the number of Ki-67 positive cells in conditions of P2X7R inhibition indicates rescue of progenitors into the cell cycle, augmenting the number of neuroblasts and consequently neurogenesis.

Conclusions

In embryonic cells, P2X7R expression and activity is upregulated, maintaining proliferation, while upon induction to neural differentiation P2X7 receptor expression and activity needs to be suppressed.     

Neuroprotective effect of exercise in rat hippocampal slices submitted to in vitro ischemia is promoted by decrease of glutamate release and pro‐apoptotic markers

The role of physical exercise as a neuroprotective agent against ischemic injury has been extensively discussed. Nevertheless, the mechanisms underlying the effects of physical exercise on cerebral ischemia remain poorly understood. Here, we investigate the hypothesis that physical exercise increases ischemic tolerance by decreasing the induction of cellular apoptosis and glutamate release. Rats (n = 50) were submitted to a swimming exercise protocol for 8 weeks. Hippocampal slices were then submitted to oxygen and glucose deprivation. Cellular viability, pro‐apoptotic markers (Caspase 8, Caspase 9, Caspase 3, and apoptosis‐inducing factor), and glutamate release were analyzed. The percentage of cell death, the amount of glutamate release, and the expression of the apoptotic markers were all decreased in the exercise group when compared to the sedentary group after oxygen and glucose deprivation. Our results suggest that physical exercise protects hippocampal slices from the effects of oxygen and glucose deprivation, probably by a mechanism involving both the decrease of glutamatergic excitotoxicity and apoptosis induction.

     

Reti trofiche e flussi di energia nei sistemi a fanerogame marine

Abstract

Food webs and energy flow in seagrass ecosystems. A review on the pathways in the food webs of seagrass ecosystems, both tropical and temperate, with a particular emphasis to Mediterranean Posidonia oceanica meadows is given. Three main pathways of energy transfer from primary producers (host plant and algal epiphytes) were identified: i) the plant itself through photosynthetic tissue; ii) the leaf detritus which in some species forms a litter compartment; iii) the algal epiphytes of leaf blades. The detritus and epiphyte ways are the most common, but they can be differently important according to the season and the spatial patterns of the meadows.     

Sperm quality of spontaneously occurring gynogenetic males in the yellowtail tetra Astyanax altiparanae

Gynogenesis is a chromosomal manipulation technique where an offspring is generated exclusively from maternal inheritance. In the yellowtail tetra (Astyanax altiparanae) almost all gynogenetic fish were females, suggesting a genetic sex determination system of XX/XY. However, due to environmental (e.g. temperature) or unknown genetic factors, the rise of males are described. Therefore, the aim of this study was to analyze the reproductive parameters of spontaneously gynogenetic males. The parameters analyzed were spermatozoon viability, motility and ploidy. Additionally, the gonads were processed for histology and the genetic inheritance confirmed by genotyping. Sperm parameters of gynogenetic males did not show differences when compared with semen of normal males. These data supports that gynogenetic males presents fertilization capacity and can be used for future studies of chromosome manipulation or possible production of monosex populations in A. altiparanae.     

Comparative Experimental Study of Wound Healing in Mice: Pelnac versus Integra

Strategies for skin regeneration have been developed to provide effective treatment for cutaneous wounds and disease. Dermal substitutes have been used to cover the lesion to facilitate cell colonization, thereby promoting dermal regeneration. However, very little is known about Pelnac matrix especially at histological level. Therefore, the present work carried out an experimental in vivo comparative analysis between Pelnac and Integra, the most used dermal templates, in a mouse model of full-thickness skin wounds. Histological sections performed at the 3^rd, 6^th and 9^th days after surgery were analyzed with regard to inflammatory response and vascularization. Both templates were completely incorporated in all animals at the end of the analyzed period. Pelnac-treated animals displayed reduced granulation tissue during the first 6 days of treatment compared to the animals treated with Integra at the same time period. The number of inflammatory cells (neutrophils) was similar in both groups during the period, significantly reducing at the end of inflammatory phase (9^th day of treatment) consistent with the progression of healing process. In addition, the density of blood vessels was also statistically similar in both matrices. Therefore, the two dermal templates displayed comparable biological behavior in tissue repair. It is noteworthy that this is the first experimental study comparing Pelnac and Integra dermal templates with focus on full-thickness skin wounds.     

Climate change and the ecophysiology of Bertholletia excelsa seedlings

Plant Growth Regulation - The Bertholletia excelsa a species native to the Amazon region of great national and international interest, mainly for the nutritional benefits of its seeds. However,...     

Presence,localization and morphology of TELOCYTES in developmental gonads of fishes

Telocytes are a new defined type of interstitial cells, considered as a stem cell, with very long and thin cytoplasmic extensions. They are present in the vertebrates, and may participate in tissue remodeling. In fish, during gonadal development, the events that culminate with the germinal epithelium formation are well known. However, the interstitial compartment remains poorly explored, although it may have a great contribution to the morpho-functional changes that occur in the gonad. As in other organisms, in fish, the interstitium consists especially of connective tissue elements. However, until now, there are no reports of the presence and the action of the telocytes in the connective tissue of gonads of fish. Thus, this study aimed to detect the presence, localization and morphology of telocytes during the gonadal development of several species of fish. The gonads were analyzed by light microscopy, transmission electron microscopy and immunohistochemistry for localization of CD34, Vimentin, and metalloproteinases. The presence of two proteins characteristics of mesenchymal cell was detected in cells of the gonads of all species. In addition, they presented a typical morphology of telocytes, showing cellular extensions. Gonadal telocytes also presented positive response to metalloproteinases. In mammals, telocytes can undergo de-differentiation contributing to the reorganization of the extracellular matrix. This role may be performed by the metalloproteinases detected here. The detection of Vimentin and CD34 in the same cellular type, associated with its morphological characteristics, allows us to conclude that some interstitial cells in Teleostei are considered telocytes, identical to the ones already described in mammals and other vertebrates.     

Detection of human bocavirus mRNA in respiratory secretions correlates with high viral load and concurrent diarrhea

Human bocavirus (HBoV) is a parvovirus recently identified in association with acute respiratory infections (ARI). Despite its worldwide occurrence, little is known on the pathogenesis of HBoV infections. In addition, few systematic studies of HBoV in ARI have been conducted in Latin America. Therefore, in order to test whether active viral replication of human bocavirus is associated with respiratory diseases and to understand the clinical impact of this virus in patients with these diseases, we performed a 3-year retrospective hospital-based study of HBoV in outpatients and inpatients with symptoms of Acute Respiratory Infections (ARI) in Brazil. Nasopharyngeal aspirates (NPAs) from 1015 patients with respiratory symptoms were tested for HBoV DNA by PCR. All samples positive for HBoV were tested by PCR for all other respiratory viruses, had HBoV viral loads determined by quantitative real time PCR and, when possible, were tested by RT-PCR for HBoV VP1 mRNA, as evidence of active viral replication. HBoV was detected in 4.8% of patients, with annual rates of 10.0%, 3.0% and 3.0% in 2005, 2006 and 2007, respectively. The range of respiratory symptoms was similar between HBoV-positive and HBoV-negative ARI patients. However, a higher rate of diarrhea was observed in HBoV-positive patients. High HBoV viral loads (>10⁸ copies/mL) and diarrhea were significantly more frequent in patients with exclusive infection by HBoV and in patients with detection of HBoV VP1 mRNA than in patients with viral co-infection, detected in 72.9% of patients with HBoV. In summary, our data demonstrated that active HBoV replication was detected in a small percentage of patients with ARI and was correlated with concurrent diarrhea and lack of other viral co-infections.