Phylogenetic and functional underdispersion in Neotropical phyllostomid bat communities

Habitat conversion creates a mosaic of land cover types, which affect the spatial distribution, diversity, and abundance of resources. We used abundance, functional, and phylogenetic information to determine if Neotropical bat communities exhibited phylogenetic or functional overdispersion or underdispersion in response to habitat conversion. Overdispersion suggests the operation of intraclade competition, niche partitioning, limiting similarity, or character displacement, whereas underdispersion indicates the operation of interclade competition, abiotic filtering, or biotic filtering. We expected (1) biotic filtering in landscapes with extensive forest loss to result in underdispersion; (2) niche partitioning in heterogeneous landscapes with intermediate forest loss to result in overdispersion; and (3) intraclade competition during times of low resource abundance (i.e., dry season) to increase, resulting in overdispersion. Most bat communities exhibited phylogenetic or functional underdispersion; none exhibited overdispersion. Expectations were not met: underdispersion did not increase with forest loss, heterogeneous landscapes did not induce overdispersion, and no evidence supported the contention that intraclade competition changed with season. Empirical responses were season‐specific, likely because resource availability may affect relationships between forest cover and underdispersion and between biodiversity and underdispersion. During the dry season, only high diversity sites exhibited underdispersion (i.e., functional or phylogenetic redundancy), whereas underdispersion occurred in low, intermediate, or high diversity communities during the wet season; we suggest that this difference likely arises due to changes in resource abundance. Communities with high diversity and redundancy occupied heterogeneous sites during the dry season, but communities with high redundancy were restricted to large forest reserves during the wet season.     

Revealing early steps of alpha2beta1 integrin-mediated adhesion to collagen type I by using single-cell force spectroscopy

We have characterized early steps of alpha(2)beta(1) integrin-mediated cell adhesion to a collagen type I matrix by using single-cell force spectroscopy. In agreement with the role of alpha(2)beta(1) as a collagen type I receptor, alpha(2)beta(1)-expressing Chinese hamster ovary (CHO)-A2 cells spread rapidly on the matrix, whereas alpha(2)beta(1)-negative CHO wild-type cells adhered poorly. Probing CHO-A2 cell detachment forces over a contact time range of 600 s revealed a nonlinear adhesion response. During the first 60 s, cell adhesion increased slowly, and forces associated with the smallest rupture events were consistent with the breakage of individual integrin-collagen bonds. Above 60 s, a fraction of cells rapidly switched into an activated adhesion state marked by up to 10-fold increased detachment forces. Elevated overall cell adhesion coincided with a rise of the smallest rupture forces above the value required to break a single-integrin-collagen bond, suggesting a change from single to cooperative receptor binding. Transition into the activated adhesion mode and the increase of the smallest rupture forces were both blocked by inhibitors of actomyosin contractility. We therefore propose a two-step mechanism for the establishment of alpha(2)beta(1)-mediated adhesion as weak initial, single-integrin-mediated binding events are superseded by strong adhesive interactions involving receptor cooperativity and actomyosin contractility.     

The E2FC-DPB Transcription Factor Controls Cell Division,Endoreplication and Lateral Root Formation in a SCFSKP2A-Dependent Manner

Cell division is a highly regulated process that has to be coordinated with cell specification and differentiation for proper development and growth of the plants. Cell cycle regulation is carried out by key proteins that control cell cycle entry, progression and exit. This regulation is controlled at different stages such as gene expression, posttranslational modification of proteins and specific proteolysis. The G₁/S and the G₂/M transitions are critical checkpoints of the cell cycle that are controlled, among others, by the activity of cyclin-dependent kinases (CDK). Different CDK activities, still to be fully identified, impinge on the retinoblastoma (RBR)/E2F/DP pathway as well as on the programmed proteolysis pathway. The specific degradation of proteins through the ubiquitin pathway in plants, highly controlled in time and space, is emerging as a powerful mechanism to regulate the levels and the activity of several proteins, including many cell cycle regulators.Key Words: cell cycle, endoreplication, E2F, DP, Ubiquitin, SCF, SKP2, lateral root, Arabidopsis     

Prevalencia de los trastornos de ansiedad en las personas mayores de 65 años: una revisión sistemática

Anxiety is an emotional problem that causes discomfort and suffering to those that suffer from it. Anxiety disorders can affect the functioning in different facets of a person's life. Studies on the prevalence of anxiety disorders in people over 65 years show variable results, ranging between 0.1% and 17.2%. Most of these studies include samples of the general population, in which the population of people over 65 years is under-represented. These studies evaluate older people with the same diagnostic tools used to assess anxiety disorders in people under 65 years, and collect data from people between 65 and 75 years old, leaving out people aged 75 and over. A systematic review of the prevalence studies of anxiety disorders in elderly people is presented. It is concluded that when representative samples of people over 65 years are used and evaluated with suitable tools, the prevalence rate of these disorders in the elderly is much higher than previously thought, reaching an annual prevalence rate of 20.8%.     

Disregulated influenza A virus-specific CD8+ T cell homeostasis in the absence of IFN-gamma signaling

Recent studies indicate that IFN-gamma may influence both the expansion and the trafficking of virus-specific CD8+ CTL, though the effects are not necessarily consistent for different models of viral and bacterial disease. Influenza A virus infection of mice deficient for IFN-gamma (IFN-gamma(-/-)) or deficient for the IFN-gamma receptor 1 (IFNGR1(-/-)) was, when compared with the wild-type (WT) B6 controls, associated with increased Ag-specific CD8+ T cell counts in the spleen and mediastinal lymph nodes. At the same time, fewer of these CTL effectors were found in the bronchoalveolar lavage population recovered from the IFN-gamma(-/-) mice. Comparable effects were observed for WT mice treated with a neutralizing IFN-gamma-specific mAb. Transfer of WT memory Thy1.1(+) CD8+ populations into Thy1.2+ B6 IFN-gamma(-/-) or IFNGR1(-/-) mice followed by intranasal virus challenge demonstrated both that IFN-gamma produced by the host was important for the regulation of Ag-specific CTL numbers and that IFN-gamma was likely to act directly on the T cells themselves. In addition, the prevalence of CTLs undergoing apoptosis in spleen was lower when measured directly ex vivo for IFN-gamma(-/-) vs WT B6 mice. The present analysis is the first comprehensive demonstration that IFN-gamma signaling can differentially regulate both Ag-specific CTL homeostasis in secondary lymphoid organs and trafficking to a site of virus-induced pathology.     

Comparison of ELISA with activity and ligand-binding methods for the determination of thymidylate synthase concentration.

The determination of enzyme levels in cellular extracts by active site titrations or by catalytic activity measurements is relevant in both science and medicine. However, these techniques assume that enzymes exhibit the same response in crude sample matrices as they do in the purified state. We report here an example of how an enzyme-linked immunosorbent assay (ELISA) was used to determine the true enzyme concentration which was compared to the effective enzyme concentration obtained by ligand binding and catalytic assay methods in a crude bacterial cell extract. Rabbit antibodies specific for Lactobacillus casei thymidylate synthase (TS) were used to develop a highly specific and sensitive heterogeneous noncompetitive ELISA assay with a typical detection limit of 1.4 fmol of TS (100 pg) and a dynamic working range of 3 orders of magnitude. The antibodies showed identical responses for TS, its inhibitory binary complex with 5-fluoro-2'-deoxyuridylate, and its inhibitory ternary complex with 5-fluoro-2'-deoxyuridylate and 5,10-methylenetetrahydrofolate in the immunoassay. L. casei cell-free extracts were subjected to extraction with CM-Sephadex and the various fractions were analyzed by ELISA, active-site titrations, and catalytic assays which demonstrated that assays which assumed full catalytic or ligand-binding competence underestimated the true enzyme level.     

Strongyloides stercoralis and Trypanosoma cruzi coinfections in a highly endemic area in Argentina

BackgroundStrongyloidiasis and Chagas disease are endemic in northern Argentina. In this study we evaluate the association between S. stercoralis and T. cruzi infections in villages with diverse prevalence levels for these parasites. Further understanding in the relationship between these Neglected Tropical Diseases of South America is relevant for the design of integrated control measures as well as exploring potential biologic interactions.MethodologyCommunity based cross-sectional studies were carried in different villages of the Chaco and Yungas regions in Argentina. Individuals were diagnosed by serology for S. stercoralis and T. cruzi. The association between S. stercoralis and T. cruzi, and between anemia and the two parasites was evaluated using two approaches: marginal (Ma) and multilevel regression (Mu).ResultsA total of 706 individuals from six villages of northern Argentina were included. A total of 37% were positive for S. stercoralis, 14% were positive for T. cruzi and 5% were positive for both. No association was found between infection with S. stercoralis and T. cruzi in any of the models, but we found a negative correlation between the prevalence of these species in the different villages (r = -0.91). Adults (> 15 years) presented association with S. stercoralis (Ma OR = 2.72; Mu OR = 2.84) and T. cruzi (Ma OR = 5.12; Mu OR = 5.48). Also, 12% and 2% of the variance of infection with S. stercoralis and T. cruzi, respectively, could be explained by differences among villages. On the other hand, anemia was associated with infection with S. stercoralis (Ma OR = 1.73; Mu OR = 1.78) and was more prevalent in adults (Ma OR = 2.59; Mu OR = 2.69).ConclusionWe found that coinfection between S. stercoralis and T. cruzi is not more frequent than chance in endemic areas. However, the high prevalence for both parasites, raises the need for an integrated strategy for the control of STH and Chagas disease.     

Regional distribution of pyroglutamyl peptidase II in rabbit brain, spinal cord, and organs.

Pyroglutamyl peptidase II (PPII) is a narrow specificity ectoenzyme that degrades thyrotropin-releasing hormone (TRH). We detected the enzyme in the brain of various mammals, with highest specific activity in rabbit brain. In this species, activity was heterogeneously distributed in the central nervous system. There was a 28-fold difference between regions of highest and lowest PPII activity. Enzyme activity was highest in the olfactory bulb and posterior cortex. In the spinal cord, activity was low but unevenly distributed, with highest values detected in the thoracic (T) region. Segments T1 and T2 activities were particularly high. Other organs contained low or undetectable levels of activity. The levels of TRH-like immunoreactivity (TRH-LI) in spinal cord segments were greatest in T3-T4 and lumbar L2-L6. Low concentrations were found in T1 and T9-T12. There was a partial correlation between the distribution of PPII activity and TRH receptors but not with TRH-LI levels. These results demonstrate that PPII is predominantly a central nervous system enzyme, and they support the hypothesis that PPII is responsible for degrading TRH released into the synaptic cleft.     

Purification and characterization of recombinant mouse thymidylate synthase

Recombinant mouse thymidylate synthase (TS) expressed at high levels in Escherichia coli was purified to homogeneity in greater than 70% yield by a rapid three-step procedure. Both 0.1% Triton X-100 and 10% glycerol were required to stabilize the enzyme whose activity remained unchanged after 1 month when stored at -20 degrees C. Thermal inactivation of the enzyme was a first-order process at 37 degrees C, with t1/2 values of 6.9, 15.6 and 3.0 min at pH 5.5, 7.0 and 8.5, respectively. The presence of saturating levels of dUMP at pH 8.5 increased the t1/2 of inactivation of 38 min. The pH profile for enzyme activity showed a narrow optimum region centered at pH 7.0, which was mirrored by the shape of the Km, dUMP/Vmax plot. The pH dependence of Kd for the covalent inhibitory ternary complex of enzyme, 5-fluoro-2'-deoxyuridylate and 5,10-methylenetetrahydrofolate exhibited a broad minimum between pH 5.5 and 8.5, and ranged between 3.1, 0.8 and 1.1 nM at pH 5.5, 7.0 and 8.5, respectively. The UV/VIS spectrum of the native enzyme exhibited a maximum at 280 nm (epsilon = 98,200 M-1 cm-1), while that of the inhibitory ternary complex showed an additional maximum at 320 nm. The 19F-NMR spectrum of the mouse enzyme:FdUMP binary complex revealed two new resonances at -2.8 and -34.8 ppm. The most deshielded resonance represented the noncovalent binary complex while the other resonance was assigned to the nucleotide covalently bound to the enzyme. The alteration of nucleotide binding equilibria produced by addition of H4 folate was exemplified by both an increase in intensity and a 5 ppm deshielding of the resonance attributed to the covalent FdUMP-enzyme complex. Addition of formaldehyde to the latter mixture produced the covalent ternary complex which resulted in the collapse of the resonances at -2.8 and -39.5 ppm and the appearance of a new resonance at -12.4 ppm.