Assessing the effects of habitat characteristics and co-occurrence with closely related species on occupancy of resident ‘wood-warblers’ in a Neotropical working landscape

The simultaneous effects of habitat traits and interspecific interactions determine the occurrence and habitat use of wildlife populations. However, little research has been devoted to examining spatial co-occurrence among closely related species while considering the effect of habitat variation and imperfect detectability of species in the field. In this study, we focused on migratory and resident 'wood-warblers' that coexist during the winter in a Neotropical working landscape in southern Mexico to understand if habitat occupancy of resident wood-warblers is influenced by habitat characteristics and by the presence of other species of resident and migratory wood-warblers. For this purpose, we implemented two-species occupancy models, which account for the imperfect detectability of these birds in the field. Our results revealed that habitat occupancy of resident wood-warblers was positively influenced by the presence of other closely related species (both migratory and resident). These positive relationships may be explained by the fact that different species of wood-warblers frequently participate in mixed-species flocks. However, these patterns of species co-occurrence were more evident among resident species than between migratory and resident species, which may be explained by micro-habitat segregation and differences in behaviours between resident and migratory wood-warblers. We also found that some habitat characteristics may mediate the observed patterns of species co-occurrence. Specifically, sites with larger trees were associated with the co-occurrence of some species of resident wood-warblers. In addition, we discuss the possibility that species co-occurrence might be the result of shared preferences for environmental factors that we did not consider. Our study highlights the importance of the interplay between species co-occurrence and habitat traits in determining the presence and habitat use of resident birds in Neotropical working landscapes.     

Productivity of outdoor algal cultures in unstable weather conditions

In the outdoor cyclic fed batch cultures of Chlorella pyrenoidosa, some typical growth kinetics patterns in unstable weather conditions were observed. On cloudy days, the biomass output rate (R) was low, but the bioenergetic growth yield (Y) was generally high. In the cloudy morning-sunny afternoon condition, the values of Y were low, especially in the afternoon. In the sunny morning-cloudy afternoon condition, both R and Y were high. A few very high short-term Y values were measured during the cloudy the cloudy afternoon. (c) 1993 Wiley & Sons, Inc.     

Evolution of several cytoskeletal proteins of astrocytes in primary culture: Effect of prenatal alcohol exposure

In the present work we have analyzed, using immunoblotting and immunofluorescence techniques, the evolution of several cytoskeletal proteins during the development of astrocytes in primary culture. The effect of prenatal exposure to alcohol on these proteins was also evaluated. Microtubular protein -tubulin decreased approximately 47% from 4 to 7 days after which its content remained practically constant. Immunofluorescence studies showed also that the content of -tubulin was greater at day 4 of culture. This increase in fluorescence was coincident with the presence of globular particles which were found in interphase astrocytes and stained with both anti - and anti--tubulin. These structures appeared only in proliferating cells. Glial fibrillary acidic protein (GFAP) and vimentin were analyzed as intermediate filament (IF) proteins. GFAP, in cytoskeletal preparations, increased regularly for 14 days followed by a decrease to day 21. In contrast, vimentin showed a progressive increase throughout the entire culture period. Fluorescence studies revealed some differences between the IF distribution patterns of GFAP and vimentin.In astrocytes obtained from rats prenatally exposed to ethanol, decreases in the amounts of all the cytoskeletal proteins studied were found during the entire culture period. In these cells a striking disorganization of cytoskeleton was also observed. The alcohol-induced decrease of GFAP in cultured astrocytes was also found when this protein was studied in preparations from whole brain developed in vivo.Special issue dedicated to Dr. Santiago Grisolia     

RECK-Mediated β1-Integrin Regulation by TGF-β1 Is Critical for Wound Contraction in Mice

Fibroblasts are critical for wound contraction; a pivotal step in wound healing. They produce and modify the extracellular matrix (ECM) required for the proper tissue remodeling. Reversion-inducing cysteine-rich protein with Kazal motifs (RECK) is a key regulator of ECM homeostasis and turnover. However, its role in wound contraction is presently unknown. Here we describe that Transforming growth factor type β1 (TGF-β1), one of the main pro-fibrotic wound-healing promoting factors, decreases RECK expression in fibroblasts through the Smad and JNK dependent pathways. This TGF-β1 dependent downregulation of RECK occurs with the concomitant increase of β1-integrin, which is required for fibroblasts adhesion and wound contraction through the activation of focal adhesion kinase (FAK). Loss and gain RECK expression experiments performed in different types of fibroblasts indicate that RECK downregulation mediates TGF-β1 dependent β1-integrin expression. Also, reduced levels of RECK potentiate TGF-β1 effects over fibroblasts FAK-dependent contraction, without affecting its cognate signaling. The above results were confirmed on fibroblasts derived from the Reck ^+/- mice compared to wild type-derived fibroblasts. We observed that Reck ^+/- mice heal dermal wounds more efficiently than wild type mice. Our results reveal a critical role for RECK in skin wound contraction as a key mediator in the axis: TGF-β1—RECK- β1-integrin.     

Modulation of the matrix redox signaling by mitochondrial Ca~(2+)

Mitochondria sense,shape and integrate signals,and thus function as central players in cellular signal transduction. Ca2+ waves and redox reactions are two such intracellular signals modulated by mitochondria. Mitochondrial Ca2+ transport is of utmost physio-pathological relevance with a strong impact on metabolism and cell fate. Despite its importance,the molecular nature of the proteins involvedin mitochondrial Ca2+ transport has been revealed only recently. Mitochondrial Ca2+ promotes energy metabolism through the activation of matrix dehydrogenases and downstream stimulation of the respiratory chain. These changes also alter the mitochondrial NAD(P)H/NAD(P)+ ratio,but at the same time will increase reactive oxygen species(ROS) production. Reducing equivalents and ROS are having opposite effects on the mitochondrial redox state,which are hard to dissect. With the recent development of genetically encoded mitochondrial-targeted redoxsensitive sensors,real-time monitoring of matrix thiol redox dynamics has become possible. The discoveries of the molecular nature of mitochondrial transporters of Ca2+ combined with the utilization of the novel redox sensors is shedding light on the complex relation between mitochondrial Ca2+ and redox signals and their impact on cell function. In this review,we describe mitochondrial Ca2+ handling,focusing on a number of newly identified proteins involved in mitochondrial Ca2+ uptake and release. We further discuss our recent findings,revealing how mitochondrial Ca2+ influences the matrix redox state. As a result,mitochondrial Ca2+ is able to modulate the many mitochondrial redox-regulated processes linked to normal physiology and disease.     

Malaria infections reinforce competitive asymmetry between two Ficedula flycatchers in a recent contact zone

Parasites may influence the outcome of interspecific competition between closely related host species through lower parasite virulence in the host with which they share the longer evolutionary history. We tested this idea by comparing the prevalence of avian malaria (Haemosporidia) lineages and their association with survival in pied and collared flycatchers (Ficedula hypoleuca and F. albicollis) breeding in a recent contact zone on the Swedish island of Öland. A nested PCR protocol amplifying haemosporidian fragments of mtDNA was used to screen the presence of malaria lineages in 1048 blood samples collected during 6 years. Competitively inferior pied flycatchers had a higher prevalence of blood parasites, including the lineages that were shared between the two flycatcher species. Multistate mark–recapture models revealed a lower survival of infected versus uninfected female pied flycatchers, while no such effects were detected in male pied flycatchers or in collared flycatchers of either sex. Our results show that a comparatively new host, the collared flycatcher, appears to be less susceptible to a local northern European malarial lineage where the collared flycatchers have recently expanded their distribution. Pied flycatchers experience strong reproductive interference from collared flycatchers, and the additional impact of species‐specific blood parasite effects adds to this competitive exclusion. These results support the idea that parasites can strongly influence the outcome of interspecific competition between closely related host species, but that the invading species need not necessarily be more susceptible to local parasites.     

Bioinformatic prediction of polymerase elements in the rotavirus VP1 protein

Rotaviruses are the major cause of acute gastroenteritis in infants world-wide. The genome consists of eleven double stranded RNA segments. The major segment encodes the structural protein VP1, the viral RNA-dependent RNA polymerase (RdRp), which is a minor component of the viral inner core. This study is a detailed bioinformatic assessment of the VP1 sequence. Using various methods we have identified canonical motifs within the VP1 sequence which correspond to motifs previously identified within RdRps of other positive strand, double-strand RNA viruses. The study also predicts an overall structural conservation in the middle region that may correspond to the palm subdomain and part of the fingers and thumb subdomains, which comprise the polymerase core of the protein. Based on this analysis, we suggest that the rotavirus replicase has the minimal elements to function as an RNA-dependent RNA polymerase. VP1, besides having common RdRp features, also contains large unique regions that might be responsible for characteristic features observed in the Reoviridae family.