Consequences of disperser behaviour for seedling establishment of a mistletoe species

The dispersal process in plants links adults and their offspring. For frugivore‐dispersed plants, animal behaviour can have a strong effect on plant fitness. Many mistletoes are totally dependent on animals that deposit seeds on suitable hosts and particular branch diameters. We characterised the seed dispersal and seedling establishment of the mistletoe Tristerix corymbosus, which at our study site, is exclusively dispersed by the marsupial Dromiciops gliroides. Mistletoes’ fruits have a viscous pulp that remains in the seed even after dispersal. This substance adheres the seed to the host branch. We estimated host branch availability in the forest and seed deposition (faeces) by the marsupial in the study area. Specifically, the branch suitability factors we assessed were host identity, branch status (alive or dead), branch diameter, height, and canopy cover. Lodged faeces were individually marked and the number of seed deposited within these droppings was counted, and we recorded the number of seedlings with true leaves that had established after 1 year to estimate the probability of seedling establishment. Branch diameter and canopy cover had a significant positive effect on seed deposition probability. Seedling establishment probability decreased with the number of seeds deposited per faeces and with canopy cover. In general, the marsupial deposited mistletoe seeds in microsites that increase the chance of seedling establishment. Thus, the movement behaviour of the marsupial has a positive effect on the regeneration process of this mistletoe species.     

Adaptive Changes in Cardiac Fibroblast Morphology and Collagen Organization as a Result of Mechanical Environment

There is a growing body of work in the literature that demonstrates the significant differences between 2D versus 3D environments in cell morphologies, spatial organization, cell-ECM interactions, and cell signaling. The 3D environments are generally considered more realistic tissue models both because they offer cells a surrounding environment rather than just a planar surface with which to interact, and because they provide the potential for more diverse mechanical environments. Many studies have examined cellular-mediated contraction of 3D matrices; however, because the 3D environment is much more complex and the scale more difficult to study, little is known regarding how mechanical environment, cell and collagen architecture, and collagen remodeling are linked. In the current work, we examine the spatial arrangement of neonatal cardiac fibroblasts and the associated collagen organization in constrained and unconstrained collagen gels over a 24 h period. Collagen gels that are constrained by their physical attachment to a mold and similar gels, which have been detached (unconstrained) from the mold and subsequently contract, offer two simple mechanical models by which the mechanisms of tissue homeostasis and wound repair might be examined. Our observations suggest the presence of two mechanical regimes in the unconstrained gels: an outer ring where cells orient circumferentially and local collagen aligns with the elongated cells; and a central region where unaligned stellate/bipolar cells are radially surrounded by collagen, similar to that seen throughout constrained gels. The evolving organization of cell alignment and surrounding collagen organization suggests that cellular response may be due to the cellular perception of the apparent stiffness of local physical environment.     

The vaccinia virus F11L gene product facilitates cell detachment and promotes migration

We previously showed that infection with vaccinia virus (VV) induces cell motility, characterized by contractility and directed migration. Motility is temporally regulated because cells are motile immediately after infection, whereas late in infection motility ceases and cells resettle. Motility and its cessation are accompanied by temporal rearrangements of both the microtubule and the actin networks. Because the F11L gene has previously been implicated in VV-induced migration, we now explore the role of F11L in contractility, migration, the cessation of motility and the cytoskeletal rearrangements. By live cell imaging using a VV that lacks an intact F11L gene, we show that F11L facilitates cell detachment and is required for migration but not for contractility. By light microscopy, F11L expression induces a remodeling of the actin, but not the microtubule, network. The lack of migration correlates with smaller plaques, indicating that this process facilitates cell-to-cell spreading of VV. Late in infection, when motility ceases, cells re-establish cell-to-cell contacts in an F11L-independent manner. We finally show that VV-induced motility and its cessation correlate with a temporal regulation of the guanosine triphosphatase RhoA as well as the expression levels of F11L during the infectious cycle.     

High-frequency stimuli preferentially release large dense-core vesicles located in the proximity of nonspecialized zones of the presynaptic membrane in sympathetic ganglia

We characterized the effect of a brief high-frequency stimulus on the number, distribution, and optical density of large dense-core vesicles (LDCVs) in the nerve terminals of the rat superior cervical ganglia. From 4.21+/-0.37 LDCVs/bouton detected in control nerve terminals, a stimulus of 40 Hz for 1 min released 41% of LDCVs, decreasing their number to 2.48+/-0.14 LDCVs/bouton (p=0.0009). In control ganglia, most dense vesicles were located close to the plasma membrane (at 相似文献   

Characterization of glycoside residues of porcine zona pellucida and ooplasm during follicular development and atresia

The glycoside residues (glycoconjugates, GC) of the zona pellucida (ZP) glycoproteins are important during the first phases of fecundation. Our aim in this work was to determine the lectin affinity pattern of porcine ZP in order to analyze the changes that take place during: (a) preantral folliculogenesis, (b) the follicular atresia process, and (c) antral growth. Several prepubertal and adult pig ovaries and different sized antral follicles were used. Conventional carbohydrate histochemical techniques and peroxidase and digoxigenin (DIG) lectins were used to reveal the acid groups and the glycosidic residues of the ZP. It was seen that the ZP forms in the preantral follicles throughout their growth period. In primordial and primary follicles, ZP in the process of formation showed neutral GC. SBA, RCA-I, MAA, WGA lectins, and AAA after methylation-saponification (MS) were positive in the ZP of primordial and primary follicles. The affinity for SBA, RCA-I, MAA, and WGA increased in the multilaminar-primary follicles and new affinities for UEA-I and LFA were observed. After MS, AAA, SNA, PNA, and SBA reactivity was observed. The ZP of antral follicle oocytes of different sizes showed the same lectin pattern as multilaminar-primary follicles. The oocyte ooplasm and the follicular fluid of large antral follicles showed less affinity for WGA and LFA lectins and less intensive staining with AB (pH 2.5). Atresia did not change the antral or preantral follicle oocyte ZP lectin pattern. In conclusion, the follicles showed substantial changes in their ZP glycosidic composition as they developed, especially, during the change from primary to multilaminar-primary follicles. The ZP glycosidic composition showed no significant change during the growth of antral follicles and follicular atresia in our study.     

Selection of breeding territory by little bustard (<Emphasis Type="Italic">Tetrax tetrax</Emphasis>) males in Central Spain: the role of arthropod availability

The influence of arthropod availability on the formation of male little bustard breeding territories in central Spain was studied in two consecutive years. Arthropods (68,217 individuals) were sampled using pitfall trapping and male territories estimated by means of kernel functions. Hymenopterans (ants), beetles, mites and spiders were the main taxa found in the samples, while the highest contributions in terms of biomass came from hymenopterans, beetles and orthopterans. The only group that exhibited significant biomass differences between territory and non-territory locations was that of the beetles; this pattern was consistent between years. Carabidae was the main beetle family in terms of biomass, followed by other large beetles such as Tenebrionidae, Cleridae, Scarabeidae and Elateridae. The biomass of Carabidae that were larger than 15 mm was significantly higher within territories than outside them. The biomass of Cleridae was greater in fallows, while Elateridae were more abundant in arable fields. The total biomass of beetles that were larger than 15 mm was higher in arable fields than in fallows. Family richness differed between years, while diversity showed differences between agricultural fields (it was highest in fallows), although these variables did not differ between territory and non-territory locations. Results indicate that large beetles (particularly carabids) seem to be a valuable food resource that is defended by little bustard males during the highly energy-demanding breeding season, which is discussed here in relation to habitat selection, the mating system and its implications for the conservation of the species.     

Determinants of abundance and effects of blood-sucking flying insects in the nest of a hole-nesting bird

Compared to non-flying nest-dwelling ectoparasites, the biology of most species of flying ectoparasites and its potential impact on avian hosts is poorly known and rarely, if ever, reported. In this study we explore for the first time the factors that may affect biting midge (Diptera: Ceratopogonidae) and black fly (Diptera: Simuliidae) abundances in the nest cavity of a bird, the hole-nesting blue tit Cyanistes caeruleus, and report their effects on adults and nestlings during reproduction. The abundance of biting midges was positively associated with nest mass, parental provisioning effort and abundance of blowflies and black flies, while negatively associated with nestling condition. Furthermore, a medication treatment to reduce blood parasitaemias in adult birds revealed that biting midges were more abundant in nests of females whose blood parasitaemias were experimentally reduced. This finding would be in accordance with these insect vectors attacking preferentially uninfected or less infected hosts to increase their own survival. The abundance of black flies in the population was lower than that of biting midges and increased in nests with later hatching dates. No significant effect of black fly abundance on adult or nestling condition was detected. Blood-sucking flying insects may impose specific, particular selection pressures on their hosts and more research is needed to better understand these host–parasite associations.     

Transgenesis of schistosomes: approaches employing mobile genetic elements

Draft genome sequences for Schistosoma mansoni and Schistosoma japonicum are now available. However, the identity and importance of most schistosome genes have yet to be determined. Recently, progress has been made towards the genetic manipulation and transgenesis of schistosomes. Both loss-of-function and gain-of-function approaches appear to be feasible in schistosomes based on findings described in the past 5 years. This review focuses on reports of schistosome transgenesis, specifically those dealing with the transformation of schistosomes with exogenous mobile genetic elements and/or their endogenous relatives for the genetic manipulation of schistosomes. Transgenesis mediated by mobile genetic elements offers a potentially tractable route to introduce foreign genes to schistosomes, a means to determine the importance of schistosome genes, including those that could be targeted in novel interventions and the potential to undertake large-scale forward genetics by insertional mutagenesis.     

Electrophoresis artefacts — a previously unrecognized cause of error in microsatellite analysis

While microsatellite genotyping has found wide application in many fields, a number of causes that could lead to error in microsatellite genotyping have been previously reported. Here we report another cause of error that we term ‘Electrophoresis Artefacts’ (EA), which arise when high concentrations of polymerase chain reaction (PCR) products are electrophoresed in ABI 377 automated sequencers. We describe the phenomenon of EAs, characterize PCR and gel running conditions that cause them and suggest a simple method of overcoming this problem.