Plasminogen is a critical host pathogenicity factor for group A streptococcal infection

Group A streptococci, a common human pathogen, secrete streptokinase, which activates the host's blood clot-dissolving protein, plasminogen. Streptokinase is highly specific for human plasminogen, exhibiting little or no activity against other mammalian species, including mouse. Here, a transgene expressing human plasminogen markedly increased mortality in mice infected with streptococci, and this susceptibility was dependent on bacterial streptokinase expression. Thus, streptokinase is a key pathogenicity factor and the primary determinant of host species specificity for group A streptococcal infection. In addition, local fibrin clot formation may be implicated in host defense against microbial pathogens.     

Illuminating the evolutionary history of chlamydiae

Chlamydiae are the major cause of preventable blindness and sexually transmitted disease. Genome analysis of a chlamydia-related symbiont of free-living amoebae revealed that it is twice as large as any of the pathogenic chlamydiae and had few signs of recent lateral gene acquisition. We showed that about 700 million years ago the last common ancestor of pathogenic and symbiotic chlamydiae was already adapted to intracellular survival in early eukaryotes and contained many virulence factors found in modern pathogenic chlamydiae, including a type III secretion system. Ancient chlamydiae appear to be the originators of mechanisms for the exploitation of eukaryotic cells.     

Muscarinic M3-like receptors, cyclic AMP and L-type calcium channels are involved in the contractile response to cholinergic agents in gut smooth muscle of the rainbow trout, Oncorhynchus mykiss

Cholinergic signalling in mammalian gut smooth muscle usually involves M3 muscarinic receptors for direct contraction via phospholipase C activation and M2 muscarinic receptors to reduce cyclic AMP levels. However, the proportion of receptor subtypes and second messengers involved varies among tissues and animals and studies in non-mammalian species will provide information on the conservation of pathways and consequently on their importance for signal transduction. In the present study we investigated receptor subtypes, involvement of calcium, phospholipase C and cyclic AMP in the cholinergic contraction of the rainbow trout gut. Intestinal and gastric smooth muscle strip preparations, with the mucosa removed, were used in functional studies, and homogenised strips were used for measurements of cyclic AMP. Calcium-free medium, the L-type calcium-channel inhibitor verapamil, the cyclic AMP-phosphodiesterase inhibitor IBMX + isoprenaline, and the M3-antagonist 4-DAMP methiodide all caused a partial or marked reduction of the response to cholinergic agonists. Neomycin, an inhibitor of phospholipase C, and SKF96365, an inhibitor of receptor-operated calcium channels, had no effect. Carbachol (0.1 mM) reduced the levels of cyclic AMP transiently. It is concluded that the cholinergic signal transduction in rainbow trout gut smooth muscle involves (1) binding to M3-like receptors, (2) a transient reduction in cyclic AMP levels, (3) influx of extracellular calcium, in part through L-type calcium-channels and (4) no involvement of phospholipase C.     

Retention patches as potential refugia for bryophytes and lichens in managed forest landscapes

Leaving small patches of forest intact at harvesting is now a standard procedure to mitigate negative effects on biodiversity. One purpose of the patches is to “life-boat” species over the forest regeneration phase, although the capacity of small forest fragments to do so is very uncertain. We investigated the survival of red-listed and indicator species of bryophytes and lichens in 74 retention patches in boreal Sweden. The patches were between 0.01 and 0.5 ha in size and of six different types with respect to tree species composition and location on the harvested area. Species presence and abundance were recorded shortly after harvest in transects covering the whole patches, and an identical inventory was carried out 6 years after the first. During this time, bryophytes generally decreased, most pronounced for liverworts. The largest decreases were found in buffer zones to streams and lakes and the smallest in tree groups dominated by deciduous trees. By contrast, among the lichens some species decreased while others increased, and there was no difference between retention patch types. Among the species abundant enough to be analyzed individually, the lichens Calicium parvum and Micarea globulosella decreased less in larger patches and the bryophyte Hylocomiastrum umbratum decreased more in patches of irregular shape. The results imply that retention patches of this size might be too small to function as refugia for sensitive bryophytes and lichens until the surrounding forest regenerates, but that some lichens appear to persist or even increase. Retention harvesting is still a young management practice and further studies on its long-term conservation benefits will be valuable.     

Length and classification of natural and created forest edges in boreal landscapes throughout northern Sweden

Forest edges have numerous implications for structure and function of forest ecosystems. Previous studies on edge quantity have used broad classifications. However, edge influence is driven by the contrast in vegetation structure between adjoining ecosystems, and thus we need detailed site-specific data to assess the role of edges in forests. We studied the variability of sharp edges in 28 boreal landscapes (4 km × 4 km) across an 830 km gradient throughout northern Sweden. Our objectives were: (1) to compare the length of natural and created edges, (2) to classify edges in detail by edge origin, maintenance and forest attributes, and (3) to examine relationships between length of edge and landscape variables. Data were collected using stereo-interpretation of high spatial resolution colour infrared aerial photographs, in combination with line intersect sampling and plots. The length of edge varied from 12 to 102 m ha⁻¹ among landscapes, with an overall mean of 54 m ha⁻¹. Created edges dominated most landscapes (mean 33 m ha⁻¹) and had greater variability than natural edges (mean 21 m ha⁻¹). Maintained edges (e.g. roads, agricultural land) were more abundant than regenerating edges caused by logging. Thirty percent of total edges adjoined narrow linear features. Seventy percent adjoined wider patches and showed high variability (35 classes). Overall, high-contrast edges towards mature forest dominated, i.e. ones that may experience strong edge influence. The amount of edge increased with percent of landscape affected by disturbance, and decreased with latitude and elevation. This study shows that edges are both abundant and highly variable in boreal forests and that forestry is the main driver behind edge creation. Detailed classification of edges based on site-specific forest and patch attributes may help to estimate edge influence at landscape level, and can guide experimental design for examining the impact of edges on structure and function of forest ecosystems.     

Initiation of somatic embryogenesis from immature zygotic embryos of oocarpa pine (Pinus oocarpa Schiede ex Schlectendal)

The focus of the current project was to establish somatic embryogenesis protocols for the tropical pine species Pinus oocarpa using immature zygotic embryos (ZEs) as explants. Somatic embryogenesis is best supported by mimicking natural seed-embryo developmental conditions, through a tissue culture medium formulation based on the mineral content of the seed nutritive tissue [megagametophyte (MG)]. A novel culture medium (P. oocarpa medium, PO) was tested in combination with different plant growth regulator (PGR) concentrations and compared with standard Pinus taeda media for the initiation of somatic embryogenesis from immature ZEs of P. oocarpa. Immature MGs containing immature ZEs of two mother trees were used with 12 and 8% extrusion rates for mother tree genotypes 3 and 5, respectively. In both mother trees the percentage capture was 2%. Multiplication of two captured cell lines (T5C2S01 and T5C1S12) was improved by lowering the concentrations of PGRs to 2.5 μM each 2,4-dichlorophenoxyacetic acid and abscisic acid (ABA) plus 1.0 μM each 6-benzylaminopurine and kinetin. Mature somatic embryos formed on 40 μM ABA, 6% (w/v) maltose, 12% (w/v) PEG 8000 and 0.6% (w/v) Phytagel. While PO medium appeared suboptimal for somatic embryo induction, it did exhibit potential for enhanced culture proliferation and subsequent improved maturation with cell line T5C2S01, where microscopic analysis revealed better embryo morphology on PO medium than on 1250 medium. However, this enhancement was not observed with cell line T5C1S12. Germination was preceded by partial desiccation for a period of 2-3 weeks before transferring the embryos to germination medium. Germination was observed after 7 days under low light, and apical primordia slowly expanded after transfer to ex vitro conditions. To our knowledge, this is the first report on the production of somatic seedlings in P. oocarpa.     

Stressed individuals’ preferences for activities and environmental characteristics in green spaces

Everyday modern life offers fewer opportunities for outdoor activities and mental restoration. Outdoor activities in urban green spaces might be a promising means to lower levels of stress. Our hypothesis is that individuals’ Level of Stress (LS) is related to the interaction between preferences for certain perceived sensory dimensions (PSDs) of the outdoor environment and certain types of outdoor activities.A total of 953 randomly selected informants, representative of the Swedish population, answered a postal questionnaire with pre-coded items. The questionnaire consisted of three parts: personal data, preferences for PSDs and for outdoor activities, and self-estimations of health. The study focuses on ill health in relation to Level of Stress (LS). The data was analysed using factor and regression analysis.The results show that individuals reporting high LS are more likely to: be younger adults, women, be on sick-leave, have small children, be dissatisfied with their home environment, experience poorer access to green spaces and, foremost, want to use public green spaces more often.Seventeen different outdoor activity types are identified. The most preferred activity type among the most stressed informants was ‘rest activities’ followed by ‘animal activities’ and ‘walking activities’. All pairs of these three activity types and PSDs showing a significant association were transformed into ‘activity-sensory dimension types’. A regression analysis shows that the most preferred activity-sensory dimension types for informants reporting high LS are ‘animal activities’ in the PSD ‘rich in species’, ‘animal activities’ in the PSD ‘refuge’, and ‘rest activities’ in the PSD ‘nature’.These results may be interpreted as providing information regarding how to plan urban green spaces with certain characteristics that could promote outdoor activities which are preferred by stressed individuals.     

Using step and path selection functions for estimating resistance to movement: pumas as a case study

Context

GPS telemetry collars and their ability to acquire accurate and consistently frequent locations have increased the use of step selection functions (SSFs) and path selection functions (PathSFs) for studying animal movement and estimating resistance. However, previously published SSFs and PathSFs often do not accommodate multiple scales or multi-scale modeling.

Objectives

We present a method that allows multiple scales to be analyzed with SSF and PathSF models. We also explore the sensitivity of model results and resistance surfaces to whether SSFs or PathSFs are used, scale, prediction framework, and GPS collar sampling interval.

Methods

We use 5-min GPS collar data from pumas (Puma concolor) in southern California to model SSFs and PathSFs at multiple scales, to predict resistance using two prediction frameworks (paired and unpaired), and to explore potential bias from GPS collar sampling intervals.

Results

Regression coefficients were extremely sensitive to scale and pumas exhibited multiple scales of selection during movement. We found PathSFs produced stronger regression coefficients, larger resistance values, and superior model performance than SSFs. We observed more heterogeneous surfaces when resistance was predicted in a paired framework compared with an unpaired framework. Lastly, we observed bias in habitat use and resistance results when using a GPS collar sampling interval longer than 5 min.

Conclusions

The methods presented provide a novel way to model multi-scale habitat selection and resistance from movement data. Due to the sensitivity of resistance surfaces to method, scale, and GPS schedule, care should be used when modeling corridors for conservation purposes using these methods.

     

Sensitivity of resource selection and connectivity models to landscape definition

Context

The definition of the geospatial landscape is the underlying basis for species-habitat models, yet sensitivity of habitat use inference, predicted probability surfaces, and connectivity models to landscape definition has received little attention.

Objectives

We evaluated the sensitivity of resource selection and connectivity models to four landscape definition choices including (1) the type of geospatial layers used, (2) layer source, (3) thematic resolution, and (4) spatial grain.

Methods

We used GPS telemetry data from pumas (Puma concolor) in southern California to create multi-scale path selection function models (PathSFs) across landscapes with 2500 unique landscape definitions. To create the landscape definitions, we identified seven geospatial layers that have been shown to influence puma habitat use. We then varied the number, sources, spatial grain, and thematic resolutions of these layers to create our suite of plausible landscape definitions. We assessed how PathSF model performance (based on AIC) was affected by landscape definition and examined variability among the predicted probability of movement surfaces, connectivity models, and road crossing locations.

Results

We found model performance was extremely sensitive to landscape definition and identified only seven top models out of our suite of definitions (<1%). Spatial grain and the number of geospatial layers selected for a landscape definition significantly affected model performance measures, with finer grains and greater numbers of layers increasing model performance.

Conclusions

Given the sensitivity of habitat use inference, predicted probability surfaces, and connectivity models to landscape definition, out results indicate the need for increased attention to landscape definition in future studies.

     

Influences on the use of urban green space – A case study in Odense,Denmark

Increasing the use of urban green space has appeared on the political agenda, primarily because increased use is expected to improve the health and well-being of the urban population. Green space is contributing to restoring mental fatigue, serving as a resource for physical activity, reducing mortality and reducing the level of stress.However, knowledge and experience on how to implement this agenda are scarce. In this paper, we use a socio-ecological model as framework when studying influences on the use of respondents’ nearest urban green space in the Danish city of Odense. Data were obtained from a survey sent to 2500 randomly selected adult residents within the central part of the city. We tested the relative importance of different factors on the frequency of use of the nearest urban green space by using a multivariate logistic regression model. The results show that almost half of the respondents did not use their nearest green space the most. Whether or not respondent used their nearest green space most depends primarily on area size, distance to the area and factors that are likely to express a reduced mobility; old age, young children and poor health.If the nearest urban green space also is the most used green space, having a dog is the only factor that significantly increases the frequency of use. Further research is needed to determine what it is that makes people use an area more, if the basic conditions of a reasonable size (>5 ha) within a reasonable distance (<600 m) are fulfilled.