The Consequences of Precipitation Seasonality for Mediterranean-Ecosystem Vegetation of South Africa

Globally, mediterranean-climate ecosystem vegetation has converged on an evergreen, sclerophyllous and shrubby growth form. The particular aspects of mediterranean-climate regions that contribute to this convergence include summer droughts and relatively nutrient-poor soils. We hypothesised that winter-precipitation implies stressful summer droughts and leaches soils due to greater water availability (i.e. balance between precipitation and potential evapotranspiration; P–PET) during cold periods. We conducted a comparative analysis of normalised difference vegetation indices (NDVI) and edaphic and climate properties across the biomes of South Africa. NDVI was strongly correlated with both precipitation and P–PET (r² = 0.8). There was no evidence, however, that winter-precipitation reduces NDVI in comparison to similar amounts of summer-precipitation. Base saturation (BS), a measure of soil leaching was, however, negatively related to P–PET (r² = 0.64). This led to an interaction between P–PET and BS in determining NDVI, indicating the existence of a trade-off between water availability and soil nutrients that enables NDVI to increase with precipitation, despite negative consequences for soil nutrient availability. The mechanism of this trade-off is suggested to be that water increases nutrient accessibility. This implies that along with nutrient-depauperate geologies and long periods of time since glaciation, the winter-precipitation may have contributed to the highly leached status of the soils. Since many of the ecophysiological characteristics of mediterranean-ecosystem flora are associated with low nutrient availabilities (e.g. evergreen foliage, sclerophylly, cluster roots), we conclude that mediterranean-climates promote convergence of growth-forms in these regions through high leaching capacity.     

Neuraminidase-associated plasminogen recruitment enables systemic spread of natural avian Influenza viruses H3N1

Repeated outbreaks due to H3N1 low pathogenicity avian influenza viruses (LPAIV) in Belgium were associated with unusually high mortality in chicken in 2019. Those events caused considerable economic losses and prompted restriction measures normally implemented for eradicating high pathogenicity avian influenza viruses (HPAIV). Initial pathology investigations and infection studies suggested this virus to be able to replicate systemically, being very atypical for H3 LPAIV. Here, we investigate the pathogenesis of this H3N1 virus and propose a mechanism explaining its unusual systemic replication capability. By intravenous and intracerebral inoculation in chicken, we demonstrate systemic spread of this virus, extending to the central nervous system. Endoproteolytic viral hemagglutinin (HA) protein activation by either tissue-restricted serine peptidases or ubiquitous subtilisin-like proteases is the functional hallmark distinguishing (H5 or H7) LPAIV from HPAIV. However, luciferase reporter assays show that HA cleavage in case of the H3N1 strain in contrast to the HPAIV is not processed by intracellular proteases. Yet the H3N1 virus replicates efficiently in cell culture without trypsin, unlike LPAIVs. Moreover, this trypsin-independent virus replication is inhibited by 6-aminohexanoic acid, a plasmin inhibitor. Correspondingly, in silico analysis indicates that plasminogen is recruitable by the viral neuraminidase for proteolytic activation due to the loss of a strongly conserved N-glycosylation site at position 130. This mutation was shown responsible for plasminogen recruitment and neurovirulence of the mouse brain-passaged laboratory strain A/WSN/33 (H1N1). In conclusion, our findings provide good evidence in natural chicken strains for N1 neuraminidase-operated recruitment of plasminogen, enabling systemic replication leading to an unusual high pathogenicity phenotype. Such a gain of function in naturally occurring AIVs representing an established human influenza HA-subtype raises concerns over potential zoonotic threats.     

Predation by and activity patterns of 'parasitic' beetles of the genus Amblyopinus (Coleoptera: Staphylinidae)

This study explores the relationship between staphylinid beetles of the genus Amblyopinus and their small mammal hosts. Previous studies had concluded that these beetles were parasitic and fed directly on blood, skin exudates, or other epidermal derivatives of their hosts. We examined the mode of attachment, behaviour, and feeding activities of 254 Amblyopinus (A. tiptoni and A. emarginatus ) on 69 hosts which were captured in Sherman live traps. In addition, similar information and diurnal activity patterns were monitored for 11 beetles kept on two hosts ( Peromyscus nudipes ) over a period of 14 days. Beetles were found to be attached to the host only by grasping clumps of fur in their mandibles. No sign of damage to the skin of the host could be found. Feeding by the beetles on parasitic arthropods was observed and concluded to be the primary feeding habit. Beetles showed a strong circadian activity pattern, in which they are attached to the host during night-time hours and actively hunt in the nest during daylight hours. Attachment to the host is hypothesized to be primarily a vehicle for tracking prey of the beetles within the variety of nests used by any individual host. We conclude that these beetles are not parasitic but, instead, highly specialized predators on ectoparasitic arthropods, with specialized behavioural and morphological adaptations for their unique life style.     

Effects of competition and shading in planktonic communities

A model for several algal species which compete both for light and for nutrients, and which are also subject to settling and diffusion, is considered. The settling speeds and diffusion coefficients are assumed to be small, in a sense to be made precise later, and a singular perturbation argument is used. In certain cases vertical segregation of the algal species is observed, and the mechanism for this is interpreted biologically.Supported by the Danish Natural Science Research Council (Grant No. 11-8321)     

Urinary Calprotectin and Posttransplant Renal Allograft Injury

Objective

Current methods do not predict the acute renal allograft injury immediately after kidney transplantation. We evaluated the diagnostic performance of urinary calprotectin for predicting immediate posttransplant allograft injury.

Methods

In a multicenter, prospective-cohort study of 144 incipient renal transplant recipients, we postoperatively measured urinary calprotectin using an enzyme-linked immunosorbent assay and estimated glomerular filtration rate (eGFR) after 4 weeks, 6 months, and 12 months.

Results

We observed a significant inverse association of urinary calprotectin concentrations and eGFR 4 weeks after transplantation (Spearman r = −0.33; P<0.001). Compared to the lowest quartile, patients in the highest quartile of urinary calprotectin had an increased risk for an eGFR less than 30 mL/min/1.73 m² four weeks after transplantation (relative risk, 4.3; P<0.001; sensitivity, 0.92; 95% CI, 0.77 to 0.98; specificity, 0.48; 95% CI, 0.31 to 0.66). Higher urinary calprotectin concentrations predicted impaired kidney function 4 weeks after transplantation, as well as 6 months and 12 months after transplantation. When data were analyzed using the urinary calprotectin/creatinine-ratio similar results were obtained. Urinary calprotectin was superior to current use of absolute change of plasma creatinine to predict allograft function 12 months after transplantation. Urinary calprotectin predicted an increased risk both in transplants from living and deceased donors. Multivariate linear regression showed that higher urinary calprotectin concentrations and older donor age predicted lower eGFR four weeks, 6 months, and 12 months after transplantation.

Conclusions

Urinary calprotectin is an early, noninvasive predictor of immediate renal allograft injury after kidney transplantation.     

Detection of induced enzyme secretion from neutrophilic granulocytes in the human--a marker of cell activation

A simple, effective method with an objective analysis for the detection of induced, i.e. not cytotoxic release of enzymes from human neutrophils (PMN) is described. As marker enzyme for lysosomes we determined lysozyme activity and as indicator of cell damage the lactatdehydrogenase activity. The PMN were isolated from peripheral blood. Latex-, zymosan particles and inactivated mycobacteria for phagocytosis model, and heat aggregated human IgG and surface-bounded immune complexes for the Fc-receptor-mediated activation were used as stimulators of enzyme secretion. With these substances we could show an increase of secretion referring to unaffected control in all tested probands. The spontaneous and also the induced secretion are influenced by strong individual variations. It is accentuated, that also without influence of cytochalasin B this process is representable and that this is the supposition to carry out functional tests with PMN under extensively physiological conditions.     

Predation by squirrel monkeys and double-toothed kites on tent-making bats

Central American squirrel monkeys (Saimiri oerstedi) appear to recognize the modified leaves that phyllostomid bats utilize for diurnal roost sites. The monkeys visually and manually search these bat tents for both bats and insects. Adult males are the most successful at capturing bats. Nonvolant juvenile bats are more vulnerable to monkey predation than are adults. Bats that escape monkey predation frequently are captured by doubletoothed kites (Harpagus bidentatus) that tend foraging troops of monkeys. Predation by squirrel monkeys, coupled with that of double-toothed kites, may be a significant source of mortality for tent-making bats.     

Improving the interaction of Myc‐interfering peptides with Myc using molecular dynamics simulations

Previously, a Myc‐interfering peptide (Mip) was identified for the targeted inactivation of the Myc:Max complex by the combination of rational design and an in vivo protein‐fragment complementation assay. In the subsequent work presented here, molecular dynamics simulations and free energy calculations based on the molecular mechanics GBSA method were performed to define the contribution of the different amino acids in the Myc:Mip coiled coil domain, and compared to wild‐type Myc:Max. For further optimization of the Myc interference, point mutations were introduced into Mip and analyzed, from which two showed much higher binding affinities in the computational studies in good agreement with the experiment. These mutants with very high potential for inactivation of Myc can now be used as starting point for further optimizations based on the computational as well as experimental protocols presented here. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.