The rarity concept and the commonness of rarity in freshwater zooplankton

1. Regional distribution, frequency of occurrence and relative abundance were scored in 2467 Norwegian lakes for all the recorded 130 species of crustacean zooplankton. The majority of species were rare in the sense that 65% of species were recorded in fewer than 10% of localities. Only six species were recorded in more than 50% of localities, and the median number of species in a given locality was 14 (i.e. 10% of the total species pool). 2. Abundances of all species were scored according to the fraction of lakes in which they were recorded, their geographical range of distribution, and their numerical abundance. Typically the most rare species were rare by all three criteria, and vice versa for the common species, pointing to rarity as an inherent property of some species. For some species this rarity reflects being on the edge of their distributional range, while for others rarity seems to be a consequence of their life cycle strategies. 3. Some of the truly rare species have high dispersal rates and high colonization abilities, but are rapidly replaced by other species. Others are confined to specific habitats, often highly eutrophic, pointing to highly specialized niche adaptations. 4. A major cause for the few truly common species seems to be the limited number of species that are able to coexist within a given locality, reflecting ‘the ghost of competition past’ and predation pressure. 5. While species composition and species richness may reflect colonization abilities and stochastic events, the presence or absence of species is not only a random lottery but also a consequence of species‐specific attributes.     

IL-21 promotes skin recruitment of CD4(+) cells and drives IFN-γ-dependent epidermal hyperplasia

Psoriasis is a chronic inflammatory disorder of the skin characterized by epidermal hyperplasia and infiltration of leukocytes into the dermis and epidermis. T cell-derived cytokines, such as IFN-γ and IL-17A, play a major role in the psoriasis-associated epidermal hyperplasia, even though factors/mechanisms that regulate the production of these cytokines are not fully understood. We have recently shown that IL-21 is synthesized in excess in psoriatic skin lesions and causes epidermal hyperplasia when injected intradermally in mice. Moreover, in the human psoriasis SCID mouse model, neutralization of IL-21 reduces both skin thickening and expression of inflammatory molecules, thus supporting the pathogenic role of IL-21 in psoriasis. However, the basic mechanism by which IL-21 promotes skin pathology remains unknown. In this study, we show that CD4(+) cells accumulate early in the dermis of IL-21-treated mice and mediate the development of epidermal hyperplasia. Indeed, IL-21 fails to induce skin damage in RAG1-deficient mice and CD4(+) cell-depleted wild-type mice. The majority of CD4(+) cells infiltrating the dermis of IL-21-treated mice express IFN-γ and, to a lesser extent, IL-17A. Studies in cytokine knockout mice show that IFN-γ, but not IL-17A, is necessary for IL-21-induced epidermal hyperplasia. Finally, we demonstrate that IFN-γ-producing CD4(+) cells infiltrating the human psoriatic plaque express IL-21R, and abrogation of IL-21 signals reduces IFN-γ expression in cultures of psoriatic CD4(+) cells. Data indicate that IL-21 induces an IFN-γ-dependent pathogenic response in vivo, thus contributing to elucidate a mechanism by which IL-21 sustains skin-damaging inflammation.     

Antibacterial Characterization of Novel Synthetic Thiazole Compounds against Methicillin-Resistant Staphylococcus pseudintermedius

Staphylococcus pseudintermedius is a commensal organism of companion animals that is a significant source of opportunistic infections in dogs. With the emergence of clinical isolates of S. pseudintermedius (chiefly methicillin-resistant S. pseudintermedius (MRSP)) exhibiting increased resistance to nearly all antibiotic classes, new antimicrobials and therapeutic strategies are urgently needed. Thiazole compounds have been previously shown to possess potent antibacterial activity against multidrug-resistant strains of Staphylococcus aureus of human and animal concern. Given the genetic similarity between S. aureus and S. pseudintermedius, this study explores the potential use of thiazole compounds as novel antibacterial agents against methicillin-sensitive S. pseudintermedius (MSSP) and MRSP. A broth microdilution assay confirmed these compounds exhibit potent bactericidal activity (at sub-microgram/mL concentrations) against both MSSA and MRSP clinical isolates while the MTS assay confirmed three compounds (at 10 μg/mL) were not toxic to mammalian cells. A time-kill assay revealed two derivatives rapidly kill MRSP within two hours. However, this rapid bactericidal activity was not due to disruption of the bacterial cell membrane indicating an alternative mechanism of action for these compounds against MRSP. A multi-step resistance selection analysis revealed compounds 4 and 5 exhibited a modest (two-fold) shift in activity over ten passages. Furthermore, all six compounds (at a subinihibitory concentration) demonstrated the ability to re-sensitize MRSP to oxacillin, indicating these compounds have potential use for extending the therapeutic utility of β-lactam antibiotics against MRSP. Metabolic stability analysis with dog liver microsomes revealed compound 3 exhibited an improved physicochemical profile compared to the lead compound. In addition to this, all six thiazole compounds possessed a long post-antibiotic effect (at least 8 hours) against MRSP. Collectively the present study demonstrates these synthetic thiazole compounds possess potent antibacterial activity against both MSSP and MRSP and warrant further investigation into their use as novel antimicrobial agents.     

The dual role of interleukin-25 in the control of immune-mediated pathologies

Interleukin-25 (IL-25) plays a key role in the initiation and expansion of T helper (Th) 2 cell-mediated immune responses, thereby contributing to allergic diseases and host defense against helminthic parasites. More recent studies have however shown that IL-25 can also control the function of non-T cells, such as antigen presenting cells and endothelial cells, and reduces Th1/Th17-mediated pathologies. These new and exciting observations reveal a broader role for IL-25 than previously anticipated, and delineate various scenarios where therapeutic interventions around IL-25 activity can be imagined.     

Effects of Hunting on Response Behaviors of Wild Reindeer

ABSTRACT Because wild reindeer (Rangifer tarandus) are hunted in southern Norway, reindeer may perceive all recreationists as threats. Potential adverse effects of hunting on reindeer behavior may be exacerbated by other forms of recreation because the number of skiers and hikers in areas inhabited by reindeer has also increased. The Norefjell-Reinsjøfjell wild reindeer area is used extensively for recreation and tourism. Reindeer hunting was introduced in the area in 1992, and harvest rate has been stable at about 38% of winter herd size. We recorded behavioral responses of reindeer to a person approaching directly on foot or skis during 1992 and again in 2002–2006. Compared to 1992, flight-initiation distance increased and fewer groups assessed the observer before taking flight during 2002–2006. In winter, when reindeer are usually comparably more vigilant than in other seasons, flight-initiation distance increased from only 60 m to 115 m and escape distance decreased from 400 m to 210 m. Neither alert distance, calf carcass weights (23.6 ± 0.7 [SE] kg to 22.4 ± 0.2 kg), nor reindeer herd size (661 ± 73 to 579 ± 15) changed during the 15 years of our study. Reindeer appeared to habituate to the observer because they initiated flight at shorter distances as the number of approaches on the same day increased. In Norefjell-Reinsjøfjell, encounters with a person on foot or skis did not result in behavioral responses likely to entail substantial energy costs for reindeer; therefore, hunting at current levels appears compatible with other recreational activities.     

The Simulium vernum group (Diptera: Simuliidae) in Europe: multiple character sets for assessing species status

The value of using characters from multiple sources – chromosomes, ecology, gene sequences, and morphology – to evaluate the species status of closely related black flies is demonstrated for three European members of the Simulium vernum group: Simulium crenobium (Knoz, 1961), Simulium juxtacrenobium Bass & Brockhouse, 1990, and Simulium vernum s.s. Macquart, 1826. Simulium juxtacrenobium is a chromosomally, molecularly, and morphologically distinct species that diverged from S. crenobium and S. vernum s.s. about 2 Mya. It is specialized for intermittent streams, is univoltine, and is recorded for the first time from northern Europe, based on collections from Finland and Sweden, representing a range extension of about 1800 km. In contrast, S. crenobium, although confirmed as a distinct species, differs from S. vernum s.s. by only a few larval and chromosomal characters, and by a breeding habitat restricted to mountain spring brooks. Whereas all four character sets independently support the specific distinctness of S. juxtacrenobium and S. vernum s.s., multiple character sets are required to establish the specific validity of S. crenobium.     

ER-bound protein tyrosine phosphatase PTP1B interacts with Src at the plasma membrane/substrate interface

PTP1B is an endoplasmic reticulum (ER) anchored enzyme whose access to substrates is partly dependent on the ER distribution and dynamics. One of these substrates, the protein tyrosine kinase Src, has been found in the cytosol, endosomes, and plasma membrane. Here we analyzed where PTP1B and Src physically interact in intact cells, by bimolecular fluorescence complementation (BiFC) in combination with temporal and high resolution microscopy. We also determined the structural basis of this interaction. We found that BiFC signal is displayed as puncta scattered throughout the ER network, a feature that was enhanced when the substrate trapping mutant PTP1B-D181A was used. Time-lapse and co-localization analyses revealed that BiFC puncta did not correspond to vesicular carriers; instead they localized at the tip of dynamic ER tubules. BiFC puncta were retained in ventral membrane preparations after cell unroofing and were also detected within the evanescent field of total internal reflection fluorescent microscopy (TIRFM) associated to the ventral membranes of whole cells. Furthermore, BiFC puncta often colocalized with dark spots seen by surface reflection interference contrast (SRIC). Removal of Src myristoylation and polybasic motifs abolished BiFC. In addition, PTP1B active site and negative regulatory tyrosine 529 on Src were primary determinants of BiFC occurrence, although the SH3 binding motif on PTP1B also played a role. Our results suggest that ER-bound PTP1B dynamically interacts with the negative regulatory site at the C-terminus of Src at random puncta in the plasma membrane/substrate interface, likely leading to Src activation and recruitment to adhesion complexes. We postulate that this functional ER/plasma membrane crosstalk could apply to a wide array of protein partners, opening an exciting field of research.     

Lateral hop movement assesses ankle dynamics and muscle activity

Ankle function is frequently measured using static or dynamic tasks in normal and injured patients. The purpose of this study was to develop a novel task to quantify ankle dynamics and muscle activity in normal subjects. Twelve subjects with no prior ankle injuries participated. Video motion analysis cameras, force platforms, and an EMG system were used to collect data during a lateral hop movement task that consisted of multiple lateral-medial hops over an obstacle. Mean (SD) inversion ankle position at contact was 4.4° (4.0) in the medial direction and -3.5° (4.4) in the lateral direction; mean (SD) tibialis anterior normalized muscle activity was 0.11 (0.08) in the medial direction and 0.16 (0.13) in the lateral direction. The lateral hop movement was shown to be an effective task for quantifying ankle kinematics, forces, moments, and muscle activities in normal subjects. Future applications will use the lateral hop movement to assess subjects with previous ankle injuries in laboratory and clinical settings.