Scale dependence of diversity measures in a leaf-litter ant assemblage

A reliable characterization of community diversity and composition, necessary to allow inter‐site comparisons and to monitor changes, is especially difficult to reach in speciose invertebrate communities. Spatial components of the sampling design (sampling interval, extent and grain) as well as temporal variations of species density affect the measures of diversity (species richness S, Buzas and Gibson's evenness E and Shannon's heterogeneity H). Our aim was to document the small‐scale spatial distribution of leaf litter ants in a subtropical dry forest of the Argentinian Chaco and analyze how the community characterization was best achieved with a minimal sampling effort. The work was based on the recent standardized protocol for collecting ants of the leaf litter (“A.L.L.”: 20 samples at intervals of 10 m). To evaluate the consistency of the sampling method in time and space, the selected site was first subject to a preliminary transect, then submitted after a 9‐month interval to an 8‐fold oversampling campaign (160 samples at interval of 1.25 m). Leaf litter ants were extracted from elementary 1 m² quadrats with Winkler apparatus. An increase in the number of samples collected increased S and decreased E but did not affect much H. The sampling interval and extent did not affect S and H beyond a distance of 10 m between samples. An increase of the sampling grain had a similar effect on S than a corresponding increase of the number of samples collected, but caused a proportionaly greater increase of H. The density of species m^?2 varied twofold after a 9‐month interval; the effect on S could only be partially corrected by rarefaction. The measure of species numerical dominance was little affected by the season. A single standardized A.L.L. transect with Winkler samples collected <45% of the species present in the assemblage. All frequent species were included but their relative frequency was not always representative. A log series distribution of species occurrences was oberved. Fisher's α and Shannon's H were the most appropriate diversity indexes. The former was useful to rarefy or abundify S and the latter was robust against sample size effects. Both parametric and Soberón and Llorente extrapolation methods outperformed non‐parametric methods and yielded a fair estimate of total species richness along the transect, a minimum value of S for the habitat sampled.     

Short‐term changes in the structure of termite assemblages associated with slash‐and‐burn agriculture in Côte d'Ivoire

Termites are major decomposers in tropical regions and play critical roles in many soil‐related processes. Studies conducted in Asia and the Neotropics suggest that habitat modification can strongly affect termite assemblages, but data on termite communities from forests in Africa, especially West Africa, are scarce. Here, we measured the short‐term impact of slash‐and‐burn agriculture on termite assemblages in an agricultural region of central Côte d'Ivoire. We assessed termite diversity and relative abundance in four habitat types: secondary forest, cleared forest, burned forest, and crop fields. The secondary forest had higher species richness compared with the other habitats, but all habitat types had similar assemblage structures. Fungus‐growing termites were the most abundant feeding group in all habitats. Soil feeders were most abundant in secondary forest, intermediately abundant in cleared and burned forests, and almost entirely absent in crop fields. Wood‐feeding species showed clear responses to burning; their abundances decreased after fire. We conclude that slash‐and‐burn agriculture does not appear to severely erode the diversity of termite assemblages. This could be due to the dominance of ecologically versatile fungus growers or to the relatively long time between clearing and burning. However, forest clearing negatively affects soil feeders, with the Apicotermitinae most affected by canopy loss.     

IRAK-mediated translocation of TRAF6 and TAB2 in the interleukin-1-induced activation of NFkappa B

The interleukin-1 (IL-1) receptor-associated kinase (IRAK) is required for the IL-1-induced activation of nuclear factor kappaB and c-Jun N-terminal kinase. The goal of this study was to understand how IRAK activates the intermediate proteins TRAF6, TAK1, TAB1, and TAB2. When IRAK is phosphorylated in response to IL-1, it binds to the membrane where it forms a complex with TRAF6; TRAF6 then dissociates and translocates to the cytosol. The membrane-bound IRAK similarly mediates the IL-1-induced translocation of TAB2 from the membrane to the cytosol. Different regions of IRAK are required for the translocation of TAB2 and TRAF6, suggesting that IRAK mediates the translocation of each protein separately. The translocation of TAB2 and TRAF6 is needed to form a TRAF6-TAK1-TAB1-TAB2 complex in the cytosol and thus activate TAK1. Our results show that IRAK is required for the IL-1-induced phosphorylation of TAK1, TAB1, and TAB2. The phosphorylation of these three proteins correlates strongly with the activation of nuclear factor kappaB but is not necessary to activate c-Jun N-terminal kinase.     

Understanding the culture of prescribing: qualitative study of general practitioners’ and patients’ perceptions of antibiotics for sore throats

Objectives: To better understand reasons for antibiotics being prescribed for sore throats despite well known evidence that they are generally of little help. Design: Qualitative study with semi-structured interviews. Setting: General practices in South Wales. Subjects: 21 general practitioners and 17 of their patients who had recently consulted for a sore throat or upper respiratory tract infection. Main outcome measures: Subjects’ experience of management of the illness, patients’ expectations, beliefs about antibiotic treatment for sore throats, and ideas for reducing prescribing. Results: Doctors knew of the evidence for marginal effectiveness yet often prescribed for good relationships with patients. Possible patient benefit outweighed theoretical community risk from resistant bacteria. Most doctors found prescribing “against the evidence” uncomfortable and realised this probably increased workload. Explanations of the distinction between virus and bacterium often led to perceived confusion. Clinicians were divided on the value of leaflets and national campaigns, but several favoured patient empowerment for self care by other members of the primary care team. Patient expectations were seldom made explicit, and many were not met. A third of patients had a clear expectation for antibiotics, and mothers were more likely to accept non-antibiotic treatment for their children than for themselves. Satisfaction was not necessarily related to receiving antibiotics, with many seeking reassurance, further information, and pain relief. Conclusions: This prescribing decision is greatly influenced by considerations of the doctor-patient relationship. Consulting strategies that make patient expectations explicit without damaging relationships might reduce unwanted antibiotics. Repeating evidence for lack of effectiveness is unlikely to change doctors’ prescribing, but information about risk to individual patients might. Emphasising positive aspects of non-antibiotic treatment and lack of efficacy in general might be helpful.

Key messages

• Doctors know that antibiotics do not help most sore throat sufferers but try not to jeopardise relationships with patients over this issue
• Patients’ expectations are seldom explicit, and satisfaction is not necessarily related to receiving an antibiotic: information and reassurance are sometimes more important
• Consulting techniques that make expectations explicit, preserve relationships, and facilitate acceptable management are important
• Opportunities for empowering patients who are not acutely ill could be better used, and emphasising positive aspects of non-antibiotic treatment, especially in children, could be fruitful
• Risks to individuals from unnecessary antibiotics (rather than trial evidence for marginal benefit) should be emphasised

     

The membrane ATPase of Escherichia coli. II. Release into solution,allotopic properties and reconstitution of membrane-bound ATPase

Membrane-bound ATPase of Escherichia coli was released in a soluble form by decreasing the Mg²⁺ concentration to 0.05 mM. The particulate fraction left behind was depleted by more than 90% from its initial ATPase activity.Soluble ATPase exhibits a number of different properties as compared with membrane-bound ATPase. These are a 2-fold increased K_m toward ATP, a shift of 1–1.5 pH units in the pH-dependence curve, a greatly increased resistance to inhibition by N,N′-dicyclohexylcarbodiimide (DCCD) and a stimulation by Dio 9 instead of an inhibition.Upon mixing the soluble fraction and the depleted membrane fraction, the initial properties of native membrane-bound ATPase reappear. This reconstitution requires Mg²⁺ and results in the physical binding of the activity to sedimentable material.Soluble ATPase and depleted membrane can be titrated against each other until an equivalence point is reached, beyond which the component in excess keeps its previous characteristics.During the release procedure, DCCD remains associated with the particulate fraction with conservation of the ATPase-binding sites.Such DCCD-treated depleted membranes behave as a specific inhibitor of soluble ATPase.     

Caste developmental potentialities in the termite Nasutitermes novarumhebridarum

The normal development pathway and caste system of Nasutitermes novarumhebridarum (N. & K. Holmgren) (Isoptera; Termitidae) conform to the general Nasutitermes pattern. Queen-removal experiments in N. novarumhebridarum resulted in the production of replacement reproductives derived from workers (ergatoids), but never from the sexual brood (nymphs and alates). Three moults are necessary to complete the tranformation from the worker to the ergatoid. This pathway is longer than those previously konwn in other termites, in which two moults are sufficient. In a colony with functional ergatoids, some nymphs gave rise to worker-like individuals. The caste potentialities of N. novarumhebridarum differ from those of the sympatric species, N. princeps and N. polygynus, in which imaginal replacement reproductives are easily obtained. Colony reproduction in N. novarumhebridarum seems to be accomplished exclusively by independent alate founders, which colinize massive, but finite and widely spaced resoures such as dead or damaged tree trunks. N. princeps and N. polygynus societies abundantly use colony budding to expand their territory, and exploit various sources of dead wood scattered over their foraging range. We suggest that N. novarumhebridarum caste potentialities are adapted to channelling a maximum of resources into the production of dispersing alates that can colonize new nest sites.

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Résumé Les voies de développement et le système de castes chez Nasutitermes novarumhebridarum sont conformes au schéma général du genre Nasutitermes. L'enlèvement expérimental de la reine chez N. novarumhebridarum entraîne le développement de sexués de remplacement à partir d'ouvriers (ergatoïdes), mais jamais à partir de la lignée sexuée (nymphes et ailés). La transformation de l'ouvrier en ergatoîde fonctionnel nécessite trois mues. Ce développement est plus long que ceux décrits précédemment chez d'autres termites, où deux mues sont suffisantes. Dans une société où se sont développés des ergatoïdes fonctionnels, quelques nymphes se sont transformées en individus rappelant les ouvriers. Les potentialités des castes de N. novarumhebridarum diffèrent de celles des espèces sympatriques N. princeps et N. polygynus, chez lesquelles des sexués de remplacement imaginaux pauvent être obtenus aisément. La reproduction des sociétés de N. novarumhebridarum semble s'effectuer uniquement par des ailés essaimants, qui colonisent des sources de nourriture massives, mais limitées et largement espacées, tels les troncs d'arbres morts ou endomagés. N. princeps et N. polygynus étendent fréquemment leurs territoires par le bourgeonnement de nouvelles sociétés, et exploitent des sources de bois mort variées, dispersées dans leur champ d'exploitation. Nous suggérons que les potentialités des castes chez novarumhebridarum sont adaptées pour diriger un maximum de ressources vers la production d'ailés qui se dispersent et peuvent ainsi coloniser de nouveaux sites favorables.

     

Spring photosynthetic onset and net CO2 uptake in Alaska triggered by landscape thawing

The springtime transition to regional‐scale onset of photosynthesis and net ecosystem carbon uptake in boreal and tundra ecosystems are linked to the soil freeze–thaw state. We present evidence from diagnostic and inversion models constrained by satellite fluorescence and airborne CO₂ from 2012 to 2014 indicating the timing and magnitude of spring carbon uptake in Alaska correlates with landscape thaw and ecoregion. Landscape thaw in boreal forests typically occurs in late April (DOY 111 ± 7) with a 29 ± 6 day lag until photosynthetic onset. North Slope tundra thaws 3 weeks later (DOY 133 ± 5) but experiences only a 20 ± 5 day lag until photosynthetic onset. These time lag differences reflect efficient cold season adaptation in tundra shrub and the longer dehardening period for boreal evergreens. Despite the short transition from thaw to photosynthetic onset in tundra, synchrony of tundra respiration with snow melt and landscape thaw delays the transition from net carbon loss (at photosynthetic onset) to net uptake by 13 ± 7 days, thus reducing the tundra net carbon uptake period. Two global CO₂ inversions using a CASA‐GFED model prior estimate earlier northern high latitude net carbon uptake compared to our regional inversion, which we attribute to (i) early photosynthetic‐onset model prior bias, (ii) inverse method (scaling factor + optimization window), and (iii) sparsity of available Alaskan CO₂ observations. Another global inversion with zero prior estimates the same timing for net carbon uptake as the regional model but smaller seasonal amplitude. The analysis of Alaskan eddy covariance observations confirms regional scale findings for tundra, but indicates that photosynthesis and net carbon uptake occur up to 1 month earlier in evergreens than captured by models or CO₂ inversions, with better correlation to above‐freezing air temperature than date of primary thaw. Further collection and analysis of boreal evergreen species over multiple years and at additional subarctic flux towers are critically needed.     

Different GABAB-Mediated Effects on Protein Kinase C Activity and Immunoreactivity in Neonatal and Adult Rat Hippocampal Slices

Abstract: The effects of GABA on protein kinase C (PKC) were investigated in rat hippocampal slices at various postnatal ages [postnatal day (P) 1-P60]. At P4, GABA (300 µ M ) induced a rapid (in 1–2 min) 40–50% increase of PKC activity in the membrane fraction and a decrease in the cytosol. These effects were mediated by GABA_B receptors because (a) they were neither blocked by 10 µ M bicuculline nor reproduced by 10 µ M isoguvacine and (b) they were mimicked by the GABA_B agonist baclofen (3–30 µ M ), an effect fully antagonized by the GABA_B antagonist 2-hydroxysaclofen (10 µ M ). A baclofen-induced increased PKC activity in the membrane fraction was only present during the early postnatal period (P1–P14); it was associated with a translocation from the cytosol to the membrane of the immunoreactivity of some PKC isoforms (α-, β-, and ε-PKCs). In contrast, after P21, PKC activity and α-, β-, ε-, and γ-PKC immunoreactivities were decreased by baclofen in the membrane fraction and increased in the cytosol. These results suggest that the stimulation of GABA_B receptors differentially modulates PKC activity via distinct second messenger pathways in developing and mature hippocampi.