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Selected AbstractsNested distributions of bat flies (Diptera: Streblidae) on Neotropical bats: artifact and specificity in host-parasite studiesECOGRAPHY, Issue 3 2009Bruce D. Patterson We examined the structure of ectoparasitic bat fly infestations on 31 well-sampled bat species, representing 4 Neotropical families. Sample sizes varied from 22 to 1057 bats per species, and bat species were infested by 4 to 27 bat fly species. Individual bats supported smaller infracommunities (the set of parasites co-occurring on an individual host), ranging from 1 to 5 fly species in size, and no bat species had more than 6 bat fly species characteristically associated with it (its primary fly species). Nestedness analyses used system temperature (BINMATNEST algorithm) because it is particularly well-suited for analysis of interaction networks, where parasite records may be nested among hosts and host individuals simultaneously nested among parasites. Most species exhibited very low system temperatures (mean 3.14°; range 0.14,12.28°). Simulations showed that nested structure for all 31 species was significantly stronger than simulated values under 2 of the 3 null hypotheses, and about half the species were also nested under the more stringent conditions of the third null hypothesis. Yet this structure disappears when analyses are restricted to "primary" associations of fly species (flies on their customary host species), which exclude records thought to be atypical, transient, or potential contaminants. Despite comprising a small fraction of total parasite records, such anomalies represent a considerable part of the statistical state-space, offering the illusion of significant ecological structure. Only well understood and well documented systems can make distinctions between primary and other occurrence records. Generally, nestedness appears best developed in host-parasite systems where infestations are long-term and accumulate over time. Dynamic, short-term infestations by highly mobile parasites like bat flies may appear to be nested, but such structure is better understood in terms of host specificity and accidental occurrences than in terms of prevalence, persistence, or hierarchical niche relations of the flies. [source] Is the distribution of nitrogen-fixing cyanobacteria in the oceans related to temperature?ENVIRONMENTAL MICROBIOLOGY, Issue 7 2009Lucas J. Stal Summary Approximately 50% of the global natural fixation of nitrogen occurs in the oceans supporting a considerable part of the new primary production. Virtually all nitrogen fixation in the ocean occurs in the tropics and subtropics where the surface water temperature is 25°C or higher. It is attributed almost exclusively to cyanobacteria. This is remarkable firstly because diazotrophic cyanobacteria are found in other environments irrespective of temperature and secondly because primary production in temperate and cold oceans is generally limited by nitrogen. Cyanobacteria are oxygenic phototrophic organisms that evolved a variety of strategies protecting nitrogenase from oxygen inactivation. Free-living diazotrophic cyanobacteria in the ocean are of the non-heterocystous type, namely the filamentous Trichodesmium and the unicellular groups A,C. I will argue that warm water is a prerequisite for these diazotrophic organisms because of the low-oxygen solubility and high rates of respiration allowing the organism to maintain anoxic conditions in the nitrogen-fixing cell. Heterocystous cyanobacteria are abundant in freshwater and brackish environments in all climatic zones. The heterocyst cell envelope is a tuneable gas diffusion barrier that optimizes the influx of both oxygen and nitrogen, while maintaining anoxic conditions inside the cell. It is not known why heterocystous cyanobacteria are absent from the temperate and cold oceans and seas. [source] Auditory activation of ,visual' cortical areas in the blind mole rat (Spalax ehrenbergi)EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2002Gilles Bronchti Abstract The mole rat (Spalax ehrenbergi) is a subterranean rodent whose adaptations to its fossorial life include an extremely reduced peripheral visual system and an auditory system suited for the perception of vibratory stimuli. We have previously shown that in this blind rodent the dorsal lateral geniculate nucleus, the primary visual thalamic nucleus of sighted mammals, is activated by auditory stimuli. In this report we focus on the manifestation of this cross-modal compensation at the cortical level. Cyto- and myeloarchitectural analyses of the occipital area showed that despite the almost total blindness of the mole rat this area has retained the organization of a typical mammalian primary visual cortex. Application of the metabolic marker 2-deoxyglucose and electrophysiological recording of evoked field potentials and single-unit activity disclosed that a considerable part of this area is activated by auditory stimuli. Previous neuronal tracing studies had revealed the origin of the bulk of this auditory input to be the dorsal lateral geniculate nucleus which itself receives auditory input from the inferior colliculus. [source] Linseed (Linum usitatissimum L.) Cultivars and Breeding Lines as Stem Biomass ProducersJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2000H. S. Sankari Linseed (Linum usitatissimum L.) stems, which contain bast fibres, make up a considerable part of the linseed biomass, but are considered a by-product of no value. The feasibility of cultivating existing linseed cultivars and breeding lines for dual-purpose use of stem and seed was studied in 1995,97 in Jokioinen, Finland. Finnish linseed cv. Helmi was compared with 10 linseed genotypes and one flax cultivar for stem yield, ratio of stem yield to seed yield, and plant stand height and density. The stem yield of cv. Helmi averaged 1317 kg dry matter ha -1. Significantly higher stem yields were produced by breeding lines Bor 15 and Bor 18 and cvs Gold Merchant, Norlin and Martta. The cv. Helmi produced lower stem yield than seed yield while breeding lines Bor 15 and Bor 18 and cvs Gold Merchant and Martta yielded more stem than seeds. The difference in the ratio of stem yield to seed yield between them and cv. Helmi was statistically significant. The mean plant stand height was 60.3 cm and the final plant density 594 plants m -2. No relationship was found between stem yield and height or density. Within 2 days of seed threshing, stems of early maturing Finnish genotypes dried up in the field to nearly 15 % moisture content, even in the middle of September (1996). The early maturing breeding lines Bor 15 and Bor 18, with their significantly higher stem yields relative to cv. Helmi, are recommended for dual-purpose use. Zusammenfassung Der bastfasernenthaltende Stengel des Ölleins (Linum usitatissimum L.) bildet einen Grossteil der oberirdischen Biomasse von Öllein, der häufig keiner Nutzung zugeführt wird. Um das Potential bestehender Ölleinsorten und -zuchtlinien für eine Doppelnutzung von Samen und Stengelbiomasse zu überprüfen, wurden in den Jahren 1995,97 in Jokioinen (Finland) Feldversuche durchgeführt. Die finnische Ölleinsorte Helmi wurde mit zehn Ölleinzuchtstämmen und einer Faserleinsorte angebaut, und der Stengelertrag, der Stengelertrag im Verhältnis zum Samenertrag und die Bestandeshöhe und -dichte wurden ermittelt. Der Stengelertrag betrug bei Helmi durchschnittlich 1317 kg Trockenmasse ha -1. Signifikant höhere Stengelerträge wurden von den Zuchtlinien Bor 15 und Bor 18, den Sorten Gold Merchant, Norlin und Martta produziert. Helmi produzierte im Mittel einen geringeren Stengel , als Samenertrag. Die Stengelerträge der Zuchtstämme Bor 15 und Bor 18 und der Sorten Gold Merchant und Martta waren höher als die Samenerträge. Zwischen diesen Genotypen und der Sorte Helmi ist der Unterschied des Ertragsverhältnisses signifikant. Die Bestandeshöhe lag im Durchschnitt bei 60,3 cm und die Bestandesdichte betrug im Mittel 594 Pflanzen m -2. Eine Korrelation zwischen dem Stengelertrag und der Bestandeshöhe bzw. -dichte konnte nicht nachgewiesen werden. Die Stengel der frühen finnischen Genotypen trockneten nach dem Dreschen auf dem Feld (Mitte September 1996) in zwei Tagen auf einen Feuchtegehalt von 15% ab. Die frühreifen Zuchtlinien Bor 15 und Bor 18 können aufgrund ihrer signifikant höheren Stengelerträge im Vergleich zu der Sorte Helmi für eine Doppelnutzung empfohlen werden. [source] Phosphatidylcholine Reverses Ethanol-Induced Increase in Transepithelial Endotoxin Permeability and Abolishes Transepithelial Leukocyte ActivationALCOHOLISM, Issue 3 2009Katja Mitzscherling Background:, Chronic alcohol abuse increases both intestinal bacterial overgrowth and intestinal permeability to macromolecules. Intestinal permeability of endotoxin, a component of the outer cell membrane of Gram-negative bacteria, plays a crucial role in the development of alcohol-induced liver disease (ALD). As impaired bile flow leads to endotoxemia and the bile component phosphatidylcholine (PC) is therapeutically active in ALD, we tested the hypothesis that conjugated primary bile salts (CPBS) and PC inhibit ethanol-enhanced transepithelial permeability of endotoxin and the subsequent transepithelial activation of human leukocytes. Methods:, For this purpose, we used a model in which intestinal epithelial cells (Caco-2) were basolaterally cocultivated with mononuclear leukocytes. Cells were challenged apically with endotoxin from Escherichia coli K12 and were incubated with or without the addition of CPBS (1.5 mM), PC (0.38 mM), pooled human bile (2%) in combination with ethanol (0 to 66 mM). Results:, Ethanol decreased integrity of intestinal epithelial cell monolayer and enhanced transepithelial permeability of endotoxin. Both the transepithelial permeability of endotoxin and the transepithelial stimulation of leukocytes were nearly completely abolished after the apical supplementation of PC with CPBS, but not by CPBS alone. Ethanol up to 66 mM was not able to reverse this effect. Conclusions:, A considerable part of the therapeutic and preventive effect of PC supplementation in ALD might result from a reduction of ethanol-enhanced permeability of endotoxin through the intestinal barrier. [source] Weight loss, body fat mass, and leptin in Parkinson's disease,MOVEMENT DISORDERS, Issue 6 2009Birgitta Lorefält RNT Abstract Weight loss is a common problem in Parkinson's disease (PD), but the causative mechanisms behind this weight loss are unclear. We compared 26 PD patients with sex and age matched healthy controls. Examinations were repeated at baseline, after one and after two years. Body fat mass was measured by Dual X-ray Absorptiometry (DXA). Seventy three per cent of the PD patients lost body weight. Loss of body fat mass constituted a considerable part of the loss of body weight. In the patients who lost weight, serum leptin levels were lower than in those who did not lose weight. The relationship between low body fat mass and low leptin levels seems to be relevant, at least for female PD patients. It is reasonable to believe that low leptin levels in these patients could be secondary to the decreased body fat mass. © 2009 Movement Disorder Society [source] Manifestation of the equilibrium hole distribution in photoluminescence of n-InNPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2005A. A. Klochikhin Abstract Photoluminescence (PL) of n-InN grown by molecular beam epitaxy with Hall concentrations from 3.6 to 7.3 × 1017 cm,3 demonstrates dependences on carrier concentration, temperature, and excitation density which give evidences of a fast energy relaxation rate of photoholes and their equilibrium distribution over localized states. The structure of the PL spectra observed at 4.2 and 77 K in the energy interval from 0.50 to 0.67 eV indicates that a considerable part of holes is trapped by deep and shallow acceptors before the interband recombi- nation with degenerate electrons occurs. At room temperature, the band-to-band recombination of free holes and electrons dominates in PL. Experimental results on PL and absorption are described by model calculations under the assumptions of a band gap equal to 0.665,0.670 eV at zero temperature and zero carrier concentration and a non-parabolic conduction band with the effective mass at the G -point equal to 0.07 of the free electron mass. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Exchanging the active site between phytases for altering the functional properties of the enzymePROTEIN SCIENCE, Issue 10 2000Martin Lehmann Abstract By using a novel consensus approach, we have previously managed to generate a fully synthetic phytase, consensus phytase-1, that was 15-26 °C more thermostable than the parent fungal phytases used in its design (Lehmann et al., 2000). We now sought to use the backbone of consensus phytase-1 and to modify its catalytic properties. This was done by replacing a considerable part of the active site (i.e., all the divergent residues) with the corresponding residues of Aspergillus niger NRRL 3135 phytase, which displays pronounced differences in specific activity, substrate specificity, and pH-activity profile. For the new protein termed consensus phytase-7, a major,although not complete,shift in catalytic properties was observed, demonstrating that rational transfer of favorable catalytic properties from one phytase to another is possible by using this approach. Although the exchange of the active site was associated with a 7.6 °C decrease in unfolding temperature (Tm) as measured by differential scanning calorimetry, consensus phytase-7 still was >7 °C more thermostable than all wild-type ascomycete phytases known to date. Thus, combination of the consensus approach with the selection of a "preferred" active site allows the design of a thermostabilized variant of an enzyme family of interest that (most closely) matches the most favorable catalytic properties found among its family members. [source] Large genetic divergence of new, morphologically similar species of sterile lichens from Europe (Lepraria, Stereocaulaceae, Ascomycota): concordance of DNA sequence data with secondary metabolitesCLADISTICS, Issue 4 2008Judith Fehrer Lichenized fungi of the genus Lepraria are known for their paucity of morphological characters. Species identification is therefore largely based on secondary chemistry. We investigated different chemotypes of the morphologically highly similar L. jackii species complex by internal transcribed spacer (ITS) sequencing. In phylogenetic analyses including all available Lepraria species, samples belonging to different chemotypes of the L. jackii agg. corresponded to four highly divergent clusters. While true L. jackii was genetically uniform, the other three clades represented previously unrecognized species. They originated from different major speciation events, and two of them were not closely related to any other species. Assessment of intraspecific genetic variability revealed four different patterns with respect to geographic scale. ITS sequences proved to be the most reliable and distinctive characters for species recognition in the Lepraria jackii complex and were in accordance with chemical and ecogeographic data. Frequent occurrence of long branches, relatively few resolved relationships despite high genetic variability, and the discovery and description of a considerable part of the Lepraria species within the last 10 years suggest that the genus is probably much larger than currently known. The diversification of this asexual group in the potential absence of recombination is discussed. © The Willi Hennig Society 2008. [source] Posturographic description of the regaining of postural stability following strokeCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 1 2005Henrik Rogind Summary Background:, Failing balance and increased liability to falling are common complaints among hemiplegic subjects. During rehabilitation much effort is put into regaining postural stability. Purpose:, To describe the regaining of postural stability during rehabilitation for the first year following stroke in hemiplegic patients Materials and methods:, Twenty-six patients were included within 5 days of suffering a stroke resulting from a CT-verified clearly defined thromboembolic lesion, localized in the vascular bed of middle cerebral artery on either side. Posturographic evaluation of sway was performed on a commercially available force plate system (Balance Master Pro®). Measured parameters included per cent maximum stability (PMS), per cent ankle strategy (AST), and average angular velocity (AVE). An additional parameter was derived by calculating the slope (SLP) of the linear relationship between stability and ankle strategy. SLP reflects the predisposition of the stroke patient to keep using ankle strategy when faced with increasingly difficult balance tasks. The presence of familiarization to the measurement method was examined by including a preliminary measurement not otherwise included in the analysis of changes during the first year of follow-up. The temporal evolvement of sway was described by measuring sway parameters 1, 2, 4, 8 and 52 weeks following stroke. The proportions of the variation in sway caused by measurement error and between patients were compared. Results:, All parameters improved over time, as demonstrated by significant improvements from each of week 1, 2, 4 and 8 to week 52. There was evidence of familiarisation for PMS, AST and AVE, but not for SLP. Estimation of variance components showed that between patient variation accounts for between two-thirds and four-fifths of the total variation. A considerable part of this variation was caused by individual differences in the temporal improvement of sway over time. Patients considered the evaluation of postural sway demanding and time consuming resulting in a relatively large loss to follow-up: 15 patients completed the 8-week visit while seven completed the 1 year visit. Conclusion:, Postural stability increases for the first year following stroke. There is evidence of familiarization towards the measurements process for the traditional posturographic parameters PMS, AST and AVE, but not for the derived parameter SLP, which might make the latter a candidate for a sway parameter reflecting basic mechanisms of upholding upright stance in hemiplegic patients. The estimated variance components stress the considerable between-patient variation and question the ability of the force plate method to monitor individual sway performance of such patients during the rehabilitation process. [source] | |||||||||||||