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Moderate Densities (moderate + density)
Selected AbstractsCrowding and disease: effects of host density on response to infection in a butterfly,parasite interactionECOLOGICAL ENTOMOLOGY, Issue 5 2009ELIZABETH LINDSEY Abstract. 1. Hosts experiencing frequent variation in density are thought to benefit from allocating more resources to parasite defence when density is high (,density-dependent prophylaxis'). However, high density conditions can increase intra-specific competition and induce physiological stress, hence increasing host susceptibility to infection (,crowding-stress hypothesis'). 2. We studied monarch butterflies (Danaus plexippus) and quantified the effects of larval rearing density on susceptibility to the protozoan parasite Ophryocystis elektroscirrha. Larvae were inoculated with parasite spores and reared at three density treatments: low, moderate, and high. We examined the effects of larval density on parasite loads, host survival, development rates, body size, and wing melanism. 3. Results showed an increase in infection probability with greater larval density. Monarchs in the moderate and high density treatments also suffered the greatest negative effects of parasite infection on body size, development rate, and adult longevity. 4. We observed greater body sizes and shorter development times for monarchs reared at moderate densities, and this was true for both unparasitised and parasite-treated monarchs. We hypothesise that this effect could result from greater larval feeding rates at moderate densities, combined with greater physiological stress at the highest densities. 5. Although monarch larvae are assumed to occur at very low densities in the wild, an analysis of continent-wide monarch larval abundance data showed that larval densities can reach high levels in year-round resident populations and during the late phase of the breeding season. Treatment levels used in our experiment captured ecologically-relevant variation in larval density observed in the wild. [source] Collisionally induced dephasing and rotational energy transfer in the CO2 Fermi dyad ,blue' Q-branch 1388 cm,1JOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2007V. G. Arakcheev Abstract In this paper we present a comparative analysis of two alternative approaches to the description of the rotational energy transfer (RET) in the ,blue' (1388 cm,1) Q-branch of the CO2,1/2,2 Fermi dyad based on the simplified spectral exchange (SE) and rotational relaxation (RR) models. The analysis was carried out using a special approximation error minimization procedure for fitting the theoretical model to experimental impulse responses obtained by time-domain CARS at low and moderate densities. At densities ,, 1 amagat, the collisional dephasing (CD) contribution to the linewidth substantially prevails over the width attributed to the rotational structure. The impulse response beating analysis and the fitting results clearly proved that in contrast to the ,red' (1285 cm,1) band, the SE model is more appropriate in comparison with the RR model for a description of the RET in the ,blue' Q-branch. Copyright © 2007 John Wiley & Sons, Ltd. [source] Histamine H3 -receptor-mediated [35S]GTP,[S] binding: evidence for constitutive activity of the recombinant and native rat and human H3 receptorsBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2002A Rouleau Constitutive activity of the recombinant and native rat and human H3 receptors (H3Rs) was studied using H3R-mediated [35S]GTP,[S] binding and [3H]-arachidonic acid release. Ciproxifan, an inverse agonist at the rat H3R (rH3R), decreased [3H]arachidonic acid release from CHO cells expressing moderate densities (,200,300 fmol mg,1 protein) of the human H3R (hH3R). This effect occurred with the same magnitude than at the rH3R. The expression of the hH3R was associated with an increase in [35S]GTP,[S] binding to membranes of CHO cells. Ciproxifan decreased [35S]GTP,[S] binding to membranes of CHO (hH3R) cells. Both effects were correlated to receptor density and revealed that constitutive activity of the hH3R, although lower than that of the rH3R in this assay, was again observed at physiological densities (<500 fmol mg,1 protein). Ciproxifan was less potent at the human than the rat receptor, not only as an antagonist (Ki=45 nM), but also as an inverse agonist (EC50=15 nM). Constitutive activity of the hH3R was also evidenced using inhibition of [35S]GTP,[S] binding by unlabelled GTP,S. The expression of the hH3R generated a high affinity binding for GTP,S which was increased by imetit, but partially decreased by ciproxifan, therefore acting as a partial inverse agonist. [35S]GTP,[S] binding to rat brain membranes was decreased in several regions by thioperamide, ciproxifan and FUB 465, three inverse agonists at the H3R, whose effects were blocked by proxyfan, a neutral antagonist. [35S]GTP,[S] binding was also decreased by an A1 -adenosine receptor inverse agonist, but remained unchanged in the presence of inverse agonists at D2/D3 dopamine, H1 and H2 histamine, ,2 -adrenergic and , opioid receptors. In conclusion, the present study shows that the recombinant rat and human H3 receptors expressed at physiological densities display constitutive activity and suggests that constitutive activity of native H3Rs is one of the highest among G-protein-coupled receptors present in rat brain. British Journal of Pharmacology (2002) 135, 383,392; doi:10.1038/sj.bjp.0704490 [source] Energetic N,N,N,,N, -Tetraaminopiperazinium SaltsCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 3 2008Haixiang Gao Prof. Abstract The formation of tetraaminopiperazinium salts using water as solvent provides a green, straightforward approach to highly energetic salts that exhibit good thermal stabilities and moderate densities. The N,N,N,,N, -tetraaminopiperazinium cation was selected for this study because of its high nitrogen,nitrogen bond content and its high positive heat of formation. Theoretical and empirical calculations on energetic salts based on this nitrogen-rich cation reveal them to have high positive molar enthalpies of formation, as high as 1034.0,kJ,mol,1, supporting the application of these new salts as potential energetic materials. [source] Ecological and socio-economic impacts of invasive water hyacinth (Eichhornia crassipes): a reviewFRESHWATER BIOLOGY, Issue 2 2010A. M. VILLAMAGNA Summary 1.,Water hyacinth (Eichhornia crassipes) is one of the world's most invasive aquatic plants and is known to cause significant ecological and socio-economic effects. 2.,Water hyacinth can alter water clarity and decrease phytoplankton production, dissolved oxygen, nitrogen, phosphorous, heavy metals and concentrations of other contaminants. 3.,The effects of water hyacinth on ecological communities appear to be largely nonlinear. Abundance and diversity of aquatic invertebrates generally increase in response to increased habitat heterogeneity and structural complexity provided by water hyacinth but decrease due to decreased phytoplankton (food) availability. 4.,Effects of water hyacinth on fish are largely dependent on original community composition and food-web structure. A more diverse and abundant epiphytic invertebrate community may increase fish abundance and diversity, but a decrease in phytoplankton may decrease dissolved oxygen concentrations and planktivorous fish abundance, subsequently affecting higher trophic levels. 5.,Little is known about the effects of water hyacinth on waterbird communities; however, increases in macroinvertebrate and fish abundance and diversity suggest a potentially positive interaction with waterbirds when water hyacinth is at moderate density. 6.,The socio-economic effects of water hyacinth are dependent on the extent of the invasion, the uses of the impacted waterbody, control methods and the response to control efforts. Ecosystem-level research programmes that simultaneously monitor the effects of water hyacinth on multiple trophic-levels are needed to further our understanding of invasive species. [source] Ultrastructural pathology of Baltic salmon, Salmo salar L., yolk sac fry with the M74 syndromeJOURNAL OF FISH DISEASES, Issue 3 2002J Lundström The ultrastructural pathology in liver, brain, skeletal and cardiac muscle of Baltic salmon yolk sac fry with the M74 syndrome is described. In the clinical stage of disease, the main pathological findings in the liver were a depletion of glycogen, condensation of nuclear chromatin, hydropic degeneration of mitochondria and a dilation of the bile canaliculi. In the terminal stage, additional findings were lipid accumulation and myelin whorls in the cytoplasm. The rough endoplasmic reticulum (RER) was degranulated and vesiculated and in some individuals, it formed concentric membranous whorls. Mitochondria showed several additional lesions, such as matrix densities, pleomorphism and cristae abnormalities. Skeletal myocytes were degenerated, and intracellular lipid accumulation was seen in the myocardium. In the brain, an increased frequency of cells exhibiting pyknosis or karryorhexis was recorded. The cytoplasm of these cells formed an amorphous mass of moderate density. The evaluation of brain and skeletal muscle was complicated by sporadic occurrence of pathological findings in the reference material, i.e. clinically healthy Baltic salmon yolk sac fry. As these yolk sac fry are suspected to have a subclinical thiamine deficiency, reference material in future studies should include salmon yolk sac fry from Atlantic populations or originating from reared broodstock. [source] Many body effects in the optical behavior of quantum well excitonsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2008V. P. Kochereshko Abstract Modulation-doped CdTe/Cd0.7Mg0.3Te quantum well structures with a two dimensional electron gas of low and moderate density (from ne = 3 × 1010 cm,2 up to ne , 1012 cm,2) have been studied. Photoluminescence spectra taken from the quantum well in magnetic fields from 0 T to 45 T at different electron densities were studied. The observed spectra were analyzed in terms of combined exciton-electron processes. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] BAC-based upgrading and physical integration of a genetic SNP map in Atlantic salmonANIMAL GENETICS, Issue 1 2010S. Lorenz Summary A better understanding of the genotype,phenotype correlation of Atlantic salmon is of key importance for a whole range of production, life history and conservation biology issues attached to this species. High-density linkage maps integrated with physical maps and covering the complete genome are needed to identify economically important genes and to study the genome architecture. Linkage maps of moderate density and a physical bacterial artificial chromosome (BAC) fingerprint map for the Atlantic salmon have already been generated. Here, we describe a strategy to combine the linkage mapping with the physical integration of newly identified single nucleotide polymorphisms (SNPs). We resequenced 284 BAC-ends by PCR in 14 individuals and detected 180 putative SNPs. After successful validation of 152 sequence variations, genotyping and genetic mapping were performed in eight salmon families comprising 376 individuals. Among these, 110 SNPs were positioned on a previously constructed linkage map containing SNPs derived from expressed sequence tag (EST) sequences. Tracing the SNP markers back to the BACs enabled the integration of the genetic and physical maps by assigning 73 BAC contigs to Atlantic salmon linkage groups. [source] | |||||||||||||