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Selected AbstractsAmong- and within-species variation in plant litter decomposition in contrasting long-term chronosequencesFUNCTIONAL ECOLOGY, Issue 2 2009David A. Wardle Summary 1Following major disturbances ecosystem development occurs but in the prolonged absence of disturbance a decline (retrogressive) phase follows in which productivity and nutrient availability diminishes. Although it is recognized that litter quality and decomposition rates decrease as retrogression proceeds, little is known about the extent to which this is driven among- vs. within-species variation across these sequences. 2We selected six long-term chronosequences that each included retrogressive stages, in New Zealand, Hawaii, Sweden, Alaska and Australia. Two involve significant species turnover across the sequence so that different species dominate at different stages, two involve low species turnover so that the same dominant species occur at all stages, and two involve some turnover of species but with certain species persisting throughout most of the sequence. 3For each chronosequence, we collected litter from each dominant plant species at each stage of that sequence. For each litter collection we measured concentrations of N and P, and performed laboratory decomposition bioassays to measure mass loss, N and P loss, and the response of mass loss to mixture with litters of coexisting species. 4We found that litter N and P concentrations often declined with increasing ecosystem age, both among- and within-species. However, the relative importance of among- and within-species effects varied across the six chronosequences. Rates of litter mass, N, and P loss during decomposition sometimes decreased with increasing ecosystem age, but most often at the among-species rather than the within-species level. 5Litter mixing effects often varied across chronosequence stages, but the magnitude and direction of these effects was inconsistent among sequences. Variation in litter mixing effects across chronosequence stages was driven mainly by among- rather than within-species variation. 6Although several recent studies have emphasized the role of within-species variation on ecosystem properties, our results point to among-species variation as a consistently important ecological driver, with within-species variation being important only for some variables and in some instances. As such they highlight that decomposition processes are most likely to be highly responsive to gradients of soil fertility (such as across chronosequences) when significant species turnover occurs across the gradient. [source] Fossil evidence and phylogeography of temperate species: ,glacial refugia' and post-glacial recolonizationJOURNAL OF BIOGEOGRAPHY, Issue 11 2009Robert S. Sommer Abstract We present a short synthesis of the Pleistocene distribution dynamics and phylogeographic recolonization hypotheses for two temperate European mammal species, the red deer (Cervus elaphus) and the roe deer (Capreolus capreolus), for which high-resolution patterns of fossil evidence and genetic data sets are available. Such data are critical to an understanding of the role of hypothesized glacial refugia. Both species show a similar pattern: a relatively wide distribution in the southern part of Central Europe 60,000,25,000 years ago, and a strong restriction to areas in southern Europe for nearly 10,000 years during the Last Glacial Maximum (LGM) and the early Late Glacial (25,000,14,700 years ago). With the beginning of Greenland Interstadial 1 (Bølling/Allerød warming, c. 14,700,11,600 years ago) a sudden range expansion into Central Europe is visible, but the colonization of most of Central Europe, including the northern European Lowlands, only began in the early Holocene. In a European context, regions where the species were distributed during the LGM and early Late Glacial are most relevant as potential origins of recolonization processes, because during these c. 10,000 years distribution ranges were smaller than at any other time in the Late Quaternary. As far as the present distribution of temperate species and their genetic lineages is concerned, so-called ,cryptic refugia' are important only if the species are actually confirmed there during the LGM, as otherwise they could not possibly have contributed to the recolonization that eventually resulted in the present distribution ranges. [source] Association of cytokine gene polymorphisms in CWP and its severity in Turkish coal workersAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 10 2008Ilker Ates PhD Abstract Background Cytokines appear to play a key role in some inflammatory reactions affecting the interactions among pro- and anti-inflammatory mechanisms that result in several diseases such as coal workers' pneumoconiosis (CWP). In this study, to determine the cytokine gene profiles of Turkish coal miners, we performed genotyping analysis to investigate the polymorphisms of CWP-related pro-inflammatory (TNFA, IL1A, IL1B, and IL6) and anti-inflammatory cytokines (IL-1RN and TGFB1). An additional goal was to observe whether these cytokine gene polymorphisms influence the development risk and severity of. Methods Genotyping was carried out by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Results TNFA (,238) gene polymorphism principally affected CWP development and severity (OR,=,3.47: 95% CI, 1.12,10.77 and OR,=,4.30: 95% CI, 1.25,14.74, respectively) and also risk of CWP (OR,=,3.79: 95% CI, 1.37,10.46). The TNFA (,308) variant was associated with a risk for the CWP severity (OR,=,2.84: 95% CI, 1.08,7.39). A protective effect of IL6 was found on the development (OR,=,0.48: 95% CI, 0.21,0.93) and severity of CWP (OR,=,0.37: 95% CI, 0.15,0.91). Conclusions We suggest that TNFA (,238) variant may be a risk factor in both development and the severity of CWP, while TNFA (,308) variant seems to be important only in disease severity. On the other hand, IL6 variant may have a protective effect on the development and disease severity. Am. J. Ind. Med. 51:741,747, 2008. Published 2008 Wiley-Liss, Inc. [source] Development of respiratory control instability in heart failure: a novel approach to dissect the pathophysiological mechanismsTHE JOURNAL OF PHYSIOLOGY, Issue 1 2006Charlotte H. Manisty Observational data suggest that periodic breathing is more common in subjects with low F, high apnoeic thresholds or high chemoreflex sensitivity. It is, however, difficult to determine the individual effect of each variable because they are intrinsically related. To distinguish the effect of isolated changes in chemoreflex sensitivity, mean F and apnoeic threshold, we employed a modelling approach to break their obligatory in vivo interrelationship. We found that a change in mean CO2 fraction from 0.035 to 0.045 increased loop gain by 70 ± 0.083% (P < 0.0001), irrespective of chemoreflex gain or apnoea threshold. A 100% increase in the chemoreflex gain (from 800 l min,1 (fraction CO2),1) resulted in an increase in loop gain of 275 ± 6% (P < 0.0001) across a wide range of values of steady state CO2 and apnoea thresholds. Increasing the apnoea threshold F from 0.02 to 0.03 had no effect on system stability. Therefore, of the three variables the only two destabilizing factors were high gain and high mean CO2; the apnoea threshold did not independently influence system stability. Although our results support the idea that high chemoreflex gain destabilizes ventilatory control, there are two additional potentially controversial findings. First, it is high (rather than low) mean CO2 that favours instability. Second, high apnoea threshold itself does not create instability. Clinically the apnoea threshold appears important only because of its associations with the true determinants of stability: chemoreflex gain and mean CO2. [source] The N -Arylamino Conjugation Effect in the Photochemistry of Fluorescent Protein Chromophores and AminostilbenesCHEMISTRY - AN ASIAN JOURNAL, Issue 9 2010Guan-Jhih Huang Abstract To understand the nonradiative decay mechanism of fluorescent protein chromophores in solutions, a systematic comparison of a series of (Z)-4-(N -arylamino)benzylidene-2,3-imidazolinones (ABDIs: 2,P, 2,PP, 2,OM, and 2,OMB) and the corresponding trans -4-(N -arylamino)-4,-cyanostilbenes (ACSs: 1,P, 1,PP, 1,OM, and 1,OMB) was performed. We have previously shown that the parameter ,f+2,,tc, in which ,f and ,tc are the quantum yields of fluorescence and trans,cis photoisomerization, respectively, is an effective probe for evaluating the contribution of twisted intramolecular charge transfer (TICT) states in the excited decays of trans -aminostilbenes, including the push,pull ACSs. One of the criteria for postulating the presence of a TICT state is ,f+2,,tc,1.0, because its formation is decoupled with the CC bond (,) torsion pathway and its decay is generally nonradiative. Our results show that the same concept also applies to ABDIs 2 with the parameter ,f+2,,ZE in which ,ZE is the quantum yield of Z,E photoisomerization. We conclude that the , torsion rather than the CC bond (,) torsion is responsible for the nonradiative decays of ABDIs 2 in aprotic solvents (hexane, THF, acetonitrile). The phenyl-arylamino CN bond (,) torsion that leads to a nonradiative TICT state is important only for 2,OM in THF and acetonitrile. If the solvent is protic (methanol and 10,20,% H2O in THF), a new nonradiative decay channel is present for ABDIs 2, but not for ACSs 1. It is attributed to internal conversion (IC) induced by solvent (donor),solute (acceptor) hydrogen-bonding (HB) interactions. The possible HB modes and the concept of , torsion-coupled proton transfer are also discussed. [source] | ||||||||||