bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal flow variation allows ‘time‐sharing’ by disparate aquatic insect communities in montane desert streams
Authors: BOGAN MICHAEL T. , LYTLE DAVID A. 
Published: December 2006

Summary1. Flow variation can drive major abiotic changes in stream environments between seasons. Theoretically, disparate biotic communities could be maintained during different seasons at a single site if suitable refuges and colonist sources were available. Using isolated montane desert streams in south‐east Arizona as a model system, we hypothesised that two disparate aquatic insect faunas (montane temperate and neotropical) could be maintained at the same sites through strong seasonal variation in abiotic conditions.2. We collected aquatic insects representing 59 families from seven streams during high‐flow (March–April) and low‐flow (June) sampling periods across two years. We assessed changes in aquatic insect community and functional feeding group composition by habitat (riffle, pool) and season (high flow, low flow).3. Within sites, wetted stream area decreased by an average of 97% between high‐flow (predominately riffles) and low‐flow (predominately pools) seasons. Community composition likewise showed strong seasonal patterns; the montane temperate fauna was strongly associated with the high‐flow season while neotropical hemipterans and coleopterans were associated with the low‐flow season. Increased water temperature was significantly associated with this shift from temperate to neotropical assemblages.4. Functional feeding group composition shifted dramatically by season. The proportion of predators increased from 24.5% (high flow) to 75.2% (low flow) while collector–filterers and shredders declined from 38.4% (high flow) to 1.7% (low flow).5. We suggest that habitat ‘time‐sharing’ by disparate communities is facilitated via strong seasonal variation in temperature and flow and the presence of high elevation refuges or diapause stages for temperate montane taxa to survive the dry season.
Persistence and colonisation as measures of success in bog restoration for aquatic invertebrates: a question of detection
Authors: MAZEROLLE MARC J. , POULIN MONIQUE 
Published: December 2006

Summary1. van Duinen et al. (Freshwater Biol., 2006) raise an interesting point regarding Mazerolle et al.’s (Freshwater Biol., 2006, 51, p. 333) conclusion on the ability of invertebrates, especially sedentary species, to colonise newly created bogs pools. We wish to clarify that Mazerolle et al. (2006) targeted large arthropods and the absence of smaller sedentary species was purely a result of sampling design.2. van Duinen et al. (2006) postulate that colonisation rates by bog specialists should be higher in Canada than in the Netherlands, given the extensive amount of intact peatlands in Canada. Here, we emphasise the importance of taking the regional context into account when assessing restoration success as our study site occurs in a landscape where most bog pools have been drained.3. An evaluation of restoration efforts should focus on both sedentary and vagile invertebrates, to resolve the importance of persistence and colonisation. Such patterns are difficult to interpret, however, when sampling designs and analyses do not account for the probability of detection: an absence may be due to non‐detection or true absence. We strongly urge investigators to directly estimate detection probability in addition to the parameters of interest (e.g. presence, abundance) to provide the best information possible regarding restoration success.
Molecular cloning and heterologous expression of an α‐adrenergic‐like octopamine receptor from the silkworm Bombyx mori
Authors: Ohtani A. , Arai Y. , Ozoe F. , Ohta H. , Narusuye K. , Huang J. , Enomoto K. , Kataoka H. , Hirota A. , Ozoe Y. 
Published: December 2006

AbstractA cDNA encoding an octopamine (OA) receptor (BmOAR1) was isolated from the nerve tissue of silkworm (Bombyx mori) larvae. Comparison of amino acid sequences showed that BmOAR1 is highly identical to OA receptors isolated from Periplaneta americana (Pa oa1), Apis mellifera (AmOA1), and Drosophila melanogaster (OAMB or DmOA1A). BmOAR1 was stably expressed in HEK‐293 cells. OA above 1 µm led to an increase in intracellular cyclic AMP concentration ([cAMP]i). The synthetic OA‐receptor agonist demethylchlordimeform also elevated [cAMP]i to the same maximal level (≈ 5‐fold over the basal level) as that induced by OA. However, other biogenic amines, tyramine and dopamine, and chlordimeform were without effects. The [cAMP]i level raised by OA was lowered by antagonists; the rank order of antagonist activity was chlorpromazine > mianserin = yohimbine. Cyproheptadine and metoclopramide had little effect. OA above 100 nm induced a transient or sustained increase in intracellular Ca2+ concentration ([Ca2+]i), depending on the concentration of OA. Sequence homology and functional analysis data indicate that BmOAR1 is an α‐adrenergic‐like OA receptor of B. mori.
Cathepsin L function in insect moulting: molecular cloning and functional analysis in cotton bollworm, Helicoverpa armigera
Authors: Liu J. , Shi G.‐P. , Zhang W.‐Q. , Zhang G.‐R. , Xu W.‐H. 
Published: December 2006

AbstractMoulting is an essential process of insect development but little is known about cysteine proteases in the process. Here, we detail a proteolytic activity profile from fifth larval instar to new pupae of the lepidopteran Helicoverpa armigera. At fifth to sixth instar moulting, the activities were significantly higher than those in non‐moulting stages, and were inhibited by the cysteine protease inhibitor, 2S, 3S‐trans‐epoxysuccinyl‐L‐leucylamido‐3‐methylbutane ethyl ester (E‐64), or by the cathepsin L‐selective inhibitor CLIK148. Further, a 1513 bp cathepsin L cDNA (Har‐CL) was isolated from the H. armigera larval cuticle and epidermis layer. Har‐CL gene expression, which is correlated closely with ecdysone, was higher during larval moulting. Injection of E‐64 or CLIK148 resulted in delayed fifth to sixth instar moulting, suggesting an essential role for cathepsin L in larval moulting.
GUEST EDITORIAL: Hello New Zealand
Authors: Trewick Steven A. , Paterson Adrian M. , Campbell Hamish J. 
Published: December 2006

AbstractIslands of the Pacific Ocean have long fascinated evolutionists. Oceanic islands, generally the products of volcanic activity, provide natural experiments as biological populations are well delimited and the age of islands can be determined using radiometric dating. ‘Continental islands’, including New Caledonia and New Zealand, provide equally valuable opportunities for evolutionary study. For students of New Zealand biogeography, the peculiar composition of the biota coupled with a limited interpretation of geology has resulted in the widespread acceptance that the flora and fauna is primarily ancient and of vicariant Gondwanan origin. There is increasing evidence from molecular data that much of this biodiversity is the product of evolution following relatively recent colonization. Such data have prompted biologists to consider geological information on New Zealand in more detail. At the heart of the issue is the question of whether modern New Zealand has a terrestrial link through time with the continent Zealandia that split from Gondwanaland some 80 Ma. Zealandia, which includes New Caledonia, Lord Howe Island and several of the subantarctic islands, is now largely submerged, and New Zealand's present terrestrial existence is the product of tectonic activity initiated around 26 Ma. We argue that for the purposes of biogeographical interpretation, New Zealand can be treated as an oceanic island.
Consequences of herbivory by native ungulates for the reproduction of a savanna tree
Authors: GOHEEN JACOB R. , YOUNG TRUMAN P. , KEESING FELICIA , PALMER TODD M. 
Published: December 2006

SummaryHerbivores may negatively impact plant populations by reducing the survival, growth and reproduction of individual plants.In African savannas, browsing by large mammalian herbivores has been shown repeatedly to reduce adult survival and growth of members of the genusAcacia, the dominant trees in these systems. However, the potential costs of mammalian herbivory toAcaciareproduction are largely unexplored, and have never been investigated experimentally in African savannas.Using a long‐term, large‐scale field experiment, we demonstrate that, in the absence of native herbivores, individual trees were twice as likely to reproduce, and those that reproduced produced a greater biomass of seeds. In addition, spine length (an indicator of past herbivory) was correlated with reduced reproduction ofAcacia drepanolobium, the dominant tree across large areas of East Africa. Browsing by native herbivores triggers the production of longer spines, an induced resistance, and spine length was significantly and negatively related both to the occurrence and magnitude of reproduction.Induced resistance appeared to mitigate the negative effects of herbivory where large herbivores were present: trees with long spines reproduced at levels comparable to trees with similarly long spine lengths in the absence of browsers.Large mammalian herbivores kill and suppress the growth of adultAcacia, and therefore often are regarded as critical in maintaining the co‐dominance of trees and grasses in African savannas. Our results provide the first experimental evidence that large mammalian herbivores can suppress reproduction inAcacia, thus highlighting an additional pathway through which these herbivores might impact population dynamics of this important and widespread genus.In savanna systems, declining populations of large herbivores may trigger a series of complex demographic responses for trees, with potentially strong consequences for the structure and function of savannas.
Identifying mechanisms of competition in multi‐species communities
Authors: WEIGELT ALEXANDRA , SCHUMACHER JENS , WALTHER TIM , BARTELHEIMER MAIK , STEINLEIN TOM , BEYSCHLAG WOLFRAM 
Published: December 2006

SummaryWe tested the hypothesis that the competitive effect of multi‐species mixtures on a single target plant can be described as a simple additive function of the effects of single species.In a controlled field competition experiment on sand, we used four common species of dry acidic grasslands (Hieracium pilosella,Jasione montana,Corynephorus canescensandFestuca ovina) to study the effects of both, single‐ and multi‐species neighbourhoods on the target speciesH. pilosella.Target plant biomass points at a competitive ranking of neighbour species withF. ovinaas the strongest competitor followed byC. canescensandH. pilosella, whileJ. montanahas a lower effect on the target. The analysis of the competitive response gives no indication of competitive release or amplification with increasing number of neighbouring species.Further analysis with yield‐density models reveals that the competition intensity of most multi‐species mixtures is well predicted by the effect of pairwise interactions. Hence, for the majority of species combinations, our results indicate additive effects of species competition.Specific species combinations, however, significantly deviate from this result. For combinations ofC. canescenswith either one of the herbs, the models show a significantly better fit if a non‐additivity parameter is included. The important missing factor to describe target plant growth is species‐specific biomass of neighbouring plants and here root biomass is the most crucial determinant. The addition of each of these factors as non‐additive parameters significantly increases the predictive power of the model.Our work adds to the increasing evidence that interactions in diverse plant communities are not simply a sum of their component species interactions. For a better understanding of the effect of competition on the structure and development of diverse plant communities, future studies need to consider both additive and non‐additive effects of competing species.
Human pregnancy‐associated malaria‐specific B cells target polymorphic, conformational epitopes in VAR2CSA
Authors: Barfod Lea , Bernasconi Nadia L. , Dahlbäck Madeleine , Jarrossay David , Andersen Pernille Haste , Salanti Ali , Ofori Michael F. , Turner Louise , Resende Mafalda , Nielsen Morten A. , Theander Thor G. , Sallusto Federica , Lanzavecchia Antonio , Hviid Lars 
Published: December 2006

SummaryPregnancy‐associated malaria (PAM) is caused by Plasmodium falciparum‐infected erythrocytes (IEs) that bind to chondroitin sulphate A (CSA) in the placenta by PAM‐associated clonally variant surface antigens (VSA). Pregnancy‐specific VSA (VSAPAM), which include the PfEMP1 variant VAR2CSA, are targets of IgG‐mediated protective immunity to PAM. Here, we report an investigation of the specificity of naturally acquired immunity to PAM, using eight human monoclonal IgG1 antibodies that react exclusively with intact CSA‐adhering IEs expressing VSAPAM. Four reacted in Western blotting with high‐molecular‐weight (> 200 kDa) proteins, while seven reacted with either the DBL3‐X or the DBL5‐ε domains of VAR2CSA expressed either as Baculovirus constructs or on the surface of transfected Jurkat cells. We used a panel of recombinant antigens representing DBL3‐X domains from P. falciparum field isolates to evaluate B‐cell epitope diversity among parasite isolates, and identified the binding site of one monoclonal antibody using a chimeric DBL3‐X construct. Our findings show that there is a high‐frequency memory response to VSAPAM, indicating that VAR2CSA is a primary target of naturally acquired PAM‐specific protective immunity, and demonstrate the value of human monoclonal antibodies and conformationally intact recombinant antigens in VSA characterization.
Phenotypic heterogeneity can enhance rare‐cell survival in ‘stress‐sensitive’ yeast populations
Authors: Bishop Amy L. , Rab Faiza A. , Sumner Edward R. , Avery Simon V. 
Published: December 2006

SummaryIndividual cells within isogenic microbial cultures exhibit phenotypic heterogeneity, an issue that is attracting intense interest. Heterogeneity could confer benefits, in generating variant subpopulations that may be better equipped to persist during perturbation. We tested this hypothesis by comparing the survival of wild‐type Saccharomyces cerevisiae with that of mutants which are considered stress‐sensitive but which, we demonstrate, also have increased heterogeneity. The mutants (e.g. vma3, ctr1, sod1) exhibited the anticipated sensitivities to intermediate doses of nickel, copper, alkaline pH, menadione or paraquat. However, enhanced heterogeneity meant that the resistances of individual mutant cells spanned a broad range, and at high stress occasional‐cell survival in most of these populations overtook that of the wild type. Green fluorescent protein (GFP) reporter studies showed that this heterogeneity‐dependent advantage was not related to perturbation of buffered gene expression. Deletion strain screens combined with other approaches revealed that vacuolar alkalinization resulting from loss of Vma‐dependent vacuolar H+‐ATPase activity was not the cause of vma mutants' net stress sensitivities. An alternative Vma‐dependent resistance mechanism was found to suppress an influence of variable vacuolar pH on the metal resistances of individual wild‐type cells. In addition to revealing new mechanisms of heterogeneity generation, the results demonstrate experimentally a benefit under adverse conditions that arises specifically from heterogeneity, and in populations conventionally considered to be disadvantaged.
The Aspergillus fumigatus metacaspases CasA and CasB facilitate growth under conditions of endoplasmic reticulum stress
Authors: Richie Daryl L. , Miley Michael D. , Bhabhra Ruchi , Robson Geoffrey D. , Rhodes Judith C. , Askew David S. 
Published: December 2006

SummaryWe have examined the contribution of metacaspases to the growth and stress response of the opportunistic human mould pathogen, Aspergillus fumigatus, based on increasing evidence implicating the yeast metacaspase Yca1p in apoptotic‐like programmed cell death. Single metacaspase‐deficient mutants were constructed by targeted disruption of each of the two metacaspase genes in A. fumigatus, casA and casB, and a metacaspase‐deficient mutant, ΔcasA/ΔcasB, was constructed by disrupting both genes. Stationary phase cultures of wild‐type A.  fumigatus were associated with the appearance of typical markers of apoptosis, including elevated proteolytic activity against caspase substrates, phosphatidylserine exposure on the outer leaflet of the membrane, and loss of viability. By contrast, phosphatidylserine exposure was not observed in stationary phase cultures of the ΔcasA/ΔcasB mutant, although caspase activity and viability was indistinguishable from wild type. The mutant retained wild‐type virulence and showed no difference in sensitivity to a range of pro‐apoptotic stimuli that have been reported to initiate yeast apoptosis. However, the ΔcasA/ΔcasB mutant showed a growth detriment in the presence of agents that disrupt endoplasmic reticulum homeostasis. These findings demonstrate that metacaspase activity in A. fumigatus contributes to the apoptotic‐like loss of membrane phospholipid asymmetry at stationary phase, and suggest that CasA and CasB have functions that support growth under conditions of endoplasmic reticulum stress.
The human anionic antimicrobial peptide dermcidin induces proteolytic defence mechanisms in staphylococci
Authors: Lai Yuping , Villaruz Amer E. , Li Min , Cha David J. , Sturdevant Daniel E. , Otto Michael 
Published: December 2006

SummaryAntimicrobial peptides (AMPs) represent a key component of innate host defence against bacterial pathogens. Bacterial resistance mechanisms usually depend on the characteristic positive charge of AMPs. However, several human cell types also produce anionic AMPs, mechanisms of resistance to which are poorly understood. Here we demonstrate that the skin commensal and leading nosocomial pathogen Staphylococcus epidermidis senses and efficiently inactivates the anionic AMP dermcidin. Dermcidin induced differential expression of global regulatory systems, leading to increased expression of proteases with the capacity to degrade dermcidin, particularly S. epidermidis SepA. A similar induction of extracellular proteolytic activity was found in Staphylococcus aureus, suggesting a common regulatory mechanism in staphylococci. Notably, human cationic AMPs also led to the activation of global regulators, but inactivation of dermcidin by SepA was much more effective than of the tested cationic peptides. The ability to react to the unusual, anionic dermcidin with effective countermeasures likely contributes to the extraordinary success of staphylococci as colonizers and infective agents on human epithelia. Our study indicates that staphylococci can react to human AMPs by specific mechanisms of resistance and establishes a crucial role for staphylococcal proteases in the interaction with human innate host defence.
Muscarinic acetylcholine receptor activation increases transcellular transport of macromolecules across mouse and human intestinal epitheliumin vitro
Authors: Cameron H. L. , Perdue M. H. 
Published: December 2006

Abstract The intestinal epithelium acts as a barrier restricting uptake of luminal macromolecules such as dietary antigens and microbes. Here, we examined the role of cholinergic signalling in the regulation of permeability to macromolecules. Mouse jejunum was mounted in Ussing chambers and permeability was determined by measuring the flux of the antigen‐sized protein, horseradish peroxidase (HRP), across the tissue. Baseline HRP permeability was significantly reduced by neural blockade with tetrodotoxin or cholinergic muscarinic antagonism with atropine, suggesting that ongoing release of endogenous acetylcholine from enteric nerves regulates barrier function. Exogenous addition of the muscarinic agonist bethanechol caused significant increases in both HRP flux and the area of HRP‐containing endosomes in enterocytes. Bethanechol‐enhanced HRP flux was abrogated by the M3 receptor antagonist, 4‐diphenylacetoxy‐N‐methylpiperidine methiodide (4‐DAMP), the phospholipase A2inhibitor quinacrine, and the cyclooxygenase inhibitor indomethacin. Complementary in vitro studies showed direct effects of bethanechol on T84 epithelial cells, where increased HRP uptake was associated with increased F‐actin, and increased cytosolic phospholipase A2(cPLA2) phosphorylation. Taken together, these results provide evidence for cholinergic regulation of transepithelial transport of macromolecules, mainly mediated by activation of M3 receptors with subsequent involvement of phospholipase A2and cyclooxygenase products.
Functional P2X7 Receptor Polymorphisms (His155Tyr, Arg307Gln, Glu496Ala) in Patients with Crohn's Disease
Authors: Haas S. L. , Ruether A. , Singer M. V. , Schreiber S. , Böcker U. 
Published: December 2006

AbstractGenetic factors contribute to inflammatory bowel diseases. Recently, the P2X7 receptor was found to be a key player in caspase‐1‐mediated processing of the proinflammatory cytokines, interleukin‐1β and interleukin‐18. We therefore aimed to determine whether the gain‐of‐function single nucleotide polymorphism (SNP) His155Tyr and the loss‐of‐function SNP Arg307Gln and Glu496Ala were associated with susceptibility to Crohn's disease (CD). For association analysis, 681 unrelated CD patients and 736 healthy controls were enrolled. Furthermore, 490 CD trios were included for segregation analysis. Genotyping was performed by the application of the TaqMan® MGB biallelic discrimination system. The Arg307Gln polymorphism revealed a borderline significant difference in genotype frequencies between CD patients and controls (P = 0.06) without implying any pathological significance because of low case numbers. Case–control statistics for the variants His155Tyr and Glu496Ala showed no association with CD phenotype (P = 0.19 and 0.99). Subsequent family‐based transmission disequilibrium test did not prove an association of the investigated single‐nucleotide polymorphisms with CD. In conclusion, the analysed intragenetic variants of the P2X7 receptor may not be a susceptibility factor for CD.
Commonly Used Reference Genes are Actively Regulated in In vitro Stimulated Lymphocytes
Authors: Røge R. , Thorsen J. , Tørring C. , Øzbay A. , Møller B. K. , Carstens J. 
Published: December 2006

AbstractQuantitative polymerase chain reaction (Q‐PCR) studies of urine sediments have demonstrated an increased expression of cytotoxin genes during episodes of acute rejection of renal allografts. To compensate for differences in initial sample size and cDNA preparation, standard Q‐PCR experiments involve normalization to a reference gene. Although stable expression of reference genes is a prerequisite for any Q‐PCR analysis, commonly used reference genes have demonstrated a varying expression across tissues and various stimuli. In this study, cellular expression of several reference genes was investigated in a mixed lymphocyte reaction as a model of gene expression during alloreactive T‐lymphocyte activation and acute rejection. Gene expression was quantified using Q‐PCR, normalized to cell counts obtained by DNA quantification and corrected for cell polyploidy using flow cytometry. Examined reference genes were 18S rRNA, β‐actin (ACTB), hydroxymethylbilane synthase (HMBS), hypoxanthine phosphoribosyltransferase (HPRT1) and peptidylprolyle isomerase B (PPIB). This study also examined two novel T‐lymphocyte‐specific reference genes: CD3E and CD8B. HMBS and HPRT were 18.8‐ and 7.4‐fold upregulated, respectively, ACTB was 5.3‐fold upregulated, PPIB was 3.2‐fold upregulated while 18S rRNA remained stably expressed. The T‐lymphocyte‐specific reference gene CD3E remained stable while CD8B was upregulated 2.3‐fold. In conclusion, several commonly used reference genes were actively regulated during alloreactive T‐lymphocyte activation. Additionally, we introduce two stable T‐lymphocyte‐specific reference genes that might be useful in a Q‐PCR analysis of T‐lymphocyte‐specific cytotoxin genes in urine sediments, as they overcome the contribution of reference gene mRNA from cells irrelevant for diagnosis.