bluuebunny/crossref_metadata_2025_split huggingface dataset:
Success and failure in a lotic crayfish invasion: the roles of hydrologic variability and habitat alteration
Authors: Light Theo 
Published: September 2003

Summary1. This paper examines the distribution, habitat relationships, and potential for spread of non‐native signal crayfish (Pacifastacus leniusculus) in streams of the Truckee River catchment, California, U.S.A. Crayfish associations with natural features and with impoundments and flow alteration were examined in a survey of 33 streams. Abundance changes were followed over 5 years, which included some of the highest and lowest flows on record, in three streams, two unregulated and one regulated. Movement of marked crayfish was studied in one 0.5 km stream reach just upstream from a reservoir.2. Signal crayfish were most abundant in low‐gradient streams and were positively associated with proximity to reservoirs (both upstream and downstream). Crayfish were more likely to be found in regulated than unregulated sites, and did not occur in sites upstream of barriers, such as culverts, that separated them from reservoirs or lakes.3. Crayfish declined in abundance in years following particularly intense and prolonged wet‐season spates, leading to a negative association between crayfish abundance and both peak discharge and duration of bankfull flows.4. Crayfish moved distances of up to 277 m, and at rates of up to 120 m day−1, suggesting significant dispersal ability. Larger crayfish moved greater distances and were more likely to move downstream. Female crayfish showed a pattern of upstream movement in early summer and downstream movement late in the summer, opposite the pattern found in two other studies.5. These results suggest that natural or artificial gradient barriers and, in regulated systems, management of flow regimes to include bankfull or greater flows may help to control invasive crayfish in streams.
The net result: evaluating species richness extrapolation techniques for littoral pond invertebrates
Authors: Foggo Andrew , Rundle Simon D. , Bilton David T. 
Published: September 2003

Summary1. Total species richness for an assemblage or site is a valuable measure in conservation monitoring and assessment, but protocols for sampling and species richness determination in wetland habitats such as ponds, bogs or mires remain largely unrefined.2. Techniques for estimation of total richness of an assemblage based upon replicated sampling offer the opportunity to derive useful estimates of total richness based upon small numbers of samples, and limit sampling‐derived disturbance which can be particularly problematic in small aquatic habitats.3. We quantified the performance of eight of the most commonly encountered estimators of species richness for a variety of littoral zone macrofauna from ponds, comparing estimated richness to maximum richness derived from sampling.4. Estimates using non‐parametric techniques based on species incidence provided the most accurate and precise estimates. The estimators Chao 2 and incidence‐based coverage estimator (ICE) from this category were reliable and consistent slight over‐estimators; the abundance‐based estimator Chao1 also performed well.5. Species inventory based on relatively small numbers of samples might be significantly improved by use of non‐parametric estimators for quantification of species richness.6. Use of non‐parametric estimators of species richness can assist biodiversity inventory by preventing erroneous rankings of habitat richness based upon observed species numbers from limited sampling.
Seasonal variation in diel activity and microhabitat use of an endemic New Zealand stream‐dwelling galaxiid fish
Authors: David Bruno O. , Closs Gerard P. 
Published: September 2003

Summary1. Seasonal variation in microhabitat use and activity of 14 giant kokopu Galaxias argenteus, a drift‐feeding galaxiid fish, was compared using radiotelemetry.2. During winter giant kokopu predominantly used low velocities and intermediate depths by night and day. Activity recorded during 24 and 72 h periods indicated that fish were consistently active at night and inactive during the day. Activity data corresponded with point‐in‐time habitat use data, both of which indicated that fish were concealed amongst cover during the day and used open water habitats at night.3. During summer, giant kokopu used higher water velocities, shallower depths and coarser substrata, particularly at night but also occasionally during the day relative to winter. Giant kokopu were active by both day and night in summer, although periods of activity were less defined and less predictable than during winter.4. Adults used predictable home reaches at base‐flow, with most individuals repeatedly using of one or two cover locations within their ‘home’ reach. Reaches used by fish were relatively short (rarely exceeding 26 m) irrespective of season and always included a single pool‐riffle sequence.5. Diel and seasonal behaviour of giant kokopu was generally comparable with that exhibited by other drift feeding fish species in small temperate streams. However, the nocturnal activity of giant kokopu contrasts with activity patterns in various salmonids, indicating that the impact of predation by different drift feeding fish may vary considerably.
Monoclonal Antibodies Inducing Conformational Changes on the Antigen Molecule
Authors: Roguin L. P. , Retegui L. A. 
Published: September 2003

AbstractMonoclonal antibodies (MoAbs) are extensively used as biological tools because of their invariable specificity. However, the interpretation of results can be misled by the behaviour of MoAb displaying allosteric effects, i.e. long‐range conformational changes on the antigen (Ag). It has been shown that some MoAbs are able to modify the spatial structure of the corresponding protein Ag, affecting in this way its biological activity as well as its binding to a second MoAb. Thus, a researcher using a MoAb as a tool to investigate some features of an antigenic molecule must be aware of the possible positive or negative allosteric properties of the antibody.
Modulation of Host Immune Responses by Overexpression of Immunodominant Antigens of Mycobacterium tuberculosis in Bacille Calmette–Guérin
Authors: Rao V. , Dhar N. , Tyagi A. K. 
Published: September 2003

AbstractBased on their immunodominant nature and ability to induce appropriate immune responses in the host, several antigens of Mycobacterium tuberculosis have shown promise of protection. However, most of the candidate vaccines developed by employing various strategies have afforded protection that is at best comparable with bacillus Calmette–Guérin (BCG) in animal models. Due to the inherent ability of BCG to prime cellular responses in the host, it has become an attractive vehicle for development of a vaccine against intracellular infections. In this study, we have cloned the genes of three immunodominant antigens of M. tuberculosis viz. the ESAT6 (Rv3875), the 19 kDa lipoprotein (Rv3763) and the 38 kDa antigen (Pst homolog) (Rv0934) in pSD5 under the transcriptional control of Trrn, a strong mycobacterial promoter, and expressed them in BCG. The19 kDa antigen and the 38 kDa antigen were expressed at levels that were approximately five and eightfolds higher in the cytosols of recombinant BCG strains rBCG19T and rBCG38T, respectively, as compared with their corresponding levels in M. bovis BCG. Both these antigens were also secreted into the extracellular medium at enhanced levels (19 kDa antigen fourfold and 38 kDa antigen twofold) by rBCG strains in comparison with the wild type BCG. ESAT6 antigen, which is absent in M. bovis BCG, was also expressed at a very high level in the cytosol of the rBCG strain (rBCGE6T). Evaluation of immune responses induced by these three rBCG strains in mice shows a markedly different pattern. The rBCG strain overexpressing the 38 kDa antigen exhibited a predominant T helper 1 (Th1) response with high levels of interferon‐γ (IFN‐γ) production, whereas overexpression of the 19 kDa antigen resulted in completely polarized Th2 responses against the BCG sonicate. The rBCG‐expressing ESAT6 antigen induced a mixed Th1/Th2 response. Our observations suggest that the 38 kDa antigen may hold excellent promise in the rBCG approach for the development of a vaccine against tuberculosis.
Release of Non‐Glycosylated Polymeric Immunoglobulin Receptor Protein
Authors: Matsumoto N. , Asano M. , Ogura Y. , Takenouchi‐Ohkubo N. , Chihaya H. , Chung‐Hsing W. , Ishikawa K. , Zhu L. , Moro I. 
Published: September 2003

AbstractUsing a recombinant vaccinia virus containing the T7 RNA polymerase, we have established a system for the transient expression of human polymeric immunoglobulin receptor (pIgR) in baby hamster kidney cells, a baby hamster‐derived fibroblastic cell line. This transfection system resulted in the successful expression of pIgR in these cells, and Western blot analysis showed that human pIgR was expressed as two different molecular weight forms of 92 and 107 kDa. Treatment with endoglycosidase H showed that the difference between these two forms was due to the glycosylation status of the protein. In order to examine the functional role of glycosylation, we treated the transfected cells with tunicamycin, which prevents a core glycosylation step in the endoplasmic reticulum. Non‐glycosylated pIgR was released into the culture medium of the transfected cells, albeit with extremely low efficiency. Taking these results together, we conclude that the glycosylation of pIgR may play a positive role in the efficient transport or release of free pIgR.
Periextubation caffeine in preterm neonates: A randomized dose response trial
Authors: Steer PA , Flenady VJ , Shearman A , Lee TC , Tudehope DI , Charles BG 
Published: September 2003

Objective:  To compare the effectiveness of three dosing regimens of caffeine for preterm infants in the periextubation period.Methods:  A randomized double‐blind clinical trial of three dosing regimens of caffeine citrate (3, 15 and 30 mg/kg) for periextubation management of ventilated preterm infants was undertaken. Infants born <32 weeks gestation who were ventilated for>48 h were eligible for the study. Caffeine citrate was given as a once daily dose for a period of 6 days commencing 24 h prior to a planned extubation, or within 6 h of an unplanned extubation. The primary outcome measure was extubation failure, defined as neonates who were unable to be extubated within 48 h of caffeine loading or who required reventilation or doxapram dose within 7 days of caffeine loading. Continuous recordings of oxygen saturation and heart rate were undertaken in a subgroup of enrolled infants.Results:  A total of 127 babies were enrolled into the study (42, 40, 45, in the 3, 15, and 30 mg/kg groups, respectively). No statistically significant difference was demonstrated in the incidence of extubation failure between dosing groups (19, 10, and 11 infants in the 3, 15, and 30 mg/kg groups, respectively), however, infants in the two higher dose groups had statistically significantly less documented apnoea than the lowest dose group. Of the 37 neonates with continuous pulse oximetry recordings, those on higher doses of caffeine recorded a statistically significantly higher mean heart rate, oxygen saturations and less time with oxygen saturations <85%.Conclusions:  This trial indicated there were short‐term benefits of decreased apnoea in the immediate periextubation period for ventilated infants born <32 weeks gestation receiving higher doses of caffeine. Further studies with larger numbers of infants assessing longer‐term outcomes are necessary to determine the optimal dosing regimen of caffeine in preterm infants.
Prevalence of fetal alcohol syndrome in the Top End of the Northern Territory
Authors: Harris KR , Bucens IK 
Published: September 2003

Objective:  To establish the prevalence of fetal alcohol syndrome (FAS) in the Top End of the Northern Territory (NT), Australia, in both the indigenous and non‐indigenous populations. Fetal alcohol syndrome is a preventable disease that is a major cause of intellectual handicap worldwide. The prevalence of FAS in the NT, and in Australia as a whole, is unknown.Methodology:  Cases were identified through retrospective review of medical records and outpatient letters of children seen by Royal Darwin Hospital paediatric staff. Cases were also identified by tracing potentially affected siblings, or incidentally during clinical work. All children were born between 1990 and 2000, and lived in the Top End of the NT.Results:  Seventeen children were identified with definite FAS. Twenty‐six children with partial FAS or alcohol‐related neurodevelopmental disorder (ARND) were also identified. The prevalence of FAS in the Top End of the NT was calculated to be 0.68 per 1000 live births. The prevalence might be as high as 1.7 per 1000 live births, if cases identified as partial FAS or ARND because of insufficient records, were assumed to have full FAS. In indigenous children, the corresponding prevalence was calculated to be between 1.87 and 4.7 per 1000 live births. The difference between indigenous and non‐indigenous rates of FAS was significant (P < 0.0001).Conclusions:  The prevalence of FAS in indigenous children of the Top End of the NT is comparable to the high rates in indigenous populations worldwide.
Factors affecting the reproductive biology of Melittobia digitata and failure to meet the sex ratio predictions of Hamilton's local mate competition theory
Authors: Cooperband M.F. , Matthews R.W. , Vinson S.B. 
Published: September 2003

Abstract Melittobia digitata Dahms (Eulophidae, Tetrastichini), a species of parasitic wasp satisfying all of Hamilton's local mate competition requisites, does not exhibit the predicted change in sex ratio with increased foundress number. A multifactorial design was used to test how age, oviposition experience, feeding experience, mating, and foundress number affect host‐acceptance, number of offspring, and sex ratio of this species developing on honey bee pupae, Apis mellifera (L.) (Apidae, Apini). All factors significantly affected the time it took for oviposition to commence. Females oviposited soonest when they were 2 days old, mated, had previous feeding and oviposition experience, and were placed on hosts with multiple foundresses. Although the age difference between 2‐ and 5‐day‐old females is small, it significantly affected reproductive behavior. Age, mating, and foundress number were found to have an effect on sex ratio, however, the foundress effect was found to be a mathematical artifact of the limited host size. After correcting for this variable, females were found to have a constant sex ratio of approximately 0.05. Several 2‐way interactions between factors were revealed: age and experience, age and foundress number, age and mating, foundress number and experience, and foundress number and mating. One 3‐way interaction was found between age, mating, and foundress number. This study demonstrates that the sex ratio of M. digitata is not altered with increased foundresses, as predicted by Hamilton, and that slight changes in preconditioning may modify reproductive behavior.
Glutathione S‐transferase detoxification as a potential pyrethroid resistance mechanism in the maize weevil, Sitophilus zeamais
Authors: Fragoso Daniel B. , Guedes Raul Narciso C. , Rezende Sebastião T. 
Published: September 2003

AbstractInsecticide resistance patterns among 16 Brazilian populations of the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), were recognized by surveying resistance to three organophosphates (chlorpyrifos‐methyl, malathion, and pirimiphos‐methyl) and three pyrethroids (cypermethrin, deltamethrin, and permethrin). Two population clusters were obtained: one with three populations (Bragança Paulista, Cristalina, and Nova Andradina) showing low frequency of cypermethrin resistance (13–36%) and negligible frequency of deltamethrin resistance (2–9%); and another with six populations (Campos dos Goytacazes, Ivinhema, Patos de Minas, Penápolis, Uberlândia, and Venda Nova) showing low to negligible levels of pyrethroid resistance (0–23%). The remaining seven populations, including a susceptible, and a DDT‐ and pyrethroid‐resistant reference populations (Sete Lagoas and Jacarezinho, respectively), were significantly different from each other and from the two recognized clusters. In contrast with pyrethroid resistance, organophosphate resistance was negligible except for chlorpyrifos‐methyl in two populations (Fátima do Sul and Penápolis). There was no correlation between geographic distance and the Mahalanobis distance estimated from the resistance pattern ordination of the populations by canonical variate analysis, suggesting local selection and/or broad dispersal of resistant populations by grain trade. The results of biochemical in vitro studies measuring the activity of detoxification enzymes (esterases and glutathion S‐transferases) in conjunction with canonical correlation analysis suggest a major involvement of enhanced conjugation by glutathione S‐transferases (> 2‐fold increase) in pyrethroid resistance and, in the case of cypermethrin resistance, enhanced phosphotriesterase activity.
Impact of a parasitoid on the bacterial symbiosis of its aphid host
Authors: Cloutier Conrad , Douglas Angela E. 
Published: September 2003

AbstractEmbryo production in aphids is absolutely dependent on the function of symbiotic bacteria, mainly Buchnera, and the growth and development of koinobiont parasitoids in aphids requires the diversion of nutrients from aphid embryo production to the parasitoid. The implication that the bacterial symbiosis may be promoted in parasitized aphids to support the growing parasitoid was explored by analysis of the number and biomass of mycetocytes, and the aphid cells bearing Buchnera, in the pea aphid Acyrthosiphon pisum Harris (Hemiptera: Aphididae) parasitized by the wasp Aphidius ervi Haliday (Hymenoptera: Braconidae). Aphids hosting a young larval parasitoid bore more mycetocytes of greater total biomass, and embryos of lower biomass than unparasitized aphids. Furthermore, one of the three aphid clones tested, which limited teratocyte growth (giant cells of parasitoid origin having a trophic role), bore smaller mycetocytes and larger embryos, than one or both of the two aphid clones with greater susceptibility to the parasitoid. These data suggest that susceptibility of the aphid‐Buchnera symbiosis to parasitoid‐mediated manipulation may, directly or indirectly, contribute to aphid susceptibility to parasitoid exploitation.
Screening for resistance in apple cultivars to lightbrown apple moth, Epiphyas postvittana, and greenheaded leafroller, Planotortrix octo, and its relationship to field damage
Authors: Wearing C.H. , Colhoun K. , Attfield B. , Marshall R.R. , McLaren G.F. 
Published: September 2003

AbstractThe mature leaves of 38 apple (Malus domestica Borkh.) (Rosaceae) cultivars were screened for resistance to laboratory colonies of Epiphyas postvittana (Walker) and Planotortrix octo Dugdale (Lepidoptera: Tortricidae) by measuring larval survival and development rate, and pupal weight, in no‐choice laboratory bioassays in early summer. There were few cultivar effects on larval mortality but Nevis 1, A40R04T119, and ‘Sir Prize’ reduced survival of E. postvittana. Effects on development time and weight were correlated, and were integrated into a single measure of resistance Rc. Rc varied greatly between cultivars for both leafroller species, and identified 15 and 11 cultivars with partial resistance to E. postvittana and P. octo, respectively. A further experiment with three of the cultivars in midsummer, using the laboratory colonies in comparison with new colonies (from field collected larvae), produced similar results for E. postvittana, but there was no survival of new colony P. octo larvae on two cultivars. These results for P. octo are consistent with other recent research showing extreme cultivar resistance and critical colony and seasonal influences. A series of 4‐year field trials with the 38 cultivars showed poor correlation between laboratory and field resistance for the dominant leafroller species in the field, E. postvittana. The combined data, however, identified ‘Red Dougherty’, ‘Sir Prize’, and A40R04T119 as potentially useful in breeding for resistance to this species. The implications of these findings for integrated pest management (IPM) programmes and for the breeding of leafroller‐resistant apple cultivars are discussed.
Second and third trophic level effects of differences in plant species reflect dietary specialisation of herbivores and their endoparasitoids
Authors: Sznajder Beata , Harvey Jeffrey A. 
Published: September 2003

AbstractIn natural populations, plants demonstrate an array of indirect and direct defence strategies that help to protect them from their herbivores and pathogens. Indirect defences include the release of odours that attract the natural enemies of herbivores, whereas direct defences may include the production of secondary compounds, allelochemicals that impair herbivore development or repel herbivore attack. Although both strategies have been well studied independently, comparatively little attention has been paid to examining the conflict that may arise between indirect and direct defences, such as when the performance of ‘recruited’ parasitoids or predators is negatively affected by plant allelochemicals. Here, we examine the growth and development of polyphagous and oligophagous folivores and their respective endoparasitoids on three crucifer species. One of the species, Brassica oleracea, was recently cultivated, whereas populations of B. nigra and Barbarea vulgaris occur naturally. Additionally, these species possess contrasting life‐history patterns and are also known to exhibit differences in secondary chemistry. The development of the generalist herbivore–parasitoid system was much more variable over the three crucifers than that exhibited by the specialists. Moreover, generalist herbivore and/or parasitoid fitness‐related traits (survival, development time, pupal, or adult size) were much more negatively affected on the wild crucifers than in the specialist association. Our results suggest that the relative importance of direct and indirect defences in plants may rest on the degree of dietary specialisation exhibited by herbivores and their natural enemies, and on the level of toxicity in the plant species under investigation.
Comparative Advantage and the Location of Production
Authors: Forslid Rikard , Wooton Ian 
Published: September 2003

AbstractThe paper returns to a familiar topic in international trade, comparative advantage, introducing it into Krugman's classic, core–periphery model of economic geography. This extra force of dispersion radically changes the stability properties of the model. Instead of the familiar result that trade liberalization leads to increased industrial concentration, lowering trade costs leads initially to increased concentration and then to dispersion of production. When a pattern of comparative advantage exists, integration may lead to international specialization of production. This may be good news for peripheral countries, which may be able to retain industry despite the attraction of the core.
Intertemporal Substitution and Terms‐of‐Trade Shocks
Authors: Cashin Paul , McDermott C. John 
Published: September 2003

AbstractThe paper examines the relationship between transitory terms‐of‐trade shocks and private saving. Using a model allowing for nonseparability between the consumption of tradables and nontradables, the paper estimates the intertemporal elasticity of substitution while accounting for the intratemporal elasticity of substitution between the consumption of tradables and nontradables. Empirical analysis of data for five industrial countries indicates that in response to transitory terms‐of‐trade shocks, intertemporal substitution of consumption and intratemporal substitution of consumption between tradables and nontradables both have large effects on private saving.