bluuebunny/crossref_metadata_2025_split huggingface dataset:
Good housekeeping: why do shelter‐dwelling caterpillars fling their frass?
Authors: Weiss Martha R. 
Published: December 2004

AbstractAlthough both feeding and elimination of waste are imperatives for all animals, ecologists and evolutionary biologists have devoted considerable attention to foraging, while largely ignoring defecation. Many organisms, however, exhibit defecation behaviours that appear to have been shaped by natural selection in a range of ecological contexts. Accumulation of waste may pose particular challenges for animals that exhibit high site fidelity or live within enclosed spaces. In a taxonomically widespread but largely unexamined behaviour, many caterpillars that construct and inhabit leaf shelters ballistically eject their individual faecal pellets (frass) great distances at great speeds. Here, I show that elimination of chemical cues for natural enemies is likely to have been a driving force behind the evolution of frass ejection behaviour in skipper caterpillars; hygiene and crowding are less important in this system.
The influence of size‐dependent life‐history traits on the structure and dynamics of populations and communities
Authors: De Roos André M. , Persson Lennart , McCauley Edward 
Published: December 2004

AbstractIndividual organisms often show pronounced changes in body size throughout life with concomitant changes in ecological performance. We synthesize recent insight into the relationship between size dependence in individual life history and population dynamics. Most studies have focused on size‐dependent life‐history traits and population size‐structure in the highest trophic level, which generally leads to population cycles with a period equal to the juvenile delay. These cycles are driven by differences in competitiveness of differently sized individuals. In multi‐trophic systems, size dependence in life‐history traits at lower trophic levels may have consequences for both the dynamics and structure of communities, as size‐selective predation may lead to the occurrence of emergent Allee effects and the stabilization of predator–prey cycles. These consequences are linked to that individual development is density dependent. We conjecture that especially this population feedback on individual development may lead to new theoretical insight compared to theory based on unstructured or age‐dependent models. Density‐dependent individual development may also cause individuals to realize radically different life histories, dependent on the state and dynamics of the population during their life and may therefore have consequences for individual behaviour or the evolution of life‐history traits as well.
Overyielding among plant functional groups in a long‐term experiment
Authors: Hooper David U. , Dukes Jeffrey S. 
Published: December 2004

AbstractA recent debate among ecologists has focused on mechanisms by which species diversity might affect net primary productivity. Communities with more species could use a greater variety of resource capture characteristics, leading to greater use of limiting resources (complementarity) and therefore greater productivity (overyielding). Recent experiments, however, have shown a variety of relationships between diversity and productivity. In an experiment on serpentine grassland communities spanning 8 years, we found that overyielding increased several years after plot establishment. Overyielding varied greatly depending on the functional characteristics of the species involved and the biotic and abiotic environment (particularly water availability). While functional differences among species led to strong complementarity and facilitation, these effects were not sufficient to cause significant transgressive overyielding or consistent increases in productivity with increased plant diversity. These results suggest that greater absolute production with greater diversity may be restricted to particular species combinations or environmental conditions.
Growth autocorrelation and animal size variation
Authors: Fujiwara Masami , Kendall Bruce E. , Nisbet Roger M. 
Published: December 2004

AbstractIt has long been recognized that variability in animal size is affected by how individual growth rate is autocorrelated in time. Earlier studies have attributed the mechanism generating the autocorrelation primarily to size‐dependent growth rate and autocorrelation in resource abundance. All of these studies have shown that positive autocorrelation in individual growth rate always translates into increased variability in size. We show that energy reserves in individuals induce growth autocorrelation by acting like a low pass filter between the resource and the internal energy that is available for metabolism, growth and reproduction. However, the reserve also reduces the variance in growth rate. Consequently, reserve‐induced growth autocorrelation has relatively little effect on size variability in the population, contradicting existing ideas about the relationship between the growth autocorrelation and size variability.
Plastic phenotypic resistance to predation by Bdellovibrio and like organisms in bacterial prey
Authors: Shemesh Yair , Jurkevitch Edouard 
Published: December 2004

SummaryPredation at the lowest trophic level, i.e. between bacteria, is poorly understood, hindering efforts to assess its impact on the structure of bacterial communities. The interaction of Bdellovibrio and Bacteriovorax (Bdellovibrio and like organisms, BLOs), a group of obligate, ubiquitous predatory bacteria, with their Gram‐negative bacterial prey results in the multiplication of the predator and in the lysis, but not in the eradication, of the prey. We show that the residual, surviving populations of prey cells exposed to predation stress differ from the populations before exposure, as they exhibit increased resistance to predation. This resistance was demonstrated in a number of Gram‐negative prey. Moreover, predation resistance is not specific for the BLO strain experienced by the prey. The phenomenon does not stem from a mutation but is a plastic response associated with a phenotypic change, and it disappears upon removal of the predator. As resistance to predation is not total, this mechanism can ensure survival of both predator and prey.
Comparative analysis of a genome fragment of an uncultivated mesopelagic crenarchaeote reveals multiple horizontal gene transfers
Authors: López‐García Purificación , Brochier Céline , Moreira David , Rodríguez‐Valera Francisco 
Published: December 2004

SummaryMarine planktonic crenarchaeota have escaped all cultivation attempts to date, all crenarchaeota growing in pure culture so far being hyperthermophiles. Here, we present a comparative genomic analysis of a 16S‐ plus 23S‐rDNA‐containing fragment of a crenarchaeote retrieved from an environmental genomic library constructed from picoplankton collected at 500 m depth in the Antarctic Polar Front. The clone DeepAnt‐EC39 contained an insert of 33.3 kbp, which was completely sequenced. DeepAnt‐EC39 appears to represent a lineage specific to deep‐sea waters but widespread geographically, as revealed by the analysis of the 16S‐23S‐rDNA intergenic spacer region. A comparison with previously sequenced marine crenarchaeotal genomic clones also containing an rrn operon (74A4, 4B7 and Cenarchaeum symbiosum strains A and B) revealed a highly variable structure involving gene rearrangements and insertions/deletions. The surroundings of the rrn operon and the contiguous glutamate‐1‐semialdehyde aminotransferase gene appear hot spots for recombination. Phylogenetic analyses of all individual predicted proteins revealed the existence of several likely cases of horizontal gene transfer both, between the two archaeal kingdoms and between the two prokaryotic domains. The most frequent horizontal transfers appear to involve genes from mesophilic methanogenic euryarchaeota related to Methanosarcinales. We hypothesise that the acquisition of genes from mesophilic bacteria and euryarchaeota has played a major role in the adaptation of Group I crenarchaeota to life at lower temperatures.
Enhanced sensitivity of DNA‐ and rRNA‐based stable isotope probing by fractionation and quantitative analysis of isopycnic centrifugation gradients
Authors: Lueders Tillmann , Manefield Mike , Friedrich Michael W. 
Published: December 2004

SummaryStable isotope probing (SIP) of nucleic acids allows the detection and identification of active members of natural microbial populations that are involved in the assimilation of an isotopically labelled compound into nucleic acids. SIP is based on the separation of isotopically labelled DNA or rRNA by isopycnic density gradient centrifugation. We have developed a highly sensitive protocol for the detection of ‘light’ and ‘heavy’ nucleic acids in fractions of centrifugation gradients. It involves the fluorometric quantification of total DNA or rRNA, and the quantification of either 16S rRNA genes or 16S rRNA in gradient fractions by real‐time PCR with domain‐specific primers. Using this approach, we found that fully13C‐labelled DNA or rRNA ofMethylobacterium extorquenswas quantitatively resolved from unlabelled DNA or rRNA ofMethanosarcina barkeriby cesium chloride or cesium trifluoroacetate density gradient centrifugation respectively. However, a constant low background of unspecific nucleic acids was detected in all DNA or rRNA gradient fractions, which is important for the interpretation of environmental SIP results. Consequently, quantitative analysis of gradient fractions provides a higher precision and finer resolution for retrieval of isotopically enriched nucleic acids than possible using ethidium bromide or gradient fractionation combined with fingerprinting analyses. This is a prerequisite for the fine‐scale tracing of microbial populations metabolizing13C‐labelled compounds in natural ecosystems.
Detection and phylogenetic analysis ofWolbachiain Collembola
Authors: Czarnetzki Alice B. , Tebbe Christoph C. 
Published: December 2004

SummaryWolbachiaare obligatory, cytoplasmatically inherited α‐Proteobacteria which are known for infecting the reproductive tissues of many arthropods. Their prevalence in the large group of Collembola, however, is not known, except for PCR detection in the parthenogenetically reproducing speciesFolsomia candida(Order: Entomobryomorpha; Family: Isotomidae). In this study, fluorescencein situhybridization on microscopic sections ofF. candidaspecimens indicated thatWolbachia‐related bacteria were restricted to tissues of the ovary and brain. PCR with primers designed to detect 16S rRNA genes ofWolbachiawere positive with specimens from all of five geographically independentF. candidabreeding stocks and with three parthenogenetic species from another order (Poduromorpha; Family Tullbergiidae), i.e.Mesaphorura italica,M. macrochaetaandParatullbergia callipygos. In contrast, negative results were obtained with the two sexually reproducing species,Isotoma viridis(Isotomidae) andProtaphorura fimata(Poduromorpha; Onychiuridae). TheftsZgene ofWolbachiacould be PCR‐amplified from allWolbachia‐positive hosts with the exception ofM. macrochaeta. The phylogenetic distances of theftsZand 16S rRNA gene sequences reflected the phylogenetic distances of the host organisms but the sequences ofWolbachiawere relatively closely related, indicating thatWolbachiainfections took place after the Collembola had diversified. Our study confirms a monophyletic branch (supergroup E) of Collembola colonizingWolbachiaand indicates that this group is a sister group of supergroup A, the latter harbouring a high diversity of host organisms within the group of insects.
A novel approach to investigate biofilm accumulation and bacterial transport in porous matrices
Authors: Dunsmore Braden C. , Bass Catherine J. , Lappin‐Scott Hilary M. 
Published: December 2004

SummaryKnowledge of bacterial transport through, and biofilm growth in, porous media is vitally important in numerous natural and engineered environments. Despite this, porous media systems are generally oversimplified and the local complexity of cell transport, biofilm formation and the effect of biofilm accumulation on flow patterns is lost. In this study, cells of the sulphate‐reducing bacterium, Desulfovibrio sp. EX265, accumulated primarily on the leading faces of obstructions and developed into biofilm, which grew to narrow and block pore throats (at a rate of 12 µm h−1 in one instance). This pore blocking corresponded to a decrease in permeability from 9.9 to 4.9 Darcy. Biofilm processes were observed in detail and quantitative data were used to describe the rate of biofilm accumulation temporally and spatially. Accumulation in the inlet zone of the micromodel was 10% higher than in the outlet zone and a mean biofilm height of 28.4 µm was measured in a micromodel with an average pore height of 34.9 µm. Backflow (flow reversal) of fluid was implemented on micromodels blocked with biofilm growth. Although biofilm surface area cover did immediately decrease (∼5%), the biofilm quickly re‐established and permeability was not significantly affected (9.4 Darcy). These results demonstrate that the glass micromodel used here is an effective tool for in situ analysis and quantification of bacteria in porous media.
A Proton Magnetic Resonance Spectroscopy Study of Metabolites in the Occipital Lobes in Epilepsy
Authors: Simister Robert J. , McLean Mary A. , Barker Gareth J. , Duncan John S. 
Published: December 2004

Summary: Purpose:γ‐Amino butyric acid (GABA) and glutamate, respectively the principal inhibitory and excitatory neurochemicals in the brain, are visible to proton magnetic resonance spectroscopy (MRS). We report a study of GABA+ (GABA plus homocarnosine) and GLX (glutamate plus glutamine) concentrations in the occipital lobes in patients with idiopathic generalised epilepsy (IGE) and in patients with occipital lobe epilepsy (OLE).Methods:Fifteen patients with IGE, 15 patients with OLE, and 15 healthy volunteers were studied. A single voxel was prescribed in the occipital lobes for each subject. PRESS localised short‐echo‐time MRS was performed to measure GLX by using LCModel. A double quantum GABA filter was used to measure GABA+. Segmented T1‐weighted images gave the tissue composition of the prescribed voxel.Results:Grey‐matter proportion, GLX, and GABA+ were all elevated in IGE. However, analysis using grey‐matter proportion as a covariable showed no significant group differences. No correlation was observed between GABA+ concentration and either seizure frequency or time since last seizure.Conclusions:GLX and GABA+ were elevated in IGE. Elevated grey‐matter content in the IGE group despite normal MRI appearance can be expected to account for some or all of this observed elevation of GLX and GABA+. GABA+ concentration did not correlate with seizure control or duration since most recent seizure.
Tolerability and Pharmacokinetics of Oral Loading with Lamotrigine in Epilepsy Monitoring Units
Authors: Lardizabal David V. , Morris Harold H. , Hovinga Collin A. , Del Mar Carreño Maria 
Published: December 2004

Summary:  Purpose: To investigate the tolerability and pharmacokinetics of oral loading with lamotrigine (LTG) among epilepsy patients after temporary drug discontinuation in an epilepsy monitoring unit.Methods: We conducted a pilot study among epilepsy patients (18 years or older) receiving maintenance doses of LTG. LTG was discontinued on admission and restarted at the end of epilepsy monitoring. LTG was given as a single oral dose calculated based on the population expected volume of distribution (Vd, 1.0 L/kg) and target blood level on admission. Baseline and serial blood levels of LTG were determined hourly for 10 to 12 h after the loading dose. Outcome measures: (a) frequency of patients with side effects; (b) time to maximum concentration (Tmax), maximum concentration (Cmax), actual volume of distribution, and half‐life.Results: Twenty‐four patients received a single oral load of LTG (mean, 6.5 ± 2.7 mg/kg). Overall, LTG loading was well tolerated with no serious adverse events or skin rash observed. Two patients had transient and mild nausea 1 to 2 h after the oral load. The mean estimated pharmacokinetic parameters are as follows: Tmax, 3.1 ± 2.1 h; Cmax, 8.2 ± 6.5 mg/L; Vd, 1.1 ± 1.0 L/kg; clearance, 0.08 ± 0.08 mg/L/h; half‐life, 22 ± 30 h. All patients reached their target blood levels.Conclusions: Epilepsy patients temporarily discontinued from LTG can be restarted with a single oral loading dose. This was well tolerated, and therapeutic levels can be achieved within 1 to 3 h.
Prolonged Low‐dose Caffeine Exposure Protects Against Hippocampal Damage but Not Against the Occurrence of Epilepsy in the Lithium‐pilocarpine Model in the Rat
Authors: Rigoulot Marie‐Aude , Leroy Claire , Koning Estelle , Ferrandon Arielle , Nehlig Astrid 
Published: December 2004

Summary:  Purpose: Acute caffeine exposure has proconvulsant effects and worsens epileptic and ischemic neuronal damage. Surprisingly, prolonged caffeine exposure decreases the susceptibility to seizures and the extent of ischemic damage. We explored whether the exposure to a low long‐term dose of caffeine could protect the brain from neuronal damage and epileptogenesis in the lithium‐pilocarpine model of temporal lobe epilepsy.Methods: Rats received either plain tap water or water containing caffeine (0.3 g/L) for 15 days before the induction of status epilepticus (SE) by lithium‐pilocarpine and for 7 days after SE. The extent of neuronal damage was assessed in the hippocampus and piriform and entorhinal cortices in brain sections stained with thionine and obtained from animals killed 7 days after SE. The latency to spontaneous recurrent seizures was controlled by video monitoring.Results: Caffeine treatment induced a marked, almost total neuroprotection in CA1 and a very limited protection in the hilus of the dentate gyrus, whereas damage in layers III–IV of the piriform cortex was slightly worsened by the treatment. All rats, whether they received caffeine or plain tap water, became epileptic after the same latency (17–19 days).Conclusions: Thus these data extend the neuroprotective effects of low long‐term caffeine exposure to epileptic damage and confirm that the sole protection of the Ammon's horn has no influence on the genesis of spontaneous recurrent seizures in this model.
An In Vitro Study of New Antiepileptic Drugs and Astrocytes
Authors: Pavone Antonino , Cardile Venera 
Published: December 2004

Summary:  Purpose: The aim of our research was to study some biochemical modifications elicited in primary rat astrocyte cultures by treatment with gabapentin (GBP), carbamazepine (CBZ), lamotrigine (LTG), topiramate (TPM), oxcarbazepine (OXC), tiagabine (TGB), and levetiracetam (LEV), commonly used in the treatment of epilepsy. We investigated the biologic effects of these anticonvulsants (AEDs) at concentrations of 1, 10, 50, and 100 μg/ml. Methods: The study was performed by examining cell viability (MTT assay), cell toxicity [lactate dehydrogenase (LDH) release in the medium], glutamine synthetase (GS) activity, reactive oxygen species (ROS) production, lipoperoxidation level (malondialdehyde; MDA), and DNA fragmentation (COMET assay). The level of the expression of 70‐kDa heat‐shock protein (HSP70) and inducible nitric oxide synthase (iNOS) as oxidative stress–modulated genes also was determined. Results: Our experiments indicate that CBZ, TPM, and OXC induce stress on astrocytes at all concentrations. GBP, LTG, TGB, and LEV, at low concentrations, do not significantly change the metabolic activities examined and do not demonstrate toxic actions on astrocytes. They do so at higher concentrations. Conclusions: Most AEDs have effects on glial cells and, when used at an appropriate cell‐specific concentrations, may be well tolerated by cortical astrocytes. However, at higher concentrations, GBP, LTG, TGB, and LEV seem to be better tolerated than are CBZ, TPM, and OXC. These findings may reveal novel ways of producing large numbers of new AEDs capable of reducing the extent of inflammation, neuronal damage, and death under pathological conditions such as epilepsy and/or traumatic brain injury.
Risk Factors for Posttraumatic Seizures in Adults
Authors: Temkin Nancy R. 
Published: December 2004

Summary:  Purpose: Traumatic brain injury has long been known to be a cause of epilepsy. Most information on risk factors for developing posttraumatic seizures is from before computed tomography (CT) scanning became universal. This article looks at factors about the injury or individual that put people at especially high risk of developing posttraumatic seizures. Methods: We considered 783 cases at high risk of developing seizures, followed up for 2 years as part of seizure prophylaxis studies. Cumulative incidence of seizures in subgroups and standardized incidence ratios were used to identify factors related to unprovoked seizure risk. Results: Subgroups with significantly elevated risk include those with evacuation of a subdural hematoma; surgery for an intracerebral hematoma; Glasgow Coma Scale in the severe range of 3 to 8; early seizures, especially delayed early seizures; time to following commands of a week or more; depressed skull fracture that was not surgically elevated; dural penetration by injury; at least one nonreactive pupil; and parietal lesions on CT scan. Conclusions: Both the risk factors and the time course of the risk are important for designing seizure‐prophylaxis studies and, if an effective prophylactic regimen is identified, for deciding on appropriate candidates for prophylaxis.
Inverse Relation Between Input Resistance and Threshold Current in Canine Cardiac Syncytium
Authors: MENDEZ CARLOS , HERNANDEZ VICENTE 
Published: December 2004

Input Resistance and Threshold Current. Introduction: The present study was designed to examine the extent to which differences in input resistance contribute to the heterogeneity of excitability in canine endocardium. Methods and Results: The experiments were performed in isolated canine right anterior papillary muscles. The preparations were superfused with oxygenated Tyrode's solution at 36° to 37°C. Conventional methods were used for recording and stimulation. To obtain pertinent data, two microelectrodes were inserted into the same cell or into two contiguous cells. One microelectrode injected intracellular hyperpolarizing current to polarize the membrane; the second microelectrode recorded the changes in transmembrane potential. The two micreoelectrodes were separated by 8 to 10 μm. The procedure used provided input resistance and threshold current values for the doubly impaled cell or the two contiguous cell units. The same procedure was repeated at different sites of the preparation. The plot of input resistance versus threshold current showed a good fit (R2= 0.97) between the experimental data and the curve for the rectangular hyperbola XY = 30 mV; therefore, the input resistance and the threshold current are inversely related. Conclusion: The results indicate that the canine cardiac syncytium is nonhomogeneous with respect to input resistance and that input resistance is inversely related to the minimal current needed to reach threshold. Accordingly, the electrical excitability of the cells studied also is inhomogeneous.