bluuebunny/crossref_metadata_2025 huggingface dataset:
fMRI of Brain Activation in a Genetic Rat Model of Absence Seizures
Authors: Tenney Jeffrey R. , Duong Timothy Q. , King Jean A. , Ferris Craig F.
Published: May 2004

Summary: Purpose: EEG‐triggered functional magnetic resonance imaging (fMRI) was used to identify areas of brain activation during spontaneous spike‐and‐wave discharges (SWDs) in an epileptic rat strain under awake conditions.

Methods: Spontaneous absence seizures from 10 WAG/Rij rats were imaged by using T2*‐weighted echo planar imaging at 4.7 Tesla. fMRI of the blood‐oxygenation‐level–dependent (BOLD) signal was triggered based on EEG recordings during imaging. Images obtained during spontaneous SWDs were compared with baseline images.

Results: Significant positive BOLD signal changes were apparent in several areas of the cortex and several important nuclei of the thalamus. In addition, no negative BOLD signal was found in any brain area.

Conclusions: We have shown that EEG‐triggered BOLD fMRI can be used to detect cortical and thalamic activation related to the spontaneous SWDs that characterize absence seizures in awake WAG/Rij rats. These results draw an anatomic correlation between areas in which increased BOLD signal is found and those in which SWDs have been recorded. In addition, no negative BOLD signal was found to be associated with these spontaneous SWDs. We also demonstrated the technical feasibility of using EEG‐triggered fMRI in a genetic rat model of absence seizure.
Severity of Histopathologic Abnormalities and In Vivo Epileptogenicity in the In Utero Radiation Model of Rats Is Dose Dependent
Authors: Kellinghaus Christoph , Kunieda Takeharu , Ying Zhong , Pan Andrew , Lüders Hans O. , Najm Imad M.
Published: May 2004

Summary:  Purpose: Malformations of cortical development (MCDs) are a frequent cause of refractory epilepsy in humans. The in utero radiation model in rats shares many clinical and histopathologic characteristics with human MCDs. Previous studies reported the presence of clinical seizures in radiated rats, but also suggested a dose‐dependent differential effect.

Methods: Time‐pregnant Sprague–Dawley rats were irradiated on embryonic day E17 with 100 cGy (low dose), 145 cGy (medium dose), 175 cGy (high dose), or were left untreated. Their adult litters were implanted with bifrontal epidural and hippocampal depth electrodes and underwent long‐term video‐EEG monitoring. After 2 weeks of monitoring, the animals were killed and their brains processed for histological studies.

Results: Spikes were most frequently found in the rats that were subjected to low‐ and medium‐dose radiation at E17 and were less frequently seen in the animals that were subjected to high‐dose radiation. No interictal spikes were found in any of the control animals. Seizures were recorded in three of five animals of the medium‐dose group. Histological studies showed a dose‐dependent decrease in cortical thickness as well as an increase of cortical and hippocampal disorganization.

Conclusions: In vivo epileptogenicity in radiated animals was present only in mild or moderate MCD. No in vivo epileptogenicity was seen in severe radiation‐induced MCD.
Evaluation of GABA System and Cell Damage in Parahippocampus of Patients with Temporal Lobe Epilepsy Showing Antiepileptic Effects after Subacute Electrical Stimulation
Authors: Cuéllar‐Herrera Manola , Velasco Marcos , Velasco Francisco , Velasco Ana Luisa , Jiménez Fiacro , Orozco Sandra , Briones Magdalena , Rocha Luisa
Published: May 2004

Summary:  Purpose: The γ‐aminobutyric acid (GABA) system and neuronal loss were evaluated in the parahippocampal cortex (PHC) of patients with intractable mesial temporal lobe epilepsy (MTLE) who received subacute electrical stimulation and showed antiepileptic effects.

Methods: GABA tissue content, GABAA and benzodiazepine (BZD) receptor levels, as well as neuronal density were determined in PHC of five patients (ESAE group) with an MTLE history of 14.8 ± 2.5 years and seizure frequency of 11 ± 2.9 per month, two (40%) of them with mesial sclerosis. This group demonstrated antiepileptic effects after subacute electrical stimulation (130 Hz, 450 μs, 200–400 μA), applied continuously during 16 to 20 days in PHC. Values were compared with those obtained from patients with severe MTLE (history of 21.7 ± 2.8 years and seizure frequency of 28.2 ± 14 per month) in whom electrical stimulation did not induce antiepileptic effects (ESWAE group, n = 4), patients with MTLE in whom no electrical stimulation was applied (MTLE group, n = 4), and autopsy material acquired from subjects without epilepsy (n = 4 obtained from three subjects).

Results: The ESAE group demonstrated high GABA tissue levels (219%), as well as a significantly higher cell count (58.5%) when compared with the MTLE group. The ESWAE group showed enhanced BZD‐receptor levels (38%), whereas their values for GABA tissue levels and GABAA receptor were similar to those obtained from the MTLE group.

Conclusions: It is suggested that subacute electrical stimulation of PHC is more effective in patients with less severe epilepsy, an effect associated with a high GABA tissue content and a low rate of cell loss.
Pharmacodynamic Analysis of the Anticonvulsant Effects of Tiagabine and Lamotrigine in Combination in the Rat
Authors: Jonker Daniël M. , Voskuyl Rob A. , Danhof Meindert
Published: May 2004

Summary:  Purpose: The pharmacodynamic interaction between the antiepileptic drugs (AEDs) tiagabine (TGB) and lamotrigine (LTG) was characterized on basis of the anticonvulsant effect in the cortical stimulation model in the rat.

Methods: The study was conducted according to a partial crossover design, in which both drugs were infused intravenously to achieve linear increases in the plasma concentration in the absence and presence of a steady‐state concentration of the second drug. The anticonvulsant effect was quantified by counts of four specific ictal signs (eye closure, forelimb clonus, forelimb extension, and head jerk). A potential pharmacokinetic interaction was accounted for by determination of total plasma concentrations of both drugs.

Results: When given separately, both TGB and LTG suppressed all ictal signs in a concentration‐dependent manner, with the exception of eye closure, which was not suppressed by LTG. The interaction between both drugs was estimated by response surface analysis by using the difference between the observed effect and the additive effect to identify synergistic drug concentrations. This analysis showed that the pharmacodynamic interaction between TGB and LTG is synergistic for the ictal signs of eye closure and head jerk. In contrast, the interaction was additive for the ictal signs of forelimb clonus and forelimb tonus.

Conclusions: This study demonstrates the usefulness of ictal‐component analysis for studying the pharmacodynamic interaction between AEDs. Quantification of both the nature and the magnitude of the interaction between TGB and LTG led to the identification of two ictal signs that were synergistically suppressed. This approach offers a theoretical basis to identify and optimize drug combinations that are useful to treat refractory epilepsy.
EEG and MEG Source Analysis of Single and Averaged Interictal Spikes Reveals Intrinsic Epileptogenicity in Focal Cortical Dysplasia
Authors: Bast Thomas , Oezkan Oezdin , Rona Sabine , Stippich Christoph , Seitz Angelika , Rupp Andre , Fauser Susanne , Zentner Josef , Rating Dietz , Scherg Michael
Published: May 2004

Summary:  Purpose: Simultaneous interictal EEG and magnetoencephalography (MEG) recordings were used for noninvasive analysis of epileptogenicity in focal cortical dysplasia (FCD). The results of two different approach methods (multiple source analysis of averaged spikes and single dipole peak localization of single spikes) were compared with pre‐ and postoperative anatomic magnetic resonance imaging (MRI).

Patients: We studied nine children and adolescents (age, 3.5–15.9 years) with localization‐related epilepsy and FCD diagnosis based on MRI. Five patients underwent epilepsy surgery, two of them after long‐term recording with subdural grid electrodes, and one after intraoperative electrocorticography.

Methods: The 122‐channel whole‐head MEGs and 33‐channel EEGs were recorded simultaneously for 25 to 40 min. Interictal spikes were identified visually and used as templates to search for similar spatiotemporal spike patterns throughout the recording. With the BESA program, similar spikes (r > 0.85) were detected, averaged, high‐pass filtered (5 Hz) to enhance spike onset, and subjected to multiple spatiotemporal source analysis with a multishell spherical head model. Peak activity from single spikes was modeled by single dipoles for the same subset of spikes. Source localization was visualized by superposition on T1‐weighted MRI and compared with the lesion identified in T1‐ and T2‐weighted MRI. In the five cases undergoing epilepsy surgery, the results were correlated with invasive recordings, postoperative MRI, and outcome.

Results: In all cases, the analysis of averaged spikes showed a localization of onset‐ and peak‐related sources within the visible lesion for both EEG and MEG. Of the single spikes, 128 (45%; total 284) were localizable at the peak in MEG, and 170 (60%) in EEG. Of these, 91% localized within the lesion with MEG, and 93.5% with EEG. In three of five patients operated on, the resected area included the onset zones of averaged EEG and MEG spike activity. These patients had excellent postoperative outcome, whereas the others did not become seizure free.

Conclusions: Consistent MEG and EEG spike localization in the lesional zone confirmed the hypothesis of intrinsic epileptogenicity in FCD.
Expression and Cellular Distribution of Multidrug Resistance–related Proteins in the Hippocampus of Patients with Mesial Temporal Lobe Epilepsy
Authors: Aronica Eleonora , Gorter Jan A. , Ramkema Marja , Redeker Sandra , Özbas‐Gerçeker Filiz , Van Vliet Edwin A. , Scheffer George L. , Scheper Rik J. , Van Der Valk Paul , Baayen Johannes C. , Troost Dirk
Published: May 2004

Summary: Purpose:This study investigated the cellular distribution of different multidrug resistance (MDR)‐related proteins such as P‐glycoprotein (P‐gp), the multidrug resistance–associated proteins (MRP) 1 and 2, and the major vault protein (MVP) in normal and sclerotic hippocampus of patients with medically refractory mesial temporal lobe epilepsy (MTLE).

Methods:Single‐ and double‐label immunocytochemistry was used on brain sections of control hippocampus and of hippocampus of refractory MTLE patients.

Results:In TLE cases with hippocampal sclerosis (HS), all four MDR proteins examined that had low or no expression in control tissue were upregulated, albeit with different cellular distribution patterns. P‐gp immunoreactivity (IR) was observed in astrocytes in regions with diffuse reactive gliosis. In 75% of HS cases, strong P‐gp IR was detected in blood vessels, with prominent endothelial labeling. Reactive astrocytes displayed low MRP1 IR. However, glial MRP1 expression was noted in glial endfoot processes around blood vessels. Neuronal MRP1 expression was observed in hypertrophic hilar neurons and in a few residual neurons of the CA1 region. Hippocampal MRP2 expression was observed in the large majority of HS cases in blood vessels. Hypertrophic hilar neurons and blood vessels within the sclerotic hippocampus expressed major vault protein (MVP).

Conclusions:These findings indicate that MDR proteins are upregulated in concert in the hippocampus of patients with refractory MTLE, supporting their role in the mechanisms underlying drug resistance. The specific cell‐distribution patterns within the sclerotic hippocampus suggest different cellular functions, not necessarily linked only to clinical drug resistance.
NBQX or Topiramate Treatment after Perinatal Hypoxia‐induced Seizures Prevents Later Increases in Seizure‐induced Neuronal Injury
Authors: Koh Sookyong , Tibayan Felicia D. , Simpson Joelle N. , Jensen Frances E.
Published: May 2004

Summary:  Purpose: To evaluate the efficacy of NBQX (2,3‐dihydroxy‐6‐nitro‐7‐sulfamoylbenzo(f) quinoxaline‐2,3‐dione) and topiramate (TPM) given after hypoxia‐induced seizures in preventing the delayed effect of hypoxia on subsequent susceptibility to seizures and neuronal injury.

Methods: We used “two‐hit” rodent seizure model to study the long‐term effect of perinatal hypoxia on later kainate (KA) seizure‐induced neuronal damage and investigated the therapeutic efficacy of a postseizure treatment protocol in reversing the conditioning effect of early‐life seizures.

Results: Hypoxia at P10 induces seizures without cell death but causes an increase in susceptibility to second seizures induced by KA as early as 96 h after hypoxia, and this lowered seizure threshold persists to adulthood. Furthermore, perinatal hypoxia increases KA‐induced neuronal injury at postnatal day (P)21 and 28/30. Repeated doses of NBQX (20 mg/kg) or TPM (30 mg/kg) given for 48 h after hypoxia‐induced seizures prevent the increase in susceptibility to KA seizure‐induced hippocampal neuronal injury at P28/30.

Conclusions: Our results suggest that α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA) receptor blockade after hypoxia prevents the priming effect of perinatal hypoxia‐induced seizures and that this protection occurs independent of its anticonvulsant action.
Testing Fox's assembly rule: does plant invasion depend on recipient community structure?
Authors: Von Holle Betsy , Simberloff Daniel
Published: May 2004

Fox's assembly rule, that relative dearth of certain functional groups in a community will facilitate invasion of that particular functional group, serves as the basis for investigation into the functional group effects of invasion resistance. We explored resistance to plant invaders by eliminating or decreasing the number of understory plant species in particular functional groups from plots at a riparian site in southwestern Virginia, USA. Our functional groups comprise combinations of aboveground biomass and rooting structure type. Manipulated plots were planted with 10 randomly chosen species from widespread native and introduced plants commonly found throughout the floodplains of Big Stony Creek. We assessed success of an invasion by plant survivorship and growth. We analyzed survivorship of functional groups with loglinear models for the analysis of categorical data in a 4‐way table. There was a significant interaction between functional groups removed in a plot and survivorship in the functional groups added to that plot. However, survivorship of species in functional groups introduced into plots with their respective functional group removed did not differ from survivorship when any other functional group was removed. Additionally, growth of each of the most abundant species did not differ significantly among plots with different functional groups manipulated. Specifically, species did not fare better in those plots that had representatives of their own functional group removed. Fox's assembly rule does not hold for these functional groups in this plant community; however, composition of the recipient community is a significant factor in community assembly.
How does timing of browsing affect above‐ and below‐ground growth of Betula pendula, Pinus sylvestris and Sorbus aucuparia?
Authors: Hester Alison J. , Millard Pete , Baillie Gordon J. , Wendler Renate
Published: May 2004

Plant responses to browsing can affect root and shoot morphology, which is important to subsequent herbivory, nutrient acquisition and competition. This paper examines the above‐ and below‐ground responses of three browse species, with different growth strategies, to simulated browsing damage at different times of year. Saplings were grown in pots in sand culture to enable whole sapling analysis. At winter dormancy or budburst, 50% of previous year's shoots (and associated leaves/buds) were clipped. Subsequent sapling growth and morphology was compared with that of unclipped control saplings. Treatment differences in growth parameters of each species were observed, including changes in branching patterns, shoot lengths, diameters and ratios, leaf sizes and end‐of‐season bud numbers. Some responses were damage‐induced per se; others differed according to timing of damage. Compensatory growth by the two deciduous species (Betula pendula, Sorbus aucuparia) resulted in few biomass differences by the end of the year of damage as compared to controls, but both above‐ and below‐ground growth of clipped Pinus sylvestris was poor, particularly those damaged at budburst, giving strong differences between control, dormant, and budburst clipped saplings.
An interaction between a specialized seed predator moth and its dioecious host plant shifting from parasitism to mutualism
Authors: Westerbergh Anna
Published: May 2004

Seed predator/pollinator and host plant interactions, which may be considered as antagonistic, have the potential to provide good model systems for the study of the early stages of evolution towards mutualism. I describe a relationship between a seed predator, the geometrid moth Perizoma affinitatum, and the dioecious plant Silene dioica. The moth is an obligate seed predator on its host plant. The searching and ovipositing behaviour of the female moths, number of eggs deposited per flower, the pollinating ability of the moths and the seed consumption by the larvae are described as different parameters and studied in two Finnish coastal populations. A high pollinating ability and limited seed consumption by the predator was found and discussed in relation to fitness models of P. affinitatum and S. dioica. In a mutualistic relationship there must be a balance between the costs and benefits so that the seed production by the moths is larger than the seed consumption by the larvae, given a net seed output larger than zero. The data of the parameters included in a seed production/consumption model give a positive seed output when the proportion of S. dioica flowers pollinated by other non‐predating insects is less than 60%. Accordingly, even if P. affinitatum would become the exclusive pollinator it would not endanger the survival of the host plant and both partners would benefit from this interaction. Limited seed consumption, high pollinating ability and host specificity as seen in the P. affinitatum and S. dioica interaction are considered to have been important pre‐existing qualities in the evolution of the obligate mutualisms between yucca and yucca moths and fig and fig wasps. In isolated serpentine populations where the gene flow is restricted and co‐pollinators are rare the interaction between P. affinitatum and S. dioica has the potential to shift from parasitism to mutualism.
Why are American mink sexually dimorphic? A role for niche separation
Authors: Thom Michael D. , Harrington Lauren A. , Macdonald David W.
Published: May 2004

American mink are highly sexually dimorphic, with males being up to twice the size of females. Sexual dimorphism may arise for several reasons, including intra‐ or inter‐sexual selection, inter‐sexual competition, or divergent reproductive roles. Whether or not dimorphism arises from competition, a degree of niche separation is expected in dimorphic species. Sexual divergence in feeding niche has been reported for many species, including mink. This is likely to be manifested in a greater degree of dimorphism in those structures, such as teeth, that are used for the acquisition of prey. We tested the hypothesis that teeth and other trophic structures of male mink would be significantly larger than those of females, after controlling for underlying skeletal size differences. Canine and carnassial teeth, and several skull dimensions, were larger than predicted in males. There is good evidence that sexual dimorphism in mink trophic apparati is greater than predicted from allometry. We examined the development of dimorphism in various features with age and found that it was not consistent. Several trophic features were dimorphic amongst juveniles, and the degree of dimorphism remained relatively constant with age. Dimorphism in canines, and in relative body mass, was less apparent amongst juveniles and increased with increasing age. We discuss our results in the light of contemporary theories on the evolution and maintenance of sexual size dimorphism and argue that niche separation as a result of dimorphism in trophic features, while probably not the driving force behind sexual size dimorphism, may play a role in its maintenance.
Sexual differences in response to larval food stress in two nuptial feeding orthopterans – implications for sexual selection
Authors: Gwynne Darryl T.
Published: May 2004

The extent to which a trait deteriorates in response to stress can indicate its fitness importance. Food limitation is a naturally‐occurring stress in the katydid Kawanaphilanartee (Orthoptera: Tettigoniidae) and should cue larvae as to the level of sexual competition expected; hunger drives adult females to compete for copulations and thus acquire spermatophore meals. This increases sexual selection on females relative to males for increased body mass. As predicted, under experimental food‐stress larval female K. nartee showed little loss of mass whereas male mass decreased. In contrast, the sizes of body parts less critical to mating success showed similar decreases in males and females. For katydids such as Conocephalusnigropleurum, where reversals in mating roles do not occur, larval food stress should result in a greater preservation of male body mass, an important trait in male mating success. This prediction was supported; male mass decreased less than that of females.
Testing life history predictions in a long‐lived seabird: a population matrix approach with improved parameter estimation
Authors: Doherty, Jr. P. F. , Schreiber E. A. , Nichols J. D. , Hines J. E. , Link W. A. , Schenk G. A. , Schreiber R. W.
Published: May 2004

Life history theory and associated empirical generalizations predict that population growth rate (λ) in long‐lived animals should be most sensitive to adult survival; the rates to which λ is most sensitive should be those with the smallest temporal variances; and stochastic environmental events should most affect the rates to which λ is least sensitive. To date, most analyses attempting to examine these predictions have been inadequate, their validity being called into question by problems in estimating parameters, problems in estimating the variability of parameters, and problems in measuring population sensitivities to parameters. We use improved methodologies in these three areas and test these life‐history predictions in a population of red‐tailed tropicbirds (Phaethon rubricauda). We support our first prediction that λ is most sensitive to survival rates. However the support for the second prediction that these rates have the smallest temporal variance was equivocal. Previous support for the second prediction may be an artifact of a high survival estimate near the upper boundary of 1 and not a result of natural selection canalizing variances alone. We did not support our third prediction that effects of environmental stochasticity (El Niño) would most likely be detected in vital rates to which λ was least sensitive and which are thought to have high temporal variances. Comparative data‐sets on other seabirds, within and among orders, and in other locations, are needed to understand these environmental effects.
Acid phosphatases from beet root (Beta vulgaris) plasma membranes
Authors: Armienta‐Aldana Eduardo , González de la Vara Luis E.
Published: May 2004

Several acid phosphatases (EC 3.1.3.2) were found in beet root (Beta vulgaris L.) plasma membranes. Two of them were partially purified by an extraction of plasma membranes with octylglucoside and successive gel‐filtration and anion‐exchange chromatographies. With p‐nitrophenyl‐phosphate (pNPP) as substrate, most of the phosphatase activity was found in a fraction containing an 82‐kDa protein. This phosphatase showed an optimum pH of 5.4 and was inhibited by Cu2+, Zn2+, molybdate or vanadate. The other phosphatase had a lower specific activity with pNPP, but was able to dephosphorylate phospho‐myelin basic protein (phospho‐MBP). This phosphatase presented two polypeptides with molecular masses of 36 and 65 kDa and was 83% inhibited by 2 nM okadaic acid, which suggests it is a PP2A protein phosphatase. As the phosphatase activity was high in soluble (non‐membrane) fractions, the possibility that phosphatases in plasma membranes were soluble contaminants was assessed. Following the method of Bérczi and Møller (Plant Physiol. 116:1029, 1998), it was found that about 45% of both acid and protein phosphatase activities could be due to soluble enzymes trapped inside membrane vesicles.
Processes contributing to photoprotection of grapevine leaves illuminated at low temperature
Authors: Hendrickson Luke , Förster Britta , Furbank Robert T. , Chow Wah Soon
Published: May 2004

Photoinactivation of photosystem II (PSII) and energy dissipation at low leaf temperatures were investigated in leaves of glasshouse‐grown grapevine (Vitis viniferaL. cv. Riesling). At low temperatures (< 15°C), photosynthetic rates of CO2assimilation were reduced. However, despite a significant increase in the amount of light excessive to that required by photosynthesis, grapevine leaves maintained high intrinsic quantum efficiencies of PSII (Fv/Fm) and were highly resistant to photoinactivation compared to other species. Non‐photochemical energy dissipation involving xanthophylls and fast D1 repair were the main protective processes reducing the ‘gross’ rate of photoinactivation and the ‘net’ rate of photoinactivation, respectively. We developed an improved method of energy dissipation analysis that revealed up to 75% of absorbed light is dissipated thermally via pH‐ and xanthophyll‐mediated non‐photochemical quenching at low temperatures (5–15°C) and moderate (800 µmol quanta m−2s−1) light. Up to 20% of the energy flux contributing to electron transport was dissipated via photorespiration when taking into account temperature‐dependent mesophyll conductance; however, this flux used in photorespiration was only a relatively small amount of the total absorbed light energy. Photoreduction of O2at photosystem I (PSI) and subsequent superoxide detoxification (water‐water cycle) was more sensitive to inhibition by low temperature than photorespiration. Therefore the water‐water cycle represents a negligibly small energy sink below 15°C, irrespective of mesophyll conductance.
Dominance and compromise in freshwater phytoplanktonic flagellates: the interaction of behavioural preferences for conflicting environmental gradients
Authors: CLEGG M. R. , MABERLY S. C. , JONES R. I.
Published: May 2004

Motile phytoplanktonic flagellates display a suite of sensory‐mediated behavioural preferences to single‐environmental gradients. However, in nature multiple gradients of essential resources are often spatially and temporally conflicting, therefore it is important to understand how flagellate behaviours interact under these conditions.

Five species of these photosynthetic micro‐organisms were exposed to combinations of representative physical and chemical gradients in laboratory preference chambers. Using single‐factor responses as templates, the effects of multiple gradients were investigated and hierarchies of preferences constructed.

Three distinct interaction responses were observed: ‘dominance’ of one of two preferences; bisecting ‘compromise’ interactions, suggesting co‐dominance while potentially optimizing resource acquisition; and an ‘extreme response’ in which preferences appeared more important than avoidance of unfavourable conditions.

In all species, preference for light was dominant over preference for temperature and phosphate. More complex dominance, compromise and extreme interaction responses were induced by combinations of light, oxygen and carbon dioxide gradients.

Construction of a hierarchy of dominant responses demonstrated that, depending on species, response to light generally superseded preferences for CO2, O2 and recessive preferences for temperature and phosphate.

Interaction responses may confer functional ecophysiological advantages, with dominant preferences influencing the spatial and temporal distribution, migration, depth regulation and succession of phytoplanktonic flagellates in freshwater ecosystems.
Competitive relationships ofAndropogon gerardii(Big Bluestem) from remnant and restored native populations and select cultivated varieties
Authors: GUSTAFSON D. J. , GIBSON D. J. , NICKRENT D. L.
Published: May 2004

Although genetic differentiation among plant populations is well known, its relevance for preserving the integrity of native ecosystems has received little attention. In a series of competition experiments withAndropogon gerardiiVitman, a dominant species of the North American Tallgrass Prairie, plant performance was related to seed provenance and restoration activities.

Glasshouse experiments showed plant performance to be a function of seed source. Differential target plant performance relative to competitor identity was observed when plant performance was assessed across a range of competitor densities. Local and non‐local plants were larger when competing against non‐local plants relative to the local and cultivar plants, while cultivar plants were consistently larger than local and non‐local plants regardless of competitor identity or density. The consistency of cultivar performance could reflect directional selection during cultivar development for consistently high fecundity, vigorous vegetative growth and resistance to pathogens.

In a field experiment, non‐local plants were half the size of local and cultivar plants, supporting recognition of seed provenances ofA. gerardiibased on differences in plant performance among source populations observed in the glasshouse study, and previous genetic analyses of the same populations.

This study establishes that seed provenance and restoration activities influence the competitive ability of a dominant species which, in turn, may affect plant community structure and potential ecosystem function.
On the statistical significance of functional diversity effects
Authors: PETCHEY O. L.
Published: May 2004

Changes in biodiversity can affect ecosystem processes through a variety of pathways, such as changes in community structure, loss of a keystone or changes in resource use patterns among species. The latter, also known as resource use complementarity, is an established mechanistic link between species and ecosystems.

At present, functional group richness is the dominant measure of the extent of resource use complementarity and has been manipulated in several experiments. These groups are constructeda prioriusing information about differences between species and a statistically significant effect is typically identified by standard parametric tests. These tests implicitly assume that thea priorifunctional groups are correct.

Avoiding this assumption requires a randomization (bootstrap) test of statistical significance that accounts for the effects of groupingper se. This test compares the observed test statistic to the distribution of the test statistic resulting from random assignment of species to groups.

Re‐analyses of experimental manipulations of plant functional diversity by bootstrapping the critical significance value changed the ecological interpretation of results in nearly half of the experiments. This occurred because random assignment of species to functional groups frequently creates a strong relationship between functional diversity and ecosystem functioning.

The significant bootstrapped results that were found perhaps represent some of the most convincing evidence that functional diversity is an important determinant of local‐scale ecosystem functioning.
Transgenerational plasticity for sexual reproduction and diapause in the life cycle of monogonont rotifers: intraclonal, intraspecific and interspecific variation in the response to crowding
Authors: SCHRÖDER T. , GILBERT J. J.
Published: May 2004

In monogonont rotifers parthenogenetic reproduction allows population growth, and mictic (sexual) reproduction leads to the production of diapausing eggs. When amictic females are exposed to a mixis stimulus, they produce mictic daughters, whose eggs develop into males or, if fertilized, into diapausing eggs. Experiments showed that mictic offspring production is initiated by crowding in females of Brachionus angularis Gosse 1851, Epiphanes senta (O.F. Müller 1773) and Rhinoglena frontalis Ehrenberg 1853, just as it is in Brachionus calyciflorus Pallas 1766 and B. plicatilis Müller 1786.

In B. calyciflorus, B. angularis, E. senta and R. frontalis, the propensity of amictic females to respond to crowding by producing mictic female offspring is low in the stem female hatching from a diapausing egg, but then increases after some generations. In many cases, only few mictic offspring are produced by crowded females of the second to the fifth generation, but the maximal response occurs only in later generations. Delayed sexual reproduction in early generations from the resting egg may be advantageous, because it first favours rapid population growth and later on maximizes resting egg production. However, it may be disadvantageous, if unpredictable environmental variation causes a population decline when sexual reproduction is still suppressed.

The extent to which sexual reproduction is delayed varies among and within species. When strains from populations in temporary and permanent habitats were compared, sexual reproduction was significantly delayed in strains from temporary habitats in all species, whereas in B. calyciflorus and R. frontalis mixis was not significantly delayed in strains from permanent habitats. In E. senta mixis was significantly delayed in clones from both habitat types.

Within all strains there was significant variation among clones in the propensity to produce mictic offspring, the extent to which sexual reproduction was delayed in the first generations after the stem female hatched, or both.
Evidence‐Based Data for the Hemodialysis Access Surgeon
Authors: Huber Thomas S. , Buhler Amy G. , Seeger James M.
Published: May 2004

The National Kidney Foundation Dialysis Outcomes Quality Initiative Clinical Practice Guidelines for Vascular Access (DOQI) have defined the access‐related care for patients with end‐stage renal disease (ESRD). However, the standard of care across the country has fallen short of the DOQI targets. One potential explanation for these shortcomings is the lack of compelling evidence in the literature to support the recommendations. This study was designed to compare the DOQI with the best available evidence in the literature for four clinical questions relevant to the hemodialysis access surgeon: the choice of access type (autogenous versus prosthetic), the type of prosthetic graft, management of the “failing” (nonthrombosed) access, and management of the thrombosed access. The electronic literature databases MEDLINE and Evidence‐Based Medicine Reviews were searched and relevant randomized controlled trials or meta‐analyses were identified for review. No randomized controlled trials comparing autogenous to prosthetic accesses were identified. However, a recent systematic review reported that the patency rates for upper extremity autogenous accesses were superior to their polytetrafluoroethylene (PTFE) counterparts. The identified randomized trials suggested that the patency rates for the different types of commercially available prosthetic grafts used for access appear comparable. They suggested that standard wall PTFE thickness and prosthetic anastomotic cuffs may be associated with better graft patency, while venous cuffs may be associated with worse patency. Furthermore, the trials suggested percutaneous angioplasty of “failing” prosthetic accesses with greater than 50% stenoses did not appear to improve patency and that routine use of intraluminal stents, as an adjunct to angioplasty, was not beneficial. They did suggest that patency after open surgical revision of “failing” prosthetic accesses was superior to that after percutaneous angioplasty. Lastly, the identified trials suggested that the patency rates after open surgical revision of thrombosed prosthetic accesses was better than after endovascular treatment. Despite the magnitude of hemodialysis‐related access problems, the quality of the evidence supporting the clinical decisions relevant to the access surgeon is limited and further clinical trials are justified.
Basic Science and Dialysis: Nitric Oxide and Hemodialysis
Authors: Sarkar Shubho R. , Kaitwatcharachai Charoen , Levin Nathan W.
Published: May 2004

Nitric oxide (NO), previously thought of as a noxious gas, is now recognized as an important mediator of vascular responsiveness. Soon after its discovery, it was realized that the actions of NO are similar to the previously described endothelium‐derived relaxing factor (EDRF). It is synthesized in the vascular endothelium utilizing the enzyme nitric oxide synthase (NOS) and diffuses in the adjacent vascular media, where it has a vasodilatory action. Opposing actions of NO and vasoconstrictor agents (such as endothelin‐1, angiotensin ΙΙ, and others) maintain the vascular tone of the renal arteries. The same balance at the level of the macula densa maintains glomerular filtration rate (GFR) during varying levels of salt excretion. Lack of NO can result in disruption of this fine balance, with resultant vasoconstriction and disease progression, hypertension, and accelerated atherosclerosis. In addition, hypertension may result from positive salt balance that occurs when macula densa NOS is inhibited. While most investigators report low levels of NO in uremic subjects, the levels in hemodialysis (HD) patients have not been characterized adequately. This is primarily because HD patients are exposed to both stimulatory and inhibitory factors for NO synthesis. Retention of inhibitors of NOS tends to decrease NO levels, whereas production of NO will be increased by cytokines generated during blood‐dialyzer interaction. There is less disagreement, however, over the finding of elevated levels in those with dialyzer reactions and dialysis‐induced hypotension. Recent developments in the isolation of inducible and constitutive forms of NOS makes understanding of its pathophysiologic effects more complete. Newer treatment directed at inhibiting only the inducible forms of NOS (sparing the constitutive forms) may soon be found useful for the treatment and prevention of hypotension and dialyzer reactions in HD patients.
Cardiac Arrest in Dialysis Patients: Taking a Small Step
Authors: Herzog Charles A.
Published: May 2004

Dialysis patients are at high risk for death, and cardiac disease accounts for 43% of all‐cause mortality. The single greatest cause of death in dialysis patients is sudden cardiac death. The survival of dialysis patients after cardiac arrest is poor. Clinical strategies for improving the outcomes of dialysis patients should include therapies to reduce the risk of cardiac arrest and the likelihood of surviving cardiac arrest. Defibrillators should be available in all dialysis centers.
Patterns of fish and sea urchin grazing on tropical Indo‐Pacific seagrass beds
Authors: Alcoverro Teresa , Mariani Simone
Published: May 2004

Thalassodendron ciliatum shoots were collected from natural populations of fished and unfished protected seagrass meadows to assess the herbivory of fish and sea urchins. Fish herbivory was restricted to unfished seagrass meadows, while sea urchin herbivory took place in fished as well as unfished areas where fish appeared not to be effective urchin predators. The results of this study confirm that grazing by sea urchins is important in tropical seagrass ecosystems and indicate that herbivorous fish graze, and probably consume, substantial amounts of seagrass production in fishing‐protected habitats. The fact that much of the information on seagrass herbivory comes from heavily‐fished meadows indicates that large‐scale studies, which include unfished areas, are necessary to provide reliable spatial patterns of seagrass grazing distribution.
Modelling species distributions in Britain: a hierarchical integration of climate and land‐cover data
Authors: Pearson Richard G. , Dawson Terence P. , Liu Canran
Published: May 2004

A modelling framework for studying the combined effects of climate and land‐cover changes on the distribution of species is presented. The model integrates land‐cover data into a correlative bioclimatic model in a scale‐dependent hierarchical manner, whereby Artificial Neural Networks are used to characterise species’ climatic requirements at the European scale and land‐cover requirements at the British scale. The model has been tested against an alternative non‐hierarchical approach and has been applied to four plant species in Britain: Rhynchospora alba, Erica tetralix, Salix herbacea and Geranium sylvaticum. Predictive performance has been evaluated using Cohen's Kappa statistic and the area under the Receiver Operating Characteristic curve, and a novel approach to identifying thresholds of occurrence which utilises three levels of confidence has been applied. Results demonstrate reasonable to good predictive performance for each species, with the main patterns of distribution simulated at both 10 km and 1 km resolutions. The incorporation of land‐cover data was found to significantly improve purely climate‐driven predictions for R. alba and E. tetralix, enabling regions with suitable climate but unsuitable land‐cover to be identified. The study thus provides an insight into the roles of climate and land‐cover as determinants of species’ distributions and it is demonstrated that the modelling approach presented can provide a useful framework for making predictions of distributions under scenarios of changing climate and land‐cover type. The paper confirms the potential utility of multi‐scale approaches for understanding environmental limitations to species’ distributions, and demonstrates that the search for environmental correlates with species’ distributions must be addressed at an appropriate spatial scale. Our study contributes to the mounting evidence that hierarchical schemes are characteristic of ecological systems.
Effects of landscape composition on farmland and red‐listed birds in boreal agricultural‐forest mosaics
Authors: Virkkala Raimo , Luoto Miska , Rainio Kalle
Published: May 2004

Farmland birds have declined in large areas of western and northern Europe. This decline has been connected with changes in the agricultural landscape. We studied the effects of landscape composition on birds in a boreal agricultural‐forest mosaic in SW Finland. This study was carried out with a grid‐based approach: bird pairs were counted in 105 grid squares of 25 ha within an area of 26.25 km2. The total density of farmland birds and density of red‐listed species were related to the land cover variables using generalized linear modelling (GLM). Farmland birds consist of a variable group of species either breeding or feeding in agricultural land. The model explained a moderate proportion (49%) of the variation in the total density of farmland birds in the landscape. In a regression analysis cover of non‐arable agricultural land (semi‐natural grasslands, built‐up areas) explained a much higher proportion (r2=0.49) of the variation in farmland bird density than that of arable land (cultivated fields and set‐aside fields, r2=0.04). Semi‐natural grasslands, which have drastically declined throughout NW Europe, and built‐up areas (mainly farmyards) had the most significant positive effects on the density of red‐listed species. The results emphasize the significance of semi‐natural grasslands for the declining red‐listed farmland bird species. Birds are usually not restricted to certain patches of habitat but use several patches in their home range. Thus, when studying bird‐landscape relations for land use planning, we also recommend grid‐based approaches covering the whole landscape variation.
Effects of aerial dispersal, habitat specialisation, and landscape structure on spider distribution across fragmented grey dunes
Authors: Bonte D. , Baert L. , Lens L. , Maelfait J.‐P.
Published: May 2004

Species distribution patterns have been explained by Hutchinson's niche theory, metapopulation theory and source‐sink theory. Empirical verification of this framework, however, remains surprisingly scant. In this paper, we test the hypothesis that landscape characteristics (patch size and connectivity), aerial dispersal ability and niche breadth interact in explaining distribution patterns of 29 spider species inhabiting fragmented grey dunes. Distribution patterns only depended on aerial dispersal potential, and the interaction between patch connectivity and area. Niche breadth, measured as the degree of habitat specialisation in the total coastal dune system, did not contribute to the observed distribution patterns. Additional variation in patch occupancy frequency was strongly species‐dependent and was determined by different responses to the degree of patch connectivity for ballooning dispersal. Results from this study suggest that dispersal ability largely affects our perception of a species “fundamental niche”, and that source‐sink and metapopulation dynamics may have a major impact on the distribution of species. From a conservation point of view, specialised (and hence intrinsically rare) species can be predicted to become rarer if fragmentation increases and connectivity decreases. This study is, to our knowledge, one of the few linking species distribution (and not patch occupancy, species diversity or richness) to landscape ecological (patch connectivity and area) and auto‐ecological (niche breadth, dispersal potential) features.
Infants' Physical World
Authors: Baillargeon Renée
Published: May 2004

Investigations of infants' physical world over the past 20 years have revealed two main findings. First, even very young infants possess expectations about physical events. Second, these expectations undergo significant developments during the first year of life, as infants form event categories, such as occlusion, containment, and covering events, and identify the variables relevant for predicting outcomes in each category. A new account of infants' physical reasoning integrates these findings. Predictions from the account are examined in change-blindness and teaching experiments.
Drugs, Environment, Brain, and Behavior
Authors: Crombag Hans S. , Robinson Terry E.
Published: May 2004

The effects of psychoactive drugs are not just a function of their pharmacological actions, but are due to complex interactions among pharmacological, psychological, and environmental factors. We discuss here how drug-environment interactions determine the likelihood that addictive drugs produce a persistent form of neurobehavioral plasticity (sensitization) thought to be involved in the pathophysiology of addiction and relapse.
Unconscious Emotion
Authors: Winkielman Piotr , Berridge Kent C.
Published: May 2004

Conscious feelings have traditionally been viewed as a central and necessary ingredient of emotion. Here we argue that emotion also can be genuinely unconscious. We describe evidence that positive and negative reactions can be elicited subliminally and remain inaccessible to introspection. Despite the absence of subjective feelings in such cases, subliminally induced affective reactions still influence people's preference judgments and even the amount of beverage they consume. This evidence is consistent with evolutionary considerations suggesting that systems underlying basic affective reactions originated prior to systems for conscious awareness. The idea of unconscious emotion is also supported by evidence from affective neuroscience indicating that subcortical brain systems underlie basic “liking” reactions. More research is needed to clarify the relations and differences between conscious and unconscious emotion, and their underlying mechanisms. However, even under the current state of knowledge, it appears that processes underlying conscious feelings can become decoupled from processes underlying emotional reactions, resulting in genuinely unconscious emotion.