bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contingent effects of water balance variation on tree cover density in semiarid woodlands
Authors: Kerkhoff Andrew J. , Martens Scott N. , Shore Gregory A. , Milne Bruce T. 
Published: May 2004

ABSTRACTAim  The local distribution of woody vegetation affects most functional aspects of semiarid landscapes, from soil erosion to nutrient cycling. With growing concern about anthropogenic climate change, it has become critical to understand the ecological determinants of woody plant distribution in semiarid landscapes. However, relatively little work has examined the determinants of local variation in woody cover. Here we examine water balance controls associated with patterns of tree cover density in a topographically complex semiarid woodland.Location  Los Pinos Mountains, Sevilleta National Wildlife Refuge LTER, New Mexico, USA.Methods  To explore the relationship between local water balance variation and tree cover density, we used a combination of high‐resolution (1 × 1 m), remotely sensed imagery and quantitative estimates of water balance variation in space and time. Regression tree analysis (RTA) was used to identify the environmental parameters that best predict variation in tree cover density.Results  Using six predictor variables, the RTA explains 39% of the deviance in tree cover density over the landscape. The relationship between water balance conditions and tree cover density is highly contingent; that is, similar tree cover densities occur under very different combinations of water balance parameters. Thus, the effect of one environmental parameter on tree cover density depends on the values of other parameters. After tree cover density is adjusted for water balance conditions, residual variation is related to tree cover density in the neighbourhood of a particular location.Conclusion  In semiarid landscapes, vegetation structure is largely controlled by water supply and demand. Results presented here indicate that localized feedbacks and site‐specific historical processes are critical for understanding the responses of semiarid vegetation to climate change.
Use of a latitudinal gradient in bald cypress (Taxodium distichum) production to examine physiological controls of biotic boundaries and potential responses to environmental change
Authors: Middleton Beth A. , McKee Karen L. 
Published: May 2004

ABSTRACTAim  Predictions of vegetation change with global warming require models that accurately reflect physiological processes underlying growth limitations and species distributions. However, information about environmental controls on physiology and consequent effects on species boundaries and ecosystem functions such as production is limited, especially for forested wetlands that are potentially important carbon sinks.Location  The bald cypress (Taxodium distichum) region of the south‐eastern United States was studied to examine how production of an important forested wetland varies with latitude and temperature as well as local hydrology.Methods  We used published data to analyse litter production across a latitudinal gradient from 26.2 to 37.8° N to determine how bald cypress swamps might respond to alternate climate conditions and what changes might occur throughout the distributional range.Results  Litterfall rates followed a bell shaped curve, indicating that production was more limited at the distributional boundaries (c. 225 g/m2 year−1) compared to the mid‐range (795–1126 g/m2 year−1). This pattern suggests that conditions are suboptimal near both boundaries and that the absence of populations outside this latitudinal range may be largely due to physiological constraints on the carbon balance of dominant species. While dispersal limitations cannot be totally discounted, competition with other wetland types at the extremes of the range does not seem likely to be important because the relative basal area of bald cypress does not decrease near the edges of the range. Impaired hydrology depressed production across the entire range, but more in the south than the north.Main conclusions  Our findings suggest that (1) physiological limitations constrain biotic boundaries of bald cypress swamps; (2) future changes in global temperature would affect litter production in a nonlinear manner across the distributional range; (3) local changes in hydrology may interact with climate to further reduce litter production, particularly at lower latitudes; and (4) southernmost forests could be extirpated if environmental conditions compromise carbon balance and water‐use efficiency of trees.
Growth of Lythrum salicaria and Phragmites australis plants originating from a wide geographical area: response to nutrient and water supply
Authors: Bastlová Daša , Čížková Hana , Bastl Marek , Květ Jan 
Published: May 2004

ABSTRACTAim  The response of L. salicaria and P. australis plants originating from a broad latitudinal gradient to mineral nutrient and water supply was studied. We suggest implications for mechanisms possibly underlying the invasiveness of these two plant species.Location  A common garden tub experiment was carried out at Třeboň, Czech Republic (49° N 14°47′ E, altitude 433 m).Methods  Plants of 30 L. salicaria and 6 P. australis populations originating from a wide geographical area in Europe and in Israel (60°−32° N latitude, 6° W−20° E longitude) were cultivated for one growing season at two water levels and three (L. salicaria) or two (P. australis) nutrient doses, respectively. At the end of cultivation, basic morphological and growth characteristics were recorded.Results  The latitude of the original geographical location was the most significant factor, affecting both the phenology and most of the plant morphological and growth characteristics measured in both plant species, with the characteristics related to plant size being negatively correlated with latitude. The effect of nutrient dose was very strong in both species, while the effect of water level was more pronounced in P. australis than in L. salicaria.Main conclusions  The results confirmed the existence of a large phenotypic variability in both plant species within their native ranges of occurrence. In both plant species, the latitudinal variation in plant morphological and growth characteristics most probably indicates the differentiation of genotypes adapted to local geographical conditions. The plants of both species originating from all geographical locations tested responded to the respective nutrient treatments in a similar manner. Exceptions were found in growth characteristics related to reproduction in L. salicaria, indicating that better nutrient supply could enhance the reproductive ability of certain genotypes. Based on the results obtained, we suggest implications for mechanisms possibly underlying the invasiveness of the plant species studied.
An account of the joint fight for human rights by Flemish Musketeers and their Tinker Ladies
Authors: Roets Griet , Van de Perre Danny , Hove Geert Van , Schoeters Ludo , Schauwer Elisabeth De 
Published: May 2004

SummaryThe Musketeer book One for All – All for One! A joint fight for human rights (Onze Nieuwe Toekomst 2002) is a disclosure of oral accounts of people with the label of ‘learning difficulties’. The Musketeer book is particularly an articulation of their individual and collective politics of resistance. With this collection of stories – taken from life – true activists and their allies hope to bring tangible shifts in beliefs and attitudes in disabling society. In this paper, the Head Musketeer Danny and his right‐hand Musketeer Ludo reflect upon their relational perspective on the process of (self‐)empowerment with their Tinker Ladies. Our experience unfolds like walking a high wire. Our Flemish perspective reveals a profound awareness of power dynamics in an intensely felt cooperative research process.
Sociocultural study of intellectual disability: moving beyond labelling and social constructionist perspectives
Authors: Klotz Jani 
Published: May 2004

SummaryThis paper outlines the development of the sociocultural study of people with an intellectual disability, focusing in particular on the pioneering work of Robert Edgerton, Robert Bogdan and Steven Taylor, David Goode and John Gleason.1 As part of this analysis, I shall critically assess the contributions and limitations of these authors. I argue that the parameters of the debate have tended to become too rigid. The sociocultural study of intellectual disability has mostly focused on the experiences of people with mild intellectual disabilities, extrapolating from these experiences conclusions about the nature of intellectual disability in general, while the experiences and life worlds of those whose impairments are severe, profound, and often multiple, are often ignored. However, the portrayal and analysis of such people's lives are essential for our greater understanding and appreciation of intellectual disability, and of human difference in all its diverse manifestations. It is also essential for understanding, accepting and respecting people with severe and profound intellectual disabilities, and recognizing that such people are already living socially meaningfully lives as they are, despite not conforming to the dominant and socially prescribed norms and expectations of meaningful action and behaviour.2 The methodological and theoretical tools that are required to engage with and interpret such lives, however, are profoundly different to those used by the majority of sociocultural theorists in the field, as shall be discussed below.
Mutations in the extracellular domains of glutamate‐gated chloride channel α3 and β subunits from ivermectin‐resistant Cooperia oncophora affect agonist sensitivity
Authors: Njue Annete I. , Hayashi Jon , Kinne Lyle , Feng Xiao‐Peng , Prichard Roger K. 
Published: May 2004

AbstractTwo full‐length glutamate‐gated chloride channel (GluCl) cDNAs, encoding GluClα3 and GluClβ subunits, were cloned from ivermectin‐susceptible (IVS) and ‐resistant (IVR) Cooperia oncophora adult worms. The IVS and IVR GluClα3 subunits differ at three amino acid positions, while the IVS and IVR GluClβ subunits differ at two amino acid positions. The aim of this study was to determine whether mutations in the IVR subunits affect agonist sensitivity. The subunits were expressed singly and in combination in Xenopus laevis oocytes. Electrophysiological whole‐cell voltage‐clamp recordings showed that mutations in the IVR GluClα3 caused a modest but significant threefold loss of sensitivity to glutamate, the natural ligand for GluCl receptors. As well, a significant decrease in sensitivity to the anthelmintics ivermectin and moxidectin was observed in the IVR GluClα3 receptor. Mutations in the IVR GluClβ subunit abolished glutamate sensitivity. Co‐expressing the IVS GluClα3 and GluClβ subunits resulted in heteromeric channels that were more sensitive to glutamate than the respective homomeric channels, demonstrating co‐assembly of the subunits. In contrast, the heteromeric IVR channels were less sensitive to glutamate than the homomeric IVR GluClα3 channels. The heteromeric IVS channels were significantly more sensitive to glutamate than the heteromeric IVR channels. Of the three amino acids distinguishing the IVS and IVR GluClα3 subunits, only one of them, L256F, accounted for the differences in response between the IVS and IVR GluClα3 homomeric channels.
Multiple sites of ethanol action in α1 and α2 glycine receptors suggested by sensitivity to pressure antagonism
Authors: Davies Daryl L. , Crawford Daniel K. , Trudell James R. , Mihic S. John , Alkana Ronald L. 
Published: May 2004

AbstractThe current study used an ethanol antagonist, increased atmospheric pressure, to test the hypothesis that ethanol acts on multiple sites in glycine receptors (GlyRs). The effects of 12 times normal atmospheric pressure of helium‐oxygen gas (pressure) on ethanol‐induced potentiation of GlyR function in Xenopus oocytes expressing human α1, α2 or the mutant α1(A52S) GlyRs were measured using two‐electrode voltage clamp. Pressure reversibly antagonized potentiation of glycine in α1 GlyR by 40–200 mm ethanol, but did not antagonize 10 and 25 mm ethanol in the same oocytes. In contrast, pressure did not significantly affect potentiation of glycine by 25–100 mm ethanol in α2 GlyRs, nor did pressure alter ethanol response in the A52S mutant. Pressure did not affect baseline receptor function or response to glycine in the absence of ethanol. These findings provide the first direct evidence for multiple sites of ethanol action in GlyRs. The sites can be differentiated on the basis of ethanol concentration, subunit and structural composition and sensitivities to pressure antagonism of ethanol. Parallel studies with butanol support this conclusion. The mutant α1(A52S) GlyR findings suggest that increased attention should be focused on the amino terminus as a potential target for ethanol action.
Neisseria meningitidis‐induced death of cerebrovascular endothelium: mechanisms triggering transcriptional activation of inducible nitric oxide synthase
Authors: Constantin Despina , Cordenier Axelle , Robinson Karen , Ala'Aldeen Dlawer A. A. , Murphy Sean 
Published: May 2004

AbstractThe intense host response to meningococcus reflects marked functional and morphological alterations in blood–brain barriers. We showed previously that mouse‐derived cerebrovascular endothelium responded to meningococcal lysates with a robust nitric oxide (NO) response, resulting in the loss of cell viability. To understand how the NO synthase‐2 gene in endothelium is activated by meningococcus, we investigated upstream roles for specific protein kinases. Using known kinase inhibitors, and measuring both mRNA expression and nitrite release, we found MAPK/ERK kinase (MEK)2, p38 kinase and phosphoinositide 3‐kinase (but not MEK1 or phospholipase C) to be implicated in the NO synthase‐2 response. Recruitment of these kinases by meningococcus did not depend on the prior release of the proinflammatory cytokines tumour necrosis factor α or interleukin‐1β from endothelium. These endothelial cells were found to express toll‐like receptors (TLR) 2, 4 and 9 and antibodies directed against TLR 2 and 4 (but not TLR 9) blocked the NO synthase‐2 response to meningococcus. Both meningococcus‐induced translocation of nuclear factor‐kB (NF‐kB) and endothelial cell death were blocked by a known inhibitor of p38 kinase. Calpain inhibitor‐1 blocked the NO synthase‐2 response to meningococcus, which is further evidence of a role for NF‐kB.
Stress‐induced activation of the immediate early gene Arc (activity‐regulated cytoskeleton‐associated protein) is restricted to telencephalic areas in the rat brain: relationship to c‐fos mRNA
Authors: Ons Sheila , Martí Octavi , Armario Antonio 
Published: May 2004

Abstract Arc is an effector immediate early gene whose expression is induced in situations of increased neuronal activity. However, there is no report on the influence of stress on Arc expression. Here, we compared the induction of both c‐fos and Arc mRNAs in the brain of rats exposed to one of three different stressful situations: novel environment, forced swimming and immobilization. An absent or weak c‐fos mRNA signal was observed in control rats, whereas those exposed to one of three stressors showed enhanced c‐fos expression in a wide range of brain areas. Constitutive Arc expression was observed in some areas such as cortex, striatum, hippocampus, reticular thalamic nucleus and cerebellar cortex. In response to stressors, a strong induction of Arc was observed, but the pattern was different from that of c‐fos. For instance, activation of Arc but not c‐fos was observed in the nucleus accumbens after immobilization and in the hippocampus after novel environment. No Arc induction was observed in diencephalic and brainstem areas. The present data show that Arc has a neuroanatomically restricted pattern of induction in the brain after emotional stress. Telencephalic activation suggests that a more intense induction of synaptic plasticity is occurring in this area after exposure to emotional stressors.
3‐Nitropropionic acid‐induced neurotoxicity – assessed by ultra high resolution positron emission tomography with comparison to magnetic resonance spectroscopy
Authors: Brownell Anna‐Liisa , Chen Y. Iris , Yu Meixiang , Wang Xukui , Dedeoglu Alpaslan , Cicchetti Francesca , Jenkins Bruce G. , Beal M. Flint 
Published: May 2004

AbstractTo explore acute and long‐term effects of 3‐nitropropionic acid (3‐NP)‐induced neurotoxicity, longitudinal positron emission tomography (PET) studies of energy metabolism and magnetic resonance spectroscopic (MRS) studies of neurochemicals were conducted in a rat model. The first injection of 3‐NP (20 mg/kg i.p.) was followed by MRS study of neurochemicals and PET study of glucose utilization using [18F]2‐fluorodeoxy‐d‐glucose (18F‐FDG). After that, 3‐NP administration was done two times a day with a dose of 10 mg/kg i.p. until animals were symptomatic or for a maximum of 5 days combined with daily PET studies. Long‐term effects were investigated 4 weeks and 4 months after cessation of 3‐NP. These studies showed a significant inter‐animal variation in response of 3‐NP toxicity. Animals that developed large striatal lesions had decreased glucose utilization in the striatum and cortex 1 day after starting 3‐NP injections. Similarly succinate and lactate/macromolecule levels were enhanced; these changes being, however, reversible. Progressive degeneration was observed by decreasing striatal glucose utilization and N‐acetylaspartate (NAA) and increasing choline. These observations paralleled with weight loss and deficits in behavior. Animals that did not develop lesions showed reversible enhancement in cortical glucose utilization and no change in striatal glucose utilization or neurochemicals or locomotor activity.
Taurine‐induced long‐lasting potentiation in the rat hippocampus shows a partial dissociation from total hippocampal taurine content and independence from activation of known taurine transporters
Authors: Dominy John , Thinschmidt Jeffrey S. , Peris Joanna , Dawson Ralph , Papke Roger L. 
Published: May 2004

AbstractPerfusion with high millimolar levels of taurine evoked a long‐lasting potentiation (LLP‐TAU) of synaptic transmission in the Schaffer‐collateral CA1 region of the rat hippocampus. Although LLP‐TAU showed some correlations to increases in the total taurine content of hippocampal slices, it could not be blocked by the taurine transport inhibitor guanidinoethanesulfonic acid (GES), which was able to significantly reduce total slice taurine uptake. Inhibition of GABA transport by either nipecotic acid or β‐guanidinopropionate failed to abolish LLP‐TAU and had no significant effect on taurine uptake. The combination of GES and nipecotic acid also had no significant effect on LLP‐TAU. Experiments with transportable structural analogs of taurine (β‐aminoisobutyric acid, homotaurine, and isethionic acid) suggest that activation of classical taurine transport pathways does not always yield a robust LLP‐TAU. Hippocampal LLP‐TAU could be significantly attenuated, however, by pre‐incubation with submillimolar levels of taurine. In summary, the development of LLP‐TAU in the rat hippocampus appears to be associated with the intracellular accumulation rather than the activation of known transporters of taurine, but the precise means of its accumulation remains to be identified.
Regulation of glycogen synthase kinase‐3β by products of lipid peroxidation in human neuroblastoma cells
Authors: Dozza Barbara , Smith Mark A. , Perry George , Tabaton Massimo , Strocchi Paola 
Published: May 2004

AbstractThe potential role of 4‐hydroxynonenal (HNE), a major product of membrane lipid peroxidation, in regulating glycogen synthase kinase‐3β (GSK3β) activity was examined in human neuroblastoma IMR‐32 cells. The inhibition of GSK3β activity by HNE was observed by in vitro kinase assays with two substrates, the synthetic glycogen synthase peptide‐2 and the human recombinant tau. GSK3β activity is regulated by Ser9 (inhibitory) and Tyr216 (stimulatory) phosphorylation. By using specific activity‐dependent phospho‐antibodies, immunoblot analysis revealed that HNE induces an increase in phosphorylation of GSK3β in Ser9, enhancing basal phosphatidylinositol 3‐kinase (PI3K)/AKT and extracellular signal‐regulated kinase 2 (ERK2) signalling pathways. Ser9‐GSK3β phosphorylation induced by HNE was abolished by treatment with LY294002 or U0126, two inhibitors of PI3K/AKT and ERK pathways, respectively. These experiments provide evidence for a crucial role of the PI3K/AKT and ERK2 pathways as intracellular targets of HNE that mediate the inhibition of GSK3β activity in regulating cellular response to HNE in viable cells under conditions in which membrane lipid peroxidation occurs. These data support a key role for GSK3β as a mediator of the signalling pathways activated by oxidative stress, and therefore it may be included among the redox‐sensitive enzymes.
Pro‐regenerative properties of cytokine‐activated astrocytes
Authors: Liberto Christina M. , Albrecht P. J. , Herx L. M. , Yong V. W. , Levison S. W. 
Published: May 2004

AbstractThe prevailing view of the astrocytic response to injury is that reactive astrocytes impede the regenerative process by forming scar tissue. As the levels of many cytokines dramatically increase following CNS insult and as this increase in cytokine expression precedes the production of the glial scar, a long‐standing view has been that cytokines diminish neuronal survival and regeneration by stimulating the formation of astrogliotic scar tissue. However, there is a wealth of data indicating that cytokines ‘activate’ astrocytes, and that cytokine‐stimulated astrocytes can promote the recovery of CNS function. Supporting evidence demonstrates that cytokine‐activated astrocytes produce energy substrates and trophic factors for neurons and oligodendrocytes, act as free radical and excess glutamate scavengers, actively restore the blood–brain barrier, promote neovascularization, restore CNS ionic homeostasis, promote remyelination and also stimulate neurogenesis from neural stem cells. Accordingly, a re‐assessment of cytokine‐activated astrocytes is necessary. Here, we review studies that promote the thesis that cytokines elicit potent neuroprotective and regenerative responses from astrocytes.
A low molecular weight copper chelator crosses the blood–brain barrier and attenuates experimental autoimmune encephalomyelitis
Authors: Offen Daniel , Gilgun‐Sherki Yossi , Barhum Yael , Benhar Moran , Grinberg Leonid , Reich Reuven , Melamed Eldad , Atlas Daphne 
Published: May 2004

AbstractIncreasing evidence suggests that enhanced production of reactive oxygen species (ROS) activates the MAP kinases, c‐Jun N‐terminal protein kinase (JNK) and mitogen‐activated protein kinase MAPK (p38). These phosphorylated intermediates at the stress‐activated pathway induce expression of matrix metalloproteinases (MMPs), leading to inflammatory responses and pathological damages involved in the etiology of multiple sclerosis (MS). Here we report that N‐acetylcysteine amide (AD4) crosses the blood–brain barrier (BBB), chelates Cu2+, which catalyzes free radical formation, and prevents ROS‐induced activation of JNK, p38 and MMP‐9. In the myelin oligodendrocyte glycoprotein (MOG)‐induced experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, oral administration of AD4 drastically reduced the clinical signs, inflammation, MMP‐9 activity, and protected axons from demylination damages. In agreement with the in vitro studies, we propose that ROS scavenging by AD4 in MOG‐treated animals prevented MMP's induction and subsequent damages through inhibition of MAPK pathway. The low toxicity of AD4 coupled with BBB penetration makes this compound an excellent potential candidate for the therapy of MS and other neurodegenerative disorders.