bluuebunny/crossref_metadata_2025_split huggingface dataset:
GABAB and group I metabotropic glutamate receptors in the striatopallidal complex in primates
Authors: SMITH YOLAND , CHARARA ALI , HANSON JESSE E. , PAQUET MARYSE , LEVEY ALLAN I. 
Published: March 2003

Glutamate and GABA neurotransmission is mediated through various types of ionotropic and metabotropic receptors. In this review, we summarise some of our recent findings on the subcellular and subsynaptic localisation of GABAB and group I metabotropic glutamate receptors in the striatopallidal complex of monkeys. Polyclonal antibodies that specifically recognise GABABR1, mGluR1a and mGluR5 receptor subtypes were used for immunoperoxidase and pre‐embedding immunogold techniques at the light and electron microscope levels. Both subtypes of group I mGluRs were expressed postsynaptically in striatal projection neurons and interneurons where they aggregate perisynaptically at asymmetric glutamatergic synapses and symmetric dopaminergic synaptic junctions. Moreover, they are also strongly expressed in the main body of symmetric synapses established by putative intrastriatal GABAergic terminals. In the globus pallidus, both receptor subtypes are found postsynaptically in the core of striatopallidal GABAergic synapses and perisynaptically at subthalamopallidal glutamatergic synapses. Finally, extrasynaptic labelling was commonly seen in the globus pallidus and the striatum.Moderate to intense GABABR1 immunoreactivity was observed in the striatopallidal complex. At the electron microscope level, GABABR1 immunostaining was commonly found in neuronal cell bodies and dendrites. Many striatal dendritic spines also displayed GABABR1 immunoreactivity. Moreover, GABABR1‐immunoreactive axons and axon terminals were frequently encountered. In the striatum, GABABR1‐immunoreactive boutons resembled terminals of cortical origin, while in the globus pallidus, subthalamic‐like terminals were labelled. Pre‐embedding immunogold data showed that postsynaptic GABABR1 receptors are concentrated at extrasynaptic sites on dendrites, spines and somata in the striatopallidal complex, perisynaptically at asymmetric synapses and in the main body of symmetric striatopallidal synapses in the GPe and GPi. Consistent with the immunoperoxidase data, immunoparticles were found in the presynaptic grid of asymmetric synapses established by cortical‐ and subthalamic‐like glutamatergic terminals.These findings indicate that both GABA and glutamate metabotropic receptors are located to subserve various modulatory functions of the synaptic transmission in the primate striatopallidal complex. Furthermore, their pattern of localisation raises issues about their roles and mechanisms of activation in normal and pathological conditions. Because of their ‘modulatory’ functions, these receptors are ideal targets for chronic drug therapies in neurodegenerative diseases such as Parkinson's disease.
Asymmetry in the epithalamus of vertebrates
Authors: CONCHA MIGUEL L. , WILSON STEPHEN W. 
Published: March 2003

abstractThe epithalamus is a major subdivision of the diencephalon constituted by the habenular nuclei and pineal complex. Structural asymmetries in this region are widespread amongst vertebrates and involve differences in size, neuronal organisation, neurochemistry and connectivity. In species that possess a photoreceptive parapineal organ, this structure projects asymmetrically to the left habenula, and in teleosts it is also situated on the left side of the brain. Asymmetries in size between the left and right sides of the habenula are often associated with asymmetries in neuronal organisation, although these two types of asymmetry follow different evolutionary courses. While the former is more conspicuous in fishes (with the exception of teleosts), asymmetries in neuronal organisation are more robust in amphibia and reptiles. Connectivity of the parapineal organ with the left habenula is not always coupled with asymmetries in habenular size and/or neuronal organisation suggesting that, at least in some species, assignment of parapineal and habenular asymmetries may be independent events.The evolutionary origins of epithalamic structures are uncertain but asymmetry in this region is likely to have existed at the origin of the vertebrate, perhaps even the chordate, lineage. In at least some extant vertebrate species, epithalamic asymmetries are established early in development, suggesting a genetic regulation of asymmetry. In some cases, epigenetic factors such as hormones also influence the development of sexually dimorphic habenular asymmetries. Although the genetic and developmental mechanisms by which neuroanatomical asymmetries are established remain obscure, some clues regarding the mechanisms underlying laterality decisions have recently come from studies in zebrafish. The Nodal signalling pathway regulates laterality by biasing an otherwise stochastic laterality decision to the left side of the epithalamus. This genetic mechanism ensures a consistency of epithalamic laterality within the population. Between species, the laterality of asymmetry is variable and a clear evolutionary picture is missing. We propose that epithalamic structural asymmetries per se and not the laterality of these asymmetries are important for the behaviour of individuals within a species. A consistency of the laterality within a population may play a role in social behaviours between individuals of the species.
Morphogenesis and evolution of vertebrate appendicular muscle
Authors: HAINES LYNN , CURRIE PETER D. 
Published: March 2003

abstractTwo different modes are utilised by vertebrate species to generate the appendicular muscle present within fins and limbs. Primitive Chondricthyan or cartilaginous fishes use a primitive mode of muscle formation to generate the muscle of the fins. Direct epithelial myotomal extensions invade the fin and generate the fin muscles while remaining in contact with the myotome. Embryos of amniotes such as chick and mouse use a similar mechanism to that deployed in the bony teleost species, zebrafish. Migratory mesenchymal myoblasts delaminate from fin/limb level somites, migrate to the fin/limb field and differentiate entirely within the context of the fin/limb bud. Migratory fin and limb myoblasts express identical genes suggesting that they possess both morphogenetic and molecular identity. We conclude that the mechanisms controlling tetrapod limb muscle formation arose prior to the Sarcopterygian or tetrapod radiation.
The aquaporin‐4 water channel and brain tumour oedema
Authors: Saadoun S. , Papadopoulos M. C. , Bell B. A. , Krishna S. , Davies D. C. 
Published: March 2003

Aquaporin‐4 (AQP4) is a water channel protein that is expressed by perimicrovessel astrocyte foot processes in normal brain. There is up‐regulation of astrocyte AQP4 mRNA in areas of the rat brain where the blood brain barrier is disrupted following focal brain ischaemia or physical injury. In contrast AQP4 knockout mice show less brain swelling and improved survival rates after water intoxication or focal cerebral ischaemia compared to wild type mice. However little is known about the expression of AQP4 in aggressive human brain tumours, even though they result in peritumoural oedema. Therefore formalin fixed samples of morphologically normal human brain (n = 5), astrocytomas (n = 10) and adenocarcinoma metastases to brain (n = 5) were embedded in paraffin wax, sections cut and investigated by AQP4 immunocytochemistry. These samples were obtained from patients who underwent craniotomy at Atkinson Morley’s Hospital during 1998–9. Immunolabelling was performed using a polyclonal AQP4 antibody (AB3068, Chemicon), visualised with immunoperoxidase and diaminobenzidine hydrochloride. Blood–brain barrier opening was visualised preoperatively, using contrast enhancement on computed tomography. AQP4 immunolabelling was confined to astrocyte foot processes surrounding microvessels in the 5 samples of normal brain and 5 low grade (Daumas‐Duport I or II) astrocytomas. In 4/5 high grade (Daumas‐Duport III or IV) astrocytomas there was strong immunolabelling over the cytoplasm of most tumour cells and/or reactive astrocytes that was not restricted to the perimicrovessel region. Up‐regulation of AQP4 immunoreactivity was also found in astrocytes adjacent to the 5 metastatic adenocarcinomas investigated. There was a significant correlation between up‐regulation of AQP4 immunolabelling and contrast enhancement on computed tomographs (P < 0.0001 Fisher exact). Therefore oedematous aggressive brain tumours and surrounding tissues demonstrate massive up‐regulation of expression of the water channel protein AQP4. The strong correlation between the presence of brain oedema and AQP4 expression suggests that AQP4 expression is intimately involved in the pathophysiology of tumour related brain oedema. However, it is not clear whether AQP4 is involved in the accumulation or clearance of brain oedema fluid.
The structural basis of pulmonary hypertension in chronic lung disease: remodelling, rarefaction or angiogenesis?
Authors: Hopkins Natalie , McLoughlin Paul 
Published: March 2003

AbstractChronic lung disease in humans is frequently complicated by the development of secondary pulmonary hypertension, which is associated with increased morbidity and mortality. Hypoxia, inflammation and increased shear stress are the primary stimuli although the exact pathways through which these initiating events lead to pulmonary hypertension remain to be completely elucidated. The increase in pulmonary vascular resistance is attributed, in part, to remodelling of the walls of resistance vessels. This consists of intimal, medial and adventitial hypertrophy, which can lead to encroachment into and reduction of the vascular lumen. In addition, it has been reported that there is a reduction in the number of blood vessels in the hypertensive lung, which could also contribute to increased vascular resistance. The pulmonary endothelium plays a key role in mediating and modulating these changes. These structural alterations in the pulmonary vasculature contrast sharply with the responses of the systemic vasculature to the same stimuli. In systemic organs, both hypoxia and inflammation cause angiogenesis. Furthermore, remodelling of the walls of resistance vessels is not observed in these conditions. Thus it has been generally stated that, in the adult pulmonary circulation, angiogenesis does not occur. Prompted by previous observations that chronic airway inflammation can lead to pulmonary vascular remodelling without hypertension, we have recently shown, using quantitative stereological techniques, that angiogenesis can occur in the adult pulmonary circulation. Pulmonary angiogenesis has also been reported in some other conditions including post‐pneumonectomy lung growth, metastatic disease of the lung and in biliary cirrhosis. Such angiogenesis may serve to prevent or attenuate increased vascular resistance in lung disease. In view of these more recent data, the role of structural alterations in the pulmonary vasculature in the development of pulmonary hypertension should be carefully reconsidered.
Congenital talipes equinovarus (clubfoot): a disorder of the foot but not the hand
Authors: Miedzybrodzka Zosia 
Published: March 2003

AbstractIdiopathic (non‐syndromic) congenital talipes equinovarus, or clubfoot, is a poorly understood but common developmental disorder of the lower limb, which affects at least 2 per 1000 Scottish births (ISD data). It is defined as a fixation of the foot in a hand‐like orientation – in adduction, supination and varus – with concomitant soft tissue abnormalities. Despite advances in treatment, disability often persists. The aetiology of the condition has been little studied and is poorly understood. Neurological, muscular, bony, connective tissue and vascular mechanisms have been proposed, but the only firm evidence is that the mildest cases appear to be associated with intra‐uterine posture. There is evidence for a genetic contribution to congenital talipes equinovarus aetiology. Its incidence varies with ethnic group, and we found that a family history is present in 24–50% of cases, depending on the population studied. Complex segregation analysis suggests that the most likely inheritance pattern is a single gene of major effect operating against a polygenic background. Possible mechanisms for congenital talipes equinovarus are discussed.
Detection of symbiosis‐related polypeptides during the early stages of the establishment of arbuscular mycorrhiza between Glomus mosseae and Pisum sativum roots
Authors: SAMRA ASSEM , DUMAS‐GAUDOT ELIANE , GIANINAZZI SILVIO 
Published: March 2003

SUMMARYChanges in polypeptide contents following inoculation of roots of Pisum sativum L. (wild type cv. Frisson (myc+, nod+)) with the arbuscular mycorrhizal fungus Glomus mosseae were analysed by two–dimensional gel electrophoresis (2D‐PAGE). A different polypeptide pattern was obtained in a mycorrhiza–resistant pea genotype P2 (myc+, nod−) inoculated with G. mosseae. In order further to characterize the polypeptide modifications detected and to provide evidence for some possible symbiosis–related (SR) proteins, a time course experiment, from appressoria formation to fully developed symbiosis, was carried out on two genotypes allowing fungal colonization: the wild type and its isogenic mutant P56 (myc+, nod−). The same experiment was done with the mycorrhiza‐resistant pea genotype (myc+, nod−). After G. mosseae inoculation, we characterized 12 additional polypeptides in the two mycorrhiza‐compatible pea genotypes which were never observed in root extracts from the mycorrhiza‐resistant mutant. Five polypeptides were first detected in the early stage of the symbiosis (5 d of inoculation) while others were observed later (8 d of inoculation). The induction and accumulation of these polypeptides seem to be more correlated to the establishment of the functional symbiosis than to the recognition stages and appressorium formation. Furthermore, none of the additional polypeptides were detected in the mycorrhiza‐resistant pea genotype. This mutant was more characterized by a great repression of polypeptides. In addition, up‐regulated and down‐regulated polypeptides from the mycorrhiza‐compatible genotypes were different from those of the mycorrhiza‐resistant genotype.
Growth and mycorrhizal colonization of three North American tree species under elevated atmospheric CO2
Authors: GODBOLD DOUGLAS L. , BERNTSON GLENN M. , BAZZAZ F. A. 
Published: March 2003

summaryWe investigated the effect of elevated CO2 on the growth and mycorrhizal colonization of three tree species native to north‐eastern American forests (Betula papyrifera Marsh., Pinus strobus L. and Tsuga Canadensis L. Carr). Saplings of the tree species were collected from Harvard Forest, Massachusetts, and grown in forest soil under ambient (c. 375 ppm) and elevated (700 ppm) atmospheric CO., concentrations for 27–35 wk.In all three species there was a trend to increasing whole‐plant, total‐root and fine‐root biomass in elevated CO2, and a significant increase in the degree of ectomycorrhizal colonization in B. papyrifera and P. strobus, but not in T. Canadensis. However, in T, Canadensis the degree of colonization with arbuscular mycorrhizas increased significantly. In both the ambient and elevated environments, on the roots of B. papyrifera and P. strobus 12 distinct ectomycorrhizal morphotypes were identified. Distinct changes in the ectomycorrhizal morphotype assemblage of B. papvrifera were observed under CO2 enrichment. This change resulted in an increase in the frequency of ectomycorrhizas with a higher incidence of emanating hyphae and rhizomorphs, and resulted in a higher density of fungal hyphae in a root exclusion chamber.
Qualitative and quantitative changes in plant nitrogen acquisition induced by anthropogenic nitrogen deposition
Authors: NÄSHOLM TORGNY 
Published: March 2003

Because nitrogen is the mineral nutrient needed in largest amounts by plants, it is usually also the limiting factor for plant growth in terrestrial ecosystems (Vitousek & Howarth, 1991). Consequently, the deposition of oxidized and reduced N compounds will almost invariably have large effects in these systems, and because N availability not only regulates plant growth but also that of organisms at other trophic levels, disturbances of several ecosystem processes might occur. The alternations introduced by deposition of atmospheric N compounds are both of a quantitative and of a qualitative nature. Moreover, N deposition can have phytotoxic as well as growth‐stimulating effects.This short commentary gives a personal view of some of the possible consequences of N deposition on plants. It refers particularly to the oral presentations given by Professor Heinz Rennenberg and Dr Marta Peréz‐Soba, and to the discussions held after their talks where appropriate. Separate attention is given to four different consequence of anthropogenic N‐deposition: N‐availability; N‐form, N‐uptake by the shoot, and the period of N‐uptake. Finally, I have tried to adopt an ecosystem perspective and discuss briefly the concept of critical loads of N.
Nitrogen deposition and its contribution to nitrogen cycling and associated soil processes
Authors: GOULDING K. W. T. , BAILEY N. J. , BRADBURY N. J. , HARGREAVES P. , HOWE M. , MURPHY D. V. , POULTON P. R. , WILLISON T. W. 
Published: March 2003

Human activity has greatly perturbed the nitrogen cycle through increased fixation by legumes, by energy and fertilizer production, and by the mobilization of N from long‐term storage pools. This extra reactive N is readily transported through the environment, and there is increasing evidence that it is changing ecosystems through eutrophication and acidification. Rothamsted Experimental Station, UK has been involved in research on N cycling in ecosystems since its inception in 1843. Measurements of precipitation composition at Rothamsted, made since 1853, show an increase of nitrate and ammonium N in precipitation from 1 and 3 kg N ha−1 yr−1, respectively, in 1855 to a maximum of 8 and 10 kg N ha−1 yr−1 in 1980, decreasing to 4 and 5 kg N ha−1 yr−1 today. Nitrogen inputs via dry deposition do, however, remain high. Recent measurements with diffusion tubes and filter packs show large concentrations of nitrogen dioxide of c. 20 μg m−3 in winter and c. 10 μg m−3 in summer; the difference is linked to the use of central heating, and with variations in wind direction and pollutant source. Concentrations of nitric acid and particulate N exhibit maxima of 1·5 and 2 μg m−3 in summer and winter, respectively. Concentrations of ammonia are small, barely rising above 1 μg m−3.Taking deposition velocities from the literature gives a total deposition of all measured N species to winter cereals of 43·3 kg N ha−1 yr−1, 84% as oxidized species, 79% dry deposited. The fate of this N deposited to the very long‐term Broadbalk Continuous Wheat Experiment at Rothamsted has been simulated using the SUNDIAL N‐cycling model: at equilibrium, after 154 yr of the experiment and with N deposition increasing from c. 10 kg ha−1 yr−1 in 1843 to 45 kg ha−1 yr−1 today, c. 5% is leached, 12% is denitrified, 30% immobilized in the soil organic matter and 53% taken off in the crop. The ‘efficiency of use’ of the deposited N decreases, and losses and immobilization increase as the amount of fertilizer N increases. The deposited N itself, and the acidification that is associated with it (from the nitric acid, ammonia and ammonium), has reduced the number of plant species on the 140‐yr‐old Park Grass hay meadow. It has also reduced methane oxidation rates in soil by c. 15% under arable land and 30% under woodland, and has caused N saturation of local woodland ecosystems: nitrous oxide emission rates of up to 1·4 kg ha−1 yr−1 are equivalent to those from arable land receiving >200 kg N ha−1 yr−1, and in proportion to the excess N deposited; measurements of N cycling processes and pools using 15N pool dilution techniques show a large nitrate pool and enhanced rates of nitrification relative to immobilization. Ratios of gross nitrification∶gross immobilization might prove to be good indices of N saturation.
Localization of calcium ions in wounded characean internodal cells
Authors: FOISSNER ILSE 
Published: March 2003

Ca2+ was localized in chemically injured internodal cells of the characean alga Nitella flexilis (L.) Ag. using alizarin red and antimonate precipitation. The presence of Ca2+ in the antimonate precipitates was verified by X‐ray analysis and EGTA chelation. Callose‐containing amorphous wound walls were induced by 0·1 mm chlortetracycline (CTC) and cellulosic fibrillar wound walls were induced by 50 mm CaCl2. Numerous precipitates were found in the amorphous wound walls and in the adjacent cytoplasm. Precipitates were mainly localized in single membrane‐bound cisternae, probably of the endoplasmic reticulum, which accumulate at the wound and become a component of the amorphous wound wall via membrane fusion. In fibrillar wound walls, which do not contain membranous residues, precipitate density was significantly lower and similar to that in the secondary cell wall.The data suggest that the high Ca2+ content of amorphous wound walls is due to incorporation of cytoplasmic Ca2+ stores. The possible function of amorphous wound walls in maintaining cellular Ca2+ homeostasis is discussed.
Tansley Review No. 95: 15N natural abundance in soil–plant systems
Authors: Högberg Peter 
Published: March 2003

The following citations were erroneously omitted from the ‘References’: Groffman PM, Zak DR, Christensen S, Mosier A, Tiedje JM. 1993. Early spring nitrogen dynamics in a temperate forest landscape. Ecology74: 1579–1585. Handley LL, Brendel O, Scrimgeour CM, Schmidt S, Raven JA, Turnbull MH, Stewart GR. 1996. The 15N natural abundance patterns of field‐collected fungi from three kinds of ecosystems. Rapid Communications in Mass Spectrometry10: 974–978. Handley LL, Daft MJ, Wilson J, Scrimgeour CM, Ingleby K, Sattar, MA. 1993. Effects of the ecto‐ and VA‐mycorrhizal fungi Hydnagium carneum and Glomus clarum on the δ15N and δ13C values of Eucalyptus globulus and Ricinus communis. Plant, Cell and Environment16: 375–382. Handley LL, Odee D, Scrimgeour CM. 1994.δ15N and δ13C patterns in savanna vegetation: dependence on water availability and disturbance. Functional Ecology8: 306–314. Handley LL, Raven JH. 1992. The use of natural abundance of nitrogen isotopes in plant physiology and ecology: commissioned review. Plant, Cell and Environment15: 965–985. Handley LL, Scrimgeour CM. 1997. Terrestrial plant ecology and 15N natural abundance: the present limits to interpretation for uncultivated systems with original data from a Scottish old field. Advances in Ecological Research27: 133–212. Hansen AP, Pate JS. 1987. Evaluation of the 15N natural abundance method and xylem sap analysis for assessing N2 fixation of understorey legumes in jarrah (Eucalyptus marginata Donn ex Sm.) forest in S.W. Australia. Journal of Experimental Botany38: 1446–1458. New Phytologist apologizes unreservedly to all authors of the above papers for this error.