bluuebunny/crossref_metadata_2025_split huggingface dataset:
De‐ and remyelination in spinal roots during normal perinatal development in the cat: a brief summary of structural observations and a conceptual hypothesis
Authors: Berthold C.‐H. , Remahl I. Nilsson 
Published: March 2003

AbstractWe have studied the perinatal development of large myelinated axons (adult D > 10 µm) in cat ventral and dorsal lumbo‐sacral spinal roots using autoradiography and electron microscopy (serial section analysis). These axons acquire their first myelin sheaths 2–3 weeks before birth and show nearly mature functional properties first at a diameter of 4–5 µm, i.e. 3–4 weeks after birth. The most conspicuous event during this development takes place around birth, when a transient primary myelin sheath degeneration strikes already well myelinated although short ‘aberrant’ Schwann cells. The aberrant Schwann cells become completely demyelinated, then measuring about 10 µm in length, and are subsequently eliminated from their parent axons. Morphometry indicates that on average 50% of the Schwann cells originally present along a prospective large spinal root axon suffer elimination. Here it should be noted that in cat lumbo‐sacral spinal roots, the longitudinal growth of myelinated Schwann cells that belong to the group containing what will be the largest fibers is on average twice that of their parent axons. The elimination phenomenon is particularly striking in the dorsal roots close to the spinal cord where CNS tissue invades the root for several hundred micrometres. Our observations suggest that, once demyelinated and then eliminated, Schwann cells (i.e. aberrant Schwann cells) colonize neighbouring axons, future myelinated as well as future unmyelinated ones. In the former case the immigrant Schwann cells appear to start myelin production, possibly risking a second demyelination and elimination. We take our observations to indicate that Schwann cells in the cat, during normal development, may switch iteratively between a ‘myelin‐producing’ and a ‘non‐myelin‐producing’ phenotype. From a functional point of view the transient presence along a myelinated axon of intercalated unmyelinated segments ∼10 µm long, due to aberrant Schwann cells, would mean a slowing down of the action potential. The rapid disappearance of aberrant Schwann cells during the two first postnatal weeks could then explain the progressing normalization of the leg‐length conduction time.
Dejerine–Sottas syndrome grown to maturity: overview of genetic and morphological heterogeneity and follow‐up of 25 patients*
Authors: Gabreëls‐Festen Anneke 
Published: March 2003

AbstractDejerine–Sottas syndrome (DSS) is an early onset demyelinating motor and sensory neuropathy with motor nerve conduction velocities below 12 m s−1. The phenotype is genetically heterogeneous, and autosomal dominant (AD) as well as autosomal recessive (AR) inheritance is described. Nerve pathology is highly variable. It is generally presumed that clinical course is severe, leading to wheelchair dependency at an early age. In this study we documented the clinical and pathological features in 25 patients with a DSS and we evaluated the clinical course. In our series 14 patients had an AD mutation and six were probably affected by an AR disorder. In three patients inheritance mode was unknown and two patients obviously suffered from an acquired disorder. The clinical course in all patients was documented. Nine of the 25 patients showed a moderate handicap in adult life; walking distance was still at least 1 km. Age at last investigation of the ambulant patients ranged from 22 to 62 years (mean 38.6 years), and ambulant patients were found in all genetic subgroups. We conclude that DSS, although in general denoting a more serious neuropathy than CMT1, does not imply a severe disability or wheelchair dependency in adult life.
The effects of high glucose on connexin 43 in human endothelial cells
Authors: Willmott T. , Leach L. 
Published: March 2003

Connexins (cx) are a family of gap junctional proteins found in most mammalian cells with cx43 being one of the residents in endothelial cells. Gap junctional communications are thought to play a major role in maintaining tissue homeostasis and in angiogenesis. The latter functions are impaired in diabetes mellitus but the specific role of connexins in this pathology is currently not known. The aim of this study was to identify any changes in surface expression of cx43 in primary endothelial cells isolated from the human umbilical cord (HUVEC) and exposed to different duration of glycaemic insult. Cells were grown in euglycaemic (5 mm D glucose) and hyperglycaemic (25 mm d‐glucose) conditions with l‐glucose as the osmotic control for 2, 7 and 14 d. Confocal microscopy using identical laser settings was employed to look at both pattern of localisation and fluorescence intensity. At d 2, under euglycaemic conditions cx43 was localised throughout the cytosol (punctate labelling) but predominantly at perinuclear regions. Cx43 was also seen at cell‐cell margins as a diffuse ‘zigzag’ pattern. By 7 d this latter staining at cell‐cell borders resembled a ‘beads on a string’ formation, indicative of discrete gap junctions. By 14 d the cells were forming tubes with punctate labelling throughout the cytosol and beads on a string localisation in the paracellular clefts. Cells cultured in 25 mm d‐glucose showed a different pattern of expression of cx43; at 2 d cx43 was present as discrete puncta at cell‐cell borders and throughout the cytosol and perinuclear region. Both fluorescent intensity and frequency of puncta appear diminished. By 7 d cell‐cell borders are immuno‐negative to cx43. By 14 d HUVEC cells had formed tubes. There was intense immunoreactivity to cx43 in the cytosol but not at paracellular clefts. This change in expression pattern is not an osmotic effect as the cells cultured in 25 mm l‐glucose reflected a similar pattern of expression as cells grown in euglycaemic conditions. In conclusion this study is a first indication that hyperglycaemia alters targetting of cx43 to cell‐cell borders and formation of connexons.Funded by Smith & Nephew & The University of Nottingham
Comparison of the effect of pulsatile and nonpulsatile shear stress on adherens junctions in human endothelial cells
Authors: Plant S. , Leach L. 
Published: March 2003

In vivo, endothelial cells experience shear stress resulting from pulsatile flow. Many publications have shown that the pulsatile nature of this flow influences endothelial function and structure including intracellular calcium concentrations, cell shape and actin stress fibre formation. A recent in vitro study using bovine aortic cells showed exposure to nonpulsatile flow caused transient disruption of adherens junctions through perturbation of VE‐cadherin and the disassembly of the actin cytoskeleton. The aim of this study was to observe the responses of the adherens junctional molecule VE‐cadherin, and F‐actin, to pulsatile and nonpulsatile flow in human endothelial cells over a 48‐h period.Human umbilical vein endothelial cells (HUVEC) were isolated from fresh umbilical cords taken from elective caesarean sections (n = 6). At passages 2–4 the cells were seeded onto glass coverslips pretreated with 3‐aminoproryaltriethoxysilane (APES). 48 h after reaching confluence the cells were transferred to a parallel plate flow chamber and exposed to slowly increased pulsatile or nonpulsatile laminar flow, producing a final shear stress of 1.5 dynes/cm2. Cells were left under flow for up to 48 h. At t = 0, 8 and 48 h immunocytochemistry was used to visualise VE‐cadherin and phalloidin‐TRITC to visualise F‐actin.At t = 0, VE‐cadherin was localised at cell‐cell contacts and the cells contained randomly oriented stress fibres and cortically located perijunctional actin. Following 8 h exposure to both types of flow no VE‐cadherin or actin could be detected. After 48 h exposure VE‐cadherin and F‐actin had returned to the junctional regions of the cells exposed to nonpulsatile flow. By comparison in cells exposed to pulsatile flow VE‐cadherin was absent from the cell periphery but was found diffusely throughout the cell. Actin, both stress fibre and cortical, was absent from these cells.These results show that reassembly of the adherens junction, with a return of VE‐cadherin to cell‐cell contacts and a reformation of the actin cytoskeleton, is only seen in cells that have been exposed to nonpulsatile flow. Further work will show whether such adaptations are merely delayed under pulsatile flow or are prevented from occurring entirely. This study highlights the importance of using pulsatile flow when studying endothelial behaviour.The financial support of EPSRC and Sulzer Vascutek Ltd is gratefully acknowledged.
Central nervous system phenotypes in craniosynostosis
Authors: Aldridge Kristina , Marsh Jeffrey L. , Govier Daniel , Richtsmeier Joan T. 
Published: March 2003

AbstractThough reduction in the number of cranial elements through loss of a suture is a recognized trend in vertebrate evolution, the premature closure of cranial sutures in humans, craniosynostosis, is considered a pathological condition. Previous research on craniosynostosis has focused primarily on the skeletal phenotype, but the intimate relationship between the developing central nervous system (CNS) and skull is well documented. We investigate the morphology of the CNS in patients with isolated craniosynostosis through an analysis of cortical and subcortical features using 3‐D magnetic resonance images (MRI). Results show that a distinct CNS phenotype can be defined for specific diagnostic categories. Many differences in CNS morphology observed in the patient samples may be anticipated based on skeletal morphology, but others are not reflected in the skull. We propose a developmental approach to determining the cause of premature suture fusion, which includes investigation of the craniofacial complex as a system, rather than study of isolated tissues.
Cerebellar connections to the rostral reticular nucleus of the thalamus in the rat
Authors: Çavdar Safiye , Onat F. Yilmaz lýz , Yananli Hasan R. , Şehirli Ümit S. , Tulay Cumhur , Saka Erdinç , Gürdal Esra 
Published: March 2003

AbstractWe studied the cerebellar connections to the reticular nucleus thalamus (RNT) by means of retrograde axonal transport of horseradish peroxidase (HRP) in the rat. Specific HRP pressure injections to the rostral RNT (1.6–1.8 mm caudal to bregma) resulted in retrograde labelling of neurones in the cerebellar nuclei. The rostral RNT showed specific topographical organization of its cerebellar connections. Microinjections into the rostral RNT, 1.6 mm caudal to bregma, produced numerous HRP‐labelled neurones within the anterior interposed (emboliform nucleus) and scarce HRP‐labelled neurones within the lateral (dentate nucleus) cerebellar nuclei, whereas injections into the rostral RNT, 1.8 mm caudal to bregma, produced numerous HRP‐labelled neurones within the posterior interposed (globose nucleus) and scarce lightly HRP‐labelled neurones within the lateral (dentate nucleus) cerebellar nuclei. Cerebellar connections with the rostral RNT were exclusively ipsilateral to the injection site. No HRP‐labelled cells were detected in the medial (fastigial nucleus) cerebellar nucleus. The cerebellar connections reach the RNT via the superior cerebellar peduncle. By contrast, HRP injections into the anterior, posterior interposed and lateral cerebellar nuclei produced no labelled cells within the RNT. This study demonstrates the existence of direct cerebello‐RNT but not RNT‐cerebellar connections. The presence of the cerebello‐RNT connections introduces a new route through which the cerebellum may influence RNT and thus cerebral cortical activity.
Purification and characterization of a β‐1,4‐endoxylanase from the ericoid mycorrhizal fungus Hymenoscyphus ericae
Authors: BURKE R. M. , CAIRNEY J. W. G. 
Published: March 2003

SUMMARYA β‐l,4‐endoxylanase from the ericoid mycorrhizal fungus H. ericae has been purified to electrophoretic homogeneity using isoelectric focusing, ion exchange and gel permeation chromatography. The enzyme has an isoelectric point of 4.85–5.20 and a molecular weight of 58.4 kDa. The apparent S0.5 of the enzyme for soluble birchwood glucuronoxylan is 3.75 mg ml−1 and the Vmax 468.0 nkatal mg−1 protein. The pH optimum for activity is 4.5 and that for stability is 3.5–4.0; these values are discussed in the context of the pH of the mor humus. The role of wall‐degrading activities in the establishment of the ericoid mycorrhizal symbiosis is considered.
Growth, heterocyst differentiation and nitrogenase activity in the cyanobacteria Anabaena variabilis and Anabaena cylindrica in response to molybdenum and vanadium
Authors: ATTRIDGE E. M. , ROWELL P. 
Published: March 2003

summaryThis paper reports effects of molybdenum and vanadium on Anabaena variabilis Kutz. (ATCC 29413) and Anabaena cylindrica Lemm. (PCC 7122), previously grown in NH4+‐containing medium deficient in Mo and V (–Mo–V) and then transferred to media lacking combined nitrogen. Diazotrophic growth of A. variabilis was dependent on the presence of Mo or V, with little growth occurring in their absence. Neither Mo nor V was required for heterocyst differentiation in either cyanobacterium, and the highest heterocyst frequencies occurred in cultures showing the lowest growth rates. Although A. cylindrica also showed Mo‐dependent diazotrophic growth and a low rate of growth in the absence of added Mo, the latter was inhibited by addition of 1 μM V. The rate of acetylene reduction by A. variabilis increased rapidly following addition of V to –Mo–V cultures, and increased ethane formation was detected in the acetylene reduction assays. Addition of Mo resulted in a smaller initial increase in the rate of acetylene reduction, but this was also accompanied by increased ethane formation, followed by a slow and much more extensive increase in acetylene reduction with a decrease in ethane formation. These observations indicate that nitrogenase polypeptides, probably those of a V‐nitrogenase, are synthesized in A. variabilis in the absence of added Mo or V, that added Mo can be incorporated into the V‐nitrogenase, and that synthesis of Mo‐nitrogenase is dependent on the presence of Mo. By contrast, A. cylindrica appears either to synthesize only a Mo‐nitrogenase, even in the absence of Mo (though 1 μM V inhibits its synthesis) or to synthesize a Mo‐ and V‐independent nitrogenase, but only in the absence of added Mo and V. Western blots using antisera against the Mo‐Fe and Fe proteins of the Mo‐nitrogenase of Rhodospirillum rubrum indicated the presence of Mo‐nitrogenase polypeptides in both Mo‐grown and –Mo–V grown A. cylindrica, providing evidence in support of the former possibility. Physiologically, the V‐nitrogenase of A. variabilis showed several distinct similarities to the Mo‐nitrogenase of A. cylindrica, including responses to metal concentrations as well as the above responses to addition of V and Mo, respectively.
Fructan biosynthesis in excised leaves of Lolium temulentum VII. Sucrose and fructan hydrolysis by a fructan‐polymerizing enzyme preparation
Authors: CAIRNS ANDREW J. , BONNETT GRAHAM D. , GALLAGHER JOSEPH A. , SIMPSON RICHARD J. , POLLOCK CHRISTOPHER J. 
Published: March 2003

A partially purified enzyme preparation from leaves of Lolium temulentum L. was previously shown to catalyse the net synthesis of oligofructans and polyfructans from sucrose. Here the same preparation is shown to catalyse the hydrolysis of both sucrose and oligofructans. The magnitude and properties of these hydrolytic activities have been determined. The significance of these catabolic activities for studies of fructan polymerization both in vitro and in tissues in a physiologically anabolic state are discussed.The preparation hydrolysed 1‐kestose, 6‐kestose, neokestose, inulin oligosaccharides of low degree of polymerization (DP 4 and 5) and endogenous oligofructans from L. temulentum, with the concomitant release of monosaccharide. The preparation also released reducing sugar at low rates from high molecular weight inulin but had no detectable activity against bacterial levan. Simultaneous incubation of sucrose and Neosugar (a commercially available mixture of predominantly β‐2, 1 linked tri‐, tetra‐ and penta‐saccharides) showed that sucrose was preferentially hydrolysed by the preparation, with Neosugar fructans being protected from hydrolysis at sucrose concentrations >30 mol m−3. The kinetic properties for hydrolysis of both sucrose and Neosugar were determined. For sucrose and Neosugar respectively, Michaelis constants at 30°C and pH 6·0 were 7·7±0·5 and 14·1±1·1 mol m−3 (as terminal fructose) and maximum velocities were 6·5±0·1 and 2·7±0·1 mg g−1 fr. wt h−1 (equivalent to 10·0 and 4·2 nkat g−1 as reducing sugar release). Maximal temperatures for activity were 45 and 44°C, and Arrhenius activation energies were 39·9 and 46·9 kJ mol−1. Preincubations for 1 h at 49 and 48°C caused 50% loss of activity in subsequent assays at 30°C. The pHs for maximal activity for the two substrates were 5·2±0·1 and 5·5±0·1.Using size exclusion chromatography (SEC), an activity catalysing the formation of fructan oligosaccharides and another catalysing sucrose hydrolysis, were not fully resolved, but exhibited distinct profiles of elution indicating Mr of 57 and 133 kD respectively. When assayed for the hydrolysis of Neosugar, the SEC eluate exhibited two peaks of activity indicative of Mr values of 57 and 133 kD.
The effects of root nitrogen supplies on the absorption of atmospheric NO2 by soybean leaves
Authors: Qiao Z. , MURRAY F. 
Published: March 2003

SUMMARYTwelve‐day‐old soybean plants were exposed to atmospheric NO2 (0.3 μM1 1−1) and simultaneously supplied, via the roots, with 5 mM or 1 mM of NaNO3 or NH4C1. After exposure for 7 d, the amount of NO2 absorbed per plant was greater in plants supplied with nitrate than in plants supplied with the same concentration of ammonium. The NO2 AR (absorption rate) decreased with increasing exposure time. At the beginning of exposure, the NO2 AR for all plants was c. 12 mg NO2 h−1 m−2μ1−11. On the day 7 of exposure, the NO2 AR declined to 8.46, 8.97, 8.27, and 9.04 mg NO2 h−1 m−2μ1 1−1 1 for plants receiving 1 mM ammonium, 1 mM nitrate, 5 mM ammonium, and 5 mM nitrate respectively. The plants supplied with nitrate had a higher concentration of leaf nitrate and a higher pH than those supplied with the equivalent concentration of ammonium. These results suggest that the NO2absorption rate might be attenuated by the accumulation of H+ produced from N uptake and assimilation.
The relation of H2S release to SO2, fumigation of lichens
Authors: GRIES CORINNA , ROMAGNI JOANNE G. , NASH THOMAS H. , KUHN UWE , KESSELMEIER JÜRGEN 
Published: March 2003

SUMMARYHydrogen sulphide emission in lichens as a response to low concentration SO2, fumigation was investigated. In an open flow‐through system several lichen species were fumigated with 36 ppb SO2, Two species were also fumigated with higher concentrations (72, 119, 122 and 198 ppb SO2,). Hydrogen sulphide emission was monitored concurrently by cryogenic trapping and analysis with gas chromatography. All tested species increased H, S emission significantly in response to fumigation with 36 ppb SO2. Parmelina tiliacea (L.) Hale and Cladina rangiferina (L.) Wigg. released significantly more H2S (0.098±0.015 and 0.073±0.013 pmol H2S g−1 d. wt s−1, respectively) than Parmelina quercina (Ach.) Hale, Ramalina menziesii Tayl. and Parmelia sulcata Tayl. (0.028 ± 0.01, 0.025±0.014 and 0.023±0.013 pmol H2S g−1 d. wt s−1, respectively). Release of H2S in Hypogymnia physodes was enhanced by increasing SO2 concentrations up to 72 ppb SO2. No significant difference in H2S emission in the dark vs. in the light was found. Generally, no correlation was found between photosynthetic activity and H2S emission for the tested species. Uptake of SO2 was similar for all species, at 24.7 ± 5.6 pmol SO2 g−1 d. wt s−1 in 36 ppb SO2 and increasing at greater SO2 concentrations. Therefore, H2S‐S release represents only 0.11–0.74% of SO2‐S uptake.
Interspecific variation in respiratory and photosynthetic parameters in Antarctic bryophytes
Authors: DAVEY MARTIN C. , ROTHERY PETER 
Published: March 2003

summaryRates of carbon flux in 14 species of Antarctic bryophytes were measured under controlled conditions using an infra‐red gas analysis system. The results were used to produce estimates of mode! parameters for respiration and photosynthesis. The relationships between respiration, photosynthesis, irradiance and temperature followed standard patterns. Temperature optima for gross and net photosynthesis were 10–20 and 0–20 °C respectively, suggesting that the plants were not truly psychrophilic. Photosynthesis was saturated at 30–270 μmol m−2s−1, consistent with the view that bryophytes are, physiologically, shade plants, although there was no evidence of photoinhibition over the range of irradiances tested (up to 700 μmol m−2s−1). Comparison of the results with environmental data suggests that photosynthesis is usually temperature‐limited during daylight in the growing season. Therefore, any change in the temperature of the habitat could affect the productivity of the bryophytes. Rates of photosynthesis varied widely between species, and these relationships were largely maintained over the range of temperatures and irradiances tested. Photosynthetic rankings were correlated with the water availability in the plant habitats, supporting the hypothesis that water is the important factor in determining the distribution of populations in Antarctic habitats.
Locating genotypes and genes for abiotic stress tolerance in barley: a strategy using maps, markers and the wild species
Authors: FORSTER B. P. , RZUSSELL J. R. , ELLIS R. P. , HANDLEY L. L. , ROBINSON D. , HACKETT C. A. , NEVO E. , WAUGH R. , GORDON D. C. , KEITH R. , POWELL W. 
Published: March 2003

summaryThis paper reviews the results of several years'study by a multidisciplinary team comprising geneticists, physiologists, ecologists and statisticians of abiotic stress tolerance in barley. The strategy involves genetic fingerprinting of wild barley lines (Hordeum spontaneum C. Koch) from a range of habitats and testing these for responses to abiotic stresses under controlled conditions. Multiple regression analysis is used to identify genetic markers associated with experimentally determined stress responses. These data are related to site‐of‐origin ecogeographic data and used to identify areas of useful wild variation. Markers associated with traits of interest can be mapped in genetic mapping populations, revealing areas of the barley genome carrying genes controlling stress responses. This paper highlights our work on associations of amplied fragment length polymorphisms with salt tolerance and describes some initial results of the use of SSRs in studying drought tolerance in barley.
Mapping physiological traits in barley
Authors: ELLIS R. P. , FORSTER B. P. , WAUGH R. , BONAR N. , HANDLEY L. L. , ROBINSON D. , GORDON D. C. , POWELL W. 
Published: March 2003

summaryAmplified fragment length polymorphisms (AFLPs) offer a reproducible, multiplex DNA assay by which to genotype mapping populations. We have evaluated physiological traits in barley seedlings grown in an hydroponic system and given a salt treatment. Multiple regression was used to show associations between AFLPs and quantitative traits. Effects at different loci were detected in stress treatments in comparison to the control implying that either novel gene action was induced by salt stress or that normal activity was reduced to a low level where alternate gene action is revealed. The QTLs occurred on all chromosomes but there appeared to be clusters of loci on chromosomes 1 (7H), 4 (4H), 5 (1H) and 6 (6H). The significance of our results is discussed in the context of studies to explore the barley genome and the application of the results of these genetical analyses to barley breeding.