bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracellular signalling involved in modulating human endothelial barrier function*
Authors: Van Hinsbergh Victor W. M. , Van Nieuw Amerongen Geerten P. 
Published: March 2003

AbstractThe endothelium dynamically regulates the extravasation of hormones, macromolecules and other solutes. In pathological conditions, endothelial hyperpermeability can be induced by vasoactive agents, which induce tiny leakage sites between the cells, and by cytokines, in particular vascular endothelial growth factor, which increase the exchange of plasma proteins by vesicles and intracellular pores. It is generally believed that the interaction of actin and non‐muscle myosin in the periphery of the endothelial cell, and the destabilization of endothelial junctions, are required for endothelial hyperpermeability induced by vasoactive agents. Transient short‐term hyperpermeability induced by histamine involves Ca2+/calmodulin‐dependent activation of the myosin light chain (MLC) kinase. Prolonged elevated permeability induced by thrombin in addition involves activation of the small GTPase RhoA and Rho kinase, which inhibits dephosphorylation of MLC. It also involves the action of other protein kinases. Several mechanisms can increase endothelial barrier function, depending on the tissue affected and the cause of hyperpermeability. They include blockage of specific receptors, and elevation of cyclic AMP by agents such as β2‐adrenergic agents. Depending on the vascular bed, nitric oxide and cyclic GMP can counteract or aggravate endothelial hyperpermeability. Finally, inhibitors of RhoA activation and Rho kinase represent a potentially valuable group of agents with endothelial hyperpermeability‐reducing properties.
The development of the gubernaculum and inguinal closure in the marsupial Macropus eugenii
Authors: Coveney Douglas , Shaw Geoffrey , Hutson John M. , Renfree Marilyn B. 
Published: March 2003

AbstractThis study reports the developmental anatomy of testicular descent and inguinal closure of the tammar wallaby (Macropus eugenii) from birth to maturity. In females the ovary migrated caudally between days 10 and 20 after birth. The gubernaculum differentiates into the round ligament in the abdomen and extra‐abdominally as the ilio‐marsupialis muscle of the mammary glands. In males the testes migrated to the internal inguinal ring by day 20 post partum (pp), coinciding with the enlargement of the gubernaculum, and from the internal inguinal ring to the scrotum between days 20 and 65 pp. During descent there was an increase in the hyaluronic acid concentration in cells of the gubernaculum and scrotum. Development of the cremaster muscle began by day 10 pp on the periphery of the gubernaculum and its basic structure was completed by day 60 pp. After descent the inguinal canal closed between days 50 and 60 pp, but a small irregular lumen persisted, somewhat similar to that seen in the congenital scrotal hydrocoele of humans. Tammars have a hopping mode of locomotion and, like humans, are essentially bipedal. We suggest that inguinal closure evolved in these two species because their upright posture may otherwise lead to a high incidence of inguinal hernias.
The diaphragm: two physiological muscles in one
Authors: Pickering Mark , Jones James F. X. 
Published: March 2003

AbstractTo the respiratory physiologist or anatomist the diaphragm muscle is of course the prime mover of tidal air. However, gastrointestinal physiologists are becoming increasingly aware of the value of this muscle in helping to stop gastric contents from refluxing into the oesophagus. The diaphragm should be viewed as two distinct muscles, crural and costal, which act in synchrony throughout respiration. However, the activities of these two muscular regions can diverge during certain events such as swallowing and emesis. In addition, transient crural muscle relaxations herald the onset of spontaneous acid reflux episodes. Studying the motor control of this muscular barrier may help elucidate the mechanism of these episodes. In the rat, the phrenic nerve divides into three branches before entering the diaphragm, and it is possible to sample single neuronal activity from the crural and costal branches. This review will discuss our recent findings with regard to the type of motor axons running in the phrenic nerve of the rat. In addition, we will outline our ongoing search for homologous structures in basal vertebrate groups. In particular, the pipid frogs (e.g. the African clawed frog, Xenopus laevis) possess a muscular band around the oesophagus that appears to be homologous to the mammalian crural diaphragm. This structure does not appear to interact directly with the respiratory apparatus, and could suggest a role for this region of the diaphragm, which was not originally respiratory.
Regulation of the depth and composition of airway surface liquid
Authors: Widdicombe J. H. 
Published: March 2003

AbstractThe airways are lined with a film of liquid about 10 µm deep that is in two layers. Around the cilia is the watery periciliary sol. Over this is a mucous blanket that traps inhaled particles. The low viscosity of the periciliary sol allows the cilia to beat and propel the mucous blanket to the mouth. In large airways, mucus comes predominantly from the mucous glands but also from goblet cells in the surface epithelium. Water is added to the airway surface by gland secretion that is driven by active Cl secretion by serous cells. During inflammation elevation of the subepithelial hydrostatic pressure may also add significant volumes of water to the airway lumen. Water is removed by active Na transport across the surface epithelium. In airway diseases, the balance is shifted from water secretion to mucus secretion. In bronchitis and asthma this is due mainly to conversion of gland serous to mucous cells. In cystic fibrosis, gland serous cells cannot secrete water because they lack functioning CFTR in their apical membranes (CFTR is the cystic fibrosis transmembrane conductance regulator, a Cl channel that is abundant in serous cells). In all three diseases, the result is secretion of excessively concentrated gland secretions that are poorly moved by the cilia and accumulate. Altered salt and water transport by the surface epithelium may also contribute to the pathology of cystic fibrosis.
Laminar bone as an adaptation to torsional loads in flapping flight
Authors: De Margerie Emmanuel 
Published: March 2003

AbstractUsing a new histometric method, the orientation of primary osteons was measured in the main long bones of adult mallards (Anas platyrhynchos). In the light of previous biomechanical and ontogenetic studies, a functional hypothesis is proposed, explaining the histological differences observed between long bones; laminar bone tissue, mainly found in the wing bones, may be a biomechanical adaptation to torsional loads caused by flapping flight.
Dissolved inorganic carbon utilization and the development of extracellular carbonic anhydrase by the marine diatom Phaeodactylum tricornutum
Authors: IGLESIAS‐RODRIGUEZ M. D. , MERRETT M. J. 
Published: March 2003

SUMMARYThe presence of extracellular carbonic anhydrase (CA) in relation to medium composition was investigated using cultures of the marine diatom Phaeodactylum tricornutum Bohlin. Large‐volume cultures, with low initial cell inocula were grown on ASP‐2 (no dissolved inorganic carbon (DIC), 550 μM NOa−), f/2 (2–0 mM DIC, 880μM NO3−) and modified f/2 (2.0 mM DIC, 20 μM NO3− media. Cells growing on ASP‐2 showed extracellular CA in the early stages of growth, whereas extracellular CA was not detected until partial depletion of total DIC in the stationary phase for cultures on f/2 or modified f/2. Both HCO3− and CO2 were important in carbon limitation, extracellular CA being present when the free‐CO2 concentration fell below 5 μM, but the HCO3− concentration needed to be below 1 mM. When carbon‐replete cells were transferred to carbon‐limited conditions, extracellular CA was recorded within minutes, the process being light‐dependent and completely inhibited by 3,3,4‐dichlorophenyl‐l, 1‐dimethylurea (DCMU). The addition of DIC to carbon‐limited cells resulted in a rapid decrease in extracellular CA activity. The membrane‐impermeable inhibitor of carbonic anhydrase, dextran‐bound sulphonamide (DBS) was used to inhibit extracellular CA activity in relation to photosynthetic rate in carbon‐replete and carbon‐limited cells. At the lowest DIC concentration (O'lOniM), for cells with maximum external CA activity, DBS gave over 80% inhibition of the photosynthetic rate, demonstrating the key role of external CA in maintaining high photosynthetic rate under conditions of carbon limitation.It is proposed that the key factor in the regulation of extracellular CA activity is the total Hux of inorganic carbon (C.) into the cell. This determines the Ci, flux into the chloroplast and when this is inadequate to support the photosynthetic rate attained by a carbon‐replete chloroplast at optimum photon flux density, extracellular CA is activated. This mechanism would explain the observed interaction of CO2 and HCO3− in the regulation of extracellular CA activity.
Involvement of the outer membrane lipopolysaccharides in the endophytic colonization of tomato roots by biocontrol Pseudomonas fluorescens strain WCS417r
Authors: DUIJFF BEN J. , GIANINAZZI‐PEARSON VIVIENNE , LEMANCEAU PHILIPPE 
Published: March 2003

SUMMARYPrevious studies demonstrated the role of the O‐antigenic side chain of the outer membrane lipopolysaccharides of Pseudomonas fluorescens strain WCS417r in its ability to induce resistance against fusarium wilt disease. The present study compared the colonization of tomato roots (Lycopersicon esculentum Mill.) by P. fluorescens strain WCS417r with that of a mutant of this strain, lacking the O‐antigenic side chain of its outer membrane lipopolysaccharides (OA −). Special attention was paid to colonization within root tissues and changes of the root ultrastructure induced by the bacterial strains. Experiments were performed with tomato plants rooted in rock wool and tomato seedlings grown on agar. Numeration of colony‐forming units showed that wild‐type strain WCS417r colonized the root interior of tomato grown in rock wool to a higher extent than its OA− mutant B4, whereas colonization of the rhizoplane did not differ between the two. Light microscopy observations of cross sections of roots grown on agar showed that (i) colonization of the root interior by both wild‐type and OA− mutant was inter‐ and intracellular, (ii) colonization of the internal root tissues mainly occurred if the Pseudomonas strains were inoculated at sites of lateral root emergence, (iii) the wild type colonized the root interior more frequently than did its OA− mutant. Thickening of the cortical cell walls, in reaction to the bacterial colonization of epidermal or hypodermal cells, or cortical intercellular spaces, suggested that local defence reactions of the plant occurred. Altogether, these results indicate the involvement of the O‐antigenic side chain of the outer membrane lipopolysaccharides in the endophytic colonization of the tomato root by P. fluorescens, WCS417r, and lead us to hypothesize that induction of disease resistance by strain WCS417r might be related to the extent of colonization of the internal root tissues.
Epicuticular wax of subarctic Scots pine needles: response to sulphur and heavy metal deposition
Authors: TURUNEN M. , HUTTUNEN S. , PERCY K. E. , McLAUGHLIN C. K. , LAMPPU J. 
Published: March 2003

summaryThe response of epicuticular wax of Scots pine (Pinus sylvestris L.) needles to dry‐ and wet‐ deposited sulphur and heavy metals was investigated at six sites located 10–110 km from the Monchegorsk Cu‐Ni smelter on the Kola Peninsula, North‐West Russia, and in a long‐term irrigation experiment where pines were exposed over four growing seasons (1991–1994) to either acid rain treatment at pH 3.1 (H2SO4), metal treatment at pH 5.7 (Cu and Ni) or a combination of these at pH 3.1. Needle wettability exhibited a closer relationship with epistomatal wax tube distribution (WTD) than with chemical composition of epicuticular wax. Water droplet contact angles (DCA) decreased towards the smelter, and significant differences due to site were noted for 26‐month‐old and 38‐month‐old needles. Significant differences due to site were determined for secondary alcohols, dehydroabietic acid and hydroxy fatty acids, the proportions of which ranged from 22–5 to 48.9%, 6.2 to 224% and 0.6 to 2.6% respectively, depending on site and needle age class. The proportion of dehydroabietic acid increased towards the smelter, but no gradient was observed in the proportion of secondary alcohols or hydroxy fatty acids. No major effect of experimentally applied pollutants on the chemical composition or structure of the epicuticular wax was observed. The effect of treatment on DCA was significant in 1993 and 1994 due to a 6.5–13.2 degree greater wettability of the 37–49–month‐old acid‐treated needles relative to the irrigated or dry controls. Sulphuric acid at pH 3.1 did not increase needle wettability when combined with copper and nickel sulphate in similar concentrations. These data indicate that S deposition, especially H2SO4, plays a more important role in needle surface deterioration than Cu and Ni. Pollutant‐induced changes in epicuticular wax structure and needle wettability mimic natural wax ageing, but at an accelerated rate. Changes in wax chemical composition might also be caused by pollutant‐induced metabolic changes in elongating needles.
Rise of fructan exohydrolase activity in stubble of Lolium perenne after defoliation is decreased by uniconazole, an inhibitor of the biosynthesis of gibberellins
Authors: MORVAN ANNETTE , CHALLE GAËLLE , PRUD'HOMME MARIE‐PASCALE , LE SAOS JOËLLE , BOUCAUD JEAN 
Published: March 2003

The objectives of this study were (i) to evaluate the relative involvement of fructans from leaf sheaths and from elongating leaf bases to regrowth after defoliation of Lolium perenne L. by following fructan exohydrolase (FEH), sucrose‐sucrose fructosyl transferase (SST) and invertase (INV) activities and (ii) to examine whether gibberellins could be implicated in regulation of FEH activity. In stubble, 36% of fructans are located in leaf bases and 64% in leaf sheaths. During the first phase of regrowth, the depletion of carbohydrates was mainly due to the decline of fructans, which represented 76% and 50% of the carbohydrates mobilized from leaf sheaths and elongating leaf bases respectively. Despite a decrease in protein content, FEH activity increased 2·5‐fold in leaf sheaths and six‐fold in elongating leaf bases, so that the fructan‐hydrolysing activity was four times higher in growing leaves than in leaf sheaths, 2 d after defoliation. INV activity also increased, whereas the pattern of SST activity was inversely related to the variations of both hydrolysing activities. SST activity, which is highest in growing leaves, declined approximately threefold in leaf sheaths and elongating leaf bases at the beginning of regrowth.The increase in activity of FEH in stubble was strongly inhibited by an inhibitor of the biosynthesis of gibberellin, uniconazole. FEH activity was decreased to c. 67%, 45% and 33% of the level in nontreated plants 24, 48 and 72 h following defoliation, respectively. The inhibition could be overcome by a subsequent treatment with gibberellic acids (GAs). For the first time, data are provided to support the view that GAs might play a role in the regulation of FEH activity, and the implication of this result is discussed.
Actinorhizal symbioses and their N2 fixation
Authors: HUSS‐DANELL KERSTIN 
Published: March 2003

summaryMore than 200 angiosperms, distributed in 25 genera, develop root nodule symbioses (actinorhizas) with soil bacteria of the actinomycetous genus Frankia. Although most soils studied contain infective Frankia, cultured strains are available only after isolation from root nodules. Frankia infects roots via root hairs in some hosts or via intercellular penetration in others. The nodule originates in the pericycle. The number of nodules in Alnus is determined by the plant in an autoregulated process that, in turn, is modulated by nutrients such as nitrogen and phosphate. Except in the genera Allocausarina and Casuarina, Frankia in nodules develops so‐called vesicles where nitrogenase is localized. Sporulation of Frankia occurs in some symbioses. As a group, actinorhizal plants show a large range of anatomical and biochemical adaptations in order to balance the oxygen tension near nitrogenase. In symbioses with well aerated nodule tissue like Alnus, the vesicles have a multilayered envelope composed mainly of lipids, bacterio‐hopanetetrol and their derivatives. This envelope is assumed to retard the diffusion of oxygen into the nitrogenase‐containing vesicle. In symbioses like Casuarina, the infected plant cells themselves, rather than Frankia, appear to retard oxygen diffusion, and high concentrations of haemoglobin indicate an infected region with a low oxygen tension. At least in Alnus spp., ammonia resulting from N2 fixation is assimilated by glutamine synthetase in the plant. The carbon compound(s) used by Frankia in nodules is not yet known. Nitrogenase activity decreases in response to a number of environmental factors but recovers upon return to normal conditions. This dynamism in nitrogenase activity is often explained by loss and recovery of active nitrogenase and has been traced to loss and recovery of the nitrogenase proteins themselves. Recovery is partly due to growth of Frankia and to development of new vesicles in the Alnus nodules. In the field, varying conditions continuously affect the plants and the measured rate of N2 fixation is a result not only of the conditions prevailing at the moment but also of the conditions experienced over preceding days. N2 fixed by actinorhizal plants is substantial and actinorhizal plants have great potential in soil reclamation and in various types of forestry. Several species are also useful in horticulture.

CONTENTS

Summary
375

I.
Introduction
376

II.
The partners of actinorhizal symbioses
377

III.
Root nodules
380

IV.
Nitrogen fixation and related processes
385

V.
Environmental effects on nitrogen fixation
389

VI.
Ecological role
397

VII.
Concluding remarks
398

Acknowledgements
398

References
398
Multiple tolerance and co‐tolerance to heavy metals in Silene vulgaris: a co‐segregation analysis
Authors: SCHAT HENK , VOOIJS RIET 
Published: March 2003

summaryPlants from metalliferous soils often exhibit combined tolerance to different heavy metals. Such tolerance could rely either on the possession of a combination of different metal‐specific tolerance mechanisms (‘multiple tolerance’), or on less specific mechanisms that pleiotropically confer tolerance to different metals (‘co‐tolerance’). In this study, we examined the co‐segregation of tolerances to Cu, Zn, Ni, Co and Cd in crosses between distinctly tolerant ecotypes of Silene vulgaris (Moench) Garcke. The results demonstrate non‐pleiotropic genetic control of tolerance to Cu, Zn and Cd. Tolerance to Ni and Co, on the other hand, seems to represent the pleiotropic byproduct of the tolerance allele of one particular locus for zinc tolerance.
From phenotype via QTL to virtual phenotype in Microseris (Asteraceae): predictions from multilocus marker genotypes
Authors: BACHMANN KONRAD , HOMBERGEN ERIK‐JAN 
Published: March 2003

summary Microseris douglasii (DC.) Sch.‐Bip. and M. bigelovii (Gray) Sch.‐Bip. are two small annual autogamous species of Compositae with nearly non‐overlapping distribution ranges in Western North America. Specifically, M. bigelovii occurs directly along the Pacific coast, whilst M. douglasii has an inland distribution including patches of serpentine soil. Both species are variable, and artificial hybrids between them vary widely in fertility depending on the individual parents. Segregating offspring of one hybrid (strain H27) is being used to analyse the genetic basis of characters differentiating the two species by QTL mapping with RAPDS and ALFPs as molecular markers. Technical problems with mapping dominant markers in a wide cross will be briefly listed and QTL analysis will be discussed. For the genetic analysis of physiological characters, the precise definition of the characters is crucial and the methods of scoring or measuring phenotypes in different environments eventually require more time and effort than the molecular characterization. We are establishing recombinant inbred lines to provide material for more complex physiological analyses requiring several plants per genotype. An increasing number of characters is being studied in this cross, and the possibility of shared pleiotropic QTLs is high. The potential number of QTL genotypes by far exceeds the number of actual genotypes in these lines. We are characterizing the gene interactions as closely as possible and making quantitative genetic models to predict the genotypes corresponding to all possible genotypes. These predictions are converted via computer modelling into an increasingly realistic three‐dimensional representation of the growing plant useful for a simulation of plant evolution.
Dissecting drought‐ and cold‐tolerance traits in the Lolium–Festuca complex by introgression mapping
Authors: HUMPHREYS MIKE , THOMAS HUW‐MARTIN , HARPER JOHN , MORGAN GARETH , JAMES ANEURIN , GHAMARI‐ZARE ABBAS , THOMAS HENRY 
Published: March 2003

summaryRecent advances in the cytogenetics of the Lolium–Festuca complex provide new opportunities for understanding and manipulating complex physiological mechanisms such as drought and cold resistance. This paper describes breeding programmes involving hybrids between two species: L. multiflorum, which offers good early growth and high nutritive value, and F. arundinacea, which is more stress tolerant. The programmes are designed to allow a rapid recovery of the Lolium genome and to restrict numbers of recombinants derived from Festuca. Use of genomic in situ hybridization (GISH) and an isozyme marker demonstrates how gene complexes from any part of the Festuca genome can be introgressed into Lolium. This enables us to construct genotypes combining desirable traits of both Lolium and Festuca species. By introgressing different Festuca genes into Lolium, quantitative traits such as tolerance to drought and cold can be ‘dissected’ into their different components, to clarify their function. Festuca genes for stress tolerance can be located by genomic in situ hybridization (GISH) and assigned to regions of chromosome arms in Lolium. Two Lolium genotypes are described, in which genes for drought resistance transferred from the F. pratensis sub‐genome of F. arundinacea onto chromosome 2 of Lolium. The two drought‐resistant lines have the high water conductance of Festuca on their adaxial leaf surface and the low abaxial conductance of Lolium. The paper also describes how androgenesis of L. multiflorum×F. arundinacea hybrids has led to the selection and characterization of genotypes with coacclimation to drought and freezing stress, in some cases exceeding that in the Festuca parent.