bluuebunny/crossref_metadata_2025_split huggingface dataset:
The phenotype of the human materno‐fetal endothelial barrier: molecular occupancy of paracellular junctions dictate permeability and angiogenic plasticity*
Authors: Leach Lopa 
Published: March 2003

AbstractIn vitromodels predict that molecular occupancy of endothelial junctions may regulate both barrier function and angiogenesis. Whether this is true in human vascular beds undergoing physiological angiogenesis has not been shown. This review presents data which demonstrate there are two distinct junctional phenotypes, ‘activated’ and ‘stable’, present in the vascular tree of the human placenta taken from two distinct highly angiogenic gestational periods (first and last trimester). Stability is conferred by the presence of occludin in tight junctions and plakoglobin in adherens junctions. Their localization may be influenced by vascular endothelial growth factor and angiopoietins 1 and 2 that have a similar temporal and site‐specific differential expression. The junctional phenotypes are reversible, as shown in studies with endothelial cells isolated from placental microvessels and grown in the presence/absence of cAMP‐enhancing agents. Reductions in protein levels and loss of junctional localization of adhesion molecules result in increased permeability to macromolecules, whilst up‐regulation and re‐targeting of these molecules inhibit cell proliferation and increase transendothelial resistance. These studies suggest junctional adhesion molecules can regulate physiological angiogenesis and vascular re‐modelling. Moreover, the activated junctional phenotype of placental microvessels allows them to participate in increased growth and proliferation. This junctional immaturity appears to be at the expense of barrier function resulting in sites of maximal materno‐fetal solute exchange.
The role of mitochondria, cytochrome c and caspase‐9 in embryonic lens fibre cell denucleation
Authors: Sanders E. J. , Parker E. 
Published: March 2003

AbstractDuring the differentiation of secondary lens fibre cells from the lens epithelium, the fibre cells lose all of their cytoplasmic organelles as well as their nuclei. The fibre cells, containing crystallins, which confer optical clarity, then persist in the adult lens. The process of denucleation of these cells has been likened to an apoptotic event which is not followed by the plasma membrane changes that are characteristic of apoptosis. We have examined the expression and subcellular translocation of molecules of the apoptotic cascade in differentiating lens epithelial cells in culture. In this culture system, the epithelial cells differentiate into lentoids composed of lens fibre cells. We find that caspase‐9, which is expressed and activated before embryonic day 12 in intact lenses, is localized in the cytosol outside mitochondria in non‐differentiating cultured cells. In lentoid cells, caspase‐9 migrates into mitochondria after the latter undergo a membrane permeability transition that is characteristic of apoptotic cells. At the same time, caspase‐9 co‐localizes with cytochrome c in the cytosol. The cytochrome c is apparently released from the mitochondria in lentoid cells after the mitochondrial membrane permeability transition and during the period of nuclear shrinkage. Also during this time, the mitochondria aggregate around the degenerating nuclei. Cytochrome c disappears rapidly, while mitochondrial breakdown occurs approximately coincident with the disappearance of the nuclei, but mitochondrial remnants persist together with cytochrome c oxidase, which is a mitochondrial marker protein. Apaf‐1, another cytosolic protein of the apoptotic cascade, also migrates to the permeabilized mitochondria and also co‐localizes with caspase‐9 and cytochrome c in the cytosol or mitochondria of denucleating cells, thus providing evidence for the formation of an ‘apoptosome’ in these cells, as in apoptotic cells. At no time did we observe the translocation of molecules between cytoplasmic compartments and the nucleus in differentiating lentoid cells. We suggest that the uncoupling of nuclear and membrane apoptotic events in these cells may be due to the early permeability changes in the mitochondria, resulting in the loss of mitochondrial signalling molecules, or to the failure of molecules to migrate to the nucleus in these cells, thus failing to activate nuclear‐plasma membrane signalling pathways.
Airway and blood vessel interaction during lung development
Authors: Hislop Alison A. 
Published: March 2003

AbstractIn the adult lung the pulmonary arteries run alongside the airways and the pulmonary veins show a similar branching pattern to the arteries, though separated from them. During early fetal development the airways act as a template for pulmonary blood vessel development in that the vessels form by vasculogenesis around the branching airways. In later lung development the capillary bed is essential for alveolar formation. This paper reviews evidence for the interaction of the airways and blood vessels in both normal and abnormal lung development.
Elastic fibre organization in the intervertebral discs of the bovine tail
Authors: Yu Jing , Peter C. , Roberts Sally , Urban Jill P. G. 
Published: March 2003

AbstractElastic fibres have been revealed by both elastin immunostaining and conventional histological orcein‐staining in the intervertebral discs of the bovine tail. These fibres are distributed in all regions of the disc but their organization varies from region to region. In the centre of the nucleus, long (> 150 µm) elastic fibres are orientated radially. In the transitional region between nucleus and annulus, the orientation of the elastic fibres changes, producing a criss‐cross pattern. In the annulus itself, elastic fibres appear densely distributed in the region between the lamellae and also in ‘bridges’ across the lamellae, particularly in the adult. Elastic fibres are apparent within the lamellae, orientated parallel to the collagen fibres of each lamella, particularly in the young (12‐day‐old) discs. In the region between the disc and the cartilaginous endplate, elastic fibres appear to anchor into the plate and terminate there. The results of this study suggest that elastic fibres contribute to the mechanical functioning of the intervertebral disc. The varying organization of the elastic fibres in the different regions of the disc is likely to relate to the different regional loading patterns.
Molecular control of arterial–venous blood vessel identity
Authors: Adams Ralf H. 
Published: March 2003

AbstractRecent research has demonstrated that not only haemodynamic factors but also genetic programmes control arterial–venous cell fate and blood vessel identity. The identification of arteries and veins was previously based solely on morphological criteria and is now greatly facilitated by specific molecular markers. Moreover, signalling pathways controlling the arterial–venous decision during embryonic development have been outlined for the first time. This review gives an up‐to‐date overview of differentially expressed genes and the regulatory processes leading to the differentiation of arteries and veins.
Epithelial mesenchymal interactions, the ECM and limb development
Authors: Lonai Peter 
Published: March 2003

AbstractIt has been long since recognized that cellular interactions are not always direct, i.e. they do not always take place between cells contacting each other, or between cells that emit soluble factors and other cells, which respond to it. In contrast, cross‐talk between cells is frequently based on signals attached to the extracellular matrix (ECM). Thus besides proximate cell‐to‐cell contact, certain interactions are mediated by the ECM in a sequence: cell‐to‐matrix, matrix‐to‐cell. ECM‐mediated interactions may take place within a group or sheet of cells or across adjacent cell sheets. A modified mat‐like ECM, the basement membrane, separates adjacent cell sheets and mediates their interactions. Since cell sheets separated by basement membranes are an elementary feature of metazoan histology, interactions with the basement membrane have considerable importance. Recently accumulated evidence emphasizes the importance of ECM‐mediated interactions. It is becoming increasingly evident that the ECM functions not only as an architectural component, but it is involved also in signal transduction. This evidence derives from four main sources: from the structure of receptor‐ligand complexes, from Drosophila and C. elegans genetics, from cell biological observations and from the analysis of mammalian development. In this review, I will touch upon recent evidence, illustrated by examples of FGF signalling in vertebrate limb development. Although the involvement of matrix components is not yet proven for all cases directly, the strength of multiple indications suggests that a better understanding of ECM‐mediated interactions will shed new light on cell differentiation.
Carbohydrate allocation patterns in citrus genotypes as affected by phosphorus nutrition, mycorrhizal colonization and mycorrhizal dependency
Authors: GRAHAM J. H. , DUNCAN L. W. , EISSENSTAT D. M. 
Published: March 2003

SUMMARYAmong closely related citrus genotypes growing in high phosphorus (P) orchard soils, there is a tendency for less mycorrhizal‐dependent (M‐dependent) species to have lower rates of root colonization than more M‐dependent species. We hypothesized that the less M‐dependent the citrus species the more limited is their carbohydrate (CHO) allocation to the M fungus. In a glasshouse study at low and high P supply, lower total incidence of Glomus intraradices FL 208, intensity of vesicles formation, and accumulation of 16: W5cis fungal fatty acid as measures of root colonization were related to lower mycorrhizal dependency (MD; M plant d. wt/non‐mycorrhizal (NM) plant d. wt expressed at low P supply) in five citrus genotypes. At high P supply, when host carbon (C) production was not affected by P nutrition, less M‐dependent genotypes had consistently lower starch concentrations in their root and shoot tissues than did more M‐dependent genotypes, irrespective of M inoculation. At low P supply, M plants were more heavily colonized by G. intraradices and had lower starch levels than the M plants supplied with additional P. At high P, M plants of the more dependent genotypes allocated more C to starch pools relative to the NM plant than the least dependent genotype. Concentration of sucrose in tissues did not vary consistently with the dependency of citrus genotypes or with M inoculation except in high P NM plants, when less M‐dependent genotypes had lower levels of sucrose in their roots than the more dependent species. At high P supply, sucrose concentrations were lower in colonized roots than in NM roots. Across citrus genotypes, sucrose in M fibrous roots decreased relative to that in NM roots with increase in root colonization suggesting that more sucrose was allocated for growth and maintenance of G. intraradices in roots of M‐dependent species. The concentration of reducing sugars in root tissues varied in relation to MD of citrus genotypes in the same way as that of starch and sucrose, but was less responsive to M colonization. Responses of total non‐structural CHO in tissues indicated that more heavily colonized plants at low P expended more C to acquire P than did M plants of similar biomass and P status grown at high P supply. Total CHO pools increased with MD of citrus genotypes, providing evidence than C allocation patterns in the host affect M colonization.
Physiological effects of copper on iron acquisition processes in Plantago
Authors: SCHMIDT W. , BARTELS M. , TITTEL J. , FÜHNER C. 
Published: March 2003

SUMMARYIn Plantago lanceolata L. the effect of Cu(II) additions to the nutrient solution on root‐associated Fe(III) reductase was studied in a factorial design with different Cu(II) and Fe(III) concentrations. Iron starvation resulted in approx. an eightfold increase in root Fe reduction at the level of intact plants and twofold enhancement in the specific activity of both NADH‐linked FeEDTA reductase and H+‐ATPase in isolated root plasma membrane vesicles. In plants exposed to low (0.3–0.7 μM.) Cu and suboptimal Fe levels, reduction activity at the root surface was further increased and associated with more severe interveinal chlorosis than plants grown in Cu‐free medium. In Fe‐sufficient plants, withholding Cu over a prolonged period slightly enhanced the reduction activity.Addition of high (5 μM) Cu concentrations to Fe‐free medium inhibited the induction of the physiological responses by Fe‐deficiency stress. In plants without Fe supply but with adequate Cu supply, short‐term application of 5 μM CuSO4 completely inhibited the reduction activity. Neither incubation of the plasma membrane vesicles before measurement nor incubation of intact plants with Cu before isolation caused a significant decrease in reductase activity. The results are interpreted as indicating different mechanisms underlying Cu‐induced alterations in iron nutrition.
Intraspecific variation of leaf pubescence and drought response in Encelia farinosa associated with contrasting desert environments
Authors: SANDQUIST DARREN R. , EHLERINGER JAMES R. 
Published: March 2003

SUMMARYTraits associated with leaf energy balance are especially important for desert plants because decoupling leaf and ambient temperatures can be critical for maximizing productivity and survival in these hot, dry regions. Deserts are also one of the most climatically unpredictable and heterogeneous biomes; thus, variation of energy balance characters due either to plasticity or genetic differentiation might also be crucial to the success of desert plant species. In a common garden environment we examined variation in the traits associated with energy balance and productivity in Encelia farinosa A. Gray (brittlebush) plants. Comparing two populations from contrasting rainfall and drought climates, we found that plants from the wetter site (Superior, Arizona) always maintained higher leaf absorptances than plants from the more xeric region (Oatman, Arizona) when at similar water potentials. Superior plants also increased stomatal conductance and photosynthesis in response to mid‐spring rainfall, whereas Oatman plants did not. Oatman plants, however, tended to have greater leaf areas and continuous spring growth, which made them larger than Superior plants, yet both populations produced the same number of flower heads. The differences for these traits, and the associations among them, agree with predictions based on the contrasting drought and rainfall environments of these two populations. Our results suggest that the differences might represent alternative suites of characters of selective importance for maximizing carbon gain over the climatically variable range of this widespread species. Furthermore, these differences, detected in common environment conditions, might have a genetic basis, which might contribute to a greater potential for local adaptation in this species.
Effects of a rapid, unseasonal rewetting event on mineral location in Antarctic lichens
Authors: HOVENDEN MARK 
Published: March 2003

summaryDuring the middle of the 1992 austral winter in the northern Windmill Islands, continental Antarctica, a highly unusual climatic event occurred in which the air temperature exceeded 0°C for some 60 h, at the end of which there was a significant rain shower before the ambient temperature returned to subzero conditions. This event caused most of the snow cover to melt and refreeze as clear ice. Lichens were thus rehydrated in the dark, in some places completely inundated, then frozen in ice. The effect that these conditions had on the distribution of K, Na, Mg and Ca within the thallus was estimated for two of the dominant macrolichen species, Umbilicaria decussata (Vill.) Zahlbr. and Usnea sphacelata R.Br, from three sites on a knoll on Clark Peninsula. One site acted as a natural control, owing to the very deep snow cover at the site, which protected lichens from the rewetting event. Despite persistent differences between species and the various sites, there was no overall effect of the climatic event on the membrane integrity of either lichen species. Only Usnea sphacelata from the most exposed site showed a significant leakage of K across the cell membrane, which indicated a loss of membrane integrity. Overall, both species were tolerant of the extreme conditions, although Umbilicaria decussata was the more tolerant.
Development of laboratory‐based methods for assessing seedling thermotolerance in pearl millet
Authors: HOWARTH CATHERINE J. , POLLOCK CHRISTOPHER J. , PEACOCK JOHN M. 
Published: March 2003

summaryIn this paper, the response to temperature of three physiological processes has been examined in detail in seedlings of sorghum and pearl millet. These have been compared with their field performance under high temperature conditions with the aim of developing laboratory‐based screening techniques for seedling thermotolerance. Membrane thermostability, as assessed by electrolyte leakage, seedling re‐growth and protein synthetic ability were measured in seedlings exposed to a range of temperatures using a thermal gradient bar. The effect of genotype, seedling age and pre‐treatment was examined. Differences between genotypes were only apparent after seedlings had been given a brief high temperature pre‐treatment (2 h at 43 °C). Similar results were found with all three methods used and their suitability for use in the screening of large numbers of entries is discussed. Significant correlation was found between the ability of membrane thermostability to acclimate and seedling survival in the field.
Outcome of interactions between genets of two Suillus spp. and different Pinus sylvestris genotype combinations: identity and distribution of ectomycorrhizas and effects on early seedling growth in N‐limited nursery soil
Authors: TIMONEN SARI , TAMMI HANNA , SEN ROBIN 
Published: March 2003

summaryThe identity of individual ectomycorrhizas, root colonization patterns and early growth responses of interconnected Scots pine (Pinus sylvestris L.) seedlings were investigated following interactions between local genets of Suillus bovinus (L. ex Fr.) O. Kuntze (SBK4b and SBK5b) and S. variegatus (Swartz ex Fr.) O. Kuntze (SVK3b) and different host‐genotype combinations. Three equidistant 39‐d‐old seedlings, in pots that contained sterile N‐limited nursery soil, were each inoculated with one of the three genets in the multiple inoculation treatment (MIT). Single inoculation treatments (SITs), involving inoculation of only one seedling in the triad with one of the three genets, and a similarly configured uninoculated treatment (UIT), were also prepared for comparative analysis. All seedling roots in the inoculated treatments, except for one SIT/SBK4b combination, hosted large numbers (>150) of Suillus‐type ectomycorrhizas after 23–25 wk growth without additional fertilization. Esterase (EST) isozyme analysis of individual ectomycorrhizas from all SIT and MIT combinations enabled efficient interspecific and intraspecific typing of fungal (genet) colonization (89 and 72 %, respectively) and identification of host genotype variation (Z locus polymorphism) at a lower rate (51 %). Species, but not 5. bovinus genet, typing within randomly sampled individual ectomycorrhizas from selected SITs was successful (50–70%) following PCR/RFLP analysis of diagnostic sequences of fungal rRNA genes. In the SITs, only the inoculated fungal genet was detected in ectomycorrhizas on all three seedlings. Roots were predominantly colonized by SBK4b in one, and SBK5b in three, of the MIT combinations, although ectomycorrhizas of the former genet were detected at low frequencies on nearly all seedlings. In the remaining MIT combination, both SBK4b and SVK3b were found to co‐dominate as ectomycorrhizas on the seedling roots. Small numbers of the latter genet were detected in ectomycorrhizas of two SBK5b‐dominated MIT combinations. However, no significant trends in host‐mycorrhiza interactions were detected using a log‐linear analysis. Compared with the UIT, significant positive mycorrhizal plant growth responses, particularly increased needle length, were recorded in all the heavily colonized seedlings in most SIT and all MIT combinations. Intermediate seedling growth was restricted to the one SIT/SBK4b combination where seedlings supported limited numbers of ectomycorrhizas. The general host‐fungal colonization patterns observed provide further below‐ground evidence supporting genet interactions previously detected through sporocarp population analyses in young Scots pine reforestation sites.
The effect of fungicides on vesicular–arbuscular mycorrhizal symbiosis. III. The influence of VA mycorrhiza on phytotoxic effects following application of fosetyl‐Al and phosphonate
Authors: SUKARNO N. , SMITH F. A. , SCOTT E. S. , JONES G. P. , SMITH S. E. 
Published: March 2003

This study compares the effects of the fungicide Aliette® (fosetyl‐Al) on non‐mycorrhizal and mycorrhizal onion (Allium cepa L.) with effects of the degradation products, aluminium (applied as aluminium chloride) and phosphonate (applied as dimethyl phosphonate). We sought to determine the extent to which the plants absorb and accumulate phosphonate and ascertain why, as shown previously, toxic effects of fosetyl‐Al on mycorrhizal plants are less severe than effects on equivalent non‐mycorrhizal plants.Fosetyl‐Al markedly reduced growth, especially of roots, and also inhibited mycorrhizal colonization. Dimethyl phosphonate caused smaller effects on growth and did not decrease colonization. Aluminium chloride did not affect growth of non‐mycorrhizal or mycorrhizal plants, or mycorrhizal colonization. In all cases, mycorrhizal plants grew better than equivalent non‐mycorrhizal plants (with no added soil phosphate), and non‐mycorrhizal plants given supplementary soil phosphate grew best.Concentrations and contents of total P in shoots were increased by dimethyl phosphonate and more so by fosetyl‐Al. Concentrations of P were also increased in roots. 31P nuclear magnetic resonance (NMR) spectroscopy was used to determine relative concentrations of phosphonate and phosphate. Application of fosetyl‐Al led to accumulation of more phosphonate than did application of dimethyl phosphonate, and non‐mycorrhizal plants treated with fosetyl‐Al accumulated much more phosphonate than did equivalent mycorrhizal plants (both with no added soil phosphate). Internal phosphate concentrations increased, especially in mycorrhizal plants, following application of both dimethyl phosphonate and fosetyl‐Al. Non‐mycorrhizal plants given supplementary soil phosphate also showed restricted growth when treated with fosetyl‐Al even though they accumulated phosphate in relatively high amounts and had lower ratios of phosphonate to phosphate, particularly in shoots. In general, high internal concentrations of phosphonate were correlated with large reductions in plant growth among treatments.Possible causes of these effects include conversion of phosphonate to phosphate in the tissues (especially in mycorrhizal plants), enhanced uptake of phosphate via mycorrhizal fungi and additional accumulation of P in plants with restricted growth. Competition for uptake between phosphate and phosphonate is also discussed.