bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aquaporin water channels and endothelial cell function*
Authors: Verkman A. S. 
Published: March 2003

AbstractThe aquaporins (AQP) are a family of homologous water channels expressed in many epithelial and endothelial cell types involved in fluid transport. AQP1 protein is strongly expressed in most microvascular endothelia outside of the brain, as well as in endothelial cells in cornea, intestinal lacteals, and other tissues. AQP4 is expressed in astroglial foot processes adjacent to endothelial cells in the central nervous system. Transgenic mice lacking aquaporins have been useful in defining their role in mammalian physiology. Mice lacking AQP1 manifest defective urinary concentrating ability, in part because of decreased water permeability in renal vasa recta microvessels. These mice also show a defect in dietary fat processing that may involve chylomicron absorption by intestinal lacteals, as well as defective active fluid transport across the corneal endothelium. AQP1 might also play a role in tumour angiogenesis and in renal microvessel structural adaptation. However, AQP1 in most endothelial tissues does not appear to have a physiological function despite its role in osmotically driven water transport. For example, mice lacking AQP1 have low alveolar‐capillary water permeability but unimpaired lung fluid absorption, as well as unimpaired saliva and tear secretion, aqueous fluid outflow, and pleural and peritoneal fluid transport. In the central nervous system mice lacking AQP4 are partially protected from brain oedema in water intoxication and ischaemic models of brain injury. Therefore, although the role of aquaporins in epithelial fluid transport is in most cases well‐understood, there remain many questions about the role of aquaporins in endothelial cell function. It is unclear why many leaky microvessels strongly express AQP1 without apparent functional significance. Improved understanding of aquaporin‐endothelial biology may lead to novel therapies for human disease, such as pharmacological modulation of corneal fluid transport, renal fluid clearance and intestinal absorption.
Transforming growth factor‐beta 2 heterozygous mutant mice exhibit Cowper's gland hyperplasia and cystic dilations of the gland ducts (Cowper's syringoceles)
Authors: Dünker Nicole , Aumüller Gerhard 
Published: March 2003

AbstractAnalyses of mutant mice with a deletion for the transforming growth factor beta 2 (Tgfβ2) gene revealed cysts in the perineal/scrotal region of male mice. We present evidence from in situ, light and electron microscopy that the cysts observed in Tgfβ2+/– heterozygous mice males derive from Cowper's gland tissue. The Cowper's glands of Tgfβ2+/– heterozygous mutant mice display all steps of glandular hyperplasia and cystic dilation. TGF‐β isoforms and TGF‐β receptor (TβR‐II) were localized immunocytochemically in sections of Cowper's glands. TGF‐β2 and TGF‐β3 were located predominantly in myoepithelial cells of the Cowper's gland whereas the TβRII was found in the plasma membrane of the acinar cells. TUNEL‐assays revealed that apoptotic cell death is significantly reduced in Cowper's glands of Tgfβ2+/– heterozygous mutant mice. The fact that Tgfβ2+/– heterozygous mutant mice exhibit hyperplasia of Cowper's gland epithelium and Cowper's gland cysts suggests a disturbance of epithelial–stromal interaction most likely due to reduced TGF‐β2 level, accompanied by a significant decrease in apoptosis.
Genetic disorders of palm skin and nail
Authors: McLean W. H. Irwin 
Published: March 2003

AbstractThe outer part of the skin, the epidermis, is specialized to protect the human body from its environment. Because of the high levels of physical stress experienced by the human hand in everyday use, the epidermis of the hand is especially toughened. In particular, the epidermis of the palm is highly specialized to resist mechanical trauma. Like the epidermis, the nails are composed of specialized epithelial cells and are especially strong. In recent years it has become apparent that the physical strength of epithelial cells comes from the keratin cytoskeleton – a dense meshwork of filaments extending throughout the cytoplasm. Keratins are a large family of intermediate filament proteins encoded by more than 50 distinct genes in humans. These different keratin genes are expressed in well‐defined combinations in specific epithelial tissues. Several keratin genes are expressed in palmoplantar epidermis and in the stratified epithelia of the nail bed. Genetic mutations in these genes lead to fragility of these tissues and result in a range of genetic disorders characterized by blistering and thickening of palm and sole skin and/or nails. Study of these diseases has shed new light on the vital structural role of keratins in maintaining the integrity of epithelial cells.
Evolution of the human hand: the role of throwing and clubbing
Authors: Young Richard W. 
Published: March 2003

AbstractIt has been proposed that the hominid lineage began when a group of chimpanzee‐like apes began to throw rocks and swing clubs at adversaries, and that this behaviour yielded reproductive advantages for millions of years, driving natural selection for improved throwing and clubbing prowess. This assertion leads to the prediction that the human hand should be adapted for throwing and clubbing, a topic that is explored in the following report. It is shown that the two fundamental human handgrips, first identified by J. R. Napier, and named by him the ‘precision grip’ and ‘power grip’, represent a throwing grip and a clubbing grip, thereby providing an evolutionary explanation for the two unique grips, and the extensive anatomical remodelling of the hand that made them possible. These results are supported by palaeoanthropological evidence.
NADH‐O2 oxidoreductase activity and mRNA expression of complex I (51 kDa, ND1) in postnatal intrinsic muscle of rat tongue
Authors: Fujita Toshiya , Sato Iwao 
Published: March 2003

AbstractComplex I is one of the respiratory chain enzymes related to NADH dehydrogenase and is an encoded gene product derived from both nuclear and mitochondrial genomes. Transcription levels of ND1 (mitochondrial) and 51 kDa (nuclear) subunits of complex I in the postnatal development of the intrinsic muscle in rat tongues were determined by Northern blot analysis. Enzyme activity levels were determined by NADH staining with tetrazolum salt, and oxygen consumption of NADH‐O2 oxidoreductase activity using a Clark‐type electrode. The detailed structure of the mitochondria was observed using electron microscopy. The cross‐sectional area of the mitochondria gradually increased during postnatal development, and the cristae also became complex, despite the length of mitochondria in muscle fibre being constant. The mitochondria density increased from birth to 15 days of age, and declined slightly afterwards. This pattern of density resembled that of NADH‐O2 oxidoreductase activity. The level of mRNA for ND1 through Northern blot analysis gradually increased from birth to 15 days of age and was highest at 21 days. For 51 kDa, the level was highest at 0 days and fell thereafter to a constant low. This suggests that the production of NADH dehydrogenase is limited by 51 kDa of Complex I derived from nuclear genomes rather than by the increase in mitochondria and composition of muscle fibre types due to changes in feeding behaviour.
Uptake and metabolism of sulphur dioxide by Arabidopsis thaliana
Authors: VAN DER KOOIJ T. A. W. , DE KOK L. J. , HANEKLAUS S. , SCHNUG E. 
Published: March 2003

SUMMARY Arabidopsis thaliana (L.) Heynh. was exposed to various concentrations of SO2 during almost the entire life cycle. No negative effects of SO2 on shoot biomass production were observed. There was a linear relation between the deposition of SO2 and the atmospheric SO2 concentration. Sulphur accumulated substantially in the shoots upon SO2 exposure. SO2 was either oxidized to sulphate or converted into extra organic sulphur compounds in a sulphate to organic sulphur ratio of 3:1, independently of the atmospheric SO2 concentration. Exposure to SO2resulted in an increase in water soluble non‐protein sulphydryl content and a slight increase in the amount of glucosinolates, but both of these play a minor role as sinks for the excess sulphur. The ratio of total nitrogen to total sulphur decreased upon SO2, exposure as a result of the increased sulphate content. The organic nitrogen to organic sulphur ratio did not change upon SO2 exposure, indicating no changes in the composition of sulphur‐containing compounds.
A comparative study of modern and fossil cone scales and seeds of conifers: a geochemical approach
Authors: STANKIEWICZ B. ARTUR , MASTALERZ MARIA , KRUGE MICHAEL A. , VAN BERGEN PIM F. , SADOWSKA ANNA 
Published: March 2003

SUMMARYModern cone scales and seeds of Pinus strobus and Sequoia sempervirens, and their fossil (Upper Miocene, c. 6 Mar) counterparts Pinus leitzii and Sequoia langsdorfii have been studied using pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), electron‐microprobe and scanning electron microscopy. Microscopic observations revealed only minor microbial activity and high‐quality structural preservation of the fossil material. The pyrolysates of both modern genera showed the presence of ligno‐cellulose characteristic of conifers. However, the abundance of (alkylated)phenols and 1,2‐benzenediols in modern S. sempervirens suggests the presence of non‐hydrolysable tannins or abundant polyphenolic moieties not previously reported in modern conifers. The marked differences between the pyrolysis products of both modern genera are suggested to be of chemosystematic significance. The fossil samples also contained ligno‐cellulose which exhibited only partial degradation, primarily of the carbohydrate constituents. Comparison between the fossil cone scale and seed pyrolysates indicated that the ligno‐cellulose complex present in the seeds is chemically more resistant than that in the cone scales. Principal component analysis (PCA) of the pyrolysis data allowed for the determination of the discriminant functions used to assess the extent of degradation and the chemosystematic differences between both genera and between cone scales and seeds. Elemental composition (C, O, S), obtained using electron‐microprobe, corroborated the pyrolysis results. Overall, the combination of chemical, microscopic and statistical methods allowed for a detailed characterization and chemosystematic interpretations of modern and fossil conifer cone scales and seeds.
Salinity tolerance in Phillyrea species
Authors: GUCCI R. , ARONNE G. , LOMBARDINI L. , TATTINI M. 
Published: March 2003

SUMMARYThe genus Phillyrea includes woody shrub species of Mediterranean maquis which can be found occasionally in saline soils or areas exposed to salt aerosols. To test salinity tolerance in Phillyrea latifolia L., plants were grown in 1–1 containers and exposed to different levels of salinity in a glasshouse over two growing seasons. Plants survived exposure to NaCl concentrations of up to 500 mM NaCl for 4 months. Analysis of the growth response to increasing salinity showed that shoot elongation was inhibited by 50% at 123 and 135 mM external NaCl after 31 and 123 d of salt treatment, respectively. Growth parameters were completely inhibited by treatment with 300 him external NaCl for 64 d. High salt tolerance in Phillyrea plants was the result of both exclusion and secretion mechanisms. Secretion of ions occurred via salt glands present mainly on the abaxial surface of the leaf. Salt glands occurred alone or in pairs and were typically formed by a highly vacuolated collecting cell, a stalk cell and a group of 10–16 secretory cells. The mean diameter of the glands was 54 μm and the average density was 6.1 mm−2 (abaxial side). Peaks of Cl, K, Ca, Na, Si, Mg, Fe and Cu were detected in salt crystals near glands by X‐ray microprobe analysis. This is the first report of salt glands in the Oleaceae family and of their role in salinity tolerance in Phillyrea species.
Identification of products formed by a fructan: fructan fructosyltransferase activity from Lolium rigidum
Authors: JOHN J. A. St , SIMS I. M. , BONNETT G. D. , SIMPSON R. J. 
Published: March 2003

SUMMARYThe products formed by a fructan: fructan fructosyltransferase (FFT) activity purified from Lolium rigidum Gaudin were identified after gas chromatography‐mass spectrometry of partially methylated alditol acetates, electrospray ionization‐mass spectrometry and reversed‐phase high‐performance liquid chromatography. The FFT activity synthesized oligofructans up to degree of polymerization (DP) 6, but did not synthesize fructans of DP > 6 even when assayed with (1,1,1)‐kestopentaose for up to 10 h. The FFT activity when assayed with 1‐kestose or 6G‐kestose synthesized fructan with fructosyl residues almost exclusively linked by β‐2,1‐glycosidic linkages. When assayed with 1‐kestose, the FFT activity synthesized tetrasaccharides and pentasaccharides with an internal glucosyl residue. The predominant tetrasaccharide was (1&6G)‐kestotetraose and the predominant pentasaccharide was (1&6G,1)‐kestopentaose. By comparison, tetrasaccharides and pentasaccharides extracted from L. rigidum also contained predominantly β‐2,1‐glycosidic linked fructans with an internal glucosyl residue. The only exception was that one of the pentasaccharides contained β‐2,1‐ and β‐2,6‐glycosidic linked fructosyl residues. This pentasaccharide was not synthesized by the FFT activity. The role of this FFT activity in formation of oligofructans in L. rigidum is discussed.
Components of pathozone behaviour
Authors: GILLIGAN C. A. , BAILEY D. J. 
Published: March 2003

summaryPathozone behaviour of soil‐borne plant pathogenic fungi is characterized by curves for the change in probability of infection with distance of inoculum from a host. We identify three major components that give rise to the pathozone profile for infection efficiency: the germinability of inoculum, given that it occurs in the pathozone (P1), the growth of the resulting fungal colony outwards to make contact with the host (P2), and the infectivity of mycelium once contact is made (P3). The probability of infection (P) is then given by the product, P1× P2× P3. Using Raphanus sativus and two contrasting types of inoculum of Rhizoctonia solani as a model experimental system, we measured each of the three components by quantifying germinability, colony architecture (to determine the chance of contact by one or more hyphae) and the change in susceptibility over time as a measure of infectivity as mycelium arrives from different distances away. The germinability of inoculum is uniform across the pathozone whereas the probability of contact declines with distance, and the net effect of host susceptibility and infectivity increases. The characteristics of these components result in pathozone profiles that vary in shape. Infection efficiency can decline in an exponential or sigmoidal fashion with increasing distance from the host or follow a curve that rises close to the host and then falls asymptotically to zero with increasing distance. Colony architecture was summarized by the distribution of the furthest extent of hyphal growth amongst colonies growing out from single inoculum units (described, because of its asymmetrical pattern, by a gamma distribution) and by the radial density of hyphae on concentric circles at different distances from the centre of the colony (described by a negative binomial distribution with parameters changing with distance).The mechanistic model for the components of pathozone behaviour is tested by comparing the magnitude and shape of pathozone profiles predicted by the model with independent estimates for P obtained by placing inoculum at fixed distances from the host, and measuring the proportion of successful infections. The shape depends on the relative magnitudes and change with distance of the three components, P1 P2 and P3, which differed between the two types of inoculum. The profiles could be reproduced accurately when the probability of contact was based on the distribution and density of hyphae reaching the host rather than on the furthest extent of hyphal growth amongst colonies. The model is used to analyse the effects of replication and stochastic variability in the components of pathozone behaviour on the comparison of treatments for disease control.
Deterrence of herbivory by zinc hyperaccumulation in Thlaspi caerulescens (Brassicaceae)
Authors: POLLARD A. JOSEPH , BAKER ALAN J. M. 
Published: March 2003

SUMMARYPlants known as hyperaccumulators take up and sequester high concentrations of potentially toxic elements from metalliferous soils. We tested the hypothesis that zinc hyperaccumulation benefits plants by deterring herbivory. In laboratory feeding trials, three species of herbivores were allowed to choose between Thlaspi caerulescens (Brassicaceae) plants grown in low‐Zn and Zn‐amended culture solution. Locusts (Schistocerca gregaria), slugs (Deroceras caruanae), and caterpillars (Pieris brassicae) all showed significant preferences for plants with lower foliar Zn concentrations. Such differential feeding could result in selection pressures favouring the evolution of hyperaccumulation. The findings are also relevant to current proposals to exploit hyperaccumulation as a means of remediating metal‐contaminated soils.
Plant nuclear migrations as indicators of critical interactions between resistant or susceptible cowpea epidermal cells and invasion hyphae of the cowpea rust fungus
Authors: HEATH MICHELE C. , NIMICHUK ZACHARY L. , XU HAIXIN 
Published: March 2003

SUMMARYLiving epidermal cells of cowpea (Vigna unguiculata (L.) Walp.) were examined by contrast‐enhanced video microscopy during penetration by invasion hyphae of the monokaryotic stage of the cowpea rust fungus (Uromyces vignae Barclay race 1). In resistant or susceptible host cvs, the plant nucleus migrated to the penetration site before the fungus had fully penetrated the plant wall and, at sites of unsuccessful infection, remained during the formation of a callose‐containing papilla. Nuclear migration was also induced by applying hemicellulase, but not H2O2, to localized sites of wall damage. Hemicellulase‐induced migration was inhibited by calcium chelators and a protein kinase inhibitor, but not catalase. In both resistant and susceptible cvs, the plant nucleus migrated away from successful infection sites at about the time that the fungal penetration peg made contact with the plant plasma membrane, and the epidermal cell showed no further cytological responses to the growth of the fungal intra‐epidermal vesicle. In the susceptible cv., the nucleus migrated back to the fungus when the latter initiated tip growth. Inhibitors of transcription or translation did not affect this migration and only slightly reduced fungal growth. In the resistant cv. in which the invaded cell exhibited a hypersensitive response (HR), the plant nucleus changed its appearance before the cessation of cytoplasmic streaming and usually did not migrate to the fungus, even if the latter initiated tip growth. Nuclear DNA cleavage usually followed the subsequent cessation of cytoplasmic streaming. Treatments that delayed cell death and increased fungal growth also increased the frequency of nuclear migration to the fungus. It is argued that these and other data suggest that U. vignae negates nonspecific, penetration‐induced, defence responses upon entering cells of both susceptible and resistant cultivars. The results also suggest that effects on the plant nucleus are one of the earliest signs of the HR in this system, often preceding the cessation of cytoplasmic streaming and detectable changes in plasma membrane permeability.
Functioning of mycorrhizal associations along the mutualism–parasitism continuum*
Authors: JOHNSON N. C. , GRAHAM J‐H. , SMITH F. A. 
Published: March 2003

SUMMARYA great diversity of plants and fungi engage in mycorrhizal associations. In natural habitats, and in an ecologically meaningful time span, these associations have evolved to improve the fitness of both plant and fungal symbionts. In systems managed by humans, mycorrhizal associations often improve plant productivity, but this is not always the case. Mycorrhizal fungi might be considered to be parasitic on plants when net cost of the symbiosis exceeds net benefits. Parasitism can be developmentally induced, environmentally induced, or possibly genotypically induced. Morphological, phenological, and physiological characteristics of the symbionts influence the functioning of mycorrhizas at an individual scale. Biotic and abiotic factors at the rhizosphere, community, and ecosystem scales further mediate mycorrhizal functioning. Despite the complexity of mycorrhizal associations, it might be possible to construct predictive models of mycorrhizal functioning. These models will need to incorporate variables and parameters that account for differences in plant responses to, and control of, mycorrhizal fungi, and differences in fungal effects on, and responses to the plant. Developing and testing quantitative models of mycorrhizal functioning in the real world requires creative experimental manipulations and measurements. This work will be facilitated by recent advances in molecular and biochemical techniques. A greater understanding of how mycorrhizas function in complex natural systems is a prerequisite to managing them in agriculture, forestry, and restoration.
Acclimation of Salix to metal stress
Authors: PUNSHON TRACY , DICKINSON NICHOLAS M. 
Published: March 2003

summaryNine different clones of six species of Salix (Salix cordata Muhlenb. non Michaux, 5. fragilis L., S. caprta L. S. cinerea L., S. burjatica Nazarov. and S. viminalis L.) and one hybrid (S.×calodendron Wimm.) were exposed to heavy metals in solution culture in an attempt to increase innate metal resistance. Resistance was estimated using comparative root measurements, and metal uptake was also studied. The first experiment entailed pre‐treatments with background nutrient solution, or 0.25 and 0.50 mg Cu I‐1amendments, and re‐exposure to each of the same concentrations. In a second experiment clones were exposed to sub‐toxic concentrations of single metals (0.15 mg Cu I‐1, 01 3 mg Cd I‐1or 2–5mgZnI‐1and dual‐combination treatments (0.075 mgCu I1+ 0.075 mg Cd l1, 0.075 mg Cd 1‐1+ 125 mg Zn T1or 0.075 mg Cd I‐1+ 1.25 mg Zn I1) with concentrations gradually raised 10–fold over 128 d. Plants tested in the first experiment, following pre‐exposure to Cu, were no more resistant to subsequent exposure to this metal. In the second experiment, gradual cumulative doses resulted in reduced phytotoxicity and increased resistance, most notably to Cd. There appeared to be an inverse relationship between metal uptake and resistance. Copper uptake was restricted to the roots, whereas Cd and Zn were more evenly distributed throughout the plant. Exposure to dual combinations of metals resulted in several interaction effects on uptake: increased root‐bound Cu in all combinations, and the increase in uptake of both Cd and Zn into the root tissues when supplied with Cu. The implications of these results for the use of willows in phytoremediation programmes are discussed.