bluuebunny/crossref_metadata_2025 huggingface dataset:
The pathophysiology of pelvic floor disorders: evidence from a histomorphologic study of the perineum and a mouse model of rectal prolapse
Authors: YIOU RENÉ , DELMAS VINCENT , CARMELIET PETER , GHERARDI ROMAIN K. , BARLOVATZ‐MEIMON GEORGIA , CHOPIN DOMINIQUE K. , ABBOU CLÉMENT‐CLAUDE , LEFAUCHEUR JEAN‐PASCAL
Published: March 2003

The muscle changes related to pelvic floor disorders are poorly understood. We conducted an anatomical and histological study of the perineum of the normal mouse and of a transgenic mouse strain deficient in urokinase‐type plasminogen activator (uPA−/−) that was previously reported to develop a high incidence of rectal prolapse. We could clearly identify the iliococcygeus (ILC) and pubococcygeus (PC) muscles and anal (SPA) and urethral (SPU) sphincters in male and female mice. The bulbocavernosus (BC), ischiocavernosus (ISC) and levator ani (LA) muscles could be found only in male mice. Histochemical analysis of the pelvic floor muscles revealed a majority of type IIA fibres. Rectal prolapses were observed only in male uPA−/− mice. The most obvious finding was an irreducible evagination of the rectal mucosa and a swelling of the entire perineal region corresponding to an irreducible hernia of the seminal vesicles through the pelvic outlet. The hernia caused stretching and thinning of the ISC, BC and LA. Myopathic damage, with degenerated and centronucleated myofibres, were observed in these muscles. The PC, ILC, SPA and SPU were not affected. This study provides an original description of a model of pelvic floor disorder and illustrates the differences existing between the perineum of humans and that of a quadruped species. In spite of these differences, the histopathologic changes observed in the pelvic floor muscles of uPA−/− mice with rectal prolapse suggest that prolonged muscular stretching causes a primary myopathic injury. This should be taken into account in the evaluation of pelvic floor disorders.
Fibre type regionalisation in lower hindlimb muscles of rabbit, rat and mouse: a comparative study
Authors: WANG L. C. , KERNELL D.
Published: March 2003

The topographical distribution of different fibre types in muscles of the lower hindlimb in rabbits and mice was quantitatively determined. The results were compared to those previously obtained, using the same new quantification methods, in homologous muscles of the rat. Type I fibres (‘slow’) were identified using myofibrillar ATPase histochemistry and mapped out at the mid proximo‐distal level for 11 ‘fast’ muscles in the rabbit and 7 ‘fast’ muscles in the mouse. For the slow soleus muscle the procedure was undertaken for the type II fibres. Furthermore, for 5 of the ‘fast’ muscles from each animal species (extensor digitorum longus; flexor digitorum and hallucis longus; gastrocnemius medialis; peroneus longus; tibialis anterior), several more proximal and distal cross‐sectional levels were also analysed. All the investigated ‘fast’ muscles showed a significant degree of topographical eccentricity in the midlevel distribution of type I fibres. For most muscles, the direction of this ‘vector regionalisation’ of type I fibres was similar between the three animal species. For homologous muscles, the degree of vector regionalisation was significantly different: mouse > rat > rabbit. The relative area of the region containing the type I fibres, inversely related to the degree of ‘area regionalisation’, was also significantly different: mouse < rat < rabbit. Also within each animal species, muscles with a marked degree of vector regionalisation tended to show a marked area regionalisation. Proximo‐distal differences in type I fibre density were observed in all the three species of animals; also these patterns showed marked inter‐species differences. The findings demonstrate the general occurrence of, and systematic relationships between, different aspects of type I fibre regionalisation. The observed interspecies differences suggest that the expression of this phenomenon is adapted to differing functional needs.
Cardiomyocyte differentiation of mouse and human embryonic stem cells*
Authors: Mummery C. , Ward D. , Van Den Brink C. E. , Bird S. D. , Doevendans P. A. , Opthof T. , De La Riviere A. Brutel , Tertoolen L. , Van Der Heyden M. , Pera M.
Published: March 2003

Ischaemic heart disease is the leading cause of morbidity and mortality in the western world. Cardiac ischaemia caused by oxygen deprivation and subsequent oxygen reperfusion initiates irreversible cell damage, eventually leading to widespread cell death and loss of function. Strategies to regenerate damaged cardiac tissue by cardiomyocyte transplantation may prevent or limit post‐infarction cardiac failure. We are searching for methods for inducing pluripotent stem cells to differentiate into transplantable cardiomyocytes. We have already shown that an endoderm‐like cell line induced the differentiation of embryonal carcinoma cells into immature cardiomyoctyes. Preliminary results show that human and mouse embryonic stem cells respond in a similar manner. This study presents initial characterization of these cardiomyocytes and the mouse myocardial infarction model in which we will test their ability to restore cardiac function.
Role of aquaporins in endothelial water transport
Authors: Verkman A. S.
Published: March 2003

The 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. There is preliminary evidence that AQP1 might 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 tumour angiogenesis, renal fluid clearance and intestinal absorption.
Tendon morphogenesis in the developing avian limb: plasticity of fetal tendon fibroblasts
Authors: Oldfield Sarah F. , Evans Darrell J. R.
Published: March 2003

The differentiation and patterning of tendon fibroblasts is at present a poorly understood aspect of musculoskeletal development in the vertebrate limb. Precursors of tendon fibroblasts originate in the somatic mesoderm adjacent to the early limb bud and gradually become incorporated into the limb mesenchyme as development proceeds. It is unclear whether these progenitor cells are committed to the tendon lineage at this early stage, or whether cells become committed only as they are incorporated into a developing tendon. Following a review of our current knowledge of early tendon development, we present recent results from our preliminary studies looking at tendon cell commitment. Using a lacZ encoding replication‐deficient retrovirus, we have mapped regions of the early limb bud that contain presumptive tendon progenitor cells, and later used these sites for implanting labelled fetal tendon fibroblasts into developing limbs. Following implantation, we found that these cells successfully re‐incorporated into developing proximal and distal tendons, but also surprisingly contributed to other tissue lineages within the limb. Our results suggest that fetal tendon fibroblasts may not be irreversibly committed to a tendon cell fate in the limb and may be somewhat plastic in their ability to integrate into other tissue lineages during development.
Microvascular assembly and cell invasion in chick mesonephros grafted onto chorioallantoic membrane
Authors: Navarro Marc , DeRuiter Marco C. , Carretero Ana , Ruberte Jesús
Published: March 2003

Embryonic tissues, in common with other tissues, including tumours, tend to develop a substantial vasculature when transplanted onto the chorioallantoic membrane (CAM). Studies conducted to date have not examined in any detail the identity of vessels that supply these grafts, although it is known that the survival of transplanted tissues depends on their ability to connect with CAM vessels supplying oxygen and nutrients. We grafted the mesonephros, a challenging model for studies in vascular development, when it was fully developed (HH35). We used reciprocal chick‐quail transplantations in order to study the arterial and venous connections and to analyse the cell invasion from the CAM to the organ, whose degeneration in normal conditions is rapid. The revascularization of the grafted mesonephros was produced by the formation of peripheral anastomoses between the graft and previous host vasculatures. The assembly of graft and CAM blood vessels occurred between relatively large arteries or veins, resulting in chimeric vessels of varying morphology depending on their arterial or venous status. Grafts showed an increased angiogenesis from their original vasculature, suggesting that the normal vascular degeneration of the mesonephros was partially inhibited. Three types of isolated host haemangioblast were identified in the mesonephros: migrating angioblast‐like cells, indicating vasculogenesis, undifferentiated haematopoietic cells and macrophages, which might have been involved in the angiogenesis. Tomato lectin was found to bind activated macrophages in avian embryos.
The late‐glacial at Lac de Creno (Corsica, France): a key site in the western Mediterranean basin
Authors: REILLE M. , GAMISANS J. , de BEAULIEU J.‐L. , ANDRIEU V.
Published: March 2003

summary

The lower part (460–650 cm) of a lacustrine sequence from Lac de Creno, Corsica (1310 m) is analysed on the basis of 68 pollen spectra and with the support of 10 14C dates (including nine A.M.S. dates). This sequence, which extends from the end of the Würm to the beginning of the Postglacial, reveals a complete late‐glacial. The absence of forest dynamics during the late glacial Interstadial in Corsica is a real mystery. Pollen data clearly suggest that Pinus laricio (=Pinus nigra Arnold ssp. laricio Maire) and perhaps other tree species did not exist in Corsica at that time.
Water distribution in fungal lesions in the wood of sycamore,Acer pseudoplatanus, determined gravimetrically and using nuclear magnetic resonance imaging
Authors: PEARCE R. B. , FISHER B. J. , CARPENTER T. A. , HALL L. D.
Published: March 2003

Water contents in healthy xylem, reaction zones (column boundary layers) and decayed wood were determined in sycamore (Acer pseudoplatanusL.) naturally infected by sooty bark disease (Cryptostroma corticale(Ellis & Everh.) Gregory & Waller) or wound‐inoculated withUstulina deusta(Fr.) Petrak. orGanoderma adspersum(Schulz) Donk. Water contents determined gravimetrically were greater in reaction zones than in healthy wood by factors of 1.1–2.1 times. Maps of imageable proton density (M0), essentially equivalent to relative water contents, were also calculated from two independent nuclear magnetic resonance (NMR) imaging (MRI) data sets, acquired fromT1orT2weighted experiments. M0values derived from these, corrected forT2andT1respectively, were in good agreement, and paralleled the results obtained when total water was determined gravimetrically, although the proportional increase inM0in reaction zones (1.3–3.7 times) was greater than the corresponding increase in total water.

Living wood saturated with water by vacuum infiltration contained approx. 1.3 times more water, determined gravimetrically, than uninfiltrated wood. The proportional increase inM0was greater (1.8–2.4 times). This was attributable to the alleviation of magnetic susceptibility effects by elimination of the gas‐water interfaces normally present in the uninfiltrated wood. The similarities between infiltrated wood and reaction zone tissues in both total gravimetric water content and NMR‐visible water suggest that the biophysical environment of the water might be similar in both. This is compatible with the hypothesis that in reaction zones the gases normally present in the lumens of empty (dead) xylem fibres are replaced by an aqueous solution of phytoalexin‐like compounds. This has been confirmed by microscopy. The implications of this in relation to antimicrobial defence and xylem function are discussed.

Although contrast in NMR images of lesions was predominantly attributable to changes inM0, a decrease in the spin‐spin relaxation time(T2)was seen in the vicinity of some lesions. Spin‐lattice relaxation times (T1) were not altered to the same extent.

Results obtained from both early and late stages of decay were much more variable than those from healthy wood or from reaction zones, and reflected both the low water content of decayed wood (and hence poor signal‐to‐noise ratios for NMR data) and the changing physical environment as the wood was degraded.
Effect of habitat disturbance on inoculum potential of ericoid endophytes of Western Australian heaths (Epacridaceae)
Authors: HUTTON B. J. , DIXON K. W. , SIVASITHAMPARAM K. , PATE J. S.
Published: March 2003

The presence of host plants was found to be a key determinant of soil infectivity for endophytes of epacrids growing in south–west Australian jarrah forest carrying a sparse epacrid understorey. A comparable Banksia woodland with higher density of epacrids showed more uniform levels of infective endophytes, presumably because of closer overlap of host–supported patches of endophyte. Disturbed sites in jarrah forest, in which topsoil had been recently returned following bauxite mining, initially showed extremely low endophyte infectivity, probably due to disruption of the hyphal network, absence of host plants and/or increased competition from soil micro–organisms antagonistic to the endophytes. As the system stabilized and epacrids recruited and grew, inoculum potential of the soil re–established and by 12 yr it equalled that of adjacent undisturbed native forest. At disturbed sites with sparsely distributed adult members of the Epacridaceae, endophyte inoculum proved to be adequate only directly adjacent to the epacrids and declined steeply to negligible levels at only 40 cm radially distant from a host plant. The significance of live epacrid root systems on survival of endophyte inoculum in Banksia woodland was examined following removal of shoots of adult plants of the endemic epacrid, Leucopogon conostephioides DC, Coincident with demise of roots of the detopped plants, endophyte inoculum potential of closely adjacent soil declined by 50% during the growing season. However, the effect was short lived and infectivity rose the following year to equal that of undisturbed adjacent woodland as mycelial matrices supported by neighbouring epacrids invaded the depleted study areas.
Eleocharis sphacelata: internal gas transport pathways and modelling of aeration by pressurized flow and diffusion
Authors: SORRELL BRIAN K. , BRIX HANS , ORR PHILIP T.
Published: March 2003

summary

The ability of diffusive gas transport and pressurized, convective flow to satisfy internal oxygen demands was examined for an aquatic sedge, Eleocharis sphacelata R. Br. Resistances to convection and diffusion through the plant were quantified from anatomical studies of the airspace dimensions, and these were used in mathematical models to calculate the fluxes required to satisfy oxygen demands measured in the tissue. The greatest resistance to diffusion in the underwater tissue was the submerged culm between the waterline and sediment surface (1560 Ms m−3 per m culm length). Resistances of the nodal intercalary meristem (52 Ms m−3) and rhizome internode (34 Ms m−3) were minor. In contrast, resistances to convection were low in the culms (38 MPa s m−3 per m culm length), and higher in the nodal meristems (93 MPa s m−3). The rhizome internodes had large cortical canals with a low convective resistance (0.75 MPa s m−3), and a parallel spongy pith with a very high resistance (518 MPa s m−3) that is probably short‐circuited by convection. The resistance of the submerged culm means that diffusion is inadequate to satisfy oxygen demands in plants growing in >10 cm of water, and that convection is therefore essential in the natural habitat of this species (water to c. 2 m depth). However, a convective oxygen influx as low as 28 × 10−8 mol s−1 per culm (equivalent to a gas flow rate of 3 μl s−1 per culm) could satisfy the entire oxygen demand of the underwater tissue; this value is well below actual rates. At this flow rate, the spongy pith in the rhizome would also remain aerobic: it has a low resistance to diffusion (73 Ms m−3) and could receive sufficient oxygen by diffusion from the node. The data agree well with previous empirical measurements of convection in this species and show that diffusion and convection are both important processes for its aeration.
Productivity of leaves of a tropical tree, Theobroma cacao, grown under shading, in relation to leaf age and light conditions within the canopy
Authors: MIYAJI KEN‐ICHI , DA SILVA WALNY S. , ALVIM PAULO de T.
Published: March 2003

summary

The photosynthetic and respiratory activities of the leaves of a tropical tree, cacao, Theobroma cacao L., grown under shading, were determined in relation to leaf age and light conditions within the canopy, in order to gain a deeper insight into characteristics of the leaf population composing a canopy.

The specific leaf weight and leaf water content varied with the height of leaves from the ground and/or the irradiance. The net photosynthetic rate also varied markedly depending on leaf age and irradiance. The leaves in full or nearly full irradiance (< 70% full daylight) attained the maximum rater. 60 d after the leaves emerged, and the rate decreased to nearly zero at a leaf age of c. 270 d.

The nocturnal leaf respiratory activity was proportional to the photosynthetic activity during the day, but the proportional ratio was not constant throughout the survival period of leaves. Within the closed canopy, the upper leaves, which much higher ratios of respiratory to photosynthetic activity, under full or nearly full irradiance, tended to have much shorter mean longevities (c. 160 d) than the lower leaves under a lower irradiance (c. 310 d).
Effect of fertilization on ozone‐induced changes in the metabolism of birch (Betula pendula) leaves
Authors: LANDOLT W. , GÜNTHARDT‐GOERG M. S. , PFENNINGER I. , EINIG W. , HAMPP R. , MAURER S. , MATYSSEK R.
Published: March 2003

summary

Cloned cuttings of Betula pendula Roth were grown in field fumigation chambers at Birmensdorf throughout one growing season in filtered air with either < 3 (control) or 90/40 nl l−1O3(day/night; ozone generated from pure oxygen). Each ozone regime was split into high and low soil nutrient regimes by watering plants with either a 0.05 % or a 0.005% solution of a fertilizer which contained macronutrients and micronutrients.

Fertilization had a strong effect on plant growth, enzyme activities and the expression of ozone‐induced effects at the biochemical level. The activities of PEPC and Rubisco were enhanced about threefold in the plants with high fertilization (HF). Significant effects of ozone were in most cases found only in the older leaves of the plants with low fertilization (LF), There, sucrose, glucose and fructose levels were enhanced. In both fertilization treatments, the number of starch granules along the minor veins was increased. These ozone effects point to a decreased or inhibited phloem loading. The increased PEPC activity and the enhanced malate levels in the ozone‐exposed plants might be the result of a redirection of carbon flow from sucrose synthesis and translocation towards anapleurotic processes, which can feed detoxification and repair of ozone injury as indicated by enhanced respiration. These findings agree well with the observed effects of ozone in lowering the root: shoot biomass ratio. Although there was a marked reduction in the O3/LF plants, O3/HF plants showed no significant response. Inositol was decreased under ozone exposure in both fertilizer treatments, contrasting with the pattern for carbohydrates.

These results demonstrate the role of fertilization as an important modifier of ozone‐induced effects at the plant biochemical level. Well fertilized plants appear to cope better with the impact of ozone on metabolism.
Within‐plant relationships among wounding, jasmonic acid, and nicotine implications for defence in Nicotiana sylvestris
Authors: OHNMEISS THOMAS E. , McCLOUD ERIC S. , LYNDS GLADYS Y. , BALDWIN IAN T.
Published: March 2003

summary

In Nicotiana sylvestris Spegazzini and Comes (Solanaceae), we examined the relationships among wounding, endogenous leaf jasmonic acid (JA) pools, and whole‐plain (WP) nicotine accumulation over a range of wounding intensities and spatial distributions, in order to explore optimal defence (OD) theory predictions. We quantitatively wounded one or four leaves and then quantified: (1) JA in damaged and undamaged leaves 90 min after wounding; (2) WP nicotine concentration after 5 d (the times when JA and nicotine attain the largest wound‐induced concentrations). We find: (1) statistically significant, positive relationships on a leaf‐by‐leaf basis among the number of leaf punctures, endogenous leaf JA, and WP nicotine accumulation; (2) that young, undamaged leaves have a higher concentration of JA than do older, undamaged leaves, and produce a greater amount of JA per puncture than older leaves, but that all leaves have the same JA content (ng JA per leaf); and (3) that a damaged leaf produces less JA when other leaves in the canopy are wounded than when it is the onh wounded leaf in the canopy, but that when it is the only wounded leaf, the phylotactically adjacent, undamaged leaves do not increase their JA concentrations. The observation that younger leaves produce more JA per puncture than do older leaves is consistent with OD theory predictions. The observation that a small amount of damage localized to a single leaf is as effective as a larger amount of damage dispersed across the canopy in increasing leaf JA and WP nicotine accumulation shows the plant's ability to differentiate between dispersed and localized damage. Because the quantity of JA in a wounded leaf 90 min after wounding is a reliable indicator of the WP nicotine response to wounding, this trait provides insight into how plants integrate information about environmental insults and tailor their defence responses.
The effect of u.v.‐B radiation on u.v.‐absorbing secondary metabolites in birch seedlings grown under simulated forest soil conditions
Authors: LAVOLA ANU , JULKUNEN‐TIITTO RIITTA , APHALO PEDRO , DE LA ROSA TANIA , LEHTO TARJA
Published: March 2003

summary

Birch (Betula pendula Roth) seedlings were grown under enhanced u.v.‐B radiation and simulated forest‐soil conditions, after which individual secondary metabolites were determined in the leaves. It was found that not all of the u.v.‐absorbing secondary metabolites of the seedlings responded to supplementary u.v.‐B radiation. Under increased u.v.‐B radiation, significant increases in concentration were observed only for the major flavonoid, quercitrin, the minor fiavonoid, myricetin‐3‐galactoside, and for chlorogenic acid. On the other hand, 3,4′dihydroxypropiophenone‐3‐β‐D‐glucopyranoside decreased under u.v.‐B irradiation. The concentration of phenolic compounds in the leaves changed during the growing season (between two harvests) but this change was not related to u.v.‐B enhancement. A low availability of mineral nutrients did not impair the capacity of the seedlings to accumulate u.v.‐protecting phenolic compounds under increased u.v.‐B radiation. The growth conditions used might have affected the intracellular concentrations of secondary metabolites, and thus furnished the birch seedlings with an increased tolerance of u.v.‐B radiation. These findings point to the significance of certain phenolic components in the protection of deciduous trees against u.v.‐B radiation.
Effects of nitrogen and water limitation and elevated atmospheric CO2on ectomycorrhiza of longleaf pine
Authors: RUNION G. B. , MITCHELL R. J. , ROGERS H. H. , PRIOR S. A. , COUNTS T. K.
Published: March 2003

summary

Longleaf pine (Pinus palustrisMill.) seedlings were exposed to two concentrations of atmospheric CO2(365 or 720 μmol mol−1) and two levels of N (0.02 or 0.20 mg N g−1soil yr−1) within open‐top chambers for 20 months. Seedlings were adequately watered for 19 wk to ensure seedling establishment, after which two water‐stress treatments (target values −0·5 or −1·5 MPa xylem pressure potential) were implemented. Fine‐root samples were collected in July and November 1993, and in March and November 1994. Ectomycorrhizal and non‐mycorrhizal short roots per unit length of fine root were quantified. The percentage of ectomycorrhizal short roots and numbers of ectomycorrhizas per unit root length were higher for seedlings grown with elevated CO2, low N and adequate water. Interactions among main treatment variables demonstrated higher percentages of ectomycorrhizal short roots, fine root length per seedling, and total numbers of ectomycorrhizas per seedling for plants grown with high CO2(compared with ambient) or adequate water (compared with water stress) only under high N conditions. Increased fine‐root length and ectomycorrhizal colonization under elevated CO2resulted in higher (almost double) numbers of ectomycorrhizas per seedling at each sampling.
Soluble acid invertase activity in leaves is independent of species differences in leaf carbohydrates, diurnal sugar profiles and paths of phloem loading
Authors: KINGSTON‐SMITH ALISON H. , GALTIER NATALIE , POLLOCK CHRISTOPHER J. , FOYER CHRISTINE H.
Published: March 2003

Leaf sucrose, starch, hexose and maximum extractable soluble acid invertase activity were compared throughout the day in source leaves of 13 plant species chosen for their putative phloem‐loading type (apoplastic or symplastic). Four species which represent the different phloem‐loading types (tomato, barley, maize and Fuchsia) were studied in detail. Using this information we wished to determine whether a positive correlation between foliar carbohydrates and acid invertase activity exists in leaves from different species and, furthermore, whether this relationship is determined by phloem‐loading type. Acid invertase activity was relatively constant throughout the day in all species. The extent of sucrose, hexose and starch accumulation and the sucrose: starch ratio measured at a given time were species‐dependent. No correlations were found between foliar soluble acid invertase activity and the hexose, sucrose or starch content of the leaves in any of the species, regardless of phloem‐loading type. The species examined could be divided into three distinct groups: (1) high sucrose, low invertase; (2) low sucrose, low invertase; and (3) low sucrose, high invertase. The absence of an inverse relationship between leaf sucrose, hexose or starch contents and endogenous soluble acid invertase suggests that this enzyme is not directly involved in carbon partitioning in leaves but serves an auxiliary function.
Effects of synthetic plant growth retardants and abscisic acid on root functions of Brassica rapa plants exposed to low root‐zone temperature
Authors: BIGOT JACQUES , BOUCAUD JEAN
Published: March 2003

Possible interactions of two synthetic plant‐growth retardants during the short‐term response of Brassica rapa L. ssp. oleifera (DC.) Metzger plants to low root‐zone temperature were investigated by pretreating with mefluidide or paclobutrazol. Water and solute transfers were studied by measuring xylem sap volume flow (under root pressure exudation) and ion flow from the roots. Relations with nitrate uptake rate were also considered. Root pretreatment with paclobutrazol strongly restricted the cold‐inducible processes which normally restore water and solute flow from the root xylem. Paclobutrazol decreased the rates of nitrate uptake and exudation flow from the root xylem (principally by reducing root hydraulic conductivity) with dramatic consequences for ion flow, especially that of nitrate.

The effects of root ABA pretreatment on plant response to root cooling were then studied separately or in association with a pretreatment with paclobutrazol. Despite a slight decrease in nitrate uptake rate, ABA pretreatment of the roots enabled the plant to develop rapid mechanisms for adaptation to cold constraint at the root level. Moreover, this action of exogenous ABA greatly reduced the effect of a simultaneous paclobutrazol pretreatment and partly restored water and solute flows.

Thus, the improvement of plant resistance to cold conditions brought about by treatments with mefluidide and paclobutrazol (previously shown in long‐term experiments) cannot simply be explained by their short‐term effects.
Short‐term polyamine response in TMV‐inoculated hypersensitive and susceptible tobacco plants
Authors: RABITI A. L. , BETTI L. , BORTOLOTTI C. , MARINI F. , CANOVA A. , BAGNI N. , TORRIGIANI P.
Published: March 2003

The short‐term polyamine response to inoculation, with tobacco mosaic virus (TMV), of TMV‐inoculated NN (hypersensitive) and nn (susceptible) plants of Nicotiana tabacum (L.) cv. Samsun was investigated. Free and conjugated polyamine concentrations, putrescine biosynthesis, evaluated through arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) activities, and putrescine oxidation, via diamine oxidase (DAO) activity, were analysed during the first 24 h from inoculation. Results were compared with those of mock‐inoculated control plants. In NN TMV‐inoculated plants undergoing the hypersensitive response (HR), free putrescine and spermidine concentrations had increased after 5 h compared with controls; polyamine conjugates also tended to increase compared with controls. In both virus‐ and mock‐inoculated plants, ADC and ODC activities generally increased whereas DAO activity, which was present in controls, was detectable only in traces in inoculated tissues.

In TMV‐infected susceptible plants, free putrescine and spermidine concentrations were lower at 5 h relative to controls, as were polyamine conjugates. No differences were revealed in ADC and ODC activities whereas DAO activity was not detectable. These results further support the hypothesis that polyamines are involved in the response of tobacco to TMV and that, only a few hours after inoculation, the response of hypersensitive plants is distinct from that of susceptible ones.
First synthesis of ericoid mycorrhizas in the Epacridaceae under axenic conditions
Authors: McLEAN C. B. , ANTHONY J. , COLLINS R. A. , STEINKE E. , LAWRIE A. C.
Published: March 2003

The first axenic synthesis of morphologically typical ericoid mycorrhizas of the Epacridaceae has been achieved in micropropagated Epacris impressa Labill. with eight fungi isolated from roots of two epacrid species, E. impressa and Astroloma pinifolium (R.Br.) Benth. Mycorrhizal synthesis has also been achieved between E. impressa and both Hymenoscyphus ericae (Read) Korf and Kernan and Oidiodendron griseum Robak, recognized endophytes of Ericaceae, suggesting that the endophytes of the Epacridaceae and Ericaceae are capable of cross‐infection. Infection rate of epidermal cells on hair roots varied from 3–77% infection and the density of hyphal coils varied widely. This synthesis makes possible studies of the roles of these endophytes in the Epacridaceae and comparison with their roles in the Ericaceae.
Host and cell type affect the mode of degradation by Meripilus giganteus
Authors: SCHWARZE F. W. M. R. , FINK S.
Published: March 2003

Wood degradation by the white‐rot basidiomycete Meripilus giganteus (Pers.: Pers.) Karst. was studied in naturally infected and artificially inoculated wood of beech (Fagus sylvatica L.) and large‐leaved lime (Tilia platyphyllos Scop.). Semi‐thin sections revealed that the secondary walls of most fibres contained internal cavities. Three distinct types of cavity formation, which differed not only between hosts, but also between cell type and location in the annual ring, were identified.

Within discoloured wood of naturally infected beech, the structure of the cavities and their formation by the associated hyphae were reminiscent of a soft‐rot. By contrast, cavity formation in artificially inoculated beech and large‐leaved lime wood differed from a soft‐rot mode of attack as extensive delignification always preceded cavity formation, and neither T‐branching, L‐bending, nor hyphal growth were found within cell walls. The formation of half‐moon shaped cavities in beech wood was present only in tension‐wood fibres. From large diameter hyphae, growing within the fibre lumen, numerous fine perforation hyphae extended transversely via helical cracks into the cell wall. Subsequent degradation of cellulose within concentric layers of the tension‐wood fibres commenced from the apices of perforation hyphae.

Sections stained with ruthenium red and hydroxlamine‐ferric chloride, revealed that M. giganteus preferentially degrades pectin‐rich regions of the middle lamellae in xylary ray cells. In large‐leaved lime, such regions were uniformly located in the middle lamellae of axial and ray parenchyma. In beech wood, degradation of pectin‐rich middle lamellae regions commenced after the delignification of secondary walls and resulted in a conspicuous hollowing of multiseriate xylem rays. Plasticity in wood degradation modes by M. giganteus in large‐leaved lime and beech wood reflects variations in cell wall structure and/or prevailing wood conditions.
Somatic and genetic factors in sun and shade population differentiation in Plantago lanceolata and Anthoxanthum odoratum
Authors: SIMS DANIEL A. , KELLEY STEVEN
Published: March 2003

Differences between individuals collected from sun and shade populations could result from either somatic or genetic differences, particularly in populations of perennial plants. Our objective in this study was to separate somatic from genetic differences. We collected Anthoxanthum odoratum and Plantago lanceolata from sun and shade populations and made measurements on both vegetatively propagated clones and seed progeny from each clone. The parental populations differed in a wide range of physiological and morphological traits. However, only photosynthetic capacity was significantly different between both the original sun and shade populations and their seed progeny. In both species, plants from the sun population had higher photosynthetic capacities than those from the shade population when grown in a common environment. This demonstrates that there was genetic differentiation between the sun and shade populations. Photosynthetic capacity of parents and offspring also differed, suggesting a somatic effect. Since many of the original clones were virus‐infected, but all but one of the offspring were virus‐free, this might have been a result of virus infection. However, in spite of the fact that the parents and offspring clones were propagated vegetatively so that the plants were at the same developmental stage at the time of measurement, we cannot rule out the possibility that differences in age of cell lines could also have been a factor.
Copper‐deficiency‐induced phytosiderophore release in in the calcicole grass Hordelymus europaeus
Authors: GRIES D. , KLATT S. , RUNGE M.
Published: March 2003

Phytosiderophore (PS) release occurs under both iron and zinc deficiencies in representative Poaceae and has been speculated to be a general adaptive response to enhance the acquisition of micronutrient metals. We tested this hypothesis within an on‐going study of the role of micronutrient metal nutrition for patterns of spontaneous vegetation in relation to soil pH and carbonate content. Hordelymus europaeus (L.) Harz, a negative grass species commonly found on soils rich in CaCO3 in Western Central Europe, was subjected to deficiencies of Fe, Zn, Mn and Cu using chelator‐buffered nutrient solutions. PS release rates were determined at 3–5 d intervals during onset and development of deficiency symptoms. Plant dry matter yields and nutrient concentrations, measured at three time points were used to construct growth curves for calculation of PS release per unit root mass. In comparison with trace metal‐sufficient control plants, dry matter production was markedly reduced in the Fe, Zn, Mn and Cu‐deficiency treatments, with final relative yields of 6, 11, 15 and 31%, respectively. The phytosiderophore produced under Fe‐ and Cu‐deficiency treatments was identified, using HPLC, as desoxymugineic acid. The highest rate of PS release (18 μmol g−1 root d. wt in 2 h) was measured in the Fe‐deficiency treatment, and there was substantial release in the Cu‐deficiency treatment (7·25 μmol g−1 root d. wt in 2 h). No PS release above control levels (2·6 μmol g−1 root d. wt in 2 h) was observed in the Zn‐ or Mn‐deficiency treatments (1·5 and 2·6 μmol g−1 root d. wt in 2 h, respectively). It remains to be clarified whether PS release in response to Cu deficiency is a primary reaction to the deficiency, or is caused by a chain of events similar to that observed in Zn‐deficient wheat, which involves internal Fe deficiency. Our results suggest that PS release in the native plant species H. europaeus is a specific response to Fe and Cu deficiency and is not significantly induced in response to deficiencies of Zn and Mn. Induction of the PS mechanism in different plant species might be more diverse than previously thought.
Sulphate uptake and xylem loading of mycorrhizal beech roots
Authors: KREUZWIESER JÜRGEN , RENNENBERG HEINZ
Published: March 2003

Beech nuts (Fagus sylvatica L.) were germinated and grown in soil inoculated with the ectomycorrhizal fungus Laccaria laccata or Paxillus involutus for 18–20 wk. The success of mycorrhizal infection was monitored by measuring the ergosterol contents of the mycorrhizas. Ergosterol levels ranged from 122±23 μg g−1 d. wt (Laccaria mycorrhizas) to 94±36 μg g−1 d. wt (Paxillus mycorrhizas), indicating that ectomycorrhizal symbiosis was established. In root incubation chambers, rates of sulphate uptake and the xylem loading of sulphate of excised mycorrhizas were investigated. Both types of mycorrhizas showed saturation kinetics in external sulphate concentrations from 2·5–1000 μmol l−1. Linearization of these kinetics revealed two phases with low apparent Km (Laccaria mycorrhizas: 15±3 μmol l−1; Paxillus mycorrhizas: 13±3 μmol l−1) and Vmax (Laccaria mycorrhizas:
19±3 nmol h−1 g−1 f. wt; Paxillus mycorrhizas: 25±4 nmol h−1 g−1 f. wt) at low external sulphate concentrations and significantly higher kinetic constants at higher sulphate supplies. Relative xylem loading, i.e. the portion of sulphate loaded into the xylem that was taken up, remained constant over the entire concentration range investigated (c. 4–7% of the sulphate taken up). If trees were supplied for 72 h with different N and sulphur concentrations, both uptake of sulphate and relative xylem loading were unaffected by sulphur availability, but modulated by N supply. Nitrogen depletion diminished the rates of sulphate uptake in Laccaria and Paxillus mycorrhizas. In response to higher N availability combined with sulphur depletion, sulphate uptake of Laccaria mycorrhizas, but not of Paxillus mycorrhizas, increased. Organic compounds considered to be possible signals for the regulation of sulphate uptake were fed to excised mycorrhizas. l‐Cysteine but not l‐methionine and glutathione (γ‐Glu‐Cys‐Gly) inhibited sulphate uptake of the two mycorrhizas and xylem loading of sulphate was stimulated rather than inhibited by l‐Cys in both types. In Paxillus mycorrhizas glutathione had a similar effect. O‐Acetyl‐l‐serine (OAS), a precursor of l‐cysteine, stimulated sulphate uptake, but did not affect xylem loading. Apparently, OAS, generated in N metabolism, and l‐cysteine, a product of assimilatory sulphate reduction, act as antagonists, together mediating regulation of sulphate uptake.
Isolation and characterization of nitrate reductase deficient mutants of the ectomycorrhizal fungus Hebeloma cylindrosporum
Authors: MARMEISSE ROLAND , JARGEAT PATRICIA , WAGNER FRANÇOISE , GAY GILLES , DEBAUD JEAN‐CLAUDE
Published: March 2003

To clarify the role of the fungal nitrate assimilation pathway in nitrate reduction by mycorrhizal plants, nitrate reductase (NR)‐deficient (NR−) mutants of the ectomycorrhizal basidiomycete Hebeloma cylindrosporum Romagnesi have been selected. These mutants were produced by u.v. mutagenesis on protoplasts originating from homokaryotic mycelia belonging to complementary mating types of this heterothallic tetrapolar species. Chlorate‐resistant mutants were first selected in the presence of different nitrogen (N) sources in the culture medium. Among 1495 chlorate resistant mycelia, 30 failed to grow on nitrate and lacked a detectable NR activity. Growth tests on different N sources suggested that the NR activity of all the different mutants is specifically impaired as a result of mutations in either the gene coding for NR apoprotein or genes controlling the synthesis of the molybdenum cofactor. Furthermore, restoration of NR activity in some of the dikaryons obtained after crosses between the different mutant mycelia suggested that not all the selected mutations mapped in the same gene. Utilization of N on a NH415NO3 medium was studied for two mutant strains and their corresponding wild‐type homokaryons. None of the mutants could use nitrate whereas 15N enrichment values indicated that 13–27% of N present in 13‐d‐old wild‐type mycelia originated from nitrate. Apparently, the mutant mycelia do not compensate their inability to use nitrate by a more efficient use of ammonium. These different NR mutants still form mycorrhizas with the habitual host plant, Pinus pinaster (Ait.), making them suitable for study of the contribution of the fungal nitrate assimilation pathway to nitrate assimilation by mycorrhizal plants.
Copper–zinc superoxide dismutase is a constituent enzyme of the matrix of peroxisomes in the cotyledons of oilseed plants
Authors: CORPAS FRANCISCO J. , SANDALIO LUISA M. , DEL RÍO LUIS A. , TRELEASE RICHARD N.
Published: March 2003

The number and type of isoforms of superoxide dismutase (SOD) and their activities were compared in mitochondria and peroxisomes isolated from cotyledons of three different oilseed seedlings. Mitochondrial and peroxisomal isoforms of SOD could be distinguished in nondenaturing polyacrylamide gels by their differential sensitivities to KCN and/or H2O2. The type of SOD was not the same for each organelle in each of the three oilseed species. For example, a single Mn–SOD was found in cotton and cucumber mitochondria, whereas four CuZn–SODs were present in mitochondria from sunflower. At least one CuZn–SOD isoform was found in the peroxisomes of all three species. Cucumber peroxisomes contained both a CuZn–SOD and a Mn–SOD, cotton peroxisomes contained a single CuZn–SOD, whilst four separate CuZn–SODs, but no Mn–SOD were found in sunflower peroxisomes. Using antibodies against CuZn–SOD from watermelon peroxisomes or from chloroplasts of Equisetum, a single polypeptide of c. 16·5 kDa was detected on immunoblots of peroxisomal fractions from the three species. Post‐embedment, electron‐microscopic double immunogold‐labelling showed that CuZn–SOD, with malate synthase used as marker enzyme of peroxisomes, was localized in the matrix of these organelles of all three species. These results suggest that CuZn–SOD is a characteristic matrix enzyme of peroxisomes in oilseed cotyledons.
The response of clones of Populus tremuloides differing in sensitivity to ozone in the field
Authors: YUN SUNG‐CHUL , LAURENCE JOHN A.
Published: March 2003

Ozone (O3)‐sensitive and tolerant clones of aspen (Populus tremuloides) were exposed to O3 at 1.0, 1.7 and 3.0 times the concentration in ambient air at Ithaca, NY, USA (×1.0, ×1.7 and ×3.0) for 3 months. Visible foliar injury occurred within a few days of the initiation of treatments and developed continuously in ×1.7 and ×3.0 treatments. Leaf senescence began earlier in trees exposed to greater‐than‐ambient treatments. Gas‐exchange variables were measured five times over the growing season. Net photosynthesis was progressively decreased and finally reduced by 40 and 70% on tolerant and sensitive clones, respectively, but stomatal conductance was not affected by the O3 treatments. As stomatal conductance (gs) values did not differ in the two types of aspen, we conclude that this is not the defense mechanism to O3 in aspen. At the end of the season, dry weight was reduced by up to 55 and 35% in sensitive and tolerant clones, respectively. Ozone effects were significant and linear on foliar injury, biomass and growth variables such as height, diameter of stem and total leaf area. The levels of two antioxidants, ascorbic acid and glutathione, were investigated to determine if a clonal difference occurred. Concentrations of the free‐radical scavengers did not differ in the clones, nor did they seem to be induced by O3. A cumulative O3 index, SUM06 (the sum of the total μl l−1 of exposure when the O3 concentration exceeded 0.06 μl l−1), was highly correlated with most foliar injury variables and gas‐exchange variables except gs in higher O3 treatments. The reduction of carbon gain due to O3 is discussed with regard to foliar damage and biomass decrease.
Ectomycorrhizal transfer of amino acid‐nitrogen to the alpine sedge Kobresia myosuroides
Authors: LIPSON DAVID A. , SCHADT CHRISTOPHER W. , SCHMIDT STEVEN K. , MONSON RUSSELL K.
Published: March 2003

Previous work in the Colorado alpine ecosystem has shown that amino acids are a potentially important N source for the sedge, Kobresia myosuroides. This plant is the only known sedge to harbour associations with ectomycorrhizal fungi. The aim of the present work was to test the hypothesis that these ectomycorrhizas transfer N from amino acids in the soil solution to the host plant, and thereby have an important role in the N nutrition of this species. We used a two‐chamber system (rhizoboxes) in which K. myosuroides plants were separated from a soil chamber by nylon mesh that allowed fungal hyphae, but not plant roots, to cross it. Injections of [15N, 2‐13C]glycine were made into the soil chamber. The hyphal crossings on half of the rhizoboxes were regularly disrupted to control for leakage of label across the barrier. Plants in the intact rhizoboxes showed significantly higher 15N enrichment than those in controls, and mycorrhizal root tips were significantly more enriched than bulk roots. The mycorrhizas transferred an average of 1.3% of the added 15N label to plants, a figure comparable to those obtained in previous studies in which plant roots were directly exposed to label. We conclude that fungal associations have an important role in the N nutrition of K. myosuroides by transferring N from amino acids to their hosts.