bluuebunny/crossref_metadata_2025_split huggingface dataset:
Astrocyte–endothelial interactions and blood–brain barrier permeability
Authors: Abbott N. J. 
Published: March 2003

The blood–brain barrier (BBB) is formed by brain endothelial cells lining the cerebral microvasculature, and is an important mechanism for protecting the brain from fluctuations in plasma composition, and from circulating agents such as neurotransmitters and xenobiotics capable of disturbing neural function. The barrier also plays an important role in the homeostatic regulation of the brain microenvironment necessary for the stable and coordinated activity of neurons. The BBB phenotype develops under the influence of associated brain cells, especially astrocytic glia, and consists of more complex tight junctions than in other capillary endothelia, and a number of specific transport and enzyme systems which regulate molecular traffic across the endothelial cells (Abbott & Romero, Mol. Medical Today2, 1996). Transporters characteristic of the BBB phenotype include both uptake mechanisms (e.g. GLUT‐1 glucose carrier, L1 amino acid transporter) and efflux transporters (e.g. P‐glycoprotein, MRP). In addition to their role in long‐term barrier induction and maintenance, astrocytes and other cells can release chemical factors that modulate endothelial permeability over a timescale of seconds to minutes.Cell culture models, both primary and cell lines, have been used to investigate aspects of barrier induction and modulation. Conditioned medium taken from growing glial cells can reproduce some of the inductive effects, evidence for involvement of diffusible factors. However for some features of endothelial differentiation and induction the extracellular matrix plays an important role. Several candidate molecules have been identified capable of mimicking aspects of glial–mediated barrier induction of brain endothelium; these include TGF(GDNF, bFGF, IL‐6 and steroids. In addition factors secreted by brain endothelial cells including leukaemia inhibitory factor (LIF) have been shown to induce astrocytic differentiation. Thus endothelium and astrocytes are involved in 2‐way mutual induction. Short‐term modulation of brain endothelial permeability has been shown for a number of small chemical mediators produced by astrocytes and other nearby cell types. Thus endothelial cells are involved in both long and short‐term chemical communication with neighbouring cells, with the perivascular end feet of astrocytes being of particular importance. The role of barrier induction and modulation in normal physiology and in pathology will be discussed.
Regional variations in the cellular matrix of the annulus fibrosus of the intervertebral disc
Authors: Bruehlmann Sabina B. , B. Rattner Jerome , R. Matyas John , A. Duncan Neil 
Published: March 2003

AbstractThe three‐dimensional architecture of cells in the annulus fibrosus was studied by a systematic, histological examination using antibodies to cytoskeletal components, in conjunction with confocal microscopy. Variations in cell shape, arrangement of cellular processes and cytoskeletal architecture were found both within and between the defined zones of the outer and inner annulus. The morphology of three, novel annulus fibrosus cells is described: extended cordlike cells that form an interconnected network at the periphery of the disc; cells with extensive, sinuous processes in the inner region of the annulus fibrosus; and cells with broad, branching processes specific to the interlamellar septae of the outer annulus. The complex, yet seemingly deliberate arrangement of various cell shapes and their processes suggests multiple functional roles. Regional variations in the organization of the actin and vimentin cytoskeletal networks is reported across all regions of the annulus. Most notable is the continuous, strand arrangement of the actin label at the disc's periphery in contrast to its punctate appearance in all other regions. The gap junction protein connexin 43 was found within cells from all regions of the annulus, including those which did not form physical connections with surrounding cells. These observations of the cellular matrix in the healthy intervertebral disc should contribute to a better understanding of site‐specific changes in tissue architecture, biochemistry and mechanical properties during degeneration, injury and healing.
Hyoid apparatus and pharynx in the lion (Panthera leo), jaguar (Panthera onca), tiger (Panthera tigris), cheetah (Acinonyx jubatus) and domestic cat (Felis silvestris f. catus)
Authors: Weissengruber G. E. , Forstenpointner G. , Peters G. , Kübber‐Heiss A. , Fitch W. T. 
Published: March 2003

AbstractStructures of the hyoid apparatus, the pharynx and their topographical positions in the lion, tiger, jaguar, cheetah and domestic cat were described in order to determine morphological differences between species or subfamilies of the Felidae. In the lion, tiger and jaguar (species of the subfamily Pantherinae) the Epihyoideum is an elastic ligament lying between the lateral pharyngeal muscles and the Musculus (M.) thyroglossus rather than a bony element like in the cheetah or the domestic cat. The M. thyroglossus was only present in the species of the Pantherinae studied. In the lion and the jaguar the Thyrohyoideum and the thyroid cartilage are connected by an elastic ligament, whereas in the tiger there is a synovial articulation. In adult individuals of the lion, tiger and jaguar the ventral end of the tympanohyal cartilage is rotated and therefore the ventral end of the attached Stylohyoideum lies caudal to the Tympanohyoideum and the cranial base. In newborn jaguars the Apparatus hyoideus shows a similar topographical position as in adult cheetahs or domestic cats. In adult Pantherinae, the Basihyoideum and the attached larynx occupy a descended position: they are situated near the cranial thoracic aperture, the pharyngeal wall and the soft palate are caudally elongated accordingly. In the Pantherinae examined the caudal end of the soft palate lies dorsal to the glottis. Differences in these morphological features between the subfamilies of the Felidae have an influence on specific structural characters of their vocalizations.
Central control of upper airway resistance regulating respiratory airflow in mammals
Authors: Paton Julian F. R. , Dutschmann Mathias 
Published: March 2003

AbstractThis article reviews recent studies on the importance of glycine receptors for both the spontaneous and the reflex respiratory modulation of the laryngeal abductors and adductors. Our findings show that strychnine blockade of glycine receptors within the brainstem changes the eupneic three‐phase respiratory pattern into two phases. This has major implications for glottal control: (i) the inspiratory glottic abduction and early expiratory adduction were both compromised – a finding mimicked by 5% hypoxia; (ii) closure of the glottis during defensive upper airway reflexes became intermittent and the reflex apnoea reversed to sustained inspiratory discharge. Based on these data, we predict that periods of prolonged hypoxia, such as those that occur during sleep apnoeas, will constrain inspiratory glottic abduction thereby impeding inhalation.
Use of sugars by intraradical hyphae of arbuscular mycorrhizal fungi revealed by radiorespirometry
Authors: SOLAIMANAND MD. ZAKARIA , SAITO MASANORI 
Published: March 2003

summaryEvolution of 14CO2 from onion roots and the intraradical hyphae of Gigaspora margarita Becker & Hall was examined by radiorespirometry after addition of 14C‐labelled glucose or sucrose to mycorrhizal or non‐mycorrhizal roots. In mycorrhizas, the respiration rate from glucose was about twice that from sucrose. The respiration rate from glucose in the mycorrhizas was much higher than that in the non‐mycorrhizal roots, but no differences between mycorrhizal and non‐mycorrhizal roots were found in the respiration from sucrose. Intraradical hyphae were isolated from mycorrhizas by enzyme digestion and homogenization followed by Percoll® gradient centrifugation. The 14C‐labelled glucose, fructose or sucrose was added to the isolated hyphae and the subsequent evolution of 14CO2 was measured. The hyphae mainly used glucose as a substrate for respiration. Although sucrose or fructose was utilized to some degree, the respiration rate from glucose was much higher than that from sucrose and fructose. This is the first direct evidence of use of glucose by the intraradical hyphae of arbuscular mycorrhizal fungi in the symbiotic state.
Growth, phosphorus uptake, and water relations of safflower and wheat infected with an arbuscular mycorrhizal fungus
Authors: BRYLA D. R. , DUNIWAY J. M. 
Published: March 2003

SUMMARYSafflower (Carthamus tinctorius L. cv. S555) and spring wheat (Triticum aestivum L. cv. Anza) were grown with or without the arbuscular mycorrhizal fungus Glomus etunicatum Becker & Gerd., under environmentally controlled conditions. Soil phosphate concentrations were adjusted before planting to produce mycorrhizal (M) and non‐mycorrhizal (NM) plants that had similar leaf areas and root length densities at the same stage of development before initiating drought stress treatments. Drought did not affect the amount of mycorrhizal infection in safflower or wheat. Interactions between water stress treatments and mycorrhizal infection on plant growth and phosphorus uptake were limited and only occurred in wheat. NM wheat plants had 28% greater shoot d. wt, slightly greater root length densities, and 39% greater P acquisition than M plants when grown under well watered conditions, but under droughted conditions plant size and tissue P contents of M and NM wheat plants were similar. Mycorrhizas did not affect stomatal behaviour during drought stress in either safflower or wheat, i.e., transpiration and stomatal conductance declined independently of infection as soil water was depleted and leaf water potentials declined. Therefore, mycorrhizal infection did not alter the intrinsic hydraulic properties of the plant/soil system. Whilst wheat maintained turgor of recently expanded leaves during severe drought and safflower did not, mycorrhizal infection had no effect on leaf turgor during drought in either plant species.
Responses of ground vegetation to prolonged simulated acid rain in sub‐arctic pine—birch forest
Authors: SHEVTSOVA A. , NEUVONEN S. 
Published: March 2003

SUMMARYThe effects of prolonged simulated acid rain on percentage cover of ground vegetation, and on growth and reproduction of two dominating dwarf shrubs (Emapetrum nigrumandVaccinium vaitisidaea)were examined in a field experiment in the Finnish Subarctic, in an area with low ambient levels of sulphur and nitrogen deposition. Acid rain treatments included moderate (pH 3.8) and high (pH 2.9) concentrations of either H2SO4, or HNO3, or a mixture of them, and were compared with irrigated (pH 6) and dry control plots.Long‐term application of acid rain caused significant alteration in the cover and composition of ground vegetation. Effects of acid ram depended on the accompanying anion and on pH. Sub‐plots under different canopy tree species differed in responses indicating that spatial heterogeneity is important in predicting the effect of acidifying pollution on this plant community.In the bottom layer, acid rain caused significant reduction in cover of the cyanobacterial lichensNephroma arcticumandPeltigeraspp. Decrease in cover of fruticose lichens, mainly composed ofCladinaspp., more likely resulted from additional watering.In the field layer, acid rain containing moderate concentrations of NO−3caused an increase in cover of graminoid species. There were only slight alterations in growth and cover of the two dominant evergreen dwarf shrubs,EnigrumandV. vitis‐idaea, indicating that these species are tolerant to acid rain of as low as pH 3. Even some positive responses of dwarf shrubs were observed, depending on canopy tree. Application of acid rain of pH 3 to plots under pine trees caused an increase in cover of I,vitis‐idaeaand, when the nitric acid only was applied, a short‐term increase in the number of new shoots ofE. nigrum.In contrast to vegetative growth, reproduction of the dwarf shrubs was more strongly affected by acid rain, but this also depended on local conditions and anion composition of acid rain. On ‘pine’ plots, rain of pH 3 reduced the number of berries and flower buds on terminal current shoot ofE. nigrum, however, this was partially compensated by an increase in berry production at the ramet level. Simulated acid rain had mainly negative effects on berry production byV. vitis‐idaea.
The use of longitudinal data analysis to study the multi‐seasonal growth responses of Norway and Sitka spruce to summer exposure to ozone: implications for the determination of critical levels
Authors: LUCAS PETER W. , DIGGLE PETER J. 
Published: March 2003

summaryA common feature of many pollutant exposure studies is that data from these experiments often consist of either plant biomass or yield, and the response to the pollutant is usually based on a simple comparison of means determined at the end of each growing season. This type of data is now being used to quantify critical levels for different types of vegetation. Such an approach is, however, inappropriate for the relatively short‐term exposure studies with trees since, due to their longevity, it is nor possible to determine a final yield. Instead these studies should be regarded as a type of intervention experiment in which only a small part of the life cycle of the tree is investigated. Moreover, critical levels as they are now defined focus on the cumulative exposure to ozone concentrations over time. Hence, any analysis of the effects of ozone on the growth of trees should similarly focus on the behaviour of growth functions over time and not on a comparison of biomass at the end of a growing season or experiment.Here we report on the statistical analysis of a longitudinal study, where the term ‘longitudinal’ refers to the analysis of repeated measurements over time, and which was used to investigate relative differences in the growth of Sitka spruce and Norway spruce seedlings during three summers'exposure to ozone over three (Norway) or four (Sitka) growing seasons. Measurements of total seedling height and stem diameter were made at frequent intervals over the period of the experiment and the above‐ground growth of individual trees (as log d2h) analysed for each growing season using a statistical model of the form:m(t) = a + b(t ‐ t0), No statistically significant differences in the growth of Norway spruce were observed after three summers of ozone exposure. The growth of Sitka spruce was, however, reduced by ozone during the third growing season and in the following year, even in the absence of the pollutant.For the Sitka spruce, the fitted model was used to calculate the time at which a 10% reduction in growth had occurred in the ozone‐exposed trees. In combination with ozone AOT40 indices for the relevant growing seasons, this was then used to determine a critical level of 21.3 ppm‐h for this species. Since the growth of the Norway spruce was unaffected by exposure to ozone it was not possible to calculate a critical level other than to surmise that it is in excess of 30 ppm‐h.
On the response of pigments and antioxidants of Pinus halepensis seedlings to Mediterranean climatic factors and long‐term ozone exposure
Authors: ELVIRA SUSANA , ALONSO ROCÍO , CASTILLO FEDERICO J. , GIMENO BENJAMÍN S. 
Published: March 2003

An experiment was carried out in open‐top chambers located in eastern Spain. One‐yr‐old Pinus halepensis Mill. seedlings were exposed during three consecutive summers to the following ozone (O3) treatments: charcoal‐filtered air (CFA), non‐filtered air (NFA) or non‐filtered air plus 40 nl l−1 O3, 9 h d−1, 5 d wk−1 (NFA+40). Seasonal variations in Aleppo pine performance were observed since reductions in chlorophyll and cellular peroxidase levels associated with increases in superoxide dismutase activity, were recorded during the summer. Similarly, a reduction in epoxidation state was found at midday during the summer, derived from an activation of the xanthophyll cycle associated to an increment in radiation and temperature levels.The first O3‐induced effects were recorded in previous‐year needles (1991) during the first summer exposure as an increase in extracellular and total peroxidase activities and in zeaxanthin levels in the NFA+40 treatment along with a trend to a higher SOD activity in this treatment. A carry‐over effect was detected since a lower winter recovery of chlorophyll levels was found in the NFA+40 seedlings along with a reduction of xanthophyll levels. A reduction in chlorophyll levels was observed in the previous‐year needles (1992) from the NFA+40 treatment at the end of the second fumigation period. Realistic ozone exposures induced alterations in plant antioxidative systems and plant pigments as shown in this paper. These observations together with the reductions in stomatal conductance and net photosynthesis recorded in the same experiment, indicate that Aleppo pine is a species sensitive to ozone.
A new dawn – the ecological genetics of mycorrhizal fungi
Authors: TAYLOR D. LEE 
Published: March 2003

Many human activities, such as ore mining and smeltering, sewage sludge treatment and fossil fuel consumption, result in toxic soil concentrations of ‘heavy metals’ (Al, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ti, Zn and others) (Gadd, 1993). There are also natural soils, such as serpentine, with levels of heavy metals that inhibit or preclude the growth of many plants and soil micro‐organisms. However, certain plants and microorganisms do grow in these metalliferous sites. Understanding the physiology, ecology and evolution of tolerance to elevated soil metal concentrations is important in an applied setting, and is also of interest in theoretical biology. Applied importance relates to the improvement of forest health in areas subject to increasing pollution, rehabilitation of severely polluted sites by phytostabilization of metals, and metal removal using hyperaccumulating plants (Krämer, 2000; Ernst, 2000). Areas of theoretical interest include the evolution of local adaptation (Sork et al., 1993) and how it is shaped by the combined influences of natural selection, gene flow and genetic architecture, as well as metal influences on various species interactions (Pollard, 2000). A paper appears on pages 367–379 in this issue by Jan Colpaert and coworkers which adroitly combines the disparate fields of physiology, genetics and ecology to answer several outstanding questions concerning heavy metal tolerance in mycorrhizal fungi.Mycorrhizal fungi, which interact mutualistically with the majority of plant species, are well known for improving the P status of their hosts (Smith & Read, 1997). Some mycorrhizal fungi are also able to mobilize N and P from organic substrates and to provide plants with improved micronutrient and water acquisition, pathogen resistance, and a variety of other benefits (Smith & Read, 1997). One of these additional benefits is the amelioration of toxicity in metalliferous soils.
Growth response of Mountain birch to air and soil temperature: is increasing leaf‐nitrogen content an acclimation to lower air temperature?
Authors: Weih M. , Karlsson P. S. 
Published: March 2003

Summary

Growth and nitrogen (N) economy of mountain birch are reported here in response to temperature change. Mechanisms of temperature effects on plant growth in temperate–arctic regions are discussed in the light of decreasing growth rates and increasing leaf‐N contents along altitudinal and latitudinal temperature gradients.
Mountain birch ( Betula pubescens ssp. czerepanovii) seedlings were grown at two soil temperatures, air temperatures and nutrient concentrations in a full‐factorial experiment during one growing season in northern Sweden.
Changes in air and soil temperature affected aboveground growth more than belowground growth. An increase in air temperature increased leaf area ratio and plant‐N productivity while decreasing plant‐N concentration and leaf‐N content. A change in soil temperature affected root‐N uptake rate and plant‐N concentration, similar to the effect of a change in nutrient supply. Air and soil temperature had interactive effects on growth rate, N productivity and leaf‐N content.
The results indicate that increasing leaf‐N content with increasing altitude and latitude is not only a passive consequence of weaker N dilution by reduced growth, but also a physiological acclimation to lower air temperature.
Leaf gas exchange responses of 13 prairie grassland species to elevated CO2 and increased nitrogen supply
Authors: Lee Tali D. , Tjoelker Mark G. , Ellsworth David S. , Reich Peter B. 
Published: March 2003

Summary

Leaf gas exchange responses to elevated CO2 and N are presented for 13 perennial species, representing four functional groups: C3 grasses, C4 grasses, legumes, and nonleguminous forbs. Understanding how CO2 and N effects interact is important to predict plant community response to global change.
Plants were field‐grown in monoculture under current ambient and elevated (560 µmol mol−1) CO2 concentrations (free‐air CO2 enrichment), in combination with soil N treatments, for two growing seasons.
All species, regardless of functional group, showed pronounced photosynthetic acclimation to elevated CO2, resulting in minimal stimulation of photosynthesis (A) averaging +15% in C3 grasses, +8% in forbs, +7% in legumes and −2% in C4 grasses. The effects of CO2 and soil N supply did not interact for any leaf traits measured. Elevated CO2 consistently decreased stomatal conductance (gs) leading to 40% increase in A/gs.
This substantial acclimation of photosynthesis was greater in magnitude than in most field studies, and was associated with the combined effects of decreased gs and decreased leaf N concentrations in response to growth under elevated CO2.
Evaluation of a maltodextrin gel as a partial replacement for fat in a high‐ratio white‐layer cake
Authors: Conforti Frank D. , Archilla Leslie 
Published: March 2003

AbstractThe performance of maltodextrin gel as a replacement (25%, 50%, 75% and 100%) for shortening along with sucrose and high fructose corn syrup‐90 (HFCS‐90), adjusted for sweetness in each treatment, was evaluated in a high‐ratio white‐layer cake formulation. Two controls were used as a reference to fat‐replaced cakes: control A (100% fat and 100% sucrose) and control B (100% fat with 50% sucrose/50% HFCS‐90), which closely matched the sugar system of the fat‐replaced cakes. Volume of cakes showed that treatment F (100% fat‐substituted) was significantly (P< 0.05) different from the other treatments. Crust and crumb L‐ and b‐values indicated that control B produced a dark crust (P< 0.05) with a light crumb (P< 0.05) whereas treatment E (75% fat substituted) produced a light crust (P< 0.05) and treatment F a darker crumb (P< 0.05) with a significantly (P< 0.05) higher moisture content. Degree of staling significantly (P< 0.05) increased over time for all treatments. Sensory results indicated that treatment F produced a significantly (P< 0.05) moister, less adhesive and cohesive cake. Tenderness and sweetness scores indicated that treatments E and F were significantly (P< 0.05) tougher and less sweet, respectively, when compared with the other treatments. Results from both the physical and sensory analyses indicated that the combination of maltodextrin gel up to a 75% reduction for shortening and sucrose/HFCS‐90 resulted in satisfactory cakes.