bluuebunny/crossref_metadata_2025 huggingface dataset:
Varying the ratio of 15N‐labelled ammonium and nitrate‐N supplied to creeping bent: effects on nitrogen absorption and assimilation, and plant growth
Authors: BAILEY J. S.
Published: March 2003

The relative rates of ammonium and nitrate‐N uptake and assimilation by creeping bent (Agrostis stolonifera), were investigated for plants grown in soil and supplied with three different ratios of ammonium and nitrate‐N. Following two preliminary defoliations, plants were supplied with the equivalent of 150 kg N ha−1, given as 15N‐(differentially) labelled NH4+ and NO3−‐N in three different ratios (20:80, 50:50 and 80:20), followed by sequential destructive harvests of shoots and roots at four points during a 35‐d regrowth period. Maximum use of labelled nitrogen and ‘exhaustion’ of soil mineral nitrogen reserves occurred much earlier when plants were supplied with half or more of their nitrogen as ammonium, than occurred when they were supplied predominately with nitrate‐N. The lack of consistency in the patterns of ammonium and nitrate‐N absorption, however, implied that the plants had no specific preference for either nitrogen form. Supplying plants with different combinations of ammonium and nitrate produced distinctive differences in plant morphology. In the high nitrate treatment, plants preferentially partitioned resources into shoot and stolon formation, whereas in the high ammonium treatment, resources were preferentially partitioned into root production. These changes in plant morphology might be adaptations to aid species survival in environments associated with a predominance of either nitrogen form.
Effects of salinization on nutrient transport to lettuce leaves: consideration of leaf developmental stage
Authors: LAZOF DENNIS B. , BERNSTEIN NIRIT
Published: March 2003

Most recent reviews of plant salinity response have included the concept of a nutritional disturbance as one likely mechanism by which shoot growth might be inhibited. None the less, few studies of dicotyledonous plants have presented data on nutrient transport into the most intensively growing shoot tissues. In this paper net nutrient deposition was followed for 3 d in 8 sequential, growing leaves of Lactuca sativa, which were grown either in conditions of moderate salinization, or in a growth‐stimulating concentration of NaCl. The nutrient deposition was studied from 0.7 to 3.7 d following completion of stepwise salinization. This deposition was followed in immature leaves, which had attained only 1–2% of ultimate leaf mass by the completion of the study. In such young leaves development is still dominated by cell division. The transport of Ca2+ specifically to the youngest leaves was reduced by more than twice as much as was K+ transport. Transport of the other major divalent cationic nutrient, Mg2+, was not decreased for these leaves. The factors of increase for Na+ and Cl− after 3.7 d after completion of salinization averaged 152 and 62% over control levels for the three youngest leaves (for Na+ and Cl−, respectively). Though significant, these increases were only 27 and 14% as great as increases in three leaf sets of more developed growing leaves. Decreases in net K+ deposition and leaf K+ concentration were not greater for the youngest than they were for the oldest leaves. Net S deposition was reduced 44% more in younger than older growing leaves, but for most leaves not beyond the level expected due to reduced sink strength. The reduction in net P deposition also seemed more related to reduced sink strength, but was reduced to approx. 50% in both younger and more developed growing leaves. While Fe concentration was not reduced by salinization at any developmental stage, Zn2+ net transport and Zn concentration were both reduced in the two youngest leaves (57 and 70%, respectively). Given the moderate treatment imposed (Na:Ca ratio of 22) the results suggest that Ca2+ transport to the youngest leaves is probably highly sensitive to salinization of the root medium and is perhaps a key physiological response in the inhibition of leaf growth.
Translocation of 32P between interacting mycelia of a wood‐decomposing fungus and ectomycorrhizal fungi in microcosm systems
Authors: LINDAHL BJÖRN , STENLID JAN , OLSSON STEFAN , FINLAY ROGER
Published: March 2003

Interactions between saprotrophic and ectomycorrhizal fungi have been largely ignored, although their mycelia often share the same microsites. The mycelial systems show general similarity to each other and, although the enzymatic potential of the saprotrophic fungi is generally considered to be higher, the importance of organic nutrient sources to ectomycorrhizal fungi is now widely accepted. In the experiments described here, nutritional interactions involving transfer of elements from one mycelium to the other have been monitored dynamically using radioactive tracers and a non‐destructive electronic autoradiography system. Microcosms were used in which mycelial systems of the ectomycorrhizal fungi Suillus variegatus and Paxillus involutus, extending from Pinus sylvestris host plants, were confronted with mycelia of the saprotroph Hypholoma fasciculare extending from wood blocks. The fungi showed a clear morphological confrontation response. The mycorrhizal mycelium often formed dense patches over the Hypholoma mycelia. Up to 25% of the 32P present in the Hypholoma mycelium was captured by the mycorrhizal fungi and translocated to the plant host within 30 d. The transfer of 32P to the saprotroph from labelled mycorrhizal mycelium was one to two orders of magnitude lower. The significance of this transfer as a ‘short cut’ in nutrient cycling is discussed.
Effects of resource availability, and fruit and ovule position on components of fecundity in Alliaria petiolata (Brassicaceae)
Authors: SUSKO DAVID J. , LOVETT‐DOUST LESLEY
Published: March 2003

In four field and glasshouse experiments designed to alter the supply of resources through manipulation of nutrients, root tissue, leaf area and fruit number in Alliaria petiolata (Brassicaceae), more than 99% of ovules per plant showed signs of fertilization, suggesting that seed production in this plant was not pollen limited. However, in all treatments a significant proportion of fruits and seeds did not develop to maturity. Total fruit and seed production did not differ significantly from controls when plants were given nutrient supplements at flowering. Removal of 50–75% of the root tissue in 1‐yr‐old plants significantly reduced fruit set, but had no effect on individual seed development. Removal of cauline leaves significantly reduced most measures of fruit and seed production, suggesting that current photosynthate is critical for fruit and seed filling. Seed maturation was significantly affected by both fruit position within an infructescence and ovule position within a fruit. Basally located fruits and ovules (within fruits) developed more mature seeds than distally positioned fruits and ovules. Plants responded to removal of basal fruits by re‐allocating resources to distal fruits that would normally have aborted. Our results suggest that fruits and seeds act as reproductive sinks competing for parental photosynthate. Patterns of resource allocation within infructescences and fruits were also modified by our experiments.
Anatomy and mycotrophy of the achlorophyllous Afrothismia winkleri
Authors: IMHOF S.
Published: March 2003

Afrothismia winkleri develops fleshy rhizomes, densely covered with small root tubercles, narrowing to filiform roots with age. The exclusively intracellular mycorrhizal fungus has distinct morphologies in different tissues of the plant. In the filiform root the hyphae grow straight and vesicles are borne on short hyphal stalks. The straight hyphae are present in the epidermis of the root tubercles, but change to loosely coiled and swollen hyphae in the rhizome tissue. No penetration from epidermis to root cortex was found. From the rhizome, a separating cell layer permits only one or rarely two hyphal penetrations into the cortex of each root tubercle. The hyphae proceed apically within the root hypodermis in a spiral row of distinctively coiled hyphae, branches of which colonize the inner root cortex. In the inner root cortex the hyphal coils degenerate to amorphous clumps. In older roots the cortex itself also deteriorates, but epidermis, hypodermis, endodermis and central cylinder persist. The mycorrhizal pattern in A. winkleri is interpreted as an elaborate exploitation system whereby the fungus provides carbon and nutrients to the plant and, simultaneously but spatially distinct, its hyphae are used to translocate and store the matter within the plant. Several features indicate that the endophyte is an arbuscular mycorrhizal fungus.
Seasonal protease activity in storage tissue of the deciduous grass Molinia caerulea
Authors: THORNTON B. , BAUSENWEIN U.
Published: March 2003

Plants of Molinia caerulea were grown in sand culture for two seasons. All nitrogen (N) supplied to the plants was enriched with 15N throughout the first season, and at natural isotopic abundance throughout the second season. A series of destructive harvests was taken during the second season. At each harvest, the N mobilized from roots and swollen basal internodes and the protease activity (ability to degrade azocasein) of these storage tissues were measured. The pH response curves of protease activity of both basal internodes and roots exhibited optima at pH 5 throughout the season. The protease activity of roots and basal internodes increased in spring, both on a unit fresh weight and unit protein basis, concomitant with mobilization of N from both these tissues to new shoot growth. In absolute terms more N was mobilized from roots than from basal internodes. However, basal internodes which, compared with roots, showed the greatest protease activity (on a f. wt or unit protein basis) were also the tissues that mobilized a greater proportion of N present in the tissue over winter to new shoot material. Individual clones of M. caerulea varied both in the amount of N mobilized from roots and in root protease activity (per plant). Individuals with a higher protease activity mobilized more N compared with individuals of lower protease activity. Therefore in M. caerulea, relationships between N mobilization and protease activity exist at several levels: (1) between different tissues; (2) temporally throughout the season; and (3) between individual clones.
Effects of ozone exposure on growth and photosynthesis of beech seedlings (Fagus sylvatica)
Authors: BORTIER KATRIEN , CEULEMANS REINHART , DE TEMMERMAN LUDWIG
Published: March 2003

The effects of ambient and elevated ozone levels on growth and photosynthesis of beech (Fagus sylvatica) were
studied by exposing seedlings in open‐top chambers for one growing season to three treatments: charcoal‐filtered
(CF), non‐filtered (NF) and non‐filtered air with addition of ozone (30 ppb ozone) on clear days for 8–10 h d−1
(NF +). Ambient levels were relatively low and accumulated to an AOT40 (accumulated exposure over a
threshold of 40 ppb) of 4055 ppb h (for the period 23 Apr–30 Sept). The NF + chambers received an AOT40
of 8880 ppb h. Throughout the growing season we measured growth and photosynthetic properties. The
treatments did not cause strong effects: measurements of gas exchange (light‐saturated assimilation rate, CO2 and light‐response curves) and chlorophyll fluorescence showed slight and mostly non‐significant reductions of several parameters. No significant differences were found for growth, though in the NF + treatment (AOT40 8880 ppb h) the relative growth rate for diameter increment was at times reduced by 12% compared with the control treatment.
The role of oxygen in submergence‐induced petiole elongation in Rumex palustris: in situ measurements of oxygen in petioles of intact plants using micro‐electrodes
Authors: RIJNDERS J. G. H. M. , ARMSTRONG W. , DARWENT M. J. , BLOM C. W. P. M. , VOESENEK L. A. C. J.
Published: March 2003

In a study on the mechanism of stimulated petiole elongation in submerged plants, oxygen concentrations in petioles of the flood‐tolerant plant Rumex palustris were measured with micro‐electrodes. Short‐term submergence
lowered petiole partial oxygen pressure to c. 19 kPa whereas prolonged submergence under continuous
illumination depressed oxygen levels to c. 8–12 kPa after 24 h. Oxygen levels in petioles depended on the presence of the lamina, even in submerged conditions, and on available light. In darkness, petiole oxygen levels in submerged plants dropped quickly to values as low as 0.5–4 kPa. It is hypothesized that prolonged submergence in the light is accompanied by a decrease in carbon dioxide in the petiole. Submergence‐enhanced petiolar elongation rate was compared with emergent plants. Peak daily elongation rates occurred at the end of the dark period in emergent plants, but in the middle of the light period in submerged plants. We suggest that this shift in daily elongation pattern is induced by dependence of growth on photosynthetically derived oxygen in submerged plants. Implications of reduced oxygen for ethylene production are raised. Levels of 1‐ aminocyclopropane‐1‐carboxylic acid synthase and 1‐aminocyclopropane‐1‐carboxylic acid oxidase and ethylene sensitivity are cited as potential factors in hypoxia‐induced ethylene release.
Cryopreservation of entrapped monoxenically produced spores of an arbuscular mycorrhizal fungus
Authors: DECLERCK S. , ANGELO‐VAN COPPENOLLE M. G.
Published: March 2003

A study was conducted to quantify the ability of entrapped, monoxenically produced spores of an arbuscular mycorrhizal fungus to germinate and reproduce the fungal life cycle after cryopreservation. No germination was obtained after incubation of entrapped spores in glycerol and mannitol and subsequent cryopreservation at −70 °C, regardless of the concentration of cryoprotectants and duration of incubation. Incubation for 1 d in 0.5 M sucrose, and for 1 and 2 d in 0.5 M trehalose, led to spore germination after cryopreservation at −70 °C. Lower cryopreservation temperatures were tested with entrapped spores incubated for 1 d in 0.5 M trehalose. The highest germination rate, estimated by the percentage of potentially infective beads (%PIB), was obtained at −100 °C. A %PIB of 95% (water agar medium) to 100% (Strullu–Romand medium) was obtained at this temperature. Thereafter, %PIB rapidly decreased at −140 and −180 °C. Heavy sporulation and high internal root colonization were obtained after re‐association of the entrapped spores, incubated for 1 d in 0.5 M trehalose and subsequently cryopreserved at −100 °C, with transformed carrot roots. This demonstrates the ability of entrapped spores to reproduce the fungal life cycle following cold treatment.
Retention and mobility of atmospheric particle‐associated organic pollutant PCDD/Fs and PAHs in maize leaves
Authors: KAUPP HEIKE , BLUMENSTOCK MARTIN , MCLACHLAN MICHAEL S.
Published: March 2003

The fate of polychlorinated dibenzo‐p‐dioxins and dibenzofurans and polycyclic aromatic hydrocarbons deposited to maize leaves under ambient conditions was investigated, with focus on those compounds that are primarily associated with particles in the atmosphere. Leaf samples collected from mature maize plants over an 8‐wk period were subjected to four extraction procedures: (1) rinsing with distilled water; (2) shaking in aqueous EDTA solution; (3) immersion in chloroform/methanol; (4) soxhlet extraction with toluene. Of the compounds deposited primarily in association with particles, > 20% of the total leaf contamination was present in the first two aqueous extracts, indicating that only a small portion of these substances was subject to ready erosion from the leaf surfaces. Some 50–60% of the chemical was present in the third extract, while 20–40% was found in the final extract. The chemical in the final extract was no longer associated with particles, since these had been removed with the first three extractions. This chemical must have desorbed from the particles with which it was originally deposited, and migrated through the epicuticular waxes. Model calculations indicated that 15–35% of the chemical in the third extract had also desorbed from the particles, and there was evidence that polychlorinated dibenzo‐p‐dioxins and dibenzofurans desorb more readily than polycyclic aromatic hydrocarbons. It is concluded that desorption of chemical from particles and subsequent transport through the cuticle is an important process determining plant accumulation of organic contaminants associated with atmospheric particles.
Effect of free‐air CO2 enrichment (FACE) on CO2 exchange at the flood‐water surface in a rice paddy field
Authors: Koizumi Hiroshi , Kibe Takeshi , Mariko Shigeru , Ohtsuka Toshiyuki , Nakadai Toshie , Mo Wenhong , Toda Hideshige , Seiichi Nishimura , Kobayashi Kazuhiko
Published: March 2003

Diurnal and seasonal changes in CO2 exchange between flooding water and the atmosphere are reported in a rice (Oryza sativa) paddy field under ambient and free‐air CO2 enrichment (FACE) conditions.

 Measurements of CO2 exchange were made in a randomized complete‐block design experiment with two CO2 mole fractions (ambient; FACE, ambient +200 mmol mol−1) and four blocks.

 Evolution of CO2 from the flooding water occurred throughout the entire day under ambient CO2, although the rate decreased in the daytime. By contrast, under FACE, CO2 evolution from the flooding water was observed at night, and CO2 absorption from the atmosphere was observed in the daytime. The time course of CO2 exchange was similar to that of solar radiation.

 The diurnal pattern is similar to that for photosynthesis of terrestrial plant communities. This suggests that photosynthesis of the free‐floating weeds and algae in the flooding water is related to the CO2 exchange between the flooding water and the atmosphere. In addition, the amplitude of the diurnal cycle of CO2 exchange was larger under the FACE than under ambient conditions.
Elevated CO2, drought and soil nitrogen effects on wheat grain quality
Authors: Kimball B. A. , Morris C. F. , Pinter P. J. , Wall G. W. , Hunsaker D. J. , Adamsen F. J. , LaMorte R. L. , Leavitt S. W. , Thompson T. L. , Matthias A. D. , Brooks T. J.
Published: March 2003

The likely consequences of future high levels of atmospheric CO2 concentration on wheat (Triticum aestivum L.) grain nutritional and baking quality were determined.

 Two free‐air CO2 enrichment (FACE; 550 mmol mol−1) experiments were conducted at ample (Wet) and limiting (Dry) levels of irrigation, and a further two experiments at ample (High‐N) and limiting (Low‐N) nitrogen concentrations. Harvested grain samples were subjected to a battery of nutritional and bread‐making quality tests.

 The Dry treatment improved grain quality slightly (protein +2%; bread loaf volume +3%). By contrast, Low‐N decreased quality drastically (protein −36%; loaf volume −26%). At ample water and N, FACE decreased quality slightly (protein −5%; loaf volume −2%) in the irrigation experiments and there was no change in the nitrogen experiments. At Low‐N, FACE tended to make the deleterious effects of Low‐N worse (protein −33% and −39%, at ambient CO2 and FACE, respectively; loaf volume −22% and −29% at ambient CO2 and FACE, respectively).

The data suggest that future elevated CO2 concentrations will exacerbate the deleterious effects of low soil nitrogen on grain quality, but with ample nitrogen fertilizer, the effects will be minor.
Novel infection process in the indeterminate root nodule symbiosis between Chamaecytisus proliferus (tagasaste) and Bradyrhizobium sp.
Authors: Vega‐Hernández M. C. , Pérez‐Galdona R. , Dazzo F. B. , Jarabo‐Lorenzo A. , Alfayate M. C. , León‐Barrios M.
Published: March 2003

The main characteristics of the symbiosis of tagasaste (Chamaecytisus proliferus ssp. proliferus var. palmensis), a woody legume forming N2‐fixing indeterminate nodules in response to infection by strains of Bradyrhizobium sp. (Chamaecytisus), are reported here.

 The infection process in this legume was examined by bright field, phase contrast and transmission electron microscopy, and was found to be unlike any other previously described.

 First steps in the infection process involve initiation of infection threads within deformed root hairs and induction of foci of host‐cell divisions in the inner root cortex. However, infection of root hairs aborts early, and instead, the bacteria use the crack‐entry mode of host infection, whereby they penetrate the periphery of the emerging nodule through an intercellular route, eventually infecting host nodule cells directly through altered cell walls. No successful infection threads were detected at any stage of primary‐host infection or nodule invasion. Indeterminate nodules were mainly formed on unbranched areas of lateral roots.

 This is the first description of such a combination of events in an infection process in the Rhizobium–legume root‐nodule symbiosis.
Mycorrhizal development in a low nodulating pea mutant
Authors: Resendes C. M. , Geil R. D. , Guinel F. C.
Published: March 2003

E107 is a pleiotropic mutant of Pisumsativum (pea) characterized by a decreased ability to form nodules. Its colonization by the arbuscular mycorrhizal fungus Glomusaggregatum is reported, and the mycorrhizal phenotype compared with the nodulation phenotype.

 Four cleared lateral roots from 21‐d‐old plants were chosen randomly, and their lengths scanned for any fungal structures. Colonization success was determined by counting the numbers of extraradical hyphae, and calculating epidermal entry and cortical entry. Graft experiments were performed to establish which organ regulates mycorrhiza‐formation.

 Two blocks to infection were obvious, at the root surface, and at the interface between the epidermis and the outermost cortical cell layer. Once the fungus breached this interface, it spread within the cortex and formed normal arbuscules. The mutant phenotype was controlled by the shoot.

 The E107 mycorrhizal phenotype was designated as app+, low pen, low coi. The development of the fungal infection was similar to that of rhizobial infection and under the same shoot control. The phenotype of the mutant E107 strongly supports the hypothesis that mycorrhiza formation and nodulation are regulated by the same processes.
Radiation modifies the effect of water availability on the carbon isotope composition of beech (Fagus sylvatica)
Authors: Geßler Arthur , Schrempp Stefan , Matzarakis Andreas , Mayer Helmut , Rennenberg Heinz , Adams Mark A.
Published: March 2003

Water availability and flux and carbon isotope and other chemical compositions of wood, foliage and phloem sap were quantified in a replicated field test examining the effects of exposure (north‐east, south‐west) and stem density on beech ecophysiology (Fagus sylvatica).

 Standard techniques for quantifying water potential, water flux in stems and carbon isotope composition of wood and foliage were complemented with chemical analysis of phloem sap collected using the ‘phloem bleeding’ technique.

 Phloem sap was similar in composition to other hardwoods. The δ13C signatures of sap reflected short‐term fluctuations in water availability and intercepted radiation, whereas foliar δ13C was a poor reflection of current environmental conditions.

 δ13C of tree rings suggested that the south‐west‐facing site experienced a greater shortage of water during summer than the paired north‐east‐facing site. However, phloem δ13C analysis showed that interpreting the effects of water availability using δ13C might be confounded by radiation. Better integration of hydrological models with reliable indices of water stress in beech will be required for reliable predictions of growth, especially if (when) climates change.
Plant reproduction under elevated CO2 conditions: a meta‐analysis of reports on 79 crop and wild species
Authors: Jablonski Leanne M. , Wang Xianzhong , Curtis Peter S.
Published: March 2003

Reproductive traits are key characteristics for predicting the response of communities and ecosystems to global change.

We used meta‐analysis to integrate data on eight reproductive traits from 159 CO 2 enrichment papers that provided information on 79 species.

Across all species, CO 2
enrichment (500–800 µl l
−1
) resulted in more flowers (+19%), more fruits (+18%), more seeds (+16%), greater individual seed mass (+4%), greater total seed mass (+25%), and lower seed nitrogen concentration, (N) (−14%). Crops and undomesticated (wild) species did not differ in total mass response to elevated CO
2
(+31%), but crops allocated more mass to reproduction and produced more fruits (+28% vs +4%) and seeds (+21% vs +4%) than did wild species when grown at high CO
2
. Seed [N] was not affected by high CO
2 concentrations in legumes, but declined significantly in most nonlegumes.

Our results provide robust estimates of average plant reproductive responses to CO 2
enrichment and demonstrate important differences among individual taxa and among functional groups. In particular, crops were more responsive to elevated CO
2 than were wild species. These differences and the substantial decline in seed [N] in many species have broad implications for the functioning of future natural and agro‐ecosystems.
Phenazines and their role in biocontrol by Pseudomonas bacteria
Authors: Chin‐A‐Woeng Thomas F. C. , Bloemberg Guido V. , Lugtenberg Ben J. J.
Published: March 2003

Various rhizosphere bacteria are potential (micro)biological pesticides which are able to protect plants against diseases and improve plant yield. Knowledge of the molecular mechanisms that govern these beneficial plant–microbe interactions enables optimization, enhancement and identification of potential synergistic effects in plant protection. The production of antifungal metabolites, induction of systemic resistance, and the ability to compete efficiently with other resident rhizobacteria are considered to be important prerequisites for the optimal performance of biocontrol agents. Intriguing aspects in the molecular mechanisms of these processes have been discovered recently. Phenazines and phloroglucinols are major determinants of biological control of soilborne plant pathogens by various strains of fluorescent Pseudomonas spp. This review focuses on the current state of knowledge on biocontrol by phenazine‐producing Pseudomonas strains and the action, biosynthesis, and regulation mechanisms of the production of microbial phenazines.
Consumer goals/skills that mothers want their children to learn
Authors: Carruth Betty Ruth , Skinner Jean D.
Published: March 2003

The study purpose was to assess consumer practices and attitudes of mothers (n= 117), and consumer goals/skills that their children were to learn. Mothers with at least one child aged 5–9 years were recruited from an ongoing study and through posters, flyers and referrals. Mail‐out surveys included a validated consumer questionnaire and requests for information related to socioeconomic status (SES), age, paid‐employment and gender/age of children. Responses were analysed using SAS, Cronbach’s alpha and qualitative analyses. Results indicated that mothers were of middle/upper SES and had 2.3 children/family, and 64% were in paid‐employment. Mother–child co‐shopping and mothers’ role modelling were major means of teaching consumer goals/skills. Children were to learn about getting the best buy and quality for the money, cost/unit comparison, being knowledgeable about products and avoidance of impulse buying. Mothers were consciously consumer training their children.
Association of nutrition concerns and socioeconomic status with exercise habits
Authors: Rimal Arbindra
Published: March 2003

The purpose of this study was to examine the association between socio‐economic characteristics and individual health behaviour patterns. Specifically, we looked at how individual demographics (i.e. age, gender, race, marital status, geographic location of households), socio‐economic status (i.e. education, income, children in the households) and respondents’ nutrition concern were related to the major health behaviour (i.e. exercise). Telephone interviews were conducted to collect the data from 2880 US households. A Poisson regression model was estimated to analyse the factors influencing physical exercise habits of adults. Results showed that the key socio‐economic variables influencing the exercise habit of US population were household income, education and family composition. The direct association of nutrition concern with exercise habits implied that health and nutrition programmes should emphasize good eating habit as well as healthy lifestyle.
Comparing online and non‐online shoppers
Authors: Lokken Sheri L. , Cross Ginger Wigington , Halbert Linda K. , Lindsey Gail , Derby Christy , Stanford Carla
Published: March 2003

A web‐based survey was completed by 130 faculty and staff from a university located in the south‐eastern United States. The purposes of this study were to investigate: (a) consumer characteristics related to online shopping; (b) benefits of online shopping as perceived by online shoppers; and (c) concerns about online shopping as perceived by non‐online shoppers. Responses were analysed using SPSS for tests of chi‐square. Findings suggest that the differences between online shoppers and non‐online shoppers correspond with Rogers’1 categories of adopters, and that the educational needs of consumers also differ based on their previous experience with online shopping.
Preferential Transfer of 2‐Docosahexaenoyl‐1‐Lysophosphatidylcholine Through an In Vitro Blood‐Brain Barrier Over Unesterified Docosahexaenoic Acid
Authors: Bernoud Nathalie , Fenart Laurence , Molière Patrick , Dehouck Marie‐Pierre , Lagarde Michel , Cecchelli Roméo , Lecerf Jean
Published: March 2003

Abstract : The passage of either unesterified docosahexaenoic acid (DHA) or lysophosphatidylcholine‐containing DHA (lysoPC‐DHA) through an in vitro model of the blood‐brain barrier was investigated. The model was constituted by a brain capillary endothelial cell monolayer set over the medium of an astrocyte culture. Cells were incubated for 4 h with a medium devoid of serum, then the endothelial cell medium was replaced by the same medium containing labeled DHA or lysoPC‐DHA and incubations were performed for 2 h. DHA uptake by cells and its transfer to the lower medium (astrocyte medium when they were present) were measured. When the lower medium from preincubation and astrocytes were maintained during incubation, the passage of lysoPC‐DHA was higher than that of unesterified DHA. The passage of both forms decreased when astrocytes were removed. The preference for lysoPC‐DHA was not seen when the lower medium from preincubation was replaced by fresh medium, and was reversed when albumin was added to the lower medium. A preferential lysoPC‐DHA passage also occurred after 2 h with brain endothelial cells cultured without astrocytes but not with aortic endothelial cells cultured and incubated under the same conditions. Altogether, these results suggest that the blood‐brain barrier cells released components favoring the DHA transfer and exhibit a preference for lysoPC‐DHA.
Differential Expression of SNAP‐25 Isoforms and SNAP‐23 in the Adrenal Gland
Authors: Grant Nancy J. , Hepp Regine , Krause Winfried , Aunis Dominique , Oehme Peter , Langley Keith
Published: March 2003

Abstract : In the rat adrenal gland, we previously observed that SNAP‐25 is not restricted to the plasmalemma in noradrenergic cells as it is in adrenergic cells, and hypothesized that SNAP‐25 isoform expression is different in the two phenotypes. Expression of SNAP‐25 isoforms and SNAP‐23 was examined by immunoblotting, immunofluorescence, and RT‐PCR. Amplifications of SNAP‐25 mRNAs were combined with Southern hybridization, restriction enzyme analysis, and sequencing of cloned PCR products to compare SNAP‐25 isoform expression in rat and bovine adrenal glands. SNAP‐25 and SNAP‐23 mRNA and protein are expressed in the glands ; SNAP‐23 is enriched in the adrenal cortex, whereas SNAP‐25 is restricted to the adrenal medulla. Furthermore, high levels of SNAP‐25 and low levels of SNAP‐23 are observed in the PC12 cells, whereas both SNAP‐25 and SNAP‐23 are expressed in adrenal medullary cultures. In all extracts, the SNAP‐23 mRNA corresponded to SNAP‐23a. SNAP‐25a is the major form expressed in rat adrenal glands (75%), as it is in PC12 cells (80%), but both SNAP‐25a and SNAP‐25b (40% vs. 60%) are expressed in bovine adrenal medulla in situ and in culture. In addition, an enriched population of adrenergic cells (93%) expressed a higher level of SNAP‐25b (70%), suggesting that this isoform may not be restricted to fast neurotransmission.
Regulation of Amyloid Precursor Protein Cleavage
Authors: Mills Julia , Reiner Peter B.
Published: March 2003

Abstract : Multiple lines of evidence suggest that increased production and/or deposition of the β‐amyloid peptide, derived from the amyloid precursor protein, contributes to Alzheimer's disease. A growing list of neuro‐transmitters, growth factors, cytokines, and hormones have been shown to regulate amyloid precursor protein processing. Although traditionally thought to be mediated by activation of protein kinase C, recent data have implicated other signaling mechanisms in the regulation of this process. Moreover, novel mechanisms of regulation involving cholesterol‐, apolipoprotein E‐, and stress‐activated pathways have been identified. As the phenotypic changes associated with Alzheimer's disease encompass many of these signaling systems, it is relevant to determine how altered cell signaling may be contributing to increasing brain amyloid burden. We review the myriad ways in which first messengers regulate amyloid precursor protein catabolism as well as the signal transduction cascades that give rise to these effects.
Decreased Brain Protein Levels of Cytochrome Oxidase Subunits in Alzheimer's Disease and in Hereditary Spinocerebella Ataxia Disorders
Authors: Kish Stephen J. , Mastrogiacomo Frank , Guttman Mark , Furukawa Yoshiaki , Taanman Jan‐Willem , Dozic Slobodan , Pandolfo Massimo , Lamarche Jacques , DiStefano Linda , Chang Li‐Jan
Published: March 2003

Abstract : Controversy exists as to the clinical importance, cause, and disease specificity of the cytochrome oxidase (CO) activity reduction observed in some patients with Alzheimer's disease (AD). Although it is assumed that the enzyme is present in normal amount in AD, no direct measurements of specific CO protein subunits have been conducted. We measured protein levels of CO subunits encoded by mitochondrial (COX I, COX II) and nuclear (COX IV, COX VIc) DNA in autopsied brain of patients with AD whom we previously reported had decreased cerebral cortical CO activity. To assess disease specificity, groups of patients with spinocerebellar ataxia type I and Friedreich's ataxia were also included. As compared with the controls, mean protein concentrations of all four CO subunits were significantly decreased (‐19 to ‐47%) in temporal and parietal cortices in the AD group but were not significantly reduced (‐12 to ‐17%) in occipital cortex. The magnitude of the reduction in protein levels of the CO subunits encoded by mitochondrial DNA (‐42 to ‐47%) generally exceeded that encoded by nuclear DNA (‐19 to ‐43%). In the spinocerebellar ataxia disorders, COX I and COX II levels were significantly decreased in cerebellar cortex (‐22 to ‐32%) but were normal or close to normal in cerebral cortex, an area relatively unaffected by neurodegeneration. We conclude that protein levels of mitochondrial‐ and nuclear‐encoded CO subunits are moderately reduced in degenerating but not in relatively spared brain areas in AD and that the decrease is not specific to this disorder. The simplest explanation for our findings is that CO is decreased in human brain disorders as a secondary event in brain areas having reduced neuronal activity or neuronal/synaptic elements consequent to the primary neurodegenerative process.
Regulation of Hemopexin Synthesis in Degenerating and Regenerating Rat Sciatic Nerve
Authors: Madore Nathalie , Camborieux Laure , Bertrand Nicolas , Swerts Jean‐Paul
Published: March 2003

Abstract : In injured peripheral nerves, hemopexin mRNA is expressed by fibroblasts, Schwann cells, and invading blood macrophages, and the protein accumulates in the extracellular matrix. This and its absence of regulation in injured central optic nerve suggest that hemopexin could play a positive role in peripheral nerve repair. Here, we studied the regulation of hemopexin expression in degenerating and regenerating nerves. After a sciatic nerve injury, both the synthesis of hemopexin and the level of its mRNA increase sharply during the first 2 days, leading to an accumulation of hemopexin in the nerve. Afterward, hemopexin expression decreases progressively in regenerating nerves. In permanently degenerated nerves, it is again transiently increased and then strongly decreased, whereas hemopexin from blood origin is accumulating. As part of the elucidation of the complex regulation of hemopexin expression in injured nerves, we demonstrate that interleukin‐6 increases hemopexin synthesis in intact nerves, whereas adult rat serum, but not purified hemopexin, inhibits it in degenerated nerves. Hemopexin, known as acute‐phase protein, is therefore one of the molecules rapidly and specifically up‐regulated in injured peripheral nerves. More generally, our findings suggest that the acute phase could be not only a systemic liverspecific response but also a reaction of injured tissues themselves.
The Levels of Leukemia Inhibitory Factor mRNA in a Schwann Cell Line Are Regulated by Multiple Second Messenger Pathways
Authors: Nagamoto‐Combs Kumi , Vaccariello Stacey A. , Zigmond Richard E.
Published: March 2003

Abstract: Axotomy of sympathetic and sensory neurons leads to changes in their neuropeptide phenotypes. These changes are mediated in part by the induction of leukemia inhibitory factor (LIF) by nonneuronal cells. In the present study, we identified satellite/Schwann cells as a possible source of the injury‐induced LIF. Using a Schwann cell line, SC‐1 cells, we examined mechanisms of LIF induction. LIF mRNA levels increased rapidly when the cells were treated with 8‐(4‐chlorophenylthio)adenosine 3′,5′‐cyclic monophosphate, phorbol 12‐myristate 13‐acetate (PMA), or A23187. Among these reagents, PMA was the most efficacious. Inhibition of protein kinase C (PKC) by GF‐109203X significantly reduced the PMA‐induced LIF mRNA levels. As PKC is known to activate the extracellular signal‐regulated kinase (ERK) signaling pathway, the involvement of this pathway in the PMA‐stimulated induction of LIF mRNA was examined. Phosphorylation of ERKs was increased following PMA treatment in SC‐1 cells. Moreover, inhibition of ERK kinase activity by PD98059 dramatically reduced PMA‐stimulated phosphorylation of ERKs and induction of LIF mRNA. These results indicate that LIF mRNA levels can be regulated by ERK activation via stimulation of PKC in Schwann cells.
Prostaglandin E1 Transported into Cells Blocks the Apoptotic Signals Induced by Nerve Growth Factor Deprivation
Authors: Kawamura Tom , Horie Satoshi , Maruyama Tomoyuki , Akira Toshiaki , Imagawa Takashi , Nakamura Norifumi
Published: March 2003

Abstract: Neuronal apoptosis in rat pheochromocytoma PC12 cells, which was confirmed by TUNEL (terminal transferase‐mediated dUTP‐biotin nick end‐labeling) staining and detection of chromatin condensation, appeared within 8 h after nerve growth factor (NGF) deprivation. Prostaglandin (PG) E1 (10−7‐10−6M) reduced the incidence of apoptotic cell death in PC12 cells. The genes encoding PG transporter specific to prostaglandins such as PGE2 or PGF2α were expressed in the cell lines as shown by RT‐PCR. Bromcresol green, an inhibitor of PG transporter, reversed the antiapoptotic effect of PGE1. Moreover, treatment of PC12 cells with an antisense oligonucleotide corresponding to PG transporter cDNA also blocked the inhibitory effects of PGE1 on apoptotic cell death. In addition, PGE1 counteracted the increased activities of stress‐activated protein kinase/c‐Jun N‐terminal kinase within 1–2 h after NGF deprivation in PC12 cells. These results indicated that the antiapoptotic effect of PGE1 in NGF‐deprived PC12 cells was achieved by inhibitory signals following uptake into neurons through the PG transporter.
Quinolinic Acid Is Extruded from the Brain by a Probenecid‐Sensitive Carrier System: A Quantitative Analysis
Authors: Morrison Paul F. , Morishige Gregory M. , Beagles Karen E. , Heyes Melvyn P.
Published: March 2003

Abstract: Although the neurotoxic tryptophan‐kynurenine pathway metabolite quinolinic acid originates in brain by both local de novo synthesis and entry from blood, its concentrations in brain parenchyma, extracellular fluid, and CSF are normally below blood values. In the present study, an intraperitoneal injection of probenecid (400 mg/kg), an established inhibitor of acid metabolite transport in brain, into gerbils, increased quinolinic acid concentrations in striatal homogenates, CSF, serum, and homogenates of kidney and liver. Direct administration of probenecid (10 mM) into the brain compartment via an in vivo microdialysis probe implanted into the striatum also caused a progressive elevation in both quinolinic acid and homovanillic acid concentrations in the extracellular fluid compartment but was without effect on serum quinolinic acid levels. A model of microdialysis transport showed that the elevations in extracellular fluid quinolinic acid and homovanillic acid levels following intrastriatal application are consistent with probenecid block of a microvascular acid transport mechanism. We conclude that quinolinic acid in brain is maintained at concentrations below blood levels largely by active extrusion via a probenecid‐sensitive carrier system.
Different Antigenic Reactivities of Bovine Brain Glutamate Dehydrogenase Isoproteins
Authors: Choi Soo Young , Hong Joung Woo , Song Min‐Sun , Jeon Seong Gyu , Bahn Jae Hoon , Lee Byung Ryong , Ann Jee‐Yin , Cho Sung‐Woo
Published: March 2003

Abstract: The structural differences between two types of glutamate dehydrogenase (GDH) isoproteins (GDH I and GDH II), homogeneously isolated from bovine brain, were investigated using a biosensor technology and monoclonal antibodies. A total of seven monoclonal antibodies raised against GDH II were produced, and the antibodies recognized a single protein band that comigrates with purified GDH II on sodium dodecyl sulfatepolyacrylamide gel electrophoresis and immunoblot. Of seven anti‐GDH II monoclonal antibodies tested in the immunoblot analysis, all seven antibodies interacted with GDH II, whereas only four antibodies recognized the protein band of the other GDH isoprotein, GDH I. When inhibition tests of the GDH isoproteins were performed with the seven anti‐GDH II monoclonal antibodies, three antibodies inhibited GDH II activity, whereas only one antibody inhibited GDH i activity. The binding affinity of anti‐GDH II monoclonal antibodies for GDH II (KD= 1.0 nM) determined using a biosensor technology (Pharmacia BIAcore) was fivefold higher than for GDH I (KD= 5.3 nM), These results, together with epitope mapping analysis, suggest that there may be structural differences between the two GDH isoproteins, in addition to their different biochemical properties. Using the anti‐GDH II antibodies as probes, we also investigated the crossreactivities of brain GDHs from some mammalian and an avian species, showing that the mammalian brain GDH enzymes are related immunologically to each other.
Uptake of 13C‐Tracer Arachidonate and γ‐Linolenate bythe Brain and Liver of the Suckling Rat Observed Using13C‐NMR
Authors: Likhodii Sergei S. , Cunnane Stephen C.
Published: March 2003

Abstract: Arachidonic acid (AA; 20:4n‐6) is one of the principal
components of the phosphoglycerides in neural cell membranes. During the
critical period of postnatal development in mammals, AA is supplied preformed,
directly from the milk or derived from precursor fatty acids such as
γ‐linolenic acid (GLA; 18:3n‐6). In this study, 13C‐NMR
spectroscopy was applied to investigate the incorporation of
[1‐13C]AA and [3‐13C]GLA into liver and brain lipids of
7‐15‐day‐old rats. The main objective was to establish the importance of
dietary GLA for tissue AA accretion relative to the contribution from
preformed dietary AA. [1‐13C]AA and [3‐13C]GLA were
injected into the stomach of 7‐day‐old rats as a mixture. 13C‐NMR
spectroscopy of lipid extracts revealed incorporation of [1‐13C]AA
and [5‐13C]AA (the latter derived from metabolism of the injected
[3‐13C]GLA) into phosphoglycerides and triacylglycerols. Preformed
AA was 10 (liver)‐17 (brain) times more efficient in contributing to tissue AA
than AA derived from precursor GLA. In separate experiments, NMR spectroscopy
was used to assess uptake of [1‐13C]AA directly in living rats and intact organs. Results showed that intact liver and brain contain an appreciable amount of NMR‐detectable lipids. The in vivo/in vitro information obtained from organs provided details on the mobility and turnover of tissue lipids.
Glycolipid‐Enriched Caveolae and Caveolae‐Like Domains in the Nervous System
Authors: Masserini Massimo , Palestini Paola , Pitto Marina
Published: March 2003

Abstract: Recent years have been characterized by a booming interest in research on caveolae and caveolae‐like membrane domains. The interest in this subject grew further, when their involvement in fundamental membrane‐associated events, such as signal transmission and lipid/protein sorting, was postulated. Substantial progress has been reached in understanding the biological role of membrane domains in eukaryotic cells. The neuron, however, which perhaps represents one of the greatest challenges to research on membrane traffic and function, has only been partially investigated. The purpose of the present review is to survey this issue in the nervous system. We confine ourselves to the presence of membrane domains in the nervous system and discuss this in the context of three facts: first, glycolipids are peculiarly enriched in both caveolae and caveolae‐like domains and are particularly abundant in the nervous system; second, the neuron is characterized by a basic dual polarity, similar in this respect to other polarized cells, where the role of glycolipid‐enriched domains for lipid/protein sorting has been better ascertained; and third, neurons evolved from, and are related to, simpler eukaryotic cells, allowing us to find analogies with more investigated nonneuronal cells.
A PC12 Variant Lacking Regulated Secretory Organelles
Authors: Pance Alena , Morgan Kevin , Guest Paul C. , Bowers Katherine , Dean Gary E. , Cutler Daniel F. , Jackson Antony P.
Published: March 2003

Abstract:A variant of the PC12 pheochromocytoma cell line (termed A35C) has been isolated that lacks regulated secretory organelles and several constituent proteins. Northern and Southern blot analyses suggested a block at the transcriptional level. The proprotein‐converting enzyme carboxypeptidase H was synthesised in the A35C cell line but was secreted by the constitutive pathway. Transient transfection of A35C cells with cDNAs encoding the regulated secretory proteins dopamine β‐hydroxylase and synaptotagmin I resulted in distinct patterns of mistargeting of these proteins. It is surprising that hybrid cells created by fusing normal PC12 cells with A35C cells exhibited the variant phenotype, suggesting that A35C cells express an inhibitory factor that represses neuroendocrine‐specific gene expression.