bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects on growth and comparison of root tissue colonization patterns of Eucalyptus viminalis by pathogenic and nonpathogenic strains of Fusarium oxysporum
Authors: SALERNO M. I. , GIANINAZZI S. , GIANINAZZI‐PEARSON V.
Published: March 2003

Soilborne pathogens, especially Fusarium oxysporum, are responsible for damping‐off and root necrosis in
Eucalyptus nurseries. New technologies are increasingly considering strategies for plant disease control other than
chemical fungicides. Among these, natural fungal antagonists, which are colonizers of the root cortex, are potential
biocontrol agents. An in vitro system was used: (1) to test the pathogenic effects of F. oxysporum strain Foeu1
which was recovered from a forest nursery soil; (2) to explore the potential of the nonpathogenic F. oxysporum
strain Fo47, which is known for its efficiency in biological control, to suppress damping‐off of Eucalyptus
seedlings; (3) to compare the patterns of root colonization and host response to invasion by the two Fusarium
strains inoculated separately in a time‐course study. Root inoculation of E. viminalis with F. oxysporum strain
Foeu1 caused damping‐off in young seedlings in vitro, whilst disease symptoms were not visible in plants
inoculated with F. oxysporum strain Fo47 or when both strains (Foeu1 + Fo47) were inoculated simultaneously. Each strain showed similarities in patterns of root tissue colonization, and in the processes of root penetration and initial colonization. Differential effects on root tissue were observed with fungal development within the cortex: ingress of strain Foeu1 was accompanied by severe host‐cell alterations whilst no tissue damage occurred with development of strain Fo47.
Growth characteristics in Hordeum spontaneum populations from different habitats
Authors: VAN RIJN CYNTHIA P. E. , HEERSCHE INGRID , VAN BERKEL YVONNE E. M. , NEVO EVIATAR , LAMBERS HANS , POORTER HENDRIK
Published: March 2003

Hordeum spontaneum shows a large genetic variation and occupies a wide range of different habitats. The aim of
this study was to quantify variation in growth characteristics of H. spontaneum from different sites in Israel and
to relate this variation to different environmental conditions. To this end, 84 accessions of 21 populations were
grown in a growth chamber in near‐optimal conditions and a range of physiological, morphological, allocation‐
related and chemical characteristics were measured. These parameters included rates of photosynthesis, shoot and
root respiration, specific leaf area, biomass allocation and seed mass. Averaged over all traits variation explained
by differences between populations was 26%, between accessions 21%, whereas that within accessions was 53%.
By contrast with most genetic studies, we found variation between populations larger than between accessions.
The largest between‐population variation (46%) was for morphological traits. In particular, seed mass, leaf
thickness and leaf width differed strongly between populations. Variation in growth characteristics between
populations was poorly related to mean annual rainfall, mean humidity or January temperature at the sites of
origin. We expect that differences between populations to be larger and correlation with environmental parameters
stronger in plants grown in stressful conditions. According to our study, seed mass is more important than relative
growth rate in determining variation in early plant biomass in H. spontaneum.
Mycorrhizal fungi have a potential role in soil carbon storage under elevated CO2 and nitrogen deposition
Authors: TRESEDER K. K. , ALLEN M. F.
Published: March 2003

In this review, we discuss the potential for mycorrhizal fungi to act as a source or sink for carbon (C) under elevated CO2 and nitrogen deposition. Mycorrhizal tissue has been estimated to comprise a significant fraction of soil
organic matter and below‐ground biomass in a range of systems. The current body of literature indicates that in
many systems exposed to elevated CO2, mycorrhizal fungi might sequester increased amounts of C in living, dead
and residual hyphal biomass in the soil. Through this process, the fungi might serve as a negative feedback on the
rise in atmospheric CO2 levels caused by fossil fuel burning and deforestation. By contrast, a few preliminary
studies suggest that N deposition might increase turnover rates of fungal tissue and negate CO2 effects on hyphal
biomass. If these latter responses are consistent among ecosystems, C storage in hyphae might decline in habitats
surrounding agricultural and urban areas. When N additions occur without CO2 enrichment, effects on
mycorrhizal growth are inconsistent. We note that analyses of hyphal decomposition under elevated CO2 and N
additions are extremely sparse but are critical in our understanding of the impact of global change on the cycling
of mycorrhizal C. Finally, shifts in the community composition of arbuscular and ectomycorrhizal fungi with
increasing CO2 or N availability are frequently documented. Since mycorrhizal groups vary in growth rate and tissue quality, these changes in species assemblages could produce unforeseeable impacts on the productivity, survivorship, or decomposition of mycorrhizal biomass.
The ups and downs of signalling between root and shoot
Authors: Beveridge Christine
Published: March 2003

It is becoming increasingly apparent that the long‐distance signalling associated with many developmental processes is complex and that novel hormone‐like signals may play substantial roles. The past decades have seen several substances (e.g. brassinosteroids, systemin and other polypeptides, mevalonic and jasmonic acids, polyamines, oligosaccharides, flavonoids, and quinones) vie for a place among the classical plant hormones (e.g. Spaink, 1996). Recent microinjection and grafting studies have also shown that RNA may act as a long‐distance signal (Jorgensen et
al., 1998; Xoconostle‐Cázares et al., 1999). In this issue,
Hannah et al. describe long‐distance signalling and the
regulation of root–shoot partitioning in dwarf lethal or
dosage‐dependent lethal (DL) mutants of common bean
(Shii et al., 1980, 1981), and present evidence indicating that substances in addition to classical plant hormones (e.g. cytokinins) may be involved.

As in the report by Hannah et al., much of the evidence for roles of unidentified long‐distance signals in the control of plant development is indirect. The possibility that a small number of long‐distance signals might control a multitude of developmental processes arises through the potential for differences in tissue sensitivity, fluctuations in hormone levels and differences in the nature of responses of different tissues to the same hormone. Consequently, particular hormones may influence numerous processes seemingly simultaneously, yet independently. Even so, long‐distance signalling is involved in processes as diverse as root–shoot balance, senescence, branching, flowering, nodulation, stress responses and nutrient uptake. Through comparison of even a few different developmental processes, progress can be made to reveal the true complexity of plant development. Using this approach it is also clear that many unknown signals may be involved.
Do species and functional groups differ in acquisition and use of C, N and water under varying atmospheric CO2 and N availability regimes? A field test with 16 grassland species
Authors: Reich Peter B. , Tilman David , Craine Joseph , Ellsworth David , Tjoelker Mark G. , Knops Jean , Wedin David , Naeem Shahid , Bahauddin Dan , Goth Jenny , Bengtson Wendy , Lee Tali D.
Published: March 2003

To evaluate whether functional groups have a similar response to global change, the responses to CO2 concentration and N availability of grassland species from several functional groups are reported here.

 Sixteen perennial grassland species from four trait‐based functional groups (C3 grasses, C4 grasses, non‐leguminous forbs, legumes) were grown in field monocultures under ambient or elevated (560 µmol mol−1) CO2 using free‐air CO2 enrichment (FACE), in low N (unamended field soil) or high N (field soil +4 g N m−2 years−1) treatments.

 There were no CO2 × N interactions. Functional groups responded differently to CO2 and N in terms of biomass, tissue N concentration and soil solution N. Under elevated CO2, forbs, legumes and C3 grasses increased total biomass by 31%, 18%, and 9%, respectively, whereas biomass was reduced in C4‐grass monocultures. Two of the four legume species increased biomass and total plant N pools under elevated CO2, probably due to stimulated N‐fixation. Only one species markedly shifted the proportional distribution of below‐ vs aboveground biomass in response to CO2 or N.

 Although functional groups varied in responses to CO2 and N, there was also substantial variation in responses among species within groups. These results suggest that current trait‐based functional classifications might be useful, but not sufficient, for understanding plant and ecosystem responses to elevated CO2 and N availability.
Patterns made of patterns: variation and covariation of leaf nutrient concentrations within and between populations of Prunus mahaleb
Authors: Alonso Conchita , Herrera Carlos M.
Published: March 2003

Patterns of within and between population variation in concentrations of nutrients (N, P, K, Ca, Na, Mg, Cu, Fe, Mn, Zn) are reported in mature leaves of individual Prunus mahaleb (Rosaceae) trees from five south‐eastern Spanish populations.

 MANOVA and canonical discriminant analysis were used to identify the contribution of individual nutrients in explaining differences between populations in average nutrient composition. Common principal components analysis was used to test whether the structure of covariation between leaf macronutrients was maintained at different populations.

 Populations differed in average nutrient composition and were separated mostly by variation along an axis defined by Ca on the positive side, and Mg on the negative one. The sign and magnitude of the correlations between individual nutrients varied between populations. Multivariate patterns of nutrient covariation differed between populations, the variation being unrelated to population differences in mean nutrient composition.

 Results suggest that, at the regional scale, phenotypic integration of the foliage concentrations of different nutrients was weak, and highlights the importance of studying nutrient covariation structures.
Exploring mycorrhizal function with NMR spectroscopy
Authors: Pfeffer Philip E. , Bago Berta , Shachar‐Hill Yair
Published: March 2003

Nuclear magnetic resonance (NMR) studies of mycorrhizal symbioses have illuminated a number of functional aspects of these complex associations. Here we review studies of the two main types of mycorrhiza (ectomycorrhizas and arbuscular mycorrhizas) to which NMR has been applied. Although the physiological questions addressed in each case are frequently the same, these two mutualistic symbioses are sufficiently different to justify separate discussion. In conjunction with isotopic labelling NMR is able to examine the transfer of substrates between the symbionts both in vivo and in vitro, as well as the production of secondary metabolites in response to colonization. In addition, this methodology is capable of determining the locations of the biosynthesis and translocations of storage compounds, such as polyphosphates, lipids and carbohydrates, in mycorrhizal fungi both in the free‐living and in the symbiotic stages of their life cycle. NMR has been useful in analysing metabolism, transport and energetics, and the results of such studies have practical and ecological significance. Models of transport and physiology to which NMR has contributed form the necessary foundation for functional genomic exploration.
The advantage of early flowering in the spring ephemeral annual plant Floerkea proserpinacoides
Authors: Houle Gilles
Published: March 2003

• Internal conflicts in the allocation of resources lead to trade‐offs or compromises that can influence fitness and the evolution of specific life‐history traits.

• Here, the reproductive schedule of Floerkea proserpinacoides plants, a spring ephemeral annual of the deciduous forests of eastern North America, was manipulated to determine the presence of potential conflicts between growth and reproduction, and the advantage of early reproduction.

• Plants on which flowering was delayed had a greater relative growth rate (RGR) and vegetative biomass than control plants after 8 wks (when control plants started to senesce). Delayed‐flowering plants took 1 week longer to senesce, which allowed them to mature almost as many seeds as did control plants in 8 wks.

• However, late flowering in F. proserpinacoides may be maladaptive. With reduced light availability through canopy closure, early flowering plants can rapidly divert most of the resources accumulated in the stem and leaves to seed maturation. Thus, the advantage of maintaining a higher RGR by delaying flowering is associated with the greater disadvantage of necessitating more time to mature seeds.
Defoliation and site differences influence vegetative spread in grassland
Authors: Barthram G. T. , Elston D. A. , Birch C. P. D. , Bolton G. R.
Published: March 2003

Plants spread vegetatively at rates that depend on both their own and their neighbours’ traits. We tested hypotheses that such rates also interact with defoliation intensity and differ between sites.

Well‐established monoculture patches (20 × 20 cm) of five grass species were arranged in plots so that every species patch had all the remaining species as neighbours. Sites were in central Scotland, UK, and at a drier location in eastern Scotland. Plots were cut at 3 cm (‘short’) or 6 cm (‘tall’), either uniformly or in a chessboard pattern.

Invasiveness and resistance to invasion followed the transitive hierarchy, Agrostis capillaris
 > 
Festuca rubra
 > 
Lolium perenne
 = 
Holcus lanatus
 > 
Poa trivialis
, except that
P. trivialis
strongly invaded
H. lanatus at the damper, more fertile site. ‘Tall’ patches spread and intermixed most, independent of species. The effects of cutting neighbouring patches depended on both invading and invaded species’ traits.

Thus, defoliation altered the relationships between species, as did differences between sites, influencing both the speed and direction of species replacement.
Arsenic hyperaccumulation by different fern species
Authors: Zhao F. J. , Dunham S. J. , McGrath S. P.
Published: March 2003

Pteris vittata
was the first identified arsenic (As) hyperaccumulator. Our aim was to test whether As hyperaccumulation occurs in other fern species, and whether
P. vittata collected from both contaminated and uncontaminated environments accumulates As similarly.

Three accessions of P. vittata
, two cultivars of
Pteris cretica
,
Pteris longifolia
and
Pteris umbrosa
were grown with 0–500 mg As kg
−1 added to the substrate. A second experiment compared As uptake by five common ferns obtained from commercial suppliers.

The results show that, in addition to P. vittata
,
P. cretica
,
P. longifolia
and
P. umbrosa
also hyperaccumulate As to a similar extent. There was little difference between different
Pteris
species, or between different accessions of
P. vittata
. By contrast,
Asplenium nidus
,
Davallia canarensis
,
Polypodium aureum
,
Polystichum tsus‐simense do not hyperaccumulate As.

This study identified three new species of As hyperaccumulators in the Pteris
genus and suggests that As hyperaccumulation is a constitutive property in
P. vittata .
Evaluation of fat replacers Avicel™, N Lite S™ and Simplesse™ in mayonnaise
Authors: Cheung I. , Gomes F. , Ramsden R. , Roberts D. G.
Published: March 2003

Samples of mayonnaise were prepared in which the oil content was reduced from 30% to 10% and replaced with the fat replacers, Avicel, N Lite S and Simplesse. The control sample had a significantly higher viscosity (P< 0.001)

and droplet size (P< 0.01) than the samples containing the replacers.

There was a significant (P< 0.001) correlation (r=

0.97) between viscosity and droplet size. Sensory analysis also showed that the control

had significantly higher scores (P< 0. 001) for the attributes

of thickness, meltability, glossiness and oiliness. There was a significant (P< 0.05) correlation (r= 0.93) between viscosity and sensory thickness. However, there was no significant preference for any of the samples, showing that variations in physical properties and sensory profile attributes do not necessarily affect preference. The use of the replacers reduced the energy values of the mayonnaises by 52% to 55%.
Impact of adoption in Ghana of an improved fish processing technology on household income, health and nutrition
Authors: Nti Christina Antwiwaa , Plahar Wisdom Annorsey , Larweh Patience Mateko
Published: March 2003

Surveys were conducted in three fishing communities in Ghana, where an improved fish smoking technology (the Chorkor smoker) had been introduced previously, to assess the impact of adopting the improved technology on household income, health and nutritional status. Fifty‐one fish processors (all women), who had adopted the improved fish processing technology, were selected for the study, in which the participatory rural appraisal (PRA) technique, nutritional survey methods and structured questionnaires were used to obtain both qualitative and quantitative data. The results revealed that there was an improvement in economic activities. This resulted in a positive impact on household income and food consumption patterns of the processors. Improvement in household income resulted from increases in the quality and quantity of output, price per unit output and profits. Improvement in food consumption pattern was mostly in respect of quality and quantity of food intake, but the types of food consumed remained the same. The nutrient intake of the respondents was good on average, with a majority exceeding the recommended daily allowance (RDA) of protein, vitamin B1 and calcium. The average body mass index (BMI) of the processors was also within the ideal range of 20–25. Adoption of the new technology also improved the health status of the respondents. Lessening of eye problems and headaches as a result of reduced exposure to smoke and heat was reported by 52% of the women. However, preschool children were undernourished as a result of poor child feeding practices. In any technology transfer process, apparently unrelated nutritional factors need to be considered.
Spouse care for children and other family members: the effects of family benefits
Authors: Garcia Inmaculada , Molina José Alberto
Published: March 2003

This paper first presents evidence from Spain on the relationship between the labour situation of both spouses within the family and the time dedicated to the care of the children, the elderly and the infirm. Second, it analyses the effect that government benefits for such care would have on the labour market and on household poverty. The results show that while Spanish society has advanced in the incorporation of women into the labour market, most of them still have to assume total responsibility for housework and the care of the children, the elderly and the infirm. Against this background, we find that benefits would decrease female participation in the labour market and the number of hours worked, while they would also contribute towards reducing poverty.
Buyer–seller relationships for promotional support in the apparel sector
Authors: Kincade Doris H. , Woodard Ginger A. , Park Haesun
Published: March 2003

Promotional supports provided by manufacturers are important to many retailers. With the intense competition for customers and heightened concern for profit margins, retailers’ cooperation is critical in the promotional process so that promotional services mutually benefit both manufacturers and retailers. The purpose of this study was to define promotional support categories offered to apparel retailers from manufacturers, to identify the retailer's perceptions of the offering frequency and importance of the promotional support, and to investigate the relationship between offering frequency and perceptions of importance. A descriptive research design was developed to survey 100 large retail organizations in the USA. Results indicated that monetary support was regarded as the promotional support offered the most and perceived by retailers to be the most important. Findings reveal an overall consistency between apparel retail buyers’ importance perception and manufacturers’ offering frequency of promotional support. A positive and significant correlation was found between items the buyers perceived as important and the frequency of offerings of these items. Indications were that manufacturers recognize their customers’ needs by matching the frequency of support offerings with which they offer the promotional support with the importance perception of buyers toward the promotional support. Future studies should identify and examine additional promotional support items. Also, examining the interrelationships among organizational variables, as well as combined effects on apparel retail buyers’ buying decision‐making using a global model, needs to be investigated.
Experience, change and vulnerability: consumer education for older people revisited
Authors: Lyon Phil , Kinney Dave , Colquhoun Anne
Published: March 2003

Everyday consumer transactions have the same potential for unexpected consequence whatever the age of the consumers involved. Young and old alike can find that products and services fail to live up to performance claims and that they are left with problems not easily resolved, or costs that are difficult to recover. While not overlooking consumer heterogeneity – especially on the basis of age – older consumers are arguably distinguishable in terms of the social and financial context in which they make decisions and attempt to redress problems. In 1988, attention was drawn to the need for consumer education to look beyond generic objectives to the specific situation of older people and their transactions. More than a decade later, in an allegedly consumer‐oriented society, the issue is revisited here to assess the argument's current relevance. Despite the increased availability of information for decisions and consumer protection, difficulties persist in the way information is presented or accessed. Chameleon‐like, old problems become manifest in new unfamiliar ways and invalidate experience. Consumer education today is as important as it was in 1988. Arguably, technological change means that the need for a better understanding of dangers, rights and redress procedures is greater than ever and the needs of older people in increasingly complex private and public sector transaction environments are all the more pressing. However, a fundamental revision of the way we approach the design of products, services and environments is needed to improve prospects for older consumers.
A comparison of alternative theoretical explanations of consumer food safety assessments
Authors: Sapp Stephen G.
Published: March 2003

The technical approach assumes that risk assessments made by technical experts are relatively objective and value‐free evaluations of the probability of negative consequences arising from use of a technology. Risk communication strategies associated with the technical approach focus upon educating an uninformed public about ‘actual’ risk. When consumer perceptions do not agree with technical assessments, consumers are deemed to be uniformed, irrational and sometimes dangerous to public health programmes. The social process approach assumes that technical assessments and applications of technology are influenced by political, social and economic interests. Consumer perceptions arise from social interaction with family and friends and depend strongly upon trust in societal institutions. Risk communication strategy emphasizes the importance of two‐way communication that encourages well reasoned public discourse and trust in societal institutions. Findings from examining the cognitive, emotional, and social determinants of perceptions of food irradiation for 164 adults residing in the Mid‐western USA indicate that the technical and social process approaches are complementary, but most of the variance in acceptance and perceived risk was explained by variables associated with the social process approach.
Factors affecting consumer acceptance of chilled ready meals on the island of Ireland
Authors: Reed Zandra , McIlveen‐Farley Heather , Strugnell Christopher
Published: March 2003

The chilled ready meal market on the island of Ireland is relatively young but is growing rapidly. This paper focused on a consumer questionnaire (n = 702), designed to examine consumer attitudes to and consumption of chilled ready meals, in both the north and south of Ireland. This formed part of a larger study, with the questionnaire findings contributing to an in‐depth sensory study on a selected range of chilled ready meals. For a significant number of Irish consumers, consumption of these products is higher than on the UK mainland. For others, the products are purchased as a convenient alternative or a weekly treat. Respondents in urban locations were significantly more likely to consume chilled ready meals, as were men and younger, single respondents. Irish consumers are becoming more accustomed to ethnic cuisine although traditional meals remain popular. There is a clear need for developers to continue to enhance the sensory quality of these products, particularly as the primary barrier to consumption was a preference for home cooked food. However, they must also strive to maintain consumer interest in the sector, fulfil the desire for convenience and satisfy a more discerning palate.
The effect of cooking and washing temperature during pilot‐scale rennet casein manufacture on casein hydration characteristics in disodium orthophosphate solution
Authors: O’sullivan Michele M , Singh Harjinder , Munro Peter A , Mulvihill Daniel M
Published: March 2003

Variations were observed in the hydration behaviour of rennet caseins in a solution (0.4%, w/w) of disodium orthophosphate (DSP). These caseins were manufactured on a pilot scale from curds cooked at 45, 65 or 75°C and from curds washed at a hot‐wash temperature of 60, 70, 78 or 86°C. The influence of cooking temperature and hot‐wash temperature on various compositional characteristics, the electrophoretic resolution and particle size parameters of the milled rennet caseins were determined. Relationships between all of these parameters and hydration characteristics in DSP solution were also investigated. Cooking temperature or hot‐wash temperature did not influence electrophoretic resolution, the level of Maillard reaction compounds or the particle size parameters of the caseins. Increasing the cooking temperature increased whey protein levels and decreased calcium levels in the curd, leading to slower hydration rates. This suggested that increased whey protein denaturation and its precipitation onto the rennet casein curd retarded subsequent rennet casein hydration. Hot‐wash temperature influenced certain aspects of rennet casein hydration in 0.4% (w/w) DSP; however, the hydration characteristics of these caseins did not appear to be related to any of the other characteristics investigated.
Proteolysis in miniature Cheddar‐type cheeses made using blends of chymosin and Cynara cardunculus proteinases as coagulant
Authors: O'Mahony James A , Sousa Maria J , Mcsweeney Paul L H
Published: March 2003

Miniature (20 g) Cheddar‐type cheeses were manufactured using blends of Cynara cardunculus proteinases and chymosin as coagulant (100 : 0, 50 : 50, 25 : 75 and 0 : 100 C. cardunculus proteinases : chymosin). There were no substantial differences between the compositions of cheeses made using any of the four coagulant blends. Cheeses manufactured with coagulant blends containing C. cardunculus proteinases exhibited higher levels of pH 4.6‐soluble nitrogen than cheese made using chymosin as coagulant. The extent of breakdown of αs1‐casein, as measured by urea‐polyacrylamide gel electrophoresis (urea‐PAGE), was greater in cheeses made using coagulant preparations containing C. cardunculus proteinases as a constituent than in cheese made using 100% chymosin as coagulant. Different reverse‐phase high‐performance liquid chromatography (RP‐HPLC) peptide profiles of the ethanol‐soluble and ‐insoluble fractions were obtained for cheeses made using either C. cardunculus proteinases or chymosin as coagulant. Principal component analysis and hierarchical cluster analysis of RP‐HPLC data confirmed that the inclusion of even small proportions (25%) of C. cardunculus proteinases with chymosin in the coagulant blend greatly altered the pattern and extent of proteolysis in miniature Cheddar‐type cheeses.
Dual Roles of Proteasome in the Metabolism of Presenilin 1
Authors: Honda Toshiyuki , Yasutake Kaori , Nihonmatsu Naomi , Mercken Mark , Takahashi Hiroshi , Murayama Ohoshi , Murayama Miyuki , Sato Kazuki , Omori Akira , Tsubuki Satoshi , Saido Takaomi C. , Takashima Akihiko
Published: March 2003

Abstract : Presenilin 1 (PS1) has been identified as a causative
gene for most early‐onset familial Alzheimer's disease. Biochemical studies
revealed that PS1 exists predominantly as two processed fragments in cells and
brain tissues. We prepared stably transfected cells expressing the wild‐type
and familial Alzheimer's disease‐associated mutants of PS1 and investigated
the enzyme that participates in the metabolism of PS1. After treatment of the
cells with proteasome inhibitors, the full‐length PS1 was significantly
accumulated. The levels of N‐ and C‐terminal fragments were also increased.
The accumulation of PS1 with a deletion of exon 10, which is unable to be
processed, on treatment of the transfected cells with lactacystin indicated
that proteasome can degrade full‐length PS1. A synthetic peptide that includes
the processing region of PS1 was cleaved by 20S proteasome at the putative
processing sites after Met288 and Glu299. Metabolic labeling experiments showed that the appearance of the N‐terminal fragment was attenuated by the inhibitor. Finally, 28‐kDa N‐ and 20‐kDa C‐terminal fragments were generated by purified PS1 in vitro. These data indicated that the proteasome pathway is involved in PS1 processing. These results demonstrate that the proteasome pathway plays dual roles in processing and degradation of PS1.
In Vivo Microdialysis of 2‐Deoxyglucose 6‐Phosphate into Brain
Authors: Kintner D. B. , Anderson M. E. , Sailor K. A. , Dienel G. , Fitzpatrick James H. , Gilboe D. D.
Published: March 2003

Abstract : A unique method for simultaneously measuring interstitial
(pHe) as well as intracellular (pHi) pH in the brains of
lightly anesthetized rats is described. A 4‐mm microdialysis probe was
inserted acutely into the right frontal lobe in the center of the area sampled
by a surface coil tuned for the collection of 31P‐NMR spectra.
2‐Deoxyglucose 6‐phosphate (2‐DG‐6‐P) was microdialyzed into the rat until a
single NMR peak was detected in the phosphomonoester region of the
31P spectrum. pHe and pHi values were
calculated from the chemical shift of 2‐DG‐6‐P and inorganic phosphate,
respectively, relative to the phosphocreatine peak. The average in vivo
pHe was 7.24 ± 0.01, whereas the average pHi was
7.05 ± 0.01 (n = 7). The average pHe value and the average
CSF bicarbonate value (23.5 ± 0.1 mEq/L) were used to calculate an
interstitial Pco2 of 55 mm Hg. Rats were then subjected to a 15‐min
period of either hypercapnia, by addition of CO2 (2.5, 5, or 10%)
to the ventilator gases, or hypocapnia (Pco2 < 30 mm Hg), by
increasing the ventilation rate and volume. pHe responded inversely
to arterial Pco2 and was well described (r2 =
0.91) by the Henderson‐Hassel‐balch equation, assuming a
pKa for the bicarbonate buffer system of 6.1 and a
solubility coefficient for CO2 of 0.031. This confirms the view
that the bicarbonate buffer system is dominant in the interstitial space.
pHi responded inversely and linearly to arterial Pco2.
The intracellular effect was muted as compared with pHe (slope =
‐0.0025, r2 = 0.60). pHe and pHi
values were also monitored during the first 12 min of ischemia produced by
cardiac arrest. pHe decreases more rapidly than pHi
during the first 5 min of ischemia. After 12 min of ischemia, pHe
and pHi values were not significantly different (6.44 ± 0.02
and 6.44 ± 0.03, respectively). The limitations, advantages, and future
uses of the combined microdialysis/31P‐NMR method for measurement
of pHe and pHi are discussed.
An Ecto‐Nucleotide Pyrophosphatase Is One of the Main Enzymes Involved in the Extracellular Metabolism of ATP in Rat C6 Glioma
Authors: Grobben Bert , Anciaux Katelijne , Roymans Dirk , Stefan Cristiana , Bollen Mathieu , Esmans Eddy L. , Slegers Herman
Published: March 2003

Abstract : The presence of a nucleotide pyrophosphatase (EC 3.6.1.9)
on the plasma membrane of rat C6 glioma has been demonstrated by analysis of
the hydrolysis of ATP labeled in the base and in the α‐and
γ‐phosphates. The enzyme degraded ATP into AMP and PPi and,
depending on the ATP concentration, accounted for ~50‐75% of the extracellular
degradation of ATP. The association of the enzyme with the plasma membrane was
confirmed by ATP hydrolysis in the presence of a varying concentration of
pyridoxal phosphate‐6‐azophenyl‐2′,4′‐disulfonic acid (PPADS), a
membrane‐impermeable inhibitor of the enzyme. PPADS concentration above 20
μM abolished the degradation of ATP into AMP and PPi.
The nucleotide pyrophosphatase has an alkaline pH optimum and a
Km for ATP of 17 ± 5 μM. The enzyme has a broad substrate specificity and hydrolyzes nucleoside triphosphates, nucleoside diphosphates, dinucleoside polyphosphates, and nucleoside monophosphate esters but is inhibited by nucleoside monophosphates, adenosine 3′,5′‐bisphosphate, and PPADS. The substrate specificity characterizes the enzyme as a nucleotide pyrophosphatase/phosphodiesterase I (PD‐I). Immunoblotting and autoadenylylation identified the enzyme as a plasma cell differentiation antigen‐related protein. Hydrolysis of ATP terminates the autophosphorylation of a nucleoside diphosphate kinase (NDPK/nm23) detected in the conditioned medium of C6 cultures. A function of the pyrophosphatase/PD‐I and NDPK in the purinergic and pyrimidinergic signal transduction in C6 is discussed.
Effects of Mitochondria and O‐Methoxybenzoylalanine on 3‐Hydroxyanthranilic Acid Dioxygenase Activity and Quinolinic Acid Synthesis
Authors: Chiarugi Alberto , Moroni Flavio
Published: March 2003

Abstract : The use of o‐methoxybenzoylalanine, a selective
kynureninase inhibitor, has been proposed with the aim of reducing brain
synthesis of quinolinic acid, an excitotoxic tryptophan metabolite. In liver
homogenates, however, this compound caused unexpected accumulation of
3‐hydroxyanthranilic acid, the product of kynureninase activity and the
precursor of quinolinic acid. To explain this observation, we investigated the
interaction(s) of o‐methoxybenzoylalanine with 3‐hydroxyanthranilic
acid dioxygenase, the enzyme responsible for quinolinic acid formation. When
the purified enzyme or partially purified cytosol preparations were used,
o‐methoxybenzoylalanine did not affect 3‐hydroxyanthranilic acid
dioxygenase activity. However, a significant reduction of this enzymatic
activity did occur when o‐methoxybenzoylalanine was tested in the
presence of mitochondria. It is interesting that addition of purified
mitochondria to 3‐hydroxyanthranilic acid dioxygenase preparations reduced the
enzymatic activity and the synthesis of quinolinic acid. In vivo,
administration of o‐methoxybenzoylalanine significantly reduced
quinolinic acid synthesis and content in both blood and brain of mice. Our
results suggest that mitochondrial protein(s) interact(s) with soluble
3‐hydroxyanthranilic acid dioxygenase and cause(s) modifications in the enzyme
resulting in a decrease in its activity. These modifications also allow the
enzyme to interact with o‐methoxybenzoylalanine, thus leading to a further reduction in quinolinic acid synthesis.
A Conserved Arginine in the Distal Third Intracellular Loop of the μ‐Opioid Receptor Is Required for G Protein Activation
Authors: Wang Hung‐Li
Published: March 2003

Abstract : In the present study, the functional significance of the
intracellular C‐terminal loop of the μ‐opioid receptor in activating
Gi proteins was determined by constructing a C‐terminal deletion
mutant μ(C ▵ 45) receptor, which lacks the carboxyl 45 amino acids.
When the truncated μ(C ▵ 45) receptor was stably expressed in human
embryonic kidney (HEK) 293 cells, the efficacy and the potency of
[D‐Ala2,N‐Me‐Phe4,Gly‐ol5]enkephalin
(DAMGO), a specific μ‐opioid receptor agonist, to inhibit
forskolin‐stimulated adenylate cyclase activity were not significantly
affected. Similar to other G‐coupled receptors, the third cytoplasmic loop of
the μ‐opioid receptor contains conserved basic residues (R276/R277/R280) at
the C‐terminal segment. Mutating these basic residues to neutral amino acids
(L276/M277/L280) greatly impaired the ability of DAMGO to inhibit
forskolin‐stimualted cyclic AMP formation. Replacing R276/R277 with L276/M277
did not affect the efficacy and potency by which DAMGO inhibits the adenylate
cyclase activity. In HEK 293 cells stably expressing mutant (R280L)
μ‐opioid receptors, the ability of DAMGO to inhibit forskolin‐stimulated
cyclic AMP production was greatly reduced. These results suggest that the
intracellular carboxyl tail of the μ‐opioid receptor does not play a
significant role in activating Gi proteins and that the arginine
residue (R280) at the distal third cytoplasmic loop is required for
Gi activation by the μ‐opioid receptor.
The Endogenous Lipid Oleamide Activates Serotonin 5‐HT7 Neurons in Mouse Thalamus and Hypothalamus
Authors: Thomas Elizabeth A. , Cravatt Benjamin F. , Sutcliffe J. Gregor
Published: March 2003

Abstract: Oleamide is an endogenous lipid that accumulates during
sleep deprivation and has hypothermic effects when administered to rodents.
The mechanisms for its activity remain unknown. Intraperitoneal injections of
oleamide elicited dramatic increases in content of c‐fos mRNA and Fos
protein in distinct brain regions, including cingulate and somatosensory
cortical areas and numerous nuclei of the thalamus and hypothalamus,
indicating that there are explicit targets for its action. In the thalamus and
hypothalamus a majority of neurons induced for c‐fos expression also
expressed the serotonin 5‐HT7 receptor, an allosteric target for
oleamide in in vitro studies. These data suggest that oleamide may act at
5‐HT7 receptors to elicit alterations in transcription that result in some of its physiological effects.
Modulation of Dopamine Transporter Activity by Nicotinic Acetylcholine Receptors and Membrane Depolarization in Rat Pheochromocytoma PC12 Cells
Authors: Huang Chuen‐Lin , Chen Hsiao‐Chun , Huang Nai‐Kuei , Yang De‐Ming , Kao Lung‐Sen , Chen Jin‐Chung , Lai Hsing‐Lin , Chern Yijuang
Published: March 2003

Abstract: To elucidate the regulation of the rat dopamine
transporter (rDAT), we established several PC12 variants overexpressing the
rDAT. Treating these cells with a nicotinic agonist
(1,1‐dimethyl‐4‐phenylpiperazinium iodide, 30 μM) depolarized the
plasma membrane potential from ‐31 ± 2 to 43 ± 5 mV and
inhibited rDAT activity significantly in a calcium‐ and protein kinase
C‐independent manner. Membrane depolarization by a high external K+
concentration or two K+ channel blockers (tetraethylammonium
hydroxide and BaCl2) also resulted in a marked inhibition of rDAT
activity. Such inhibition of dopamine uptake is due to a reduction in
Vmax, with no marked effect on the Km
for dopamine. The potency of cocaine in inhibiting dopamine uptake was not
significantly altered, whereas that of amphetamine was slightly enhanced by
membrane depolarization. Removing extracellular Ca2+ or blocking the voltage‐sensitive L‐type calcium channels using nifedipine did not exert any significant effect on the inhibition of rDAT activity by depolarization. These data confirm that calcium influx on depolarization is not required for inhibition of the rDAT. Collectively, our data suggest that rDAT activity can be altered by a neurotransmitter that modulates the membrane potential, thus suggesting an exquisite mechanism for the fine‐tuning of dopamine levels in the synapse.
Sepsis Increases Intracellular Free Calcium in Brain
Authors: Anderson Stasia A. , Song Sheng‐Kwei , Ackerman Joseph J. H. , Hotchkiss Richard S.
Published: March 2003

Abstract: Using magnetic resonance methods and a clinically relevant
rodent model of sepsis, we have made in vivo measurements of increased
intracellular calcium in a pathologic state in the CNS. The intracellular
calcium concentration was increased nearly twofold in septic rat brain
compared with controls (p < 0.0001). This result, in a fully
intact functioning mammalian system, ties together a previous spectrum of
indirect evidence from numerous laboratories suggesting an important role for
elevated intracellular calcium in sepsis. In addition, levels of the
proinflammatory cytokine tumor necrosis factor‐α were elevated threefold
in septic rat brain (p < 0.02), and electron microscopic examination revealed scattered injury in ∼0.25% of glial cells. These findings are discussed in light of the current understanding of the pathophysiology of sepsis.
The CholecystokininB Receptor Is Coupled to Two Effector Pathways Through Pertussis Toxin‐Sensitive and ‐Insensitive G Proteins
Authors: Pommier Blandine , Da Nascimento Sophie , Dumont Stéphanie , Bellier Bruno , Million Emmanuelle , Garbay Christiane , Roques Bernard P. , Noble Florence
Published: March 2003

Abstract: Previous binding studies have suggested the existence of two affinity states for type B cholecystokinin receptors (CCKBR), which could correspond to different coupling states of the receptor to G proteins. To test this hypothesis, we have further investigated signal transduction pathways coupled to rat CCKBR stably transfected in Chinese hamster ovary cells. We show that CCKBR are coupled to two distinct transduction pathways involving two different G proteins, a pertussis toxin‐insensitive/phospholipase C pathway leading to the production of inositol phosphate and arachidonic acid, and a pertussis toxin‐sensitive/phospholipase A2 pathway leading to the release of arachidonic acid. We further demonstrate that the relative degree of activation of each effector pathway by different specific CCKBR agonists is the same, and that a specific CCKBR antagonist, RB213, can differentially antagonize the two signal transduction pathways elicited by these agonists. Taken all together, these data could be explained by the recently proposed theory assuming that the receptor can exist in a three‐state model in which two active conformations corresponding to the complex formed by the receptor with two different G proteins coexist. According to this model, agonists or antagonists could recognize preferentially either conformation of the activated receptor, leading to variable behavior in a system containing a single receptor type.
Activation of Phosphatidylinositol 3‐Kinase, but Not Extracellular‐Regulated Kinases, Is Necessary to Mediate Brain‐Derived Neurotrophic Factor‐Induced Motoneuron Survival
Authors: Dolcet Xavier , Egea Joaquim , Soler Rosa M. , Martin‐Zanca Dionisio , Comella Joan X.
Published: March 2003

Abstract: Chick embryo spinal cord motoneurons develop a trophic response to some neurotrophins when they are maintained in culture in the presence of muscle extract. Thus, after 2 days in culture, brain‐derived neurotrophic factor (BDNF) promotes motoneuron survival. In the present study we have analyzed the intracellular pathways that may be involved in the BDNF‐induced motoneuron survival. We have observed that BDNF activated the extracellular‐regulated kinase (ERK) mitogen‐activated protein (MAP) kinase and the phosphatidylinositol (Pl) 3‐kinase pathways. To examine the contribution of these pathways to the survival effect triggered by BDNF, we used PD 98059, a specific inhibitor of MAP kinase kinase, and LY 294002, a selective inhibitor of Pl 3‐kinase. PD 98059, at doses that significantly reduced the phosphorylation of ERKs, did not show any prominent effect on neuronal survival. However, LY 294002 at doses that inhibited the phosphorylation of Akt, a down‐stream element of the Pl 3‐kinase, completely abolished the motoneuron survival effects of BDNF. Moreover, cell death triggered by LY 294002 treatment exhibited features similar to those observed after muscle extract deprivation. Our results suggest that the Pl 3‐kinase pathway plays an important role in the survival effect triggered by BDNF on motoneurons, whereas activation of the ERK MAP kinase pathway is not relevant.
Secreted Form of Amyloid Precursor Protein Enhances Basal Glucose and Glutamate Transport and Protects Against Oxidative Impairment of Glucose and Glutamate Transport in Synaptosomes by a Cyclic GMP‐Mediated Mechanism
Authors: Mattson Mark P. , Guo Zhi Hong , Geiger Jonathan D.
Published: March 2003

Abstract : Synaptic dysfunction and degeneration are believed to

underlie the cognitive deficits that characterize Alzheimer's disease, and

overactivation of glutamate receptors under conditions of increased oxidative

stress and metabolic compromise may contribute to the neurodegenerative

process in many different disorders. The secreted form of amyloid precursor

protein (sAPPα), which is released from neurons in an activity‐dependent

manner, can modulate neurite outgrowth, synaptic plasticity, and neuron

survival. We now report that sAPPα can enhance glucose and glutamate

transport in synaptic compartments. Treatment of cortical synaptosomes with

nanomolar concentrations of sAPPα resulted in an attenuation of

impairment of glutamate and glucose transport induced by exposure to amyloid

β‐peptide and Fe2+. The protective effect of sAPPα was mimicked by treatment with 8‐bromo‐cyclic GMP and blocked by a cyclic GMP‐dependent protein kinase inhibitor, suggesting that protective action of sAPPα is mediated by cyclic GMP. Our data suggest that glucose and glutamate transport can be regulated locally at the level of the synapse and further suggest important roles for sAPPα and cyclic GMP in modulating synaptic physiology under normal and pathophysiological conditions.