bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular events in senescing Arabidopsis leaves
Authors: Lin Ji‐Feng , Wu Shu‐Hsing
Published: July 2004

Senescence is the final stage of leaf development. Although it means the loss of vitality of leaf tissue, leaf senescence is tightly controlled by the development to increase the fitness of the whole plant. The molecular mechanisms regulating the induction and progression of leaf senescence are complex. We used a cDNA microarray, containing 11 500 Arabidopsis DNA elements, and the whole‐genome Arabidopsis ATH1 Genome Array to examine global gene expression in dark‐induced leaf senescence. By monitoring the gene expression patterns at carefully chosen time points, with three biological replicates each time, we identified thousands of up‐ or down‐regulated genes involved in dark‐induced senescence. These genes were clustered and categorized according to their expression patterns and responsiveness to dark treatment. Genes with different expression kinetics were classified according to different biological processes. Genes showing significant alteration of expression patterns in all available biochemical pathways were plotted to envision the molecular events occurring in the processes examined. With the expression data, we postulated an innovative biochemical pathway involving pyruvate orthophosphate dikinase in generating asparagine for nitrogen remobilization in dark‐treated leaves. We also surveyed the alteration in expression of Arabidopsis transcription factor genes and established an apparent association of GRAS, bZIP, WRKY, NAC, and C2H2 transcription factor families with leaf senescence.
Phosphate transport in Arabidopsis: Pht1;1 and Pht1;4 play a major role in phosphate acquisition from both low‐ and high‐phosphate environments
Authors: Shin Heungsop , Shin Hwa‐Soo , Dewbre Gary R. , Harrison Maria J.
Published: July 2004

Of the mineral nutrients essential for plant growth, phosphorus plays the widest diversity of roles and a lack of phosphorus has profound effects on cellular metabolism. At least eight members of the Arabidopsis Pht1 phosphate (Pi) transporter family are expressed in roots and Pht1;1 and Pht1;4 show the highest transcript levels. The spatial and temporal expression patterns of these two genes show extensive overlap. To elucidate the in planta roles of Pht1;1 and Pht1;4, we identified loss‐of‐function mutants and also created a double mutant, lacking both Pht1;1 and Pht1;4. Consistent with their spatial expression patterns, membrane location and designation as high‐affinity Pi transporters, Pht1;1 and Pht1;4 contribute to Pi transport in roots during growth under low‐Pi conditions. In addition, during growth under high‐Pi conditions, the double mutant shows a 75% reduction in Pi uptake capacity relative to wildtype. Thus, Pht1;1 and Pht1;4 play significant roles in Pi acquisition from both low‐ and high‐Pi environments.
Metabolism of avenanthramide phytoalexins in oats
Authors: Okazaki Yozo , Isobe Taishi , Iwata Yoichi , Matsukawa Tetsuya , Matsuda Fumio , Miyagawa Hisashi , Ishihara Atsushi , Nishioka Takaaki , Iwamura Hajime
Published: July 2004

Oat leaves produce phytoalexins, avenanthramides, in response to infection by pathogens or treatment with elicitors. The metabolism of avenanthramides was investigated using low molecular weight, partially deacetylated chitin as an elicitor. When oat leaf segments are floated on the elicitor solution, avenanthramides accumulate in the solution. The transfer of elicited oat leaves to solutions containing stable‐isotope‐labeled avenanthramides resulted in a rapid decrease in the labeled avenanthramides, suggesting the metabolism of avenanthramides. The rate of decrease was enhanced by elicitor treatment, and was dependent on the species of avenanthramides, with avenanthramide B decreasing most rapidly. The rates of biosynthesis and metabolism of avenanthramides A and B were measured using a model of isotope‐labeling dynamics. Avenanthramide B was found to be more actively biosynthesized and metabolized than avenanthramide A. Radiolabeled avenanthramide B was incorporated into the cell wall fraction and 99% of incorporated activity was released by alkaline treatment. Gel filtration indicated that high‐molecular‐weight compounds derived from avenanthramide B were released by alkaline treatment. The decrease in stable‐isotope‐labeled avenanthramides was suppressed by catalase, salicylhydroxamic acid, and sodium ascorbate, suggesting the involvement of peroxidase in the metabolism. Consistent with this, peroxidase activity that accepts avenanthramide B as a substrate was induced in apoplastic fractions by elicitor treatment. The appearance of multiple basic isoperoxidases was observed by activity staining with 3‐amino‐9‐ethylcarbazole coupled with isoelectric focusing of proteins from elicitor‐treated leaves. These findings suggest that accumulated avenanthramides are further metabolized in apoplasts in oat leaves by inducible isoperoxidases.
Stromule formation is dependent upon plastid size, plastid differentiation status and the density of plastids within the cell
Authors: Waters Mark T. , Fray Rupert G. , Pyke Kevin A.
Published: July 2004

Stromules are motile extensions of the plastid envelope membrane, whose roles are not fully understood. They are present on all plastid types but are more common and extensive on non‐green plastids that are sparsely distributed within the cell. During tomato fruit ripening, chloroplasts in the mesocarp tissue differentiate into chromoplasts and undergo major shifts in morphology. In order to understand what factors regulate stromule formation, we analysed stromule biogenesis in tobacco hypocotyls and in two distinct plastid populations in tomato mesocarp. We show that increases in stromule length and frequency are correlated with chromoplast differentiation, but only in one plastid population where the plastids are larger and less numerous. We used tobacco hypocotyls to confirm that stromule length increases as plastids become further apart, suggesting that stromules optimize the plastid–cytoplasm contact area. Furthermore, we demonstrate that ectopic chloroplast components decrease stromule formation on tomato fruit chromoplasts, whereas preventing chloroplast development leads to increased numbers of stromules. Inhibition of fruit ripening has a dramatic impact on plastid and stromule morphology, underlining that plastid differentiation status, and not cell type, is a significant factor in determining the extent of plastid stromules. By modifying the plastid surface area, we propose that stromules enhance the specific metabolic activities of plastids.
A Mixed Modelling Approach for Randomized Experiments with Repeated Measures
Authors: Piepho H. P. , Büchse A. , Richter C.
Published: July 2004

Repeated measurements on the same experimental unit are common in plant research. Due to lack of randomization and the serial ordering of observations on the same unit, such data give rise to correlations, which need to be accounted for in statistical analysis. Mixed modelling provides a flexible framework for this task. The present paper proposes a general method to formulate mixed models for designed experiments with repeated measurements. The approach is exemplified by way of several examples.
Environmental and Genotypic Effects on Pod Characteristics Related to Common Bean Quality
Authors: De Ron A. M. , Casquero P. A. , González A. M. , Santalla M.
Published: July 2004

A collection of 121 common bean (Phaseolus vulgaris L.) landraces from Spain and Portugal (Iberian Peninsula) was evaluated in six environments (three locations and 2 years). Significant differences among landraces were found for period of flowering, pod maturity and pod morphology (weight, length, width/thickness and curvature). Wide variation among landraces was revealed by the range of variation observed. Environmental effects were not significant although year × location and landrace × year × location interactions were significant for all traits studied except for pod curvature. Poor consistent expression across the different environments for most of the traits studied was expressed by the low values of constancy (C) with the exception of width/thickness indicating that pod shape (round or flat) was expressed regularly across different environments. Principal component analysis enhanced differences among environments affecting the performance of the bean landraces evaluated. Analysis by environment showed that 51 landraces were adapted to specific environments and only four of them had broad geographical adaptability with similar performance under different conditions. These results could be a starting point for selection of new inbred lines adapted to distinct environments with potential for the improvement of current snap bean cultivars.
Comparison of Fatty Acid Metabolism of Two Oleic and One Conventional Sunflower Hybrids: A New Hypothesis
Authors: Lagravère T. , Kleiber D. , Surel O. , Calmon A. , Bervillé A. , Dayde J.
Published: July 2004

Studies on oleic sunflower (Helianthus annuus L.) were carried out in order to determine which mechanism produces oleic and linoleic acids in oleic hybrids. The fatty acid composition of different lipid fractions (structural and storage forms) was followed during the achene development of three hybrids including cv. Santiago (non‐oleic hybrid), cv. Olbaril and cv. Trisun 870 (high oleic hybrids). In addition, a simple physiological model of fatty acid accumulation was developed. In order to complete this biochemical approach, a molecular study of desaturase gene accumulation has been preformed. The evolution of oleic and linoleic acid contents in achenes revealed the lack of Δ12‐desaturase activity in oleic hybrids and also indicated differences between oleic genotypes related to linoleic acid content in the first days after pollination and until maturity. Molecular studies (using Northern blot analysis) confirmed that the Δ12‐desaturase transcript was not expressed at the same time in oleic hybrids. These observations were confirmed by studies on the selective dispatching of oleic and linoleic acids in different lipid fractions during achene development. Trisun 870 showed a very low content of linoleic acid in triglycerides throughout achene maturation, whereas Olbaril presented a higher initial content followed by a rapid decrease. These results led us to put forward a new hypothesis for fatty acid biosynthesis in the oleic sunflower hybrids.
Effects of Reduced Tillage and Fertilization Practices on Soil Characteristics, Plant Water Status, Growth and Yield of Upland Cotton
Authors: Karamanos A. J. , Bilalis D. , Sidiras N.
Published: July 2004

Three different tillage practices, conventional (mouldboard ploughing at 22–25 cm plus one rotary hoeing at 5–6 cm, CT), minimum (one rotary hoeing at 12–15 cm, MT), and no‐tillage (direct drilling in soil covered by vetch residues, NT), combined with three fertilization treatments, inorganic (50 kg N ha−1 as ammonium sulphate), cattle manuring (30 t ha−1), and control (no‐fertilizer), were applied on a cotton crop (Gossypium hirsutum L. cv. Acala SJ‐2) grown on a clay loam soil in the field of the Agricultural University of Athens. Soil (gravimetric water content, bulk density, and penetration resistance in the top 40 cm) and plant parameters (root growth, leaf water potential, leaf area growth and seedcotton yield) were recorded throughout the cultivation period in all treatments. No‐tillage was associated with significantly higher values of soil water throughout the observation period caused by the vetch mulch. Bulk density and penetration resistance were initially higher in the no‐tilled plots, but they became significantly lower after 2–3 months from sowing. These beneficial effects on soil properties favoured root growth, expressed as root surface density, in the NT‐plots at the top soil layer. Similar, although less spectacular, effects were observed in the manured plots. Plant water status, expressed in terms of the water potential index, was significantly and consistently best in the NT‐ and worst in the CT‐plots throughout crop growth. In addition, NT favoured a better foliage growth and resulted in significantly higher yields than the other tillage practices. In general, NT, and in second instance, MT considerably improved plant water status, and hence foliage growth and yield in comparison with CT by maintaining higher levels of soil water and improving root growth. Manuring positively interacted with the reduced tillage practices for most soil and plant parameters.
Effects of Partial Defoliation on Sucrose Accumulation, Enzyme Activity and Agronomic Parameters in Sugar cane (Saccharum spp.)
Authors: Gutiérrez‐Miceli F. A. , Morales‐Torres R. , De Jesús Espinosa‐Castañeda Y. , Rincón‐Rosales R. , Montes‐Molina J. , Oliva‐Llaven M. A. , Dendooven L.
Published: July 2004

Mechanical defoliation of sugar cane plants (Saccharum spp.) will provide leaves that can be used as fodder. The effect of partial mechanical defoliation on sucrose content, enzyme activities and agronomic parameters of sugar cane is still unknown. We investigated how sucrose accumulation, activities of sucrose phosphate synthase, soluble acid invertase, sucrose synthase, neutral invertase, brix grades, purity grade, moisture content, fibre content, maturity index and reduced sugars of two commercial sugar cane plants (Mex 69‐290 and Mex 57‐473) were affected in a field experiment. The concentration of sucrose in stems of partial defoliated plants was not significantly different from that found in intact plants. Agronomic parameters and enzyme activities were not different in defoliated plants compared with intact plants except for the moisture content which was higher in defoliated plants than in intact ones. These results indicated that sugar cane plants could be partially defoliated without changing sucrose production and agronomic parameters while providing leaves that could be used as fodder.
Effects of Drought and Competition by a Ryegrass Sward on the Seedling Growth of a Range of Grassland Species
Authors: Hofmann M. , Isselstein J.
Published: July 2004

In de‐intensified grassland where an increased seedling recruitment is seen as a prerequisite to enhance plant species diversity, establishment success of introduced seeds of wildflower species is often poor. Outshading by the existing sward and dry weather spells when seedlings are at an early stage of development are major reasons for a low seedling establishment. The effects of drought and competition by an existing Lolium perenne sward on the growth of seedlings of seven wildflower species were investigated under standardized environmental conditions. Without competition (control), the relative growth rate of the wildflower seedlings varied between 103 (Tragopogon pratensis) and 184 mg g−1 day−1 (Leontodon autumnalis). Species differed in the extent of growth reduction by competition. Compared with the control, reduction of seedling dry weight ranged from 45 % (Trifolium pratense) up to 88 % (Daucus carota). The time range between onset of desiccation and first effects on growth varied between species, with T. pratense showing early and strong growth reduction in contrast to D. carota being least affected. It can be concluded, that those species which maintain a comparatively high growth rate supported by adapted shoot‐root allocation are most promising for establishment in grassland as they can exploit profiles of higher resource availability.
Adipocyte lipolysis, hormonal and metabolic changes in ethanol‐drinking rats
Authors: Szkudelski T. , Bialik I. , Szkudelska K.
Published: July 2004

The effect of ethanol drinking on some hormonal and metabolic changes in the rat and on lipolysis in isolated adipocytes was tested. Male growing Wistar rats divided into two groups were used in the experiment. Ten per cent ethanol solution as the only drinking fluid for 2 weeks depressed body weight gain. The diminution of blood insulin with simultaneous increase in leptin concentration found in these rats suggest that the physiological regulation of leptin secretion is disturbed by ethanol. Liver triglycerides content was substantially augmented due to ethanol ingestion. Adipocytes were isolated from both groups of rats by collagenase digestion and the lipolytic activity of these cells was compared. Isolated cells (106/ml) were incubated for 90 min in Krebs–Ringer buffer (pH 7.4, 37 °C) containing 3 mm glucose and different lipolytic modulators: adrenaline (1 μm), insulin (1 nm), dibutyryl‐cAMP (1 mm) and DPCPX (a selective antagonist of adenosine A1 receptor, 1 μm). To determine basal lipolysis cells were incubated without lipolytic agents. Lipolysis was determined by the amount of glycerol released from cells to the incubation medium. Basal and adrenaline‐induced lipolysis was depressed in adipocytes of ethanol‐drinking rats. The antilipolytic activity of insulin was the same in both groups of isolated cells. Lipolysis induced by dibutyryl‐cAMP was only slightly reduced due to ethanol consumption, whereas triglycerides breakdown evoked by adenosine A1 receptor antagonism was unchanged. Results obtained in vitro indicate that subchronic ethanol drinking attenuates basal and stimulated lipolysis in adipocytes, however, the antilipolytic effect of insulin and the adenosine pathway are unchanged.
Consequences of eicosapentaenoic acid (n‐3) and arachidonic acid (n‐6) supplementation on mast cell mediators
Authors: Gueck T. , Seidel A. , Fuhrmann H.
Published: July 2004

Mast cells are important players in the pathogenesis of atopic diseases. These cells release immediate‐phase and late‐phase mediators of inflammation. Fatty acids are incorporated in cellular membranes and therefore seem to influence mediator production and release. A study was conducted to assess the effects of eicosapentaenoic acid (EPA, 20:5n‐3) and arachidonic acid (AA, 20:4n‐6) on mast cell mediators in a canine mastocytoma cell line (C2). Cells were cultured in a basic medium (Dulbecco's modified Eagle's medium/HAM's F12 1 : 1, DEH), DEH supplemented with 14.0 μm EPA (DEH‐EPA) or 14 μm AA (DEH‐AA). The DEH‐AA cultured cells had increased spontaneous and mastoparan‐stimulated PGE2 production and histamine release. Furthermore, the tryptase activity was increased. The DEH‐EPA cultured cells rendered elevated levels of PGE2 and histamine release compared with DEH only after stimulation. These levels were significantly lower in comparison to DEH‐AA. The increased PGE2 production of C2 cultured in DEH‐AA is the consequence of the AA enrichment, because AA is the precursor of PGE2. However, the different effects by AA and EPA on mast cell mediators possibly reflect the higher susceptibility of long chain polyunsaturated fatty acids (PUFA) to undergo lipid peroxidation, because it is known that altered cellular redox state influences mediator production and release.
Diurnal rhythm in heat production and oxidation of carbohydrate and fat in pigs during feeding, starvation and re‐feeding
Authors: Chwalibog A. , Tauson A.‐H. , Thorbek G.
Published: July 2004

Diurnal rhythm in heat production (HE), oxidation of carbohydrate (OXCHO) and fat (OXF) was calculated from daily measurements of gas exchange in 12 pigs [20–40 kg live weight, (LW)] during 6 days of near ad libitum feeding, followed by 4 days of starvation and 4 days of re‐feeding. All measurements, divided in five times intervals from 12.00 to 8.00, showed the highest values of HE, reflecting the animals’ energy requirements, between 12.00 and 16.00 gradually declining to the lowest values between 4.00 and 8.00. The values measured in the interval 4.00–8.00 were considered as a basal metabolic rate (BMR), being in all measurements 25% lower than during 12.00–4.00. The lowest BMR was measured on the fourth day of starvation (21.7 kJ/h·kg0.75). By transition from feeding to starvation, OXCHO declined gradually, but was for 16 h able to cover the energy requirement with no contribution from OXF. The decline in OXCHO proceeded for 40 h and reached zero between 4.00 and 8.00 on the first day of starvation with the energy requirement being covered by OXF. The HE during starvation was 25–30% lower than during feeding caused by absence of feed‐induced thermogenesis and by the transition from OXCHO to OXF. Immediately after re‐feeding dietary carbohydrates were oxidized, however, there was still a substantial OXF, proceeding until the next feeding. From the second day of re‐feeding the contribution of substrates to the total HE was re‐established with no OXF and the same level of HE as during feeding.
Lipid concentrations of fillets, liver, plasma and lipoproteins of African catfish, Clarias gariepinus (Burchell 1822), fed diets with varying protein concentrations
Authors: Matter F. , Peganova S. , Eder K.
Published: July 2004

This study investigated the effect of the dietary protein concentration on lipid concentrations in fillet and liver and concentrations of lipids in plasma and lipoproteins in African catfish. Two experiments were carried out, in which African catfish were fed diets with various protein concentrations. In experiment 1, semisynthetic diets with various concentrations of casein (350, 450 or 550 g protein/kg) were used. In experiment 2, diets were based on a commercial trout diet supplemented with various amounts of casein or carbohydrates, resulting in protein concentrations between 282 and 545 g/kg diet. In both experiments, the dietary protein concentration had a significant effect on growth, feed conversion ratio and carcass composition. Maximum of body weight gains and feed efficiency ratios were reached in both experiments at the highest dietary protein concentrations. Increasing the dietary protein concentration continuously increased masses of fillets and reduced masses of the liver and adipose tissue in the abdominal cavity. Fish fed the diets with the highest protein concentrations had the lowest concentration of total lipids, triglycerides and cholesterol in the fillets, the highest percentage of polyunsaturated fatty acids (PUFA) in total lipids of fillets and the lowest concentrations of saturated fatty acids (SFA). Fish fed the diets with the highest protein concentration also had the lowest concentrations of triglycerides in the liver, the highest percentages of PUFA in liver total lipids and the lowest percentages of SFA. Moreover, fish fed diets with high protein concentrations (501 and 545 g/kg) had significantly lower concentrations of triglycerides, cholesterol and phospholipids in plasma than fish fed diets with lower protein concentrations. In conclusion, this study shows that the dietary protein concentration does not only influence growth, feed efficiency and carcass composition in African catfish, but also influences their lipid metabolism and lipid concentrations of liver and fillet.
Effect of glycine and vitamin supplementation on sulphur amino acid utilization by growing cattle
Authors: Lambert B. D. , Titgemeyer E. C. , Löest C. A. , Johnson D. E.
Published: July 2004

Effects of glycine (Gly) and B‐vitamins on sulphur amino acid (AA) utilization were studied in growing steers maintained under conditions where methionine (Met) was first limiting. Conditions were generated by limit feeding a diet low in ruminally non‐degraded protein and abomasally infusing an AA mixture limiting in Met. Retained N tended (p = 0.07) to improve when steers received 10 mg folate, 10 mg vitamin B6, and 0.10 mg vitamin B12 daily. Hepatic vitamin B12 (p = 0.08) and folate (p = 0.05) concentrations increased with vitamin supplementation. In another trial, factorial treatments were 2 or 5 g/day l‐Met and 0 or 50 g/day Gly infused abomasally. Retained N increased (p < 0.05) in response to Met, and responses were numerically larger in the presence of supplemental Gly. In a different trial, factorial treatments were 0 or 2.4 g/day l‐cysteine (Cys) and 0 or 40 g/day Gly. Retained N was not affected by Cys in the absence of Gly, but was increased by Cys when Gly was supplemented (interaction, p = 0.01). B‐vitamin status may affect sparing of Met by Cys. Supplemental Gly improved responses to supplemental Met and Cys.
Relationship between the in vitro‐estimated utilizable crude protein and the Cornell Net Carbohydrate and Protein System crude protein fractions in feeds for ruminants
Authors: Zhao G. Y. , Cao J. E.
Published: July 2004

The objectives of this experiment were to study the regression relationship between the in vitro‐estimated utilizable crude protein (uCP) and the Cornell Net Carbohydrate and Protein System (CNCPS) crude protein fractions, i.e. PA, PB1, PB2, PB3 and PC of feeds for ruminants, and the possibility of using CNCPS crude protein fractions for the estimation of uCP of feeds for ruminants. The CP, the non‐protein nitrogen (NPN), the soluble cru de protein (SCP), the neutral detergent insoluble crude protein (NDICP) and the acid detergent insoluble crude protein (ADICP) of 30 single feeds were determined and the CP fractions, i.e. PA, PB1, PB2, PB3 and PC, were then calculated based on CNCPS. The uCP of the 30 feeds was estimated using the in vitro incubation technique of Zhao and Lebzien (2000). It was found that there was a significant multiple regression relationship between the uCP [g/kg dry matter (DM)] and the CNCPS crude protein fractions, i.e. PA (% DM), PB1 (% DM), PB2 (% DM), PB3 (% DM) and PC (% DM) of the feed samples. uCP = (9.95 ±2.73)PA + (2.92 ± 1.36)PB1 + (7.24 ± 0.86)PB2 + (8.20 ± 3.33)PB3 + (17.67 ± 3.79) PC + (63.26 ± 18.02), r2 = 0.90, n = 30, p < 0.0001. It was suggested that the multiple regression relationship shown above could be used for the estimation of the uCP of feeds based on the CNCPS crude protein fractions PA, PB1, PB2, PB3 and PC of feeds for ruminants.
International collaboration to address common problems in health care: processes, practicalities and power
Authors: Rolfe M. K. , Bryar R. M. , Hjelm K. , Apelquist J. , Fletcher M. , Anderson B.‐L.
Published: July 2004

This article reports on an international collaborative study into the management of chronic leg ulcers by nurses working in the community in Kronoberg, Sweden and the East Riding and Hull, UK. The management of leg ulcers like many other services provided by nurses working in the community is one that is growing out of community need, often without matching resources. This article reports on some of the processes that were involved and some of the practical considerations that were faced and addressed in formulating and conducting an international collaborative study. The article also explores the ‘power’ international collaboration brings to the research enterprise.
Foreign Aid, Innovation, and Technology Transfer in a North–South Model with Learning‐by‐Doing
Authors: Benarroch Michael , Gaisford James D.
Published: August 2004

The paper examines foreign aid in the context of a dynamic Ricardian model of trade and development that highlights the role of learning in both the initial adoption of new technologies and products and their eventual transfer from developed to developing countries. When aid is paid as a pure unilateral transfer, the conventional short‐run terms‐of‐trade improvement that results from a home bias in consumption causes harmful delays in the transfer of technology that can lead to mutual immiserization. Conversely, aid that directly or indirectly expedites technology transfer and learning in developing countries can be mutually beneficial.
Cost‐effectiveness Analysis of Demand‐ and Supply‐side Education Interventions: the Case of PROGRESA in Mexico
Authors: Coady David P. , Parker Susan W.
Published: August 2004

The paper is concerned with the issue of the most cost‐effective way of improving access to education for poor households in developing countries. The authors consider two alternatives: extensive expansion of the school system (i.e., bringing education to the poor), and subsidizing investment in education by the poor (i.e., bringing the poor to the education system). To this end, the authors evaluate PROGRESA, a large poverty‐alleviation program recently introduced in Mexico, which subsidizes education. Using double‐difference regression estimators on data collected before and after the program for randomly selected “control” and “treatment” households, the relative impacts of the demand‐ and supply‐side program components are estimated. Combining these estimates with cost information, it is found that the demand‐side subsidies are substantially more cost‐effective than supply‐side expansions.
Multilateral Reforms of Trade and Environmental Policy
Authors: Turunen‐Red Arja H. , Woodland Alan D.
Published: July 2004

The paper analyzes environmental tax policy reform using a competitive model of world trade that includes production‐generated environmental damage (pollution) and trade tariffs. The authors examine the feasibility of Pareto‐improving multilateral reforms of environmental taxes, and show that any environmental tax reform that is mutually welfare‐improving when compensating lump‐sum transfers are assumed is also welfare‐improving when a suitable tariff reform (but no transfers) is combined with the tax changes. Several specific reform proposals are developed. These results expand the feasible set of mutually improving policy proposals for international policy initiatives.
Code‐sharing Agreements and Interconnections in Markets for International Flights
Authors: Hassin Orit , Shy Oz
Published: July 2004

The paper investigates the consequences of code‐sharing agreements among airline firms competing on international routes, where some passengers interconnect to flights originating or terminating at cities not served by foreign airlines. The authors calculate the precise market share captured by flights operated under code sharing. They compare airfares, market shares, profits, and passengers’ welfare before and after the implementation of a code‐sharing agreement and demonstrate that code sharing is Pareto‐improving.
The Influence of Social Context on Partnerships in Canadian Health Systems
Authors: Scott Catherine M. , Thurston Wilfreda E.
Published: August 2004

Partnerships, collaboration, joined‐up government; these terms have become common elements of global health and social policy discourse. The terms may be pervasive but there remain significant challenges to collaborative ways of working. We argue that some of these challenges arise from a failure to account explicitly for the influence of social context. Between 1999 and 2001 we conducted a comparative case study of partnerships in Canadian health systems in which we examined specifically the roles of social context and gender. Social structures directly linked to formalized health systems are embedded in social institutions based on patriarchal and bureaucratic practices that do not traditionally support the relational practices required for the development of partnerships. While individuals within such organizations may have the knowledge, skills and commitment to collaborate, in such an environment, tremendous resource expenditures are required to achieve and maintain collaborative advantage.
Receptor‐mediated control of regulatory volume decrease (RVD) and apoptotic volume decrease (AVD)
Authors: Okada Yasunobu , Maeno Emi , Shimizu Takahiro , Dezaki Katsuya , Wang Jun , Morishima Shigeru
Published: August 2004

A fundamental property of animal cells is the ability to regulate their own cell volume. Even under hypotonic stress imposed by either decreased extracellular or increased intracellular osmolarity, the cells can re‐adjust their volume after transient osmotic swelling by a mechanism known as regulatory volume decrease (RVD). In most cell types, RVD is accomplished mainly by KCl efflux induced by parallel activation of K+ and Cl− channels. We have studied the molecular mechanism of RVD in a human epithelial cell line (Intestine 407). Osmotic swelling results in a significant increase in the cytosolic Ca2+ concentration and thereby activates intermediate‐conductance Ca2+‐dependent K+ (IK) channels. Osmotic swelling also induces ATP release from the cells to the extracellular compartment. Released ATP stimulates purinergic ATP (P2Y2) receptors, thereby inducing phospholipase C‐mediated Ca2+ mobilization. Thus, RVD is facilitated by stimulation of P2Y2 receptors due to augmentation of IK channels. In contrast, stimulation of another G protein‐coupled Ca2+‐sensing receptor (CaR) enhances the activity of volume‐sensitive outwardly rectifying Cl− channels, thereby facilitating RVD. Therefore, it is possible that Ca2+ efflux stimulated by swelling‐induced and P2Y2 receptor‐mediated intracellular Ca2+ mobilization activates the CaR, thereby secondarily upregulating the volume‐regulatory Cl− conductance. On the other hand, the initial process towards apoptotic cell death is coupled to normotonic cell shrinkage, called apoptotic volume decrease (AVD). Stimulation of death receptors, such as TNFα receptor and Fas, induces AVD and thereafter biochemical apoptotic events in human lymphoid (U937), human epithelial (HeLa), mouse neuroblastoma × rat glioma hybrid (NG108‐15) and rat phaeochromocytoma (PC12) cells. In those cells exhibiting AVD, facilitation of RVD is always observed. Both AVD induction and RVD facilitation as well as succeeding apoptotic events can be abolished by prior treatment with a blocker of volume‐regulatory K+ or Cl− channels, suggesting that AVD is caused by normotonic activation of ion channels that are normally involved in RVD under hypotonic conditions. Therefore, it is likely that G protein‐coupled receptors involved in RVD regulation and death receptors triggering AVD may share common downstream signals which should give us key clues to the detailed mechanisms of volume regulation and survival of animal cells. In this Topical Review, we look at the physiological ionic mechanisms of cell volume regulation and cell death‐associated volume changes from the facet of receptor‐mediated cellular processes.
Effects of ryanodine on calcium sparks in cut twitch fibres of Rana temporaria
Authors: Hui Chiu Shuen , Bidasee Keshore R. , Besch Henry R.
Published: August 2004

Localized calcium release events (calcium sparks) were studied in voltage‐clamped cut twitch fibres of Rana temporaria.

A histogram of thousands of spontaneous sparks displayed a monotonically decreasing amplitude distribution from the low to the high limit of > 7 ΔF/F0 units.

Several effects of low micromolar concentrations of ryanodine (0.4‐2 μm) on spontaneous sparks, reproducing the agent's effects on single ryanodine receptor channel current in bilayers, were observed collectively for the first time in live fibres, namely (a) increases in spark frequency followed by (b) conversions of sparks into steady glows lasting tens of seconds, (c) occasional interruptions of the glows by brief gaps of darkness, and (d) abolition of sparks at the locations of the glows. The glow could reflect the incessant Ca2+ flux through a single (or a few) calcium release channel locked in the semi‐open state, which was allowed to make occasional transitions to the closed state but not to the fully open state.

Higher concentrations of ryanodine (≥ 20 μm) suppressed the spontaneous sparks effectively and permanently, presumably by deactivating the ryanodine receptors.

Depolarization‐evoked sparks elicited with small pulses had higher frequencies and larger amplitudes than spontaneous sparks and were abolished by both concentrations of ryanodine.

With 1‐2 μm ryanodine, however, a uniform non‐sparking calcium release persisted during the pulse, with the globally averaged increase in fluorescence intensity being about half that of the control. A possible origin of this non‐sparking release may be related to the structural coupling between the voltage sensors and the ryanodine receptors that can exist only in live fibres but not in the bilayer preparation.
Muscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications
Authors: Proske U. , Morgan D. L.
Published: August 2004

In eccentric exercise the contracting muscle is forcibly lengthened; in concentric exercise it shortens. While concentric contractions initiate movements, eccentric contractions slow or stop them. A unique feature of eccentric exercise is that untrained subjects become stiff and sore the day afterwards because of damage to muscle fibres. This review considers two possible initial events as responsible for the subsequent damage, damage to the excitation‐contraction coupling system and disruption at the level of the sarcomeres. Other changes seen after eccentric exercise, a fall in active tension, shift in optimum length for active tension, and rise in passive tension, are seen, on balance, to favour sarcomere disruption as the starting point for the damage. As well as damage to muscle fibres there is evidence of disturbance of muscle sense organs and of proprioception. A second period of exercise, a week after the first, produces much less damage. This is the result of an adaptation process. One proposed mechanism for the adaptation is an increase in sarcomere number in muscle fibres. This leads to a secondary shift in the muscle's optimum length for active tension. The ability of muscle to rapidly adapt following the damage from eccentric exercise raises the possibility of clinical applications of mild eccentric exercise, such as for protecting a muscle against more major injuries.
Modulation of hypoglossal motoneuron excitability by NK1 receptor activation in neonatal mice in vitro
Authors: Yasuda Kouichi , Robinson Dean M. , Selvaratnam Subramaniam R. , Walsh Carmen W. , McMorland Angus J. C. , Funk Gregory D.
Published: August 2004

The effects of substance P (SP), acting at NK1 receptors, on the excitability and inspiratory activity of hypoglossal (XII) motoneurons (MNs) were investigated using rhythmically active medullary‐slice preparations from neonatal mice (postnatal day 0‐3).

Local application of the NK1 agonist [SAR9,Met (O2)11]‐SP (SPNK1) produced a dose‐dependent, spantide‐ (a non‐specific NK receptor antagonist) and GR82334‐(an NK1 antagonist) sensitive increase in inspiratory burst amplitude recorded from XII nerves.

Under current clamp, SPNK1 significantly depolarized XII MNs, potentiated repetitive firing responses to injected currents and produced a leftward shift in the firing frequency‐current relationships without affecting slope.

Under voltage clamp, SPNK1 evoked an inward current and increased input resistance, but had no effect on inspiratory synaptic currents. SPNK1 currents persisted in the presence of TTX, were GR82334 sensitive, were reduced with hyperpolarization and reversed near the expected EK.

Effects of the α1‐noradrenergic receptor agonist phenylephrine (PE) on repetitive firing behaviour were virtually identical to those of SPNK1. Moreover, SPNK1 currents were completely occluded by PE, suggesting that common intracellular pathways mediate the actions of NK1 and α1‐noradrenergic receptors. In spite of the similar actions of SPNK1 and PE on XII MN responses to somally injected current, α1‐noradrenergic receptor activation potentiated inspiratory synaptic currents and was more than twice as effective in potentiating XII nerve inspiratory burst amplitude.

GR82334 reduced XII nerve inspiratory burst amplitude and generated a small outward current in XII MNs. These observations, together with the first immunohistochemical evidence in the newborn for SP immunopositive terminals in the vicinity of SPNK1‐sensitive inspiratory XII MNs, support the endogenous modulation of XII MN excitability by SP.

In contrast to phrenic MNs (Ptak et al. 2000), blocking NMDA receptors with AP5 had no effect on the modulation of XII nerve activity by SPNK1.

In conclusion, SPNK1 modulates XII motoneuron responses to inspiratory drive primarily through inhibition of a resting, postsynaptic K+ leak conductance. The results establish the functional significance of SP in controlling upper airway tone during early postnatal life and indicate differential modulation of motoneurons controlling airway and pump muscles by SP.
Role of α2‐adrenoceptors in the sympathetic inhibition of motility reflexes of guinea‐pig ileum
Authors: Stebbing M. J. , Johnson P. J. , Vremec M. A. , Bornstein J. C.
Published: August 2004

Sympathetic regulation of the motility of guinea‐pig ileum was investigated using mesenteric nerve (MN) stimulation to inhibit motility reflexes, in vitro.

Transmural electrical stimulation (5 Hz, 1 s) in intact intestinal segments, or inflation of a balloon against the mucosa in opened segments, evoked contractions of the circular and longitudinal muscles oral to the stimulus.

MN stimulation (10 Hz, 5 s) usually abolished contractions of the longitudinal and circular muscles evoked by either electrical or mechanical stimuli.

The inhibition was mimicked by UK14,304 (70‐100 nm) and abolished by idazoxan (100 nm), revealing an enhancement of circular muscle contractions. There was no evidence for α2‐receptors on the muscle, suggesting sympathetic inhibition was via the myenteric plexus.

Possible sites of action of noradrenaline released from sympathetic nerves were investigated using intracellular recordings from the circular muscle in a multichambered organ bath.

When in the stimulation chamber, UK14,304 depressed (by 50 %) excitatory junction potentials (EJPs) recorded oral to a distension stimulus, but did not affect inhibitory junction potentials (IJPs) recorded anal to the stimulus. When added to a chamber between the stimulus and recording chambers, UK14,304 depressed EJPs by 40 %, but did not alter IJPs. When in the recording chamber, UK14,304 depressed EJPs by 20 %, but had no effect on IJPs. IJPs were inhibited, however, when UK14,304 was applied to the whole bath.

It is concluded that sympathetic activity inhibits intestinal motility mainly via α2‐adrenoceptors on ascending interneurons and intrinsic sensory neurons of the orally directed reflex pathway.
Neural prostheses
Authors: Prochazka Arthur , Mushahwar Vivian K. , McCreery Douglas B.
Published: August 2004

Assuming that neural regeneration after spinal cord injury (SCI) will eventually become a clinical reality, functional recovery will probably remain incomplete. Assistive devices will therefore continue to play an important role in rehabilitation. Neural prostheses (NPs) are assistive devices that restore functions lost as a result of neural damage. NPs electrically stimulate nerves and are either external or implanted devices. Surface stimulators for muscle exercise are now commonplace in rehabilitation clinics and many homes. Regarding implantable NPs, since 1963 over 40 000 have been implanted to restore hearing, bladder control and respiration. Epidural spinal cord stimulators and deep brain stimulators are routinely implanted to control pain, spasticity, tremor and rigidity. Implantable NPs have also been developed to restore limb movements using electrodes tunnelled under the skin to muscles and nerves. Spinal cord microstimulation (SCμstim) is under study as an alternative way of restoring movement and bladder control. Improvement in bladder and bowel function is a high priority for many SCI people. Sacral root stimulation to elicit bladder contraction is the current NP approach, but this usually requires dorsal rhizotomies to reduce reflex contractions of the external urethral sphincter. It is possible that the spinal centres coordinating the bladder‐sphincter synergy could be activated with SCμstim. Given the large and growing number of NPs in use or development, it is surprising how little is known about their long‐term interactions with the nervous system. Physiological research will play an important role in elucidating the mechanisms underlying these interactions.
Regulation of KChIP2 potassium channel β subunit gene expression underlies the gradient of transient outward current in canine and human ventricle
Authors: Rosati Barbara , Pan Zongming , Lypen Steven , Wang Hong‐Sheng , Cohen Ira , Dixon Jane E. , McKinnon David
Published: August 2004

Expression of four members of the KChIP family of potassium channel β subunits was examined in canine heart. Only one member of the gene family, KChIP2, was expressed in heart.

There was a steep gradient of KChIP2 mRNA expression across the canine ventricular free wall. KChIP2 mRNA was 25‐fold more abundant in the epicardium than in the endocardium, and this gradient paralleled the gradient in transient outward current (Ito) expression. In contrast, Kv4.3 potassium channel α subunit mRNA was expressed at equal levels across the ventricular wall.

There was no difference in the pharmacological sensitivity of epicardial and endocardial Ito channels to flecainide, suggesting that the current is produced by the same channel in the two tissues.

A similar gradient of KChIP2 expression was found across the ventricular wall of human heart, but not rat heart.

It is concluded that transcriptional regulation of the KChIP2β subunit gene, rather than the Kv4.3α subunit gene, is the primary determinant regulating the transmural gradient of Ito expression in the ventricular free wall of canine and human heart.
The cortical deficit in humans with strabismic amblyopia
Authors: Barnes G. R. , Hess R. F. , Dumoulin S. O. , Achtman R. L. , Pike G. B.
Published: August 2004

To further our understanding of the cortical deficit in strabismic amblyopia, we measured, compared and mapped functional magnetic resonance imaging (fMRI) activation between the fixing and fellow amblyopic eyes of ten strabismic amblyopes.

Of specific concern was whether the function of any visual area was spared in strabismic amblyopia, as recently suggested by both positron emission tomography (PET) and fMRI studies, and whether there was a close relationship between the fMRI response and known psychophysical deficits.

To answer these questions we measured the psychophysical deficit in each subject and used stimuli whose relationship to the psychophysical deficit was known.

We observed that stimuli that were well within the amblyopic passband did produce reduced fMRI activation, even in visual area V1. This suggests that V1 is anomalous in amblyopia. A similar level of reduction was observed in V2.

In two subjects, we found that stimuli outside the amblyopic passband produced activation in visual area V3A.

We did not find a close relationship between the fMRI response reduction in amblyopia and either of the known psychophysical deficits even though the fMRI response reduction in amblyopia did covary with stimulus spatial frequency.
Ca2+ signalling and PKCα activate increased endothelial permeability by disassembly of VE—cadherin junctions
Authors: Sandoval Raudel , Malik Asrar B. , Minshall Richard D. , Kouklis Panos , Ellis Chad A. , Tiruppathi Chinnaswamy
Published: August 2004

The role of intracellular Ca2+ mobilization in the mechanism of increased endothelial permeability was studied. Human umbilical vein endothelial cells (HUVECs) were exposed to thapsigargin or thrombin at concentrations that resulted in similar increases in intracellular Ca2+ concentration ([Ca2+]i). The rise in [Ca2+]i in both cases was due to release of Ca2+ from intracellular stores and influx of extracellular Ca2+.

Both agents decreased endothelial cell monolayer electrical resistance (a measure of endothelial cell shape change) and increased transendothelial 125I‐albumin permeability. Thapsigargin induced activation of PKCα and discontinuities in VE‐cadherin junctions without formation of actin stress fibres. Thrombin also induced PKCα activation and similar alterations in VE‐cadherin junctions, but in association with actin stress fibre formation.

Thapsigargin failed to promote phosphorylation of the 20 kDa myosin light chain (MLC20), whereas thrombin induced MLC20 phosphorylation consistent with formation of actin stress fibres.

Calphostin C pretreatment prevented the disruption of VE‐cadherin junctions and the decrease in transendothelial electrical resistance caused by both agents. Thus, the increased [Ca2+]i elicited by thapsigargin and thrombin may activate a calphostin C‐sensitive PKC pathway that signals VE‐cadherin junctional disassembly and increased endothelial permeability.

Results suggest a critical role for Ca2+ signalling and activation of PKCα in mediating the disruption of VE‐cadherin junctions, and thereby in the mechanism of increased endothelial permeability.