bluuebunny/crossref_metadata_2025 huggingface dataset:
U.S. Farm Safety Nets and the 2000 Agricultural Risk Protection Act
Authors: Goodwin Barry K.
Published: July 2005

Although crop insurance programs have been an important part of U.S. agricultural policy since the 1930s, the “safety net” matra has taken on new relevance and importance in recent policy deliberations and rhetoric. This paper contains a non technical review of issues underlying the safety net concept in U.S. agricultural policy. We outline recent changes in U.S. crop insurance programs and review provisions of the 2000 Agricultural Risk Protection Act (ARPA), which had a significant impact on U.S. risk management programs by expanding crop and revenue insurance subsidies and stimulating new product development. A simple empirical analysis of how these changes may have affected program participation is considered. We then outline points relevant to 2002 Farm Bill deliberations. As is pointed out, the safety net concept seems pervasive to all policy discussions. Countercylical payments, even when provided on an ad hoc basis, may distort production and trade conditions.
Alternative Firm Strategies for Signaling Quality in the Food System
Authors: Sporleder Thomas L. , Goldsmith Peter D.
Published: July 2005

Dynamics in the global food system, coupled with rapid advance in agricultural biotechnology, have resulted in additional demands for capturing information and sharing information vertically within the supply chain. Food safety and quality characteristics are a cornerstone of this information demand. Events such as foot‐and‐mouth disease (FMD) and bovine spongiform encephalopathy (BSE), genetic engineering and animal welfare concerns have laid the foundation for additional information need.

Managers of private firms within the food supply chain must decide how to respond to the situation. A crucial component of the problem is what and how to provide information to downstream customers as well as stipulate what and how information is received from upstream suppliers. Alternative signaling mechanisms abound. The choice among these alternative signals, or combination of alternatives, has both short‐ and long‐run implications for the reputation of the firm, its products or services, and the efficiency with which it conducts its business. The signaling problem in the supply chain is bidirectional and has three critical dimensions: information asymmetry, incentive asymmetry, and arduous measurability. From a broad perspective, the choice set for signaling includes: strategies that rely on third‐party protocols and procedures; differentiation through branding and reputation; indemnification strategies such as insurance, warranties, and bonding; and coordination strategies such as strategic alliances and vertical integration (intemalization). Each mechanism for signaling differentially influences the three dimensions of the signaling problem. No globally optimal strategy solution exists. Differentiation through branding and reputation mitigate the signaling problem relatively well compared with the other alternatives.
The Economics of Controlling Infectious Diseases on Dairy Farms
Authors: Chi Junwook , Weersink Alfons , VanLeeuwen John A. , Keefe Gregory P.
Published: July 2005

Cost‐effective disease control on the dairy farm can enhance productivity and subsequently profitability. Previous economic studies on animal disease have focused on production losses and evaluation of disease eradication programs and have provided little guidance on the optimal prevention action. This paper presents a theoretical model on the economics of livestock disease and develops an empirical model to determine the optimal set of control strategies for four production‐limiting cattle diseases: bovine viral diarrhea (BVD), enzootic bovine leukosis (EBL), Johne's Disease (JD) and neosporosis. Control functions indicating the prevalence of infection with each of the four diseases for each of the 10 strategies are estimated. The optimal strategies that minimize total disease cost (direct production losses and control expenditures) are provided for each disease on the basis of farm survey results from the maritime provinces. The results emphasize the importance of introduction checks before new animals enter the herd and adequate vaccination protection as cost‐effective control strategies.

Lutter contre la maladie d'une manière rentable dans les élevages de bovins laitiers peut déboucher sur un meilleur rendement et des profits plus élevés. Les études économiques antérieures s'intéressant à cet aspect portaient essentiellement sur les pertes de production et l'évaluation des programmes d'éradication. Elles donnaient peu d'indications sur la solution idéale au niveau de la prévention. Cet article présente un modèle théorique de l'économique des maladies du bétail et aboutit à un modèle empirique permettant d'établir le jeu optimal de moyens pour lutter contre quatre maladies réduisant la production animale : la diarrhée à virus des bovins (DVB), la leucose bovine enzootique (LBE), la paratuberculose et la néosporose. Les auteurs estiment les fonctions qui indiquent la prévalence d'une infection pour chacune des quatre maladies retenues, dans le cadre des dix stratégies examinées. Ensuite, ils présentent les meilleures stratégies, à savoir celles qui minimisent le coût total de la maladie (pertes de production directes et dépenses associées à la lutte contre la maladie), pour chaque maladie en fonction des résultats d'un sondage auprès des éleveurs des provinces de l'Atlantique. Tout indique que les méthodes de lutte les plus rentables sont l'examen de l'animal avant son addition au troupeau et une vaccination qui protègera les bêtes de manière adéquate.
Termination of the WGTA: An Examination of Factor Market Distortions, Input Subsidies anc Compensation
Authors: Schmitz Troy G. , Highmoor Tim , Schmitz Andrew
Published: July 2005

Input subsidies are common in North American agriculture and create production and trade distortions. As the theoretical discussion in this paper shows, the Crow transportation subsidy was no exception. The Crow benefit was eliminated in 1996 with the elimination of the Western Grain Transportation Act. Under the “pay the producer” approach, farmers in western Canada were compensated for the removal of the Crow subsidy, but the compensation was nowhere near that required to make grain and oilseed producers in western Canada at least as well off as before the Crow subsidy was removed. This policy change satisfied the compensation principle but not the Pareto principle. Reasons are given why this was the case, including very divergent views from various farm groups such as the National Farmers Union, the Alberta Cattle Commission, and the Alberta Barley Growers Association.

Les intrants du secteur agricole sont souvent subventionnés en Amérique du Nord, ce qui fausse la production et les échanges. Comme l'illustre la discussion dans cet article, il en a été ainsi pour le tarif du Pas‐du‐Nid‐du‐Corbeau, dans les transports. Cette subvention a été abolie en 1996 avec l'abrogation de Loi sur le transport du grain de l'Ouest. Les producteurs de céréales et d'oléagineux de l'Ouest canadien ont été indemnisés, mais la somme qui leur a été versée était largement insuffisante pour qu'ils restent aussi bien lotis qu'avant l'abolition de la subvention. La nouvelle politique a satisfait le principe de la compensation, mais pas celui de Pareto. On explique le pourquoi de cette situation, l'une des raisons étant les points de vue tràs divergents de diverses associations agricoles.
Biotechnology Piracy: Rethinking the International Protection of Intellectual Property
Authors: Gaisford James D. , Tarvydas Robert , Hobbs Jill E. , Kerr William A.
Published: July 2005

Access to international markets will be an important factor in investment decisions for firms engaging in the research and development of agricultural biotechnology. International market access can be restricted in two ways: the imposition of trade barriers and intellectual property piracy. This paper develops a model of the enforcement game between a developing country=s government and a foreign biotechnology firm to examine the efficacy of the World Trade Organization=s Agreement on Trade Related Aspects of Intellectual Property Rights (TRIPS) agreement for the protection of intellectual property in agricultural biotechnology. The conclusion is that the TRIPS is unlikely to provide sufficient protection and, thus, will lead to suboptimal levels of investment.

L'accès aux marchés étrangers jouera un rôle capital dans les décisions des entreprises qui souhaitent investir dans la recherche et le développement en biotechnologie agricole. Deux éléments peuvent entraver l'accès au marché international: les barrières commerciales et le piratage de la propriété intellectuelle. Dans cet article, les auteurs modélisent les interactions entre le gouvernement d'un pays en développement et une entreprise de biotechnologie étrangère en vue d'établir dans quelle mesure l'Accord sur les ADPIC de l'OMC protège la propriété intellectuelle dans le secteur de la biotechnologie agricole. De cet exercice, ils concluent que la protection assurée par l'Accord sur les ADPIC est insuffisante, donc qu'on assistera à des investissements inférieurs aux investissements optimaux.
Optimal Input Use When Inputs Affect Price and Yield
Authors: Smith Elwin G. , McKenzie Ross H. , Grant Cynthia A.
Published: July 2005

Input use has been shown to impact the variance of output and therefore risk. When inputs affect both output level and the price of the output, the variance of revenue and profit depend on each effect and their interactions. We analyze the effect of nitrogen (N) use rate applied to wheat on the variance of yield, revenue, and the price of wheat, when protein premiums (discounts) are applied. We find that N use rate increases the variance of yield, but reduces the variance of price. The net effect of N use rate on revenue and profit is variance increasing, but the variance effect is less than for yield alone. Optimal rates of N are about 60% higher with protein payments compared with a constant wheat price over all protein levels. Risk‐averse producers apply less N than risk‐neutral producers but, because revenue and profit risk is lower with protein payments, the reduction in N is less than if based on a constant price over all protein levels.
Growth and the Environment in Canada: An Empirical Analysis
Authors: Day Kathleen M. , Grafton R. Quentin
Published: July 2005

Standard reduced‐form models are estimated for Canada to examine the relationships between real per capita gross domestic product and four measures of environmental degradation. Of the four chosen measures of environmental degradation, only concentrations of carbon monoxide appear to decline in the long run with increases in real per capita income. The data are also tested for the presence of unit roots and for the existence of cointegration between each of the measures of environmental degradation and per capita income. ADF and Phillips‐Perron tests indicate unit roots in the logs of the measures of all variables. The Engle‐Granger test and Johansen's maximum eigenvalue test suggest that a long‐term relationship between per capita income and the measures of environmental degradation does not exist. Causality tests also indicate bidirectional causality, not unidirectional causality, from income to the environment. The results suggest that Canada does not have the luxury of being able to grow out of its environmental problems. The implication is that to prevent further environmental degradation, Canada requires concerted policies and incentives to reduce pollution intensity per unit of output across sectors, to shift from more to less pollution‐producing outputs and to lower the environmental damage associated with aggregate consumption.
Cost‐effective Targeting of Riparian Buffers
Authors: Yang Wanhong , Weersink Alfons
Published: July 2005

This paper develops an integrated economic, hydrologic and GIS modeling framework to examine the cost‐effective targeting of land retirement for establishing riparian buffers in agricultural watersheds. Previous studies have examined the efficiency of targeting large land parcels for retirement or targeting management practices such as conservation tillage but have not considered narrow variable buffer strips. An empirical application of the framework in the Canagagigue Creek watershed in Ontario shows that average and marginal costs of sediment abatement increase at an increasing rate as the environmental goal becomes more stringent. The locations of the buffer strips vary across the watershed and are not necessarily located on those sites with greatest slope or those adjacent to visible streams. Cost effectiveness is further increased if the targeting is extended to allow for the width of the buffer strip to vary by location rather than assume a uniform width. The modeling results have important policy implications for the design of conservation stewardship programs such as setting appropriate environmental health goals based on marginal abatement costs relative to marginal benefits, and setting physical characteristics of the riparian buffers for selection along the drainage network in targeted sub‐catchments.
Developing Hedging Strategies for Québec Hog Producers under Revenue Insurance
Authors: Gervais Jean‐Philippe , Doyon Maurice
Published: July 2005

The paper investigates the optimal hedging strategies of Québec hog producers when they participate in a publicly funded revenue insurance program known as ASRA (Régime d'assurance‐stabilisation des revenus agricoles). A forecast model of local cash and futures prices is built and Monte Carlo methods are used to derive the optimal futures and option positions of Québec hog producers. The positive correlation between forecasts of futures and cash spot prices induces positive sales of futures and put options to hedge price risk. ASRA provides put options to hog producers at actuarially advantageous terms. Producers can increase the expected utility of profits by selling back a portion of these put options using financial markets. Options are attractive to manage price risk given the nonlinearity in the profit function induced by the revenue insurance scheme. Speculative incentives to use futures and options are also discussed in the context of ASRA.
Pricing‐to‐Market: Simple Theoretical Insights, Formidable Econometric Challenges
Authors: Larue Bruno
Published: July 2005

Pricing‐to‐market (PTM) arises when firms endowed with market power alter their pricing decisions in response to exchange rate changes. I argue that the empirical models commonly used in the literature are not properly specified, especially the ones pertaining to agri‐food trade. The nature of the relation between the export price and the exchange rate can be influenced by the time‐series properties of the data, by the choice of currency to be used for invoicing, by menu costs which posit that it is costly for firms to change prices, and by the production technology of the products traded. With menu costs, only large enough exchange rate changes can trigger systematic changes in export prices. The empirical implication is to test for threshold effects. Constant return to scale is analytically and empirically convenient, as it is a necessary assumption to support the typical single‐equation PTM specification. When goods are produced under increasing returns, there are also domestic PTM effects, and a system of equations is required to properly analyze the impacts of the exchange rate on pricing decisions at home and abroad. Jointness in production, so prevalent in the agri‐food sector, can support so‐called perverse PTM effects, even when firms maximize profits and there are no switching costs.

Il y a tarification en fonction du marché (TFM) quand des entreprises exerçant une influence sur le marché modifient leurs prix d'après les fluctuations du cours du change. L'auteur soutient que les modèles empiriques couramment mentionés dans les textes ne sont pas assez bien spécifiés, en particulier ceux se rapportant au secteur agroalimentaire. La relation entre les prix d'exportation et la devise peut subir diverses influences, en l'occurrence celle des propriétés des données chronologiques, celle de la devise employée pour la facturation, celle des coûts d'ajustement, qui supposent que modifier les prix est une opération onéreuse pour l'entreprise, et celle des technologies de fabrication propres aux produits dont on fait le négoce. Avec les coǔts d'ajustement, seul un taux de change assez élevé enclenchera la modification systématique des prix d'exportation. L'implication empirique est qu'il faut vérifier les effets de seuil. Des rendements d'échelle constants s'avèrent commodes sur les plans analytique et empirique, et demeurent une hypothèse indispensable avec les spécifications typiques de la TFM à une équation. Quand le rendement s'accroît avec la production cependant, la TFM influe aussi sur le marché intérieur et l'on a besoin d'un jeu d'équations pour analyser correctement l'impact du taux de change sur les prix au pays et à l'étranger. Le regroupement des productions, si fréquent dans le secteur agroalimentaire, peut conforter les prétendus effets pervers de la TFM même quand les enterprises maximisent leurs bénéfices et le changement de fournisseur n'entraîne aucun frais.
Structural and Biochemical Properties of Fibroblast Growth Factor 23
Authors: Yamashita Takeyoshi
Published: July 2005

Abstract:  Fibroblast growth factor (FGF) 23 shares a fundamentally common structure with the members of the FGF family and has a unique sequence extension at the C‐terminus. The molecular behavior of FGF23 as a systemic factor can be justified by the altered conformation of the β‐trefoil structure similar to that suspected in FGF19. On the other hand, the biological activity of FGF23 is quite distinct from those of other FGFs and requires the C‐terminal unique extended structure. Two types of enzyme‐linked immunosorbent assays (ELISA) have been developed to detect the intact mature form of FGF23 and its C‐terminal portion. The former ELISA method enables the detection of rodent FGF23 and human FGF23. Studies on experimental animal models and laboratory examinations of physiologic and disordered conditions using these assays are contributing toward elucidating the physiology and pathophysiology of FGF23.
Maxacalcitol is a Possible Less Phosphatemic Vitamin D Analog
Authors: Kazama Junichiro J , Maruyama Hiroki , Narita Ichiei , Gejyo Fumitake
Published: July 2005

Abstract:  The phosphatemic property of maxacalcitol, a newly developed artificial active vitamin D analog, has not been compared with that of calcitriol. Non‐diabetic hemodialysis patients with plasma intact parathyroid hormone (PTH) levels greater than 300 pg/mL were included in this analysis. They were treated with either maxacalcitol or calcitriol for 24 weeks. In total, 80 patients were treated with maxacalcitol and 46 were treated with calcitriol. Pretreatment circulating levels of intact PTH, calcium (Ca) and inorganic phosphate (Pi) were comparable in both treatment groups. Both treatments significantly decreased plasma intact PTH levels (P < 0.0001) and increased serum Ca levels (P < 0.0001). However, the intact PTH levels were significantly lower in the maxacalcitol group after 24 weeks of the treatments (P < 0.01). The decreasing tendency of plasma intact PTH level was significantly evident in the maxcalcitol group (P < 0.01). However, the increasing tendency of the serum Pi level was significantly greater in the calcitriol group (P < 0.05). Thus, maxacalcitol is a possible less phosphatemic active vitamin D agent, if not non‐phosphatemic agent, which might reduce the risk of extraskeletal calcification.
Long‐term Erythropoietin Therapy Improves Response in Myelodysplastic Syndrome
Authors: Ohshima Miho , Ubara Yoshifumi , Tagami Tetsuo , Sawa Naoki , Suwabe Tatsuya , Yamakawa Kenjirou , Hoshino Junichi , Katori Hideyuki , Takemoto Fumi , Hara Shigeko , Miyakoshi Jyusaburou , Takaichi Kenmei
Published: July 2005

Abstract:  We report on a 53‐year‐old Japanese female on hemodialysis with myelodysplastic syndrome whose condition improved with recombinant human erythropoietin (epoetin) therapy. In 1992, based on a diagnosis of folic acid deficiency anemia, folate derivatives were administered. However, the anemia did not improve, and red blood cells had to be transfused subsequently. The transfusion volume was gradually increased afterward, as renal failure progressed, probably due to nephropathy by phenacetin. In 1998, when hemodialysis started, epoetin therapy was started with a dose of 3000 units three times per week. In July 2001, myelodysplastic syndrome (MDS) of a refractory anemia type was diagnosed through bone marrow aspiration. Myelodysplastic syndrome might cause an epoetin‐resistant renal anemia. Afterwards the transfusion volume was gradually reduced, and transfusions were not performed after March 2002. Improvements of histological findings of MDS as well as anemia were confirmed by bone marrow aspiration in July 2003. This is an unusual case of a patient with a previously existing MDS, who subsequently develops end stage renal disease, and has an amelioration of her underlying MDS with the administration of epoetin over a long‐term period, while being treated with chronic hemodialysis, even when not effective for a short‐term.
Factors determining the precision of the correlated firing generated by a monosynaptic connection in the cat visual pathway
Authors: Veredas Francisco J. , Vico Francisco J. , Alonso Jose‐Manuel
Published: July 2005

Across the visual pathway, strong monosynaptic connections generate a precise correlated firing between presynaptic and postsynaptic neurons. The precision of this correlated firing is not the same within thalamus and visual cortex. While retinogeniculate connections generate a very narrow peak in the correlogram (peak width < 1 ms), the peaks generated by geniculocortical and corticocortical connections have usually a time course of several milliseconds. Several factors could explain these differences in timing precision such as the amplitude of the monosynaptic EPSP (excitatory postsynaptic potential), its time course or the contribution of polysynaptic inputs. While it is difficult to isolate the contribution of each factor in physiological experiments, a first approximation can be done in modelling studies. Here, we simulated two monosynaptically connected neurons to measure changes in their correlated firing as we independently modified different parameters of the connection. Our results suggest that the precision of the correlated firing generated by strong monosynaptic connections is mostly determined by the EPSP time course of the connection and much less by other factors. In addition, we show that a polysynaptic pathway is unlikely to emulate the correlated firing generated by a monosynaptic connection unless it generates EPSPs with very small latency jitter.
A single CaVβ can reconstitute both trafficking and macroscopic conductance of voltage‐dependent calcium channels
Authors: Dalton Stanislava , Takahashi Shoji X. , Miriyala Jayalakshmi , Colecraft Henry M.
Published: July 2005

Voltage‐dependent calcium‐channel β subunits (CaVβ) strongly modulate pore‐forming α1 subunits by trafficking channel complexes to the plasma membrane and enhancing channel open probability (Po). Despite their central role, it is unclear whether binding of a single CaVβ, or multiple CaVβs, to an α1 subunit governs the two distinct functions. Conventional experiments utilizing coexpression of α1 and CaVβ subunits have been unable to resolve the ambiguity due to difficulties in establishing their stoichiometry in functional channels. Here, we unambiguously establish a 1: 1 stoichiometry by covalently linking CaVβ2b to the carboxyl terminus of α1C (CaV1.2), creating α1C·β2b. Recombinant L‐type channels reconstituted in HEK 293 cells with α1C·β2b supported whole‐cell currents to the same extent as channels reconstituted via coexpression of the individual subunits. Analysis of gating charge showed α1C·β2b fully restored channel trafficking to the plasma membrane. Co‐transfecting CaVβ2a with α1C·β2b had little further impact on function. To rule out the possibility that fused CaVβ2b was interacting in trans with neighbouring α1 molecules, α1C·β2b was cotransfected with α1B (CaV2.2), and pharmacological block with nimodipine showed an absence of α1B trafficking. These results establish that association of a single CaVβ with a pore‐forming α1 subunit captures the functional essence of HVA calcium channels, and introduce α1–CaVβ fusion proteins as a powerful new tool to probe structure–function mechanisms.
Modelling and Design of Direct Solar Steam Generating Collector Fields
Authors: Eck M. , Steinmann W.-D.
Published: July 2005

The direct steam generation (DSG) is an attractive option regarding the economic improvement of parabolic trough technology for solar thermal electricity generation in the multi megawatt range. According to Price, H., Lu¨pfert, E., Kearney, D., Zarza, E., Cohen, G., Gee, R. Mahoney, R., 2002, “Advances in Parabolic Trough Solar Power Technology,” J. Sol. Energy Eng., 124 and Zarza, E., 2002, DISS Phase II-Final Project Report, EU Project No. JOR3-CT 980277 a 10% reduction of the LEC is expected compared to conventional SEGS like parabolic trough power plants. The European DISS project has proven the feasibility of the DSG process under real solar conditions at pressures up to 100 bar and temperatures up to 400°C in more than 4000 operation hours (Eck, M., Zarza, E., Eickhoff, M., Rheinla¨nder, J., Valenzuela, L., 2003, “Applied Research Concerning the Direct Steam Generation in Parabolic Troughs,” Solar Energy 74, pp. 341–351). In a next step the detailed engineering for a precommercial DSG solar thermal power plant will be performed. This detailed engineering of the collector field requires the consideration of the occurring thermohydraulic phenomena and their influence on the stability of the absorber tubes.
Heat Transfer During Phase Change of Paraffin Wax Stored in Spherical Shells
Authors: Ettouney Hisham , El-Dessouky Hisham , Al-Ali Amani
Published: July 2005

This study concerns experimental evaluation of heat transfer during energy storage and release for the phase change of paraffin wax in spherical shells. Measurements are made using air as the heat transfer fluid (HTF), copper spheres with diameters of 2, 3, 4, and 6 cm. A detailed temperature field is obtained within the spheres using 10 thermocouple wires. Values of the air velocity and temperature used in the experiments are 4–10 m/s and 60–90°C, respectively. Measured times for melting and solidification varied over a range of 5–15 and 2–5 minutes, respectively. Calculations show that the Nusselt number in the phase change material (PCM) during melting is one order of magnitude higher than during solidification. Results indicate that the Nusselt number for melting has a strong dependence on the sphere diameter, lower dependence on the air temperature, and a negligible dependence on the air velocity. Variations in the Fourier number for melting and solidification show similar trends. An increase in the Nusselt number for a larger sphere diameter is attributed to increase in natural convection cells in the PCM inside the spheres. The larger volume allows for the free motion for the descent and rise of cooler and hotter molten wax. During the solidification process, the solid wax is evenly formed through the sphere, starting from the outer surface and moving inward. As the solidification proceeds, the melt volume decreases with a simultaneous decrease in the magnitude of natural convection within the melt. The higher values of Fourier number for melting indicate the consumption of a large part of the HTF energy in heating the molten wax rather than melting of the solid wax.
Thermal Analysis of Composite Phase Change Drywall Systems
Authors: Darkwa K. , Kim J. S.
Published: July 2005

The main barriers affecting the performance of phase change materials (PCM) wallboard system during energy recovery mode are identified as inadequate heat transfer and overall reduction in thermal conductivities. In order to assess the extent of these barriers, two integrated PCM drywall systems (i.e., randomly mixed and laminated PCM systems) have been evaluated numerically. The results showed a great advantage of the laminated PCM-wallboard system over the randomly mixed PCM type in terms of enhanced thermal performance and rapid heat transfer rates under narrow temperature swing. For instance, the maximum instantaneous enhancement in heat flux obtained was between 20% and 50% higher during the phase change process and up to about 18% more heat storage and release capacity. Experimental evaluation is, however, required towards validation and development of the laminated system.
Building-Integrated Photovoltaics for Low-Slope Commercial Roofs
Authors: Miller William A. , Brown Ed , Livezey Rita Jo
Published: July 2005

A photovoltaic (PV) distributed energy resource (DER) was established to support the Tennessee Valley Authority’s Green Power Switch program, which allows utility customers to purchase blocks of electricity generated by solar resources. The PV DER was also used to study the potential shading benefits of roof-mounted PV systems for commercial buildings. Test data derived by monitoring an offset-mounted PV array shading a built-up low-slope roof system shows that the annual savings per square foot of low-slope roof can be as high as $0.18 ($1.95 per square meter) in Phoenix, AZ.
Drosophila
RNAi Screen Reveals CD36 Family Member Required for Mycobacterial Infection
Authors: Philips Jennifer A. , Rubin Eric J. , Perrimon Norbert
Published: July 2005

Certain pathogens, such as
Mycobacterium tuberculosis
, survive within the hostile intracellular environment of a macrophage. To identify host factors required for mycobacterial entry and survival within macrophages, we performed a genomewide RNA interference screen in
Drosophila
macrophage-like cells, using
Mycobacterium fortuitum
. We identified factors required for general phagocytosis, as well as those needed specifically for mycobacterial infection. One specific factor, Peste (Pes), is a CD36 family member required for uptake of mycobacteria, but not
Escherichia coli
or
Staphylococcus aureus
. Moreover, mammalian class B scavenger receptors (SRs) conferred uptake of bacteria into nonphagocytic cells, with SR-BI and SR-BII uniquely mediating uptake of
M. fortuitum
, which suggests a conserved role for class B SRs in pattern recognition and innate immunity.
THE PLASTIC HUMAN BRAIN CORTEX
Authors: Pascual-Leone Alvaro , Amedi Amir , Fregni Felipe , Merabet Lotfi B.
Published: July 2005

Plasticity is an intrinsic property of the human brain and represents evolution's invention to enable the nervous system to escape the restrictions of its own genome and thus adapt to environmental pressures, physiologic changes, and experiences. Dynamic shifts in the strength of preexisting connections across distributed neural networks, changes in task-related cortico-cortical and cortico-subcortical coherence and modifications of the mapping between behavior and neural activity take place in response to changes in afferent input or efferent demand. Such rapid, ongoing changes may be followed by the establishment of new connections through dendritic growth and arborization. However, they harbor the danger that the evolving pattern of neural activation may in itself lead to abnormal behavior. Plasticity is the mechanism for development and learning, as much as a cause of pathology. The challenge we face is to learn enough about the mechanisms of plasticity to modulate them to achieve the best behavioral outcome for a given subject.
AN INTEGRATIVE THEORY OF LOCUS COERULEUS-NOREPINEPHRINE FUNCTION: Adaptive Gain and Optimal Performance
Authors: Aston-Jones Gary , Cohen Jonathan D.
Published: July 2005

Historically, the locus coeruleus-norepinephrine (LC-NE) system has been implicated in arousal, but recent findings suggest that this system plays a more complex and specific role in the control of behavior than investigators previously thought. We review neurophysiological and modeling studies in monkey that support a new theory of LC-NE function. LC neurons exhibit two modes of activity, phasic and tonic. Phasic LC activation is driven by the outcome of task-related decision processes and is proposed to facilitate ensuing behaviors and to help optimize task performance (exploitation). When utility in the task wanes, LC neurons exhibit a tonic activity mode, associated with disengagement from the current task and a search for alternative behaviors (exploration). Monkey LC receives prominent, direct inputs from the anterior cingulate (ACC) and orbitofrontal cortices (OFC), both of which are thought to monitor task-related utility. We propose that these frontal areas produce the above patterns of LC activity to optimize utility on both short and long timescales.
Metabolism of threonine in newborn infants
Authors: Parimi Prabhu S. , Gruca Lourdes L. , Kalhan Satish C.
Published: July 2005

Threonine kinetics, threonine oxidative pathway, and the relationship between threonine and whole body protein turnover were quantified in 10 healthy term infants during the first 48 h after birth. The kinetic data were obtained 6 h after the last feed (fasting) and in response to formula feeding, using [U-13C4,15N]threonine, [2H5]phenylalanine, and [15N]glycine tracers. The rate of carbon dioxide production (V̇co2) and13C enrichment of the expired CO2were measured to quantify the rate of oxidation of threonine. The rate of appearance (Ra) of threonine (136 ± 37 μmol·kg−1·h−1) was higher in newborn infants than that reported in adults. Formula feeding resulted in a significant decrease in threonine Ra( P < 0.05). A significant positive correlation was seen between phenylalanine Raand threonine Ra, both during fasting and after formula feeding ( r2= 0.65). In contrast to a 1:1 ratio of threonine and phenylalanine in mixed muscle protein, threonine Rarelative to phenylalanine Rawas 2.2 ± 0.4. The fractional rate of threonine flux oxidized was 20% during fasting and 26% ( P < 0.05) in response to nutrient administration. There was a significant correlation between plasma threonine concentration and threonine oxidation ( r2= 0.75). No measurable incorporation of threonine in plasma glycine was seen. These data suggest that threonine is exclusively degraded by the glycine-independent serine/threonine dehydratase pathway. A higher flux of threonine relative to phenylalanine indicates higher turnover of threonine enriched proteins.
1α,25-Dihydroxyvitamin D3upregulates FGF23 gene expression in bone: the final link in a renal-gastrointestinal-skeletal axis that controls phosphate transport
Authors: Kolek Olga I. , Hines Eric R. , Jones Marci D. , LeSueur Loren K. , Lipko Maciej A. , Kiela Pawel R. , Collins James F. , Haussler Mark R. , Ghishan Fayez K.
Published: July 2005

Fibroblast growth factor (FGF)23 is a phosphaturic hormone that decreases circulating 1α,25-dihydroxyvitamin D3[1,25(OH)2D3] and elicits hypophosphatemia, both of which contribute to rickets/osteomalacia. It has been shown recently that serum FGF23 increases after treatment with renal 1,25(OH)2D3hormone, suggesting that 1,25(OH)2D3negatively feedback controls its levels by inducing FGF23. To establish the tissue of origin and the molecular mechanism by which 1,25(OH)2D3increases circulating FGF23, we administered 1,25(OH)2D3to C57BL/6 mice. Within 24 h, these mice displayed a dramatic elevation in serum immunoreactive FGF23, and the expression of FGF23 mRNA in bone was significantly upregulated by 1,25(OH)2D3, but there was no effect in several other tissues. Furthermore, we treated rat UMR-106 osteoblast-like cells with 1,25(OH)2D3, and real-time PCR analysis revealed a dose- and time-dependent stimulation of FGF23 mRNA concentrations. The maximum increase in FGF23 mRNA was 1,024-fold at 10−7M 1,25(OH)2D3after 24-h treatment, but statistically significant differences were observed as early as 4 h after 1,25(OH)2D3treatment. In addition, using cotreatment with actinomycin D or cycloheximide, we observed that 1,25(OH)2D3regulation of FGF23 gene expression occurs at the transcriptional level, likely via the nuclear vitamin D receptor, and is dependent on synthesis of an intermediary transfactor. These results indicate that bone is a major site of FGF23 expression and source of circulating FGF23 after 1,25(OH)2D3administration or physiological upregulation. Our data also establish FGF23 induction by 1,25(OH)2D3in osteoblasts as a feedback loop between these two hormones that completes a kidney-intestine-bone axis that mediates phosphate homeostasis.
Vitamin E at high doses improves survival, neurological performance, and brain mitochondrial function in aging male mice
Authors: Navarro Ana , Gómez Carmen , Sánchez-Pino María-Jesús , González Hipólito , Bández Manuel J. , Boveris Alejandro D. , Boveris Alberto
Published: July 2005

Male mice receiving vitamin E (5.0 g α-tocopherol acetate/kg of food) from 28 wk of age showed a 40% increased median life span, from 61 ± 4 wk to 85 ± 4 wk, and 17% increased maximal life span, whereas female mice equally supplemented exhibited only 14% increased median life span. The α-tocopherol content of brain and liver was 2.5-times and 7-times increased in male mice, respectively. Vitamin E-supplemented male mice showed a better performance in the tightrope (neuromuscular function) and the T-maze (exploratory activity) tests with improvements of 9–24% at 52 wk and of 28–45% at 78 wk. The rates of electron transfer in brain mitochondria, determined as state 3 oxygen uptake and as NADH-cytochrome c reductase and cytochrome oxidase activities, were 16–25% and 35–38% diminished at 52–78 wk. These losses of mitochondrial function were ameliorated by vitamin E supplementation by 37–56% and by 60–66% at the two time points considered. The activities of mitochondrial nitric oxide synthase and Mn-SOD decreased 28–67% upon aging and these effects were partially (41–68%) prevented by vitamin E treatment. Liver mitochondrial activities showed similar effects of aging and of vitamin E supplementation, although less marked. Brain mitochondrial enzymatic activities correlated negatively with the mitochondrial content of protein and lipid oxidation products ( r2= 0.58–0.99, P < 0.01), and the rates of respiration and of complex I and IV activities correlated positively ( r2= 0.74–0.80, P < 0.01) with success in the behavioral tests and with maximal life span.
Nitric oxide and cardiopulmonary hemodynamics in Tibetan highlanders
Authors: Hoit Brian D. , Dalton Nancy D. , Erzurum Serpil C. , Laskowski Daniel , Strohl Kingman P. , Beall Cynthia M.
Published: July 2005

When O2 availability is reduced unavoidably, as it is at high altitude, a potential mechanism to improve O2 delivery to tissues is an increase in blood flow. Nitric oxide (NO) regulates blood vessel diameter and can influence blood flow. This field study of intrapopulation variation at high altitude tested the hypothesis that the level of exhaled NO (a summary measure of pulmonary synthesis, consumption, and transfer from cells in the airway) is directly proportional to pulmonary, and thus systemic, blood flow. Twenty Tibetan male and 37 female healthy, nonsmoking, native residents at 4,200 m (13,900 ft), with an average O2 saturation of hemoglobin of 85%, participated in the study. The geometric mean partial pressure of NO exhaled at a flow of 17 ml/s was 23.4 nmHg, significantly lower than that of a sea-level reference group. However, the rate of NO transfer out of the airway wall was seven times higher than at sea level, which implied the potential for vasodilation of the pulmonary blood vessels. Mean pulmonary blood flow (measured by cardiac index) was 2.7 ± 0.1 (SE) l/min, and mean pulmonary artery systolic pressure was 31.4 ± 0.9 (SE) mmHg. Higher exhaled NO was associated with higher pulmonary blood flow; yet there was no associated increase in pulmonary artery systolic pressure. The results suggest that NO in the lung may play a key beneficial role in allowing Tibetans at 4,200 m to compensate for ambient hypoxia with higher pulmonary blood flow and O2 delivery without the consequences of higher pulmonary arterial pressure.
Ventilation is unstable during drowsiness before sleep onset
Authors: Thomson Stuart , Morrell Mary J. , Cordingley Jeremy J. , Semple Stephen J.
Published: July 2005

Ventilation is unstable during drowsiness before sleep onset. We have studied the effects of transitory changes in cerebral state during drowsiness on breath duration and lung volume in eight healthy subjects in the absence of changes in airway resistance and fluctuations of ventilation and CO2 tension, characteristic of the onset of non-rapid eye movement sleep. A volume-cycled ventilator in the assist control mode was used to maintain CO2 tension close to that when awake. Changes in cerebral state were determined by the EEG on a breath-by-breath basis and classified as alpha or theta breaths. Breath duration and the pause in gas flow between the end of expiratory airflow and the next breath were computed for two alpha breaths which preceded a theta breath and for the theta breath itself. The group mean (SD) results for this alpha-to-theta transition was associated with a prolongation in breath duration from 5.2 (SD 1.3) to 13.0 s (SD 2.1) and expiratory pause from 0.7 (SD 0.4) to 7.5 s (SD 2.2). Because the changes in arterial CO2 tension (PaCO2) are unknown during the theta breaths, we made in two subjects a continuous record of PaCO2 in the radial artery. PaCO2 remained constant from the alpha breaths through to the expiratory period of the theta breath by which time the duration of breath was already prolonged, representing an immediate and altered ventilatory response to the prevailing PaCO2. In the eight subjects, the CO2 tension awake was 39.6 Torr (SD 2.3) and on assisted ventilation 38.0 Torr (1.4). We conclude that the ventilatory instability recorded in the present experiments is due to the apneic threshold for CO2 being at or just below that when awake.
Spatio-Temporal Separation of Roll and Pitch Balance-Correcting Commands in Humans
Authors: Grüneberg C. , Duysens J. , Honegger F. , Allum J.H.J.
Published: July 2005

This study was designed to provide evidence for the hypothesis that human balance corrections in response to pitch perturbations are controlled by muscle action mainly about the ankle and knee joints, whereas balance corrections for roll perturbations are controlled predominantly by motion about the hip and lumbro-sacral joints. A dual-axis rotating support surface delivered unexpected random perturbations to the stance of 19 healthy young adults through eight different directions in the pitch and the roll planes and three delays between pitch and roll directions. Roll delays with respect to pitch were no delay, a short 50-ms delay of roll with respect to pitch movements, (chosen to correspond to the onset time of leg muscle stretch reflexes), and a long 150-ms delay between roll and pitch movements (chosen to shift the time when trunk roll velocity peaks to the time when trunk peak pitch velocity normally occurs). Delays of stimulus roll with respect to pitch resulted in delayed roll responses of the legs, trunk, arms, and head consistent with stimulus delay without any changes in roll velocity amplitude. Delayed roll perturbations induced only small changes in the pitch motion of the legs and trunk; however, major changes were seen in the time when roll motion of the trunk was arrested. Amplitudes and directional sensitivity of short-latency (SL) stretch reflexes in ankle muscles were not altered with increasing roll delay. Small changes to balance correcting responses in ankle muscles were observed. SL stretch reflexes in hip and trunk muscles were delayed, and balance-correcting responses in trunk muscles became split into two distinct responses with delayed roll. The first of these responses was small and had a directional responsiveness aligned more along the pitch plane. The main, larger, response occurred with an onset and time-to-peak consistent with the delay in trunk roll displacement and its directional responsiveness was roll oriented. The sum of the amplitudes of these two types of balance-correcting responses remained constant with roll delay. These results support the hypothesis that corrections of the body's pitch and roll motion are programmed separately by neural command signals and provide insights into possible triggering mechanisms. The evidence that lower leg muscle balance-correcting activity is hardly changed by delayed trunk roll also indicates that lower leg muscle activity is not predominant in correcting roll motion of the body. Lower leg and trunk muscle activity appears to have a dual action in balance corrections. In trunk muscles the main action is to correct for roll perturbations and the lesser action may be an anticipatory stabilizing reaction for pitch perturbations. Likewise, the small changes in lower leg muscle activity may result from a generalized stabilizing reaction to roll perturbations, but the main action is to correct for pitch perturbations.
Genomes Optimize Reproduction: Aging as a Consequence of the Developmental Program
Authors: de Magalhães João Pedro , Church George M.
Published: July 2005

Natural selection shapes genomes for reproduction, not for postreproductive survival. One hypothesis then is that the developmental program, optimized for reproduction, inadvertently regulates aging in mammals. Herein we review, revive, and refine the developmental theory of aging. Implications and experimental approaches for studying the progressive deterioration of physiological function that we call aging are also discussed.
Protein-Protein Interactions in the Tetraspanin Web
Authors: Levy Shoshana , Shoham Tsipi
Published: July 2005

Tetraspanins are evolutionarily conserved membrane proteins that tend to associate laterally with one another and to cluster dynamically with numerous partner proteins in membrane microdomains. Consequently, members of this family are involved in the coordination of intracellular and intercellular processes, including signal transduction; cell proliferation, adhesion, and migration; cell fusion; and host-parasite interactions.
A nonlinear boundary problem involving the p‐bilaplacian operator
Authors: El Khalil Abdelouahed , Kellati Siham , Touzani Abdelfattah
Published: July 2005

We show some new Sobolev′s trace embedding that we
apply to prove that the fourth‐order nonlinear boundary conditions in Ω and −(∂/∂n)(|Δu|p−2Δu) = λρ|u|p−2u on ∂Ω possess at least one nondecreasing sequence of positive eigenvalues.
On the eigenvalues which express antieigenvalues
Authors: Seddighin Morteza , Gustafson Karl
Published: July 2005

We showed previously that the first antieigenvalue and the components of the first antieigenvectors of an accretive compact normal operator can be expressed either by a pair of eigenvalues or by a single eigenvalue of the operator. In this paper, we pin down the eigenvalues of T that express the first antieigenvalue and the components of the first antieigenvectors. In addition, we will prove that the expressions which state the first antieigenvalue and the components of the first antieigenvectors are unambiguous. Finally, based on these new results, we will develop an algorithm for computing higher
antieigenvalues.
Convergence of implicit iterates with errors for mappings with unbounded domain in Banach spaces
Authors: Fukhar-Ud-Din Hafiz , Khan Abdul Rahim
Published: July 2005

We prove that an implicit iterative process with errors converges weakly and strongly to a common fixed point of a finite family of asymptotically quasi‐nonexpansive mappings on unbounded sets in a uniformly convex Banach space. Our results generalize and improve upon, among others, the corresponding recent results of Sun (2003) in the following two different directions: (i) domain of the mappings is unbounded, (ii) the iterative sequence contains an error term.