bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of intermediaries in enhancing market efficiency in the Ethiopian grain market
Authors: Gabre‐Madhin Eleni Z.
Published: August 2005

This paper investigates the impact of the institution of brokerage on the optimal search behaviour and the welfare gains and losses of traders in the Ethiopian grain market. Without brokers, the privately optimal search diverges from the socially optimal search due to the positive spill‐over of individual search behaviour. Numerical analysis using the actual distribution of search costs and search efficiency obtained from primary data collected in Ethiopia reveals that this externality is partially internalised by the presence of brokers and that total welfare increases significantly due to a more efficient allocation of search effort.
A fresh meat almost ideal demand system incorporating negative TV press and advertising impact
Authors: Verbeke Wim , Ward Ronald W.
Published: August 2005

This paper investigates fresh meat consumption in Belgium during “1995” through the specification of a three‐equation almost ideal demand system (AIDS) incorporating a media index of TV coverage and advertising expenditures as explanatory variables. Estimated parameters and elasticity coefficients are plausible and consistent with demand theory. Own‐price elasticities are relatively low, indicating a low fresh meat demand sensitivity to price changes over this period which was dominated by mass media reports about the potential health risks associated with meat consumption. The scope of the paper extends beyond the estimation of elasticity coefficients and includes the specification of a media index and simulations that provide insights into the impact of negative press relative to advertising efforts. Specifically, the impact of television publicity is shown to have been particularly negative on beef/veal expenditures in favour of pork/mixture. This finding corroborates expectations since mass media issues mainly pertained to BSE (mad cow disease) and hormone residues during the investigated period. With relatively little effort being undertaken and with its current strategy, fresh meat advertising is found to have only a minor impact compared with negative press.
Optimal weed control under static and dynamic decision rules
Authors: Wu JunJie
Published: August 2005

Dynamic and static weed control decision rules are derived analytically and compared. The dynamic rule leads to increased farm profits and greater control of weeds and weed seeds than the static rule, while total herbicide use is unchanged. The magnitude of the differences is estimated for atrazine control of foxtail and cocklebur in corn production. Incorporating weed dynamics into weed control strategies increases farm profits between 1.0 and 1.4%.
Why do farmers have so little interest in futures markets?
Authors: Simmons Phil
Published: August 2005

A farm financial model with leverage and investment in two farm enterprises is specified. The model is extended to incorporate futures hedging and the Separation Theorem is used to show that optimal hedging is zero. The assumption of a risk‐free asset is relaxed and, while this leads to a violation of the Separation Theorem, the result that optimal hedging is zero is maintained providing that futures markets are efficient. It is concluded that if capital markets are efficient then farmers will have little interest in futures markets except to speculate.
Downward sloping demand for environmental amenities and international compensation: elephant conservation and strategic culling
Authors: Bulte Erwin , van Kooten G. Cornelis
Published: August 2005

Conventional wisdom holds that monetary compensation for positive transboundary externalities will promote conservation of resource amenities. We demonstrate that, in the case of elephant conservation, international transfers may also result in strategic behavior by host countries, with adverse implications for global welfare and in situ stocks.
Adoption of improved chickpea varieties: KRIBHCO experience in tribal region of Gujarat, India
Authors: Shiyani R.L. , Joshi P.K. , Asokan M. , Bantilan M.C.S.
Published: August 2005

The study aims to track adoption of improved chickpea varieties, and assess their on‐farm benefits in some remote and backward tribal villages in Gujarat, India, where few newly developed varieties were introduced by a non‐government organization. It also determines key factors which were influencing their adoption. The study found that adoption of improved chickpea varieties was gradually increasing by replacing a prominent local variety. Duration of crop maturity, farm size, yield risk, and farmers' experience of growing chickpea crop were significantly influencing their adoption. The on‐farm benefits as a result of improved varieties were realized in terms of increased yield levels, higher income and labor productivity, more marketable surplus, price premium and stabilized yields in fluctuating weather. Breeding short duration varieties with stable yield levels under varying weather, and organizing seed multiplication and dissemination in regions, where moisture stress is a problem during maturity of chickpea, are the major suggestions.
Non‐parametric estimation of decision makers' risk aversion
Authors: Lien Gudbrand
Published: August 2005

A new non‐parametric method to estimate a decision maker's coefficient of absolute risk aversion from observed economic behaviour is explained. The method uses the expected value‐variance (E‐V) framework and quadratic programming. An empirical illustration is given using Norwegian farm‐level data.
Acreage response in Pakistan: a co‐integration approach
Authors: Mushtaq Khalid , Dawson P.J.
Published: August 2005

This paper seeks to quantify the acreage responses of wheat, cotton, sugarcane and rice in Pakistan using co‐integration techniques and impulse response analysis. Results indicate that acreages of wheat and basmati rice do not respond significantly to shocks in own‐price while cotton, sugarcane and high yielding variety (HYV) rice do, and that long‐run equilibrium is re‐established after about 4 years. Irrigated area is an important determinant of acreage.
Assets, activities and income generation in rural Mexico: factoring in social and public capital⋆
Authors: Winters Paul , Davis Benjamin , Corral Leonardo
Published: August 2005

In recent years, there has been increasing emphasis in the rural development literature on the multiple income‐generating activities undertaken by rural households and the importance of assets in determining the capacity to undertake these activities. Controlling for the endogeneity of activity choice and applying Lee's generalisation of Amemiya's two‐step estimator to a simultaneous equation model, household returns to assets from multiple activities are explored for the Mexico ejido sector. To incorporate the multiple variables representing social and public capital into the analysis, factor analysis is used. The results indicate that the asset position of the household has a significant effect on household participation in income‐generating activities and returns to those activities. Furthermore, the inclusion of measures of social and public capital into the analysis show that these assets play an important role in income‐generating activities and that the influence is dependent on the type of social and public capital as well as the particular activity.
Cost‐effectiveness of alternative green payment policies for conservation technology adoption with heterogeneous land quality
Authors: Khanna Madhu , Isik Murat , Zilberman David
Published: August 2005

This paper quantitatively analyses the cost‐effectiveness of alternative green payment policies designed to achieve a targeted level of pollution control by heterogeneous microunits. These green payment policies include cost‐share subsidies that share the fixed costs of adoption of a conservation technology and/or input reduction subsidies to reduce the use of a polluting input. The paper shows that unlike a pollution tax that achieves abatement through three mechanisms, a negative extensive margin effect, a negative intensive margin effect and a technology switching effect, a cost‐share subsidy and an input reduction subsidy are much more restricted in the types of incentives they provide for conservation of polluting inputs and adoption of a conservation technology to control pollution. Moreover, they may lead to varying levels of expansion of land under production. Costs of abatement with alternative policies and implications for production and government payments are compared using a simulation model for controlling drainage from irrigated cotton production in California, with drip irrigation as a conservation technology.
Measuring managerial efficiency: the case of commercial greenhouse growers
Authors: Trip G. , Thijssen G.J. , Renkema J.A. , Huirne R.B.M.
Published: August 2005

Recently the managerial decision making process has been given new attention, both in theoretical studies as well as in empirical research explaining differences in farm results. However, while critical to explaining efficiency, managerial ability has been difficult to measure and therefore often ignored. This study attempts to measure managerial ability. It divides the decision making process into four steps: goal formulation, planning, monitoring and evaluation. The quality of each step is measured in a panel of 26 specialised flower producers, The impact of decision making on the firms' efficiencies is measured by means of a stochastic frontier production function. A one‐step procedure is used in which technical and decision making parameters are jointly estimated. The results show positive associations between firm efficiency and the quality of decision making (especially monitoring and firm evaluation), indicating that this procedure has been potentially successful and is a move towards successfully measuring a critical input.
Spatially explicit micro‐level modelling of land use change at the rural–urban interface
Authors: Bella Kathleen P. , Irwin Elena G.
Published: August 2005

This paper describes micro‐economic models of land use change applicable to the rural‐urban interface in the US. Use of a spatially explicit micro‐level modelling approach permits the analysis of regional patterns of land use as the aggregate outcomes of many, disparate individual land use decisions distributed across space. In contrast to the models featured by Nelson and Geoghegan, we focus on models that require spatially articulated data on parcel‐level land use changes through time. In characterising the spatially disaggregated models, we highlight issues uniquely related to the management and generation of spatial data and the estimation of micro‐level spatial models.
Adding value to spatially managed inputs by understanding site‐specific yield response
Authors: Bullock David S. , Lowenberg‐DeBoer Jess , Swinton Scott M.
Published: August 2005

Many mechanized crop producers and agribusinesses are fascinated with precision agriculture technology, but adoption has lagged behind the expectations. Among the reasons for slow adoption of precision agriculture technology is that initial users focused excessively on in‐field benefits from variable‐rate fertilizer application using regional average fertilizer recommendations. This article illustrates how greater use of site‐specific crop response information can improve variable rate input application recommendations.

Precision agriculture is spatial information technology applied to agriculture. The technologies include global position systems (GPS), geographic information systems (GIS), yield monitoring sensors, and computer controlled within‐field variable rate application (VRA) equipment. Experimentation with these technologies is occurring everywhere there is large scale mechanized agriculture. Commercial use has been greatest in the US, where 43% of farm retailers offered VRA services in 2001. Except for certain high‐value crops like sugar beet, farmer adoption of VRA has been modest. The farm level profitability of VRA continues to be questionable for bulk commodity crops.

The theoretical model and illustration presented here suggest that VRA fertilization has not yet reached its profitability potential. Most VKA field trials to date have relied upon existing state‐wide or regional input rate recommendations. Unobserved soil characteristics can potentially interact with an input to make its effect on yield vary site‐specifically within fields. Failure to use site‐specific response functions for VRA applications may lead to a misallocation of inputs just as great as that which results from using uniform applications instead of VRA.

Agricultural economists have a long history of estimating output response to input applications. Several have started to develop tools to estimate site‐specific responses from yield monitor and other precision agriculture data. Likewise, agricultural economists have developed an important body of research results on information value based on managing variability—typically in temporal settings. With these tools, a major potential exists to develop further benefits from precision agriculture technologies that permit truly spatially tailored input applications.
Temporal and spatial modelling of tropical deforestation: a survival analysis linking satellite and household survey data
Authors: Vance Colin , Geoghegan Jacqueline
Published: August 2005

We estimate a spatially explicit model of the forest clearance process among smallholder farmers in an agricultural frontier of southern Mexico. Our analysis takes as its point of departure a simple utility‐maximising model that suggests many possible determinants of deforestation in an economic environment characterised by missing or thin markets. Hypotheses from the model are tested on a data set that combines a time series of satellite imagery with data collected from a survey of farm households whose agricultural plots were geo‐referenced using a global positioning system (GPS). We implement a survival analysis to identify the effect of household level explanatory variables on the probability of deforestation. This approach allows us to introduce a measure of the time until clearance as a covariate, thereby affording a control for the effect of potentially important explanatory variables that vary through time but are not directly observable. In addition to identifying several variables relevant for policy analysis, including household demographics, proximity to roads, and government provision of agricultural support, model results suggest that the deforestation process is characterised by non‐linear duration dependence, with the probability of forest clearance first decreasing and then increasing with the passage of time.
Spatial dimensions of precision agriculture: a spatial econometric analysis of millet yield on Sahelian coversands
Authors: Florax Raymond J.G.M. , Voortman Roelf L. , Brouwer Joost
Published: August 2005

The identification of local soil variability caused by within‐field differences of macronutrients and ecological features is of paramount importance for the effectiveness of precision agriculture. We present several spatial statistical and econometric techniques to capture local differences in soil variation, ecological characteristics, and yield more effectively than the analytical techniques traditionally used in agronomy. The application of these techniques is illustrated in a case study dealing with precision agriculture in the West African Sahel. The production of millet on acid sandy soils constitutes a typical example of low soil fertility areas exhibiting small absolute but large relative differences in crop production conditions over short distances.
Production of osteopontin by cultured porcine epithelial cell rests of Malassez
Authors: Rincon Julio C. , Xiao Yin , Young William G. , Bartold P. Mark
Published: August 2005

Background:  The epithelial cell rests of Malassez (ERM) are derived from Hertwig's epithelial root sheath (HERS). During development the cells of HERS deposit a variety of molecules on the newly forming root surface. The possibility that ERM retain this potential after root development is completed and secrete bone or cementum‐related proteins needs to be investigated. The purpose of this study was to determine the expression of the non‐collagenous proteins osteopontin (OPN) and bone sialoprotein (BSP) by cells derived from the epithelial cell rests of porcine periodontium.

Methods:  ERM and fibroblasts were cultured from porcine periodontal ligament. The cells were identified and characterized using transmission electron microscopy, immunohistochemistry, western blot analysis of proteins, reverse transcription–polymerase chain reaction and ability to form mineralized nodules in culture. In particular the expression of the mineralized tissue‐related proteins, BSP and OPN, was studied.

Results:  Cells from porcine periodontal ligaments were successfully cultured; separated and characterized as being of either an epithelial or fibroblastic phenotype. Although the ERM did not form mineralized nodules in culture, they did express a significant amount of mRNA for OPN.

Conclusion:  The results from this study provide evidence that ERM express mRNA for at least one bone/cementum‐related protein. Whether this function would be consistent with a role for ERM in tissue formation, inflammation and regeneration remains to be established.
Irritation and cytotoxic potential of denture adhesives
Authors: Al Ronald H. , Dahl Jon E. , Morisbak Else , Polyzois Gregory L.
Published: August 2005

Objective:  The present study aimed to examine the in vitro biocompatibility of denture adhesives.

Background:  Denture adhesives absorb water to become viscous and sticky, and by this process, other constituents like colouring, flavouring, wetting and preserving agents may be released. Some of these constituents may induce adverse reactions among users of denture adhesives.

Materials and methods:  Five commercially available denture adhesives; three different creams, a powder, and a cushion were included in the study. The irritation and cytotoxic potential was evaluated using the Hen's Egg Test Chorioallantoic Membrane (HET‐CAM) method and three cell culture methods; filter diffusion, dimethylthiazol diphenyltetrazolium bromide (MTT) assay and agar diffusion.

Results:  None of the tested denture adhesives showed a noteworthy acute irritation as evaluated by the HET‐CAM method. None of the tested denture adhesives induced cytotoxicity in the filter diffusion test. One of the denture adhesives induced a severe cytotoxic reaction in both the MTT and agar diffusion assays. These tests employ longer exposure times than in both the filter diffusion and the HET‐CAM test.

Conclusion:  Denture adhesives are commonly used throughout the day, and our results raise the concern that denture adhesives may contribute to mucosal inflammation in denture wearers.
Mechanisms of Acute Inhalation Effects of (+) and(−)‐α‐Pinene in BALB/c Mice
Authors: Nielsen Gunnar Damgård , Larsen Søren Thor , Hougaard Karin Sørig , Hammer Maria , Wolkoff Peder , Clausen Per Axel , Wilkins Cornelius Kendall , Alarie Yves
Published: August 2005

Abstract: The effects of (+)‐α‐pinene and (−)‐α‐pinene vapours were studied for respiratory effects in BALB/c mice. The (+) enantiomer showed persistent sensory irritation effect on the upper respiratory tract during exposures in the range of 100 to 3691 ppm. The threshold concentration for this effect was calculated to be about 70 ppm, which is close to the no‐effect level of about 40 ppm in humans. A significant airflow limitation occurred from exposure concentrations of 200 ppm and higher. No irritating effect was observed at the alveolar level and no central nervous system effect was obvious. In the exposure range from 218 to 5213 ppm, the (−) enantiomer produced only a short‐lasting sensory irritation effect during the first 10 min. of exposure and only at concentrations above 2900 ppm. The tidal volume decreased significantly from ∼400 ppm, but it was first conspicuous above 1000 ppm. Airflow limitation appeared consistently from ∼2000 ppm. The (−) enantiomer also induced anesthesia/and or pulmonary irritation as well as sudden death at concentrations above 2600 ppm. Overall, the enantiomers showed different time‐dependent and stereoselective effects. The lower sensory irritation effect of the (−) enantiomer probably being due to less of the molecule being adsorbed to a sensory irritant receptor.
Gastrointestinal Symptoms as an Important Sign in Premature Newborns with Severely Increased S‐Digoxin
Authors: Nybo Mads , Damkier Per
Published: August 2005

Abstract: The aim is to emphasize the importance of extracardiac symptoms of digoxin intoxication in newborns. The most common intoxication symptoms in adults are of cardiac origin, but due to altered symptomatology, digoxin overdose in infants are not always discovered on symptomatic basis. In preterm infants, this is even more pronounced due to diminished digoxin sensitivity. Also, tissue distribution is altered in newborns, which, combined with the need for higher doses in newborns to obtain clinical effect, underscores the need for the utmost care, when newborns receive digoxin treatment to avoid intoxication. We report a case of severe digoxin intoxication in a preterm newborn infant, leading to distinct gastrointestinal symptoms, but only minor cardiac affection. The literature concerning digoxin intoxication and digoxin measurement is reviewed to elucidate the case report. In conclusion, alertness should be drawn to extracardiac symptoms of digoxin intoxication, especially in newborns, and P‐Potassium can serve as a predictor and thereby strengthen any given suspicion. Therapeutic drug monitoring should be performed, as soon as digoxin overdose due to the above‐mentioned signs is suspected in spite of vague cardiac symptoms.
Microsomal UDP‐Glucuronyltransferase in Rat Liver: Oxidative Activation
Authors: Letelier María Eugenia , Pimentel Alejandra , Pino Patricia , Lepe Ana María , Faúndez Mario , Aracena Paula , Speisky Hernán
Published: August 2005

Abstract: Activation of microsomal UDP‐glucuronyltransferase (UDPGT) activity by treatment of hepatic microsomes with either detergents or Fe3+/ascorbate pro‐oxidant system has been reported; however, definite mechanisms underlying these effects have not been clarified. In this work, we characterize Fe3+/ascorbate‐induced activation of UDPGT activity prior to solubilization with Triton X‐100 and after the oxidation process provoked the solubilization of the enzyme. We observed a time‐dependent increase in UDPGT activity up to 20 min. incubation of the microsomes with Fe3+/ascorbate (3‐times); after 20 min. incubation, however, we observed a time‐dependent decrease in this activity to basal levels after 4 hr incubation. Treatment of microsomes with 0.1% Triton X‐100 (5 min.) lead to a similar increase in UDPGT activity; higher detergent concentrations produced a dose‐dependent decrease in this activity to basal levels with 1% Triton X‐100. Interestingly, UDPGT activity was susceptible to activation only when associated to microsomal membranes and the loss of activation correlated with the solubilization of this activity. UDPGT activation by either Fe3+/ascorbate or Triton X‐100 was correlated with an increase in p‐nitrophenol apparent Km and Vmax values. This activation was prevented or reversed by the reducing agents glutathione, cysteine or dithiothreitol when it was induced by the Fe3+/ascorbate. Furthermore, the latter provoked a significant decrease in microsomal thiol content, effect not observed after treatment with Triton X‐100. Our results suggest that the main mechanism responsible for Fe3+/ascorbate‐induced UDPGT activation is likely to be the promotion of protein sulfhydryl oxidation; this mechanism appears to be different from detergent‐induced UDPGT activation.
Effect of Ribose Cysteine Pretreatment on Hepatic and Renal Acetaminophen Metabolite Formation and Glutathione Depletion
Authors: Slitt Angela M. Lucas , Dominick Pamela K. , Roberts Jeanette C. , Cohen Steven D.
Published: August 2005

Abstract: Ribose cysteine (2(R,S)‐D‐ribo‐(1′,2′,3′,4′‐tetrahydroxybutyl)thiazolidine‐4(R)‐carboxylic acid) protects against acetaminophen‐induced hepatic and renal toxicity. The mechanism for this protection is not known, but may involve inactivation of the toxic electrophile via enhancement of glutathione (GSH) biosynthesis. Therefore, the goal of this study was to determine if GSH biosynthesis was required for the ribose cysteine protection. Male CD‐1 mice were injected with either acetaminophen or acetaminophen and ribose cysteine. The ribose cysteine cotreatment antagonized the acetaminophen‐induced depletion of non‐protein sulfhydryls in liver as well as GSH in kidney. Moreover, ribose cysteine cotreatment significantly increased the concentration of acetaminophen‐cysteine, hepatic acetaminophen‐mercapturate in liver and renal acetaminophen‐GSH metabolites in kidney 4 hr after acetaminophen. To determine whether protection against acetaminophen‐induced liver and kidney damage involved ribose cysteine dependent GSH biosynthesis, buthionine sulfoximine was used to selectively block γ‐glutamylcysteine synthetase (γ‐GCS). Plasma sorbitol dehydrogenase (SDH) activity and blood urea nitrogen from mice pretreated with buthionine sulfoximine and challenged with acetaminophen indicated that both liver and kidney injury had occurred. While co‐treatment with ribose cysteine had previously protected against acetaminophen‐induced liver and kidney injury, it did not diminish the acetaminophen‐induced damage to either organ in the buthionine sulfoximine‐treated mice. In conclusion, ribose cysteine serves as a cysteine prodrug that facilitates GSH biosynthesis and protects against acetaminophen‐induced target organ toxicity.
Regulation of calcium-activated chloride channels in smooth muscle cells: a complex picture is emerging
Authors: Leblanc Normand , Ledoux Jonathan , Saleh Sohag , Sanguinetti Amy , Angermann Jeff , O'Driscoll Kate , Britton Fiona , Perrino Brian A , Greenwood Iain A
Published: August 2005

Calcium-activated chloride channels (ClCa) are ligand-gated anion channels as they have been shown to be activated by a rise in intracellular Ca2+concentration in various cell types including cardiac, skeletal and vascular smooth muscle cells, endothelial and epithelial cells, as well as neurons. Because ClCachannels are normally closed at resting, free intracellular Ca2+concentration (~100 nmol/L) in most cell types, they have generally been considered excitatory in nature, providing a triggering mechanism during signal transduction for membrane excitability, osmotic balance, transepithelial chloride movements, or fluid secretion. Unfortunately, the genes responsible for encoding this class of ion channels is still unknown. This review centers primarily on recent findings on the properties of these channels in smooth muscle cells. The first section discusses the functional significance and biophysical and pharmacological properties of ClCachannels in smooth muscle cells, and ends with a description of 2 candidate gene families (i.e., CLCA and Bestrophin) that are postulated to encode for these channels in various cell types. The second section provides a summary of recent findings demonstrating the regulation of native ClCachannels in vascular smooth muscle cells by calmodulin-dependent protein kinase II and calcineurin and how their fine tuning by these enzymes may influence vascular tone. Key words: calcium-activated chloride channels, vascular smooth muscle cells, ion channels, calmodulin-dependent protein kinase II, calcineurin
Endogenous prolactin modulated the calcium absorption in the jejunum of suckling rats
Authors: Amnattanakul Suwimol , Charoenphandhu Narattaphol , Limlomwongse Liangchai , Krishnamra Nateetip
Published: August 2005

Prolactin has been reported to stimulate intestinal calcium absorption in young and mature, but not aging rats. The present study was performed on suckling rats to elucidate the actions of endogenous prolactin on calcium absorption in various intestinal segments. Before measuring the calcium fluxes, 9-day-old rats were administered for 7 days with 0.9% NaCl, s.c. (control), 3 mg/kg bromocriptine, i.p., twice daily to abolish secretion of endogenous pro lac tin, or bromocriptine plus exogenous 2.5 mg/kg prolactin, s.c. Thereafter, the 16-day-old rats were experimented upon by instilling the45Ca-containing solution into the intestinal segments. The results showed that, under a physiological condition, the jejunum had the highest rate of calcium absorption compared with other segments (1.4 ± 0.35 µmol·h1·cm1, p < 0.05). The duodenum and ileum also manifested calcium absorption, whereas the colon showed calcium secretion. Lack of endogenous prolactin decreased lumen-to-plasma and net calcium fluxes in jejunum from 2.07 ± 0.31 to 1.19 ± 0.12 and 1.40 ± 0.35 to 0.88 ± 0.18 µmol·h1·cm1(p < 0.05), respectively, and exogenous prolactin restored the jejunal calcium absorption to the control value. Endogenous prolactin also had an effect on the duodenum but, in this case, exogenous prolactin did not reverse the effect of bromocriptine. However, neither ileal nor colonic calcium fluxes were influenced by prolactin. Because luminal sodium concentration has been demonstrated to affect calcium absorption in mature rats, the effect of varying luminal sodium concentrations on calcium fluxes in suckling rats was evaluated. The jejunum was used due to its highest rate of calcium absorption. After filling the jejunal segments with 124 (control), 80, 40 mmol/L Na+-containing or Na+-free solution, increases in calcium absorption were found to be inversely related to luminal sodium concentrations in both control and bromocriptine-treated rats. The plasma concentration of45Ca under luminal sodium free condition was also higher than that of the control condition (2.26% ± 0.07% vs. 2.01% ± 0.09% administered dose, p < 0.05). However,3H-mannitol, a marker of the widening of tight junction that was introduced into the lumen, had a stable level in the plasma during an increase in plasma45Ca, suggesting that the widening of tight junction was not required for enhanced calcium absorption. In conclusion, calcium absorption in suckling rats was of the highest rate in the jejunum where endogenous prolactin modulated calcium absorption without increasing the paracellular transport of mannitol. Key words: calcium absorption, intestinal segments, prolactin, suckling rats.
Effects of human pregnancy and aerobic conditioning on alveolar gas exchange during exercise
Authors: McAuley Sonja E , Jensen Dennis , McGrath Michael J , Wolfe Larry A
Published: August 2005

This study examined the effects of aerobic conditioning during the second and third trimesters of human pregnancy on ventilatory responses to graded cycling. Previously sedentary pregnant women were assigned randomly to an exercise group (n = 14) or a nonexercising control group (n = 14). Data were collected at 15–17 weeks, 25–27 weeks and 34–36 weeks of pregnancy. Testing involved 20 W·min–1 increases in work rate to a heart rate of 170 beats·min–1 and (or) volitional fatigue. Breath-by-breath ventilatory and alveolar gas exchange measurements were compared at rest, a standard submaximal [Formula: see text]O2 and peak exercise. Within both groups, resting [Formula: see text]E, [Formula: see text]A, and VT/TI increased significantly with advancing gestation. Peak work rate, O2 pulse [Formula: see text]O2/HR, [Formula: see text]E, [Formula: see text]A respiratory rate, VT/TI, [Formula: see text]O2, [Formula: see text]CO2, and the ventilatory threshold (Tvent) were increased after physical conditioning. Chronic maternal exercise has no significant effect on pregnancy-induced changes in ventilation and (or) alveolar gas exchange at rest or during standard submaximal exercise. Training-induced increases in Tvent and peak oxygen pulse support the efficacy of prenatal fitness programs to improve maternal work capacity. Key words: human gestation, respiration, chronic exercise.
THEORY OF PULSE PROPAGATION IN OPTICAL DIRECTIONAL COUPLERS
Authors: CHIANG KIN SENG
Published: August 2005

Since the existence of intermodal dispersion or coupling coefficient dispersion in an optical directional coupler was highlighted ten years ago, a number of theoretical studies for the understanding of the significance of this dispersion effect on pulse propagation in a directional coupler under various situations have been reported. This paper provides a review of these studies. Both the normal-mode theory and the coupled-mode theory of the coupler are described. The application of the more popular coupled-mode theory to the study of nonlinear pulse switching, soliton interaction, soliton formation, and active couplers is discussed. Experimental works are also described briefly.
THERMO-OPTIC COEFFICIENT OF DIFFERENT PHOTOSENSITIVE ACRYLATE POLYMERS FOR OPTICAL APPLICATION
Authors: RAZALI N. , MOHAMED R. , EHSAN A. A. , KUANG C. S. , SHAARI S.
Published: August 2005

Thermo-optic (TO) effect in materials can be exploited in the fabrication of optical devices such as optical switches and couplers. These optical devices play a key function in communication networks because by changing the temperature they have control over the optical path. Recently, polymer materials have begun to receive attention for the application of the TO switch in integrated optics. The polymers exploited for the variation of refractive index with temperature in our work involve the use of cyclomer acrylate, which is compared to the fluorinated acrylate available in the market. We focus the on cyclomer acrylate resin potential to be employed in fabricating optical devices especially the optical waveguide and optical switch. Formerly, this polymer is used as an adhesive and coating only. Different acrylate formulations from cyclomer acrylates have been exploited. Both acrylates show negative TO effects with temperature i.e. decrease of refractive index result in the increase in temperature. This is expected as the refractive index of the polymers are reduced, as density typically decreases with increasing temperature. This is in accordance to the dependence of polarizability and density of a particular material, to its refractive index. For both types of polymers, the change of the refractive index as a function of temperature is linear. The slope can give the dn/dT of the film. The dn/dT of polymers are as high as the order of 10-4, which is comparable to those of optical polymers. Higher values are shown by the cyclomer acrylate compared to the fluorinated type.
CRIMINAL DISENFRANCHISEMENT
Authors: Uggen Christopher , Behrens Angela , Manza Jeff
Published: August 2005

▪ Abstract  Felon disenfranchisement has recently emerged as an issue of intense public concern and scholarly interest. This review highlights the broad range of socio-legal issues implicated by the practice of denying convicted felons the right to vote by considering the history, impact, and contemporary legal and scholarly debates surrounding the practice. Although race-neutral on their face, many U.S. laws stem from a history of racial discrimination and serve as an example of advantaged groups using the law as a mechanism to control disadvantaged groups. The practice of disenfranchising criminals has survived numerous legal challenges, raising questions about the fundamental nature of the right to vote in the United States and the representativeness of a democracy that systematically excludes a large group of citizens.
Classroom Goal Structure, Student Motivation, and Academic Achievement
Authors: Meece Judith L. , Anderman Eric M. , Anderman Lynley H.
Published: August 2005

Over the past 25 years, achievement goal theory has emerged as one of the most prominent theories of achievement motivation. This chapter uses an achievement goal framework to examine the influence of classroom and school environments on students' academic motivation and achievement. Considerable evidence suggests that elementary and secondary students show the most positive motivation and learning patterns when their school settings emphasize mastery, understanding, and improving skills and knowledge. Whereas school environments that are focused on demonstrating high ability and competing for grades can increase the academic performance of some students, research suggests that many young people experience diminished motivation under these conditions. The implications of achievement goal theory for examining the impact of school reform are discussed.
Explanation and Understanding
Authors: Keil Frank C.
Published: August 2005

The study of explanation, while related to intuitive theories, concepts, and mental models, offers important new perspectives on high-level thought. Explanations sort themselves into several distinct types corresponding to patterns of causation, content domains, and explanatory stances, all of which have cognitive consequences. Although explanations are necessarily incomplete—often dramatically so in laypeople—those gaps are difficult to discern. Despite such gaps and the failure to recognize them fully, people do have skeletal explanatory senses, often implicit, of the causal structure of the world. They further leverage those skeletal understandings by knowing how to access additional explanatory knowledge in other minds and by being particularly adept at using situational support to build explanations on the fly in real time. Across development and cultures, there are differences in preferred explanatory schemes, but rarely are any kinds of schemes completely unavailable to a group.
Estimation of dose-response curves and identification of peaks in hormone pulsations: classic marriages of statistics to science
Authors: Curran-Everett Douglas
Published: August 2005

This essay examines the historical significance of two APS classic papers that are freely available online: De Léan A, Munson PJ, and Rodbard D. Simultaneous analysis of families of sigmoidal curves: application to bioassay, radioligand assay, and physiological dose-response curves. Am J Physiol Endocrinol Metab Gastrointest Physiol 235: E97–E102, 1978 ( http://ajplegacy.physiology.org/cgi/reprint/235/2/E97 ). Merriam GR and Wachter KW.Algorithms for the study of episodic hormone secretion. Am J Physiol Endocrinol Metab 243: E310–E318, 1982 ( http://ajplegacy.physiology.org/cgi/reprint/243/4/E310 ).
Temporal gene expression profiling of liver from periparturient dairy cows reveals complex adaptive mechanisms in hepatic function
Authors: Loor Juan J. , Dann Heather M. , Everts Robin E. , Oliveira Rosane , Green Cheryl A. , Guretzky Nicole A. Janovick , Rodriguez-Zas Sandra L. , Lewin Harris A. , Drackley James K.
Published: August 2005

Long-term molecular adaptations in liver from high-producing dairy cows are virtually unknown. Liver from five Holstein cows was biopsied at −65, −30, −14, +1, +14, +28, and +49 days relative to parturition for transcript profiling using a microarray consisting of 7,872 annotated cattle cDNA inserts. More than 5,000 cDNA elements represented on the microarray were expressed in liver. From this set we identified 62 differentially expressed genes related to physiological state, with a false discovery rate threshold of P = 0.20. The dominant expression pattern consisted of upregulation from day −30 through day +1, followed by downregulation through day +28. There was a threefold decrease from day −65 through day +14 in expression of IGFBP3, GSTM5, and PDPK1. These genes mediate IGF-I transport, oxidative stress, and glucose homeostasis, respectively. IGFBP3, EIF4B, and GSTM5 mRNA levels were positively correlated with blood serum total protein. Correlation analysis showed positive associations between serum nonesterified fatty acids and mRNA expression for SAA1, CPT1A, ACADVL, and TFAP2A. Transcript levels of ACSL1, PPARA, and TFAP2A were positively correlated with serum β-hydroxybutyrate. Expression patterns for certain genes (e.g., IGFBP3, HNF4A, GPAM) revealed adaptations commencing well ahead of parturition, suggesting they are regulated by factors other than periparturient hormonal environment. Results provide evidence that hepatic inflammatory responses occurring near parturition initiate or augment adipose catabolism. In this context, cytokines, acute-phase proteins, and serum nonesterified fatty acids are key players in periparturient cow metabolism. We propose a model for integrating gene expression, metabolite, and liver composition data to explain physiological events in placenta, adipose, and liver during the periparturient period.
Differing Administration Time-Dependent Effects of Aspirin on Blood Pressure in Dipper and Non-Dipper Hypertensives
Authors: Hermida Ramón C. , Ayala Diana E. , Calvo Carlos , López José E. , Mojón Artemio , Rodríguez Marta , Fernández José R.
Published: August 2005

Aspirin is a potent antioxidative agent that reduces vascular production of superoxide, prevents angiotensin II–induced hypertension, and induces NO release. Low-dose aspirin administered at bedtime, but not on awakening, has also been shown to reduce blood pressure, possibly enhancing the nocturnal trough in NO production. Because endothelium-dependent vasodilation is blunted through a decrease in NO release in non-dipper compared with dipper patients, we compared the administration time-dependent influence of aspirin on ambulatory blood pressure in dipper and non-dipper hypertensive subjects. We studied 257 patients with mild hypertension (98 men and 159 women), 44.6±12.5 years of age, randomly assigned to receive 100 mg per day of aspirin either on awakening or at bedtime. Ambulatory blood pressure was measured for 48 hours at baseline and after 3 months of intervention. Blood pressure was slightly elevated after aspirin on awakening (increase of 1.5/1.0 mm Hg in the 24-hour mean of systolic/diastolic blood pressure;
P
<0.028). A highly significant blood pressure reduction was observed in patients who received aspirin at bedtime (decrease of 7.2/4.9 mm Hg in systolic/diastolic blood pressure;
P
<0.001). The reduction in nocturnal blood pressure mean was double in non-dippers (11.0/7.1 mm Hg) compared with dippers (5.5/3.3 mm Hg;
P
<0.001). This prospective trial corroborates the significant administration time-dependent effect of low-dose aspirin on blood pressure, mainly in non-dipper hypertensive patients. The timed administration of low-dose aspirin could thus provide a valuable approach, beyond prevention of cardiovascular disease, in the blood pressure control of patients with mild hypertension.
Aldosterone Stimulates Collagen Gene Expression and Synthesis Via Activation of ERK1/2 in Rat Renal Fibroblasts
Authors: Nagai Yukiko , Miyata Kayoko , Sun Guang-Ping , Rahman Matlubur , Kimura Shoji , Miyatake Akira , Kiyomoto Hideyasu , Kohno Masakazu , Abe Youichi , Yoshizumi Masanori , Nishiyama Akira
Published: August 2005

Recently, we demonstrated that in rats treated chronically with aldosterone and salt, severe tubulointerstitial fibrosis is associated with the activation of mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinases (ERK1/2). Here, we investigated whether aldosterone stimulates collagen synthesis via ERK1/2-dependent pathways in cultured rat renal fibroblasts. Gene expression of mineralocorticoid receptor (MR) and types I, II, III, and IV collagen was measured by real-time polymerase chain reaction (PCR). MR protein expression and ERK1/2 activity were evaluated by Western blotting analysis with anti-MR and anti–phospho-ERK1/2 antibodies, respectively. Collagen synthesis was determined by [
3
H]-proline incorporation. Significant levels of MR mRNA and protein expression were observed in rat renal fibroblasts. Treatment with aldosterone (0.1 to 10 nmol/L) increased ERK1/2 phosphorylation in a concentration-dependent manner with a peak at 5 minutes. Aldosterone (10 nmol/L) also increased the mRNA levels of types I, III, and IV collagen at 36 hours but had no effect on the type II collagen mRNA level. [
3
H]-proline incorporation was significantly increased by aldosterone in both the medium and cell layer at 48 hours. Aldosterone-induced ERK1/2 phosphorylation was markedly attenuated by pretreatment with eplerenone (10 μmol/L), a selective MR antagonist, or PD98059 (10 μmol/L), a specific inhibitor of MAPK kinase/ERK kinase, which is the upstream activator of ERK1/2. In addition, both eplerenone and PD98059 prevented the aldosterone-induced increases in types I, III, and IV collagen mRNA and [
3
H]-proline incorporation. These results suggest that aldosterone stimulates collagen gene expression and synthesis via MR-mediated ERK1/2 activation in renal fibroblasts, which may contribute to the progression of aldosterone-induced tubulointerstitial fibrosis.
Detection of Angiotensin II in Supernatants of Stimulated Mononuclear Leukocytes by Matrix-Assisted Laser Desorption Ionization Time-of-Flight/Time-of-Flight Mass Analysis
Authors: Jankowski Vera , Vanholder Raymond , van der Giet Markus , Henning Lars , Tölle Markus , Schönfelder Gilbert , Krakow Anja , Karadogan Sevil , Gustavsson Niklas , Gobom Johan , Webb Jessie , Lehrach Hans , Giebing Günther , Schlüter Hartmut , Hilgers Karl F. , Zidek Walter , Jankowski Joachim
Published: August 2005

Angiotensin II (Ang II) is the major vasoactive component of the renin-angiotensin system. Several components of the renin-angiotensin system have been demonstrated in different tissues. Whereas the roles of tissue and renal renin-angiotensin system have been studied in detail, much less is known on whether the corpuscular elements of circulating blood contribute to Ang II production. Here we examined whether, in addition to vasculature, blood cells also contribute to the circulating Ang II levels. Mononuclear leukocytes were obtained from healthy subjects and were incubated. The resulting supernatant was chromatographed using different chromatographic methods. The vasoconstrictive effects of aliquots of the resulting fractions were tested. Each fraction with a vasoconstrictive effect was analyzed by mass spectrometry. In one fraction with a strong vasoconstrictive effect, Ang II was identified. Mononuclear lymphocytes produced Ang II in amounts sufficient to stimulate Ang II type 1 receptors. Moreover, in mononuclear leukocytes, renin as well as angiotensin-converting enzyme mRNA expression was detectable by RT-PCR. These findings demonstrate that mononuclear leukocytes are a source of Ang II. Ang II secretion by these cells may play a significant role in humoral vascular regulation. In conclusion, the isolation of Ang II in supernatants of mononuclear leukocytes adds a further physiological source of Ang II to the current view of angiotensin metabolism. The quantitative role of lymphocyte-derived Ang II secretion compared with the other sources of Ang II should be defined further, but the release found under the present conditions is at least sufficient to elicit vasoconstrictive effects.