Metallothionein as an indicator of water quality: assessment of the bioavailability of cadmium, copper, mercury and zinc in aquatic animals at the cellular level

The study of metallothioneins (MTs) has greatly improved our understanding of body burdens, metal storage and detoxification in aquatic organisms subjected to contamination by the toxic heavy metals, Cd, Cu, Hg and Zn. These studies have shown that in certain organisms MT status can be used to assess impact of these metals at the cellular level and, whilst validation is currently limited to a few examples, this stress response may be linked to higher levels of organisation, thus indicating its potential for environmental quality assessment. Molluscs, such as Mytilus spp., and several commonly occurring teleost species, are the most promising of the indicator species tested. Natural variability of MT levels caused by the organism's size, condition, age, position in the sexual cycle, temperature and various stressors, can lead to difficulties in interpretation of field data as a definitive response-indicator of metal contamination unless a critical appraisal of these variables is available. From laboratory and field studies these data are almost complete for teleost fish. Whilst for molluscs much of this information is lacking, when suitable controls are utilised and MT measurements are combined with observations of metal partitioning, current studies indicate that they are nevertheless a powerful tool in the interpretation of impact, and may prove useful in water quality assessment

On the Coexistence of Spot and Contract Markets: a Delivery Requirement Explanation

A model is presented in which spot and contract market exchange co-exist. A contract consists of a delivery requirement between an upstream and a downstream party. Contract formation determines to a certain extent the probability distribution of the spot market price. This contract formation externality entails the removal of high reservation price buyers and various sellers from the spot market. The first effect decreases the expected spot market price when the number of contracts is small, whereas the decrease in the number of sellers and additional residual contract demand increase the expected spot market price beyond a certain number of contracts. It implies an endogenous upper bound on the number of contracts. Contract prices are positively related to the number of contracts. Finally, additional contracts reduce the variance of the spot market price when the number of contracts is sufficiently large.Spot market, contract externality, co-existence, delivery requirement, Marketing, D40, L10,

Grower Heterogeneity and Governance: Authority, Access, and Countervailing Power

The increasing differentiation on the supply side of agricultural and horticultural markets has resulted in many governance structure changes between growers and wholesalers. For example, marketing cooperatives are restructured, heterogeneous associations split up in various one-product associations, growers integrate forward into wholesaling, and so on. These developments are analysed with an incomplete contracting model addressing horizontal as well as vertical relationships in a multilateral setting. The interactions between authority, access, and countervailing power in the choice of governance structure are highlighted.Industrial Organization,

Competing Screening Rules

Various studies show that agricultural cooperatives behave differently than their investor-owned counterparts. One explanation may be that the internal decision making process differs in these two governance structures. A model is developed to explore how endogenous screening rules affect efficient organizational choices and industrial structures. It is shown that screening level choice may outweigh architecture choice and that screening rules are strategic substitutes. Conditions are derived under which cooperatives are efficient organizational forms. It is also shown that competition may increase the attractiveness of investor-owned firms and circumstances are determined in which cooperatives and investor owned firms coexist in equilibrium.architecture, screening, cooperatives, duopoly, Agribusiness, Q13,

Coordination and Governance: The case of Cooperatives versus IOFs

Agribusiness,

Collective action of small farmers: A case study of Ruoheng farmer watermelon cooperative in China

Watermelon production investments, incomes and the access to markets between members of a cooperative and individual small farmers are compared. The results of the case study regarding members of a watermelon cooperative and five individual small farmers in Zhejiang province in China indicate that members of the cooperative are prone to produce food of higher quality, have obvious advantage in accessing modern food supply chains over individual small farmers, and subsequently gain a significantly higher return or income than individual small farmers.farmer cooperative, benefit, income, Consumer/Household Economics,

Organization and Strategy of Farmer Specialized Cooperatives in China

A description and analysis of China's Farmer Specialized Cooperatives is presented. Data is presented regarding the historical development of farmer cooperatives in China, the membership composition of a sample of 66 farmer cooperatives in the Zhejiang province, and the various attributes (governance, quality control system, and strategy) of a watermelon cooperative in this province. Many cooperatives are being transformed in organizations with a market orientation. These cooperatives exhibit substantial heterogeneity, in terms of farmers being member and skewness in the distribution of control rights. Human asset specificity in terms of establishing and maintaining relations and access to markets seems to be more important than physical asset specificity in accounting for governance structure choice in the current institutional setting.Farmer Cooperative, China, Governance Structure, Business Strategy, Agribusiness, Q13,

Structural relationships between the NADH dehydrogenases of Paracoccus denitrificans and bovine heart mitochondria as revealed by immunological cross-reactivities

AbstractAn antibody raised against two subunits (Mr, 48000 and 25000) of NADH dehydrogenase from Paracoccusdenitrificans cross-reacts with one of more than 20 polypeptides that form the bovine heart mitochondrial NADH dehydrogenase. The cross-reacting subunit has Mr, 51000 and is believed to be the NADH-binding subunit of the enzyme. Antibodies raised against certain subunits of the bovine heart NADH dehydrogenase were tested for cross-reactivity withP. denitrificans cytoplasmic membranes. Of those tested, only one, an antibody specific for the 49 kDa subunit of mitochondrial NADH dehydrogenase, cross-reacted with the bacterial membranes. It recognised a polypeptide of approximate Mr, 46000. This is an indication for a previously undetected third subunit of NADH dehydrogenase from P. denitrificans. The immunological crossreactions indicate that the NADH dehydrogenases from P. denitrificans and bovine heart mitochondria are related structurally

Alendronate or alfacalcidol in glucocorticoid-induced osteoporosis

BACKGROUND: Treatment with glucocorticoids is associated with bone loss starting soon after therapy is initiated and an increased risk of fracture. METHODS: We performed a randomized, double-placebo, double-blind clinical trial of 18 months' duration among patients with a rheumatic disease who were starting glucocorticoids at a daily dose that was equivalent to at least 7.5 mg of prednisone. A total of 201 patients were assigned to receive either alendronate (10 mg) and a placebo capsule of alfacalcidol daily or alfacalcidol (1 mu g) and a placebo tablet of alendronate daily. The primary outcome was the change in bone mineral density of the lumbar spine in 18 months; the secondary outcome was the incidence of morphometric vertebral deformities. RESULTS: A total of 100 patients received alendronate, and 101 received alfacalcidol; 163 patients completed the study. The bone mineral density of the lumbar spine increased by 2.1 percent in the alendronate group (95 percent confidence interval, 1.1 to 3.1 percent) and decreased by 1.9 percent in the alfacalcidol group (95 percent confidence interval, -3.1 to -0.7 percent). At 18 months, the mean difference of change in bone mineral density between the two groups was 4.0 percent (95 percent confidence interval, 2.4 to 5.5 percent). Three patients in the alendronate group had a new vertebral deformity, as compared with eight patients in the alfacalcidol group (of whom three had symptomatic vertebral fractures) (hazard ratio, 0.4; 95 percent confidence interval, 0.1 to 1.4). CONCLUSIONS: During this 18-month trial in patients with rheumatic diseases, alendronate was more effective in the prevention of glucocorticoid-induced bone loss than was alfacalcidol

Surface structure and solidification morphology of aluminum nanoclusters

Classical molecular dynamics simulation with embedded atom method potential had been performed to investigate the surface structure and solidification morphology of aluminum nanoclusters Aln (n = 256, 604, 1220 and 2048). It is found that Al cluster surfaces are comprised of (111) and (001) crystal planes. (110) crystal plane is not found on Al cluster surfaces in our simulation. On the surfaces of smaller Al clusters (n = 256 and 604), (111) crystal planes are dominant. On larger Al clusters (n = 1220 and 2048), (111) planes are still dominant but (001) planes can not be neglected. Atomic density on cluster (111)/(001) surface is smaller/larger than the corresponding value on bulk surface. Computational analysis on total surface area and surface energies indicates that the total surface energy of an ideal Al nanocluster has the minimum value when (001) planes occupy 25% of the total surface area. We predict that a melted Al cluster will be a truncated octahedron after equilibrium solidification.Comment: 22 pages, 6 figures, 34 reference