Physiological performance of common carp (Cyprinus carpio, L., 1758) exposed to a sublethal copper/zinc/cadmium mixture.

In a natural ecosystem, fish are subjected to a multitude of variable environmental factors. It is important to analyze the impact of combined factors to obtain a realistic understanding of the mixed stress occurring in nature. In this study, the physiological performance of juvenile common carp (Cyprinus carpio) exposed for one week to an environmentally relevant metal mixture (4.8 µg/L of copper; 2.9 µg/L of cadmium and 206.8 µg/L of zinc) and to two temperatures (10 °C and 20 °C), were evaluated. After 1, 3 and 7 days, standard (SMR) and maximum metabolic rate (MMR) were measured and aerobic scope (AS) was calculated. In addition, hematocrit, muscle lactate, histology of the gills and metal accumulation in gills were measured. While SMR, MMR and AS were elevated at the higher temperature, the metal mixture did not have a strong effect on these parameters. At 20 °C, SMR transiently increased, but no significant changes were observed for MMR and AS. During metal exposure, hematocrit levels were elevated in the 20 °C group. The bioaccumulation of Cd in the gills reflected the increased metabolic rate at the higher temperature, with more accumulation at 20 °C than at 10 °C. Anaerobic metabolism was not increased, which corresponds with the lack of significant histopathological damage in the gill tissue. These results show that common carp handled these metal exposures well, although increased temperature led to higher Cd accumulation and necessitated increased hematocrit levels to maintain aerobic performance.

Transdisciplinary synthesis for ecosystem science, policy and management: The Australian experience.

Mitigating the environmental effects of global population growth, climatic change and increasing socio-ecological complexity is a daunting challenge. To tackle this requires synthesis: the integration of disparate information to generate novel insights from heterogeneous, complex situations where there are diverse perspectives. Since 1995, a structured approach to inter-, multi- and trans-disciplinary(1) collaboration around big science questions has been supported through synthesis centres around the world. These centres are finding an expanding role due to ever-accumulating data and the need for more and better opportunities to develop transdisciplinary and holistic approaches to solve real-world problems. The Australian Centre for Ecological Analysis and Synthesis (ACEAS ) has been the pioneering ecosystem science synthesis centre in the Southern Hemisphere. Such centres provide analysis and synthesis opportunities for time-pressed scientists, policy-makers and managers. They provide the scientific and organisational environs for virtual and face-to-face engagement, impetus for integration, data and methodological support, and innovative ways to deliver synthesis products. We detail the contribution, role and value of synthesis using ACEAS to exemplify the capacity for synthesis centres to facilitate trans-organisational, transdisciplinary synthesis. We compare ACEAS to other international synthesis centres, and describe how it facilitated project teams and its objective of linking natural resource science to policy to management. Scientists and managers were brought together to actively collaborate in multi-institutional, cross-sectoral and transdisciplinary research on contemporary ecological problems. The teams analysed, integrated and synthesised existing data to co-develop solution-oriented publications and management recommendations that might otherwise not have been produced. We identify key outcomes of some ACEAS working groups which used synthesis to tackle important ecosystem challenges. We also examine the barriers and enablers to synthesis, so that risks can be minimised and successful outcomes maximised. We argue that synthesis centres have a crucial role in developing, communicating and using synthetic transdisciplinary research.

Evaluation of medigoxin in outpatients.

We compared our ability to predict the dose of medigoxin and of digoxin required to achieve a fixed serum concentration (the dose requirement) in 33 outpatients. Preliminary work supported the assumptions that the steady state glycoside concentration achieved was proportional to the daily dose given to an individual, and that the bioavailability of the different tablet presentations was similar for either glycoside. We were not able to predict the dose requirement from patient characteristics with any more certainty for medigoxin than for digoxin. Not only the between-patient variability in dose requirement, but also the within-patient variability, was similar for the two glycosides. However the digoxin used had a dissolution rate of over 90% in 1 h. When comparing medigoxin with digoxin of lower, or more variable dissolution rate, medigoxin may be preferable.

Ideal sampling time for drug assays.

Estimation of the mean steady state serum concentration of a drug from an isolated sample apparently requires a knowledge of both the timing of the sample within the dose interval and of the pharmacokinetic constants of the drug in the individual. Data from 80 general medical outpatients receiving maintenance digoxin has been used to derive a relationship between the serum digoxin concentration at any given time (C) and the mean steady state concentration (C), but this did not allow for individual variation in drug handling. It can be demonstrated theoretically that, for a one compartment model with instantaneous drug distribution and first order elimination, the ratio, C/C, is dependent on the half time of the drug, the dose interval and the time of sampling. Moreover, for higher values of half time the ratio is virtually constant at 11 h after a daily dose. This, then, would be an ideal sampling time. The above approach can be extended to any drug provided that its half time is at least 15 h in healthy subjects and that the concentration/time curve approximates to a simple exponential decay during virtually the entire dose interval. Orally administered digoxin meets both of these provisions, the ratio at 11 h being 0.97, which is only slightly different from the 1.02 of the theoretical model. Ideal sampling times and the conditions under which they apply may be derived for other dose intervals.

A score for prescribing digoxin.

A simple method of selecting a maintenance dose of digoxin, suitable for an adult patient, was derived from data on 129 patients taking digoxin. Eight items of readily available information are required for entry into the prescribing aid: out/inpatient status, sex, age (less/not less than 70 years), weight (allocated to one of four ranges), whether or not chronically house/chair bound, cardiac rhythm (sinus/other), serum creatinine concentration (allocated to one of four ranges), and diuretic therapy (prescribed/not prescribed). The recommended dose is given in terms of size and number of tablets to be prescribed. Using this method 72.3 per cent of patients are expected to achieve mean steady state serum digoxin concentrations within the therapeutic range, 6.5 per cent above and 21.2 per cent below. This performance would be considerably better than that expected from the use of other prescribing aids. If available, routine measurement of the serum digoxin concentration during follow-up is recommended to detect those who might benefit from a change, usually an increase, in dose.