Field studies using fish biomarkers – How many fish are enough?

Significant efforts are invested in field studies using fish, and it is important to optimize the number of organisms collected to evaluate the possible impacts of contamination. This paper provides ecotoxicologists with the approximate numbers of fish needed to identify statistically significant differences among samples using physiological indices and biochemical markers of fish health. The numbers of fish to collect are reported for ethoxyresorufin-o-deethylase (EROD); ethoxycoumarin-o-deethylase (ECOD), serum sorbitol dehydrogenase (sSDH), stress proteins, gonadosomatic index, liver somatic index, condition factor, and biliary metabolites of polycyclic aromatic hydrocarbons. The number of fish to collect was as few as four for ECOD activity (with a power of 80%), but as high as 106 for CF (with a power of 95%). Achieving statistical significance between sites does not help in the interpretation of the biological significance of a parameter, but well-planned field samplings will maximize the chances of correctly identifying areas of concern

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

Influence of ration level and rearing temperature on hepatic GHR1 and 2, and hepatic and intestinal TR alpha and TR beta gene expression in late stages of rainbow trout embryos

The study examined whether the early life-history temperature experience of rainbow trout Oncorhynchus mykiss embryos affects subsequent growth and expression of growth-related genes in the growing-up juveniles in response to variations in ration levels. Embryos were reared in a Heath incubator at either 8.5 degrees C (E-8.5) or 6.0 degrees C (E-6.0) until hatching, at which time they were transferred to grow-up tanks supplied with water at 8.5 degrees C. At swim-up, the late stage embryos were subsequently fed a salmonid starter diet at levels of 5, 2 or 0.5% of live body mass per day. The body mass and proximate composition of the juveniles was examined when yolk absorbance was complete (21 days after the fish commenced feeding). Quantitative RT-PCR was used to examine the expression of mRNA encoding for growth hormone receptors 1 and 2 (GHR1 and GHR2) in the liver, and the two isoforms of thyroid hormone receptor (TR alpha and TR beta) in the liver and intestinal tract. Final body mass and total length, liver and intestinal masses, and total lipid content of the E-8.5 treatment group were directly related to increased ration size. These variables in the E-6.0 treatment group fed the 5% ration were significantly lower than for the comparable E-8.5 treatment group, suggesting an effect of embryo rearing temperature on the subsequent growth of these late stage embryos as they undergo the transition from embryo to early juvenile. Intestinal TR alpha and TR beta mRNA abundance was directly related to ration size in the E-8.5 treatment group, but not in the E-6.0 treatment group. Conversely, hepatic TR alpha and TR beta mRNA abundance was significantly affected by ration size only in the E-6.0 group, with TR beta and TR alpha abundance showing direct and inverse relationships with ration size, respectively. Hepatic GHR1 mRNA abundance was significantly and directly related to ration size in both the E-8.5 and E-6.0 treatment groups, but there were no differences in the abundance of hepatic GHR2 mRNA among any treatments.(c) 2007 The Authors Journal compilation. (c) 2007 The Fisheries Society of the British Isles