Development of non-lethal sampling of carbon and nitrogen stable isotope ratios in salmonids: effects of lipid and inorganic components of fins.

The preferred tissue for analyses of fish stable isotope ratios for most researchers is muscle, the sampling of which typically requires the specimen to be sacrificed. The use of non-destructive methods in fish isotopic research has been increasing recently, but as yet is not a standard procedure. Previous studies have reported varying levels of success regarding the utility of non-lethally obtained stable isotope materials, e.g. fins, but none have accounted for the potential compounding effects of inorganic components of fin rays or lipids. Comparisons of carbon (δ(13)C) and nitrogen (δ(15)N) stable isotope ratios of muscle with adipose and caudal fin of two salmonids, Atlantic salmon (Salmo salar L.) and brown trout (Salmo trutta L.), revealed that caudal fin can be used as a non-destructive surrogate for muscle in stable isotope analysis, but that adipose fin, where available, is a better proxy. The use of a published model to inexpensively counteract the confounding effect of lipids, which are depleted in (13)C, greatly improved the relationship between fish muscle and fins. However, efforts to account for the inorganic components of fin rays were counterproductive and required twice the biomass of fins clipped from each fish. As this experiment was conducted on wild fish, controlled laboratory studies are required to confirm these field observations.

What is the lowest dose of aspirin for maximum suppression of in vivo thromboxane production after a transient ischemic attack or ischemic stroke?

BACKGROUND: There is still worldwide disagreement about the optimal lowest dose of aspirin to be used in patients after a transient ischemic attack (TIA) or nondisabling stroke. We measured the urinary 11-dehydro-thromboxane-B(2) (uTXB(2)) excretion to compare the degree of suppression of in vivo platelet activation by various low doses of aspirin. METHODS: 60 patients were randomly allocated to treatment with either 30, 50, 75 or 325 mg of aspirin. All patients received a 413-mg loading dose of carbasalate calcium (equivalent to 325 mg of aspirin) on day 0. The study population was stratified into a subgroup with acute ischemic stroke (AIS; n = 20; onset of symptoms <48 h) and a subgroup with a recent TIA or minor stroke (TIA/mS; n = 40) with onset of symptoms beyond 30 days, but less than a year previously. Urine samples were collected on day 0, 1, 5, 11 and 28 in patients with AIS, and on day 0, 11 and 28 in the patients with a TIA/mS. RESULTS: On day 28, mean uTXB(2) levels were 241, 130, 217 and 187 pmol/mmol creatinine in the four treatment groups (ANOVA, p = 0.43). In the AIS subgroup, uTXB(2) remained suppressed on days 5 and 11 in all except the patients with the lowest dose (mean uTXB(2) on days 5 and 11: 475 and 392 pmol/mmol creatinine; log-transformed ANOVA, p = 0.05). CONCLUSION: In patients with a TIA or nondisabling stroke, a daily dose of 30 mg of aspirin provides sufficient suppression of thromboxane synthesis. No indication of a dose-effect relationship was found. However, whether such a low dose adequately suppresses thromboxane synthesis in patients with acute stroke is uncertain.

Training background as a factor in the conversion rate of laparoscopic cholecystectomy.

The present study reports findings concerning the impact of the learning environment on the conversion rate of laparoscopic cholecystectomy (LC) to open cholecystectomy (OC). At Metro-West Medical Center (Framingham, MA) seven surgeons performed 866 LCs between 1990 and 1995. Group I consisted of three surgeons who learned the procedure as part of their General Surgery Residency training, whereas the remaining four surgeons representing Group II learned the procedure through private courses. We emphasize the importance of the surgeons' training background on the conversion rates, operative times, and length of hospitalization for patients undergoing LC. The conversion rates, operative times, and complication rates were analyzed with and without a 2-year period of adjustment to compensate for the learning curve of early procedures. Operative times and conversion rates from LC to OC were lower for cases done by surgeons from Group I, even when the learning curve was corrected. The complication rates were higher for surgeons in Group II, but this did not reach statistical significance. As surgeons from Group II gained more experience their operation times and conversion rates decreased. However, there still was a statistically significant difference in favor of surgeons who learned the procedure as part of a structured curriculum. These data suggest a long-lasting influence of the learning environment on the conversion rates and operative times.