Unusual patterns in ¹⁵N blood values after a diet switch in red knot shorebirds.

When a diet switch results in a change in dietary isotopic values, isotope ratios of the consumer's tissues will change until a new equilibrium is reached. This change is generally best described by an exponential decay curve. Indeed, after a diet switch in captive red knot shorebirds (Calidris canutus islandica), the depletion of (13)C in both blood cells and plasma followed an exponential decay curve.

From food to offspring down: tissue-specific discrimination and turn-over of stable isotopes in herbivorous waterbirds and other avian foraging guilds.

Isotopic discrimination and turn-over are fundamental to the application of stable isotope ecology in animals. However, detailed information for specific tissues and species are widely lacking, notably for herbivorous species. We provide details on tissue-specific carbon and nitrogen discrimination and turn-over times from food to blood, feathers, claws, egg tissues and offspring down feathers in four species of herbivorous waterbirds.

Direct chemical ionization-mass spectrometric profiling of urine in premenstrual syndrome.

In search of the pathophysiological background of premenstrual syndrome, direct chemical ionization-mass spectrometric profiling was applied to urine samples from 17 patients and 18 control subjects, collected on days 11 and 25 of the menstrual cycle. Oestrogenic compounds and hippuric acid were found to be involved in differences between these groups. Quotient profiles calculated for each subject from their profiles of days 11 and 25 showed cycle day-dependent group differences.

Simultaneous determination of the major acidic metabolites of catecholamines and serotonin in urine by liquid chromatography with electrochemical detection after a one-step sample clean-up on Sephadex G-10; influence of vanilla and banana ingestion.

A simple method is described for the simultaneous determination of vanilmandelic acid (VMA), 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindole-3-acetic acid (5-HIAA) and homovanillic acid (HVA) in urine. The compounds are isolated by a one-step sample clean-up on Sephadex G-10, separated by ion-pair reversed-phase liquid chromatography and detected electrochemically. A single analysis is completed within 65 min.