Comparison of postprandial oleic acid, 9c,11t CLA and 10t,12c CLA oxidation in healthy moderately overweight subjects.

Few studies report the individual effect of 9c,11t- and 10t,12c-CLA on human energy metabolism. We compared the postprandial oxidative metabolism of 9c,11t- and 10t,12c-CLA and oleic acid (9c-18:1) in 22 healthy moderately overweight volunteers. After 24 weeks supplementation with 9c,11t-, 10t,12c-CLA or 9c-18:1 (3 g/day), subjects consumed a single oral bolus of the appropriate [1-(13)C]-labeled fatty acid.

Effect of age and food intake on dietary carbon turnover recorded in sheep wool.

We present the results of a series of controlled feeding experiments with sheep, designed to investigate the effects of age and level of food intake on the kinetics of incorporation of the dietary carbon signal into wool. Four different groups of three sheep each, ranging in age from 6 to 78 months, were fed a C(3) diet and switched to a C(4) diet for up to 250 days. Different quantities of the same C(4) diet were provided to each group, in order to achieve different growth rates (high, low, and no growth).

Three-dimensional growth of bovine hoof as recorded by carbon stable isotope ratios.

To investigate the usefulness of bovine hooves as incremental tissues, the objective of this research was to gain a better understanding of hoof growth in three dimensions. In a controlled experiment, cattle were switched from a barley-based diet to a maize-based diet (C isotopic spacing between diets was 13.6 per thousand) and maintained on this experimental diet for 168 days.

Monitoring the arsenic and iodine exposure of seaweed-eating North Ronaldsay sheep from the gestational and suckling periods to adulthood by using horns as a dietary archive.

Trace elements often accumulate in keratin-rich tissues. Hair, nails, and horns grow steadily but once formed are metabolically inactive and provide an archive of trace element exposure when analyzed in segments. Here we demonstrate the use of laser ablation ICP-MS for the high-resolution monitoring of trace elements in the horns of seaweed-eating sheep from North Ronaldsay, which live on grass only during lambing time.

Using hooves for high-resolution isotopic reconstruction of bovine dietary history.

The objective of this study was to ascertain whether sequential sampling and isotopic analysis of bovine hooves could be used to reconstruct the dietary history of cattle. A controlled, on-farm experiment was conducted in which cattle were switched from a barley-based diet to an isotopically different diet incorporating maize, urea and seaweed (the isotopic spacing between diets was 13.6 per thousand for delta(13)C and 8.

Alteration of the carbon and nitrogen stable isotope composition of beef by substitution of grass silage with maize silage.

This study investigated the effect of substituting grass silage (C3 photosynthetic plant product) with maize silage (C4 photosynthetic plant product) on the natural abundance carbon (delta13C) and nitrogen (delta15N) stable isotope composition of bovine muscle tissue. Forty-five continental crossbred heifers were assigned to one of three diets consisting of 3 kg of a barley-based concentrate plus grass silage, maize silage or an equal mixture (dry matter basis) of grass silage and maize silage, fed ad libitum, for 167 days. Substitution resulted in less negative delta13C values (P<0.

Stable isotope probing analysis of the influence of liming on root exudate utilization by soil microorganisms.

Rhizosphere microorganisms play an important role in soil carbon flow, through turnover of root exudates, but there is little information on which organisms are actively involved or on the influence of environmental conditions on active communities. In this study, a 13CO2 pulse labelling field experiment was performed in an upland grassland soil, followed by RNA-stable isotope probing (SIP) analysis, to determine the effect of liming on the structure of the rhizosphere microbial community metabolizing root exudates. The lower limit of detection for SIP was determined in soil samples inoculated with a range of concentrations of 13C-labelled Pseudomonas fluorescens and was found to lie between 10(5) and 10(6) cells per gram of soil.

Flux and turnover of fixed carbon in soil microbial biomass of limed and unlimed plots of an upland grassland ecosystem.

The influence of liming on rhizosphere microbial biomass C and incorporation of root exudates was studied in the field by in situ pulse labelling of temperate grassland vegetation with (13)CO(2) for a 3-day period. In plots that had been limed (CaCO(3) amended) annually for 3 years, incorporation into shoots and roots was, respectively, greater and lower than in unlimed plots. Analysis of chloroform-labile C demonstrated lower levels of (13)C incorporation into microbial biomass in limed soils compared to unlimed soils.

Seaweeds in cold seas: evolution and carbon acquisition.

Much evidence suggests that life originated in hydrothermal habitats, and for much of the time since the origin of cyanobacteria (at least 2.5 Ga ago) and of eukaryotic algae (at least 2.1 Ga ago) the average sea surface and land surface temperatures were higher than they are today.

Mechanistic interpretation of carbon isotope discrimination by marine macroalgae and seagrasses.

The literature, and previously unpublished data from the authors' laboratories, shows that the δC of organic matter in marine macroalgae and seagrasses collected from the natural environment ranges from -3 to -35‰. While some marine macroalgae have δC values ranging over more than 10‰ within the thallus of an individual (some brown macroalgae), in other cases the range within a species collected over a very wide geographical range is only 5‰ (e.g.