[en] The use of natural ¹³C isotopes allows to get important information on the study of the intermediate metabolism in physiology and human pathology. One of the major interests of such a method is that it allows to avoid the use of radioactive nuclides. Results reported in this work with a natural ¹³C-labelled glucose are in accordance with some previous results obtained with a small number of subjects, using an artificial ¹³C-enriched glucose, a product which is actually rare and very expensive (G.C.)

[en] Numerious review articles have already been published on the biological effects of deuterium. The most important of these effects are briefly recalled with special emphasis on the consequences of deuteriation on living organisms. The toxicity of low doses of deuterium is examined, particularly in the light of a hypothesis associating deuterium with ageing processes. The natural variations of deuterium concentration are considered in this connection. The use of the isotopic properties for modifying the pharmacological efficiency of various substances is also examined. In conclusion, the authors discuss the effects of two other stable isotopes, carbon-13 and oxygen-18. (author)

[en] Following the work undertaken by Duchesne et al., a synthesis of the results obtained since 1968 is presented. Differences up to 10 per mil are observed in the isotopic ratio ¹³C/¹²C of the CO₂ exhaled by various animals as a function of their diet and especially of the presence in their diet of vegetables characterized by a C4 photosynehetic pathway (such as maize). Weak but significant variations of the CO₂ isotopic ratio are also observed during starvation, after injection of hormones which regulate the glycaemia or even simply in relation to the metabolic rhythms of normal digestion; these variations seem to be correlated with the modifications arising in the relative proportion of substrates from which carbon dioxide is formed. Small isotopic fractionations, appearing mainly in bones and fats, were also shown by combustion of various tissues. Moreover, a change in diet (use of corn) affects clearly, not only the exhaled CO₂, but also, within a few days, the mean ¹³C content of organs, mainly in the case of the liver. These metabolic fractionations remain, however, limited enough to use the ¹³C content, naturally a little higher, of C4 photosynthetic vegetables as a tracer in order to follow some metabolic processes. An application of this is presented by way of a flucose tolerance test

[en] In the gulf of Calvi, Corsica, three main plant carbon pools are entering the constitution of detrital organic matter : Phytoplankton, Posidonia meadows and benthic macroalgae. By the use of ¹³C/¹²C ratio analyses performed on various plants and animals, it was tried to determine the relative shares of these three pools in the detrital matter ingested by particles feeders. It appears that Posidonia, notwithstanding their important biomass, are a minor food source for zoobenthos. (Author)

[en] It is known that heavy water has multiple effects in biological systems but these are still far from being fully understood especially those concerning perturbations in basal metabolism. It was shown that there exist isotopic effects which affect the ¹³C/¹²C ratio of exhaled CO₂ in the case of intermediary metabolism variations induced, for instance, by starvation or hormone injections. It was then interesting to study how heavy water affects this metabolism by the way of modifications at the level of the ¹³C content of CO₂. For this purpose, rats, receiving heavy water in such a way that their blood reaches a 27% content in D₂O, were observed and the ¹³C/¹²C of their CO₂ was measured daily. An important ¹³C variation was detected following the increase as well as the decrease of the ²H content variations. Unfortunately, it was shown that this effect was mainly related to a variation in ¹⁷O content of the CO₂ from which the mass is affected in the same way as from a ¹³C variation. This ¹⁷O enrichment comes from the fact (apparently usually neglected) that deuterium enriched waters have not exactly the same content in oxygen isotopes as natural waters. Despite the necessity of this important correction for ¹⁷O, a residual effect of ¹³C variation is still observed

[en] Following the work undertaken by Duchesne et al. since 1968, results from the use of a new method in the area of glucose metabolism are presented. Because of differences in their photosynthetic pathway, some vegetables, e.g., maize and sugarcane, are a little richer in ¹³C than most common foodstuffs. This weak, but significant, enrichment allows the use of maize glucose as a natural and nonradioactive tracer. In this procedure the variations of the ¹³C/¹²C ratio of exhaled CO₂ are measured by mass spectrometry. By this method, we can follow, in man, the complete conversion of an oral glucose load into CO₂ during a glucose tolerance test. At the same time, measurements of blood glucose and of respiratory quotient are made. They permit a useful comparison of the level of glucose in blood, the total amount of glucose consumed, and the fraction of exogenous glucose burned in the hours following oral administration. New information was obtained from these studies concerning glucose metabolism. The method was used in normal subjects and in obese and diabetic patients. Some of the diabetics were receiving an oral antidiabetic treatment. Significant differences were obtained in these cases, not only between them but also with the information given by the classical methods