Antoni Pons

Semi-quantification of carotenoids by high-performance liquid chromatography: saponification-induced losses in fatty foods

Abstract Reversed-phase liquid chromatography, with a non-linear gradient and photodiode array detection (350–550 nm range), have been used to analyse fat-cured crude sausage (“Sobrassada”) in which the main ingredient is paprika. Saponification is seen to produce the underestimation of some carotenoids. The effects of saponification on carotenoid stability were characteristic of each individual carotenoid and depended on food type. Saponification produced a greater underestimation of capsanthin in a cured fatty food like Sobrassada, than in powdered paprika used as an ingredient in Sobrassada, 46% and 22%, respectively. In contrast, saponification produced a similar underestimation of β-carotene in this cured fatty food as in powdered paprika, 49% and 48%, respectively.

Regulation of rat erythrocyte l-glutamine, 1-glutamate and l-lysine uptake by short term starvation

1. The kinetic parameters (Km, Vmax and Kd) of L-glutamine, L-glutamate and L-lysine uptake by isolated red blood cells in fed and 24 hr starved rats have been determined. 2. L-Lysine and L-glutamine uptake was best fitted by a two transport component: a saturable component and a diffusion one. 3. Starvation brought about important decreases in the Km and Vmax for both L-lysine and L-glutamine uptake. 4. The Kd for L-glutamine showed a significant increase whereas that corresponding to L-lysine did not change by starvation. 5. L-Glutamate uptake adjusted to diffusion kinetics, with a Kd which did not change due to starvation. 6. It is concluded that the amino acid uptake showed specific regulation by starvation. 7. The mechanism involved is not dependent on protein synthesis--given the unnucleated nature of mammal red cells. 8. The magnitude of the changes observed in the uptake kinetic parameters may account for the extent of the blood amino acid pool changes as those produced in vivo over physiological limits.

FATTY ACID COMPOSITION OF BROWN ADIPOSE TISSUE IN DIETARY OBESE RATS

The effects of both dietary obesity and a food deprivation period of 24 hours on fatty acid composition of brown adipose tissue have been investigated. Long time exposure to a hypercaloric high‐fat diet such as the cafeteria diet induced an important tissue fatty acid accumulation, mainly for the major saturated and monounsaturated fatty acids. Notable metabolic differences have been observed in the behaviour of control and obese rats facing a food deprivation period: a preferential utilization of the most abundant saturated fatty acids in control rats and a minor response in obese rats, with a greater fat accumulation in the interscapular brown adipose tissue.

Changes in fatty acid composition in rat adipose tissue induced by dietary obesity.

The aim of the study was to evaluate the effects of cafeteria feeding on the composition of fatty acids in retroperitoneal fat pad and also to determine what happens to fatty acids when rats previously fed the cafeteria diet are returned to regular rat chow. The study of the post‐cafeteria rats enabled us to determine the effects of dietary induced excess weight in the absence of artefactual interferences from the diet because these rats, unlike the cafeteria obese rats, ate the same diet as controls.

Decrease of the pool of amino acids adsorbed on blood cell membranes caused by starvation in rats

The effect of 24 h starvation on the pool of amino acids adsorbed on the blood cell membranes was determined in Wistar rats. Aortic and iliac blood was analysed. 24 h starvation induced a significant decrease in the combined essential amino acids adsorbed on the blood cell membranes, in both arterial and venous blood, without affecting whole-blood levels (adsorbed + non-adsorbed). The same tendency was extended to most of the individual amino acids. This finding indicates that this pool of adsorbed amino acids has a rapid turnover and probably plays a physiological role in a situation of exogenous food deprivation.

Combined enzymic and chromatographic techniques to determine specific radioactivity in free and triglyceride fatty acid plasma fractions

A reliable method to determine both free and triglyceride fatty acids and simultaneously to determine the specific radioactivity in each fraction has been developed. The procedure can be used to analyse a large number of samples. Lipoprotein lipase was used to hydrolyse triglyceride fatty acids, and a Carbopack B column was used to isolate free fatty acids. The radiolabeled fatty acids were determined by liquid scintillation counting, and individual fatty acid levels in each fraction were determined by gas chromatography. Free and triglyceride fatty acids were eluted in different fractions from the Carbopack B column. No interferences from other compounds were significant.

Metabolic utilization of muscular l-proline in 24-hr starved rats

1. The aim of this paper was to study the in vivo skeletal muscle L-proline related to its destination to other key tissues such as liver and intestine as well as to give some insight into the role of blood cells in proline handling. 2. L-U-[14C]Proline was injected intramuscularly and following by sampling of blood, liver, intestine and contralateral muscle at 20 and 30 min after injection. 3. The distribution of radioactivity between blood cells and plasma and in total and individual amino acids, protein and glycogen fractions was determined in the above tissues. 4. The pattern of well fed rats was compared with those submitted to 24-hr complete starvation. 5. During starvation a minor degree of proline oxidation occurs. 6. The main destruction of proline in the liver seem to be the synthesis of proteins. 7. The radioactivity recovered in the blood proline fraction of starved rats is twice that of the fed rats and that it could be attributed mainly to plasma protein. 8. We have obtained in vivo evidence for the role of erythrocyte in the interorgan proline transport.