José Antonio Lupiáñez

Succinic acid production by yeasts grown under different hypoxic conditions

SummarySaccharomyces cerevisiae grown under different hypoxic conditions (oxygen deprivation, high hexose concentrations and inhibition of the mitochondrial synthesis of proteins) accumulates significant amounts of succinic acid as an end product. Similar results have been obtained with the impaired respiration mutant.The succinate accumulation supports the postulated reductive function of a branch of the tricarboxylic acid cycle leading from oxalacetate to succinate in hypoxia.

Alterations in the fractional protein turnover rates in rainbow‐trout liver and white muscle caused by an Aminoacid‐based diet and changes in the feeding frequency 1

We have studied the effects of an aminoacid‐based diet, ABD, (15% free aminoacids plus 30% fish‐meal protein) as well as feeding frequency (two and four times day) on various protein‐turnover‐rate parameters in the liver and white muscle of rainbow trout (Oncorhynchus mykiss) and have related these parameters with the growth rate and RNA and DNA cell contents. Our results showed that in both types of tissue the fractional rates (Ks) and efficiency, (KRNA) of protein synthesis significantly increased when fishes were fed four times compared to those fed only twice. The considerable differences between the fractional rates of protein synthesis (Ks) and protein degradation (KD) in white muscle compared to hepatic tissue explains the high percentage of protein deposition in the former. Thus, about ninety‐three percent of the protein synthesized in white muscle contributes to growth, while only eleven percent goes towards growth in the liver.

Maslinic Acid, a Natural Triterpene, Induces a Death Receptor-Mediated Apoptotic Mechanism in Caco-2 p53-Deficient Colon Adenocarcinoma Cells.

Maslinic acid (MA) is a natural triterpene present in high concentrations in the waxy skin of olives. We have previously reported that MA induces apoptotic cell death via the mitochondrial apoptotic pathway in HT29 colon cancer cells. Here, we show that MA induces apoptosis in Caco-2 colon cancer cells via the extrinsic apoptotic pathway in a dose-dependent manner. MA triggered a series of effects associated with apoptosis, including the cleavage of caspases -8 and -3, and increased the levels of t-Bid within a few hours of its addition to the culture medium. MA had no effect on the expression of the Bax protein, release of cytochrome-c or on the mitochondrial membrane potential. This suggests that MA triggered the extrinsic apoptotic pathway in this cell type, as opposed to the intrinsic pathway found in the HT29 colon-cancer cell line. Our results suggest that the apoptotic mechanism induced in Caco-2 may be different from that found in HT29 colon-cancer cells, and that in Caco-2 cells MA seems to work independently of p53. Natural antitumoral agents capable of activating both the extrinsic and intrinsic apoptotic pathways could be of great use in treating colon-cancer of whatever origin.

Dissociation between renal gluconeogenesis and ammoniagenesis after acute liver intoxication

Renal glucose and ammonia production as well as phosphoenolpyruvate carboxykinase and phosphate-dependent glutaminase activities were measured for acute liver intoxication. Gluconeogenesis and phosphoenolpyruvate carboxykinase activity increased, whereas ammonia production and phosphate-dependent glutaminase showed no changes with respect to the controls. The dissociation between gluconeogenesis and ammoniagenesis may be explained by the differential effect on the enzymes in these conditions.