Search PubMed⌕ Search

Biomedical subjects

L Leclerc

Publications and source records attributed to L Leclerc.

At least 55 records · Page 3Linked to original sources
PubMed1984

The effect of anions and cations on cardiac adenylate cyclase: interactions with isoprenaline and GTP.

Anions stimulated rabbit heart adenylate cyclase in the order chloride greater than phosphate greater than acetate, while the cations sodium and potassium had little effect. Activation by KCI was multiplicative with that of fluoride. Isoprenaline (10(-4) M) and GTP(10(-4) M) stimulated the cyclase independently, and their combined effects were multiplicative. GTP stimulated less than chloride but more than acetate. Activation by chloride or acetate was more than additive with that by GTP. The effect of isoprenaline was reduced in the presence of chloride or acetate, and this reduction was not modified by sodium or potassium. It was concluded that ionic influence may be biologically important in modifying cyclase activity and the extent of beta-receptor stimulation.

Acetates↗
PubMed1981

[Effect of physical training on the metabolic response of the isolated working heart during hypoxia (author's transl)].

The increased tolerance to O2 deprivation of the myocardium after physical training was studied using the isolated working heart preparation and rats moderately trained by swimming. Glycolytic utilization of exogenous glucose and lactate production were determined under oxygenated conditions (Po2 # 500 Torr, 10 min), during severe hypoxia (P02 less than 50 Torr, 10 min) and during post-hypoxic perfusion (Po2 # 500 Torr, 15 min). The energetic state (CP, ATP, ADP, AMP) and glycogen store were determined at the end of the experimental procedure. The beneficial effect of training was evidenced by the restoration of aortic flow in the post-hypoxic period in hearts from trained animals (CE), whereas it did not return to the prehypoxic level in hearts from sedentary animals (CS). The increase in glycolytic utilization of exogenous glucose during hypoxia (x 2.5) was not very different in CE and CS, whereas lactate production was higher (+ 50%) and of longer duration in CE than in CS, This higher lactate production was the consequence of the larger glycogen store in CE than in CS. Moreover, glycogen resynthesis during the post-hypoxic period was higher in CE than in CS. Thus, a changed glycogen metabolism, and also higher CP and ATP contents in CE compared to CS, are examples of metabolic events implicated in the increased tolerance to O2 deprivation of the myocardium induced by physical training.

Animals↗
PubMed1980

[Possible contribution of amino-acids in myocardium response to hypoxia (author's transl)].

The purpose of the present report is to review current knowledge on amino-acid metabolism during hypoxia in vivo and in vivo, mainly in the myocardium. We have first considered biochemical events occurring in muscles during anoxia either in facultative anaerobic invertebrates or in aerobic vertebrates. In the invertebrate muscle, simultaneous utilization of carbohydrate and amino acids in anoxia leads to ATP formation and accumulation of CO2, alanine and succinate. In aerobic species, ATP production in anoxic conditions is mostly or totally derived from glycolysis, lactate being the end product. Recent studies from various authors have suggested that amino acid utilization may be present in aerobic species exposed to hypoxia and contribute to energy production under these conditions. Experiments using the isolated rat heart preparation have demonstrated the accumulation of alanine and succinate in addition to that of lactate during short period of hypoxia (Fig. 8). The relative importance of these biochemical events in term of energy production is discussed. It is also postulated that the accumulation of alanine and succinate in the myocardium during hypoxia may be involved in other physiological processes.

Aerobiosis↗
PubMed1980

Effect of fasting on liver and muscle glycogen in rats and guinea pigs.

The effect of a 48 hr fasting period on liver and muscle glycogen was studied in rats and guinea pigs. Total content of glycogen in the liver was similar in both species of fed animals and was totally exhausted after the fasting period. Muscle glycogen was twice as high in fed guinea pigs as in fed rats. The loss during fasting in guinea pigs was also twice that in rats. The differences in glycogen stores may explain the different metabolic response to fasting previously observed in the two species : hypoglycemia and decreased glucose production in fasted rats and constancy of these parameters in fasted guinea pigs.

Animals↗
PubMed1980

[Simultaneous use of carbohydrates and amino acids during total ischemia in the isolated rat heart (author's transl)].

The simultaneous utilization of carbohydrates and amino acids in the metabolic response to oxygen deprivation was studied i the isolated rat heart initially perfused according to Langendorff and submitted to periods of 2, 5, 10 and 15 min of complete ischemia. The results of the measurement of metabolite contents showed : (1) an immediate decrease of glycogen, pyruvate, alpha-ketoglutarate and aspartate; (2) a delayed decrease of citrate and glutamate; (3) an immediate and continuous increase of lactate and succinate; (4) a delayed increase of alanine; (5) a transient increase of malate + fumarate. The end products of anaerobic metabolism are lactate, which is an index of glycolytic activity, and alanine and succinate, which are indexes of amino acid fermentation. Succinate originates from aspartate, and alanine originates from glutamate. The amino acid pathway does not seem of importance in the production of ATP compared to glycolysis. However, its eventual role and the physiological implication of these reactions in the resistance of strict aerobic organisms to oxygen deprivation are discussed.

Alanine↗
PubMed1979

[Effects of alanine on the metabolism of lactate and glucose in the isolated perfused rat heart (author's transl)].

Perfused non working isolated rat heart preparations have been used to study whether alanine (0,89 gl-1) could represent an energy source for the myocardium. Its influence on glucose and lactate metabolism in the heart was also studied. The use of 14C labelled compounds permitted the estimation of the oxidation rate of these three metabolites. The results show that: 1) Alanine was not utilized by the heart. 2) Alanine did not alter myocardial glucose metabolism or lactate oxidation. 3) Alanine lowered lactate uptake by the myocardium which may indicate that alanine influences lactate transport through the cell membranes. One may speculate that in vivo, alanine will not interfere with glucose or lactate metabolism by the heart as, even in acute physiological conditions (exercice, hypoxie, fasting) lactate is always present in blood at higher concentration than alanine.

Alanine↗
PubMed1979

Lactate kinetics estimated by single injection and continuous infusion of [14C-(U)]-lactate in rats.

1 Identical values of the rate of lactate turnover determined with [14C-(U)]-lactate were found with single injection or continuous infusion techniques in anaesthetized and mechanically ventilated rats. 2 The mean transit time and total minimal body mass of lactate determined graphically (Katz et al., 1974 a, b) were higher with single injection than with continuous infusion of the tracer.

Animals↗
PubMedDate not supplied

Analysis of altered gene expression in rat soleus muscle atrophied by disuse.

The present study involved a global analysis of genes whose expression was modified in rat soleus muscle atrophied after hindlimb suspension (HS). HS muscle unloading is a common model for muscle disuse that especially affects antigravity slow-twitch muscles such as the soleus muscle. A cDNA cloning strategy, based on suppression subtractive hybridization technology, led to the construction of two normalized soleus muscle cDNA libraries that were subtracted in opposite directions, i.e., atrophied soleus muscle cDNAs subtracted by control cDNAs and vice versa. Differential screening of the two libraries revealed 34 genes with altered expression in HS soleus muscle, including 11 novel cDNAs, in addition to the 2X and 2B myosin heavy chain genes expressed only in soleus muscles after HS. Gene up- and down-regulations were quantified by reverse Northern blot and classical Northern blot analysis. The 25 genes with known functions fell into seven important functional categories. The homogeneity of gene alterations within each category gave several clues for unraveling the interplay of cellular events implied in the muscle atrophy phenotype. In particular, our results indicate that modulations in slow- and fast-twitch-muscle component balance, the protein synthesis/secretion pathway, and the extracellular matrix/cytoskeleton axis are likely to be key molecular mechanisms of muscle atrophy. In addition, the cloning of novel cDNAs underlined the efficiency of the chosen technical approach and gave novel possibilities to further decipher the molecular mechanisms of muscle atrophy.

Age Factors↗
PubMedDate not supplied

[Postpartum thyroiditis. 31 cases].

Postpartum thyroiditis. 31 cases. Between 1977 and 1986, 29 women consulted in three internal medicine and endocrinology departments for clinical disorders which could be ascribed to 31 episodes of thyroiditis developed within 9 months of giving birth. Thyroiditis was diagnosed clinically on the basis of acute diffuse (11 cases) or nodular (7 cases) goitre formation, signs of dysthyroidism (16 cases) revealed by menstrual disturbances and/or galactorrhoea (11 cases). A thyrotoxic episode was observed in 9 patients; it was either without sequelae (5 cases) of followed by transient hypothyroidism (4 cases). In other patients transient hypothyroidism was observed in 11 cases and permanent hypothyroidism in 5 cases. Six patients showed no sign of dysthyroidism, and the diagnosis was made by immunological, cytological and/or histological examination of the thyroid gland. Circulating anti-thyroid antibodies were present in two-thirds of the patients. The results of radioisotope scanning varied according to the stage of the disease. In these patients, only the absence of goitre was predictive, in 4 out of 5 cases, of subsequent permanent hypothyroidism; in all other patients the prognosis was highly favourable, even without specific treatment.

Adult↗
PubMedDate not supplied

[Hyperalaninaemia during acute hypoxia in the anesthetized rabbit (author's transl)].

Blood alanine (Ala), an important glucose precursor, has been demonstrated to result mainly from the transamination of pyruvate derived from glucose in muscle [10]. A positive relationship between blood pyruvate and blood alanine was reported during muscular exercise and fasting. The alanine/pyruvate relationship in arterial blood has been studied in male fasted anesthetized rabbits before, during and after a short term hypoxic stress (50 minutes). Three groups of animals were studied : normoxic control (FIO2 = 0.28 ; n = 3) (C), hypoxic hypoxia (FIO2 = 0.10 ; n = 4) (HH) and hypoxia induced by respiring the animals with a carbon monoxide containing gas mixture (FIO2 = 0.28, FICO = 0.002 ; n = 6) (HCO). The hypoxic stress was of similar magnitude in HH and HCO groups. During the hypoxic periods an increase of [Ala] was observed along with hyperlactatemia and hyperpyruvatemia. Hyperalaninemia and hyperlactatemia was higher in HH than in HCO groups and hyperglycemia was observed only in HH group (adrenergic stimulation). In normoxic conditions [Ala] correlates positively with pyruvate. This relationship vanishes during the hypoxic and post hypoxic periods. The percentage increase of [Ala] during hypoxia was larger than that of pyruvate. These data, as well as recent reports in the literature, suggest that elevated [Ala] during hypoxia may result from increased muscular production from glycolytic pyruvate and other amino acids and decreased hepatic utilization (gluconeogenesis).

Acute Disease↗