Archives internationales de physiologie, de biochimie et de biophysique最新文献

Twelve healthy male volunteers, either trained or untrained, performed a maximal exercise on a cycloergometer. Venous blood samples were taken for analysis during the effort and the following recovery. Blood concentrations of lactate and ammonia, and plasmatic concentrations of alanine, glutamate and glutamine were measured. At the beginning on the effort, ammonia decreased by 32% (P < 0.01) in comparison with its mean level at rest; at 77% and 78% of maximum load there was a steeper ascent of blood ammonia and lactate vs load curve. There was a high correlation (P < 0.001) between ammonia and lactate during exercise. At the end of the effort, these two variables had significantly increased in comparison with their values at rest (P < 0.01 for ammonia and P < 0.001 for lactate), but they did not correlate with VO2max. The negative correlation existing between ammonia and VO2max at the beginning of the recovery period may imply that muscle NH3 release is inversely proportional to the subject's sports training level, this relation being less evident when blood lactate vs VO2max correlation was considered. Increase in blood glutamate level was greater in trained subjects (P < 0.05). This finding suggests that ammonia elimination is favoured by physical training. In conclusion, ammonia measurements during exercise provide a valuable information about muscle cell oxidative capacity.

In rat jejunal brush-border membranes (BBM), ATP hydrolysis activity was specifically stimulated by CaCl2 and by MgCl2, allowing to identify Ca(2+)-ATPase and Mg(2+)-ATPase activities with a broad pH optimum near 8.0. Nonspecific ATPase activity (in the absence of cations) had a pH optimum above 9.5 as alkaline phosphatase. The effects of Ca2+ and Mg2+ concentrations on ATPase activity evidenced two apparent KA for each cation. At high concentrations, a similar affinity for both cations was recorded (KA: 0.35 mM). At low concentrations, the affinity for Mg2+ was greater than for Ca2+ (KA: 0.02 mM and 0.07 mM respectively). In an attempt to differentially solubilize alkaline phosphatase and ATPase activities, eleven different detergents were assayed. They more or less successfully released Ca(2+)-ATPase and Mg(2+)-ATPase activities from BBM but the more membranes were solubilized by a detergent, the more activities were lost, suggesting a close dependence on integration in BBM. As to alkaline phosphatase and nonspecific ATPase, they almost co-solubilized with Ca(2+)-ATPase and Mg(2+)-ATPase but their total activity was little affected. After treatment of BBM with phosphatidylinositol-specific phospholipase C (E.C. 3.1.4.10), 58% of alkaline phosphatase activity and 45% of nonspecific ATPase activity were released in the supernatant while Ca(2+)-ATPase and Mg(2+)-ATPase activities remained totally incorporated in BBM pellets. These last results definitively demonstrate that Ca(2+)-ATPase and Mg(2+)-ATPase activities are not manifestations of alkaline phosphatase, as earlier suggested, but rather result from the existence of one or several intrinsic membrane enzymes.

The chewing abnormalities are frequently evoked during odontological and medical examinations. Unfortunately, few means of investigation are available to appreciate the functional disorders. The aim of this paper was to assess masticatory parameters from observation and audiosignals of mastication with a simple analysis of records. In a first time, sixty five students (mean age = 20) applied the sugar test for the salivary capacity (dissolution time = 2 to 3 minutes). Then the chewing movements were analysed with three types (I, II, III) of salt or sweet cookies. The total duration of activity was 29.8 and 28.2 seconds respectively for the tests I and II, only 18.2 seconds for the test III. The number of cycles were 32.5, 28.1 and 19.2 mastications for respectively I, II and III tests. The later type (III) had a softer consistency than the formers. The duration Dc of masticatory cycles was constant for the same type of aliment. The values were between 0.70 for the test II and 0.90 second for the I and II ones. Signal analysis showed an important and rapid decrease of amplitude AS with an exponential-like pattern. The time constant appeared in relation with the softness. Thus, our method allows to characterize the pattern of mastication and could be used for appreciation of degrees in salivary and/or cranio-mandibular functional abnormalities.

Effects of partial hepatectomy on blood coagulation factors were investigated in rats. Analysis were performed 24, 48 and 72 hours after surgery. Howell's time was significantly higher after 24 and 48 h compared to the control value. Prothrombin time was significantly prolonged after 24 h. Partial thromboplastin time did not differ significantly in any time. FII values were significantly reduced after 24 and 48 h, but FV values only after 24 h. FVII showed significant decrease after 24 h, but significant increase at 48 h. FVIII and ATIII average values were significantly lower after 24, 48 and 72 h. Plasma fibrinogen increased. Significant differences were observed 48 and 72 h after surgery. Differences in normalization time of these coagulation factors are most probably the consequence of their synthesis in various cell types, regenerated at different periods after partial hepatectomy.

The effects of 24R, 25-dihydroxyvitamin D3 (24, 25 (OH)2 D3) on alkaline phosphatase (ALP), gamma-glutamyltransferase (GGT) and acid phosphatase (ACP) activities were investigated on renal cortex of hypophysectomized (Hx) rats. ALP activity was increased by +27, +56 and +60% as compared to controls respectively 3, 6 and 12 h after intraperitoneal administration of the secosteroid (10 pmoles/100 g body weight). Stimulations of GGT activity began only after 6 h (+30%) and 12 h (+ 46%). ACP activity was not modified. In vivo, the two enzymatic inductions in kidneys of Hx rats were higher and longer than those obtained in vitro.

The cellular uptake of (14C)-thiamin hydrochloride was studied in the isolated perfused guinea pig heart, using the rapid single circulation, paired-tracer technique, in which D-(3H)-mannitol serves as an extracellular marker. Cellular uptake of this vitamin was estimated by directly comparing venous dilution profiles of (14C) and (3H) radioactivities in the absence and presence of unlabelled thiamin hydrochloride and pyrithiamin hydrobromide. The maximal cellular uptake (Umax) of thiamin was very low (5.31 +/- 1.79%), while in the presence of 10 mM unlabelled thiamin and 1 mM pyrithiamin, Umax was significantly greater (9.71 +/- 1.57% and 12.30 +/- 0.82%, respectively). Our data suggest that there is a saturable mechanism of sarcolemmal thiamin transport out of myocardial cell, while this transport into the cell is unsaturable.

The lipid component of Drosophila ananassae have been identified qualitatively. Neutral and phospholipid fractions are specific for pupal, larval or adult extracts. Some of these lipid components are identical with those obtained from the temperate D. melanogaster and other species. This demonstrates biochemical convergence between geographically isolated species groups.

Binding sites of atrial natriuretic factor (ANF) and bradykinin (BDK) have been described in discrete areas of central nervous system of the rat. The interaction between ANF and BDK on noradrenaline (NA) uptake were studied in hypothalamus (Hyp) and medulla oblongata (MO). One hundred nM ANF in both regions and 100pM BDK in Hyp and 1nM BRD in MO increased total NA uptake. Subthreshold concentrations of ANF (1nM) reversed the effect of not modify the increase produced by 100nM ANF in both central regions. Effective concentrations of ANF and BDK did not induce additive effect in total 3H-NA uptake neither in Hyp nor in MO. Threshold concentrations of ANF and BDK increased only neuronal NA uptake in Hyp as well as MO. These results suggest an ANF-BDK interaction at the neuronal NA control mechanisms involved in the regulation of blood pressure, electrolytes and water balances, and neuroendocrine processes.

During two human experimental dives at 26 ATA (helium-nitrogen-oxygen gaz mixture; PIO2 = 400 mbar), the cardiac frequency (Fc) and radial arterial pulse were continuously recorded, at rest and during periods of maximal expiratory (Valsalva) or inspiratory (Müller) manoeuvres, used to increase or decrease the intrathoracic pressure, respectively. Cardiovascular variables were measured at 1 and 26 ATA in resting individuals and during the maximal respiratory manoeuvres. Discontinuous measurement of arterial blood pressure using a sphygomanometer allowed to calculate the mean arterial pressure. The value of mean arterial pressure was maintained against the membrane of a radial pulse sensor. This procedure, proposed by Posey et al. (1969), gives a continuous approximation and recording of arterial blood pressure and its components. The present results did not show significant variation in the values of Fc nor systolic or diastolic blood pressures measured at rest or during Müller manoeuvres performed at 1ATA at the maximal depth. On the other hand, Valsalva manoeuvres performed at depth induced significant variations in circulatory variables compared to the normobaric response. The most important effect was an enlargement of differential pressure due to a marked decrease in the diastolic blood pressure. These observations are discussed in terms of enlarged sensitivity of the baroreflex arch under hyperbaric condition.

The chronotropic response of rat atria to beta adrenergic stimulation required higher concentrations of agonist in the presence of adenosine. This anti beta-adrenergic effect could attenuate the tachycardia induced by the increased sympathetic tone during cardiac ischemia. The sensitivity to alpha adrenergic stimulation did not change in the presence of adenosine.