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One of the most obvious and deleterious changes occurring with aging is a progressive loss of skeletal muscle mass and strength, a physiological process named sarcopenia. Amongst the multiple theories that have been put forward to explain sarcopenia, the mitochondrial theory of aging, which postulates that the accumulation of mitochondrial dysfunctions with aging plays a causal role in muscle atrophy, has focused intense research effort and attention in the past decades. The generally accepted view of this theory is that, due to the reactive oxygen species (ROS) production inherent to respiratory chain activity, oxidative damage to mitochondrial proteins, lipids and DNA accumulates with aging. This damage is thought to (i) exacerbate mitochondrial ROS production, (ii) impair the capacity of mitochondria to adequately match the cellular ATP demand and (iii) trigger mitochondrial-mediated apoptosis. Although very appealing, this theory remains controversial. The aims of the present review are (i) to provide the reader with a short, but comprehensive review of the current literature linking mitochondrial dysfunction and sarcopenia and (ii) to briefly discuss the potential mechanisms underlying the accumulation of mitochondrial dysfunction with muscle aging., (© 2017 médecine/sciences – Inserm.)

Lung ischemia-reperfusion is characterized by diffuse alveolar damage arising from the first hours after transplantation. The first etiology of the primary graft dysfunction in lung is ischemia-reperfusion. It is burdened by an important morbi-mortality. Lung ischemia-reperfusion increases the oxidative stress, inactivates the sodium pump, increases the intracellular calcium, leads to cellular death and the liberation of pro-inflammatory mediators. Researches relative to the reduction of the lung ischemia-reperfusion injuries are numerous but few of them found a place in common clinical practice, because of an insufficient level of proofs. Ex vivolung evaluation is a suitable technique in order to evaluate therapeutics supposed to limit lung ischemia-reperfusion injuries., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

Most anticancer agents are thought to act through direct induction of tumoral, stromal and endothelial cell death by apoptosis or necrosis. In a 2008 issue of Bulletin de l'Académie Nationale de Médecine, we described an alternative (or complementary) theory whereby the immune system participates in the antitumoral effects of some chemotherapy or radiotherapy regimens by promoting an immunogenic cell death pathway. In particular, we showed the critical importance of two pre-mortem stressors that determine the immunogenicity of dying tumor cells. The first, an ER stress response culminating in calreticuline exposure at the tumor cell surface, is mandatory for the uptake and efficient phagocytosis of apoptotic bodies by dendritic cells. In the second, autophagy leads to the release of ATP by dying tumor cells, resulting in the recruitment of inflammatory phagocytes and antigen-presenting cells, and also triggering the inflammasome that causes IL-1beta release and CD8+ T cell polarization. The tumor microenvironment changes following chemotherapy, favoring sequential accumulation of a series of innate and cognate effectors that act in a coordinated fashion to promote tumor eradication. These findings will help to identify immune predictors of the response to conventional anticancer treatments and to design innovative combinatorial immunochemotherapy regimens.

Metabolic syndrome defined as the joint manifestation on the same subject of several risk factors (at least 3 in the majority of definitions) within the following parameters : hypertriglyceridemia, hypertension, abdominal obesity, low concentration of HDL-Cholesterol (HDL-C), and high fasting blood glucose is increasingly reported in children, mainly in the presence of overweight/obesity. In fact, up to 50 % of overweight/obese children can be affected by this syndrome. Furthermore, the metabolic syndrome acquired during childhood has been shown to impact highly into adulthood including by its clinical complications such as type 2 diabetes or cardiovascular diseases. Among the practical preventive and therapeutic measures to be taken in children, physical activity appears to be an option of choice. This review indicates that physical activity programs based either on aerobic exercise, resistance training, or a combination of these 2 types of activity may promote insulin sensibility and weaken or suppress the metabolic syndrome of children. More interestingly, usual physical activity including free-living activities of an intensity equivalent to a brisk walking should be encouraged earlier among children for its positive influence on parameters involved in the metabolic syndrome.

Introduction: Many studies were carried out in vivo and/or in vitro for better understanding toxic effects of exhausts or particles emitted by Diesel vehicles. Few studies were interested in Gazoline engines when progress of metrology made it possible to highlight the presence of small particles with a strong capacity of penetration within pulmonary tissue. The aim of this study is to compare the toxic impact of the emissions of Diesel and Gasoline engines of recent technology., Materials and Methods: Biological material was constituted by an organotypic rat lung precision slice. It was exposed to a continuous flow exhausts thanks to a preparation and dilutions system of these emissions placed on the line of exhaust. A measurement of the biological markers involved in the process of the lung tissue reaction to the air-contaminants was carried out., Results: With Diesel exhausts, the results showed a stability of the rate of ATP and an increase in enzymatic activities of the antioxydant system (GPx and catalase). Gazoline emissions, as for them, were responsible for a cytotoxic attack of the pulmonary tissue defined by a reduction in the rate of ATP as well as a deterioration of the system of detoxication with reduction in the antioxydant enzymatic activities., Conclusion: These results show that toxicological profiles obtained with this system of exposure depends on the engine technology used, highlighting thus the specific response of the model in relation with the type of atmospheres which it is exposed.

The deep-sea hydrothermal vents are located along the volcanic ridges and are characterized by extreme conditions such as unique physical properties (temperature, pression), chemical toxicity, and absence of photosynthesis. However, life exists in these particular environments. The primary producers of energy and organic molecules in these biotopes are chimiolithoautotrophic bacteria. Many animals species live in intimate and complex symbiosis with these sulfo-oxidizing and methanogene bacteria. These symbioses imply a strategy of nutrition and a specific metabolic organization involving numerous interactions and metabolic exchanges, between partners. The organisms of these ecosystems have developed different adaptive strategies. In these environments many microorganisms are adapted to high temperatures. Moreover to survive in these environments, living organisms have developed various strategies to protect themselves against toxic molecules such as H2S and heavy metals.

The 5' AMP-activated protein kinase (AMPK) is a sensor of cellular energy homeostasis well conserved in all eukaryotic cells. AMPK is activated by rising AMP and falling ATP, either by inhibiting ATP production or by accelerating ATP consumption, by a complex mechanism that results in an ultrasensitive response. AMPK is a heterotrimeric enzyme complex consisting of a catalytic subunit alpha and two regulatory subunits beta and gamma. AMP activates the system by binding to the gamma subunit that triggers phosphorylation of the catalytic alpha subunit by the upstream kinases LKB1 and CaMKKbeta. Once activated, it switches on catabolic pathways (such as fatty acid oxidation and glycolysis) and switches off ATP-consuming pathways (such as lipogenesis) both by short-term effect on phosphorylation of regulatory proteins and by long-term effect on gene expression. Dominant mutations in the regulatory gamma subunit isoforms cause hypertrophy of cardiac and skeletal muscle providing a link in human diseases caused by defects in energy metabolism. As well as acting at the level of the individual cell, the system also regulates food intake and energy expenditure at the whole body level, in particular by mediating the effects of adipokines such as leptin and adiponectin. Moreover, the AMPK system is one of the probable target for the anti-diabetic drug metformin and rosiglitazone. The relationship between AMPK activation and beneficial metabolic effects provides the rationale for the development of new therapeutic strategies. Thus, pharmacological AMPK activation may, through signaling, metabolic and gene expression effects, reduce the risk of Type 2 diabetes, metabolic syndrome and cardiac diseases.

In this article, we first report the importance of lipid metabolism in the fulfilling of energy requirements through nutritional states and describe the structures implied in this pathway. We thereafter present in detail the catabolic pathway allowing energy to be produced from fatty acid beta-oxidation, and we point out the essential role of the chemical structure of these fatty acids. Lastly, we focus on the fact that this pathway is regulated in many differents ways. The different steps of the catabolism may be submitted to biochemical or gene regulation control (such as that mediated by carnitine palmitoyltransferase I or fatty acid regulation of gene transcription via PPAR).

Gemcitabine is a pyrimidine analog which has demonstrated antitumoral activity in a variety of solid tumors including bladder, non-small cell lung and pancreatic cancers. Gemcitabine is a potent radiosensitizer of human tumor cells. This review summarizes preclinical studies designed to elucidate the mechanism of action of gemcitabine with ionizing radiation. Phase I-II ongoing trials of combination of radiation therapy and gemcitabine are trying to determine the optimal dose and schedule which could be used in daily clinical activity. The mechanism of radiosensitization is thought to be simultaneously gemcitabine-induced dATP (deoxyadenosine triphosphate) depletion and cell cycle redistribution into the S phase. Although there are no real study which has proven supra-additive combination, the recent acute side effects in several clinical studies oblige physicists to determine with precision the maximum tolerated dose of gemcitabine in association with ionizing radiation. Radiosensitization conditions can be obtained either with a long exposition to a low concentration or a short exposition to a high concentration. Radiation sensitivity begin to be detected four hours after treatment for 48 hours. A dose about 100 mg/m2/week of gemcitabine could be used with radiation therapy according to recent phase I results. This limiting dose is approaching to a radiosensitization context where the effect of one agent is increased by another agent which is inactive or poorly active for the effect under consideration. In this type of regimen, the two modalities do interact with a frequent inhibition of recovery from potentially lethal damage and a probably increase of late side effects of radiation therapy. In contrast, radio-chemotherapy combination is used for a therapeutic advantage when the drug by itself is active against the tumor but does not enhance late side effects of radiation on the critical normal tissues within the irradiated volume. Gemcitabine surely is a strong radiosensitizer even at low doses with future extended combined modality therapeutic indications. The ultimate goal of combined treatments should be an increased therapeutic ratio.

In man, three kinds of sympathetic neurons reach the skin. Some cholinergic neurons stimulate the sweat glands, they are excited by temperature-regulating centers. Adrenergic neurons release noradrenaline and ATP to reduce cutaneous blood flow while cholinergic neurons release acetylcholine and a co-transmitter to dilate skin blood vessels. The excitation of both latter types of nerve cells depends on influences from temperature-regulating centers, baroreceptors and exercise. Moreover, in cutaneous blood vessels, a synthesis of NO is enhanced by an increase of body temperature and overall by direct heating of the skin. Burns are associated with axon reflexes and release of inflammatory mediators. The involvement of these various influences is described.

Although we all possess the capability for anaerobic and aerobic energy metabolism, the capacity for each form of energy transfer varies considerably among individuals. Sports such as football or weightlifting, rely almost exclusively on energy derived from the muscles's pool of high-energy phosphates. Researchers have proposed different tests to estimate the power-generating capacity of high energy phosphates: stair-sprinting power tests, jumping-power tests or sprint cycling. In reality, however, it is difficult to obtain precise physiological or biochemical data during all-out exercise of brief duration.

Using an experimental model of anoxia-reoxygenation applied to suspensions of mitochondria isolated from rat cortex, we have searched the effects of resveratrol added to the suspension or previously injected to rats from which mitochondria were extracted. With this model, we observe that resveratrol counteracts decoupling effects induced by anoxia-reoxygenation. It also fully inhibits intermembrane cytochrome c release, initial step of mitochondrial apoptosis and blocks ATP generation which achieves it. These effects are concentration-dependent and take place at low concentrations. It is concluded that resveratrol limits or suppresses the mitochondrial deleterious effects promoted by anoxia followed by reoxygenation.

In this review we discuss data obtained by our group regarding the entry of toxins, especially ricin, diphtheria toxin (DT) and Pseudomonas exotoxin A (PE) into animal cells. We studied the translocation process of these toxins using endosomes purified from lymphocytes. This process is rate-limiting for toxicity and enables these toxins to reach the cytosol where they will inactivate the protein synthesis system and kill the cell. We could show that each of these toxins uses a different strategy to cross the endosome membrane. Whereas ricin transmembrane transport only relies on cytosolic ATP hydrolysis, PE first requires exposure to the low endosomal pH (pH-6), presumably to insert into the endosome membrane, before being translocated via a process which also requires cytosolic ATP hydrolysis. DT translocation is directly triggered and energized by the endosome-cytosol pH gradient. Using conjugates with dihydrofolate reductase we could indirectly show that ricin and PE require unfolding for translocation. A deletion approach enabled to produce a more cytotoxic PE mutant by increasing its translocation activity.

The cardiomyocyte capacity to regulate ATP production to face any change in energy demand is a major determinant of cardiac function. This process is based on a balanced fatty acid (FA) metabolism, because FA is the main fuel of the heart, although the most expensive one in oxygen. The pathway is, however, weakly controlled by the cardiac myocyte which can well regulate FA mitochondrial entry but not cell FA uptake. For this reason, several pathological situations often result from either harmful accumulation of FA and derivatives or excess FA-oxidation. Control of the FA/glucose balance by decreased energy production from FA would thus offer an alternative strategy in the treatment of ischaemia, providing the cardiomyocytes weak ability in handling the non-metabolised FA is controlled. The initiation and the regulation of cardiac contraction both result from membrane activity; the other major role of lipids in the heart is their contribution to membrane homeostasis through phospholipid synthesis pathways and phospholipases. The anti-anginal activity of Trimetazidine, reported as a cytoprotective effect without a haemo-dynamic component; is associated with reduced use of FA for energy. However, accumulation of FA and derivatives has never been observed. Trimetazidine is reported to increase significantly the synthesis of phospholipids without influencing the other lipid classes, thus increasing the incorporation of FA in membrane structures. This cytoprotection appears to be based on the redirection of the use of FA to phospholipid synthesis, which would decrease their availability for energy production. This class of compounds, with the same properties as Trimetazidine, offers a metabolic approach to the treatment of ischaemia.

The functional defect of the pancreatic beta cell represents one of the main therapeutic targets in type 2 diabetes mellitus. Among the currently available oral antidiabetic drugs, only hypoglycaemic sulfonylureas exhibit beta cell stimulating properties. However, their use has some limits, particularly those related to the risk of hypoglycaemia and the frequent secondary therapeutic failure. These drugs have largely contributed to the knowledge of the mechanisms of insulin secretion. Besides some galenic modifications of existing sulfonylureas and the development of new drugs of this family with original properties, like glimepiride, the research is essentially focused on drugs derived from the non sulfonylurea moiety of some sulfonylureas, particularly the meglitinide family, which will probably be available for the clinician in the near future. These drugs act however grossly by the same mechanism than sulfonylureas, even if their binding site on a protein coupled with the ATP sensitive K channel appears different. Among the other possible approaches suggested by the theoretical data concerning the mechanisms of insulin secretion, GLP-1 derivatives probably represent good candidates, if stable analogues are developed.

Cellular homeostasis requires permanent energy production and consumption. Adenosine triphosphate (ATP) is the major energy component for the cell. Its synthesis occurs mainly in mitochondria where the oxidative phosphorylations realise the coupling between oxygen consumption and phosphorylation of adenosine diphosphate. The anaerobic production of ATP plays an important role in the intermediary metabolism. The enzymatic complexes of the mitochondrial respiratory chain are energy transducers acting as proton pumps. In cardiomyocytes, the phosphocreatine circuit allows a substrate channelling between mitochondria and myofibrils. This metabolic compartmentation explains the difficulties of studying energetic metabolism in the beating heart and the lack of correlation between cardiac function and the usual energy parameters. Mitochondria are a potential site of action of anaesthetic agents. Lipophilic local anaesthetics impair cellular energy metabolism and mitochondrial ATP production. Such effects could be associated with toxic effects of these molecules. NMR or near-infrared spectroscopy are non invasive techniques for monitoring energetic metabolism in vivo. Clinical applications are developed for analysing brain, muscle or cardiac function in physiological and pathological conditions.

Cytoskeleton based molecular motors support most of the cellular movements and by consequence they are associated with a variety of human disorders. The wide functional diversity of these molecular motors is now explained by the presence of three different families: the myosin, kinesin and dynein families. Although they are functionally distinct, these motors present unexpected structural homologies at the ATP and actin or microtubule binding sites. However, these homologies do not seem sufficient to design a common molecular mechanism which allows these proteins to move along the cytoskeleton.

The functional dilatory response in the streptozotocin-induced diabetic rat was investigated using thoracic aortas and coronary microcirculation. The aortas were cut in 4 mm intact or denuded rings and mounted into 20-ml organ baths. Coronary microcirculation was evaluated with isolated hearts perfused under constant flow conditions. Firstly, vasodilation to iloprost (Ilo) was examined. Dose-response curves to Ilo (10 pM-10 microM) on phenylephrine (PE, 30 nM for endothelium-denuded, and 0.3 microM for intact) preconstricted rings of diabetics and age-matched controls were comparable (n = 6). Decreased vasodilation in diabetic group was observed when dose-response curves to Ilo (1 nM-0.1 microM) were realized in isolated hearts (-22 +/- 3.3% vs -46 +/- 3.9%, n = 6, p < 0.05). Secondly, dose-response curves to forskolin (FSK), an adenylate-cyclase activator, performed in hearts (1 nM-3 microM), and on PE preconstricted rings (10 pM-10 microM) of diabetics and age-matched controls were comparable. Finally, the effect of an activator of ATP sensitive potassium channels (KATP), cromakalim (CMK), was evaluated in coronary circulation (0.3 nM-3 microM) and in aortas (10 pM-10 microM). Decreased vasodilation to CMK was observed in diabetic hearts (-10.5 +/- 4.3 vs -30.1 +/- 2.8%, n = 6, p < 0.05). In conclusion, under our experimental conditions, diabetes affects selectively the coronary vasodilation to iloprost. This modification of vascular reactivity may be due to a decrease of KATP channels sensitivity but not to a decreased activity of adenylate-cyclase.

Calcium loading of a rat parotid microsomal fraction is greatly increased by an ATP-regenerating system (phosphocreatine and creatine phosphokinase). This effect is neither a consequence of a rise in the ATP concentration nor of an increased formation of inorganic phosphate originating from hydrolysis of ATP or phosphocreatine. Addition of ADP to the incubation medium provokes an inhibition of Ca2+ influx and a stimulation of Ca2+ efflux by the microsomal fraction. These results suggest that the stimulation of Ca2+ uptake by the ATP-regenerating system is due, at least in part, to an increase of Ca2+ influx and a slowing down of Ca2+ efflux as consequence of a decrease of ADP availability. It is proposed that the effect of ADP on Ca2+ movements could account for the action of certain agonists on intracellular Ca2+ concentration. Moreover, the InsP3 responsive Ca2+ pool was also shown to be enlarged by the ATP-regenerating system without modification of InsP3 sensitivity.

The capacity of certain individuals to resist certain diseases, including leprosy, has for a long time been considered as being influenced by genetic factors. The clinical and pathological spectrum of leprosy, epidemiological heterogeneity, both geographic and ethnic, in the prevalence of polar forms, may be explained by genetic differences in host resistance. While the specific genes in question have not been identified, recent studies suggest a genetic basis for differences in the capacity of macrophages in the host to reduce bacterial multiplication. Experimental models analyzing the reactions of antimycobacterial defence have underscored at existing differences in resistance or vulnerability to infection (M. bovis, BCG, M. lepraemurium, M. tuberculosis) were guided by a dominant gene which exists in two allelic forms, bcgr and bcg5. The bcgr allele confers resistance and is more dominant than the bcgs allele which represents greater vulnerability to infection. The murine candidate gene for the bcg gene has been named NRAMP (Natural Resistance-associated Macrophage Protein). Even though the exact function of NRAMP is not currently known, it has been demonstrated that this gene is expressed mainly in macrophages, and that it brings about increased bacteriostatic capacity in these cells. NRAMP is structurally homologous to the family of membranous proteins having a transport function linking ATP. NRAMP is similar to the membranous bacterial system transporting nitrites. The NRAMP protein is also involved as a signal of transduction during the activation of macrophages. It is therefore possible to conceive of genetic polymorphism at this locus intervening in specific and non-specific immune responses to infection. Apart from such potential polymorphism during the initial phase of infection, immunogenetic studies suggest that the polymorphism of class II HLA molecules could intervene in the evolution of secondary immune response to M. leprae. Knowing that HLA molecules are expressed in a co-dominant form, and attributing extraordinary allelic polymorphism to this locus, there may be a rather wide range of immune responses to the M. leprae antigens in subjects with discordant HLA and in populations which have varied genetic profiles. In general it has been acknowledged that HLA-DR isotypes are associated with protective response, while HLA-DQ isotypes are said to be associated with multibacillary lepromatous forms. The chief role of the HLA systems controlling cell-mediated immunity leads to the probability that differences in HLA haplotypes could contribute to the wide spectrum of immune responses observed in leprosy. Genetic determinants of resistance to leprosy cannot be described in a straightforward manner using a classic approach because the complex mechanisms of resistance, yet to be clarified and for which at least two loci are believed to be contributory, may be re-assessed like a multifactorial, multigenetic complex in which environmental events linked to the transmission of M. leprae, its duration, intensity and host factors, varying as a function of time, intervene. A close study of each element and better understanding of the physiological and pathological mechanisms of infection and disease are necessary in order to state the influence of genetic factors on each of them with greater precision.

Two cases of polymyositis were followed using phosphorus nuclear magnetic resonance spectroscopy. The spectra recorded during remission were normal, but those collected from the gastrocnemius muscle during the active phase of the diseases showed an increased inorganic phosphate level or a decreased phosphocreatine content. The intracellular pH was normal. These findings may be related to an impairement in mitochondrial metabolism secondary to the inflammatory process. Moreover, the fact that the abnormalities observed disappeared after treatment suggests that phosphorus NMR spectroscopy could be used as a non-invasive method in the follow-up of polymyositis, but this must be confirmed by further studies.

Cell-free extracts prepared from in vitro cultured Mycobacterium lepraemurium catalysed phosphorylation coupled to the oxidation of NADH and succinate, yielding P/O ratios of 0.52 and 0.34, respectively. No ATP synthesis occurred during oxidation of ascorbate. Oxidative phosphorylation was uncoupled by dinitrophenol and dibromophenol. Oxidation of NADH and coupled phosphorylation was markedly inhibited by rotenone, whereas this inhibitor had no effect on succinate oxidation and associated ATP synthesis. Oxidative phosphorylations and coupled oxidations of NADH and succinate were strongly inhibited by antimycin A and cyanide.

In this study we have investigated the effects of hepatocytes glycogen storage on the quality of livers for transplantation. Rats were fed or fasted for 24 h and hepatocytes isolated and cold stored in UW solution for 24 and 48 hours. Viability of the cells was analyzed by LDH release after 2 hours incubation in L15 with O2. Also, rabbits were fed, fasted (48 h) or glucose fed (48 h) and livers cold stored for 6, 24 and 48 h in UW solution. Functions of the livers were analyzed by isolated perfusion for 2 hours. Hepatocytes from fasted rats released significantly more LDH than hepatocytes from fed rats after 24 and 48 h cold storage. In rabbit livers, fasting depleted glycogen by 85% but had no effect on ATP or glutathione concentration. Livers from fasted rabbits produced similar amount of bile, released similar concentrations of lactate dehydrogenase and aspartate transaminase into the perfusate, maintained similar concentrations of glutathione after 24 hours preservation when compared to fed animals. After 48 h preservation livers from fasted animals were less viable than livers from fed animals and the decrease of liver functions in livers from fasted animals preserved for 48 hours was prevented by feeding glucose. This study shows that liver glycogen storage in hepatocyte is an important metabolite for successful liver preservation. Glycogen may be a source for ATP and antioxydant synthesis during the early period of reperfusion.

The ATP-sensitive K channel opener, SR 44866, was applied to intact extensor digitorum muscle of the mouse. Electrically stimulated maximal twitch contractions of the muscle were decreased by SR 44866 with a KD of 7.4 microM and a Hill coefficient of 1.2 at 34 degrees C. The effect of SR 44866 was antagonized by glibenclamide and reduced at 24 degrees C. We suggest that these results represent the consequence of activation of ATP-sensitive K channels in mammalian skeletal muscle.

Mechanical performance, tissue content of high-energy phosphates (ATP and CP), glycogen and phosphorylase activity were measured in isolated rat hearts either just after excision (hearts arrested by plunging in ice-cold perfusate) or during long time perfusions (6 h) at 37 degrees C. Arrested hearts exhibited : (1) higher total phosphorylase activity (a + b); (2) higher percentage of phosphorylase a; (3) lower CP content. During perfusion, high energy phosphates appeared well maintained whereas glycogen content and phosphorylase activity decreased with a significant correlation between these two parameters. The validity of this isolated heart model and possible implications of the variations in phosphorylase activity are discussed.

Assay of bacterial intracellular ATP levels using the firefly bioluminescence system allows a very sensitive monitoring of bacterial growth. This test has been used in some laboratories fro performing a rapid microbiological assay of the concentration of antibiotics in the serum of treated patients. Rapidity of antibiotic determination is especially important in the case of antibiotics for which therapeutic concentration are close to toxic concentration. In the present work we have used the bacterial strain Klebsiella edwardsii var. atlantae for a rapid assay of gentamicin in the serum. We show that this assay is very accurate in the range of therapeutic serum concentrations. It may be readily performed in a routine laboratory with commercially available ATP extractors and luciferine-luciferose mixtures. This assay has been shown to correlate optimally with the classical plate diffusion assay (r = 0,983) and to be independent of the presence of beta-lactams in the serum.

Secondary active transport is defined as the transport of a solute in the direction of its increasing electrochemical potential coupled to the facilitated diffusion of a second solute (usually an ion) in the direction of its decreasing electrochemical potential. The coupling agents are membrane proteins (carriers), each of which catalyzes simultaneously the facilitated diffusion of the driving ion and the active transport of a given solute. The review starts with some considerations on the energetics followed by a presentation of the kinetics of secondary active transport. Examples of information which may be gained by such studies are discussed. In the second part, some examples of secondary transport are given; we also describe the characteristics of the corresponding carriers. The various transport systems presented are: the D-glucose/Na+ symport in brush-border membranes, the lactose/H+ symport in E. coli, the Na+/H+ antiport, the different transport systems in the inner mitochondrial membrane.

14C adenine was supplied to isolated Rat heart retrograde perfused. The experiment was continued by aortic or atrial perfusion and the evolution of the specific radioactivity of ATP was estimated. Aortic perfusion did not reduce ATP content and the specific radioactivity decreased, expressing the turnover of adenine nucleotides. On the contrary, working heart perfusion provoked a breakdown of ATP and an increase of ATP specific radioactivity. When myocardial ATP was decreased prior to the perfusion with isoproterenol, the incorporation of 14C adenine was enhanced, a further aortic perfusion induced a greater decrease of ATP specific activity than in controls. Atrial perfusion did not change the concentration and the specific activity of ATP. These data seem to provide experimental evidences for a compartmentalization of myocardial ATP.

The release of ATP after potassium depolarization was measured on fragments of electric tissue incubated in a solution containing the firefly extract. Light emission was proportional to the extracellular KCL concentration. In contrast to the release of ATP after single nerve impulses, the release after direct KCL depolarization was insensitive to curare of eserin.

This study was designed to investigate the rheological and plasmatic parameters from multiple transfused patients and patients undergoing surgery non transfused. Blood filtrability compared with the erythrocyte electrophoretic mobility shows the perturbance resulting from the delay of conservation and the importance of the transfused blood. The 2-3 DPG, ATP and oxygen-hemoglobin affinity suggest the excellent recuperation of the erythrocyte metabolic function in vitro. The rheological parameters seems to be a good mean in the supervision of red massive transfusion blood cell.

Retinal excitation implies transmembrane ion movement in the retinal neurones. In order to maintain excitability, the neurones utilize energy derived from the hydrolysis of ATP. ATP is produced in the mitochondria, which consume O2 and carbohydrates for this purpose. Thus, O2 consumption is essential for maintaining ATP in the retinal neurons and, therefore, for maintaining excitability. O2 is delivered to the retinal mitochondria by the microcirculation, where variations of the blood flow cause dramatic fluctuations in the local PO2 in the tissue. The retinal blood flow can be impaired by experimental changes in the pH of the glial cells surrounding the arterioles. According to a hypothesis, intraglial pH modulates the release of a mediator (prostaglandins) which in turn acts on the smooth musculature of the arteriole wall and thus controls vascular motility.

Various amino acids and guanidines (L-lysine, L-aspartic and L-glutamic acids, creatine, taurocyamine and glycocyamine), studied in ileal ligated loops, increased intestinal calcium absorption in the rat. L-arginine was effective per os. Since these compounds are highly phosphorylable, a phosphorylation mechanism may be involved in the stimulation of calcium absorption. The phosphorylated derivative of creatine was detected in the ileal mucosa of rats receiving creatine in the ileal ligated loop. Modified amino acids, such as 5-methyl-L-glutamate, asparagine or glutamine, whose phosphorylable function was masked by a methyl or an amide radical, were not effective in enhancing calcium absorption. Assays in vitro showed that an ileal mucosa extract phosphorylated arginine, lysine, glycocyamine and taurocyamine in the presence of ATP, acting as a phosphate donor.