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Graphene in water is electrically charged in most conditions. The level of charge can be large enough to stabilize single (or few) layer graphene colloidal dispersions in water, without the need of using any other additive. In this work, potentiometric titration, isothermal titration calorimetry, electrokinetic measurements, Density Functional Theory calculations, Raman Spectroscopy, and direct force measurements using Atomic Force Microscopy to investigate this charge and explore its origin are combined. The body of data collected suggests that this charge is a consequence of the interaction between water ions (hydroxide and hydronium) and graphene, and can be conveniently tuned (in magnitude and sign) by changing the pH of water. [ABSTRACT FROM AUTHOR]

Mastering graphene preparation is an essential step to its integration into practical applications. For large‐scale purposes, full graphite exfoliation appears as a suitable route for graphene production. However, it requires overpowering attractive van der Waals forces demanding large energy input, with the risk of introducing defects in the material. This difficulty can be overcome by using graphite intercalation compounds (GICs) as starting material. The greater inter‐sheet separation in GICs (compared with graphite) allows the gentler exfoliation of soluble graphenide (reduced graphene) flakes. A solvent exchange strategy, accompanied by the oxidation of graphenide to graphene, can be implemented to produce stable aqueous graphene dispersions (Eau de graphene, EdG), which can be readily incorporated into many processes or materials. In this work, we prove that electrostatic forces are responsible for the stability of fully exfoliated graphene in water, and explore the influence of the oxidation and solvent exchange procedures on the quality and stability of EdG. We show that the amount of defects in graphene is limited if graphenide oxidation is carried out before exposing the material to water, and that gas removal of water before the incorporation of pre‐oxidized graphene is advantageous for the long‐term stability of EdG. [ABSTRACT FROM AUTHOR]

Attaining personalized healthy aging requires accurate monitoring of physiological changes and identifying subclinical markers that predict accelerated or delayed aging. Classic biostatistical methods most rely on supervised variables to estimate physiological aging and do not capture the full complexity of inter‐parameter interactions. Machine learning (ML) is promising, but its black box nature eludes direct understanding, substantially limiting physician confidence and clinical usage. Using a broad population dataset from the National Health and Nutrition Examination Survey (NHANES) study including routine biological variables and after selection of XGBoost as the most appropriate algorithm, we created an innovative explainable ML framework to determine a Personalized physiological age (PPA). PPA predicted both chronic disease and mortality independently of chronological age. Twenty‐six variables were sufficient to predict PPA. Using SHapley Additive exPlanations (SHAP), we implemented a precise quantitative associated metric for each variable explaining physiological (i.e., accelerated or delayed) deviations from age‐specific normative data. Among the variables, glycated hemoglobin (HbA1c) displays a major relative weight in the estimation of PPA. Finally, clustering profiles of identical contextualized explanations reveal different aging trajectories opening opportunities to specific clinical follow‐up. These data show that PPA is a robust, quantitative and explainable ML‐based metric that monitors personalized health status. Our approach also provides a complete framework applicable to different datasets or variables, allowing precision physiological age estimation. [ABSTRACT FROM AUTHOR]

External diffusion may be exploited as a tool to purify materials in a way thought to be inaccessible from a chemical reactivity point of view. A mixture of two carbonaceous materials, graphite and carbon black, are thermally oxidized in either i) outside total diffusion‐limited regime or ii) total diffusion‐limited regime. Depending on the treatment applied it is possible to purify either graphite, a trivial task, or carbon black, a task thought impossible. Introducing geometrical selectivity, controlled total diffusion‐limited chemistry exceeds by far the field of carbon materials and can be used as an engineering tool for many materials purification, original synthesis, or to introduce asymmetry in a system. Several examples for direct applications of the findings are mentioned. [ABSTRACT FROM AUTHOR]

Combustion is arguably as old as homo sapiens ability to observe and use fire. Despite the long tradition of using carbon combustion for energy production, this reaction is still not fully understood. This can be related to several facts that are intertwined and complicate the investigation, such as the large variety of possible carbon structures, the actual surface structure, porosity, the solid‐gas nature of this reaction, diffusion limitation and fundamental reaction steps. In this review, a brief history of carbon combustion science is given, followed by a detailed discussion of the most important aspects of carbon combustion. Special attention is given to limitations for example diffusion. In carbon combustion, kinetic control can rarely be observed. The literature of the fundamental reaction steps actually occurring on the carbon framework is reviewed and it becomes apparent that the reaction is occurring primarily on defects on the basal plane. Thus, the reaction between oxygen and carbon may be used as an analytical tool to provide further insights into novel materials, for example synthetic carbon materials, fibres and graphene type materials. Mastering the combustion reaction in all its complexity may prove to be very valuable in the future. [ABSTRACT FROM AUTHOR]

A wide range of evidence indicates that olfactory perception is strongly involved in food intake. However, the polysynaptic circuitry linking the brain areas involved in feeding behavior to the olfactory regions is not well known. The aim of this article was to examine such circuits. Thus, we described, using hodological tools such as transsynaptic viruses (PRV152) transported in a retrograde manner, the long‐distance indirect projections (two to three synapses) onto the main olfactory bulb (MOB). The ß‐subunit of the cholera toxin which is a monosynaptic retrograde tracer was used as a control to be able to differentiate between direct and indirect projections. Our tracing experiments showed that the arcuate nucleus of the hypothalamus, as a major site for regulation of food intake, sends only very indirect projections onto the MOB. Indirect projections to MOB also originate from the solitary nucleus which is involved in energy homeostasis. Other indirect projections have been evidenced in areas of the reward circuit such as VTA and accumbens nucleus. In contrast, direct projections to the MOB arise from melanin‐concentrating hormone and orexin neurons in the lateral hypothalamus. Functional significances of these projections are discussed in relation to the role of food odors in feeding and reward‐related behavior. [ABSTRACT FROM AUTHOR]

Kinetic data, for example, activation energy and reaction order, are crucial for the understanding of chemical reactions and processes. Here, we describe a novel method for obtaining kinetic data based on thermogravimetric measurements (TGA) that exploits in each measurement multiple successive isothermal steps (SIS). We applied this method to the notoriously challenging carbon combustion process for vastly different carbons for oxygen molar fractions between 1.4 % and 90 %. Our obtained apparent EA values are within the wide range of results in the literature and vary in a systematic way with the oxygen partial pressure. The improved accuracy and large amount of obtainable data allowed us to show that the majority of experimentally obtained apparent data for apparent EA are neither in a kinetic regime nor in a diffusion‐controlled one but rather in a transition regime. [ABSTRACT FROM AUTHOR]

Background and Purpose: The link between type 2 diabetes mellitus (T2DM) and depression is bidirectional. However, the possibility that metabolic disorders may elicit anxiogenic-like/depressive-like symptoms or alter the efficacy of antidepressant drugs remains poorly documented. This study explored the influence of T2DM on emotionality and proposed a therapeutic strategy that might be used in depressed diabetic patients.Experimental Approach: Mice were fed a high-fat diet (HFD) and subjected to a full comprehensive metabolic and behavioural analysis to establish correlations between metabolic and psychiatric disorders. In vivo intra-hippocampal microdialysis was also applied to propose a mechanism underpinning the phenotype of mice fed the HFD. Finally, we tested whether chronic administration of the selective 5-HT reuptake inhibitor escitalopram or HFD withdrawal could reverse HFD-induced metabolic and behavioural anomalies.Key Results: The increased body weight, hyperglycaemia and impaired glucose tolerance in response to HFD were correlated with anxiogenic-like/depressive-like symptoms. Moreover, this phenotype was associated with decreased extracellular 5-HT levels in the hippocampus which may result from increased sensitivity of the dorsal raphe 5-HT1A autoreceptor. Interestingly, the beneficial effect of prolonged administration of escitalopram was abolished in HFD-fed mice. On the contrary, HFD withdrawal completely reversed metabolic impairments and positively changed symptoms of anxiety, although some behavioural anomalies persisted.Conclusions and Implications: Our data provide clear-cut evidence that both pathologies are finely correlated and associated with impaired 5-HT mediated neurotransmission in the hippocampus. Further experiments are warranted to define the most adequate strategy for the treatment of such co-morbidity.Linked Articles: This article is part of a themed section on Updating Neuropathology and Neuropharmacology of Monoaminergic Systems. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.13/issuetoc. [ABSTRACT FROM AUTHOR]

Graphenide solutions, comprising charged graphene layers in aprotic organic solutions, are exploited as a chemical platform to graft transition‐metal oxide nanoparticles, namely nickel, manganese, copper, and cobalt oxide, onto the carbon framework. The reduction process is driven and controlled by the graphenide solution yielding nanoparticles with comparable sizes for all studied metal salts, well below 10 nm. The synthesis is generic and is not limited by the type of metal salt, because the reduced graphene layers serve simultaneously as both substrates and reducing agents. This reaction is reliable, reproducible, and versatile, generating materials for catalytic purposes without requiring any kind of stabilization or capping agents. Graphenide solutions have been exploited to generate transition‐metal oxide nanoparticles directly grafted onto the carbon framework. By only varying the metal precursor in the synthesis, nanoparticles smaller than 10 nm are generated and these are highly sought‐after for catalytic purposes. [ABSTRACT FROM AUTHOR]

Abstract: Biodegradability of graphene is one of the fundamental parameters determining the fate of this material in vivo. Two types of aqueous dispersible graphene, corresponding to single‐layer (SLG) and few‐layer graphene (FLG), devoid of either chemical functionalization or stabilizing surfactants, were subjected to biodegradation by human myeloperoxidase (hMPO) mediated catalysis. Graphene biodegradation was also studied in the presence of activated, degranulating human neutrophils. The degradation of both FLG and SLG sheets was confirmed by Raman spectroscopy and electron microscopy analyses, leading to the conclusion that highly dispersed pristine graphene is not biopersistent. [ABSTRACT FROM AUTHOR]

Synergy between graphitic nanocarbon, obtainable from food waste through cracking of biomethane, and iron oxide nanoparticles provides access to efficient bifunctional electro catalysts. Dissolution of potassium-intercalated graphitic nanocarbons yields graphenide solutions with calibrated, small lateral size-reduced graphenes that are used subsequently as reducing agents of iron metal salts. This results in the strong binding of small size (2-5 nm) nanoparticles on the carbon framework homogeneously within the composite material, accessibility of the catalytic centers, and good conductivity provided by the underlying carbon framework. The iron oxide nanocarbon electrocatalyst performances are highlighted by the overall overpotential of approximately 1 V needed to reach the benchmark threshold of 10 mA cm−2 for the oxygen reduction reaction and the particular activity towards oxygen evolution reaction ( η≈0.4 V at 10 mA cm−2), comparable to that of the precious RuO2 and IrO2 catalysts. This iron oxide/nanocarbon electrocatalyst is versatile, remarkably active, stable, and truly sustainable. [ABSTRACT FROM AUTHOR]

We synthesized KC8 by simply mixing molten potassium and graphite at 180 °C under inert atmosphere. The KC8 shows typical shiny bronze color, Raman characteristics and XRD pattern of an efficiently intercalated stage 1 GIC, and is of sufficient quality to produce fully exfoliated graphenide solutions in tetrahydrofuran (THF) and subsequently single layer graphene in water as 'eau de graphene' (EdG). The evolution of absorption and Raman spectroscopic signatures of the EdG as a function of processing conditions give key indications on the number of layers of the graphene flakes dispersed in EdG. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Keywords: carbon nanomaterials; combustion; diffusion; kinetics; surface reactions EN carbon nanomaterials combustion diffusion kinetics surface reactions 1 1 1 09/30/22 20220927 NES 220927 B Although carbon combustion b has a long tradition to be used for energy production, there are still limitations to the complete understanding of the reaction. Carbon nanomaterials, combustion, diffusion, kinetics, surface reactions A brief summary of the history of carbon combustion together with a detailed discussion of its most important aspects is given in the Review article by F. Hof et al (DOI: 10.1002/chem.202200117). [Extracted from the article]

Graphite intercalation compounds, due to charge transfer between layers of graphite and intercalants, have a strongly shifted Fermi level. Potassium is known to give its electron leading to a large charge transfer f c close to [ABSTRACT FROM AUTHOR]

The aim of this study was to gain further insight into β-carotene thermal degradation in oils. Multiresponse modeling was applied to experimental high-performance liquid chromatography-diode array detection (HPLC-DAD) data ( trans-, 13- cis-, and 9- cis-β-carotene concentrations) during the heat treatments (120-180 °C) of two β-carotene-enriched oils, i.e., palm olein and copra. The test of different reaction schemes showed that β-carotene isomerization reactions were dominant and reversible. The resulting cis isomers and trans-β-carotene simultaneously underwent oxidation and cleavage reactions at the same rate constant. From the kinetic analysis, it appeared that-contrary to oxidation and cleavage reactions-isomerization rate constants did not follow the Arrhenius law. However, the isomerization equilibrium constant increased with temperature, favoring isomer production, particularly 9- cis-β-carotene. Its production was shown to be concomitant with oxidation and cleavage reactions, indicating that 9- cis-β-carotene could be a good degradation indicator during oil storage or processing. [ABSTRACT FROM AUTHOR]

Abstract: Aims: To determine the effect of transplantation of undifferentiated and cardiac pre-differentiated adipose stem cells compared with bone marrow mononuclear cells (BM-MNC) in a chronic model of myocardial infarction. Methods: Ninety-five Sprague–Dawley rats underwent left coronary artery ligation and after 1 month received by direct intramyocardial injection either adipose derived stem cells (ADSC), cardiomyogenic cells (AD-CMG) or BM-MNC from enhanced-Green Fluorescent Protein (eGFP) mice. The control group was treated with culture medium. Heart function was assessed by echocardiography and 18F-FDG microPET. Cell engraftment, differentiation, angiogenesis and fibrosis in the scar tissue were also evaluated by (immuno)histochemistry and immunofluorescence. Results: One month after cell transplantation, ADSC induced a significant improvement in heart function (LVEF 46.3±9.6% versus 27.7±8% pre-transplant) and tissue viability (64.78±7.2% versus 55.89±6.3% pre-transplant). An increase in the degree of angiogenesis and a decrease in fibrosis were also detected. Although transplantation of AD-CMG or BM-MNC also had a positive, albeit smaller, effect on angiogenesis and fibrosis in the infarcted hearts, this benefit did not translate into a significant improvement in heart function or tissue viability. Conclusion: These results indicate that transplantation of adipose derived cells in chronic infarct provides a superior benefit to cardiac pre-differentiated ADSC and BM-MNC. [Copyright &y& Elsevier]

Abstract: Close relationships have been demonstrated between adipose tissue and the inflammatory/immune system. Furthermore, obesity is increasingly considered as a state of chronic inflammation. Cytofluorometric analysis reveals the presence of significant levels of lymphocytes in the stroma-vascular fraction of white adipose tissues. In epididymal (EPI) fat, lymphocytes display an “ancestral” immune system phenotype (up to 70% of natural killer (NK), γδ+ T and NKT cells among all lymphocytes) whereas the inguinal (ING) immune system presents more adaptive characteristics (high levels of αβ+ T and B cells). The percentage of NK cells in EPI fat was decreased in obese mice fed with a high-fat diet, whereas γδ positive cells were significantly increased in ING fat. These data support the notion that adipose tissue may elaborate immunological mechanisms to regulate its functions which might be altered in obesity. [Copyright &y& Elsevier]

In humans, the role of bone marrow (BM) adipocytes in supporting haematopoiesis has been questioned. A co-culture system of CD34+ cells seeded onto either BM undifferentiated mesenchymal stem cells or differentiated adipocytes showed that BM adipocytes did not support the maintenance of immature progenitors but enabled their complete differentiation along the myeloid and lymphoid pathways. These properties appear to be opposite to those of osteoblasts, although both cell types share a common mesenchymal progenitor. These results suggest that stromal cells play a variety of roles in the haematopoietic microenvironment, which could be significant in situations such as osteoporosis or ageing. [ABSTRACT FROM AUTHOR]

The detection of changes in glucose level constitutes the first step of the control of glucose homeostasis. Glucose sensors are therefore expected to be present in different parts of the body and particularly in the central nervous system. Some studies have already attempted to determine glucose-sensitive cerebral structures either after a glucoprivic stimulus or after prolonged hyperglycaemia. By analogy to beta cells, it was postulated that the glucose sensors in the brain could involve GLUT2, glucokinase and/or ATP-sensitive K+ channels. Surprisingly, GLUT2 was mainly found in astrocytes. Thus, the aims of the present investigation were to determine, in awake rats: (i) the hypothalamic areas that respond to acute hyperglycaemic condition induced by an intracarotid injection of glucose and (ii) the involvement of astrocytes in glucose-sensing by the use of a glial drug, methionine sulfoximine. Rats were given intracarotid injections of glucose solution to trigger a transient insulin secretion without change in peripheral glycaemia, thus involving only central nervous regulation. Hypothalamic activation was determined by immunodetection of the immediate early gene c-fos protein. Acute glucose injection induces significant activation of arcuate and paraventricular nuclei. This stimulation mainly affects neurones in both nuclei, but also astrocytes in the former as illustrated by double immunohistochemistry (Fos and neuronal nuclei or glial fibrillary acidic protein). After specific impairment of astrocyte metabolism by methionine sulfoximine, cerebral activation disappears in the arcuate nucleus, correlated with the lack of cerebral glucose-induced insulin secretion. Therefore, arcuate and paraventricular hypothalamic nuclei are able to detect acute cerebral hyperglycaemia, leading to a peripheral stimulation of insulin secretion. Arcuate nucleus and more especially astrocytes in this nucleus play a pivotal role in glucose-sensing. [ABSTRACT FROM AUTHOR]

Preadipocytes are present and can proliferate to increase fat mass throughout adult life. The importance of mitochondria in these cells has never been investigated, although we recently reported that mitochondrial oxidative metabolism is non-negligible in white preadipocytes. Mitochondrial reactive oxygen species generation is intimately associated with respiratory chain function. An increasing number of reports support their role as signalling molecules. The aim of this work was to study the effects of mitochondrial reactive oxygen species on proliferation of white preadipocytes. Rotenone and oligomycin, inhibitors of complex I and of ATP synthase respectively, increased H2O2 and inhibited cell growth of preadipocytes (without inducing necrosis or apoptosis). These effects were partly prevented by addition of radical scavengers. A chemical uncoupler had opposite effects on reactive oxygen species generation and cell growth. Propofol, which inhibits complex I but also scavenges free radicals, had effects similar to those of the uncoupler on both parameters. Thus, mitochondrial reactive oxygen species can influence development of adipose tissue by affecting the size of the white preadipocyte pool. [Copyright &y& Elsevier]

We previously showed that a 48-h intravenous lipid infusion in rats induces pancreatic β-cell hypersensitivity to catecholamines. Our aim was to study the lipid-related changes that may account for such hypersensitivity in pancreatic islets. We show here that a 48-h increase in plasma FFA alters the binding characteristics of β-cell α2 adrenoceptors in rats. Lipid infusion decreases pancreatic norepinephrine (NE) turnover rate by 28%, reflecting a reduction of pancreatic NE stores. Following lipid infusion, the density of α2 adrenoceptor binding sites is significantly lower and receptor affinity higher, both in islet homogenates (by three- and fivefold, respectively) and isolated whole β-cells (by two- and sixfold, respectively). These changes correlate with the elevated insulin response to glucose found in lipid-infused rats. We also found a modification of islet phospholipid content, particularly in phosphoethanolamine species containing infused FA such as palmitate, oleate, stearate, and linoleate. This may account for the modifications in receptor affinity. These results suggest that hyperlipidemia-associated pathologies such as diabetes and obesity not only may result from alterations of metabolic pathways but also may be a consequence of early modifications in nervous firing rates and signal transduction pathways. [ABSTRACT FROM AUTHOR]

Most of the oxygen consumed by aerobic organisms is reduced to water by the enzyme cytochrome c oxidase in the terminal reaction of the mitochondrial respiratory chain. A significant proportion of the oxygen molecules are converted to superoxide anion radicals by complexes I and III via a nonenzymatic process. A cascade of enzymes, some of them inside the mitochondria themselves, scavenges superoxide anions in order to protect cells from oxidative damage induced by reactive oxygen species (ROS). Unfortunately, the quantification of the fluxes of mitochondrial ROS inside living cells is currently almost impossible, and this in turn limits our knowledge. Presently, the involvement of mitochondrial ROS can only be demonstrated by indirect strategies and among them knockout techniques are the most convincing. The yield of superoxide generation and subsequently ROS production depend mostly on oxygen concentration but can be efficiently modulated by mitochondrial uncoupling. This role could be assumed in part by one of the Uncoupling Proteins (UCPs). These proteins have coenzyme Q as an obligatory partner and we present here the hypothesis of UCPs as a crucial element of the respiratory chain. ROS have been mostly involved in degenerative processes including ageing. More recently, numerous studies point out the role of ROS as true intracellular second messengers. A putative role of mitochondrial ROS as the sensing element of energy metabolism is discussed here. We propose that UCPs could play a central role in modulation of ROS-dependent signalling pathways and metabolic sensing via the modulation of ROS generation. [ABSTRACT FROM AUTHOR]

We have previously shown that rats made obese by lesion of ventromedial hypothalamus (VMH) nuclei, demonstrate an hyper-responsiveness to insulin with regard to whole-body glucose utilization one week after injury. This is mainly due to an increased glucose uptake in white adipose tissue. Six weeks after the lesion, glucose utilization in white adipose tissue returns to normal values. These modifications in insulin responsiveness could be mediated by altered activity and/or concentration of intracellular insulin effectors. I n this study, we have measured the expression of the insulin-sensitive glucose transporter, Glut 4 and the activities and expression of key lipogenic enzymes (fatty-acid synthase and acetyl-CoA carboxylase) in white adipose tissue, one and six weeks after the lesion. All these parameters, as well as glucose transport and metabolism determined in white adipocytes, were markedly increased one week after the lesion. They returned to control values within six weeks in VMH-lesioned rats. These results indicate the existence of an increased expression of Glut 4 and lipogenic enzymes in white adipose tissue of VMH-lesioned rats which decreased with time and were parallel to glucose utilization determined in vivo. [ABSTRACT FROM AUTHOR]

Titelbild: Thermal Oxidation of Carbonaceous Nanomaterials Revisited: Evidence of Mechanism Changes (Angew. Die Ergebnisse deuten darauf hin, dass die chemische Reaktion bei der Kohlenstoffverbrennung noch lange nicht verstanden wurde, was auf spannende weitere Studien hindeutet. Die Ergebnisse deuten darauf hin, dass die chemische Reaktion bei der Kohlenstoffverbrennung noch lange nicht verstanden wurde, was auf spannende weitere Studien hindeutet. [Extracted from the article]

Sustainable graphitic nanocarbons were intercalated and dissolved to obtain graphenide solutions. These represent versatile precursors for the generation of iron oxide nanocarbon composite materials, utilizing redox chemistry. The synthetic protocol is based on the use of only earth ‐ abundant elements, featuring a significant contribution to the search towards renewable technologies. The derived catalytic system in question exhibits remarkable activity both in the oxygen reduction reaction (ORR) and in the oxygen evolution reaction (OER), matching much more complex, precious, and involved reference systems. For the full story see the Communication by F. Paolucci, A. Pénicaud et al. on page 15283 ff. [ABSTRACT FROM AUTHOR]

Abstract Melatonin is a neurohormone synthesized in the pineal gland during the dark period in all species, including humans. The diversity and differences in melatonin receptor distribution in the brain and extracerebral organs suggest multiple functional roles for melatonin. Administration of melatonin agonists reduces neophobia and treatment with a melatonin antagonist during the dark period reverses the anxiolytic-like effect of endogenous melatonin. Chronic treatment with agonists prevents various perturbations induced by chronic mild stress. Melatonin in vivo directly constricts cerebral arterioles in rats and decreases the lower limit of cerebral blood flow autoregulation, suggesting that melatonin may diminish the risk of hypoperfusion-induced cerebral ischemia. At the extracerebral level, melatonin regulates intestinal motility in rats. The intestinal postprandial motor response is shorter in the dark phase than in the light phase and this reduction is reversed in animals pretreated with a melatonin antagonist. Moreover, melatonin reduces the duration of cholecystokinin excitomotor effect. Endogenous melatonin may modulate intestinal motility to coordinate intestinal functions such as digestion and transit and control the metabolism of the animal. An adipocyte melatonin binding site may also participate in this control. Melatonin is involved in a wide range of physiological functions. The question remains as to whether evolution, adaptation and diurnal life have modified the physiological role of melatonin in humans. Moreover, the functional role of each of the receptor subtypes has to be characterized to design selective ligands to treat specific diseases. [ABSTRACT FROM AUTHOR]

Abstract The hypothalamus participates in the regulation of carbohydrate metabolism involving a feedback loop between the brain and the periphery in which glucose-sensitive hypothalamic areas appear to be involved. We have previously shown that a glucose injection (9 mg/kg) in the carotid artery toward the brain, in an amount that did not modify glycaemia, caused a rapid and transient increase in plasma insulin concentrations. To determine whether central insulin could influence this response, we investigated the change in central glucose-induced insulin secretion in intracerebroventricular (i.c.v) insulin-injected rats and in hyperinsulinaemic obese Zucker rats. Central glucose-induced insulin secretion was increased by 50% in i.c.v. insulin-injected rats compared to control rats. When a similar test was performed at a lower dose of glucose (3 mg/kg), a significant insulin secretion was observed only in rats submitted to a prior central insulin injection. These data indicate an increase in the brain response to glucose after insulin treatment. Using an identical lower glucose dose, we also demonstrated an enhanced brain glucose sensitivity in hyperinsulinaemic and insulin-resistant obese Zucker rats. Together, these results indicate that acute i.c.v. insulin or pathological hyperinsulinaemic state (i.e. obese Zucker rat) modulates the nervous control of insulin secretion by increasing the brain response to glucose. [ABSTRACT FROM AUTHOR]

Graphite intercalation compounds, due to charge transfer between layers of graphite and intercalants, have a strongly shifted Fermi level. Potassium is known to give its electron leading to a large charge transfer f c close to [ABSTRACT FROM AUTHOR]