Decrease In Glucose Consumption Research Articles

Glut-1 Translocation in FRTL-5 Thyroid Cells: Role of Phosphatidylinositol 3-Kinase and N-Glycosylation

It was previously demonstrated that insulin or TSH treatment of FRTL-5 cells resulted in an elevation of glucose transport and in an increase of cell surface expression of the glucose transporter Glut-1. However, the signaling mechanisms leading to the insulin or TSH-induced increase in the cell surface expression of Glut-1 were not investigated. In the present study, we demonstrated that wortmannin and LY294002, two specific inhibitors of phosphatidylinositol 3-kinase (PI3-kinase), interfere both in the signaling pathways of insulin and TSH leading to glucose consumption enhancement and Glut-1 translocation. Two hours after insulin treatment, TSH or cAMP analog (Bu)2cAMP stimulation, glucose transport was increased and most of the intracellular Glut-1 pool was translocated to plasma membranes. Wortmannin or LY294002 blocked the insulin, (Bu)2cAMP, and the TSH-induced translocation of Glut-1. Wortmannin or LY294002 alone did not alter the basal ratio between intracellular and cell surface Glut-1 molecules. These results suggest that in FRTL-5 cells wortmannin and LY294002 inhibited the insulin, (Bu)2cAMP and TSH events leading to Glut-1 translocation from an intracellular compartment to the plasma membrane. Likewise, (Bu)2cAMP effects on glucose transport and Glut-1 translocation to plasma membrane were repressed by PI3-kinase inhibitors but not by the protein kinase A (PKA) inhibitor H89. We suggest that (Bu)2cAMP stimulates Glut-1 translocation to plasma membrane through PI3-kinase-dependent and PKA-independent signaling pathways. To further elucidate mechanisms that regulate the translocation of Glut-1 to cell membrane, we extended this study to the role played by the N-glycosylation in the translocation and in the biological activity of Glut-1 in FRTL-5 cells. For this purpose we used tunicamycin, an inhibitor of the N-glycosylation. Our experiments with tunicamycin clearly showed that both the glycosylated and unglycosylated forms of the transporter reached the cell surface. Likewise, a decrease in glucose consumption (−50%) after treatment of cells with tunicamycin was accompanied by a decrease (−70% vs. control) in the membrane expression of a 50-kDa form of Glut-1 and an increase in its unglycosylated 41-kDa form. These results suggest that carbohydrate moiety is essential for the biological activity of glucose transport but is not required for the translocation of Glut-1 from the intracellular membrane pool to the plasma membrane.

Glut-1 translocation in FRTL-5 thyroid cells: role of phosphatidylinositol 3-kinase and N-glycosylation.

It was previously demonstrated that insulin or TSH treatment of FRTL-5 cells resulted in an elevation of glucose transport and in an increase of cell surface expression of the glucose transporter Glut-1. However, the signaling mechanisms leading to the insulin or TSH-induced increase in the cell surface expression of Glut-1 were not investigated. In the present study, we demonstrated that wortmannin and LY294002, two specific inhibitors of phosphatidylinositol 3-kinase (PI3-kinase), interfere both in the signaling pathways of insulin and TSH leading to glucose consumption enhancement and Glut-1 translocation. Two hours after insulin treatment, TSH or cAMP analog (Bu)2cAMP stimulation, glucose transport was increased and most of the intracellular Glut-1 pool was translocated to plasma membranes. Wortmannin or LY294002 blocked the insulin, (Bu)2cAMP, and the TSH-induced translocation of Glut-1. Wortmannin or LY294002 alone did not alter the basal ratio between intracellular and cell surface Glut-1 molecules. These results suggest that in FRTL-5 cells wortmannin and LY294002 inhibited the insulin, (Bu)2cAMP and TSH events leading to Glut-1 translocation from an intracellular compartment to the plasma membrane. Likewise, (Bu)2cAMP effects on glucose transport and Glut-1 translocation to plasma membrane were repressed by PI3-kinase inhibitors but not by the protein kinase A (PKA) inhibitor H89. We suggest that (Bu)2cAMP stimulates Glut-1 translocation to plasma membrane through PI3-kinase-dependent and PKA-independent signaling pathways. To further elucidate mechanisms that regulate the translocation of Glut-1 to cell membrane, we extended this study to the role played by the N-glycosylation in the translocation and in the biological activity of Glut-1 in FRTL-5 cells. For this purpose we used tunicamycin, an inhibitor of the N-glycosylation. Our experiments with tunicamycin clearly showed that both the glycosylated and unglycosylated forms of the transporter reached the cell surface. Likewise, a decrease in glucose consumption (-50%) after treatment of cells with tunicamycin was accompanied by a decrease (-70% vs. control) in the membrane expression of a 50-kDa form of Glut-1 and an increase in its unglycosylated 41-kDa form. These results suggest that carbohydrate moiety is essential for the biological activity of glucose transport but is not required for the translocation of Glut-1 from the intracellular membrane pool to the plasma membrane.

Structural and functional imaging in children with partial epilepsy.

Imaging plays an increasingly important role in the evaluation of children with complex partial seizures. Most partial epilepsy, especially of temporal lobe origin, begins during childhood. Structural imaging with high-resolution MRI can help identify the etiology of partial seizure disorders in many children. MRI studies also show the more widespread effect of seizures on brain structure. Progressive volume loss of the hippocampal formation in some patients with temporal lobe epilepsy provides evidence that continued seizures may be associated with progressive neuronal injury. FDG-PET studies show regional decreases in glucose consumption in the cortical zone from which seizures arise. Functional abnormalities often are more extensive than the seizure focus. Studies in children with recent-onset epilepsy show that metabolic abnormalities are considerably less common than in adults with partial epilepsy, supporting the notion that in some patients there may be progressive metabolic changes that occur with continued seizures. Functional MRI may be used to identify language areas in children with partial epilepsy. fMRI language tasks reliably identify the dominant hemisphere for language dominance when compared to the intracarotid amytal procedure. Tests of verbal fluency and semantic decision identify frontal lobe language areas, while reading text paradigms and auditory passage paradigms are better for identifying temporal language areas. A panel of paradigms is best used to identify language areas in children being considered for epilepsy surgery. fMRI is a valuable tool for elucidating the impact of chronic neurologic disease states on the functional organization of language networks during development.

Structural and functional imaging in children with partial epilepsy

Imaging plays an increasingly important role in the evaluation of children with complex partial seizures. Most partial epilepsy, especially of temporal lobe origin, begins during childhood. Structural imaging with high-resolution MRI can help identify the etiology of partial seizure disorders in many children. MRI studies also show the more widespread effect of seizures on brain structure. Progressive volume loss of the hippocampal formation in some patients with temporal lobe epilepsy provides evidence that continued seizures may be associated with progressive neuronal injury. FDG-PET studies show regional decreases in glucose consumption in the cortical zone from which seizures arise. Functional abnormalities often are more extensive than the seizure focus. Studies in children with recent-onset epilepsy show that metabolic abnormalities are considerably less common than in adults with partial epilepsy, supporting the notion that in some patients there may be progressive metabolic changes that occur with continued seizures. Functional MRI may be used to identify language areas in children with partial epilepsy. fMRI language tasks reliably identify the dominant hemisphere for language dominance when compared to the intracarotid amytal procedure. Tests of verbal fluency and semantic decision identify frontal lobe language areas, while reading text paradigms and auditory passage paradigms are better for identifying temporal language areas. A panel of paradigms is best used to identify language areas in children being considered for epilepsy surgery. fMRI is a valuable tool for elucidating the impact of chronic neurologic disease states on the functional organization of language networks during development. MRDD Research Reviews 6:220–226, 2000. Published 2000 Wiley-Liss, Inc.

THE EFFECT OF TRAINING ON MACROPHAGE METABOLISM AND FUNCTION

1591 A series of studies have demonstrated that acute exercise affects macrophage function, enhancing the phagocytic and migratory capacity of both murine and human cells. One such effect is possibly related to the changes of the hormonal and cytokine profile induced by exertion. Little is known, however, about the influence of exercise upon macrophage metabolism, which is closely related to cell function. These cells utilise glucose and glutamine at high rates and the pattern of metabolisation of these substrates is regulated by various hormones, as insulin, epinephrine and thyroid hormones. We have thus investigated the changes of macrophage metabolism and function(phagocytosis and hydrogen peroxide production) as induced by a treadmill training protocol. Male Wistar rats were trained for 7 weeks, 4 days a week, at 70% VO2 max. Glucose utilisation was reduced (as shown by a 34% decrease of hexokinase maximal activity and a 18% decrease of glucose consumption) in the macrophages of trained rats (n=5) in relation to the sedentary rats cells (n=5). Lactate production was also reduced in the trained group (35%), what suggests the diversion of the carbon moieties derived from glucose to the Krebs cycle. Indeed, citrate synthase activity was higher in the cells from the trained rats (38.4 ± 0.7nmol/min/mg protein) as compared with the control group (26.4 ± 0.6 nmol/min/mg protein). In the trained group glutamine derived carbons flux through the Krebs cycle was enhanced 2-fold in comparison with controls. Phagocytosis and hydrogen peroxide production were also higher in the trained group cells in relation to controls (28 and 20%, respectively), important functions related to the bactericidal and tumouricidal capacities of the macrophage. Taken together, the results herein reported show that the training protocol adopted is able to induce changes in the metabolism and function of macrophages, enhancing phagocytosis and hydrogen peroxide production, possibly due to the increase of the cell capacity of oxidation of its main substrates.

Bicarbonate versus Lactate Buffer in Peritoneal Dialysis Solutions: The Beneficial Effect on Rbc Metabolism

Using the erythrocyte as a model for other kinds of cells not directly exposed to peritoneal dialysis (PD) solutions, we investigated the tolerance of the cell metabolism to lactate and bicarbonate buffers. We studied, in vivo (in two groups of 5 PD patients each) and in vitro, the Embden-Meyerhof pathway (EMP) because it represents a potential target for the unphysiological effects of lactate or bicarbonate buffers. The EMP is the main glucose-utilizing route in the red blood cell (RBC), producing energy and reducing power. The enzymatic activities of the key steps in the glycolytic pathway and the energy charge (EC), determined by the levels of phosphorylated adenine nucleotides, were investigated spectrophotometrically and by high performance liquid chromatography (HPLC) in two groups of patients undergoing lactate (L-group) and bicarbonate (B-group) PD, respectively. The in vitro effects of both bicarbonate and lactate buffers on some EMP enzyme activities and energy production were determined. Cellular pH (pHi) was also investigated. The B-group showed an EC value near the control levels, while in the L-group a significantly lower EC value was observed (t-test: p < 0.05 vs both B-group and controls). The key enzymes in the EMP, and in particular hexokinase, were higher in the L-versus B-group (p < 0.03 for the comparison of the Hk mean values). As demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, the bound form of glyceraldehyde-3-phosphate dehydrogenase (G-3-PD), an inactive form of this EMP enzyme, was significantly higher in the L-group with respect to the B-group (p < 0.004). In the in vitro experiments, high lactate concentrations acutely inhibited the key enzymatic steps of glycolysis, producing a significant decrease in glucose consumption and adenosine triphosphate production. These effects were not observed when bicarbonate was used in the incubations. Both in vivo and in vitro lactate, but not bicarbonate, induce a significant drop in pHi (p < 0.05). Decreased levels of pHi like those observed in the lactate-incubated RBC were demonstrated to be able to inhibit G-3-PD activity (25 +/- 2%) here used as an indicator of the actual decrease in pH. This study provides evidence for a damaging action of lactate with respect to bicarbonate buffer on the RBC metabolism. This condition was demonstrated observing a cell energy depletion, which coincides in vitro with an acute EMP impairment; the lactate accumulation together with the consequent lowering of pHi seem to be responsible for this effect, which was not observed when bicarbonate was used instead of lactate.

Human erythrocyte metabolism is modulated by the O 2-linked transition of hemoglobin

The metabolic behaviour of human erythrocytes has been investigated with particular regard to the effect of their oxygenation state. Experiments performed at high phosphate concentration (80 mM) within the pH range 7.0–7.8 on erythrocytes at high (HOS) and low (LOS) oxygen saturation showed that at any pH value: (1) glucose consumption was independent of the oxygenation state; (2) pentose phosphate pathway (PPP) flux was about 2 times higher in the HOS than in the LOS state. At low phosphate concentration (1.0 mM) the PPP flux doubled in HOS as well as in LOS erythrocytes, whereas the decrease in glucose consumption was more marked in the HOS state. Metabolism of LOS erythrocytes approached that of HOS erythrocytes under the following conditions: (1) erythrocytes having band 3 modified by 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid; (2) CO-saturated erythrocytes. These data support the hypothesis of a modulation of the relative rates of PPP and glycolysis achieved through competition between deoxy-hemoglobin (deoxy-Hb) and glycolytic enzymes for the cytoplasmic domain of band 3.

Positron emission tomography metabolic data corrected for cortical atrophy using magnetic resonance imaging.

The correct interpretation of clinical positron emission tomography (PET) data depends largely on the physical limits of the PET scanner. The partial volume effect (PVE) is related to the size of the studied object compared to the spatial resolution. It represents one of the most important limiting factors in quantitative data analysis. This effect is increased in the case of atrophy, as in patients with Alzheimer disease (AD), and it influences measurement of the metabolic reduction generally seen in cerebral degeneration. In this case, interpretation can be biased, because cortical activity will be underestimated due to the atrophy. In general, anatomical images of AD patients have shown diffuse atrophy, while PET studies have found widespread hypometabolism affecting the parietal and temporal lobes. Although hypometabolic areas usually correspond to atrophic regions, they also occur without such changes. Thus, the aim is to differentiate authentic hypometabolism (decrease of glucose consumption per unit volume of gray matter) from that due to PVE from atrophy (cell loss). Consequently, we are using a method for three-dimensional (3D) correction of human PET data with 3D magnetic resonance imaging (MRI). We measured atrophy and metabolism by using both T1-weighted MR images and high and medium resolution PET scans. We injected 12 patients and controls with [18F]fluorodeoxyglucose for glucose consumption measurements. Atrophy was estimated in the following way. We isolated the cerebral structures, using a segmentation technique on the MRI scans, into gray matter (GM), white matter, and cerebrospinal fluid. We superimposed the PET images onto the MR images to obtain anatomo-functional correlations. We degraded the segmented MR images to the resolution of the PET images by a convolution process to create a PET image correction map. We corrected the metabolic PET data for the PVE. We studied the cerebral metabolic rate of glucose in the GM where metabolic variation is the most relevant to AD. By dealing with problems relating to the sensitivity to the segmentation and to the PET-MRI coregistration, computation of MRI convolution processes provided the degree of PVE on a pixel-by-pixel basis, allowing correction of hypometabolisms contained in GM PET values. Global cortical metabolism increased after correction for PVE by, on average, 29 and 24% for tomographs acquired with medium (TTV03 LETI) and high (ECAT 953B CTI/Siemens) resolution, respectively, whereas the cortical metabolism increased by 75 and 65% for the respective tomographs in AD patients. The difference of metabolism between scans after correction for PVE was less than before correction, decreasing from 31 to 17%. This difference was most marked in the frontal and temporal lobes. Fusion imaging allowed correction for PVE in metabolic data using 3D MRI and determination of whether a change in the apparent radiotracer concentration in PET data reflected an alteration in GM volume, a change in radiotracer concentration per unit volume of GM, or both.

Simulated weightlessness and bone metabolism: gravitational stimulation enhances insulin sensitivity

The effect of simulated weightlessness on bone metabolism was investigated in skeletal unloading for 4 days. Skeletal unloading was designed using the model of hindlimb hang in rats. Skeletal unloading with hindlimb hang cased a significant decrease of alkaline phosphatase activity, deoxyribonucleic acid (DNA) content, and glucose consumption in the femoral diaphysis, but not in the calvaria. When femoral-diaphyseal tissues were cultured in the presence of insulin (10(-8) M), the hormone produced a significant increase of alkaline phosphatase activity and decrease of glucose consumption in the femoral-diaphyseal tissues obtained from normal rats. This hormonal effect was not seen in the femoral diaphysis, but in the calvaria, of rats with skeletal unloading. However, insulin effect was seen in the femoral diaphysis obtained at 3 days after the removal of skeletal unloading. Meanwhile, the presence of other bone-regulating factors (10(-8) M parathyroid hormone [1-34] and 10(-4) M zinc sulfate) revealed an appreciable effect on alkaline phosphatase activity in the femoral diaphysis from rats with skeletal unloading. These results suggest that gravitational stimulation can directly enhance a specific insulin sensitivity in the regulation of bone metabolism.

Simulated weightlessness and bone metabolism: evidence for direct gravitational effect and its related insulin action

The effect of simulated weightlessness on bone metabolism was investigated in skeletal unloading for 4 days. Skeletal unloading was designed using the model of hind-limb hang in rats. In hypokinetic state, rats were fed while the right hind limb was weighed down and the left hind limb was unloaded (a state of weightlessness). Bone metabolism in normal rats did not vary significantly in the femoral diaphysis in right and left hind limb. Alkaline phosphatase activity and DNA content in the femoral diaphysis were not significantly altered by hypokinetic state without skeletal unloading, while the unloading caused an appreciable decrease in the enzyme activity and DNA content. However, femoral-diaphyseal zinc content and glucose consumption was significantly decreased by hypokinetic state with and without skeletal unloading. When femoral-diaphyseal tissues were cultured in the presence of insulin (10 nM), the hormone produced a significant increase of alkaline phosphatase activity and decrease of glucose consumption in the femoral-diaphyseal tissues obtained from normal and hypokinetic rats. This hormonal effect was not seen in bone tissues from hypokinetic rats with skeletal unloading. These results suggest that skeletal unloading-induced disorder of bone metabolism is directly related to gravitational effect and that gravitational stimulation may be involved in insulin action.

Metabolic substrate utilization by tumour and host tissues in cancer cachexia

Utilization of metabolic substrates in tumour and host tissues was determined in the presence or absence of two colonic tumours, the MAC16, which is capable of inducing cachexia in recipient animals, and the MAC13, which is of the same histological type, but without the effect on host body composition. Glucose utilization by different tissues was determined in vivo by the 2-deoxyglucose tracer technique. Glucose utilization by the MAC13 tumour was significantly higher than by the MAC16 tumour, and in animals bearing tumours of either type the tumour was the second major consumer of glucose after the brain. This extra demand for glucose was accompanied by a marked decrease in glucose utilization by the epididymal fat-pads, testes, colon, spleen, kidney and, in particular, the brain, in tumour-bearing animals irrespective of cachexia. The decrease in glucose consumption by the brain was at least as high as the metabolic demand by the tumour. This suggests that the tissues of tumour-bearing animals adapt to use substrates other than glucose and that alterations in glucose utilization are not responsible for the cachexia. Studies in vitro showed that brain metabolism in the tumour-bearing state was maintained by an increased use of lactate and 3-hydroxybutyrate, accompanied by a 50% increase in 3-oxoacid CoA-transferase. This was supported by studies in vivo which showed an increased metabolism of 3-hydroxybutyrate in tumour-bearing animals. Thus ketone bodies may be utilized as a metabolic fuel during the cancer-bearing state, even though the nutritional conditions mimic the fed state.

RU 24722, a new eburnamine derivative, induces selective alterations in cerebral glucose utilization in freely moving rat

The effect of a new eburnamine derivative, RU 24722, a putative phasic activator of catecholaminergic systems on local cerebral glucose utilization was studied in freely moving rats 15 min, 90 min and 6 h after the intraperitoneal administration of the drug (25 mg/kg). Of the 53 brain regions examined, 9 exhibited significant time-dependent increases of glucose utilization (up to 45–55%). Some changes were early and transient, as in the substantia nigra reticulata and the paraventricular nuclei. Other areas showed sustained (median septal nucleus) or delayed increases of glucose utilization (lateral septum, dorsal subiculum, hippocampal fimbria, fronyo-parietal motor cortex and ventral cochlear nucleus). No significant alterations of glucose utilization could be elicited in the locus coeruleus and raphe nuclei, and none of the brain regions showed a decrease in glucose consumption. Our findings suggest that RU 24722 preferentially stimulates the activity in some brain areas involved in cognitive, vegetative and locomotor functions.

Dexamethasone inhibits antitumor potential of activated macrophages by a receptor mediated action

The capacity to inhibit P815 mastocytoma growth was induced in macrophages elicited by trehalose dimycolate by a short in vitro treatment with 10 ng/ml LPS. Activation by LPS was associated with a 3 fold increase in the rate of glucose consumption by macrophages. Incubation of activated macrophages with the glucocorticoid dexamethasone (≥ 10 −8M) for several hours (≥ 5 h) resulted in an inhibition of antitumoral activity and a decrease of glucose consumption. Hydrogen peroxide production is a property expressed by trehalose dimycolate-elicited macrophages independently of the presence of LPS. The capacity to release hydrogen peroxide upon triggering was not affected by a pretreatment of macrophages by dexamethasone. The antiglucocorticoid compound RU 38486, known to bind with a high affinity to glucocorticoid receptors without agonist effect, prevented the inhibitory actions of dexamethasone, indicating that these are receptor-mediated.

Proton NMR spectroscopy of glucose consumption by cultured lens epithelial cells.

Proton NMR spectroscopy was performed on media collected from cultured lens epithelial cells of the rabbit eye incubated with Krebs-Ringer's solution containing 5.5mM 13C-glucose (labeled at the C-1 position). Comparing proton resonance intensities of the lactate-methyl group of the C-3 carbon (both 12C and 13C) enabled us to quantify the hexose monophosphate shunt (HMPS) activity. Our results showed that the epithelial cells remained stable in both lactate production and HMPS activity for at least 8 hours. In addition, although tBHP (1mM) resulted in an increase of glucose flow through the HMPS, the rate of lactate production was not affected. In contrast, KCN (2mM) caused a 72% increase of lactate production and a slight (6%) decrease of glucose consumption through the HMPS.

Cerebral metabolic and circulatory effects of 1,1,1-trichloroethane, a neurotoxic industrial solvent. 1. Effects on local cerebral glucose consumption and blood flow during acute exposure.

The effects of inhaled 1,1,1-trichloroethane (3500, 6000, and 7800 ppm) on behavior, local cerebral blood flow, and local cerebral glucose consumption were studied in awake rats. The effect of the solvent inhalation on the EEG pattern and local cerebral blood flow was also studied in paralyzed animals under N2O analgesia. Exposure of awake animals to 6000 ppm 1,1,1-trichloroethane induced a decrease in motility and exploratory behavior. At 7800 ppm the rats were clearly ataxic. The local cerebral glucose consumption in 23 brain regions was studied by the [14C]deoxyglucose technique. A decrease was observed ranging from 14 to 55% of control values. The inferior colliculus and substantia nigra displayed the largest reductions. In exposed animals the local cerebral blood flow increased in 11 brain structures by 28-45%. In animals under N2O analgesia, 7400 ppm 1,1,1-trichloroethane induced a depression of the EEG activity. In these animals the local cerebral blood flow increased by 12-99%, with a large variability in blood flow between the different structures. It is concluded that exposure of rats to subanesthetic doses of 1,1,1-trichloroethane induces an increase in cerebral blood flow in spite of a concomitant decrease in glucose consumption and depression of cerebral function.

Electrographic, clinical and pathological alterations following systemic administration of kainic acid, bicuculline or pentetrazole: Metabolic mapping using the deoxyglucose method with special reference to the pathology of epilepsy

Kainic acid, bicuculline or pentetrazole have been injected systemically in rats. Clinical, electrographic and metabolic alterations (using the deoxyglucose method), have been studied in relation to subsequently demonstrated neuropathology using stains for degenerating nerve fibers or neurons. Twenty minutes after administration of the toxin (9–12 mg/kg i.p.), the animals displayed ‘wet shakes’; their frequency of occurrence was steadily increased before subsiding 60 min later when the overt typical limbic motor seizures started. The latter progressively evolved into status epilepticus. Epileptiform activity started (approximately 20 min after the injections) in the temporal pole of the hippocampal formation (in particular the entorhinal cortex) and propagated to the rostral Ammon's horn, the amygdala, medial thalamus and pre-frontal cortex and diffusely to the cortical electroencephalogram. Postictal depressions were exclusively seen in the hippocampal formation, thus further stressing the central position occupied by this structure in the electrographic effects of the toxin. At longer delays (3–6 days), rhythmic spikes were exclusively present in the amygdaloid complex. Less than l h after administration of kainic acid, i.e. before the occurrence of the first limbic motor seizure, the autoradiographic deoxyglucose maps revealed an increase in glucose consumption exclusively in the hippocampal formation and lateral septum. At longer delays (2–5 h) the increase in radioactive material progressively involved: (1) structures projected upon directly by the hippocampal formation through the pre- and post-commissural fornix system (in addition to the lateral septum, the infralimbic cortex, the nucleus accumbens, ventral putamen and antero-medial thalamic nuclei); (2) the rostral limbic cortex (in particular the deep layers of the pre-limbic and agranular insular cortices) and structures which have direct connections with the rostral limbic cortex including the cingulate, retrosplenial and perirhinal cortices as well as the claustrum; (3) the amygdaloid complex, the stria terminalis fiber tract and its bed nucleus. In contrast, there was a concomitant decrease in glucose consumption in ‘non-limbic’ cortical structures as well as in most regions of the forebrain, mesencephalon and brain stem. At longer delays (2–3 days) the metabolism was decreased in the entire brain with a few noticeable exceptions, including the amygdala. There is, therefore, a remarkable correlation between the electrographic changes and the rise in metabolism. Furthermore, the pathological alterations (signs of degeneration) were almost exclusively present in structures in which there had been a rise in metabolism (in particular the hippocampal formation, lateral septum, amygdala, medial thalamus and claustrum). In contrast, bicuculline (0.4–0.8 mg/kg i.v.) or pentetrazole (60 mg/kg i.p.) produced less than 1 min after the injection a typical tonico-clonic generalized convulsive seizure with severe post-ictal depressions in several brain structures including the frontal and occipital cortices. Short delays (less than 1 h) after single or a few generalized convulsive seizures, the most conspicuous rise in metabolism was noted in the cerebellum and vestibular nuclei, the red nucleus, substantia nigra, nucleus of the occulomotor nerve and the neocortex. In contrast, a decrease in glucose consumption was manifested in limbic structures, in particular, the hippocampal formation and the amygdala. Thus, in several respects, the image produced by the deoxyglucose maps and its electrographic correlates is the opposite of that obtained after kainic acid. After short delays, the most conspicuous brain damage seen with the FinkHeimer stain consists of fine argyorphilic grains surrounding the cerebellar Purkinje perikarya, which appear to reflect degenerative changes in basked cell innervation. It is suggested that the systemic administration of kainic acid may provide a useful animal model for the study of both the preferential susceptibility of limbic structures to epileptogenic procedures and their vulnerability to the pathological consequences of epilepsy.

The influence of adenosine on intermediary metabolism of isolated hepatocytes

The effect of adenosine was tested on the energetic metabolism of fed rat liver cells after isolation. The cells were incubated in a buffered saline medium with glucose (5 mM) and adenosine (1 mM) for 30 minutes at 37 degrees C. This increased the concentration of the adenylic nucleotides ATP (+57 per cent, ADP (+39 per cent). Cyclic AMP was increased (+50 per cent) and the intracellular inorganic phosphate decreased (-22 per cent). These changes were accompaned by a decrease of glycogenolysis, glucose consumption and lactate production. Measurement of glycolytic intermediates showed decreased concentrations of fructose 1,6-bis-phosphate and 3-phosphoglycerate proportional to the increase in ATP concentration. The near-equilibrium of the glyceraldehyde 3-phosphate dehydrogenase-phosphoglycerate kinase system was not modified by adenosine. The decrease of the NAD+/NADH ratio along with the increase of the ATP/ADP X PO4 ratio explains the decrease of 3-phosphoglycerate. The decrease in glucose consumption can be explained by the cross over at the phosphofructokinase stage with the decrease of fructose 1,6-bisphosphate. The major part of adenosine was deaminated as indicated by an increase in the production of ammonia and urea. The effects of inosine, or adenosine along with an inhibitor of adenosine deaminase (pentostatin) suggest that adenosine acts on the glucose consumption through adenylic nucleotides. However the increase of the adenylic nucleotide level cannot totally explain the other metabolic changes: decrease of the NAD+/NADH cytoplasmic ratio, constancy of this ratio in mitochondria, decrease of gluconeogenesis from lactate. A direct action of adenosine can therefore be expected.

Effect of dissolved oxygen and Eh and Bacteroides fragilis during continuous culture.

Bacteroides fragilis subsp. fragilis was maintained in a chemostat modified for anaerobic conditions to test the effects of dissolved oxygen and Eh on growth. Using a defined medium containing glucose and a dilution rate of 0.16 h -1, a stable population of 3 X 10(9) colony-forming units/ml was present. At this steady state, the pH was 5.6, the Eh was -50 mV, and the dissolved oxygen concentration was 0% atmospheric saturation. The Eh was then adjusted to +300 mV by adding potassium ferricyanide while oxygen was excluded; in this system there were no demonstrable changes from the steady state in viable cells, pH, glucose concentration, or volatile fatty acid production. In other experiments oxygen was introduced into the original steady state at a dissolved oxygen concentration of 10% atmospheric saturation for a period of 6 to 8 h. During O2 exposure, the viable cell count decreased at a rate comparable to the theoretical washout rate for a static bacterial culture. Similar results were obtained with a dissolved oxygen concentration of 25 and 100%. Other effects of O2 exposure included an increase in Eh from -50 to +250 mV, a decrease in glucose consumption, and a decrease in volatile fatty acid production. These results suggest that dissolved oxygen has a bacteriostatic effect on B. fragilis in continuous culture, which may be independent of changes in Eh alone.

Metabolism of forearm tissues in man. Studies with glucagon.

The role of glucagon in regulating peripheral tissue metabolism in man was assessed in the present studies. To do this, glucagon was infused for two hours into the brachial artery to produce a high but physiologic increment in the glucagon content of arterial blood supplying ipsilateral tissues. Metabolic effects on muscle and on subcutaneous adipose tissue plus skin were sought in seven overnight-fasting subjects and seven subjects starved briefly (60 hours). In the overnight-fasted group the infusion increased bassl glucagon concentration by 1,216 pg./ml. but was without effect on forearm tissue metabolism of glucose, lactate,glycerol, or amino acids. Starvation significantly reduced basal insulin (11.0 to 7.4 muU./ml.) and increased endogenous glucagon (116 to 134 pg./ml.). Basally, there was substantial ketone utilization and a decrease in glucose consumption by both muscle and subcutaneous adipose tissue plus skin. The glucagon infusion increased basal glucagon by 784 pg./ml. Muscle balances of glucose, lactate, acetoacetate, amino acids, and glycerol were unaffected. The metabolism of glucose, lactate, acetoacetate, glycerol, and free fatty acids by subcutaneous adipose tissue plus skin was also unchanged. It is concluded that physiologic increments of glucagon lasting two hours are without effect on forearm tissues in overnight-fasted and briefly starved man.

Glucose consumption by red cells of diabetic patients and normal subjects. Effect of ethanol

Glucose consumption was measured in the red cells of 15 diabetic patients and 13 normal subjects. The red cells were incubated in auto logo us serum with the glucose concentration adjusted to approximately 500 mg per 100 ml. Mean glucose consumption, both total and via the pentose phosphate pathway, by the red cells of the diabetic patients was not significantly different from that by the red cells of the normal subjects. Stimulation of the pentose phosphate pathway with ascorbate or methylene blue similarly revealed no difference between the two groups. Exposure of the red cells to ethanol in the incubation medium had no discernible effect on total glucose consumption but caused a decrease in glucose consumption by the pentose phosphate pathway. An effect of ethanol on glucose consumption by the pentose phosphate pathway was not evident in the presence of ascorbate or methylene blue. No difference in response to ethanol by the red cells of the diabetic patients and normal subjects was observed.