JOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2006
J. NOLASCO JR.
ABSTRACT Thermal degradation of sugars contained in sugarcane must (21.5°Brix, pH 6.14) was evaluated at temperatures of 110, 120, 130 and 140C, using the thermal-death-time tube method, determining remaining sugars by high-pressure liquid chromatography. The study analyzed thermal degradation kinetics of both the total reducing sugars (TRS) and glucose and fructose individually. All curves of remaining sugars presented strong nonlinearity, with initial shoulder and final tail adjusted by an extended logistic model that was adapted for two species for TRS, and a simple logistic model for the monosaccharides. It was shown that rate constants are influenced by temperature according to two irreconcilable methods: the Arrhenius and the Bigelow methods. Obtained activation energies for fructose and glucose were quite coincident, 140.37 and 140.23 kJ/mol, respectively. Thermal resistance parameters were 21.59 and 21.61C, respectively. Comparison of the rate constants revealed that fructose degraded approximately 9,10 times faster than glucose. [source]

EFFECTS OF ADMINISTRATION OF ORAL MAGNESIUM ON PLASMA GLUCOSE AND PATHOLOGICAL CHANGES IN THE AORTA AND PANCREAS OF DIABETIC RATS

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 8 2005
Nepton Soltani
SUMMARY 1.,Magnesium deficiency has recently been proposed as a novel factor implicated in the pathogenesis of the complications of diabetes. The purpose of the present study was to determine the relationship between oral Mg supplementation and changes in plasma glucose, calcium, haemogolobin, Ca/Mg ratio, blood pressure and the histology of the pancreas and vascular system in streptozotocin-induced diabetic rats. 2.,Ten days after the induction of diabetes in male Wistar rats, half the diabetic animals were divided into six groups, receiving 0, 1, 3, 10, 30 or 50 g/L MgSO4 added into the drinking water for 8 weeks. Plasma glucose and Mg were measured at days 1, 2, 3, 5, 7, 14 and 21 to find the optimum dose of Mg and the time-course of its effect. In addition, histological observations were undertaken. Eight weeks later, all animals were decapitated, the pancreas and thoracic aorta were removed carefully and immersed immediately in 10% formaldehyde for histological study. 3.,To evaluate the effects of Mg on plasma glucose, calcium, haemoglobin, Mg and blood pressure, another group of animals was divided into four experimental groups, as follows: (i) non-diabetic controls received tap water for 8 weeks; (ii) acute diabetics received tap water for 10 days; (iii) chronic diabetic controls received tap water for 8 weeks; and (iv) Mg-treated chronic diabetic rats received 10 g/L MgSO4 added into the drinking water 10 days after the induction of diabetes for 8 weeks. 4.,Magnesium dose dependently affects plasma glucose levels. The peak effect was reached during the first 24 h following oral administration. Administration of 10 g/L MgSO4 results in the return of normal structure in the diabetic pancreas and aorta. Moreover, this concentration of MgSO4 causes glucose, haemoglobin, calcium, the Ca/Mg ratio and blood pressure to reach normal levels. Although the Mg level increases slightly following the administration of 10 g/L MgSO4 to diabetic rats, it never reaches control levels. 5.,On the basis of the results of the present study, it may be concluded that chronic Mg administration may have beneficial effects on diabetes. [source]

Regulation of glucose transporter 4 traffic by energy deprivation from mitochondrial compromise

ACTA PHYSIOLOGICA, Issue 1 2009
A. Klip
Abstract Skeletal muscle is the major store and consumer of fatty acids and glucose. Glucose enters muscle through glucose transporter 4 (GLUT4). Upon insufficient oxygen availability or energy compromise, aerobic metabolism of glucose and fatty aids cannot proceed, and muscle cells rely on anaerobic metabolism of glucose to restore cellular energy status. An increase in glucose uptake into muscle is a key response to stimuli requiring rapid energy supply. This chapter analyses the mechanisms of the adaptive regulation of glucose transport that rescue muscle cells from mitochondrial uncoupling. Under these conditions, the initial drop in ATP recovers rapidly, through a compensatory increase in glucose uptake. This adaptive response involves AMPK activation by the initial ATP drop, which elevates cell surface GLUT4 and glucose uptake. The gain in surface GLUT4 involves different signals and routes of intracellular traffic compared with those engaged by insulin. The hormone increases GLUT4 exocytosis through phosphatidylinositol 3-kinase and Akt, whereas energy stress retards GLUT4 endocytosis through AMPK and calcium inputs. Given that energy stress is a component of muscle contraction, and that contraction activates AMPK and raises cytosolic calcium, we hypothesize that the increase in glucose uptake during contraction may also involve a reduction in GLUT4 endocytosis. [source]

Inadequacies of absolute threshold levels for diagnosing prediabetes

DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 1 2010
Michael Bergman
Abstract Prediabetes comprising Impaired Fasting Glucose (IFG) and Impaired Glucose Tolerance (IGT) represents an intermediate stage of altered glucose metabolism between normal glucose levels and type 2 diabetes mellitus and is associated with an increased risk for the development of diabetes and cardiovascular disease. There is considerable evidence that glucose levels lower than those meeting the current definition of prediabetes may also be associated with similar risks particularly in high-risk individuals. Prediabetes is often unrecognized and therefore constitutes a major public health concern suggesting the need for earlier intervention than is currently recommended. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Leptin and endothelin-1 mediated increased extracellular matrix protein production and cardiomyocyte hypertrophy in diabetic heart disease

DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 5 2009
Pijush Majumdar
Abstract Background We investigated the role of leptin and its interaction with endothelin 1 (ET-1) in fibronectin (FN) synthesis and cardiomyocyte hypertrophy, two characteristic features of diabetic cardiomyopathy. Methods Endothelial cells [human umbilical vein endothelial cells (HUVECs)] were examined for FN production and neonatal rat cardiomyocytes for hypertrophy, following incubation with glucose, ET-1, leptin and specific blockers. FN, ET-1, leptin and leptin receptors mRNA expression and FN protein were measured. Myocytes were also morphometrically examined. Furthermore, hearts from streptozotocin-diabetic rats were analysed. Results Glucose caused increased FN mRNA and protein expression in HUVECs and cardiomyocytes hypertrophy along with upregulation of ET-1 mRNA, leptin mRNA and protein. Glucosemimetic effects were seen with leptin and ET-1. Leptin receptor antagonist (leptin quadruple mutant) and dual endothelin A endothelin B (ETA/ETB) receptor blocker bosentan normalized such abnormalities. Hearts from the diabetic animals showed hypertrophy and similar mRNA changes. Conclusion These data indicate that in diabetes increased FN production and cardiomyocyte hypertrophy may be mediated through leptin with its interaction with ET-1. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Impaired glucose regulation, elevated glycated haemoglobin and cardiac ischaemic events in vascular surgery patients

DIABETIC MEDICINE, Issue 3 2008
H. H. H. Feringa
Abstract Aims Cardiac morbidity and mortality is high in patients undergoing high-risk surgery. This study investigated whether impaired glucose regulation and elevated glycated haemoglobin (HbA1c) levels are associated with increased cardiac ischaemic events in vascular surgery patients. Methods Baseline glucose and HbA1c were measured in 401 vascular surgery patients. Glucose < 5.6 mmol/l was defined as normal. Fasting glucose 5.6,7.0 mmol/l or random glucose 5.6,11.1 mmol/l was defined as impaired glucose regulation. Fasting glucose , 7.0 or random glucose , 11.1 mmol/l was defined as diabetes. Perioperative ischaemia was identified by 72-h Holter monitoring. Troponin T was measured on days 1, 3 and 7 and before discharge. Cardiac death or Q-wave myocardial infarction was noted at 30-day and longer-term follow-up (mean 2.5 years). Results Mean (± sd) level for glucose was 6.3 ± 2.3 mmol/l and for HbA1c 6.2 ± 1.3%. Ischaemia, troponin release, 30-day and long-term cardiac events occurred in 27, 22, 6 and 17%, respectively. Using subjects with normal glucose levels as the reference category, multivariate analysis revealed that patients with impaired glucose regulation and diabetes were at 2.2- and 2.6-fold increased risk of ischaemia, 3.8- and 3.9-fold for troponin release, 4.3- and 4.8-fold for 30-day cardiac events and 1.9- and 3.1-fold for long-term cardiac events. Patients with HbA1c > 7.0% (n = 63, 16%) were at 2.8-fold, 2.1-fold, 5.3-fold and 5.6-fold increased risk for ischaemia, troponin release, 30-day and long-term cardiac events, respectively. Conclusions Impaired glucose regulation and elevated HbA1c are risk factors for cardiac ischaemic events in vascular surgery patients. [source]

Amperometric Determination of Glucose at Conventional vs.

ELECTROANALYSIS, Issue 12 2010
Nanostructured Gold Electrodes in Neutral Solutions
Abstract The conventional gold electrodes were compared with recently published electrodes based on gold nanoparticles and gold nanostructured films as amperometric sensors for glucose in pH,7.40 phosphate buffer solutions. The conventional electrodes provided similar electroanalytical benefits while required much simpler and shorter preparation. It is recommended that the future reports on the development of electrochemical sensors based on metal nanoparticles/nanostructures include also the analytical figures of merit obtained at relevant conventional metal electrodes. The voltammetric studies indicated that, in contrast to phosphate buffers, the Tris buffers were not suitable for activation of gold surface toward the direct oxidation of glucose. [source]

Influence of Metal Nanoparticles on the Electrocatalytic Oxidation of Glucose by Poly(NiIIteta) Modified Electrodes

ELECTROANALYSIS, Issue 5 2010
Pratap Azad
Abstract Conductive polymeric [NiII(teta)]2+ (teta=C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane) films (poly(Ni)) have been deposited on the surface of glassy carbon (GC), Nafion (Nf) modified GC (GC/Nf) and Nf stabilized Ag and Au nanoparticles (NPs) modified GC (GC/Ag-Nf and GC/Au-Nf) electrodes. The cyclic voltammogram of the resulting electrodes, show a well defined redox peak due to oxidation and reduction of poly(Ni) system in 0.1,M NaOH. They show electrocatalytic activity towards the oxidation of glucose. AFM studies reveal the formation of poly(Ni) film on the modified electrodes. Presence of metal NPs increases electron transfer rate and electrocatalytic oxidation current by improving the communication within the Nf and poly(Ni) films. In the presence of metal NPs, 4 fold increase in current for glucose oxidation was observed. [source]

Electrocatalytic Oxidation of Glucose by the Glucose Oxidase Immobilized in Graphene-Au-Nafion Biocomposite

ELECTROANALYSIS, Issue 3 2010
Kangfu Zhou
Abstract Graphene was successfully prepared and well separated to individual sheets by introducing SO3,. XRD and TEM were employed to characterize the graphene. UV-visible absorption spectra indicated that glucose oxidase (GOx) could keep bioactivity well in the graphene-Au biocomposite. To construct a novel glucose biosensor, graphene, Au and GOx were co-immobilized in Nafion to further modify a glassy carbon electrode (GCE). Electrochemical measurements were carried out to investigate the catalytic performance of the proposed biosensor. Cyclic voltammograms (CV) showed the biosensor had a typical catalytic oxidation response to glucose. At the applied potential +0.4,V, the biosensor responded rapidly upon the addition of glucose and reached the steady state current in 5,s, with the present of hydroquinone. The linear range is from 15,,M to 5.8,mM, with a detection limit 5,,M (based on the S/N=3). The Michaelis-Menten constant was calculated to be 4.4,mM according to Lineweaver,Burk equation. In addition, the biosensor exhibits good reproducibility and long-term stability. Such impressive properties could be ascribed to the synergistic effect of graphene-Au integration and good biocompatibility of the hybrid material. [source]

Fabrication of Nanoporous Copper Film for Electrochemical Detection of Glucose

ELECTROANALYSIS, Issue 21 2009
Sirilak Sattayasamitsathit
Abstract A nanoporous copper film was fabricated on a copper wire by electrodeposition of copper/zinc alloy and chemically etching of zinc. The surface morphology was investigated by SEM. When applied to detect glucose in an amperometric flow injection system the porous copper electrode provided 12 times higher sensitivity than solid copper. It could be continuously used up to 50 times (%RSD=5.7). Different preparations of the porous film provided reproducible responses (P<0.05). Detection of glucose in E. coli cultivation medium compared well with spectrophotometric technique (P<0.05). This simple technique can produce a nanoporous electrode with good performances and can easily be applied to other metals and analytes. [source]

Development of Prototype Wireless Transmission Measurement for Glucose in Subcutaneous and Brain Striatum

ELECTROANALYSIS, Issue 9 2008
Farook Ahmad
Abstract Monitoring of glucose in subcutaneous and brain striatum have been extensively studied in the past. While biocompatibility was one of the limitations, others included the messy measuring equipments preclude monitoring in a complex environment. This study tried to establish an amperometric measurement of glucose in pre- and post-insulin-administration on diabetic and hyperglycemia rats via wireless. The results have indicated that the wireless sensing kit used was capable of monitoring glucose in both subcutaneous and brain. The physiological data have also shown a new insight on the fabrication of implantable glucose sensors. [source]

Integrating an Enzyme-Entrapped Conducting Polymer Electrode and a Prereactor in a Microfluidic System for Sensing Glucose

ELECTROANALYSIS, Issue 6 2008
Po-Chin Nien
Abstract In this study, the flow injection analysis was applied to the enzyme-entrapped electrode on a chip for sensing glucose. The on-chip microelectrode was fabricated by the standard photolithography in clean-room environment and the microfluidic channel height of 100,,m on the chip was formed by poly(dimethylsiloxane). The conducting polymer, poly(3,4-ethylenedioxythiophene), PEDOT, was electropolymerized to entrap the coexisting glucose oxidase (GOD) by cyclic voltammetry (CV). The amount of enzyme entrapped in the matrix measured spectroscopically was about 0.101,U/cm2. At a flow rate of 10,ml/hr, the working electrode (Pt/PEDOT/GOD, WE1) was set at 0.7,V (vs. Ag/AgCl) and sensing of H2O2 was carried out by injecting samples with various concentrations of glucose (Glu). A linear relationship between the sensing current and the glucose concentration, ranging from 1 to 20,mM, was obtained with a sensitivity of 8,nA mm,2 mM,1. The response time and the recovery time were about 30 and 230,s, respectively. For a single-potential test, the oxidation currents of 0.08,mM ascorbic acid (AA) and a blend of 0.08,mM AA and 10,mM Glu reached 31.3% and 145.5%, respectively, when compared with the oxidation current of 10,mM Glu alone. However, when a pre-reactor (WE2) was set at the same potential (0.7,V) before the main enzyme integrated electrode (WE1), the oxidation current for the above mixed solution reached 99.6% of the original one. [source]

Development of Novel Glucose and Pyruvate Biosensors at Poly(Neutral Red) Modified Carbon Film Electrodes.

ELECTROANALYSIS, Issue 8 2006
Application to Natural Samples
Abstract Amperometric biosensors based on the corresponding oxidase enzyme with poly(neutral red) redox mediator have been developed for the determination of glucose and pyruvate. The enzymes have been immobilized on top of poly(neutral red) modified carbon film electrodes with glutaraldehyde as the cross-linking agent. The biosensors were characterized by cyclic voltammetry and by electrochemical impedance spectroscopy. The glucose biosensor exhibited a linear response in the range 90,,M to 1.8,mM with a detection limit of 22,,M and the pyruvate biosensor in the range 90 to 600,,M with a detection limit of 34,,M. The relative standard deviations were found to be 2.1% (n=3) and 2.8% (n=4) respectively. The interference effects of various compounds were also studied. The glucose content of several types of wine and the amount of pyruvate in onion and garlic were determined and the results were compared with those obtained by standard spectrophotometric methods. [source]

On-line biosensors for simultaneous determination of glucose, choline, and glutamate integrated with a microseparation system

ELECTROPHORESIS, Issue 18 2003
Guoyue Shi
Abstract An effective microseparation system integrated with ring-disc electrodes and two microfluidic devices was fabricated for in vivo determination using a microdialysis pump. The major interference of ascorbic acid (AA) was excluded by direct oxidation with ascorbate oxidase. Glucose, glutamate, and choline were successfully determined simultaneously through the biosensors modified with a bilayer of osmium-poly(4-vinylpyridine)gel-horseradish peroxidase (Os-gel-HRP)/glucose oxidase (GOD), glutamate oxidase (GlutaOD) or choline oxidase (ChOD). To stabilize the biosensors, 0.2% polyethylenimine (PEI) was mixed with the oxidases. The cathodic currents of glucose, glutamate, and choline biosensors started to increase after the standard solutions were injected into the microseparation system. The on-line biosensors show a wide calibration range (10,7,10,5 mol/L) with a detection limit of 10,8 mol/L at the working potential of ,50 mV. The variations of glucose, glutamate, and choline were determined simultaneously in a free moving rat when we perfused the medial frontal cortex with 100 ,mol/L N -methyl- D -aspartate (NMDA) solution, which is the agonist of the NMDA receptor. [source]

Glucose inhibits the formation of gas vesicles in Haloferax volcanii transformants

ENVIRONMENTAL MICROBIOLOGY, Issue 1 2008
Torsten Hechler
Summary The effect of glucose on the formation of gas vesicles was investigated in Haloferax mediterranei and Hfx.volcanii transformants containing the mc- gvp gene cluster of Hfx. mediterranei (mc-vac transformants). Increasing amounts of glucose in the medium resulted in a successive decrease in the amount of gas vesicles in both species, with a complete inhibition of their formation at glucose concentrations of > 70 mM in mc-vac transformants, and 100 mM in Hfx. mediterranei. Maltose and sucrose imposed a similar inhibitory effect, whereas xylose, arabinose, lactose, pyruvate and 2-deoxy-glucose had no influence on the gas vesicle formation in mc-vac transformants. The activities of the two mc-vac promoters were strongly reduced in mc-vac transformants grown in the presence of > 50 mM glucose. The gas vesicle overproducing ,D transformant (lacking the repressing protein GvpD) also showed a glucose-induced lack of gas vesicles, indicating that GvpD is not involved in the repression. The addition of glucose was useful to block gas vesicle formation at a certain stage during growth, and vice versa, gas vesicle synthesis could be induced when a glucose-grown culture was shifted to medium lacking glucose. Both procedures will enable the investigation of defined stages during gas vesicle formation. [source]

Ecophysiology of a group of uncultured Gammaproteobacterial glycogen-accumulating organisms in full-scale enhanced biological phosphorus removal wastewater treatment plants

ENVIRONMENTAL MICROBIOLOGY, Issue 3 2006
Yunhong Kong
Summary The presence of glycogen-accumulating organisms (GAOs) in enhanced biological phosphorus removal (EBPR) plants can seriously deteriorate the biological P-removal by out-competing the polyphosphate-accumulating organisms (PAOs). In this study, uncultured putative GAOs (the GB group, belonging to the Gammaproteobacteria) were investigated in detail in 12 full-scale EBPR plants. Fluorescence in situ hybridization (FISH) revealed that the biovolume of the GB bacteria constituted 2,6% of total bacterial biovolume. At least six different subgroups of the GB bacteria were found, and the number of dominant subgroups present in each plant varied between one and five. Ecophysiological investigations using microautoradiography in combination with FISH showed that, under aerobic or anaerobic conditions, all subgroups of the GB bacteria could take up acetate, pyruvate, propionate and some amino acids, while some subgroups in addition could take up formate and thymidine. Glucose, ethanol, butyrate and several other organic substrates were not taken up. Glycolysis was essential for the anaerobic uptake of organic substrates. Polyhydroxyalkanoates (PHA) but not polyphosphate (polyP) granules were detected in all GB bacterial cells. Polyhydroxyalkanoate formation after anaerobic uptake of acetate was confirmed by measuring the increase in fluorescence intensity of PHA granules inside GB bacterial cells after Nile blue staining. One GB subgroup was possibly able to denitrify, and several others were able to reduce nitrate to nitrite. PAOs were also enumerated by FISH in the same treatment plants. Rhodocyclus -related PAOs and Actinobacteria -related PAOs constituted up to 7% and 29% of total bacterial biovolume respectively. Rhodocyclus -related PAOs always coexisted with the GB bacteria and showed many physiological similarities. Factors of importance for the competition between the three groups of important bacteria in EBPR plants are discussed. [source]

Possible mechanisms for the anticonvulsant activity of fructose-1,6-diphosphate

EPILEPSIA, Issue 2008
Janet L. Stringer
Summary Fructose-1,6-diphosphate (FDP), an intracellular metabolite of glucose, has anticonvulsant activity in several models of acute seizures in laboratory animals. The anticonvulsant effect of FDP is most likely due to a direct effect since intraperitoneal and oral administration results in significant increases in brain levels. A number of mechanisms have been proposed for this action of FDP. One possibility is that peripheral administration of FDP results in changes in brain metabolism that are anticonvulsant. Glucose can be metabolized through the glycolytic or pentose phosphate pathway. There is evidence that the pentose phosphate pathway is more active in the brain than in other tissues, and that, in the presence of elevated levels of FDP, the majority of glucose is metabolized by the pentose phosphate pathway. The pentose phosphate pathway generates NADPH, which is used to reduce glutathione. The reduced form of endogenous glutathione has been shown to have anticonvulsant activity. Taken together, the data suggest a hypothesis that exogenously administered FDP gets into the brain and astrocytes where it increases the flux of glucose through the pentose phosphate pathway, generating additional NADPH for the reduction of glutathione. [source]

Caloric Restriction Inhibits Seizure Susceptibility in Epileptic EL Mice by Reducing Blood Glucose

EPILEPSIA, Issue 11 2001
Amanda E. Greene
Summary: ,Purpose: Caloric restriction (CR) involves underfeeding and has long been recognized as a dietary therapy that improves health and increases longevity. In contrast to severe fasting or starvation, CR reduces total food intake without causing nutritional deficiencies. Although fasting has been recognized as an effective antiseizure therapy since the time of the ancient Greeks, the mechanism by which fasting inhibits seizures remains obscure. The influence of CR on seizure susceptibility was investigated at both juvenile (30 days) and adult (70 days) ages in the EL mouse, a genetic model of multifactorial idiopathic epilepsy. Methods: The juvenile EL mice were separated into two groups and fed standard lab chow either ad libitum (control, n = 18) or with a 15% CR diet (treated, n = 17). The adult EL mice were separated into three groups; control (n = 15), 15% CR (n = 6), and 30% CR (n = 3). Body weights, seizure susceptibility, and the levels of blood glucose and ketones (,-hydroxybutyrate) were measured over a 10-week treatment period. Simple linear regression and multiple logistic regression were used to analyze the relations among seizures, glucose, and ketones. Results: CR delayed the onset and reduced the incidence of seizures at both juvenile and adult ages and was devoid of adverse side effects. Furthermore, mild CR (15%) had a greater antiepileptogenic effect than the well-established high-fat ketogenic diet in the juvenile mice. The CR-induced changes in blood glucose levels were predictive of both blood ketone levels and seizure susceptibility. Conclusions: We propose that CR may reduce seizure susceptibility in EL mice by reducing brain glycolytic energy. Our preclinical findings suggest that CR may be an effective antiseizure dietary therapy for human seizure disorders. [source]

Synthesis of Hybrids of D -Glucose and D -Galactose with Pyrrolidine-Based Iminosugars as Glycosidase Inhibitors

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 34 2008
Venkata Ramana Doddi
Abstract Sugar,iminosugar hybrid molecules made up of D -glucose and D -galactose with pyrrolidine-based iminosugars, viz. 1,4-dideoxy-1,4-imino- L -xylitol and 1,4-dideoxy-1,4-imino- L -lyxitol, are synthesized from glycal epoxides and found to be moderate glycosidase inhibitors. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

A New Glucose: Towards Conformationally Locked Hexoses through Annulation

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 11 2005
Goverdhan Mehta
Abstract A new family of surface-modified carbohydrates with locked, axial-rich conformations and bipolarofacial architectures has been developed with the aid of carbocyclic ring annulation. These novel trans -decalin-based carbohydrates have been synthesized, from simple aromatic precursors such as tetralin, through the ozonolysis of an appropriately protected allylic alcohol, followed by a cascade of intramolecular acetalizations to generate the sugar pyran moiety. The stereoselective synthesis of (racemic) cyclohexane-annulated ,-glucopyranoside and ,-glucofuranoside from a common annulated trans -cyclohexadiene diol (trans -CHD) precursor underscores the versatility of our approach. The efficacy of the annulation stratagem in generating carbohydrate diversity has been demonstrated through the synthesis of two regioisomeric annulated gulose derivatives, which differ only in the site of ring annulation on the sugar moiety. The mapping of the MLP surface and solid-state architecture of the new sugar shows that cycloalkane annulation results in surface modification and fine-tuning of sugar hydrophilicity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

D -Glucose as a Pentavalent Chiral Scaffold

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2003
Till Opatz
Abstract A novel carbohydrate-based scaffold for combinatorial chemistry has been developed. This scaffold allows the selective attachment of five different side chains, giving rise to products of enormous structural diversity. As a demonstration of its usefulness, a series of model compounds has been prepared in high purity and yield by multistep parallel synthesis on a solid phase. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Renal Response to Arginine Vasopressin During the Oestrous Cycle in the Rat: Comparison of Glucose and Saline Infusion Using Physiological Doses of Vasopressin

EXPERIMENTAL PHYSIOLOGY, Issue 1 2002
David E. Hartley
The renal response to arginine vasopressin in the rat has been shown to depend on reproductive status. However there is no consensus as to when the kidney is most responsive. The varying results could depend on the protocol and the dose of hormone used. A study has been performed, with physiological doses of vasopressin, comparing the responses during infusion of hypotonic saline and glucose. After an equilibration period of 150 min, conscious rats were infused on each of the four days of the oestrous cycle with either isotonic saline (0.077 M) or 0.14 M glucose for a control period of 45 min. Vasopressin was then infused at 10-40 fmol min,1 for 1 h, followed by a recovery period of 90 min. Timed urine samples were collected for determination of volume, sodium concentration and osmolality. During the control period urine flow was greatest at oestrus and dioestrus day 2 and sodium excretion on dioestrus day 2 irrespective of the infusate. Vasopressin concentrations achieved lay within the physiological range and no difference was observed between the different days for a given dose. Infusion of vasopressin in both saline and glucose produced a dose-dependent antidiuresis, the greatest responses being seen of pro-oestrus and dioestrus day 2. It was only with the highest rate of infusion that a significant increase in sodium excretion was seen on each day of the cycle and the greatest responses were seen on pro-oestrus and dioestrus day 1 for both infusates. Thus the kidney shows the greatest response to physiological doses of vasopressin at pro-oestrus and dioestrus day 1 irrespective of the infusate employed. [source]

Glucose sensing in the intestinal epithelium

FEBS JOURNAL, Issue 16 2003
Jane Dyer
Dietary sugars regulate expression of the intestinal Na+/glucose cotransporter, SGLT1, in many species. Using sheep intestine as a model, we showed that lumenal monosaccharides, both metabolisable and nonmetabolisable, regulate SGLT1 expression. This regulation occurs not only at the level of transcription, but also at the post-transcriptional level. Introduction of d -glucose and some d -glucose analogues into ruminant sheep intestine resulted in >,50-fold enhancement of SGLT1 expression. We aimed to determine if transport of sugar into the enterocytes is required for SGLT1 induction, and delineate the signal-transduction pathways involved. A membrane impermeable d -glucose analogue, di(glucos-6-yl)poly(ethylene glycol) 600, was synthesized and infused into the intestines of ruminant sheep. SGLT1 expression was determined using transport studies, Northern and Western blotting, and immunohistochemistry. An intestinal cell line, STC-1, was used to investigate the signalling pathways. Intestinal infusion with di(glucos-6-yl)poly(ethylene glycol) 600 led to induction of functional SGLT1, but the compound did not inhibit Na+/glucose transport into intestinal brush-border membrane vesicles. Studies using cells showed that increased medium glucose up-regulated SGLT1 abundance and SGLT1 promoter activity, and increased intracellular cAMP levels. Glucose-induced activation of the SGLT1 promoter was mimicked by the protein kinase A (PKA) agonist, 8Br-cAMP, and was inhibited by H-89, a PKA inhibitor. Pertussis toxin, a G-protein (Gi)-specific inhibitor, enhanced SGLT1 protein abundance to levels observed in response to glucose or 8Br-cAMP. We conclude that lumenal glucose is sensed by a glucose sensor, distinct from SGLT1, residing on the external face of the lumenal membrane. The glucose sensor initiates a signalling pathway, involving a G-protein-coupled receptor linked to a cAMP,PKA pathway resulting in enhancement of SGLT1 expression. [source]

Effect of acetic acid and pH on the cofermentation of glucose and xylose to ethanol by a genetically engineered strain of Saccharomyces cerevisiae

FEMS YEAST RESEARCH, Issue 4 2010
Elizabeth Casey
Abstract A current challenge of the cellulosic ethanol industry is the effect of inhibitors present in biomass hydrolysates. Acetic acid is an example of one such inhibitor that is released during the pretreatment of hemicellulose. This study examined the effect of acetic acid on the cofermentation of glucose and xylose under controlled pH conditions by Saccharomyces cerevisiae 424A(LNH-ST), a genetically engineered industrial yeast strain. Acetic acid concentrations of 7.5 and 15 g L,1, representing the range of concentrations expected in actual biomass hydrolysates, were tested under controlled pH conditions of 5, 5.5, and 6. The presence of acetic acid in the fermentation media led to a significant decrease in the observed maximum cell biomass concentration. Glucose- and xylose-specific consumption rates decreased as the acetic acid concentration increased, with the inhibitory effect being more severe for xylose consumption. The ethanol production rates also decreased when acetic acid was present, but ethanol metabolic yields increased under the same conditions. The results also revealed that the inhibitory effect of acetic acid could be reduced by increasing media pH, thus confirming that the undissociated form of acetic acid is the inhibitory form of the molecule. [source]

One-Pot Preparation of Polymer,Enzyme,Metallic Nanoparticle Composite Films for High-Performance Biosensing of Glucose and Galactose

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2009
Yingchun Fu
Abstract New polymer,enzyme,metallic nanoparticle composite films with a high-load and a high-activity of immobilized enzymes and obvious electrocatalysis/nano-enhancement effects for biosensing of glucose and galactose are designed and prepared by a one-pot chemical pre-synthesis/electropolymerization (CPSE) protocol. Dopamine (DA) as a reductant and a monomer, glucose oxidase (GOx) or galactose oxidase (GaOx) as the enzyme, and HAuCl4 or H2PtCl6 as an oxidant to trigger DA polymerization and the source of metallic nanoparticles, are mixed to yield polymeric bionanocomposites (PBNCs), which are then anchored on the electrode by electropolymerization of the remaining DA monomer. The prepared PBNC material has good biocompatibility, a highly uniform dispersion of the nanoparticles with a narrow size distribution, and high load/activity of the immobilized enzymes, as verified by transmission/scanning electron microscopy and electrochemical quartz crystal microbalance. The thus-prepared enzyme electrodes show a largely improved amperometric biosensing performance, e.g., a very high detection sensitivity (99 or 129,µA cm,2 mM,1 for glucose for Pt PBNCs on bare or platinized Au), a sub-micromolar limit of detection for glucose, and an excellent durability, in comparison with those based on conventional procedures. Also, the PBNC-based enzyme electrodes work well in the second-generation biosensing mode. The proposed one-pot CPSE protocol may be extended to the preparation of many other functionalized PBNCs for wide applications. [source]

Characterization and Origin of Dissolved Organic Carbon in Yegua Ground Water in Brazos County, Texas

GROUND WATER, Issue 5 2001
Joyanto Routh
Dissolved organic carbon (DOC) concentrations in five shallow (< 20 m) and three deeper wells (27 to 30 m) in the Eocene Yegua Formation (Brazos County in east-central Texas) ranged from 92 to 500 ,m. Characterization of high, intermediate, and low molecular weight DOC fractions (HMW > 3000 amu, IMW 1000 to 3000 amu, and LMW 500 to 1000 amu) and combined neutral sugar analyses provide information on organic matter sources in the Yegua aquifers. Combined neutral sugars ranged in concentration from 0.6 to 2.7 ,mol/L and comprised 0.8% to 6.7% of DOC in ground water. Glucose was the most abundant neutral sugar, followed by xylose and galactose, arabinose, mannose, rhamnose, and fucose. These combined neutral sugars were more diagenetically altered in shallow, oxic ground water as indicated by high mole % fucose + rhamnose and low neutral sugar yield. The precursors for neutral sugars are most probably angiosperm leaves, which show a similar distribution pattern of neutral sugars. Ground water DOC was depleted in 13C relative to soil-zone organic matter (OM) (,16, to ,19,). The ,13C values of bulk DOC and HMW DOC ranged from ,24, to ,32,, whereas LMW and IMW DOC ranged from ,32, to ,34, and ,16, to ,28,, respectively. This variability in ,13C values is probably related to microbial processes and selective preservation of OM. Carbon isotope analyses in bulk and different molecular weight DOC fractions imply a predominantly C3 OM source and a low contribution of soil-zone OM to DOC. [source]

Template Synthesis of Aligned Carbon Nanotube Arrays using Glucose as a Carbon Source: Pt Decoration of Inner and Outer Nanotube Surfaces for Fuel-Cell Catalysts,

ADVANCED FUNCTIONAL MATERIALS, Issue 6 2008
Zhenhai Wen
A facile method is developed to synthesize aligned arrays of open-ended carbon nanotubes (CNTs) via in situ glucose polymerization in the inner pores of anodic aluminum oxide templates under hydrothermal conditions, followed by carbonization at high temperature. Pt nanoparticles are decorated on the surfaces of the as-prepared CNTs using the incipient wet method based on the use of NaBH4 as a reductant. Characterization of the resulting structures by transmission electron microscopy and field-emission scanning electron microscopy demonstrates that the Pt nanoparticles are anchored on both the inner and outer walls of CNTs, thus giving rise to a shell,core,shell-like nanotube composite. The electrocatalytic properties of the Pt,CNT,Pt electrodes are investigated for methanol oxidation by cyclic voltammetry and chronoamperometric measurements. It is found that the hybrid electrodes show superior catalytic performance compared to commercial carbon-black-supported Pt. The increased catalytic efficiency of Pt might be a result of the unique morphology of these structures. [source]

Low Leptin Levels in Migraine: A Case Control Study

HEADACHE, Issue 7 2008
Baburhan Guldiken MD
Background., Obesity has been shown to be a risk factor for transformation of episodic migraine to chronic form, and adipocytokines have been implicated to modulate some of the cytokins such as interleukin-6 and tumor necrosis factor, which also act in the neurogenic inflammation in migraine. The aim of the study was to assess leptin levels, one of the adipocytokines, in headache-free period of migraine patients and investigate its relation to vascular risk factors. Material and Methods., Sixty-one patients with episodic migraine headaches and 64 control subjects were enrolled in the study. Demographic data and anthropometric measurements were obtained from all participants; body mass index and fat mass values were calculated. Glucose and lipid parameters were measured by oxidase technique and cholesterol esterase enzymatic assays, and leptin levels were measured by ELISA in serum samples obtained after an overnight fasting. Results., Leptin levels were found significantly lower in migraineurs than controls (40.1 ± 21.2 ng/mL, 48.5 ± 24.5 ng/mL; P < .05). Although body mass index did not differ between 2 groups, fat mass, and fat percentages were significantly lower in migraine patients (19.4 ± 8.8 kg, 26.0 ± 8.7 kg; P < .001 and 28 ± 9%, 34 ± 5%; P < .001, respectively). Conclusion., Migraine patients have low leptin levels and fat mass which may be related to the pathogenesis of migraine. The importance and impact of our findings on the prevalence, characteristics, and treatment of migraine needs to be investigated in further detailed studies. [source]

Synthesis of the Cyclopentyl Nucleoside (,)-Neplanocin A from D -Glucose via Zirconocene-Mediated Ring Contraction

HELVETICA CHIMICA ACTA, Issue 6 2005

Two approaches for the conversion of d- glucose to (,) -neplanocin A (2), both based on the zirconocene-promoted ring contraction of a vinyl-substituted pyranoside, are herein evaluated (Scheme,1). In the first pathway (Scheme,2), the substrate possesses the , - d- allo configuration (see 6) such that ultimate introduction of the nucleobase would require only an inversion of configuration. However, this precursor proved unresponsive to Cp2Zr (=[ZrCl2(Cp)2]), an end result believed to be a consequence of substantive nonbonded steric effects operating in a key intermediate (Scheme,5). In contrast, the C(2) epimer (see 7) experienced the desired metal-promoted conversion to an enantiomerically pure polyfunctional cyclopentane (see 5 in Scheme,3). The substituents in this product are arrayed in a manner such that conversion to the target nucleoside can be conveniently achieved by a double-inversion sequence (Scheme,4). Recourse to palladium(0)-catalyzed allylic alkylation did not provide an alternate means of generating 2. [source]

Screening des Glucose-/Insulin-Metabolismus bei Männern mit multiplen gestielten Fibromen im Nacken

JOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 10 2008
Emilio Sudy
First page of article [source]