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At least 721 records · Page 40Linked to original sources
PubMed2004

Quantitative on-line monitoring of cellular glucose and lactate metabolism in vitro with slow perfusion.

An on-line in vitro perfusion technique is described that allows the continuous quantification of cellular glucose metabolism in vitro. Using biosensor technology, we measure glucose and lactate metabolism at a minute-to-minute time resolution for periods up to several days. The application of our perfusion-detection technique for in vitro monitoring is demonstrated in a wide variety of cells, including primary neuronal and astroglia cultures, yeast cells, and human lymphocytes. The method shows that variations in oxygen delivery or exposure to a noncompetitive pseudosubstrate (here 2-deoxyglucose) affects normal glucose metabolism. The innovative advantage of the present system is that, in contrast to other devices including a recently described system, metabolism per cell can be quantified. The potential of in vitro on-line monitoring is discussed for application in studying normal and abnormal metabolism, toxic and nontoxic drug effects, and human tissue biopsies.

Animals↗
PubMed1988

Interaction of sympathomimetics and insulin with hepatic glucose production by isolated perfused rat livers: effects of continuous versus pulsatile infusion.

To elucidate the efficacy of continuous vs. intermittent exposure to epinephrine, phenylephrine, and insulin, hepatic glucose production was monitored in isolated perfused rat livers (means +/- SE, n = 6 each). To this end livers of fed rats were perfused with 5 mM glucose Krebs-Ringer buffer in a nonrecirculating system. Using this model it was shown that intermittent exposure (3 min on/off period, dose reduction -50%) to epinephrine (0.4 microM, alpha + beta-agonist) and phenylephrine (5 microM, alpha-agonist) elicited an almost identical rise in hepatic glucose production [epinephrine: 0.72 +/- 0.08 mmol/(86 min X 100 g BW); phenylephrine: 0.68 +/- 0.07 mmol/(86 min X 100 g BW) as their continuous administration (epinephrine: 0.78 +/- 0.06 mmol/(86 min X 100 g BW); phenylephrine: 0.74 +/- 0.09 mmol/(86 min X 100 g BW)]. Inhibition by insulin (100 mU/liter) given either continuously or intermittently (3 min on/off intervals; dose reduction -50%) was equipotent for epinephrine- and phenylephrine-stimulated hepatic glucose production. When the off period was doubled to 6 min, thereby reducing the total insulin dose to 33%, no significant suppression of epinephrine- and phenylephrine-stimulated hepatic glucose production was observed. From this we conclude that 1) the effect on hepatic glucose production of pulsatile (3 min on/off, dose reduction 50%) and continuous administration is equipotent for the respective action of epinephrine, phenylephrine as well as of insulin; and 2) insulin is more effective (P less than 0.02) in inhibiting hepatic glucose production stimulated by an alpha-agonist (phenylephrine; 5.0 microM) than in counteracting alpha + beta-agonist action (epinephrine; 0.4 microM). The characteristics of hepatic glucose release as stimulated by alpha- and/or beta-adrenergic agonists and its inhibition by continuously or intermittently infused insulin were simulated and described by a computer model. Thereby, no qualitative difference could be demonstrated in alpha- vs. beta-adrenergic agonists action on stimulated hepatic glucose production.

Animals↗
PubMed1981

Enzyme electrodes as practical biosensors.

An enzyme can be combined with an electrochemical sensor to produce an electrode that will measure the substrate for that enzyme. Such electrodes, known as enzyme electrodes, have enabled assay of many compounds of biochemical interest. However, they remain largely unexploited in medical measurement. The review gives the basic principles and describes electrodes used in biological solutions, together with an outline of the problems. The development of enzyme electrodes for continuous in vivo monitoring is emphasised.

Blood Glucose↗
PubMed1982

Intensive conventional and insulin pump therapies in adult type I diabetes. A crossover study.

We examined the relative efficacy of two modes of insulin therapy in five patients with insulin-dependent diabetes. Using a crossover protocol, therapy with multiple insulin injections was compared with the use of continuous subcutaneous insulin infusion (pump therapy); both therapies were regulated by home blood glucose monitoring. Although both therapies were equally effective during 2 to 4 days of inpatient management, pump therapy was clearly superior in the outpatient setting. Mean plasma glucose and hemoglobin A1c concentrations and the frequency of hypoglycemic reactions were significantly less with pump therapy despite apparently equal compliance with both therapies. We conclude that in compliant adult patients with type I diabetes continuous insulin infusion is more effective in achieving normalization of plasma glucose concentration than intensified conventional therapy in the outpatient setting. Although these patients found pump therapy preferable to intensive conventional therapy, the superiority of pump therapy is not explained by this bias. Whether these results are applicable in a more standard treatment setting remains to be established.

Adult↗
PubMed2006

Improving glycemic control: the case for self-monitoring blood glucose levels.

Diabetes can be potentially identified, monitored, treated, and prevented more easily now than at any other time in history. Yet, the prevalence of diabetes continues to grow and the complications associated with it continue to afflict millions of Americans. Glycemic control, or the maintenance of appropriate levels of blood sugar, measured through the self-monitoring of blood glucose or a glycated hemoglobin test, represents the best opportunity for persons with diabetes to prevent complications by helping them understand the effect of their lifestyle choices and medications on their health. Despite the numerous advantages of glycemic control, a number of barriers prevent individuals from monitoring their blood sugar concentrations and achieving the health benefits that come with the proper understanding of their condition.

Blood Glucose↗
PubMed2006

A patient with severe, recurrent hypoglycemia and glycemic lability who underwent islet transplantation.

BACKGROUND: A 48-year-old woman who was diagnosed with type 1 diabetes at 5 years of age presented to our Clinical Islet Transplant Program with severe, recurrent hypoglycemia and glycemic lability. She was diligent with her diet, used a continuous subcutaneous insulin infusion pump (32 U per day), and monitored her glucose levels typically eight times a day. The patient usually had one hypoglycemic reaction a day, experienced a severe reaction once a month, and had marked variability of her glucose values. On presentation, her HYPO score was 584 and her lability index was 868 mmol/l(2)/h per week. INVESTIGATIONS: HYPO score, lability index score, screening for diabetes complications, and routine pretransplant evaluation. DIAGNOSIS: Severe, recurrent hypoglycemia and glycemic lability associated with type 1 diabetes. MANAGEMENT: The patient underwent islet transplantation. Post-transplant, the problems with hypoglycemia abated and excellent stable glycemic control was attained, although some side effects from the immunosuppressive drug, sirolimus, were evident. Insulin was reinstituted 2.5 years after surgery, at lower doses than before the transplant because of deterioration in graft function. Occasional episodes of hypoglycemia have occurred and some glycemic lability has recurred, although endogenous insulin secretion is still preserved.

Blood Glucose↗
PubMed1995

Effect of halothane anesthesia on glucose utilization and production in adolescents.

BACKGROUND: It should be possible to avoid variations in plasma glucose concentration during anesthesia by adjusting glucose infusion rate to whole-body glucose uptake. To study this hypothesis, we measured glucose utilization and production, before and during halothane anesthesia. METHODS: After an overnight fast, six adolescents between 12 and 17 yr of age were infused with tracer doses of [6,6-2H2]glucose for 2 h before undergoing anesthesia, and the infusion was continued after induction, until the beginning of surgery. Plasma glucose concentration was monitored throughout, and free fatty acids, lactate, insulin, and glucagon concentrations were measured before and during anesthesia. RESULTS: Despite the use of a glucose-free maintenance solution, plasma glucose concentration increased slightly but significantly 5 min after induction (5.3 +/- 0.4 vs. 4.5 +/- 0.4 mmol.l-1, P < 0.05). This early increase corresponded to a significant increase in endogenous glucose production over basal conditions (4.1 +/- 0.4 vs. 3.6 +/- 0.2 mg.kg-1.min-1, P < 0.05), with no concomitant change in peripheral glucose utilization. Fifteen minutes after induction, both glucose utilization and production rates decreased steadily and were 20% less than basal values by 35 min after induction (2.9 +/- 0.3 vs. 3.6 +/- 0.2 mg.kg-1.min-1, P < 0.05). Similarly, glucose metabolic clearance rate decreased by 25% after 35 min. Despite the increase in blood glucose concentration, anesthesia resulted in a significant decrease in plasma insulin concentration. CONCLUSIONS: These data suggest that halothane anesthesia per se affects glucose metabolism. The decrease in peripheral glucose utilization and metabolic clearance rates and the blunted insulin release question the relevance of glucose infusion in these clinical settings.

Adolescent↗
PubMed1993

Interaction of Propionibacterium acnes with skin lipids in vitro.

Propionibacterium acnes is the predominant microbial resident within the pilosebaceous follicles of sebum-rich areas of human skin. This study investigated the effects of known hydrophobic components of sebum on the physiology and nutrition of this microorganism, grown anaerobically at 33 degrees C, under defined conditions using continuous culture techniques. The medium used was chemically defined, comprising eight amino acids, with glucose as the main carbon energy source, and the culture pH was maintained at 5.6. The range of sebum lipids assayed was based on the C18 monounsaturated fatty acid 9-cis-octadecenoic acid (oleic acid). Stock micronized solutions were aseptically pulsed into continuous cultures in the presence and absence of glucose, and nutritional effects monitored. None of the lipid substrates significantly affected P. acnes growth either in terms of maximum specific growth rate (mu max) or final culture biomass yield. Glycerol (3 mg ml-1) was found to be a poor carbon/energy source in comparison to glucose. Bacterial cells did, however, adhere with varying degrees, to the different lipid species, with maximum adherence occurring with the free fatty acid. This observation was confirmed by preliminary uptake experiments using [14C]oleic acid. The interactive site for cell adherence may be the lipid-fibrillar layer associated with the cell surface of P. acnes, as discerned in electron microscopical studies. The findings of this investigation suggest that one function of the P. acnes lipase may be to aid colonization within the pilosebaceous follicle, by promoting cell adherence to components such as oleic acid.

Glucose↗
PubMed1985

Gas chromatographic assay for in vitro complementation of Pseudomonas aeruginosa mutants deficient in nitrate reduction.

An electron capture gas-chromatographic technique was developed to continuously measure nitrate (NO3-) reduction during in vitro complementation tests with extracts from Pseudomonas aeruginosa mutants deficient in both assimilatory and dissimilatory nitrate reduction as a result of a single genetic mutation. The procedure involves coupling nitrate reduction to nitrous oxide (N2O) evolution via a series of reactions specific to the denitrification pathway. The assay was dependent on nitrate concentration, and optimal activity was obtained with a final concentration of 0.2% potassium nitrate. The reduction exhibited a stoichiometry of 2:1 (NO3-/N2O), and succinate was the best electron source for the reaction, followed by glucose, pyruvate, and malate. The technique can also be used for continuously monitoring nitrate reduction. The optimal nitrite concentration in the nitrite reductase assay was 0.025%. The initial complementation studies of mutant extracts demonstrated that at least two genes are shared between the two nitrate reduction pathways in P. aeruginosa.

Chromatography, Gas↗
PubMed1990

Effects of stress and exercise on rat hippocampus and striatum extracellular lactate.

Extracellular lactate was continuously monitored (lactography) to determine the effect of various stressors to assess glucose metabolism in the rat hippocampus and striatum. It appeared that immobilization, emotional stress, and exercise (physiological stress) all resulted in an increase in hippocampal extracellular lactate. Exercise had the most pronounced effect. These increases were different for rats raised in different laboratories. Only during exercise a transient increase in lactate was seen in striatum. Peripheral infusions of epinephrine and/or corticosterone did not affect the basal levels of hippocampal lactate. Adrenodemedullated rats showed an attenuated lactate increase compared with control rats during and shortly after exercise. Administration of ipsapirone, an anxiolytic drug, attenuated the stress-induced formation of the hippocampal lactate. The present study demonstrates the usefulness of lactography to monitor regional brain metabolism in freely moving animals, exposed to various stressors, breeding conditions, or drugs. The observed different responsiveness of the two brain-region studies emphasizes the different involvement of the striatum and hippocampus in motor and emotional behavior, respectively. Lactate formation is stimulated by excitatory neuronal activity, presumably originating in the cerebral cortex, although adrenal hormones appear to contribute.

Adrenal Medulla↗
PubMed1988

Utilisation of energy substrates in treadmill-exercised domestic fowl (Gallus gallus domesticus): blood glucose.

1. Blood glucose concentration, glucose turnover and gas exchange were monitored in adult male domestic fowl at rest and during 90 min of continuous treadmill exercise. 2. During exercise oxygen consumption increased to about three times its resting value. Blood glucose concentration fell by 26% by the end of exercise. 3. Blood glucose turnover was not altered by exercise and oxidation showed only a moderate increase (35%). Glucose oxidation accounted for 23% of the total energy expenditure at rest and this value fell to 10% during exercise. At the same time the plasma free fatty acid concentration rose to three times its resting value suggesting an increased mobilisation of this substrate. 4. It is concluded that during exercise of this relatively moderate intensity glucose is a quantitatively minor fuel for the working muscles.

Animals↗
PubMed1996

Enhanced sympathetic nervous system activity. The linchpin between insulin resistance, hyperinsulinemia, and heart rate.

This study was undertaken to see whether insulin resistant individuals, who are chronically hyperinsulinemic, have a higher heart rate (HR) than insulin sensitive, normoinsulinemic subjects. A total of 45 normotensive, nondiabetic individuals had insulin-mediated glucose disposal quantified by the insulin suppression test. In an effort to minimize variables known to modify heart rate, such as diet, exercise, and emotional distress, heart rate was continuously monitored during sleep by an electronic device measuring RR intervals. The average heart rate (as calculated by a mean of 30,720 +/- 208 beats per subject over a monitoring time of 6.9 +/- 0.6 h) was significantly related (r = 0.61; P < .001) to insulin resistance as expressed by the steady-state plasma glucose (SSPG) response to a continuous infusion of glucose, insulin and somatostatin and to the plasma insulin response to a 75 g of oral glucose challenge (r = 0.51; P < .001). These significant relationships between HR and both SSPG and plasma insulin response persisted after adjustment by stepwise regression analysis for age, gender distribution, body mass index, physical activity, and family history of either diabetes or hypertension. These results show that insulin resistant individuals, with compensatory hyperinsulinemia, have a higher nocturnal heart rate: a finding consistent with the possibility that the increased nocturnal heart rates are secondary to insulin-induced sympathetic activity.

Adult↗
PubMed1975

Growth in vitro and metabolism of Plasmodium vinckei chabaudi.

An in vitro system, based on the rocker dilution technic, has been developed that supports intraerythrocytic growth of a rat-adapted strain of Plasmodium vinckei chabaudi from ring to schizont stages; some reinvasion was obtained, although invariably, this was associated with a decrease in parasite numbers. Pertinent features were the very high buffer content of the medium and the low oxygen tension of the gaseous phase. Lactate production, glucose utilization, and 3H-leucine and 3H-adenosine incorporations were investigated for their suitability to monitor parasite growth. Throughout an 18-hr incubation there was a continuous and increasing production of lactate and utilization of glucose, which correlated well with the development of the parasites from ring to schizont stages. During the same period, there was a low but continuous and increasing incorporation of 3H-leucine into parasite protein. However, 3H-adenosine was incorporated only for the 1st hr of incubation, after which time no net incorporation occurred. Parasites grew normally from ring to schizont stages even in the absence of adenosine from the dilution medium.

Adenosine↗
PubMed1990

[Antidiabetic treatment and monitoring during pregnancy in diabetes].

In pregnant diabetic women one of the goals of antidiabetic treatment and monitoring is to maintain blood glucose near normal values between 4.4 and 6.1 mmol/l. If possible such values should be obtained before conception. To reach these goals four components of health care delivery are of major importance. Education dealing with contraception and planification of the pregnancy, diet modified according to the state of pregnancy, self blood glucose monitoring to allow anticipatory optimized insulin therapy. During pregnancy the systematic use of continuous subcutaneous insulin infusion does not seem to be associated with any significant benefit dealing with metabolic control or the perinatal and neonatal morbidity and mortality. In pregnant diabetic patients the usefulness of the dosage of glycated haemoglobin is limited due to the spontaneous fluctuations of this value during pregnancy, as well as the delay of the variation of this index during a period of poor glycemic control. In this condition glycated proteins as fructosamine may be more useful but many technical problems for this determination are still to be solved.

Biomarkers↗
PubMed1996

Evaluation of a pharmaceutical care model on diabetes management.

OBJECTIVE: To assess the effectiveness of a pharmaceutical care model on the management of non-insulin-dependent diabetes mellitus (NIDDM) in urban African-American patients. DESIGN: Eligible patients were randomized to either a pharmacist intervention or control group and followed over a 4-month period. Patients in the intervention group received diabetes education, medication counseling, instructions on dietary regulation, exercise, and home blood glucose monitoring, and evaluation and adjustment of their hypoglycemic regimen. Patients in the control group continued to receive standard medical care provided by their physicians. SETTING: A university-affiliated internal medicine outpatient clinic. PARTICIPANTS: The study population consisted of urban African American patients with NIDDM currently attending the clinic. MAIN OUTCOME MEASURES: Primary outcome measures included fasting plasma glucose and glycated hemoglobin concentrations. Secondary outcome endpoints included blood pressure, serum creatinine, creatinine clearance, microalbumin to creatinine ratio, total cholesterol, triglycerides, high-density lipoprotein, and low density lipoprotein concentrations. Quality-of-life assessments were performed in both groups at baseline and at the end of the study. RESULTS: Thirty-nine patients (17 intervention, 22 control) completed the study. The intervention group consisted of 12 women and 5 men with a mean +/- SD age of 59 +/- 12 years, total body weight (TBW) of 93 +/- 22 kg, body mass index (BMI) of 34 +/- 7 kg/m2, and duration of NIDDM 6.8 +/- 6.5 years. The control group consisted of 15 women and 7 men with a mean age of 65 +/- 12 years, TBW of 88 +/- 19 kg, BMI of 33 + 7 kg/m2, and a duration of NIDDM of 6.2 +/- 4.8 y. Significant improvement in glycated hemoglobin (p = 0.003) and fasting plasma glucose (p =0.015) was achieved in the intervention group. No change in glycemia was observed in the control subjects. Statistically significant differences in the final glycated hemoglobin (p = 0.003) and fasting plasma glucose (p = 0.022) concentrations were noted between groups. No significant changes in blood pressure control, lipid profile, renal function parameters, weight, or quality-of-life measures were noted within or between groups. CONCLUSIONS: Our data demonstrate the effectiveness of pharmaceutical care in the reduction of hyperglycemia associated with NIDDM in a group of urban African-American patients.

Aged↗
PubMed1980

Metabolism of Specifically Labeled Glucose, Glucose 1-Phosphate, and Glucose 6-Phosphate via the Oxidative Pentose Phosphate Cycle in a Reconstituted Spinach Chloroplast System in Darkness and in the Light.

Using isolated spinach (hybrid 424) chloroplasts deprived of their envelopes (reconstituted chloroplast system), the metabolism of glucose, glucose 1-phosphate, and glucose 6-phosphate via the oxidative pentose phosphate cycle was analyzed. The activity of oxidative pentose phosphate cycle was monitored by continuous sampling of the CO(2) released during the decarboxylation process of 6-phosphogluconate.The rate of CO(2) released in the dark from [C-1-(14)C]glucose 6-phosphate was 4 to 6 micromoles per milligram chlorophyll per hour. A CO(2) release from the C-6 position of [C-6-(14)C]glucose 6-phosphate was hardly measurable within 60 minutes of incubation. Glucose 1-phosphate was readily converted to glucose 6-phosphate without externally added glucose bisphosphate and was metabolized via the oxidative pentose phosphate cycle. The phosphorylation of glucose to glucose 6-phosphate was mediated by hexokinase present in the reconstituted system. This step was rate-limiting for the over-all reaction of the oxidative pentose phosphate cycle with glucose being the substrate (0.5 micromoles per milligram chlorophyll per hour). Addition of hexokinase increased the rate of CO(2) release to 5 micromoles per milligram chlorophyll per hour.The flow of carbon through the oxidative pentose phosphate cycle was greatly reduced upon the addition of NADPH and ATP. Whereas NADPH inhibited the metabolism of [C-1-(14)C]glucose 6-phosphate via the oxidative pentose phosphate cycle, ATP stimulated carbon flow into the 3-phosphoglycerate, dihydroxyacetone phosphate, and bisphosphates pools via the glycolytic pathway mediated by phosphofructokinase. This regulatory phenomenon could also be demonstrated with the reconstituted system undergoing a dark-light-dark transition. Data are presented indicating the conditions under which glucose 6-phosphate or glucose 1-phosphate are metabolized via the oxidative pentose phosphate cycle and the glycolytic pathway.

Journal Article↗
PubMed1997

[Treatment and glycemic control of 1200 diabetic patients enrolled at the National Institute of Disease-Disability Insurance diabetes convention].

We have studied the characteristics of insulin therapy and home blood glucose monitoring of 1.200 diabetic patients (590 males, 610 females), mainly type I adults (age: 43 +/- 19 years, mean +/- 1 SD), attending a licensed diabetes center in Belgium which benefits from a National Health Service convention system for providing education and home blood glucose monitoring kits and disposables to diabetic subjects. 50% of these patients were treated with 2 daily insulin injections, while 22% were treated with 3 and 24% with 4 daily injections. 4% of the subjects were treated with a continuous subcutaneous insulin infusion. Patients treated with four daily injections were younger than those treated with other insulin schemes (p < 0.001). Home blood glucose monitoring strip consumption was 2.2 patient-1 day-1. The mean HbA1C level was 8.63 +/- 1.55% [8.54 +/- 1.46 in males and 8.72 +/- 1.62% in females (NS)]. In more than one third of the subjects treated with injections, HbA1C was lower than 8% HbA1C was also below 8% in 50% of patients using 1100-1200 strips year-1.

Adolescent↗