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At least 757 records · Page 42Linked to original sources
PubMed1991

On-line monitoring of extracellular brain glucose using microdialysis and a NADPH-linked enzymatic assay.

A method to monitor extracellular glucose in freely moving rats, based on intracerebral microdialysis coupled to an enzyme reactor is described. The dialysate is continuously mixed with a solution containing the enzymes hexokinase and glucose-6-phosphate dehydrogenase, and the fluorescence of NADPH formed enables the on-line registration of extracellular glucose. The method is applied to monitor changes in extracellular brain glucose during the infusion of glucose, electrically induced seizure, immobilization stress, and repetitive hypoxia. After glucose loading or after seizure, hippocampus dialysate glucose concentration was increased transiently. During immobilization, there was a short-lasting decrease and, thereafter, an increase in the extracellular hippocampus glucose. During repetitive hypoxia in rats with a unilaterally occluded carotid artery, the content of glucose of striatal dialysates followed closely changes in blood pressure. These results illustrate the usefulness of the method in studying changes in brain glucose concentrations under pathological and physiological conditions.

Animals↗
PubMed1984

Increased fetal activity with low maternal blood glucose levels in pregnancies complicated by diabetes.

Ten diabetic pregnant women were studied during the thirty-sixth to fortieth weeks of gestation to determine whether maternal blood glucose levels influence fetal activity. Maternal blood glucose level was monitored and controlled utilizing an artificial pancreas (Biostator) while fetal activity and heart rate were quantitated by continuous ultrasonic and electrocardiac fetal monitoring. Fetal activity was confirmed independently by a maternal controlled event marker. There was no difference in fetal movement with heart rate accelerations between periods of maternal normoglycemia defined as blood glucose levels between 60 and 140 mg/dl (3.3-7.8 mMol/L) and periods of maternal hyperglycemia (blood glucose level greater than 140 mg/dl or 7.8 mMol/L). Maternal blood glucose levels of less than 60 mg/dl (3.3 mMol/L) were accompanied by a significant (p less than 0.001) increase in fetal activity (19.9 +/- 3.9 SEM episodes of fetal movement per 20-minute observation period versus 8.0 +/- 5 episodes during periods of hyperglycemia). These observations indicate that hyperglycemia does not stimulate fetal activity and that the obstetric practice of beverages with high glucose content administered during antepartum testing (in an attempt to increase fetal movement) should be reevaluated in diabetic women.

Adult↗
PubMed1997

Metabolic control and renal dysfunction in type I glycogen storage disease.

This study was undertaken to determine the effect on renal function of continuous glucose therapy from early childhood. Twenty-three subjects, median age 13.9 years, range 5.9-26.9 years, with type I glycogen storage disease (GSDI) treated with continuous glucose therapy from a median age of 1.3 years, range 0.1-12.9 years, had 24 h monitoring of metabolites and glucoregulatory hormones on their home feeding regimen to assess metabolic control at approximately yearly intervals for a median duration of 8 years. During the most recent evaluation, 24 h urinary albumin excretion rate (AER), kidney size, and creatinine clearance (Ccr) were measured. CCr was unrelated to age and was increased (> 2.33 ml/s per 1.73 m2) in 10/23 (43%). Mean kidney length exceeded 2SD in 16/23 (70%). AER was normal in all five subjects < 10 years and was increased (> 10 micrograms/min) in 8/23 (35%), all > 10 years of age. AER was significantly greater in subject of similar age who started continuous glucose therapy later in childhood and was significantly higher in subjects with lower mean 24 h plasma glucose concentrations and higher mean 24 h blood lactate concentrations, both at the time of assessment of renal function and over the preceding 5 years. GSDI subjects with persistently elevated concentrations of blood lactate, serum lipids and uric acid are at increased risk of nephropathy. Optimal dietary therapy instituted early in life may delay, prevent, or slow the progression of renal disease.

Adolescent↗
PubMed1990

Lack of effect of drinking water barium on cardiovascular risk factors.

Higher cardiovascular mortality has been associated in a single epidemiological study with higher levels of barium in drinking water. The purpose of this study was to determine whether drinking water barium at levels found in some U.S. communities alters the known risk factors for cardiovascular disease. Eleven healthy men completed a 10-week dose-response protocol in which diet was controlled (600 mg cholesterol; 40% fat, 40% carbohydrate, 20% protein; sodium and potassium controlled at the subject's pre-protocol estimated intake). Other aspects of the subjects' lifestyles known to affect cardiac risk factors were controlled, and the barium content (as barium chloride) of the drinking water (1.5 L/day) was varied from 0 (first 2 weeks), to 5 ppm (next 4 weeks), to 10 ppm (last 4 weeks). Multiple blood and urine samples, morning and evening blood pressure measurements, and 48-hr electrocardiographic monitoring were performed at each dose of barium. There were no changes in morning or evening systolic or diastolic blood pressures, plasma cholesterol or lipoprotein or apolipoprotein levels, serum potassium or glucose levels, or urine catecholamine levels. There were no arrhythmias related to barium exposure detected on continuous electrocardiographic monitoring. A trend was seen toward increased total serum calcium levels with exposure to barium, which was of borderline statistical significance and of doubtful clinical significance. In summary, drinking water barium at levels of 5 and 10 ppm did not appear to affect any of the known modifiable cardiovascular risk factors.

Adult↗
PubMed1985

Provocation test for children with bronchial asthma monitored by 81mKr ventilation and perfusion lung scans.

A provocation test of bronchial asthma was performed on two children. The test involved the continuous inhalation of krypton-81m gas and intermittent intravenous injections of krypton-81m glucose solution. The patient's response was carefully monitored in order to clarify the relationship between the time of the appearance and the intensity of ventilation and perfusion defects. The bronchial sensitivity of each patient was determined according to the dose of allergen or bronchoconstrictor delivered before the first ventilation defects were observable. The test was sensitive enough for the children not to develop asthmatic symptoms during and after the test. The results showed that perfusion defects appeared after ventilation defects and were less intense. The perfusion defects disappeared rapidly and before the ventilation defects had become undetectable.

Adolescent↗
PubMed1984

Continuous noninvasive monitoring of pH and temperature in rat Walker 256 carcinoma during normoglycemia and hyperglycemia.

The extracellular pH and temperature of Walker 256 carcinoma and of normal subcutaneous tissue were measured continuously in unanesthetized female Sprague-Dawley rats for up to 20 hours following glucose or galactose administration. The pH was monitored with flexible glass electrodes contained in micropore chambers implanted in the flank of a rat. Temperature was measured with miniature thermistor probes incorporated in the tumor or in subcutaneous tissue. The pH in the untreated Walker 256 carcinoma decreased linearly from approximately 7.3 to 6.2 with increasing tumor mass up to 50 g. Administration of glucose (6 g/kg body wt, ip) in tumor-bearing rats increased glucose concentrations in blood and tumor, as well as lactic acid concentration in tumor, and had no significant effect on lactic acid concentration in blood. Plasma volume was not affected by either glucose or galactose loading as compared to that in rats given saline alone. However, the blood viscosity increased by up to 30% within 30 minutes after galactose injection, but not after glucose injection, and this significant difference in viscosities persisted for approximately 6 hours after glucose and galactose injections. In small tumors (less than 10 g), a decrease of up to 1 pH unit was observed within 6 hours after glucose administration, and the return of pH to pretreatment values began about 10 hours after glucose injection. Response of large ulcerated tumors (greater than 20 g) was not as uniform; the pH decreased by about 0.5 to 1 pH unit for only a brief period. After galactose injection, pH in some tumors remained unchanged, whereas in others an average decrease of about 0.2 pH units was observed. The pH in normal tissue was not affected by glucose or galactose administration. Both glucose and galactose decreased tumor temperature by about 7 degrees C.

Animals↗
PubMed1995

Continuous measurement of ATP by 31P-NMR in term human dually perfused placenta in vitro: response to ischemia.

ATP was examined in dually perfused term human placentas by using 31P-nuclear magnetic resonance (NMR) spectroscopy. 31P-NMR spectra were acquired every 30 min starting approximately 30 min after establishing fetal and maternal perfusions, and maternal perfusate samples were obtained to monitor glucose utilization, lactate production, and human chorionic gonadotropin (hCG) and human placental lactogen (hPL) release. In continuous-perfusion experiments, placentas were perfused as long as 10 h. ATP increased and Pi fell after initiation of perfusion. Fetal volume loss was < 2 ml/h, and constant production of hCG, hPL, and lactate as well as constant utilization of glucose were observed. In additional experiments, ischemia was produced by halting maternal and fetal perfusion pumps after a 2-h control period. After 2, 3, or 4 h of ischemia, ATP decreased 46 +/- 17, 51 +/- 5, and 85% of control, respectively. When perfusion was reinitiated, ATP increased and was maintained for the duration of the experiment (an additional 2 h). Recovery of ATP after reperfusion was not paralleled by recovery in glucose utilization, lactate production, or hPL and hCG release. However, during the reperfusion period, fetal pressure was < 70 mmHg and fetal volume loss was < 2 ml/h. These investigations suggest that the dually perfused human placental lobule can maintain ATP for > or = 10 h. Although the perfused human placenta recovers ATP and maintains fetal perfusion volume after ischemia lasting up to 4 h, utilization of glucose, production of lactate, and production and release of hCG and hPL are impaired.

Adenosine Triphosphate↗
PubMed1982

Safety of continuous subcutaneous insulin infusion: metabolic deterioration and glycaemic autoregulation after deliberate cessation of infusion.

To assess the rate of metabolic deterioration and potential risks of failure of continuous subcutaneous insulin infusion during basal insulin delivery, we deliberately stopped infusion in nine insulin dependent diabetics. Plasma glucose, blood 3-hydroxybutyrate and plasma free insulin were measured for 9 h whilst the patients remained supine and fasting. Mean plasma glucose remained unchanged at normal fasting levels for the first hour, then rose to plateau at about 10 mmol/l until the end of the experiment. The final plateau level of glucose varied from patient to patient; two C-peptide secreting diabetics plateaued at low glucose levels. In contrast, blood 3-hydroxybutyrate rose progressively, without plateauing. PLasma free insulin concentrations fell during the withdrawal period and there was a highly significant negative correlation between free insulin and 3-hydroxybutyrate. No patient was more than mildly unwell after 9 h of insulin deprivation. We conclude that under these experimental conditions there is glycaemic autoregulation and that ketones may sometimes be a more appropriate monitor of insulin deficiency or loss of diabetic control than is glucose. Accidental failure of continuous subcutaneous insulin infusion and interruption of basal delivery in resting and fasting diabetics will probably not cause dangerous metabolic or clinical deterioration.

3-Hydroxybutyric Acid↗
PubMed2004

A wire-based dual-analyte sensor for glucose and lactate: in vitro and in vivo evaluation.

Continuous measurement of lactate is potentially useful for detecting physical exhaustion and for monitoring critical care conditions characterized by hypoperfusion, such as heart failure. In some conditions, it may be desirable to monitor more than one metabolic parameter concurrently. For this reason, we designed and fabricated twisted wire-based microelectrodes that can measure both lactate and glucose. These dual-analyte sensors were characterized in vitro by measuring their response to the analyte of interest and to assess whether they were susceptible to interference from the other analyte. When measured in stirred aqueous buffer, lactate sensors detected a very small amount of crosstalk from glucose in vitro, although this signal was less than 3% of the response to lactate. Glucose sensors did not detect crosstalk from lactate. Sensors were implanted subcutaneously in rats and tested during infusions of lactate and glucose. Each sensing electrode responded rapidly to changes in its analyte concentration, and there was no evidence of in vivo crosstalk. This study constitutes proof of the concept that oxidase-based, amperometric wire microsensors can detect changes in glucose and lactate during subcutaneous implantation in rats.

Animals↗
PubMed1991

The effects of continuous glucose infusion on blood, plasma, and brain glucose in anesthetized rats.

In models of cerebral ischemia, it is important to rigidly control brain glucose in the peri-ischemic period because alterations in brain glucose can affect the severity of the postischemic injury. The following study evaluated the effect of a continuous glucose infusion as a means of producing stable increases in brain glucose that could be monitored by measuring either blood or plasma glucose. Fifty-four halothane-anesthetized rats were studied. Rats received either no treatment (control group; N = 6), saline 2 ml/h (N = 24), or glucose 1 g/kg per h in saline 2 ml/h (N = 24). In the latter two groups, samples of blood, plasma, and brain glucose were obtained at either 30, 60, 120, or 180 min of the infusion (N = 6 per group per sample period). Saline infusion had no effect on either blood, plasma, or brain glucose. In contrast, glucose infusion produced a significant increase in all three variables, achieving plateau increases during the 60-180 min measurement periods [blood glucose = 197 +/- 20 mg/dl (mean +/- S.D.) at 60 min, 220 +/- 34 mg/dl at 120 min, and 217 +/- 22 mg/dl at 180 min versus control blood glucose = 89 +/- 10 mg/dl]. Regardless of the treatment group, there was excellent correlation between blood and plasma glucose (r = 0.99; P much less than 0.001), blood and brain glucose (r = 0.96; P much less than 0.001), and plasma and brain glucose (r = 0.97; P much less than 0.001). The authors conclude that continuous glucose infusions are an effective method to produce stable increases in brain glucose in experimental models; and, in contrast to other methods for achieving brain glucose increases, the brain glucose increases can be accurately assessed by measuring blood or plasma glucose.

Anesthesia↗
PubMed2002

Contribution of glycolytic and mitochondrial pathways in glucose-induced changes in islet respiration and insulin secretion.

The different roles of glycolytic and mitochondrial pathways in glucose-induced metabolic activation and insulin secretion were studied in islets of Langerhans. Single islets were perifused with 3 mM glucose together with agents affecting the production or consumption of ATP. Subsequently, glucose was raised to 11 mM and the effects of the agents on metabolic and secretory responses were evaluated. Metabolism was monitored continuously with an oxygen-sensitive microelectrode inserted into the islet. Insulin secretion was determined by assaying insulin in perifusate with ELISA. Inhibitors of mitochondrial ATP production reduced the metabolic and secretory response to glucose. When glycolytic ATP production was reduced, initial but not sustained glucose-stimulated insulin release was observed. Inhibition of mitochondrial pyruvate transport reduced the glucose-induced decline in pO(2). Although mitochondrial metabolism was eventually similar to normal, insulin release was only 20% of normal. Increased energy expenditure also changed the kinetics of the glucose-induced decline in pO(2) and decreased the insulin release by 50%. In conclusion, glucose-induced enhancement of insulin release was only seen when the rise of the sugar concentration triggered a rapid and sustained increase of mitochondrial metabolism. This activation of mitochondrial metabolism required a good metabolic state prior to the glucose challenge.

Animals↗
PubMed1991

A new generation of oral hypoglycemics. Their use, measurement, and effects on insurance risk assessment.

The increased use of oral hypoglycemics among the more than 14 million diabetics in the United States and the development of new pharmaceutical formulations requires the continued surveillance of their use in the insurance applicant population. Routine monitoring of urine glucose or even blood glucose or fructosamine measurements often fail to detect the diabetic using oral hypoglycemics. Urine analysis for the use of first generation sulfonylureas has shown a declining prevalence of their use due to the increased number of prescriptions written for newer and more effective drugs. In order to monitor the use of these second-generation oral hypoglycemics, an immunoassay was developed to detect the use of glyburide, 1-[4-[2-(5 chloro-2-methoxybenzamido) ethyl]-phenyl] sulfonyl]-3-cyclohexylurea. After testing in a defined population of known users of this class of sulfonylureas, the assay was applied to a random population of 12,000 applicants applying for life insurance. Results demonstrate the predictive value of this assay in determining the prevalence of use of this drug in the insurance-buying population and its assistance in risk assessment.

Diabetes Mellitus↗
PubMed1984

Research and practice in the treatment of insulin-dependent diabetes: a survey of 53 pediatric diabetologists.

New techniques are available for the treatment of children with insulin-dependent diabetes mellitus. These include more intensive methods of insulin delivery by multiple daily injections or continuous subcutaneous infusion by portable pumps combined with patient self-monitoring of blood glucose. Long-term diabetic control can be evaluated by measurement of glycosylated hemoglobin, HbA1 or HbA1c. Pediatric practitioners may be in doubt as to the extent to which these techniques should be incorporated into their own practices. In order to provide some guidance in this quandary, the treatment practices as of June 1982, of 53 physicians with a special interest in the treatment of diabetic children were surveyed by questionnaire. The respondents estimated that they cared for 12,350 diabetic patients less than 19 years of age. Among their patients, 72% received twice-daily injections of insulin, 3% received three or more injections daily, and only 195 patients (2.7% of the total) were treated with insulin pumps. Among patients older than 10 years of age, 50% performed self-monitoring of blood glucose four times daily on one or more days per week and 32% of these patients did so daily. Two thirds of the patients utilized glucose oxidase-impregnated strips for blood glucose estimation and the remainder used reflectance meters. Essentially all respondents utilized glycosylated hemoglobin to evaluate quality of control. The mean number of determinations was 3.8 per year. Reasons for introducing pump therapy or discontinuing its use, glycemic targets for pump patients, and experience with utilization of the pump are described.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2003

Frequency characterization of blood glucose dynamics.

Examples of the frequency range of blood glucose dynamics of normal subjects and subjects with diabetes are reported here, based on data from the literature. The frequency band edge was determined from suitable, frequently sampled blood glucose recordings using two methods: frequency domain estimation and signal reconstruction. The respective maximum acceptable sampling intervals, or Nyquist sampling periods (NSP), required to accurately represent blood glucose dynamics were calculated. Preliminary results based on the limited data available in the literature indicate that although blood glucose NSP values are higher in most diabetic subjects, values in some diabetic subjects are indistinguishable from those of normal subjects. High fidelity monitoring sufficient to follow the intrinsic blood glucose dynamics of all diabetic subjects requires a NSP of approximately 10 min, corresponding to a continuous frequency band edge of approximately 1 x 10(-3) Hz. This analysis provides key information for the design of clinical studies that include blood glucose dynamics and for the design of new glucose monitoring systems.

Blood Glucose↗
PubMed1980

Use of electrochemical sensors for on-line monitoring of ionized calcium, potassium, and glucose in whole blood of living dogs.

We report the development and evaluation of electrochemical sensors for continuous on-line measurement of whole-blood ionized calcium, potassium, and glucose in living animals. Ionized calcium and potassium are measured with ion-selective electrodes, by using a unique differential approach. A polarographic sensor coupled with a membrane with bound glucose oxidase is used in the glucose analyzer. The modular concept of instrument design permits one mainframe, computer, and pump system to house any analyzer module or a combination of modules. A small volume of venous blood (about 2 mL/h) is continuously withdrawn from the subject through a double-lumen catheter and pumped through the analyzer(s). Results of in vitro correlation studies and studies in normal dogs (including responses of ionized calcium, potassium, and glucose to various stresses) support the validity of the measurements.

Animals↗
PubMed2003

Early autonomic dysfunction in glucose-tolerant but insulin-resistant offspring of type 2 diabetic patients.

In type 2 diabetes, both insulin resistance and hyperglycemia are considered responsible for autonomic dysfunction, but the specific role of these two abnormalities is not clear. To test the specific role of insulin resistance on autonomic dysfunction, we studied 69 glucose-tolerant offspring of type 2 diabetic patients, comparing the most insulin-resistant tertile (IR) with the most insulin-sensitive tertile (IS) and comparable control subjects, all undergoing the oral glucose tolerance test, impedentiometry, 24-hour blood pressure and ECG monitoring, and an intravenous glucose tolerance test (IVGTT) followed by a euglycemic hyperinsulinemic clamp, with continuous blood pressure and ECG measurements. Sympathovagal balance was evaluated as low- to high-frequency ratio (LF:HF) by spectral analysis on R-R intervals. The change of systolic and diastolic blood pressure was calculated as [(day-night/d)]x100. In IR, the changes of systolic and diastolic blood pressure were significantly lower versus IS (9.2+/-5.0% versus 12.4+/-3.6%, P<0.02; 13.2+/-6.5% versus 17.4+/-5.2%, P<0.02). During the night, LF:HF fall was reduced in IR (43.1+/-21.0 versus 61.4+/-16.9, P<0.02). Hyperinsulinemia (IVGTT) rapidly and significantly increased LF:HF in IR (4.9+/-3.3 versus basal: 2.3+/-1.4, P=0.03) but not in IS. In offspring of type 2 diabetic patients with normal glucose tolerance and normal blood pressure values, insulin resistance is associated with abnormal control of blood pressure and sympathetic activation. Insulin resistance may therefore be responsible for some early derangements of the autonomic nervous tone control and thus contributes to increase the incidence of arterial hypertension and/or diabetes.

Adult↗
PubMed2003

Quantitative on-line monitoring of hippocampus glucose and lactate metabolism in organotypic cultures using biosensor technology.

Quantitative glucose and lactate metabolism was assessed in continuously perfused organotypic hippocampal slices under control conditions and during exposure to glutamate and drugs that interfere with aerobic and anaerobic metabolism. On-line detection was possible with a system based on slow perfusion rates, a half-open (medium/air interface) tissue chamber and a flow injection analytic system equipped with biosensors for glucose and lactate. Under basal conditions about 50% of consumed glucose was converted to lactate in hippocampal slice cultures. Using medium containing lactate (5 mm) instead of glucose (5 mm) significant lactate uptake was observed, but this uptake was less than the net uptake of lactate equivalents in glucose-containing medium. Glucose deprivation experiments suggested lactate efflux from glycogen stores. The effects of drugs compromising or stimulating energy metabolism, i.e. 2-deoxyglucose, 3-nitropropionic acid, alpha-cyano-4-hydroxycinnamate, l-glutamate, d-asparate, ouabain and monensin, were tested in this flow system. The data show that maintaining Na+ and K+ gradients consumed much of the energy but do not support the hypothesis that l-glutamate stimulates glycolysis in hippocampal slice cultures.

Animals↗