Notes on the glucose oxidase method

Design, synthesis and biological evaluation of novel 5-(imidazolyl-methyl) thiazolidinediones as antidiabetic agents

A newly designed series of imidazolyl-methyl- l-2,4-thiazolidinediones 9 (a-m) were synthesized and In Silico studies were carried out to rationalize their anti-diabetic activity. Generally, all newly synthesized thiazolidinediones had anti-hyperglycemic activity compared with a diabetic-control group, without toxicity in 3T3 cells (viability ≥ 90%). These studies revealed that the compounds 9e and 9b (11∗10^-6mol/kg) lowered blood glucose more effectively when compared to pioglitazone at the same dose. Following the administration of compound 9e, no weight gains or any serious side effects on liver and pancreas were observed. Moreover, the glucose consumption assay results showed a significant glucose-lowering effect (p < 0.001) in HepG2 cells, which were exposed to 11 mM of glucose at concentrations of 1.25-10 mM of compound 9e. Also, the PPAR-γ gene expression study revealed that pioglitazone and 9e showed similar behavior relative to the control group.

Preconception air pollution exposure and glucose tolerance in healthy pregnant women in a middle-income country

BACKGROUND

Preconception exposure to air pollution has been associated with glucose tolerance during pregnancy. However, the evidence in low and middle-income countries (LMICs) is under debate yet. Therefore, this study aimed to assess the relationship between exposure to ambient particulate matter (PM) and traffic indicators with glucose tolerance in healthy pregnant women in Sabzevar, Iran (2019).

METHODS

Two-hundred and fifty healthy pregnant women with singleton pregnancies and 24-26 weeks of gestations participated in our study. Land use regression (LUR) models were applied to estimate the annual mean of PM1, PM2.5 and PM10 at the residential address. Traffic indicators, including proximity of women to major roads as well as total streets length in 100, 300 and 500 m buffers around the home were calculated using the street map of Sabzevar. The oral glucose tolerance test (OGTT) was used to assess glucose tolerance during pregnancy. Multiple linear regression adjusted for relevant covariates was used to estimate the association of fasting blood glucose (FBG), 1-h and 2-h post-load glucose with PMs and traffic indicators.

RESULTS

Exposure to PM1, PM2.5 and PM10 was significantly associated with higher FBG concentration. Higher total streets length in a 100 m buffer was associated with higher FBG and 1-h glucose concentrations. An interquartile range (IQR) increase in proximity to major roads was associated with a decrease of - 3.29 mg/dL (95% confidence interval (CI): - 4.35, - 2.23, P-value < 0.01) in FBG level and - 3.65 mg/dL (95% CI, - 7.01, - 0.28, P-value = 0.03) decrease in 1-h post-load glucose.

CONCLUSION

We found that higher preconception exposure to air pollution was associated with higher FBG and 1-h glucose concentrations during pregnancy.

Decreased glucose utilization in discrete brain regions of rat in thioacetamide-induced hepatic encephalopathy as measured with [3H]-deoxyglucose

To evaluate the possible contribution of bioenergetic failure in the particular brain regions to the pathomechanism of hepatic encephalopathy (HE), local cerebral metabolic rate for glucose (LCMRglue) was evaluated from [3H]-deoxyglucose uptake in frontal, visual and auditory cortex, striatum, cerebellum and medulla oblongata of rats with acute HE induced with a hepatotoxin--thioacetamide (TAA). HE caused a decrease of LCMRglue in all the regions studied. The strongest decrease (about 65%) was noted in hippocampus and cerebral cortex--the two regions rich in glutamatergic neurons. The results indicate a possible link between decreased energy metabolism and impaired excitatory, glutamatergic neurotransmission--the two factors whose contribution to HE has so far been implicated separately.

Glucose phosphorylation rate in rat parietal cortex during normoglycemia, hypoglycemia, acute hyperglycemia, and in diabetes-prone rats

Cerebral metabolic rate for glucose (CMRglc) was studied in rats using [6-14C]glucose. After intravenous injection, the radioactivity of the parietal cortex was corrected for loss of labeled CO2 and divided by the integral of the arterial plasma glucose concentration, determined during tracer circulation. Treatment with insulin, resulting in plasma glucose concentrations less than 2.6 mmol/l, reduced CMRglc to 64% of the values found in control animals. CMRglc did not change in animals with acute hyperglycemia produced by intraperitoneal injection of a glucose solution or in diabetes-prone rats with or without insulin treatment.

Regional glucose phosphorylation rate in rat brain during acute ethanol intoxication

The effect of ethanol on regional cerebral metabolic rate for glucose (rCMRglc) was studied in rats using [6-14C]glucose. After intravenous injection, radioactivity was determined in 14 brain regions, corrected for loss of label, and divided by the integral of the arterial plasma glucose concentration measured during tracer circulation. When blood ethanol concentration was maintained at 6 g/l by intravenous infusion of ethanol for approximately 1 h, rCMRglc was found to be reduced significantly in 7 forebrain regions, compared to values of conscious control animals. In 7 further regions including brain stem regions, rCMRglc was not significantly reduced. We conclude that the effects of severe acute alcohol intoxication resemble those of global anesthesia.

Glucagon responses to intravenous arginine and oral glucose in insulin-dependent diabetic patients during six months conventional or continuous subcutaneous insulin infusion

To elucidate the impact of subcutaneous insulin infusion (CSII) treatment on the glucagon response to intravenous (IV) arginine and to oral glucose a 6-month prospective randomized study in insulin-dependent diabetics was carried out. The effects were investigated of CSII (7-patients) and conventional insulin treatment (UCT) (9 patients) on the changes in glucagon, growth hormone, glucose, lactate, glycerol, 3-hydroxybutyrate, and alanine to IV arginine and to oral glucose in insulin-dependent diabetics who were made euglycemic and isoinsulinemic using the artificial pancreas (Biostator, Miles, Elkhart, IN). HbA1c was significantly lower in the group treated by CSII. Despite the improved glycemic control no significant change in the responses of A-cell secretion to arginine or glucose challenges was found. In addition, there were no significant differences in hormone or metabolite values between the two groups at entry to the study or after 6 months of either therapy. Thus, normalization of the A-cell sensitivity to glucose in insulin-dependent diabetic subjects requires further amelioration of the intermediary metabolism than can be achieved with insulin pump treatment.

Regional cerebral glucose phosphorylation and blood flow after insertion of a microdialysis fiber through the dorsal hippocampus in the rat

Local cerebral glucose metabolism (LCMRglc) and local cerebral blood flow (LCBF) were studied following implantation of a microdialysis fiber in rat dorsal hippocampus. Recovery time after implantation varied from 0 to 24 h. All rats showed pronounced disturbances in LCMRglc and LCBF during the first 2 h of implantation. The changes consisted of (a) a general decrease in blood flow and glucose phosphorylation and (b) small areas (spots) around the fiber with increased glucose phosphorylation and decreased blood flow. Animals allowed to recover for 24 h demonstrated a near normalization of LCMRglu and LCBF, and the focal disturbances (spots) of glucose phosphorylation and blood flow disappeared. The slight reduction in blood flow and glucose metabolism at this time must be accepted, because extension of the recovery period beyond 24 h may give interpretation problems due to the developing gliosis.

Metabolism of exercising skeletal muscle during beta 1-selective adrenoceptor blockade

Concentrations of glycogen, glucose, glucose-6-phosphate and lactate in the lateral vastus muscle were measured in seven subjects before and after dynamic muscle exercise at a work load of 75% of each subject's maximal working capacity, and with and without intravenous administration of the beta 1-selective beta-adrenoceptor blocking agent, atenolol. Pulmonary oxygen uptake was measured during exercise. Heart rate and arterial blood pressure were measured throughout the study. Arterial concentrations of glucose, lactate and free fatty acids were measured at rest and during exercise. The muscle concentration of glycogen and the extent of glycogen depletion with exercise were not influenced by the beta 1-adrenoceptor blocker. Similarly, there was no change in the muscle concentrations of glucose, glucose-6-phosphate and lactate. Heart rate decreased at rest and during exercise. Arterial blood pressure was not influenced by beta-blockade. Pulmonary oxygen uptake decreased by 6.5%. The exercise induced rise in arterial blood concentration of free fatty acids was abolished by beta 1-selective beta-blockade. It is concluded that the decrease in lactate release from exercising muscles during beta 1-adrenoceptor blockade seen in other studies cannot be explained by an impaired breakdown of muscle glycogen. It may be inferred, however, that a reduced availability of free fatty acids in the exercising muscles during beta 1-selective (and non-selective) beta-blockade may enhance the combustion of pyruvic acid and thereby decrease the production of lactate.

Effects of a thiazide diuretic (hydroflumethiazide) and a loop diuretic (bumetanide) on the endocrine pancreas: studies in vitro

Treatment with thiazide diuretics causes an impairment of the glucose metabolism. To study whether this is due to a direct effect on the endocrine pancreas, the effects of the thiazide hydroflumethiazide on the release of glucagon, insulin, and somatostatin from the isolated perfused pancreas of normal and alloxan diabetic dogs were examined. Hydroflumethiazide at concentrations ranging from 1 to 50 micrograms/mL stimulated the normal secretion of glucagon (P less than 0.001), insulin (P less than 0.001), and somatostatin (P less than 0.001) in a dose-dependent manner. The normal hormone responses evoked by 50 micrograms/mL of the thiazide were, however, modified by the prevailing glucose level: higher insulin (P less than 0.05) and somatostatin (P less than 0.05) and lower glucagon (P less than 0.05) were obtained at the high glucose concentration of 11 mmol/L rather than at the low glucose concentration of 1.3 mmol/L. In alloxan diabetes, insulin secretion was almost extinct and did not respond to hydroflumethiazide, whereas glucagon was dose-dependently stimulated (P less than 0.001). In addition, we looked at the effect of the loop diuretic, bumetanide. The infusion of bumetanide at doses ranging from 0.5 to 3 micrograms/mL did not alter the release of glucagon, insulin, and somatostatin in the presence of 5.5 mmol/L glucose. The results suggest that hydroflumethiazide possesses the ability to directly stimulate A cell secretion in the normal and alloxan diabetic pancreas. Whether this effect is of clinical importance for the diminution in glucose tolerance observed during thiazide therapy remains, however, uncertain.

Double-tracer study of the fine regional blood-brain glucose transfer in the rat by computer-assisted autoradiography

Glucose is transported from blood to brain tissue by facilitated diffusion of limited capacity. The regional variation of the glucose transport capacity is not known in detail because methods used previously have been too gross to detect fine regional differences. Therefore, it is not known to what extent the glucose transport capacity varies in proportion to regional blood flow and metabolic rate. To resolve this question, we used double-tracer, dual-label autoradiography to measure blood-brain glucose clearance and blood flow simultaneously in hypo-, normal, and hyperglycemic rats. From the values of glucose clearance and blood flow at various plasma glucose levels, we calculated the affinity constant and maximal transport capacity of the glucose transport system. The transport capacity (Tmax) varied in approximate proportion to the blood flow and, by inference, the metabolic rate. In contrast, the affinity constant (Kt) did not vary systematically between the regions (mean value 7.1 mM). The variation of Tmax from 270 to 890 mumol hg-1 min-1 reflected a parallel variation of total regional capillary length and surface. We conclude from the study that the cerebral capillary is a fixed unit, i.e., that the number of glucose transporters per unit of capillary surface area is the same in all regions. Regional differences are the result of different capillary densities in the regions of the brain.

The effect of glucose upon restitution after transient cerebral ischemia: a summary

The study describes a reproducible model of complete brain ischemia in rats. Rats with different plasma glucose concentrations were exposed to 10 min of complete cerebral ischemia achieved by compression of neck vessels by a pneumatic cuff. All 30 rats, except one, in which pre-ischemic plasma glucose level were lower than 22 mM (range 1.6-22) survived 10 min complete ischemia and made a similar recovery. Ten rats with pre-ischemic plasma glucose levels above 22 mM (range 22-47.2) died from seizures in the post-ischemic period. Post-ischemic treatment of seizures and hyperglycemia in the hyperglycemic rats significantly improved recovery. In conclusion, pre-ischemic hyperglycemia above 22 mM impairs recovery after complete ischemia by inducing seizures, post-ischemic hyperglycemia and lactic acidosis.

Blood-brain transfer of galactose in experimental galactosemia, with special reference to the competitive interaction between galactose and glucose

The interaction between glucose and galactose during transport across the cerebral capillary endothelium was studied in anesthetized rats. Although galactose is present in the diet of suckling mammals and is a potential substrate for brain metabolism in adult mammals, its effect on glucose transport in adult rats is unknown. A kinetic model was formulated to analyze the effect of chronically elevated galactose levels on glucose transport in adult rats. The analysis indicated that galactose and glucose compete for the same transport mechanism in the cerebral capillary endothelium. The Tmax of glucose and galactose were both about 380 mumol 100 g-1 min-1 and the Kt of galactose (30 mM) was about three times that of glucose (10 mM). During prolonged galactosemia in adult rats, neither the Tmax, nor the Kt of either competitor changed substantially when compared with rats subjected to acute galactosemia. At 10 mM galactose in plasma in rats with acute galactosemia, the inhibition of glucose transport, simulated a 25% reduction of plasma glucose, and in rats with chronic galactosemia a 20% reduction. This moderate effect is in contrast to the effect of galactose in suckling rats in which 10 mM galactose in plasma reduced the glucose transport to a level corresponding to a 50% reduction of the plasma glucose concentration.

The effect of heating and central cooling on serum TSH, GH, and norepinephrine in resting normal man

The effects of central cooling and exterior heating on serum concentrations of thyrotropin (TSH), growth hormone (GH), and norepinephrine were studied in 10 normal males under resting conditions. Cooling was induced by ingestion of ice while the subjects were immersed in water of a temperature prone to elicit only minor cutaneous thermal reflexes. TSH and thyroid hormones changed neither during cooling nor during heating. Cooling induced a virtually complete suppression of GH-secretion whereas heating had the opposite effect: pronounced increase, also without previous cooling. Plasma norepinephrine rose by a factor of 2.5 and 1.7 during cooling and heating, respectively. It is concluded that the pituitary-thyroid system does not take part in short-term thermoregulation in man--as opposed to the situation in some smaller mammals. The mechanisms and the physiological role of the GH-responses to cooling and heating are as yet unknown, but the latter stimulus is an advantageous tool in clinical and pathophysiological studies of pituitary function as it is both safe and convenient.

Hyperglycemic ischemia of rat brain: the effect of post-ischemic insulin on metabolic rate

To identify the mechanism by which hyperglycemia impairs recovery after cerebral ischemia, cortical blood flow (CBF), cortical metabolic rate for oxygen (CMRO2), and the cortical phosphorylation rate for glucose (CPRg1c) were measured in rats 1 h after a global ischemic insult of the brain. A control group remained hyperglycemic after ischemia. The experimental group received insulin which reduced plasma glucose during the period of recirculation after ischemia. Thus, the brains of both groups were hyperglycemic before and during ischemia. The CMRO2 after ischemia was higher in insulin-treated rats than in hyperglycemic rats (250 vs 168 mumol . 100 g-1 . min-1) while the CPRg1c was lower (22 vs 58 mumol . 100 g-1 . min-1). We conclude that glucose-induced inhibition of oxygen consumption in brain contributes to the impaired recovery after ischemia.

Calculation of cerebral glucose phosphorylation from brain uptake of glucose analogs in vivo: a re-examination

The 2-deoxyglucose (2-DG) method of functional neuroanatomical mapping25 was re-examined in order to (1) obtain physical descriptions of the transfer constants K1 and k2, (2) estimate the changes of the 'lumped constant' with the condition of the experimental animals, and (3) examine the use of 3-O-methylglucose (3-O-MG) to estimate the fraction of unphosphorylated 2-DG in the tissue, and the value of the 'lumped constant'. The transfer constants K1 and k2 were shown to be simple exponential forms of the apparent permeability of the cerebral capillary endothelium to glucose and glucose analogs. The 'lumped constant' was shown to be influenced by any reduction of the ratio between glucose transport and glucose phosphorylation in the tissue, e.g. by hypoglycemia and increased glycolysis, while hyperglycemia and decreased glycolysis resulted in very minor changes of the 'lumped constant'. The glucose analog 3-O-MG was shown accurately to trace unphosphorylated 2-DG in brain and to be an index of the brain content of glucose and the regional value of the 'lumped constant'. In addition, 3-O-MG proved to be an accurate tracer of unphosphorylated 2-DG for experimental times as low as 10 min.

Blood-brain glucose transfer in spreading depression

Spreading depression in rat brain cortex is associated with a twofold increase of cerebral blood flow. It is not known whether this increase is coupled to increases of cerebral metabolic rate and glucose transport from blood to brain. During the passage of a single spreading depression, we measured blood-brain glucose transport and glucose metabolism in rat cerebral cortex by single intravenous injection of tracer glucose. Blood flow and tissue content of glucose were measure as well. Reduction of tissue glucose and the consequent increase of net transfer of glucose from blood to brain were consistent with a threefold increase of the consumption of glucose before the increase of blood flow. There was no increase of unidirectional blood-brain transfer.

Hyperglycemia in the reperfusion period hampers recovery from cerebral ischemia

Glucose treatment prior to cerebral ischemia is followed by similar metabolic and hemodynamic recovery (Siemkowicz & Gjedde 1980), and normalisation of brain extracellular ions (Siemkowicz & Hansen 1981). In view of this, the present study investigated whether post-ischemic hyperglycemia influenced recovery from cerebral ischemia. In rats which received 50% glucose during a 10 min period of cerebral ischemia, and which had a plasma glucose level of 28.5 mM after 10 min of recirculation, recovery was inferior to that of rats receiving either 8% NaCl or 0.9% NaCl (and hence the rats were normoglycemic). Furthermore, rats which had been rendered hyperglycemic (39 mM) prior to ischemia, and which had plasma glucose lowered to 15 mM by insulin treatment during ischemia, did not recover and died within 4 days. Conversely, rats with somewhat lower preischemic hyperglycemia (28 mM), and which had plasma glucose lowered to 12 mM by insulin treatment during ischemia, recovered as well as the normoglycemic rats. In conclusion, preischemic and postischemic hyperglycemia is detrimental to recovery from cerebral ischemia.

Brain uptake of mannitol and sucrose after cerebral ischemia: effect of hyperglycemia

The effect of 10 min cerebral ischemia on blood-brain barrier permeability to mannitol and sucrose was evaluated in normo- and hyperglycemic rats. In the period immediately after ischemia (1-4 min) the PS (permeability-surface area product) for mannitol was 159% +/- 75 of control (0.17 +/- 0.02 mg/100 g min) in the hyperglycemic rats (plasma glucose 8 mM) and 204% +/- 30 of control (0.09 +/- 0.02 mg/100 g min) in the hyperglycemic rats (plasma glucose 28 mM). Two hours after ischemia, PS for mannitol returned to the control levels in the normoglycemic rats and remained elevated in hyperglycemic animals. The mannitol/sucrose ratios-2.3 +/- 0.4 in normoglycemic rats and 2.6 +/- 0.1 in hyperglycemic rats-remained unchanged after ischemia. As there was no significant difference in the effects of ischemia on normo- and hyperglycemic rats, it was concluded that the deleterious effect of hyperglycemic on clinical recovery after cerebral ischemia in rats (Siemkowicz & Hansen 1978) is not related to enhancement of BBB damage.

Brain extracellular ion composition and EEG activity following 10 minutes ischemia in normo- and hyperglycemic rats

Hyperglycemia severely impairs the outcome from cerebral ischemia. In order to sort out whether impaired brain ion homeostasis contributes extracellular "K+], [Ca++], and [H+] concentrations, [K+]e, [Ca++]e and [H+]e, of the brain cortex, as well as the EEG, were monitored during and after 10 minutes of complete cerebral ischemia in normo- and hyperglycemic rats. In both groups, the EEG-activity disappeared in 10-20 seconds of ischemia, at a time when [K+]e, [Ca++]e and [H+]e started to increase. After about 1.5 min, [K+]e showed an abrupt increase and [Ca++]e a steep decrease in the normoglycemic group. In the hyperglycemic group the same event took place after about 3 min of ischemia. pHe decreased to 6.6 and 6.1 in the normoglycemic and hyperglycemic group, respectively. Following the ischemic episode [K+]e reached pre-ischemic level after 4 min, [Ca++]e after 13 min, and [H+]e after 30 min in both groups. Recovery of the EEG, however, was clearly different in the 2 groups. EEG-activity reappeared later in the hyperglycemic group and showed after one hour a pattern of burst-suppression activity while the normoglycemic group showed asynchronous activity resembling the control pattern. It is concluded that high glucose content in brain prior to ischemia - and hence lower brain pH during ischemia - does not interfere with the return of normal extracellular ion composition after cerebral ischemia, whereas the return and pattern of EEG activity is severely affected.

Effect of a beta 2-sympathomimetic on gastrin release, acid secretion, and blood glucose during basal conditions and in response to insulin, 2-deoxy-D-glucose, and feeding in the dog

The effect of a selective beta 2-adrenoceptor agonist on basal volume and on insulin-, 2-deoxy-D-glucose (2-DG)-, and food-induced gastrin release was studied in conscious gastric fistula dogs. Acid output and blood glucose changes were also studied, except in the food experiments. Basal acid secretion and serum gastrin were unchanged after beta 2-sympathetic infusion, whereas a slight increase in blood and glucose was found. The beta 2-agonist almost prevented acid output and gastrin release after insulin hypoglycaemia. However, the hypoglycaemia was also inhibited. Gastric acid secretion stimulated by 2-DG was inhibited, as was probably the gastrin release. 2-DG increased the blood glucose level, and no significant differences were found after beta 2 infusion. After feeding, gastrin release was initially decreased for one of five doses of the beta 2-agonist, and higher doses of the beta 2-agonist prevented the subsequent fall in serum gastrin after the initial peak value. This pattern was also found for the histamine H2-blocker cimetidine in a dose that blocks acid output. The beta 2-agonist and 2-DG increased pulse rate. It is concluded that beta 2-sympathetic stimulation inhibits acid output and gastrin release after insulin and 2-DG stimulation, but one should be cautions in drawing conclusions from the insulin experiments. The effect on gastrin release is small compared with the effect on the acid secretion, and it is unlikely that the inhibition of acid secretion acts through a change in gastrin release.

Blood-brain glucose transport in the conscious rat: comparison of the intravenous and intracarotid injection methods

The unidirectioal transfer of D-glucose from blood to parietal cortex tissue of the brain of awake rats was measured by single intravenous injection of tracer glucose, as well as by single intracarotid injection according to the method of Oldendorf. The maximal unidirectional blood-brain glucose transfer rate (Tmax) was 407 mumol (100 g)-1 min-1 when measured by intravenous injection, and 352 mumol (100 g)-1 min-1 when measured by intracarotid injection. The half-saturation constants (Km) were 7.8 mM and 16.8 mM, respectively. The comparison shows that the two methods give similar results when cerebral perfusion is assessed accurately.

Pentobarbital anesthesia reduces blood-brain glucose transfer in the rat

Pentobarbital anesthesia (40 mg kg-1) was accompanied by a 50% decrease of blood flow and a 40% decrease of unidirectional blood-brain glucose transfer in the parietal cortex of the rat brain. The correlation was explained by a decrease of the number of perfused capillaries. The maximal transport capacity, Tmax, decreased from 409 to 235 mumol 100 g-1 min-1 and the half-saturation constant, Km, from 8.8 to 4.9 mM. At 8.3-8.7 mM-glucose in arterial plasma, the transfer constant (clearance) for unidirectional blood-brain transfer decreased from 0.195 +/- 0.011 in awake rats to 0.132 +/- 0.005 ml g-1 min-1 in anesthetized rats. Half of the decrease was due to less complete diffusion-limitation of glucose uptake at the low plasma flow rate in brain, the other half to the decreased Tmax.

Post-ischemic coma in rat: effect of different pre-ischemic blood glucose levels on cerebral metabolic recovery after ischemia

Hyper-, normo-, and hypoglycemic rats were exposed to 10 min of complete cerebral ischemia. Regional cerebral blood flow (CBF), blood-brain glucose transfer, and cerebral consumption of oxygen and glucose were measured before, as well as three and 60 minutes after ischemia. Three min after ischemia, no differences were observed between the 3 groups of rats. One h after ischemia, the hyperglycemic rats in comparison to those of the other groups had similar whole-brain CBF and glucose consumption but appreciately lower oxygen consumption, indicating continued non-oxidative use of glucose in the hyperglycemic group. In general, regional CBF values exceeded the control value by 100-200% 3 min after ischemia and were reduced to 50% of control at 1 h after ischemia, at which time the rats were still comatose. In the brain stem of hyperglycemic rats, blood flow, however, remained elevated after ischemia. Thus, the significantly increased mortality observed in rats hyperglycemic before, during and after ischemia (Siemkowicz & Hansen 1978) was the result, not of impaired postischemic CBF, but of ischemic or postischemic damage to brain cells. We suggest that the damaging factor in the hyperglycemic group is increased lactacidosis associated with prolonged anaerobic glycolysis.

Improvement of restitution from cerebral ischemia in hyperglycemic rats by pentobarbital or diazepam

Hyperglycemic rats were exposed to 10 min of complete cerebral ischemia. Rats with 26 mM (range 23-27 mM) plasma glucose levels died. Rats with the same degree of hyperglycemia, treated after ischemia with pentobarbital (75-95 mg/kg) or diazepam (10-13 mg/kg), survived the observation period of 21 days and recovered, albeit incompletely. The same treatment given to rats with higher degrees of hyperglycemia did not prevent death. It is concluded that postischemic treatment with anticonvulsive drugs may improve clinical restitution from ischemia in moderately hyperglycemic rats.

Rapid simultaneous determination of regional blood flow and blood-brain glucose transfer in brain of rat

A new method was developed and used in rat to measure regional and whole-brain blood flow and blood-brain glucose transfer simultaneously and in 20 s. This simple method consisted of i.v. bolus injection of labeled butanol and tracer glucose, determination of the average arterial tracer concentration and subsequent assay of cerebral tissue activity 20 s after bolus injection. The whole-brain blood flow rate averaged 129 ml (100 g)-1 min-1. The unidirectional blood-brain glucose transfer was twice as high as previously estimated in similar studies on rat, or 144 mumol (100 g)-1 min-1 at 10 mM glucose in plasma. The magnitude is sufficient to explain the high cerebral glucose consumption rates recently determined by means of autoradiographic 2-deoxy-D-glucose method of Sokoloff et al. (1977).

Rapid steady-state analysis of blood-brain glucose transfer in rat

A new kinetic analysis of blood-brain glucose transport is described, based on a steady-state model that takes account of cerebral blood flow, mean capillary glucose concentration, and cerebral metabolic rate. The maximal rate (Tmax) and half-saturation constant (Km) of glucose transport from blood to brain were determined in rats by measuring the rate of blood-to-brain glucose transfer at different blood glucose concentrations. Each determination lasted 20 seconds. For whole-brain, Tmax and Km averaged 258 +/- 33 (S.E.) mumol L(100 g)-1 min-1 and 5.9 +/- 1.6 (S.E.) mmol 1-1, respectively. The regional variations were insignificant. The new approach permits kinetic parameters to be measured locally in brain in rapidly changing functional states.

Streptozotocin diabetes: a glucoreceptor dysfunction affecting D cells as well as B and A cells

Somatostatin release from the isolated pancreas of 3 normal and 6 streptozotocin diabetic dogs has been measured in response to various stimuli to determine whether abnormalities in somatostatin release are present in the diabetic pancreas. Simultaneous measurement of glucagon secretion was also made. In the pancreas from normal dogs increases in perfusate glucose from 25 to 200 mg/100 ml induced a 2--3 fold increase in somatostatin release and a two thirds decrease in glucagon secretion. In contrast, in the diabetic pancreas glucose caused no change in the secretion of the two hormones. In the diabetic pancreas addition of insulin to the perfusate (25,000 microU/ml) for periods from 10 to 75 minutes aimed at restoring normal extracellular insulin levels in the islets failed to restore either somatostatin or glucagon secretion to normal. In contradistinction to the lack of effect of glucose, the somatostatin and glucagon responses to arginine (5 mmol/l), isoproterenol (2 ng/ml) and calcium (5 mmol/l) were normal in the diabetic pancreas. The data suggests the presence of a selective glucoreceptor abnormality of the D as well as of B and A cells in the streptozotocin diabetic dog.

Insulinoma: clinical manifestations, diagnosis and treatment. The significance of the prolonged fasting test and of the fasting blood glucose-insulin relationship

This paper describes the clinical manifestations and the significance of the fasting blood glucose-insulin relationship and the prolonged fasting test in the diagnosis of insulinoma. Pre-and postoperative results are reported. In addition, a description is given of the angiographic demonstration and the results of the surgical removal of the insulinomas.

Control of blood glucose levels in the streptozotocin diabetic rat using a long-acting heat-treated insulin

Diurnal plasma glucose levels have been studied two hourly in streptozotocin diabetic rats during insulin treatment. Protamine Zinc Insulin induced a very steep fall in plasma glucose level from 359 +/- 100 (SD) mg/100 ml to 91 +/- 49 mg/100 ml within two hours. Plasma glucose was then low (13-60 mg/100 ml) until after 18 hours when an equally steep rise in glucose concentration ocurred. Six other insulin preparations and several insulin treatment regimens were tested with the aim of normalising the 24 hour plasma glucose profile of streptozotocin diabetic rats. One preparation, a non-commercial, very long acting Ultralente NOVO (Mc, ox pH 5.5) yielded a diurnal plasma glucose profile reasonably close to normal when it was administered once a day and when the dose was based on daily blood glucose measurements. Mean plasma glucose was 122 +/- 55 mg/100 ml with a nadir of 55 +/- 15 and a maximal of 187 +/- 99 mg/100 ml.

The role of adrenaline and of the vagus in gastrin release and acid secretion in dogs

Serum gastrin, gastric acid secretion and plasma adrenaline in response to intravenous injection of 2-deoxy-D-glucose and to insulin were measured in six dogs with gastric fistulae before and after denervation of the antrum and the intestine (antral-intestinal vagotomy). Serum gastrin and gastric acid secretion were also measured in the same dogs during intravenous infusion of adrenaline in doses which produced an elevation of plasma adrenaline to levels occurring during hypoglycaemia and after the injection of 2-deoxy-D-glucose. Antral-intestinal vagotomy reduced basal gastrin concentration slightly and basal gastric acid secretion considerably. The rise in serum gastrin in response to 2-deoxy-D-glucose and hypoglycaemia was abolished while the increase in gastric acid secretion was reduced after antral-intestinal vagotomy. Beef meal-stimulated gastrin secretion was the same before and after vagotomy. Intravenous infusion of adrenaline had no effect on either serum gastrin or gastric acid secretion. It is concluded that in the dog, in contradistinction to man, gastrin release after insulin is dependent on an intact vagus. Release of gastrin by adrenaline in the dog does not appear to be physiological since it is not achieved by the amount of adrenaline released in response to hypoglycaemia.

Extracellular fluid volume determined by a single injection of inulin in men with untreated essential hypertension

The extracellular volume (ECV) and plasma volume (PV) were determined simultaneously in nine men with untreated essential hypertension and in nine healthy matched control subjects, using a single injection of inulin and of 131I-labelled human serum albumin, respectively. The average mean arterial blood pressure in the hypertensive group was 178/118 mmHg. ECV was nearly the same in the two groups, viz. 151 ml/kg body weight (SD 17) in the hypertensive group compared to 147 ml/kg (SD 16) in the control group. The corresponding figures for PV were 38.2 ml/kg body weight (SD 4.7) and 43.7 ml/kg (SD 7.9) respectively (P less than 0.1). The calculated interstitial fluid volume (IV) was 113 ml/kg (SD 16) and 103 ml/kg (SD 10) (P less than 0.2). The PV/IV ratio was significantly lower (P less than 0.02) in the hypertensive group (0.34, SD 0.06) than in the normal group (0.42, SD 0.06). The difference might suggest increased transcapillary water filtration in hypertension.

Inhibition of parathyroid hormone secretion by isoproterenol

Intravenous infusion of the beta-adrenergic agonist isoproterenol produced a fall in the serum concentration of parathyroid hormone. It also produced a pronounced fall in the serum phosphate concentration, and significant increases in blood glucose and serum insulin concentration and in pulse rate. The fall in serum parathyroid hormone was abolished by beta-adrenergic blockage with propranolol. Oral glucose loads produced a pronounced fall in serum phosphate concentration, comparable to the fall after isoproterenol infusion, but no significant changes in serum parathyroid hormone. It is concluded that the fall in serum parathyroid hormone after isoproterenol is due to a beta-adrenergic effect. It is unknown, if isoproterenol acts directly on the parathyroid hormone secreting cell, or the fall in serum parathyroid hormone is secondary to the effect of isoproterenol on other endocrine glands or the cardiovascular system.

The effect of standing and exercise on plasma catecholamines, serum insulin, and serum gastrin

Glucose-stimulated insulin secretion was measured in six normal subjects in the resting supine position, during standing, and during a period of moderate exercise in the supine position. Plasma noradrenaline averaged 0.26 ng/ml in the supine, resting position and rose to 0.57 and 0.61 ng/ml at the end of the standing experiment and the exercise period, respectively. Plasma adrenaline was unchanged in the standing position but rose threefold during exercise (to 0.09 ng/ml). Serum gastrin tended to decrease in all three experiments after the injection of glucose. Glucose-stimulated insulin secretion was the same during the first 10 min after the injection of glucose in the three experiments. It is concluded that a moderate increase in adrenergic activity has no influence on glucose-stimulated insulin secretion.

The role of the beta-adrnergic receptor in the secretion of gastrin: studies in normal subjects and in patients with duodenal ulcers

Intravenous infusion of isoproterenol, a beta-adrenergic receptor stimulatory agent, increased serum gastrin concentration significantly more in patients with a duodenal ulcer than in healthy subjects. The rise in pulse rate, blood glucose concentration and in serum insulin was the same in both groups of subjects. Gastrin secretion was also increased significantly more in the patients than in the control subjects after a beef-meal. Basal serum gastrin concentrations were higher in the patients than in the control subjects and correlated to the rise in serum gastrin during both tests in the patients with a duodenal ulcer. Isoproterenol and meal stimulated gastrin secretion, expressed as percent of the basal value, were twice as higher in the patients as in the control subjects. The combined administration of isoproterenol and the meal had an additive effect on the rise in serum gastrin. Isoproterenol stimulated gastrin secretion was completely suppressed by propranolol, a beta-adrenergic receptor blocking agent, which had no effect on meal stimulated gastrin secretion. It is concluded that the mechanism of the hypersecretion of gastrin in patients with a duodenal ulcer did not involve a specific abnormality of the beta-adrenergic receptor or the receptor which recognized proteins and their digested products. There is no established role of beta-adrenergic receptor activity in the hypersecretion of gastrin in patients with duodenal ulcers. It is suggested that the beta-adrenergic receptor may have some yet unknown function unrelated to the acute secretory response of gastrin.

Inhibition of meal-stimulated gastrin secretion after oral glucose

Serum gastrin concentration was measured in six male subjects before and after a beef meal, with and without 100 g of oral glucose being given 30 min previously. There was a pronounced inhibition of beef-stimulated gastrin secretion after the oral glucose load.

Failure of somatostatin to correct manifest diabetic ketoacidosis

Juvenile diabetic patients were studied 60-72 hours after insulin withdrawal when moderate ketoacidosis had developed. Somatostatin infusion for 4 hours in five patients resulted in almost complete suppression of plasma pancreatic glucagon and growth hormone, a fall in plasma-cyclic-adenosine-monophosphate (A.M.P.) concentrations, and a large fall in plasma-glucose concentration. After infusion plasma concentrations of these substances rose again. Blood-ketone-bodies, plasma-free-fatty-acids (F.F.A.), and plasma glycerol concentrations, however, did not decrease appreciably with somatostatin administration. In three patients 2 to 3 h somatostatin infusions were twice superimposed upon a continuous 9-5 h insulin infusion (1 unit/h). An insulin effect was noticeable within 30 minutes, with pronounced falls in the concentrations of plasma glucose, pancreatic glucagon, F.F.A., and blood-ketone-bodies. There was no significant change in these patterns when somatostatin was administered or withdrawn. These results do not indicate that somatostatin infusion would be useful in the treatment of manifest diabetic ketoacidosis.

The effect of somatostatin on plasma noradrenaline and plasma adrenaline concentrations during exercise and hypoglycemia

The effect of somatostatin, on the secretion of noradrenaline and adrenaline was studied in eight normal subjects during exercise and in insulin induced hypoglycemia. Plasma growth hormone response to exercise and hypoglycemia was almost totally suppressed by somatostatin. Plasma noradrenaline during exercise tended to be lower during the infusion of somatostatin but the difference was not significant. During the infusion of somatostatin the secretion of adrenaline was increased. This was seen during exercise but was much more pronounced during hypoglycemia. The blood glucose concentration attained after insulin injection was lower during the infusion of somatostatin and evidence is presented which indicates that the higher adrenaline values during hypoglycemia were due to the lower blood glucose values attained. In conclusion the secretion of catecholamines are not inhibited by a dose of somatostatin which nearly totally suppresses the secretion of growth hormone.

Plasma catecholamines and blood substrate concentrations: studies in insulin induced hypoglycaemia and after adrenaline infusions

Plasma adrenaline-blood glucose interrelationships in insulin-induced hypoglycaemia in man have been studied using a sensitive double-isotope derivative method for adrenaline estimation. Plasma adrenaline reached a peak of 1.24 ng/ml at 45 minutes after insulin while blood glucose reached a nadir of 22 mg/100 ml at 30 minutes. There was a strong correlation both between the rise in adrenaline and the degree of hypoglycaemia and between the rise in adrenaline and the post-hypoglycaemic rise in glucose. Plasma noradrenaline rose from 0.29 to 0.59 ng/ml, the rise correlating with the rise in adrenaline. Changes in pulse rate preceded and were unrelated to changes in plasma catecholamines. Fuel mobilisation in response to adrenaline infusion (6 mug/min. for 20 min.) in normoglycaemic man was also studied. Plasma adrenaline concentration rose from a mean of 0.02 ng/ml to 0.71 ng/ml while plasma noradrenaline concentration was unchanged. Blood glucose rose from 71 to 98 mg/100 ml while plasma insulin decreased from 11 to 8 muU/ml. Blood lactate rose by 0.85 mM while pyruvate concentration remained unchanged. Blood glycerol concentration rose twofold and ketone body concentration threefold but there was little change in the concentrations of the glucogenic amino acids, alanine, glutamate and glutamine. Both the 3-hydroxybutyrate/acetoacetate ratio and the lactate/pyruvate ratio rose implying a more reduced intracellular state due presumably to increased hepatic fatty acid oxidation. It is concluded that adrenaline enhances the recycling of lactate and spares glucose through the mobilitsation of lipids but that amino acids are little affected.

The relationship between diagnostic information obtained from three tests for detecting mild diabetes mellitus

The purpose of the study was to evaluate and compare the most commonly used criteria for the interpretation of the oral (OGTT) and intravenous (IVGTT) glucose tolerance tests and the intravenous tolbutamide test (IVTT) and to establish the criteria that give the highest degree of diagnostic agreement. The highest degree of diagnostic agreement was obtained with the following limits: a) blood glucose greater than or smaller than or equal to 120 mg/100 ml within 2 1/2 h after a 100 g OGTT together with b) a k-value of greater than or smaller than or equal to 1.05 as a limit for a 25 g IVGTT and c) a 30 min blood glucose level as percentage of fasting of greater than or smaller than or equal to 77 as limit for a 1 g IVTT. Using these criteria the three tests deemed the same subjects either diabetic or nondiabetic in about 2/3 of the cases. The best correlation between the blood glucose values of the OGTT and the k-values of the IVGTT and the 30 min values of the IVTT was obtained using the blood glucose concentrations of the last part of the OGTT. The 2 and the 3 hr values were however equal to the 2 1/2 hr values with regard to the degree of correlation with the values of the intravenous test. The results indicated that the diagnostic disagreement reported previously between the three tests may partly be due to the use of blood glucose values in the first part of the OGTT for the classification of the test and partly due to the screening limits chosen for interpretation of the three test.

Plasma catecholamines and carbohydrate metabolism in patients with acute myocardial infarction

Blood glucose, glucose tolerance, serum insulin, free fatty acids in serum, plasma noradrenaline, and plasma adrenaline were measured in 10 patients with acute myocardial infarction (AMI) as well as in healthy subjects. Both noradrenaline and adrenaline in plasma were elevated in patients with AMI, the level being fairly constant in the individual patients and dependent on their degree of illness. In the fasting state, blood glucose, serum insulin, and free fatty acids were elevated in patients with AMI. Plasma noradrenaline showed a highly significant correlation with the fasting blood glucose concentration, but not with serum insulin or free fatty acids. The concentration of free fatty acids in serum could be predicted only if both plasma noradrenaline and the basal insulin concentration were known. Intravenous glucose tolerance was reduced in patients with AMI, especially in patients with high plasma noradrenaline and a low initial rise in insulin. There was a significant negative correlation between the initial rise in insulin expressed in percentage of the basal insulin concentration and the plasma noradrenaline level. The statistical effects of serum insulin and plasma noradrenaline on the glucose tolerance could not be separated from each other. The decline in free fatty acids after intravenous injection of glucose showed a negative correlation with plasma noradrenaline and a positive correlation with the initial rise in insulin. Plasma adrenaline did not correlate with any of the metabolic parameters mentioned above. The plasma noradrenaline concentration was elevated to such a degree in patients with AMI that the observed changes in metabolism might have been caused directly by the circulating noradrenaline. During the glucose tolerance tests, the effects of noradrenaline was probably carried out indirectly via a suppression of insulin secretion. It is conceivable that any effect of plasma noradrenaline on the basal insulin secretion was neutralized by the fasting hyperglycemia.