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Biomedical subjects

M Nedergaard

Publications and source records attributed to M Nedergaard.

At least 55 records · Page 3Linked to original sources
PubMed1990

Dicarboxy-dichlorofluorescein: a new fluorescent probe for measuring acidic intracellular pH.

Derivatives of fluorescein sensitive to pH are extensively utilized for the determination of intracellular pH (pHi). Available dyes have pKa values of approximately 7.0, and are not well suited for measuring acidic pHi. We examined the fluorescein derivative, 5 (and 6)-carboxy-2',7'-dichlorofluorescein (CDCF) for its potential in the microspectrofluorometric measurement of pHi during acidic conditions. CDCF showed intense fluorescence and pH sensitivity near its "effective" pKa value of 4.2, using a 495/440 nm dual excitation wave-length ratio method. Protein interactions caused fluorescence ratio deviations which were most pronounced at the extremes of pH, whereas calcium and magnesium concentrations had little effect on the fluorescent ratio intensity. Intracellular calibration performed using nigericin in the presence of high potassium eliminated the need to correct for protein interactions, and the ratio method minimized any variations due to dye concentration differences or instrument fluctuation. Intracellular retention of the dye was high, and 95% of the initial signal remained after 1 h. Fluorescence bleaching was 14.5% after 1 h of continuous excitation and cell survival was not affected by dye loading. We conclude that CDCF is an excellent intracellular pH indicator in the pH range of 4-5.

Acids↗
PubMed1990

Regional brain glucose metabolism and blood flow in streptozocin-induced diabetic rats.

Brain regional glucose metabolism and regional blood flow were measured from autoradiographs by the uptake of [3H]-2-deoxy-D-glucose and [14C]iodoantipyrine in streptozocin-induced diabetic (STZ-D) rats. After 2 days of diabetes, glucose metabolism in the neocortex, basal ganglia, and white matter increased by 34, 37, and 8%, respectively, whereas blood flow was unchanged. After 4 mo, glucose metabolism in the same three regions was decreased by 32, 43, and 60%. This reduction was paralleled by a statistically nonsignificant reduction in blood flow in neocortex and basal ganglia. It is suggested that the decrease of brain glucose metabolism in STZ-D reflects increased ketone body oxidation and reduction of electrochemical work.

Aging↗
PubMed1988

Spreading depression is not associated with neuronal injury in the normal brain.

This study was performed in order to evaluate whether waves of spreading depression (SD) induces irreversible neuronal injury. SD was elicited by topical application of 3 M KCl to the exposed cortex for 4-5 h and the resulting change of the cortical electrical potential showing the occurrence of SD, was recorded by glass microelectrodes. Histological examination of cerebral cortex revealed no signs of neuronal injury outside the area of KCl application as examine after 4 days recovery. The results indicate that recurrent waves of SD do not induce irreversible neuronal injury in the otherwise normal rat brain.

Animals↗
PubMed1988

Experimental cerebral ischemia: barbiturate resistant increase in regional glucose utilization.

During the first hours after experimental occlusion of the middle cerebral artery (MCA) cerebral glucose utilization increases in the tissue adjacent to ischemic focus. To test whether the increased glucose utilization was a consequence of increased neuronal activity, the effect of preocclusion pentobarbital administration was investigated. Rats in barbiturate-induced coma showed a metabolic response to MCA occlusion similar to those seen with light halothane anesthesia. This indicates that the enhanced glucose utilization adjacent to the ischemic core is not a result of increased neuronal activity.

Animals↗
PubMed1988

Autoradiographic determination of cerebral glucose content, blood flow, and glucose utilization in focal ischemia of the rat brain: influence of the plasma glucose concentration.

Focal cerebral ischemia was produced by occlusion of the middle cerebral artery in rats. Cerebral blood flow measured with [14C]iodoantipyrine was severely reduced in the lateral portion of neostriatum. This area of dense ischemia was sharply demarcated against the surroundings. The adjacent cortex was perfused at one-third of normal, whereas blood flow in the medial neostriatum was only slightly reduced. This pattern of perfusion was independent of the plasma glucose concentration of the animal. In contrast, the glucose utilization calculated from the 2-[3H]deoxyglucose accumulation depended on the plasma glucose concentration. Enhanced glucose utilization was evident in the border areas surrounding the ischemic focus in normoglycemic animals. Neither acutely nor chronically diabetic animals had such an increase of metabolism in the borderzone. Moderately hyperglycemic rats had a narrow rim of enhanced glucose utilization immediately surrounding the ischemic core, whereas animals with plasma glucose values above 22 mmol/L had no such rim. In mild hypoglycemia (2-4 mmol/L), the glucose utilization was slightly enhanced in the border areas, but during severe hypoglycemia (less than 2.5 mmol/L), the glucose utilization declined gradually toward the ischemic core. Glucose content, and thereby the lumped constant (measured by 3-0-[14C]methylglucose) showed little regional variation, except in the ischemic core. These findings indicate that blood flow alterations after occlusion of the middle cerebral artery in rats are not influenced by the plasma glucose utilizations. In contrast, glucose utilization depends on a combination of plasma glucose concentration and blood flow instead of blood flow per se.

Animals↗
PubMed1988

Middle cerebral artery occlusion in presence of low perfusion pressure increases infarct size in rats.

A model was set up in order to evaluate the importance of hemispheric perfusion pressure when the middle cerebral artery (MCA) is occluded in anaesthetized rats. In 6 animals the internal carotid artery (ICA) was occluded prior to ipsilateral MCA occlusion; in 17 animals the MCA only was occluded; 6 animals underwent the same preparation, but the vessels were left unoccluded. Four days after surgery the infarct volume was measured with a computerized image analyser. The infarcted areas were significantly larger in the ICA + MCA occluded group compared with the MCA occluded group (p less than 0.005), which in turn had larger infarcts than the sham-operated animals (p less than 0.001). These results indicate that patients with hypoperfusion, due to severe ICA stenosis and impaired collateral blood supply, are at higher risk of developing major stroke, when embolism into a cerebral artery occurs, as compared to patients with no, or only minor, reduction in hemispheric perfusion pressure.

Animals↗
PubMed1988

Mechanisms of brain damage in focal cerebral ischemia.

Ischemic stroke is a major disabling disease. There are 500,000 new cases in U.S. every year, and the middle cerebral artery (MCA) is the artery most often occluded. In this paper recent results of experimental MCA occlusion are reviewed, with special emphasis on those factors contributing to irreversible damage. Occlusion of MCA in the rat causes a pronounced decline of flow in the neostriatum to less than 10% of normal. The area of low flow is surrounded by a zone 0.2-0.5 mm wide, across which blood flow increases steeply. Beyond this zone, changes in flow are more gradual, and perfusion is reduced to about 1/3 of normal in the adjacent ipsilateral cortex. The MCA occlusion leads to a sharply demarcated infarct and to scattered neuronal injury in the adjacent cortical tissue. It is suggested that the ischemic core is identical with the tissue infarct, i.e. that it is the initial pattern of blood flow which determines the volume and topography of infarction. Waves of spreading depression are detected in the cortical low perfusion area during the first hours of MCA occlusion, and glucose consumption is increased, presumably due to an increased demand for ionic transport. In hyperglycemic animals, the number of spreading depressions is reduced as is the glucose consumption. The repeated waves of spreading depression in combination with partial energy depletion may induce selective neuronal injury in the peri-infarct zone, a suggestion which finds support in the fact that hyperglycemia ameliorates neuronal injury around the infarction.

Animals↗
PubMed1987

Transient focal ischemia in hyperglycemic rats is associated with increased cerebral infarction.

To study whether transient ischemia is influenced by hyperglycemia, the middle cerebral artery was occluded for 5, 10 and 15 min in normo- and hyperglycemic rats. Five-minute ischemia induced minor lesions in both groups. After 10-min ischemia a significant greater infarct volume was found in hyperglycemia compared with normoglycemia (29 +/- 9 mm3 vs 4 +/- 4 mm3, P less than 0.001). Fifteen-minute artery occlusion induced even more damage in both hyper- and normoglycemia (63 +/- 20 mm3 vs 13 +/- 12 mm3, P less than 0.006). The lateral part of striatum was infarcted in all hyperglycemic animals exposed to 10 or 15 min of ischemia. In the same area selective neuronal injury occurred in 6 out of 9 normoglycemic animals. The findings show that hyperglycemia increases brain damage during transient ischemia by conversion of selective neuronal injury into cerebral infarction.

Animals↗
PubMed1987

Neuronal injury in the infarct border: a neuropathological study in the rat.

Focal ischemia was induced in rats by occlusion of the middle cerebral artery (MCA). Infarction developed primarily in the basal ganglia. The development, density and distribution of neuronal injury in the cortex adjacent to the infarct were studied from 4 h to 1 year after occlusion of the artery. The brains were perfusion fixed, sub-serially sectioned, and stained with H + E, acid fuchsin/cresyl violet, and ad modum Klüver-Barrera. The number of injured neurons was assessed by direct visual counting. Four hours after the artery occlusion, the infarct was clearly outlined in the corpus striatum, whereas the cortical border became sharp 1 to 2 days after ligation of MCA. After 1 day triangular injured neurons with eosinophilic cytoplasm and pyknotic nuclei were seen outside the infarct. The number of injured neurons at day 1, 2, 3, 4, and 5 was the same, i.e. no evidence for delayed neuronal death was found. Neuron counts at day 1, 4, 10, 17, 27, and 365 were reduced according to the number of acutely injured neurons. Most injured neurons were observed less than 3 mm from the margin of the infarct and the greatest number was found in the cortical layers 2 and 3. The border zone in the medial part of the striatum showed selective neuronal necrosis only in a zone of 200 micron. The fact that the number of injured neurons was constant from day 1 to 5 after artery occlusion indicates that the damage is acute and that a delayed loss of neurons is of minor significance.

Animals↗
PubMed1987

Focal ischemia of the rat brain, with special reference to the influence of plasma glucose concentration.

Focal cerebral ischemia was induced by occlusion of the right middle cerebral artery in hypoglycemic, normoglycemic, as well as in acute and chronic diabetic rats. The brain damage was studied after 4 days. The volume of infarction was decreased in hypoglycemia (29 +/- 19 mm3 (mean +/- SD) versus 58 +/- 35 mm3, P less than 0.0046), unaltered in acute diabetes (61 +/- 45 mm3), and increased in chronic diabetes (91 +/- 22 mm3, P less than 0.0463). The cortex adjacent to the infarct showed selective neuronal injury affecting the cortical layers 2 and 3. The damage was enhanced by hypoglycemia and prevented in most of the diabetic animals. The findings indicate that different mechanisms cause infarction and selective neuronal injury outside infarcts, but that both are influenced by the plasma glucose concentration.

Animals↗
PubMed1987

Hyperglycaemia protects against neuronal injury around experimental brain infarcts.

Regional glucose utilization was measured in the rat brain after occlusion of the middle cerebral artery. Normoglycaemic rat had increased glucose use in the cerebral cortex adjacent to the infarct. A fraction of the nerve cells were irreversibly injured in this region. In hyperglycaemic rats, the glucose metabolism remained normal and no nerve cell loss was found around the infarct. The findings indicate that hyperglycaemia protects against nerve cell injury in the areas next to experimental brain infarcts.

Animals↗
PubMed1986

Infarct rim: effect of hyperglycemia on direct current potential and [14C]2-deoxyglucose phosphorylation.

Focal ischemia was produced by occlusion of the right middle cerebral artery (MCA) in normo- and hyperglycemic rats. In the cortical infarct rim, regional [14C]2-deoxyglucose [( 14C]2-DG) phosphorylation was correlated to spontaneous transient changes in extracellular potassium recorded as direct current (DC) potential deflections. In normoglycemic rats the DC potential showed transient but recurrent deflections in the first hours following MCA occlusion. The 2-DG phosphorylation was elevated by 200% in the same area. In contrast, hyperglycemic rats had no, or a single, deflection of the DC potential in the rim, and the 2-DG phosphorylation remained normal. The same pattern was obtained by application of 3 M KCl to the exposed cortex. In normoglycemia potassium application resulted in recurrent deflections of the DC potential, and 2-DG phosphorylation increased in most parts of the hemisphere. Hyperglycemic animals had a nearly stable DC potential, and 2-DG phosphorylation increased only in the tissue area situated directly below the site of potassium application. The results indicate that metabolism in the cortical infarct rim is stimulated by spontaneous and recurrent changes in extracellular potassium--a phenomenon that may be related to spreading depression--and that the metabolism remained normal in the same area in hyperglycemic animals owing to an inhibition of transient increases of extracellular potassium.

Action Potentials↗
PubMed1986

Focal ischemia of the rat brain: autoradiographic determination of cerebral glucose utilization, glucose content, and blood flow.

Focal cerebral ischemia was induced in rats by occlusion of the middle cerebral artery. By a triple-tracer technique, cerebral glucose utilization, glucose content, and blood flow were simultaneously determined. Computer-assisted autoradiography revealed a core of dense ischemia in the lateral two-thirds of the striatum. A border zone of increased 2-deoxy-D-glucose (DG) uptake surrounded the ischemic insult in the acute stage. The lumped constant was increased only moderately in the border zone. Therefore, the enhanced DG uptake reflected increased glucose consumption. CBF was reduced to 20-30% in the cortical border, while minor depression and in some animals hyperemia were evident in the striate border. Six hours after the insult, the border zones of increased glucose consumption had disappeared in half the animals. In no animals examined after 20 h was glucose consumption enhanced. The study indicated a stable metabolic response to a reproducible focal insult. We conclude that continued enhancement of glucose consumption in marginally perfused areas indicates neuronal damage.

Animals↗
PubMed1983

Irradiation protects against pancreatic islet degeneration and hyperglycaemia following streptozotocin treatment of mice.

Five daily injections of streptozotocin (40 mg/kg) produce islet inflammation, necrosis of pancreatic B cells and hyperglycaemia in the mouse. Anti-pancreatic autoimmunity has been suggested as part of the cause of these events. We have studied the possible effect of total-body irradiation in long-term studies (246 days) and report here that insulitis, islet necrosis and insulin depletion are reduced after irradiation. In parallel the level of hyperglycaemia is reduced. It is concluded that immunological mechanisms are to some extent responsible for the development of streptozotocin-induced diabetes.

Animals↗
PubMed1982

The low dose streptozotocin murine model of type 1 (insulin-dependent) diabetes mellitus: studies in vivo and in vitro of the modulating effect of sex hormones.

The influence of sex on pancreatic islet B cell susceptibility to streptozotocin was studied in mice given multiple low doses of streptozotocin. Male C3 D2 F1 mice developed a steadily increasing blood glucose level after a lag period of about 3 weeks, in contrast to females who were resistant. Spleen cells from streptozotocin treated female animals produced hyperglycaemia in total body irradiated syngeneic female recipients, but only if the recipients were treated with testosterone. Testosterone treatment of donors did not affect blood glucose levels of recipients. Streptozotocin cytotoxicity in vitro determined by a 51Cr-release assay revealed an increased sensitivity to streptozotocin in dispersed islet cells from adult male animals as compared with cells from adult female mice. The incubation of islet cells from animals of either sex with testosterone, or oestradiol plus progesterone, did not enhance the susceptibility to streptozotocin. Islet cells from sexually immature male or female mice were less susceptible to streptozotocin. The results demonstrate that sex determines susceptibility to streptozotocin in vivo and in vitro.

Animals↗
PubMed1977

Health care and hospital pharmacy in Denmark.

Health services and community and hospital pharmacy practice in Denmark are discussed. Topics covered include the education and training of pharmacists and technicians, pharmaceutical manufacturing by community and hospital pharmacies, hospital drug distribution, and drug information services. Pharmacy is unique in Denmark inthe 40% of the drug products on the market are manufactured by pharmacies, under the auspicies of the pharmacy proprietors' association. As in other Scandinavian countries, the number and location of community pharmacies are controlled by the state. Ninety pharmacists are employed in 13 hospital pharmacies; half of the pharmacists are occupied bb drug product manufacturing.

Delivery of Health Care↗