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Biomedical subjects

M Lauritzen

Publications and source records attributed to M Lauritzen.

At least 19 recordsLinked to original sources
PubMed1992

On the evidence of auditory evoked magnetic fields as an objective measure of tinnitus.

The purpose of the present study was to determine the utility of auditory evoked magnetic fields as an objective measure of tinnitus. The auditory evoked magnetic fields of 14 patients with tinnitus and of 14 sex- and age-matched controls were measured by means of a 7-channel BTI neuromagnetometer. Stimuli were 1 kHz tone-bursts presented randomly. Tinnitus patients and controls were similar with respect to latencies and amplitudes of the N100m and P200m, and with respect to the locations and moments of the equivalent current dipoles. The present study could not support the notion that specific abnormalities of the auditory evoked magnetic fields are characteristic of patients with tinnitus.

Acoustic Stimulation↗
PubMed1992

The effect of glutamate receptor blockade on anoxic depolarization and cortical spreading depression.

We examined the effect of blockade of N-methyl-D-aspartate (NMDA) and non-NMDA subtype glutamate receptors on anoxic depolarization (AD) and cortical spreading depression (CSD). [K+]e and the direct current (DC) potential were measured with microelectrodes in the cerebral cortex of barbiturate-anesthetized rats. NMDA blockade was achieved by injection of (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate [MK-801; 3 and 10 mg/kg] or amino-7-phosphonoheptanoate (APH; 4.5 and 10 mg/kg). Non-NMDA receptor blockade was achieved by injection of 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(F)quinoxaline (NBQX; 10 and 20 mg/kg). MK-801 and APH blocked CSD, while NBQX did not. In control rats, the latency from circulatory arrest to AD was 2.1 +/- 0.1 min, while the amplitude of the DC shift was 21 +/- 1 mV, and [K+]e increased to 50 +/- 6 mM. All variables remained unchanged in animals treated with MK-801, APH, or NBQX. Finally, MK-801 (14 mg/kg) and NBQX (40 mg/kg) were given in combination to examine the effect of total glutamate receptor blockade on AD. This combination slightly accelerated the onset of AD, probably owing to circulatory failure. In conclusion, AD was unaffected by glutamate receptor blockade. In contrast, NMDA receptors play a crucial role for CSD.

2-Amino-5-phosphonovalerate↗
PubMed1992

Placebo-controlled comparison of captopril, metoprolol, and hydrochlorothiazide therapy in non-insulin-dependent diabetic patients with primary hypertension.

The antihypertensive effect of captopril, metoprolol, and hydrochlorothiazide was compared in 23 non-insulin-dependent (NIDDM) diabetic patients less than or equal to 75 years of age, with borderline to moderate primary hypertension. In a double blind, placebo-controlled cross-over trial the patients were treated with 25 to 50 mg captopril, 50 to 100 mg metoprolol, 12.5 to 25 mg hydrochlorothiazide, and placebo, each given twice daily for 8 weeks. Antidiabetic treatment remained unchanged during the study. After receiving placebo for a 4 week run-in period, arterial blood pressure was 168/101 +/- 93/10 (mean +/- SEM) mm Hg. Diastolic blood pressure was lowered significantly during all active treatment periods compared to the placebo value of 97 +/- 2 mm Hg: captopril, 92 +/- 1 mm Hg; metoprolol, 90 +/- 1 mm Hg; hydrochlorothiazide, 91 +/- 1 mm Hg. Metabolic variables were not significantly altered by captopril and metoprolol, while hydrochlorothiazide treatment increased hemoglobin A1c from 7.5 +/- 0.3 to 8.2 +/- 0.4% (P less than .001), decreased high-density lipoprotein-cholesterol from 1.19 +/- 0.08 to 1.10 +/- 0.06 mmol/L (P less than .05). Glomerular filtration rate, urinary albumin excretion, orthostatic blood pressure response, and digital systolic blood pressure in the lower limb remained unchanged during the active treatment periods. The frequency of subjective adverse effects was acceptable during active treatment and not significantly different compared to placebo. We conclude that antihypertensive treatment for 8 weeks with captopril or metoprolol in NIDDM patients is well-tolerated and causes no deterioration in metabolic control and kidney function, while hydrochlorothiazide causes a slight deterioration in glycemic control and lipid profile.

Aged↗
PubMed1992

Spreading depression and migraine.

Cortical spreading depression (CSD) is a slowly-moving suppression of electrical activity that travels across the cortex at a rate of 2-5 min-1. CSD is transient, and accompanied by a severe disruption of ion homeostasis, depolarization of nerve cells and enhanced energy metabolism. The slow march of migraine prodromes has many features in common with CSD. On this background it has been suggested that CSD is a mechanism of migraine. Recently, the notion has gained renewed credibility with the demonstration of unique abnormalities of brain blood flow, energy metabolism and magnetoencephalography during migraine attacks which have been replicated point-by-point in the animal model during CSD. Simultaneously, a series of experiments have indicated that CSD is closely linked to activity of the N-methyl-D-aspartate (NMDA)-subtype of the glutamate-receptor. It is suggested, that N-methyl-D-aspartate-antagonism could be the next bid of a rational migraine therapy.

Cerebrovascular Circulation↗
PubMed1991

Prevalence of micro- and macroalbuminuria, arterial hypertension, retinopathy and large vessel disease in European type 2 (non-insulin-dependent) diabetic patients.

The prevalence of micro- and macroalbuminuria was determined in Type 2 (non-insulin-dependent) diabetic patients, less than 76 years of age, attending a diabetic clinic during 1987. All eligible patients (n = 557) were asked to collect a 24-h urine sample for quantitative albumin analysis. Urine collections were obtained in 296 males and 253 females (96%). Normoalbuminuria were defined as urinary albumin excretion less than or equal to 30 mg/24 h (n = 323), microalbuminuria as 31-299 mg/24 h (n = 151), and macroalbuminuria as greater than or equal to 300 mg/24 h (n = 75). The prevalence of macroalbuminuria was significantly higher in males (20%) than in females (6%), while the prevalence of microalbuminuria was almost identical in males (26%) and females (29%). The prevalence of arterial hypertension increased with increased albuminuria, being 48%, 68%, and 85% in patients with normoalbuminuria, microalbuminuria, and macroalbuminuria respectively. Prevalence of proliferative retinopathy rose with increasing albuminuria, being 2%, 5% and 12% in patients with normoalbuminuria, microalbuminuria, and macroalbuminuria respectively. Prevalence of coronary heart disease, based on Minnesota coded electrocardiograms, was more frequent in patients with macroalbuminuria (46%) compared to patients with microalbuminuria (26%) and patients with normoalbuminuria (22%). Foot ulcers were more frequent in micro- and macroalbuminuric patients, being 13% and 25%, respectively, compared to 5% in patients with normoalbuminuria. This cross-sectional study has revealed a high prevalence of microalbuminuria (27%) and macroalbuminuria (14%) in Type 2 diabetic patients. Patients with raised urinary albumin excretion are characterized by obesity, elevated haemoglobin Alc, increased frequency of arterial hypertension, proliferative retinopathy, coronary heart disease and foot ulcers.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed1991

Orthodromic sensory conduction along the ring finger in normal subjects and in patients with a carpal tunnel syndrome.

The purpose of the present study was to examine the value of measuring sensory conduction along the median and ulnar nerves of the fourth finger in the diagnosis of a carpal tunnel syndrome (CTS). In 23 controls, sensory conductions along median and ulnar nerves were identical. In 28 of 38 patients with CTS, stimulation of the ring finger revealed a reduced conduction velocity along sensory median nerve fibres in contrast to normal conduction along ulnar sensory nerve fibres. In 5 patients, a sensory action potential was absent over the median nerve and in another 5 sensory conduction was normal along both nerves. We conclude that testing of sensory conduction along the ring finger is useful in about 74% of patients with CTS, while in the remaining 26% other fingers must be examined to establish the diagnosis.

Adult↗
PubMed1991

Prepro-vasoactive intestinal polypeptide-derived peptide sequences in cerebral blood vessels of rats: on the functional anatomy of metabolic autoregulation.

This study describes the distribution of peptide sequences derived from the prepro-vasoactive intestinal polypeptide (preproVIP) molecule in perivascular nerves of rat brain arteries and arterioles. The peptides were identified by immunohistochemistry using highly specific antibodies. Five peptide sequences (preproVIP 60-76, peptide histidine isoleucine (PHI), preproVIP 111-122, VIP, and preproVIP 156-170) were identified in the perivascular nerves throughout the arterial cerebral circulation. The density of the immunoreactive fibers was highest in the nerves of the larger extracerebral arteries, declining in smaller branching arteries. All peptide sequences were identified in the nerves of small pial arterioles overlying the cortical convexity, whereas capillaries and veins contained no immunoreactive material. Dendritic processes of neocortical neurons immunoreactive for VIP and PHI could be followed towards the brain surface where the processes penetrated into the pial layer, often close to the pial vasculature. Some of the processes were also observed to enter the Virchow-Robin space, close to the arterioles. It is possible that cortical nerve cells containing VIP and PHI release the peptides in the perivascular space during periods of activity and thereby contribute to local vasodilatation associated with changes of neuronal function.

Animals↗
PubMed1991

Effect of insulin-induced hypoglycaemia on absorption of unmodified insulin after subcutaneous or intramuscular injection.

The effect of insulin-induced hypoglycaemia on the absorption of iodine-125 labelled unmodified insulin (10 U) from thigh after subcutaneous or intramuscular injection was studied in eight immobilized, supine, normal subjects. Ultrasonic determination of the subcutaneous thickness was used to accurately localize the site for insulin injection. Insulin absorption was studied twice during hypoglycaemia or normoglycaemia in random order. Insulin absorption was similar after subcutaneous and intramuscular injections (residual activity at 5 h: SC 59.3 +/- 5.0 (+/- SE) %; IM 55.2 +/- 3.7%). Hypoglycaemia did not change the disappearance rate of iodine-125 insulin after either subcutaneous (55.0 +/- 4.4%) or intramuscular injection (52.6 +/- 5.7%), despite a plasma glucose nadir of 1.7 +/- 0.2 mmol I-1. In a controlled study under standardized conditions hypoglycaemia has no effect on insulin absorption rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1991

Absorption of NPH (isophane) insulin in resting diabetic patients: evidence for subcutaneous injection in the thigh as the preferred site.

The absorption kinetics of NPH (isophane) insulin injected subcutaneously into the abdominal wall and subcutaneously (SC) and intramuscularly (IM) into the thigh was studied in 11 Type 1 diabetic patients. The thickness of the subcutaneous adipose tissue layer was measured by ultrasound. NPH (isophane) insulin injected IM into the thigh was absorbed faster than NPH insulin injected SC into the thigh (T50%, IM 8.0 +/- 0.6 h and SC 10.3 +/- 0.7 h, p less than 0.05). No difference in T50% values was found for injection into the abdominal wall (9.7 +/- 1.2h) compared with the thigh. The mean absorption rate from 1.5 to 13.5 h after injection was higher after injection IM into the thigh (6.4 +/- 0.3% of initial dose injected absorbed per h) than after SC injection into the thigh (5.2 +/- 0.3% h-1) and SC into the abdominal wall (5.1 +/- 0.3% h-1) (p less than 0.01). The most constant absorption rate was obtained after SC injection into the thigh (within-study day CV of the mean absorption rate 19.9 +/- 3.2% vs 34.4 +/- 3.2% after IM injection into the thigh and 27.1 +/- 4.9% after SC injection into the abdominal wall (p less than 0.02]. The study provides further evidence that the subcutaneous tissue of the thigh is the preferred injection site for NPH insulin.

Absorption↗
PubMed1990

Cortical spreading depression is associated with arachidonic acid accumulation and preservation of energy charge.

The present study aimed to study the relation between the release of arachidonic acid (AA) and the energy state in cerebral cortices of rats during single episodes of cortical spreading depression (CSD). The changes in concentrations of AA, labile phosphate compounds [ATP, ADP, AMP, and phosphocreatine (PCr)], and glycolytic metabolites (lactate, pyruvate, glucose, and glycogen) were studied during and following the large change of the local direct current (DC) potential. Free AA increased markedly during the DC shift, continued to increase during the subsequent 3 min, and returned to control levels at 4-5 min after CSD. PCr decreased by 38% in the first minutes following the DC shift, while ADP increased by 38%. Both returned to normal within a few minutes. ATP, AMP, and energy charge remained constant throughout the experimental period. Glucose decreased by 47% and glycogen by 34% for a few minutes following CSD, while lactate increased by 105% at 2-3 min and by 77% at 4-5 min after CSD. The metabolites returned to control levels at 10 min after CSD. Considering the constant energy charge at all time points during CSD, it is suggested that the AA rise reflects augmented phospholipase activity due to either increased intracellular [Ca2+] or receptor stimulation or both. The possibility that N-methyl-D-aspartate receptors play a role in the release of AA, and that free AA in turn could be part of the mechanism of CSD, is discussed.

Animals↗
PubMed1990

Influence of MK-801 on brain extracellular calcium and potassium activities in severe hypoglycemia.

The purpose of the present study was to examine the effect of blockade of N-methyl-D-aspartate (NMDA) receptors on the depolarization associated with severe hypoglycemia, which is commonly preceded by one or a few transient depolarizations reminiscent of cortical spreading depression (CSD). In the cerebral cortices of rats [K+]e and [Ca2+]e were measured with ion-selective microelectrodes. NMDA blockade was achieved by injection of MK801 in doses that block CSD. In control rats, the latency from the time point when blood glucose reached minimal levels to onset of ionic shifts was 33.2 +/- 3.5 min, and [K+]e rose from 3.2 +/- 0.2 to 55 +/- 5 mM. All variables remained unchanged in rats treated with MK801. In another four rats treated with MK801, [Ca2+]e declined from 1.06 +/- 0.22 to 0.12 +/- 0.02 mM. Plasma glucose measurements indicated that the cortex depolarized at a plasma glucose concentration between 0.7 and 0.8 mM, i.e., within a narrow range, suggesting a threshold phenomenon. In conclusion, activation of NMDA receptors seems of minor importance for hypoglycemic depolarization. The ionic transients that precede the persistent hypoglycemic depolarization are probably mediated by mechanisms distinct from those of electrically induced CSD.

Animals↗
PubMed1990

Intramuscular versus subcutaneous injection of unmodified insulin: consequences for blood glucose control in patients with type 1 diabetes mellitus.

Using the perpendicular injection technique lean diabetic patients may often inject insulin intramuscularly (IM). Guided by ultrasound measurements of the subcutaneous (SC) thickness of the thigh, the aim of the present study was to re-evaluate the absorption kinetics of unmodified insulin from IM and SC injection sites and to evaluate the consequences of IM injection of unmodified insulin for blood glucose control in Type 1 diabetic patients. T50% values (time until 50% of the injected insulin is absorbed from the injection site) of SC injected, radioactively labelled, human unmodified insulin (125I-Actrapid) were 338 +/- 13 (+/- SE) min, 289 +/- 27 min, and 287 +/- 27 min during rest, light physical activity, and strenuous exercise, respectively. Intramuscularly injected unmodified insulin was absorbed faster, T50% 232 +/- 20 min, 113 +/- 13 min, and 112 +/- 5 min during the same levels of physical activity in the same order. When unmodified insulin (Actrapid) was given IM 30 min before breakfast, lunch, and dinner together with intermediate-acting insulin (Protaphane) SC at 2200 h, a more physiological profile of plasma free insulin and a more stable blood glucose profile was obtained than with SC administration into the thigh. The coefficient of variation of blood glucose concentration during the study (3 days each route) was lower with IM than with SC injection of unmodified insulin (33 +/- 4 vs 43 +/- 3%, p less than 0.01). No difference in frequency of hypoglycaemic attacks was found and patients claimed that IM injection was no more painful than SC injection. These data suggest that IM injection of soluble insulin into the thigh is beneficial.

Adipose Tissue↗
PubMed1990

Variation in absorption of NPH insulin due to intramuscular injection.

To evaluate the importance of accidental intramuscular injection of NPH insulin, we measured disappearance rates of 125I-labeled NPH insulin (Protaphane) from subcutaneous and intramuscular injection sites in the thighs of 11 insulin-dependent diabetes mellitus patients. Both subcutaneous and intramuscular absorption rates were measured four times in each patient. NPH insulin was absorbed much faster when given intramuscularly than when given subcutaneously (T50% = 5.3 vs. 10.3 h, P less than 0.0001). The intrapatient (day-to-day) coefficient of variation (C.V.) of T50% values (C.V. T50%) for subcutaneously injected NPH insulin in this study, where all injections were guided by ultrasound determination of the subcutaneous fat layer, was 18.4%. Intrapatient variation of absorption was significantly lower for subcutaneously than intramuscularly injected NPH insulin (C.V. T50% = 18.4 vs. 29.8%, P less than 0.01) and was also lower than interpatient variation for subcutaneously injected insulin (C.V. T50% = 18.4 vs. 50%, P less than 0.0001). The faster absorption rate and shorter duration of action, together with the higher day-to-day variation in absorption, led us to conclude that intramuscular injection of NPH insulin should be avoided.

Absorption↗