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Biomedical subjects

A Persson

Publications and source records attributed to A Persson.

At least 145 records · Page 8Linked to original sources
PubMed1986

Autonomic system dysfunction and polyneuropathy in nondiabetic uremia. A one-year follow-up study after renal transplantation.

Polyneuropathy and autonomic dysfunction were studied in 15 patients with nondiabetic terminal uremia before renal transplantation and again at 6 and 12 months after the transplantation. Beat-to-beat variation of the electrocardiogram (ECG) relative to mean beat interval was used as an observation of the function of the parasympathetic vagal reflex arc. Marked autonomic dysfunction--i.e., reduced beat-to-beat variation and a mild diffuse polyneuropathy--was found. The neuropathy was mainly of axonal type, but a slowing of conduction velocities was also found. The latter was markedly improved after transplantation and is suggested to be caused by a toxic metabolic factor, possibly causing nodal dysfunction. Action potential amplitudes and autonomic function did not improve during the study. This implies a structural damage that is not repaired in 12 months. Neurological examination should be included in the care of patients with uremia, and the results should be one of the factors considered when transplantation is discussed.

Autonomic Nervous System↗
PubMed1986

Peripheral benzodiazepine binding sites in human gliomas evaluated with positron emission tomography.

A specific ligand for peripheral type benzodiazepine receptors, Ro5-4864, was synthesised and labelled with 11C for use in positron emission tomography (PET). Four patients with suspected glioma, two patients with high grade astrocytoma and two with low grade astrocytoma, as well as one patient with meningioma were examined with PET after the administration of 200 MBq 11C-Ro5-4864. The images as well as kinetic analyses revealed lower uptake of the ligand in tumor as compared with cortical tissue. Markedly elevated uptake in the thalamus suggests a functional role of the ligand.

Benzodiazepinones↗
PubMed1985

Imaging of [11C]-labelled Ro 15-1788 binding to benzodiazepine receptors in the human brain by positron emission tomography.

The benzodiazepine antagonist Ro 15-1788 was labelled with [11C] and examined for possible use as ligand for PET scan studies on benzodiazepine receptors in the brain of cynomolgus monkeys and human subjects. [11C] Ro 15-1788 allowed the in vivo visualization of benzodiazepine receptor binding in cerebral and cerebellar cortical areas as well as in basal brain nuclei in PET scan images. [11C] Ro 15-1788 exhibited a high ratio of specific benzodiazepine receptor binding (cerebral cortex) to non-specific binding (pons) and the kinetics of binding should be satisfactory for quantitative clinical PET scan studies using [11C]. The in vivo binding of [11C] Ro 15-1788 in the cerebral cortex of cynomolgus monkeys and healthy human subjects was reduced by approximately 90% within 10 min after the intravenous injection of a high dose of unlabelled Ro 15-1788 (0.5 mg/kg i.v.). Different areas of the healthy human brain showed an approximately 10-fold variation in maximal [11C] Ro 15-1788 binding that corresponded to the previously known distribution of benzodiazepine receptors in these regions. The highest degree of binding was obtained in the medial occipital cerebral cortex followed by frontal cortex, cerebellum, thalamus, striatum and pons. Two psychiatric patients with anxiety syndromes who had been treated for a long time with high doses of benzodiazepines had roughly the same degree of maximal [11C] Ro 15-1788 binding in brain regions as the healthy subjects but the rate of decline of [11C] Ro 15-1788 in the brain was higher. This indicates that there is measurable competition between [11C] Ro 15-1788 binding and clinical benzodiazepine concentrations in the body fluids of psychiatric patients. The results demonstrate that [11C] Ro 15-1788 should be a valuable tool for quantitative analyses of benzodiazepine receptor characteristics and receptor occupancy in the brain of patients with neuropsychiatric disorders.

Adult↗
PubMed1985

Nerve conduction in diabetic pregnancy. A prospective study.

Repeated neurographic examinations were performed during and after the pregnancies of 32 diabetic women who had no signs of neuropathy before pregnancy or at the initial examination during the first trimester. The motor conduction velocity, the sensory conduction velocity and the peak amplitude of the compound action potential of the investigated peripheral nerves were not affected by pregnancy. It is concluded that pregnancy does not impair nerve conduction or induce neuropathy in most diabetic women.

Action Potentials↗
PubMed1985

Autonomic dysfunction in experimental allergic neuritis.

Beat-to-beat variation (R-R variation) in the electrocardiogram was studied in experimental allergic neuritis in the Sprague-Dawley rat. Reduced R-R variations were found in 2 of 10 animals, probably as a sign of autonomic dysfunction. The vagal nerves from these two animals, studied in vitro, showed disturbed conduction. In one animal prolonged conduction latencies to supramaximal electrical stimuli were found. Vagal nerves from controls and from animals without clinical symptoms showed normal conduction. Histologically, the vagal nerves from affected animals showed a slight inflammatory cell infiltration and signs of demyelination but there was no evidence of involvement of the brainstem vasomotor nuclei. Thus, we suggest that the autonomic dysfunction in experimental allergic neuritis, measured as reduced R-R variations, is caused by a peripheral vagal neuropathy.

Animals↗
PubMed1985

Autonomic dysfunction in non-diabetic terminal uraemia.

R-R variations in the ECG were studied as a sign of autonomic dysfunction in 44 non-diabetic patients with terminal uraemia treated with intermittent haemodialysis. A severe impairment of this parasympathetic vagal reflex was found though there were only mild signs of diffuse polyneuropathy. No acute effect was associated with haemodialysis. There was no correlation between either the R-R variations and the polyneuropathy-index or the total dialysis time. Patients with chronic glomerulonephritis, pyelonephritis and polycystic kidney disease were equally affected.

Adolescent↗
PubMed1984

Do large diameter cutaneous afferents have a role in the transmission of nociceptive messages?

In recent studies, it has been reported that high-frequency stimulation restricted to A alpha beta fibers in man can be perceived as painful and evoke a nociceptive flexion reflex. These results would indicate that some patterns of activity in low-threshold mechanoreceptors can lead to painful sensations. Because of the theoretical importance of this question, the above studies were extended by recording the evoked neural activity with the technique of percutaneous microneurography. Painful sensations and the nociceptive reflex did not appear unless the evoked nerve response contained activity in A delta fibers. The results support the theory that painful sensations occur in normal man only when nociceptor afferents are activated.

Acoustic Stimulation↗
PubMed1984

Subarachnoid injection of salmon calcitonin does not induce analgesia in rats.

It has been proposed that the polypeptide calcitonin (CT) occurs in the central nervous system and may have a neuromodulatory role in endogenous pain relief pathways. However, recent results suggest that CT is not present in the central nervous system. Intrathecal (IT) injection of CT on the lumbar enlargement of rats caused a reversible increase of the hindpaw lick latency in the hot plate test. No analgesia was observed with the vocalization test to electrical stimulation of the tail. In contrast 10 micrograms morphine hydrochloride IT caused analgesia in both tests. It is concluded that IT CT does not cause analgesia, but has a reversible blocking effect on motor responses.

Analgesia↗
PubMed1984

Surface defects on thin cryosections.

The electron microscopic observation of thin cryosections is frequently impaired by the occurrence of surface defects. To investigate the possible causes of these surface defects the structure of cryosections ( CTEM ) from frozen biological material was correlated with the structure of the block-face (SEM) from which the sections were obtained. Both sections and block-face showed steps with a periodicity larger than 0.5 micron. Upon dry sectioning of hard plastic comparable features were observed in the section ( CTEM /SEM) and block-face (SEM). Thin cryosections cut below 143 K were found to be smooth apart from defects introduced by imperfections of the knife. In addition to "long" wave length distortions, a periodical distortion smaller than 120 nm can be observed in cryosections from biological material. At a given temperature the frequency is related to the sectioning speed. At all sectioning temperatures studied, distortions of this high frequency/short wave length type have been observed although they were less conspicuous in thinner sections. The surface defects observed in cryosections from biological material resemble the defects found after metal cutting and chip-formation. Shear forces seem to be the main causes for the observed periodic deformations on both cryosections as well as on sections from metals and plastics. This may imply that material is collected and periodically shedded from a dead zone around the knife edge. In metal cutting such a dead zone can have the form of a built-up-edge on top of the knife or as a small overhang in front of the knife edge.

Animals↗
PubMed1983

EEG topogram--an aid in describing EEG to the clinician.

The investigation presents a simple, reliable method to show localized EEG abnormalities in a topographical display. The aim of the study was to find a method which could be used in clinical practice, and which in topographical form could complement the written EEG report with information about degree and localization of an EEG abnormality. The EEG was recorded on a 21-channel polygraph (Siemens-Elema). The source derivation recording technique was used. Besides being displayed as a conventional EEG record, the signals were fed to a small computer that calculated an abnormality feature based on the time domain descriptors activity, mobility and complexity. Obtained values were converted into ink density in topograms by modulating the displacement velocity of the ink jet beam. The dynamic range was chosen so that maximum and minimum densities represented 1.5 and 0.5 times the average for each descriptor. The ink density in the topogram was thus related to the degree of EEG abnormality. The recording procedure followed the ordinary clinical routine except that the conventional EEG display was interrupted several times for a few seconds, on command by the EEG technician, to write out the topogram on the EEG paper. It is concluded that EEG topograms produced on line as part of the EEG examination procedure may greatly enhance EEG information conveyed from the neurophysiologist to the clinician. Furthermore, they permit direct visual comparison with other diagnostic topographic displays such as CT scan.

Brain↗
PubMed1983

Kinetics of clonazepam in relation to electroencephalographic and clinical effects.

The aim of this study was to see if the immediate EEG and clinical response to an intravenous dose of clonazepam was predictive for the effect of oral clonazepam maintenance therapy. Four children with petit mal epilepsy were given clonazepam intravenously during continuous EEG recording. Clonazepam plasma concentrations were determined repeatedly with a high performance liquid chromatographic method using a reversed phase system. The day after the intravenous dose the patients were given oral therapy with clonazepam. Repeated long-term EEG recordings were made and plasma concentrations of clonazepam were determined. There was no clinically satisfactory effect of clonazepam during oral maintenance treatment in three of the children who responded well to the intravenous dose of clonazepam. Thus, the immediate response to intravenous clonazepam was not a good predictor of the long-term effects in our patients.

Adolescent↗
PubMed1983

R-R variations, a test of autonomic dysfunction.

Beat-to-beat variation of the heart rate was studied as a test of autonomic function. Recordings were made during quiet breathing, deep breathing and tilting from supine to upright position. The heart rate variations were expressed as a % of mean R-R interval. In order to establish normal criteria, the influence of age, wakefulness and intra-individual variations was studied in healthy volunteers. A negative correlation with age was found for all measured parameters. Patients with diabetic polyneuropathy differed from age-matched controls. Patients with symptoms of autonomic failure showed smaller variations than those without such symptoms.

Adult↗
PubMed1983

R-R variations in Guillain-Barré syndrome: a test of autonomic dysfunction.

As we have earlier shown, variations in the R-R interval of the ECG can be used as a measure of autonomic function. This test was applied to 6 patients with Guillain-Barré syndrome at different times during the course of the disease. Severe but temporary impairment of autonomic function was found, which was maximal at 2-6 weeks after the onset of clinical symptoms and gradually improved to normal levels over a period of 3-18 months. This paralleled clinical recovery. The results suggest that this test of R-R variations is a reliable method for establishing and following an autonomic dysfunction in patients with Guillain-Barré syndrome.

Adolescent↗
PubMed1982

Concerning the nature of the cryosectioning process.

Intentional melting of frozen-thin-sections induces ultrastructural alterations. Cross sections through frozen dried and embedded cryosections revealed that even at the surface of such a section no melting artefacts are visible. One surface of the cryosection (obtained at 168 K) has a saw-teeth appearance whereas the other surface is rather smooth. The rate of freeze-drying in the cryochamber of the microtome was estimated to be in order 3.3 nm/min at 183 K and 22.5 nm/min at 193 K for sections, about 120 nm thick, of rat kidney frozen in freon 22 without any chemical fixation of cryoprotection. Although freeze-drying will normally not interfere with the cryo-sectioning process itself, it is a process which cannot be neglected during handling of sections. The available evidence indicated that frozen-thin-sections represent the frozen tissue with respect to the ultrastructure an probably also with respect to the chemical composition.

Animals↗