Biomedical subjects

L Friberg

Publications and source records attributed to L Friberg.

At least 55 records · Page 3Linked to original sources

PubMed1993

Ischaemia-induced (symptomatic) migraine attacks may be more frequent than migraine-induced ischaemic insults.

Fifteen consecutive patients with a diagnostic problem of ischaemia-induced migraine with aura (symptomatic migraine) or migraine-associated ischaemia (migrainous infarction) were studied in order to elucidate the mechanisms. Three had a 1 month flurry of daily attacks of migraine auras with or without headache. A severe internal carotid stenosis/occlusion and reduced regional cerebral blood flow (rCBF) was demonstrated. Borderline ischaemia may thus prime the brain for developing migrainous aura with or without migraine (symptomatic migraine). Four patients had a combination of permanent deficits after the very first migraine attack, severe atherosclerosis, risk factors for stroke, high age and no family history of migraine. In these cases the evidence indicates that thromboembolic ischaemia had triggered an attack of migraine with aura (likely symptomatic migraine). Three young females presented long-lasting typical and severe idiopathic migraine with aura. Attack-associated rCBF reduction was likely to have caused permanent, mild, visual or somatosensory deficits (migrainous infarction). In five patients the relationship between migraine and stroke remained unresolved. It seems that ischaemia-induced migraine attacks may be more frequent than migraine-induced ischaemic insults. Therefore, migraine is not as strong a risk factor for stroke as indicated by the mere coincidence of the two disorders.

Adult↗

PubMed1993

Disparity in regional cerebral blood flow during electrically induced seizure.

This is a presentation of 2 cases in which the intraictal regional cerebral blood flow distribution was measured with the 99mTc-HMPAO single photon emission computerized tomography technique during an electrically induced seizure. Although the seizure was verified as generalized on electroencephalography, the regional neuronal activity expressed as rCBF unexpectedly was markedly asymmetrical in one of the cases. These findings demonstrated that the 99mTc-HMPAO technique makes it possible to discriminate intraictal variation in cortical and subcortical activation between the hemispheres during electroencephalography-verified generalized seizures.

Aged↗

PubMed1993

Biological monitoring of toxic metals.

The biological monitoring of metals, when used properly, allows total exposure to a particular metal to be measured from various media. It takes into consideration inter- and intraindividual variations in uptake due to differences in metabolism and physical work load and can be used to identify individuals, or groups of individuals, with high exposure or at high risk. As many metals are retained for long periods, biological monitoring may not only provide information on recent exposure, but also on exposure which occurred a long time ago. Under optimal conditions, the concentration of a metal in biological media can be used to assess exposure, the concentration of the metal in the target or critical organ (ie, the organ where the adverse effects are first observed) and the risks for adverse effects. This paper gives an overview of several important aspects of biological monitoring but does not provide detailed information on particular metals.

Environmental Exposure↗

PubMed1992

Potential language and attentional networks revealed through factor analysis of rCBF data measured with SPECT.

We used changes in regional cerebral blood flow (rCBF) to disclose regions involved in central auditory and language processing in the normal brain. rCBF was quantified with a fast-rotating, single-photon emission computerized tomograph (SPECT) and inhalation of 133Xe. rCBF data were obtained simultaneously from parallel, transverse slices of the brain. The lower slice was positioned to include both Broca's and Wernicke's areas. The upper slice included regions generally regarded by neurobehaviorists as less related to primary auditory or linguistic functions. We presented three types of auditory stimuli to ten healthy, young volunteers: (a) diotically presented Danish speech, (b) dichotic word stimulation, and (c) white noise. Wilcoxon's signed ranks sum test revealed increased rCBF in language-related areas of cortex, viz., Wernicke's area and its right-sided homologous area as well as in Broca's area (left hemisphere), when subjects listened to narrative speech, compared to white noise (baseline). No significant rCBF differences were detected with this test during dichotic stimulation vs. white noise. A more sophisticated statistical method (factor analysis) disclosed patterns of functionally intercorrelated regions. The factor analysis reduced the highly intercorrelated rCBF measures from 28 regions of interest to a set of three independent factors. These factors accounted for 77% of the total variation in rCBF values. These three factors appeared to represent statistical analogues of independent brain networks involved in (I) auditory/linguistic, (II) attentional, and (III) visual imaging activity.

Acoustic Stimulation↗

PubMed1992

Mental stress and cognitive performance do not increase overall level of cerebral O2 uptake in humans.

We measured cerebral metabolic rate of oxygen (CMRO2), cerebral blood flow (CBF), and cerebral lactate output during rest, during the execution of mental arithmetic, and during mental stress induced by physical and psychological annoyance. Measurements were performed in healthy volunteers by use of the Kety-Schmidt technique with 133Xe as the inert gas. Electroencephalographic desynchronization and highly significant increases in plasma catecholamines and heart rate verified that the test measurements were performed during conditions differing distinctly from the resting state. In accordance with an earlier study (Sokoloff et al. J. Clin. Invest. 34: 1101-1108, 1985), a minimal and nonsignificant 1% reduction of global CMRO2 during mental arithmetic was observed, signifying that this form of mental activation was unassociated with any detectable increase in overall cerebral synaptic activity. Mental stress induced a slight but highly significant (P less than 0.002) 6% reduction in global CMRO2. This finding is in contrast to results from earlier investigations and contradicts the generally accepted notion of an association between mental arousal and a diffuse upregulation of cerebral synaptic activity. During mental arithmetic and mental stress, cerebral lactate output increased by 207 and 344%, respectively, but because of large individual variations in the measured responses, the elevations reached statistical significance only during mental arithmetic.

Adult↗

PubMed1992

Effects of axillary blockade on regional cerebral blood flow during dynamic hand contractions.

Regional cerebral blood flow (rCBF) was measured at orbitomeatal (OM) plane +5.0 and +9.0 cm in 10 subjects at rest and during dynamic hand contractions before and after axillary blockade. Handgrip strength was significantly reduced, and rating of perceived exertion increased after blockade. During hand contractions before blockade, contralateral hemispheric cerebral blood flow (CBF) at OM +9.0 increased from a resting value of 58 (49-75) to 63 (52-82) ml.100 g-1.min-1; contralateral motor sensory rCBF at OM +9 from 58 (50-77) to 71 (64-84); motor sensory rCBF at OM +5 from 67 (54-76) to 77 (64-87) and 70 (62-84) contralaterally and ipsilaterally, respectively; and supplementary motor area (SM) rCBF from 64 (53-69) to 75 (67-88) ml.100 g-1.min-1. During dynamic hand contractions after axillary blockade, CBF did not increase at OM +5 or in the SM. Furthermore, contralateral motor sensory rCBF at OM +9 increased much less. Axillary blockade had no effect on resting CBF, rCBF, or increases in the two during hand contractions of the opposite hand. Thus neural feedback from the contracting muscle is necessary for the increases in SM bilateral OM +5 motor sensory rCBF and the maximal increase in contralateral OM +9 motor sensory rCBF during dynamic hand contractions.

Adult↗

PubMed1992

Effects of thyrotropin-releasing hormone on regional cerebral blood flow in man.

To assess the regional changes in cerebral blood flow, 10 healthy volunteers were given 400 micrograms thyrotropin-releasing hormone iv in a double-blind, randomized, cross-over study. Regional cerebral blood flow was determined simultaneously in two slices of the brain, using a single photon emission computerized tomograph and inhalation of 133Xe. Thyrotropin-releasing hormone caused a significant mean increase of 3.7% (range -8.8-22.7) in blood flow in a region consistent with the left thalamus compared to placebo (3.2% decrease). In 25 other regions no significant change was detected. The thalamic region has previously been shown to be a region especially affected by thyrotropin-releasing hormone in animal studies. The thyrotropin-releasing hormone injection was followed by a minor rise in systemic blood pressure, but not a rise that could affect the cerebral blood flow. The effect of thyrotropin-releasing hormone on the regional cerebral blood flow in the thalamic region was much lower compared to changes found in sedated animals given a hundredfold higher dose of thyrotropin-releasing hormone.

Adult↗

PubMed1991

[Surgical treatment of epilepsy resistant to drug therapy. A review].

The prevalence of epilepsy is 7-9 cases per 1,000 population, corresponding to 440,000 individuals in Denmark. Approximately 1/4 of these individuals have seizures refractory to anticonvulsant medications and most of them have an epileptic focus in the temporal lobe. Epilepsy refractory to anticonvulsant medication is an incapacitating disease with high costs for the person and the society. The main problems are polypharmacy with side effects, suspicion of neurodegenerative consequences and a higher mortality. The modern era of epilepsy surgery began more than 100 years ago and since then, the developments in neurophysiology and neuroimaging have made it possible to demonstrate the epileptic focus with relatively high precision. As a consequence of this, the volume of the resected tissue has diminished and the operative complications become less frequent. The somatic and neuropsychological effects of a cortical resection are discrete and compensated by a general improvement in performance. Surgical treatment of epilepsy should no longer be considered as a last resort, but as a realistic treatment in cases of medication failure.

Anticonvulsants↗

PubMed1991

[3-year experiences with surgical treatment of epilepsy at the Hvidovre hospital].

The results of a retrospective survey of 48 patients submitted to neurosurgery for medically intractable epilepsy are presented. Twenty-eight patients were treated with selective amygdalohippocampectomy, one with temporal lobe resection, 12 with anterior callosotomy and seven with a total callosotomy. Of the amygdalohippocampectomized patients and the one with temporal lobe resection (n = 29), 52% were seizure free, 17% experienced rare seizures, 7% had a worthwhile improvement while 24% observed no worthwhile improvement (follow-up time 6 to 36 months). Of the callosotomized patients, 11% were free from generalized seizures, 69% had a significant seizure reduction and 18% experienced no worthwhile improvement. The observed neurological complications were: one patient had hemianopia, one had superior quadrant anopia, four developed unilateral anosmia and one complete anosmia. The callosotomized patients, with two exceptions, were all mentally and physically handicapped. In the callosotomy group, two patients died, one from a intracerebral hematoma three months after the operation and another patient seven months postoperatively from unknown causes.

Adult↗

PubMed1991

Migraine pain associated with middle cerebral artery dilatation: reversal by sumatriptan.

The combination of measurements of regional cerebral blood flow (rCBF) and blood velocity in the middle cerebral arteries (MCA) by transcranial doppler sonography was used to investigate cerebrovascular involvement in migraine. Ten migraine patients with unilateral headache were studied during an attack and when they had been free of attacks for 5 days (non-attack). On both occasions they were given as intravenous infusion of sumatriptan (2 mg), a 5-HT1-like receptor agonist, which relieved the symptoms within 30 min without affecting rCBF. The MCA velocity was normal on both sides on the non-attack day and on the unaffected side during the attack. However, during the attack the MCA velocity on the headache side was significantly lower than that on the non-headache side (45 vs 61 cm/s:mean difference 16.3 [95% confidence interval 10.3-22.3]; p = 0.02). The MCA velocity on the headache side returned to normal after treatment with sumatriptan and recovery. Since rCBF in the MCA supply territory was unaffected, the lower velocity can be explained only by dilatation of the MCA. The mean MCA diameter increase was estimated to be 20%. Thus, headache was associated with intracranial large arterial dilatation on the headache side. Sumatriptan predominantly had effects on the distended artery, which suggests that the 5-HT receptor system has a role in the pathogenesis of migraine.

Adult↗

PubMed1991

Cerebrovascular instability in a subset of patients with stroke and transient ischemic attack.

In six patients, we observed remarkably unsteady blood flow and indications of vasospasms on the arteriolar level in connection with episodes of focal cerebral ischemia. The patients originated from a prospective consecutive study of 53 patients with stroke and transient ischemic attack who had been examined by cerebral angiography and rapidly repeated regional cerebral blood flow measurements using the intracarotid xenon 133 method. In 47 patients, regional cerebral blood flow values, flow patterns, and clinical condition were stable during the repeated regional cerebral blood flow measurements. In six patients, pronounced regional hypoperfusion and hyperperfusion developed during the course of examination. In the hypoperfused regions, flow was transiently reduced to values consistent with ischemia, and in four of these patients this was accompanied by transient neurological deficits. The arteriogram and isotope angiograms ruled out spasms of large arteries or thromboembolism. A condition of cerebrovascular instability on the arteriolar level probably was induced by the examination procedure. These patients were hypersensitive to the provoking stimuli either habitually or as a consequence of previous ischemic accidents. It is suggested that in some patients with focal cerebral ischemia, the primary cause might be spasms of the smallest resistance vessels rather than thromboembolism.

Aged↗

PubMed1991

Altered modulation of prefrontal and subcortical brain activity in newly diagnosed schizophrenia and schizophreniform disorder. A regional cerebral blood flow study.

To measure prefrontal and subcortical activity during a cognitive task, we examined 19 newly diagnosed schizophrenics and patients with schizophreniform psychosis. Seven healthy volunteers served as controls. The patients were drug naive or had received neuroleptics for a few days only. Cerebral blood flow distribution was depicted by single photon emission computed tomography at rest and during activation with the Wisconsin Card Sorting Test. A significant relative activation deficit in the left inferior-prefrontal region was revealed during the Wisconsin Card Sorting Test in the patient group. Furthermore, the patients had impaired striatal suppression on the left side during the cognitive task. The test performance was significantly impaired in the patients. The inability to reduce striatal activity may be due to a lack of corticostriatal feedback during prefrontal activation.

Adult↗

PubMed1991

Scientific basis for an occupational standard for cadmium.

The U.S. Occupational Safety and Health Administration (OSHA) has proposed a revised 8-hour permissible exposure limit (PEL) for cadmium in air of either 1 or 5 micrograms/m3, based upon the prevention of lung cancer and kidney dysfunction. To evaluate the scientific basis for these alternative standards, we compare the OSHA estimates of risk, derived from mathematical modelling of selected studies, to empirical data on lung cancer and kidney dysfunction in the published literature. At least seven epidemiologic studies examine renal tubular proteinuria by cumulative cadmium exposure. Three suggest increased proteinuria at cumulative exposures below 500 micrograms/m3-year (equivalent to a PEL of 11.1 micrograms/m3 over 45 working years). One shows prevalence increasing at cumulative exposures between 100 and 299 micrograms/m3 (equivalent to a PEL between 2.2 and 6.6 micrograms/m3). Insufficient data exist to estimate a no-effect level for kidney toxicity. For lung cancer, qualitative evidence of carcinogenicity in humans is seen in four of five occupational cohorts. Quantitative estimates of risk based on epidemiologic data provide lower and more plausible estimates of lifetime risk than do estimates from a rodent bioassay. The data overall suggest that the PEL for cadmium should not exceed 5 micrograms/m3 to protect workers from kidney dysfunction and lung cancer over a working lifetime.

Air Pollutants, Occupational↗

PubMed1991

Cerebral blood flow changes in migraine: methods, observations and hypotheses.

A number of basically different methods have been used in studies of the cerebrovascular changes which occur in migraine and each individual set of findings seems to be dependent on which method is used. One method on its own can only disclose a part of all the pathophysiological events. This review is an attempt to consider the capabilities of each method and to bring together the results from different studies on migraine in order to create a complete picture of the cerebrovascular changes which occur during the course of a migraine attack.

Animals↗

PubMed1991

Methods for integrated exposure monitoring of lead and cadmium.

An international pilot monitoring study on exposure to lead (Pb) and cadmium (Cd) has been implemented in Beijing, Yokohama, Stockholm, and Zagreb as part of the UNEP/WHO human exposure assessment locations (HEAL) Program. The main objective was to develop and test methods, including methods for quality assurance, for monitoring of personal exposure to Pb and Cd. The study included analytical training for Pb and Cd in blood, air filters, dust, diets, and feces, as well as exposure monitoring activities in small groups of nonsmoking women, 23-53 years of age, during 7 consecutive days. Airborne particulates, duplicate diets, feces, and blood were collected. An extensive quality assurance program was implemented in order to assure the reliability and comparability of the monitoring data. The main problem in the sample collection was associated with the air monitoring. The pumps were noisy, and the batteries had to be recharged every 6-8 hr. Collection of duplicate diets during 1 week gave good estimates of average dietary intakes of Pb and Cd. The metal contents in feces were found useful for evaluation of total peroral intakes. The methods used made it possible to demonstrate that the diet was the main source of Cd exposure at all the HEAL sites.

Adult↗

PubMed1991

Human regional cerebral blood flow during rapid-eye-movement sleep.

Owing to the coupling between CBF and neuronal activity, regional CBF is a reflection of neural activity in different brain regions. In this study we measured regional CBF during polysomnographically well-defined rapid-eye-movement (REM) sleep by the use of single photon emission computerized tomography and the new tracer 99mTc-dl-hexamethylpropyleneamine. Eleven healthy volunteers aged between 22 and 27 years were studied. CBF was measured on separate nights during REM sleep and during EEG-verified wakefulness. On awakening from REM sleep, all subjects reported visual dreams. During REM sleep CBF increased by 4% (p less than 0.01) in the associative visual area, while it decreased by 9% (p less than 0.01) in the inferior frontal cortex. The CBF increase in the associative visual area suggests that activation of cerebral structures processing complex visual material is correlated to visual dream experiences. On the other hand, the reduced involvement of the inferior frontal cortex observed during REM sleep might explain the poor temporal organization and bizarreness often experienced in dreams.

Adult↗

PubMed1991

Cerebral O2 metabolism and cerebral blood flow in humans during deep and rapid-eye-movement sleep.

It could be expected that the various stages of sleep were reflected in variation of the overall level of cerebral activity and thereby in the magnitude of cerebral metabolic rate of oxygen (CMRO2) and cerebral blood flow (CBF). The elusive nature of sleep imposes major methodological restrictions on examination of this question. We have now measured CBF and CMRO2 in young healthy volunteers using the Kety-Schmidt technique with 133Xe as the inert gas. Measurements were performed during wakefulness, deep sleep (stage 3/4), and rapid-eye-movement (REM) sleep as verified by standard polysomnography. Contrary to the only previous study in humans, which reported an insignificant 3% reduction in CMRO2 during sleep, we found a deep-sleep-associated statistically highly significant 25% decrease in CMRO2, a magnitude of depression according with studies of glucose uptake and reaching levels otherwise associated with light anesthesia. During REM sleep (dream sleep) CMRO2 was practically the same as in the awake state. Changes in CBF paralleled changes in CMRO2 during both deep and REM sleep.

Adult↗

PubMed1991

Effect of axillary blockade on regional cerebral blood flow during static handgrip.

Regional cerebral blood flow (rCBF) was determined at rest and during static handgrip before and after regional blockade with lidocaine. A fast rotating single photon emission computer tomograph system with 133Xe inhalation was used at orbitomeatal plane (OM) +2.5 and +6.5 cm in eight subjects. Median handgrip force during the control study was 41 (range 24-68) N, which represented 10% of the initial maximal voluntary contraction (MVC) and was 24 (18-36) N after axillary blockade (P less than 0.05), which represented 21% of the new MVC. During static handgrip, the rating of perceived exertion was 14 (10-16) exertion units before and 18 (15-20) after blockade (P less than 0.05). Hemispheric mean CBF did not change during handgrip. However, premotor rCBF increased from 55 (44-63) to 60 (50-69) ml.100 g-1.min-1 (P less than 0.05) and motor sensory rCBF from 57 (46-65) to 63 (55-71) ml.100 g-1.min-1 (P less than 0.05) to both the ipsilateral and contralateral sides during handgrip before, but not after, axillary blockade. There was no change in rCBF to other regions of the brain. Regional anesthesia with lidocaine did not alter resting rCBF. However, despite a greater sense of effort during static handgrip, there was no increase in rCBF after partial sensory and motor blockade. Thus bilateral activation occurs in the premotor and motor sensory cortex during static handgrip, and this activation requires neural feedback from the contracting muscles.

Adult↗