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Biomedical subjects

L Friberg

Publications and source records attributed to L Friberg.

At least 73 records · Page 4Linked to original sources
PubMed1991

Clearance of xenon-133 from bone marrow in patients with small-cell lung cancer.

The aim of this study was to estimate bone-marrow blood flow (BMBF) in man and to correlate this with myelosuppression induced by cytostatic treatment dosed as a function of surface area. Twenty-four patients suffering from small-cell lung cancer participated in the study. Blood flow was measured with the xenon-133 washout technique. The 133Xe clearance measurement took place in conjunction with the pre-treatment bone-marrow staging procedure (ad modern Radner). Tissue samples were taken for microscopy and for the determination of the blood-to-tissue partition coefficient lambda. After the bone-marrow aspiration, 0.1-0.2 ml of 133Xe in saline was injected into the bone marrow and the cannula was removed. Following a hyperaemic phase of 12 min (7-16 min), monoexponential washouts were demonstrated. The median washout rate constant was 0.0063 min-1 (0.0038-0.0098 min-1). Lambda values of 0.3-3.5 ml g were found, but microscopy of the bone marrow showed a fairly large admixture of peripheral blood. Therefore, the lambda values should be taken with caution and absolute blood-flow values were not calculated. The results demonstrated no correlation between 133Xe clearance from crista iliaca and leucocyte or platelet suppression.

Aged↗
PubMed1991

Personal monitoring of lead and cadmium exposure--a Swedish study with special reference to methodological aspects.

Methods for determining personal exposure to lead and cadmium were tested in Stockholm in 1988. Lead and cadmium in breathing-zone air, 24-h duplicate diets, and feces of 15 nonsmoking women (27-46 years of age) were studied. Blood was collected at the beginning of and immediately after the test period (seven consecutive days). An extensive quality assurance program was included. Most technical problems were encountered in the 24-h collection of airborne particles. The pumps were noisy, and the batteries had to be recharged every 6-8 h. The lead and cadmium levels in feces were found to be useful indicators of the total ingested amounts of these metals. Because of the large day-to-day variation in the dietary intake of lead and cadmium, the sampling period for duplicate diets and feces should be at least 5-6 d.

Adult↗
PubMed1990

[Migraine aura--vascular or neuronal disease?].

During the migraine-aura cerebral blood flow (CBF) is reduced in areas corresponding to the neurological deficits and symptoms. Whether this CBF reduction is the primary cause of the neurological deficits (the vascular theory) or a secondary result of primary neuronal dysfunction in particular "spreading depression" (SD) (the neurogenic theory) is still under discussion. The latter theory is supported by CBF investigations performed during attacks of migraine with aura (MA). The CBF reduction was found to be modest (20-35%) and not sufficient to cause ischemia which usually demands reduction of CBF by more than 50%. In addition the low-flow area appeared to "spreading" in the same manner as that seen in SD in the rat ("spreading oligemia"). Recent studies indicate, however, that the CBF reduction in most cases, after all, is sufficient to cause ischemia and that "spreading oligemia" might be an artifact caused by "scattered radiation". Persistent neurological deficits, EEG abnormalities and infarcts on CT-scans are seen after MA, thus further supporting the theory of vascular dysfunction (vasospasm) and ischemia as the cause of the migraine-aura.

Cerebrovascular Circulation↗
PubMed1990

Immature pattern of brain activity in Rett syndrome.

Seven girls with Rett syndrome, a progressive degenerative encephalopathy affecting girls, were studied with single photon emission computed tomography and compared with an aged-matched control group of nine normal children. Global cerebral blood flow was significantly lower in Rett syndrome (54 vs 69 mL/100 g per minute), and the flows in prefrontal and temporoparietal association regions of the telencephalon were markedly reduced, whereas the primary sensorimotor regions were relatively spared. The flow distribution in Rett syndrome is very similar to the distribution of brain metabolic activity in infants of a few months of age. The abnormal regional cerebral blood flow distribution most likely reflects the widespread functional disturbances in the brain of patients with Rett syndrome, whereas computed tomographic and neuropathologic examination only reveal slight changes when compared with normal children.

Adolescent↗
PubMed1990

Timing and topography of cerebral blood flow, aura, and headache during migraine attacks.

Ten years of study has resulted in considerable but fragmented knowledge about regional cerebral blood flow in migraine with aura (classic migraine). In the present study, the number of repeatedly studied patients (n = 63) was large enough to determine statistically significant sequences of events and statistically significant spatial relations. The first observable event was a decrease of regional cerebral blood flow posteriorly in one cerebral hemisphere. Further development of this pathological process was accompanied by the aura symptoms. Thereafter headache occurred while regional cerebral blood flow remained decreased. During the headache phase, regional cerebral blood flow gradually changed from abnormally low to abnormally high without apparent change in headache. In some patients headache disappeared while regional cerebral blood flow remained increased. Although regional cerebral blood flow reduction and aura symptoms in the great majority of patients were unilateral, one-third had bilateral headache. Unilateral headache usually localized to the side on which regional cerebral blood flow was reduced and from which the aura symptoms originated (i.e., aura symptoms were perceived to occur contralaterally but presumably originated in the hypoperfused hemisphere). Our results suggest a simple model for migraine attacks: A pathological disturbance in one cerebral hemisphere causes the aura symptoms and after a time delay, it also causes the headache by stimulating local vascular nociceptors. Bilateral headache caused by a unilateral cerebral disturbance may be explained by recent neuroanatomical and neurophysiological findings.

Adolescent↗
PubMed1990

The effect of the benzodiazepine antagonist flumazenil on regional cerebral blood flow in human volunteers.

The influence of the benzodiazepine antagonist flumazenil on regional cerebral blood flow (rCBF) was investigated in ten healthy, alert volunteers. The design was a randomized, placebo-controlled, double-blind, cross-over study. rCBF was measured by 133-Xe inhalation and single photon emission computerized tomography, SPECT, immediately before, and 5 and 35 min after intravenous injection of flumazenil 1.0 mg or placebo. In addition, mean arterial blood pressures or PaCO2, rCBF were analysed for changes in various regions of interest (RoI). No alterations were found either in the global CBF or in rCBF in RoI after flumazenil injection. The results showed that a clinically active dose of flumazenil did not directly affect the cerebral circulation in the normal brain and indicated absence of significant intrinsic activity of the drug.

Adult↗
PubMed1990

Cerebral blood flow and end-tidal PCO2 during prolonged acetazolamide treatment in humans.

One oral dose of 1,000 mg of acetazolamide caused an acute 38% increase in cerebral blood flow (CBF) in eight healthy volunteers. During the following 10 days the subjects took 1,000 mg acetazolamide daily. CBF normalized within the first 2 days. The drug induced mild hyperventilation, gradually decreasing alveolar PCO2 to 70% of the control value at the end of the treatment period. In healthy humans the hyperventilation will not increase brain oxygenation significantly at sea level. But at high altitudes the enhanced ventilatory drive will improve oxygenation of the brain, and this may account for the beneficial effects of the drug on the symptoms of acute mountain sickness. During the treatment there was a significant 10% decrease of the hematocrit but an unaltered hemoglobin concentration. In combination with data in the literature our studies suggest that the initial CBF increase is a consequence of a transient extracellular acidosis dilating brain arterioles, whereas increased ventilatory drive results from a gradually increasing mild intracellular acidosis in the brain.

Acetazolamide↗
PubMed1989

Mercury accumulation in tissues from dental staff and controls in relation to exposure.

Samples, mainly from occipital cortex and pituitary gland, but also from rental cortex, olfactory bulbs, thyroid gland and liver were collected from autopsies of 8 dental staff cases and 27 controls. These samples were analysed for total mercury content using radiochemical neutron activation analyses. The results revealed high mercury concentrations (median 815, range 135-4,040 micrograms Hg/kg wet weight) in pituitaries from the dental staff cases compared to controls (N = 23, median 23 range 6-1, 170 micrograms Hg/kg). In occipital cortex, the cases had a median of 17, range of 4-300 micrograms Hg/kg and the controls (N = 20) had a median of 10, range 2-29 micrograms Hg/kg. A few samples from olfactory bulbs show low mercury concentrations for both cases and controls. Renal cortex was analysed from three cases and contained clearly higher concentrations (945, 1,545, 2,110 micrograms Hg/kg) compared to controls (N = 12, median 180, range 21-810 micrograms Hg/kg). There is no control material for the other analysed samples, but one thyroid sample had an extremely high concentration of 28,000 micrograms Hg/kg.

Adolescent↗
PubMed1988

Delayed hyperemia following hypoperfusion in classic migraine. Single photon emission computed tomographic demonstration.

Regional cerebral blood flow (rCBF) was measured in seven patients during classic migraine attacks. Single photon emission computed tomography was performed soon after hospital admission, and three to eight hours, 20 to 24 hours, and one week later after the onset of symptoms. Initially reduced rCBF persisting up to three hours was observed in the hemisphere appropriate to the focal neurologic deficit; hyperperfusion was noted later in the same region in these patients. At 24 hours rCBF was normal in four patients, hyperemia persisted in two patients, and one patient was not restudied. The area of interest demonstrated a mean decrease of 19% +/- 7% in side-to-side asymmetry when compared with the contralateral region. In three to eight hours this reversed to a mean increase of 19% +/- 4% (delayed hyperemia). No asymmetries were observed after one week. The late hyperemic asymmetry often persisted beyond the duration of the clinical headache. It is postulated that this tardive regional hyperperfusion is a consequence of previous focal arteriolar vasoconstriction. This vascular sequence of events further delineates the diagnostic merit of studying rCBF by noninvasive single photon emission computed tomography in migraine.

Adult↗
PubMed1988

Neuroticism, extraversion, and related traits in adult twins reared apart and reared together.

The relative importance of genetic and environmental factors for neuroticism, extraversion, impulsivity, and monotony avoidance were estimated in a sample of 99 monozygotic and 229 dizygotic pairs of twins reared apart (TRA) and a matched sample of 160 monozygotic and 212 dizygotic pairs of twins reared together (TRT). The average age was 58.6 (SD = 13.6); 72% of the twins were 50 or older. Model-fitting analyses verified the importance of genetic factors for all four measures; from 23% to 45% of the total variation was attributable to genetic sources. There was considerable evidence that these factors were operating in a nonadditive manner for extraversion and impulsivity. Shared environment accounted for less than 10% of the variance; some evidence for selective placement was found for neuroticism.

Diseases in Twins↗
PubMed1988

The retention of [99mTc]-d,l-HM-PAO in the human brain after intracarotid bolus injection: a kinetic analysis.

[99mTc]-d,l-HM-PAO (HM-PAO) was injected rapidly into the internal carotid artery and its retention in the brain was recorded by external scintillation cameras in eight human subjects. A model is described based on three compartments: the lipophilic tracer in the blood pool of the brain, the lipophilic tracer inside the brain, and the hydrophilic form retained in the brain. The retention curve initially drops abruptly, corresponding to the nonextracted fraction of the injectate leaving the brain; it then falls exponentially towards the asymptotic level of the fractional steady-state retention R. Cerebral blood flow (F) was measured using the xenon-133 intracarotid injection method. The first-pass extraction E of HM-PAO was calculated from F using an empiric regression equation. The residue curves for the whole brain after intracarotid HM-PAO injection were analyzed to yield a retention fraction (R') and the brain clearance backflux constant of lipophilic HM-PAO (k). From the kinetic model and the measured values of R', k, and F, the following parameter values could be calculated: the average retained fraction of all tracer supplied to the brain, R = 0.38 +/- 0.05 (mean +/- SD), the conversion rate constant (lipophilic to hydrophilic tracer) in the brain k3 = 0.80 +/- 0.12 min-1, the efflux rate constant (brain to blood) k2 = 0.69 +/- 0.11 min-1, the conversion/clearance ratio alpha = k3/k2 = 1.18 +/- 0.25, the influx (blood clearance) constant K1 = 0.45 +/- 0.11 ml/g/min, and the brain/blood partition ratio lambda = K1/k2 = 0.67 +/- 0.23 ml/g. Using the kinetic model and assuming constancy of alpha, an algorithm was developed that corrects for the blood flow dependent backflux of HM-PAO and results in a more linear relation between regional cerebral blood flow (rCBF) and HM-PAO distribution.

Adult↗
PubMed1988

The effect of the GABA-A agonist THIP on regional cortical blood flow in humans. A new test of hemispheric dominance.

We studied the effect of a gamma-aminobutyric acid (GABA)-A receptor-induced postsynaptic inhibition on regional CBF (rCBF) in awake humans. For this purpose we used a new specific GABA-A agonist, 4,5,6,7-tetrahydroisoxazolo(5,4)-pyridin-3-ol (THIP). As part of a new diagnostic procedure for the determination of which hemisphere subserved language, THIP was infused into the internal carotid artery 20 s before measurement of the rCBF. Administered by this route the THIP is distributed to the neocortex and neostriatum. THIP induced a dosage-dependent decrease of the rCBF. The rCBF decrease was not due to any direct effect on the cerebral vessels. The efficiency of the THIP-induced postsynaptic inhibition was tested by having the subjects voluntarily activate the inhibited cortex. During submaximal inhibition the subjects were able voluntarily to counteract decreases of rCBF in superior frontal cortex and motor cortex. Larger doses of THIP abolished this response and depressed the rCBF to baseline levels (20 ml/100 g/min). This was associated with 10-min total depression of function of the anterior two-thirds of the injected hemisphere. An analysis of the changes of rCBF in activated and nonactivated cortex--with and without THIP-induced inhibition--showed that it would be very unlikely that average increases in synaptic inhibition would increase rCBF in neocortical areas. Intracarotid injection of the water-soluble, nonirritative THIP is a very useful alternative to sodium amytal injection for determination of hemispheric dominance.

Adolescent↗
PubMed1988

Smoking and mortality: a 21-year follow-up based on the Swedish Twin Registry.

Data on smoking and mortality from the Swedish Twin Registry were analysed as a prospective cohort study and as a co-twin control study. The twin method involves control of genetic and early environmental factors and thereby a general control of the nested factors that may act as confounders, adjustments not obtainable in ordinary study designs. In the cohort analyses the following relative risks for cigarette smokers were found for men and women, respectively: death all causes 1.4 (90% Cl 1.3; 1.5), 1.4 (1.3; 1.5), CHD death 1.4 (1.3; 1.7), 1.6 (1.3; 2.0), lung cancer 19.7 (9.1; 42.7), 5.1 (3.0; 8.7), and other cancers 1.2 (1.0; 1.4), 1.2 (1.0-1.4). The comparison of deaths in cigarette-smoking twins and their non-smoking co-twins gave the following risk estimates for monozygotic (MZ) men: death all causes 1.6 (35 versus 22 first deaths), CHD death 2.8 (11 versus 4). The results for dizygotic (DZ) males and for females were in agreement. Four lung-cancer deaths occurred in MZ and 17 in DZ smoker twins while the non-smoker co-twins showed two such cases (DZ women). Other cancer deaths did not occur more often in the smoker than in the non-smoker twin. The impact of smoking on mortality, CHD death and lung cancer is also valid among smoking discordant twins.

Adult↗
PubMed1988

Physiological activation of the human cerebral cortex during auditory perception and speech revealed by regional increases in cerebral blood flow.

Specific types of brain activity as sensory perception auditory, somato-sensory or visual -or the performance of movements are accompanied by increases of blood flow and oxygen consumption in the cortical areas involved with performing the respective tasks. The activation patterns observed by measuring regional cerebral blood flow CBF after intracarotid Xenon-133 injection are reviewed with emphasis on tests involving auditory perception and speech, and approach allowing to visualize Wernicke and Broca's areas and their contralateral homologues in vivo. The completely atraumatic tomographic CBF methods, that are based of the use of radioactive tracers, can be applied in the same manner for mapping cortex activity. In particular single photon tomography SPECT is readily applicable to clinical audiology, so that the cortical components of the auditory processing can be more closely investigated.

Auditory Perception↗
PubMed1987

Ischemia may be the primary cause of the neurologic deficits in classic migraine.

This study investigates whether the cerebral blood flow reduction occurring in attacks of classic migraine is sufficient to cause neurologic deficits. Regional cerebral blood flow measured with the xenon 133 intracarotid injection technique was analyzed in 11 patients in whom a low-flow area developed during attacks of classic migraine. When measured with this technique, regional cerebral blood flow in focal low-flow areas will be overestimated because of the effect of scattered radiation (Compton scatter) on the recordings. In this study, this effect was particularly taken into account when evaluating the degree of blood flow reduction. During attacks of classic migraine, cerebral blood flow reductions averaging 52% were observed focally in the 11 patients. Cerebral blood flow levels known to be insufficient for normal cortical function (less than 16 to 23 mL/100 g/min) were measured in seven patients during the attacks. This was probably also the case in the remaining four patients, but the effect of scattered radiation made a reliable evaluation of blood flow impossible. It is concluded that the blood flow reduction that occurs during attacks of classic migraine is sufficient to cause ischemia and neurologic deficits. Hence, this study suggests a vascular origin of the prodromal neurologic deficits that may accompany attacks of classic migraine.

Adult↗