[Abscess of the spleen caused by Salmonella typhi: case report].
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Abscess↗
Biomedical subjects
J C Baron
Publications and source records attributed to J C Baron.
In vivo quantitative imaging of dopamine receptors in human brain using positron emission tomography and [76Br]bromospiperone.
The brain regional distribution and kinetics of [76Br]bromospiperone, a derivative of a neuroleptic (spiperone) labeled with the positron emitter bromine-76, were studied by time-of-flight tomography after i.v. injection in man. In a control subject the kinetic distribution study showed an accumulation of radioactivity which reached a maximum 3 h postinjection in the frontal cortex and cerebellum regions and 4-5 h postinjection in the basal ganglia. Thereafter the striatal activity remained essentially constant over a period of 25 h. In a group of 13 control subjects, the mean value for the striatum-to-cerebellum ratio, at 4.5 h postinjection, was 1.84 (S.D. 0.21). In two schizophrenics treated with high doses of haloperidol, this ratio was found to be only 1.22. These data indicate that radiolabeled bromospiperone is very suitable for human pharmacological or pathological investigations of the central dopaminergic system.
Adult↗
Progressive supranuclear palsy: loss of striatal dopamine receptors demonstrated in vivo by positron tomography.
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Aged↗
Kinetics and displacement of [11C]RO 15-1788, a benzodiazepine antagonist, studied in human brain in vivo by positron tomography.
The brain regional distribution and kinetics of RO 15-1788, a benzodiazepine (BZD) antagonist labeled with 11C was studied by time-of-flight positron tomography after intravenous injection in four normal human volunteers. In two control studies, there was a high uptake of [11C]RO 15-1788 in gray matter structures initially (brain/blood ratio approximately 3), and subsequent retention that was highest in cerebral cortex, a structure known to have a high density of BZD receptors in vitro. Variation in tissue kinetics of [11C]RO among different gray matter structures may, however, suggest regional differences in binding characteristics or environment of BZD receptors. In two displacement studies, unlabeled RO 15-1788 was injected ten minutes after the radioligand: there was an immediate and marked washout of [11C]brain radioactivity that reached 70% in the occipital cortex with a 0.05 mg/kg dose (indicating a high specific to non-specific binding ratio) but was less prominent with a 0.01 mg/kg dose. These data suggest that [11C]RO 15-1788 may be useful for in vivo mapping of human brain BZD receptors using positron tomography.
Adult↗
The 15O continuous-inhalation method: correction for intravascular signal using C15O.
Cerebral oxygen metabolism (CMRO2) and fractional extraction (OEF) regional values obtained using the 15O steady-state method and positron-emission tomography (PET) were corrected for the activity remaining in blood vessels (a source of overestimation of the OEF neglected in the simple steady-state model) using an additional scan during continuous inhalation of nontoxic amounts of carbon monoxide labeled with 15O (C15O). The method was applied to ten serial PET studies. In normal tissue, OEF overestimation was 11% +/- 2.6% and 9% +/- 2.0% in gray and white matter, respectively. In pathological tissue, the OEF overestimation was, on average, higher than in normal tissue (28% +/- 17% in the core of lesions), but more variable. In both normal and abnormal tissue, however, it was found that (1) the lower the real OEF, the larger the correction applied, and (2) the correction appears to be particularly necessary in situations of abnormally low OEF. The use of C15O continuous inhalation is a simple, direct, and accurate method for blood-activity correction when the 15O steady-state technique is employed to study pathophysiology.
Aged↗
Positron tomography in cerebral ischemia. A review.
This paper reviews the advances provided by positron emission tomography in the understanding of the pathophysiology of cerebral ischemic disorders in humans. The main focuses are on the evaluation of tissue integrity in recent stroke, distant metabolic effects of circumscribed vascular lesions, and hemodynamic consequences of internal carotid artery occlusion.
Acid-Base Equilibrium↗
Ischemic strokes and migraine.
The coincidence of migraine and ischemic strokes is rare but unequivocal. Some of the cases described are recalled and the possible mechanisms discussed.
Brain↗
Tomographic measurement of cerebral blood flow by the 68Ga-labelled-microsphere and continuous-C15O2-inhalation methods.
The measurement of cerebral blood flow (CBF) by continuous C15O2 inhalation has only been validated previously by indirect experimental protocols. In the present study using baboons, these measurements were compared directly with those obtained by injection of 68Ga-labelled serum-albumin microspheres in the left cardiac ventricle. Using a modified labelling technique, no elution of 68 Ga occurred in vivo. Both methods provided similar regional CBF values, which could be described by a significant linear correlation (CBFCO2 = 0.82 CBFmicrospheres + 5.7; P less than 0.001). The validity of the labelled-microsphere-injection method was verified. The feasibility of stable in vivo labelling of 68Ga to serum-albumin microspheres provides a reference method for organ blood-flow measurements using positron-emission tomography.
Animals↗
Tomographic mapping of brain intracellular pH and extracellular water space in stroke patients.
Functional images of regional intracellular pH (pHi) and of fractional volume of extracellular water (FVECW) were obtained in 10 patients with recent hemispheric infarction (between 10 and 19 days after onset of symptoms) using positron emission tomography (PET). The volume of extracellular water relative to that of total water was evaluated in each pixel of the PET scan 7-8 h after injection of 76Br. The pHi image was calculated from the data obtained after injection of [11C]5,5-dimethyl-2,4-oxazolidinedione and from the FVECW image. Regional CBF, oxygen extraction, and oxygen metabolism were also measured in the same patients. In normal hemisphere, mean +/- SD values for FVECW and pHi were 0.12 +/- 0.01 and 6.86 +/- 0.11, respectively. FVECW was increased in the infarcted area in most patients. pHi was increased in the infarct in seven patients and unchanged in three. The increase in pHi was not correlated with changes in FVECW, CBF, or CMRO2, but there was a significant correlation with the decrease in oxygen extraction fraction in the same region. Thus, the decreased H+ content in the infarcted area was correlated with the occurrence of perfusion in excess of metabolic demand. An alkaline shift in pHi enhances the glycolysis rate and could explain why the glucose metabolism is less affected than the oxygen metabolism in recent cerebral infarction. The pHi measured in the infarct could represent mainly the pHi of phagocytic cells that use aerobic glycolysis to synthesize hydrogen peroxide.
Adult↗
Subcortical dementia. Frontal cortex hypometabolism detected by positron tomography in patients with progressive supranuclear palsy.
The dementia associated with progressive supranuclear palsy (PSP) is considered to be subcortical because the cerebral cortex, unlike the subcortical structures, is usually free from major neuropathological lesions; the characteristic symptoms point to a dysfunction of the prefrontal lobe. The regional cerebral metabolic rate of glucose (rCMR Glu) was studied by positron emission tomography and 18F-fluoro-2-deoxyglucose18FDG in 6 patients presumed to have PSP and was compared with values found in 8 control subjects of similar age. The results obtained showed a highly significant rCMR Glu decrease in the prefrontal cortex of our patients. The loss of several subcortical afferents to prefrontal cortex may be responsible for the frontal cortical hypometabolism present in PSP.
Aged↗
Dopaminergic receptor sites in human brain: positron emission tomography.
Positron emission tomography (PET) and 11C-labeled pimozide were used to study the dopaminergic (DA) receptor sites in the human striatum by comparing the latter with the cerebellum, which lacks DA receptors. Although 11C-pimozide concentration was not different in these two brain structures up to 53 minutes after IV injection (thus implying large nonspecific binding), a significant retention of radioactivity in striatum relative to cerebellum was found in controls but not in subjects pretreated with the unlabeled competitor haloperidol. This suggests that the striatal retention seen in controls was due to specific binding of 11C-pimozide to DA receptor sites, whereas prior occupation of the receptor sites by the unlabeled competitor was achieved in pretreated subjects.
Adult↗
[In vivo study of central serotoninergic receptors in man using positron tomography].
In an attempt to characterize in vivo the central serotonergic (5-HT2) receptors in humans with positron emission tomography (PET), we have used 11C-labeled-ketanserin, a seratonergic antagonist that has high affinity and selectivity for the 5-HT2 receptors in vitro. Earlier in vivo studies in rats had demonstrated a preferential accumulation of 3H-ketanserin in the frontal cortex relative to cerebellum, in accordance with known differences in density of 5-HT2 receptor in these two brain structures (5-HT2 receptors are dense in frontal cortex and sparse or absent in cerebellum). In rats, tracer accumulation in frontal cortex represented specific binding of 3H-ketanserin to 5-HT2 receptors in vivo as demonstrated by inhibition, saturation, and displacement studies. In 5 control subjects, we found a statistically significant retention of 11C-ketanserin in frontal cortex relative to cerebellum after intravenous injection of a tracer dose of the radioligand, suggesting specific in vivo binding of 11C-ketanserin to frontal cortex. To substantiate this hypothesis, we studied 4 subjects administered unlabeled chlorpromazine (CPZ) intramuscularly in therapeutic amounts (75 mg) two hours before the PET study. Pretreatment with CPZ decreased significantly the retention of 11C-ketanserin by the frontal cortex, indicating that almost total occupation of the ketanserin receptors by CPZ had been achieved prior to the injection of the radioligand. Despite these positive results, both the duration and the magnitude of tracer retention by frontal cortex in control subjects were much smaller than was reported in rats, presumably indicating lower specific binding, higher nonspecific binding, and faster drug metabolism in humans.(ABSTRACT TRUNCATED AT 250 WORDS)
Brain↗
[Regional hemodynamic and metabolic consequences of temporo-sylvian anastomosis. Study of 15 patients by positron emission tomography].
Cerebral Blood Flow (CBF), Oxygen Extraction Fraction, and Oxygen utilization (CMRO2) have been studied in 15 patients before and After Extra-Intracranial Arterial bypass (EIAB), using PET and 150 steady-State Inhalation technique. Fourteen patients had carotid artery obstructive lesions and the last one a middle cerebral artery occlusion. In the whole group of patients, both CBF and CMRO2 increased significantly on both cerebral hemispheres after the EIAB. This effect was more marked in patients with extensive occlusive disease of neck vessels. This metabolic improvement afforded by EIAB in our patients suggests that long-standing hemodynamic failure may induce a metabolic depression that's still potentially reversible by surgical revascularization. On the other hand, improvement of focal CBF abnormalities depends, in our patients, upon the preoperative coupling of CBF-CMRO2 (mainly misery perfusion syndrome) as reported earlier.
Adult↗
[Severe stenoses and persistent occlusions of the middle cerebral artery: hemodynamic and metabolic consequences studied by positron tomography].
Using positron emission tomography and the 15O continuous inhalation technique, we have measured the regional cerebral blood flow (rCBF) oxygen extraction fraction (rOEF) and oxygen consumption (rCMRO2) of non-infarcted tissue in six patients with either tight stenosis (N = 3) or occlusion (N = 3) of the trunk of the middle cerebral artery (MCA); these arterial lesions were shown to be persistent on late and/or repeated angiograms. The patients were studied 1 to 6 months after their last cerebral ischemic event. The data were analyzed in 4 cm2 regions of interest (fig. 1) and were compared to age-matched control values. Regional right/left ratios were tested for significance individually by comparison to 95 p. 100 confidence limits found in control subjects. We found a significant reduction in mean rCBF in the affected MCA territory; concomitantly, there was a lesser decrease in rCMRO2 significant only in the peri-sylvian area; this was associated with a moderate but significant increase in rOEF in the same areas (Table II, fig. 2 and 3). Individually, the reduction in rCBF and the increased rOEF were significant in 5/6 and 2/6 patients, respectively (Table III). These data indicate that rCBF is decreased distal to persistent hemodynamic MCA obstruction in most patients. This hypoperfusion appears due in part to a mild degree of cerebral ischemia (as demonstrated by the occurrence of "misery perfusion"), indicating inadequate perfusion pressure distal to the MCA obstruction. This was associated with a metabolic depression of the cortex possibly resulting from either neuronal loss, or deactivation (diaschisis), or long-standing hemodynamic local failure or any combination of the three.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
[Peritonitis following appendectomy].
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Adolescent↗
Local interrelationships of cerebral oxygen consumption and glucose utilization in normal subjects and in ischemic stroke patients: a positron tomography study.
With the use of positron emission tomography (PET) and the 15O steady-state-[18F]fluorodeoxyglucose combined method, the local interrelationships between the cerebral metabolic rate for oxygen (CMRO2) and the cerebral metabolic rate for glucose ( CMRGlc ) were investigated in control subjects and in stroke patients. In addition to the classic in vivo autoradiographic approach, a kinetic method was used to measure CMRGlc because it was expected to be more reliable in cerebral ischemia. In control subjects local coupling between CBF, CMRO2, and CMRGlc was confirmed, and acceptable values for the CMRO2/ CMRGlc ratio were found; the latter, however, was lower in white matter than in gray. Uncoupling between CMRO2 and CMRGlc was observed in all stroke patients, suggesting that (1) enhanced anaerobic glycolysis occurred both in reperfused recent infarcts and in chronically ischemic tissue, and (2) substrates other than blood-borne glucose were being oxidized at the borders of recent infarcts. However, methodological uncertainties presently make such observations only tentative. Finally, a coupled depression of CMRO2 and CMRGlc was found in the contralateral cerebellum.
Aged↗
Local cerebral glucose utilisation in treated and untreated patients with Parkinson's disease.
Using the 18f-fluoro-2-deoxy-d-glucose technique and positron emission tomography (PET), the local cerebral glucose utilisation (1CMRGlc) was measured in four non-demented patients with early-onset, bilateral Parkinson's disease characterised by the predominance of akinesia. The study was done twice, first in the untreated condition, and then after levodopa had been resumed. Despite a marked clinical improvement, we found no alteration in 1CMRGlc between the first and second studies in any of the brain structure analysed. Compared to control values, 1CMRGlc in the basal ganglia was moderately increased in both studies. These essentially negative findings agree with most previous human or animal studies, and indicate that the functional alterations in the central dopaminergic systems of patients with Parkinson's disease have metabolic correlates that are too small to be demonstrated by current PET devices.
Antiparkinson Agents↗
Effects of normal aging on regional CBF and CMRO2 in humans.
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Adult↗