Biomedical subjects

D Labar

Publications and source records attributed to D Labar.

44 records · Page 3Linked to original sources

PubMed1991

Noninvasive measurement of liver regeneration with positron emission tomography and [2-11C]thymidine.

The feasibility of liver regeneration determination with [2-11C]thymidine and positron emission tomography was investigated in partially hepatectomized rats. Serial tomographic scans were performed over a 120-minute period after injection of [2-11C]thymidine together with tritium-labeled thymidine. Within 10 minutes after injection, positron emission tomography scans showed a twofold higher hepatic uptake in regenerating than in nonregenerating livers. Time-activity curves over the liver area indicated that the maximal uptake was followed by a faster decrease of 11C radioactivity in controls than in regenerating animals, so that total 11C activity remaining in the liver at 120 minutes accounted for 68% of maximum in regenerating and only 38% in controls. Tissue distribution studies performed at 120 minutes showed that total 11C radioactivity, expressed in percent injected dose per gram, was six times higher in regenerating livers than in controls (0.62% +/- 0.07% in regenerating livers and 0.10% +/- 0.03% in nonregenerating livers; P less than 0.001) and correlated with 3H radioactivity measured in the nuclear fraction (r = 0.92; P less than 0.001). When the hepatic uptake was expressed in percent of dose per organ, the difference between both groups increased (2.31% +/- 0.23% in regenerating livers and 0.29% +/- 0.02% in nonregenerating livers; P less than 0.001) because of higher weight of regenerating livers than of nonregenerating livers (3.83 +/- 0.11 g in regenerating livers and 2.96 +/- 0.16 g in nonregenerating livers; P less than 0.001). In other organs examined, no difference in 11C radioactivity was found between the two groups of rats. These results indicated the potential usefulness of [2-11C]thymidine and positron emission tomography for noninvasive measurement of liver regeneration.

Animals↗

PubMed1991

Median nerve somatosensory evoked potentials in patients with lacunar and other small subcortical strokes.

We recorded median nerve somatosensory evoked potentials (SSEPs) in 42 patients with small subcortical strokes associated with lacunar syndromes. Seventeen patients had abnormal SSEPs. The P22 component was most often affected; changes in N20 and N18 were less common. Four patients with pure motor strokes (PMS) had abnormal SSEPs. Abnormalities of P22 correlated best with motor findings; those of N20 with sensory signs and symptoms. Similar SSEP abnormalities were produced by lesions in various locations. P22 and N20 abnormalities occurred independently and together. We conclude: (1) abnormal SSEPs are common in patients with small subcortical strokes associated with lacunar syndromes, including pure motor stroke; (2) P22 and N20 have separate cortical generators; and (3) P22 may be generated within sensory pathways which are adjacent to or influenced by motor pathways.

Adult↗

PubMed1991

Production of [2-11C]thymidine for quantification of cellular proliferation with PET.

A three-step synthesis of [2-11C]thymidine, using [11C]urea as precursor, is described. [2-11C]Thymine was obtained by cyclization of [11C]urea and diethyl beta-methylmalate in fuming sulfuric acid. After purification of the reaction mixture, [2-11C]thymine and 2'-deoxyribose-1-phosphate were incubated in the presence of thymidine phosphorylase to form [2-11C]thymidine. The whole synthesis procedure, including purification and pharmaceutical package, was achieved within 60 min with a decay corrected yield of 30-35%.

Carbon Radioisotopes↗

PubMed1990

Neurophysiological abnormalities in adolescents with type I Crigler-Najjar syndrome.

We report neurophysiological abnormalities in two adolescents with type I Crigler-Najjar syndrome, an autosomal recessive disorder characterized by severe unconjugated hyperbilirubinemia. Electroencephalograms (EEGs) demonstrated frequent generalized single and polyspikes, and background slowing. Normal pattern reversal evoked responses (PRVERs) and normal central brain-stem auditory evoked responses (BAERs) were recorded in both patients. These findings differ from the EEG triphasic wave pattern seen in the EEG in hepatic encephalopathy and the central BAER abnormalities seen in many infants with kernicterus. Thus these findings most likely result from complex multifactorial processes and are not simply the result of the hyperbilirubinemia which is common to all 3 conditions.

Acoustic Stimulation↗

PubMed1990

In vitro pharmacological profile of 3-N-(2-fluoroethyl)spiperone.

The binding affinities of spiperone and 3-N-(2-fluoroethyl)spiperone (FESP) have been compared for several rodent brain receptor sites and for inhibition of monoamine release and uptake sites. FESP and spiperone have almost identical profiles, namely a high affinity for dopamine-D2 and serotonin-S2 receptors, a low affinity for alpha 1-adrenergic receptors, and negligible binding to other sites. These results suggest that available data on spiperone binding may be applied to the interpretation of PET data obtained with FESP.

Animals↗

PubMed1989

Positron tomography demonstrates frontal lobe hypometabolism in progressive supranuclear palsy.

A regional analysis of cerebral glucose metabolism was carried out in 9 patients with progressive supranuclear palsy by using positron emission tomography with fluorodeoxyglucose as the tracer. A consistent metabolic map of frontal hypometabolism was found in 7 patients. Brain metabolism was normal in 1 subject and diffusely decreased in another. In the 7 patients with selective hypofrontality, motor and premotor areas were severely hypometabolic, while heteromodal association cortex and paralimbic regions were comparatively less affected. Although this pattern of frontal alterations, probably due to disconnection, appeared consistent with the clinical features of the disease, it proved difficult to correlate the metabolic maps with neuropsychological disturbances.

Aged↗

PubMed1988

In vivo measurement of carbon-11 thymidine uptake in non-Hodgkin's lymphoma using positron emission tomography.

Carbon-11 thymidine (TdR) uptake using positron emission tomography (PET) has been measured in ten patients with non-Hodgkin's lymphoma (NHL). The rate of TdR uptake (mean +/- s.d.) was of 0.009 +/- 0.006 mumol.100 cc-1.min-1 in low-grade NHL. This rate was 0.063 +/- 0.049 mumol.100 cc-1.min-1 in intermediate-grade NHL and 0.159 mumol.100 cc-1.min-1 in a patient with high-grade NHL. Lymphoma radioactivity reached a plateau at 0.42 +/- 0.22%. 100 cc-1 of the injected dose from 10 min after injection. The highest 11C uptakes were observed in the kidneys and in the liver (3.30 +/- 1.30 and 2.10 +/- 0.05%. 100 cc-1 of the injected dose, respectively). The lymphoma-to-muscle ratio was of 11.8 +/- 1.7, whereas the lymphoma-to-intestine ratio was of 1.5 +/- 0.7. Accordingly, the measurement of [11C]TdR uptake in the abdomen may need other imaging methods for adequate interpretation. The results suggest that [11C]TdR uptake using PET might be a method for noninvasively measuring cell proliferation in vivo.

Carbon Radioisotopes↗

PubMedDate not supplied

Intracranial EEG monitoring in Landau-Kleffner syndrome associated with left temporal lobe astrocytoma.

A 3 1/2-year-old boy developed partial complex seizures with right-sided motor activity, occasionally secondarily generalized at age 18 months. Initial EEG showed left-sided focal epileptiform discharges. Seizures became refractory to antiepileptic drugs (AEDs). At age 3 years, there was severe language deterioration consistent with Landau-Kleffner syndrome (LKS). At that time, an EEG showed almost continual generalized spikes and polyspikes, worse during sleep. Video-EEG showed generalized tonic seizures associated with generalized EEG ictal activity. Magnetic resonance imaging (MRI) showed a cystic and solid lesion of the left hippocampal and parahippocampal gyri without surrounding edema. Subdural strip electrodes under the left temporal and overlying the left frontal lobes demonstrated interictal spikes simultaneously in all recording contacts. Ictal EEG activity occurred in the temporal electrodes 0.2-1 s before appearing in the frontal electrodes. After left temporal lobectomy with subtotal resection of a low-grade astrocytoma, he had an immediate marked decrease in seizures. In 1 month he was seizure-free, and in 6 months had no further seizures and markedly improved language. These findings provide further evidence that left temporal structural epileptogenic lesions may contribute significantly to the pathophysiology of LKS.

Aphasia↗