G. Del Fiore

Cortical Processing of Noxious Somatosensory Stimuli in the Persistent Vegetative State

The persistent vegetative state (PVS) is a devastating medical condition characterized by preserved wakefulness contrasting with absent voluntary interaction with the environment. We used positron emission tomography to assess the central processing of noxious somatosensory stimuli in the PVS. Changes in regional cerebral blood flow were measured during high-intensity electrical stimulation of the median nerve compared with rest in 15 nonsedated patients and in 15 healthy controls. Evoked potentials were recorded simultaneously. The stimuli were experienced as highly unpleasant to painful in controls. Brain glucose metabolism was also studied with [(18)F]fluorodeoxyglucose in resting conditions. In PVS patients, overall cerebral metabolism was 40% of normal values. Nevertheless, noxious somatosensory stimulation-activated midbrain, contralateral thalamus, and primary somatosensory cortex in each and every PVS patient, even in the absence of detectable cortical evoked potentials. Secondary somatosensory, bilateral insular, posterior parietal, and anterior cingulate cortices did not show activation in any patient. Moreover, in PVS patients, the activated primary somatosensory cortex was functionally disconnected from secondary somatosensory, bilateral posterior parietal, premotor, polysensory superior temporal, and prefrontal cortices. In conclusion, somatosensory stimulation of PVS patients, at intensities that elicited pain in controls, resulted in increased neuronal activity in primary somatosensory cortex, even if resting brain metabolism was severely impaired. However, this activation of primary cortex seems to be isolated and dissociated from higher-order associative cortices.

Experience-dependent changes in cerebral functional connectivity during human rapid eye movement sleep

One function of sleep is hypothesized to be the reprocessing and consolidation of memory traces (Smith, 1995; Gais et al., 2000; McGaugh, 2000; Stickgold et al., 2000). At the cellular level, neuronal reactivations during post-training sleep in animals have been observed in hippocampal (Wilson and McNaughton, 1994) and cortical (Amzica et al., 1997) neuronal populations. At the systems level, using positron emission tomography, we have recently shown that some brain areas reactivated during rapid-eye-movement sleep in human subjects previously trained on an implicit learning task (a serial reaction time task) (Maquet et al., 2000). These cortical reactivations, located in the left premotor area and bilateral cuneus, were thought to reflect the reprocessing--possibly the consolidation--of memory traces during post-training rapid-eye-movement sleep. Here, the experience-dependent functional connectivity of these brain regions is examined. It is shown that the left premotor cortex is functionally more correlated with the left posterior parietal cortex and bilateral pre-supplementary motor area during rapid-eye-movement sleep of subjects previously trained to the reaction time task compared to rapid-eye-movement sleep of untrained subjects. The increase in functional connectivity during post-training rapid-eye-movement sleep suggests that the brain areas reactivated during post-training rapid-eye-movement sleep participate in the optimization of the network that subtends subjects visuo-motor response. The optimization of this visuo-motor network during sleep could explain the gain in performance observed during the following day.

Solid phase extraction : An alternative to the use of rotary evaporators for solvent removal in the rapid formulation of PET radiopharmaceuticals

Solid phase extraction (SPE) was used for the formulation of several radiopharmaceuticals. The method involves dilution of the previously purified HPLC compound with water, trapping of the activity on an SPE bed, washing off the support, elution of the radiopharmaceutical with a small volume of ethanol (<1 mL) and dilution with sterile isotonic saline solution. Recovery of the radiopharmaceuticals was always higher than 97%. Two different methods of automation were developed for the formulation of [11C] and [18F]radiopharmaceuticals. In all cases, organic solvent levels in the injectable solution were below the recommended limits. This fast (3–6 min.) and easy to automate process can be considered as an alternative to the conventional methods (rotary evaporators). Copyright

Automated preparation of carbon-11 ethanol and carbon-11 butanol for human studies using positron emission tomography

An automated continuous flow process has been developed for the synthesis of11C-ethanol and11C-butanol. These alcohols were synthesized via the same route. The reaction of11CO2 with methylmagnesium bromide or with n-propylmagnesium chloride, followed by a lithium aluminum hydride reduction and hydrolysis produced respectively11C-ethanol and11C-butanol. Preparation can be completed in 25 min. In each case the radiochemical purity, as determined by high pressure liquid chromatography /HPLC/ was greater than 98%. Biological quality control shows that the products are suitable for human use. The process has been completely automated to limit radiation exposure to personnel, reduce preparation time, and increase reproducibility.

Precise determination of uranium in rocks and minerals by neutron activation analysis using 133I fission product

Abstract A radiochemical neutron activation technique for uranium determination in rock and mineral samples is presented. The method is based on an alkaline fusion, a selective oxidation of iodine by a sodium-nitrite solution, followed by an iodine distillation technique for the isolation of the 133 I produced in fission. The outlined scheme is rapid, sensitive and reliable. Determination of uranium in U.S. Geological Survey standard rocks (G-1, W-1, G-2, BCR-1, AGV-1, GSP-1), C.R.P.G. Nancy geochemical standards (GA, GH, BR, Mica-Fe, Mica-Mg), C.A.A.S. reference syenite rocks (SY-1, SY-2, SY-3) and other analysed rock samples are reported. These results are compared with those obtained by other methods.

INVESTIGATION OF MYOCARDIAL VIABILITY AFTER AN ACUTE MYOCARDIAL INFARCTION USING POSITRON EMISSION TOMOGRAPHY

Assessment of myocardial viability after an acute myocardial infarction is needed because the prognosis after the acute phase of a coronary event and the indication for revascularization therapy by percutaneous coronary angioplasty or coronary artery bypass grafting are linked to the amount of residual viable and contractile myocardium. Among noninvasive techniques of investigation, positron emission tomography can evaluate the myocardial viability by comparing the regional study of myocardial metabolism to flow.

Determination of Regional Cerebral Glucose Transport and Utilization Rates in Man with 11C-Glucose: Preliminary Results

This paper describes the methodology and the first results of a method of measurement of the cerebral metabolic rate of glucose, using 11C-glucose and regional detection by probes. The pres

Preparation of iodine-123 from gaseous tellurium hexafluoride targets

Abstract The reactions 122 Te ( 3 He , 2n) 123 Xe and 123 Te ( 3 He , 3n) 123 Xe 123 I are very attractive provided one can separate the xenon-123 from the matrix. In principle, this would lead to very pure iodine-123 by the use of enriched tellurium with the 122- or 123-isotope. So far only methods relying on the diffusion phenomena to extract the xenon from enriched tellurium solid targets have been used. To avoid the drawbacks of such targets we tried using a gaseous target. Telllurium hexafluoride behaves perfectly well under the helium-3 beam. The yields of 123-iodine are of the same order as the best ones obtained from the so-called “cyclic method”, typically 20 μCi/μAH starting from natural tellurium including less than 1% of contaminating 121-iodine. This will be improved by refining the separation with the adjustment of a tested technique.

Essai d'une cible de polyphenyle tritie productrice de neutrons de 14 MeV

Abstract An organic tritiated target has been prepared from polyphenyl polymer of very high specific activity. The behaviour of this target has been tested under a beam of 180 W/cm 2 deuterons. The 14 MeV neutrons yield and half life of the target have been compared with those obtained from a titanium tritiated target. The lack of conductivity of the organic material limits the performances of the organic target.