Experimental evidence of excited multicharged atomic fragments coming from laser-induced coulomb explosion of molecules

Direct experimental evidence is presented for the production of excited multicharged atomic fragments in the laser-induced Coulomb explosion of molecules. The comparison of the fluorescence signals of several atomic and molecular species shows that the excited fragments come from transient excited multicharged molecules. The atomic fluorescence spectra recorded with NH3, N2, and N2O, in the 50-120 nm wavelength range, show that the excitation increases noticeably from NH3 to N2O. This effect is interpreted in terms of the initial electronic configuration, which favors a stronger excitation when the electronic density is more delocalized on the molecular nuclear structure.

Brain activation induced by estimation of duration: a PET study.

Duration information about a visual stimulus requires processing as do other visual features such as size or intensity. Using positron emission tomography, iterative H215O infusions, and statistical parametric mapping, we investigated the neural correlates of time processing. Nine normal subjects underwent six serial rCBF. Three tasks were studied: (a) A temporal generalization task (D task) in which the subjects had to judge (by pressing one of two keys) whether the duration of the illumination of a green LED was equal to or different from that of a previously presented standard; (b) An intensity generalization task (I task) in which the judgment concerned the intensity of the LED; and (c) A control task (C task) in which the subjects had to press one of the two keys at random in response to LED illumination. A significant increase in rCBF during the D task, compared to that during the C task, was observed in right prefontal cortex, right inferior parietal lobule, anterior cingulate cortex, vermis, and a region corresponding to the left fusiform gyrus. A significant increase in rCBF during the I task, compared to that during the C task, was observed in right prefontal cortex, right inferior parietal lobule, right extrastriate cortex, anterior cingulate cortex, left inferior parietal lobule, vermis, and two symmetrical regions corresponding to the fusiform gyri. No significant activation was observed in the D task when compared to that in the I task. We propose that these cortical maps are best explained by the recruitment of visual attention and memory structures, which play a major role in prospective time judgements as indicated by behavioral studies. The data also suggest that the temporal dimension of a visual stimulus is processed in the same areas as other visual attributes.

Different cytoskeletal organization in two maturation stages of Discoglossus pictus (Anura) oocytes: thickness and stability of actin microfilaments and tropomyosin immunolocalization.

In Discoglossus pictus oocytes, the germinative area (GA) contains long and irregular microvilli where actin microfilaments are located. In the egg, the funnel-shaped dimple that originates by invagination of the GA is present. In the dimple both microvilli and microfilament bundles have a very orderly appearance. This report extends previous observations (Campanella and Gabbiani, Gamete Res 3:99-114, 1980) and shows that GA microfilaments are thinner (36 A average) than dimple microfilaments (60 A average), as measured in ultrathin section. Moreover, the interfilament distance is smaller in GA bundles than in the dimple bundles. To get an insight into actin organization in oocytes and eggs, we used an actin-depolymerizing factor (ADF) in which cryostat sections were incubated prior to immunofluorescent staining with antiactin antibodies. The microfilaments of the GA microvilli and partially of the oocyte cortex are resistant to ADF when compared to those in the dimple and the rest of the egg cortex. We also investigated immunocytochemically the presence of tropomyosin and found that this protein is localized in the dimple and in the cortex of oocytes and eggs but is absent in the GA.

Effect of exercise on the leg distribution of C15O2 and 15O2 in normals and in patients with peripheral ischemia: a study using positron tomography.

In order to evaluate regional muscle blood flow and oxygen utilization, we study with positron emission tomography (PET) the distribution of C15O2 and 15O2 in 17 subjects: 5 normals (24 +/- 3 years) and 12 patients (63 +/- 13.5 years). C15O2 and 15O2 are inhalated with a steady-state technique. Positron tomograms are recorded in supine position at the greatest diameter of the leg. Exercise consists in simultaneous ankle flexions. In all normals, C15O2 and 15O2 are distributed homogeneously and symmetrically in both legs. At rest, they concentrate in the region of vascular pedicle. After exercise, C15O2 and 15O2 are electively distributed in the anterolateral region of the leg. In patients, this pattern of distribution is similar but asymmetrical. Moreover, the regional uptake of C15O2 and 15O2 often dissociates. In conclusion, C15O2 and 15O2 allow to study repeatedly muscle blood flow and oxygen utilization in patients with peripheral ischemia, both at rest and after exercise. The broad spectrum of pathological changes observed in this study needs further metabolic investigations.

[Regional blood flow and oxygen consumption in the leg muscles of normal subjects and in those with arterial insufficiency. Study of the distribution of C15O2 and of 15O2 using positron emission tomography]. / Débit sanguin régional et extraction de l'oxygène dans les muscles de la jambe chez le sujet normal et l'insuffisant artériel. Etude de la distribution du C15O2 et de l'15O2 par tomographie à émission de positons.

We first studied the distribution of radioactivity during continuous inhalation of C15O2 and 15O2 in traverse tomograms of the greatest diameter of legs, at rest and immediately after exercise (ankle flexions). C15O2 and 15O2 were distributed homogeneously and symmetrically in both legs of normal subjects at rest. The activity accumulated in the anterolateral region after exercise. In patients, this pattern of distribution was similar but asymmetrical, depending on the arterial pathology. No systematic distribution of either C15O2 or 15O2 was observed. In a second step, we studied quantitatively blood flow (F), oxygen uptake (R) and oxygen extraction (E) in 11 subjects: 5 normals (23 +/- 1 years) and 6 patients (60 +/- 11 years) suffering from unilateral intermittent claudication. We used the bolus inhalation technique of C15O2 and 15O2. In the normal leg at rest, ranges were 2.5 to 8.0 ml/min.hg for F, 0.9 to 21.3 mumol/min.hg for R and 3.6 to 33.4% for E. In the pathological leg at rest, ranges were 3.7 to 11.3 ml/min.hg for F, 3.8 to 10.6 mumol/min.hg for R and 7.1 to 24.5% for E. After exercise, ranges were 6.4 to 62.8 ml/min.hg for F, 66.0 to 386.3 mumol/min.hg for R and 29.2 to 89.5% for E in both legs. There was no straight difference between normal and pathological legs soon after exercise. This study allows us to expect that the demonstration of such a difference implies a longer delay of data acquisition following the slow post-ischemia recovery.

Additives for immobilized pH gradient two-dimensional separation of particulate material: comparison between commercial and new synthetic detergents.

We describe the synthesis of two detergents, L and A15, whose performances as solubilizing agents and as additives in the first-dimension step of a two-dimensional separation are compared with those of some commercial compounds, i.e., Nonidet P-40, 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonate(Chaps), and sulfobetaine, on three membrane protein preparations: rat RBC ghosts, beef kidney microvilli, and spinach thylakoids. L is 3-]3-dodecylamidoprophylcbdimethylammonio propane-1-sulfonate; owing to the substitution of a dodecylamido for the dodecyl residue of SB 3-12, the concentration of urea compatible with 2% detergent increases from 4.5 M for the parent molecule up to 7 M. With all three biological samples on which the panel of different detergents has been tested in parallel, L + urea scores as the most effective solubilization medium. On red blood cells a notable qualitative difference is observed with the selective extraction by L as well as by N-dodecyl-N,N-dimethylammonio-3-propanesulfonate of a major protein (pI = ca. 5.5, Mr = ca. 100,000). A15 is derived from a tertiary amine, with one alkylic substituent (either C11 or C13) and two poly(ethylene oxide) tails (totaling 15 ethoxy residues), which is reacted with propane sultone. Approximately 30% of the product corresponds to the N-adduct and is a truly zwitterionic detergent, while 60% is an O-derivative and still contains a titratable amino group (with a pK of 7.2). A15 can thus be used for isoelectric focusing on immobilized pH gradients, as in this work, but would not be compatible with carrier ampholyte isoelectric focusing.(ABSTRACT TRUNCATED AT 250 WORDS)

[Study of cerebral metabolism and blood flow in partial complex epilepsy and status epilepticus in man using positron emission tomography]. / Etude chez l'homme, par tomographie à émission de positons, du métabolisme et du débit sanguin cérébral dans les épilepsies partielles complexes et dans différents états de mal.

Positron Emission Tomography (PET) with the oxygen-15 steady state inhalation technique was used to provide quantitative values of regional cerebral blood flow (CBF), oxygen consumption (CMRO2) and oxygen extraction ratio (OER) in 25 patients with partial complex seizures during the interictal state, in 1 patient with recurrent temporal seizures and in 3 patients whose EEGs were characterized by periodic lateralized epileptiform discharges (PLEDs). Interictal scans showed temporal zone(s) of hypoperfusion and hypometabolism in 80% of patients with normal X-ray CT Scan. In all cases, ictal scans revealed a focal or multifocal increase in CBF and CMRO2. The localization of the most affected regions correlated well with the spatial distribution of the EEG abnormalities. Comparison of the different values of CBF, CMRO2 and OER showed that the increase in perfusion always exceeded that of oxygen consumption and hence was accompanied by a significant decrease in OER, the latter was always the most prominent in the region of the focus determined by serial EEG recordings. The observed imbalance between blood flow and oxidative glucose metabolism could suggest an impairment of O2 utilization by the mitochondria in the epilepticus focus during seizures or status epilepticus.

Which electrodic solutions for immobilized pH gradients?

Carrier ampholytes covering a pH range corresponding to, or narrower than, the span of the immobilized pH gradient (IPG) are a most suitable electrodic solution for IPGs. They are able to collect, and completely remove from the gel, much higher amounts of non-buffering ions than are solutions of acidic and basic amino acids. This makes it possible to directly run IPGs just after their polymerization, without the need of a washing step to remove catalysts and unreacted Immobiline monomers. The same applies most advantageously when the gel formulation includes urea and/or detergents. Ions contributed by the sample solution are also prevented from casting high-conductivity ridges around the electrodes, without any need either of a dialysis step or of an increased slab size with pH plateaus. The migration of the sample proteins toward their equilibrium position is faster in the presence of carrier ampholytes. The effective concentrations of the latter are in the range 0.3-1%.

Myocardial blood flow and glucose uptake after myocardial infarction.

Position emission tomography can picture the distribution of flow tracers as well as of metabolic substrates or analogs. Studies of the distribution of these tracers allow to infer information about regional myocardial clearance (flow X extraction) and substrate utilization. In a study of 32 patients after myocardial infarction, we have contrasted flow and substrate utilization to demonstrate ischemic but viable myocardium in the arterial territory of the infarct in a number of patients also specially after fibrinolytic reperfusion. Restoration of blood flow to the ischemic but viable myocardium through coronary bypass or dilatation improves flow from 56.3% to 84.2% of control and restores substrate utilization. In another group of 32 patients studied with the Strontium-82/Rubidium-82 generator, we have demonstrated perfusion changes both in the myocardial infarct area and at a distance. These changes predominate in patients with multiple vessel disease. Combined PET studies of flow and substrate utilization are new tools to study early intervention after myocardial infarction and to document the benefits of revascularization.

The cortical endoplasmic reticulum and its possible role in activation of Discoglossus pictis (Anura) eggs.

The role of endoplasmic reticulum was investigated in the egg of Discoglossus pictus; recent findings suggest that this organelle is the source of Ca2+ sequestration and release at activation. In the egg of Discoglossus the dimple is the only site where sperm-egg fusion occurs. Microvilli containing microfilament bundles penetrate into the dimple cytoplasm and thus define a cortical layer containing cortical granules, tubular cisternae 35 nm thick and vacuoles. In the underlying cytoplasm are clusters of small cisternae and mitochondria. In the region of the egg cortex outside of the dimple, clusters of cisternae, some vacuoles and a heterogeneous population of small granules are found. In eggs activated by pricking contraction starts from the site of pricking and travels to the antipode. Sections of eggs, fixed 20 to 60 s following fertilization or pricking, show that the tubular cisternae have disappeared and the clusters of cisternae have opened to give rise to longer cisternae arranged in chains. These chains pile up below the vacuoles which are now flat and long because of multiple fusion. A network of cisternae is thus formed whose constituents lean against the microfilament bundles and within 5 min from activation approach the plasma membrane. The flattened vacuoles and the cortical granules are exocytozed. Some cisternae fuse with the microvillar membrane thus participating in microvilli elongation. The microfilament rootlets grandually rearrange and become shorter. In the cortex outside the dimple the cisternae clusters do not open, whereas exocytosis of granules occurs. In eggs treated with A23187, vacuoles and cortical granules undergo exocytosis; however a cisternal network is not formed. The possible stimuli that cause the cisternae network to form at activation only in the dimple and in a matter of seconds are discussed. Our observations, namely exocytosis, formation of cortical wave of contraction and changes in the cytoskeleton organization at activation are consistent with an increase of free Ca2+. Vacuoles and cisternae appear to be good candidates for the sequestration and release of Ca2+ as well an important source for the increase in total plasma membrane at activation.

Regional cerebral blood flow and metabolic rates in human focal epilepsy and status epilepticus.

Positron emission tomography with the oxygen-15 steady state or bolus inhalation technique was used to provide quantitative values of regional cerebral blood flow (CBF), oxygen extraction ratio (OER) and oxygen consumption (CMRO2) in 25 patients with partial complex seizures during the interictal state and in 5 patients during status epilepticus. Glucose utilization (CMRglu) was also studied in one case of status epilepticus with the 18F-fluorodeoxyglucose technique (18FDG). Interictal scans showed zone(s) of hypoperfusion and hypometabolism without significant variation of the OER in approximately 80% of patients. In 62%, there was a strong correlation between the overall EEG localization and the area(s) of hypoperfusion and hypometabolism. In all cases, ictal scans revealed a focal or multifocal increase in CBF and CMRO2. The localization of the most affected regions correlated well with the spatial distribution of the electroencephalograph (EEG) abnormalities. Comparison of the different values of CBF, CMRO2, and OER showed that the increase in perfusion always exceeded that of oxygen consumption and hence was accompanied by a significant decrease of OER; the latter was always the most prominent in the region of the epilepticus focus determined by serial EEG recordings. These results showed that the supply of oxygen by blood flow is large enough to meet metabolic demand. When comparing these values with CMRglu, it appeared that the relative changes in CMRglu and CBF were very similar, indicating that the increase in blood flow correlated with the enhancement in glucose utilization. The observed imbalance between blood flow, glucose utilization, and oxygen consumption could suggest that an impairment of oxygen utilization by the mitochondria could occur in the epileptic focus during prolonged status epilepticus.

Pulmonary regional ventilation. C15O2 single breath method. New technical improvements.

After a single inhalation of C15O2 labelled air, from residual volume to total lung capacity, followed by a few seconds apnea, it is possible to record in four or six lung zones the regional activity changes on a time basis. A first fast rise in activity is seen during the inhalation phase, corresponding to the ventilation in the region of interest (ROI). During the apnea, a slower decreasing component is observed in the different ROI, proportional to the regional blood flow, as almost instantaneously C15O2 is converted to labelled water. After the pioneer work of West & Dollery (1962) very few papers appeared on the subject despite technical improvements as, for instance, coincidence counting of radioactive events. We thus decided to improve the reproducibility and accuracy of the method which were of such a poor quality that no individual measurements were possible in the past. Were of critical importance: a careful positioning of the patients between the counters, a faster electronics improving true coincidence counting. In six healthy volunteers (age 22-35) the values obtained for regional ventilation with the C15O2 single breath were compared to the values given by the inhalation of a poorly soluble gas (Nitrogen13). The correlation between the two sets of measurements is high (r = 0.975). The slope of the regression line is 0.859, ordinate at origin is 2.35. This reveals a systematic error. A mathematical model was therefore developed to take into account the "washout" occurring during the constitution of the ventilation peak, and to correct its value.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiocardiographic evaluation of left ventricular function after inhalation of C15O2.

Inhalation of C15O2 delivers a bolus of labelled water into the pulmonary veins and the left atrium; analysis of the left ventricular curve provides an easy method for the evaluation of left ventricular function. the patient was seated before six collimated probes positioned toward the lungs. An additional probe was directed toward the heart in a modified 15 to 20 degrees left anterior oblique projection. One to two mCi C15O2 was administered per study. The left ventricular curve was analysed and the ejection fraction was calculated using a new method. The background was first calculated for the cycle with the largest diastolic counts using characteristic points of the curve before and after transit of the indicator through the left ventricle. For the other cycles, the background was considered to be a constant fraction of the end-diastolic counts. The left ventricular ejection fraction was obtained for each cycle after corresponding background subtraction as the ratio of diastolic activity minus systolic activity over diastolic activity. The ejection fraction thus determined in 20 patients was highly reproducible from beat to beat and from study to study in the same patient (r = 0.97 and 0.96). It corresponded closely to the ejection fraction determined using a camera-computer system (r = 0.92). We conclude that C15O2 inhalation is an easy, rapid, reproducible and attractive method to assess left ventricular function.

[Positron tomographic study of the behavior of 13N-labeled nitrous oxide in the human brain]. / Etude par tomographie à positron du comportement dans le cerveau humain protoxyde d'azote marqué à l'azote-13.

The synthesis of 13N-labelled nitrous oxide was made following NICKLES' method. After a partial denitrogenisation by breathing pure oxygen for 3 min, the subject inhaled a bolus of 13N-labelled nitrous oxide diluted in 2 l of oxygen (a mixture of 5% 13N2O and 95% O2). After an apnea of 30 sec the subject began to breathe in a closed respiratory system containing a mixture of 10% N2O and 90% O2. Eight images of the brain taken at level OM + 3 in 4 subjects showed an important uptake in the cerebellum and in the frontal and temporal cortex. Six min after inhalation of the bolus, the radioactivity in the cerebellum showed a clear decrease, whereas little decrease was observed in the frontal cortex and only a slight decrease in the temporal cortex. In order to suppress the activity due to the vascular comportment, an experiment was performed under the same conditions as the previous one, but using sodium pyrophosphate containing tin and 25 mCi of Tc-99m pertechnetate. The correction factors vary from 0.394 to 0.894 depending on the R.O.I. The activity curves after correction showed a predominance in the frontal cortex. It can therefore be concluded that some specific zones of the brain are receptive to N2O and in particular the frontal cortex. These results were compared with the data obtained from the electrophysiological recording of the frontal region of the brain (C.N.V.: Contingent Negative Variation).