Evaluation of a wheelchair prototype with non-conventional, manual propulsion.

OBJECTIVE: To evaluate the results of a user satisfaction questionnaire on a new type of lever-propelled wheelchair designed to avoid the discomfort and potential repetitive strain injuries related to conventional hand-rim propulsion. METHODS: Seventeen participants filled out a questionnaire to rate their conventional wheelchair and the prototype (after 2 days' use) in terms of comfort, adjustability, steering/ride, manoeuvrability, stability when crossing obstacles, safety, weight, size, portability and appearance. Overall satisfaction was also scored. RESULTS: According to the user questionnaire results, the lever-propelled prototype chair was rated as significantly superior than conventional wheelchairs in terms of comfort, safety and overall satisfaction. The prototype was rated significantly inferior in terms of size, adaptability, appearance and crossing obstacles. CONCLUSION: We conclude that the prototype wheelchair is highly acceptable and comfortable and can be recommended to disabled sportspersons. The prototype's weak points are mainly related to ergonomic aspects, which could be improved in future models.

Oxygen uptake kinetics during heavy submaximal exercise: Effect of sickle cell trait with or without alpha-thalassemia.

Sickle cell trait (SCT) is a genetic disease affecting the synthesis of normal hemoglobin (Hb) marked by the heterozygous presence of HbA and HbS. It is thought that exercise tolerance and aerobic capacity could be limited in SCT carriers, but that the co-existence of alpha-thalassemia with SCT (SCTAT) could improve exercise response. To examine these issues, we compared the characteristics of VO2 kinetics during a constant heavy exercise among athletes carrying either the SCT (n = 6), the SCTAT (n = 9), or the normal Hb (control group; n = 10). After determination of maximal power output (Ppeak), all subjects underwent a constant heavy cycling exercise lasting 9 min at approximately 70 % Ppeak. Pulmonary VO2 and cardio-respiratory parameters were measured breath-by-breath and the VO2 response was modelled using non-linear regression techniques. The time constant of the VO2 primary component and oxygen deficit were not significantly different among the three groups. The VO2 slow component was 28 % and 33 % higher (p < 0.05) in SCT and SCTAT than in the control groups, respectively. Altogether, athletes with the SCT and the SCTAT had higher heart rate at the beginning (+ 5.2 %) and the end (+ 7.4 %) of the slow component compared to the control group (p < 0.05). These results suggest that SCT and SCTAT subjects are not limited during the first exercise minutes, but are prone to exercise intolerance and to lower aerobic capacity thereafter, due to a higher VO2 slow component, and that alpha-thalassemia does not improve exercise response. The finding of a higher slow component in SCT and SCTAT athletes was possibly due to the loss of O2 availability to muscles, additional fiber recruitment and/or higher cardiac load with time.

Influence of mental motor imagery on the execution of a finger-to-thumb opposition task.

The present fMRI study compares regional distribution of the cortical activity during the execution of unilateral hand movements (finger-to-thumb opposition) preceded or not by their motor simulation (S + E and E condition, respectively). The results show that, overall, the number and the spatial distribution of activated voxels are both increased in the S + E with respect to the E condition. The motor performance preceded by mental rehearsal is related to selective increase of the cortical activity. Among the motor areas that are found active during the simple motor execution a significant enhancement of functional activation during the S + E condition ipsilateral primary motor regions (M1). The activity increase may be accounted by a sort of neural recruiting that is made possible by the overlapping of cortical networks involved in both motor output and motor imagery. The beneficial effects of "mental practice" on the physical performance may rely to the close temporal association between motor rehearsal and actual performance.

Metabolism of [1-13C] glucose in extracts and in immobilized rat glioma C6 cell cultures: effects of hypoxia.

The metabolism of [1-13C] glucose was followed in C6 rat glioma cells immobilized on a gel thread and in perchloric extracts of the same cells in culture. The results showed that the main metabolite of [1-13C] glucose is [3-13C] lactate. The effects of hypoxia were followed in the perchloric acid extracts of C6 cells. In normoxic conditions, the main metabolites produced by the cells were [3-'3C] lactate, [3-13C] alanine, [2-13C], [3-13C] and [4-13C] glutamate. Lactate newly synthesized from glucose appeared to be exported in the perfusion medium when living cells were immobilized in gel threads made of extracellular matrix. After 5 h of hypoxia, the lactate labelling measured in PCA cell extracts was increased that of glutamate decreased and the appearance of a spectral line at 66.01 ppm, identified as [1-13C] glycerol-3-phosphate, was observed. The data suggest that the synthesis of glycerol-3-phosphate in these cells might represent a sign of hypoxia.

Glutamate agonists release excitatory aminoacids from rat astrocytes.

Astrocytes release glutamate (Glu) by the mobilisation of intracellular concentrations of Ca++. The rationale of the present work was to test whether Glu and its agonists, known to affect intracellular Ca++ content via the activation of metabotropic and ionotropic receptors, could modulate the astrocytic release of excitatory aminoacids. NMR experiments showed that Glu released uniformly labelled [13C] Glu in the incubation medium of rat astrocytes in primary cultures. Further experiments confirmed this finding and showed that the incubation of these cells with agonists and antagonists of Glu ionotropic and metabotropic receptors, produced a different modulation of Glu and aspartate release. The observed activations of the various receptors suggest a complex modulation of the release of the excitatory aminoacids. Such a release of is interpreted in terms of metabolic microzonation.

MRI measurement of the functional blood flow changes in a large superficial vein draining the motor cortex.

In this study, phase-contrast MR techniques are applied in order to measure the blood flow changes induced by a motor task in a large superficial vein draining the motor cortex. The measurements were applied to six healthy volunteers, in motor rest conditions and during performance of a motor task. The latter consisted of sequential finger-to-thumb opposition. The task was actually executed and mentally simulated. Significant blood flow increases were found when changing from from mental simulation to actual execution of the motor task (increases ranging between 1.6 and 10.3 ml/min, i.e. 9% and 45%, respectively) and from resting conditions to actual execution of the motor task (increases ranging between 1.7 and 14.0 ml/min, i.e. 32% and 72%, respectively).

The effect of eliprodil on the evolution of a focal cerebral ischaemia in vivo.

The purpose of the present study was to evaluate in vivo the effect of a non competitive antagonist of the NMDA receptor, eliprodil, on the size of a focal ischaemic insult and on its temporal evolution in a rat model, using a spin-echo diffusion magnetic resonance imaging multislice technique. Rats were either injected with 1 mg/kg i.v. of eliprodil or with the vehicle only (placebo) 5 min after middle cerebral artery occlusion, or not injected (controls). Ten coronal slices were acquired every hour, up to 7 h after occlusion of the artery, and the volume of hyperintense signals was measured at each time point and for each animal. Diffusion magnetic resonance images revealed that the administration of eliprodil reduced significantly (by 50% or more) the volume of ischaemia, up to 7 h after occlusion, particularly in the cortex of the ipsilateral hemisphere. The results show the potential efficacy of eliprodil to reduce the cerebral ischaemic volume after arterial occlusion, thus confirming the interest of glutamate receptor antagonists in the treatment of ischaemia.

Evidence that mobile lipids detected in rat brain glioma by 1H nuclear magnetic resonance correspond to lipid droplets.

Mobile lipids have been detected by proton nuclear magnetic resonance (NMR) in animal and human tumors (cultured cells, biopsies, and in vivo), but their origin and subcellular location are still unclear. They have been associated with malignancy, metastatic ability, drug resistance, and necrosis. We wanted to determine whether these lipids are located within plasma membrane microdomains or in lipid droplets for a C6 cell-induced rat glioma. NMR-visible mobile lipids were found in all subcellular fractions isolated from the rat tumor, except in the cytosolic supernatants. Transmission electron microscopy showed that lipid droplets were present in all subcellular fractions containing NMR-visible lipids and in the necrotic and perinecrotic areas of the tumor. The mean diameter of droplets isolated by flotation in the subcellular fractionation protocol was 0.97 microm (n = 682; droplet profile diameter range between 0.2 and 5.0 microm). The apparent diffusion coefficient for these lipids (46 +/- 17 microm2 s(-1) measured in vivo by proton spectroscopy was four orders of magnitude higher than would be expected if mobile lipids were inside plasma membrane microdomains. The combined results demonstrated that mobile lipids detected in vivo by proton NMR in the C6 rat glioma are located in large lipid droplets, associated with the necrotic process.

In vivo study of rabbit irradiated skeletal muscle by MRI--a long-term follow-up.

The delay in the appearance and the extent of a lesion induced by gamma-irradiation, in rabbit iliospinalis muscles, have been evaluated in vivo by MRI. The left side rabbit muscle was irradiated with an 192Ir sealed source at two skin surface doses: 40 Gy and 80 Gy. The progress of the lesion was followed on a long-term basis (12 months) by using T2 weighted spin echo imaging. The irradiation induced lesions were detected by MRI 22 weeks after irradiation for the 40 Gy group and 17 weeks for the 80 Gy group. The atrophy of the muscle and the extent of the lesion increased as a function of the dose at the skin surface. The threshold depth dose, corresponding to the deepest border of the lesion, was calculated by using the monoexponential attenuation law. The results gave the value of 20 +/- 7 Gy for the 40 Gy group and 16 +/- 3 Gy for the 80 Gy group.

Delayed progression of cytotoxic oedema in focal cerebral ischemia after treatment with a torasemide derivative: a diffusion-weighted magnetic resonance imaging study.

Diffusion-weighted magnetic resonance imaging (MRI) was used to assess the effect of an astrocytic Na+2Cl-K+ cotransporter inhibitor, a novel torasemide derivative, on the time course and spatial evolution of a focal cerebral ischemia in the rat. The drug (1 mg/ kg, i.p.) was injected 30 min before middle cerebral artery occlusion and diffusion-weighted images were acquired at various times thereafter. The results showed that the drug reduced the size of the hyperintensity during the first hours, but did not affect the time constant of growth or the final size. The temporary reduction of the cytotoxic oedema induced by the torasemide derivative, demonstrates an antioedematous activity.

Stimulation of phospholipase C activity by norepinephrine, t-ACPD and bombesin in LA-N-2 cells.

The release of [3H]inositol phosphates from myo-[3H]inositol-prelabeled LA-N-2 cells was measured in the presence of beta-adrenoceptor, metabotropic glutamate and bombesin agonists. Norepinephrine and isoproterenol increased the formation of [3H]inositol phosphates in a dose-dependent manner, with an EC50 of 100 microM for norepinephrine and an EC50 of 5 microM for isoproterenol. These stimulations were abolished by propranolol, a beta-adrenoceptor antagonist, with an IC50 in the range of 50-55 microM for both norepinephrine and isoproterenol. The stimulation of [3H]inositol phosphate appearance occurred with varying concentrations of trans-1-amino-1,3-cyclopentanedicarboxylic acid (t-ACPD), a metabotropic glutamate receptor agonist. This release of [3H] inositol phosphates was blunted by its antagonist, 2-amino-3-phosphonopropionic acid (AP-3). Bombesin and neuromedin-B, a bombesin-like peptide, also increased the appearance of [3H]inositol phosphates. This was blunted by the antagonist [Tyr4, D-Phe12] bombesin. The appearance of [3H]inositol phosphates stimulated by t-ACPD was coupled through a cholera toxin-sensitive G-protein and the bombesin-stimulated appearance of [3H]inositol phosphates was coupled through a pertussis toxin-sensitive G-protein. The norepinephrine-stimulated appearance of [3H]inositol phosphates was toxin insensitive. The stimulation of the [3H]inositol phosphate appearance by these three agonists was protein kinase and Ca2+ independent.

Possible involvement of primary motor cortex in mentally simulated movement: a functional magnetic resonance imaging study.

The role of the primary motor cortex (M1) during mental simulation of movement is open to debate. In the present study, functional magnetic resonance imaging (fMRI) signals were measured in normal right-handed subjects during actual and mental execution of a finger-to-thumb opposition task with either the right or the left hand. There were no significant differences between the two hands with either execution or simulation. A significant involvement of contralateral M1 (30% of the activity found during execution) was detected in four of six subjects. Premotor cortex (PM) and the rostral part of the posterior SMA were activated bilaterally during motor imagery. These findings support the hypothesis that motor imagery involves virtually all stages of motor control.

Molecular species analysis of 1,2-diglycerides on phorbol ester stimulation of LA-N-1 neuroblastoma cells during proliferation and differentiation.

1,2-Diacyl-sn-glycerol (DAG) is a product of cell activation that has emerged as an important intracellular messenger whose primary function appears to be the activation of protein kinase C. They originate by the activation of phospholipases, which hydrolyze different phospholipids depending on the external stimulus and the nature of the cells, leading to the production of different molecular species. In the present study the quantitative changes in the total mass and the molecular species of DAG formed on phorbol ester (12-O-tetradecanoyl-phorbol 13-acetate) stimulation were investigated in proliferating and retinoic acid (RA)-differentiated human LA-N-1 cells. The TPA treatment of both cell types elicited an increase in the total amount of DAG. The increase was biphasic; i.e., an initial peak at 2-5 min was followed by a sustained increase that persisted for > 30 min. The analysis of the molecular species of DAG and phospholipids showed that in proliferating LA-N-1 cells, the DAG increase corresponds to the production of mainly saturated/monounsaturated (16:0-18:1, 18:0-18:1) and saturated/saturated (16:0-16:0, 16:0-18:0) species, suggesting that they originate essentially from the hydrolysis of phosphatidylcholine. In contrast, RA-differentiated cells responded to TPA treatment by increasing the level of saturated/polyunsaturated (16:1-22:6, 18:0-22:6, 16:0-20:4, 18:0-20:4) and monounsaturated/monounsaturated (18:1-18:1) species, suggesting mainly a phosphatidylethanolamine origin. These findings indicate that the treatment of LA-N-1 cells with TPA generates different molecular species of DAG depending on their physiological state. These observations suggest in turn that different phospholipases are activated by TPA in proliferating and RA-differentiated cells.

Intracranial gradient-echo and spin-echo functional MR angiography in humans.

PURPOSE: To investigate the predominance of venous signal intensity at 1.5-T gradient-echo (GRE) functional magnetic resonance (MR) imaging of motor activity and to demonstrate the contribution from task-induced changes in flow velocity to the functional MR imaging signal intensity. MATERIALS AND METHODS: Functional MR imaging of motor activity was performed in healthy volunteers. In a first examination, conventional two-dimensional GRE blood oxygenation level-dependent (BOLD) functional MR imaging techniques were used, and the image planes were carefully positioned with respect to the veins that responded to the motor task. In a second examination, two-dimensional spin-echo (SE) techniques were used, and the image planes were oriented axially and measured in a sequential multisection manner. The areas of hyperintensity on functional MR images were eventually processed by means of maximum intensity projection. RESULTS: Functional MR angiograms were obtained in both examinations. The possibility to generate SE functional MR angiograms demonstrates that venous inflow effects may contribute substantially to signal intensity in conventional two-dimensional GRE BOLD functional MR imaging of motor activity. CONCLUSION: Veins have a substantial role in BOLD functional MR imaging of motor activity.

Uptake and metabolism of boronophenylalanine in human uveal melanoma cells in culture Relevance to boron neutron capture therapy of cancer cells.

The transport of boronophenylalanine (BPA) and its metabolic fate have been studied in a human uveal melanoma cell line isolated from a primary enucleated tumor. The boronated compound was rapidly incorporated into the cells reaching a peak of incorporation in two hours. This was followed by a trough between 10 and 24 hours and by an increase thereafter. The analogy with the amino acids phenylalanine (Phe) and tyrosine (Tyr) was studied in competition experiments incubating cultures of cell line MK-T, isolated in this laboratory, with [(3)H]-Phe and [(125)I]-Tyr, in the presence or absence of various concentrations of BPA, between 0 and 5 min. The presence of BPA severely reduced the uptake of both amino acids. The kinetics of the transport of [(3)H]-Phe and [(3)H]-Tyr in the presence of BPA, measured after 10 sec of incubation, showed that the boronated compound exerted a competitive inhibition on both transport systems. The intracellular metabolism of BPA was followed by measuring boron concentration (measured with Ionization Coupled Mass Spectrometry) in subcellular fractions and after membrane extraction by the detergent Triton X-100. The results showed that BPA remained in the supernatant and was not metabolized into macromolecules. These results and the relative absence of melanine in these cells, as observed by electron microscopy, suggest that BPA may be actively transported into melanoma cells but not metabolized. The results may have a relevance in studies on Boron Neutron Capture Therapy.

The conversion of ethanolamine and of its metabolites to choline in human neuroblastoma clones: effect of differentiation induced by retinoic acid.

The sequential methylation of ethanolamine (Etn) or phosphorylethanolamine to the corresponding choline (Cho) derivatives was studied in both undifferentiated and retinoic acid (RA) differentiated human neuroblastoma clones LA-N-1 and LA-N-2. Conversion of Etn derivatives to the respective Cho metabolites was low in both cell types. However, after treatment of the cultures with ethanol or RA, the methylation of phosphoryl-Etn was stimulated while that of phosphatidyl-Etn was severely reduced in both cholinergic LA-N-2 and catecholaminergic LA-N-1 cells.

Modulation of phosphatidylserine synthesis by a muscarinic receptor occupancy in human neuroblastoma cell line LA-N-1.

The incorporation of [3H]serine into lipids, water-soluble metabolites and proteins by the human neuroblastoma cell line LA-N-1 exposed to oxotremorine-M, a muscarinic agonist, was investigated. Oxotremorine-M increased the incorporation of this labelled precursor into phosphatidylserine and proteins in a concentration-dependent manner, with the maximal stimulation at 250 microM. This activation was blunted by 100 microM atropine. There were no detectable changes of the radioactivity in the water-soluble metabolites. Acetylcholine, another muscarinic agonist, slightly decreased the serine incorporation into lipids, but did not affect the protein or water-soluble compartments. Several other muscarinic agonists, including 250 microM pilocarpine, 100 microM McN-A-343 and 1 mM carbachol, did not effect these [3H]serine incorporations. Preincubation of cells with 1 mM oxotremorine M, or 1 mM carbachol, or 1 mM McN-A-343, for 4 h prevented the oxotremorine-M-induced increase of serine incorporation. These observations are consistent with the oxotremorine-M action being mediated by muscarinic-receptor occupancy. The G-protein inhibitor guanosine 5'-[beta-thio]diphosphate (1 mM) and the G-protein activators, guanosine 5'-[gamma-thio]triphosphate (100 microM) and A1F3, prevented the oxotremorine stimulation. The muscarinic agonists, 250 microM oxotremorine-M, 1 mM carbamoylcholine and 500 microM acetylcholine, triggered the accumulation of inositol mono- and di-phosphates by cells that had been prelabelled with myo-[3H]inositol, and this phospholipase C activation was blunted by 100 microM atropine. The protein kinase C inhibitor H7 prevented the oxotremorine-M stimulation of serine incorporation. Over-night exposure of LA-N-1 cells to 100 nM phorbol 12-myristate 13-acetate resulted in a decrease of cytosolic protein kinase C activity, and prevented the oxotremorine-M stimulation of serine incorporation. Neither oxotremorine-M nor acetylcholine caused a redistribution of protein kinase C activity between the cytosol and membrane compartments. In addition, oxotremorine-M did not activate phospholipase D of the LA-N-1 cells.

Functional MRI of the human brain: predominance of signals from extracerebral veins.

This study demonstrates the predominance of extracerebral vascular signals in gradient-echo functional magnetic resonance imaging of motor activity at 1.5 Tesla. The demonstration is based upon a novel experimental approach. Maximum intensity projection images are derived from a large set of contiguous 2D functional MR images, and compared with MR angiograms obtained from the volume covered by the set of functional MR images. The comparison shows that the hyperintensities in the functional MR images cover extensive areas, which can be superimposed with a number of veins in the MR angiograms. These results should trigger a general caution in interpretation of the observations in 1.5 Tesla functional MRI.

[Morphological characterization of cell lines of human uveal melanoma]. / Caractérisation morphologique de lignées cellulaires de mélanome uvéal humain.

Several cell lines have been derived from an ocular melanoma obtained from an enucleated patient. Three cell types are observed during the time in culture of all the cell lines under study. Two of them have epithelial and spindle shape respectively. A third cell type, having a spheroidal shape, is formed from spindle cells and may be transformed into epithelial cells upon re-seeding. Further experiments showed that the same cell may change of shape following the cycle: spheroidal-->epithelial-->fusiform-->spheroidal. Scanning microscopy shows the coexistence of the three cell shapes in the same culture and the presence of several filaments and processes protruding at the surface of the cells. Transmission electron microscopy shows that the cell lines, in general, contain melanosomes empty or fairly pigmented and several filaments and microtubules. The presence of melanin may be stimulated by seeding of melanoma cells over a "feeder layer" of fibroblasts.

Molecular species of choline and ethanolamine glycerophospholipids in rat brain myelin during development.

The composition of the molecular species of various phospholipid subclasses was examined in myelin isolated from brain of 15-, 21- and 90-day-old rats. The molecular species of diacylglycerophosphocholine (PtdCho), diacylglycerophosphoethanolamine (PtdEtn) and plasmenyl-ethanolamine (PlsEtn) were quantified by high-performance liquid chromatography (HPLC) after phospholipase C treatment and dinitrobenzoyl derivatization. In rat brain myelin, each phospholipid subclass showed a specific pattern of molecular species that changed during development. PtdCho contained large amounts of saturated/monounsaturated and disaturated species and low amounts of saturated/polyunsaturated species. During brain development, the levels of saturated/monounsaturated molecular species increased whereas those of the disaturated and saturated/polyunsaturated species decreased. PtdEtn were characterized by their low levels of disaturated species and a high content of saturated/monounsaturated and saturated/polyunsaturated species, of which those containing fatty acids of the n-3 series decreased, whereas those containing fatty acids of the n-6 series did not change during brain development. The levels of saturated/monounsaturated species increased in PtdEtn. No disaturated molecular species could be detected in PlsEtn. This alkenylacyl subclass contained large amounts of saturated/polyunsaturated, saturated/monounsaturated and dimonounsaturated molecular species. During development, the levels of saturated/polyunsaturated molecular species decreased while those of the two others increased. The data indicated that myelin sheaths undergo phospholipid changes during brain development and maturation.