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Biomedical subjects

J Chambron

Publications and source records attributed to J Chambron.

At least 19 recordsLinked to original sources
PubMed2002

Detection of late epilepsy by the texture analysis of MR brain images in the lithium-pilocarpine rat model.

The aim of the study was to detect by texture analysis non easily visible anomalies of magnetic resonance (MR) images of piriform and entorhinal cortices relevant to the lithium-pilocarpine (Li-Pilo) model of temporal lobe epilepsy in rats. Status epilepticus was induced by Li-Pilo in twenty male rats 21 day-old. T(2)-weighted MR images of their brain, were obtained before injection of Li-Pilo and one day after status epilepticus. An hyperintense signal was found in the piriform and entorhinal cortices of six rats, which developed chronic epilepsy after a latent period of one to three months. Among the 14 other rats which displayed images similar to those obtained before injection, four remained healthy but 10 rats developed late epileptic symptoms, raising the problem of hidden cortical damage which may be too subtle to be detected by classic MRI examination. A numeric treatment of digital images was then undertaken by texture analysis, to derive image information from a purely computational point of view. The combined texture and discriminant analyses based on pixels pattern anomalies, selected 3 texture parameters derived from co-occurrence matrix which characterized structural abnormalities relevant to the hyperintense signal, not only in the modified images of 6 rats but also in images of 10 rats with apparently non modified images. These three texture's parameters allowed to classify the twenty rats of our experiment as follows: sixteen epileptic rats were effectively classified with cortical lesions, two non epileptic were correctly classified with healthy cortex, but two healthy rats were not correctly classified. This misclassification is discussed on the basis of the time dependence of the onset of seizure in the Li-Pilo model. These promising results suggest to apply this method to MRI examinations for an improvement of the early diagnostic of human epilepsy.

Animals↗
PubMed2001

Existence of contralateral abnormalities revealed by texture analysis in unilateral intractable hippocampal epilepsy.

We selected 23 patients with unilateral temporal lobe epilepsy characterized by ipsilateral hippocampal sclerosis and an apparently normal contralateral hippocampus on MR imaging. Images were acquired on a 0.28 T MR scanner using a conventional Carr-Purcell Meiboom Gill sequence in all patients and in 9 healthy subjects. Texture analysis was applied to axial MR images of the first and tenth echoes. Texture analysis detects macroscopic lesions and microscopic abnormalities that can not be observed visually. The presence of texture differences in the between normal (controls) and sclerotic hippocampi was ascertained by statistical discriminant analysis. The apparently normal contralateral hippocampi can be classified into three categories in terms of texture: 4 apparently healthy, 8 similar to sclerosis, and 11 different from either healthy or sclerosis. These findings are related to a certain degree of hippocampal alteration, which further investigation might help better characterize.

Adult↗
PubMed1999

Distinct patterns of active and non-active plaques using texture analysis on brain NMR images in multiple sclerosis patients: preliminary results.

The benefits of texture analysis of magnetic resonance images have been assessed in multiple sclerosis (MS) patients. Out of thirty-two lesions identified in eight MS patients, nine were considered active, judging from their gadolinium uptake. Texture analysis allowed to obtain forty-two characterizing parameters for each lesion. Using discriminant analysis as a statistical method allowed to classify the lesions into two groups: active or non-active. An attempt to classify their level of activity by using only co-occurrence matrices was unsuccessful. Alternately, the same type of analysis performed on runlength analysis criteria allowed the accurate classification of 88% of active lesions and 96% of non-active lesions. Using incremental discriminate analysis can reduce the number of useful parameters. This method showed that among the 42 parameters, 8 only were highly significant and permitted an accurate classification. Five of these parameters are runlength parameters, and three others are more directly related to the global distribution. The main interest of runlength parameters is that they allowed to demonstrate that the lesion structure was different in active and non-active plaques. This preliminary work suggests that using texture analysis could be of interest in the follow-up of MS patients because it provides an opportunity to identify active lesions without frequent gadolinium injections.

Adult↗
PubMed1996

Assessment of painful ureterohydronephrosis during pregnancy by MR urography.

The purpose of this study was to assess the value of the fast imaging sequence called RARE (rapid acquisition with relaxation enhancement) MR urography (or RMU) in pregnant women with painful ureterohydronephrosis. A total of 17 pregnant women with an acute flank pain were examined with RMU. Results were compared with those of US, X-rays and the evolution of symptoms. The gold standard techniques used to evaluate the results of MR urography were US when it showed the entire dilated urinary tract and the nature of the obstruction (9 cases), limited intravenous urography (IVU) when performed (3 cases) or endoscopic procedure (5 cases). The accuracy of RMU in the detection of urinary tract dilatation and the localization of the level of obstruction was excellent (sensitivity 100% in our series). The determination of the type of obstruction, intrinsic vs extrinsic, was always exact. The RMU technique alone could not specify the exact nature of the obstruction. The RMU technique is able to differentiate a physiological from a pathological ureterohydronephrosis during pregnancy. It could be considered as the procedure of choice when US failed to establish the differential diagnosis.

Adult↗
PubMed1996

Biological assessment and MRI monitoring of the therapeutic efficacy of a monoclonal anti-T CD4 antibody in multiple sclerosis patients.

An initial group of 21 patients plus a second group of 14 patients with active multiple sclerosis (MS) (18 progressive and 17 relapsing-remitting forms) were treated with a murine monoclonal anti-T CD4/BF5 antibody as part of a phase I open trial. Tolerance was relatively good: minor general side-effects occurred in 22 patients only upon the first mAb infusion. One year later, functional disability was stabilised in only six of the 35 patients and after 2 years in two patients only (among 21). One year after treatment, nine of the 17 relapsing-remitting patients were relapse-free. CD4 counts decreased dramatically 2 h after treatment. These counts were back to baseline counts at 3 months. A transient increase was found in IL-6 and TNF alpha levels 2 h after treatment, which probably accounts for the observed side effects. Cell adhesion molecule levels were not modified. Serial MRI scans were performed in the second group of 14 patients. In all of these patients, lesion modifications were observed in the three scans performed prior to treatment. Yet, no changes in the lesions were noted on the MRI scans performed over the following 3 months. These findings demonstrate the feasibility of this treatment insofar as it induced a marked CD4 lymphocyte depletion. However, it did not seem to stabilise the evolution of the disease--although one must be careful in drawing such conclusions in a phase I trial--or to curb the evolution of MRI-documented lesions.

Antibodies, Monoclonal↗
PubMed1995

NMR relaxation rates and blood oxygenation level.

A linear relationship between the proton relaxation rates and the fraction of deoxyhemoglobin of circulating whole blood (fHb) has been established in vitro at 4.7 T. These results have been interpreted on the basis of the additivity of relaxation rates. The slope of the lines of transverse relaxation rates (R2) versus fHb was found to increase with interpulse delay in Carr-Purcell Meiboom-Gill (CPMG) experiments. The Luz-Meiboom relation applied to this interpulse delay dependence of R2 suggests a two-site chemical exchange rather than a diffusion mechanism. The 1-ms water proton exchange time derived from these observations has been interpreted in terms of exchange between exchangeable protons close to the paramagnetic center of hemoglobin and protons of bulk water.

Animals↗
PubMed1995

Dynamic nuclear polarization with nitroxides dissolved in biological fluids.

The most widely used free radicals for dynamic nuclear polarization (DNP) experiments or related Overhauser imaging are nitroxides. The DNP parameters in biological fluids were measured in order to provide guidelines for the design of new nitroxides, adapted to the biological applications of DNP. Eighteen nitroxides were studied at a concentration of 1 mM. Extrapolation at complete electron paramagnetic resonance saturation and proton longitudinal-relaxation-time measurements enable calculation of the coupling factor between nitroxide free electrons and water protons. In deoxygenated phosphate-buffered solutions, the NMR signal enhancement by DNP ranged from -36.3 to -6.7, and the coupling factor ranged from 0.31 to 0.03. Nitroxides with a long side chain yield poor enhancement, although their relaxivity is far greater than that of nitroxides with small chains. In a 1 mM albumin solution, the loss in enhancement factor is mainly caused by the fact that proton relaxation occurs via interactions, not only with the dissolved free radicals but also with the albumin macromolecules. In serum, the enhancement factor is lower than that in an albumin solution, because of the higher protein concentration in serum. In red-blood-cell suspensions, the enhancement factor was further decreased. Two effects contribute to this decrease: first, the increased viscosity due to the presence of red blood cells, and second, the susceptibility effects of the paramagnetism of deoxyhemoglobin. The high sensitivity to oxygen of DNP in phosphate-buffered solution is also greatly reduced when nitroxides are dissolved in blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗
PubMed1995

Quality assessment in in vivo NMR spectroscopy: VI. Multicentre quantification of MRS test signals.

In this paper the results are presented of a joint European quantitative data-analysis study on a series of in vivo NMR time-domain test signals. The purpose of this study was to investigate, whether the quantitative MRS results from the various European biomedical research-centres can be made more comparable and reproducible. From the results of the study it can be concluded that in case of heavily overlapping NMR lines the quantifications should be done by some form of model function fitting and that, whenever possible, prior knowledge on the quantitative parameters should be incorporated into the quantification algorithms.

Magnetic Resonance Spectroscopy↗
PubMed1995

Fast imaging MR assessment of ureterohydronephrosis during pregnancy.

PURPOSE: to assess the value of the fast imaging sequence called RARE-MR-Urography (RMU) for the diagnosis of pathologic ureterohydronephrosis during pregnancy. MATERIALS AND METHODS: 15 pregnant women with an acute flank pain were examined with RMU. Results were compared with those of ultrasonography (US), X-rays, and the evolution of symptoms. RESULTS: the accuracy of RMU in the detection of urinary tract dilatation and the localization of the level of obstruction was excellent (100%). The determination of the type of obstruction, intrinsic vs. extrinsic, was always exact. RMU alone cannot specify the exact nature of the intrinsic obstruction. Ultrasonography gave less sensitive information in terms of level (60%) and type of obstruction (53%). CONCLUSION: RMU is able to differentiate a physiological from a pathologic ureterohydronephrosis during pregnancy. It could be considered as a procedure of choice for special cases when US failed to establish this differential diagnosis.

Adult↗
PubMed1995

Determination of free triiodothyronine by six different methods in patients with non-thyroidal illness and in patients treated with amiodarone.

We performed a methodological comparison of free triiodothyronine (FT3) estimates in patients with liver cirrhosis and renal failure. Patients were classified in terms of severity of illness on the basis of their total triiodothyronine, total thyroxine and reverse triiodothyronine profiles. FT3 levels, measured in direct dialysis, microchromatography, labelled analogue and two-step immunoextraction assays were significantly (P < 0.01) lower than the control group in all patient categories. However, FT3 measured by a labelled antibody radioimmunoassay was significantly reduced only in the most severely ill sub-group of patients. In a further group of patients on long-term amiodarone therapy for cardiac disease all FT3 methods, with the exception of the labelled antibody radioimmunoassay and an analogue method, yielded significantly (P < 0.01) reduced levels. A significant negative association between FT3 and subject age was demonstrated for all methods except the labelled antibody radioimmunoassay, and a weak but significant negative correlation between log thyrotropin and FT3 was only seen with this assay. Three methods demonstrated a correlation (P < 0.02) with albumin levels in patients with the 'low T3 syndrome'. In this group, albumin had a predictive value (P < or = 0.02) for four out of six assays as determined by stepwise variable selection. Our findings suggest that users of FT3 assays should exercise caution in interpreting results in non-thyroidal illness and amiodarone treated patients, as there are method-related differences in the profiles obtained.

Adult↗
PubMed1994

Local administration of 7 beta-hydroxycholesteryl-3-oleate inhibits growth of experimental rat C6 glioblastoma.

The effect of 7 beta-hydroxycholesteryl-3-oleate on rat brain C6 glioblastoma cells was studied. Three days after the inoculation of 2 x 10(5) C6 cells into the frontal cortex of 6-day-old Wistar rats, two types of liposomes [consisting of either phosphatidylcholine and monosialoganglioside (PG:GM1, 10:1 mol/mol) only, or containing 7 beta-hydroxycholesterol, 7 beta-hydroxycholesteryl-3-oleate, 7 alpha-hydroxycholesteryl-3-oleate, or 7-ketocholesteryl-3-oleate] were injected into the xenograft. Ten days later, the animals were sacrificed, the tumors were stained with cresyl violet or hematoxylin/eosin, their volumes determined by image analysis, and their development followed by magnetic resonance imaging. The mean (+/- SE) tumor volume was 4.4 +/- 1.0 mm3. The injection of liposomes without oxysterol had no effect on tumor growth, whereas injection of liposomes containing 7 beta-hydroxycholesteryl-3-oleate (36 nmol) gave rise to a marked decrease in tumor volume (from 4.4 +/- 1.0 to 0.7 +/- 0.4 mm3). Seven nmol had no effect on tumor growth, 72 nmol were as efficient as 36 nmol, and 144 nmol attenuated the tumor volume by 50% only. Liposomes containing 72 nmol of oleic acid enhanced the tumor volume 4-fold. These findings were confirmed by magnetic resonance imaging. Thus, following induction of tumors in both the right and left sides of the cortex and treatment of the right side, magnetic resonance imaging indicated a significant decrease in tumor volume on the right side only. When C6 cells and 7 beta-hydroxycholesteryl-3-oleate were simultaneously injected, tumors did not develop in 80% of the animals. The clearance of [3H]7 beta-hydroxycholesteryl-3-oleate, of which 75% was converted to cholesterol, reached 99% after 48 h. Other oxysterols did not affect the tumor volume except that 7-keto-cholesteryl-3-oleate decreased the tumor volume by 50%. Thus, the 3-fatty acyl ester and 7 beta-hydroxyl groups are apparently required for the antitumor growth effect. Taken together, these data suggest that 7 beta-hydroxycholesteryl-3-oleate might be useful for local glioblastoma chemotherapy.

Administration, Topical↗
PubMed1994

Localized T2 measurements using an OSIRIS-CPMG method. Application to measurements of blood oxygenation and transverse relaxation free of diffusion effect.

This work presents a new method allowing localized T2 measurements, based upon the OSIRIS scheme. A train of 180 degrees pulses is applied after the OSIRIS preparation cycle, recording directly the transverse magnetization decay. The method was verified for two nuclei, 1H and 19F, with phantoms and in vivo on rats. The accuracy of the T2 values is discussed, as well as possible applications of the OSIRIS-CPMG method to proton transverse spin relaxation measurements, free of diffusion effects, and to non-invasive in vivo blood oxygenation measurements, through the use of an emulsion of perfluorooctylbromide, a blood substitute containing fluorine.

Animals↗
PubMed1994

Hyperbaric oxygen treatment in acute experimental allergic encephalomyelitis. Contribution of magnetic resonance imaging study.

Magnetic resonance imaging (MRI) has been performed to determine the efficacy of hyperbaric oxygen treatment (HBO) on experimental allergic encephalomyelitis (EAE) in Lewis rats. The animals were exposed for 2 x 3 h in a 24-h period at 2 ATA pure O2. Three HBO treatment protocols were used: a 10-day preventive treatment (beginning on the 1st day postimmunization), a 3-day preventive treatment (beginning on the 1st day postimmunization), and a 10-day symptomatic treatment (beginning on the 11th day postimmunization). Based on clinical and MRI observations, this study demonstrates: (i) that HBO treatment does not reduce the blood-brain barrier (BBB) disturbance and cerebral edema in EAE, (ii) that in an opposite way, it provokes reversible BBB breakdown, and (iii) that preventive HBO treatments results in modification of the course of EAE, possibly by immunosuppression effect during the initial sensitization step.

Animals↗
PubMed1994

Magnetic resonance imaging of antibody-mediated demyelinating experimental allergic encephalomyelitis.

Two models of demyelinating experimental allergic encephalomyelitis (EAE) were studied on Lewis rats in whom the disease was induced by injections of either (i) lentil-lectin binding myelin glycoproteins plus myelin basic protein (MBP)-specific T cells (36 rats), or (ii) myelin/oligodendrocyte glycoprotein-specific monoclonal antibody plus MBP-specific T cells (16 rats). In our 24 control rats, 20 received MBP-specific T cells only, and four received myelin glycoproteins plus purified protein derivative-specific T cells. The extent of the resulting blood-brain barrier (BBB) permeability, vasogenic oedema and/or demyelination was assessed in vivo using magnetic resonance imaging (MRI) techniques. The results show that in both demyelinating EAE models the disease appeared more quickly, progressed very rapidly and was more severe than when induced with a similar number of MBP-specific T cells alone. Almost all animals developed hyperacute EAE, with a very high mortality rate. MRI showed a very intense BBB breakdown and vasogenic oedema in all the normally 'leaky' areas of the central nervous system, and focal lesions corresponding to plaque formation in the brain stem or spinal cord near the 'leaky' areas. During the 40-day observation period, the rare survivors of this hyperacute form of EAE presented a chronic form of EAE with serious sequelae. Our results demonstrate that the synergistic effect observed between MBP-specific T cells and antibodies to myelin glycoproteins, especially to myelin/oligodendrocyte glycoprotein, does not only induce demyelinating lesions and chronic clinical signs, but is further responsible, via the normally 'leaky areas', for the fatal increase of the BBB breakdown and vasogenic oedema of which there are ample acute clinical signs.

Animals↗
PubMed1994

The role of Mycobacterium tuberculosis in experimental allergic encephalomyelitis.

Various detergents used in preparative membrane protein chemistry were added to a complete Freund's adjuvant/water emulsion in order to increase the solubility and/or immunologic availability of the Mycobacterium tuberculosis membrane and to explain its role in blood-brain barrier (BBB) permeability. Magnetic resonance imaging was used for in vivo determination of the BBB breakdown and cerebral edema. The results showed that with 1% 10 tridecyl ether, which increases emulsion stability, abundant BBB breakdown and cerebral edema were observed, similar to those encountered in experimental allergic encephalomyelitis (EAE). We suggest that the immunologic response triggered off by M. tuberculosis largely contributes to the BBB permeability changes observed during EAE, probably by an action on the endothelial cells of the cerebral blood vessels.

Animals↗
PubMed1994

[Magnetic Resonance Imaging study of the role of the blood-brain barrier in the pathogenesis of experimental allergic encephalomyelitis: application to multiple sclerosis].

Nuclear magnetic resonance imaging (MRI) proved to be, from the first, a very sensitive method, allowing the visualisation of multiple sclerosis lesions, yet which never permitted to establish a non equivocal relationship between the semeiology of such lesions and the clinical signs. The multifocal aspect of disseminated multiple sclerosis lesions is probably one of several factors accounting for this discrepancy. The study of an autoimmune disease, experimental allergic encephalomyelitis (EAE), regarded as a suitable model for multiple sclerosis in humans, has been performed using MRI in order to unravel the pathogenesis of the disease and apprehend the mechanisms responsible for the formation of multiple sclerosis lesions. The study focused on the part played by the blood-brain barrier (BBB) in the induction process of an autoimmune disease, since the central nervous system is normally screened from immunological supervision, by this barrier. Models both of acute EAE, induced by active or passive transfer of the antigen (myelin basic protein-MBP)--and chronic EAE, induced by passive transfer of MBP-specific T cells and myelin glycoproteins or MOG-specific monoclonal antibodies, have been reproduced, and their evolution followed up using high field MRI. Every time, the crucial role of the BBB was evidenced by the synchronism existing between the clinical signs, the appearance of lesions, preferentially in the most sensitive or permeable areas, and the BBB breakdown encouraged by the action of adjuvants. The physiopathological study of EAE using MRI is suggestive of the concept of systemic disease for multiple sclerosis, according to a two-step process, involving, in a first stage some primary viral or bacterial infection, causing T-cells to be sensitized to the host's own proteins by molecular mimicry, and in a second stage some bacterial infection or accidental circumstances which, resulting in a BBB breakdown, would provide immunocompetent cells with an opportunity to reach their target.

Animals↗
PubMed1993

Photoacoustic detection of photosensitized oxygenations in highly absorbing samples.

A photoacoustic (PA) study of the relaxation processes of the excited states of photosensitizers in the presence of oxygen and chemical acceptors is described. It has been predicted theoretically that the ratio of PA amplitudes with and without acceptor depends on two parameters alpha and beta, related to the sensitizer and to the acceptor properties, respectively. Experimental studies were carried out on solutions of hematoporphyrin IX and methylene blue. The addition of an acceptor, specific to the singlet oxygen, like tetramethyl ethylene or furfuryl alcohol, appears to decrease significantly the photoacoustic signal amplitude within the band of absorption.

Hematoporphyrins↗