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Biomedical subjects

J Roger

Publications and source records attributed to J Roger.

At least 19 recordsLinked to original sources
PubMed2004

Platelet storage solution affects on the accuracy of laboratory tests for platelet function: a multi-laboratory study.

BACKGROUND AND OBJECTIVES: Extent of shape change (ESC) and hypotonic shock response (HSR) have been widely used to characterize the in vitro function of platelets and have been shown to correlate with in vivo viability. These assays have been routinely performed using platelet-poor plasma (PPP) as the test sample diluent. Because of the increasing popularity of storing platelets in synthetic media, it is important to understand the effects of using these synthetic media as test diluents for ESC and HSR measurements. The objective of this study was to determine the effect of using platelet storage solutions vs. plasma for the in vitro testing of ESC and HSR. MATERIALS AND METHODS: Six laboratories participated in this study. Platelets were prepared by apheresis, the platelet-rich plasma (PRP) method, or derived from buffy-coats. Each platelet preparation was divided, half being stored in plasma and the other half in storage solution. ESC and HSR testing were performed in duplicate on days 1 and 5, using each of three diluents: autologous plasma; fresh-frozen plasma; or storage solution. RESULTS: For both ESC and HSR, dilutions made in each of the three diluents yielded significantly different results. Dilutions made in storage solutions were more than 30% lower for ESC and HSR than those made in autologous plasma (P < 0.0001). Dilutions made in thawed fresh-frozen plasma were more than 16% lower for ESC and HSR than those made in liquid autologous plasma (P < 0.0005). CONCLUSIONS: ESC and HSR test results are significantly affected by the test diluent. Platelets should be diluted in plasma (preferably autologous) for the in vitro testing of ESC and HSR, regardless of the media in which they are stored.

Blood Platelets↗
PubMed2003

Intracellular uptake of anionic superparamagnetic nanoparticles as a function of their surface coating.

A new class of superparamagnetic nanoparticles bearing negative surface charges is presented. These anionic nanoparticles show a high affinity for the cell membrane and, as a consequence, are captured by cells with an efficiency three orders of magnitude higher than the widely used dextran-coated iron oxide nanoparticles. The surface coating of anionic particle with albumin strongly reduces the non specific interactions with the plasma membrane as well as the overall cell uptake and at the same time restores the ability to induce specific interactions with targeted cells by the coadsorption on the particle surface of a specific ligand. Kinetics of cellular particle uptake for different cell lines are quantitated using two new complementary assays (Magnetophoresis and Electron Spin Resonance).

Animals↗
PubMed2002

Binding of biological effectors on magnetic nanoparticles measured by a magnetically induced transient birefringence experiment.

We have investigated the relaxation of the magnetically induced birefringence in a suspension of magnetic nanoparticles in order to detect the binding reaction of polyclonal antibodies on the particle surface. The birefringence relaxation is driven by the rotational diffusion of the complex formed by the magnetic nanoparticles bound to the antibody and thus is directly related to the hydrodynamic size of this complex. Birefringence relaxations are well described by stretched exponential laws revealing a polydisperse distribution of hydrodynamic diameters. Comparing the size distribution of samples with different initial ratios of immunoglobuline added per magnetic nanoparticles, we evidence the graft of an antibody on particle and eventually the onset of particles aggregation. Measurements on samples separated in size by gel filtration demonstrate the robustness of our experiment for the determination of size distribution and its modification due to the adsorption of a macromolecule. The immunoglobuline binding assay is performed comparatively for ionic magnetic nanoparticles with different coatings.

Journal Article↗
PubMed2002

Storage of platelets in additive solutions: a pilot in vitro study of the effects of potassium and magnesium.

BACKGROUND AND OBJECTIVES: Platelet additive solutions (PAS) have been shown to be suitable for extended platelet storage but have required the carryover of substantial (30%) amounts of plasma for success. Improving platelet quality by optimizing the composition of PAS may allow a reduction to be made in the amount of plasma carried over. Reducing the proportion of plasma carried over would facilitate some methods of viral inactivation and make available greater amounts of plasma for other needs. MATERIALS AND METHODS: Platelets from six pools of 25 buffy coat platelet units and five apheresis platelet units were aliquoted for storage in plasma, or converted to PAS units in either a specific additive solution (PAS-III), with 30% or 20% plasma, or a modification of PAS-III containing 5.0 mm potassium and 1.5 mm magnesium (PAS-IIIM), with 30% or 20% plasma. Units were stored at room temperature with agitation for 7 days with in vitro testing for biochemical, haematological and functional parameters. RESULTS: Storage of platelets in PAS-IIIM resulted in a reduced rate of glycolysis and better retention of pH, morphology score and ATP levels. Platelets initially showed less evidence of activation when stored in PAS-IIIM, with reduced P-selectin expression. Storage in PAS-IIIM with 20% (rather than the standard 30%) plasma appeared to result in the retention of in vitro properties, similarly to storage in standard PAS-III with 30% plasma. CONCLUSIONS: Storing platelets in an additive solution containing magnesium and potassium improves the functionality of the platelets, as measured by in vitro testing, and may allow a reduction of the amount of plasma required to be carried over to the final unit.

Adenosine Triphosphate↗
PubMed2001

Cutting edge: Ly49A inhibits TCR/CD3-induced apoptosis and IL-2 secretion.

To evaluate the importance of Ly49A on TCR-induced cellular events, we established clones of the 1F2 T cell hybridoma expressing either Ly49A or a chimeric version, Ly49A/H, where the Ly49A cytoplasmic domain has been replaced by the Ly49H cytoplasmic domain. Ligation of Ly49A, but not Ly49A/H, with its ligand H-2D(d) or anti-Ly49A mAbs caused a specific inhibition of TCR/CD3-induced IL-2 secretion. Moreover, flow cytometry analysis of hypodiploid DNA and annexin V binding revealed that ligation of Ly49A protected cells from apoptosis induced by anti-CD3 mAbs or Ag. In contrast, ligation of the Ly49A/H chimeric receptor had no antiapoptotic effect. In addition, engagement of Ly49A selectively inhibited TCR-induced Fas ligand expression whereas TCR-induced Fas expression was not significantly affected. Expression of Ly49 inhibitory receptors on T cells may represent an important mechanism for the regulation of T cell survival in vivo by inhibiting TCR-induced apoptosis and IL-2 secretion.

Animals↗
PubMed1999

Detection of phosphatidylserine surface exposure on human erythrocytes using annexin V-ferrofluid.

The asymmetric transbilayer distribution of phospholipids in the plasma membrane and the regulation of phosphatidylserine (PS) exposure at the cell surface of animal cells are of high physiological significance. It has been shown previously that annexin V is one of the most sensitive tools with which the presence of small amounts of PS on the outer surface of eukaryotic cells can be detected. We present here the covalent coupling of annexin V molecules to magnetic nanoparticles of maghemite. The resulting annexin V-ferrofluid is used in the magnetic separation of PS exposing cells, as illustrated for human erythrocytes modified in their phospholipid transbilayer asymmetry by the use of a calcium ionophore. Results on stored human erythrocytes and comparison with results obtained using iodinated and fluorescein-labeled annexin V are also presented.

Annexin A5↗
PubMed1999

Are there generalised spike waves and typical absences in benign rolandic epilepsy?

Generalised 3 Hz spike wave (SW) discharges with or without absences have been described in children with benign epilepsy with centrotemporal spikes (BECTS), leading to speculations about a continuum between childhood absence epilepsy (CAE) and BECTS. We thus decided to evaluate the prevalence of absence seizures (AS) and generalised 3 Hz SW in patients with BECTS. All patients with BECTS first referred since 1986 have been identified prospectively. Their medical and electroencephalograph (EEG) records were analysed retrospectively, in the search for AS and generalised SW discharges. Over a period of 11 years, we found typical rolandic spikes in 66 newly referred patients; 64 had seizures typical for the condition (18 female, 46 male), two were asymptomatic and were not further analysed. All had routine waking EEG recordings, and 49 children (76%) had at least one sleep EEG. AS or classical generalised 3 Hz SW were never recorded from history or EEG data, respectively. However, 17 patients had some diffuse SW discharges, lasting 1-5 s, which appeared as grossly symmetrical in only seven children, with a clearly asymmetrical aspect in the others. Among these seven patients, the discharges were only seen on awakening in one, both during waking and nREM sleep stage I or II in one and only during nREM sleep stage I or II in five. They were apparently subclinical in all. We thus found neither AS nor classical 3 Hz SW discharges among 64 consecutive patients with BECTS. Brief bursts of bilateral abnormalities occur in about 25% of the cases, mostly with sleepiness. Such findings do not substantiate the existence of a continuum between CAE and BECTS.

Child↗
PubMed1998

Surface modification of superparamagnetic nanoparticles (Ferrofluid) studied with particle electrophoresis: application to the specific targeting of cells.

Colloidal aqueous suspension of superparamagnetic nanoparticles (9 nm in diameter) composed of maghemite (gamma Fe2O3) and forming an ionic ferrofluid in aqueous solution are covalently coupled with lectins, enzymes or antibodies, using specific thiol chemistry. The surface charge modifications of nanoparticles, caused by ligand coupling, were monitored by measuring their electrophoretic mobilities using laser-Doppler velocimetry. Particle electrophoretic mobility (PEM) changes are shown to correlate well with the amount of ligand fixed on the particles, as probed by its biological activity. The PEM method provides a useful tool to optimize ligand immobilization at the surface of nanoparticles, and may be advantageous when biological activity measurements are not convenient.

Animals↗
PubMed1997

Thiolation of Maghemite Nanoparticles by Dimercaptosuccinic Acid

Magnetic particle-effector conjugates are widely used in vitro for cell sorting in various pathologies. The coupling between the particles and the effectors being realized through S-S bridges, the particles must first be thiolated before the coupling. In this work, the synthesis, in aqueous medium, of nanoparticles of maghemite thiolated by dimercaptosuccinic acid is described. The superficial complexation by a thiol-containing ligand induces a reductive dissolution of the oxide and leads to the adsorption of polydisulfide species coming from the oxidation of the ligand. Adsorption and redox reactions being strongly correlated to the composition of the medium, the amount of adsorbed ligand and the quantity of iron(II) released into the medium have been simultaneously determined, at various pH, for different concentrations of ligand added. The charge of the particles is drastically modified in the presence of a chelating agent; as a consequence, the colloidal stability is greatly affected and so the flocculation ranges of the complexed particles have been established for different pH. When the quantity of ligand added is sufficient (0.05 mol/mol of iron), the ferrofluid based on thiolated maghemite particles is stable between pH 3 and 11 and can be used for biomedical applications. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Membrane modifications of red blood cells in Alzheimer's disease.

Red blood cells (RBC) from 24 Alzheimer's disease (AD) patients, 18 age- and sex-matched nondemented (ND) patients, hospitalized in the same facility for orthopedic problems, and 18 healthy volunteers aged 30-52 years were studied in order to gain insight into the nature of RBC membrane modifications in AD. Significant differences were found between RBC from AD and ND patients or young controls respectively for annexin V-binding (45.5 +/- 18.0% vs 27.1 +/- 14.7 and 2.7 +/- 1.9, p = .003), fraction of glycerol resistant cells (30.8 +/- 11.1% vs 19.6 +/- 6.4 and 10.2 +/- 3.1, p = .026), cell electrophoretic mobility in polymer (1.028 +/- 0.022 microns sec-1 V-1 cm vs 1.046 +/- 0.022 and 1.053 +/- 0.021, p = .02) and only limited significance for the filterability (1.46 +/- 0.12 msec vs 1.58 +/- 0.11 and 1.54 +/- 0.11, p = 0.1). A logistic analysis, using simultaneously several features as independent variables, suggested the combined use of annexinV- binding, glycerol resistance, and cell filterability which allowed the assignment of 95% of patients from this cohort to the right group. A prospective analysis of a larger cohort is required for the estimation of the diagnostic value of this test battery. In addition, the high level of annexin binding is characteristic of a disruption of the phospholipid asymmetry in aged or damaged cells, while the high glycerol resistance combined with low electrophoretic mobility an rigidity characterize young RBC, thus indicating an enhanced turnover of RBC in Alzheimer's disease.

Adult↗
PubMed1997

Prognostic factors for childhood and juvenile absence epilepsies.

To assess prognostic factors for absence epilepsy (AE), we analyzed data from 80 patients treated for childhood AE (CAE; n = 53) or juvenile AE (JAE; n = 27) in our epilepsy clinic between 1985 and 1992. All patients were classified according to the International Classification of Epileptic Syndromes which was proposed by the International League against Epilepsy in 1989. Patients were separated into two groups based on the course of disease under adequate treatment: Complete response group (CRG): disappearance of absence seizures (AS) or generalized tonic-clonic seizures (GTCS). Poor response group (PRG): persistence of AS and/or GTCS. Approximately 40% of both CAE and JAE patients had poor response. One parameter was associated with poor prognosis in CAE patients, the presence of polyspikes or polyspikes and waves during sleep. No statistical correlation was made for JAE patients. GTCS were frequent in JAE and GTCS occurrence in CAE patients was associated significantly with age at onset after 8 (p < 0.05). The fact that social and educational performance was poorer in the PRG of both types of AE underlines the importance of therapeutic response in patient rehabilitation.

Adolescent↗
PubMed1995

[Misleading aspects of the standard electroencephalogram in juvenile myoclonic epilepsy: a retrospective study of 56 consecutive cases].

Atypical clinical and/or EEG presentation may complicate the diagnosis of juvenile myoclonic epilepsy (JME). To assess the sensitivity of a standard EEG recording, we retrospectively evaluated the EEG performed at their first referral in 56 consecutive JME patients first seen between 1986 and 1992 (26 M, 30 F, aged 12-53, mean 24.4, with onset of JME at age 10-33, mean 14.3). The diagnosis had been made in none of these patients prior to referral, and was often confirmed only during follow-up. A 20-minute standard EEG was recorded, including hyperventilation (HV) and intermittent light stimulation (ILS). This EEG was normal in 15 cases (27%), showing aspecific or misleading changes in 11 cases (20%) and typical changes in only 30 cases (54%). The baseline EEG was normal in 25 (45%), atypical in 11 (20%), and typical for JME in only 20 (35%). HV and ILS yielded 37 and 39 normal, 10 and 7 aspecific and 9 and 10 specific findings, respectively. A single standard EEG without activation may thus be inconclusive or misleading for the diagnosis of JME in more than 50% of newly referred patients.

Adolescent↗