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Biomedical subjects

M Remy

Publications and source records attributed to M Remy.

At least 19 recordsLinked to original sources
PubMed2005

The storage of sewage sludge: influence of liming on the evolution of copper chemical fractions.

Sewage sludge re-used in agriculture has to be stabilized and is often stored for several months before land spreading. Stabilization treatment may affect the behaviour of heavy metals such as Cu, which is an element potentially toxic to the environment. In the present study, the chemical forms of copper have been investigated in heaps of limed and unlimed sludge coming from the wastewater treatment plant of Roselies (Belgium). These limed and unlimed aerobically digested sludges were stored during 4 mo in controlled conditions close to field ones. The sequential extraction procedure developed by Tessier was used to determine the copper chemical forms of representative samples taken in the outer shell and in the depth of the heaps. The physico-chemical properties (pH, organic matter, dry matter and temperature) of these samples were also monitored. This study shows that liming transforms part of organically-bound copper into both exchangeable and residual copper. These changes mainly occur during the first 2 wk of storage. After several months of storage, copper passes from the residual fraction to the exchangeable and oxide fractions. During the whole experiment, changes occur faster in the outer shell than in the depth of the heaps. Thus, we demonstrate that the distribution of the copper forms depends on the storage time and it is different in the outer shell from that in the depth of the heaps.

Calcium Compounds↗
PubMed2005

A general model of reaction kinetics in biological systems.

Dynamic mathematical models in biotechnology require, besides the information about the stoichiometry of the biological reaction system, knowledge about the reaction kinetics. Modulation phenomena like limitation, inhibition and activation occur in different forms of competition with the key enzymes responsible for the respective metabolic reaction steps. The identification of a priori unknown reaction kinetics is often a critical task due to the non-linearity and (over-) parameterization of the model equations introduced to account for all the possible modulation phenomena. The contribution of this paper is to propose a general formulation of reaction kinetics, as an extension of the Michaelis-Menten kinetics, which allows limitation/activation and inhibition effects to be described with a reduced number of parameters. The versatility of the new model structure is demonstrated with application examples.

Algorithms↗
PubMed1998

[Male osteoporosis].

AN UPCOMING PUBLIC HEALTH PROBLEM: There has been a considerable focus on osteoporosis in men recently. Bone mass is high in men who have larger bones than women. The frequency of fractures is also higher due to post-trauma lesions. Femoral neck fractures have also increased over the last few years although the F/M ratio remains about 2.8. Overall, there is a trend towards an increased incidence of masculine osteoporosis (and vertebral fractures) due to population aging. FAVORING FACTORS IN MEN: The most important factors are hypoandrogenism, hypoestrogenism (pre or post-puberty), the alcohol-smoking association, malnutrition, lack of sun exposure and chronic liver disease. Other causes of osteoporosis (hyperthyroidism, Cushing's disease, hemochromatosis, gastrectomy, inflammatory rheumatic disease, tubulopathy, hypercalciuria and iatrogenic causes) should also be taken into consideration. PRETHERAPY WORK-UP: All the different possible etiologies should be investigated. Therapeutic protocols should provide hormone replacement when required, withdrawal of causal drugs, better nutrition and reduced alcohol and tobacco use.

Bone Density↗
PubMed1998

Dynamic model of airway pressure drop.

A multipath model of the mechanical behaviour of healthy lungs subject to a plethysmographic test (close to quiet breathing conditions) has been developed, which includes the main physiological nonlinearities. This model is built on a symmetric branching scheme based on Weibel's data, and uses non-linear fluid equations for the upper and lower airways. The alveolar gas compression, the changes in airway dimensions related to lung volume and/or transmural pressure, and the respiratory swings in glottic aperture have been taken into account. As clinically observed, the behaviour of the lungs, taken as a whole, seems linear, but it is confirmed by simulation that this linearity is only apparent. Simplifications and linearisations therefore need to be made carefully, only after their impact on the global behaviour of the lung is evaluated.

Computational Biology↗
PubMed1997

Up-regulation of thrombomodulin is inducible on an endothelialized polyester.

The concept of endothelial cell seeding of vascular prostheses is designed as a method for improving long-term patency substitutes because endothelium is considered as the haemocompatible surface of reference. The assessment of the functionality of cells lining a biomaterial is thus of crucial importance. We have reported encouraging results concerning the ability of a polyester coated with albumin and chitosan (M 11) to be lined by a confluent monolayer of cultured human endothelial cells (EC). The aim of the present work was to study the expression of thrombomodulin (membrane glycoprotein responsible for anticoagulant activity) in EC lying on M.11 by anticoagulant activity and mRNA level with and without stimulation. Results obtained in basal conditions showed that EC on M.11 have a comparable expression of TM mRNA when compared to control (EC on tissue culture plates) despite a lower TM surface activity for EC on the biomaterial. In terms of ratio (stimulated cells to unstimulated ones) the response in activity for EC on M.11 is comparable to that of the control. These results indicate that cells lying on M.11 are able to respond to physiological-like stimuli, despite a tendency for these cells to express a procoagulant phenotype when compared with control EC.

Journal Article↗
PubMed1996

Erdheim-Chester disease. Clinical and radiologic characteristics of 59 cases.

We made a retrospective evaluation of clinical and radiologic features, treatment, and outcome of Erdheim-Chester disease, a rare non-Langerhans cell histiocytosis. We had 7 patients coming from 3 French teaching hospitals and reviewed 52 cases from the literature. These cases were considered to have Erdheim-Chester disease when they had either typical bone radiographs (symmetrical long bones osteosclerosis) and/or histologic criteria disclosing histiocytic infiltration without features for Langerhans cell histiocytosis (no S-100 protein, no intracytoplasmic Birbeck granules). Ages at diagnosis ranged from 7 to 84 years (mean +/- SD = 53 +/- 14 yr) with a male/female ratio of 33/26. Bone pain was the most frequent clinical sign (28/59), mostly located in the lower limbs. Exophthalmos and diabetes insipidus were found in respectively 16/59 and 17/59 patients. General symptoms (fever, weight loss) and "xanthomas" (mainly located on the eyelids) were present in 11/59 patients. Retroperitoneal involvement was found in 17/59 patients. Skeletal X-ray showed typical osteosclerosis of the diaphysis of the long bones in 45/59 patients. Bone radiographs showed osteolytic lesions of the flat bones (skull, ribs) in 8 patients. Histologic diagnosis was performed after a bone biopsy (28 patients), a retroorbital biopsy (9 patients), and/or a biopsy of the retroperitoneal infiltration or the kidney (11 patients). Six of our 7 patients but only 5 of 52 patients from the literature had the complete histologic criteria, disclosing no Birbeck granules or S-100 immunostaining. In other cases, histologic results usually described a xanthogranulomatous infiltration by foamy histiocytes nested in fibrosis. Treatment was corticotherapy (20/59), chemotherapy (8/59), radiotherapy (6/59), surgery (3/59) and immunotherapy (1 patient). Twenty-two patients died after a mean follow-up of 32 +/- 30 mo (range, 3-120 mo). In conclusion, Erdheim-Chester disease may be confused with Langerhans cell histiocytosis as it sometimes shares the same clinical (exophthalmos, diabetes insipidus) or radiologic (osteolytic lesions) findings. However, it also appears to have distinctive features. Patients are older and have a worse prognosis than those with Langerhans cell histiocytosis, and the diagnosis relies on the association of specific radiologic and histologic findings.

Adolescent↗
PubMed1995

Beware of commercial human thrombins used to stimulate cultured endothelial cells.

In the field of in vitro biocompatibility testing, the investigation of cell response at the interface with a biomaterial is of great importance; there is a need for standard conditions and thus of well-defined and reliable sources of materials for an objective evaluation of cellular function. Thrombin is often used in vitro as a stimulating agent to check the specific functions of cultured endothelial cells. In the present work, and in order to select a thrombin of commercial origin, two criteria were borne in mind: purity towards the presence of the von Willebrand factor (vWF) and effectiveness towards vWF release by human umbilical venous endothelial cells (HUVEC) that have been submitted to four human commercial thrombins. We detected the presence of vWF in some thrombin solutions that have not yet been in contact with HUVEC. The different thrombins contained vWF antigen ranging from less than 0.1 mUnit per NIH unit of thrombin (from Diagnostica Stago and Sigma Chemical Co.) to 10-20 mUnit per NIH unit of Fibrindex thrombin (from Ortho Diagnostic Systems). Thus, if vWF is present in commercial thrombins, it contributes to and overestimates the vWF appearance in the media resulting from cell stimulation. Consequently, we fixed on thrombin from Diagnostica Stago for further studies involving HUVEC on biomaterials.

Biocompatible Materials↗
PubMed1995

Thermal behavior of the constant volume body plethysmograph.

The thermal behavior of the constant volume body plethysmograph under the thermal effect of the patient and the thermostatic bag is modeled by two relations: the first is between the temperature in the box and the heat flux generated by the patient and the bag, and the second is between the pressure in the box and the same flux. When the heat flux evolves as a step function, the temperature and the pressure are characterized by four time constants, the theoretical values of which are functions of the heat transfer coefficients by natural convection between the faces of the walls, and the air inside and outside the box. Only two of these four theoretical constants can be experimentally measured with reasonable precision. One of these is responsible for an important delay between the installation of the patient in the box and the disappearance of the disturbance thereby created in the pressure signal. Investigations with patients and with three different plethysmographs each built of a different material (wood, PVC, and Perspex) show the influence of the construction material on the waiting period before the disappearance of the disturbance in the pressure signal.

Equipment Design↗
PubMed1994

Evaluation of cell colonization on biomaterials: preventing cell attachment to plastic containers.

In biocompatibility evaluation involving cell culture models, we use samples of biomaterials of different forms and sizes. During cell seeding onto biomaterials of an inadequate size to cover the bottom of the culture wells completely, cells have the opportunity to attach to the plastic. As described in this report with two culture models and two biomaterials, we use an agarose gel sublayer to prevent this phenomenon.

Biocompatible Materials↗
PubMed1992

Jaw movement kinematics and jaw muscle (EMG) activity during drinking in the pigeon (Columba livia).

Movements of the maxilla and mandible were recorded during drinking in the head-fixed pigeon and correlated with electromyographic activity in representative jaw muscle groups. During drinking, each jaw exhibits opening and closing movements along both the dorso-ventral and rostro-caudal axes which may be linked with or independent of each other. All subjects showed small but systematic increases in cycle duration over the course of individual drinking bouts. Cyclic jaw movements during drinking were correlated with nearly synchronous activity in the protractor (levator) of the upper jaw and in several jaw closer muscles, as well as with alternating activity in tongue protractor and retractor muscles. No EMG activity was ever recorded in the lower jaw opener muscle, suggesting that lower jaw opening in this preparation is produced, indirectly, by the contraction of other muscles. The results clarify the contribution of the individual jaws to the generation of gape variations during drinking in this species.

Animals↗
PubMed1991

Retinal afferents to the tectum opticum and the nucleus opticus principalis thalami in the pigeon.

The retinal afferents of the tectum opticum and the n. opticus principalis thalami (OPT) were studied with fluorescent tracers in pigeons. Injections into the tectum opticum revealed topographically related areas of high density labelling in the contralateral retina. In these areas up to 15,000 cells/mm2 were labelled. After tectal injections the soma sizes of labelled retinal ganglion cells in the area centralis ranged from 5 to 23 microns with a mean of 7.5 microns. Afferents from the ipsilateral retina could not be demonstrated. Injections into the OPT labelled neurons throughout the retina without a clear topographical relation to the locus of injection. The density never exceeded 150 cells per mm2. The soma size range was 8 to 35 microns with a mean of 14.6 microns. Independently of the injection area within the OPT, the red field in the dorsotemporal retina was always extremely sparsely labelled. The number of labelled ganglion cells in this area never exceeded 25 neurons/mm2. After OPT injections the average density of labelling per unit area was six times higher in the yellow than in the red field. The results confirm previous reports of a massive and topographically organized retinal projection onto the optic tectum. The projection onto the OPT was clearly smaller and with the retrograde tracing techniques in use, an orderly topography has not been demonstrated. The paucity of red field projections onto the OPT suggests that the role of the thalamofugal pathway in binocular integration is very limited.

Animals↗
PubMed1991

Directional dependence of intraocular transfer of stimulus detection in pigeons (Columba livia).

The eyes of the pigeon (Columba livia) are positioned laterally in the head. Thus, there is only a small area of binocular overlap, which constitutes the frontal visual field and a large area of monocular vision in the lateral visual fields. The conditions were examined under which intraocular transfer occurs in pigeons; that is, the transfer of information between both portions of the visual field of one eye. Different groups of head-fixed birds learned to discriminate the presence of a bright light from its absence in an instrumental conditioning situation with water as reinforcer. After the animals had acquired the task when the stimuli were viewed in either the frontal or lateral visual field, the stimuli were moved into the converse visual field. Transfer was shown to be directionally selective: It occurred when stimulus presentation was changed from the lateral to the frontal visual field but not when this change was in the opposite direction.

Animals↗
PubMed1990

The topographical projection of the nucleus isthmi pars parvocellularis (Ipc) onto the tectum opticum in the pigeon.

The projection of the nucleus isthmi pars parvocellularis (Ipc) onto the tectum opticum was studied with tectal injections of three different fluorescent tracers and wheat germ-agglutinated horseradish peroxidase (WGA-HRP) in 21 pigeons. In frontal sections obtained, the relationship between position and size of the tectal injection and the location of the retrogradely labelled Ipc neurons were analyzed. The results reveal a topographically organized system with reciprocal projections in which the dorsoventral axis of the tectum receives afferents from the lateromedial axis of the Ipc. The caudorostral tectal axis is innervated by neurons situated along the caudorostral axis of the Ipc. Specific points on the tectal surface do not correspond to single points within the Ipc, but to column-like strings of Ipc neurons extending through the dorsoventral aspect of the nucleus.

Animals↗
PubMed1990

Assistant programming software: a new tool for an improved programming of pacemakers.

Programming the new DDD pacemakers is becoming increasingly difficult. One must take into account the pacemaker's complexity, the fact that some parameters are linked to others, and the clinical profile of the patient. This difficult problem will lead to the design of software to assist programming, which will help the implanting physicians in choosing adequate programmed settings adapted to the functioning of the device and to the physiology and pathology of the patient. These programming aides should meet certain basic requirements to make them safe, efficient, and easy to use. One such system designed by ELA Médical, "Programming Assistant" is herein described. The preliminary results of an initial study on the acceptance of this programming aide among physicians involved in cardiac pacing are given and discussed.

Adult↗
PubMed1989

Behavioral spectral sensitivities of different retinal areas in pigeons.

The spectral sensitivity of the red and the yellow retinal fields of head-fixed pigeons was separately measured for wavelengths between 340 and 640 nm by a behavioral perimetric technique. Within this spectral range the mean spectral sensitivity of both fields was found to be maximal at 584 nm and minimal at the lower ultraviolet wavelengths. Differences in sensitivity were found, however, at shorter wavelengths, with the yellow field being more sensitive than the red at wavelengths below 500 nm and especially in the ultraviolet spectral range. These sensitivity differences are discussed in relation to other functional differences between the pigeon's retinal fields.

Animals↗