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Biomedical subjects

P Marchal

Publications and source records attributed to P Marchal.

16 recordsLinked to original sources
PubMed2001

Amphiphilic derivatives of sodium alginate and hyaluronate for cartilage repair: rheological properties.

Various amphiphilic derivatives of sodium alginate and hyaluronate were prepared by covalent fixation of long alkyl chains (dodecyl and octadecyl) with various ratios on the polysaccharide backbones via ester functions. In the semidilute regime, aqueous solutions of the resulting compounds exhibited the typical rheological properties of hydrophobically associating polymers: tremendous enhancement of zero shear rate Newtonian viscosity, steep shear-thinning behavior, and formation of physically cross-linked gel-like networks. The influence of the alkyl chain length, its content on the polysaccharide and of the polymer concentration in the solution was well identified. All obtained results are discussed with respect to the schedule of conditions related to materials, which could be used for cartilage repair, such as in synovial fluid viscosupplementation as well as in cartilage replacement. In particular, it is seen that HA-C(12)-5 (hyaluronate substituted with 5% of dodecyl chains) and HA-C(18)-1 (hyaluronate substituted with 1% of octadecyl chains) in a 0.15N NaCl solution at 8 g/L have rheological properties quite similar to those of healthy synovial fluid. On the other hand, the rheological parameters of solutions at 8 g/L in 0.15N NaCl of some of derivatives, such as, for example, AA-C(12)-8 (alginate substituted with 8% of dodecyl chains) or HA-C(18)-2, are well fitted for a use in cartilage repair.

Alginates↗
PubMed2000

1H nuclear magnetic resonance relaxometric characterization of fat and water states in soft and hard cheese.

The aim of this work was to study the spin spin (T2) relaxation components of one hard cheese and three soft cheeses to characterize fat and water states. NMR signals were measured at 6 degrees C with a 0.47 T NMR device. The transverse relaxation decay was fitted using the Marquardt method. The T2 relaxometric behaviour of the cheeses under consideration was characterized by four relaxation components. To understand the chemical composition of each NMR component, we studied anhydrous milk fat extracted from each cheese analysed. At 6 degrees C, the fat was 60% crystalline. In cheese, the solid fat was found mainly in the shorter relaxation component with a T2 of 17 micros. The intensity of the NMR relaxation with a T2 > 1 ms was explained by the amount of water, liquid fat and proteins, and the associated relaxation time varied as a function of the process used. The composition of each relaxation component was confirmed by the temperature effect and the influence of the fat content on the NMR cheese signal. NMR relaxometry was able to provide information on water behaviour (i.e. the quantity and level of interactions with proteins) and on the solid:liquid ratio of anhydrous milk fat in the cheese.

Cheese↗
PubMed2000

Fatal Mycobacterium tuberculosis brain abscess in an immunocompetent patient.

A non-HIV-infected 63-y-old woman presented seizures and coma during the course of Mycobacterium tuberculosis infection. Computerized tomography scan led to the diagnosis of a large compressive brain abscess. The patient died with multiorgan failure. Systematic central nervous system investigations should be done in cases of disseminated tuberculosis.

Brain Abscess↗
PubMed2000

Streptococcus salivarius acute meningitis with latent petromastoiditis.

A 48-y-old woman, with a previous history of neurosurgical intervention for a trigeminal neurinoma, presented with acute meningitis due to Streptococcus salivarius. There were significant changes in the petrous region, as revealed by MRI, leading to the diagnosis of associated latent subacute mastoiditis.

Acute Disease↗
PubMed1999

Embryonic electronics.

Within the general domain of bio-inspired computing, a particular trend over the past few years has been that of constructing actual hardware devices that are inspired by nature. This paper describes one such project-Embryonics (embryonic electronics)-inspired in particular by the process of embryogenesis. Our ultimate objective is the construction of large-scale integrated circuits, exhibiting the properties of self-repair (healing) and self-replication, found until now only in living beings. We present the silicon-based artificial cell, followed by a description of mechanisms operating at the cellular level: cellular differentiation, cellular division, regeneration, and replication. We then present the cell's composition as an ensemble of lower-level elements, known as 'molecules'. As electronic chips grow evermore complex, the need for self-repair capabilities will become increasingly crucial. The Embryonics approach represents one possible way of confronting this pivotal problem.

Cell Differentiation↗
PubMed1998

John von Neumann: the founding father of artificial life.

Aside from being known for his contributions to mathematics and physics, John von Neumann is considered one of the founding fathers of computer science and engineering. Not only did he do pioneering work on sequential computing systems, but he also carried out a major investigation of parallel architectures, leading to his work on cellular automata. His exceptional vision and daring, borrowing from biology the concept of genomic information even before the discovery of DNA's double helix, led him to propose the concept of self-reproducing automata.

Artificial Intelligence↗
PubMed1994

Eye fixations near corners: evidence for a centre of gravity calculation based on contrast, rather than luminance or curvature.

Subjects scanned line drawings of polygons in order to count the number of corners. The positions their eyes fixated were studied as a function of the size of the angle and whether the apex of the angle was present or absent. The results showed that the eyes tended to land at a position near the centre of gravity of the corner configurations. The observed landing positions were coherent with the hypothesis that the centre of gravity was calculated within an attentional spotlight centered on the apex of the corners, and that the calculation was based not on the total luminance distribution, nor on the distribution of energy in a neurophysiologically motivated curvature detector, but simply on the basis of a contrast detector.

Adult↗
PubMed1990

Irreversible inhibition of rat S-adenosylmethionine decarboxylase by 5'-([(Z)-4-amino-2-butenyl]methylamino)-5'-deoxyadenosine.

5'-([(Z)-4-Amino-2-butenyl]methylamino)-5'-deoxyadenosine [Z)-AbeAdo) was tested in vitro and in vivo as a potential inhibitor of S-adenosyl-L-methionine decarboxylase (AdoMetDC), a pyruvoyl-containing enzyme, purified from rat liver. In vitro (Z)-AbeAdo produces a time- and dose-dependent irreversible inhibition of the enzyme. Saturation kinetics are observed when the enzyme is preincubated with (Z)-AbeAdo in the presence of 50 microM putrescine, a known activator of AdoMetDC. Under these conditions kinetic constants were measured (Ki = 0.56 +/- 0.04 microM; tau 1/2 = 0.51 +/- 0.03 min). The inhibition is not relieved by prolonged dialysis of the inactivated enzyme. The turnover number for (Z)-AbeAdo, i.e. the number of inactivator molecules required to inactivate one enzyme molecule, is approximately 1.5. The selectivity of (Z)-AbeAdo was explored: the compound is not a substrate of adenosine deaminase, mitochondrial monoamine oxidase and diamine oxidase, but is slowly oxidized by benzylamine oxidase from rat aorta. The (E)-isomer of AbeAdo, is at least 100-fold less active than (Z)-AbeAdo as a time-dependent inhibitor of rat liver AdoMetDC. In rats, intraperitoneal administration of (Z)-AbeAdo produces a rapid, long-lasting and dose-dependent decrease of AdoMetDC activity in ventral prostate, testis and brain.

Adenosylmethionine Decarboxylase↗
PubMed1989

Selective inactivation of MAO-B by benzyl-dimethyl-silyl-methanamines in vitro.

The alpha-silyl amines benzyl-dimethyl-silyl-methanamine and the p-fluoro and p-chloro derivatives are potent time-dependent inhibitors of rat brain MAO-B. The inhibition exhibits saturation kinetics, takes place in the enzyme active-site and is irreversible. The most potent inhibitor in the series is 4-fluorobenzyl-dimethyl-silyl-methanamine (KI = 11 microM, tau 1/2 = 2.3 min). Its selectivity for the B-form relative to the A-form of rat brain MAO is higher than 10(4). Benzyl-dimethyl-silyl-methanamines may represent a new family of anti-Parkinsonian agents.

Animals↗
PubMed1981

[Not Available].

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Belgium↗
PubMedDate not supplied

Fetal-maternal hydrops syndrome in human parvovirus infection.

A case of maternal generalized edema with hyponatremia, hypoosmolality and secondary hyperaldosteronism was associated with pseudomolar plasma human chorionic gonadotropin (hCG) concentrations in a case of fetal and placental hydrops due to parvovirus B19 infection. Digoxigenin in situ hybridization techniques were effective in demonstrating parvovirus B19 infection on fixed tissues. Hydropic changes in the placenta may have massively increased the maternal plasma hCG concentration with subsequent fluid imbalance leading to maternal hydrops mimicking molar pregnancy.

Chorionic Gonadotropin↗