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Biomedical subjects

C Michel

Publications and source records attributed to C Michel.

At least 217 records · Page 12Linked to original sources
PubMed1992

Toxic effects and detection of oxygen free radicals on cultured articular chondrocytes generated by menadione.

The aim of this work was to study the proliferation pathological perturbations of cultured chondrocytes in response to menadione, an oxygen free radicals producing drug. Rabbit articular chondrocytes in monolayer culture were treated with 10(-5) M, 1.5.10(-5) M and 2.10(-5) M of menadione during three days. A dose dependent decrease of the proliferative capacity was observed. Flow cytometry analysis revealed a perturbation of the cell cycle progression consisting in an accumulation of cells in the S and G2 + M phases. This growth perturbation was due to oxygen radicals production since a treatment with catalase suppressed these toxic effects. Furthermore, to identify oxygen derived radicals in the cellular suspension of cultures treated with menadione, we used a technique of spin-trapping coupled with electron spin resonance (ESR). The ESR signal corresponding to the DMPO hydroxyl radical adduct (DMPO-OH) has been detected. The spectra observation indicated the actual production of hydroxyl radical. However, superoxide anions have not been identified; this fact can be explained by the low reactivity of these anions with DMPO and by the decomposition of signal DMPO-OOH to DMPO-OH.

Animals↗
PubMed1992

[Cardiac output studied by a non invasive method in hypertensive patients].

We measured by thoracic bioimpedance (BoMed, NCCOM3-R7) non invasive cardiac index (CI), stroke index (SI) and systemic vascular resistance index (SVRI) in 48 hypertensive patients (OMS) compared to 30 normotensive. The mean arterial pressure (MAP) and the SVRI were significantly higher in the hypertensive group while the CI are significantly lower, as that was shown in previous invasive studies. We found an inverse correlation between age and CI (r = -.30, p < or = .05) in relation with a negative correlation between SI and age (r = -.35, p < or = .05) and no correlation between heart rate and age. Furthermore we divided normotensive and hypertensive patients in three groups of CI (low CI < 2.8 l/min/m2, 2.8 < or = normal CI < or = 4.2 l/min/m2, high CI > 4.2 l/min/m2) and in three groups of SVRI (low SVRI < 1660 Flohms/m2, 1660 < or = normal SVRI < or = 2580 Flohms/m2, high SVRI > 2580 Flohms/m2). Despite CI diminution in hypertension, high CI percentage's was the same in normotensive and hypertensive patients. In conclusion, these results confirm previous studies by using a simple, easy, non invasive and reproducible method.

Adult↗
PubMed1992

[Adenocarcinoma on endobrachyesophagus. Results and prognostic factors apropos of 19 cases surgically-treated].

The authors report about a retrospective series of 19 operated patients with adenocarcinomas in a columnar lined esophagus. The resection rate was 95%, the postoperative mortality rate was 5.5%. The survival rate following curative exeresis (n = 14) was 32% (+/- 14) at 5 years. All patients with a stage III lesion died after 2 years, while 46% (+/- 19) of those with stage I or II tumors (p less than 0.001) survived at 5 years. In a multivariative analysis, the most important prognostic factor is the histological grade (p less than 0.01), then the extension to the lymph nodes (p less than 0.1). As the adenocarcinoma often reveals the columnar lined esophagus, the improvement of the prognosis certainly depends on the evaluation of the treatment, which combines pre- or postoperative radiation and chemotherapy, in multidepartmental prospective studies.

Adenocarcinoma↗
PubMed1992

[Antibacterial resistance induced by injection of ascitic fluid (with IgM partially removed) and natural monoclonal antibodies of human origin in rainbow trout].

Human monoclonal immunoglobulins M from myeloma shown to have the typical polyspecificity of natural antibodies, were precipitated from the ascitic fluid that originally contained them. The IgM and their supernatant were injected in parallel, intraperitoneally into rainbow trout (Oncorhynchus mykiss) to test passive protection against experimental furunculosis. Protection was observed in both cases (significant protection at 2%). However, only trout treated with IgM were still protected against polybacterial cross-infections which occurred 10 days later (significant protection at 1%). These results confirm the passive mammalian protection conferred by biologic fluids injected in vivo in fish and provide further evidence for participation of natural antibodies in antibacterial defences.

Animals↗
PubMed1992

[Subcardial stomach diverticulum and gastroesophageal reflux].

Gastric diverticulum is a rare disease, often benign and specifically located in the right paracardial region. The authors report a case of left paracardial diverticulum with gastro-oesophageal reflux. This association should be treated surgically with resection of the diverticulum, after failure of medical treatment.

Barium Sulfate↗
PubMed1992

Association of chronic interstitial cystitis, protein-losing enteropathy and paralytic ileus with seronegative systemic lupus erythematosus: case report and review of the literature.

We report the case of a female patient with seronegative lupus and predominant bladder and intestinal involvement in the form of interstitial cystitis and protein-losing enteropathy. This association is exceptional in the literature but may be underestimated because of frequent latency of interstitial cystitis. It may define a peculiar subgroup of lupus patients usually responsive to steroid therapy. In this case, only cyclophosphamide markedly improved the protein-losing enteropathy but did not influence the bladder disease.

Adult↗
PubMed1991

Purification of the coenzyme B12-containing 2-methyleneglutarate mutase from Clostridium barkeri by high-performance liquid chromatography.

Two methods are described by which the enzymes 2-methyleneglutarate mutase and 3-methylitaconate delta-isomerase from Clostridium barkeri have been separated by high-performance liquid chromatography on a much larger scale than reported previously. First, the mutase eluted before the delta-isomerase after incubation with the mild detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulphonate (CHAPS) followed by high-performance anion-exchange chromatography on Mono Q in the presence of the same detergent. Second, an even better separation, although with a lower yield of mutase, was obtained by hydrophobic interaction chromatography on phenyl-Sepharose HiLoad, whereby the enzymes were eluted in the reverse order. Final high-performance anion-exchange chromatography of the latter preparation on Mono Q at pH 8 gave highly purified 2-methyleneglutarate mutase (greater than 95% purity) which had a pink-orange colour (lambda max 280, 375, 470 and 532 nm). The enzyme was active in the absence of coenzyme B12 (adenosylcobalamin) and contained 2.1 mol of this coenzyme per homotetramer (molecular mass, m = 300 kilodalton).

Amino Acid Sequence↗
PubMed1991

[Different strategies of substitute treatment of end-stage chronic kidney failure by dialysis].

The development, diversification and improvement of haemodialysis and transplantation techniques have radically altered the prognosis of end-stage chronic renal failure, a condition that is still inexorably lethal in many countries. In France, it is estimated that up to 20,000 patients are being kept alive by these treatments, including transplantation. The available follow-up data show that a survival of 30 years, and perhaps more, can now be expected, at the cost of cardiovascular and osteo-articular complications the incidence and severity of which should be reduced in the years to come. It is by a carefully planned recourse, based on each patient's clinical status and occupation, to the whole range of these complementary treatments that survival time and quality will be further improved.

Clinical Protocols↗
PubMed1991

Coenzyme B12-dependent 2-methyleneglutarate mutase from Clostridium barkeri. Protection by the substrate from inactivation by light.

Partially purified 2-methyleneglutarate mutase from Clostridium barkeri was separated from 3-methylitaconate delta-isomerase by treatment with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) followed by FPLC on the anion exchange column Mono Q in the presence of the detergent. When purified in the dark, the active mutase contained a corrinoid, most probably coenzyme B12. The enzyme was inactivated by light at the same wavelength (lambda less than 620 nm) and rate as free coenzyme B12. The rate was not influenced by oxygen or by temperature (0-37 degrees C). Reactivation of up to 50% of the original activity was achieved by incubation with coenzyme B12 and dithiothreitol. The substrates 2-methyleneglutarate (up to 40 mM) or (R)-3-methylitaconate specifically protected the enzyme from inactivation by visible light. This effect was enhanced 3-fold by raising the temperature from 0 degrees C to 37 degrees C. The data indicate that during catalysis, the Co-C bond of the coenzyme is cleaved and cannot be affected any more by light.

Carbon-Carbon Double Bond Isomerases↗
PubMed1991

Radiobiological fundamentals in radioepidemiology and radiation protection.

Radiation is a convenient tool to study fundamental processes of life. Biological effects of irradiation may result from indirect actions which are mediated by free radicals (e.g. OH-radicals) or from direct actions which involve ionizations in the DNA and other biomolecules. Damage to the DNA is the principal, but not exclusive target for cell death, loss of reproductive integrity, mutation, cancer, developmental anomalies and other radiobiological effects. Repair of damaged DNA and cellular recovery processes play an essential role in affecting the survival of cells. Dose, dose rate, radiation quality, biological and chemical modifiers also have a pronounced effect upon the extent of radiation responses. The biological effects of ionizing radiation are somatic or hereditary and can further be classified into stochastic and deterministic effects. For radiation epidemiology and protection the stochastic action is more relevant because the probability of an effect is a function of dose, without a threshold. Induction of cancer, hereditary diseases and probably also mental retardation are regarded as stochastic effects.

Cell Survival↗
PubMed1991

A normalization technique for 3D PET data.

Prior to reconstruction, emission data from a multi-ring PET camera must be corrected (normalized) for variations in detector sensitivity. The appropriate correction coefficients are obtained by measuring the response of all coincidence lines to a calibrated source of activity (a blank scan). State-of-the-art cameras may contain up to a million such lines of response (LORs), and therefore around 400 million counts will be required to calibrate each LOR to a statistical accuracy of 5%. Alternatively, by modelling the LOR sensitivity as the product of the individual detector efficiencies and a geometrical factor, a calibration procedure has been proposed which requires the determination of only 6000 parameters from this same data set. A significant improvement in the statistical accuracy of the coefficients can therefore be expected. Recently, multi-ring scanners have been operated with the septa retracted, increasing the number of measured LORs by a factor of eight. The acquisition of the calibration data necessary to achieve adequate statistical accuracy then becomes prohibitive. We show that, by modelling the LOR sensitivity, it is possible, with certain approximations, to normalize a septa-retracted emission data set with good accuracy. The input to the model is a high statistics blank scan acquired with the septa extended, which offers a number of practical advantages.

Calibration↗
PubMed1991

The effect of site of administration in the gastrointestinal tract on the absorption of insulin from nanocapsules in diabetic rats.

Isobutylcyanoacrylate nanocapsules have been used as drug carriers for the enteral absorption of insulin. Their absorption has been studied by measuring fasted glycaemia in streptozotocin-induced diabetic rats after a single administration of encapsulated insulin (100 units kg-1) at various sites along the gastrointestinal tract. Glycaemia decreased from the second day, the intensity and duration depending on the site of administration (65% ileum, 59% stomach, 52% duodenum and jejunum, 34% colon). This hypoglycaemic effect lasted up to the 18th day after administration for ileum and jejunum, the 15th day for stomach and duodenum, and the 13th day for colon. In-vitro, nanocapsules protect insulin against proteolysis from pepsin, chymotrypsin and trypsin. These results suggest (i) that insulin is protected by nanocapsules in the gastrointestinal tract, (ii) that it is absorbed in an active form, and (iii) that ileum is the most potent site of absorption.

Animals↗