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Biomedical subjects

C Michel

Publications and source records attributed to C Michel.

At least 307 records · Page 17Linked to original sources
PubMed1987

Determination of sulfite radical (SO.3-) reaction rate constants by means of competition kinetics.

The sulfite radical anion (SO.3-) was found to react rapidly with the flavonoid quercetin (k = 2.5 x 10(8) dm3mol-1s-1) and the carotenoids crocin (k = 1.0 x 10(9) dm3mol-1s-1) and crocetin (k = 1.5 x 10(9) dm3mol-1s-1). The reactions can easily be monitored due to the strong absorptions of the substrates and, in the case of quercetin, the formation of a strongly absorbing transient species. Using these substances, we determined by means of competition kinetics rate constants of SO.3- reactions with nucleic acid components, polyunsaturated fatty acids, and glutathione.

Carotenoids↗
PubMed1987

Brain glucose metabolism in children with the autistic syndrome: positron tomography analysis.

Brain glucose metabolism was measured in 18 autistic children, using high resolution positron emission tomography. Global brain glucose utilization in the autistic population was slightly more elevated than in young adult volunteers but did not differ significantly from that of control children. Regional metabolic maps were also normal, although there was evidence for heterogeneities, particularly at the level of prefrontal and parieto-temporo-occipital association areas: 6 children showed a relative hyperfrontality whilst hypofrontality was found in 2 cases; these heterogeneities were not correlated with clinical symptoms. These data suggest that both the rate and the regional distribution of brain glucose metabolism are normal in autistic children. Variations in terms of relative metabolic rates in association cortex remains to be investigated further.

Adolescent↗
PubMed1987

Interaction between radiation and cadmium or mercury in mouse embryos during organogenesis.

The response of mouse embryos to different concentrations of cadmium or mercury with or without low LET radiation was measured in terms of gross morphological anomalies and cellular changes. Single doses of the heavy metals (2 mg/kg body weight) were injected i.p. on day 8 of gestation 30 min before whole-body irradiation. Combined exposures to CdCl2 and X-rays led to a significant reduction in the rate of exencephaly compared with the high frequency after cadmium alone. The hypothesis that metallothionein, a sulphur-rich and metal-binding protein, may be responsible for the antagonism observed could not be confirmed. Mercuric chloride alone induced a low rate of exencephaly and the data on combined treatment suggest additivity with 0.5 and 1.0 Gy X-rays. Regarding cellular criteria, cell death in the eye anlage on day 9 of gestation was significantly suppressed after 0.5 Gy and especially after CdCl2 plus 0.5 Gy compared to cadmium alone. It is assumed that the reduction of cell lethality is correlated with the low occurrence of exencephaly. Concerning the proliferation of neuroblasts, cadmium stimulated the mitotic activity whereas X-rays depressed the proliferation capacity. After the combined treatment a distinct antimitotic effect was established.

Abnormalities, Drug-Induced↗
PubMed1987

Synergistic interaction between vindesine and X-rays in the prenatal development of mice.

The modification of radiation damage by various concentrations of the oncolytic drug vindesine was studied macroscopically, using mouse embryos during the early organogenesis (days eight and nine of gestation) as the test system. The analysis at term showed that the developmental toxicity of vindesine depends on the dosage and the time of administration. In the lower dose-range (0.25 and 0.35 mg/kg), the only reaction was growth retardation, whereas higher concentrations (0.5 and 1.0 mg/kg) led mainly to an early resorption of implants. The more differentiated stage (day nine) exhibited a much higher sensitivity to vindesine than the embryo on day eight. Conversely, the harmful action of 0.9 Gy X-rays was restricted to the earlier period of organogenesis. The incidence of abnormalities after irradiation on day eight was 4.5 times higher than the one following exposure on day nine. The combined exposures showed a radiosensitizing capacity of the drug with respect to the teratogenic response on day eight only. The pretreatment with 0.25 mg/kg vindesine potentiated the radiation-induced malformation rate by a factor of 1.7, and the one with 0.35 mg/kg vindesine by a factor of 2.4.

Abnormalities, Drug-Induced↗
PubMed1987

Embolization of the systemic arteries of the lung.

Embolization of the systemic arteries of the lung (described by Remy and colleagues in 1973) is now a useful method for the treatment of hemoptysis or hemorrhagic lesions of the lung prior to surgical treatment, or for local treatment of hemoptysis when surgery is contraindicated or unnecessary. The technique is based on the anatomy of the different divisions of the systemic circulation (bronchial and extrabronchial), which for various physiologic reasons may develop hypervascularization. The results, complications, and contraindications of systemic embolization have previously been described and the technique is now commonly practiced.

Embolization, Therapeutic↗
PubMed1987

Multiple myeloma and severe renal failure: a clinicopathologic study of outcome and prognosis in 34 patients.

Renal failure (RF) occurring in the course of multiple myeloma is often judged irreversible and generally considered an ominous complication. The aim of the present study was to re-evaluate the outcome, triggering conditions and prognostic factors of severe RF in a series of 34 patients, 33 to 90 years old. RF was totally reversible in 7 patients and partially reversible in 9 although 6 of them had to be temporarily dialyzed. However, the improvement in renal function was often very slow as indicated by an average recovery time of 115 days. The high rate of RF reversibility was associated with markedly lengthened survival. Review of triggering events confirmed the leading role of dehydration and hypercalcemia, but further suggested that intake of nonsteroidal anti-inflammatory drugs and renal infection might play a part in the development of RF. Systematic statistical analysis of potential prognostic factors showed that the outcome was significantly more severe in females, but age, myeloma characteristics including tumor mass, calcemia, and triggering events had no predictive value. The most reliable prognostic indicators were provided by analysis of kidney biopsy performed in 30 patients. Complete recovery from RF was observed only in the absence of global tubular atrophy and interstitial damage. In contrast, cast-induced tubular obstruction detected by the presence of Tamm-Horsfall protein in urinary space of glomeruli did not seem to influence the outcome of RF. Finally, we analyzed the prognostic value of immunochemical properties of light chains (LC). Lambda LC were unexpectedly detected in 2 of 3 patients, as compared to a ratio of 1 to 3 in the population of normal and monoclonal Ig, but LC type did not correlate with the course of RF. Isoelectric points of LC measured in 32 patients were dispersed from 5.2 to 8.9 and bore only weak prognostic significance. These results underline the value of kidney biopsy and justify aggressive treatment including dialysis and chemotherapy.

Acute Kidney Injury↗
PubMed1987

Intrinsic nerves of the pancreas after celiac and superior mesenteric ganglionectomy in rats: a morphologic study of acetylcholinesterase activity and catecholamine histofluorescence.

The effect of surgical celiac and superior mesenteric ganglionectomy (GGX) on intrinsic pancreatic innervation was studied in male Wistar rats. Neurons were stained in the pancreas of control and ganglionectomized rats with histochemical methods evidencing the acetylcholinesterase (AChE) activity and the induced fluorescence of catecholamines. Two segments of the head of the pancreas ("duodenal" and "splenic" segments) were studied. The surface density of neuronal cell bodies was larger in the splenic segment than in the duodenal segment of the head of the pancreas (p less than 0.01), both in control and in ganglionectomized rats. The surface density of the neuronal cell bodies and the intensity of AChE staining were not significantly different in control and in ganglionectomized rats. Most AChE-positive fibers survived after ganglionectomy; only some of them disappeared. These disappearing fibers corresponded to the thinnest fiber bundles found in the pancreatic tissue of control rats. Only 10% of catecholamine fibers remained after ganglionectomy. Some of the remaining fibers may run through direct duodenopancreatic pathways.

Acetylcholinesterase↗
PubMed1987

Assessment of bone marrow blood flow using positron emission tomography: no relationship with bone marrow cellularity.

Bone marrow blood flow has been assessed using positron emission tomography and the 15O-labelled carbon dioxide steady-state technique. The measurements were performed at the site of the posterior iliac crest. The bone marrow blood flow was 10.0 ml/min/100 cm3 +/- 3.0 (SD) in normal volunteers. It was markedly increased in patients with polycythaemia vera (26.9 +/- 4.6), chronic granulocytic leukaemia (25.2 +/- 3.9) and myelofibrosis (35.1 +/- 7.3). However, bone marrow blood flow did not differ from normal in patients with aplastic anaemia, chronic haemolysis or chronic lymphocytic leukaemia. There was no relationship between bone marrow cellularity and bone marrow blood flow. The data show that bone marrow blood flow is markedly elevated in polycythaemia vera, myelofibrosis and chronic granulocytic leukaemia and suggest that bone marrow cellularity is not a major factor in regulating bone marrow blood flow.

Bone Marrow↗
PubMed1987

Transmucosal passage of polyalkylcyanoacrylate nanocapsules as a new drug carrier in the small intestine.

The enteral absorption of particles has been investigated in the dog using a colloidal drug carrier, polyalkylcyanoacrylate nanocapsules loaded with an iodized oil (Lipiodol), as a tracer for X-ray microprobe analysis in a scanning electron microscope. Nanocapsules are spherical capsules, 100 to 200 nm in diameter, with a continuous polymeric wall surrounding a cavity which encapsulates the drug. Administered in the jejunal lumen, Lipiodol nanocapsules improved the absorption of the tracer as indicated by increased concentration of iodine in the plasma of mesenteric blood. In order to follow nanocapsules at the cellular level, all tissue compartments were preserved in a life-like state by cryofixation and freeze-drying of intestinal biopsies. Nanocapsules appeared in the intestinal lumen close to the mucus, then in intercellular spaces and defects of the mucosa and finally in the lamina propria and blood capillaries; in this latter compartment, the iodine content was four-fold higher than after intra-jejunal administration of Lipiodol emulsion. This complete phenomenon occurred only at the tip of the villi and happened within less than 60 min. We conclude that nanocapsules enhance the rate of absorption of Lipiodol and transport the drug from the intestinal lumen to the vascular compartment using a paracellular pathway. Thus they may be useful as drug carrier for oral administration of many chemicals.

Animals↗
PubMed1987

Rapid information processing and concomitant event-related brain potentials in smokers differing in CO absorption.

The present study relates subject-paced rapid information processing to different components of event-related brain potentials in an attempt to gain more information about changes in mental performance in relation to alveolar smoke absorption as assessed by expired air CO measurement. The task consisted in the presentation of pseudorandom sequences of single digits, and the subjects had to respond to each sequence of three odd or three even digits. The triplets evoked a typical late negativity in the event-related potential between the second and third digit as well as a P300 component following the third digit. In 21 smokers, task performance, event-related potentials and tidal air CO concentration were measured before and after smoking a cigarette. The results revealed increases in performance and P300 magnitude from pre- to postsmoking which were unaffected by the amount of CO absorption. A differential trend was seen, however, with the late negativity, which increased from pre- to postsmoking only in subjects with a large amount of CO absorption. The results support the assumption of the distraction arousal model used as an interpretation of these effects on contingent negative variation and suggest that high CO absorbing smokers possibly depend more on neuropharmacological effects of smoking than smokers with a low amount of CO absorption.

Adolescent↗
PubMed1987

The reaction of sulfite radical anion with nucleic acid components.

The sulfite radical anion (SO3.-) is the first intermediate in the autoxidation of sulfite to sulfate. Using competition kinetics, its reactivities with the nucleic acid bases and the corresponding nucleosides were investigated. The second order rate constants were found to be rather low, k less than or equal to 1 x 10(6) dm3mol-1s-1 at pH 7. As a competitor, the carotenoid crocin was used, which was found to be bleached very efficiently by SO3.- (k = 1.0 x 10(9) dm3mol-1 s-1).

Carotenoids↗
PubMed1987

[Prosthesis without puncture, 3d generation of vascular access for hemodialysis: a study of Hemasite in 10 patients].

Hemasite is a new vascular access for hemodialysis. The device has a carbon coated T-shaped body with a resealable silicon septum that obviates the need for skin punctures. It is implanted with attached PTFE grafts. Since August 1984, 10 Hemasite have been placed in 10 patients. After one year, 63% of Hemasite are still permeable: this success rate is at least similar to usual synthetic grafts. There is no infectious complication. The rate of thrombosis is high, but Hemasite offers the interesting facility to perform local infusion of thrombolytic drugs and/or painless angioplasty through its removable septum in case of venous stenosis. Patients and staff acceptance has been excellent.

Adult↗
PubMed1987

In vitro and in vivo study of an antimicrobial activity displayed by the redmouth disease agent, Yersinia ruckeri.

A soluble antimicrobial product has been detected in Yersinia ruckeri cultures. The contract droplets technique and the double agar layer method allowed to assess its bacteriostatic effect and the high susceptibility of other bacterial fish pathogens like Vibrio and Aeromonas. But it did not inhibit other strains of Y ruckeri. No correlation was found between the antimicrobial activity and the virulence of the strains. As mixed infections with A salmonicida and Y ruckeri could be obtained experimentally, the factor does not seem to confer any competitive advantage in fish tissues colonization.

Animals↗