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Biomedical subjects

C Michel

Publications and source records attributed to C Michel.

At least 163 records · Page 9Linked to original sources
PubMed1995

Delineation of myocardial viability with PET.

UNLABELLED: Relative flow and metabolic imaging (the "mismatch pattern") with PET have been proposed to identify the presence of viable myocardium in patients with ischemic left ventricular dysfunction. Yet, optimal criteria to identify dysfunctional but viable myocardium and predict significant functional improvement have not been fully defined. METHODS: Dynamic PET imaging with 13N-ammonia and 18F-deoxyglucose to assess absolute myocardial perfusion and glucose uptake was performed in 25 patients (20 men, 5 women; mean age 57 +/- 12 yr, range 30-72 yr) scheduled for coronary revascularization because of coronary artery disease, anterior wall dysfunction and mildly depressed left ventricular ejection fraction (49% +/- 11%). Global and regional left ventricular function was evaluated by contrast left ventriculography at baseline and after revascularization. RESULTS: As judged from the changes in end-systolic volume and resting anterior wall motion before and after revascularization, 17 patients with improved wall motion score and decreased end-systolic volume were considered to have viable myocardium, whereas 8 patients with either no change in regional wall motion or increased end-systolic volume were considered to have nonviable myocardium. Before revascularization, viable myocardium showed higher absolute myocardial blood flow (77 +/- 20 versus 51 +/- 9 ml (min.100 g)-1, p = 0.004) and absolute regional myocardial glucose uptake (36 +/- 14 versus 24 +/- 11 mumole (min.100 g)-1, p = 0.04) than nonviable myocardium. CONCLUSION: This study identified absolute myocardial blood flow and normalized glucose extraction as the most powerful predictors of the return of contractile function after coronary revascularization in patients with ischemic anterior wall dysfunction.

Adult↗
PubMed1995

[How to diagnose and treat peritoneal infections in patients with terminal chronic renal insufficiency treated by peritoneal dialysis].

There have been improvements in the technique of peritoneal dialysis (PD) over the last ten years. However, peritoneal infections remain the major complication associated with this treatment, and the risk of infection cannot be accurately predicted. Nevertheless, it is widely accepted that simple connections should be replaced by improved systems of connection, and that patient training is important. Peritoneal infection should be suspected when the dialysate is turbid, whether or not associated with peritoneal irritation. None of the various techniques used for the culture of dialysates has been shown to be either more sensitive or more specific than any of the others. Thus, collaboration between the physicians supervising the dialysis and microbiologists is necessary to choose the culture techniques best adapted. The sensitivity should be at least 85 to 90%. If the sensitivity is lower, the techniques used should be reconsidered. There have been several hundred publications assessing treatments of peritoneal infections associated with PD. However, no particular antibiotic treatment has been demonstrated to be systematically superior. The use of associated antibiotics seems to be preferable initially, until the causative agent has been identified. For example, vancomycin with a third generation cephalosporin seems to be the association of choice, because of its efficacy, tolerance and ease of use. The optimal duration of treatment has not been established by randomised study, but 10 days is commonly used for Gram-positive infections, and longer for Gram-negative. Whatever the treatment used, the success rate should be at least 80 to 90%. Randomised trials with sufficiently large numbers of patients are required to determine the indications and delay before withdrawal of the DP catheter in cases of peritonitis which do not respond to antibiotics.

Anti-Bacterial Agents↗
PubMed1995

Report of a patient with syndrome X due to excessive adenosine effect: myocardial migraine without myocardial ischemia.

A 53-year-old female presented with disabling chest pain. The pain had most of the characteristics of ischemic pain; however, the results of the initial clinical investigation were consistent with the diagnosis of syndrome X. That is, her treadmill exercise test was positive but her coronary angiogram was normal. A dipyridamole-thallium test resulted in severe chest pain, marked ST abnormalities, but no evidence of any focal reduction in flow. A dipyridamole stress echocardiogram revealed that left ventricular function was entirely normal during the dipyridamole-induced pain and ST segment abnormalities, making ischemia an unlikely cause for either. To attempt to account for this paradox, the hypothesis was generated that both the pain and ST segment abnormalities were due to a primary abnormality of adenosine metabolism rather than secondary to ischemia. Accordingly, adenosine-MIBI scans were done with and without pretreatment with aminophylline. Infusion of adenosine virtually immediately resulted in crushing chest pain and profound ST abnormalities again without any evidence of focal abnormalities of MIBI estimated flow. By contrast, administration of adenosine after pretreatment with aminophylline failed to produce either chest pain or ST abnormalities. Moreover, long term therapy with aminophylline almost entirely relieved the symptoms which had been so distressing. This case indicates that there is a subset of patients with syndrome X--in which faults in adenosine metabolism result in excessive adenosine accumulation or effect and this results, in turn, in adenosine-induced ischemic-like chest pain and adenosine-induced ST abnormalities. There is, however, no actual ischemia of the myocardium. Given the known effects of adenosine on coronary flow, the problem in this subset of patients appears to be equivalent to an attack of myocardial migraine and blockers of adenosine action might be of help to other patients with a similar pathophysiology for their chest pain.

Adenosine↗
PubMed1995

Health control policies in fish viral diseases.

Viral infections cause significant levels of mortality in intensive fish farming. There is no treatment, and, because vaccination is not yet feasible, prevention is only possible through fish health control measures or policies. The transportation of fish or fish products represents a major means of virus dissemination. For this reason, official systems of inspection and certification have focused mainly on exported shipments. A need for unanimity among the various systems has been recognized. Standardized rules and procedures have been encouraged by the international organizations (the FAO and the OIE) through the publication of technical documents, guidelines and codes. Health control systems can be effective, but they may be affected by many socio-economic factors and should always be associated with other preventive measures.

Animal Husbandry↗
PubMed1994

Reactions of hydrogen peroxide with superoxide dismutase from Propionibacterium shermanii--an enzyme which is equally active with iron or manganese--are independent of the prosthetic metal.

Propionibacterium shermanii contains a single constitutive superoxide dismutase (SOD) which is active with either iron or manganese incorporated in the same protein moiety. Copper and cobalt can also be incorporated by the bacteria in the active center of the SOD under conditions of metal deficiency, but in this case the enzyme is enzymatically inactive. In contrast to other bacterial SODs, the Fe-SOD of P. shermanii remains highly resistant to inactivation by hydrogen peroxide, as does Mn-SOD. Both SOD types cannot be distinguished by their inactivation patterns. Incubation with hydrogen peroxide results in a concentration- and time-dependent decrease in tryptophan fluorescence, independent of the metal present in the active center. Moreover, the Fe-SOD shows a time-dependent decrease in spin concentration after addition of hydrogen peroxide, which reflects alterations in the environment of the metal rather than a reduction of Fe3+ to Fe2+. No obvious correlations exist, however, between these effects and the enzymatic activity of the enzyme. The resistance of the SODs from P. shermanii to inactivation by hydrogen peroxide seems to be caused by the fact that a tryptophan residue near the metal-chelating histidine-75--which is present in all Fe-SODs being rapidly inactivated by this agent--is exchanged for valine.

Amino Acid Sequence↗
PubMed1994

Modification of in vitro mouse embryogenesis by X-rays and fluorochromes.

In view of planned studies using single particle irradiation at the Institute for Medical Radiobiology (IMR), confocal microscopy will become an important tool to visualise subtle changes in embryo morphology. Therefore, the influence of X-rays and that of three different fluorochromes on the in vitro development of murine 2-cell stage embryos was investigated. Embryos of B6C3F1 mice were cultured at 32 h post-conception (pc) and treated with X-rays, acridine orange (AO), ethidium bromide (EB) or propidium iodide (PI), respectively, in various doses (0.0-3.0 Gy) or concentrations (AO: 0.05-2.00 micrograms/ml; EB and PI: 0.50-10.00 micrograms/ml). Additional experiments using combinations of AO and irradiation were performed. The embryos were cultivated for a total of 7 days and checked for their vital status by morphological endpoints such as the percentage of embryos that reached the blastocyst stage and the hatching rate. After treatment of the 2-cell embryos with AO, EB and PI, the dose-effect curves with the endpoint 'hatching rate' showed a 23-fold reduction of the ED50 for AO (0.23 microgram/ml) compared with EB (5.30 micrograms/ml). Despite the higher toxicity, AO had much better staining qualities in subtoxic concentrations than EB. PI showed no toxicity in these experiments and was used as an inverse control for embryo vitality. No synergistic modification of the radiogenic effects could be seen in combination experiments (AO+X-rays).

Acridine Orange↗
PubMed1994

Poly(L-lactide): a long-term degradation study in vivo. Part II: Physico-mechanical behaviour of implants.

Three different poly(L-lactide) rods (25 x 3 x 2 mm) were produced either by injection moulding or machined out of a solid as-polymerized polylactide block and were implanted for 1-116 months into the dorsal muscle of rats. After recovery, the polylactide specimens were carefully cleaned, dried, photographed and weighed. Bending strength and Young's modulus of elasticity were determined. The surfaces of the broken rods were examined by scanning electron microscopy. Block polylactide samples initially looked milky. They became friable and broke into white or brownish fragments during the implantation period, whereas total disintegration could not be observed. Electron scanning microscopy revealed a porous surface with crystalline elements persisting for the whole time. Mechanical stability fell from 127 +/- 3 MPa at implantation time to about half after 3 wk (61 +/- 4 MPa) and about a quarter (32 +/- 4 MPa) after 6 wk. Both injection-moulded polyactides (A1 and A2) were clear and transparent initially. After implantation they gradually became whitish, fragmented after about 64 wk and disintegrated 90 wk later into small parts and powder. Electron scanning microscopy at first showed a homogeneous surface. A kind of cortex developed after about 4 wk and deep cracks ran through the rod after 32 wk. Round pores of 1.5-10 microns diameter developed after 1 yr of implantation. Bending strengths were 130 +/- 8 MPa (A1) and 115 +/- 14 MPa (A2); these remained nearly stable over about 12 wk, then declined linearly. Although a higher initial mechanical strength is desirable for use in osteosynthetic devices, mechanical stability of amorphous injection-moulded polylactides over the first 12 wk and total disintegration thereafter approaches the requirements for their use as a material for osteosynthesis.

Animals↗
PubMed1994

The effects of azapirones on serotonin1A neurons of the dorsal raphe.

1. The effects of buspirone, gepirone, ipsapirone and tandospirone on spontaneously discharging serotonergic neurons of the dorsal raphe were determined under the same experimental conditions. 2. Buspirone, gepirone, ipsapirone and tandospirone were equally efficacious and acted in a dose-dependent manner to totally inhibit the spontaneous activity of serotonergic neurons. 3. Based on their effects six min after administration (i.p.), their ED50 values were: buspirone, 134 micrograms/kg; ipsapirone, 220 micrograms/kg; gepirone, 225 micrograms/kg; tandospirone, 198 micrograms/kg. 4. The similarity of these ED50 data suggest that they share a similar chemical structure that binds to the 5-HT1A receptor, most likely it is "N-C-C-C-C-N" aliphatic backbone. 5. Buspirone and tandospirone required 4 or more min to totally block the spontaneous activity, while gepirone and ipsapirone blocked it in 3 min. 6. The dose-response curves from buspirone and tandospirone demonstrated enough dissimilarity to the dose-response curves from gepirone and ipsapirone to suggest differences in their rates of absorption, and/or differences in the production of active and inactive metabolites.

Animals↗
PubMed1994

Autoimmune haemolytic anaemia after ABO-match, ABDR full match kidney transplantation.

We report a case of autoimmune haemolysis after an ABO- and ABDR-identical kidney transplantation which leads to the discussion of the role of cyclosporin A (CsA). A 46-year-old woman with end-stage renal disease and no history of auto-immune disease received an ABO- and ABDR-identical first renal allograft from a cadaver donor. On day 16, while on a heavy sequential immunosuppressive regimen including anti-thymoglobulins, azathioprine (Aza), prednisolone (Pred) and CsA, she developed an autoimmune haemolysis with positive Coombs test, IgM+C type. Elution of antierythrocyte antibodies did not enable us to identify any specificity. Haemolysis lasted 45 days before haemoglobin slowly increased after CsA had been greatly reduced. Direct antiglobulin tests remained positive 5 months after transplantation and became negative the following month. Eight months after the transplantation the patient had a normal haemoglobin level and normal renal function. Although the typing of autoantibodies was not possible, our data suggest that this patient's haemolysis may be related to the clonal development of donor B lymphocytes in the recipient, favoured by an HLA A-B-DR identity and post-transplant CsA therapy, as exceptionally reported in the literature.

ABO Blood-Group System↗
PubMed1994

Brain glucose utilisation in acquired childhood aphasia associated with a sylvian arachnoid cyst: recovery after shunting as demonstrated by PET.

Regional brain glucose utilisation was investigated with PET and fluorodeoxyglucose (FDG) in a case of epileptic aphasia (Landau-Kleffner syndrome) associated with a left sylvian arachnoid cyst. CT and MRI had failed to disclose any mass effect of the cyst on surrounding brain structures. Sequential metabolic measurements showed a comparable pronounced hypometabolism in cortical regions around the cyst, involving speech areas, and suggested mild but chronic compression of the developing brain. After placement of a cyst-peritoneal shunt system, significant metabolic improvement occurred in all cortical regions, especially the inferior frontal gyrus and the perisylvian area, with predominant residual deficit in the left superior temporal gyrus. These findings were correlated with a pronounced increase in word fluency and slower progress in verbal auditory comprehension. This report suggests that PET is able to evaluate the functional disturbances associated with expanding arachnoid cysts, and to follow the neurological improvement after drainage.

Aphasia↗
PubMed1994

Skeletal muscle phosphate metabolism abnormalities in volume-overload experimental heart failure.

We studied skeletal muscle phosphate metabolism abnormalities to examine their contribution at an early stage of congestive heart failure (CHF) in rats with aortocaval fistula (ACF) 4 wk after the procedure. In a group of 26 rats (13 with ACF and 13 sham operated), we assessed the degree of CHF. The ACF produced a significant rise in heart weight and plasma atrial natriuretic peptide. In a second group of 26 rats (13 ACF and 13 sham operated), we performed 31P-magnetic resonance spectroscopy in the gastrocnemius muscle during motor activity produced by electrical stimulation. The rate of phosphocreatine depletion, expressed by its initial slope, was higher in the ACF rats compared with controls (0.078 +/- 0.01 vs. 0.041 +/- 0.007; P < 0.03). pH and ATP decreased and phosphodiesters increased in all rats during electrical stimulation, with no difference between ACF rats and controls. The kinetics of phosphocreatine recovery were not different between ACF rats and controls. Together with previous studies, our present results suggest that muscle metabolism abnormalities in CHF may vary according to the experimental model and may be observed early in the course of the disease.

Adenosine Triphosphate↗
PubMed1994

Fungal peritonitis in patients on peritoneal dialysis.

Fungal peritonitis (FP) is a serious complication of peritoneal dialysis, both in terms of morbidity and mortality. Available data on the effectiveness of fluconazole in eradicating FP without catheter removal are still controversial. We reviewed 20 FP cases that occurred among 325 patients who underwent peritoneal dialysis in our center between January 1984 and January 1992, in order to establish whether a profile of patients at risk of developing FP could be identified and to evaluate the effectiveness of fluconazole in treating FP (7 cases). Age, sex, a particular cause of end-stage renal disease, and the presence of diabetes did not correlate significantly with the development of FP. The risk of FP increased in patients on immunosuppressive treatment. Sixteen of our 20 patients had bacterial peritonitis during the month before they developed FP. Nineteen were treated with antibiotics. Neither the type of bacterial organism isolated during the bacterial peritonitis preceding FP nor modality and duration of antibiotic treatment correlated significantly with the development of FP. Patients who subsequently developed FP were more frequently treated with antibiotics while in hospital (p < 0.001). Candida species accounted for 15 of our 20 FP cases (75%), with Candida albicans being by far the most common isolate. Treatment strategies varied among the 20 patients. The combination of intravenous or intraperitoneal administration of 5-fluorocytosine and oral administration of fluconazole was used in 7 cases: only 1 patient was cured without catheter removal, 1 patient died within the first 4 days of treatment, removal of peritoneal catheter was necessary in the other 5 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Brain glucose metabolism in postanoxic syndrome due to cardiac arrest.

Using positron emission tomography (PET), thirteen studies of regional brain glucose utilization were performed in 12 patients with postanoxic syndrome due to cardiac arrest. Investigations were carried out at least one month after brain anoxia. Seven subjects were in a persistent vegetative state. The others had regained normal consciousness with various residual neurological signs. When compared with normal values obtained in 16 normal, age-matched subjects, mean cerebral glucose metabolism was drastically decreased (+/- 50%) in vegetative cases, and to a lesser degree (+/- 25%) in conscious subjects. The most consistent regional alterations were observed in the parieto-occipital cortex (9 cases), the frontier between vertebral and carotid arterial territories. Other selective anomalies were found in the frontomesial junction (5 cases), the striatum (3 cases with dystonia), and the visual cortex (2 cases with cortical blindness). This study suggests that cerebral anoxia results in a global brain hypometabolism, which appears related to the vigilance state, as well as in regional disturbances preferentially located in arterial border zones. Although our findings remain to be confirmed in larger series, they suggest that PET provides a useful index of residual brain tissue function after anoxia and may assist in the monitoring of postanoxic encephalopathies.

Adult↗