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Biomedical subjects

L Michel

Publications and source records attributed to L Michel.

At least 55 records · Page 3Linked to original sources
PubMed1996

[Radiation exposure in interventional radiology as exemplified by the chemoembolization of hepatocellular carcinoma and laser angioplasty of the pelvic arteries].

PURPOSE: Estimation of radiogenic risks for patient and radiologist in chemoembolisation of hepatocellular carcinoma (HCC) and laser angioplasty of the pelvic arteries. METHODS: In 5 chemoembolisations of HCC (4 males, one female) and 6 laser angioplasties of the pelvic arteries (5 males, one female) the surface doses received by patient and operator were measured using thermoluminescent dosimeters in standardised positions. The organ doses of the patient were derived by conversion factors employed on the measured surface doses. Effective dose was determined according to the recommendations of ICRP 60. RESULTS: The risk of lethal malignant disease and genetic disorder derived from the doses in the patient was found to be of the magnitude of 10(-4)-10(-5). The thresholds for transient erythema of the skin and depression of hematopoiesis can be reached after high expositions. A theoretical maximum of 700 laser angioplasties of the pelvic arteries allowable in one year was calculated based on the dose to the operator's left hand. For chemoembolisation of HCC, the dose to the left eye lens would reach the yearly maximum after approximately 1000 procedures. Remarkable risks for malignant disease of skin and thyroid as well as detectable opacities of the eye lens can occur after frequent interventions for many years. CONCLUSIONS: Because of the lower life expectancy the patient's risk for stochastic effect can be seen as minimal. No clinically relevant deterministic effects will occur. In the case of frequent interventions, the dose absorbed by the radiologist is likely to exceed the prescribed dose limit and to cause remarkable risk for stochastic and non-stochastic effects after many years.

Aged↗
PubMed1996

Unusual presentation of papillary thyroid carcinoma: about two cases.

The papillary carcinoma is the most common cancer of thyroid but its presentation may be unexpected. In the first case, a 18-year-old girl complained of a painful enlargement of the right thyroid lobe. Upon the basis of a CT scan revealing punctuate calcifications suggesting psammoma bodies and a right-sided cold nodule on thyroid radioiodine scanning, the patient had a thyroidectomy. The second case was a discovery of papillary carcinoma in a 49-year-old woman who had a thyroidectomy for Graves' disease. This association may not be fortuitous. The cancer could be more aggressive in this group of patients, as TSI play a pathogenic role.

Adolescent↗
PubMed1996

Unusual hypokalaemia.

A 72-year-old man, presenting with hypernephroma and infraclinic adrenal adenoma, developed severe hypokalaemia in the course of treatment for colonic perforation. Amikacin-induced hyperkaliuric hypokalaemia was suspected, and confirmed by withdrawal of the drug as well as observation of an unnoticed similar episode in the medical record of the patient.

Abscess↗
PubMed1996

UVA-induced immune suppression in human skin: protective effect of vitamin E in human epidermal cells in vitro.

UVA (320-400 nm) radiation damage to membranes, proteins, DNA and other cellular targets is predominantly related to oxidative processes. In the present study, we demonstrated that cutaneous UVA-induced immunosuppression can be related, at least in part, to the appearance of these oxidative processes. The UVA-induced oxidative processes in freshly isolated epidermal cells were monitored by measuring the thiobarbituric acid reactive substances (TBARS) as an index of peroxidation. The in vitro immunosuppressive effects of UVA were demonstrated by measuring the allogeneic lymphocyte proliferation induced by epidermal cells or purified Langerhans cells in the mixed epidermal cell-lymphocyte reaction (MECLR). In addition, the effects of a potent antioxidant (vitamin E) on these two UVA-induced processes were analysed. Our results showed that the antigen-presenting function of Langerhans cells measured in the MECLR is dose-dependently decreased by UVA radiation (up to 20J/cm2). Overnight incubation of epidermal cells with vitamin E (400 mumol/l) before irradiation partially protected epidermal cells from the immunosuppressive effects of UVA radiation, and decreased TBARS release into the supernatant (a decrease of 35% compared with a control without vitamin E). Our results suggest that UVA radiation may alter cell-presenting antigen function partly via the generation of reactive oxygen species which trigger peroxidative processes, and these data contribute to the understanding of the role of oxidative mechanisms in immune suppression induced by UVA radiation. Our in vitro model can be used to quantify UV-mediated epidermal cell damage and the degree of immune photoprotection provided by various agents.

Adolescent↗
PubMed1996

[Effects of temporary dual-chamber cardiac pacing in refractory cardiac failure].

The authors studied 18 patients (15 men, 3 women) with an average age of 67 +/- 8 years with refractory cardiac failure. In order to determine the potential of pacing to raise cardiac output in severe cardiac failure. The average ejection fraction was 26 +/- 6.5%. All patients were in sinus rhythm:resting cardiac output was 3.35 l/min. Two temporary pacing catheters were positioned in the right atrium and at the apex of the right ventricle for dual-chamber mode pacing triggered by the spontaneous P waves. Changes in cardiac output were measured by Doppler echocardiography at different values of atrioventricular delay. Patients were considered to be responders if their cardiac outputs rose by 15%. In 7 patients meeting this criterion, the average increase in cardiac output was 27% (2.99 +/- 0.7 to 3.81 +/- 0.86 l/mn; p < 0.01); all had dilated cardiomyopathies with left bundle branch block and the optimal AV delay was 103 +/- 21 ms (80-140 ms); the duration of diastolic filling increased from 212 +/- 98 to 292 +/- 116 ms (p = 0.02). In the non-responding group (11 patients with an increase of cardiac output of only 3.6 +/- 0.09 to 3.9 +/- 0.92 l/mn; p < 0.01), the underlying disease process was mainly ischaemic. Two predictive factors of efficacy of dual-chamber pacing were identified: a short ventricular filling period (29 +/- 8% of the RR interval in the responders vs 44 +/- 9% in the non-responders; p < 0.01) and the presence of 1st degree atrioventricular block. Dual-chamber pacing could be a valuable method of increasing resting cardiac outputs in a selected group of patients with severe, refractory, cardiac failure.

Aged↗
PubMed1995

The nitric oxide donors, azide and hydroxylamine, inhibit the programmed cell death of cytokine-deprived human eosinophils.

Azide and hydroxylamine release nitric oxide (NO) enzymatically in biological conditions. We observed that both compounds were able to inhibit in vitro the programmed cell death of human eosinophils from peripheral blood. This protective effect could be mimicked by permeable cGMP analogs and by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. Moreover, the soluble guanylate cyclase inhibitor LY-83583 inhibited in a dose-response manner the effects of the NO donors. Consequently, via the increase of eosinophil survival, NO could contribute to the amplification of inflammatory and allergic processes. This effect appears to be mediated, at least in part, by the soluble guanylate pathway.

1-Methyl-3-isobutylxanthine↗
PubMed1995

Mapping of the pyrophosphate binding sites of beef heart mitochondrial F1-ATPase by photolabelling with azidonitrophenyl [alpha-32P]pyrophosphate.

4-Azido-2-nitrophenyl [alpha-32P]pyrophosphate (azido-[alpha-32P]PPi) mimics ADP and PPi by some of its binding properties when assayed in the absence of photoirradiation with mitochondrial F1-ATPase. Upon photoirradiation, both alpha- and beta-subunits of F1-ATPase were covalently labelled. Following chemical and enzymatic cleavages of each of the two photolabelled subunits, peptides containing the covalently bound radioactivity were separated by HPLC and identified by amino acid sequencing. Bound azido-[alpha-32P]PPi was found to be concentrated in two distant sequences of the alpha-subunit, namely Asp194-Thr221 and Lys386-Met437, and in a single sequence of the beta-subunit Glu294-Met358 with most of the photoprobe bound to beta-Tyr-311 and beta-Tyr-345. These results are discussed in terms of a model in which the pyrophosphate binding sites of F1 are located in regions of the alpha- and beta-subunits exposed at the interface between the two subunits and correspond to non-catalytic and catalytic adenine nucleotide binding sites, respectively.

Affinity Labels↗
PubMed1995

Exogenous nitric oxide elicits chemotaxis of neutrophils in vitro.

Nitric oxide (NO) has been shown to be both an intercellular and intracellular messenger. We propose here that exogenous NO induces chemotactic locomotion of human neutrophils. Indeed, when human neutrophils were placed in a gradient of a nitric oxide donor (S-nitroso-N-acetylpenicillamine; SNAP), a directed locomotion was induced, as evidenced by experiments of chemotaxis under agarose. Degraded SNAP (i.e., SNAP solution which had previously released NO) did not induce directed locomotion. Moreover, oxyhemoglobin, a scavenger of free NO, suppressed the chemotactic effect of SNAP, whereas LY-83583, a soluble guanylate cyclase inhibitor, inhibited the SNAP-mediated chemotaxis in a dose-response manner. Other unrelated NO donors, SIN-1 and S-nitroso-cysteine--a natural S-nitroso-compound, also induced a directed locomotion of neutrophils. Taken together, these in vitro experiments indicate that exogenous NO could mediate the chemotaxis of neutrophils and thus suggest that NO could contribute to neutrophil recruitment in vivo.

Aminoquinolines↗
PubMed1995

Human eosinophils in culture undergo a striking and rapid shrinkage during apoptosis. Role of K+ channels.

In the absence of appropriate stimulus, eosinophils in vitro rapidly exhibit the features of apoptotic cells (nuclear pycnosis, cell shrinkage, DNA fragmentation). By using electronic cell sizing, we precisely measured the volume distribution of human eosinophils during apoptosis. We observed that apoptosis of eosinophils was accompanied by a marked cell volume decrease (approximately 60%). Moreover, analysis of the volume distribution in different experimental conditions (kinetics of apoptosis, inhibition of apoptosis by cytokines) revealed that the cell shrinkage, once triggered, was a fast process in which the intermediate states between normal and shrunken volume had a short half-life. As a model of apoptosis, the eosinophil model allowed us to test the hypothesis that apoptotic cell shrinkage was linked to osmotic changes due to leakage of internal ions. Indeed, in the presence of K+ channel blockers, the shrinkage was inhibited in a dose-dependent manner. In conclusion, our results suggest that eosinophil shrinkage during apoptosis is a striking and rapid phenomenon and osmotic changes due to K+ efflux could be responsible, at least in part, of the volume decrease.

Apoptosis↗
PubMed1995

Abdominal pain: do not forget Thorotrast!

The use of Thorotrast (25% thorium dioxide), a radiologic contrast agent used up until the mid-1950s, was associated with a wide range of malignancies, mainly of hepatic origin. We report a case of Thorotrast-induced hepatocarcinoma in an 82-year-old woman.

Aged↗
PubMed1995

Lipolysis-stimulated receptor: a newcomer on the lipoprotein research scene.

It has been widely accepted that the remnants of the intestinally-derived lipoprotein chylomicrons, i.e., chylomicron remnants (CMR), are cleared from the circulation by a receptor genetically distinct from the well-known LDL-receptor. This second receptor was initially considered as a receptor specific for apo E, in contrast to the LDL-receptor, which binds both apo B and apoE. This article critically examines the current dogma of the putative CMR receptor, as well as both supporting and conflicting evidence for the recently-proposed identity of this receptor with the LDL-receptor related protein (LRP). Next, we introduce the lipolysis-stimulated receptor, LSR, which bears all the biochemical characteristics of the CMR receptor. In addition, the apparent number of LSR expressed in the liver is inversely correlated with nonfasting levels of plasma triglycerides. A change in LSR expression and parallel inverse change in plasma triglycerides is observed in rats treated with hyperlipidemic (retinoic acid) or hypolipidemic (fish oil in MaxEPA) agents, indicating that LSR represents a definite target for pharmacological management of hyperlipidemia. In support of this notion is the observation that MaxEPA, which causes an increase in LSR expression, also reduces both plasma triglyceride and cholesterol levels in the thus far intractable homozygous Watanabe heritable hyperlipidemic rabbit.

Animals↗
PubMed1994

Internalization of surface HLA-DR molecules by human epidermal Langerhans cells: analysis by flow cytometry and confocal microscopy.

Langerhans cells (LC) play a pivotal role in antigen processing and presentation to T cells during delayed-type hypersensitivity reaction in the skin. Antigen presentation involves the interaction between the class II molecules of MHC (HLA-DR) expressed by LC and T receptor of CD4+ T lymphocytes. It is now recognized that class II molecules are internalized into LC and can be associated with processed immunogenic peptides. This process involves receptor-mediated endocytosis. The aim of this study was to investigate the time-course of endocytosis of HLA-DR by freshly isolated human LC. Epidermal cells, obtained from normal skin samples, were labeled by indirect immunofluorescence using anti-HLA-DR monoclonal antibodies (MAb). The cell suspension was incubated at 37 degrees C for different periods (15, 30, 45, 60 and 90 min) and then analyzed by flow cytometry and confocal microscopy. Flow cytometry analysis showed decreased HLA-DR molecule expression by LC after incubation at 37 degrees C. Confocal microscopic analysis showed different strain patterns depending on the incubation time: (1) T = 0, continuous peripheral staining; (2) T = 15 min, patchy peripheral staining; (3) T = 30 min, patches or intracellular vesicular staining; (4) T = 45 min, intracellular vesicular staining; (5) T = 60 min, diffuse intracellular staining; (6) T = 90 min, aggregated staining. In our study model, flow cytometry provides quantitative information for the HLA-DR endocytosis, whereas confocal microscopy provides qualitative results concerning the intracellular distribution of internalized HLA-DR molecules.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMed1994

Complement activation on the nasal mucosal surface--a feature of the immediate allergic reaction in the nose.

Complement is a system of functionally linked serum proteins that interact to exert biologic effects in inflammatory and immunologic processes. As part of a larger study with a potential topical antiallergic drug, we measured C3a des Arg and C5a des Arg in 13 patients with seasonal allergic rhinitis and in five nonatopic controls after placebo treatment. After 1 week of placebo treatment, a nasal allergen challenge with increasing doses of pollens was performed in both allergic subjects and controls. A symptom score method was used, and in returned nasal lavage fluid, the activity of C3a des Arg and C5a des Arg was measured. We found that allergen challenge in the allergic subjects induced nasal symptoms concomitantly with increased levels of C3a des Arg and C5a des Arg (P < 0.05). No increases either in symptoms or in the very low base-line levels of C3a des Arg and C5a des Arg were observed in the nonallergic controls. We conclude that the activation of the complement cascade is one part of the vasculature exudative response during the immediate allergic reaction in the upper airways. Because of their biologic potency, these proteins may be an essential part of the exudative response which perpetuates the ongoing inflammatory reaction.

Adult↗
PubMed1994

[Status of 3 years of hyperthyroidism treatment with iodine 131].

We analysed retrospectively the results obtained during 3 years in the treatment of thyrotoxicosis with 131-iodine. A group of 32 patients, including 21 Graves' diseases, 10 multinodular toxic goitres and 1 toxic adenoma has been collected. The therapeutic efficacy of one dose of radioiodine, assessed after 6 months was 100% in toxic multinodular goitres and 57% in Graves' diseases. No acute complications were observed. The best radiosensitivity of toxic multinodular goitres compared with diffuse goitres is probably due to the mechanisms themselves of thyrotoxicosis in these diseases. Results also suggest that multinodular toxic goitres in our country should be systematically treated with antithyroid drugs before radioiodine. In Graves' disease, no predictive factor of the early response to therapy could be definitely evidenced. Finally, clinicians should be aware of the advantages of such a treatment of thyrotoxicosis which is not very aggressive and at least definitive.

Adult↗