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Biomedical subjects

C Michel

Publications and source records attributed to C Michel.

At least 271 records · Page 15Linked to original sources
PubMed1989

Separate and combined psychophysiological effects of cigarette smoking and alcohol consumption.

The present study on the separate and the combined effects of cigarette smoking and alcohol consumption on behavioral, electrocortical and cardiovascular functions involved 20 young female smokers, repeatedly tested on their performance in a visual information processing task before and after drug treatment. Each subject participated in four sessions where they received in a balanced sequence 0.7 g/kg alcohol or placebo followed by either real or sham smoking of a cigarette. The mental task required the subjects to detect sequences of three odd or even digits in a pseudorandom series of single digits presented on a TV screen. By using a variable subject-paced interstimulus interval, mental performance was analyzed continuously in terms of the achieved processing rate. The multivariate assessment of psychophysiological functions included the electrocardiogram, the finger plethysmogram and the electroencephalogram (EEG) measured on four electrode locations (Fz, Cz, P3, P4). The EEG was analyzed both for tonical changes in frequency distribution and for phasic responses to the correctly detected triads (Event-Related Potentials, ERP), yielding a CNV after the second digit and a late positive wave (LP) after the third digit. Cigarette smoking increased the processing rate, while it was decreased by alcohol. Smoking after alcohol diminished the performance decline due to alcohol. Heart rate acceleration and peripheral vasoconstriction were observed after smoking. Alcohol caused dilatation of the finger vessels which was prevented by smoking a cigarette after the drink.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Online brain attenuation correction in PET: towards a fully automated data handling in a clinical environment.

We have improved the calculation of the brain attenuation correction in positron emission tomography (PET) and set up a procedure which allows the clinician to get a fully corrected image in a single reconstruction step, without human intervention. By using a general object description scheme based on polygonal contour trees we are able to calculate the attenuation correction for brain tissue, bone and head holder. The head contour is generated from the emission sinogram. On a set of 15 adult patients, the emission values obtained using this calculated attenuation compare favorably with those obtained with an attenuation resulting from a transmission measurement. Residual discrepancies are attributed to incomplete scatter compensation between emission and transmission. The robustness of the algorithm has been tested on more than 100 brain fluorodeoxyglucose (18FDG) studies in adult patients, including pathological cases. Its applicability for 18FDG studies in children and for other tracers such as water (H2 15O) and fluoroethylspiperone (18FESP) is also presented.

Adult↗
PubMed1989

Lectinhistochemical study of cell surface alterations in mouse embryos exposed to low radiation doses.

The peroxidase-coupled Dolichos biflorus agglutinin (DBA) served as a marker for cell surface alterations in embryonic mouse tissues exposed to low-dose radiation during the early organogenesis (day 9 post conception). In unirradiated embryos, DBA bound selectively to various organ primordia, depending on their differentiation state. The auditory vesicles and the developing blood vessels were the only tissues staining strongly with the lectin. The vascular endothelia also showed the highest radiosensitivity, expressed by the maximal reaction already at 12.5 cGy. Marked surface changes as well were registered in the basal part of the Rathke's pocket and in the roof of the diencephalon. After exposure to 25 cGy, a transient amplification of the reaction as compared with 12.5 cGy occurred firstly in the Rathke's pocket, then in the infundibulum and in auditory vesicles. The most distinct effects were achieved with 50 cGy. Remarkable is the prompt rise of the DBA-affinity in a narrow area of the myelencephalon, and subsequently also in the roof of the diencephalon. Furthermore, the infundibulum and the Rathke's pocket, both anlagen of the pituitary gland, bound heavily DBA during the entire examination period of 24 h. The present study demonstrated the outstanding suitability of the Dolichos biflorus agglutinin for histochemical detection of subtle cellular alterations by small radiation doses.

Animals↗
PubMed1989

The peak bone mass concept.

Peak bone mass (PBM), i.e. the bone mass developed after growth in early adult life, is a major determinant for bone mass in the senescence, resp. for the risk of osteoporosis. Individual differences among young adults are so important that a person with a high PBM has a relatively low risk for osteoporosis, even if its annual bone loss is fast. PBM is conditioned by genetic, hormonal, and nutritional factors, and by physical activity, the latter two offering possible impact for preventive measures. Preservation of PBM through the early, resp. premenopausal life, can be favoured by adequate nutrition and physical activity, both together being capable of postponing the appearance of osteoporosis by several years. But various parts of the skeleton decrease constantly through life, starting already in the twenties; even when absorptiometry shows no loss of bone density until menopause, resp. during early adult life, there is a constant decrease of the mechanical properties of the bone with age. Therefore, the development of an optimal PBM is probably more effective in preventing osteoporosis than the measures for preservation of bone.

Adolescent↗
PubMed1989

Biochemical analysis of young rats homozygous for the cataract mutation cat.

Cataractogenesis was studied in young rats homozygous for the radiation-induced recessive cataract mutation cat. Homozygous cat/cat rats have reduced body weight (about two-thirds of the wild type) when 3 weeks old. The litter size is also diminished to about two-thirds of the wild type. For lens-specific parameters, as compared with homozygous wild type, the wet weight of the cataractous lenses is reduced, although the concentration of water-soluble lens proteins per wet weight is the same. No major alterations could be detected in the pattern of the water-soluble lens proteins separated by isoelectric focusing or gel electrophoresis run with or without mercaptoethanol. Additionally, no statistically significant alterations could be detected in the biochemical parameters of the lens used as indicators for osmotic stress (water content of the lens and the Na+-K+-dependent ATPase), for the energy state (ATP) and for the redox state (oxidized glutathione and superoxide dismutase). In contrast, the activity of transglutaminase is significantly enhanced in lenses as well as in the liver of young cat-rats, which might be understood as a biochemical marker for alterations in the developmental program. Cataractogenesis in the cat-rat is, therefore, suggested to be part of a syndrome including dwarfism and reduced litter size.

Adenosine Triphosphatases↗
PubMed1989

Effects of hydroxyethyl rutosides upon the permeability of single capillaries in the frog mesentery.

1. We have investigated the effects of a standardised mixture of hydroxyethyl rutosides (HR) upon the permeability of the walls of single capillaries and venules of the frog mesentery. 2. In each experiment a single vessel was perfused via a micropipette with frog Ringer solutions containing bovine serum albumin (10 mg ml-1) and Ficoll 70 (40 mg ml-1) first in the absence of HR and then with HR added to the perfusate. The permeability of the vessel walls was assessed during each perfusion by using a development of the Landis micro-occlusion technique to estimate their hydraulic permeability (Lp) and the effective osmotic pressure (sigma delta pi) exerted across them by the perfusate macromolecules. 3. Measurements were made both in vessels which appeared to be healthy and in vessels showing signs of stasis or inflammation before perfusion. 4. HR at concentrations of 1.0, 0.1 and 0.01 mg ml-1 reduced hydraulic permeability to approximately half of its value in the absence of HR. It increased sigma delta pi to macromolecules at concentrations of 10, 1.0, 0.1, 0.01 and 0.001 mg ml-1. The effects of HR upon permeability were not reversed within 10 min of perfusion with an HR-free solution. 5. Ultrastructural examination of a number of vessels in which initial high values of permeability were reduced to values within the normal range of permeabilities by HR, showed clear signs of damage to the endothelium, with large gaps between adjacent endothelial cells. 6. These observations suggest that HR does reduce microvascular permeability both in healthy vessels and vessels showing of inflammation. The reduction in permeability of inflamed vessels does not appear to be the result of closure of the gaps between adjacent endothelial cells.

Animals↗
PubMed1989

Experience with the Hemasite vascular prosthesis.

A 3-year experience with the no-needle vascular prosthesis Hemasite, implanted in 10 patients who underwent hemodialysis and have a long history of multiple vascular access failures, is described. During 182 months of follow-up study, 30 thromboses occurred, while nine of 10 patients did not receive any antiplatelet aggregant treatment. Hemasite was declotted 12 times with a local infusion of urokinase and 12 more times by thrombectomy. A surgical procedure was performed only in the other cases, and the rate of surgical intervention fell from 0.18 interventions per patient per month before Hemasite implantation to 0.027 after implantation.

Adult↗
PubMed1989

Oxidative stress and inherited cataracts in mice.

To determine whether an unbalanced redox state might accompany the development of particular inherited mouse cataracts, the lenticular content of oxidized glutathione (GSSG) and the activity of superoxide dismutase (SOD) were chosen as markers. For wild-type lenses, an enhanced GSSG content could be observed in females as compared to males. Such a sex effect could not be detected for the SOD activity. In the mutants, GSSG content in cataractous lenses was found to be enhanced in 2 of 7 cases; the increases in other mutants were not significant. Changes of the SOD activity were even less consistent and only a random correlation of GSSG content and SOD activity with cataractogenesis could be deduced.

Animals↗
PubMed1989

Insulin autoantibodies in non-obese diabetic (NOD) mice.

Anti-insulin autoantibodies were detected in NOD mice using ELISA. The antibodies were detected as early as at 5 weeks of age, long before onset of clinically overt diabetes, especially in diabetes-prone female mice. The anti-insulin specificity was verified by passage on affinity chromatography insulin columns and demonstration that the anti-insulin activity was located on the F(ab')2 region of the immunoglobulins. The presence of anti-insulin antibodies in prediabetic NOD mice provides a unique possibility for studying their significance and their eventual pathogenic role in the development of insulin-dependent diabetes.

Animals↗
PubMed1989

[Peritoneal dialysis, the method of treatment for end-stage renal insufficiency: development of indications during the past 10 years in relation to the initial renal disease and extra-renal pathology].

A decade after its first introduction, the advantages and drawbacks of continuous ambulatory peritoneal dialysis over hemodialysis remain controversial. This present paper is a review of the literature, focused on the indications of this dialysis modality in different circumstances: extra-renal pathology, systemic diseases (lupus erythematosus--diffuse scleroderma--plasma cell disorders--amyloidosis--HIV infected patients) and complications related to hemodialysis.

Humans↗
PubMed1989

[Recovery of renal function after treatment with continuous ambulatory peritoneal dialysis].

The methods of dialysis were rarely studied as factors of recovery of renal function, in patients receiving long term dialysis. The authors report their experience about 400 end-stage renal disease patients treated between 1983 and 1988. The frequency of renal function recovery was 3.9%, irrespective of the dialysis modality. The two main favorable factors were the type of the primary renal disease and the associated potentially reversible factors at the onset of the dialysis. As the hemodialysis group and the peritoneal dialysis group differed regarding these factors, no definite answer could be given. No conclusion will be drawn up without a prospective randomized trial.

Acute Kidney Injury↗
PubMed1988

High metabolic activity in the visual cortex of early blind human subjects.

Glucose metabolism has been studied in the visual cortex of early blind human subjects. In the forebrain of these subjects, regional glucose utilization was the highest in the striate and prestriate cortical areas. Furthermore, this activity was higher than in blindfolded sighted subjects, whether at rest or during an auditory or tactile task. These observations raise the question of the functionality of the blind's visual cortex.

Blindness↗