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Biomedical subjects

C Michel

Publications and source records attributed to C Michel.

At least 91 records · Page 5Linked to original sources
PubMed1999

Opposite effects of gentle handling on body temperature and body weight in rats.

Opposite effects of gentle handling on body temperature and body weight in rats. PHhe aim of this study was to measure the body weight set point when rats are being handled gently and thus experience emotional rise in body temperature. Wistar male rats were used in this experiment, and each rat was its own control. Body weight set point was estimated from the rat's food hoarding behavior. The set point is the intersection of the regression line for hoarding with the X axis. During hoarding sessions the experimenter handled the rat and took its colonic temperature six to eight times, an action sufficient to arouse emotional fever. On alternate days the rats were not handled. Thus, body weight set point was obtained for each rat without handling and with handling. In sessions with handling, rats raised their body temperature, ate less, and defecated more than in control sessions. When handled, the body weight set point declined from 388 +/- 44 g to 366 +/- 47 g (p = 0.048, t = 2,39). The decline in the set point induced by gentle handling is believed to result from an elevation of the hypothalamic CRH.

Animals↗
PubMed1999

Antioxidant capacity of flavanols and gallate esters: pulse radiolysis studies.

Reactivities of several proanthocyanidins (monomers of condensed tannins) and gallate esters (representing hydrolyzable tannins) with hydroxyl radicals, azide radicals, and superoxide anions were investigated using pulse radiolysis combined with kinetic spectroscopy. We determined the scavenging rate constants and the decay kinetics of the aroxyl radicals both at the wavelength of the semiquinone absorption (275 nm) and the absorption band of the gallate ester ketyl radical (400-420 nm). For most compounds second-order decay kinetics were observed, which reflect disproportionation of the semiquinones. In the case of the oligomeric hydrolysable tannins, pentagalloyl glucose and tannic acid, the decay kinetics were more complex involving sequential first-order and second-order reactions, which could only be resolved by kinetic modeling. A correlation of the reaction rates with hydroxyl radicals (k*OH) with the number of adjacent aromatic hydroxyl groups (i.e., representing catechol and/or pyrogallol structures) was obtained for both condensed and hydrolyzable tannins. Similar correlation for the reactions with azide radicals and superoxide anions are less obvious, but exist as well. We consider proanthocyanidins superior radical scavenging agents as compared with the monomeric flavonols and flavones and propose that these substances rather than the flavonoids proper represent the antioxidative principle in red wine and green tea.

Anions↗
PubMed1999

Production of viable cultures of Flavobacterium psychrophilum: approach and control.

Although the fish pathogen Flavobacterium psychrophilum is a major source of concern in salmonid hatcheries, few studies have been conducted on its pathogenicity. Difficulties are often experienced when trying to control or quantify standard procedures for in vitro culture of the bacterium. Plate enumeration and counting chamber enumeration combined with epifluorescent microscopy with fluorescent dyes determined that no more than 25% of the bacterial cells present in the cultures were able to produce colonies on agar media. This was strongly dependent upon different medium components. Tryptone-enriched Anacker and Ordal medium proved more suitable than tryptone-yeast extract-salts with skimmed milk. Adding horse serum and trace elements in controlled proportions offered the most reproducible results. Viable but nonculturable forms were apparently not responsible for the difficulties in production of F. psychrophilum, but the cells were highly susceptible to osmotic conditions. Improvements in the media and careful handling of the bacteria in isotonic suspension media resulted in predictable production of viable bacteria and allowed an absorbance/colony-forming-units relation curve to be established.

Animals↗
PubMed1999

Enhancement of butyrate production in the rat caecocolonic tract by long-term ingestion of resistant potato starch.

Some data suggest that the colonic microflora may adapt to produce more butyrate if given time and the proper substrate. To test this hypothesis, we investigated the effect of prolonged feeding of resistant potato starch on butyrate production. Rats were fed on either a low-fibre diet (basal) or the same diet supplemented with 90 g resistant potato starch/kg (PoS) for 0.5, 2 and 6 months. Short-chain fatty acid (SCFA) concentrations were determined in caecal and colonic contents at the end of each ingestion period. Total SCFA concentration increased over time throughout the caecocolonic tract with PoS, but was not modified with the basal diet. While propionate concentration was unchanged, butyrate concentration was highly increased by PoS at each time period in both the caecum and colon. Moreover, the butyrogenic effect of PoS increased over time, and the amount of butyrate was increased 6-fold in the caecum and proximal colon and 3-fold in the distal colon after 6 months compared with 0.5 months. Accordingly, the ratio butyrate:- total SCFA increased over time throughout the caecocolonic tract (12.6 (SE 2.8) v. 28 (SE 1.8)% in the caecum, 10.5 (SE 1.4) v. 26.8 (SE 0.9)% in the proximal colon, and 7.3 (SE 2.4) v. 23.9 (SE 2.7)% in the distal colon at 0.5 v. 6 months respectively), while the proportion of acetate decreased. Neither the proportion nor the concentration of butyrate was modified over time with the basal diet. Butyrate production was thus promoted by long-term ingestion of PoS, from the caecum towards the distal colon, which suggests that a slow adaptive process occurs within the digestive tract in response to a chronic load of indigestible carbohydrates.

Animals↗
PubMed1999

Prolonged intake of fructo-oligosaccharides induces a short-term elevation of lactic acid-producing bacteria and a persistent increase in cecal butyrate in rats.

While the prebiotic effects of fructo-oligosaccharides (FOS), short-chain polymers of fructose, have been thoroughly described after 2-3 wk of ingestion, effects after intake for several months are unknown. We tested the hypothesis that these effects would differ after ingestion for short and long periods in rats. Rats were fed a basal low-fiber diet (Basal) or the same diet containing 9 g/100 g of FOS for 2, 8 or 27 wk, and cecal contents were collected at the end of each time period. Cecal short-chain fatty acid concentration was higher in rats fed FOS than in those fed Basal, and this effect persisted over time: 83.8 +/- 4.1 vs. 62.4 +/- 6.5 micromol/g at 2 wk and 103.5 +/- 5.8 vs. 73.2 +/- 7.4 micromol/g at 27 wk (P < 0.05). The molar butyrate ratio was higher in rats fed FOS regardless of the time period (14.8 +/- 0.6% vs. 6.7 +/- 1.1% at 27 wk, P < 0.05). Lactate concentration in rats fed FOS was elevated after 2 wk and then decreased: 63.5 +/- 21.6 micromol/g at 2 wk vs. 8.8 +/- 3.3 micromol/g at 8 wk (P < 0.05). After 2 wk, FOS increased the concentrations of total lactic acid-producing bacteria, and Lactobacillus sp. (P < 0.05), without modifying total anaerobes. However, most of these effects were abolished after 8 and 27 wk of FOS consumption. In the long term, the FOS-induced increase in intestinal lactic acid-producing bacteria was lost, but the butyrogenic properties of FOS were maintained.

Animals↗
PubMed1999

The influence of automated peritoneal dialysis on the decrease in residual renal function.

BACKGROUND: Automated peritoneal dialysis (APD) has been increasingly used in recent years. Our purpose was to investigate whether the good preservation of residual renal function (RRF) that has been reported in patients on continuous ambulatory peritoneal dialysis (CAPD) is also observed in APD. METHODS: RRF was determined and compared prospectively over 1 year in two groups of peritoneal dialysis (PD) patients: 18 consecutive new patients starting on APD (12 continuous cyclic peritoneal dialysis (CCPD) patients and six nightly intermittent peritoneal dialysis (NIPD) patients) and 18 selected patients who had started on CAPD at the same time and were matched for baseline characteristics. RRF was assessed on normalized creatinine clearance (ml/min/1.73 m2) measured before the start of PD, at 6 months, and at 1 year. Wilcoxon's rank sum test was used to compare differences between the two groups. RESULTS: Creatinine clearance (ClCr) was 6.1 ml/min in the APD group and 6 ml/min in the CAPD group at the start of PD. The monthly rate of ClCr decrease was significantly higher in the APD group: -0.28 ml/min vs -0.1 ml/min (P = 0.04) at 6 months and -0.26 ml/min vs -0.13 ml/min (P = 0.005) at 1 year. RRF decreased at the same rate in patients treated with NIPD or CCPD. The daily instilled volume of 3.86% glucose dialysis solution (l/day) was higher in APD patients than in CAPD patients: 2.5 vs 0 at 6 months and 1 year but there was no significant difference in ultrafiltration rate (l/day) between APD and CAPD patients at these timepoints: 0.53 vs 0.6 and 0.88 vs 0.7 respectively. There was no difference between the two groups in body weight and blood pressure, which remained stable in both groups throughout the study period. CONCLUSIONS: RRF declined rapidly in APD patients whereas it was well preserved in CAPD patients. This may be explained by the less stable fluid and osmotic load together with the intermittent nature of APD and the larger use of hypertonic dialysate. RRF should be closely monitored in APD patients in order to adjust PD prescriptions and maintain adequacy.

Creatinine↗
PubMed1999

A standardized blood sampling scheme in quantitative FDG-PET studies.

Quantitative estimation of brain glucose metabolism (rCMRGlc) with positron emission tomography and fluorodeoxyglucose involves arterial blood sampling to estimate the delivery of radioactivity to the brain. Usually, for an intravenous injection of 30 s duration, an accurate input curve requires a frequency of one sample every 5 s or less to determine the peak activity in arterial plasma during the first 2 min after injection. In this work, 13 standardized sampling times were shown to be sufficient to accurately define the input curve. This standardized input curve was subsequently fitted by a polynomial function for its rising part and by spectral analysis for its decreasing part. Using the measured, the standardized, and the fitted input curves, rCMRGlc was estimated in 32 cerebral regions of interest in 20 normal volunteers. Comparison of rCMRGlc values obtained with the measured and the fitted input curves showed that both procedures gave consistent results, with a maximal relative error in mean rCMRGlc of 1% when using the autoradiographic method and 2% using kinetic analysis of dynamic data. This input-curve-fitting technique, which is not dependent on the peak time occurrence, allows an accurate determination of the input-curve shape from reduced sampling schemes.

Adult↗
PubMed1999

Exact rebinning methods for three-dimensional PET.

The high computational cost of data processing in volume PET imaging is still hindering the routine application of this successful technique, especially in the case of dynamic studies. This paper describes two new algorithms based on an exact rebinning equation, which can be applied to accelerate the processing of three-dimensional (3-D) PET data. The first algorithm, FOREPROJ, is a fast-forward projection algorithm that allows calculation of the 3-D attenuation correction factors (ACF's) directly from a two-dimensional (2-D) transmission scan, without first reconstructing the attenuation map and then performing a 3-D forward projection. The use of FOREPROJ speeds up the estimation of the 3-D ACF's by more than a factor five. The second algorithm, FOREX, is a rebinning algorithm that is also more than five times faster, compared to the standard reprojection algorithm (3DRP) and does not suffer from the image distortions generated by the even faster approximate Fourier rebinning (FORE) method at large axial apertures. However, FOREX is probably not required by most existing scanners, as the axial apertures are not large enough to show improvements over FORE with clinical data. Both algorithms have been implemented and applied to data simulated for a scanner with a large axial aperture (30 degrees), and also to data acquired with the ECAT HR and the ECAT HR+ scanners. Results demonstrate the excellent accuracy achieved by these algorithms and the important speedup when the sinogram sizes are powers of two.

Algorithms↗
PubMed1999

[Percutaneous treatment of a superficial femoral artery aneurysm using an intravascular stent-prosthesis].

One case of superficial femoral aneurysm treated percutaneously by endovascular stent graft (Passager Boston) is reported. The initial radiographic evaluation included arteriography and color doppler sonography which enable analysis of the flow path, the extent of the wall thrombus, the choice of stended graft size. The procedure of implantation was technically trouble free. The post-procedure 3D CT and arteriography demonstrated occlusion of the aneurysm and resaturation of normal flow path. The six and twelve month check confirmed the stability of the results locally and the integrity of run off vessels. In weakened and specially elderly patient percutaneous treatment of superficial femoral artery aneurysm can be carried out easily. The contribution of 3D CT is essential in follow up to ensure an optimal result and to detect any complication.

Aged↗
PubMed1999

Isolation of an acid fraction from a fish protein hydrolysate with a calcitonin-gene-related-peptide-like biological activity.

The possibility of obtaining calcitonin and/or calcitonin-gene-related peptide (CGRP) immunorelated molecules from partly digested proteins was investigated with fish and shrimp hydrolysates. These two peptides were quantified by both radioimmunoassay and radioreceptor assay; the positive extracts were partly purified. Different hydrolysates were analysed: cod head, stomach and viscera hydrolysates, a shrimp hydrolysate and two sardine hydrolysates. Although each cod extract interacted in the CGRP radioimmunoassay, none of these extracts was able to displace the CT binding to its antibody. In contrast, shrimp and sardine hydrolysates interacted with both radioimmunoassays. Radioreceptor assays performed on the same extracts demonstrated that only three extracts contained the structural determinants that allowed them to interact in the CGRP radioreceptor assay. No interaction with the calcitonin radioreceptor assay could be demonstrated. Molecular sieving of the two sardine extracts showed that the immunoreactivity was resolved into two main fractions. The higher-molecular-mass fraction interacted only in the CGRP radioreceptor assay. The results obtained suggest the presence of a biologically related CGRP molecule in peptone hydrolysates and requires further investigation into the role of these peptide fragments in the regulation of intestinal function by partly digested proteins.

Animals↗
PubMed1998

In vitro prebiotic effects of Acacia gums onto the human intestinal microbiota depends on both botanical origin and environmental pH.

Acacia gums are commonly used food additives. It is currently unclear how extensively these non-digestible polysaccharides are fermented in the human large intestine. However, they have been shown to support bifidobacterial growth in vitro and may represent useful candidate prebiotics. In these investigations, in vitro 24-h batch incubations and chemostat continuous-cultures of human faecal bacteria were conducted using two acacia gums (Fibregum standard and Fibregum AS). Our aim was to study the effects of these gums on bacterial ecology and fermentation in the large bowel. Fructooligosaccharides (Actilight-950P) were also investigated as a reference. Both Acacia gums were extensively fermented by intestinal flora although there were marked differences in fermentation product formation and ecological effects, probably due to their differing botanical origins and/or biochemical characteristics. In particular, fermentation of Fibregum AS led to significantly higher proportions of propionate both in batch and chemostat experiments. Both gums decreased Clostridium sp. levels but only Fibregum-standard induced higher Lactobacillus sp. counts compared to control. These bacterial modifications were highly dependent of the operating pH of the fermentation system with acidic conditions promoting both the prebiotic and the butyrogenic effects of fructooligosaccharides. In these studies, we have demonstrated that, similarly to fructooligosaccharides, Acacia gums can exert putatively beneficial effects on host health through both the improvement of the composition of the large intestine microflora and SCFA formation.

Journal Article↗
PubMed1998

Physostigmine results in an increased decrement in brain glucose consumption in Alzheimer's disease.

The responsibility of cerebral cholinergic lesions for the weak clinical response to cholinergic neurotransmission enhancement of Alzheimer's disease (AD) was studied by measuring the effects of physostigmine on glucose consumption and neuropsychological tests. Ten AD and ten aged normals (AN) were examined twice, under placebo and under maximal tolerated dose of physostigmine, in randomized order and blind fashion. Under physostigmine, both groups showed better performances in tests measuring attention (P < 0.05-0.001) but not long-term memory, and cerebral glucose consumption was regionally modified (P < 0.0001). We observed a regional decrease in AD and in AN which was larger in AD, where each patient exhibited a mean metabolic decrease. With normalized values, AD and AN showed a similar decrease in the metabolic values of prefrontal cortex and striatum (P = 0.0003). These findings suggest that cholinergic neurotransmission enhancement depresses glucose consumption and increases selective attention in similar ways in both groups, but to a larger extent in AD. This suggests that brain metabolism in AD over-responds to enhancement of cholinergic neurotransmission. The observed weak response of clinical symptomatology to anticholinesterase agents does not appear to be due to the failure to enhance the activity of the cholinergic system in AD.

Aged↗
PubMed1998

[Perioperative antibiotic prophylaxis in orthodontic bone operations of the facial skull].

Intraoral orthognathic surgical procedures are clean-contaminated operations because of the facultative pathogenic flora of the oral cavity. Without antibiotic prophylaxis in this kind of operation a postoperative wound infection can be expected in 20-31% of cases. Therefore, a retrospective analysis of the clinical course of 545 patients with various dentofacial deformities was performed to evaluate the importance of perioperative antibiotic prophylaxis. The total rate of wound infections was 2.8% and lower than rates published in other comparable studies without antibiotic prophylaxis. The rate of wound infection after single mandibular osteotomy (4.1%) was significantly higher than the analogous amount after single maxillary osteotomy (0.8%) because of the mechanical strain of the surgical wound in the region of the mandibular angle and because of the high retention of food particles and other decay products in this area. The recognized rise in the wound infection rate by increasing the length of operation demonstrates that the extent of bacterial contamination of the surgical wound depends on the dimension and duration of surgery. Bacterial flora caused the noticed wound infections in 61.5% of cases aerobic-anaerobic mixed infections, which is in accordance with the results of similar publications. With increasing length of antibiotic prophylaxis, an increase in the incidence of antibiotic-associated side effects and in the wound infection rate could be observed. Therefore, an antibiotic prophylaxis which exceeds 3 days does not seem to be useful. In this study, in which cephalosporins were mostly used, the total rate of antibiotic-associated side effects (4.6%) was lower than analogous amounts of other groups of antibiotics. The analysis demonstrates that a short-term prophylaxis with broad-spectrum cephalosporins such as cefatoxime of 48 h is very effective and useful.

Adolescent↗
PubMed1998

Evolution of brain glucose metabolism with age in epileptic infants, children and adolescents.

During the first years of life, the human brain undergoes repetitive modifications in its anatomical, functional, and synaptic construction to reach the complex functional organization of the adult central nervous system. As an attempt to gain further insight in those maturation processes, the evolution of cerebral metabolic activity was investigated as a function of age in epileptic infants, children and adolescents. The regional cerebral metabolic rates for glucose (rCMRGlc) were measured with positron emission tomography (PET) in 60 patients aged from 6 weeks to 19 years, who were affected by complex partial epilepsy. They were scanned at rest, without premedication, in similar conditions to 20 epileptic adults and in 49 adult controls. The distribution of brain metabolic activity successively extended from sensorimotor areas and thalamus in epileptic newborns to temporo-parietal and frontal cortices and reached the adult pattern after 1 year of age. The measured rCMRGlc in the cerebral cortex, excluding the epileptic lesions, increased from low values in infants to a maximum between 4 and 12 years, before it declined to stabilize at the end of the second decade of life. Similar age-related changes in glucose metabolic rates were not observed in the adult groups. Despite the use of medications, the observed variations of rCMRGlc with age in young epileptic humans confirm those previously described in pediatric subjects. These metabolic changes are in full agreement with the current knowledge of the synaptic density evolution in the human brain.

Adolescent↗
PubMed1998

[Prediction by means of endogenous and exogenous evoked potentials of the favorable evolution of a prolonged coma].

A neurophysiological follow-up (EEG, exogenous and endogenous evoked potentials--EP) was performed over a 4-month period in a patient who presented a long-lasting coma following a cardiac arrest and an amniotic embolism. A pure anoxic aetiology was ruled out starting from the second day on the basis of a dissociation between mildly altered flash visual EP and markedly altered somatosensory EP, indicating focal brain-stem pathology. Endogenous EP reappeared after 12 days. This patient recovered consciousness after 51 days. Despite the absence of MRI abnormalities, we put forward the hypothesis that a brain-stem embolism had, in fact, worsened the clinical picture of an actually moderate anoxia. This case exemplifies the interest of an integrated neurophysiological approach (EEG, exogenous three-modality EP and endogenous EP) in the early evaluation of coma. It also illustrates the complement between structural imaging and functional assessment of the nervous system.

Adult↗
PubMed1998

PET study of human voluntary saccadic eye movements in darkness: effect of task repetition on the activation pattern.

Using H2(15)O 3D Positron Emission Tomography (PET), regional cerebral blood flow (rCBF) was measured in six human subjects under two different conditions: at rest and while performing self-paced horizontal saccadic eye movements in darkness. These two conditions were repeated four times each. First, the comparison between the four saccadic and four resting conditions was investigated in a group and a single subject analysis. Saccades elicited bilateral rCBF increases in the medial part of the superior frontal gyrus (supplementary eye field), precentral gyrus (frontal eye field), superior parietal lobule, anterior medial part of the occipital lobe involving striate and extrastriate cortex (lingual gyrus and cuneus), and in the right inferior parietal lobule. At the subcortical level, activations were found in the left putamen. These results mainly replicate previous PET findings on saccadic control. Second, the interaction between the experimental conditions and their repetition was examined. When activations throughout repetition of the same saccadic task are compared, the supplementary eye fields show a progressive increase of activation. On the contrary, the activation in the cerebellum, left superior parietal lobule and left occipital cortex progressively decreases during the scanning session. Given the existence of such an interaction, the pattern of activations must be interpreted as a function of task repetition. This may be a factor explaining some apparent mismatch between different studies.

Adult↗