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Biomedical subjects

C Michiels

Publications and source records attributed to C Michiels.

85 records · Page 5Linked to original sources
PubMed1986

A new experimental model to study oxygen toxicity.

An experimental model was developed in order to study the protective effect of antioxidant molecules. Human diploid WI-38 fibroblasts were cultivated under 2 atm of 95% O2. Antioxidants like alpha-tocopherol or superoxide dismutase (SOD) were added respectively in the culture medium or directly inside the cell through a microinjection technique. With both antioxidant molecules a protection was observed. In the control experiment, cells died within 6 or 8 days depending on the confluency and the malonaldehyde content increased sharply. This model represents a new tool in order to test other antioxidant systems towards an oxidative stress.

Antioxidants↗
PubMedDate not supplied

Cellular aging and the importance of energetic factors.

The in vitro aging of human fibroblasts has become a classical model for studying cellular aging. This model was lately redefined by showing that these cells represent a stem cell system in which they progressively pass through seven morphotypes. Experimental data showed that external conditions that can be considered as stresses for the cells, can modulate the genome expression by speeding up the passage of the cells from one morphotype to the other. In this article, we will interpret these observations from the point of view of the thermodynamics of far from equilibrium open systems, which shows the importance of the production and the use of energy, both responsible for the generation of a given amount of entropy production. In stable systems like these cell morphotypes, such a production is constant but external stresses can prematurely destabilize the steady state of entropy production and, in doing so, accelerate the process of aging. It is also predicted that cells submitted to a stress will use part of their energy in response to the stress. Some experimental data in favor of such an interpretation have been obtained and more will be presented here that show that both cell death and accelerated cell aging under stress are modulated by the level of energy metabolism. All theoretical and experimental arguments presented in this article will show that cellular aging is related to stress and also to energy production through a very elaborate system of regulatory processes necessary for the cell to survive and to perform specific functions according to its differentiated state. This regulatory system also permits the cell to adapt its response according to the intensity of external as well as internal challenges and one of these responses will influence the cellular aging rate.

Cell Death↗
PubMedDate not supplied

Protection by bilobalide of the ischaemia-induced alterations of the mitochondrial respiratory activity.

Ischaemia is a common feature of most vascular diseases. There is evidence from experimental and clinical studies that Ginkgo biloba extract protects tissues from ischaemia/reperfusion damages. Bilobalide seems to be responsible, at least in part, for this activity. However, the mechanism of the protection afforded by bilobalide is not yet known. In this work, the effects of bilobalide on mitochondrial respiration were investigated during liver and brain ischaemia, since mitochondria alteration is an early event in ischaemia-induced damage. Bilobalide could prevent the decrease in respiratory activity induced by ischaemia in liver and in brain, both when glutamate/malate or succinate was used as substrate. Ischaemia decreased state 3 respiration rate and bilobalide prevented this decrease. While bilobalide was not able to prevent the decrease in adenine translocase activity, it protected complex I activity. Bilobalide allows mitochondria to maintain their respiratory activity in ischaemic conditions by protecting complex I and probably complex III activities. Hence, the energetic pool of tissues is preserved during the ischaemic period as well as its viability. This mechanism provides, a possible explanation for the anti-ischaemic properties of bilobalide and of Ginkgo biloba extract in therapeutic interventions.

Animals↗
PubMedDate not supplied

[Disposable versus reusable biopsy forceps. A prospective cost analysis in the gastrointestinal endoscopy unit of the Dijon University Hospital].

AIMS: The goal of this study was to compare the cost of a biopsy session performed with a disposable and a reusable endoscopic biopsy forceps. MATERIAL AND METHODS: Over a 10-month period, 15 new reusable forceps (10 gastric and 5 colonic) were prospectively tracked. A biopsy session performed with a reusable forceps included its current purchase price, the sterilization cost and the number of uses. A biopsy session performed with a disposable forceps was calculated with its current purchase price and its incineration cost. RESULTS: At the end of the study, only one reusable forceps had broken and the number of uses was 65. The cost of a biopsy session performed with a gastric reusable forceps was euro 7.52 (including euro 1.92 of sterilization cost) and euro 8.67 for a reusable colonic forceps (with the same sterilization cost). The cost of a biopsy session performed with a gastric or a colonic disposable forceps was euro 11.98. From 44 uses for a colonic forceps and 37 uses for a gastric one, a biopsy session performed with a reusable forceps was already cheaper. CONCLUSION: In this study, a biopsy session performed with a reusable forceps was less expensive than with a disposable one. However, the extra cost generated by the disposable forceps may be offset by an easier inventory control and the reduction of the cross contamination risk.

Biopsy↗
PubMedDate not supplied

[Epidemiology and prevention of colorectal cancer].

Colorectal carcinoma is very common in western countries. It is in the front line of malignant pathology in France. The estimated number of new cases is almost 26,000 per year. The role played by diet in the onset of colorectal carcinomas is well established. The majority of studies indicate the protective role played by green vegetables. The role of other factors remains controversial: protective role of fibres, calcium and vitamins and favorizing role of fats, proteins, red meat, alcohol and calorie intake. The role of bile salts in increasing the size of adenomas and their malignant change is accepted. A number of therapeutic trials have involved modifications in bile salt concentrations. These should enable the proposal of a primary prevention strategy. The early detection of carcinomas and the secondary prevention of colorectal carcinoma (by detection of the adenomas which precede a high proportion of carcinomas) are areas of great interest. Detection of occult blood in stools as a mass screening test is currently being evaluated. Methods used to obtain a high participation rate among the population vary from one country to another, but are now well-defined. It will be necessary to wait for 2 years before being able to determine the effect on mortality and an even longer period to evaluate the effect on the incidence of colorectal carcinoma.

Adenoma↗
PubMedDate not supplied

[The relation between venous stasis and the occurrence of pain].

Venous stasis is a situation encountered commonly in varicose disorders. The potential implications of this decrease in oxygen levels in terms of the status of the cells of the vein were assessed. When endothelial cells are subjected to hypoxia, there is stimulation of the cells which shows itself as increased synthesis of prostaglandins and of PAF (Platelet Activating Factor). The synthesis of these typical mediators of inflammation results from activation by the calcium of phospholipase A2 which releases the arachidonic acid of phospholipids and this increase in intracellular calcium results itself from a fall in efficacy of calcium pumps due to the fall in ATP caused by hypoxia. Thus the fall in oxygen leads to the production of mediators of inflammation which activate leucocytes and result in local micro-inflammation which can be very rapidly eliminated if the circulation is restored but which can also cause irreversible damage to the vein by changes in venous tissue due to activated leucocytes which release proteases and free radicals after having penetrated the intima of the vein. These processes offer an explanation for the histological changes seen in varicose veins and the onset of localised pain during the development of such disease.

Humans↗
PubMedDate not supplied

[A comparative study of the protective effect of different phlebotonic agents on endothelial cells in hypoxia].

Numerous reported findings indicate that the etiology of venous diseases is multifactorial. One of the chief factors is certainly stasis of blood in the veins of the lower limbs during long periods spent standing up. This stasis causes tissue hypoxia which first affects the venous wall. Because of their location at the interface between blood and vein wall and because of their fragility, endothelial cells are the first to suffer from the lack of oxygen. With the aim of understanding these events, the authors have developed a model of endothelial cells in culture subjected to hypoxia in vitro which mimics the conditions encountered clinically. This model has enabled us to test various drugs commonly used in venous disease. These included GbE, the active ingredient of GINKOR FORT, diosmin and procyanidol oligomers. It was thus shown that only GbE was not toxic to endothelial cells. GbE was also found to be capable of effectively protecting cells exposed to hypoxia. Protection under the influence of diosmin was obtained only at concentrations very close to toxic doses. In contrast, procyanidol oligomers offered no protection. The protective effect of GbE is believed to be due to the action of terpenes on the energy metabolism of the cell.

Antihypertensive Agents↗
PubMedDate not supplied

[A comparative study of the protective effect of various phlebotonic agents on hypoxic endothelial cells].

Many findings indicate that the etiology of venous disease is multifactorial. One of the chief factors is certainly the stasis of blood in the lower limbs during long periods of standing. This stasis causes tissue hypoxia which first affects the venous wall. Because of their site at the blood/vein wall interface as well as their fragility, endothelial cells are the first to suffer from lack of oxygen. In order to understand these events, the authors have developed a model of endothelial cells in culture subjected to hypoxia in vitro which imitates conditions encountered clinically. This model was used to test different drugs commonly used in venous pathology. These included GbE, the active ingredient of GINKOR FORT, diosmine and procyanidolic oligomers. It was thus shown that only GbE was not toxic to endothelial cells. Furthermore, GbE was capable of effectively protecting cells subjected to hypoxia. Protection with diosmine was obtained only at concentrations very close to toxic doses. In contrast, procyanidolic oligomers afforded no protection. The protective effect of GbE is believed to be due to the action of terpenes on cellular energy metabolism.

Antihypertensive Agents↗
PubMedDate not supplied

[Behavior of human endothelial cells in hyperoxia and hypoxia: effect of Ginkor Fort].

Recent discoveries have shown that venous diseases have a multifactorial etiology. One of the factors which is definitely involved in this pathologic process is the change in the concentration of oxygen. An increase in the concentration of oxygen, hyperoxia, or reoxygenation following hypoxia, damages the tissues by stepping up the production of free radicals. In addition, a reduction in oxygen concentration, or hypoxia, is also damaging, probably through a reduction in ATP synthesis. From a therapeutic standpoint, the veins, and more particularly the endothelium, must be protected against the impact on the tissue of these changes in oxygen concentration. In this study, the effects of Ginkor Fort were tested on cultured endothelial cells subjected to varying oxygen pressures. The results show that Ginkor Fort can provide good protection of endothelial cells against hyperoxia and hypoxia-reoxygenation. These beneficial effects are probably due to the presence of flavonoids in the Ginko biloba extract; these flavonoids have an anti-oxidant effect. In addition, this substance also protects the cells against hypoxia, possibly by increasing the availability of oxygen for ATP synthesis. This dual protective effect, which is produced by two different mechanisms, may account for the wide spectrum of Ginkor Fort in its use in venous diseases.

Cell Survival↗