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Biomedical subjects

J Duchesne

Publications and source records attributed to J Duchesne.

At least 19 recordsLinked to original sources
PubMed2004

An allometric model for trees.

This paper presents a general mathematical model for the morphometric description of trees. This model is based on the introduction of fractal theory, and more particularly of the concept of self-similarity, into a statistical physics rationale. Fractal theory provides the necessary tools to describe the complexity of tree structure. Statistics, when applied to physics, makes it possible to explain the properties of complex objects starting from their components. The combination of both tools allowed us to develop a theoretical model that is the probability density function of the morphometric lengths of trees. An example of validation of this law is given here: the theoretical model of morphometric lengths is compared with experimental data of Cupressocyparis.

Cupressus↗
PubMed2002

[A new in vitro test to simulate gastric absorption of copper, lead, tin and zinc from polluted soils].

Metals in polluted soils can be ingested by young children and cause toxicity through gastro-intestinal absorption. Very few tests are used to evaluate the gastric absorption of metals from polluted soils. The Toxicity Characteristics Leaching Procedure (TCLP) of the Environmental Protection Agency of the United States is indirectly used as usually no action is taken on a polluted soil if lead is less than 5 mg l(-1) in the test. This paper presents a new In vitro simple screening test to detect soils polluted by metals which can cause gastric absorption. The gastric juice simulation test (GJST) is based on the chemistry of the stomach. The TCLP and the GJST has been applied to six different size fractions of 5 soils. Lead carbonate was the main form of lead pollution. Lead oxide, lead silicate, lead phosphate and PbaSnbOc(CO3)d, PbaTibOc(CO3)d and PbaCrbOc were also present. Copper is mainly found as elemental copper partly carbonated while zinc is as zinc oxide or carbonate. Tin is usually associated with iron alloy or oxide or in PbaSnbOc(CO3)d. The percentage of the surface occupied by a polluting phase is higher in small particles. The proportion of particles for which pollution is located near the surface of the particle is more important for small particles. The GJST leaches more copper, lead and zinc than the TCLP, particularly on small size fractions. Inorganic tin is not solubilised by the TCLP or the GJST. The percentage of metal leached from small particles is very important with the GJST, but not with the TCLP. The pH 5 of the TCLP is too high to solubilise much metals and is not a good test to evaluate polluted soils if gastric absorption is to be considered. For two soils out of five, the TCLP didn't detect problematic soils as detected with the Integrated Exposure Uptake Biokinetic model of the USEPA. The GJST detected all the problematic soils and is better to evaluate the chemical solubility of metals in the gastric environment. The GJST better represents the stomach environment (Cl-, pH 2, T = 37 degrees C). The GJST appears to be a good test to detect metal contaminated soils.

Absorption↗
PubMed1981

Cancer prevention and therapy.

Based on a consideration of biochemical mechanisms, rational methods for the prevention of cancer and for its positive regression are presented. It is demonstrated that the means employed are fundamentally opposed so that if the preventive method were to be used after the onset of cancer, it would only accelerate its development. The solution to these subtle questions rests notably on the established fact that a spontaneous cancer is nothing else but a phenomenon of anti-ageing. Thus, it is evident that all living beings that attain maximal longevity would necessarily die of cancer. Nevertheless, the malignant tumour is, from a certain aspect, hereditarily linked, since its early appearance in young children can only be explained by premature tissue ageing which is itself genetically derived.

Aging↗
PubMed1977

Malignant diseases among patients with multiple sclerosis.

The frequency of malignant diseases among 1866 living and 340 deceased multiple sclerosis (MS) patients was investigated in Finland. The study revealed a low prevalence (0.64%) and mortality (0.07%) rate of cancer among MS patients. The difference between MS patients and general population was significant. The highest rate was found in the group from 40 to 49 years while in the general population the rate of cancer among MS patients tended to fall after the age of 50. The possible role of selenium, one of the antioxidants in the pathogenesis of MS and cancer, is discussed because recent data have shown a very high negative correlation between selenium and cancer death rates.

Adult↗
PubMed1976

Quantitative evaluation of the oxidation of an exogenous glucose load using naturally labeled 13C-glucose.

Maize glucose was used as a natural tracer for studies of metabolism. It is richer in 13C than common vegetables and foods derived from these, and the C02 formed from it is consequently richer in 13C than the CO2 expired by man fed on a diet of common vegetables. The quantitative results, obtained by measurement of delta 13C of the expired CO2 and of VCO2 during the oxidation of an exogenous glucose load (about 100 g) in eight normal subjects over 7 hr, have shown a consumption of 28.64 +/- 1.44 g of glucose (mean +/- SEM), which represents about 30% of the load given. A comparison is made with the results obtained from other methods and the originality and usefulness of this new quantitative procedure is outlined.

Adult↗
PubMed1975

[Effect of antioxidant substances on the level of free organic radicals naturally present in the rat diaphragm].

Using the electron spin resonance method, the effect of antioxydants on the number of natural organic free radicals is studied in the case of the diaphragm of the Rat. The effect observed shows an important decrease in the free radical concentration, which may, in the case of ascorbic acid and BHT, lead to their complete disappearance. These results are discussed in the light of the hypothesis according to which antioxydants play a role in the lengthening of the life span because of their fundamental character of inhibitors of free radicals.

Animals↗
PubMed1975

Free radical evolution in rat liver following the ingestion of DAB.

The effect of the ingestion of the carcinogenic substance DAB on the density and distribution of organic free radicals in rat liver is studied by the electron spin resonance method. There is a remarkable parallelism between what is known about the evolution of the activity of mitochondria and the concentration variations of free radicals.

Animals↗
PubMed1975

Naturally labeled 13C-glucose. Metabolic studies in human diabetes and obesity.

The 13C/12C ratio in most commercial preparations of glucose used in clinical investigation is much higher than that of expired air. Variations in expired air 13C, after glucose load, are indicative of the catabolism of this exogenous glucose. The changes in the 13C/12C ratio of CO2 in expired air after oral administration of glucose were determined by mass spectrometry. Results in eleven healthy volunteers and seven obese subjects with normal oral glucose tolerance tests (OGTT) are reported. In all cases, the administration of glucose resulted in a marked rise in the 13C/12C ration of expired CO2, reaching its maximum at the fourth hour and then declining progressively. In seven obese patients with chemical diabetes and in five insulin-dependent diabetics, the 13C/12C ratio of expired CO2 during OGTT was significantly reduced, in comparison with the results obtained from the control groups. This study demonstrates the potential of this procedure using "naturally labeled" 13C glucose for the metabolic studies in man as anticipated from previous studies of Duchesne and his coworkers.

Adolescent↗