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Biomedical subjects

M Le Lous

Publications and source records attributed to M Le Lous.

At least 19 recordsLinked to original sources
PubMed1985

Age related evolution of stable collagen reticulation in human skin.

The relaxation time of hydrothermal isometric tensions (HIT) was measured in different tissues during collagen hydrolysis. This hydrolysis was shown to have the same activation energy in all skin samples studied, whatever the species and age. Therefore, variations in the HIT relaxation half-time at the boiling point, exclusively reflected variations in the reticulation degree of the stable infinite network of denatured collagen. Stable collagen reticulation was studied in human skin from birth to 70 yrs of age in 113 biopsies, by measuring the relaxation half-time of hydrothermal isometric tension (HIT) at boiling point. This time was observed to vary in three different ways as a function of age: 1) from birth to eight or 10 yrs and from 14-15 yrs until adulthood, it increased constantly, and at the same rate; 2) during early puberty, the striking observation was the dramatic decrease of relaxation time value which remained low for 4-5 yrs thereafter, and 3) from adulthood to 70 yrs of age, relaxation time values were scattered along several plateaux, apparently separated by similar incremental steps. A parallel study on rat and pig skin showed a similar age-related evolution for collagen stable reticulation i.e., a sudden drop of reticulation at puberty, and low values for several months thereafter, followed by a linear increase, at the same rate as that observed for human skin. The study of collagen reticulation in various pathological situations may help to clarify and increase our understanding of the different mechanisms involved in collagen modifications during in vivo growth and aging.

Adolescent↗
PubMed1985

Tendon adaptation to different long term stresses and collagen reticulation in soleus muscle.

Leg immobilization with or without soleus muscle denervation was studied in young rabbits. Muscle and tendon were maintained in extension, i.e., in the most lengthened position. Length measurements performed on sarcomeres, muscle fibers and tendon-plus-muscle complexes suggest the following progression in tendon growth rates: normal less than denervated-extended less than innervated-extended. Collagen reticulation was studied as a function of fiber location along these tendons by measuring hydrothermal isometric tension (HIT). Large variations were observed depending on fiber location, and significant modifications were induced by immobilization in extension. The results are discussed in relation to stress as a possible factor controlling collagen maturation in connective tissues.

Adaptation, Physiological↗
PubMed1983

Hydrothermal isometric tension curves from different connective tissues. Role of collagen genetic types and noncollagenous components.

Variations in hydrothermal isometric tension (HIT) were recorded in tendons, ligaments, skin, blood vessels, nerves, palatal mucosa, lungs, muscles, cartilages, demineralized bones and dentine from donors of different ages and species. The curves obtained during a linear rise in temperature from 37 degrees C to 100 degrees C at a rate of 1.15 degrees C/min were classified into three major families, A, B and C, depending on whether these curves displayed an early maximum, two shoulders or a late maximum. The ratio of heat-labile to heat-stable cross-links in the tissue's collagen network was shown to determine the type of curve obtained, but the genetic types of collagen in the tissue and the amount and quality of its noncollagenous components were not important in this respect. These results are discussed in the light of the accepted view that HIT variations are due to the rubber-elastic properties of gelatin.

Animals↗
PubMed1983

Tendon adaptation to bone shortening.

The ability of tendon to adapt its length to imposed conditions was tested in rat soleus. Shortening of one tibia left tendon insertions intact, but reduced the distance between them. Tendon lengths were found to decrease after a short period of recovery (1 or 2 months) whether surgery was performed in young or adult animals. Comparison of tibia and tendon length correlation in control rats of different ages and in experimental animals showed that adaptation was more complete in young rats than in adult rats. A long period of recovery seemed to improve adaptation only in young rats. Hydrothermal isometric tension measurements indicated that collagen remodeling occurred during tendon adaptation to bone length, with the process being more marked at the muscle-tendon junction.

Adaptation, Physiological↗
PubMed1982

The rate of collagen maturation in rat and human skin.

Hydrothermal Isometric Tension (HIT) relaxation was observed at the boiling point in rat, cat and human skin samples of different ages, after raising the temperature from 37 degrees to 100 degrees C at a rate of 1.15 degrees C/min. A Maxwellian relaxation to nearly zero was observed at the boiling point. A given velocity constant characterized a given tissue whether experiments were performed under pressure or under tensile stress. However, the velocity constant of the relaxation decreased as a function of age for all three species during the period studied. Moreover, the velocity constant decreased at the same constant rate for skin samples of cats aged 1 to nearly 5 years, of rats aged from 9 to 28 months and of children from birth to 10 years. We propose a model, based on the well known rubber-elastic properties of the denatured collagen network. In this model (1) HIT decreases as an exponential function of time during bond scission along the polymeric chains; (2) the velocity constant of the relaxation process is proportional to the rate of bond rupture and inversely proportional to the number of stable polymeric chains originally present per unit volume; (3) the evolution of the velocity constant as a function of aging finds an explanation. The HIT test should find useful applications in pathology and pharmacology, since it provides rapid, precise information on the stable state of collagen reticulation in small biopsies.

Age Factors↗
PubMed1981

Lipid composition of two types of chondrocytes in primary culture.

Chondrocytes from articular and growth plate cartilage were grown in primary culture. The lipid content, distribution into different types, as well as the fatty acid patterns of these lipids were compared when the cells had reached stationary phase and were synthesizing maximal amounts of proteoglycans. Numerous significant differences were observed, depending on the origin of the chondrocytes. In particular, growth plate chondrocytes showed increased dry weight, increased lipid content (phosphatides and triglycerides), and decreased cholesterol to phosphatide ratio when compared to articular chondrocytes; they also incorporated more of C18:1 and less C16:0 into their major lipid types. Whether these differences arise from specific metabolic regulation or are a consequence of chondrocyte organization in primary culture remains unclear.

Animals↗
PubMed1981

[Tissular collagen polymerization (author's transl)].

The type of collagen reticulation exerts an influence on biological, physiological and mechanical properties of tissues, thus the utility of its study. Chemical techniques allow both localization and evaluation of levels and origin (Schiff base or aldol) of reducible bonds in collagen. Physical techniques allow evaluation of the thermolability or thermostability, as well as the degree of collagen reticulation in a given tissue for all collagen bridges. Results by these methods have shown that the mode of tissular collagen reticulation evolves from the embryonic phase to senescence, the rate varying as a function of the tissue and species of the donor. Thus, during tissular reparation, the newly formed collagen network itself undergoes transformations. Cicatricial tissue thus gives rise to an anisotropic zone in particular in terms of mechanical properties, in the organ. This can have grave pathological consequences. In addition to these wide areas of study, a certain number of specific diseases, frequently genetic, show pathological changes in collagen polymerization, the molecular mechanisms for which are now becoming better known.

Bone Diseases↗
PubMed1980

Normal lipid composition of fibroblasts from a case of type II achondrogenesis.

Fibroblasts from a case of achondrogenesis type II and fibroblasts from a normal control donor were subcultivated in vitro in parallel. The lipid study on these cells showed similar total lipid content, free cholesterol level, phospholipid distribution and fatty acid patterns, while neutral glycerides were slightly more elevated in the control fibroblasts. The histological finding of Laxova et al. (1973) could not be confirmed.

Achondroplasia↗
PubMed1980

Biochemistry and histology of the connective tissue of Dupuytren's disease lesions.

When compared to age-matched control aponeurosis, lesions of Dupuytren's disease contain higher contents of water, collagen and chondroitin-sulphate, as well as increased proportions of soluble collagens and of reducible cross-links; these indicate synthesis of new collagen. The lesions show also increased amounts of type III collagen and an increased hydroxylation and glycosylation of the reducible cross-links. All these parameters are characteristic of granulation and scar tissues. Type III collagen was located by means of immunofluorescence on thin argyrophilic fibres and also within the large fibre bundles which appeared to be disrupted into microbundles. The increase of type III collagen and the presence of myofibroblasts in the apparently unaffected aponeurosis show that the disease is widespread and suggest that it is initiated within the aponeurosis and propagated by the cells migrating along the collagen bundles.

Adult↗
PubMed1980

Isometric tensions developed during the hydrothermal swelling of rat skin.

Isometric tensions developed in connective tissue under the influence of temperature have previously been measured by their effect on a "shrinkage" phenomenon observed along the main axis of the collagen fibers. A new device, built and tested in our laboratory enabled us to obtain isometric tension curves by measuring a "swelling" phenomenon observed in other directions. Curves recorded in the two systems have been compared. Shapes were unchanged and the parameters chosen to define these morphologies showed the same values in both types of experiments. The parameters, which are independent of maximal tension, were also found to be independent of the total collagen content of the sample. Interpretation of the results suggests that these parameters depend not only on the nature but also on the density of the collagen crosslinks. The new device is applicable to minute tissue samples, whatever their fragility and fiber orientation.

Aging↗
PubMed1977

[Variations in the hydrothermic contraction of the rat skin as a function of the age of the animals].

The tension developed in Rat skin by hydrothermal shrinkage is modified with ageing of the animals: the temperature of maximum tension decreases from birth to 1 month, then very slowly increases with age. At higher temperatures than that of maximum tension a relaxation occurs very rapidly in young Rats and in not yet senescent adult skins. These modifications appeared to be related to those of the nature of the intermolecular collagen cross-links with ageing.

Aging↗
PubMed1976

Collagen and myofibroblasts of granulation tissue. A chemical, ultrastructural and immunologic study.

In granulation tissue produced in the rat by subcutaneous injection of turpentine oil or polyvynile sponge implantation, the great majority of fibroblasts (myofibroblasts) possess a contractile apparatus which makes them similar to smooth-muscle cells. Chemical analysis shows that these granulation tissues contain a high proportion of Type III collagen, a genetically distinct collagen normally associated with embryonic dermal tissue. Type III collagen may persist up to 9 months after sponge implantation and myofibroblasts are seen in granulation tissue by means of electron microscopy and immunofluorescence. When granulation tissue is resorbed 50 days after turpentine oil injection, myofibroblasts disappear and the dermis contains Type I collagen. The concurrent presence of myofibroblasts and Type III collagen suggests that myofibroblasts, in addition to their contractile activity, synthetize, at least in part, type III collagen.

Animals↗
PubMed1976

Collagen in granulation tissues.

Collagen is abundantly synthesized in granulation tissues and reaches a concentration higher than in normal neighbouring tissues. Such newly formed collagen is characterized by an abnormally low solubility and an easy degradation by collagenases and collagenolytic cathepsins. The activities of these two types of enzymes are high (especially collagenases) in tissues of acute inflammations when the granuloma is resorbing. These activities are lower in sub-acute inflammation and the collagen content of the persistent granuloma remains high. The collagen synthesized in granulation tissues is cross linked by hydroxylysino-5-keto-norleucine, the stable cross-link of collagen in embryonic skin. It is progressively replaced by the two aldimine cross links of normal adult skin when the granuloma is resorbed (acute inflammations induced in rats; human normal scars). The cross link of embryonic skin, on the contrary, is permanently present in collagen of tissues of subacute, chronic inflammations (sponge implants in rats, human hypertrophic scars and keloids. Studies of the structure of alpha-chains revealed that type III collagen (embryonic collagen) is present in granulation tissues.

Animals↗
PubMed1976

Urinary excretion of hydroxylysyl glycosides during acute inflammation in the rat.

1. Subcutaneous inflammatory granuloma were induced in young rats and the urinary excretion of hydroxyproline and hydroxylysyl glycosides was observed during the period of acute inflammation. 2. All collagen metabolites were increased in the urine and excretion of glucosyl-galactosyl-hydroxylysine was much greater than excretion of galactosyl-hydroxylysine in the first days. 3. It is argued that urinary glucosyl-galactosyl-hydroxylysine is probably derived from hydroxylysyl residues of soluble collagen. 4. This study affords new arguments in favour of the dermal origin of urinary glucosyl-galactosyl-hydroxylysine, at least in skin inflammation.

Acute Disease↗
PubMed1975

Collagen polymorphism in human scars.

Collagen similar to the collagen found in embryonic skin (same intermolecular cross-links and same structure of the polypeptide chains) is synthesized in young human scars. Later on, in normal scars, this collagen is replaced by the collagen of adult skin progressively. In contrast, in hypertrophic scars, a high proportion of collagen of "embryonic" type is present permanently. In granulation tissues of chronic inflammation, experimentally developed in rats, similar "embryonic" collagen has been found ; these granuloma are proposed as a model in laboratory animals of human hypertrophic scars.

Animals↗