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Biomedical subjects

F X Maquart

Publications and source records attributed to F X Maquart.

86 records · Page 5Linked to original sources
PubMed1980

Rates of DNA and protein syntheses by fibroblast cultures in the presence of various glucose concentrations.

Fibroblast cells derived from human derm used between the 5th and 10th passage and submitted to an increase of over 16.5 mM in the glucose concentration of the medium, react by a decrease in the incorporation of [3H] thymidine into DNA. The intracellular proline pool is largely increased by the rise in glucose concentration while the incorporation of [U-14C] proline into total proteins and proteins digested by purified bacterial collagenase is also significantly enhanced. There is no specific effect on collagen synthesis and the apparent activation of total protein synthesis may depend on the enhancement of the free proline pool.

Cells, Cultured↗
PubMed1978

[Microestimation of haemoglobins A2 and F by measurement of their peroxydase activity (author's transl)].

A microtechnique of evaluation for the haemoglobins A2 and F is presented, in which the final measurement is made more sensitive by evaluation of peroxidatic activity. Haemoglobin A2 is previously separated by chromatography on a very small column of DEAE cellulose and haemoglobin F is obtained through a microtechnique of alkaline precipitation. The sensitivity of this evaluation is increased by a factor of 20.25 microliter of hemolyzate are enough for a determination. Results obtained are in accordance with those given by the classical methods.

Fetal Hemoglobin↗
PubMed1978

[Hemoglobin A1c: a new factor in the supervision of diabetes (author's transl)].

Hemoglobin A1c is one of the minor components of normal human hemoglobin. It differs from Hb A by the presence of one molecule of glucose fixed to the N-terminal extremity of every beta chain. It is synthesized from Hb A by a very slow and only slightly reversible mechanism which continuously occurs during the 120 days of the red cell life. Hb A1c represents nearly 5% of total hemoglobin of the normal subject. In patients suffering of diabetes mellitus, its level seems to reflect closely the degree of equilibrium of the disease for 4 to 5 weeks which preceeded the evaluation.

Chemical Phenomena↗
PubMedDate not supplied

Matrikines in the regulation of extracellular matrix degradation.

The term "matrikines" was coined for designating peptides liberated by partial proteolysis of extracellular matrix macromolecules, which are able to regulate cell activities. Among these peptides, some of them may modulate proliferation, migration, protease production, or apoptosis. In this review, we summarize the activity of matrikines derived from elastin and interstitial or basement membrane collagens on the regulation of matrix metalloproteinases expression and/or activation, and on the plasminogen/plasmin system. Due to their activity, matrikines may play a significant role in physiological or pathological processes such as wound healing or tumor invasion.

Animals↗
PubMedDate not supplied

[Serum protein immunofixation in malignant hemopathies other than multiple myeloma and Waldenstrom's macroglobulinemia].

The interest of serum protein immunofixation in myeloma and Waldenstr m's macroglobulinemia is widely known. It is not so well defined in other malignant hemopathies. The purpose of this study was to determine immunofixation abnormalities in malignant hemopathies other than multiple myeloma and Waldenstr m's macroglobulinemia. We selected serum immunofixations of 61 patients affected by malignant hemopathies and 53 patients affected by other pathologies susceptible to give immunofixation's alterations. We showed that the frequency of immunofixation abnormalities was more important in patients affected by malignant hemopathies than in patients affected by other pathologies (70.5% vs 35.8%). A high frequency of monoclonal immunoglobulins was found in patients with lymphoma (53.3%) and oligoclonal immunoglobulins in other hemopathies (48.2%). No significant difference of the frequency of the monoclonal immunoglobulin isotypes was found. In summary, this retrospective study demonstrates a high frequency of immunofixation abnormalities in malignant hemopathies other than multiple myeloma and Waldenstr m's macroglobulinemia and different immunofixation characteristics between lymphomas and other hemopathies.

Aged↗
PubMedDate not supplied

[Aging mechanisms of proteins].

All the living molecules appear to suffer from the deleterious effects of aging, but the primary mechanisms of this inexorable evolution are still unknown. In the case of proteins, two major types of chemical reactions participate in the aging phenomena: 1) structural transformations induced by the addition of radicals by enzymic or non-enzymic reactions, 2) proteolytic cleavages. Among the reactions of the first group, the nonenzymatic glycation is the more generalized, not only in diabetic patients but also in non diabetic subjects. This glycation depends on the probabilities of encounters between circulating glucose molecules and free amino groups existing either at the N-terminal end of the polypeptide chains or on the lysyl side chains. These reactions are more frequent in the extracellular spaces and connective tissues because glucose circulates freely in these spaces, because the level of glucose is better controlled inside the cells (and even lower in diabetes mellitus), and finally because the proteins of these regions, such as the collagens, fibronectin and elastin, are relatively long lived, even if their life-span is really shorter than it was precedently believed. The binding of sugar residues to protein amino groups determines frequent modifications of structure that often make the molecule inactive. For instance, when a glucose unit binds to a lysyl radical located in the active center of an enzyme, it suppresses the activity of this enzyme. More generally, in the case of the connective tissue proteins that participate in complex supramolecular assemblies, the presence of additional radicals on some ponctual locations may interfere with the correct association of molecules. This is particularly true for basement membranes whose structure is impaired in diabetes. Glycation might also introduce abnormal cross-links between polypeptides or modify the antigenic power of some proteins and explain the formation of autoantibodies. Another property of glycated proteins is their reaction with oxygen leading to the formation of superoxide. The binding of a reducing sugar on an amino function is followed by an Amadori rearrangement that forms a ketol group. Ketols groups have the property to transmit electrons to molecular oxygen, and to forming superoxide radicals. Superoxide is capable of degrading only one protein: collagen, but it is also able to transform itself into hydrogen peroxide and hydroxyl radicals, which are far more toxic than O2-. The result of the formation of these oxygen free radicals from glycated proteins is the initiation of the degradation of several types of proteins, like the collagens.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMedDate not supplied

Glycation of proteins as a source of superoxide.

For the monitoring of diabetes mellitus, the concentration of serum glycated proteins is currently measured by a colorimetric reaction using the dye nitroblue tetrazolium. As this reduction may depend on superoxide ions (O2-), we checked whether glycated proteins were capable of generating O2- in vitro. We incubated ferricytochrome c with glucose, fructose, 1-deoxy-1-morpholino-D-fructose (an analog of the 1-desoxy-1-amino-fructose radical found in glycated proteins) and glycated proteins prepared from diabetic blood serum. We found that these substances, except free glucose, were all able to generate O2- not only at alkaline pH, but even at pH 7.4 with a slower rate. The possibility of O2- formation from glycated proteins may explain some long term complications of diabetes mellitus.

Blood Proteins↗
PubMedDate not supplied

[Molecular mechanisms of wound scarring].

A few years ago, the discovery of growth factors, their pharmaceutical obtention at a purified grade, their powerful effects on cells in vitro, resulted in demeasured hopes that they could be applied easily and successfully to the treatment of wounds. Now, the process of healing is still uncompletely understood. The interplay of epithelial and matrix cells, the multiplicity of cell types involved, the huge number of growth factors implicated and the difficulties in describing the specific timing of their action on the cells present in wounds, explain why therapy of wound has not yet been revolutioned. An important distinction must be made between normal healing, which leads to a solid functional, reparation tissue, and scarring which opposes any functional healing by making extensive granulation tissue or even keloids. Recent studies pointed out the necessity of a convenient balance between the concentrations of growth factors present in the wound during the different stages of healing. Excess connective tissue production (scarring) would be more particularly due to an excess of TGF beta 1, whereas predominance of TGF beta 3 conducts to harmonious healing.

Animals↗