Biomedical subjects
Publications and source records attributed to A Randoux.
A fraction of structural glycoproteins (SGP) extracted from rabbit dermis exerted a concentration-dependent inhibition on the multiplication of normal dermal fibroblasts and of mouse sarcoma fibroblastic cells CCRF S-180 II. The inhibition was fully reversible when the SGP was eliminated from the culture medium.
Human red blood cells (RBC) are separated by centrifugation into young and old ones, as demonstrated by lower enzymatic activities and lower potassium content of the older ones. The young RBC fraction represents 5% of total RBC. After incubation for 24 h in a neutral buffer, the young RBC HbA1c content increases significantly from 4.2 to 5.2% of total Hb. No increase is found in the case of old RBC. When young RBC have been extracted for 1 h by a neutral buffer prior to incubation, there is no more increase of HbA1c. The extract contains a glycoconjugate that is both soluble in neutral buffers and in chloroform. A glycolipid extractable from the young RBC membrane contributes to HbA1c formation but disappears from old RBC, in which glycosylation by free glucose occurs. These processes are stereospecific.
Fibrils of collagen reconstituted in vitro by dialysis against sodium formate are exposed to free oxy radicals generated by three different systems: (i) xanthine oxidase + hypoxanthine, (ii) gamma-rays originating from a cobalt bomb; (iii) pulse radiolysis in a particle accelerator. A degradation of the collagen fibres is demonstrated by determination of the amount of hydroxyproline-containing peptides in the supernatant after incubation. Types I and III collagen are sensitive to the effect, whereas type V collagen is not. The effect persists when collagen is specially delipidated.
This paper summarizes the results of hormonal studies applying to collagen metabolism that were published during the last 10 years. This general review demonstrates that most of the hormones, when they act on this metabolism, either decrease the amount of synthesized collagen or increase its catabolism. This effect is demonstrated on whole living animals, in isolated organs, in pathological cases such as corticosteroid induced osteoporosis, and more directly in cell cultures. At physiological levels, some of the effects may be slight or biphasic but at pharmacological levels glucocorticoids and estrogens are strongly inhibiting. These inhibiting effects may be ascribed to various stages of collagen biosynthesis: transcription of the genes, translation of mRNA, post-translational reactions, that are particularly developed in the case of collagen and particularly sensitive to the hormone action. Intracellular degradation of collagen represents an important way of control for this biosynthesis and is noticeably activated by the system of cAMP and some prostaglandins. Finally, collagenases acting on the extracellular fibrils are stimulated by several groups of hormones such as thyroid hormone, testosterone, parathyroid hormone. This increase in catabolism acts in the sense of a fast decrease in the amount of collagen, confirming that most of the hormonal systems are aimed at decreasing both the synthesis of new collagen and the number of mature fibers existing in a given connective tissue. On the other hand, many growth factors and several hormones such as insulin and somatomedins are able to activate the mitoses in the cells that are know to produce collagen, and for this reason, indirectly stimulate the synthesis of this fibrous protein. It is of interest to point out that every time the organism needs depositing more collagen in any zone of the extracellular matrix, it has to send mobile cells from other tissues or to activate the divisions of the cells already present in the concerned tissue. This process is particularly conspicuous in the case of inflamed tissues. It is proposed as a general rule that decreases in the collagen amounts may be triggered by very fast hormonal mechanisms acting both to stop biosynthesis and to activate degradation, whereas the increase in collagen layering depends on indirect and slow mechanisms in which cell divisions represent the first event.
During the course of diabetes mellitus, several lines of evidence demonstrate that connective matrix is involved. This relationship is still ambiguous and the biological techniques of study are more related to research than to routine. Skin biopsy followed by cultivation of the fibroblasts permits to demonstrate that the diabetic cells divide more slowly than the normal ones. The collagens of the diabetic patients do not seem to be modified according to any genetical abnormality. The evaluation of serum collagens and procollagens by radioimmunological techniques recently showed that the type IV collagen, which derivates from basement membranes, should be in increased amount. In the case of experimental diabetes, in animals, the skin collagen concentration is decreased whereas the amount of intermediate degradation products increases. The method of skin collagen evaluation is not used for clinical purposes and the degradation products found in human diabetic urine are not in increased amounts. The thickening of basement membrane is a well established phenomenon in the diabetes mellitus patients, but the chemical nature of the lesions is not well understood. A non-enzymatic hyperglycosylation of collagen and the other molecules of the basement membrane is possible but does not explain completely this thickening on a quantitative basis, inasmuch that hemoglobin glycosylation, that serves as a model for all the nonenzymatic glycosylations, is presently under discussion as regards its mechanism and seems more complicated than previously suggested.(ABSTRACT TRUNCATED AT 250 WORDS)
Explore the source record for details and available documents.
Calf skin acid-soluble collagen in microfibrillar form was incubated with free oxygen radicals produced by the system xanthine oxidase + hypoxanthine. This incubation liberated peptides of a size smaller than that of alpha-chains, as demonstrated by SDS-PAGE and by evaluation of the 4-hydroxyproline contained in small peptides. The amount of liberated peptides was found to increase with time. The process was inhibited by addition of superoxide dismutase to the medium but not by addition of catalase. Two flavonoids extracted from bilberries and a third one from grapes were demonstrated to protect collagen against this non-enzymatic proteolytic activity. This work confirms that collagen may be degraded during the process of inflammation and that some flavonoids are endowed with protective properties.
It was demonstrated in a previous paper that the sulfation activity of somatomedin A (SM-A) depends on the presence of a low molecular weight cofactor (CoF) present in human serum. In this paper, the effects of the two factors on human dermis fibroblast proliferation and syntheses of proteins and collagen were studied. The addition of SM-A alone to the culture medium had no mitogenic effect but modified the distribution of newly synthesized proteins, since 14C-proline incorporation was increased into proteins of the cell layer and decreased into proteins of the medium. The addition of CoF alone had no significant effect. Simultaneous addition of SM-A and CoF restarted cell divisions and increased the inhibiting activity of SM-A on the secretion of proteins into cell supernatant.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Red blood cell (RBC) membranes are rich in a glycoconjugate that is extractable in chloroform/methanol solutions (2/1, v/v) and contains several hexoses, such as glucose. Old and young RBC are separated and their respective glycoconjugates are prepared. HbA0 is purified by column chromatography and incubated with solutions of this conjugate. After 24-h incubation, Hb is dialyzed and the amount of glycosylated Hb is measured by a method of column chromatography adapted from Trivelli. A very significant amount of HBAlc is formed when young RBC extracts are incubated: 3.6% of total Hb becomes HBAlc with the extracts, versus 3.2% with free glucose, and only 2.5% for controls. No increase in HbAlc is obtained when extracts of old RBC are incubated. Another difference between the action of the glycoconjugate and free glucose is that the former induces the increase of only the HBAlc fraction, whereas glucose induces the increase of all the minor Hb fractions. The evaluation of glucose contained in the conjugate before and after the glycosylation reaction demonstrates that it is due to an exchange of glucose units from the conjugate to Hb. The reaction is stereospecifically inhibited by p-nitrophenyl-beta-D-glucoside. The nature of the formed HbAlc is demonstrated by isoelectric focusing. A slight increase of HbAlc observed in the incubated controls may be due to an internal migration of some residues of glucose primitively bound to lysyl residues in an unstable form and also to some degree of denaturation during the incubation.
Explore the source record for details and available documents.
The renal excretion of 3 hydroxyproline (3 HYP) and 4 hydroxyproline (4 HYP) was investigated in control subjects and in patients with various renal diseases. In normal adult subjects urinary 3 HYP was 12.5 +/- 3.5 (SD) mumoles/24 hr, 4 HYP was 226 +/- 62 mumoles/24 hr and the percentage ratio 3 HYP/4 HYP 5.4 +/- 0.5. This ratio was reduced during growth because of a relative excess of 4 HYP. In patients with acute glomerular disease (n = 12) 3 HYP was increased to 17.1 +/- 5.8 mumoles/24 hr (P less than 0.01), and the ratio 3 HYP/4 HYP was 7.3 +/- 0.7% (P less than 0.01). Such an increase in 3 HYP was not observed in patients with chronic glomerulonephritis (n = 24) where 3 HYP was 9.6 +/- 5.0 mumoles/24 hr and 3 HYP/4 HYP 5.7 +/- 1.6% or with diabetic glomerulopathy (n = 6). In patients with chronic interstitial nephritis (n = 8) the 3 HYP/4 HYP ratio was decreased except in patients with polycystic renal disease (PKD) where it was increased (P less than 0.001). The daily urinary content of 3 HYP and 4 HYP was slightly altered by renal insufficiency. Urinary 3 HYP did not change significantly in patients with GN with the nephrotic syndrome whatever the histological lesion. These results indicate that urinary 3 HYP: 1) is increased when glomerulonephritis is clinically acute or subacute; 2) is increased in PKD whatever the level of renal insufficiency.
Samples of human Common Iliac Arteries, obtained post-mortem from patients without evidence of atherosclerosis, were analyzed for their content in the various types of collagens using alternatively sonication, pepsin digestion and dithiothreitol reduction followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis of the extracts. A final average proportion of 66% of the total collagen was solubilized. The statistical calculation of the proportions of the different collagens, deduced from the densitometric scannings of the electrophoretic runs, showed that a larger amount of type I was extracted when the extraction was more complete. Type I collagen appeared as the most insoluble collagen in these arteries and its final proportion was probably higher than 60% of the total collagen.
Explore the source record for details and available documents.
A technique using alternatively dithiothreitol reduction, sonication and pepsin digestions permits the extraction of 75% of the insoluble collagen from human common iliac arteries. The pattern of the collagen types obtained by acrylamide gel electrophoresis is far different from that of the aortic wall: type I averages 44 +/- 14% of the total, type III 48.5 +/- 14% and a supplementary fraction, probably belonging to type V, 9 +/- 5% of the total in females and 6 +/- 2% in males.
A fully automatic method permits fractionation in a Biogel P2 column of the hydroxyproline-containing peptides into two fractions. The alkaline hydrolysis and the colorimetric evaluation of the liberated hydroxyproline are also completely automatic and allow calculation of the percentages of the two fractions. The first one, termed F1 fraction, contains the peptides of molecular weight larger than 1500, while the other, termed F2, contains the smaller peptides. The method was used for 223 assays. The F1 fraction is decreased in cases of Paget's bone disease. It is increased in cases of metastatic cancer of bone. Statistical analysis of the data demonstrates that this techique greatly improves the certainty of diagnosis when coupled to the assay of total hydroxyproline. When both total urinary hydroxyproline and the F1 fraction percentage are increased over threshold values of 485 mumol per 24 h and 28.4% respectively, the probability of the presence of a bone metastasis is 100%.
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.