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Biomedical subjects

M Adam

Publications and source records attributed to M Adam.

At least 163 records · Page 9Linked to original sources
PubMed1986

Evidence for a pool of non-recycling transferrin receptors in peripheral sheep reticulocytes.

Sheep reticulocytes from phlebotomized animals have a total transferrin binding potential that may exceed by an order of magnitude the surface binding capacity. Steady state uptake of transferrin at 37 degrees C is generally less than 50% of the total transferrin binding capacity. During long-term incubation of the reticulocytes, all transferrin binding ability is lost, the ability to internalize being lost most rapidly. The loss in ability to bind transferrin during long-term incubation is independent of the number of surface transferrin binding sites, since removal of surface receptors with pronase does not affect the rate of loss of the internal pool of receptors during long-term incubation. Moreover, after removing surface receptors with pronase, only a fraction of the original number of receptors is restored to the surface, despite the presence of a large pool of internal receptors. These data suggest that only a fraction of the internal pool of receptors is capable of recycling to the cell surface in sheep reticulocytes.

Animals↗
PubMed1986

Monosaccharide composition of lipopolysaccharides from Campylobacter jejuni and Campylobacter coli.

The monosaccharide composition of the LPS from 5 Campylobacter jejuni strains and 7 Campylobacter coli strains has been studied. All LPS's contained KDO, heptose, glucosamine, glucose, and (with one exception) galactose. All C. jejuni and 3 C. coli LPS's contained greater than 1% galactosamine. 3-Amino-3.6-dideoxyglucose was present in all but one C. coli LPS and in only one C. jejuni LPS.

Campylobacter↗
PubMed1986

Determination of larger urinary peptides in osteoarthrosis by high-performance liquid chromatography.

Urinary peptides larger than 4000 were fractionated by HPLC on reversed phase. Urines of osteoarthrotic patients were compared with those of healthy persons and rheumatoid patients. The profile of urinary peptides of patients with mild form of osteoarthrosis differed significantly from that of other groups studied. The results of patients with rheumatoid arthritis were similar to those of patients with activated or severe form of osteoarthrosis.

Adult↗
PubMed1985

Poly(2-hydroxyethyl methacrylate)--collagen composites which promote muscle cell differentiation in vitro.

A new simple method has been developed which allows the mixing of poly(2-hydroxyethyl methacrylate)--polyHEMA--and fibrillar collagen in any desired ratio. PolyHEMA alone was shown to be an unsuitable cultivation substrate for primary cultures of chicken embryonic skeletal muscle cells. Composites containing polyHEMA and 50% (w/w) or more collagen supported myogenesis. Such layers, firmly adhered to the bottom of plastic Petri dishes, were mechanically stable and biologically active, thus favourably combining properties of both the original materials. It is suggested that polyHEMA-collagen composite layers may be used for cultivation of differentiating cells in vitro.

Animals↗
PubMed1985

Electron microscopic evidence for externalization of the transferrin receptor in vesicular form in sheep reticulocytes.

Using ferritin-labeled protein A and colloidal gold-labeled anti-rabbit IgG, the fate of the sheep transferrin receptor has been followed microscopically during reticulocyte maturation in vitro. After a few minutes of incubation at 37 degrees C, the receptor is found on the cell surface or in simple vesicles of 100-200 nm, in which the receptor appears to line the limiting membrane of the vesicles. With time (60 min or longer), large multivesicular elements (MVEs) appear whose diameter may reach 1-1.5 micron. Inside these large MVEs are round bodies of approximately 50-nm diam that bear the receptor at their external surfaces. The limiting membrane of the large MVEs is relatively free from receptor. When the large MVEs fuse with the plasma membrane, their contents, the 50-nm bodies, are released into the medium. The 50-nm bodies appear to arise by budding from the limiting membrane of the intracellular vesicles. Removal of surface receptor with pronase does not prevent exocytosis of internalized receptor. It is proposed that the exocytosis of the approximately 50-nm bodies represents the mechanism by which the transferrin receptor is shed during reticulocyte maturation.

Animals↗
PubMed1984

In vitro acylation of the transferrin receptor.

In vitro fatty acylation of the transferrin receptor with [3H]tetradecanoate or [3H]tetradecanoyl-CoA has been demonstrated for isolated sheep reticulocyte plasma membranes. Although less than 5% of the receptor was labeled in vitro, the acylated protein could be readily observed after sodium dodecyl sulfate-gel electrophoresis. The acylated transferrin receptor in the reticulocyte membrane was specifically precipitated with a monoclonal antibody and was absent from mature red cell membranes. Incorporation of fatty acid was dependent on ATP, and fatty acid was 5-10 times less effective as an acyl donor than the acyl-CoA derivative, pointing out the strong potential of this reagent for in vitro acylation of membrane proteins. During in vitro maturation of reticulocytes, the receptor is released in vesicles into the incubation medium. Using reticulocytes labeled with [3H]tetradecanoate, it can be shown that the 3H-labeled receptor is transferred from the cells to the vesicles without loss of acyl groups, suggesting that the vesiculation process does not involve deacylation.

Acyl Coenzyme A↗
PubMed1984

Degenerated annulus fibrosus of the intervertebral disc contains collagen type II.

Collagen has been isolated and purified from the pronase digest of the outer annulus fibrosus of degenerated and unaffected intervertebral discs obtained at necropsy. The mixture of different collagen types has been purified and fractionated by 2 subsequent DEAE-cellulose chromatographic procedures according to established methods. Collagen chain polymers were then isolated by molecular sieving. Their reduction with 2-mercaptoethanol followed by agarose chromatography resulted in the separation of 3 major peaks corresponding to gamma, beta, and alpha chains. Cyanogen bromide (CNBr) peptides and aminoacid analyses revealed the identity of the isolated alpha-chain as alpha 1(III). Further support for this finding was obtained by immunofluorescence. It is suggested that the presence of collagen type III in the outer annulus fibrosus may be related to intervertebral disc prolapse.

Aged↗
PubMed1984

Phosphorylation of the transferrin receptor in isolated sheep reticulocyte plasma membranes.

The transferrin receptor of sheep reticulocyte plasma membranes undergoes phosphorylation with [gamma-32P]ATP in isolated plasma membranes. The phosphorylation is stimulated by Mn2+, Co2+, and Mg2+, but not by Ca2+, Ba2+, Zn2+, Fe2+, or Cu2+. There is no detectable effect of cyclic nucleotides on the phosphorylation of the receptor. Transferrin and a monoclonal antibody against the transferrin receptor have no apparent effect on receptor phosphorylation in intact cells or isolated membranes. Immunoprecipitates of the receptor retain ability to phosphorylate the receptor. The phosphorylation appears to be at a serine residue which turns over with a half time of 20-30 min. ATP appears to be the best, but not the only substrate for receptor phosphorylation.

Amino Acids↗
PubMed1984

The fate of the transferrin receptor during maturation of sheep reticulocytes in vitro.

The transferrin receptor of sheep reticulocytes is excised from the cell during in vitro maturation to erythrocytes. The excised receptor may be recovered from the medium by centrifugation at 100 000 X g. Loss of transferrin-binding activity parallels the loss of binding of anti-receptor antibody, as well as RNA content. The released receptor retains the molecular size of the receptor isolated from the plasma membranes (93 000 monomer, 186 000 dimer), has an identical iodotyrosyl peptide map, and is still capable of binding transferrin, as well as an antibody directed against the receptor. The receptor is released in a vesicular form. The major peptides of the vesicles are the receptor and an unidentified peptide of 70 000 whose iodotyrosyl peptide map is distinct from that of the receptor. Although the transferrin receptor has been shown to undergo posttranslational modification (phosphorylation, acylation, and glycosylation) in cultured cells, it has not been established whether any of the transformations are retained in nongrowing cells. In the present communication, it is shown that isolated reticulocyte plasma membranes are capable of receptor phosphorylation, a process previously shown only with intact, cultured cells. The phosphorylating activity is retained in immunoprecipitates of the receptor, but is absent in the vesicles released during maturation. No evidence has been obtained for an effect of either transferrin or an anti-receptor antibody on receptor phosphorylation in intact cells or isolated membranes.

Animals↗
PubMed1984

Effect of glycosaminoglycan polysulphate on the metabolism of cartilage ribonucleic acid.

The effect of glycosaminoglycan polysulphate (GAGPS, Arteparon) on the metabolism of cartilage ribonucleic acid (RNA), collagen, and proteoglycan was studied. GAGPS stimulated the synthesis of collagen and the both components of proteoglycan. The effect of GAGPS on RNA was compared with those of chondroitin sulphate and heparin. All three investigated substances enhanced the RNA synthesis, GAGPS, however, had a comparable effect in concentrations ten times smaller.

Animals↗
PubMed1984

Changes in collagen metabolism--another look at osteoarthrosis.

Collagen types I and III were isolated from osteoarthrotic cartilage. Immunofluorescence study has shown that these two collagen types are present in the deep layers of cartilage. Additional staining for fibronectin revealed the presence of the cell-adhesive protein in osteoarthrotic cartilage. Neither collagen type I and type III nor fibronectin were found in control cartilage. A passive haemagglutination assay determined anticollagen antibodies (against types I, II and III) in sera of some osteoarthrotic patients.

Cartilage, Articular↗
PubMed1984

Application of enzyme immunoassays to coagulation testing.

Enzyme immunoassays are very useful for the detection of low concentrations of coagulation proteins and pathological markers in plasma. Analytes in the ng/mL range are measurable with good reproducibility with intra- and interassay CVs of less than 5% to 10%. "Sandwich" methods have been developed for von Willebrand factor (plasma concentration about 8 micrograms/mL, Factor IX (5 micrograms/mL), protein C (4 micrograms/mL), and Factor X (10 micrograms/mL). However, this technique is only suitable for macromolecules; for low-molecular-mass peptides such as fibrinopeptide A a competitive method is used. Normal concentrations of fibrinopeptide A are below 3 ng/mL, with greater values suggesting in vivo generation of thrombin; thus this test is quite useful in detecting thrombosis. Reagents for both the sandwich and competitive methods are commercially available and cost effective, and have a longer shelf-life than those for radioimmunoassays.

Binding, Competitive↗
PubMed1983

[Antidigoxin Fab-fragments in suicidal digoxin poisoning. Successful treatment of recurrent ventricular fibrillation].

A 49-year-old woman took about 12.5 mg digoxin with suicidal intent. Severe arrhythmias, including recurrent ventricular fibrillation, occurred. Sheep Fab fragments of digoxin-specific antibodies were administered i. v. at a dose of 480 mg. Serum free-digoxin concentration fell within half an hour to 0, with simultaneous rise of total digoxin from 13 micrograms/l to a maximum of 176 micrograms/l after 2 hours. At the same time there was marked improvement in the clinical condition with restoration of a stable sinus rhythm. There were no side effects to the Fab fragment administration.

Antibodies↗
PubMed1983

Altered expression of collagen phenotype in osteoarthrosis.

Immunofluorescence studies have shown the presence of collagen type III in addition to types I and II in osteoarthrotic cartilage. The presence of collagen type III was verified biochemically: collagen was isolated and purified from the pronase digest of osteoarthrotic cartilage. Mixtures of different collagen types were fractionated first by two different DEAE-cellulose runs and then the collagen polymers were isolated by molecular sieve chromatography. Afterwards the collagenous material was reduced, Alkylated, and rechromatographed on an agarose column. Three major peaks corresponding to gamma-, beta- and alpha-chains were observed. Amino acid analyses and the CNBr peptide pattern indicated the identity of the alpha peak as alpha 1 (III). Additional staining of control and disease cartilages for fibronectin revealed the presence of this protein in the diseased tissue.

Bone Diseases↗
PubMed1983

Evidence for vitamin D dependent gamma-carboxylation in osteocalcin related proteins.

The content of gamma-carboxyglutamic acid (gla) was determined in rat femoral bone and kidney cortex in rachitic and vitamin D treated animals. It was demonstrated that the level of gla is decreased in vitamin D depleted animals both in kidney cortex and femoral bone. Supplementation of vitamin D deprived animals with this vitamin resulted in an increase in the gla concentration to almost normal levels. Also the incorporation of 14C NaHCO3 in renal cortex microsomes from rachitic animals was blocked. It is suggested that the absence of gla resulted from the direct action of vitamin D on mRNA for the Ca-binding protein.

1-Carboxyglutamic Acid↗