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A B Belcourt

Publications and source records attributed to A B Belcourt.

12 recordsLinked to original sources
PubMed1983

Amelogenins. Sequence homologies in enamel-matrix proteins from three mammalian species.

Partial amino acid sequences for selected amelogenin polypeptides isolated from the developing enamel of cow, pig and human foetuses are reported. It was found that there was an identity of sequence for the initial 28 residues of the polypeptides analysed, irrespective of their origin or size. A tyrosine-rich polypeptide was shown to be the N-terminal fragment of the principal higher-molecular-weight amelogenins, although a leucine-rich polypeptide of similar size was not identified in any other amelogenin structure. The findings demonstrate a striking degree of sequence conservation for the amelogenin proteins of the extracellular enamel matrix and support the concept of a discrete fragmentation of an initial 30 000 Da amelogenin molecule during the mineralization of the enamel.

Amelogenin↗
PubMed1983

Bovine high molecular weight amelogenin proteins.

The existence of high molecular weight amelogenins in the matrix of developing fetal bovine dental enamel was investigated. After ion-exchange and gel filtration chromatography, a 40,000 dalton amelogenin protein has been isolated. This species was homogeneous on both guanidine hydrochloride gel filtration and sodium dodecyl sulfate (SDS) gel electrophoresis, but heterogeneous on conventional gel electrophoresis. This high molecular weight amelogenin may be a precursor to the complex of smaller sized amelogenins characteristic of the secretory phase of enamel formation.

Amelogenin↗
PubMed1983

Molecular composition of the protein matrix of developing human dental enamel.

The protein matrix of fetal human dental enamel was isolated and fractionated by chromatographic and electrophoretic procedures. Nine principal protein fractions were isolated and characterized. Possible inter-relationships of these proteins and their comparison with data from other species were examined. Significant differences between human proteins and those described for cow or pig enamel were identified.

Amino Acids↗
PubMed1982

Comparative protein biochemistry of developing dental enamel matrix from five mammalian species.

The matrix proteins of the developing dental enamel of five mammalian species were isolated and subjected to chromatographic, electrophoretic, and amino acid analyses. It was found that the principal chromatographic fractions showed similarities of both size and amino acid composition among species. The major amelogenin protein of the cow, hamster, human, and sheep was of about 30,000 daltons and of the pig enamel matrix about 20,000 daltons. In each species a higher molecular weight fraction, greater than 40,000 daltons, was detected. In the lower molecular weight range an amelogenin polypeptide enriched in leucine, a fraction rich in tyrosine, and a fraction of intermediate size (Bovine matrix "Component-14") were identified in each case. It is suggested that these characteristic proteins arise during the degradation of the matrix which accompanied mineralization.

Amelogenesis↗
PubMed1981

Mineral and collagen-binding proteins of fetal calf bone.

Subperiosteal fetal calf bone is subjected to sequential dissociative extraction in the presence of protease inhibitors first with guanidine HCl and then with guanidine HCl/EDTA. Over two-thirds of the total noncollagenous protein is recovered in the second extraction step, which operationally solubilizes proteins associated with the apatite of mineralized bone lamellae. Three new proteins, comprising over 40% of the fetal bone noncollagenous protein, are purified from the second extract by gel filtration in 4 M guanidine HCl and ion exchange in 7 M urea. These are two glycoproteins both containing organic phosphate at apparent molecular sizes of 32,000 and 62,000 daltons and a protein of 24,000 daltons containing both hydroxyproline and organic phosphate. Of these three proteins, the Mr = 32,000 species binds to apatite and collagen with the greatest affinity. It comprises 25% of the fetal calf bone noncollagenous protein and is selectively adsorbed both by apatite crystals in 4 M guanidine HCl and on gelatin affinity columns at physiological pH and ionic strength.

Amino Acids↗
PubMed1981

Dental enamel matrix: sequences of two amelogenin polypeptides.

The amino acid sequences of a leucine-rich amelogenin polypeptide (LRAP) and a tyrosine-rich amelogenin polypeptide (TRAP), isolated from foetal bovine enamel matrix, were determined. Both LRAP and TRAP occurred in two forms; in each case, one of the molecular species appeared to be shortened at the COOH terminus by 2 and 4 residues, respectively. A striking finding was that LRAP and TRAP had identical sequences for the first 33 residues but were almost completely different for the remaining 12 amino acids.

Amelogenin↗
PubMed1980

Properties of dissociatively extracted fetal tooth matrix proteins. I. Principal molecular species in developing bovine enamel.

A sequential dissociative extraction scheme is described in which tooth matrix proteins are extracted first in 4 M guanidine HCl, pH 7.4, and then in 4 M guanidine HCl, 0.5 M EDTA, pH 7.4, both with protease inhibitors present. The latter step dissolves the mineralized portion of the tissue and extracts noncollagenous proteins closely associated with hydroxyapatite crystallites in the mineralized matrix. In fetal bovine enamel, the initial dissociative extraction step completely removes proline-rich amelogenins from the tissue without dissolving the enamel apatite. The amelogenin proteins consist of several species on polyacrylamide gel electrophoresis with sodium dodecyl sulfate, but display anomalous migration behavior relative to conventional marker proteins in this technique. Subsequent extraction of fetal bovine enamel with guanidine HCl/EDTA removes matrix enamelins, acidic glycoproteins that are tightly bound to the enamel hydroxyapatite. This latter fetal protein type has not been isolated previously. The enamelins are adsorbed strongly by DEAE-cellulose in 7 M urea and totally adsorb to synthetic apatite, even in 4 M guanidine HCl. The enamelins display normal behavior on polyacrylamide gels and stain positively for sialic acid/phosphate and carbohydrate. With advancing tooth maturation, amelogenins disappear while enamelins are conserved. Gel filtration chromatography in 4 M guanidine HCl showed amelogenin components at apparent molecular weights of approximately 25,000, 15,000, 9,500, 7,500, and 6,000, while the enamelins eluted at Mr positions of approximately 72,000, 56,000, 42,000, 30,000, 21,000, 13,000, and 8,000. The gel filtration data showed a clear shift in molecular size population from higher to lower components for both amelogenins and enamelins with progressive enamel maturation.

Amino Acids↗
PubMed1980

Properties of dissociatively extracted fetal tooth matrix proteins. II. Separation and purification of fetal bovine dentin phosphoprotein.

After an initial 4 M guanidine HCl extraction to remove enamel contaminants, subsequent guanidine HCl/EDTA extraction of fetal bovine molar dentin removes almost all of the high molecular weight phosphoprotein from the tissue in a single step. The fetal bovine dentin phosphoprotein is then purified by a series of ion exchange (DEAE-cellulose or DEAE-Se-phacel) and gel filtration (Sepharose CL-6B) chromatographic steps, all under denaturing elution conditions in 7 M urea (ion exchange) or 4 M guanidine HCl (gel filtration). The final purified phosphoprotein product was chromatographically and electrophoretically homogenous. The apparent molecular weight for this fetal bovine dentin phosphoprotein was approximately 100,000 both by 4 M guanidine HCl gel filtration and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. This value is considerably higher than those previously reported for any other dentin phosphoprotein preparation. Roughly half of the total serine residues in the protein were phosphorylated and these residues together with aspartic acid comprised approximately 80% of the total polypeptide backbone. The purified fetal bovine dentin phosphoprotein was also glycosylated, containing approximately 6 galactosamine, 2 to 3 glucosamine, and 2 to 3 sialic acid residues/mol.

Amino Acids↗
PubMedDate not supplied

Biochemical study of whole saliva from children with chronic renal failure.

The biochemical composition of unstimulated whole saliva was studied on ten children suffering from chronic renal failure and who, at the same time, displayed a very low caries activity. Various salivary components were studied before (T) and after (To) dialysis and were compared with similar elements of a control group, as well as with blood values. A mean salivary urea concentration of 513 +/- 210 mg/100 ml was found prior to dialysis, whereas after treatment this value dropped to 241 +/- 82 mg/100 ml, about twice as much as in the control group, 110 +/- 48 mg/100 ml. The mean urea concentrations in blood at T and To were respectively 196 +/- 38 mg/100 ml and 53 +/- 22 mg/100 ml. The various free amino acids in the whole saliva of these patients showed different changes in their concentrations as a result of dialysis, with the basic amino acids being considerably increased. Blood electrolytes remained close to the normal range, although calcium was depleted and magnesium lowered by a factor of 10 when compared before and after dialysis, as well as versus the control group.

Adolescent↗