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Biomedical subjects

E C Reynolds

Publications and source records attributed to E C Reynolds.

81 records · Page 5Linked to original sources
PubMed1982

Phosphoprotein inhibition of hydroxyapatite dissolution.

A chromatography column containing hydroxyapatite beads was used to study the effect of different proteins on the rate of hydroxyapatite dissolution. The four phosphoproteins tested (phosvitin, alpha sl-casein, beta-casein and kappa-casein) markedly reduced the rate of hydroxyapatite dissolution. Three nonphosphorylated proteins had a relatively smaller effect. The effect of the protein in reducing the hydroxyapatite dissolution rate has been attributed to protein binding to the surface of hydroxyapatite. The reduction in dissolution rate, expressed as the change in nmol calcium released per min per nmol of phosphoprotein bound to hydroxyapatite, increased with increasing number of phosphoserine residues of the protein. The results are consistent with the proposition that phosphoproteins have a regulatory role in mineralization processes and could provide a mechanism by which dietary and salivary phosphoproteins exert an anticariogenic effect.

Animals↗
PubMed1979

Deoxyribonucleoside triphosphate pools and differential thymidine sensitivities of cultured mouse lymphoma and myeloma cells.

The effects of various concentrations of thymidine on DNA synthesis and deoxyribonucleoside triphosphate contents of a highly thymidine-sensitive cultured mouse lymphoma cell line (WEHI-7) and a relatively resistant mouse myeloma cell line (HPC-108) have been studied by 32P-labelling techniques. DNA synthesis in the myeloma cells was inhibited by thymidine at concentrations of 10(-3) M or greater, while DNA synthesis in the lymphoma cells was inhibited by concentrations 30-fold lower, consistent with the 25-fold difference between the two cell lines in sensitivity to growth inhibition by thymidine. Thymidine caused marked elevation of the dTTP and dGTP pools, slight elevation or no change in the dATP pool and a marked decrease in the dCTP pool in cells of both lines. The greater resistance of HPC-108 cells to thymidine inhibition was related to the finding that they normally contained a much higher concentration of dCTP than did the WEHI-7 cells. Pool size measurements on thymidine-treated (10(-4) M) cells of an additional seven sensitive lymphoma and six relatively resistant myeloma cell lines indicated that in all 15 lines studied, with one exception, a critical concentration of dCTP of about 32 nmol per ml of cell volume was required for the maintenance of normal rates of DNA synthesis. The dCTP content found normally in the lymphoma cells was only a little above this concentration. Amongst the myeloma lines, three contained similarly low levels of dCTP, but were more resistant to thymidine inhibition probably because of their inefficient production of dTTP from thymidine. Cells of the other four myeloma lines (including HPC-108) normally contained much higher dCTP concentrations. The mechanism of thymidine action was explained by reference to the known allosteric properties of ribonucleotide reductase.

Animals↗
PubMed1979

Effect of thymidine on the sensitivity of cultured mouse tumor cells to 1-beta-D-arabinofuranosylcytosine.

Assays of thirteen cell lines, derived from mouse lymphomas, myelomas, myeloid tumors, and a mastocytoma, for sensitivity to growth inhibition by 1-beta-D-arabinofuranosylcytosine (ara-C) revealed a spectrum between the most and least sensitive which differed 100-fold from each other. An inverse correlation between sensitivity and cellular deoxycytidine 5'-triphosphate (dCTP) content was found, and this suggested that sensitivity of cells might be increased if the dCTP content was lowered during cell exposure to ara-C. Previous work has shown that thymidine treatment of cells lowers their dCTP content, and the effect of thymidine on the sensitivity of six of the cell lines to ara-C was therefore measured. Concentrations of thymidine below those inhibitory to cell growth by themselves caused an increase in ara-C sensitivity by up to 3-fold in 4 cell lines in which thymidine causes a depression in dCTP content but not in 2 myeloid lines in which the dCTP content was found not to be depressed by the same thymidine treatment. The results confirm an important role for dCTP in determining cellular sensitivity to ara-C. The finding that the sensitivity of 2 lymphoma cell lines to ara-C could be increased by concentrations of thymidine in the region of 10 micrometer, which are attainable clinically in humans, suggests that a combination of ara-C with thymidine might be useful in the treatment of some human tumors.

Cell Line↗
PubMedDate not supplied

Anticariogenic complexes of amorphous calcium phosphate stabilized by casein phosphopeptides: a review.

Using laboratory, animal, and human in situ caries models, investigators have shown that casein phosphopeptide amorphous calcium phosphate complexes (CPP-ACP) exhibit an anticariogenic activity. The casein phosphopeptides (CPP) are produced from a tryptic digest of the milk protein casein by aggregation with calcium phosphate and purification by ultrafiltration. The CPP have a remarkable ability to stabilize calcium phosphate in solution and substantially increase the level of calcium phosphate in dental plaque. Through their multiple phosphoseryl residues, the CPP bind to forming clusters of amorphous calcium phosphate (ACP) in metastable solution, preventing their growth to the critical size required for nucleation and precipitation. The proposed mechanism of anticariogenicity for the CPP-ACP is that they localize ACP in dental plaque, which buffers the free calcium and phosphate lon activities, thereby helping to maintain a state of supersaturation with respect to tooth enamel depressing demineralization and enhancing remineralization. The CPP-ACP, unlike fluoride, can be added to sugar-containing foods and therefore have commercial potential as an additive to foods as well as to toothpastes and mouthwashes for the control of dental caries.

Amino Acid Sequence↗
PubMedDate not supplied

Acid resistance of enamel subsurface lesions remineralized by a sugar-free chewing gum containing casein phosphopeptide-amorphous calcium phosphate.

The aim of this clinical study was to investigate the acid resistance of enamel lesions remineralized in situ by a sugar-free chewing gum containing casein phosphopeptide-amorphous calcium phosphate nanocomplexes (CPP-ACP: Recaldent). The study utilized a double-blind, randomized, crossover design with two treatments: (i) sugar-free gum containing 18.8 mg of CPP-ACP, and (ii) sugar-free gum not containing CPP-ACP as control. Subjects wore removable palatal appliances with insets of human enamel containing demineralized subsurface lesions and chewed the gum for 20 min 4 times per day for 14 days. After each treatment the enamel slabs were removed and half of each lesion challenged with acid in vitro for 8 or 16 h. The level of remineralization was determined using microradiography. The gum containing CPP-ACP produced approximately twice the level of remineralization as the control sugar-free gum. The 8- and 16-hour acid challenge of the lesions remineralized with the control gum resulted in 65.4 and 88.0% reductions, respectively, of deposited mineral, while for the CPP-ACP-remineralized lesions the corresponding reductions were 30.5 and 41.8%. The acid challenge after in situ remineralization for both control and CPP-ACP-treated lesions resulted in demineralization underneath the remineralized zone, indicating that the remineralized mineral was more resistant to subsequent acid challenge. The results show that sugar-free gum containing CPP-ACP is superior to an equivalent gum not containing CPP-ACP in remineralization of enamel subsurface lesions in situ with mineral that is more resistant to subsequent acid challenge.

Acetic Acid↗
PubMedDate not supplied

Adding casein phosphopeptide-amorphous calcium phosphate to sports drinks to eliminate in vitro erosion.

PURPOSE: Enamel erosion can occur with frequent consumption of sports drinks. The purpose of this study was to determine a minimal concentration of casein phosphopeptide-stabilized amorphous calcium phosphate (CPP-ACP) which when added to a sports drink would eliminate such erosion in vitro. METHODS: Human enamel specimens were immersed in: (1) the sports drink Powerade; (2) Poweradeplus 4 concentrations of CPP-ACP (0.063%, 0.09%, 0.125%, 0.25%); or (3) double deionized water. Windows of test and control enamel were profiled, and the enamel surface characteristics were examined under scanning electron microscopy (SEM). RESULTS: The pH of test solutions increased and the titratable acidity decreased with increasing CPP-ACP concentrations. Erosive step lesions occurred in specimens immersed in Powerade (mean depth=38.70kA +/- 5.60), which were eliminated by the addition of CPP-ACP to Powerade at all test concentrations except 0.063% CPP-ACP. Microscopic surface irregularities on test enamel were observed, apparent as adherent granules or globules. These may represent redeposited mineral phases following mobilization of calcium and phosphate from CPP-ACP. Tasters in a taste panel could not distinguish Powerade from Powerade plus 0.125% CPP-ACP. CONCLUSIONS: Adding casein phosphopeptide-stabilized amorphous calcium phosphate to the sports drink Powerade significantly reduced the beverage's erosivity without affecting the product's taste.

Analysis of Variance↗