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Biomedical subjects

P R Stone

Publications and source records attributed to P R Stone.

At least 37 records · Page 2Linked to original sources

Comparison of glucose polymer and glucose for screening and tolerance tests in pregnancy.

Forty-eight of 100 pregnant women received a 100-g (nonfasting) glucose screening test at about 28 weeks' gestation, followed by a 100-g glucose tolerance test. Another 52 received a 100-g (nonfasting) glucose polymer screening test followed by a 100-g glucose polymer tolerance test. Mean plasma glucose one hour after the glucose screening test was significantly lower than after the glucose polymer screening test. A further 178 women received a glucose polymer screening test and a glucose polymer tolerance test (230 in total). These women and the infants they delivered were studied to derive diagnostic criteria for the 100-g glucose polymer tolerance test by correlating maternal carbohydrate tolerance with indexes of neonatal metabolic performance, and to determine an adequate method of screening for carbohydrate intolerance of pregnancy (gestational diabetes). Diagnostic criteria similar to those of O'Sullivan and Mahan were also developed for the glucose polymer tolerance test. These values are up to 5% lower than those recommended by the National Diabetes Data Group (1979) for the 100-g glucose tolerance test.

Adult↗

Comparison of glucose and a glucose polymer for testing oral carbohydrate tolerance in pregnancy.

Forty-six pregnant patients with potential diabetes were studied to compare the use of glucose and a glucose polymer for carbohydrate tolerance testing. The first 26 patients had a glucose tolerance test and a glucose polymer tolerance test in randomized order an average of one week apart. The mean tolerance curves and insulin curves were similar for both agents. Patients preferred glucose polymer to glucose because of a lower incidence of associated nausea. A second group of 20 patients was randomly divided so that patients had two glucose tolerance tests or two glucose polymer tolerance tests an average of one week apart. Comparison of the variability and correlation of the incremental areas under the paired tolerance curves showed that the reproducibility of the glucose polymer tolerance test exceeded that of the glucose tolerance test.

Administration, Oral↗

Effect of DNA on poly (ADP-ribose) glycohydrolase and the degradation of histone H1-poly (ADP-ribose) complex from HeLa cell nuclei.

A poly(ADP-ribose)-H1 histone complex has been isolated from HeLa cell nuclei incubated with NAD. The rate of poly(ADP-ribose) glycohydrolase catalyzed hydrolysis of the polymer in the complex is only 1/9 that of free poly(ADP-ribose), indicating that the polymer is in a protected environment within the complex. Comparison of the rate of hydrolysis of free poly(ADP-ribose) in the presence or absence of H1 to that in the complex synthesized de novo indicates a specific mode of packaging of the complex. This is further indicated by the fact that alkaline dissociation of the complex followed by neutralization markedly exposes the associated poly(ADP-ribose) to the glycohydrolase. The complex also partially unfolds when it binds to DNA as evidenced by a 2-fold increase in the rate of glycolytic cleavage of poly(ADP-ribose). This effect of DNA is not due to a stimulation of the glycohydrolase per se since hydrolysis of free polymer by the enzyme is strongly inhibited by DNA, especially single-stranded DNA. Inhibition of glycohydrolase by DNA results from the binding of the enzyme to DNA and conditions which decrease this binding (increased ionic strength or addition of histone H1 which competes for DNA binding) relieve the DNA inhibition.

Cell Nucleus↗

Properties of the complex between histone H1 and poly(ADP-ribose synthesised in HeLa cell nuclei.

Preparations of H1 histone from HeLa cell nuclei incubated with [3H]NAD to permit poly(ADP-ribose) synthesis were electrophoresed on polyacrylamide gels. The incorporated radioactivity migrated as a sharply defined peak in association with a protein band which moved more slowly than H1, the major protein component. The following observations indicate that this complex is composed of two molecules of H1 and a single chain of poly(ADP-ribose) with one detectable covalent linkage of polymer to protein. 1. The [14C]arginine/[3H]lysine ratio is identical in H1 histone and in the protein moiety of the complex. 2. Protein is displaced from H1 histone to the complex during poly(ADP-ribose) synthesis. At least 90% of the protein in the complex (stainable protein and labelled protein) is derived from H1. 3. Sedimentation rate studies indicate a molecular weight of the complex about twice that of H1 histone. 4. The average chain length of the polymer is 15 ADP-ribose units and there are 7--8 ADP-ribose units for each molecule of H1 histone in the 'complex'. 5. Poly(ADP-ribose) glycohydrolase, which hydrolyses the polymer exoglycosidically from the AMP terminus, degrades the complex producing ADP-ribose and mono-ADP-ribosylated H1 histone which co-electrophoreses with unmodified H1. Although only one covalent linkage between protein and polymer has been detected, the 'complex' does not dissociate when electrophoresed on dodecylsulfate gels. Nor can the noncovalently linked H1 histone of the complex readily exchange with free H1. Complex formation does not occur when purified poly(ADP-ribose) and H1 are mixed.

Amino Acids↗

Conversion of ADP-ribose to 5'-AMP by alkaline treatment and its use for an optical quantitation of mono and poly(ADP-ribose) residues in the micromolar range.

ADP-Ribose is nearly quantitatively split to 5'-AMP by treatment with alkali at elevated temperatures. This unique behaviour, which is not shown by ADP and other adenine derivatives, was used as the basis of an optical test for the selective determination of ADPR in the presence of other adenine compounds including RNA. Poly(ADPR) could also be quantified when the polymer was degraded by poly(ADPR) glycohydrolase prior to alkaline treatment. When combined with the determination of the terminal AMP residues released by phosphodiesterase I treatment, the chain length of the polymer could be calculated. Application of the method to the quantitation of protein-bound mono(ADPR) residues in Ehrlich ascites tumor cells under different growth conditions is described.

Adenosine Diphosphate Sugars↗

Quantitative determination of poly(adenosine diphosphate ribose) in different hepatic tissues by an isotope dilution procedure.

A procedure has been developed for the quantitation of poly(ADP-ribose) in intact tissues. It is based on the dilution of added [3H]poly(ADP-ribose) by the endogenous polymer. 5 - 6 nanomoles protein-bound ADP-ribose per mg DNA were found in adult and neonatal rat liver, while Zajdela hepatoma cells had significantly lower values. A comparison with mono(ADP-ribose) residues in adult rat liver revealed similar levels of monomeric and polymeric ADP-ribose residues. This means that far more proteins (or acceptor sites on proteins) must be occupied by single ADP-ribose residues than by oligo or poly(ADP-ribose) chains. While the poly(ADP-ribose) levels of the different tissues do not correlate with the corresponding proliferation rates, the amount of mono(ADP-ribose) does show a certain Correlation, being low in rapidly growing tissues.

Animals↗