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Biomedical subjects

A W Miller

Publications and source records attributed to A W Miller.

At least 55 records · Page 3Linked to original sources
PubMed1987

Factors affecting the retention and fit of gold castings.

A study was designed to simulate clinical conditions. Several factors were evaluated for effect on retention and fit (margin adaptation) of gold castings. Twenty-six castings (13 pairs) were made by different investigators using a standard preparation but with varying fabrication techniques. One of each pair of castings was made on a spaced die and one on an unspaced die. A significant difference in the postcementation retention was observed in the varying techniques of each investigator. Retentive values varied from 29 to 129 lbs. Complete seating of the castings during cementation was improved by the use of die spacer. Castings made on the spaced dies had more retention than corresponding unspaced castings. Die spacing has positive benefit when properly used. Moderate roughness of axial surfaces improves retention when zinc phosphate cement is used. Physical properties of restorative materials are important, but the individual technique and care of each investigator has a major effect on the ultimate fit and retention of the cast restoration.

Cementation↗
PubMed1986

Detection of dextransucrase and levansucrase on polyacrylamide gels by the periodic acid-Schiff stain: staining artifacts and their prevention.

One use of the periodic acid-Schiff (PAS) stain is to detect dextransucrase and levansucrase activities on polyacrylamide gels by staining their polysaccharide products, dextran and levan. When gels with heavy dextran or levan bands were PAS stained, proteins other than dextransucrase and levansucrase also were stained, and a high background developed during storage. The staining of proteins other than dextransucrase and levansucrase is caused by the diffusion of the periodate-oxidized carbohydrate before and after staining. This diffusion could be greatly slowed, and the staining artifact decreased, by following the PAS stain by a crosslinking treatment of the carbohydrate-dye complex. Protein staining artifacts could be prevented by using chymotrypsin to remove the protein from the gel at the stage after polysaccharide synthesis but before the PAS stain.

Chymotrypsin↗
PubMed1986

Inhibition of dextransucrase by Zn2+, Ni2+, Co2+, and Tris(hydroxymethyl)aminomethane (Tris).

Initial rate kinetics of polysaccharide formation indicate that Zn2+, Ni2+, and Co2+ inhibit dextransucrase [sucrose: 1,6-alpha-D-glucan 6-alpha-D-glucosyltransferase, EC 2.4.1.5] by binding to two types of metal ion sites. One type consists of a single site and has a low apparent affinity for Ca2+. At the remaining site(s), Ca2+ has a much higher apparent affinity than Zn2+, Ni2+, or Co2+, and prevents inhibition by these metal ions. These findings are consistent with a two-site model previously proposed from studies with Ca2+ and EDTA. Initial rate kinetics also show that Tris is competitive with sucrose, but that, unlike Zn2+, Tris does not bind with significant affinity to a second site. This argues that there is a site which is both the sucrose binding site and a general cation site.

Binding Sites↗
PubMed1986

Flow cytometric analysis of deparaffinized nuclei in urinary bladder carcinoma. Comparison with cytogenetic analysis.

Both cytogenetic analysis and flow cytometry (FCM) have prognostic efficacy in the analysis of transitional cell carcinoma (TCC) of urinary bladder. To correlate results of the two methods, we studied a unique group of patients whose tumors had undergone prospective conventional cytogenetic analysis. Paraffin blocks of these tumors were processed for FMC, then analyzed for nuclear DNA content. Of the 34 tumors processed, 30 (88%) yielded interpretable DNA histograms. In 26 (87%) of these, there was good correlation between the two methods with respect to the presence or absence of a hyperdiploid cell line. Discrepancies may have resulted from sampling error or from interpretation of a tetraploid peak as a prominent G2M region. Retrospective FCM analysis of paraffinized TCC tissue correlates well with conventional, prospective cytogenetic analysis and is applicable to the majority of urinary bladder transitional cell carcinomas.

Adult↗
PubMed1986

Functional molecular size and structure of dextransucrase by radiation inactivation and gel electrophoresis.

Robyt et al. have proposed a mechanism for dextransucrase in which dextran is synthesized by the cooperative action of two equivalent nucleophiles (Robyt, J.F., Kimble, B.K. and Walseth, T.F. (1974) Arch. Biochem. Biophys. 165, 634-640). To distinguish between the possibilities that the enzyme is a monomer bearing both nucleophiles, or a dimer with each subunit bearing one nucleophile, the molecular weight of the enzyme was determined by SDS-polyacrylamide gel electrophoresis and by radiation inactivation. Two major forms of dextransucrase from Leuconostoc mesenteroides NRRL B-512F were found on SDS-polyacrylamide gel electrophoresis, with Mr 177 000 and 158 000, and sometimes a minor form with Mr 168 000. No form of dextransucrase smaller than Mr 158 000 was found, either in the presence or absence of dextran T10, although levansucrase was detected at Mr 92 000 and 116 000. On irradiation with 60Co, dextransucrase behaved as a single species with a maximum size of Mr 201 000. Because Mr 201 000 is much smaller than the minimum dimer size of Mr 316 000 (= 2 X 158 000), it is concluded that both nucleophiles are probably located on the same peptide, rather than one on each subunit of a dimer, and that peptide association is probably not required for dextran synthesis.

Electrophoresis, Polyacrylamide Gel↗
PubMed1986

Milligram to gram scale purification and characterization of dextransucrase from Leuconostoc mesenteroides NRRL B-512F.

A sequence of dextranase treatment, DEAE-cellulose chromatography, affinity chromatography on Sephadex G-200, and chromatography on DEAE-Trisacryl M has been optimized to give a dextransucrase preparation with low carbohydrate content (1-100 micrograms/mg protein) and high specific activity (90-170 U/mg protein) relative to previous procedures, in 30-50% yield. Levansucrase was absent after DEAE-cellulose chromatography, and dextranase was undetectable after Sephadex G-200 chromatography. The method could be scaled up to produce gram quantities of purified enzyme. The purified dextransucrase had a pH optimum of 5.0-5.5, a Km of 12-16 mM, and produced the same lightly branched dextran as before purification. The purified enzyme was not activated by added dextran, but the rate of dextran synthesis increased abruptly during dextran synthesis at a dextran concentration of approximately 0.1 mg/mL. The enzyme had two major forms, of molecular weight 177,000 and 158,000. The 177,000 form predominated in fresh preparations of culture supernatant or purified enzyme, whereas the amount of the 158,000 form increased at the expense of the 177,000 form during storage of either preparation.

Chromatography, Affinity↗
PubMed1986

Activation and inhibition of dextransucrase by calcium.

Initial rate kinetics of dextran synthesis by dextransucrase (sucrose:1,6-alpha-D-glucan-6-alpha-D-glucosyltransferase, EC 2.4.1.5) from Leuconostoc mesenteroides NRRL B-512F showed that below 1 mM, Ca2+ activated the enzyme by increasing Vmax and decreasing the Km for sucrose. Above 1 mM, Ca2+ was a weak competitive inhibitor (Ki = 59 mM). Although it was an activator at low concentration, Ca2+ was not required for dextran synthesis, either of main chain or branch linkages. Neither was it required for sucrose hydrolysis, acceptor reactions, or enzyme renaturation after SDS-polyacrylamide gel electrophoresis. A model for dextran synthesis is proposed in which dextransucrase has two Ca2+ sites, one activating and one inhibitory. Ca2+ at the inhibitory site prevents the binding of sucrose.

Calcium↗
PubMed1986

The incompletely fractured tooth.

Signs and symptoms of the incompletely fractured tooth have been presented with emphasis on the role of occlusion in etiology and diagnosis. Early recognition and treatment are paramount.

Bruxism↗
PubMed1985

Expression of blood-group-related antigens in carcinoma in situ of the urinary bladder.

Expression of epithelial ABH blood group antigens and the T (Thomsen-Friedenreich)-antigen was quantitatively studied by immunoperoxidase techniques in nine cystectomy specimens containing extensive carcinoma in situ (CIS), and also histologically benign epithelium. CIS areas typically showed abnormal expression of both ABH and T-antigens and a distinctive vascular architecture, revealed by endothelial ABH staining. Histologically normal epithelium generally was antigenically normal, but occasionally showed abnormalities of either ABH or T-antigens. Antigen expression was variable in histologically atypical epithelium, with significant segments showing abnormalities of either ABH or T-antigen, and sometimes of both antigenic markers. It is postulated that histologically benign, but antigenically abnormal, epithelium may represent low-grade CIS of the urinary bladder. Assessment of blood-group-related antigen expression in flat atypical epithelium of the urinary bladder may be useful for predicting the biologic potential of these lesions.

ABO Blood-Group System↗
PubMed1985

Esthetic matching.

A chart that allows the reader to appreciate the diverse factors involved in esthetic matching has been presented. Although substantial information is presented in the chart, it is incomplete; and future research will contribute additional information. The chart is not intended as a substitute for learning, but a stimulus to further study.

Audiovisual Aids↗
PubMed1985

Pathology of superficial bladder cancer with emphasis on carcinoma in situ.

The coexistence of carcinoma in situ in flat epithelium adjacent to tumors is prognostically significant and is associated with an increased incidence of tumor recurrence and invasion. Recent investigations have been aimed at finding markers that will help identify flat areas of dysplasia or low-grade papillary transitional cell carcinomas that have a high potential to evolve into invasive tumors. Both DNA and karyotype analyses, as well as cell surface markers, have been examined in some detail and could have clinical value in certain settings. The tumor DNA index as measured by flow cytometry of nuclei retrieved from deparaffined sections may be particularly useful as a predictor of tumor recurrences and, possibly, tumor invasion as well. The diagnosis of superficial disease rests on urine cytology and the histopathologic assessment of tissue biopsies; however, intra- and inter-observer reproducibility of tissue and cytologic diagnoses by pathologists is a significant problem. The application of new technologies, such as flow cytometric analysis of deparaffined nuclei, may reduce the subjectivity involved in the light microscopic assessment of pathology specimens.

Adenocarcinoma↗
PubMed1984

Stabilization of dextransucrase from Leuconostoc mesenteroides NRRL B-512F by nonionic detergents, poly(ethylene glycol) and high-molecular-weight dextran.

Dextransucrase (sucrose: 1,6-alpha-D-glucan 6-alpha-D-glucosyltransferase, EC 2.4.1.5) (3 IU/ml culture supernatant) was obtained by a modification of the method of Robyt and Walseth (Robyt, J.F. and Walseth, T.F. (1979) Carbohydr. Res. 68, 95-111) from a nitrosoguanidine mutant of Leuconostoc mesenteroides NRRL B-512F selected for high dextransucrase production. Dialyzed, concentrated culture supernatant (crude enzyme) was treated with immobilized dextranase (EC 3.2.1.11) and chromatographed on a column of Bio-Gel A-5m. The resulting, purified enzyme lost activity rapidly at 25 degrees C or on manipulation, as did the crude enzyme when diluted below 1 U/ml. Both enzyme preparations could be stabilized by low levels of high-molecular-weight dextran (2 micrograms/ml), poly(ethylene glycol) (e.g., 10 micrograms/ml PEG 20 000), or nonionic detergents (e.g., 10 micrograms/ml Tween 80). The stabilizing capacity of poly(ethylene glycol) and of dextran increased with molecular weight. Calcium had no stabilizing action in the absence of other additions, but reduced the inactivation that occurred in the presence of 0.5% bovine serum albumin or high concentrations (greater than 0.1%) of Triton X-100. In summary, dextransucrase could be stabilized against activity losses caused by heating or by dilution through the addition of low concentrations of nonionic polymers (dextran, PEG 20000, methyl cellulose) or of nonionic detergents at or slightly below their critical micelle concentrations.

Calcium↗
PubMed1983

Prognosis in carcinoma of the urinary bladder based upon tissue blood group abh and Thomsen-Friedenreich antigen status and karyotype of the initial tumor.

Several markers of initial bladder carcinomas described recently may be clinically significant predictors of biological behavior of future recurrences. Comparison of the marker systems and assessment of the value of using multiple markers have been difficult, because the various markers have been studied in different patients. In this study, we compared four markers [chromosome mode, marker chromosomes, and expression of the ABH "blood group" antigens and the Thomsen-Friedenreich antigen (using immunoperoxidase or lectin immunoperoxidase methods)] in 39 patients presenting initially with low-stage bladder carcinoma and followed 3 to 11 years or until deep muscle invasion occurred. Each of the markers was significantly related to subsequent recurrences with deep muscle invasion, and each marker system was able to identify those patients with a very low risk of subsequent invasion. For detection of a subpopulation of patients with Grade II carcinomas who were at high risk for development of subsequent invasion, combinations of markers, especially hyperdiploidy and abnormal expression of the Thomsen-Friedenreich antigen, were significantly more effective than any single marker system.

ABO Blood-Group System↗