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D M Anderson

Publications and source records attributed to D M Anderson.

At least 163 records · Page 9Linked to original sources
PubMed1977

Synthesis of heterogeneous nuclear RNA in full-grown oocytes of Xenopus laevis (Daudin).

At various times following injection of either 3H-GTP or 32PO4 into full-grown (stage 6) Xenopus laevis oocytes, RNA has been extracted and fractionated on polyacrylamide gels. Based on size, base composition and incorporation data, we have defined the kinetics of synthesis and accumulation of ribosomal RNA (40S, 28S, 18S), heterogeneous RNA of high molecular weight (greater than 40S) and heterogeneous RNA migrating with molecular weights of from 4S to 40S. Nuclear isolations have been performed to determine the cellular distribution of these classes of RNA as a function of time. Evidence is presented which shows that stage 6 oocytes synthesize RNA which by virtue of its size, base composition, rapid turnover and nuclear location is equivalent to the heterogeneous nuclear RNA observed in somatic cells. In addition, the data suggest synthesis of a class of nuclear RNA with a half-life of several hours. A small fraction (5%) of the nuclear RNA is stable, enters the cytoplasm and may represent RNA added to the stockpile of maternal transcripts known to be present in stage 6 oocytes.

Animals↗
PubMed1977

Relationship of Streptococcus mutans biotypes to dental caries prevalence in Saudi Arabian naval men.

A group of 217 Saudi Arabian naval recruits were examined clinically, radiographically, and microbiologically for the prevalence of Streptococcus mutans. Caries experience was considerably lower than in US recruits of comparable age and showed a significant positive correlation with the prevalence of S mutans in dental plaque samples. The distribution of S mutans biotypes and their relationship to dental caries in the Saudi Arabians were studied.

Adolescent↗
PubMed1977

Corticosteroids in dentistry.

The application of corticosteroids to cut dentine following cavity preparation, to carious dentine in indirect pulp capping, to the exposed pulp or to pulp remnants and periapical tissues during root canal therapy has been claimed to eliminate post operative pain and inflammation. Other investigators have thrown doubt on the validity of these claims and have reported continued inflammation progressing to necrosis following such applications. This paper reports detailed clinical and histological findings in a series of over 500 teeth some of which received conventional treatment while others were treated with various corticosteroids including Mosteller's solution, tritiated prednisolone, and Ledermix paste and cement. The results confirm the fact that no clear correlation exists between symptoms and histological findings in pulp disease. The absence of pain following application of corticosteroids cannot therefore be taken as evidence of a specific therapeutic effect. In some cases pain returned after a period and histologic examination showed the slow development of inflammatory changes coupled with calcification in pulp tissue and on the walls of the canal. Further investigation is needed to clarify the relative contribution of the removal of toxic products by instrumentation and the anti-inflammatory properties of corticosteroids in the reduction of pain of pulpal origin.

Adrenal Cortex Hormones↗
PubMed1976

Iodination of DNA. Studies of the reaction and iodination of papovavirus DNA.

Iodination of DNA by the reaction originally described by S. L. Commerford ((1971), Biochemistry 10, 1993) is extremely sensitive to the secondary structure of the DNA. Cytidines in denatured simian virus 40 (SV40) DNA react at a slightly slower rate than free cytidine monophosphate; hydrogen-bonded cytidines in SV40 form I DNA are iodinated considerably more slowly; elimination of the negative supercoils in form I DNA by conversion to form II or form III reduces reactivity even further. The residual reactivity of form II or form III duplex DNA is not due to preferential iodination of unpaired cytidines near phosphodiester bond breaks; rather iodination occurs throughout the molecule. Cytidine monophosphate has been used as a model for DNA, to enable spectral measurements of its reaction with iodine and T1C13. At temperatures above 42 degrees C and at pH 5.0, formation of 5-iodocytidine is limited by the rate of formation of an intermediate, probably 5-iodo-6-hydroxydihydrocytidine. At lower temperatures, the conversion of intermediate to product is rate limiting, but can be accelerated by lowering the pH. By appropriate adjustment of pH, or temperature, the formation of intermediate or its conversion to product can be accelerated. Iodination destabilizes the DNA duplex. Iodocytosines in SV40 DNA are preferentially removed by S1 nuclease. Heavily iodinated DNA does not reassociate normally, but DNA with only 5-10% of its cytosines iodinated appears to reassociate with normal kinetics, if duplex formation is measured by hydroxylapatite chromatography. Conditions are described to permit preparation of DNA, which reassociates normally, having a specific activity of 10(8) cpm/mug.

Binding Sites↗
PubMed1976

Evidence against the involvement of chemotaxis in swarming of Proteus mirabilis.

Nonswarming and nonchemotactic mutants of Proteus mirabilis were isolated after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine or ultraviolet light. These mutants were used in experiments to determine if chemotaxis is involved in the swarming of P. mirabilis. Nonchemotactic mutants failed to form chemotactic bands in a semisolid casein hydrolysate medium, yet they swarmed on the same medium containing 1.5% agar. Nonswarming mutants were attracted towards individual amino acids and components of tryptose. In cross-feeding experiments, no evidence was obtained to indicate the production of a diffusable chemical repellent. In studies with the wild-type P. mirabilis, no clear-cut negative chemotaxis was seen even though three different assays were used and numerous chemicals were tested. Additional evidence against the involvement of chemotaxis in swarming comes from finding that dialysis does not interfere with swarming; swarm cells will swarm immediately when transferred to fresh media, and swarm cells will swarm on an agar-water medium supplemented with a surfactant. These data indicate that chemotaxis is not involved in the swarming of P. mirabilis.

Amino Acids↗
PubMed1974

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Comprehensive Health Care↗