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Biomedical subjects

R Mayer

Publications and source records attributed to R Mayer.

At least 19 recordsLinked to original sources
PubMed1979

Models of interaction between nucleic acids and proteins. Hydrogen bonding of arginine with nucleic acid bases, phosphate groups and carboxylic acids.

Complex formation between the side chain of arginine and nucleic acid bases has been investigated by proton magnetic resonance in dimethylsulfoxide. Simultaneous formation of two hydrogen bonds leads to a selectivity of arginine interaction towards cytosine and guanine. A comparison is made of the interaction of arginine side chain with nucleic acid bases, phosphate and carboxylate anions. It is shown that interaction between carboxylate and arginine is stronger than between phosphate and arginine. These results are discussed with respect to the selective recognition of nucleic acid bases by arginine side chains and by the arginyl-glutamyl ion pair which could form in proteins interacting with nucleic acids.

Arginine↗
PubMed1979

The role of tyrosine in the association of proteins and nucleic acids. Specific recognition of single-stranded nucleic acids by tyrosine-containing peptides.

Oligopeptides containing tyrosyl, lysyl, and alanyl residues bind to polynucleotides and nucleic acids as shown by proton magnetic resonance, fluorescence spectroscopy, and difference absorption spectroscopy. Proton magnetic resonance data indicate that stacking of tyrosyl residues with nucleic acid bases takes place only in single-stranded structures (such as poly(A) or denatured DNA). Stacking interactions lead to a quenching of tyrosine fluorescence. However, the tyrosyl fluorescence of the peptides is quenched in their complexes with both single-stranded and double-stranded nucleic acids. A comparison of the behavior of homologous peptides containing Tyr, methoxytyrosine, and Phe leads to the conclusion that hydrogen bonding of tyrosine with bases or phosphates is not involved in the investigated complexes. An energy transfer mechanism from tyrosine to nucleic acid bases is proposed to account for fluorescence quenching in oligopeptide complexes with double-stranded DNAs. Due to the specificity of its stacking interaction for single-stranded nucleic acid structures, tyrosine might be involved through such interactions in the selective recognition of single strands by proteins.

Alanine↗
PubMed1979

An investigation of the uterine luminal environment of non-pregnant and pregnant pony mares.

Uterine flushings were collected from 30 non-pregnant Pony mares on Days 8, 12, 14, 16, 18 or 20 after oculation. Mares were allowed a recovery period of one oestrous cycle and were mated at the next oestrus. They were then ovario-hysterectomized on days which corresponded to the day of the oestrous cycle to which they were assigned. Uterine flushings were analysed for total recoverable protein and acid phosphatase activity. Least squares analysis indicated a status X day interaction for total protein (P less than 0.10) and acid phosphatase activity (P less than 0.005) in which the latter was higher in uterine flushings during pregnancy. Peripheral plasma oestrone and oestradiol concentrations were measured by radioimmunoassay and results indicated that plasma oestrone concentrations in pregnant and non-pregnant mares were not different, and oestradiol was lower (P less then 0.005) in the peripheral plasma during pregnancy. conceptus membranes were incubated in vitro for 120 min in a chemically defined medium. Incubation medium was then assayed to assess oestrone and oestradiol production capacilities at Days 8, 12, 14, 16, 18 and 20 of pregnancy. Conceptus membrane production of oestradios (pg/5 ml/h) increased (P less than 0.05) from Day 8 (243 pg/5 ml) to Day 20 (108 763 pg/5 ml). A similar trend, but of lower magnitude, existed for oestrone production.

Acid Phosphatase↗
PubMed1978

Circulating immune complexes in patients following clinically curative resection of colorectal cancer.

Sixty-nine patients have been followed prospectively after curative resection of Dukes-Kirklin B-2 or C colorectal cancer. Serial plasma samples were studied in selected patients to determine changes in circulating immune complex concentrations (CIC) following primary tumor resection, and to compare serial plasma CIC and carcinoembryonic antigen (CEA) levels. CIC was determined in an average of seven serial samples per patient by inhibition of antibody-dependent cell-mediated cytotoxicity (ADCC). CEA assays were performed by the Hanson Z-gel method. Two distinct patterns of serial CIC have emerged. In seven patients with no known tumor recurrences, serial CEA levels and CIC oscillated regularly and were inversely related. In seven of eight patients whose tumors recurred, both CEA and CIC rose together. In three patients with elevated plasma CEA levels due to inflammatory bowel disease, serial Ag-Ab complex concentrations did not vary, nor did separated Ag or Ab fractions inhibit ADCC. These data suggest that, in patients following curative resection of colorectal cancer, serial changes in circulating immune complexes may discriminate between transient CEA elevations which occur despite no known tumor recurrence and tumor recurrence which is beyond the capacity of adequate host antitumor defense.

Adenocarcinoma↗
PubMed1978

[Dentin wound dressings in a radioisotope test].

On standardised test bodies, the imperviousness of the materials Dycal, guttapercha, Reocap and zince oxide-oil of cloves was examined with the help of a solution of 131J. This revealed rates of impulse and therefore values of imperviousness which varied greatly in all materials, depending on time, enable appropriate recommendations for practice to be made.

Dental Materials↗
PubMed1978

[Scanning electromicroscopic studies of the surface of teeth. I. After manual treatment with tooth cleansers. II. Tooth cleaning with power-driven instruments].

Scanning electron microscopic examination of tooth surfaces after using manually operated instruments to remove calculus showed distinct lesions on the hard substances of the tooth. The extent of damage depends considerably on the area of the tooth treated (the border between the enamel and the cementum is particularly endangered), the amount of force used, and the length of time required for treatment. Examination of tooth surfaces following application of various types of power-driven scaling instruments revealed that lesions of the hard substances on the tooth are possible. The extent of the damage depends on several different factors, particularly the pressure applied and the area of the tooth treated. The border between the enamel and the cementum is particulary endangered.

Dental Cementum↗
PubMed1977

[Dislocations of the face and skull. Report of 20 cases].

The authors present a serie of 20 cases of craniofacial injuries with or without CSF leakage. They propose a simple classification in 2 groups following the impact: braniofacial injury or orbitofacial injury. For their, craniofacial or orbitofacial injuries are to be operated in one stage by an neurosurgical and maxillofacial team. The best time for operation is approximately around the 10th day following trauma.

Facial Bones↗
PubMed1977

[The shaping of the margin in cast objects in oral rehabilitation].

Various preparations of margins in cast replacements as well as their insertion and finishing are studied and measured by means of radioactive isotopes. It was found, in particular, that the conventional preparation of cavity margins and the finishing of cast margins of tightly cemented cast replacements should be discontinued.

Cementation↗