Contemporary treatment strategies for root surface dental caries.
Explore the source record for details and available documents.
Actinomyces↗
Biomedical subjects
L R Brown
Publications and source records attributed to L R Brown.
Evaluation of ethylene-vinyl acetate copolymer as a non-inflammatory alternative to Freund's complete adjuvant in rabbits.
Ethylene-vinyl acetate copolymer (EVAc) was evaluated as an antigen delivery device in laboratory rabbits. Bovine serum albumin (BSA) was incorporated with EVAc in a pellet, which was implanted subcutaneously. Serum antibody titers to BSA in four implanted rabbits were equal to titers in four rabbits injected twice with BSA in complete Freund's adjuvant. Three of four rabbits implanted with EVAc displayed no inflammation or systemic illness in response to the pellet. The fourth rabbit repeatedly developed a small abscess at the implantation site, but the lesions were less severe than complete Freund's adjuvant injection sites. The EVAc pellet is recommended as a non-inflammatory alternative method to Freund's adjuvants for producing serum antibody in rabbits.
Adjuvants, Immunologic↗
Interaction of myelin basic protein with micelles of dodecylphosphocholine.
Interactions of myelin basic protein (MBP) and peptides derived from it with micelles of dodecylphosphocholine (DPC) and perdeuterated DPC have been studied by proton nuclear magnetic resonance (NMR) at 400 MHz and by circular dichroism (CD). When MBP binds to DPC micelles, it acquires about 18% alpha-helicity. The CD spectra of various peptides derived by cleavage of MBP indicate that a major alpha-helical region occurs in residues 85-99 just before the sequence of three prolyl residues 100-102. From line broadenings by fatty acid spin-labels in the micelles and from changes in chemical shifts, the NMR data identify specific residues in MBP that participate in lipid binding. One such sequence is an alpha-helical region from residues 85 to 95, and others occur around methionine-21 and between residues 117 and 135. The different effects of C5, C12, and C16 spin-labels suggest that some segments of the protein may penetrate beyond the dipolar interfacial region of the micelles into the hydrophobic interior, but no part of the protein is protected by the micelles against rapid exchange of its amide groups with the aqueous environment. Even at a lipid to protein molar ratio of 200/1, most NMR resonances from side chains of amino acid residues are not appreciably broadened, suggesting that much of the polypeptide remains highly mobile.
Animals↗
Ethylene-vinyl acetate copolymer microspheres for controlled release of macromolecules.
A simple technique has been devised for preparing ethylene-vinyl acetate copolymer microspheres containing macromolecular drugs. Beads with good sphericity were formed by a simple extrusion process that can easily be repeated by any laboratory without special equipment. The extruded droplets gelled on immediate contact with cold ethanol in a dry ice-ethanol bath. The ethanol also served to remove the solvent and harden the microspheres as they warmed to room temperature. Release of bovine serum albumin followed the expected trends, i.e., initial linearity with the square root of time and faster release rates with greater drug loading.
Chemistry, Pharmaceutical↗
The basis for colored silver-protein complex formation in stained polyacrylamide gels.
Using a modified silver stain of Merril et al. [(1981) Science 211, 1437-1438] for staining polypeptides in sodium dodecyl sulfate-polyacrylamide gels, protein bands reproducibly stain different shades of blue, yellow, red, and gray. The procedure is highly temperature dependent, with optimal color formation at 42 degrees C. The procedure may be completed within 2 h. Color formation is due to silver ion complexes with charged amino acid side chains. The color of the silver-protein complex can be predicted if the amino acid sequence is known, although some exceptions are discussed. This provides another dimension to the characterization of proteins by gel electrophoresis.
Chemical Phenomena↗
Magnetic resonance imaging of the chest: a diagnostic comparison with computed tomography and hilar tomography.
Computed tomography (with and without contrast enhancement) provides excellent diagnostic accuracy for the evaluation of the chest. Oblique (55 degrees) and anteroposterior hilar tomography is accurate for the evaluation of hilar nodes and masses. Magnetic resonance techniques provide excellent differentiation of vascular and nonvascular structures and therefore should be useful in the hilum and mediastinum. Magnetic resonance imaging was used in 55 patients with known pathologic conditions in the mediastinum, hilum, and lungs to determine the accuracy and efficacy of this technique compared with computed and hilar tomography. The pathologic conditions included primary and metastatic neoplasms, benign masses, vascular abnormalities, and pulmonary nodules and infiltrates. Spatial resolution with magnetic resonance imaging is less than with computed tomography with our instrument (0.15 T resistive magnet). However, in the hilum and mediastinum, magnetic resonance imaging provided diagnostic information equal to that of computed tomography with contrast in 90% of patients. Vascular and nonvascular structures were more easily differentiated than with hilar tomography. Computed tomography was far superior in the evaluation of multiple pulmonary nodules. Lesions of the chest wall were better seen with magnetic resonance imaging because of the improved soft tissue contrast.
Adolescent↗
New type of oxygenase involved in the metabolism of propane and isobutane.
Nocardia paraffinicum (Rhodococcus rhodochrous), a hydrocarbon-degrading microorganism, was used in a study of propane and isobutane metabolism. The bacterium was able to utilize propane or isobutane as a sole source of carbon, and oxygen was found to be essential for its metabolism. Gas chromatographic analysis showed that n-propanol was the major compound recovered from the metabolism of propane by resting cells, although trace amounts of isopropanol and acetone were detected. When a mixture of propane and isobutane was used, drastic inhibition (72 to 88%) of hydrocarbon utilization by resting cells occurred. The ratio of hydrocarbon to oxygen consumed was found to be approximately 2:1 during the metabolism of propane or isobutane by resting cells when these substrates were provided individually to the organism. Gas chromatographic-mass spectrometric analysis of products formed from O(2) confirmed that the initial oxidative step in the metabolism of these substrates involved molecular oxygen. The proportion of the alcohol containing O was the same as that of O(2) in the gas mixture. Only a negligible amount of O was detected in the alcohol when H(2)O was incorporated into the system. The observed 2:1 ratio of hydrocarbon to oxygen consumption suggests that the oxygenase in N. paraffinicum, unlike the conventional mono- or dioxygenases, requires two hydrocarbon-binding sites for each of the oxygen-binding sites and is therefore an intermolecular dioxygenase. The newly described oxygenase, which catalyzes the reaction of two molecules of propane with one molecule of oxygen to yield two molecules of a C(3) alcohol, is proposed as the initial oxidation step of the hydrocarbon substrate.
Journal Article↗
Combined use of COSY and double quantum two-dimensional NMR spectroscopy for elucidation of spin systems in polymyxin B.
Two-dimensional single quantum correlation NMR spectroscopy (COSY) and two-dimensional double quantum NMR spectroscopy (2QT) are used to study spin systems in the 1H NMR spectrum of polymyxin B. Because of different frequency relationships, the two types of two-dimensional NMR experiments are found to be highly complementary. This is demonstrated by combined use of COSY and 2QT spectroscopy to obtain a complete analysis of the complicated spectral overlap which occurs in the 1H NMR spectrum of polymyxin B.
Magnetic Resonance Spectroscopy↗
In vivo and in vitro release of macromolecules from polymeric drug delivery systems.
In vivo release rates of a macromolecule from an ethylene-vinyl acetate copolymer have been shown to be indistinguishable from those of identical implants tested in vitro. The studies were conducted for approximately 2 months, and two different techniques were used to assess release rates. One of these techniques, using [3H]inulin as a marker, may be particularly useful in future studies assessing in vivo release rates from drug delivery systems. The appearance of [3H]inulin in the urine of rats bearing implants allowed continuous monitoring of release. A histological evaluation of tissue sections surrounding polymer implanted for 7 months showed no inflammatory cell reaction.
Delayed-Action Preparations↗
Extracellular dextranase activity produced by human oral strains of the genus Bifidobacterium.
Three strains of anaerobic, dextranase-producing, gram-positive, rod-shaped bacteria were isolated from human dental plaque associated with root carious lesions. The isolates produced a molar ratio of acetate to lactate from glucose fermentation ranging from 1.1 to 1.9. Each strain also produced fructose-6-phosphate phosphoketolase. The isolates were identified as belonging to the genus Bifidobacterium, but from their carbohydrate fermentation patterns they did not appear to be strains of Bifidobacterium dentium. These microorganisms fermented high-molecular-weight dextrans. A partial characterization of the dextranase activity was included in this study and revealed an extracellular dextranase with a pH optimum of 7.1. Analysis of the dextran degradation products demonstrated the liberation of saccharides larger than 1 glucose unit. It was concluded that this enzyme used an endohydrolytic mode of dextran cleavage.
Bifidobacterium↗
Effect of continuous fluoride gel use on plaque fluoride retention and microbial activity.
Twelve consecutive wk of daily five-minute topical applications of 1% NaF gel by non-cancer control subjects did not significantly affect plaque concentrations of Streptococcus mutans or Lactobacillus spp. Plaque F- levels increased 150% (P less than .001), while production of acetate and lactate decreased 40% (P less than .007) and 66% (P less than .001), respectively. Long-term (12 wk to more than five yr) fluoride gel use by post-irradiation xerostomic cancer patients was associated with increases in plaque F- and decreases in acidogenesis similar to those observed in the control subjects. Plaque concentrations of cariogenic organisms increased during the first yr of radiation-induced xerostomia and fluoride gel use, before starting to decline. Although sustained fluoride treatment increased (P less than .001) the ratio of fluoride-resistant to fluoride-sensitive strains, the number of patients harboring detectable S. mutans was diminished (P less than .001).
Acetates↗
Computed tomography of the thorax. Current perspectives.
With improvement in computed tomography (CT) technology, including faster scanning and images with better detail, the indications for CT of the thorax have expanded. In many instances, data collected on earlier-generation scanners no longer apply. This report is an update of CT scanning of the thorax and includes information on the role of CT in diagnosis when specific clinical syndromes and diseases are suspected. It also addresses controversial subjects, such as the role of CT scanning in the staging of bronchogenic carcinoma and the evaluation of the solitary pulmonary nodule, as well as suggesting guidelines for deciding when a CT scan of the thorax is indicated.
Aortic Dissection↗
The value of computed tomography in myasthenia gravis.
Explore the source record for details and available documents.
Adolescent↗
Proliferative responses to a nonspecific factor produced by irradiated stimulating cells can simulate antigen-specific secondary responses in the primed lymphocyte test.
The primed lymphocyte test (PLT) was utilized to investigate the biologic relationship between alloantigens and soluble environmental antigens. Human lymphocytes primed in vitro to the soluble antigens Candida (CAN), Tetanus (TET), or Purified Protein Derivative of Tuberculin (PPD) gave a strong proliferative response when restimulated with the initial soluble antigen in the presence of irradiated peripheral blood lymphocytes (PBL) acting as antigen-presenting cells (APC). Surprisingly, the soluble antigen-primed cells as well as alloantigen-primed cells responded to other soluble antigens in the presence of APC. By testing primed cells with supernatants derived from irradiated lymphocytes plus soluble antigen, it was apparent that the responses observed were in part due to stimulation by a soluble factor produced by the irradiated "APC" in response to the soluble antigen rather than to recognition of widespread cross-reactivity by the primed cells. This "nonspecific" factor production could be diminished by increasing the dose of irradiation to the APC or by using a T lymphocyte depleted- (SRBC-E-) APC population. In addition, certain antigen-reactive T cell clones did not respond to the nonspecific factor to the same degree as the primed bulk cultures. Nevertheless, the recognition of nonspecific stimulation induced by factors produced by irradiated lymphocytes is critical in the interpretation of primed lymphocyte responses to alloantigens or soluble antigens.
Antigens, Fungal↗
ScrFI: a new sequence-specific endonuclease from Streptococcus cremoris.
A novel sequence-specific endonuclease has been isolated from Streptococcus cremoris F. ScrFI recognises the sequence: (formula; see text) and cleaves as indicated by the arrow ( ). It is the first enzyme to recognise this sequence and the first endonuclease reported from the lactic streptococci used in dairy fermentations.
Base Sequence↗
RNA polymerase subunit biosynthesis in Bacillus subtilis.
The relative rates of RNA polymerase biosynthesis in Bacillus subtilis has been examined under steady-state growth conditions. The synthesis of RNA polymerase subunits (alpha, beta, beta', omega) has been followed by subunit fractionation of immunoprecipitated [3H]-labelled samples on SDS-polyacrylamide gels. The stoichiometries of alpha:beta:beta':omega subunits have been determined from cultures pulse-labelled during steady-state growth. The results suggest that an unassembled pool of the alpha-subunit exists from which the holoenzyme is formed. Upon shift-up from acetate to glycerol containing medium, a rapid rise in the differential rate of core enzyme synthesis was observed, while the rate of synthesis of the alpha-subunit was not stimulated. During shift-down, a concomitant reduction in the rate of synthesis of all subunits occurred for the first 20 min after the shift; thereafter, a rate of synthesis characteristic of the new growth rate was established. As cultures enter sporulation, an immediate reduction in the rate of beta beta'-subunit synthesis was demonstrated.
Bacillus subtilis↗
Bvui: a site-specific endonuclease from Bacillus vulgatis.
A site-specific endodeoxyribonuclease was partially purified from an extract of osmotically shocked spheroplasts of a Bacillus vulgatis strain; the enzyme has been designated BvuI and its activity was characterized. The locations of BvuI-generated cleavages on bacteriophage lambda and M13 derivatives mp7, mp8 and mp9, SV40 and PBR322 DNA molecules were determined. BvuI was shown to recognize the DNA sequence decreases 5'-G-Pu-G-C-Py-C-3' 3'-C-Py-C-G-Pu-G-5' increases and cleaves it at the positions indicated by arrows. Two identical BvuI recognition sites separated by fourteen nucleotide pairs were shown to occur within the tetracycline resistance gene of PBR322; BvuI should be useful for molecular cloning in that plasmid vector.
Bacillus↗
High resolution nuclear magnetic resonance studies of the conformation and orientation of melittin bound to a lipid-water interface.
Previously, the size and stoichiometry of mixed micelles of perdeuterated dodecylphosphocholine and melittin were characterized and the 1H NMR spin systems of most amino acid residues of micelle-bound melittin identified. One- and two-dimensional 1H-1H Overhauser experiments have now been used to obtain qualitative information on intramolecular proton-proton distances. These data show that the N-terminal and the C-terminal segments of melittin form two spatially distinct, compact domains; using lipid spin labels these could be located near the micelle surface. For the C-terminal domain a detailed conformation was determined by using the distance contraints from the Overhauser studies as input for a distance geometry algorithm.
Animals↗