Corrosion of silver cones in bone: a scanning electron microscope and microprobe analysis

Sections of silver cones were implanted in tibial bone wounds in 36 Sprague-Dawley rats. Groups of six rats each were killed at monthly intervals, and the specimens were examined by scanning electron microscopy and by X-ray microanalysis. The silver cones had corroded rapidly, but they were well tolerated by the tissues. Elements of silver, chlorine, and sulfur were found in the tissues adjacent to the implants.

Postdebridement retention of endodontic reagents: a quantitative measurement with radioactive isotope

Forty freshly extracted human teeth were biomechanically prepared for endodontic obturation using a radioisotopically labeled EDTA-urea peroxide-Carbowax compound. The amount of radiolabeled mixture remaining in the canals after through cleansing was about 3.8% of that originally applied. The amount of residue did not decrease with reinstrumentation and irrigation.

Localization of bacteria on the rat tongue with scanning and transmission electron microscopy

Scanning microscopy of rat tongue showed that bacterial habitation of the tongue was almost completely localized to the middle third of the anterior surface of the filiform papillae. Transmission microscopy showed coccal forms attached to the surface of the epithelium by means of fibrillar strands and present up to four cell layers deep within the epithelium.

Corrosion of endodontic silver cones in humans: a scanning electron microscope and X-ray microprobe study

Analyses with the scanning electron microscope and the X-ray microprobe were performed on 13 silver cones removed from 12 patients. The cones showed changes that ranged from surface dulling to black corrosion and pitting. Sulfur and chlorine were detected at the apical end of the cones and in the biopsy specimens of periapical tissues.

Ouabain-sensitive adenosine triphosphatase from human kidneys

Adenosine triphosphatase (ATPase) was studied in tissue homogenates and subcellular fractions derived from human cadaver kidneys maintained in an organ preservation unit for transplantation. The activity of ouabain-sensitive ATPase was highest in the medulla, intermediate in the cortex and lowest in the papilla, The cortical enzyme activity diminished with time during maintenance perfusion of the kidneys. Similar concentrations of K+, Na+, Mg++, ATP and MgATP were required for half-maximal rates of ouabain-sensitive ATPase activity from the cortex or the medulla. The sensitivity of the enzyme to ouabain from both parts of the kidney was similar. K+ antagonized inhibition of the enzyme by ouabain. Chlormerodrin, mersalyl, mercaptomerin and ethacrynic acid were inhibitors of the enzyme.

The effects of two ultrasonic instruments on root surfaces

The Orbison ultrasonic instrument and the Cavitron ultrasonic dental unit were compared for the smoothness of the root surfaces they produced. Twenty teeth were analyzed with the scanning electron microscope and classified as to rough or smooth. Both instruments produced similar degrees of smoothness on the root surfaces with minimal scarring. Application of these instruments to the root surface apical to the epithelial attachment produced residual smearing of some of the collagenous fibrils.

Oubain-sensitive adenosine triphosphatase from human kidneys

Adenosine triphosphatase (ATPase) was studied in tissue homogenates and subcellular fractions derived from human cadaver kidneys maintained in an organ preservation unit for transplantation. The activity of ouabain-sensitive ATPase was highest in the medulla, intermediate in the cortex and lowest in the papilla. The cortical enzyme activity diminished with time during maintenance perfusion of the kidneys. Similar concentrations of K+, Na+, Mg++, ATP and MgATP were required for half-maximal rates of ouabain-sensitive ATPase activity from the cortex or the medulla. The sensitivity of the enzyme to ouabain from both parts of the kidney was similar. K+ antagonized inhibition of the enzyme by ouabain. Chlormerodrin, mersalyl, mercaptomerin and ethacrynic acid were inhibitors of the enzyme.

Electron microscopic study of the effect of water jet lavage devices on dental plaque

The maxillary posterior teeth of nine rhesus monkeys were treated with a pulsating water lavage instrument at 70 psi (high setting). Electron microscopic studies of pre- and post-lavage plaque samples showed that water jet devices as used in this experiment either removed the plaque completely or caused irreversible damage to the microbial forms in the plaque matrix.

Transition of chemolithotroph Ferrobacillus ferrooxidans to obligate organotrophy and metabolic capabilities of glucose-grown cells

Transition of chemolithotrophic Ferrobacillus ferrooxidans to organotrophy occurred after 60 hr of incubation in an organic medium. Three distinct phases, based on metabolic activities of cells, were observed during the course of transition. Conversion of cellular nutrition to organotrophy resulted in a gradual loss of Fe(2+) oxidation and cessation of CO(2) fixation. These changes were concomitant with a rapid increase in uptake of glucose and phosphate during the latter part of transition period. The outcome of transition was governed by the pH of the medium, temperature of incubation, availability of oxygen, age of the chemolithotrophic cells, and the type of energy and carbon source available to the bacterium. Presence or absence of p-aminobenzoic acid and Fe(2+) ions did not influence transition of cells. A defined medium containing glucose, mineral salts, and p-aminobenzoic acid at pH 2.5 was found to be most suitable for transition and for culture of heterotrophic convertants. Maximum growth rate of the heterotrophic cells was attained with vigorous aeration at 35 C. The bacterium could be cultured on a variety of organic compounds, including complex organic media, provided they were used in low concentrations. Serological studies on autotrophic cells and the heterotrophic convertant have shown a definite antigenic relationship between the two cell types.