Color characterization of denture base material.

The time taken to create a more natural prosthesis by twisting a tooth, carving wax and applying a few basic colors can make a world of difference for patients wearing dental prosthesis. The technician can achieve a natural resemblance of tissue coloration in the oral cavity when these procedures are applied.

Percutaneous gallstone lithotripsy. Results in acute and chronic swine models.

The authors describe here a rotary catheter for the percutaneous fragmentation of gallstones. Gallstones are drawn into the rotating impeller by a powerful vortex and mechanically fragmented. Fragments are aspirated from the gallbladder following use of the device. The safety and efficacy of the device was tested after placement of human gallstones in the pig's gallbladder in 19 acute, 15 chronic, and two control experiments. In 27 completed experiments, 206 human gallstones (6-20 mm) were implanted. Most residual fragments were less than 2 mm; 24 fragments were 2 to 4 mm and seven were 5 to 8 mm. Acute histologic changes included focal loss of mucosa, mucosal and submucosal hemorrhage, and deposition of biliary material in the mucosa and submucosa. At 30 and 90 days, gallbladder histology revealed regeneration of the mucosa with isolated granuloma formation.

A single-parameter family of adjustments for fitting enzyme kinetic models to progress-curve data.

Current methods for fitting integrated rate equations to enzyme progress curves treat each observation as if it were an independent measurement. When the data are obtained by taking several successive readings from each of a series of progress curves, the data will not be truly independent and will exhibit autocorrelation. Here we propose a simple pragmatic extension of integrated rate equations which takes account of first-order autocorrelations. The value of the method is assessed when applied to five sets of experimental data.

The hazard of ingested alkaline disk batteries in children.

We have treated eight cases of childhood ingestion of alkaline disk batteries, one resulting in an esophagotracheal fistula. These batteries are capable of rapid tissue destruction on contact with moist membranes. We recommend that packaging include proper warning of this hazard and urge that retained batteries be promptly removed from the esophagus and stomach by endoscopy or laparotomy. If the battery has reached the small intestine, further transit should be monitored carefully by roentgenographic studies until recovery. Perforation is possible after eight-hour retention at a specific site.

Dinitrophenol inhibits the rejoining of radiation-induced DNA breaks by L-cells.

The production and rejoining of X-ray-induced single-stranded DNA breaks was studied using the alkaline sucrose density gradient technique and by measuring the disappearance of both 5' termini and 3'-OH termini using polynucleotide kinase and DNA polymerase, respectively. All studies were conducted using L-cell suspensions irradiated both in the presence and absence of 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation. Results show that the induction of single-stranded DNA breaks probably includes a nucleolytic component in addition to indirect free radical effects. A greater number of breaks were produced in the absence of DNP, suggesting that depressed adenosine triphosphate (ATP) levels reduce endogenous nucleolytic activity. The rejoining mechanism is enzymatic and requires an available ATP supply for operation. In the presence of DNP no DNA rejoining was observed following 30 min incubation after 10,000 rad. These results suggest that DNA breaks produced may be characterized by 5'-PO(4)-3'-OH termini and are rejoined by DNA ligase.