Biomedical subjects
Publications and source records attributed to R B Price.
A technique for computed tomography directed percutaneous liver biopsy using small gauge (18-20) needles is described. In 51 procedures performed on 50 patients tissue specimens adequate for diagnosis were obtained 49 times (96%). There was one false negative diagnosis. The correct diagnosis was made in 48 of 51 (94%) procedures on 48 of 50 (96%) patients. There were no significant complications.
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Singing muscles of the katydid, Neoconocephalus robustus (Insecta, Tettigoniidae) are neurogenic, yet perform at contraction-relaxation frequencies as high as 212 Hz (Josephson and Halverson, '71). The mechanical and electrical responses of different bands of one of these muscles (the dorsal longitudinal muscle, DLM) has been examined with respect to ultrastructural features of each part which may be related to muscle performance. The DLM is composed of three bands and is innervated by four motoneurones. The cell bodies of three of these motoneurones occur ipsilaterally in the prothroracic ganglion; the cell body of the other motoneurone is contralateral in the mesothoracic ganglion. Three of the motoneurones (as yet unidentified fast axons) initiate extraordinarily fast twitches (rise time equal 7.3 msec, half duration equals 14.3 msec, 25 C), the fourth (an unidentified slower axon) evokes twitches which are considerably slower (rise time equals 18.9 msec, half duration equals 5.10 msec). Whereas the ventral and medial bands of the muscle are innervated only by fast axons (some fibers of the medial band are doubly innervated), the dorsal band is innervated by both a fast axon and the slower axon. A few fibers of the dorsal band are doubly innervated. The structure of fibers from the ventral and medial bands is very similar, with short sarcomeres (4.0 and 4.3 mum, respectively) and thin strap-like myofibrils delineated by well-developed sarcoplasmic reticulum (SR). Twenty-four percent of the volume of ventral band fibers is SR and the diffusion distance from SR to the center of the adjacent myofibril averages 0.083 mum. Twenty percent of the medial band fiber volume is SR, with a diffusion distance of 0.118 mum. Ventral and medial band fibers contain about 40% mitochondria, and 33% myofibrils. The dorsal band fibers have longer sarcomeres (9.5 mum), and only 10% of the fiber volume is SR. The muscle fibrils of the dorsal band are larger and consequently the diffusion distance is greater (0.227 mum) than in the ventral and medial bands. Mitochondria comprise 23% of the volume of dorsal band fibers. Most dorsal band mitochondria are aggregated into distinct clumps. Although some dorsal band fibers are innervated by a fast axon and some by the slower axon, the dorsal band fibers are structurally homogeneous, suggesting that neurotrophic effects are not important in maintaining the structure of dorsal band fibers. The mechanical-electrical performance and ultrastructure of the ventral and medial bands suggest their roll as fast, metabolically active but weak muscles, used in singing; the dorsal band as a slower but stronger muscle, perhaps involved in postural movements of the wing during singing.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
PURPOSE: Surface roughness can affect microbial colonization of long-term denture liners, alloys, and denture acrylic. The purpose of the present study was to examine the effect of finishing and polishing procedures on surface roughness of 4 temporary resilient denture liners (tissue conditioners). MATERIALS AND METHODS: Mean surface roughness was measured for 4 materials (Lynal, Visco-gel, Coe-Soft, and Functional Impression Tissue Toner [FITT]) finished in 4 ways: unfinished (control); polished; reduced, unpolished; and reduced, polished. Samples were allowed to polymerize at 37 degrees C for 24 hours, and the surface roughness was measured using a Mitutoyo Surftest 212. RESULTS: Mean surface roughness ranged from 1.8 +/- 0.8 microns for polished Lynal to 7.8 +/- 1.1 microns for reduced, unpolished FITT. All polished samples were smoother than unpolished samples (including controls), whether or not the samples were reduced with a bur. CONCLUSION: Polished samples of tissue conditioning material had lower mean surface roughness measurements than control or reduced, unpolished samples at the 95% level of confidence. There was no difference in mean surface roughness measurements of control samples and unpolished samples reduced with a bur at the 95% level of confidence. Mean surface roughness differed significantly between the materials tested.
PURPOSE: Interchangeability between articulators allows mounted casts to be transferred accurately from one articulator to another. The purpose of this study was to evaluate the interchangeability of 109 new, unused interchangeable articulators in the centric position. MATERIALS AND METHODS: The interchangeability of 38 unused Whip Mix model #2240 and 71 unused model #3040 semiadjustable articulators was evaluated using the Whip Mix #2245 check system as the standard. Vertical discrepancies between the check system cylinders were also measured. RESULTS: Within the standard for interchangeability established by the Whip Mix #2245 check system (< 94 microns horizontal discrepancy), 101 (93%) of 109 articulators were interchangeable (34 were model #2240 and 67 were model #3040). Overall, the amount of vertical space between the check system cylinders was < or = 52 microns in 99.4% of the model #2240 articulators and 99.7% of the #3040 articulators. CONCLUSION: New, unused Whip Mix model #2240 and #3040 articulators are potentially interchangeable in the centric position.
Light-curing units used for polymerizing restorative resins produce heat during operation. Newer curing units with concentrating light guides or different light sources may require shorter curing times, however, the effect of such modifications on temperature transfer to the pulp is unknown. This study examined the effect of high output light-curing units on temperature transfer through resin composite and dentin. Temperature rise was measured for 40 seconds for one curing light (Optilux 401 Curing Light) with either a standard 8 mm light guide tip or a light-concentrating tip (Turbo Light Guide), and for three seconds with a plasma arc lamp (Apollo 95E Curing Light). Temperatures were directly recorded at the tip of the light guide and through a sandwich composed of a 1 mm thick pre-cured cylinder of resin composite and dentin (dentin thickness either 0.58 mm or 1.45 mm). The mean temperature rise ranged from 1.8degrees C, measured through the sandwich of 1 mm of composite and 1.45 mm of dentin with the plasma are unit, to 26.4degrees C measured directly on the Turbo light guide. For each light guide, the temperature increase was greatest when measured directly on the curing tip and least when measured through the composite and 1.45 mm dentin specimens. When measured through the composite/dentin sandwich, the plasma arc unit produced the lowest temperature increase (0.58 mm thick dentin specimen = 5.1 degrees C; 1.45 mm thick dentin specimen = 1.8 degrees C). For a given thickness of resin, the differences in temperature change for all comparisons among the three curing unit/light guides were significant at the 95% level of confidence. Also, for a given light, the differences in temperature for all comparisons among the dentin thicknesses were significant at the 95% level of confidence. However, there were three comparisons of light unit and dentin thickness interaction that were not significant at the 95% leyel of confidence. For all other comparisons of interaction, significant differences were found at the 95% level of confidence. The temperature increased by 42% to 56% when the Turbo Light Guide was used compared to the standard light guide for thick and thin dentin specimens, respectively.
This study determined the dimensional accuracy of dies made using a combination of four impression materials and three Type IV die stones. A metal die was prepared for a molar complete cast crown, and 10 stone replicas were made using 12 different combinations of impression materials and die stones. The distances between reference points on the metal and stone dies were measured in three directions with a traveling microscope. Analysis of variance and Duncan's MR comparisons (P less than or equal to .05) showed that all of the stone dies were larger than the metal die. Although there were significant differences between some of the impression material/die stone combinations, all of the stone dies were measured to be within 9 microns of each other. No one impression material/die stone combination consistently produced the smallest or largest die in the three measured directions.