Biomedical subjects
Publications and source records attributed to R R Johnson.
Product line management places new financial reporting demands on healthcare organizations. The new reports should provide profitability information that helps management make decisions and fairly evaluate the roles that operating managers and product managers have in their organizations.
True venous aneurysms are uncommon complications in patients undergoing hemodialysis through prosthetic grafts. We report the case of a large cephalic venous aneurysm that occurred proximal to a polytetrafluoroethylene hemodialysis fistula. The incidence, management, and possible cause of this unusual complication of prosthetic arteriovenous fistulas are reviewed.
The effect of cyclic AMP (cAMP) analogs and phosphodiesterase (PDE) inhibitors on neurite outgrowth was studied in explant cultures of olfactory neurons. Nasal pits from 5- or 6-day-old chick embryos were minced, explanted into culture dishes, and grown in a serum-free medium. One of the cyclic AMP analogs, dibutyryl cyclic AMP (dbcAMP) or 8-bromo-cyclic AMP (8-Br-cAMP), or one of the PDE inhibitors, theophylline or isobutylmethylxanthine (IBMX), was added to the culture medium. The explants were examined for neurite outgrowth after 2 days in vitro. Db-cAMP increased the number of explants expressing neurites by 25-35% over control cultures, whereas 8-Br-cAMP had essentially no effect at the same concentrations. Addition of dibutyryl cyclic GMP (dbcGMP) gave no increase in neurite outgrowth, thus indicating that the effect of enhancing neuritic growth is specific to cAMP and not cyclic nucleotides in general. The resulting increase in neurite outgrowth is due to the cyclic nucleotide component of dbcAMP, since both IBMX and theophylline, which elevate intracellular cAMP, also increased neurite outgrowth significantly. When forskolin was added to the culture medium, there was a trend to increased neurite outgrowth; this was significantly enhanced when a subthreshold concentration of theophylline was added in addition to the forskolin.
Resistance to gas diffusion through the avian eggshell resides in the microscopic pores which penetrate the shell. We calculated the resistance to water vapor diffusion of individual pores in the shells of 23 species of avian eggs, based on measurements of pore dimensions taken from drawings of 321 pore casts published by Tyler (1962, 1964, 1965) and Tyler and Simkiss (1959). Diffusive resistances were calculated from Fick's first law, using a 100-segment model of each pore. In addition, we added 2 series resistances, calculated from Stefan's law, to account for boundary layer resistances at the inner and outer pore apertures. Convective resistances for the same 100-segment model were computed from Poiseuille's law. A special, symmetrically branching model is presented for the diffusive resistance of the branched pores of ostrich eggshells, based on the drawings of Tyler and Simkiss (1959). The total aperture resistance was less than 6.2% of total pore resistance, while the outside aperture effect was on average only 1.5%. The calculated average pore conductance for all species was 5.4 micrograms (day Torr)-1, about three times higher than the average value of 1.6 micrograms (day Torr)-1 obtained by dividing measured shell conductance by the number of pores (Ar and Rahn, 1985). A possible explanation for this discrepancy is advanced. However, it is to be noted that in spite of the discrepancy, both calculated and functional values of pore conductance appear to be independent of egg mass.
We describe the influence of pore shape in the hen's eggshell on calculated resistance to diffusion. These calculations are based on measurements of 70 pore casts, pictures of which were published by Tyler (In: Recent Advances in Food Sciences, Butterworth, London, Vol. 1, 1962). Single-pore resistance was estimated from Fick's first law as the summed resistances of 100 cylindrical segments in series and the calculated boundary layer resistance at the pore apertures. In addition, we constructed an average pore profile from all measurements. The calculated average single pore water vapor conductance (3.2 micrograms X day-1 X torr-1) is about twice the measured literature value. The presence of organic material in the pore openings is discussed as one of several possible reasons for this discrepancy. Average diameter should not be used to calculate conductance of trumpet-shaped pores. The narrow part of the pores plays a dominant role in total pore conductance, and pore shape must be taken into account when estimating conductance from pore dimensions.
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In order to study the influence of residual stresses on dimensional accuracy and mechanical properties of denture bases, an experimental model was devised for measurement of residual stresses in acrylic denture base polymers. Rectangular bar coupons were cut from resin plates heat processed by conventional dental methods. They included samples which had been slow and fast cooled after polymerization and had been stored in dry and wet environments. Uniaxial residual stress distributions for each coupon were disclosed by removing layers of known thicknesses and measuring the ensuing deflection of the specimens. Coupons of a commercial acrylic resin were annealed and used as controls. ANOVA and Scheffe's test were used to compare experimental conditions at the 95% confidence level. Dry specimens exhibited residual surface compressive stresses from 0.43-0.83 MPa (62-120 psi). Water-stored specimens showed higher stress levels, 2.86-3.24 MPa (414-470 psi). Slow cooled pigmented acrylic coupons which were dry showed higher residual stresses compared with other dry but nonpigmented specimens. No significant differences were found between pigmented or clear coupons which contained moisture.
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Plano-parallel specimens of human dentin cut from vital and endodontically treated teeth were tested by the punch shear test. Shear strength values were found to positively correlate with approximate toughness values. Statistically significant differences were found between shear strength and toughness values for vital and endodontically treated teeth, the latter showing lower values. The clinical impression that endodontically treated teeth are weaker and more brittle than vital teeth has therefore been quantitated. Anatomically different teeth or the methods used to store and cut teeth could not be consistently correlated with punch shear and toughness values. When dentin slices were constrained during punching so that bending was prevented, the precision of the results was improved and higher values were recorded.
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Ruminal production and interchange rates of volatile fatty acids (VFA) were measured for steers fed corn grain in the whole or ground form. Liquid turnover rate was 29% greater (P less than .10) with steers fed the corn in the whole form. On a molar basis (mol/100 mol), ruminal concentrations of propionate were lower while those of butyrate, 3-methyl butyrate, valerate and caproate were greater with whole than with ground corn diets. Acid production differences followed similar trends with de novo production of butyrate being seven times greater and irreversible butyrate loss three times greater with whole than with ground corn diets. Conversion of acetate to butyrate was about 70% greater with whole than with ground corn diets. This conversion far exceeded other VFA exchange rates. Outflow of VFA to the omasum was calculated to equal 20, 25 and 12% of the irreversible loss of acetate, propionate and butyrate, respectively. Ruminal output of energy as VFA from the rumen equaled 60 and 43% of consumed energy with the whole and ground grain diets, respectively. Production rates of VFA were poorly correlated with ruminal concentrations except for butyrate. Less than 10% of the labeled carbon from acetate and butyrate was detected in plasma glucose, but the transfer coefficient from propionate uncorrected for crossover of label was 59%. Gluconeogenesis from propionate alone exceeded literature estimates for basal glucose requirements of nonlactating ruminants.
Current investigations of telephone crisis intervention effectiveness have neglected the evaluation of broad patterns of interaction between the crisis center and the larger community. This study describes the development and implementation of a Caller Frequency Category System (CAFS) which is based upon the frequency and type of contacts between callers and the center. Data collected for 100 clients from a crisis intervention center suggest that the system can be applied reliably and does differentiate among clients by the type of interaction they have with the center. Two unexpected findings were that (a) longer-term callers tended to be older men or teenage girls, and (b) the greatest proportion of total telephone use involved calls initiated by the center itself to people other than crisis clients. Revisions to the CAFS are proposed which will clarify the role which a crisis center serves in the community-wide resolution of personal crises.
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Thirty male neonatal pigs were obtained by cesarean section and randomly allotted from littermate groups to three diets containing 2%, 17%, and 32% fat on a dry matter basis. Butterfat was used to replace glucose in the isoenergetic liquid, semipurified diets. Each pig was placed in a sterile isolator and fed ad libitum five times daily. After 14 days, pigs were weighed, killed, and samples of liver and backfat were obtained. The carcass of each pig was ground and samples obtained for determination of total body fat and protein. An increase in the level of dietary fat resulted in a significant increase in 14 day weight gain and a tendency for improved feed efficiency. These results demonstrate not only that the neonatal pig can utilize semipurified liquid diets high in butterfat content, but also that energy from butterfat appears to be used as efficiently as energy from glucose from growth purposes. Increasing dietary fat level decreased the activity of fatty acid synthetase and citrate cleavage enzyme in adipose tissue and liver, and decreased the activity of malic enzyme in adipose tissue. The specific activities of these three enzymes were higher in adipose tissue than in liver.
Full-fat, ground soy flour (GSF) was treated with 37% formaldehyde (HCHO) and evaluated by in vitro and in vivo criteria to determine the protection afforded linoleic acid against ruminal biohydrogenation when the materials described above were fed as a protein supplement to rations for growing lambs. The supplements compared were soybean meal (SBM), uked for 2 hours. Organoleptic evaluations were conducted to determine if any flavor differences in meat from lambs fed these supplements could be detected. Excellent protection of linoleic acid, the major polyunsaturated fatty acid in soybeans, was noted both in vitro and in vivo. Rump, shoulder, kidney knob and omental fat depots of lambs fed the HCHO treated GSF ration had significantly more linoleic acid than lambs fed untreated GSF while lambs fed untreated GSF had significantly, more linoleic acid in their fat depots than lambs fed SBM. Linoleic acid content of intramuscular (loin) fat from lambs fed HCHO treated GSF was not significantly different from lambs fed untreated GSF, but lambs fed untreated GSF had significantly more loin linoleic acid than lambs fed SBM. No significant differences were noted in daily feed intake, feed efficiency or average daily gain for lambs fed growing-finishing rations containing any of the products tested as the protein supplement. A taste panel could not detect any differences in flavor of ground loin among any of the treatments.
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Explore the source record for details and available documents.