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Biomedical subjects

C R Anderson

Publications and source records attributed to C R Anderson.

At least 73 records · Page 4Linked to original sources
PubMed1976

Light-weight RTV silicone for maxillofacial prostheses.

Weight is a problem in retention of large skin-textured maxillofacial prostheses. The purpose of this investigation was to test the feasibility of mixing foam RTV silicone rubber with conventional RTV silicone rubber to obtain a light-weight material. Various mixtures of foam and conventional silicone rubber were formulated and tested for strength, accuracy of molding, color application, color stability, and texture. A special flask to support the mold was necessary in order to overcome expansion problems associated with gas formation of the foam silicone rubber. The mold required venting to release the gas and to reduce the expansion of the prosthesis in order to maintain accuracy. Molding, accuracy, texture, and color problems were overcome. Reduction of weight proportionate to reduction of tear strength of the material formulated, however, did not allow routine use of mixtures of foam and conventional silicone. When the weight of a prosthesis is critical and excessive and thickness is sufficient to give adequate strength, the foam and conventional silicone mixture can be used.

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PubMed1975

The relative resistance of dengue-immune monkeys to yellow fever virus.

Dengue-immune rhesus monkeys were challenged with a South American and two African strains of yellow fever virus. Levels of viremia were reduced as compared with control nonimmunized monkeys. The results support the hypothesis that immunity to dengue in a human population acts as a barrier to establishment of yellow fever in that population.

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PubMed1973

Voltage clamp analysis of acetylcholine produced end-plate current fluctuations at frog neuromuscular junction.

1. Acetylcholine produced end-plate current (e.p.c.) noise is shown to be the results of statistical fluctuations in the ionic conductance of voltage clamped end-plates of Rana pipiens.2. These e.p.c. fluctuations are characterized by their e.p.c. spectra which conform to a relation predicted from a simple model of end-plate channel gating behaviour.3. The rate constant of channel closing alpha is determined from e.p.c. spectra and is found to depend on membrane potential V according to the relation alpha = Be(AV) (B = 0.17 msec(-1)+/-0.04 S.E., A = 0.0058 mV(-1)+/-0.0009 S.E. at 8 degrees C) and to vary with temperature T with a Q(10) = 2.77, at -70 mV. A and B in this expression both vary with T and therefore produce a membrane potential dependent Q(10) for alpha.4. Nerve-evoked e.p.c.s and spontaneous miniature e.p.c.s decay exponentially in time with a rate constant which depends exponentially on V. The magnitude and voltage dependence of this decay constant is exactly that found from e.p.c. spectra for the channel closing rate alpha.5. The conductance gamma of a single open end-plate channel has been estimated from e.p.c. spectra and is found not to be detectibly dependent on membrane potential, temperature and mean end-plate current. gamma = 0.32+/-0.0045 (S.E.) x 10(-10) mhos. Some variation in values for gamma occurs from muscle to muscle.6. It is concluded that the relaxation kinetics of open ACh sensitive ionic channels is the rate limiting step in the decay of synaptic current and that this channel closing has a single time constant. The relaxation rate is independent of how it is estimated (ACh produced e.p.c. fluctuations, e.p.c., m.e.p.c.), and is consistent with the hypothesis that individual ionic channels open rapidly to a specific conductance which remains constant for an exponentially distributed duration.7. The voltage and temperature dependence of the channel closing rate constant agree with the predictions of a simple dipole-conformation change model.

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