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Biomedical subjects

R A Brandon

Publications and source records attributed to R A Brandon.

25 records · Page 2Linked to original sources
PubMed1981

The pharmacokinetics of thiopentone.

The pharmacokinetics of thiopentone was studied in six mongrel dogs using a high-performance liquid chromatographic method for measurement of the drug in the plasma. An intravenous bolus dose (20 mg/kg) of 2.5% thiopentone sodium solution was injected into the cephalic vein. While the two- and three-compartment models were used in the analysis of the experimental data, the disposition curve was adequately described by a biexponential equation. Plasma protein binding of thiopentone was determined in vitro using the equilibrium dialysis technique. The drug was bound to a moderately high extent (73.8 +/- 4.1%). The half-time of the initial phase, which comprises distribution/redistribution, was 14.9 +/- 3.3 mins. The apparent volume of distribution was quite high for an organic acid (843 +/- 194 ml/kg). This may be attributed to the high lipid solubility of the thiobarbiturate. The half-life was 6.99 +/- 2.18 h and a body clearance value of 1.51 +/- 0.60 ml/kg-min was obtained. It can be concluded from this study that the half-time of the distribution/redistribution phase approximates the duration of anaesthetic effect. Consequently, physiological conditions and disease states which influence distribution/redistribution rather than those affecting hepatic biotransformation of the drug are likely to affect anaesthesia.

Aging↗
PubMed1976

Effects of continuous light and darkness on the eyes of the troglobitic salamander Typhlotriton spelaeus.

Larval Typhlotriton spelaeus collected from five caves in Pulaski Co., Missouri, were kept as larvae or induced to transform in darkness or continuous fluorescent illumination. Larvae maintained in darkness for 215 and 279 days had smaller eyes, smaller rod inner and outer segments, and fewer metaphase figures in the germinative zone of the neural retina than comparable larvae maintained in light (258 lux). Except for visual cell size, differences were small and for each characteristic exceptions were observed. One larva kept in light showed early retinal degeneration comparable to that in transformed adults to T. spelaeus. All larvae exhibited optomotor behavior both before and after the experiment. Among animals induced to transform by L-thyroxin and maintained in darkness 111 to 366 days, visual cell and pigment epithelium degeneration was more extensive and more frequent than in animals kept for the same length of time in light (237-298 lux). In darkness the frequency of animals with retinal degeneration increased between 111 and 366 days. In light some animals exhibited pigment epithelium reduction with normal visual cells, and others had free, pigmented cells in the subretinal space. These effects were not comparable to degeneration in darkness. Eyelids covered the eyes of only a few animals in both light and dark treatments. The extent of eyelid encroachment over the eye greater in darkness than in light. Most animals exhibited optomotor responses after experiments, but responses of animals kept in darkness were impaired in comparison to those of animals kept in light.

Animals↗