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Biomedical subjects

H Davson

Publications and source records attributed to H Davson.

At least 55 records · Page 3Linked to original sources
PubMed1971

The permeation of several materials into the fluids of the rabbit's brain.

1. (24)Na, (36)Cl and (35)S thiourea were infused I.V. in rabbits according to schedules designed to yield approximately level activity in plasma for periods up to 5 hr. Cerebrospinal fluid was sampled before ending the experiment by decapitation and the radioactivities in cerebrospinal fluid and in homogenized brain were compared in each case to a time weighted mean value for plasma.2. The results are considered in terms of a simplified model which specifically acknowledges the continuity of the extracellular and cerebrospinal fluids and thus the coupling between processes which occur at the interfaces bordering those fluids.3. From the rate constants for exchange across the blood-brain interface that were necessary for simulation of the observed behaviours, permeability coefficients for that interface were estimated for the materials studied and, from experiments of others, for (42)K.

Animals↗
PubMed1970

The effects of some inhibitors and accelerators of sodium transport on the turnover of 22Na in the cerebrospinal fluid and the brain.

1. The purpose of the experiments was to discover whether the turnover of (22)Na in the c.s.f., which is largely determined by its rate of secretion, is affected in the same manner by inhibitors or accelerators of active transport as the turnover in the brain tissue since there is reason to believe that the composition of the extracellular fluid of brain is controlled by active processes.2. Although acetazolamide (Diamox) inhibits rate of secretion of c.s.f. and the turnover of (22)Na in this fluid it does not appreciably affect the turnover of (22)Na in the brain tissue of either rat or rabbit, the small inhibition observed being probably secondary to the effects on the c.s.f.3. Ouabain inhibits secretion of c.s.f. and turnover of (22)Na in this fluid, but it, also, has no effect on turnover of (22)Na in the brain tissue alone or in combination with Diamox.4. Amphotericin B and amiloride, the anti-aldosterone spirolactone S.C. 114266, all inhibited secretion of c.s.f. without affecting turnover of (22)Na in the brain tissue; actinomycin D, puromycin and cycloheximide, however, had no effect on secretion of c.s.f.5. Vasopressin inhibited secretion of c.s.f. and turnover of (22)Na in this fluid but increased the turnover in the brain by some 16%.6. In the ventriculo-cisternally perfused rabbit, replacement of 80% of the NaCl in the perfusion fluid by choline chloride caused a slowing of the passage of (22)Na from blood into the perfusion fluid.7. On the basis of these results it is concluded that the brain extracellular fluid is not renewed by appreciable bulk-flow, in contrast with the c.s.f.

Acetazolamide↗
PubMed1966

Factors affecting the distribution of iodide and bromide in the central nervous system.

1. Even when a steady level of (131)I(-) is maintained in the blood for long periods, the uptake by brain and spinal cord is very small, and the possibility that this is due to an active transport of I(-) from brain-tissue to blood has been examined.2. Most of the phenomena, however, can be explained on the basis of a slow passive diffusion across the blood-brain barrier associated with an active transport of (131)I(-) out of the c.s.f. across the choroid plexuses, so that, except possibly for the spinal cord, active transport from central nervous parenchyma into the blood need not be postulated. If it does occur, it contributes very little to the net exchanges between the three compartments, plasma, c.s.f. and extracellular fluid.3. The steady-state distribution of bromide between plasma and c.s.f. is normally such that the concentration in the c.s.f. is only some 70% of that in plasma; it has been shown that this is most probably due to an active transport of Br(-) across the choroid plexuses.

Journal Article↗