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

Abstract

SUMMARY1. 24Na, 36CI and 35S 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 42K.

The effect of hypercapnia on a blood‐brain barrier mechanism in foetal and new‐born sheep.

“…In the present experiments a change in extracellular space cannot account for the results since it was actually considerably reduced by hypercapnia; this is indicated by the 90 min ventriculo-cisternal perfusion spaces in hypercapnic and control animals ( Welch, 1971). The rate constant for sucrose entry into brain can be calculated from the curve for sucrose penetration into brain (Fig.…”

Quantitative Measurement of Blood—Brain Barrier Permeability Using Rubidium-82 and Positron Emission Tomography

“…Normal brain is relatively impermeable to K + cat ions (Bradbury and Davson, 1965), and perme ability coefficients of 8.5 x 10 -7 cm s -1 (Davson and Welch, 1971) and 2.8 x 10-7 cm S-1 (Hansen et aI., 1977) have been previously estimated for K + passage across the BBB. Potassium transport across the BBB is thought to be regulated by AT Pases situated in its endothelial membranes (Mrsulja et aI., 1984;Sweadver and Goldin, 1980;Cervos-Navarro et aI., 1983).…”

Barriers and Fluids of the Eye and Brain

“…I began studies of the blood-CSF barrier in, I suppose, about 1953, having first completed a study on the blood-aqueous in collaboration with my personal technician, Parnel Matchett, who moved with me, along with Mr Purvis from the Institute of Ophthalmology, in, I think, 1951. After publishing this study with Matchett (11), I studied the blood-aqueous and blood-CSF barriers simultaneously in the rabbit, using partly chemical and partly isotopic techniques, 24 Na having become available on a weekly basis. While doing this initial study, which lasted some two years, I decided that I must get to know the literature of the CSF and blood-brain barrier and, as the easiest way to do this, wrote a book.…”

“…When Segal left to go to St. Thomas's, where Bradbury had taken a job, Keasley Welch decided to spend a year with me; he had taught himself a lot of mathematics and so was able to analyse the blood-CSF, blood-nerve and blood-brain barriers in a manner that I, with my more limited knowledge of mathematics, would not have attempted (24).…”