The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.
Free myo-inositol (inositol) transport into the cerebrospinal fluid (CSF), brain, and choroid plexus and out of the cerebrospinal fluid was measured in rabbits. In vivo, inositol transport from blood into choroid plexus, CSF, and brain was saturable with an apparent affinity constant (K-t) of approximately 0.1 mM. The relative turnover of free inositol in choroid plexus (16 percent/h) was higher than in CSF 4percent/h) and brain (0.3percent/h) when meausred by tissue penetration of tracer [3-H]-labeled inositol injected into blood. However, the passage of tracer inositol was not greater than the passage of mannitol into brain when measured 15 s after a rapid injection of inositol and mannitol into the left common carotid artery. From the CSF, the clearance of inositol relative to inulin was saturable after the intraventricular injection of various concentrations of inositol and inulin. Moreover, a portion of the inositol cleared from the CSF entered brain by a saturable mechanism. In vitro, choroid plexuses, isolated from rabbits and incubated in artificial CSF, accumulated [3-H-labeled myo-inositol against a concentration gradient by a specific, active, saturable process with a K-t of 0.2 mM inositol. These results were interpreted as showing that the entry of inositol into the central nervous system from blood is regulated by a saturable transport system, and that the locus of this system may be, in part, in the choroid plexus.
Methyltetrahydrofolic acid or folic acid was infused intravenously at a constant rate into conscious untreated or methotrexate-pretreated rabbits. After 150 min, at equivalent plasma concentrations, folic acid or methyltetrahydrofolic acid readily entered the cerebrospinal fluid and probably brain by a saturable transport system. In contrast, after intraventricular injections, folic acid but not methyltetrahydrofolic acid was cleared from cerebrospinal fluid to blood by a saturable system. Intraventribular injection of folic acid at concentrations that saturated folic acid clearance from cerebrospinal fluid did not affect the transport of methyltetrahydrofolic acid from blood into cerebrospinal fluid. These results suggest that the transport system for mehtyltetrahydrofolic acid, which is about half-saturated at normal plasma concentrations, helps maintain the cerebrospinal fluid and probably brain methyltetrahydrofolic acid concentrations within relatively narrow limits. Moreover, folic acid, which the brain cannot utilize, is transported from cerebrospinal fluid. A possible locus for the systems that transport folic acid from and methyltetrahydrofolic acid into the cerebrospinal fluid is the choroid plexus.
Temporary alteration of cerebrovascular permeability to plasma protein during drug-induced seizures. Am. J. Physiol. 223(2): 268-277. 1972.-The blood-brain barrier normally restricts the entry of plasma proteins into the central nervous system. Regional increases in the penetration of albumin-1251' into brain were observed in paralyzed, artificially respired animals convulsed for 5, 15, 30, and 60 min with pentylenetetrazol.
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