Transport of 1-aminocyclopentanecarboxylic acid from feline cerebrospinal fluid.

1-Aminocyclopentanecarboxylic acid was cleared from cerebrospinal fluid of the cat by a saturable mechanism. Clearance was inhibited by naturally occurring neutral amino acids. Carrier transport may explain the low ratio of amino acid in spinal fluid to that in plasma.

Light-evoked release of endogenous glycine into the perfused vitreous of the intact rat eye.

Glycine, a putative neurotransmitter, is released into the perfused vitreous of anesthetized pigmented rats when the eye is stimulated by intermittent flashes of bright light. Other amino acids do not show stimulated release. This result provides further evidence for the role of glycine as a neural transmitter in the retina.

Factors influencing the vitreous potassium concentration in the rat.

The vitreous of the intact eye of the rate was perfused with artificial medium to study factors that influence the vitreous potassium concentration. The vitreous potassium concentration in anesthetized rats was 5.07 mM. Perfusion with media containing higher or lower potassium concentrations led to passive diffusion of potassium out of or into the vitreous, respectively. Ouabain caused a release of potassium from the retina into the vitreous. Photic stimulation reduced the vitreous potassium concentration, presumably as a result of neuronal hyperpolarization. Glutamate raised and glycine lowered the vitreous potassium concentration, effects that also may be related to retinal depolarization and hyperpolarization, respectively.

The effect of penicillin on the release of gamma-aminobutyric acid from cerebral cortex slices.

Penicillin is known to block the depressant action of GABA on cortical and spinal neurons. In this study we examined the effect of penicillin on the release of endogenous amino acids from rat cerebral cortex slices. The principal finding was that penicillin blocked the potassium-stimulated release of GABA, a calcium-dependent process. It did not block the veratridine-stimulated release of GABA, a calcium-independent process. It did not affect the release of other putative transmitter amino acids. Inhibition of GABA release from nerve endings may explain in part the ability of penicillin to depress synaptic inhibitory mechanisms.

Bidirectional movement of gamma-aminobutyric acid in cerebral cortex slices incubated in small volumes of medium.

Rat cerebral cortex slices were incubated in small volumes of medium in order to study the bidirectional movements of gamma-aminobutyric acid (GABA) between tissue and medium, and to measure the extent of release of endogenous amino acids of interest as potential neurotransmitters. The apparent uptake, real uptake, and net change of GABA were calculated from the changes in [14C]GABA and endogenous GABA in the medium. The extent of release of endogenous amino acids was dependent upon the amino acid the duration of incubation, and the volume of incubating medium. Substantial amounts of endogenous amino acids may accumulate in the medium under conditions commonly employed in amino acid uptake studies. The accumulation of endogenous GABA may affect the calculation of GABA uptake when this is based on the initial specific activity of exogenous [14C]GABA. The difference between apparent uptake and real uptake was particularly prominent in the presence of the depolarizing agents, potassium or veratridine, which caused a marked increase in GABA release. Exchange or net release of GABA was found when slices were incubated briefly in media containing 1.3 micrometer or 12.5 micrometer exogenous GABA; net uptake accounted for 50% of observed uptake when slices were incubated in media containing 25 micrometer GABA.

Release of (3H)GABA and (14C)glutamic acid from rat cortex slices: the relationship between the tissue pool size and rates of spontaneous and electrically induced release.

A constant fraction of the existing tissue pool of (3H)GABA or (14C)glutamic acid was released during electrical stimulation of rat cortex slices. The sum of the amounts of labeled amino acids released spontaneously and by electrical stimulation was constant when stimulated slices were superfused with normal medium or media containing ouabain or a high K+ concentration. The fraction of the total amount released that was attributable to electrical stimulation varied inversely with the amount released spontaneously. Pentobarbital inhibited the accelerated spontaneous release produced by ouabain or high K+ and restored the ability of the slice to respond to electrical stimulation. Electrically induced release was felt to be limited by a theoretical maximum transport velocity of efflux of approximately 5.5% per min.

Maturational changes of amino acid concentration in cerebrospinal fluid of the rat.

The cisternal spinal fluid (CF), plasma, and brain stem concentrations of 6 amino acids were measured in suckling rats between birth and one months of age. Each of the amino acids studied had its distinctive maturational pattern of CF concentration. Presumably these amino acids have separate mechanisms of transport from CF, which mature at different times.

The release of endogenous amino acids into the vitreous of the intact eye of the albino rat: effect of light, potassium, and ouabain.

The vitreal space of the intact eye of albino rats was perfused in vivo. The concentration of several endogenous amino acids in the vitreal effluent was measured by the [3H]microdansylation procedure. GABA was never detected despite a sensitivity of the method of 0.5 pmol. In contrast to previous results obtained in pigmented rats, photic stimulation with flashing white light did not alter the release of glycine or any of the other amino acids. Potassium (60 mM) and ouabain (0.1 mM) evoked a specific release of glycine. The potassium-evoked release was blocked by magnesium suggesting a neuronal site of origin of glycine. Ouabain-evoked release was not blocked by magnesium. The results were contrasted with experiments on radiolabeled amino acid release from retinas preloaded and superfused in vitro, a condition in which glial localization of exogenous amino acids predominates.

Improved antioxidant activity of BKOS Thai jasmine rice.

Thai jasmine rice (Oryza sativa L. cv. KDML105) is highly valued due to its subtle aroma, robust seed characteristics and high nutritional quality. Low-energy ion-beam bombardment was chosen to improve the quality of jasmine rice by mutation induction. One mutated variety, named BKOS, was found to exhibit a deep purple colour due to an increased accumulation of anthocyanin. The total phenolic content and antioxidant activities of cooked and uncooked rice extracts were compared with KDML105, BKOS and other rice mutants created by a low-energy ion beam. The BKOS extracts showed the highest total phenol content (0.140 and 0.096 mg of gallic acid equivalent (GAE) g(-1) dry extract from uncooked and cooked rice, respectively). The BKOS extracts also had improved antioxidant activities, determined using three standard methods: 2,2'-diphenyl-1-picrylhdrazyl (DPPH) free radical scavenging, ABTS radical cation (ABTS•(+)) decolourisation and ferric-reducing antioxidant power assays. BKOS extracts showed 2-2.5-fold increased levels for each method. Interestingly, there was no significant difference between the antioxidant activities of the cooked and uncooked BKOS rice extracts. The increased quantity of antioxidants in this anthocyanin-based natural product could allow antioxidants to be consumed by a wider population than what is currently possible.