Ascorbic acid brain

Lyne and O Neil [117] reported the in vivo detection of dopamine using stearate-modified carbon-Nujol paste electrodes. Prior to their work, the detection of dopamine by voltammetric techniques was hindered primarily due to the coexisting ascorbic acid in the extracellular fluid of the mammalian brain. Ascorbic acid oxidizes at electric potentials similar to that of dopamine on many electrode materials. These authors found that the use of stearate-modified carbon-Nujol paste electrodes retards the electro-oxidation of anionic species (such as ascorbate) to such an extent that the cationic dopamine species could be detected in their presence. 

As mentioned above, ascorbic acid acts as a neuroprotective agent in in vitro models of scurvy. Therefore, it is a surprise that no symptoms of brain cell damage have been reported in conditions involving severe systemic ascorbic acid deficiency. This may be explained by the fact that the scorbutic state cannot be produced in the intact animal brain because of the brain s homeostatic mechanisms such as the highly specific ascorbic acid transport system in the choroid plexus (Spector, 1989) and the inability of ascorbic acid to cross the blood-brain barrier, which effectively isolate the ascorbic acid content of the intact brain from the rest of the body s ascorbic acid pool. The active transport of ascorbic acid from blood to cerebrospinal fluid (Spector and Eells, 1984), together with cellular uptake mechanisms, represents the base for homeostasis of brain ascorbic acid concentrations (see also Section 2). This is in agreement with the report about normal ascorbic acid concentrations in brains from patients with Parkinson s disease (Riederer et al., 1989), in which free radical damages are postulated to be involved (see below). 

Seregi, A., Schafer, A., and Komlos, M., 1978, Protective role of brain ascorbic acid content against lipid peroxidation, Experientia 34 1056-1057. 

L-Tyrosine metabohsm and catecholamine biosynthesis occur largely in the brain, central nervous tissue, and endocrine system, which have large pools of L-ascorbic acid (128). Catecholamine, a neurotransmitter, is the precursor in the formation of dopamine, which is converted to noradrenaline and adrenaline. The precise role of ascorbic acid has not been completely understood. Ascorbic acid has important biochemical functions with various hydroxylase enzymes in steroid, dmg, andhpid metabohsm. The cytochrome P-450 oxidase catalyzes the conversion of cholesterol to bUe acids and the detoxification process of aromatic dmgs and other xenobiotics, eg, carcinogens, poUutants, and pesticides, in the body (129). The effects of L-ascorbic acid on histamine metabohsm related to scurvy and anaphylactic shock have been investigated (130). Another ceUular reaction involving ascorbic acid is the conversion of folate to tetrahydrofolate. Ascorbic acid has many biochemical functions which affect the immune system of the body (131). 

The adrenal glands and pituitary glands have the highest tissue concentration of ascorbic acid. The brain, Hver, and spleen, however, represent the largest contribution to the body pool. Plasma and leukocyte ascorbic acid levels decrease with increasing age (152). Elderly people require higher ascorbic acid intakes than children to reach the same plasma and tissue concentration (153). 

In addition to its role in preventing scurvy (see Human Biochemistry box Ascorbic Acid and Scurvy and also Chapter 6), ascorbic acid also plays important roles in the brain and nervous system. It also mobilizes iron in the body, prevents anemia, ameliorates allergic responses, and stimulates the immune system. 

Ascorbic acid is photosensitive and unstable in aqueous solution at room temperature. During storage of foods, vitamin C is inactivated by oxygen. This process is accelerated by heat and the presence of catalysts. Ascorbic acid concentration in human organs is highest in adrenal and pituitary glands, eye lens, liver, spleen, and brain. Potatoes, citrus fruits, blade currants, sea buckthorns, acerola, rose hips, and red paprika peppers are among the most valuable vitamin C sources [1,2]. 

Dr. Rebec also said that the brains on post mortem studies of schizophrenics tended to be mushy and to have very low levels of ascorbic acid in their constituent tissue. 

Brain tissue Homogenization in coid 0.01 M NaOH. Centrifuge and resuspend pellet add zinc acetate and ascorbic acid readjust pH use continuous flow gas dialysis system to separate sulfide. Gas dialysis/ion chromatography with ECD 0.02 pg/g 95-100% Goodwin et al. 1989... 

Classic antioxidants, vitamin E, vitamin C, and others can suppress the activation of apoptosis. For example, ascorbic acid prevented cytochrome c release and caspase activation in human leukemia cells exposed to hydrogen peroxide [128], Pretreatment with A -acctylcystcinc, ascorbate, and vitamin E decreased homocysteine thiolactone-induced apoptosis in human promyelocytic leukemia HL-60 cells [129]. Resveratrol protected rat brain mitochondria from anoxia-reoxygenation damage by the inhibition of cytochrome c release and the reduction of superoxide production [130]. However, it should be mentioned that the proapoptotic effect of ascorbate, gallic acid, or epigallocatechin gallate has been shown in the same human promyelocytic leukemia cells [131]. 

Norepinephrine Blood circulation increase blood pressure peripheral vasoconstrictor without change or slight decrease in output and heart rate. No flow increase in brain, liver, or muscle Ascorbic acid protects against oxidation of norepinephrine... 

Sofic E., Riederer P., Killian W., and Rett A. (1987). Reduced concentrations of ascorbic acid and glutathione in a single case of Rett syndrome a postmortem brain study. Brain Dev. 9 529-531. 

Amperometric detection was achieved on two patches of C films (formed by CVD of 3,4,9,10-perylenetetracarboxylie dianhydride) on a glass chip. The microchannels were formed using a 23- im-thick photoresist as a spacer. Glucose oxidase and lactate oxidase were immobilized with HRP on the C films via a coated film of osmium PVPD polymer. Simultaneous measurements of glucose and lactate in rat brain cerebrospinal fluid (first perfused with 50 mM veratridine) were achieved. These two films were spatially separated in order to avoid interdiffusion of H202 formed from the two separate enzymatic reactions. Moreover, the two films were preceded by a third C film immobilized with ascorbate oxidase in order to remove ascorbic acid interference [759]. 

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