Homeostasis in brain

Soy isoflavone improves the impairment of learning and memory of rats induced by AplJ42, maintains Ap homeostasis in brain, and regulates the disordered expressions of RAGE/LRP-1 and restrain RAGE related NF-kB and inflammatory cytokines activation in neurovascular structure [295]. 

Cao, G., Bales, K. R, DeMattos, R. B., Paul, S. M. Liver X receptor-mediated gene regulation and cholesterol homeostasis in brain relevance to Alzheimer s disease therapeutics. Curr. Alzheimer Res. 2007,... 

Glial cells are cells within the central or peripheral nervous system which are not immediately involved in information processing. Glial cells play an mportant role in the metabolic homeostasis of brain tissue and in nervous system development. 

CYP46 hydroxylates cholesterol at the 24-position, a reaction that appears to play a role for cholesterol homeostasis in the brain. 

As its name suggests, the hypothalamus lies beneath the thalamus and above the pituitary gland. Although it is quite small, accounting for only about 4 g of the total 1400 g of the adult human brain, it plays a vital role in maintenance of homeostasis in the body. It is composed of numerous cell groups and fiber pathways, each with a specific function. 

Patients sustain convulsions and neurological deterioration. The urine contains low levels of the metabolites of serotonin, norepinephrine and dopamine. The reductase also plays a role in the maintenance of tetrahydrofolate levels in brain, and some patients have had low folate levels in the serum and CNS. Treatment has been attempted with tryptophan and carbidopa to improve serotonin homeostasis and with folinic acid to replete diminished stores of reduced folic acid. This therapy is sometimes effective. Diagnosis involves assay of DHPR in skin fibroblasts or amniotic cells. Phenylalanine hydroxylase activity is normal. 

Alterations in brain iron metabolism have been reported, resulting in increased iron accumulation in Huntington s disease. This was particularly the case in basal ganglia from patients with HD compared to normal controls. In studies in embryonic stem cells, huntingtin was found to be iron-regulated, essential for the function of normal nuclear and perinuclear organelles and to be involved in the regulation of iron homeostasis. 

It has been estimated that there are several billion neurons that comprise the mammalian brain which, together with their surrounding glial cells, form a unique network of connections which are ultimately responsible for aU thoughts and actions. While the glial cells may play a critical role in brain development, their main function in the mature brain is to maintain the structure and metabolic homeostasis of the neurons which they surround. 

The mechanism of AD pathogenesis still remains unclear. However, one mechanism, amyloid (3 (A(3) accumulation, may be due to the disturbance in metal homeostasis in AD brains [Strausak et al., 2001]. A(3 peptides are the major constituents of the amyloid core of senile plaques, which are derived from the amyloid precursor protein (APP) and are secreted into extracelluar spaces. Both APP and A(3 contain a copper-binding domain [Hesse et al., 1994 Atwood et al., 1998]. High concentrations of copper, zinc, and iron have been found within the amyloid deposits in AD brains [Lovell et al., 1998], A(3 peptides can be rapidly precipitated by copper under mildly acidic conditions and by zinc at low physiological (submicromolar) concentrations [Bush et al., 1994], An age-dependent binding between A(3 peptides with excess brain metals (copper, iron, and zinc) induces A(3 peptides to precipitate into metal-enriched plaques [Bush, 2002],... 

Copper is essential for some of the enzymes that have a role in brain metabolism. Sophisticated mechanisms balance copper import and export to ensure proper nutrient levels (homeostasis) while minimizing toxic effects. Several neurodegenerative diseases including AD are characterized by modified copper homeostasis. This change seems to contribute either directly or indirectly to increased oxidative stress, an important factor in neuronal toxicity. The association of misfolded proteins and modified copper homeostasis appears to be important in the pathological progression of AD [Donnelly et al., 2007],... 

The findings demonstrated that DRD is caused by a partial BH4 deficiency in the brain. In general, disorders caused by an inborn error of metabobsm show recessive inheritance, as half of the enzyme activity is usually sufficient enough to maintain homeostasis in vivo. To the contrary, DRD is a dominant disorder with low penetrance, even though the causative gene for DRD is that for an enzyme, GCH. The marked decrease (to approximately 20% of controls) in the neopterin content in the CSF (cerebrospinal fluid) from DRD patients suggests that GCH activity in the brain of DRD patients is also about 20% of that for normal individuals. Because neopterin is a metabolite of dihy-droneopterin triphosphate, the product of GCH, the neopterin content in the CSF is thought to reflect the GCH activity in the brain. 

Trachsel L, Edgar DM, Seidel WF, Heller HC, Dement WC. Sleep homeostasis in suprachiasmatic nuclei-lesioned rats effects of sleep deprivation and triazolam administration. Brain Res 1992 589 253-261. 

Sarin S, Julka D, Gill KD. 1997b. Regional alterations in calcium homeostasis in the primate brain following chronic aluminum exposure. Mol Cell Biochem 168 95-100. 

Other strategies include detailed studies of the changes in brain carbohydrate metabolism in ageing and how this may differ in patients with Alzheimer s disease. Changes in the composition and biophysical properties of neuronal membranes may also be of crucial importance in regulating the cytosolic free calcium, which could affect cellular homeostasis. 

Besides the well-established role of cytokines in the immune system, several recent reports demonstrated that chemokines also play a role in the central nervous system (CNS) (B2, Ml3). In the CNS, chemokines are constitutively expressed by microglial cells, astrocytes, and neurons, and their expression can be increased after induction with inflammatory mediators (M13). Chemokines are involved in brain development and in the maintenance of normal brain homeostasis, and play a role in the migration, differentiation, and proliferation of glial and neuronal... 

Jansson A, Descarries L, Comea-Hebert V, et al. Transmitter-receptor mismatches in central dopamine, serotonin, and neuropeptide systems. In Walz W, ed., The neuronal environment Brain homeostasis in health and disease. Totowa NJ Humana, 2001 pp. 83-108. 

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