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PUFAs and Neurodegeneration
Sharon, R., I. Bar-Joseph, et al. (2003). "The formation of highly soluble oligomers of alpha-synuclein is regulated by fatty acids and enhanced in Parkinson's disease." Neuron 37(4): 583-95.
Accumulation of misfolded proteins as insoluble aggregates occurs in several neurodegenerative diseases. In Parkinson's disease (PD) and dementia with Lewy bodies (DLB), alpha-synuclein (alpha S) accumulates in insoluble inclusions. To identify soluble alpha S oligomers that precede insoluble aggregates, we probed the cytosols of mesencephalic neuronal (MES) cells, normal and alpha S-transgenic mouse brains, and normal, PD, and DLB human brains. All contained highly soluble oligomers of alpha S whose detection was enhanced by delipidation. Exposure of living MES neurons to polyunsaturated fatty acids (PUFAs) increased alpha S oligomer levels, whereas saturated FAs decreased them. PUFAs directly promoted oligomerization of recombinant alphaS. Transgenic mice accumulated soluble oligomers with age. PD and DLB brains had elevated amounts of the soluble, lipid-dependent oligomers. We conclude that alpha S interacts with PUFAs in vivo to promote the formation of highly soluble oligomers that precede the insoluble alpha S aggregates associated with neurodegeneration.
Hogyes, E., C. Nyakas, et al. (2003). "Neuroprotective effect of developmental docosahexaenoic acid supplement against excitotoxic brain damage in infant rats." Neuroscience 119(4): 999-1012.
Long-chain polyunsaturated fatty acid (LC-PUFA) composition of neural membranes is a key factor for brain development, in chemical communication of neurons and probably also their survival in response to injury. Viability of cholinergic neurons was tested during brain development following dietary supplementation of fish oil LC-PUFAs (docosahexaenoic acid [DHA], eicosapentaenoic acid, arachidonic acid) in the food of mother rats. Excitotoxic injury was introduced by N-methyl-D,L-aspartate (NMDA) injection into the cholinergic nucleus basalis magnocellularis of 14-day-old rats. The degree of loss of cholinergic cell bodies, and the extend of axonal and dendritic disintegration were measured following immunocytochemical staining of cell bodies and dendrites for choline acetyltransferase and p75 low-affinity neurotrophin receptor and by histochemical staining of acetylcholinesterase-positive fibres in the parietal neocortex. The impact of different feeding regimens on fatty acid composition of neural membrane phospholipids was also assayed at 12 days of age. Supplementation of LC-PUFAs resulted in a resistance against NMDA-induced excitotoxic degeneration of cholinergic neurones in the infant rats. More cholinergic cells survived, the dendritic involution of surviving neurons in the penumbra region decreased, and the degeneration of axons at the superficial layers of parietal neocortex also attenuated after supplementing LC-PUFAs. A marked increment in DHA content in all types of phospholipids was obtained in the forebrain neuronal membrane fraction of supplemented rats. It is concluded that fish oil LC-PUFAs, first of all DHA, is responsible for the neuroprotective action on developing cholinergic neurons against glutamate cytotoxicity.
Bassett, C. N. and T. J. Montine (2003). "Lipoproteins and lipid peroxidation in Alzheimer's disease." J Nutr Health Aging 7(1): 24-9.
Alzheimer's Disease (AD) is a clinical-pathological entity that probably derives from different causes. Mounting evidence strongly implicates regionally increased oxidative damage to brain beyond what occurs with aging as one of the processes that may contribute to AD progression. While several different classes of molecules may be affected, lipid peroxidation is thought to be a prominent and especially deleterious form of oxidative damage in brain due to this organ's relative enrichment in polyunsaturated fatty acids. Our laboratory recently has demonstrated that lipoproteins in AD brain extracellular fluid are more vulnerable to oxidation than lipoproteins in control brain extracellular fluid. Apolipoprotein E (apoE) is the principal apolipoprotein in the central nervous system (CNS), and it serves as the major apolipoprotein that is capable of lipid transport and regulation of lipid metabolism through known receptor-mediated processes. Moreover, inheritance of the APOE4 allele represents the strongest genetic risk factor for sporadic AD. Evidence suggests that apoE isoforms may specifically influence the cellular distribution of lipid peroxidation products in brain and may therefore contribute to the stratification of risk for AD associated with APOE. Here, we review possible mechanisms whereby lipoprotein trafficking and lipid peroxidation converge to contribute to neurodegeneration in AD brain.
Aruoma, O. I. (2003). "Methodological considerations for characterizing potential antioxidant actions of bioactive components in plant foods." Mutat Res 523-524: 9-20.
The study of free radicals and antioxidants in biology is producing medical revolution that promises a new age of health and disease management. From prevention of the oxidative reactions in foods, pharmaceuticals and cosmetics to the role of reactive oxygen species (ROS) in chronic degenerative diseases including cancer, autoimmune, inflammatory, cardiovascular and neurodegenerative (e.g. Alzheimer's disease, Parkinson's disease, multiple sclerosis, Downs syndrome) and aging challenges continue to emerge from difficulties associated with methods used in evaluating antioxidant actions in vivo. Our interest presently is focused on development of neurodegeneration models based on the integrity of neuronal cells in the central nervous system and how they are protected by antioxidants when challenged by neurotoxins as well as Fenton chemistry models based on the profile of polyunsaturated fatty acids (PUFAs) for the assessment of antioxidant actions in vivo. Use continues to be made of several in vitro analytical tools to characterise the antioxidant propensity of bioactive compounds in plant foods and supplements. For example, the oxygen radical absorbance capacity (ORAC), ferric reducing antioxidant power (FRAP), total oxidant scavenging capacity (TOSC), the deoxyribose assay, assays involving oxidative DNA damage, assays involving reactive nitrogen intermediates (e.g. ONOO(-)), Trolox equivalent antioxidant capacity (TEAC) and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. There is need to agree governance on in vitro antioxidant methods based on an understanding of the mechanisms involved. Because some of the assays are done in non-physiological pH values, it is impossible to extrapolate the results to physiological environment. The consensus of opinion is that a mix of these tools should be used in assessing the antioxidant activities in vitro. The proof of bio-efficacy must emanate from application of reliable in vivo models where markers of baseline oxidative damage are examined from the standpoint of how they are affected by changes in diet or by antioxidant supplements.
Farkas, E., M. C. de Wilde, et al. (2002). "Chronic cerebral hypoperfusion-related neuropathologic changes and compromised cognitive status: window of treatment." Drugs Today (Barc) 38(5): 365-76.
Neurodegenerative disorders, and dementia in particular, have been shown to have a cerebrovascular pathogenic component often in the form of reduced cerebral blood flow. The debate whether such a reduced brain perfusion is a primary trigger or a secondary symptom in the neuropathological progression of dementia has not been conclusively decided yet. However, compelling experimental evidence has been collected to demonstrate an initiating role of reduced cerebral blood flow in neurodegenerative processes. Along these lines, experimental cerebral hypoperfusion in rodents was shown to impair spatial learning and to generate neuronal damage and associated gliosis in sensitive brain regions like the hippocampus and frontoparietal cortex. Since suboptimal cerebral blood supply was thus identified as a potential trigger of cognitive decline, the improvement of cerebral blood flow in cognitive disorders has emerged as an alternative treatment to moderate the symptoms and to delay the onset of advanced dementia. Various drugs, such as cholinergic compounds, hemorheologic agents and vascular smooth muscle relaxants, have already been tested in some instances for their efficacy to increase brain perfusion. In this respect, both clinical and preclinical trials delivered positive data. Furthermore, not only the treatment but also the prevention of the development of cognitive deficiency can target the cerebrovascular system. For this purpose, long-chain polyunsaturated fatty acids derived from fish oil (also known as n-3 PUFAs) have been considered as dietary supplements. These fatty acids appeared particularly effective in the prevention of hypertension-associated vascular pathology. The present review provides an overview of the actions of these compounds focusing on cerebral blood flow, neurodegeneration and cognitive decline.
Das, U. N. (2002). "Estrogen, statins, and polyunsaturated fatty acids: similarities in their actions and benefits-is there a common link?" Nutrition 18(2): 178-88.
OBJECTIVES: To investigate whether there is any common link between estrogen, statins, and polyunsaturated fatty acids (PUFAs), which have similar actions and benefits. METHODS: To critically review the literature pertaining to the actions of estrogen, statins, and various PUFAs. RESULTS: Estrogen, statins, and PUFAs enhance nitric oxide synthesis, suppress the production of proinflammatory cytokines such as tumor necrosis factor(alpha), interleukin-1, interleukin-2, and interleukin-6, show antioxidant-like and antiatherosclerotic properties, have neuroprotective actions, and by themselves or their products inhibit tumor cell proliferation and improve osteoporosis. Estrogen, statins, and PUFAs not only have similar actions but also appear to interact with each other. For instance, the binding of estrogen to its receptor on the cell membrane may be determined by its lipid content, statins and PUFAs inhibit 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, statins influence the metabolism of PUFAs, and PUFA deficiency enhances 3-hydroxy-3-methylglutaryl coenzyme A reductase activity. Statins and PUFAs inhibit tumor cell proliferation, suppress ras activity, and may prevent neurodegeneration and improve cognitive functions such as learning and memory. This suggests that PUFAs might be mediators of the actions of statins. Estrogen boosts cognitive performance in women after menopause and may protect against Alzheimer's disease. CONCLUSIONS: The common link between estrogen, statins, and PUFAs may be nitric oxide. Hence, a combination(s) of estrogen or its derivatives, statins, and various PUFAs may form a novel approach in the management of various conditions such as hyperlipidemias, coronary heart disease, atherosclerosis, osteoporosis, cancer, neurodegenerative conditions, and to improve memory.
Blondeau, N., C. Widmann, et al. (2002). "Polyunsaturated fatty acids induce ischemic and epileptic tolerance." Neuroscience 109(2): 231-41.
The findings reported in this work show that pretreatment with polyunsaturated fatty acids, particularly linolenic acid, present in vegetable oils, can provide a potent tolerance against neurodegeneration in two models of neuronal death-generating treatments such as kainic acid injection and global ischemia. Rats were injected i.v. with 500 nmol/kg of linolenic acid as long as 3 days prior to 6 min global ischemia or received an injection of linolenic acid as long as 3 days prior to a dose of 7.5 mg/kg kainic acid. Neuronal degeneration, assessed by analysis of neuronal density on Cresyl Violet-stained hippocampal sections, was significantly reduced in linolenic acid-treated rats (94-85% of cell survival in the ischemic model and 99-79% of cell survival in the epileptic model in respective CA1 and CA3 subfields). The neuroprotection observed following the injection of linolenic acid 3 days prior to induction of a severe ischemic or epileptic challenge was associated with the induction of the neuroprotective HSP70 heat shock protein within the time window of protection. The injection of 500 nmol/kg of linolenic acid induced a maximal HSP70 expression of 387% at 72 h. In contrast, the overexpression of one well-known protein inducer of neuronal cell death, Bax, which is induced by both ischemic and kainic acid-induced epileptic insults, was prevented by linolenic acid in the 3-day window of protection.These results strengthen the idea of an interesting potential therapeutical value of polyunsaturated fatty acids in neuronal protection.
Rauhala, P. and C. C. Chiueh (2000). "Effects of atypical antioxidative agents, S-nitrosoglutathione and manganese, on brain lipid peroxidation induced by iron leaking from tissue disruption." Ann N Y Acad Sci 899: 238-54.
A fluorescent assay of brain lipid peroxidation was used for screening new antioxidants for the prevention of neurodegeneration caused by free radicals. Incubation of rat brain homogenates led to a temperature-dependent increase in production of fluorescent adducts of peroxidized polyunsaturated fatty acids; it was inhibited completely by lowering the incubation temperature to 4 degrees C. This tissue disruption-induced brain lipid peroxidation at 37 degrees C was blocked by deferoxamine (IC50 = 0.3 microM) and EDTA; it was augmented by adding submicromolar iron and hemoglobin. Ferrous ion's pro-oxidative activities were five times more potent than ferric ion. Micromolar manganese completely inhibited lipid peroxidation, confirming earlier unexpected in vivo reports. Trolox and vitamin C suppressed brain lipid peroxidation with IC50 values of 20 and 500 microM, respectively. U-78517F was approximately 20 times more potent than Trolox. 17 beta-Estradiol, hydralazine, S-nitrosoglutathione and 3-hydroxybenzylhydrazine were as potent as Trolox. Melatonin, glutathione, alpha-lipoic acid and l-deprenyl were about 20 times less potent than Trolox. Surprisingly, N-tert-butyl-alpha-phenylnitrone was a weak antioxidant. Furthermore, this procedure can also detect pro-oxidative side effects of vitamin C, oxidized glutathione, penicillamine and Angeli's salt. The present results obtained from this selective fluorescent assay are consistent with earlier reports that iron complexes promote while manganese inhibits brain lipid peroxidation caused by cell disruption. S-Nitrosoglutathione, melatonin, 17 beta-estradiol, and manganese have been successfully tested in cell/animal models for their potential neuroprotective effects. In conclusion, monitoring fluorescent adducts of peroxidizing polyunsaturated fatty acids in brain homogenates is a simple, quantitative method for studying iron-dependent brain lipid peroxidation and for screening of potential neuroprotective antioxidants in both in vitro and in vivo preparations.
Poli, G. and R. J. Schaur (2000). "4-Hydroxynonenal in the pathomechanisms of oxidative stress." IUBMB Life 50(4-5): 315-21.
Here we review the current knowledge on the biochemistry and molecular pathology of oxidative stress with specific regard to a major aldehydic end-product stemming from peroxidation of biomembranes, that is 4-hydroxynonenal (HNE). This multifunctional molecule, which derives from the most represented class of polyunsaturated fatty acids in the membranes, is potentially able to undergo a number of reactions with proteins, phospholipids, and nucleic acids. Despite an active metabolism in most of the cell types, HNE can be detected in several biological tissues by means of sufficiently precise methods, although with different sensitivity. In particular, relatively high steady-state levels of HNE are often detectable in a large variety of human disease processes, pointing to some involvement of the aldehyde in their pathogenesis. Among the prominent pathobiochemical effects of HNE is its remarkable stimulation of fibrogenesis and inflammation, which indicates a potential contribution of the aldehyde to the pathogenesis of several chronic diseases, whose progression is indeed supported by inflammatory reactions and characterized by fibrosis. Further, of interest appears to be the ability of HNE to modulate cell proliferation through interference with the activity of cyclins and protein kinases and with the apoptotic machinery. Finally, on the basis of the already achieved evidence, pursuing investigation of the role of HNE in signal transduction and gene expression seems very promising.
Lovell, M. A., C. Xie, et al. (2000). "Acrolein, a product of lipid peroxidation, inhibits glucose and glutamate uptake in primary neuronal cultures." Free Radic Biol Med 29(8): 714-20.
Oxidative stress has been implicated in the pathogenesis of several neurodegenerative disorders including Alzheimer's disease (AD). Increased lipid peroxidation, decreased levels of polyunsaturated fatty acids, and increased levels of 4-hydroxynonenal (HNE), F(2)-isoprostanes, and F(4)-neuroprostanes are present in the brain in patients with AD. Acrolein, an alpha,beta-unsaturated aldehydic product of lipid peroxidation has been demonstrated to be approximately 100 times more reactive than HNE and is present in neurofibrillary tangles in the brain in AD. We recently demonstrated statistically significant elevated concentrations of extractable acrolein in the hippocampus/parahippocampal gyrus and amygdala in AD compared with age-matched control subjects. Concentrations of acrolein were two to five times those of HNE in the same samples. Treatment of hippocampal cultures with acrolein led to a time- and concentration-dependent decrease in cell survival as well as a concentration-dependent increase in intracellular calcium. In cortical neuron cultures, we now report that acrolein causes a concentration-dependent impairment of glutamate uptake and glucose transport in cortical neuron cultures. Treatment of cortical astrocyte cultures with acrolein led to the same pattern of impairment of glutamate uptake as observed in cortical neuron cultures. Collectively, these data demonstrate neurotoxicity mechanisms of arolein that might be important in the pathogenesis of neuron degeneration in AD.
Kidd, P. M. (2000). "Parkinson's disease as multifactorial oxidative neurodegeneration: implications for integrative management." Altern Med Rev 5(6): 502-29.
Parkinson's disease (PD) is the most common movement pathology, severely afflicting dopaminergic neurons within the substantia nigra (SN) along with non-dopaminergic, extra-nigral projection bundles that control circuits for sensory, associative, premotor, and motor pathways. Clinical, experimental, microanatomic, and biochemical evidence suggests PD involves multifactorial, oxidative neurodegeneration, and that levodopa therapy adds to the oxidative burden. The SN is uniquely vulnerable to oxidative damage, having high content of oxidizable dopamine, neuromelanin, polyunsaturated fatty acids, and iron, and relatively low antioxidant complement with high metabolic rate. Oxidative phosphorylation abnormalities impair energetics in the SN mitochondria, also intensifying oxygen free radical generation. These pro-oxidative factors combine within the SN dopaminergic neurons to create extreme vulnerability to oxidative challenge. Epidemiologic studies and long-term tracking of victims of MPTP (1-methyl-4-phenyl-1,2,3,6,-tetrahydropyridine) poisoning, suggest oxidative stress compounded by exogenous toxins may trigger the neurodegenerative progression of PD. Rational, integrative management of PD requires: (1) dietary revision, especially to lower calories; (2) rebalancing of essential fatty acid intake away from pro-inflammatory and toward anti-inflammatory prostaglandins; (3) aggressive repletion of glutathione and other nutrient antioxidants and cofactors; (4) energy nutrients acetyl L-carnitine, coenzyme Q10, NADH, and the membrane phospholipid phosphatidylserine (PS), (5) chelation as necessary for heavy metals; and (6) liver P450 detoxification support.
Farooqui, A. A., L. A. Horrocks, et al. (2000). "Glycerophospholipids in brain: their metabolism, incorporation into membranes, functions, and involvement in neurological disorders." Chem Phys Lipids 106(1): 1-29.
Neural membranes contain several classes of glycerophospholipids which turnover at different rates with respect to their structure and localization in different cells and membranes. The glycerophospholipid composition of neural membranes greatly alters their functional efficacy. The length of glycerophospholipid acyl chain and the degree of saturation are important determinants of many membrane characteristics including the formation of lateral domains that are rich in polyunsaturated fatty acids. Receptor-mediated degradation of glycerophospholipids by phospholipases A(l), A(2), C, and D results in generation of second messengers such as arachidonic acid, eicosanoids, platelet activating factor and diacylglycerol. Thus, neural membrane phospholipids are a reservoir for second messengers. They are also involved in apoptosis, modulation of activities of transporters, and membrane-bound enzymes. Marked alterations in neural membrane glycerophospholipid composition have been reported to occur in neurological disorders. These alterations result in changes in membrane fluidity and permeability. These processes along with the accumulation of lipid peroxides and compromised energy metabolism may be responsible for the neurodegeneration observed in neurological disorders.
Farooqui, A. A., L. A. Horrocks, et al. (2000). "Deacylation and reacylation of neural membrane glycerophospholipids." J Mol Neurosci 14(3): 123-35.
The deacylation-reacylation cycle is an important mechanism responsible for the introduction of polyunsaturated fatty acids into neural membrane glycerophospholipids. It involves four enzymes, namely acyl-CoA synthetase, acyl-CoA hydrolase, acyl-CoA: lysophospholipid acyltransferase, and phospholipase A2. All of these enzymes have been purified and characterized from brain tissue. Under normal conditions, the stimulation of neural membrane receptors by neurotransmitters and growth factors results in the release of arachidonic acid from neural membrane glycerophospholipids. The released arachidonic acid acts as a second messenger itself. It can be further metabolized to eicosanoids, a group of second messengers involved in a variety of neurochemical functions. A lysophospholipid, the second product of reactions catalyzed by phospholipase A2, is rapidly acylated with acyl-CoA, resulting in the maintenance of the normal and essential neural membrane glycerophospholipid composition. However, under pathological situations (ischemia), the overstimulation of phospholipase A2 results in a rapid generation and accumulation of free fatty acids including arachidonic acid, eicosanoids, and lipid peroxides. This results in neural inflammation, oxidative stress, and neurodegeneration. In neural membranes, the deacylation-reacylation cycle maintains a balance between free and esterified fatty acids, resulting in low levels of arachidonic acid and lysophospholipids. This is necessary for not only normal membrane integrity and function, but also for the optimal activity of the membrane-bound enzymes, receptors, and ion channels involved in normal signal-transduction processes.
Markesbery, W. R. and J. M. Carney (1999). "Oxidative alterations in Alzheimer's disease." Brain Pathol 9(1): 133-46.
There is increasing evidence that free radical damage to brain lipids, carbohydrates, proteins, and DNA is involved in neuron death in neurodegenerative disorders. The largest number of studies have been performed in Alzheimer's disease (AD) where there is considerable support for the oxidative stress hypothesis in the pathogenesis of neuron degeneration. In autopsied brain there is an increase in lipid peroxidation, a decline in polyunsaturated fatty acids (PUFA) and an increase in 4-hydroxynonenal (HNE), a neurotoxic aldehyde product of PUFA oxidation. Increased protein oxidation and a marked decline in oxidative-sensitive enzymes, glutamine synthetase and creatinine kinase, are found in the brain in AD. Increased DNA oxidation, especially 8-hydroxy-2'-deoxyguanosine (8-OHdG) is present in the brain in AD. Immunohistochemical studies show the presence of oxidative stress products in neurofibrillary tangles and senile plaques in AD. Markers of lipid peroxidation (HNE, isoprostanes) and DNA (8-OHdG) are increased in CSF in AD. In addition, inflammatory response markers (the complement cascade, cytokines, acute phase reactants and proteases) are present in the brain in AD. These findings, coupled with epidemiologic studies showing that anti-inflammatory agents slow the progression or delay the onset of AD, suggest that inflammation plays a role in AD. Overall these studies indicate that oxidative stress and the inflammatory cascade, working in concert, are important in the pathogenetic cascade of neurodegeneration in AD, suggesting that therapeutic efforts aimed at both of these mechanisms may be beneficial.
Hall, E. D., J. A. Oostveen, et al. (1997). "Immunocytochemical method for investigating in vivo neuronal oxygen radical-induced lipid peroxidation." J Neurosci Methods 76(2): 115-22.
The investigation of oxygen radical-induced lipid peroxidative neuronal damage in the context of acute and chronic neurodegenerative disorders has been largely limited to the use of ex vivo analytical methodologies. These are often fraught with sensitivity or specificity problems, or they are indirect. Furthermore, none of the analytical methods allow precise anatomical identification of the cells that are undergoing peroxidative injury. This paper describes an immunocytochemical method for localization of central nervous system (CNS) lipid peroxidation (LP) that employs a rabbit-derived antibody raised against malondialdehyde (MDA)-modified rabbit serum albumin (RSA). MDA is a breakdown product of peroxidized membrane polyunsaturated fatty acids that avidly binds to cellular proteins. Using the anti-MDA-RSA, we herein illustrate increased MDA-derived immunostaining: (1) in the spinal cord of transgenic familial amyotrophic lateral sclerosis (ALS) mice; and (2) in the selectively vulnerable gerbil hippocampal CA1 region after a 5 min episode of forebrain ischemia and its relationship to the time course of neuronal degeneration.
Fressinaud, C., J. M. Vallat, et al. (1987). "Changes in composition of endoneurial and perineurial fatty acids during glycerol-induced Wallerian degeneration and regeneration in the sciatic nerve of the adult rat." J Neurochem 49(3): 797-801.
Intraneural injection of pure glycerol induces Wallerian degeneration with subsequent regeneration. In agreement with other reports, we observed an increase in endoneurial polyunsaturated fatty acids 8 days after the glycerol injection. Levels then fell until day 30. After a period of 5 months, there was an increase in C18:2(n-6) in the intrafascicular tissue, concomitant with a marked fall in this fatty acid in the remaining extrafascicular perineurium. The rise in C18:2(n-6) in endoneurium correlated with infiltration of this tissue by perineurial cells. Interactions between perineurium and endoneurium during nerve regeneration are discussed.
Yao, J. K., P. J. Dyck, et al. (1981). "Free fatty acid composition of human and rat peripheral nerve." J Neurochem 36(3): 1211-8.
The free fatty acid (FFA) composition of peripheral nerve resembles that of erythrocytes but the composition of both is different from that of brain and other tissues. Approximately 75% of FFAs of nerve and erythrocytes are saturated and less than 5% are polyunsaturated whereas in brain and other tissues, 30-45% of FFAs are saturated and 25-50% are polyunsaturated. Approximately 10-15% of the total FFA of nerve have very long chain lengths [C24, C26, C28, and C30]. The presence of these very long-chain FFAs in endoneurium cannot be accounted for by the retention of erythrocytes or by lipid degradation. During Wallerian degeneration a significant increase of 18:1, associated with a decrease of saturated FFAs, was found in rat sciatic endoneurium, but normal values were approached when fiber regeneration was well under way. The FFA composition with chain length greater than or equal to C26 were not, however, significantly altered with degeneration or repair of nerves. The metabolic significance of this striking difference between nerve and brain FFA composition is unknown but may reflect different functional properties.