Brain lipids study

The distribution of endosulfan and endosulfan sulfate was evaluated in the brains of cats given a single intravenous injection of 3 mg/kg endosulfan (Khanna et al. 1979). Peak concentrations of endosulfan in the brain were found at the earliest time point examined (15 minutes after administration) and then decreased. When tissue levels were expressed per gram of tissue, little differential was observed in distribution among the brain areas studied. However, if endosulfan levels were expressed per gram of tissue lipid, higher initial levels were observed in the cerebral cortex and cerebellum than in the spinal cord and brainstem. Loss of endosulfan was most rapid from those areas low in Upid. Endosulfan sulfate levels peaked in the brain at 1 hour postadministration. In contrast, endosulfan sulfate levels in liver peaked within 15 minutes postadministration. The time course of neurotoxic effects observed in the animals in this study corresponded most closely with endosulfan levels in the central nervous system tissues examined. 

In a study using doses of 0.1 and 300 mg/kg intraperitoneally-administered hexachlorobutadiene, the label was found in the liver, kidney, and adipose tissue. Very little of the label was found in the brain, lung, heart, and muscle tissue at 48 hours after dosing (Davis et al. 1980). The reported levels in the brain in this study differ from those reported at 72 hours following oral administration (Reichert et al. 1985). This may indicate that there is a gradual deposition of labeled hexachlorobutadiene and/or its metabolites in the brain lipids over time. 

A solution of brain lipids was brushed across a small hole in a 5-ml. polyethylene pH cup immersed in an electrolyte solution. As observed under low power magnification, the thick lipid film initially formed exhibited intense interference colors. Finally, after thinning, black spots of poor reflectivity suddenly appeared in the film. The black spots grew rapidly and evenutally extended to the limit of the opening (5, 10). The black membranes have a thickness ranging from 60-90 A. under the electron microscope. Optical and electrical capacitance measurements have also demonstrated that the membrane, when in the final black state, corresponds closely to a bimolecular leaflet structure. Hence, these membranous structures are known as bimolecular, black, or bilayer lipid membranes (abbreviated as BLM). The transverse electrical and transport properties of BLM have been studied usually by forming such a structure interposed between two aqueous phases (10, 17). 

In the present study various surface measurements were made on interfacial lipid films to analyze in more detail the nature of interactions of lipids, Ca2+, ATP, and the glycolate esters. Surface pressure-area and surface potential-area diagrams were obtained on surface films of stearic acid, lecithin, and a mixture of brain lipids with Ca2+, ATP, and the drugs present in the subsolution, individually or in combination. Using radioactive Ca2+, ATP, and drug, quantitative measurements were made on the surface adsorption of these substances to lipid films. In addition, electron microscopy was performed on brain lipid films formed in the presence or absence of Ca2+ and ATP. Our objective was to establish the existence of surface complexes involving these substances with the hope... 

The adsorption of ATP-14C to surface films of stearic acid and brain lipid was examined over an extended period of time under various conditions (Table I and Figure 6B). Table I shows the short-term results, where adsorption was studied during the first 30 minutes, and evaporation was not a factor. Upon adding stearic acid or brain lipid the measurable radioactivity decreased, probably as a result of displacement of ATP-14C from the surface layer and self-absorption of the beta particles by the lipid film. When PMCG was present, there was a slight but significant increase in the surface adsorption of ATP. The amount of ATP adsorbed was 4 X 10 10 moles/sq. cm. for stearic acid and 2.5 X 10"10 moles/sq. cm. for brain lipid. If the lipid concentration in the surface is assumed to be about 8 X 10 10M (as phospholipid in the case of brain lipid), the molar ratio of ATP to lipid would be about 0.5 for stearic acid and 0.3 for brain lipid. 

The surface adsorption of tritiated PMCG was studied as a function of its bulk concentration (Figure 7). In the absence of brain lipid the surface adsorption increased sharply as the concentration approached 10"4M, reaching a maximum at 5 X 10 3M. When brain lipid (5 X 10 9 moles, as phospholipid) was added, the surface adsorption of PMCG was significantly reduced. If the solutions were allowed to dry, the concentration-radioactivity curve was essentially parallel to that obtained for PMCG in solution. When brain lipid was present as the samples were dried, the radioactivity increased twofold. Since the residue could not be dried as a uniform layer, it is not possible to make any reasonable estimation of the amount of PMCG adsorbed to the dried lipid film. 

Similarly, apolipoprotein E expression increases in neurotoxicity mediated by KA (Table 6.3) (Boschert et al., 1999). Apolipoprotein E is a major lipoprotein in the brain. It is involved in the transport, distribution, and other aspects of cholesterol homeostasis. Apolipoprotein E also plays a dominant role in the mobilization and redistribution of brain lipids in repair, growth, and maintenance of nerve cells (Mahley, 1988). The secretion of apolipoproteins E and D may be differentially regulated in cultured astrocytes. In cell culture systems this depends upon the extracellular lipid milieu (Patel et al., 1995). During neurotoxicity mediated by KA, apolipoprotein E levels increase moderately in astrocytes and apolipoprotein E mRNA increases very strongly in clusters of CA1 and CA3 pyramidal neurons. Based on hybridization in situ and immunohistochemical studies, expression of apolipoprotein E in neurons may be a part of a rescue program to counteract neurodegeneration mediated by KA (Boschert et al., 1999). 

In a subsequent brain-tumor study (ref. 526) using LCM along with a lipid-specific stain (cf. 569), a detailed evaluation of the actual distribution of lipid-coated microbubbles in the tumor and surrounding organ was conducted and compared to the distribution of echoes (from the microbubbles) on the sonogram. 

In this study, the TC-CCC system was applied to solve the problem of emulsification, and satisfactory stationary phase retention was obtained. Human brain lipids could then be separated. We established the solvent systems that are used for the separation of most of the phospholipids, glycolipids, and less-polar hpids of the human brain. Furthermore, we demonstrated that molecular species, which are derived from variations of the hydrophobic tail group, were separated by optimizing the composition of the solvents. TC-CCC is available for analyzing the hydrophobicities of various lipid molecules in biomembranes. 

In atwo-generafion study (Lamptey, 1976) rats were fed diets containing 10% soybean oil or 10% safflower oil. The effect on brain lipids was primarily that the first group was... 

These studies showed that there was little apparent accumulation of labeled ALA in liver and brain lipids however, half of the dose was found in the carcass lipids. The next experiment was designed to determine the distribution of ALA in the whole body and the various major tissue compartments for fatty acids. 

It seems that a large proportion of adult rat, rabbit, or chicken brain cholesterol undergoes very slow metabolism. Since about 70% of brain cholesterol is located in the myelin sheath, it is probable that at least part of this structure is metabolically a relatively stable tissue component. Other studies on brain lipids support this view. Thus distribution of rat brain cerebroside sulfate is similar to that of cholesterol and turnover of sulfatide is also exceedingly slow. Furthermore, Davison and Gregson (1962) found that persisting radioactivity was associated primarily with the myelin fraction prepared from brains of rats previously injected with S -sulfate or methionine. 

Applications of countercurrent distribution to lipid purification were already reported in the 1950s. These included the isolation of PC, SPM, or cerebrosides from brain tissue, or the placenta. It was then mentioned that lipids easily emulsify, and this adversely affects the ability to separate them. Therefore these methods were only used for crude separation. The method also requires a long time for phase separation before each phase transfer, and this procedure needs to be repeated 500-3000 times. Otsuka and Yamakawa reported the application of droplet CCC to the purification of phospholipids and glycohpids. Because the stationary phase retention is much more stable in TC-CCC than with HS-CCC, it has become possible to select appropriate two-phase solvent systems. In this study, we showed the successful separation of human brain lipids by using TC-CCC. Additionally, if an isolated band can be observed on HPTLC, the lipid can be purified by using silica column chromatography after TC-CCC cmde separation. 

In the method described below, the processes of bilayer deformation can be studied using synthetic hposomes of any defined lipid composition. Liposomes are incubated with the protein of interest and observed in the electron microscope to reveal changes in liposome conformation accompanied with protein binding. In many of our studies where we did not know the precise hpid composition to use, we have instead used Folch brain lipids (Sigma, St. Louis, MO). 

Different animal species eat different foods in which the fatty acids vary considerably. Adaptation to different food structures throughout evolution could have led either to differences in brain lipids or, if the resistance to change was sufficiently great, the same lipid profile would evolve, but associated with differnet degrees of brain development. In this paper we wish to present data from a comparative analysis of 45 different animal species together with results obtained from the study of the fetal accumulation of the brain EFA in the human and in the guinea-pig. 

The results demonstrate that the fetus is not simply dependent on maternal food intake, but that both placenta and fetus actively reprocess the essential fatty acids with the result that long-chain polyenoic acids are incorporated into the developing brain lipids. Although this process is clearly of great importance to brain development, the conversion of a —linolenic acid to docosahexaenoic acid is slow. A low desaturation rate of parent essential fatty acids is consistent with the Zn )iXKO studies reported by Professor Brenner and Dr. Sprecher earlier in this conference and with our iyi )AJ00 observations in the rat (Hassam, Sinclair Crawford, 1975 Hassam Crawford, 1976 Hassam, Rivers Crawford, 1976). In the cat the desaturase was not detected (Rivers, Sinclair Crawford, 1975) iyi )lvo. 

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