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Synthesis and transport of cerebrosides and sulfatides in rat brain during development.

Synthesis and transport of nonhydroxy fatty acid (NFA)- and hydroxy fatty acid (HFA)-containing ceramides, cerebrosides, and sulfatides were studied in vivo in rat brain during development. After an intracerebral injection of [3H]serine, incorporation into these lipids of microsomal and myelin membranes was analyzed after HPLC. Distribution of amounts and incorporation of radioactivity were also determined in individual molecular species of these lipids. The results showed that HFA-ceramides and long-chain NFA-ceramides have small pool sizes and rapid turnover rates in the microsomal membranes and are preferentially utilized for the synthesis of long-chain (greater than or equal to 20:0) HFA- and NFA-galactocerebrosides of both microsomal and myelin membranes. Glucocerebrosides are not expressed in myelin and their synthesis in microsomal membranes is predominant before the onset of myelination. With development, synthesis and accumulation of HFA-cerebrosides increase over NFA-cerebrosides in both microsomal and myelin membranes. In myelin, incorporation of radioactivity into HFA-cerebrosides is even higher than that expected by transport alone from microsomal membranes and it is possible that part of the HFA-cerebrosides in myelin could be due to de novo synthesis by myelin itself. The amount of NFA- and HFA-sulfatides is about equal, both in myelin and microsomal membranes, and this relative proportion does not change with development. Similar relative rates of incorporation of radioactivity into sulfatides of microsomal and myelin membranes are consistent with the notion that both NFA and HFA sulfatides are synthesized in the microsomal (Golgi) membranes and are transported to myelin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Characterization and direct quantitation of cerebroside molecular species from lipid extracts by shotgun lipidomics.

By using shotgun lipidomics based on the separation of lipid classes in the electrospray ion source (intrasource separation) and two-dimensional (2D) MS techniques (Han, X., and R. W. Gross. 2004. Shotgun lipidomics: electrospray ionization mass spectrometric analysis and quantitation of the cellular lipidomes directly from crude extracts of biological samples. Mass Spectrom. Rev. First published on June 18, 2004; doi: 10.1002/mas.20023, In press), individual molecular species of most major and many minor lipid classes can be quantitated directly from biological lipid extracts. Herein, we extended shotgun lipidomics to the characterization and quantitation of cerebroside molecular species in biological samples. By exploiting the differential fragmentation patterns of chlorine adducts using electrospray ionization (ESI) tandem mass spectrometry, hydroxy and nonhydroxy cerebroside species are readily identified. The hexose (either galactose or glucose) moiety of a cerebroside species can be distinguished by examination of the peak intensity ratio of its product ions at m/z 179 and 89 (i.e., 0.74 +/- 0.10 and 4.8 +/- 0.7 for galactose- and glucose-containing cerebroside species, respectively). Quantitation of cerebroside molecular species (as little as 10 fmol) from chloroform extracts of brain tissue samples was directly conducted by 2D ESI/MS after correction for differences in (13)C-isotopomer intensities. This method was demonstrated to have a greater than 1,000-fold linear dynamic range in the low concentration region; therefore, it should have a wide range of applications in studies of the cellular sphingolipid lipidome.

Animals↗

Influence of nicotinic acid on cerebroside synthesis in the brain of developing rats.

The effect of nicotinic acid on synthesis of cerebroside was studied during brain development. Nicotinic acid concentration in the whole brain and liver of rats fed on nicotinic acid-deficient diet for 10 days after weaning was lower than that of animals fed on nicotinic acid-supplemented diet. The cerebroside concentration was markedly lower and the total lipid concentration was slightly lower in the brain of nicotinic acid-deficient animals than in those receiving nicotinic acid-supplemented diet. Therefore, the ratio of cerebrosides to total lipids of nicotinic acid-deficient rats was significantly lower than that of nicotinic acid-supplemented rats. In nicotinic acid-deficient rats, the ratio of long-chain to short-chain fatty acid (C20-24/C14-18) was decreased in the nonhydroxy fatty acid fraction. Moreover, the ratio of synthesis of cerebrosides with hydroxy fatty acid to nonhydroxy fatty acid of nicotinic acid-deficient rats was higher than that of rats fed on nicotinic acid-supplemented diet. These observations suggest that nicotinic acid affects the synthesis of cerebrosides with nonhydroxy fatty acid.

Animals↗

[Comparative research on the cerebroside and sulfocerebroside content of the mammalian brain].

Data are presented on cerebroside and sulfocerebroside content of the brain for 31 mammalian species from 8 orders. The increase in concentration of both glycolipids in the brain of mammals in phylogenesis was demonstrated. Low levels of cerebrosides and sulfocerebrosides were found in the brain of lower mammals (Insectivora, Chiroptera) and high ones--in the brain of higher mammals (Carnivora, Primates). Irrespectively from taxonomic position and ecological factors, in the brain of all mammals investigated higher content of cerebrosides with hydroxy acids was found as compared to the content of cerebrosides with normal fatty acids. The ratio of these cerebrosides in the brain of terrestrial mammals is 2-3 times higher than in aquatic and semi-aquatic ones. The data obtained are discussed in relation to the development of the brain of mammals during their phylogenesis.

Animals↗

The effects of cerebrosides on model membrane shape.

Model membranes composed of phosphatidylcholine, various cerebrosides, and cholesterol have been studied by electron microscopy, deuterium NMR, and phosphorus-31 NMR. Large variations in phosphatidylcholine membrane morphology are observed when cerebrosides are present in phosphatidylcholine bilayers. Large spherical liposomes, small spherical liposomes, and long tubular liposomes are formed, depending on the relative acyl chain lengths of the phosphatidylcholine and cerebroside. In some cases, cholesterol can reverse the morphological effects of cerebrosides. These results suggest that cerebrosides, which are found in high concentrations in certain highly specialized membranes, can affect membrane shape and may be involved in the mechanism of formation of membranes with unusual morphology, e.g. neural myelin and the brush border membrane of the intestinal epithelium.

1,2-Dipalmitoylphosphatidylcholine↗

Inhibition of cerebroside synthesis in the brains of mice treated with L-cycloserine.

Subcutaneous injection of L-cycloserine resulted in a 28% reduction in cerebroside levels in mouse brain but had no effect on the levels of gangliosides. In contrast, intraperitoneal injection results in a reduction of ganglioside as well as cerebroside + sulfatide levels. The route of injection influenced the degree of 3-ketodihydrosphingosine synthase inhibition. Intraperitoneal injection caused a rapid decrease in synthase activity followed by recovery over 48 hr, whereas subcutaneous injection resulted in no inhibition over this time; only after daily injection for a week was synthase activity reduced 35%. One week following cessation of L-cycloserine administration, enzyme activity had recovered, whereas the cerebroside level continued to fall. All lipids and enzymes showed normal levels 3 weeks post-cycloserine administration. L-[3H]serine incorporation into glycolipids showed that cerebroside synthesis was most affected, whereas sulfatide synthesis was less affected. One week after cessation of cycloserine treatment, cerebroside synthesis was still severely inhibited, whereas sulfatide levels were near normal. Two weeks after cessation of L-cycloserine administration, synthesis of these glycolipids was similar to that of controls.

Animals↗

[Fatty acids of the cerebrosides (1-beta-glycosylceramides) and sulfatides (sulfoglycosylceramides) of the brain of the river lamprey Lampetra fluviatilis].

The analysis of the fatty acids of cerebrosides and sulfatides from the brain of the lamprey L. fluviatilis has been carried out. Only normal fatty acids were revealed by TLC of total methyl esters of the fatty acid of cerebrosides and sulfatides. The hydroxy fatty acids are apparently absent. The composition of the normal fatty acids of cerebrosides and sulfatides is very similar. TLC revealed fatty acids containing from 14 to 27 C mainly saturated and small amount of monoenes. The fatty acid pattern of cerebrosides and sulfatides from lamprey brain resembles that from the brain of other vertebrates. The peculiarity of the fatty acid composition of these glycolipids in the lamprey brain is the high proportion of short chain (C14--C18) saturated acids, especially of palmitic acid. The fatty acid composition of cerebrosides and sulfatides from lamprey brain which does not contain myelin is rather similar to that of mammalian brain in early development before the onset of myelination.

Animals↗

Concentration and fatty acid composition of cerebrosides and sulfatides in mature and immature human brain.

The fatty acid composition of cerebrosides and sulfatides from frontal lobe gray and white matter was determined for five fresh and four formalinized adult brains and for eight infants. Fatty acid patterns were unaffected by formalinization, but varied considerably from one another in the proportion of saturated to unsaturated fatty acids. The percentages of 24:0 and 24:1 increased with age. Cerebrosides obtained from areas such as the brainstem and cerebellum, where myelination was more advanced, tended to have a larger proportion of long-chain fatty acids than samples extracted from frontal or parietal lobe white matter. Hydroxy fatty acids showed an adult pattern in all instances in which amounts sufficient for accurate quantification could be isolated. Lipid hexose, cerebroside + sulfatide hexose, and methanoleluted hexose were measured in the brains of 12 infants ranging in age from a 4 month fetus to 2 yr. In the most immature, the majority of lipid hexose was in the form of glycolipids more polar than cerebrosides and sulfatides. These have tentatively been identified as hematosides and globosides. With maturation, cerebrosides and sulfatides increased progressively, but the amounts of the more polar glycolipids remained constant in relation to the total lipid content of tissue.

Adult↗

Determination of less than a nanomol of cerebrosides by high performance liquid chromatography with gradient elution analysis.

A gradient elution high performance liquid chromatography method with detection at 230 nm for the analysis of perbenzoylated cerebrosides containing hydroxy and nonhydroxy fatty acids is described. The quantitative range of the method is 0.5-10 nmol of cerebrosides. The limit of detection for injected sample is about 10 picomol. The analysis time by liquid chromatography is less than 5 minutes and prior purification of the cerebrosides from other lipids in brain lipid extracts is not necessary. The cerebrosides are first perbenzoylated with 50 micronl of 10% benzoyl chloride in pyridine and then separated on a chromatographic column of Zipax. The gradient elution is with 2.8-5.5% of dioxane in hexane. This gradient elution micromethod is at least 10 times more sensitive than isocratic elution methods with detection at 280 nm. The method is applicable to other biological materials containing minute amounts of cerebrosides if the glycolipid fraction is first isolated from the lipid extracts. A further fourfold increase in the sensitivity is achieved by replacing air in the reference cell of the detector by gradient elution solvent.

Animals↗

Effect of neonatal undernutrition upon cerebroside sulfate degradation in the developing rat brain.

In order to find out if the decreased accumulation of cerebroside sulfates observed in 21-d-old undernourished rats was in part the result of an increased rate of catabolism of these galactolipids, the in vivo degradation of brain cerebroside sulfates was studied in 18-d-old normal and undernourished rats. Two hours after the intracranial injection of the precursor (0 time), the animals were injected intraperitoneally with unlabeled sodium sulfate. Labeled cerebroside sulfates were measured in the brain up to 48 h after the chase. In normal animals, the radioactivity decreased at 24 h and 48 h to 55% and 41%, respectively, of the value obtained at 0 time. In undernourished animals, degradation was negligible, since the radioactivity attained at 0 time remained almost constant up to 48 h. The lack of in vivo degradation of cerebroside sulfates observed in the starved rats cannot be explained by a deficiency of Arylsulfatase A, since the pattern of activity of the enzyme was similar in both groups of animals.

Aging↗

Isolation and characterization of cerebrosides of the hydrocarbon-assimilating yeast Yarrowia lipolytica.

Yarrowia lipolytica yeast was grown batchwise on n-hexadecane as the carbon and energy source. Two cerebroside species were quantitatively isolated from sphingolipid fractions of total lipids by a combination of column chromatography and preparative high-performance thin-layer chromatography. The cerebroside content accounted for 1.3% of the total cell lipids. Glucose was detected as the sole sugar constituent in cerebrosides. The fatty acid composition of cerebrosides was characterized by a high proportion of hydroxylated long-chain saturated fatty acids. The major fatty acids were h16:0 and 16:0. The long-chain bases composition shows a preponderance of trihydroxy bases and a small amount of dihydroxy bases. The striking finding was a high proportion of 19-phytosphingosine.

Alkanes↗

Intramyelinic conversion of cerebrosides into acylgalactosylceramides.

Acylgalactosylceramide (AGC) synthesis was measured in vivo, and in a cell free system. 24 hours post-injection of [3H] palmitic acid into rat brain, more than 60% of the AGC radioactivity was associated with an ester linkage. Isolated rat myelin was incubated in the presence of [14C] palmitic acid, 2mM ATP, 50 microM CoA and 10 mM MgCl2 and acylation of myelin cerebrosides occurred at a linear rate for at least 60 min. Incubation of isolated myelin under standard conditions with [3H] cerebrosides and [14C] palmitic acid produced double labeled AGC. Labeling of AGC was maximum at pH 7.5 and 37 degrees C and appeared to be enzyme mediated inasmuch as it was reduced by myelin incubation with trypsin and drastically reduced by preheating the myelin for 5 min at 80 degrees C. Omission of ATP, CoA, MgCl2 or all three did not reduce fatty acid incorporation into AGC when compared to the values in the complete system. Addition of Triton X100 or Sodium Dodecyl Sulfate had little or no effect on the acylation of cerebrosides. Pulse chase experiments indicated that the reaction involved the net addition of fatty acid to the cerebrosides, rather than a rapid fatty acid exchange.

Animals↗

The long-term administration of L-cycloserine to mice: specific reduction of cerebroside level.

Short-term experiments in which L-cycloserine, the inhibitor of 3-ketodihydrosphinogosine synthase, was injected subcutaneously in young mice have shown that cerebroside synthesis is inhibited specifically. Studies on the effect of long term L-cycloserine treatment on sphingolipid synthesis were performed to determine whether mice could tolerate continued cerebroside reduction and whether or not the synthesis of other sphingolipids would be inhibited. L-cycloserine, when injected at a low dose for a period of two months resulted in significantly reduced brain cerebroside level with little or no reduction in sulfatide, ganglioside, or sphingomyelin levels; liver and spleen glucocerebroside levels were also significantly reduced. The rate of cerebroside synthesis in brain was greatly reduced, whereas synthesis of sulfatides was much less affected by L-cycloserine indicating that a portion of newly synthesized galactocerebroside is shunted to synthesis of sulfatides.

Animals↗

Deuterium NMR studies of cerebroside-phospholipid bilayers.

2H-NMR was used to probe the interaction of non-hydroxy fatty acid cerebroside and 2-hydroxy fatty acid cerebroside with the polar head group and with the acyl chains of dipalmitoylphosphatidylcholine in unsonicated bilayers. It is shown that the interior of the bilayer exhibits uniformly increasing orientational order as the concentration of both types of cerebroside increases, whereas the surface of the bilayer, as reflected by the head group motion, becomes disordered. The extent of the disorder at the surface is dependent upon the type and concentration of the cerebroside. These results are discussed in terms of hydrogen-bonding interactions.

Cerebrosides↗

Interaction of myelin basic protein and polylysine with synthetic species of cerebroside sulfate.

The effect of myelin basic protein on the myelin lipid cerebroside sulfate was studied by differential scanning calorimetry and use of the fatty acid spin label, 16-S-SL, in order to determine (i) the effect of basic protein on the metastable phase behavior experienced by this lipid, and (ii) to determine if basic protein perturbs the lipid packing as it does with some acidic phospholipids. The effects of basic protein on the thermodynamic parameters of the lipid phase transition were compared with those of polylysine which has an ordering effect on acidic phospholipids as a result of its electrostatic interactions with the lipid head groups. Different synthetic species of cerebroside sulfate of varying fatty acid chain length and with and without a hydroxy fatty acid were used. The non-hydroxy fatty acid forms of cerebroside sulfate undergo a transition from a metastable to a more ordered stable state while the hydroxy fatty acid forms remain in the metastable state at the cation concentration used in this study (0.01 M Na+ or K+). The non-hydroxy fatty acid forms were still able to go into a stable state in the presence of both basic protein and polylysine. At low concentrations, basic protein increased the rate of the transition to the stable state, while polylysine decreased it for the longest chain length form studied. However, at high concentrations, basic protein probably prevented formation of the stable state. The hydroxy fatty acid forms did not go into the stable state in the presence of basic protein and polylysine. It is argued that the increased rate of formation of the stable state in the presence of basic protein and decreased rate in the presence of polylysine are consistent with interdigitation of the lipid acyl chains in the stable state. Basic protein also had a small perturbing effect on the lipid. It decreased the total enthalpy of the lipid phase transition. When added to the non-hydroxy fatty acid forms it increased the temperature of the liquid crystalline to metastable phase transition and decreased the temperature of the stable to liquid crystalline phase transition. It significantly decreased the transition temperature of the hydroxy fatty acid forms but only a portion of the lipid was affected. In contrast, polylysine increased the transition temperature of the metastable and stable states of all forms of cerebroside sulfate but had a greater effect on the non-hydroxy fatty acids forms than on the hydroxy fatty acid forms.(ABSTRACT TRUNCATED AT 400 WORDS)

Calorimetry, Differential Scanning↗

The sulphatase of ox liver. XXII. Further observations on the cerebroside sulphatase activity of sulphatase A.

Further studies have been made of the cerebroside sulphatase activity of the sulphatase A (aryl-sulphate sulphohydrolase, EC 3.1.6.1) of ox liver. It is concluded that a cerebroside sulphate-modified form of the enzyme is not produced and that the kinetics of the reaction can be explained by the utilisation of the substrate and accumulation of (SO4)2-. The hypothesis is advanced that this difference between the cerebroside sulphatase and arylsulphatase activities arises from non-polar binding of the cerebroside to the enzyme. Possible reasons for the differences between these results and those of other (Stinshoff, K. and Jatzkewitz, H. (1975) Biochim. Biophys. Acta 377, 126-138) are considered.

Animals↗

The effect of the interdependence of protein and bile salt concentrations on the measurement of cerebroside sulphate sulphatase activity in human leucocyte and fibroblast extracts.

The previously observed differences in properties of human leucocyte and fibroblast cerebroside sulphate sulphatase (cerebroside-3-sulphate 3-sulphohydrolase, EC 3.1.6.8) measured in vitro have been found to be due to subtle differences in incubation conditions. Maximum enzyme activity was observed with either crude sodium taurocholate or with pure sodium taurodeoxycholate. The optimum bile salt concentration of the enzyme in leucocyte or fibroblast extracts, but not the pure ox liver enzyme, was critically dependent on protein concentration. At low concentrations of the latter (less than 0.1 mg/ml), maximum activity was observed at taurocholate concentrations less than 0.5 mg/ml; at protein concentrations greater than 0.20 mg/ml substantially more bile acid (more than 1.3 mg/ml) was required to stimulate maximum activity. Addition of Triton X-100 or bovine serum albumin to the incubation mixtures increased the optimum taurocholate concentration. The dependence of the bile salt optimum on protein concentration appears to be related to the binding of the lipid substrate to membranous protein present in the tissue extracts. Release of the bound lipid is effected either by increasing the bile salt concentration or by adding Triton X-100. In the presence of excess bile salt human leucocyte, fibroblast and liver cerebroside sulphate sulphatase activity is stimulated by Triton at low protein concentrations; under identical conditions the pure or crude ox-liver enzyme is substatially inhibited. Our data also show that cerebroside sulphate sulphatase activity measured in extracts from leucocytes and fibroblasts, the tissues normally used to effect a diagnosis of metachromatic leucodystrophy, is the result of a complex interaction of bile salt, protein, Triton X-100 and probably the substrate itself. Any slight alteration in any of those factors, without a corresponding change in any or all of the others, can have a marked effect on the measured enzyme activity, and may lead to errors in the diagnosis of metachromatic leucodystrophy.

Animals↗

Sodium ion diffusion through liposome membranes containing cerebroside.

Na+ efflux from liposomes (small unilamellar vesicles, SUV) of various compositions was studied, using 22Na+ and 3H-labelled stachyose in simultaneous dual isotope measurements, stachyose being used as a measure of liposome disintegration. Dialysis was utilised to separate liposomes from extra-liposomal activity. Liposomes were made from egg lecithin and sphingomyelin and from mixtures of egg lecithin, sphingomyelin, cerebroside, sulphatide and cholesterol. All mixtures produced more leaky and less stable SUVs than pure lecithin and pure sphingomyelin. The incorporation of cerebroside is significantly smaller than that of the phospholipids including sphingomyelin. It was found that membranes containing cerebroside had a significantly higher Na+ permeability than membranes without cerebroside.

Cerebrosides↗