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Plasma membrane lipids in the resurrection plant Ramonda serbica following dehydration and rehydration.

Plants of Ramonda serbica were dehydrated to 3.6% relative water content (RWC) by withholding water for 3 weeks, afterwards the plants were rehydrated for 1 week to 93.8% RWC. Plasma membranes were isolated from leaves using a two-phase aqueous polymer partition system. Compared with well-hydrated (control) leaves, dehydrated leaves suffered a reduction of about 75% in their plasma membrane lipid content, which returned to the control level following rewatering. Also the lipid to protein ratio decreased after dehydration, almost regaining the initial value after rehydration. Lipids extracted from the plasma membrane of fully-hydrated leaves were characterized by a high level of free sterols and a much lower level of phospholipids. Smaller amounts of cerebrosides, acylated steryl glycosides and steryl glycosides were also detected. The main phospholipids of control leaves were phosphatidylcholine and phosphatidylethanolamine, whereas sitosterol was the free sterol present in the highest amount. Following dehydration, leaf plasma membrane lipids showed a constant level of free sterols and a reduction in phospholipids compared with the well-hydrated leaves. Both phosphatidylcholine and phosphatidylethanolamine decreased following dehydration, their molar ratio remaining unchanged. Among free sterols, the remarkably high cholesterol level present in the control leaves (about 14 mol%) increased 2-fold as a result of dehydration. Dehydration caused a general decrease in the unsaturation level of individual phospholipids and total lipids as well. Upon rehydration the lipid composition of leaf plasma membranes restored very quickly approaching the levels of well-hydrated leaves.

Cerebrosides↗

Occurrence of 2-O-acyl galactosyl ceramide in whale brain.

Four glycolipids (Fr. I, II, III, and IV) were isolated from whale brain and three (Fr. I, II, and III) of them were demonstrated to be galactosyl ceramide combined with fatty acid by ester linkage. Fr. IV was shown to be a monoalkyl monoacyl galactosyl glycerol. For determining the substituted position of the acyl group on the galactose moiety, free hydroxyl groups of ester cerebrosides were protected with dihydropyran, deacylated by mild alkali treatment, and then subjected to permethylation. Finally, the methylated galactitol acetates obtained by hydrolysis and reduction were detected by gas chromatography and identified by gas chromatography-mass spectrometry. By this procedure, Fr. I was shown to be an acyl ester of kerasine, with the ester group at the 6-position of galactose. Fr. II and III were demonstrated to be acyl esters of phrenosine, in which the acyl groups were attached to the 6- and 2-position of the galactose, respectively. While the ester-linked acyl group of Fr. I, II, and III was composed of only normal fatty acids, predominantly palmitic acid, and the amide-linked fatty acids showed a heterogeneous composition of normal and hydroxy fatty acids, C16 to C24.

Animals↗

Abnormal metabolism of 35SO4-sulfatide in jimpy brains expressed in brain organotypic cultures.

Cerebroside-sulfotransferase (CST), creatine-phosphokinase (CPK), and 3-hydroxy-3-methylglutaroyl CoA (HMG CoA) reductase activity, protein, and DNA content were measured in an easy-to-perform organotypic culture system of newborn normal and jimpy brains. The defective sulfatide synthesis which has been shown in vivo in jimpy brains could also be demonstrated in organ cultures of jimpy mice in the form of lowered CST activity in the homogenate as well as reduced 35SO4 incorporation into 35SO4-sulfatide. HMG CoA reductase was reduced to 60% of that found in 16-day-old normal cultures, similar to the findings in vivo. DNA of jimpy cultures was significantly lower than that in normal cultures, suggesting the possibility of an arrest in the differentiation or increased cellular death of presumptive oligodendrocytes, as was found in vivo. Organ cultures of jimpy mouse brain can serve as an appropriate model for further study of the primary defect in this animal mutant.

Animals↗

Late juvenile metachromatic leukodystrophy (MLD) in three patients with a similar clinical course and identical mutation on one allele.

Metachromatic leukodystrophy (MLD) is an autosomal, recessively inherited, lysosomal storage disease caused by arylsulfatase A (ASA) activity deficit. Arylsulfatase A initiates the degradation of sulfatide (cerebroside sulfate), which is an essential component of myelin. The main clinical symptoms are caused by progressive demyelination. At least 34 MLD-related ASA mutations are known to date. I179S (E3P799) is a disease-related mutation, described for the first time by Fluharty in 1991. This aberration appears to substantially reduce, but not completely eliminate ASA activity, and was detected in individuals with late-onset (juvenile or adult) forms of MLD. This paper deals with the peculiar clinical course in three unrelated juveniles with late-onset MLD carrying the I179S mutations on one allele. In the three described patients with the I179S mutation, psychiatric disturbances and intellectual impairment dominated the clinical picture, while the neurological lesions progressed more slowly. Although the symptoms appeared rather early, making it possible to classify this as the juvenile type of MLD, the clinical picture was more that of the adult type. Although the mutations on the second allele in our patients are unknown, one can speculate, that the mutation I179S plays an important role in the characteristic clinical course (psychiatric impairment, slower neurological deterioration, but relatively early onset). It seems that I179S mutation on one allele with another mutation on the other allele reduces ASA activity, but the enzyme can still cope with a part of the substrate influx, leading to late-juvenile-onset MLD with such strikingly similar phenotypes remaining a little bit of the adult (psychiatric) type. This could be one more argument in favour of phenotype-genotype correlation in patients with MLD.

Adolescent↗

Fatty acid analysis of galactolipids and ganglioside in the brains of four cases of Nasu-Hakola disease.

A study was conducted on the fatty acid composition of cerebroside, sulfatide and ganglioside in the brains of 4 cases of Nasu-Hakola disease. The percentage of short carbon chain (C.16-C.18) nonhydroxy fatty acids of sulfatide in the cortex was much higher than that of the control and long-chain (C.24-) fatty acids showed a lower percentage. Sulfatide in the white matter was of the same tendency. The percentage of C.16:0 palmitic acid of ganglioside in the cortex was much larger than that of the control. Referring to the fatty acid composition of lipids in the literature, abnormalities of the fatty acid concentration, namely a high percentage of short-chain fatty acids of sulfatide and ganglioside in the cerebral cortex of the present cases, were confirmed.

Adult↗

Gene therapy for metachromatic leukodystrophy.

Metachromatic leukodystrophy (MLD) is an inherited metabolic disease which is characterized by a deficiency of arylsulfatase A (ASA). This deficiency causes progressive accumulation of cerebroside sulfate in oligodendrocytes (OL) in the brain, resulting in dysmyelination. Approaches being developed by the authors to treating MLD are based on direct delivery of ASA genes into the brain. In the present report, it has been shown that the recombinant adenovirus (Adex1SRLacZ) was able to transduce the OL very efficiently. Moreover, primary fibroblasts from MLD patients were exposed to recombinant adenovirus expressing the ASA gene (Adex1SRASA) and the cells expressed the transgene. The influence of overexpression of ASA on the activity of other sulfatases was also tested in fibroblasts from patients with MLD using a retrovirus vector (MFG-ASA). It was demonstrated that the overexpression of ASA reduces the activity of various sulfatases by a small amount but does not induce an accumulation of glycosaminoglycan. These results indicate that the influence of ASA overexpression on other sulfatases is different from that of the N-acetygalactosamine-4-sulfatase overexpression in a previous report. It was concluded that the correction of ASA deficiency by a recombinant adenovirus that potentially could be used to transfer the gene to the brain, and gene therapy for MLD based on gene transfer of the ASA gene to mutant cells will be feasible because the overexpression of ASA in cells does not lead to profound deficiency of other sulfatases or result in a new phenotype.

Adenoviridae↗

Delay of myelin formation in arylsulphatase A-deficient mice.

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder caused by the deficiency of arylsulphatase A (ASA). This leads to the accumulation of the sphingolipid 3-O-sulphogalactosylceramide (sulphatide) and progressive demyelination in the nervous system of MLD patients. The mechanisms and development of pathology in the disease are still largely unknown. In this study we investigate how the inability to degrade sulphatide affects the formation of myelin in ASA-deficient (ASA-/-) mice. In mice at 2 weeks of age there was a substantial reduction in myelin basic protein (MBP) mRNA and protein. This was confirmed by an immunohistochemical analysis. MBP mRNA and protein, however, reach normal levels at 3 weeks of age. Proteolipid protein (PLP) and MAL mRNA were also reduced in ASA-/- mice at 2 weeks of age; whereas the level of PLP mRNA was normal at 26 weeks of age, MAL mRNA expression remained reduced up to this age. In situ hybridization revealed no significant changes in the number of myelinating oligodendrocytes or oligodendrocyte precursor cells in ASA-/- mice. These results suggest that oligodendrocyte differentiation was normal in ASA-/- mice. No differences were found in the expression of the sulphatide synthesizing enzymes cerebroside sulphotransferase and UDP-galactose : ceramide galactosyltransferase. Our data demonstrate a delay in myelin formation in ASA-/- mice. This raises the possibility that similar alterations in MLD patients may contribute to the pathology of the disease.

Animals↗

Accessibility of galactosyl ceramides to probe reagents in central nervous system myelin.

The suitability of isolated central nerve myelin preparations for probe labelling studies was assessed and the accessibility of galactosyl ceramides in myelin to galactose oxidase and sodium periodate was determined. Isolated myelin preparations present a uniform external membrane surface to added probes because lamellae in the myelin sheath separate at their external apposition surfaces exclusively during isolation. The cytoplasmic apposition remains intact in isolated myelin. Cationised ferritin can gain access along external apposition regions of inner lamellae in multilamellar fragments of isolated myelin, indicating that proteins and lipids on the external membrane surface will be accessible to probes. Over 50% of the total galactosyl ceramides of myelin are accessible to galactose oxidase attack; hydroxy fatty acid- and nonhydroxy fatty acid-containing cerebrosides are equally attacked. Sodium periodate attacks over 90% of the galactosyl ceramides in isolated myelin at 20 degrees C and electron micrographs of the periodate-treated myelin reveal changes at the external apposition only. Galactosyl ceramides in vesicles of myelin lipid vesicles are not so readily attacked by periodate. The disposition of galactosyl ceramides in the myelin lamellae is discussed.

Animals↗

Inhibition of sphingolipid synthesis by cycloserine in vitro and in vivo.

D- and L-cycloserine were shown to be irreversible inhibitors of the first enzyme of the sphingolipid pathway, 3-ketodihydrosphingosine synthetase, in a study using bacterial and brain microsomal enzymes. L-Cycloserine was shown to be 100 times more inhibitory than the D-isomer for the brain microsomal enzyme in vitro. In vivo, L-cycloserine caused a 70% inhibition of brain microsomal enzyme. Following one injection, enzyme activity recovered 80% of normal after 16 hours. Daily dosages of L-cycloserine on a regimen of intraperitoneal injection for 7 days caused a significant reduction in total brain ganglioside and cerebroside plus sulfatide levels.

Animals↗

Neurological mutation characterized by dysmyelination in NCTR-Balb/C mouse with lysosomal lipid storage disease.

Morphological and biochemical studies were performed on the CNS of neurologically affected NCTR-Balb/C mouse. Histological and electron microscopic techniques demonstrated severe myelin deficiency in the affected brains. Neither the presence of lipid-containing macrophages nor reactive gliosis was apparent. Analysis of myelin-associated lipids and proteins revealed prominent depletion of galactocerebroside, sulfatide, and proteolipid proteins. In contrast to the scarcity of myelin-specific constituents a marked accumulation of GM2 and GM3 gangliosides and several neutral glycolipids, i.e., glucocerebroside, lactosylceramide, gangliotriaosylceramide, and gangliotetraosylceramide were found in affected CNS. These abnormalities were already apparent in 12-day-old pups as well as in 65-day-old mice. A significant deficit in the proportion of long-chain fatty acids (C24), notable in both normal and alpha-hydroxy acids of cerebrosides from affected white matter, was measured. The lack of reactive gliosis, the observed depletion of galactocerebroside and sulfatide at the early age of 12 days, and the relative decrease in long-chain fatty acids in affected CNS strongly suggest a defect in myelinogenesis in this mutant rather than a secondary process of myelin breakdown.

Animals↗

Cerebellum lipids in rats after chronic ethanol treatment.

Eighteen male Wistar rats weighing approximately 200 g were divided into three groups of six animals each. The experimental animals were maintained on nutritionally complete diets in which ethanol comprised 45% of the available energy. Control animals were pair-fed an equivalent diet in which sucrose was substituted isocalorically for ethanol. An additional control group received unlimited access to standard pelleted laboratory food and water. The investigations were carried out over 24 weeks. The effects on phospholipid, monogalactosyl glycolipid, and ganglioside composition after 24 weeks of feeding 43% alcohol were studied. There is abundant evidence that the changes in the cerebellum membrane phospholipids (phosphatidylethanolamine and phosphatidylcholine), gangliosides (GT1b), and myelin lipids (phosphatidylserine, sphingophospholipid, phosphatidylinositol, cerebrosides with hydroxy fatty acids, sulfoglycolipids, and monosialoganglioside GM1) occur as a result of chronic ethanol treatment.

Animals↗

A micromethod for the isolation of large and small microvessels from frozen autopsied human brain.

Microvessels were isolated from autopsied human brain using a simple procedure involving disruption, sieving, and centrifugation on a sucrose density gradient. The present procedure is characterized by isolation, from frozen autopsied brain, of materials either from the cerebral cortex or white matter, and subsequent separation of the capillary fraction from the large vessel fraction. The preparation appears highly purified under phase-contrast microscopic examination. The purity was also established by the enrichment of gamma-glutamyl transpeptidase activity and by the nearly negligible cerebroside content in the vessel fractions as compared to the brain homogenate.

Brain↗

Brain galactolipid content in a patient with pseudoarylsulfatase A deficiency and coincidental diffuse disseminated sclerosis, and in patients with metachromatic, adreno-, and other leukodystrophies.

A 4-year old boy died of diffuse disseminated sclerosis (DDS) of the brain and was found to have also pseudoarylsulfatase A deficiency (PASAD) with about 20% residual arylsulfatase A (ASA) and cerebroside sulfatase (CS) activity. The reexamination of lipids did not show any sulfatide accumulation in the patient's organ extracts. Although the residual CS activity in the patient's extracts was clearly demonstrable only after partial purification, it was concluded that this activity protects organ tissues from sulfatide accumulation in PASAD, since in sulfatide lipidosis (metachromatic leukodystrophy, MLD) no residual CS activity was detectable. The study of residual ASA activity in the patient's fibroblasts by gel electrofocusing resulted in an almost normal enzyme microheterogeneity. However, the detailed study of the brain galactolipids in the patient revealed an elevated ratio of sulfatide/galactocerebroside content, despite the decrease of both lipids. In tissues of other patients with severe demyelinating diseases different from DDS and MLD, this galactolipid ratio was also found to be increased, especially in three patients with adrenoleukodystrophy. A general mechanism of this anomaly in severe demyelination is considered.

Adolescent↗

Lysosulfatide (galactosylsphingosine-3-O-sulfate) from metachromatic leukodystrophy and normal human brain.

The glycosphingolipid pattern was examined in three cases of late infantile metachromatic leukodystrophy (MLD): one with a relatively short (2.5 years), one with a long (7.8 years), and one with a very long (13.2 years) survival time. All values were compared with those of age-matched normal controls. The cerebroside concentration was reduced to 25, 12, and 4%, respectively, in the MLD white matter, whereas the sulfatide concentration was increased up to 200% of the control value. The yield of myelin was reduced to less than 15% in the early case and to less than 3 and 1%, respectively, in the two later cases. There was no sign of increased sulfatide proportion in the myelin. The ganglioside pattern was normal in cerebral gray matter, but in the white matter, contents of gangliosides of the lacto series were significantly increased, in particular, the ganglioside suggested by us as being characteristic of reactive astrocytosis. For the first time, lysosulfatide was identified in MLD and normal human brains by mass spectrometry and radioimmunoaffinity TLC using specific monoclonal antibody. Its quantity was found to be similar in normal and MLD brains. These findings support our postulation that the lysoglycosphingolipids are synthesized de novo from sphingosine and that they do not play a key role in pathogenetic mechanisms.

Adolescent↗

Tellurium-induced neuropathy: metabolic alterations associated with demyelination and remyelination in rat sciatic nerve.

Rats fed a diet containing 1.25% elemental tellurium initiated on postnatal day 20 undergo a transient neuropathy characterized by synchronous demyelination of peripheral nerves. In sciatic nerve, the extent of demyelination was maximal after 5 days of tellurium exposure; there was a loss of 25% of the myelin, as assayed by concentration of myelin-specific P0 protein. Tellurium-induced alterations in the metabolic capacity of Schwann cells were examined by measuring the synthesis of myelin lipids in vitro in isolated sciatic nerve segments. Exposure to tellurium resulted in an early marked decrease of approximately 50% in overall incorporation of [14C]acetate into lipids, with a preferential depression in synthesis of cerebrosides, cholesterol, and ethanolamine plasmalogens (components enriched in myelin). Most dramatically, within 1 day of initiation of tellurium exposure, there was a profound increase in [14C]acetate-derived radioactivity in squalene; 23% of incorporated label was in this intermediate of cholesterol biosynthesis, compared to less than 0.5% in controls. In association with the remyelinating phase seen after 5 days of tellurium exposure, synthesis of myelin components gradually returned to normal levels. After 30 days, metabolic and morphologic alterations were no longer apparent. We suggest that the sequence of metabolic events in sciatic nerve following tellurium treatment initially involves inhibition of the conversion of squalene to 2,3-epoxysqualene, and that this block in the cholesterol biosynthesis pathway results, either directly or indirectly, in the inhibition of the synthesis of myelin components and breakdown of myelin.

Acetates↗

A variant form of metachromatic leucodystrophy in a patient suffering from another congenital degenerative neurological disease.

A woman aged 21 with a variant form of metachromatic leucodystrophy (MLD) combined with another form of leucodystrophy is described. The clinical symptoms were retinitis pigmentosa and progressive neurological deficits such as mental retardation, dystonia, pyramidal tract involvement and peripheral neuropathy. The biochemical findings were marked deficiency of arylsulfatase-A and cerebroside-sulfatase in cultured fibroblasts and excretion of sulfatides in the urine. Sulfatide-loading of cultured fibroblasts showed almost normal uptake and degradation of sulfatides. The patient's sister suffers from a clinically similar neurological disease, but normal activity of arylsulfatase-A was found in her leucocytes. A severe oral-facial dystonia in the patient was successfully controlled by l-dopa.

Adult↗

Polyunsaturated fatty acid lipidosis. II. Lipid biochemical studies.

Lipid analyses were performed on cerebral tissue from three children who had died of a progressive encephalopathy and from one living child in an early stage of the disease. In the terminal stage of the disease, the cortex and white matter content of all lipid classes, particularly the sphingolipids, were very low. The concentration of gangliosides of the cerebral cortex was 10%, and of cerebrosides in white matter, 2-3% of the normal values for the age. The porportion of the minor gangliosides with short carbohydrate chains was increased because the reduction affected mainly the four major brain gangliosides GM1, GD1a, GD1b and GT1. In the child from whom the biopsy specimen was obtained in an early phase of the disease the cerebral lipid pattern appeared to be normal. A patient who had died of neuronal ceroid-lipofuscinosis (Janský-Bielschowsky) did not show any major lipid changes. The fatty acid patterns of the phosphoglycerides showed such changes as have never been observed in any other disease. In the three advanced cases the fatty acid compositions in cerebral cortex and white matter were identical. In ethanolamine phosphoglycerides the proportions of 18: 1 and 20: 4 (n-6) were increased, while those of 22: 4 (n-6) and 22: 6 (n-3) were markedly diminished. Similar changes in the fatty acid patterns were found in the other phosphoglycerides. In the early phase of the disease 22: 4 (n-6) was decreased and 18: 1 increased. We propose that this new disease be termed polyunsaturated fatty acid lipidosis (PFAL).

Adolescent↗

An unusual form of arylsulfatase A deficiency combined with sulfatide-excretion and a normal sulfatide-loading.

A 7-year-old girl who showed retarded psychomotor development and generalized hypotonia without any signs of progression is described. Marked deficiency of arylsulfatase A activity in leukocytes and fibroblasts was observed. Both parents showed activity in cultured fibroblasts within the heterozygote-normal range. Cerebroside-sulfatase activity was absent in cultured fibroblasts from the patient. Urinary analyses revealed a pathologically increased sulfatide excretion. Normal sensory nerve conduction velocity was found, but no metachromatic material was found in a sural nerve biopsy. Loading of the patient's fibroblasts with sulfatides resulted in normal uptake and normal degradation.

Cerebroside-Sulfatase↗