Human brain gangliosides in development, aging and disease.

In this study, brain gangliosides in prenatal and postnatal human life and Alzheimer's disease were analyzed. Immunohistochemically, the presence of the "c"-series of gangliosides (GQ1c) was only registered in the embryonic brain at 5 weeks of gestation. Biochemical results indicated a two-fold increase in ganglioside concentration in the human cortex between 16 and 22 weeks of gestation. The increasing ganglioside concentration was based on an increasing GD1a ganglioside fraction in all regions analyzed except in the cerebellar cortex, which was characterized by increasing GT1b. During prenatal human development, regional differences in ganglioside composition could only be detected between the cerebrum ("a"-pathway) and the cerebellum ("b"-pathway). Between birth and 20-30 years of age, a cerebral neocortical difference of ganglioside composition occurred, characterized by the lowest GD1a in visual cortex. Analyzing the composition of gangliosides in cortical regions during aging, they were observed to follow region-specific alterations. In the frontal cortex, there was a greater decrease in GD1a and GM1 than in GT1b and GD1b, but in the occipital (visual) cortex there was no change in individual gangliosides. In hippocampus, GD1a moderately decreased, whereas other fractions were stable. In the cerebellar cortex, GD1b and GT1b fractions decreased with aging. In Alzheimer's disease, we found all ganglio-series gangliosides (GM1, GD1a, GD1b, GT1b) to be decreased in regions (temporal and frontal cortex and nucleus basalis of Meynert) involved in pathogenesis of disease. In addition, in Alzheimer's disease we found simple gangliosides (GN2, GM3) to be elevated in the frontal and parietal cortex, which might correlate accelerated lysosomal degradation of gangliosides and/or astrogliosis occurring during neuronal death.     

Developmental Changes in Ganglioside Composition and Synthesis in Embryonic Rat Brain

Developmental changes in ganglioside composition and biosynthesis was studied in rat brain between embryonic day (E) 14 and birth. In E14 brains, GM3 and GD3 were predominant. At E16, "b" series gangliosides, such as GD1b, GT1b, and GQ1b, increased in content. After E18, "a" series gangliosides such as GM1, GD1a, and GT1a increased in content, and the content of GM3 and GD3 markedly decreased. Because of these changes in composition, we determined the activities, in homogenates of embryonic brains, of two key enzymes of ganglioside synthesis: sialyltransferase for the synthesis of GD3 from GM3 and N-acetylgalactosaminyltransferase for GM2 synthesis from GM3. The sialyltransferase activity (GM3----GD3) was constant between E14 and E18 but decreased rapidly from E18 to birth. In contrast, the N-acetylgalactosaminyltransferase activity (GM3----GM2) increased between E14 and E18 but was constant from E18 to birth. These changes in ganglioside composition and enzymatic activities indicate that during development there is a shift from synthesis of the simplest gangliosides of the "a" and "b" pathways to synthesis of the more complex gangliosides.     

Age-related changes in GM1, GD1a, GT1b components of gangliosides in Wistar albino rats

In this study, age-related changes of GM1, GD1a, GT1b fractions of gangliosides were investigated in whole brain of male Wistar albino rats. Insignificant increases were detected in GM1 values from the third to the 24th month, whereas GD1a and GT1b concentrations of ganglioside in 24-month-old rats decreased significantly as compared to 6-month-old rats. Although there were no significant differences in the GD1a/GT1b ratio of any groups, GM1/GD1a and GM1/GT1b ratios were significantly increased as compared to 6-month-old rats. The increase in the ratios of gangliosides are not due to an increase of GM1 fractions; they result from a decrease of GD1a and GT1b fractions of gangliosides. In conclusion, the concentration of ganglioside decreased with ageing.     

Differential distribution of major gangliosides in rat central nervous system detected by specific monoclonal antibodies

We investigated the localization of major gangliosides in adultrat brain by an immunofluorescence technique with mouse monoclonalantibodies (MAbs). Five MAbs (GMB16, GMR17, GGR12, GMR5 andGMR13) that specifically recognize gangliosides GM1, GD1a, GD1b,GT1b and GQ1b, respectively, were used. We have found that thereis a cell type-specific expression of the ganglioside in therat central nervous system. In cerebellar cortex, GM1 was expressedin myelin and some glial cells. GD1a was detected exclusivelyin the molecular layer. GD1b and GQ1b were present restrictedlyon the granular layer; GD1b was detected on the surface of thegranular cell bodies, whereas GQ1b was present in the cerebellarglomerulus. GT1b was distributed intensely in both the molecularlayer and the granular layer. In cerebral cortex, GM1 was detectedin some glial cells. Dense staining was limited to the whitematter. GD1a was distributed in layers I, II/III and Va, andthe upper part of layer VI, whereas GQ1b was localized in layersIV and Vb, and the lower part of layer VI. GD1b was detectedbeneath layer III. GT1b appeared to be distributed throughoutall layers. In other regions, such as hippocampal formationand spinal cord, the expression of the ganglioside was alsohighly localized to a specific cell type and layer. ganglioside monoclonal antibody rat brain     

Gangliosides in various brain areas of three inbred strains of mice

The ganglioside patterns of cerebellum, cortex, pons-medulla, hypothalamus, hippocampus and caudate nucleus of three inbred strains of mice (C57BL/6J, DBA/2J and BALB/cJ) have been analysed. All brain areas contained both the simple and complex species of gangliosides. GD1a was the major ganglioside in cortex, hippocampus and caudate nucleus whereas GT1b was the major species in cerebellum, hypothalamus and pons-medulla. In hippocampus, the percentages of GT1b and GD1a were quite similar. Pons and medulla exhibited the highest levels of GM1 (which approaches the value of GT1b) and the lowest values of GD1a. A ganglioside, termed here GT1L, was located between GD1b and GT1b. This ganglioside, which was present in highest amounts in cerebellum disappeared after alkali treatment. Highly significant differences were observed in the amounts and patterns of gangliosides among brain areas of the three strains. Highly significant differences (p<0.001) were also found in the ganglioside distribution of various brain areas among the strains, especially for tri-and tetrasialogangliosides between Balb and DBA. A significant difference of GM1 was observed in the cerebellum when comparing DBA with the two other strains. It is likely that the differences might be related to their relative abundances in certain cell types and for defining synaptic circuits in brain areas of some strains.     

Subcellular distribution and biosynthesis of rat liver gangliosides

Gangliosides have generally been assumed to be localized primarily in the plasma membrane. Analysis of gangliosides from isolated subcellular membrane fractions of rat liver indicated that 76% of the total ganglioside sialic acid was present in the plasma membrane. Mitochondria and endoplasmic reticulum fractions, while containing only low levels of gangliosides on a protein basis, each contained approx. 10% of total ganglioside sialic acid. Gangliosides also were present in the Golgi apparatus and nuclear membrane fractions, and soluble gangliosides were in the supernatant. Individual gangliosides were non-homogeneously distributed and each membrane fraction was characterized by a unique ganglioside composition. Plasma membrane contained only 14 and 28% of the total GD1a and GD3, respectively, but 80-90% of the GM1, GD1b, GT1b and GQ1b. Endoplasmic reticulum, when corrected for plasma membrane contamination, contained only trace amounts of GM1, GD1b, GT1b and GQ1b, but 11 and 5% of the total GD1a and GD3, respectively. The ganglioside composition of highly purified endoplasmic reticulum was similar. Ganglioside biosynthetic enzymes were concentrated in the Golgi apparatus. However, low levels of these enzymes were present in the highly purified endoplasmic reticulum fractions. Pulse-chase experiments with [3H]galactose revealed that total gangliosides were labeled first in the Golgi apparatus, mitochondria and supernatant within 10 min. Labeled gangliosides were next observed at 30 min in the endoplasmic reticulum, plasma membrane and nuclear membrane fractions. Analysis of the individual gangliosides also revealed that GM3, GM1, GD1a and GD1b were labeled first in the Golgi apparatus at 10 min. These studies indicate that gangliosides synthesized in the Golgi apparatus may be transported not only to the plasma membrane, but to the endoplasmic reticulum and to other internal endomembranes as well.     

Developmental profiles of gangliosides in trisomy 19 mice

The ganglioside composition of the cerebrum, cerebellum, brainstem, liver, heart, and spleen was analyzed quantitatively in trisomy 19 (Ts19) mice aged 4 to 12 days postpartum. The developmental profiles of cerebral gangliosides were similar in Ts19 mice and control littermates: Total ganglioside-sialic acid as well as the proportions of the individual gangliosides GD1a and GM1 increased with age, while the percentages of GQ1b and GT1b decreased during development. Both the accretion of the total ganglioside content and the development of the individual ganglioside fractions were delayed by 2-3 days in the Ts19 telencephalon. Likewise, the shift from the b- to the a-pathway of ganglioside synthesis was retarded. Ganglioside development was equally delayed in the cerebellum and the brainstem of Ts19 mice. Since in Ts19 mice, morphogenesis of several brain regions is similarly delayed by 2 days, these results confirm the usefulness of gangliosides as biochemical markers for brain maturation. In contrast to brain gangliosides, the ganglioside composition of the Ts19 livers was clearly distinguished from that of control livers. Total ganglioside-bound sialic acid was increased by 35-50% in Ts19 livers. This elevation in ganglioside content not explicable by a simple delay in development was mainly due to an increase in GD3 and fraction 2, which is likely to contain GD1a and GD1b. In contrast, GM2 which increased considerably with age in control mice persisted on a low level in Ts19 livers. Comparable alterations of the ganglioside pattern were neither observed in the spleen nor in the heart of Ts19 mice. The data presented give additional evidence that ganglioside synthesis in the liver is under a different regulation mechanism than that in the brain, heart, and spleen.     

Characterization of nuclear gangliosides in rat brain: concentration, composition, and developmental changes

Nuclear gangliosides were characterized using two distinct fractions of large (N1) and small (N2) nuclear populations from rat brain. The ganglioside concentration of N1 nuclei from adult rat brain was 0.92 microg sialic acid/mg protein, which was about 3.8 times higher than that of N2 nuclei. N1 and N2 nuclear gangliosides showed similar compositional profiles; they contained major gangliosides of GM1, GD1a, GD1b, and GT1b, with GM3 in lesser amounts. c-Series gangliosides such as GT3, GQ1c, and GP1c were also detected in both nuclear preparations. Nuclear localization of gangliosides was confirmed by immunofluorescence with anti-GM1 antibody, cholera toxin B subunit, and c-series ganglioside-specific monoclonal antibody A2B5. Developmental changes of nuclear gangliosides were examined using rats of different ages ranging from embryonic day 14 (E14) to postnatal 7 weeks. The concentration of N1 nuclear gangliosides changed only slightly during development and did not correlate with that of whole-brain gangliosides. The developmental pattern of ganglioside composition of N1 nuclei was also distinguished from that of microsomal membranes; the ganglioside changes in N1 nuclei included reduced expression of di- and polysialogangliosides at E16 and higher proportions of GM3 at early and late stages of the period. These findings suggest that gangliosides in nuclear membranes are developmentally regulated in a distinct manner in brain cells.     

A new thin-layer chromatographic approach for separation of multisialogangliosides: Novel gangliosides fractions in the embryonic chicken brain

A novel thin-layer chromatographic procedure has been developed that permits rapid, high-resolution separation of complex ganglioside mixtures and direct densitometric quantification. A special advantage of the new procedure, performed by two different consecutive runs on high-performance thin-layer chromatography plates, is an excellent separation of multisialogangliosides containing more than three sialic acid residues. Using the new procedure, 10 unidentified fractions were detected in embryonic chick brains. These gangliosides were clearly distinguishable from the known gangliosides, GM1, GD3, GD1a, GD2, GD1b, GT1b, and GQ1b. Eight of these “additional” fractions were also found in the brains of rays. From published data on the cod fish brain, 6 of the novel fractions are suggested to correspond to GT3, GT2, GT1c, GQ1c, GP1c, and GP1b. Four fractions, moving on thin-layer chromatography plates below the suggested GP1c have not been reported previously in any vertebrate. Due to their very slow migration rates they may contain gangliosides with six, seven, or more sialic acid residues. During development of the chicken, the relative amounts of the newly detected fractions decrease in favor of GT1b and GD1a.     

Topographical Atlas of the Gangliosides of the Adult Human Brain

Forty different brain samples, consisting of neocortical, archicortical, and paleocortical areas; telencephalic, diencephalic, and mesencephalic subcortical nuclei; and the cerebellum as well as some of the corresponding white matter bundles were analyzed with respect to total content of ganglioside-sialic acid and the ganglioside pattern. The total content of gangliosides seems to depend mainly on the proportions of gray and white matter. Thus, neocortical areas, which are rich in gray matter, have a four- to fivefold higher ganglioside content (per milligram of protein) than white matter-rich samples such as optic chiasm, capsula interna, or corpus callosum. White matter-rich regions, although very heterogeneous in ganglioside composition, are further characterized by appreciable amounts of the myelin-enriched GM4. In the neocortex a remarkable degree of regional pattern differences was revealed. In the frontal and parietal areas there is a moderate, and in the temporal region a strong preponderance of sialic acid bound to gangliosides of the a-pathway (GD1a, GM1). In contrast, the occipital cortex favors the b-pathway of ganglioside synthesis (GQ1b, GT1b, GD1b). A predominance of "b-gangliosides" was found in all structures that are related to the visual system (optic chiasm, pulvinar-thalamus, superior colliculi, visual cortex) as well as in the cerebellum and the nucleus ruber. All diencephalic nuclei tend to favor slightly "b-gangliosides," while the mesencephalic nuclei are very heterogeneous in their ganglioside composition. A preponderance of "a-gangliosides" was found in the periamygdalar cortex, putamen, inferior colliculi, substantia nigra, frontal white matter, internal capsule, globus pallidus, basal nucleus of Meynert, and corpus callosum as well as in the frontal, parietal, and temporal cortices. An exceptional predominance of GM1 and GD1a was revealed for the hippocampal archicortex and the amygdala, suggesting a possible functional correlation to glutaminergic synaptic transmission.     

GANGLIOSIDE1−COMPOSITION OF BRAIN IN TAY-SACHS DISEASE: INCREASED AMOUNTS OF GD2 AND N-ACETYL-β-D-GALACTOSAMINYL GD1a GANGLIOSIDE

Abstract— The ganglioside composition of the brain of a patient with Tay-Sachs disease (TS-brain) was determined by a newly developed ganglioside-mapping procedure and compared with that of an age-matched control brain. GM2 ganglioside was the predominant component in TS-brain and the following gangliosides were also found, GM1, GD1a, GD1b and GT1 (major gangliosides in normal brain), and GM3, GD3, GD2 and GD1a-GAN (minor or undetectable components of normal brain). Individual gangliosides were isolated by column chromatography using a combination of DEAE-Sepharose, Iatrobeads and Silica Gel 60 and their structures were confirmed by comparing them with authentic standards using TLC, analysing their carbohydrate compositions by gas-liquid chromatography and cleaving them sequentially with glycosidases. The amounts of individual components were measured by quantitative densitometric scanning of the thin-layer plates. As a reflection of myelin breakdown, no sialosylgalactosyl ceramide was detectable in TS-brain. Although the total amounts of all gangliosides except GM2 in TS-brain were low, there were normal molar ratios of the main gangliosides in normal brain, that is, GM1, GD1a, GD1b and GT1. In comparison with the amount of GDla ganglioside, the amounts of GM2, GD2 and GD1a-GAN, which contain N-acetylgalactosamine as a terminal carbohydrate residue, were all elevated in TS-brain. The long chain bases of individual gangliosides contained both C-18 and C-20 sphingosine in different ratios and the ratio of C-20 to C-18 increased in the gangliosides in the order: GM2 < GM1 < GD1a < GD1a-GAN < GD1b < GT1 in both normal brain and TS-brain. In contrast, GD2 and GD3 gangliosides consisted mainly of C-18 sphingosine. The C-20 to C-18 ratios of individual gangliosides in the TS-brain were lower than those of age-matched control brain. Hexosaminidase from Turbo cornutus showed the same specific activity and K_m value in catalysing the cleavage of terminal N-acetylgalactosaminyl residues from GM2, GD2 and GD1a-GAN, suggesting that the brain gangliosides that increase in Tay-Sachs disease may be cleaved by the same enzyme.     

Sulfatide is expressed in neurons and astrocytes and accumulates at degradation deficiency

Few studies of lipid rafts have investigated gangliosides in brain tissue. This study focus on analyses of lipids and the major brain gangliosides (GM1, GD1a, GD1b, GT1b) in human cortex (frontal, temporal) and corresponding detergent resistant membranes (DRMs), i.e. rafts. A high proportion of the gangliosides (18–26%) as well as of cholesterol (21%) and sphingomyelin (38%) was found in rafts, while lower yields was observed for ganglioside GM2 (9%), phospholipids (8%) and in particular proteins (2%). Significant alterations in lipid composition was noticed in rafts from Alzheimer brain tissue. These results show that sphingolipids and cholesterol are major constituents of rafts also in the human brain and that the main brain gangliosides are distributed in rafts to a similar degree. Moreover, lipid rafts might be considered in the pathology of Alzheimer's disease.     

Modulation of phospholipase A2 activity by neutral and anionic glycosphingolipids in monolayers.

The effect of neutral (galactocerebroside and asialo-ganglioside GM1) or anionic (sulphatide and gangliosides GM1, GD1a and GT1b) glycosphingolipids on the activity of phospholipase A2 from pig pancreas was studied in mixed monolayers of dilauroyl phosphatidylcholine with the glycosphingolipids in different molar fractions at various constant surface pressures. The activity of the enzyme depends on the proportion and type of glycosphingolipid in the interface. Sulphatide activates the enzyme at all proportions, whereas galactocerebroside shows inhibition or activation depending on its proportion in the film. Asialo-ganglioside GM1 and gangliosides GM1, GD1a and GT1b can strongly inhibit the enzyme at relatively low molar fractions in the film in the following order: asialo-ganglioside GM1 less than ganglioside GM1 less than ganglioside GT1b less than ganglioside GD1a. The changes of activity are not due to a direct action of the lipids on the active centre or interfacial recognition region of the enzyme.     

Changes in the Ganglioside Long-Chain Base Composition of Rat Cerebellar Granule Cells During Differentiation and Aging in Culture

Abstract: Changes in the ganglioside long-chain base (LCB) composition in rat cerebellar granule cells in culture were studied during differentiation and aging. The total native ganglioside mixtures, extracted from the cells maintained in culture up to 22 days, were fractionated by reversed-phase HPLC, each ganglioside homogeneous in the oligosaccharide chain as well as in the LCB being quantified. Two main LCBs were components of the ganglioside species of cultured cells, the C18:1 LCB and the C20:1 LCB. The content of C20:1 ganglioside molecular species was low and quite constant during differentiation, comprising ∼8% of the total ganglioside species content, the C20:1 LCB appearing to be represented more in the ganglioside of the "b series" (GD1b, GT1b, and GQ1b) than in the "a series" (GM1 and GD1a). During aging in culture, for 8–22 days, the content of the C20:1 species of all gangliosides increased, being more pronounced for GM1 and GD1a.     

Human brain gangliosides: developmental changes from early fetal stage to advanced age

The developmental profiles of the four major brain gangliosides, GM1, GD1a, GD1b, and GT1b, were examined in human frontal lobe covering the period from 10 fetal weeks to 80 years of age. The ganglioside concentration increased approx. 3-fold from the 10th gestational week to the age of about 5 years. Gangliosides GM1 and GD1a increased 12-15-fold during the same period. The most rapid increase of GM1 and GD1a occurred around term, during the period for dendrite arborization, outgrowth of axons and synaptogenesis. GT1b showed a quite different developmental curve. It was the major ganglioside during the 3rd to 5th gestational month, whereafter its concentration dropped rapidly to term, from which time the concentration then increased up to 50 years of age. Similar curves were found for the other gangliosides of the b-series, GD3, GD2, GD1b and GQ1b. Ganglioside 3'-isoLM1 was a characteristic early fetal ganglioside which dropped rapidly to the 5th gestational month, reached a small peak around term and then disappeared during adulthood. The concentration of gangliosides of the neolacto series was larger than that of the lacto series during the whole developmental period. In the beginning of the second trimester, 3'-LM1 constituted 2% and LD1 10% of total ganglioside sialic acid. The new findings demonstrate more dynamic changes of the ganglioside patterns during development than noted in previous studies.     

Age-Related Changes in the Ceramide Composition of the Major Gangliosides Present in Rat Brain Subcellular Fractions Enriched in Plasma Membranes of Neuronal and Myelin Origin

Abstract: Age-related changes of the ceramide composition of gangliosides were studied in the synaptosomal and myelin fractions from rat brain, carrying plasma membranes of neuronal and glial origin, respectively. The five major gangliosides (GM1, GD1 a, GD1 b, GT1 b, and GQ1 b) present in these fractions were separated and quantitated by normal-phase HPLC. Each ganglioside was then fractionated by reverse-phase HPLC into the molecular species carrying a single long-chain base (LCB). The largely preponderant LCBs in the synaptosomal and myelin fractions were the C18:1 and C20:1. The content of C20.1 LCB, generally low at 1 month, increased with age in all analyzed gangliosides and in all subcellular fractions and was greater in the "b series" than in the "a series" gangliosides. Remarkably, GM1 was the only ganglioside where the proportion of LCB 20:1 was higher in the synaptosomal fraction than in the myelin fraction. The fatty acid composition of the C18:1 or C20:1 LCB species of the different gangliosides in the synaptosomal and myelin fractions did not undergo appreciable changes with age. Stearic acid was largely predominant in all the gangliosides of the synaptosomal fraction, more in the C18:1 than in the C20:1 LCB species (80–90% vs. 60–70%). The gangliosides of the myelin fraction were characterized by a lower content of 18:0 and a much higher content of 16:0 and 18:1 fatty acids than those of the synaptosomal fraction. Thus, the ceramide composition is different in the gangliosides of neuronal and myelin origin and appears to be subjected to an age-related control.     

Lipid analyses of human brain rafts

Few studies of lipid rafts have investigated gangliosides in brain tissue. This study focus on analyses of lipids and the major brain gangliosides (GM1, GD1a, GD1b, GT1b) in human cortex (frontal, temporal) and corresponding detergent resistant membranes (DRMs), i.e. rafts. A high proportion of the gangliosides (18–26%) as well as of cholesterol (21%) and sphingomyelin (38%) was found in rafts, while lower yields was observed for ganglioside GM2 (9%), phospholipids (8%) and in particular proteins (2%). Significant alterations in lipid composition was noticed in rafts from Alzheimer brain tissue. These results show that sphingolipids and cholesterol are major constituents of rafts also in the human brain and that the main brain gangliosides are distributed in rafts to a similar degree. Moreover, lipid rafts might be considered in the pathology of Alzheimer's disease.     

Gangliosides of rat eye lens: a severe reduction in the content of C-series gangliosides following streptozotocin treatment

Gangliosides of eye lenses from normal and experimentally induced diabetic rats were investigated by methods including glycolipid-overlay techniques. Adult rat eye lens showed a complex ganglioside pattern that consisted of six major ganglioside components. These gangliosides were identified as GM3, GD3, GD1a, GD1b, GT1b, and GQ1b based upon their reactivity to anti-GM1 antibody after in situ sialidase treatment and mobility on thin-layer chromatography (TLC). Gangliosides in eye lens were further characterized by TLC-immunostaining with A2B5, a specific monoclonal antibody directed toward c-series gangliosides. Eye lens contained GT3 as the main c-series ganglioside component. Unexpectedly, the relative concentration of GT3 in total gangliosides of eye lens was highest among neural and extra-neural tissues examined. Administration of streptozotocin to rats caused a severe reduction in the GT3 content in eye lenses as early as day 3 without apparent changes in the composition of major gangliosides. Alloxan failed to produce such an effect despite producing similar hyperglycemic conditions. These results suggest that rat eye lens probably contains a streptozotocin-susceptible cell type(s), which is highly enriched with c-series gangliosides.     

Gangliosides in rat kidney: composition, distribution, and developmental changes

Gangliosides in rat kidney were analyzed for their composition, regional distribution, and developmental changes. Renal tissue from 7-week-old rats showed a GM3-dominant pattern with GD3 and several minor ganglioside components including GM4, GM2, GD1a, and an unknown ganglioside (ganglioside X). The tissue also contained c-series gangliosides that included GT3 as the main component with GT2 in a lesser amount. Ganglioside analysis of cortical and medullary regions of renal tissue suggested the restricted localization of some gangliosides. While GM4 and GD3 were enriched in the cortical region, GM2 was distributed mainly in the medullary area. Renal gangliosides showed unique developmental profiles during a period from Embryonic Day 20 (E20) to 7 weeks postnatal. The content of renal gangliosides increased from E20, reached the highest around Postnatal Day 1, and thereafter, decreased rapidly to the adult level. The ratio of N-glycolylneuraminic acid to total sialic acids in gangliosides tended to change in inverse proportion to the amount of total sialic acids. The composition of major gangliosides in renal tissues shifted from GD3-dominant to GM3-dominant patterns with advancing ages. While GM1 was expressed only at early stages of the development, GM4, GM2, and ganglioside X appeared after Postnatal Day 3. The expression of c-series gangliosides was less affected through the period examined. These results suggest that gangliosides may be implicated with development and function of rat kidney.     

Activities of Five Different Sialyltransferases in Fish and Rat Brains

Abstract: To investigate the role of Sialyltransferases in the metabolism of brain gangliosides, we examined activities of five different Sialyltransferases (GM3-, GD3-, GT3-, GD1a-, and GT1a-synthase) using total membrane preparations from cichlid fish and Sprague-Dawley rat brains, and analyzed the relationship between the enzyme activities and the ganglloside compositions. The patterns of sialyltransferase activities in fish and rat brains differed from each other. In fish brain, the GM3-synthase activity was lower than GD3-synthase activity, whereas the opposite relationship was observed in rat brain. The GT3-synthase reaction with fish brain membranes produced radiolabeled GM3, GD3, and a ganglioside that was identified as GT3 based on mobility on TLC using two different solvent systems. No GT3-synthase activity was detected in rat brain. The GD1a-and GT1a-synthase activities in fish brain were higher than those in rat brain. Although GT1a was a single radiolabeled ganglioside in fish GT1a-synthase reaction, this ganglioside could not be detected in rat brain. The ratios of GM3-, GD3-, GT3-, GD1a-, and GT1a-synthase activities in fish and rat brain were 23:31:4:28:14 and 61:21:0:18:0, respectively. Ganglioside analysis showed that fish brain was enriched with c-series gangliosides including GT3 and polysialo-species, whereas a-and b-se-ries gangliosides were major components in rat brain. These results suggest that the species-specific expression of gangliosides in brain tissues may be regulated, at least in part, at the level of sialyltransferase activities.