Glycoconjugate changes in aging and age-related diseases.

The significance of glycosphingolipids and glycoproteins is discussed in their relation to normal aging and pathological aging, aging with diseases. Healthy myelin that looks stable is found to be gradually degraded and reconstructed throughout life for remodeling. An exciting finding is that myelin P0 protein is located in neurons and glycosylated in aging brains. In pathological aging, the roles of glycosphingolipids and glycoproteins as risk factors or protective agents for Alzheimer's and Parkinson's diseases are discussed. Intensive studies have been performed aiming to remove the risks from and to restore the functional deficits of the brain. Some of them are expected to be translated to therapeutic means.

Anti-Chol-1 antigen, GQ1bα, antibodies are associated with Alzheimer's disease.

The interaction of amyloid ß-proteins (Aß) with membrane gangliosides has been reported to be an early event in Aß fibril formation in Alzheimer's disease (AD). Neuronal degeneration in AD has been postulated to be associated with the presence of anti-ganglioside antibodies in patient sera. Using an enzyme-linked immunosorbent assay (ELISA) and high-performance thin-layer chromatography (HPTLC) immunostaining, sera from 27 individuals (10 with AD, 6 with vascular dementia (VD), and 11 non-demented age-matched pathological controls) were examined in order to detect anti-glycosphingolipid (GSL) antibodies, including anti-cholinergic-specific antigen (Chol-1α; GQ1bα) antibodies. All sera had natural antibodies against ganglio-N-tetraosyl gangliosides (brain-type gangliosides). However, sera of demented patients with AD and VD had significantly higher titers of anti-GSL antibodies than those in age-matched pathological controls. Although most serum antibodies, including anti- GM1, -GT1b, -GQ1b, -GQ1bα, were of the IgM type, the presence of the IgG type antibodies was also significantly elevated in the sera of demented patients with AD. Anti-GT1b antibodies of the IgG type were elevated in AD (90%, 9 of 10 cases) and VD (100%), respectively. Most surprisingly, anti-GQ1bα antibodies (IgM) were found in 90% (9/10) and 100% (6/6) in the sera of patients with AD and VD, respectively. Since GQ1bα is present in the cerebral cortex and hippocampus, the presence of anti-GQ1bα antibodies may play an important role in disrupting cholinergic synaptic transmission and may participate in the pathogenesis of dementia. We conclude that elevated anti-GSL antibody titers may be useful as an aid for clinical diagnosis of those dementias.

Brain gangliosides of a transgenic mouse model of Alzheimer's disease with deficiency in GD3-synthase: expression of elevated levels of a cholinergic-specific ganglioside, GT1aα.

In order to examine the potential involvement of gangliosides in AD (Alzheimer's disease), we compared the ganglioside compositions of the brains of a double-transgenic (Tg) mouse model [APP (amyloid precursor protein)/PSEN1 (presenilin)] of AD and a triple mutant mouse model with an additional deletion of the GD3S (GD3-synthase) gene (APP/PSEN1/GD3S(-/-)). These animals were chosen since it was previously reported that APP/PSEN1/GD3S(-/-) triple-mutant mice performed as well as WT (wild-type) control and GD3S(-/-) mice on a number of reference memory tasks. Cholinergic neuron-specific gangliosides, such as GT1aα and GQ1bα, were elevated in the brains of double-Tg mice (APP/PSEN1), as compared with those of WT mice. Remarkably, in the triple mutant mouse brains (APP/PSEN1/GD3S(-/-)), the concentration of GT1aα was elevated and as expected there was no expression of GQ1bα. On the other hand, the level of c-series gangliosides, including GT3, was significantly reduced in the double-Tg mouse brain as compared with the WT. Thus, the disruption of the gene of a specific ganglioside-synthase, GD3S, altered the expression of cholinergic neuron-specific gangliosides. Our data thus suggest the intriguing possibility that the elevated cholinergic-specific ganglioside, GT1aα, in the triple mutant mouse brains (APP/PSEN1/GD3S(-/-)) may contribute to the memory retention in these mice.

Ability of barrier coat S-PRG coating to arrest artificial enamel lesions in primary teeth.

PURPOSE: To evaluate the effects of a surface pre-reacted glass-ionomer (S-PRG) filled coating material to arrest artificial enamel lesions in primary teeth. METHODS: Buccal and lingual enamel was demineralized in 0.1 M lactic acid buffer solution (pH 4.75) for 5 days and then divided in the PRG-applied and non-PRG areas. Proximal surfaces were used as a control area without demineralization and coating application. Teeth were divided into three groups (n = 4) according to the 1-week immersion in different solutions: Group 1 (distilled water), Group 2 (demineralizing solution) and Group 3 (artificial saliva). Hardness and Young's modulus by nano-indentation test, and elemental contents and ultrastructure by SEM/EDX analysis were obtained. Data were statistically analyzed using ANOVA and Fisher's PLSD at alpha = 0.05. RESULTS: Only for the non-PRG area in Group 1, the hardness and Young's modulus of the demineralized surface enamel were significantly lower than those of the enamel 30-60 microm beneath the surface. Demineralized enamel of non-PRG and PRG-applied areas showed similar SEM views. Only for the non-PRG area in Group 2 and control area in Group 3, the Ca/P of the surface enamel was significantly higher than that of the enamel 5-10 microm beneath the surface. There was no significant difference of the Ca/P among the measuring points from the surface to 10 microm depth of enamel for the PRG applied area in Group 2.

Effects of polishing on surface roughness and gloss of S-PRG filled flowable resin composite.

PURPOSE: To evaluate the effects of polishing on surface roughness (Ra, microm) and gloss of different shades of a surface pre-reacted glass-ionomer (S-PRG) filled flowable resin composite. METHODS: Resin disks of 15 mm diameter and 2 mm thickness and final polish with 3000-grit SiC paper (#3000), super fine cut diamond point (FG) and Super-Snap mini-disk red (SNAP) were made with Beautifil Flow Plus (shades: A2, A20, Inc). The surface roughness and gloss were measured 1-week after curing. Data was analyzed with ANOVA and Fisher's PLSD with alpha=0.05. RESULTS: The order of Ra differed among the composite shades. For all shades in all polishing groups, the Ra was over 0.5 microm. For all shades, the gloss of the #3000 group was significantly higher than that of the FG and SNAP groups with no significant difference between the FG and SNAP groups except for the A20 shade. For A20 shade, the gloss of the SNAP group was significantly higher than that of the FG group.

Effect of warm air-drying on dentin bond strength of single-step self-etch adhesives.

The effect of warm air-drying on the dentin bond strengths of the single-step self-etch adhesives was determined. The adhesives were applied to bovine dentin followed by drying in a stream of warm air for 5, 10, and 15 s at 37°C. Resin composites were condensed into a mold and polymerized. Specimens were stored in distilled water at 37°C for 24 h, then shear tested. The surface free-energies were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The dentin bond strengths varied according to the air-drying time. The value of the acid component increased slightly when drying was performed with a stream of warm air, whereas that of the base component decreased significantly. These data suggested that warm air-drying was essential to obtain adequate bond strengths, although increasing the drying time did not significantly influence the bond strength.

Neuronal dysfunction with aging and its amelioration.

The author focused on the functional decline of synapses in the brain with aging to understand the underlying mechanisms and to ameliorate the deficits. The first attempt was to unravel the neuronal functions of gangliosides so that gangliosides could be used for enhancing synaptic activity. The second attempt was to elicit the neuronal plasticity in aged animals through enriched environmental stimulation and nutritional intervention. Environmental stimuli were revealed neurochemically and morphologically to develop synapses leading to enhanced cognitive function. Dietary restriction as a nutritional intervention restored the altered metabolism of neuronal membranes with aging, providing a possible explanation for the longevity effect of dietary restriction. These results obtained with aging and dementia models of animals would benefit aged people.

Influence of temporary cement contamination on the surface free energy and dentine bond strength of self-adhesive cements.

OBJECTIVES: The surface free energy and dentine bond strength of self-adhesive cements were examined after the removal of temporary cements. METHODS: The labial dentine surfaces of bovine mandibular incisors were wet ground with #600-grit SiC paper. Acrylic resin blocks were luted to the prepared dentine surfaces using HY Bond Temporary Cement Hard (HY), IP Temp Cement (IP), Fuji TEMP (FT) or Freegenol Temporary Cement (TC), and stored for 1 week. After removal of the temporary cements with an ultrasonic tip, the contact angle values of five specimens per test group were determined for the three test liquids, and the surface-energy parameters of the dentine surfaces were calculated. The dentine bond strengths of the self-adhesive cements were measured after removal of the temporary cements in a shear mode at a crosshead speed of 1.0mm/min. The data were subjected to one-way analysis of variance (ANOVA) followed by Tukey's HSD test. RESULTS: For all surfaces, the value of the estimated surface tension component γ(S)(d) (dispersion) was relatively constant at 41.7-43.3 mJm(-2). After removal of the temporary cements, the value of the γ(S)(h) (hydrogen-bonding) component decreased, particularly with FT and TC. The dentine bond strength of the self-adhesive cements was significantly higher for those without temporary cement contamination (8.2-10.6 MPa) than for those with temporary cement contamination (4.3-7.1 MPa). CONCLUSIONS: The γ(S) values decreased due to the decrease of γ(S)(h) values for the temporary cement-contaminated dentine. Contamination with temporary cements led to lower dentine bond strength. CLINICAL SIGNIFICANCE: The presence of temporary cement interferes with the bonding performance of self-adhesive cements to dentine. Care should be taken in the methods of removal of temporary cement when using self-adhesive cements.

Influence of refractive index on optical parameters of experimental resin composites.

OBJECTIVE: Color characteristics of the experimental resin composites were determined to know the influence of different refractive index (RI) on optical parameters. MATERIALS AND METHODS: Four experimental light-cured resin composites of the same shade but with different RI were used. The colorimetric values of the specimens were measured against black and white backgrounds using spectrophotometry. The results were converted to CIE L*a*b* color-space values. The chroma (C*ab), color difference (ΔE), translucency parameter (TP) and opacity (OP, opposite property of TP) values were calculated. Surface gloss (GS) of the specimen was also measured. RESULTS: The L* coordinate, a* coordinate and ΔE*ab values increased as the difference in RI increased. The OP and GS values increased and the TP values decreased as the refractive-index difference increased. The L* and C*ab values increased as the value of the RI increased. The TP, OP and GS values were highly correlated with the RI value. The TP value decreased and the OP and GS values increased, as the RI value increased. CONCLUSIONS: Refractive index of resin composites is important when thinking about improving the color appearance of esthetic restorations.

pH changes upon mixing of single-step self-etching adhesives with powdered dentin.

PURPOSE: Single-step self-etching adhesives have been developed as a bonding material that adheres to the tooth surface. The adhesives contain acidic resin monomers that penetrate the dentin but can be neutralized to stop the reaction. This study aimed to improve understanding of the pH changes that occur when self-etching adhesives are mixed with dentin powder. MATERIALS AND METHODS: Dentin disks obtained from extracted bovine incisors were milled and pulverized into a fine powder. The powder was mixed with diluted self-etching adhesives, and pH changes were measured by a solid-state pH sensor connected to a pH meter at various time points after the start of mixing. Data were analyzed by Tukey's Honestly Significant Difference (HSD) test and Dunnett's test at a significance level of 0.05. Precipitates from the adhesive/ dentin powder mixture were observed by scanning electron microscopy (SEM). RESULTS: The baseline pH values of the self-etching adhesives ranged from 0.97 to 2.83. After mixing with the dentin powder, the pH values significantly increased, ranging from 6.30 to 7.11 at 180 s after mixing. SEM observation revealed products of the reaction between dentin powder and self-etching adhesive which indicate a chemical reaction between the functional monomer and dentin. CONCLUSION: Dentin has a strong modulation effect against the acidity of self-etching adhesives.

Ganglioside metabolism in a transgenic mouse model of Alzheimer's disease: expression of Chol-1α antigens in the brain.

The accumulation of Aß (amyloid ß-protein) is one of the major pathological hallmarks in AD (Alzheimer's disease). Gangliosides, sialic acid-containing glycosphingolipids enriched in the nervous system and frequently used as biomarkers associated with the biochemical pathology of neurological disorders, have been suggested to be involved in the initial aggregation of Aß. In the present study, we have examined ganglioside metabolism in the brain of a double-Tg (transgenic) mouse model of AD that co-expresses mouse/human chimaeric APP (amyloid precursor protein) with the Swedish mutation and human presenilin-1 with a deletion of exon 9. Although accumulation of Aß was confirmed in the double-Tg mouse brains and sera, no statistically significant change was detected in the concentration and composition of major ganglio-N-tetraosyl-series gangliosides in the double-Tg brain. Most interestingly, Chol-1α antigens (cholinergic neuron-specific gangliosides), such as GT1aα and GQ1bα, which are minor species in the brain, were found to be increased in the double-Tg mouse brain. We interpret that the occurrence of these gangliosides may represent evidence for generation of cholinergic neurons in the AD brain, as a result of compensatory neurogenesis activated by the presence of Aß.

Acetyl-L-carnitine improves aged brain function.

The effects of acetyl-L-carnitine (ALCAR), an acetyl derivative of L-carnitine, on memory and learning capacity and on brain synaptic functions of aged rats were examined. Male Fischer 344 rats were given ALCAR (100 mg/kg bodyweight) per os for 3 months and were subjected to the Hebb-Williams tasks and AKON-1 task to assess their learning capacity. Cholinergic activities were determined with synaptosomes isolated from brain cortices of the rats. Choline parameters, the high-affinity choline uptake, acetylcholine (ACh) synthesis and depolarization-evoked ACh release were all enhanced in the ALCAR group. An increment of depolarization-induced calcium ion influx into synaptosomes was also evident in rats given ALCAR. Electrophysiological studies using hippocampus slices indicated that the excitatory postsynaptic potential slope and population spike size were both increased in ALCAR-treated rats. These results indicate that ALCAR increases synaptic neurotransmission in the brain and consequently improves learning capacity in aging rats.

Influence of adhesive application time on enamel bond strength of single-step self-etch adhesive systems.

This study examined the relationship between the adhesive application time and enamel bond strength of several single-step self-etch adhesive systems. The adhesives used were: Bond Force (BF, Tokuyama Dental Corporation, Tokyo, Japan), Clearfil tri-S Bond (CT, Kuraray Medical Inc, Tokyo, Japan), iBond Self-Etch (IB, Heraeus Kulzer, Armonk, NY) and OptiBond All-in-One (OB, sds Kerr). Bovine mandibular incisors were mounted in self-curing resin and wet ground with #600-grit silicon carbide paper to expose labial enamel. Adhesives were applied for 10, 20 or 40 seconds and the resin composites were condensed into a mold (phi4 x 2 mm) on the enamel and light irradiated. Ten samples per test group were stored in 37 degrees C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/minute. One-way ANOVA and the Tukey HSD test (alpha = 0.05) were performed within each adhesive system. The enamel surfaces after adhesive application were also observed in a Field Emission Electron Probe Surface Roughness Analyzer and the Ra value was calculated. The enamel bond strength ranged from 13.6 to 17.8 MPa for BF, 13.6 to 15.9 MPa for CT, 14.3 to 16.2 MPa for IB and 13.4 to 19.8 MPa for OB. Significant increases in bond strength were found for the 40-second application groups, except for IB. No changes in Ra value were found for BF and IB, while significant decreases in Ra value were recorded with 40-second application for CT and OB. The data suggested that the duration of the single-step self-etch adhesive application was a crucial factor for determining the enamel bond strengths of some of the single-step self-etch adhesives employed in the current study.

Influence of previous acid etching on dentin bond strength of self-etch adhesives.

The purpose of this study was to investigate the effect of previous phosphoric acid etching on the dentin bond strength of single-step self-etch adhesive systems. Facial surfaces of bovine teeth were wet ground with #600 SiC paper. Adhesives were applied with and without previous phosphoric acid etching, and light irradiated. Resin composite was bonded to the adherend surface, followed by light irradiation and storage in water at 37 degrees C. Four groups (n = 10) were made per adhesive system: with and without previous acid etching and with and without thermal cycling between 5 degrees C and 55 degrees C for 10,000 cycles. Specimens were tested in a shear mode at a crosshead speed of 1.0 mm/min. Two-way ANOVA and Tukey HSD test at a level of 0.05 were performed. The changes in dentin bond strengths were different among the adhesive systems tested. In all experimental conditions of this study, the dentin bond strength decreased or remained unchanged with previous acid etching. From the results of this study, previous acid etching might not be acceptable for increasing dentin bond strength of the single-step self-etch adhesive systems.

Self-etching primer systems: changes in dentin bond strength with time.

The purpose of this study was to investigate the development of shear bond strength of resin composites using self-etching primer systems. Four different types of self-etching primer systems with different combinations of their recommended resin composites were used. Bovine incisors were mounted in self-curing resin and the facial surfaces were wet ground on #600-SiC paper to expose the dentin. The shear bond strengths of ten samples per test group were measured at a crosshead speed of 1.0 mm/min after storage for 5, 10, and 60 min, and 24 h in distilled water at 37 degrees C. One-way ANOVA followed by Dunnett's test (alpha = 0.05) was used to examine the significance of differences between the mean bond strength at 24 h and each of the other storage periods. The dentin bond strengths of all the materials tested increased with prolonged storage time. Such differences in the changes in bond strength might have clinical implications if a restoration is subjected to high stress immediately after it has been placed. It is important to consider the development of dentin bond strength to allow the materials sufficient maturation time prior to functional loading or application of other forms of external stress.

Effects of specular component on color differences of different filler type resin composites after aging.

OBJECTIVE: This study evaluated the effects of specular component mode of specular component excluded (SCE) and specular component included (SCI) on color changes of different filler type resin composites after aging of 1 week and 1 year. METHODS: Resin composites and shades used in this study were submicron-filled Estelite Sigma (Sigma: Inc, A2, A3, B3, C2, OA2, OA3) and nanofilled Filtek Supreme XT (XT: Clear, A2E, A2B, A3B, C2B, A2D, A3D). Resin disks of 2mm in thickness and final polish with 2400-grit silicon carbide paper were stored in 100% relative humidity. One-week and 1-year after curing, the colors of the composite disks were measured with a spectrophotometer in SCI and SCE modes. RESULTS: For both 1-week and 1-year specimens, the values of L* with SCI were significantly higher than SCE for all shades of Sigma and XT; however, a* and b* were depended on brands and shades. Comparing 1-week and 1-year values, DeltaE*ab ranged 1.5 (A3 and B3)-2.9 (Inc) with SCI and 1.4 (A3)-2.9 (Inc) with SCE for Sigma, and 1.1 (A3D)-7.1 (Clear) with SCI and 1.4 (A3D)-7.6 (Clear) with SCE for XT. The values of DeltaE*ab with SCE were higher than those of SCI for all shades of XT; however, for Sigma, the differences varied with shades. CONCLUSION: Specular component mode (SCE vs. SCI) significantly influenced L* values; however, the color differences affected by aging were dependent on brands and shades of the resin composites tested.

Color characteristics of resin composites in different color modes and geometries.

Color characteristics of the shades for different filler type resin composites were compared in the reflectance and transmittance modes, and specular component included (SCI) and specular component excluded (SCE) geometries for reflectance mode. Resin composites and shades used in this study were submicron filled Estelite Sigma (Sigma: Inc, A2, A3, B3, C2, OA2, OA3) and nanofilled Filtek(TM) Supreme XT (XT: Clear, A2E, A2B, A3B, C2B, A2D, A3D). Resin disks of 2 mm in thickness and final polish with 2,400-grit silicon carbide paper were kept in 100% humidity. One week after curing, color of the resin disks were measured with a spectrophotometer. Both for Sigma and XT, reflectance of each of all shades measured with SCI were significantly higher than those with SCE. Compared to the values with SCI and SCE, the L with SCI were significantly higher for all shades of Sigma and XT, however, a and b were depended with brands and shades. Different filler type resin composites showed different color characteristics, reflectance, transmittance and L a b distribution. In some shades, color difference between the measurement with SCI and SCE was visually perceptible level. It would be concluded that the color of resin composite measured with the SCI and SCE geometries differed.

Effect of prior acid etching on bonding durability of single-step adhesives.

This study investigated the effect of prior phosphoric acid etching on the enamel bond strength of five single-step self-etch adhesive systems: Absolute, Clearfil tri-S Bond, Fluoro Bond Shake One, G-Bond and One-Up Bond F Plus. Bovine mandibular incisors were mounted in self-curing resin, and the facial surfaces were wet ground with #600 silicon carbide paper. Adhesives were applied to the enamel surfaces with or without prior phosphoric-acid etching and light irradiated. The resin composites were condensed into a mold and light irradiated. In total, 40 specimens were tested per adhesive system with and without prior acid etching and were further divided into two groups: those stored in water at 37 degrees C for 24 hours without cycling and those stored in water at 37 degrees C for 24 hours followed by thermal cycling between 5 degrees C and 55 degrees C with 10,000 repeats. After storage under each set of conditions, the specimens were tested in shear mode at a crosshead speed of 1.0 mm/minute. Two-way analysis of variance, the Student's t-test and the Tukey HSD test were used to analyze the data at a significance level of 0.05. For the specimens without prior acid etching, the mean bond strengths to enamel ranged from 11.0 to 14.6 MPa after 24-hour storage in water, while the corresponding values for specimens with prior acid etching ranged from 15.2 to 19.3 MPa. When these specimens were subjected to thermal cycling, the mean bond strengths ranged from 11.3 to 17.0 MPa without prior acid etching and from 12.3 to 23.2 MPa with prior acid etching. The changes in enamel bond strengths differed among the adhesive systems tested. After 24-hour storage in water, the most common failure modes were adhesive failure and mixed failure for specimens with and without prior acid etching, respectively. Thus, through a careful choice of adhesive system, prior acid etching can increase the bond strengths of single-step self-etch adhesive systems.

Effect of adhesive application methods on bond strength to bovine enamel.

Single-step self-etch adhesive systems have been developed to simplify and shorten bonding procedures. With the gain in popularity of these simplified systems, their reliability has become a focus of interest. The purpose of this study was to determine the effect of adhesive application method on enamel bond strength. Two commercial single-step self-etch adhesive systems, Clearfil tri-S Bond, and G-Bond, were used. Bovine mandibular incisors were mounted in self-curing resin and the facial enamel surfaces were ground wet on 600-grit SiC paper. Adhesives were only applied without agitation (inactive) or were agitated by a brush (active), and resin composites were condensed into the mold on the enamel surface and light-activated. Ten specimens per test group were stored in water at 37 degrees C for 24 h, then shear-tested at a cross-head speed of 1.0 mm/min. Two-way ANOVA followed by the Tukey HSD test were used. The bond strengths for active application were higher than those for inactive application. Significant differences were found for both adhesive systems. From the results of this study, active application of single-step self-etch adhesive may help to ensure the creation of a roughened enamel surface and enhance the penetration of resin monomer into the subsurface demineralized enamel.

Developmental changes of glycosphingolipids and expression of glycogenes in mouse brains.

Glycosphingolipids (GSLs) and their sialic acid-containing derivatives, gangliosides, are important cellular components and are abundant in the nervous system. They are known to undergo dramatic changes during brain development. However, knowledge on the mechanisms underlying their qualitative and qualitative changes is still fragmentary. In this investigation, we have provided a detailed study on the developmental changes of the expression patterns of GSLs, GM3, GM1, GD3, GD1a, GD2, GD1b, GT1b, GQ1b, A2B5 antigens (c-series gangliosides such as GT3 and GQ1c), Chol-1alpha (GT1aalpha and GQ1balpha), glucosylceramide, galactosylceramide (O1 antigen), sulfatide (O4 antigen), stage-specific embryonic antigen-1 (Lewis x) glycolipids, and human natural killer-1 glycolipid (sulfoglucuronosyl paragloboside) in developing mouse brains [embryonic day 12 (E12) to adult]. In E12-E14 brains, GD3 was a predominant ganglioside. After E16, the concentrations of GD3 and GM3 markedly decreased, and the concentrations of a-series gangliosides, such as GD1a, increased. GT3, glucosylceramide, and stage-specific embryonic antigen-1 were expressed in embryonic brains. Human natural killer-1 glycolipid was expressed transiently in embryonic brains. On the other hand, Chol-1alpha, galactosylceramide, and sulfatide were exclusively found after birth. To provide a better understanding of the metabolic basis for these changes, we analyzed glycogene expression patterns in the developing brains and found that GSL expression is regulated primarily by glycosyltransferases, and not by glycosidases. In parallel studies using primary neural precursor cells in culture as a tool for studying developmental events, dramatic changes in ganglioside and glycosyltransferase gene expression were also detected in neurons induced to differentiate from neural precursor cells, including the expression of GD3, followed by up-regulation of complex a- and b-series gangliosides. These changes in cell culture systems resemble that occurring in brain. We conclude that the dramatic changes in GSL pattern and content can serve as useful markers in neural development and that these changes are regulated primarily at the level of glycosyltransferase gene expression.