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T N Seyfried

Publications and source records attributed to T N Seyfried.

At least 19 recordsLinked to original sources
PubMed1998

Ganglioside composition of a mouse brain tumor grown in the severe combined immunodeficiency (SCID) mouse.

The content and composition of gangliosides were examined in an experimental mouse brain tumor, EPEN, that was grown subcutaneously in the flank of the syngeneic C57BL/6J (B6) host and in the B6 severe combined immunodeficiency (SCID) host. SCID mice lack functional T- and B-lymphocytes, but have a normal complement of macrophages. The content and distribution of the brain tumor gangliosides were similar whether the tumor was grown in the immunocompetent B6 host or in the B6-SCID host. N-acetylneuraminic acid- (NeuAc) containing GM3 was the major ganglioside in the subcutaneous tumors and in the cultured EPEN cells. Significant amounts of N-glycolylneuraminic acid- (NeuGc) containing gangliosides were found in the tumor grown in both mouse hosts. NeuGc-containing gangliosides are not expressed in normal mouse brain, but are present in macrophages and serum. An extremely complex pattern of minor gangliosides was found in the subcutaneous tumors on two-dimensional, high-performance thin-layer chromatograms. Most of the minor gangliosides comigrated with those found in mouse macrophages. The results show that the absence of functional T- and B-lymphocytes does not markedly affect brain tumor ganglioside composition and suggest that NeuGc-containing gangliosides in the EPEN can be derived from tumor infiltrating host cells (mostly macrophages) and from the extracellular milieu (serum).

Animals↗
PubMed1998

Inhibition of glycosphingolipid biosynthesis does not impair growth or morphogenesis of the postimplantation mouse embryo.

Whole embryo culture (WEC) of organogenesis-stage mouse embryos was adapted for glycosphingolipid (GSL) metabolic studies to evaluate the hypothesis that de novo GSL biosynthesis is a prerequisite for growth and morphogenesis of the early postimplantation embryo. WEC supports the growth and development of postimplantation mouse embryos to stages that are indistinguishable from those achieved in vivo. N-Butyldeoxygalactonojirimycin (NB-DGJ) is an N-alkylated imino sugar that specifically inhibits biosynthesis of all glucosylceramide-based GSLs. NB-DGJ inhibited glucosylceramide and lactosylceramide biosynthesis nearly completely and inhibited ganglioside biosynthesis approximately 90% in both the embryo and visceral yolk sac. NB-DGJ also significantly reduced total ganglioside content in both the embryo and visceral yolk sac as estimated by the cholera toxin immunooverlay technique. A shift in expression from the structurally simple to the structurally complex gangliosides was also observed in NB-DGJ-treated embryos and yolk sacs. Despite causing major changes in GSL biosynthesis and composition, NB-DGJ had no effect on embryo viability, growth, or morphology. The findings suggest that de novo GSL biosynthesis may not be a prerequisite for the growth and morphogenesis of the organogenesis-stage mouse embryo.

1-Deoxynojirimycin↗
PubMed1997

Ganglioside biosynthetic gene expression in experimental mouse brain tumors.

The genes for cytidine monophospho-N-acetylneuraminic acid hydroxylase (NeuAc-H) and beta-1,4-N-acetylgalactosaminyl transferase (GalNAc-T) were examined using reverse transcription-PCR in two experimental mouse brain tumors, EPEN and CT-2A. NeuAc-H is required for the synthesis of gangliosides containing N-glycolylneuraminic acid, whereas GalNAc-T is required for the synthesis of ganglioside GM2. The genes were analyzed in solid tumors grown in vivo and in tumor cells grown in vitro. NeuGc-containing gangliosides are abundant in cells of the mouse immune system, including macrophages, but are undetectable in normal mouse brain. GM2 is expressed in both neural and nonneural mouse cells and tissues. The EPEN tumor cells synthesize only ganglioside GM3, whereas the CT-2A tumor cells synthesize GM3, GM2, GM1, and GD1a. NeuAc-H gene expression was detected in both solid tumors grown in vivo but was undetectable in either tumor cell line. The presence or absence of NeuAc-H gene expression in the tumor tissues and cells correlates with the presence or absence, respectively, of NeuGc-containing gangliosides. Differences in GalNAc-T gene expression between the solid tumors and the cultured tumor cells correlate with the expression of ganglioside GM2. The findings suggest that the differences in ganglioside biosynthetic gene expression between brain tumors grown in vivo and in vitro are associated with the presence or absence, respectively, of tumor-infiltrating host cells.

Animals↗
PubMed1997

Synaptic vesicle glutamate uptake in epileptic (EL) mice.

The ATP-dependent glutamate uptake system of synaptic vesicles was investigated in epileptic (EL) mice to determine whether glutamate uptake activity correlates with seizure susceptibility or development. Given the focal seizure onset, glutamate uptake activity was measured in four separate brain regions: cerebrum (minus hippocampus), hippocampus, cerebellum, and brain stem. The EL values were compared to those of age-matched controls; DDY and ABP/LeJ (ABP) mice. The glutamate uptake specific activity for EL cerebrum was significantly higher than that for the control mice (approx. 400 days old), but was not elevated prior to seizure onset (46 days old). No difference in glutamate uptake was observed between the strains in the other brain regions. We conclude that increased synaptic vesicle glutamate uptake is brain-region specific (cerebrum) and is associated with the development or maintenance, rather than the initial cause, of seizures in the EL model of epilepsy.

Adenosine Triphosphate↗
PubMed1997

Genomic imprinting and audiogenic seizures in mice.

Audiogenic seizure (AGS) susceptibility in mice is a multifactorial behavioral disorder that involves severe generalized convulsions in response to loud, high-frequency sound. The inheritance of AGS susceptibility was examined in crosses between AGS-susceptible DBA/2J (D2) mice and epilepsy-prone (EP) mice. The EP mice were selected for high AGS susceptibility in a BALB/c-derived line. The AGS phenotype was similar in the EP and D2 mice at 30 days of age. The frequency of generalized clonic-tonic AGS was high in both the D2 and the EP mice (53 and 83%, respectively) but was low in the reciprocal EPD2F1 and D2EPF1 hybrids (14 and 19%, respectively). In the backcross to the EP parent, no significant associations were found between AGS susceptibility and microsatellite markers linked to Asp1 or Asp2, AGS genes located on Chromosomes 12 and 4, respectively. Significant associations were found for markers linked to Asp3, which is located in the proximal region of Chromosome 7. The influence of Asp3 on AGS susceptibility was seen in the EP x EPD2F1 backcross but not in the reciprocal EPD2F1 x EP backcross, suggesting that Asp3 expression is influenced by genomic imprinting. A model is proposed where genomic imprinting represses the maternal Asp3 allele, providing an influence largely from the paternal allele.

Acoustic Stimulation↗
PubMed1997

Influence of ganglioside GM3 and high density lipoprotein on the cohesion of mouse brain tumor cells.

Previous findings with various murine tumor cell lines suggest an association between ganglioside GM3 and cell cohesive properties. The influence of GM3 on cohesion was studied in two mouse brain tumor cell lines: ependymoblastoma (EPEN) and CT-2A. In culture, the EPEN cells grow as islands and contain GM3 as the only ganglioside, whereas the CT-2A cells grow as a fusiform cell monolayer and contain GM2, GM1, and GD1a as major gangliosides and low amounts of GM3. To examine the role of GM3 in cohesion, both cell lines were treated with 1) C. perfringens neuraminidase, 2) anti-GM3 monoclonal antibody (mAb DH2), or 3) were grown in serum-free medium. All three treatments caused a significant increase in the number of non-cohesive and protoplasmic process-bearing cells for the EPEN, but had no effect on the morphology of the CT-2A cells. The neuraminidase treatment removed GM3 from both cell lines and caused a significant accumulation of GM1 in the CT-2A cells. EPEN cell cohesion and GM3 content returned to control levels after removal of neuraminidase. EPEN cell cohesion was restored in serum-free medium with added high density lipoprotein (HDL). The HDL effect on the EPEN cell cohesion was dose-dependent and was not seen with other lipoproteins. We suggest that EPEN cell cohesion could involve an interaction between extracellular HDL, acting as a bridge, and GM3 molecules on opposing cell surfaces.

Animals↗
PubMed1996

Influence of host cell infiltration on the glycolipid content of mouse brain tumors.

Previous studies showed that levels of some glycosphingolipids (GSLs) expressed in solid brain tumors grown in vivo were reduced or undetectable in cultured cells prepared from the tumors. This phenomenon has been attributed either to suppressed glycolipid synthesis from unknown forces of the tissue culture environment or to the absence of host cells that normally infiltrate the solid tumors growing in vivo. To test further the host cell hypothesis, we examined host cell markers in two experimental mouse brain tumors, the ependymoblastoma and the CT-2A, that were grown as subcutaneous solid tumors in the flank of C57BL/6J (B6) mice or as cultured cells in vitro. The markers included ganglioside N-glycolylneuraminic acid (NeuGc), GA1 (asialo-GM1), and Fc receptor-bearing cells. NeuGc-containing gangliosides, GA1, and Fc receptors are expressed by macrophages and lymphoid-type cells of the mouse host immune system but are not normally expressed by mouse neural cells. Differences in the relative content of Fc receptor-bearing cells in ependymoblastoma and CT-2A tumors grown in vivo (8.3 and 16.8%, respectively) were proportional to differences in the relative content of NeuGc-containing gangliosides (25.5 and 45.1%) and GA1 (8.5 and 13.8%), respectively. Neither cultured tumor cell line expressed Fc receptors, GA1, or NeuGc-containing gangliosides. These findings suggest that non-neoplastic host infiltrating cells (macrophages) contribute significantly to the GSL composition of solid tumors growing in vivo.

Animals↗
PubMed1994

Phylogenetic conservation of ganglioside GD3 expression during early vertebrate ontogeny.

Gangliosides were investigated in adult brains and in 5-vesicle stage embryos of representatives belonging to the four vertebrate classes: Chondrichthyes, Amphibia, Aves and Mammalia. Considerable variability in brain ganglioside composition and concentration was observed among the adult vertebrates. The ganglioside patterns of the developmentally matched vertebrate embryos were similar in that each comprised GD3 as the predominant ganglioside. The phylogenetic conservation of abundant GD3 expression during early vertebrate ontogeny is interpreted as biochemical evidence consistent with von Baer's theory of increasing differentiation and suggests that GD3 is of critical importance for normal vertebrate development.

Animals↗
PubMed1994

Ceruloplasmin gene defect associated with epilepsy in EL mice.

Epilepsy is a dominant trait in EL mice, a model for human complex partial seizures. We recently mapped the major gene, El-1, to chromosome 9 near the predicted location for the ceruloplasmin (Cp) gene. We now present evidence for a partial duplication in the Cp gene in EL mice. This Cp duplication is coinherited with seizures in backcross generations and is associated with enhanced expression of Cp mRNA and increased Cp oxidase activity. Moreover, the duplication is associated with an enhanced frequency of double recombinants, simulating negative interference. The findings are relevant to the basic mechanisms of epilepsy and to theories of genetic recombination and gene mapping.

Animals↗
PubMed1994

Enhanced aspartate release related to epilepsy in (EL) mice.

Previous studies have shown that potassium-evoked, calcium-dependent, endogenous aspartate release is greater from hippocampal slices of adult epileptic (EL) mice than from nonepileptic control C57BL/6J (B6) mice. To examine further the association between epilepsy and enhanced aspartate release in EL mice, endogenous neurotransmitter release from hippocampal slices was studied in young, seizure-free EL mice and in two nonseizure control mouse strains, DDY and B6. DDY is the parental strain from which EL arose, and it has a genetic background similar to EL. Released amino acid neurotransmitters were quantitated by HPLC with fluorescent detection and were expressed as picomoles of amino acid released per minute of incubation per slice +/- SEM. Aspartate release was significantly higher in EL mice (15.8 +/- 0.8) than in either the control B6 or DDY mice (8.5 +/- 1.4 and 8.4 +/- 1.7, respectively). No significant differences were found among the B6, DDY, and EL mice for the release of glutamate (23.0 +/- 2.0, 32.3 +/- 5.8, and 25.9 +/- 2.6, respectively) or GABA (23.5 +/- 0.7, 19.5 +/- 3.2, and 21.8 +/- 3.2, respectively). Thus, enhanced aspartate release precedes the onset of EL seizures and may be related to the cause rather than to the effects of seizure activity.

Aging↗
PubMed1994

Genetic analysis of nucleotide triphosphatase activity in the mouse brain.

A Ca(2+)- or Mg(2+)-stimulated ecto-ATPase is thought to regulate the hydrolysis of extracellular ATP in nervous tissues. The hydrolysis of nucleotide triphosphates (NTPs) was analyzed in brain microsomal fractions from crosses of DBA/2J (D2) and C57BL/6J (B6) mice. The nucleotide triphosphatase (NTPase) activity was significantly reduced in D2 mice as compared to B6 mice, and B6D2F1 hybrids had activities intermediate to the parentals. A significant positive correlation was found between the hydrolysis of four NTPs (ATP, CTP, GTP and UTP) in 24 B6 x D2 (BXD) recombinant inbred (RI) strains of mice and in 80 B6D2F1 x D2 backcross mice. The RI strains and backcross mice fell into two distinct groups with respect to the NTPase activity. Linkage of NTPase activity was suggested with the chromosome 2 markers, D2Mit6 and Ass-1, in the RI strains, and was confirmed by analysis of other markers in the backcross population. These data suggest that the Ca(2+)- or Mg(2+)-stimulated hydrolysis of NTPs, designated Ntp, is regulated by a single gene located on proximal chromosome 2. Although an association was observed previously between Ca(2+)-ATPase activity and susceptibility to audiogenic seizures (AGS), no significant association was observed for the expression of Ntp and AGS susceptibility.

Animals↗
PubMed1994

Effect of Golgi membrane phospholipid composition on the molecular species of GM3 gangliosides synthesized by rat liver sialyltransferase.

Previous studies have demonstrated that there is a change in the molecular species specificity of CMP-N-acetylneuraminate:lactosylceramide alpha 2,3-sialyltransferase (LacCer alpha 2,3-ST) when the lipid composition of the Golgi membrane is altered (Kadowaki, Grant, and Williams, 1993. J. Lipid Res. 34: 905-914). To understand the basis of this phenomenon, the molecular species specificity of rat liver LacCer alpha 2,3-ST was determined under conditions in which the phospholipid class composition of the Golgi membrane was changed to resemble that of cultured mouse neuroblastoma NB2a cells, a cell line in which LacCer alpha 2,3-ST exhibits no molecular species specificity. The change in the lipid composition of the Golgi membrane was accomplished by incubating the Golgi membrane vesicles with nonspecific lipid transfer protein and a 10-fold excess of liposomes prepared with various proportions of purified rat liver lipids. The molecular species specificity of LacCer alpha 2,3-ST was also determined under conditions where the phospholipid molecular species composition but not the phospholipid class composition of the Golgi membrane was changed, and in which both the phospholipid class and molecular species compositions were changed by using liposomes prepared with lipids purified from a mouse brain tumor (ependymoblastoma). When using liposomes prepared with rat liver lipids, a change in the phospholipid class composition of the Golgi membrane to a composition similar to that of NB2a cells increased rather than decreased the molecular species specificity of rat liver LacCer alpha 2,3-ST.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Ganglioside biosynthesis in mouse embryos: sialyltransferase IV and the asialo pathway.

The in vitro activity of sialyltransferase IV (SAT-IV), which catalyzes the transfer of sialic acid to the terminal galactose of different gangliotetraosylceramides (GA1, GM1a and GD1b), was examined in membrane-enriched preparations from mouse embryos at embryonic day 12 (E-12). Gangliosides GD1a and GT1b were the only reaction products using GM1a and GD1b as substrates, respectively. The Km values for GM1a and GD1b were 53 microM and 42 microM, respectively. Competitive inhibition experiments showed that the same enzyme (SAT-IV) catalyzed sialic acid transfer to the terminal galactose residues of both GM1a and GD1b. Two labeled ganglioside products were obtained, however, using GA1 as a substrate. One product was identified as ganglioside GM1b and the enzymatic reaction for its formation was maximal at pH 6.0, similar to that for GD1a and GT1b formation. The second product, synthesized by a different sialyltransferase, was identified as GD1 alpha based on results from TLC immunostaining, neuraminidase digestion, and periodate oxidation-borohydride reduction. The pH dependence curve for GD1 alpha formation had a different shape than that for GM1b formation with a maximum at pH 6.3. GD1 alpha is apparently synthesized from GM1b by an endosialyltransferase that catalyzes the transfer of a second sialic acid to the internal N-acetylgalactosamine of GM1b. The formation of both GM1b and GD1 alpha was linear over protein concentration. The ratio of GD1 alpha/GM1b formation varied from 0.25 to 1.20 depending on the GA1 substrate concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Serum gangliosides in mice with metastatic and non-metastatic brain tumors.

The content of serum gangliosides was examined in VM and C57BL/6J (B6) mice that contained subcutaneous metastatic (VM) and non-metastatic (CT-2A) brain tumors, respectively. Gas-liquid chromatography (GLC) and high performance thin-layer chromatography (HPTLC) were used to analyze the serum gangliosides. N-glycolylneuraminic acid (NeuGc) accounted for greater than 90% of the total serum sialic acid content in each mouse strain (5.53 nmol and 2.05 nmol per ml serum, respectively). GM2-NeuGc was the major serum ganglioside detectable in both the normal and tumor-bearing mice of each strain. Shedding of tumor gangliosides into the serum occurs in various murine non-neural tumors and in human gliomas and neuroblastomas, but has not been previously studied in murine brain tumors. Our results show that serum ganglioside concentration was reduced in VM mice bearing the metastatic VM tumor, but was increased in B6 mice bearing the non-metastatic CT-2A tumor. These changes in concentration, however, were not associated with marked changes in serum ganglioside distribution. As serum gangliosides are synthesized in the liver, the differences in serum ganglioside concentration in the tumor-bearing mice may arise more from changes in liver function than from differences in tumor shedding.

Animals↗
PubMed1993

The influence of ImuVert, a biological response modifier, on the growth and ganglioside composition of murine neural tumors.

ImuVert is a biological response modifier (BRM) that has antitumor effects in humans and rats. The influence of ImuVert on the ganglioside composition of two experimental brain tumors, ependymoblastoma and CT-2A, was studied in C57BL/6J mice. Gangliosides are expressed on plasma membranes and can serve as markers to distinguish neural cells from nonneural cells in mouse brain tumors. N-acetylneuraminic (NeuAc) is the predominant sialic acid in mouse neural cells, whereas N-glycolylneuraminic (NeuGc) is a major sialic acid in nonneural cells, e.g., macrophages and lymphocytes. ImuVert treatment increased the NeuGc ganglioside concentration in the ependymoblastoma, but had no effect on the sialic acid concentration in the CT-2A brain tumor. ImuVert also had a slight inhibitory effect on the growth of both brain tumors.

Animals↗
PubMed1992

Altered ganglioside composition in virally transformed rat embryo fibroblasts.

The composition of gangliosides was examined in a normal rat embryo fibroblast cell line (REF52) and in two viral transformants: a polyoma transformant (REF52-PyMLV) and a simian viral 40 transformant (REF52-SV40). The distribution of gangliosides in the cell lines was determined using gas-liquid chromatography and high-performance thin-layer chromatography. N-acetylneuraminic acid was the predominant sialic acid species detected in the three cell lines. The total ganglioside concentration (microgram/100 mg dry weight of cells) in the normal, PyMLV, and SV40 lines was 144.7 +/- 10.4, 153.8 +/- 9.2, and 86.1 +/- 6.8, respectively. Gangliosides GM3, GM2, GM1, and GD1a were the major species in the normal and transformed lines. The distribution of these gangliosides, however, differed markedly between the normal and the transformed lines and also between the transformed lines themselves. The transformed cells also differed from the normal cells in growth rate, morphology, and social behavior. The cell line with highest GM3 content (PyMLV) formed islands, whereas the normal and SV40 cell lines, which had lower GM3 levels, grew as monolayers. The findings suggest that PyMLV and SV40 transformation can have multiple and different effects on cellular ganglioside distribution and growth behavior.

Animals↗
PubMed1992

Neutral glycolipid abnormalities in a t-complex mutant mouse embryo.

The content of neutral glycolipids was studied in normal and twl/twl mutant mouse embryos at embryonic day 11 (E-11). The twl mutation is part of the T/t complex on chromosome 17 and causes embryonic lethality from defects in the developing neural tube. Previous studies suggested that the mutation could involve a defect in ganglioside biosynthesis. Although the total neutral glycolipid content was similar in the normal and mutant whole embryos (approximately 80 nmol glucose/100 mg dry weight), marked differences were detected for the distribution of specific glycolipids. The content of lactosylceramide, globotriaosylceramide, and globotetraosylceramide was significantly higher in the mutant than in the normal embryos, whereas that of glucosylceramide was significantly reduced. The Forssman glycolipid was slightly elevated. The neutral glycolipid composition was similar in embryonic head and body regions of normal embryos, suggesting that the glycolipid abnormalities observed in the mutants are expressed in most embryonic cells and tissues. These and the previously reported ganglioside abnormalities in the twl/twl mutants could result from an inherited defect in glycolipid biosynthesis.

Animals↗