Monoclonal antibody-defined antigen of human uterine endometrial carcinomas is Leb

A monoclonal antibody, MSN-1, generated by immunizing a mouse with a human uterine endometrial adenocarcinoma cell line, SNG-II, was strongly and specifically reactive with neutral glycosphingolipids from cancer tissues of patients with uterine endometrial adenocarcinomas. The glycosphingolipid antigen was purified from pooled human meconia, which contained the antigen at the concentration of 1.95 mumol/g dry weight. Its structure was determined by NMR, negative ion FABMS, permethylation analysis, and TLC-immunostaining with monoclonal anti-Lc4Cer antibody, and was concluded to be the III4IV2Fuc2Lc4Cer,Leb antigen of the human Lewis blood system. On ELISA, the monoclonal antibody was found to be strongly reactive with Leb, slightly with Lea and not at all with A, B, H, or IV2FucGg4Cer. The amount of Leb in cancerous regions in the patients with the Lea-b+ blood group was significantly increased compared to that in normal regions in the same patients, and it was a newly appearing antigen in the cancerous tissue of a patient with the Lea+b- blood group.

Differential exposure of the major gangliosides in rabbit thymocytes to Vibrio cholerae neuraminidase

Neuraminidase treatment of lymphocytes is known to cause changes of cellular responses in several biological phenomena, but the molecules modified on the cell surface by neuraminidase are not known in detail. Rabbit thymocytes, which contain tissue-characteristic gangliosides, were treated with Vibrio cholerae neuraminidase, and the susceptibility of the cell surface sialic acid residues was examined. The amount of sialic acid released from the thymocytes at the highest level was 42.4 nmol per 1 X 10(9) cells, among which 26.5% was from gangliosides. Ninety-three percent of the VI3NeuGc-nLc6Cer, 84% of the IV3NeuGc-nLc4Cer, and 50% of the II3NA2-LacCer in the thymocytes was hydrolyzed to nLc6Cer, nLc4Cer, and LacCer, respectively, but II3NA-LacCer was completely cryptic. Also, among the molecular species of II3NA2-LacCer, C20:0- to C24:0-containing, but not C16:0- to C18:0-containing molecules, were susceptible to neuraminidase. After neuraminidase treatment, nLc4Cer and nLc6Cer became the major glycosphingolipids, and a 15-fold increase of radioactivity incorporated into the glycosphingolipids was observed by the galactose oxidase-sodium borotritide procedure, suggesting that the beta-galactose of the glycosphingolipids produced by neuraminidase treatment is accessibly to the several ligands which are functionally associated with lymphocytes.

[The composition of glycosphingolipids and the effect of neuraminidase on cultured glioma cell lines]

The composition of glycosphingolipid on human cultured glioma cell line U 251 and rat glioma cell line C6 was analysed by high performance thin layer chromatography. As a result, the major gangliosides were simple gangliosides such as GM3 (U 251: 7.7%, C6: 84.3%), GM2 (U 251: 32.6%) and SPG (U 251: 30.0%) on glioma cells whereas the major neutral glycosphingolipids were CDH, CTH and globoside. After treatment with neuraminidase 2.92 nmol/mg dry weight and 3.73 nmol/mg dry weight of sialic acid were freed from U 251 cells and C6 cell, but only 8.11% (U 251 cell) and 11.24% (C 6 cell) of these sialic acids originated from glycolipid, and thus the major part of sialic acid might be released from glycoprotein of the cells. The gangliosides that react to neuraminidase are SPG, GD1a and GD1b in U 251 cells and are GM1a and little GM3 in C 6 cells. The biolabelling study using N-acetyl-14C-mannosamine as a precursor of sialic acid demonstrated that the precursor was mainly incorporated into both or either of GM3 and SPG in the acidic glycolipid fraction. In addition, no significant change on proliferation and morphology of glioma cells after neuraminidase treatment was observed in this study.

[Functional significance of glycolipid as an important plasma membrane constituent]

Glycolipids are ubiquitous membrane components in various mammalian cells and participate in several functions through membrane. Until now, about 180 glycolipids with different carbohydrate structures have been characterized. Since alteration in glycolipids during cellular proliferation, differentiation and transformation is dramatic in general, several approaches have been attempted to clarify the meaning. Our findings that ganglioside composition in human milk is characteristically changed during the periods of lactation and that N-(O-linoleoyl-omega-hydroxylignoceroyl) sphingosyl glucose (ester CMH) in mammalian skin is characteristically synthesized during differentiation of epidermis are the examples to indicate the close association of glycolipids in cellular functions. GM3 ganglioside appeared in the later period of lactation has an activity to suppress cell growth of human breast cancer and ester CMH has an activity to promote the keratinization of epidermal cells, respectively. The observations indicate that glycolipids synthesized during cellular differentiation function as an signal transducer through plasma membrane. Structural bases of glycolipids to give such physiological activities are summarized and discussed in this communication.

Islet cell-activating protein reverses anti-fucosyl GM1 ganglioside antibody-induced inhibition of adenosine 3',5'-monophosphate production in FRTL-5 rat thyroid cells

Our previous study revealed that a specific antibody against fucosyl GM1 ganglioside (fGM1) inhibits basal and ligand-stimulated cAMP production in FRTL-5 rat thyroid cells. To further elucidate the mechanism of this inhibitory action of the antibody, the involvement of guanine nucleotide-binding proteins was studied using islet cell-activating protein (IAP) and cholera toxin. When FRTL-5 cells were pretreated with IAP and incubated with the antibody, the inhibitory activity of the antibody on cAMP production was completely abolished. Furthermore, the inhibitory activity of the antibody on TSH- or forskolin-stimulated cAMP production was also abolished by IAP preincubation. The inhibitory activity of the antibody by pretreatment of the cells was also reversed by the addition of IAP. Coincubation of FRTL-5 cells with the antibody and cholera toxin reduced the cAMP inhibitory action of the antibody. Similar results were obtained with anti-fGM1 pretreatment before cholera toxin stimulation. These results provide evidence that anti-fGM1 antibody acts via guanine nucleotide-binding proteins in inhibiting cAMP production in FRTL-5 cells.

Characteristic mode of action of gangliosides in selective modulation of CD4 on human T lymphocytes

We have explored the possible mechanisms for selective modulation by gangliosides of CD4 on human T lymphocytes and subsequent re-expression of CD4. Indirect immunofluorescence staining with anti-CD4 antibodies revealed newly internalized CD4 in ganglioside-treated cells after membrane permeabilization with 0.1% saponin. Cycloheximide and other metabolic inhibitors did not alter the modulation but inhibited significantly the re-expression of CD4. These results suggest both selective modulation of CD4 by a process of endocytosis and re-expression of CD4 through de novo protein synthesis.

Tumor-associated mucin-type glycoprotein (CA54/61) defined by two monoclonal antibodies (MA54 and MA61) in ovarian cancers

Two monoclonal antibodies, MA54 and MA61, were established by immunizing with culture medium supernatants of a lung adenocarcinoma cell line, and a double-determinant sandwich enzyme immunoassay system was developed by using these two monoclonal antibodies. The antigen recognized by this assay (CA54/61) was found to be often high in the sera of several cancers. The antigen recognized by MA54 (CA54) or MA61 (CA61) proved to be carbohydrate chain on a high molecular weight mucin-type glycoprotein, and CA54 has NeuAc alpha 2-6galactose in the terminal residue. CA54/61 was frequently found in the sera of ovarian cancer patients, the positive rate being 67, 64, 40, and 78% in serous, mucinous, endometrioid, and mesonephroid cancers, respectively, when the cut off value was set at mean + 4 SD. Since the positive rate of CA125, which is now the most widely used for the diagnosis of ovarian cancers, is rather low (approximately less than 50%) in mucinous cystoadenocarcinoma, CA54/61 will be of clinical value. In addition, CA61 was detected immunohistochemically in the fetal red blood cells with nuclei, indicating its oncodevelopmental character in nature.

Menstrual cycle-associated alteration of sulfogalactosylceramide in human uterine endometrium: possible induction of glycolipid sulfation by sex steroid hormones

The human uterine endometrium is a tissue in which cell proliferation and differentiation are strictly controlled by sex steroid hormones, and these hormone-controlled cellular events occurring in association with the menstrual cycle of the uterine endometrium should be accompanied by characteristic molecular and metabolic changes. To characterize the menstrual cycle at the molecular level, we analyzed the glycolipids of human uterine endometrium in the proliferative and secretory phases of the menstrual cycle. Neutral glycosphingolipids from uterine endometrium comprised globo-series glycosphingolipids, such as GlcCer, LacCer, Gb3Cer, and Gb4Cer, and the relative concentrations remained constant in the two phases. However, in the case of acidic glycosphingolipids, although the concentrations of sialoglycosphingolipids remained at constant levels in the two phases, sulfatide, I3-SulfoGalCer, dramatically increased from the proliferative to the secretory phase, amounting to 7-17 nmol/g dry weight in the proliferative phase and 115-245 nmol/g dry weight in the secretory phase. Since sulfatide was the only glycolipid that changed in association with the menstrual cycle, it is likely that the sulfotransferase responsible for the synthesis of sulfatide might be induced by sex steroid hormones, estrogen and progesterone, and that sulfatide might play an essential biological role in the secretory phase of the menstrual cycle in the uterine endometrium.

A new approach to the modification of cell membrane glycosphingolipids: ganglioside composition of JTC-12 P3 cells altered by feeding with galactose as a sole carbohydrate source in protein- and lipid-free synthetic medium

A significant difference in the glycosphingolipid composition of JTC-12 P3 cells established from monkey kidney tissue was observed when cells cultured in a protein- and lipid-free synthetic medium containing glucose (DM-160) as a sole carbohydrate source were transferred and cultured in the same medium containing galactose and pyruvic acid (DM-170) in place of glucose. In particular, the amounts of gangliosides GM3, GM2, and GD3 in the cells cultured in DM-170 were 5.3-, 17.8-, and more than 8-fold those in the cells cultured in DM-160, respectively, indicating that anabolism of gangliosides is greatly enhanced in cells cultured in the presence of galactose and pyruvic acid, as compared with cells cultured in the presence of glucose. In fact, after cultivation of cells in the medium with N-acetyl-D-[14C]mannosamine for 96 h, the radioactivity incorporated into the gangliosides of the cells in DM-170 was 10-fold that of the cells in DM-160. Among the gangliosides of the cells in DM-170, highly sialylated molecules such as GD3, GD1a, GD1b, and GT1b were preferentially labeled, indicating that the sialyltransferases responsible for the synthesis of gangliosides are significantly more activated in cells cultured in DM-170 than in DM-160. These observations reveal that the glycosphingolipid composition of the plasma membrane can be modified epigenetically under well-defined conditions and provide important clues for clarifying the roles of glycosphingolipids associated with particular cell functions.

Uncoupling of intracellular cyclic AMP and dome formation in cultured canine kidney epithelial cells: effects of gangliosides and vasopressin

Cultured MDCK cells were treated with various gangliosides and sialylated compounds and their effects on the intracellular level of cAMP were compared to those of arginine vasopressin (AVP) and other substances which elevate cAMP. Since all those agents could stimulate dome formation, its correlation with cAMP production is discussed. Most gangliosides increased intracellular cAMP 3-4-fold, the increase being dose-dependent up to 25 microM ganglioside. AVP and cAMP analogs increased intracellular cAMP 3-40-fold. A unique feature of the ganglioside-induced cAMP increase was its extremely long time course (70 h), as compared to that induced by other agents which show much faster and less prolonged effects in other biological systems. This might indicate that gangliosides differ from AVP and other agents in the mechanisms by which they stimulate intracellular cAMP increase. The time course and the level of cAMP increase induced by GM3 or AVP did not correlate with those of dome formation. Furthermore, the ability of some gangliosides and other agents to induce dome formation did not correspond to their ability to elevate cAMP. It is suggested that although the remarkable dome-stimulating activity of gangliosides may be induced in part by a cAMP-dependent mechanism, gangliosides also act directly on the cellular components influencing dome formation, without involving changes in intracellular cAMP.

Region-specific distribution of glycosphingolipids in the rabbit gastrointestinal tract: preferential enrichment of sulfoglycolipids in the mucosal regions exposed to acid

Neutral and acidic glycosphingolipids from various regions of the rabbit gastrointestinal tract showed different but characteristic patterns. In particular, sulfatides were found to be present in high concentrations in the mucosal regions frequently exposed to gastric acid, such as the gastric mucosa and proximal intestinal mucosa (duodenum and jejunum). The majority of sulfatides in these tissues have been identified as GalCer-I3-sulfate, with alpha-hydroxy long-chain fatty acids, by chemical procedures including analysis by negative ion fast atom bombardment mass spectrometry. The concentrations of GalCer-I3-sulfate in the fundic mucosa, antral mucosa, duodenum, and jejunum were 394.0, 356.9, 829.3, and 378.1 nmol/g of dry weight, respectively. These concentrations exceed those in the kidney, which has been reported to contain the highest concentration of sulfatides, with the exception of the nervous system, also, especially in the fundic mucosa, gangliosides were drastically reduced, in contrast to sulfatides: the molar ratio of sulfatides to GM3, the major ganglioside, was about 11:1. In addition, in the acid hydrolysis experiment, using the same concentration of HCl as that present in the gastric juices, sulfatide proved to be much more resistant to acid than GM3. Therefore, the preferential distribution of sulfatides in the mucosal regions exposed to acid may be related to mucosal functions, such as acid secretion and protection from acidic environments.

Selective terminal alpha 2-3 and alpha 2-6 sialylation of glycosphingolipids with lacto-series type 1 and 2 chains in human meconium

Human meconium was found to contain two kinds of gangliosides with the same carbohydrate sequence belonging to the lacto-series. They were detected by TLC-immunostaining with monoclonal antibodies directed to the NeuAc alpha 2-6Gal and Lc4Cer structures. One of these two gangliosides, a major one, which migrated on TLC to a position below that of standard IV3NeuAcnLc4Cer from human erythrocytes, reacted with the antibody to NeuAc alpha 2-6Gal. The other minor one, which migrated on TLC to a position corresponding to standard IV3NeuAcnLc4Cer, was detected with the antibody to Lc4Cer only when the plate, on which the individual gangliosides were separated, was subjected to prior treatment with Vibrio cholerae sialidase. The structures of the gangliosides, each identified by means of permethylation anaylsis with Vibrio cholerae sialidase. The structures of the gangliosides, each identified by means of permethylation anaylsis and enzyme treatment after isolation with antibody monitoring, were shown to be IV6NeuAcnLc4Cer for the former and IV3NeuAcLc4Cer for the latter, indicating that the lacto-series type 2 (nLc4Cer) and 1 (Lc4Cer) chains are sialylated at different linkages, alpha 2-6 and alpha 2-3, respectively. IV6NeuAcLc4Cer and IV3NeuAcnLc4Cer were not detected, even in trace amounts, on TLC-immunostaining with the monoclonal antibodies. The concentrations of IV6NeuAcnLc4Cer and IV3NeuAcLc4Cer were 448 and 18 nmol/g dry wt of human meconium.

Distinct differences in lipid composition between epidermis and dermis from footpad and dorsal skin of guinea pigs

All lipids, including neutral lipids, phospholipids and glycolipids, in the dermis and epidermis from footpad and dorsal skin of guinea pigs were quantitatively determined, and distinct and characteristic differences in lipid composition were observed in both regions. Ceramides, cerebrosides and cholesterol sulfate were abundant in the epidermis, the amounts being 8.8-12.0, 2.8-4.0 and 6.0-6.5 times higher than those in the dermis, respectively, whereas sulfatide was predominantly found in the dermis. Four and six bands of ceramides, and three and four bands of cerebrosides were detected for the lipids from both the epidermis and dermis on TLC, respectively, two of the ceramides and one of the cerebrosides being found to be esterified. Cerebrosides in the epidermis were predominantly glucocerebrosides, whereas those in the dermis comprised a mixture of gluco- and galactocerebrosides. In addition, an esterified cerebroside, glucosyl N-(O-linoleoyl-omega-hydroxylignoceroyl) sphingosine, was present in the epidermis as a tissue-characteristic compound and this finding seems to be common for several animal species. The marked differences in lipid components between the epidermis and dermis should be quite useful for discriminating these functionally as well as histologically different regions on a biochemical basis.

Neosynthesis of neolacto- and novel ganglio-series gangliosides in a rat fibroblastic cell line brought about by transfection with the v-fes oncogene-containing Gardner-Arnstein strain feline sarcoma virus-DNA

Transfection of retrovirus DNA from Gardner-Arnstein strain feline sarcoma virus containing v-fes oncogene into a rat fibroblastic cell line 3Y1 caused not only cell transformation but also a remarkable change in ganglioside expression. The ganglioside phenotype of the 3Y1 cells was characterized by the exclusive expression of GM3, along with a trace amount of "A" pathway-related gangliosides (GM2-GM1a-GD1a), whereas in the transfected transformant, 3Y1-GA, sialosylparagloboside containing N-acetyl neuraminic acid (NeuAc) and novel ganglio-series gangliosides (presumably GM1b and GD1 alpha) were expressed in addition to GM3. Thus, the Gardner-Arnstein strain feline sarcoma virus DNA transfection open two new ganglioside metabolic pathways, one leading to the synthesis of neolacto-series and the other to that of ganglio-series gangliosides. These results were in striking contrast to the cases of transfection with so-called "intranuclearly expressed" transforming genes, adenovirus E1, SV40-T, and myc, with which the same 3Y1 cells newly expressed GD3 with a concomitant decrease in precursor ganglioside GM3. The difference in underlying mechanisms of ganglioside metabolism shown by these two different types of oncogenes might reflect differences in the modes of action of the oncogenes and their biological activities.

[On the clinical usefulness of a few sugar antigens and a galactosyl-transferase]

Using human cultured cell lines or lymphocytes, two kinds of murine- and one human-monoclonal antibodies were produced, respectively and their clinical usefulness were investigated, and the possibility of galactosyl-transferase as a new tumor maker was also discussed. (1) A murine monoclonal antibody MSN-1, which was raised against human endometrial cancer cell line and recognized blood type sugar chain Leb, reacted with about 85% of endometrial cancer tissues, indicating that useful clinical information may be obtained by applying MSN-1 to immunohistochemistry and flow cytometry. (2) A new assay system using two murine monoclonal antibodies MA54 and MA61, which were raised against human lung cancer cell line and reacted with mucin sugar residues, revealed 76% positive rate in ovarian cancer patients, especially 82% in mucinous cystadenocarcinoma, indicating the clinical effectiveness as a new tumor maker compensating for the drawbacks of CA-125. (3) Galactosyl-transferase isozyme GT-2 was analyzed by the assay system using a newly produced monoclonal antibody. GT-2 was positive in 74% of ovarian cancers, especially in 89% of meso-nephroid cancer, indicating that GT-2 could be a useful tumor maker in ovarian tumors. (4) Human monoclonal antibody, which recognized "type 1 sugar chain" or iso-paragloboside, reacted about one half of endometrial cancer tissues. The production of human monoclonal antibody may contribute to the cancer imaging and the missile therapy.

Gangliosides stimulate dome formation in cultured canine kidney epithelial cell line (MDCK)

The effect of exogenous gangliosides on the occurrence of domes in MDCK cell cultures was investigated in view of the involvement of both dome formation and gangliosides in cell growth, differentiation and transepithelial transport. Dome formation was increased by gangliosides in medium free of fetal calf serum. Among the gangliosides tested, GM3 and GD3 isolated from porcine kidney were most active, increasing the dome number 12-17-fold. Since gangliosides from kidney were more active than those from brain and erythrocytes, the hydrophobic moiety as well as sialic acid might be involved in this activity. These results indicate that tissue-specific molecules of gangliosides function as inducers or mediators of dome formation. The mechanism probably involves adenylate-cyclase or another transmembrane biosignal-transducing system.

Diplococcal beta-galactosidase with a specificity reacting to beta 1-4 linkage but not to beta 1-3 linkage as a useful exoglycosidase for the structural elucidation of glycolipids

Diplococcal beta-galactosidase, which is known to be useful for the structural studies of glycoprotein-linked oligosaccharides, was found to show the same substrate specificity in cleaving Gal beta 1-4 linkages of glycolipids as that of the oligosaccharides. The optimum conditions of beta-galactosidase in the 80% ammonium sulfate precipitates of the culture medium of Streptococcus (Diplococcus) pneumoniae were determined with nLcOse4Cer radiolabeled by the galactose oxidase-NaB3H4 procedure. Detergent was required for the highest activity, and different combinations of several buffers and detergents showed different properties in stimulating beta-galactosidase, and in enhancing or suppressing N-acetyl-beta-hexosaminidase which was contaminated in the enzyme preparation. The optimum pH was found to be at 6.5, and specific activity and Km were 8.1 nmol/mg protein/h and 1 nmol, respectively. While more than 70% of beta-galactose was liberated from LacCer and nLcOse4Cer within 1 h under the optimum conditions to form GlcCer and nLcOse3Cer, respectively, none was liberated from LcOse4Cer, GalCer, GgOse4Cer, GbOse3Cer, IV3 alpha GalnLcOse4Cer, and Il3NeuAcGgOse4Cer, showing the substrate specificity solely to Gal beta 1-4 linkage.

Thyroid antigen-antibody nephritis: possible involvement of fucosyl-GM1 as the antigen

Hyperthyroidism, microscopic hematuria, and proteinuria developed in an 11-year-old girl. Proteinuria decreased during treatment of hyperthyroidism with an antithyroid drug. On admission, serum anti-thyroglobulin antibody, antimicrosomal antibody, and immune complex were present. The thyrotropin binding inhibitory immunoglobulin (TBII) level was low. On the other hand, an antibody to the ganglioside component (fucosyl-GM1) was detected by an enzyme linked immunosolvent assay (ELISA). A thyroid biopsy specimen showed massive lymphocytic infiltration and interstitial fibrosis. A renal biopsy specimen showed marked proliferation of mesangial cells and increased mesangial matrix with focal segmental capillary wall abnormality. Electron microscopec studies demonstrated mild paramesangial dense deposits. By indirect immunofluorescence, granular glomerular basement membrane and mesangial staining were not detected with rabbit antibody to thyroglobulin, but were detected with rabbit antibody to fucosyl GM1. Fucosyl GM1 was also seen along the basilar aspect of the thyroid follicular epithelial cells. These observation suggests the development of glomerulonephritis mediated by thyroid antigen, particularly ganglioside component.

Selective expression of cholera toxin-receptor in rat medullary thymocytes

Cholera toxin binding sites in frozen sections of rat thymus were studied by indirect immunofluorescence and were found to be localized selectively in the medulla of thymic lobules. By flow cytometric analysis, two populations of thymocytes differing in size and reactivity towards cholera toxin were detected; the small thymocytes comprising 15% of the total thymocytes were found to express the receptor. The two kinds of cells isolated were not however, distinctly different in morphology. But ganglioside GM1, the cholera toxin binding site in the small thymocytes, when quantified by TLC-immunostaining, was contained at a higher concentration than in the large thymocytes. These results indicate that GM1 should be a useful marker for analysis of thymocyte differentiation, and that cholera toxin-mediated thymocyte proliferation might only occur in the small medullary thymocytes.

Analysis of ceramide and monohexaosyl glycolipid derivatives by high-performance liquid chromatography and its application to the determination of the molecular species in tissues

Several molecular species of monohexaosyl glycolipids and ceramides were analyzed as their benzoyl derivatives by high-performance liquid chromatography on a silica column with mixtures of dioxane and hexane as eluents. Monohexaosyl glycolipid derivatives were classified according to their hydrophobic structures, and ceramides were separated based on the fatty acid groups and the long-chain bases. The method allowed us to observe the heterogeneities in the molecular species of cerebrosides and ceramides from the epidermis and dermis of the guinea pig, and clear differences in the molecular species were observed between the different regions.

Analysis of long-chain bases in sphingolipids by positive ion fast atom bombardment or matrix-assisted secondary ion mass spectrometry

The structures of long-chain bases are expressed as [CH2C(NH2) = CHR]+ (Z+) in the positive ion mode spectra obtained on fast atom bombardment (FAB) mass spectrometry or liquid-matrix-assisted secondary ion mass spectrometry (SIMS) [Benninghoven, A., Ed. (1983) Ion Formation from Organic Solids, Springer, Berlin]. This phenomenon is common to sphingolipids in general: glycosphingolipids [see reviews by Sweeley and Nunez [Sweeley, C. C., & Nunez, H. A. (1985) Annu. Rev. Biochem. 54, 765] and Kanfer and Hakomori [Kanfer, J. N., & Hakomori, S. (1983) Handb. Lipid Res. 3]] and phosphonosphingolipids [Hayashi, A., & Matsubara, T. (1982) in New Vistas in Glycolipid Research (Makita, A., Handa, S., Taketomi, T., & Nagai, Y., Eds.) p 103, Plenum, New York], inclusive. Phytosphingosine compounds show the same type of fragmentation without additional dehydration if a neutral matrix is used. A Z+ ion is easily detected in the lower mass region (m/z 200-400) as an even mass number fragment ion, and confirmation is made by means of B/E constant and B2/E constant linked scan techniques [Boyd, R. K., & Beynon, J. H. (1977) Org. Mass Spectrom. 12, 163; Boyd, R. K., & Shushan, B. (1981) Int. J. Mass Spectrom. Ion Phys. 37, 355; Macdonald, C. G., & Lacey, M. J. (1984) Org. Mass Spectrom. 19, 55]. [Principles of linked scannings are explicitly summarized by Jennings and Mason [Jennings, K. R., & Mason, R. S. (1983) in Tandem Mass Spectrometry (McLafferty, F. W., Ed.) p 197, Wiley, New York] besides the cited literature.]

Wide distribution of rat hepatoma asialo GM1 and its different responses to anti-asialo GM1 antibody-mediated in vitro and in situ cell killing

By means of TLC immunostaining with anti-asialo GM1 antiserum and conventional structural analyses including exoglycosidase treatment, permethylation and negative ion FABMS, asialo GM1 was found to be widely distributed in rat ascites hepatomas, AH130, AH109A, AH44, AH272, AH41C, AH60C, AH414, AH7974, AH66, AH66 alpha F, AH66F and AH13, and Yoshida sarcoma cells. However, reactivity of asialo GM1, when measured by flow cytometry and complement-mediated cytotoxicity assay with anti-asialo GM1 antiserum, was only observed on AH13 and AH66F, and did not necessarily correspond to the concentration of asialo GM1 on the cells, indicating a cryptic or unreactive nature of glycosphingolipids with respect to their antibodies. On the other hand, although rats injected with 10(7) cells of AH66F died within 7 days, treatment of the rats with anti-asialo GM1 antiserum was found to be effective for their cure or for prolonging their survival, indicating an in situ cytotoxic effect of antiserum. For the in situ cytotoxicity, the timing and period of injection and the dose of antiserum were found to be important.

Biological effect of anti-fucosyl GM1 ganglioside antibody on cyclic adenosine 3',5'-monophosphate production in FRTL5 rat thyroid cells

Addition of specific anti-fucosyl GM1 antibody raised in a rabbit caused dose-dependent inhibition of endogenous and thyrotropin (TSH)- or thyroid stimulating antibody-stimulated cyclic adenosine 3',5'-monophosphate (cAMP) production in cultured FRTL5 rat thyroid cells. Further, the antibody inhibited the cAMP increase induced by prostaglandin E1 and forskolin. However, anti-fucosyl GM1 antibody did not affect the binding of [125I]bovine TSH to solubilized porcine thyroid TSH receptor or to FRTL5 cells. In conclusion, fucosyl GM1 is one of the specific membrane components of thyrocytes and appears to be involved in adenylate cyclase stimulation or cAMP generation. Further, the biological effects of the ganglioside do not seem to be mediated by the TSH receptor, suggesting a post receptor mechanism.