A fluorometric assay of ceramide glycanase with 4-methylumbelliferyl beta-D-lactoside derivatives

4-Methylumbelliferyl 6'-O-benzyl-beta-D-lactoside (6'Bn-MU-Lac) and some related compounds were synthesized via different selective reactions including phase-transfer glycosylation. Their suitability as substrates for a fluorometric assay of ceramide glycanase (CGase) was evaluated. Among others, the 6'Bn-MU-Lac, which is resistant to exogalactosidase, was found to be a suitable substrate for routine assay of the CGase activity. For American leech CGase, the K(m) value is 0.232 mM at pH 5.

Characterization of an alternatively spliced GM2 activator protein, GM2A protein. An activator protein which stimulates the enzymatic hydrolysis of N-acetylneuraminic acid, but not N-acetylgalactosamine, from GM2

GM2 activator protein is a protein cofactor which stimulates the enzymatic hydrolysis of both GalNAc and NeuAc from GM2. We have previously isolated two cDNA clones, GM2 activator cDNA and GM2A cDNA, for human GM2 activator protein (Nagarajan, S., Chen, H.-C., Li, S.-C., Li, Y.-T., and Lockyer, J. M. (1992) Biochem. J. 282, 807-813). GM2A mRNA is an RNA alternative splicing product that contains exons 1, 2, 3, and intron 3 of the genomic DNA sequence of GM2 activator protein (Klima, H., Tanaka, A., Schnabel, D., Nakano, T., Schröder, M., Suzuki, K., and Sandhoff, K. (1991) FEBS Lett. 289, 260-264). GM2A cDNA encodes a protein (GM2A protein) containing 1-109 of the 160 amino acids of human GM2 activator protein, plus a tripeptide (VST) encoded by intron 3 at the COOH terminus. Thus, GM2A protein can be regarded as a form (truncated version) of GM2 activator protein. We have expressed GM2A cDNA in Escherichia coli using pT7-7 as the vector. The recombinant GM2A protein was purified to an electrophoretically homogeneous form and was found to stimulate the hydrolysis of NeuAc from GM2 by clostridial sialidase, but not the hydrolysis of GalNAc from GM2 by beta-hexosaminidase A. Like GM2 activator protein, GM2A protein also specifically recognized the terminal GM2 epitope in GalNAc-GD1a and stimulated the hydrolysis of only the external NeuAc from this ganglioside by clostridial sialidase. These results enabled us to discern the enzymatic hydrolyses of GalNAc and NeuAc from the GM2 epitope and established that the NeuAc recognition domain of GM2 activator protein is located within amino acids 1-109. The presence of GM2A mRNA in human tissues and the selective stimulation of NeuAc hydrolysis by GM2A protein indicate that this activator protein may be involved in the catabolism of GM2 through the asialo-GM2 pathway.

Two different sialidases, KDN-sialidase and regular sialidase in the starfish Asterina pectinifera

We have found the coexistence of two different sialidases in the entrails of the starfish Asterina pectinifera: a regular sialidase (RS), which cleaves sialic acid from sialoglycoconjugates, and a KDN-sialidase (KS) which releases the sialic acid analogue KDN (2-keto-3-deoxy-D-glycero-d-galacto-nononic acid) from KDN-containing glycoconjugates that are resistant to RS. The 6700-fold purified KS and 1300-fold purified RS were prepared to study the properties of these two sialidases. KS and RS from Asterina starfish differ in several properties other than glycon specificity, including molecular mass, isoelectric point (pI) and susceptibility to competitive and non-competitive inhibitors. KS has a molecular mass of 31 kDa and a pI of 8.3 while RS has a molecular mass of 128 kDa and a pI of about 4.8. 2,3-dehydro-2-deoxy-N-acetylneuraminic acid (NeuAc2en), but not 2,3-dehydro-2-deoxy-KDN (KDN2en), is a potent competitive inhibitor of RS (Ki approximately 0.007 mM); however, both NeuAc2en and KDN2en are moderate inhibitors of KS (K1 approximately 0.04 mM). Hg2+ is a potent non-competitive inhibitor of RS but not of KS. KS and RS were examined for their ability to hydrolyse KDN- and NeuAc-containing glycoconjugates. KS hydrolyses 4-methyl-umbelliferyl-alpha-KDN (MU-KDN) 20 times faster than 4-methylumbelliferyl-alpha-NeuAc (MU-NeuAc), while RS hydrolyses MU-NeuAc 88 times faster than MU-KDN at the pH optimum of 4.0 KS effectively hydrolyses KDN-GM3 (where GM3 is NeuAc alpha 2 --> 3Gal beta 1 --> 4Glc beta 1-1' Cer, and Cer is ceramide), KDN alpha 2 --> 3lactose, KDN alpha 2 --> 6lactose, KDN alpha 2 --> 6N-acetylgalactosaminitol, KDN alpha 2 --> 6 (KDN alpha 2 --> 3)N-acetylgalactosaminitol and KDN alpha 2 --> 6(GlcNAc beta 1 --> 3) N-acetylgalactosaminitol. However, under the same conditions, these KDN-containing glycoconjugates are refractory to RS. Conversely, GM3, NeuAc alpha 2 --> 3lactose and NeuAc alpha 2 --> 6lactose are effectively hydrolysed by RS but not by KS.

Isolation of three novel cholinergic neuron-specific gangliosides from bovine brain and their in vitro syntheses

In the present study, three extremely minor but novel Chol-1 antigens, termed X1, X2, and X3 have been isolated from bovine brain gangliosides. Based on the results of sialidase degradation, TLC-immunostaining with anti-Chol-1 antibody and fast atom bombardment mass spectrometry, their chemical structures were identified as: III6NeuAc-GgOse4Cer (X1: GM1 alpha) III6NeuAc,II3NeuAc-GgOse4Cer (X2: GD1a alpha) III6NeuAc,II3NeuAc-NeuGc-GgOse4Cer (X3: GT1b alpha) The yields of GM1 alpha, GD1a alpha, and GT1b alpha, were approximately 150, 20, and 10 micrograms, respectively, from 10 g of the bovine brain ganglioside mixture. In conjunction with our previous observations, all gangliosides with anti-Chol-1 reactivity were found to contain a common sialyl alpha 2-6 N-acetylgalactosamine residue, indicating that this unique sialyl linkage is the specific antigenic determinant. We subsequently examined the biosynthesis of the three novel Chol-1 gangliosides using rat liver Golgi fraction as an enzyme source. The results showed that GM1 alpha, GD1a alpha, and GT1b alpha were synthesized from asialo-GM1, GM1a, and GD1b, respectively, by the action of a GalNAc alpha 2-6sialyltransferase.

Isolation and structural characterization of N-acetyl- and N-glycolylneuraminic-acid-containing GalNAc-GD1a isomers, IV4GalNAcIV3Neu5AcII3Neu5GcGgOse4Cer and IV4GalNAcIV3Neu5GcII3Neu5AcGgOse4Cer, from bovine brain

A ganglioside preparation containing two structurally related minor gangliosides (Gg 1 + 2) was isolated from bovine brain ganglioside mixture and characterized. Treatment of 50 g ganglioside mixture with Clostridium perfrigens sialidase, followed by chromatography on DEAE-Sepharose and silica gel columns, yielded 20 mg Gg 1 + 2. By chemical analyses, 1H- and 13C-NMR spectroscopy, enzymic hydrolyses using human beta-hexosaminidase A and clostridial sialidase, and TLC overlay with the conjugated cholera toxin B subunit, the two novel gangliosides Gg 1 and Gg 2 were identified to be: Gg 1, GalNAc-GD1a(Neu5Ac/Neu5Gc), beta-GalNAc-(1-4)-[alpha-Neu5Ac-(2-3)]-beta- Gal-(1-3)-beta-GalNAc-(1-4)-[alpha-Neu5Gc-(2-3)]-beta-Gal-(1-4)-be ta- Glc-(1-1)-Cer; Gg 2, GalNAc-GD1a(Neu5Gc/Neu5Ac), beta-GalNAc-(1-4)-[alpha-Neu5Gc-(2-3)]- beta-Gal-(1-3)-beta-GalNAc-(1-4)-[alpha-Neu5Ac-(2-3)]-beta-Gal-(1- 4)-beta- Glc-(1-1)-Cer. These two gangliosides contain the identical pentasaccharide backbone except that the substitution of the two sialic acids, Neu5Ac and Neu5Gc, are in the reversed position of the external and the internal Gal residues. Our analyses showed that the content of Gg 1 and Gg 2 were approximately 0.12% and 0.08%, respectively, of the total brain ganglioside mixture.

Specific recognition of N-acetylneuraminic acid in the GM2 epitope by human GM2 activator protein

GM2 Activator is a low molecular weight protein cofactor that stimulates the enzymatic conversion of GM2 into GM3 by human beta-hexosaminidase A and also the conversion of GM2 into GA2 by clostridial sialidase (Wu, Y.-Y., Lockyer, J.M., Sugiyama, E., Pavlova, N.V., Li, Y.-T., and Li, S.-C. (1994) J. Biol. Chem. 269, 16276-16283). Among the five known activator proteins for the enzymatic hydrolysis of glycosphingolipids, only GM2 activator is effective in stimulating the hydrolysis of GM2. However, the mechanism of action of GM2 activator is still not well understood. Using a unique disialosylganglioside, GalNAc-GD1a, as the substrate, we were able to show that in the presence of GM2 activator, GalNAc-GD1a was specifically converted into GalNAc-GM1a by clostridial sialidase, while in the presence of saposin B, a nonspecific activator protein, GalNAc-GD1a was converted into both GalNAc-GM1a and GalNAc-GM1b. Individual products generated from GalNAc-GD1a by clostridial sialidase were identified by thin layer chromatography, negative secondary ion mass spectrometry, and immunostaining with a monoclonal IgM that recognizes the GM2 epitope. Our results clearly show that GM2 activator recognizes the GM2 epitope in GalNAc-GD1a. Thus, GM2 activator may interact with the trisaccharide structure of the GM2 epitope and render the GalNAc and NeuAc residues accessible to beta-hexosaminidase A and sialidase, respectively.

Enzymatic sialylation of N-linked oligosaccharides using an alpha-(2,3)-specific trans-sialidase from Trypanosoma cruzi: structural identification using a three-dimensional elution mapping technique

alpha-(2,3)-Sialylated biantennary and triantennary oligosaccharides were enzymatically prepared from pyridyl-2-amino-oligosaccharides with terminal Gal residues, using an alpha-(2,3)-specific trans-sialidase from Trypanosoma cruzi (Lee, K. B., and Lee, Y. C. (1994) Anal. Biochem. 216, 358-364). From the pyridyl-2-amino-derivatives of neutral and alpha-(2,6)-monosialylated biantennary oligosaccharides from human fibrinogen, 5 different sialyl biantennary oligosaccharides were obtained. From two different asialo-triantennary oligosaccharides from fetuin, 35 sialyl oligosaccharides were obtained. The trans-sialidase transferred sialic acids effectively and indiscriminately to different galactosyl residues in the different positions on the substrates. Since the starting materials are neutral oligosaccharide of established structure, and the only alpha-(2,3)-sialyl residues are added to the nonreducing Gal terminal residues, the structures of these oligosaccharides could be identified unambiguously by using the three-dimensional mapping technique (Takahashi, N., Nakagawa, H., Fujikawa, K., Kawamura, Y., and Tomiya, N. (1995) Anal. Biochem. 226, 139-146.) in combinations with strategic digestion with beta-galactosidase, beta-N-hexosaminidase, and sialidase L.

The glycan keratan sulfate in inner ear crystals

The otoconial matrix (OM) of chicks (Gallus domesticus) inner ear was analyzed. Histochemically the OM was reacted with phosphotungstic acid (PTA) and immunohistochemically with the monoclonal antibody antikeratan sulfate (antiKS). The OM was digested with the enzyme endo-beta-galactosidase (E beta Galase) or separated by 1D and 2D gel electrophoresis. PTA which reacts with glycoproteins precipitated the OM, suggesting that the OM contains glycoproteins. A central core in each crystal had no PTA staining, suggesting that the core lacked glycoproteins. Anti KS antibody stained the OM with increased density in older embryos as determined by color thresholding. E beta Galase, which cleaves the lactosamine repeating units in KS, decreased the immunostain by 30% in the OM and by 20% in the cartilage. The OM from the utricle, saccule and macula lagena contained similar molecular weight bands. Five dense bands in the OM were less dense in tissue and blood controls, suggesting that such bands are enriched in the OM. Isoelectric focusing of the OM showed a negatively charged high molecular weight smear not present in blood and faint in tissue controls. The high affinity of the OM for the cationic PTA stain, the strong immunohistochemical reaction of the OM with anti KS antibody and high molecular weight negative smear in 2D gels taken together suggest that: a) the OM contains large amounts of glycoproteins and glycans, one of which is keratan sulfate, because its immuno stain with antiKS antibody was decreased by the enzyme E beta Galase, b) the utricle, saccule and macula lagena may have similar composition, and c) the concentration of KS may increase gradually until complete mineralization of the OM is reached.

Effect of protein and starch degradation rates on rumen metabolism in Taiwan native goat

Six ruminal and duodenal cannulated Taiwan native goats (body weight = 20 kg) were fed 35% roughage, 65% concentrate diet (crude protein = 9.5%) in a 6 x 6 Latin square design to study the effect of the combination of 3 varying starch (corn) and 2 varying protein (soybeans) ruminal degradation rates on ruminal microbial density and ruminal nutrient digestibilities. Goats in treatment consisting of both rapid starch and protein ruminal degradation rates had higher total bacterial and protozoal numbers than did those in other treatments (p < 0.05). The combination of rapid starch degradation rate and slow protein degradation rate supported the highest numbers of Holotrichs whereas the combination of both rapid starch and protein degradation rate supported the highest numbers of Entodiniomorphs. Ruminal starch digestibilities were higher for treatment diets with autoclaved corn than for those with raw corn whereas ruminal digestibility of protein was greater in diets with raw soybeans than in those with heated ones. Higher neutral detergent fiber digestibilities in the rumen were found with the raw corn rations and the raw soybean rations.

Detection of noncovalent FKBP-FK506 and FKBP-Rapamycin complexes by capillary electrophoresis-mass spectrometry and capillary electrophoresis-tandem mass spectrometry

The well known biospecific noncovalent receptor-ligand association complexes between the immunophilin FKBP and the immunosuppressive drugs FK506 and Rapamycin (RM) were investigated by on-line capillary electrophoresis-mass spectrometry (CE-MS) under selected ion monitoring (SIM) conditions and by CE-MS with tandem mass spectrometry (CE-MS/MS) under selected reaction monitoring (SRM) conditions. Solutions of hFKBP (33.3 µM) were dissolved in 50 mM ammonium acetate at pH 7.5. Samples that contained 100 µM of FK506 or RM also were prepared under the same solution conditions. By using these aqueous pH neutral conditions, samples were analyzed by SIM CE-MS and SRM CE-MS and the target complexes were separated by CE with mass spectrometer detection of the individual complexes between FKBP and FK506 [hFKBP + FK506 + 7HJ(7+) as well as FKBP and RM [hFKBP + RM + 7HJ(7+). In an experiment where a mixture of FK506 and RM was analyzed in the presence of FKBP, a nine-to-one ratio of ion current abundances between the RM and FK506 complexes was observed as reported in the literature from other studies. These results suggest that CE-MS and CE-MS/MS may be yet another analytical method for studying noncovalent interactions of biologically important macromolecules under physiological conditions.

Characterization of a deaminated neuraminic acid-containing glycoprotein from the skin mucus of the loach, Misgurnus anguillicaudatus

Using NMR spectroscopy and mass spectrometry, the major sialic acid of the skin mucus of the loach, Misgurnus anguillicaudatus was found to be 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN). We have subsequently devised a method to isolate a KDN-containing glycoprotein preparation from loach skin mucus. The method involves the sonication of the skin mucus with 0.05 M Tris-HCl, pH 8.0, to solubilize the glycoprotein, followed by DE52-cellulose chromatography of the extract, Nuclease P1 treatment, and Sepharose CL-4B gel filtration. The purified glycoprotein preparation was found to contain 38.5% KDN, 0.4% NeuAc, 24.6% GalNAc, 3.3% Gal, and 28.2% amino acids (w/w). The amino acid composition of this glycoprotein preparation revealed that it is unusually rich in Thr, and 6 amino acids, Thr, Ser, Glu (or Gln), Pro, Gly and Ala, account for 83% of the total amino acids. This glycoprotein is extremely poor in Cys, Met, Tyr, Phe, Arg, and Trp. Treatment of this glycoprotein with alkali resulted in the destruction of 83% of Thr suggesting that most of the sugar chains in this glycoprotein are linked through Thr. Alkaline borohydride treatment of 100 mg of the glycoprotein preparation, followed by Sephadex G-25 (superfine) gel filtration, yielded two major oligosaccharide alditols, I (15.4 mg) and II (15.6 mg). Using liquid secondary ion mass spectrometry and methylation analysis, I was identified to be KDN alpha 2-->6GalNAc-ol and II, KDN alpha 2-->6(KDN alpha 2-->3)-GalNAc-o1. KDN alpha 2-->6GalNAc is structurally similar to NeuAc alpha 2-->GalNAc found in ovine submaxillary glycoprotein while II represents a novel structure which contains two sialic acids linked to a GalNAc through both alpha 2-->3 and alpha 2-->6 linkages. This structure has never been found in mucin type glycoproteins including mammalian epithelial mucin glycoproteins. This is the first report of the presence of a mucin type glycoprotein which contains KDN instead of NeuAc or NeuGc in fish skin mucus.

Nicotinic cholinergic system involvement in eyeblink classical conditioning in rabbits

A nicotinic cholinergic antagonist, mecamylamine (MEC), was administered to rabbits tested on eyeblink classical conditioning (EBCC) in the 750-ms delay paradigm for 10 90-trial sessions. Nicotinic receptors were measured in 3 brain regions in 5 treatment groups: paired conditioned stimulus-unconditioned stimulus (CS-US) presentations with (a) vehicle, young; (b) vehicle, older; (c) 0.5 mg/kg MEC, young; unpaired CS-US with (d) 0.5 mg/kg MEC, young; and (e) vehicle, young. Daily MEC injections disrupted acquisition in young rabbits (769 trials to learning criterion vs. 323 trials for vehicle-treated young rabbits). MEC-treated young rabbits learned similarly to older rabbits. Brain nicotinic receptors were not affected by 10 daily MEC injections. To our knowledge, this experimental protocol, using a low MEC dose to selectively inhibit nicotinic cholinergic receptors, is the first to demonstrate a role for nicotinic cholinergic receptors in EBCC.

Biosynthetic pathway for a new series of gangliosides, GT1a alpha and GQ1b alpha

A new class of gangliosides, GT1a alpha and GQ1b alpha, were initially identified as cholinergic neuron-specific antigens in bovine brain. These gangliosides have in common alpha 2-6 NeuAc linked to the GalNAc residue in the gangliotetraose core structure. In this study, we have determined the biosynthetic pathways of GT1a alpha and GQ1b alpha using rat liver Golgi fraction. The results showed that GT1a alpha and GQ1b alpha were synthesized from GD1a and GT1b, respectively, by the action of a GalNAc alpha 2-6 sialyltransferase. It was also demonstrated that these two gangliosides were found to exist as extremely minor components in rat liver.

Purification and characterization of sialidase L, a NeuAc alpha 2-->3Gal-specific sialidase

Sialidase L releases 2,7-anhydro-NeuAc from sialoglycoconjugates (Li, Y.-T., Nakagawa, H., Ross, S. A., Hansson, G., and Li, S.-C. (1990) J. Biol. Chem. 265, 21629-21633). This enzyme has been purified more than 10,000-fold from Macrobdella leech. The final preparation gives a single protein band on SDS-polyacrylamide gel electrophoresis with the molecular mass of 84 kDa. The pI is determined to be 6.0 using isoelectric focusing. With 4-methylumbelliferyl-alpha-NeuAc as substrate, the pH optimum is between pH 5.5-7.0. Unlike regular sialidases, sialidase L is not inhibited by 2-deoxy-2,3-dehydro-NeuAc. Two of the seven tryptic peptides derived from sialidase L contain the consensus repeat S-X-D-X-G-X-T-W that has been found in the regular sialidases. Among various sialoglycoconjugates tested, sialidase L cleaves only the NeuAc alpha 2-->3Gal linkage. NeuAc alpha 2-->6Gal, NeuAc alpha 2-->6GalNAc, NeuAc alpha 2-->6GlcNAc, NeuAc alpha 2-->8-NeuAc, and NeuAc alpha 2-->9NeuAc linkages are not hydrolyzed. At pH 7.0, sialidase L and Clostridial sialidase release 46 and 92% of sialic acid, respectively, from bovine fetuin, indicating that sialidase L selectively cleaves NeuAc alpha 2-->3Gal linkages in fetuin. Sialidase L is the first sialidase found to exhibit a strict specificity toward the hydrolysis of the NeuAc alpha 2-->3Gal linkage, and it should become useful for the selective cleavage of NeuAc alpha 2-->3Gal linkages in sialoglycoconjugates without destroying other sialosyl linkages.

Expression and specificity of human GM2 activator protein

The cDNA encoding GM2 activator was expressed in the Escherichia coli/pT7-7 system. The yield of the GM2 activator with greater than 99% purity was about 3 mg per liter culture. The recombinant GM2 activator was found to be as active as that isolated from human kidney. The availability of the recombinant GM2 activator enabled us to critically examine the specificity of this activator protein. Our results show that the specificity of GM2 activator is not as strict as that reported previously. Although GM2 activator stimulates most efficiently the degradation of GM2 carried out by beta-N-acetylhexosaminidase A (Hex A), this activator also stimulates the following reactions: (a) conversion of GM2 to GA2 by clostridial sialidase; (b) hydrolysis of GalNAc from dipalmitoylphosphatidylethanolamine-II3NeuAcGgOse3 by Hex A; and (c) liberation of Gal from GM1 by beta-galactosidase at a high activator concentration. Thus, this activator does not differentiate between GM2 and dipalmitoylphosphatidylethanolamine-II3NeuAcGgOse3 or between Hex A and clostridial sialidase. The micellar forms of GD2 and GalNAc-GD1a were found to be more readily hydrolyzed by Hex A than GM2 in the absence of GM2 activator. Our results also show that saposin B can enhance the stimulatory activity of GM2 activator, but it cannot promote the stimulatory activity of sodium taurodeoxycholate. Taken together, our results suggest that the mechanism of action of GM2 activator is different from saposin B, and the action of GM2 activator is more than to solubilize lipid substrates. The effectiveness of GM2 activator in stimulating the hydrolysis of GM2 may be due to its ability to recognize the specific trisaccharide structure of the GM2 epitope, GalNAc beta 1-->4(NeuAc alpha 2-->3)Gal-, and to modify the GalNAc-NeuAc interaction in this structure.

Nicotinic cholinergic system involvement in eyeblink classical conditioning in rabbits

A nicotinic cholinergic antagonist, mecamylamine (MEC), was administered to rabbits tested on eyeblink classical conditioning (EBCC) in the 750-ms delay paradigm for 10 90-trial sessions. Nicotinic receptors were measured in 3 brain regions in 5 treatment groups: paired conditioned stimulus-unconditioned stimulus (CS-US) presentations with (a) vehicle, young; (b) vehicle, older; (c) 0.5 mg/kg MEC, young; unpaired CS-US with (d) 0.5 mg/kg MEC, young; and (e) vehicle, young. Daily MEC injections disrupted acquisition in young rabbits (769 trials to learning criterion vs. 323 trials for vehicle-treated young rabbits). MEC-treated young rabbits learned similarly to older rabbits. Brain nicotinic receptors were not affected by 10 daily MEC injections. To our knowledge, this experimental protocol, using a low MEC dose to selectively inhibit nicotinic cholinergic receptors, is the first to demonstrate a role for nicotinic cholinergic receptors in EBCC.

A nicotinic agonist (GTS-21), eyeblink classical conditioning, and nicotinic receptor binding in rabbit brain

The septo-hippocampal cholinergic system is of demonstrated involvement in eyeblink classical conditioning (EBCC). To determine if a nicotinic cholinergic agonist, GTS-21, would facilitate acquisition of EBCC in older rabbits, three doses (0.1, 0.5, 1.0 mg/kg) in sterile saline vehicle and vehicle alone were administered to older rabbits (n = 48; mean age = 29.8 months). A control group of vehicle-treated young rabbits (n = 12; mean age = 3.5 months) was included. Rabbits were conditioned for fifteen 90-trial sessions in the 750 ms delay paradigm with a tone conditioned stimulus and corneal airpuff unconditioned stimulus. Dependent measures of trials to learning criterion, percentage of conditioned responses (CRs) and CR amplitude consistently showed significant improvement in older rabbits treated with 0.5 and 1.0 mg/kg of GTS-21. Acquisition was similar in vehicle-treated young and GTS-treated older rabbits. Vehicle-treated older rabbits conditioned more poorly than vehicle-treated young rabbits. No non-associative learning effects were observed in GTS-21 treated animals. Nicotinic receptor binding was similar in all groups of older rabbits, indicating that GTS-21 administration over a 15-day period did not affect nicotinic receptors. Alzheimer's disease (AD) has been associated with significant loss of nicotinic cholinergic receptors, and patients diagnosed with probable AD are seriously impaired on EBCC. These results demonstrating that the nicotinic agonist, GTS-21, facilitated EBCC in older rabbits suggest that the compound should receive additional investigation for its potential to affect cognition in AD.

Studies of non-covalent interactions of actinomycin D with single-stranded oligodeoxynucleotides by ion spray mass spectrometry and tandem mass spectrometry

Non-covalent binding of actinomycin D (AMD) to single-stranded DNA (ssDNA) was observed by ion spray mass spectrometry. Interactions between AMD and different sequences of non-self-complementary oligodeoxynucleotides were investigated as a function of pH. Non-covalent AMD/ssDNA complexes disappeared at low pH, and no ssDNA complexes were detected with rifampicin (RP). Moreover, the different binding affinities between AMD and ssDNA with and without 5'G-C3' or 5'C-G3' base sequences were also demonstrated using ion spray mass spectrometry. Additional support for the non-covalent nature of binding in AMD/ssDNA complexes was obtained from tandem mass spectrometry.

A novel sialidase capable of cleaving 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN)

We have examined the tissues of several species of fish and found that the liver of the loach (Misgurnus fossilis) contains a novel sialidase capable of efficiently hydrolyzing 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN) from the 4-methylumbelliferyl alpha-ketoside of KDN, KDN alpha 2-->3Gal beta 1-->4GlcCer and KDN alpha 2-->6 N-acetylgalactosaminitol as well as Neu5Ac from the 4-methylumbelliferyl alpha-ketoside of Neu5Ac and GM3. The pH optimum for this enzyme was determined to be 4.6, and the Km using the 4-methylumbelliferyl alpha-ketoside of KDN and 4-methylumbelliferyl alpha-ketoside of Neu5Ac as substrates were 0.07 and 0.12 mM, respectively. The enzyme was stable in the pH range of 4 to 5 but very unstable above pH 6. This is the first report of a sialidase capable of efficiently cleaving glycosidically linked KDN.

[Clinical study on the use of multiglycosides of Tripterygium wilfordii after cadaveric kidney transplantation]

Based on the animal experiments, we first used the multiglycosides of Tripterygium wilfordii (GTW) as a main immunosuppressive agent to treat the patients with cadaveric kidney transplantation instead of Azathioprine (Aza) from 1990. By clinical observation and 3-year follow-up, the result showed the GTW having a satisfactory immunosuppressive effect. In this study, there were 85 cases in control group (Aza+CSA+Pred) and 87 cases in therapeutic group (GTW+CSA+Pred). The normalizing times of graft function after transplantation taked 18.17 +/- 1.61 days in control group and 10.9 +/- 0.18 days in therapeutic group respectively. The 1-, and 2-year graft survival rates were 89.3 +/- 0.3% and 87.0 +/- 0.3% in control group, 96.1 +/- 0.2% and 90.4 +/- 0.6% in therapeutic group respectively. The difference of the normalization times of graft function and graft survival rates between the two groups had statistically significant (P < 0.01). The incidence of complication such as infection, liver function damaging, etc, in therapeutic group was lower than in control group.

Nefiracetam (DM-9384): effect on eyeblink classical conditioning in older rabbits

The nootropic compound nefiracetam was evaluated in 88 older rabbits in a 750-ms delay paradigm of eyeblink classical conditioning (EBCC). Rabbits (mean age = 28.7 months) were assigned in groups of eight to one of six conditions in experiment 1: paired tone conditioned stimulus (CS)-corneal airpuff unconditioned stimulus (US) presentations and 1, 3, or 10 mg nefiracetam/kg or sterile saline vehicle; explicitly unpaired CS and US presentations and 3 mg nefiracetam/kg or sterile saline vehicle. Animals in the paired conditions received 10 daily sessions of 90 paired trials and animals in the unpaired conditions received 10 daily sessions of 180 unpaired CS and US presentations. The six conditions in experiment 2 were 5, 10, and 15 mg nefiracetam/kg and vehicle in 15 sessions of paired presentations; 10 mg nefiracetam/kg and vehicle in 15 sessions of unpaired conditioning. In both experiments 1 and 2, acquisition measured by trials to learning criterion was significantly faster at the 10 mg/kg dose of nefiracetam. In the repeated measures analyses comparing six doses in the paired conditions, all dependent measures [percentage conditioned responses (CRs), CR amplitude, and response latency] indicated significantly better conditioning in rabbits treated with 10 mg nefiracetam/kg, but this dose did not increase motor responding or responding in the unpaired condition. Nefiracetam facilitated acquisition of EBCC in older rabbits. EBCC is performed poorly by older humans and is seriously impaired in Alzheimer's disease. These preclinical data in an animal model with clear parallels in humans suggest that nefiracetam may prove effective as a cognition enhancer in clinical trials.

[Cephradine delivery into the eye with domestic collagen shield]

The author reports that enhancement by the native made collagen-shield on the permeation of cephradine into the eye is 1.5 times and 1.3 times versus controls when the corneal epithelium is intact or defect, and is 10 times versus frequent eyedrops instillation. On the other hand, the enhancement of the collagen-shield is about the same as that of the soft contact lens impregnated with cephradine solution, but the drug concentration in aqueous humor is increased by collagen-shield 1-2 times than that by the wet soft contact lens. These results indicate that the collagen-shield can effectively increase the drug concentration in aqueous humor.