Maternal oxycodone treatment causes pathophysiological changes in the mouse placenta

INTRODUCTION

Pregnant women are increasingly being prescribed and abusing opioid drugs. As the primary communication organ between mother and conceptus, the placenta may be vulnerable to opioid effects but also holds the key to better understanding how these drugs affect long-term offspring health. We hypothesized that maternal treatment with oxycodone (OXY), the primary opioid at the center of the current crisis, deleteriously affects placental structure and gene expression patterns.

METHODS

Female mice were treated daily with 5 mg OXY/kg or saline solution (Control, CTL) for two weeks prior to breeding and until placenta were collected at embryonic age 12.5. A portion of the placenta was fixed for histology, and the remainder was frozen for RNA isolation followed by RNAseq.

RESULTS

Maternal OXY treatment reduced parietal trophoblast giant cell (pTGC) area and decreased the maternal blood vessel area within the labyrinth region. OXY exposure affected placental gene expression profiles in a sex dependent manner with female placenta showing up-regulation of many placental enriched genes, including Ceacam11, Ceacam14, Ceacam12, Ceacam13, Prl7b1, Prl2b1, Ctsq, and Tpbpa. In contrast, placenta of OXY exposed males had alteration of many ribosomal proteins. Weighted correlation network analysis revealed that in OXY female vs. CTL female comparison, select modules correlated with OXY-induced placental histological changes. Such associations were lacking in the male OXY vs. CTL male comparison.

DISCUSSION

Results suggest OXY exposure alters placental histology. In response to OXY exposure, female placenta responds by upregulating placental enriched transcripts that are either unchanged or downregulated in male placenta. Such changes may shield female offspring from developmental origins of health and disease-based diseases.

Naramycin B, an Antibiotic from Streptomyces griseus Strain 587 with Herbicidal Properties-Fermentation, Isolation, and Identification

From the culture filtrate of Streptomyces griseus strain 587 a herbicidal active fraction was isolated by adsorption on Lewapol® , methanolic desorption, and chromatography on Sephadex® LH-20. Further purification was achieved by HPLC. The pure product was characterized by TLC and different colour reactions. By MS, 1H-NM R, IR and ORD spectroscopy the herbicidal compound could be identified as naramycin B. Naramycin B is an optical isomer of cycloheximide (naramycin A, Actidione®, Acti-Aid®). This communication reports on the fermentative production of naramycin B with strain 587, its isolation, identification, and herbicidal activity.

Glycal Glycosylation and 2-Nitroglycal Concatenation, a Powerful Combination for Mucin Core Structure Synthesis

A 3,4-O-unprotected galactal derivative having bulky 6-O-TIPS protection (compound 2) could be regioselectively 3-O-glycosylated with O-(galactopyranosyl) trichloroacetimidates; depending on the protecting group pattern stereoselectively alpha- and beta-linked disaccharides were obtained. With O-(2-azido-2-deoxyglucopyransyl) trichloroacetimidate as donor (compound 10A), glycosylation of 2 and of a 6-O-unprotected galactal derivative led in acetonitrile as solvent exclusively to a beta(1-3)- and a beta(1-6)-linked disaccharide, respectively. Nitration of the galactal moieties of the saccharides followed by Michael-type addition of serine and threonine derivatives (7a,b) installed the alpha-galacto-configuration, thus readily furnishing O-glycosyl amino acid building blocks for the incorporation of core 1, core 2, core 3, core 6, and core 8 structures into glycopeptides. 2-Nitrogalactal and 2-nitroglucal derivatives could be also successfully employed in glycoside bond formation via Michael-type addition in a reiterative manner, affording the corresponding core 5, core 7, and core 6 building blocks. In this approach, highly stereoselective glycoside bond formations were based exclusively on Michael-type addition to the nitro-enol ether moiety of the 2-nitroglycals. Hence, 2-nitroglycals are versatile intermediates for base-catalyzed glycoside bond formation.

A Staphylococcus aureus lipoteichoic acid (LTA) derived structural variant with two diacylglycerol residues

Based on 1,2-O-isopropylidene-sn-glycerol five chiral building blocks containing differently modified glycerol residues were required for the synthesis of the target molecule 2. One of these building blocks is diacylglyceryl beta-gentiobioside carrying a phosphite residue at 6b-O position. Ligation of these five building blocks led to the desired glycerol phosphate backbone to which d-alanyl residues were attached, thus generating after O-deprotection the target molecule 2, a bisamphiphilic structural variant of Staphylococcus aureus LTA. This compound displayed higher potency in terms of cytokine release by human blood leukocytes than the monoamphiphilic variant LTA.

A polymorphic motif in the small subunit of ADP-glucose pyrophosphorylase modulates interactions between the small and large subunits

The heterotetrameric, allosterically regulated enzyme, adenosine-5'-diphosphoglucose pyrophosphorylase (AGPase) catalyzes the rate-limiting step in starch synthesis. Despite vast differences in allosteric properties and a long evolutionary separation, heterotetramers of potato small subunit and maize large subunit have activity comparable to either parent in an Escherichia coli expression system. In contrast, co-expression of maize small subunit with the potato large subunit produces little activity as judged by in vivo activity stain. To pinpoint the region responsible for differential activity, we expressed chimeric maize/potato small subunits in E. coli. This identified a 55-amino acid motif of the potato small subunit that is critical for glycogen production when expressed with the potato large subunit. Potato and maize small subunit sequences differ at five amino acids in this motif. Replacement experiments revealed that at least four amino acids of maize origin were required to reduce staining. An AGPase composed of a chimeric potato small subunit containing the 55-amino acid maize motif with the potato large subunit exhibited substantially less affinity for the substrates, glucose-1-phosphate and ATP and an increased Ka for the activator, 3-phosphoglyceric acid. Placement of the potato motif into the maize small subunit restored glycogen synthesis with the potato large subunit. Hence, a small polymorphic motif within the small subunit influences both catalytic and allosteric properties by modulating subunit interactions.

Both subunits of ADP-glucose pyrophosphorylase are regulatory

The allosteric enzyme ADP-Glc pyrophosphorylase (AGPase) catalyzes the synthesis of ADP-Glc, a rate-limiting step in starch synthesis. Plant AGPases are heterotetramers, most of which are activated by 3-phosphoglyceric acid (3-PGA) and inhibited by phosphate. The objectives of these studies were to test a hypothesis concerning the relative roles of the two subunits and to identify regions in the subunits important in allosteric regulation. We exploited an Escherichia coli expression system and mosaic AGPases composed of potato (Solanum tuberosum) tuber and maize (Zea mays) endosperm subunit fragments to pursue this objective. Whereas potato and maize subunits have long been separated by speciation and evolution, they are sufficiently similar to form active mosaic enzymes. Potato tuber and maize endosperm AGPases exhibit radically different allosteric properties. Hence, comparing the kinetic properties of the mosaics to those of the maize endosperm and potato tuber AGPases has enabled us to identify regions important in regulation. The data herein conclusively show that both subunits are involved in the allosteric regulation of AGPase. Alterations in the small subunit condition drastically different allosteric properties. In addition, extent of 3-PGA activation and extent of 3-PGA affinity were found to be separate entities, mapping to different regions in both subunits.

Heterologous expression of cDNAs encoding Chlorella sorokiniana NADP-specific glutamate dehydrogenase wild-type and mutant subunits in Escherichia coli cells and comparison of kinetic and thermal stability properties of their homohexamers

Full-length cDNAs encoding the alpha- and beta-subunits and a truncated mutant subunit of the Chlorella sorokiniana NADP-GDH isozymes were constructed and expressed in Escherichia coli cells. The kinetic and thermal stability properties of the resultant homohexamers were examined. The electrophoretic mobility of the recombinant alpha- and beta-subunits was identical to that of the native subunits as determined by immunoblotting. The homohexamers were purified by anion-exchange and gel-filtration chromatography. The alpha- and beta-homohexamers that were synthesized in the bacterial cells were shown to have similar Michaelis constants for their substrates as previously shown after synthesis in C. sorokiniana cells (Bascomb and Schmidt, 1987). The alpha homohexamer synthesized in the bacterium was allosteric with respect to NADPH but to a lesser degree than when isolated from the alga. The mutant homohexamer was composed of subunits that were truncated by 40 amino acids at their N-termini. This mutant isozyme was kinetically similar to the larger, anabolic alpha-homohexamer, but it did not display the allosteric response to NADPH shown by the alpha-homohexamer. The three isozymes had significant thermal tolerance and were stable at 50 degrees C. The temperature optimum for catalytic activity for the alpha- and beta-homohexamers was 60 degrees C, and 65 degrees C for the delta40N homohexamer. This study demonstrated that most of the kinetic properties of the Chlorella sorokiniana NADP-GDH isozymes were retained after their synthesis in a heterologous system, and that the distinctive N-terminal domains of these isozymes have dramatic effects on their biochemical characteristics.

Solid-phase synthesis of a branched hexasaccharide using a highly efficient synthetic strategy

The solid-phase synthesis of branched lacto-N-neohexaose derivative 1 occurring in human milk is described. The new building block of lactose 3 bearing the orthogonal temporary hydroxy protecting groups 9-fluorenylmethyloxycarbonyl (Fmoc) and levulinoyl (Lev) has been prepared. Its use, together with that of lactosamine donor 4, glucosamine donor 5, and O-galactosyl trichloroacetimidate 6, has enabled the preparation of hexasaccharide 22 following two different approaches in excellent overall yield (43%, 90% per step over eight steps). An additional key feature of this work is the successful use of newly prepared ester-type linker 2, having a benzylic spacer connected to the anomeric oxygen. This linker presents the advantage of producing a benzylic anomeric moiety after cleavage from the polymer support, which could be easily removed to obtain the unprotected oligosaccharide 1.

Synthesis of the fully phosphorylated GPI anchor pseudohexasaccharide of Toxoplasma gondii

Retrosynthesis of the fully phosphorylated glycosylphosphatidyl inositol (GPI) anchor pseudohexasaccharide 1a led to building blocks 2-6, of which 5 and 6 are known. The formation of pseudodisaccharide building block 2 is based on readily available building block 7, which gave, via derivative 11 and its glycosylation with known donor 12, the desired compound 2. Building block 3, with the required access to all hydroxy groups being permitted, was prepared from mannose in five steps. From a readily available precursor, building block 4 was obtained, which on reaction with 3 gave disaccharide 23. The synthesis of the decisive pseudohexasaccharide intermediate 32 was based on the reaction of 23 with 5, then with 6, and finally with 2. To obtain high stereoselectivity and good yields in the glycosylation reactions, anchimeric assistance was employed. To enable regioselective attachment of the two different phosphorus esters, the 6f-O-silyl group of 32 was first removed and the aminoethyl phosphate residue was attached. Then the MPM group was oxidatively removed, and the second phosphate residue was introduced. Unprotected 1a was then liberated in two steps: treatment with sodium methanolate removed the acetyl protecting groups, and finally, catalytic hydrogenation afforded the desired target molecule, which could be fully structurally assigned.

De novo synthesis of a methylene-bridged Neu5Ac-alpha-(2,3)-gal C-disaccharide

A general strategy toward the synthesis of C-ketosides of N-acetylneuraminic acid (Neu5Ac) has been developed and successfully applied to the synthesis of methylene-bridged Neu5Ac-alpha-(2,3)-Gal C-disaccharide 2. The key strategic element of this novel approach is a stereoselective, 6-exo-trig selective, electrophilic cyclization of the appropriate open chain precursor 4 by means of phenylselenyl triflate. The open chain precursor was formed by the addition of lithiated iodide 18 accessible from D-galactose to open chain aldehyde 5a obtained from D-glucono-delta-lactone by chain elongation. Subsequent C1-incorporation using Tebbe-reagent, formation of a cyclic carbonate, and deprotection of the two isopropylidene ketals afforded tetrol 4 which, upon treatment with phenylselenyl triflate, was stereoselectively cyclized in a 6-exo-trig selective manner. A selena-Pummerer rearrangement, oxidation, and esterification readily led to methyl ester 37 which, after deacetylation, could be regioselectively tetrabenzoylated with benzoyl cyanide. Triflate activation of the axial hydroxyl group in 40 and nucleophilic displacement by azide ion with inversion of configuration afforded azide 41, which was reduced with hydrogen and Pearlman's catalyst. Concomitant removal of the benzyl ethers and subsequent saponification of all ester moieties successfully completed the de novo synthesis of the desired methylene bridged Neu5Ac-alpha-(2,3)-Gal C-disaccharide 2.

Synthesis of ganglioside GD3 and its comparison with bovine GD3 with regard to oligodendrocyte apoptosis mitochondrial damage

2,3-Dehydroneuraminic acid derivative 5 was transformed in five efficient steps into sialyl donor 2, which has a phenylthio group on the beta-side of the 3-position for anchimeric assistance and a diethyl phosphite residue as leaving group at the anomeric carbon. The known GM3 intermediate 10 was transformed into the 4b,4c,8c-O-unprotected acceptor 3, which was then allowed to react with 2 by using TMSOTf as catalyst and acetonitrile as solvent to afford the desired tetrasaccharide 12, which has an alpha(2-8)-linkage between two neuraminic acid residues. Removal of the phenylthio group gave intermediate 13, which was transformed into O-tetraosyl trichloroacetimidate 16 as glycosyl donor. Application of the azidosphingosine glycosylation procedure furnished GD3 (1) in high overall yield. Comparison of synthetic GD3 with bovine-brain-derived GD3 showed that there were similar effects in GD3-triggered uncoupling of mitochondrial respiration and in induction of apoptosis in oligodendrocytes.

Synthesis of chitotetraose and chitohexaose based on dimethylmaleoyl protection

tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranoside was readily transformed into the disaccharide glycosyl donor, 3,4,6-tri-O-acetyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranosyl-(1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-alpha/beta-D-glucopyranosyl trichloroacetimidate, and the disaccharide glycosyl acceptor, tert-butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranosyl-(1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranoside. A TMSOTf-catalysed coupling of the acceptor with the donor afforded the respective tetrasaccharide derivative, which can be transformed to chitotetraose. tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-4-O-phenoxyacetyl-beta-D-glucopyranosyl-(1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranoside was converted into donor 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-4-O-phenoxyacetyl-beta-D-glucopyranosyl-(1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranosyl trichloroacetimidate. Its coupling with benzyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranosyl-(1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranoside, followed by dephenoxyacetylation, gave benzyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranosyl-(1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranosyl-(1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranosyl-(1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranoside, whose glycosylation furnished, after replacement of the DMM-group by the acetyl moiety and subsequent deprotection, chitohexaose.

A new phenoxyacetate-based linker system for the solid-phase synthesis of oligosaccharides

[structure: see text]. A novel linker system has been designed, and its first application to solid-phase oligosaccharide synthesis is described. The use of the highly reactive o-nitro-phenoxyacetate linker allows a fast and quantitative cleavage using mild basic conditions. This method combined with the trichloroacetimidate glycosylation exhibits highly promising results as demonstrated for the synthesis of tetrasaccharide 1 (n = 3) containing glucose beta(1 --> 4) and beta(1 --> 6) linkages.

Total synthesis of the natural antigen involved in the hyperacute rejection response to xenotransplants

The major glycosphingolipid in pig vascular endothelium is the ceramide pentasaccharide Gal alpha(1 --> 3)Gal beta(1 --> 4)GlcNAc beta(1 --> 3)Gal beta(1 --> 4)Glc beta(1 --> 0)Cer (1), which binds specifically to human anti-Gal antibody and is involved in the hyperacute rejection response in xenotransplantation from pig to man. The synthesis of 1 and its methyl glycoside 2 is described.

O-Glycosyl trichloroacetimidates bearing Fmoc as temporary hydroxy protecting group: a new access to solid-phase oligosaccharide synthesis

Different O-glycosyl trichloroacetimidates bearing base sensitive Fmoc protected hydroxy groups were efficiently prepared with CCl(3)CN using a catalytic amount of sodium hydride. The resulting glycosyl donors were engaged in glycosylation reactions both in solution and on solid support with a new ester-type linker with good results. In both approaches, Fmoc groups were afterward quantitatively cleaved using mild basic conditions.

Total synthesis of alpha-galactosyl cerebroside

A highly convergent synthetic approach was developed to obtain alpha-galactosyl cerebroside O-(alpha-D-galactopyranosyl)-2-hexacosylamino-D-ribo-1,3,4-octa decantriol, which has previously been demonstrated to have immunostimulatory activity. Known 4,6-O-benzylidene galactose was the starting material for both the required alpha-galactosyl and the phytosphingosine building blocks O-(2,3-di-O-benzyl-4,6-O-benzylidene-D-galactopyranosyl) trichloroacetimidate (4) and 2-O-methanesulfonyl-D-arabino-1,2,3,4-octadecantetrol (5). The key step of the synthetic strategy is the highly regio- and stereoselective O-galactosylation of 1,3,4-O-unprotected phytosphingosine acceptor 5 using known 4 as donor. The total synthesis required only 11 synthetic steps starting from galactose.

Synthesis of the sialyl Lewis X epitope attached to glycolipids with different core structures and their selectin-binding characteristics in a dynamic test system

Sialyl Lewis X (sLeX)/selectin-mediated leukocyte rolling along endothelial cells has recently gained wide interest. In this paper the influence of the spacer length of laterally clustered neoglycolipids 1a-d on cell rolling in a dynamic test system is investigated. The required di-O-hexadecyl glycerols with none, and with three, six, or nine ethylene glycol units as spacer groups (compounds 4a-d) could be readily obtained. The synthesis of 1-O-thexyldimethylsilyl-protected sLeX 24 was based on sialylation of 2,3,4-O-unprotected galactose derivative 11 with sialyl phosphite 8 as donor; this afforded the desired disaccharide 12, which was transformed into trichloroacetimidate 14 as disaccharide donor. Reaction of 3-O-unprotected glucosamine derivative 18 with fucosyl donor 20 afforded disaccharide 21, which was transformed into the 4-O-unprotected derivative 23. Reaction of 14 with 23 furnished the desired tetrasaccharide 24 in good yield. Transformation of 24 into the trichloroacetimidate 26 as donor, followed by the reaction with 4a-d as acceptor gave, after deprotection, the target molecules 1a-d. For comparison, 4d was also connected with a sialyl residue (-->31) and with an N-acetylglucosamine residue (-->34). Compounds 1c and 1d with a hexaethylene glycol and a nonaethylene glycol spacer, respectively, were much more efficient in mediating selectin-dependent cell rolling in the dynamic test system than compounds 1a and 1b, which had no spacer (1a), or only a triethylene glycol spacer (1b).

Bilayer properties of totally synthetic C16:0-lactosyl-ceramide

Differential scanning calorimetry (DSC) and x-ray diffraction have been used to study the structural and thermal properties of totally synthetic D-erythro-N-palmitoyl-lactosyl-C(18)-sphingosine (C16:0-LacCer). Over the temperature range 0-90 degrees C, fully hydrated C16:0-LacCer shows complex thermal transitions characteristic of polymorphic behavior of exclusively bilayer phases. On heating at 5 degrees C/min, hydrated C16:0-LacCer undergoes a complex two-peak endothermic transition with maxima at 69 degrees C and 74 degrees C and a total enthalpy of 14.6 kcal/mol C16:0-LacCer. At a slower heating rate (1.5 degrees C/min), two endothermic transitions are observed at 66 degrees C and 78 degrees C. After cooling to 0 degrees C, the subsequent heating run shows three overlapping endothermic transitions at 66 degrees C, 69 degrees C, and 71.5 degrees C, followed by a chain-melting endothermic transition at 78 degrees C. Two thermal protocols were used to completely convert C16:0-LacCer to its stable, high melting temperature (78 degrees C) form. As revealed by x-ray diffraction, over the temperature range 20-78 degrees C this stable phase exhibits a bilayer structure, periodicity d approximately 65 A with an ordered chain packing mode. At the phase transition (78 degrees C) chain melting occurs, and C16:0-LacCer converts to a liquid crystalline bilayer (L(alpha)) phase of reduced periodicity d approximately 59 A. On cooling from the L(alpha) phase, C16:0-LacCer converts to metastable bilayer phases undergoing transitions at 66-72 degrees C. These studies allow comparisons to be made with the behavior of the corresponding C16:0-Cer (. J. Lipid Res. 36:1936-1944) and C16:0-GluCer and C16:0-GalCer (. J. Lipid Res. 40:839-849). Our systematic studies are aimed at understanding the role of oligosaccharide complexity in regulating glycosphingolipid structure and properties.

Specific inhibition of an alpha-galactosyltransferase from Trypanosoma brucei by synthetic substrate analogues

Since the alpha-D-galactose-(1-->3)-D-galactose epitope has been identified to be the major target in the process of hyperacute rejection of xenografts transplanted from nonprimate donors to humans, specific inhibitors of alpha-galactosyltransferases are of broad interest. Using Trypanosoma brucei, a protozoan parasite causing sleeping sickness and Nagana, we have a very useful model system for the investigation of alpha-galactosyltransferase inhibitors, since the variant surface glycoprotein (VSG) accounts for about 10% of the total cell protein an this parasite expresses many different galactosyltransferases including the one catalysing the formation of the Galalpha1-->3Gal epitope. In order to study inhibition of galactosylation on the VSG from Trypanosoma brucei, we designed, synthesized and tested substrate analogues of trypanosomal alpha-galactosyltransferases. Effective inhibitors were a pair of diastereoisomeric UDP-galactose analogs, in which the galactose residue is linked to UDP via a methylene bridge rather than an ester linkage. Hence, galactose cannot be transferred to the respective acceptor substrate VSG or the synthetic acceptor substrate Manalpha1-->6Manalpha1S-(CH2)7-CH3, which was previously proven to replace VSG effectively [Smith et al. (1996) J Biol Chem 271:6476-82]. Inhibitors have been prepared starting from 1-formyl galactal. The final condensation was performed using UMP morpholidate leading to a pair of diastereomeric compounds in 39% or 30% yield, respectively. These compounds were tested using alpha-galactosyltransferases prepared from T. brucei membranes and lactose synthetase from bovine milk. While the K(M)-value for UDP-galactose was determined as 59 microM on bovine lactose synthetase, the K(I)-values for both inhibitors were 0.3 mM and 1.1 mM respectively, showing that these inhibitors are unable to inhibit enzyme activity significantly. However, using the N-glycan specific alpha-galactosyltransferase from trypanosomes, the K(M)-value was determined as 20 microM, while the K(I)-values were 34 microM and 21 microM respectively. Interestingly, other trypanosomal alpha-galactosyltransferases, which modify the GPI membrane anchor, are 2 orders of magnitude less effected by the inhibitor.

Structure and properties of totally synthetic galacto- and gluco-cerebrosides

The structural and thermal properties of aqueous dispersions of the totally synthetic cerebrosides, D-erythro-N-palmitoyl galactosyl- and glucosyl-C18-sphingosine (C16:0-GalCer and C16:0-GluCer, respectively) have been studied using differential scanning calorimetry (DSC) and X-ray diffraction. Over the temperature range 0-100 degrees C, both C16:0-GalCer and C16:0-GluCer show complex thermal transitions characteristic of polymorphic behavior of exclusively bilayer phases. On heating, hydrated C16:0-GalCer undergoes an exothermic bilayer-bilayer transition at 59 degrees C to produce a stable bilayer crystal form. X-ray diffraction at 70 degrees C reveals a bilayer structure with an ordered hydrocarbon chain-packing arrangement. This ordered bilayer phase undergoes an endothermic chain-melting transition at 85 degrees C to the bilayer liquid crystalline state. Similar behavior is exhibited by hydrated C16:0-GluCer which undergoes the exothermic transition at 49 degrees C and a chain-melting transition at 87 degrees C. The exothermic transitions observed on heating hydrated C16:0-GalCer and C16:0-GluCer are irreversible and dependent upon previous chain melting, prior cooling rate, and time of incubation at low temperatures. Thus, the structure and properties of totally synthetic C16:0-GalCer and C16:0-GluCer with identical sphingosine (C18:1) and fatty acid (C16:0) chains are quite similar, suggesting that the precise isomeric structure of the linked sugar plays only a minor role in regulating the properties of hydrated cerebrosides. Further, these studies indicate that the complex thermal behavior and bilayer phase formation exhibited by these single-sugar cerebrosides are intrinsic properties and not due to the heterogeneity of the sphingosine base found in natural and partially synthetic cerebrosides.

Inhibition of some hepatic lysosomal glycosidases by ethanolamines and phenyl 6-deoxy-6-(morpholin-4-yl)-beta-D-glucopyranoside

The hepatic lysosomal glycosidases alpha-glucosidase and beta-glucuronidase were inhibited in vitro and in vivo by mono- and diethanolamines. The in vivo inhibition is dose dependent and occurs at a value less than LD50. Phenyl 6-deoxy-6-(morpholin-4-yl)-beta-D-glucopyranoside inhibited alpha-glucosidase both in vitro and in vivo. The treatment of the enzymes in vitro by ethanolamine exhibited a reversible inhibition of the mixed and competitive types for alpha-glucosidase and beta-glucuronidase, respectively. Diethanolamine showed a reversible inhibition of the competitive type for both enzymes. It is a potent inhibitor for beta-glucuronidase, in vitro, whose inhibition constant (Ki) is 5 x 10(-5) M. Phenyl 6-deoxy-6-(morpholin-4-yl)-beta-D-glucopyranoside is a potent inhibitor only for hepatic alpha-glucosidase with a Ki value of 1.6 x 10(-5) M. The pattern of the pH dependence of enzymic activity was not affected by ethanolamine inhibition. The magnitude of the inhibition of enzymes is dependent on the structure of the inhibitor.

Synthesis of lacto-N-neotetraose and lacto-N-tetraose using the dimethylmaleoyl group as amino protective group

The disaccharide donor O-[2,3,4,6-tetra-O-acetyl-beta-D- galactopyranosyl)-(1-->4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido - alpha,beta-D-glucopyranosyl] trichloroacetimidate (7) was prepared by reacting O-(2,3,4,6-tetra-O-acetyl- alpha-D-galactopyranosyl) trichloroacetimidate with tert-butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2- dimethylmaleoylamido-glucopyranoside to give the corresponding disaccharide 5. Deprotection of the anomeric center and then reaction with trichloroacetonitrile afforded 7. Reaction of 7 with 3'-O-unprotected benzyl (2,4,6-tri-O-benzyl-beta-D-galactopyranosyl)- (1-->4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside (8) as acceptor afforded the desired tetrasaccharide benzyl (2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-(1-->4)-(3,6-di-O- benzyl-2-deoxy-2-dimethylmaleimido-beta-D-glucopyranosyl)-(1-->3)- (2,4,6- tri-O-benzyl-beta-D-galactopyranosyl)-(1-->4)-2,3,6-tri-O-benzyl-beta-D- glucopyranoside. Replacement of the N-dimethylmaleoyl group by the acetyl group, O-debenzylation and finally O-deacetylation gave lacto-N-neotetraose. Similarly, reaction of O-[(2,3,4,6-tetra-O-acetyl-beta- D-galactopyranosyl)-(1-->3)-4,6-O-benzylidene-2-deoxy-2-dimethylmalei mido- alpha,beta-D-glycopyranosyl] trichloroacetimidate as donor with 8 as acceptor afforded the desired tetrasaccharide benzyl (2,3,4,6-tetra-O-acetyl-beta-D- galactopyranosyl)-(1-->3)-(4,6-benzylidene-2-deoxy-2-dimethylmaleimid o- beta-D-glucopyranosyl)-(1-->3)-(2,4,6-tri-O-benzyl-beta-D-galactopyranos yl)- (1-->4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside. Removal of the benzylidene group, replacement of the N-dimethylmaleoyl group by the acetyl group and then O-acetylation afforded tetrasaccharide intermediate 15, which carries only O-benzyl and O-acetyl protective groups. O-Debenzylation and O-deacetylation gave lacto-N-tetraose (1). Additionally, known tertbutyldimethylsilyl (2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-(1-->3)-4,6-O-benzylide ne- 2-deoxy-2-dimethylmaleimido-beta-D-glucopyranoside was transformed into O-[2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)- (1-->3)-4,6-di-O-acetyl-2-deoxy-2-dimethylmaleimido-alpha,beta-D- glucopyranosyl] trichloroacetimidate as glycosyl donor, to afford with 8 as acceptor the corresponding tetrasaccharide 22, which is transformed into 15, thus giving an alternative approach to 1.

Sphingosine 1-phosphate-induced cell rounding and neurite retraction are mediated by the G protein-coupled receptor H218

Sphingosine 1-phosphate (SPP) is a lipid second messenger that also acts as a first messenger through the G protein-coupled receptor Edg-1. Here we show that SPP also binds to the related receptors H218 and Edg-3 with high affinity and specificity. SPP and sphinganine 1-phosphate bind to these receptors, whereas neither sphingosylphosphorylcholine nor lysophosphatidic acid compete with SPP for binding to either receptor. Transfection of HEK293 cells with H218 or edg-3, but not edg-1, induces rounded cell morphology in the presence of serum, which contains high levels of SPP. SPP treatment of cells overexpressing H218 cultured in delipidated serum causes cell rounding. A similar but less dramatic effect was observed in cells overexpressing Edg-3 but not with Edg-1. Cell rounding was correlated with apoptotic cell death, probably as a result of loss of attachment. Nerve growth factor-induced neuritogenesis in PC12 cells was inhibited by overexpression of H218 and to a lesser extent Edg-3. SPP treatment rapidly enhanced neurite retraction in PC12 cells overexpressing Edg-1, Edg-3, or H218. Thus, H218, and possibly Edg-3, may be the cell surface receptors responsible for cell rounding and neurite retraction induced by SPP. Moreover, the identification of these two additional SPP receptors indicates that a family of highly specific receptors exists that mediate different responses to SPP.

Synthesis of N-acetylglucosamine containing Lewis A and Lewis X building blocks based on N-tetrachlorophthaloyl protection--synthesis of Lewis X pentasaccharide

Phenyl 6-O-benzyl-2-deoxy-2-tetrachlorophthalimido-1-thio-beta-D- glucopyranoside (5a) and thexyldimethylsilyl 6-O-benzyl-2-deoxy-2-tetrachlorophthalimido-beta-D- glucopyranoside (5b) gave with O-(2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl)trichloroacetimida te (8) in the presence of BF3.Et2O as catalyst exclusively lactosamine derivatives 7a and 7b, respectively, in high yields. Ensuing reaction with O-(3, 4-di-O-acetyl-2-O-benzyl-alpha-L-fucopyranosyl) trichloroacetimidate (9) in the presence of TMSOTf as catalyst afforded Le(x) trisaccharide intermediates 10a,b. With fucosyl donor 9 and 5a,b as acceptors in the presence of TMSOTf as catalyst glycosylation either at the 3-O or the 4-O was observed, thus leading to mixtures of disaccharides 11a/12a and 11b/12b, respectively; their reaction with 8 furnished Le(x) trisaccharide intermediates 10a,b and Le(a) trisaccharide intermediates 14a,b. Transformation of 10b into the corresponding trichloroacetimidate 17 and reaction with lactose acceptor 19 in the presence of Zn(OTf)2 as catalyst gave protected Le(x) pentasaccahride intermediate 21, which on deprotection led to unprotected Le(x) pentasaccharide 1.

The role of glycolipids in mediating cell adhesion: a flow chamber study

Selectins constitute a family of proteins that mediate leukocyte tethering and rolling along the vascular endothelium by recognizing various carbohydrate ligands in response to inflammation. To test the hypothesis that multivalent binding of selectins to their ligands is the molecular basis for achieving sufficient binding forces, we have performed this flow chamber study. Selectin-containing Chinese hamster ovarial cells (CHO-E) bind and roll along a support-fixed phospholipid membrane containing a defined concentration of a synthetic Sialyl Lewisx (sLex) glycolipid ligand. Ligands are either homogeneously distributed, or arranged in defined lateral clusters, as illustrated here for the first time. The lateral glycolipid clusters which appear as recognition motifs are essential for mediating cell rolling. Furthermore, the transition from firm cell adhesion to cell rolling depends on the site density of ligands. Rolling velocity shows little dependence on shear forces within a broad range. As we found out that cells do not roll along the model membranes with homogeneous ligand distribution, our results therefore support the hypothesis of multivalent binding events. Since these investigations suggest that lipid-anchored sLex, functionally embedded in a lipid matrix, can mediate cell rolling, this study demonstrates the relationship between dynamic glycolipid binding to selectins with the hypothesis of multivalency of binding for the first time.

Alternative splicing of a precursor-mRNA encoded by the Chlorella sorokiniana NADP-specific glutamate dehydrogenase gene yields mRNAs for precursor proteins of isozyme subunits with different ammonium affinities

Chlorella sorokiniana has seven ammonium-inducible, chloroplastic NADP-specific glutamate dehydrogenase (NADP-GDH) isozymes composed of varying ratios of alpha- and beta-subunits. Southern blot and allele-specific PCR analyses indicate that the C. sorokiniana genome possesses a single 7178 bp nuclear NADP-GDH gene. cDNA cloning and sequencing, 5'-RACE-PCR analysis, and RNase protection analysis identified two NADP-GDH mRNAs that are identical with the exception of a 42 nt sequence located within the 5'-coding region of the longer mRNA. The 42 nt sequence, termed an auxon because it serves as an exon or intron, appears to undergo alternative splicing from the precursor mRNA by a process that is regulated by both nutritional and environmental signals. Depending upon whether the auxon is included or excluded in a mature mRNA, the gene can be considered to consist of 22 or 23 exons, respectively. The 2074 and 2116 nt mRNAs encode precursor proteins of 56,350 and 57,850 Da, respectively. The N-termini of the purified mature alpha- and beta-subunits were sequenced, identifying full-length subunits of 53,501 and 52,342 Da, respectively. The sequences of the subunits are identical except for an 11 amino acid extension at the N-terminus of the alpha-subunit. The alpha-subunit has an additional alpha-helical domain at its N-terminus compared with the beta-subunit. By correlating the abundances of the two mRNAs with the levels (and relative turnover rates) of the alpha- and beta-subunit antigens during induction in Chlorella, the larger mRNA is proposed to encode the larger subunit.

New sialyltransferase inhibitors based on CMP-quinic acid: development of a new sialyltransferase assay

Quinic acid (4) was transformed into phosphitamides 6, 14, and 15, which could be readily linked to 5'-O-unprotected cytidine derivative 7; ensuing oxidation of the obtained phosphite triesters with tert-butylhydroperoxide furnished the corresponding phosphate triesters 8, 16, and 17, respectively. Hydrogenolytic debenzylation of the phosphate moiety, base catalysed removal of acetyl protective groups, and basic hydrolysis of the methylester of the quinic acid moiety furnished CMP-Neu5Ac analogues 1-3. In order to measure their inhibition of sialyltransferases, a nonradioactive sialyltransferase assay [employed for alpha(2-6)-sialyltransferase from rat liver (EC 2.4.99.1)] based on reversed-phase HPLC separation of UV-labelled acceptor 20 (p-nitrophenyl glycoside of N-acetyllactosamine) from the UV-labelled product 21 (p-nitrophenyl glycoside of sialyl alpha(2-6')-N-acetyllactosamine) and p-nitrophenylalanine as internal standard was developed. The assay reproduced the reported K(M) values for CMP-Neu5Ac and N-acetyllactosamine and the Ki values for CDP. 1 and 2 turned out to be potent sialyltransferase inhibitors.

Synthesis of a thio-linked Lewis A (Le(a)) epitope

The synthesis of heptyl (alpha-L-fucopyransoyl)-(1-->4)-S-[(beta-D-galactopyranosyl)-(1--> 3)] -1,4-dithio-beta-D-glucopyranoside (2), as thio-linked Lewis A analogue was based on thexyldimethylsilyl 3-O-allyl-2-O-benzoyl-6-O-(4-methoxybenzyl)-4-thio-beta-D-glucopyranosid e (15) which was readily obtained from D-galactose. Reaction of 15 with O-3,4-di-O-acetyl-2-O-(4-methoxybenzyl)-alpha-L-fucopyranosyl trichloroacetimidate (8) as fucosyl donor afforded the alpha-(1-->4)-thio-linked disaccharide. Replacement of the 4-methoxybenzyl groups by acetyl groups and removal of the 3a-O-allyl group afforded as 3a-O-unprotected acceptor thexyldimethylsilyl (2,3,4-tri-O-acetyl-alpha-L-fucopyranosyl)-(1-->4)-S-6-O-acetyl-2-O-benz oyl -4-thio-beta-D-glucopyranoside (19), which gave with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl trichloroacetimidate as galactosyl donor (20) the trisaccharide. Transformation into a trichloroacetimidate as glycosyl donor, glycosylation of heptylmercaptan, and then removal of the O-acyl protective groups afforded target molecule 2.

A simple access to lactose-derived building blocks required in glycoconjugate synthesis

Lactose was readily transformed into thexyldimethylsilyl (3,4-O-isopropylidene-beta-D-galactopyranosyl)-(1-->4)-beta- D-glucopyranoside (5); this compound served as intermediate for the generation of partially O-protected lactose building blocks required in oligosaccharide and glycoconjugate synthesis. Thus, from 5 via per-O-benzoylation, desilylation, trichloroacetimidate formation, glycosylation of the Lemieux spacer, and acid-catalyzed de-O-isopropylidenation methoxycarbonyloctyl (2,6-di-O-benzoyl-beta-D-galactopyranosyl)- (1-->4)-2,3,6-tri-O-benzoyl-beta-D-glucopyranoside (12) was obtained. Regioselective benzoylation of 5 with benzoyl cyanide under various conditions afforded 3-O- (13), 2,3,2'-O- (14), 3,2'-O- (16), and 2,2'-O-unprotected (17) lactoside, respectively. De-O-isopropylidenation of 16 gave thexyldimethylsilyl (6-O-benzoyl-beta-D-galactopyranosyl)-(1-->4)-2, 6-di-O-benzoyl-beta-D-glucopyranoside (18), an important 2',3',4'-O-unprotected lactose derivative. Fucosylation of 13 and then de-O-isopropylidenation afforded thexyldimethylsilyl 2,6-di-O-benzoyl-beta-D-galactopyranosyl)-(1-->4)-[(3,4-di-O-acetyl-2-O- benzoyl-alpha-L-fucopyranosyl)-(1-->3)]-2,6-di-O-benzoyl-beta-D- glucopyranoside (21), an important fucosyllactose building block.

cis-4-Methylsphingosine decreases sphingolipid biosynthesis by specifically interfering with serine palmitoyltransferase activity in primary cultured neurons

The effect of six different structurally modified sphingosine analogues on biosynthesis of sphingolipids was studied in primary cultured murine cerebellar neurons. Treatment of cells with cis-4-methylsphingosine at micromolar levels resulted in a markedly decreased sphingolipid biosynthesis, whereas the other compounds examined, trans-4-methylsphingosine, cis-5-methylsphingosine, trans-5-methylsphingosine, cis-sphingosine, and 1-deoxysphingosine, inhibited sphingolipid biosynthesis less efficiently. The inhibition of sphingolipid biosynthesis by the various compounds was paralleled by a decrease of serine palmitoyltransferase activity in situ. For cis-4-methylsphingosine the inhibitory effect on serine palmitoyltransferase activity was shown to be concentration- and time-dependent. Half-maximal reduction of enzyme activity occurred after 24 h of treatment with 10 microM of the compound. The activity of other enzymes of sphingolipid biosynthesis as well as phospholipid and protein biosynthesis was not affected. Analysis of the sphingoid moiety of cellular sphingolipids suggests that the sphingosine analogues listed above were subject to degradation rather than being utilized as precursors for sphingolipid biosynthesis by cultured neurons. Except of 1-deoxysphingosine, the other five sphingosine analogues were shown to be substrates for sphingosine kinase in vitro. After 24 h of treatment of primary cerebellar neurons with the various sphingosine analogues the relative percentage of the respective intracellular 1-phosphate derivatives paralleled exactly the inhibitory effect on serine palmitoyltransferase activity observed when cells were treated with the unphosphorylated compounds. In contrast to the respective 1-phosphate derivatives of the other methyl-branched sphingosine analogues examined, cis-4-methylsphingosine 1-phosphate showed an intracellular accumulation suggesting a delayed turnover rate in cultured murine neurons for this compound. These results suggest that the inhibitory effect of the sphingosine analogues on serine palmitoyltransferase is mediated by their respective 1-phosphate derivatives and that the pronounced effect of cis-4-methylsphingosine is caused by a high intracellular concentration of cis-4-methylsphingosine 1-phosphate. cis-4-Methylsphingosine, in addition, caused drastic changes in cell morphology of primary cerebellar neurons, which were not observed when these cells were treated with one of the other sphingosine analogues examined.

Bilateral absence of the ovaries and distal fallopian tubes. A case report

BACKGROUND

Bilateral tuboovarian absence is extremely rare and is associated with infantile sexual development, primary amenorrhea and primary infertility.

CASE

A 23-year-old woman presented for evaluation of primary amenorrhea. Her examination revealed hypoplastic breasts, genitalia and uterus; ovaries could not be identified. Marked estrogen deficiency was confirmed by endocrinologic testing. The karyotype was normal female. The patient was started on combined hormone replacement therapy and subsequently developed normal menses; physical maturation progressed normally. At the age of 29 she underwent diagnostic laparoscopy for evaluation of her fertility potential, at which time the absence of both ovaries and distal fallopian tubes was confirmed.

CONCLUSION

Bilateral tuboovarian absence is an extremely rare cause of primary amenorrhea and is associated with infantile sexual development and primary infertility. Its etiology includes tuboovarian torsion and congenital malformation. In this case, congenital malformation appears to have been the more likely cause.

Use of shoulder flexors to achieve isometric elbow extension in C6 tetraplegic patients during weight shift

The anterior deltoid muscle has been found to be active during elbow extension in normal volunteers and in C6 tetraplegic patients lacking a functional triceps. Using surface electromyography (EMG) on normal volunteers and on patients with spinal cord injury (SCI) at the C6 motor level, we evaluated whether the anterior deltoid and biceps brachii muscles are active during closed chain elbow extension in a simulated weight shift position. Thirteen normal volunteers performed isometric contractions at 5 submaximal levels of force ranging from 4-25 kg. Six SCI patients performed isometric contractions at force levels of 20%, 40%, 60%, 80% and 100% maximum voluntary contraction (MVC). Surface EMG over the right biceps, triceps, and anterior deltoid muscles was recorded for each participant and the root mean square (rms) electromyographic activity level for each muscle was determined at each level of force. Statistical analyses using repeated ANOVA with Tukey HSD post-hoc tests were performed for each level of force. The results indicated increasing rms activity of the triceps and anterior deltoid muscles with increasing force in normal volunteers to a significant degree (P < 0.05). SCI patients showed significant increasing activity of the anterior deltoid with increasing force, but showed minimal triceps rms activity. In both groups, the biceps showed minimal rms activity. SCI patients exhibited significantly greater rms activity of the anterior deltoid at low force compared with normal volunteers. The results suggest that the anterior deltoid aids in isometric elbow extension during a simulated weight shift maneuver.

N-trichloroethoxycarbonyl-glucosamine derivatives as glycosyl donors

D-Glucosamine can be readily transformed into 1,3,4,6-tetra-O-acetyl-2-deoxy-2-(2,2,2-trichloroethoxycarbonylamino+ ++) -D-glucopyranose (2). From this intermediate valuable glycosyl donors can be obtained; reaction with ethanethiol in the presence of boron trifluoride etherate afforded ethyl 3,4,6-tri-O-acetyl-2-deoxy-1-thio-2-(2,2, 2-trichloroethoxycarbonylamino)-beta-D-glucopyranoside (4) which gave, upon N-acetylation, the N-acetyl-N-trichloroethoxycarbonyl derivative (5). Selective removal of the 1-O-acetyl group in 2 followed by treatment with trichloroacetonitrile in the presence of base afforded 3,4,6-tri-O-acetyl-2-deoxy-2-(2,2,2-trichloroethoxycarbonylamino)- alpha -D-glucopyranosyl trichloroacetimidate (6). Reaction of 5 with five selectively protected glycosides as glycosyl acceptors in the presence of N-iodosuccinimide/trifluoromethanesulfonic acid as the promoter system furnished the corresponding beta-glycosides in good yields, thus exhibiting the valuable glycosyl donor properties of 5. Reductive removal of the trichloroethoxycarbonyl (Teoc) group afforded the corresponding N-acetyl-protected saccharides in high yields. The imidate 6 reacted with three of the above acceptors in the presence of catalytic amounts of trimethylsilyl trifluoromethanesulfonate to give the beta-linked disaccharides in even better yields. The direct replacement of the N-Teoc group by the N-acetyl group using zinc/acetic anhydride, via the free amines as transient intermediates, adds to the high efficiency and convenience of this methodology.

Differential effects of synthetic sphingosine derivatives on melanoma cell motility, growth, adhesion and invasion in vitro

Cancer cell surface glycosphingolipids are considered to play a critical role in tumor growth and metastasis. However, the implications of glycoconjugates in the control of cell motility, which is considered to be involved in tumor invasion, are not fully understood. In this study, the effects of a series of synthetic sphingosine derivatives, obtained by the chemical transformation of azidosphingosines, on directional migration of K1735-M2 melanoma cells grown on type I collagen-coated surfaces were investigated. Following the application of 60 microM (2R, 3S, 4E)-2, 3-epimino-4-octadecen-3-ol (S4) the migration rate was 94 +/- 10 microns/day, compared with 377 +/- 22 microns/day in the control experiment. Six other analogues were not as potent. S4 also considerably down-modulated melanoma single cell motility. Inhibition of motile activity was associated with changes in the actin filament organization as well as with changes in the number and distribution of vinculin plaques. Moreover, the compound reduced the attachment abilities of melanoma cells to basement membrane Matrigel. Tumor cell invasion, however, was less affected and proliferation remained unimpaired after treatment with S4. These data suggest at least one intracellular mode of action of this particular synthetic sphingosine derivative by modulation of cytoskeletal organization. Melanoma cell motility and growth may be controlled independently via glycosphingolipids.

Surgical anatomy of the vertebral arteries

STUDY DESIGN

This study compared direct measurements of the distances between the vertebral arteries in the cervical spines of human cadaver specimens with data obtained from axial computed tomography images of these specimens.

OBJECTIVE

To determine whether the information obtained from a computed tomography scan can be used reliably to predict the true anatomic location of the vertebral arteries and, in so doing, provide accurate guidelines for the lateral extent of anterior cervical decompressive procedures.

SUMMARY OF BACKGROUND DATA

Iatrogenic vertebral artery injury during anterior cervical surgery is uncommon, potentially catastrophic, and avoidable.

METHODS

The means and standard deviation of measurements of the location of the cervical segment of the vertebral arteries obtained with high-precision, digital calipers by direct gross anatomic dissection of 16 adult (eight male, eight female) cadaver specimens were recorded. These measurements were compared with computed tomography scan data obtained on the same specimens.

RESULTS

The mean distances between the vertebral arteries progressively increased from C3 to C6. Computed tomography scan measurements of the distance between the cervical foramina transversaria were consistently smaller than direct measurements of the gross specimens. At C6, the computed tomography scan data were significantly less than the gross anatomic data.

CONCLUSIONS

According to these data, computed tomography scan measurements may be used safely and accurately to plan the lateral extent of anterior cervical decompressive surgical procedures. Although the data obtained from the gross anatomic dissections may serve as guidelines to assist the surgeon, the authors recommend a careful review of the preoperative computed tomography scan on an individual case-by-case basis as the safest method to plan for anterior cervical surgery.

Structural requirements of sphingosylphosphocholine and sphingosine-1-phosphate for stimulation of activator protein-1 activity

The sphingolipids sphingosine-1-phosphate (SPP) and sphingosylphosphocholine (SPC) stimulate mitogenesis in Swiss 3T3 fibroblasts and stimulate DNA binding activity of activator protein-1 (AP-1). We show that SPP and SPC were more potent agents than nonphosphorylated sphingosines and N-acyl-sphingolipids (ceramides) with respect to DNA synthesis, AP-1 DNA binding activity, and AP-1 trans-activation, illustrating the importance of the terminal phosphate group. The free 2-amino group and the 4E double bond of SPC and SPP were found to be important for these activities. Although the combination of decreasing the sphingoid backbone chain length of SPC by two carbons and hydrogenating the 4E bond only slightly reduced its effects, in contrast, the same modifications in SPP significantly decreased its mitogenic and AP-1 trans-activation effects. Furthermore, substitution of the 3-hydroxyl group in SPP with hydrogen decreased its ability to stimulate DNA synthesis and to stimulate AP-1 transcriptional activity. Thus, critical sphingolipid structural components for AP-1 activation and mitogenic stimulation include the free 2-amino group, the free 3-hydroxyl group, the 4,5-trans double bond, and terminal phosphorylation. These observations may be relevant for clinical uses of these compounds in applications such as wound healing and inhibition of metastasis.

Ceramide-1-phosphate sugars: new types of glycophospholipids

Ceramide-1-phosphate sugars were synthesized by direct glycosyl phosphite/phosphate and O-glycosyl trichloroacetimidate/phosphate exchange reactions, respectively. Thus, ceramide-1-O-phosphoric acid 5 gave with sialyl phosphite 1 as sialyl donor directly beta-linked sialyl phosphate 6; deprotection afforded the corresponding glycophospholipid ceramide-1-phosphate N-acetylneuraminate 7. Similarly, from O-glucosyl- and O-galactosyltrichloroacetimidate 10 and 13 with phosphoric acid derivative 5 glycosyl ceramide-1-phosphate sugars 12 and 15, respectively, were obtained.

Solid-phase synthesis of a glycosylated hexapeptide of human sialophorin, using the trichloroacetimidate method

A hexapeptide containing a beta-D-Gal p-(1-->3)-alpha-D-Gal pNAc-(1-->O)-L-threonine unit was synthesized using glycosylated pentafluorophenyl esters in an Fmoc-based strategy. In all of the glycosylation reactions, trichloroacetimidates were successfully employed. The disaccharide moiety was prepared from tetra-O-acetyl-alpha-D-galactopyranosyl trichloroacetimidate and tert-butyldimethylsilyl 2-azido-6-O-benzoyl-2-deoxy-beta-E-galactopyranoside with boron trifluoride etherate as a catalyst. The glycosylated active esters were obtained in the reaction of alpha and beta 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl-(1-->3)-4-O-acetyl-2-azid o-6- O-benzoyl-2-deoxy-D-galactopyranosyl trichloroacetimidates with Fmoc-protected pentafluorophenyl esters of L-serine and L-threonine in the presence of trimethylsilyl trifluoromethanesulfonate as Lewis acid. The glycosylated pentafluorophenyl ester of L-threonine was transformed into glycopeptides via a solid-phase synthesis. Azide reduction and N-acetylation were performed on the solid phase with a thioacetic acid-pyridine mixture. The glycopeptide was then cleaved from the resin with strong acid, also removing the acid-labile protecting groups of the peptide chain. Finally, the acyl groups used for sugar protection were cleaved with sodium methoxide, affording the completely deprotected N-acetyl-L-leucyl-L-glutamyl-O-[beta-D-galactopyranosyl-(1-->3)-2- acetamido-2-deoxy-alpha-D-galactopyranosyl]-L-threonyl-L-seryl-L-threony l- glycinamide (1) in high purity.

A convenient synthesis of nucleoside monophosphate-N-acetylneuraminic acids (NMP-Neu5Ac)

Reaction of sialyl phosphites 2a,b with acetyl-protected ribonucleoside monophosphates 3C, 3U, 3A and 3G furnished without addition of a catalyst directly the corresponding beta-configurated sialyl ribonucleoside monophosphates 4C, 4U, 4A and 4G, respectively. Treatment of these compounds with sodium methanolate in methanol and sodium hydroxide afforded the disodium salts of CMP-Neu5Ac (1C), UMP-Neu5Ac (1U), AMP-Neu5Ac (1A), and GMP-Neu5Ac (1G).

Stereospecificity of sphingosine-induced intracellular calcium mobilization and cellular proliferation

Sphingosine is a positive regulator of cell growth in Swiss 3T3 fibroblasts (Zhang, H., Buckley, N. E., Gibson, K., and Spiegel, S. (1990) J. Biol. Chem. 265, 76-81). The present study investigated the stereospecificity of sphingosine-induced cell proliferation and its mitogenic signal transduction mechanisms. D-(+)-erythro Stereoisomers (cis and trans) stimulated DNA synthesis, whereas neither L-(-)-threo-sphingosine (cis or trans) nor DL-threo-dihydrosphingosine had any effect. Previously, we have shown that sphingosine-1-phosphate may mediate the mitogenic effect of sphingosine (Zhang, H., Desai, N. N., Olivera, A., Seki, T., Brooker, G., and Spiegel, S. (1991) J. Cell Biol. 114, 155-167). However, no major differences were found in the formation of D-(+)-erythro- and L-(-)-threo- sphingosine-1-phosphate derived from the respective sphingosine isomers in intact cells. Thus, the stereospecificity of the response to sphingosine may reside at the level of specific intracellular targets for sphingosine-1-phosphate. Sphingosine-1-phosphate triggers dual signal transduction pathways of activation of phospholipase D leading to increases in the levels of phosphatidic acid and mobilization of calcium from internal stores. Both D-(+)-erythro- and L-(-)-threo-sphingosine isomers induced similar increases in phosphatidic acid concomitant with identical decreases in phosphatidylcholine levels. In contrast, only the D-(+)-erythro-stereoisomers (cis and trans) were effective in releasing calcium from intracellular stores. Our results suggest that the formation of phosphatidic acid is not sufficient to mediate sphingosine-stimulated DNA synthesis. However, the stereospecificity of the sphingosine-induced mobilization of calcium from internal stores seems to correlate with the induction of DNA synthesis by sphingosine stereoisomers.