Thermotropic liquid crystalline glycolipids.

Are the liquid crystalline properties of the materials of living systems important in biological structures, functions, diseases and treatments? There is a growing consciousness that the observed lyotropic, and often thermotropic liquid crystallinity, of many biological materials that possess key biological functionality might be more than curious coincidence. Rather, as the survival of living systems depends on the flexibility and reformability of structures, it seems more likely that it is the combination of softness and structure of the liquid-crystalline state that determines the functionality of biological materials. The richest sources of liquid crystals derived from living systems are found in cell membranes, of these glycolipids are a particularly important class of components. In this critical review, we will examine the relationship between chemical structure and the self-assembling and self-organising properties of glycolipids that ultimately lead to mesophase formation.

Influence of a neoglycolipid and its PEO-lipid moiety on the organization of phospholipid monolayers.

The surface properties of the neoglycolipid (GlcNAcE(3)G(28)) and of its PEO-lipid (E(3)G(28)) moiety mixed with phospholipids (dipalmitoylphosphatidylcholine, DPPC; distearoylphosphatidylcholine, DSPC; diarachidoylphosphatidylcholine, DAPC; and dibehenoylphosphatidylcholine, DBPC) were studied in Langmuir monolayers at various mixture compositions and surface pressures. The pi-A isotherms of the pure compounds revealed that because of the presence of the sugar group in its molecule, GlcNAcE(3)G(28) collapsed at a higher surface pressure and occupied a larger molecular area than the PEO-lipid moiety. It was also observed that the presence of the PEO-lipid (E(3)G(28)) in the mixtures triggered a strong alteration of both phospholipid pi-A isotherm profiles and surface diffraction spectra, an indication that the disordering of the initially structured phospholipid monolayers took place. Unlike E(3)G(28), GlcNAcE(3)G(28) did not disorganize phospholipid monolayers but generated a partial segregation of the film-forming components. The calculated excess free energies of mixing (DeltaG(exc)) for GlcNAcE(3)G(28)-phospholipid mixtures enabled us to predict the stability of such systems.

Syntheses and interfacial behaviour of neoglycolipid analogues of glycosyl ceramides.

Four glycosyl ceramides analogues having D-galactose or 2-acetamido-2-deoxy-D-glucose moieties linked to enantiomeric lipids have been synthesised to study their interfacial behaviour at the air/water interface. The lipid chains were prepared in two steps by opening 1,2-epoxyhexadecane using Jacobsen kinetic hydrolytic resolution (KHR) followed by an azidosilylation reaction of the diol so obtained. Glycosylation reactions were realised either with 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate or 1,3,4,6-tetra-O-acetyl-2-allyloxycarbonylamino-2-deoxy-beta-D-glucopyranose as donors and (2R)- or (2S)-2-azidohexadecanol derivatives as acceptors. Transformation of the azido glycosides into N-acylated products was done by a modified Staudinger reaction in the presence of fatty acyl chlorides. The four neoglycolipids are able to form a condensed monolayer at the air/water interface; their pi-A isotherm diagrams are similar to that described for the natural glycosyl ceramides. The detailed analysis of the isotherms, taking into account the chirality of the lipid chains, allowed to determine the contribution of the different parts of the molecule under the monolayer packing.

Syntheses of neoglycolipids with hexitol spacers between the saccharidic and the lipidic parts.

Four neoglycolipids having 2-amino-2-deoxy-D-glucose or D-galactose moieties linked to the lipidic part by a glucitol or a mannitol spacer-arm have been synthesized. The key step of the synthetic strategy was the regiospecific or regioselective beta-glycosylation of partially protected glucitol or mannitol acceptors by either 3,4,6-tri-O-acetyl-2-deoxy-2-iodo-alpha-D-mannopyranosyl azide or 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate donors.

[Accuracy of pressure measurements obtained with a new rectal balloon catheter]. / Exactitude des mesures de pression obtenues par une nouvelle sonde rectale à ballonnet à air.

UNLABELLED: The accuracy of measurements performed by a balloon catheter used to record abdominal pressure during urodynamic investigations was verified on a test bench. OBJECTIVE: To study the accuracy and precision of the pressure measurements obtained with a new rectal balloon catheter (ref. 95018 Laboratoires Vermed), designed to record abdominal pressure during urodynamic assessments. The clinical value of this catheter, using air for pressure transmission, is its simplicity, as there is no contamination of the perfusion circuit or transducer, no purging of the circuit, and artefacts related to movements of the tubing are eliminated. METHOD: The catheter was placed in a pressure chamber fitted with a precise, calibrated regulation system allowing programmed pressure variations from 10 to 150 cmH2O. Pressures recorded by the test catheter were compared to reference pressures applied to the chamber. The frequency of acquisition of pressure measurements was 100 Hertz and the resolution was 10 Hertz. This model was used to study the accuracy of pressure measurements and the response times of the catheter. Measurements were performed with a volume of 2 ml of air introduced into the catheter (volume recommended by the manufacturer), and the optimal volume was investigated by inflating the catheter until the best result was obtained. The evaluation was based on calculation of the mean difference observed between the two measurements and the scatter of the differences observed. RESULTS: When the catheter was filled with 2 ml of air, pressures measured by the catheter were overestimated an average of 1.1 cmH2O (standard deviation = 1), and 95% of the differences between the two measurements were within +/- 2.15 cmH2O. The optimal air volume was found to be 1.5 ml. With this air volume, no significant difference was observed between the two measurements. The mean observed difference was 0.2 cmH2O (SD = 1.2), which means that 95% of the differences were situated within the range of +/- 2.35 cmH2O. CONCLUSION: The pressure recording method with this new catheter is validated in terms of physical parameters.

Fucosyled neoglycolipids: synthesis and interaction with a phospholipid.

The interfacial behavior of the neoglycolipids formed of Guerbet alcohol (G(28)) bound to a triethylene glycol spacer (E(3)) and to a sugar moiety (alpha- and beta-fucose) spread at the air/water interface has been studied under dynamic conditions of compression. Although the alpha (alpha-FucE3G28)- and beta-fucose (beta-FucE3G28) derivatives possessed the same chemical structure, the positioning of the sugar moiety relative to the whole molecule had a significant influence on the organization of neoglycolipid molecules in the spread monolayers. Thus, beta-fucose molecules exhibited higher compressibilities and larger molecular areas than a alpha/beta (84/16%) mixture (alpha(84)-FucE3G28). The comparison of the compressional behavior of the fucose derivatives with that of Guerbet alcohol in the absence and in the presence of the triethylene glycol spacer shows that the presence of the E(3) chain is necessary to stabilize the lipid at the interface and that the incorporation of a sugar moiety into the molecule resulted in an important expansion of a monolayer. Despite their different interfacial behaviors, the two sugar derivatives formed ideal mixtures when cospread at the air/water interface. Conversely, in the presence of a phospholipid, such as DMPC, repulsive interactions were observed and appeared to be stronger for DMPC/alpha(84)-FucE3G28 mixed monolayers. The membrane fluidity of DMPC liposomes bearing the studied amphiphilic molecules was assessed by fluorescence depolarization measurements. The results reveal that whereas G(28) was deeply inserted into the liposome bilayers, the presence of a E(3) chain and of a sugar moiety in these bilayers induced a transfer of the amphiphilic derivatives from the hydrophobic core towards polar headgroups of phospholipid molecules.

Syntheses of amphiphilic glycosylamides from glycosyl azides without transient reduction to glycosylamines.

Protected glycosyl azides react with acyl chlorides in the presence of triphenylphosphine to afford glycosylamides in high yields, at room temperature. Starting from the beta-glycosyl azides, the reaction is highly stereoselective and occurs with retention of configuration, whereas the alpha-azido anomers display a lower stereoselectivity giving rise to alpha/beta mixtures of glycosylamides. The reaction was applied to several monosaccharidic azides and to lactosyl azide with various acyl chlorides; it was shown to be of general use for preparing 1,2-trans beta-glycosylamides.

Development of an ELISA for pantothenic acid (vitamin B5) for application in the nutrition and biological fields.

Immunological assays appear to be the only alternative to the microbiological method for analysis of pantothenic acid in foods and blood. In order to evaluate the influence of the linker on the immunogenicity of the hapten, we have tried to raise antisera against pantothenic acid in rabbits using different conjugates. The hapten was coupled to a carrier protein (BSA or thyroglobulin) using adipoyl dichloride (adipoyl conjugate) or bromoacetyl bromide (acetyl conjugate). Only the acetyl conjugate has induced the production of a specific antibody. With this antibody, an assay on microplate using the ELISA inhibition technique was developed to measure pantothenic acid. The use of pantothenic acid coupled to thyroglobulin with adipoyl dichloride as the capture antigen has improved the sensitivity of the ELISA. This assay was applied to food products and blood.

[Endoscopic treatment of residual vesico-ureteral reflux after reimplantation in children: twelve cases]. / Traitement endoscopique du reflux vésico-urétéral résiduel après réimplantation chez l'enfant: a propos de 12 observations.

OBJECTIVE: To evaluate the safety and efficacy of endoscopic treatment of vesicoureteric reflux in children persisting after surgical reimplantation. MATERIAL AND METHODS: 12 children between the ages of 17 and 103 months were treated by endoscopic injection after failure of Cohen ureterovesical reimplantation. An associated uropathy was present in 4 children. Reflux was unilateral in every case. The operation was performed as a day-only procedure. All children were reviewed at 3 months. RESULTS: No early complications were observed. The follow-up cystography was normal in 10 children. The same degree of reflux persisted in 2 children, requiring a second ureterovesical reimplantation. A meatal stricture occurred 2 years after injection. The mean follow-up was 24.7 months. The success rate of the technique was 75% in this series. CONCLUSION: This technique is reliable, simple and can be performed in the day hospital. However, these good results must not mask the risk of long-term recurrence, requiring prolonged surveillance.

[Inguinal lymphadenectomy in cancer of the penis: surgical techniques and indications]. / Lymphadénectomie inguinale dans le cancer du pénis: techniques chirurgicales et indications.

Lymph node invasion is one of the major prognostic factors of cancer of the penis. However, as it is difficult to evaluate clinically and by means of complementary investigations, inguinal or even ilioinguinal lymph node dissection is still indicated. As this surgery carries a certain morbidity (necrosis of skin edges, infection, lymphorrhoea and subsequent lymphoedema), the indications are presented according to the presence or absence of palpable inguinal lymph nodes and the stage of the primary tumour. Various surgical techniques are proposed: Superficial and deep inguinal lymph node dissection in the case of mobile and palpable inguinal nodes, simplified and superficial inguinal lymph node dissection in the absence of palpable inguinal nodes and in the case of invasive primary tumour.

[Sarcomatoid variant of chromophobe renal cell carcinoma. Report of 2 cases]. / Variante sarcomatoïde du carcinome rénal à cellules chromophobes. A propos de 2 observations.

In this paper, we report two cases of sarcomatoid carcinoma arising in chromophobe carcinoma. The sarcomatoid component appeared as white, shiny areas, occupying less than 10% of each tumor and containing numerous mitotic figures. Whereas both components expressed cytokeratin, only the carcinomatous cells were positive for epithelial membrane antigen and only the sarcomatoid cells were found to express vimentine. Sarcomatoid transformation in chromophobe cell carcinoma has been reported exceptionally. An aggressive behavior may be expected. The variable proportion of sarcomatoid component may lead to multiplication of the samples, especially when white, firm and shiny areas are detected on gross findings.

Selective protections on 2-allyloxycarbonylamino-1,6-anhydro-2-deoxy-beta-D-glucopyranose.

Regioselective monoacetylation of 2-allyloxycarbonylamino-1,6-anhydro-2-deoxy-beta-D-glucopyranose (1) gave a mixture of 3-O-acetyl and 4-O-acetyl derivatives, the structures of which were established by two-dimensional, phase-sensitive NOESY and confirmed by chemical proofs. The benzylation of 1, on the other hand, led to 2-allyloxycarbonylamino-1,6-anhydro-3,4-di- (5) or 2-allyloxycarbonylamino-1,6-anhydro-2-N-benzyl-3,4-di-O-benzyl-2-d eoxy-beta-D- glucopyranose (10). The regioselective cleavage of 5 with titanium tetrachloride gave the expected 3-O-benzyl derivative, the structure of which was ascertained by chemical proofs; the same reaction performed on 10 led to the opening of the anhydro ring to afford 3-benzyl-[3,4-di-O-benzyl-1,2-dideoxy-alpha-D-glucopyrano]-[2,1-d] -2- oxazolidone.

Monitoring of urinary excretion of modified nucleosides in cancer patients using a set of six monoclonal antibodies.

Monoclonal antibodies were produced and characterized in order to allow the monitoring of the urinary excretion of six modified nucleosides. The specificity of each antibody was determined and competitive solid-phase enzyme-linked immunoassays were designed, the sensitivity of which lay in the pmol range. Detection and quantitation of 5-methylcytidine (5-MeCyd), 4-acetylcytidine (4-AcCyd), 1-methylinosine (1-MeIno), 1-methyladenosine (1-MeAdo), 7-methylguanosine (7-MeGuo) and pseudouridine (psi-Urd) can be performed in small volumes (70 microliters) of untreated urine. Results can be obtained from as many as 20 different samples, for one molecule, within 3 h. With this technique, values observed for three commonly measured nucleosides in urine from healthy subjects (psi-Urd, 1-MeAdo and 1-MeIno) are in good agreement with those reported by other authors after analysis by high performance liquid chromatography. Results obtained in urine from cancer patients show significantly increased levels of the six haptens quantitated by this immunoassay.

The use of N-alkoxycarbonyl derivatives of 2-amino-2-deoxy-D-glucose as donors in glycosylation reactions.

1,3,4,6-Tetra-O-acetyl-2-alkoxycarbonylamino-2-deoxy-beta-D-glu copyranoses and 3,4,6-tri-O-acetyl-2-alkoxycarbonylamino-2-deoxy-alpha-D-glucopyra nosyl bromides have been used as donors in glycosylation reactions with model alcohols. beta-Glycosides were obtained in good yields and with a high degree of 1,2-trans stereoselectivity. An oxazolidinone was formed as the main product from the reaction of some of the glucopyranosyl bromides with alcohols of low reactivity, but the formation of all products could be interpreted by a strong participation of the alkoxycarbonylamino group.

Study of Staphylococcus aureus teichoic acid immunodominant site by help of synthetic haptens.

The beta ribitol teichoic acid was extracted and purified from Staphylococcus aureus strain Wood 46 and chemically and immunologically characterised. Rabbit antiserum was prepared against formalin killed Staphylococcus aureus cells. Liquid phase immunoprecipitation of the beta ribitol teichoic acid-anti-Staphylococcus aureus serum system was studied by laser nephelometry. Various mono- and disaccharides (N-acetyl-glucosamine-ribitol with alpha- or beta-linkage and N-acetyl-glucosamine-ribitol-phosphate with beta-linkage) were prepared by organic synthesis, reproducing part of the ribitol teichoic acid molecule. Inhibition by those mono- or disaccharides of the precipitation of the beta-ribitol teichoic acid-Staphylococcus aureus antibodies system was studied quantitatively by determining inhibitory ratio of each inhibitor. Glucose, ribitol and glucosamine were weak inhibitors whereas N-acetyl-glucosamine was a better one, stronger than disaccharide with an alpha-linkage. The beta linked disaccharide and beta-methyl-N-acetyl-glucosamine gave comparable inhibition and both compounds were effective inhibitors. The most potent inhibitor was phosphorylated beta-linked disaccharide which inhibited 25% more than the same disaccharide without phosphorus. Thus, the function of phosphorus in Staphylococcus aureus beta ribitol teichoic acid recognition by antibodies was demonstrated.

Application of 125I radioimmunoassay to measure inhibition of precipitin reactions using carbohydrate-specific antibodies.

Antibodies raised to an artificial antigen with beta-D-galactopyranosyl groups as antigenic determinants were purified using an immunoadsorbent prepared from the hapten involved in the synthesis of the antigen. In order to study the specificity of these antibodies, 125I radiolabelling of either the artificial antigen or the antibody was used in the study of inhibitions of the precipitin reaction. The method, involving labelling of the artificial antigen and counting radioactivity in the supernatant, was found to be more accurate and faster than the usual methods based on measuring the amount of protein precipitated by chemical or spectroscopic methods.