Concentrations of monosaccharides and their amino and alcohol derivatives in human preovulatory follicular fluid

The study purpose was to compare sugar and polyol concentrations in preovulatory ovarian follicular fluid (FF) with those in the circulation. Samples of FF and peripheral venous blood were obtained after an overnight fast from 14 women attending an IVF program. High performance liquid chromatography measurements of seven polyols, two aminohexoses and four hexoses were the main outcome measures. Glucose concentrations in FF and plasma were 2781.26 +/- 205.64 and 4431.25 +/- 65.17 microM, respectively (P < 0.001). Mannose concentration in FF was 38.99 +/- 3.33 microM, significantly lower than plasma concentration (55.38 +/- 2.29 microM; P < 0.001). A concentration gradient from plasma to FF was also significant for glycerol (99.41 +/- 8.47 versus 74.32 +/- 6.54 microM; P < 0.002), galactose (31.69 +/- 1.58 versus 26.73 +/- 1.93 microM; P < 0.01) and galactosamine (11.49 +/- 0.69 versus 6.38 +/- 0.59 microM; P < 0.001). The plasma-to-FF concentration difference was greatest for glucose (1649.99 +/- 204.09 microM). There was a significant correlation between plasma and FF concentrations for galactose and glycerol. This study supports a substantial utilization of glucose by the oocyte/granulosa cells complex, and documents a significant concentration gradient from plasma to FF for glycerol, mannose, galactose and galactosamine. These plasma-FF differences may reflect both utilization of these carbohydrates by the cells of the preovulatory ovarian follicle and/or transport characteristics of these cells.

Hydrogen peroxide derived from amine oxidation mediates the interaction between aminosugars and semicarbazide-sensitive amine oxidase

Semicarbazide-sensitive amine oxidase (SSAO) also functions as a vascular-adhesion protein (VAP-1). The nature of the target site on lymphocytes to which endothelial-cell SSAO/VAP-1 binds is unknown. We have shown that amino sugars (galactosamine, glucosamine and mannosamine), which are not SSAO substrates, can bind to the enzyme as reversible inhibitors. Thus, they serve as a model system in which to study the interaction process. Binding occurred during substrate (benzylamine) oxidation but not when the amino sugar was incubated, for extended periods, with SSAO alone. These results suggest that one, or more of the products of the SSAO-catalysed amine oxidation might be necessary for the inhibitory process to occur. Two of the reaction products of benzylamine oxidation, benzaldehyde and ammonia were found to have no effect on the inhibition of SSAO by galactosamine. Preincubation of the enzyme with galactosamine plus H(2)O(2) was, however, found to result in time-dependent inhibition. This is not a result of the non-enzymic reaction between H(2)O(2) and the amino sugar, since preincubation of galactosamine with H(2)O(2) alone, for extended periods, did not give rise to an inhibitory species. The amount of exogenously added H(2)O(2) necessary for inhibition was very much greater than that formed during substrate oxidation. These results suggest that the H(2)O(2) formed as a product of the SSAO-catalysed oxidation reaction is more efective in promoting the binding of amino sugars.

A metabonomics study of the hepatotoxicants galactosamine, methylene dianiline and clofibrate in rats

The efficacy of high-resolution (1)H nuclear magnetic resonance ((1)H-NMR) spectroscopy-based metabonomics was studied in a model of rat liver toxicity. Hepatotoxicities were induced in male rats using methylene dianiline, clofibrate and galactosamine. Twenty-four-hr urine from days 1 to 5 after treatment were subjected to (1)H-NMR evaluation of the biochemical effects. Blood were also taken at Days 2, 3 and 5 to examine biochemical changes associated with hepatotoxicities, and histopathological changes were evaluated at termination. Increases in liver enzymes were observed in animals treated with methylene dianiline or galactosamine, and histopathological analysis revealed changes associated with hepatobiliary damage and hepatocellular necrosis in methylene dianiline- and galactosamine-treated animals, respectively. Principal component analysis and statistical Spotfire analyses were used to visualize similarities and differences in urine biochemical profiles produced by (1)H-NMR spectra. The biochemical effects of methylene dianiline and galactosamine were characterized by elevated levels of glucose, fructose, beta-hydroxybutyrate, alanine, acetoacetate, lactate and creatine and decreased levels of hippurate, 2-oxoglutarate, citrate, succinate, trimethylamine-N-oxide, taurine and N-acetylglutamate in rat urine. Clofibrate treatment elevated the levels of N-methylnicotinamide and 3,4-dihydroxymandelate and decreased the levels of 2-oxoglutarate and N-acetylaspartate. This work shows that combinations of (1)H-NMR and pattern recognition are powerful tools in the evaluation of the biochemical effects of xenobiotics in liver.

Structure and biosynthesis of free lipid A molecules that replace lipopolysaccharide in Francisella tularensis subsp. novicida

Francisella tularensis subsp. novicida U112 phospholipids, extracted without hydrolysis, consist mainly of phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, and two lipid A species, designated A1 and A2. These lipid A species, present in a ratio of 7:1, comprise 15% of the total phospholipids, as judged by 32Pi labeling. Although lipopolysaccharide is detectable in F. tularensis subsp. novicida U112, less than 5% of the total lipid A is covalently linked to it. A1 and A2 were analyzed by electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry, gas chromatography/mass spectrometry, and NMR spectroscopy. Both compounds are disaccharides of glucosamine, acylated with primary 3-hydroxystearoyl chains at positions 2, 3, and 2' and a secondary palmitoyl residue at position 2'. Minor isobaric species and some lipid A molecules containing a 3-hydroxypalmitoyl chain in place of 3-hydroxystearate are also present. The 4'- and 3'-positions of A1 and A2 are not derivatized, and 3-deoxy-d-manno-octulosonic acid (Kdo) is not detectable. The 1-phosphate groups of both A1 and A2 are modified with an alpha-linked galactosamine residue, as shown by NMR spectroscopy and gas chromatography/mass spectrometry. An alpha-linked glucose moiety is attached to the 6'-position of A2. The lipid A released by mild acid hydrolysis of F. tularensis subsp. novicida lipopolysaccharide consists solely of component A1. F. tularensis subsp. novicida mutants lacking the arnT gene do not contain a galactosamine residue on their lipid A. Formation of free lipid A in F. tularensis subsp. novicida might be initiated by an unusual Kdo hydrolase present in the membranes of this organism.

Red potato extract protects from D-galactosamine-induced liver injury in rats

The protective effects of red potato extract (RPE) as to liver damage were determined in D-galactosamine (GalN)-intoxicated rats. Increases in serum aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase activities, all of which were induced by GalN injection, decreased in RPE administered rats, suggesting that RPE acts as a functional food showing anti-hepatotoxicity.

Sequence analyses of fimbriae subunit FimA proteins on Actinomyces naeslundii genospecies 1 and 2 and Actinomyces odontolyticus with variant carbohydrate binding specificities

Background

Actinomyces naeslundii genospecies 1 and 2 express type-2 fimbriae (FimA subunit polymers) with variant Galβ binding specificities and Actinomyces odontolyticus a sialic acid specificity to colonize different oral surfaces. However, the fimbrial nature of the sialic acid binding property and sequence information about FimA proteins from multiple strains are lacking.

Results

Here we have sequenced fimA genes from strains of A.naeslundii genospecies 1 (n = 4) and genospecies 2 (n = 4), both of which harboured variant Galβ-dependent hemagglutination (HA) types, and from A.odontolyticus PK984 with a sialic acid-dependent HA pattern. Three unique subtypes of FimA proteins with 63.8–66.4% sequence identity were present in strains of A. naeslundii genospecies 1 and 2 and A. odontolyticus. The generally high FimA sequence identity (>97.2%) within a genospecies revealed species specific sequences or segments that coincided with binding specificity. All three FimA protein variants contained a signal peptide, pilin motif, E box, proline-rich segment and an LPXTG sorting motif among other conserved segments for secretion, assembly and sorting of fimbrial proteins. The highly conserved pilin, E box and LPXTG motifs are present in fimbriae proteins from other Gram-positive bacteria. Moreover, only strains of genospecies 1 were agglutinated with type-2 fimbriae antisera derived from A. naeslundii genospecies 1 strain 12104, emphasizing that the overall folding of FimA may generate different functionalities. Western blot analyses with FimA antisera revealed monomers and oligomers of FimA in whole cell protein extracts and a purified recombinant FimA preparation, indicating a sortase-independent oligomerization of FimA.

Conclusion

The genus Actinomyces involves a diversity of unique FimA proteins with conserved pilin, E box and LPXTG motifs, depending on subspecies and associated binding specificity. In addition, a sortase independent oligomerization of FimA subunit proteins in solution was indicated.

Activation of mitogen activated protein kinase (MAPK) during D-galactosamine intoxication in the rat liver

A significant increase in plasma glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase was observed 6 h after intraperitoneal administration of D-galactosamine (D-Galn). Three hours after administration of D-Galn, the vitamin C concentration in the liver decreased significantly compared to that in a control group and thereafter the hepatic vitamin C concentration remained at a significantly lower level. Phosphorylated JNK (c-Jun NH2-terminal kinase) and phosphorylated ERK (extracellular signal-regulated kinase) started increasing 3 h after D-Galn treatment and remained at a high level for 6-12 h after the treatment, while phosphorylated p38 MAPK increased significantly 6 h after D-Galn administration. These results indicated that oxidative stress and the activation of JNK and ERK took place almost simultaneously, followed by the activation of p38 MAPK.

Bone marrow progenitors are not the source of expanding oval cells in injured liver

Liver progenitor/oval cells differentiate into hepatocytes and biliary epithelial cells, repopulating the liver when the regenerative capacity of hepatocytes is impaired. Recent studies have shown that hematopoietic bone marrow (BM) stem/progenitor cells can give rise to hepatocytes in diseased/damaged liver. One study has reported that BM cells can transdifferentiate into liver progenitor/oval cells, but it has not been proven that the latter can repopulate the liver. To answer this question, we have lethally irradiated female DPP4(-) mutant F344 rats and transplanted them with 50 million wild-type male F344 BM cells. One month after transplantation, the recipient BM was reconstituted with male hematopoietic cells, determined by quantitative polymerase chain reaction using primers for Y chromosome-specific sry gene. In addition, DPP4(+) cells, single or in clusters and predominantly in the periportal region, were detected in all liver sections of recipient rats. Animals were subjected to the following three different liver injury protocols for activation and expansion of oval cells: D-galactosamine, retrorsine/partial hepatectomy (Rs/PH), and 2-acetylaminofluorene/partial hepatectomy (2-AAF/PH). In all three models, prominent expansion and accumulation of cytokeratin 19-positive (CK-19(+)) oval cells was observed. However, most of the DPP4(+) clusters dispersed over time, and their total number decreased. Very few oval cells (less than 1%) showed double DPP4/CK-19 labeling. None of the small hepatocytic clusters in the Rs/PH or 2-AAF/PH model were comprised of DPP4(+) cells. These data demonstrate that the sources of oval cells and small hepatocytes in the injured liver are endogenous liver progenitors and that they do not arise through transdifferentiation from BM cells.

Cellular addresses; step one in creating a glycocode

In this issue of Chemistry & Biology, a library screening approach reveals at least four types of enzymes that attach galactosamine to build cell surface mucin-type glycoproteins. A better molecular understanding of how these information-carrying oligosaccharides are created sets the stage for designing more selective inhibitors and potential therapeutics.

In vivo and in vitro cytokine modulatory activity of newly synthesised 2-aminotetraline derivatives

In the present study, the protective effect of newly synthesised 2-aminotetralines was investigated in murine models of toxic shock. A few derivatives protected mice against lethality induced by lipopolysaccharide from different bacterial strains and shock induced by staphylococcal enterotoxin B in mice sensitized by D-Galactosamine (D-Galn). Notably, one derivative, S(-)-2-amino-6-fluoro-7-methoxy-1,2,3,4 tetrahydronaphthalene hydrochloride (ST1214), was also effective when administered orally (30 mg kg-1) in a therapeutic regimen. ST1214 markedly inhibited the production of the proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), Interleukin-1beta (IL-1beta), Interleukin-12 (IL-12), interferon-gamma (IFN-gamma), as well as the inflammatory mediator nitric oxide (NO), and concurrently enhanced the production of the anti-inflammatory cytokine IL-10. Moreover, ST1214 dose-dependently reduced TNF-alpha production by human peripheral blood mononuclear cells and promonocytic THP-1 cells in vitro. In the latter, ST1214 was found to inhibit lipopolysaccharide-induced TNF-alpha secretion but not cytokine mRNA accumulation. These results suggest that the mechanism of action of ST1214 involves blockade of posttranscriptional events of TNF-alpha production, apparently independent of p38 and ERK kinase activity. These results show beneficial effects of 2-aminotetralines in murine shock models and indicate a distinct counter-regulatory activity in down-regulating proinflammatory cytokine response, and upregulating IL-10. One derivative, i.e., ST1214, can be regarded as a lead compound in the development of novel drugs effective in anti-inflammatory strategies.

The glycine analogue, aminomethanesulfonic acid, inhibits LPS-induced production of TNF-alpha in isolated rat Kupffer cells and exerts hepatoprotective effects in mice

The activation of Kupffer cells represents a central mechanism of liver injury involving the production of TNF-alpha. It is known that glycine prevents LPS-induced production of TNF-alpha in isolated Kupffer cells. In this study, the possibility that glycine analogues might affect Kupffer cells was investigated. As a result, aminomethanesulfonic acid (AMS) inhibited the production of TNF-alpha in LPS-stimulated Kupffer cells. Furthermore, LPS treatment caused a transient increase in intracellular calcium ([Ca(2+)](i)) which was blunted by AMS. Thus, the addition of AMS is protective against the LPS-induced increase [Ca(2+)](i) and subsequent production of TNF-alpha. Moreover, in vivo studies demonstrated that pretreatment of mice with AMS increased the rate of survival after injection with LPS/d-gal and reduced the TNF-alpha serum level and the mRNA level in the liver. These results indicate that intake of AMS attenuates the LPS-induced hepatotoxicity resulting from activation of Kupffer cells.

d-Hexosaminate production by oxidative fermentation

Microbial production of D-hexosaminate was examined by means of oxidative fermentation with acetic acid bacteria. In most strains of acetic acid bacteria, membrane-bound D-glucosamine dehydrogenase (synonymous with an alternative D-glucose dehydrogenase distinct from quinoprotein D-glucose dehydrogenase) oxidized D-hexosamines to the corresponding D-hexosaminates in a stoichiometric manner. Conversion of D-hexosamines to the corresponding D-hexosaminates was observed with growing cells of acetic acid bacteria, and D-hexosaminate was stably accumulated in the culture medium even though D-hexosamine was exhausted. Since the enzyme responsible is located on the outer surface of the cytoplasmic membrane, and the enzyme activity is linked to the respiratory chain of the organisms, resting cells, dried cells, and immobilized cells of acetic acid bacteria were effective catalysts for D-hexosaminate production. D-Mannosaminate and D-galactosaminate were also prepared for the first time by means of oxidative fermentation, and three different D-hexosaminates were isolated from unreacted substrate by a chromatographic separation. In this paper, D-hexosaminate production by oxidative fermentation carried out mainly with Gluconobacter frateurii IFO 3264 is exemplified as a typical example.

Amino sugar phosphate levels in Giardia change during cyst wall formation

The parasite Giardia intestinalis exists as a trophozoite (vegetative) that infects the human small intestine, and a cyst (infective) that is shed in host faeces. Cyst viability in the environment depends upon a protective cyst wall, which consists of proteins and a unique beta(1-3) GalNAc homopolymer. UDP-GalNAc, the precursor for this polysaccharide, is synthesized from glucose by an enzyme pathway that involves amino sugar phosphate intermediates. Using a novel method of microanalysis by capillary electrophoresis, the levels of amino sugar phosphate intermediates in trophozoites before encystment, during a period of active encystment and after the peak of encystment were measured. These levels were used to deduce metabolic control of amino sugar phosphates associated with encystment. Levels of amino sugar phosphate intermediates increased during encystment, and then decreased to nearly non-encysting levels. The most pronounced increase was in glucosamine 6-phosphate, which is the first substrate unique in this pathway, and which is the positive effector for the pathway's putative rate-controlling enzyme, UDP-GlcNAc pyrophosphorylase. Moreover, more UDP-GalNAc than UDP-GlcNAc, its direct precursor, was detected at 24 h. It is postulated that the enhanced UDP-GalNAc is a result of enhanced synthesis of UDP-GlcNAc by the pyrophosphorylase, and its preferential conversion to UDP-GalNAc. These results suggest that kinetics of amino sugar phosphate synthesis in encysting Giardia favours the direction that supports cyst wall synthesis. The enzymes involved in synthesis of UDP-GalNAc and its conversion to cyst wall might be potential targets for therapeutic inhibitors of Giardia infection.

The genes and enzymes for the catabolism of galactitol, D-tagatose, and related carbohydrates in Klebsiella oxytoca M5a1 and other enteric bacteria display convergent evolution

Enteric bacteria (Enteriobacteriaceae) carry on their single chromosome about 4000 genes that all strains have in common (referred to here as "obligatory genes"), and up to 1300 "facultative" genes that vary from strain to strain and from species to species. In closely related species, obligatory and facultative genes are orthologous genes that are found at similar loci. We have analyzed a set of facultative genes involved in the degradation of the carbohydrates galactitol, D-tagatose, D-galactosamine and N-acetyl-galactosamine in various pathogenic and non-pathogenic strains of these bacteria. The four carbohydrates are transported into the cell by phosphotransferase (PTS) uptake systems, and are metabolized by closely related or even identical catabolic enzymes via pathways that share several intermediates. In about 60% of Escherichia coli strains the genes for galactitol degradation map to a gat operon at 46.8 min. In strains of Salmonella enterica, Klebsiella pneumoniae and K. oxytoca, the corresponding gat genes, although orthologous to their E. coli counterparts, are found at 70.7 min, clustered in a regulon together with three tag genes for the degradation of D-tagatose, an isomer of D-fructose. In contrast, in all the E. coli strains tested, this chromosomal site was found to be occupied by an aga/kba gene cluster for the degradation of D-galactosamine and N-acetyl-galactosamine. The aga/kba and the tag genes were paralogous either to the gat cluster or to the fru genes for degradation of D-fructose. Finally, in more then 90% of strains of both Klebsiella species, and in about 5% of the E. coli strains, two operons were found at 46.8 min that comprise paralogous genes for catabolism of the isomers D-arabinitol (genes atl or dal) and ribitol (genes rtl or rbt). In these strains gat genes were invariably absent from this location, and they were totally absent in S. enterica. These results strongly indicate that these various gene clusters and metabolic pathways have been subject to convergent evolution among the Enterobacteriaceae. This apparently involved recent horizontal gene transfer and recombination events, as indicated by major chromosomal rearrangements found in their immediate vicinity.

Lectin-binding sites in newborn human testis

The present investigation has been performed to obtain a complete distributional map of the oligosaccharidic component of the glycoconjugates in the testis of the human newborn. For this purpose seven eight HRP-conjugated lectins (SBA, DBA, PNA, WGA, OOA, UEAI, LTA and ConA) along with enzymatic treatments, were used. The Sertoli cells were characterized by the same sugar residues detected in the testes of adult healthy subject. Beta-N-acetyl-D-galactosamine in the Leydig's cells and a-N- acetyl-D-galactosamine anomer in the spermatogonia seem to be an unique feature of the newborn testis. For this fact SBA and DBA could be considered markers respectively of the Leydig's cells and of the spermatogonia in the newborn testis. Differences in lectin binding, between the newborn and the adult testis as the interstitial tissue and the endothelial cells of the capillary vessels are reported.

Mucin binding mitogenic lectin from freshwater Indian gastropod Belamyia bengalensis: purification and molecular characterization

A lectin was purified from the hemolymph of the freshwater Indian gastropod Belamyia bengalensis. The purification involved successive ion-exchange chromatography on Resource Q and gel filtration on Superose 12 column in FPLC system. Homogeneity of the protein was confirmed by polyacrylamide gel electrophoresis. Belamyia bengalensis lectin (BBL) was a monomeric protein with a molecular weight of 33 kDa as demonstrated by gel filtration and SDS-PAGE. It is a glycoprotein containing 6% total sugar and its activity is highly dependent on Ca(2+). BBL agglutinated human erythrocytes and is a blood group non-specific lectin. It agglutinated animal erythrocytes also. Hapten inhibition studies indicated that BBL shows binding specificity only for N-acetyl-D-glucosamine and N-acetyl-D-galactosamine at a high concentration among the mono- and oligosaccharides tested. Among the glycoproteins used for hemagglutination-inhibition assay, porcine submaxillary mucin was found to be the best inhibitor. Chemical modification studies indicated that Lys, Arg, and Trp are essential for the sugar-binding activity of BBL. Circular dichroism spectra revealed high content of alpha-helical structure in the lectin. BBL is a potent mitogen as it stimulated the T-lymphocyte proliferation, specifically the Th1 subset.

Bilirubin release induced by tumor necrosis factor in combination with galactosamine is toxic to mice

Application of tumor necrosis factor (TNF) in combination with galactosamine (GalN) in mice causes severe apoptosis of hepatocytes, resulting in complete destruction of the liver. Administration of high levels of unconjugated bilirubin and abnormally high production of unconjugated bilirubin have been reported to cause liver damage and are associated with several human pathologies. Serum alanine aminotransferase as well as total and direct bilirubin levels in mice were determined. Bilirubin levels are shown to significantly increase after a challenge with TNF/GalN in mice. Pretreatment with a heme oxygenase-1 inhibitor significantly prevents this release in bilirubin and offers significant protection against TNF/GalN-induced lethality. A correlation between the release of unconjugated bilirubin and the toxicity accompanied with this release is provided.

Small scale rat hepatocyte primary culture with applications for screening hepatoprotective substances

Isolated hepatocytes are known to maintain their physiological functions for over a week when cultured on Matrigel, artificially reconstituted from basement membrane components. Although this culture technique has been frequently used in research on hepatocyte functions, there has been a limitation on its application for small scale experiments due to some technical problems. By using micro-culture plates with 96 round-bottom wells, we succeeded in coating the wells uniformly with Matrigel. When the cultured hepatocytes were treated with either 10 mM, 15 mM, or 20 mM of acetaminophen or 1 mM, 10 mM, or 20 mM of D-galactosamine, the viability of the hepatocytes became 91.1%, 75.3%, 64.7%, and 79.0%, 43.8%, 26.2% of the non-treated control at 48 hours, respectively. Fractionated extracts of Glycyrrhiza glabra L. and Schisandra chinensis Baillon inhibited the action of acetaminophen or D-galactosamine in this model. From these results, we concluded that the microculture system presented here is capable of maintaining the in vivo characteristics of hepatocytes and is suitable for the screening of hepatoprotective substances.

Spherical bodies present within the germinal vesicle of Podarcis sicula previtellogenic oocyte derive from the temporaneous inactivation of ribosomal genes

In the present paper we have investigated the origin of the spherical bodies (SBs) present within the germinal vesicle of about 400 microm previtellogenic oocytes in the lizard Podarcis sicula. In particular, we have attempted to clarify whether they derive from the single, large nucleolus present in early diplotenic oocyte as a consequence of ribosomal gene inactivation. We have, therefore, experimentally induced a decrease in rRNA synthesis by injecting animals with D-galactosamine or by exposing them to low temperatures. The investigations carried out have demonstrated that both treatments induce significant ultrastructural changes in the nucleolar apparatus and in particular fragmentation and the formation of SBs comparable to those observed in germinal vesicle under physiological conditions. These results indicate that the germinal vesicle of Podarcis sicula has a nucleolar apparatus that significantly changes its aspect according to its functional status and reveal that in this species, the time course of rRNA synthesis is peculiar with respect to any other vertebrate oocyte studies so far.

Primary cultures of human hepatocytes as a tool in cytotoxicity studies: cell protection against model toxins by flavonolignans obtained from Silybum marianum

The aim of this study was to evaluate the cytoprotective effects upon primary human hepatocytes of silymarin extract and its main flavonolignans following exposure to the cytotoxic actions of model toxins. The conditions for the hepatocyte intoxication were optimised for allyl alcohol, carbon tetrachloride, D-galactosamine and paracetamol. Silymarin extract, silychristin and silydianin did not exert cytotoxicity (10-100 microM), whereas silybin and isosilybin at higher concentrations and after longer incubation periods were cytotoxic. All main flavonolignans of silymarin tested displayed concentration-dependent cytoprotection against the toxic effects of both allyl alcohol and carbon tetrachloride but neither paracetamol nor galactosamine. The best protection was achieved by silydianin and silychristin and to a lesser degree by silymarin, while silybin and isosilybin were less effective. It is concluded that these differing outcomes result from the varying abilities of the Silybum marianum substances tested to stabilize the cell membrane, exert antioxidant properties and exhibit intrinsic toxicity.

Capillary electrophoresis separation of autocondensation glycation products of glucosamine

Glucosamine nonenzymatically forms autocondensation glycation products under physiological conditions. Many studies have reported the effectiveness of oral doses of glucosamine alone or in combination with the galactosamine containing chondroitin in treating osteoarthritis. However, none of these studies has considered whether it is the glucosamine itself and/or one or more of its autocondensation products that exert this effect. A capillary electrophoresis method was developed to monitor the nonenzymatic formation of autocondensation glycation products of glucosamine, galactosamine, and mannosamine under physiological conditions. Major components were detected and separated by CE with a UV detector. The effects of concentration and incubation time on product species were determined. The method described is simple, rapid, and effective.

Metabolic profiling of the effects of D-galactosamine in liver spheroids using (1)H NMR and MAS-NMR spectroscopy

We report here the combined application of (1)H magic angle spinning (MAS) and high-resolution NMR spectroscopy and pattern recognition methods to study the effects of a model toxin (D-galactosamine) in liver spheroid cultures. (1)H NMR spectra of metabolic profiles of spheroids showed closer similarities to intact liver spectra than those of isolated hepatocytes, suggesting their superiority as an in vitro model system. Batches of spheroids were prepared from male Sprague Dawley rat livers and incubated in control hepatocyte medium or medium containing D-galactosamine (4 or 20 mM) for 4 or 24 h. Intact spheroids were packed into rotors and analyzed using MAS-NMR spectroscopy or homogenized and analyzed using conventional (1)H NMR spectroscopy. Principal components analysis, (PCA), of the NMR data revealed separation of control and D-galactosamine-treated spheroids based on changes in the concentrations of the triglycerides and elevations in cholesterol and esters. The absence of cholesterol in hepatocytes and the relative under-representation of the lipid resonances offer an important advantage of spheroids over hepatocytes for the (1)H NMR studies of fatty liver. Orthogonal signal correction (OSC) was used as a data filter to remove non-dose-dependent variation from the NMR spectra, improving the classification of treated spheroids and controls. This work shows that useful metabolic information can be obtained on drug toxicity by the use of combined MAS-NMR and high-resolution NMR of liver spheroids and that such studies may enhance the validation of in vitro techniques against in vivo models for metabolic profiling.

Biosynthesis of tunicamycin and metabolic origin of the 11-carbon dialdose sugar, tunicamine

Tunicamycin is a reversible inhibitor of polyprenol-phosphate: N-acetylhexosamine-1-phosphate translocases and is produced by several Streptomyces species. We have examined tunicamycin biosynthesis, an important but poorly characterized biosynthetic pathway. Biosynthetic precursors have been identified by incorporating radioactive and stable isotopes, and by determining the labeling pattern using electrospray ionization-collision induced dissociation-mass spectrometry (ESI-CID-MS), and proton, deuterium, and C-13 nuclear magnetic resonance (NMR) spectroscopy. Preparation and analysis of [uracil-5-(2)H]-labeled tunicamycin established the complete ESI-CID-MS fragmentation pathway for the major components of the tunicamycin complex. Competitive metabolic experiments indicate that 7 deuteriums incorporate into tunicamycin from [6,6'-(2)H,(2)H]-labeled D-glucose, 6 of which arise from D-GlcNAc and 1 from uridine and/or D-ribose. Inverse correlation NMR experiments (heteronuclear single-quantum coherence (HSQC)) of (13)C-labeled tunicamycin enriched from D-[1-(13)C]glucose suggest that the unique tunicamine 11-carbon dialdose sugar backbone arises from a 5-carbon furanose precursor derived from uridine and a 6-carbon N-acetylamino-pyranose precursor derived from UDP-D-N-acetylglucosamine. The equivalent incorporation of (13)C into both the alpha-1" and beta-11' anomeric carbons of tunicamycin supports a direct biosynthesis via 6-carbon metabolism. It also indicates that the tunicamine motif and the alpha-1"-linked GlcNAc residue are both derived from the same metabolic pool of UDP-GlcNAc, without significant differential metabolic processing. A biosynthetic pathway is therefore proposed for tunicamycin for the first time: an initial formation of the 11-carbon tunicamine sugar motif from uridine and UDP-GlcNAc via uridine-5'-aldehyde and UDP-4-keto-6-ene-N-acetylhexosamine, respectively, and subsequent formation of the anomeric-to-anomeric alpha, beta-1",11'-glycosidic bond.

Bacterial peptidoglycan-associated lipoprotein is released into the bloodstream in gram-negative sepsis and causes inflammation and death in mice

Gram-negative bacterial sepsis commonly causes organ dysfunction and death in humans. Although circulating bacterial toxins trigger inflammation in sepsis, little is known about the composition of bacterial products released into the blood during sepsis or the contribution of various bacterial components to the pathogenesis of sepsis. We have shown that diverse Gram-negative bacteria release bacterial peptidoglycan-associated lipoprotein (PAL) into serum. The present studies explored release of PAL into the blood during sepsis and tested the hypothesis that PAL contributes to bacterial virulence and inflammation in Gram-negative sepsis. Released PAL was detected in the blood of 94% of mice following cecal ligation and puncture. Picomolar to nanomolar levels of PAL stimulated macrophages and splenocytes from lipopolysaccharide-hyporesponsive (C3H/HeJ) mice. Injection of PAL into C3H/HeJ mice stimulated production of serum cytokines and increased pulmonary and myocardial expression of inflammatory markers. PAL caused death in sensitized C3H/HeJ mice. Mutant Escherichia coli bacteria with reduced levels of PAL or truncated PAL were less virulent than wild-type bacteria, as indicated by higher survival rates and lower circulating levels of interleukin 6 and bacteria in a model of peritonitis in lipopolysaccharide-responsive mice. The studies suggest that PAL may be an important bacterial mediator of Gram-negative sepsis.