I. Darren Grice

The immunologically distinct O antigens from Francisella tularensis subspecies tularensis and Francisella novicida are both virulence determinants and protective antigens.

ABSTRACT We have determined the sequence of the gene cluster encoding the O antigen in Francisella novicida and compared it to the previously reported O-antigen cluster in Francisella tularensis subsp. tularensis. Immunization with purified lipopolysaccharide (LPS) from F. tularensis subsp. tularensis or F. novicida protected against challenge with Francisella tularensis subsp. holarctica and F. novicida, respectively. The LPS from F. tularensis subsp. tularensis did not confer protection against challenge with F. novicida, and the LPS from F. novicida did not confer protection against challenge with F. tularensis subsp. holarctica. Allelic replacement mutants of F. tularensis subsp. tularensis or F. novicida which failed to produce O antigen were attenuated, but exposure to these mutants did not induce a protective immune response. The O antigen of F. tularensis subsp. tularensis appeared to be important for intracellular survival whereas the O antigen of F. novicida appeared to be critical for serum resistance and less important for intracellular survival.

Inhibition of platelet aggregation and 5-HT release by extracts of Australian plants used traditionally as headache treatments.

To identify potential migraine therapeutics, extracts of eighteen plants were screened to detect plant constituents affecting ADP induced platelet aggregation and [14C]5-hydroxytryptamine (5-HT) release. Extracts of the seven plants exhibiting significant inhibition of platelet function were reanalysed in the presence of polyvinyl pyrrolidone (PVP) to remove polyphenolic tannins that precipitate proteins. Two of these extracts no longer exhibited inhibition of platelet activity after removal of tannins. However, extracts of Crataegus monogyna, Ipomoea pes-caprae, Eremophila freelingii, Eremophila longifolia, and Asteromyrtus symphyocarpa still potently inhibited ADP induced human platelet [14C]5-HT release in vitro, with levels ranging from 62 to 95% inhibition. I. pes-caprae, and C. monogyna also caused significant inhibition of ADP induced platelet aggregation. All of these plants have been previously used as traditional headache treatments, except for C. monogyna which is used primarily for protective effects on the cardiovascular system. Further studies elucidating the compounds that are responsible for these anti-platelet effects are needed to determine their exact mechanism of action.

Investigation into the Feasibility of Thioditaloside as a Novel Scaffold for Galectin-3-Specific Inhibitors

Galectin‐3 is extensively involved in metabolic and disease processes, such as cancer metastasis, thus giving impetus for the design of specific inhibitors targeting this β‐galactose‐binding protein. Thiodigalactoside (TDG) presents a scaffold for construction of galectin inhibitors, and its inhibition of galectin‐1 has already demonstrated beneficial effects as an adjuvant with vaccine immunotherapy, thereby improving the survival outcome of tumour‐challenged mice. A novel approach—replacing galactose with its C2 epimer, talose—offers an alternative framework, as extensions at C2 permit exploitation of a galectin‐3‐specific binding groove, thereby facilitating the design of selective inhibitors. We report the synthesis of thioditaloside (TDT) and crystal structures of the galectin‐3 carbohydrate recognition domain in complexes with TDT and TDG. The different abilities of galactose and talose to anchor to the protein correlate with molecular dynamics studies, likely explaining the relative disaccharide binding affinities. The feasibility of a TDT scaffold to enable access to a particular galectin‐3 binding groove and the need for modifications to optimise such a scaffold for use in the design of potent and selective inhibitors are assessed.

Temperature-dependent phenotypic variation of Campylobacter jejuni lipooligosaccharides

BackgroundCampylobacter jejuni is a major bacterial cause of food-borne enteritis, and its lipooligosaccharide (LOS) plays an initiating role in the development of the autoimmune neuropathy, Guillain-Barré syndrome, by induction of anti-neural cross-reactive antibodies through ganglioside molecular mimicry.ResultsHerein we describe the existence and heterogeneity of multiple LOS forms in C. jejuni strains of human and chicken origin grown at 37°C and 42°C, respectively, as determined on sodium dodecyl sulphate-polyacrylamide electrophoresis gels with carbohydrate-specific silver staining and blotting with anti-ganglioside ligands, and confirmed by nuclear magnetic resonance (NMR) spectroscopy. The C. jejuni NCTC 11168 original isolate (11168-O) was compared to its genome-sequenced variant (11168-GS), and both were found to have a lower-Mr LOS form, which was different in size and structure to the previously characterized higher-Mr form bearing GM1 mimicry. The lower-Mr form production was found to be dependent on the growth temperature as the production of this form increased from ~5%, observed at 37°C to ~35% at 42°C. The structure of the lower-Mr form contained a β-D-Gal-(1→3)-β-D-GalNAc disaccharide moiety which is consistent with the termini of the GM1, asialo-GM1, GD1, GT1 and GQ1 gangliosides, however, it did not display GM1 mimicry as assessed in blotting studies but was shown in NMR to resemble asialo-GM1. The production of multiple LOS forms and lack of GM1 mimicry was not a result of phase variation in the genes tested of NCTC 11168 and was also observed in most of the human and chicken isolates of C. jejuni tested.ConclusionThe presence of differing amounts of LOS forms at 37 and 42°C, and the variety of forms observed in different strains, indicate that LOS form variation may play a role in an adaptive mechanism or a stress response of the bacterium during the colonization of different hosts.

Isolation of bioactive compounds that relate to the anti-platelet activity of Cymbopogon ambiguus.

Infusions and decoctions of Cymbopogon ambiguus have been used traditionally in Australia for the treatment of headache, chest infections and muscle cramps. The aim of the present study was to screen and identify bioactive compounds from C. ambiguus that could explain this plants anti-headache activity. A dichloromethane extract of C. ambiguus was identified as having activity in adenosine-diphosphate-induced human platelet aggregation and serotonin-release inhibition bioassays. Subsequent fractionation of this extract led to the isolation of four phenylpropenoids, eugenol, elemicin, eugenol methylether and trans-isoelemicin. While both eugenol and elemicin exhibited dose-dependent inhibition of ADP-induced human platelet serotonin release, only eugenol displayed potent inhibitory activity with an IC50 value of 46.6 μM, in comparison to aspirin, with an IC50 value of 46.1 μM. These findings provide evidence to support the therapeutic efficacy of C. ambiguus in the non-conventional treatment of headache and inflammatory conditions.

Phosphitylation via the Mitsunobu reaction

Treatment of a dialkyl phosphite with triphenylphosphine and diisopropyl azodicarboxylate in toluene, followed by addition of an alcohol, results in the formation of the corresponding trialkyl phosphite. Similarly, dialkyl phosphonites can be synthesised from monoalkyl phosphites (alkyl phosphinates).

Aqueous and Ethanol Extracts of Australian Cane Toad Skins Suppress Pro-Inflammatory Cytokine Secretion in U937 Cells via NF-κB Signaling Pathway

Toad skin extracts, such as aqueous extracts (AE) of Chinese toad skins, have demonstrated therapeutic benefits for a range of diseases including pain, inflammation, swelling, heart failure, and various types of cancers. In this study, we investigated the anti‐inflammatory potential of an AE (0.1–10 μg/mL) and a 60% ethanol extract (EE; 0.1–10 μg/mL) from Australian cane toad (Bufo marinus) skins and the known bioactive compound, bufotenine (BT; 0.1–10 nM). The assay employed a model of the human monocyte cell line U937 stimulated with lipopolysaccharide (LPS) and phorbol 12‐myristate 13‐acetate (PMA) for the release of tumor necrosis factor (TNF)‐α and interleukin (IL)‐6. We demonstrated that AE, EE, and BT significantly inhibited the release and expression of TNF‐α and IL‐6 in a dose‐dependent manner when the cells were pre‐treated at non‐cytotoxic concentrations. Further investigation revealed that the inhibition of TNF‐α and IL‐6 release and expression was associated with the suppression of nuclear factor (NF)‐kappa (κ)B activation. These results indicate that AE, EE, and BT are strong inflammation inhibitors, thus have the potential for further development as anti‐inflammatory therapeutic agents from a natural source regarded as a feral pest in Australia. J. Cell. Biochem. 117: 2769–2780, 2016.

Indolealkylamines from Toad Vertebrates and Sea Invertebrates - Their Identification and Potential Activities on the Central Nervous System

Indolealkylamines (IAAs) are biogenic amines and derivatives of 5-hydroxytryptamine, acting primarily on serotonin receptors. IAAs are often considered the most thoroughly investigated group of aromatic amines in the amphibian skin. On the contrary, at present the detailed knowledge of these compounds in lower organisms is still limited and the biogenic amine receptors, mediating hormonal and modulatory functions, are largely unknown in primitive invertebrates. However, some active research is currently underway investigating this class of biogenic amines. Notably, during the last three decades several investigations have demonstrated the biological activity of endogenous biogenic amines in cnidarians, which are known to be the lowest beings equipped with an effective, even though rudimentary, nervous system. Toads, especially those from the Bufonidae family, constitute a significant part of the amphibian family and are an identified source of IAAs. To date fourteen IAAs have been identified in the skins of toad species. All are 5-substituted IAA derivatives acting mainly on the central nervous system (CNS), with most exhibiting some degrees of 5-HT2A receptor selectivity. This selective ability presents potential for their use in the development of treatments for various disorders such as schizophrenia, depression, anxiety, obsessive-compulsive disorders and chronic pain conditions. There are indications that some IAAs may also show subclass selectivity through binding to multiple 5-HT receptor subtypes. Thus, there exists an additional promising platform for the development of therapeutics targeting multiple 5-HT receptors. In this review, IAAs occurring naturally in various species of toad skins, which have been identified and isolated since 1944 are summarized and comparisons are made with similar biogenic amines recognized in cnidarians to date. Such comparisons highlight the potential to utilize existing knowledge gathered from vertebrates, such as toads in order to improve the understanding of the activities of such compounds in lower invertebrates.

A new cytotoxic diterpenoid glycoside from the leaves of Blumea lacera and its effects on apoptosis and cell cycle

Abstract A new diterpenoid glycoside, 6E,10E,14Z-(3S)-17-hydroxygeranyllinalool-17-O-β-d-glucopyranosyl-(1 → 2)-[α-l-rhamnopyranosyl-(1 → 6)]-β-d-glucopyranoside (1) together with the known diterpenoid glycoside (2) and two known flavonoid glycosides (3, 4) were isolated from the methanol extract of Blumea lacera leaves. The structures were determined by the interpretation of their spectroscopic data and comparison with the literature. All compounds were isolated for the first time from B. lacera and evaluated for their cytotoxic activity. Only the new compound (1) showed strong cytotoxic activity with the lowest IC50 value (8.3 μM) being displayed against MCF-7 breast cancer cells. In apoptosis and cell cycle analysis, 1 revealed strong apoptotic activity against MCF-7 cells (45.5% AV+/PI−) after 24 h, but showed no arresting of any of the cell cycle phases in MCF-7.

Analytical Approaches Towards the Structural Characterization of Microbial Wall Glycopolymers

Publisher Summary Glycans are structurally complex molecules and, as such, their structural characterization is a challenging task. The precise strategy to be applied is dictated by the level of information required and the expertise of the research team involved; however, the most comprehensive and informative studies employ aspects of enzymatic, chemical, chromatographic, MS, and NMR methods to complete the characterization process. This chapter outlines the strategies for the use of the analytical techniques of nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) toward the elucidation of the structures of microbial wall glycans. Specifically, the determination of the structure of capsular polysaccharide, core oligosaccharide or O-antigen utilizing 1D, 1D selective and 2D homonuclear, and heteronuclear NMR experiments and database resources is presented. Also described is the application of high-resolution magic angle spinning techniques for studying glycopolymer structures. MS sample derivatization strategies along with associated gas chromatography-mass spectrometry, sugar, linkage, and absolute configuration analyses are outlined. The use of fast atom bombardment, matrix-assisted laser desorption ionization, and electrospray-mass spectrometry ionization techniques along with their associated mass analyzers are presented for characterizing oligosaccharide, lipid A, lipooligosaccharide, lipopolysaccharide, and capsular polysaccharide glycan structures.