Mechanism of attenuation of skeletal muscle atrophy by zinc-α2-glycoprotein

The mechanism by which the adipokine zinc-a2-glycoprotein (ZAG) increases the mass of gastrocnemius, but not soleus muscle of diabetic mice, has been evaluated both in vivo and in vitro. There was an increased phosphorylation of both double-stranded RNA-dependent protein kinase and its substrate, eukaryotic initiation factor-2a, which was attenuated by about two-thirds in gastrocnemius but not soleus muscle of ob/ob mice treated with ZAG (50 µg, iv daily) for 5 d. ZAG also reduced the expression of the phospho forms of p38MAPK and phospholipase A2, as well as expression of the ubiquitin ligases (E3) muscle atrophy F-box/atrogin-1 and muscle RING finger protein, and the increased activity of both caspase-3 and casapse-8 to values found in nonobese controls. ZAG also increased the levels of phospho serine-threonine kinase and mammalian target of rapamycin in gastrocnemius muscle and reduced the phosphorylation of insulin receptor substrate-1 (Ser307) associated with insulin resistance. Similar changes were seen with ZAG when murine myotubes were incubated with high glucose concentrations (10 and 25 mm), showing that the effect of ZAG was direct. ZAG produced an increase in cAMP in murine myotubes, and the effects of ZAG on protein synthesis and degradation in vitro could be replicated by dibutyryl cAMP. ZAG increased cAMP levels of gastrocnemius but not soleus muscle. These results suggest that protein accretion in skeletal muscle in response to ZAG may be due to changes in intracellular cAMP and also that ZAG may have a therapeutic application in the treatment of muscle wasting conditions.

A combinatorial approach to the chemical synthesis and biological evaluation of 3,4,5-trisubstiituted furan-2(5H)-ones

Many important natural products contain the furan-2(5H)-one structure. The structure of this molecule lends itself to manipulation using combinatorial techniques due to the presence of more than one site for the attachment of different suhstituents. By developing different reaction schemes at the three sites available for attachment on the furan-2(5H)-one scaffold, combinatorial chemistry techniques can be employed to assemble libraries of novel furan 2(5H)-ones. These libraries can then be entered into various biological screening programmes. This approach will enable a vast diversity or compounds to be examined, in the hope or finding new biologically active Iead structures. The work in this thesis has investigated the potential that combinatorial chemistry has in the quest for new biologically active lead structures based on the furan-2(5H)-one structure. Different reactions were investigated with respect to their suitability for inclusion in a library. Once sets of reactions at the various sites had been established, the viability of these reactions in the assembly of combinatorial libraries was investigated. Purification methods were developed, and the purified products entered into suitable biological screening tests. Results from some of these tests were optimised using structure activity relationships, and the resulting products re-screened. The screening tests performed were for anticancer and antimicrobial activity, cholecystokinin (CCK-B) antagonism and anti-inflammatory activity (in the quest for novel cyclo-oxygenase (COX-2) selective non-steroidal anti-inflammatory drugs). It has been shown that many reactions undergone by the furan-2(5H)-one structure are suitable for the assembly of a combinatorial library. Investigation into the assembly of different libraries has been carried out with initial screening results included. From this work, further investigation into combinatorial library assembly and structure activity relationships of screened reaction products can be undertaken.

Identifying a novel functional domain within the p115 tethering factor required for Golgi ribbon assembly and membrane trafficking

The tethering factor p115 has been shown to facilitate Golgi biogenesis and membrane traffic in cells in culture. However, the role of p115 within an intact animal is largely unknown. Here, we document that RNAi-mediated depletion of p115 in C. elegans causes accumulation of the yolk protein (YP170) in body cavity and the retention of the yolk receptor RME-2 in the ER and the Golgi within oocytes.Structure-function analyses of p115 have identified two homology (H1-2) regions within the N-terminal globular head and the coiled-coil 1 (CC1) domain as essential for p115 function. We identify a novel C-terminal domain of p115 as necessary for Golgi ribbon formation and cargo trafficking. We show that p115 mutants lacking the fourth CC domain (CC4) act in a dominant negative manner to disrupt Golgi and prevent cargo trafficking in cells containing endogenous p115. Furthermore, using RNAi-mediated "replacement" strategy we show that CC4 is necessary for Golgi ribbon formation and membrane trafficking in cells depleted of endogenous p115.p115 has been shown to bind a subset of ER-Golgi SNAREs through CC1 and CC4 domains (Shorter et al., 2002). Our findings show that CC4 is required for p115 function and suggest that both the CC1 and the CC4 SNARE-binding motifs may participate in p115-mediated membrane tethering.

Assembly of a high-dielectric constant thin TiOX layer directly on H-terminated semiconductor diamond

A high-dielectric constant (high-k) TiOx thin layer was fabricated on hydrogen-terminated diamond (H-diamond) surface by low temperature oxidation of a thin titanium layer in ambient air. The metallic titanium layer was deposited by sputter deposition. The dielectric constant of the resultant TiOx was calculated to be around 12. The capacitance density of the metal-oxide-semiconductor (MOS) based on the TiOx/H-diamond was as high as 0.75 µF/cm2 contributed from the high-k value and the very thin thickness of the TiOx layer. The leakage current was lower than 10-13 A at reverse biases and 10-7A at the forward bias of -2 V. The MOS field-effect transistor based on the high-k TiOx/H-diamond was demonstrated. The utilization of the high-k TiOx with a very thin thickness brought forward the features of an ideally low subthreshold swing slope of 65 mV per decade and improved drain current at low gate voltages. The advantages of the utilization high-k dielectric for diamond MOSFETs are anticipated.

A hydrothermally stable transition alumina by condensation-enhanced self-assembly and pyrolysis crystallization:application in the steam reforming of methane

The preparation of a steam-based hydrothermally stable transition alumina is reported. The gel was derived from a synthetic sol-gel route where Al-tri-sec-butoxide is hydrolysed in the presence of a non-ionic surfactant (EO20PO70EO20), HCl as the catalyst and water (H2O/Al = 6); the condensation was enhanced by treating the hydrolysed gel with tetrabutylammonium hydroxide (TBAOH), after which it was dried at 60 °C by solvent evaporation. The so-obtained mesophase was crystallized under argon at 1200 °C (1 h) producing a transition alumina containing δ/α, and possibly θ, alumina phases. Due to its surface acidity, the pyrolysis conditions transform the block copolymer into a cross-linked char structure that embeds the alumina crystallites. Calcination at 650 °C generates a fully porous material by burning the char; a residual carbon of 0.2 wt.% was found, attributed to the formation of surface (oxy)carbides. As a result, this route produces a transition alumina formed by nanoparticles of about 30 nm in size on average, having surface areas in the range of 59-76 m2 g-1 with well-defined mesopores centered at 14 nm. The material withstands steam at 900 °C with a relative surface area rate loss lower than those reported for δ-aluminas, the state-of-the-art MSU-X γ-alumina and other pure γ-aluminas. The hydrothermal stability was confirmed under relevant CH4 steam reforming conditions after adding Ni; a much lower surface area decay and higher CH4 conversion compared to a state-of-the-art MSU-X based Ni catalyst were observed. Two effects are important in explaining the properties of such an alumina: the char protects the particles against sintering, however, the dominant effect is provided by the TBAOH treatment that makes the mesophase more resistant to coarsening and sintering. This journal is © the Partner Organisations 2014.