Disparate effects of adhesion and degranulation of platelets on myocardial and coronary function in postischaemic hearts

Pre-mRNA splicing is an important regulatory step in the expression of most eukaryotic genes. In vitro studies have shown splicing to occur within 50-60 S multi-component ribonucleoprotein (RNP) complexes termed spliceosomes. Studies of mammalian cell nuclei have revealed larger complexes that sediment at 200 S in sucrose gradients, termed large nuclear RNP (lnRNP) particles. These particles contain all factors required for pre-mRNA splicing, including the spliceosomal U snRNPs and protein splicing factors. Electron microscopy has shown them to consist of four apparently similar substructures. In this study, mass measurements by scanning transmission electron microscopy of freeze-dried mammalian lnRNP preparations, both confirm the similarity between the lnRNP particles and reveal the mass uniformity of their subunits. Thus, the tetrameric lnRNP particle has a mass of 21.1(+/-1.6) MDa, while each repeating subunit has a mass of 4.8(+/-0.5) MDa, which is close to the estimated mass of the fully assembled 60 S spliceosome. The 1.9 MDa discrepancy between the lnRNP particle's mass and the cumulative masses of its four subunits may be attributed to an additional domain frequently observed in the micrographs. Notably, strands and loops of RNA were often seen emanating from lnRNP particles positively stained with uranyl formate. Our results support the idea that the nuclear splicing machine is a supraspliceosome complex. For clarity, we define spliceosomes devoid of pre-mRNA as spliceosome cores, and propose that the supraspliceosome is constructed from one pre-mRNA, four spliceosome cores, each composed mainly of U snRNPs, and additional proteins. In this way a frame is provided to juxtapose exons about to be spliced.     

New cis-configured aziridine-2-carboxylates as aspartic acid protease inhibitors

A series of 52 cis‐configured 1‐alkyl‐3‐phenylaziridine‐2‐carboxylates were synthesized as new pseudo‐irreversible inhibitors of Candida albicans secreted aspartic acid protease 1 (SAP1), SAP2, SAP3, and SAP8. Some of the compounds, which were obtained as diastereomers with S,S‐ and R,R‐configured aziridine rings by Cromwell synthesis of racemic (2R,3S+2S,3R)‐dibromophenylpropionic acid ester with amines, followed by ester hydrolysis and coupling to hydrophobic amino acid esters, were separated by preparative HPLC. The absolute configuration of the aziridine ring was assigned by a combination of experimental circular dichroism (CD) investigations and quantum chemical CD calculations. In agreement with previous docking studies, the diastereomers all exhibit similar activity. The compounds were found to be more active against the related mammalian enzyme cathepsin D, presumably due to productive interactions of the N‐alkyl substituent with the highly lipophilic S2 pocket. The most active inhibitors ( 5 , 9 , 10 , 21 , and 28 ), characterized by benzyl, cyclohexylmethyl, tert‐butyl, or 1,4‐dimethylpentyl moieties at the aziridine nitrogen atom, exhibit k_2nd values between 500 and 900×10³ M ^?1 min^?1 and K_i values near or below 1 μM for cathepsin D.     

Development of novel peptidomimetics containing a vinyl sulfone moiety as proteasome inhibitors

Proteasome inhibition is a topic of great interest in anticancer research. The proteolytic activity of this multicatalytic complex relies on three subunits, β1, β2 and β5, containing a caspase-like, a trypsin-like and a chymotrypsin-like active site, respectively. Several studies have demonstrated that, of the three activities, the chymotrypsin-like activity was the most necessary for cell viability and protein processing. Thus, most efforts towards the development of proteasome inhibitors have focused on the selective inhibition of the β5 subunit active site. Herein, we report the design and synthesis of a series of conformationally constrained tripeptidyl vinyl sulfones were determined to be good inhibitors of the chymotrypsin-like activity of proteasome, with K(I) values in the sub-micromolar to micromolar range. These compounds were also tested against bovine pancreatic α-chymotrypsin and human cathepsin B and L, revealing a good selectivity for the target enzyme over these related enzymes.     

High pressure/temperature treatments to inactivate highly infectious prion subpopulations

High hydrostatic pressure can be used for gentle pasteurization of food as well as a physical parameter to study the stability and energetics of biomolecules. High pressure has been recently postulated as a feasible technology to decontaminate scrapie infectious materials. Here we discuss the kinetic parameters driving the inactivation of the Transmissible Spongiform Encephalopathy agents and the perspectives of pressure as a thermodynamic parameter to obtain a deeper insight into the aggregation of the 263K strain of scrapie. At 60–80 °C an efficient pressure inactivation of infectious scrapie prions was observed during short pressure treatments at 800 MPa (3 × 5 min cycles). However, discrepancies between in vivo infectivity counts and the results of an enzyme immunoassay further revealed that the infectivity was inactivated faster and much more efficiently than PrP^res was degraded, indicating that pressure affects a highly infectious subpopulation of scrapie prions.

Industrial relevance

Conventional inactivation methods for the agents of the Transmissible Spongiform Encephalopathies are not compatible with food processing due to the required aggressive conditions. High pressure assisted thermal sterilization methods are nowadays attracting attention as a food preservation technology able to preserve quality attributes. Here the stark effects in the secondary prion structure of high pressure combined with heat below the usual denaturing conditions were investigated with specific tests. This technology was proven to be a feasible alternative to achieve the decontamination of TSE risk materials at milder conditions. Kinetic data provided here should be useful to establish criteria to inactivate prions under pressure.     

PROGRESS REPORT ON INVESTIGATION OF SAGGER CLAYS. VI The Life of the Sagger as Affected by Varying Certain Properties1

This report presents the results obtained in a study of sagger bodies and represents an enlargement of a similar study of a preliminary nature, the results of which have been published. The clays and grogs are combined to give bodies having wide variations in body structure and in the several properties which were studied. Data are given on the modulus of elasticity, transverse breaking strength, plastic flow, thermal expansion, and resistance to failure due to heat shock of thirty-five laboratory prepared bodies and ten commercial bodies after firing at from one to three different temperatures. For comparative purposes data are given on two series of bodies, the one series containing coarse grog and the other fine grog. In addition body compositions were varied in order to compare the effect on sagger life of using open- and close-firing grogs.     

Improving the tribological characteristics of tool and mould surfaces by machine hammer peening

The surface treatment by machine hammer peening can be applied in order to functionalise surfaces made of different materials. Especially in mould and die making high potentials can be found by improved tribological properties. Particularly due to the fact that an orthogonal impact direction of the used plunger tool cannot be realised at all events, the influence of a given impact angle is investigated as part of this work. Furthermore the possibility of embedding WC particles into the near-surface zones of tool steel materials is presented, which offers new possibilities to improve the tribological performance of components.