A segmented polyurethane elastomer, originally developed for elastic thread, is now being used for molded prostheses. Performance of this material when used for components of a heart-assist system warrants a thorough investigation of its effectiveness in a variety of biomedical devices.

The genome of the extremely thermophilic bacterium Caldicellulosiruptor kronotskyensis encodes 19 surface layer (S-layer) homology (SLH) domain-containing proteins, the most in any Caldicellulosiruptor species genome sequenced to date. These SLH proteins include five glycoside hydrolases (GHs) and one polysaccharide lyase, the genes for which were transcribed at high levels during growth on plant biomass. The largest GH identified so far in this genus, Calkro_0111 (2,435 amino acids), is completely unique to C. kronotskyensis and contains SLH domains. Calkro_0111 was produced recombinantly in Escherichia coli as two pieces, containing the GH16 and GH55 domains, respectively, as well as putative binding and spacer domains. These displayed endo-and exoglucanase activity on the ␤-1,3-1,6-glucan laminarin. A series of additional truncation mutants of Calkro_0111 revealed the essential architectural features required for catalytic function. Calkro_0402, another of the SLH domain GHs in C. kronotskyensis, when produced in E. coli, was active on a variety of xylans and ␤-glucans. Unlike Calkro_0111, Calkro_0402 is highly conserved in the genus Caldicellulosiruptor and among other biomass-degrading Firmicutes but missing from Caldicellulosiruptor bescii. As such, the gene encoding Calkro_0402 was inserted into the C. bescii genome, creating a mutant strain with its S-layer extensively decorated with Calkro_0402. This strain consequently degraded xylans more extensively than wild-type C. bescii. The results here provide new insights into the architecture and role of SLH domain GHs and demonstrate that hemicellulose degradation can be enhanced through non-native SLH domain GHs engineered into the genomes of Caldicellulosiruptor species.Many bacteria (1, 2) and archaea (3) produce a two-dimensional, para-crystalline array of protein that covers the outside of the cell, referred to as a surface layer (S-layer).5 In bacteria, the majority of S-layer proteins are non-covalently associated with the bacterial cell surface via specialized domains at their N or C terminus, typically from one of three distinct but analogous domain categories: surface layer homology (SLH) (4, 5), CWB2 (pfam04122) (6), or NCAD (previously SLAP, pfam03217) (7,8). In archaea, S-layer proteins are most often attached to the cell membrane. S-layer proteins can be anchored to the membrane via a C-terminal transmembrane helix domain (3, 9) or covalently attached to cell membrane lipid via an archaeosortase, as shown in Haloferax volcanii (10,11). In most microorganisms, the S-layer is composed entirely of one or two proteins (SLPs), which self-assemble. In addition to these SLPs, some Firmicutes produce a family of proteins that also contain SLH, CWB2, or NCAD domains and, as such, are predicted to be associated with the S-layer (12). SLPs and S-layer associated proteins can also contain domains with specialized functions allowing the S-layer to play a role in adherence and biofilm formation (13-16), biogenesis of the cell envelope (17), cell division (18...

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Reduction of the arterial elastance with intra-aortic balloon pumping improved the ventriculoarterial coupling ratio and increased stroke volume. Leftward shift of the pressure-volume loop resulted in the reduction of pressure-volume area, which suggests the conservation of the myocardial oxygen consumption.

Unreliable quantification of flow pulsatility has hampered many efforts to assess the importance of pulsatile perfusion. Generation of pulsatile flow depends upon an energy gradient. It is necessary to quantify pressure flow waveforms in terms of hemodynamic energy levels to make a valid comparison between perfusion modes during chronic support. The objective of this study was to quantify pressure flow waveforms in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE) levels in an adult mock loop using a pulsatile ventricle assist system (VAD). A 70 cc Pierce-Donachy pneumatic pulsatile VAD was used with a Penn State adult mock loop. The pump flow rate was kept constant at 5 L/min with pump rates of 70 and 80 bpm and mean aortic pressures (MAP) of 80, 90, and 100 mm Hg, respectively. Pump flows were adjusted by varying the systolic pressure, systolic duration, and the diastolic vacuum of the pneumatic drive unit. The aortic pressure was adjusted by varying the systemic resistance of the mock loop EEP (mm Hg) = (integral of fpdf)/(integral of fdt) SHE (ergs/cm3) = 1,332 [((integral of fpdt)/(integral of fdt))--MAP] were calculated at each experimental stage. The difference between the EEP and the MAP is the extra energy generated by this device. This difference is approximately 10% in a normal human heart. The EEP levels were 88.3 +/- 0.9 mm Hg, 98.1 +/- 1.3 mm Hg, and 107.4 +/- 1.0 mm Hg with a pump rate of 70 bpm and an aortic pressure of 80 mm Hg, 90 mm Hg, and 100 mm Hg, respectively. Surplus hemodynamic energy in terms of ergs/cm3 was 11,039 +/- 1,236 ergs/cm3, 10,839 +/- 1,659 ergs/cm3, and 9,857 +/- 1,289 ergs/cm3, respectively. The percentage change from the mean aortic pressure to EEP was 10.4 +/- 1.2%, 9.0 +/- 1.4%, and 7.4 +/- 1.0% at the same experimental stages. Similar results were obtained when the pump rate was changed from 70 bpm to 80 bpm. The EEP and SHE formulas are adequate to quantify different levels of pulsatility for direct and meaningful comparisons. This particular pulsatile VAD system produces near physiologic hemodynamic energy levels at each experimental stage.

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