Cellular Responses to Mechanical Stress: Invited Review: Pulmonary capillary stress failure

Thepulmonary blood-gas barrier is an extraordinary bioengineeringstructure because of its vast area but extreme thinness. Despite this,almost no attention has been given to its mechanical properties. Theremarkable area and thinness come about because gas exchange occurs bypassive diffusion. However, the barrier also needs to be immenselystrong to withstand the very high stresses in the capillary wall whencapillary pressure rises during exercise. The strength of the thinregion of the barrier comes from type IV collagen in the basementmembranes. When the stresses in the capillary walls rise to highlevels, ultrastructural changes occur in the barrier, a condition knownas stress failure. Physiological conditions that alter the propertiesof the barrier include severe exercise in elite human athletes. Animalsthat have been selectively bred for high aerobic activity, such asThoroughbred racehorses, consistently break their pulmonary capillariesduring galloping. Pathophysiological conditions causing stress failureinclude high-altitude pulmonary edema and overinflation of the lung,which frequently occurs with mechanical ventilation. Remodeling of thecapillary wall occurs in response to increased wall stress in diseasessuch as mitral stenosis. The barrier is able to maintain its extreme thickness with sufficient strength as a result of continual regulation of its wall structure. How it does this is a central problem in lung biology.

     

Biomass Production from Electricity Using Ammonia as an Electron Carrier in a Reverse Microbial Fuel Cell

The storage of renewable electrical energy within chemical bonds of biofuels and other chemicals is a route to decreasing petroleum usage. A critical challenge is the efficient transfer of electrons into a biological host that can covert this energy into high energy organic compounds. In this paper, we describe an approach whereby biomass is grown using energy obtained from a soluble mediator that is regenerated electrochemically. The net result is a separate-stage reverse microbial fuel cell (rMFC) that fixes CO₂ into biomass using electrical energy. We selected ammonia as a low cost, abundant, safe, and soluble redox mediator that facilitated energy transfer to biomass. Nitrosomonas europaea, a chemolithoautotroph, was used as the biocatalyst due to its inherent capability to utilize ammonia as its sole energy source for growth. An electrochemical reactor was designed for the regeneration of ammonia from nitrite, and current efficiencies of 100% were achieved. Calculations indicated that overall bioproduction efficiency could approach 2.7±0.2% under optimal electrolysis conditions. The application of chemolithoautotrophy for industrial bioproduction has been largely unexplored, and results suggest that this and related rMFC platforms may enable biofuel and related biochemical production.     

Biophysically Inspired Rational Design of Structured Chimeric Substrates for DNAzyme Cascade Engineering

The development of large-scale molecular computational networks is a promising approach to implementing logical decision making at the nanoscale, analogous to cellular signaling and regulatory cascades. DNA strands with catalytic activity (DNAzymes) are one means of systematically constructing molecular computation networks with inherent signal amplification. Linking multiple DNAzymes into a computational circuit requires the design of substrate molecules that allow a signal to be passed from one DNAzyme to another through programmed biochemical interactions. In this paper, we chronicle an iterative design process guided by biophysical and kinetic constraints on the desired reaction pathways and use the resulting substrate design to implement heterogeneous DNAzyme signaling cascades. A key aspect of our design process is the use of secondary structure in the substrate molecule to sequester a downstream effector sequence prior to cleavage by an upstream DNAzyme. Our goal was to develop a concrete substrate molecule design to achieve efficient signal propagation with maximal activation and minimal leakage. We have previously employed the resulting design to develop high-performance DNAzyme-based signaling systems with applications in pathogen detection and autonomous theranostics.     

Detection of bacteriophage tracers in bivalve molluscan shellfish

Procedures to enumerate commonly used bacteriophage tracers in bivalve molluscan shellfish were evaluated. Bacteriophages specific to Serratia marcescens, Escherichia coli and Enterobacter cloacae can be recovered from shellfish flesh by chloroform treatment of homogenates and subsequent clarification of samples by centrifugation. Bacteriophages were enumerated using a soft agar overlay technique. Hard clams appeared to release toxic compounds during homogenization which dramatically reduced counts of Ent. clocae bacteriophage.     

Cellulose acetate electrophoresis of casein proteins.

Samples of the milk proteins α_s1-casein and β-casein partially dephosphorylated by means of bovine spleen phosphoprotein phosphatase have been electrophoretically analysed using cellulose acetate as the supporting medium and Procion blue as the protein dye. Sufficient resolution was obtained in 1 hr to allow quantification of the proteins present. Skimmed-milk samples and acid-precipitated whole casein samples have been analysed by the same technique. The advantages of the method are discussed in relation to the more conventional electrophoretic techniques normally used to analyse these milk proteins.     

Galactoside transport dissociated from proton movement in mutants of Escherichia coli

Two mutants of Escherichia coli have been described in which the transport of β-galactosides is partly uncoupled from the metabolic reactions which drive active transport. It is shown that the effective inflow of H⁺, caused by the addition of β-galactoside, is much less in these mutants than in the parental strains, and it is concluded that β-galactoside transport is partly uncoupled from H⁺ transport.