Direct imaging of aligned neurofilament networks assembled using in situ dialysis in microchannels.

We report a technique to produce aligned neurofilament networks for direct imaging and diffraction studies using in situ dialysis in a microfluidic device. The alignment is achieved by assembling neurofilaments from protein subunits confined within microchannels. Resulting network structure was probed by polarized optical microscopy and atomic force microscopy, which confirmed a high degree of protein alignment inside the microchannels. This technique can be expanded to facilitate structural studies of a wide range of filamentous proteins and their hierarchical assemblies under varying assembly conditions.

Titanium-based dielectrophoresis devices for microfluidic applications.

To date, materials selection in microfluidics has been restricted to conventional micromechanical materials systems such as silicon, glass, and various polymers. Metallic materials offer a number of potential advantages for microfluidic applications, including high fracture toughness, thermal stability, and solvent resistance. However, their exploitation in such applications has been limited. In this work, we present the application of recently developed titanium micromachining and multilayer lamination techniques for the fabrication of dielectrophoresis devices for microfluidic particle manipulation. Two device designs are presented, one with interdigitated planar electrodes defined on the floor of the flow channel, and the other with electrodes embedded within the channel wall. Using these devices, two-frequency particle separation and Z-dimensional flow visualization of the dielectrophoresis phenomena are demonstrated.

Microchannel systems in titanium and silicon for structural and mechanical studies of aligned protein self-assemblies.

We report a technique for the alignment of self-assembled protein systems, such as F-actin bundles and microtubules, in a surface-modified titanium or silicon microfluidic device. Assembling filamentous protein systems in a confined geometry produces highly aligned samples for structural and mechanical studies. Biomolecular self-assembly can be investigated in a controlled fashion under different molecular concentration gradients and conditions along a channel length. We have shown that surface-modified devices produced via a high aspect ratio etch process in titanium and silicon can be used to confine and control such macromolecular assemblies and present examples of F-actin bundles and microtubules in this system.

The in vivo delivery of heterologous proteins by microencapsulated recombinant cells.

The microencapsulation of recombinant cells is a novel and potentially cost-effective method of heterologous protein delivery. A 'universal' cell line, genetically modified to secrete any desired protein, is immunologically protected from tissue rejection by enclosure in microcapsules. The microcapsule can then be implanted in different recipients to deliver recombinant proteins in vivo.

Acetaminophen: a practical pharmacologic overview.

Acetaminophen is an effective analgesic and antipyretic agent with few adverse effects when used in recommended dosages. The drug is metabolized mainly in the liver, and the several end products have no harmful effects. An intermediate compound in a minor metabolic pathway, however, is toxic; it is normally inactivated by glutathione. In the case of an acetaminophen overdose the hepatic stores of glutathione seem to become depleted, leaving the toxic intermediate free to damage liver tissue. Such damage is unlikely to occur unless the plasma concentration of acetaminophen peaks above 150 micrograms/mL--a level far in excess of the 5 to 20 micrograms/mL achieved with therapeutic doses of the drug. Long-term therapeutic use of acetaminophen does not appear to be associated with liver damage, although some case reports suggest the possibility. Acetaminophen poisoning follows an acute overdose and, if untreated, is manifested clinically by an initial phase of nonspecific signs and symptoms, a latent period in which the liver transaminase levels rise and then, 3 to 5 days after the ingestion, signs of more serious hepatic dysfunction. Most patients do not progress beyond the first or second phase. They and those who survive the third phase recover with no residual injury to the liver. Appropriate antidotal therapy markedly reduces the severity of the initial damage.

Stability of methacholine chloride in bronchial provocation test solutions.

The stability of methacholine chloride (5 mg/ml) in 0.9% sodium chloride solution was measured. A reliable colorimetric assay (530 nm) based on the formation of a hydroxamic acid-iron complex was used. At appropriate time intervals, samples were removed from solutions stored at 4, 20, 37, 60, or 80 degrees C and assayed. The degradation of methacholine chloride followed apparent first-order kinetics of methacholine chloride followed apparent first-order kinetics at all temperatures, with observed half-lives ranging from 29.3 days at 80 degrees C to 693 days 4 degrees C. Methacholine chloride in 0.9% sodium chloride solution does not degrade as rapidly as previously suggested. According to an Arrhenius plot, storage of such solutions at 30 or 4 degrees C would result in not more than 10% degradation over a period of approximately two or five months, respectively. Thus, it should be possible to prepare stock solutions of this deliquescent drug.