Comparison of the heavy chains of physiologically different myosins by isoelectric focusing

The technique of isoelectric focusing in polyacrylamide gels was used to determine whether differences could be distinguished between the heavy chains of myosin prepared from physiologically different muscles of chicken. The results of focusing a mixture of fast, slow, embryonic skeletal and cardiac myosin indicated that two different heavy chains only were resolved. In fast, slow and embryonic myosin these were present in approximately equal amounts but the chain with the more acidic isoelectric point was present in greater quantity in cardiac myosin.     

Generation of aspartate aminotransferase multiple forms by deamidation.

The development of aspartate aminotransferase subforms in vitro was followed by densitometry after thin-film isoelectric focusing. At the same time ammonia production was measured. Each reaction can be expressed in terms of a first-order process in which 2 mol of glutamine or asparagine/mol of dimer are deamidated with a half time of 22 days. The more negatively charged subforms developed in vitro were almost fully active. Another process occurred leading to inactivation by coenzyme modification, and this was independent of deamidation. Although the enzyme formed absorbed maximally at 340nm, it was different from the naturally occurring inactive enzyme that absorbs at this wavelength.     

Simulating Microdosimetry in a Virtual Hepatic Lobule

The liver plays a key role in removing harmful chemicals from the body and is therefore often the first tissue to suffer potentially adverse consequences. To protect public health it is necessary to quantitatively estimate the risk of long-term low dose exposure to environmental pollutants. Animal testing is the primary tool for extrapolating human risk but it is fraught with uncertainty, necessitating novel alternative approaches. Our goal is to integrate in vitro liver experiments with agent-based cellular models to simulate a spatially extended hepatic lobule. Here we describe a graphical model of the sinusoidal network that efficiently simulates portal to centrilobular mass transfer in the hepatic lobule. We analyzed the effects of vascular topology and metabolism on the cell-level distribution following oral exposure to chemicals. The spatial distribution of metabolically inactive chemicals was similar across different vascular networks and a baseline well-mixed compartment. When chemicals were rapidly metabolized, concentration heterogeneity of the parent compound increased across the vascular network. As a result, our spatially extended lobule generated greater variability in dose-dependent cellular responses, in this case apoptosis, than were observed in the classical well-mixed liver or in a parallel tubes model. The mass-balanced graphical approach to modeling the hepatic lobule is computationally efficient for simulating long-term exposure, modular for incorporating complex cellular interactions, and flexible for dealing with evolving tissues.