The Voronoi theory of the normal liver lobular architecture and its applicability in hepatic zonation.

The precise characterization of the lobular architecture of the liver has been subject of investigation since the earliest historical publications, but an accurate model to describe the hepatic lobular microanatomy is yet to be proposed. Our aim was to evaluate whether Voronoi diagrams can be used to describe the classic liver lobular architecture. We examined the histology of normal porcine and human livers and analyzed the geometric relationships of various microanatomic structures utilizing digital tools. The Voronoi diagram model described the organization of the hepatic classic lobules with overall accuracy nearly 90% based on known histologic landmarks. We have also designed a Voronoi-based algorithm of hepatic zonation, which also showed an overall zonal accuracy of nearly 90%. Therefore, we have presented evidence that Voronoi diagrams represent the basis of the two-dimensional organization of the normal liver and that this concept may have wide applicability in liver pathology and research.

Development of a cost-effective torsional unit for rodent long bone assessment.

Thorough mechanical testing of rodent bones requires an understanding of bone behavior in a variety of loading modes including tension, compression, bending and shear. While these tests are easily conducted with single axis mechanical testing machines, it may also be desirable to determine torsional properties of bone. Although higher-end materials testing machines will enable torsional and/or rotational testing, simpler, less expensive systems rarely offer these capabilities. In this work, we illustrate the development of a torsional system that uses a simple rack and pinion concept to deliver a rotary motion to bones given the linear motion of a testing machine. As the bone field becomes increasingly interdisciplinary, more biologists and non-test engineers need cost-effective mechanical testing capabilities and the torsional system described here has proven to be more than adequate for standard biomechanical testing requirements. Furthermore, given the small-scale size of rodent long bones, a series of potting/testing fixtures were developed that enabled preparation and handling of the specimens without incurring damage to the bone shafts. Once fabricated the system was used to destructively load mice humeri and femurs and quantify torsional properties.