A novel approach to increase robustness, precision and high-throughput capacity of single cell gel electrophoresis

The routine use of single cell gel electrophoresis assay in medical diagnostics and biomonitoring is prevented by its high variability. Several factors have been identified and can be grouped into four main categories: 1) the biological sample, 2) the assay protocol, 3) the physical parameters during electrophoresis and 4) the analysis. Even though the scientific knowledge on assay variability is available, not much has been done so far to tackle the issues from the technological side. Therefore, this study addresses the question in how far the precise and accurate control over the physical parameters of electrophoresis is able to reduce variability of single cell gel electrophoresis assay results. All four above mentioned categories make up the overall assay variability. To resolve the contribution from a single category, the remaining three have to be kept as constant as possible. To achieve this we generated a set of x-ray treated control cells, worked according to a well-defined standard operating procedure and one single operator performed the analysis. Thereby variability resulting from the electrophoresis tank could be elucidated. We compared assay performance in two such tank systems: a newly developed electrophoresis tank that accurately controls voltage, temperature during the electrophoretic run and the homogeneity of the electric field, and a widely used commercially available standard platform tank. In summary, our results demonstrate that, irrespective of the cellular sample and its intrinsic biological variability, accurate control over physical parameters considerably increases repeatability, reproducibility and precision of single cell gel electrophoresis.

Reduction of phase artifacts in differential phase contrast computed tomography

X-ray differential phase contrast computed tomography (DPC CT) with a Talbot-Lau interferometer setup allows visualizing the three-dimensional distribution of the refractive index by measuring the shifts of an interference pattern due to phase variations of the X-ray beam. Unfortunately, severe reconstruction artifacts appear in the presence of differential phase wrapping and clipping. In this paper, we propose to use the attenuation contrast, which is obtained from the same measurement, for correcting the DPC signal. Using the example of a DPC CT measurement with pronounced phase artifacts, we will discuss the efficiency of our phase artifact correction method.

Identification of molecules in a muscle extracellular matrix extract that promotes process outgrowth from cultured adult frog motoneurons

The molecular composition of the substrate on which neurons are cultured is critical for their attachment, survival, and extension of processes. The aim of the present experiments was to characterize the molecules in an extracellular matrix (ECM) extract that promotes the outgrowth of processes from cultured adult frog motoneurons. An extract was made of skeletal muscle ECM and tested as a substrate for cultured motoneurons. The average total process length of motoneurons cultured on this crude ECM extract is greater than when the neurons are cultured on concanavalin A, poly-L-lysine or mouse tumor (EHS) laminin. Gel filtration of the ECM extract yielded fractions with an increased specific activity for promoting process outgrowth. The most active fractions exhibit a single major polypeptide band of ca. 1 mD and two minor bands of ca. greater than 1 mD and 205 kD upon sodium dodecyl sulfate gel electrophoresis. Under reducing conditions, three major bands were seen of 340, 205, and 200 kD. Electron microscopy of rotary-shadowed ECM fractions showed macromolecules with a cross-shaped structure similar to vertebrate and invertebrate laminin, a rod-like molecule resembling vertebrate and invertebrate collagen type IV, and a third molecule similar in appearance to vertebrate fibrillin. These results represent the first step in analyzing the role of substrate molecules in promoting neuromuscular reinnervation.