An Ion-exchange Bone Demineralization Method for Improved Time, Expense, and Tissue Preservation.

Here, we describe an ethylenediaminetetraacetic acid (EDTA)-based bone demineralization procedure that uses cation-exchange resin and dialysis tubing. This method does not require solution changes or special equipment, is faster than EDTA alone, is cost-effective, and is environmentally friendly. Like other EDTA-based methods, this procedure yields superior tissue preservation than formic acid demineralization. Greater protein antigenicity using EDTA as opposed to formic acid has been described, but we also find significant improvements in carbohydrate-based histological staining. Histological staining using this method reveals cartilage layers that are not distinguishable with formic acid demineralization. Carbohydrate preservation is relevant to many applications of bone demineralization, including the assessment of osteoarthritis from bone biopsies and the use of demineralized bone powder for tissue culture and surgical implants. The improvements in time, expense, and tissue quality indicate this method is a practical and often superior alternative to formic acid demineralization.

Distal spinal nerve development and divergence of avian groups.

The avian transition from long to short, distally fused tails during the Mesozoic ushered in the Pygostylian group, which includes modern birds. The avian tail embodies a bipartite anatomy, with the proximal separate caudal vertebrae region, and the distal pygostyle, formed by vertebral fusion. This study investigates developmental features of the two tail domains in different bird groups, and analyzes them in reference to evolutionary origins. We first defined the early developmental boundary between the two tail halves in the chicken, then followed major developmental structures from early embryo to post-hatching stages. Differences between regions were observed in sclerotome anterior/posterior polarity and peripheral nervous system development, and these were consistent in other neognathous birds. However, in the paleognathous emu, the neognathous pattern was not observed, such that spinal nerve development extends through the pygostyle region. Disparities between the neognaths and paleognaths studied were also reflected in the morphology of their pygostyles. The ancestral long-tailed spinal nerve configuration was hypothesized from brown anole and alligator, which unexpectedly more resembles the neognathous birds. This study shows that tail anatomy is not universal in avians, and suggests several possible scenarios regarding bird evolution, including an independent paleognathous long-tailed ancestor.