Determining biological fine structure by differential absorption of soft x-rays

The use of soft x-ray contact microscopy in examining histochemically treated human tissue embedded in plastic and exposed as unstained thin sections is demonstrated. When our preliminary data revealed that we could clearly image not only the histochemical reaction product, but the unstained biological fine structure of the surrounding tissues, we decided to test our hypothesis further and see if we could image unstained biological molecular aggregates as well. For this part of the investigation, we chose to examine hydrated proteoglycan aggregates. Proteoglycans are an essential component of the organic matrix of cartilage, and play a primary role in the retention and maintenance of extracellular water. To avoid any artifacts due to the introduction of exogeneous materials, and examine the proteoglycan aggregates in their hydrated, natural configuration, we made contact x-ray images of isolated proteoglycan aggregates in water