The lungs are paired respiratory organs that continuously carry out the processes of inspiration and expiration in healthy individuals. The organs are organized into a highly branched system divided into a number of different levels between the trachea and the bronchioles.

A wide variety of diseases can affect the lungs, including cancer, pneumonia, bronchitis, and Legionnaire's disease, to name but a few. In humans, lung cancer, which is often associated with cigarette smoking, has been of particular concern. Today, more men and women die from lung cancer than any other type of cancer.

Animal models, including sheep, are commonly used to characterize the progression of human diseases and to test potential treatments. One notable recent study utilizing sheep focused upon using an artificial implantable lung as a temporary solution for lung failure. The pre-clinical testing of the device developed by researchers at the University of Michigan, which utilizes minute hollow fibers containing numerous micropores and the pumping force of the heart to oxygenate blood, was generally considered very promising. If further testing of the new artificial lung with sheep, and eventually human subjects, is similarly successful, the device may someday find use among patients on lung transplant waiting lists, perhaps decreasing the number of individuals that die before an organ ever becomes available to them.

The sample of sheep lung tissue presented in the digital image above was labeled with Alexa Fluor 350 (blue fluorescence) conjugated to wheat germ agglutinin, a lectin that selectively binds N-acetylglucosamine and sialic acid residues. The specimen was also labeled with Alexa Fluor 488 (green) conjugated to phalloidin and SYTOX Orange, targeting F-actin and nuclear DNA, respectively. Images were recorded in grayscale with a 12-bit digital camera coupled to either a Nikon E-600 or Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.