The oviducts are tubular tracts that ova travel through to the uterus or to the outside of the body from the ovaries in egg-producing female animals. In humans, they are commonly referred to as fallopian tubes. The internal environment provided by the oviducts is conducive to fertilization of ova and the first stages of conceptus development. An egg enters an oviduct at the broad portion of the tube known as the infundibulum and moves along the tube with the help of the ciliated epithelium that lines it. The cilia beat with a wavelike motion, propelling a released ovum toward the uterus. When an egg is unfertilized, it typically degenerates in the ampulla, the mid-region of the fallopian tube. A fertilized egg will continue along the path, which terminates in the isthmus, the final portion of the oviduct before reaching the uterus.

Typically fertilized eggs of mammals are implanted in the endometrial lining of the uterus after they are released from the oviduct. Occasionally, however, a fertilized ovum will become lodged in the oviduct instead, resulting in ectopic pregnancy. Approximately 95 percent of all ectopic pregnancies occur in the oviduct. If undiagnosed, a tubal pregnancy can rupture the oviduct, which has limited space available for the growing embryo. Rupture can result in severe blood loss and may endanger the mother’s life. Individuals that experience an ectopic pregnancy likely have about a 15 percent chance of a second ectopic pregnancy.

In order to localize a green fluorescent tag to F-actin in the sample of rat oviduct tissue presented in the digital image above, the specimen was labeled with Alexa Fluor 488 conjugated to phalloidin, a phallotoxin derived from the toxic death cap mushroom. Texas Red conjugated to the lectin wheat germ agglutinin, which selectively binds to N-acetylglucosamine and N-acetylneuraminic residues, was also applied to the tissue sample, as was the DNA probe Hoechst 33342. Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon 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.