The kidneys are paired organs that function chiefly in the filtration of the blood supply, maintenance of water balance, and expulsion of waste products. Mammalian kidneys, which notably differ from the kidneys of birds, fish, and amphibians, are composed of numerous small lobules organized into an outer cortex and an inner medulla.

Nephrons are the basic functional units of the kidneys and are responsible for the production of urine as they remove unneeded materials from the blood. In mammals, nephrons are very long narrow tubes that are closed and folded at one end into a structure known as Bowman’s capsule that encases a group of capillaries collectively termed the glomerulus.

Mouse kidneys are similar in many respects to human kidneys and are, consequently, commonly utilized in scientific investigations focusing on the organs and the various problems that can afflict them. Indeed, researchers have greatly expanded the knowledge base regarding many forms of kidney disease by utilizing special strains of genetically engineered mice as models. In recent years, some scientists have also experimented with using human stem cells to grow organs in kidney deficient mice. The success of such endeavors may eventually lead to advances that enable human kidney patients to produce their own replacement organs.

Lectins are carbohydrate-binding proteins that bind to specific configurations of sugar molecules, which enables them to be utilized to identify various cell types and cell constituents. The lectin wheat germ agglutinin (WGA) binds to N-acetylglucosamine and sialic acid residues and is commonly used to identify the Golgi complex in mammalian cells. The mouse kidney tissue sample presented in the digital image above was labeled with Alexa Fluor 488 conjugated to WGA. In addition, the specimen was labeled for F-actin and DNA with Alexa Fluor 568 conjugated to phalloidin and DAPI, 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.

Triple Fluorophore Labeling Mouse Kidney Tissue Samples - The mouse kidney tissue sample presented in this section was triple labeled before imaging. Alexa Fluor 568 (red fluorescence emission) conjugated to phalloidin was utilized to target polymerized actin (F-actin) and Alexa Fluor 488 (green emission) conjugated to wheat germ agglutinin was used to target sialic acid and N-acetylglucosaminyl residues. The popular nuclear and chromosome counterstain DAPI, which emits blue fluorescence upon binding to AT regions of DNA, was also employed.

Localizing DNA, Filamentous Actin, and Oligosaccharide Residues in Mouse Kidneys - Similar to the previous sample, Alexa Fluor 488 conjugated to the lectin wheat germ agglutinin, which selectively binds to N-acetylglucosamine and N-acetylneuraminic (sialic acid) residues and is frequently used to localize the Golgi network in mammalian cells, was utilized to label the mouse kidney tissue sample featured in this section. The specimen was stained for filamentous actin with Alexa Fluor 568 conjugated to phalloidin and for nuclear DNA with 4',6-diamidino-2-phenylindole (DAPI).

Murine Tissue with Alexa Fluor 488, Alexa Fluor 568, and DAPI - In order to localize a red fluorescent tag to filamentous actin in a mouse kidney tissue sample, the specimen was labeled with Alexa Fluor 568 conjugated to phalloidin, a phallotoxin often utilized in cell biology. Alexa Fluor 488 conjugated to the lectin wheat germ agglutinin was also applied to the tissue sample. Cell nuclei were counterstained with DAPI.

Utilizing Dye-Labeled Phallotoxins to Target F-Actin in Kidney Tissue Samples - Phalloidin is a phallotoxin isolated from the highly poisonous Amanita phalloides mushroom that binds polymerized actin. Alexa Fluor 568 conjugated to phalloidin was utilized to target the filamentous actin in the mouse kidney tissue sample presented in this section. Alexa Fluor 488 conjugated to the lectin wheat germ agglutinin and the nucleic acid stain DAPI were was also employed to label the specimen.