VOLUME 17, 1963 | MARILYN G. FARQUHAR, Ph.D., and GEORGE E. PALADE, M.D.
The article by Farquhar and Palade describes the characteristic junctional complex found between adjacent cells in various epithelia of the rat and guinea pig. This complex, consisting of three components—zonula occludens (tight junction), zonula adhaerens (intermediate junction), and macula adhaerens (desmosome)—is observed in mucosal epithelia such as the stomach, intestine, gall bladder, uterus, and oviduct, as well as in glandular epithelia like the liver, pancreas, parotid, thyroid, and in the epithelia of pancreatic, hepatic, and salivary ducts. The tight junction, located closest to the lumen, is characterized by the fusion of adjacent cell membranes, resulting in the obliteration of the intercellular space. The intermediate junction, located between the tight junction and the desmosome, is characterized by a true intercellular space and a dense cytoplasmic matrix. The desmosome, located farthest from the lumen, is characterized by laminar densities in the intercellular space and high concentrations of dense amorphous and fibrillar material in the cytoplasmic matrix. Experiments using hemoglobin as a mass tracer show that the tight junction acts as a barrier to the diffusion of the tracer, while the desmosome and intermediate junction may represent intercellular attachment devices. The authors propose specific nomenclature for these junctional elements and discuss their structural and functional significance.The article by Farquhar and Palade describes the characteristic junctional complex found between adjacent cells in various epithelia of the rat and guinea pig. This complex, consisting of three components—zonula occludens (tight junction), zonula adhaerens (intermediate junction), and macula adhaerens (desmosome)—is observed in mucosal epithelia such as the stomach, intestine, gall bladder, uterus, and oviduct, as well as in glandular epithelia like the liver, pancreas, parotid, thyroid, and in the epithelia of pancreatic, hepatic, and salivary ducts. The tight junction, located closest to the lumen, is characterized by the fusion of adjacent cell membranes, resulting in the obliteration of the intercellular space. The intermediate junction, located between the tight junction and the desmosome, is characterized by a true intercellular space and a dense cytoplasmic matrix. The desmosome, located farthest from the lumen, is characterized by laminar densities in the intercellular space and high concentrations of dense amorphous and fibrillar material in the cytoplasmic matrix. Experiments using hemoglobin as a mass tracer show that the tight junction acts as a barrier to the diffusion of the tracer, while the desmosome and intermediate junction may represent intercellular attachment devices. The authors propose specific nomenclature for these junctional elements and discuss their structural and functional significance.