Undulating membraneous structures associated with the endoplasmic reticulum in tumour cells.

The morphology and occurrence of tubuloreticular and undulating membraneous structures (TRS and UMS) associated with the endoplasmic reticulum were examined under normal and pathologic conditions. It was concluded that TRS and UMS are cytoplasmic inclusions of similar type but of different organization. The occurrence of UMS in a human cell line derived from a carcinoma of the lung and in a transplantable chicken hepatoma derived from an MC-29 virus-induced liver tumour is described.