Freeze-fracture study of the plasma membrane of Leishmania mexican amazonensis.

The fine structure of the plasma membrane of promastigotes of Leishmania mexicana amazonensis was studied by freeze-fracture techniques. Measurement of the number of intramembranous particles per square micrometer of membrane area revealed a particle density of 2,040 +/- 213/micron2 on the P-face and 890 +/- 186/micron2 on the E-face. The particle density of the flagellar membrane was 448 +/- 53/micron2. Clusters of intramembranous particles were seen on the flagellar membrane at the region of adhesion between the flagellum and the cell body. Aggregation of particles was observed in both P- and E-faces of the plasma membrane of some cells.