A comparison of some methods of preparation of thin sections of virus-infected leaves for electron microscopy

Midgut ultrastructure of Culex tarsalis (Diptera: Culcidae) before and after a bloodmeal

The midgut ultrastructure of rasin-and blood-fed female mosquitoes, Culex tarsalis Coquillentt, was examined. The raisin-fed midgut is characterized by: (1) large nuclei, (2) small mitochondria, (3) short segments of rough endoplasmic reticulum, (4) rough endoplasmic reticular vesicular vesicles in the posterior midgut only, and (5) increased autophagic acitivity with age. Blood feeding elicits drastic changes in midgut epithelial structures: (1) nuclei are smaller, (2) mitochondria are much enlarged, (3) rough endoplasmic reticular vesicles disappear, (4) rough endoplasmic reticular whorls appear, (5) residual lyosomal figures are abundant, and (6) an intercellular accumulation of an electron-opaque material is noted. The significance of rough endoplasmic reticular whorls and vesicles in bloodmeal digestion is discussed. In addition, the concept of a functional host 'gut barrier' to infection by pathogens is examined as related to a possible by-pass mechanism.

Cytoplasmic particles in Tropaeolum majus

Solitary (S) bodies were present in the cytoplasm of the cells of many cultivars of Tropaeolum majus. However, cultivars have also been found which completely lack these S bodies. The S bodies occur in all cells of all kinds of tissues and organs of the plant. In the anthers they occur in the cells of the endothecium tissue as well as in the tapetum layer, and even in the pollen cells. The shape of the S bodies is nearly spherical (diameter ca. 60 nm) with a tail-like appendage with a length of ca. 90-150 nm and a diameter of ca. 16 nm. The nature of the S bodies is unknown. Transmission studies by mechanical inoculation and by grafting gave no indications of a virus nature of these bodies. Reciprocal crosses between plants containing and lacking these S bodies showed that the bodies were transmitted to the progeny only if they occur in the mother plant, that is, indicated a cytoplasmic inheritance.