Comparative ultrastructure of Clara cells in neonatal and older cattle.

Calf lungs were fixed with glutaraldehyde and examined by scanning (SEM) and transmission (TEM) electron microscopy to compare the ultrastructure of Clara cells in terminal bronchioles of neonatal calves and older cattle. In the neonatal calf, SEM revealed numerous smooth-surfaced Clara cells protruding above a similar number of ciliated cells, whereas in older animals the surface of Clara cells was lobulated. Thin sections examined by TEM revealed numerous cuboidal to columnar Clara cells with indented nuclei and a pale cytoplasm filled with faintly granular glycogen in the neonatal calf. Some cells were characterized by apical dense and/or pale membrane-bound granules or secretory droplets. Many cells had an apical tubular network of cisternae that were partly smooth and partly decorated with ribosomes. Ultrastructural comparison of Clara cells in a 2-day-old calf with those of 14- and 19-day-old, 4- and 5. 5-month-old, and 3.5-year-old cattle revealed a striking reduction in the amount of glycogen per cell after 14 days. The number of cells with apical granules was small at all ages, and the density of the secretory granules varied greatly in different cells. A variable amount of smooth endoplasmic reticulum (SER) was present but was less prominent than cisternae of ribosomal endoplasmic reticulum (RER). In older cattle, the limited amount of SER compared to the RER and secretory granules suggests that bovine Clara cells are more likely to be secretory than detoxifying.

Light and electron microscopic studies of Isospora chalchidis (Amoudi, 1989) infecting Chalcides ocellatus in Egypt.

Oocysts of Isospora chalchidis (Amoudi, 1989) were described from the faeces of the skink Chalcides ocellatus in Egypt. Non-sporulated oocysts were spheroidal, measuring 20 (18.5-21) microns in diameter and contained granulated zygotes. Sporulated oocysts had the same dimensions of the nonsporulated ones and each contained two sporocysts. Sporocysts were ovoid with stieda and sporocyst residual bodies. Sporulation time was 50 hours at room temperature. Merogony and gamogony occurred in the intestinal mucosa. Electron microscopic investigations showed that meronts, merozoites, gamonts and gametes developed in a narrow parasitophorous vacuole within the host-cell nucleus. Nuclei of meronts were surrounded by rough endoplasmic reticulum. Merozoites showed the main characteristics of motile stages of Apicomplexa. Macrogametes contained a large nucleus, two types of wall-forming bodies and a large amount of lipid inclusions. Nuclei of microgamonts were peripherally arranged and lacked nucleoli. Microgametes were flagellated.