Transmission electron microscopy of the epithelium of distal airways and pulmonary parenchyma of the goat lung.

Lungs from eight goats of mixed sexes and breeds (Cashmere, Nubian and Toggenburg) aged between 10 and 48 months were used in this study. Tissues from lung parenchyma were minced and routinely prepared for transmission electron microscopy (TEM) after using different methods of fixation. Thick sections were examined with a light microscope and samples, to include terminal bronchioles, respiratory bronchioles, alveolar ducts and alveolar membrane, were selected for ultrathin sectioning. Six cell types, ciliated, non-ciliated bronchiolar epithelial, mucus-producing, alveolar Type I, alveolar Type II and capillary endothelial cell were identified and characterised cytologically. It was established that the cell population in the distal airways is similar to that observed in other domestic mammals. The mucus-producing cell, which appears to be a common cell type in the distal airways of man and Rhesus monkey, was encountered particularly in adult goats in the present study. This study has also established that the Clara cell of the goat shows some cytological differences from those of some other mammalian species by having a large amount of SER, particularly in the apical region. Lipid vacuoles were seen to be a feature of the alveolar Type II cells; these do not appear to have been reported in other mammalian species. The study has provided a basic understanding of the morphological features of the cell population of the epithelium lining the distal airways in the goat's respiratory tract. The difference in junctional complexes between the various alveolar epithelial cells perhaps signify a different pattern of intercellular transport, thus influencing the pathogenesis and resolution of alveolar pulmonary edema.

An ultrastructural study of the cere of the domestic pigeon (Columba livia).

The relative scarcity of primary and secondary skin infections in birds depends, at least in part, on the functional morphological barrier presented by the avian integument. Both transmission and scanning electron microscopical techniques were used to study the ultrastructural morphology of the epidermal barrier in the cere of the domestic racing pigeon. The epidermis is composed of sebokeratocytes which are responsible for producing not only the keratin proteins of the keratinized stratum corneum, but also the lipid emulsion forming the surface lipid layer and filling the intercellular spaces. The possible importance and role of these components in the defensive barrier presented by the skin is discussed.

Extravascular cells within the perisinusoidal space of the avian liver.

Ultrastructural studies of the perisinusoidal space in the avian liver have demonstrated the presence of 2 extravascular cell types--a fat-storing cell and a free mesenchyme cell or histiocyte. This latter cell type is capable of participating in the formation of a bile canaliculus with the hepatic parenchymal cell. The possibility of the fat-storing cell differentiating from the histiocyte is suggested.

The respiratory epithelium of the lung in the green turtle (Chelonia mydas L.).

The chelonian lung exhibits reptilian, mammalian and avian features. The respiratory epithelium is typically vertebrate, i.e. pseudostratified columnar with cilia; gaseous exchange areas appear at all levels from the respiratory bronchi down to the alveoli. The latter are invested with a capillary network and both type I and type II cells are present. The possible functional significance of the distribution of collagen, elastic tissue, cartilage and smooth muscle is discussed.

Scanning electron microscopy of the respiratory epithelium of chicks fumigated with formaldehyde vapour.

1. Hatching chicks were exposed to 10.9 ppm of formaldehyde vapour during the last 3 d of incubation in a commercial situation. 2. Samples from pre-selected regions of the entire respiratory tract, taken at 0, 6, 30 and 54 h post-vaporisation of formaldehyde, were examined by scanning electron microscopy for surface morphological features and associated pathological changes. 3. Clumping of cilia, blebs on the cilial wall, deciliation and exfoliation of the epithelium were all observed under the scanning electron microscope. 4. Lesions were more severe in chicks exposed for 54 h as compared to those exposed for 6 and 30 h. There were no regional differences in the lesions throughout the respiratory tract of all the chicks. 5. Limited observations suggest that the passage of formaldehyde vapour across the egg shell wall may influence the morphology of the respiratory lining of the developing embryo.

Plastid changes during the conversion of chloroplasts to chromoplasts in ripening tomatoes.

Methods were developed for the isolation of plastids from mature green and ripening tomatoes (Lycopersicon esculentum Mill.) and purification by sucrose or Percoll density-gradient centrifugation. Assessment of the purity of preparations involved phase-contrast and electron microscopy, assays for marker enzymes and RNA extraction and analysis. Proteins were extracted from isolated plastids at different ripening stages and separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The profiles obtained from chloroplasts and chromoplasts showed many qualitative and quantitative differences. Labelling of proteins with [(35)S]methionine in vivo showed that there was active protein synthesis throughout ripening, but there was a change in the plastid proteins made as ripening proceeded. The cellular location of synthesis of specific proteins has yet to be established.