Tissue cultures of HeLa cells were grown in media containing colloidal gold, and after various intervals, the cells were fixed, embedded, and sectioned for electron microscopy. Uncoated grids with small holes were used in many of the experiments. Intracellular particles of gold were identified in areas surrounded by single membranes, in moderately dense granules, in globoid bodies, and in the cytoplasmic matrix. Gold particles were not found in typical mitochondria, Golgi complex, ergastoplasm (granular forms of endoplasmic reticulum), or nuclei. The phenomenon of pinocytosis was considered to be the most likely means by which the gold particles were ingested, and the locations of gold particles appeared to have significance concerning theories that membranous organelles of the cytoplasm may be derived from the cell membrane.

HeLa cells were infected with adenoviruses (types 1–4) and sectioned for electron microscopy after intervals of 20 to 48 hours. Clusters of virus-like particles were found within the nuclei of infected cultures but not in those of uninfected controls. The particles were often arranged in rows as if in crystalline formation. Maximal diameter of particles was approximately 65 mµ, and internal bodies were demonstrated. Lesions of infected cells included target-like structures of the nuclear membrane, large nuclear vacuoles (type 2), and increased numbers of large irregular electron-dense granules in the cytoplasm 48 hours after infection. Examination of infected cultures by light microscopy, using the Feulgen reaction, showed intranuclear inclusion bodies and a cytopathogenic effect consisting of clumping of cells without pyknosis of nuclei. A lipide stain showed numerous cytoplasmic granules that were not identical with the large, irregular, electron-dense granules of the cytoplasm. Practically all the cells showed the viral cytopathogenic effect, but only a minority of cells were found to contain virus-like particles or intranuclear inclusion bodies.

A study of bronchial cilia in mice was carried out in order to obtain evidence as to how influenza viral infection of the mouse lung lowers rcsistancc to secondary pneumococcal pneumonia. Earlier work had shown that this effect is associated with the viral lesion rather than the presence of the virus per se and had suggested that viral infection damages antibacterial mechanisms of the lung (I). Particular attention was given to cilia because of the histologic evidence that influenza viral infection of the mouse causes necrosis of the bronchial epithelium (I-8). In addition, it has bccn shown that ciliary action removes foreign particles from the respiratory passages and therefore probably serves as an important mechanism of nativc resistance to bacterial infection of the respiratory tract (9-20). I When severe infection with influenza virus was induced in mice, it was found that active ciliary beat persisted in the bronchi of involved lungs and that cilia could be shown to be present in stained sections of the viral lesion. = These findings were unexpected because it was thought that this viral infection causes destruction of bronchial epithelial cells. For this reason, further experiments were done to clarify the nature of the viral lesion. The result of this investigation has revealed no evidence that actual destruction of the epithelium takes place. Instead of nuclear changes in the early viral lesion, basophilic intracytoplasmic inclusion bodies have bccn found. Evidence has also been obtained to indicate that portions of the cytoplasm of non-ciliated cells become detached and are shed into the lumen. EXPERIMENTAL METHODS AND RESULTS Wave-Like Movements of the Bronch~ ~In order to ascertain the effect of viral infection on broncial cilia, it was necessary to have a method for evaluation of ciliary action. A technique frequently

No abstract

Recently improved methods for visualization of thin tissue sections by electron microscopy have been applied to the study of early changes in the bronchial epithelium of mice infected by inhalation of aerosols of influenza virus. In confirmation of previous findings by the authors, inclusion bodies have been demonstrated in ciliated and non-ciliated cells of infected bronchial epithelium. In addition to 3 strains of mouse-adapted Type A virus, 2 unadapted strains gave qualitatively the same results. The inclusion bodies were found to be composed largely of particles of a size estimated to correspond to the known size of influenza virus. The viral lesion of the cytoplasm was also associated with linear formations which were thought to be abnormal forms of endoplasmic reticulum. Well developed microvilli were found on the ciliated borders of ciliated cells, but no evidence was found of viral growth in this region.