Electron microscopic examination of human cytomegalovirus (HCMV) inoculum, as used in the laboratory and generated by infection of human fibroblasts at low multiplicity, led to the distinction of 7 different structures. Complete virions constituted 38% of the inoculum. Non-infectious enveloped particles (NIEP) were also quite numerous (4.7%). Inoculum also contained other enveloped and non-enveloped particles. Dense bodies were the most numerous (50.2%). The Feulgen-like osmium ammine/SO2 reaction applied to ultrathin sections of inoculum suggests that NIEP, considered to be lacking DNA, may contain small and varying amounts of DNA. This DNA was lightly stained and appeared as a filamentous ring in the core structure, extending to the limits of the capsid. A correlation was established between particles identifiable in HCMV-infected cells and their free counterparts in the inoculum, which revealed that all intracytoplasmic particles are present in the inoculum. All of these elements could potentially contribute to virus-induced phenomena associated with HCMV infection of cells in vitro.

Cell Nucleus↗

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Hyperimmediate entry of human cytomegalovirus virions and dense bodies into human fibroblasts.

Previous ultrastructural and cytochemical examination of the HCMV inoculum as used in the laboratory enabled the distinction of 7 morphologically different types of structures including complete virions, other enveloped and non-enveloped particles and dense bodies (Topilko and Michelson, 1994). In the present study, electron microscopy was used to investigate the kinetics and modalities of the earliest interactions between these components of inoculum and human foreskin fibroblasts (FSF). Particles did not attach to cells during incubation at 4 degrees C. However, when FSF were adsorbed with virus for 30 seconds at 37 degrees C, HCMV particles attached to the cell surface. Particle attachment was mediated by fine virus envelope-cell membrane bridges. Within 60 seconds, numerous virions had fused with cell membranes, and nucleocapsids had entered the cytoplasm. Enveloped particles with translucent cores, designated non-infectious enveloped particles (NIEP), were also seen to enter cells in the same way and with the same kinetics as complete virions. Uptake of dense bodies followed the same kinetics and mode of penetration as complete virus particles. These findings reveal that in vitro, enveloped particles (virions and NIEP) and dense bodies enter the cytoplasm of the host cell simultaneously, immediately (< 60 seconds) after contact with the cell membrane. Our results suggest that activation of immediate early cellular responses may not simply be due to transmembrane signal transduction, but that hyperimmediate entry of these elements into cells may participate directly in host cell activation.

Adsorption↗

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Nasal mucosa in the iron deficient state. A clinical and electron-microscopic study.

Good results of iron therapy obtained in ozena patients with significantly lowered serum iron level encouraged studies on the pathogenesis of the disease. In electron microscopic examinations, special attention was paid to the considerable disintegration of connective-tissue stroma in the mucosa. In some connective-tissue cells ferruginous micelles were found in the mitochondrial matrix. Mitochondrial deposits may be a morphological expression of disturbed iron metabolism at subcellular levels.

Cytoplasm↗

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