The ultrastructural morphogenesis of squirrel monkey retrovirus (SMRV) and Mason-Pfizer monkey virus (MPMV) growth in cell culture were compared. Both viruses develop by a process that begins with the formation of intracytoplasmic A particles which are then enveloped at the plasma membrane during budding. SMRV also develops as a crescent-shaped nucleoid beneath a bulging plasma membrane, a development characteristic of type C oncornaviruses. Free extra-cellular mature SMRV was generally round with a centrally located electron-dense nucleoid enclosed by the viral envelope. In contrast, mature MPMV had a tubular-shaped nucleoid. Negative stained preparations of both viruses yielded head-tail forms with surface projections. By uranyl acetate/critical point drying, SMRV particles were usually round with an eccentric electron-dense nucleoid enclosed by the viral envelope, whereas MPMV particles were round and contained an electron-dense bar-shaped nucleoid. These morphological observations indicate that SMRV more closely resembles MPMV, presently the only member of genus oncornavirus type D, than other retroviruses species. However, since SMRV can be morphologically, biochemically, and immunologically distinguished from MPMV, it represents a new species within genus oncornavirus type D.
The pathology of pulmonary toxicity induced by the anticancer drug 1, 3-bis(2-chloroethyl)-1-nitrosourea (BCNU) was studied in F344 rats. The compound was administered in a multiple-dose regimen comparable to the dose schedule commonly given patients. Morphological aspects were investigated by light and electron microscopy in a serial sacrifice experiment. All animals developed pulmonary fibrosis accompanied by formation of peribronchial and peribronchiolar foci of granulomatous tissue. The first morphologically detectable changes were identified in alveolar type II cells and were suggestive of disturbed surfactant synthesis. Endothelial damage accompanied by pronounced plasma cell infiltration developed subsequently and was followed by the development of diffuse interstitial fibrosis.
The sensitivity and specificity of the unlabeled antibody-hemocyanin bridge method for immunoelectron microscopic localization of virion and cell surface antigens has been demonstrated using a hyperimmune serum to the Rauscher murine leukemia virus structural envelope glycoprotein (gp 70). The technique localized the gp70 on the viral envelope and on the infected cell surface at dilutions of greater than 10(-3) for the primary antiviral serum. Little or no nonspecific binding of hemocyanin was detected in control experiments using high concentrations of normal nonreacting or adequately absorbed antiviral primary sera and excess antibody bridge and marker; thus, the system is highly specific. Furthermore, sensitivity can be increased approximately fivefold by marked amplification steps whereby a specimen fixing only a slight amount of hemocyanin can be subsequently treated with antihemocyanin antibody, followed by hemocyanin.
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