Cell surface membrane organization revealed by freeze-drying

Reexamination of the morphogenetic block of a putative late-stage, temperature-sensitive mutant of Moloney murine leukemia virus

The ts3 temperature-sensitive mutant of Moloney murine leukemia virus has been reported to have a morphogenetic block in a late stage of the budding process. As evidence, previously published electron micrographs of cells maintained at the nonpermissive temperature (39 degrees C) revealed numerous budding virions on the cell surface. However, it appears now that these micrographs reflected budding that occurred not at 39 degrees C, but after cells were removed from the incubator before fixation. The morphogenesis of ts3 is actually blocked at an earlier stage of development.

Structure of and alterations to defective murine sarcoma virus particles lacking envelope proteins and core polyprotein cleavage

HTG2 hamster cells produce a defective murine sarcoma virus lacking gp70 and, consequently, viral surface projections (knobs), but the lack of knobs appears to have no effect on intramembrane particle distribution. In addition, it has been noted that the core of the virus remains in the "immature" form as a result of the failure of the polyprotein precursor (p65) to undergo cleavage. However, incubation of HTG2 virus with avian myoblastosis virus was found to yield specific cleavage products of p65.

Early event of C-type virus budding in cells infected with a Rauscher leukemia virus temperature-sensitive mutant

Surface replicas of ts25-infected cells reveal the organization of virus-specific knobs prior to and during the early stage of budding, and antibody-mediated ferritin labeling suggests a transmembrane association of viral envelope and core components.

A simple technique for the examination of urothelial surface morphology by transmission electron microscopy: platinum-carbon replicas of critical point dried bladder tissue

A simple technique is described for the examination of bladder luminal surface morphology by transmission electron microscopy (TEM). Pieces of bladder tissue are critical point dried and replicated with platinum-carbon in the manner standard for freeze-fracture. The large intact areas of replica produced show improved resolution of detail compared with scanning electron microscopy (SEM), and allow the survey of larger expanses of membrane than is possible with standard TEM techniques. Comparison of the structure observed in platinum-carbon replicas of critical point dried tissue with that seen in frozen-surface replicas, freeze-fracture replicas and thin-sections reveals the presence of artefacts in the critical point dried specimens which are not detected by SEM. Similar artefacts are evident in replicas of partially freeze-dried samples. The nature and origin of these artefacts are discussed. It is concluded that replicas of critical point dried specimens provide useful information on surface morphology at magnifications intermediate between those normally used with standard TEM and SEM techniques. The details of surface morphology viewed by this method are discussed with particular reference to the structure of the intercellular boundary.