This study demonstrates for the first time that ICC are present in human extrahepatic bile ducts where they are more densely aggregated than in the gallbladder. This cellular network is likely to be involved in biliary tract motility and its related disorders.

Cryofixation by high-pressure freezing (HPF) followed by freeze substitution (FS) is a preferred method to prepare biological specimens for ultrastructural studies. It has been shown to achieve uniform vitrification and ultrastructure preservation of complex structures in different cell types. One limitation of HPF is the small sample volume of <200 µm thickness and about 2000 µm across. A wool follicle is a rare intact organ in a single sample about 200 µm thick. Within each follicle, specialized cells derived from multiple cell lineages assemble, mature and cornify to make a wool fibre, which contains 95% keratin and associated proteins. In addition to their complex structure, large density changes occur during wool fibre development. Limited water movement and accessibility of fixatives are some issues that negatively affect the preservation of the follicle ultrastructure via conventional chemical processing. Here, we show that HPF-FS of wool follicles can yield highquality tissue preservation for ultrastructural studies using transmission electron microscopy.

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Enveloped viruses hijack cellular membranes in order to provide the necessary material for virion assembly. In particular, viruses that replicate and assemble inside the nucleus have developed special approaches to modify the nuclear landscape for their advantage. We used electron microscopy to investigate cellular changes occurring during nudivirus infection and we characterized a unique mechanism for assembly, packaging, and transport of new virions across the nuclear membrane and through the cytoplasm. Our three-dimensional reconstructions describe the complex remodeling of the nuclear membrane necessary to release vesicle-associated viruses into the cytoplasm. This is the first report of nuclear morphological reconfigurations that occur during nudiviral infection. IMPORTANCE The dynamics of nuclear envelope has a critical role in multiple cellular processes. However, little is known regarding the structural changes occurring inside the nucleus or at the inner and outer nuclear membranes. For viruses assembling inside the nucleus, remodeling of the intranuclear membrane plays an important role in the process of virion assembly. Here, we monitored the changes associated with viral infection in the case of nudiviruses. Our data revealed dramatic membrane remodeling inside the nuclear compartment during infection with Oryctes rhinoceros nudivirus, an important biocontrol agent against coconut rhinoceros beetle, a devastating pest for coconut and oil palm trees. Based on these findings, we propose a model for nudivirus assembly in which nuclear packaging occurs in fully enveloped virions.

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