Annulate lamellae‐soleplate nuclei associations in skeletal muscle fibers of rats during chronic high‐dose exposure to neostigmine

Abstract

To investigate annulate lamellae (AL) with nuclear changes, ultrastructural time course studies were done of the reversible end-plate myopathy in the soleus muscles of rats exposed chronically to a high dose of the anticholinesterase drug neostigmine. At the earliest stage (2 hours) in which severe subjunctional damage involving a nuclear lesion (nuclear pyknosis) was prominent, AL profiles were undetectable. At the intermediate stage (7, 21 days), in which the subjunctional organelles tended to cluster and nuclear pyknosis often accompanied degenerative features, most AL laid near the surface of the abnormal nuclei, where there were signs of elimination or formation of pores, as well as a progression of changes leading to the loss of pores. At the late stage (56 days), in which muscle repair was nearly completed and euchromatic nuclei usually were found, there was a concomitant enhanced formation of false nuclear inclusions and of the AL profiles in these sites. Pores are packed on nuclear envelopes, which detach themselves from the nucleus and take the same profile as AL. This phenomenon can be envisioned not only in the euchromatic but also in the abnormal (pyknotic or degenerated) nuclei. Following nuclear reconstitution, the nuclear envelope folding is accelerated to induce the usual pattern of AL organization, i.e., budding from the invaginated nuclear envelope.

Defining the EM-signature of successful cell-transfection

“…Finally, another absolutely unique and notable ultrastructural feature that defines nearly all of the lipofectamine/ribosome inclusions that we have observed in the cytoplasm of transfected cells is that they finally end up enclosed in "annulate lamellae." These "annulate lamellae" are of course defined as nuclear-pore-studded domains of ER that occur in all cells, but are normally most elaborated in cells involved in rapid cell division or rapid nuclear envelope growth, such as oocytes or egg cells (Cordes et al, 1996; Erenpreisa et al, 2002; Eymieux et al, 2021; Haggag and Gilloteaux, 2005; Huber et al, 2020; Imreh and Hallberg, 2000; Kawabuchi et al, 1989; Kessel, 1983a; Kessel, 1983b; Raghunayakula et al, 2015; Walter and Tandler, 1989). In transfected cells however, we find that such annulate lamellae are invariably and strikingly over-abundant, and that they specifically direct themselves to enclosing the late Lipofectamine/ribosome inclusions, after the aforementioned ER- elaborations have retreated to their peripheries (Fig.7).…”