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

Defining the EM-signature of successful cell-transfection

In this report, we describe the architecture of Lipofectamine 2000 and 3000 transfection- reagents, as they appear inside of transfected cells, using classical transmission electron microscopy (EM). We also demonstrate that they provoke consistent structural changes after they have entered cells, changes that not only provide new insights into the mechanism of action of these particular transfection-reagents, but also provide a convenient and robust method for identifying by EM which cells in any culture have been successfully transfected. This also provides clues to the mechanism(s) of their toxic effects, when they are applied in excess. We demonstrate that after being bulk-endocytosed by cells, the cationic spheroids of Lipofectamine remain intact throughout the entire time of culturing, but escape from their endosomes and penetrate directly into the cytoplasm of the cell. In so doing, they provoke a stereotypical recruitment and rearrangement of endoplasmic reticulum (ER), and they ultimately end up escaping into the cytoplasm and forming unique 'inclusion-bodies.' Once free in the cytoplasm, they also invariably develop dense and uniform coatings of cytoplasmic ribosomes on their surfaces, and finally, they become surrounded by 'annulate' lamellae' of the ER. In the end, these annulate-lamellar enclosures become the ultrastructural 'signatures' of these inclusion-bodies, and serve to positively and definitively identify all cells that have been effectively transfected. Importantly, these new EM-observations define several new and unique properties of these classical Lipofectamines, and allow them to be discriminated from other lipoidal or particulate transfection-reagents, which we find do not physically break out of endosomes or end up in inclusion bodies, and in fact, provoke absolutely none of these 'signature' cytoplasmic reactions.

1 alpha,25-dihydroxyvitamin D3 regulates the expression of carbonic anhydrase II in nonerythroid avian bone marrow cells

1 alpha,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the active metabolite of the steroid hormone vitamin D, is a potent regulator of macrophage and osteoclast differentiation. The mature osteoclast, unlike the circulating monocyte or the tissue macrophage, expresses high levels of carbonic anhydrase II (CAII). This enzyme generates protons and bicarbonate from water and carbon dioxide and is involved in bone resorption and acid-base regulation. To test whether 1,25(OH)2D3 could induce the differentiation of myelomonocytic precursors toward osteoclasts rather than macrophages, we analyzed its effects on the expression of CAII in bone marrow cultures containing precursors common to both cell types. The expression of CAII was markedly increased by 1,25(OH)2D3 in a dose- and time-dependent manner. In bone marrow, this increase occurred at the mRNA and protein levels and was detectable as early as 24 hr after stimulation. 1,25(OH)2D3 was also found to induce CAII expression in a transformed myelomonocytic avian cell line. These results suggest that 1,25(OH)2D3 regulates the level at which myelomonocytic precursors express CAII, an enzyme that is involved in the function of the mature osteoclast.