Al3+ and Zn2+-induced structural changes and localization in a fully-hydrated live eukaryotic cellular model

This study combined techniques that did not require preparation protocols that were potentially harmful to the cell, making it possible to investigate cells at, or close to, their natural physiological state. We used the freshwater protozoon Chilomonas paramecium as a eukaryotic cellular model to locate sites of Al3+ or Zn2+ accumulation and quantify the associated structural changes. Cells were fully hydrated throughout the study, which used a combination of differential interference contrast light microscopy, confocal laser scanning microscopy and transmission X-ray microscopy. The latter technique allowed high resolution (50 nm) and high contrast imaging of live cells in solution. For confocal laser scanning microscopy the relatively new fluorochrome Newport Green was used. This made fluorescent complexes with intracellular Al3+ and Zn2+, allowing localisation of metal-containing granules and vesicles, After long term exposure a previously unreported annular-shaped site of metal accumulation was found, signifying a vesicle with metal accumulated in the periphery only. After exposure to Al3+ and Zn2+, the cell pellicle was thinner and the majority of rounded-up cells had a concentric layering of organelles. By combining a variety of techniques it was possible to gain high resolution structural and chemical information on cells minimally exposed to potentially artefact-inducing procedures. (C) 2001 Academic Press.