In order to obtain a three-dimensional view of the plastid-dividing ring (PD ring) and promote the biochemical study of plastid division, we developed a procedure to isolate structurally intact dividing chloroplasts (rhodoplasts) possessing PD rings from a highly synchronized culture of the unicellular red alga Cyanidioschyzon merolae. The procedure consists of five steps. (1) The chloroplast division cycle is synchronized by light/dark cycles and treatment with 5-fluorodeoxyuridine. (2) The synchronized cells are treated with hypotonic solution. (3) The swollen cells are lysed in a French Pressure Cell. (4) The lysate is treated with DNase I. (5) The intact chloroplasts are separated by density-gradient centrifugation. The PD ring was visualized by fluorescence microscopy, after labeling the surface proteins of isolated chloroplasts with N-hydroxy-sulfo-succinimidyl biotin and detecting them with fluorescein isothiocyanate avidin. Scanning electron microscopy (SEM) showed that the outer envelopes and PD rings were conserved on the isolated dividing chloroplasts. These are the first fluorescence microscopic and SEM images of the PD ring and they clearly show PD rings encircling isolated dividing chloroplasts in three dimensions.

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Manganese (Mn) accumulates at a higher level in the pancreas than in any other organs when excess Mn is administered to the rat. The present study is carded out to analyze the intracellular localization of Mn existed in the pancreatic cell of Mn‐treated rats. Transmission electron microscope and X‐ray micro‐analysis connected with a rapid freezing fixation technique showed that a large amount of Mn was localized in tysosomal particles of the pancreatic cell of Mn‐treated rats. The Mn‐rich particles disappeared when the element‐administration was discontinued, showing that the accumulation of Mn is reversible. To confirm that Mn is in the lysosomes, a centrifugal subcellular‐fractionation and a neutron activation analysis were carried out. The result indicated that much Mn existed in the lysosomal fraction.

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By using a transmission electron microscope equipped with an energy dispersive spectrometer, it Was possible to detect the morphological, structural, and chemical characteristics of individual asbestos fibers and clay minerals without any realignment of the equipment. A rapid and convenient procedure for semiquantitative analysis is proposed. Analyses are given for 21 hydrous silicates, asbestos and clay minerals, by both ordinary chemical and energy dispersive methods. The energy dispersive results were comparable to those obtained by chemical analysis. Application of this procedure to asbestos fibers proved this method to be practical and valid for characterization of asbestos in environmental and tissue samples.