Article

The cytoplasmic matrix of the adrenal chromaffin cells of rats under normal and stressed conditions.

Department of Anatomy, Kanazawa University School of Medicine, Japan.
Journal of Electron Microscopy Technique 09/1989; 12(4):356-63. DOI: 10.1002/jemt.1060120408
Source: PubMed

ABSTRACT In embedment-free electron microscopy with polyethylene glycol embedding and subsequent deembedding, the conventional cytoplasm of the chromaffin cells was revealed to consist of a three-dimensional lattice of microtrabeculae and gives the impression that the chromaffin granules are held in place by the lattice. After the restraint stress, a substantial number of chromaffin cells were almost free of granules, and the microtrabecular lattice was much more compact than that in cytoplasmic regions occupied with remaining granules or increased mitochondria. In immunocytochemistry, actin immunofluorescence was confined to the subplasmalemmal regions, while tubulin and tropomyosin immunofluorescence appeared throughout the entire cytoplasm of normal chromaffin cells. After the stress, the immunofluorescence for actin and tubulin increased in intensity, while that for tropomyosin decreased. Immunogold labelings for actin and tubulin were found mainly on the thinner subplasmalemmal microtrabeculae and the thicker perikaryal ones, respectively, while some were deposited in the form of small aggregates on portions of microtrabeculae. No specific association between the gold labelings for actin or tubulin and the chromaffin granules was found, even in the subplasmalemmal regions. A hypothetical interpretation was proposed in which a more compact lattice of the microtrabeculae in spatial association with a looser lattice represents a gelated state of the cytoplasm. The significance of the gel-sol transition of the cytoplasmic matrix in relation to the secretory mechanism was discussed.

0 Bookmarks
 · 
22 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: TEM of any in situ cells in embedment-free sections--regardless of specimen-fixation methods--clearly shows strand-lattices occupying the cytoplasmic matrix. The cytoplasmic matrix is assumed to be a site of soluble proteins; however, it appears indistinct as conventional TEM cannot target it. Strand-lattices similar to the cytoplasmic ones are duplicated in bovine serum albumin as well as solated gelatin fixed at warm temperatures and at appropriate concentrations, while lattices from gelatin gelated by cooling before fixation are much more compact than those from solated gelatin at a given concentration. Based on the finding of the in vitro proteins, a new interpretation of cell ultrastructures in embedment-free section TEM is proposed: first, differences in the compactness of cytoplasmic lattices represent those in the protein concentration in the cytoplasmic matrix; second, when loose and compact lattices are contiguous within a cell, the cytoplasmic matrix domain occupied by the compact lattice is in a gel state while the remaining domain of the same cell is in a sol state. The explanation for the states of the gel and sol based on the lattice-compactness is applicable to changes in the lattice-compactness of the cytoplasmic matrix of neurohypophyseal axons under intense secretion.
    Advances in Colloid and Interface Science 10/2010; 160(1-2):49-55. · 8.64 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Embedment-free electron microscopy using polyethylene glycol as a transient embedment has revealed that slender strands, originally termed microtrabeculae and microtrabecular lattices, interconnect every organelle and conventional cytoskeletons as well as plasma membranes, resulting in the formation of 3-D meshworks in all portions of the cytoplasmic matrix of every cell. The microtrabeculae correspond well to the wispy components in the cytoplasmic matrix of conventionally epoxy-sectioned cell specimens that have been looked at but often neglected because of their poorly defined images due to the presence of embedding media having a substantial electron-scattering property. Because of the occurrence of similar meshworks in specimens that are supposed to be unstructured, such as the intramitochondrial matrix and blood plasma, together with the failure to detect any predictable changes of the microtrabecular lattices by experimental manipulation of cellular environments, it is inaccurate to conclude that all microtrabecular lattice represent structures equivalent to those in a living state of cells simply because of their clear appearance. Instead, three possible interpretations are newly proposed for the biological significance of the microtrabecular lattices. The first is that the appearance of lattices represents the presence of proteins, and that their approximate concentrations are speculated based on the compactness of the lattice. The second is that when an intracellular microdomain composed of more compact lattices is contiguous with another domain composed of looser lattices in a given cell, the former might represent the gelated state and the latter the solated state. Possible examples for these two interpretations are also proposed, possibly leading us to further elaborate the significance of microtrabecular lattices.
    Anatomical Science International 04/2003; 78(1):17-24. · 0.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: With higher contrast and transparency due to the absence of epon and stereo-viewing effect due to thicker sections than conventional electron microscopy as methodological advantages, the renal glomerular slits were re-examined in embedment-free section electron microscopy. In addition to clear demonstration of strands bridging the slits in forms of ladders with highly irregular intervals and various extension-directions and length, this study disclosed clearly for the first time in the "section" TEM thin sheets which partially spanned the slit together with the strand-ladders. No strands were found to align in forms of typical zippers in normal kidney. Furthermore, en-face ultrastructure of the basal lamina in situ was clearly demonstrated in superimposed sites of the endothelial fenestrae with the slits.
    Microscopy Research and Technique 02/2011; 74(2):142-7. · 1.59 Impact Factor