Author(s): Krylova MI, Krylova MI
Abstract Share this page
Abstract Electron microscopic observations of the lymph hearts of tadpoles and yearling frogs of Rana temporaria showed that mast cells (MCs) were present not only between muscle fibers (population of resident MCs), but in the cavities of lymph heart (population of circulating MCs), too. There were some differences in the ultrastructure of the resident MCs at each studied stage of larval development. The first recognizable MCs were revealed in the lymph hearts at premetamorphosis (stages 39-41). MCs presented as mononuclear relatively small and slightly elongated cells with a few immature secretory granules and numerous free ribosomes, polysomes and short cisternae of rough endoplasmic reticulum (RER) in the cytoplasm. Chromatin of their nuclei was poorly condensed; the Golgi apparatus was moderately developed. At pro-metamorphosis (stages 44-45), we revealed MCs at different levels of their differentiation. Some MCs demonstrated an active process of granulogenesis in their cytoplasm. Among densely packed cytoplasmic organelles, immature secretory granules were closely associated with cisternae of RER and free ribosomes. Other MCs appeared as more differentiated cells. They were characterized by a predominantly heterochromatic nuclei and cytoplasm filled with polymorphic and heterogeneous granules. MCs also showed a reduction in the number of free ribosomes and cisternae of RER in the cytoplasm. On the contrary, the Golgi apparatus was well developed. Stacks of Golgi cisternae, detaching vacuoles, and progranules occupied the perinuclear region. The majority of the outlines above ultrastructural features of differentiated MCs were typical for MCs of yearling frogs. At metamorphic climax (stages 52-53), MCs often tightly contacted with macrophages. We did not reveal apoptotic MCs. However, some MCs exhibited morphological features typical for programmed necrosis-like death, which was characterized by mitochondria swelling, dilatation of cisternae of RER and nuclear envelope, plasma membrane rupture and subsequent loss of intracellular contents. Electron microscopical immunocytochemistry revealed the localization of atrial natriuretic peptide (ANP), substance S (SP) and heat shock protein (Hsp70) in the secretory granules of the resident and circulating MCs at different stages of tadpole development and in yearling frogs.
This article was published in Tsitologiia
and referenced in Molecular Biology: Open Access