Rodlet cells development in the intestine of sea bass (Dicentrarchus labrax)

Abstract

The enigmatic rodlet cells (RCs) are characterized by conspicuous inclusions named "rodlets". They were discovered over 100 years ago and were considered as parasites but shortly afterward interpreted as endogenous cells. The RCs have been described in different tissues of marine and freshwater teleosts, but their origin and function remain unknown. This work was designed to an ultrastructural study on RCs development and distribution in intestinal epithelium of Dicentrarchus labrax. Three different stages of RCs development from early precursor cells to mature phase were observed, as well as a migration and finally an extrusion of their contents. In this study, the immature cells were found near the basal epithelium membrane. They were mainly identified by a rough endoplasmic reticulum with dilated cisternae, by developing rodlets and a thin fibrillar coat. The maturing RCs, localized in the middle zone of the epithelium, appeared to be undergoing a reorganization of the cell organelles. The mature RCs, placed near the free surface, showed a thick subplasmalemmar fibrillar coat. Most of the organelles were aggregated at the cell apex with a basally located nucleus. A cellular polarity was more evident. One of the most conspicuous features was the occurrence of mature rodlets club-sac in shape orientated toward the cell apex. Adhesive junctions between surface epithelial cells and RCs, while discharging their contents, were seen. We have connected morphological figures and distribution to different stages of development in RCs, supporting the hypothesis of their secretory function.

Tyrosine phosphatase inhibitor triggers rodlet cell discharge in sunfish scale epidermis cultures

“…; Laurà et al . ). The distinctive characteristic of these pear‐shaped cells is the cytoplasmic collection of rodlets, the linear namesake structures situated in the cytoplasm.…”

Tropomyosin and alpha‐actinin in teleost rodlet cells

“…(1979) identified densely packed filaments within the rodlet cell cortex that resembled the contractile microfilament system in smooth muscle. Several studies also identified electron‐dense plaques within the cortex that appeared similar to the dense plaques present in smooth muscle (Barber et al., 1979; Desser & Lester, 1975; Hawkins, 1984; Laurà et al., 2012; Leino, 2002; Smith, Caceci, Marei, & El‐Habback, 1995). Combined with ultrastructural studies showing empty rodlet cell carcasses within fish epithelium (Hawkins, 1984; Leino, 1974, 2002; Smith et al., 1995), it was suggested that the rodlet cell expels its contents via a smooth muscle‐like contraction of the fibrous capsule that forces the rodlets and other intracellular material out into the extracellular milieu (Leino, 2002).…”

“…Rodlet cells contract, resulting in the discharge of rodlet cells from the epidermal surface (in the case of skin; Figure 1d‐f)) or into the extracellular milieu (in the case of, e.g. intestinal epithelium; Laurà et al., 2012; Leino, 1974). Rodlet ejection has been proposed to occur by contraction of the fibrous capsule as noted above but Bielek (2005) and Schmachtenberg (2007) have suggested a buildup of intracellular pressure may drive expulsion.…”

The morphology of photophores in the garrick, cyclothone braueri (Family: Gonostomatidae): an ultrastructure study

“…Finally, the sections were obtained with a Reichert Jung Ultracut E. Semi‐thin sections (1 lm) were stained with toluidine blue and examined by a light microscope. Ultrathin sections (700 A°) were obtained from selected areas of the semi‐thin sections, stained with uranyl acetate and lead citrate; thus, they were examined and photographed by a Jeol JEM 100 SX transmission electron microscope (Laurà et al ., ,b).…”