No abstract

The existence of telocytes (TCs) has not yet been established in the pancreases of aquatic reptiles. Here, we report TCs in the exocrine pancreas of Pelodiscus sinensis using transmission electron microscope (TEM), immunohistochemistry (IHC), and immunofluorescence (IF) techniques. TCs surrounded the acini and ducts of the connective tissue of the exocrine pancreas and between lobules and gland cells. The cells were located preferably close to the blood vessels, interlobular ducts, and nerve fibers. Ultrastructurally, TCs exhibited small and large bodies with thick and thin portions, podoms, and podomers, and prolongations that form dichotomous branching with hetero-cellular and homo-cellular junctions. The podom (thick) portions showed caveolae, mitochondria, rough endoplasmic reticulum, and vesicles. The nucleus carries heterochromatin and is irregular in shape. The shape of TCs depends on the number of telopodes (Tps) bearing long, short, spindle, triangular, and “beads on a string” shapes with twisted, tortuous prolongations and ramifications. Shed extracellular vesicles and exosomes were found frequently released from projections and Tps within connective tissue in the vicinity of the acini and collagen fibers. IHC and IF results showed CD34+, α-SMA+, and vimentin+, long and triangle-shaped TCs, consistent with the TEM findings. The presence of shaded vesicles from TCs might implicate their possible role in immune surveillance, tissue regeneration as well as regulatory functions in the reptilian pancreas.

We investigated the structure of the soft-shelled turtle, Pelodiseus sinensi, spleen and demonstrated that there were several microanatomical peculiarities by light and transmission electron microscopy. In the spleen, the white pulp of the spleen was composed of two compartments, the periarteriolar lymphatic sheath (PALS) and periellipsoidal lymphatic sheath (PELS). No lymph nodules and marginal zones were found. The spleen-blood barrier stood in the PELS and the ellipsoid. The high endothelial lining of penicilliform capillary contained small channels. These channels allowed circulating substances or lymphocytes to enter the ellipsoid. The distal portion of the penicilliform capillaries directly opened to pulp cords. The ellipsoid-associated cell (EAC) was located at the surface of the ellipsoid. Reticular fibers were mainly distributed in ellipsoid and the outer PELS. Both reticular cells and macrophages were distributed in the outer layers of PELS. S-100 protein positive dendritic cells were mainly distributed in out cells layer of the PELS and all over the PALS. Forty minutes after injection, carbon particles of Indian ink were mainly observed in the ellipsoid. Few carbon particles were observed in the outer PELS and fewer carbon particles in the red pulp. These findings suggested that a blood-spleen barrier indeed existed in the soft-turtle, P. sinensi, and it was a complex composed of an ellipsoid (including supporting cells, EAC, and reticular fibers) and the outer compartments of PELS (including dendritic cells, reticular fibers and cells, macrophages).

The ultrastructure of the interstitial cells of Cajal (ICC) has been examined in birds, but the distribution of these cells remains obscure because a suitable marker is lacking. In the present study, the identification and expression of c-Kit-positive cells in the chicken intestine were demonstrated by means of in situ hybridization histochemistry and the expression of the c-Kit gene by real-time quantitative PCR. Two types of cells stained positive for c-Kit mRNA. The first group consisted of spindle-shaped or bipolar cells identified as ICC. The ICC were found at a variety of locations: at the level of the myenteric plexus between the circular and longitudinal muscle and intermingled with smooth muscle cells within muscle bundles in the circular and longitudinal muscle layers. The ICC were also identified along the submucosal layer. The second group was composed of round-shaped cells, which resembled mast cells. Mast cells were mainly found in the lamina propria region as well as in the submucosal layer. The expression of the c-Kit gene by real-time quantitative PCR revealed the expression of c-Kit mRNA throughout the lamina muscularis and mucosa of the intestine; however, the quantitation was variable in different regions. This study reveals conclusively for the first time the distribution of ICC, quantifies the expression of c-Kit mRNA in the intestine of adult chicken, and also compares the c-Kit-positive cell types morphologically.