Duct-forming Cells Research Articles

Ultrastructure of the female reproductive organs of the diving beetle Deronectes moestus incospectus (Leprieur, 1876) (Dytiscidae, Hydroporinae)

We describe the ultrastructure of the female reproductive organs of Deronectes moestus (Dytiscidae Hydroporinae). The long spermathecal duct has a simple epithelium lined internally by a thin cuticle and externally by a thick layer of muscle cells. The wide duct lumen contains electron-dense material, among which remnants of extracellular material are visible. This material consists of tubular structures assembled around sperm bundles previously described in the male deferent ducts. The so-called gland, disposed along the spermathecal duct, is a structure with epithelial cells lined by an irregular cuticle bearing a rich system of microvilli. Many mitochondria are visible in the apical cytoplasm of the epithelial cells, and a few spheroidal bodies are close to the basal nuclei. Since the epithelial ultrastructure of the gland suggests it is involved in fluid uptake from the lumen rather than secretory activity, the term gland, coined by other authors to describe this organ, is inappropriate. The spermatheca is a large structure with a complex epithelium showing secretory and duct-forming cells. The lumen of this organ contains sperm with the distinctive ultrastructural features of those described in the male deferent ducts, namely having a mitochondrial matrix with a small crystallized area and electron-dense dots. Because to its overall organization, the spermatheca of D. moestus can be considered a more integrated organ than those in previously studied hydroporine species.

The Structure of the Female Genital System of the Diving Beetle Scarodytes halensis (Fabricius, 1787) (Hydroporinae, Dytiscidae), and the Organization of the Spermatheca and the Spermathecal Gland Complex

The fine structure of the female reproductive organs of the diving beetle Scarodytes halensis has been described, with particular attention to the complex organization of the spermatheca and the spermathecal gland. These organs are fused in a single structure whose epithelium is involved in a quite different activity. The secretory cells of the spermathecal gland have a large extracellular cistern with secretions; duct-forming cells, by their efferent duct, transport the secretions up to the apical cell region where they are discharged into the gland lumen. On the contrary, the spermatheca, filled with sperm, has a quite simple epithelium, apparently not involved in secretory activity. The ultrastructure of the spermatheca is almost identical to that described in a closely related species Stictonectes optatus. Sc. halensis has a long spermathecal duct connecting the bursa copulatrix to the spermatheca-spermathecal gland complex. This duct has a thick outer layer of muscle cells. Through muscle contractions, sperm can be pushed forwarding up to the complex of the two organs. A short fertilization duct allows sperm to reach the common oviduct where eggs will be fertilized. The different organization of the genital systems of Sc. halensis and S. optatus might be related to a different reproductive strategy of the two species.

Fine structure of the female genital system of diving beetle Stictonectes optatus (Seidlitz, 1887) (Dytiscidae-Hydroporinae) and evidence of mating plug formation

The general organization of the female genital system of the diving beetle Stictonectes optatus was studied, clarifying the complex structure of the spermatheca and spermathecal gland. The two structures adhere closely to each other, sharing a small area of their cuticular epithelium. A long duct connects the bursa copulatrix to the spermatheca, where the sperm are stored. The sperm reach the common oviduct, where egg fertilization occurs, via a fertilization duct. The spermathecal gland cells have extracellular cisterns where secretions are stored. Thin ducts composed of duct-forming cells transport these secretions to the apical gland region and into the spermathecal lumen. Soon after mating, the bursa copulatrix is almost completely occupied by a plug secreted by the male accessory glands. The secretions of the bursa epithelium seem to contribute to plug formation. Later this plug becomes large and spherical, obstructing the bursa copulatrix.

Differential regulation of transposable elements (TEs) during the murine submandibular gland development

The submandibular gland (SG) is a relatively simple organ formed by three cell types: acinar, myoepithelial, and an intricate network of duct-forming epithelial cells, that together fulfills several physiological functions from assisting food digestion to acting as an immune barrier against pathogens. Successful SG organogenesis is the product of highly controlled and orchestrated genetic and transcriptional programs. Mounting evidence links Transposable Elements (TEs), originally thought to be selfish genetic elements, to different aspects of gene regulation in mammalian development and disease. To our knowledge, the role of TEs during murine SG organogenesis has not been studied. Using novel bioinformatic tools and publicly available RNA-Seq datasets, our results indicate that a significant number of genic and intergenic TEs are differentially expressed during the SG development. Furthermore, changes in expression of specific TEs correlated with that of genes involved in cellular division and differentiation, critical aspects for SG maturation. Altogether, we propose that TEs modulate gene networks that operate during SG development.

The ultrastructure of sperm and female sperm storage organs in the water strider Gerris lacustris L. (Heteroptera) and a possible example of genital coevolution

The fine structural organization of the male and the female inner reproductive apparatuses of the water-strider Gerris lacustris was studied. The sperm of the species shows a long helicoidal acrosome provided with longitudinal tubules, and a short nucleus. The flagellum is characterized by crescent mitochondrial derivatives and a 9 + 9 + 2 axoneme, as occurs in all Heteroptera. The female reproductive apparatus is characterized by an extremely long spermathecal duct, filled with sperm, which plays the role of the main sperm storage organ. The duct has a thin epithelium surrounded by a complex of secretory and duct-forming cells. The spermathecal duct flows into the gynatrial sac. This region, together with the fertilization chamber, exhibits a simple epithelium with deep apical plasma membrane invaginations, and it does not show conspicuous secretions. The basal cell region shows plasma membrane infoldings forming thin cytoplasmic bands hosting mitochondria and large intercellular spaces. This organization is typical of epithelia active in fluid reabsorption. Two lateral large gynatrial glands open into the gynatrial sac. Such glands also exhibit secretory and duct forming cells. The same structure of these glands is also present along the proximal region of the fecundation canal. The duct forming cells of these regions have very wide ducts with peculiar cuticular finger-like structures at their opening into the gland duct lumen. The results of the present study suggest the occurrence of a coevolution between the sperm and the spermathecal duct lengths.

Spermatheca of the scorpionfly Sinopanorpa tincta (Navás, 1931) (Mecoptera: Panorpidae).

The spermathecal structure of the scorpionfly Sinopanorpa tincta (Navás, 1931) was investigated using light microscopy, scanning, and transmission electron microscopy. The spermatheca consists of a bean-shaped spermathecal reservoir and an elongated spermathecal duct. The spermathecal reservoir can be subdivided into a distal portion with well-developed muscles and a proximal transitional portion connected to the spermathecal duct. The spermathecal duct is slender for its basal three-fourths and is greatly thicker for its distal one-fourth, which is mainly responsible for secretory function. A spermathecal pump formed from longitudinal muscle fibers was attached to the reservoir to control the transport of sperm. The lumen of the spermathecal reservoir is lined with a cuticle and filled with spermatozoa after copulation. The epithelium of the distal reservoir comprises a single type of epithelial cells, while the epithelium of the proximal reservoir and the spermathecal duct has three types of cells: secretory cells, duct-forming cells, and common epithelial cells. The secretory cells are rich in mitochondria, rough endoplasmic reticulum, and electron-dense secretory vesicles. The duct-forming cells form cuticular ducts, which connect the secretory cells to the lumen of the spermatheca. The spermathecal reservoir mainly serves as the storage of sperm, but the proximal reservoir as well as the spermathecal duct serves as secretory functions that maintain sperm viability.

Ultrastructure of male accessory glands in the scorpionfly Sinopanorpa tincta (Navás, 1931) (Mecoptera: Panorpidae)

The ultrastructure of male reproductive accessory glands was investigated in the scorpionfly Sinopanorpa tincta (Navás, 1931) (Mecoptera: Panorpidae) using light and transmission electron microscopy. The male accessory glands comprise one pair of mesodermal glands (mesadenia) and six pairs of ectodermal glands (ectadenia). The former opens into the vasa deferentia and the latter into the ejaculatory sac. The mesadenia consist of a mono-layered elongated columnar epithelium, the cells of which are highly microvillated and extrude secretory granules by means of merocrine mechanisms. The epithelium of ectadenia consists of two types of cells: the large secretory cells and the thin duct-forming cells. These two types of cells that join with a cuticular duct constitute a functional glandular unit, corresponding to the class III glandular cell type of Noirot and Quennedey. The cuticular duct consists of a receiving canal and a conducting canal. The secretory granules were taken up by the receiving canal and then plunged into the lumen through the conducting canal.

Comparative morphology and ultrastructure of the prosomal salivary glands in the unfed larvae Leptotrombidium orientale (Acariformes, Trombiculidae), a possible vector of tsutsugamushi disease agent.

The prosomal salivary glands of the unfed larvae Leptotrombidium orientale (Schluger) were investigated using transmission electron microscopy. In total, four pairs of the prosomal glands were identified--three pairs, the lateral, the medial and the anterior, belong to the podocephalic system, and one pair, the posterior, is separate having an own excretory duct. All glands are simple alveolar/acinous with prismatic cells arranged around a relatively small intra-alveolar lumen with the duct base. The cells of all glands besides the lateral ones contain practically mature electron-dense secretory granules ready to be discharged from the cells. The secretory granules in the lateral glands undergo formation and maturation due to the Golgi body activity. The cells of all gland types contain a large basally located nucleus and variously expressed rough endoplasmic reticulum. Specialized duct-forming cells filled with numerous freely scattered microtubules are situated in the middle zone of each gland's acinus and form the intra-alveolar lumen and the duct base. Both the acinar (secretory) and the duct-forming cells contact each other via gap junctions and septate desmosomes. Axons of nerve cells come close to the basal extensions of the duct-forming cells where they form the bulb-shaped synaptic terminations. The process of secretion is under the control of the nerve system that provides contraction of the duct-forming cells and discharge of secretion from the secretory cells into the intra-alveolar lumen and further to the exterior. Unfed larvae of L. orientale, the potential vector of tsutsugamushi disease agents, contain the most simply organized salivary secretory granules among known trombiculid larvae, and this secretion, besides the lateral glands, does not undergo significant additional maturation. Thus, the larvae are apparently ready to feed on the appropriate host just nearly after hatching.

Abstract 2032: TGF-β differentiates immortalized pancreatic epithelial cells to form duct architecture in 3D culture

Abstract A genetically engineered mouse (GEM) strain T26 having a transgene “CAG-loxP-βgeo-pA-loxP-SV40 tsA58 large T antigen (=tsTAg)-pA” was created by us, which expressed tsTAg in cells Cre/loxP recombination occurred. In a previous study, T26; Tie2-Cre mice were created, and their vascular and lymphatic endothelial cells expressing tsTAg could be cultured in vitro at 33°C (Yamaguchi et al., FEBS J., 2008). In this study, we established immortalized and cloned pancreatic epithelial cell lines from T26; Pdx1-Cre mice which expressed tsTAg in pancreatic epithelial cells in vivo by pancreas-specific Cre/loxP recombination. The cell lines were categorized into 1) ductal epithelial cell group which expressed CK19 and Sox9, and 2) acinar cell group which expressed Amylase2A of a digestive enzyme. In order to elucidate regulatory mechanisms of ductal cell differentiation and their plasticity, the immortalized ductal cell lines were cultured in collagen gel. A part of the cells formed spheroid or elongated and blanched architecture in the gel. Confocal or electron microscopic analysis indicated that their architectures had lumens with micro villi inside, and a part of them had tight junction at intercellular domain. It is noteworthy that the spheroid property changed into the elongated ductal (tubular) property by TGF-β stimulation in the 3D culture system, and the ductal architecture formation was suppressed by inhibitor of TGF-β signaling. 3D time-laps microscopic analysis demonstrated that a part of sphere-forming cells could change into duct-forming cells by TGF-β, which suggested existence of stem cells with susceptibility to TGF-β stimulation. The effect of TGF-β to change sphere-forming property into duct-forming property could be confirmed partially in some originally established murine pancreatic cancer cell lines. Taken together, these results suggested that TGF-β is an important factor for pancreatic duct and cancer differentiation and their architecture formation. Citation Format: Takashi Yamaguchi, Sanae Ikehara, Yuzuru Ikehara. TGF-β differentiates immortalized pancreatic epithelial cells to form duct architecture in 3D culture. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2032. doi:10.1158/1538-7445.AM2014-2032

The intermediate sperm type and genitalia of Zorotypus shannoni Gurney: evidence supporting infraordinal lineages in Zoraptera (Insecta)

The sperm ultrastructure and the male and female genital apparatus of Zorotypus shannoni were examined and documented in detail, mainly using transmission electron microscopy micrographs. The findings suggest an evolutionary trend shared with Z. hubbardi and Z. impolitus. The three species are characterized by enlarged mitochondrial derivatives and related modifications. Giant sperm are probably a synapomorphy of Z. hubbardi and Z. impolitus, whereas an intermediate condition of this feature is found in Z. shannoni. The monophyletic origin of Z. caudelli, Z. magnicaudelli, Z. huxleyi and Z. weidneri is suggested by characteristically modified axonemes. The presence of extra-acrosomal material is also an unusual feature for Zoraptera, but this condition also occurs in the majority of polyneopteran groups. The long and convoluted female spermathecal duct with secretory and duct-forming cells is a constant feature in Zoraptera. The enlarged seminal receptacle suggests an evolutionary link between the male genital structures and the sperm size on one hand, and the size of the female spermatheca on the other. The small and otherwise uniform group Zoraptera exhibits a remarkable variation of sperm types and genital structures, suggesting the impact of different types of selection. It is likely that cryptic female choice plays a major role in shaping the genital apparatus.

Ultrastructure of female accessory glands in the scorpionfly Panorpa sexspinosa Cheng (Mecoptera: Panorpidae)

The histology and ultrastructure of the female accessory glands in the scorpionfly Panorpa sexspinosa Cheng was studied using light and transmission electron microscopy. The glands consist of a pair of distal elongate gland tubes and a basal common duct, which opens in the genital cavity at the dorsal side of the genital plate. The whole gland tubes and common duct are similar histologically and ultrastructurally. The epithelium of female accessory glands consists of two cell types: the outer secretory cells and the inner duct-forming cells. These two cells that join with a cuticular duct connecting to the inner intima constitute a functional glandular unit belonging to Class 3 glandular cells of epidermal glands. The secretory cells are rich in organelles, such as mitochondria, rough endoplasmic reticulum, and Golgi complex, indicating that they are active in secretion. The duct-forming cells are flattened with sparse-distributed organelles. These two kinds of cells are connected by septate junctions. The cuticular duct consists of a receiving and a conducting canal and is responsible for transferring the secretions of the secretory cell to the lumen. The receiving canal is formed of interrupted multilayered inner epicuticle and located in the irregular extracellular cavity of the secretory cell, bounded by microvilli. The conducting canal connects the inner intima and opens into the central lumen. The tentative functions of the secretions are briefly discussed.

Ultrastructure of the accessory gland in the parthenogenetic thrips heliothrips haemorrhoidalis (Bouché) (Thysanoptera : Thripidae)

The fine structure of the reproductive accessory gland of the parthenogenetic thrips Heliothrips haemorrhoidalis (Thysanoptera : Thripidae) is reported. It consists of an apical bulb and a fine gland duct. The former consists of an epithelium with secretory and duct-forming cells surrounding a large gland lumen lined with a thin cuticle and filled with dense secretion. Spent secretory cells degenerate and are eliminated from the epithelium. The gland duct is characterized by an irregular, branched lumen surrounded by a very flat epithelium. A valve controls the opening of the duct lumen. The proximal gland duct runs through a cuticular papilla that opens between the dorsal ovipositor valves. The secretions may serve for ovipositor valve lubrication and possibly to protect laid eggs. Observations of serial sections through the vagina exclude the presence of a spermatheca in this species.

Fine structure of spermatheca and accessory gland of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)

The spermatheca of the thrips Frankliniella occidentalis (Thysanoptera: Thripidae) is a small brownish-orange organ that adheres to the vagina; the accessory gland is a large structure with an apical bulb and a long duct opening into the vagina separately from the spermatheca. Both organs consist of an epithelium with secretory and duct-forming cells. A dense secretion fills the apical bulb of the accessory gland. The long duct has an epithelium lined by an annular cuticular intima; the spermatheca has duct-forming cells, unexpectedly rich in inclusions that possibly contain pigment. These cells also form the first short part of the spermathecal duct, which is continuous with the part formed by a diverticulum of the vaginal epithelium. This epithelium provides anchorage for the muscle fibers controlling the opening of the duct lumen.

Hidradenoma Papilliferum of the Upper Eyelid Arising from the Apocrine Gland of Moll

Hidradenoma papilliferum is derived from apocrine sweat glands and was originally described as a tumor located in the anogenital area. The authors recently examined a 78-year-old man with a hidradenoma papilliferum at the margin of the upper eyelid. While the tumor was located in the dermis, serial sections showed a connection to the epidermis and neoplastic cells partially replacing a gland of Moll. There were glandular structures with luminal cells that showed apical decapitation-type secretion, indicating the apocrine origin of the tumor. The luminal cells also contained granules that stained with periodic acid-Schiff (PAS) stain and were diastase resistant. Results of examination of the duct-forming cells by transmission electron microscopy showed adluminal villi, focal decapitation secretion, luminal cytoplasmic debris, and electron-dense cytoplasmic secretory granules. Because the apocrine glands of Moll are localized adjacent to the eyelid cilia, hidradenoma papilliferum and other tumors of apocrine origin should be considered in the clinical setting of a mass at the eyelid margin.