Development and Holocrine Secretion of Resin Ducts in Kielmeyera appariciana (Calophyllaceae).

The modes of formation and release of secretion are complex processes that occur in secretory ducts and their description has great divergence in some species. The use of modern techniques to detect hydrolytic enzymes, cytoskeleton arrangement and indicators of programmed cell death may help clarify the processes involved during the ontogeny of that gland. The goal of our study was to analyze subcellular changes during schizogenous formation and secretion production and release into the lumen in resin ducts of Kielmeyera appariciana. Our results demonstrate the participation of pectinase through the loosening of the central cells of the rosette, which subsequently split from each other through polarized growth mediated by a rearrangement of the microtubules. The resin is mainly synthesized in plastids and endoplasmic reticulum and is observed inside vesicles and small vacuoles. The secretion release is holocrine and occurs through programmed cell death related to the release of reactive oxygen species, causing cytoplasm darkening, chromatin condensation, vacuole rupture and plastid and mitochondria degeneration. Cellulase activity was identified prior to the rupture of the cell wall, causing the release of secretion into the lumen of the duct. The participation of the cytoskeleton was observed for the first time during schizogeny of ducts as well as programmed cell death as part of the process of the release of holocrine secretion. This type of secretion release may be a key innovation in Kielmeyera since it has not been observed in ducts of any other plant thus far.

Overview of Human Salivary Glands: Highlights of Morphology and Developing Processes.

Salivary glands are essential organs that produce and secrete saliva to the oral cavity. During gland morphogenesis, many developmental processes involve a series of coordinated movements and reciprocal interactions between the epithelium and mesenchyme that generate the ductal system and the secretory units. Recent studies have shown new findings about salivary gland development, particularly regarding lumen formation and expansion, with the involvement of apoptosis and cell polarization, respectively. Moreover, it has been observed that human minor salivary glands start forming earlier than previously published and that distinct apoptotic mediators can trigger duct lumen opening in humans. This review summarizes updated morphological and cellular features of human salivary glands and also explores new aspects of the human developmental process. Anat Rec, 300:1180-1188, 2017. © 2017 Wiley Periodicals, Inc.