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The burrower bug Scaptocoris castanea Perty, 1830 (Hemiptera: Cydnidae) is an agricultural pest feeding on roots of several crops. The histology and ultrastructure of the salivary glands of S. castanea were described. The salivary system has a pair of principal salivary glands and a pair of accessory salivary glands. The principal salivary gland is bilobed with anterior and posterior lobes joined by a hilus where an excretory duct occurs. The accessory salivary gland is tubular with a narrow lumen that opens into the hilus near the excretory duct, suggesting that its secretion is stored in the lumen of the principal gland. The cytoplasm of the secretory cells is rich in the rough endoplasmic reticulum, secretory vesicles with different electron densities and mitochondria. At the base of the accessory gland epithelium, there were scattered cells that do not reach the gland lumen, with the cytoplasm rich in the rough endoplasmic reticulum, indicating a role in protein production. Data show that principal and accessory salivary glands of S. castanea produce proteinaceous saliva. This is the first morphological description of the S. castanea salivary system that is similar to other Hemiptera Pentatomomorpha, but with occurrence of basal cells in the accessory salivary gland.

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MAIN CONCLUSION: Different autophagy pathways are a driver of vacuolar biogenesis and are development stage specific during the extrafloral nectary development in Citharexylum myrianthum. Plant autophagy plays an important role in various developmental processes such as seed germination, pollen maturation and leaf senescence. However, studies that address the evidence of autophagy and its role in the development of plant glands are scarce and largely restricted to laticifers. Regarding nectary, studies have repeatedly pointed to signs of degradation associated with the end of the secretory cycle, without exploring autophagy. Likewise, the relationship between autophagy and biogenesis of vacuoles remains an unexplored issue. In this study, using conventional and microwave fixation in association with ultracytochemical methods for transmission electron microscopy, we investigated the occurrence of autophagy and its implication in the differentiation of extrafloral nectary in Citharexylum myrianthum (Verbenaceae) under natural conditions, focusing on the vacuole biogenesis. We described a variety of vacuole types associated with the stage of nectary epidermis development, which differs with respect to origin, function and nature of the products to be stored. Three distinct autophagy pathways were detected: macroautophagy, microautophagy (both restricted to the undifferentiated epidermal cells, at the presecretory stage) and megaautophagy (circumscribed to the differentiated epidermal cells, at the postsecretory stage). Our study clearly demonstrated that the vacuole variety and autophagy processes in the nectary epidermal cells are development specific. This study highlights the role of autophagy in vacuole biogenesis and its implications for the development of nectary and opens new venues for future studies on regulation mechanisms for autophagy in plant secretory structures under normal conditions.

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The osmeterium, found in papilionoid larvae, is an eversible organ with an exocrine gland that produces substances in response to the mechanical disturbances caused by natural enemies. The anatomy, histology and ultrastructure of the osmeterium, and the chemical composition of its secretion in Heraclides thoas (Lepidoptera: Papilionidae) were studied. Heraclides thoas larvae have a Y-shaped osmeterium in the thorax. The surface of the osmeterium has a rough cuticle lining cells with papillae and irregular folds, whereas the cells that limited the gland pores are irregular, folded, and devoid of papillae. Two types of cells are found: (i) cuticular epidermal cells on the surface of the tubular arms of the osmeterium and (ii) secretory cells of the ellipsoid gland within the region of the glandular pore. Cuticular epidermal cells show a thick cuticle, with several layers divided into epicuticle and lamellar endocuticle. Secretory cells are polygonal, with extensive folds in the basal plasma membrane that formed extracellular channels. The cytoplasm has mitochondria, ribosomes, and numerous vacuoles, whereas the nucleus is irregular in shape with decondensed chromatin. The chemical composition of the osmeterial secretion comprised (Z)-α-bisabolene (25.4%), α-bisabol (20.6%), ß-bisabolene (13.1%), (E)-α-bisabolene 8%), ß-pinene (9.91%), longipinene epoxide (8.92%), (Z)-ß-farnesene (6.96%), ß-caryophyllene (2.05%), farnesol (1.86%), linalyl propionate (1.86%), and 1-octyn-4-ol (1.07%). The morphological features suggest that the cuticular epidermal cells play a major role in the maintenance and protection of the osmeterium, whereas secretory cells are responsible for production of osmeterial secretions.

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In cattle, the oviduct plays a major role in the reproductive process; however, molecular control of oviduct receptivity to the embryo is poorly understood. A model for receptivity based on size of the pre-ovulatory follicle (POF) was used to compare oviductal morphology, cellular proliferation, and candidate transcript abundance. Growth of the POF of Nelore (Bos indicus) cows was manipulated to produce two groups: a large POF-large corpus luteum (CL) group (LF-LCL; greater receptivity) and a small POF-small CL group (SF-SCL). Samples of the ampulla and isthmus ipsilateral and contralateral to CL were collected 4 days after GnRH-induced ovulation. Tissues were either embedded in paraffin for Harris-Hematoxylin and Eosin and periodic acid-Schiff staining and KI67 immunostaining, followed by morphological analyses, or stored at -80 °C for RNA extraction, cDNA synthesis, and qPCR analyses. The effects of group (LF-LCL and SF-SCL), region (ampulla and isthmus), and side (ipsilateral and contralateral) were analyzed using three-way nested ANOVA. The ipsilateral ampulla of the LF-LCL group presented more primary mucosal folds, a greater mucosal-folding grade and luminal perimeter, and more secretory cells and proliferating cells when compared with the ampulla of the SF-SCL group and with the contralateral ampulla of both groups. There were no morphological differences in the isthmus between groups and sides. Changes in transcript abundance are suggestive of LF-LCL-stimulated secretory activity. In summary, ovulation of a larger POF generates a periovulatory endocrine milieu that modulates morphological and functional features of the bovine oviduct which may support embryo survival and development.

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The metathoracic scent system in Heteroptera produces and releases defensive volatile compounds. The odor produced by predatory stink bugs differs from phytophagous bugs, suggesting a variation between the structure and function of the metathoracic scent system. The anatomy and ultrastructure of the external thoracic efferent system, scent gland, and reservoir in the stink bug predators Brontocoris tabidus, Podisus nigrispinus, and Supputius cincticeps (Heteroptera: Pentatomidae: Asopinae) were studied. External thoracic efferent systems of B. tabidus, P. nigrispinus, and S. cincticeps have anatomical differences in ostiole, peritreme, and evaporatorium. Scent glands have a secretory portion and a reservoir. The reservoir has irregular projections, and in B. tabidus, it is enlarged and heart shaped, whereas in P. nigrispinus and S. cincticeps it is flattened and semicircular. The secretory tissue of the scent gland has well-developed globular secretory cells that produce odorous compounds, and the reservoir has a single layer of cubical cells lined by a cuticular intima. Secretory cells are type III with an intracellular end apparatus, well-developed nucleus with decondensed chromatin, and cytoplasm rich in mitochondria, lysosomes, granules, and smooth endoplasmic reticulum. These findings suggest that there are differences in physiological function of the odoriferous system and the volatile compounds produced by the secretory cells, which may indicate variation in defensive behavior of these species.

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Cimicidae are temporary ectoparasites, which means that they cannot obtain food continuously. Both Cimex species examined here, Cimex lectularius (Linnaeus 1758) and Cimex pipistrelli (Jenyns 1839), can feed on a non-natal host, C. lectularius from humans on bats, C. pipistrelli on humans, but never naturally. The midgut of C. lectularius and C. pipistrelli is composed of three distinct regions-the anterior midgut (AMG), which has a sack-like shape, the long tube-shaped middle midgut (MMG), and the posterior midgut (PMG). The different ultrastructures of the AMG, MMG, and PMG in both of the species examined suggest that these regions must fulfill different functions in the digestive system. Ultrastructural analysis showed that the AMG fulfills the role of storing food and synthesizing and secreting enzymes, while the MMG is the main organ for the synthesis of enzymes, secretion, and the storage of the reserve material. Additionally, both regions, the AMG and MMG, are involved in water absorption in the digestive system of both Cimex species. The PMG is the part of the midgut in which spherites accumulate. The results of our studies confirm the suggestion of former authors that the structure of the digestive tract of insects is not attributed solely to diet but to the basic adaptation of an ancestor.

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Podisus distinctus (Hemiptera: Pentatomidae) is a zoophytophagous insect with significant potential for use as a biological control agent in agriculture and forestry because their nymphs and adults actively prey on diverse insect species. The saliva of this insect possesses active substances that cause paralysis and death of the prey. As the first step in identifying compounds of P. distinctus saliva, this study describes the ultrastructure of the salivary glands of this predator. The salivary system of P. distinctus possesses a pair of main salivary glands with a short anterior lobe, a long posterior lobe, and a pair of tubular accessory glands. The main salivary gland of P. distinctus has no associated muscles, suggesting that the saliva-release mechanism occurs with the help of certain thorax muscles. The main salivary gland epithelium has a single layer of cells (varying from cubical to columnar) with cytoplasm rich in rough endoplasmic reticulum, spherical granules of different sizes, a nucleus with a predominance of decondensed chromatin, and nucleolus. The apical cell region has a few short microvilli and the basal region has plasma membrane infoldings. The epithelium of the accessory salivary glands possesses a single-layered epithelium of cubic cells delimiting a narrow lumen. The apical cell region has a high density of microvilli and pleomorphic mitochondria, whereas the central cell region is rich in rough endoplasmic reticulum with a well-developed nucleus and decondensed chromatin. The basal cell region is characterized by the presence of several basal plasma membrane infoldings associated with mitochondria and numerous openings to the hemocoel forming large channels. The ultrastructural characteristics suggest that the main salivary glands and accessory salivary glands play a vital role in protein synthesis for saliva production and that the accessory glands are involved in transport of materials of the hemolymph.

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The endoplasmic reticulum (ER) is a key subcellular compartment involved in the folding and maturation of around one-third of the total proteome. Accumulation of misfolded proteins in the ER lumen engages a signal transduction pathway known as unfolded protein response (UPR) that feedback to recover ER homeostasis or to trigger apoptosis of irreversible damaged cells. The UPR is initiated by three main stress sensors including protein kinase RNA-like ER kinase (PERK), activating transcription factor 6 (ATF6), and inositol-requiring protein 1α (IRE1α), which reprogram the genome through the control of downstream transcription factors. In this article, the authors have reviewed most relevant studies uncovering the physiological function of the UPR in different organs and tissues based on the phenotypes observed after genetic manipulation of the pathway in vivo. Biomedical applications of targeting the UPR on a disease context are also discussed.

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Girardia biapertura was described with sperm ducts penetrating the penis bulb, subsequently opening separately at the tip of the penis papilla and receiving the abundant secretion of penial glands. In the present work, the penial glands of this species have been histologically and histochemically analysed, and four types of secretory cells are distinguished. The openings of the penial glands into the intrabulbar and intrapapillar sperm ducts, designated here as intrapenial ducts, allow for the distinction between three histologically differentiated regions. The most proximal region possibly corresponds to the bulbar cavity of other freshwater triclads whereas the median and distal portions correspond to the ejaculatory duct. The proximal region of the intrapenial ducts receives mainly the openings of a secretory cell type (type I) that produces a proteinaceous secretion. A second type of secretory cell (type II) that secretes neutral mucopolyssacharides opens into the median region of the intrapenial ducts. The distal portion of the ducts receives two types of secretory cells (types III and IV) which secret glycoprotein and glycosaminoglycans, respectively. Types III and IV open also directly into the male atrium through the epithelium of the penis papilla. A comparison with the results presented here and those of other authors for species of Girardia is provided and the importance of the study of the penial glands for taxonomic characterisation of freshwater triclads is emphasised.

A espécie Girardia biapertura apresenta, segundo sua descrição original, ductos espermáticos penetrando o bulbo penial e, subseqüentemente, desembocando separadamente na ponta da papila penial e recebendo abundante secreção das glândulas peniais. No presente trabalho, as glândulas peniais dessa espécie foram analisadas histológica e histoquimicamente, sendo constatados quatro tipos de células secretoras. A desembocadura das glândulas peniais nas porções intrabulbar e intrapapilar dos ductos espermáticos, aqui designados como ductos intrapeniais, permite diferenciar três regiões histologicamente distintas. A região mais proximal desses ductos provavelmente corresponde à cavidade bulbar, enquanto as porções média e distal, ao ducto ejaculatório de outros tricladidos. A região proximal dos ductos intrapeniais recebe principalmente a desembocadura de um tipo de célula secretora (tipo I), cuja secreção é protéica. Na região média dos ductos intrapeniais desemboca um segundo tipo de célula secretora (tipo II), contendo mucopolissacarídeos neutros. A porção mais distal dos ductos intrapeniais recebe a desembocadura de dois tipos de células secretoras (tipos III e IV) que secretam glicoproteína e glicosaminoglicanas, respectivamente. As células dos tipos III e IV desembocam, também, diretamente no átrio masculino através do epitélio de revestimento da papila penial. Comparam-se os resultados obtidos com aqueles de outros autores para espécies do gênero Girardia e enfatiza-se a importância do estudo das glândulas peniais para a caracterização taxonômica das espécies de tricladidos dulcícolas.

RESUMO

Girardia biapertura was described with sperm ducts penetrating the penis bulb, subsequently opening separately at the tip of the penis papilla and receiving the abundant secretion of penial glands. In the present work, the penial glands of this species have been histologically and histochemically analysed, and four types of secretory cells are distinguished. The openings of the penial glands into the intrabulbar and intrapapillar sperm ducts, designated here as intrapenial ducts, allow for the distinction between three histologically differentiated regions. The most proximal region possibly corresponds to the bulbar cavity of other freshwater triclads whereas the median and distal portions correspond to the ejaculatory duct. The proximal region of the intrapenial ducts receives mainly the openings of a secretory cell type (type I) that produces a proteinaceous secretion. A second type of secretory cell (type II) that secretes neutral mucopolyssacharides opens into the median region of the intrapenial ducts. The distal portion of the ducts receives two types of secretory cells (types III and IV) which secret glycoprotein and glycosaminoglycans, respectively. Types III and IV open also directly into the male atrium through the epithelium of the penis papilla. A comparison with the results presented here and those of other authors for species of Girardia is provided and the importance of the study of the penial glands for taxonomic characterisation of freshwater triclads is emphasised.

A espécie Girardia biapertura apresenta, segundo sua descrição original, ductos espermáticos penetrando o bulbo penial e, subseqüentemente, desembocando separadamente na ponta da papila penial e recebendo abundante secreção das glândulas peniais. No presente trabalho, as glândulas peniais dessa espécie foram analisadas histológica e histoquimicamente, sendo constatados quatro tipos de células secretoras. A desembocadura das glândulas peniais nas porções intrabulbar e intrapapilar dos ductos espermáticos, aqui designados como ductos intrapeniais, permite diferenciar três regiões histologicamente distintas. A região mais proximal desses ductos provavelmente corresponde à cavidade bulbar, enquanto as porções média e distal, ao ducto ejaculatório de outros tricladidos. A região proximal dos ductos intrapeniais recebe principalmente a desembocadura de um tipo de célula secretora (tipo I), cuja secreção é protéica. Na região média dos ductos intrapeniais desemboca um segundo tipo de célula secretora (tipo II), contendo mucopolissacarídeos neutros. A porção mais distal dos ductos intrapeniais recebe a desembocadura de dois tipos de células secretoras (tipos III e IV) que secretam glicoproteína e glicosaminoglicanas, respectivamente. As células dos tipos III e IV desembocam, também, diretamente no átrio masculino através do epitélio de revestimento da papila penial. Comparam-se os resultados obtidos com aqueles de outros autores para espécies do gênero Girardia e enfatiza-se a importância do estudo das glândulas peniais para a caracterização taxonômica das espécies de tricladidos dulcícolas.