Ultrastructure of submandibular salivary glands of mouse: TEM and HRSEM observations

Three-dimensional analysis of the intracellular architecture by scanning electron microscopy

The two-dimensional observation of ultrathin sections from resin-embedded specimens provides an insufficient understanding of the three-dimensional (3D) morphological information of membranous organelles. The osmium maceration method, developed by Professor Tanaka's group >40 years ago, is the only technique that allows direct observation of the 3D ultrastructure of membrane systems using scanning electron microscopy (SEM), without the need for any reconstruction process. With this method, the soluble cytoplasmic proteins are removed from the freeze-cracked surface of cells while preserving the integrity of membranous organelles, achieved by immersing tissues in a diluted osmium solution for several days. By employing the maceration method, researchers using SEM have revealed the 3D ultrastructure of organelles such as the Golgi apparatus, mitochondria and endoplasmic reticulum in various cell types. Recently, we have developed new SEM techniques based on the maceration method to explore further possibilities of this method. These include: (i) a rapid osmium maceration method that reduces the reaction duration of the procedure, (ii) a combination method that combines agarose embedding with osmium maceration to elucidate the 3D ultrastructure of organelles in free and cultured cells and (iii) a correlative immunofluorescence and SEM technique that combines cryosectioning with the osmium maceration method, enabling the correlation of the immunocytochemical localization of molecules with the 3D ultrastructure of organelles. In this paper, we review the novel osmium maceration methods described earlier and discuss their potential and future directions in the field of biology and biomedical research.

p130Cas is required for androgen-dependent postnatal development regulation of submandibular glands

Salivary glands develop through epithelial-mesenchymal interactions and are formed through repeated branching. The Crk-associated substrate protein (p130Cas) serves as an adapter that forms a complex with various proteins via integrin and growth factor signaling, with important regulatory roles in several essential cellular processes. We found that p130Cas is expressed in ductal epithelial cells of the submandibular gland (SMG). We generated epithelial tissue-specific p130Cas-deficient (p130Cas^Δepi-) mice and aimed to investigate the physiological role of p130Cas in the postnatal development of salivary glands. Histological analysis showed immature development of granular convoluted tubules (GCT) of the SMG in male p130Cas^Δepi- mice. Immunofluorescence staining showed that nuclear-localized androgen receptors (AR) were specifically decreased in GCT cells in p130Cas^Δepi- mice. Furthermore, epidermal growth factor-positive secretory granules contained in GCT cells were significantly reduced in p130Cas^Δepi- mice with downregulated AR signaling. GCTs lacking p130Cas showed reduced numbers and size of secretory granules, disrupted subcellular localization of the cis-Golgi matrix protein GM130, and sparse endoplasmic reticulum membranes in GCT cells. These results suggest that p130Cas plays a crucial role in androgen-dependent GCT development accompanied with ER-Golgi network formation in SMG by regulating the AR signaling.

Morfologia das glândulas salivares maiores em cutias (Dasyprocta leporina Linnaeus, 1766)

Resumo: Estudos acerca da morfologia de animais silvestres servem de subsídio para trabalhos de manejo e preservação de diferentes espécies, pois fornecem informações para a tomada de medidas que auxiliem na manutenção destes em cativeiro, na preservação em habitat natural ou mesmo para ações voltadas a reintrodução ao habitat de origem. Estudos referentes à morfologia de cutias abordam os diversos sistemas, mas nenhum faz referência à arquitetura ou estrutura de suas glândulas salivares. Assim este trabalho objetivou descrever macro e microscopicamente as glândulas salivares maiores de cutias. Foram utilizados dez animais adultos para o desenvolvimento de metodologias relativas à macroscopia propriamente dita das glândulas, microscopia de luz, microscopia eletrônica de transmissão e microscopia eletrônica de varredura. Foram identificadas quatro glândulas salivares maiores nos animais estudados, denominadas parótida, mandibular, zigomática e sublingual. As glândulas apresentaram-se como sendo do tipo tubuloacinares e contendo em seu parênquima ductos dos mais variados tamanhos. Com exceção da glândula parótida, que era estritamente serosa, as demais eram mistas. Da mesma forma, apenas a glândula mandibular foi identificada a presença de ducto do tipo granuloso. Apresentando as cutias os quatro pares de glândulas salivares maiores, estes animais podem servir de modelo para os estudos acerca das mudanças anatômicas sofridas pelos roedores para se adaptar aos diversos habitat do planeta.

Melatonin inhibits embryonic salivary gland branching morphogenesis by regulating both epithelial cell adhesion and morphology

Many organs, including salivary glands, lung, and kidney, are formed by epithelial branching during embryonic development. Branching morphogenesis occurs via either local outgrowths or the formation of clefts that subdivide epithelia into buds. This process is promoted by various factors, but the mechanism of branching morphogenesis is not fully understood. Here we have defined melatonin as a potential negative regulator or "brake" of branching morphogenesis, shown that the levels of it and its receptors decline when branching morphogenesis begins, and identified the process that it regulates. Melatonin has various physiological functions, including circadian rhythm regulation, free-radical scavenging, and gonadal development. Furthermore, melatonin is present in saliva and may have an important physiological role in the oral cavity. In this study, we found that the melatonin receptor is highly expressed on the acinar epithelium of the embryonic submandibular gland. We also found that exogenous melatonin reduces salivary gland size and inhibits branching morphogenesis. We suggest that this inhibition does not depend on changes in either proliferation or apoptosis, but rather relates to changes in epithelial cell adhesion and morphology. In summary, we have demonstrated a novel function of melatonin in organ formation during embryonic development.

Morfologia das glândulas salivares de Glironia venusta Thomas, 1912 (Didelphimorphia)

O objetivo deste trabalho foi descrever a morfologia das glândulas salivares de Glironia venusta. Foi utilizado um exemplar coletado no resgate de fauna da Usina Hidroeletrica Teles Pires. Este foi fixado com solução de formaldeído a 10%. Para a análise macroscópica, as glândulas foram dissecadas e fotografadas in situ e para a microscopia foram retirados fragmentos das glândulas. Estes foram desidratados em concentrações crescentes de álcool, diafanizados em xilol, inclusos em parafina e corados com HE. G. venusta apresentou as glândulas mandibulares, parótidas, sublinguais, labiais e zigomáticas. As mandibulares se mostraram como estruturas alongadas, constituídas por lobos não septados e localizadas na porção anterior da região cervical. De formato triangular, a parótida estava localizada na depressão do masseter, ventral à cartilagem auricular. As sublinguais encontravam-se ventrais ao ramo da mandíbula, caudais ao digástrico. Foi observado na porção dorsoposterior à comissura labial, dorsal ao músculo orbicular da boca, as glândulas labiais, que apresentaram formato de "U". Já as glândulas zigomáticas acompanhavam a forma da porção anterior do arco zigomático, na margem infraorbital. As glândulas mandibulares e sublinguais apresentaram ácinos do tipo mucosos, com alguns ácinos serosos. A parótida era constituída por ácinos puramente serosos. Na glândula labial foi observado ácinos do tipo mistos ou seromucosos. Para a glândula zigomática não foi possível a realização da análise microscópica devido problemas de procedimento histológico. As características das glândulas salivares observadas em G. venusta se assemelham a de outros mamíferos onívoros, entretanto, apresentaram pequenas diferenças no que se refere à sua localização e forma.

Análise microscópica e ultraestrutural das glândulas salivares mandibulares de Procyon cancrivorus

Devido a importância ecológica dos Procyon cancrivorus, o objetivo deste trabalho foi caracterizar morfologicamente e ultra estruturalmente a glândula salivar mandibular desta espécie. Foram utilizadas 10 pares (direita e esquerda) de glândulas salivares mandibulares de cinco animais adultos. As glândulas salivares mandibulares foram dissecadas e mensuradas com paquímetro de precisão e posteriormente processadas por técnica rotineira de histologia e coradas por HE (hematoxilina e eosina) e Picrossírius. Fragmentos das glândulas foram processados para análise em microscopia eletrônica de varredura (MEV). As glândulas salivares mandibulares direitas e esquerdas de P. cancrivorus apresentaram-se lobuladas, formato ovalado, e posicionadas entre a fossa atlantis e o osso basihyoideum do crânio. Microscopicamente, estas glândulas estavam revestidas por uma cápsula de tecido conjuntivo denso não modelado, a qual adentra a glândula através de septos, dividindo-a em lóbulos. Nos septos de tecido conjuntivo estão presentes vasos sanguíneos e nervos, além de ductos interlobulares excretores. Dentro dos lóbulos das glândulas salivares mandibulares, são encontrados ductos do tipo estriado e intercalar, além de predomínio de ácinos do tipo mucoso. Os resultados permitem concluir que as glândulas salivares mandibulares dos Procyon cancrivorus, seguem o padrão estrutural descrito em outras espécies de mamíferos. No entanto os tipos de ácinos podem variar entre as espécies, sendo, portanto, necessários futuros estudos histoquímicos e de biologia celular para desvendar a importância dessa variação para a espécie aqui estudada, comparando com seu hábito alimentar.

Structural and ultrastructural features of the agouti tongue (Dasyprocta aguti Linnaeus, 1766)

The agouti (Dasyprocta aguti Linnaeus, 1766) is a wild rodent belonging to the family Dasyproctidae that is found throughout Brazil and feeds on fruits and seeds. The aim of the present study was to describe the following features of the tongue of agouti: its morphological structures, the three-dimensional characteristics of the lingual papillae surface, the connective tissue cores (CTCs) and the epithelial cell ultrastructure. Four types of papillae were observed on the dorsal surface of the tongue with a triangular shape: filiform, fungiform, foliate and vallate. Filiform papillae were distributed throughout the tongue surface, and removal of the epithelial surface revealed conical CTCs and multifilaments. Fungiform papillae were observed in the rostral and middle regions, whereas foliate papillae developed in pairs on the lateral margin of the caudal region. Removal of the epithelium in these regions revealed CTCs with parallel laminar conformation. Vallate papillae were arranged in a V-shape in the caudal region, and their CTCs ranged in shape from elongate to ovoid. The ultrastructural components of the dorsal epithelium were the basal, spinous, granular and keratinised layers. A broad area with cytoplasmic projections was identified in the interface region between the lamina propria and the basal layer. Flattened cells with intermediate filaments were observed in the transitional region between spinous and granular layers. The keratinised layer was composed of superimposed epithelial cells where desmosomes and cell-surface microridges were observed. These structural features, including the three-dimensional aspects of the lingual papillae, the CTCs and the epithelial ultrastructure, indicate that when compared with other animals, particularly other rodent species, the morphological features of the tongue of agouti are relatively well developed, especially regarding foliate and vallate papillae.

Morphometric, quantitative, and three-dimensional analysis of the heart muscle fibers of old rats: transmission electron microscopy and high-resolution scanning electron microscopy methods

This research investigated the morphological, morphometric, and ultrastructural cardiomyocyte characteristics of male Wistar rats at 18 months of age. The animals were euthanized using an overdose of anesthesia (ketamine and xylazine, 150/10 mg/kg) and perfused transcardially, after which samples were collected for light microscopy, transmission electron microscopy, and high-resolution scanning electron microscopy. The results showed that cardiomyocyte arrangement was disposed parallel between the mitochondria and the A-, I-, and H-bands and their M- and Z-lines from the sarcomere. The sarcomere junction areas had intercalated disks, a specific structure of heart muscle. The ultrastructural analysis revealed several mitochondria of various sizes and shapes intermingled between the blood capillaries and their endothelial cells; some red cells inside vessels are noted. The muscle cell sarcolemma could be observed associated with the described structures. The cardiomyocytes of old rats presented an average sarcomere length of 2.071 ± 0.09 μm, a mitochondrial volume density (Vv) of 0.3383, a mitochondrial average area of 0.537 ± 0.278 μm(2), a mitochondrial average length of 1.024 ± 0.352 μm, an average mitochondrial cristae thickness of 0.038 ± 0.09 μm and a ratio of mitochondrial greater length/lesser length of 1.929 ± 0.965. Of the observed mitochondrial shapes, 23.4% were rounded, 45.3% were elongated, and 31.1% had irregular profiles. In this study, we analyzed the morphology and morphometry of cardiomyocytes in old rats, focusing on mitochondria. These data are important for researchers who focus the changes in cardiac tissue, especially changes owing to pathologies and drug administration that may or may not be correlated with aging.

Alimentary Canal of the Adult Blow Fly, Chrysomya megacephala (F.) (Diptera: Calliphoridae)-Part I: Ultrastructure of Salivary Glands

The salivary gland ultrastructure of the adult male blow fly, Chrysomya megacephala (F.) (Diptera: Calliphoridae), was investigated at the ultrastructural level using light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The salivary glands are paired structures composed of a single median deferent duct bifurcated into two long, narrow efferent ducts connected to the coiled tubular glands. The SEM image of the gland surface revealed that the basal lamina is relatively smooth in general, but the whole surface appeared as a trace of rough swollen insertion by intense tracheal ramification. Ultrastructurally, the salivary gland is enclosed within the basal lamina, and interdigitation cytoplasmic extensions were apparent between the adjacent gland cells. The basement membrane appeared infoldings that is similar to the complex of the labyrinth channel. The cytoplasm characteristic of the gland revealed high activity, based on the abundance of noticeable secretory granules, either singly or in an aggregated reservoir. In addition, mitochondria were found to intersperse among rich parallel of arrays rough endoplasmic reticulum. Thick cuticle, which was well-delineated and electron dense, apically lined the gland compartments, with discontinuity of the double-layer cuticle revealing a trace of secretion discharged into the lumen. Gross anatomy of the adult salivary gland was markedly different from that of the third instar of the same species, and structural dissimilarity is discussed briefly.

Ultrastructural features of the myotendinous junction of the sternomastoid muscle in Wistar rats: from newborn to aging

The myotendinous junction (MTJ) is a major area for transmitting force from the skeletal muscle system and acts in joint position and stabilization. This study aimed to use transmission electron microscopy to describe the ultrastructural features of the MTJ of the sternomastoid muscle in Wistar rats from newborn to formation during adulthood and possible changes with aging. Ultrastructural features of the MTJ from the newborn group revealed pattern during development with interactions between muscle cells and extracellular matrix elements with thin folds in the sarcolemma and high cellular activity evidenced through numerous oval mitochondria groupings. The adult group had classical morphological features of the MTJ, with folds in the sarcolemma forming long projections called "finger-like processes" and sarcoplasmic invaginations. Sarcomeres were aligned in series, showing mitochondria near the Z line in groupings between collagen fiber bundles. The old group had altered "finger-like processes," thickened in both levels of sarcoplasmic invaginations and in central connections with the lateral junctions. We conclude that the MTJ undergoes intense activity from newborn to its formation during adulthood. With increasing age, changes to the MTJ were observed in the shapes of the invaginations and "finger-like processes" due to hypoactivity, potentially compromising force transmission and joint stability.