We describe the morphological adaptations of the tongue and gastrointestinal tract of the striped sand snake Psammophis sibilans and discuss their functional importance. Using standard histological, histochemical, and scanning electron microscopy techniques, we analyzed 11 adult snakes of both sexes. Our findings showed that the bifurcated non-papillate tongue exhibited chemoreceptive adaptions to squamate foraging behavior. The lingual apex tapered terminally with sensory spines, and the body of the tongue possesses a characteristic central odor–receptor chamber that might serve to trap and retain scent molecules. Furthermore, the intrinsic musculature showed interwoven and well-developed transverse, vertical and longitudinal muscle fibers that control contraction and retraction during probing and flicking. The esophagus displayed highly folded mucosa lined with columnar epithelium with goblet cells. In contrast, the stomach mucosa formed finger-like gastric rugae, encompassing tubular glands with dorsal gastric pits. The intestine is distinct from other vertebrates in lacking the crypts of Lieberkühn in the tunica mucosa and submucosa. The intestine mucosa is mostly arranged in interdigitating villi oriented perpendicular to the luminal surface. We extrapolated subtle variations for both acid and neutral mucopolysaccharides and glycoproteins localization as well as collagen fibers using histochemical analyses. The elaborate histo-morphological and functional adaptation of the tongue and digestive tract plays a pivotal role in foraging and feeding behavior.

Post-testicular maturation of spermatozoa is crucial for attaining the morphological and functional capabilities needed for successful fertilization. Epididymal epithelia offer a favorable environment for spermatozoa that are stored long term in the turtle epididymis; however, sperm–epithelial interactions during storage, which are enormously important for sperm functional and morphological maturation, are still largely unknown in turtles. The present study examined the epididymis during the sperm-storage period (November–April) in the Chinese soft-shelled turtle (Pelodiscus sinensis). Light and transmission electron microscopy were used to determine the cellular features of each epididymal segment (caput, corpus, and cauda) and their epithelial interactions with the spermatozoa. Spermatozoa were mainly located in the lumena of caput, corpus, and cauda epididymides. Numerous spermatozoa were bound to apical surfaces of the epithelia, and several were even embedded in the epithelial cytoplasm of the caput and corpus epididymides. No embedded spermatozoa were found in the cauda epididymis. In all epididymal segments, principal and clear cells showed the synthetic activity, evidenced by a well-developed endoplasmic reticulum network and high and low electron-dense secretory materials, respectively. Principal and clear cells in the caput and corpus segments showed embedded spermatozoa in electron-dense secretions and in the lipid droplets within the cytoplasm. No lysosomes were observed around the embedded spermatozoa. The lumena of the caput and corpus segments showed few apocrine and low electron density secretions. In the lumen of the cauda epididymidis, different secretions, such as holocrine with low and high electron density and their fragmentation, apocrine, and dictyosome, were found and are summarized. Altogether, sperm physical interactions with secretions either in the cytoplasm of epithelium or in the lumen may support the viability, morphological maintenance, and transfer of various proteins involved in long-term sperm storage in the turtle. This interaction could help us to understand the mechanisms of long-term sperm storage and provide more insights into the reproductive strategies of turtle sperm preservation.

Studying the dermal skeleton in fish is valuable for phylogenetic specification. The current study describes the detailed structure of the plecostomus dermal skeleton, including its morphogenesis and distribution in the skin. The denticles have a crown and a basal part and are embedded in bony depressions, to which they are attached by denticle ligaments. During denticle morphogenesis, denticle papillae formed from denticle precursor cells align in two cellular layers: an outer ameloblast precursor layer and an inner odontoblast precursor layer. The ameloblast precursors and odontoblast precursors differentiate and secrete enamel and dentine, respectively. We used different histochemical techniques, including Crossmon's trichrome staining, Weigert–Van Gieson staining, periodic acid–Schiff (PAS) staining, combined Alcian blue (AB; pH 2.5)/PAS staining, Weigert–Van Gieson staining, Mallory trichrome staining, and AB staining to distinguish the dentine and denticle ligaments. We used acridine orange to detect lysosome activity during denticle eruption. Transmission electron microscopy was used to detect the denticle ultrastructure, and scanning electron microscopy was used to detect the topographic distributions of different types of dermal tissues in different anatomical regions.

Constitutive heterochromatin typically exhibits low gene density and is commonly found adjacent or close to the nuclear periphery, in contrast to transcriptionally active genes concentrated in the innermost nuclear region. In Triatoma infestans cells, conspicuous constitutive heterochromatin forms deeply stained structures named chromocenters. However, to the best of our knowledge, no information exists regarding whether these chromocenters acquire a precise topology in the cell nuclei or whether their 18S rDNA, which is important for ribosome function, faces the nuclear center preferentially. In this work, the spatial distribution of fluorescent Feulgen-stained chromocenters and the distribution of their 18S rDNA was analyzed in Malpighian tubule cells of T. infestans using confocal microscopy. The chromocenters were shown to be spatially positioned relatively close to the nuclear periphery, though not adjacent to it. The variable distance between the chromocenters and the nuclear periphery suggests mobility of these bodies within the cell nuclei. The distribution of 18S rDNA at the edge of the chromocenters was not found to face the nuclear interior exclusively. Because the genome regions containing 18S rDNA in the chromocenters also face the nuclear periphery, the proximity of the chromocenters to this nuclear region is not assumed to be associated with overall gene silencing.

Gilding threads collected from Spanish and Portuguese palaces and from the embroideries and adornments of sculptures of the Virgin and Christ that form part of Sevillian Holy Week were analyzed and compared (20 artifacts were evaluated). The study covered a broad time period with examples from the 13th to 14th centuries, 18th to 20th centuries, and also including modern embroideries. A combination of scanning electron microscopy and energy-dispersive X-ray spectroscopy was used. The knowledge of the layered structures of the threads has provided very valuable information regarding the manufacturing techniques. The different metal threads found in the embroidery studied consisted of gold, silver, copper, and alloys of these metals and aluminium. The fabrication procedures often differed in the different workshops and changed with time. In the modern embroideries, a decrease of precious metal concentration was detected. The threads were wound around a core of silk threads.

Telocytes (TCs) are very long, non-neuronal, somatic cells whose function is widely believed to be involved in providing connections between different cells within the body. The cellular characteristics of TCs in various organs have been studied by immunohistochemistry, double immunofluorescence and electron microscopy in different vertebrate species, and here we investigate the proposed properties of these cells in the context of the “meridian” in Chinese Traditional Medicine (CTM). The results show that TCs and their long extensions, telopodes (Tps) develop a complicated network by homo- and heterocellular junctions in the connective tissue throughout the body, which can connect the skin with distant organs. In concept, this is the analogue of ancient meridian maps connecting skin acupoints with the viscera. Various active cells and extracellular vesicles including exosomes move along Tps, which, along with developed mitochondria within the podoms of Tps, may account for the structural evidence for “Qi” (vital energy and signal communication) in CTM. Morphological associations of TCs with the nerve, vascular, endocrine, and immune systems are also compatible with previously proposed meridian theories in CTM. Close relationships exist between TCs and collagen fiber bundles and some structures in skin fascia provide the microanatomical support for acupuncture treatment based on the meridian principle. The dynamicity in the distribution and structure of TCs reflects the plasticity of the meridian at the cellular level. As the same attribute, both the meridian and the TC have been associated with various diseases. Here, we summarize structural analogues between the TC and the meridian, suggesting that TCs have the cytological characteristics of the CTM meridian. We, therefore, hypothesize that TCs are the “essence cells” of the CTM meridian, which can connect and integrate different cells and structures in the connective tissue.

The spleen is considered a key player in birds’ immunity. The stroma and the parenchyma of the spleen of the adult quail were demonstrated histologically, histochemically, and ultrastructurally. A thin capsule and the absence of trabeculae were the most characteristics of spleen stroma. The demarcation between white pulp and red pulp was not observed in the quail. White pulp formed from the periarterial lymphatic sheath and the periellipsoidal lymphatic sheath, both of which were surrounded by arteriole and ellipsoid, respectively. Ellipsoids appeared more numerous and were characterized by cuboidal lining of the epithelium and supporting cells. Red pulp consisted of sinuses and cords. White pulp and red pulp of the quail spleen contained various cells, such as red blood cells, macrophages, heterophils with characteristic granules, lymphocytes of different sizes, dendritic cells, plasma cells, and telocytes. In addition, closed circulation and open circulation established the blood flow on the spleen.

The present study describes in detail the morphological characteristics of the process of ovarian follicular atresia in Redbelly tilapia (Coptodon zillii) during the nonbreeding season using light and electron microscopy and immunohistochemistry. The follicular regression process was initiated with shrinkage and disintegration of the nuclear membrane of oocytes resulting in dispersing of chromatin within the ooplasm, followed by marked hyperplasia and hypertrophy of follicular and granulosa cells, which exhibited a strong phagocytic activity to engulf the liquefied yolk particles. Rodlet cells and granulocytes were recorded on the follicular wall and invaded the regressed follicles. Rodlet cells expressed a strong immunoreactivity to matrix metalloperoxidase (MMP-9) and α-smooth muscle actin, while neutrophils expressed a strong reactivity to Myeloperoxidase-3 (MPO). In the advanced stage of follicular atresia, the yolk was almost phagocytized and resorbed and the regressed follicle lost its integrity and appeared to be formed of a cellular mass of phagocytic cells. Transmission electron microscopy revealed the presence of neutrophils, eosinophils, and dendritic cells within the atretic follicle in between these phagocytic cells. Moreover, numerous lysosomes, granules, and phagosomes were observed within the cytoplasm of both phagocytic cells and granulocytes. Telocytes were also demonstrated within the highly thickened richly vascularized theca layer during the late stages of follicular atresia. Immunohistochemical staining for caspase-3 established the participation of apoptosis in the advanced stages of follicular regression. Immune cells, rodlet cells, and telocytes in combination with follicular cells play an essential role in follicular atresia. In conclusion, the present study provides a new evidence on the role of both somatic and immune cells in the phenomenon of ovarian follicular atresia in Redbelly tilapia (Coptodon zillii) during the nonbreeding season.

Mauritia flexuosa palms inhabit wetland environments in the dry, seasonal Brazilian savanna (Cerrado) and produce mucilaginous secretions in the stem and petiole that have a medicinal value. The present study sought to characterize the chemical natures of those secretions and to describe the anatomical structures involved in their synthesis. Chemical analyzes of the secretions, anatomical, histochemical analyses, and electron microscopy studies were performed on the roots, stipes, petioles, and leaf blades. Stipe and petiole secretions are similar, and rich in cell wall polysaccharides and pectic compounds such as rhamnose, arabinose, xylose, mannose, galactose, and glucose, which are hydrophilic largely due to their hydroxyl and carboxylate groups. Mucilaginous secretions accumulate in the lumens of vessel elements and sclerenchyma fibers of the root, stipe, petiole, and foliar veins; their synthesis involves cell wall loosening and the activities of dictyosomes. The outer faces of the cell walls of the parenchyma tissue in the mesophyll expand to form pockets that rupture and release pectocellulose substances into the intercellular spaces. The presence of mucilage in the xylem, extending from the roots to the leaf veins and continuous with the leaf apoplast, and sub-stomatal chambers suggest a strategy for plant water economy.

Micropropagation techniques allow producing large numbers of clones of genetically identical plants. However, there is evidence of disorders in internal structures due to sophisticated in vitro conditions. Such variations are responsible for the mortality of plantlets in the field and cause huge loss to the tissue culture industry. Anatomical evaluation at different growth conditions allows for understanding structural repair of in vitro raised plantlets. Therefore, the present study was aimed to identify the structural changes that occurred in micropropagated plants of Vitex negundo under heterotrophic, photomixotrophic, and photoautotrophic conditions. To achieve this, structural variations were analyzed in the plantlets obtained from in vitro, greenhouse and field transferred stages using light microscopy. Underdeveloped dermal tissues, palisade cells, intercellular spaces, mechanical tissues, vascular bundles, and ground tissues were observed with the plants growing under in vitro conditions. The self-repairing of structural disorders and transitions in vegetative anatomy was observed during hardening under the greenhouse environment. Field transferred plantlets were characterized by well-developed internal anatomy. These findings showed that the micropropagated plantlets of V. negundo were well-adapted through a series of self-repairing the in vitro induced structural abnormalities at the subsequent stages of plant development.

Cytological responses in different organs of sentinel organisms have proven to be useful tools for characterizing the health status of those organisms and assessing the impact of environmental contaminants. Our study shows that nickel (II) accumulated in both germ cells (oogonia and developing oocytes) and somatic cells (muscle cells, follicle cells) in the Astacus leptodactylus ovary. Muscle cells from ovarian wall show disorganization and the disruption of cytoplasmic microtubules and pyknosis of the cell nucleus. Follicle cells, both those that surround the developing oocytes and also those that are not associated with the oocytes contained within the cytoplasm vacuoles of different sizes, degenerated mitochondria, myelin bodies, disorganized microtubules, and pyknotic nuclei. The most evident pathological phenomenon was the alteration and disorganization of the basal matrix, which separates the ovarian interstitium from ovarian follicles compartment. Exposure to nickel induces cytoplasmic vacuolation in oogonia and developing oocytes, structural alteration of the developing yolk granules and condensation of the nucleoli. Ultrastructural autometallography has shown grains of silver-enhanced nickel inside the cytoplasm of the muscle cells with altered morphology, including the cytoplasm, nucleus, and basal matrix of the follicle cells, and in intracisternal granules and developing yolk granules of the oocytes.