Showing papers on "Ultrastructure published in 2019"

Imaging cellular ultrastructures using expansion microscopy (U-ExM).

Abstract: Determining the structure and composition of macromolecular assemblies is a major challenge in biology. Here we describe ultrastructure expansion microscopy (U-ExM), an extension of expansion microscopy that allows the visualization of preserved ultrastructures by optical microscopy. This method allows for near-native expansion of diverse structures in vitro and in cells; when combined with super-resolution microscopy, it unveiled details of ultrastructural organization, such as centriolar chirality, that could otherwise be observed only by electron microscopy.

Correlative single-molecule localization microscopy and electron tomography reveals endosome nanoscale domains

Abstract: Many cellular organelles, including endosomes, show compartmentalization into distinct functional domains, which, however, cannot be resolved by diffraction-limited light microscopy. Single molecule localization microscopy (SMLM) offers nanoscale resolution but data interpretation is often inconclusive when the ultrastructural context is missing. Correlative light electron microscopy (CLEM) combining SMLM with electron microscopy (EM) enables correlation of functional subdomains of organelles in relation to their underlying ultrastructure at nanometer resolution. However, the specific demands for EM sample preparation and the requirements for fluorescent single-molecule photo-switching are opposed. Here, we developed a novel superCLEM workflow that combines triple-color SMLM (dSTORM & PALM) and electron tomography using semi-thin Tokuyasu thawed cryosections. We applied the superCLEM approach to directly visualize nanoscale compartmentalization of endosomes in HeLa cells. Internalized, fluorescently labeled Transferrin and EGF were resolved into morphologically distinct domains within the same endosome. We found that the small GTPase Rab5 is organized in nanodomains on the globular part of early endosomes. The simultaneous visualization of several proteins in functionally distinct endosomal sub-compartments demonstrates the potential of superCLEM to link the ultrastructure of organelles with their molecular organization at nanoscale resolution.

Ultrastructure and secretion of glandular trichomes in species of subtribe Cajaninae Benth (Leguminosae, Phaseoleae)

Abstract: The subtribe Cajaninae of papilionoid legumes has a pantropical distribution and comprises approximately 490 species. These species have diversified throughout dry environments where there are high temperatures and strong light. The subtribe stands out because all its representatives have vesicular glands. In addition, bulbous-based and capitate trichomes are important secretory structures present in all genera of the Cajaninae. We analyzed the ultrastructure and histochemistry of these glandular trichome types in leaflets of the three species of the subtribe. Using transmission electron microscopy and histochemical analyses, we link the glandular secretions to subcellular structures. We here report for the first time the type of exudate and ultrastructure of the glands of subtribe Cajaninae. Terpenoids and phenolics were confirmed by histochemistry tests, and we observed that the organelles responsible for biosynthesis of oils are the most representative in these glands. Each glandular trichome showed particular ultrastructural features compatible with the compounds produced. We suggest that these glandular trichomes, with their respective exudates, act in defense against herbivory and against possible damage by ultraviolet radiation.

Structural and Ultrastructural Changes in Nanoparticle Exposed Plants

Abstract: The applications of nanoparticles on aquatic and terrestrial ecosystems are increasing and receiving a great scientific attention due to its toxicity effects. The phytotoxicity of nanoparticles is mainly expressed by suppressed germination percentage, impact on morphometric parameters, for instance, root and shoot length, root hairs, biomass, bio-molecules, and cellular damages such as lipid peroxidation, protein damage, membrane destruction, chlorophyll fluorescent, transpiration rate, and photosynthesis. Recent studies indicate several changes in plant cell organelles such as a disruption in the cell wall, cell membrane, chloroplast structure, thylakoids, abnormal size of plastoglobules and starch granules, destructive changes in peroxisomes, swollen mitochondrial cristae, abnormal nucleus, loose, rough and thin mesophyll cells, epidermal, cortical, and stellar cells. Deposition of electronically dense materials near cell walls is also observed. These changes in plant cells impact the plant growth. This is the first chapter to highlight the toxicity of nanoparticles on the plants at anatomical and ultrastructural level.

Improved Electron Microscopy Fixation Methods for Tracking Autophagy-Associated Membranes in Cultured Mammalian Cells.

Abstract: Autophagy-related organelles, including omegasomes, isolation membranes (or phagophores), autophagosomes, and autolysosomes, are characterized by dynamic changes in lipid membranes including morphology as well as their associated proteins. Therefore, it is critical to define and track membranous elements for identification and detailed morphological analyses of these organelles. However, it is often difficult to clearly observe these organelles with good morphology in conventional electron microscopy (EM), thus hampering 3D analyses and correlative light-electron microscopy (CLEM). Here, we focus on describing fixation procedures using (1) ferrocyanide-reduced osmium for CLEM and (2) aldehyde/OsO4 mixture for detecting omegasome structures and isolation membrane-associated tubules (IMATs). These methods can be easily applied to cultured mammalian cells for conventional and cutting-edge EM analyses, leading to a better understanding of ultrastructural details in autophagosome formation.

FAM92A1 is a BAR domain protein required for mitochondrial ultrastructure and function.

Abstract: Mitochondrial function is closely linked to its dynamic membrane ultrastructure. The mitochondrial inner membrane (MIM) can form extensive membrane invaginations known as cristae, which contain the respiratory chain and ATP synthase for oxidative phosphorylation. The molecular mechanisms regulating mitochondrial ultrastructure remain poorly understood. The Bin-Amphiphysin-Rvs (BAR) domain proteins are central regulators of diverse cellular processes related to membrane remodeling and dynamics. Whether BAR domain proteins are involved in sculpting membranes in specific submitochondrial compartments is largely unknown. In this study, we report FAM92A1 as a novel BAR domain protein localizes to the matrix side of the MIM. Loss of FAM92A1 caused a severe disruption to mitochondrial morphology and ultrastructure, impairing organelle bioenergetics. Furthermore, FAM92A1 displayed a membrane-remodeling activity in vitro, inducing a high degree of membrane curvature. Collectively, our findings uncover a role for a BAR domain protein as a critical organizer of the mitochondrial ultrastructure that is indispensable for mitochondrial function.

Ultrastructural analysis of spores from diverse Bacillales species isolated from Brazilian soil

Abstract: Many species in the order Bacillales form a specialized cell type called a spore that is resistant to a range of environmental stresses. Transmission electron microscopy (TEM) reveals that the spore is comprised of a series of concentric shells, surrounding an interior compartment harbouring the spore DNA. The outermost of these shells varies considerably in morphology among species, likely reflecting adaptations to the highly diverse niches in which spores are found. To better characterize the variation in spore ultrastructure among diverse species, we used TEM to analyse spores from a collection of 23 aerobic spore-forming bacteria from the Solo do Distrito Federal (SDF strains), spanning the genera Bacillus, Lysinibacillus, Paenibacillus and Brevibacillus, isolated from soil from central Brazil. We found that the structures of these spores varied widely, as expected. Interestingly, even though these isolates are novel strains of each species, they were structurally very similar to the known examples of each species in the literature. Because in most cases, the species we analysed are poorly characterized, our data provide important evidence regarding which structural features are likely to be constant within a taxon and which are likely to vary.

Effects of rotary cell culture system‐simulated microgravity on the ultrastructure and biological behavior of human MDA‐MB‐231 breast cancer cells

Abstract: This study aimed to investigate changes in the ultrastructure, apoptosis, cycle progression, and migration ability of human MDA‐MB‐231 breast cancer cells under simulated microgravity conditions.

In vitro Characteristics of Heterogeneous Equine Hoof Progenitor Cell Isolates.

Abstract: Damage to an ectodermal-mesodermal interface like that in the equine hoof and human finger nail bed can permanently alter tissue structure and associated function. The purpose of this study was to establish and validate in vitro culture of primary progenitor cell isolates from the ectodermal-mesodermal tissue junction in equine hooves, the stratum internum, with and without chronic inflammation known to contribute to lifelong tissue defects. The following were evaluated in hoof stratum internum cell isolates up to 5 cell passages (P): expansion capacity by cell doublings and doubling time; plasticity with multi-lineage differentiation and colony-forming unit (CFU) frequency percentage; immunophenotype with immunocytochemistry and flow cytometry; gene expression with RT-PCR; and ultrastructure with transmission electron microscopy. The presence of keratin (K)14, 15 and K19 as well as cluster of differentiation (CD)44 and CD29 was determined in situ with immunohistochemistry. To confirm in vivo extracellular matrix (ECM) formation, cell-scaffold (polyethylene glycol/poly-L-lactic acid and tricalcium phosphate/hydroxyapatite) constructs were evaluated with scanning electron microscopy 9 weeks after implantation in athymic mice. Cultured cells had characteristic progenitor cell morphology, expansion, CFU frequency percentage and adipocytic, osteoblastic, and neurocytic differentiation capacity. CD44, CD29, K14, K15 and K19 proteins were present in native hoof stratum internum. Cultured cells also expressed K15, K19 and desmogleins 1 and 3. Gene expression of CD105, CD44, K14, K15, sex determining region Y-box 2 (SOX2) and octamer-binding transcription factor 4 (OCT4) was confirmed in vitro. Cultured cells had large, eccentric nuclei, elongated mitochondria, and intracellular vacuoles. Scaffold implants with cells contained fibrous ECM 9 weeks after implantation compared to little or none on acellular scaffolds. In vitro expansion and plasticity and in vivo ECM deposition of heterogeneous, immature cell isolates from the ectodermal-mesodermal tissue interface of normal and chronically inflamed hooves are typical of primary cell isolates from other adult tissues, and they appear to have both mesodermal and ectodermal qualities in vitro. These results establish a unique cell culture model to target preventative and restorative therapies for ectodermal-mesodermal tissue junctions.

Correlative Light and Electron Microscopy of Autophagosomes.

Abstract: Live-cell imaging has been widely used to study autophagosome biogenesis and maturation. When combined with correlative electron microscopy, this approach can be extended to reveal ultrastructural details in three dimensions. The resolution of electron microscopy is needed when membrane contact sites and tubular connections between organelles are studied.

Glandular Trichomes on the Leaves of Nicotiana tabacum: Morphology, Developmental Ultrastructure, and Secondary Metabolites

Abstract: Gopal RK, Ekiert HM, Goyal S, editors. Plant Cell and Tissue Differentiation and Secondary Metabolites. Springer, Cham; 2020. p. 1–37. (Reference Series in Phytochemistry).

Life at the edge – the cytology and physiology of the biotroph to necrotroph transition in Hymenoscyphus fraxineus during lesion formation in ash

Abstract: The progress of colonization of ash stems from ascospore inocula of Hymenoscyphus fraxineus was examined by light and electron microscopy. The main aim of the study was to characterize the cytology of the biotroph to necrotroph transition during lesion formation. Following direct penetration into epidermal cells, the fungus produced intracellular hyphae that invaded up to five cells before plant cells died. A lack of close attachment between the hyphal cell wall and plant cell membrane was revealed by plasmolysis of epidermal cells. Plant cells died at the centre of the infection but hyphae at the edge were typically found in living plant cells even around large lesions. During biotrophic invasion, the cytoplasm of penetrated plant cells showed very little response despite the plant cell membrane being in direct contact with the fungal cell wall. Before plant cell death, dark staining of the cytoplasm and proliferation of small vesicles was noted, but organelles retained normal ultrastructure. Dead plant cells contained dark brown, osmiophilic droplets. Penetration between epidermal or collenchyma cells was usually targeted to shared pits and involved constriction of hyphae. The transition to necrotrophy was not associated with a clear change in hyphal morphology. Biotrophic intracellular hyphae contained dense cytoplasm but hyphae in dead plant cells were more vacuolated. Remarkably little plant cell wall degradation was observed despite the fungus penetrating up to 18 cells deep into stem tissue. Features of the development of the ash dieback fungus are compared with other hemibiotrophic pathogens.

Complex insight on microanatomy of larval “human broad tapeworm” Dibothriocephalus latus (Cestoda: Diphyllobothriidea)

Abstract: In Europe, the tapeworm Dibothriocephalus latus (syn. Diphyllobothrium latum) is a well-known etiological agent of human diphyllobothriosis, which spreads by the consumption of raw fish flesh infected by plerocercoids (tapeworm’s larval stage). However, the process of parasite establishment in both intermediate and definitive hosts is poorly understood. This study was targeted mainly on the scolex (anterior part) of the plerocercoid of this species, which facilitates penetration of the parasite in intermediate paratenic fish hosts, and subsequently its attachment to the intestine of the definitive host. Plerocercoids were isolated from the musculature of European perch (Perca fluviatilis) caught in Italian alpine lakes. Parasites were examined using confocal microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Immunofluorescence tagging was held on whole mount larvae. The organisation of the central and peripheral nervous system was captured in D. latus plerocercoids, including the ultrastructure of the nerve cells possessing large dense neurosecretory granules. Two types of nerve fibres run from the body surface toward the nerve plexus located in the parenchyma on each side of bothria. One type of these fibres was found to be serotoninergic and possessed large subtegumental nerve cell bodies. A well-developed gland apparatus, found throughout the plerocercoid parenchyma, produced heterogeneous granules with lucent core packed in a dense layer. Three different types of microtriches occurred on the scolex and body surface of plerocercoids of D. latus: (i) uncinate spinitriches; (ii) coniform spinitriches; and (iii) capilliform filitriches. Non-ciliated sensory receptors were observed between the distal cytoplasm of the tegument and the underlying musculature. Confocal laser scanning microscopy and electron microscopy (SEM and TEM) showed the detailed microanatomy of the nervous system in the scolex of plerocercoids, and also several differences in the larval stages compared with adult D. latus. These features, i.e. well-developed glandular system and massive hook-shaped uncinate spinitriches, are thus probably required for plerocercoids inhabiting fish hosts and also for their post-infection attachment in the human intestine.

Histopathological and Ultrastructure Changes in the Embryonic Development of Schistocerca Gregaria (Forskal) (Orthoptera): Acrididae Induced by Lufenuron (CSI) and Rice Bran Extract (Waste Product)

Abstract: Background: Waste product compound of rice bran and lufenuron are considered safe compounds to the human and to the environment. They can be used to control Schistocerca gregaria.Objective: The aim of the present study is to examine the ultrastructural changes and histopathological alteration in the Schistocerca gregaria embryogenesis induced by selected waste product compound of rice bran (Oryza sativa) and a chitin synthesis inhibitor (lufenuron).Materials and Methods: Histological and ultrastructure study of normal and affected eggs of Schistocerca gregaria were conducted to demonstrate the effects of lufenuron and rice bran extract on the embryogenesis. Cleavages started about 5 hrs post oviposition (pop) and continue to divide until formation of cellular blastodrem by 1 day pop. By 2 days pop germ band is formed, differentiated into ectoderm and mesoderm. At 3 days pop segmentation of germ band into mouthpart and three thoracic segments occur. Antenna was observed at 3 days pop. Fore and midgut were detected by 5 days pop. Hindgut was also observed by 5 days pop. By 4 days pop, eyes and brain appeared. Brain appeared as two ganglionic masses separated by oesophagus, which by 5 days pop appears as 2 large interconnect cerebral lobes enwrapped by neurilemma. Histological section of affected eggs showed great effects on brain, alimentary canals and compound eyes.Results: Ultrastructure study of newly deposited eggs showed that, the chorion consists of several easily distinguishable layers and in 30-hour-old eggs, cleavage nuclei of different shapes could be observed. The nuclei of the blastoderm cell have spindle shape and have condensed chromatin, which attaches to nuclear membrane. Electron micrograph of lufenuron-affected eggs revealed abnormal chorion and cleavage nuclei. In rice bran affected eggs, disintegrated blastoderm that failed to arranged and sever malformed nuclei were seen. Vaculation and lysis of cell components leaving cavities within the ooplasm were detected in both treatments.Conclusion: The tested compounds induced serious changes to the embryos of Schistocerca gregaria as revealed by the histological and ultrastructure studies

Anterior sense organs in Sabellaria alveolata (Annelida, Sedentaria, Spionida) with special reference to ultrastructure of photoreceptor elements presumably involved in shadow reflex

Abstract: The reef-building sedentary polychaete, Sabellaria alveolata, is well known for its specialized anterior end, the operculum, which is exposed to the environment during vital activities, such as feeding or as it seals its tube when the animal withdraws. This region represents the most important sensory structure in Sabellariidae. It comprises two lobes, tentacular filaments, protective chaetae (paleae), a median organ, and a median ridge, and bears various pigmented spots. Worms swiftly withdraw into tubes triggered by abrupt light change (shadow reflex). We suspected that the pigmented spots were photoreceptive and responsible for the shadow response. To test this hypothesis, the median organ and median ridge of S. alveolata were investigated by applying light microscopy, confocal laser scanning microscopy, scanning, and transmission electron microscopy. Besides unciliated supportive cells, these organs consist of numerous multiciliated and glandular cells on their ventral surfaces. The multiciliated cells are of two types: epidermal supportive and receptor cells. The median organ is innervated directly from the brain by two longitudinal basiepithelial nerves. The presence of multiciliated cells and mucocytes suggests that the organ is sensory, involved in both feeding and tube-building behavior. Furthermore, we found two pairs of eyespots on the lateral posterior part of the median ridge, situated close to the neurite bundles anterior to the brain. These eyes are simple in structure and resemble larval-type eyes. They are composed of only two cells each, one rhabdomeric photoreceptor cell and one pigmented supportive cell. The pigmented eyes on the median ridge are clearly involved in photoreception and very likely involved in shadow reflex.

Interrenal tissue, chromaffin cells and corpuscles of Stannius of Nile tilapia (Oreochromis niloticus).

Abstract: Twenty-three fishes were used to study the structure and ultrastructure of interrenal tissue, chromaffin cells and corpuscles of Stannius of Nile tilapia. The interrenal tissue and chromaffin cells are present within the head kidney. The interrenal tissue is arranged in the form of highly convoluted cords, bordered by the lining endothelium of the adjacent sinusoids. It has no connective tissue capsule. The cytoplasm of the interrenal cells contains abundance of mitochondria, vacuoles and smooth endoplasmic reticulum, characterizing of steroid-producing tissues. Two types of chromaffin cells; noradrenaline (NA) cells and adrenaline cells (A) could be recognized by light microscope using chromaffin reaction, as well as by electron microscope they could be distinguished depending on the size and electron density of their granules. The corpuscles of Stannius are two in number and located on the dorsal aspect of the tail kidney. Each corpuscle is surrounded by thick connective tissue capsule. The parenchyma is divided into lobules, each of which is surrounded by distinct basal lamina and has a pseudo lumen. Depending on the presence of secretory granules and the relative abundance of cell organelles, three cell types could be recognized; granular cell, agranular cell (Type I) and agranular cell (Type II). In conclusion, the morphological and ultrastructural analysis of the endocrine tissues of the kidney of Nile tilapia has revealed only one type of interrenal cells, two types of chromaffin cells and three staged-cells of Stannius corpuscles.

Ultrastructure of the scolex of Orygmatobothrium schmittii (Cestoda: Phyllobothriidea).

Abstract: The ultrastructure of the scolex of Orygmatobothrium schmittii (Cestoda: Phyllobothriidae) was studied using histochemistry, scanning, and transmission electron microscopy. The central bothridial structure resulted in a glandulomuscular organ formed by a mass of syncytial glands and radial muscles, with glycoprotein secretions potentially adhesive. Among the sensory receptors found on the scolex, a particular type was found surrounding the glandulomuscular organ, which might be related in the regulation of the secretions. The internal structure of the microtriches revealed a diversity of configurations according to their morphotype and distribution on the scolex. Microtriches with larger caps are thought to be useful for attachment purposes. In addition, the thick bounding membranes of the attachment organs and the circular musculature in the bothridia, seem to aid to the attachment of the scolex to the mucosa of the host. © 2019 Wiley Periodicals, Inc.

Morphological and optical properties of human immature platelet-enriched population produced in immunodeficient mice

Abstract: Ultrastructure analysis of immature platelets is difficult because of the lack of a suitable marker and their relatively low concentration in total platelets.We investigated the morphological and o...

Ultrastructure of sensilla on the maxillary and labial palps of three species (Coleoptera: Staphylinidae: Staphylininae)

Abstract: Most species of Staphylinidae are predators in an agroecosystem. They acquire prey information from their environment through receptors. In this study, the sensilla on maxillary and labial palps of Philonthus kailiensis, Philonthus lewisius and Quedius robustus were examined with scanning electron microscopy to identify and analyse the external morphology and distribution of the sensilla to enhance our knowledge of the sensilla of Staphylinidae and provide a rationale of taxonomical studies on the two genus. Results showed that the sensilla are classified into six types: Böhm bristles, sensilla chaetica, sensilla furcate, sensilla coeloconica, sensilla placodea and sensilla basiconica. No sexual dimorphism exists among the three species. The relationships and functions of sensilla on maxillary and labial palps were also speculated. There may be a certain correlation between the sensilla on maxillary and labial palps of the staphylinid and its habitat.

Functional Ultrastructure of the Excretory Gland Cell in Zoonotic Anisakids (Anisakidae, Nematoda).

Abstract: Excretory and secretory products are crucial for parasite infectivity and host immunomodulation, but the functioning and ultrastructure of the excretory gland cell (EC) that produces these products are still scarcely understood and described. In light of growing reports on anisakiasis cases in Europe, we aimed to characterise the EC of larval Anisakis pegreffii and adult Pseudoterranova azarasi. In the latter, EC starts 0.85 mm from the head tip, measuring 1.936 × 0.564 mm. Larval EC shows a long nucleus with thorn-like extravaginations toward the cytoplasm, numerous electron-dense and -lucent secretory granules spanning from the perinuclear to subplasmalemmal space, an elevated number of free ribosomes, small, spherical mitochondria with few cristae and a laminated matrix, small and few Golgi apparatuses, and few endoplasmic reticula, with wide cisternae complexes. Ultrastructure suggests that anaerobic glycolysis is the main metabolic pathway, obtained through nutrient endocytosis across the pseudocoelomic surface of the EC plasmalemma and its endocytic canaliculi. Thorn-like extravaginations of EC karyotheca likely mediate specific processes (Ca2+ signaling, gene expression, transport, nuclear lipid metabolism) into the extremely wide EC cytosol, enabling focal delivery of a signal to specific sites in a short time. These functional annotations of parasitic EC should help to clarify anisakiasis pathogenesis.

The importance of insect sperm: Sperm ultrastructure of Hermetia illucens (black soldier fly).

Abstract: Sperm structure and ultrastructure of Hermetia illucens was determined by light microscopy and transmission electron microscopy. The main sperm components were similar as for other Dipteran subspecies, while the ultrastructure revealed distinguishing features in the zone of overlap and anterior flagellar region. Sperm varied in size indicating sperm polymorphism. The head region is lacking an acrosome. The zone of overlap consisted of uniquely organized centriolar adjunct material, partly forming electron dense areas to finally form an outer ring separating the mitochondrial derivatives from the 9 + 9 + 2 axoneme. Accessory bodies arising from the zone of overlap are flanked by smaller to large mitochondrial derivatives into the anterior flagellum. This study confirms sperm structure diversity between brachyceran subspecies and support its relationship with nematoceran subspecies.

Ultrastructural morphology is distinct among primary progenitor cell isolates from normal, inflamed, and cryopreserved equine hoof tissue and CD105+K14+ progenitor cells

Abstract: The equine hoof dermal-epidermal interface requires progenitor cells with distinct characteristics This study was designed to provide accurate ultrastructural depictions of progenitor cells isolated from inflamed tissue and normal tissue before and after cryopreservation and following selection of cells expressing both keratin (K) 14 (ectodermal) and cluster of differentiation (CD) 105 (mesodermal) Passage 3 cell ultrastructure was assessed following 2D culture and after 3D culture on decellularized hoof tissue scaffolds Outcome measures included light, transmission electron, and scanning electron microscopy, immunocytochemistry, and CD105+K14+ cell trilineage plasticity Cells from normal tissue had typical progenitor cell characteristics Those from inflamed tissue had organelles and morphology consistent with catabolic activities including lysosomes, irregular rough endoplasmic reticulum, and fewer vacuoles and early endosomes than those from normal tissue Cryopreserved tissue cells appeared apoptotic with an irregular cell membrane covered by cytoplasmic protrusions closely associated with endocytic and exocytic vesicles, chromatin aggregated on the nuclear envelop, abundant, poorly organized rough endoplasmic reticulum, and plentiful lysosomes Cells that were CD105+K14+ were distinguishable from heterogenous cells by infrequent microvilli on the cell surface, sparse endosomes and vesicles, and desmosomes between cells Cells expressed ectodermal (K15) and mesodermal (CD105) proteins in 2D and 3D cultures Inflamed and cryopreserved tissue isolates attached poorly to tissue scaffold while normal tissue cells attached well, but only CD105+K14+ cells produced extracellular matrix after 4 d The CD105+K14+ cells exhibited osteoblastic, adipocytic, and neurocytic differentiation Ultrastructural information provided by this study contributes to understanding of equine hoof progenitor cells to predict their potential contributions to tissue maintenance, healing, and damage as well post-implantation behavior

Ultrastructure of the rectum of the soil-spraying larva in Bittacus cirratus (Mecoptera: Bittacidae)

Abstract: The larvae of Bittacidae have an interesting behavior of spraying soil particles on their body surface through the anus. However, the hindgut specialization associated with this behavior has rarely been studied hitherto. Here, we investigated the fine structure of the larval rectum in the hangingfly Bittacus cirratus Tjeder using light and transmission electron microscopy. The results show that the larvae of B. cirratus have a tubular rectum without rectal pads or papillae. The rectum consists of well-developed visceral muscle layers, a non-cellular basal lamina, a single-layer epithelium with a cuticular intima, and a central lumen. The folded rectal epithelium consists of two types of flattened epithelial cells: electron-dense type I cells and electron-lucent type II cells. The apical and basal plasma membranes are infolded and are associated with mitochondria in the epithelial cells. The epithelial cells are held by septate and scalariform junctions. The lateral cell membranes are combined with mitochondria among type I cells and generate mitochondria-scalariform junction complexes. These features suggest that the epithelial cells are active in water and ion reabsorption. We conclude that the absence of rectal pads or papillae and the presence of developed circular muscles are likely morphological adaptations of these larvae to the soil-spraying behavior.

Ultrastructure of spermiogenesis and the distribution of spermatozoal nuclear histones in the Japanese mantis shrimp, Oratosquilla oratoria (Crustacea: Stomatopoda).

Abstract: The Japanese mantis shrimp Oratosquilla oratoria (Stomatopoda; Crustacea) is one of the most economically important aquatic species of Pacific shrimp and it is distributed from Japan to the coast of China, the Philippines, the Malay Peninsula, and the Hawaiian Islands. Early studies described certain characteristics of spermatogenesis and the sperm ultrastructure in Stomatopoda, but the composition of sperm basic nuclear proteins (SBNPs) remains completely unknown. We studied the sperm ultrastructure of O. oratoria using transmission electron microscopy and the histone composition using immunofluorescence and immunoelectron microscopy. We found that the spherical nucleus is adjacent to the electron translucent external coat, which occurs in early spermatids. The acrosomal structure begins to form at the junction of the nucleus and the external coat. At the mid-spermatid stage, part of the chromatin appears to be more electron-dense than the external coat side. The aflagellate sperm of O. oratoria, are rounded or slightly ovoid in shape and have a consistent granular nucleus, an acrosome structure of pushpin shape and a spherical vesicular body in which faintly granular material is scattered. The acrosome consists of an acrosomal vesicle, perforatorium, and subacrosomal material. The sperm contains histones H2A, H2B, H3, H4, H3.3, H2AX, and H2AZ as well as some histone modifications, that is, H3K9me3, H3K4me2, H3S10ph, H4Kac, and H2A + H4S1ph. Histones are localized not only in the nucleus of the sperm but also in other structures outside the nucleus. The results may provide new perspectives for systematic studies of crustaceans and their sperm chromatin components. These findings extend the study of the sperm structure of Stomatopoda and provide basic data to elucidate the epigenetic mechanism of fertilization.