scholarly journals The localization of chitin synthase mediates the patterned deposition of chitin in developing Drosophila bristles

2019 ◽  
Author(s):  
Paul N. Adler
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Complex Structure ◽  
Chitin Synthase ◽  
Cell Type ◽  
Body Regions ◽  
Transmission Electron ◽  
Successful Group ◽  
Sensory Bristles ◽  
Parallel Arrays

AbstractThe insect exoskeleton is a complex structure that is a key for the life style of this very successful group of animals. It contains proteins, lipids and the N-acetyl glucosamine polymer chitin. Chitin is synthesized by the enzyme chitin synthase. In most body regions, chitin fibrils are found in a stack of parallel arrays that can be detected by transmission electron microscopy. Each array is rotated with respect to the layers above and below. In sensory bristles, chitin primarily accumulates in bands parallel to the proximal/distal axis of the bristle. These bands are visible by confocal microscopy providing experimental advantages. We have used this cell type and an edited chitin synthase gene to establish that the bands of chitin are closely associated with stripes of chitin synthase, arguing the localization of chitin synthase plays an important role in mediating the patterned deposition of chitin. This is reminiscent of what has been seen for chitin and chitin synthase in fungi and between cellulose and cellulose synthase in plants. Several genes are known to be essential for proper chitin deposition. We found one of these, Rab11 is required for the insertion of chitin synthase into the plasma membrane and a second, duskylike is required for plasma membrane chitin synthase to localize properly into stripes. We also established that the actin cytoskeleton is required for the proper localization of chitin synthase and chitin in developing sensory bristles.

scholarly journals A novel exosome biogenesis mechanism: multivesicular structures budding and rupturing at the plasma membrane

2019 ◽  
Author(s):  
Stephanie Leon Quinonez ◽  
Ian R. Brown ◽  
Helen E. Grimsley ◽  
Jindrich Cinatl ◽  
Martin Michaelis ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Membrane Association ◽  
Dense Layer ◽  
Physiological Processes ◽  
Exosome Biogenesis ◽  
Transmission Electron ◽  
Typical Morphology ◽  
Intercellular Signalling ◽  
Microscopy Images

AbstractExosomes are small vesicles secreted by the cells, which mediate intercellular signalling and systemic physiological processes. Exosomes are known to originate from the intraluminal vesicles of the multivesicular endosome that fuses with the plasma membrane. We found that the non-small cell lung cancer (NSCLC) cell lines, HCC15 and A549, secreted exosomes with typical morphology and protein contents. Unexpectedly, transmission electron microscopy images indicated that the cells formed multivesicular structures that protruded from the plasma membrane and ruptured to release the exosomes. There were smooth multivesicular structures surrounded by an ordinary looking membrane, multivesicular structures coated by an electron dense layer with regular spacing pattern, and intermediate forms that combined elements of both. Electron microscopy images suggested that exosomes are release from these structures by burst events and not by the conventional fusion process. The molecular details of this novel mechanism for membrane association, deformation and fusion is to be unveiled in the future.

Ultrastructural observations of the tegument of Postorchigenes gymnesicus (Digenea: Lecithodendriidae)

1996 ◽  
Vol 70 (1) ◽  
pp. 13-19 ◽  
Author(s):  
J.R. Ferrer ◽  
M. Gracenea ◽  
M. Trullols ◽  
O. Gonzalez-Moreno
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Protein Content ◽  
Basal Lamina ◽  
Apical Membrane ◽  
General Body ◽  
Body Regions ◽  
Transmission Electron ◽  
Direct Association

AbstractThe tegument of Postorchigenes gymnesicus has been studied by scanning and transmission electron microscopy. The general body tegument is spinous and contains mitochondria, biconcave disc-shaped vesicles bounded by an unitary membrane and displaying a protein content, and scarce spherical bodies. The tegument covering specialized body regions is aspinous. Few vesicles were evident in the tegument covering the suckers and oesophagus, being more abundant in the metraterm and cirrus where the tegument is thicker. Laurer's canal has a thick tegument with sparse vesicles, mostly arranged close to the apical membrane. A direct association was evident between the basal lamina underlying the spines and the muscular subtegumental fibres, suggesting a motile character for the spine.

The comparative ultrastructure of spermatozoa from Bothrimonus sturionis Duv. 1842 (Pseudophyllidea), Pseudanthobothrium hanseni Baer, 1956 (Tetraphyllidea), and Monoecocestus americanus Stiles, 1895 (Cyclophyllidea)

1984 ◽  
Vol 62 (6) ◽  
pp. 1059-1066 ◽  
Author(s):  
Barbara M. MacKinnon ◽  
Michael D. B. Burt
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Plasma Membrane ◽  
Main Body ◽  
Posterior Portion ◽  
Transmission Electron ◽  
Dense Nucleus ◽  
Comparative Ultrastructure ◽  
Electron Lucent ◽  
Mature Spermatozoa

The mature spermatozoa from Bothrimonus sturionis (Pseudophyllidea), Pseudanthobothrium hanseni (Tetraphyllidea), and Monoecocestus americanus (Cyclophyllidea) were examined using transmission electron microscopy. Transverse sections of the sperm of B. sturionis indicate that the number of sperm axonemes varies from one to eight, with approximately one-third of the sperm containing two axonemes. Likewise, the number of peripheral microtubules lying just within the external plasma membrane varies from 12 to 20. The nucleus is electron lucent and fibrous in appearance. The spermatozoa of B. sturionis show great variation in the material examined and the majority of them are believed to be aberrant. The spermatozoon of P. hanseni contains a single axoneme with the nucleus wrapped in a crescent around it in the anterior region of the sperm. The posterior portion of the spermatozoon is characterized by a helical flange which projects from the main body of the sperm. The spermatozoon of M. americanus is elongate and slender, containing a single axoneme with an electron-dense nucleus coiled around it in the anterior one-third of the sperm. Electron-opaque bodies, which may be glycogen, fill the cytoplasm. The spermatozoa of all three species contain neither an acrosome nor mitochondria. The flagella of all the spermatozoa have a 9 + "1" arrangement of microtubules. The importance of the ultrastructure of spermatozoa in the phylogeny and taxonomy of cestodes is discussed.

The Microstructure and Electromigration Performance of Damascene-Fabricated Aluminum Interconnects

1997 ◽  
Vol 473 ◽  
Author(s):  
Paul R. Besser ◽  
John E. Sanchez ◽  
David P. Fields ◽  
Shekhar Pramanick ◽  
Kashmir Sahota
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Aluminum Alloy ◽  
Crystallographic Texture ◽  
Local Electron ◽  
Electron Backscattered Diffraction ◽  
Transmission Electron ◽  
Parallel Arrays ◽  
Aluminum Interconnects

ABSTRACTNovel metal deposition stack and damascene processing methods have been used to fabricate electrically isolated parallel arrays of 1.0 μm deep aluminum-alloy interconnect trenches varying in width from 0.5 μm to 16 μm. The grain size and crystallographic texture of the Al in these trenches has been characterized using transmission electron microscopy (TEM) and local electron backscattered diffraction (EBSD), respectively. Narrow lines (0.5 and 1.0 μm wide) have a bamboo microstructure, intermediate widths (2.0 μm wide) are nearly bamboo, and wide lines (4.0 μ and wider) are polycrystalline. The <111> texture of the lines degrades with decreasing linewidth. A secondary <100> component is demonstrated and its origin proposed. The electromigration reliability of the narrow damascene Al lines was measured, and the observed enhancement of damascene Al interconnects compared to conventionally-fabricated Al interconnects is correlated with the microstructure.

The fine structure of Thioploca araucae and Thioploca chileae

1990 ◽  
Vol 36 (6) ◽  
pp. 438-448 ◽  
Author(s):  
Siegfried Maier ◽  
Horst Völker ◽  
Marita Beese ◽  
Victor A. Gallardo
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Coastal Upwelling ◽  
The Other ◽  
Surface Topology ◽  
Cytoplasmic Material ◽  
Transmission Electron ◽  
Soft Bottoms ◽  
Sulfur Inclusions

Thioploca araucae and Thioploca chileae from the sublittoral soft bottoms of the coastal upwelling ecosystem off central Chile were examined by scanning and transmission electron microscopy. Except for filament diameter (30–43 and 12–20 μm, respectively) and slight differences in other dimensions and surface topology, the details of fine structure were essentially identical in the two species. The wall consisted of five layers, and only the inner layer was present in the septum. Multiple membrane intrusions dissected the procaryotic cytoplasmic material, which was restricted to a relatively thin layer within the wall. Sulfur inclusions and two other extracytoplasmic inclusions, as well as one kind of intracytoplasmic inclusion, were described. The central part of each cell consisted of one large vacuole, extending from septum to septum and representing a volume at least more than three times larger than the combined volume of wall and cytoplasm. The vacuole was separated from the other cell parts by a membrane. Electron-dense material was deposited between vacuole membrane and plasma membrane, between plasma membrane and wall, and inside membrane intrusions. A continuity between the vacuolar membrane and the other membranes was never encountered. The possible origin of such an extracytoplasmic membrane is discussed. Key words: benthos, electron microscopy, fine structure, Thioploca.

scholarly journals Ultrastructure and Functional Morphology of the Appendages in the Reef-Building Sedentary Polychaete Sabellaria Alveolata (Annelida, Sedentaria, Sabellida)

2020 ◽  
Author(s):  
Christian Meyer ◽  
Thomas André ◽  
Günter Purschke
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Blood Vessels ◽  
Laser Scanning ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Entire Body ◽  
Receptor Cells ◽  
Body Regions ◽  
Transmission Electron

Abstract Background: The sedentary polychaete Sabellaria alveolata, the sandcastle or honeycomb worm, possesses four different kinds of appendages besides the parapodia: opercular papillae, tentacular filaments, palps, and branchiae. It exhibits a highly specialized anterior end, the operculum, formed by the prostomium, peristomium, and two anterior segments. Besides the median organ, the operculum comprises opercular papillae, tentacular filaments, and palps. Paired branchiae are present from the second thoracic chaetiger onwards on the posteriorly following segments except for the last ones. Only the palps have been studied thus far by transmission electron microscopy in late larvae of a different species. In order to bridge the data gap, we investigated the appendages of S. alveolata by applying light microscopy, confocal laser scanning microscopy, scanning, and transmission electron microscopy. Results: In S. alveolata the entire body is covered by a thin cuticle characterized by the absence of layers of parallel collagen fibers with no differentiation between the various body regions including the branchiae. The opercular papillae bear numerous tufts of receptor cells and lack motile cilia. The tentacular filaments show a distinctive ciliation pattern; their most conspicuous morphological feature is their cell-free cartilaginous endoskeletal structure enclosed by ECM. Besides musculature the filaments include a single coelomic cavity but blood vessels are absent. The palps are ciliated with two coelomic cavities and a single blind-ending blood vessel. Besides external ciliation and receptor cells, the coelomate branchiae are highly vascularized and equipped with numerous blood spaces extending deep into the basal regions of the epidermal cells (diffusion distances: 150–400nm). Conclusions: All appendages, including the branchiae, bear receptor cells and, as such, are sensory. The opercular papillae resemble typical parapodial cirri. In contrast, the tentacular filaments have a double function: sensing, collecting and transporting particles. A similarity to branchiae can be excluded. The palps are typical grooved palps similar to another sabellariid studied. A revised classification of polychaete branchiae is suggested; thereby, the branchiae of S. alveolata belong to the most common type comprising coelom, musculature, and blood vessels. The results indicate that diffusion distances between blood and environment have been underestimated in many cases.

scholarly journals A multi-layered and dynamic apical extracellular matrix shapes the vulva lumen in Caenorhabditis elegans

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Jennifer D Cohen ◽  
Alessandro P Sparacio ◽  
Alexandra C Belfi ◽  
Rachel Forman-Rubinsky ◽  
David H Hall ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Caenorhabditis Elegans ◽  
Cell Types ◽  
Extracellular Matrices ◽  
Cell Type ◽  
Transmission Electron ◽  
Genetic Perturbations ◽  
Lipid Transporters ◽  
Matrix Factors

Biological tubes must develop and maintain their proper diameter to transport materials efficiently. These tubes are molded and protected in part by apical extracellular matrices (aECMs) that line their lumens. Despite their importance, aECMs are difficult to image in vivo and therefore poorly understood. The Caenorhabditis elegans vulva has been a paradigm for understanding many aspects of organogenesis. Here we describe the vulva luminal matrix, which contains chondroitin proteoglycans, Zona Pellucida (ZP) domain proteins, and other glycoproteins and lipid transporters related to those in mammals. Confocal and transmission electron microscopy revealed, with unprecedented detail, a complex and dynamic aECM. Different matrix factors assemble on the apical surfaces of each vulva cell type, with clear distinctions seen between Ras-dependent (1°) and Notch-dependent (2°) cell types. Genetic perturbations suggest that chondroitin and other aECM factors together generate a structured scaffold that both expands and constricts lumen shape.

scholarly journals Myogenesis of Siboglinum fiordicum sheds light on body regionalisation in beard worms (Siboglinidae, Annelida)

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Nadezhda Rimskaya-Korsakova ◽  
Nadezda Karaseva ◽  
Timofei Pimenov ◽  
Hans Tore Rapp ◽  
Eve Southward ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
The Body ◽  
Body Region ◽  
Competent Larva ◽  
Body Regions ◽  
Transmission Electron ◽  
Chaetopterus Variopedatus ◽  
Mode Of Life ◽  
Anterior Body

Abstract Background Many annelids, including well-studied species such as Platynereis, show similar structured segments along their body axis (homonomous segmentation). However, numerous annelid species diverge from this pattern and exhibit specialised segments or body regions (heteronomous segmentation). Recent phylogenomic studies and paleontological findings suggest that a heteronomous body architecture may represent an ancestral condition in Annelida. To better understand the segmentation within heteronomous species we describe the myogenesis and mesodermal delineation of segments in Siboglinum fiordicum during development. Results Employing confocal and transmission electron microscopy we show that the somatic longitudinal musculature consists of four separate strands, among which ventrolateral one is the most prominent and is proposed to drive the search movements of the head of the late metatrochophore. The somatic circular musculature lies inside the longitudinal musculature and is predominantly developed at the anterior end of the competent larva to support the burrowing behaviour. Our application of transmission electron microscopy allows us to describe the developmental order of the non-muscular septa. The first septum to form is supported by thick bundles of longitudinal muscles and separates the body into an anterior and a posterior region. The second group of septa to develop further divides the posterior body region (opisthosoma) and is supported by developing circular muscles. At the late larval stage, a septum reinforced by circular muscles divides the anterior body region into a forepart and a trunk segment. The remaining septa and their circular muscles form one by one at the very posterior end of the opisthosoma. Conclusions The heteronomous Siboglinum lacks the strict anterior to posterior sequence of segment formation as it is found in the most studied annelid species. Instead, the first septum divides the body into two body regions before segments are laid down in first the posterior opisthosoma and then in the anterior body, respectively. Similar patterns of segment formation are described for the heteronomous chaetopterid Chaetopterus variopedatus and serpulid Hydroides elegans and may represent an adaptation of these annelids to the settlement and transition to the sedentarian-tubiculous mode of life.

scholarly journals A multi-layered and dynamic apical extracellular matrix shapes the vulva lumen in Caenorhabditis elegans

2020 ◽  
Author(s):  
Jennifer D. Cohen ◽  
Alessandro P. Sparacio ◽  
Alexandra C. Belfi ◽  
Rachel Forman-Rubinsky ◽  
David H. Hall ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Types ◽  
Extracellular Matrices ◽  
Cell Type ◽  
C Elegans ◽  
Transmission Electron ◽  
Genetic Perturbations ◽  
Lipid Transporters ◽  
Matrix Factors

AbstractBiological tubes must develop and maintain their proper diameter in order to transport materials efficiently. These tubes are molded and protected in part by apical extracellular matrices (aECMs) that line their lumens. Despite their importance, aECMs are difficult to image in vivo and therefore poorly understood. The C. elegans vulva has been a paradigm for understanding many aspects of organogenesis. Here we describe the vulva luminal matrix, which contains chondroitin proteoglycans, Zona Pellucida (ZP) domain proteins, and other glycoproteins and lipid transporters related to those in mammals. Confocal and transmission electron microscopy revealed, with unprecedented detail, a complex and dynamic aECM. Different matrix factors assemble on the apical surfaces of each vulva cell type, with clear distinctions seen between Ras-dependent (1°) and Notch-dependent (2°) cell types. Genetic perturbations suggest that chondroitin and other aECM factors together generate a structured scaffold that both expands and constricts lumen shape.

scholarly journals Myogenesis of Siboglinum Fiordicum Sheds Light on Body Regionalisation in Beard Worms (Siboglinidae, Annelida)

2021 ◽  
Author(s):  
Nadezhda Nikolaevna Rimskaya-Korsakova ◽  
Nadezda Karaseva ◽  
Timofei Pimenov ◽  
Hans Tore Rapp ◽  
Eve Southward ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
The Body ◽  
Body Region ◽  
Body Regions ◽  
Transmission Electron ◽  
Chaetopterus Variopedatus ◽  
Anterior Body ◽  
Longitudinal Muscles ◽  
Posterior Body Region

Abstract BackgroundMany annelids, including well-studied species such as Platynereis, show similar structured segments along their body axis (homonomous segmentation). However, numerous annelid species diverge from this pattern and exhibit specialised segments or body regions (heteronomous segmentation). Recent phylogenomic studies and paleontological findings suggest that a heteronomous body architecture may represent an ancestral condition in Annelida. To better understand the segmentation within heteronomous species we describe the myogenesis and mesodermal delineation of segments in Siboglinum fiordicum during development. ResultsEmploying confocal and transmission electron microscopy we show that the somatic circular musculature lies inside the longitudinal musculature and is predominantly developed at the anterior end of the larva. The longitudinal musculature consists of four separate strands at the ventral, dorsal, and ventrolateral body sides. Posteriorly, the longitudinal strands form a continuous layer. Our application of transmission electron microscopy allows us to describe the developmental order of the non-muscular septa. The first septum to form is supported by thick bundles of longitudinal muscles and separates the body into an anterior and a posterior region. The second group of septa to develop further divides the posterior body region (opisthosoma) and is supported by developing circular muscles. At the late larval stage, a septum reinforced by circular muscles divides the anterior body region into a forepart and a trunk segment. The remaining septa and their circular muscles form one by one at the very posterior end of the opisthosoma. Functionally, the prominent ventrolateral longitudinal muscles in the larva are proposed to drive the search movements of the head, while the anterior circular muscles and the posterior continuous layers of longitudinal muscles support the burrowing behaviour of the larva.ConclusionsThe heteronomous Siboglinum lacks the strict anterior to posterior sequence of segment formation as it is found in the most studied annelid species. Instead, the first septum divides the body into two body regions, before segments are layed down in first the posterior opisthosoma and then in the anterior body, respectively. Similar pattern of segment formation is described for the heteronomous chaetopterid Chaetopterus variopedatus and may represent an ancestral segmentation process in Annelida.

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