scholarly journals Pseudocnidae of ribbon worms (Nemertea): ultrastructure, maturation, and functional morphology

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10912
Author(s):  
Timur Yu Magarlamov ◽  
James M. Turbeville ◽  
Alexei V. Chernyshev
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Core Layer ◽  
Outer Core ◽  
Type I ◽  
Type Ii ◽  
The Core ◽  
Transmission Electron ◽  
Core Rod ◽  
Eleven Species

The fine structure of mature pseudocnidae of 32 species of nemerteans, representatives of 20 genera, six families, and two classes was investigated with scanning and transmission electron microscopy. Pseudocnidae are composed of four layers (cortex, medulla, precore layer, and core) in most species investigated, but the degree of development and position of each layer can vary between different species. The secretion products comprising immature pseudocnidae segregate into separate layers: a thin envelope, which subsequently separates into the cortex and medulla and an extensive internal layer. We distinguish two pseudocnida types: type I is characterized by a two-layered core and type II by a three-layered core. Type I pseudocnidae are present in archinemertean species, Carinoma mutabilis, and in all pilidiophoran species, except Heteronemertea sp. 5DS; type II pseudocnidae occur in all studied species of Tubulanidae and the basal Heteronemertea sp. 5DS. Based on the structure of the discharged pseudocnidae observed in eleven species of palaeonemerteans and in eight species of pilidiophorans, we distinguish three different mechanisms (1–3) of core extrusion/discharge with the following characteristics and distribution: (1) the outer core layer is everted simultaneously with the tube-like layer and occurs in type I pseudocnidae of most species; (2) the extruded core is formed by both eversion of the outer core layer and medullar layer, and occurs in type I pseudocnidae of Micrura cf. bella; (3) the eversion of the outer core layer begins together with the core rod and core rod lamina and occurs in type II pseudocnidae. Morpho-functional comparison with other extrusomes (cnidae, sagittocysts, rhabdtites, and paracnids) confirm that pseudocnidae are homologous structures that are unique to nemerteans.

Structure and synthesis of the peritrophic membrane in Trichoptera larvae

Zoosymposia ◽  
2011 ◽  
Vol 5 (1) ◽  
pp. 63-70
Author(s):  
CARLA CORALLINI
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cardiac Valve ◽  
Food Type ◽  
Peritrophic Membrane ◽  
Type I ◽  
Type Ii ◽  
Food Ingestion ◽  
Transmission Electron ◽  
Anterior Midgut

The peritrophic membrane (PM) in Trichoptera larvae was examined by light, scanning and transmission electron microscopy. The gut of most insects produces 2 fundamental types of PM: Type I is synthesized and secreted by the entire midgut epithelium in response to the ingestion of food; type II is synthesized by specialized cells of the cardiac valve located in the anterior midgut independent from food ingestion. Corallini (2003) described, in the midgut of Limnephilidae larvae, a type I PM which is also secreted by unfed larvae. In this study, both types of PM were observed. Type I PM was evident in larvae of Rhyacophilidae, Leptoceridae, Sericostomatidae and Odontoceridae; the type II PM was observed in larvae of Philopotamidae, Polycentropodidae and Hydropsychidae.

Formation of bismuth iron oxide based core–shell structures and their dielectric, ferroelectric and magnetic properties

2019 ◽  
Vol 7 (5) ◽  
pp. 1280-1291 ◽  
Author(s):  
Alaka Panda ◽  
R. Govindaraj ◽  
R. Mythili ◽  
G. Amarendra
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Magnetic Properties ◽  
Iron Oxide ◽  
Shell Structures ◽  
Core Shell ◽  
Bismuth Iron Oxide ◽  
The Core ◽  
Shell Nanostructures ◽  
Transmission Electron

Bismuth and iron oxides subjected to ball milling followed by controlled annealing treatments showed the formation of core–shell nanostructures with Bi2Fe4O9 as the core and a shell of BiFeO3 and Bi25FeO40 phases as deduced based on the analysis of transmission electron microscopy results.

Modeling Congenital Dyserythropoietic Anemia Type I Through Patient-Derived Induced Pluripotent Stem Cells

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3196-3196
Author(s):  
Orna Steinberg Shemer ◽  
Yu Yao ◽  
Gary M. Kupfer ◽  
Hannah Tamary ◽  
Mitchell J. Weiss
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Light Microscopy ◽  
Chromatin Structure ◽  
Pluripotent Stem Cells ◽  
Type I ◽  
Transmission Electron ◽  
Erythroid Precursors ◽  
Induced Pluripotent ◽  
I Cells

Abstract Abstract 3196 Congenital dyserythropoietic anemias (CDAs) are rare inherited disorders characterized by impaired red blood cell formation (dyserythropoiesis) and signature cytopathologies. CDA type I is an autosomal recessive disease with macrocytic anemia and occasional bone abnormalities. Erythroid precursors exhibit pathognomonic abnormalities including internuclear chromatin bridges and spongy (“Swiss cheese”) heterochromatin. The disease is caused by biallelic mutations in the gene CDANI (Dgany et al., 2002), which encodes codanin-1, a ubiquitously expressed protein that is believed to have fundamental roles in cell cycle control and chromatin structure (Noy-Lotan et. al, 2009). Animal models for the study of CDA I are suboptimal and clinical samples are scarce. Thus, we have developed an experimental model for the study of CDA I by generating induced pluripotent stem cells (iPSCs) from affected patients. We reprogrammed fibroblasts from CDA I patients and normal subjects using a single lentiviral vector encoding OCT4, KLF4, SOX2, and MYC. The resultant iPSCs exhibited standard criteria for pluripotency and the integrated reprogramming vector was excised using Cre-lox technology. We differentiated CDA I and control iPSCs into erythroid progenitors by inducing the formation of embryoid bodies (EBs) with stepwise additions of supportive cytokines. Beginning at about day 8, hematopoietic progenitors with erythroid potential were detected within EBs and as free-floating cells in the medium. Our differentiation protocol showed two waves of erythroid precursor production. Early EBs (days 12 to 23) produced erythroid cells that expressed mainly epsilon globin, resembling early yolk sac type “primitive” erythropoiesis. In contrast, erythroblasts produced from later EBs (days 27 to 50) expressed mainly gamma globins, resembling “definitive” erythroid cells produced by late stage yolk sac and fetal liver. Our preliminary studies, indicate that CDA I iPSCs produce normal numbers of primitive and definitive erythrocytes. No defects in survival or maturation were detected by flow cytometry assessing the expression of annexin V and the developmental stage markers CD235/CD71/forward scatter. However, definitive type (but not primitive) erythroblasts derived from CDA I iPSCs exhibit some characteristic pathological features including occasional internuclear chromatin bridging visible by light microscopy and spongy “Swiss cheese” heterochromatin revealed by transmission electron microscopy. Thus, patient-derived iPSCs can model at least some aspects of CDA I and provide the basis for future studies to define the actions of codanin-1 and the pathophysiology of this disorder. Figure: Patient iPSC-derived erythroblasts recapitulate CDA I pathology. Light microscopy and transmission electron microscopy (TEM) of normal and CDA I iPSC-derived erythroblasts generated in ∼30 day differentiation cultures. Inserts show higher magnification of the marked areas. CDA I cells exhibit occasional internuclear bridges on light microscopy (third panel). TEM showed abnormal spongy chromatin structure in most CDA I erythroid precursors (fourth panel). Figure:. Patient iPSC-derived erythroblasts recapitulate CDA I pathology. Light microscopy and transmission electron microscopy (TEM) of normal and CDA I iPSC-derived erythroblasts generated in ∼30 day differentiation cultures. Inserts show higher magnification of the marked areas. CDA I cells exhibit occasional internuclear bridges on light microscopy (third panel). TEM showed abnormal spongy chromatin structure in most CDA I erythroid precursors (fourth panel). Disclosures: No relevant conflicts of interest to declare.

Preparation of Carbon-Encapsulated Fe Core-Shell Nanostructures by Confined Arc Plasma

2011 ◽  
Vol 688 ◽  
pp. 245-249 ◽  
Author(s):  
Zhi Qiang Wei ◽  
Xiao Yun Wang ◽  
Hua Yang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Particle Size ◽  
Specific Surface ◽  
Surface Area ◽  
Core Shell ◽  
Arc Plasma ◽  
X Ray ◽  
The Core ◽  
Transmission Electron

Special carbon encapsulated Fe core-shell nanoparticles with a size range of 15–40 nm were successfully prepared via confined arc plasma method. The composition, morphology, microstructure, specific surface area, particle size of the product by this process were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray energy dispersive spectrometry (XEDS) and BET N2adsorption. The experiment results shown that the carbon encapsulated Fe nanoparticles with clear core-shell structure, the core of the particles is body centered cubic (BCC) structure Fe, and the shell of the particles is disorder carbons. The particle size of the nanocapsules ranges from 15 to 40nm，with an averaged value about 30nm, the particles diameter of the core is about 16nm and the thickness of the shells is about 6-8 nm, and the specific surface area is 24 m2/g.

Point Defect Detector Studies of Ge+ Implanted Silicon upon Oxidation

1992 ◽  
Vol 262 ◽  
Author(s):  
H. L. Meng ◽  
S. Prusstn ◽  
K. S. Jones
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Point Defect ◽  
Point Defects ◽  
Type Ii ◽  
Dislocation Loops ◽  
Furnace Annealing ◽  
Plan View ◽  
Atom Concentration ◽  
Transmission Electron

ABSTRACTPrevious results [1] have shown that type II (end-of-range) dislocation loops can be used as point defect detectors and are efficient in measuring oxidation induced point defects. This study investigates the interaction between oxidation-induced point defects and dislocation loops when Ge+ implantation was used to form the type II dislocation loops. The type II dislocation loops were introduced via Ge+ implants into <100> Si wafers at 100 keV to at doses ranging from 2×1015 to l×1016/cm2. The subsequent furnace annealing at 900 °C was done for times between 30 min and 4 hr in either a dry oxygen or nitrogen ambient. The change in atom concentration bound by dislocation loops as a result of oxidation was measured by plan-view transmission electron microscopy (PTEM). The results show that the oxidation rate for Ge implanted Si is similar to Si+ implanted Si. Upon oxidation a decrease in the interstitial injection was observed for the Ge implanted samples relative to the Si implanted samples. With increasing Ge+ dose the trapped atom concentration bound by the loops actually decreases upon oxidation relative to the inert ambient implying oxidation of Ge+ implanted silicon can result in either vacancy injection or the formation of an interstitial sink.

Investigation on Ti-Deoxidized Products Inducing Formation of Intragranular Ferrite

2011 ◽  
Vol 266 ◽  
pp. 229-232
Author(s):  
Jiang Hua Qi ◽  
Jie Wu ◽  
Jin Ping Suo ◽  
Zheng Liang Xue
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Outer Layer ◽  
Precipitation Amount ◽  
The Core ◽  
Intragranular Ferrite ◽  
Transmission Electron ◽  
Deoxidation Process ◽  
Scanning Electron

Steel samples were prepared using a vacuum carbon deoxidization process combined with a final Ti-deoxidation process. Ti-deoxidized products inducing formation of intragranular ferrite (IGF) was investigated by using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) through various specimens by different methods, as follows: metallographic specimens, electrolyzation, ion thinning technology, RTO method and so on. Mn is found to be more extensively distributed than S in the core of inclusion, which shows that Ti2O3 has character of absorbing Mn. The Mn-depleted zone (MDZ) exists in the peripheral steel of inclusion, the more near the inclusion, the more obvious depletion of Mn. It is also found that outer layer of inclusion exists S-rich and Mn depletion area in specimens prepared using RTO method under TEM. Mn- depleted zone in steel and Mn-depleted but S-rich layer in the periphery of the inclusion indicate that Mn diffuses and diverts is step by step in steel and inclusion, and the extent of S-rich and Mn depletion area should be related with degree of Mn absorbed by Ti2O3 and original precipitation amount of MnS.

Characterization of Cyanobacterial Picoplankton in Lake Ontario by Transmission Electron Microscopy

1987 ◽  
Vol 44 (12) ◽  
pp. 2173-2177 ◽  
Author(s):  
Gary G. Leppard ◽  
Dina Urciuoli ◽  
F. R. Pick
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cell Envelope ◽  
Lake Ontario ◽  
Nuclear Material ◽  
Major Type ◽  
Type I ◽  
Transmission Electron ◽  
Numerous Cell ◽  
Chroococcoid Cyanobacteria

Many chroococcoid cyanobacteria from Lake Ontario, characterized by epifluorescence in concert with transmission electron microscopy, had a Type I ultrastructure, the major type in oceanic waters. Such cells had a multilayered cell envelope and their polyhedral bodies were interspersed with the central nuclear material. All thylakoids were peripheral and were arranged concentrically, with no intrusion into the nuclear region. Related chroococcoid types were also seen but these were much less abundant. The most numerous cell type in all water samples was a small, Gram-negative, rodlike bacterium. Many of these rods were sufficiently small to pass a filter of 0.45-μm pore size but none had a diameter less than 0.2 μm. Attempts to isolate and describe the cyanobacterial picoplankton presented some unusual difficulties having a potential to mislead limnological analyses. These are described and, to some extent, they are resolved here.

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