Structural and ultrastructural characterization of maize coenocyte and endosperm cellularization

2007 ◽  
Vol 85 (2) ◽  
pp. 216-223 ◽  
Author(s):  
Paulo Monjardino ◽  
Jorge Machado ◽  
Fabíola S. Gil ◽  
Rui Fernandes ◽  
Roberto Salema
Keyword(s):  
Developmental Stages ◽  
Endosperm Development ◽  
Central Vacuole ◽  
Primary Endosperm Nucleus ◽  
Temperature Regimes ◽  
Transmission Electron ◽  
Ultrastructural Characterization ◽  
Poaceae Family ◽  
Periclinal Walls

Maize coenocytic and cellularizing endosperm development were characterized at optical and transmission electron microscopy levels. Samples were collected daily in 3 consecutive years under different temperature regimes; therefore, the developmental stages were expressed on a growing degree basis. Soon after the primary endosperm nucleus is formed, it starts dividing without cytokinesis, leading to the formation of the coenocyte. The nuclei divide freely on the periphery of the coenocyte and spread from the micropylar region toward the chalazal region. The first anticlinal walls are formed as the nuclei come closer to each other, followed by periclinal wall formation also starting in the micropylar region. As cellularization proceeds, new anticlinal and periclinal walls assume a less organized pattern until the central vacuole is fully occupied by newly formed cells. Overall, our findings suggest that the developmental pattern of maize coenocytic and cellularizing endosperm has many similarities to other species of the Poaceae family.

scholarly journals Morphological and Ultrastructural Characterization of Hemocytes in an Insect Model, the Hematophagous Dipetalogaster maxima (Hemiptera: Reduviidae)

Insects ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 640
Author(s):  
Natalia R. Moyetta ◽  
Fabián O. Ramos ◽  
Jimena Leyria ◽  
Lilián E. Canavoso ◽  
Leonardo L. Fruttero
Keyword(s):  
Cell Biology ◽  
Cell Types ◽  
Transmission Electron ◽  
Ultrastructural Characterization ◽  
Current Classification ◽  
Contrast Microscopy ◽  
First Time ◽  
Controversial Aspect

Hemocytes, the cells present in the hemolymph of insects and other invertebrates, perform several physiological functions, including innate immunity. The current classification of hemocyte types is based mostly on morphological features; however, divergences have emerged among specialists in triatomines, the insect vectors of Chagas’ disease (Hemiptera: Reduviidae). Here, we have combined technical approaches in order to characterize the hemocytes from fifth instar nymphs of the triatomine Dipetalogaster maxima. Moreover, in this work we describe, for the first time, the ultrastructural features of D. maxima hemocytes. Using phase contrast microscopy of fresh preparations, five hemocyte populations were identified and further characterized by immunofluorescence, flow cytometry and transmission electron microscopy. The plasmatocytes and the granulocytes were the most abundant cell types, although prohemocytes, adipohemocytes and oenocytes were also found. This work sheds light on a controversial aspect of triatomine cell biology and physiology setting the basis for future in-depth studies directed to address hemocyte classification using non-microscopy-based markers.

scholarly journals Cytoplasmic nanojunctions between lysosomes and sarcoplasmic reticulum are required for specific calcium signaling

2014 ◽  
Author(s):  
Nicola Fameli ◽  
Oluseye A. Ogunbayo ◽  
Cornelis van Breemen ◽  
A. Mark Evans
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Ryanodine Receptor ◽  
Membrane Separation ◽  
Quantitative Model ◽  
Transmission Electron ◽  
Ultrastructural Characterization ◽  
Health And Disease ◽  
Pulmonary Artery Smooth Muscle ◽  
Subtype 3

We demonstrate how nanojunctions between lysosomes and sarcoplasmic reticulum (L-SR junctions) serve to couple lysosomal activation to regenerative, ryanodine receptor-mediated cellular calcium (Ca2+) waves. In pulmonary artery smooth muscle cells (PASMCs) nicotinic acid adenine dinucleotide phosphate (NAADP) may trigger increases in cytoplasmic Ca2+ via L-SR junctions, in a manner that requires initial Ca2+ release from lysosomes and subsequent Ca2+-induced Ca2+ release (CICR) via ryanodine receptor (RyR) subtype 3 on the SR membrane proximal to lysosomes. L-SR junction membrane separation has been estimated to be <400 nm and thus beyond the resolution of light microscopy. This study utilizes transmission electron microscopy to provide a thorough ultrastructural characterization of the L-SR junctions in PASMCs. These junctions are prominent features in these cells and we estimate that the membrane separation and extension are about 15 nm and 300 nm, respectively. We also develop a quantitative model of the L-SR junction using these measurements, prior kinetic and specific Ca2+ signal information as input data. Simulations of NAADP-dependent junctional Ca2+ transients show that the magnitude of these signals can breach the threshold for CICR via RyR3. By correlation analysis of live cell Ca2+ signals and simulated L-SR junctional Ca2+ transients, we estimate that "trigger zones" with a 60-100 junctions are required to confer a signal of similar magnitude. This is compatible with the 130 lysosomes/cell estimated from our ultrastructural observations. Most importantly, our model shows that increasing the L-SR junctional width above 50 nm lowers the magnitude of junctional [Ca2+] such that there is a failure to breach the threshold for CICR via RyR3. L-SR junctions are therefore a pre-requisite for efficient Ca2+ signal coupling and may contribute to cellular function in health and disease.

Electron Microscopy Findings inN-Methyl-N-Nitrosourea-Induced Mammary Tumors

2016 ◽  
Vol 22 (5) ◽  
pp. 1056-1061
Author(s):  
Ana I. Faustino-Rocha ◽  
Ana M. Calado ◽  
Adelina Gama ◽  
Rita Ferreira ◽  
Mário Ginja ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Rat Model ◽  
Mammary Tumors ◽  
Female Rats ◽  
Ultrastructural Studies ◽  
Transmission Electron ◽  
Chemically Induced ◽  
Ultrastructural Characterization ◽  
Human Mammary Tumors

AbstractAlthough the rat model of mammary tumors chemically induced byN-methyl-N-nitrosourea (MNU) has been frequently used by several research teams, there is a lack of ultrastructural studies in this field. The main aim of this work was to perform an ultrastructural characterization of MNU-induced mammary tumors in female rats. Some alterations previously reported in human mammary tumors, such as nucleus size and shape, accumulation of heterochromatin in the perinuclear region, and interdigitating cytoplasmic processes between cancer cells were also observed in MNU-induced mammary tumors. Although a low number of samples were analyzed by transmission electron microscopy in the present study, we consider that it may contribute to a better understanding of MNU-induced mammary carcinogenesis in a rat model. The ultrastructural characteristics of the two most frequently diagnosed mammary carcinomas described in the present work can be useful to differentiate them from other histological patterns. In addition, the loss of cytoplasm in neoplastic cells and formation of vacuoles were described.

Ultrastructural Characterization of Liposomes Using Transmission Electron Microscope

2008 ◽  
Vol 55-57 ◽  
pp. 709-711 ◽  
Author(s):  
Prukswan Chetanachan ◽  
P. Akarachalanon ◽  
D. Worawirunwong ◽  
Pisutti Dararutana ◽  
A. Bangtrakulnonth ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Polymeric Nanoparticles ◽  
Staining Technique ◽  
Bilayer Membrane ◽  
Multilamellar Vesicles ◽  
Transmission Electron ◽  
Ultrastructural Characterization ◽  
Film Method

A liposome is a spherical vesicle composed of phospholipids and cholesterol bilayer membrane and contains a core of aqueous solution. Liposomes are polymeric nanoparticles used for drug delivery due to their unique properties. It can carry both hydrophobic and hydrophilic molecules. In this study, we showed the benefit of using transmission electron microscope (TEM) with negative staining technique to investigate the morphology of liposomes produced by thin film method. At the same magnification of micrograph results, we could see the multilamellar vesicles of liposomes in various figures and different sizes.

scholarly journals Identification and Characterization of the ATG8, a Marker of Eimeria tenella Autophagy

2021 ◽  
Vol 30 (1) ◽  
Author(s):  
Nanshan Qi ◽  
Shenquan Liao ◽  
Juan Li ◽  
Caiyan Wu ◽  
Minna Lv ◽  
...  
Keyword(s):  
Developmental Stages ◽  
Future Research ◽  
Biological Macromolecules ◽  
Structure And Properties ◽  
Related Gene ◽  
Quantitative Real Time Pcr ◽  
Apicomplexan Parasites ◽  
Transmission Electron ◽  
Identification And Characterization

Abstract Autophagy plays an important role in maintaining cell homeostasis through degradation of denatured proteins and other biological macromolecules. In recent years, many researchers focus on mechanism of autophagy in apicomplexan parasites, but little was known about this process in avian coccidia. In our present study. The cloning, sequencing and characterization of autophagy-related gene (Etatg8) were investigated by quantitative real-time PCR (RT-qPCR), western blotting (WB), indirect immunofluorescence assays (IFAs) and transmission electron microscopy (TEM), respectively. The results have shown 375-bp ORF of Etatg8, encoding a protein of 124 amino acids in E. tenella, the protein structure and properties are similar to other apicomplexan parasites. RT-qPCR revealed Etatg8 gene expression during four developmental stages in E. tenella, but their transcriptional levels were significantly higher at the unsporulated oocysts stage. WB and IFA showed that EtATG8 was lipidated to bind the autophagosome membrane under starvation or rapamycin conditions, and aggregated in the cytoplasm of sporozoites and merozoites, however, the process of autophagosome membrane production can be inhibited by 3-methyladenine. In conclusion, we found that E. tenella has a conserved autophagy mechanism like other apicomplexan parasites, and EtATG8 can be used as a marker for future research on autophagy targeting avian coccidia.

scholarly journals Endosperm development in Dyckia pseudococcinea (Pitcairnioideae - Bromeliaceae)

Rodriguésia ◽  
2021 ◽  
Vol 72 ◽  
Author(s):  
Simone Petrucci Mendes ◽  
Cecília Goncalves da Costa ◽  
Karen Lucia Gama De Toni
Keyword(s):  
In Vitro Culture ◽  
Atlantic Forest ◽  
Developmental Stages ◽  
Endosperm Development ◽  
Aleurone Layer ◽  
Endosperm Cell ◽  
Primary Endosperm Nucleus ◽  
Anatomical Analysis ◽  
Systematic Relationships

Abstract Dyckia pseudococcinea is a threatened species endemic to the restingas of the Atlantic Forest, an area under strong anthropic impact. From the perspective of conservation, plant embryology is interesting by the variety of approaches for in vitro culture of seedlings. With this in mind, the present study describes the endospermogenesis of D. pseudococcinea to provide data for conservation studies and indicate characters that may contribute to the systematics of Pitcairnioideae. Using anatomical analysis, samples of flowers and fruits at different developmental stages were analyzed. We observed the establishment of the primary endosperm nucleus and then the primary endosperm cell (PEC). Upon expansion of the central vacuole of PEC, nuclei migrate to the chalazal, peripheral, and micropylar domains. An early centripetal cellularization begins in the chalazal region, characterizing the endosperm as coenocytic/multicellular type. With cellularization, the endosperm enfolds the embryo. In addition, in the outermost layer of the endosperm, an aleurone layer is visible. These observations allowed some embryological characters to be identified, thus helping to clarify the systematic relationships of Pitcairnioideae and also the genus Dyckia, such as the presence of hypostasis, the persistence of the antipodals and synergids during the early stages of endospermogenesis and coenocytic/multicellular endospermogenesis. Having established the details of endospermogenesis, we then set forth guidelines for the development of in vitro culture protocols aimed at the conservation of D. pseudococcinea, an endangered Bromeliad species of the Atlantic Forest.

Ultrastructural characterization of an inner envelope that confines Azolla endosymbionts to the leaf cavity periphery

1989 ◽  
Vol 67 (9) ◽  
pp. 2711-2719 ◽  
Author(s):  
S. A. Nierzwicki-Bauer ◽  
H. Aulfinger ◽  
E. B. Braun-Howland
Keyword(s):  
Hair Cells ◽  
Peripheral Region ◽  
Central Cavity ◽  
Transmission Electron ◽  
Ultrastructural Characterization ◽  
Young Leaves ◽  
Ultrastructural Characteristics ◽  
Membrane Ultrastructure ◽  
Inner Envelope

Ultrastructural characteristics of Azolla leaf cavities were examined using transmission electron microscopy. An extracellular inner envelope, which forms a boundary between the central cavity region and the peripheral region containing cyanobacteria and (or) bacteria, was found in all closed leaf cavities of symbiotic and Anabaena-free Azolla species. In the youngest leaf, which is in the process of developing a cavity, a continuous inner envelope was never observed. However, in young leaves that contained closed cavities, and in older leaves, continuous inner envelopes were always observed. The inner envelope may serve to restrict the symbionts to the cavity periphery. The inner envelope was similar in appearance to the outer envelope, which encloses the symbionts and hair cells within leaf cavities. Examination of the inner envelope using three different fixation procedures revealed that it was most distinct in fronds fixed in potassium permanganate, suggesting that it is membranelike in structure. The envelope was occasionally seen folded back upon itself or curled, which is also characteristic of a membranelike structure. Nevertheless, the envelope did not exhibit typical tripartite membrane ultrastructure. The occurrence of the inner envelope in Anabaena-free Azolla indicates that this envelope is of eubacterial or plant origin.

Characterization of the Cell Surface of Perkinsus marinus, a Pathogen of the Eastern Oyster, Crassostrea virginica Utilizing Electron Microscopy, Light Microscopy and Epifluorescent Microscopy.

1998 ◽  
Vol 4 (S2) ◽  
pp. 1146-1147
Author(s):  
Julie Neimark
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Crassostrea Virginica ◽  
Developmental Stages ◽  
Eastern Oyster ◽  
Wide Distribution ◽  
Perkinsus Marinus ◽  
Transmission Electron ◽  
A Cell

Perkinsus marinus is a protistan parasite that infects the Eastern Oyster, Crassostrea virginica, and is one factor responsible for the reduced productivity of oyster fisheries. This parasite (or related species) has a wide distribution and has also been found to infect the oysters in the Tampa Bay region. A significant aspect of this organism has been its enigmatic taxonomic position. Originally classified in two separate fungal genera, it currently is considered an Apicomplexan (Kingdom Protista) based on transmission electron microscopy studies of the zoospore revealing an apical complex. However, rRNA studies have shown that P. marinus may be more closely related to the dinoflagellates. The focus of my study has been on surface features of certain developmental stages that may aid in a definitive taxonomic placement of this organism.Transmission electron microscopy observations of the trophozoite and hypnospore stages show variation in both the size of the organism and the presence of a cell wall.

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