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.

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

F1000Research ◽  
2014 ◽  
Vol 3 ◽  
pp. 93 ◽  
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 ◽  
Junctional Coupling ◽  
Health And Disease ◽  
Pulmonary Artery Smooth Muscle

Herein we demonstrate how nanojunctions between lysosomes and sarcoplasmic reticulum (L-SR junctions) serve to couple lysosomal activation to regenerative, ryanodine receptor-mediated cellular Ca2+ waves. In pulmonary artery smooth muscle cells (PASMCs) it has been proposed that nicotinic acid adenine dinucleotide phosphate (NAADP) triggers 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, which has restricted detailed investigations of the junctional coupling process. The present study utilizes standard and tomographic transmission electron microscopy to provide a thorough ultrastructural characterization of the L-SR junctions in PASMCs. We show that L-SR nanojunctions are prominent features within these cells and estimate that the junctional membrane separation and extension are about 15 nm and 300 nm, respectively. Furthermore, we 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 demonstrate that the magnitude of these signals can breach the threshold for CICR via RyR3. By correlation analysis of live cell Ca2+ signals and simulated Ca2+ transients within L-SR junctions, we estimate that “trigger zones” comprising 60–100 junctions are required to confer a signal of similar magnitude. This is compatible with the 110 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.

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 Alignment of sarcoplasmic reticulum-mitochondrial junctions with mitochondrial contact points

2011 ◽  
Vol 301 (5) ◽  
pp. H1907-H1915 ◽  
Author(s):  
Cecília García-Pérez ◽  
Timothy G. Schneider ◽  
György Hajnóczky ◽  
György Csordás
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Sarcoplasmic Reticulum ◽  
Ryanodine Receptor ◽  
Mitochondrial Membrane ◽  
Inner Mitochondrial Membrane ◽  
Mitofusin 2 ◽  
Atp Production ◽  
Contact Points ◽  
Transmission Electron

Propagation of ryanodine receptor (RyR2)-derived Ca2+ signals to the mitochondrial matrix supports oxidative ATP production or facilitates mitochondrial apoptosis in cardiac muscle. Ca2+ transfer likely occurs locally at focal associations of the sarcoplasmic reticulum (SR) and mitochondria, which are secured by tethers. The outer mitochondrial membrane and inner mitochondrial membrane (OMM and IMM, respectively) also form tight focal contacts (contact points) that are enriched in voltage-dependent anion channels, the gates of OMM for Ca2+. Contact points could offer the shortest Ca2+ transfer route to the matrix; however, their alignment with the SR-OMM associations remains unclear. Here, in rat heart we have studied the distribution of mitochondria-associated SR in submitochondrial membrane fractions and evaluated the colocalization of SR-OMM associations with contact points using transmission electron microscopy. In a sucrose gradient designed for OMM purification, biochemical assays revealed lighter fractions enriched in OMM only and heavier fractions containing OMM, IMM, and SR markers. Pure OMM fractions were enriched in mitofusin 2, an ∼80 kDa mitochondrial fusion protein and SR-mitochondrial tether candidate, whereas in fractions of OMM + IMM + SR, a lighter (∼50 kDa) band detected by antibodies raised against the NH2 terminus of mitofusin 2 was dominating. Transmission electron microscopy revealed mandatory presence of contact points at the junctional SR-mitochondrial interface versus a random presence along matching SR-free OMM segments. For each SR-mitochondrial junction at least one tether was attached to contact points. These data establish the contact points as anchorage sites for the SR-mitochondrial physical coupling. Close coupling of the SR, OMM, and IMM is likely to provide a favorable spatial arrangement for local ryanodine receptor-mitochondrial Ca2+ signaling.

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.

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.

Sign in / Sign up

Export Citation Format

Share Document