scholarly journals Glycogen Phosphorylase in Acanthamoeba spp.: Determining the Role of the Enzyme during the Encystment Process Using RNA Interference

2008 ◽  
Vol 7 (3) ◽  
pp. 509-517 ◽  
Author(s):  
Jacob Lorenzo-Morales ◽  
Jarmila Kliescikova ◽  
Enrique Martinez-Carretero ◽  
Luis Miguel De Pablos ◽  
Bronislava Profotova ◽  
...  
Keyword(s):  
Rna Interference ◽  
Cyst Wall ◽  
Glycogen Phosphorylase ◽  
Catalytic Domain ◽  
Present Report ◽  
Light And Electron Microscopy ◽  
Main Tool ◽  
Lower Eukaryotes ◽  
Free Glucose

ABSTRACT Acanthamoeba infections are difficult to treat due to often late diagnosis and the lack of effective and specific therapeutic agents. The most important reason for unsuccessful therapy seems to be the existence of a double-wall cyst stage that is highly resistant to the available treatments, causing reinfections. The major components of the Acanthamoeba cyst wall are acid-resistant proteins and cellulose. The latter has been reported to be the major component of the inner cyst wall. It has been demonstrated previously that glycogen is the main source of free glucose for the synthesis of cellulose in Acanthamoeba, partly as glycogen levels fall during the encystment process. In other lower eukaryotes (e.g., Dictyostelium discoideum), glycogen phosphorylase has been reported to be the main tool used for glycogen breakdown in order to maintain the free glucose levels during the encystment process. Therefore, it was hypothesized that the regulation of the key processes involved in the Acanthamoeba encystment may be similar to the previously reported regulation mechanisms in other lower eukaryotes. The catalytic domain of the glycogen phosphorylase was silenced using RNA interference methods, and the effect of this phenomenon was assessed by light and electron microscopy analyses, calcofluor staining, expression zymogram assays, and Northern and Western blot analyses of both small interfering RNA-treated and control cells. The present report establishes the role of glycogen phosphorylase during the encystment process of Acanthamoeba. Moreover, the obtained results demonstrate that the enzyme is required for cyst wall assembly, mainly for the formation of the cell wall inner layer.

The Role of Mitochondria in the Genesis of Neuroaxonal Dystrophy in the Brains of Aging Mice

1975 ◽  
Vol 33 ◽  
pp. 372-373
Author(s):  
J.E. Johnson
Keyword(s):  
Electron Microscopy ◽  
Present Report ◽  
Light And Electron Microscopy ◽  
Dorsal Column ◽  
Neuroaxonal Dystrophy ◽  
Nucleus Gracilis ◽  
Dystrophic Axons ◽  
The Brain ◽  
Nucleus Cuneatus

Although neuroaxonal dystrophy (NAD) has been examined by light and electron microscopy for years, the nature of the components in the dystrophic axons is not well understood. The present report examines nucleus gracilis and cuneatus (the dorsal column nuclei) in the brain stem of aging mice.Mice (C57BL/6J) were sacrificed by aldehyde perfusion at ages ranging from 3 months to 23 months. Several brain areas and parts of other organs were processed for electron microscopy.At 3 months of age, very little evidence of NAD can be discerned by light microscopy. At the EM level, a few axons are found to contain dystrophic material. By 23 months of age, the entire nucleus gracilis is filled with dystrophic axons. Much less NAD is seen in nucleus cuneatus by comparison. The most recurrent pattern of NAD is an enlarged profile, in the center of which is a mass of reticulated material (reticulated portion; or RP).

scholarly journals Viroids as a Tool to Study RNA-Directed DNA Methylation in Plants

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1187
Author(s):  
Michael Wassenegger ◽  
Athanasios Dalakouras
Keyword(s):  
Dna Methylation ◽  
Rna Interference ◽  
Gene Silencing ◽  
Plant Cells ◽  
Transcriptional Gene Silencing ◽  
Rnai Machinery ◽  
Double Stranded Rna ◽  
Post Transcriptional Gene Silencing ◽  
Cumulative Amount

Viroids are plant pathogenic, circular, non-coding, single-stranded RNAs (ssRNAs). Members of the Pospiviroidae family replicate in the nucleus of plant cells through double-stranded RNA (dsRNA) intermediates, thus triggering the host’s RNA interference (RNAi) machinery. In plants, the two RNAi pillars are Post-Transcriptional Gene Silencing (PTGS) and RNA-directed DNA Methylation (RdDM), and the latter has the potential to trigger Transcriptional Gene Silencing (TGS). Over the last three decades, the employment of viroid-based systems has immensely contributed to our understanding of both of these RNAi facets. In this review, we highlight the role of Pospiviroidae in the discovery of RdDM, expound the gradual elucidation through the years of the diverse array of RdDM’s mechanistic details and propose a revised RdDM model based on the cumulative amount of evidence from viroid and non-viroid systems.

scholarly journals Morphological Alterations and Increased S100B Expression in Epidermal Langerhans Cells Detected in Skin from Patients with Progressive Vitiligo

Life ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 579
Author(s):  
Fei Yang ◽  
Lingli Yang ◽  
Lanting Teng ◽  
Huimin Zhang ◽  
Ichiro Katayama
Keyword(s):  
Electron Microscopy ◽  
Langerhans Cells ◽  
Critical Role ◽  
Light And Electron Microscopy ◽  
Morphological Alterations ◽  
Birbeck Granules ◽  
Immuno Electron Microscopy ◽  
Skin Biopsies ◽  
Epidermal Langerhans Cells

The role of Langerhans cells (LCs) in vitiligo pathogenesis remains unclear, with published studies reporting contradictory results regarding the quantity of LCs and no data on the features of LCs in vitiligo. Here, we aimed to analyze the presence, density, and morphological features of LCs in the epidermis of patients with vitiligo. Skin biopsies were stained for LCs using anti-CD1a/anti-langerin antibodies and analyzed by immunocytochemistry with light and electron microscopy. Compared with healthy controls, we detected significantly increased numbers of epidermal LCs in lesional skin from vitiligo in the progressive state. These LCs exhibited striking morphological alterations, including an elevated number of dendrites, with increased length and more branches than dendrites from controls. Ultrastructure examination via immuno-electron microscopy revealed markedly reduced Birbeck granules (BGs) and shorter BG rods in LCs from progressive vitiligo, with higher expression of langerin. Additionally, expression of S100B, the activity biomarker of vitiligo, was increased in these LCs. This work provides new insight on the cellular composition of LCs in vitiliginous skin, revealing altered morphology and increased LC numbers, with elevated S100B expression. Our data suggest LCs might play a critical role in vitiligo pathogenesis and thus may represent a novel therapeutic target for this disease.

scholarly journals Innovative Work Behavior—A Key Factor in Business Performance? The Role of Team Cognitive Diversity and Teamwork Climate in This Relationship

2021 ◽  
Vol 14 (4) ◽  
pp. 185
Author(s):  
Nadežda Jankelová ◽  
Zuzana Joniaková ◽  
Juraj Mišún
Keyword(s):  
Business Performance ◽  
Main Tool ◽  
Work Behavior ◽  
Cognitive Diversity ◽  
Staff Perceptions ◽  
Innovative Work Behavior ◽  
Positive Effects ◽  
Key Factor ◽  
Innovative Work

The aim of our paper is to examine whether the support of innovative work behavior by management is positively related to business performance and at the same time, whether this relationship is mediated by the teamwork climate and cognitive diversity of teams. Cognitive diversity is defined as differences in knowledge and perspective, which arise from professional diversity and account for its positive effects. A teamwork climate represents staff perceptions of collaboration between personnel. Business performance is defined by the level of sales. Our sample consisted of 211 managers of companies operating in Slovakia, and data collection took place in the form of a questionnaire. The main tool for examining the mechanism of operation of the investigated relationships is mediation using regression analysis and the Sobel test to determine the significance of the indirect effect of mediation variables. The findings point to a significant direct relationship between the innovative work behavior of company employees and business performance. The intensity of this relationship can be partly influenced by promoting cognitive diversity, especially in the area of knowledge and ways of thinking. The significant role of a teamwork climate was not demonstrated in the examined model.

Encystment and germination of the parasitic chytrid Rozella allomycis on host hyphae

1973 ◽  
Vol 51 (10) ◽  
pp. 1825-1835 ◽  
Author(s):  
Abraham A. Held
Keyword(s):  
Cyst Wall ◽  
Germ Tube ◽  
Light And Electron Microscopy ◽  
Multivesicular Bodies ◽  
Cell Periphery ◽  
General Sequence ◽  
Obligate Intracellular ◽  
Host Cytoplasm ◽  
Intracellular Parasites ◽  
Three Stages

Zoospores of the obligately parasitic chytrid Rozella allomycis which settle upon hyphae of the water mold host, Allomyces arbuscula, encyst and germinate before their protoplasts penetrate into the host cytoplasm. This process has been examined by light and electron microscopy. Three stages which follow the attachment to the host and the retraction of the zoospore's flagellum are described: (1) the early cyst lacks a wall; it is discoid, and its shape is maintained by the coil of the retracted axoneme which forms its rim; (2) a cyst wall is formed while multivesicular bodies occur at the cell periphery and eventually disappear; a germ tube starts to grow at the point of attachment; and (3) the firm-walled cyst is spheroidal; it has a fully developed germ tube with a specialized class of vesicles; it also forms a distal, flattened vacuole whose swelling eventually injects the Rozella protoplast into the host; at this stage the retracted axoneme has disappeared and the cell's organelles have undergone extensive changes. Electron-dense, "gamma-like" granules enclosed in vacuoles may play a major role in the formation of both the cyst wall and the distal vacuole. These granules appear to give rise to small vesicles, and thus to multivesicular bodies; the distal vacuole appears to form by coalescense of gamma-like vacuoles.The general sequence of encystment and germination resembles that found in other Chytridiomycetes, both saprophytic and parasitic. However, the distal vacuole and the vesicles in the germ tube appear to be parasitic adaptations and are shared by obligate intracellular parasites from several unrelated groups of zoosporic fungi.

scholarly journals The kinase activity of human Rio1 is required for final steps of cytoplasmic maturation of 40S subunits

2012 ◽  
Vol 23 (1) ◽  
pp. 22-35 ◽  
Author(s):  
Barbara Widmann ◽  
Franziska Wandrey ◽  
Lukas Badertscher ◽  
Emanuel Wyler ◽  
Jens Pfannstiel ◽  
...  
Keyword(s):  
Rna Interference ◽  
Protein Kinases ◽  
18S Rrna ◽  
Kinase Activity ◽  
Ribosomal Biogenesis ◽  
Ribosomal Subunits ◽  
Binding Partner ◽  
Rrna Maturation ◽  
Cytoplasmic Maturation

RIO proteins form a conserved family of atypical protein kinases. Humans possess three distinct RIO kinases—hRio1, hRio2, and hRio3, of which only hRio2 has been characterized with respect to its role in ribosomal biogenesis. Here we show that both hRio1 and hRio3, like hRio2, are associated with precursors of 40S ribosomal subunits in human cells. Furthermore, we demonstrate that depletion of hRio1 by RNA interference affects the last step of 18S rRNA maturation and causes defects in the recycling of several trans-acting factors (hEnp1, hRio2, hLtv1, hDim2/PNO1, and hNob1) from pre-40S subunits in the cytoplasm. Although the effects of hRio1 and hRio2 depletion are similar, we show that the two kinases are not fully interchangeable. Moreover, rescue experiments with a kinase-dead mutant of hRio1 revealed that the kinase activity of hRio1 is essential for the recycling of the endonuclease hNob1 and its binding partner hDim2 from cytoplasmic pre-40S. Kinase-dead hRio1 is trapped on pre-40S particles containing hDim2 and hNob1 but devoid of hEnp1, hLtv1, and hRio2. These data reveal a role of hRio1 in the final stages of cytoplasmic pre-40S maturation.

scholarly journals Heterologous desensitization of the cyclic AMP-independent glycogenolytic response in rat liver cells

1981 ◽  
Vol 200 (3) ◽  
pp. 509-514 ◽  
Author(s):  
B Bréant ◽  
S Keppens ◽  
H De Wulf
Keyword(s):  
Cyclic Amp ◽  
Glycogen Phosphorylase ◽  
Liver Glycogen ◽  
Receptor Interaction ◽  
Alpha Adrenergic Receptors ◽  
Rat Liver Cells ◽  
Heterologous Desensitization ◽  
Highly Correlated ◽  
Alpha Agonist

Vasopressin and alpha-adrenergic agonists are known to be potent cyclic AMP-independent Ca2+-dependent activators of liver glycogen phosphorylase. When hepatocytes are pre-incubated with increasing concentrations of vasopressin or of the alpha-agonist phenylephrine, they become progressively unresponsive to a second addition of the respective agonist. The relative abilities of six vasopressin analogues and of five alpha-agonists to activate glycogen phosphorylase and to cause subsequent desensitization are highly correlated, indicating that the same vasopressin and alpha-adrenergic receptors are involved in both responses. About 5-times-higher peptide concentrations are needed to desensitize the cells than to activate their glycogen phosphorylase, whereas the concentrations of alpha-agonists required for the desensitization are only twice those needed for the activation of phosphorylase. The desensitization is not mediated by a perturbation in the agonist-receptor interaction. It is clearly heterologous, i.e. it is not agonist-specific, and must therefore involve a mechanism common to both series of agonists. The evidence for a role of Ca2+ movements or phosphatidylinositol turnover is briefly discussed.

scholarly journals Purinergic Modulation of Interleukin-1β Release from Microglial Cells Stimulated with Bacterial Endotoxin

1997 ◽  
Vol 185 (3) ◽  
pp. 579-582 ◽  
Author(s):  
Davide Ferrari ◽  
Paola Chiozzi ◽  
Simonetta Falzoni ◽  
Stefania Hanau ◽  
Francesco Di  Virgilio
Keyword(s):  
Plasma Membrane ◽  
P2x7 Receptor ◽  
Purinergic Receptor ◽  
Present Report ◽  
Physiological Role ◽  
Bacterial Endotoxin ◽  
Microglial Cells

Microglial cells express a peculiar plasma membrane receptor for extracellular ATP, named P2Z/P2X7 purinergic receptor, that triggers massive transmembrane ion fluxes and a reversible permeabilization of the plasma membrane to hydrophylic molecules of up to 900 dalton molecule weight and eventual cell death (Di Virgilio, F. 1995. Immunol. Today. 16:524–528). The physiological role of this newly cloned (Surprenant, A., F. Rassendren, E. Kawashima, R.A. North and G. Buell. 1996. Science (Wash. DC). 272:735–737) cytolytic receptor is unknown. In vitro and in vivo activation of the macrophage and microglial cell P2Z/P2X7 receptor by exogenous ATP causes a large and rapid release of mature IL-1β. In the present report we investigated the role of microglial P2Z/P2X7 receptor in IL-1β release triggered by LPS. Our data suggest that LPS-dependent IL-1β release involves activation of this purinergic receptor as it is inhibited by the selective P2Z/P2X7 blocker oxidized ATP and modulated by ATP-hydrolyzing enzymes such as apyrase or hexokinase. Furthermore, microglial cells release ATP when stimulated with LPS. LPS-dependent release of ATP is also observed in monocyte-derived human macrophages. It is suggested that bacterial endotoxin activates an autocrine/paracrine loop that drives ATP-dependent IL-1β secretion.

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