scholarly journals THE INTERACTION BETWEEN TOXOPLASMA GONDII AND MAMMALIAN CELLS

1972 ◽  
Vol 136 (5) ◽  
pp. 1173-1194 ◽  
Author(s):  
Thomas C. Jones ◽  
James G. Hirsch
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Acid Phosphatase ◽  
Toxoplasma Gondii ◽  
Mammalian Cells ◽  
Cell Function ◽  
Vacuolar Membrane ◽  
Thorium Dioxide ◽  
Phosphatase Cytochemistry ◽  
Secondary Lysosomes

Electron microscope methods have been used to study delivery of macrophage primary or secondary lysosomal contents to phagocytic vacuoles containing living or dead toxoplasmas. Secondary lysosomes were labeled by culturing the cells in colloidal thorium dioxide (thorotrast) or in ferritin. Acid phosphatase cytochemistry was employed for detection of primary as well as secondary lysosomal constituents. These various lysosomal labels were present in nearly all vacuoles containing toxoplasmas killed with glutaraldehyde, or in vacuoles containing those parasites undergoing degeneration 1 hr after the uptake of living toxoplasmas. In contrast, at times ranging from 1 to 20 hr after infection, no vacuoles containing morphologically normal, apparently viable toxoplasmas were thorotrast or ferritin positive, and only rarely did these vacuoles react for acid phosphatase. In many instances vacuoles containing viable toxoplasmas and no lysosomal markers were situated in the same cell nearby to vacuoles containing degenerating toxoplasmas and lysosomal constituents, thus indicating that the determinants of lysosomal fusion were operating locally in the immediate vicinity of the phagocytic vacuole, and not operating to influence general cell function. Thus, some toxoplasmas are able to prevent the delivery of lysosomal contents, and apparently the phagocytic vacuole provides for these parasites a sheltered microenvironment ideal for their growth. Morphologic evidence indicated that living toxoplasmas altered the phagocytic vacuolar membrane in macrophages, fibroblasts, and HeLa cells. Within minutes after phagocytosis, the vacuole became surrounded by closely apposed strips of endoplasmic reticulum and mitochondria; somewhat later, microvillous protrusions of the membrane into the vacuole were seen. These morphologic features of phagocytic vacuoles containing living toxoplasmas may be of importance in relation to the absence of lysosomal fusion, or they may serve some function in protecting the host cell or in nourishing the parasite.

scholarly journals The Legionnaires' disease bacterium (Legionella pneumophila) inhibits phagosome-lysosome fusion in human monocytes.

1983 ◽  
Vol 158 (6) ◽  
pp. 2108-2126 ◽  
Author(s):  
M A Horwitz
Keyword(s):  
Acid Phosphatase ◽  
Legionella Pneumophila ◽  
Thorium Dioxide ◽  
Live Bacteria ◽  
Phosphatase Cytochemistry ◽  
Legionnaires Disease ◽  
Intracellular Multiplication ◽  
Erythromycin A ◽  
Secondary Lysosomes ◽  
Bacterial Protein Synthesis

The interactions between the L. pneumophila phagosome and monocyte lysosomes were investigated by prelabeling the lysosomes with thorium dioxide, an electron-opaque colloidal marker, and by acid phosphatase cytochemistry. Phagosomes containing live L. pneumophila did not fuse with secondary lysosomes at 1 h after entry into monocytes or at 4 or 8 h after entry by which time the ribosome-lined L. pneumophila replicative vacuole had formed. In contrast, the majority of phagosomes containing formalin-killed L. pneumophila, live Streptococcus pneumoniae, and live Escherichia coli had fused with secondary lysosomes by 1 h after entry into monocytes. Erythromycin, a potent inhibitor of bacterial protein synthesis, at a concentration that completely inhibits L. pneumophila intracellular multiplication, had no influence on fusion of L. pneumophila phagosomes with secondary lysosomes. However, coating live L. pneumophila with antibody or with antibody and complement partially overcame the inhibition of fusion. Also activating the monocytes promoted fusion of a small proportion of phagosomes containing live L. pneumophila with secondary lysosomes. Acid phosphatase cytochemistry revealed that phagosomes containing live L. pneumophila did not fuse with either primary or secondary lysosomes. In contrast to phagosomes containing live bacteria, the majority of phagosomes containing formalin-killed L. pneumophila were fused with lysosomes by acid phosphatase cytochemistry. The capacity of L. pneumophila to inhibit phagosome-lysosome fusion may be a critical mechanism by which the bacterium resists monocyte microbicidal effects.

Demonstration of Secondary Lysosomes in Bovine Megakaryocytes and Platelets Using Acid Phosphatase Cytochemistry with Cerium as a Trapping Agent

1990 ◽  
Vol 63 (01) ◽  
pp. 127-132 ◽  
Author(s):  
Michèle Ménard ◽  
Kenneth M Meyers ◽  
David J Prieur
Keyword(s):  
Acid Phosphatase ◽  
Electron Density ◽  
Golgi Complex ◽  
Initial Report ◽  
Cerium Phosphate ◽  
Virtual Absence ◽  
Phosphatase Cytochemistry ◽  
Secondary Lysosomes ◽  
Trapping Agent

SummaryThe ultrastructure of lysosomes from bovine megakaryocytes (MK) and platelets was characterized using acid phosphatase cytochemistry with beta-glycerophosphate as substrate and cerium as a trapping agent. The technique was easily reproducible; cerium-phosphate precipitates were uniform, readily visualized, and there was a virtual absence of nonspecific reaction product. Acid phosphatase was localized in the trans aspect of the Golgi complex and/or granules of less than 50 nm to 650 nm diameters in MK at all stages of maturation. Forty percent of the MK lysosomes contained inclusions of variable shapes, sizes and electron-density and were classified as secondary lysosomes. Twenty-four percent of the platelet sections contained acid phosphatase-positive granules. Fifty-four percent of these were secondary lysosomes. This is the initial report demonstrating secondary lysosomes in either resting MK or platelets using acid phosphatase cytochemistry. These findings suggest that MK and platelet lysosomes have an intracellular function in resting MK and platelets.

scholarly journals Acidocalcisomes in Toxoplasma gondii tachyzoites

1996 ◽  
Vol 313 (2) ◽  
pp. 655-659 ◽  
Author(s):  
Silvia N. J. MORENO ◽  
Li ZHONG
Keyword(s):  
Endoplasmic Reticulum ◽  
Toxoplasma Gondii ◽  
Mammalian Cells ◽  
Specific Inhibitor ◽  
Mitochondrial Atpase ◽  
Bafilomycin A1 ◽  
Atpase Inhibitor ◽  
Extracellular Medium ◽  
Acidic Compartment ◽  
Acidic Organelles

Toxoplasma gondii tachyzoites were loaded with the fluorescent indicator fura 2 to investigate the transport mechanisms involved in maintaining their intracellular Ca2+ homoeostasis. The mitochondrial ATPase inhibitor oligomycin and the endoplasmic-reticulum Ca2+-ATPase inhibitor thapsigargin increased the intracellular Ca2+ concentration ([Ca2+]i), thus indicating the requirement for ATP and the involvement of the endoplasmic reticulum in maintaining intracellular Ca2+ homoeostasis. The effect of thapsigargin was more accentuated in the presence of extracellular Ca2+, clearly showing that, as occurs with other eukaryotic cells, depletion of intracellular Ca2+ pools led to an increase in the uptake of Ca2+ from the extracellular medium. In addition to these results, we found evidence that, in contrast with what occurs in mammalian cells, T. gondii tachyzoites possess a significant amount of Ca2+ stored in an acidic compartment, termed the acidocalcisome, as indicated by: (1) the increase in [Ca2+]i induced by bafilomycin A1 (a specific inhibitor of H+-ATPases), nigericin (a K+/H+ exchanger) or the weak base NH4Cl, in the nominal absence of extracellular Ca2+ to preclude Ca2+ entry; and (2) the effect of ionomycin, a Ca2+-releasing ionophore that cannot take Ca2+ out of acidic organelles and that was more effective after alkalinization of these compartments by addition of bafilomycin A1, nigericin or NH4Cl. Considering the relative importance of the ionomycin-releasable and the ionomycin+NH4Cl-releasable Ca2+ pools, it is apparent that T. gondii tachyzoites contain a significant amount of Ca2+ stored in acidocalcisomes.

scholarly journals The distribution of lysosomal cathepsin D in cardiac myocytes.

1980 ◽  
Vol 28 (3) ◽  
pp. 231-237 ◽  
Author(s):  
R S Decker ◽  
M L Decker ◽  
A R Poole
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Golgi Apparatus ◽  
Cardiac Myocytes ◽  
Cathepsin D ◽  
Immunohistochemical Method ◽  
Acid Proteinase ◽  
Reproducible Method ◽  
Secondary Lysosomes ◽  
Subcellular Level

Lysosomal cathepsin D has been localized with the electron microscope employing an indirect immunohistochemical method using peroxidase labeled, monospecific antibody Fab' subunits. The acid proteinase has been demonstrated within secondary lysosomes of cardiac myocytes and interstitial cells, but not in components of the Golgi apparatus or endoplasmic reticulum. Incubations with a variety of peroxidatic inhibitors suggests that the staining that is observed in secondary lysosomes is attributable to the peroxidase-labeled antibody and not to endogenous oxidation of DAB. The protocol outlined here provides a reproducible method to localize the major lysosomal acid proteinase of the heart at the subcellular level.

Desiccation causes the proliferation of multicellular hairs, but not mucilage papillae, in Cryptothallus mirabilis (Hepatophyta): a correlated light and electron microscope study

1990 ◽  
Vol 68 (3) ◽  
pp. 697-706 ◽  
Author(s):  
Jeffrey G. Duckett ◽  
Karen S. Renzaglia ◽  
Keith Pell
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Acid Phosphatase ◽  
Endophytic Fungus ◽  
Electron Microscope Study ◽  
Secretory Phase ◽  
Golgi Bodies ◽  
Dense Cytoplasm ◽  
Thin Walled ◽  
Multicellular Hair

When Cryptothallus dries out over periods of 4–20 days, the dorsal surfaces of the thalli become covered with multicellular hairs. The distribution of mucilage papillae and the endophytic fungus are not affected by desiccation. The hairs are thin walled and highly vacuolated whereas the mucilage papillae, like their secretory counterparts in Marchantia and mosses, are thick walled with dense cytoplasm containing stacks of endoplasmic reticulum and numerous Golgi bodies. Cytochemistry shows that the secretion is rich in carbohydrates and is derived from Golgi vesicles. After an active secretory phase, senescence of the mucilage papillae is associated with acid phosphatase activity. Key words: Aneura, Cryptothallus, desiccation, liverwort, mucilage papilla, multicellular hair, ultrastructure.

scholarly journals FIT2 is an acyl–coenzyme A diphosphatase crucial for endoplasmic reticulum homeostasis

2020 ◽  
Vol 219 (10) ◽  
Author(s):  
Michel Becuwe ◽  
Laura M. Bond ◽  
Antonio F.M. Pinto ◽  
Sebastian Boland ◽  
Niklas Mejhert ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Lipid Metabolism ◽  
Mammalian Cells ◽  
Metabolic Flux ◽  
Coenzyme A ◽  
Cell Function ◽  
Lipid Synthesis ◽  
Fatty Acyl ◽  
Molecular Function ◽  
Acyl Coenzyme A

The endoplasmic reticulum is a cellular hub of lipid metabolism, coordinating lipid synthesis with continuous changes in metabolic flux. Maintaining ER lipid homeostasis despite these fluctuations is crucial to cell function and viability. Here, we identify a novel mechanism that is crucial for normal ER lipid metabolism and protects the ER from dysfunction. We identify the molecular function of the evolutionarily conserved ER protein FIT2 as a fatty acyl–coenzyme A (CoA) diphosphatase that hydrolyzes fatty acyl–CoA to yield acyl 4′-phosphopantetheine. This activity of FIT2, which is predicted to be active in the ER lumen, is required in yeast and mammalian cells for maintaining ER structure, protecting against ER stress, and enabling normal lipid storage in lipid droplets. Our findings thus solve the long-standing mystery of the molecular function of FIT2 and highlight the maintenance of optimal fatty acyl–CoA levels as key to ER homeostasis.

scholarly journals Normal rabbit alveolar macrophages. II. Their primary and secondary lysosomes as revealed by electron microscopy and cytochemistry.

1976 ◽  
Vol 144 (4) ◽  
pp. 920-932 ◽  
Author(s):  
B A Nichols
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Acid Phosphatase ◽  
Rough Endoplasmic Reticulum ◽  
Alveolar Macrophages ◽  
Digestive Enzymes ◽  
Acid Hydrolases ◽  
Secondary Lysosomes ◽  
Enzymatic Machinery ◽  
Cytochemical Markers

In this investigation, vacuoles containing tubular myelin proved to be digestive compartments with cytochemical reactivity for acid phosphatase and arylsulfatase. These cytochemical markers identify the secondary lysosomes, known to contain enzymes capable of hydrolyzing phospholipids like surfactant. Therefore, it appears that alveolar macrophages possess the enzymatic machinery for the degradation of the tubular myelin found in their digestive vacuoles. Although it thus appears evident that alveolar macrophages participate in the turnover of surfactant, the quantitative significance of this route of disposal is undetermined. This investigation has also established that acid hydrolases, so prominently displayed in the secondary lysosomes, are also localized in the rough endoplasmic reticulum and in Golgi-endoplasmic reticulum-lysosomes (GERL). Moreover, small vesicles which are produced from GERL serve as primary lysosomes in transporting digestive enzymes to the vacuoles.

scholarly journals The Fine Structure of the Adipose Cell of the Leech Glossiphonia complanata

1958 ◽  
Vol 4 (5) ◽  
pp. 603-608 ◽  
Author(s):  
S. Bradbury ◽  
G. A. Meek
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Electron Microscope ◽  
Calcium Ions ◽  
Mammalian Cells ◽  
Histochemical Study ◽  
Adipose Cell ◽  
Electron Microscope Investigation ◽  
Electron Microscope Image ◽  
Size And Structure

The two distinct types of cytoplasm seen with the light microscope in the adipose cell of the leech Glossiphonia complanata have been identified in the electron microscope image of this cell. One of these, the basophil cytoplasm, contains many well oriented, paired membranes which are much more clearly evident when calcium ions are added to the fixative. The membranes sometimes appear as concentric arrays of lamellae and are thought to represent sections through a phospholipide-containing body. The paired membranes and the concentric lamellae have granules attached to them and resemble in size and structure the membranes of the endoplasmic reticulum encountered in many mammalian cells. Small dense cytoplasmic particles are present throughout the cell; they may be ferritin molecules, derived from the breakdown of haemoglobin taken in as food. On the basis of a previous histochemical study and the present electron microscope investigation, it is suggested that these paired membranes are similar to the organized type of mammalian ER and the results seem to confirm the belief that these membranes are composed of layers of phospholipoprotein together with attached particles of ribonucleoprotein.

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