scholarly journals Phagotrophy and Two New Structures in the Malaria Parasite Plasmodium berghei

1959 ◽  
Vol 6 (1) ◽  
pp. 103-112 ◽  
Author(s):  
Maria A. Rudzinska ◽  
William Trager
Keyword(s):  
Plasma Membrane ◽  
Plasmodium Berghei ◽  
Food Vacuole ◽  
The Body ◽  
Host Cells ◽  
Butyl Methacrylate ◽  
Host Cytoplasm ◽  
Mitochondrial Functions ◽  
Food Vacuoles ◽  
Almost All

Blood collected from rats infected with Plasmodium berghei was centrifuged and the pellet was fixed for 1 hour in 1 per cent buffered OsO4 with 4.9 per cent sucrose. The material was embedded in n-butyl methacrylate and the resulting blocks sectioned for electron microscopy. The parasites were found to contain, in almost all sections, oval bodies of the same density and structure as the host cytoplasm. Continuity between these bodies and the host cytoplasm was found in a number of electron micrographs, showing that the bodies are formed by invagination of the double plasma membrane of the parasite. In this way the host cell is incorporated by phagotrophy into food vacuoles within the parasite. Hematin, the residue of hemoglobin digestion, was never observed inside the food vacuole but in small vesicles lying around it and sometimes connected with it. The vesicles are pinched off from the food vacuole proper and are the site of hemoglobin digestion. The active double limiting membrane is responsible not only for the formation of food vacuoles but also for the presence of two new structures. One is composed of two to six concentric double wavy membranes originating from the plasma membrane. Since no typical mitochondria were found in P. berghei, it is assumed that the concentric structure performs mitochondrial functions. The other structure appears as a sausage-shaped vacuole surrounded by two membranes of the same thickness, density, and spacing as the limiting membrane of the body. The cytoplasm of the parasite is rich in vesicles of endoplasmic reticulum and Palade's small particles. Its nucleus is of low density and encased in a double membrane. The host cells (reticulocytes) have mitochondria with numerous cristae mitochondriales. In many infected and intact reticulocytes ferritin was found in vacuoles, mitochondria, canaliculi, or scattered in the cytoplasm.

Membrane recycling at the cytoproct of Tetrahymena

1979 ◽  
Vol 35 (1) ◽  
pp. 217-227
Author(s):  
R.D. Allen ◽  
R.W. Wolf
Keyword(s):  
Plasma Membrane ◽  
Single Cells ◽  
Tetrahymena Pyriformis ◽  
Food Vacuole ◽  
Membrane Recycling ◽  
Vacuole Membrane ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Food Vacuoles ◽  
Spherical Vesicles

Exocytosis and membrane recycling at the cytoproct (cell anus) of Tetrahymena pyriformis were studied using thin-section electron microscopy. Single cells were fixed at specific times relative to the elimination of the vacuole's contents—before elimination, at elimination, 3–5 s and 10–15 s following elimination. The closed cytoproct is distinguished from other pellicular regions by a single membrane at the cell surface which is circumscribed by an electron-opaque flange that links or welds the plasma membrane to the underlying alveolar margins. Microtubules originating in the flange pass inward where they lie over, and possibly guide, the approaching food vacuoles to the cytoproct. Food facuoles near the cytoproct are also accompanied by coats of microfilaments. These microfilaments appear to be active in the channelling and endocytosis of food vacuole membrane. Upon cytoproct opening the plasma membrane and food vacuole membrane fuse. Elimination seems to be essentially passive and is accomplished by re-engulfment of the old food vacuole membrane which is constantly associated with microfilaments. Reengulfment of all the food vacuole membrane requires 10–15 s and results in a closed cytoproct. The membrane remnants embedded in microfilaments form a cluster under the closed cytoproct. At the periphery of this cluster remnants take the shape of 70–130-nm spherical vesicles or 0.2-micrometer-long flattened vesicles.

The Osmoregulatory System of the Amoeba, Acanthamoeba Castellanii

1972 ◽  
Vol 57 (1) ◽  
pp. 55-76
Author(s):  
R. A. PAL
Keyword(s):  
Plasma Membrane ◽  
Polyethylene Glycol ◽  
Ethylene Glycol ◽  
Surface Membrane ◽  
Acanthamoeba Castellanii ◽  
Sodium Sulphate ◽  
The Body ◽  
Contractile Vacuole ◽  
Body Volume ◽  
Food Vacuoles

1. It is estimated that Acanthamoeba castellanii eliminates a volume of water equal to its body volume in about 15-30 min. About 7% of the vacuolar discharge enters the body by means other than osmosis through the surface membrane. Food vacuoles fusing with the contractile vacuole do not significantly affect the rate of output. 2. Vacuolar output declines with the age of culture so that during the stationary phase of growth it is about half of that during early log phase of growth. 3. The rate of output of the contractile vacuole decreases with an increase of concentration of a non-penetrating solute in the external medium and shows a rectilinear relationship up to 0.07 M concentration. A low residual output after 0.07 M may be due to food vacuoles and pinocytic vacuoles. 4. On the basis of vacuolar output the excess internal osmotic pressure and permeability constant of water has been estimated as 0.07 M non-electrolyte and 0.04µm min-1 atm.-1 respectively. 5. On the basis of vacuolar behaviour it is concluded that the relative permeabilities of the plasma membrane to different solutes follows this order: methyl alcohol > ethylene glycol > urea > glycerol. On certain assumptions the permeability of the plasma membrane to ethylene glycol has been estimated provisionally as 0.107 x 10-16 mol/sec/µm2/mol/l. 6. Vacuolar behaviour suggests that sodium chloride, sodium nitrate, sodium sulphate and potassium chloride, but not magnesium chloride and calcium chloride, pass into the cell freely. 7. Growth of populations of A. castellanii is almost normal in polyethylene glycol 600 up to 0.07 M concentration but in higher concentrations it is low. There are some indications of an increase in volume of A . castellanii in cultures of polyethylene glycol 600 up to 0.07 M concentration, but not in higher concentrations. For amoebae cultured in media containing polyethylene glycol 600 the rate of output of the contractile vacuole declines sharply with an increase of polyethylene glycol 600 up to 0.07 M concentration and then more gradually.

Dual capacity for nutrient uptake in Tetrahymena. V. Utilization of amino acids and proteins

1979 ◽  
Vol 36 (1) ◽  
pp. 343-353
Author(s):  
E. Orias ◽  
L. Rasmussen
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Tetrahymena Thermophila ◽  
Amino Acid Uptake ◽  
Food Vacuole ◽  
Transport Systems ◽  
Acid Uptake ◽  
Vacuole Formation ◽  
Carrier Mediated Transport ◽  
Food Vacuoles

We investigated the relative contributions of phagocytosis and plasma membrane transport to the uptake of amino acids and a protein (egg albumin) in amounts which allow Tetrahymena thermophila to grow and multiply. We used a mutant capable of indefinite growth without food vacuole formation (phagocytosis) and its wild type (phagocytosis-competent) isogenic parental strain. Our results suggest that phagocytosis is not required for free amino acid uptake, most or all of which can be attributed to carrier-mediated transport systems, apparently located on the plasma membrane. In contrast, phagocytosis is required for utilization of the protein. Proteins can supply required amino acids in amounts sufficient for growth only when food vacuoles are formed. We conclude that Tetrahymena thermophila either possesses no endocytic mechanisms at the cell surface other than food vacuole formation or, if it does, these putative mechanisms are not capable of nutritionally meaningful rates of protein uptake.

THE HAUSTORIUM OF ERYSIPHE CICHORACEARUM AND THE HOST–PARASITE INTERFACE ON HELIANTHUS ANNUUS

1966 ◽  
Vol 44 (10) ◽  
pp. 1299-1306 ◽  
Author(s):  
W. E. McKeen ◽  
R. Smith ◽  
N. Mitchell
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Helianthus Annuus ◽  
The Body ◽  
Erysiphe Cichoracearum ◽  
Host Cytoplasm ◽  
Dense Bodies ◽  
Host Membrane ◽  
Host Parasite ◽  
Surrounding Membrane

Electron microscopy showed that the haustoria of Erysiphe cichoracearum which were randomly scattered in the epidermal cells of sunflower bathed in a cavity which was surrounded by the plasma membrane of the host. After infection of the sunflower cells, an increase in concentration of the host cytoplasm was noted. The haustorium was an elongated ellipsoidal body with tortuose branches which emerged from each end and wove back over the body. The branches seldom came into contact with each other or the body of the haustorium or the surrounding membrane. The possibility of the branches being vestigial or functional is discussed. The haustorial body and branches contained numerous chondriosomes, vesicles, and large electron-dense bodies. These bodies formed in vesicles by coalescence of smaller dense bodies. The chondriosomes were mainly the chondriocont type. In the body of the haustorium a nucleus and an opaque nucleolus with two electron-transparent areas were observed. Encapsulation material was scattered irregularly along the host membrane and was structureless, which suggests that it was waste material. The rest of the cavity was filled with a solution through which interchange between the host and fungus occurred. Active transport from the host protoplasm to the fungus was suggested. No evidence was obtained for cytoplasmic connections between the parasite and the host.

The fine structure of Leucocytozoon simondi. VI. Hepatic schizogony

1973 ◽  
Vol 51 (6) ◽  
pp. 605-609 ◽  
Author(s):  
Sherwin S. Desser
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Host Cells ◽  
Central Nucleus ◽  
Stages Of Development ◽  
Separate Family ◽  
Host Cytoplasm ◽  
Parenchymal Cells

Most of the maturing schizonts in hepatic parenchymal cells consist of large electron-dense, multinucleate cytomeres. These are bounded by a trilaminar plasma membrane and lie within membrane-bounded vacuoles in the host cytoplasm. Extensive invagination and multiple cleavage of the cytomeres culminate in the production of uninucleate merozoitcs. Each merozoite is bounded by a single trilaminar plasmalemma and contains a large central nucleus, a mitochondrion, electron-dense paired rhoptries, and several smaller micronemes. Occasionally a second type of schizont has been observed, in which many small parasite inclusions are scattered in the hepatocyte cytoplasm. Clearly defined differences are apparent between comparable stages of development of Leucocytozoon and the more closely related Plasmodium and Haemoproteus. These differences include the location of the schizont in their host cells, the formation of merozoitcs, and the nature of the membranes that invest the merozoites. On the basis of these differences it is proposed that the inclusion of Leucocytozoon spp. into a separate family is warranted.

scholarly journals Application of a C. trachomatis expression system to identify C. pneumoniae proteins translocated into host cells

2021 ◽  
Author(s):  
Izumi Yanatori ◽  
Koshiro Miura ◽  
Yi-Shan Chen ◽  
Raphael H. Valdivia ◽  
Fumio Kishi
Keyword(s):  
Plasma Membrane ◽  
Expression System ◽  
Effector Proteins ◽  
Host Cells ◽  
Cell Protein ◽  
Secretion Systems ◽  
Cellular Functions ◽  
Host Cytoplasm ◽  
Pathogen Effector ◽  
Specific Proteins

Chlamydia pneumoniae is a Gram-negative, obligate intracellular pathogen that causes community-acquired respiratory infections. C. pneumoniae uses a cell contact-dependent type-III secretion (T3S) system to translocate pathogen effector proteins that manipulate host cellular functions. While several C. pneumoniae T3S effectors have been proposed, few have been experimentally confirmed in Chlamydia. In this study, we expressed 382 C. pneumoniae genes in C. trachomatis as fusion proteins to an epitope tag derived from glycogen synthase kinase 3β (GSK3β) which is the target of phosphorylation by mammalian kinases. Based on the detection of the tagged C. pneumoniae protein with anti-phospho GSK3β antibodies, we identified 49 novel C. pneumoniae-specific proteins that are translocated by C. trachomatis into the host cytoplasm and thus likely play a role as modifiers of host cellular functions. In this manner, we identified and characterized a new C. pneumoniae effector CPj0678 that recruits the host cell protein PACSIN2 to the plasma membrane. These findings indicate that C. trachomatis provides a powerful screening system to detect candidate effector proteins encoded by other pathogenic and endosymbiotic Chlamydia species. Importance Chlamydia injects numerous effector proteins into host cells to manipulate cellular functions important for bacterial survival. Based on findings in C. trachomatis, it has been proposed that between 5-10% of the C. pneumoniae genome, a related respiratory pathogen, encodes secreted effectors. However only a few C. pneumoniae effectors have been identified and experimentally validated. With the development of methods for the stable genetic transformation of C. trachomatis, it is now possible to use C. trachomatis shuttle plasmids to express and explore the function of proteins from other Chlamydia in a more relevant bacterial system. In this study, we experimentally determined that 49 C. pneumoniae-specific proteins are translocated into the host cytoplasm by Chlamydia secretion systems, and identify a novel effector required to recruit the host factor PACSIN2 to the plasma membrane during infection.

scholarly journals ASSEMBLY OF LIPIDS INTO MEMBRANES IN ACANTHAMOEBA PALESTINENSIS

1971 ◽  
Vol 50 (3) ◽  
pp. 634-651 ◽  
Author(s):  
Francis J. Chlapowski ◽  
R. Neal Band
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Specific Activity ◽  
Food Vacuole ◽  
Cell Fractionation ◽  
Membrane Phospholipids ◽  
Golgi Membranes ◽  
Cytoplasmic Vesicles ◽  
Food Vacuoles ◽  
Phospholipid Pool

The membranes of Acanthamoeba palestinensis were studied by examination in fixed cells, and then by following the movements of glycerol-3H-labeled phospholipids by cell fractionation. Two previously undescribed structures were observed: collapsed cytoplasmic vesicles of cup shape, and plaques in food vacuole and plasma membrane similar in size to the collapsed vesicles. It appeared that the plaques formed by insertion of collapsed vesicles into membranes and/or that collapsed vesicles formed by pinching off of plaques. Fractions were isolated, enriched with nuclei, rough endoplasmic reticulum (RER), plasma membrane, Golgi-like membranes, and collapsed vesicles. The changes in specific activity of glycerol-3H-labeled phospholipids in these membranes during incorporation, turnover, and after pulse-labeling indicated an ordered sequence of appearances of newly synthesized phospholipids, first in nuclei and RER, then successively in Golgi membranes, collapsed vesicles, and finally, plasma membrane. In previous work we had found no large nonmembranous phospholipid pool in A. palestinensis. These observations are consistent with the hypothesis that membrane phospholipids are synthesized, perhaps as integral parts of membranes, in RER and nuclei. Subsequently, some of the newly synthesized phospholipids are transported to the Golgi complex to become integrated into the membranes of collapsed vesicles, which are precursors of the plasma membrane. Collapsed vesicles from the plasma membrane by inserting into it as plaques. When portions of the plasmalemma from food vacuoles, collapsed vesicles pinch off from their membranes and are recycled back to the cell surface.

An Ultrastructural Study of Pericytes

1968 ◽  
Vol 26 ◽  
pp. 66-67
Author(s):  
T. M. Murad ◽  
E. von Haam
Keyword(s):  
Plasma Membrane ◽  
Endothelial Cell ◽  
Basement Membrane ◽  
Blood Vessel ◽  
Vascular Endothelial Cells ◽  
Myoepithelial Cells ◽  
Capillary Blood ◽  
The Body ◽  
Capillary Blood Vessel ◽  
Outer Plasma Membrane

Pericytes are vascular satellites present around capillary blood vessels and small venules. They have been observed in almost every tissue of the body and are thought to be related to vascular smooth muscle cells. Morphologically pericytes have great similarity to vascular endothelial cells and also slightly resemble myoepithelial cells.The present study describes the ultrastructural morphology of pericytes in normal breast tissue and in benign tumor of the breast. The study showed that pericytes are ovoid or elongated cells separated from the endothelial cell of the capillary blood vessel by the basement membrane of endothelial cell. The nuclei of pericytes are often very distinctive. Although some are round, oval, or elongated, others show marked irregularity and infolding of the nuclear membrane. The cytoplasm shows mono-or bipolar extension in which the cytoplasmic organelles are located (Fig. 1). These cytoplasmic extensions embrace the capillary blood vessel incompletely. The plasma membrane exhibits multiple areas of focal condensation called hemidesmosomes (Fig. 2, arrow). A variable number of pinocytotic vesicles are frequently seen lining the outer plasma membrane. Normally pericytes are surrounded by a basement membrane which is found more consistently on the outer plasma membrane separating the pericytes from the stromal connective tissue.

Digestibility of nutrients and milk productivity of cows when using the concentrate mixture with the inclusion of rapeseed presscake

2020 ◽  
pp. 48-53
Author(s):  
L. Yarmots ◽  
G. Yarmots ◽  
A. Belenkaya
Keyword(s):  
Protein Digestibility ◽  
High Energy ◽  
Negative Influence ◽  
The Body ◽  
Milk Productivity ◽  
Lactating Cows ◽  
Low Protein ◽  
Concentrate Mixture ◽  
Almost All ◽  
Experimental Group

For ruminants, especially high-yielding animals in addition to the complete supply of animals with protein, its digestibility in the rumen is important. With low protein digestibility in the rumen, the released ammonia will be more effectively used by the rumen microflora, and the undigestible protein in the subsequent sections of the digestive tract can serve as a source of amino acids for the body. The use of concentrate mixtures with the inclusion of local, affordable and cheaper grain feeds, in particular a high-energy and protein ingredient- rapeseed presscake makes it possible to increase the milk productivity of cows throughout lactation. These presscakes are well balanced in their amino acid composition and belong to feeds whose protein has a low degree of digestibility in the rumen. The purpose of the researches was to study the digestibility of nutrients and milk productivity of cows when using the concentrate mixture with the inclusion of rapeseed presscake. In the scientific and economic experiment has been carried out on lactating cows, where the cows of the experimental group in the concentrate mixture of peas has been replaced with rapeseed presscake the digestibility of nutrients in the ration, energy metabolism and milk productivity have been studied. Studies have shown that almost all the nutrients were significantly better digested by the animals of the experimental group. Energy in milk was more allocated by cows of the experimental group by 6,29 MJ. From cows of the experimental group for 100 and 305 days of lactation has been obtained more milk by 6,27 and 7,06 %, respectively, than from control herdmates. The biochemical parameters of blood were within the limits of the physiological norm in animals of both groups. Thus, the replacement of peas with rapeseed presscake in the concentrate mixture did not have a negative influence on the metabolic processes and helped to increase the milk productivity of cows.

scholarly journals Cannabinoid receptors distribution in mouse cortical plasma membrane compartments

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Hajar Miranzadeh Mahabadi ◽  
Haseeb Bhatti ◽  
Robert B. Laprairie ◽  
Changiz Taghibiglou
Keyword(s):  
Plasma Membrane ◽  
Lipid Raft ◽  
Cannabinoid Receptors ◽  
Gradient Centrifugation ◽  
Brain Regions ◽  
Cb1 Receptor ◽  
The Body ◽  
Cb2 Receptor ◽  
Cortical Tissue ◽  
Ionic Detergent

AbstractThe type 1 and type 2 cannabinoid receptors (CB1 and CB2 receptors) are class A G protein-coupled receptors (GPCRs) that are activated by endogenous lipids called endocannabinoids to modulate neuronal excitability and synaptic transmission in neurons throughout the central nervous system (CNS), and inflammatory processes throughout the body. CB1 receptor is one of the most abundant GPCRs in the CNS and is involved in many physiological and pathophysiological processes, including mood, appetite, and nociception. CB2 receptor is primarily found on immunomodulatory cells of both the CNS and the peripheral immune system. In this study, we isolated lipid raft and non-lipid raft fractions of plasma membrane (PM) from mouse cortical tissue by using cold non-ionic detergent and sucrose gradient centrifugation to study the localization of CB1 receptor and CB2 receptor. Lipid raft and non-lipid raft fractions were confirmed by flotillin-1, caveolin-1 and transferrin receptor as their protein biomarkers. Both CB1 receptor and CB2 receptor were found in non-raft compartments that is inconsistent with previous findings in cultured cell lines. This study demonstrates compartmentalization of both CB1 receptor and CB2 receptor in cortical tissue and warrants further investigation of CB1 receptor and CB2 receptor compartmental distribution in various brain regions and cell types.

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