Fine structure and RNA synthesis of Tetrahymena during cytochalasin B inhibition of phagocytosis

1977 ◽  
Vol 27 (1) ◽  
pp. 115-126
Author(s):  
J.R. Nilsson
Keyword(s):  
Fine Structure ◽  
Rna Synthesis ◽  
Cytochalasin B ◽  
High Rate ◽  
Large Numbers ◽  
Food Vacuoles

Cytochalasin B inhibits the formation of normal-sized food vacuoles in Tetrahymena but the cells do not starve. Treated cells differ from starved cells in that they retain a high rate of incorporation of tritiated uridine. Large numbers of smaller vacuoles, about 1 micrometer in diameter, are formed, presumably by pinocytic activity of the cytopharyngeal membrane. This effect may perhaps be due to interference with the mechanism by which food vacuoles are sealed off at the cytostome, in which microfilaments may participate. Inhibited organisms may form tubes continuous with the cytopharynx instead of separate food vacuoles. It is not clear, however, why the formation of the small vacuoles is resistant to the drug.

Fine Structure of Cytochalasin Induced Polyploid Cells

1968 ◽  
Vol 26 ◽  
pp. 122-123
Author(s):  
Awtar Krishan ◽  
Nestor Bohonos
Keyword(s):  
Fine Structure ◽  
Cytochalasin B ◽  
Present Report ◽  
Cell Monolayer ◽  
Polyploid Cell ◽  
Specific Cell ◽  
Nuclear Surface ◽  
Unsuccessful Attempt ◽  
Daughter Cells ◽  
Polyploid Cells

Cytochalasin B, a mould metabolite from Helminthosporium dermatioideum has been shown to interfere with specific cell activities such as cytoplasmic cleavage and cell movement. Cells undergoing nuclear division in the presence of cytochalasin B are unable to complete the separation of the resulting daughter cells. In time-lapse studies, the daughter cells coalesce after an initial unsuccessful attempt at separation and form large multinucleate polyploid cells. The present report describes the fine structure of the large polyploid cells induced in Earle's L-cell monolayer cultures by exposure to cytochalasin B (lγ/ml) for 92 hours.In the present material we have seen as many as 7 nuclei in these polyploid cells. Treatment with cytochalasin B for longer periods of time (6 to 7 days, with one medium change on the 3rd day) did not increase the number of nuclei beyond the 7 nuclei stage. Figure 1 shows a large polyploid cell with four nuclei. These nuclei are indistinguishable in their fine structure from those of the cells from control cultures but often show unusually large numbers of cytoplasmic invaginations and extensions of the nuclear surface (Figure 2).

The developmental potential of a euploid male teratocarcinoma cell line after blastocyst injection

Development ◽  
1982 ◽  
Vol 70 (1) ◽  
pp. 99-112
Author(s):  
J. Rossant ◽  
M. W. McBurney
Keyword(s):  
Cell Line ◽  
Normal Karyotype ◽  
High Rate ◽  
Normal Male ◽  
Teratocarcinoma Cell ◽  
Developmental Potential ◽  
Normal Tissues ◽  
Large Numbers ◽  
Ec Cells ◽  
Cell Variation

A karyotypically normal male embryonal carcinoma (EC) cell line, PI 9, produced large numbers of chimaeras in midgestation after groups of cells were injected into mouse blastocysts. A wide variety of apparently normal tissues were colonized by the EC cells but most chimaeras were also morphologically abnormal. Few live chimaeras were produced and all contained tumours of EC cell origin as well as EC contributions to normal tissues. This apparently incomplete regulation of the EC cells by the embryonic environment was not due to EC cell variation, since a clonal subline, P19S18, produced similar patterns of colonization. It was also not caused by the inability of the blastocyst to regulate large numbers of injected EC cells, since a single P19S18 cell could contribute to both normal and tumour tissue in the same mouse. Neither a high rate of colonization of the embryo nor a normal karyotype is, therefore, sufficient to ensure reversion of EC cells to normal embryonic behaviour.

scholarly journals Cooperation between PDGF and FGF converts slowly dividing O-2Aadult progenitor cells to rapidly dividing cells with characteristics of O-2Aperinatal progenitor cells.

1992 ◽  
Vol 118 (4) ◽  
pp. 889-900 ◽  
Author(s):  
G Wolswijk ◽  
M Noble
Keyword(s):  
Progenitor Cells ◽  
Adult Brain ◽  
High Rate ◽  
Adult Rat ◽  
Large Numbers ◽  
Dividing Cells ◽  
Rapid Generation ◽  
And Migration

We have shown previously that oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells isolated from adult rat optic nerves can be distinguished in vitro from their perinatal counterparts on the basis of their much slower rates of division, differentiation, and migration when grown in the presence of cortical astrocytes or PDGF. This behavior is consistent with in vivo observations that there is only a modest production of oligodendrocytes in the adult CNS. As such a behavior is inconsistent with the likely need for a rapid generation of oligodendrocytes following demyelinating damage to the mature CNS, we have been concerned with identifying in vitro conditions that allow O-2Aadult progenitor cells to generate rapidly large numbers of progeny cells. We now provide evidence that many slowly dividing O-2Aadult progenitor cells can be converted to rapidly dividing cells by exposing adult optic nerve cultures to both PDGF and bFGF. In addition, these O-2Aadult progenitor cells appear to acquire other properties of O-2Aperinatal progenitor cells, such as bipolar morphology and high rate of migration. Although many O-2Aadult progenitor cells in cultures exposed to bFGF alone also divide rapidly, these cells are multipolar and migrate little in vitro. Oligodendrocytic differentiation of O-2Aadult progenitor cells, which express receptors for bFGF in vitro, is almost completely inhibited in cultures exposed to bFGF or bFGF plus PDGF. As bFGF and PDGF appear to be upregulated and/or released after injury to the adult brain, this particular in vitro response of O-2Aadult progenitor cells to PDGF and bFGF may be of importance in the generation of large numbers of new oligodendrocytes in vivo following demyelination.

Inactivation of the Bacteriophage MS2 by the Ciliated Protozoan, Tetrahymena thermophila

2008 ◽  
Vol 43 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Marcel D.O. Pinheiro ◽  
Mary E. Power ◽  
Barb J. Butler ◽  
Vivian R. Dayeh ◽  
Robin Slawson ◽  
...  
Keyword(s):  
Cytochalasin B ◽  
Tetrahymena Thermophila ◽  
Biological Mechanisms ◽  
Ciliated Protozoan ◽  
Viral Inactivation ◽  
Free Living ◽  
Bacteriophage Ms2 ◽  
Sybr Gold ◽  
Food Vacuoles ◽  
Formalin Fixed

Abstract Because the range of biological mechanisms responsible for the inactivation of viruses in man-made and natural water systems is poorly understood, the involvement of the free-living ciliated protozoan, Tetrahymena thermophila, in viral inactivation was investigated. The ciliate was found to remove the bacteriophage MS2 when the phage and ciliate were co-incubated in a simple salt solution. MS2 was enumerated as plaque forming units (pfus). MS2 removal was achieved only by living and not formalin-fixed ciliates, and was blocked by treatments that impaired the formation of food vacuoles. These treatments were cytochalasin B and low temperature. When fluorescently labelled with SYBR gold prior to co-incubation, MS2 were seen inside Tetrahymena within vesicles that had the shape and size of food vacuoles. The number of pfus associated with Tetrahymena was low. This suggests that the engulfment of the phage into food vacuoles led to the inactivation of MS2, which is frequently used as a surrogate for poliovirus in environmental microbiology. In the future, a broader understanding of the capacity of ciliates to inactivate viruses could lead to methods for improving water quality through the manipulation of ciliate populations and activities.

Identification and Cloning of Genes fromPorphyromonas gingivalis after Mutagenesis with a Modified Tn4400 Transposon from Bacteroides fragilis

2000 ◽  
Vol 68 (1) ◽  
pp. 420-423 ◽  
Author(s):  
Tsute Chen ◽  
Hong Dong ◽  
Yixin P. Tang ◽  
Mary M. Dallas ◽  
Michael H. Malamy ◽  
...  
Keyword(s):  
Southern Hybridization ◽  
Bacteroides Fragilis ◽  
High Rate ◽  
E Coli ◽  
Delivery Vector ◽  
Large Numbers ◽  
Single Mating ◽  
Genomic Dnas ◽  
Lactamase Gene

ABSTRACT Porphyromonas gingivalis is a gram-negative, black-pigmented, oral anaerobe strongly associated with adult periodontitis. Previous transposon mutagenesis studies with this organism were based on the Bacteroides transposon Tn4351. Characterization of Tn4351-disrupted genes by cloning has not been an efficient way to analyze large numbers of mutants and is further complicated by the high rate of cointegration of the suicide delivery vector containing Tn4351. In this study, we mutagenized P. gingivalis with a modified version of the Bacteroides fragilis transposon Tn4400. Plasmid pYT646B carrying the transposon was mobilized fromEscherichia coli to P. gingivalis ATCC 33277 by conjugation. Both normal and inverse transposition frequencies were similar (3 × 10−8). However, the inverse transposon (Tn4400′) contains a pBR322 replicon and a β-lactamase gene; thus, the cloning of disrupted genomic DNAs from inverse transposition mutants was easily accomplished after ligation of genomic fragments and transformation into E. coli. Thousands of transconjugants could be obtained in a single mating experiment, and inverse transposition was random as demonstrated by Southern hybridization. By this procedure the disrupted genes from P. gingivalis pleiotropic mutants were quickly cloned, sequenced, and identified.

The Fine Structure ofColpoda maupasiwith Special Emphasis on Food Vacuoles*

1966 ◽  
Vol 13 (3) ◽  
pp. 440-459 ◽  
Author(s):  
MARIA A. RUDZINSKA ◽  
GEORGE J. JACKSON ◽  
MICHEL TUFFRAU
Keyword(s):  
Fine Structure ◽  
Food Vacuoles

Organization of ampullary electric receptors in Gymnotidae (Pisces)

1968 ◽  
Vol 169 (1017) ◽  
pp. 345-378 ◽  
Keyword(s):  
Fine Structure ◽  
Evolutionary Relationships ◽  
Type I ◽  
Type Ii ◽  
Sense Organs ◽  
Large Numbers ◽  
Mode Of Operation ◽  
Points Of View ◽  
Eigenmannia Virescens ◽  
Electron Microscopes

Investigation of 14 species of gymnotid has established that large numbers of ampullary lateralis sense organs are present in each case. These organs have been examined with the light and electron microscopes. Two distinct types occur, and these are referred to as type I and type II; the latter is more common. The fine structure of the receptors in one species ( Eigenmannia virescens ) is described in detail, and is discussed from two points of view: (i) the function and mode of operation of the organs, and (ii) the evolutionary relationships to different receptors of the vertebrate acoustic-lateralis system.

Acquired tolerance of foreign cells in newborn animals

1956 ◽  
Vol 146 (922) ◽  
pp. 78-90 ◽  
Keyword(s):  
Direct Injection ◽  
Chorioallantoic Membrane ◽  
Later Life ◽  
High Rate ◽  
Direct Result ◽  
In Ovo ◽  
Large Numbers ◽  
High Degree ◽  
Experimental Interference ◽  
Very High

Acquired tolerance of skin homografts may be brought about experimentally by the introduction of the antigenic stimulus, in the form of living homologous tissue cells, into the embryo before its immunological defence mechanism has become functionally mature (Billingham, Brent & Medawar 1953, 1956). In practice, this may be accomplished in one or other of the following ways, depending on the species concerned: ( a ) in mice, rats and rabbits, by direct injection of cells into the foetus; ( b ) in birds, by the injection of blood into the chorioallantoic circulation, or ( c ) by the parabiosis of embryos, an ingenious technique devised by Hašek (I953) which leads to an exchange of blood cells, or ( d ) by the transplantation of tissues to the chorioallantoic membrane. Although any one of these techniques is capable of inducing a very high degree of tolerance in respect of skin homografts transplanted in later life each, unfortunately, has its own technical shortcomings. In particular, these techniques are all severely restricted by a very high rate of mortality which is a direct result of experimental interference in utero or in ovo . For this and other reasons they do not easily lend themselves to the analysis of problems which require the use of relatively large numbers of tolerant animals.

The fine structure of the developing retina in Xenopus laevis

Development ◽  
1972 ◽  
Vol 28 (3) ◽  
pp. 659-666
Author(s):  
J. S. Dixon ◽  
J. R. Cronly-Dillon
Keyword(s):  
Fine Structure ◽  
Xenopus Laevis ◽  
Retinal Cell ◽  
Optic Vesicle ◽  
Cell Specification ◽  
Ciliary Margin ◽  
Large Numbers ◽  
Outer Aspect ◽  
Cell To Cell Transfer ◽  
Pigment Epithelial Cells

The fine structure of the developing retinal cells in Xenopus laevis was studied from stages 26 to 36. At all stages examined the cells contained large numbers of free ribosomes, polysomes, small mitochondria, lipid and yolk droplets and scanty granular reticulum. A basal lamina covered the smooth internal margin of the optic vesicle and also the external aspect of the germinal pigment epithelial cells. At all stages examined zonulae adhaerentes occurred between adjacent cells at the outer aspect of the optic vesicle and maculae adhaerentes diminutae were occasionally observed. A third type of intercellular junction, characterized by a narrow gap of 3–9 nm, occurred throughout the retina up to stage 30 but only at the periphery beyond this stage. It is suggested that the disappearance of these junctions from the central portion of the retina may be correlated with retinal cell specification* which is known to occur at stage 30–31. These junctions may represent sites for the cell to cell transfer of small molecules which are required for cell differentiation. Since new cells are continually being added to the retina from the ciliary margin beyond stage 30 the persistence of junctions in this region may explain how these new cells also become specified.*

scholarly journals Visualization of Altered Replication Dynamics after DNA Damage in Human Cells

2004 ◽  
Vol 279 (19) ◽  
pp. 20067-20075 ◽  
Author(s):  
Catherine J. Merrick ◽  
Dean Jackson ◽  
John F. X. Diffley
Keyword(s):  
Dna Damage ◽  
Dna Synthesis ◽  
Replication Fork ◽  
S Phase ◽  
High Rate ◽  
Yeast Cells ◽  
Origin Firing ◽  
Large Numbers ◽  
Dependent Inhibition ◽  
Fork Stalling

Eukaryotic cells respond to DNA damage within the S phase by activating an intra-S checkpoint: a response that includes reducing the rate of DNA synthesis. In yeast cells this can occur via checkpoint-dependent inhibition of origin firing and stabilization of ongoing forks, together with a checkpoint-independent slowing of fork movement. In higher eukaryotes, however, the mechanism by which DNA synthesis is reduced is less clear. We have developed strategies based on DNA fiber labeling that allow the quantitative assessment of rates of replication fork movement, origin firing, and fork stalling throughout the genome by examining large numbers of individually labeled replication forks. We show that exposing S phase cells to ionizing radiation induces a transient block to origin firing but does not affect fork rate or fork stalling. Alkylation damage by methyl methane sulfonate causes a slowing of fork movement and a high rate of fork stalling, in addition to inducing a block to new origin firing. Nucleotide depletion by hydroxyurea also reduces replication fork rate and increases stalling; moreover, in contrast to a recent report, we show that hydroxyurea induces a strong block to new origin firing. The DNA fiber labeling strategy provides a powerful new approach to analyze the dynamics of DNA replication in a perturbed S phase.

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