Cytoplasmic streaming in Chara: a cell model activated by ATP and inhibited by cytochalasin B

1975 ◽  
Vol 17 (3) ◽  
pp. 655-668
Author(s):  
R.E. Williamson
Keyword(s):  
Actin Filaments ◽  
Cytoplasmic Streaming ◽  
Cytochalasin B ◽  
Cell Model ◽  
Motive Force ◽  
Inorganic Pyrophosphate ◽  
A Cell ◽  
Shear Type

After vacuolar perfusion of Chara internode cells, the cytoplasm remaining in situ can be reactivated by ATP to give full rates of streaming. Observations during both perfusion and reactivation indicated that the generation of the motive force was associated with fibres consisting of bundles of microfilaments. In the absence of ATP, the remaining endoplasmic organelles were immobilized along such fibres. When ATP was introduced, organelles moved along the fibres at speeds up to 50 mum S minus 1, but but were progressively released from contact to leave the fibres in a conspicuously clean state. Inorganic pyrophosphate freed the organelles from the fibres without supporting movements. Motility required millimolar Mg2nlevels, free Ca2nat 10 minus 7 M or less and was inhibited by high levels of Clminus and by pH's on either side of 7.0. The reactivated movements were rapidly and completely inhibited by 25mug ml minus 1 cytochalasin B. The results are interpreted in terms of actin filaments in the stationary cortex interacting with a myosin-like protein which is able to link to endoplasmic organelles. Movement results from an active shear type of mechanism.

scholarly journals Interaction of Actin Filaments with the Plasma Membrane in Amoeba proteus. Studies Using a Cell Model and Isolated Plasma Membrane.

2000 ◽  
Vol 25 (4) ◽  
pp. 269-277 ◽  
Author(s):  
Tomomi Kawakatsu ◽  
Asako Kikuchi ◽  
Teruo Shimmen ◽  
Seiji Sonobe
Keyword(s):  
Plasma Membrane ◽  
Actin Filaments ◽  
Cell Model ◽  
Amoeba Proteus ◽  
A Cell

scholarly journals Effects of cytochalasin B on membrane-associated microfilaments in a cell-free system.

1981 ◽  
Vol 91 (2) ◽  
pp. 524-530 ◽  
Author(s):  
M J Phillips ◽  
M Oda ◽  
I M Yousef ◽  
K Funatsu
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
Rat Liver ◽  
Mode Of Action ◽  
Actin Filaments ◽  
Cytochalasin B ◽  
Bile Canaliculus ◽  
Free System ◽  
A Cell

The mode of action of cytochalasin B was examined in vitro using bile canaliculus-enriched plasma membrane fractions isolated from rat liver. The pericanalicular microfilaments, which are mainly actin filaments and which are normally attached to the canalicular membranes, were dissociated from the membranes by cytochalasin B treatment. A microfilamentous network was found in the supernate of the cytochalasin B treatment. A microfilamentous network was found in the supernate of the cytochalasin-treated specimens and a number of polypeptides, of which a polypeptide corresponding in molecular weight to actin was a notable member. These results suggest that actin filaments become detached from the canaliculus membranes by cytochalasin B.

scholarly journals Mechanism of Ca2+ inhibition of cytoplasmic streaming in lily pollen tubes

1988 ◽  
Vol 91 (4) ◽  
pp. 501-509 ◽  
Author(s):  
TADASHI KOHNO ◽  
TERUO SHIMMEN
Keyword(s):  
Actin Filaments ◽  
Cytoplasmic Streaming ◽  
Lilium Longiflorum ◽  
Pollen Tubes ◽  
Ionophore A23187 ◽  
Filamentous Actin ◽  
Actin Bundles ◽  
Lily Pollen ◽  
Subsequent Decrease

Using a Ca2+ ionophore, A23187, the free Ca2+ concentration ([Ca2+]) in the cytoplasm of pollen tubes of Lilium longiflorum was controlled from the cell exterior. At [Ca2+] higher than 1.0x10−5M (pCa5.0), cytoplasmic streaming was inhibited, and the inhibition was irreversible. The ATP content did not change, but actin filaments were fragmented and formed aggregates. A subsequent decrease in [Ca2+] almost stopped the progress of the actin filament fragmentation, but filamentous actin did not re-form from the fragmented actin. In a previous paper, we reported that pollen tube organelle movement along characean actin bundles was inhibited by Ca2+ at 10−5M levels and the inhibition was reversible. In the present study, the reversibility was also demonstrated using an in situ Ca2+ treatment. Organelles were isolated from pollen tubes that had been treated with high [Ca2+] and A23187. They moved along characean actin bundles in Ca2+-free medium. It is concluded that Ca2+ inhibition of cytoplasmic streaming can be attributed to both inactivation of myosin and fragmentation of actin. The irreversibility of Ca2+ inhibition in situ is attributed to the irreversible fragmentation of actin filaments.

INVERSE UNCERTAINTY QUANTIFICATION OF A CELL MODEL USING A GAUSSIAN PROCESS METAMODEL

2020 ◽  
Vol 10 (4) ◽  
pp. 333-349
Author(s):  
Kevin de Vries ◽  
Anna Nikishova ◽  
Benjamin Czaja ◽  
Gábor Závodszky ◽  
Alfons G. Hoekstra
Keyword(s):  
Gaussian Process ◽  
Uncertainty Quantification ◽  
Cell Model ◽  
A Cell

Preincubation with Sn-complexes causes intensive intracellular retention of 99mTc in thyroid cells in vitro

2012 ◽  
Vol 51 (05) ◽  
pp. 179-185 ◽  
Author(s):  
M. Wendisch ◽  
D. Aurich ◽  
R. Runge ◽  
R. Freudenberg ◽  
J. Kotzerke ◽  
...  
Keyword(s):  
Cell Model ◽  
Low Energy ◽  
Thyroid Cells ◽  
Low Energy Electrons ◽  
A Cell ◽  
Vitro Model ◽  
Uptake Studies ◽  
Radiobiological Effects ◽  
Radioactivity Retention

SummaryTechnetium radiopharmaceuticals are well established in nuclear medicine. Besides its well-known gamma radiation, 99mTc emits an average of five Auger and internal conversion electrons per decay. The biological toxicity of these low-energy, high-LET (linear energy transfer) emissions is a controversial subject. One aim of this study was to estimate in a cell model how much 99mTc can be present in exposed cells and which radiobiological effects could be estimated in 99mTc-overloaded cells. Methods: Sodium iodine symporter (NIS)- positive thyroid cells were used. 99mTc-uptake studies were performed after preincubation with a non-radioactive (cold) stannous pyro - phosphate kit solution or as a standard 99mTc pyrophosphate kit preparation or with pure pertechnetate solution. Survival curves were analyzed from colony-forming assays. Results: Preincubation with stannous complexes causes irreversible intracellular radioactivity retention of 99mTc and is followed by further pertechnetate influx to an unexpectedly high 99mTc level. The uptake of 99mTc pertechnetate in NIS-positive cells can be modified using stannous pyrophosphate from 3–5% to >80%. The maximum possible cellular uptake of 99mTc was 90 Bq/cell. Compared with nearly pure extracellular irradiation from routine 99mTc complexes, cell survival was reduced by 3–4 orders of magnitude after preincubation with stannous pyrophosphate. Conclusions: Intra cellular 99mTc retention is related to reduced survival, which is most likely mediated by the emission of low-energy electrons. Our findings show that the described experiments constitute a simple and useful in vitro model for radiobiological investigations in a cell model.

scholarly journals Gambogic acid protects LPS-induced apoptosis and inflammation in a cell model of neonatal pneumonia through the regulation of TrkA/Akt signaling pathway

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Xu Gao ◽  
Jingya Dai ◽  
Guifang Li ◽  
Xinya Dai
Keyword(s):  
Western Blot ◽  
Signaling Pathway ◽  
Cell Model ◽  
Akt Signaling ◽  
Gambogic Acid ◽  
Akt Signaling Pathway ◽  
Western Blot Assay ◽  
A Cell ◽  
Induced Apoptosis ◽  
Apoptosis And Inflammation

Abstract Objective In this work, we investigated the effects of gambogic acid (GA) on lipopolysaccharide (LPS)-induced apoptosis and inflammation in a cell model of neonatal pneumonia. Method Human WI-38 cells were maintained in vitro and incubated with various concentrations of GA to examine WI-38 survival. GA-preincubated WI-38 cells were then treated with LPS to investigate the protective effects of GA on LPS-induced death, apoptosis and inflammation. Western blot assay was utilized to analyze the effect of GA on tropomyosin receptor kinase A (TrkA) signaling pathway in LPS-treated WI-38 cells. In addition, human AKT serine/threonine kinase 1 (Akt) gene was knocked down in WI-38 cells to further investigate the associated genetic mechanisms of GA in protecting LPS-induced inflammation and apoptosis. Results Pre-incubating WI-38 cells with low and medium concentrations GA protected LPS-induced cell death, apoptosis and inflammatory protein productions of IL-6 and MCP-1. Using western blot assay, it was demonstrated that GA promoted TrkA phosphorylation and Akt activation in LPS-treated WI-38 cells. Knocking down Akt gene in WI-38 cells showed that GA-associated protections against LPS-induced apoptosis and inflammation were significantly reduced. Conclusions GA protected LPS-induced apoptosis and inflammation, possibly through the activations of TrkA and Akt signaling pathway. This work may broaden our understanding on the molecular mechanisms of human neonatal pneumonia.

scholarly journals Positively Charged Lipid as Potential Tool to Influence the Fate of Ethosomes

2021 ◽  
Vol 11 (15) ◽  
pp. 7060
Author(s):  
Antonia Mancuso ◽  
Maria Chiara Cristiano ◽  
Massimo Fresta ◽  
Daniele Torella ◽  
Donatella Paolino
Keyword(s):  
Cell Model ◽  
Human Keratinocytes ◽  
Skin Delivery ◽  
Physico Chemical ◽  
Cell Mortality ◽  
Mean Size ◽  
A Cell ◽  
Negative Surface ◽  
Cytotoxic Studies

Ethosomes® are one of the main deformable vesicles proposed to overcome the stratum corneum. They are composed of lecithin, ethanol and water, resulting in round vesicles characterized by a narrow size distribution and a negative surface charge. Taking into account their efficiency to deliver drugs into deeper skin layers, the current study was designed to evaluate the influence of different lipids on the physico-chemical features of traditional ethosomes in the attempt to influence their fate. Three lipids (DOPE, DSPE and DOTAP) were used for the study, but only DOTAP conferred a net positive charge to ethosomes, maintaining a narrow mean size lower than 300 nm and a good polydispersity index. Stability and in vitro cytotoxic studies have been performed using Turbiscan Lab analysis and MTT dye exclusion assay, respectively. Data recorded demonstrated the good stability of modified ethosomes and a reasonable absence of cell mortality when applied to human keratinocytes, NCTC 2544, which are used as a cell model. Finally, the best formulations were selected to evaluate their ability to encapsulate drugs, through the use of model compounds. Cationic ethosomes encapsulated oil red o and rhodamine b in amounts comparable to those recorded from conventional ethosomes (over 50%). Results recorded from this study are encouraging as cationic ethosomes may open new opportunities for skin delivery.

Steam temperature regulation characteristics in a flexible ultra-supercritical boiler with a double reheat cycle based on a cell model

Energy ◽  
2021 ◽  
Vol 229 ◽  
pp. 120701
Author(s):  
Haojie Fan ◽  
Wei Xu ◽  
Jian Zhang ◽  
Zhongxiao Zhang
Keyword(s):  
Temperature Regulation ◽  
Cell Model ◽  
Steam Temperature ◽  
A Cell
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