scholarly journals Studies in the Metabolism of Plant Cells

1955 ◽  
Vol 8 (2) ◽  
pp. 164 ◽  
Author(s):  
RN Robertson ◽  
Marjorie J Wilkins ◽  
AB Hope ◽  
Lydia Nestel
Keyword(s):  
Surface Membrane ◽  
Diffusion Constant ◽  
Plant Cells ◽  
Membrane Thickness ◽  
Ionic Balance ◽  
Animal Cells ◽  
Concentration Difference ◽  
Donnan Equilibrium ◽  
Mobile Anions ◽  
Order Of Magnitude

The respiratory activity and ionic balance of mitochondria isolated from carrot and beet tissues by differential centrifugation have been studied. The oxygen uptake of the mitochondria with different substrates was investigated. The mitochondria hold both cations and anions in concentrations greater than those in the supernatant. Experiments on the time of adjustment to a changed concentration of chloride in the supernatant solution have been used to calculate the diffusion constant of salt in the particle. On the assumption that most of the resistance to diffusion is in the surface membrane (thickness about 200 A), the apparent diffusion constant of chloride in the membrane was shown to be of the order of 10-1:> cm~/sec. This agrees with that found for heart muscle sarcosomes under similar conditions and is of the order expected in a !ipo-protein membrane. The concentrations of mobile cations (Na + and K +) in the mitochondria are considerably greater than those in the supernatant. It is suggested that the internal concentrations are largely due to a Donnan equilibrium based on the immobile anions of the particle. Since no simple Donnan equilibrium will account for the simultaneous concentration of both mobile cations and mobile anions, it is suggested that the mobile anions might be accumulated by an accumulatory mechanism. The anion concentration difference between the inside and outside of the particles is of the order of magnitude to be expected if the electron carrier of� respiration were acting as the anion carrier of accumulation. The results are therefore not inconsistent with the em'lier hypotheses for the interdependence of the two processes. The results support the hypothesis that mitochondria are probably involved in electrolyte accumulation in plant cells and in secretion in animal cells such as those of the gastric mucosa.

Experimental Investigation of Effects of Extrusion Pressure on Cell Growth of Bioprinted Algae Cells in Green Bioprinting

2020 ◽  
Author(s):  
Laura Jerpseth ◽  
Ketan Thakare ◽  
Zhijian Pei ◽  
Hongmin Qin
Keyword(s):  
Cell Growth ◽  
Cell Count ◽  
Plant Cells ◽  
Extrusion Pressure ◽  
Layer By Layer ◽  
Animal Cells ◽  
Physical Damage ◽  
The Third ◽  
Cell Counts ◽  
The Difference

Abstract In bioprinting, biomaterials are deposited layer-by-layer to fabricate structures. Bioprinting has many potential applications in drug screening, tissue engineering, and regenerative medicine. Both animal cells and plant cells can be used to synthesize bioinks. Green bioprinting uses bioinks that have been synthesized using plant cells. Constructs fabricated via green bioprinting contain immobilized plant cells, with these cells arranged at desired locations. The constructs provide scaffolds for cell growth. Printing parameters affecting the growth of cells in green bioprinted constructs include print speed, needle diameter, extrusion temperature, and extrusion pressure. This paper reports a study to examine effects of extrusion pressure on cell growth (measured by cell count) in bioprinted constructs, using bioink containing Chlamydomonas reinhardtii algae cells. Three levels of extrusion pressure were used: 3, 5, and 7 bar. Cell counts in the bioprinted constructs were measured on the third and sixth days after bioprinting. It was found that, as extrusion pressure increased, cell count decreased on both the third and sixth days after bioprinting. Furthermore, the difference in cell counts between the third and the sixth days decreased as extrusion pressure increased. These trends suggest that increasing extrusion pressure during green bioprinting negatively affects cell growth. A possible reason for these trends is physical damage to or death of cells in the bioprinted constructs when extrusion pressure became higher.

The pH of Plant Cells The pH of Animal Cells

1955 ◽  
Author(s):  
James Small ◽  
Floyd J. Wiercinski
Keyword(s):  
Plant Cells ◽  
Animal Cells

The Cell's Biological Rods and Ropes

MRS Bulletin ◽  
1999 ◽  
Vol 24 (10) ◽  
pp. 27-31 ◽  
Author(s):  
David Boal
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Chemical Composition ◽  
Intermediate Filaments ◽  
Plant Cells ◽  
Cell Type ◽  
Animal Cells ◽  
Limited Variation ◽  
A Cell ◽  
Mechanical Elements

Despite a variety of shapes and sizes, the generic mechanical structure of cells is remarkably similar from one cell type to the next. All cells are bounded by a plasma membrane, a fluid sheet that controls the passage of materials into and out of the cell. Plant cells and bacteria reinforce this membrane with a cell wall, permitting the cell to operate at an elevated osmotic pressure. Simple cells, such as the bacterium shown in Figure 1a, possess a fairly homogeneous interior containing the cell's genetic blueprint and protein workhorses, but no mechanical elements. In contrast, as can be seen in Figure 1b, plant and animal cells contain internal compartments and a filamentous cytoskeleton—a network of biological ropes, cables, and poles that helps maintain the cell's shape and organize its contents.Four principal types of filaments are found in the cytoskeleton: spectrin, actin, microtubules, and a family of intermediate filaments. Not all filaments are present in all cells. The chemical composition of the filaments shows only limited variation from one cell to another, even in organisms as diverse as humans and yeasts. Membranes have a more variable composition, consisting of a bi-layer of dual-chain lipid molecules in which are embedded various proteins and frequently a moderate concentration of cholesterol. The similarity of the cell's mechanical elements in chemical composition and physical characteristics encourages us to search for universal strategies that have developed in nature for the engineering specifications of the cell. In this article, we concentrate on the cytoskeleton and its filaments.

scholarly journals Dynamic continuity of cytoplasmic and membrane compartments between plant cells.

1988 ◽  
Vol 106 (3) ◽  
pp. 715-721 ◽  
Author(s):  
O Baron-Epel ◽  
D Hernandez ◽  
L W Jiang ◽  
S Meiners ◽  
M Schindler
Keyword(s):  
Cell Communication ◽  
Plant Cells ◽  
Tumor Promoter ◽  
Ionophore A23187 ◽  
Animal Cells ◽  
Root Cells ◽  
Dynamic Membrane ◽  
Membrane Compartments ◽  
Intercellular Movement ◽  
Soybean Cell

Fluorescence photobleaching was employed to examine the intercellular movement of fluorescein and carboxyfluorescein between contiguous soybean root cells (SB-1 cell line) growing in tissue culture. Results of these experiments demonstrated movement of these fluorescent probes between cytoplasmic (symplastic) compartments. This symplastic transport was inhibited with Ca2+ in the presence of ionophore A23187, and also with the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Both of these agents have previously been demonstrated to inhibit gap junction-mediated cell-cell communication in animal cells. In a companion experiment, a fluorescent phospholipid analogue, N-4-nitrobenzo-2-oxa-1,3-diazole phosphatidylcholine (NBD-PC), was incorporated into soybean cell membranes to examine whether dynamic membrane continuity existed between contacting cells, a transport route not existing between animal cells. Photobleaching single soybean cells growing in a filamentous strand demonstrated that phospholipid did exchange between contiguous cells.

scholarly journals iDePP: a genetically encoded system for the inducible depletion of PI(4,5)P2 in Arabidopsis thaliana

2020 ◽  
Author(s):  
Mehdi Doumane ◽  
Léia Colin ◽  
Alexis Lebecq ◽  
Aurélie Fangain ◽  
Joseph Bareille ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Plasma Membrane ◽  
Protein Localization ◽  
Cortical Microtubule ◽  
Plant Cells ◽  
Actin Dynamics ◽  
Animal Cells ◽  
Compensatory Mechanisms ◽  
Microtubule Organization ◽  
Membrane Contact Sites

ABSTRACTPhosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is a low abundant lipid present at the plasma membrane of eukaryotic cells. Extensive studies in animal cells revealed the pleiotropic functions of PI(4,5)P2. In plant cells, PI(4,5)P2 is involved in various cellular processes including the regulation of cell polarity and tip growth, clathrin-mediated endocytosis, polar auxin transport, actin dynamics or membrane-contact sites. To date, most studies investigating the role of PI(4,5)P2 in plants have relied on mutants lacking enzymes responsible for PI(4,5)P2 synthesis and degradation. However, such genetic perturbations only allow steady-state analysis of plants undergoing their life cycle in PI(4,5)P2 deficient conditions and the corresponding mutants are likely to induce a range of non-causal (untargeted) effects driven by compensatory mechanisms. In addition, there are no small molecule inhibitors that are available in plants to specifically block the production of this lipid. Thus, there is currently no system to fine tune PI(4,5)P2 content in plant cells. Here we report a genetically encoded and inducible synthetic system, iDePP (Inducible Depletion of PI(4,5)P2 in Plants), that efficiently removes PI(4,5)P2 from the plasma membrane in different organs of Arabidopsis thaliana, including root meristem, root hair and shoot apical meristem. We show that iDePP allows the inducible depletion of PI(4,5)P2 in less than three hours. Using this strategy, we reveal that PI(4,5)P2 is critical for cortical microtubule organization. Together, we propose that iDePP is a simple and efficient genetic tool to test the importance of PI(4,5)P2 in given cellular or developmental responses but also to evaluate the importance of this lipid in protein localization.Research OrganismA. thaliana

scholarly journals About precipitates in boron doped Si investigated by dynamical X-ray diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C1184-C1184
Author(s):  
Johannes Will ◽  
Alexander Gröschel ◽  
Erdmann Spiecker ◽  
Andreas Magerl
Keyword(s):  
Ostwald Ripening ◽  
Diffusion Constant ◽  
Misfit Strain ◽  
Dynamical Theory ◽  
Precipitation Kinetics ◽  
Precipitation Behavior ◽  
Boron Doped ◽  
Novel Approach ◽  
Long Time ◽  
Order Of Magnitude

Thickness-dependent Pendellösung oscillations as described in the dynamical theory of diffraction are highly sensitive to strain fields from defects in a host crystal. Based on this, we present a novel approach to determine the precipitation kinetics of oxygen in silicon (Si) at the early stages of clustering at high temperatures. We present in-situ measurements up to 11000C performed with the characteristic Kα1-line at 59.31 keV. The extracted static Debye-Waller factors are evaluated as a function of annealing time within a diffusion limited model of growing spherical precipitates. We investigated moderately p- ([B] ≍ 1015 1/cm3) and highly p+ ([B] ≍ 1018 1/cm3) boron doped Czochralski Si crystals at different nucleation and growth temperatures to determine the nucleation and precipitation kinetics as well as the long time precipitation behavior. At 6500C the diffusion constant found is enhanced compared to the extrapolated value for normal diffusion [1], and it is one order of magnitude lower compared to SIMS data [2]. However, it is close to the value obtained from dislocation unlocking experiments [3]. Moreover, the nucleation rates in p+ material are enhanced at 4500C and 7800C compared to the p- samples. The acceleration at 4500C can be explained with boron enhanced oxygen dimer diffusion, whereas the nucleation rate at 7800C is much too high to be accounted for by the enhanced oxygen dimer diffusivity alone. An analysis of the misfit strain yields a platelet morphology of the precipitates with a higher aspect ratio in the p- than in the p+ case. The long time precipitation behavior at 9000C shows a second growth regime of comparable amplitude in both materials. This can be interpreted as Ostwald ripening and gives access to the surface energy of the precipitates.

scholarly journals Combined microspectrophotometry and automated quantitative autoradiography applied to the analysis of the plant cell cycle

1979 ◽  
Vol 39 (1) ◽  
pp. 235-245
Author(s):  
A.R. Gould
Keyword(s):  
Cell Cycle ◽  
Plant Cells ◽  
Cell Cycle Phase ◽  
Cycle Phase ◽  
Plant Protoplasts ◽  
Animal Cells ◽  
Grain Number ◽  
Virus Particles ◽  
Before And After ◽  
Silver Grains

Two methods, which relate grain number to cell cycle phase in Feulgen-stained autoradiographic preparations, have been developed and compared. Both methods automate grain number estimations, one by taking integrated absorbance measurements at different wavelengths, the other by measuring absorption at a single wavelength before and after chemical removal of silver grains. With tritium-labelled tobacco mosaic virus as a probe, a quantitative analysis has been made of the binding of virus particles to plant protoplasts in different compartments of the DNA replication and partition cycle. The preliminary results indicate that the quantity of virus bound by protoplasts is related to their cell cycle phase. Whilst in this case, the methods have been used with plant cells, both techniques are equally applicable to animal cells.

scholarly journals Cytoskeletal organization in isolated plant cells under geometry control

2020 ◽  
Vol 117 (29) ◽  
pp. 17399-17408 ◽  
Author(s):  
Pauline Durand-Smet ◽  
Tamsin A. Spelman ◽  
Elliot M. Meyerowitz ◽  
Henrik Jönsson
Keyword(s):  
Cell Shape ◽  
Flexural Rigidity ◽  
Persistence Length ◽  
Plant Cells ◽  
Cytoskeletal Proteins ◽  
Three Dimensions ◽  
Animal Cells ◽  
Living Plant ◽  
Cytoskeletal Organization ◽  
Actin Organization

The cytoskeleton plays a key role in establishing robust cell shape. In animals, it is well established that cell shape can also influence cytoskeletal organization. Cytoskeletal proteins are well conserved between animal and plant kingdoms; nevertheless, because plant cells exhibit major structural differences to animal cells, the question arises whether the plant cytoskeleton also responds to geometrical cues. Recent numerical simulations predicted that a geometry-based rule is sufficient to explain the microtubule (MT) organization observed in cells. Due to their high flexural rigidity and persistence length of the order of a few millimeters, MTs are rigid over cellular dimensions and are thus expected to align along their long axis if constrained in specific geometries. This hypothesis remains to be testedin cellulo. Here, we explore the relative contribution of geometry to the final organization of actin and MT cytoskeletons in single plant cells ofArabidopsis thaliana. We show that the cytoskeleton aligns with the long axis of the cells. We find that actin organization relies on MTs but not the opposite. We develop a model of self-organizing MTs in three dimensions, which predicts the importance of MT severing, which we confirm experimentally. This work is a first step toward assessing quantitatively how cellular geometry contributes to the control of cytoskeletal organization in living plant cells.

Repairing a torn cell surface: make way, lysosomes to the rescue

2002 ◽  
Vol 115 (5) ◽  
pp. 873-879 ◽  
Author(s):  
Paul L. McNeil
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Actin Polymerization ◽  
Surface Membrane ◽  
Cell Cortex ◽  
Yolk Granule ◽  
Protein Markers ◽  
Filamentous Actin ◽  
Animal Cells ◽  
Fusion Plasma

Biological membranes are often described as `self-sealing' structures. If indeed membranes do have an inherent capacity for repair, does this explain how a cell can rapidly reseal a very large (1-1000 μm2)disruption in its plasma membrane? It is becoming increasingly clear that, in nucleated animal cells, the cytoplasm plays an active and essential role in resealing. A rapid and apparently chaotic membrane fusion response is initiated locally in the cytoplasm by the Ca2+ that floods in through a disruption: cytoplasmic vesicles are thereby joined with one another(homotypically) and with the surrounding plasma membrane (exocytotically). As a consequence, internal membrane is added to cell surface membrane at the disruption site. In the case of large disruptions, this addition is hypothesized to function as a `patch'. In sea urchin eggs, the internal compartment used is the yolk granule. Several recent studies have significantly advanced our understanding of how cells survive disruption-inducing injuries. In fibroblasts, the lysosome has been identified as a key organelle in resealing. Protein markers of the lysosome membrane appear on the surface of fibroblasts at sites of disruption. Antibodies against lysosome-specific proteins, introduced into the living fibroblast,inhibit its resealing response. In gastric eptithelial cells, local depolymerization of filamentous actin has been identified as a crucial step in resealing: it may function to remove a barrier to lysosome-plasma membrane contact leading to exocytotic fusion. Plasma membrane disruption in epithelial cells induces depolymerization of cortical filamentous actin and, if this depolymerization response is inhibited, resealing is blocked. In the Xenopus egg, the cortical cytoskeleton has been identified as an active participant in post-resealing repair of disruption-related damage to underlying cell cortex. A striking, highly localized actin polymerization response is observable around the margin of cortical defects. A myosin powered contraction occurring within this newly formed zone of F-actin then drives closure of the defect in a purse-string fashion.

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