Cytoplasmic streaming

Controls for Membrane Impermeance. Some fluoro-chromes can enter protoplasts via probenecid-sensitive anion channels (19) and control experiments must establish membrane impermeance. Soak the tissues in the fluorochrome at the concentration used for up to 12 h, rinsing and examining the tissues for fluorescence at hourly intervals. Cell viability is assessed by rate of cytoplasmic streaming, or by chloroplast autofluorescence, which declines in dead cells. 

Actin filaments are the thinnest of the cytoskeletal filaments, and therefore also called microfilaments. Polymerized actin monomers form long, thin fibers of about 8 nm in diameter. Along with the above-mentioned function of the cytoskeleton, actin interacts with myosin ( thick ) filaments in skeletal muscle fibers to provide the force of muscular contraction. Actin/Myosin interactions also help produce cytoplasmic streaming in most cells. 

It acts as the motor for movement of animal cells. Not only muscle cells (see p. 332), but also cells of noncontractile tissues contain many different motor proteins, which they use to achieve coordinated and directed movement Cell movement shape changes during growth, cytoplasmic streaming, and cell division are all made possible by components of the cytoskeleton. 

Aim to inject into the cytoplasm or the high yolk, just below the cytoplasm. You may need to roll the embryo in its chorion to get a good angle. Cytoplasmic streaming will then carry the injectable up into the cell (see Note 11). 

Intracellular movement None Cytoplasmic streaming, endocytosis, phagocytosis, mitosis, vesicle transport... 

Ameboid movements of protozoa and of cells from higher organisms, the ruffling movements of cell membranes, phagocystosis, and the cytoplasmic streaming characteristic of many plant cells2893 have all been traced to actin filaments or actin cables rather... 

While other plant studies were conducted relative to other morphological observations and interactions with exogenously applied plant growth regulators such as indole-3-acetic acid and abscisic acid, the major message was that CB influenced cytoplasmic streaming, but not cell division perse, in plants. 

The role of the position of microfilaments in cells relative to cytoplasmic streaming were generally conducted in early 1962 as problems to be solved in plant physiology24,25,30 31,33,41 and in retrospect it seems strange that later work evaluating the potential effects on mitosis were not reported earlier, albeit that the effects were nil ... 

Streaming and microfilaments in cells have an intimate relationship in that the microfilaments most likely supply the moving force that governs streaming. Importantly, the microfilaments are in bundles and are proximal to the cytoplasmic stream and account for the relationship, and here exogenously applied CB has produced some interesting results. 

In 1972, Williamson43 used two organisms, Chara corralina and Nitella translucens, to examine the effects of CB on cytoplasmic streaming. Whole cells from rhizoidal and small leaf internode tissue were treated with the metabolite at concentrations of 1-50 pg/mL in dimethylsulfoxide (DMSO). There was a concentration, time dependent result so that 50 pg/mL inhibited streaming in a few minutes, whereas it took 6 h to induce the same effect with 1 pg/mL. Washing the cells with a DMSO solution, used at the same concentration in which the CB had... 

O Brien, T. P. and Thimann, K. V. 1966. Intracellular fibers in oat coleoptile cells and their possible significance in cytoplasmic streaming. Proc. Nat. Acad. Sci. 56, 888-894... 

Actin filaments are about 6imi in diameter and composed of two intertwined actin chains. They are mostly concentrated just beneath the cell membrane, and are responsible for resisting tension and maintaining cellular shape, and participating in ceU-cell and cell-matrix junctions in these latter roles they are essential to intracellular signal transduction processes. They are also important for cytokinesis (division of the cytoplasm in mitosis) and cytoplasmic streaming in most cells. 

They can grow large because cytoplasmic streaming allows rapid transport across the cell -100 jim. 

Microfilaments, which are small (5-7 nm in diameter) fibers composed of the protein actin, perform their functions by interacting with certain cross-linking proteins. Important roles of microfilaments include involvement in cytoplasmic streaming (a process that is most easily observed in plant cells in which cytoplasmic currents rapidly displace organelles such as chloroplasts) and ameboid movement (a type of locomotion created by the formation of temporary cytoplasmic protrusions). 

Facilitation of coherent cellular movement. Large-scale cellular movement such as the cytoplasmic streaming that occurs in plant cells and the ameboid movement seen in some animal cells is made possible by a dynamic cytoskeleton that can rapidly assemble and disassemble its structural elements according to the cell s immediate needs. 

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