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K T Edds

Publications and source records attributed to K T Edds.

13 recordsLinked to original sources
PubMed1993

Effects of cytochalasin and colcemid on cortical flow in coelomocytes.

Sea urchin coelomyocytes naturally flatten on a substratum into a discoid morphology and display striking, centripetally directed cortical flow along the radii of the cell when viewed with time lapse, video enhanced microscopy. The rate of cortical flow averaged 4.5 microns/min in the peripheral most 10 microns of cytoplasm but slows considerably in the perinuclear region. Cytochalasin B causes: (1) the flow to stop, (2) the buildup of an actin filament-rich peripheral ridge of cytoskeletal material, (3) the centrifugal dissolution of a portion of the actin cytoskeleton, and (4) the contraction of other portions of the cytoskeleton into foci. Cytochalasin D (CD), on the other hand, causes the flowing actin meshwork to become severed from the edge of the cell and allows it to be drawn at least part way in towards the nucleus. A smaller peripheral ridge of actin filament buildup is also seen with CD. Colcemid induces another striking change in the cytoskeleton. The centripetal progression of the actin is not stopped by colcemid, but shortly after leaving the periphery of the cell, the linear elements within the flow become reoriented into arcs. The long axis of the arcs is roughly parallel with the cell's edge. The effects of all three drugs are reversible. The results are discussed in light of other systems and potential mechanisms for cortical flow.

Actin Cytoskeleton↗
PubMed1983

Coelomocyte motility.

We have utilized a video-enhanced contrast system coupled to a DIC-equipped microscope to examine the motility of both whole coelomocytes and individual filopodia. When the cells are left in diluted coelomic fluid, they exhibit a fibroblast-like mode of translocation across the substrate. These cells extend lamellipodia at their advancing margin and develop retraction fibers at the trailing edge. Filopodia are actively extended from the lamellipodia of the advancing margin. Cells that are washed free of the coelomic fluid and placed in an isotonic buffer lose their ability to translocate. Filopodia on these stationary cells are seen to undergo a series of waving and bending motions. These motions are rapid and result in a filopodium folding back upon itself only to re-extended later. Both forms of motility are discussed in light of the existing structural and biochemical knowledge of this and other cell types.

Animals↗
PubMed1983

Coelomocyte spectrin.

We have investigated the presence and localization of an alpha-spectrinlike protein and its potential role in the morphological transformation of sea urchin coelomocytes. In immunofluorescence images there is a diffuse fluorescence throughout the petaloid cytoplasm, indicating a random distribution of the spectrinlike protein prior to the transformation. As these cells from filopodia, there is a coincident appearance of a spectrinlike protein, as seen in fluorescent images, at the site of filopodial initiation. As the filopodia continue to form and lengthen, the spectrin localization parallels their development. There is a single polypeptide observed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gels of whole coelomocyte lysates that cross-reacts with the anti-alpha-spectrin immunogen and comigrates with it at 240 kilodaltons.

Animals↗
PubMed1981

Cytoplasmic streaming in a heliozoan.

A method is described utilizing deuterium oxide stabilization of microtubules that allows the separation of stable axopodia from the cell body. In some instances the isolated axopodia are broken open and display two classes of cytoplasmic linear elements, microtubules and microfilaments, lying side by side. This morphological arrangement is consistent with the hypothesis that microtubules support a microfilament-based contractile apparatus in heliozoans and probably other cell types as well. Also included is a description of pseudopodial formation from axopodial cytoplasm in response to mechanical stimulation. The pseudopodial motility is discussed in relation to the particle saltations also observed in these cells and to different levels of organization or activation of the contractile machinery.

Animals↗
PubMed1980

The formation and elongation of filopodia during transformation of sea urchin coelomocytes.

Sea urchin coelomocytes were examined during their morphological transformation from petaloid to filopodial forms by scanning electron microscopy and ciné film analysis, Petaloid coelomocytes have a variable morphology but, in general, consist of numerous thin sheets of cytoplasm, the petals, arranged in three dimensions around a central nuclear region. The transition to the filopodial form can occur in either substrate-attached or suspended cells and begins with the formation of several microspikes at the edge of each petal. These become more apparent as the cytoplasm between each microspike/filopodium is retracted centripetally. Concomitantly, the diameter of the flattened cell is increased by as much as twofold as the filopodia actively lengthen at a uniform, average rate of 0.5 microns/minute. The transformation process requires ca 15 minutes and is complete when the cell diameter no longer increases. These filopodia are functionally distinct from the passively produced retraction fibers observed in cultured mammalian cells. The formation of filopodia is biphasic and includes both a cytoplasmic retraction phase and an active extension phase.

Actins↗
PubMed1979

Isolation and characterization of two forms of a cytoskeleton.

Isolated petaloid coelomocytes from the sea urchin Strongylocentrotus droebachiensis transform to a filopodial morphology in hypotonic media. Electron micrographs of negatively stained Triton-insoluble cytoskeletons show that the petaloid form consists of a loose net of microfilaments while the filopodial form consists of paracrystalline bundles of microfilaments. Actin is the major protein of both forms of the cytoskeleton. Additional polypeptides have molecular weights of approximately 220,000, 64,000, 57,000, and 27,000 daltons. Relative to actin the filopodial cytoskeletons have an average of 2.5 times as much 57k polypeptide as the petaloid cytoskeletons. Treatment with 0.25 M NaCl dissociates the filament bundles into individual actin filaments free of the actin-associated polypeptides. Thus, one or more of these actin-associated polypeptides may be responsible for crosslinking the actin filaments into bundles and maintaining the three-dimensional nature of the cytoskeletons.

Actins↗
PubMed1977

Dynamic aspects of filopodial formation by reorganization of microfilaments.

The coelomocytes of the sea urchin, Strongylocentrotus droebachiensis, may be prevented from clotting with 50 mM ethylene glycol-bis(beta-aminoethyl)-N,N,N',N'-tetraacetate, 50 mM Tris-HCl, pH 7.8 and subsequently separated into various cell types on sucrose gradients. One cell type, the petaloid coelomocyte, spontaneously undergoes a striking morphological transformation to a form exhibiting numerous, t-in cytoplasmic projections (filopodia). Moreover, the transformation is reversible. Ultrastructurally, the formation of the filopodia results from a progressive reorganization of actin-containing filaments into bundles that are radially oriented. The formation of the filament bundles is initiated at the cell's periphery and proceeds inward. Simultaneously, the cytoplasm in between the bundles is withdrawn, exposing finger-like filopodia. Ultimately, the filopodia can be extended by up to four times their original length. Biochemically, actin is the most abundant protein in while cell homogenates and is extractable in milligram quantities via acetone powders. An actomyosin complex may also be isolated from these cells and is presumed to be active in producing the various forms of motility observed.

Actins↗
PubMed1975

Motility in Echinosphaerium nucleofilum. I. An analysis of particle motions in the axopodia and a direct test of the involvement of the axoneme.

The motion of particles in the axopodia of Echinosphaerium nucleofilum is saltatory. In the present study, photokymograph records of 123 motions from six axopodia have been analyzed. Particles followed rectilinear paths of from 1 to 15 mum while in continuous motion at an average velocity of 0.66 plus or minus 0.32 mum/s. The velocity of the particles was variable in 36% of the cases measured. Some motions were punctuated by pauses either before continuing in the same direction or reversing. Frequently, several particles were moving at the same velocity, but neighboring particles showed no motion or moved in the opposite direction. Two particles occasionally contacted one another and travelled as a unit for varying lengths of time but subsequently moved independently. These motions reflect the underlying mechanism of motive force production. Furthermore, a glass microneedle can be substituted for the microtubular axoneme in the axopodia. In these artificial axopodia, bidirectional particle motions occurred which were similar to those in normal axopodia. Colchicine, at the threshold dose for axonemal dissolution, had no affect on these particel motions. It is concluded that the microtubular axoneme is not responsible for particle motions and also that individual microtubules are unlikely candidates for motive force production in this system.

Animals↗
PubMed1975

Motility in Echinosphaerium nucleofilum. II. Cytoplasmic contractility and its molecular basis.

Echinosphaerium nucleofilum exhibits at least three kinds of movement: locomotion by the bending and shortening of its many axopodia, feeding by means of food-cup pseudopodia formed from its cortical cytoplasm, and saltatory motion of cytoplasmic particles, especially in the cortex and axopodia. Since previously presented evidence indicated that the microtubular axoneme is not essential for particle motion, the cytoplasm was investigated for the possible existence of contractile behavior and for the possible presence of linear elements other than microtubules. Cytoplasm can be isolated in physiological media in which rigor, relaxation, and contraction can be induced, as in muscle, by manipulating the concentrations of calcium ions and magnesium-adenosine triphosphate. Contraction is initiated by calcium ions at concentrations above 2.4 times 10-minus 7 M. The rigor-to-relaxation transition occurs at subthreshold calcium concentrations on the addition of 10-minus 3 M ATP. Negatively stained preparations of isolated cytoplasm show two types of filaments: thin filaments identified as cytoplasmic actin by virtue of their binding heavy meromyosin from striated muscle in characteristic arrowhead arrays, and thicker filaments which do not strictly resemble myosin aggregates from muscle or amoeba but could conceivably by myosin aggregated in an unfamiliar form.

Actins↗