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PubMed1997

[The ways of transmission of liver cell cytoplasma components to differential erythroblasts in erythropoiesis].

Intercellular interactions consisting of cytoplasmatic bridges and net-like ductal structures were revealed while electron-microscopic investigation in erythropoietic foci of hepar of mammals and amphibians. Hepatic microenvironment cells may influence the erythroblasts via the vascular net of the blood-producing foci and via the cytoplasm of interspaced cells of microenvironment of another kind. The presence of such morphologic structures makes possible to suppose the possibility of transit of ribosomes, protein molecules, lipids and other components of the microenvironmental cells cytoplasm into differentiating erythroblasts. Significant acceleration of maturing process of the red blood cells in erythropoietic foci was promoted by entrance of the cytoplasm components of the microenvironmental cells into erythroblasts.

Animals↗
PubMed1986

Confirmation of gravisensitivity in the slime mold Physarum polycephalum under near weightlessness.

We have investigated Physarum polycephalum, a unicellular organism with no special gravity receptors, on its ability to react to gravity. The first experiments were 0 g-simulation experiments on the fast-rotating clinostat conducted with plasmodial strands of this acellular slime mold. In these earth-bound experiments the observed parameters were periodicity of the contractions and dilatations of the strand's ectoplasm as well as the periodicity and velocity of the striking cytoplasmic (endoplasmic) shuttle streaming. During 0 g-simulation these parameters showed significant changes indicating the existence of a gravisensitivity of the slime mold. The Space-Shuttle experiment (ESA-Biorack in D 1-Mission) should demonstrate the validity of the 0 g-simulation on the fast-rotating clinostat. The experiment was designed in a way enabling the registration of the same parameters as on the clinostat (using the light microscope in combination with a photo diode and a cinecamera). Only one of the two planned measurement sessions was fully successful and provided us with data confirming the results gained on the fast-rotating clinostat: The slime mold showed under real near weightlessness in the D 1-Space Shuttle Mission a transient frequency increase in tis contraction rhythmicity and a (steady) increase in the streaming velocity of its endoplasm.

Animals↗
PubMed1996

Cytomorphologic characteristics of thermal injury related to endocervical brushing following loop electrosurgical excision procedure (LEEP).

Loop electrosurgical excision procedure (LEEP) is gaining popularity in the United States as an alternative to other ablative and cone methods of treatment for preneoplastic conditions of the uterine cervix. The major advantage is that it is an outpatient procedure using local anesthesia. Post-LEEP evaluation of the endocervical canal can be accomplished by either endocervical curettage or cytobrush. We reviewed the immediate post-LEEP cytobrushes from 33 patients. Artifact related to the procedure was seen in all cases and included: 1) elongated endocervical cells with cytoplasmic "tails" and streaming nuclei ("taffy pulled"); 2) loose cellular aggregates with coalesced cytoplasm and "hockey stick" nuclei; 3) sheets of cells with frothy cytoplasm and shrunken thumbprinted nuclei; 4) nuclear enlargement; and 5) smudgy nuclear chromatin. The background ranged from bloody coagulum to watery proteinaceous material. Original diagnoses were negative in 25 cases. Eleven (44%) were considered abnormal on review. Of these, four were interpreted as having squamous intraepithelial lesions (SIL), one was atypical squamous cells of undetermined significance (ASCUS), and six had atypical glandular cells of undetermined significance (AGUS). It was not always possible to grade the degree of dysplasia. There was review agreement with 14 negatives, one SIL, one ASCUS, and one unsatisfactory specimen. Three AGUS were upgraded to SIL, and one unsatisfactory specimen was considered atypical on review. In conclusion it is possible to separate artifact from actual pathology on post-LEEP cytobrush specimens. Recognition of the characteristic changes seen on cytologic specimens obtained immediately following diathermy loop treatment will allow accurate identification of true abnormalities.

Adult↗
PubMed1991

Heat-induced disturbances of intracellular movement and the consistency of the aqueous cytoplasm in HeLa S-3 cells: a laser-Doppler and proton NMR study.

Intracellular particle movements, of both saltatory and streaming types, in HeLa S-3 cells were simultaneously interrupted after 1 h exposure of cells to 43 degrees C, within 10 min at 44 degrees C and within 5 min at 45 degrees C. Intracellular movement inhibited after 15 min at 44 degrees C and 10 min at 45 degrees C was not reversible in cells rescued at 37 degrees C. Brownian motion was not observed in heat-treated cells while they were maintained at elevated temperatures, but became pronounced in blebbing which occurred shortly after they were returned to 37 degrees C. Returning these cells to 45 degrees C intensified the Brownian activity inside blebs, and rapidly induced cell lysis. The same heat-treated cells were simultaneously studied by laser-Doppler microscopy, which confirmed: a) that flow (cytoplasmic streaming) is completely arrested at 44 degrees C within 10 min, b) flow recovered in 10-15 min in cells rescued after 10-15 min at 44 degrees C, c) submicroscopic particles down to the size of water molecules had faster self-diffusion coefficients at 44 degrees C than at 37 degrees C. Proton nmr studies on cells exposed from 4 to 45 degrees C gave corrected relaxation times T1 and T2 which rose with temperature in a predictable manner. Inhibition of cellular movement at elevated temperatures was not specifically attributable to the depletion of intracellular ATP levels.

Adenosine Triphosphate↗
PubMed1997

The endomembrane sheath: a key structure for understanding the plant cell?

Recent evidence suggests that integrin is abundant in endomembranes of plant cells, and the endomembranes are clad by a sheath of cytoskeleton including F-actin. A role for endomembrane integrin and the endomembrane sheath is proposed: this system might orchestrate metabolic regulation by providing and modulating loci for channelling, and might accelerate channeling as needed by dragging the endoplasmic reticulum (ER) and organelles through the cytoplasm. To accomplish this "streaming", F-actin might lever against the rest of the endomembrane sheath and the ER might also lever against adhesion sites (i.e., plasmodesmata and plasmalemmal control centers). As an important agent in the control of cellular activities, according to this model, the endomembrane sheath would play a major part in responses to diverse signals and stresses, and under extreme stress cell survival would depend on the ability of the system to maintain enough integrity to direct critical syntheses and degradations.

Actins↗
PubMed1978

Functions of cytoplasmic fibers in intracellular movements in BHK-21 cells.

After trypsinization and replating, BHK-21 cells spread and change shape from a rounded to a fibroblastic form. Time-lapse movies of spreading cells reveal that organelles are redistributed by saltatory movements from a juxtanuclear position into the expanding regions of cytoplasm. Bidirectional saltations are seen along the long axes of fully spread cells. As the spreading process progresses, the pattern of saltatory movements changes and the average speed of saltations increases from 1.7 MICROMETER/S during the early stages of spreading to 2.3 micrometer/s in fully spread cells. Correlative electron microscope studies indicate that the patterns of saltatory movements that lead to the redistribution of organelles during spreading are closely related to changes in the degree of assembly, organization, and distribution of microtubules and 10-nm filaments. Colchicine (10 microgram/ml of culture medium) reversibly disassembles the microtubule-10-nm filament complexes which form during cell spreading. This treatment results in the disappearance of microtubules and the appearance of a juxtanuclear accumulation of 10-nm filaments. These changes closely parallel an inhibition of saltatory movements. Within 30 min after the addition of the colchicine, pseudopod-like extensions form rapidly at the cell periphery, and adjacent organelles are seen to stream into them. The pseudopods contain extensive arrays of actinlike microfilament bundles which bind skeletal-muscle heavy meromyosin (HMM). Therefore, in the presence of colchicine, intracellular movements are altered from a normal saltatory pattern into a pattern reminiscent of the type of cytoplasmic streaming seen in amoeboid organisms. The streaming may reflect either the activity or the contractility of submembranous microfilament bundles. Streaming activity is not seen in cells containing well-organized microtubule-10-nm filament complexes.

Cell Line↗
PubMed1989

Rapid deformation of "passive" polymorphonuclear leukocytes: the effects of pentoxifylline.

Entry times for spherical (no pseudopods) polymorphonuclear leukocytes (PMNs) into a 4 microns micropipet have been measured as a function of pipet suction pressure (2,500-20,000 dyn/cm2) and concentration of the drug pentoxifylline (PTX, 0.1-10.0 mM). For control cells (0 mM PTX), entry rates (reciprocal entry times) increased almost linearly with increasing suction pressure, indicating a Newtonian-like behavior. With incubation in PTX solutions, entry rate vs. suction pressure became increasingly non-linear, suggesting a shear-thinning effect for the dissipative structure. At a given suction pressure the rate of entry showed a dose-dependent increase with increasing PTX concentration, the effect being most pronounced at high suction pressures (20,000 dyn/cm2). Also, with increasing PTX concentration two other effects were observed: i) there was a decreased incidence of cells that displayed pseudopodia, and ii) there was an increased incidence of cells forming hernias and an increased streaming of cell cytoplasm during aspiration. The first observation points to a down-regulation of the cell's functional ability to "activate" in response to surface/chemical stimuli, and the second indicates that both the cortical and cytoskeletal networks are weakened either by disruption and/or reduction in density of the protein polymers. These observations are in line with other recently published experiments which suggest that the rheological effects of pentoxifylline on PMNs may be associated with the state of actin.

Actins↗
PubMed1995

Pseudocleavage is dispensable for polarity and development in C. elegans embryos.

The first cleavage of the Caenorhabditis elegans embryo is asymmetrical, producing daughters with different cell fates. During the first cell cycle, P granules, cytoplasmic components that are segregated to the germ-line, are localized to the posterior of the embryo. It has been hypothesized that the asymmetrical behavior of the daughters of the first division results from a similar localization of developmental determinants. A process called pseudocleavage also occurs during the first cell cycle: Anterior cortical contractions culminate in a single partial constriction of the embryo called the pseudocleavage furrow. Coincident with pseudocleavage, there is an anteriorly directed flow of cortical cytoplasm and a posteriorly directed flow of internal cytoplasm. Foci of filamentous cortical actin become asymmetrically distributed into an anterior cap. Roles for these various first cell cycle events in cytoplasmic localization and development have been suggested but remain unclear. We have isolated a maternal effect mutation, nop-1(it142), which abolishes the anterior cortical contractions and the pseudocleavage furrow. In addition, cortical actin foci remain uniformly distributed in most embryos. Despite these defects, cytoplasmic and cortical streaming is present and P granules are localized to the posterior of early embryos. In most embryos from mutant mothers, development proceeds normally and the embryos hatch and grow into fertile adults. We conclude that the pseudocleavage contractions and furrow are dispensable for the development of C. elegans.

Animals↗
PubMed1994

Blocked endocytotic uptake by the oocyte causes accumulation of vitellogenins in the haemolymph of the female-sterile mutants quitPX61 and stand stillPS34 of Drosophila.

The developmental lesions in two female-sterile mutants, quitPX61 (qui) and stand stillPS34 (stil), of Drosophila have been analysed. Previtellogenic development is normal in mutant qui ovarioles but, during vitellogenic stages, only small quantities of yolk accumulate in the oocyte. The nurse-cell cytoplasm does not stream into the oocyte. However, the follicle cells continue their developmental program and synthesize an excessive quantity of eggshell material. In the mutant stil, the oocyte remains small and contains only a fraction of the yolk proteins present in wild-type follicles. Histological and ultrastructural observations and the failure to incorporate trypan blue indicate that the yolk proteins present in the mutant follicles are neither derived from the fat body nor from the follicle cells. Since, in both mutants, the uptake mechanism of vitellogenin is affected, the 3 polypeptides accumulate in the haemolymph (in stil, the protein concentration is up to 4 times higher than in wild-type females) and the haemolymph volume increases. Reciprocal transplantations of ovarioles show that the developmental lesions in both mutants are ovary-autonomous. Furthermore, genetic chimeras of stil show that the activity of the stil gene is required in the germline cells and not in the somatic tissues.

Animals↗
PubMed2001

[A clear cell type meningioma in the upper eyelid ascertained by immunohistochemical examination].

BACKGROUND: We encountered a rare case of clear cell meningioma in the upper eyelid. CASE: A 66-year-old man presented with a slow by progressive, well-defined, soft globelar tumor in the left upper eyelid. The tumor showed homogeneous isodensity and was contrasty in a computed tomograph. Histologically, oval-shaped cells with clear cytoplasm had both streamed and whorl configurations, but showed neither psammomas nor calcification. Immunohistochemically, vimentin, epithelial membrane antigen, and protein S-100 were expressed by the tumor cells. CONCLUSIONS: Eyelid meningioma may originate from embryonal remains of the arachnoid in the sheath around the trigeminal nerve, and may vary histologically. Immunohistochemical examination helps to define cases of uncommon subtypes of meningioma.

Aged↗
PubMed1989

One-dimensional steady continuum model of retraction of pseudopod in leukocytes.

A one-dimensional steady state continuum mechanics model of retraction of pseudopod in leukocytes is developed. The retracting pseudopod is assumed to move bodily toward the main cell body, the bulk motion of which can be represented by cytoplasmic flow within a typical stream tube through the leukocyte. The stream tube is approximated by a frictionless tube with prescribed geometry. The passive rheological properties of cytoplasm in the main cell body and in the pseudopod are modeled, respectively, by Maxwell fluid and Hookean solid. The two regions are assumed to be separated by a sharp interface at which actin gel solates and thereby changes its rheological properties as it flows from the pseudopod to the main cell body. The driving mechanism responsible for the active retraction motion is hypothesized to be a spontaneous deformation of the actin gel, analogous but not necessarily equal to the well known actin-myosin interaction. This results in an active contractile stress being developed in the pseudopod as well as in the cell cortex. The transverse traction pulls against the inclined wall of the stream tube and is transduced into an axial stress gradient, which in turn drives the flow. The tension on the tube wall is picked up by the prestressed cortical shell. Governing equations and boundary conditions are derived. A solution is obtained. Sample data are computed. Comparison of the theory with experiments shows that the model is compatible to the observations.

Cell Movement↗
PubMed1975

On the nature of hyaline zones in the cytoplasm of Amoeba proteus.

Investigations with the Nomarski DIC (differential interferece contrast) microscope and the electron microscope on the nature of hyaline zones in the cytoplasm of Amoeba proteus revealed that these regions represent pure ground cytoplasm. Differences between specimens 1) treated with 2% ethanol, 2) released from high hydrostatic pressure or 3) preincubated at 35 degrees C for 30 minutes could not be observed. Only dying cells undergoing lysis contained a watery solution within the zones of hyaline appearance. The existence of a so-called cell surface complex composed of the plasma membrane and an electron dense filamentous layer of groundplasm was demonstrated by the electron microscopical analysis of narcotized and pre-heated amoebae. This complex corresponds morphologically to the cell surface complexes in tissue cells. Hence it seems possible that the cell surface complex of amoebae is also responsible for changes of the cell shape and movements of the cell membrane. Observations with the DIC microscope also revealed the existence of two types of hyaline caps in A. proteus: in pseudopodia extending during normal locomotion the hyaline cap consists of pure ground cytoplasm, whereas in specimens showing fountain-like streaming the cap is built up by a large vacuole containing a watery fluid.

Amoeba↗
PubMed1997

Cytoplasmic flows localize injected oskar RNA in Drosophila oocytes.

BACKGROUND: The oskar (osk) gene encodes a determinant of posterior identity in Drosophila, and the localization of osk RNA to the pole plasm at the posterior pole of the oocyte is essential for development of the embryo. The mechanisms by which osk RNA is localized are unknown. RESULTS: To study the mechanisms underlying localization of osk RNA, we have injected fluorescently labelled RNA into oocytes at stages 9, 10 and 11. Injected osk RNA localizes to the pole plasm, reproducing localization of the endogenous RNA. In oocytes at stages 10 and 11, the long-range movement of injected osk RNA is promoted by a vigorous, microtubule-dependent cytoplasmic flow, or ooplasmic streaming. Treatment with colchicine, a microtubule-destabilizing drug, inhibits ooplasmic streaming and prevents localization of the RNA from an injection site distal to the posterior pole. If the RNA is injected close to the posterior pole, however, it localizes even in the presence of colchicine. Similarly, in small oocytes, such as stage 9 oocytes, localization of injected osk RNA is insensitive to colchicine. CONCLUSIONS: These results reveal that microtubule-dependent cytoplasmic flows could contribute to the long-range transport of osk RNA, whereas microtubule-independent processes could mediate short-range transport. These results also highlight the role of the osk RNA anchor in the localization process.

Animals↗
PubMed1992

Model of the Ca2+ oscillator for shuttle streaming in Physarum polycephalum.

We propose a mechanism for the cytoplasmic Ca++ oscillator which is thought to power shuttle streaming in strands of the slime-mold Physarum polycephalum. The mechanism uses a phosphorylation-dephosphorylation cycle of myosin light chain kinase. This kinase is bistable if the kinase phosphorylation chain, through adenylate cyclase and cAMP, is activated by calcium. Relaxation oscillations can then occur if calcium is exchanged between the cytoplasm and internal vacuoles known to exist in physarum. As contractile activity in physarum myosin is inhibited by calcium, this model can give calcium oscillations 180 degrees out of phase with actin filament tension as observed. Oscillations of ATP concentration are correctly predicted to be in phase with the tension, provided the actomyosin cycling rate is comparable with ATPase rates for phosphorylation of the myosin light chain and its kinase.

Adenosine Triphosphatases↗
PubMed1986

The mechanics of motility in dissociated cytoplasm.

We stimulate the dynamical behavior of dissociated cytoplasm using the Reactive Flow Model (Dembo, M., and F. Harlow, 1986, Biophys. J., 50:109-121). We find that for the most part the predicted dynamical behavior of the cytoplasm is governed by three nondimensional numbers. Several other nondimensional parameters, the initial conditions, and boundary conditions are found to have lesser effects. Of the three major nondimensional parameters, one (D#) controls the percentage of ectoplasm, the second (C#) controls the sharpness of the endoplasm-ectoplasm boundary, and the third (R#) controls the topological complexity of the endoplasm-ectoplasm distribution. If R# is very small, then the cytoplasm contracts into a single uniform mass, and there is no bulk streaming. If R# is very large, then the cytoplasmic mass breaks up into a number of clumps scattered throughout the available volume. Between these clumps the solution undergoes turbulent or chaotic patterns of streaming. Intermediate values of R# can be found such that the mass of cytoplasm remains connected and yet undergoes coherent modes of motility similar to flares (Taylor, D.L., J.S. Condeelis, P.L. Moore, and R.D. Allen, 1973, J. Cell Biol., 59:378-394) and rosettes (Kuroda, K., 1979, Cell Motility: Molecules and Organization, 347-362).

Algorithms↗
PubMed1988

Cytoskeletal organization of a cloned hemopoietic stromal cell line during attachment and spreading.

The cell membrane of a cloned murine bone marrow stromal cell line D2XRII was extracted in situ using Triton X-100 detergent and the cytoskeletal structure studied during the process of adherence and spreading. During this process, three zones can be identified in the cytoplasm: the perinuclear zone, which was the fixed part of the cell; the peripheral mixed filamentous zone, which formed the core of long cytoplasmic projections; and an outer zone, which formed the boundary of cytoplasmic projections and contained only intermediate filaments. The process of spreading appeared to originate from very long strips of microfilaments emanating from the second zone, crossing the width of the outer zone, and extending beyond for a long distance. The second and third zones then appeared to "stream out" around the axis of this strip, and in this fashion the cytoplasm spreads over the substratum.

Animals↗