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At least 199 records · Page 11Linked to original sources
PubMed1983

Quantitative analysis of changes in cell shape of Amoeba proteus during locomotion and upon responses to salt stimuli.

A new parameter expressing the complexity of cell shape defined as (periphery)2/(area) in 2D projection was found useful for a quantitative analysis of changes in the cell shape of Amoeba proteus and potentially of any amoeboid cells. During locomotion the complexity and the motive force of the protoplasmic streaming in amoeba varied periodically, and the Fourier analysis of the two showed a similar pattern in the power spectrum, giving a rather broad peak at about 2.5 X 10(-3) Hz. The complexity increased mainly due to elongation of the cell as external Ca2+ increased. This effect was blocked by La3+, half the inhibition being attained at 1/200 amount of the coexisting Ca2+. On the other hand, the complexity decreased due to rounding up of the cell as the concentration of other cations, such as Sr2+, Mg2+, Co2+, Ni2+, Na+, K+ etc., increased. Irrespective of the opposite effects of Ca2+ and other cations on the cell shape, the ATP concentration in amoeba decreased in both cases with increase of all these cations. The irregularity in amoeboid motility is discussed in terms of a dynamic system theory.

Adenosine Triphosphate↗
PubMed2004

Cell shape and growth of budding yeast cells in restrictive microenvironments.

Effects of limited growth space on the cell morphology and cell growth are investigated by creating rigid outside environments. The cube-shaped holes big enough for a single cell of the budding yeast Saccharomyces cerevisiae were prepared with a focused ion-beam (FIB), commonly used for processing semiconductors. We demonstrated that the outline of the cells changes their ellipsoidal morphology into a cubic form when the daughter cells are grown in the holes, indicating that yeast cells change their shape in response to external limited space. The yeast cells grown in the microenvironments exhibit neither bud formation nor nuclear division. Although restricted growth caused by the physical barriers leads to the block of cell cycle progression in the wild-type cells, swe1Delta cells defective in the morphogenesis checkpoint become binucleate after being grown in the microenvironments. These results suggest that yeast cells under spatial restriction arrest cell cycle progression in a Swelp-dependent manner.

Cell Cycle↗
PubMedDate not supplied

The 1996 Lindberg Award. Calcium antagonists alter cell shape and induce procollagenase synthesis in keloid and normal human dermal fibroblasts.

Fibroblast cytomorphology is tightly coupled to phenotypic expression, particularly as it relates to extracellular matrix protein synthesis and degradation. We have observed that calcium antagonists, such as verapamil and trifluoperazine, depolymerize actin filaments and alter fibroblast cell shape from bipolar to spherical. Characteristically, the depolymerization of actin filaments, which mediates the cell shape change, turns on procollagenase gene expression in normal human skin fibroblasts. We have found the same effects of calcium antagonists on cell shape, cytoskeletal components, and induction of procollagenase in the keloid fibroblasts of three cell lines, CB792, CW792, and WT949. Rounded cells were seen in 74.8% of verapamil-treated and 86.7% of trifluoperazine-treated cells, whereas only 1.1% of the control cells were spherical. The percentage of cells that synthesized collagenase in the control, verapamil-treated, and trifluoperazine-treated groups was 3.8%, 42.8%, and 53.4%, respectively. Approximately 60% of rounded cells exhibited increased collagenase synthesis when the cells were treated with a calcium antagonist. These results indicate considerable heterogeneity in the phenotypic response to morphologic change. The amount of procollagenase synthesized in a cell was estimated by the fluorescence intensity of the fluorescein-labeled antibody. The normalized fluorescence intensity of procollagenase in the control cells was about 2 to 2.6 times that of background. In contrast, the normalized fluorescence intensity of procollagenase in the calcium antagonist-treated cells was about 2.4 to 12 times that of background. This high intensity level indicates an increase in procollagenase production in the calcium antagonist-treated cells. Calcium green dye used to study cytosolic calcium revealed that after cells were treated with verapamil, the cytosolic calcium ion concentration first increased and then decreased. The change of cytosolic calcium ion concentration may be related to the depolymerization of actin filaments and the alteration of cell shape.

Awards and Prizes↗
PubMed1980

Red blood cell preservation in protein-poor media. 2. Studies of changes in red cell shape during storage.

Red cells stored for up to 35 days have been studied by scanning electron microscopy. Formation of spicules occurred under all storage conditions in CPD and CPD-adenine whole blood, CPD-adenine red cell concentrate, and saline-adenine-glucose red cell concentrate. The number of cells with normal or near normal shape was larger if the blood was stored as a moderately concentrated suspension in saline-adenine-glucose medium or in autologous plasma as compared to the storage as whole blood. The occurrence of echinocytes during storage at +4 degrees C was not correlated to red cell ATP. It was shown that a drastic reduction of ATP leads to an increased formation of both spherocytes and echinocytes. The change of red cell shape during storage at +4 degrees C thus can be due to two processes, one unrelated to ATP and another related to ATP. Why storage as red cell concentrate is superior is not fully understood.

Blood Specimen Collection↗
PubMed2006

Numerical determination of transmembrane voltage induced on irregularly shaped cells.

The paper presents an approach that reduces several difficulties related to the determination of induced transmembrane voltage (ITV) on irregularly shaped cells. We first describe a method for constructing realistic models of irregularly shaped cells based on microscopic imaging. This provides a possibility to determine the ITV on the same cells on which an experiment is carried out, and can be of considerable importance in understanding and interpretation of the data. We also show how the finite-thickness, nonzero-conductivity membrane can be replaced by a boundary condition in which a specific surface conductivity is assigned to the interface between the cell interior (the cytoplasm) and the exterior. We verify the results obtained using this method by a comparison with the analytical solution for an isolated spherical cell and a tilted oblate spheroidal cell, obtaining a very good agreement in both cases. In addition, we compare the ITV computed for a model of two irregularly shaped CHO cells with the ITV measured on the same two cells by means of a potentiometric fluorescent dye, and also with the ITV computed for a simplified model of these two cells.

Animals↗
PubMed1991

Extracellular matrix and cell shape: potential control points for inhibition of angiogenesis.

Capillary endothelial (CE) cells require two extracellular signals in order to switch from quiescence to growth and back to differentiation during angiogenesis: soluble angiogenic factors and insoluble extracellular matrix (ECM) molecules. Soluble endothelial mitogens, such as basic fibroblast growth factor (FGF), act over large distances to trigger capillary growth, whereas ECM molecules act locally to modulate cell responsiveness to these soluble cues. Recent studies reveal that ECM molecules regulate CE cell growth and differentiation by modulating cell shape and by activating intracellular chemical signaling pathways inside the cell. Recognition of the importance of ECM and cell shape during capillary morphogenesis has led to the identification of a series of new angiogenesis inhibitors. Elucidation of the molecular mechanism of capillary regulation may result in development of even more potent angiogenesis modulators in the future.

Animals↗
PubMed2000

Neuronal cell shape and neurite initiation are regulated by the Ndr kinase SAX-1, a member of the Orb6/COT-1/warts serine/threonine kinase family.

The Caenorhabditis elegans sax-1 gene regulates several aspects of neuronal cell shape. sax-1 mutants have expanded cell bodies and ectopic neurites in many classes of neurons, suggesting that SAX-1 functions to restrict cell and neurite growth. The ectopic neurites in sensory neurons of sax-1 mutants resemble the defects caused by decreased sensory activity. However, the activity-dependent pathway, mediated in part by the UNC-43 calcium/calmodulin-dependent kinase II, functions in parallel with SAX-1 to suppress neurite initiation. sax-1 encodes a serine/threonine kinase in the Ndr family that is related to the Orb6 (Schizosaccharomyces pombe), Warts/Lats (Drosophila), and COT-1 (Neurospora) kinases that function in cell shape regulation. These kinases have similarity to Rho kinases but lack consensus Rho-binding domains. Dominant negative mutations in the C. elegans RhoA GTPase cause neuronal cell shape defects similar to those of sax-1 mutants, and genetic interactions between rhoA and sax-1 suggest shared functions. These results suggest that SAX-1/Ndr kinases are endogenous inhibitors of neurite initiation and cell spreading.

Amino Acid Sequence↗
PubMed1983

Effect of cell shape change on the function and differentiation of rabbit mammary cells in culture.

We examined the role of cell shape, cytodifferentiation, and tissue topography on the induction and maintenance of functional differentiation in rabbit mammary cells grown as primary cultures on two-dimensional collagen surfaces or in three-dimensional collagen matrices. Mammary glands from mid-pregnant rabbits were dissociated into single cells, and epithelial cells were enriched by isopycnic centrifugation. Small spheroids of epithelial cells (approximately 50 cells) that formed on a rotary shaker were plated on or embedded in collagen gels. The cells were cultured for 1 d in serum-containing medium and then for up to 25 d in chemically defined medium. In some experiments, epithelial monolayers on gels were mechanically freed from the dishes on day 2 or 5. These gels retracted and formed floating collagen gels. On attached collagen gels, flat monolayers of a single cell type developed within a few days. The cells synthesized DNA until the achievement of confluence but did not accumulate milk proteins. No morphological changes were induced by prolactin (PRL). On floating gels, two cell types appeared in the absence of cell proliferation. The cells in direct contact with the medium became cuboidal and developed intracellular organelles typical of secretory cells. PRL-induced lipogenesis, resulting in large fat droplets filling the apical cytoplasm and accumulation of casein and alpha-lactalbumin in vesicles surrounding the fat droplets. We detected tranferrin in the presence or absence of PRL intracellularly in small vesicles but also in the collagen matrix in contact with the cell layer. The second cell type, rich in microfilaments and reminiscent of the myoepithelial cells, was situated between the secretory cell layer and the collagen matrix. In embedding gels, the cells formed hollow ductlike structures, which grew continuously in size. Secretory cells formed typical lumina distended by secretory products. We found few microfilament-rich cells in contact with the collagen gels. Storage and secretion of fat, caseins and alpha-lactalbumin required the presence of PRL, whereas the accumulation and vectorial discharge of transferrin was prolactin independent. There was no differentiation gradient between the tip and the cent of the outgrowth, since DNA synthesis and milk protein storage were random along the tubular structures. These results indicate that establishment of functional polarity and induction of cytodifferentiation are influenced by the nature of the interaction of the cells with the collagen structure. The morphological differentiation in turn plays an important role in the synthesis, storage, and secretion of fat and milk proteins.

Animals↗
PubMed2000

A common step for changing cell shape in fruiting body and starvation-independent sporulation of Myxococcus xanthus.

Myxococcus xanthus can sporulate in either of two ways: at the end of the program of fruiting body development or after exposure of growing cells to certain reagents such as concentrated glycerol. Fruiting body sporulation requires starvation, while glycerol sporulation requires rapid growth, and since the two types of spores are structurally somewhat different, it has generally been assumed that the two processes are different. However, a Tn5 Lac insertion mutation, Omega7536, has been isolated which simultaneously blocks the development of fruiting body spores as well as glycerol-induced spores. Both sporulation pathways are blocked in the mutant within the process that converts a rod-shaped cell into a spherical spore. The Omega7536 locus is expressed at the time of cell shape change appropriate to each process, early after glycerol induction and late after starvation induction. On the C-signal response pathway, it is possible to identify positions for the normal function of the Omega7536 locus and for the inducing stimulus from glycerol that are unique and consistent with the observations. Although the two sporulation pathways differ in certain respects, it is shown that they share at least one step for changing a rod-shaped cell into a spherical spore.

Bacterial Proteins↗
PubMed1996

Hormone-induced changes in cell shape: role of cytoskeletal proteins.

Shape is a characteristic phenotype for a given cell. It is affected by various physiological and pathological factors. Hormones, which are the chemical messengers affecting a wide range of biological phenomena, also alter cell morphology by influencing the expression and post-translational modifications of cytoskeletal proteins. The assembly/disassembly of cytoskeletal proteins and their interactions with intracellular components, the plasma membrane and extracellular matrix, is mainly responsible for determining cell shape. The role of hormones in the induction of altered cell shape due to changes in the cytoarchitecture in varied biological tissues under both in vivo and in vitro conditions, are discussed in this review.

Animals↗
PubMed2005

Regulation of tissue factor and angiogenesis-related genes by changes in cell shape.

During development, tissue injury, and cancer, epithelial cells engage in communication with the vascular system by using several molecular mediators acting directly or through changes in the haemostatic system.The latter category is epitomised by the procoagulant cellular receptor known as tissue factor (TF). Here, we show that when cellular architecture is altered by a shift in culture conditions from monolayer to three-dimensional multicellular spheroids, expression of multiple angiogenesis effectors (VEGF, TSP-1, TSP-2, Ang-1, and TF) is profoundly altered. In particular, TF is dramatically upregulated in a transformed murine breast epithelial cell line (EMT6) under these conditions. This appears to be linked to a particular change in cell shape and cytoskeletal (actin) reorganisation, as treatment of these cells with cytochalasin D (Cyt D), but not with latrunculin B, recapitulates and potentiates TF upregulation. Collectively, these results suggest that the ability of epithelial cells to interact with the vascular system via expression of the TF gene (and other effectors) is under the control of complex alterations in cellular architecture.

Actins↗
PubMed1981

Effects of Ca+2 and Mg+2 deprivation of cell shape in cultured ovarian granulosa cells.

After 3 days in culture, rat ovarian granulosa cells assume a flattened epitheloid organization. Ca+2 and Mg+2 deprivation results in cellular rounding which is reversible and was monitored by phase-contrast time-lapse cinematography. Concomitant with the shape change is a dispersion of the structural proteins actin and alpha-actinin. The arrays of large actin-containing bundles (stress fibers) are converted to a diffuse network as observed by electron microscopy. Alpha-actinin, which was observed by immunocytochemistry to be in a periodic array along the actin bundles, is disrupted also and redistributed in the periphery of the cell upon rounding. Measurements made of the culture medium during the rounding process indicate that there is a loss of Ca+2 and Mg+2 from the cell interior. These data led us to speculate that Ca+2 and/or Mg+/ are necessary in order to maintain the integrity of stress fibers and/or restrict the movement of alpha-actinin anchoring sites within the membrane.

Actinin↗
PubMed1995

A new monoclonal antibody (IE8) reactive with dendritically shaped cells in the human tonsil.

A new monoclonal antibody (mAb), 1E8 (IgG1, kappa), was obtained from a hybridoma prepared by fusion of mouse myeloma cells (NS-1) with splenic cells of mice immunized with a human B blastic malignant lymphoma cell line, HPE-Ret-3 (Ret-3). The mAb showed a reactivity unrestricted to a specific cell lineage on flow cytometrical analysis of the reactivity with human lympho-hematopoietic cell lines. In peripheral blood, 1E8 reacted with the cells of all lineage, that is, lymphocytes, monocytes, granulocytes and platelets, even though its intensity was very low by immunohistochemistry. Immunohistochemical examination of human tonsil with 1E8 showed a characteristic staining pattern. Positive cells scattered in follicular (mantle zone and germinal center), parafollicular (T-dependent area), subepithelial and interstitial connective tissue areas. These positive cells seemed to be categorized into dendritically shaped cells (DSC), including dendritic cells (DC) and a subpopulation of macrophages in follicles, interdigitating cells (IDC) and irregularly shaped mononuclear cells. The localization of 1E8 antigen staining was similar to that of integrin CD11c, although its distribution on hematopoietic cell lines did not coincide with that of 1E8 antigen. Immunobiochemical studies showed that 1E8 bound two cell surface proteins with molecular size of 70,000-90,000 and 35,000 Da each. Consequently, 1E8 antigen might be a novel marker of DSC.

Animals↗
PubMed1996

The function of intermediate filaments in cell shape and cytoskeletal integrity.

This study describes the development and use of a specific method for disassembling intermediate filament (IF) networks in living cells. It takes advantage of the disruptive effects of mimetic peptides derived from the amino acid sequence of the helix initiation 1A domain of IF protein chains. The results demonstrate that at 1:1 molar ratios, these peptides disassemble vimentin IF into small oligomeric complexes and monomers within 30 min at room temperature in vitro. Upon microinjection into cultured fibroblasts, these same peptides induce the rapid disassembly of IF networks. The disassembly process is accompanied by a dramatic alteration in cell shape and the destabilization of microtubule and actin-stress fiber networks. These changes in cell shape and IF assembly states are reversible. The results are discussed with respect to the roles of IF in cell shape and the maintenance of the integrity and mechanical properties of the cytoplasm, as well as the stability of the other major cytoskeletal systems.

3T3 Cells↗
PubMed1978

[Possible nature of the biogenic amine in the dumbbell-shaped cells of frog taste buds].

An attempt was made to identify specific monoamines contained in the dumb-bell shape cells of the frog taste bud by means of histochemical analysis. It was shown by fluorescent microscopy that preliminary administration of exogenous serotonin into the blood channel of frog tongue resulted in a sharp increase of specific fluorescence of the dumb-bell shape cells, whereas serotonin synthesis inhibition with p-chlorphenylalanine led to reduction and elimination of specific fluorescence. It was concluded that-specific monoamine of the dumb-bell shape cells was possibly of serotonin-like nature.

Animals↗
PubMed1982

The role of microtubules in cell shape and pigment distribution in spreading erythrophores.

In order to investigate the role of microtubules in determining overall shape of the cell and distribution of pigment granules, a correlative whole cell electron microscopic and immunofluorescence light microscopic study was done of microtubule distribution during spreading of cultured erythrophores from scales of the squirrel fish, Holocentrus. After dissociation from the scale and immediately after attachment, erythrophores are round with long thin processes containing bundles of microtubules with associated pigment granules. In time these processes attach, and elongate, and cytoplasmic ground substance fills areas between microtubule bundles, preceding the appearance of microtubules in these areas of the cell. By 8 h cells are fully spread (star-shaped), prominent microtubule bundles have disappeared, and microtubules (along with pigment granules) are more evenly dispersed throughout the cell. After 24 h cells have increased in size, in number of microtubules, and in the length of preexisting tubules. The sequence of events in normal spreading is altered if cytochalasin D, cycloheximide, or nocodazole is included in the culture medium. Cytochalasin D, a microfilament-disrupting drug, prevents attachment and spreading, but allows elongation to occur. Cycloheximide, a protein synthesis inhibitor, allows for attachment and elongation, but no spreading. Nocodazole, a microtubule-disrupting drug, allows for attachment and spreading, but an irregular cell outline is the result. Even though spreading can occur without them, it is concluded that a normal number and distribution of microtubules are required for the development of normal cell shape and pigment distribution.

Animals↗
PubMed2002

Cell shape change precedes staurosporine-induced stabilization and accumulation of p27kip1.

The requirement of an intact cytoskeleton organization for G1/S cell cycle progression has been demonstrated in cultured cells. In the non-small-cell lung carcinoma cell line A549, the kinase inhibitor staurosporine induced G1 cell cycle arrest with an accumulation of the cyclin-dependent kinase inhibitor p27kip1. Staurosporine induced also a drastic change in cell shape that was accompanied by changes in the actin cytoskeleton. The cytoskeleton disruption agents, cytochalasin D (cyto D) and 2,3-butanedione 2-monoxime (BDM), also induced G1 cell cycle arrest in A549 cells but without an accumulation of p27kip1. A comparison of the cell shape changes caused by these agents revealed that a conversion from an epithelial polygonal shape to an elongated fibroblast-like shape was specific for staurosporine. The shape change induced by staurosporine preceded the accumulation of p27kip1 by about 4 h. The accumulation of p27kip1 was not due to enhanced transcription but to stabilization of the protein resulting from the inhibition of proteolytic degradation. Staurosporine, however, did not inhibit directly the proteasome that was involved in the cell-cycle-dependent p27kip1 degradation. The results indicate that the cell shape change caused by staurosporine correlates with the accumulation of p27kip1 and that staurosporine interferes with the p27kip1-specific proteolysis activity.

Cell Cycle↗
PubMed1996

Mechanism of endothelial cell shape change and cytoskeletal remodeling in response to fluid shear stress.

Endothelium exposed to fluid shear stress (FSS) undergoes cell shape change, alignment and microfilament network remodeling in the direction of flow by an unknown mechanism. In this study we explore the role of tyrosine kinase (TK) activity, intracellular calcium ([Ca2+]i), mechanosensitive channels and cytoskeleton in the mechanism of cell shape change and actin stress fiber induction in bovine aortic endothelium (BAE). We report that FSS induces beta-actin mRNA in a time- and magnitude-dependent fashion. Treatment with quin2-AM to chelate intracellular calcium release and herbimycin A to inhibit TK activity abolished BAE shape change and actin stress fiber induction by FSS, while inhibition of protein kinase C with chelerythrine had no effect. Altering intermediate filament structure with acrylamide did not affect alignment or F-actin induction by FSS. Examining the role of the BAE cytoskeleton revealed a critical role for microtubules (MT). MT disruption with nocodazole blocked both FSS-induced morphological change and actin stress fiber induction. In contrast, MT hyperpolymerization with taxol attenuated the cell shape change but did not prevent actin stress fiber induction under flow. Mechanosensitive channels were found not to be involved in the FSS-induced shape change. Blocking the shear-activated current (IK.S) with barium and the stretch-activated cation channels (ISA) with gadolinium had no effect on the shear-induced changes in morphology and cytoskeleton. In summary, FSS has a profound effect on endothelial shape and F-actin network by a mechanism which depends on TK activity, intracellular calcium, and an intact microtubule network, but is independent of protein kinase C, intermediate filaments and shear- and stretch-activated mechanosensitive channels.

Acrylamide↗