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At least 685 records · Page 38Linked to original sources
PubMed2003

The sphingosine 1-phosphate receptor S1P4 regulates cell shape and motility via coupling to Gi and G12/13.

Sphingosine 1-phosphate (S1P) receptors represent a novel subfamily of G-protein-coupled receptors binding S1P specifically and with high affinity. Although their in vivo functions remain largely unknown, in vitro extracellular application of S1P induces distinct S1P receptor-dependent cellular responses including proliferation, differentiation, and migration. We have analyzed signaling pathways engaged by S1P(4), which is highly expressed in the lymphoid system. Here we show that S1P(4) couples directly to Galpha(i) and even more effectively to Galpha(12/13)-subunits of trimeric G-proteins, but not to Galpha(q) unlike other S1P receptors. Consequently, CHO-K1 cells ectopically expressing S1P(4) potently activate the small GTPase Rho and undergo cytoskeletal rearrangements, inducing peripheral stress fiber formation and cell rounding, upon S1P stimulation. Overexpression of S1P(4) in Jurkat T cells induces pertussis toxin-sensitive cell motility even in the absence of exogenously added S1P. In addition, S1P(4) is internalized upon binding of S1P. The capacity of S1P(4) to mediate cellular responses, such as motility and shape change through Galpha(i)- and Galpha(12/13)-coupled signaling pathways may be important for its in vivo function which is currently under investigation.

Amino Acid Sequence↗
PubMed2004

Altered cell shapes, hyperplasia, and secondary growth in Arabidopsis caused by beet curly top geminivirus infection.

Arabidopsis Sei-O ecotype was found to be hypersusceptible to the BCTV-Logan strain in that it developed very severe symptoms, including severely deformed inflorescences with the callus-like structure, and accumulated high level of viral DNA. Microscopic studies of the BCTV-induced cell divisions demonstrated that the activation of cell divisions was preceded by the phloem disruption and the callus-like structure seemed to be originated from the cortex nearby disrupted phloem. We have further defined the callus-like structure formed by BCTV infection using molecular and histochemical analyses. Results indicate that BCTV infection causes the phloem disruption, following by cell enlargement and elongation in cortex and even epidermis. Finally, BCTV induced symptomatic secondary growth in cortex by de novo anticlinal and periclinal cell divisions. Expression of cdc2 and saur from BCTV-infected Arabidopsis correlates with symptom development. These results suggest a critical role of auxin in symptom development in the interactions between Arabidopsis and BCTV.

Arabidopsis↗
PubMed2002

Tissue-engineered cartilage on biodegradable macroporous scaffolds: cell shape and phenotypic expression.

OBJECTIVE: The purpose of the study was to establish in vitro culture of chondrocytes on biodegradable, poly(D,L-lactic-co-glycolic acid) [PLGA] scaffolds. STUDY DESIGN: Laboratory experiment using cartilage of rat rib and biodegradable scaffolds. METHODS: Chondrocytes were cultured on a poly-hydroxyethyl methacrylate (poly-HEMA)-coated dish, proliferated, and transferred into the PLGA scaffolds. Phenotypic expression of cells was examined according to the condition of poly-HEMA coating. Morphological, biochemical, and immunohistochemical characteristics of cells cultured within PLGA scaffolds were also examined. RESULTS: Chondrocytes cultured on a poly-HEMA-coated dish aggregated into distinct nodules containing large clusters of spherical cells and showed cartilage-specific phenotype, collagen type II. The results of immunostaining andreverse transcriptase-polymerase chain reaction of cells cultured within PLGA scaffolds showed cartilage-specific morphological appearance and structural characteristics such as lacunae and expression of collagen type II. CONCLUSION: The chondrocytes cultured on a poly-HEMA-coated dish and PLGA scaffolds showed chondrocyte-specific phenotypes and morphological appearance.

Animals↗
PubMed1988

short gastrulation, a mutation causing delays in stage-specific cell shape changes during gastrulation in Drosophila melanogaster.

Mutations at the short gastrulation locus affect the timing of certain early morphogenetic events occurring during gastrulation in Drosophila melanogaster. Specifically, the invagination and subsequent closing of the posterior midgut and the anterior midgut appear to be delayed in these embryos. In addition, their germbands do not extent the full distance anteriorly on the dorsal side of the embryo. The dorsal cells are abnormally thick and fall into extremely deep dorsal folds as the germband extends. sog embryos continue development, but form disorganized first instar larvae. Normal sog expression is required in the zygote, but not in the mother for normal embryonic development and viability. Analysis of adult and larval gynandromorphs indicates that sog expression is required only in the ventral and/or anterior and posterior ends of the embryo, arguing that the dorsal abnormalities caused by the mutation are secondary consequences of defects elsewhere in mutant embryos.

Alleles↗
PubMed2000

Neutral endopeptidase-24.11 (NEP) deactivates PDGF- and TGF-beta-induced cell shape changes in invertebrate immunocytes.

Using a cytofluorimetric assay, we found that immunocytes of the mollusc, Mytilus galloprovincialis, express CD10, a surface antigen known to be identical to neutral endopeptidase-24.11 (NEP). The spectrofluorimetric analysis demonstrates that the growth factors PDGF-AB and TGF-beta1 provoke an increase in NEP-like activity in membrane preparations from the immunocytes, but have no effect on the soluble form in the serum. On the other hand, computer-assisted microscopic image analysis reveals that NEP deactivates the PDGF-AB- and TGF-beta1-induced shape changes in immunocytes. However, Western blots show that, in solution, NEP does not cleave PDGF-AB or TGF-beta1, indicating that the inactivation is not due to proteolysis. These results suggest a functional interplay in invertebrate immunocytes between growth factors and NEP, as previously shown in vertebrate cells.

Animals↗
PubMedDate not supplied

[Membrane organization in the plane of the membrane and cell shape. Biological consequences of the theory].

The second part of the work deals with the solution of the equation system derived in the previous paper. This equation system describes the ratio between the shape of the membrane and its chemical composition. The energy of membrane particle was calculated. The forces were found transferring such particles in lateral direction, if the curvature of the membrane changes from one point to another. The shape of the membrane was calculated with the presence of clusters on it, the mechanical properties of which differ from the other part of the membrane. A detailed discussion was carried out about the relation between the composition and shape of the membrane and about the initiation of the membrane lateral organization. A great number of experimental data found in literature is analysed in terms of the theory presented.

Biomechanical Phenomena↗
PubMed2003

Cell shape, division and development: the 2002 American Society for Microbiology (ASM) conference on prokaryotic development.

In the last decade, the use of cytological techniques, together with the analysis of complete genomes, has dramatically advanced our understanding of bacterial development. Work on several well-developed model systems such as Bacillus subtilis, Caulobacter crescentus, Myxococcus xanthus and Streptomyces spp., has provided us with an in-depth understanding of processes such as sporulation, multicellular behaviour and the bacterial cell cycle. At the same time, these studies have revolutionized our view of the bacterial cell and shown it to be a highly complex entity with spatial and temporal organization. The recent American Society for Microbiology (ASM) conference on prokaryotic development demonstrated that several laboratories have now started to connect data obtained through functional genomic analysis with subcellular organization, thereby generating three-dimensional regulatory networks. This meeting report highlights new findings in the field, such as regulation of protein localization during sporulation and the cell cycle, control of cell-cell interaction and the initiation of cell division.

Bacillus subtilis↗
PubMed1995

Cytochalasin D induces changes in cell shape and promotes in vitro chondrogenesis: a morphological study.

One of the initial events required for the expression of cartilage-specific macromolecules in monolayer cultures is the reversion to the initial round shape of chondrocytes. Thus, considerable research efforts have focused on developing reliable procedures to maintain a round morphology of cultured chondrocytes. Our study focuses on evaluating the response of dedifferentiated fetal rat chondrocytes to cytochalasin D, an actin-disrupting agent, with special emphasis on the morphological events. Immediately after exposure to the drug, cells round up but flatten again after removing the agent. However, immunocytochemical procedures revealed a disorganization of microfilaments and intermediate filaments. Phase-contrast and scanning electron microscopic observations revealed that on day 6 of culture, cells located at the top of the cell layer adopted a spherical morphology. Prominent differences were noted in control cultures where cells had to aggregate prior to overt chondrogenesis. Transmission electron microscopy confirmed the round morphology of the cells situated at the top layer but also revealed the presence of cell contacts between the cells. In addition, cells located at the central part of the cell layer displayed a typical morphology of mature chondrocytes, separated by an extensive extracellular matrix. These morphological changes occurred parallel to the expression of type II collagen and chondroitin sulfate, both hallmarks of the chondrocyte phenotype strong in experimental cultures, relatively weak in control cultures, and only restricted on areas of polygonal cellular aggregates. Furthermore, [35S]-sulfate incorporation into sulfated glycosaminoglycans increased rapidly with the period of culture to a maximum after 7 days and was then two-fold in treated cultures. Taken together, these findings indicated that cytochalasin D stimulates chondrogenesis in response to modification of cytoskeleton architecture and the subsequent rounding up of the cells.

Actin Cytoskeleton↗
PubMed1988

Identification of new actin-associated polypeptides that are modified by viral transformation and changes in cell shape.

By using a monoclonal antibody we have identified a new polypeptide doublet (C4h and C4l) of Mr approximately 21 kD and pI 8 and 7, respectively, that is associated with and (at the immunofluorescence level) uniformly distributed on actin filament bundles in rat, mouse, and other vertebrate species. C4 is absent in neurones, erythrocytes, and skeletal muscle but the epitope is evolutionarily conserved as it is present in invertebrates such as molluscs and crustaceans. C4h is not found in cells such as lymphocytes and oncogenically transformed mesenchymal cells where actin stress fiber bundles are reduced in number or absent. C4l, on the other hand, is always present. C4h expression can also be blocked by switching normal nontransformed mesenchymal cells from adherent to suspension culture. Reexpression of C4h occurs 24 h after these cells are returned to normal adherent culture conditions, but can be blocked by either actinomycin D or cycloheximide, suggesting that the expression of this epitope is regulated at the transcriptional level.

Actin Cytoskeleton↗
PubMed1984

Isolation and genetic analysis of Caulobacter mutants defective in cell shape and membrane lipid synthesis.

In this paper we report the isolation, characterization and genetic analysis of several C. crescentus mutants altered in membrane lipid synthesis. One of these, a fatty acid bradytroph, AE6002, was shown to be due to a mutation in the fatA gene. In addition to the presence of the fatA506 mutation, this strain was found to contain two other mutations, one of which caused the production of a water-soluble brown-orange pigment (pigA) and another which caused formation of helical cells (hclA). Expression of the latter two phenotypes required complex media and both were repressed by glucose. However, the lesions were mapped to loci that are separated by a substantial distance. The hclA and the fatA genes mapped close together, possibly implying that comutation had occurred in AE6002. Data are presented that allow the unambiguous identification of a second Fat gene (fatB) in C. crescentus. The map position of another mutation in membrane lipid biogenesis, the glycerol-3-PO4 auxotroph gpsA505, was also determined. During this study the flaZ gene was fine-mapped and the positions of proC and rif changed from the previously reported location.

Chromosome Mapping↗
PubMed1986

Neuronal influence on antigenic marker profile, cell shape and proliferation of cultured astrocytes obtained by microdissection of distinct layers from the early postnatal mouse cerebellum.

To study the cellular heterogeneity of astrocytes from early postnatal mouse cerebellum in culture, Bergmann glia were enriched by hand-dissection of Purkinje, molecular and external granular layers ('outer' layer) and fibrous astrocytes of white matter and deep cerebellar nuclei ('inner' layer). Both populations of GFA protein and vimentin-positive astrocytes express N-CAM and the L2/HNK-1 epitope, but not tetanus toxin receptors or A2B5 antigen, at levels detectable by indirect immunofluorescence procedures. The two astrocyte populations are thus indistinguishable from each other. Expression of tetanus toxin receptors and A2B5 antigen in these astrocytes can, however, be induced by removal of neurons. The expression of tetanus toxin receptors is again reduced by readdition of purified populations of small cerebellar neurons. Morphology and proliferation of astrocytes from both layers is also dependent on the presence of neurons: removal of neurons leads to an epithelioid, rather than star-shaped morphology and a severalfold increase in proliferation. Readdition of neurons induces astrocytes to return to their star-shaped morphology. Epidermal growth factor increases proliferation in both populations of astrocytes. We conclude that neither antigenic marker profile, morphology nor proliferative responses serve to distinguish between enriched Bergmann glia and enriched fibrous astrocytes.

Animals↗
PubMed1996

Cortexillins, major determinants of cell shape and size, are actin-bundling proteins with a parallel coiled-coil tail.

Cortexillins I and II of D. discoideum constitute a novel subfamily of proteins with actin-binding sites of the alpha-actinin/spectrin type. The C-terminal halves of these dimeric proteins contain a heptad repeat domain by which the two subunits are joined to form a two-stranded, parallel coiled coil, giving rise to a 19 nm tail. The N-terminal domains that encompass a consensus actin-binding sequence are folded into globular heads. Cortexillin-linked actin filaments form preferentially anti-parallel bundles that associate into meshworks. Both cortexillins are enriched in the cortex of locomoting cells, primarily at the anterior and posterior ends. Elimination of the two isoforms by gene disruption gives rise to large, flattened cells with rugged boundaries, portions of which are often connected by thin cytoplasmic bridges. The double-mutant cells are multinucleate owing to a severe impairment of cytokinesis.

Actins↗
PubMed1987

Effect of growth rate and cell shape on the peptidoglycan composition in Escherichia coli.

The muropeptide composition of peptidoglycan from Escherichia coli W7 cultivated at different growth rates in chemostat cultures was compared by using high-pressure liquid chromatography. At a low growth rate (D = 0.1 h-1), about 40% more covalently bound lipoprotein and at least twofold more diaminopimelyl-diaminopimelic acid cross-bridges were found than at a high growth rate (D = 0.8 h-1). The total degree of cross-linkage was only slightly increased, and the fraction of trimeric muropeptides and the average length of the glycan chains were not changed significantly. Analysis of the peptidoglycan from a morphological variant strain of W7 revealed that the altered peptidoglycan composition in slowly growing W7 cells was not correlated with the observation that these cells, due to their decreased cell length, were relatively enriched in polar material. In fact, our results suggested that peptidoglycan forming cell poles is chemically identical to that forming lateral wall.

Chromatography, High Pressure Liquid↗
PubMed1997

X-ray micrography and imaging of Escherichia coli cell shape using laser plasma pulsed point x-ray sources.

High-resolution x-ray microscopy is a relatively new technique and is performed mostly at a few large synchrotron x-ray sources that use exposure times of seconds. We utilized a bench-top source of single-shot laser (ns) plasma to generate x-rays similar to synchrotron facilities. A 5 microlitres suspension of Escherichia coli ATCC 25922 in 0.9% phosphate buffered saline was placed on polymethylmethyacrylate coated photoresist, covered with a thin (100 nm) SiN window and positioned in a vacuum chamber close to the x-ray source. The emission spectrum was tuned for optimal absorption by carbon-rich material. Atomic force microscope scans provided a surface and topographical image of differential x-ray absorption corresponding to specimen properties. By using this technique we observed a distinct layer around whole cells, possibly representing the Gram-negative envelope, darker stained areas inside the cell corresponding to chromosomal DNA as seen by thin section electron microscopy, and dent(s) midway through one cell, and 1/3- and 2/3-lengths in another cell, possibly representing one or more division septa. This quick and high resolution with depth-of-field microscopy technique is unmatched to image live hydrated ultrastructure, and has much potential for application in the study of fragile biological specimens.

Escherichia coli↗
PubMed1997

PDGF- and TGF-beta-induced changes in cell shape of invertebrate immunocytes: effect of calcium entry blockers.

The cellular activity of hemocytes from the marine mollusc Mytilus galloprovincialis was studied using computer-assisted microscopic image analysis. PDGF-AB and TGF-beta 1 caused changes in cellular shape and induced the immunocytes to migrate in a chemotactic manner. The effect of PDGF-AB was more potent than that of TGF-beta 1, and the responses were dose-correlated for PDGF-AB, while they were dose-dependent up to 5 pg/ml for TGF-beta 1. Moreover, the PDGF-AB response was extracellular Ca(2+)-independent, while TGF-beta 1 was Ca(2+)-dependent.

Animals↗
PubMed1998

Impaired redistribution of aminophospholipids with distinctive cell shape change during Ca2+-induced activation of platelets from a patient with Scott syndrome.

We have investigated phospholipid redistribution, membrane vesicle shedding, shape change, and granule release following A23187 activation of platelets from a patient with Scott syndrome, characterized by impaired transmembrane migration of phosphatidylserine (PS) accompanied by haemorrhagic complications, and two of her children. Electron spin resonance spectroscopy measurement of phospholipids redistribution showed that the internalization of PS was unaffected by the disorder but, after activation, PS exposure was significantly reduced in platelets from the homozygous-type patient. Vesicle shedding was also reduced in these platelets. However, the slow redistribution of phosphatidylcholine was similar to that observed in normal platelets. When treated with calpeptin, platelets from the homozygous-type patient, unlike normal or heterozygous Scott syndrome platelets, showed a smoothly rounded shape without filopods after activation. Following A23187 activation of normal platelets, filopod formation was consecutive to the re-exposition of aminophospholipids on the outer leaflet of the plasma membrane, and the existence of a floppase (outward aminoPLs translocase) has been suggested. In homozygous Scott syndrome platelets the deficiency in PS re-exposition, the absence of filopod formation, and low vesicle shedding are correlated with each other, and argue in favour of a disruption of the proposed floppase activity.

Biological Transport↗
PubMed1997

Disruption of three phosphatidylinositol-polyphosphate 5-phosphatase genes from Saccharomyces cerevisiae results in pleiotropic abnormalities of vacuole morphology, cell shape, and osmohomeostasis.

As a result of the genome sequencing project in Saccharomyces cerevisiae, three open reading frames were found in the yeast genome that contain sequences with strong homology to all the domains conserved among the four mammalian phosphatidylinositol-phosphate 5-phosphatases: inpp5bp, ocrl1p, synaptojanin, and ship. In addition, all three yeast gene products shared with synaptojanin regions of homology to the SAC1 gene of yeast. Disruption of each of these genes singly and in pairs produced mutant strains that were viable but demonstrated variable phenotypes of abnormal vacuolar and plasma membrane morphology as well as increased sensitivity to osmotic stress. Total phosphatidylinositol-(4,5)-bisphosphate 5-phosphatase activity was reduced to varying degrees in each of the strains. No defect in carboxypeptidase Y sorting was seen in a processing and targeting assay. Abnormal actin cytoskeleton morphology was present in some of the strains carrying mutations in two of the genes.

Amino Acid Sequence↗
PubMed1986

A quantitative method for the analysis of cell shape and locomotion.

A rapid, semiautomated system to quantitate and analyze leukocyte shape and locomotion was developed. Video images of moving leukocytes were obtained using a Vidicon camera mounted on a Nikon phase microscope. The video signal was either inputted directly, or indirectly via a video cassette recorder, to a Datacube video analog-digital, digital-analog converter. A Digital Equipment Corporation LSI 11/23 computer using the RT-11/TSX-Plus operating system and computer programs written in FORTRAN and MARCO assembly language permitted image segmentation, image display, and calculation of position, speed, direction of movement and orientation of each leukocyte at 10 s intervals. These data were stored on a winchester disk for subsequent evaluation of the leukocyte orientation, speed and direction of movement using statistical and graphical methods. The reproducibility of measurements made with the video system was tested by comparison with manual measurements; a correlation coefficient of 0.998 was obtained for the two methods. Rates of chemokinesis were then determined for unstimulated and chemokinetically stimulated polymorphonuclear leukocytes (PMNs) and found to average 12.8 micron/min and 18.1 micron/min, respectively. The high speed, ease of data analysis, and potential for multiparameter evaluation makes this system useful for directly evaluating leukocyte locomotion.

Cell Movement↗