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At least 37 records · Page 2Linked to original sources
PubMed1979

A cinematographical study of the development of vitally stained Dictyostelium discoideum.

We report observations from time-lapse films of the development of Dictyostelium discoideum (Dd) stained with the vital dye neutral red. We have used this dye to enable us to track individual cells, as they move through multicellular tissues in later Dd stages. Our observations lead us to new conclusions about the control of cell movement and cell contact during Dd development, including the tentative conclusion that the aggregation control competences regulate cell behaviour throughout the whole of Dd. development. We are led to specific hypotheses for the mechanisms of later morphogenetic movements and pattern formation.

Dictyostelium↗
PubMed1975

Action of cytochalasin D on cells of established lines. III. Zeiosis and movements at the cell surface.

The projection of knobby protuberances at the cell surface (zeiosis) is a general cellular response to cytochalasin D (CD), resulting from herniation of endoplasm through undefended places of the cortex during cell contractions and displacement of microfilaments induced by CD. Zeiosis is prevented by agents that interfere with the contractile response to CD, such as inhibitors of energy metabolism or cyclic AMP. The developed protrusions, which remain relatively stable in the presence of CD, contain chiefly mono- or subribosomes, and occasionally other organelles normally resident in endoplasm; compact microfilament felt occupies their bases and extends into their proximal stalks. Protein synthesis in the knobs is less than half of that in the polyribosome-containing endoplasm residual in the main body of the cell. Knobs first protrude singly near the margin of the contracting cells and rapidly cluster into small groups in the periphery even at lower temperature. The clusters then migrate centripetally and coalesce into a large aggregate near the apex of the immobilized and retracted cell: this movement is energy- and temperature-dependent. Aggregation is more prominent and stable in cell lines of epithelial derivation than in fibroblastic or other lines in which nuclear extrusion occurs more readily. The latter is regarded as a special manifestation of zeiosis. Macromarkers, such as latex spherules, migrate like the zeiotic knobs on the cell surfaces in the presence of CD. The aggregated knobs, although persistent for days in the presence of CD, are rapidly recessed after withdrawal of the agent as ruffling is resumed and the cells spread. These movements are discussed in terms of current concepts of mobility of the cell membrane.

Amino Acids↗
PubMed1977

Histogenesis of mouse cerebellum in microwell cultures. Cell reaggregation and migration, fiber and synapse formation.

A microwell culture system was developed for analysis of cell movements and interactions during nervous system histogenesis. Cells from trypsinized 7-day-old mouse cerebellum reaggregated within hours into clusters which later developed interconnections consisting of either sheets of migrating cells and cell processes or cables of fiber bundles with cells migrating along their surfaces. Granule cells in several stages of differentiation, basket and/or stellate neurons, some larger neurons, and two types of neuroglial cells were identified in reproducible, nonrandom patterns by scanning and transmission electron microscopy. Axonal and dendritic processes, both with growth cones, and numerous synapses were generated in vitro.

Animals↗
PubMed1976

Cyclic nucleotides, thioldisulfide status of proteins, and cellular control processes.

It is shown that cyclic nucleotides can have a variety of effects on cell division, cell shape, cell adhesion, and cell movement, depending on the cells selected and the conditions under which they are used. For example, while CHO cells elongate under the influence of exogenous dibutyryl CAMP, Y-1 adrenal tumor cells round up and polyoma-transformed 3T3 cells show no change in shape. The totality of experience with cyclic nucleotides suggests that where they have been used by cells as control elements involving the four processes listed above, they are superimposed on basic cellular processes that progress in their absence--that is, they must be acting indirectly. In attempting to understand the inhibitory action of methyl xanthines on egg development, we were forced to abandon the idea that they acted through cyclic nucleotides. We found that methyl xanthines inhibited the activation of glutathione reductase and that glutathione oxidizing agents act as mitotic inhibitors. Further, we found that tubulin polymerizability, NAD-kinase activity, and a mitotic apparatus associated Ca+2-ATP-ase were all inhibited by oxidation of some of their sulfhydryls and were activated by reduction of the resulting disulfides. These results are discussed in terms of reported cycles and activations of glutathione reductase (GR) in cells and reports that mixed disulfides of glutathione and proteins can act as substrates for GR. Using the fact that a CAMP-dependent protein kinase has been reported to be activated by glutathione, we have suggested potential sites where sulfhydryl control processes and cyclic nucleotide control processes and cyclic nucleotide control processes may interact in certain restricted cases.

Adenosine Triphosphatases↗
PubMed1979

Sequential effects of thyroxine on the developing cerebellum of rats made hypothyroid by propylthiouracil.

Young rats made hypothyroid by propylthiouracil (PTU) received a daily physiological dose of thyroxine (T4) from day 0, 4, 6, 8, 10, 11, 12 or 13 and their cerebella were studied on day 14. With the very low doses of T4 used and when the treatment was started at birth, cerebellar development was nearly normal in terms of the parameters studied (cell formation, migration, maturation and death). The effect of T4 on cell formation appeared after two days. With the same latency, T4 induced migration of the newly-formed granule cells. The effects on those processes requiring cell movements over long distances, e.g. the number of cells in the internal granular layer or the thickness of the molecular layer, were longer to appear. The most rapidly affected parameter was the pyknotic index in the internal granular layer. This index was half. The increased cell death in the cerebellum of hypothyroid rats is probably related to the decreased synaptogenetic competence of Purkinje cells. The rapidity of the effect of T4 on the pyknotic index may be related to an important effect of this hormone on the formation of synapses and, more generally, on the mechanisms of neuronal maturation.

Animals↗
PubMed1976

Effect of exogenous cyclic AMP and other adenine nucleotides on neutrophil chemotaxis and motility.

Cyclic AMP placed in the bottom of the modified Boyden chemotaxis chamber is weakly chemotactic for rabbit peritoneal neutrophils. Dibutyryl-cyclic AMP under similar conditions gives a biphasic response, being weakly chemotactic at low concentrations and inhibiting cell movement at higher concentrations. When mixed with the cells in the upper compartment of the chemotaxis chamber, cyclic AMP and dibutyryl-cyclic AMP enhance neutrophil spontaneous motility; on the other hand, dibutyryl-cyclic AMP mixed with the cells in the upper compartment consistently inhibits neutrophil chemotactic responsiveness, while cyclic AMP has a variable effect on chemotaxis. The effect of ADP and ATP was to inhibit chemotaxis and spontaneous motility. AMP is totally without effect.

Adenine Nucleotides↗
PubMed1979

The role of contractile proteins in wound healing and fibrocontractive diseases.

During the healing of an open wound, the majority of granulation tissue fibroblasts (myofibroblasts) acquire morphological, biochemical, pharmacological, and immunological characteristics typical of contractile cells. The presence of contractile proteins and the appearance of gap junctions between several myofibroblasts make them similar to cultivated fibroblasts; these have been proven to develop in vitro a contractile force similar to that exerted by granulation tissue during wound contraction. These observations suggest that myofibroblasts are responsible for granulation tissue contraction. Epidermal cells moving over an open wound also develop a contractile apparatus and many cellular connections in the form of gap junctions. These changes may be the morphological support for epithelial cell movements. The presence of gap junctions between myofibroblasts and healing epidermal cells shows that granulation tissue contraction and epithelial cell movement are probably synchronized rather than individual phenomena.

Actomyosin↗
PubMed1977

Dibutyryl cyclic AMP treatment of 3T3 and SV40 virus-transformed 3T3 cells in aggregates. Effects on mobility and cell contact ultrastructure.

The random cell movement of BALB/c 3T3 and SV40 virus-transformed BALB/c 3T3 cells within homogeneous aggregates was studied by observing the degree of penetration of newly attached [3H]thymidine-labeled cells into the interior of the aggregates. The 3T3 cells penetrated into 3T3 aggregates an average of 0.89 cell diameter in 1.5 days, whereas the SV40-3T3 cells penetrated into SV40-3T3 aggregates an average of 3.20 cell diameters in the same time. Treatment of the aggregates with theophylline, theophylline plus prostaglandin E1, or theophylline plus dibutyryl cyclic AMP all decreased the penetration of the SV40-3T3 cells into SV40-3T3 aggregates (2.36, 1.22, and 0.79 cell diameters, respectively). The same treatments had little effect on 3T3 aggregates. The ultrastructure of 3T3 and SV40-3T3 cells in aggregates was examined by transmission electron microscopy. The 3T3 cells in aggregates were surrounded by microvilli and lamellipodia which were in contact with neighboring cells, whereas SV40-3T3 cells were nearly devoid of microvilli and lamellipodia and made contact at broader, less regular surface undulations. Treatment with theophylline plus dibutyryl cyclic AMP resulted in the appearance of microvilli on SV40-3T3 cells and also appeared to increase the area of intercellular contacts in both 3T3 and SV40-3T3 cells. These observations were supported for the surface cells of the aggregates by scanning electron microscopy.

Bucladesine↗
PubMed1978

Effect of phagocytosis and Fc receptor occupancy on complement-dependent neutrophil chemotaxis.

Neutrophil migration was assessed following cell interaction with IgG or after phagocytosis of antibody-coated EA or latex. The migration of these neutrophil preparations was markedly impaired as studied in an agarose medium with ZAS as the chemoattractant. Neutrophils which had interacted with EA retained some capacity for directed migration toward synthetic tripeptides and E. coli filtrate. Rosette formation with EA(IgM)C3 did not impair cell movement. The reduced cell migration observed after immune or nonimmune ingestion was reversible following a prolonged incubation period. The results suggest that phagocytosis or Fc receptor occupancy transiently blocks the ability of neutrophils to migrate.

Adult↗
PubMed1979

Interaction between inner cell mass and trophectoderm of the mouse blastocyst. II. The fate of the polar trophectoderm.

Selective labelling of polar trophectoderm cells in early mouse blastocysts has allowed the fate of polar cells to be followed during in vitro and in vivo blastocyst development. Results show that there is cell movement from polar to mural regions as blastocysts grow. This indicates that trophectoderm cells directly opposite the inner cell mass are the oldest mural cells. However, after implantation polar cells invaginate into the blastocoelic cavity and contribute to the extra-embryonic ectoderm. It is suggested that the morphogenetic changes occurring in the mouse embryo at implantation result from the maintenance of a balance between (a) regional differences in rates of cellular proliferation, and (b) mechanical constraints on the direction in which growth can occur.

Animals↗
PubMed1978

A scanning electron microscope study of cell shape and cell appendages in the primitive streak region of the rat and chick embryo.

This report provides a scanning electron microscopic account of cell shapes and cell appendages that are observed in the primitive streak region of the rat and chick embryos. Epiblast cells become progressively elongated in the primitive streak region until flask cells predominate medially. The flask cells have a broad basal end directed toward the endoderm. In addition to fine filopodia, broad lamellipodia are found anchoring the flask cells to subjacent cells. The primary mesenchyme cells are at first round in shape and closely packed, but laterally are flattened and more dispersed. The mesenchyme cells are associated with each other by filopodia and lamellipodia and with the epiblast and endoderm by filopodia. On the basis of this description it is suggested that cell movement through the primitive streak occurs by cell extension, attachment by basal lamellipodia, and cell shortening that results in the movement of individual cells in a cell stream.

Animals↗
PubMed1978

Computer simulation of aggregation in Dictyostelium discoideum.

The aggregation phase of development of the cellular slime mould Dictyostelium discoideum is simulated on a computer. The simulation is performed in 2 dimensions, and produces animated graphical output similar to time-lapse films. It is based on observations of cell behaviour as expressed by a set of rules for each cell, involving cell movement and release of and response to chemical signals. Following these rules, the simulation has reproduced many observed aggregation patterns: propagating waves of cell movement; formation of branching streams; entrainment of slower centres; and spiral centre formation. The simulation has proved to be an important adjunct to experimental work.

Cell Aggregation↗
PubMed1979

Identification of myosin in human epithelial cancers with immunofluorescence.

The location of myosin in neoplastic cells from human breast, colonic, gastric, bronchial, skin, esophageal, and renal carcinomas has been examined using an immunofluorescence technique with an antibody raised against human smooth muscle myosin. Normal tissues and fibroblast cell cultures were also investigated. In all the tumors myosin was located in the cytoplasm adjacent to the plasma membrane. Cancer cells appeared more strongly immunofluorescent than normal tissues. The precise pattern of immunofluorescence in neoplastic cells varied with the histologic type of the tumor. Linear immunofluorescence around the outer border of the cytoplasm was the most common pattern observed, but in well differentiated adenocarcinomas, myosin was located chiefly in relation to the microvillous border. In three of the squamous carcinomas a granular pattern of immunofluorescence was observed. Undifferentiated breast carcinomas did not contain more myosin than better differentiated tumors, and the intensity of immunofluorescence was no greater in invasive cancer cells than noninvasive tumor cells. The results suggest that myosin is present in greater amounts in neoplastic cells than normal cells and may be concerned with cell shape and polarity as well as cell movement.

Animals↗
PubMed1978

Pattern formation by cultured human epidermal cells: development of curved ridges resembling dermatoglyphs.

In cultures made from disaggregated human epidermal cells, growth to a confluent cell layer is followed by the emergence of patterns resembling those of human dermatoglyphs. These patterns reflect intrinsic properties of kertinocytes. In vivo, only the epidermis of the volar surfaces forms patterns, but in culture, patterns are formed by epidermal cells from other sites as well. Patterns develop by a process of cell movement which first produces ridges and then curves the ridges into figures of increasing complexity, ultimately whorls.

Cell Differentiation↗