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Results for “Cytoplasmic Streaming”

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PubMed1979

Dual-laser flow cytometry of single mammalian cells.

An improved dual-laser flow cytometric system for quantitative analysis and sorting of mammalian cells has been developed using a low-power argon and high-power krypton laser as illumination sources, thus permitting the excitation of fluorescent dyes having absorption regions ranging from the ultraviolet to infrared. Cells stained in liquid suspension with fluorescent dyes enter a flow chamber where they intersect two spatially separated laser beams. Separate pairs of quartz beam-shaping optics focus each beam onto the cell stream. Electro-optical sensors measure fluorescence and light scatter signals from cells that are processed electronically and displayed as frequency distribution histograms. Cells also can be electronically separated and microscopically identified. The ease and versatility of operation designed into this system represent a marked technological improvement for dual-laser excited flow systems. Details of this instrument are described along with illustrative examples of cells stained with mithramycin and rhodamine and analyzed for DNA content, total protein, and nuclear and cytoplasmic diameter.

Animals↗

PubMed2006

Late Quaternary history of Hippophaë rhamnoides L. (Elaeagnaceae) inferred from chalcone synthase intron (Chsi) sequences and chloroplast DNA variation.

Fossil pollen records indicate that Hippophaë rhamnoides (Sea Buckthorn) was widespread on late- and early postglacial raw soils throughout much of central and northern Europe, but that Early Holocene reforestation restricted populations to northern coastal habitats, or along mountain streams in the Alps, Pyrenees, and Carpathians. We used sequence variation at the nuclear chalcone synthase intron (Chsi), in conjunction with chloroplast DNA-restriction fragment length polymorphism data, to investigate the intraspecific phylogeny, phylogeographic structure, and expansion demographic history of this dioecious and wind-pollinated shrub at its range-wide scale in Europe and Asia Minor. Four major Chsi phylogroups of unresolved relationships were identified with estimated divergences approximately 172,000 years ago. Large-scale phylogeographic structures of nuclear and cytoplasmic markers were congruent in identifying (i) southeastern Europe as the most likely source of colonization into central Europe and Scandinavia, and (ii) the area just north of the Alps as a contact zone between populations from the Alps and the east/central European-Scandinavian lineage. Coalescence-based analyses (i.e. nested clade analysis and mismatch distributions) of Chsi variation were able to detect at least four major episodes of population growth, all within about the last 40,000 years. In particular, these analyses identified a nearly synchronized timing of population expansions in various parts of the species' range in central-eastern Europe/Asia Minor, most likely correlating with the Younger Dryas Stadial ( approximately 13,000-11,600 years ago). It remains to be established whether the phylogeographic history of H. rhamnoides, and particularly its rapid response to the rapid environmental changes of the Younger Dryas cold snap, is unique to the species, or whether it is shared with other cold-tolerant shrub (or grassland) species known from late-glacial raw soils in Europe.

Acyltransferases↗

PubMed2005

beta-catenin expression, DNA ploidy and clinicopathological features in ovarian cancer: a study in 253 patients.

The CTNNB1 gene and its product beta-catenin, a regulator of the Wnt signalling pathway, is often mutated and deregulated in human malignancies. Down stream targets of the Wnt signalling pathway are linked to genomic instability. In this study, the impact of beta-catenin expression on genomic instability in ovarian carcinoma, as determined by DNA ploidy, was investigated. Expression of beta-catenin was examined by immunohistochemistry in 253 ovarian carcinomas. The results were related to genomic instability and clinicopathological features of the patients. Membrane associated staining of beta-catenin was detected in nearly all cases with no correlation to clinical parameters. Most of the samples also had cytoplasmic (84%), while only 13% had nuclear beta-catenin localisation. A significant association between beta-catenin expression (cytoplasmic and nuclear) and histological subtype and degree of differentiation was observed. Nuclear beta-catenin was almost exclusively present in endometroid carcinomas. 53% of all endometroid tumours were positive for nuclear beta-catenin expression (P<0.0001). Mucinous carcinomas had the highest degree of cytoplasmic beta-catenin expression (92%), followed by endometroid (92%), mixed (90%), serous (82%), unclassified adenocarcinomas (81%), carcinomas clear cell and (70%), (P=0.01). Tumours with differentiation grade 1 (16%) and 2 (24%) had higher nuclear beta-catenin expression than grade 3 and clear cell carcinomas (6%) (P=0.012). Better prognostic outcome was found for patients with nuclear beta-catenin localisation as compared to the cases without (P=0.027). In conclusion, the study showed no correlation between beta-catenin expression in ovarian carcinoma and FIGO stage and genomic instability as determined by DNA ploidy status. However, nuclear beta-catenin expression was strongly associated with endometroid histological subtype. Finally, in ovarian cancer, although beta-catenin staining seems to be of prognostic importance with respect to nuclear staining in univariate analysis, only DNA ploidy status, histological grade and FIGO staging were of independent prognostic significance in multivariate analysis.

Cytoskeletal Proteins↗

PubMed2004

The NK1 receptor localizes to the plasma membrane microdomains, and its activation is dependent on lipid raft integrity.

The spatial targeting of receptors to discrete domains within the plasma membrane allows their preferential coupling to specific effectors, which is essential for rapid and accurate discrimination of signals. Efficiency of signaling is further increased by protein and lipid segregation within the plasma membrane. We have previously demonstrated the importance of raft-mediated signaling in the regulation of smooth and skeletal muscle cell contraction. Since G protein-coupled receptors (GPCRs) are key components in the regulation of smooth muscle contraction-relaxation cycles, it is important to determine whether GPCR signaling is mediated by lipid rafts and raft-associated molecules. Neurokinin 1 receptor (NK1R) is expressed in central and peripheral nervous system as well as in endothelial and smooth muscle cells and involved in mediation of pain, inflammation, exocrine secretion, and smooth muscle contraction. The NK1 receptor was transiently expressed in HEK293 and HepG2 cell lines and its localization in membrane microdomains investigated using biochemical methods and immunofluorescent labeling. We show that the NK1 receptor, similar to the earlier described beta(2)-adrenergic receptor and G proteins, localizes to lipid rafts and caveolae. Protein kinase C (PKC) is one of the downstream effectors of the NK1 activation. Its active form translocates from the cytoplasm to the plasma membrane. Upon stimulation of the NK1 receptor with Substance P, the activated PKC relocated to lipid rafts. Using cholesterol extraction and replenishment assays we show that activation of NK1 receptor is dependent on the microarchitecture of the plasma membrane: NK1R-mediated signaling was abolished after cholesterol depletion of the receptor-expressing cells with methyl-beta-cyclodextrin. Our results demonstrate that reorganization of the plasma membrane has an effect on the activation of the raft-associated NK1R and the down-stream events such as recruitment of protein kinases.

Animals↗

PubMed1997

A-kinase anchor protein 75 increases the rate and magnitude of cAMP signaling to the nucleus.

A-kinase anchor protein 75 (AKAP75) binds regulatory subunits (RIIalpha and RIIbeta) of type II protein kinase A (PKAII) isoforms and targets the resulting complexes to sites in the cytoskeleton that abut the plasma membrane [1-7]. Co-localization of AKAP75-PKAII with adenylate cyclase and PKA substrate/effector proteins in cytoskeleton and plasma membrane effects a physical and functional integration of up-stream and downstream signaling proteins, thereby ensuring efficient propagation of signals carried by locally generated cyclic AMP (cAMP) [4-9]. An important, but previously untested, prediction of the AKAP model is that efficient, cyclic nucleotide-dependent liberation of diffusible PKA catalytic subunits from cytoskeleton-bound AKAP75-PKAII complexes will also enhance signaling to distal organelles, such as the nucleus. We tested this idea by suing HEK-A75 cells, in which PKAII isoforms are immobilized in cortical cytoskeleton by AKAP75. Abilities of HEK-A75 and control cells (with cytoplasmically dispersed PKAII isoforms) to respond to increases in cAMP content were compared. Cells with anchored PKAII exhibited a threefold higher level of nuclear catalytic subunit content and 4-10-fold greater increments in phosphorylation of a regulatory serine residue in cAMP response element binding protein (CREB) and in phosphoCREB-stimulated transcription of the c-fos gene. Each effect occurred more rapidly in cells containing targeted AKAP75-PKAII complexes. Thus, anchoring of PKAII in actin cortical cytoskeleton increases the rate, magnitude and sensitivity of cAMP signaling to the nucleus.

Carrier Proteins↗

PubMed1987

Angiogenesis from mononuclear cells in thrombi.

In organizing thrombi angiogenesis is not dependent on invasion of vasa vasora from the vascular wall. Mononuclear cells of the monohistiocytic system are always present within the clotted blood and are capable of differentiation into various types of mesenchymal cells, including endothelial cells. At first autolytic slits and clefts appear in the fibrinous superficial areas of the thrombus. They are gradually lined by spindle-shaped "pre-endothelial" cells that already possess immunohistological properties of endothelial cells but still resemble primitive mesenchymal cells ultrastructurally. Later these cells gain connection with each other by pseudopodia, overlapping and interdigitation until the channels in the fibrinous matrix are covered by an uninterrupted layer of cells. These cells are now characterized ultrastructurally by the appearance of specific endothelial organelles (Weibel-Palade bodies). Circulation within these channels begins from the blood stream. In addition, angiogenesis by sprouting of vasa vasora from the vascular wall occurs in those areas of the thrombus in contact with the vessel wall. In blood vessels with on unimpaired intimal layer, angiogenesis by invasion of capillaries occurs at an earlier date than capillary formation by mononuclear cells.

Adolescent↗

PubMed2001

Is a NAD pyrophosphatase activity necessary for Haemophilus influenzae type b multiplication in the blood stream?

Haemophilus influenzae has an absolute requirement for factor V because it lacks all the biosynthetic enzymes necessary for the de novo synthesis of NAD. Factor V can be provided as either nicotinamide adenosine dinucleotide (NAD), nicotinamide mono-nucleotide (NMN) or nicotinamide riboside (NR) in vitro, but little is known about the source or the mechanism of uptake for factor V in vivo. Recently, a hypothetical open reading frame (ORF), termed nadN, was identified to encode a gene product essential for H. influenzae growth on NAD. Here, we report its role in the virulent H. influenzae serotype b strain Eagan. Our results indicate that NadN of type b Eagan strains is involved in NAD uptake and in processing NAD to NR, which appears to be the substrate for an as yet unidentified cytoplasmic membrane NR transport system. Furthermore, we present data showing that H. influenzae type b nadN mutants are able to survive as well as Eagan, in vivo in the five-day-old infant rat model of human invasive disease. NAD pyrophosphatase and NMN 5'-nucleotidase activities were present in rat and human serum, implying that under infection conditions H. influenzae may obtain NR directly from its host.

Animals↗

PubMed1994

CD28 signaling causes a sustained down-regulation of I kappa B alpha which can be prevented by the immunosuppressant rapamycin.

CD28, an important T cell surface molecule, mediates a costimulatory signal in the activation of T cell immune responses. CD28 signaling is resistant to the immunosuppressant cyclosporin A (CsA) but sensitive to the immunosuppressant rapamycin. CD28 costimulation induces transcription from the interleukin (IL)-2 promoter via the CD28 response element. The levels of c-Rel, a CD28 response element-binding factor, were found previously to be increased by CD28 costimulation. Therefore, we focused our present study on the mechanism(s) of c-Rel up-regulation by CD28 signaling in Jurkat T cells. In this paper, we showed that CD28 costimulation accelerated the kinetics of nuclear translocation of c-Rel. We showed that CD28 signaling, distinct from other stimuli such as phorbol 12-myristate 13-acetate, IL-1, and tumor necrosis factor-alpha, caused a sustained down-regulation of the inhibitor I kappa B alpha in Jurkat T cells. However, the levels of two other c-Rel inhibitors, namely NFKB1 (p105) and NFKB2 (p100), were not affected. Remarkably, the CD28-mediated down-regulation of I kappa B alpha was prevented by rapamycin but not by CsA. The counter-regulation of I kappa B alpha by CD28 signaling and rapamycin observed in Jurkat T cells is also reproducible in primary T cells. In contrast, the phorbol 12-myristate 13-acetate/ionomycin-mediated down-regulation of I kappa B alpha was prevented by CsA but not by rapamycin. Our data suggest that I kappa B alpha is the down-stream target of both CD28 signaling and rapamycin; a continued down-regulation of I kappa B alpha by CD28 costimulation leads to enhanced nuclear translocation of c-Rel, which in turn causes a sustained up-regulation of IL-2 gene expression.

CD28 Antigens↗

PubMed1977

[Systemic lupus erythematosus and congestive heart failure. Heart histological and ultrastructural study (author's transl)].

Histological and ultrastructural studies were performed on myocardial biopsies and aortic and mitral valve leaflets obtained during an operation on a patient with Systemic Lupus Erythematosus (S.L.E.). Congestive heart failure and valvular dysfunction appeared five years after the diagnosis of S.L.E. was made. On histological study, aortic and mitral valve leaflets are uniformly thickened by fibrous tissue with a nodular appearance. No active endocarditis was associated with the fibrous scarring. Atrial myocardium and papillary muscle countain a fibrous net-work discret in the former, extensive in the latter. The scattered foci of fibrosis in the papillary muscle surround vessels without obliteration or parietal necrosis. Ultrastructurally their lumina appears narrowed by prominent endothelial cells with cytoplasmic aggregates of tubuloreticular structures (T.R.S.). These tubules are also present in some endocardial endothelial cells but are rare in the normal intrapapillary or atrial vessels that are not associated with a scar. Myocardial fibrous foci enclose atrophic and severely degenerated cardiac muscle cells; other cells situated at the periphery of the foci are normal in size or hypertrophic and moderately degenerated. The most altered muscle cells show an important loss of myofibrils, a proliferation of sarcoplasmic reticulum in myofibril free spaces, or necrosis with macrophagic resorption. Focal changes with loss of myofilaments, Z material streaming and concentric lamellar bodies are found in moderately degenerate cardiac muscle cells. The remaining papillary muscle cells and the atrial cells are all hypertrophied without degeneration. These changes suggest that focal myocardial fibrosis and associated cardiac muscle cell degeneration may be responsible for impaired cardiac performance in some patients with S.L.E. According to the constant topographic relation between the narrowed vessels whose endothelial cells contain T.R.S. and the surrounding fibrous foci, we believe that the myocardial fibrous patches may correspond to scarring of microinfarcts related to active S.L.E. vascularitis.

Aortic Valve↗

PubMed1992

Electron microscopic identification of luteinizing hormone-releasing hormone-immunoreactive neurons in the medial olfactory placode and basal forebrain of embryonic mice.

Luteinizing hormone-releasing hormone is a decapeptide found in the brain and nose of all vertebrates that have been examined by immunocytochemical procedures with antiserum to luteinizing hormone-releasing hormone. It regulates the release of both luteinizing hormone and follicle-stimulating hormone from the gonadotropes of the anterior pituitary gland and promotes mating behavior. After about 11 days of embryogenesis in mice, luteinizing hormone-releasing hormone-immunoreactive cells are detected by immunocytochemical procedures in the medial olfactory placode, in the primordium of the vomeronasal organ. As they leave the olfactory placode, they run under the epithelial layer of the nasal septum associated with vomeronasal and terminalis nerves. Clustered, they stream toward the primordium of the olfactory bulb, passing along its ventromedial surface. Eventually, the largest numbers reach the septal and preoptic areas of the brain. Electron microscopic immunocytochemistry showed that luteinizing hormone-releasing hormone-immunoreactive product is accumulated just outside the nuclear envelope and in the lumen of rough endoplasmic reticulum adjacent to the cell nucleus of cells in and adjacent to the olfactory placode. As luteinizing hormone-releasing hormone-immunoreactive neurons migrate, they assume a fusiform shape and the immunoreaction product extends from the area around the nucleus throughout the cytoplasm, notably in processes which extend toward the direction of migration. Before and during migration, luteinizing hormone-releasing hormone was not detected in the Golgi apparatus or neurosecretory granules. It is inferred that as far as ultrastructural evidence is concerned, these neurons do not have a secretory function before they attain their target organs.

Animals↗

PubMedDate not supplied

[Cartilaginous torus epithelium of the vomeronasal organ of swine and sheep].

The vomeronasal organ consists of receptor cells of microvillous type, supporting and basal cells. According to their ultrastructural organization the microvillar cells are analogous to those in the main olfactory organ in the pig and have all signs of the receptor cell: microvilli at the top and centrioles in cytoplasm, as well as the central process getting off the cell body. Both in the pig and in the sheep the supporting cells contain in their apical region a number of basal bodies with cilia, getting them off. In the receptor zones of epithelium albuminous glands predominate, in the respiratory zones--mucous ones. A great amount of liquid mucus, excreted on the surface of the epithelium by numerous glands and supporting cells, apparently, facilitates adsorption and desorption of odorous molecules from the receptor cells after their stimulation. The cilia of the supporting cells probably from the stream of the vomeronasal mucus. The cartilagenous torus epithelium of the vomeronasal organ of the pig and sheep has in general a similar structural organization. This demonstrates general for Vertebrata receptor mechanisms of odorous substances, evidently connected with perception of feramones or contact olfaction.

Animals↗

PubMed1990

Microenvironmental organization and stromal cell associations of B lymphocyte precursor cells in mouse bone marrow.

B lymphocyte precursor cells expressing B220 glycoprotein have been examined in mouse bone marrow (BM) by the in vivo binding of monoclonal antibody (mAb) 14.8 visualized by light and electron microscope radio autography. Young mice were injected intravenously with 125I-labeled mAb 14.8 and then perfused to remove unbound antibody. Quantitative analysis of radioauto graphic sections of femoral BM revealed many labeled mAb 14.8-binding cells which were situated both singly and in groups throughout the extravascular BM parenchyma. Groups of large 14.8+ cells were located in patchy areas in the peripheral regions of the BM near the endosteum. These cells were shown to include proliferating precursor B cells by using mice given vincristine sulfate to stop cells in metaphase and mice treated from birth with anti-IgM antibodies to delete mature B lymphocytes. Electron microscopy revealed clusters of 14.8+ cells intimately associated with the processes of stromal reticular cells. Other 14.8+ cells were in close contact with macrophages; in some instances the intervening cell membranes were indistinct and the macrophages contained 14.8+ material in their cytoplasm. In addition, 14.8+ small lymphocytes were highly concentrated within the lumen of some sinusoids. The present method of detecting B lineage precursor cells in situ has led to a working model of the microenvironmental organization of primary B cell genesis in vivo. The model proposes (a) a centrally directed sequence of differentiation initiated by early precursor cells situated peripherally near the surrounding bone; (b) close associations between precursor B cells and stromal reticular cells; (c) deletion of ineffective B cells by macrophages, and (d) an intravascular maturation phase before B lymphocytes are finally delivered into the blood stream.

Animals↗

PubMed1988

Contact-mediated triggering of lamella formation by Dictyostelium amoebae on solid surfaces.

Amoebae of the slime mould Dictyostelium discoideum form broad ultrathin cytoplasmic lamellae by a centripetal contractile process soon after they have spread on certain solid surfaces. We have investigated the surface requirements for initial triggering of this contact-mediated signalling system. The lamellar response is not normally evoked by glass, but is seen on glass covalently derivatized with paraffinic chains, as well as on glass covalently derivatized with amine groups and on glass bearing adsorbed polylysine. We have recorded the frequency of the lamellar response on these surfaces as a function of ionic strength and pH, and have measured the electrostatic potentials of the surfaces by the streaming potential method. Using these data we have concluded that the general trigger for the lamellar response is not a 'simple' physical or chemical property of the substrata: it is not dependent on specific chemical groups, degree of hydrophobicity, electrostatic potential, or charge density, taken as isolated factors. It seems likely that triggering is dependent on the overall energetics of cell-substratum interaction.

Cell Adhesion↗

PubMed1988

Myosin and Ca2+-sensitive streaming in the alga Chara: detection of two polypeptides reacting with a monoclonal anti-myosin and their localization in the streaming endoplasm.

A monoclonal antibody to the heavy chain of myosin from mouse 3T3 cells was used to detect and localize related proteins in the green alga Chara. Proteins of 200,000 and 110,000 Mr reacted on immunoblots of proteins precipitated rapidly with trichloroacetic acid to minimize proteolysis. Immunofluorescence of whole cells localized these proteins to organelles of the streaming endoplasm, to a system of endoplasmic strands and to the subcortical actin bundles. Except that fewer endoplasmic strands and organelles were found and the strands were tangled, the localization pattern was similar in cells rapidly perfused to remove the bulk of the streaming endoplasm. Actin was confined almost entirely to the system of subcortical actin bundles in both whole and perfused cells. Myosin that was associated with the tangled endoplasmic strands but not that associated with the organelles or actin bundles was removed by concentrations of Ca2+ inhibiting ATP-dependent streaming in perfused cells. ATP extracted both organelles and endoplasmic strands but left a continuous pattern of myosin immunostaining along the actin bundles. The findings are discussed in relation to the possible existence of two forms of myosin and of separate mechanisms moving the bulk endoplasm and individual organelles.

Actins↗

PubMed1990

Epidemic non-A, non-B hepatitis in Xinjiang. Clinical and pathologic observations.

131 cases of epidemic hepatitis from two villages in Xinjiang, were admitted to the provisional infectious diseases hospital from February to April 1987. In 125 (95%) patients neither anti-HAV IgM nor anti-HBc IgM were positive. 118 (90%) were drinking water from a local stream of the Hotan River. The study was conducted on 125 patients aged from 5 to 90 years, with a mean of 26.4 years. There were slightly more males than females, a ratio of 1.5 to 1. The incubation period was roughly estimated to be 17 to 37 days (mean 24.8 days). All subjects were jaundiced. 12 patients (including 6 pregnant women) had cholestatic symptoms. Except one woman who died of postpartum bleeding, all patients ran a benign course without fulminant hepatic failure. Pathologic changes of liver biopsies from 35 cases included lobular damage and inflammation, ballooned hepatocytes with clear cytoplasm and delineated cell membrane which were named "clear cell". There were cholestasis of different degrees in the acute icteric stage and fatty changes in the convalescent stage. It was seen under the electron microscope that the livers of 8 cases had neither tubular structure nor sponge-like inclusions, but had nuclear changes including curled edge of nuclear membrane and nuclear heterochromatin condensed in masses. Liver biopsies were repeated in 7 cases followed up for 6-13 months, and hepatohistology was normal in 5. Of the other two cases there was one of each.

Adolescent↗

PubMed1997

Microtubule assembly in clarified Xenopus egg extracts.

Crude cytoplasmic extracts made from Xenopus eggs have proven to be uniquely useful in the studies of the mechanism of spindle microtubule assembly dynamics and chromosome movement during progression through the cell cycle. We examined microtubule dynamic instability in the Xenopus system using video-enhanced differential interference contrast microscopy (VE-DIC), which required high-speed centrifugation in order to clarify crude Xenopus extracts of refractile particles. Surprisingly, the resultant clarified, undiluted extracts exhibited virtually no microtubule catastrophe, even in the presence of high MPF (cyclin B/p34cdc2 kinase) activity and mitogen-activated protein (MAP) kinase activity, a down-stream kinase also implicated in regulating microtubule dynamics. Microtubule elongation occurred at plus ends, and interphase microtubules grew at 17-30 microns/min while metaphase [meiotic, myelin basic protein kinase activity which is diagnostic for cytostatic factor (CSF)-arrested] microtubules grew at about 10 microns/min. Plus-end shortening rates for both interphase and metaphase extracts were > 50 microns/min. Addition of okadaic acid, a protein phosphatase inhibitor known to activate MAP kinase activity and cause an increase in microtubule turnover in extracts made from sea urchin eggs, had no effect on microtubule catastrophe in either interphase or metaphase Xenopus extracts. In addition, the microtubules assembled in interphase extracts were less sensitive to dilution than those in metaphase. This study is the first to describe the dynamic instability of microtubules in Xenopus extracts without the addition of exogenous tubulins or other buffer contaminants.

Animals↗

PubMedDate not supplied

The flow of thought and the flow of substance in the brain.

Many neuroactive substances undergo cytoplasmic transport along the axons and dendrites of cerebral neurons, and the expression of their activities is determined by the time occupied by their transport. Such substances include cyclic nucleotides which are formed postsynaptically as mediators by several neurotransmitters including catecholamines, and which are capable of acting at numerous postsynaptic sites during their subsequent intracellular translocation. Temporally patterned changes in cell-firing tendency during some seconds or minutes following brief stimuli are attributed to movement of such compound, as is also the subjective sense of a flow of thought. Descriptions are appraised which indicate that components experienced as part of a stream of thought can be initiated by drive-inducing catecholaminergic systems acting through cyclic nucleotides, thus affording endogenous signals that contribute to electrophysiological matching processes in perception and recall. Roles for satiety mechanisms involving opioid peptides are also assessed.

Animals↗

PubMed1985

Coupling of cytoskeleton functions for fibroblast locomotion.

Using a chick cell phenotype specialised for locomotion with morphometric measurements made possible by modern instrumentation technology, we have reinvestigated motile functions in fibroblast locomotion. Quantitative analysis of rapid fluctuations in cell form and organelle distribution during locomotion showed many significant correlations between different parts of the cell despite much irregularity in individual displacements over the time scale of the order of one second. These broke down when external perturbations caused changes in shape or direction. Partial energy deprivation caused the cells to lose control of shape and organelle distribution even though forward protrusion continued unaffected. Cytoplasmic displacements shown by marker mitochondria correlated with adjacent fluctuations at the leading edge, and drug treatments which increased the amplitude of mitochondrial movements caused visible protrusions in projected positions at the leading edge. We conclude that fibroblast locomotion may be driven coordinately by a common set of motility mechanisms and that this coordination may be lost as a result of physical or pharmacological disturbance. Taking our evidence with results from other Laboratories, we propose the following cytoskeleton functions. (i) Protrusive activity, probably based on solation--gelation cycles of the actin based cytoskeleton and membrane recycling which provides cellular and membrane components for streaming through the cell body to the leading edge; this is Ca++ sensitive but relatively energy insensitive. (ii) Constraining activity on the cell membrane and on certain organelles to maintain shape and so facilitate directionality and the drawing along of the trailing body; this is Ca++ insensitive but relatively energy sensitive. (iii) Channeling function of microtubules to direct the flow towards multiple foci on the leading edge, and so determine cell polarity. Such a mechanism of locomotion for fibroblasts has many features consistent with evidence for other cell types, especially amoebae and leukocytes.

Animals↗