Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Microscopy, Video”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources
PubMed1995

cGMP and atrial natriuretic factor regulate cell volume of rabbit atrial myocytes.

Atrial natriuretic factor (ANF) reduces the volume of atrial myocytes by inhibiting Na+/K+/2Cl- cotransport. We determined the role of cGMP and cAMP in ANF-induced shrinkage by using digital video microscopy to measure cell volume; volumes are reported relative to control. ANF (1 mumol/L) reversibly reduced atrial cell volume from 1.0 to 0.915 +/- 0.005 (mean +/- SEM). This effect was mimicked by 10 mumol/L 8-bromo-cGMP (8-Br-cGMP), which decreased myocyte volume to 0.894 +/- 0.007 with an ED50 of 0.99 +/- 0.05 mumol/L. In contrast, 100 mumol/L 8-bromo-cAMP (8-Br-cAMP) did not affect volume, and activating the cAMP pathway with 100 mumol/L 8-Br-cAMP did not alter the volume decrease caused by 8-Br-cGMP or ANF. Inhibition of Na+/K+/2Cl- cotransport with bumetanide (1 mumol/L) also reduced cell volume and prevented further shrinkage on subsequent exposure to 8-Br-cGMP. Similarly, 8-Br-cGMP (10 mumol/L) prevented further shrinkage by ANF. Block of Na(+)-H+ exchange, a participant in volume regulation in other cells, did not alter the response to 8-Br-cGMP. More evidence implicating cGMP was obtained by altering its metabolism. LY83583 (10 mumol/L), a guanylate cyclase inhibitor, blocked ANF-induced cell shrinkage. Zaprinast (100 mumol/L), a cGMP-specific phosphodiesterase inhibitor, markedly potentiated the effect of a threshold concentration of ANF (0.01 mumol/L). The actions of ANF, LY83583, and zaprinast on cGMP levels were verified by radioimmunoassay. These data strongly support the idea that the cGMP cascade is the intracellular signaling pathway responsible for ANF-induced atrial cell shrinkage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Fibroblast growth factor-2 potentiates vascular smooth muscle cell migration to platelet-derived growth factor: upregulation of alpha2beta1 integrin and disassembly of actin filaments.

Fibroblast growth factor-2 (FGF-2) has been implicated in vascular smooth muscle cell (SMC) migration, a key process in vascular disease. We demonstrate here that FGF-2 promotes SMC motility by altering beta1 integrin-mediated interactions with the extracellular matrix (ECM). FGF-2 significantly increased surface expression of alpha2beta1, alpha3beta1, and alpha5beta1 integrins on human SMCs, as assessed by flow cytometry. The greatest increase was for the collagen-binding alpha2beta1 integrin. Despite this, FGF-2 did not increase SMC adhesion to type I collagen but instead promoted SMC elongation and SMC motility. The latter was evaluated by using a microchemotaxis chamber and by digital time-lapse video microscopy. Although FGF-2 was not chemotactic for human SMCs, cells preincubated with FGF-2 displayed a 3.1-fold increase in migration to the undersurface of porous type I collagen-coated membranes and a 2.1-fold increase in migration speed on collagen. Furthermore, chemotaxis to platelet-derived growth factor-BB on collagen was significantly greater in SMCs exposed to FGF-2. FGF-2-induced elongation and migration on collagen were inhibited by a blocking anti-alpha2beta1 antibody; however, SMC adhesion to collagen was unaffected. SMC migration on fibronectin was also enhanced by FGF-2, although less prominently: migration through porous membranes increased 1.8-fold, and migration speed increased 1.3-fold. Also, FGF-2 completely disassembled the smooth muscle alpha-actin-containing stress fiber network contemporaneously with the change in integrin expression and cell shape. We conclude that (1) exogenous FGF-2 promotes SMC migration and potentiates chemotaxis to PDGF-BB; (2) the promigratory effect of FGF-2 is especially prominent on type I collagen and is mediated by upregulation of alpha2beta1 integrin; and (3) FGF-2 disassembles actin stress fibers, which may promote differential utilization of alpha2beta1 integrin for motility but not adhesion. This dynamic SMC-ECM interplay may be an important mechanism by which FGF-2 facilitates SMC motility in vivo.

Actin Cytoskeleton↗
PubMed1998

Persistent activation of a swelling-activated cation current in ventricular myocytes from dogs with tachycardia-induced congestive heart failure.

The hypothesis that cellular hypertrophy in congestive heart failure (CHF) modulates mechanosensitive (ie, swelling- or stretch-activated) channels was tested. Digital video microscopy and amphotericin-perforated-patch voltage clamp were used to measure cell volume and ion currents in ventricular myocytes isolated from normal dogs and dogs with rapid ventricular pacing-induced CHF. In normal myocytes, osmotic swelling in 0.9x to 0.6x isosmotic solution (296 mOsm/L) was required to elicit an inwardly rectifying swelling-activated cation current (I(Cir,swell)) that reversed near -60 mV and was inhibited by 10 micromol/L Gd3+, a mechanosensitive channel blocker. Block of I(Cir,swell) by Gd3+ simultaneously reduced the volume of normal cells in hyposmotic solutions by up to approximately 10%, but Gd3+ had no effect on volume in isosmotic solution. In contrast, I(Cir,swell) was persistently activated under isosmotic conditions in CHF myocytes, and Gd3+ decreased cell volume by approximately 8%. Osmotic shrinkage in 1.1x to 1.5x isosmotic solution inhibited both I(Cir,swell) and Gd3+-induced cell shrinkage in CHF cells, whereas osmotic swelling only slightly increased I(Cir,swell). The K0.5 and Hill coefficient for Gd3+ block of I(Cir,swell) and Gd3+-induced cell shrinkage were estimated as approximately 2.0 micromol/L and approximately 1.9, respectively, for both normal and CHF cells. In both groups, the effects of Gd3+ on current and volume were blocked by replacing bath Na+ and K+ and were linearly related with varying Gd3+ concentration and the degree of cell swelling. CHF thus altered the set point for and caused persistent activation of I(Cir,swell). This current may contribute to dysrhythmias, hypertrophy, and altered contractile function in CHF and may be a novel target for therapy.

Animals↗
PubMed2005

Myocyte volume and function in response to osmotic stress: observations in the presence of an adenosine triphosphate-sensitive potassium channel opener.

BACKGROUND: Hypothermic hyperkalemic cardioplegia results in significant myocyte swelling and impaired contractility. These detrimental effects may be eliminated by the addition of an adenosine triphosphate-sensitive potassium (KATP) channel opener. This study evaluated the hypothesis that a KATP channel opener (diazoxide) would benefit volume homeostasis by limiting volume and subsequent contractility changes during osmotic stress. METHODS AND RESULTS: Isolated rabbit ventricular myocyte volume and contractility were evaluated using video microscopy and field stimulation after exposure to osmotic stress at 37 degrees C. Myocytes were exposed to Tyrode's physiological solution for 20 minutes and test solution for 20 minutes, and then reexposed to Tyrode's for 20 minutes. Test solutions included control Tyrode's (1T) and osmotically altered Tyrode's (2.6T, 0.9T, and 0.6T) solutions with or without the KATP channel opener diazoxide. Severe osmotic stress (2.6T and 0.6T) resulted in significant cell shrinkage and swelling, respectively. This was unchanged by the addition of diazoxide. Mild hyposmotic stress (0.9T) resulted in significant cell swelling that was eliminated by the addition of diazoxide. Cell swelling was associated with reduced contractility. CONCLUSIONS: Cell swelling, but not shrinkage, was detrimental to myocyte contractility. Diazoxide eliminated volume change due to mild hyposmotic stress, similar to that previously noted with hyperkalemic cardioplegia, but did not alter volume change secondary to severe osmotic stress.

Adenosine Triphosphate↗
PubMed2001

Localization of c-Myb and induction of apoptosis by antisense oligonucleotide c-Myb after angioplasty of porcine coronary arteries.

Previous studies have shown that inhibition of the proto-oncogene c-myb inhibits neointimal formation in various animal models. However, the temporal and spatial expression of c-Myb in the vessel wall after injury is not known, and the mechanism of action of antisense oligonucleotide (AS-ODN-c-myb) inhibition remains unclear. One potential effect of cell cycle dysregulation by inhibition of c-myb is an increase in the rates of apoptosis. In this study, c-Myb expression after percutaneous transluminal coronary angioplasty (PTCA) injury and induction of apoptosis after AS-ODN-c-myb treatment were determined. Immunohistochemistry and cellular phenotyping were used to localize c-Myb expression in porcine coronary arteries at various time intervals after PTCA. In vitro, the effects of AS-ODN-c-myb on the apoptosis of porcine vascular smooth muscle cells (PVSMCs) and endothelial cells were determined by using a cell-death ELISA and time-lapse video microscopy. In vivo, local delivery of AS-ODN-c-myb was performed after PTCA of pig coronary arteries, and apoptosis was quantified at 6 hours. c-Myb is induced in pig coronary arteries after angioplasty, with maximal expression in inflammatory cells at 18 hours and in vascular smooth muscle cells at 3 to 7 days. In vitro, AS-ODN-c-myb enhanced PVSMCs (6.8+/-0.8% [P=<0.001] versus 0.5% serum) but not endothelial cell apoptosis (1.4+/-0.5% [P=NS] versus 0.5% serum). In vivo, 6 hours after porcine coronary angioplasty and delivery of AS-ODN-c-myb, the proportion of apoptotic cells within the media was 4.2+/-0.8% (PTCA alone), 2.3+/-0.2% (PTCA+vehicle), and 9.0+/-1.1% (PTCA+AS-ODN-c-myb; P<0.05 versus PTCA alone and P<0.01 versus PTCA+saline). c-Myb is expressed after PTCA of pig coronary arteries, and AS-ODN-c-myb induces apoptosis of PVSMCs in vitro and medial cells in vivo.

Angioplasty, Balloon, Coronary↗
PubMed1997

Migration of guinea pig airway epithelial cells in response to bombesin analogues.

Bombesin-like peptides within neuroepithelial cells elicit proliferation of normal and malignant airway epithelial cells. It is not clear that these peptides also elicit epithelial cell migration, a necessary component of airway repair after injury. We studied the effects of the bombesin analogues, gastrin releasing peptide (GRP) and neuromedin B (NMB), on guinea pig tracheal epithelial cell (GPTEC) migration. Primary GPTEC were allowed to migrate through 8-microm-pore gelatin-coated filters for 6 h in a chemotaxis chamber, after which the number of migrated cells per 10 high power fields (10 hpf) were counted. Both neuropeptides elicited migration of GPTEC: 24.8 +/- 4.5 cells for 10(-11) M NMB (P < 0.001 versus control, n = 4) and 16.8 +/- 1.2 cells for 10(-12) M GRP (P < 0.001 versus control, n = 8). Migration was attenuated substantially by a bombesin receptor antagonist. To investigate further the relationship of migration through a filter to the repair of a damaged epithelium, we studied the repair of epithelial cells by video microscopy. A 0.3- to 0.5-microm2 wound was created in a confluent monolayer of GPTEC, and wound closure was followed over 24 h. There was no significant acceleration in the rate of repair of GRP- or NMB-stimulated monolayers compared to control. These data demonstrate that GRP and NMB elicit migration of airway epithelial cells but may not play a significant role in the early repair of the airway epithelium in culture.

Animals↗
PubMed1998

Stimulation of migration and wound repair of guinea-pig airway epithelial cells in response to epidermal growth factor.

Repair of the airway epithelium after injury involves cell proliferation, migration, and spreading into the injury site. The growth factor, epidermal growth factor (EGF), elicits proliferation of many epithelial cell types in vitro and in vivo, including airways epithelium. However, its effects on cell migration and spreading are less clear. We studied the effects of EGF on guinea-pig tracheal epithelial cell (GPTEC) chemotaxis and migration during wound repair. Primary GPTEC were allowed to migrate through a gelatin-coated filter for 6 h in a chemotaxis chamber, after which the number of migrated cells were counted. EGF elicited migration of GPTEC that was substantial and concentration-dependent. Treatment with EGF accelerated closure of small wounds in confluent epithelial monolayers substantially as measured by video microscopy over 24 h. These effects of EGF were concentration-dependent and seen in monolayer wounds of different size. Effects of EGF did not depend on the underlying matrix on which cells were grown; cells grown on laminin, fibronectin, or collagen had similar wound closure velocities in response to EGF. Early effects of EGF on wound closure were not due to cell proliferation at the wound edge. These data demonstrate that EGF elicits both chemotaxis and migration of airway epithelial cells in culture.

Animals↗
PubMed1997

BCR/ABL induces multiple abnormalities of cytoskeletal function.

The BCR/ABL oncogene causes human chronic myelogenous leukemia (CML), a myeloproliferative disease characterized by massive expansion of hematopoietic progenitor cells and cells of the granulocyte lineage. When transfected into murine hematopoietic cell lines, BCR/ABL causes cytokine-independence and enhances viability. There is also growing evidence that p210(BCR/ABL) affects cytoskeletal structure. p210(BCR/ABL) binds to actin, and several cytoskeletal proteins are tyrosine phosphorylated by this oncoprotein. Also, at least one aspect of cytoskeletal function is abnormal, in that the affinity of beta1 integrins for fibronectin is altered in CML cells. However, isolated changes in beta1 integrin function would be unlikely to explain the clinical phenotype of CML. We used time-lapse video microscopy to study cell motility and cell morphology on extracellular cell matrix protein-coated surfaces of a series of cell lines before and after transformation by BCR/ABL. BCR/ABL was associated with a striking increase in spontaneous motility, membrane ruffling, formation of long actin extensions (filopodia) and accelerated the rate of protrusion and retraction of pseudopodia on fibronectin-coated surfaces. Also, while untransformed cells were sessile for long periods, BCR/ABL-transformed cells exhibited persistent motility, except for brief periods during cell division. Using cell lines transformed by a temperature-sensitive mutant of BCR/ABL, these kinetic abnormalities of cytoskeletal function were shown to require BCR/ABL tyrosine kinase activity. Similar abnormalities of cytoskeletal function on fibronectin-coated surfaces were observed when hematopoietic progenitor cells purified by CD34 selection from patients with CML were compared with CD34 positive cells from normal individuals. Interestingly, alpha-interferon treatment was found to slowly revert the abnormal motility phenotype of BCR/ABL-transformed cells towards normal. The increase in spontaneous motility and other defects of cytoskeletal function described here will be useful biological markers of the functional effects of BCR/ABL in hematopoietic cells.

3T3 Cells↗
PubMed1997

Localization of endogenous furin in cultured cell lines.

Furin is a dibasic endopeptidase responsible for the proteolytic maturation of many precursor proteins in the secretory and endocytic pathways of mammalian cells. The levels of furin expression in most cells are very low, and this has hampered attempts to identify the intracellular compartments in which endogenous furin is localized. We have used a specific antibody reagent to a sequence in the carboxy terminus of furin to perform immunofluorescent staining of mammalian cell lines. This antibody was sensitive enough to detect staining for furin in various cell lines. For the most part, furin staining was confined to a juxtanuclear structure characteristic of the Golgi complex. Analyses by video microscopy and confocal microscopy showed that the distribution of furin was distinct from that of mannosidase II, a marker of the Golgi stack, and most closely resembled that of TGN38, a marker of the trans-Golgi network. Therefore, our results suggest that endogenous furin is predominantly localized to the area of the Golgi complex, most likely within the trans-Golgi network.

Amino Acid Sequence↗
PubMed1997

Inhibition of oligodendrocyte precursor motility by oligodendrocyte processes: implications for transplantation-based approaches to multiple sclerosis.

Transplantation of oligodendrocyte precursor cells represents a promising approach to the treatment of the chronic demyelinated lesions of multiple sclerosis. In view of the multi-focal nature of the disease it will be necessary for the transplanted oligodendrocyte precursor cells to migrate through normal white matter between lesions. Work in other systems has shown that differentiated oligodendrocytes within white matter express molecules inhibitory for axon outgrowth. In light of this we have examined the effect of oligodendrocytes on the migration of oligodendrocyte precursors in vitro using time lapse video microscopy. We find that oligodendrocytes induce collapse and loss of motility in oligodendrocyte precursor processes, with this effect being lost as oligodendrocytes undergo programmed cell death. We conclude that the inhibitory factors present on differentiated oligodendrocytes may prevent effective migration between lesion in vivo, and that strategies to overcome this inhibition may be required for successful repair.

Animals↗
PubMed2003

Control of T lymphocyte morphology by the GTPase Rho.

BACKGROUND: Rho family GTPase regulation of the actin cytoskeleton governs a variety of cell responses. In this report, we have analyzed the role of the GTPase Rho in maintenance of the T lymphocyte actin cytoskeleton. RESULTS: Inactivation of the GTPase Rho in the human T lymphocytic cell line HPB-ALL does not inhibit constitutively high adhesion to the integrin beta1 substrate fibronectin. It did however result in the aberrant extension of finger-like dendritic processes on the substrates VCAM-1, Fn, and mAb specific to beta1 integrins. Time-lapse video microscopy demonstrated that C3 induced extensions were primarily the result of an altered pseudopod elongation rather than retraction. Once the stellate pseudopodia extended, none retracted, and cells became completely immobile. Filipodial structures were absent and the dendritic-like processes in C3 treated cells were rich in filamentous actin. Immunolocalization of RhoA in untreated HPB-ALL cells spreading on fibronectin demonstrated a diffuse staining pattern within the pseudopodia. In C3 treated cells, clusters of RhoA were pronounced and localized within the altered extensions. CONCLUSIONS: GTPase Rho is actively involved in the regulation of T lymphocyte morphology and motility.

ADP Ribose Transferases↗
PubMed2000

Comparison of the phagocytic response of rat and hamster alveolar macrophages to man-made vitreous fibers in vitro.

Rats and hamsters are well known for their disparate response to inhaled mineral fibers/particles. Alveolar macrophages (AM) play an important role in the pulmonary clearance and retention of mineral fibers/particles mainly through the process of phagocytosis. The aim of this study was to investigate whether there exist differences in the phagocytic response and release of reactive oxygen species (ROS) between rat and hamster AM upon exposure to man-made vitreous fibers (MMVF) in vitro. AM were obtained by bronchoalveolar lavage and macrophage-enriched cultures were exposed to MMVF10 and MMVF21 fibers for 20 h. The phagocytic response of macrophages was determined by computer-assisted video-microscopy and the superoxide anion production was evaluated by cytochrome c reduction. A significantly higher percentage of rat AM underwent frustrated phagocytosis of both types of MMVF compared to hamster AM. This was associated with a higher ROS release by rat AM compared to hamster AM. These data may help to explain the cellular mechanisms underlying the disparate pulmonary response of rat and hamster to inhaled particulate matter.

Animals↗
PubMed2002

Hepatocyte growth factor/scatter factor facilitates migration of GN-11 immortalized LHRH neurons.

The molecular cues regulating the migratory process of LHRH neurons from the olfactory placode into the brain are not well known, but gradients of chemotropic and chemorepellent factors secreted by the targets are likely to play a key role in guidance mechanisms. Hepatocyte growth factor/scatter factor (HGF/SF) is a pleiotropic cytokine inducing cell migration. It is involved in a variety of developmental processes through interaction with its receptor c-Met. Here we show that c-Met-antibody labels LHRH migrating neurons in the olfactory mesenchyme of E12 mouse and analyze the potential chemotropic effect of HGF/SF on two immortalized LHRH cell lines, GT1-7 and GN11, isolated from tumors developed in the hypothalamus and in the olfactory bulb, respectively. By RT-PCR analysis, Western blotting, and immunocytochemistry, we provide evidence for a high level of c-Met expression in GN11, but not in GT1-7, cells. In addition, HGF/SF treatment promotes specific migratory activity of GN11 cells, as demonstrated by collagen gel assay, time-lapse video microscopy, and Boyden's chamber experiments. Such promotion is inhibited by the neutralizing antibody. The data reported here represent the first direct evidence of a chemotactic effect of HGF/SF on immortalized LHRH neurons.

Animals↗
PubMed1994

Cell intercalation during Drosophila germband extension and its regulation by pair-rule segmentation genes.

After the onset of gastrulation, the Drosophila germband undergoes a morphological change in which its length along the anterior-posterior axis increases over two-and-a-half fold while its width along the dorsal-ventral axis simultaneously narrows. The behavior of individual cells during germband extension was investigated by epi-illumination and time-lapse video microscopy of living embryos. Cells intercalate between their dorsal and ventral neighbors during extension, increasing the number of cells along the anterior-posterior axis while decreasing the number of cells along the dorsal-ventral axis. Mutations that reduce segmental subdivision of the embryo along the anterior-posterior axis decrease both germband extension and its associated cell intercalation. In contrast, cell intercalation and germband extension are still detected in embryos that lack dorsal-ventral polarity. Characterization of germband extension and cell intercalation in mutant embryos with altered segmentation gene expression indicates that these processes are regionally autonomous and are dependent upon the establishment of striped expression patterns for certain pair-rule genes. Based on these observations, we propose a model for germband extension in which cell intercalation results from the establishment of adhesive differences between stripes of cells by pair-rule genes.

Animals↗
PubMed1995

Order and coherence in the fate map of the zebrafish nervous system.

The zebrafish is an excellent vertebrate model for the study of the cellular interactions underlying the patterning and the morphogenesis of the nervous system. Here, we report regional fate maps of the zebrafish anterior nervous system at two key stages of neural development: the beginning (6 hours) and the end (10 hours) of gastrulation. Early in gastrulation, we find that the presumptive neurectoderm displays a predictable organization that reflects the future anteroposterior and dorsoventral order of the central nervous system. The precursors of the major brain subdivisions (forebrain, midbrain, hindbrain, neural retina) occupy discernible, though overlapping, domains within the dorsal blastoderm at 6 hours. As gastrulation proceeds, these domains are rearranged such that the basic order of the neural tube is evident at 10 hours. Furthermore, the anteroposterior and dorsoventral order of the progenitors is refined and becomes aligned with the primary axes of the embryo. Time-lapse video microscopy shows that the rearrangement of blastoderm cells during gastrulation is highly ordered. Cells near the dorsal midline at 6 hours, primarily forebrain progenitors, display anterior-directed migration. Cells more laterally positioned, corresponding to midbrain and hindbrain progenitors, converge at the midline prior to anteriorward migration. These results demonstrate a predictable order in the presumptive neurectoderm, suggesting that patterning interactions may be well underway by early gastrulation. The fate maps provide the basis for further analyses of the specification, induction and patterning of the anterior nervous system, as well as for the interpretation of mutant phenotypes and gene-expression patterns.

Animals↗
PubMed1998

Intrinsic programs of patterned cell lineages in isolated vertebrate CNS ventricular zone cells.

Using long-term, time-lapse video-microscopy, we investigated how single progenitor cells isolated from the early embryonic cerebral cortex produce neurons and glia over time. Clones of 10 cells or less were produced by short symmetric or asymmetric division patterns, commonly terminating in a 'pair progenitor' for two morphologically identical neurons. Larger trees were composites of these short sub-lineages: more prolific neuroblasts underwent repeated asymmetric divisions, each producing a minor neuroblast that typically made (3/4)10 progeny, and a sister cell capable of generating more progeny. Particular division patterns were seen repeatedly. In contrast, glioblasts underwent a prolonged series of symmetric divisions. These patterned lineage trees were generated from isolated cells growing on plastic, suggesting they are largely intrinsically programmed. Our data demonstrate for the first time that CNS progenitor cells have stereotyped division patterns, and suggest that as in invertebrates, these may play a role in neural development.

Animals↗
PubMed2002

BDNF stimulates migration of cerebellar granule cells.

During development of the nervous system, neural progenitors arise in proliferative zones, then exit the cell cycle and migrate away from these zones. Here we show that migration of cerebellar granule cells out of their proliferative zone, the external granule cell layer (EGL), is impaired in Bdnf(-/-) mice. The reason for impaired migration is that BDNF directly and acutely stimulates granule cell migration. Purified Bdnf(-/-) granule cells show defects in initiation of migration along glial fibers and in Boyden chamber assays. This phenotype can be rescued by exogenous BDNF. Using time-lapse video microscopy we find that BDNF is acutely motogenic as it stimulates migration of individual granule cells immediately after addition. The stimulation of migration reflects both a chemokinetic and chemotactic effect of BDNF. Collectively, these data demonstrate that BDNF is directly motogenic for granule cells and provides a directional cue promoting migration from the EGL to the internal granule cell layer (IGL).

Animals↗
PubMed2003

Individual microtubule dynamics contribute to the function of mitotic and cytoplasmic arrays in fission yeast.

Schizosaccharomyces pombe is an excellent organism for studying microtubule dynamics owing to the presence of well-defined microtubule arrays that undergo dramatic rearrangements during various stages of the cell cycle. Using sensitive time-lapse video microscopy and kymographic analysis, we have determined the polymerization/depolymerization kinetics of individual microtubules within these arrays throughout the fission yeast cell cycle. Interphase bundles are composed of 4-7 microtubules that act autonomously, demonstrating that individual microtubules are responsible for mediating the functions ascribed to these arrays. The nucleation and growth of cytoplasmic microtubules is inhibited upon cellular transition into mitosis, leading to their gradual disappearance. At the onset of mitosis, microtubules form on the nuclear face of the spindle pole body and exhibit dramatically increased dynamics. The presence of these intra-nuclear astral microtubules (INA) is reminiscent of spindle assembly and the search and chromosome capture mechanism observed in metazoan cells. Consistent with other in vivo studies, we do not observe microtubule flux in the anaphase B spindle. Finally, the depolymerization of individual microtubules alternates between each half-spindle, resulting in spindle collapse during telophase. On the basis of these observations, we conclude that microtubules in these diverse cytoskeletal arrays have autonomous behaviors that are an essential component of any model describing cell-cycle-dependent changes in the behavior and function of microtubule arrays.

Anaphase↗