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At least 559 records · Page 31Linked to original sources
PubMed1992

Lowering extracellular chloride concentration alters outer hair cell shape.

In general, increasing external K+ concentration, as well as exposure to hypotonic medium, induces a shortening of outer hair cells (OHCs) accompanied by an increase in width and volume. One possible mechanism suggested for these changes is a movement of Cl- and/or water across the cell membrane. We therefore examined the role of Cl- in OHC volume maintenance by testing the effect of decreasing extracellular Cl- concentration on OHC length and shape. In addition, the effect of hypotonic medium was examined. OHCs were isolated from guinea pig cochleae, mechanically dissociated and dispersed, and placed in a modified Hanks balanced salt solution (HBS). Exposing the cells to a Cl(-)-free HBS produced an initial shortening, which was rapidly followed by an increase in length. After about 9 min of exposure to Cl(-)-free HBS, the cells appeared to lose all water and collapsed. Upon return to normal HBS, the OHCs returned to their normal shape. We speculate that the collapse of the OHCs may be due to the loss of intracellular Cl-, which, in turn, resulted in the loss of intracellular K+ and water. The results indicate that Cl- contributes greatly to the maintenance of OHC volume. In addition, we confirmed that isolated OHCs swell in hypotonic medium and maintain their swollen state until returned to normal medium. The mechanism for maintenance of the swollen state is unknown.

Animals↗
PubMed1983

Fibronectin modulation of cell shape and lipogenic gene expression in 3T3-adipocytes.

The differentiation of 3T3-F442A cells is accompanied by changes in cell morphology, decreased synthesis and assembly of cytoskeletal proteins, and increased biosynthesis of lipogenic enzymes. The differentiation-dependent alterations in actin assembly can be prevented by culture of cells on fibronectin matrices. Under these conditions, morphological change is prevented and the induction of lipogenic enzymes such as glycerophosphate dehydrogenase and fatty acid synthetase is sharply reduced. In contrast, the differentiation-linked decreases in actin and tubulin biosynthesis occur normally. Hybridization of cytoplasmic and nuclear RNA to cloned cDNA probes indicates that the inhibition of lipogenic protein biosynthesis occurs because of reduced levels of specific mRNA production. The inhibitory effects of fibronectin can be reversed by keeping cells in a rounded configuration or by exposing cells to either cytochalasin D, which disrupts the actin cytoskeleton, or insulin, a key lipogenic hormone. These results demonstrate that fibronectin can regulate gene expression for lipogenic proteins and they suggest that it interferes with cytoskeletal and morphological changes necessary for new gene expression.

Actins↗
PubMed1976

Cell-cycle, cell-shape mutant with features of the Go state.

A cold-sensitive mutant of CHO cells has features of "reverse transformation" at the non-premissive temperature of 33 degrees C. Cells accumulate at G1 with altered morphology and remain viable and quiescent for more than 40 d. Such cultures are synchronised by a temperature shift back to the permissive 39 degrees C.

Bucladesine↗
PubMed1999

[Value of scanning electron microscopy in evaluation of peripheral red blood cells shape in patients with pulmonary tuberculosis for treatment effectiveness evaluation].

The morphology of red blood cells in patients with pulmonary tuberculosis was studied by scanning electron microscopy during enterosorption. The use of an enterosorbent caused a significant decrease in the count of abnormally changed cell elements and an increase in normocytes, which suggests that detoxification has a stimulating effect. Enterosorption promotes less content of altered peripheral red blood cells, which leads to improvement of its cellular composition in the presence of clinical manifestations of the decreased rate of a tuberculous process in the lung and which is suggestive of the detoxifying impact of this treatment.

Enterosorption↗
PubMed1996

Cell shape change reveals the cyclic AMP-mediated action of follicle stimulating hormone, human chorionic gonadotrophin and vasoactive intestinal peptide in primary cultured human granulosa-lutein cells.

Granulosa cells are known to be the site of action of various hormones and agents that regulate ovarian function. This study was conducted to evaluate the effects of gonadotrophins, vasoactive intestinal peptide (VIP), prostaglandin (PG) F2 alpha and angiotensin II on the cyclic AMP (c-AMP) signalling transduction pathway in human granulosa-lutein cells. Exposure to agents that elevate c-AMP or mimic c-AMP action caused the cells to become rounded in a process that was rapid and reversible. We were able to demonstrate this cell rounding process in the presence of gonadotrophins and VIP, but not in the presence of PGF 2 alpha or angiotensin II. In addition, incubation of the cells with various selective phosphodiesterase (PDE) inhibitors revealed that the PDE type IV isoform, but not type III, catalyses c-AMP degradation in human granulosa-lutein cells. Alteration in c-AMP-dependent cytomorphology appears to be a convenient method to analyse the regulation of c-AMP-mediated events in the human granulosa-lutein cells.

Adenosine Monophosphate↗
PubMed1989

Respiratory burst oscillations in human neutrophils and their correlation with fluctuations in apparent cell shape.

Neutrophils pretreated with phorbol 12-myristate 13-acetate (1-10 nM) and stimulated with low concentrations of chemotactic agonists (1-10nM) exhibited a marked increase in respiratory burst activity that was characterized by regular oscillations. These were accompanied by parallel oscillations in turbidity having the same phase and period. Four different agonists, f-Met-Leu-Phe, complement fragment C5a, platelet-activating factor, and leukotriene B4, induced virtually identical oscillations, with mean periods of 7.9 +/- 0.6 s (respiratory burst) and 7.9 +/- 0.8 s (turbidity) at 37 degrees C. No burst oscillations were observed at high agonist concentrations (50-100 nM) unless the fungal metabolite 17-hydroxywortmannin was added prior to stimulation. In the absence of phorbol 12-myristate 13-acetate, the respiratory burst activity was inhibited by 17-hydroxywortmannin, the protein kinase C inhibitor staurosporine, and calcium depletion, while agonist-dependent turbidity changes including the oscillations were unaffected. Turbidity changes reflect corresponding changes in cell size and/or shape, suggesting that cyclic alterations in morphology such as lamellipod extension and retraction physically affect the catalytic efficiency of the membrane-bound burst enzyme NADPH-oxidase. The oscillations appear to be controlled via receptor-dependent activation mechanisms which do not involve PKC activation or the rise in internal calcium presumably derived from phospholipase C activation.

Androstadienes↗
PubMed1988

Factors influencing cell shape in the mutans group of streptococci.

Electron and light microscopic and growth studies of representatives of the diverse species of mutans streptococci revealed the cells to be either bacillary or coccoid in shape. Some strains changed from bacillary to coccoid if the HCO3-/K+ ratio of the media was increased and from coccoid to bacillary if the ratio was decreased. Doubling times of rods and cocci were the same despite an HCO3-/K+ ratio change between 0.008 and 2.84. For strain 10449S, no tested anions or cations substituted for HCO3- or K+ to produce this effect, except for B4O7(2-). Strain 10449S grown at a high B4O7(2-)/K+ ratio became ellipsoid, and this phenomenon was associated with slower doubling times. Up to three incomplete septa could be observed in one rod, but no more than one incomplete septum could be observed in either ellipsoid or spherical cells. Interseptal distances were greatest in rods, shorter in spheres, and shortest in ellipses. All of the above differences were statistically significant (P less than 0.001).

Microscopy, Electron↗
PubMed1980

Co-expression of differentiation markers in hybrids between Friend cells and lymphoid cells and the influence of the cell shape.

We have studied the regulation of differentiation within the hemopoietic system by fusing mouse Friend cells (which can be induced to undergo red blood cell differentiation) to various mouse lymphomas and myelomas which express characteristic T and B lymphocytes surface antignes. Our results show that both erythroid and lymphoid differentiation markers can be co-expressed within the same cell. To determine whether this result applies to other differentiation states, we fused suspension Friend cells to three adherent fibroblast cell lines, and isolated both adherent and suspension hybrids. In fact, suspension hybrid clones were inducible for hemoglobin, whereas adherent clones were not. No obvious differences in overall chromosome balance were evident between the adherent and suspension hybrids. A similar correlation between suspension morphology and inducibility of hemoglobin was found in hybrids between suspension Friend cells and an adherent lymphoma line. These results show that different developmental programs can be co-expressed within the same hybrid cell; but the strongly adherent type of morphology is inconsistent with expression of the red blood cell phenotype, both in hybrid cells derived entirely from hemopoietic parental cells and in cells from widely different lineages.

Animals↗
PubMed1996

The repertoire of T cells shaped by a single MHC/peptide ligand.

Although the thymus produces many immature thymocytes, few of these cells mature. Positive selection has been thought to limit thymocyte development. In thymuses expressing a single MHC/peptide combination, however, surprisingly large numbers of thymocytes are selected to mature. Many of these react with the selecting MHC, bound to other self-peptides. Therefore, the number of thymocytes that mature is limited by the fact that positively selected cells die because they react too well with MHC bound to self-peptides that are not identical to those involved in positive selection. T cells that mature in thymuses expressing a single MHC/peptide ligand react frequently with foreign MHC, suggesting that the repertoire of alpha beta receptors may be more biased toward reaction with MHC than was previously thought.

Animals↗
PubMed2000

Perillyl alcohol inhibits TCR-mediated [Ca(2+)](i) signaling, alters cell shape and motility, and induces apoptosis in T lymphocytes.

Perillyl alcohol (POH) inhibits isoprenylation and has shown anticancer and chemopreventive properties in rodent models. The mechanism that underlies the anticancer activity of POH and other isoprenylation inhibitors is unknown but has been postulated to involve decreased levels of isoprenylated Ras and Ras-related proteins. Previously we demonstrated that POH effectively inhibits human T cell proliferation in vitro and can prevent acute and chronic rejection in a rat cardiac transplant model. In this report, we investigate the effects of POH on T lymphocytes at the single-cell level. POH disrupts the polarized shape and motility of antigen-specific murine 1E5 T cells. Using an optical trap to position anti-CD3-coated beads in contact with 1E5 T cells, we demonstrate that POH inhibits their TCR-mediated calcium response. Furthermore, we show that POH preferentially induces apoptosis in PHA-activated human T cells as well as in 1E5 T cells.

Adult↗
PubMed1976

Flow microfluorometric analysis of sperm DNA content: effect of cell shape on the fluorescence distribution.

The DNA content of individual sperm from populations of acriflavine-stained cells was investigated by analysis of fluorescence frequency distributions obtained with high-resolution flow-systems instruments. Sperm with spherical or cylindrical heads from three mollusk species produce narrow, symmetric fluorescence distributions. Flat sperm heads from six eutherian species produce asymmetric distributions consisting of a peak with a lateral extension to higher fluorescence values. The unexpected shape of these distributions was shown to be due to the flat geometry and high refractive index of the sperm heads in conjunction with the orthogonal axes of flow, excitation, and detection in the flow-systems instruments. The theoretical and experimeytal results indicate that the lateral extension can be eliminated either by controlling the sperm orientation with planar flow conditions or by accounting for sperm orientation by means of orientation sensing.

Acridines↗
PubMed2003

Syllectometry: the effect of aggregometer geometry in the assessment of red blood cell shape recovery and aggregation.

Syllectometry is a measuring method that is commonly used to assess red blood cell (RBC) aggregability. In syllectometry, light is incident on a layer of whole blood initially exposed to shear flow. The backscattered light is measured after abruptly stopping the driving mechanism. The resultant time-dependent intensity plot is called the syllectogram. Parameters that quantify RBC aggregability are obtained by analyzing the syllectogram. As we will show in this paper, the upstroke in the initial part of the syllectogram contains the information for measurement of RBC-shape recovery in whole blood as well. To estimate RBC-shape recovery, we extended the existing two-exponential mathematical representation of the syllectogram by a third exponent that describes the upstroke. To investigate the feasibility of RBC-shape recovery measurement from the upstroke, we derived an analytical model of the flow decay that follows after abruptly stopping the driving mechanism. The model reveals that for large gaps the flow decay may interfere with the true RBC-shape recovery process. These theoretical findings were confirmed by velocity measurements in a Couette-type aggregometer. Syllectograms obtained using large gaps differ in many respects from those obtained using small gaps. As predicted by our model large gaps show a prolonged apparent shape-recovery time-constant. Moreover, a delayed intensity peak, a reduced upstroke of the intensity peak and a considerable increase of the half-life parameter are observed. The aggregation indices for large gaps are lower than for small gaps. This paper yields a better understanding of the velocity and shear-rate decay following upon abruptly stopping the driving mechanism. A better mathematical representation of the syllectogram and recommendations for a maximum gap width enables both RBC-shape recovery and aggregation measurements in whole blood using syllectometry.

Blood Flow Velocity↗
PubMedDate not supplied

Cell shape, intracellular pH, and fibroblast growth factor responsiveness during transdifferentiation of retinal pigment epithelium into neuroepithelium in vitro.

In this report we show that some retinal pigment epithelial (RPE) cells, with no expression of neural cell adhesion molecule (N-CAM) (RPEN-CAM-), spontaneously lose pigment and start to express N-CAM in culture. Chick RPE cells normally do not express N-CAM, while the protein is present in chick neural retina. Thus some of the RPE cells in culture started to transdifferentiate into a neuroepithelium (NEN-CAM+). We have measured intracellular pH (pHi) in the RPE cultures and followed its changes in response to basic fibroblast growth factor (bFGF). The depigmented cells protrude above the RPE cell sheet and have a lower resting pHi (approximately 7.05) than the pigmented RPE cells (approximately 7.15). The majority of cells with low resting pHi express N-CAM. The difference in the resting pHi between RPEN-CAM- and NEN-CAM+ cells is not due to the N-CAM expression by NEN-CAM+ cells, as their pHi is the same as the pHi of freshly plated single "round" RPEN-CAM- cells that have not spread yet. NEN-CAM+ cells respond to bFGF with a quick and sustained pHi rise. In contrast, neither the cuboidal RPEN-CAM- cells in a colony centre nor single round RPEN-CAM- cells respond to bFGF with cytoplasmic alkalinization. RPE cells do not proliferate in response to bFGF, while NE cells respond to bFGF with a stimulation of growth. We conclude that bFGF acts not on the fully differentiated RPEN-CAM-, but only on those cells which have already started to transdifferentiate and changed their shape and (or) adhesive status.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Lateral diffusion of lectin receptors in fibroblast membranes as a function of cell shape.

Anchorage-dependent fibroblasts respond to biochemical growth signals only when attached to and spread on a suitable substrate surface. Attachment of fibroblasts initiates a cytoskeletal assembly process that results in the organization of long actin stress fibers and microtubules which may be required for transmembrane signal transduction. Fibroblasts maintained in suspension, however, remain spherical with no apparent stress fibers or lengthy microtubules. Because of the significant differences in cytoskeletal organisation induced by shape modification, and the resulting possible changes in organization and dynamics of membrane receptors, the technique of fluorescence redistribution after photobleaching (FRAP) was employed to examine the lateral mobility of wheat germ agglutinin (WGA) and succinylated concanavalin A (sCon A) receptors in the plasma membrane of untransformed and Kirsten murine sarcoma virus-transformed Balb/c 3T3 fibroblasts in the spread and spherical state. An examination of FITC-WGA and FITC-sCon A binding to the plasma membrane for both cell lines in a spread or spherical state demonstrated no significant differences in the number of WGA or Con A receptors as a function of shape or transformation. The primary observations from this study are (a) membrane WGA and sCon A receptors in spherical Balb/c 3T3 fibroblasts display mobility 12 times faster than in the spread state, while phospholipid mobility is similar and apparently shape independent, (b) transformed cells in the spread state have WGA and sCon A receptor mobilities similar to those of untransformed cells in the spread state, (c) flat adherent, but not unattached spherical, Balb/c 3T3 fibroblasts are subject to Con A-induced global modulation and (d) transformed cells in the spherical state contain a significant population of cells (approximately 30%) with WGA receptor mobilities faster than those observed in spherical untransformed cells. These observations are discussed in terms of a linked matrix model for membrane protein diffusion.

Actins↗
PubMed1993

Coordinate effects of Concanavalin A on cytoskeletal organization, cell shape, glycosaminoglycan accumulation and exoglycosidase activity in chick embryonic cultured fibroblasts.

The effects of Concanavalin A on cell morphology, cytoskeleton arrangement and some metabolic activities of 11-day chick embryo fibroblasts were examined. In fibroblasts, Con A caused a dose-dependent round morphology and a change in tubulin, actin and alpha-actinin arrangement, whereas it did not modify 3H-thymidine incorporation. In addition, lectin stimulated more hyaluronic acid than sulphated glycosaminoglycan synthesis, affected glycosaminoglycan sulphation, and also reduced beta-N-acetyl-D-glucosaminidase, beta-N-acetyl-D-galactosaminidase and beta-glucuronidase activities.

Animals↗