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PubMed1991

Modulation of endothelial cell shape and growth by retinoids.

Physiologic concentrations of retinol (1 X 10(-6) M) caused capillary and aortic endothelial cells (EC) to undergo a morphologic change, characterized by a rounder cell body, increased refractility at cell edges, and longer cytoplasmic processes distributed in a bipolar fashion. Computer image analysis of retinoid-treated EC revealed that both retinoic acid and retinol affected cellular area. Twenty-four hours following retinoic acid treatment, EC occupied a greater area than control (P less than 0.03) or retinol-treated EC (P less than 0.02). By Day 7, however, retinoic acid-treated EC occupied equivalent cellular areas as compared to control cells (P = 0.8). In contrast, by Day 7, retinol-treated EC occupied a smaller cellular area than control (P less than 0.002) or retinoic acid-treated EC (P less than 0.001). Proliferation studies revealed that within the first 72 hr of retinol treatment, basal EC growth was inhibited by 33% and the cells exhibited a lowered responsiveness to basic fibroblast growth factor (bFGF). In contrast, EC treated with retinoic acid and pericytes treated with each of the retinoids were not inhibited. The inhibitory effect of the 72 hr retinol treatment was reversible. Following 3 days exposure to retinol, EC given fresh media without retinoid underwent a population doubling in a subsequent 3-day period. However, in the continued presence of retinol, EC were 100% growth-inhibited. After a 3-day pretreatment with retinol, with or without continued retinol treatment, EC were refractile to the mitogenic action of bFGF in a subsequent 3-day period. These results demonstrate that retinol inhibits the basal and growth factor-stimulated growth of EC and causes a significant shape alteration of EC, supporting our hypothesis that vitamin A may be one of the signals that modify the growth and phenotype of EC.

Adrenal Cortex↗
PubMed1990

Intracellular distribution of actin in cells of the organ of Corti: a structural basis for cell shape and motility.

Immunofluorescence staining and phalloidin labeling have provided localization of actin in the sensory and supporting cells of the inner ear at the light microscopic level. However, with electron microscopy, neither actin nor actin filaments have been found in the outer hair cell body. This paper describes various techniques utilized to preserve and identify cytoplasmic actin at the ultrastructural level. Post-embedding staining of Lowicryl K4M sections, pre-embedding staining of permeabilized cells of the organ of Corti, pre-embedding staining of vibratome sections, and pre-embedding staining of permeabilized dissociated cells documented the presence of actin, but each of these techniques was best suited to localize actin in specific parts of the cell. Cytoplasmic actin was labeled when isolated cells were lightly fixed and membranes were permeabilized with detergent--conditions under which the cell ultrastructure was compromised. Under conditions of optimal fixation, cytoplasmic filaments embedded in the dense granular matrix of the hair cell cytoplasm were observed.

Actins↗
PubMed1995

The Drosophila tumor suppressor gene warts encodes a homolog of human myotonic dystrophy kinase and is required for the control of cell shape and proliferation.

Homozygous loss of the warts (wts) gene of Drosophila, caused by mitotic recombination in somatic cells, leads to the formation of cell clones that are fragmented, rounded, and greatly overgrown compared with normal controls. Therefore, the gene is required for the control of the amount and direction of cell proliferation as well as for normal morphogenesis. The absence of wts function also results in apical hypertrophy of imaginal disc epithelial cells. Secretion of cuticle over and between the domed apical surfaces of these cells leads to a honeycomb-like structure and gives the superficial wart-like phenotype of mitotic clones on the adult. One wts allele allows survival of homozygotes to the late larval stage, and these larvae show extensive imaginal disc overgrowth. Because of the excess growth and abnormalities of differentiation that follow homozygous loss, we consider wts to be a tumor suppressor gene. The wts gene is defined by the breakpoints of overlapping deficiencies in the right telomeric region of chromosome 3, region 100A, and by lethal P-element insertions and excisions. It encodes a protein kinase that is most similar to human myotonic dystrophy kinase, the Neurospora cot-1 protein kinase, two cell-cycle regulated kinases of yeast, and several putative kinases from plants. These proteins define a new subfamily of protein kinases that are closely related to but distinct from the cyclic AMP-dependent kinases. Although myotonic dystrophy is defined by a neuromuscular disorder, it is sometimes associated with multiple pilomatrixomas, which are otherwise rare epithelial tumors, and with other tumors including neurofibromas and parathyroid adenomas. Our results raise the possibility that homozygous loss of the myotonic dystrophy kinase may contribute to the development of these tumors.

Amino Acid Sequence↗
PubMed1983

Motility, cell shape, and locomotion of neutrophil granulocytes.

Activation of the motile apparatus by chemokinetic factors cannot be reliably assessed in cells that are attached to a solid substratum because motility can be totally abolished by excessive adhesion. It is however, necessary to quantify the activation of the motile apparatus in order to analyze and understand chemokinetic responses. It was the purpose of the present work to establish morphological criteria that can be used to quantify motility in nonadherent (floating) neutrophils and to predict the locomotor response under conditions of limited adhesion. The proportion of neutrophils performing crawling-like movements (polarized cells) in suspension correlates very closely with stimulated locomotion at low to optimal concentration of f-Met-Leu-Phe, ie, under conditions of limited adhesion. Reduced locomotion at supraoptimal concentrations of f-Met-Leu-Phe has also morphological correlates. The major feature is the decrease in the proportion of neutrophils performing crawling-like movements and the corresponding appearance of cells that are motile but not polarized in suspension and that do not locomote on the substratum. Concentration-dependent changes in neutrophil length and in the proportion of polarized neutrophils with and without tail were also observed. The locomotor potential of neutrophils under conditions of limited contact with the substratum can be predicted on the basis of their motile behavior, in particular the proportion of cells showing crawling-like movements, in suspension. In combination with measurements of adhesion the procedure should permit a more complete analysis of the regulation of chemokinetic responses.

Cell Adhesion↗
PubMedDate not supplied

Cell shape and increased free cytosolic calcium [Ca2+]i induced by growth factors.

Growth factors stimulate DNA synthesis of neoplastic cells but not of non-neoplastic cells in suspension cultures. Similarly, growth ceases in dense monolayers of non-neoplastic cells, while crowded neoplastic cells continue to grow. The mechanism of these important phenotypic changes is unknown; the block in growth stimulation could occur in early events of signal transduction at the plasma membrane or in a late step in the final steps of gene activation and induction of DNA synthesis. One particular early intracellular event, [Ca2+]i increases, is in fact necessary for the induction of DNA synthesis in attached non-neoplastic Balb/c 3T3 cells stimulated by platelet-derived growth factor (PDGF). We therefore used digital image analysis of intracellular Fura-2 fluorescence to determine whether PDGF can stimulate [Ca2+]i transients in suspension or in dense monolayer cultures of Balb/c 3T3 cells. In dense cells (greater than 8 x 10(4) cells/cm2) the basal [Ca2+]i and [Ca2+]i response to PDGF stimulation were both lower than those in sparser, more spread cells. PDGF also did not release internal stores of Ca2+ or produce Ca2+ influx in completely suspended cells. Remarkably, attachment alone, with minimal cell spreading, was enough to reinitiate the entire early signalling mechanism stimulated by PDGF. Thus, a block in PDGF-induced [Ca2+]i increases may contribute to the inability of PDGF to stimulate DNA synthesis in suspended non-neoplastic cells. This early block in signal transduction must be abrogated in neoplastic cells growing in suspension and dense monolayer cultures.

Animals↗
PubMed2003

Betacap73-ARF6 interactions modulate cell shape and motility after injury in vitro.

To understand the role that ARF6 plays in regulating isoactin dynamics and cell motility, we transfected endothelial cells (EC) with HA-tagged ARF6: the wild-type form (WT), a constitutively-active form unable to hydrolyze GTP (Q67L), and two dominant-negative forms, which are either unable to release GDP (T27N) or fail to bind nucleotide (N122I). Motility was assessed by digital imaging microscopy before Western blot analysis, coimmunoprecipitation, or colocalization studies using ARF6, beta-actin, or beta-actin-binding protein-specific antibodies. EC expressing ARF6-Q67L spread and close in vitro wounds at twice the control rates. EC expressing dominant-negative ARF6 fail to develop a leading edge, are unable to ruffle their membranes (N122I), and possess arborized processes. Colocalization studies reveal that the Q67L and WT ARF6-HA are enriched at the leading edge with beta-actin; but T27N and N122I ARF6-HA are localized on endosomes together with the beta-actin capping protein, betacap73. Coimmunoprecipitation and Western blot analyses reveal the direct association of ARF6-HA with betacap73, defining a role for ARF6 in signaling cytoskeletal remodeling during motility. Knowledge of the role that ARF6 plays in orchestrating membrane and beta-actin dynamics will help to reveal molecular mechanisms regulating actin-based motility during development and disease.

ADP-Ribosylation Factor 6↗
PubMed1993

Possible role of a choline-containing teichoic acid in the maintenance of normal cell shape and physiology in Streptococcus oralis.

Streptococcus oralis ATCC 35037 took up radioactively labeled choline from growth medium. Most of the choline (80 to 90%) was incorporated into the cell wall teichoic acid, and about 10% was localized in the plasma membrane. While cells grew in choline-free medium, they did so at slow rates and produced cell walls with greatly reduced amounts of phosphate and no detectable choline. Cells grown in choline-free medium had grossly abnormal shape and size. Both biochemical and morphological abnormalities were reversible by addition of choline to the medium.

Choline↗
PubMed1994

Dynamics of mitochondria in living cells: shape changes, dislocations, fusion, and fission of mitochondria.

Mitochondria are semi-autonomous organelles which are endowed with the ability to change their shape (e.g., by elongation, shortening, branching, buckling, swelling) and their location inside a living cell. In addition they may fuse or divide. These dynamics are discussed. Dislocation of mitochondria may result from their interaction with elements of the cytoskeleton, with microtubules in particular, and from processes intrinsic to the mitochondria themselves. Morphological criteria and differences in the fate of some mitochondria argue for the presence of more than one mitochondrial population in some animal cells. Whether these reflect genetic differences remains obscure. Emphasis is laid on the methods for visualizing mitochondria in cells and following their behaviour. Fluorescence methods provide unique possibilities because of their high resolving power and because some of the mitochondria-specific fluorochromes can be used to reveal the membrane potential. Fusion and fission often occur in short time intervals within the same group of mitochondria. At sites of fusion of two mitochondria material of the inner membrane, the matrix compartment seems to accumulate. The original arrangement of the fusion partners is maintained for some minutes. Fission is a dynamic event which, like fusion, in most cases observed in vertebrate cell cultures is not a straight forward process but rather requires several "trials" until the division finally occurs. Regarding fusion and fission hitherto unpublished phase contrast micrographs, and electron micrographs have been included.

Animals↗
PubMed1993

Analysis of multi-parameter video measurements of human neutrophil movement and its relation to cell shape and cytosolic calcium.

We have developed a software system for the analysis of multiparameter video image data derived from cell tracking experiments. The software is part of an integrated system for the study of human neutrophil motility. Input is taken from a file produced by a separate tracking program. The present software calculates several analytic parameters related to movement as well as novel relations between the distribution of fluorescent probes within the cell and vectors which represent cell movement. The software is designed to facilitate data analysis on several platforms by taking input and producing output as ASCII files.

Calcium↗
PubMed2002

Regulation of endothelial cell shape and barrier function by chromogranin A.

We have found that chromogranin A (CgA), a protein released in circulation by neuroendocrine cells and neurons, prevents the vascular leakage induced by tumor necrosis factor (TNF) in a mouse model. Studies of the mechanism of action showed that CgA and its NH(2)-terminal fragments inhibit TNF-induced vascular permeability by preventing endothelial cytoskeleton rearrangements. We propose that neuronal/endocrine secretion of CgA could contribute to the regulation of endothelial barrier function and the protection of vessels against plasma leakage in inflammatory diseases.

Animals↗
PubMed1992

The value of urinary red cell shape in the diagnosis of glomerular and post-glomerular haematuria. A meta-analysis.

The proportion of dysmorphic red cells (DRC) in the urinary sediment and their mean corpuscular volume (MCV) have been claimed to discriminate between glomerular and postglomerular sources of haematuria. To determine the diagnostic value of urinary DRC and MCV, we searched the literature and critically reviewed 21 published studies using a predetermined set of criteria for evaluation. All studies originated from referral centres. Interobserver variability in identifying urinary DRC was reported in four studies and found to be unacceptably large in one. Although reproducible over different samples of the same individual, urinary MCV was unreliable in cases of low-grade haematuria because of interfering debris. Weighted averages and 95% confidence limits of the sensitivity and specificity of the DRC proportion for glomerular disease were 0.88 (0.86-0.90) and 0.95 (0.93-0.97), respectively; those of a low MCV were 1.00 (0.98-1.00) for sensitivity and 0.87 (0.80-0.91) for specificity. Sensitivity and specificity values derived from in-patients were slightly higher than those in referred outpatients. No studies of urinary DRC or MCV in patients with incidentally detected microhaematuria in the primary care setting were found. We conclude that at present the diagnostic value of urinary DRC and MCV is limited. In referral centres, that is, in patients with a high probability of postglomerular haematuria, the test cannot rule out urological lesions, because its specificity for glomerular disease may be as low as 0.80. In the primary care setting, that is, in unselected patients with incidentally detected low-grade haematuria, the accuracy of the test has not been studied but may be even lower. The use of urinary DRC or MCV as an indicator of the source of haematuria is in need of further experimental development and confirmation.

Diagnosis, Differential↗