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At least 595 records · Page 33Linked to original sources
PubMed1977

Effect of procaine HCLl on ATP: calcium-dependent alterations in red cell shape and deformability.

Procaine hydrochloric acid, a cationic anesthetic, although unable to prevent the effect of calcium ionophore A23187 on erythrocytes, inhibited the discocyte--echinocyte transformation, increased viscosity, and decreased filterability of red cells undergoing ATP depletion. The effects were abolished by washing ATP-depleted, procaine HCl-treated red cells prior to these determinations. Procaine HCl had no effects on volume, incubated osmotic fragility, or monovalent cation composition of ATP-depleted red cells. The drug increased 45Ca uptake by ATP-depleted red cells but did not change the fraction of membrane-bound calcium. Sodium dodecyl sulfate acrylamide gel electrophoresis of membrane proteins from ATP-depleted red cells revealed formation of high molecular weight protein complexes, which were not formed when biconcave shape and ATP content were maintained by incubation with adenine (0.54 mM) and inosine (12.7 mM); Formation of these complexes was not prevented when the biconcave shape was maintained by procaine HCl. It was concluded that the maintenance of the biconcave shape and normal deformability during ATP depletion by procaine HCl was not related to a displacement of membrane-bound calcium and inhibition of ATP-dependent rearrangement of red cell membrane proteins.

Adenosine Triphosphate↗
PubMed1976

Cell shape changes and transmembrane receptor uncoupling induced by tertiary amine local anesthetic.

Tertiary amine local anesthetics (dibucaine, tetracaine, procaine, etc.) modify cell morphology, concanavalin A (Con A)-mediated agglutinability and redistribution of Con A receptors. Con A agglutination of untransformed mouse 3T3 cells was enhanced at low concentrations of local anesthetics, and the dynamics of fluorescent-Con A indicated that ligand-induced clustering was increased in the presence of the drugs. In contast, these drugs inhibited Con A-induced receptor capping on mouse spleen cells. These effects can be duplicated by combinations of vinblastine (or colchicine) and cytochalasin B suggesting that local anesthetics act on microtubule and microfilament assemblies which are involved in the trans-membrane control of cell surface receptor mobility and distribution. It is proposed that tertiary amine local anesthetics displace plasma membrane-bound Ca2+, resulting in disengagement of microfilament systems from the plasma membrane and increased cellular Ca2+ concentration to levels which disrupt microtubular organization. The possible involvement of cellular Ca2+ in cytoskeletal destruction by local anesthetics was investigated utilizing Ca2+-specific ionophores A23187 and X537A. In media containing Ca2+ and cytochalasin B these ionophores caused effects similar to tertiary amine local anesthetics.

Agglutination↗
PubMed1992

Estradiol promotes cell shape changes and glial fibrillary acidic protein redistribution in hypothalamic astrocytes in vitro: a neuronal-mediated effect.

We have previously shown that in hypothalamic mixed neuronal-glial cultures both astrocytic shape and distribution of glial fibrillary acidic protein (GFAP) are modified by estradiol. In the present study, we have investigated whether or not the presence of neurons is necessary for these hormonal effects. In mixed neuronal-glial hypothalamic cultures the proportion of process-bearing GFAP-immunoreactive cells was significantly increased after treatment for 30 min with 10(-12) M 17 beta estradiol. This effect was present for at least 1 day and was reverted by incubating the cells in estradiol-free medium. Estradiol incubation resulted in a progressive differentiation of GFAP-immunoreactive cells from a flattened epithelioid morphology to bipolar, radial, and stellate shapes. This effect was not observed in pure hypothalamic glial cultures. Furthermore, incubation of hypothalamic glial cells with medium conditioned by estradiol-treated mixed hypothalamic cultures did not affect the shape of GFAP-immunoreactive astrocytes. In contrast, addition of hypothalamic neurons, but not cerebellar neurons or fibroblasts, to established hypothalamic glial cultures affected the development of estradiol sensitivity in astrocytes. These results indicate that estradiol induction of shape changes in hypothalamic astrocytes is not only dependent on the presence of hypothalamic neurons, but that physical contact between astrocytes and neurons is necessary for the manifestation of the effect of this hormone.

Animals↗
PubMed1990

Bending undulations and elasticity of the erythrocyte membrane: effects of cell shape and membrane organization.

The undulatory excitations (flickering) of human and camel erythrocytes were evaluated by employing the previously used flicker spectroscopy and by local measurements of the autocorrelation function K (t) of the cell thickness fluctuations using a dynamic image processing technique. By fitting theoretical and experimental flicker spectra relative values of the bending elastic modulus Kc of the membrane and of the cytoplasmic viscosity eta were obtained. The effects of shape changes were monitored by simultaneous measurement of the average light intensity I0 passing the cells and by phase contrast microscopic observation of the cells. Evaluation of the cellular excitations in terms of the quasi-spherical model yielded values of Kc/R3(0) and mu.R0 (R0 = equivalent sphere radius) and allowed us to account (1) for volume changes, (2) for effects of surface tension and spontaneous curvature and (3) for the non-exponential decay of K (t). From the long time decay of K (t) we obtained an upper limit of the bending elastic modulus of normal cells of Kc = 2-3 x 10(-19) Nm which is an order of magnitude larger than the value found by reflection interference contrast microscopy (RICT, Kc = 3.4 x 10(-20) Nm, Zilker et al. 1987) but considerably lower than expected for a bilayer containing 50% cholesterol (Kc = 5 x 10(-19) Nm, Duwe et al. 1989). The major part of the paper deals with long time measurements (order of hours) of variations of the apparent Kc and eta values of single cells (and their reversibility) caused (1) by osmotic volume changes, (2) by discocyte-stomatocyte transitions induced by albumin and triflouperazine, (3) by discocyte-echinocyte transitions induced by expansion of the lipid/protein bilayer (by incubation with lipid vesicles) and by ATP-depletion in physiological NaCl solution, (4), by coupling or decoupling of bilayer and cytoskeleton using wheat germ agglutinin or erythrocytes with elliptocytosis and (5) by cross-linking the cytoskeleton using diamide. These experiments showed: (1) Kc and eta are minimal at physiological osmolarity and temperature and well controlled over a large range of these parameters. (2) Echinocyte formation does not markedly alter the apparent membrane bending stiffness. (3) During swelling the cell may undergo a transient discocyte-stomatocyte transition. (4) Strong increases of the apparent Kc and eta after cup-formation or strong swelling and deflation are due to the effect of shear elasticity and surface tension. Our major conclusions are: (1) The erythrocyte membrane exhibits a shear free deformation regime which requires ATP for its maintenance.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2005

Proliferation and cell shape changes during ciliary body morphogenesis in the mouse.

Very little is known about the structure and development of the ciliary processes in the mouse eye. Our scanning electron microscope (SEM) studies reveal that, unlike other mammals, the ciliary processes form an irregular pattern, crossing over and interweaving rather than lying parallel to one another. Histological and SEM studies from embryonic day (E) 14.5 to postnatal day (P) 7 reveal that the first morphological sign of the ciliary zone is an annular bulge; this is then gradually molded to form discrete ciliary processes. The striking similarity between the developing capillary network and the adult ciliary folds suggests that the patterning template for the ciliary processes could be the underlying capillary network. Cell proliferation measurements and cell height assessments indicated that one of the first events occurring during the morphogenesis of ciliary processes is a proliferative surge around P0 in the outer ciliary epithelium. It is likely that this surge together with increasing cell heights leads to a bulging of this layer. After a slight delay, the inner ciliary epithelium responds by proliferating and extending inward toward the lens. Final shaping of the ciliary processes is achieved through cell height reductions in the inner ciliary epithelium. Thus, in the mouse, the temporal correlation between mitotic and cell height changes during ciliary body morphogenesis suggests that these processes play an integral role in the shaping of ciliary processes.

Animals↗
PubMed1997

Mutation of the protein kinase C phosphorylation site on rat alpha1 Na+,K+-ATPase alters regulation of intracellular Na+ and pH and influences cell shape and adhesiveness.

The enzyme Na+,K+-ATPase creates the transmembrane Na+ gradient that is of vital importance for functioning of all eukaryotic cells. Na+, K+-ATPase can be phosphorylated by protein kinase A (PKA) and protein kinase C (PKC), and these sites of phosphorylation have been identified. In the present study, we have examined the physiological significance of PKC phosphorylation of rat Na+,K+-ATPase. In COS cells transfected with wild type rat Na+,K+-ATPase alpha1, intracellular Na+ was higher and pH was lower than in cells transfected with rat Na+,K+-ATPase alpha1 in which the PKC phosphorylation site, Ser-23, had been mutated into alanine. Phorbol dibutyrate inhibited Na+,K+-ATPase-dependent ATP hydrolysis and Rb+ uptake in cells expressing wild type Na+,K+-ATPase but not in cells expressing S23A Na+,K+-ATPase. Cells expressing the S23A mutant had a more rounded appearance and attached less well to fibronectin than did untransfected cells or cells transfected with wild type rat Na+, K+-ATPase alpha1. These results indicate a functional role for PKC-mediated phosphorylation of rat Na+,K+-ATPase alpha1 and suggest a connection between this enzyme and cell adhesion.

Animals↗
PubMed2003

Rho GTPase signaling modulates cell shape and contractile phenotype in an isoactin-specific manner.

Rho family small GTPases (Rho, Rac, and Cdc42) play an important role in cell motility, adhesion, and cell division by signaling reorganization of the actin cytoskeleton. Here, we report an isoactin-specific, Rho GTPase-dependent signaling cascade in cells simultaneously expressing smooth muscle and nonmuscle actin isoforms. We transfected primary cultures of microvascular pericytes, cells related to vascular smooth muscle cells, with various Rho-related and Rho-specific expression plasmids. Overexpression of dominant positive Rho resulted in the formation of nonmuscle actin-containing stress fibers. At the same time, alpha-vascular smooth muscle actin (alphaVSMactin) containing stress fibers were disassembled, resulting in a dramatic reduction in cell size. Rho activation also yielded a disassembly of smooth muscle myosin and nonmuscle myosin from stress fibers. Overexpression of wild-type Rho had similar but less dramatic effects. In contrast, dominant negative Rho and C3 exotransferase or dominant positive Rac and Cdc42 expression failed to alter the actin cytoskeleton in an isoform-specific manner. The loss of smooth muscle contractile protein isoforms in pericyte stress fibers, together with a concomitant decrease in cell size, suggests that Rho activation influences "contractile" phenotype in an isoactin-specific manner. This, in turn, should yield significant alteration in microvascular remodeling during developmental and pathologic angiogenesis.

Actins↗
PubMed1983

The band 3-rich membrane of llama erythrocytes: studies on cell shape and the organization of membrane proteins.

The erythrocyte membrane of the llama was characterized in comparison to that of the human. The llama erythrocyte was an elliptical disk that resisted shape alterations in hyperosmotic buffers and following metabolic depletion, both of which induce speculation of the human red cell. Lysophosphatidylcholine incorporation produced minor serrations of the edge of the llama disk but no spicules, whereas human red cells became sphero-echinocytes. The polypeptide profiles in the membranes of the two species were similar, except for several noteworthy differences: a marked elevation in the relative content of band 3; the absence of membrane-bound band 6; and simpler glycoprotein pattern in the llama. The concentration of band 3 in llama was about two and a half to three times that in the human and intramembrane particles in the protoplasmic leaflet of freeze-fractured llama membrane were correspondingly increased. The selective solubilization of bands 1, 2 and 5 in low ionic strength buffer, and all of the peripheral proteins in high alkaline buffer were similar except for increased retention of ankyrin by the llama membrane. These data suggest a similar disposition of membrane proteins. The llama membrane was markedly resistant to the solubilization of integral proteins by the nonionic detergent, Triton X-100. This property and the general resistance to shape changes may be related to the high concentration of band 3.

Animals↗
PubMed2006

Role of Rho GTPases and Rho-GEFs in the regulation of cell shape and integrity in fission yeast.

The Rho family of GTPases are highly conserved molecular switches that control some of the most fundamental processes of cell biology, including morphogenesis, vesicular transport, cell division and motility. Guanine nucleotide-exchange factors (GEFs) are directly responsible for the activation of Rho-family GTPases in response to extracellular stimuli. In fission yeast, there are seven Dbl-related GEFs and they activate six Rho-type GTPases within a particular spatio-temporal context. The failure to do so might have consequences reflected in aberrant phenotypes and in some cases lead to cell death. In this review, we briefly summarize the role of Rho GTPases and Rho-GEFs in the establishment and maintenance of cell polarity and cell integrity in Schizosaccharomyces pombe.

Cell Polarity↗
PubMed2000

Tribolium embryogenesis: a SEM study of cell shapes and movements from blastoderm to serosal closure.

Embryogenesis in the beetle Tribolium is of increasing interest to both molecular and evolutionary biology because it differs from the Drosophila paradigm by its type of segment specification (short- vs. long-germ) and by the extensive epithelial envelopes - amnion and serosa - that are typical of most insects but not of higher dipterans. Using scanning electron microscopy of DAPI staged embryos we document development in Tribolium castaneum from blastoderm to completion of the envelopes, recording many details not otherwise accessible; we also provide a time table of the respective stages at 30 degrees C. The nascent blastoderm cells remain basally confluent with the yolksac until after the 13th (=last synchronous) mitotic cycle. The cells in the prospective serosa - the first domain to segregate visibly from the uniform blastoderm - carry surface protrusions likely to contact the overlying vitelline envelope. The embryonic rudiment, the other (and larger) blastodermal domain, gives rise to amnion and germ anlage. In the latter, visible differentiation begins with a "primitive pit" reminiscent of the posterior midgut rudiment of Drosophila. The subsequent invagination of the mesoderm resembles Drosophila gastrulation, except in the head region where the median groove extends through the entire preoral region. The prospective amnion starts differing visibly from the germ anlage during early gastrulation. It then folds underneath the spreading serosa and, advancing with the latter, closes the amniotic cavity at the ventral face of the germband. The largest (=posterior) amniotic fold covers a crestlike protrusion of the yolksac. Together with marked changes in the shape and arrangement of the amnion cells, this protrusion may contribute to the fold's elevation and early progress.

Amnion↗