Reversible changes in size of cell nuclei isolated from Amoeba proteus: Role of the cytoskeleton

2000 ◽  
Vol 78 (4) ◽  
pp. 487-494 ◽  
Author(s):  
Pawel Pomorski ◽  
Lucyna Grebecka ◽  
Andrzej Grebecki ◽  
Robert Makuch
Keyword(s):  
Amoeba Proteus ◽  
Cell Nuclei

Reversible changes in size of cell nuclei isolated from Amoeba proteus: Role of the cytoskeleton

2000 ◽  
Vol 78 (4) ◽  
pp. 487-494 ◽  
Author(s):  
Pawel Pomorski ◽  
Lucyna Grebecka ◽  
Andrzej Grebecki ◽  
Robert Makuch
Keyword(s):  
External Medium ◽  
Amoeba Proteus ◽  
Distilled Water ◽  
Sectional Area ◽  
Cell Nuclei ◽  
Cross Sectional ◽  
Isolated Nuclei ◽  
Rigor State ◽  
Osmotic Effects

Micrurgically isolated interphasal nuclei of Amoeba proteus, which preserve F-actin cytoskeletal shells on their surface, shrink after perfusion with imidazole buffer without ATP, and expand to about 200% of their cross-sectional area upon addition of pyrophosphate. These changes in size may be reproduced several times with the same nucleus. The shrunken nuclei are insensitive to the osmotic effects of sugars and distilled water, whereas the expanded ones react only to the distilled water, showing further swelling. The shrinking-expansion cycles are partially inhibited by cytochalasins. They are attributed to the state of actomyosin complex in the perinuclear cytoskeleton, which is supposed to be in the rigor state in the imidazole buffer without ATP, and to dissociate in the presence of pyrophosphate. Inflow of external medium to the nuclei during dissociation of the myosin from the perinuclear F-actin may be due to colloidal osmosis depending on other macromolecular components of the karyoplasm.Key words: Amoeba proteus, isolated nuclei, perinuclear cytoskeleton.

Membrane Potentials in Amoeba Proteus

1966 ◽  
Vol 45 (2) ◽  
pp. 251-267
Author(s):  
M. S. BINGLEY
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Morphological Changes ◽  
Amoeba Proteus ◽  
Membrane Potentials ◽  
The Other ◽  
The Earth ◽  
Electrode Resistance ◽  
Alternating Voltage

1. Amoebae can be penetrated by microelectrodes at either end. One records voltage and the other supplies alternating current. 2. Step-like increases in alternating voltage superimposed on potentials recorded by the voltage electrode when in either the pseudopod or rear region demonstrate that low potentials recorded from a pseudopod and high ones from the rear region exist across a discrete impedance barrier. The only structure so far shown to fulfil this function is the plasma membrane. 3. A resistance inserted in the earth path monitors current flowing through the system and confirms observations made when recording with single electrodes that there is a reduction of electrode resistance when the cell is entered. 4. Pronounced depolarization in the rear region is shown when the current-carrying electrode penetrates the pseudopod, but not vice versa. 5. Morphological changes associated with membrane potential reversal are illustrated. 6. Consideration is given to the role of step-like potential changes in movement.

The role of follicle cell nuclei in amphibian oocyte maturation

1989 ◽  
Vol 27 ◽  
pp. 160 ◽  
Author(s):  
M.N. Skoblina ◽  
O.T. Kondratieva ◽  
E.V. Orlov
Keyword(s):  
Oocyte Maturation ◽  
Follicle Cell ◽  
Cell Nuclei ◽  
Amphibian Oocyte

scholarly journals Nucleoplasmic Lamin C Rapidly Accumulates at Sites of Nuclear Envelope Rupture with BAF and cGAS

2022 ◽  
Author(s):  
Yohei Kono ◽  
Stephen A. Adam ◽  
Karen Reddy ◽  
Yixian Zheng ◽  
Ohad Medalia ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Nuclear Lamina ◽  
Structural Components ◽  
Cell Nuclei ◽  
Embryonic Fibroblasts ◽  
Nuclear Lamins ◽  
Laser Microirradiation

In mammalian cell nuclei, the nuclear lamina (NL) underlies the nuclear envelope (NE) to maintain nuclear structure. The nuclear lamins, the major structural components of the NL, are involved in the protection against NE rupture induced by mechanical stress. However, the specific role of the lamins in repair of NE ruptures has not been fully determined. Our analyses using immunofluorescence and live-cell imaging revealed that lamin C but not the other lamin isoforms rapidly accumulated at sites of NE rupture induced by laser microirradiation in mouse embryonic fibroblasts. The immunoglobulin-like fold domain and the NLS were required for the recruitment from the nucleoplasm to the rupture sites with the Barrier-to-autointegration factor (BAF). The accumulation of nuclear BAF and cytoplasmic cyclic GMP-AMP (cGAMP) synthase (cGAS) at the rupture sites was in part dependent on lamin A/C. These results suggest that nucleoplasmic lamin C, BAF and cGAS concertedly accumulate at sites of NE rupture for repair.

scholarly journals Role of Coactivators and Corepressors in Steroid and Nuclear Receptor Signaling: Potential Markers of Tumor Growth and Drug Sensitivity

2001 ◽  
Vol 16 (3) ◽  
pp. 151-166 ◽  
Author(s):  
E. Cottone ◽  
F. Orso ◽  
N. Biglia ◽  
P. Sismondi ◽  
M. De Bortoli
Keyword(s):  
Nuclear Receptors ◽  
Nuclear Receptor ◽  
Response To Therapy ◽  
Cell Nuclei ◽  
Knock Out ◽  
Structure Lead ◽  
Estrogen Receptor Pathway ◽  
Coregulatory Proteins ◽  
Complete Inversion

Nuclear receptors regulate target gene expression in response to steroid and thyroid hormones, retinoids, vitamin D and other ligands. These ligand-dependent transcription factors function by contacting various nuclear cooperating proteins, called coactivators and corepressors, which mediate local chromatin remodeling as well as communication with the basal transcriptional apparatus. Nuclear receptors and their coregulatory proteins play a role in cancer and other diseases, one leading example being the estrogen receptor pathway in breast cancer. Coregulators are often present in limiting amounts in cell nuclei and modifications of their level of expression and/or structure lead to alterations in nuclear receptor functioning, which may be as pronounced as a complete inversion of signaling, i.e. from stimulating to repressing certain genes in response to an identical stimulus. In addition, hemizygous knock-out of certain coactivator genes has been demonstrated to produce cancer-prone phenotypes in mice. Thus, assessment of coactivator and corepressor expression and structure in tumors may turn out to be essential to determine the role of nuclear receptors in cancer and to predict prognosis and response to therapy.

scholarly journals Role of glucose in cloned mouse embryo development

2008 ◽  
Vol 295 (4) ◽  
pp. E798-E809 ◽  
Author(s):  
Zhiming Han ◽  
Rita Vassena ◽  
Maggie M. Y. Chi ◽  
Santhi Potireddy ◽  
Miriam Sutovsky ◽  
...  
Keyword(s):  
Glucose Metabolism ◽  
Beneficial Effect ◽  
Embryo Development ◽  
Glucose Transporter ◽  
Cumulus Cell ◽  
Blastocyst Stage ◽  
Cell Nuclei ◽  
Cell Stage ◽  
Positive Effects

Cloned mouse embryos display a marked preference for glucose-containing culture medium, with enhanced development to the blastocyst stage in glucose-containing medium attributable mainly to an early beneficial effect during the first cell cycle. This early beneficial effect of glucose is not displayed by parthenogenetic, fertilized, or tetraploid nuclear transfer control embryos, indicating that it is specific to diploid clones. Precocious localization of the glucose transporter SLC2A1 to the cell surface, as well as increased expression of glucose transporters and increased uptake of glucose at the one- and two-cell stages, is also seen in cloned embryos. To examine the role of glucose in early cloned embryo development, we examined glucose metabolism and associated metabolites, as well as mitochondrial ultrastructure, distribution, and number. Clones prepared with cumulus cell nuclei displayed significantly enhanced glucose metabolism at the two-cell stage relative to parthenogenetic controls. Despite the increase in metabolism, ATP content was reduced in clones relative to parthenotes and fertilized controls. Clones at both stages displayed elevated concentrations of glycogen compared with parthenogenetic controls. There was no difference in the number of mitochondria, but clone mitochondria displayed ultrastructural alterations. Interestingly, glucose availability positively affected mitochondrial structure and localization. We conclude that cloned embryos may be severely compromised in terms of ATP-dependent processes during the first two cell cycles and that glucose may exert its early beneficial effects via positive effects on the mitochondria.

scholarly journals Cryptochrome 1 in Retinal Cone Photoreceptors Suggests a Novel Functional Role in Mammals

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Christine Nießner ◽  
Susanne Denzau ◽  
Erich Pascal Malkemper ◽  
Julia Christina Gross ◽  
Hynek Burda ◽  
...  
Keyword(s):  
Mammalian Species ◽  
Retinal Cell ◽  
Cone Photoreceptors ◽  
Cell Nuclei ◽  
Western Blots ◽  
C Terminus ◽  
Mammalian Retina ◽  
Cryptochrome 1 ◽  
Retinal Cone

Abstract Cryptochromes are a ubiquitous group of blue-light absorbing flavoproteins that in the mammalian retina have an important role in the circadian clock. In birds, cryptochrome 1a (Cry1a), localized in the UV/violet-sensitive S1 cone photoreceptors, is proposed to be the retinal receptor molecule of the light-dependent magnetic compass. The retinal localization of mammalian Cry1, homologue to avian Cry1a, is unknown and it is open whether mammalian Cry1 is also involved in magnetic field sensing. To constrain the possible role of retinal Cry1, we immunohistochemically analysed 90 mammalian species across 48 families in 16 orders, using an antiserum against the Cry1 C-terminus that in birds labels only the photo-activated conformation. In the Carnivora families Canidae, Mustelidae and Ursidae and in some Primates, Cry1 was consistently labeled in the outer segment of the shortwave-sensitive S1 cones. This finding would be compatible with a magnetoreceptive function of Cry1 in these taxa. In all other taxa, Cry1 was not detected by the antiserum that likely also in mammals labels the photo-activated conformation, although Western blots showed Cry1 in mouse retinal cell nuclei. We speculate that in the mouse and the other negative-tested mammals Cry1 is involved in circadian functions as a non-light-responsive protein.

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