scholarly journals SMALL GRANULES IN THE AMPHIBIAN OOCYTE NUCLEUS AND THEIR RELATIONSHIP TO RNA

1956 ◽  
Vol 2 (4) ◽  
pp. 393-396 ◽  
Author(s):  
Joseph G. Gall
Keyword(s):  
Endoplasmic Reticulum ◽  
Salivary Gland ◽  
Nuclear Envelope ◽  
Oocyte Nucleus ◽  
Balbiani Ring ◽  
Lampbrush Chromosomes ◽  
Small Particles ◽  
Amphibian Oocyte

Small particles (100 to 300 A in diameter) are seen in sections of nucleoli, the loops of the amphibian lampbrush chromosomes, and the Balbiani-ring regions of dipteran salivary-gland chromosomes. All of these structures contain cytochemically demonstrable RNA. Furthermore, the annuli seen on the nuclear envelope are composed of small particles which are similar to or identical with those commonly associated with the endoplasmic reticulum. It seems likely that ribonucleoproteins are organized as small particulates in the nucleus as well as in the cytoplasm.

scholarly journals THE PERMEABILITY OF THE AMPHIBIAN OOCYTE NUCLEUS, IN SITU

1972 ◽  
Vol 54 (3) ◽  
pp. 609-625 ◽  
Author(s):  
Samuel B. Horowitz
Keyword(s):  
Plasma Membrane ◽  
Nuclear Envelope ◽  
Sucrose Concentration ◽  
Short Circuit ◽  
Pure Water ◽  
Oocyte Nucleus ◽  
Bathing Solution ◽  
Cytoplasmic Inclusions ◽  
Amphibian Oocyte ◽  
Water As Solvent

Ultralow temperature radioautography, suitable for the quantitative localization of diffusible solutes, was used to study the permeability of the nuclear envelope in the intact amphibian oocyte Sucrose-3H solutions were injected into mature oocytes, in volumes of 0 016–0 14% of that of the cell, and the subsequent movement of the solute was recorded. The resultant radioautographs show diffusion gradients in the cytoplasm and nucleus, and concentration gradients across the nuclear envelope Analysis of these gradients discloses that the nuclear envelope is as permeable as a comparable structure composed of cytoplasm, and is about 108 times more permeable than the oocyte plasma membrane The diffusion coefficient of sucrose in cytoplasm is 2 x 10-6 cm2/sec, or about one-third its diffusivity in pure water. This reduction can probably be accounted for by an effective lengthening of the diffusional path because of obstruction by cytoplasmic inclusions. The nuclear: cytoplasmic sucrose concentration ratio at diffusional equilibrium is about 3 05, or 1.6 times as great as expected from the water content of the two compartments This asymmetry is attributed to an unavailability of 36% of the cytoplasmic water as solvent Finally, sucrose entry into oocytes from a bathing solution was monitored by whole cell analysis and radioautography. These and the microinjection results are consistent with a model in which sucrose entry into the cell is entirely limited by the permeability of the plasma membrane. The results are inconsistent with cell models that hypothesize a short-circuit transport route from the extracellular compartment to the nucleus, and with models in which cytoplasmic diffusion is viewed as limiting the rate of solute permeation.

The role of Lampbrush Chromosomes in the formation of Nucleoli in Amphibian Oocytes

1965 ◽  
Vol s3-106 (75) ◽  
pp. 215-228
Author(s):  
H. C. MACGREGOR
Keyword(s):  
Phase Contrast ◽  
Nucleolar Organizer ◽  
Plethodon Cinereus ◽  
Oocyte Nucleus ◽  
Lampbrush Chromosomes ◽  
Triturus Cristatus ◽  
Amphibian Oocyte ◽  
Ambystoma Jeffersonianum ◽  
And Function

Theories concerning the mode of origin of peripheral nucleoli in amphibian oocytes have been examined and tested. In Triturus cristatus the giant fusing loops of the 3 shortest lampbrush bivalents resemble nucleoli when viewed in phase contrast and may be considered as possible sites of production of nucleoli. Giant fusing loops, however, differ from peripheral nucleoli in certain important respects, and animals lacking giant fusing loops on their lampbrush chromosomes nevertheless have normal peripheral nucleoli. Therefore, similarity in appearance between objects attached to lampbrush chromosomes and free peripheral nucleoli may not be significant. In oocytes of T. c. carnifex, T. c. karelinii, and T. c. danubialis, peripheral nucleoli do not increase in number during the lampbrush phase of oogenesis, except by division of pre-existing nucleoli towards the end of oogenesis. There are about 1,000 nucleoli per oocyte nucleus in each of these sub-species. In T. c. cristatus there are more nucleoli in large oocytes than in small ones, and it seems likely that in this sub-species the giant fusing loops add to the existing population of nucleoli in an oocyte by successively growing and shedding new nucleoli. A similar situation probably holds in Plethodon cinereus. Hexaploid oocytes from triploid females of Ambystoma jeffersonianum have 3 times as many nucleoli as diploid oocytes from diploid females of the same species. The number of nucleoli in an amphibian oocyte nucleus is therefore related to the number of sets of chromosomes in the cell. In yolky oocytes from hypophysectomized newts most peripheral nucleoli are firmly attached to the inner surface of the nuclear membrane; whereas in similar oocytes from unoperated or gonadotrophin-treated animals none of the nucleoli is so attached. On the basis of these observations 2 mechanisms are suggested for the formation of amphibian oocyte nucleoli. The first of these mechanisms probably operates in T. c. carnifex, where all peripheral nucleoli are formed before or soon after the chromosomes assume the lampbrush form, and no part of a lampbrush chromosome is involved in a process which adds to the existing population of nucleoli. The second mechanism probably operates in T. c. cristatus, where most of the peripheral nucleoli are formed before the lampbrush phase of oogenesis but a nucleolar organizer on the lampbrush chromosomes continues to grow and detach nucleoli throughout oogenesis. Both these mechanisms are discussed in terms of what is known of the chemical composition and function of peripheral nucleoli.

A Cycloid Model for the Chromosome

1967 ◽  
Vol 2 (1) ◽  
pp. 9-22
Author(s):  
H. L. K. WHITEHOUSE
Keyword(s):  
Salivary Gland ◽  
Messenger Rna ◽  
Nucleolar Organizer ◽  
Duplicate Genes ◽  
Crossing Over ◽  
Lampbrush Chromosomes ◽  
Circular Dna ◽  
Dna Molecule ◽  
Amphibian Oocyte ◽  
Identical Nucleotide

Investigations of lampbrush chromosomes and the nucleolar organizer have suggested that each gene may be duplicated many times in consecutive linear series within one DNA molecule. This conclusion is in direct conflict with recombination data which indicate, not only that each gene is represented only once per chromatid, but that different genes are contiguous. This paradox is resolved by postulating that the chromosome has the form of a cycloid. Each loop of the cycloid would correspond to a set of copies of a gene forming a chromomere. It is suggested that at meiosis the copies of the gene are detached as a result of intrachromatid crossing-over between the first and last members of the series. The master copy remaining in the chromatid would then be in a position to undergo crossing-over with a homologous chromatid, while the duplicate copies in the detached chromomere would all be included in a single circular DNA molecule. They could subsequently be restored to the chromatid by crossing-over between one of their number and the master copy. This intrachromatid crossing-over would imply that the chromosome can alternate between two states with each set of duplicate genes either detached as a circle or integrated with the DNA axis. Callan's model for matching slave genes against a master copy so that all acquire identical nucleotide sequences is modified to facilitate coiling and uncoiling of nucleotide chains, by postulating breakage of the matching chains at one end of the gene. Matching of only one chain of the slaves against the master is proposed or, if necessary, subsequent matching of the second slave chain to the first. It is suggested that matching may regularly precede the synthesis of messenger RNA. Investigations of dipteran salivary gland chromosomes and amphibian oocyte nucleoli have established that the chromomere is the unit of replication of the chromosome. On the cycloid model the replicons would be adjacent to one another, and each would comprise a master gene and all the copies. It is suggested that the replicator may correspond to the operator of the master copy of the gene. This hypothesis provides an explanation for several previously unexplained features of crossing-over, including its occurrence at the four-strand stage.

Compound Symbiosis in Peridinium Balticum

1973 ◽  
Vol 31 ◽  
pp. 500-501
Author(s):  
R. N. Tomas
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
The Other ◽  
Exact Nature ◽  
Symbiotic Relationship

Peridinium balticum appears to be unusual among the dinoflagellates in that it possesses two DNA-containing structures as determined by histochemical techniques. Ultrastructurally, the two dissimilar nuclei are contained within different protoplasts; one of the nuclei is characteristically dinophycean in nature, while the other is characteristically eucaryotic. The chloroplasts observed within P. balticum are intrinsic to an eucaryotic photosynthetic endosymbiont and not to the dinoflagellate. These organelles are surrounded by outpocketings of endoplasmic reticulum which are continuous with the eucaryotic nuclear envelope and are characterized by thylakoids composed of three apposed lamellae. Girdle lamellae and membranebounded interlamellar pyrenoids are also present. Only the plasmalemma of the endosymbiont segregates its protoplast from that of the dinophycean cytoplasm. The exact nature of this symbiotic relationship is at present not known.

Temporal and spatial interrelationships of confronting cisternae to nuclear envelope

1992 ◽  
Vol 50 (1) ◽  
pp. 930-931
Author(s):  
John R. Palisano
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Tumor Cells ◽  
Hela Cells ◽  
Microscopic Investigation ◽  
Electron Microscopic Investigation ◽  
Serial Sections ◽  
Electron Microscopic ◽  
Fetal Rat ◽  
Temporal And Spatial

Although confronting cistemae (CC) have been observed in a variety of tumor cells and normal fetal rat, mouse, and human epithelial tissues, little is known about their origin or role in mitotic cells. While several investigators have suggested that CC arise from nuclear envelope (NE) folding back on itself during prophase, others have suggested that CC arise when fragments of NE pair with endoplasmic reticulum. An electron microscopic investigation of 0.25 um thick serial sections was undertaken to examine the origin of CC in HeLa cells.

scholarly journals OASIS/CREB3L1 is a factor that responds to nuclear envelope stress

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Yasunao Kamikawa ◽  
Atsushi Saito ◽  
Koji Matsuhisa ◽  
Masayuki Kaneko ◽  
Rie Asada ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Genome Instability ◽  
Nuclear Lamina ◽  
Nuclear Deformation ◽  
Membrane Domain ◽  
Stress Response Pathway ◽  
Envelope Stress ◽  
Genome Activity

AbstractThe nuclear envelope (NE) safeguards the genome and is pivotal for regulating genome activity as the structural scaffold of higher-order chromatin organization. NE had been thought as the stable during the interphase of cell cycle. However, recent studies have revealed that the NE can be damaged by various stresses such as mechanical stress and cellular senescence. These types of stresses are called NE stress. It has been proposed that NE stress is closely related to cellular dysfunctions such as genome instability and cell death. Here, we found that an endoplasmic reticulum (ER)-resident transmembrane transcription factor, OASIS, accumulates at damaged NE. Notably, the major components of nuclear lamina, Lamin proteins were depleted at the NE where OASIS accumulates. We previously demonstrated that OASIS is cleaved at the membrane domain in response to ER stress. In contrast, OASIS accumulates as the full-length form to damaged NE in response to NE stress. The accumulation to damaged NE is specific for OASIS among OASIS family members. Intriguingly, OASIS colocalizes with the components of linker of nucleoskeleton and cytoskeleton complexes, SUN2 and Nesprin-2 at the damaged NE. OASIS partially colocalizes with BAF, LEM domain proteins, and a component of ESCRT III, which are involved in the repair of ruptured NE. Furthermore, OASIS suppresses DNA damage induced by NE stress and restores nuclear deformation under NE stress conditions. Our findings reveal a novel NE stress response pathway mediated by OASIS.

scholarly journals Rtn1p Is Involved in Structuring the Cortical Endoplasmic Reticulum

2006 ◽  
Vol 17 (7) ◽  
pp. 3009-3020 ◽  
Author(s):  
Johan-Owen De Craene ◽  
Jeff Coleman ◽  
Paula Estrada de Martin ◽  
Marc Pypaert ◽  
Scott Anderson ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Fluorescent Protein ◽  
Cell Cortex ◽  
Proteomic Screen ◽  
Wide Range ◽  
Membrane Spanning ◽  
Green Fluorescent ◽  
Hydrophilic Loop ◽  
Yeast Mutants

The endoplasmic reticulum (ER) contains both cisternal and reticular elements in one contiguous structure. We identified rtn1Δ in a systematic screen for yeast mutants with altered ER morphology. The ER in rtn1Δ cells is predominantly cisternal rather than reticular, yet the net surface area of ER is not significantly changed. Rtn1-green fluorescent protein (GFP) associates with the reticular ER at the cell cortex and with the tubules that connect the cortical ER to the nuclear envelope, but not with the nuclear envelope itself. Rtn1p overexpression also results in an altered ER structure. Rtn proteins are found on the ER in a wide range of eukaryotes and are defined by two membrane-spanning domains flanking a conserved hydrophilic loop. Our results suggest that Rtn proteins may direct the formation of reticulated ER. We independently identified Rtn1p in a proteomic screen for proteins associated with the exocyst vesicle tethering complex. The conserved hydophilic loop of Rtn1p binds to the exocyst subunit Sec6p. Overexpression of this loop results in a modest accumulation of secretory vesicles, suggesting impaired exocyst function. The interaction of Rtn1p with the exocyst at the bud tip may trigger the formation of a cortical ER network in yeast buds.

scholarly journals Growth of the nuclear envelope in the vegetative phase of the green alga Acetabularia. Evidence for assembly from membrane components synthesized in the cytoplasm.

1975 ◽  
Vol 66 (3) ◽  
pp. 681-689 ◽  
Author(s):  
W W Franke ◽  
H Spring ◽  
U Scheer ◽  
H Zerban
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Green Alga ◽  
Special Form ◽  
Vegetative Phase ◽  
Primary Nucleus ◽  
Membrane Components

The primary nucleus of the green alga Acetabularia grows about 25,000-fold in volume while it is separated from the endoplasmic reticulum and the whole cytoplasm by a special paranuclear cisterna of a vacuolar labyrinthum system which shows only very few (two to six per square micrometer) and small (ca. 40-120 nm in diamter) fenestrations. The nuclear envelope does not bear polyribosomes, nor do they occur in the entire zone intermediate between the nuclear envelope and the paranuclear cisterna. It is suggested that this special form of nuclear envelope growth takes place by assembly from cytoplasmically synthesized proteins that are translocated across the paranuclear cisterna in a nonmembrane-structured form.

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