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At least 19 recordsLinked to original sources
PubMedDate not supplied

[Aspects of bacteriophage-eukaryotic cell relationships].

The present work deals with bacteriophage--eukaryotic cell interrelationship, including:--Data on the possible presence of bacteriophages in calf serum and viral vaccines.--Methodological problems of research on phage--eukaryotic cell relations.--Data concerning the effects of phage infection on eukaryotic cells (demonstration of phage infection of the eukaryotic cell; integration of phage genetic material in the genome of the eukaryotic cell; coding of phage proteins in phage-infected eukaryotic cells; modified multiplication parameters and transformed potential of some phage-infected eukaryotic cells).--Indications for solving some of the problems.

Bacteriophages↗
PubMed1978

Phylogenetic affinities between eukaryotic cells and a thermophilic mycoplasma.

Thermoplasma acidophilum, a thermophilic mycoplasma, has several unusual features suggesting a possible relationship to eukaryotic cells. One feature is a histone-like protein that is associated with the DNA, condensing it into subunits similar to those in eukaryotic chromatin. A second feature is an association of cytoplasmic proteins that resembles eukaryotic actin and myosin. These two components are widely distributed in different groups of eukaryotic cells, but are typically lacking in prokaryotic cells. Furthermore, T. acidophilum lacks cytochromes and respires by enzymes that apparently are not coupled to oxidative phosphorylation. This primitive type of respiration resembles that of microbodies, another feature which is represented in the cytoplasm of all groups of eukaryotic cells. Furthermore, since T. acidophilum lacks a cell wall and appears to have a primitive correlate of endocytosis, it would appear to be mechanically capable of acquiring a symbiotic mitochondrion. Thus, our observations are consistent with the symbiotic hypothesis for the origin of eukaryotic cells. We suggest that an organism similar to T. acidophilum was the host cell for the original symbiosis, becoming the nucleus and cytoplasm of modern eukaryotic cells.

Actomyosin↗
PubMed1979

Long-range dielectric aspects of the eukaryotic cell cycle.

The phases of the eukaryotic cell cycle are described in terms of H. Fröhlich's theory of long-range coherence in biological systems. A phonon condensation is believed to initiate the S phase of the cycle. Following this event, an increasing polarization of the cell should occur, resulting in a phase transition to a metastable ferroelectric state at the beginning of mitosis. This polarized state is expected to be dissipated after mitosis is completed. It is believed that malignant cells possess a ferroelectric state throughout their life cycles.

Animals↗
PubMed1978

Implications of RNA-RNA splicing in evolution of eukaryotic cells.

The differences in the biochemistry of messenger RNA formation in eukaryotes compared to prokaryotes are so profound as to suggest that sequential prokaryotic to eukaryotic cell evolution seems unlikely. The recently discovered noncontiguous sequences in eukaryotic DNA that encode messenger RNA may reflect an ancient, rather than a new, distribution of information in DNA and that eukaryotes evolved independently of prokaryotes.

Adenoviruses, Human↗
PubMed1978

[Structure of the mRNA of eukaryotic cells].

A review is given of the principal achievements in studying the structure of mRNA in eukaryotic cells. The data are provided on the size and life time, complexity and distribution of different kinds of mRNA by the frequency of repetitions; composition and structure of mRNP. The structures of individual mRNA's and general pattern of the structure of eukaryotic mRNA and mRNP are considered.

Animals↗
PubMedDate not supplied

Functional genetic damages and their possible role in the aging of eukaryote cells.

As a result of investigations of the functional acitivty of eukaryote cells damaged by ionizing radiation and alkylating mutagens under conditions of extreme loading, the authors have suggested that natural aging and aging accelerated by mutagens are based on a process of accumulation of functional genetic damages. The molecular nature of these damages differs from the mutational changes and repairable damages of DNA.

Aging↗
PubMed1977

In situ detection and characterization of DNA polymerase activities in the nucleus of eukaryotic cells.

We have developed a cytoenzymological method for localizing DNA polymerase activities in situ and for studying their responses to various chemical agents or environmental conditions. The incubation mixtures and the stimulatory or inhibitory agents added to these media were defined with reference to in vitro biochemical tests used to detect and to characterize DNA polymerases-alpha or -beta found in eukaryotic cells. This method has already been used to study DNA polymerase activities during cell differentiation or cell senescence. Apart from two exceptions found with lower organisms, the nuclear DNA polymerase activity was always higher under conditions which favoured the in vitro expression of DNA polymerase-beta rather than DNA polymerase-alpha. --In the various cell types studied, the cellular DNA polymerase activities were almost exclusively found in the nuclei. It is hoped that this methodology will be useful for obtaining more complete biochemical data on the intracellular localization of various DNA polymerases.

Animals↗
PubMed1978

A rapid method for the purification of extrachromosomal DNA from eukaryotic cells.

A simple and efficient procedure to purify the low molecular weight extrachromosomal DNA from eukaryotic cells is described. Gentle lysis of cells with urea and sodium dodecyl sulfate in 0.24 M phosphate buffer (pH 6.8) is followed by the removal of high molecular weight bulk DNA by centrifugation. Protein and RNA are removed from the supernatant by hydroxyapatite chromatography in urea/phosphate buffer. Urea is then removed with 0.15 M phosphate buffer and the extrachromosomal DNA, virtually free from protein and RNA, is finally eluted in 0.5 M phosphate buffer. The procedure allows the recovery of about 99% simian virus 40 (SV40) DNA from infected monkey kidney cells in the extrachromosomal fraction. In normal mouse, monkey, andhuman cells, approximately 1% of total cell DNA appears to be extrachromosomal.

Cell Line↗
PubMed1977

Protein degradation during the differentiation of eukaryotic cells: studies on the sporulation of Saccharomyces cerevisiae and on the formation of the neuromuscular junction in the chick embryo.

The role of protein degradation in cell and tissue differentiation has been investigated during the sporulation of Saccharomyces cerevisiae and during endplate formation in developing avian muscle. The results suggest that a variety of proteolytic processes as enzyme inactivation, degradation of mitochondrial membrane constituents and removal of embryonic cell surface proteins exert stringent controls over the sequence of differentiation in eukaryotic cells.

Animals↗
PubMed1979

[Comparative study of cytoplasmic RNA-binding proteins of eukaryotic cells: content and polypeptide composition].

The specific RNA-binding activity of cytoplasmic extracts of a number of eukaryotic cells and tissues was determined by sorption of radioactive RNA on nitrocellulose filters. This activity varies within a wide range: from 0,5 up to 80 microgram of 23S-RNA per mg of extract protein. The percentage of RNA-binding proteins as measured by their adsorption on RNA-Sepharose is 0,3--60% of total protein of cytoplasmic extracts and is well-correlated with their RNA-binding activity. The variability of the RNA-binding activity of the isolated preparations of RNA-binding proteins (from 100 to 300 microgram of 23S-RNA per mg of protein) is indicative of their qualitative differences. The analysis of the polypeptide composition of RNA-binding proteins revealed that the set of the major polypeptide chains is rather simple (with few exceptions) and includes both universal components with mol. weights of about 36,000, 49,000 and 95,000 characteristic of a number of cells and tissues and tissue- and species-specific polypeptides. Upon differentiation of rabbit reticulocytes into erythrocytes the percentage of RNA-binding proteins is decreased 4-fold and one of the three main polypeptides with the mol. weight of about 95,000 disappears. After fecundation of sea urchin ovicelles the polypeptide with the mol. weight of 37,000 disappears from the preparations of RNA-binding proteins and at the morula stage two new components with the mol. weights of about 35,000 and 26,000 appear instead of it. The germination of wheat embryos results in a two-fold increase of the percentage of RNA-binding proteins without any essential changes of the set of main polypeptide chains.

Animals↗
PubMed1978

Calcium-dependent regulator protein: localization in mitotic apparatus of eukaryotic cells.

Calcium-dependent regulator protein is a low molecular weight (17,000), thermostable, calcium binding protein which is structurally homologous to skeletal muscle troponin C. This protein is present in all nonmuscle cells and has been shown to decorate stress fibers in interphase cells by indirect immunofluorescence. Using this procedure we have investigated the distribution of the protein during mitosis of eukaryotic cells. As the cells enter prophase, the distinct cytoplasmic localization disappears commensurate with the dissolution of the cytoskeleton. The regulator protein seems to be randomly distributed throughout the prophase cell, including the region around the condensed chromosomes. However, at prometaphase, it is localized in association with the half-spindles of the mitotic apparatus. Through metaphase and most of anaphase, the protein remains localized between the chromosomes and the poles of the spindle. During late anaphase the protein is also found in the interzone region but rapidly condenses into two small regions, one on each side of the midbody that separates the daughter cells. The regulator protein is not localized in the cleavage furrow during telophase, whereas actin is demonstrable in this region. Indeed, placement of the protein during mitosis is distinct from both that of actin and that of tubulin. The localization of calcium-dependent regulator protein during mitosis suggests that it may mediate the calcium effects on the mitotic apparatus and thus play a role in chromosome movement.

Actins↗
PubMed1978

Effect of antabuse (disulfiram) on Rous sarcoma virus and on eukaryotic cells.

Antabuse (disulfiram) is widely used in the treatment of chronic alcoholism. We have examined the effect of this drug on malignant transformation by Rous sarcoma virus, on eukaryotic cell synthesis, and on nucleic acid binding. It was found that: (1) Disulfiram inhibits the activity of the RNA dependent DNA polymerase of Rous sarcoma virus and inactivates the ability of the virus to malignantly transform chick embryo cells. The monomer of disulfiram, diethyldithiocarbamate does not affect the virus. (2) Disulfiram induced the synthesis of four proteins in normal chick embryo and human foreskin cells. The monomer diethyldithiocarbamate, induced these proteins also. Cellular DNA synthesis is more sensitive to disulfiram than are RNA and protein synthesis. (3) Disulfiram binds to neither DNA or RNA in the presence or absence of copper. However, diethyldithiocarbamate in the presence of, but not in the absence of, copper binds to HeLa cell DNA and to Rous sarcoma virus 70 S genome RNA. These results indicate that this compound, which causes no symptoms in people who do not consume alcohol, may have significant effects on a cellular level.

Animals↗