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At least 145 records · Page 8Linked to original sources
PubMed1976

A possible mechanism for concentrating sodium and potassium in the cell nucleus.

A dynamic, nonequilibrium mechanism is proposed for concentrating both Na+ and K+ in the cell nucleus. The model is consistent with experiment observations and with known properties of cell membranes. This model could explaing the high nucleoplasm to cytoplasm ratios of Na+ and/or K+ reported for liver kidney, thymus, frog skin, ascites cells, and amphibian oocytes.

Animals↗
PubMed2005

Modeling lateral geniculate nucleus cell response spectra and Munsell reflectance spectra with cone sensitivity curves.

We find that the cell response spectra of lateral geniculate nucleus cells, as well as the reflectance spectra of Munsell color chips, may be modeled by using the cone sensitivity functions of the long and medium cones. We propose a simple model for how the neural signals from the photoreceptors might be combined in the retina to closely approximate the reflectance spectra of Munsell color chips without input from the short cone.

Animals↗
PubMed1997

Human deoxycytidine kinase is located in the cell nucleus.

Human deoxyribonucleoside kinases are required for the pharmacological activity of several clinically important anticancer and antiviral nucleoside analogs. Human deoxycytidine kinase and thymidine kinase 1 are described as cytosolic enzymes in the literature, whereas human deoxyguanosine kinase and thymidine kinase 2 are believed to be located in the mitochondria. We expressed the four human deoxyribonucleoside kinases as fusion proteins with the green fluorescent protein to study their intracellular locations in vivo. Our data showed that the human deoxycytidine kinase is located in the cell nucleus and the human deoxyguanosine kinase is located in the mitochondria. The fusion proteins between green fluorescent protein and thymidine kinases 1 and 2 were both predominantly located in the cytosol. Site-directed mutagenesis of a putative nuclear targeting signal, identified in the primary structure of deoxycytidine kinase, completely abolished nuclear import of the protein. Reconstitution of a deoxycytidine kinase-deficient cell line with the wild-type nuclear or the mutant cytosolic enzymes both restored sensitivity toward anticancer nucleoside analogs. This paper reports that a deoxyribonucleoside kinase is located in the cell nucleus and we discuss the implications for deoxyribonucleotide synthesis and phosphorylation of nucleoside analogs.

Amino Acid Sequence↗
PubMed2005

The crystal structure of human adenylate kinase 6: An adenylate kinase localized to the cell nucleus.

Adenylate kinases (AKs) play important roles in nucleotide metabolism in all organisms and in cellular energetics by means of phosphotransfer networks in eukaryotes. The crystal structure of a human AK named AK6 was determined by in-house sulfur single-wavelength anomalous dispersion phasing methods and refined to 2.0-A resolution with a free R factor of 21.8%. Sequence analyses revealed that human AK6 belongs to a distinct subfamily of AKs present in all eukaryotic organisms sequenced so far. Enzymatic assays show that human AK6 has properties similar with other AKs, particularly with AK5. Fluorescence microscopy showed that human AK6 is localized predominantly to the nucleus of HeLa cells. The identification of a nuclear-localized AK sheds light on nucleotide metabolism in the nucleus and the energetic communication between mitochondria and nucleus by means of phosphotransfer networks.

Active Transport, Cell Nucleus↗
PubMed1998

An autoantibody is modified for use as a delivery system to target the cell nucleus: therapeutic implications.

A murine monoclonal anti-dsDNA antibody was found to penetrate living cells and localize in the nucleus without pathologic effects. A single mutation in VH markedly enhanced cellular penetration. The mutant antibody was produced as recombinant Fab and single chain antibody fragments to investigate its use as a delivery system to target the cell nucleus. Complexes were made containing Fab fragments and alkaline phosphatase conjugated goat antibodies to mouse |gk chains. Fab fragments transported 305 kDa goat antibody-enzyme complexes into the nucleus in COS-7 and CHO cells. A single chain antibody cDNA was constructed by splice overlap extension PCR and expressed in COS-7 cells. Binding of the single chain antibody to dsDNA was shown by ELISA, and cellular penetration and nuclear localization were demonstrated in COS-7 and CHO cells. The single chain antibody cDNA was ligated into the expression vector, pEGFP, to produce a fusion protein with green fluorescent protein. The fusion protein penetrated COS-7 cells and localized in the cell nucleus. The single chain antibody produced during sustained expression in CHO cells re-entered antibody-producing cells and localized in the nucleus without affecting cell viability. Our results demonstrate the potential use of a modified autoantibody as a delivery system to target the cell nucleus.

Animals↗
PubMed1998

An illustrative comparison of the event-size distributions for gamma-rays and alpha-particles in the whole mammalian cell nucleus.

PURPOSE: Recent laboratory studies of endpoints designated as due to radiation-induced genomic instability have cast doubt on the validity of the current theoretical framework. Under this framework extrapolations are made from directly determined risks of radiation-induced cancer to those circumstances for which no direct information exists, namely at low doses and dose rates at low LET and at low dose exposures to high LET radiations. Based upon an approach in which the 'state' of the genome, as exemplified by the pattern of gene expression, rather than the base sequence of the genomic DNA, is taken to be the origin of genomic stability, it is hypothesized that the critical factor determining the likelihood of destabilization by ionizing radiation is the dose to the whole cell nucleus. CALCULATIONS: The frequency distributions of event sizes from two qualities of radiation, low LET y-rays and 5 MeV alpha-particles, are compared with 60Co gamma-rays being taken to be a low LET reference radiation in determining the RBE of other radiation qualities. In the absence of measured event-size distributions for 60Co gamma-rays in spheres of similar size to the human cell nucleus, the 4.5 microm sphere has been chosen as illustrative. Frequency distributions for 5 MeV alpha-particles are derived, based on the idealized situation of a parallel beam of constant LET, with all particles traversing the sphere. RESULTS: When compared for a dose of 1 mGy the event-size (dose) distributions of the two qualities do not intersect. It is estimated that only 0.4% of the energy from the alpha-particles falls in the range of event sizes that can be produced by 60Co gamma-rays. CONCLUSIONS: Contrary to belief over the past 50 years, there is, in this low dose range, no 'continuum' based upon quantities such as LET or lineal energy that would provide a basis for extrapolation from measured RBE values. RBE is thus seen to be purely empirical. In addition, the potential to induce effects in bystander cells is not considered when deriving weighting factors for alpha-particles of the type that contribute significantly to public exposure to environmental radiation.

Alpha Particles↗
PubMedDate not supplied

[Changes in the macromolecular composition and organization of the cell nucleus during gameto-, embryo- and histogenesis].

Data about changes in the molecular organization of the cell nucleus during the organism development and tissue differentiation are summarized. The peculiarities of the nucleus organization of gametes, its changes in the course of fertilization and early embryogenesis are discussed. Data concerning different objects of developmental biology are reviewed separately. The data about tissue specificity of the chromatin structure and characteristic features of nuclei of nervous, muscle, epithelial, and connective tissue cells are also presented. Different levels of chromatin organization, i.e., the primary and secondary DNA structure, protein composition, nucleosomal and supranucleosomal structures, DNA supercoiling in chromatin domains, nuclear skeleton structures, are specifically concerned in each particular case.

Animals↗