Abstract:
:Magnetic interactions between dissolved oxygen and nitroxide radical spin probes lead to broadening of the ESR lines. We have used a closed-chamber method based on this property to determine the maximum rate of O2 uptake per cell (Vmax per cell) in cultured mammalian cells. A suitable spin probe and a cell suspension are mixed in an aerated medium, and the rate of disappearance of dissolved O2 is measured. The effects of temperature, pH, and microwave power on the determination of dissolved oxygen in solution were studied. For asynchronous Chinese hamster ovary cells, oxygen uptake is 3.8 X 10(7) oxygen molecules per cell per sec and appears to be enzymatically limited at oxygen concentrations greater than 10 microM. About 5-10 X 10(5) cells were used for each measurement, making it possible to study mitotically synchronized cells. Using this method, we have found that Vmax per unit cell volume changes during the cell cycle of Chinese hamster ovary cells from a minimum in mitosis to maxima in both G1 and late S phases. Advantages and limitations of spin probes for studying the O2 uptake of intact cells are discussed.
journal_name
Proc Natl Acad Sci U S Aauthors
Lai CS,Hopwood LE,Hyde JS,Lukiewicz Sdoi
10.1073/pnas.79.4.1166subject
Has Abstractpub_date
1982-02-01 00:00:00pages
1166-70issue
4eissn
0027-8424issn
1091-6490journal_volume
79pub_type
杂志文章abstract::Arsenate is an abundant oxyanion that, because of its ability to mimic the phosphate group, is toxic to cells. Arsenate reductase (EC; encoded by the arsC gene in bacteria) participates to achieve arsenate resistance in both prokaryotes and yeast by reducing arsenate to arsenite; the arsenite is then exported by a spe...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.241397198
更新日期:2001-11-20 00:00:00
abstract::Oxygen isotherms of human hemoglobin measured in distilled water and in solutions of sodium chloride in the concentration range from 0.02 to 3.0 M indicate that the oxygen affinity decreases up to about 1 M salt and then begins to increase. The isotherms obtained in the range from 0.02 to 0.6 M sodium chloride, at 37 ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.74.10.4135
更新日期:1977-10-01 00:00:00
abstract::A series of hairpin pyrrole-imidazole polyamide-fluorescein conjugates were synthesized and assayed for cellular localization. Thirteen cell lines, representing 11 human cancers, one human transformed kidney cell line, and one murine leukemia cell line, were treated with 5 microM polyamide-fluorescein conjugates for 1...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.2035074100
更新日期:2003-10-14 00:00:00
abstract::Using a novel technique of modulated photo-dissociation of carbon monoxide from hemoglobin, we have obtained the rates for conversion between the two quaternary states, R, and T, at 3-fold ligation. Our measurements at pH 7 and 22 degrees give rates of 780 +/- 40 sec-1 for going from R to T, and 2500 +/- 200 sec-1 fro...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.73.12.4497
更新日期:1976-12-01 00:00:00
abstract::Transposition is a multistep process in which a transposable element DNA sequence moves from its original genetic location to a new site. Early steps in this process include the formation of a transposition complex in which the end sequences of the transposable element are brought together in a structurally precise fa...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.91.23.10834
更新日期:1994-11-08 00:00:00
abstract::A genetic defect in a CC-chemokine receptor (CCR)-5, the principal coreceptor for the macrophage-tropic HIV type 1 (HIV-1), recently was found to naturally protect CCR-5-defective, but healthy, individuals from HIV-1 infection. In this study, we mimic the natural resistance of the CCR-5-defective individuals by design...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.94.21.11567
更新日期:1997-10-14 00:00:00
abstract::Ubiquitination, the crucial posttranslational modification that regulates the eukaryotic proteome, is carried out by a trio of enzymes, known as E1 [ubiquitin (Ub)-activating enzyme], E2 (Ub-conjugating enzyme), and E3 (Ub ligase). Although most E2s can work with any of the three mechanistically distinct classes of E3...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1705060114
更新日期:2017-08-08 00:00:00
abstract::Two decades after the discovery of the first animal microRNA (miRNA), the number of miRNAs in animal genomes remains a vexing question. Here, we report findings from analyzing 1,323 short RNA sequencing samples (RNA-seq) from 13 different human tissue types. Using stringent thresholding criteria, we identified 3,707 s...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1420955112
更新日期:2015-03-10 00:00:00
abstract::The addition of insulin to a mixture of plasma membrane and mitochondrial fractions from rat adipocytes results in a decrease in the phosphorylation of a mitochondrial protein identified as the alpha subunit of pyruvate dehydrogenase [pyruvate:lipoamide oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.77.1.77
更新日期:1980-01-01 00:00:00
abstract::After each round of protein biosynthesis, the posttermination complex (PoTC) consisting of a ribosome, mRNA, and tRNA must be disassembled into its components for a new round of translation. Here, we show that a Saccharomyces cerevisiae model PoTC was disassembled by ATP and eukaryotic elongation factor 3 (eEF3). GTP ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1006247107
更新日期:2010-06-15 00:00:00
abstract::A polar lipid containing about 20 per cent of the lipid soluble inositol has been purified from cells of Saccharomyces cerevisiae. This compound labeled with (3)H-inositol, (32)P(i), or (14)C glucose was isolated from aqueous pyridine extracts by means of paper chromatography. Unlabeled compound was obtained by a diff...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.64.3.1042
更新日期:1969-11-01 00:00:00
abstract::A technique is described for isolation of plasmid DNA in closed and open circular double-stranded forms from bacterial cells, by use of ATP-dependent deoxyribonuclease purified from Micrococcus luteus. This DNase, acting only upon linear DNA molecules, degrades all bacterial chromosomal DNA extracted in the linear for...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.70.10.2884
更新日期:1973-10-01 00:00:00
abstract::Conjugative DNA transfer of the self-transmissible broad-host-range plasmid RP4 is initiated by strand- and site-specific cleavage at the nick site (nic) of the transfer origin (oriT). Cleavage results in covalent attachment of the plasmid-encoded relaxase (TraI) to the 5'-terminal 2'-deoxycytidine residue at nic. We ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.90.7.2925
更新日期:1993-04-01 00:00:00
abstract::Nannofossils section sign here described are from the middle Proterozoic Paradise Creek Formation, along Paradise Creek in northwestern Queensland, Australia. These fossils, in chert blebs associated with branched stromatolites, comprise cubic colonies analogous to living Eucapsis, a member of the blue-green algal fam...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.62.1.56
更新日期:1969-01-01 00:00:00
abstract::Necessary conditions are derived for a spherical vortex in a perfect fluid to be stationary in the case when the velocities depend on a single surface harmonic. The motion is indeterminate unless an additional condition is imposed. In the case when this condition is incompressibility, the equations are solved, yieldin...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.69.9.2460
更新日期:1972-09-01 00:00:00
abstract::We demonstrate two kinds of visual stimuli that exhibit motion in one direction when viewed from near and in the opposite direction from afar. These striking reversals occur because each kind of stimulus is constructed to simultaneously activate two different mechanisms: a short-range mechanism that computes motion fr...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.86.8.2985
更新日期:1989-04-01 00:00:00
abstract::Fumarase C was strongly induced by paraquat in a parental strain of Escherichia coli but was not induced in a strain lacking the soxRS response. Moreover, a strain that constitutively expresses the soxRS regulon contained more fumarase C than did the parental strain. The Mn-containing superoxide dismutase and glucose-...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.89.13.5892
更新日期:1992-07-01 00:00:00
abstract::Puf proteins bind RNA sequence specifically and regulate translation and stability of target mRNAs. A "code" for RNA recognition has been deduced from crystal structures of the Puf protein, human Pumilio1, where each of eight repeats binds an RNA base via a combination of three side chains at conserved positions. Here...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0606294103
更新日期:2006-09-12 00:00:00
abstract::We predict by first principles a phase transition in alumina at approximately 3.7 Mbar and room temperature from the CaIrO(3)-type polymorph to another with the U(2)S(3)-type structure. Because alumina is used as window material in shock-wave experiments, this transformation should be important for the analysis of sho...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0711925105
更新日期:2008-05-06 00:00:00
abstract::Active coping underlies a healthy stress response, but neural processes supporting such resilient coping are not well-known. Using a brief, sustained exposure paradigm contrasting highly stressful, threatening, and violent stimuli versus nonaversive neutral visual stimuli in a functional magnetic resonance imaging (fM...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1600965113
更新日期:2016-08-02 00:00:00
abstract::The functional significance of the portal vascular link between the beta cells of the pancreatic islets and the liver has not been established. Previous studies indicated that insulin does not acutely regulate glucose metabolism by a direct hepatic effect. More recent observations suggest that the role of insulin in r...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.84.20.7300
更新日期:1987-10-01 00:00:00
abstract::Specific protein domains and amino acids responsible for the apparent capacity of P-glycoprotein (mdr) to recognize and transport a large group of structurally unrelated drugs have not been identified. We have introduced a single Ser----Phe substitution within the predicted TM11 domain of mdr1 (position 941) and mdr3 ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.88.16.7289
更新日期:1991-08-15 00:00:00
abstract::The compact steep-spectrum sources (CSSs) are an interesting class of objects which are of subgalactic dimensions; they occur more frequently in high-frequency surveys because their spectra often turn over at lower frequencies. We have estimated the symmetry parameters of a well-defined sample of CSSs and compared the...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.92.25.11417
更新日期:1995-12-05 00:00:00
abstract::The POT1-TPP1 heterodimer, the major telomere-specific single-stranded DNA-binding protein in mammalian cells, protects chromosome ends and contributes to the regulation of telomerase. The recent discovery of telomeric RNA raises the question of how POT1 faithfully binds telomeric ssDNA and avoids illicit RNA binding ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0911099107
更新日期:2010-01-12 00:00:00
abstract::hK7 or human stratum corneum chymotryptic enzyme belongs to the human tissue kallikrein (hKs) serine proteinase family and is strongly expressed in the upper layers of the epidermis. It participates in skin desquamation but is also implicated in diverse skin diseases and is a potential biomarker of ovarian cancer. We ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0707811104
更新日期:2007-10-09 00:00:00
abstract::Walker-256 carcinosarcoma cells grown in tissue culture medium containing inhibitory DNA prepared from the tumor are shown to have an unaltered growth in vitro, but a diminished capacity to produce malignant tumors on injection into the rat. Coincident with this change in virulence is the induction of tRNA methylase i...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.67.4.1827
更新日期:1970-12-01 00:00:00
abstract::Thyrotropin-releasing hormone (TRH) binds to specific receptors on GH4C1 pituitary tumor cells. A fluorescently labeled analog of TRH was synthesized by coupling pGlu-His-ProNH(CH2)6NH2 to fluorescein isothiocyanate. The fluorescein-labeled peptide (FL-TRH) stimulated prolactin synthesis and release by GH4C1 cultures ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.78.1.587
更新日期:1981-01-01 00:00:00
abstract::Teratocarcinoma is a germ-line carcinoma giving rise to an embryoid tumor with structures derived from the three embryonic layers: mesoderm, endoderm, and ectoderm. Teratocarcinoma is widely used as an in vitro model system to study regulation of cell determination and differentiation during mammalian embryogenesis. M...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.91.13.6088
更新日期:1994-06-21 00:00:00
abstract::The photosynthetic apparatus converts light into chemical energy by a series of reactions that give rise to a coupled flow of electrons and protons that generate reducing power and ATP, respectively. A key intermediate in these reactions is plastoquinone (PQ), the most abundant electron and proton (hydrogen) carrier i...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.84.23.8424
更新日期:1987-12-01 00:00:00
abstract::Exposure of human monocyte-macrophages to as little as 50 microliters of cultured medium from lymphocytes stimulated by concanavalin A (Con A) resulted in a dramatic decrease in the activities of the low density lipoprotein (LDL) receptor pathway, the LDL-dextran sulfate pathway, and the scavenger receptor pathway. Th...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.79.3.922
更新日期:1982-02-01 00:00:00