Showing papers by "Oak Ridge National Laboratory published in 1972"
TL;DR: Six stages of oocyte development in the anuran Xenopus laevis can be divided into six stages based on the anatomy of the developing oocyte, and these stages have been correlated with physiological and biochemical data related to oogenesis.
Abstract: Oogenesis in the anuran Xenopus laevis can be divided into six stages based on the anatomy of the developing oocyte. Stage I consists of small (50 to 100 μ) colorless oocytes whose cytoplasm is transparent. Their large nuclei and mitochondrial masses are clearly visible in the intact oocyte. Stage II oocytes range up to 450 μ in diameter, and appear white and opaque. Stage I and II are both previtellogenic. Pigment synthesis and yolk accumulation (vitellogenesis) begins during Stage III. Vitellogenesis continues through Stage IV (600 to 1000 μ), the oocytes grow rapidly, and the animal and vegetal hemispheres become differentiated. By Stage V (1000 to 1200 μ) the oocytes have nearly reached their maximum size and yolk accumulation gradually ceases. Stage VI oocytes are characterized by the appearance of an essentially unpigmented equatorial band. They range in size from 1200 to 1300 μ, are postivtellogenic and ready for ovulation. These stages of oocyte development have been correlated with physiological and biochemical data related to oogenesis in Xenopus.
1,744 citations
TL;DR: In this paper, it was shown that cells frozen rapidly in 0.4 M solutions of sucrose, glycerol, and dimethyl sulfoxide are inactivated to a much greater extent by slow warming than are cells frozen slowly in those solutions; that is, cells frozen at rates greater than the optimum are considerably more sensitive to slow warming.
847 citations
TL;DR: Mouse embryos survived freezing to -196�C and when approximately 1000 of the survivors, including some frozen to -269�C (4�K), were transferred into foster mothers, 65 percent of the recipients became pregnant and more than 40 percent gave rise to normal, living full-term fetuses or newborn mice.
Abstract: Mouse embryos survived freezing to -196 degrees C. Survival required slow cooling (0.3 degrees to 2 degrees C per minute) and slow warming (4 degrees to 25 degrees C per minute). Depending on the specific rates used, 50 to 70 percent of more than 2500 frozen and thawed early embryos developed into blastocysts in culture after storage at -196 degrees C for up to 8 days. When approximately 1000 of the survivors, including some frozen to -269 degrees C (4 degrees K), were transferred into foster mothers, 65 percent of the recipients became pregnant. More than 40 percent of the embryos in these pregnant mice gave rise to normal, living full-term fetuses or newborn mice.
844 citations
TL;DR: In this article, the frequencies of normal modes of vibration of the graphite lattice have been studied on samples of high-quality pyrolytic graphite by coherent, inelastic-neutron-scattering techniques.
Abstract: The frequencies of certain normal modes of vibration of the graphite lattice have been studied on samples of high-quality pyrolytic graphite by coherent, inelastic-neutron-scattering techniques. Some of the data are not compatible with certain restrictions imposed by the valence-bond model as presented by Young and Koppel. Therefore, the data have been analyzed in terms of a simple axially symmetric, Born-von K\'arm\'an force-constant model. The results show that appreciable interactions exist between third nearest neighbors in the basal plane. The force model has been used to calculate a frequency distributio function and the lattice specific heat of graphite. These calculations are in excellent agreement with the specific heat measured for natural graphite in the temperature range 1.5-300\ifmmode^\circ\else\textdegree\fi{}K.
592 citations
TL;DR: The relationship between the scientist and the politician is thus far more complicated than the simple model described above as mentioned in this paper, in particular because even where there are clear scientific answers to the scientific questions involved in a public issue, ends and means are hardly separable.
Abstract: Much has been written about the responsibility of the scientist in resolving conflicts which arise from the interaction between science and society. Ordinarily the assumption is made that a particular issue on which scientific knowledge is drawn into the resolution of a political conflict for example, whether or not to build a supersonic transport (SST) or whether or not to proceed with a trip to the moon can be neatly divided into two clearly separable elements, one scientific, the other political. Thus the scientist is expected to say whether a trip to the moon is feasible or whether the SST will cause additional skin cancer. The politician, or some other representative of society, is then expected to say whether the society ought to proceed in one direction or another. The scientist and science provide the means; the politician and politics decide the ends. This view of the role of the scientist, and indeed of science itself, is, of course, oversimplified, in particular because even where there are clear scientific answers to the scientific questions involved in a public issue, ends and means are hardly separable. What is thought to be a political or social end turns out to have numerous repercussions, the analysis of which must fall into the legitimate jurisdiction of the scientist, and each of these repercussions must also be assessed in moral and political terms; or what is thought to be a scientific means has non-scientific implications which also must be assessed in these terms. The relationship between the scientist and the politician is thus far more complicated than the simple model described above.
501 citations
TL;DR: To determine whether the gaps in the daughter strands opposite the pyrimidine dimers are filled in with newly synthesized DNA by a recombinational mechanism or by de novo synthesis, irradiated cells were pulse-labeled with radioactive thymidine, followed by incubation in bromodeoxyuridine and exposure to light of wavelength 313 nm.
416 citations
TL;DR: In this article, the Lenz-Jensen statistical model for the stopping power of a particle of charge at a given impact parameter with an electron bound isotropically and harmonically to the origin with a frequency was considered.
Abstract: We consider in a classical formulation the interaction of a particle of charge ${Z}_{1}e$ incident at a given impact parameter with an electron bound isotropically and harmonically to the origin with a frequency $\ensuremath{\omega}$. Using a perturbation expansion that assumes that the displacement of the bound electron is small compared to the impact parameter, and integrating over the impact parameter from some minimum value to infinity, we are led to an expression for the stopping power. The leading term in this expansion is proportional to ${({Z}_{1}{e}^{2})}^{2}$ and is the usual result for this type of model, while the second term gives us the ${({Z}_{1}{e}^{2})}^{3}$ correction. The ${Z}_{1}^{3}$ correction for the Lenz-Jensen statistical model for the atom is presented. The predictions of this theory are in excellent agreement with available experimental data.
253 citations
TL;DR: The GeMSAEC Fast Analyzer, in conjunction with a small computer, provides a means of performing routine enzymatic substrate analysis and offers the following advantages: on-line data reduction, resulting in rapid calculation and output of results and the minimization of data handling errors.
Abstract: Enzymatic substrate analysis is an attractive means of analysis in clinical chemistry because of its sensitivity and specificity. The GeMSAEC Fast Analyzer, in conjunction with a small computer, provides a means of performing routine enzymatic substrate analysis and offers the following advantages: ( a ) selectivity of approaches to enzymatic analysis, i.e., end-point or kinetic; ( b ) essentially parallel analyses of multiple samples, yielding a unique method for performing kinetic fixed-time analysis; ( c ) on-line data reduction, resulting in rapid calculation and output of results and the minimization of data handling errors; and ( d ) a small reagent volume per test (400 µl), which reduces the cost of analysis. The analysis of substrate with enzymatic end-point and kinetic procedures is examined by use of a computer-interfaced Fast Analyzer. Computer programs were written to facilitate this study. Glucose (hexokinase/GPD), urea (urease/GMD), and uric acid (uricase) have been used as examples in evaluating both end-point and kinetic analyses. The advantages and limitations of each type of analysis are presented, with the emphasis being placed on enzymatic substrate analysis and means by which the computer-interfaced Fast Analyzer can facilitate both end-point and kinetic analyses.
237 citations
TL;DR: In this paper, the photoelectron spectrum of tungsten metal using Al Kα X-rays has been studied as a function of a Tungsten oxide layer on the surface.
206 citations
TL;DR: In this article, the concept of an equivalent ellipsoid, whose charge and moments equal those of the nucleus, is employed for determining nuclear shapes, which is equally valid for spherical, deformed, and intermediate nuclei.
Abstract: A new method of determining nuclear shapes is proposed which avoids the assumption of a specific nuclear model. The concept of an equivalent ellipsoid, whose charge and moments equal those of the nucleus, is employed. But the method is equally valid for spherical, deformed, and intermediate nuclei. It can be employed for any nucleus (evev-evevn, odd-$\mathbf{A}$, or odd-odd) provided enough $E2$ matrix elements are available. The example of $^{152}\mathrm{Sm}$ is discussed.
168 citations
TL;DR: This laboratory demonstrated that the DNA polymerase of the Rauscher leukaemia virus is strongly inhibited in vitro by unprimed, single stranded polyribonucleotides as a result of competition between the polymers and the active template for the same enzyme binding site.
Abstract: A PREVIOUS communication from this laboratory demonstrated that the DNA polymerase of the Rauscher leukaemia virus is strongly inhibited in vitro by unprimed, single stranded polyribonucleotides1 as a result of competition between the polymers and the active template for the same enzyme binding site. This inhibition was apparently specific, since partially purified preparations of DNA polymerase from Escherichia coli and BALB/c mouse embryos were not inhibited in the same conditions. We attempted to determine therefore whether single stranded polyribonucleotides would have any effect on the activities of oncogenic RNA viruses in cultured cells.
TL;DR: The results suggest that F pili are resorbed by the cell during infection with the bacteriophage f1, and parallel experiments with noninfected cultures further suggest that pilus resorption may be a normal cellular phenomenon.
Abstract: Early stages of infection of Escherichia coli with the filamentous bacteriophage f1 were examined in the electron microscope. Purified phage-bacteria complexes were prepared at various time intervals after the initiation of synchronous infection. Cells were scored for the total number of F pili, the number of F pili with f1 attached, the number of intact phage particles which occurred at the surface of the cell, and F pilus length. Electron microscope autoradiographs were also prepared at each time interval. The results showed that the average number of F pili with f1 attached decreased with time as phage deoxyribonucleic acid (DNA) entered the cell. Concomitant with this loss, the remaining F pili became shorter. The rate of entry of phage DNA into the cell followed, with a short lag, the rate of loss of F pili with f1 attached. During the lag period, intact phage particles accumulated at the surface of the cell. The results from radioautographs showed that no phage DNA could be located within the F pilus. These results suggest that F pili are resorbed by the cell during infection with the bacteriophage f1. Parallel experiments with noninfected cultures further suggest that pilus resorption may be a normal cellular phenomenon.
TL;DR: Man may nevertheless be exposed to nitrosamines formed in vivo from ingested nitrite and secondary amines, and the exposure of man to the many tertiary nitrogen compounds which are drugs must also be considered.
Abstract: NITROSAMINES are compounds with broad carcinogenic activity in many animal species, but have seldom been detected in the environment in significant quantities. Man may nevertheless be exposed to nitrosamines formed in vivo from ingested nitrite and secondary amines1–3. Nitrite is a common constituent of the diet, as are several secondary amines4. Since tertiary amines can also react with nitrite5 in the mildly acid conditions of the mammalian stomach, the exposure of man to the many tertiary nitrogen compounds which are drugs6 must also be considered.
TL;DR: In this article, a new method for the integration of the extended Nernst-Planck equations in the hyperfiltration of multicomponent solutions through ion exchange membranes is proposed.
TL;DR: Structural aspects of the activity of specific genes are demonstrated here using representatives of both eukaryotic and prokaryotic cell types using the use of relatively simple techniques for isolating portions of active genomes.
Abstract: Publisher Summary The numerous electron microscope autoradiographic studies of eukaryotic cells show that RNA synthesis is localized in dispersed chromatin in both nucleolar and non-nucleolar compartments of the nucleus. Alternatively, autoradiography of thin sections of pulse-labeled bacteria shows the localization of RNA synthesis near the interface of the ribosome-containing areas of the cell and the nucleoid regions that contain most of the bacterial DNA. An example of the structural resolution of genetic activity obtainable by thin-sectioning methods is presented in this chapter. In none of the thin-section studies with either eukaryotic or prokaryotic cells, however, could a distinct genetic unit be resolved within the regions active in RNA synthesis. More recently, direct visualization of the fine structure of individual, active genes in both cell types has been accomplished through novel isolation techniques. This chapter discusses the current status of these studies. Structural aspects of the activity of specific genes are demonstrated here using representatives of both eukaryotic and prokaryotic cell types. In both cases, inherent characteristics of the cells permitted the use of relatively simple techniques for isolating portions of active genomes.
TL;DR: It is concluded that the UV-sensitive cells lack an early step in the repair of UV-induced pyrimidine dimers, which makes them less photoreactivable in vivo, although remaining photoreactivateable in vitro.
Abstract: Crude extracts from ultraviolet (UV)-irradiated yeast cells compete with UV-irradiated transforming deoxyribonucleic acid (DNA) for photoreactivating enzyme. The amount of competition is taken as a measure of the level of cyclobutyl pyrimidine dimers in the yeast DNA. A calibration of the competition using UV-irradiated calf thymus DNA indicates that an incident UV dose (1,500 ergs/mm2) yielding 1% survivors of wild-type cells produces between 2.5 × 104 to 5 × 104 dimers per cell. Wild-type cells irradiated in the exponential phase of growth remove or alter more than 90% of the dimers within 220 min after irradiation. Pyrimidine dimers induced in stationary-phase wild-type cells appear to remain in the DNA; however, with incubation, they become less photoreactivable in vivo, although remaining photoreactivable in vitro. In contrast, exponentially growing or stationary-phase UV-sensitive cells (rad2-17) show almost no detectable alteration of dimers. We conclude that the UV-sensitive cells lack an early step in the repair of UV-induced pyrimidine dimers.
TL;DR: The data suggest a model that views chromatin condensation as a close packing of superhelical nucleohistone threads but still permits condensed chromatin to respond rapidly to alterations in solvent environment.
Abstract: The degree of chromatin condensation in isolated rat liver nuclei and chicken erythrocyte nuclei was studied by phase-contrast microscopy as a function of solvent pH, K+ and Mg++ concentrations Data were represented as "phase" maps, and standard solvent conditions selected that reproducibly yield granular, slightly granular, and homogeneous nuclei Nuclei in these various states were examined by ultraviolet absorption and circular dichroism (CD) spectroscopy, low-angle X-ray diffraction, electron microscopy, and binding capacity for ethidium bromide Homogeneous nuclei exhibited absorption and CD spectra resembling those of isolated nucleohistone. Suspensions of granular nuclei showed marked turbidity and absorption flattening, and a characteristic blue-shift of a crossover wavelength in the CD spectra. In all solvent conditions studied, except pH < 2 3, low-angle X-ray reflections characteristic of the native, presumably superhelical, nucleohistone were observed from pellets of intact nuclei. Threads (100–200 A diameter) were present in the condensed and dispersed phases of nuclei fixed under the standard solvent conditions, and examined in the electron microscope after thin sectioning and staining Nuclei at neutral pH, with different degrees of chromatin condensation, exhibited similar binding capacities for ethidium bromide. These data suggest a model that views chromatin condensation as a close packing of superhelical nucleohistone threads but still permits condensed chromatin to respond rapidly to alterations in solvent environment.
TL;DR: In this paper, the excitation of the giant dipole and quadrupole states in nuclei was investigated and two simple models were used for the transition densities and potentials in the dipole excitation.
TL;DR: In this article, the potential energy curve of CO − 2 ( 2 A 1 ) lies below that of CO 2 ( 1 A 1 ), and an unfavorable Franck-Condon overlap exists between the bent ion (134°) and the linear neutral parent.
TL;DR: The principal conclusion reached from these studies is that at least 99% of the protein present in the yolk platelet crystal is derived from a source outside the oocyte.
TL;DR: Cells from normal individuals and from individuals with xeroderma pigmentosum were treated with the carcinogen N-acetoxy-2-acetylaminofluorene and repair of the damage to DNA was estimated by incubating the cells in BrdUrd and photolyzing the BrUra-containing repaired regions with 313-nm radiation.
TL;DR: In this article, the stopping power of C, Al, Ni, Ag, and Au foils was measured using the Oak Ridge Tandem Accelerator (ATP) and compared with various theoretical predictions.
Abstract: Uranium ions of energies in the range 30-90 MeV from the Oak Ridge Tandem accelerator were used to measure stopping powers for C, Al, Ni, Ag, and Au foils. Foil thicknesses were determined by $\ensuremath{\alpha}$-particle energy-loss measurements. The results are compared with various theoretical predictions. Subtraction of an assumed nuclear-stopping component leaves a residual electronic stopping power which is velocity proportional but does not appear to extrapolate to the origin, in disagreement with theory. Comparisons with other ions indicate that heavier ions exhibit larger discrepancies with theory in that the velocity-proportional stopping extrapolates to zero stopping at larger values of velocity.
TL;DR: The analgesic aminopyrine, 4-dimethylaminoantipyrine (pyramidon), is examined, as being representative of many commonly used tertiary amine drugs.
Abstract: IN experimental conditions, nitrite can interact with secondary amines in the rodent stomach at mildly acid pH to form nitrosamines1–4, a large number of which are potent carcinogens5. As tertiary amines also react in this way6, we have examined the analgesic aminopyrine, 4-dimethylaminoantipyrine (pyramidon), as being representative of many commonly used tertiary amine drugs.
TL;DR: In this article, the average number and average energy of fission neutrons emitted within 5 nsec after fission have been determined as function of fragment mass and as functions of fragment masses and total kinetic energy in two-dimensional representations.
Abstract: The average number and average energy of $\ensuremath{\gamma}$ rays emitted within \ensuremath{\sim}5 nsec after fission have been determined as functions of fragment mass and as functions of fragment mass and total kinetic energy in two-dimensional representations. In a four-parameter experiment, energies of coincident pairs of fission fragments were measured with surface-barrier detectors and $\ensuremath{\gamma}$-ray energies were measured with a large NaI(Tl) detector, which was located 89 cm from a thin $^{235}\mathrm{U}$ target and positioned coaxially with the fragment detectors. The time difference between detection of a fission fragment and a $\ensuremath{\gamma}$ ray was measured to allow time-of-flight discrimination against fission neutrons. The $\ensuremath{\gamma}$-ray data were analyzed with a "weighting method" proposed by Maier-Leibnitz to deduce average numbers and energies of $\ensuremath{\gamma}$ rays from measured pulse heights. The Doppler shift in the laboratory angular distribution of $\ensuremath{\gamma}$ emission was utilized to obtain the number and energy of $\ensuremath{\gamma}$ rays as functions of single fragment mass. The results, for both average number and average energy as functions of single fragment mass, are characterized by a sawtooth behavior similar to that which is well known for neutron emission. The over-all average number and energy of $\ensuremath{\gamma}$ rays emitted per fission were found to be 6.51 \ifmmode\pm\else\textpm\fi{} 0.3 and 6.43 \ifmmode\pm\else\textpm\fi{} 0.3 MeV, respectively, giving an average photon energy of 0.99 \ifmmode\pm\else\textpm\fi{} 0.07 MeV.
TL;DR: In this article, the magnetic-moment distribution in the metal was measured with both polarized and unpolarized neutrons, and the results were in excellent agreement with the free ion calculations, except at very small scattering angles.
Abstract: Neutron-diffraction experiments with both polarized and unpolarized neutrons have been carried out on single-crystal specimens of $^{160}\mathrm{Gd}$ in order to measure the magnetic-moment distribution in the metal. Data have been obtained in the ferromagnetic state at 96 \ifmmode^\circ\else\textdegree\fi{}K for all ($\mathrm{hk}0$) reflections out to $\frac{(sin\ensuremath{\theta})}{\ensuremath{\lambda}}=1.275$ and nearly all ($0kl$) peaks to $\frac{(sin\ensuremath{\theta})}{\ensuremath{\lambda}}=1.04$. Measurements have been made as well at a temperature above the Curie point. The shape of the spin distribution appears to be identical at the elevated temperature (313 \ifmmode^\circ\else\textdegree\fi{}K) to that observed at 96 \ifmmode^\circ\else\textdegree\fi{}K. The form-factor data can logically be separated into diffuse and localized components, which may be identified with the conduction electrons and $4f$ electrons, respectively. The $4f$ density is spherically symmetric, and it has a radial dependence which is significantly expanded relative to Hartree-Fock wave functions for the free trivalent ion. Good agreement can be achieved with theoretical form factors based on relativistic Hartree-Fock-Slater wave functions. The diffuse density does not have the distribution expected for $5d$ or $6s$ orbitals: It is long range and oscillatory, however, as one expects for conduction electrons in the rare earths. Measurements of the form factor of ${\mathrm{Gd}}^{+3}$ in paramagnetic ${\mathrm{Gd}}_{2}$${\mathrm{O}}_{3}$ have also been made, and the results are in excellent agreement with the free-ion calculations, except at very small scattering angles.
TL;DR: The photoelectron spectra of CF 4, SiF 4, GeF 4, C(CH 3 ) 4, Si(CH 2 ) 4), Ge(CH 1 ) 4, Sn(CH3 ) 4 ) and Pb(CH 4 ) 4 h are described in this article.
TL;DR: Results indicate that the mechanism of filling the gaps in DNA synthesized after irradiation involves the insertion of ∼ 103 nucleotides pe...
Abstract: SummaryThe DNA synthesized in human cells shortly after u.v.-irradiation is of lower molecular weight than that in unirradiated cells. Within several hours after irradiation, these smaller DNA units are both elongated and joined together. To determine if this process involves incorporation of exogenous precursors, cells were irradiated, pulse-labelled, and incubated in medium containing bromodeoxyuridine. They were then exposed to different fluxes of 313-nm radiation, and the number of breaks in the DNA was determined by sedimentation in alkaline sucrose. If bromodeoxyuridine, rather than exclusively premade DNA, is used to elongate and join the small DNA segments synthesized after u.v.-irradiation, photolysis by 313-nm radiation would yield the lower molecular weight segments that are present immediately after u.v.-irradiation. This expectation was fulfilled, and our results indicate that the mechanism of filling the gaps in DNA synthesized after irradiation involves the insertion of ∼ 103 nucleotides pe...
TL;DR: Results show that the small analyzer possesses the previously demonstrated advantages of Fast Analyzers and, in addition, has several beneficial features arising from miniaturization.
Abstract: Design features and operation of a prototype miniaturized Fast Analyzer are described, and some results obtained with it are presented. The Analyzer occupies only one cubic foot of space. It has a 17-cuvet plastic rotor that rotates through a stationary optical system at speeds up to 5000 rpm. The resulting centrifugal force is utilized to transfer and mix a series of sample(s) and reagent(s) into the cuvets. The ensuing reactions are monitored spectrophotometrically, and the data evaluated in real time by an on-line computer. Samples (1 to 10 µl) and reagents (70 to 110 µl) are loaded into the rotor either discretely or dynamically; various rotor configurations can be used to do this. Many of the standard clinical analyses, including most of the NADH-linked enzymatic analyses, have been adapted for use with this analyzer. Precision obtained ranges from 1 to 4%. This report considers, specifically, analyses of some serum enzymes. Results show that the small analyzer possesses the previously demonstrated advantages of Fast Analyzers and, in addition, has several beneficial features arising from miniaturization.