Nuclear Purity Research Articles

Steady-state grain growth in UO2

The authors have observed steady-state grain growth in sintered UO{sub 2} pellets of nuclear purity at 2,003 K under H{sub 2}. The behavior of the grain size distribution at different instants is consistent with the grain growth model proposed by one of the authors. The total number of grains was estimated using the Saltykov`s method, and the evolution is in accordance with the model proposed by Rhines and Craig. The parabolic growth law was observed for the mean intercept length with n = 0.4.

ICP-AES and D.C.arc-AES determination of Sc, Y and lanthanides in nuclear grade graphite

Inductively Coupled Plasma-Atomic Emission Spectrometric and Direct Current Arc-Emission Spectrometric methods have been developed for the determination of rare earths in nuclear grade graphite. The graphite matrix was selectively removed from the analytes by controlled heating in air at 900°C in a muffle furnace. The residual ash containing analytes was dissolved and analysed by ICP-AES for rare earths specially required for assessing the nuclear purity, viz. Dy, Eu, Gd and Sm and for all rare earths, Sc and Y by D.C.arc-AES by photographing their spectra in III order on an 3.4 M Ebert Spectrograph. The recovery of rare earths after ashing was confirmed using γ-activities of141Ce,152–154Eu,153Gd,170Tm and169Yb which was found to be quantitative within experimental error.

Relationship between Concentrations of Extractable and Matrix-Bound Nuclear Androgen Receptor and Clinical Response to Endocrine Therapy for Prostatic Adenocarcinoma

The relationship between androgen receptor concentrations and clinical response to endocrine therapy for prostatic adenocarcinoma was investigated for 13 stage D patients. Both cytoplasmic and nuclear androgen receptors were quantified. For nuclear androgen receptor, nuclei were isolated and treated with high ionic strength buffer (0.6M KCl) to yield a KCl-extractable fraction; the nuclei were then treated with DNase I to yield nuclear matrices. Electron microscopy confirmed the relative nuclear purity and revealed matrix morphology. An hydroxylapatite binding assay and methyltrienolone (R1881) were used to quantify androgen receptor in cytosol, the KCl-extract and matrix preparations. Following 6 months of hormonal therapy, the clinical status of patients was re-evaluated and the patients were grouped according to disease response. The androgen receptor data obtained prior to therapy were compared for the disease response groups. The mean concentrations of cytoplasmic androgen receptor, KCl-extractable nuclear androgen receptor and nuclear matrix-bound androgen receptor, respectively, in those patients with disease progression or death (no. = 6), were 671 ± 232, 45 ± 17 and 119 ± 34fmol. per gm. of tissue ± S.E.M., and for those with disease regression or stabilization (no. = 7), 1427 ± 435, 193 ± 53 and 611 ± 92fmol. per gm. of tissue ± S.E.M. While cytoplasmic androgen receptor concentrations were not related to clinical status, both extractable and matrix-bound nuclear androgen receptor concentrations were significantly higher in the group which responded to hormonal therapy. These results suggest that nuclear-extractable and nonextractable androgen receptor concentrations are useful indices for the prediction of hormone-dependence of prostatic cancer.

Chapter 3 Isolation of Nuclei Using Hexylene Glycol

Publisher Summary This chapter describes a general procedure for the isolation of nuclei in buffered 2-methyl-2,4-pentanediol (hexylene glycol) solutions that meets the requirements of nuclear purity and general applicability. The hexylene glycol-PIPES buffer is efficacious both in vivo and in vitro . The tissues from mouse brain, chicken liver, rat liver, rat uterus, chick oviduct, hen oviduct, rabbit oviduct, and Novikoff hepatoma ascites cells and from the tissue culture cell lines Chinese hamster ovary and HeLa are chosen to demonstrate the minor modifications necessary for general applicability of the isolation method. The purity and morphology of the hexylene glycol-isolated nuclei is established using several criteria. Phase microscopic observations indicate that the preparations are not contaminated with cytoplasmic structures, and electron microscopy shows that the nuclear fine structure is well preserved. Chemical composition data indicates that the RNA/DNA, protein/DNA, acid-soluble protein/DNA, and phospholipid/DNA ratios are similar to those reported for nuclei obtained by other isolation methods.

Sea urchin embryo chromatin and nuclear ribonucleoproteins fractionated by anion exchange chromatography

Chromatin and ribonucleoproteins released from sea urchin embryo nuclei were characterized on the basis of sedimentation properties, buoyant densities and fractionation by anion exchange chromatography. DEAE- and ECTEOLA-cellulose chromatography was used to assay nuclear purity, insofar as ribosomes and polyribosomes could be readily distinguished from ribonucleoproteins released from nuclei. This chromatography was used to separate chromatin fragments on the basis of DNA size, to prepare chromatin fragments substantially enriched in nonhistone proteins, and to analyze nuclear ribonucleoproteins. Solubilized chromatin is fractionated into major and minor components by ECTEOLA-cellulose chromatography. The DNA of these chromatin fractions was analyzed with respect to buoyant density and hybridization with nuclear RNA.

Magnetic field dependence of the specific heat peak at 0.6–0.7°k in soft carbons

The magnetic field dependence of the specific heat peak was investigated for a polycrystalline graphite of nuclear purity neutron irradiated for 50 hr and for a soft carbon heattreated to HTT 1250°C. It was found that the relatively broader peak for irradiated graphite is located at 0.72°K and the sharper one for the soft carbon at 0.635°K. In both cases the dependence on the magnetic field is similar, —the specific heat increases with the magnetic field from 0 to 20 kG in the whole range of temperature investigated (0.4–4.5°K), the increase on the high temperature side of the peak being greater than on the low temperature side. The peak's maximum shifts slightly to higher temperature with increase of the field (by 10% at 20 kG). The increase in the total specific heat at the peak's maximum is at 20 kG around 80% for the irradiated graphite and only 50% for the 1250°C carbon. It is shown that the peak is due to a cooperative antiferromagnetic interaction between localized electronic spins distributed at random throughout the material. The reasons for various complications in the overall effect are discussed.

Labelling of proteins by isolated rat liver nuclei.

Rat liver nuclei, isolated in hypertonic sucrose solution and washed with Triton X-100, incorporate radioactive amino acids into hot trichloroacetic acid insoluble materials.Optical and biochemical evidence of nuclear purity is presented. The temperature-dependent incorporation continued for 20–30 min, and was proportional to the concentrations of both nuclear protein between 0.5–1.5 mg/ml, and radioactive amino acid. The radioactive product was degraded by pronase, and a number of inhibitors reduced incorporation, but only if present at [Formula: see text]. Proteins extracted from labelled nuclei and microsomes and examined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis at pH 7.2 exhibited different patterns of radioactivity. This provides further support for the concept of protein synthesis intrinsic to rat liver nuclei.A teleological argument for the function of nuclear protein synthesis is discussed.

Effects of androgen in vivo on some properties of isolated rat ventral prostate nuclei

The effects of (1) the presence or absence of androgen in vivo, and (2) treatment with Triton-X-100 in vitro upon some chemical and biochemical properties of rat ventral prostate nuclei, isolated in hypertonic sucrose, are described and compared with results reported for rat liver nuclei. Light- and electron microscopic evidence of nuclear purity, hormone-induced changes in the content of homogenate and nuclear protein, RNA and DNA, and the effect of detergent-washing on the composition of isolated nuclei are presented. Nuclei obtained from castrated rats contained less protein and RNA than those from normal animals, while androgen restored the content of these macromolecules. The association of several marker enzymes with prostate nuclei was examined: nuclei washed with detergent appear to retain cytochrome oxidase, an acid phosphatase and glucose-6-phosphatase activity; with the methods employed lactic dehydrogenase and uricase were not detected. Nuclear RNA, NAD and putative protein synthesis were not adversely affected by detergent. The effect of androgen on this apparent nuclear protein synthesis is being investigated.

Nuclear Cytidine 5'-Monophosphosialic Acid Synthetase

Abstract Evidence is presented documenting the nuclear location of the enzyme, cytidine 5'-monophosphosialic acid (CMP-sialic acid) synthetase. This enzyme catalyzes the reaction: [see PDF for equation] From previous studies it had been inferred that this enzyme was cytoplasmic. Studies are reported here that describe the following. (a) The purity of the nuclei that were used in these investigations. Nuclei were isolated from hypertonic sucrose solutions from the retina of the hog and from liver, kidney, spleen, and brain of the rat. Nuclear purity (i.e. absence of cytoplasmic contamination) was established on the basis of enzymatic, chemical, and morphological criteria. (b) The activity of CMP-sialic acid synthetase in these nuclei. The yields of CMP-sialic acid synthetase in the nuclei recovered from the different tissues varied from 18 to 53% of the activities present in the initial homogenates. When corrected for the yield of nuclei, based on DNA content, the yields of enzyme ranged from 54 to 90%. This was accompanied by increases in specific activities of 3- to 13-fold. CMP-sialic acid synthesized by nuclei from the retina of the hog was identified by chemical, enzymatic, chromatographic, and electrophoretic procedures. (c) Some of the properties of nuclear CMP-sialic acid synthetase are described. The following apparent Km values were observed for the enzyme from nuclei of rat liver: N-acetylneuraminic acid, 0.72 mm; N-glycolylneuraminic acid, 1.4 mm; CTP, 0.48 mm; Mg2+, 6.75 mm. The optimal pH for the reaction is between 8.3 and 8.6 in Tris buffer. The effect of other metals and nucleotide triphosphates on the activity of the enzyme was measured.

Eventualite du glissement visqueux aux joints des grains, au cours du fluage d'eprouvettes d'uranium de purete nucleaire courante

In view of the important role played by viscous displacement at grain boundaries during creep in many metals, we have sought to investigate this phenomenon in uranium of normal nuclear purity. In the first place we showed that at a temperature near 1 2 T t deformation by viscous displacement at grain boundaries seems to be of negligible importance in comparison with intergranular slip. For this reason we went on to establish the creep conditions which are known to be favourable, in other metals, for grain boundary displacement, i.e. a temperature above 1 2 T t , low load, low creep rate, and small grain size. We showed that the phenomenon for uranium in qualitatively identical with that observed in other metals, but that in a quantitative sense its role seems distinctly less important than in other metals. This is no doubt due to the poor purity of the uranium used in these experiments.

Effet des traitements thermiques et de l'irradiation par les neutrons sur les proprietes physiques et mecaniques de l'oxyde de beryllium fritte sous charge

The fabrication of blocks of beryllium oxide by sintering under load is briefly described. This method permits dense compacts of “nuclear purity” to be obtained. Annealing at 1300° C relieves internal stresses in blocks which have been made by sintering under load. Prolonged heat treatment at 1400° C results in an appreciable reduction of the density and deterioration of the mechanical properties of these compacts; this is associated with the precipitation of bubbles of gas at grain boundaries. The effects were examined of neutron irradiation in a reactor on the crystal parameters of beryllium oxide, the length of specimens, the thermal conductivity and the compressive strength of blocks made by sintering under load. These tests showed a sensitive influence of the oxide density and the irradiation temperature on the stability of the material under neutron irradiation. At a temperature below 100° C, irradiation produces a highly anisotropic dilatation of the crystal lattice. ( Δc c ) is about ten times greater than ( Δa a ). This distortion is the cause of the deterioration of the mechanical properties of the compacts. An irradiation of 2 × 10 20 neutrons/cm 2 leads to complete disintegration of the compacts (for an irradiation temperature below 100° C). Suitable post-irradiation heat treatment of beryllium oxide compacts made by sintering under load permit the original characteristics of the material to be restored approximately; however, liberation of gas in a compact can lead to a serious deterioration of mechanical properties. Agglomeration of gas at grain boundaries is detectable from 1000° C upwards in irradiated compacts.