Primary standardization and determination of gamma ray emission intensities of Ho-166.

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN-CNEN/SP, in São Paulo, for the primary standardization of 166Ho is described. The activity of 166Ho was determined by the efficiency extrapolation technique applied to a 4πß(PC)-γ coincidence system using a gas flow proportional counter in 4π geometry coupled to a 76 × 76 mm NaI(Tl) crystal. The results for the γ-rays intensities at 80.57 and 1379.45 keV were 0.0651(11) and 0.00904(11), respectively.

Consistency test of coincidence-summing calculation methods for extended sources.

An internal consistency test of the calculation of coincidence-summing correction factors FC for volume sources is presented. The test is based on exact equations relating the values of FC calculated for three ideal measurement configurations. The test is applied to a number of 33 sets of FC values sent by 21 teams. Most sets passed the test, but not the results obtained using the quasi-point source approximation; in the latter case the test qualitatively indicated the magnitude of the bias of FC.

Determination of k0 and Q0 for 74Se, 113In, 186W and 191Ir targets applying covariance analysis.

In the present work, the determinations of k0 and Q0 for 74Se, 113In, 186W and 191Ir targets were performed. The irradiations were conducted near the core of the IEA-R1 4.5 MW swimming-pool nuclear research reactor of the Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN/SP - Nuclear and Energy Research Institute), in São Paulo, Brazil. The irradiation position was chosen where the neutron spectrum shape parameter α is very close to zero. For this reason, the correction to be applied for the determination of Q0 is very close to one, thus improving the accuracy of the results. For each experiment, two irradiations were carried out in sequence: the first one with bare samples and the second with a cadmium cover around the samples. All partial uncertainties were considered, applying the covariance matrix methodology. The final results were compared with the literature.

SUMCOR: Cascade summing correction for volumetric sources applying MCNP6.

The main features of code SUMCOR developed for cascade summing correction for volumetric sources are described. MCNP6 is used to track histories starting from individual points inside the volumetric source, for each set of cascade transitions from the radionuclide. Total and FEP efficiencies are calculated for all gamma-rays and X-rays involved in the cascade. Cascade summing correction is based on the matrix formalism developed by Semkow et al. (1990). Results are presented applying the experimental data sent to the participants of two intercomparisons organized by the ICRM-GSWG and coordinated by Dr. Marie-Cristine Lépy from the Laboratoire National Henri Becquerel (LNE-LNHB), CEA, in 2008 and 2010, respectively and compared to the other participants in the intercomparisons.

Uranium deposition in bones of Wistar rats associated with skeleton development.

Sixty female Wistar rats were submitted to a daily intake of ration doped with uranium from weaning to adulthood. Uranium in bone was quantified by the SSNTD (solid state nuclear track detection) technique, and bone mineral density (BMD) analysis performed. Uranium concentration as a function of age exhibited a sharp rise during the first week of the experiment and a drastic drop of 70% in the following weeks. Data interpretation indicates that uranium mimics calcium. Results from BMD suggest that radiation emitted by the incorporated Uranium could induce death of bone cells.

Measurements of k0 and Q0 values for 64Zn(n,γ)65Zn and 68Zn(n,γ)69mZn reactions with covariance analysis.

The values of k(0) and Q(0) for (64)Zn(n,γ)(65)Zn and (68)Zn(n,γ)(69m)Zn reactions were determined experimentally. The irradiations were performed near the core of the IEA-R1 3.5MW nuclear research reactor of the Nuclear and Energy Research Institute - IPEN-CNEN/SP, in São Paulo, Brazil. The results for the neutron field parameters f and α were 49.7(19) and -1.1(31)×10(-3), respectively. The resulting values of k(0) and Q(0) for (64)Zn(n,γ)(65)Zn reaction were 5.63(8)×10(-3) and 1.69(6), respectively, and the corresponding values for (68)Zn(n,γ)(69m)Zn reaction were 4.00(6)×10(-4) and 2.34(4), respectively. These results were compared with the literature.

Long-term accumulation of uranium in bones of Wistar rats as a function of intake dosages.

Groups of Wistar rats were fed with ration doped with uranyl nitrate at concentration A ranging from 0.5 to 100 ppm, starting after the weaning period and lasting until the postpuberty period when the animals were sacrificed. Uranium in the ashes of bones was determined by neutron activation analysis. It was found that the uranium concentration in the bones, as a function of A, exhibits a change in its slope at approximately 20 ppm-a probable consequence of the malfunctioning of kidneys. The uranium transfer coefficient was obtained and an analytical expression was fitted into the data, thus allowing extrapolation down to low doses. Internal and localized doses were calculated. Absorbed doses exceeded the critical dose, even for the lowest uranium dosage.

Morphological study of Osteoplate 2000-extension implants after bending.

Unfavorable anatomical conditions of implant sites often require the insertion of implants in a direction that may interfere with the positioning of suprastructural elements in a functionally and esthetically satisfying manner. In some implant systems, bending of the implant neck is one of the possible methods for optimizing the insertion angle for the superimposed prosthesis. The aim of this study was to investigate whether bending procedures of the implant neck cause changes in the surface properties at the implant neck area. After bending of the implant neck up to 30 degrees, scanning electron microscopy revealed changes in the surface texture of the titanium. Superficial rips approximately 5 microns wide and 100 microns long had formed. These findings were confirmed by metallographic examinations. Values of Vickers hardness testing in the implant neck area after bending of 30 degrees showed significant differences between the compression or stretched zone and the neutral zone of the bending area. Bending of the implant neck between 0 and 20 degrees may influence the surface morphology, promoting superficial rips. Plaque accumulation and mechanically induced mucosal irritations due to changes of surface morphology and properties by bending should be further analyzed.

Dual adaptation and adaptive generalization of the human vestibulo-ocular reflex.

In two experiments, we examined the possibility that the human vestibulo-ocular reflex (VOR) is subject to dual adaptation (the ability to adapt to a sensory rearrangement more rapidly and/or more completely after repeated experience with it) and adaptive generalization (the ability to adapt more readily to a novel sensory rearrangement as a result of prior dual adaptation training). In Experiment 1, the subjects actively turned the head during alternating exposure to a visual-vestibular rearrangement (target/head gain = 0.5) and the normal situation (target/head gain = 0.0). These conditions produced both adaptation and dual adaptation of the VOR but no evidence of adaptive generalization when tested with a target/head gain of 1.0. Experiment 2, in which exposure to the 0.5 gain entailed externally controlled (i.e., passive) whole body rotation, resulted in VOR adaptation but no dual adaptation. As in Experiment 1, no evidence of adaptive generalization was found.

Acute fulminant symmetrical vasculitic polyneuropathy: need for early biopsy.

We report 2 patients with acute symmetrical axonal motor and sensory polyneuropathy associated with vasculitis. The clinical presentation in each case was not that of a mononeuritis multiplex. Serial electrophysiological studies in 1 of the patients documented the development of confluent axonal degeneration involving several motor and sensory territories over the same period of time. In both patients the diagnosis of necrotizing vasculitis was established by peripheral nerve biopsy and recovery followed treatment with prednisone and cyclophosphamide. Biopsy of an involved nerve should be routinely sought in unexplained acute axonal polyneuropathies.

Alterations in the U3 region of the long terminal repeat of an infectious thymotropic type B retrovirus.

We isolated and characterized a type B thymotropic retrovirus (DMBA-LV) which is highly related to mouse mammary tumor virus (MMTV) isolates and which induces T-cell thymomas with a high incidence and a very short latent period. Regions of nonhomology between the DMBA-LV genome and the MMTV genome were identified by heteroduplex mapping and nucleotide sequence studies. In the electron microscope heteroduplex mapping studies the EcoRI-generated 5' and 3' fragments of the DMBA-LV genome were compared with the corresponding fragments of the MMTV (C3H and GR) genome isolated from mammary tumors. The results indicated that DMBA-LV contained a region of nonhomologous nucleotide sequences in the 3' half of the U3 region of the long terminal repeat (LTR). Nucleotide sequence studies confirmed these results and showed that in this region 440 nucleotides of the MMTV (C3H) sequences were deleted and substituted with a segment of 122 nucleotides. This substituted segment in the form of a tandem repeat structure contained nucleotide sequences derived exclusively from sequences which flanked the substitution loop. The distal glucocorticoid regulatory element was unaltered, and two additional copies of the distal glucocorticoid regulatory element-binding site were present in the substituted region. The restriction endonuclease map of the reconstructed molecular clone of DMBA-LV was identical to that corresponding to unintegrated linear DMBA-LV DNA present in DMBA-LV-induced tumor cell lines. Since the nucleotide sequences of the LTRs present in four different DMBA-LV proviral copies isolated from a single thymoma were identical, we concluded that they were derived from the same parental virus and that this type B retrovirus containing an alteration in the U3 region of its LTR could induce thymic lymphomas. Thus, DMBA-LV represents the first example of a productively replicating type B retrovirus that contains an LTR modified in the U3 region and that has target cell and disease specificity for T cells.

Purification, characterisation and reconstitution of glutaconyl-CoA decarboxylase, a biotin-dependent sodium pump from anaerobic bacteria.

Glutaconyl-CoA decarboxylase from Acidaminococcus fermentans is a biotin enzyme, which is integrated into membranes. It is activated by Triton X-100 and inhibited by avidin. The results obtained by a combination of both agents indicate that biotin and the substrate-binding site are located on the same side of the membrane. The decarboxylase was solubilized with Triton X-100 and purified by affinity chromatography on monomeric avidin-Sepharose. The enzyme is composed of three types of polypeptides: the group of alpha chains (Mr 120000-140000) containing the biotin, the beta chain (60000) and an apparently hydrophobic gamma chain (35000). Sodium ions specifically protected the latter chain from tryptic digestion. It was supposed, therefore, that this chain might function as the Na+ channel. The beta and gamma chains but not the alpha chain could be labelled by N-ethyl-[14C]maleimide. Similar decarboxylases but with much smaller biotin peptides (Mr 15000-20000) were isolated from Peptococcus aerogenes and Clostridium symbiosum. The decarboxylases from all three organisms could be reconstituted to active sodium pumps by incubation with phospholipid vesicles and octylglucoside followed by dilution. The Na+ uptake catalysed by the enzyme from A. fermentans was completely inhibited by monensin and activated twofold by valinomycin/K+ indicating an electrogenic Na+ pump. The coupling between Na+ transport and decarboxylation was not tight. During the reaction the ratio decreased from initially 1 to 0.2. The three organisms mentioned above and Clostridium tetanomorphum without glutaconyl-CoA decarboxylase are able to ferment glutamate and require 10 mM Na+ for rapid growth. There is no correlation between the concentration of monensin necessary to inhibit growth and the presence of decarboxylase in these organisms.

A biotin-dependent sodium pump: glutaconyl-CoA decarboxylase from Acidaminococcus fermentans.

The decarboxylation of glutaconyl-CoA to crotonyl-CoA in the anaerobic bacterium Acidaminococcus fermentans is catalysed by a membrane-bound, biotin-dependent enzyme which requires Na+ for activity. Inverted vesicles from A. fermentans accumulated Na+ only if glutaconyl-CoA was decarboxylated. The Na+ uptake was inhibited by avidin but not by the avidin biotin complex. Detergents and ionophores such as monensin also prevented the Na+ transport. The results indicate that the enzyme is able to convert the free energy of decarboxylation (delta Go' approximately equal to -30 kJ/mol) into a Na+ gradient.

Glutaconate CoA-transferase from Acidaminococcus fermentans.

1. Glutaconate CoA-transferase catalyses the transfer of CoAS- from acetyl-CoA preferentially to (E)-glutaconate, but glutarate, (R)-2-hydroxyglutarate, acrylate and propionate are also good acceptors. No reaction was observed with (Z)-glutaconate and C4-dicarboxylic acids. 2. The product of the reaction of acetyl-CoA with (E)-glutaconate is the 1-isomer of glutaconyl-CoA, i.e. the thiol ester is conjugated with the double bond. Other results indicate, however, that with (R)-2-hydroxyglutarate as substrate both possible isomers are generated. 3. Glutaconate CoA-transferase was purified from cell-free extracts of Acidaminococcus fermentans to apparent homogeneity and crystallized. The relative molecular mass of the enzyme is approximately 275000. It consists of two different polypeptide chains (M, 32000 and 34000). On the catalytic pathway a thiolester is formed between CoASH and a carboxylate of the smaller polypeptide chain. 4. The structural and functional relationships between glutaconate CoA-transferase and other CoA-transferases are discussed. 5. Glutaconate CoA-transferase is also present in other bacteria fermenting glutamate via hydroxyglutarate. Experiments with an antiserum against the enzyme indicate that the transferase is necessary for the decarboxylation of glutaconate but not for the dehydration of (R)-2-hydroxyglutarate.

Improved fluoride incorporation and new in vitro fluorine elemental determination.

The CPA technique was shown to be very useful in nondestructively determining the concentration profiles of fluoride in extracted teeth. By means of this technique, it was found that in vitro treatment with K2ZrF6 incorporated substantially more fluoride into the enamel than NaF or APF by factors of 5 and more than 50, respectively. The concentration profile was determined from the tooth surface to a depth of 2.1 mum, with a resolution of 0.07 mum at the surface and 0.15 mum at a 2.1-mum depth. Proton-stimulated X-ray fluorescence was used to detect the elements heavier than Mg, for example, P, Cl, K, Ca, Ti, Fe, Ni, Ca, Zn, Zr, and Pb.