National Nuclear Energy Commission

About: National Nuclear Energy Commission is a government organization based out in Rio de Janeiro, Brazil. It is known for research contribution in the topics: Dosimetry & Laser. The organization has 3816 authors who have published 4694 publications receiving 59951 citations.

Nanosecond Nd:YAG laser on dental enamel: compositional analysis by X-ray fluorescence

Abstract: Non-invasive methods such as X-ray Fluorescence has been applied to study of the distinct pathologies and contamination levels analysis in various biological tissues among them nails, hair, and tooth. On the other hand, several works have demonstrated that the laser could be induced chemical and morphological alterations on the enamel surface occupying an important role as co-adjuvant in the caries disease prevention. Here, we have combined X-ray fluorescence using Fundamental Parameters method aiming to evaluate the variation in the chemical contend. The Ca and P concentrations as well as the Ca/P ratio were estimated in sound human and bovine enamel surface by X-ray fluorescence (XRF). We also evaluated the effect of the lactic and the acetic acids on the sound and irradiated bovine enamel surface by Scanning Electron Microscopy (SEM) verifying the acid attack changes in the sound and irradiated bovine enamel. The laser parameters applied produced lower ablation depths, but sufficient to induce compositional changes. Our results have indicating an alteration statically significative to Ca/P ratio and also indicated an increase in the Ca/P ratio for the irradiated groups in comparison to sound groups. We also verified that the acid attack is more pronounced to sound bovine enamel surface in relation to irradiated to the bovine enamel surface indicating that the nanosecond laser can be used to reduce the demineralization process.

High-level synthesis of human prolactin in Chinese-Hamster ovary cells.

Abstract: Two eukaryotic human prolactin (hPRL) expression vectors, based on a selectable dihydrofolate reductase (dhfr) marker, were used to transfect dhfr(-) Chinese- hamster ovary (CHO) cells. One vector, p658-hPRL, contains the hepatitis-B virus-X cDNA coding for a viral transactivator and sequences mediating dhfr mRNA degradation. The other, pEDdc-hPRL, carries the encephalomyocarditis virus leader sequence coupled to hPRL cDNA to provide high-level protein expression, possibly via a mechanism of internal translation initiation in dicistronic mRNA. Without methotrexate (MTX) amplification, p658-hPRL-transfected stable cell lines, secreting up to approximately 10 microg of hPRL/10(6) cells per day, could be rapidly obtained; production by pEDdc-hPRL-transfected cells was about 10-fold lower. However, a three-step MTX amplification of the latter led to clones secreting up to approximately 30 microg of hPRL/10(6) cells per day. A pilot production using a hollow-fibre bioreactor indicated that highly concentrated hormone levels in the medium could be obtained, with a production of up to 150 microg of hPRL/ml per day. SDS/PAGE analysis indicated that recombinant hPRL contained approximately 10% glycosylated PRL. Chromatographically purified non-glycosylated and glycosylated recombinant hPRL had bioactivities of 35 and 16 i.u./mg, respectively (Nb2 cell bioassay). This appears to be the first report describing production and purification of recombinant hPRL from CHO cells, secreted at levels higher than reported thus far in eukaryotic systems.