Research Triangle Park

About: Research Triangle Park is a nonprofit organization based out in Durham, North Carolina, United States. It is known for research contribution in the topics: Population & Receptor. The organization has 24961 authors who have published 35800 publications receiving 1684504 citations. The organization is also known as: RTP.

Interleaved Boost Converter With Intrinsic Voltage-Doubler Characteristic for Universal-Line PFC Front End

Abstract: A novel, two-inductor, interleaved power-factor-corrected (PFC) boost converter, that exhibits voltage-doubler characteristic when it operates with a duty cycle greater than 0.5 is introduced. The voltage-doubler characteristic of the proposed converter makes it quite suitable for universal-line (90-264 VRMS) PFC applications. Because the proposed PFC boost rectifier operates as a voltage doubler at low line, its low-line range efficiency is greatly improved compared to that of its conventional counterpart. The performance of the proposed PFC rectifier was evaluated on an experimental 1.3-kW universal-line PFC prototype.

Chromosome aberrations, micronuclei, aneuploidy, sister chromatid exchanges, and cancer risk assessment.

Abstract: This paper describes the four cytogenetic endpoints most frequently used in hazard identification assays as the first step in the risk assessment process. These are structural chromosome aberrations, micronuclei, aneuploidy, and sister chromatid exchanges. The biological mechanisms involved in the formation of the alterations observed in each assay are briefly discussed. Variations in and recent improvements to each assay are described, with an emphasis on the use of molecular techniques to improve the sensitivity of the assay, and to allow for detection of specific alterations that are, or could be, associated with cancer induction. This, in turn, will make the data obtained in the cytogenetic assays more useful in cancer and genetic risk assessment. Thus, the aim of this paper is to encourage cytogeneticists to design their experiments in such a way that the data obtained will be of maximum possible benefit for characterizing and quantifying adverse human health effects, particularly cancer.

DMT1: A mammalian transporter for multiple metals

Abstract: DMT1 has four names, transports as many as eight metals, may have four or more isoforms and carries out its transport for multiple purposes. This review is a start at sorting out these multiplicities. A G185R mutation results in diminished gastrointestinal iron uptake and decreased endosomal iron exit in microcytic mice and Belgrade rats. Comparison of mutant to normal rodents is one analytical tool. Ectopic expression is another. Antibodies that distinguish the isoforms are also useful. Two mRNA isoforms differ in the 3' UTR: +IRE DMT1 has an IRE (Iron Responsive Element) but -IRE DMT1 lacks this feature. The +/-IRE proteins differ in the distal 18 or 25 amino acid residues after shared identity for the proximal 543 residues. A major function is serving as the apical iron transporter in the lumen of the gut. The +IRE isoform appears to have that role. Another role is endosomal exit of iron. Some evidence indicts the -IRE isoform for this function. In our ectopic expression assay for metal uptake, four metals--Fe2+, Mn2+, Ni2+ and Co2+--respond to the normal DMT1 cDNA but not the G185R mutant. Two metals did not--Cd2+ and Zn2+--and two--Cu2+ and Pb2+--remain to be tested. In competition experiments in the same assay, Cd2+, Cu2+ and Pb2+ inhibit Mn2+ uptake but Zn2+ did not. In rodent mutants, Fe and Mn appear more dependent on DMT1 than Cu and Zn. Experiments based on ectopic expression, specific antibodies that inhibit metal uptake and labeling data indicate that Fe3+ uptake depends on a different pathway in multiple cells. Two isoforms localize differently in a number of cell types. Unexpectedly, the -IRE isoform is in the nuclei of cells with neuronal properties. While the function of -IRE DMT1 in the nucleus is speculative, one may safely infer that this localization identifies new role(s) for this multifunctional transporter. Management of toxic challenges is another function related to metal homeostasis. Airways represent a gateway tissue for metal entry. Preliminary evidence using specific PCR primers and antibodies specific to the two isoforms indicates that -IRE mRNA and protein increase in response to exposure to metal in lungs and in a cell culture model; the +IRE form is unresponsive. Thus the -IRE form could be part of a detoxification system in which +IRE DMT1 does not participate. How does iron status affect other metals' toxicity? In the case of Mn, iron deficiency may enhance cellular responses.