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At least 595 records · Page 33Linked to original sources
PubMed2005

Interventional magnetic resonance angiography with no strings attached: wireless active catheter visualization.

Active instrument visualization strategies for interventional MR angiography (MRA) require vascular instruments to be equipped with some type of radiofrequency (RF) coil or dipole RF antenna for MR signal detection. Such visualization strategies traditionally necessitate a connection to the scanner with either coaxial cable or laser fibers. In order to eliminate any wire connection, RF resonators that inductively couple their signal to MR surface coils were implemented into catheters to enable wireless active instrument visualization. Instrument background to contrast-to-noise ratio was systematically investigated as a function of the excitation flip angle. Signal coupling between the catheter RF coil and surface RF coils was evaluated qualitatively and quantitatively as a function of the catheter position and orientation with regard to the static magnetic field B0 and to the surface coils. In vivo evaluation of the instruments was performed in interventional MRA procedures on five pigs under MR guidance. Cartesian and projection reconstruction TrueFISP imaging enabled simultaneous visualization of the instruments and vascular morphology in real time. The implementation of RF resonators enabled robust visualization of the catheter curvature to the very tip. Additionally, the active visualization strategy does not require any wire connection to the scanner and thus does not hamper the interventionalist during the course of an intervention.

Animals↗
PubMedDate not supplied

5'-secondary structure formation, in contrast to a short string of non-preferred codons, inhibits the translation of the pyruvate kinase mRNA in yeast.

The effects of poor codon bias and secondary structure formation upon the translation of the pyruvate kinase (PYK1) mRNA have been investigated in Saccharomyces cerevisiae. Following insertion mutagenesis at the 5'-end of the PYK1 coding region, the gene was transformed into yeast, and translation assessed directly in vivo by determining the distribution of the modified PYK1 mRNAs across polysomes fractionated by sucrose density gradient centrifugation. The chromosomally-encoded (wild-type) PYK1 mRNA, and the actin, ribosomal protein L3 and glyceraldehyde-3-phosphate dehydrogenase mRNAs were used to control for minor differences between polysome preparations. An insertion containing 13 non-preferred codons at the 5'-end of the coding region was found to have no significant effect upon PYK1 mRNA translation. In contrast, translation was inhibited by an insertion which increased the formation of secondary structures at the 5'-end of the mRNA (overall delta G = -36.6 kcal/mol). Control insertions were also analysed to exclude the possibility that alterations to the amino acid sequence of pyruvate kinase affect the translation of its mRNA. These insertions, which introduced preferred codons or restored wild-type levels of secondary structure formation, did not significantly influence PYK1 mRNA translation.

Amino Acid Sequence↗
PubMed1991

Meiotic mapping of murine chromosome 17: the string of loci around l(17)-2Pas.

We describe a genetic analysis of l(17)-2Pas, an embryonic lethal mutation on murine chromosome 17. Males transmitted the l(17)-2 allele to only 38% of their offspring, whereas females transmitted this allele at 50%. Two-point crosses revealed tight linkage between l(17)-2 and brachyury (T), and deletion mapping placed l(17)-2 outside of the hairpin-tail deletion (Thp). To map this mutation more precisely, we intercrossed hybrid mice that carry distinct alleles at many classical and DNA loci on chromosome 17 and obtained 172 animals recombinant in the T to H-2 region. Strong positive interference was observed over the 14 cM interval from T to H-2K. Thus, a single recombinant can be informative; one such recombinant places l(17)-2 distal of the molecular marker D17Leh66D. Robust genetic maps can be constructed with multilocus crosses that share anchor loci. DNA markers can be interpolated onto these maps retrospectively.

Animals↗
PubMed1994

Molecular cloning of cDNAs encoding variants of meiotin-1. A meiotic protein associated with strings of nucleosomes.

Meiotin-1 is a chromatin-associated protein, originally isolated from microsporocytes of Lilium longiflorum, which is found predominantly in cells undergoing meiotic prophase. Chromatin fractionation studies demonstrated that meiotin-1 has an unusual stoichiometry relative to that of histone H1 and the core histones in chromatin fibers. The protein is found less frequently than is histone H1, and appears to be distributed once every 5 to 13 nucleosomes. This distribution may approximate the number of nucleosomes per turn of the chromatin solenoid. A truncated cDNA was identified by immunoscreening of an expression library, and the cDNA was used as a hybridization probe to select a full length cDNA. Variations between the sequence of the predicted polypeptide and sequenced peptides, and variations between the amino acid composition of the protein and the deduced protein indicate that the cDNAs encode minor variants of mature meiotin-1. RNA gel blot hybridization studies reveal that the meiotin-1 mRNA is restricted to anthers in which meiosis is occurring. Computer analysis of the polypeptide deduced from the cDNA indicates that the protein begins with a region highly homologous to the conserved central globular domain of histone H1 molecules. DNA gel blotting experiments demonstrate that homologous sequences exist in the genomes of a fern, a fungus, and both mono- and dicotyledonous plants. Meiotin-1 has been evolutionarily conserved and I propose that it arose from histone H1 to fulfill a role in organizing meiotic chromatin.

Amino Acid Sequence↗