Evaluation of Low-Loss Polymer Switches for Multinuclear MRI/S.

Implementation of multinuclear MRI/S as a diagnostic tool in clinical settings faces many challenges. One of those challenges is the development of highly sensitive multinuclear RF coils. Current multi-tuning techniques incorporate lossy components that impact the highest achievable SNR for at least one of the coil frequencies. As a result, optimization of multinuclear coil designs continues to be a priority for RF hardware engineers. To address this challenge, a new frequency switching technology that incorporates stimuli-responsive polymer materials was explored. Q measurements were used as a comparison metric between single-tuned, a standard switching network, and the proposed switching technology. The Q losses measured in the new switching method remained below 38% when compared to single-tuned coils. These results are consistent with low loss values reported using traditional switching networks. Furthermore, preliminary testing indicates that there is potential for improvement. These results establish the new technology as a promising alternative to traditional switching techniques.Clinical Relevance- A low loss multi-tuning technique for MRI radiofrequency coils has the potential of improving the study and diagnosis of disease.

The complete genome sequence of the rumen methanogen Methanosarcina barkeri CM1.

Methanosarcina species are the most metabolically versatile of the methanogenic Archaea and can obtain energy for growth by producing methane via the hydrogenotrophic, acetoclastic or methylotrophic pathways. Methanosarcina barkeri CM1 was isolated from the rumen of a New Zealand Friesian cow grazing a ryegrass/clover pasture, and its genome has been sequenced to provide information on the phylogenetic diversity of rumen methanogens with a view to developing technologies for methane mitigation. The 4.5 Mb chromosome has an average G + C content of 39 %, and encodes 3523 protein-coding genes, but has no plasmid or prophage sequences. The gene content is very similar to that of M. barkeri Fusaro which was isolated from freshwater sediment. CM1 has a full complement of genes for all three methanogenesis pathways, but its genome shows many differences from those of other sequenced rumen methanogens. Consequently strategies to mitigate ruminant methane need to include information on the different methanogens that occur in the rumen.

Considerations in the use of fluorescence in situ hybridization (FISH) and confocal laser scanning microscopy to characterize rumen methanogens and define their spatial distributions.

In this study, methanogen-specific coenzyme F420 autofluorescence and confocal laser scanning microscopy were used to identify rumen methanogens and define their spatial distribution in free-living, biofilm-, and protozoa-associated microenvironments. Fluorescence in situ hybridization (FISH) with temperature-controlled hybridization was used in an attempt to describe methanogen diversity. A heat pretreatment (65 °C, 1 h) was found to be a noninvasive method to increase probe access to methanogen RNA targets. Despite efforts to optimize FISH, 16S rRNA methanogen-specific probes, including Arch915, bound to some cells that lacked F420, possibly identifying uncharacterized Methanomassiliicoccales or reflecting nonspecific binding to other members of the rumen bacterial community. A probe targeting RNA from the methanogenesis-specific methyl coenzyme M reductase (mcr) gene was shown to detect cultured Methanosarcina cells with signal intensities comparable to those of 16S rRNA probes. However, the probe failed to hybridize with the majority of F420-emitting rumen methanogens, possibly because of differences in cell wall permeability among methanogen species. Methanogens were shown to integrate into microbial biofilms and to exist as ecto- and endosymbionts with rumen protozoa. Characterizing rumen methanogens and defining their spatial distribution may provide insight into mitigation strategies for ruminal methanogenesis.

Single nucleotide repeat analysis of B. anthracis isolates in Canada through comparison of pyrosequencing and Sanger sequencing.

Several technology platforms have been developed to resolve the phylogenetic placement of B. anthracis. However, these methods lack the resolution to identify differences between closely related strains within an outbreak due to the highly clonal nature of B. anthracis. Single Nucleotide Repeats (SNRs) are a type of rapidly evolving genetic marker that can be used to track epidemiological distribution in the event of an outbreak. Four SNR targets were used to detect and type 35 B. anthracis isolates in our collection; 18 from across Canada obtained between 1972 and 2005 and 17 from the 2006 Anthrax outbreak in north eastern Saskatchewan. A control sequence was developed for pyrosequencing which yielded consistent and accurate reads of SNRs. However, when DNA from the isolates was tested using pyrosequencing the results were inconsistent and did not reflect the number of SNRs obtained by Sanger sequencing. The SNR numbers derived from the Sanger sequencing show two of the four SNR loci could provide information on subtype, whereas the other two were not discriminatory. There is variation in SNRs between strains isolated from different outbreaks, the subset of 2006 outbreak strains showed very little difference in SNR number, and thus suggests low diversity among the strains sampled from the same outbreak.

Simultaneous detection of eight single nucleotide polymorphisms in the ovine prion protein gene.

Amino acid polymorphisms in the prion protein gene (PrP) affect the susceptibility of sheep to scrapie, a transmissible spongiform encephalopathy (TSE). In particular, amino acid substitutions at codons 136, 154 and 171 of the ovine PrP gene are associated with different degrees of susceptibility to the classical form of scrapie, caused by 'typical' scrapie strains. Existing genotyping tests for scrapie susceptibility normally interrogate only the single nucleotide polymorphisms (SNPs) most relevant to 'typical' strains. Recently, however, a number of novel variants of the scrapie agent have been discovered. The ability of these new, 'atypical' scrapie variants to infect sheep that are resistant to 'typical' variants has raised concerns about the reduction in genetic variability that may result from intense selection for resistance to classical scrapie. Furthermore, a growing interest in a potential role for specific PrP genotypes in modulating performance traits is also driving a move toward more extensive characterization of haplotypes at the PrP locus. Here, we describe a single-tube method for the interrogation of eight SNPs within seven codons (112, 136, 141, 154, 171, 231 and 241) of the ovine PrP gene. This method is as accurate as sequencing, yet more affordable, and can easily be automated for high-throughput sample screening. Moreover, it can be modified to accommodate genetic variations that are found in local and heritage breeds.

Characterization of the bovine ampkgamma1 gene.

AMP-activated protein kinase (AMPK) represents the mammalian form of the core component of a kinase cascade that is conserved between fungi, plants, and animals. AMPK plays a major role in protecting mammalian cells from metabolic stress by switching off biosynthetic pathways that require ATP and switching on ATP-regenerating pathways. In this report, we describe the isolation and characterization of the gene for the noncatalytic bovine gamma1 subunit of AMPK. The bovine ampkgamma1 (PRKAG1) gene spans in excess of 14 kb and is located at BTA 5q21-q22. It consists of 12 exons ranging in size from 38 b to 166 b, interspersed with 11 introns that range between 97 b and 6753 b in length. The coding region of the bovine gene shares 93% and 90% nucleotide sequence similarity with its human and rat counterparts, and the bovine AMPKgamma1 protein is 98% and 95% identical to its human and rat homologs, respectively, in amino acid sequence. SNP discovery using a cattle DNA panel revealed a number of polymorphisms that may be useful for the evaluation of ampkgamma1 as a candidate gene for energy metabolism-related production traits.