PubMed · 14917543
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
1952-04-26. RADIOGRAPHY with radioactive isotopes.. https://doi.org/10.1001/jama.1952.02930170048011
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Site-selective DNA cleavage by diastereoisomers of Ni(II) x Gly-Gly-His-derived metallopeptides was investigated through high-resolution gel analyses and molecular dynamics simulations. Ni(II) x L-Arg-Gly-His and Ni(II) x D-Arg-Gly-His (and their respective Lys analogues) targeted A/T-rich regions; however, the L-isomers consistently modified a subset of available nucleotides within a given minor groove site, while the D-isomers differed in both their sites of preference and their ability to target individual nucleotides within some sites. In comparison, Ni(II) x L-Pro-Gly-His and Ni(II) x D-Pro-Gly-His were unable to exhibit a similar diastereoselectivity. Simulations of the above systems, along with Ni(II) x Gly-Gly-His, indicated that the stereochemistry of the amino-terminal amino acid produces either an isohelical metallopeptide that associates stably at individual DNA sites (L-Arg or L-Lys) or, with D-Arg and D-Lys, a noncomplementary metallopeptide structure that cannot fully employ its side chain nor amino-terminal amine as positional stabilizing moieties. In contrast, amino-terminal Pro-containing metallopeptides of either stereochemistry, lacking an extended side chain directed toward the minor groove, did not exhibit a similar diastereoselectivity. While the identity and stereochemistry of amino acids located in the amino-terminal peptide position influenced DNA cleavage, metallopeptide diastereoisomers containing L- and D-Arg (or Lys) within the second peptide position did not exhibit diastereoselective DNA cleavage patterns; simulations indicated that a positively charged amino acid in this location alters the interaction of the metallopeptide equatorial plane and the minor groove leading to an interaction similar to Ni(II) x Gly-Gly-His.
Approximately 70% of acute coronary artery disease is caused by unstable (vulnerable) plaques with an inflammation of the overlying cap and high lipid content. A rupturing of the inflamed cap of the plaque results in propagation of the thrombus into the lumen, blockage of the artery and acute ischaemic syndrome or sudden death. Morphological imaging such as angiography or intravascular ultrasound cannot determine inflammation status of the plaque. A radiotracer such as 18F-FDG is accumulated in vulnerable plaques due to higher metabolic activity of the inflamed cap and could be used to detect a vulnerable plaque. However, positron emission tomography (PET) cannot detect the FDG-labelled plaques because of respiratory and heart motions, small size and low activity of the plaques. Plaques can be detected using a miniature particle (positron) detector inserted into the artery. In this work, a new detector concept is investigated for intravascular imaging of the plaques. The detector consists of a storage phosphor tip bound to the end of an intravascular catheter. It can be inserted into an artery, absorb the 18F-FDG positrons from the plaques, withdrawn from the artery and read out. Length and diameter of the storage phosphor tip can be matched to the length and the diameter of the artery. Monte Carlo simulations and experimental evaluations of coronary plaque imaging with the proposed detector were performed. It was shown that the sensitivity of the storage phosphor detector to the positrons of 18F-FDG is sufficient to detect coronary plaques with 1 mm and 2 mm sizes and 590 Bq and 1180 Bq activities in the arteries with 2 mm and 3 mm diameters, respectively. An experimental study was performed using plastic tubes with 2 mm diameter filled with an FDG solution, which simulates blood. FDG spots simulating plaques were placed over the surface of the tube. A phosphor tip was inserted into the tube and imaged the plaques. Exposure time was 1 min in all simulations and experiments. Experiments showed that detecting the coronary plaques using the proposed technique is possible. The proposed technique has the potential for fast and accurate detection of vulnerable coronary and other intravascular plaques.
Recent studies indicate that a focal, limited, inflammatory response can be safely elicited after direct bronchial instillation of small doses of endotoxin into a single lung segment. Because the radiotracer [18F]fluorodeoxyglucose ([18F]FDG) is taken up at accelerated rates within inflamed tissues, we hypothesized that we could detect and quantify this regional inflammatory response with positron emission tomography (PET). We imaged 18 normal volunteers in a dose-escalation study with 3 endotoxin dosing groups (n = 6 in each group): 1 ng/kg, 2 ng/kg, and 4 ng/kg. Endotoxin was instilled by bronchoscopy into a segment of the right middle lobe, with imaging performed approximately 24 h later, followed by bronchoalveolar lavage (BAL). A "subtraction imaging analysis" was performed in the highest dose cohort to identify the area of inflammation, using the preendotoxin scan as a baseline. BAL neutrophil counts were significantly higher in the highest dose group compared with the other two groups (1,413 +/- 625 vs. 511 +/- 396 and 395 +/- 400 cells/mm3; P < 0.05). Autoradiography performed on cells harvested by BAL showed specific [3H]deoxyglucose ([3H]DG) uptake limited to neutrophils. In vitro [3H]DG uptake in BAL neutrophils in the 4 ng/kg dose group (but not in the 2 ng/kg group) was statistically greater than in peripheral blood neutrophils obtained before endotoxin instillation. The rate of [18F]FDG uptake was greatest in the 4 ng/kg group, with a consistent, statistically significant increase in the rate of uptake after endotoxin instillation compared with baseline. We conclude that the inflammatory response to low-dose endotoxin in a single lung segment can be visualized and quantified by imaging with FDG-PET.