PubMed · 6600116
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
J E Burns. 1983. Equivalent half-value layers.. https://pubmed.ncbi.nlm.nih.gov/6600116/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The use of Green's function has played a fundamental role in transport calculations for high-charge high-energy (HZE) ions. Two recent developments have greatly advanced the practical aspects of implementation of these methods. The first was the formulation of a closed-form solution as a multiple fragmentation perturbation series. The second was the effective summation of the closed-form solution through nonperturbative techniques. The nonperturbative methods have been recently extended to an inhomogeneous, two-layer transport media to simulate the lead scattering foil present in the Lawrence Berkeley Laboratories (LBL) biomedical beam line used for cancer therapy. Such inhomogeneous codes are necessary for astronaut shielding in space. The transport codes utilize the Langley Research Center atomic and nuclear database. Transport code and database evaluation are performed by comparison with experiments performed at the LBL Bevalac facility using 670 A MeV 20Ne and 600 A MeV 56Fe ion beams. The comparison with a time-of-flight and delta E detector measurement for the 20Ne beam and the plastic nuclear track detectors for 56Fe show agreement up to 35%-40% in water and aluminium targets, respectively.
Amylin is co-secreted with insulin from the pancreas of patients with non-insulin dependent diabetes mellitus, and its deposition may contribute to the central nervous system (CNS) manifestations of this disease. Amylin, but not its mRNA, is found in brain, suggesting that CNS amylin is derived from the circulation. This would require amylin to cross the blood-brain barrier (BBB). We used multiple-time regression analysis to determine the unidirectional influx constant (Ki) of blood-borne, radioactively labeled amylin (I-Amy) into the brain of mice. The Ki was 8.99(10(-4)) ml/g-min and was not inhibited with doses up to 100 micrograms/kg, but it was inhibited by aluminum (Al). About 0.11 to 0.13 percent of the injected dose of I-Amy entered each gram of brain. Radioactivity recovered from brain and analyzed by HPLC showed that the majority of radioactivity taken up by the brain represented intact I-Amy. Capillary depletion confirmed that blood-borne I-Amy completely crossed the BBB to enter the parenchymal/interstitial fluid space of the cerebral cortex. Taken together, these results show that blood-borne amylin has access to brain tissue and may be involved in some of the CNS manifestations of diabetes mellitus.
The in vivo effects of [D-Pen2,D-Pen5]enkephalin, a cyclic peptide agonist with high affinity and selectivity for the delta opioid receptors, on the endogenous aluminum content of selected areas of rat brain and spinal cord were studied by means of atomic absorption spectrophotometry. Intracerebroventricular injection of a subanalgesic dose of [D-Pen2,D-Pen5]enkephalin (0.2 microgram/3 microliters) produced a transient, time-dependent reduction of the aluminum content. This effect was statistically significant in the frontal cortex, hippocampus and striatum, but did not reach the level of significance in the medulla and thoracic spinal cord. The partial depleting effect of [D-Pen2,D-Pen5]enkephalin on aluminum content, in the range of 0.2-1.0 micrograms/3 microliters, was dose-dependent and could be reversed by naloxone pretreatment. Serum aluminum levels were unchanged after [D-Pen2,D-Pen5]enkephalin treatment. Chronic (five weeks), systemic AlCl3 treatment increased the endogenous aluminum content in all central nervous system areas examined. Interestingly, [D-Pen2,D-Pen5]enkephalin i.c.v. produced a slight depletion of this elevated metal level in these areas to values not significantly different from those of the respective control values. Chronic in vivo, as well as in vitro, effects of aluminum on opioid receptor binding characteristics were also studied. Neither the specific binding of [3H][D-Pen2,D-Pen5]enkephalin nor [3H]Tyr-D-Ala-Gly-NMePhe-Gly-ol to membranes of frontal or parietal cortices, striatum or hippocampus, prepared from rats chronically treated with AlCl3, were affected.(ABSTRACT TRUNCATED AT 250 WORDS)