You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Tissue accumulation and species-specific metabolism of technical pentabrominated diphenyl ether (DE-71) in two predator fish. The tissue-specific accumulation and species-specific metabolism of polybrominated diphenyl ethers (PBDEs) in two predator fish species (redtail catfish and oscar fish) feeding on the same prey (tiger barb) that was exposed to technical pentabrominated diphenyl ether (DE-71) in the laboratory were investigated. The trends in the wet-weight tissue concentration of PBDEs in two predatory fish species suggested that the tissue distribution of PBDEs occurs through a series of events involving passive diffusion to the lipid compartment. A comparison of the fugacities of PBDEs in various tissues and in the serum revealed that the liver, gill, and perivisceral adipose tissue readily achieved equilibrium with the serum, but the muscle, kidney, and intestine exhibited the potential to accumulate PBDEs. The lower fugacities of PBDEs in the intestine may have significance in the transportation of PBDEs from prey to predatory fish. No tissue-specific differences in PBDE congener profiles were found, while interspecies differences in PBDE profiles were evident. The difference in profiles between two species could be attributed to species-specific debromination of PBDE. No metabolic debromination of PBDE was observed in redtail catfish, but extensive debromination of PBDEs occurred in oscar fish. Several hydroxylated PBDEs (OH-PBDEs) were detected in serum samples from the two fish species, but no methoxylated PBDEs were found. The similarities in the OH-PBDE congener profile and the ratio of OH-PBDEs to total PBDEs between the two fish species indicated that the hydroxylation of PBDEs might not be species-specific.
{"Chemical": ["PBDE", "polybrominated diphenyl ethers", "hydroxylated PBDEs", "OH-PBDE", "DE-71", "pentabrominated diphenyl ether", "PBDEs", "OH-PBDEs"]}