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:

FGF signalling through Fgfr2 isoform IIIb regulates adrenal cortex development. Developmental signalling pathways are implicated in the formation and maintenance of the adrenal gland, but their roles are currently not well defined. In recent years it has emerged that Sonic hedgehog (Shh) and Wnt/β catenin signalling are crucial for the growth and development of the adrenal cortex. Here we demonstrate that Fibroblast growth factor receptor (Fgfr) 2 isoforms IIIb and IIIc are expressed mainly in the adrenal subcapsule during embryogenesis and that specific deletion of the Fgfr2 IIIb isoform impairs adrenal development, causing reduced adrenal growth and impaired expression of SF1 and steroidogenic enzymes. The hypoplastic adrenals also have thicker, disorganised capsules which retain Gli1 expression but no longer express Dlk1. Fgfr2 ligands were detected in both the capsule and the cortex, suggesting the importance of signalling between the capsule and the cortex in adrenal development.
{"Chemical": []}