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:

Estradiol negative and positive feedback in a prenatal androgen-induced mouse model of polycystic ovarian syndrome. Gonadal steroid hormone feedback is impaired in polycystic ovarian syndrome (PCOS), a common endocrine disorder characterized by hyperandrogenism and an associated increase in LH pulse frequency. Using a prenatal androgen (PNA)-treated mouse model of PCOS, we aimed to investigate negative and positive feedback effects of estrogens on the hypothalamic-pituitary axis regulation of LH. PNA-treated mice exhibited severely disrupted estrous cycles, hyperandrogenism, significantly reduced fertility, and altered ovarian morphology. To assess the negative feedback effects of estrogens, LH was measured before and after ovariectomy and after estradiol (E2) administration. Compared with controls, PNA-treated mice exhibited a blunted postcastration rise in LH (P < .001) and an absence of LH suppression after E2 administration. To assess E2-positive feedback, control and PNA-treated GnRH-green fluorescent protein transgenic mice were subjected to a standard ovariectomy with E2-replacement regimen, and both plasma and perfusion-fixed brains were collected at the time of the expected GnRH/LH surge. Immunocytochemistry and confocal imaging of cFos and green fluorescent protein were used to assess GnRH neuron activation and spine density. In the surged group, both control and PNA-treated mice had significantly increased LH and cFos activation in GnRH neurons (P < .05) compared with nonsurged animals. Spine density was quantified in cFos-positive and -negative GnRH neurons to examine whether there was an increase in spine density in cFos-expressing GnRH neurons of surged mice as expected. A significant increase in spine density in cFos-expressing GnRH neurons was evident in control animals; however, no significant increase was observed in the PNA-treated mice because spine density was elevated across all GnRH neurons. These data support that PNA treatment results in a PCOS-like phenotype that includes impaired E2-negative feedback. Additionally, although E2-positive feedback capability is retained in PNA mice, elevated GnRH neuron spine density may reflect altered synaptic regulation.
{"Chemical": ["Estradiol", "estrogens", "steroid", "estradiol", "androgen"]}