Establishment of a cell-free bioassay for detecting dioxin-like compounds.

Dioxins are byproducts from incomplete combustion processes and belong to a group of mostly toxic chemicals known as persistent organic pollutants, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is considered to be the most toxic species of all dioxin-like compounds. Analytical chemical processes are employed to determine the specific dioxin content in environmental samples. However, cost-ineffectiveness and excess time consumption limit their routine utilization. The aryl hydrocarbon receptor (AhR) is the major TCDD receptor. Upon binding to dioxin, the AhR dissociates from Hsp90 and other cofactors. TCDD-bound AhR subsequently translocates to the nucleus and interacts with the AhR nuclear translocator (Arnt) to induce signal transduction. Here, we describe a highly sensitive and cost-effective alternative assay based on detecting stability of bioluminescence signals. We generated cells that stably co-express Renilla luciferase tagged-AhR (AhR-RL), Ah receptor-interacting protein (AIP), p23 and yellow fluorescent protein-tagged Arnt (Arnt-YFP) (AAPA cells) for detection of dioxin-like compounds. Treatment with 3-methylcholanthrene (3MC), AhR agonist, enhanced the interaction between AhR and Arnt and avoided proteosomal degradation. In addition, treatment with 3MC or TCDD stabilized Renilla luminescence from AhR-RL of AAPA cell-free extracts in a concentration-dependent manner. The TCDD detection limit in this cell-free system was as low as 10(-18 )M. These results highlight the potential of AAPAA cell-free extracts to detect dioxin-like pollutants.

Crossed cheiro-oral syndrome.

OBJECTIVES: Cheiro-oral syndrome is characterized by sensory impairment confined to perioral area and ipsilateral fingers/hand. It results from an involvement of the ascending sensory tracts above the pons. However, a crossed pattern of perioral and acral paresthesia was rarely reported before. PATIENTS AND METHODS: This study reports the neuroanatomic relationship, course and clinical significance of perioral and contralateral acral paresthesia in four patients. We term it the crossed cheiro-oral syndrome. RESULTS: All patients had lateral or dorsolateral medullary infarctions that were ipsilateral to their perioral paresthesia. The contributory origin is considered a diagonal lesion involving the par oralis fibers within the descending trigeminal sensory tract and acral portion of the lateral spinothalamic tract at the lateral portion of medulla oblongata. Despite of a restricted sensory disturbance at initial, progressive neurological disability terminated to Wallenberg's syndrome ensued in three patients and disabling deficits persisted in two of them. CONCLUSION: The crossed cheiro-oral syndrome seems a mild form of Wallenberg's syndrome. Therefore, it predicts medullary involvement and is also a warning sign for progression.