Strikwerda, John R.

Abstract Adrenal cysts are a rare benign adrenal pathology. Although the majority of adrenal cysts are asymptomatic, large cysts may present with debilitating symptoms of mass effect. Surgical adrenalectomy or cyst fenestration has been the primary mode of management for such symptomatic cysts, but these interventions can be associated with excessive morbidity, particularly when considered in the context of benign disease. Here, we present a case of a 34-year-old female with a longstanding, growing, benign left adrenal cyst associated with nonspecific abdominal symptoms. After multidisciplinary discussion, the patient was managed with primary ultrasound/fluoroscopic guided percutaneous sclerotherapy of her adrenal cyst. This technique achieved complete cyst resolution that was durable on 7-month follow-up and was associated with significant improvement of the patient's symptoms. This case illustrates the potential for primary percutaneous sclerotherapy for primary management of benign adrenal cysts.

Background and Purposeα4β2 nicotinic ACh receptors (nAChRs) comprise the most abundant class of nAChRs in the nervous system. They assemble in two stoichiometric forms, each exhibiting distinct functional and pharmacological signatures. However, whether one or both forms are modulated by calcium or magnesium has not been established.Experimental ApproachTo assess the functional consequences of calcium and magnesium, each stoichiometric form was expressed in clonal mammalian fibroblasts and single‐channel currents were recorded in the presence of a range of ACh concentrations.Key ResultsIn the absence of divalent cations, each stoichiometric form exhibits high unitary conductance and simple gating kinetics composed of solitary channel openings or short bursts of openings. However, in the presence of calcium and magnesium, the conductance and gating kinetics change in a stoichiometry‐dependent manner. Calcium and magnesium reduce the conductance of both stoichiometric forms, with each cation producing an equivalent reduction, but the reduction is greater for the (α4)2(β2)3 form. Moreover, divalent cations promote efficient channel opening of the (α4)3(β2)2 stoichiometry, while minimally affecting the (α4)2(β2)3 stoichiometry. For the (α4)3(β2)2 stoichiometry, at high but not low ACh concentrations, calcium in synergy with magnesium promote clustering of channel openings into episodes of many openings in quick succession.Conclusion and ImplicationsModulation of the α4β2 nAChR by divalent cations depends on the ACh concentration, the type of cation and the subunit stoichiometry. The functional consequences of modulation are expected to depend on the regional distributions of the stoichiometric forms and synaptic versus extrasynaptic locations of the receptors.

Whether ion channel gating is independent of ion permeation has been an enduring, unresolved question. Here, applying single channel recording to the archetypal muscle nicotinic receptor, we unmask coupling between channel gating and ion permeation by structural perturbation of a conserved intramembrane salt bridge. A charge-neutralizing mutation suppresses channel gating, reduces unitary current amplitude, and increases fluctuations of the open channel current. Power spectra of the current fluctuations exhibit low- and high-frequency Lorentzian components, which increase in charge-neutralized mutant receptors. After aligning channel openings and closings at the time of transition, the average unitary current exhibits asymmetric relaxations just after channel opening and before channel closing. A theory in which structural motions contribute jointly to channel gating and ion conduction describes both the power spectrum and the current relaxations. Coupling manifests as a transient increase in the open channel current upon channel opening and a decrease upon channel closing.