Glia-mediated modulation of extracellular potassium concentration determines the sexually dimorphic output frequency of a model brainstem oscillator.

Sexual dimorphism in behavior is widespread among animals, but the cellular mechanisms underlying neural control of this phenomenon are largely unknown. One behavior that has provided some important clues about how such sex differences might develop is the electric organ discharge of Apteronotus leptorhynchus. In this weakly electric fish, the mean discharge frequencies of males and females are 880 Hz and 740 Hz, respectively, with little overlap of the two frequency bands. The discharges are controlled, in a one-to-one fashion, by the neural oscillations of the pacemaker nucleus in the medulla oblongata. Experimental evidence has shown that the astrocytic syncytium associated with the neural network that generates these oscillations is significantly larger, and stronger coupled via gap junctions, in females than in males. In the present study, modeling of this network was performed to test the hypotheses that the sex-dependent differences in the structure and properties of the astrocytic syncytium mediate better buffering of extracellular potassium in females than in males, which in turn causes, via a lowering of the potassium equilibrium potential, a decrease in the oscillation frequency. Simulations of the neural activity of the pacemaker nucleus and its individual components demonstrated that under both spontaneous and induced conditions the oscillation frequency and the potassium equilibrium potential are strongly positively correlated. These simulations predict that sufficient separation of the electric organ discharge frequencies for establishment of the sexual dimorphism can be achieved by rather minor alterations in the concentration of the extracellular potassium concentration in the pacemaker nucleus.

Bilateral Implant-based Breast Reconstruction with Unilateral Radiotherapy: A Matched Cohort Study Comparing Nipple-sparing Mastectomy and Skin-sparing Mastectomy.

Background: Nipple-sparing mastectomy (NSM) preserves the natural nipple-areola complex and entire native breast skin, with the goal of better cosmetic outcomes in breast reconstruction. In bilateral TE/implant-based reconstruction requiring unilateral postmastectomy radiotherapy (PMRT), progressive radiation-induced fibrosis can lead to increasing nipple asymmetry with cosmetic dissatisfaction. Thus, PMRT may ultimately negate the intended positive cosmetic value of NSM compared with skin-sparing mastectomy (SSM). This study compares (1) surgical complications, (2) patient satisfaction, and (3) aesthetic outcomes between NSM versus SSM in bilateral implant-based reconstruction with unilateral PMRT. Methods: This retrospective matched cohort study included consecutive NSM patients with bilateral TE/implant breast reconstruction + unilateral PMRT matched 1:2 to SSM group. Patients completed PMRT and TE exchange to implants. Demographics, oncologic stage, comorbidities, and complications were collected. Patient satisfaction was evaluated by BREAST-Q. Aesthetic outcomes were assessed by blinded reviewers with a five-point Likert scale. Results: Among 58 patients who underwent bilateral TE/implant reconstruction with unilateral PMRT, 17 NSM patients were matched to 41 SSM patients by age, body mass index, and comorbidities. No significant differences existed in overall surgical complications and individual BREAST-Q questionnaire scores between cohorts. However, aesthetic outcomes scores were higher in SSM compared with NSM. Conclusions: Although NSM is generally associated with superior cosmetic outcomes compared with SSM, it has far less impact in bilateral implant-based breast reconstruction with unilateral PMRT due to the negative postradiotherapy effect on nipple symmetry.

Postdischarge Pain and Opioid Use After Cardiac Surgery: A Prospective Cohort Study.

BACKGROUND: The rate of chronic opioid use after cardiac surgery is high compared with other surgical specialties; however evidence regarding optimal prescribing is limited. The purpose of this study was to evaluate patterns of opioid consumption after cardiac surgery to guide prescribing practices. METHODS: Consecutive patients undergoing sternotomy-based cardiac operations were considered for enrollment. Patients with opioid use within 3 months of surgery and those discharged to a nonhome facility were excluded. A patient diary and researcher-directed pill count was used to track pain and opioid use for 10 days after discharge. RESULTS: One hundred four patients were included in the final analysis. Of the 63 patients discharged with an opioid, 22 (34.9%) used none and 12 (19.0%) used fewer than half of the pills prescribed. Overall, pain and opioid consumption decreased significantly throughout the discharge period (P < .001). In those who used opioids after discharge, median total consumption was 64 morphine milligram equivalents (interquartile range, 38-128), or the equivalent of 9 oxycodone 5-mg tablets. Patients who used opioids were younger (60.9 vs 70.0, P < .001), but there were no differences based on sex, history of substance use, smoking, or procedure. After risk adjustment the mean pain score ≥ 3 on the day of discharge was predictive of opioid use (odds ratio, 2.9; 95% confidence interval, 1.8-4.8; P < .001). Most patients (88.5%) were satisfied or very satisfied with pain management. CONCLUSIONS: Fewer than half of all patients used opioids after discharge in this study. These data support the need for the development of prescription recommendations after cardiac surgery.