BK channels sustain neuronal Ca2+ oscillations to support hippocampal long-term potentiation and memory formation.

Mutations of large conductance Ca2+- and voltage-activated K+ channels (BK) are associated with cognitive impairment. Here we report that CA1 pyramidal neuron-specific conditional BK knock-out (cKO) mice display normal locomotor and anxiety behavior. They do, however, exhibit impaired memory acquisition and retrieval in the Morris Water Maze (MWM) when compared to littermate controls (CTRL). In line with cognitive impairment in vivo, electrical and chemical long-term potentiation (LTP) in cKO brain slices were impaired in vitro. We further used a genetically encoded fluorescent K+ biosensor and a Ca2+-sensitive probe to observe cultured hippocampal neurons during chemical LTP (cLTP) induction. cLTP massively reduced intracellular K+ concentration ([K+]i) while elevating L-Type Ca2+ channel- and NMDA receptor-dependent Ca2+ oscillation frequencies. Both, [K+]i decrease and Ca2+ oscillation frequency increase were absent after pharmacological BK inhibition or in cells lacking BK. Our data suggest that L-Type- and NMDAR-dependent BK-mediated K+ outflow significantly contributes to hippocampal LTP, as well as learning and memory.

Motives for digital social multitasking (DSMT) and problematic phone use among adolescents.

INTRODUCTION: Phone use during face-to-face interactions (i.e., digital social multitasking [DSMT]) is a growing activity among adolescents. DSMT appears to be a risk factor for problematic phone use, but little is known about why adolescents engage in DSMT and how different motives of DSMT would be associated with problematic phone use. Drawing on the framework of DSMT and the uses and gratifications theory, this study explored (1) the motives of adolescent DSMT and (2) the direct and indirect relationships between DSMT motives and problematic phone use via the level and perception of DSMT. METHOD: The study involved survey data from 517 adolescents in the United States recruited through the Qualtrics panels (Mage = 14.83, SD = 1.93) in the fall of 2020. The sample's gender and racial/ethnic distributions were nationally representative. RESULTS: We developed a scale measuring adolescent DSMT motives, which showed that adolescents engaged in DSMT because of enjoyment and connection, boredom, information, and habitual use. The motive of habitual use was associated with problematic phone use both directly and indirectly via level of DSMT and perceived distraction caused by DSMT. The information motive was directly associated with problematic phone use, while the boredom motive was indirectly associated with problematic phone use via perceived distraction. Conversely, the motive of enjoyment and connection was related to lower problematic phone use both directly and indirectly via lower perceived distraction. CONCLUSION: The study identifies DSMT-related risk and protective factors for problematic phone use. The findings should help adults recognize adaptive versus maladaptive forms of DSMT among adolescents and develop proper guidance and intervention.

The Na+-activated K+ channel Slack contributes to synaptic development and plasticity.

Human mutations of the Na+-activated K+ channel Slack (KCNT1) are associated with epilepsy and intellectual disability. Accordingly, Slack knockout mice (Slack-/-) exhibit cognitive flexibility deficits in distinct behavioral tasks. So far, however, the underlying causes as well as the role of Slack in hippocampus-dependent memory functions remain enigmatic. We now report that infant (P6-P14) Slack-/- lack both hippocampal LTD and LTP, likely due to impaired NMDA receptor (NMDAR) signaling. Postsynaptic GluN2B levels are reduced in infant Slack-/-, evidenced by lower amplitudes of NMDAR-meditated excitatory postsynaptic potentials. Low GluN2B affected NMDAR-mediated Ca2+-influx, rendering cultured hippocampal Slack-/-neurons highly insensitive to the GluN2B-specific inhibitor Ro 25-6981. Furthermore, dephosphorylation of the AMPA receptor (AMPAR) subunit GluA1 at S845, which is involved in AMPAR endocytosis during homeostatic and neuromodulator-regulated plasticity, is reduced after chemical LTD (cLTD) in infant Slack-/-. We additionally detect a lack of mGluR-induced LTD in infant Slack-/-, possibly caused by upregulation of the recycling endosome-associated small GTPase Rab4 which might accelerate AMPAR recycling from early endosomes. Interestingly, LTP and mGluR LTD, but not LTD and S845 dephosphorylation after cLTD are restored in adult Slack-/-. This together with normalized expression levels of GluN2B and Rab4 hints to developmental "restoration" of LTP expression despite Slack ablation, whereas in infant and adult brain, NMDAR-dependent LTD induction depends on this channel. Based on the present findings, NMDAR and vesicular transport might represent novel targets for the therapy of intellectual disability associated with Slack mutations. Consequently, careful modulation of hippocampal Slack activity should also improve learning abilities.

Digital Social Multitasking (DSMT), Friendship Quality, and Basic Psychological Needs Satisfaction Among Adolescents: Perceptions as Mediators.

Most existing research assumes "phone use during face-to-face interactions" to be psychosocially detrimental. Drawing on the digital social multitasking framework, this study explored not only the negative but also positive implications of the behavior. A sample of 517 adolescents (Mage = 14.83, S.D. = 1.93; 50% female) recruited through the Qualtrics panel completed an online survey. Results showed that adolescents' and their friend's digital social multitasking were both associated with (1) greater perceived efficiency, which, in turn, was associated with competence need satisfaction, and (2) greater perceived connection, which, in turn, was associated with better friendship quality, autonomy need satisfaction, and relatedness need satisfaction. Adolescents' own multitasking also had an indirect, negative relationship with friendship quality through perceived distraction, but friend's multitasking did not compromise friendship quality. The study provides a more balanced picture, showing that despite the potential harm of digital social multitasking, adolescents' phone use during face-to-face peer interactions also involves potential benefits for teens' psychosocial well-being.

Critical Role of Macrophage FcγR Signaling and Reactive Oxygen Species in Alloantibody-Mediated Hepatocyte Rejection.

Humoral alloimmunity negatively impacts both short- and long-term cell and solid organ transplant survival. We previously reported that alloantibody-mediated rejection of transplanted hepatocytes is critically dependent on host macrophages. However, the effector mechanism(s) of macrophage-mediated injury to allogeneic liver parenchymal cells is not known. We hypothesized that macrophage-mediated destruction of allogeneic hepatocytes occurs by cell-cell interactions requiring FcγRs. To examine this, alloantibody-dependent hepatocyte rejection in CD8-depleted wild-type (WT) and Fcγ-chain knockout (KO; lacking all functional FcγR) transplant recipients was evaluated. Alloantibody-mediated hepatocellular allograft rejection was abrogated in recipients lacking FcγR compared with WT recipients. We also investigated anti-FcγRI mAb, anti-FcγRIII mAb, and inhibitors of intracellular signaling (to block phagocytosis, cytokines, and reactive oxygen species [ROS]) in an in vitro alloantibody-dependent, macrophage-mediated hepatocytoxicity assay. Results showed that in vitro alloantibody-dependent, macrophage-mediated hepatocytotoxicity was critically dependent on FcγRs and ROS. The adoptive transfer of WT macrophages into CD8-depleted FcγR-deficient recipients was sufficient to induce alloantibody-mediated rejection, whereas adoptive transfer of macrophages from Fcγ-chain KO mice or ROS-deficient (p47 KO) macrophages was not. These results provide the first evidence, to our knowledge, that alloantibody-dependent hepatocellular allograft rejection is mediated by host macrophages through FcγR signaling and ROS cytotoxic effector mechanisms. These results support the investigation of novel immunotherapeutic strategies targeting macrophages, FcγRs, and/or downstream molecules, including ROS, to inhibit humoral immune damage of transplanted hepatocytes and perhaps other cell and solid organ transplants.

The evolutionary origination of a novel expression pattern through an extreme heterochronic shift.

The evolutionary origins of morphological structures are thought to often depend upon the redeployment of old genes into new developmental settings. Although many examples of cis-regulatory divergence have shown how pre-existing patterns of gene expression have been altered, only a small number of case studies have traced the origins of cis-regulatory elements that drive new expression domains. Here, we elucidate the evolutionary history of a novel expression pattern of the yellow gene within the Zaprionus genus of fruit flies. We observed a unique pattern of yellow transcript accumulation in the wing disc during the third larval instar, a stage that precedes its typical expression pattern associated with cuticular melanization by about a week. The region of the Zaprionus wing disc that expresses yellow subsequently develops into a portion of the thorax, a tissue for which yellow expression has been reported for several fruit fly species. Tests of GFP reporter transgenes containing the Zaprionus yellow regulatory region revealed that the wing disc pattern arose by changes in the cis-regulatory region of yellow. Moreover, the wing disc enhancer activity of yellow depends upon a short conserved sequence with ancestral thoracic functions, suggesting that the pupal thorax regulatory sequence was genetically reprogrammed to drive expression that commences much earlier during development. These results highlight how novel domains of gene expression may arise by extreme shifts in timing during the origins of novel traits.

Living donor liver transplantation for inborn errors of metabolism - An underutilized resource in the United States.

Inborn metabolic diseases of the liver can be life-threatening disorders that cause debilitating and permanent neurological damage. Symptoms may manifest as early as the neonatal period. Liver transplant replaces the enzymatically deficient liver, allowing for metabolism of toxic metabolites. LDLT for metabolic disorders is rarely performed in the United States as compared to countries such as Japan, where they report >2000 cases performed within the past two decades. Patient and graft survival is comparable to that of the United States, where most of the studies are based on deceased donors. No living donor complications were observed, suggesting that LDLT is as safe and effective as deceased donor transplants performed in the USA. Increased utilization of living donors in the USA will allow for early transplantation to prevent permanent neurological damage in those with severe disease. Pediatric transplant centers should consider utilizing living donors when feasible for children with metabolic disorders of the liver.

Well-Being Implications of Digital Social Multitasking in Adolescent Friendship: A Latent Profile Analysis.

Adolescents' phone use during face-to-face interactions (i.e., digital social multitasking [DSMT]) has gained increasing attention because of its prevalence as well as implications for well-being. However, most studies have focused on only one dimension of the behavior and relied on variable-centered approaches. Informed by the DSMT framework, we adopted a person-centered approach to identify different groups of adolescents based on their levels, perceptions, and motives of phone use during face-to-face interactions with friends. We also examined how these groups differed in five well-being variables (loneliness, depressive symptoms, digital stress, friendship quality, and satisfaction of basic psychological needs). A total of 517 adolescents (Mage = 14.83, standard deviation [SD] = 1.93; 50 percent female) completed an online survey. Three profiles were identified: the Intentional (low levels, quite positive perceptions, motivated for clear goals), the Embracers (high levels, highly positive perceptions, strong motives), and the Unimpressed (low levels, low positive perceptions, low motives). The Embracers scored the highest on both positive and negative indicators of well-being, whereas the Unimpressed scored the lowest on all well-being scales. The Intentional appeared to be the most adaptive group. Implications are discussed.

Slack K+ channels limit kainic acid-induced seizure severity in mice by modulating neuronal excitability and firing.

Mutations of the Na+-activated K+ channel Slack (KCNT1) are associated with terrible epilepsy syndromes that already begin in infancy. Here we report increased severity of acute kainic acid-induced seizures in adult and juvenile Slack knockout mice (Slack-/-) in vivo. Fittingly, we find exacerbation of cell death following kainic acid exposure in organotypic hippocampal slices as well as dissociated hippocampal cultures from Slack-/- in vitro. Furthermore, in cultured Slack-/- neurons, kainic acid-triggered Ca2+ influx and K+ efflux as well as depolarization-induced tetrodotoxin-sensitive inward currents are higher compared to the respective controls. This apparent changes in ion homeostasis could possibly explain altered action potential kinetics of Slack-/- neurons: steeper rise slope, decreased threshold, and duration of afterhyperpolarization, which ultimately lead to higher action potential frequencies during kainic acid application or injection of depolarizing currents. Based on our data, we propose Slack as crucial gatekeeper of neuronal excitability to acutely limit seizure severity.

CD8+ T cells negatively regulate IL-4-dependent, IgG1-dominant posttransplant alloantibody production.

We have previously reported that CD8(+) T cells significantly influence Ab production based on the observation that posttransplant alloantibody levels in CD8-deficient murine hepatocyte transplant recipients are markedly enhanced. However, the precise mechanisms contributing to enhanced alloantibody production in the absence of CD8(+) T cells is not understood. We hypothesized that alloactivated CD8(+) T cells inhibit Ab production by skewing toward a proinflammatory cytokine profile, whereas when these cells are absent, an anti-inflammatory cytokine profile shifts the alloimmune response toward alloantibody production. To investigate this possibility, alloantibody isotype profiles were examined in CD8-deficient and wild-type hepatocyte recipients. We found that IgG1 (IL-4-dependent isotype) was the dominant alloantibody isotype in wild-type recipients as well as in CD8-deficient recipients, although the amount of alloantibody in the latter group was substantially higher. Utilizing real-time PCR we found that CD4(+) T cells from wild-type recipients significantly upregulated IFN-γ but not IL-4 mRNA. In contrast, in the absence of CD8(+) T cells, CD4(+) T cells switched to significantly upregulate IL-4 mRNA, while IFN-γ was downregulated. IL-4 knockout mice do not produce any posttransplant alloantibody. However, adoptive transfer of wild-type CD4(+) T cells into CD8-depleted IL-4 knockout mice restores high alloantibody levels observed in CD8-depleted wild-type recipients. This suggests that IL-4-producing CD4(+) T cells are critical for posttransplant alloantibody production. Additionally, this CD8-mediated regulation of posttransplant alloantibody production is IFN-γ-dependent. Further elucidation of the mechanisms by which CD8(+) T cells influence Ab production will significantly contribute to development of therapies to manipulate humoral responses to Ag.

Predictors of Outcomes of Patients Referred to a Transplant Center for Urgent Liver Transplantation Evaluation.

Liver transplantation (LT) is definitive treatment for end-stage liver disease. This study evaluated factors predicting successful evaluation in patients transferred for urgent inpatient LT evaluation. Eighty-two patients with cirrhosis were transferred for urgent LT evaluation from January 2016 to December 2018. Alcohol-associated liver disease was the common etiology of liver disease (42/82). Of these 82 patients, 35 (43%) were declined for LT, 27 (33%) were wait-listed for LT, 5 (6%) improved, and 15 (18%) died. Psychosocial factors were the most common reasons for being declined for LT (49%). Predictors for listing and receiving LT on multivariate analysis included Hispanic race (odds ratio [OR], 1.89; P = 0.003), Asian race (OR, 1.52; P = 0.02), non-Hispanic ethnicity (OR, 1.49; P = 0.04), hyponatremia (OR, 1.38; P = 0.04), serum albumin (OR, 1.13; P = 0.01), and Model for End-Stage Liver Disease (MELD)-Na (OR, 1.02; P = 0.003). Public insurance (i.e., Medicaid) was a predictor of not being listed for LT on multivariate analysis (OR, 0.77; P = 0.02). Excluding patients declined for psychosocial reasons, predictors of being declined for LT on multivariate analysis included Chronic Liver Failure Consortium (CLIF-C) score >51.5 (OR, 1.26; P = 0.03), acute-on-chronic liver failure (ACLF) grade 3 (OR, 1.41; P = 0.01), hepatorenal syndrome (HRS) (OR, 1.38; P = 0.01), and respiratory failure (OR, 1.51; P = 0.01). Predictors of 3-month mortality included CLIF-C score >51.5 (hazard ratio [HR], 2.52; P = 0.04) and intensive care unit (HR, 8.25; P < 0.001). Conclusion: MELD-Na, albumin, hyponatremia, ACLF grade 3, HRS, respiratory failure, public insurance, Hispanic race, Asian race, and non-Hispanic ethnicity predicted liver transplant outcome. Lack of psychosocial support was a major reason for being declined for LT. The CLIF-C score predicted being declined for LT and mortality.

First lung and kidney multi-organ transplant following COVID-19 Infection.

As the world responds to the global crisis of the COVID-19 pandemic an increasing number of patients are experiencing increased morbidity as a result of multi-organ involvement. Of these, a small proportion will progress to end-stage lung disease, become dialysis dependent, or both. Herein, we describe the first reported case of a successful combined lung and kidney transplantation in a patient with COVID-19. Lung transplantation, isolated or combined with other organs, is feasible and should be considered for select patients impacted by this deadly disease.

Transoral incisionless fundoplication for gastroesophageal reflux disease in an unselected patient population.

BACKGROUND: EsophyX is an endolumenal approach to the treatment of gastroesophageal reflux disease (GERD). This report describes one of the earliest and largest North American experiences with this device. METHODS: Prospective data were gathered on consecutive patients undergoing EsophyX fundoplication for a 1-year period between September 2007 and March 2009. During this time, the procedure evolved to the current technique. A P value less than 0.05 was considered significant. RESULTS: The study enrolled 26 patients with a mean age of 45 years. The patients included 16 women (62%) with a mean body mass index (BMI) of 28 and an American Society Anesthesiology (ASA) classification of 2. These patients included 11 with associated small hiatal hernias, 3 with Barrett's esophagus, and 5 with esophageal dysmotility. The procedure time was 65 min (range, 29-137 min), and the length of hospital stay was 1 day (range, 0-6 days). The postoperative valve circumference was 217 degrees, and the valve length was 2.7 cm. Two complications of postoperative bleed occurred, requiring transfusion. The mean follow-up period was 10 months. Comparison of pre- and postoperative Anvari scores (34-17; P = 0.002) and Velanovich scores (22-10; P = 0.0007) showed significant decreases. Although 68% of the patients were still taking antireflux medications, 21% had reduced their dose by half. Three patients had persistent symptoms requiring Nissen fundoplication, and there was one late death unrelated to the procedure. CONCLUSION: This study represents an initial single-institution experience with EsophyX. According to the findings, 53% of the patients had either discontinued their antireflux medication (32%) or had decreased their dose by half (21%). Both symptoms and health-related quality-of-life (HRQL) scores significantly improved after treatment. Further follow-up evaluation and objective testing are required.

Mixed chimerism and acceptance of kidney transplants after immunosuppressive drug withdrawal.

Preclinical studies have shown that persistent mixed chimerism is linked to acceptance of organ allografts without immunosuppressive (IS) drugs. Mixed chimerism refers to continued mixing of donor and recipient hematopoietic cells in recipient tissues after transplantation of donor cells. To determine whether persistent mixed chimerism and tolerance can be established in patients undergoing living donor kidney transplantation, we infused allograft recipients with donor T cells and hematopoietic progenitors after posttransplant lymphoid irradiation. In 24 of 29 fully human leukocyte antigen (HLA)-matched patients who had persistent mixed chimerism for at least 6 months, complete IS drug withdrawal was achieved without subsequent evidence of rejection for at least 2 years. In 10 of 22 HLA haplotype-matched patients with persistent mixed chimerism for at least 12 months, reduction of IS drugs to tacrolimus monotherapy was achieved. Withdrawal of tacrolimus during the second year resulted in loss of detectable chimerism and subsequent rejection episodes, unless tacrolimus therapy was reinstituted. Posttransplant immune reconstitution of naïve B cells and B cell precursors was more rapid than the reconstitution of naïve T cells and thymic T cell precursors. Robust chimerism was observed only among naïve T and B cells but not among memory T cells. No evidence of rejection was observed in all surveillance graft biopsies obtained from mixed chimeric patients withdrawn from IS drugs, and none developed graft-versus-host disease. In conclusion, persistent mixed chimerism established in fully HLA- or haplotype-matched patients allowed for complete or partial IS drug withdrawal without rejection.

Living Kidney Donation: Strategies to Increase the Donor Pool.

End-stage renal disease (ESRD) is a significant health care burden. Although kidney transplantation is the optimal treatment modality, less than 25% of waiting list patients are transplanted because of organ shortage. Living kidney donation can lead to better recipient and graft survival and increase the number of donors. Not all ESRD patients have potential living donors, and not all living donors are a compatible match to recipients. Kidney paired exchanges allow incompatible pairs to identify compatible living donors for living donor kidney transplants for multiple recipients. Innovative modifications of kidney paired donation can increase the number of kidney transplants, with excellent outcomes.

Socioeconomic Status in Non-directed and Voucher-based Living Kidney Donation.

BACKGROUND: Little has been reported about the socioeconomic status (SES) and demographics of non-directed (altruistic) and voucher-based donation. OBJECTIVE: To analyze common characteristics amongst altruistic donors in order to promote non-directed and voucher-based donation. DESIGN, SETTING, AND PARTICIPANTS: Information regarding altruistic donations from 2008 to 2015 and voucher-based donors was obtained from the National Kidney Registry. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: An SES index, created and validated by the Agency for Healthcare Research and Quality (AHRQ), was created by geocoding the donor's zip code and linking it to seven publicly available SES variables found in the 2010 United States Census data. RESULTS AND LIMITATIONS: In total, 267 non-directed and 3 voucher-based donations were identified. Non-directed donors were predominantly female (58%), with an average age of 45.6 yr (range, 21-72). The mean SES index score was 55.6 (SD=3.2), which corresponds to the 77th percentile of 1.5 million MediCare beneficiaries as reported by the AHRQ in 2008. Voucher-based donors were Caucasian males of high SES. The study was limited by the number of voucher-based donations. CONCLUSIONS: Non-directed and voucher-based donors are in the upper end of the economic spectrum. The voucher-based program has built within it the inherent capacity to remove disincentives to donation, which currently limit altruistic donation. PATIENT SUMMARY: We wanted to determine what types of people donated their kidneys altruistically, so that we could understand how to motivate more people to donate their kidneys. The voucher-based program was recently started and is a promising tool to motivate many people to donate kidneys by removing major disincentives to donation.

Acute Kidney Injury After Liver Transplantation.

Since the implementation of the Model of End-stage Liver Disease score-based allocation system, the number of transplant candidates with impaired renal function has increased. The aims of this review are to present new insights in the definitions and predisposing factors that result in acute kidney injury (AKI), and to propose guidelines for the prevention and treatment of postliver transplantation (LT) AKI. This review is based on both systematic review of relevant literature and expert opinion. Pretransplant AKI is associated with posttransplant morbidity, including prolonged post-LT AKI which then predisposes to posttransplant chronic kidney disease. Prevention of posttransplant AKI is essential in the improvement of long-term outcomes. Accurate assessment of baseline kidney function at evaluation is necessary, taking into account that serum creatinine overestimates glomerular filtration rate. New diagnostic criteria for AKI have been integrated with traditional approaches in patients with cirrhosis to potentially identify AKI earlier and improve outcomes. Delayed introduction or complete elimination of calcineurin inhibitors during the first weeks post-LT in patients with early posttransplant AKI may improve glomerular filtration rate in high risk patients but with higher rates of rejection and more adverse events. Biomarkers may in the future provide diagnostic information such as etiology of AKI, and prognostic information on renal recovery post-LT, and potentially impact the decision for simultaneous liver-kidney transplantation. Overall, more attention should be paid to pretransplant and early posttransplant AKI to reduce the burden of late chronic kidney disease.

Exertional leg pain: teasing out arterial entrapments.

Vascular causes of exertional lower extremity pain are relatively rare, but may be the answer in athletes refractory to treatment for the more common overuse syndromes of the lower extremities. It is important to differentiate these vascular causes from chronic exertional compartment syndrome (CECS), medial tibial stress syndrome (MTSS), and stress fractures in order to develop appropriate treatment plans, avoid complications, and return athletes to play expeditiously. Important vascular etiologies to be considered are popliteal artery entrapment syndrome (PAES), endofibrotic disease, popliteal artery aneurysm, cystic adventitial disease, and peripheral arterial dissections. The diagnostic workup involves angiography or noninvasive vascular studies such as Doppler ultrasound or magnetic resonance angiography in both the neutral and provocative positions. Treatment of these vascular abnormalities typically involves surgical correction of the vascular anomaly.

Kidney paired exchange and desensitization: Strategies to transplant the difficult to match kidney patients with living donors.

With organs in short supply, only a limited number of kidney transplants can be performed a year. Live donor donation accounts for 1/3rd of all kidney transplants performed in the United States. Unfortunately, not every donor recipient pair is feasible because of Human leukocyte antigen (HLA) sensitization and ABO incompatibility. To overcome these barriers to transplant, strategies such as kidney paired donation (KPD) and desensitization have been developed. KPD is the exchange of donors between at least two incompatible donor-recipient pairs such that they are now compatible. Desensitization is the removal of circulating donor specific antibodies to prevent graft rejection. Regardless of the treatment strategy, highly sensitized patients whose calculated panel reactive antibody (cPRA) is ≥95% remain difficult to transplant with match rates as low as 15% in KPD pools. Desensitization has proved to be difficult in those with high antibody titers. A novel approach is the combination of both KPD and desensitization to facilitate compatible and successful transplantation. A highly sensitized patient can be paired with a better immunological match in the KPD pool and subsequently desensitized to a lesser degree. This article reviews the current progress in KPD and desensitization and their use as a combined therapy.