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The kappa opioid receptor (KOR) and its endogenous agonist dynorphin have been implicated in multiple psychiatric conditions including psychotic disorders. We tested the hypotheses that kappa expression is elevated and associated with psychotic symptoms in schizophrenia. We measured kappa expression in unmedicated patients with schizophrenia (7 female, 6 male) and matched controls (7 female, 6 male) with positron emission tomography (PET). We also acquired a measurement of cumulative dopamine activity over the life span in the same subjects using neuromelanin sensitive MRI. We hypothesized that neuromelanin accumulation would be higher in patients than controls and that in patients there would be a positive association between KOR availability and neuromelanin accumulation. Fourteen patients and thirteen controls were enrolled. Whole brain dynamic PET imaging data using the KOR selective tracer [ 18 F]LY245998 were acquired. Distribution volume (V T ) was measured with region of interest analysis in 14 brain regions. Neuromelanin accumulation in midbrain dopaminergic nuclei was assessed in the same subjects. Positive and negative symptoms were measured by a clinical psychologist. We did not observe group level differences in KOR expression, neuromelanin accumulation or relationships of these to positive symptoms. Unexpectedly, we did observe strong positive associations between KOR expression and symptoms of anhedonia in the patients (Pearson r > 0.7, uncorrected p < 0.01 in 8 cortical brain regions). We also observed moderate associations between KOR expression and neuromelanin levels in patients. In conclusion, we did not observe a relationship between kappa and symptoms of psychosis but the observed relationship to the negative symptom of anhedonia is in line with recent work testing kappa antagonism as a therapy for anhedonia in depression., (© 2024. The Author(s), under exclusive licence to American College of Neuropsychopharmacology.)

Objective: Midbrain dopamine function plays a key role in translational models of substance use disorders. Whether midbrain dopamine function is associated with substance use frequency and severity or reward function in 20-24 year-olds remains a critical gap in knowledge. The authors collected neuromelanin-sensitive magnetic resonance imaging (NM-MRI), a validated index of lifetime dopamine function in the substantia nigra/ventral tegmentum area (SN-VTA) complex, to characterize altered dopamine function., Method: Midbrain NM-MRI contrast-to-noise ratio (CNR) was acquired in 135 20-24 year-olds (105 women and 30 men). A composite measure of cumulative substance use was derived from factor analysis of lifetime alcohol intoxications, lifetime cannabis use, use of nicotine in heaviest month, number of classes of drugs used, and ever meeting DSM-5 criteria for a SUD. Trait reward function was assessed by self-report., Results: Cumulative substance use was significantly positively associated with NM-MRI CNR in a large area of the bilateral SN-VTA complex, an effect which was driven by women (who comprised most of the sample) and by voxels with greater NM-MRI CNR, including the ventral tegmentum area. NM-MRI CNR was not associated with individual differences in trait reward function., Conclusions: History of substance use is associated with greater NM signal in NM-rich areas of the midbrain, especially in women. Future longitudinal studies with repeated NM-MRI assessments, especially in younger cohorts and while including more men, are warranted to evaluate whether aberrant dopamine function predates, follows, or is modulated by substance use., Competing Interests: Dr. Abi-Dargham serves on the Scientific Advisory Board for Neurocrine, Sunovion, and Abbvie; on the Data Safety Monitoring Board for Merck; and as the Deputy Editor of Biological Psychiatry; holds stock options in Herophilus and Terran Life Sciences; and has received consulting fees/honoraria from Boehringer Ingelheim, Merck, Neurocrine, Otsuka, Roche, and Sunovion. Dr Horga reports an investigator-initiated sponsored research agreement from Terran Biosciences outside the submitted work and having filed patents for the analysis and use of neuromelanin-sensitive magnetic resonance imaging in central nervous system disorders licensed to Terran Biosciences with no royalties received (WO2021034770A1, WO2022192728A3, AU2021377338A1, AU2019359377A1). Dr Wengler reports having filed patents for the analysis and use of neuromelanin-sensitive magnetic resonance imaging in central nervous system disorders licensed to Terran Biosciences with no royalties received (WO2021034770A1, WO2022192728A3, AU2021377338A1). The remaining authors report no financial relationships with commercial interests.

Background: Individuals with substance use disorder show impaired self-awareness of ongoing behavior. This deficit suggests problems with metacognition, which has been operationalized in the cognitive neuroscience literature as the ability to monitor and evaluate the success of one's own cognition and behavior. However, the neural mechanisms of metacognition have not been characterized in a population with drug addiction., Methods: Community samples of participants with opioid use disorder (OUD) (n = 27) and healthy control participants (n = 29) performed a previously validated functional magnetic resonance imaging metacognition task (perceptual decision-making task along with confidence ratings of performance). Measures of recent drug use and addiction severity were also acquired., Results: Individuals with OUD had lower metacognitive sensitivity (i.e., disconnection between task performance and task-related confidence) than control individuals. Trial-by-trial analyses showed that this overall group difference was driven by (suboptimally) low confidence in participants with OUD during correct trials. In functional magnetic resonance imaging analyses, the task engaged an expected network of brain regions (e.g., rostrolateral prefrontal cortex and dorsal anterior cingulate/supplementary motor area, both previously linked to metacognition); group differences emerged in a large ventral anterior cluster that included the medial and lateral orbitofrontal cortex and striatum (higher activation in OUD). Trial-by-trial functional magnetic resonance imaging analyses showed group differences in rostrolateral prefrontal cortex activation, which further correlated with metacognitive behavior across all participants. Exploratory analyses suggested that the behavioral and neural group differences were exacerbated by recent illicit opioid use and unexplained by general cognition., Conclusions: With confirmation and extension of these findings, metacognition and its associated neural circuits could become new, promising therapeutic targets in addiction., (Copyright © 2024 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Background: Despite longstanding interest in the central cholinergic system in schizophrenia (SCZ), cholinergic imaging studies with patients have been limited to receptors. Here, we conducted a proof-of-concept positron emission tomography study using [ 18 F]-VAT, a new radiotracer that targets the vesicular acetylcholine transporter as a proxy measure of acetylcholine transmission capacity, in patients with SCZ and explored relationships of vesicular acetylcholine transporter with clinical symptoms and cognition., Methods: A total of 18 adult patients with SCZ or schizoaffective disorder (the SCZ group) and 14 healthy control participants underwent a positron emission tomography scan with [ 18 F]-VAT. Distribution volume (V T ) for [ 18 F]-VAT was derived for each region of interest, and group differences in V T were assessed with 2-sample t tests. Functional significance was explored through correlations between V T and scores on the Positive and Negative Syndrome Scale and a computerized neurocognitive battery (PennCNB)., Results: No group differences in [ 18 F]-VAT V T were observed. However, within the SCZ group, psychosis symptom severity was positively associated with V T in multiple regions of interest, with the strongest effects in the hippocampus, thalamus, midbrain, cerebellum, and cortex. In addition, in the SCZ group, working memory performance was negatively associated with V T in the substantia innominata and several cortical regions of interest including the dorsolateral prefrontal cortex., Conclusions: In this initial study, the severity of 2 important features of SCZ-psychosis and working memory deficit-was strongly associated with [ 18 F]-VAT V T in several cortical and subcortical regions. These correlations provide preliminary evidence of cholinergic activity involvement in SCZ and, if replicated in larger samples, could lead to a more complete mechanistic understanding of psychosis and cognitive deficits in SCZ and the development of therapeutic targets., (Copyright © 2024 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Membrane proteins play critical physiological roles as receptors, channels, pumps, and transporters. Despite their importance, however, low expression levels often hamper the experimental characterization of membrane proteins. We present an automated and web-accessible design algorithm called mPROSS (https://mPROSS.weizmann.ac.il), which uses phylogenetic analysis and an atomistic potential, including an empirical lipophilicity scale, to improve native-state energy. As a stringent test, we apply mPROSS to the Kv1.2-Kv2.1 paddle chimera voltage-gated potassium channel. Four designs, encoding 9-26 mutations relative to the parental channel, were functional and maintained potassium-selective permeation and voltage dependence in Xenopus oocytes with up to 14-fold increase in whole-cell current densities. Additionally, single-channel recordings reveal no significant change in the channel-opening probability nor in unitary conductance, indicating that functional expression levels increase without impacting the activity profile of individual channels. Our results suggest that the expression levels of other dynamic channels and receptors may be enhanced through one-shot design calculations., (© 2024 The Authors. Protein Science published by Wiley Periodicals LLC on behalf of The Protein Society.)

Advances in DNA sequencing and machine learning are providing insights into protein sequences and structures on an enormous scale 1 . However, the energetics driving folding are invisible in these structures and remain largely unknown 2 . The hidden thermodynamics of folding can drive disease 3,4 , shape protein evolution 5-7 and guide protein engineering 8-10 , and new approaches are needed to reveal these thermodynamics for every sequence and structure. Here we present cDNA display proteolysis, a method for measuring thermodynamic folding stability for up to 900,000 protein domains in a one-week experiment. From 1.8 million measurements in total, we curated a set of around 776,000 high-quality folding stabilities covering all single amino acid variants and selected double mutants of 331 natural and 148 de novo designed protein domains 40-72 amino acids in length. Using this extensive dataset, we quantified (1) environmental factors influencing amino acid fitness, (2) thermodynamic couplings (including unexpected interactions) between protein sites, and (3) the global divergence between evolutionary amino acid usage and protein folding stability. We also examined how our approach could identify stability determinants in designed proteins and evaluate design methods. The cDNA display proteolysis method is fast, accurate and uniquely scalable, and promises to reveal the quantitative rules for how amino acid sequences encode folding stability., (© 2023. The Author(s).)

Until now, membrane-protein stabilization has relied on iterations of mutations and screening. We now validate a one-step algorithm, mPROSS, for stabilizing membrane proteins directly from an AlphaFold2 model structure. Applied to the lipid-generating enzyme, ceramide synthase, 37 designed mutations lead to a more stable form of human CerS2. Together with molecular dynamics simulations, we propose a pathway by which substrates might be delivered to the ceramide synthases., (© 2023. The Author(s).)

White-rot fungi secrete a repertoire of high-redox potential oxidoreductases to efficiently decompose lignin. Of these enzymes, versatile peroxidases (VPs) are the most promiscuous biocatalysts. VPs are attractive enzymes for research and industrial use but their recombinant production is extremely challenging. To date, only a single VP has been structurally characterized and optimized for recombinant functional expression, stability, and activity. Computational enzyme optimization methods can be applied to many enzymes in parallel but they require accurate structures. Here, we demonstrate that model structures computed by deep-learning-based ab initio structure prediction methods are reliable starting points for one-shot PROSS stability-design calculations. Four designed VPs encoding as many as 43 mutations relative to the wildtype enzymes are functionally expressed in yeast, whereas their wildtype parents are not. Three of these designs exhibit substantial and useful diversity in their reactivity profiles and tolerance to environmental conditions. The reliability of the new generation of structure predictors and design methods increases the scale and scope of computational enzyme optimization, enabling efficient discovery and exploitation of the functional diversity in natural enzyme families directly from genomic databases.

Patients with schizophrenia have a high prevalence of cigarette smoking and respond poorly to conventional treatments, highlighting the need for new therapies. We conducted a mechanistic, proof-of-concept study using bilateral deep repetitive transcranial magnetic stimulation (dTMS) of insular and prefrontal cortices at high frequency, using the specialized H4 coil. Feasibility of dTMS was tested for disruption of tobacco self-administration, insula target engagement, and insula circuit modulation, all of which were a priori outcomes of interest. Twenty patients completed the study, consisting of weekday dTMS sessions (randomization to active dTMS or sham; double-blind; 10 patients per group), a laboratory tobacco self-administration paradigm (pre/post assessments), and multimodal imaging (three MRI total sessions). Results showed that participants assigned to active dTMS were slower to initiate smoking their first cigarette compared with sham, consistent with smoking disruption. The imaging analyses did not reveal significant Time × Group interactions, but effects were in the anticipated directions. In arterial spin labeling analyses testing for target engagement, an overall decrease in insula blood flow, measured during a post-treatment MRI versus baseline, was numerically more pronounced in the active dTMS group than sham. In fMRI analyses, resting-state connectivity between the insula and default mode network showed a numerically greater change from baseline in the active dTMS group than sham, consistent with a functional change to insula circuits. Exploratory analyses further suggested a therapeutic effect of dTMS on symptoms of psychosis. These initial observations pave the way for future confirmatory studies of dTMS in smoking patients with schizophrenia., (© 2022. The Author(s).)

Stabilizing antigenic proteins as vaccine immunogens or diagnostic reagents is a stringent case of protein engineering and design as the exterior surface must maintain recognition by receptor(s) and antigen-specific antibodies at multiple distinct epitopes. This is a challenge, as stability enhancing mutations must be focused on the protein core, whereas successful computational stabilization algorithms typically select mutations at solvent-facing positions. In this study, we report the stabilization of SARS-CoV-2 Wuhan Hu-1 Spike receptor binding domain using a combination of deep mutational scanning and computational design, including the FuncLib algorithm. Our most successful design encodes I358F, Y365W, T430I, and I513L receptor binding domain mutations, maintains recognition by the receptor ACE2 and a panel of different anti-receptor binding domain monoclonal antibodies, is between 1 and 2°C more thermally stable than the original receptor binding domain using a thermal shift assay, and is less proteolytically sensitive to chymotrypsin and thermolysin than the original receptor binding domain. Our approach could be applied to the computational stabilization of a wide range of proteins without requiring detailed knowledge of active sites or binding epitopes. We envision that this strategy may be particularly powerful for cases when there are multiple or unknown binding sites., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Recent studies have established a clear topographical and functional organization of projections to and from complex subdivisions of the striatum. Manual segmentation of these functional subdivisions is labor-intensive and time-consuming, and automated methods are not as reliable as manual segmentation., Purpose: To utilize multitask learning (MTL) as a method to segment subregions of the striatum consisting of pre-commissural putamen (prePU), pre-commissural caudate (preCA), post-commissural putamen (postPU), post-commissural caudate (postCA), and ventral striatum (VST)., Study Type: Retrospective., Population: Eighty-seven total data sets from patients with schizophrenia and matched controls., Field Strength/sequence: 1.5 T and 3.0 T, T 1 -weighted (SPGR SENSE, 3D BRAVO)., Assessment: MTL-generated segmentations were compared to the Imperial College London Clinical Imaging Center (CIC) atlas. Dice similarity coefficient (DSC) was used to compare the automated methods to manual segmentations. Positron emission tomography (PET) imaging: 60 minutes of emission data were acquired using [ 11 C]raclopride. Data were reconstructed by filtered back projection (FBP) with computed tomography (CT) used for attenuation correction. Binding potential values, BP ND , and region of interest (ROI) time series and whole-brain connectivity using functional magnetic resonance imaging (fMRI) images were compared between manual and both automated segmentations., Statistical Tests: Pearson correlation and paired t-test., Results: MTL-generated segmentations showed excellent spatial agreement with manual (DSC ≥0.72 across all striatal subregions). BP ND values from MTL-generated segmentations were shown to correlate well with manual segmentations with R 2  ≥ 0.91 in all caudate and putamen subregions, and R 2  = 0.69 in VST. Mean Pearson correlation coefficients of the fMRI data between MTL-generated and manual segmentations were also high in time series (≥0.86) and whole-brain connectivity (≥0.89) across all subregions., Data Conclusion: Across both PET and fMRI task-based assessments, results from MTL-generated segmentations more closely corresponded to results from manually drawn ROIs than CIC-generated segmentations did. Therefore, the proposed MTL approach is a fast and reliable method for three-dimensional striatal subregion segmentation with results comparable to manually segmented ROIs., Level of Evidence: 2 TECHNICAL EFFICACY STAGE: 1., (© 2021 International Society for Magnetic Resonance in Medicine.)

Background: Neuromelanin-sensitive magnetic resonance imaging (NM-MRI) is a validated measure of neuromelanin concentration in the substantia nigra-ventral tegmental area (SN-VTA) complex and is a proxy measure of dopaminergic function with potential as a noninvasive biomarker. The development of generalizable biomarkers requires large-scale samples necessitating harmonization approaches to combine data collected across sites., Purpose: To develop a method to harmonize NM-MRI across scanners and sites., Study Type: Prospective., Population: A total of 128 healthy subjects (18-73 years old; 45% female) from three sites and five MRI scanners., Field Strength/sequence: 3.0 T; NM-MRI two-dimensional gradient-recalled echo with magnetization-transfer pulse and three-dimensional T1-weighted images., Assessment: NM-MRI contrast (contrast-to-noise ratio [CNR]) maps were calculated and CNR values within the SN-VTA (defined previously by manual tracing on a standardized NM-MRI template) were determined before harmonization (raw CNR) and after ComBat harmonization (harmonized CNR). Scanner differences were assessed by calculating the classification accuracy of a support vector machine (SVM). To assess the effect of harmonization on biological variability, support vector regression (SVR) was used to predict age and the difference in goodness-of-fit (Δr) was calculated as the correlation (between actual and predicted ages) for the harmonized CNR minus the correlation for the raw CNR., Statistical Tests: Permutation tests were used to determine if SVM classification accuracy was above chance level and if SVR Δr was significant. A P-value <0.05 was considered significant., Results: In the raw CNR, SVM MRI scanner classification was above chance level (accuracy = 86.5%). In the harmonized CNR, the accuracy of the SVM was at chance level (accuracy = 29.5%; P = 0.8542). There was no significant difference in age prediction using the raw or harmonized CNR (Δr = -0.06; P = 0.7304)., Data Conclusion: ComBat harmonization removes differences in SN-VTA CNR across scanners while preserving biologically meaningful variability associated with age., Level of Evidence: 2 TECHNICAL EFFICACY: 1., (© 2021 International Society for Magnetic Resonance in Medicine.)

Summary: Many natural and designed proteins are only marginally stable limiting their usefulness in research and applications. Recently, we described an automated structure and sequence-based design method, called PROSS, for optimizing protein stability and heterologous expression levels that has since been validated on dozens of proteins. Here, we introduce improvements to the method, workflow and presentation, including more accurate sequence analysis, error handling and automated analysis of the quality of the sequence alignment that is used in design calculations., Availability and Implementation: PROSS2 is freely available for academic use at https://pross.weizmann.ac.il., (© The Author(s) 2020. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Cognitive behavioral therapy (CBT) including exposure and response prevention is a well-established treatment for obsessive-compulsive disorder (OCD) and is based on the principles of fear extinction. Fear extinction is linked to structural and functional variability in the ventromedial prefrontal cortex (vmPFC) and has been consistently associated with glutamate neurotransmission. The relationship between vmPFC glutamate and fear extinction and its effects on CBT outcome have not yet been explored in adults with OCD. We assessed glutamate levels in the vmPFC using 3T magnetic resonance spectroscopy, and fear extinction (learning and recall) using skin conductance responses during a 2-day experimental paradigm in OCD patients (n = 17) and in healthy controls (HC; n = 13). Obsessive-compulsive patients (n = 12) then received manualized CBT. Glutamate in the vmPFC was negatively associated with fear extinction recall and positively associated with CBT outcome (with higher glutamate levels predicting a better outcome) in OCD patients. Glutamate levels in the vmPFC in OCD patients were not significantly different from those in HC, and were not associated with OCD severity. Our results suggest that glutamate in the vmPFC is associated with fear extinction recall and CBT outcome in adult OCD patients.

Rationale & Objective: Hemodialysis patients are at increased risk for coronavirus disease 2019 (COVID-19) transmission due in part to difficulty maintaining physical distancing. Our hemodialysis unit experienced a COVID-19 outbreak despite following symptom-based screening guidelines. We describe the course of the COVID-19 outbreak and the infection control measures taken for mitigation., Study Design: Retrospective cohort study., Setting & Participants: 237 maintenance hemodialysis patients and 93 hemodialysis staff at a single hemodialysis center in Toronto, Canada., Exposure: Universal screening of patients and staff for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)., Outcomes: The primary outcome was detection of SARS-CoV-2 in nasopharyngeal samples from patients and staff using reverse transcriptase-polymerase chain reaction (RT-PCR)., Analytical Approach: Descriptive statistics were used for clinical characteristics and the primary outcome., Results: 11 of 237 (4.6%) hemodialysis patients and 11 of 93 (12%) staff members had a positive RT-PCR test result for SARS-CoV-2. Among individuals testing positive, 12 of 22 (55%) were asymptomatic at time of testing and 7 of 22 (32%) were asymptomatic for the duration of follow-up. One patient was hospitalized at the time of SARS-CoV-2 infection and 4 additional patients with positive test results were subsequently hospitalized. 2 (18%) patients required admission to the intensive care unit. After 30 days' follow-up, no patients had died or required mechanical ventilation. No hemodialysis staff required hospitalization. Universal droplet and contact precautions were implemented during the outbreak. Hemodialysis staff with SARS-CoV-2 infection were placed on home quarantine regardless of symptom status. Patients with SARS-CoV-2 infection, including asymptomatic individuals, were treated with droplet and contact precautions until confirmation of negative SARS-CoV-2 RT-PCR test results. Analysis of the outbreak identified 2 index cases with subsequent nosocomial transmission within the dialysis unit and in shared shuttle buses to the hemodialysis unit., Limitations: Single-center study., Conclusions: Universal SARS-CoV-2 testing and universal droplet and contact precautions in the setting of an outbreak appeared to be effective in preventing further transmission., (Copyright © 2020 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Neuromelanin-sensitive MRI (NM-MRI) purports to detect the content of neuromelanin (NM), a product of dopamine metabolism that accumulates with age in dopamine neurons of the substantia nigra (SN). Interindividual variability in dopamine function may result in varying levels of NM accumulation in the SN; however, the ability of NM-MRI to measure dopamine function in nonneurodegenerative conditions has not been established. Here, we validated that NM-MRI signal intensity in postmortem midbrain specimens correlated with regional NM concentration even in the absence of neurodegeneration, a prerequisite for its use as a proxy for dopamine function. We then validated a voxelwise NM-MRI approach with sufficient anatomical sensitivity to resolve SN subregions. Using this approach and a multimodal dataset of molecular PET and fMRI data, we further showed the NM-MRI signal was related to both dopamine release in the dorsal striatum and resting blood flow within the SN. These results suggest that NM-MRI signal in the SN is a proxy for function of dopamine neurons in the nigrostriatal pathway. As a proof of concept for its clinical utility, we show that the NM-MRI signal correlated to severity of psychosis in schizophrenia and individuals at risk for schizophrenia, consistent with the well-established dysfunction of the nigrostriatal pathway in psychosis. Our results indicate that noninvasive NM-MRI is a promising tool that could have diverse research and clinical applications to investigate in vivo the role of dopamine in neuropsychiatric illness., Competing Interests: The authors declare no conflict of interest.

Diabetic kidney disease (DKD) is a group of chronic kidney diseases that is associated with significant cardiovascular as well as all-cause morbidity and mortality. Although DKD is often progressive in nature, its evolution can be modified by intensive management of glycemia and blood pressure and inhibition of the renin-angiotensin-aldosterone system. This review provides an overview of how multifactorial interventions can provide renal protection and includes a discussion of the nonglycemic effects of incretin-based diabetes therapies (glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase 4 inhibitors) and sodium-glucose cotransporter-2 inhibitors within the kidney in patients with type 2 diabetes., (Copyright © 2017 Diabetes Canada. Published by Elsevier Inc. All rights reserved.)

Recent genetic, molecular and post-mortem studies suggest impaired dopamine (DA)-D2 receptor (D2R) trafficking in patients with schizophrenia (SZ). Imaging and preclinical studies have shown agonist-induced D2R internalization can be imaged with positron emission tomography (PET) using D2R radiotracers combined with psychostimulant challenge. This is feasible if radiotracer binding is measured when postchallenge DA levels have returned to baseline, following the initial competition phase between DA and radiotracer for binding to D2R. Here we used 'late-phase' imaging after challenge to test the hypothesis that impaired D2R internalization in SZ leads to blunted late-phase displacement, or a faster return to baseline, in patients compared with healthy controls (HCs). We imaged 10 patients with SZ and 9 HCs with PET and [ 11 C]raclopride at baseline and two times (3-5 and 6-10 h) following 0.5 mg kg -1 dextroamphetamine. We measured binding potential relative to non-displaceable compartment (BP ND ) and derived percent reduction from baseline (ΔBP ND ) for each postamphetamine scan. To test the hypothesis that time course of return of striatal BP ND to baseline differed between SZ and HCs, we implemented a linear model with ΔBP ND as dependent variable, time after amphetamine as repeated measure and time after amphetamine and diagnostic group as fixed effects. Neither diagnostic group nor interaction of diagnostic group-by-time after amphetamine significantly affected striatal ΔBP ND (F=1.38, P=0.26; F=0.51, P=0.61). These results show similar pattern of return of BP ND to baseline as a function of time in patients with SZ and HC, suggesting that striatal D2R internalization as measured by our imaging paradigm is normal in patients with SZ.

Hallucinations, a cardinal feature of psychotic disorders such as schizophrenia, are known to depend on excessive striatal dopamine. However, an underlying cognitive mechanism linking dopamine dysregulation and the experience of hallucinatory percepts remains elusive. Bayesian models explain perception as an optimal combination of prior expectations and new sensory evidence, where perceptual distortions such as illusions and hallucinations may occur if prior expectations are afforded excessive weight. Such excessive weight of prior expectations, in turn, could stem from a gain-control process controlled by neuromodulators such as dopamine. To test for such a dopamine-dependent gain-control mechanism of hallucinations, we studied unmedicated patients with schizophrenia with varying degrees of hallucination severity and healthy individuals using molecular imaging with a pharmacological manipulation of dopamine, structural imaging, and a novel task designed to measure illusory changes in the perceived duration of auditory stimuli under different levels of uncertainty. Hallucinations correlated with a perceptual bias, reflecting disproportional gain on expectations under uncertainty. This bias could be pharmacologically induced by amphetamine, strongly correlated with striatal dopamine release, and related to cortical volume of the dorsal anterior cingulate, a brain region involved in tracking environmental uncertainty. These findings outline a novel dopamine-dependent mechanism for perceptual modulation in physiological conditions and further suggest that this mechanism may confer vulnerability to hallucinations in hyper-dopaminergic states underlying psychosis., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Most drugs of abuse lead to a general blunting of dopamine release in the chronic phase of dependence, which contributes to poor outcome. To test whether cannabis dependence is associated with a similar dopaminergic deficit, we examined striatal and extrastriatal dopamine release in severely cannabis-dependent participants (CD), free of any comorbid conditions, including nicotine use. Eleven CD and 12 healthy controls (HC) completed two positron emission tomography scans with [ 11 C]-(+)-PHNO, before and after oral administration of d-amphetamine. CD stayed inpatient for 5-7 days prior to the scans to standardize abstinence. Magnetic resonance spectroscopy (MRS) measures of glutamate in the striatum and hippocampus were obtained in the same subjects. Percent change in [ 11 C]-(+)-PHNO-binding potential (ΔBP ND ) was compared between groups and correlations with MRS glutamate, subclinical psychopathological and neurocognitive parameters were examined. CD had significantly lower ΔBP ND in the striatum (P=0.002, effect size (ES)=1.48), including the associative striatum (P=0.003, ES=1.39), sensorimotor striatum (P=0.003, ES=1.41) and the pallidus (P=0.012, ES=1.16). Lower dopamine release in the associative striatum correlated with inattention and negative symptoms in CD, and with poorer working memory and probabilistic category learning performance in both CD and HC. No relationships to MRS glutamate and amphetamine-induced subclinical positive symptoms were detected. In conclusion, this study provides evidence that severe cannabis dependence-without the confounds of any comorbidity-is associated with a deficit in striatal dopamine release. This deficit extends to other extrastriatal areas and predicts subclinical psychopathology., Competing Interests: Dr. Haney has received partial salary support for investigator-initiated studies from Insys Therapeutics Inc, and Lifeloc Technologies and has served as a consultant to Aelis Farma and Health Advances LLC. Dr. Kegeles has received research support from Amgen. Dr. Slifstein has received research support from Forest Laboratories, Pierre-Fabre, CHDI, and Otsuka and has provided consultation for Amgen. Dr. Abi-Dargham has received research support from Takeda and Forest Pharmaceuticals and has served on advisory boards for Roche, Forum, and Otsuka. Drs. Van de Giessen, Weinstein, Cassidy, Dong, Ghazzaoui, Ojeil, Xu, Vadhan and Volkow report no competing interests.

In light of the clinical evidence implicating dopamine in schizophrenia and the prominent hypotheses put forth regarding alterations in dopaminergic transmission in this disease, molecular imaging has been used to examine multiple aspects of the dopaminergic system. We review the imaging methods used and compare the findings across the different molecular targets. Findings have converged to suggest early dysregulation in the striatum, especially in the rostral caudate, manifesting as excess synthesis and release. Recent data showed deficit extending to most cortical regions and even to other extrastriatal subcortical regions not previously considered to be "hypodopaminergic" in schizophrenia. These findings yield a new topography for the dopaminergic dysregulation in schizophrenia. We discuss the dopaminergic innervation within the individual projection fields to provide a topographical map of this dual dysregulation and explore potential cellular and circuit-based mechanisms for brain region-dependent alterations in dopaminergic parameters. This refined knowledge is essential to better guide translational studies and efforts in early drug development., Competing Interests: Dr. Kegeles has received research support from Amgen. Dr. Slifstein has received research support from Forest Laboratories, Pierre-Fabre, CHDI, and Otsuka and has provided consultation for Amgen. Dr. Abi-Dargham has received research support from Takeda and Forest Pharmaceuticals and has served on advisory boards for Roche, Forum, and Otsuka. Drs. Moore, Chohan, and Weinstein report no biomedical financial interests or potential conflicts of interest., (Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Background: The neural correlates of working memory (WM) impairment in schizophrenia remain a key puzzle in understanding the cognitive deficits and dysfunction of dorsolateral prefrontal cortex observed in this disorder. We sought to determine whether patients with schizophrenia exhibit an alteration in the inverted-U relationship between WM load and activation that we recently observed in healthy individuals and whether this could account for WM deficits in this population., Methods: Medicated (n = 30) and unmedicated (n = 21) patients with schizophrenia and healthy control subjects (n = 45) performed the self-ordered WM task during functional magnetic resonance imaging. We identified regions exhibiting an altered fit to an inverted-U relationship between WM load and activation that were also predictive of WM performance., Results: A blunted inverted-U response was observed in left dorsolateral prefrontal cortex in patients and was associated with behavioral deficits in WM capacity. In addition, suppression of medial prefrontal cortex during WM was reduced in patients and was associated with poorer WM capacity in patients. Finally, activation of visual cortex in the cuneus was elevated in patients and associated with improved WM capacity. Together, these findings explained 55% of the interindividual variance in WM capacity when combined with diagnostic and medication status, which alone accounted for only 22% of the variance in WM capacity., Conclusions: These findings identify a novel biomarker and putative mechanism of WM deficits in patients with schizophrenia, a reduction or flattening of the inverted-U relationship between activation and WM load observed in healthy individuals in left dorsolateral prefrontal cortex., (Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

The energetics of membrane-protein interactions determine protein topology and structure: hydrophobicity drives the insertion of helical segments into the membrane, and positive charges orient the protein with respect to the membrane plane according to the positive-inside rule. Until recently, however, quantifying these contributions met with difficulty, precluding systematic analysis of the energetic basis for membrane-protein topology. We recently developed the dsTβL method, which uses deep sequencing and in vitro selection of segments inserted into the bacterial plasma membrane to infer insertion-energy profiles for each amino acid residue across the membrane, and quantified the insertion contribution from hydrophobicity and the positive-inside rule. Here, we present a topology-prediction algorithm called TopGraph, which is based on a sequence search for minimum dsTβL insertion energy. Whereas the average insertion energy assigned by previous experimental scales was positive (unfavorable), the average assigned by TopGraph in a nonredundant set is -6.9 kcal/mol. By quantifying contributions from both hydrophobicity and the positive-inside rule we further find that in about half of large membrane proteins polar segments are inserted into the membrane to position more positive charges in the cytoplasm, suggesting an interplay between these two energy contributions. Because membrane-embedded polar residues are crucial for substrate binding and conformational change, the results implicate the positive-inside rule in determining the architectures of membrane-protein functional sites. This insight may aid structure prediction, engineering, and design of membrane proteins. TopGraph is available online (topgraph.weizmann.ac.il)., Competing Interests: The authors declare no conflict of interest.

Background: In-centre nocturnal hemodialysis (INHD, 7-8 hours/session, 3 times/week) is an increasingly utilized form of dialysis intensification, though data on the cardiovascular benefits of this modality are limited., Methods: In this prospective cohort study, we enrolled 67 prevalent conventional hemodialysis (CHD, 4 hours/session, 3 times/week) recipients at 2 medical centres in Canada, of whom 37 converted to INHD and 30 remained on CHD. The primary outcome was the change in left ventricular mass (LVM) after 1 year as assessed by cardiac magnetic resonance imaging. Secondary outcomes included changes in serum phosphate concentration, phosphate binder burden, haemoglobin, erythropoiesis stimulating agent usage, and blood pressure., Results: Conversion to INHD was associated with a 14.2 (95% confidence interval [CI] 1.2-27.2) g reduction in LVM as compared with continuation on CHD. This result was maintained after adjustment for baseline imbalances between the groups and in ancillary analyses. There was a trend toward a larger drop in systolic blood pressure (9.8 [95% CI, -1.4-20.9] mm Hg) among INHD recipients with a significant reduction in the number of prescribed antihypertensive agents (0.7 [95% CI, 0.3-1.1] agents). Serum phosphate declined by 0.40 (95% CI, 0.16-0.63) mmol/L among INHD recipients without any difference in calcium-based phosphate binder requirements, as compared with those who remained on CHD., Conclusions: Compared with continuation of CHD, conversion to INHD was associated with significant LVM regression and reduction in serum phosphate concentration at 1 year., (Copyright © 2016 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Depression remains a great societal burden and a major treatment challenge. Most antidepressant medications target serotonergic raphé nuclei. Acute tryptophan depletion (ATD) modulates serotonin function. To better understand the raphé's role in mood networks, we studied raphé functional connectivity in depression. Fifteen depressed patients were treated with sertraline for 12 weeks and scanned during ATD and sham conditions. Based on our previous findings in a separate cohort, resting state MRI functional connectivity between raphé and other depression-related regions (ROIs) was analyzed in narrow frequency bands. ATD decreased raphé functional connectivity with the bilateral thalamus within 0.025-0.05 Hz, and also decreased raphé functional connectivity with the right pregenual anterior cingulate cortex within 0.05-0.1 Hz. Using the control broadband filter 0.01-0.1 Hz, no significant differences in raphé-ROI functional connectivity were observed. Post-hoc analysis by remission status suggested increased raphé functional connectivity with left pregenual anterior cingulate cortex in remitters (n=10) and decreased raphé functional connectivity with left thalamus in non-remitters (n=5), both within 0.025-0.05 Hz. Reducing serotonin function appears to alter coordination of these mood-related networks in specific, low frequency ranges. For examination of effects of reduced serotonin function on mood-related networks, specific low frequency BOLD fMRI signals can identify regions implicated in neural circuitry and may enable clinically-relevant interpretation of functional connectivity measures. The biological significance of these low frequency signals detected in the raphé merits further study., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Background: Increased left ventricular mass (LVM) is associated with adverse outcomes in patients receiving chronic hemodialysis. Among patients receiving conventional hemodialysis (CHD, 3×/week, 4 hrs/session), we evaluated whether dialysis intensification with in-centre nocturnal hemodialysis (INHD, 3×/week, 7-8 hrs/session in the dialysis unit) was associated with regression of LVM., Methods: We conducted a retrospective cohort study of CHD recipients who converted to INHD and received INHD for at least 6 months. LVM on the first echocardiogram performed at least 6 months post-conversion was compared to LVM pre-conversion. In a secondary analysis, we examined echocardiograms performed at least 12 months after starting INHD. The effect of conversion to INHD on LVM over time was also evaluated using a longitudinal analysis that incorporated all LVM data on patients with 2 or more echocardiograms., Results: Thirty-seven patients were eligible for the primary analysis. Mean age at conversion was 49 ± 12 yrs and 30% were women. Mean pre-conversion LVM was 219 ± 66 g and following conversion, LVM declined by 32 ± 58 g (p = 0.002). Among patients whose follow-up echocardiogram occurred at least 12 months following conversion, LVM declined by 40 ± 56 g (p = 0.0004). The rate of change of LVM decreased significantly from 0.4 g/yr before conversion, to -11.7 g/yr following conversion to INHD (p < 0.0001)., Conclusion: Conversion to INHD is associated with a significant regression in LVM, which may portend a more favourable cardiovascular outcome. Our preliminary findings support the need for randomized controlled trials to definitively evaluate the cardiovascular effects of INHD.