Emerging structures and dynamic mechanisms of γ-secretase for Alzheimer's disease.

γ-Secretase, called "the proteasome of the membrane," is a membrane-embedded protease complex that cleaves 150+ peptide substrates with central roles in biology and medicine, including amyloid precursor protein and the Notch family of cell-surface receptors. Mutations in γ-secretase and amyloid precursor protein lead to early-onset familial Alzheimer's disease. γ-Secretase has thus served as a critical drug target for treating familial Alzheimer's disease and the more common late-onset Alzheimer's disease as well. However, critical gaps remain in understanding the mechanisms of processive proteolysis of substrates, the effects of familial Alzheimer's disease mutations, and allosteric modulation of substrate cleavage by γ-secretase. In this review, we focus on recent studies of structural dynamic mechanisms of γ-secretase. Different mechanisms, including the "Fit-Stay-Trim," "Sliding-Unwinding," and "Tilting-Unwinding," have been proposed for substrate proteolysis of amyloid precursor protein by γ-secretase based on all-atom molecular dynamics simulations. While an incorrect registry of the Notch1 substrate was identified in the cryo-electron microscopy structure of Notch1-bound γ-secretase, molecular dynamics simulations on a resolved model of Notch1-bound γ-secretase that was reconstructed using the amyloid precursor protein-bound γ-secretase as a template successfully captured γ-secretase activation for proper cleavages of both wildtype and mutant Notch, being consistent with biochemical experimental findings. The approach could be potentially applied to decipher the processing mechanisms of various substrates by γ-secretase. In addition, controversy over the effects of familial Alzheimer's disease mutations, particularly the issue of whether they stabilize or destabilize γ-secretase-substrate complexes, is discussed. Finally, an outlook is provided for future studies of γ-secretase, including pathways of substrate binding and product release, effects of modulators on familial Alzheimer's disease mutations of the γ-secretase-substrate complexes. Comprehensive understanding of the functional mechanisms of γ-secretase will greatly facilitate the rational design of effective drug molecules for treating familial Alzheimer's disease and perhaps Alzheimer's disease in general.

Radiotherapy and theranostics: a Lancet Oncology Commission.

Following on from the 2015 Lancet Oncology Commission on expanding global access to radiotherapy, Radiotherapy and theranostics: a Lancet Oncology Commission was created to assess the access and availability of radiotherapy to date and to address the important issue of access to the promising field of theranostics at a global level. A marked disparity in the availability of radiotherapy machines between high-income countries and low-income and middle-income countries (LMICs) has been identified previously and remains a major problem. The availability of a suitably trained and credentialled workforce has also been highlighted as a major limiting factor to effective implementation of radiotherapy, particularly in LMICs. We investigated initiatives that could mitigate these issues in radiotherapy, such as extended treatment hours, hypofractionation protocols, and new technologies. The broad implementation of hypofractionation techniques compared with conventional radiotherapy in prostate cancer and breast cancer was projected to provide radiotherapy for an additional 2·2 million patients (0·8 million patients with prostate cancer and 1·4 million patients with breast cancer) with existing resources, highlighting the importance of implementing new technologies in LMICs. A global survey undertaken for this Commission revealed that use of radiopharmaceutical therapy-other than 131I-was highly variable in high-income countries and LMICs, with supply chains, workforces, and regulatory issues affecting access and availability. The capacity for radioisotope production was highlighted as a key issue, and training and credentialling of health professionals involved in theranostics is required to ensure equitable access and availability for patient treatment. New initiatives-such as the International Atomic Energy Agency's Rays of Hope programme-and interest by international development banks in investing in radiotherapy should be supported by health-care systems and governments, and extended to accelerate the momentum generated by recognising global disparities in access to radiotherapy. In this Commission, we propose actions and investments that could enhance access to radiotherapy and theranostics worldwide, particularly in LMICs, to realise health and economic benefits and reduce the burden of cancer by accessing these treatments.

Occupational Participation Among Older Adults During the COVID-19 Pandemic.

Background. The COVID-19 pandemic led to abrupt occupational disruption for all people. However, some populations, like older adults, were disproportionately impacted particularly in the earlier waves. Purpose. The purpose of this study was to explore and understand how the occupational participation of community-dwelling older adults was experienced during the COVID-19 pandemic, using the Canadian Model of Occupational Participation (CanMOP) to contextualize findings. Method. Sixty-seven older adults participated in semi-structured interviews from September 2020 to May 2021, 37 of which also participated in a follow-up interview one-year later. Findings. Using reflexive thematic analysis, four themes were generated: (1) experiences of loss are complex and layered for older adults, (2) technology as a medium for occupational participation, (3) risk perception influences return to occupation, and (4) age-related challenges for older adults resuming volunteer work. Conclusion. Increasing frequency and severity of influenza pandemics and other disasters are a global concern, and OTs can use their skillsets to foster participation and expand occupational possibilities for older adults. The CanMOP was a helpful tool to understand the nuances underlying the participation of older adults in this context.

RREACT: A mobile multidisciplinary response to overdose.

Opioid overdose is a leading cause of death in the United States, and engaging with patients following overdose to provide harm reduction and recovery resources can prove difficult. Quick response models use mobile, multidisciplinary teams to establish a time-sensitive connection between individuals who overdosed and harm reduction and recovery resources that improve outcomes. These quick response models are consistent with the broader field of mobile-integrated health programs that are growing in number and acceptability, though the literature base is sparse and programs vary. We describe the 5-year reach, effectiveness, adoption, implementation and maintenance (RE-AIM) framework of the Rapid Response Emergency Addiction and Crisis Team (RREACT), a fire/emergency medical services-led, multidisciplinary (firefighter/paramedic, law enforcement officer, social worker) mobile outreach team. RREACT provides harm reduction, linkage/transportation to care and wrap-around services to individuals following a nonfatal opioid overdose that resulted in an emergency response in Columbus, Franklin County, Ohio, United States. Between 2018 and 2022, RREACT made 22,157 outreach attempts to 11,739 unique patients. RREACT recorded 3,194 direct patient contacts during this time, resulting in 1,200 linkages to care: 799 direct transports to opioid use disorder treatment and 401 warm handoffs to community treatment agencies. Furthermore, RREACT's staffing increased from 4 full-time equivalent staff in 2018 to 15.5 in 2022 and was supported by the surrounding community through 287 community outreach events and the development of an alumni program. These preliminary results further support the deployment of multidisciplinary mobile outreach teams to increase access to harm reduction and recovery resources following opioid overdose.

Sequential early-life viral infections modulate the microbiota and adaptive immune responses to systemic and mucosal vaccination.

Increasing evidence points to the microbial exposome as a critical factor in maturing and shaping the host immune system, thereby influencing responses to immune challenges such as infections or vaccines. To investigate the effect of early-life viral exposures on immune development and vaccine responses, we inoculated mice with six distinct viral pathogens in sequence beginning in the neonatal period, and then evaluated their immune signatures before and after intramuscular or intranasal vaccination against SARS-CoV-2. Sequential viral infection drove profound changes in all aspects of the immune system, including increasing circulating leukocytes, altering innate and adaptive immune cell lineages in tissues, and markedly influencing serum cytokine and total antibody levels. Beyond changes in the immune responses, these exposures also modulated the composition of the endogenous intestinal microbiota. Although sequentially-infected mice exhibited increased systemic immune activation and T cell responses after intramuscular and intranasal SARS-CoV-2 immunization, we observed decreased vaccine-induced antibody responses in these animals. These results suggest that early-life viral exposures are sufficient to diminish antibody responses to vaccination in mice, and highlight the potential importance of considering prior microbial exposures when investigating vaccine responses.

Impact of blood volume, air exposure duration, transport duration, and testing delay on plasma total carbon dioxide in simulated open collections using microtainers.

BACKGROUND: Exposing blood specimens to air reduces plasma total carbon dioxide (TCO2). We evaluated the degree of TCO2 reduction in simulated open collection of neonatal blood in BD microtainers® (microtainers), microtainer transport duration and delayed testing of open plasma aliquots. METHODS: Venous blood was aliquoted into open microtainers in a 3x4 factorial design to simulate combined effects of blood volume (0.2-0.6 mL) and air exposure duration (0-5 min), with blood drawn in vacutainers as a control. Separate effects of in-hospital transport duration (0-120 min; whole blood), off-site transport duration (0-24 h; centrifuged whole blood), and duration plasma aliquots remained open (0-120 min) were evaluated by repeated testing. Findings were analyzed using repeated-measures ANOVA and Student's T-tests. RESULTS: In the factorial experiment, mean plasma TCO2 in all microtainers was on average 3.5 mmol/L lower than in vacutainers. Smaller blood volume but not greater air exposure duration significantly (p < 0.05) reduced TCO2. Mean TCO2 in filled (0.6 mL; 1-5 min air exposure) microtainers was on average 2.9 mmol/L lower than in vacutainers. Simulated off-site transport of microtainers containing centrifuged whole blood significantly reduced TCO2 (4 h; mean -1.5 mmol/L), as did delayed testing of aliquoted plasma (15 min; mean -1.3 mmol/L). CONCLUSIONS: Plasma TCO2 decreased with reduced microtainer blood volume, extended transport duration of centrifuged blood and testing delay of aliquoted plasma. To minimize TCO2 reduction, microtainers should be fully filled and tested rapidly. Laboratories should also consider whether an interpretive comment, correction factor or separate reference intervals are appropriate for these tests.

A Novel Preoperative Risk Score to Identify Patients at High Risk for Non-Home Discharge After Elective Open Abdominal Aortic Aneurysm Repair.

BACKGROUND: Non-home discharge (NHD) to a rehabilitation or skilled nursing facility after vascular surgery is poorly described despite its impact on patients. For home-dwelling patients undergoing elective surgery, the need for postoperative NHD can have meaningful implications on quality of life, long-term outcomes, and healthcare spending. Understanding post-surgical NHD risk is essential to preoperative counseling and shared decision making. This is particularly true for the treatment of abdominal aortic aneurysms as the postoperative course can vary between open and endovascular surgery. We aimed to identify independent predictors of NHD following elective open abdominal aortic aneurysm repair (OAR), and to create a clinically useful preoperative risk score. METHODS: Elective OAR cases were queried from the SVS Vascular Quality Initiative from years 2013-2022. A risk score was created by splitting the data set into two-thirds for development and one-third for validation. A parsimonious stepwise hierarchical multivariable logistic regression controlling for hospital level variation was performed in the development dataset, and the beta-coefficients were used to assign points for a risk score. The score was then validated, and model performance assessed. RESULTS: Overall, 8,274 patients were included and 1,502 (18.2%) required NHD. At baseline, patients who required NHD were more likely to be ≥ 80 years old (23.6% vs. 6.5%), female (35.9% vs. 23.1%), not independently ambulatory (14.6% vs. 4.3%), anemic (24.4% vs. 13.9%), have COPD (41.6% vs. 30.7%), ASA class ≥ 4 (41.0% vs. 32.5%), and a supraceliac proximal clamp (9.8% vs. 5.7%; all P<0.05). Multivariable analysis in the development group identified the following independent predictors of NHD: age ≥ 80 years, not independently ambulatory, proximal clamp location, hypogastric artery occlusion, anemia (Hb <12 g/dL), chronic obstructive pulmonary disease, female sex, hypertension, and American Society of Anesthesiologists class ≥ 4. These were then used to create a 14-point risk score. Patients were stratified into three groups based upon their risk score: low risk (0-4 points; n=4,966) with an NHD rate of 9.9%, moderate risk (5-6 points; n=2,442) with an NHD rate of 25.5%, and high risk (≥ 7 points; n=886) with an NHD rate of 44.6%. The risk score had good predictive ability with c-statistic=0.73 for model development and c-statistic=0.72 in the validation dataset. CONCLUSIONS: This novel risk score can predict NHD following elective OAR using characteristics that can be identified preoperatively. Utilization of this score may allow for improved risk assessment, preoperative counseling, and shared decision making.

Promoting sustained access to cognitive behavioral therapy for insomnia in Australia: a system-level implementation program.

STUDY OBJECTIVES: Insomnia is a highly prevalent and debilitating disorder. Cognitive behavioral therapy for insomnia (CBTi) is the recommended 'fist line' treatment, but is accessed by a minority of people with insomnia. This paper describes a system-level implementation program to improve access to CBTi in Australia to inform CBTi implementation in other locations. METHODS: From 2019 to 2023, we conducted a program of work to promote sustained change in access to CBTi in Australia. Three distinct phases included 1) Scoping and mapping barriers to CBTi access, 2) Analysis and synthesis of barriers and facilitators to devise change goals, and 3) Structured promotion and coordination of change. We used a system-level approach, knowledge brokerage, and co-design, and drew on qualitative, quantitative, and implementation science methods. RESULTS: We identified barriers to CBTi access from the perspectives of people with insomnia, primary care clinicians, and the health system. A stakeholder advisory committee was convened to co-design change goals, identify modifiable barriers, devise program logic and drive change strategies. We commenced a program to promote system-level change in CBTi access via; improved awareness and education of insomnia among primary care clinicians, self-guided interventions, and advocating to Government for additional CBTi funding mechanisms. CONCLUSIONS: This implementation program made significant progress toward improving access to CBTi in Australia. Ongoing work is required to continue this program, as long-term system-level change requires significant and sustained time, effort and resources from multiple stakeholders. This program may be used to inform CBTi implementation activities in other locations.

α,ω-Alkanedibromides Form Low Conductance Chemisorbed Junctions with Silver Electrodes.

Chemical groups capable of connecting molecules physically and electrically between electrodes are of critical importance in molecular-scale electronics, influencing junction conductance, variability, and function. While the development of such linkage chemistries has focused on interactions at gold, the distinct reactivity and electronic structure of other electrode metals provides underexplored opportunities to characterize and exploit new binding motifs. In this work we show that α,ω-alkanedibromides spontaneously form well-defined junctions using silver, but not gold, electrodes through application of the glovebox-based scanning tunneling microscope-based break junction method. We systematically evaluate, through a series of additional studies, whether these molecular components form physisorbed or chemisorbed contact geometries, and if they undergo secondary chemical reactions at the silver surface. Critically, we find that the same junctions form when using different halide, or trimethylstannyl, terminal groups, suggestive of an electronically transparent silver-carbon(sp3) contact chemistry. However, the experimental conductance of the junctions we measure with silver electrodes is ∼30× lower than that observed for such junctions comprising gold-carbon(sp3) contacts, which does not align with predictions based on first-principles calculations. We further exclude the possibility that the proposed silver alkyl species undergo α- or ß-hydride elimination reactions that result in a distinct contact chemistry through conductance measurements of control molecules that cannot undergo such processes. Applying insights provided from prior temperature-programmed desorption studies and a robust series of atomistic simulations, we ultimately propose that in these experiments we measure alkoxide-terminated junctions formed from the reaction of the chemisorbed alkyl with oxygen that is coadsorbed on the silver surface. This work, in demonstrating that high conductance contact chemistries established using model gold electrodes may not be readily transferred to other metals, underscores the need to directly characterize the interfacial electronic properties and reactivity of electrode metals of wider technological relevance.

Natural and Nature-Inspired Catechol Siderophores: A Promising Strategy for Rice Blast Management.

The rice-blast fungus Pyricularia oryzae poses a significant threat to rice production worldwide. Ferroptosis, an iron-dependent form of regulated cell death, has recently been reported to be involved in P. oryzae pathogenicity during plant-fungal interactions. Ferroptosis regulates the developmental cell death of conidia necessary for appressorium maturation. In this study, we have established that a series of benzamides containing a chelating catechol moiety suppresses the formation/maturation of appressoria, which are essential for host infection by the rice blast fungus. Moreover, for the most active compounds we have shown that their activity can be at least partially reversed by adding exogenous Fe3+. These results highlight the close association between iron availability and appressorium maturation, opening new avenues for the development of targeted strategies for P. oryzae management.

Phase II Trial of Gemcitabine and nab-Paclitaxel for Recurrent Osteosarcoma with Serial Monitoring Using Liquid Biopsy: A Report from the National Pediatric Cancer Foundation.

BACKGROUND: The combination of gemcitabine and docetaxel is often used to treat patients with recurrent osteosarcoma. Nab-paclitaxel has preclinical activity against osteosarcoma and is potentially less myelosuppressive than docetaxel. We conducted a prospective multi-institutional phase II trial combining gemcitabine and nab-paclitaxel for patients 12-30 years with recurrent osteosarcoma and measurable disease. METHODS: A Simon's two-stage design was used to test a 4-month progression-free survival (PFS-4) of 10% vs. 35%. Patients received nab-paclitaxel 125 mg/m2 and gemcitabine 1000 mg/m2 weekly x 3 in 4-week cycles. Immunohistochemical analysis of archival tissue and serial assessment of circulating tumor cells (CTC) and circulating tumor DNA (ctDNA) using ultralow passage whole-genome sequencing were performed to identify potential biomarkers of response. RESULTS: Eighteen patients received 56 total cycles (median 2, range 1 - 12). Two patients (11%) experienced confirmed partial response, and 6 (33%) received > 2 cycles. The PFS-4 was 28% (95% CI 13-59%). Six patients required dose reductions and three patients were removed due to toxicities. All 18 patients had detectable CTCs, and 10 had ctDNA identified. All 8 patients with MYC amplification at study-entry experienced disease progression. CONCLUSIONS: Gemcitabine and nab-paclitaxel demonstrated similar clinical activity and toxicity compared to previous retrospective reports utilizing gemcitabine and docetaxel in patients with recurrent osteosarcoma. Serial analysis of CTC and ctDNA was feasible in this prospective multi-institution study and provides preliminary data on the use of these assays in patients with relapsed disease.

A spectrometer design that eliminates incoherent mixing signals in 2D action spectroscopies.

Action spectroscopies use a readout created by the action of light on the molecules or material rather than optical absorption. Ultrafast 2D photocurrent and 2D fluorescence spectroscopies are two such action spectroscopies. Despite their utility, multidimensional action spectroscopies suffer from a background created by incoherent population mixing. These backgrounds appear when the action of one molecule impacts that of another, creating a signal that mimics a fourth-order population response but is really just the convolution of two linear responses. The background created by incoherent mixing is often much larger than the desired foreground signals. In this paper, we describe the physical mechanisms that give rise to the incoherent signals, drawing Feynman paths for each. There are three variations of incoherent signals, differing by their pulse ordering. They all have the same phase dependence as the desired fourth-order population signals and so cannot be removed by standard phase cycling, but they do differ in their polarization responses and dephasing times. We propose, and implement, a spectrometer design that eliminates the background signals for isotropically oriented samples, leaving only the desired fourth-order 2D action spectra. Our spectrometer utilizes a TWINS interferometer and a pulse shaper interferometer, each driven with a different white-light source so that the pulse pairs within each interferometer are phase stable, but not between the two. The lack of phase stability between the two interferometers eliminates two of the three incoherent responses. The third incoherent response is eliminated with the polarization scheme ⟨0, π/2, π/4, π/4⟩. Our spectrometer also enables both 2D photocurrent and 2D white-light spectra to be collected simultaneously, thereby enabling a direct comparison between action and optical detection under identical conditions and at the exact same position on the sample. Using this spectrometer and photovoltaic devices made from thin films of semiconducting carbon nanotubes, we demonstrate 2D photocurrent spectra free of incoherent background.

Definitions of white matter hyperintensity change: impact on estimates of progression and regression.

BACKGROUND: White matter hyperintensity (WMH) progression is well documented; WMH regression is more contentious, which might reflect differences in defining WMH change. We compared four existing WMH change definitions in one population to determine the effect of definition on WMH regression. METHODS: We recruited patients with minor non-disabling ischaemic stroke who underwent MRI 1-3 months after stroke and 1 year later. We assessed WMH volume (in absolute mL and % intracranial volume) and applied four different definitions, including two thresholds (based on SD or mL), percentile and quintile approaches. RESULTS: In 198 participants, mean age 65.5 (SD=11.13), baseline WMH volume was 15.46 mL (SD=19.2), the mean net WMH volume change was 0.98 mL (SD=2.84), range -7.98 to +12.84 mL. Proportion regressing/stable/progressing WMH were threshold 1 (SD), 29.8%/55.6%/14.6%; threshold 2(mL), 29.8%/16.7%/53.5%; percentile approach, 28.3%/21.2%/50.5%. The quintile approach includes five groups with quintile 3 reflecting no change (N=40), quintiles 1 and 2 any WMH decrease (N=80) and quintiles 4 and 5 any WMH increase (N=78). CONCLUSIONS: Different WMH change definitions cause big differences in how participants are categorised; additionally, non-normal WMH distribution precludes use of some definitions. Consistent use of an appropriate definition would facilitate data comparisons, particularly in clinical trials of potential WMH treatments.

PSMA PET/CT patterns of recurrence after mono-brachytherapy in men with low and intermediate prostate cancer and subsequent management.

PURPOSE: Brachytherapy as monotherapy is a recommended treatment option for men with low to intermediate risk prostate cancer. Local recurrence is difficult to identify. This study investigated PSMA PET/CT for recurrence after brachytherapy, as well as their subsequent management when recurrence occurred only within the prostate. METHODS: We performed a retrospective single-center analysis for patients who were treated with brachytherapy as monotherapy for prostate cancer from May 2002 to May 2021 and who underwent a PSMA PET/CT for BCR. We report the findings on PSMA PET/CT, quantitative parameters, as well as the later management of the patients. RESULTS: Forty patients were identified, who underwent PSMA PET/CT to investigate a rising PSA at a median (IQR) of 7 years (3.0-10.8) after initial therapy. Median (IQR) PSA at time of PSMA PET/CT was 6.54 ng/mL (3.9-15.5). On PSMA PET/CT, 20/40 (50%) men had prostate-only recurrence. Of the 20 patients with prostate-only recurrence, 8/20 (40%) had recurrence in a high-dose radiation zone, versus 7/20 (35%) in an under-covered zone. On PSMA PET/CT, recurrence within the prostate had median (IQR) SUVmax 10.4 (5.1-15.7) and volume 2.9 mL (2.0-11.2). Subsequent management of these patients with local recurrence included surveillance followed by ADT (9/20, 45%). For those with surveillance followed by ADT, the mean time before introduction of ADT was 4.1 years (range 1-8 years).

Children's exposure to chemical contaminants: Demographic disparities and associations with the developing basal ganglia.

Children are regularly exposed to chemical contaminants that may influence brain development. However, relatively little is known about how these contaminants impact the developing human brain. Here, we combined silicone wristband exposure assessments with neuroimaging for the first time to examine how chemical contaminant mixtures are associated with the developing basal ganglia-a brain region key for the healthy development of emotion, reward, and motor processing, and which may be particularly susceptible to contaminant harm. Further, we examined demographic disparities in exposures to clarify which children were at highest risk for any contaminant-associated neurobiological changes. Participants included 62 community children (average age 7.00 years, 53% female, 66% White) who underwent structural neuroimaging to provide data on their basal ganglia structure and wore a silicone wristband for seven days to track their chemical contaminant exposure. 45 chemical contaminants-including phthalates and their alternatives, brominated flame retardants, organophosphate esters, pesticides, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls-were detected in over 75% of wristbands. Notable demographic disparities in exposure were present, such that Non-White and lower-income children were more exposed to several contaminants. Exposure to chemical contaminant mixtures was not associated with overall basal ganglia volume; however, two organophosphate esters (2IPPDPP and 4IPPDPP) were both associated with a larger globus pallidus, a basal ganglia sub-region. Results highlight demographic disparities in exposure and suggest possible risks to a brain region key for healthy emotional development.

Beyond Pallidal or Subthalamic Deep Brain Stimulation to Treat Dystonia.

Deep brain stimulation of the subthalamic nucleus and globus pallidus internus is approved by the Food and Drug Administration for treating dystonia. Both targets have shown effectiveness in improving symptoms, but post-operative outcomes can vary significantly among patients. This variability has led researchers to explore alternative neuromodulation targets that might offer more consistent results. Emerging research has highlighted several promising new targets for DBS in dystonia. This review examines pre-clinical and clinical data on novel DBS targets for dystonia and explores non-invasive neuromodulation studies that shed light on the disease's underlying pathological circuitry.