Comparative analytical performance of multiple plasma Aβ42 and Aβ40 assays and their ability to predict positron emission tomography amyloid positivity

INTRODUCTION: This report details the approach taken to providing a dataset allowing for analyses on the performance of recently developed assays of amyloid beta (Aβ) peptides in plasma and the extent to which they improve the prediction of amyloid positivity. METHODS: Alzheimer's Disease Neuroimaging Initiative plasma samples with corresponding amyloid positron emission tomography (PET) data were run on six plasma Aβ assays. Statistical tests were performed to determine whether the plasma Aβ measures significantly improved the area under the receiver operating characteristic curve for predicting amyloid PET status compared to age and apolipoprotein E (APOE) genotype. RESULTS: The age and APOE genotype model predicted amyloid status with an area under the curve (AUC) of 0.75. Three assays improved AUCs to 0.81, 0.81, and 0.84 (P < .05, uncorrected for multiple comparisons). DISCUSSION: Measurement of Aβ in plasma contributes to addressing the amyloid component of the ATN (amyloid/tau/neurodegeneration) framework and could be a first step before or in place of a PET or cerebrospinal fluid screening study. HIGHLIGHTS: The Foundation of the National Institutes of Health Biomarkers Consortium evaluated six plasma amyloid beta (Aβ) assays using Alzheimer's Disease Neuroimaging Initiative samples. Three assays improved prediction of amyloid status over age and apolipoprotein E (APOE) genotype. Plasma Aβ42/40 predicted amyloid positron emission tomography status better than Aβ42 or Aβ40 alone

Measures of Resting State EEG Rhythms for Clinical Trials in Alzheimer’s Disease:Recommendations of an Expert Panel

The Electrophysiology Professional Interest Area (EPIA) and Global Brain Consortium endorsed recommendations on candidate electroencephalography (EEG) measures for Alzheimer's disease (AD) clinical trials. The Panel reviewed the field literature. As most consistent findings, AD patients with mild cognitive impairment and dementia showed abnormalities in peak frequency, power, and "interrelatedness" at posterior alpha (8-12Hz) and widespread delta (&lt;4Hz) and theta (4-8Hz) rhythms in relation to disease progression and interventions. The following consensus statements were subscribed: (1) Standardization of instructions to patients, resting state EEG (rsEEG) recording methods, and selection of artifact-free rsEEG periods are needed; (2) power density and "interrelatedness" rsEEG measures (e.g., directed transfer function, phase lag index, linear lagged connectivity, etc.) at delta, theta, and alpha frequency bands may be use for stratification of AD patients and monitoring of disease progression and intervention; and (3) international multisectoral initiatives are mandatory for regulatory purposes

Acetate Causes Alcohol Hangover Headache in Rats

Background: The mechanism of veisalgia cephalgia or hangover headache is unknown. Despite a lack of mechanistic studies, there are a number of theories positing congeners, dehydration, or the ethanol metabolite acetaldehyde as causes of hangover headache. Methods: We used a chronic headache model to examine how pure ethanol produces increased sensitivity for nociceptive behaviors in normally hydrated rats. Results: Ethanol initially decreased sensitivity to mechanical stimuli on the face (analgesia), followed 4 to 6 hours later by inflammatory pain. Inhibiting alcohol dehydrogenase extended the analgesia whereas inhibiting aldehyde dehydrogenase decreased analgesia. Neither treatment had nociceptive effects. Direct administration of acetate increased nociceptive behaviors suggesting that acetate, not acetaldehyde, accumulation results in hangover-like hypersensitivity in our model. Since adenosine accumulation is a result of acetate formation, we administered an adenosine antagonist that blocked hypersensitivity. Discussion: Our study shows that acetate contributes to hangover headache. These findings provide insight into the mechanism of hangover headache and the mechanism of headache induction

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

PAIN FACILITATING NEURONS IN THE BRAINSTEM MEDIATE CUTANEOUS ALLODYNIA IN AN EXPERIMENTAL MODEL OF HEADACHE-RELATED PAIN

Migraine patients often demonstrate cutaneous allodynia, defined as a hypersensitivity of the skin to touch or mechanical stimuli that is considered non-noxious under normal circumstances. The allodynia sometimes begins intracranially and spreads, via unknown mechanisms, to extracranial regions. The goal of the study was to develop and validate a model of cutaneous allodynia triggered by dural inflammation for pain associated with headaches, and to explore neuronal and glial mechanisms underlying generalized allodynia. Inflammatory mediators (IM) were applied to the dura of unanesthetized rats via previously implanted cannulas and sensory thresholds of the face and hindpaws were characterized. IM elicited robust and time-related facial and hindpaw allodynia which peaked after approximately three hours as well as FOS expression in the trigeminal nucleus caudalis (TNC), indicative of central sensitization. These effects were reminiscent of cutaneous allodynia seen in patients with migraine or other primary headache conditions, and were reversed by agents used clinically in the treatment of migraine including sumatriptan, naproxen, CGRP-antagonist, and morphine. Consistent with clinical observations, the allodynia was unaffected by an NK-1 antagonist. Having established facial and hindpaw allodynia as a useful animal surrogate of headache-associated allodynia, we next showed that blocking pain-facilitating processes from the rostral ventromedial medulla (RVM) interfered with its expression. Inactivation of the RVM with local anesthetic, destruction of putative pain-facilitation cells, and blockade of cholecystokinin receptors all prevented or significantly attenuated IM-induced allodynia. Electrophysiological studies confirmed activation of pain-facilitating "ON" cells and transient suppression of "OFF" cells in the RVM following IM. Additionally, microinjection of the RVM with a microglial inhibitor or sumatriptan also inhibited the expression of IM-induced cutaneous allodynia as well as microglial activation. Facial and hindpaw allodynia associated with dural stimulation is a useful surrogate of pain associated with primary headache including migraine and may be exploited mechanistically for the development of novel therapeutic strategies for headache pain. The data also demonstrate a requirement for activation of descending facilitation from the RVM, likely reliant on neuronal-glial interactions, for the expression of cranial and extracranial cutaneous allodynia. Consequently, the findings are consistent with a brainstem generator of allodynia associated with headache disorders

PAIN FACILITATING NEURONS IN THE BRAINSTEM MEDIATE CUTANEOUS ALLODYNIA IN AN EXPERIMENTAL MODEL OF HEADACHE-RELATED PAIN

Migraine patients often demonstrate cutaneous allodynia, defined as a hypersensitivity of the skin to touch or mechanical stimuli that is considered non-noxious under normal circumstances. The allodynia sometimes begins intracranially and spreads, via unknown mechanisms, to extracranial regions. The goal of the study was to develop and validate a model of cutaneous allodynia triggered by dural inflammation for pain associated with headaches, and to explore neuronal and glial mechanisms underlying generalized allodynia. Inflammatory mediators (IM) were applied to the dura of unanesthetized rats via previously implanted cannulas and sensory thresholds of the face and hindpaws were characterized. IM elicited robust and time-related facial and hindpaw allodynia which peaked after approximately three hours as well as FOS expression in the trigeminal nucleus caudalis (TNC), indicative of central sensitization. These effects were reminiscent of cutaneous allodynia seen in patients with migraine or other primary headache conditions, and were reversed by agents used clinically in the treatment of migraine including sumatriptan, naproxen, CGRP-antagonist, and morphine. Consistent with clinical observations, the allodynia was unaffected by an NK-1 antagonist. Having established facial and hindpaw allodynia as a useful animal surrogate of headache-associated allodynia, we next showed that blocking pain-facilitating processes from the rostral ventromedial medulla (RVM) interfered with its expression. Inactivation of the RVM with local anesthetic, destruction of putative pain-facilitation cells, and blockade of cholecystokinin receptors all prevented or significantly attenuated IM-induced allodynia. Electrophysiological studies confirmed activation of pain-facilitating "ON" cells and transient suppression of "OFF" cells in the RVM following IM. Additionally, microinjection of the RVM with a microglial inhibitor or sumatriptan also inhibited the expression of IM-induced cutaneous allodynia as well as microglial activation. Facial and hindpaw allodynia associated with dural stimulation is a useful surrogate of pain associated with primary headache including migraine and may be exploited mechanistically for the development of novel therapeutic strategies for headache pain. The data also demonstrate a requirement for activation of descending facilitation from the RVM, likely reliant on neuronal-glial interactions, for the expression of cranial and extracranial cutaneous allodynia. Consequently, the findings are consistent with a brainstem generator of allodynia associated with headache disorders

The Alzheimer's Association appropriate use recommendations for blood biomarkers in Alzheimer's disease

Blood-based markers (BBMs) have recently shown promise to revolutionize the diagnostic and prognostic work-up of Alzheimer's disease (AD), as well as to improve the design of interventional trials. Here we discuss in detail further research needed to be performed before widespread use of BBMs. We already now recommend use of BBMs as (pre-)screeners to identify individuals likely to have AD pathological changes for inclusion in trials evaluating disease-modifying therapies, provided the AD status is confirmed with positron emission tomography (PET) or cerebrospinal fluid (CSF) testing. We also encourage studying longitudinal BBM changes in ongoing as well as future interventional trials. However, BBMs should not yet be used as primary endpoints in pivotal trials. Further, we recommend to cautiously start using BBMs in specialized memory clinics as part of the diagnostic work-up of patients with cognitive symptoms and the results should be confirmed whenever possible with CSF or PET. Additional data are needed before use of BBMs as stand-alone diagnostic AD markers, or before considering use in primary care

Activation of TRPA1 on dural afferents: a potential mechanism of headache pain

Activation of transient receptor potential ankyrin-1 (TRPA1) on meningeal nerve endings has been suggested to contribute to environmental irritant-induced headache, but this channel may also contribute to other forms of headache, such as migraine. The preclinical studies described here examined functional expression of TRPA1 on dural afferents and investigated whether activation of TRPA1 contributes to headache-like behaviors. Whole-cell patch-clamp recordings were performed in vitro with 2 TRPA1 agonists, mustard oil (MO), and the environmental irritant umbellulone (UMB) on dural-projecting trigeminal ganglion neurons. Application of MO and UMB to dural afferents produced TRPA1-like currents in approximately 42% and 38% of cells, respectively. By means of an established in vivo behavioral model of migraine-related allodynia, dural application of MO and UMB produced robust time-related tactile facial and hind paw allodynia that was attenuated by pretreatment with the TRPA1 antagonist HC-030031. Additionally, MO or UMB were applied to the dura, and exploratory activity was monitored for 30min with an automated open-field activity chamber. Dural MO and UMB decreased the number of vertical rearing episodes and the time spent rearing in comparison to vehicle-treated animals. This change in activity was prevented in rats pretreated with HC-030031 as well as sumatriptan, a clinically effective antimigraine agent. These data indicate that TRPA1 is expressed on a substantial fraction of dural afferents, and activation of meningeal TRPA1 produces behaviors consistent with those observed in patients during migraine attacks. Further, they suggest that activation of meningeal TRPA1 via endogenous or exogenous mechanisms can lead to afferent signaling and headache