All-optical frequency division on-chip using a single laser.

The generation of spectrally pure microwave signals is a critical functionality in fundamental and applied sciences, including metrology and communications. Optical frequency combs enable the powerful technique of optical frequency division (OFD) to produce microwave oscillations of the highest quality1,2. Current implementations of OFD require multiple lasers, with space- and energy-consuming optical stabilization and electronic feedback components, resulting in device footprints incompatible with integration into a compact and robust photonic platform3-5. Here we demonstrate all-optical OFD on a photonic chip by synchronizing two distinct dynamical states of Kerr microresonators pumped by a single continuous-wave laser. The inherent stability of the terahertz beat frequency between the signal and idler fields of an optical parametric oscillator is transferred to a microwave frequency of a Kerr soliton comb, and synchronization is achieved via a coupling waveguide without the need for electronic locking. OFD factors of N = 34 and 468 are achieved for 227 GHz and 16 GHz soliton combs, respectively. In particular, OFD enables a 46 dB phase-noise reduction for the 16 GHz soliton comb, resulting in the lowest microwave noise observed in an integrated photonics platform. Our work represents a simple, effective approach for performing OFD and provides a pathway towards chip-scale devices that can generate microwave frequencies comparable to the purest tones produced in metrological laboratories.

JBrowse Jupyter: a Python interface to JBrowse 2.

MOTIVATION: JBrowse Jupyter is a package that aims to close the gap between Python programming and genomic visualization. Web-based genome browsers are routinely used for publishing and inspecting genome annotations. Historically they have been deployed at the end of bioinformatics pipelines, typically decoupled from the analysis itself. However, emerging technologies such as Jupyter notebooks enable a more rapid iterative cycle of development, analysis and visualization. RESULTS: We have developed a package that provides a Python interface to JBrowse 2's suite of embeddable components, including the primary Linear Genome View. The package enables users to quickly set up, launch and customize JBrowse views from Jupyter notebooks. In addition, users can share their data via Google's Colab notebooks, providing reproducible interactive views. AVAILABILITY AND IMPLEMENTATION: JBrowse Jupyter is released under the Apache License and is available for download on PyPI. Source code and demos are available on GitHub at https://github.com/GMOD/jbrowse-jupyter.

Integrated organismal responses induced by projected levels of CO2 and temperature exposures in the early life stages of lake sturgeon.

Atmospheric CO2 and temperature are rising concurrently, and may have profound impacts on the transcriptional, physiological and behavioural responses of aquatic organisms. Further, spring snowmelt may cause transient increases of pCO2 in many freshwater systems. We examined the behavioural, physiological and transcriptomic responses of an ancient fish, the lake sturgeon (Acipenser fulvescens) to projected levels of warming and pCO2 during its most vulnerable period of life, the first year. Specifically, larval fish were raised in either low (16°C) or high (22°C) temperature, and/or low (1000 µatm) or high (2500 µatm) pCO2 in a crossed experimental design over approximately 8 months. Following overwintering, lake sturgeon were exposed to a transient increase in pCO2 of 10,000 µatm, simulating a spring melt based on data in freshwater systems. Transcriptional analyses revealed potential connections to otolith formation and reduced growth in fish exposed to high pCO2 and temperature in combination. Network analyses of differential gene expression revealed different biological processes among the different treatments on the edges of transcriptional networks. Na+/K+-ATPase activity increased in fish not exposed to elevated pCO2 during development, and mRNA abundance of the ß subunit was most strongly predictive of enzyme activity. Behavioural assays revealed a decrease in total activity following an acute CO2 exposure. These results demonstrate compensatory and compounding mechanisms of pCO2 and warming dependent on developmental conditions in lake sturgeon. Conserved elements of the cellular stress response across all organisms provide key information for how other freshwater organisms may respond to future climate change.

Suture Augmentation of a Four-Strand Semitendinosus Graft Improves Time-Zero Biomechanical Properties.

PURPOSE: To compare the time-zero biomechanical properties of hamstring graft preparations with or without suture augmentation for anterior cruciate ligament reconstruction (ACLR) in a full-construct cadaveric model. METHODS: Hamstring grafts were harvested from 24 fresh frozen human cadavers and prepared in 1 of 3 ways: quadrupled SemiTendinosus (SemiT), and quadrupled SemiT with suture augmentation (SemiT+2.0-mm tape or SemiT+1.3-mm tape; n = 8 per group). Adjustable loop suspensory implants and cortical buttons were used for fixation on a porcine tibia and acrylic block. Testing included force-controlled cyclic loading at 250 N and 400 N followed by load to failure. RESULTS: The 2 suture augmentation groups had less total elongation and increased stiffness compared to the nonsuture-augmented group (P = .025). The SemiT+2.0-mm tape group had 36% less total elongation and 34% increased stiffness compared to SemiT+1.3mm tape (P < .001). CONCLUSIONS: Suture augmentation improves construct biomechanics at time zero following hamstring tendon ACLR. Augmentation with 2.0-mm tape suture improves construct biomechanics compared to 1.3-mm tape suture. CLINICAL RELEVANCE: Independent suture augmentation of a quadrupled SemiT graft improves ACLR construct biomechanics. Outcomes were improved with augmentation using 2.0-mm tape suture compared to 1.3-mm tape suture.

Gene flow influences the genomic architecture of local adaptation in six riverine fish species.

Understanding how gene flow influences adaptive divergence is important for predicting adaptive responses. Theoretical studies suggest that when gene flow is high, clustering of adaptive genes in fewer genomic regions would protect adaptive alleles from recombination and thus be selected for, but few studies have tested it with empirical data. Here, we used restriction site-associated sequencing to generate genomic data for six fish species with contrasting life histories from six reaches of the Upper Mississippi River System, USA. We used four differentiation-based outlier tests and three genotype-environment association analyses to define neutral single nucleotide polymorphisms (SNPs) and outlier SNPs that were putatively under selection. We then examined the distribution of outlier SNPs along the genome and investigated whether these SNPs were found in genomic islands of differentiation and inversions. We found that gene flow varied among species, and outlier SNPs were clustered more tightly in species with higher gene flow. The two species with the highest overall FST (0.0303-0.0720) and therefore lowest gene flow showed little evidence of clusters of outlier SNPs, with outlier SNPs in these species spreading uniformly across the genome. In contrast, nearly all outlier SNPs in the species with the lowest FST (0.0003) were found in a single large putative inversion. Two other species with intermediate gene flow (FST  ~ 0.0025-0.0050) also showed clustered genomic architectures, with most islands of differentiation clustered on a few chromosomes. Our results provide important empirical evidence to support the hypothesis that increasingly clustered architecture of local adaptation is associated with high gene flow.

The full spectrum tuning of fluorescent molecules via a one-pot multicomponent reaction.

Fluorogenic probes for imaging enable visualization and analysis of difficult-to-reach cells and organelles. However, there are limited efficient examples of tuning these fluorescent molecules to higher wavelengths. This is vital since different tissues are sensitive to varying wavelength emissions. To address this need, we report the discovery, tuning, structure-photophysical property relationships (SPPR), and time-dependent DFT (TD-DFT) computations of 400-700+ nm fluorescent pyrido[2',1':2,3]imidazo[4,5-c]isoquinolines and substituted imidazo[1,2-a]pyridin-3-amines. The syntheses involve the trimethylsilylcyanide (TMSCN) modified Groebke-Blackburn-Bienaymé (GBB) multicomponent reaction as well as the TMSCN modified GBB combined with subsequent condensation of an aldehyde, and Aza-Friedel-Crafts-Intramolecular Cyclization-Oxidation all in one pot. The SPPR reveals that electron-withdrawing strength in the para-position of the aminopyridine starting material has direct control over the absorption and fluorescence emission wavelengths of these molecules. The TD-DFT computations show the changes in the natural transition orbitals (NTOs) with differing substitutions to the parent molecule that dictate the observed excitations, emissions, and fluorescence intensities. These findings give insights and directions for tuning the fluorescent properties of these motifs for various uses as probes and imaging agents.

Location and Progression of Chondral Injuries at the Time of Revision ACL Surgery Varies by Sex.

PURPOSE: To quantify progression of chondral and meniscal injuries between primary and revision anterior cruciate ligament (ACL) surgery. METHODS: Patients who underwent both index and revision ACL reconstruction between 2000 and 2020 at our institution were identified, and dates of injury and surgery, demographics, and clinical data were obtained from operative reports. Outerbridge grade was recorded in each compartment, along with presence and location of meniscal injury. The frequency of each injury between first and second cases was calculated. Differences in injury and progression were compared over time as well as between patient sex and age. RESULTS: The study included 189 patients (96 female, 93 male). Age at first surgery was 31.7 ± 13.2 years. Mean time to second injury was 3.3 ± 3.0 years. In total, 116 patients had a new or previous chondral injury (odds ratio, 1.6; 95% CI, 1.2-2.1). The medial femoral condyle (31%) and the patella (21%) accounted for the highest proportion of new injury to articular surfaces, whereas new injury to menisci was comparable between the medial (25%) and lateral (23%) meniscus. At the time of revision ACL reconstruction, females had a high prevalence of chondral injuries to the lateral compartment, whereas males had a high prevalence of chondral injury to the medial femoral condyle. The prevalence of new chondral injuries was comparable between sexes, with males having a slightly higher proportion. While time between surgeries, sex, and age had graphical evidence of moderating risk, the effects were small and imprecise. CONCLUSIONS: Revision ACL reconstruction carried a 1.6 increase in the odds for new or progressive chondral lesions in our cohort. At the time of revision, females had a relatively higher proportion of lateral-sided chondral injuries, whereas males had a relatively higher proportion of medial femoral condyle injuries. The greatest increase in the prevalence of new and progressive lesions was observed in the medial femoral condyle and trochlea. This progression appeared to be moderated by time between surgeries, patient sex, and age; however, the differences were small and imprecise. STUDY DESIGN: Level IV, therapeutic case series.

The "Syringe Hickey": An Alternative Skin Marking Method for Lumbar Puncture.

BACKGROUND: Lumbar puncture is a procedure that is commonly performed in emergency departments. Despite their absence from procedure kits, emergency physicians often use skin markers to delineate landmarks for a lumbar puncture. We prefer to create a temporary indentation in the skin using the suction of a syringe. This "syringe hickey" eliminates the need for a skin marker. DISCUSSION: We created a photo demonstration comparing the syringe hickey to a skin marker for site marking. The syringe hickey was created using a 10-mL syringe aspirated to 5 mL on the forearm for 1 min. The syringe hickey lasted over 30 min on a range of skin tones across the Fitzpatrick Scale. The skin marker faded but the syringe hickey maintained its definition after application of ultrasound gel and sterilization with either chlorhexidine or betadine. CONCLUSIONS: The syringe hickey is a simple skin marking technique that is resistant to antiseptic agents and ultrasound gel. The syringe hickey may be useful for other procedures that require puncture site marking.

Ultrasound evaluation of intraluminal magnets in an ex vivo model.

PURPOSE: The management of foreign body ingestion proves to be a challenge. Magnets pose a unique set of risks when ingested due to their attractive forces and subsequent risk of adherence, pressure necrosis, and perforation complications. Radiographs only provide a limited snapshot in the setting of multiple magnet ingestion when the risk of complication is highest. We hypothesize that abdominal ultrasound (US) has the potential to supplement radiographs in assessing ingested magnets by determining the presence of bowel loop entrapment and of any extraluminal fluid. METHODS: We recreated various scenarios of magnet configurations using animal cadaveric bowel models. X-ray and US images were obtained in various bowel-magnet orientations. RESULTS: We identified several key US features to suggest bowel wall tethering. These include direct visualization of bowel wall entrapment between magnets (what we term the "dangerous V sign"), anti-dependent positions of the magnets, and inability to separate loops of bowel with compression. CONCLUSION: These findings could potentially provide valuable information when directing the urgency of intervention in foreign body ingestion. Ultrasound may supplement and improve the current guidelines in management of magnet ingestion.

DRAM for distilling microbial metabolism to automate the curation of microbiome function.

Microbial and viral communities transform the chemistry of Earth's ecosystems, yet the specific reactions catalyzed by these biological engines are hard to decode due to the absence of a scalable, metabolically resolved, annotation software. Here, we present DRAM (Distilled and Refined Annotation of Metabolism), a framework to translate the deluge of microbiome-based genomic information into a catalog of microbial traits. To demonstrate the applicability of DRAM across metabolically diverse genomes, we evaluated DRAM performance on a defined, in silico soil community and previously published human gut metagenomes. We show that DRAM accurately assigned microbial contributions to geochemical cycles and automated the partitioning of gut microbial carbohydrate metabolism at substrate levels. DRAM-v, the viral mode of DRAM, established rules to identify virally-encoded auxiliary metabolic genes (AMGs), resulting in the metabolic categorization of thousands of putative AMGs from soils and guts. Together DRAM and DRAM-v provide critical metabolic profiling capabilities that decipher mechanisms underpinning microbiome function.

Second-generation IL-2 receptor-targeted diphtheria fusion toxin exhibits antitumor activity and synergy with anti-PD-1 in melanoma.

Denileukin diftitox (DAB-IL-2, Ontak) is a diphtheria-toxin-based fusion protein that depletes CD25-positive cells including regulatory T cells and has been approved for the treatment of persistent or recurrent cutaneous T cell lymphoma. However, the clinical use of denileukin diftitox was limited by vascular leak toxicity and production issues related to drug aggregation and purity. We found that a single amino acid substitution (V6A) in a motif associated with vascular leak induction yields a fully active, second-generation biologic, s-DAB-IL-2(V6A), which elicits 50-fold less human umbilical vein endothelial cell monolayer permeation and is 3.7-fold less lethal to mice by LD50 analysis than s-DAB-IL-2. Additionally, to overcome aggregation problems, we developed a production method for the fusion toxin using Corynebacterium diphtheriae that secretes fully folded, biologically active, monomeric s-DAB-IL-2 into the culture medium. Using the poorly immunogenic mouse B16F10 melanoma model, we initiated treatment 7 days after tumor challenge and observed that, while both s-DAB-IL-2(V6A) and s-DAB-IL-2 are inhibitors of tumor growth, the capacity to treat with higher doses of s-DAB-IL-2(V6A) could provide a superior activity window. In a sequential dual-therapy study in tumors that have progressed for 10 days, both s-DAB-IL-2(V6A) and s-DAB-IL-2 given before checkpoint inhibition with anti-programmed cell death-1 (anti-PD-1) antibodies inhibited tumor growth, while either drug given as monotherapy had less effect. s-DAB-IL-2(V6A), a fully monomeric protein with reduced vascular leak, is a second-generation diphtheria-toxin-based fusion protein with promise as a cancer immunotherapeutic both alone and in conjunction with PD-1 blockade.

Chemogenetic Modulation and Single-Photon Calcium Imaging in Anterior Cingulate Cortex Reveal a Mechanism for Effort-Based Decisions.

The ACC is implicated in effort exertion and choices based on effort cost, but it is still unclear how it mediates this cost-benefit evaluation. Here, male rats were trained to exert effort for a high-value reward (sucrose pellets) in a progressive ratio lever-pressing task. Trained rats were then tested in two conditions: a no-choice condition where lever-pressing for sucrose was the only available food option, and a choice condition where a low-value reward (lab chow) was freely available as an alternative to pressing for sucrose. Disruption of ACC, via either chemogenetic inhibition or excitation, reduced lever-pressing in the choice, but not in the no-choice, condition. We next looked for value coding cells in ACC during effortful behavior and reward consumption phases during choice and no-choice conditions. For this, we used in vivo miniaturized fluorescence microscopy to reliably track responses of the same cells and compare how ACC neurons respond during the same effortful behavior where there was a choice versus when there was no-choice. We found that lever-press and sucrose-evoked responses were significantly weaker during choice compared with no-choice sessions, which may have rendered them more susceptible to chemogenetic disruption. Together, findings from our interference experiments and neural recordings suggest that a mechanism by which ACC mediates effortful decisions is in the discrimination of the utility of available options. ACC regulates these choices by providing a stable population code for the relative value of different options.SIGNIFICANCE STATEMENT The ACC is implicated in effort-based decision-making. Here, we used chemogenetics and in vivo calcium imaging to explore its mechanism. Rats were trained to lever press for a high-value reward and tested in two conditions: a no-choice condition where lever-pressing for the high-value reward was the only option, and a choice condition where a low-value reward was also available. Inhibition or excitation of ACC reduced effort toward the high-value option, but only in the choice condition. Neural responses in ACC were weaker in the choice compared with the no-choice condition. A mechanism by which ACC regulates effortful decisions is in providing a stable population code for the discrimination of the utility of available options.

Long-Term Characterization of Hippocampal Remapping during Contextual Fear Acquisition and Extinction.

Hippocampal CA1 place cell spatial maps are known to alter their firing properties in response to contextual fear conditioning, a process called "remapping." In the present study, we use chronic calcium imaging to examine remapping during fear retrieval and extinction of an inhibitory avoidance task in mice of both sexes over an extended period of time and with thousands of neurons. We demonstrate that hippocampal ensembles encode space at a finer scale following fear memory acquisition. This effect is strongest near the shock grid. We also characterize the long-term effects of shock on place cell ensemble stability, demonstrating that shock delivery induces several days of high fear and low between-session place field stability, followed by a new, stable spatial representation that appears after fear extinction. Finally, we identify a novel group of CA1 neurons that robustly encode freeze behavior independently from spatial location. Thus, following fear acquisition, hippocampal CA1 place cells sharpen their spatial tuning and dynamically change spatial encoding stability throughout fear learning and extinction.SIGNIFICANCE STATEMENT The hippocampus contains place cells that encode an animal's location. This spatial code updates, or remaps, in response to environmental change. It is known that contextual fear can induce such remapping; in the present study, we use chronic calcium imaging to examine inhibitory avoidance-induced remapping over an extended period of time and with thousands of neurons and demonstrate that hippocampal ensembles encode space at a finer scale following electric shock, an effect which is enhanced by threat proximity. We also identify a novel group of freeze behavior-activated neurons. These results suggest that, more than merely shuffling their spatial code following threat exposure, place cells enhance their spatial coding with the possible benefit of improved threat localization.

14-3-3 proteins protect AMPK-phosphorylated ten-eleven translocation-2 (TET2) from PP2A-mediated dephosphorylation.

Ten-eleven translocation-2 (TET2) is a member of the methylcytosine dioxygenase family of enzymes and has been implicated in cancer and aging because of its role as a global epigenetic modifier. TET2 has a large N-terminal domain and a catalytic C-terminal region. Previous reports have demonstrated that the TET2 catalytic domain remains active independently of the N-terminal domain. As such, the function of the N terminus of this large protein remains poorly characterized. Here, using yeast two-hybrid screening, co-immunoprecipitation, and several biochemical assays, we found that several isoforms of the 14-3-3 family of proteins bind TET2. 14-3-3 proteins bound TET2 when it was phosphorylated at Ser-99. In particular, we observed that AMP-activated protein kinase-mediated phosphorylation at Ser-99 promotes TET2 stability and increases global DNA 5-hydroxymethylcytosine levels. The interaction of 14-3-3 proteins with TET2 protected the Ser-99 phosphorylation, and disruption of this interaction both reduced TET2 phosphorylation and decreased TET2 stability. Furthermore, we noted that protein phosphatase 2A can interact with TET2 and dephosphorylate Ser-99. Collectively, these results provide detailed insights into the role of the TET2 N-terminal domain in TET2 regulation. Moreover, they reveal the dynamic nature of TET2 protein regulation that could have therapeutic implications for disease states resulting from reduced TET2 levels or activity.

Influenza and SARS-CoV-2 Co-infections in California, USA, September 2020-April 2021.

During September 1, 2020-April 30, 2021, the California Department of Public Health, Richmond, California, USA, received 255 positive influenza molecular test results that matched with severe acute respiratory syndrome coronavirus 2 molecular test results; 58 (23%) persons were co-infected. Influenza activity was minimal in California, and co-infections were sporadic.

A mobile sex-determining region, male-specific haplotypes and rearing environment influence age at maturity in Chinook salmon.

Variation in age at maturity is an important contributor to life history and demographic variation within and among species. The optimal age at maturity can vary by sex, and the ability of each sex to evolve towards its fitness optimum depends on the genetic architecture of maturation. Using GWAS of RAD sequencing data, we show that age at maturity in Chinook salmon exhibits sex-specific genetic architecture, with age at maturity in males influenced by large (up to 20 Mb) male-specific haplotypes. These regions showed no such effect in females. We also provide evidence for translocation of the sex-determining gene between two different chromosomes. This has important implications for sexually antagonistic selection, particularly that sex linkage of adaptive genes may differ within and among populations based on chromosomal location of the sex-determining gene. Our findings will facilitate research into the genetic causes of shifting demography in Chinook salmon as well as a better understanding of sex determination in this species and Pacific salmon in general.

Copper-Free Click Enabled Triazabutadiene for Bioorthogonal Protein Functionalization.

Aryl diazonium ions have long been used in bioconjugation due to their reactivity toward electron-rich aryl residues, such as tyrosine. However, their utility in biological systems has been restricted due to the requirement of harsh conditions for their generation in situ, as well as limited hydrolytic stability. Previous work describing a scaffold known as triazabutadiene (TBD) has shown the ability to protect aryl diazonium ions allowing for increased synthetic utility, as well as triggered release under biologically relevant conditions. Herein, we describe the synthesis and application of a novel TBD, capable of installation of a cyclooctyne on protein surfaces for later use of copper-free click reactions involving functional azides. The probe shows efficient protein labeling across a wide pH range that can be accomplished in a convenient and timely manner. Orthogonality of the cyclooctyne modification was showcased by labeling a model protein in the presence of hen egg proteins, using an azide-containing fluorophore. We further confirmed that the azobenzene modification can be cleaved using sodium dithionite treatment.

Protein Modification via Mild Photochemical Isomerization of Triazenes to Release Aryl Diazonium Ions.

This work describes the development of phenyl diazenyl piperidine triazene derivatives that can be activated to release aryl diazonium ions for labeling of proteins using light. These probes show marked bench stability at room temperature and can be photoisomerized via low-intensity UVA irradiation at physiological pH. Upon isomerization, the triazenes are rendered more basic and readily protonate to release reactive aryl diazonium ions. It was discovered that the intensity and duration of the UV light was essential to the observed diazonium ion reactivity in competition with the traditionally observed photolytic radical pathways. The combination of their synthetic efficiency coupled with their overall stability makes triazenes an attractive candidate for use in bioconjugation applications. Bioorthogonal handles on the triazenes are used to demonstrate the ease by which proteins can be modified.

Instantaneous microwave-photonic spatial-spectral channelization via k-space imaging.

The ability to both spatially and spectrally demultiplex wireless transmitters enables communication networks with higher spectral and energy efficiency. In practice, demultiplexing requires sub-millisecond latency to map the dynamics of the user space in real-time. Here, we present a system architecture, referred to as k-space imaging, which channelizes the radio frequency signals both spatially and spectrally through optical beamforming, where the latency is limited only by the speed of light traversing the optical components of the receiver. In this architecture, a phased antenna array samples radio signals, which are then coupled into electro-optic modulators (EOM) that coherently up-convert these signals to the optical domain, preserving their relative phases. The received signals, now optical sidebands, are transmitted in optical fibers of varying path lengths, which act as true time delays that yield frequency-dependent optical phases. The output facets of the optical fibers form a two-dimensional optical phased array in an arrangement preserving the phases generated by the angle of arrival (AoA) and the time-delay phases. Directing the beams emanating from the fibers through an optical lens produces a two-dimensional Fourier transform of the optical field at the fiber array. Accordingly, the optical beam formed at the back focal plane of the lens is steered based upon the phases, providing the angle of arrival and instantaneous frequency measurement (IFM), with latency determined by the speed of light over the optical path length. We present a numerical evaluation and experimental demonstration of this passive AoA- and frequency-detection capability.

Endocannabinoids and related lipids in serum from patients with amyotrophic lateral sclerosis.

BACKGROUND: The goals of this study were to determine whether serum concentrations of endocannabinoids (eCB) and related lipids predict disease status in patients with amyotrophic lateral sclerosis (ALS) relative to healthy controls, and whether concentrations correlate with disease duration and severity. METHODS: Serum concentrations of the eCBs 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (AEA), and related lipids palmitoylethanolamine (PEA), oleoylethanolamine (OEA), and 2-oleoylglycerol (2-OG), were measured in samples from 47 patients with ALS and 19 healthy adults. Hierarchical binary logistic and linear regression analyses assessed whether lipid concentrations predicted disease status (ALS or healthy control), duration, or severity. RESULTS: Binary logistic regression revealed that, after controlling for age and gender, 2-AG, 2-OG and AEA concentrations were unique predictors of the presence of ALS, demonstrating odds ratios of 0.86 (P = .039), 1.03 (P = .023), and 42.17 (P = .026), respectively. When all five lipids and covariates (age, sex, race, ethnicity, body mass index, presence of a feeding tube) were included, the resulting model had an overall classification accuracy of 92.9%. Hierarchical linear regression analyses indicated that in patients with ALS, AEA and OEA inversely correlated with disease duration (P = .030 and .031 respectively), while PEA demonstrated a positive relationship with disease duration (P = .013). None of the lipids examined predicted disease severity. CONCLUSIONS: These findings support previous studies indicating significant alterations in concentrations of circulating lipids in patients with ALS. They suggest that arachidonic and oleic acid containing small lipids may serve as biomarkers for identifying the presence and duration of this disease.