The subthreshold-active KV7 current regulates neurotransmission by limiting spike-induced Ca2+ influx in hippocampal mossy fiber synaptic terminals

Little is known about the properties and function of ion channels that affect synaptic terminal-resting properties. One particular subthreshold-active ion channel, the Kv7 potassium channel, is highly localized to axons, but its role in regulating synaptic terminal intrinsic excitability and release is largely unexplored. Using electrophysiological recordings together with computational modeling, we found that the KV7 current was active at rest in adult hippocampal mossy fiber synaptic terminals and enhanced their membrane conductance. The current also restrained action potential-induced Ca2+ influx via N- and P/Q-type Ca2+ channels in boutons. This was associated with a substantial reduction in the spike half-width and afterdepolarization following presynaptic spikes. Further, by constraining spike-induced Ca2+ influx, the presynaptic KV7 current decreased neurotransmission onto CA3 pyramidal neurons and short-term synaptic plasticity at the mossy fiber-CA3 synapse. This is a distinctive mechanism by which KV7 channels influence hippocampal neuronal excitability and synaptic plasticity.

Acetylcholine and cholinergic receptors

This review provides a distillate of the advances in knowledge about the neurotransmitter functions of acetylcholine over the 50-year period between 1967 and 2017, together with incremental information about the cognate nicotinic and muscarinic acetylcholine receptors, and some brief comments on possible advances in the near future. The text is supplemented by a timelines figure indicating the dates of some key advances in knowledge about acetylcholine receptors and a box-figure providing a snapshot of selected papers about acetylcholine published in the year 1967.

The latitude-dependent autoimmune disease risk genes ZMIZ1 and IRF8 regulate mononuclear phagocytic cell differentiation in response to vitamin D

Epidemiological, molecular and genetic studies have indicated that high serum vitamin D levels are associated with lower risk of several autoimmune diseases. The vitamin D receptor (VDR) binding sites in monocytes and dendritic cells (DCs) are more common in risk genes for diseases with latitude dependence than in risk genes for other diseases. The transcription factor genes Zinc finger MIZ domain-containing protein 1 (ZMIZ1) and interferon regulatory factor 8 (IRF8)-risk genes for many of these diseases-have VDR binding peaks co-incident with the risk single nucleotide polymorphisms (SNPs). We show these genes are responsive to vitamin D: ZMIZ1 expression increased and IRF8 expression decreased, and this response was affected by genotype in different cell subsets. The IL10/IL12 ratio in tolerogenic DCs increased with vitamin D. These data indicate that vitamin D regulation of ZMIZ1 and IRF8 in DCs and monocytes contribute to latitude-dependent autoimmune disease risk.

Walking and balance outcomes for stroke survivors: a randomized clinical trial comparing body-weight-supported treadmill training with versus without challenging mobility skills

Background

Treadmill training, with or without body-weight support (BWSTT), typically involves high step count, faster walking speed, and higher heart-rate intensity than overground walking training. The addition of challenging mobility skill practice may offer increased opportunities to improve walking and balance skills. Here we compare walking and balance outcomes of chronic stroke survivors performing BWSTT with BWSTT including challenging mobility skills.

Methods

Single-blind randomized clinical trial comparing two BWSTT interventions performed in a rehabilitation research laboratory facility over 6 weeks. Participants were 18+ years of age with chronic (≥5 months) poststroke hemiparesis due to a cortical or subcortical ischemic or hemorrhagic stroke and walking speeds < 1.1 m/s at baseline. A hands-free group (HF; n = 15) performed BWSTT without assistance from handrails or assistive devices, and a hands-free plus challenge group (HF + C; n = 14) performed the same protocol while additionally practicing challenging mobility skills. The primary outcome was change in comfortable walking speed (CWS), with secondary outcomes of fast walk speed (FWS), six-minute walk distance, Berg Balance Scale (BBS) scores, and Activities Specific Balance Confidence (ABC) scores.

Results

Significant pre-post improvement of CWS (Z = − 4.2, p ≤ 0.0001) from a median of 0.35 m/s (range 0.10 to 1.09) to a median of 0.54 m/s (range 0.1 to 1.17), but no difference observed between groups (U = 96.0, p = 0.69). Pre-post improvements across all participants resulted in reclassified baseline ambulation status from sixteen to ten household ambulators, three to seven limited community ambulators, and ten to twelve community ambulators. Secondary outcomes showed similar pre-post improvements with no between-group differences.

Conclusions

The addition of challenging mobility skills to a hands-free BWSTT protocol did not lead to greater improvements in CWS following 6 weeks of training. One reason for lack of group differences may be that both groups were adequately challenged by walking in an active, self-driven treadmill environment without use of handrails or assistive devices.

Trial registration

NCT02787759 Falls-based Training for Walking Post-Stroke (FBT); retrospectively registered June 1st, 2016.

Parental reactions to weight screening in young children: a randomized controlled trial

BACKGROUND

Parental inability to recognize child overweight and physician reluctance to instigate discussion prevents behaviour change.

OBJECTIVE

To evaluate parental acceptance of child overweight status following screening.

METHODS

Interviewers used motivational interviewing or best practice care to discuss overweight status of 271 young children (BMI ≥ 85^th ) with parents using simple traffic-light BMI charts. Follow-up sessions two weeks later (n = 251, 93%) were coded qualitatively to assess parental reactions to the information (overweight diagnosis) and how it was presented (feedback condition).

RESULTS

Eight-two percent of parents rated the charts positively with few (8-10%) feeling judged. Motivational interviewing parents viewed feedback as more empathetic (relative risk, 95% CI: 4.07, 1.64-10.09), but more uncomfortable (12.2, 1.48-100.1) than best practice care parents. Overall, 65.2% of parents accepted their child was overweight, 22.1% were ambivalent and 12.7% rejected the information. Although motivational interviewing parents were less likely to accept it (OR, 95% CI: 0.49, 0.37-0.64) and more likely to be ambivalent (2.01, 1.17-3.47), the most important predictor of acceptance was a positive experience of feedback (P < 0.001).

CONCLUSIONS

Simple traffic-light charts facilitate discussion of child overweight status with parents. Style of feedback is less relevant than ensuring a positive experience for parents to increase acceptance of the weight information.

Common gut microbial metabolites of dietary flavonoids exert potent protective activities in β-cells and skeletal muscle cells

Flavonoids are dietary compounds with potential anti-diabetes activities. Many flavonoids have poor bioavailability and thus low circulating concentrations. Unabsorbed flavonoids are metabolized by the gut microbiota to smaller metabolites, which are more bioavailable than their precursors. The activities of these metabolites may be partly responsible for associations between flavonoids and health. However, these activities remain poorly understood. We investigated bioactivities of flavonoid microbial metabolites [hippuric acid (HA), homovanillic acid (HVA), and 5-phenylvaleric acid (5PVA)] in primary skeletal muscle and β-cells compared to a native flavonoid [(-)-epicatechin, EC]. In muscle, EC was the most potent stimulator of glucose oxidation, while 5PVA and HA simulated glucose metabolism at 25 μM, and all compounds preserved mitochondrial function after insult. However, EC and the metabolites did not uncouple mitochonndrial respiration, with the exception of 5PVA at10 μM. In β-cells, all metabolites more potently enhanced glucose-stimulated insulin secretion (GSIS) compared to EC. Unlike EC, the metabolites appear to enhance GSIS without enhancing β-cell mitochondrial respiration or increasing expression of mitochondrial electron transport chain components, and with varying effects on β-cell insulin content. The present results demonstrate the activities of flavonoid microbial metabolites for preservation of β-cell function and glucose utilization. Additionally, our data suggest that metabolites and native compounds may act by distinct mechanisms, suggesting complementary and synergistic activities in vivo which warrant further investigation. This raises the intriguing prospect that bioavailability of native dietary flavonoids may not be as critical of a limiting factor to bioactivity as previously thought.

Proteolipid domains form in biomimetic and cardiac mitochondrial vesicles and are regulated by cardiolipin concentration but not monolyso-cardiolipin

Cardiolipin (CL) is an anionic phospholipid mainly located in the inner mitochondrial membrane, where it helps regulate bioenergetics, membrane structure, and apoptosis. Localized, phase-segregated domains of CL are hypothesized to control mitochondrial inner membrane organization. However, the existence and underlying mechanisms regulating these mitochondrial domains are unclear. Here, we first isolated detergent-resistant cardiac mitochondrial membranes that have been reported to be CL-enriched domains. Experiments with different detergents yielded only nonspecific solubilization of mitochondrial phospholipids, suggesting that CL domains are not recoverable with detergents. Next, domain formation was investigated in biomimetic giant unilamellar vesicles (GUVs) and newly synthesized giant mitochondrial vesicles (GMVs) from mouse hearts. Confocal fluorescent imaging revealed that introduction of cytochrome c into membranes promotes macroscopic proteolipid domain formation associated with membrane morphological changes in both GUVs and GMVs. Domain organization was also investigated after lowering tetralinoleoyl-CL concentration and substitution with monolyso-CL, two common modifications observed in cardiac pathologies. Loss of tetralinoleoyl-CL decreased proteolipid domain formation in GUVs, because of a favorable Gibbs-free energy of lipid mixing, whereas addition of monolyso-CL had no effect on lipid mixing. Moreover, murine GMVs generated from cardiac acyl-CoA synthetase-1 knockouts, which have remodeled CL acyl chains, did not perturb proteolipid domains. Finally, lowering the tetralinoleoyl-CL content had a stronger influence on the oxidation status of cytochrome c than did incorporation of monolyso-CL. These results indicate that proteolipid domain formation in the cardiac mitochondrial inner membrane depends on tetralinoleoyl-CL concentration, driven by underlying lipid-mixing properties, but not the presence of monolyso-CL.

Ultrafine Particulate Matter Increases Cardiac Ischemia/Reperfusion Injury via Mitochondrial Permeability Transition Pore

Ultrafine particulate matter (UFP) has been associated with increased cardiovascular morbidity and mortality. However, the mechanisms that drive PM-associated cardiovascular disease and dysfunction remain unclear. We examined the impact of oropharyngeal aspiration of 100 μg UFP from the Chapel Hill, NC, air shed in Sprague-Dawley rats on cardiac function, arrhythmogenesis, and cardiac ischemia/reperfusion (I/R) injury using a Langendorff working heart model. We found that exposure to UFP was capable of significantly exacerbating cardiac I/R injury without changing overall cardiac function or major changes in arrhythmogenesis. Cardiac I/R injury was attenuable with administration of cyclosporin A (CsA), suggesting a role for the mitochondrial permeability transition pore (mPTP) in UFP-associated cardiovascular toxicity. Isolated cardiac mitochondria displayed decreased Ca²⁺ buffering before opening of the mPTP. These findings suggest that UFP-induced expansion of cardiac I/R injury may be a result of mPTP Ca²⁺ sensitization resulting in increased mitochondrial permeability transition and potential initiation of mPTP-associated cell death pathways.

Effect of forward-directed aiding force on gait mechanics in healthy young adults while walking faster

BACKGROUND

Forces can be applied to people while they are walking on a treadmill in different ways that aid individuals to walk at faster walking speeds with potentially less effort. Forward-directed aiding forces (FAF) are a special class of aiding forces where "push" or "pull" forces are mechanically applied to the person's pelvis in the forward direction.

OBJECTIVE

To determine if FAF, applied by a robotic interface, can be effective in providing assistance to walk at a faster walking speed with reduced kinetic requirements.

METHODS

Twenty non-neurologically impaired physical active young adults were recruited and biomechanical gait mechanics were measured during walking at two constant treadmill belt speeds (1.0 m/s and 1.6 m/s), with the robotic device in aiding mode to provide FAF (FAF), and also outside of the robotic device (no-FAF). The spatiotemporal gait parameters, anterior-posterior force, sagittal impulse, and hip, knee and ankle power and net work were calculated from kinematic and kinetic data, comparing changes in parameters from slower to faster speeds within each mode, and then, comparing values between each mode.

RESULTS

The spatiotemporal gait parameters were not different between conditions, but in FAF condition, the propulsive force impulse change was not increased, there was smaller propulsion increase, and smaller maximal power generation and ankle work done at the faster speed, whereas all of these parameters were appropriately increased in the no-FAF condition.

CONCLUSIONS

These results indicate that providing FAF at the pelvis is an effective means for reducing the amount of mechanical effort required to walk faster and thus could be used as a training tool to improve walking ability.

CD200 is a useful diagnostic marker for identifying atypical chronic lymphocytic leukemia by flow cytometry

INTRODUCTION

Immunophenotyping by flow cytometry is routinely employed in distinguishing between chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL). Inclusion of CD200 has been reported to contribute to more reliable differentiation between CLL and MCL. We investigated the value of CD200 in assessment of atypical CLL cases.

METHODS

CD200 expression on mature B cell neoplasms was studied by eight-color flow cytometry in combination with a conventional panel of flow cytometry markers. The study included 70 control samples, 63 samples with CLL or atypical CLL phenotype, 6 MCL samples, and 40 samples of other mature B cell neoplasms.

RESULTS

All CLL samples were positive for CD200, whereas MCL samples were dim or negative for CD200. Of the CLL samples, 7 were atypical by conventional flow cytometry, with Matutes scores ≤3. These cases were tested for evidence of a t(11;14) translocation, characteristic of MCL, and all were negative, consistent with their classification as atypical CLL. All these atypical CLL samples were strongly positive for CD200.

CONCLUSION

CD200 proved to be a useful marker for differentiation between CLL and MCL by flow cytometry. In particular, CD200 was useful in distinguishing CLL samples with atypical immunophenotypes from MCL.

Kv7 channels are upregulated during striatal neuron development and promote maturation of human iPSC-derived neurons

Kv7 channels determine the resting membrane potential of neurons and regulate their excitability. Even though dysfunction of Kv7 channels has been linked to several debilitating childhood neuronal disorders, the ontogeny of the constituent genes, which encode Kv7 channels (KNCQ), and expression of their subunits have been largely unexplored. Here, we show that developmentally regulated expression of specific KCNQ mRNA and Kv7 channel subunits in mouse and human striatum is crucial to the functional maturation of mouse striatal neurons and human-induced pluripotent stem cell-derived neurons. This demonstrates their pivotal role in normal development and maturation, the knowledge of which can now be harnessed to synchronise and accelerate neuronal differentiation of stem cell-derived neurons, enhancing their utility for disease modelling and drug discovery.

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω_{0}^{T}<5.58×10^{-8}, Ω_{0}^{V}<6.35×10^{-8}, and Ω_{0}^{S}<1.08×10^{-7} at a reference frequency f_{0}=25  Hz.

The SET1 Complex Selects Actively Transcribed Target Genes via Multivalent Interaction with CpG Island Chromatin

Chromatin modifications and the promoter-associated epigenome are important for the regulation of gene expression. However, the mechanisms by which chromatin-modifying complexes are targeted to the appropriate gene promoters in vertebrates and how they influence gene expression have remained poorly defined. Here, using a combination of live-cell imaging and functional genomics, we discover that the vertebrate SET1 complex is targeted to actively transcribed gene promoters through CFP1, which engages in a form of multivalent chromatin reading that involves recognition of non-methylated DNA and histone H3 lysine 4 trimethylation (H3K4me3). CFP1 defines SET1 complex occupancy on chromatin, and its multivalent interactions are required for the SET1 complex to place H3K4me3. In the absence of CFP1, gene expression is perturbed, suggesting that normal targeting and function of the SET1 complex are central to creating an appropriately functioning vertebrate promoter-associated epigenome.

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The CFP1/SET1 complex engages in dynamic and stable chromatin-binding events

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CFP1 uses multivalent chromatin interactions to select active CpG island promoters

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SET1A occupancy at CpG island promoters is predominately defined by CFP1

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CFP1 targets SET1 to shape promoter-associated H3K4me3 and gene expression

Minimizing Postural Demands of Walking While Still Emphasizing Locomotor Force Generation for Nonimpaired Individuals

In motor control studies, the interdependent nature of the neural controllers for posture and locomotion makes it difficult to separate components of stepping control from postural maintenance functions. To better understand the separate influences of postural versus locomotor control during walking, we fabricated a novel postural support apparatus. This apparatus was intended to minimize the postural demands of walking but allow for matched locomotor force generation, thus isolating the control of stepping. We tested the ability of this support apparatus to minimize the postural demands of walking tasks for nonimpaired participants ( ) and characterized the behavior of these participants when walking in this environment. We demonstrated that the apparatus reduced trunk motion in flexion/extension, lateral flexion, and transverse rotation, minimized peak vertical ground reaction forces to 15.8% body weight, and reduced total positive and negative work compared to walking with typical postural demands. In addition, using visual feedback, participants were able to successfully match vertical forces during supported walking to those of walking with typical postural demands. We plan to use this apparatus to design future experiments exploring mechanisms underlying postural and locomotor control in both nonimpaired walking and of individuals with impaired coordination of posture and stepping.

Mechanisms by Which Dietary Fatty Acids Regulate Mitochondrial Structure-Function in Health and Disease

Mitochondria are the energy-producing organelles within a cell. Furthermore, mitochondria have a role in maintaining cellular homeostasis and proper calcium concentrations, building critical components of hormones and other signaling molecules, and controlling apoptosis. Structurally, mitochondria are unique because they have 2 membranes that allow for compartmentalization. The composition and molecular organization of these membranes are crucial to the maintenance and function of mitochondria. In this review, we first present a general overview of mitochondrial membrane biochemistry and biophysics followed by the role of different dietary saturated and unsaturated fatty acids in modulating mitochondrial membrane structure-function. We focus extensively on long-chain n-3 (ω-3) polyunsaturated fatty acids and their underlying mechanisms of action. Finally, we discuss implications of understanding molecular mechanisms by which dietary n-3 fatty acids target mitochondrial structure-function in metabolic diseases such as obesity, cardiac-ischemia reperfusion injury, obesity, type 2 diabetes, nonalcoholic fatty liver disease, and select cancers.

A Meta-Analysis of Genome-Wide Association Studies of Growth Differentiation Factor-15 Concentration in Blood

Blood levels of growth differentiation factor-15 (GDF-15), also known as macrophage inhibitory cytokine-1 (MIC-1), have been associated with various pathological processes and diseases, including cardiovascular disease and cancer. Prior studies suggest genetic factors play a role in regulating blood MIC-1/GDF-15 concentration. In the current study, we conducted the largest genome-wide association study (GWAS) to date using a sample of ∼5,400 community-based Caucasian participants, to determine the genetic variants associated with MIC-1/GDF-15 blood concentration. Conditional and joint (COJO), gene-based association, and gene-set enrichment analyses were also carried out to identify novel loci, genes, and pathways. Consistent with prior results, a locus on chromosome 19, which includes nine single nucleotide polymorphisms (SNPs) (top SNP, rs888663, p = 1.690 × 10^-35), was significantly associated with blood MIC-1/GDF-15 concentration, and explained 21.47% of its variance. COJO analysis showed evidence for two independent signals within this locus. Gene-based analysis confirmed the chromosome 19 locus association and in addition, a putative locus on chromosome 1. Gene-set enrichment analyses showed that the“COPI-mediated anterograde transport” gene-set was associated with MIC-1/GDF15 blood concentration with marginal significance after FDR correction (p = 0.067). In conclusion, a locus on chromosome 19 was associated with MIC-1/GDF-15 blood concentration with genome-wide significance, with evidence for a new locus (chromosome 1). Future studies using independent cohorts are needed to confirm the observed associations especially for the chromosomes 1 locus, and to further investigate and identify the causal SNPs that contribute to MIC-1/GDF-15 levels.

Visual feedback during pedaling allows individuals poststroke to alter inappropriately prolonged paretic vastus medialis activity

Individuals who have experienced a stroke often demonstrate inappropriate muscle activity phasing in the paretic leg during locomotion. Past research has demonstrated that inappropriate paretic phasing varies between behavioral contexts and is reduced during unilateral pedaling with the nonparetic leg inactive. We investigated whether individuals could voluntarily alter activity in a target muscle of the paretic limb in a consistent behavioral context and whether this voluntary change differed between bilateral and unilateral pedaling. During a fixed-speed motorized pedaling task, participants were asked to use visual feedback to deactivate the vastus medialis (VM) before a 90° target region of the pedaling cycle, as measured by surface electromyography and by change in fraction of total cycle amplitude in the target region. We based the start of this target region on the earliest observed deactivation for this muscle (found in fast pedaling), which allowed us to challenge both the paretic and nonparetic VM. During visual feedback, participants significantly reduced the fraction of activity found in the target region, with no significant difference in degree of reduction between paretic and nonparetic legs or between bilateral and unilateral pedaling. Surprisingly, in bilateral pedaling, individuals with greater clinical impairment demonstrated greater paretic limb response to feedback. Our results demonstrated that during this tightly constrained task, the paretic VM showed a surprisingly similar flexibility of muscle activity to the nonparetic VM. Our findings show that participants were able to use provided visual feedback to modulate the degree of an observed poststroke muscle-phasing impairment. NEW & NOTEWORTHY This study demonstrates that by using visual feedback during a constrained task with minimized kinematic control requirements, participants with poststroke hemiplegia can voluntarily change muscle activity phase in the vastus medialis. Surprisingly, we did not observe a significant difference in ability to alter phasing between paretic and nonparetic legs or between bilateral and unilateral pedaling. In this visual feedback task, participants appear to modify muscle activity well in both the paretic and nonparetic legs.

GW170817: Implications for the Stochastic Gravitational-Wave Background from Compact Binary Coalescences

The LIGO Scientific and Virgo Collaborations have announced the event GW170817, the first detection of gravitational waves from the coalescence of two neutron stars. The merger rate of binary neutron stars estimated from this event suggests that distant, unresolvable binary neutron stars create a significant astrophysical stochastic gravitational-wave background. The binary neutron star component will add to the contribution from binary black holes, increasing the amplitude of the total astrophysical background relative to previous expectations. In the Advanced LIGO-Virgo frequency band most sensitive to stochastic backgrounds (near 25 Hz), we predict a total astrophysical background with amplitude Ω_{GW}(f=25  Hz)=1.8_{-1.3}^{+2.7}×10^{-9} with 90% confidence, compared with Ω_{GW}(f=25  Hz)=1.1_{-0.7}^{+1.2}×10^{-9} from binary black holes alone. Assuming the most probable rate for compact binary mergers, we find that the total background may be detectable with a signal-to-noise-ratio of 3 after 40 months of total observation time, based on the expected timeline for Advanced LIGO and Virgo to reach their design sensitivity.

Step-by-step variability of swing phase trajectory area during steady state walking at a range of speeds

BACKGROUND

Step kinematic variability has been characterized during gait using spatial and temporal kinematic characteristics. However, people can adopt different trajectory paths both between individuals and even within individuals at different speeds. Single point measures such as minimum toe clearance (MTC) and step length (SL) do not necessarily account for the multiple paths that the foot may take during the swing phase to reach the same foot fall endpoint. The purpose of this study was to test a step-by-step foot trajectory area (SBS-FTA) variability measure that is able to characterize sagittal plane foot trajectories of varying areas, and compare this measure against MTC and SL variability at different speeds. We hypothesize that the SBS-FTA variability would demonstrate increased variability with speed. Second, we hypothesize that SBS-FTA would have a stronger curvilinear fit compared with the CV and SD of SL and MTC. Third, we hypothesize SBS-FTA would be more responsive to change in the foot trajectory at a given speed compared to SL and MTC. Fourth, SBS-FTA variability would not strongly co-vary with SL and MTC variability measures since it represents a different construct related to foot trajectory area variability.

METHODS

We studied 15 nonimpaired individuals during walking at progressively faster speeds. We calculated SL, MTC, and SBS-FTA area.

RESULTS

SBS-FTA variability increased with speed, had a stronger curvilinear fit compared with the CV and SD of SL and MTC, was more responsive at a given speed, and did not strongly co-vary with SL and MTC variability measures.

CONCLUSION

SBS foot trajectory area variability was sensitive to change with faster speeds, captured a relationship that the majority of the other measures did not demonstrate, and did not co-vary strongly with other measures that are also components of the trajectory.

First Search for Nontensorial Gravitational Waves from Known Pulsars

We present results from the first directed search for nontensorial gravitational waves. While general relativity allows for tensorial (plus and cross) modes only, a generic metric theory may, in principle, predict waves with up to six different polarizations. This analysis is sensitive to continuous signals of scalar, vector, or tensor polarizations, and does not rely on any specific theory of gravity. After searching data from the first observation run of the advanced LIGO detectors for signals at twice the rotational frequency of 200 known pulsars, we find no evidence of gravitational waves of any polarization. We report the first upper limits for scalar and vector strains, finding values comparable in magnitude to previously published limits for tensor strain. Our results may be translated into constraints on specific alternative theories of gravity.

Comparison of Resistance-Based Walking Cardiorespiratory Test to the Bruce Protocol

Hurt, CP, Bamman, M, Naidu, A, and Brown, DA. Comparison of resistance-based walking cardiorespiratory test to the Bruce Protocol. J Strength Cond Res 34(12): 3569-3576, 2020-Cardiorespiratory fitness is assessed through graded exercise tests that determine the maximum amount of sustained mechanical work that an individual can perform while also providing health- and fitness-related information. This article describes a novel method to perform graded exercise tests that use posteriorly directed resistive forces. The purpose of this investigation was to validate a novel resistance-based test (RBT) in comparison with a traditional speed- and incline-based test (SIBT) in a cohort of nonimpaired individuals. Twenty nonimpaired individuals, 8 men and 20 women age 28.4 ± 9.6, range 20-54 years old performed 2 maximal exercise tests. The SIBT used the Bruce Protocol and increased treadmill incline and speed every 3 minutes. The RBT used a robotic device interfaced with the treadmill that provided specified horizontal resistive forces at the center of mass calculated to match each Bruce Protocol stage while individuals walked at 1.1 m·s. Subjects obtained ∼3% higher maximum V[Combining Dot Above]O2 measure using the speed- and incline-based method (dependent t-test p = 0.08). V[Combining Dot Above]O2peaks between tests were strongly correlated (r = 0.93, p < 0.001). Peak values of secondary physiologic measures (i.e., max heart rate and respiratory exchange ratio) were within 3% between tests. We found a significant linear relationship between mass-specific work rate and measured V[Combining Dot Above]O2 stage by stage for both tests, but no significant difference between each linear fit (p = 0.84). These data suggest that horizontal resistive forces, while walking on a treadmill, can be used to increase aerobic effort in a way that closely simulates work rates of the Bruce Protocol.