Attentional, anticipatory and spatial cognition fluctuate throughout the menstrual cycle: potential implications for female sport

Current research suggests that menstruating female athletes might be at greater risk of musculoskeletal injury in relation to hormonal changes throughout the menstrual cycle. A separate body of work suggests that spatial cognition might also fluctuate in a similar manner. Changes in spatial cognition could, in theory, be a contributing risk factor for injury, especially in fast-paced sports that require precise, millisecond accuracy in interactions with moving objects in the environment. However, existing theories surrounding causes for increased injury risk in menstruating females largely focus on biomechanical mechanisms, with little consideration of possible cognitive determinants of injury risk. Therefore, the aim of this proof-of-principle study was to explore whether menstruating females exhibit fluctuations in cognitive processes throughout their cycle on a novel sport-oriented cognitive test battery, designed to measure some of the mental processes putatively involved in these sporting situations. A total of 394 participants completed an online cognitive battery, a mood scale and a symptom questionnaire twice, 14 days apart. After exclusions, 241 eligible participants were included in the analyses (mean: 28 ± 6 years) (male = 96, female(menstruating) = 105, female(contraception) = 47). Cycle phase for menstruating females was based on self-reported information. The cognitive battery was designed to measure reaction times, attention, visuospatial functions (including 3D mental rotation) and timing anticipation. Three composite scores were generated using factor analysis with varimax rotation (Errors, Reaction Time, Intra-Individual Variability). Mixed model ANOVAs and repeated measures ANOVAs were performed to test for between and within-subject effects. There was no group difference in reaction times and accuracy between males and females (using contraception and not). However, within subject analyses revealed that regularly menstruating females performed better during menstruation compared to being in any other phase, with faster reaction times (10ms c.ca, p < .01), fewer errors (p < .05) and lower dispersion intra-individual variability (p < .05). In contrast they exhibited slower reaction times (10ms c.ca, p < .01) and poorer timing anticipation (p < .01) in the luteal phase, and more errors in the predicted ovulatory phase (p < .01). Self-reported mood, cognitive and physical symptoms were all worst during menstruation (p < .01), and a significant proportion of females felt that their symptoms were negatively affecting their cognitive performance during menstruation on testing day, which was incongruent with their actual performance. These findings suggest that visuospatial and anticipatory processes may fluctuate throughout the menstrual cycle in the general population, with better performance during the menstrual phase and poorer performance during the luteal phase. If these extend to associations between phase-specific cognitive performance and injury incidence, they would support a cognitive theory of determinants of injury risk in cycling female athletes, opening an opportunity to develop mitigation strategies where appropriate.

Burn pit-related smoke causes developmental and behavioral toxicity in zebrafish: Influence of material type and emissions chemistry

Combustion of mixed materials during open air burning of refuse or structural fires in the wildland urban interface produces emissions that worsen air quality, contaminate rivers and streams, and cause poor health outcomes including developmental effects. The zebrafish, a freshwater fish, is a useful model for quickly screening the toxicological and developmental effects of agents in such species and elicits biological responses that are often analogous and predictive of responses in mammals. The purpose of this study was to compare the developmental toxicity of smoke derived from the burning of 5 different burn pit-related material types (plywood, cardboard, plastic, a mixture of the three, and the mixture plus diesel fuel as an accelerant) in zebrafish larvae. Larvae were exposed to organic extracts of increasing concentrations of each smoke 6-to-8-hr post fertilization and assessed for morphological and behavioral toxicity at 5 days post fertilization. To examine chemical and biological determinants of toxicity, responses were related to emissions concentrations of polycyclic hydrocarbons (PAH). Emissions from plastic and the mixture containing plastic caused the most pronounced developmental effects, including mortality, impaired swim bladder inflation, pericardial edema, spinal curvature, tail kinks, and/or craniofacial deformities, although all extracts caused concentration-dependent effects. Plywood, by contrast, altered locomotor responsiveness to light changes to the greatest extent. Some morphological and behavioral responses correlated strongly with smoke extract levels of PAHs including 9-fluorenone. Overall, the findings suggest that material type and emissions chemistry impact the severity of zebrafish developmental toxicity responses to burn pit-related smoke.

Nonlinear effects at the electrode-tissue interface of deep brain stimulation electrodes

Objective.The electrode-tissue interface provides the critical path for charge transfer in neurostimulation therapies and exhibits well-established nonlinear properties at high applied currents or voltages. These nonlinear properties may influence the efficacy and safety of applied stimulation but are typically neglected in computational models. In this study, nonlinear behavior of the electrode-tissue interface impedance was incorporated in a computational model of deep brain stimulation (DBS) to simulate the impact on neural activation and safety considerations.Approach.Nonlinear electrode-tissue interface properties were incorporated in a finite element model of DBS electrodesin vitroandin vivo,in the rat subthalamic nucleus, using an iterative approach. The transition point from linear to nonlinear behavior was determined for voltage and current-controlled stimulation. Predicted levels of neural activation during DBS were examined and the region of linear operation of the electrode was compared with the Shannon safety limit.Main results.A clear transition of the electrode-tissue interface impedance to nonlinear behavior was observed for both current and voltage-controlled stimulation. The transition occurred at lower values of activation overpotential for simulatedin vivothanin vitroconditions (91 mV and 165 mV respectively for current-controlled stimulation; 110 mV and 275 mV for voltage-controlled stimulation), corresponding to an applied current of 30μA and 45μA, or voltage of 330 mV at 1 kHz. The onset of nonlinearity occurred at lower values of the overpotential as frequency was increased. Incorporation of nonlinear properties resulted in activation of a higher proportion of neurons under voltage-controlled stimulation. Under current-controlled stimulation, the predicted transition to nonlinear behavior and Faradaic charge transfer at stimulation amplitudes of 30μA, corresponds to a charge density of 2.29μC cm-2and charge of 1.8 nC, well-below the Shannon safety limit.Significance.The results indicate that DBS electrodes may operate within the nonlinear region at clinically relevant stimulation amplitudes. This affects the extent of neural activation under voltage-controlled stimulation and the transition to Faradaic charge transfer for both voltage- and current-controlled stimulation with important implications for targeting of neural populations and the design of safe stimulation protocols.

Influence of Methylene Blue or Dimethyl Sulfoxide on Larval Zebrafish Development and Behavior

The use of larval zebrafish developmental testing and assessment, specifically larval zebrafish locomotor activity, has been recognized as a higher throughput testing strategy to identify developmentally toxic and neurotoxic chemicals. There are, however, no standardized protocols for this type of assay, which could result in confounding variables being overlooked. Two chemicals commonly employed during early-life stage zebrafish assays, methylene blue (antifungal agent) and dimethyl sulfoxide (DMSO, a commonly used vehicle) have been reported to affect the morphology and behavior of freshwater fish. In this study, we conducted developmental toxicity (morphology) and neurotoxicity (behavior) assessments of commonly employed concentrations for both chemicals (0.6-10.0 μM methylene blue; 0.3%-1.0% v/v DMSO). A light-dark transition behavioral testing paradigm was applied to morphologically normal, 6 days postfertilization (dpf) zebrafish larvae kept at 26°C. Additionally, an acute DMSO challenge was administered based on early-life stage zebrafish assays typically used in this research area. Results from developmental toxicity screens were similar between both chemicals with no morphological abnormalities detected at any of the concentrations tested. However, neurodevelopmental results were mixed between the two chemicals of interest. Methylene blue resulted in no behavioral changes up to the highest concentration tested, 10.0 μM. By contrast, DMSO altered larval behavior following developmental exposure at concentrations as low as 0.5% (v/v) and exhibited differential concentration-response patterns in the light and dark photoperiods. These results indicate that developmental DMSO exposure can affect larval zebrafish locomotor activity at routinely used concentrations in developmental neurotoxicity assessments, whereas methylene blue does not appear to be developmentally or neurodevelopmentally toxic to larval zebrafish at routinely used concentrations. These results also highlight the importance of understanding the influence of experimental conditions on larval zebrafish locomotor activity that may ultimately confound the interpretation of results.

Inconsistencies in variable reporting and methods in larval zebrafish behavioral assays

New approaches in developmental neurotoxicity (DNT) screening are needed due to the tens of thousands of chemicals requiring hazard assessments. Zebrafish (Danio rerio) are an alternative vertebrate model for DNT testing, but without a standardized protocol for larval behavioral assays, comparison of results among laboratories is challenging. To evaluate the congruence of protocols across laboratories, we conducted a literature review of DNT studies focusing on larval zebrafish behavior assays and cataloged experimental design consistencies. Our review focused on 51 unique method variables in publications where chemical exposure occurred in early development and subsequent larval locomotor evaluation focused on assays that included a light/dark photoperiod transition. We initially identified 94 publications, but only 31 exclusively met our inclusion criteria which focused on parameters that are important to an assay employed by our laboratory. No publication reported 100% of the targeted variables; only 51 to 86% of those variables were reported in the reviewed publications, with some aspects of the experimental design consistent among laboratories. However, no protocol was exactly the same for any two publications. Many of these variables had more than one parameter/design reported, highlighting the inconsistencies among methods. Overall, there is not only a strong need for the development of a standardized testing protocol for larval zebrafish locomotor assays, but there is also a need for a standardized protocol for reporting experimental variables in the literature. Here we include an extensive guideline checklist for conducting larval zebrafish developmental behavior assays.

Stimulation-induced changes at the electrode-tissue interface and their influence on deep brain stimulation

OBJECTIVE

During deep brain stimulation (DBS) the electrode-tissue interface forms a critical path between device and brain tissue. Although changes in the electrical double layer and glial scar can impact stimulation efficacy, the effects of chronic DBS on the electrode-tissue interface have not yet been established.

APPROACH

In this study, we characterised the electrode-tissue interface surrounding chronically implanted DBS electrodes in rats and compared the impedance and histological properties at the electrode interface in animals that received daily stimulation and in those where no stimulation was applied, up to eight weeks post-surgery. A computational model was developed based on the experimental data, which allowed the dispersive electrical properties of the surrounding encapsulation tissue to be estimated. The model was then used to study the effect of stimulation-induced changes in the electrode-tissue interface on the electric field and neural activation during voltage- and current-controlled stimulation.

MAIN RESULTS

Incorporating the observed changes in simulations in silico, we estimated the frequency-dependent dielectric properties of the electrical double layer and surrounding encapsulation tissue. Through simulations we show how stimulation-induced changes in the properties of the electrode-tissue interface influence the electric field and alter neural activation during voltage-controlled stimulation. A substantial increase in the number of stimulated collaterals, and their distance from the electrode, was observed during voltage-controlled stimulation with stimulated ETI properties. In vitro examination of stimulated electrodes confirmed that high frequency stimulation leads to desorption of proteins at the electrode interface, with a concomitant reduction in impedance.

SIGNIFICANCE

The demonstration of stimulation-induced changes in the electrode-tissue interface has important implications for future DBS systems including closed-loop systems where the applied stimulation may change over time. Understanding these changes is particularly important for systems incorporating simultaneous stimulation and sensing, which interact dynamically with brain networks.

Targeted therapies for pancreatic adenocarcinoma

The majority of patients diagnosed with adenocarcinoma of the pancreas have advanced disease at presentation, with only 20% surviving beyond one year. Even among the 10% to 15% of patients who present with localized disease, only 20% will be alive 5 years post surgical resection. Systemic therapy for pancreatic adenocarcinoma to date has failed to provide more than a very modest survival benefit for patients with advanced disease. However, the past decade has seen significant advances in the understanding of the molecular pathogenesis of pancreatic cancer, culminating in the sequencing of the pancreatic cancer genome. New generations of therapeutic agents targeting key oncogenic cellular signaling pathways are currently under evaluation in advanced pancreatic adenocarcinoma. Although thus far only erlotinib has been shown to improve survival when compared to gemcitabine monotherapy, the authors anticipate that further developments in biomarker analysis and pharmacogenomics, along with the identification of new drugs will help maximize the benefit of novel therapeutics by directing effective use in the future. Herein the authors review the evidence to date for the use of novel cytotoxic and molecularly targeted agents in pancreatic adenocarcinoma, and discuss key areas for future therapeutic development.

Rectification and non-linear pre-processing of EMG signals for cortico-muscular analysis

Rectification of the electromyographic (EMG) signal is a commonly used pre-processing procedure that allows detection of significant coherence between EMG and measured cortical signals. However, despite its accepted and wide-spread use, no detailed analysis has been presented to offer insight into the precise function of rectification. We begin this paper with arguments based on single motor unit action potential (AP) trains to demonstrate that rectification effectively enhances the firing rate information of the signal. Enhancement is achieved by shifting the peak of the AP spectrum toward the lower firing rate frequencies, whilst maintaining the firing rate spectra. A similar result is obtained using the analytic envelope of the signal extracted using the Hilbert transform. This argument is extended to simulated EMG signals generated using a published EMG model. Detection of firing rate frequencies is obtained using phase randomised surrogate data, where the original EMG power spectrum exceeds the averaged rectified surrogate spectra at integer multiples of firing rate frequencies. Model simulations demonstrate that this technique accurately determines grouped firing rate frequencies. Extraction of grouped firing rate frequencies prior to coherency analyses may further aid interpretation of significant cortico-muscular coherence findings.

Electromyogram median frequency, spectral compression and muscle fibre conduction velocity during sustained sub-maximal contraction of the brachioradialis muscle

Changes in the median frequency of the power spectrum of the surface electromyogram (EMG) are commonly used to detect muscle fatigue. Previous research has indicated that changes in the median frequency are related to decreases in muscle fibre conduction velocity (MFCV) during sustained fatiguing contractions. However, in experimental studies the median frequency has been consistently observed to decrease by a relatively greater amount than MFCV. In this paper, a new estimate of EMG frequency compression, the Spectral Compression Estimate (SCE), is compared with the median frequency of the EMG power spectrum, the median frequency of the EMG amplitude spectrum and MFCV measured during sustained, isometric, fatiguing contractions of the brachioradialis muscle at 30, 50 and 80% maximum voluntary contraction (MVC). The SCE is found to provide a better estimate of the observed changes in MFCV than the median frequency of either the EMG power spectrum or EMG amplitude spectrum.

Finite element modeling of electromagnetic signal propagation in a phantom arm

Improving the control of artificial arms remains a considerable challenge. It may be possible to graft remaining peripheral nerves in an amputated limb to spare muscles in or near the residual limb and use these nerve-muscle grafts as additional myoelectric control signals. This would allow simultaneous control of multiple, degrees of freedom (DOF) and could greatly improve the control of artificial limbs. For this technique to be successful, the electromyography (EMG) signals from the nerve-muscle grafts would need to be independent of each other with minimal crosstalk. To study EMG signal propagation and quantify crosstalk, finite element (FE) models were developed in a phantom-arm model. The models were validated with experimental data collected by applying sinusoidal excitations to a phantom-arm model and recording the surface electric potential distribution. There was a very high correlation (r > 0.99) between the FEM data and the experimental data, with the error in signal magnitude generally less than 5%. Simulations were then performed using muscle dielectric properties with static, complex, and full electromagnetic solvers. The results indicate that significant displacement currents can develop (> 50% of total current) and that the fall-off of surface signal power varies with how the signal source is modeled. Index Terms-Control, electromyography (EMG), finite element (FE), modeling, prosthesis.

The impact of a clinical pathway for gastric bypass surgery on resource utilization

BACKGROUND

Clinical pathways are believed to improve patient care and reduce costs. Our hypothesis was that a gastric bypass pathway would decrease hospital resource utilization and cost of care without adversely affecting patient care.

METHODS

The prepathway (Pre) group consisted of 16 gastric bypasses (6/98 to 3/99). The postpathway (Post) group includes 12 gastric bypass procedures performed after institution of the clinical pathway (4/99 to 12/99). The impact of the clinical pathway on hospital length of stay (LOS) and resource utilization was investigated. A comparison of costs was performed using cost/charge ratios. Hospital readmissions and postoperative complications were also examined.

RESULTS

Despite increased obesity/medical acuity of the Post group, hospital LOS decreased by 3 days (P < 0.0001). Total hospital costs decreased by over $1600/case (>15%). Postpathway savings were greatest for room and board (34%), supplies (41%), and lab/radiology costs (50%). An increase in OR costs (22%) was observed in the Post group. This was due to an increase in anesthesia time (epidural catheter placement) and equipment costs (ultrasonic shears). Despite reductions in hospital LOS and resource utilization, the complication rate (Pre 12%, Post 16%) was similar and two patients in each group required brief readmission.

CONCLUSIONS

A pathway for gastric bypass decreased hospital LOS and resource utilization. OR-related expenses account for 34-50% of total costs and must be monitored closely for surgical patients. The reduction in costs observed with this clinical pathway was not associated with an increase in postoperative complications or hospital readmission.

The impact of anterior cruciate ligament deficiency and reconstruction on bilateral thigh muscle activity during stair descent

Aim: To assess electromyographic (EMG) gait pattern changes during stair descent in subjects with chronic anterior cruciate ligament (ACL) deficiency, and in subjects after ACL reconstruction.Methods: Thirteen ACL deficient subjects (ACLdef), 8 ACL reconstructed subjects (ACLrec), and 10 controls (CON) participated in the study. All subjects were assessed for functional and lean thigh volume (LTV) differences in the injured and uninjured limb. All subjects then stepped off a bench with EMG electrodes on the vastus medialis, vastus lateralis and hamstrings muscles of both limbs.Results: Step down activity caused similar EMG responses in the injured and supporting limb in the ACLdef group compared to that in the control group. In contrast, in the ACLrec group, the onset of EMG activity occurred earlier during the step down activity in the vastus medialis and vastus lateralis of the supporting limb. There was significantly greater EMG activity in the vastus lateralis and hamstring muscles of the supporting limb (p < 0.05) in the ACLrec group compared to ACLdef and control groups. The changes in EMG activity did not appear to be related to differences in LTV, since greater LTV deficits were present in the ACLdef compared to the ACLrec group (p < 0.01).Conclusions: In ACL reconstructed subjects, changes in muscle recruitment patterns in the supporting limb during step down activity have been identified. This altered activity pattern was not present in the supporting limb of ACL deficient subjects

A campaign with street cred to target teenagers with asthma

Failure to use asthma medication among young people has contributed to significant levels of morbidity. This report describes an attempt to address this issue through the development of a teenage-asthma initiative focusing on an inhaler rap record. The help of Byker Grove stars, the former Newcastle United player Scott Sellars and many other famous names was enlisted to facilitate the campaign. A nine-minute pop video which has been produced in collaboration with the multidisciplinary health care team forms the campaign's centerpiece. The video is supported by karaoke version of the inhaler rap, aerobic type exercises, posters, T-shirts and baseball caps. An education quiz is used to evaluate the programme.

Subarachnoid hemorrhage simulating myocardial infarction

We describe a patient with a subarachnoid hemorrhage that presented with electrocardiographic evidence of transmural myocardial infarction. The patient was found to have normal coronaries and on autopsy revealed generalized myocytolysis with no evidence of transmural myocardial infarction. This case illustrates the value of acute coronary angiography in patients with altered mental status and suspected myocardial infarction.

Cytogenetic findings in a case of congenital mesoblastic nephroma

Congenital mesoblastic nephroma (CMN) is a benign, but locally aggressive, renal tumor of early infancy. Few metastases have been reported, but local recurrence is well documented. CMN is histologically distinct from Wilms' tumor and other childhood renal tumors, and is typically treated by surgical excision without adjuvant therapy. Cytogenetic abnormalities in these tumors have been described and are often compared with abnormalities seen in leiomyomas, fibromatoses, and infantile fibrosarcomas. In particular, trisomy 11 has been suggested as a nonrandom occurrence in CMNs. We describe a case of CMN in a 4-month-old female infant. The diagnostic histologic features included a monophasic mesenchymal appearance, prominent staghorn vascular spaces, and extensive infiltration of the adjacent kidney. Cytogenetic analysis showed a hyperdiploid chromosome number and a single structural abnormality involving a translocation between chromosomes 12 and 15. The composite karyotypic interpretation was: 46-47,XX,-X, +8, +11,t(12;15)(p12;q25), +17, +20[cp14]. The significance of karyotypic changes in this tumor is currently unknown. A genetic basis for histologic variability and progression may exist if certain cytogenetic abnormalities, such as trisomy 11 or specific translocations, confer a proliferative advantage. Additional cases are required to correlate cytogenetic findings with the biologic behaviors of CMN. We present this case as a contribution to existing literature describing these relatively rare and interesting renal tumors.

LAMP in L.A.'s skid row: a model for community-based support services

In most states, we reneged on our promise to provide community-based program support to persons deinstitutionalized from psychiatric hospitals. Now many people are blaming those with mental illness for their failure to thrive and have begun creating new laws and methods for reinstitutionalization. This chapter describes a community-based program that is demonstrably effective. It involves the full participation of homeless people diagnosed with mental illness and attests to what can work.

Interrelationship of variable coupling, multiformity and repetitive forms: implications for classification of ventricular arrhythmias

One hundred 24-hour ambulatory electrocardiograms were prospectively examined to determine the relationship of variable coupling and multiformity of single premature ventricular complexes to repetitive forms. Premature ventricular complexes were present in 86 patients and were categorized by a three-tier decision-making tree using (1) multiformity confirmed in two channels, (2) variable coupling of greater than 80 msec of premature ventricular complexes of similar QRS morphologies, and (3) repetitive forms of greater than or equal to 2 premature ventricular complexes. Variable coupling was present in 51 patients, among whom 35 (69%) had repetitive forms; multiformity was present in 46 patients, among whom 37 (80%) had repetitive forms; repetitive forms were present in 41 patients, among whom only one patient (2%) did not demonstrate multiformity or variable coupling. Variable coupling, multiformity, or either were significantly associated with the occurrence of repetitive forms (chi square = 34, 15, 29, respectively, each p less than 0.005). There was a bimodal distribution between patients with uniform, fixed coupled premature ventricular complexes who had rare repetitive forms (1 of 26) and patients with multiformity and variable coupling of premature ventricular complexes who had significantly more repetitive forms (30 of 37; p less than 0.001). The frequency distribution of repetitive form length suggested a natural break point between five and six consecutive complexes.(ABSTRACT TRUNCATED AT 250 WORDS)