Chytrid infections exhibit historical spread and contemporary seasonality in a declining stream-breeding frog.

Species with extensive geographical ranges pose special challenges to assessing drivers of wildlife disease, necessitating collaborative and large-scale analyses. The imperilled foothill yellow-legged frog (Rana boylii) inhabits a wide geographical range and variable conditions in rivers of California and Oregon (USA), and is considered threatened by the pathogen Batrachochytrium dendrobatidis (Bd). To assess drivers of Bd infections over time and space, we compiled over 2000 datapoints from R. boylii museum specimens (collected 1897-2005) and field samples (2005-2021) spanning 9° of latitude. We observed a south-to-north spread of Bd detections beginning in the 1940s and increase in prevalence from the 1940s to 1970s, coinciding with extirpation from southern latitudes. We detected eight high-prevalence geographical clusters through time that span the species' geographical range. Field-sampled male R. boylii exhibited the highest prevalence, and juveniles sampled in autumn exhibited the highest loads. Bd infection risk was highest in lower elevation rain-dominated watersheds, and with cool temperatures and low stream-flow conditions at the end of the dry season. Through a holistic assessment of relationships between infection risk, geographical context and time, we identify the locations and time periods where Bd mitigation and monitoring will be critical for conservation of this imperilled species.

Unclassified white matter disorders: A diagnostic journey requiring close collaboration between clinical and laboratory services.

BACKGROUND: Next generation sequencing studies have revealed an ever-increasing number of causes for genetic disorders of central nervous system white matter. A substantial number of disorders are identifiable from their specific pattern of biochemical and/or imaging findings for which single gene testing may be indicated. Beyond this group, the causes of genetic white matter disorders are unclear and a broader approach to genomic testing is recommended. AIM: This study aimed to identify the genetic causes for a group of individuals with unclassified white matter disorders with suspected genetic aetiology and highlight the investigations required when the initial testing is non-diagnostic. METHODS: Twenty-six individuals from 22 families with unclassified white matter disorders underwent deep phenotyping and genome sequencing performed on trio, or larger, family groups. Functional studies and transcriptomics were used to resolve variants of uncertain significance with potential clinical relevance. RESULTS: Causative or candidate variants were identified in 15/22 (68.2%) families. Six of the 15 implicated genes had been previously associated with white matter disease (COL4A1, NDUFV1, SLC17A5, TUBB4A, BOLA3, DARS2). Patients with variants in the latter two presented with an atypical phenotype. The other nine genes had not been specifically associated with white matter disease at the time of diagnosis and included genes associated with monogenic syndromes, developmental disorders, and developmental and epileptic encephalopathies (STAG2, LSS, FIG4, GLS, PMPCA, SPTBN1, AGO2, SCN2A, SCN8A). Consequently, only 46% of the diagnoses would have been made via a current leukodystrophy gene panel test. DISCUSSION: These results confirm the importance of broad genomic testing for patients with white matter disorders. The high diagnostic yield reflects the integration of deep phenotyping, whole genome sequencing, trio analysis, functional studies, and transcriptomic analyses. CONCLUSIONS: Genetic white matter disorders are genetically and phenotypically heterogeneous. Deep phenotyping together with a range of genomic technologies underpin the identification of causes of unclassified white matter disease. A molecular diagnosis is essential for prognostication, appropriate management, and accurate reproductive counseling.

Surveillance imaging with FDG-PET/CT in the post-operative follow-up of stage 3 melanoma.

Background: As early detection of recurrent melanoma maximizes treatment options, patients usually undergo post-operative imaging surveillance, increasingly with FDG-PET/CT (PET). To assess this, we evaluated stage 3 melanoma patients who underwent prospectively applied and sub-stage-specific schedules of PET surveillance. Patients and methods: From 2009, patients with stage 3 melanoma routinely underwent PET +/- MRI brain scans via defined schedules based on sub-stage-specific relapse probabilities. Data were collected regarding patient characteristics and outcomes. Contingency analyses were carried out of imaging outcomes. Results: One hundred and seventy patients (stage 3A: 34; 3B: 93; 3C: 43) underwent radiological surveillance. Relapses were identified in 65 (38%) patients, of which 45 (69%) were asymptomatic. False-positive imaging findings occurred in 7%, and 6% had treatable second (non-melanoma) malignancies. Positive predictive values (PPV) of individual scans were 56%-83%. Negative scans had predictive values of 89%-96% for true non-recurrence [negative predictive values (NPV)] until the next scan. A negative PET at 18 months had NPVs of 80%-84% for true non-recurrence at any time in the 47-month (median) follow-up period. Sensitivity and specificity of the overall approach of sub-stage-specific PET surveillance were 70% and 87%, respectively. Of relapsed patients, 33 (52%) underwent potentially curative resection and 10 (16%) remained disease-free after 24 months (median). Conclusions: Application of sub-stage-specific PET in stage 3 melanoma enables asymptomatic detection of most recurrences, has high NPVs that may provide patient reassurance, and is associated with a high rate of detection of resectable and potentially curable disease at relapse.

Automatic determination of EMG-contaminated components and validation of independent component analysis using EEG during pharmacologic paralysis.

OBJECTIVE: Validate independent component analysis (ICA) for removal of EMG contamination from EEG, and demonstrate a heuristic, based on the gradient of EEG spectra (slope of graph of log EEG power vs log frequency, 7-70 Hz) from paralysed awake humans, to automatically identify and remove components that are predominantly EMG. METHODS: We studied the gradient of EMG-free EEG spectra to quantitatively inform the choice of threshold. Then, pre-existing EEG from 3 disparate experimental groups was examined before and after applying the heuristic to validate that the heuristic preserved neurogenic activity (Berger effect, auditory odd ball, visual and auditory steady state responses). RESULTS: (1) ICA-based EMG removal diminished EMG contamination up to approximately 50 Hz, (2) residual EMG contamination using automatic selection was similar to manual selection, and (3) task-induced cortical activity remained, was enhanced, or was revealed using the ICA-based methodology. CONCLUSION: This study further validates ICA as a powerful technique for separating and removing myogenic signals from EEG. Automatic processing based on spectral gradients to exclude EMG-containing components is a conceptually simple and valid technique. SIGNIFICANCE: This study strengthens ICA as a technique to remove EMG contamination from EEG whilst preserving neurogenic activity to 50 Hz.

Measurement of neural signals from inexpensive, wireless and dry EEG systems.

Electroencephalography (EEG) is challenged by high cost, immobility of equipment and the use of inconvenient conductive gels. We compared EEG recordings obtained from three systems that are inexpensive, wireless, and/or dry (no gel), against recordings made with a traditional, research-grade EEG system, in order to investigate the ability of these 'non-traditional' systems to produce recordings of comparable quality to a research-grade system. The systems compared were: Emotiv EPOC (inexpensive and wireless), B-Alert (wireless), g.Sahara (dry) and g.HIamp (research-grade). We compared the ability of the systems to demonstrate five well-studied neural phenomena: (1) enhanced alpha activity with eyes closed versus open; (2) visual steady-state response (VSSR); (3) mismatch negativity; (4) P300; and (5) event-related desynchronization/synchronization. All systems measured significant alpha augmentation with eye closure, and were able to measure VSSRs (although these were smaller with g.Sahara). The B-Alert and g.Sahara were able to measure the three time-locked phenomena equivalently to the g.HIamp. The Emotiv EPOC did not have suitably located electrodes for two of the tasks and synchronization considerations meant that data from the time-locked tasks were not assessed. The results show that inexpensive, wireless, or dry systems may be suitable for experimental studies using EEG, depending on the research paradigm, and within the constraints imposed by their limited electrode placement and number.

Surface Laplacian of scalp electrical signals and independent component analysis resolve EMG contamination of electroencephalogram.

The serious impact of electromyogram (EMG) contamination of electroencephalogram (EEG) is well recognised. The objective of this research is to demonstrate that combining independent component analysis with the surface Laplacian can eliminate EMG contamination of the EEG, and to validate that this processing does not degrade expected neurogenic signals. The method involves sequential application of ICA, using a manual procedure to identify and discard EMG components, followed by the surface Laplacian. The extent of decontamination is quantified by comparing processed EEG with EMG-free data that was recorded during pharmacologically induced neuromuscular paralysis. The combination of the ICA procedure and the surface Laplacian, with a flexible spherical spline, results in a strong suppression of EMG contamination at all scalp sites and frequencies. Furthermore, the ICA and surface Laplacian procedure does not impair the detection of well-known, cerebral responses; alpha activity with eyes-closed; ERP components (N1, P2) in response to an auditory oddball task; and steady state responses to photic and auditory stimulation. Finally, more flexible spherical splines increase the suppression of EMG by the surface Laplacian. We postulate this is due to ICA enabling the removal of local muscle sources of EMG contamination and the Laplacian transform being insensitive to distant (postural) muscle EMG contamination.

Short-term evaluation of visible implant alpha tags in juveniles of three fish species under laboratory conditions.

Visible implant alpha (VI alpha) tag-induced changes in mortality and condition, as well as tag retention and readability, were examined during a 4-week period for juveniles of three fish species: tiger muskellunge Esox masquinongy × Esox lucius (91 ± 7 mm total length, L(T), mean ± s.d.), Snake River cutthroat trout Oncorhynchus clarki behnkei (84 ± 8 mm) and rainbow trout Oncorhynchus mykiss (85 ± 5 mm). Mortality and condition did not differ between tagged fish and control fish for any species and overall tag retention rates were high (92% for E. masquinongy × E. lucius, 91% for O. c. behnkei and 100% for O. mykiss). Short-term readability of VI alpha tags was low in juvenile E. masquinongy × E. lucius and juvenile O. c. behnkei. Therefore, it is not recommend to use VI alpha tags in juvenile E. masquinongy × E. lucius or juvenile O. c. behnkei for periods >2 weeks, but VI alpha tags seem to be suitable for juvenile O. mykiss for a period of at least 4 weeks.

Effects of anesthetic agents on seizure-induction with intra-cortical injection of convulsants.

RATIONALE: Studies of partial or generalized seizure pathophysiology often require the use of intact animals. Additionally, anesthesia may be required for ethical reasons or paralysis if instrumental measures require immobilization. We examined three commonly used injected anesthetic for their impact on seizures induced by three convulsant agents. METHODS: We prepared rats, under pentobarbitone anesthesia (65 mg/kg) with a catheter, electrodes and a dural window, for later non-noxious experimentation. Three to seven days later, kainic acid (1.25 µg), picrotoxin (225 ng) or fluorocitrate (0.8 nmol) were injected intra-cortically in animals paralysed with succinylcholine, or anesthetised with pentobarbitone, urethane or fentanyl plus droperidol. We recorded EEG activity, the latencies to seizure discharges, the occurrence of spreading depressions and the presence of movements in response to the convulsants. RESULTS: Fentanyl plus droperidol was the only anesthetic agent permissive for seizure-discharges and spreading depressions. No significant differences in the time for seizure onset for fentanyl plus droperidol compared to paralyzed unanesthetised rats were seen for any of the convulsants (Student's t-test p>0.20). Movements during seizures as well as other drug-induced behaviors continued to be expressed during anesthesia. CONCLUSION: Fentanyl plus droperidol has useful properties as an anesthetic agent in studies of seizure induction with different convulsants.

Implications of stunting on morphology of freshwater fishes.

The purpose of this study was to assess morphological differences between stunted and non-stunted white perch Morone americana and green sunfish Lepomis cyanellus. Few female M. americana were captured; thus, morphological differences between adult males and juveniles were assessed for M. americana. Similarly, few immature (juvenile) L. cyanellus were captured for the stunted morphotype; thus, male and female morphological differences were assessed for L. cyanellus. Features of the head tended to be relatively larger in stunted fish of both species, whereas the mid-body tended to be relatively larger in non-stunted M. americana, but not in non-stunted L. cyanellus. Adult and juvenile morphology overlapped considerably in non-stunted M. americana, but there was a clear distinction between adult and juvenile morphology of stunted M. americana. There was little sexual dimorphism in shape in stunted L. cyanellus, whereas sexual dimorphism was evident in non-stunted L. cyanellus. It appears that selective forces imposed by predation and food limitation may contribute to morphological diversification between stunted and non-stunted fishes.

Removal of EEG noise and artifact using blind source separation.

A study was performed to investigate and compare the relative performance of blind signal separation (BSS) algorithms at separating common types of contamination from EEG. The study develops a novel framework for investigating and comparing the relative performance of BSS algorithms that incorporates a realistic EEG simulation with a known mixture of known signals and an objective performance metric. The key finding is that although BSS is an effective and powerful tool for separating and removing contamination from EEG, the quality of the separation is highly dependant on the type of contamination, the degree of contamination, and the choice of BSS algorithm. BSS appears to be most effective at separating muscle and blink contamination and less effective at saccadic and tracking contamination. For all types of contamination, principal components analysis is a strong performer when the contamination is greater in amplitude than the brain signal whereas other algorithms such as second-order blind inference and Infomax are generally better for specific types of contamination of lower amplitude.

Cell swelling, seizures and spreading depression: an impedance study.

The cellular processes that take place during the transition from pre-seizure state to seizure remain to be defined. In this study in awake, paralyzed rats, we used an electrical impedance measure of changes in extra-cellular intracranial volume to estimate changes in cell size in acute models of epilepsy. Animals were prepared with extradural electroencephalographic (EEG)/impedance electrodes and a venous catheter. On a subsequent day, animals were paralyzed, ventilated and treated with picrotoxin, kainic acid or fluorocitrate in doses that usually induce epileptiform discharges. We now report that increases in baseline impedance were induced by kainic acid and smaller increases by picrotoxin. We also demonstrated that epileptiform discharges were preceded by small, accelerated increases in impedance. Increases in baseline impedance were highly correlated with increases in power of non-ictal high frequency EEG activity. Seizures were accompanied by increases in impedance and all treatments induced transient, relatively large, increases in impedance often associated with unilateral reductions in low frequency EEG, likely periods of spreading depression. We conclude: cerebral cells swell in convulsant models of epilepsy, that there are pre-ictal accelerations in cell swelling, and that spreading depression-like events are frequently associated with seizures.

Gamma rhythms are not integral to EEG spindle phenomena.

OBJECTIVE: Gamma rhythms (30-100 Hz) have been shown to be associated with spindling activity induced by picrotoxin. To determine if gamma power is unique to picrotoxin spindles or is an integral part of physiological and pathological spindling activity we analysed and compared the strength and brain distribution of gamma EEG power during 4 spindling activities in the rat. METHODS: The electroencephalogram (EEG) was recorded from rats with chronically implanted electrodes during natural sleep, barbiturate anaesthesia, during naturally occurring absence epilepsy spike and wave discharges and following the systemic application of picrotoxin. Spectral analysis was applied off-line to compare the strength and brain distribution of gamma EEG power during the 4 spindling activities. RESULTS: Each spindle type contained significantly different levels of gamma power. Gamma power was significantly increased over background levels during picrotoxin spindles, slightly increased during absence spindles, slightly decreased during sleep spindles and significantly suppressed during barbiturate spindles CONCLUSIONS: Changes in the power of gamma frequencies during spindle types suggest that gamma frequencies are neither the cause of nor an integral part of a spindle. They appear to be correlated with levels of consciousness and may contribute to the process of epileptogenesis. SIGNIFICANCE: The findings are consistent with high frequency EEG activity being related to seizure-tendency.

Localised astroglial dysfunction disrupts high-frequency EEG rhythms.

We used cerebral cortex injections of fluorocitrate to determine if selective astrocytic disturbances affect the electroencephalogram (EEG). Rats were halothane-anaesthetized and 0.8 nmol of sodium fluorocitrate was injected into hindlimb (motor-sensory) cortex. Extra-dural EEG electrodes were implanted after which the anaesthesia was ceased. EEG was recorded at 1, 3, 5, 7, 24 and 48 hours. There was a broad-band reduction in frequencies in the EEG between 20 and 100 Hz commencing within 1 hour of injection and largely restricted to the side of injection and to frontal cortex, and maximal at 3 hours. Halothane had a suppressive effect on gamma power after citrate injection, but also prevented EEG suppression caused by fluorocitrate, consistent with the hypothesis that some of the action of fluorocitrate depended on gap-junctions. The findings are consistent with the hypothesis that primary astroglial dysfunction leads to reduced neuronal transmission and further supports gap-junctions as mediating fluorocitrate-induced astroglial effects.

Cognitive tasks augment gamma EEG power.

OBJECTIVE: Gamma EEG oscillations are low amplitude rhythms in the 30-100 Hz range that correlate with cognitive task execution. They are usually reported using time-locked averaging of EEG during repetitive tasks. We tested the hypothesis that continuous gamma EEG would be measurable during mental tasks. METHODS: We investigated sustained human gamma EEG oscillations induced by 8 cognitive tasks (Visual Checkerboard, Expectancy, Reading, Subtraction, Music, Expectancy, Word learning, Word recall, and a Video Segment) in 20 subjects using standard digital EEG recording and power spectral analysis. RESULTS: All of the cognitive tasks augmented gamma power relative to a control condition (eyes open watching a blank computer screen). This enhancement was statistically significant at more than one scalp site for all tasks except checkerboard. The Expectancy, Learning, Reading and Subtraction tasks expressed the most impressive gamma response, up to 5 fold above the control condition and there was some task-related specificity of the distribution of increased gamma power, especially in posterior cortex with visual tasks. CONCLUSIONS: Widespread gamma activation of cortical EEG can easily be demonstrated during mental activity. SIGNIFICANCE: These results establish the feasibility of measuring high frequency EEG rhythms with trans-cranial recordings, demonstrate that sustained gamma EEG activity correlates with mentation, and provides evidence consistent with the temporal binding model.

Observation of parity nonconservation in møller scattering.

We report a measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: A(PV)=[-175+/-30(stat)+/-20(syst)] x 10(-9). This first direct observation of parity nonconservation in Møller scattering leads to a measurement of the electron's weak charge at low energy Q(e)(W)=-0.053+/-0.011. This is consistent with the standard model expectation at the current level of precision: sin((2)theta(W)(M(Z))((-)MS)=0.2293+/-0.0024(stat)+/-0.0016(syst)+/-0.0006(theory).

Bedout: a possible end-Permian impact crater offshore of northwestern Australia.

The Bedout High, located on the northwestern continental margin of Australia, has emerged as a prime candidate for an end-Permian impact structure. Seismic imaging, gravity data, and the identification of melt rocks and impact breccias from drill cores located on top of Bedout are consistent with the presence of a buried impact crater. The impact breccias contain nearly pure silica glass (SiO2), fractured and shock-melted plagioclases, and spherulitic glass. The distribution of glass and shocked minerals over hundreds of meters of core material implies that a melt sheet is present. Available gravity and seismic data suggest that the Bedout High represents the central uplift of a crater similar in size to Chicxulub. A plagioclase separate from the Lagrange-1 exploration well has an Ar/Ar age of 250.1 +/- 4.5 million years. The location, size, and age of the Bedout crater can account for reported occurrences of impact debris in Permian-Triassic boundary sediments worldwide.

Scanning tunnelling microscopy imaging of [3 x 3] Mn nonanuclear grids.

The scanning tunnelling microscopy imaging of [3 x 3] Mn(II) nonanuclear grids on gold substrates is described. Self-assembled behaviour is observed at both high and low coverage, with submolecular resolution of individual molecules displayed at low deposition concentrations. The importance of proper image processing techniques is demonstrated in resolving the layer structure at high coverage.

Realistic human head model for EEG from both the geometry and conductivity aspects.

This paper describes modelling and simulation of a had model which incorporates both the geometries and conductivities of the human head. It focuses on the inclusion of tissue conductivity inhomogeneity in a realistically-shaped head model, and investigates the impact of this inclusion on the potential distribution within the model. The result show that the impact, which has been neglected in realistic head models so far, is significant.

Persistent abnormality detected in the non-ictal electroencephalogram in primary generalised epilepsy.

OBJECTIVES: Gamma oscillations (30-100 Hz gamma electroencephalographic (EEG) activity) correlate with high frequency synchronous rhythmic bursting in assemblies of cerebral neurons participating in aspects of consciousness. Previous studies in a kainic acid animal model of epilepsy revealed increased intensity of gamma rhythms in background EEG preceding epileptiform discharges, leading the authors to test for intensified gamma EEG in humans with epilepsy. METHODS: 64 channel cortical EEG were recorded from 10 people with primary generalised epilepsy, 11 with partial epilepsy, and 20 controls during a quiescent mental state. Using standard methods of EEG analysis the strength of EEG rhythms (fast Fourier transformation) was quantified and the strengths of rhythms in the patient groups compared with with controls by unpaired t test at 1 Hz intervals from 1 Hz to 100 Hz. RESULTS: In patients with generalised epilepsy, there was a threefold to sevenfold increase in power of gamma EEG between 30 Hz and 100 Hz (p<0.01). Analysis of three unmedicated patients with primary generalised epilepsies revealed an additional 10-fold narrow band increase of power around 35 Hz-40 Hz (p<0.0001). There were no corresponding changes in patients with partial epilepsy. CONCLUSIONS: Increased gamma EEG is probably a marker of the underlying ion channel or neurotransmitter receptor dysfunction in primary generalised epilepsies and may also be a pathophysiological prerequisite for the development of seizures. The finding provides a new diagnostic approach and also links the pathophysiology of generalised epilepsies to emerging concepts of neuronal correlates of consciousness.

Picrotoxin-induced generalised convulsive seizure in rat: changes in regional distribution and frequency of the power of electroencephalogram rhythms.

OBJECTIVES: It is unknown how generalised discharges in primary generalised epilepsy (PGE) develop from background brain electrical activity or how widespread these discharged are throughout the brain. Here we address this by determining which neural structures and rhythms lead to and participate in generalised discharges in the picrotoxin rat model of PGE. METHODS: Rats with chronically implanted electrodes were infused with picrotoxin until a seizure occurred. This process we refer to as acute epileptogenesis. The electroencephalogram (EEG) was recorded and spectral analysis applied off-line to determine changes in the spectral power of contributing frequencies in 13 brain regions. RESULTS: Two types of generalised discharge occurred, spindles and seizure, which were present in all brain regions studied. None of the frequencies (1-100 Hz) were significantly increased in background EEG before either spindles or seizure. Within the generalised discharges, power changes revealed significant increases in 6-8 Hz, most powerful in ventrolateral thalamus and neocortex. Gamma frequencies were increased significantly in neocortical structures during spindles with further increases in most structures at seizure onset. 1 Hz was significantly increased in parietal cortex during spindles with differential increases at seizure onset. CONCLUSIONS: We conclude that gamma, 1 and 6-8 Hz frequencies do not appear to contribute to picrotoxin epileptogenesis but do play a role in generalised seizures. The distribution of these frequencies during discharges suggests that the spindles are thalamocortical events and that the seizure is a cortical event with downstream effects on other brain regions.