Search

Background: The success of minimally invasive parathyroidectomy (MIP) relies on accurate localization of the abnormal parathyroid glands. Concordant findings on ultrasound (US) and 99mTc-scintigraphy (sestamibi) are currently considered the ‘gold standard’. Computed tomography (CT) has also recently been used in preoperative planning. We sought to assess the accuracy of CT for localization of abnormal parathyroid glands in such patients. Methods: An audit of 75 patients with primary hyperparathyroidism (PHPT) who underwent neck US and CT between 2017 and 2019 at our center as their first-line imaging. Results: All 75 patients underwent US and CT and 54 (72.0%) also had sestamibi. CT alone identified a potential target in all patients, of which the location was correct in 63 (84.0%). The overall combined sensitivity of US and CT was 88% (95% CI 78–94) and was higher than the combined sensitivity of US and sestamibi (65% [95% CI 53–76]; p< 0.001). Twenty-one patients (28.0%) had an ectopic gland, and the sensitivity of US and CT was 86% (95% CI 64–96) versus US and sestamibi (57% [95% CI 34–77]; p= 0.016). For adenomas < 1.0 g (n= 36; 48%), the accuracy of CT was 81% (95% CI 64–91) compared with 62% (95% CI 44–77) for US and sestamibi (p= 0.04). The correct preoperative diagnosis of multiglandular disease (n= 9; 12%) seemed to be the most difficult, with similar accuracy for US and sestamibi (40% [95% CI 14–73]) and US and CT (50% [95% CI 20–80]) (p> 0.99). Conclusion: The combination of US and CT was able to correctly identify the location of the abnormal parathyroid in 88% of patients and, in comparison with US and sestamibi, had better diagnostic accuracy, especially for smaller and ectopic adenomas. This finding suggests that US and CT could be considered as a first-line imaging modality in patients with PHPT considered for MIP.

The fast Van Allen radiation belt electron dynamics during geomagnetic storms have not yet been fully explained, in part due to limitations of standard satellite missions in both orbit and the number of spacecraft. Here we overcome these limitations using measurements from the Global Positioning System (GPS) constellation during an acceleration event on 26 August 2018. We show that the acceleration of relativistic electrons occurs in two distinct bursts, each dominated by a different acceleration mechanism. The first burst enhances the radiation belt electrons by four orders of magnitude in 2 hr and is consistent with ULF‐wave radial diffusion. The second burst is likely caused by the local acceleration and delivers an order‐of‐magnitude increase in 20 min. This work demonstrates how distributed, operational measurements can be used to resolve phenomena not observable with previous capabilities, and that rapid energization of the radiation belt can occur much faster than previously reported. In this paper, we present a detailed analysis of terrestrially‐trapped electron space radiation during the August 2018 geomagnetic storm. This event is characterized by a very fast enhancement in the trapped electron population that increases particle counts by more than a factor of a thousand over only 6 hr. Such fast dynamics cannot be resolved by typical survey missions due to their long orbital periods. We instead use measurements from 20 satellites in the Global Positioning System (GPS) constellation, which allows us to perform an analysis of the space radiation dynamics on much shorter timescales. These GPS data reveal that the fast enhancement during the August 2018 storm occurred in two distinct bursts. By introducing a novel technique for GPS particle data analysis, we also determine that each of the bursts is governed by different physical processes that act on different timescales. The revealed fast dynamics of near‐Earth trapped radiation point toward a need to reevaluate the classic paradigm that the changes in the radiation levels are slow and can be revealed by surveys with a low number of spacecraft. Indeed, we foresee a critical role for constellation measurements, such as from GPS, in the future of radiation belt science. Constellation measurements of the Van Allen radiation belt electrons can be used to reveal fast nonadiabatic changes at sub‐orbit timescalesElectron acceleration during the August 2018 storm consists of two distinct acceleration bursts governed by different physical processesULF‐wave radial diffusion and local acceleration can significantly alter radiation belt electron content on timescales of minutes to hours Constellation measurements of the Van Allen radiation belt electrons can be used to reveal fast nonadiabatic changes at sub‐orbit timescales Electron acceleration during the August 2018 storm consists of two distinct acceleration bursts governed by different physical processes ULF‐wave radial diffusion and local acceleration can significantly alter radiation belt electron content on timescales of minutes to hours

Fast dropout of relativistic and ultrarelativistic electrons at both high and low L* regions were observed during the intense coronal mass ejection driven storm in June 2015. An improved radial diffusion model, using an event‐specific last closed drift shell and newly available radial diffusion coefficients (DLL), is implemented to simulate the magnetopause shadowing loss of electrons. The model captures the fast shadowing loss of electrons well at high L* regions after both interplanetary shocks, and reproduces the initial adiabatic loss of the high‐energy storage ring at low L* regions after the second strong shock. We show for the first time that using the event‐specific and K‐dependent last closed drift shell and improved DLLis critical to reproduce the observed dropout features, including the timing, location, and the butterfly electron pitch angle distribution. Future inclusion of the electromagnetic ion cyclotron wave scattering process is needed to model the observed further depletion of the storage ring. A radial diffusion model with event‐specific and K‐dependent LCDS and recent DLLis used to simulate the electron magnetopause shadowing lossThe model captures the fast shadowing loss of electrons at high L* and the initial adiabatic loss of the high‐energy storage ring at low L*Future inclusion of the EMIC wave scattering process is needed to model the observed further depletion of the storage ring

In this paper, we study electron radial diffusion coefficients derived from Pc4‐Pc5 ultralow frequency (ULF) wave power during the intense geomagnetic storm on 17–18 March 2015. During this storm the population of highly relativistic electrons was depleted within 2 hr of the storm commencement. This radial diffusion, depending upon the availability of source populations, can cause outward radial diffusion of particles and their loss to the magnetosheath, or inward transport and acceleration. Analysis of electromagnetic field measurements from Geostationary Operational Environment Satellite (GOES), Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite, and ground‐based magnetometers shows that the main phase storm‐specific radial diffusion coefficients do not correspond to statistical estimates. Specifically, during the main phase, the electric diffusion ( DLLE) is reduced, and the magnetic diffusion ( DLLB) is increased, compared to empirical models based on Kp. Contrary to prior results, the main phase magnetic radial diffusion cannot be neglected. The largest discrepancies, and periods of dominance of DLLBover DLLE, occur during intervals of strongly southward IMF. However, during storm recovery, both magnetic and electric diffusion rates are consistent with empirical estimates. We further verify observationally, for the first time, an energy coherence for both DLLBand DLLEwhere diffusion coefficients do not depend on energy. We show that, at least for this storm, properly characterizing main phase radial diffusion, potentially associated with enhanced ULF wave magnetopause shadowing losses, cannot be done with standard empirical models. Modifications, associated especially with southward IMF, which enhance the effects of DLLBand introduce larger main phase outward transport losses, are needed. Event‐specific electric and magnetic diffusion both show coherent energy dependence during the intense March 2015 magnetic stormMain phase event‐specific diffusion coefficients are poorly represented by empirical Kp‐dependent solar cycle averaged statistical modelsIntervals of southward IMF during the main phase drive strong compressional perturbations significantly enhancing magnetic diffusion

The “Quantitative Assessment of Radiation Belt Modeling” focus group was in place at Geospace Environment Modeling from 2014 to 2018. The overarching goals of this focus group were to bring together the current state‐of‐the‐art models for the acceleration, transport, and loss processes in Earth's radiation belts; develop event‐specific and global inputs of wave, plasma, and magnetic field to drive these models; and combine all these components to achieve a quantitative assessment of radiation belt modeling by validating against contemporary radiation belt measurements. This article briefly reviews the current understanding of radiation belt dynamics and related modeling efforts, summarizes the activities and accomplishments of the focus group, and discusses future directions. The “Quantitative Assessment of Radiation Belt Modeling” focus group was in place at GEM (Geospace Environment Modeling) from 2014 to 2018This article briefly reviews the current understandings of radiation belt dynamics and their modeling effortsThe article also summarizes the activities and accomplishments of the focus group and discusses future directions

We present the temporal evolution of electron Phase Space Density (PSD) in the outer radiation belt during the intense March 2015 geomagnetic storm. Comparing observed PSD profiles as a function of L* at fixed first, M, and second, K, adiabatic invariants with those produced by simulations is critical for determining the physical processes responsible for the outer radiation belt dynamics. Here we show that the bulk of the accelerated and enhanced outer radiation belt population consists of electrons with K < 0.17 G1/2Re. For these electrons, the observed PSD versus L* profiles during the recovery phase of the storm have a positive radial gradient. We compare the observed temporal evolution of the PSD profiles during the recovery phase with those produced by radial diffusion simulations driven by observed Ultralow Frequency wave power as measured on the ground. Our results indicate that the dominant flux enhancement, inside L* < 5, in the heart of the outer radiation belt during the March 2015 geomagnetic storm is consistent with that produced by fast inward radial diffusion of electrons from a dynamic outer boundary driven by enhanced Ultralow Frequency wave power. The March 2015 outer radiation belt flux enhancement was dominated by a population of accelerated low‐K electrons with K < 0.17 G1/2ReDuring the flux recovery phase no growing PSD peaks occurred inside L*≲5, suggesting local heating was not the dominant acceleration processThe observed flux enhancement inside L* < 5 is reproduced by our ULF wave radial diffusion simulation without including local acceleration

Radiation belt behavior is often analyzed in terms of adiabatic invariants, of which the third roughly characterizes the radial distance of particle drift shells. The outermost, or lastclosed drift shell, can be an important boundary for numerical modeling, especially for drift‐averaged treatments such as three‐dimensional diffusion codes. Here we discuss calculation of the last closed drift shell, using the widely used International Radiation Belt Environment Modeling (IRBEM) Library, the LanlGeoMag code, and a guiding center code named AFRL‐Shell, in conjunction with a variety of current magnetic field models. We present results for the four events in 2013, comprising the radiation belt challengeorganized by the Quantitative Assessment of Radiation Belt Modeling focus group of the Geospace Environment Modeling (GEM) program. Several codes to calculate L* in realistic magnetic field models are presentedMethods for finding last closed drift shells with these codes are discussedResults for four GEM radiation belt challengeevents, using a variety of magnetic field models, are compared

We present observations of very fast radiation belt loss as resolved using high time resolution electron flux data from the constellation of Global Positioning System (GPS) satellites. The time scale of these losses is revealed to be as short as ∼0.5–2 hr during intense magnetic storms, with some storms demonstrating almost total loss on these time scales and which we characterize as radiation belt extinction. The intense March 2013 and March 2015 storms both show such fast extinction, with a rapid recovery, while the September 2014 storm shows fast extinction but no recovery for around 2 weeks. By contrast, the moderate September 2012 storm which generated a three radiation belt morphology shows more gradual loss. We compute the last closed drift shell (LCDS) for each of these four storms and show a very strong correspondence between the LCDS and the loss patterns of trapped electrons in each storm. Most significantly, the location of the LCDS closely mirrors the high time resolution losses observed in GPS flux. The fast losses occur on a time scale shorter than the Van Allen Probes orbital period, are explained by proximity to the LCDS, and progress inward, consistent with outward transport to the LCDS by fast ultralow frequency wave radial diffusion. Expressing the location of the LCDS in L*, and not model magnetopause standoff distance in units of RE, clearly reveals magnetopause shadowing as the cause of the fast loss observed by the GPS satellites. GPS electron flux data reveal very fast radiation belt losses, which can be as short as  0.5–2 hr during radiation belt extinction eventsDynamics of the last closed drift shell mirrors the observed loss in studied storms indicating magnetopause shadowing was the dominant causeElectron populations with different energies show similar loss patterns indicating an inward loss propagation, with fast outward transport

Quasiperiodic energetic particle injections have been observed at geosynchronous orbit on the duskside during a steady magnetospheric convection event. We examine high‐resolution auroral imager data and ground magnetometer data associated with the first of these injections and conclude that it was not associated with classical substorm signatures. It is proposed that these injections are caused by the explosive nonlinear growth of a shear flow‐ballooning instability in the region where subauroral polarization streams (SAPS) also occur. It is suggested that interchange will occur preferentially in the low‐conductivity SAPS region since the magnetic Richardson number is lowest there and the “line‐tying” effect will also be least stabilizing there. We propose that the observed particle injection signatures and auroral morphology constitute a new type of SAPS‐associated explosive “onset‐like” disturbance that can occur during intervals of strong convection. A new type of explosive injection‐associated auroral disturbance on the duskside is presentedIt followed development of ripples on the equatorward edge of the oval and expanded equatorwardUnusual disruption of the equatorward edge in SAPS region suggests a shear‐driven instability at plasmapause

To achieve a better understanding of the dominant loss mechanisms for the rapid dropouts of radiation belt electrons, three distinct radiation belt dropout events observed by Van Allen Probes are comprehensively investigated. For each event, observations of the pitch angle distribution of electron fluxes and electromagnetic ion cyclotron (EMIC) waves are analyzed to determine the effects of atmospheric precipitation loss due to pitch angle scattering induced by EMIC waves. Last closed drift shells (LCDS) and magnetopause standoff position are obtained to evaluate the effects of magnetopause shadowing loss. Evolution of electron phase space density (PSD) versus L* profiles and the μand K(first and second adiabatic invariants) dependence of the electron PSD drops are calculated to further analyze the dominant loss mechanisms at different L*. Our findings suggest that these radiation belt dropouts can be classified into distinct classes in terms of dominant loss mechanisms: magnetopause shadowing dominant, EMIC wave scattering dominant, and combination of both mechanisms. Different from previous understanding, our results show that magnetopause shadowing can deplete electrons at L* < 4, while EMIC waves can efficiently scatter electrons at L* > 4. Compared to the magnetopause standoff position, it is more reliable to use LCDS to evaluate the impact of magnetopause shadowing. The evolution of electron PSD versus L* profile and the μ, Kdependence of electron PSD drops can provide critical and credible clues regarding the mechanisms responsible for electron losses at different L* over the outer radiation belt. Radiation belt dropouts can be classified into three distinct classes in terms of dominant loss mechanismsMagnetopause shadowing can deplete electrons at L* < 4, while EMIC waves can efficiently scatter electrons at L* > 4The μ, Kdependence of electron PSD drops can provide critical and credible clues regarding the electron loss mechanisms at different L*

The most significant unknown regarding relativistic electrons in Earth's outer Van Allen radiation belt is the relative contribution of loss, transport, and acceleration processes within the inner magnetosphere. Detangling each individual process is critical to improve the understanding of radiation belt dynamics, but determining a single component is challenging due to sparse measurements in diverse spatial and temporal regimes. However, there are currently an unprecedented number of spacecraft taking measurements that sample different regions of the inner magnetosphere. With the increasing number of varied observational platforms, system dynamics can begin to be unraveled. In this work, we employ in situ measurements during the 13–14 January 2013 enhancement event to isolate transport, loss, and source dynamics in a one‐dimensional radial diffusion model. We then validate the results by comparing them to Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms observations, indicating that the three terms have been accurately and individually quantified for the event. Finally, a direct comparison is performed between the model containing event‐specific terms and various models containing terms parameterized by geomagnetic index. Models using a simple 3/Kploss time scale show deviation from the event‐specific model of nearly 2 orders of magnitude within 72 h of the enhancement event. However, models using alternative loss time scales closely resemble the event‐specific model. Transport, loss, and source terms individually determined for enhancement eventModel results using event‐specific terms are validated by using Van Allen Probe and THEMIS observations1‐D diffusion models, with various loss and transport terms, are compared

Mechanisms for electron injection, trapping, and loss in the near‐Earth space environment are investigated during the October 2012 “double‐dip” storm using our ring current‐atmosphere interactions model with self‐consistent magnetic field (RAM‐SCB). Pitch angle and energy scattering are included for the first time in RAM‐SCB using Land magnetic local time (MLT)‐dependent event‐specific chorus wave models inferred from NOAA Polar‐orbiting Operational Environmental Satellites (POES) and Van Allen Probes Electric and Magnetic Field Instrument Suite and Integrated Science observations. The dynamics of the source (approximately tens of keV) and seed (approximately hundreds of keV) populations of the radiation belts simulated with RAM‐SCB is compared with Van Allen Probes Magnetic Electron Ion Spectrometer observations in the morning sector and with measurements from NOAA 15 satellite in the predawn and afternoon MLT sectors. We find that although the low‐energy (E< 100 keV) electron fluxes are in good agreement with observations, increasing significantly by magnetospheric convection during both SYM‐Hdips while decreasing during the intermediate recovery phase, the injection of high‐energy electrons is underestimated by this mechanism throughout the storm. Local acceleration by chorus waves intensifies the electron fluxes at E≥50 keV considerably, and RAM‐SCB simulations overestimate the observed trapped fluxes by more than an order of magnitude; the precipitating fluxes simulated with RAM‐SCB are weaker, and their temporal and spatial evolutions agree well with POES/Medium Energy Proton and Electron Detectors data. First RAM‐SCB simulations with 2‐D (MLT‐ and L‐dependent) event‐specific chorus wave models inferred from LEO and RBSP dataThe measured low‐energy trapped and precipitating electron fluxes are well reproduced by magnetospheric convectionLocal acceleration by chorus waves intensifies the electron fluxes at energies E greater than approximately 50 keV and overestimates observations

As electromagnetic ion cyclotron (EMIC) waves may play an important role in radiation belt dynamics, there has been a push to better include them into global simulations. How to best include EMIC wave effects is still an open question. Recently many studies have attempted to parameterize EMIC waves and their characteristics by geomagnetic indices. However, this does not fully take into account important physics related to the phase of a geomagnetic storm. In this paper we first consider how EMIC wave occurrence varies with the phase of a geomagnetic storm and the SYM-H, AE, and Kpindices. We show that the storm phase plays an important role in the occurrence probability of EMIC waves. The occurrence rates for a given value of a geomagnetic index change based on the geomagnetic condition. In this study we also describe the typical plasma and wave parameters observed in Land magnetic local time for quiet, storm, and storm phase. These results are given in a tabular format in the supporting informationso that more accurate statistics of EMIC wave parameters can be incorporated into modeling efforts. The occurrence of EMIC waves is not well described by a single geomagnetic indexEMIC wave occurrence is highly dependent upon geomagnetic storm phaseThe local plasma conditions when there is EMIC wave activity differ significantly from those when no EMIC waves are seen

Dropout events are dramatic decreases in radiation belt electron populations that can occur in as little as 30 minutes. Loss to magnetopause due to a combination of magnetopause shadowing and outward radial transport plays a significant role in these events. We examine the dropout of relativistic electron populations during the October 2012 geomagnetic storm using simulated electron phase space density, evaluating the contribution of different processes to losses across the magnetopause. We compare loss contribution from outward transport calculated using a standard empirical radial diffusion model that assumes a dipolar geomagnetic field to an event‐specific radial diffusion model evaluated with a non‐dipolar geomagnetic field. We additionally evaluate the contribution of Shabansky type 1 particles, which bounce along magnetic field lines with local equatorial maxima, to the loss calculated during this event. We find that the empirical radial diffusion model with a dipolar background field underestimates the contribution of radial diffusion to this dropout event by up to 10% when compared to the event‐specific, non‐dipolar radial diffusion model. We additionally find that including Shabansky type 1 particles in the initial electron phase space density, that is, allowing some magnetic field lines distorted from the typical single‐minima configuration in drift shell construction, increases the calculated loss by an average of 0.75%. This shows that the treatment of the geomagnetic field significantly impacts the calculation of electron losses to the magnetopause during dropout events, with the non‐dipolar treatment of radial diffusion being essential to accurately quantify the loss of outer radiation belt populations. Geomagnetic field treatment greatly affects loss quantification during dropout eventsNon‐dipolar radial diffusion models are required to precisely quantify loss across the magnetopauseShabansky particles may significantly contribute to total loss across the magnetopause Geomagnetic field treatment greatly affects loss quantification during dropout events Non‐dipolar radial diffusion models are required to precisely quantify loss across the magnetopause Shabansky particles may significantly contribute to total loss across the magnetopause

The DREAM3D diffusion model is applied to Van Allen Probes observations of the fast dropout and strong enhancement of MeV electrons during the October 2012 “double‐dip” storm. We show that in order to explain the very different behavior in the two “dips,” diffusion in all three dimensions (energy, pitch angle, and L*) coupled with data‐driven, event‐specific inputs, and boundary conditions is required. Specifically, we find that outward radial diffusion to the solar wind‐driven magnetopause, an event‐specific chorus wave model, and a dynamic lower‐energy seed population are critical for modeling the dynamics. In contrast, models that include only a subset of processes, use statistical wave amplitudes, or rely on inward radial diffusion of a seed population, perform poorly. The results illustrate the utility of the high resolution, comprehensive set of Van Allen Probes' measurements in studying the balance between source and loss in the radiation belt, a principal goal of the mission. DREAM3D uses event‐specific driving conditions measured by Van Allen ProbesElectron dropout is due to outward radial diffusion to compressed magnetopauseEvent‐specific chorus and seed electrons are necessary for the enhancement

Phase Space Density (PSD) matching can be used to identify the presence of nonadiabatic processes, evaluate accuracy of magnetic field models, or to cross‐calibrate instruments. Calculating PSD in adiabatic invariant coordinates requires a global specification of the magnetic field. For a well specified global magnetic field, nonadiabatic processes or inadequate cross calibration will give a poor PSD match. We have calculated PSD(μ, K) for both Van Allen Probes using a range of models and compare these PSDs at conjunctions in L* (for given μ, K). We quantitatively assess the relative goodness of each model for radiation belt applications. We also quantify the uncertainty in the model magnetic field magnitude and the related uncertainties in PSD, which has applications for modeling and particle data without concurrent magnetic field measurements. Using this technique, we show the error in PSD for an energy spectrum observed by the relativistic electron‐proton telescope (REPT) is a factor of ∼1.2 using the TS04 model. PSD matching shows TS04 model best represents inner magnetosphere configurationPSD error from a model 1st adiabatic invariant is small (factor of 1.16)The REPT instruments are confirmed to be well cross‐calibrated

Two high‐head dams on the Elwha River in Washington State (USA) have changed the migratory patterns of resident and anadromous fish, limiting Pacific salmon to the lower 7.9 km of a river that historically supported large Pacific salmon runs. To document the effects of the dams prior to their removal, we measured carbon and nitrogen stable isotope ratios of primary producers, benthic macroinvertebrates, and fish, and water chemistry above, between and below the dams. We found that δ15N was significantly higher in fish, stoneflies, black flies, periphyton and macroalgae where salmon still have access. Fish and chloroperlid stoneflies were enriched in δ13C, but the values were more variable than in δ15N. For some taxa, there were also differences between the two river sections that lack salmon, suggesting that factors other than marine‐derived nutrients are structuring longitudinal isotopic profiles. Consistent with trophic theory, macroalgae had the lowest δ15N, followed by periphyton, macroinvertebrates and fish, with a range of 6.9, 6.2 and 7.7‰ below, between, and above the dams, respectively. Water chemistry analyses confirmed earlier reports that the river is oligotrophic. Phosphorous levels in the Elwha were lower than those found in other regional rivers, with significant differences among regulated, unregulated and reference sections. The removal of these dams, among the largest of such projects ever attempted, is expected to facilitate the return of salmon and their marine‐derived nutrients (MDN) throughout the watershed, possibly altering the food web structure, nutrient levels and stable isotope values that we documented. Published in 2010 by John Wiley & Sons, Ltd.

One of the current challenges in docking studies is the inclusion of receptor flexibility. This is crucial because the binding sites of many therapeutic targets sample a wide range of conformational states, which has major consequences on molecular recognition. In this paper, we make use of very large sets of X-ray structures of cyclin dependent kinase 2 (CDK2) and heat shock protein 90 (HSP90) to assess the performance of flexible receptor docking in binding-mode prediction and virtual screening experiments. Flexible receptor docking performs much better than rigid receptor docking in the former application. Regarding the latter, we observe a significant improvement in the prediction of binding affinities, but owing to an increase in the number of false positives, this is not translated into better hit rates. A simple scoring scheme to correct this limitation is presented. More importantly, pitfalls inherent to flexible receptor docking have been identified and guidelines are presented to avoid them.

Recent advances in structure determination and computational methods have encouraged the development of structure-based virtual screening. Here we survey progress in the field and review the most recent methods, validation experiments and real applications, including an in-house example of hit identification for the oncology target Hsp90. These results provide a basis for discussing the current state of structure-based virtual screening and to outline the developments that are expected to have a major impact in the near future.

We have grown an antimicrobial polymer directly on the surfaces of glass and paper using atom transfer radical polymerization (ATRP). The method described here results in potentially permanent nonleaching antibacterial surfaces without the need to chemically graft the antimicrobial material to the substratum. The tertiary amine 2-(dimethylamino)ethyl methacrylate was polymerized directly onto Whatman #1 filter paper or glass slides via atom transfer radical polymerization. Following the polymerization, the tertiary amino groups were quaternized using an alkyl halide to produce a large concentration of quaternary ammonium groups on the polymer-modified surfaces. Incubating the modified materials with either Escherichia coli or Bacillus subtilis demonstrated that the modified surfaces had substantial antimicrobial capacity. The permanence of the antimicrobial activity was demonstrated through repeated use of a modified glass without significant loss of activity. Quaternary amines are believed to cause cell death by disrupting cell membranes allowing release of the intracellular contents. Atomic force microscopic imaging of cells on modified glass surfaces supports this hypothesis.

Many options of varying complexity are available for the management of congenital short digits resulting from aphalangia in symbrachydactyly and constriction ring syndrome. We have used non-vascularized free toe phalanx transfers for these children when a vascularized toe transfer has been contraindicated. We describe our technique and experience with 22 children who underwent a total of 64 transfers of the proximal (35) or middle (29) toe phalanges (average 3 per child). The mean age at initial surgery was 15 months, and the mean follow-up was 5 years. Duration of time until epiphyseal closure could not be determined accurately, but total digital elongation averaged 6 mm. Complications of this technique include joint instability, premature epiphyseal closure and, in one patient, infection and graft loss. Donor site deformity was determined according to measured growth deficit and toe function. This technique is a simple option for digital elongation and, if performed in the appropriate age group in short fingered and monodactylous subtypes of symbrachydactyly, has the potential to allow growth and function with minimal donor site deficit.

The serine proteinase inhibitors (serpins) are a superfamily of proteins with a diverse set of functions, including the control of blood coagulation, complement activation, programmed cell death and development. The most abundant serpins in human plasma are α1-antitrypsin (AAT) and α1-antichymotrypsin (ACT). During inflammation, circulating levels can increase by up to 3-fold for the former and by 4–5-fold for the latter. The major site for increased synthesis is the liver. Other tissues, such as the lung, are also capable of synthesizing AAT and ACT, and expression can be increased by up to 100-fold by cytokines. There is a tissue-specific promoter for the liver, and alternative promoters for other tissues that express AAT. Basal AAT expression is regulated by the synergistic action of the tissue-specific transcription factors hepatocyte nuclear factors 1α and 4. An enhancer positioned approx. 1.2 kb from the end of the last exon in the 3′ flanking sequence modulates cytokine-induced expression by interleukin-6 and oncostatin M. Microcell hybrid transfection studies have shown that a sequence containing 15 kb of 5′ flanking sequence is sufficient to allow stable expression of AAT in a position-independent manner. There is probably a single promoter for ACT. Oncostatin M-inducible elements have been identified in the 5′ flanking sequence approx. 100 bp upstream from the transcription initiation site, and a further interleukin-1-responsive enhancer has been identified approx. 13 kb upstream. The pathways for a humoral response are being mapped at high resolution.

Mutations in keratin genes give rise to a number of inherited skin fragility disorders, demonstrating that the intermediate filament cytoskeleton has an essential function in maintaining the structural integrity of epidermis and its appendages. Epidermolysis bullosa simplex (EBS) is an autosomal dominant disorder caused by mutations in keratins K5 or K14, which are expressed in the basal layer of stratified epithelia. Using a keratinocyte cell line established from an EBS patient, we investigated whether the muscle-specific intermediate filament protein desmin would be able to functionally complement a mutant keratin 14 in cultured keratinocytes. We show that in stably transfected EBS cells, desmin forms an extended keratin-independent cytoskeleton. Immunogold-EM analysis demonstrated that in the presence of numerous keratin filaments attached to desmosomes, desmin could nevertheless interact with desmosomes in the same cell, indicating the dynamic nature of the filament-desmosome association. When desmin-transfected cells were subjected to heat shock, the mutant keratin filaments showed a transient collapse while desmin filaments were maintained. Thus the defective keratin filaments and the wild-type desmin filaments appear to coexist in cells without interference. Expression of a type III intermediate filament protein like desmin may offer a strategy for the treatment of patients suffering from epidermal keratin mutations.

Sydney's successful bid to host the 2000 Olympic Games has resulted in a spectacular Olympic stadium which forms the centre-piece of a coordinated suite of venues. The stadium will provide 115 000 seats during the 2000 Olympics and Paralympics, and a post-games capacity of 80 000. At a cost of A$463 million, the stadium will have a greater seating capacity than any other Olympic stadium ever built. The selection of the development consortium was based on many factors including an inspired financial and operational plan but, above all, a powerful design statement. The stadium will become the model for the next generation of international stadia, its flexible structure allowing multiple sports usage and integrated mass communications. In a subject matter as vast as this, this paper seeks only to present highlights of the structural design aspects; and in particular the inspirational roof of the Olympic stadium, in the context of a fast-track programme which achieved a grand opening in March 1999, some 18 months before the 2000 Olympics.

The 5'-cap structure and poly(A) tail of eukaryotic mRNAs function synergistically to promote translation initiation through a physical interaction between the proteins that bind to these regulatory elements. In this study, we have examined the effect of leader length and the presence of secondary structure on the translational competence and the function of the cap and poly(A) tail for mRNAs microinjected into Xenopus oocytes. Increasing the length of the 5'-leader from 17 to 144 nt resulted in a 2- to 4-fold increase in expression from an mRNA containing an unstructured leader but increased expression up to 20-fold for an mRNA containing 5'-proximal structure. Consequently, the presence of secondary structure was less inhibitory for those mRNAs with a longer 5'-leader. Co-injection of poly(A)-binding protein (PABP) mRNA increased the function of the cap and poly(A) tail in promoting translation from poly(A)(+) but not poly(A)(-) mRNAs, particularly for mRNAs containing secondary structure. In the absence of an internal ribosome entry site, expression from the distal cistron of a dicistronic mRNA increased as a function of the length of the intercistronic region and the concentration of PABP. The inhibitory effect of intercistronic located secondary structure on translation was position-dependent. Indeed, the effect of secondary structure was abolished if positioned 134 nt upstream of the distal cistron. These data suggest that the length of a leader, the presence of secondary structure and the concentration of PABP determine the extent to which the cap and poly(A) tail regulate translation.

Serum stimulation of cultured Xenopus kidney cells results in enhanced phosphorylation of the translational initiation factor (eIF) 4E and promotes a 2.8-fold increase in the binding of the adapter protein eIF4G to eIF4E, to form the functional initiation factor complex eIF4F. Here we demonstrate the serum-stimulated co-isolation of the poly(A)-binding protein (PABP) with the eIF4F complex. This apparent interaction of PABP with eIF4F suggests that a mechanism shown to be important in the control of translation in the yeast Saccharomyces cerevisiae also operates in vertebrate cells. We also present evidence that the signaling pathways modulating eIF4E phosphorylation and function in Xenopus kidney cells differ from those in several mammalian cell types studied previously. Experiments with the immunosuppressant rapamycin suggest that the mTOR signaling pathway is involved in serum-promoted eIF4E phosphorylation and association with eIF4G. Moreover, we could find little evidence for regulation of eIF4E function via interaction with the specific binding proteins 4E-BP1 or 4E-BP2 in these cells. Although rapamycin abrogated serum-enhanced rates of protein synthesis and the interaction of eIF4G with eIF4E, it did not prevent the increase in association of eIF4G with PABP. This suggests that serum stimulates the interaction between eIF4G and PABP by a distinct mechanism that is independent of both the mTOR pathway and the enhanced association of eIF4G with eIF4E.

A whole-blood assay (WBA), which assesses the complete bactericidal activity of blood, was compared with the serum bactericidal assay (SBA), which measures antibody and complement mediated cell lysis. Twenty children infected with serogroup B strains and 25 infected with serogroup C strains were studied 8–12 weeks after disease, and 29 healthy children were used as controls. The infecting strain (convalescent children only) and two reference strains, MC58 (B:15:P1.7, 16) and NCTC 8554 (C:NT:P1.5) were used. In children previously infected with a serogroup B strain, bactericidal activity was detected in 95% and 85% to their infecting strain by the WBA (>50% killing) and the SBA (s), respectively. Bactericidal activity to the reference serogroup B and C strain was detected by WBA in 70 and 75% of children, respectively, and the SBA in 45% and 20%. In contrast bactericidal activity was detected to both serogroup C strains in >80% of children previously infected with a serogroup C strain using either assay and in 48% (WBA) and 20% (SBA) to the reference serogroup B strain. Levels of bactericidal activity were detectable in fewer control children. Children convalescing from meningococcal disease develop an immune response to their infecting strain, detectable by both the WBA and SBA, which is independent of age. However, the WBA appears to be a more sensitive measure of bactericidal activity to heterologous strains than the SBA.

The foot and mouth disease virus, a picornavirus, encodes two forms of a cysteine proteinase (leader or L protease) that bisects the EIF4G polypeptide of the initiation factor complex eIF4F into N‐terminal (Nt) and C‐terminal (Ct) domains. Previously we showed that, although in vitro cleavage of the translation initiation factor, eIF4G, with L protease decreases cap‐dependent translation, the cleavage products themselves may directly promote cap‐dependent protein synthesis. We now demonstrate that translation of uncapped mRNAs normally exhibits a strong requirement for eIF4F. However, this dependence is abolished when eIF4G is cleaved, with the Ct domain capable of supporting translation in the absence of the Nt domain. In contrast, the efficient translation of the second cistron of bicistronic mRNAs, directed by two distinct Internal Ribosome Entry Segments (IRES), exhibits no requirement for eIF4E but is dependent upon either intact eIF4G or the Ct domain. These results demonstrate that: (i) the apparent requirement for eIF4F for internal initiation on IRES‐driven mRNAs can be fulfilled by the Ct proteolytic cleavage product; (ii) when eIF4G is cleaved, the Ct domain can also support cap‐independent translation of cellular mRNAs not possessing an IRES element, in the absence of eIF4E; and (iii) when eIF4G is intact, translation of cellular mRNAs, whether capped or uncapped, is strictly dependent upon eIF4E. These data complement recent work in other laboratories defining the binding sites for other initiation factors on the eIF4G molecule.

A number of neuropsychological studies have revealed that memory problems are relatively common in patients with multiple sclerosis (MS). It may be useful to compare MS with conditions such as Huntington's disease (HD), which have been referred to as subcortical dementia. A characteristic of these conditions may be an impairment in implicit (unconscious) memory, but not in explicit (conscious) memory. The present study examined the functioning of explicit and implicit memory in MS. Results showed that implicit memory was not significantly impaired in the MS subjects, and that they were impaired on recall but not recognition. A correlation was found between implicit memory performance and disability status in MS patients. Findings also suggest the possibility of long-term priming of implicit memory in the control subjects. The implications of these results are discussed.

Carbonic anhydrase (EC 4.2.1.1) activity was investigated in normal human oesophageal mucosa using the Hansson and Ridderstråle catalytic cobalt methods. The enzyme was detected in the cell membranes and nuclei and, to a lesser extent, in the cytoplasm of the epithelial cells of the mucosa giving a ‘chicken wire’ appearance. Activity decreased towards the lumen. Other stratified squamous epithelia - buccal mucosa, ectocervix and skin - gave a similar pattern. Acinar cells of oesophageal submucosal glands also exhibited activity for the enzyme, but the ducts did not. The formation of reaction product was prevented by acetazolamide and ethoxzolamide and by the omission of bicarbonate from the substrate medium. Carbonic anhydrase in oesophageal squamous epithelium may be involved in the control of intra- and extracellular pH, while that in the glands is more likely to be concerned with bicarbonate secretion.

Four modifications to the COSMIC molecular mechanics force field are described, which greatly increase both its versatility and the accuracy of calculated conformational energies. The Hill non-bonded van der Waals potential function has been replaced by a two-parameter Morse curve and a new H-H potential, similar to that in MM3, incorporated. Hydrocarbon energies in particular are much improved.

The sequence of a cDNA encoding the corticotropin-releasing factor precursor has been identified by screening lambda gt11 libraries constructed from poly(A)+ RNA of the hypothalamic region of the white sucker Catostomus commersoni brain with synthetic oligonucleotide probes deduced from the sequence of the rat corticotropin-releasing factor. The amino acid sequence of corticotropin-releasing factor of the sucker is strikingly conserved when compared to its counterpart from rat and differs only in two positions at the carboxyl terminus; in contrast, there is little similarity between their cryptic regions.

The secretion of renin from granules stored in renal juxtaglomerular cells plays a key role in blood pressure homeostasis. The synthesis and release of renin and the extent of granulation is regulated by several mechanisms including signaling from the macula densa, neuronal input, and blood pressure. Through the use of a gene-targeting vector containing homology arms generated using the polymerase chain reaction, we have inactivated the Ren-1(d) gene, one of two mouse genes encoding renin, and report that lack of renin-1(d) results in altered morphology of the macula densa of the kidney distal tubule and complete absence of juxtaglomerular cell granulation. Furthermore, Ren-1(d-/-) mice exhibit sexually dimorphic hypotension. The altered growth morphology of the macula densa in Ren-1(d)-null mice should provide a tool for the investigation of the JG cell-macula densa signaling. Furthermore, the current data indicate that expression of the Ren-1(d) gene is a prerequisite for the formation of storage granules, even though the related protein renin-2 is present in these mice, suggesting that renin-1(d) and renin-2 are secreted by distinct pathways in vivo.

The cap-binding eukaryotic initiation factor, eIF4E, is a key target for the regulation of translation in mammalian cells and is widely thought to be present at very low molar concentrations. Here we present observations with the reticulocyte lysate that challenge this view. When reticulocyte ribosomes are harvested by centrifugation, most (approximately 75%) of the eIF4E remains in the postribosomal supernatant (PRS). In a reconstituted translation system we find that the ribosome-associated eIF4E alone can sustain much of the overall activity, suggesting that much of the factor in the PRS is functionally redundant. Consistent with this, our estimates of eIF4E in the reticulocyte lysate reveal much higher concentrations than previously reported. The association of a small proportion of eIF4E with the ribosome fraction appears to be functional and dependent on interaction with the factor eIF4G. This fraction of eIF4E is, as expected, more highly phosphorylated than that in the PRS; however, at least half the total phosphorylated eIF4E in reticulocyte lysate translation systems resides in the PRS fraction, suggesting that, while phosphorylation may enhance activity, it is not in itself sufficient to promote utilization of the factor. We also show that the eIF4E-binding factor, eIF4E-BP1 or PHAS-I, which regulates eIF4E activity in insulin-responsive cells, is present in the reticulocyte PRS at an approximately 1:1 molar ratio relative to eIF4E and demonstrate by co-immunoprecipitation studies that the binding of PHAS-I and eIF4G to eIF4E is mutually exclusive. These data are consistent with a potential regulatory role for PHAS-I in the reticulocyte lysate.

Receptors for the hormones vasopressin, angiotensin II, and thyrotropin-releasing hormone have been studied electrophysiologically in Xenopus laevis oocytes previously injected with poly(A)+ RNA from the respective receptor-containing tissues. The injected oocytes responded to the hormones by demonstrating oscillations in membrane currents as recorded by the voltage-clamp method. The response was dependent on the hormone concentrations and detectable between 5 and 1000 nM concentrations. Size fractionation of poly(A)+ RNA from the respective tissues showed that the mRNAs encoding the three hormone receptors were larger than 18S rRNA, suggesting a length of at least 2 kilobases. When vasopressin was added to the oocyte bath, an inward membrane current was generated in oocytes injected with rat poly(A)+ RNA from liver but not from kidney. This suggests that the V1-type (liver), not the V2-type (kidney), vasopressin receptor can be expressed and electrophysiologically identified in the oocyte. A V1-specific, but not a V2-specific, antagonist suppressed the vasopressin-dependent effect. Application of angiotensin II to liver poly(A)+ RNA-injected oocytes elicited oscillations in membrane current, indicating that these oocytes also expressed receptors for angiotension II; the antagonist [Sar1, O-methionyl-Tyr4]angiotensin II blocked this effect. Poly(A)+ RNA from tumor-derived GH3B6 cells, known to contain receptors for thyrotropin-releasing hormone, injected into oocytes induced receptors responding to thyrotropin-releasing hormone; the drug chlordiazepoxide suppressed the thyrotropin-releasing hormone response.

The bovine gene for the steroidogenic acute regulatory protein (StAR) was cloned and sequenced, including 2 kb of the upstream control region of the gene. The gene comprises seven exons arranged similarly to those of the human and mouse gene sequences. The sequence analysis identified three cis elements corresponding to the binding motif for the transcription factor SF-1/Ad4BP, at - 100, - 240 and - 1190 from the transcription start site. Electrophoretic mobility shift analysis (EMSA) using nuclear proteins from bovine corpus luteum and bovine adrenal as well as in vitro transcribed/translated SF-1/Ad4BP consistently showed that only the site at -1190 bound the transcription factor significantly. Very weak binding was detectable also at the - 240 site, but none at the -100 site. Heterologous transfection of StAR promoter deletion-reporter constructs into Hela cells cotransfected with an expression vector for bovine SF-1/Ad4BP, showed that this transcription factor can specifically act on the bovine StAR gene promoter, but preferentially in regions corresponding to the two proximal SF-1/Ad4BP elements at - 100 and - 240, though with only low relative effect. Furthermore, additional cotransfection of a construct expressing a constitutive protein kinase A catalytic subunit to mimic the effects of cAMP stimulation, led to a small SF-1/Ad4BP-dependent increase in reporter activity mediated only by the same proximal sites. Since the bovine StAR gene promoter does not appear to have a functional cAMP responsive element (CRE), either this effect is mediated in this system directly by SF-1/Ad4BP, or by other factors interacting with this transcription factor, but which do not involve CRE-mediated gene activation. Taken together, the results show that there is a discrepancy between the results of the EMSA experiments and those using transfection of promoter-reporter constructs, which needs to be resolved before a clear understanding of SF-1/Ad4BP-mediated regulation of the StAR gene is attained.