Gene expression, evolution, and the genetics of electrosensing in the smalltooth sawfish, Pristis pectinata

Sawfishes (Pristidae) are large, highly threatened rays named for their tooth-studded rostrum, which is used for prey sensing and capture. Of all five species, the smalltooth sawfish, Pristis pectinata, has experienced the greatest decline in range, currently found in only ~20% of its historic range. To better understand the genetic underpinnings of these taxonomically and morphologically unique animals, we collected transcriptomic data from several tissue types, mapped them to the recently completed reference genome, and contrasted the patterns observed with comparable data from other elasmobranchs. Evidence of positive selection was detected in 79 genes in P. pectinata, several of which are involved in growth factor/receptor tyrosine kinase signaling and body symmetry and may be related to the unique morphology of sawfishes. Changes in these genes may impact cellular responses to environmental conditions such as temperature, dissolved oxygen, and salinity. Data acquired also allow for examination of the molecular components of P. pectinata electrosensory systems, which are highly developed in sawfishes and have likely been influential in their evolutionary success.

Fission chamber data acquisition system for neutron flux measurements on the Mega-Amp Spherical Tokamak Upgrade

Neutron flux measurements are important in fusion devices for both safety requirements and physics studies. A new system has been built for the Mega-Amp Spherical Tokamak Upgrade (MAST Upgrade) that provides neutron count, DC, and Campbell mode measurements for a 1 µs period at 1 MHz. The acquisition system uses a Red Pitaya board to sample current from two fission chambers mounted on the side of the MAST-U vessel. The system-on-chip design of the Zynq-7020 on the Red Pitaya also allows a web server implementation using Flask for data retrieval and diagnostic configuration over the MAST Upgrade network.

Tiger Shark Attack on a Scuba Diver in New Caledonia

Herein we report an unprovoked shark attack on a scuba diver in New Caledonia. The species responsible for the attack was identified as a tiger shark (Galeocerdo cuvier), based on both the victim's testimony and forensic examination. The victim suffered significant loss of soft tissues from one thigh, which resulted in hemorrhagic shock. Even though the event occurred at a remote location, miles away from the nearest hospital, appropriate first aid, immediate deployment of an alert system, and prompt helicopter transfer by an emergency rescue team allowed the victim to be transferred to an intensive care unit in stable condition and to undergo surgery within 4 h of being bitten. Early coverage of exposed bone was performed, followed up with negative pressure dressing, antibiotic treatment, hyperbaric oxygen therapy, and a split skin graft. In spite of the massive muscular loss incurred, the victim was able to regain her ability to walk within 6 wk of the incident. Shark attacks on scuba divers are rare and seldom reported, especially in New Caledonia.

Morphological and Molecular Evidence Reveals the Longnose Skate Zearaja brevicaudata (Marini, 1933) to be a Senior Synonym of Dipturus lamillai Concha, Caira, Ebert & Pompert 2019

Longnose skates have great economic importance in South American fisheries, and in order to preserve them, it is important to have a well-defined taxonomic status of their species. Dipturus lamillai was recently described for Malvinas Islands waters based on morphological and molecular comparisons with Zearaja chilensis. Although D. lamillai has been compared with several congeneric species, it was not properly compared with the morphologically similar Zearaja brevicaudata, the most abundant longnose skate in the Southwest Atlantic. Here, these species were compared by morphological and molecular analyses in order to evaluate their conspecificity. Linear morphometric variables of holotype and paratypes of D. lamillai and 69 specimens of Z. brevicaudata were compared and investigated using Principal Component Analysis. In addition, thorn patterns, denticle distributions, color, and clasper morphology were compared. No body proportions or other single character that could differentiate D. lamillai from Z. brevicaudata were found. Molecular analyses comprised of the comparison of the Cytochrome oxidase subunit I (COI) and the NADH dehydrogenase subunit 2. The results of the Maximum Likelihood (ML) carried out for each molecular marker showed that sequences from D. lamillai clustered together with those of Z. brevicaudata, and the molecular distance determined by Kimura two-parameter were lower than the expected for different species. Additionally, the Automatic Barcode Gap Discovery method and the Bayesian implementation of the Poisson tree processes were carried out with COI sequences to explore species limits, and their results were consistent with ML analyses. In summary, the results obtained showed that there are no morphological or molecular differences between these nominal species of the valid skate genus Zearaja, leading to the conclusion that they are conspecific. Therefore, we designated Z. brevicaudata as a senior synonym of D. lamillai.

The digital mirror Langmuir probe: Field programmable gate array implementation of real-time Langmuir probe biasing

High bandwidth, high spatial resolution measurements of electron temperature, density, and plasma potential are valuable for resolving turbulence in the boundary plasma of tokamaks. While conventional Langmuir probes can provide such measurements, either their temporal or spatial resolution is limited: the former by the sweep rate necessary for obtaining I-V characteristics and the latter by the need to use multiple electrodes, as is the case in triple and double probe configurations. The Mirror Langmuir Probe (MLP) bias technique overcomes these limitations by rapidly switching the voltage on a single electrode cycling between three bias states, each dynamically optimized for the local plasma conditions. The MLP system on Alcator C-Mod used analog circuitry to perform this function, measuring T_e, V_F, and I_sat at 1.1 MSPS. Recently, a new prototype digital MLP controller has been implemented on a Red Pitaya Field Programmable Gate Array (FPGA) board which reproduces the functionality of the original controller and performs all data acquisition. There is also the potential to provide the plasma parameters externally for use with feedback control systems. The use of FPGA technology means the system is readily customizable at a fraction of the development time and implementation cost. A second Red Pitaya was used to test the MLP by simulating the current response of a physical probe using C-Mod experimental measurements. This project is available as a git repository to facilitate extensibility (e.g., real-time control outputs and more voltage states) and scalability through collaboration.

Modifications to the synthetic aperture microwave imaging diagnostic

The synthetic aperture microwave imaging diagnostic has been operating on the MAST experiment since 2011. It has provided the first 2D images of B-X-O mode conversion windows and showed the feasibility of conducting 2D Doppler back-scattering experiments. The diagnostic heavily relies on field programmable gate arrays to conduct its work. Recent successes and newly gained experience with the diagnostic have led us to modify it. The enhancements will enable pitch angle profile measurements, O and X mode separation, and the continuous acquisition of 2D DBS data. The diagnostic has also been installed on the NSTX-U and is acquiring data since May 2016.

Three new stingrays (Myliobatiformes: Dasyatidae) from the Indo-West Pacific

Three undescribed stingrays were discovered as part of a broader revision of the family Dasyatidae that formed part of the Chondrichthyan Tree of Life project. This research forms part of a sequence of papers on rays aimed at describing unnamed species for inclusion in a multi-authored guide to rays of the world. The first part of this series focused on a redefinition of genera of the family Dasyatidae. The new Indo-West Pacific taxa are represented by separate genera from three dasyatid subfamilies: Himantura australis sp. nov. (northern Australia and Papua New Guinea), Taeniura lessoni sp. nov. (Melanesia) and Telatrygon biasa sp. nov. (Indo-Malay Archipelago). Himantura australis sp. nov., which belongs to a complex of four closely related reticulate whiprays, differs subtly from its congeners in coloration, morphometrics and distribution. Taeniura lessoni sp. nov. is the second species in a genus containing the widely-distributed T. lymma, which is possibly the most abundant stingray in shallow coral-reef habitats of the Indo-Pacific, with the new species apparently restricted to Melanesia. Taeniura lessoni sp. nov. is distinguishable by the absence of a distinctive pair of vivid blue longitudinal stripes on the dorsolateral edges of the tail which is one of the most distinctive features of T. lymma. Telatrygon biasa sp. nov. belongs to a small, recently designated genus of stingrays represented by four species in the tropical Indo-West Pacific. Telatrygon biasa sp. nov. differs from these species in morphometrics. The new species differs markedly from T. zugei in its NADH2 sequence. Telatrygon crozieri is resurrected as a valid northern Indian Ocean representative of the T. zugei complex.

Edge Thomson scattering diagnostic on COMPASS tokamak: installation, calibration, operation, improvements

The core Thomson scattering diagnostic (TS) on the COMPASS tokamak was put in operation and reported earlier. Implementation of edge TS, with spatial resolution along the laser beam up to ∼1/100 of the tokamak minor radius, is presented now. The procedure for spatial calibration and alignment of both core and edge systems is described. Several further upgrades of the TS system, like a triggering unit and piezo motor driven vacuum window shutter, are introduced as well. The edge TS system, together with the core TS, is now in routine operation and provides electron temperature and density profiles.

Design of a real-time two-color interferometer for MAST Upgrade

A single chord two-color CO2/HeNe (10.6/0.633 μm) heterodyne laser interferometer has been designed to measure the line integral electron density along the mid-plane of the MAST Upgrade tokamak, with a typical error of 1 × 10(18) m(-3) (∼2° phase error) at 4 MHz temporal resolution. To ensure this diagnostic system can be restored from any failures without stopping MAST Upgrade operations, it has been located outside of the machine area. The final design and initial testing of this system, including details of the optics, vibration isolation, and a novel phase detection scheme are discussed in this paper.

Rhinobatos whitei, a new shovelnose ray (Batoidea: Rhinobatidae) from the Philippine Archipelago

A new shovelnose ray, Rhinobatos whitei sp. nov., is described from material collected at fish markets of the southern Philippines. This ray was first formally indentified as an undescribed species more than a decade ago as part of a WWF funded survey of sharks and rays of the Philippines. It was considered to be most closely related to another shovelnose ray found nearby in the western North Pacific, R. schlegelii, but differs from that species in body shape and aspects of coloration, meristics and morphometry. It differs from all other shovelnose rays of the region in its NADH2 sequence, clustering together with an Indonesian species R. jimbaranensis, and another undescribed species from Borneo.

A field programmable gate array unit for the diagnosis and control of neoclassical tearing modes on MAST

A real-time system has been developed to trigger both the MAST Thomson scattering (TS) system and the plasma control system on the phase and amplitude of neoclassical tearing modes (NTMs), extending the capabilities of the original system. This triggering system determines the phase and amplitude of a given NTM using magnetic coils at different toroidal locations. Real-time processing of the raw magnetic data occurs on a low cost field programmable gate array (FPGA) based unit which permits triggering of the TS lasers on specific amplitudes and phases of NTM evolution. The MAST plasma control system can receive a separate trigger from the FPGA unit that initiates a vertical shift of the MAST magnetic axis. Such shifts have fully removed m∕n = 2∕1 NTMs instabilities on a number of MAST discharges.

The interface of protein structure, protein biophysics, and molecular evolution

Abstract The interface of protein structural biology, protein biophysics, molecular evolution, and molecular population genetics forms the foundations for a mechanistic understanding of many aspects of protein biochemistry. Current efforts in interdisciplinary protein modeling are in their infancy and the state-of-the art of such models is described. Beyond the relationship between amino acid substitution and static protein structure, protein function, and corresponding organismal fitness, other considerations are also discussed. More complex mutational processes such as insertion and deletion and domain rearrangements and even circular permutations should be evaluated. The role of intrinsically disordered proteins is still controversial, but may be increasingly important to consider. Protein geometry and protein dynamics as a deviation from static considerations of protein structure are also important. Protein expression level is known to be a major determinant of evolutionary rate and several considerations including selection at the mRNA level and the role of interaction specificity are discussed. Lastly, the relationship between modeling and needed high-throughput experimental data as well as experimental examination of protein evolution using ancestral sequence resurrection and in vitro biochemistry are presented, towards an aim of ultimately generating better models for biological inference and prediction.

Magnetic reconnection triggering magnetohydrodynamic instabilities during a sawtooth crash in a Tokamak plasma

Thomson scattering measurements with subcentimeter spatial resolution have been made during a sawtooth crash in a Mega Ampere Spherical Tokamak fusion plasma. The unparalleled resolution of the temperature profile has shed new light on the mechanisms that underlie the sawtooth. As magnetic reconnection occurs, the temperature gradient at the island boundary increases. The increased local temperature gradient is sufficient to make the helical core unstable to ideal magnetohydrodynamic instabilities, thought to be responsible for the rapidity of the collapse.

Design and implementation of a full profile sub-cm ruby laser based Thomson scattering system for MAST

A major upgrade to the ruby Thomson scattering (TS) system has been designed and implemented on the Mega-ampere spherical tokamak (MAST). MAST is equipped with two TS systems, a Nd:YAG laser system and a ruby laser system. Apart from common collection optics each system provides independent measurements of the electron temperature and density profile. This paper focuses on the recent upgrades to the ruby TS system. The upgraded ruby TS system measures 512 points across the major radius of the MAST vessel. The ruby laser can deliver one 10 J 40 ns pulse at 1 Hz or two 5 J pulses separated by 100-800 μs. The Thomson scattered light is collected at F/15 over 1.4 m. This system can resolve small (7 mm) structures at 200 points in both the electron temperature and density channels at high optical contrast; ∼50% modulated transfer function. The system is fully automated for each MAST discharge and requires little adjustment. The estimated measurement error for a 7 mm radial point is <4% of T(e) and <3% of n(e) in the range of 40 eV to 2 keV, for a density of n(e)=2×10(19) m(-3). The photon statistics at lower density can be increased by binning in the radial direction as desired. A new intensified CCD camera design allows the ruby TS system to take two snapshots separated with a minimum time of 230 μs. This is exploited to measure two density and temperature profiles or to measure the plasma background light.

A 130 point Nd:YAG Thomson scattering diagnostic on MAST

A Thomson scattering diagnostic designed to measure both edge and core physics has been implemented on MAST. The system uses eight Nd:YAG lasers, each with a repetition rate of 30 Hz. The relative and absolute timing of the lasers may be set arbitrarily to produce fast bursts of measurements to suit the time evolution of the physics being studied. The scattered light is collected at F/6 by a 100 kg six element lens system with an aperture stop of 290 mm. The collected light is then transferred to 130 polychromators by 130 independent fiber bundles. The data acquisition and processing are based on a distributed computer system of dual core processors embedded in 26 chassis. Each chassis is standalone and performs data acquisition and processing for five polychromators. This system allows data to be available quickly after the MAST shot and has potential for real-time operations.

MAST YAG Thomson scattering upgrade alignment system

The recent upgrade to the MAST YAG Thomson scattering while enhancing the diagnostic capabilities increased the complexity of the system. There are eight YAG lasers now operational, doubling the number from the previous setup. This means alignment between each laser individually and reference points is essential to guarantee data quality and diagnostic reliability. To address this issue an alignment system was recently installed. It mimics the beams alignment in MAST by sampling 1% of the laser beam that is sent into a telescope which demagnifies by a factor of 8. The demagnified beam is viewed with a CCD camera. By scanning the camera the profile and position of the beams in the scattering zone and in a range of several meters inside MAST can be determined. Therefore alignment is checked along the beam path without having to sample it inside the vessel. The experimental apparatus and test procedures are described.

Laser system for high resolution Thomson scattering diagnostics on the COMPASS tokamak

A new Thomson scattering diagnostic has been designed and is currently being installed on the COMPASS tokamak in IPP Prague in the Czech Republic. The requirements for this system are very stringent with approximately 3 mm spatial resolution at the plasma edge. A critical part of this diagnostic is the laser source. To achieve the specified parameters, a multilaser solution is utilized. Two 30 Hz 1.5 J Nd:YAG laser systems, used at the fundamental wavelength of 1064 nm, are located outside the tokamak area at a distance of 20 m from the tokamak. The design of the laser beam transport path is presented. The approach leading to a final choice of optimal focusing optics is given. As well as the beam path to the tokamak, a test path of the same optical length was built. Performance tests of the laser system carried out using the test path are described.

Laser beam combiner for Thomson scattering core LIDAR

The light detection and ranging Thomson scattering (TS) diagnostic is advantageous since it only requires a single view port into the tokamak. This technique requires a short pulse laser at high energy, usually showing a limited repetition rate. Having multiple lasers will increase the repetition rate. This paper presents a scanning mirror as a laser beam combiner. Measurements of the position accuracy and jitter show that the pointing stability of the laser beam is within ±25 μrad for over tens of seconds. A control feedback loop is implemented to demonstrate the long term stability. Such a system could be applied for ITER and JET.

Synchronization of Thomson scattering measurements on MAST using an FPGA based "Smart" trigger unit

The MAST Thomson scattering diagnostic has recently been upgraded to make electron density and temperature measurements at 130 points across the 1.5 m diameter of the plasma. The new system is able to take 240 measurements per second using eight Nd:YAG lasers, each running at 30 Hz. The exact firing time of these lasers is adjusted with 100 ns precision using a field programmable gate array based trigger unit. Trigger pulses are produced to fire the lamps of all lasers and the Q switches with the appropriate delay depending on the warm-up status. The lasers may be fired in rapid bursts so as to achieve a high temporal resolution over eight points separated down to the microsecond level. This trigger unit receives optical trigger events and signals from external sources, allowing the trigger sequences to be resynchronized to the start of the plasma pulse and further events during the shot such as the entry of a fuelling pellet or randomly occurring plasma events. This resynchronization of the laser firing sequence allows accurate and reproducible measurements of fast plasma phenomena.

Absolute calibration of LIDAR Thomson scattering systems by rotational Raman scattering

Absolute calibration of LIDAR Thomson scattering systems on large fusion devices may be achieved using rotational Raman scattering. The choice of calibrating gas molecule presents different options and design trade-offs and is likely to be strongly dependent on the laser wavelength selected. Raman scattering of hydrogenic molecules produces a very broad spectrum, however, with far fewer scattered photons than scattering from nitrogen or oxygen at the same gas pressure. Lower laser wavelengths have the advantage that the Raman cross section increases, sigma(Raman) proportional to 1/lambda(0)(4), but the disadvantage that the spectral width of the scattered spectrum decreases, Deltalambda(Raman) proportional to lambda(0)(2). This narrower spectrum makes measurement closer to the laser wavelength necessary. The design of the calibration technique presents a number of challenges. Some of these challenges are generic to all Thomson scattering systems. These include detecting a sufficient number of photoelectrons and designing filters that measure close to the laser wavelength while simultaneously achieving adequate blocking of the laser wavelength. An issue specific to LIDAR systems arises since the collection optics operates over a wide range of depth of field. This wide depth of field has the effect of changing the angle of light incident on the optical interference filter with plasma major radius. The angular distribution then determines the effective spectral transmission function of the interference filter and hence impacts on the accuracy of the absolute calibration. One method that can be used to increase absolute calibration accuracy is collecting both Stokes and anti-Stokes lines with optical filter transmission bands specifically designed to reduce systematic uncertainty.

The Dogfish Scyliorhinus canicula: A Reference in Jawed Vertebrates

INTRODUCTIONDue to their large size and long generation times, chondrichthyans have been largely ignored by geneticists. However, their key phylogenetic position makes them ideal subjects to study the molecular bases of the important morphological and physiological innovations that characterize jawed vertebrates. Such analyses are crucial to understanding the origin of the complex genetic mechanisms unraveled in osteichthyans. The small spotted dogfish Scyliorhinus canicula, a representative of the largest order of extant sharks, presents a number of advantages in this context. Due to its relatively small size among sharks, its abundance, and easy maintenance, the dogfish has been an important model in comparative anatomy and physiology for more than a century. Recently, revived interest has occurred with the development of large-scale transcriptomic and genomic resources, together with the establishment of facilities allowing massive egg and embryo production. These new tools open the way to molecular analyses of the elaborate physiological and sensory systems used by sharks. They also make it possible to take advantage of unique characteristics of these species, such as organ zonation, in analyses of cell proliferation and differentiation. Finally, they offer important perspectives to evolutionary developmental biology that will provide a better understanding of the origin and diversifications of jawed vertebrates. The dogfish whole-genome sequence, which may shortly become accessible, should establish this species as an essential shark reference, complementary to other chondrichthyan models. These analyses are likely to reveal an organism of an underestimated complexity, far from the primitive prototypical gnathostome anticipated in gradistic views.

Design of a new Nd:YAG Thomson scattering system for MAST

A new infrared Thomson scattering system has been designed for the MAST tokamak. The system will measure at 120 spatial points with approximately 10 mm resolution across the plasma. Eight 30 Hz 1.6 J Nd:YAG lasers will be combined to produce a sampling rate of 240 Hz. The lasers will follow separate parallel beam paths to the MAST vessel. Scattered light will be collected at approximately f/6 over scattering angles ranging from 80 degrees to 120 degrees. The laser energy and lens size, relative to an existing 1.2 J f/12 system, greatly increases the number of scattered photons collected per unit length of laser beam. This is the third generation of this polychromator to be built and a number of modifications have been made to facilitate mass production and to improve performance. Detected scattered signals will be digitized at a rate of 1 GS/s by 8 bit analog to digital converters (ADCs.) Data may be read out from the ADCs between laser pulses to allow for real-time analysis.

Digit preference in Goldmann applanation tonometry: the hedgehog effect

PURPOSE

Digit preference is a subconscious bias towards numbers that end in certain digits. We conducted a study to assess for digit preference in intraocular pressure measurement using the Goldmann applanation tonometer.

DESIGN

Prospective study with masked and unmasked phases.

METHODS

The study was conducted in general ophthalmic clinics in a District General Hospital in Blackpool, United Kingdom, by 6 clinical ophthalmologists. Consecutive right eye intraocular pressure measurements were collected for a 2-month period for the masked phase and were repeated for the unmasked phase. The proportion of even numbers was the main outcome measure.

RESULTS

Six ophthalmologists completed both phases: 555 of 917 readings were even in the masked phase (P = .075), and 679 of 1056 readings were even in the unmasked phase (P = .022).

CONCLUSIONS

Our results suggest that digit preference influences measurements from the Goldmann applanation tonometer and that this persists when observers are aware of digit preference. This bias may influence both clinical decision-making and trial results.

A gene-specific DNA sequencing chip for exploring molecular evolutionary change

Sequencing by hybridization (SBH) approaches to DNA sequencing face two conflicting constraints. First, in order to ensure that the target DNA binds reliably, the oligonucleotide probes that are attached to the chip array must be >15 bp in length. Secondly, the total number of possible 15 bp oligonucleotides is too large (>4(15)) to fit on a chip with current technology. To circumvent the conflict between these two opposing constraints, we present a novel gene-specific DNA chip design. Our design is based on the idea that not all conceivable oligonucleotides need to be placed on a chip--only those that capture sequence combinations occurring in nature. Our approach uses a training set of aligned sequences that code for the gene in question. We compute the minimum number of oligonucleotides (generally 15-30 bp in length) that need to be placed on a DNA chip to capture the variation implied by the training set using a graph search algorithm. We tested the approach in silico using cytochrome-b sequences. Results indicate that on average, 98% of the sequence of an unknown target can be determined using the approach.

Setting up a quality assurance program in endoscopy

BACKGROUND

Both patients and government demand proof of quality of care and value for money. Our unit ist in a large teaching hospital, performing over 6000 procedures per year. We have designed and implemented a Quality Assurance (QA) program, the basis of which we believe could be a model for endoscopy QA.

METHODS

A QA team was formed and a literature search undertaken. An initial 3 month audit was then performed into indications for, and complications of, all procedures. The results of this initial audit led us to concentrate on colonoscopy and ERCP. The specific items of data collected were based on the "Core Quality Indicators" developed by the American Society for Gastrointestinal Endoscopy (ASGE). We also analysed data relating to endoscope disinfection, equipment failure and carried out a patient satisfaction survey. The data were presented at 3-monthly QA meeting, and appropriate action taken.

RESULT

We performed a detailed audit of ERCP (217 procedures) and colonoscopy (904 procedures). Patients risk was stratified using the American Society of Anaesthesiology (ASA) classification. Using these data we established our technical success and complication rates for colonoscopy and ERCP. Audit of equipment revealed that on average an endoscope was away for repair 9 % of the time. Contamination of endoscopes was frequent with glutaraldehyde disinfection; the rate of contamination fell dramatically when we changed our disinfection method.

CONCLUSION

A QA program can be implemented in busy endoscopy units. There are significant problems, however, in ensuring that such a program is effective: these include inadequate funding/staffing, lack of suitable information technology and lack of clear guidelines for dealing with poor performance.

Evaluation of posturing in macular hole surgery

AIM

To objectively evaluate the postoperative face down posturing in macular hole surgery.

MATERIALS AND METHODS

An electronic device called 'Maculog' was developed consisting of three basic components, a mercury switch triggered by the angle of tilt placed inside an earpiece, a data-recording device connected to the earpiece with cables and a windows based software program, specially written to analyse the recorded data in the form of tables and graphs. Ten patients undergoing macular hole surgery were fitted with the device on the first postoperative day before discharge. They were also asked for a subjective record of their posturing times. Four patients were given a posturing chair to take home. The device was retrieved after the first week and the data were downloaded to a PC for analysis. The actual posturing times recorded on the device were compared to the patients' own recollections. Results In all ten patients the actual posturing time was less than the time they had recorded themselves. The average actual posturing time was 48% of the perceived posturing time. The worst time for posturing, as expected, was between midnight and early morning. The compliance was better in patients who used the posturing chair.

CONCLUSIONS

It is feasible to quantify the time of posturing using an electronic device and computer analysis. The study has shown that the actual posturing time is significantly less than the perceived posturing time. A further large study using 'Maculog' is now planned to correlate actual posturing time to the results of macular hole surgery.

Dietary antioxidants and DNA damage in patients on long-term acid-suppression therapy: a randomized controlled study

Free radicals and reactive species produced in vivo can trigger cell damage and DNA modifications resulting in carcinogenesis. Dietary antioxidants trap these species limiting their damage. The present study evaluated the role of vitamins C and E in the prevention of potentially premalignant modifications to DNA in the human stomach by supplementing patients who, because of hypochlorhydria and possible depletion of gastric antioxidants, could be at increased risk of gastric cancer. Patients undergoing surveillance for Barrett's oesophagus (n 100), on long-term proton pump inhibitors were randomized into two groups: vitamin C (500 mg twice/d) and vitamin E (100 mg twice/d) for 12 weeks (the supplemented group) or placebo. Those attending for subsequent endoscopy had gastric juice, plasma and mucosal measurements of vitamin levels and markers of DNA damage. Seventy-two patients completed the study. Plasma ascorbic acid, total vitamin C and vitamin E were elevated in the supplemented group consistent with compliance. Gastric juice ascorbic acid and total vitamin C levels were raised significantly in the supplemented group (P=0.01) but supplementation had no effect on the mucosal level of this vitamin. However, gastric juice ascorbic acid and total vitamin C were within normal ranges in the unsupplemented group. Mucosal malondialdehyde, chemiluminescence and DNA damage levels in the comet assay were unaffected by vitamin supplementation. In conclusion, supplementation does not affect DNA damage in this group of patients. This is probably because long-term inhibition of the gastric proton pump alone does not affect gastric juice ascorbate and therefore does not increase the theoretical risk of gastric cancer because of antioxidant depletion.

Using the business excellence model to develop a strategy for a healthcare organisation

This article examines the appropriateness of the Business Excellence Model in developing a strategy for Bolton Hospitals NHS Trust to measure organisational performance. The need for a strategy to measure organisational performance and to improve organisational performance was highlighted with the production of the Government White Paper, The New NHS: Modern and Dependable. At the heart of recommendations there is emphasis on improving quality and driving efficiency. Greater emphasis will be placed on organisations measuring their performance. By utilising the conceptual framework, which consisted of The European Foundation for Quality Management (EFQM) Model, it became evident that, although tools were in existence within Bolton Hospitals to measure organisational performance, several critical areas needed addressing. By addressing these key areas, the organisation could begin to work towards its goal of business excellence. The conclusions drawn from this project demonstrated that there was scope for Bolton Hospitals to improve on organisational performance. It was highlighted that the Trust was functioning well in some areas of the EFQM Model, but not in others. For Bolton Hospitals NHS Trust to improve organisational performance, the EFQM Model should be adopted.

Carotid artery Doppler ultrasonography in retinal macroaneurysms

It is postulated that retinal arterial macroaneurysms (RAMs) occur at the site of incomplete embolic occlusion of a branch retinal artery. Embolic events of the retinal vessels are related to the state of the carotid artery tree and therefore Doppler ultrasonography of the carotid arteries in these patients is of particular interest. We have examined 13 patients with retinal artery macroaneurysms with carotid artery Doppler ultrasonography (CADU). Eight of these patients (61.5%) exhibited atheromatous plaques on the same side as the RAM with a moderate degree of arterial narrowing. Although our group of patients did not show advanced carotid artery disease, alterations of the arterial wall found at the level of the carotid artery were higher than expected in a similar hypertensive population. To our knowledge this is the first study of the carotid arterial tree in these patients. Our results support the theory that RAMs may be of embolic origin. Furthermore they demonstrate that CADU is a useful investigation in patients with RAMs.

Technical and audiological factors in the implementation and use of digital signal processing hearing aids

Fully digital hearing aids, to be worn behind or within the ear, are coming on to the market. The new possibilities and challenges of such aids are both technological and audiological in character. This paper describes some of the challenges, and one manufacturer's approach to them. The signal processing structure in one current digital hearing aid is presented, and justified in audiological terms, as a background to discussions of (i) the relative urgency of further advances in technology and audiological knowledge, and (ii) the challenges to the practice of hearing aid dispensing. It is concluded that further advances in rehabilitative audiology are more pressing than further major technological progress, and that the potential client benefits of the new generation of digital hearing aids will only be realized if the challenges they present to software design and dispensing practice are recognized and met.

Thymic regression and apoptosis in the rat after treatment with the Leydig cell cytotoxin ethylene dimethanesulphonate (EDS)

Ethylene dimethanesulphonate (EDS) is an alkylating agent which is widely assumed to specifically kill Leydig cells leaving other biological systems intact. However, after EDS treatment of the male rat the thymus reversibly involutes and the gonadal regional lymph nodes are activated. In the present experiments we have demonstrated that EDS has a direct action upon the thymus both in vivo and in vitro. EDS treatment of the intact and castrated male rat and the intact female rat caused regression of the thymus by up to 50% 3 days later. Total cellularity decreased while the proliferative index increased suggesting a compensatory mechanism. Thymocytes were exposed to EDS in vitro and the response compared to the glucocorticoid methylprednisolone (P), a well characterised thymic apoptotic stimulant. EDS and P increased apoptosis in the thymocyte as characterised by the appearance of cells containing nuclei with apoptotic morphology and with DNA fragmentation visualised by a characteristic ladder after agarose gel electrophoresis. The effects of both EDS and P were time and dose dependent but, in contrast to the effects in Leydig cells, P was the most effective apoptotic stimulus (for instance 100%-P compared to 30%-EDS or 7% control/DMSO after 24 h incubation). The immunological responses of the gonadal lymph nodes were not associated with testicular regression as it was seen in the castrated rat but may be related to a direct action upon the epididymis. In conclusion, tissue specificity of the Leydig cell cytotoxin needs to be extended to the thymus and epididymis. The mode of cell death in Leydig cells and thymocytes after both glucocorticoids and EDS is apoptosis which suggests that they possess some common mechanism(s) which is responsible for the toxicity of these diverse compounds.

Comparison of two conservative methods of treating an isolated fracture of the lateral malleolus

We compared two conservative methods of treating Weber B1 (Lauge-Hansen supination-eversion 2) isolated fractures of the lateral malleolus in 65 patients. Treatment by immediate weight-bearing and mobilisation resulted in earlier rehabilitation than immobilisation for four weeks in a plaster cast. There was no significant difference in the amount of pain experienced or in the requirement for analgesics and early mobilisation was not associated with any complications. We therefore advocate early mobilisation for these stable ankle fractures.

Randomized trial of blunt-tipped versus cutting needles to reduce glove puncture during mass closure of the abdomen

Eighty-five consecutive patients were randomized to undergo mass closure of the abdomen with no. 1 polydioxanone mounted on either a blunt-tipped (n = 46) or cutting (n = 39) needle. Gloves were changed before closure and tested for perforation afterwards using standard air or water techniques. Fourteen pairs of gloves were punctured when using a cutting needle, and three pairs when a blunt-tipped needle was used. The majority of punctures were to the non-dominant glove. The surgeon was aware of the puncture in eight of the 14 instances involving a sharp needle and in one of the three involving a blunt-tipped needle. Blunt-tipped needles, while not eliminating the risk, significantly reduced the incidence of surgical glove puncture (P < 0.001, Fisher's exact test). The use of cutting needles for abdominal closure should be abandoned.

Comparison of two conservative methods of treating an isolated fracture of the lateral malleolus

We compared two conservative methods of treating Weber B1 (Lauge-Hansen supination-eversion 2) isolated fractures of the lateral malleolus in 65 patients. Treatment by immediate weight-bearing and mobilisation resulted in earlier rehabilitation than immobilisation for four weeks in a plaster cast. There was no significant difference in the amount of pain experienced or in the requirement for analgesics and early mobilisation was not associated with any complications. We therefore advocate early mobilisation for these stable ankle fractures.

The management of post-keratoplasty astigmatism by post-operative adjustment of a single continuous suture

Penetrating keratoplasty was performed in 39 consecutive patients. A 16 bite 10-0 nylon continuous suture was used. Post-operatively, the suture was adjusted to reduce astigmatism, as determined by refraction, keratoscopy and keratometry. Suture adjustment was performed if astigmatism was over 4 dioptres (D). The suture was tightened in the flatter meridian and loosened in the steeper meridian. Twenty-one patients had suture adjustment performed. Prior to adjustment, mean (+/- standard deviation) astigmatism measured 6.33 +/- 1.38 D. Following adjustment, mean astigmatism was significantly reduced to 2.69 +/- 1.14 D (p < 0.0001). The average final astigmatism for the entire group was 2.66 +/- 1.12 D. The use of a continuous adjustable suture in penetrating keratoplasty significantly reduced the post-operative astigmatism in a group of patients undergoing penetrating keratoplasty.

Iris prolapse; who? When? Why?

A 12-month period was reviewed to identify the incidence of iris prolapse following cataract surgery, and any predisposing factors. Of 1408 routine manual extracapsular cataract extractions, 29 eyes (2.06%) sustained an iris prolapse. Iris prolapse was commoner in Asian patients and when less experienced surgeons were operating. Twenty-five per cent of cases occurred in patients with obstructive airways disease or post-operative cough. Thirty-four per cent of iris prolapses were identified on the first post-operative day and 86% within 2 weeks. Prolapse probably occurs because of raised intraocular pressure in association with poor wound construction or closure. More emphasis should be given to wound construction and closure during surgical training, with extra diligence when operating on patients likely to cough postoperatively. Clinicians must ensure non-English speaking patients understand about ocular aftercare following cataract surgery.

Comparison of the Keeler Pulsair 2000 non-contact tonometer with Goldmann applanation

The Pulsair 2000 non-contact tonometer (Keeler Ltd, UK) is compared with the Goldmann applanation tonometer. Data from 80 eyes were acquired by four experienced observers. A linear regression analysis showed the relationship between the instruments to be: Pulsair = 0.66 + 0.95 Goldmann. Individual components of variation were analysed by analysis of variance which indicated a significant variation in the slope of the regression equation due to observers (p = 0.02) but not to the order in which topical anaesthesia was administered. Differences between two Pulsair instruments were of marginal significance (p = 0.07). The intercept of the regression equation was unaffected by any of the components of variation. Seventy-nine per cent of averaged intraocular pressure measurements obtained with the Pulsair 2000 fell on or within +/- 3 mmHg of those measured with the Goldmann tonometer. It is concluded that the Pulsair 2000 can provide clinically useful measurements of intraocular pressure.

Ophthalmic complications of amniocentesis

Reports of ocular damage from amniocentesis needles are rare. We report four cases of ocular perforation in which an amniocentesis needle may have been the cause and a proven case of central nervous system perforation during amniocentesis which resulted in hemianopia and gaze palsy. Ocular damage during amniocentesis may be commoner than the paucity of reports would suggest, and should be considered in all cases of congenital ocular conditions.

Intercapsular versus extracapsular cataract extraction

Forty-five eyes that have undergone routine extracapsular cataract extraction with insertion of a posterior chamber intraocular lens were compared with a similar group of eyes that had undergone intercapsular extraction. Capsular fixation was more predictable following intercapsular (78%) than it was following extracapsular extraction (22%). Gonioscopy revealed prominence of the lens haptic in 22% of the intercapsular group, with peripheral anterior synechiae (PAS) in 18%; haptics were prominent in 78% of the extracapsular group, with synechiae in 55%. Lens eccentricity of 2 mm or more was seen in 2 patients (4%) following intercapsular and in 10 (22%) following extracapsular extraction. Pupil irregularities were noted in three of the intercapsular group (7%) and in eight of the extracapsular group, (13%) with peripheral iris tucking alone in three. These data strongly support the view that intercapsular is superior to extracapsular cataract surgery in terms of facilitating capsular fixation of posterior chamber intraocular lenses.

Gonioscopic findings following insertion of Pearce Lasagap and Nova Curve Kratz posterior chamber intraocular lenses in extrapsular cataract extraction

The gonioscopic appearances of 45 eyes that had undergone extracapsular cataract extraction with insertion of a Pearce Lasagap posterior chamber intraocular lens (group A) were compared with those of 45 eyes that had undergone the same procedure except for insertion of a Nova Curve Kratz posterior chamber lens (group B). Prominence of one or both loops was seen in 35 eyes (78%) of group A, with peripheral anterior synechiae (PAS) in 25 (55%). Prominence of one loop was seen in 14 eyes (31%) of group B, with PAS in 8 (18%) (P less than 0.001). Final visual acuity was comparable in both groups, 98% achieving 6/12 (20/40) or better. Although not statistically significant, the incidence of pigment dispersion, uveitis, discomfort and visual aberrations was greater in group A than in group B. We suggest that the apparent superiority of the Nova Curve Kratz lens in terms of the smaller incidence of loop prominence, as well as the reduced incidence of these other complications, is due to the fact that its haptic is inserted into the optic's edge rather than into the anterior surface of the lens optic, as is the case with the Lasagap lens.