Rheumatoid arthritis and incident fracture in women: a case-control study

BACKGROUND

To examine fracture incidence in women with rheumatoid arthritis (RA) for an entire geographical region of south-eastern Australia.

METHODS

Women aged 35 years and older, resident in the Barwon Statistical Division (BSD) and clinically diagnosed with RA 1994-2001 were eligible for inclusion as cases (n = 1,008). The control population (n = 172,422) comprised the entire female BSD population aged 35 years and older, excluding those individuals identified as cases. Incident fractures were extracted from the prospective Geelong Osteoporosis Study Fracture Grid. We calculated rate ratios (RR) and 95% confidence intervals (CI) to compare the age-adjusted rate of fracture between the RA and non-RA populations, and used a chi-square test to compare proportions of fractures between women with and without RA, and a two-sided Mann-Whitney U-test to examine age-differences.

RESULTS

Among 1,008 women with RA, 19 (1.9%) sustained a fracture, compared to 1,981 fractures sustained by the 172,422 women without RA (1.2%). Fracture rates showed a trend for being greater among women diagnosed with RA (age-adjusted RR 1.43, 95%CI 0.98-2.09, p = 0.08). Women with RA sustained vertebral fractures at twice the expected frequency, whereas hip fractures were underrepresented in the RA population (p < 0.001). RA status was not associated with the likelihood of sustaining a fracture at sites adjacent to joints most commonly affected by RA (p = 0.22).

CONCLUSION

Given that women with RA have a greater risk of fracture compared to women without RA, these patients may be a suitable target population for anti-resorptive agents; however, larger studies are warranted.

A retrospective chart review of the use of rituximab for the treatment of rheumatoid arthritis in Australian rheumatology practice

AIM

Rituximab is one of nine biologic agents approved for the treatment of rheumatoid arthritis (RA) in Australia. The primary study objective was to analyze the factors that lead to the therapeutic decision to use rituximab in RA.

METHOD

A cross-sectional, retrospective chart review was conducted to identify patients who were treated with rituximab and to evaluate their response to treatment.

RESULTS

Factors influencing the prescription of rituximab were identified. The most commonly reported reason for prescribing rituximab was the presence of comorbidities and the presence of seropositive disease. Median rituximab treatment duration was 32.5 months and mean number of treatment cycles was 4.1. Disease activity scores showed significant improvement from baseline to most recent visit. Rituximab treatment was well-tolerated in this group of RA patients.

CONCLUSIONS

Rituximab was effective in a refractory group of RA patients and appears to be safe in a population with a high prevalence of comorbidities, including malignancy and recurrent infections/bronchiectasis. This study may assist rheumatologists in selecting appropriately targeted therapy in RA.

The SMILE study -- safety of methotrexate in combination with leflunomide in rheumatoid arthritis

OBJECTIVE

To assess the safety of treating patients with rheumatoid arthritis with a combination of methotrexate (MTX) and leflunomide (LEF) in comparison to MTX monotherapy, in clinical practice.

METHODS

The Safety of Methotrexate in Combination with Leflunomide in Rheumatoid Arthritis (SMILE) study was a multicenter, observational, cross-sectional, retrospective safety study. The study was conducted by the Optimising Patient Outcomes in Australian Rheumatology-Quality Use of Medicines Initiative (OPAL QUMI). Data were deidentified for patient, clinic, and clinician prior to collection from 13 participating rheumatology practices (25 rheumatologists). Comparative analysis of safety for the different treatments, primarily with regard to neutropenia and liver abnormalities, was performed.

RESULTS

In total, 2975 patients were included in the study: 74% female, 26% male, mean age 62 years (SD 13.6). Distribution of therapy: MTX monotherapy 52.2%, LEF monotherapy 7.3%, MTX plus LEF 13.9%, and neither MTX nor LEF 26.6%. Comorbid liver disease was reported in 8.1% of patients. Liver function abnormalities were reported in 12% of the MTX monotherapy group, 16% of the LEF monotherapy group, 19% of the MTX-LEF combination group, and 14% of the group not taking either drug. Neutropenia was reported in 2.3% of the MTX monotherapy group, 5.5% of the LEF monotherapy group, 3.9% of the MTX-LEF combination group, and 4.2% of the group not taking either drug.

CONCLUSION

The combination of MTX and LEF was well tolerated, with adverse events comparable to those of monotherapy and the other nonbiologic disease-modifying antirheumatic drug treatment group.

Competing carboxylases: circadian and metabolic regulation of Rubisco in C3 and CAM Mesembryanthemum crystallinum L

The temporal co-ordination of ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPc) activities by Mesembryanthemum crystallinum L. in C(3) and crassulacean acid metabolism (CAM) modes was investigated under conventional light-dark (LD) and continuous light (LL) conditions. When C(3) , net CO(2) assimilation rate increased during each subjective night under LL with maximum carboxylation unrelated to Rubisco activation state. The CAM circadian rhythm of CO(2) uptake was more pronounced, with CO(2) assimilation rate maximal towards the end of each subjective night. In vivo and in vitro techniques were integrated to map carboxylase enzyme regulation to the framework provided by CAM LL gas exchange activity. Rubisco was activated in vitro throughout each subjective dark period and consistently deactivated at each subjective dawn, similar to that observed at true dawn in constitutive CAM species. Instantaneous carbon isotope discrimination showed in vivo carboxylase co-dominance during the CAM subjective night, initially by Rubisco and latterly C(4) (PEPc), despite both enzymes seemingly activated in vitro. The circadian rhythm in titratable acidity accumulation was progressively damped over successive subjective nights, but maintenance of PEPc carboxylation capacity ensures that CAM plants do not become progressively more 'C(3) -like' with time under LL.

High but not dry: diverse epiphytic bromeliad adaptations to exposure within a seasonally dry tropical forest community

• Vascular epiphytes have developed distinct lifeforms to maximize water uptake and storage, particularly when delivered as pulses of precipitation, dewfall or fog. The seasonally dry forest of Chamela, Mexico, has a community of epiphytic bromeliads with Crassulacean acid metabolism showing diverse morphologies and stratification within the canopy. We hypothesize that niche differentiation may be related to the capacity to use fog and dew effectively to perform photosynthesis and to maintain water status. • Four Tillandsia species with either 'tank' or 'atmospheric' lifeforms were studied using seasonal field data and glasshouse experimentation, and compared on the basis of water use, leaf water δ(18) O, photosynthetic and morphological traits. • The atmospheric species, Tillandsia eistetteri, with narrow leaves and the lowest succulence, was restricted to the upper canopy, but displayed the widest range of physiological responses to pulses of precipitation and fog, and was a fog-catching 'nebulophyte'. The other atmospheric species, Tillandsia intermedia, was highly succulent, restricted to the lower canopy and with a narrower range of physiological responses. Both upper canopy tank species relied on tank water and stomatal closure to avoid desiccation. • Niche differentiation was related to capacity for water storage, dependence on fog or dewfall and physiological plasticity.

Frequency-difference MIT imaging of cerebral haemorrhage with a hemispherical coil array: numerical modelling

The feasibility of detecting a cerebral haemorrhage with a hemispherical MIT coil array consisting of 56 exciter/sensor coils of 10 mm radius and operating at 1 and 10 MHz was investigated. A finite difference method combined with an anatomically realistic head model comprising 12 tissue types was used to simulate the strokes. Frequency-difference images were reconstructed from the modelled data with different levels of the added phase noise and two types of a priori boundary errors: a displacement of the head and a size scaling error. The results revealed that a noise level of 3 m degrees (standard deviation) was adequate for obtaining good visualization of a peripheral stroke (volume approximately 49 ml). The simulations further showed that the displacement error had to be within 3-4 mm and the scaling error within 3-4% so as not to cause unacceptably large artefacts on the images.

Forward modelling of magnetic induction tomography: a sensitivity study for detecting haemorrhagic cerebral stroke

For a magnetic induction tomography (MIT) system operating at 10 MHz, the signals produced by a haemorrhagic cerebral stroke were computed using an anatomically realistic, multi-layer, finite element (FE) head model comprising 12 tissues. The eddy-current problem was approximated using the commercial FE package, Comsol Multiphysics, and the numerical techniques employed were validated using a benchmark test. Mesh convergence for the head model was investigated for first- and second-order elements. MIT signals were computed for strokes of different sizes and locations in the brain to judge the sensitivity of the MIT configuration. The results revealed that for a large peripheral stroke (volume 50 cm(3)), 27% of the signals were above the phase noise level achievable in our current data-collection hardware (approximately 20 m degrees). In order to detect the same percentage of the signals due to a centrally located small stroke, a reduction in phase noise to 1 m degrees was necessary.

Imaging cerebral haemorrhage with magnetic induction tomography: numerical modelling

Magnetic induction tomography (MIT) is a new electromagnetic imaging modality which has the potential to image changes in the electrical conductivity of the brain due to different pathologies. In this study the feasibility of detecting haemorrhagic cerebral stroke with a 16-channel MIT system operating at 10 MHz was investigated. The finite-element method combined with a realistic, multi-layer, head model comprising 12 different tissues, was used for the simulations in the commercial FE package, Comsol Multiphysics. The eddy-current problem was solved and the MIT signals computed for strokes of different volumes occurring at different locations in the brain. The results revealed that a large, peripheral stroke (volume 49 cm(3)) produced phase changes that would be detectable with our currently achievable instrumentation phase noise level (17 m degrees ) in 70 (27%) of the 256 exciter/sensor channel combinations. However, reconstructed images showed that a lower noise level than this, of 1 m degrees , was necessary to obtain good visualization of the strokes. The simulated MIT measurements were compared with those from an independent transmission-line-matrix model in order to give confidence in the results.

Can abdominal bioelectrical impedance refine the determination of visceral fat from waist circumference?

Ryo et al (2005 Diabetes Care 28 451-3) reported a new method for measuring the visceral fat area (VFA) by combining abdominal bioelectrical impedance analysis (BIA) with measurement of waist circumference (WC), but very few methodological details were provided. Furthermore, the study did not test the use of WC alone as an indicator of VFA even though others had previously reported a strong correlation. We sought to determine the optimal measurement technique and analysis for measuring VFA by abdominal BIA and WC. 18 volunteers (age 23-64 years) underwent measurement of WC, abdominal impedance (Bodystat 500 four-electrode system) and a single cross-sectional CT scan at the umbilicus. VFA derived using WC(3) and measurements of abdominal impedance from electrode pairs sited at the flank predicted the value of VFA measured by CT with correlation r = 0.904 (p < 0.0001); the optimizing power of WC was 3.3 (r = 0.905). However, the use of WC(1.9) alone, without involving BIA at all, provided a similar correlation (r = 0.923). Our small preliminary study shows that abdominal BIA is potentially a practicable non-invasive technique for measurement of VFA but casts doubt on whether it adds any value to the use of WC alone. Larger studies are now required to test this finding.

Residual capacitive coupling and the measurement of permittivity in magnetic induction tomography

In an ideal magnetic induction tomography (MIT) system, the coupling between the coils and the sample is entirely by the magnetic field. In a practical system, unwanted electric-field (capacitive) coupling can also exist and cause large errors in the MIT measurements unless the hardware is designed carefully. A series of tests was carried out to assess the magnitude of capacitive coupling present in a 10 MHz MIT system designed for biomedical use and other applications involving low-conductivity samples (<or=10 S m(-1)). The tests indicated that, even with the individual coils left unscreened, the signal contamination from capacitive coupling was very small compared with the true MIT signal. Because the contamination was small, it was demonstrated possible to derive the permittivity of the sample from the real part of the MIT signal. This was shown to work well when the conductivity of the sample was less than about 0.5 S m(-1), but for higher conductivities, when the skin depth became comparable with the width of the sample, the commonly used theoretical expression for the MIT signal began to break down. This implies that the measurement of permittivity (and permeability) in real biological tissues (which have conductivities of up to 2 S m(-1)) will require a more detailed derivation taking into account both the real and imaginary parts of the signals.

An analysis of the CFH Y402H genotype in AMD patients and controls from the UK, and response to PDT treatment

AIM

Mutation in the complement factor H (CFH) gene is an important risk factor for age-related macular degeneration (AMD). In this study, we identified the strength of the CFH Y402H gene variant association in a UK AMD cohort and tested the hypothesis that this variant may influence the biological response of choroidal neovascularisation (CNV) following photodynamic therapy (PDT) for CNV.

METHODS

A total of 557 cases with AMD and 551 normal controls were genotyped for the CFH Y402H (1277 C/T) variant using the 5' nuclease TaqMan assay for allelic discrimination. The CFH gene association for AMD, for the different CNV subtypes and for patients needing PDT was estimated. Twenty-seven PDT-treated patients were followed up for 15 months with ETDRS-derived vision, clinical examination, and fundus angiography. Individuals with different CFH genotypes were then analysed for any association with visual change following PDT.

RESULTS

The risk association for AMD with the CFH CC genotype (odd ratio (OR)=3.62, Pc<0.0001) was similar to that reported in other Caucasian cohorts. The magnitude and strength of this association was stronger in AREDS stages 2-4 (ORs=4.48, 2.69, and 5.17). ORs for the risk of predominantly classic CNV were significantly raised for both the CC (OR=17.87, P<0.0001) and CT (OR=9.06, P=0.0002) genotypes. The number of patients carrying the high-risk C allele was 70.4% in those requiring PDT as compared to 52.3% in the non-PDT group (OR=2.16, P=0.011), and presence of the CC genotype significantly increased the risk of PDT (OR=5.48, P=0.015). The degree of visual loss following PDT was significantly higher in the CFH CC genotype group (P=0.038); 50% of CC cases (n=13) and 45% of the CT cases (n=12) lost 15 or more ETDRS letters at final follow-up.

CONCLUSION

In this UK cohort of AMD patients, the CFH Y402H variant was significantly enriched in patients with predominantly classic CNV. Patients homozygous for the CFH Y402H genotype seem to have worse visual acuity after PDT.

Hearing threshold assessment post grommet insertion. Is it reliable?

We aimed to investigate whether auditory brainstem response (ABR), assessed immediately after grommet insertion, was an accurate measure of hearing threshold.

Ten children were recruited (20 ears). Patients underwent transient evoked otoacoustic emission (TEOAE) and ABR tests before and after grommet insertion under general anaesthetic. A third assessment was conducted at a six-week review, without anaesthetic or sedation. The hearing threshold in dB and the presence of TEOAE were recorded by senior audiologists. The results of each investigation were compared. At review, only 15 ABR and 17 TEOAE tests, of a possible 20, were recorded.

Transient evoked otoacoustic emissions were recorded in 30 per cent of ears pre-operatively, 20 per cent of ears post-operatively and 82 per cent of ears at six-week review. The average ABR thresholds were 23.75 dB (range 10–45 dB) pre-operatively, 27.25 (range 15–40 dB) post-operatively and 15 dB (range 5–25 dB) at six-week review. Comparing pre- and post-operative assessment, decreased thresholds were seen in six ears and elevated thresholds in 11. Comparing the six-week review ABR with the post-operative ABR, 13 ears had decreased thresholds, by as much as 20 dB. Thresholds of 35 dB or greater were measured in six ears immediately after grommet insertion (maximum 40 dB). Threshold shifts of 15 dB or greater was observed in seven ears. The intra-subject variation was shown to be significant (p<0.001) when repeated measures analysis of variance was applied.

We conclude that there is evidence that ABR can be inaccurate after grommet insertion, overestimating hearing thresholds. We believe that the mechanism by which the error is realised is temporary threshold shift.

Positioning critically ill patients in hospital

Although moving and handling is an important aspect of nurse training, the emphasis is often more on the health and safety of the nurse than on the importance of the correct therapeutic positioning of patients. This article outlines optimum patient positioning in different critical care settings and for different medical conditions.

The use of ezetimibe in achieving low density lipoprotein lowering goals in clinical practice: position statement of a United Kingdom consensus panel

There is no doubt that lowering serum cholesterol levels reduces the risk of major coronary events. This evidence has led treatment guidelines to set progressively lower targets for low density lipoprotein cholesterol (LDL-C). However, despite widespread use of statins, substantial numbers of patients do not achieve the LDL-C goals. Using higher doses of statins in an attempt to achieve these targets may increase the risk of serious adverse effects. Furthermore, the use of combination therapy with agents such as bile acid sequestrants, niacin and fibrates has been limited by increased potential for side effects, drug interactions and poor compliance. Ezetimibe, a selective cholesterol transport inhibitor, reduces the intestinal uptake of cholesterol without affecting absorption of triglycerides or fat-soluble vitamins. In clinical studies, ezetimibe 10 mg, in combination with statins or as monotherapy, was well tolerated and reduced LDL-C by 34-53% and 17-18%, respectively. The available evidence for ezetimibe is reviewed. The role of ezetimibe in increasing the proportion of patients attaining LDL-C treatment goals is discussed.

A comparison of sensors for minimizing the primary signal in planar-array magnetic induction tomography

In magnetic induction tomography reducing the influence of the primary excitation field on the sensors can provide a significant improvement in SNR and/or allow the operating frequency to be reduced. For the purposes of imaging, it would be valuable if all, or a useful subset, of the detection coils could be rendered insensitive to the primary field for any excitation coil activated. Suitable schemes which have been previously suggested include the use of axial gradiometers and coil-orientation methods (Bx sensors). This paper examines the relative performance of each method through computer simulation of the sensitivity profiles produced by a single sensor, and comparison of reconstructed images produced by sensor arrays. A finite-difference model was used to determine the sensitivity profiles obtained with each type of sensor arrangement. The modelled volume was a cuboid of dimensions 50 cmx50 cmx12 cm with a uniform conductivity of 1 S m-1. The excitation coils were of 5 cm diameter and the detection coils of 5 mm diameter. The Bx sensors provided greater sensitivity than the axial gradiometers at all depths, other than on the surface layer of the volume. Images produced using a single-planar array were found to contain distortion which was reduced by the addition of a second array.

Design and performance of a planar-array MIT system with normal sensor alignment

In this study the performance of a planar array for magnetic induction tomography (MIT) was investigated and the results of measurements to determine the precision and sensitivity of the sensor were undertaken. A planar-array MIT system utilizing flux-linkage minimization for the primary field has been constructed and evaluated. The system comprises 4 printed excitation coils of 4 turns which were shielded, 8 surface-mount inductors of inductance 10 microH as sensor, mounted such that in principle no primary-field flux threads them, and a calibration coil to produce a strong primary field. The excitation current was multiplexed via relays to drive the excitation and reference coils. The noise values were similar in real and imaginary components in the lower frequencies and the factor to which the primary field could be reduced was greatest in the nearest coil. Methods for determining the true real and imaginary components and for flux-linkage minimization for the primary field for variations in channel sensitivities are described and the results of measurements of the system's noise and drift are given. A SNR of 47 dB was observed at 4 MHz when a 0.3 Sm-1 saline filled tank of dimensions 20 cmx20 cmx10 cm was placed centrally over the array. Finally, images were reconstructed from measurements of saline samples in a free space background, with the samples moved past the array in 21 1 cm steps to emulate mechanical scanning of the array. The image reconstruction characteristics of the planar array in conjunction with the reconstruction technique employed are discussed.

A primary field compensation scheme for planar array magnetic induction tomography

In biomedical magnetic induction tomography (MIT), measurement precision may be improved by incorporating some form of primary field compensation/cancellation scheme. Schemes which have been described previously include gradiometric approaches and the use of 'back-off' coils. In each of these methods, however, the primary field cancellation was achieved only for a single transmitter/receiver combination. For the purpose of imaging, it would be desirable for a fully electronically scanned MIT system to provide a complete set of measurements, all with the primary field cancelled. A single channel suitable for incorporation into an MIT system with planar-array geometry is described. The transmitter is a 6-turn coil of wire 5 cm in diameter. The receiver is a surface mount inductor, of inductance 10 microH, mounted such that, in principle, no net primary field flux threads it. The results of measurements carried out with the single channel system suggest that the signal due to the primary excitation field can be reduced on average by a factor of 298 by the sensor geometry over the operating frequency range 1-10 MHz. The standard deviation and drift of the signal with the system adjusted for maximum primary field cancellation, expressed as a percentage of the signal when the receiver coil was rotated until its axis of sensitivity lay along the primary field, were 0.0009% and 0.009%, respectively. The filter time constant used was 30 ms.

Parapharyngeal abscess: diagnosis, complications and management in adults

Parapharyngeal abscess may cause life-threatening complications. Peritonsillar abscess and tonsillitis may result in parapharyngeal abscess. Since the introduction of antibiotics, the incidence of parapharyngeal abscess secondary to tonsillitis and peritonsillar abscess has decreased dramatically. We present five cases of parapharyngeal abscess resulting from tonsillitis and peritonsillar infection extending to the parapharyngeal space in adult patients. Two were complicated by mediastinitis despite early treatment by wide spectrum antibiotics. We believe that early diagnosis and aggressive antibiotic treatment with early surgical drainage in cases associated with pus collection are the key points in preventing serious and fatal complications. We emphasize the diagnostic role of computerized tomography (CT) scan and the importance of early and proper drainage of these abscesses.

Normal complement C4 values do not exclude hereditary angioedema

This report describes a patient with hereditary angioedema (HAE) in whom complement C4 values were consistently normal. There was a family history of HAE, for which the patient had previously been screened, but in view of her normal C4 values she was deemed unaffected. However, at 10 years of age she presented with an eight month history of episodes of swelling affecting her hands and recurrent episodes of abdominal pain over the previous few months. In view of the recent clinical history of swellings and the family history of HAE, C4 and C1 inhibitor (C1inh) were measured. The C4 concentration was found to be within the normal range but the C1inh value was low (0.07 g/litre; normal range, 0.18-0.37). The patient was started on tranexamic acid and at an outpatient review three months later her episodes of swelling were occurring less often and were less severe. Although recent papers have suggested that the diagnosis of HAE can be excluded if complement C4 concentrations are normal, this case highlights the fact that C4 concentrations can be normal in this condition, and it is recommended that both C4 and C1inh concentrations should be measured to exclude HAE.

Does asbestos cause laryngeal cancer?

Asbestos is a known carcinogen. Its role in the aetiology of laryngeal cancer has been investigated and debated for the last three decades. Here, we consider much of the published evidence from post-mortem studies, cross-sectional, case-control and cohort studies. We feel that the weight of evidence does not support a causal association for asbestos with laryngeal cancer. The 'positive studies' raise important questions regarding an association; the opportunity may present itself to answer some of these as the incidence of asbestos-related malignancy is increasing in the UK and Europe.

Magnetic induction tomography: phase versus vector-voltmeter measurement techniques

In magnetic induction tomography (MIT) the in-quadrature component, and hence the phase, of the received signal contains information about the conductivity of the tissue. The quality of imaging will depend on the precision with which phase can be measured. Preliminary studies suggest that a precision of 10 m degrees may be required for a practical biomedical MIT system operating at 10 MHz. This paper describes the results of measurements carried out with a 16-channel, downconverting, 10 MHz, MIT system utilizing two types of data extraction techniques: direct-phase measurement and measurement of the in-phase and in-quadrature components of the signal with a vector voltmeter. The basic precision provided by each technique was 50 m degrees, with thermal drift representing the major limiting factor. Preliminary measurements of average conductivity and permittivity for a human thigh in vivo are given.

The voltage-sensitive release mechanism of excitation contraction coupling in rabbit cardiac muscle is explained by calcium-induced calcium release

The putative voltage-sensitive release mechanism (VSRM) was investigated in rabbit cardiac myocytes at 37 degrees C with high resistance microelectrodes to minimize intracellular dialysis. When the holding potential was adjusted from -40 to -60 mV, the putative VSRM was expected to operate alongside CICR. Under these conditions however, we did not observe a plateau at positive potentials of the cell shortening versus voltage relationship. The threshold for cell shortening changed by -10 mV, but this resulted from a similar change of the threshold for activation of inward current. Cell shortening under conditions where the putative VSRM was expected to operate was blocked in a dose dependent way by nifedipine and CdCl2 and blocked completely by NiCl2. "Tail contractions" persisted in the presence of nifedipine and CdCl2 but were blocked completely by NiCl2. Block of early outward current by 4-aminopyridine and 4-acetoamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid (SITS) demonstrated persisting inward current during test depolarizations despite the presence of nifedipine and CdCl2. Inward current did not persist in the presence of NiCl2. A tonic component of cell shortening that was prominent during depolarizations to positive potentials under conditions selective for the putative VSRM was sensitive to rapidly applied changes in superfusate [Na+] and to the outward Na+/Ca2+ exchange current blocking drug KB-R7943. This component of cell shortening was thought to be the result of Na+/Ca2+ exchange-mediated excitation contraction coupling. Cell shortening recorded under conditions selective for the putative VSRM was increased by the enhanced state of phosphorylation induced by isoprenaline (1 microM) and by enhancing sarcoplasmic reticulum Ca2+ content by manipulation of the conditioning steps. Under these conditions, cell shortening at positive test depolarizations was converted from tonic to phasic. We conclude that the putative VSRM is explained by CICR with the Ca2+ "trigger" supplied by unblocked L-type Ca2+ channels and Na+/Ca2+ exchange.

Hib vaccination in infants born prematurely

AIMS

To document the immunogenicity and persistence of antibody to polyribosyl-ribitol phosphate (PRP) as well as the clinical protection against invasive Haemophilus influenzae type b (Hib) disease in premature infants immunised at the routine schedule.

METHODS

Blood was obtained at 2, 5, 12, and 64 months of age from a cohort of prematurely born infants (<or=32 weeks gestation). Anti-PRP antibody concentrations were compared with those of a control cohort of infants born at full term and vaccinated at the same schedule. Hib vaccine failures occurring between October 1992 and October 2000 were reported by paediatricians through an active, prospective, national survey in the UK and Republic of Ireland. The number of prematurely born children with vaccine failure was compared with the corresponding number born at term.

RESULTS

Twenty seven prematurely born infants were followed to 5 years of age. Compared with term infants they had a significantly lower geometric mean concentration of anti-PRP antibody and/or a significantly lower proportion above one or both of the conventional protective antibody concentrations (0.15 and 1.0 micro g/ml) at all ages. A total of 165 cases of invasive Hib disease were identified over eight years of national surveillance. Eighteen were premature (<37 weeks); approximately 12 would be expected. The relative risk of UK premature infants developing disease compared with term infants was 1.5 (95% CI 0.9 to 2.6).

CONCLUSIONS

Premature infants develop lower antibody concentrations than term infants following Hib conjugate vaccination. Premature infants may also have an increased risk of clinical vaccine failure, but interpretation is limited by the small number of premature infants developing invasive Hib disease over eight years of national surveillance. Overall, vaccination with Hib conjugate vaccines affords a high level of protection to premature babies.

Risk-adjusted comparative audit. Is Possum applicable to head and neck surgery?

Possum (the physiological and operative severity score for the enumeration of mortality) is used in many surgical specialities for comparative audit. We investigated its validity in relation to head and neck surgery by retrospectively scoring 301 operative interventions. We also applied the P-Possum (Portsmouth Possum) equation for mortality. We compared our observed with the predicted outcomes. We introduced two new variables, radiotherapy and previous surgery to the operative site, to test their association with outcome. We found that Possum is valid for morbidity but predicts more accurately for high-risk than for low-risk groups. Neither Possum or P-Possum accurately predicts mortality. Radiotherapy and previous surgery were both significant for the development of postoperative complications (P = 0.002, P = 0.007 respectively) and are worthy of inclusion in a Possum score for head and neck surgery.

Plant responses to water stress

This Special Issue comprises a series of papers that develops the theme of plant responses to water stress, encompassing recent developments at the molecular level, through responses of photosynthesis and metabolism, to their application in crop selection and yield. The consideration of water deficits is particularly timely, given the huge developments in this area in the past decade. This issue specifically sets out to place molecular and physiological processes and their agronomic applications in an environmental context.

Analysis of the operation of the SCD Response intermittent compression system

The work assessed the performance of the Kendall SCD Response intermittent pneumatic compression system for deep vein thrombosis prophylaxis, which claimed to set its cycle according to the blood flow characteristics of individual patient limbs. A series of tests measured the system response in various situations, including application to the limbs of healthy volunteers, and to false limbs. Practical experimentation and theoretical analysis were used to investigate influences on the system functioning other than blood flow. The system tested did not seem to perform as claimed, being unable to distinguish between real and fake limbs. The intervals between compressions were set to times unrealistic for venous refill, with temperature changes in the cuff the greatest influence on performance. Combining the functions of compression and the measurement of the effects of compression in the same air bladder makes temperature artefacts unavoidable and can cause significant errors in the inter-compression interval.

Frequency downconversion and phase noise in MIT

High-frequency (3-30 MHz) operation of MIT systems offers advantages in terms of the larger induced signal amplitudes compared to systems operating in the low- or medium-frequency ranges. Signal distribution at HF, however, presents difficulties, in particular with isolation and phase stability. It is therefore valuable to translate received signals to a lower frequency range through heterodyne downconversion, a process in which relative signal amplitude and phase information is in theory retained. Measurement of signal amplitude and phase is also simplified at lower frequencies. The paper presents details of measurements on a direct phase measurement system utilizing heterodyne downconversion and compares the relative performance of three circuit configurations. The 100-sample average precision of a circuit suitable for use as a receiver within an MIT system was 0.008 degrees for input amplitude -21 dBV. As the input amplitude was reduced from -21 to -72 dBV variation in the measured phase offset was observed, with the offset varying by 1.8 degrees. The precision of the circuit deteriorated with decreasing input amplitude, but was found to provide a 100-sample average precision of <0.022 degrees down to an input amplitude of -60 dBV. The characteristics of phase noise within the system are discussed.

New tools for oligonucleotide fingerprinting

Oligonucleotide fingerprinting is an attractive, high-throughput complement to tag sequencing methods to determine the spectrum and abundance of genes in cDNA libraries. This method currently relies on the sequential hybridizations of short, radioactively labeled DNA oligonucleotides to clone arrays. Here, we describe a new environment that substantially improves this technology. Fluorescently labeled peptide nucleic acid (PNA) oligonucleotides are used as hybridization probes. Hybridization results are recorded with a large-field, high-resolution laser scanner developed for this purpose. Automated image analysis allows easy handling of large numbers of hybridization images. Signal interference effects, which limit the gridding density in the radioactive approach, are strongly reduced. The sensitivity of the fluorescence detection demonstrated permits the convenient use of nylon membranes. Hybridization data quality is improved, and its generation is substantially accelerated, simplified, and less expensive.

Hydrophobic trichome layers and epicuticular wax powders in Bromeliaceae

The distinctive foliar trichome of Bromeliaceae has promoted the evolution of an epiphytic habit in certain taxa by allowing the shoot to assume a significant role in the uptake of water and mineral nutrients. Despite the profound ecophysiological and taxonomic importance of this epidermal structure, the functions of nonabsorbent trichomes in remaining Bromeliaceae are not fully understood. The hypothesis that light reflection from these trichome layers provides photoprotection was not supported by spectroradiometry and fluorimetry in the present study; the mean reflectance of visible light from trichome layers did not exceed 6.4% on the adaxial surfaces of species representing a range of ecophysiological types nor was significant photoprotection provided by their presence. Several reports suggesting water repellency in some terrestrial Bromeliaceae were investigated. Scanning electron microscopy (SEM) and a new technique-fluorographic dimensional imaging (FDI)-were used to assess the interaction between aqueous droplets and the leaf surfaces of 86 species from 25 genera. In the majority of cases a dense layer of overlapping, stellate or peltate trichomes held water off the leaf epidermis proper. In the case of hydrophobic tank-forming tillandsioideae, a powdery epicuticular wax layer provided water repellency. The irregular architecture of these indumenta resulted in relatively little contact with water droplets. Most mesic terrestrial Pitcairnioideae examined either possessed glabrous leaf blades or hydrophobic layers of confluent trichomes on the abaxial surface. Thus, the present study indicates that an important ancestral function of the foliar trichome in Bromeliaceae was water repellency. The ecophysiological consequences of hydrophobia are discussed.

Radiologic case study. Pigmented villonodular synovitis

Pigmented villonodular synovitis is a benign, locally aggressive disorder characterized by a unique clinical radiographic, and histopathologic presentation. While it is considered to be a rare disorder, a delay in diagnosis and treatment can potentially result in severe disruption of joint function due to subchondral invasion. Once the diagnosis is confirmed, treatment should consist of complete synovectomy. Recurrence is common, but malignant transformation is rare. The etiology of PVNS is still unknown, and perhaps its future discovery will assist in the definitive treatment of this disorder.