A practical method to standardise and optimise the Philips DoseRight 2.0 CT automatic exposure control system

Given the increasing use of computed tomography (CT) in the UK over the last 30 years, it is essential to ensure that all imaging protocols are optimised to keep radiation doses as low as reasonably practicable, consistent with the intended clinical task. However, the complexity of modern CT equipment can make this task difficult to achieve in practice. Recent results of local patient dose audits have shown discrepancies between two Philips CT scanners that use the DoseRight 2.0 automatic exposure control (AEC) system in the 'automatic' mode of operation. The use of this system can result in drifting dose and image quality performance over time as it is designed to evolve based on operator technique. The purpose of this study was to develop a practical technique for configuring examination protocols on four CT scanners that use the DoseRight 2.0 AEC system in the 'manual' mode of operation. This method used a uniform phantom to generate reference images which form the basis for how the AEC system calculates exposure factors for any given patient. The results of this study have demonstrated excellent agreement in the configuration of the CT scanners in terms of average patient dose and image quality when using this technique. This work highlights the importance of CT protocol harmonisation in a modern Radiology department to ensure both consistent image quality and radiation dose. Following this study, the average radiation dose for a range of CT examinations has been reduced without any negative impact on clinical image quality.

Validation of a technique for estimating organ doses for kilovoltage cone-beam CT of the prostate using the PCXMC 2.0 patient dose calculator

The use of cone beam CT in common radiotherapy treatments is increasing with the growth of image guided radiotherapy. Whilst the benefits that this technology offers are clear, such as improved patient positioning prior to treatment, it is always important to consider the implications of such intensive imaging regimes on the patient, especially when considering the fundamental radiation protection requirements for justification and optimisation.The purpose of this study was to develop a technique that uses readily available dose calculation software (PCXMC 2.0) to estimate the organ and effective doses that result from these types of examination in prostate treatments on the Varian OBI system. It has been shown that by separating these types of examinations into 28 different projections, with a range of x-ray beam qualities, it is possible to reproduce the complex geometry that is used on these imaging systems in PCXMC i.e. asymmetric radiation field with a half bowtie filter rotating 360° around the patient.This new technique has been validated with thermo-luminescent dosimeter measurements in the Rando anthropomorphic phantom, and has been shown to give excellent agreement with this established method (R(2) = 0.995). This technique will prove to be valuable to radiotherapy departments that are looking to optimise their CBCT imaging protocols as it allows a rapid evaluation of the impact of any changes on patient dose. It also serves to further highlight the levels of dose that these types of patient are subject to when having daily CBCT scans as part of the treatment, which further reinforces the need for optimisation of both patient dose and image quality on these systems.

Investigating the use of an antiscatter grid in chest radiography for average adults with a computed radiography imaging system

OBJECTIVE

The aim of this study was to investigate via simulation a proposed change to clinical practice for chest radiography. The validity of using a scatter rejection grid across the diagnostic energy range (60-125 kVp), in conjunction with appropriate tube current-time product (mAs) for imaging with a computed radiography (CR) system was investigated.

METHODS

A digitally reconstructed radiograph algorithm was used, which was capable of simulating CR chest radiographs with various tube voltages, receptor doses and scatter rejection methods. Four experienced image evaluators graded images with a grid (n = 80) at tube voltages across the diagnostic energy range and varying detector air kermas. These were scored against corresponding images reconstructed without a grid, as per current clinical protocol.

RESULTS

For all patients, diagnostic image quality improved with the use of a grid, without the need to increase tube mAs (and therefore patient dose), irrespective of the tube voltage used. Increasing tube mAs by an amount determined by the Bucky factor made little difference to image quality.

CONCLUSION

A virtual clinical trial has been performed with simulated chest CR images. RESULTS indicate that the use of a grid improves diagnostic image quality for average adults, without the need to increase tube mAs, even at low tube voltages.

ADVANCES IN KNOWLEDGE

Validated with images containing realistic anatomical noise, it is possible to improve image quality by utilizing grids for chest radiography with CR systems without increasing patient exposure. Increasing tube mAs by an amount determined by the Bucky factor is not justified.

Correlation of the clinical and physical image quality in chest radiography for average adults with a computed radiography imaging system

OBJECTIVE

The purpose of this study was to examine the correlation between the quality of visually graded patient (clinical) chest images and a quantitative assessment of chest phantom (physical) images acquired with a computed radiography (CR) imaging system.

METHODS

The results of a previously published study, in which four experienced image evaluators graded computer-simulated postero-anterior chest images using a visual grading analysis scoring (VGAS) scheme, were used for the clinical image quality measurement. Contrast-to-noise ratio (CNR) and effective dose efficiency (eDE) were used as physical image quality metrics measured in a uniform chest phantom. Although optimal values of these physical metrics for chest radiography were not derived in this work, their correlation with VGAS in images acquired without an antiscatter grid across the diagnostic range of X-ray tube voltages was determined using Pearson's correlation coefficient.

RESULTS

Clinical and physical image quality metrics increased with decreasing tube voltage. Statistically significant correlations between VGAS and CNR (R=0.87, p<0.033) and eDE (R=0.77, p<0.008) were observed.

CONCLUSION

Medical physics experts may use the physical image quality metrics described here in quality assurance programmes and optimisation studies with a degree of confidence that they reflect the clinical image quality in chest CR images acquired without an antiscatter grid.

ADVANCES IN KNOWLEDGE

A statistically significant correlation has been found between the clinical and physical image quality in CR chest imaging. The results support the value of using CNR and eDE in the evaluation of quality in clinical thorax radiography.

Use of a digitally reconstructed radiograph-based computer simulation for the optimisation of chest radiographic techniques for computed radiography imaging systems

OBJECTIVES

The purpose of this study was to derive an optimum radiographic technique for computed radiography (CR) chest imaging using a digitally reconstructed radiograph computer simulator. The simulator is capable of producing CR chest radiographs of adults with various tube potentials, receptor doses and scatter rejection.

METHODS

Four experienced image evaluators graded images of average and obese adult patients at different potentials (average-sized, n=50; obese, n=20), receptor doses (n=10) and scatter rejection techniques (average-sized, n=20; obese, n=20). The quality of the images was evaluated using visually graded analysis. The influence of rib contrast was also assessed.

RESULTS

For average-sized patients, image quality improved when tube potential was reduced compared with the reference (102 kVp). No scatter rejection was indicated. For obese patients, it has been shown that an antiscatter grid is indicated, and should be used in conjunction with as low a tube potential as possible (while allowing exposure times <20 ms). It is also possible to reduce receptor air kerma by 50% without adversely influencing image quality. Rib contrast did not interfere at any tube potential.

CONCLUSIONS

A virtual clinical trial has been performed with simulated chest CR images. Results indicate that low tube potentials (<102 kVp) are optimal for average and obese adults, the former acquired without scatter rejection, the latter with an anti-scatter grid. Lower receptor (and therefore patient doses) than those used clinically are possible while maintaining adequate image quality.

Validation of a large-scale audit technique for CT dose optimisation

The expansion and increasing availability of computed tomography (CT) imaging means that there is a greater need for the development of efficient optimisation strategies that are able to inform clinical practice, without placing a significant burden on limited departmental resources. One of the most fundamental aspects to any optimisation programme is the collection of patient dose information, which can be compared with appropriate diagnostic reference levels. This study has investigated the implementation of a large-scale audit technique, which utilises data that already exist in the radiology information system, to determine typical doses for a range of examinations on four CT scanners. This method has been validated against what is considered the 'gold standard' technique for patient dose audits, and it has been demonstrated that results equivalent to the 'standard-sized patient' can be inferred from this much larger data set. This is particularly valuable where CT optimisation is concerned as it is considered a 'high dose' technique, and hence close monitoring of patient dose is particularly important.

Intravenous administration of human embryonic stem cell-derived neural precursor cells attenuates cuprizone-induced central nervous system (CNS) demyelination

AIMS

Previous studies have demonstrated the therapeutic potential for human embryonic stem cell-derived neural precursor cells (hES-NPCs) in autoimmune and genetic animal models of demyelinating diseases. Herein, we tested whether intravenous (i.v.) administration of hES-NPCs would impact central nervous system (CNS) demyelination in a cuprizone model of demyelination.

METHODS

C57Bl/6 mice were fed cuprizone (0.2%) for 2 weeks and then separated into two groups that either received an i.v. injection of hES-NPCs or i.v. administration of media without these cells. After an additional 2 weeks of dietary cuprizone treatment, CNS tissues were analysed for detection of transplanted cells and differences in myelination in the region of the corpus callosum (CC).

RESULTS

Cuprizone-induced demyelination in the CC was significantly reduced in mice treated with hES-NPCs compared with cuprizone-treated controls that did not receive stem cells. hES-NPCs were identified within the brain tissues of treated mice and revealed migration of transplanted cells into the CNS. A limited number of human cells were found to express the mature oligodendrocyte marker, O1, or the astrocyte marker, glial fibrillary acidic protein. Reduced apoptosis and attenuated microglial and astrocytic responses were also observed in the CC of hES-NPC-treated mice.

CONCLUSIONS

These findings indicated that systemically administered hES-NPCs migrated from circulation into a demyelinated lesion within the CNS and effectively reduced demyelination. Observed reductions in astrocyte and microglial responses, and the benefit of hES-NPC treatment in this model of myelin injury was not obviously accountable to tissue replacement by exogenously administered cells.

A method to produce and validate a digitally reconstructed radiograph-based computer simulation for optimisation of chest radiographs acquired with a computed radiography imaging system

OBJECTIVES

The purpose of this study was to develop and validate a computer model to produce realistic simulated computed radiography (CR) chest images using CT data sets of real patients.

METHODS

Anatomical noise, which is the limiting factor in determining pathology in chest radiography, is realistically simulated by the CT data, and frequency-dependent noise has been added post-digitally reconstructed radiograph (DRR) generation to simulate exposure reduction. Realistic scatter and scatter fractions were measured in images of a chest phantom acquired on the CR system simulated by the computer model and added post-DRR calculation.

RESULTS

The model has been validated with a phantom and patients and shown to provide predictions of signal-to-noise ratios (SNRs), tissue-to-rib ratios (TRRs: a measure of soft tissue pixel value to that of rib) and pixel value histograms that lie within the range of values measured with patients and the phantom. The maximum difference in measured SNR to that calculated was 10%. TRR values differed by a maximum of 1.3%.

CONCLUSION

Experienced image evaluators have responded positively to the DRR images, are satisfied they contain adequate anatomical features and have deemed them clinically acceptable. Therefore, the computer model can be used by image evaluators to grade chest images presented at different tube potentials and doses in order to optimise image quality and patient dose for clinical CR chest radiographs without the need for repeat patient exposures.

Dietary strategy to manipulate ad libitum macronutrient intake, and glycaemic index, across eight European countries in the Diogenes Study

The aim of this study was to describe the development and implementation of a multifaceted, low-fat, weight-loss strategy for a Pan-European randomized controlled dietary intervention study, Diogenes. There were 891 families with at least one overweight/obese parent who underwent screening. Eligible, overweight/obese adults followed an 8-week weight-loss phase with a fixed low-energy diet (800 kcal). On attaining weight loss of > or = 8%, families were randomized to a 6- or 12-month low-fat (25-30%E) diet either based on national dietary guidelines or one of four interventions: low protein (LP)/low glycaemic index (LGI), LP/high GI (HGI), high protein (HP)/LGI and HP/HGI. The impact of each diet in preventing weight (re)gain was tested. A points-based system was used to manipulate dietary protein and carbohydrate. Manipulating carbohydrate composition involved substituting foods with a relatively high or low GI. A questionnaire was designed and completed by study investigators, providing feedback on the dietary intervention methods used to inform future interventions. The points system allowed macronutrient manipulations without compromising dietary flexibility or enforcing energy restrictions. Reported centre/participant differences in the ease of implementing the intervention may reflect dietary diversity and personal preferences for specific weight-management strategies. The points system provides a useful starting point for designing improved experimental paradigms for the manipulation of dietary intake in future trials.

Investigating the exposure class of a computed radiography system for optimisation of physical image quality for chest radiography

The purpose of this study was to investigate whether the exposure (speed) class (EC) of an Agfa computed radiography (CR) system could be used to optimise chest radiography. The frequency-dependent normalised noise-power spectra (NNPS(f)) were determined for a range of EC settings (25-1200) for a receptor dose of 4 microGy. Signal-to-noise ratios (SNRs) were measured in the lung, heart and diaphragm areas of a chest phantom with ECs of 400 and 600 at four tube voltages (60, 75, 90 and 125 kVp). As anatomical background can be a factor in detection of lung nodules, a tissue to rib ratio (TRR), which measures the ratio of pixel values in the nodule to that of rib, was measured in the lung region of the phantom to assess the suppression of the rib at ECs of 400 and 600. The NNPS(f) at ECs lower than 400 was relatively high. The NNPS(f) at EC 600 was found to be 7% lower when averaged over all frequencies than that at EC 400. The statistical significance of this difference was verified. The EC 800 and EC 1200 settings offered no extra advantages in terms of lowering frequency-dependent noise. The EC 600 setting offered improvements in SNR of between 10% and 18% in the lung, 11% and 16% in the heart, and 15% and 20% in the diaphragm compared with EC 400. Statistical analysis verified the significant difference. The EC 600 setting increased the TRR, thereby helping to suppress rib. This work indicates that an exposure class setting of 600 is the most appropriate for standard chest radiography, but clinical verification is required.

Investigation of optimum X-ray beam tube voltage and filtration for chest radiography with a computed radiography system

The purpose of this study was to determine the optimum tube voltage and amount of added copper (Cu) filtration for processed chest radiographs obtained with an Agfa 75.0 Computed Radiography (CR) system. The contrast-to-noise ratio (CNR) was measured in the lung, heart/spine and diaphragm compartments of a validated chest phantom using various tube voltages and amounts of Cu filtration. The CNR was derived as a function of air kerma at the CR plate and with the effective dose. As rib contrast can interfere with detection of nodules in chest radiography, a tissue-to-rib ratio (TRR) was derived to investigate which tube voltages suppress the contrast of rib. Although processing algorithms affect the signal and noise in a way that is hard to predict, we found that, for a given set of processing parameters, the CNR was related to the plate air kerma and effective dose in a logarithmic manner (all R(2) >or=0.97). For imaging of the lung region, a low voltage (60 kVp) produced the highest CNR, whereas a high voltage (125 kVp) produced the highest TRR. In the heart/spine region, 80-125 kVp produced the highest CNR, while in the diaphragm region 60-90 kVp produced the highest CNR. For chest radiography with this CR system, the optimal tube voltage depends upon the region of interest. Of the filters tested, a 0.1 mm Cu thickness was found to provide a statistically significant increase in the CNR in the diaphragm region with tube potentials of 60 kVp and 80 kVp, without affecting the CNR in the other anatomical compartments.

Expression of the inhibitor of apoptosis protein family in multiple sclerosis reveals a potential immunomodulatory role during autoimmune mediated demyelination

A failure of autoreactive T cells to undergo apoptosis may contribute to the pathogenesis of multiple sclerosis (MS). The role of the inhibitor of apoptosis (IAP) family of anti-apoptotic proteins such as X-linked IAP (XIAP), human inhibitor of apoptosis-1 (HIAP-1), human inhibitor of apoptosis-2 (HIAP-2), neuronal apoptosis inhibitory protein (NAIP) and Survivin in relapsing–remitting, secondary-progressive, primary-progressive or benign forms of MS is unclear. We report here that expression of the IAP family of genes in peripheral blood samples and brain tissues from MS cases support a role for differential regulation of these potent anti-apoptotic proteins in the pathology of MS. XIAP mRNA and protein levels were elevated in peripheral blood mononuclear cells from patients with active disease relative to normal subjects. In patients with active MS, HIAP-1 and HIAP-2 mRNA levels were elevated in resting T cells while NAIP mRNA was increased in whole blood. In post-mortem MS brain tissue, XIAP and HIAP-1 in myelin lesions were co-localized with microglia and T cells, respectively. Only in primary-progressive patients was Survivin expression elevated suggestive of a distinct pathological basis for this subtype of MS. Taken together, these results suggest that patterns of inhibitor of apoptosis expression in immune cells may have value in distinguishing between MS subtypes and offer insight into the mechanisms responsible for their distinct clinical courses.

A method to optimize the processing algorithm of a computed radiography system for chest radiography

A test methodology using an anthropomorphic-equivalent chest phantom is described for the optimization of the Agfa computed radiography "MUSICA" processing algorithm for chest radiography. The contrast-to-noise ratio (CNR) in the lung, heart and diaphragm regions of the phantom, and the "system modulation transfer function" (sMTF) in the lung region, were measured using test tools embedded in the phantom. Using these parameters the MUSICA processing algorithm was optimized with respect to low-contrast detectability and spatial resolution. Two optimum "MUSICA parameter sets" were derived respectively for maximizing the CNR and sMTF in each region of the phantom. Further work is required to find the relative importance of low-contrast detectability and spatial resolution in chest images, from which the definitive optimum MUSICA parameter set can then be derived. Prior to this further work, a compromised optimum MUSICA parameter set was applied to a range of clinical images. A group of experienced image evaluators scored these images alongside images produced from the same radiographs using the MUSICA parameter set in clinical use at the time. The compromised optimum MUSICA parameter set was shown to produce measurably better images.

The impact of long chain n-3 polyunsaturated fatty acid supplementation on inflammation, insulin sensitivity and CVD risk in a group of overweight women with an inflammatory phenotype

BACKGROUND

Inflammation is strongly related to obesity and the risk of cardiovascular disease (CVD). The metabolic benefits of long chain (LC) n-3 polyunsaturated fatty acid (PUFA) may be attributable to its anti-inflammatory properties.

OBJECTIVE

To investigate whether an individual's habitual inflammatory status influences the impact of a LC n-3 PUFA intervention on CVD risk.

DESIGN

The study was a randomized crossover design. Subjects received LC n-3 PUFA capsules or a placebo for 12 weeks, with 4-week washout between phases. Thirty women, in the top and bottom tertiles of baseline sialic acid concentration, formed raised inflammatory status (top, n = 12) and reference (bottom, n = 18) groups. Baseline data were analysed using one-way anova, differences between treatment phases were calculated at each timepoint and analysed using a random effects model.

RESULTS

At baseline, the raised inflammatory status group had significantly higher body mass index and area under the curve (AUC) insulin than the reference group. With LC n-3 PUFA supplementation, both groups showed significantly higher plasma eicosapentaenoic acid and docosahexaenoic acid at 4 and 12 weeks (p < 0.001), and lower triacylglycerols (4 weeks p < 0.01 and 12 weeks p < 0.05). The difference in AUC insulin between the two treatment phases at 12 weeks was significantly greater in the raised inflammatory status group compared to the reference group (p < 0.05). Inflammatory markers were significantly lower after 12 weeks LC n-3 PUFA supplementation compared to baseline (C-reactive protein p < 0.05 and interleukin-6 p < 0.01), but there was no significant group effect.

CONCLUSIONS

Habitual inflammatory status influences the impact of LC n-3 PUFA supplementation, but it is not clear whether the effect of LC n-3 PUFA on AUC insulin is mediated through inflammatory mechanisms.

Neuroanatomical and pharmacological assessment of Fos expression induced in the rat brain by the phosphodiesterase-4 inhibitor 6-(4-pyridylmethyl)-8-(3-nitrophenyl) quinoline

A major obstacle in the therapeutic development of phosphodiesterase-4 (PDE4) inhibitors is the production of adverse side effects such as nausea and vomiting. Immunohistochemical detection of Fos-like immunoreactivity (FLI) was used to address the neuroanatomical basis for the pharmacological actions of PDE4 inhibitors. The potent and selective PDE4 inhibitors 6-(4-pyridylmethyl)-8-(3-nitrophenyl) quinoline (PMNPQ) and rolipram elevated FLI in brain regions potentially relevant to the anti-depressant and emetic effects of PDE4 inhibition. PMNPQ and rolipram elevated FLI in the locus coeruleus, habenula, paraventricular nucleus of the thalamus, amygdala and nucleus accumbens, all structures with strong limbic connectivity implicated in arousal, memory and affective aspects of behaviour. Consistent with the emetic effects of PDE4 inhibitors such as PMNPQ and rolipram, these compounds elevated FLI in caudal brainstem nuclei such as the area postrema and nucleus of the solitary tract. Administration of the NK(1) antagonist RP 67580 prior to PMNPQ reversed increases in FLI produced by PMNPQ in these regions. RP 67580 did not, however, reduce PMNPQ-induced FLI in limbic structures. These findings suggest that PDE4 inhibitors produce emesis by increasing NK(1) receptor activation in the AP/NTS and implicate brain regions associated with reward and mood such as the amygdala, paraventricular nucleus of the thalamus, habenula and nucleus accumbens in the anti-depressant activity of such compounds.

Intermittent vs continuous administration of epidural ropivacaine with fentanyl for analgesia during labour †

BACKGROUND

Many years ago regular intermittent bolus administration of epidural local anaesthetic solution was recognized to produce more effective analgesia than continuous infusion, but only recently has the development of suitable pumps allowed the former technique's wider evaluation.

METHODS

In this randomized, double-blind trial, 40 primigravid patients had a lumbar epidural catheter inserted, and plain ropivacaine 0.2% 15-20 ml was titrated until analgesia and bilateral sensory block to T10 were produced (time zero). Patients were then given either an infusion of ropivacaine 2 mg ml(-1) with fentanyl 2 microg ml(-1) at 10 ml h(-1), or hourly boluses of 10 ml of the same solution. Pain, sensory block and motor block were measured frequently. If requested, additional 10 ml boluses of the study mixture were given for analgesia.

RESULTS

There were no differences between the two groups in patient characteristics, obstetric/neonatal outcome, or in sensory or motor block. A total of 12 (60%) patients in the continuous group required one or more additional boluses compared with 4 (20%) patients in the intermittent group (95% CI 9.6-61.7%, P=0.02). Therefore the intermittent group received a lower total drug dose than the infusion group (P=0.02). Duration of uninterrupted analgesia (time to first rescue bolus) was longer in the intermittent group (P<0.02).

CONCLUSIONS

The intermittent group required fewer supplementary injections and less drug to maintain similar pain scores, sensory and motor block compared with the continuous group. This represents a more efficacious mode of analgesia.

Peripheral phosphodiesterase 4 inhibition produced by 4-[2-(3,4-Bis-difluoromethoxyphenyl)-2-[4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)-phenyl]-ethyl]-3-methylpyridine-1-oxide (L-826,141) prevents experimental autoimmune encephalomyelitis

Administration of phosphodiesterase 4 (PDE4) inhibitors suppresses the pathogenesis associated with experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). In the present study, we compared the effects of rolipram and 4-[2-(3,4-bis-difluoromethoxyphenyl)-2-[4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)-phenyl]-ethyl]-3-methylpyridine-1-oxide (L-826,141), a novel nonbrain penetrant PDE4 inhibitor, on the onset and severity of clinical signs in a chronic, nonrelapsing/remitting model of EAE. Both rolipram (10 mg/kg p.o.) and L-826,141 (3 mg/kg p.o.) reduced the severity of EAE relative to controls, whereas L-826,141 (3 mg/kg p.o.) also delayed disease onset. To assess whether L-826,141 prevented EAE progression after the first signs of clinical onset, rolipram (10 mg/kg p.o.) or L-826,141 (3 or 30 mg/kg p.o.) were administered 24 h after the first signs of EAE were observed. Only L-826,141 at a dose of 30 mg/kg p.o. significantly decreased the clinical severity of EAE compared with vehicle controls. Immunohistochemical detection of the neuronal activity marker Fos confirmed that L-826,141 did not reach concentrations in the central nervous system sufficient to activate central neurons. Lipopolysaccharide-induced tumor necrosis factor-alpha in whole blood and plasma concentrations of L-826,141 revealed that only the 30-mg/kg dose resulted in levels sufficient to produce a near complete inhibition of PDE4 activity in immune cells. Taken together, these results demonstrate that peripheral PDE4 inhibition, produced by L-826,141, prevents the progression of EAE after the first onset of clinical signs, and suggest that similar compounds may have clinical efficacy in the treatment of MS.

Additive benefits of long-chain n-3 polyunsaturated fatty acids and weight-loss in the management of cardiovascular disease risk in overweight hyperinsulinaemic women

BACKGROUND

Obesity, inflammation, insulin resistance and cardiovascular disease (CVD) risk are inter-related. Both weight-loss and long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) are independently known to reduce metabolic risk, but the combined effects are unclear.

OBJECTIVE

This study examines whether addition of LC n-3 PUFA to a low fat/high carbohydrate weight-loss programme results in greater improvements in inflammation, insulin sensitivity and CVD risk, than weight-loss alone.

DESIGN

One hundred and sixteen overweight insulin-resistant women entered a 24-week randomised intervention study. Thirty-nine women were randomised to a weight-loss programme, with LC n-3 PUFA (WLFO), 38 to a weight-loss programme with placebo oil (WLPO), and 39 to receive placebo oil, with no weight-loss programme (control).

RESULTS

Ninety-three women completed the study (35 WLFO, 32 WLPO and 26 control), with significant weight-loss in WLFO (10.8+/-1.0%) and WLPO (12.4+/-1.0%) compared to the control group (P<0.0001). The WLFO, but not WLPO or control group, showed significant increases in adipose tissue LC n-3 PUFA (0.34+/-0.20 vs 0.17+/-0.10 and 0.16+/-0.10 %DHA, P<0.0001). Weight-loss showed significant improvements in insulin sensitivity (P<0.001), lipid profile (triglycerides P<0.05) and inflammation (sialic acid P<0.05). Time*group effects showed significant decreases in triglycerides (P<0.05) and increases in adiponectin (P<0.01) with LC n-3 PUFA, in the WLFO vs WLPO groups.

CONCLUSIONS

Weight-loss improved risk factors associated with CVD, with some additional benefits of LC n-3 PUFA on triglycerides and adiponectin. Given the current low dietary intake of LC n-3 PUFA, greater attention should be given to increase these fatty acids in the treatment of obesity.

Human PRRX1 and PRRX2 genes: cloning, expression, genomic localization, and exclusion as disease genes for Nager syndrome

In this study, we extend our examination of the function of the Prrx1 (a.k.a Mhox, Prx1, K-2, and Pmx1) as well as Prrx2 (a.k.a. S8 and Prx2) genes by characterizing the expression of the human orthologs and their potential for causing specific human malformations. The expression pattern of PRRX2 and its close relative, PRRX1, were analyzed in human tissue by RT-PCR. Although the expression of these human genes is similar to their mouse orthologs, there are notable differences in expression. PRRX2 was detected in the human kidney and lung, whereas in mice and chickens neither of these tissues has been reported to express Prrx2. For PRRX1 the expression pattern was quite similar to other vertebrates, but the ratio of the two isoforms was reversed. To begin the search for the gene-disease connection, both genes were mapped to human chromosomes by FISH. The PRRX1 locus maps to 1q23, whereas the PRRX2 locus maps to 9q34.1. This localization, along with the recently described phenotypes of the gene-targeted Prrx1, Prrx2 and double mutant mice, enabled us to search the human disease databases for similar malformations. This examination suggested that mutations at the PRRX1 and/or PRRX2 loci could result in Nager Acrofacial Dysostosis (NAFD) syndrome. We obtained DNA samples from eight patients with NAFD, as well as two patients with Miller syndrome, and analyzed them for mutations in the PRRX1 and PRRX2 genes. The data excludes mutations in the presumed coding sequences of these genes from causing NAFD.

A cre-lox recombination system for the targeted integration of circular yeast artificial chromosomes into embryonic stem cells

The ability to produce embryonic stem (ES) cell lines containing different yeast artificial chromosomes (YACs) integrated into the same location in the genome provides a system for comparing the bio-logical effects of YAC transgenes without the confounding influences of integration site and copy number. A targeting system was developed for the directed integration of circular YACs into mouse ES cells. The system combines Cre-lox recombination technology, specifically a positive-selection integration system, with circular YAC lipofection technology to achieve single copy targeted integration of a transgene. Three independent germline competent ES cell lines [lox-containing ES lines (designated LES)] were created that contain a '-neo-lox' cassette integrated at different sites within the ES genome. A plasmid containing YAC vector sequences and a complementary '-neo-lox' cassette was used to circularize two linear YACs containing genomic DNA from human chromosome 21. The circularized YACs were then targeted to the lox sites of the LES cell lines. Polymerase chain reaction and Southern analysis demonstrated that 21% (5 of 24) of lox-recombinants contain a full-length intact YAC. This system will make the study of YAC transgenic mice more reliable and reproducible, allowing the potential for direct comparison of different transgenes expressed from the same site within the genome.

Human X inactivation center induces random X chromosome inactivation in male transgenic mice

X chromosome inactivation is the means to downregulate the transcriptional output of X chromosomes in female mammals. Essential DNA from the murine X inactivation center (Xic) has been identified by introducing it into male embryonic stem (ES) cells. To identify the essential sequences on human X chromosomes, we transfected male mouse ES cells with a YAC transgene containing 480 kb of the putative human X inactivation center (XIC). Despite little DNA sequence conservation, the human transgene is recognized as a second Xic in these XY mouse cells and induces random inactivation in chimeric mice derived from these cells. Inactivation is extensive on the X chromosome, but more localized on chromosome 11 carrying the transgene, demonstrating that initial inactivation and spreading of inactivation signals along the chromosome are independent events. Our results show for the first time that the DNA included in the human XIC transgene is sufficient to initiate random X inactivation, even in cells of another species. Interspecies XIC trangenes should facilitate further investigation of this process in humans and other mammals.

Integration of cytogenetic with recombinational and physical maps of mouse chromosome 16

To link the cytogenetic map for mouse chromosome 16 (Chr 16) to the more detailed recombinational and physical maps, multiple probes were mapped by fluorescence in situ hybridization (FISH). Sixteen large insert clones (YACs, BACs, and PACs) containing markers that have been assigned to the Chr 16 recombinational map were localized to a cytogenetic band or subband by high-resolution FISH. This linkage of the cytogenetic and recombinational maps provides a useful tool for assigning new probe locations and for defining breakpoints in mice with chromosomal rearrangements. A direct application of these probes is demonstrated by identifying mice trisomic for distal Chr 16 using FISH analysis of interphase nuclei.

Revised genomic organization of FBN1 and significance for regulated gene expression

FBN1 encodes fibrillin-1, an extracellular matrix protein that is defective in Marfan syndrome. This gene is divided into 65 exons and was previously reported to be approximately 110 kb in length. The existence of 3 exons upstream of the exon containing the putative initiating methionine left open the possibility of alternative fibrillin-1 isoforms that vary at their N-termini. Detailed examination of YACs containing human FBN1 reveal that the gene is 200 kb, almost twice as large as previously thought. Characterization of the porcine FBN1 cDNA and 5' flanking sequence demonstrates extreme conservation between the pig and the human predicted proteins and argues against the possibility of alternative amino-terminal coding sequence. These data further our understanding of the regulatory requirements for gene expression and establish a framework for recombinant expression of fibrillin-1.

Genomic structure of PEX13, a candidate peroxisome biogenesis disorder gene

The peroxisome biogenesis disorders (PBDs) are a set of lethal genetic diseases characterized by peroxisomal metabolic deficiencies, multisystem abnormalities, mental retardation, and premature death. These disorders are genetically heterogeneous and are caused by mutations in genes, termed PEX genes, required for import of proteins into the peroxisomal matrix. We have previously reported the identification of human PEX13, the gene encoding the docking factor for the PTS1 receptor, or PEX5 protein. As such, mutations in PEX13 would be expected to abrogate peroxisomal protein import and result in PBD phenotypes. We report here the structure of the human PEX13 gene. PEX13 spans approximately 11 kb on chromosome 2 and contains four exons, one more than previously thought. The corrected PEX13 cDNA is predicted to encode a protein product with a molecular mass of 44,312 Da. We examined the ability of PEX13 expression to rescue the peroxisomal protein import defects of fibroblast cells representing all known PBD complementation groups. No complementation was observed, suggesting that this gene is not mutated in any set of existing patients. However, given that complementation group assignments have been determined for only a subset of PBD patients, it is possible that PEX13-deficient patients may exist at a low frequency within our existing PBD patient population or within ethnic groups underrepresented in our patient pool.

Expression and function of activin beta A during mouse cardiac cushion tissue formation

The formation of cardiac cushion tissue, which ultimately contributes to formation of the valves and septa, is dependent on the regional activation of cardiac endothelial cells to undergo an epithelial-mesenchymal transition. This endothelial transition was correlated with activin betaA mRNA expression by Northern and in situ hybridization in both a temporal and spatial manner in developing mouse embryos. Activin betaA was the only subunit of the inhibin family detected during the initial phase of endothelial cell transition; activin betaB was detected at later stages, and inhibin alpha was not detectable in the heart. An in vitro assay that has been used to study mesenchymal cell formation in chick was modified for use with mammalian embryos. Conditioned media from embryonic mouse cardiocyte cultures was shown to substitute for the endogenous inductive signal in these assays. The presence of activin betaA was demonstrated by Western blot analysis of the cardiocyte conditioned media (CCM). Modified antisense oligonucleotides to activin betaA inhibited the endothelial-mesenchymal transition in the assay system, which was not affected by control oligonucleotides. Adapting the avian culture system for use with mice enabled the use of tissue from mice with a null allele for activin betaA. CCM produced from embryos homozygous for the mutant betaA allele did not contain activin betaA and was used in in vitro assays. CCM lacking activin betaA produced fewer mesenchymal cells from cardiac endothelial monolayers than CCM with activin betaA. Localized expression of activin betaA in the embryonic heart indicates a possible role in the endothelial-mesenchymal transition. Bioassays in which activin betaA expression is blocked or activin betaA is absent from the media indicate that activin betaA promotes the formation of mesenchymal cells in the endothelial cushions, which are required for normal septation.

Audit of imported and domestic malaria cases at Kuala Lumpur Hospital

The clinical, haematological and biochemical profiles of all domestic and imported malaria cases admitted to the Hospital Kuala Lumpur were analysed. The most common malaria types were Plasmodium falciparum (39.5%) and Plasmodium vivax (42%). The most common patient type was men aged 29-40 years (reflecting the high mobility of this group, many of whom were illegal immigrants). Misdiagnosis on admission was frequently due to the variable clinical presentation of the disease and the difficulties of obtaining an accurate history. Associated haematological abnormalities were common. Chloroquine resistance was diagnosed in four P. falciparum patients and in one P. falciparum/vivax patient. Overall, imported malaria did not seem more severe than domestic. The three patients with cerebral malaria survived. One patient died of acute liver failure. The large influx of illegal immigrants to Malaysia has resulted in a surge in malaria infection; illegal immigrants remain a source of chloroquine resistance.

A human T cell tumor which expresses the putative T cell antigen receptor

A monoclonal antibody (mAb) called H1-2D4 which reacts only with the T cell line HPB-ALL and not with other T cell lines, normal or activated peripheral blood cells, B lymphoblasts (B-LCL), or thymocytes has been developed. This mAb cocaps the T3 antigen on HPB-ALL and anti-T3 mAb cocaps the antigen which reacts with H1-2D4. Purified H1-2D4 precipitates a heterodimer from HPB-ALL cells which has components with molecular weights of 51 000 and 39 000. The properties of the molecule recognized by H1-2D4 suggest that it is the HPB-ALL equivalent of the putative human T cell antigen receptor.