Evaluating backscattering polarized light imaging microstructural mapping capabilities through neural tissue and analogous phantom imaging

Significance

Knowledge of fiber microstructure and orientation in the brain is critical for many applications. Polarized light imaging (PLI) has been shown to have potential for better understanding neural fiber microstructure and directionality due to the anisotropy in myelin sheaths surrounding nerve fibers of the brain. Continuing to advance backscattering based PLI systems could provide a valuable avenue for in vivo neural imaging.

Aim

To assess the potential of backscattering PLI systems, the ability to resolve crossing fibers, and the sensitivity to fiber inclination and curvature are considered across different imaging wavelengths.

Approach

Investigation of these areas of relative uncertainty is undergone through imaging potential phantoms alongside analogous regions of interest in fixed ferret brain samples with a five-wavelength backscattering Mueller matrix polarimeter.

Results

Promising phantoms are discovered for which the retardance, diattenuation and depolarization mappings are derived from the Mueller matrix and studied to assess the sensitivity of this polarimeter configuration to fiber orientations and tissue structures.

Conclusions

Rich avenues for future study include further classifying this polarimeter's sensitivity to fiber inclination and fiber direction to accurately produce microstructural maps of neural tissue.

Risk of thrombosis with thrombocytopenia syndrome after COVID‐19 vaccination prior to the recognition of vaccine‐induced thrombocytopenia and thrombosis: A self‐controlled case series study in England

Background

Objectives

Methods

Results

Conclusions

Diffusion Tensor Orientation as a Microstructural MRI Marker of Mossy Fiber Sprouting After TBI in Rats

Diffusion tensor imaging (DTI) metrics are highly sensitive to microstructural brain alterations and are potentially useful imaging biomarkers for underlying neuropathologic changes after experimental and human traumatic brain injury (TBI). As potential imaging biomarkers require direct correlation with neuropathologic alterations for validation and interpretation, this study systematically examined neuropathologic abnormalities underlying alterations in DTI metrics in the hippocampus and cortex following controlled cortical impact (CCI) in rats. Ex vivo DTI metrics were directly compared with a comprehensive histologic battery for neurodegeneration, microgliosis, astrocytosis, and mossy fiber sprouting by Timm histochemistry at carefully matched locations immediately, 48 hours, and 4 weeks after injury. DTI abnormalities corresponded to spatially overlapping but temporally distinct neuropathologic alterations representing an aggregate measure of dynamic tissue damage and reorganization. Prominent DTI alterations of were observed for both the immediate and acute intervals after injury and associated with neurodegeneration and inflammation. In the chronic period, diffusion tensor orientation in the hilus of the dentate gyrus became prominently abnormal and was identified as a reliable structural biomarker for mossy fiber sprouting after CCI in rats, suggesting potential application as a biomarker to follow secondary progression in experimental and human TBI.

Can machine learning augment clinician adjudication of events in cardiovascular trials? A case study of major adverse cardiovascular events (MACE) across CVRM trials

Background and introduction

Accurate identification of clinical outcome events is critical to obtaining reliable results in cardiovascular outcomes trials (CVOTs). Current processes for event adjudication are expensive and hampered by delays. As part of a larger project to more reliably identify outcomes, we evaluated the use of machine learning to automate event adjudication using data from the SOCRATES trial (NCT01994720), a large randomized trial comparing ticagrelor and aspirin in reducing risk of major cardiovascular events after acute ischemic stroke or transient ischemic attack (TIA).

Purpose

We studied whether machine learning algorithms could replicate the outcome of the expert adjudication process for clinical events of ischemic stroke and TIA. Could classification models be trained on historical CVOT data and demonstrate performance comparable to human adjudicators?

Methods

Using data from the SOCRATES trial, multiple machine learning algorithms were tested using grid search and cross validation. Models tested included Support Vector Machines, Random Forest and XGBoost. Performance was assessed on a validation subset of the adjudication data not used for training or testing in model development. Metrics used to evaluate model performance were Receiver Operating Characteristic (ROC), Matthews Correlation Coefficient, Precision and Recall. The contribution of features, attributes of data used by the algorithm as it is trained to classify an event, that contributed to a classification were examined using both Mutual Information and Recursive Feature Elimination.

Results

Classification models were trained on historical CVOT data using adjudicator consensus decision as the ground truth. Best performance was observed on models trained to classify ischemic stroke (ROC 0.95) and TIA (ROC 0.97). Top ranked features that contributed to classification of Ischemic Stroke or TIA corresponded to site investigator decision or variables used to define the event in the trial charter, such as duration of symptoms. Model performance was comparable across the different machine learning algorithms tested with XGBoost demonstrating the best ROC on the validation set for correctly classifying both stroke and TIA.

Conclusions

Our results indicate that machine learning may augment or even replace clinician adjudication in clinical trials, with potential to gain efficiencies, speed up clinical development, and retain reliability. Our current models demonstrate good performance at binary classification of ischemic stroke and TIA within a single CVOT with high consistency and accuracy between automated and clinician adjudication. Further work will focus on harmonizing features between multiple historical clinical trials and training models to classify several different endpoint events across trials. Our aim is to utilize these clinical trial datasets to optimize the delivery of CVOTs in further cardiovascular drug development.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): AstraZenca Plc

Targeted anti-corruption in LMICs: developmental governance and health systems research

Traditional approaches to anti-corruption have relied upon broad-based legal change and the introduction transparency and accountability measures. The evidence to date shows that these have been unsuccessful in reducing corruption in health and other sectors in low and middle income countries. Traditional approaches often assume that corruption is driven by individual greed, immorality or opportunism caused by a lack of accountability measures and that once corruption is rendered visible that there will be a channel through which it can be acted upon. In many LMICs, however, corruption and rule breaking is widespread and much better understood as a systemic problem. In these settings, health workers often break rules to solve the problems of working in overstretched, underfunded health systems. In these settings, policy often does not match the realities of an underfunded health system, and so sticking to the rules can have harm career progression or the ability to care for ones family. New approaches to anti-corruption based on Mushtaq Khan's idea of developmental governance take these context specific factors into account and look for targeted, feasible and high impact action that can create improvements of rule abiding behaviour that benefit the health system and the delivery of care. This presentation examines how it can be applied to the health system and the adaptations that it makes in the ways that we work on anti-corruption in health. It examines the ways in which policy can be changed so that groups of actors in the system are be incentivised to engage in abiding behaviour as they recognize that it is in their interests to do so.

Advanced Primary Care Orthopedics: Bridging the Gap in Musculoskeletal Education

BACKGROUND AND OBJECTIVES

Musculoskeletal problems are common in primary care, yet many family physicians lack confidence and competence in this area. The Advanced Primary Care Orthopedics (APCO) course utilizes hands-on physical exam instruction, interactive cases, and intentional repetition to teach anatomy, a standardized exam, and important diagnoses. This study assesses the effectiveness of APCO in improving musculoskeletal exam knowledge and confidence.

METHODS

APCO is a 1.5-day course taught annually to family medicine residents. A 1-day course has also been conducted as a preconference workshop targeting faculty physicians. Participants completed pre- and postcourse assessments to evaluate their knowledge and confidence with the musculoskeletal exam. We compared results using mean differences with paired t-test statistics.

RESULTS

In the 2018 and 2019 resident courses, 23 of 30 participants (77%) completed the knowledge assessment and 25 of 30 participants (83%) completed the confidence assessment. Knowledge assessment scores improved by 9.5 points (P<.05) after completion of the course. Confidence in the musculoskeletal exam, as assessed on a 5-point Likert scale (1-not confident at all; 5-very confident), improved from 2.2 to 3.8 after the course (P<.05). In the 2018 preconference workshop, 23 of 36 participants (64%) completed the confidence assessment. Confidence increased from 2.17 to 3.61 (P<.05) after course completion.

CONCLUSIONS

Participation in the APCO course increased short-term musculoskeletal knowledge and confidence. APCO has many potential applications for residency curricula, faculty development, and continuing medical education.

Brain phenotyping in Moebius syndrome and other congenital facial weakness disorders by diffusion MRI morphometry

In this study, we used a novel imaging technique, DTI (diffusion tensor imaging)-driven tensor-based morphometry, to investigate brain anatomy in subjects diagnosed with Moebius syndrome (n = 21), other congenital facial weakness disorders (n = 9) and healthy controls (n = 15). First, we selected a subgroup of subjects who satisfied the minimum diagnostic criteria for Moebius syndrome with only mild additional neurological findings. Compared to controls, in this cohort, we found a small region of highly significant volumetric reduction in the paramedian pontine reticular formation and the medial longitudinal fasciculus, important structures for the initiation and coordination of conjugate horizontal gaze. Subsequently, we tested if volume measurements from this region could help differentiate individual subjects of the different cohorts that were included in our study. We found that this region allowed discriminating Moebius syndrome subjects from congenital facial weakness disorders and healthy controls with high sensitivity (94%) and specificity (89%). Interestingly, this region was normal in congenital facial weakness subjects with oculomotor deficits of myopathic origin, who would have been classified as Moebius on the basis of purely clinical diagnostic criteria, indicating a potential role for diffusion MRI morphometry for differential diagnosis in this condition. When the entire Moebius syndrome cohort was compared to healthy controls, in addition to this 'landmark' region, other areas of significantly reduced volume in the brainstem emerged, including the location of the nuclei and fibres of cranial nerve VI (abducens nerve), and fibres of cranial nerve VII (facial nerve), and a more rostral portion of the medial longitudinal fasciculus. The high sensitivity and specificity of DTI-driven tensor-based morphometry in reliably detecting very small areas of volumetric abnormality found in this study suggest broader applications of this analysis in personalized medicine to detect hypoplasia or atrophy of small pathways and/or brainstem nuclei in other neurological disorders.

What Does a Mutually Beneficial Global Health Partnership in Family Medicine Residency Look Like?

Motivated by interest in enhancing their clinical experience and contributing to communities in need, US medical resident physicians are increasingly keen to train abroad. Guidelines are needed to help ensure that trainee, institutional, and faculty engagement in global health is ethically appropriate and mutually beneficial for all involved. Supported by the nonprofit organization Seed Global Health, the WWAMI-University of Malawi/College of Medicine partnership leverages long-term US faculty to structure rotations for Malawian and American trainees and endorses strong onboarding, monitoring, and evaluation practices and a mutually beneficial bidirectional international partnership and exchange model.

The Global Health Service Partnership: An Academic-Clinical Partnership to Build Nursing and Medical Capacity in Africa

The World Health Organization estimates a global deficit of about 12.9 million skilled health professionals (midwives, nurses, and physicians) by 2035. These shortages limit the ability of countries, particularly resource-constrained countries, to deliver basic health care, to respond to emerging and more complex needs, and to teach, graduate, and retain their future health professionals—a vicious cycle that is perpetuated and has profound implications for health security. The Global Health Service Partnership (GHSP) is a unique collaboration between the Peace Corps, President’s Emergency Plan for AIDS Relief, Seed and host-country institutions, which aims to strengthen the breadth and quality of medical and nursing education and care delivery in places with dire shortages of health professionals. Nurse and physician educators are seconded to host institutions to serve as visiting faculty alongside their local colleagues. They serve for 1 year with many staying longer. Educational and clinical best practices are shared, emphasis is placed on integration of theory and practice across the academic–clinical domains and the teaching and learning environment is expanded to include implementation science and dissemination of locally tailored and sustainable practice innovations. In the first 3 years (2013–2016) GHSP placed 97 nurse and physician educators in three countries (Malawi, Tanzania, and Uganda). These educators have taught 454 courses and workshops to 8,321 trainees, faculty members, and practicing health professionals across the curriculum and in myriad specialties. Mixed-methods evaluation included key stakeholder interviews with host institution faculty and students who indicate that the addition of GHSP enhanced clinical teaching (quality and breadth) resulting in improved clinical skills, confidence, and ability to connect theory to practice and critical thinking. The outputs and outcomes from four exemplars which focus on the translation of evidence to practice through implementation science are included. Findings from the first 3 years of GHSP suggest that an innovative, locally tailored and culturally appropriate multi-country academic–clinical partnership program that addresses national health priorities is feasible and generated new knowledge and best practices relevant to capacity building for nursing and medical education. This in turn has implications for improving the health of populations who suffer a disproportionate burden of global disease.

Efficient experimental designs for isotropic generalized diffusion tensor MRI (IGDTI)

PURPOSE

We propose a new generalized diffusion tensor imaging (GDTI) experimental design and analysis framework for efficiently measuring orientationally averaged diffusion-weighted images (DWIs), which remove bulk signal modulations attributed to diffusion anisotropy and quantify isotropic higher-order diffusion tensors (HOT). We illustrate how this framework accelerates the clinical measurement of rotation-invariant tissue microstructural parameters derived from HOT, such as the HOT-Trace and the mean t-kurtosis.

THEORY AND METHODS

For a large range of b-values, we compare orientationally averaged DWIs measured with high angular resolution diffusion imaging to those obtained with the proposed isotropic GDTI (IGDTI) experimental design. We compare rotation-invariant microstructural parameters measured with IGDTI to those derived from HOTs measured explicitly with GDTI.

RESULTS

In both fixed-brain microimaging and in vivo clinical experiments, IGDTI accurately quantifies mean apparent diffusion coefficient (mADC)-weighted DWIs over a wide range of b-values and allows efficient computation of HOT-derived scalar tissue parameters from a small number of DWIs.

CONCLUSIONS

IGDTI provides direct and accurate estimates of orientationally averaged tissue water mobilities over a wide range of b-values. This efficient method may enable new, sensitive, and quantitative assessments for clinical applications in which changes in mADC can be observe,d such as detecting and characterizing stroke, cancers, and neurodegenerative diseases. Magn Reson Med 79:180-194, 2018. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

A phenomenological exploration of the patient learning J experiences of 16—19 year-old women accessing a young people's rheumatology service in the UK

Sustaining the needs of people with chronic illness is a challenge facing health and social care services. Patients' knowledge about their disease can impact on improving the management of their care and may offer opportunity for increasing support (Department of Health, 2000, 2001, 2003, 2005). This small phenomenological enquiry sought to understand how six young women aged between 16 and 19 years experienced learning about their rheumatological illness, and their preferred learning options relating to treatment and management. Data was collected through the use of semi-structured interviews. Interviews were analysed using a modified version of Colaizzi's seven stage process (Hantikainen and Kappeli, 2000). Findings offer insight into perceived health knowledge needs of young women with rheumatological illness in the UK. Data gathered indicated that communication was of concern for the sample, particularly within lay environments such as schools, work and home. Opportunities for service improvement are discussed within the context of existing evidence, including tailoring of materials for young people, and development of services that facilitate effective communication. The involvement of `experienced patients' may be beneficial in facilitating self-care management of young women with rheumatological disease.

Cancer Therapeutic Resistance: Progress and Perspectives (April 7-8, 2016 - Barcelona, Spain)

At the Cancer Therapeutic Resistance: Progress and Perspectives conference, in Barcelona, Spain, April 7-8, 2016, researchers, clinicians and students gathered to discuss our current understanding of intrinsic and acquired resistance of tumors to cancer therapies and to explore how to translate strategies to predict risk or overcome resistance to the clinic. The sessions covered a wide range of topics, including cancer omics, molecular classification, clinically relevant tumor models, biomarkers and novel therapeutic targets, and personalized medicine, with talks from many international experts in the field. This report highlights the main presentations that demonstrate the progress being made in predicting and identifying drug resistance in patients with cancer, personalized approaches to direct treatment and understanding the mechanisms involved. With better models of human cancer and powerful high-throughput screening techniques, translation to the clinic leading to tangible benefits for patients is attainable.

Age-dependent long-term structural and functional effects of early-life seizures: evidence for a hippocampal critical period influencing plasticity in adulthood

Neural activity promotes circuit formation in developing systems and during critical periods permanently modifies circuit organization and functional properties. These observations suggest that excessive neural activity, as occurs during seizures, might influence developing neural circuitry with long-term outcomes that depend on age at the time of seizures. We systematically examined long-term structural and functional consequences of seizures induced in rats by kainic acid, pentylenetetrazol, and hyperthermia across postnatal ages from birth through postnatal day 90 in adulthood (P90). Magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and electrophysiological methods at ⩾P95 following seizures induced from P1 to P90 demonstrated consistent patterns of gross atrophy, microstructural abnormalities in the corpus callosum (CC) and hippocampus, and functional alterations in hippocampal circuitry at ⩾P95 that were independent of the method of seizure induction and varied systematically as a function of age at the time of seizures. Three distinct epochs were observed in which seizures resulted in distinct long-term structural and functional outcomes at ⩾P95. Seizures prior to P20 resulted in DTI abnormalities in CC and hippocampus in the absence of gross cerebral atrophy, and increased paired-pulse inhibition (PPI) in the dentate gyrus (DG) at ⩾P95. Seizures after P30 induced a different pattern of DTI abnormalities in the fimbria and hippocampus accompanied by gross cerebral atrophy with increases in lateral ventricular volume, as well as increased PPI in the DG at ⩾P95. In contrast, seizures between P20 and P30 did not result in cerebral atrophy or significant imaging abnormalities in the hippocampus or white matter, but irreversibly decreased PPI in the DG compared to normal adult controls. These age-specific long-term structural and functional outcomes identify P20-30 as a potential critical period in hippocampal development defined by distinctive long-term structural and functional properties in adult hippocampal circuitry, including loss of capacity for seizure-induced plasticity in adulthood that could influence epileptogenesis and other hippocampal-dependent behaviors and functional properties.

A framework for accurate determination of the T₂ distribution from multiple echo magnitude MRI images

Measurement of the T2 distribution in tissues provides biologically relevant information about normal and abnormal microstructure and organization. Typically, the T2 distribution is obtained by fitting the magnitude MR images acquired by a multi-echo MRI pulse sequence using an inverse Laplace transform (ILT) algorithm. It is well known that the ideal magnitude MR signal follows a Rician distribution. Unfortunately, studies attempting to establish the validity and efficacy of the ILT algorithm assume that these input signals are Gaussian distributed. Violation of the normality (or Gaussian) assumption introduces unexpected artifacts, including spurious cerebrospinal fluid (CSF)-like long T2 components; bias of the true geometric mean T2 values and in the relative fractions of various components; and blurring of nearby T2 peaks in the T2 distribution. Here we apply and extend our previously proposed magnitude signal transformation framework to map noisy Rician-distributed magnitude multi-echo MRI signals into Gaussian-distributed signals with high accuracy and precision. We then perform an ILT on the transformed data to obtain an accurate T2 distribution. Additionally, we demonstrate, by simulations and experiments, that this approach corrects the aforementioned artifacts in magnitude multi-echo MR images over a large range of signal-to-noise ratios.

Chronic neurological deficits in mice after perinatal hypoxia and ischemia correlate with hemispheric tissue loss and white matter injury detected by MRI

We investigated the effects of perinatal hypoxia-ischemia (HI) on brain injury and neurological functional outcome at postnatal day (P)30 through P90. HI was induced by exposing P9 mice to 8% O(2) for 55 min using the Vannucci HI model. Following HI, mice were treated with either vehicle control or Na(+)/H(+) exchanger isoform 1 (NHE1) inhibitor HOE 642. The animals were examined by the accelerating rotarod test at P30 and the Morris water maze (MWM) test at P60. T(2)-weighted MRI was conducted at P90. Diffusion tensor imaging (DTI) was subsequently performed in ex vivo brains, followed by immunohistochemical staining for changes in myelin basic protein (MBP) and neurofilament protein expression in the corpus callosum (CC). Animals at P30 after HI showed deficits in motor and spatial learning. T(2) MRI detected a wide spectrum of brain injury in these animals. A positive linear correlation was observed between learning deficits and the degree of tissue loss in the ipsilateral hemisphere and hippocampus. Additionally, CC DTI fractional anisotropy (FA) values correlated with MBP expression. Both FA and MBP values correlated with performance on the MWM test. HOE 642-treated mice exhibited improved spatial learning and memory, and less white matter injury in the CC. These findings suggest that HI-induced cerebral atrophy and CC injury contribute to the development of deficits in learning and memory, and that inhibition of NHE1 is neuroprotective in part by reducing white matter injury. T(2)-weighted MRI and DTI are useful indicators of functional outcome after perinatal HI.

Children with new-onset epilepsy exhibit diffusion abnormalities in cerebral white matter in the absence of volumetric differences

The purpose of this investigation was to examine the diffusion properties of cerebral white matter in children with recent onset epilepsy (n=19) compared to healthy controls (n=11). Subjects underwent DTI with quantification of mean diffusion (MD), fractional anisotropy (FA), axial diffusivity (D(ax)) and radial diffusivity (D(rad)) for regions of interest including anterior and posterior corpus callosum, fornix, cingulum, and internal and external capsules. Quantitative volumetrics were also performed for the corpus callosum and its subregions (anterior, midbody and posterior) and total lobar white and gray matter for the frontal, parietal, temporal and occipital lobes. The results demonstrated no group differences in total lobar gray or white matter volumes or volume of the corpus callosum and its subregions, but did show reduced FA and increased D(rad) in the posterior corpus callosum and cingulum. These results provide the earliest indication of microstructural abnormality in cerebral white matter among children with idiopathic epilepsies. This abnormality occurs in the context of normal volumetrics and suggests disruption in myelination processes.

Sport-related differences in biomarkers of bone resorption and cartilage degradation in endurance athletes

OBJECTIVE

By measuring urinary cross-linked N-telopeptide (NTx) as a bone resorption marker and urinary C-telopeptide of type II collagen (CTx-II) as a cartilage degradation marker, we asked whether differences in skeletal stresses in college athletes undergoing high-intensity training for diverse types of aerobic sports affect their skeletal metabolism and, if so, differentially or in unison.

METHODS

The study was cross-sectional at a Division 1 college campus with 60 student athletes representing crew, cross-country running and swimming. Controls were 16 non-athlete undergraduates. Urine samples were collected for NTx and CTx-II analysis by enzyme-linked immunosorbent assay, normalizing results to creatinine. Two-way analysis of variance models and pair-wise comparisons were used to test whether biomarker levels differed by sport and the significance when adjusted for body mass index (BMI).

RESULTS

NTx and CTx-II showed significant differences between groups before and after adjusting for BMI. NTx was highest in the rowers, and higher in rowers and runners than in swimmers or controls. CTx-II was significantly higher in runners than in crew, swimmers or controls, when unadjusted for BMI. After adjusting for BMI, these group differences remained significant except for runners over crew.

CONCLUSION

Athletes in-training in the three sports show significant differences in these markers of bone resorption and cartilage collagen degradation. The results suggest that crew undergo the highest bone remodeling and runners the highest cartilage degradation. The results also show how these markers can vary physiologically between individuals, at extremes of skeletal exercise.

The effects of a double blind, placebo controlled, artificial food colourings and benzoate preservative challenge on hyperactivity in a general population sample of preschool children

AIMS

To determine whether artificial food colourings and a preservative in the diet of 3 year old children in the general population influence hyperactive behaviour.

METHODS

A sample of 1873 children were screened in their fourth year for the presence of hyperactivity at baseline (HA), of whom 1246 had skin prick tests to identify atopy (AT). Children were selected to form the following groups: HA/AT, not-HA/AT, HA/not-AT, and not-HA/not-AT (n = 277). After baseline assessment, children were subjected to a diet eliminating artificial colourings and benzoate preservatives for one week; in the subsequent three week within subject double blind crossover study they received, in random order, periods of dietary challenge with a drink containing artificial colourings (20 mg daily) and sodium benzoate (45 mg daily) (active period), or a placebo mixture, supplementary to their diet. Behaviour was assessed by a tester blind to dietary status and by parents' ratings.

RESULTS

There were significant reductions in hyperactive behaviour during the withdrawal phase. Furthermore, there were significantly greater increases in hyperactive behaviour during the active than the placebo period based on parental reports. These effects were not influenced by the presence or absence of hyperactivity, nor by the presence or absence of atopy. There were no significant differences detected based on objective testing in the clinic.

CONCLUSIONS

There is a general adverse effect of artificial food colouring and benzoate preservatives on the behaviour of 3 year old children which is detectable by parents but not by a simple clinic assessment. Subgroups are not made more vulnerable to this effect by their prior levels of hyperactivity or by atopy.

Oxygen in nitrogen versus nitrous oxide during pediatric general anesthesia

BACKGROUND

Induction of anesthesia decreases lung volumes, giving areas of non-ventilated lung. Nitrogen is a slowly-absorbed gas that could prevent resorption of gases from these closed spaces, preventing atelectasis and improving oxygen saturations during recovery.

METHODS

We evaluated oxygen saturations during emergence after intra-operative administration of 33% oxygen in nitrogen versus 33% oxygen in nitrous oxide in 62 children having elective urologic surgery. Patients were randomly assigned to either group A (2.5 L/min air with 0.5 L/min oxygen) or group N (2 L/min nitrous oxide and 1 L/min oxygen). Flowmeters were covered to maintain blinding. Anesthetic technique was standardized (laryngeal mask airway, caudal, halothane, and deep extubation). Patients breathed room air during emergence, while a blinded observer recorded duration of desaturations by stopwatch for 15 min.

RESULTS

We found similar desaturations in both groups. The difference in desaturations < 94% at an interim 2-min total probably reflects diffusion hypoxia and was not significant at 15 min. The frequency of desaturations < 87% during emergence was significantly greater in children who were crying during induction.

CONCLUSIONS

The intra-operative use of air versus nitrous oxide has no substantial effect on oxygen saturations during emergence from anesthesia in children. These results are consistent with a recently published mathematical model.

Can parents accurately perceive hyperactivity in their child?

In all, 1872 children were recruited as part of a larger study concerning food additives and behaviours in preschool children. This figure represented 70% of the whole population of 3 1/4 -year-old children resident on the Isle of Wight, UK. Parents completed an assessment concerning their perceptions of their child's behaviour. The results of this assessment were compared with scores on two validated parental questionnaires, the Weiss Werry Peters (WWP) hyperactivity scale and the Emotionality, Activity and Sociability Temperament Questionnaire (EAS), which were used to assess hyperactivity. The accuracy of parents in perceiving hyperactivity in their children was found to be around 50% if the child was hyperactive, and 89% if the child was not hyperactive. The implications of these findings for services are discussed. Frequencies of potential risk groups for future Attention Deficit Hyperactivity Disorder (ADHD) and Conduct Disorder were also suggested.

Assessing outcome in lumbar disc surgery using patient completed measures

Measuring outcome after spinal surgery is difficult. The objective of this study was to assess the use of four measures in establishing outcome in patients undergoing lumbar discectomy. Forty-six consecutive patients who had undergone two operations for lumbar disc prolapse and 54 patients who had undergone one operation for the same condition over the same period were identified. The SF-36 questionnaire was used to assess general health. The Roland-Morris questionnaire and a simple modification of the Roland-Morris questionnaire were used to assess back and leg related disability, respectively. Analogue pain scales were used to measure back pain and sciatica. The SF-36 scores revealed significantly worse health status in the two operation compared with the one operation patients and in all patients compared with the normal population. Using the Roland-Morris and the leg disability questionnaires, patients who had undergone two operations reported significantly worse disability (Roland-Morris, 53%, poor outcome) than those who had undergone one operation (Roland-Morris, 19%, poor outcome). There was significantly greater back disability than leg disability in both groups of patients and this was confirmed by the analogue pain scales. In patients who had undergone two operations, 25% classified their back pain as very bad or unbearable, and 22.5% described very bad or unbearable leg pain. For the one operation patients these figures were 9.5 and 2.4%, respectively. The results demonstrate that both generic and condition specific patient completed measures have the potential to detect differences in outcome between patients who have undergone either one or two lumbar disc operations. The study provides support for the use of these patient completed measures in assessing outcome in lumbar disc surgery.

A novel human GnRH receptor homolog gene: abundant and wide tissue distribution of the antisense transcript

Gonadotropin releasing hormone (GnRH) regulates the reproductive system through a specific G-protein-coupled receptor (GPCR) in pituitary gonadotropes. The existence of two (or more) forms of GnRH in most vertebrates suggested the existence of GnRH receptor subtypes (I and II). Using sequence information for extracellular loop 3 of a putative Type II GnRH receptor from a reptile species, we have looked for a Type II GnRH receptor gene in the human genome EST (expressed sequence tag) database. A homolog was identified which has 45% and 41% amino acid identity with exons 2 and 3 of the known human GnRH pituitary receptor (designated Type I) and much lower homology with all other GPCRs. A total of 27 contiguous ESTs was found and comprised a continuous sequence of 1642 nucleotides. The EST sequences were confirmed in the cloned human gene and in PCR products of cDNA from several tissues. All EST transcripts detected were in the antisense orientation with respect to the novel GnRH receptor sequence and were highly expressed in a wide range of human brain and peripheral tissues. PCR of cDNA from a wide range of tissues revealed that intronic sequence equivalent to intron 2 of the Type I GnRH receptor was retained. The failure to splice out putative intron sequences in transcripts which spanned exon-intron boundaries is expected in antisense transcripts, as candidate donor and acceptor sites were only present in the gene when transcribed in the orientation encoding the GnRH receptor homolog. No transcripts extended 5' to the sequence corresponding to intron 2 of the Type I GnRH as the antisense transcripts terminated in poly A due to the presence of a polyadenylation signal sequence in the putative intron 2 when transcribed in the antisense orientation. These findings suggest that a Type II GnRH receptor gene has arisen during vertebrate evolution and is also present in the human. However, the receptor may have become vestigial in the human, possibly due to the abundant and universal tissue transcription of the opposite DNA strand to produce antisense RNA.

American Society of Gene Therapy--First Annual Meeting. Education session: the ABCs of non-viral vectors for gene therapy. 28-31 May 1998, Seattle, Washington, USA

In July 1996, the American Society of Gene Therapy (ASGT) was established in San Francisco by George Stamatoyannopoulos (President of ASGT, Professor of Genetics and Medical Genetics at the University of Washington, USA), James M Wilson (President Elect of ASGT, Director of the Institute for Human Gene Therapy, University of Pennsylvania, USA) and other gene therapy experts. In May 1998, this society held its first annual meeting, in Seattle, WA. The aim of the annual meeting is to provide a forum for all investigators, including students, young scientists, academic researchers and those working in industry. To avoid the risk of bias through election of one program committee, symposia, workshops and poster sessions are organized by different committees. There are nine committees in total, so each discipline within the diverse field of gene therapy is properly represented. An education program was organized by Savio LC Woo (Mount Sinai of Medicine, New York, USA) and there was a high school student symposium to encourage interest from the younger generation. Professor Stamatoyannopoulos said that he would like to see the NIH establishing centers of excellence of gene therapy, as they did for cancer 25 years ago. James Wilson then thanked George for all his work founding the society, as he took over as president. There are already 14,000 members of the ASGT and more than 1500 scientists attended this conference. There were 18 sessions of oral presentations and 750 abstracts.

The feasibility of MRI feedback control for intracavitary phased array hyperthermia treatments

Temperature feedback control has the potential to enhance hyperthermia treatments by providing more uniform heating of the target volume and improving the transient temperature response. A multivariable least squares batch algorithm was used to estimate system parameters for simulated prostate hyperthermia treatments. A multi-input, multi-output (MIMO) linear quadratic regulator (LQR) controller was designed for prostate hyperthermia treatments with an intracavitary phased array. A parametric study was performed for the one-dimensional control case, investigating factors relevant to magnetic resonance imaging (MRI) feedback control such as spatial resolution of temperature measurements (size of the averaging volume), sampling rate (image acquisition time), thermometry noise, control width, control depth, physiological parameter changes and reference input structure. Simulations utilizing the two dimensional (2-D) thermometry of MRI and the 2-D focusing capabilities of phased arrays demonstrated that near field heating can be controlled such that the size and shape of the heated volume can be tailored in 2-D. The control algorithms developed in this study show promising potential for incorporation into a non-invasive prostate hyperthermia system utilizing MRI feedback.

Survey of human immunodeficiency virus infection among pregnant women in England and Wales: 1990-93

We report on the first four years (1990-93) of a survey within the national HIV prevalence monitoring programme. The survey's objective is to monitor the prevalence of infection with the human immunodeficiency virus (HIV) in pregnant women in London and elsewhere in England. The survey--based in forty centres that offer antenatal care in London, Greater Manchester, West Yorkshire, and adjacent non-metropolitan areas--uses repeated cross sectional serosurveillance for anti-HIV-1 and 2 and the unlinked anonymous test method on blood left over from specimens collected for antenatal screening for immunity to rubella. The seroprevalence of HIV-1 ranged from 0.007% (1 in 14,530) in non-metropolitan areas, to 0.011% (1 in 8790) in metropolitan areas outside London, and 0.23% (1 in 440) in London. Evidence of HIV-2 infection was found in only four specimens, in London (1 in 50,300). The seroprevalence of HIV-1 in London varied more than tenfold between centres, from 0.03% (1 in 3190) to 0.51% (1 in 200). The highest prevalence of infection was in London in women aged between 20 and 30 (0.30%; 1 in 335). The seroprevalence in London centres rose from 0.18% in 1990 (1 in 560) to 0.26% in 1993 (1 in 390) and the rise was significant in all age groups. If voluntary confidential HIV testing (with counselling) among pregnant women in England were to be promoted, its cost effectiveness would be greater if focused on particular centres that provide antenatal care in London.

Lamellar ichthyosis with episodic psoriasiform reaction pattern

The skin of a girl born with the typical appearance of "collodion baby," evolved into an exfoliative erythroderma that clinically was lamellar ichthyosis. However, biopsy specimens done in early infancy showed psoriasis. Over the ensuing sixteen years she has continued to have clinical lamellar ichthyosis with rare occasions of febrile episodes and superficial pustules. Some biopsy specimens have been diagnosed as showing lamellar ichthyosis, while others have again shown psoriasis.

Methicillin-resistant Staphylococcus aureus (MRSA): risk and outcome of colonized vs. infected patients

A retrospective study of 204 patients culture positive for methicillin-resistant Staphylococcus aureus compared infected and colonized patients. Seventy-eight patients were colonized and never developed infection (C), 24 were colonized and subsequently infected (C----I), and 102 patients had 1 or more nosocomial infections with MRSA at time of first culture (I). The most prevalent sites of infection were wound (26.5%) and blood-stream (20.7%), whereas the respiratory tract and surgical wounds were both frequent sites of colonization. Stepwise discriminant analysis found the most important factors in differentiating likelihood of colonization vs. infection were recent prior hospitalization, history of wound debridement, and number of invasive procedures. Ten percent of (C) died and 25.5% of (I) died. MRSA contributed to death in 57.6% of the (I) deaths (p less than .05). These results underscore the importance of differentiating (C) vs. (I) in hospitals where MRSA is endemic so that early specific treatment may be initiated. Risk factors for infection should be discriminated from those for acquisition of the organism.