Two-point Dixon and six-point Dixon magnetic resonance techniques in the detection, quantification and grading of hepatic steatosis

BACKGROUND

Hepatic steatosis is a very common problem worldwide.

AIM

To assess the performance of two- and six-point Dixon magnetic resonance (MR) techniques in the detection, quantification and grading of hepatic steatosis.

METHODS

A single-center retrospective study was performed in 62 patients with suspected parenchymal liver disease. MR sequences included two-point Dixon, six-point Dixon, MR spectroscopy (MRS) and MR elastography. Fat fraction (FF) estimates on the Dixon techniques were compared to the MRS-proton density FF (PDFF). Statistical tests used included Pearson's correlation and receiver operating characteristic.

RESULTS

FF estimates on the Dixon techniques showed excellent correlation (≥ 0.95) with MRS-PDFF, and excellent accuracy [area under the receiver operating characteristic (AUROC) ≥ 0.95] in: (1) Detecting steatosis; and (2) Grading severe steatosis, (P < 0.001). In iron overload, two-point Dixon was not evaluable due to confounding T2* effects. FF estimates on six-point Dixon vs MRS-PDFF showed a moderate correlation (0.82) in iron overload vs an excellent correlation (0.97) without iron overload, (P < 0.03). The accuracy of six-point Dixon in grading mild steatosis improved (AUROC: 0.59 to 0.99) when iron overload cases were excluded. The excellent correlation (> 0.9) between the Dixon techniques vs MRS-PDFF did not change in the presence of liver fibrosis (P < 0.01).

CONCLUSION

Dixon techniques performed satisfactorily for the evaluation of hepatic steatosis but with exceptions.

Multiparametric MR assessment of liver fat, iron, and fibrosis: a concise overview of the liver "Triple Screen"

Chronic liver disease (CLD) is a common source of morbidity and mortality worldwide. Non-alcoholic fatty liver disease (NAFLD) serves as a major cause of CLD with a rising annual prevalence. Additionally, iron overload can be both a cause and effect of CLD with a negative synergistic effect when combined with NAFLD. The development of state-of-the-art multiparametric MR solutions has led to a change in the diagnostic paradigm in CLD, shifting from traditional liver biopsy to innovative non-invasive methods for providing accurate and reliable detection and quantification of the disease burden. Novel imaging biomarkers such as MRI-PDFF for fat, R2 and R2* for iron, and liver stiffness for fibrosis provide important information for diagnosis, surveillance, risk stratification, and treatment. In this article, we provide a concise overview of the MR concepts and techniques involved in the detection and quantification of liver fat, iron, and fibrosis including their relative strengths and limitations and discuss a practical abbreviated MR protocol for clinical use that integrates these three MR biomarkers into a single simplified MR assessment. Multiparametric MR techniques provide accurate and reliable non-invasive detection and quantification of liver fat, iron, and fibrosis. These techniques can be combined in a single abbreviated MR "Triple Screen" assessment to offer a more complete metabolic imaging profile of CLD.

Tips for improving consistency of thyroid nodule interpretation with ACR TI-RADS

Thyroid nodules are very common in the general population. Most are benign and even those that are malignant are typically slow-growing and do not require treatment. Overdiagnosis and overtreatment of thyroid nodules has resulted in significant healthcare costs. ACR TI-RADS was developed to address these concerns, and reduce the number of unnecessary biopsies and follow-up intervals. ACR TI-RADS offers a point-based risk stratification system centered on five sonographic features: consistency, echogenicity, shape, margins and echogenic foci. While the system has noticeable benefits and comparable accuracy with other available risk stratification systems (ATA, EU-TIRADS and K-TIRADS), there are inherent challenges relating to suboptimal inter-reader agreement. In this article, we include 10 educational tips that may be helpful to the ultrasound practitioner for improving the consistency of nodule interpretation with ACR TI-RADS.

Effect of training on resident inter-reader agreement with American College of Radiology Thyroid Imaging Reporting and Data System

BACKGROUND

The American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS) was introduced to standardize the ultrasound characterization of thyroid nodules. Studies have shown that ACR-TIRADS reduces unnecessary biopsies and improves consistency of imaging recommendations. Despite its widespread adoption, there are few studies to date assessing the inter-reader agreement amongst radiology trainees with limited ultrasound experience. We hypothesize that in PGY-4 radiology residents with no prior exposure to ACR TI-RADS, a statistically significant improvement in inter-reader reliability can be achieved with a one hour training session.

AIM

To evaluate the inter-reader agreement of radiology residents in using ACR TI-RADS before and after training.

METHODS

A single center retrospective cohort study evaluating 50 thyroid nodules in 40 patients of varying TI-RADS levels was performed. Reference standard TI-RADS scores were established through a consensus panel of three fellowship-trained staff radiologists with between 1 and 14 years of clinical experience each. Three PGY-4 radiology residents (trainees) were selected as blinded readers for this study. Each trainee had between 4 to 5 mo of designated ultrasound training. No trainee had received specialized TI-RADS training prior to this study. Each of the readers independently reviewed the 50 testing cases and assigned a TI-RADS score to each case before and after TI-RADS training performed 6 wk apart. Fleiss kappa was used to measure the pooled inter-reader agreement. The relative diagnostic performance of readers, pre- and post-training, when compared against the reference standard.

RESULTS

There were 33 females and 7 males with a mean age of 56.6 ± 13.6 years. The mean nodule size was 19 ± 14 mm (range from 5 to 63 mm). A statistically significant superior inter-reader agreement was found on the post-training assessment compared to the pre-training assessment for the following variables: 1. “Shape” (k of 0.09 [slight] pre-training vs 0.67 [substantial] post-training, P < 0.001), 2. “Echogenic foci” (k of 0.28 [fair] pre-training vs 0.45 [moderate] post-training, P = 0.004), 3. ‘TI-RADS level’ (k of 0.14 [slight] pre-training vs 0.36 [fair] post-training, P < 0.001) and 4. ‘Recommendations’ (k of 0.36 [fair] pre-training vs 0.50 [moderate] post-training, P = 0.02). No significant differences between the pre- and post-training assessments were found for the variables 'composition', 'echogenicity' and 'margins'. There was a general trend towards improved pooled sensitivity with TI-RADS levels 1 to 4 for the post-training assessment while the pooled specificity was relatively high (76.6%-96.8%) for all TI-RADS level.

CONCLUSION

Statistically significant improvement in inter-reader agreement in the assigning TI-RADS level and recommendations after training is observed. Our study supports the use of dedicated ACR TI-RADS training in radiology residents.

235 An Audit of The Post-Op Day One (Pod1) Discharge After Bariatric Surgery – The Effect on Length of Hospital Stay And 30-Day Re-Admission Rate

Introduction

Discharge protocols after bariatric surgery are multi modal. At the Sunderland Royal Hospital, the standard protocol is POD 2 as long as patient satisfies the entire requirements. With the recent drive towards enhanced recovery after surgery, some consultants introduced the POD 1 discharge protocol.

Method

Using our prospectively maintained bariatric data set POD 1 and POD 2 groups were identified. The length of stay (LOS) and 30-day re- admission was analyzed.

Results

The average LOS was 2 days for POD 2 group. 19 % of patients were discharged on POD 1, 69% on POD 2 and 6% on POD 3 and 4 each. There were no 30-day re- admissions. In the POD 1 group, the average LOS was 1.4 days. 69% were discharged on POD 1, 25% on POD 2 and 6% on POD 4 with no 30-day re-admission.

Conclusions

There was significant decrease in LOS with POD 1 discharge with no difference in 30-day re- admission. Therefore, patients could be potentially discharged safely on POD 1 after bariatric surgery.

Abdominal and pelvic radiographs of medical devices and materials- part 2: neurologic and genitourinary devices and materials

Radiographs of the abdomen and pelvis are routinely obtained as a standard part of clinical care for the abdomen and pelvis. Brisk advances in technology over the last few decades have resulted in a multitude of medical devices and materials. Recognizing and evaluating these devices on abdominal and pelvic radiographs are critical, yet increasingly a difficult endeavor. In addition, multiple devices serving different purposes may have a similar radiographic appearance and position causing confusion for the interpreting radiologist. The role of the radiologist is to not only identify accurately these medical objects, but also to confirm for their accurate placement and to recognize any complications that could affect patient care, management or even be potentially life threatening. An extensive online search of literature showed our review article to be the most comprehensive work on medical devices and materials of the abdomen and pelvis, and in this second part of our two-part series, we discuss in depth about the neurologic and genitourinary devices seen on abdominal and pelvic radiographs.

Abdominal and pelvic radiographs of medical devices and materials-Part 1: gastrointestinal and vascular devices and materials

When compared with chest radiographs, medical devices of the abdomen and pelvis are less frequently seen. However, with recent advances in technology the interpreting radiologists are seeing more medical objects on these radiographs. The identification of these devices and materials are crucial for not only enabling the radiologist to understand the underlying background pathology but also for evaluating any related complications. An online survey of literature showed our review article to be the most detailed. In this first part of our two-part series, we discuss about the various gastrointestinal and vascular devices and materials seen on abdominal and pelvic radiographs.

Accuracy of findings in the diagnosis of uterine adenomyosis on ultrasound

PURPOSE

MRI is the current imaging gold standard to diagnose adenomyosis, but access is often limited by high costs and availability. Transvaginal ultrasound provides a cost-effective, accurate and readily available alternative. The objective of our study was to determine the diagnostic accuracy of commonly described sonographic findings in predicting uterine adenomyosis.

METHODS

This retrospective study evaluated 649 MRI studies performed to investigate adenomyosis with a preceding transvaginal ultrasound within 12 months between 2013 and 2018. Two blinded reviewers assessed the presence or absence of six sonographic features: bulky uterus, heterogeneous myometrium, streaky myometrium, myometrial cysts, endometrial-myometrial interface ill-definition, and echogenic linear striations. The sensitivity, specificity, positive and negative predictive values of these features were calculated individually and in combination when compared to MRI as the standard of reference.

RESULTS

Adenomyosis was found in 315 (48.5%) cases on MRI. Ultrasound had a high specificity of 91.8% (95% CI 88.4 to 94.6%) but was less sensitive (36.8% (95% CI 31.5 to 42.4%)) for detecting adenomyosis. Comorbid fibroids or focal adenomyosis did not affect diagnostic accuracy. All six variables were significantly more common in patients with adenomyosis compared to those without. Individually, 'bulky uterus' and 'heterogenous myometrium' each demonstrated a mean sensitivity and specificity > 50%. The best dual combined variables were 'bulky uterus' + 'ill definition of the endometrial-myometrial interface' (sensitivity 39%, specificity 91%). The best triple combined variables were 'bulky uterus', 'heterogeneous myometrium' + 'ill definition of the endometrial-myometrial interface' (sensitivity 38%, specificity 93%).

CONCLUSION

Transvaginal ultrasound is highly specific for diagnosing uterine adenomyosis, providing a cost-effective and readily available alternative to MRI.

C-51 Long Term Neuropsychological Follow-Up of Radiation Induced Cognitive Decline (RICD) in Cerebellar Medulloblastoma

Objective

We expanded upon an early case study suggesting long-term, sequential neurocognitive evaluation and academic interventions following pediatric cerebellar medulloblastoma. This five-year-old patient (now forty) has indeed undergone lifespan assessment and clearly benefitted from appropriate interventions to date.

Method

This left-handed, white, male is status post (s/p) gross total resection and whole brain radiation. In adulthood, he developed radiation necrosis with hemorrhage and refractory seizures (s/p right temporal lobectomy). More recently, radiation induced bilateral parietal meningiomas were identified (s/p gamma knife).

Results

We analyzed cognitive, medical/oncological, imaging and interventional data at developmentally meaningful time points and found consistent declines in intellectual skills and cognitive function spanning attention/concentration, processing speed, visual perceptual/organization and visually based learning/memory; however, we noted stabilization and even improvement in important areas. Areas of age-appropriate functioning were noted in expressive vocabulary, verbal abstract reasoning, delayed verbal memory, and problem-solving, among others.

Conclusions

Although some studies have addressed long-term outcomes in pediatric medulloblastoma, we provide a unique perspective to the literature by documenting serial neurocognitive findings in addition to interventions across the lifespan. Our findings suggest that appropriate academic interventions/neurocognitive rehabilitation strategies are in fact meaningful at the individual level and propose that a focus on strengths can improve outcomes. We propose that this previously recommended model of assessment/intervention truly become the available standard of care in all pediatric oncologic populations.

A practical imaging classification for the non-invasive differentiation of renal cell carcinoma into its main subtypes

AIM

Renal cell carcinoma (RCC) is a heterogeneous disease which encompasses various subtypes that exhibit differing biologic behavior and imaging findings. Non-invasive subtype differentiation by imaging facilitates prognostication and treatment selection. The aim of the study was to evaluate the performance of a diagnostic imaging key based on tumor morphology, T2 signal intensity on MRI, and tumor vascularity for differentiating RCC into its subtypes.

MATERIALS AND METHODS

Using a custom-designed diagnostic imaging key, three blinded fellowship-trained abdominal radiologists independently evaluated the cross-sectional imaging of 50 histologically proven RCCs and categorized these into subtypes in two sessions. The diagnostic performance of the imaging key was evaluated and compared to the baseline performance without the key.

RESULTS

The 50 RCCs comprised 20 (40%) clear cell, 17 (34%) papillary, and 13 (26%) chromophobe tumors. All expert readers demonstrated an improvement in diagnostic accuracy by an average of 5.3% with the use of the key. The readers showed good to excellent diagnostic performance for clear cell RCC (area under the receiver operating curve, AUROC of 0.86-0.91) and papillary RCC (AUROC of 0.82-0.87), and fair performance with chromophobe RCC (AUROC of 0.67-0.77). The Reader-to-SOR (standard of reference) agreement increased from 0.53 (moderate) to 0.67 (good) with the use of the key.

CONCLUSION

The diagnostic imaging key facilitates RCC subtype characterization and can be used as a decision support tool.

Glutathione transferase P1 interacts strongly with the inner leaflet of the plasma membrane

GSH transferases (GSTs) are a superfamily of proteins best known for detoxifying harmful electrophilic compounds by catalyzing their conjugation with GSH. GSTP1 is the most prevalent and widely distributed GST in human tissues, helping to detoxify a diverse array of carcinogens and drugs. In contrast with its protective role, overexpression of GSTP1 in a variety of malignancies is associated with a poor prognosis due to failure of chemotherapy. Although GSTP1 is classified as a cytosolic GST, we discovered previously that it is associated with the plasma membrane of the small cell lung cancer cell lines, H69 and H69AR. In the current study, endogenous and overexpressed GSTP1 in human embryonic kidney (HEK) 293 and MCF-7 cell lines, respectively, were found also to associate with the plasma membrane, indicating that this interaction is not unique to H69 and H69AR cells. GSTP1 immunostaining in HEK293 and MCF7-GSTP1 cells only occurred under permeabilized conditions, suggesting that GSTP1 is associated with the intracellular surface of the plasma membrane. Cell surface biotinylation studies confirmed this finding. Immunogold electron microscopy revealed the presence of GSTP1 in close proximity to the plasma membrane. GSTP1 was not dissociated from plasma membrane sheets by high salt [potassium iodide (KI; 1 M) or KI/EDTA (1 M/2 mM)] or alkaline Na(2)CO(3) (100 mM, pH 11.4), conditions known to strip peripherally associated membrane proteins. Thus, we report for the first time that GSTP1 is associated with the inner leaflet of the plasma membrane through a remarkably strong interaction.

Characterisation of prosthetic feet used in low-income countries

Eleven kinds of prosthetic feet that were designed for use in low-income countries were mechanically characterised in this study. Masses of the different kinds of prosthetic feet varied substantially. Dynamic properties, including damping ratios and resonant frequencies, were obtained from step unloading tests of the feet while interacting with masses comparable to the human body. Data showed that for walking, the feet can be appropriately modeled using their quasistatic properties since natural frequencies were high compared to walking frequencies and since damping ratios were small. Roll-over shapes, the effective rocker (cam) geometries that the feet deform to under walking loads, were determined using a quasistatic loading technique and a spatial transformation of the ground reaction force's centre of pressure. The roll-over shapes for most of the prosthetic feet studied were similar to the roll-over shape of the SACH (solid-ankle cushioned heel) prosthetic foot. All roll-over shapes showed a lack of forefoot support, which may cause a "drop-off" experience at the end of single limb stance and shorter step lengths of the contralateral limb. The roll-over shapes of prosthetic feet appear useful in characterization of foot function.

Alignment of trans-tibial prostheses based on roll-over shape principles

The authors examined the roll-over shape alignment hypothesis, which states that prosthetic feet are aligned by matching their roll-over shapes with an "ideal" shape. The "ideal" shape was considered to be the roll-over shape of the able-bodied foot-ankle system. An alignment algorithm and computational alignment system were developed to set trans-tibial alignments based on this hypothesis. Three prosthetic feet with considerably different roll-over shapes were either aligned using the alignment system or not aligned (i.e. used previous foot's alignment), and then were aligned by a team of prosthetists. No significant differences were found between roll-over shapes aligned by the computational alignment system and those based on standard clinical techniques (p = 0.944). Significant differences were found between the "no alignment" shapes and the prosthetist alignment shapes (p = 0.006), and between the "no alignment" shapes and the computational alignment system shapes (p = 0.024). The results of the experiment support the hypothesis that the goal of alignment is to match the prosthetic foot's roll-over shape, as closely as possible, with an "ideal" shape. The hypothesis is also supported by its ability to explain the results of previous studies. Using an "ideal" roll-over shape or surface as a goal for prosthetic alignment could lead to a priori alignment, eliminating the need for alignment hardware in some cases. Being able to build the alignment into a prosthesis without special hardware could be beneficial in low-income countries and in the fabrication of lightweight prostheses for the elderly.

Osteoporosis and risk of fracture in men with spinal cord injury

STUDY DESIGN

Cross-sectional study to evaluate bone mineral density (BMD) and fracture history after spinal cord injury (SCI).

OBJECTIVES

To determine frequency of osteoporosis and fractures after SCI, correlate extent of bone loss with frequency of fractures after SCI, and determine fracture risk in SCI patients.

SETTING

The Hines Veterans Affairs Hospital in Hines, Illinois, USA.

METHODS

Femoral neck BMD was measured in 41 individuals with a history of traumatic or ischemic SCI using dual-energy X-ray absorptiometry (DEXA Lunar Whole Body Densitometer Model).

RESULTS

Twenty-five patients (61%) met the World Health Organization (WHO) criteria for osteoporosis, eight (19.5%) were osteopenic, and eight (19.5%) were normal. Fracture after SCI had occurred in 14 patients (34%). There were significant differences between the femoral neck BMD and SCI duration in patients with a fracture history compared to those without. For patients in the same age group, each 0.1 gm/cm(2) and each unit of standard deviation (SD) (t-value) decrement of BMD at the femoral neck increased the risk of fracture 2.2 and 2.8 times, respectively. Considered simultaneously with age, duration of SCI, and level of SCI, BMD was the only significant predictor of the number of fractures.

CONCLUSION

Osteoporosis and an increased frequency of fractures occur after SCI. Measurement of femoral neck BMD can be used to quantify fracture risk in SCI patients.

Decolorization of Orange II dye by white-rot fungi

Agitation, temperature, inoculum size, initial pH and pH of buffered medium affected the decolorization of Orange II dye by Coriolus versicolor and Funalia trogii. The optimum temperature and initial pH value for decolorization were 30 degrees C and 6.5-7.0, respectively; pH 4.5 was the most efficient in buffered cultures. High decolorization extents were reached at all agitation rates. At an inoculum size of more than 1 mL, the extent of decolorization changed only slightly. High extents were obtained using immobilized fungi at repeated batch mode.

Desmin knockout muscles generate lower stress and are less vulnerable to injury compared with wild-type muscles

The functional role of the skeletal muscle intermediate filament system was investigated by measuring the magnitude of muscle force loss after cyclic eccentric contraction (EC) in normal and desmin null mouse extensor digitorum longus muscles. Isometric stress generated was significantly greater in wild-type (313 +/- 8 kPa) compared with knockout muscles (276 +/- 13 kPa) before EC (P < 0.05), but 1 h after 10 ECs, both muscle types generated identical levels of stress ( approximately 250 kPa), suggesting less injury to the knockout. Differences in injury susceptibility were not explained by the different absolute stress levels imposed on wild-type versus knockout muscles (determined by testing older muscles) or by differences in fiber length or mechanical energy absorbed. Morphometric analysis of longitudinal electron micrographs indicated that Z disks from knockout muscles were more staggered (0.36 +/- 0. 03 microm) compared with wild-type muscles (0.22 +/- 0.03 microm), which may indicate that the knockout cytoskeleton is more compliant. These data demonstrate that lack of the intermediate filament system decreases isometric stress production and that the desmin knockout muscle is less vulnerable to mechanical injury.

Low glutathione peroxidase activity in Gpx1 knockout mice protects jejunum crypts from gamma-irradiation damage

Gpx1 knockout (KO) mice had a higher number of regenerating crypts in the jejunum than did Gpx2-KO or wild-type mice analyzed 4 days after > or =10 Gy gamma-irradiation. Without gamma-irradiation, glutathione peroxidase (GPX) activity in the jejunal and ileal epithelium of Gpx1-KO mice was <10 and approximately 35%, respectively, of that of the wild-type mice. Four days after exposure to 11 Gy, GPX activity in wild-type and Gpx1-KO ileum was doubled and tripled, respectively. However, jejunal GPX activity was not changed. Thus the lack of GPX activity in the jejunum is associated with better regeneration of crypt epithelium after radiation. Gpx2 gene expression was solely responsible for the increase in GPX activity in the ileum, since radiation did not alter GPX activity in Gpx2-KO mice. The intestinal Gpx2 mRNA levels of Gpx1-KO and wild-type mice increased up to 14- and 7-fold after radiation, respectively. Although the Gpx1-KO jejunum had higher levels of PGE(2) than the wild-type jejunum after exposure to 0 or 15 Gy, these differences were not statistically significant. Thus whether GPX inhibits PG biosynthesis in vivo remains to be established. We can conclude that the Gpx2 gene compensates for the lack of Gpx1 gene expression in the ileal epithelium. This may have abolished the protective effect in Gpx1-KO mice against the radiation damage in the ileum.

Gene trapping of two novel genes, Hzf and Hhl, expressed in hematopoietic cells

Using an expression gene trapping strategy, we have identified and characterized two novel hematopoietic genes, Hzf and Hhl. Embryonic stem (ES) cells containing a gene trap vector insertion were cultured on OP9 stromal cells to induce hematopoietic differentiation and screened for lacZ reporter gene expression. Two ES clones displaying lacZ expression within hematopoietic cells in vitro were used to generate mice containing the gene trap integrations. Paralleling this in vitro expression pattern, both Hzf and Hhl were expressed in a tissue-specific manner during hematopoietic development in vivo. Hzf encodes a novel protein containing three C(2)H(2)-type zinc fingers predominantly expressed in megakaryocytes and CFU-GEMM. Hhl encodes a novel protein containing a putative phosphotyrosine binding (PTB) domain expressed in megakaryocytes, CFU-GEMM and BFU-E. These results demonstrate the utility of expression trapping to identify novel hematopoietic genes. Future studies of Hzf and Hhl should provide valuable information on the role these genes play during megakaryocytopoiesis.

Aquarius, a novel gene isolated by gene trapping with an RNA-dependent RNA polymerase motif

In a retinoic acid (RA) gene trap screen of mouse embryonic stem (ES) cells, a novel gene, named Aquarius (Aqr), was identified and characterized. The promoterless lacZ marker was used to trap the genomic locus and to determine the expression pattern of the gene. Aqr transcripts are strongly induced in response to RA in vitro. During embryogenesis, Aqr is expressed in mesoderm, in the neural crest and its target tissues, and in neuroepithelium. Expression was first detected at 8.5 days postcoitum, when neural crest cells are visible at the lateral ridges of the neural plate. The gene-trapped Aqr locus was transmitted through the mouse germ line in three genetic backgrounds. In the F2 generation, the expected mendelian ratio of 1:2:1 was observed in all backgrounds, indicating that homozygous mice are viable. Homozygotes are normal in size and weight and breed normally. The gene trap insertion, however, does not seem to generate a null mutation, because Aqr transcripts are still present in the homozygous mutant animals. The Aqr open reading frame has weak homology to RNA-dependent RNA polymerases (RRPs) of the murine hepatitis viruses and contains an RRP motif. Aqr was mapped to mouse chromosome 2 between regions E5 through F2 by using fluorescence in situ hybridization analysis.

A novel family of repeat sequences in the mouse genome responsive to retinoic acid

Repetitive DNA sequences form a substantial portion of eukaryotic genomes and exist as members of families that differ in copy number, length, and sequence. Various functions, including chromosomal integrity, gene regulation, and gene rearrangement have been ascribed to repetitive DNA. Although there is evidence that some repetitive sequences may participate in gene regulation, little is known about how their own expression may be regulated. During the course of gene trapping experiments with embryonic stem (ES) cells, we identified a novel class of expressed repetitive sequences in the mouse, using 5' rapid amplification of cDNA ends-polymerase chain reaction (5' RACE-PCR) to clone fusion transcripts from these lines. The expression of these repeats was induced by retinoic acid (RA) in cultured ES cells examined by Northern blot analyses. In vivo, their expression was spatially restricted in embryos and in the adult brain as determined by RNA in situ hybridization. We designated this family of sequences as Dr (developmentally regulated) repeats. The members of the Dr family, identified by cDNA cloning and through database search, are highly similar in sequence and show peculiar structural features. Our results suggest the expression of Dr-containing transcripts may be part of an ES cell differentiation program triggered by RA.

An induction gene trap screen in embryonic stem cells: Identification of genes that respond to retinoic acid in vitro

We have developed a novel induction gene trap approach that preselects in vitro for integrations into genes that lie downstream of receptor/ligand-mediated signaling pathways. Using this approach, we have identified 20 gene trap integrations in embryonic stem cells, 9 of which were induced and 11 of which were repressed after exposure to exogenous retinoic acid (RA). All but one of these integrations showed unique spatially restricted or tissue-specific patterns of expression between 8.5 and 11.5 days of embryogenesis. Interestingly, expression was observed in tissues that are affected by alterations in RA levels during embryogenesis. Sequence analysis of fusion transcripts from six integrations revealed five novel gene sequences and the previously identified protooncogene c-fyn. To date, germ-line transmission and breeding has uncovered one homozygous embryonic lethal and three homozygous viable insertions. These studies demonstrate the potential of this induction gene trap approach for identifying and mutating genes downstream of signal transduction pathways.

Access to adult liver transplantation in Canada: a survey and ethical analysis

OBJECTIVES

To describe the substantive and procedural criteria used for placing patients on the waiting list for liver transplantation and for allocating available livers to patients on the waiting list; to identify principal decision-makers and the main factors limiting liver transplantation in Canada; and to examine how closely cadaveric liver allocation resembles theoretic models of source allocation.

DESIGN

Mailed survey.

PARTICIPANTS

Medical directors of all seven Canadian adult liver transplantation centres, or their designates. Six of the questionnaires were completed.

OUTCOME MEASURES

Relative importance of substantive and procedural criteria used to place patients in the waiting list for liver transplantation and to allocate available livers. Identification of principal decision-makers and main limiting factors to adult liver transplantation.

RESULTS

Alcoholism, drug addiction, HIV positivity, primary liver cancer, noncompliance and hepatitis B were the most important criteria that had a negative influence on decisions to place patients on the waiting list for liver transplantation. Severity of disease and urgency were the most important criteria used for selecting patients on the waiting list for transplantation. Criteria that were inconsistent across the centres included social support (for deciding who is placed on the waiting list) and length of time on the waiting list (for deciding who is selected from the list). Although a variety of people were reported as being involved in these decisions, virtually all were reported to be health to be health care professionals. Thirty-seven patients died while waiting for liver transplantation in 1991; the scarcity of cadaveric livers was the main limiting factor.

CONCLUSIONS

Criteria for resource allocation decisions regarding liver transplantation are generally consistent among the centres across Canada, although some important inconsistencies remain. Because patients die while on the waiting list and because the primary limiting factor is organ supply, increased organ acquisition efforts are needed.

Canadian outpatients and advance directives: poor knowledge and little experience but positive attitudes

OBJECTIVE

To examine the knowledge of, previous experience with, attitudes toward and perceived barriers to completing advance directives among outpatients at two general medicine clinics.

DESIGN

Cross-sectional questionnaire administered in face-to-face structured interviews.

SETTING

General internal-medicine outpatient clinics at a university teaching hospital.

PATIENTS

One hundred and five adult outpatients who could communicate in spoken English and who consented to be interviewed.

RESULTS

Of 167 patients approached, 58 were excluded because they could not communicate in spoken English, and 4 refused to participate. Of the remaining 105 patients, 17 (16%) knew about living wills, 12 (11%) about durable powers of attorney for health care and 4 (4%) about advance directives. Twenty-three (22%) had thought about their preferences for life-sustaining treatment, 20 (19%) had discussed them, none had written them down, and 45 (43%) had thought about choosing a proxy. Sixty-one (58%) wanted to think about their preferences for treatment, 65 (62%) wanted to discuss them, 32 (30%) wanted to write them down, and 80 (76%) wanted to choose a proxy. The perceived barriers to completing an advance directive were inability to write, the belief that an advance directive was unnecessary, a fatalistic attitude, previous discussion of preferences, a desire to leave the decision to doctors, uncertainty about preferences, a desire to discuss preferences rather than document them, a desire to wait until the situation arose, a desire to write down preferences in the future and a desire to avoid thinking about preferences or advance directives. Respondents with more knowledge of life-sustaining treatments were more likely to want to complete an advance directive.

CONCLUSIONS

Outpatients have positive attitudes toward advance directives, but their knowledge and experience are limited. These data underscore the need for patient education and for policies to eliminate the barriers to completing advance directives that patients face.

Pick's disease: a case clinically resembling amyotrophic lateral sclerosis

A 50-year-old woman with a progressive neurologic illness clinically resembling amyotrophic lateral sclerosis had Pick's disease verified at autopsy. This case represents another example of Pick's disease in which the early manifestations were not those of dementia. This patient also showed some unusual histopathologic features, including degeneration of the substantia nigra and occasional "compound Pick bodies."

Characterization of a 70Z/3 pre-B cell derived macrophage clone. Differential expression of Hox family genes

An adherent cell line was established from the much studied pre-B cell line 70Z/3. The adherent cell line had the morphological features of a macrophage and stained positive for non-specific esterase. In addition, this line expressed high levels of RNA for the macrophage specific enzyme, lysozyme. Although the 70Z/3 macrophage variant has lost the ability to respond to lipopolysaccharide and interferon-gamma by expressing RNA transcripts for immunoglobulin light chain, it exhibited a new response characterized by increased levels of I-A RNA transcripts. Both the pre-B and macrophage variants also expressed RNA transcripts which hybridize to a Hox 2.3 probe. In contrast, transcripts which hybridize to Hox 1.1, 2.1, and 6.1 probes are expressed in the pre-B line but could not be detected in the macrophage.

RsaI polymorphism of a human immunoglobulin VH5 subclass locus

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