A signal/noise analysis of quasi-static MR elastography

In quasi-static magnetic resonance elastography, strain images of a tissue or material undergoing deformation are produced. In this paper, the signal/noise (S/N) ratio [SNR] of elastographic strain images, as measured by a phase-contrast technique, is analyzed. Experiments are conducted to illustrate how diffusion-mediated signal attenuation limits maximum strain SNR in small displacement cases, while the imaging point-spread function limits large displacement cases. A simple theoretical treatment agrees well with experiments and shows how an optimal displacement encoding moment can be predicted for a given experimental set of parameters to achieve a maximum strain SNR. A further experiment demonstrates how the limitation on strain SNR posed by the imaging point-spread function may potentially be overcome.

A simple automated solution for removing and applying sealing microplate lids

With the improved reliability and efficiency of automation, there has been an increased desire to integrate automated sample management with automated screening systems. In order to store samples "on line" for an extended period of time, an automation-compatible means for sealing and unsealing microplates is necessary. Numerous commercial solutions are available for removing loose-fitting microplate lids; however, the task of removing a tight-fitting matted lid such as the RoboLid is more challenging. This paper discusses the design of an automated workstation for the application and removal of such tight-fitting microplate lids.

A constrained modulus reconstruction technique for breast cancer assessment

A reconstruction technique for breast tissue elasticity modulus is described. This technique assumes that the geometry of normal and suspicious tissues is available from a contrast-enhanced magnetic resonance image. Furthermore, it is assumed that the modulus is constant throughout each tissue volume. The technique, which uses quasi-static strain data, is iterative where each iteration involves modulus updating followed by stress calculation. Breast mechanical stimulation is assumed to be done by two compressional rigid plates. As a result, stress is calculated using the finite element method based on the well-controlled boundary conditions of the compression plates. Using the calculated stress and the measured strain, modulus updating is done element-by-element based on Hooke's law. Breast tissue modulus reconstruction using simulated data and phantom modulus reconstruction using experimental data indicate that the technique is robust.

Toxicity of irinotecan (CPT-11) and hepato-renal dysfunction

Various clinical and laboratory parameters have been investigated for their ability to predict toxicity arising from the use of the anticancer drug, irinotecan (CPT-11). In particular, patients deficient in the conjugation of SN-38, a metabolite of CPT-11, are known to be at greater risk. We describe one case of a patient with metastatic colorectal cancer treated with a single dose of CPT-11 at 125 mg/m(2). Although this patient lacked any known predictive factors for toxicity, he experienced severe side-effects several days later. We hypothesized that the toxicity in this patient was due to compromised SN-38 conjugation. Plasma samples were analyzed by reversed-phase high-performance liquid chromatography assay for CPT-11 and its metabolites at 96, 144, 168, 192 and 288 h post-administration. We observed that the concentrations of both the parent drug and its metabolites were markedly raised (11- to 60-fold expected). Additionally the estimated terminal half-lives were 1.5-7 times those expected (29.5, 101, 39.6 and 41.8 h for CPT-11, APC, SN-38G and SN-38, respectively). We conclude that the toxicity in this patient was not caused by deficient SN-38 conjugation, but by decreased drug excretion through both hepatic and renal routes.

Accuracy of thin-layer cytology in patients undergoing cervical cone biopsy

OBJECTIVE

To compare the accuracy of thin-layer cytology with Autocyte PREP (TriPath Imaging Inc., Burlington, North Carolina, U.S.A.) with conventional smears in 500 women undergoing cervical cone biopsy.

STUDY DESIGN

The study was performed among 500 consecutive women presenting for cone biopsy for high grade cervical intraepithelial neoplasia (CIN) on biopsy in 350 (70%) and discrepant cytology/colpohistology in 150 (30%). Before performing a cone biopsy, two cervical samples were collected for conventional smears and thin-layer cytologic slides, with randomization of the order. Conventional smears were stained and diagnosed at Pasteur Cerba, while thin-layer cytologic slides were processed at a local TriPath office (Meylan, France) and sent in a masked fashion for screening at Pasteur Cerba. Any slides initially read as normal were reviewed again and reported without knowledge of the other cytologic or cone biopsy data. The final cytologic diagnoses for the two methods were compared with histopathology of the cone biopsy.

RESULTS

The conventional smear was unsatisfactory in 58 (11.6%) of cases, while there were 4 (0.8%) unsatisfactory thin-layer cytologic slides (P < .001). Endocervical cells were missing from 31 (6.2%) of conventional smears and 34 (6.8%) of thin-layer cytologic slides. For the pooled data, sensitivities of conventional smear and thin layer for detecting high grade CIN (0.82% and 0.86%, respectively) were similar as were specificities (0.40% and 0.43%, respectively). When first samples were compared, the sensitivities of the conventional smear and thin layer for high grade CIN were 0.79% and 0.89%, respectively (P = .02), with corresponding specificities of 0.41% and 0.36% (P < .01).

CONCLUSION

When controlled for sample order, the sensitivity of thin-layer cytology for detecting high grade CIN was significantly higher than that of conventional smears in patients with previous abnormal cytology, but at the expense of specificity.

Evaluation of inter-scorer and inter-laboratory reliability of the mouse epididymal sperm aneuploidy (m-ESA) assay

The mouse epididymal sperm aneuploidy (mESA) assay using 3-chromosome fluorescence in situ hybridization (FISH) was recently developed for assessing the aneugenic potential of chemicals on male germ cells. This study was designed to identify the major technical factors that affect inter-scorer and inter-laboratory variability of the mESA assay. Two laboratories participated in this study (GSF and Lawrence Livermore National Laboratory, LLNL). Mice (102/ElxC3H/El) F(1) were exposed in one laboratory (GSF) to vinblastine (VBL; single intraperitoneal injection of 0, 0.5, 1.0 or 2.0 mg/kg), one of the 10 priority compounds of the Commission of the European Communities (CEC) Aneuploidy Program. Twenty-two days later the mESA assay was applied to analyze sperm aneuploidy. In the initial evaluation, small but statistically significant differences were found between the two laboratories in baseline frequencies and there was also disagreement in the determination of a VBL aneuploid effect. Therefore, experiments were conducted to identify the sources of the inter-laboratory differences and technical factors that affected assay reliability and the VBL study was repeated. A harmonization experiment was conducted by bringing the microscope scorers from both laboratories to the same site (LLNL) for a cross-training exercise. Following this exercise, a second group of VBL-treated and control mice were evaluated, and we concluded that VBL is not a sperm aneugen. Our research has identified scoring criteria as the major source of inter-laboratory variation and emphasizes the importance of strict technical controls for the mESA assay, including controlling slide preparations for treatment-induced reductions in sperm count, coding of slides and selection of statistical tests. These considerations are particularly important for the interpretation of small effects (< or =2-fold) on sperm aneuploidy. Our findings suggest that 2-fold differences in frequencies can result from differences among scorers, samples and treatment groups, and are readily within the normal variation for the mESA assay. Such small differences should be viewed with caution until independently confirmed.

Systematic review concerning the age of introduction of complementary foods to the healthy full-term infant

OBJECTIVES

To evaluate existing data from published studies investigating outcomes (growth, nutritional status and morbidity) in relation to the age of introduction of complementary foods to the healthy full-term infant. To assess the methodological quality of current scientific evidence on which infant feeding recommendations are based.

SEARCH STRATEGY

A database was created following a search of electronic databases MEDLINE and BIDS, a handsearch of relevant journals and consultation with international experts in infant feeding practices. The search was conducted during a 6-month period and encompassed the years 1982-1998.

INCLUSION CRITERIA

Randomised/non-randomised controlled trials and cohort studies investigating the relationship to the health of full-term infants of the introduction of complementary foods to childhood health.

DATA COLLECTION AND ANALYSIS

Assessment of studies for inclusion and their compliance with methodological criteria was undertaken independently by two reviewers and discrepancies were resolved by discussion.

RESULTS

From over 400 published papers identified, 33 met specific inclusion criteria. Significant differences in baseline characteristics of subjects in included studies meant that data were not amenable to meta-analysis. The consensus of the authors was that, of the 33 included publications, 13 contained data supporting the current WHO recommendations which attempt to accommodate all infants, including those whose nutritional requirements are not met by exclusive breast-feeding for 6 months. An equal number contained data that would support a recommendation for delaying the introduction of complementary foods until 6 months of age within the study population. The remaining seven were unable to provide evidence to support a change from the current WHO infant feeding recommendations which state that 'infants should be fed exclusively on breast milk from birth to 4-6 months of age'. None of the studies met all the methodological criteria.

CONCLUSIONS

This review has shown that there is a lack of clear evidence to either support or refute a change to the current recommendations for the age of introduction of complementary foods to the breast milk or formula fed infant. Whilst exclusive breast feeding for the first 6 months of life can support growth and development in some infants, sub-groups have been identified within certain populations who may require complementary feeding prior to this age.

Carboplatin and vinorelbine in untreated locally advanced and metastatic non-small cell lung cancer

The aim of this study was to assess the activity and toxicity of carboplatin/vinorelbine combination chemotherapy in unresectable locally advanced and metastatic non-small cell lung cancer. Between April 1997 and June 1999 30 patients (22 M, eight F, median age 62) received treatment with carboplatin AUC 6 on day 1, and vinorelbine 25mg/m(2) on days 1, 8 and 15. Treatment was given every 28 days for six cycles unless progressive disease occurred. Twenty-three patients (77%) had stage IV disease, and seven (23%) stage IIIB. Ninety-three percent were WHO performance status 0-1. Twenty-three patients were fully assessable. Nine patients achieved partial responses (9/23, 39%) for an overall objective response rate of 9/30 (30%; 95% CI 15-49%). The median duration of response was 2.75 months (range 1-13 months). The median progression-free survival was 2 months and the median survival 5.25 months. The actuarial 1-year survival was 20%. The median number of cycles completed was two (range 1-6). Day 15 vinorelbine was administered in only 18% of cycles. The main toxicity was myelosuppression. WHO grade III/IV neutropenia was experienced in 50% of patients, however, there were only three episodes of febrile neutropenia. Eight patients required blood transfusion and one developed grade III thrombocytopenia. Treatment was ceased in one patient because of grade IV autonomic neuropathy. No patient had significant nausea and vomiting. There were no treatment-related deaths. These results indicate that carboplatin/vinorelbine is well tolerated and has similar activity to cisplatin/vinorelbine in patients with unresectable non-small cell lung cancer, however, the median survival was considerably shorter.

Biomechanical 3-D finite element modeling of the human breast using MRI data

Breast tissue deformation modeling has recently gained considerable interest in various medical applications. A biomechanical model of the breast is presented using a finite element (FE) formulation. Emphasis is given to the modeling of breast tissue deformation which takes place in breast imaging procedures. The first step in implementing the FE modeling (FEM) procedure is mesh generation. For objects with irregular and complex geometries such as the breast, this step is one of the most difficult and tedious tasks. For FE mesh generation, two automated methods are presented which process MRI breast images to create a patient-specific mesh. The main components of the breast are adipose, fibroglandular and skin tissues. For modeling the adipose and fibroglandular tissues, we used eight noded hexahedral elements with hyperelastic properties, while for the skin, we chose four noded hyperelastic membrane elements. For model validation, an MR image of an agarose phantom was acquired and corresponding FE meshes were created. Based on assigned elasticity parameters, a numerical experiment was performed using the FE meshes, and good results were obtained. The model was also applied to a breast image registration problem of a volunteer's breast. Although qualitatively reasonable, further work is required to validate the results quantitatively.

Expression pattern of Drosophila ret suggests a common ancestral origin between the metamorphosis precursors in insect endoderm and the vertebrate enteric neurons

The RET gene, encoding a receptor tyrosine kinase, is unusual among human protooncogenes in that its mutant alleles are implicated in a developmental defect involving enteric neurons as well as in tumorigenesis. The cells affected in both types of disorders are derived from the neural crest. Targeted disruption of mouse ret has revealed an additional role in kidney development. Here we report the analysis of a ret homolog in Drosophila melanogaster, an arthropod with no neural crest. Drosophila ret (D-ret) encodes a protein of 1,235 amino acids that has all of the domains identified in the vertebrate ret, including a cadherin motif. During embryogenesis, D-ret mRNA is first detected in the yolk sac at the late gastrula stage. In the postgastrula, D-ret is expressed in the foregut neurons, excretory system, peripheral ganglia, and the central nervous system. Thus, despite the wide divergence of early embryonic fate maps between vertebrates and invertebrates, D-ret is expressed in cells that are presumed to be the functional equivalents of the ret-expressing cells in vertebrates. Unexpectedly, D-ret is also expressed in the imaginal islands of the endodermal gut. These cells are proliferation-competent precursors for adult midgut that are diffusely embedded in the growth-arrested juvenile gut. These ret-expressing nonneuronal cells are strikingly analogous to vertebrate enteric neurons in their topography, but not in their cell fate. Our finding suggests a previously unrecognized phylogenetic relationship between the ret-expressing cells in vertebrates and the precursor reserves of metamorphosing insects.

Non-specific antiviral activity of antisense molecules targeted to the E1 region of human papillomavirus

Antisense phosphorothioate oligonucleotides (ODN1 0x5 OMe) directed against the E1 start region of human papillomavirus 11 (HPV11) can inhibit papillomavirus induced growth of implanted human foreskin in a mouse xenograft model. Administration of a mismatch control oligonucleotide (ODN9 0x5 OMe), in which guanine was replaced with adenine in the same model, had no effect on papilloma induced growth. However, the apparent antiviral activity of ODN1 0x5 OMe was also shown in a lethal mouse cytomegalovirus (CMV) model, in which the oligonucleotides are not expected to have antisense activity. To understand the mechanisms of action of these oligonucleotides, a mismatch oligonucleotide (ODN61 0x5 OMe) was prepared which retained the CpG motifs of ODN1 0x5 OMe. This was tested in the mouse xenograft model and shown to have moderate inhibitory activity. As a definitive experiment, a comparison was made between the efficacy of the active oligonucleotide ODN1 0x5 OMe against two papilloma viruses HPV11 and HPV40. Both these viruses cause benign genital warts, but differ by four bases in their E1 sequence that was the target for ODN1 0x5 OMe. Papillomavirus induced growth in the mouse xenograft model was inhibited by ODN1 0x5 OMe in both cases, suggesting that oligonucleotide molecules have a non-specific antiviral activity that is not directly related to their antisense sequence.

Influence of chronic barbiturate administration on sleep apnea after hypersomnia presentation: case study

When sleepiness is excessive, undesirable, inappropriate or unexplained, it often indicates a clinical disorder that is generically termed hypersomnia. One of the leading causes of hypersomnia is sleep apnea. We present the case of a 44-year-old woman with a history of bipolar spectrum disorder and epilepsy who initially showed evidence of hypersomnia. The hypersomnia settled with changes to her medication, but the patient was subsequently found to have severe obstructive sleep apnea. The relation between the patient's medication and sleep apnea is discussed, and the possible respiratory-suppressant effects of chronic barbiturate treatment are considered. The role of other evoking factors within the context of this case and the mechanisms by which drug interactions and psychotropic treatment may worsen, obscure or perpetuate sleep apnea are also examined.

Two-dimensional MR elastography with linear inversion reconstruction: methodology and noise analysis

A methodology for imposing approximate plane strain conditions in magnetic resonance elastography through physical constraint is described. Under plane strain conditions, data acquisition and analysis may be conducted in two dimensions, which reduces imaging and reconstruction time significantly compared with three-dimensional analysis. Simulations and experiments are performed to illustrate the constraint concept. A signal/noise analysis of a two-dimensional linear inversion technique for relative elastic modulus is undertaken, and modifications to the numerical method are described which can reduce the SNR requirements by a factor of two to four. Experimentally measured data are reconstructed to illustrate the performance of the method.

Gender roles and geographic location as predictors of emotional distress in Australian women

This paper examines the emotional distress of women in urban, rural and remote areas of Queensland. A randomised telephone survey of 394 women found that geographical location was not significantly related to perceptions of life quality or distress. Contrary to expectation, urbanisation and isolation were not significant predictors of mental health and factors other than geographical location appear more influential in determining people's emotional wellbeing. One such factor, the gender role that women perceive themselves as fulfilling, was examined in this study and found to be significantly related to emotional distress. Women who saw their role as being submissive, dependent, gentle and timid reported significantly higher rates of distress and women perceiving themselves as bossy, rude and superior reported higher stress, irrespective of where they lived. Scores for the positive gender role of being sensitive, emotional and responsible grew significantly higher as the respondents became more rural/remote. Conversely, scores in the bossy, rude and superior domain were significantly higher in urban areas. This paper discusses the limitations of health research using global urban/rural classification schemes based on size of town or distance from major centres. There is mounting evidence that geographically based classification schemes are essentially minimalist and that more complex grouping variables such as gender role need to be identified.

Visualization and quantification of breast cancer biomechanical properties with magnetic resonance elastography

A quasistatic magnetic resonance elastography (MRE) method for the evaluation of breast cancer is proposed. Using a phase contrast, stimulated echo MRI approach, strain imaging in phantoms and volunteers is presented. First-order assessment of tissue biomechanical properties based on inverse strain mapping is outlined and demonstrated. The accuracy of inverse strain imaging is studied through simulations in a two-dimensional model and in an anthropomorphic, three-dimensional finite-element model of the breast. To improve the accuracy of modulus assessment by elastography, inverse methods are discussed as an extension to strain imaging, and simulations quantify MRE in terms of displacement signal/noise required for robust inversion. A direct inversion strategy providing information on tissue modulus and pressure distribution is described along with a novel iterative method utilizing a priori knowledge of tissue geometry. It is shown that through the judicious choice of information from previous contrast-enhanced MRI breast images, MRE data acquisition requirements can be significantly reduced while maintaining robust modulus reconstruction in the presence of strain noise. An experimental apparatus for clinical breast MRE and preliminary images of a normal volunteer are presented.

Refining the DFNB7-DFNB11 deafness locus using intragenic polymorphisms in a novel gene, TMEM2

The combined DFNB7-DFNB11 deafness locus maps to chromosome 9q13-q21 between markers D9S1806 and D9S769. We have determined the cDNA sequence and genomic structure of a novel gene, TMEM2, that maps to this interval and is expressed in the cochlea. The mouse orthologue of this gene (Tmem2) maps to the murine dn (deafness) locus on mouse chromosome 19. Screens for transmembrane helices reveal the presence of at least one putative transmembrane domain in the TMEM2 protein. To determine whether mutations in TMEM2 cause hearing loss at the DFNB7-DFNB11 locus, we screened the coding region of this gene in DFNB7-DFNB11 affected families by direct sequencing. All DNA variants that segregated with the deafness and changed the predicted amino acid sequence of TMEM2 were common polymorphisms, as demonstrated by allele-specific amplification of pooled control DNA. Northern blot analysis showed no difference in transcript size or expression level of Tmem2 in dn/dn and control mice. The intragenic polymorphisms in TMEM2 represent a novel centromeric boundary for the DFNB7-DFNB11 interval.