Digit ratio (2D:4D) in women and men with lung cancer.

A prenatal sex steroid environment of high prenatal testosterone and low prenatal oestrogen inhibits lung development and may predispose individuals to be vulnerable to lung disease in later life. Therefore, the aim of this report was to investigate whether there is an association between right and left 2D:4D (biomarker of prenatal sex steroids exposure) and primary lung cancer in women and men. Also, we considered the relationship between right-left 2D:4D (Δ2D:4D, a negative correlate of high prenatal testosterone and low prenatal oestrogen) and the age of lung cancer diagnosis. The study included 109 patients (61 men) with lung cancer and 197 controls (78 men). In the study we found that: (i) women with lung cancer have lower 2D:4D compared to controls (the effect was independent of smoking), (ii) among women with cancer, age at diagnosis was positively related to 2D:4D, i.e. women with masculinized 2D:4D present earlier with the cancer than women with feminized 2D:4D, (iii) among men with lung cancer, those with the most aggressive form (small-cell lung cancer) had masculinized (low) Δ2D:4D compared to those with the less aggressive form (non-small cell lung cancer). The data suggests that masculinized right 2D:4D and Δ2D:4D are associated with a predisposition to lung cancer and/or the more aggressive forms of lung cancer.

Association of five SNPs with human hair colour in the Polish population.

Twenty-two variants (single nucleotide polymorphisms - SNPs) of the genes involved in hair pigmentation (OCA2, HERC2, MC1R, SLC24A5, SLC45A2, TPCN2, TYR, TYRP1) were genotyped in a group of 186 Polish participants, representing a range of hair colours (45 red, 64 blond, 77 dark). A genotype-phenotype association analysis was performed. Using z-statistics we identified three variants highly associated with different hair colour categories (rs12913832:A>G in HERC2, rs1805007:T>C and rs1805008:C>T in MC1R). Two variants: rs1800401:C>T in OCA2 and rs16891982:C>G in SLC45A2 showed a high probability of a relation with hair colour, although that probability did not exceed the threshold of statistical significance after applying the Bonferroni correction. We created and validated mathematical logistic regression models in order to test the usefulness of the sets of polymorphisms for hair colour prediction in the Polish population. We subjected four models to stratified cross-validation. The first model consisted of three polymorphisms that proved to be important in the associative analysis. The second model included, apart from the mentioned polymorphisms, additionally rs16891982:C>G in SLC45A. The third model included, apart from the variants relevant in the associating analysis, rs1800401:C>T in OCA. The fourth model consisted of the set of polymorphisms from the first model supplemented with rs16891982:C>G in SLC45A and rs1800401:C>T in OCA. The validation of our models has shown that the inclusion of rs16891982:C>G in SLC45A and rs1800401:C>T in OCA increases the prediction of red hair in comparison with the algorithm including only rs12913832:A>G in HERC2, rs1805007:T>C and rs1805008:C>T in MC1R. The model consisting of all the five above-mentioned genetic variants has shown good prediction accuracies, expressed by the area under the curve (AUC) of the receiver operating characteristics: 0.84 for the red-haired, 0.82 for the dark-haired and 0.71 for the blond-haired. A genotype-phenotype association analysis brought results similar to those in other studies and confirmed the role of rs16891982:C>G, rs12913832:A>G, rs1805007:T>C and rs1805008:C>T in hair colour determination in the Polish population. Our study demonstrated for the first time the possibility of a share of the rs1800401:C>T SNP in the OCA2 gene in hair colour determination. Including this single nucleotide polymorphism in the actual hair colour predicting models would improve their predictive accuracy.

Parental smoking during pregnancy shortens offspring's legs.

One of the most severe detrimental environmental factors acting during pregnancy is foetal smoke exposure. The aim of this study was to assess the effect of maternal, paternal and parental smoking during pregnancy on relative leg length in 7- to 10-year-old children. The research conducted in the years 2001-2002 included 978 term-born children, 348 boys and 630 girls, at the age of 7-10 years. Information concerning the birth weight of a child was obtained from the health records of the women. Information about the mother's and the father's smoking habits during pregnancy and about the mothers' education level was obtained from a questionnaire. The influence of parental smoking on relative leg length, controlled for age, sex, birth weight and the mother's education, as a proxy measure of socioeconomic status, and controlled for an interaction between sex and birth weight, was assessed by an analysis of covariance, where relative leg length was the dependent variable, smoking and sex were the independent variables, and birth weight as well as the mother's education were the covariates. Three separate analyses were run for the three models of smoking habits during pregnancy: the mother's smoking, the father's smoking and both parents' smoking. Only both parents' smoking showed a significant effect on relative leg length of offspring. It is probable that foetal hypoxia caused by carbon monoxide contained in smoke decelerated the growth of the long bones of foetuses.

Resolution recovery for Compton camera using origin ensemble algorithm.

PURPOSE: Compton cameras (CCs) use electronic collimation to reconstruct the images of activity distribution. Although this approach can greatly improve imaging efficiency, due to complex geometry of the CC principle, image reconstruction with the standard iterative algorithms, such as ordered subset expectation maximization (OSEM), can be very time-consuming, even more so if resolution recovery (RR) is implemented. We have previously shown that the origin ensemble (OE) algorithm can be used for the reconstruction of the CC data. Here we propose a method of extending our OE algorithm to include RR. METHODS: To validate the proposed algorithm we used Monte Carlo simulations of a CC composed of multiple layers of pixelated CZT detectors and designed for imaging small animals. A series of CC acquisitions of small hot spheres and the Derenzo phantom placed in air were simulated. Images obtained from (a) the exact data, (b) blurred data but reconstructed without resolution recovery, and (c) blurred and reconstructed with resolution recovery were compared. Furthermore, the reconstructed contrast-to-background ratios were investigated using the phantom with nine spheres placed in a hot background. RESULTS: Our simulations demonstrate that the proposed method allows for the recovery of the resolution loss that is due to imperfect accuracy of event detection. Additionally, tests of camera sensitivity corresponding to different detector configurations demonstrate that the proposed CC design has sensitivity comparable to PET. When the same number of events were considered, the computation time per iteration increased only by a factor of 2 when OE reconstruction with the resolution recovery correction was performed relative to the original OE algorithm. We estimate that the addition of resolution recovery to the OSEM would increase reconstruction times by 2-3 orders of magnitude per iteration. CONCLUSIONS: The results of our tests demonstrate the improvement of image resolution provided by the OE reconstructions with resolution recovery. The quality of images and their contrast are similar to those obtained from the OE reconstructions from scans simulated with perfect energy and spatial resolutions.

Efficacy and safety of lenalidomide treatment in multiple myeloma (MM) patients--Report of the Polish Myeloma Group.

UNLABELLED: The aim of the multi-centre retrospective study was to evaluate the efficacy and safety of lenalidomide (LEN) therapy in patients with resistant or relapsed multiple myeloma (MM) as well as in patients with stable disease (LEN used due to neurological complications). The primary endpoint of this study was an overall response rate (ORR). The secondary endpoints were as follows: time to progression (TTP), overall survival (OS) and the safety of drug use. Data were collected in 19 centres of the Polish Multiple Myeloma Study Group. The study group consisted of 306 subjects: 153 females and 153 males. In 115 patients (38.8%, group A), a resistant myeloma was diagnosed; in 135 (44.1%, group B) a relapse, and in 56 (18.3%, group C) a stable disease were stated. In 92.8% of patients, LEN+DEX combination was used; in remaining group, LEN monotherapy or a combination therapy LEN+bortezomib or LEN+bendamustine and other were used. In the entire study group, ORR was 75.5% (including 12.4% patients achieving complete remission [CR] or stringent CR [sCR]). Median time to progression (TTP) was 20 months. Median overall survival (OS) was 33.3 months. The regression model for "treatment response" was on the borderline of statistical significance (p=0.07), however the number of LEN treatment cycles ≥ 6 (R(2)=17.2%), baseline LDH level (R(2)=1.1%) and no ASCT use (R(2)=1.7%) where the factors most affecting treatment response achievement. The regression model for dependant variable--"overall survival"--was statistically significant (p=0.0000004). Factors with the most impact on OS were as follows: number of LEN cycles treatment ≥ 6 (R(2)=16.7%), treatment response achievement (R(2)=6.9%), ß-2-microglobulin (ß-2-M) level (R(2)=4.8%), renal function (R(2)=3.0%) and lack of 3/4 grade adverse events (R(2)=1.4%). SUMMARY: LEN is an effective and safe therapeutic option, even in intensively treated resistant and relapsed MM patients, as well as in patients with stable disease and previous treatment-induced neurological complications. In particular, the number of LEN treatment cycles ≥ 6 was the factor which affected treatment response achievement the most, together with an important impact on OS.

Sensitivity estimation in time-of-flight list-mode positron emission tomography.

PURPOSE: An accurate quantification of the images in positron emission tomography (PET) requires knowing the actual sensitivity at each voxel, which represents the probability that a positron emitted in that voxel is finally detected as a coincidence of two gamma rays in a pair of detectors in the PET scanner. This sensitivity depends on the characteristics of the acquisition, as it is affected by the attenuation of the annihilation gamma rays in the body, and possible variations of the sensitivity of the scanner detectors. In this work, the authors propose a new approach to handle time-of-flight (TOF) list-mode PET data, which allows performing either or both, a self-attenuation correction, and self-normalization correction based on emission data only. METHODS: The authors derive the theory using a fully Bayesian statistical model of complete data. The authors perform an initial evaluation of algorithms derived from that theory and proposed in this work using numerical 2D list-mode simulations with different TOF resolutions and total number of detected coincidences. Effects of randoms and scatter are not simulated. RESULTS: The authors found that proposed algorithms successfully correct for unknown attenuation and scanner normalization for simulated 2D list-mode TOF-PET data. CONCLUSIONS: A new method is presented that can be used for corrections for attenuation and normalization (sensitivity) using TOF list-mode data.

Prenatal factors associated with the neonatal line thickness in human deciduous incisors.

The neonatal line (NNL) is used to distinguish developmental events observed in enamel which occurred before and after birth. However, there are few studies reporting relationship between the characteristics of the NNL and factors affecting prenatal conditions. The aim of the study was to determine prenatal factors that may influence the NNL thickness in human deciduous teeth. The material consisted of longitudinal ground sections of 60 modern human deciduous incisors obtained from full-term healthy children with reported birth histories and prenatal factors. All teeth were sectioned in the labio-lingual plane using diamond blade (Buechler IsoMet 1000). Final specimens were observed using scanning electron microscopy at magnifications 320×. For each tooth, linear measurements of the NNL thickness were taken on its labial surface at the three levels from the cemento-enamel junction. The difference in the neonatal line thickness between tooth types and between males and females was statistically significant. A multiple regression analyses confirmed influence of two variables on the NNL thickness standardised on tooth type and the children's sex (z-score values). These variables are the taking of an antispasmodic medicine by the mother during pregnancy and the season of the child's birth. These two variables together explain nearly 17% of the variability of the NNL. Children of mothers taking a spasmolytic medicine during pregnancy were characterised by a thinner NNL compared with children whose mothers did not take such medication. Children born in summer and spring had a thinner NNL than children born in winter. These results indicate that the prenatal environment significantly contributes to the thickness of the NNL influencing the pace of reaching the post-delivery homeostasis by the newborn's organism.

Self-assessment of attractiveness of persons with body decoration.

Tattoos and body piercing are forms of body decoration that have been known for ages. The use of such ornamentation is becoming more and more common. Researchers attempt to explain the meaning of this phenomenon within the discipline of behavioural ecology, attributing a sexual selection aspect to body decoration, and thus interpreting it in an evolutionary sense. The hypothesis that superior biological quality of individuals is indicated by body modification is becoming more and more popular. In the present study, this hypothesis is tested on the basis of physical attractiveness as an indicator of genotype quality. The total of 64 males and 52 females with tattoos and body piercings were subjected to tests consisting of the self-assessment of the attractiveness of their bodies. The control group comprised 86 subjects (38 males and 48 females) without body decoration. The results confirm that both women and men with body decoration assess the attractiveness of different parts of their bodies higher (regardless whether the decoration is located there or not) than people without tattoos and body piercing. Thus, the hypothesis has been confirmed that body decoration is a signal of superior biological quality of individuals.

Is increased constitutive skin and hair pigmentation an early sign of puberty?

The paper analyzes data concerning the constitutive skin and hair pigmentation of 7-10-year-old Polish children to examine whether the hormonal activity of the gonads, which increases in this period, causes changes in pigmentation levels that may be considered an early sign of puberty. The study involved 289 children (151 girls and 138 boys). Skin pigmentation was examined on the medial side of the arm, while hair pigmentation on strands of hair close to the scalp in the occipital area. Additionally, body height (B-v) was measured and compared with population norms. On this basis, it was ascertained that the studied sample was representative of the population from which it was taken and that it represented the prepubertal and early pubertal stages of ontogeny (prior to the pubertal growth spurt or the first menstruation in the studied girls). It was found that in 7-10-year-old Polish children there is a statistically significant (p=0.001) increase in skin and hair pigmentation levels, while the degree of pigmentation of both structures at this stage of ontogeny is sexually dimorphic: girls are characterized by stronger pigmentation than boys. At the age of 10 years, the dimorphic differences in skin pigmentation intensify due to a rapid rise in pigmentation in girls. This change may be deemed an early morphological sign of puberty, as it precedes the pubertal growth spurt and menarche. This fast increase in skin pigmentation is not paralleled by an analogous change in hair pigmentation.

Practical implementation of tetrahedral mesh reconstruction in emission tomography.

This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio projection datasets. The results demonstrate that the reconstructed images represented as tetrahedral meshes based on point clouds offer image quality comparable to that achievable using a standard voxel grid while allowing substantial reduction in the number of unknown intensities to be reconstructed and reducing the noise.

The effect of the season of birth and of selected maternal factors on linear enamel thickness in modern human deciduous incisors.

OBJECTIVE: Development of human tooth enamel is a part of a foetus's development; its correctness is the outcome of genetic and maternal factors shaping its prenatal environment. Many authors reported that individuals born in different seasons experience different early developmental conditions during pregnancy. In this study, we investigated the effects of season of birth and selected maternal factors on enamel thickness of deciduous incisors. DESIGN: Dental sample comprises 60 deciduous incisors. The parents who handed over their children's teeth for research fill in questionnaires containing questions about the course of pregnancy. All teeth were sectioned in the labio-linqual plane using diamond blade (Buechler IsoMet 1000). The final specimens were observed by way of scanning electron microscopy at magnifications 80× and 320×. The thickness of total enamel (TE), prenatally (PE) and postnatally (PSE) formed enamel was measured. RESULTS: Children born in summer and in spring (whose first and second foetal life fall on autumn and winter) have the thinnest enamel. Season of birth, number of children in family, diseases and spasmolytic medicines using by mother during pregnancy explained almost 13% of the variability of TE. Regression analysis proved a significant influence of the season of birth and selected maternal factors on the PE thickness - these factors explained over 17% of its variability. Neither of analysed variables had influenced PSE. CONCLUSIONS: Our findings suggests that the thickness of enamel of deciduous incisors depends on the season of birth and some maternal factors. The differences were observed only in the prenatally formed enamel.

Frequency of under- and overweight among children and adolescents during the economic transition in Poland.

The aim of this study is to examine the prevalence of underweight, overweight and obesity, using International Obesity Task Force (IOTF) criteria, in four cohorts of children and adolescents living in Poland in different economic eras: communist economy (1977/1978), crisis of the 1980s (1987/1988), political and economic transformation (1992/1994) and the free market economy (2002/2004). Analysis was conducted on a database including 10,934 records for children of the age 7-18 years. In Poland, in the last 26 years of economic and political transformations, the epidemic of obesity was not noticed but the growing incidence of children and adolescents with body mass deficit was observed (p<0.0001) (20.2% of girls in 2002/2004 vs. 11.0% in 1977/1978 and 12.1% of boys in 2002/2004 vs. 7.2% in 1977/1978). Lower parental education and a higher number of children in a family resulted in a higher prevalence of underweight (odds ratio [OR] fluctuated from 1.26 to 1.63). The social effects of the political transformation in Poland significantly affected families with low socio-economic status (SES), and especially more eco-sensitive boys. This result is opposite to the trends observed in Western countries and makes an important contribution to the current knowledge of the course of further changes in weight-to-height ratio at a global scale.

Evaluation of a 3D point cloud tetrahedral tomographic reconstruction method.

Tomographic reconstruction on an irregular grid may be superior to reconstruction on a regular grid. This is achieved through an appropriate choice of the image space model, the selection of an optimal set of points and the use of any available prior information during the reconstruction process. Accordingly, a number of reconstruction-related parameters must be optimized for best performance. In this work, a 3D point cloud tetrahedral mesh reconstruction method is evaluated for quantitative tasks. A linear image model is employed to obtain the reconstruction system matrix and five point generation strategies are studied. The evaluation is performed using the recovery coefficient, as well as voxel- and template-based estimates of bias and variance measures, computed over specific regions in the reconstructed image. A similar analysis is performed for regular grid reconstructions that use voxel basis functions. The maximum likelihood expectation maximization reconstruction algorithm is used. For the tetrahedral reconstructions, of the five point generation methods that are evaluated, three use image priors. For evaluation purposes, an object consisting of overlapping spheres with varying activity is simulated. The exact parallel projection data of this object are obtained analytically using a parallel projector, and multiple Poisson noise realizations of these exact data are generated and reconstructed using the different point generation strategies. The unconstrained nature of point placement in some of the irregular mesh-based reconstruction strategies has superior activity recovery for small, low-contrast image regions. The results show that, with an appropriately generated set of mesh points, the irregular grid reconstruction methods can out-perform reconstructions on a regular grid for mathematical phantoms, in terms of the performance measures evaluated.

Representation of photon limited data in emission tomography using origin ensembles.

Representation and reconstruction of data obtained by emission tomography scanners are challenging due to high noise levels in the data. Typically, images obtained using tomographic measurements are represented using grids. In this work, we define images as sets of origins of events detected during tomographic measurements; we call these origin ensembles (OEs). A state in the ensemble is characterized by a vector of 3N parameters Y, where the parameters are the coordinates of origins of detected events in a three-dimensional space and N is the number of detected events. The 3N-dimensional probability density function (PDF) for that ensemble is derived, and we present an algorithm for OE image estimation from tomographic measurements. A displayable image (e.g. grid based image) is derived from the OE formulation by calculating ensemble expectations based on the PDF using the Markov chain Monte Carlo method. The approach was applied to computer-simulated 3D list-mode positron emission tomography data. The reconstruction errors for a 10 000 000 event acquisition for simulated ranged from 0.1 to 34.8%, depending on object size and sampling density. The method was also applied to experimental data and the results of the OE method were consistent with those obtained by a standard maximum-likelihood approach. The method is a new approach to representation and reconstruction of data obtained by photon-limited emission tomography measurements.

Secular changes in the physical development of students of the Medical University of Lódz.

This study analyses, using selected somatometric features, secular trend changes which have occurred over a quarter of a century in female and male students of the Medical University of Lódz. The study is based on the results of an anthropometric survey carried out among first-year students who commenced their studies in the academic years 1978/79 (240 females and 193 males), 1982/83 (347 females and 188 males), 1988/89 (178 females and 165 males) and 2003/04 (188 females and 77 males). The following features were examined in all participants in the survey: body height (B-v), the height of the lower body segment measured from a floor base to the crista iliaca at the point on the mid-axillary line (B-ic), shoulder width (a-a), intertrochanteric distance (tro-tro) and resting chest circumference. To compare average values Student's t-test was used with assumptions of equal and unequal variances. To gauge the magnitude of changes in specific features in the course of a quarter of a century a percentage difference in results was calculated for the years 2003/2004 and 1978/1979. The basis for the calculations was the initial value of a feature at the beginning of the period analysed. It was determined that in the 25-year period analysed (1978-2003) the young people commencing studies at the Medical University of Lódz exhibited an acceleration in the height of the lower body segment (B-ic) and of the intertrochanteric distance (tro-tro) and a deceleration in resting chest circumference. Additionally, an increase in shoulder width has been noted in female students; no significant intergenerational changes were noted in body height, although the last 15 years display certain symptoms of deceleration; there is an emerging tendency towards a blurring of the differences in body proportions between the sexes in the environment of the young people studying at the Medical University of Lódz.

Reconstruction of dynamic renal tomographic data acquired by slow rotation.

UNLABELLED: Nuclear medicine renal studies can be performed using slow-rotation SPECT, but reconstruction of such data is largely underdetermined. METHODS: A new method of reconstruction of data acquired using slow camera rotations was developed. In this method we used a factor model of the data in which the factors and factor coefficients were determined by modeling their relationship directly with the projection measurements. This was done by solving a least-squares problem that fits the projections of factors and factor coefficients to the projection data with nonnegativity constraints imposed on the solution. The method was tested on computer simulations and applied to experimental renal (99m)Tc-mercaptoacetyltriglycine canine and patient studies. RESULTS: Computer simulations showed that the extracted time-activity curves of kidneys agreed well with the simulated curves for data with noise levels similar to those in the experimental studies. In the canine study, the method showed that >2 factors were necessary to adequately reproduce the kinetics of the kidney. In the patient study, the method was able to extract separate factors that correspond to the kidney cortex and the kidney pelvis. CONCLUSION: The computer simulation, the canine study, and the patient study all show that reconstructions of the data obtained with 1 detector displayed artifacts, whereas reconstructions of the data obtained with 2 and 3 detectors were free of artifacts. Computer simulations showed that the method gives accurate results that allow quantitation.

Factor analysis with a priori knowledge--application in dynamic cardiac SPECT.

Two factor analysis of dynamic structures (FADS) methods for the extraction of time-activity curves (TACs) from cardiac dynamic SPECT data sequences were investigated. One method was based on a least squares (LS) approach which was subject to positivity constraints. The other method was the well known apex-seeking (AS) method. A post-processing step utilizing a priori information was employed to correct for the non-uniqueness of the FADS solution. These methods were used to extract 99mTc-teboroxime TACs from computer simulations and from experimental canine and patient studies. In computer simulations, the LS and AS methods, which are completely different algorithms, yielded very similar and accurate results after application of the correction for non-uniqueness. FADS-obtained blood curves correlated well with curves derived from region of interest (ROI) measurements in the experimental studies. The results indicate that the factor analysis techniques can be used for semi-automatic estimation of activity curves derived from cardiac dynamic SPECT images, and that they can be used for separation of physiologically different regions in dynamic cardiac SPECT studies.

Multiple line source array for SPECT transmission scans: simulation, phantom and patient studies.

UNLABELLED: Accurate attenuation and scatter corrections in quantitative SPECT studies require attenuation maps of the density distribution in the scanned object. These can be obtained from simultaneous emission/transmission scans. METHODS: A new method has been developed using a multiple line source array (MLA) for transmission scans, and its performance has been investigated using computer simulations and experimental data. The activity in the central lines of the MLA was higher than at the edges of the system, so that more transmission photons would be directed toward the thicker parts of the human body. A series of transmission-only and simultaneous emission/transmission studies were performed for different phantom configurations and human subjects. Attenuation maps were generated and used in reconstruction of attenuation-corrected emission images. RESULTS: The mu coefficients for attenuation maps obtained using the MLA system and simulated and experimental data display no artifacts and are qualitatively and quantitatively correct. For phantoms, the agreement between the measured and the true value of mu for water was found to be better than 4%. The attenuation-corrected emission images for the phantom studies demonstrate that the activity in the heart can be accurately reconstructed. A significant qualitative improvement was also obtained when the attenuation correction was used on patient data. CONCLUSION: Our results indicate that the MLA transmission source can be used in simultaneous transmission/emission imaging to generate accurate attenuation maps. These maps allow for performing an object-specific, attenuation correction of the emission images.

1H-NMR studies on association of mRNA cap-analogues with tryptophan-containing peptides.

1H-NMR spectroscopy was applied to a study of the mode of interaction, in aqueous medium in the pH range 5.2-8.5 and at low and high temperatures, between several mono- and dinucleotide analogues of the mRNA cap m7GpppG and a selected tripeptide Trp-Leu-Glu, and a tetrapeptide Trp-Glu-Asp-Glu, the sequence of which corresponds to one of the suspected binding sites in the mRNA cap-binding protein (CBP). A program, GEOSHIFT, was developed, based on ring-current anisotropy theory, for analysis of experimentally observed changes in chemical shifts accompanying interactions between aromatic heterocyclic rings. This permitted quantitative evaluation of stacking interactions between the m7G cap and the tryptophan indole ring, and the relative orientations of the planes of the two rings, spaced about 3.2 angstroms apart. The structures of the stacked complexes were determined. In particular, stacking between m(2,2,7)3G (which has no free amino group for hydrogen bonding) and the indole ring is weaker and quite different from that between m7G and m(2,7)2G and indole. With the dinucleotide cap-analogues, only the m7G component stacks with the indole ring, without disruption of intramolecular stacking. In contrast to numerous earlier reports, the calculated stacking interactions are quantitatively in accord with the values derived from fluorescence measurements. It also has been shown that the positively charged (cationic) form of m7G stacks much more efficiently with the indole ring than the zwitterionic form resulting from dissociation of the guanine ring N1H (pKa approximately 7.3).