Use of an in-house approach to study the three-dimensional structures of various outer membrane proteins: structure of the alcaligin outer membrane transporter FauA from Bordetella pertussis.

Bordetella pertussis is the bacterial agent of whooping cough in humans. Under iron-limiting conditions, it produces the siderophore alcaligin. Released to the extracellular environment, alcaligin chelates iron, which is then taken up as a ferric alcaligin complex via the FauA outer membrane transporter. FauA belongs to a family of TonB-dependent outer membrane transporters that function using energy derived from the proton motive force. Using an in-house protocol for membrane-protein expression, purification and crystallization, FauA was crystallized in its apo form together with three other TonB-dependent transporters from different organisms. Here, the protocol used to study FauA is described and its three-dimensional structure determined at 2.3 A resolution is discussed.

Comparisons of preoperative three-dimensional planning and surgical reconstruction in primary cementless total hip arthroplasty.

Reconstruction of important parameters such as femoral offset and torsion is inaccurate, when templating is based on plain x-rays. We evaluate intraoperative reproducibility of pre-operative CT-based 3D-templating in a consecutive series of 50 patients undergoing primary cementless THA through an anterior approach. Pre-operative planning was compared to a postoperative CT scan by image fusion. The implant size was correctly predicted in 100% of the stems, 94% of the cups and 88% of the heads (length). The difference between the planned and the postoperative leg length was 0.3 + 2.3 mm. Values for overall offset, femoral anteversion, cup inclination and anteversion were 1.4 mm ± 3.1, 0.6° ± 3.3°, -0.4° ± 5° and 6.9° ± 11.4°, respectively. This planning allows accurate implant size prediction. Stem position and cup inclination are accurately reproducible.

Contrast agent-enhanced, free-breathing, three-dimensional coronary magnetic resonance angiography.

For free-breathing, high-resolution, three-dimensional coronary magnetic resonance angiography (MRA), the use of intravascular contrast agents may be helpful for contrast enhancement between coronary blood and myocardium. In six patients, 0.1 mmol/kg of the intravascular contrast agent MS-325/AngioMARK was given intravenously followed by double-oblique, free-breathing, three-dimensional inversion-recovery coronary MRA with real-time navigator gating and motion correction. Contrast-enhanced, three-dimensional coronary MRA images were compared with images obtained with a T2 prepulse (T2Prep) without exogenous contrast. The contrast-enhanced images demonstrated a 69% improvement in the contrast-to-noise ratio (6.6 +/- 1.1 vs. 11.1 +/- 2.5; P < 0.01) compared with the T2Prep approach. By using the intravascular agent, extensive portions (> 80 mm) of the native left and right coronary system could be displayed consistently with sub-millimeter in-plane resolution. The intravascular contrast agent, MS-325/AngioMARK, leads to a considerable enhancement of the blood/muscle contrast for coronary MRA compared with T2Prep techniques. The clinical value of the agent remains to be defined in a larger patient series. J. Magn. Reson. Imaging 1999;10:790-799.

Breathhold three-dimensional coronary magnetic resonance angiography using real-time navigator technology.

The acquisition duration of most three-dimensional (3D) coronary magnetic resonance angiography (MRA) techniques is considerably prolonged, thereby precluding breathholding as a mechanism to suppress respiratory motion artifacts. Splitting the acquired 3D volume into multiple subvolumes or slabs serves to shorten individual breathhold duration. Still, problems associated with misregistration due to inconsistent depths of expiration and diaphragmatic drift during sustained respiration remain to be resolved. We propose the combination of an ultrafast 3D coronary MRA imaging sequence with prospective real-time navigator technology, which allows correction of the measured volume position. 3D volume splitting using prospective real-time navigator technology, was successfully applied for 3D coronary MRA in five healthy individuals. An ultrafast 3D interleaved hybrid gradient-echoplanar imaging sequence, including T2Prep for contrast enhancement, was used with the navigator localized at the basal anterior wall of the left ventricle. A 9-cm-thick volume, with in-plane spatial resolution of 1.1 x 2.2 mm, was acquired during five breathholds of 15-sec duration each. Consistently, no evidence of misregistration was observed in the images. Extensive contiguous segments of the left anterior descending coronary artery (48 +/- 18 mm) and the right coronary artery (75 +/- 5 mm) could be visualized. This technique has the potential for screening for anomalous coronary arteries, making it well suited as part of a larger clinical MR examination. In addition, this technique may also be applied as a scout scan, which allows an accurate definition of imaging planes for subsequent high-resolution coronary MRA.

Measurements of three-dimensional glenoid erosion when planning the prosthetic replacement of osteoarthritic shoulders.

The three-dimensional (3D) correction of glenoid erosion is critical to the long-term success of total shoulder replacement (TSR). In order to characterise the 3D morphology of eroded glenoid surfaces, we looked for a set of morphological parameters useful for TSR planning. We defined a scapular coordinates system based on non-eroded bony landmarks. The maximum glenoid version was measured and specified in 3D by its orientation angle. Medialisation was considered relative to the spino-glenoid notch. We analysed regular CT scans of 19 normal (N) and 86 osteoarthritic (OA) scapulae. When the maximum version of OA shoulders was higher than 10°, the orientation was not only posterior, but extended in postero-superior (35%), postero-inferior (6%) and anterior sectors (4%). The medialisation of the glenoid was higher in OA than normal shoulders. The orientation angle of maximum version appeared as a critical parameter to specify the glenoid shape in 3D. It will be very useful in planning the best position for the glenoid in TSR.

Three-dimensional patient-specific dosimetry in radioimmunotherapy with 90Y-ibritumomab-tiuxetan.

Aim of the present article was to perform three-dimensional (3D) single photon emission tomography-based dosimetry in radioimmunotherapy (RIT) with (90)Y-ibritumomab-tiuxetan. A custom MATLAB-based code was used to elaborate 3D images and to compare average 3D doses to lesions and to organs at risk (OARs) with those obtained with planar (2D) dosimetry. Our 3D dosimetry procedure was validated through preliminary phantom studies using a body phantom consisting of a lung insert and six spheres with various sizes. In phantom study, the accuracy of dose determination of our imaging protocol decreased when the object volume decreased below 5 mL, approximately. The poorest results were obtained for the 2.58 mL and 1.30 mL spheres where the dose error evaluated on corrected images with regard to the theoretical dose value was -12.97% and -18.69%, respectively. Our 3D dosimetry protocol was subsequently applied on four patients before RIT with (90)Y-ibritumomab-tiuxetan for a total of 5 lesions and 4 OARs (2 livers, 2 spleens). In patient study, without the implementation of volume recovery technique, tumor absorbed doses calculated with the voxel-based approach were systematically lower than those calculated with the planar protocol, with average underestimation of -39% (range from -13.1% to -62.7%). After volume recovery, dose differences reduce significantly, with average deviation of -14.2% (range from -38.7.4% to +3.4%, 1 overestimation, 4 underestimations). Organ dosimetry in one case overestimated, in the other underestimated the dose delivered to liver and spleen. However, both for 2D and 3D approach, absorbed doses to organs per unit administered activity are comparable with most recent literature findings.

Expression of the proto-oncogene c-fos in three-dimensional fetal brain cell cultures and the lack of correlation with maturation-inducing stimuli.

Previous work has shown that aggregating fetal brain cell cultures are able to attain a highly differentiated state, and that their development is greatly enhanced by growth and/or differentiation factors such as epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), and the protein kinase C-activating tumor promoter mezerein. The present study shows that in these 3-dimensional cultures the peptide growth factors EGF and bFGF as well as mezerein are able to induce the expression of the proto-oncogene c-fos. This induction was rapid and transient, in good agreement with observations reported from a wide variety of cell types in vitro. The maximal levels of c-fos mRNA found after stimulation were low in immature cultures and increased greatly as maturation progressed. Of the three factors tested, mezerein was the most potent inducer of c-fos. In contrast to the peptide growth factors EGF and bFGF which were found to induce c-fos only in glial cells, mezerein was stimulatory in glial cells as well as in neurons. A similar cell type specificity has been observed previously for the maturation-enhancing response in immature aggregate cultures. However, in the present study no correlation was found between the degree of c-fos induction and the extent of the maturation-enhancing stimulation. Immature cultures known to be most sensitive and responsive to these maturation-enhancing agents required relatively high doses of peptide growth factors for the induction of c-fos, and the maximal levels of c-fos mRNA elicited were much lower than those in differentiated cultures which did not show any long-term response to these stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)

Improved coronary artery definition with T2-weighted, free-breathing, three-dimensional coronary MRA.

BACKGROUND: Three-dimensional (3D) navigator-gated and prospectively corrected free-breathing coronary magnetic resonance angiography (MRA) allows for submillimeter image resolution but suffers from poor contrast between coronary blood and myocardium. Data collected over >100 ms/heart beat are also susceptible to bulk cardiac and respiratory motion. To address these problems, we examined the effect of a T2 preparation prepulse (T2prep) for myocardial suppression and a shortened acquisition window on coronary definition. METHODS AND RESULTS: Eight healthy adult subjects and 5 patients with confirmed coronary artery disease (CAD) underwent free-breathing 3D MRA with and without T2prep and with 120- and 60-ms data-acquisition windows. The T2prep resulted in a 123% (P<0. 001) increase in contrast-to-noise ratio (CNR). Coronary edge definition was improved by 33% (P<0.001). Acquisition window shortening from 120 to 60 ms resulted in better vessel definition (11%; P<0.001). Among patients with CAD, there was a good correspondence with disease. CONCLUSIONS: Free-breathing, T2prep, 3D coronary MRA with a shorter acquisition window resulted in improved CNR and better coronary artery definition, allowing the assessment of coronary disease. This approach offers the potential for free-breathing, noninvasive assessment of the major coronary arteries.

Three-dimensional computed cementless custom femoral stems in young patients: midterm followup.

We prospectively evaluated the results of our custom cementless femoral stems to ascertain whether this technology produced reasonable clinical function, complication rates, and loosening rates at midterm. Fifty-seven consecutive patients had surgery in 62 hips for primary osteoarthritis at a mean age of 57 years using a three-dimensional computed custom cementless stem. Patients were reviewed at a mean followup of 94.9 months. At review, the mean Harris hip score was 98.8 points (range, 84-100) compared with 61.1 (range, 28-78) points preoperatively. No patient complained of thigh pain. No migration or subsidence was observed. All stems were considered stable according to the radiographic criteria defined by Engh et al. There were no dislocations, no infections, and no reoperations. Our results are comparable with published results from clinical and radiologic points of view. Two problems remain unsolved: the price of a custom stem is twice as expensive as a standard stem; and we need longer term results before definitely recommending this technology as a reasonable alternative to current arthroplasties in younger patients. The data support the continued exploration of this technology with controlled clinical followup. LEVEL OF EVIDENCE: Therapeutic study, Level II-1 (prospective cohort study). See the Guidelines to Authors for a complete description of levels of evidence.

Three-dimensional ordered-subset expectation maximization iterative protocol for evaluation of left ventricular volumes and function by quantitative gated SPECT: a dynamic phantom study.

The purposes of this study were to characterize the performance of a 3-dimensional (3D) ordered-subset expectation maximization (OSEM) algorithm in the quantification of left ventricular (LV) function with (99m)Tc-labeled agent gated SPECT (G-SPECT), the QGS program, and a beating-heart phantom and to optimize the reconstruction parameters for clinical applications. METHODS: A G-SPECT image of a dynamic heart phantom simulating the beating left ventricle was acquired. The exact volumes of the phantom were known and were as follows: end-diastolic volume (EDV) of 112 mL, end-systolic volume (ESV) of 37 mL, and stroke volume (SV) of 75 mL; these volumes produced an LV ejection fraction (LVEF) of 67%. Tomographic reconstructions were obtained after 10-20 iterations (I) with 4, 8, and 16 subsets (S) at full width at half maximum (FWHM) gaussian postprocessing filter cutoff values of 8-15 mm. The QGS program was used for quantitative measurements. RESULTS: Measured values ranged from 72 to 92 mL for EDV, from 18 to 32 mL for ESV, and from 54 to 63 mL for SV, and the calculated LVEF ranged from 65% to 76%. Overall, the combination of 10 I, 8 S, and a cutoff filter value of 10 mm produced the most accurate results. The plot of the measures with respect to the expectation maximization-equivalent iterations (I x S product) revealed a bell-shaped curve for the LV volumes and a reverse distribution for the LVEF, with the best results in the intermediate range. In particular, FWHM cutoff values exceeding 10 mm affected the estimation of the LV volumes. CONCLUSION: The QGS program is able to correctly calculate the LVEF when used in association with an optimized 3D OSEM algorithm (8 S, 10 I, and FWHM of 10 mm) but underestimates the LV volumes. However, various combinations of technical parameters, including a limited range of I and S (80-160 expectation maximization-equivalent iterations) and low cutoff values (< or =10 mm) for the gaussian postprocessing filter, produced results with similar accuracies and without clinically relevant differences in the LV volumes and the estimated LVEF.

A fully adaptive numerical approximation for a two-dimensional epidemic model with nonlinear cross-diffusion

An epidemic model is formulated by a reactionâeuro"diffusion system where the spatial pattern formation is driven by cross-diffusion. The reaction terms describe the local dynamics of susceptible and infected species, whereas the diffusion terms account for the spatial distribution dynamics. For both self-diffusion and cross-diffusion, nonlinear constitutive assumptions are suggested. To simulate the pattern formation two finite volume formulations are proposed, which employ a conservative and a non-conservative discretization, respectively. An efficient simulation is obtained by a fully adaptive multiresolution strategy. Numerical examples illustrate the impact of the cross-diffusion on the pattern formation.

Submillimeter three-dimensional coronary MR angiography with real-time navigator correction: comparison of navigator locations.

Three-dimensional free-breathing coronary magnetic resonance angiography was performed in eight healthy volunteers with use of real-time navigator technology. Images acquired with the navigator localized at the right hemidiaphragm and at the left ventricle were objectively compared. The diaphragmatic navigator was found to be superior for vessel delineation of middle to distal portions of the coronary arteries.

Three-dimensional aspects of fluid flows in channels. II. Effects of meniscus and thin film regimes on viscous fingers

We perform a three-dimensional study of steady state viscous fingers that develop in linear channels. By means of a three-dimensional lattice-Boltzmann scheme that mimics the full macroscopic equations of motion of the fluid momentum and order parameter, we study the effect of the thickness of the channel in two cases. First, for total displacement of the fluids in the channel thickness direction, we find that the steady state finger is effectively two-dimensional and that previous two-dimensional results can be recovered by taking into account the effect of a curved meniscus across the channel thickness as a contribution to surface stresses. Second, when a thin film develops in the channel thickness direction, the finger narrows with increasing channel aspect ratio in agreement with experimental results. The effect of the thin film renders the problem three-dimensional and results deviate from the two-dimensional prediction.

Three-dimensional aspects of fluid flows in channels. I. Meniscus and thin film regimes

We study the forced displacement of a fluid-fluid interface in a three-dimensional channel formed by two parallel solid plates. Using a lattice-Boltzmann method, we study situations in which a slip velocity arises from diffusion effects near the contact line. The difference between the slip and channel velocities determines whether the interface advances as a meniscus or a thin film of fluid is left adhered to the plates. We find that this effect is controlled by the capillary and Péclet numbers. We estimate the crossover from a meniscus to a thin film and find good agreement with numerical results. The penetration regime is examined in the steady state. We find that the occupation fraction of the advancing finger relative to the channel thickness is controlled by the capillary number and the viscosity contrast between the fluids. For high viscosity contrast, lattice-Boltzmann results agree with previous results. For zero viscosity contrast, we observe remarkably narrow fingers. The shape of the finger is found to be universal.