Engineered bacterial host for genetic encoding of physiologically stable protein nitration.

Across scales, many biological phenomena, such as protein folding or bioadhesion and cohesion, rely on synergistic effects of different amino acid side chains at multiple positions in the protein sequence. These are often fine-tuned by post-translational modifications that introduce additional chemical properties. Several PTMs can now be genetically encoded and precisely installed at single and multiple sites by genetic code expansion. Protein nitration is a PTM of particular interest because it has been associated with several diseases. However, even when these nitro groups are directly incorporated into proteins, they are often physiologically reduced during or shortly after protein production. We have solved this problem by using an engineered Escherichia coli host strain. Six genes that are associated with nitroreductase activity were removed from the genome in a simple and robust manner. The result is a bacterial expression host that can stably produce proteins and peptides containing nitro groups, especially when these are amenable to modification. To demonstrate the applicability of this strain, we used this host for several applications. One of these was the multisite incorporation of a photocaged 3,4-dihydroxyphenylalanine derivative into Elastin-Like Polypeptides. For this non-canonical amino acid and several other photocaged ncAAs, the nitro group is critical for photocleavability. Accordingly, our approach also enhances the production of biomolecules containing photocaged tyrosine in the form of ortho-nitrobenzyl-tyrosine. We envision our engineered host as an efficient tool for the production of custom designed proteins, peptides or biomaterials for various applications ranging from research in cell biology to large-scale production in biotechnology.

Halogenation of tyrosine perturbs large-scale protein self-organization.

Protein halogenation is a common non-enzymatic post-translational modification contributing to aging, oxidative stress-related diseases and cancer. Here, we report a genetically encodable halogenation of tyrosine residues in a reconstituted prokaryotic filamentous cell-division protein (FtsZ) as a platform to elucidate the implications of halogenation that can be extrapolated to living systems of much higher complexity. We show how single halogenations can fine-tune protein structures and dynamics of FtsZ with subtle perturbations collectively amplified by the process of FtsZ self-organization. Based on experiments and theories, we have gained valuable insights into the mechanism of halogen influence. The bending of FtsZ structures occurs by affecting surface charges and internal domain distances and is reflected in the decline of GTPase activities by reducing GTP binding energy during polymerization. Our results point to a better understanding of the physiological and pathological effects of protein halogenation and may contribute to the development of potential diagnostic tools.

IL-6-induced FOXO1 activity determines the dynamics of metabolism in CD8 T cells cross-primed by liver sinusoidal endothelial cells.

Liver sinusoidal endothelial cells (LSECs) are liver-resident antigen (cross)-presenting cells that generate memory CD8 T cells, but metabolic properties of LSECs and LSEC-primed CD8 T cells remain understudied. Here, we report that high-level mitochondrial respiration and constitutive low-level glycolysis support LSEC scavenger and sentinel functions. LSECs fail to increase glycolysis and co-stimulation after TLR4 activation, indicating absence of metabolic and functional maturation compared with immunogenic dendritic cells. LSEC-primed CD8 T cells show a transient burst of oxidative phosphorylation and glycolysis. Mechanistically, co-stimulatory IL-6 signaling ensures high FOXO1 expression in LSEC-primed CD8 T cells, curtails metabolic activity associated with T cell activation, and is indispensable for T cell functionality after re-activation. Thus, distinct immunometabolic features characterize non-immunogenic LSECs compared with immunogenic dendritic cells and LSEC-primed CD8 T cells with memory features compared with effector CD8 T cells. This reveals local features of metabolism and function of T cells in the liver.

Efficient Unnatural Protein Production by Pyrrolysyl-tRNA Synthetase With Genetically Fused Solubility Tags.

Introducing non-canonical amino acids (ncAAs) by engineered orthogonal pairs of aminoacyl-tRNA synthetases and tRNAs has proven to be a highly useful tool for the expansion of the genetic code. Pyrrolysyl-tRNA synthetase (PylRS) from methanogenic archaeal and bacterial species is particularly attractive due to its natural orthogonal reactivity in bacterial and eukaryotic cells. However, the scope of such a reprogrammed translation is often limited, due to low yields of chemically modified target protein. This can be the result of substrate specificity engineering, which decreases the aminoacyl-tRNA synthetase stability and reduces the abundance of active enzyme. We show that the solubility and folding of these engineered enzymes can become a bottleneck for the production of ncAA-containing proteins in vivo. Solubility tags derived from various species provide a strategy to remedy this issue. We find the N-terminal fusion of the small metal binding protein from Nitrosomonas europaea to the PylRS sequence to improve enzyme solubility and to boost orthogonal translation efficiency. Our strategy enhances the production of site-specifically labelled proteins with a variety of engineered PylRS variants by 200-540%, and further allows triple labeling. Even the wild-type enzyme gains up to 245% efficiency for established ncAA substrates.

Virtual Quality Control in Middle Ear Surgery: Is Image-guided Tympanoscopy a Valuable Tool for Depicting Borderline Situations?

HYPOTHESIS: Before modern imaging was introduced, revision surgery was the only way to evaluate possible reasons for inadequate improvement in hearing after ossicular replacement during reconstructive middle ear surgery. BACKGROUND: The aim of this study was to evaluate freely navigable virtual tympanoscopy using different computed tomographic modalities. We compared cone-beam computed tomography (CBCT), flat panel computed tomography (FPCT), and conventional computed tomography in helical mode (CTH), volume mode (CTV), and ultra high resolution mode (CTD). METHODS: Four temporal bone specimens were reconstructed with partial or total ossicular replacement prostheses. The best functional results for prosthetic coupling were achieved under the control of laser Doppler vibrometry (LDV). Afterward, a progressive step-by-step decoupling of the prostheses was carried out. Different prosthesis positions were evaluated by LDV as well as different computed tomographic modalities with 3D reconstruction of each dataset. RESULTS: Anatomical structures were better depicted and the best position and coupling of inserted prostheses were achieved using CBCT. All imaging techniques could be used to control the position of middle ear prostheses, but CBCT provided the highest resolution and the best image quality in both 2D and 3D reformations and in 3D-animated video representation. CONCLUSION: Compared with several other imaging modalities, CBCT was best at depicting miscellaneous coupling problems. Noninvasive detection of coupling problems caused by minimal loss of contact between prostheses and middle ear ossicles will influence the clinical outcome. This early detection will help to determine whether revision surgery is needed.

Regulatory myeloid cells paralyze T cells through cell-cell transfer of the metabolite methylglyoxal.

Regulatory myeloid immune cells, such as myeloid-derived suppressor cells (MDSCs), populate inflamed or cancerous tissue and block immune cell effector functions. The lack of mechanistic insight into MDSC suppressive activity and a marker for their identification has hampered attempts to overcome T cell inhibition and unleash anti-cancer immunity. Here, we report that human MDSCs were characterized by strongly reduced metabolism and conferred this compromised metabolic state to CD8+ T cells, thereby paralyzing their effector functions. We identified accumulation of the dicarbonyl radical methylglyoxal, generated by semicarbazide-sensitive amine oxidase, to cause the metabolic phenotype of MDSCs and MDSC-mediated paralysis of CD8+ T cells. In a murine cancer model, neutralization of dicarbonyl activity overcame MDSC-mediated T cell suppression and, together with checkpoint inhibition, improved the efficacy of cancer immune therapy. Our results identify the dicarbonyl methylglyoxal as a marker metabolite for MDSCs that mediates T cell paralysis and can serve as a target to improve cancer immune therapy.

rAAV Engineering for Capsid-Protein Enzyme Insertions and Mosaicism Reveals Resilience to Mutational, Structural and Thermal Perturbations.

Recombinant adeno-associated viruses (rAAV) provide outstanding options for customization and superior capabilities for gene therapy. To access their full potential, facile genetic manipulation is pivotal, including capsid loop modifications. Therefore, we assessed capsid tolerance to modifications of the structural VP proteins in terms of stability and plasticity. Flexible glycine-serine linkers of increasing sizes were, at the genetic level, introduced into the 587 loop region of the VP proteins of serotype 2, the best studied AAV representative. Analyses of biological function and thermal stability with respect to genome release of viral particles revealed structural plasticity. In addition, insertion of the 29 kDa enzyme ß-lactamase into the loop region was tested with a complete or a mosaic modification setting. For the mosaic approach, investigation of VP2 trans expression revealed that a Kozak sequence was required to prevent leaky scanning. Surprisingly, even the full capsid modification with ß-lactamase allowed for the assembly of capsids with a concomitant increase in size. Enzyme activity assays revealed lactamase functionality for both rAAV variants, which demonstrates the structural robustness of this platform technology.

Antimicrobial Peptides Produced by Selective Pressure Incorporation of Non-canonical Amino Acids.

Nature has a variety of possibilities to create new protein functions by modifying the sequence of the individual amino acid building blocks. However, all variations are based on the 20 canonical amino acids (cAAs). As a way to introduce additional physicochemical properties into polypeptides, the incorporation of non-canonical amino acids (ncAAs) is increasingly used in protein engineering. Due to their relatively short length, the modification of ribosomally synthesized and post-translationally modified peptides by ncAAs is particularly attractive. New functionalities and chemical handles can be generated by specific modifications of individual residues. The selective pressure incorporation (SPI) method utilizes auxotrophic host strains that are deprived of an essential amino acid in chemically defined growth media. Several structurally and chemically similar amino acid analogs can then be activated by the corresponding aminoacyl-tRNA synthetase and provide residue-specific cAA(s) → ncAA(s) substitutions in the target peptide or protein sequence. Although, in the context of the SPI method, ncAAs are also incorporated into the host proteome during the phase of recombinant gene expression, the majority of the cell's resources are assigned to the expression of the target gene. This enables efficient residue-specific incorporation of ncAAs often accompanied with high amounts of modified target. The presented work describes the in vivo incorporation of six proline analogs into the antimicrobial peptide nisin, a lantibiotic naturally produced by Lactococcus lactis. Antimicrobial properties of nisin can be changed and further expanded during its fermentation and expression in auxotrophic Escherichia coli strains in defined growth media. Thereby, the effects of residue-specific replacement of cAAs with ncAAs can deliver changes in antimicrobial activity and specificity. Antimicrobial activity assays and fluorescence microscopy are used to test the new nisin variants for growth inhibition of a Gram-positive Lactococcus lactis indicator strain. Mass spectroscopy is used to confirm ncAA incorporation in bioactive nisin variants.

Experimental Simulation of Clinical Borderline Situations in Temporal Bone Specimens After Ossiculoplasty.

OBJECTIVES: One reason for insufficient hearing improvement with a distinct air-bone gap after ossiculoplasty with implantation of partial or total ossicular replacement prostheses can be the dislocation or minimal shifting of the prosthesis. The aim of this study was the simulation of common clinical borderline situations with minimal shifting of the prosthesis in temporal bone specimens after ossiculoplasty. It was furthermore the goal to identify these specific situations through imaging by cone beam computed tomography (cbCT) and direct visual inspection using the operation microscope. Additionally, the functional status was evaluated using laser-Doppler vibrometry (LDV). DESIGN: We used a total of four temporal bone specimens for this study. A reconstruction with a partial ossicular replacement prostheses was performed in three specimens and with a total ossicular replacement prostheses in one specimen, with good initial acoustic properties. Subsequently, one specific type of prosthesis failure was simulated in each specimen, respectively, by minimally shifting, tilting, or bending the prostheses from their initial positions. These changes were introduced step-by-step until a borderline situation just short of complete acoustic decoupling was reached. Each step was examined using both LDV and cbCT and observed through the operation microscope. RESULTS: LDV was able to quantify the mechanic function of the ossicular chain after most of the manipulation steps by demonstrating the effect of any shifting of the prosthesis on the middle ear transfer function. However, in some situations, the middle ear transfer function was better with a visually more advanced failure of the prosthesis. In addition, cbCT showed most of the steps with excellent resolution and was able to delineate changes in soft tissue (e.g., cartilage covering). CONCLUSION: cbCT seems to be a promising imaging technique for middle ear problems. As cbCT and LDV exhibited slightly different advantages and disadvantages regarding the demonstration of borderline situations, the combination of both techniques allowed for a more precise evaluation of middle ear reconstructions. Knowledge of the specific characteristics of these methods and their possible combination might help otologists and otosurgeons to refine indications for revision surgery and improve their personal patient counseling.

Differentiating locally recurrent rectal cancer from scar tissue: Value of diffusion-weighted MRI.

OBJECTIVES: To determine a cut-off apparent diffusion coefficient (ADC) value distinguishing local recurrence from scar tissue in patients with rectal cancer treated with complete surgical tumour removal. METHODS: 72 patients were retrospectively included. Patients underwent 1.5T MRI including multiplanar T2-weighted turbo-spin-echo sequences (TSE) and axial single-shot epi-diffusion-weighted sequences (EPSE). Two independent observers measured mean tumour and scar tissue ADCs by manually drawing regions of interest (ROIs). The t-test and ROC analysis were used for comparison and determining an optimal discrimination threshold. As reference standard histopathological results were used in 23 patients (32%) and clinical follow-up in 49 patients (68%). RESULTS: Recurrent rectal cancer was found in 30 patients (4 female, 26 male, median age 63.13 years) and treatment related changes such as scar tissue in 42 patients (11 female, 31 male, median age 63.67 years). The mean ADC value of tumour recurrence was 1.02×10(-3)mm(2)/s (0.63-1.44×10(-3)mm(2)/s) and of scar tissue 1.77×10(-3)mm(2)/s (1.11-2.41×10(-3)mm(2)/s) showing a statistically significant difference (p<0.001). The cut-off ADC value was 1.34×10(-3)mm(2)/s with a sensitivity, specificity, and accuracy of 93%, 91%, and 92% respectively. CONCLUSIONS: Diffusion weighted MRI allows for the differentiation of tumour recurrence from scar tissue after surgical resection of rectal cancer.

Gastroenteropancreatic neuroendocrine tumours (GEP-NET) - Imaging and staging.

Detection of gastroenteropancreatic neuroendocrine tumours (GEP-NETs) and monitoring of treatment response relies mainly on morphological imaging such as computed tomography (CT) and magnetic resonance imaging (MRI). Molecular imaging techniques also in combination with CT (hybrid imaging) greatly benefit patient management, including better localization of occult tumours and better staging. Somatostatin receptor scintigraphy (SRS) and somatostatin receptor (SSTR) positron emission tomography (PET) play a central role in the diagnostic work-up of patients with well-differentiated GEP-NETs. SSTR PET/CT is superior to SRS and should be used whenever available. (18)F-DOPA and (18)F-FDG PET/CT is inferior to SSTR PET/CT at least in patients with well-differentiated GEP-NETs. Both SSTR PET/CT and SRS have limitations, such as relatively low detection rate of benign insulinomas, poorly differentiated GEP-NETs and liver metastases. New innovations such as SSTR PET/MRI, radiolabelled SSTR antagonists and glucagon-like peptide-1 receptor (GLP-1R) agonists might further improve imaging of GEP-NETs.

Extremity-dedicated low-field MRI shows good diagnostic accuracy and interobserver agreement for the diagnosis of the acutely injured knee.

OBJECTIVES: To estimate diagnostic accuracy and interobserver agreement of extremity-dedicated low-field magnetic resonance imaging (lfMRI) for meniscal tears, anterior cruciate ligament (ACL) tears and knee fractures. METHODS: We enrolled 62 patients with acute knee trauma and 19 patients with suspected knee fracture. Arthroscopy/Computed tomography was regarded the gold standard for cruciate ligament and meniscal tears/fractures. RESULTS: Arthroscopy showed 39 meniscal tears. Sensitivity/Specificity of lfMRI was 95.8%/97.4% (reader 1)/100%/100% (reader 2) for medial and 93.3%/100% (reader 1)/93.3%/93.6% (reader 2) for lateral meniscal tears. Sensitivity/Specificity was 100% for ACL tears and fractures. Interobserver agreement was very good. CONCLUSION: lfMRI showed reproducible high sensitivity and specificity for the diagnosis of the acutely injured knee.

To band or not to band--early results of banded sleeve gastrectomy.

Laparoscopic sleeve gastrectomy (LSG) is the procedure with the fastest growing numbers worldwide. Although excellent weight loss can be achieved, one major obstacle of LSG is weight regain due to sleeve dilatation. Banded sleeve gastrectomy (BLSG) has been described as an option to counteract sleeve dilatation and ameliorate weight loss over time. In a retrospective study, we analysed 25 patients who underwent BLSG using a MiniMizer® ring. Twenty five patients who had previously undergone a conventional LSG were selected for matched-pair analysis. Patient follow-up was 12 months in both groups. Mean preoperative BMI was 56.1 ± 7.2 kg/m(2) for BLSG and 57.0 ± 6.3 kg/m(2) for LSG, P = 0.522. Operative time was significantly shorter for BLSG (53 ± 27 min vs. 68 ± 20 min, P = 0.0025). Excess weight loss (%EWL) was equal in both groups with %EWL at 12 months of 58.0 ± 14.6 % for BSLG patients vs. 58.4 ± 19.2 % for LSG patients. There was no procedure-related mortality in either group. At 12 months postoperative, vomiting was significantly increased in BSLG patients (OR 6.75, P = 0.035). New onset reflux was equal in both groups (OR 0.67, P = 0.469). Ring implantation does not increase the duration of surgery or early surgical complications. Weight loss in the first follow-up year is not influenced, but the incidence of vomiting is raised after 12 months when patients start to increase eating volume.

Modular adeno-associated virus (rAAV) vectors used for cellular virus-directed enzyme prodrug therapy.

The pre-clinical and clinical development of viral vehicles for gene transfer increased in recent years, and a recombinant adeno-associated virus (rAAV) drug took center stage upon approval in the European Union. However, lack of standardization, inefficient purification methods and complicated retargeting limit general usability. We address these obstacles by fusing rAAV-2 capsids with two modular targeting molecules (DARPin or Affibody) specific for a cancer cell-surface marker (EGFR) while simultaneously including an affinity tag (His-tag) in a surface-exposed loop. Equipping these particles with genes coding for prodrug converting enzymes (thymidine kinase or cytosine deaminase) we demonstrate tumor marker specific transduction and prodrug-dependent apoptosis of cancer cells. Coding terminal and loop modifications in one gene enabled specific and scalable purification. Our genetic parts for viral production adhere to a standardized cloning strategy facilitating rapid prototyping of virus directed enzyme prodrug therapy (VDEPT).

Temporally constrained respiratory gating improves continuously moving table MRI during free breathing.

PURPOSE: To evaluate a novel breathing motion correction algorithm for continuously moving table magnetic resonance imaging (CMT-MRI) that optimizes motion consistency in a fixed time span. MATERIALS AND METHODS: In 22 patients CMT-MRI was performed during free breathing. During a preparatory phase (constant) or continuously during the scan (adaptive) gating thresholds were computed from breathing states that should allow for motion consistent k-space sampling. After data from a first k-space traversal was acquired irrespective of breathing motion, subsequently k-space lines with discordant breathing states were reacquired below the gating threshold. Time constraints of CMT-MRI were respected, because a fixed time was allocated for reacquisition. Image quality and lesion depiction were evaluated on images reconstructed from the first traversal and motion-corrected images. RESULTS: Compared to constant thresholds, gating with adaptive thresholds led to a higher number of reacquired k-space lines (60.1%/41.7%) and a larger fraction of motion consistent final k-space lines (96.6%/78.8%). Adaptive gating induced a significant increase in image quality for all regions affected by breathing motion. Only one of 22 lesions was not depicted on the adaptively corrected images, whereas 15 were readily appreciable. CONCLUSION: Temporally constrained respiratory gating with adaptive thresholds allows for fully sampled, motion-corrected CMT-MRI acquisitions during free breathing.

Dose reduction does not affect detection of bone marrow lesions with dual-energy CT virtual noncalcium technique.

RATIONALE AND OBJECTIVES: The aim of this study was to evaluate if a dose-reduced, dose-neutral dual-energy computed tomographic (CT) virtual noncalcium technique can equally detect posttraumatic bone marrow lesions (BMLs) of the knee. MATERIALS AND METHODS: Fifty patients underwent DE CT imaging with either a standard dose (group A) or a dose equal to that of a single-energy CT scan (group B) (28% dose reduction) and magnetic resonance imaging for knee trauma workup. Calcium was virtually subtracted from the images. Two radiologists rated the presence of abnormal soft tissue-like attenuation in the bone marrow in a total of 12 femoral and tibial regions and performed Hounsfield unit measurements thereafter. Receiver-operating characteristic curve analysis was used for four-point rating scores and Hounsfield unit measurements. Fractures were classified. RESULTS: Magnetic resonance imaging depicted 170 BMLs (35 femoral, 135 tibial). Mean age, number of fractures, attenuation values and number of regions with BMLs were not significantly different between the groups. Visual rating revealed overall areas under the curves of 0.983 and 0.979 for observers 1 and 2, respectively. Visual judgment was superior to attenuation measurements for femoral regions regardless of the dose applied. Analysis of variance of all CT values revealed a significant influence for the presence of edema (P < .001) but no differences for the radiation dose used (P = .424). Interobserver agreement was excellent (κ = 0.944). CONCLUSIONS: Dose reduction does not affect the detectability of posttraumatic BMLs with a dual-energy CT virtual noncalcium technique, thereby providing potential additional information compared with single-energy CT imaging without additional radiation dose.

Revisionary bariatric surgery: indications and outcome of 100 consecutive operations at a single center.

BACKGROUND: A growing number of revisionary and secondary bariatric operations have been performed in recent years, with the number of operations doubling each year at the authors' center. Diagnostics, indications, and most revisionary operations should be performed by an experienced bariatric surgeon. This study was undertaken to evaluate indications and outcomes of revisionary bariatric operations at a specialized center. METHODS: At the Centre of Obesity and Metabolic Surgery (University of Freiburg, Germany), 100 consecutive revisionary bariatric operations performed between March 2007 and September 2009 were analyzed concerning indications and outcomes. RESULTS: Only 9 of the 100 revisions were due to early complications (<30 days after the primary operation). The indication for most revisions was poor weight loss (n = 55). A mean body mass index reduction of 10 points could be achieved in 1 year, which equals a 56% excess weight loss (EWL). No significant difference in weight reduction between restrictive and malabsorptive revisions was observed. Revisions due to implant-related problems also were frequent (n = 25). Laparoscopic revision was possible in 95% of the cases. CONCLUSION: Insufficient weight loss is the most frequent indication for revisionary bariatric surgery. The surgery can be performed laparoscopically in most cases, and a significant EWL (> 50%) can be achieved in 1 year if the right revisionary procedure is chosen.

Three-dimensional stomach analysis with computed tomography after laparoscopic sleeve gastrectomy: sleeve dilation and thoracic migration.

BACKGROUND: Laparoscopic sleeve gastrectomy (LSG) is frequently performed as a definitive bariatric procedure today. Quantitative data on the detailed anatomy of the stomach after LSG are yet sparse. METHODS: Thirty-two multislice computed tomography (MSCT) data sets acquired in 27 LSG patients (22 female, 5 male) with a dedicated examination protocol and post-processing were evaluated for gastric volume, stomach length, sleeve length, antrum length, staple line length, and maximum cross-sectional sleeve area. Obtained parameters were compared to time after surgery, weight loss, and the occurrence of postsurgical regurgitation. RESULTS: Mean gastric volume was 186.5±88.4 ml. Gastric volume correlated significantly with the time interval after surgery. Sleeve sizes of 105.3±30.2 ml during early follow-up confirmed correct primary sizing of the sleeve, whereas marked dilation to 196.8±84.3 ml was found in patients with a follow-up of 6 months and longer (p=0.038). Sleeve area and staple line length were also positively correlated with time after surgery. No correlation was found between gastric volume and excess weight loss. In ten patients an intrathoracic migration of the staple line could be noted, with four of these patients developing persistent regurgitation after LSG. Regurgitation was present in only 2 of 17 patients without sleeve herniation. CONCLUSION: Multislice computed tomography allows for a comprehensive and quantitative evaluation of the anatomy after LSG and thus provides new insights in the process of sleeve dilation. Intrathoracic migration of the staple line could be identified as a possible cause of persistent regurgitation.

Time-resolved MRI after ingestion of liquids reveals motility changes after laparoscopic sleeve gastrectomy--preliminary results.

BACKGROUND: Laparoscopic sleeve gastrectomy (LSG) is generally considered a restrictive procedure. However, studies with nuclear medicine techniques have demonstrated that gastric motility changes occur following LSG. These motility changes could represent complementary mechanisms of weight loss. Therefore, we analyzed the stomach motility before and after LSG by means of dynamic MRI. METHODS: In this prospective pilot study, five female patients with a mean BMI of 51.6 kg/m(2) underwent MRI 1 day before LSG and 6 days and 6 months after LSG. Dynamic steady-state free precession sequences were used to analyze the gastric motility after ingestion of 500 ml water with a temporal resolution of 0.86 s. Axial image stacks were also repeatedly acquired to determine the intragastric fluid volume over time. RESULTS: Mean excess body mass index loss was 60.6% after 6 months. Dynamic analysis showed that antral propulsive peristalsis was preserved immediately after surgery and during follow-up, but fold speed increased significantly from 2.7 mm/s before LSG to 4.4 mm/s after 6 months. The sleeve itself remained without recognizable peristalsis in three patients and showed only uncoordinated or passive motion in two patients. Consequently, the fluid transport through the sleeve was markedly delayed, whereas the antrum showed accelerated propulsion with the emptying half-time decreasing from 16.5 min preoperatively to 7.9 min 6 months after surgery. CONCLUSIONS: Owing to the LSG procedure, the stomach is functionally divided into a sleeve without propulsive peristalsis and an accelerated antrum. Accelerated emptying seems to be caused by faster peristaltic folds.

Influence of arm positioning on radiation dose for whole body computed tomography in trauma patients.

BACKGROUND: Multislice whole body computed tomography is regarded as the method of choice for primary investigation of hemodynamically stable patients with multiple injuries. However, a disadvantage of this method is the high level of radiation to which the patient is exposed. Various recommendations on how to position the patient's arms during whole body computed tomography have been given in the literature, but conclusive data are missing. Therefore, the aim of our study was to investigate the relationship between different arm positions and radiation dose in patients undergoing whole body computed tomography. METHODS: In a retrospective analysis of available data derived from former whole body computed tomography screening of patients with multiple injuries, we calculated the effective radiation dose and scanning time for different arm positions (both arms up, both arms at sides, right arm up, and left arm up). Statistical analysis was performed using the independent t test with 95% confidence intervals. Statistical significance was set at 0.05. RESULTS: The data evaluated had been recorded for 956 patients during a period of 18 months. Of these patients, 710 were included in the study. In 487 cases (68%), both arms were up; in 82 cases (12%), down by the sides; in 90 cases (13%), the right arm was up; and in 44 cases (6%), the left arm was up. Overall, the radiation dose was statistically significantly higher with both arms at sides (24.69 mSv ± 6.91 mSv) than with both arms up (19.18 mSv ± 4.99 mSv; p < 0.0000001). Statistically significant differences in effective radiation dose were not found for either the right arm up (23.52 mSv ± 5.23 mSv; p = 0.211) or the left arm up (22.53 mSv ± 5.4 mSv; p = 0.076) compared with both arms down at sides. Comparison of scan lengths for the thorax or abdomen did not yield any significant differences between arms down and any other arm position. Analysis of scanning times did not reveal any significant differences for whole body computed tomography with both arms down (07:31 minutes ± 02:53 minutes) compared with both arms up (07:30 minutes ± 02:04 minutes; p = 0.94), right arm up (07:15 minutes ± 01:43 minutes; p = 0.582), or left arm up (07:18 minutes ± 01:24 minutes; p = 0.707). CONCLUSION: Based on our retrospective investigation, it can be recommended with reference to whole body computed tomography screening that the arms should be in the arms-up position during thorax or abdomen scanning of a severely injured patient, provided there are no clear clinical indications of shoulder injury. For the patient, this position is associated with a significantly reduced radiation dose without noticeable loss of time.