Endogenous neuropeptide Y depresses the afferent signaling of gastric acid challenge to the mouse brainstem via neuropeptide Y type Y2 and Y4 receptors

Vagal afferents signal gastric acid challenge to the nucleus tractus solitarii of the rat brainstem. This study investigated whether nucleus tractus solitarii neurons in the mouse also respond to gastric acid challenge and whether this chemonociceptive input is modified by neuropeptide Y acting via neuropeptide Y receptors of type Y2 or Y4. The gastric mucosa of female mice was exposed to different concentrations of HCl or saline, excitation of neurons in the nucleus tractus solitarii visualized by c-Fos immunohistochemistry, gastric emptying deduced from the gastric volume recovery, and gastric lesion formation evaluated by planimetry. Relative to saline, intragastric HCl (0.15-0.35 M) increased the number of c-Fos-expressing cells in the nucleus tractus solitarii in a concentration-dependent manner, inhibited gastric emptying but failed to cause significant hemorrhagic injury in the stomach. Mice in which the Y2 or Y4 receptor gene had been deleted responded to gastric acid challenge with a significantly higher expression of c-Fos in the nucleus tractus solitarii, the increases amounting to 39 and 31%, respectively. The HCl-induced inhibition of gastric emptying was not altered by deletion of the Y2 or Y4 receptor gene. BIIE0246 ((S)-N2-[[1-[2-[4-[(R,S)-5,11-dihydro-6(6H)-oxodibenz[b,e] azepin-11-yl]-1-piperazinyl]-2-oxoethyl]cyclopentyl] acetyl]-N-[2-[1,2-dihydro-3,5 (4H)-dioxo-1,2-diphenyl-3H-1,2,4-triazol-4-yl]ethyl]-argininamide; 0.03 mmol/kg s.c.), a Y2 receptor antagonist which does not cross the blood-brain barrier, did not modify the c-Fos response to gastric acid challenge. The Y2 receptor agonist peptide YY-(3-36) (0.1 mg/kg intraperitoneally) likewise failed to alter the gastric HCl-evoked expression of c-Fos in the nucleus tractus solitarii. BIIE0246, however, prevented the effect of peptide YY-(3-36) to inhibit gastric acid secretion as deduced from measurement of intragastric pH. The current data indicate that gastric challenge with acid concentrations that do not induce overt injury but inhibit gastric emptying is signaled to the mouse nucleus tractus solitarii. Endogenous neuropeptide Y acting via Y2 and Y4 receptors depresses the afferent input to the nucleus tractus solitarii by a presumably central site of action.

Kombination von dynamischem MR-Sellink und MR-Kolonographie zur Diagnostik des Morbus Crohn

PURPOSE

To investigate whether a combined examination with MRI enteroclysis and MRI colonography is practicable and would provide additional findings in the regions seen with ileo-colonoscopy in the work-up of patients with Crohn's disease.

MATERIAL AND METHODS

Twenty-five consecutive patients with Crohn's disease (CD) (age range 19 to 42 years, mean age 29.2 years, gender ratio male:female 8:17) were retrospectively studied. All patients underwent conventional ileo-colonoscopy as a standard of reference followed by a combined examination of MRI enteroclysis and MRI colonography at 1.5T within 15 days. Two blinded radiologists evaluated the MRI examinations and compared them with the colonoscopic results.

RESULTS

The MRI examination detected 31 inflamed bowel segments in 25 patients. In comparison to colonoscopy, 5 additional, endoscopically inaccessible lesions were found by MRI and only 2 lesions were missed by MRI. Compared to colonoscopy, MRI found 7 of 10 fistulas detected by colonoscopy, and 3 otherwise indiscernible abscesses. The detection of inflamed bowel segments by means of MRI (endoscopy) revealed a sensitivity of 88.8 % (100 %), specificity of 80 % (100 %) and an overall accuracy of 96 % (100 %).

CONCLUSION

This study provides strong evidence that the combination of MRI enteroclysis and MRI colonography is practicable and supplies additional results regarding the regions which are not seen with ileo-colonoscopy in the work-up of patients with Crohn's disease.

Colon dissection: a new three-dimensional reconstruction tool for computed tomography colonography

PURPOSE

To improve the sensitivity of computed tomography (CT) colonography in the detection of polyps by comparing the 3D reconstruction tool "colon dissection" and endoluminal view (virtual colonoscopy) with axial 2D reconstructions.

MATERIAL AND METHODS

Forty-eight patients (22 M, 26 F, mean age 57 +/- 21) were studied after intra-anal air insufflation in the supine and prone positions using a 16-slice helical CT (16 x 0.625 mm, pitch 1.7; detector rotation time 0.5 s; 160 mAs und 120 kV) and conventional colonoscopy. Two radiologists blinded to the results of the conventional colonoscopy analyzed the 3D reconstruction in virtual-endoscopy mode, in colon-dissection mode, and axial 2D slices.

RESULTS

Conventional colonoscopy revealed a total of 35 polyps in 15 patients; 33 polyps were disclosed by CT methods. Sensitivity and specificity for detecting colon polyps were 94% and 94%, respectively, when using the "colon dissection", 89% and 94% when using "virtual endoscopy", and 62% and 100% when using axial 2D reconstruction. Sensitivity in relation to the diameter of colon polyps with "colon dissection", "virtual colonoscopy", and axial 2D-slices was: polyps with a diameter >5.0 mm, 100%, 100%, and 71%, respectively; polyps with a diameter of between 3 and 4.9 mm, 92%, 85%, and 46%; and polyps with a diameter < 3 mm, 89%, 78%, and 56%. The difference between "virtual endoscopy" and "colon dissection" in diagnosing polyps up to 4.9 mm in diameter was statistically significant.

CONCLUSION

3D reconstruction software "colon dissection" improves sensitivity of CT colonography compared with the endoluminal view.

Auswirkung der Feldstärke bei der standardisierten Kernspintomographie des Gehirns am Beispiel der Darstellung von Hirnnerven und Gefäßen in den basalen Zisternen: Vergleich zwischen 1,5 und 3,0 Tesla

PURPOSE

Comparison of MR images acquired as routine examinations at a field strength of 3.0 T and 1.5 T to determine whether and to which degree the image quality improves at the higher field strength of 3.0 T.

MATERIALS AND METHODS

Routine MR images of 200 patients were examined retrospectively, with 100 images obtained at 1.5 T and 100 obtained at 3.0 T. The examinations were performed with a quadrature head coil and focused on the basal cisterns because of the abundance of small distinct structures in this region. We selected the T2-weighted 2D-FSE sequence in transverse direction for comparison. At both field strengths, the same section thickness of 5 mm and a matrix of 512 x 388 (FOV: 220 mm) were used. The quality of the images was evaluated with regard to depicting the cranial nerves N. III, V - X, the AICA and PICA. For comparison, image quality was rated with a score from 1 (well defined) to 5 (not depicted).

RESULTS

A score of 1 was obtained in 46 % of the anatomic structures examined at 3.0 T and in only 9.2 % at 1.5 T. A score of 2 was given in 27.6 % of the anatomic structures at 3.0 T vs. 23.5 % at 1.5 T, a score of 3 in 17.2 % vs. 28.1 %, a score of 4 in 8.6 % vs. 28.7 %, and a score of 5 in 0.4 % vs. 10.3 %, respectively. The Mann-Whitney U test showed significance at p < 0.001 for the comparison of images at 1.5 and 3.0 Tesla.

CONCLUSION

Routine magnetic resonance imaging using the same quadrature coil technique and similar acquisition times at 3.0 T and 1.5 T shows an improvement for T2-weighted images at the higher field strength.

Attenuation correction of SPECT images based on separately performed CT: Effect on the measurement of regional uptake values

AIM

A new software approach uses separately acquired CT images for attenuation correction after retrospective fusion with the SPECT data. This study evaluates the effect of this CT-based attenuation correction on indium-111-pentetreotide-SPECT images.

METHODS

Indium-111-pentetreotide-SPECT imaging using a dual-head gamma camera e.cam (Siemens Medical Solutions, Erlangen, Germany) as well as separate spiral computed tomography (CT) was performed in 13 patients. After fusion of SPECT and CT data, the bilinear attenuation coefficients were calculated for each pixel in the CT image volume using their Hounsfield unit values and attenuation-corrected images were reconstructed iteratively (OSEM 2D). Regions of interest (ROIs) were drawn on 24 suspicious foci and background, and target to background ratios were calculated for corrected (TBAC) and uncorrected (TBNAC) images. The shortest distance from the centre of the lesion to the surface of the body (DS) was measured on the corresponding CT slice. Furthermore, ROIs were drawn over the rim and the centre of the liver. Ratios of hepatic count rates for corrected (LRAC) and uncorrected (LRNAC) images were also compared.

RESULTS

In lesions located more centrally, TBAC was up to 52% higher, whereas in peripherally located lesions, TBAC was up to 63% lower than TBNAC. The TBAC/TBNAC quotient was linearly correlated with DS. In the liver, attenuation correction resulted in a 35% increase of LRAC compared with LRNAC.

CONCLUSIONS

Attenuation correction of SPECT images performed by separately acquired CT data is quick and simple. It improves the contrast between target and background for lesions located more centrally in the body and improves homogeneity of the visualisation of tracer uptake in the liver.

[Detection of airways stenoses: comparison of virtual and flexible bronchoscopy]

PURPOSE

To compare virtual with flexible bronchoscopy for the detection of bronchial stenoses.

MATERIALS AND METHODS

In a retrospective study, we compared the results of 26 patients, who had clinical suspected pathologies of the tracheobronchial airways and underwent both flexible bronchoscopy and multislice CT with 3D surface rendering of the airways. Flexible bronchoscopy and virtual bronchoscopy were compared as to the rate of detecting bronchial stenoses. For statistical analysis, we divided the tracheobronchial tree in the following sections: trachea, 2 main bronchi, 6 lobar bronchi, 18 segmental bronchi and 36 subsegmental bronchi, corresponding to 63 bronchial sections for each patient (on average) and a total of 1638 bronchial sections for all 26 patients. We graded the bronchial stenosis as less than 50 %, as 50 to 95 % and as complete obstruction.

RESULTS

Virtual bronchoscopy detected 25 bronchial stenoses, while flexible bronchoscopy only revealed 17 stenoses. Stenoses with a diameter less than 50 % were found with virtual bronchoscopy 14 times and with flexible bronchoscopy 10 times. Stenoses with a diameter between 50 and 95 % were detected 7 and 4 times, respectively, and complete obstructions 4 and 3 times, respectively. Tracheobronchial stenoses were well recognized with virtual bronchoscopy. Moreover, the virtual method enabled the visualization of high-grade stenoses and post-stenotic areas that could not be passed by the fiberoptic bronchoscope. Virtual bronchoscopy detected stenoses at a higher rate but the difference was not statistically significant (stenoses < 50 %: p = 0.352, 50 - 95 %: p = 0.339, complete obstruction: p = 0.696).

CONCLUSION

Virtual bronchoscopy is a useful non-invasive method for the diagnostic evaluation of the tracheobronchial tree. In comparison with flexible bronchoscopy, virtual bronchoscopy is superior in revealing high-grade stenoses and visualizing post-stenotic areas.

Compensatory changes in [125I]-PYY binding in Y receptor knockout mice suggest the potential existence of further Y receptor(s)

Gene knockout approaches have helped to better understand the functions of the different Y receptors. However, some results obtained from these knockout mice are unexpected and differ from the results of pharmacological intervention experiments. One possible explanation for this is that germ-line gene deletion of a particular Y receptor can influence expression and function of the remaining Y receptors. Here we show that such compensation in mRNA and protein expression does occur in Y receptor single, double and triple knockout models. Radio-ligand binding experiments using [(125)I]-PYY revealed significant up- and down-regulation of remaining Y receptor binding sites in various Y receptor knockout models compared to results from control mice employing Y receptor preferring agonist or antagonists for displacement of the radio-ligand. The most obvious change can be seen in the hippocampus of Y(1) knockout mice, where the level of the remaining Y receptors is strongly down-regulated. In Y(2) knockout mice no such trend can be seen, however, the expression pattern is significantly changed with a strong up-regulation of [(125)I]-PYY specific binding in the dentate gyrus. Interestingly, this pattern was also seen in Y(1)Y(2)Y(4) triple knockout mice. Y(5) receptor mRNA was approximately 20% higher in the hippocampus and dentate gyrus in the triple knockout mice compared to wild-type controls, while Y(6) mRNA expression could not be detected. However, competition binding experiments in Y(1)Y(2)Y(4) triple knockout mice with the Y(5) receptor preferring ligands [Leu(31), Pro(34)] NPY and [A(31), Aib(32)] NPY were able to replace only approximately 50% of [(125)I]-PYY binding in the dentate gyrus suggesting the existence of further yet unidentified Y receptor(s).

Y1-receptors regulate the expression of Y2-receptors in distinct mouse forebrain areas

Y-receptor-knockout mice have become an important tool to elucidate specific physiological roles of individual Y-receptors. However, their phenotypes are not always confirmatory to results obtained by pharmacological investigations in vivo or in vitro. These discrepancies may, at least in part, be due to compensatory changes in the expression of remaining Y-receptor types. To determine whether deletion of individual Y-receptors results in altered mRNA expression and/or binding toward other Y-receptor types, we applied in-situ hybridization and radioligand-binding studies on brain slices of Npy1r-, Npy2r- or Npy5r-knockout mice. Significant changes were seen in Y1-receptor-deficient mice. Thus, Y2-receptor mRNA and (125)I-peptide YY(3-36) binding in the hippocampus proper were increased by up to 55% and 89%, respectively. Similar increases in (125)I-peptide YY(3-36) binding were observed in the caudo-dorsal extension of the lateral septum, an area heavily targeted by hippocampal projections and involved in Y1-receptor-regulated anxiety. Increased (125)I-peptide YY(3-36) binding and Y2-receptor mRNA levels were also observed in the medial amygdaloid nucleus. In contrast, (125)I-peptide YY(3-36) binding was reduced in the central amygdaloid nucleus. Y2-receptor mRNA in the intermediate part of the lateral septum was reduced by 42%. Only minimal changes were observed in Y2- or Y5-receptor-deficient mice. Our results demonstrate that compensatory changes in the expression of Y2-receptors occur in Y1-receptor-deficient mice. These adaptations are likely to contribute to changed physiological function. Thus, alterations in Y2-receptors have to be taken in account upon discussion of Y1-receptor function, especially in emotional aspects like anxiety and aggression, but also alcoholism.

[CT-guided interstitial brachytherapy of lung malignancies. Technique and first results]

CT-guided interstitial brachytherapy of lung malignancies is a novel technique combining (192)Iridium brachytherapy with modern CT guidance for applicator positioning and 3D dosimetry. Initially, this technique has been developed for the treatment of liver malignancies. In the following we describe this novel technique as well as initial results for the treatment of lung malignancies.

[Short-term CT findings after osteosynthesis of fractures of the vertebral spine]

PURPOSE

Evaluation of a correlation between surgical stabilization of fractures of the vertebral spine and postoperative short-term CT findings with special attention to degenerative changes.

MATERIALS AND METHODS

The pre- and post-operative CT of 55 patients (43male, 12 female, age: 7 - 73 years, mean = 37.7 years) with traumatic fractures of the vertebral spine who underwent surgical stabilization using an internal fixator were analyzed retrospectively. The interval between surgical intervention and first postoperative CT control did not exceed one week. The interval to the second short-term follow-up CT ranged from 6 up to 24 months (mean: 10.3 +/- 2.7 months). The consensus reading of the short-term CT by two experienced radiologists was compared to the pre- and immediately postoperative CT examinations and with the neurologic findings. Statistical analysis was done using the chi-square- or the Fisher's exact-test.

RESULTS

No statistically significant correlation (p > 0.05) was found between the patient's age and the postoperative incidence of osteoporosis, spondylarthrosis, scoliosis, spondylolisthesis or disc protrusion after posttraumatic surgical stabilization using an internal fixator. Also, there was no significant correlation between the fracture's type or location, presence of polytraumatization, the technique of surgical intervention, and the incidence of postoperative degenerative changes in the neighboring segments. The thesis has not been verified (p > 0.05) that polysegment stabilization or prior surgical interventions at the vertebral spine with scar induction are responsible for a higher rate of degeneration. The only risk factor observed for postoperative scoliosis was the burst rotation fracture type C1.3 (AO-classification).

CONCLUSIONS

No short-term acceleration of degenerative changes after surgical intervention in vertebral spine fractures was observed. However, due to the short-term interval between surgical intervention and follow-up CT (mean: 10.3 +/- 2.7 months), a final conclusion cannot yet be drawn. A follow-up CT seems to be indicated in patients with increasing complaints during this period. Thus, low grade complications can be diagnosed early.

Magnetresonanztomographiegesteuerter fokussierter Ultraschall (MRgFUS) in der Tumortherapie?eine neuartige nichtinvasive Therapieoption

The demand for minimal or non-invasive therapies especially in tumor therapy is increasing constantly. High frequency focussed ultrasound represents an effective and safe alternative to established thermoablative procedures. In this article we report the advantages of MR-guidance for focussed ultrasound. We describe first clinical experiences in the treatment of uterine fibroids, breast cancer and fibroadenomas of the breast employing MR-guided focussed ultrasound surgery (MRgFUS). This method offers strong potential in the treatment also of other tumorentities since it provides excellent accuracy. Currently numerous efforts are undertaken to introduce MRgFUS for the therapy of liver or cerebral tumors.

FDG PET imaging in hereditary thyroid cancer

AIM

To report the role of different imaging methods in staging individuals with multiple endocrine neoplasia 2A (MEN2A) or familial medullary thyroid carcinoma (FMTC).

MATERIAL AND METHODS

Fourteen newly diagnosed gene carriers underwent cervical ultrasound scanning (US), cervical and mediastinal CT, MRI and whole-body meta-[131I]iodobenzylguanidine (MIBG) scintigraphy and [18F]fluorodeoxyglucose (FDG) PET scanning.

RESULTS

US identified seven true primary cancer. CT and MRI located only tumors > or =5 mm in diameter. MIBG scintigraphy and FDG PET could not identify MTC foci within the thyroid. Whole-body FDG PET identified two true-positive and one false-positive lymph node metastases. MIBG scintigraphy did not identify lymph node metastases. Total thyroidectomy was performed in 12 cases, and subtotal thyroidectomy in two subjects.

CONCLUSIONS

Whole-body FDG PET and cervical US help stage individuals carrying mutant genes verifying MEN2A or FMTC.

[Diagnostic value of three-dimensional reconstruction in CT of traumatic spinal fractures]

PURPOSE

Evaluation of the diagnostic value of three-dimensional CT-reconstruction in the pre-operative evaluation of traumatic fractures of the spine, compared with axial slices and two-dimensional reconstruction.

MATERIALS AND METHODS

The CT image data of 65 patients with 85 different acute traumatic spine fractures (C 2 through L 5) were collected in a period of 42 months. Retrospectively performed 2D- and 3D-reconstructions were analyzed independently by three CT-experienced readers using the Magerl classification and the readings compared with intraoperative findings or the final diagnoses.

RESULTS

The fractures were classified according to the AO-classification as 56 compression, 16 distraction and 13 rotation fractures. Axial slices alone incorrectly classified 2 (1.2 %) of 168 (56 fractures x 3 readers) type A fractures. The CT classification was incorrect in 17 (35.4 %) of 48 (16 fractures x 3 readers) type B fractures and in 31 (79.5 %) of 39 (13 fractures x 3 readers) type C fractures. The 2D-reconstruction increased the percentage of incorrect diagnoses to 13 (7.7 %) type A, to 26 (54.2 %) type B and to 27 (69.2 %) type C fractures. The 3D-mode incorrectly classified 2 of 168 type A fractures (1.2 %), 6 of 48 type B fractures (12.5 %), and 1 of 39 type C fractures (2.6 %). The axial mode was superior to the 2D-reconstructions in type A and type B fractures, but inferior in type C fractures. The percentage of correctly classified type B fractures was significantly higher (p < 0.05) with 3D-reconstruction than with the 2D-mode. In type C fractures, this percentage was significantly higher (p < 0.001) with the 3D-mode than with axial slices or 2D-reconstruction. The interactive monitor analysis of the 3D-reconstructions with additional virtual cutting by the reader improved the analysis, especially the evaluation of the spinal canal.

CONCLUSION

The 3D-reconstruction in traumatic spine fractures significantly improves the diagnostic outcome, especially the visualization and classification of rotation fractures. Its disadvantages are a slight increase in artifacts and impaired visualization of small details. Interactive monitor analysis and post-processing of the 3D-mode proved to be advantageous.