Coupling of endothelin receptors to the ERK/MAP kinase pathway. Roles of palmitoylation and G(alpha)q.

Endothelins are potent mitogens that stimulate extracellular signal-regulated kinases (ERK/MAP kinases) through their cognate G-protein-coupled receptors, ET(A) and ET(B). To address the role of post-translational ET receptor modifications such as acylation on ERK activation and to identify relevant downstream effectors coupling the ET receptor to the ERK signaling cascades we have constructed a panel of palmitoylation-deficient ET receptor mutants with differential G(alpha) protein binding capacity. Endothelin-1 stimulation of wild-type ET(A) or ET(B) induced a fivefold to sixfold increase in ERK in COS-7 and CHO cells whereas full-length nonpalmitoylated ET(A) and ET(B) mutants failed to stimulate ERK. A truncated ET(B) lacking the C-terminal tail domain including putative phosphorylation and arrestin binding site(s) but retaining the critical palmitoylation site(s) was still able to fully stimulate ERK activation. Using mutated ET receptors with selective G-protein-coupling we found that endothelin-induced stimulation of G(alpha)q, but not of G(alpha)i or G(alpha)s, is essential for endothelin-mediated ERK activation. Inhibition of protein kinases A and C or epidermal growth factor receptor kinase failed to prevent ET(A)- and ET(B)-mediated ERK activation whereas blockage of phospholipase C-beta completely abrogated endothelin-promoted ERK activation through ET(A) and ET(B) in recombinant COS-7 and native C6 cells. Complex formation of Ca2+ or inhibition of Src family tyrosine kinases prevented ET-1-induced ERK-2 activation in C6-cells. Our results indicate that endothelin-promoted ERK/MAPK activation criticially depends on palmitoylation but not on phosphorylation of ET receptors, and that the G(alpha)q/phospholipase C-beta/Ca2+/Src signaling cascade is necessary for efficient coupling of ET receptors to the ERK/MAPK pathway.

Determination of bradykinin B2 receptor in vivo phosphorylation sites and their role in receptor function.

Reversible phosphorylation plays important roles in G protein-coupled receptor signaling, desensitization, and endocytosis, yet the precise location and role of in vivo phosphorylation sites is unknown for most receptors. Using metabolic 32P labeling and phosphopeptide sequencing we provide a complete phosphorylation map of the human bradykinin B2 receptor in its native cellular environment. We identified three serine residues, Ser(339), Ser(346), and Ser(348), at the C-terminal tail as principal phosphorylation sites. Constitutive phosphorylation occurs at Ser(348), while ligand-induced phosphorylation is found at Ser(339) and Ser(346)/Ser(348) that could be executed by several G protein-coupled receptor kinases. In addition, we found a protein kinase C-dependent phosphorylation of Ser(346) that was mutually exclusive with the basal phosphorylation at Ser(348) and therefore may be implicated in differential regulation of B2 receptor activation. Functional analysis of receptor mutants revealed that a low phosphorylation stoichiometry is sufficient to initiate receptor sequestration while a clustered phosphorylation around Ser(346) is necessary for desensitization of the B2 receptor-induced phospholipase C activation. This was further supported by the specifically reduced Ser(346)/Ser(348) phosphorylation observed upon stimulation with a nondesensitizing B2 receptor agonist. The differential usage of clustered phosphoacceptor sites points to distinct roles of multiple kinases in controlling G protein-coupled receptor function.

[Comparison of CT and MRI methods in diagnosis of tumors of the para- and retropharyngeal space and temporal bone]. / Methodenvergleich von CT und MRT in der Diagnostik von Tumoren des Para- und Retropharyngealraumes und des Schläfenbeines.

The aim of this paper was to compare the diagnostic value of computed tomography (CT) and magnetic resonance imaging (MRI) in the evaluation of malignant tumors of the temporal bone, of paragangliomas of the glomus tympanicum and jugulare as well as of malignant tumors of the para- and retropharyngeal space. 67 patients with tumors of the temporal bone--28 cases with malignant tumors and 39 cases with paragangliomas--were examined with MRI and CT. MRI had true-positive findings in nearly 93, CT in 89% of the patients with malignant tumors of the temporal bone. MRI is therefore recommended as the primary imaging investigation of malignant tumors of the temporal bone. Whereas the temporal bone is best visualized by high-resolution CT with thin slices, the tumor extension--especially cranial spread into the middle and posterior cranial fossa and caudal spread into the infratemporal fossa--is better detected on MRI. Enhanced T1-weighted spin-echo images with fat-signal suppression are most suitable for this purpose. Using 3D sequences, partial volume effects can be avoided with an attainable slice thickness of 0.8-1.0 mm. Furthermore, arbitrary slices--very helpful when studying the complex anatomy of the skull base--can be calculated from a 3D data set. MRI had true-positive findings in 97, CT in nearly 90% of the patients with paragangliomas. Furthermore, the response of paragangliomas to radiotherapy can be more accurately assessed on MR--independent of and before volumetric changes.(ABSTRACT TRUNCATED AT 250 WORDS)

[Comparison of CT and MRI in diagnosis of tumors of the nasopharynx, the inner nose and the paranasal sinuses]. / Vergleich von CT und MRT in der Diagnostik von Tumoren des Nasopharynx, der inneren Nase und der Nebenhöhlen.

A total of 292 patients with tumors of the nasopharynx, the nose and the paranasal sinuses--264 cases with malignant tumors--were examined with magnetic resonance imaging (MRI) and computed tomography (CT) for comparison. MRI yielded better results than CT in the detection and staging of neoplasms of the nasopharynx (detection: CT 84.9%, MRI 96.7%; staging: CT 75.2%, MRI 92.4%). The walls and septae of the paranasal sinuses and of the skull base were in all cases best visualized on high-resolution CT with thin slices. Tumor detection, differentiation of tumor and inflammatory tissue and staging, however, were better achieved using MRI than CT (detection: CT 84.7%, MRI 91.6%; staging: CT 78.6%, MRI 80.9%). The use of fast and ultrafast MR sequences (alternatively or additionally to 'conventional' spin echo sequences) improved the tumor diagnosis. We therefore recommend that patients with tumors of the nasopharynx, the nose and the paranasal sinuses undergo MRI with fast spin echo and gradient echo sequences as first imaging modality.

Delayed myelination in children with West syndrome: an MRI-study.

Eighteen children with West syndrome underwent MRI-examination of the brain. Five children were examined twice. Myelination of ten regions of the brain was retrospectively assessed on the MRI-examinations. The children could be divided in three groups of main diagnosis (cryptogenic West syndrome, tuberous sclerosis, pre-/perinatally acquired brain lesions). Delays in myelination were found in 17 out of a total of 23 examinations. In children with cryptogenic West syndrome and with tuberous sclerosis myelination was normal or only mildly delayed in the first month after onset of the spasms, but delays seemed to increase in the course of the West syndrome in these groups. In children with pre- or perinatally acquired brain lesions severe delays of myelination could be found already in the first weeks after the onset of the West syndrome. The assessment of myelination can therefore contribute to the diagnosis and understanding of the underlying disease in children with West syndrome.

MRI and CT of tumors of the pharynx: comparison of the two imaging procedures including fast and ultrafast MR sequences.

The aim of this prospective study was to compare the diagnostic value of computed tomography (CT) and magnetic resonance imaging (MRI) in the evaluation of tumors of the nasopharynx, oropharynx and hypopharynx. For this reason, we performed CT and MRI in a total of 473 patients with neoplasms of the nasopharynx [116], oropharynx [282] and hypopharynx [39]. Furthermore, the MR imaging protocol had to be optimized including 2D and 3D gradient echo sequences. We compared the use of conventional and fast spin echo and 3D gradient echo sequences for the evaluation of tumors of the nasopharynx and the skull base, and we evaluated 2D fast and ultrafast MR sequences for the detection and delineation of tumors of the oropharynx and hypopharynx. MRI yielded better results than CT in the detection of pharyngeal neoplasms. The differentiation of tumor and inflammatory tissue was best achieved using MRI. Contrast-enhanced 3D GE sequences improved the diagnostic value of MRI of the nasopharynx. Fast and ultrafast 2D MR sequences increased the contrast between orofacial tumors and surrounding tissues. Functional MR images (phonation studies, Valsalva's maneuver) were attainable using ultrafast sequences thus enhancing the diagnostic value of MRI in the case of tumors of the hypopharynx. T2-weighted turbo (fast) spin echo sequences with relatively short acquisition times proved to be superior to conventional T2-weighted spin echo sequences. In conclusion, MRI is the imaging modality of choice in the evaluation of pharyngeal neoplasms. Conventional T2-weighted SE should be substituted by fast T2-weighted SE sequences. 3D GE sequences should be integrated in the MR imaging protocol of the nasopharynx. Fast and ultrafast 2D GE sequences should be applied in the evaluation of tumors of the oropharynx and hypopharynx.

[CT and MRI in tumors of the hypopharynx and larynx--comparison of methods with reference to rapid and ultra-fast MR pulse sequences]. / CT und MRT bei Tumoren des Hypopharynx und des Larynx--Methodenvergleich unter Berücksichtigung von schnellen und ultraschnellen MR-Pulssequenzen.

A total of 86 patients with malignant tumours of the hypopharynx and larynx were examined with CT and MRI. The most frequent malignant tumours of the larynx namely, the glottic carcinomas, were better detected with CT than with MRI. The other tumours of the larynx, however, were better visualised with MRI. MRI proved superior to CT in the detection and staging of carcinomas of the hypopharynx. Functional MR images (phonation studies, Valsalva's manoeuvre) were attainable using ultrafast sequences, thus enhancing the diagnostic value of MRI. MRI proved superior to CT enabling a better differentiation of recurrent tumours, inflammatory tissue and scar. For this purpose, T1-weighted plain and contrast-enhanced spin-echo images and T2-weighted spin-echo images were necessary in most cases. T2 weighting turbo spin-echo sequences with relatively short acquisition times proved superior to conventional T2 weighting spin-echo sequences; thanks to shorter acquisition times, the motion artifacts could be reduced and the image quality improved.

MRI assessment of myelination: an age standardization.

777 cerebral MRI examinations of children aged 3 days to 14 years were staged for myelination to establish an age standardization. Staging was performed using a system proposed in a previous paper, separately ranking 10 different regions of the brain. Interpretation of the results led to the identification of four clinical diagnoses that are frequently associated with delays in myelination: West syndrome, cerebral palsy, developmental retardation, and congenital anomalies. In addition, it was found that assessment of myelination in children with head injuries was not practical as alterations in MRI signal can simulate earlier stages of myelination. Age limits were therefore calculated from the case material after excluding all children with these conditions. When simplifications of the definition of the stages are applied, these age limits for the various stages of myelination of each of the 10 regions of the brain make the staging system applicable for routine assessment of myelination.

[CT and MRI in tumors of the mouth and oropharynx--comparison of methods with reference to fast and ultra-fast MR pulse sequences]. / CT und MRT bei Tumoren des Mundes und des Oropharynx-Methodenvergleich unter Berücksichtigung von schnellen und ultraschnellen MR-Pulssequenzen.

A total of 488 patients with neoplasms (in 474 cases with malignant tumours) of the oropharynx, floor of the mouth and oral cavity, were examined with MRI and CT. MRI proved superior to CT, on account of its coronal and sagittal slice orientation enabling not only a better demonstration of findings, but also improved tumour detection and staging. The diagnostic value of MRI was further enhanced with additional fast and ultrafast MR sequences rather than spin echo sequences alone, as previously practised.

Myelination of the brain in MRI: a staging system.

In a retrospective study 516 cranial MRI examinations of children aged 1 month to 14 years were re-evaluated for myelination. An objective staging system for the assessment of the degree of myelination was designed, based on the characteristic patterns of myelin-typical signal which develop in the course of brain maturation. Thus myelination can be estimated using only routine MRI examinations; no additional measurements of signal intensities are necessary. In order to obtain detailed information, ten regions of the brain are ranked separately, with comparisons of the T1- and T2-weighted images for each region. The application of the staging system to the case material revealed typical age ranges for the stages, and retarded myelination in some children. In most cases the observed retardation affected several regions but never the whole brain. Such delays can only be detected by separate assessment of the degree of myelination in each region of the brain.

[Structures of the knee joint in nuclear magnetic resonance tomography. Improved representation with 3D volume imaging]. / Kniegelenksstrukturen in der Kernspintomographie. Verbesserte Darstellung durch das 3D-Volumen-Imaging.

Despite 3D gradient echo technique has a better spacial resolution than spin echo sequences, 3D imaging is not well accepted for clinical routine. Because of the large amount of data evaluation cannot be done by single photo-documented slices. Postprocessing of the 3D data sets with an image analysis system is indispensable. A maximum of two different gradient echo sequences (FLASH, FISP) are necessary for imaging of the whole interesting volume with continuous slices. Time of examination is shorter (16 resp. 32 minutes) compared with conventional spin echo sequences. In our opinion 3D gradient echo-sequences are a reliable noninvasive technique for the evaluation of pathological changes of the knee joint which could replace diagnostic arthroscopy in the future.

Adaptation of two commercially available DNA probes for the detection of E. coli and Staphylococcus aureus to selected fields of dairy hygiene--an exemplary study.

The application of two commercially available colorimetric DNA hybridization tests (GENE-TRAK E. coli and Staphylococcus aureus) to selected aspects of dairy hygiene was investigated. Bacterial isolates of different origin, naturally contaminated cheese varieties, nonfat dry milk, milk concentrates, artificially contaminated milk and raw milks from udder quarters were examined. Based on the observation that the sensitivity of the E. coli DNA probe was comparable to that of the beta-D-glucuronidase-based fluorescence reaction (with 4-methyl-umbelliferyl-beta-D-glucuronide) of E. coli strains in Fluorocult lauryl sulfate broth, a Most Probable Number technique for enumerating E. coli in cheese using the DNA probe was developed. Another specific DNA probe was applied for the detection of S. aureus as a mastitis agent. By using a modified sample preparation, specific diagnosis of this microorganism in milk from udder quarters was enabled within 6 hours. This procedure is recommended to be used in screening tests. Based on the examples presented the potential of these tests in several fields of hygiene was illustrated.

[The extension of MR diagnosis in dissecting aortic aneurysms by means of FLASH and snapshot-FLASH sequences]. / Erweiterung der MR-Diagnostik bei dissezierenden Aortenaneurysmen mittels FLASH- und Snapshot-FLASH-Sequenzen.

Using a combination of T1 weighted snapshot-flash sequences and intravenous contrast bolus it was possible to demonstrate intraluminal signal differences in a period of seconds. 5 confirmed aortic lesions were studied; 2 old aortic dissections (with differentiation between the true and false lumen), 1 acute aortic dissection and a partially thrombosed thoracic aortic aneurysm were demonstrated. The advantage of this technique lies in its simplicity and reproducibility. Difficulties in interpreting the intraluminal phases arising from spin echo and flash techniques are made easier by interpreting the available signals from this method.

[Value of MRT for therapy of para-sellar tumors]. / Die Bedeutung der MRT für die Therapie sellanaher Geschwülste.

When planning treatment of tumours in the sella region it is of the utmost importance to obtain precise information about the localization, spread, and (if possible) the type of alteration. Aside from the classic radiographic methods of native diagnosis, angiography, and CT, MRI has been available for some years now. This is a method whereby images can be gained from the various stages of an energetic reaction in the biological substrate: tomograms are possible for any desired plane--those routinely needed for cerebral diagnosis from the horizontal, coronary, and sagittal planes and, given a further improvement of this technology, from special oblique planes which can be matched to the direction of a probable surgical approach. A number of examples demonstrate the significance of this new method, which is a valuable addition to the procedures used up to now: indeed, in some cases it is superior to them. It has been shown that most of the neighbouring structures which border on or have been pushed aside by the tumour in the sella region (blood vessels, brain, optic chiasma, subarachnoid spaces, and occasionally even bone structures) can be identified better than with the procedures used up to now. MRI has thus proved to be valuable, and occasionally indispensable, for the correct choice when considering the many therapeutic methods available for tumours in the sella region.

[Thrombocytopenia-induced parenchyma hemorrhage in a newborn infant. A contribution to the etiology of so-called arachnoid cysts]. / Thrombozytopenisch bedingte Parenchymblutung bei einem Neugeborenen. Ein Beitrag zur Atiologie von sogenannten Arachnoidalzysten.

We report on a newborn baby with thrombocytopenia who developed neonatal seizures caused by a temporal lobe hemorrhage as shown by cerebral ultrasonography. This hemorrhage was followed by a cyst isodense to intracerebral fluid. Differential diagnostic aspects concerning the etiology of arachnoideal cysts will be discussed in relation to the post-hemorrhagic course and the sonographic or the magnetic resonance tomography findings respectively.

[Use of the 3D procedure in nuclear magnetic resonance tomography in ENT diagnostics]. / Einsatz des 3D-Verfahrens der Kernspintomographie in der HNO-Diagnostik.

The use of 3D-gradient-echo sequences improved the diagnosis of malignant tumors of the skull base, the nasopharynx, the nasal cavities, the paranasal sinuses and the upper parts of the parapharyngeal space with relation to the skull base. Therefore the tumor extent and infiltration may be better appreciated than in conventional 2D-spin-echo or gradient echo sequences. Using this method, the examinations of 22 patients with carcinomas could be compared. Precise tumor delineation was achieved in six of these patients when compared with surgical and histological findings. The 3D sequences most frequently used were FLASH 40 degrees with TR of 40 ms and the shortest TE (5 to 6 ms). 3D turbo-FLASH (MPRage) with Gad-DTPA was applied in order to shorten the acquisition time by half and especially to reduce motion artefacts.

[Significance of reprocessed 3D gradient echo sequences in spinal MRT for surgical interventions in syringomyelia]. / Bedeutung der nachverarbeiteten 3D-Gradienten-Echosequenzen bei spinaler MRT für operative Massnahmen bei Syringomyelie.

Taking a patient with advanced syringomyelia as an example, the article presents a method in which reprocessed 3D-gradient echo sequences from spinal MRI allow centred reconstructions which show all sections of the syrinx, even where the spinal column is curved. This method played an essential role in satisfactorily determining the position of the syrinx for a median myelotomy which, according to clinical criteria, brought about an effective reduction in pressure from the syrinx.