Helix movement is coupled to displacement of the second extracellular loop in rhodopsin activation

The second extracellular loop (EL2) of rhodopsin forms a cap over the binding site of its photoreactive 11-cis retinylidene chromophore. A crucial question has been whether EL2 forms a reversible gate that opens upon activation or acts as a rigid barrier. Distance measurements using solid-state 13C NMR spectroscopy between the retinal chromophore and the β4 strand of EL2 show that the loop is displaced from the retinal binding site upon activation, and there is a rearrangement in the hydrogen-bonding networks connecting EL2 with the extracellular ends of transmembrane helices H4, H5 and H6. NMR measurements further reveal that structural changes in EL2 are coupled to the motion of helix H5 and breaking of the ionic lock that regulates activation. These results provide a comprehensive view of how retinal isomerization triggers helix motion and activation in this prototypical G protein-coupled receptor. © 2009 Nature America, Inc. All rights reserved

Myocardial tagging by Cardiovascular Magnetic Resonance: evolution of techniques--pulse sequences, analysis algorithms, and applications

Cardiovascular magnetic resonance (CMR) tagging has been established as an essential technique for measuring regional myocardial function. It allows quantification of local intramyocardial motion measures, e.g. strain and strain rate. The invention of CMR tagging came in the late eighties, where the technique allowed for the first time for visualizing transmural myocardial movement without having to implant physical markers. This new idea opened the door for a series of developments and improvements that continue up to the present time. Different tagging techniques are currently available that are more extensive, improved, and sophisticated than they were twenty years ago. Each of these techniques has different versions for improved resolution, signal-to-noise ratio (SNR), scan time, anatomical coverage, three-dimensional capability, and image quality. The tagging techniques covered in this article can be broadly divided into two main categories: 1) Basic techniques, which include magnetization saturation, spatial modulation of magnetization (SPAMM), delay alternating with nutations for tailored excitation (DANTE), and complementary SPAMM (CSPAMM); and 2) Advanced techniques, which include harmonic phase (HARP), displacement encoding with stimulated echoes (DENSE), and strain encoding (SENC). Although most of these techniques were developed by separate groups and evolved from different backgrounds, they are in fact closely related to each other, and they can be interpreted from more than one perspective. Some of these techniques even followed parallel paths of developments, as illustrated in the article. As each technique has its own advantages, some efforts have been made to combine different techniques together for improved image quality or composite information acquisition. In this review, different developments in pulse sequences and related image processing techniques are described along with the necessities that led to their invention, which makes this article easy to read and the covered techniques easy to follow. Major studies that applied CMR tagging for studying myocardial mechanics are also summarized. Finally, the current article includes a plethora of ideas and techniques with over 300 references that motivate the reader to think about the future of CMR tagging

The Sino-Nasal Outcome Test (SNOT): can we make it more clinically meaningful?

OBJECTIVE: To test whether subscales should be used when analyzing the Sino-Nasal Outcome Test (SNOT). STUDY DESIGN AND SETTING: Prospective cohort study involved 87 acute NHS hospitals in England and Wales. RESULTS: With the use of exploratory factor analysis we found evidence for the existence of four unique constructs within the SNOT. Two constructs address symptoms (rhinologic and ear/facial) and two address aspects of health-related quality of life (psychological issues and sleep function). Subscales of the SNOT that correspond to these constructs provided clinically meaningful information over and above that provided by the SNOT total score on the type of surgical benefits gained by patients with different sino-nasal conditions. CONCLUSION: The SNOT is not unidimensional and a SNOT total score will mask variation in the true underlying constructs. SIGNIFICANCE: The SNOT would have greatly improved clinical use if it was scored with appropriate subscales. Such a measure would allow us to tease out the differential impact of sino-nasal conditions, in addition to allowing greater understanding of treatment effects

Intractable Anemia: A Case of Bleeding Nasal Cavernous Hemangioma

Cavernous haemangioma of the nose is rare, but when it occurs it usually presents with severe epistaxis. This nasal pathology is mostly seen in adult patient patients. Standard approach to dealing with such haemangiomas is surgical resection. A 30-year-old woman presented to General Physician with history of haemoptysis, haematemesis and weakness. She was admitted for investigation of her severe anaemia. On examination there was no obvious source of bleeding in the mouth or oropharynx, and Upper GI endoscopy did not reveal any pathology. She was referred to us after a trivial episode of epistaxis. Anterior and posterior rhinoscopy did not reveal any abnormality. Her extreme anxiety made indirect laryngoscopy and post-nasal space examination difficult but no obvious abnormality was seen. Diagnostic nasal endoscopy was done, and a small haemangiomatous mass was found in the postero superior part of inferior turbinate. Excision of the mass was done under local anaesthesia and sent for histopathological evaluation. The mass on histopathology came out to be Cavernous haemangioma