Imaging of pharyngeal pathology.

The pharynx plays a significant role in swallowing and speech, and this is reflected in both its complex anatomy and degree of physiological motility. Patients who present with pharynx-related symptoms such as sore throat, globus, dysphagia or dysphonia will usually undergo visual and nasal endoscopic examination in the first instance. Imaging is frequently required to supplement clinical assessment and this typically involves MRI and CT. However, fluoroscopy, ultrasound and radionuclide imaging are valuable in certain clinical situations. The aforementioned complexity of the pharynx and the myriad of pathologies which may arise within it often make radiological evaluation challenging. In this pictorial review, we aim to provide a brief overview of cross-sectional pharyngeal anatomy and present the radiological features of a variety of pharyngeal pathologies, both benign and malignant.

Image challenge: A diabetic man with facial swelling following recent Covid-19 infection.

A 68-year-old man with diabetes presented with shortness of breath, left sided facial swelling, and nasal discharge. He had recently returned from India and PCR was positive for SARS-CoV-2 Delta variant. CT head and diffusion-weighted MRI sinuses were performed and the patient underwent endoscopic sinus surgery before being transferred to a specialist skull base centre.

Mechanism of genetic complementation of ammonium transport in yeast by human erythrocyte Rh-associated glycoprotein.

The Rh blood group proteins are erythrocyte proteins important in neonatal and transfusion medicine. Recent studies have shed new light on the possible biological function of Rh proteins as members of a conserved family of proteins involved in ammonium transport. The erythrocyte Rh-associated glycoprotein (RhAG) mediates uptake of ammonium when expressed in Xenopus laevis oocytes, and functional studies indicate that RhAG might function as an NH(4)(+)-H(+)-exchanger. To further delineate the functional properties of RhAG, in this study we have expressed RhAG in both a Saccharomyces cerevisiae ammonium-transport mutant (mep1Delta mep2Delta mep3Delta) and a wild-type strain. RhAG was able to complement the transport mutant, with complementation strictly pH-dependent, requiring pH 6.2-6.5. RhAG also conferred resistance to methylamine (MA), a toxic analog of ammonium, and expression in wild-type cells revealed that resistance was correlated with efflux of MA. RhAG-mediated resistance was pH-dependent, being optimal at acid pH. The opposite pH dependence of ammonium complementation (uptake) and MA resistance (efflux) is consistent with bidirectional movement of substrate counter to the direction of the proton gradient. This report clarifies and expands previous observations of RhAG-mediated transport in yeast and supports the hypothesis that ammonium transport is coupled to the H(+) gradient and that RhAG functions as a NH(4)(+)/H(+) exchanger.