A Case of Nasal Rhinosporidiosis in the United States

Rhinosporidiosis, an infectious granulomatous disease, is seldom encountered in the United States. We present a case of rhinosporidiosis in a 26-year-old man, who presented with an unusual mass in his nasal cavity. Suspicion for rhinosporidiosis was high due to the patient's travel and activity history. After imaging and proper diagnosis, surgery was performed to excise the lesion. As international travel resumes during the COVID-19 pandemic, the potential for encountering this rare organism is heightened.

Channel Gating in Kalium Channelrhodopsin Slow Mutants

Kalium channelrhodopsin 1 from Hyphochytrium catenoides (HcKCR1) is the first discovered natural light-gated ion channel that shows higher selectivity to K+ than to Na+ and therefore is used to silence neurons with light (optogenetics). Replacement of the conserved cysteine residue in the transmembrane helix 3 (Cys110) with alanine or threonine results in a >1,000-fold decrease in the channel closing rate. The phenotype of the corresponding mutants in channelrhodopsin 2 is attributed to breaking of a specific interhelical hydrogen bond (the "DC gate"). Unlike CrChR2 and other ChRs with long distance "DC gates", the HcKCR1 structure does not reveal any hydrogen bonding partners to Cys110, indicating that the mutant phenotype is likely caused by disruption of direct interaction between this residue and the chromophore. In HcKCR1_C110A, fast photochemical conversions corresponding to channel gating were followed by dramatically slower absorption changes. Full recovery of the unphotolyzed state in HcKCR1_C110A was extremely slow with two time constants 5.2 and 70 min. Analysis of the light-minus-dark difference spectra during these slow processes revealed accumulation of at least four spectrally distinct blue light-absorbing photocycle intermediates, L, M1 and M2, and a UV light-absorbing form, typical of bacteriorhodopsin-like channelrhodopsins from cryptophytes. Our results contribute to better understanding of the mechanistic links between the chromophore photochemistry and channel conductance, and provide the basis for using HcKCR1_C110A as an optogenetic tool.

Light-gated channelrhodopsin sparks proton-induced calcium release in guard cells

Although there has been long-standing recognition that stimuli-induced cytosolic pH alterations coincide with changes in calcium ion (Ca2+) levels, the interdependence between protons (H+) and Ca2+ remains poorly understood. We addressed this topic using the light-gated channelrhodopsin HcKCR2 from the pseudofungus Hyphochytrium catenoides, which operates as a H+ conductive, Ca2+ impermeable ion channel on the plasma membrane of plant cells. Light activation of HcKCR2 in Arabidopsis guard cells evokes a transient cytoplasmic acidification that sparks Ca2+ release from the endoplasmic reticulum. A H+-induced cytosolic Ca2+ signal results in membrane depolarization through the activation of Ca2+-dependent SLAC1/SLAH3 anion channels, which enabled us to remotely control stomatal movement. Our study suggests a H+-induced Ca2+ release mechanism in plant cells and establishes HcKCR2 as a tool to dissect the molecular basis of plant intracellular pH and Ca2+ signaling.

Tumoral cutaneous rhinosporidiosis: Case report and review of literature

Rhinosporidiosis is a chronic granulomatous disease caused by Rhinosporidium seeberi commonly affecting nasal mucosa, conjunctiva, and urethra. Subcutaneous tumor nodule presentation is rare and often mimics as sarcoma. Such tumoral rhinosporidiosis has been reported rarely. This report describes a 60-year male who presented with a solitary, firm, nontender swelling in posterior aspect of right leg with an ulcer and mimicking clinically as soft tissue sarcoma. Histopathology was diagnostic. Surgical excision was found to be useful.

Naso-Bronchial Rhinosporidiosis

Rhinosporidiosis is a chronic mucocutaneous granulomatous disease caused by Rhinosporidium seeberi, commonly affecting the nose and nasopharynx. Endobronchial involvement is of rare occurrence but can pose challenging problems for diagnosis, surgical excision and anaesthetic management. We report a 40-year-old man with a history of recurrent nasal rhinosporidiosis who presented with unilateral nasal obstruction, cough, shortness of breath and a radiological feature of left lung collapse. Eight years since the last surgery, he presented with a recurrent lesion in the nose with concurrent endobronchial involvement. The patient underwent excision of the nasal and the endobronchial lesion successfully under general anaesthesia without any complication and good symptomatic improvement. The clinical presentation and the management of endobronchial rhinosporidiosis are discussed here. The surgical difficulties faced during the procedure are highlighted.

An erosive mass involving the nasal cavity and maxillary sinus: rhinosporidiosis

Rhinosporidiosis is a chronic granulomatous inflammatory disease of the mucous membranes caused by Rhinosporidium seeberi. The disease is endemic in India, but is very rare in other countries. A review of the literature shows that our patient is the second documented case from Turkey. Involvement and erosion of the anterior wall of the maxillary sinus as in this case is very rare. A 47-year-old-male is presented with the clinicopathological features and transmission of the disease is discussed.

Rhinosporidiosis in a Nigerian

A case of rhinosporidiosis in a Hausa man from northern Nigeria is reported. This apparently constitutes the first case recorded from Nigeria.