A cost-effective protocol for the over-expression and purification of fully-functional and more stable Erwinia chrysanthemi ligand-gated ion channel.

The Erwinia chrysanthemi ligand-gated ion channel, ELIC, is considered an excellent structural and functional surrogate for the whole pentameric ligand-gated ion channel family. Despite its simplicity, ELIC is structurally capable of undergoing ligand-dependent activation and a concomitant desensitization process. To determine at the molecular level the structural changes underlying ELIC's function, it is desirable to produce large quantities of protein. This protein should be properly folded, fully-functional and amenable to structural determinations. In the current paper, we report a completely new protocol for the expression and purification of milligram quantities of fully-functional, more stable and crystallizable ELIC. The use of an autoinduction media and inexpensive detergents during ELIC extraction, in addition to the high-quality and large quantity of the purified channel, are the highlights of this improved biochemical protocol.

A Rare Presentation of a Large Left Atrial Myxoma with Gastrointestinal Symptoms.

Atrial myxoma is a rare primary tumour of the heart that typically arises from the left atrium. Patients typically present with obstructive symptoms such as dyspnoea, but constitutional and embolic symptoms can be seen as well. Gastrointestinal symptoms in the absence of embolisation are rarely reported in the literature. Our case presents a 55-year-old female who was found to have a large left atrial myxoma after presenting with gastrointestinal symptoms, which resolved upon resection of the tumour. This case illustrates that atrial myxomas can have an atypical presentation with gastrointestinal symptoms, which could be related to inflammation of gastric mucosa from interleukin-6 produced by the tumour cells. Careful history-taking followed by early detection and prompt treatment is important as atrial myxomas can lead to potentially devastating complications. LEARNING POINTS: Atrial myxomas are primary tumours of the heart that can present with a wide spectrum of symptoms.Early consideration and recognition of atypical presentations of atrial myxomas can be crucial in preventing serious consequences such as cardiac arrest.

Sinus of Valsalva aneurysm presenting with chest pain.

Sinus of Valsalva aneurysm is a rare aortic root defect that can be dangerous due to its serious complications. It is defined as dilatation of one or more of the aortic valve sinuses. It is usually asymptomatic, and patients rarely present with chest pain, arrhythmias, or heart failure. We report a 29-year-old man who presented with atypical chest pain of 8 months with a normal cardiovascular exam. His laboratory work was unremarkable. Transthoracic echocardiography and transesophageal echocardiography showed a calcified sinus of Valsalva aneurysm arising from the noncoronary cusp. The patient underwent aneurysm repair surgery with no complications, and his chest pain resolved.

An Escherichia coli-Based Assay to Assess the Function of Recombinant Human Hemichannels.

Connexins form the gap junctional channels that mediate cell-to-cell communication, and also form hemichannels present at the plasma membrane. Hemichannels are permeable to small hydrophilic compounds, including molecules involved in autocrine and paracrine signaling. An abnormal hemichannel opening causes or contributes to cell damage in common human disorders (e.g., cardiac infarct, cerebrovascular accidents, deafness, skin diseases, and cataracts) and is therefore a potential pharmacological target. The discovery of useful hemichannels inhibitors has been hampered in part by the lack of suitable high-throughput functional assays. Here, we developed and characterized an assay useful to assess the function of hemichannels formed by human connexins expressed in a genetically modified Escherichia coli strain. The LB2003 cells, devoid of three key K+ uptake transport mechanisms, cannot grow in low-[K+] medium, but expression of Cx26, Cx43, or Cx46 rescues their growth defect (growth complementation). We developed a protocol for a simple, inexpensive, easily scalable, reproducible, and sensitive assay that should be useful for the discovery of new and better hemichannel inhibitors based on the analysis of small-compound libraries.