Oceanic cyanobacteria are the most abundant oxygen-generating phototrophs on our planet, and therefore, important to life. These organisms are infected by viruses called cyanophages, recently shown to encode metabolic genes that modulate host photosynthesis, phosphorus cycling and nucleotide metabolism. Herein, we report the characterisation of a wild type flavin-dependent viral halogenase (VirX1) from a cyanophage. Notably, halogenases have been previously associated 2 with secondary metabolism, tailoring natural products. Exploration of this viral halogenase reveals it capable of regioselective halogenation of a diverse range of substrates, with a preference for forming aryl iodide species; this has potential implications for the metabolism of the infected host. Until recently, a flavin-dependent halogenase (FDH) capable of iodination in vitro had not been reported. VirX1 is interesting from a biocatalytic perspective showing strikingly broad substrate flexibility, and a clear preference for iodination, as illustrated by kinetic analysis. These factors together render it an attractive tool for synthesis. The selective formation of carbon-halogen (C-X) bonds is of great importance to the pharmaceutical and agrochemical industries 1,2. The introduction of a halogen (X) into a molecule can be used to modulate bioactivity, bioavailability and metabolic stability 1-3. Traditional chemical methodologies of halogenating aromatic substrates generally employ highly reactive reagents and generate harmful waste. As traditional reagents lack components that enable the tuning of product selectivity, they oftentimes generate products in which either only the most nucleophilic position is halogenated or mixtures of products are produced. Conversely, biosynthetic (enzymatic) halogenation is mild, highly selective and utilises simple salts such as NaCl or NH 4 Br as the source of halide while oxygen serves as the oxidant 1-3. Consequently, the discovery and structural characterisation of flavin-dependent halogenases (FDHs) capable of selectively forming C-Cl and C-Br bonds 4,5 and the discovery of a S-adenosylmethionine (SAM)-dependent fluorinase 6 , able to mediate nucleophilic C-F bond formation, attracted considerable attention. Until recently, a FDH capable of generating C-I bonds remained to be discovered and characterised 7 .
Transient osteoporosis is a rare musculoskeletal condition that has been reported in pregnant women and middle-aged men. We present a bilateral case in a young man. A 20-year-old man presented with spontaneous onset left hip pain. Investigations excluded other differential diagnoses such as infection or fracture. The pain resolved completely; 6 months later the patient presented with a similar episode of pain in the contralateral hip. This also resolved spontaneously. Doctors need to be aware of the possibility of spontaneous onset musculoskeletal pain due to transient osteoporosis occurring in young men. The typical presentation is of spontaneous onset progressive pain, often affecting the hip. Other pathology must be excluded. The investigation of choice is MRI, and the treatment is simple analgesia.
Figure 1 Coronal multiplanar reconstructed CT: thrombosed left external iliac vein (short arrow) and left psoas collection (long arrow)Phlegmasia cerulea dolens (PCD) is a severe form of proximal venous thrombosis that often threatens viability of the lower extremity. We report a case of PCD as a complication of spontaneous psoas abscess in a diabetic patient. The underlying processes described in the literature include malignancy, protein C deficiency, antithrombin III deficiency and thrombocytopenia.1,2 Venous congestion with massive fluid sequestration can lead to circulatory collapse and shock. Early investigations with Doppler ultrasound and computed tomography (CT) have been advocated in the literature.3 Treatments used include thrombectomy, thrombolysis and anticoagulation with heparin. A combination of different treatment modalities is often employed for a successful outcome.Spontaneous psoas abscess is a rare condition and predisposing conditions include intravenous drug use, diabetes mellitus and bleeding diatheses such as haemophilia A.4 CT with contrast enhancement is the most useful diagnostic imaging modality. Percutaneous drainage under CT or ultrasound guidance is the preferred initial therapeutic approach, followed by surgery. 5 Case historyA 45-year-old man with type 2 diabetes presented with a 7-day history of increasing left groin pain associated with swelling and purple discolouration of the left lower extremity. The patient was admitted under a physician with a working diagnosis of deep vein thrombosis of the left leg and treated with a heparin infusion. A Doppler ultrasound scan confirmed iliac vein thrombosis. The patient was in septic shock with tachycardia and hypotension. Inflammatory markers were raised with C-reactive protein levels at 423 and a white cell count of 34,000. Chest radiograph and urine analysis, performed as part of a septic screen, were negative. The patient was initially treated with aggressive fluid resuscitation, anticoagulation and empirical antibiotics. A CT scan of the abdomen revealed left external iliac vein thrombosis and left psoas swelling but no obvious collection (Fig 1). Phlegmasia cerulea dolens (PCD) is a limb-threatening venous disorder involving massive proximal venous thrombosis. The clinical manifestations are of oedema, cyanosis and pain of lower extremity. Patients presenting with PCD have an underlying pathological condition that predisposes to the thrombotic process. We report a diabetic patient who presented with PCD and septicaemia due to a spontaneous psoas abscess. Anticoagulation with heparin and treatment of the underlying psoas abscess led to complete resolution of symptoms. An understanding of the underlying pathological process responsible is vital to early recognition and successful outcome in this rare limb-and life-threatening venous disorder.
We present a case of a 46-year-old male presenting with a 10 year history of pain and paraesthesia in the median nerve distribution together with a palpable lump in the upper arm. X-rays confirmed a supracondylar process of the humerus. Intra-operatively it was found that there was an aberrant insertion of one of the heads of pronater teres from the process. After surgical removal of the process and release of the head of pronator teres his symptoms improved.
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