Identification of an Infected Urachal Cyst Using Point-of-Care Ultrasound.

ABSTRACT: This case describes a 6-year-old girl who presented to the pediatric emergency department with 3 days of fever and suprapubic pain in the setting of 1 month of worsening, dull abdominal pain. On presentation, she had a tender, erythematous, and fluctuant mass on her lower abdomen. Point-of-care ultrasound was used to identify an abnormal fluid collection anterior to her bladder, suspicious for an infected urachal cyst. In this case, point-of-care ultrasound helped identify this uncommon finding in a timely fashion, which expedited definitive care and prevented unnecessary exposure to ionizing radiation.

Heme-coordinating inhibitors of neuronal nitric oxide synthase. Iron-thioether coordination is stabilized by hydrophobic contacts without increased inhibitor potency.

The heme-thioether ligand interaction often occurs between heme iron and native methionine ligands, but thioether-based heme-coordinating (type II) inhibitors are uncommon due to the difficulty in stabilizing the Fe-S bond. Here, a thioether-based inhibitor (3) of neuronal nitric oxide synthase (nNOS) was designed, and its binding was characterized by spectrophotometry and crystallography. A crystal structure of inhibitor 3 coordinated to heme iron was obtained, representing, to our knowledge, the first crystal structure of a thioether inhibitor complexed to any heme enzyme. A series of related potential inhibitors (4-8) also were evaluated. Compounds 4-8 were all found to be type I (non-heme-coordinating) inhibitors of ferric nNOS, but 4 and 6-8 were found to switch to type II upon heme reduction to the ferrous state, reflecting the higher affinity of thioethers for ferrous heme than for ferric heme. Contrary to what has been widely thought, thioether-heme ligation was found not to increase inhibitor potency, illustrating the intrinsic weakness of the thioether-ferric heme linkage. Subtle changes in the alkyl groups attached to the thioether sulfur caused drastic changes in the binding conformation, indicating that hydrophobic contacts play a crucial role in stabilizing the thioether-heme coordination.

Traumatic bone cyst of the mandible in a 10-year-old boy.

Although rare, the presentation of mandibular cysts in children can be difficult for medical providers to recognize. We present a case of a 10-year-old boy who presented to our pediatric emergency department with a painful swelling of his chin on multiple occasions before the diagnosis of a traumatic mandibular bone cyst with superinfection was made. A review of the literature regarding the presentation and management of cystic lesions of the mandible in children is presented.

Crystal structures and proposed structural/functional classification of three protozoan proteins from the isochorismatase superfamily.

We have determined the crystal structures of three homologous proteins from the pathogenic protozoans Leishmania donovani, Leishmania major, and Trypanosoma cruzi. We propose that these proteins represent a new subfamily within the isochorismatase superfamily (CDD classification cd004310). Their overall fold and key active site residues are structurally homologous both to the biochemically well-characterized N-carbamoylsarcosine-amidohydrolase, a cysteine hydrolase, and to the phenazine biosynthesis protein PHZD (isochorismase), an aspartyl hydrolase. All three proteins are annotated as mitochondrial-associated ribonuclease Mar1, based on a previous characterization of the homologous protein from L. tarentolae. This would constitute a new enzymatic activity for this structural superfamily, but this is not strongly supported by the observed structures. In these protozoan proteins, the extended active site is formed by inter-subunit association within a tetramer, which implies a distinct evolutionary history and substrate specificity from the previously characterized members of the isochorismatase superfamily. The characterization of the active site is supported crystallographically by the presence of an unidentified ligand bound at the active site cysteine of the T. cruzi structure.