Enzymatic synthesis of M(1)G-deoxyribose.

Adducts formed between electrophiles and nucleic acid bases are believed to play a key role in chemically induced mutations and cancer. M(1)G-dR is an endogenous exocyclic DNA adduct formed by the reaction of the dicarbonyl compound malondialdehyde with a dG residue in DNA. It is an intermediate in the synthesis of a class of modified oligodeoxyribonucleotides that are used to study the mutagenicity and repair of M(1)G. This unit presents methods for synthesizing M(1)G-dR by enzymatic coupling.

Structural analysis of UDP-sugar binding to UDP-galactose 4-epimerase from Escherichia coli.

UDP-galactose 4-epimerase from Escherichia coli catalyzes the interconversion of UDP-galactose and UDP-glucose through the transient reduction of the tightly bound cofactor NAD+. The enzyme is unique among the NAD+-dependent enzymes in that it promotes stereospecific reduction of the cofactor but nonstereospecific hydride return during normal catalysis. In addition to hydride transfer, the reaction mechanism of epimerase involves two key features: the abstraction of a proton from the 4'-hydroxyl group of glucose or galactose by an active site base and the rotation of a 4-ketopyranose intermediate in the active site pocket. To address the second issue of movement within the active site, the X-ray structures of reduced epimerase complexed with UDP-mannose, UDP-4-deoxy-4-fluoro-alpha-D-galactose, or UDP-4-deoxy-4-fluoro-alpha-D-glucose have been determined and refined to 1.65, 1.8, and 1.65 A resolution, respectively. A comparison of these models to that of the previously determined epimerase/NADH/UDP-glucose abortive complex reveals that the active site accommodates the various sugars by simple rearrangements of water molecules rather than by large changes in side chain conformations. In fact, the polypeptide chains for all of the epimerase/NADH/UDP-sugar complexes studied thus far are remarkably similar and can be superimposed with root-mean-square deviations of not greater than 0.24 A. The only significant differences between the various enzyme/UDP-sugar models occur in two of the dihedral angles defining the conformation of the UDP-sugar ligands.

Iliac osteosarcoma in a patient with SAPHO syndrome.

Extrathoracic sclerotic bone involvement of SAPHO syndrome are sometimes very difficult to differentiate from a bone infection or bone tumor. The authors report the case of a 46-year-old patient with a history of palmo-plantar pustulosis, recurrent suppurative hidradenitis, and bilateral sternocostal arthropathy who was evaluated for a sclerotic lesion in an iliac wing. The clinical course, computed tomography findings, and histologic features of a surgical biopsy specimen established the diagnosis of osteoblastic osteosarcoma with SAPHO syndrome.

[Singular diaphragm-like colonic stricture and short-term administration of a non-steroidal anti-inflammatory drug]. / Diaphragme colique unique et prise brève d'anti-inflammatoire non stéroïdien.

A case of diaphragm-like stricture of the colon induced by non steroidal anti-inflammatory drug (diclofénac LP) is reported in a 65-year-old man who presented abdominal pain. Colonoscopy revealed ulcer in the transverse right colon. The patient gradually developed diaphragm-like stricture in the transverse right colon. A right hemicolectomy was performed.

[Nephroblastoma with symptomatic neuronal differentiation]. / Néphroblastome avec différentiation neuronale symptomatique.

We report the anatomoclinical analysis of a child with a renal tumor: the preoperative diagnosis was neuroblastoma, because of elevated dopamine urinary excretion and positive MIBG scintigraphy. The histopathological and immunohistochemical analysis revealed a prominent neural differentiation in a multicystic nephroblastoma. This observation recalls the Masson's proposed neuroectodermal histogenesis of Wilms tumor; however the currently accepted metanephrogenic blastematous origin is not reconsidered. This is the first case of nephroblastoma with a neural differentiation detectable otherwise from by pathological analysis.