Pseudo-first-order rate constants governing the deuterium exchange of 8-CH groups in guanosine 5'-monophosphate (5'-rGMP) and guanosine 3':5'-monophosphate (cGMP) were determined as a function of temperature in the range 30-80 degrees C by means of laser-Raman spectroscopy. For each guanine nucleotide the logarithm of the rate constant exhibits a strictly linear dependence on reciprocal temperature: i.e., k psi = Ae-Ea/RT with A = 8.84 X 10(14) h-1 and Ea = 24.6 kcal/mol for 5'-rGMP and A = 3.33 X 10(13) h-1 and Ea = 22.2 kcal/mol for cGMP. Exchange of the 8-CH groups in guanine nucleotides is generally 2-3 times more rapid than in adenine nucleotides [cf. g. j. thomas, Jr., & J. Livramento (1975) Biochemistry 14, 5210-5218]. As in the case of adenine nucleotides, cyclic and 5' nucleotides of guanine exchange at markedly different rates at lower temperatures, with exchange in the cyclic nucleotide being the more facile. Each of the guanine nucleotides was prepared in four different isotopic modifications for Raman spectral analysis. The Raman frequency shifts resulting from the various isotopic substitutions have been tabulated, and assignments have been given for most of the observed vibrational frequencies.

A 66-year-old woman had been living in an area endemic for schistosomiasis in the northeast of the State of Minas Gerais, Brazil, since childhood. Over the last 10 years, she presented two episodes of hematemesis (1999 and 2008). Small-caliber esophageal and gastric varices were observed during upper digestive endoscopy. She has been receiving beta-blockers for prophylaxis of digestive tract hemorrhage since 2008. Liver function tests were normal. Abdominal ultrasound revealed that the liver surface was slightly lobular. Magnetic resonance imaging of the liver showed hyperintense periportal thickening compatible with Symmers fibrosis. The serological markers for hepatitis B and C tested negative. An intrahepatic venous shunt with communication between the right portal branch and the right hepatic vein was documented (Figure A-arrow). Saccular aneurysmal dilatation of the splenic artery was also observed. A helical CT scan with 3D reconstruction showed the splenic artery aneurysm and the intrahepatic venous shunt (Figures B and C-arrows). Out of 82 patients with hepatosplenic schistosomiasis evaluated in our hospital using imaging techniques, this was the first case (1.2%) of splenic artery aneurysm and intrahepatic shunt. These findings were not seen during ultrasound examination. The patient refused surgical treatment and is being followed up in the outpatient clinic. A paciente, de 66 anos, vive desde a infância em área endêmica de esquistossomose no nordeste de Minas Gerais, Brasil. Ela apresentou, nos últimos 10 anos, dois episódios de hematêmese (1999 e 2008). Observou-se à endoscopia digestiva alta, varizes esofagianas e gástricas de fino calibre. Ela está em uso de beta-bloqueador para profilaxia de hemorragia digestiva desde 2008. A função hepática era normal. À ultrassonografia abdominal, o fígado apresentava contorno levemente lobulado. À ressonância magnética do fígado notou-se espessamento hiper-intenso periportal compatível com fibrose de Symmers. Os marcadores sorológicos para hepatites virais (B e C) resultaram negativos. Descreveu-se shunt venoso intra-hepático: comunicação do ramo portal direito com a veia hepática direita (Figura A-seta). Evidenciou-se, também, dilatação aneurismática sacular da artéria esplênica. A tomografia computadorizada helicoidal com reconstrução em três dimensões mostra o aneurisma da artéria esplênica e o shunt venoso intra-hepático (Figuras B e C-setas). De 82 pacientes com esquistossomose hepatoesplênica examinados pelos métodos de imagem em nosso hospital, este é o primeiro caso (1,2%) de aneurisma da artéria esplênica e shunt intra-hepático. Os achados não foram vistos ao ultra-som de abdômen. A paciente recusou tratamento cirúrgico e é acompanhada em nosso ambulatório. REFERENCES 1. Lambertucci JR, Serufo JC, Gerspacher-Lara R, Rayes AAM, Teixeira R, Nobre V, et al. Schistosoma mansoni: assessment of morbidity before and after control. Acta Trop 2000; 77: 101-109. 2. Lambertucci JR, Silva LC, Andrade LM, de Queiroz LC, Pinto-Silva RA. Magnetic resonance imaging an...

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