Kinetics of hydrolysis and cyclization of ethyl 2-(aminosulfonyl)benzoate to saccharin.

The cyclization of ethyl 2-(aminosulfonyl)benzoate (ASB) to give saccharin was investigated in aqueous solutions at pH between 5.2 and 9.5 and in the temperature range of 296.2-334.2 K. The initial concentration of the reactant was varied between 1.45 x 10(-5) and 3.86 x 10(-4) M. Ultraviolet spectroscopy was used to obtain the kinetic data. The reaction is acid catalyzed and follows pseudo-first-order kinetics. The experimental rate constant, k(obs), increases with temperature and pH. Its dependence on the temperature and pH is well described by: k(obs) = k1 [OH-] = [(2.52 +/- 0.9) x 10(16) exp(-20.2 +/- 1 kcalmol(-1)/RT) s(-1)][OH-] A mechanism is proposed and the half-life of ethyl ASB is calculated.

[Moyamoya disease. Its clinical picture, diagnosis and new therapies]. / Doença de Moyamoya. Clínica, diagnóstico, novas terapêuticas.

Moyamoya disease is a chronic cerebral vasculopathy that leads to a slow progressive narrowing and occlusion of the principal arteries responsible for the anterior circulation of the brain. It causes a cerebrovascular insufficiency with the development of multiple anastomoses between internal and external carotid arteries. The diagnosis is based on the peculiar appearance in angiography. Although rare, it is not possible to omit it in the differential diagnosis of ischemic vascular accidents in children. The authors describe a case of a eight year old female caucasian whose diagnosis was suspected by means of the non invasive technique of angiographic magnetic resonance imaging and confirmed by angiography. Based on this case, the main aspects of the disease are described, with particular emphasis on clinical features, diagnosis and treatment.

[Neural tube defects. The 10-year experience of a central maternity hospital]. / Defeitos do tubo neural. Experiência de 10 anos numa maternidade central.

OBJECTIVES: 1) To determine trends in prevalence of neural tube defects and the impact of therapeutic abortion. 2) To review perinatal management of spina bifida. DESIGN: All spontaneous and therapeutic abortions, still births and live births affected by neural tube defects registered in Alfredo da Costa Maternity in Lisbon, from 1983 to 1992, were retrospectively analysed. RESULTS: Eighty-two cases with neural tube defects are reported and myelomeningocele and anencephaly++ were the most frequent ones. Total prevalence for all defects was 0.78:1000 births with a small upward trend during the last two years. Birth prevalence was 0.6:1000, with a clear downward trend, due to therapeutic abortion. Prenatal diagnosis improved significantly, from 9% of all defects detected in 1983-87 to 77.5% in 1988-92. Since 1989, all cases of anencephaly were detected before birth. Most cases of spina bifida were vaginally delivered, and elective cesarean section occurred in 4. Early closure of the defect was undertaken in 87.6% of the newborns with open spina bifida. CONCLUSION: While total prevalence of neural tube defects remained stable, with only a small upward trend, prenatal diagnosis and therapeutic abortion resulted in a 56.3% fall in birth prevalence. Optimal management of open spina bifida demands a multidisciplinary team with an individual program for each case.