Sucrase-isomaltase and cystic fibrosis

Calmodulin in normal and cystic fibrosis human intestine at different developmental stages

Calmodulin concentrations and localisation have been analysed as a function of development in human intestinal epithelial cells from normal and cystic fibrosis individuals. In normal fetuses up to eight weeks of gestation intestinal epithelial cells which were still undifferentiated were not immunoreactive and their calmodulin content was low. From eight weeks onwards there was a significant overall increase in calmodulin content concomitant with its segregation to the apical side of epithelial cells. At 14 weeks of gestation calmodulin concentrations and localisation closely resembled those of adults. The developmental pattern of calmodulin appeared to parallel the morphological and functional maturation of brush borders which occurs during the first trimester of pregnancy. In the intestinal epithelial cells from a 19 weeks cystic fibrosis fetus and a cystic fibrosis newborn infant neither calmodulin concentration, nor its localisation were affected. Similarly, brush border calmodulin binding proteins and enzymatic activities were similar in normal subjects and the cystic fibrosis intestine.

Prenatal detection of cystic fibrosis; comparative study of maltase and alkaline phosphatase activities in amniotic fluid

The potential value of microvillar enzymes in the prenatal diagnosis of cystic fibrosis (CF) has previously been demonstrated and is corroborated in the present comparative study. Maltase and alkaline phosphatase (ALP) activities were studied in the amniotic fluids of 57 pregnancies with a 1 in 4 risk for CF or with a known CF outcome and in 489 controls. A simple assay for maltase activity (MU-maltase) with the fluorogenic substate 4-methylumbelliferyl alpha-glucoside, offers great technical advantages and an at least equal detection rate of CF, when compared to the previously used test with maltose as substrate. Intestinal ALP was estimated either as phenylalanine inhibitable activity (PI-ALP) or as the proportions of residual activity in the presence of the inhibitors phenylalanine or homoarginine. MU-maltase and PI-ALP appeared the most successful methods: both tests were able to detect 14 of the 16 (88 per cent) pregnancies with fetal CF. Each of the two tests alone also allowed a correct prediction in 24 of the 25 pregnancies at risk but with normal outcome; however all 25 cases could be correctly predicted by a combined evaluation. It is suggested that more than one intestinal enzyme activity should be evaluated to allow optimal results in the prenatal monitoring of pregnancies at high risk for CF.