Mineral content of calcified tissues in cystic fibrosis mice

Although abnormal hard tissue mineralization is a recognized complication of cystic fibrosis (CF), the pathogenesis leading from the defective cystic fibrosis transmembrane conductance regulator (CFTR) protein is poorly understood. We hypothesized that CFTR plays a direct role in the mineralization of bone and teeth and tested the hypothesis using CF mouse models [CFTR(−) mice]. In vivo measurements by dual-emission X-ray absorpitometry (DEXA) indicated that bone mineral density (BMD) was reduced in CF mice as compared to gender-matched littermates. However, no change was evident after correction of BMD for the covariant of body weight. The latter finding was confirmed in isolated femurs and nasal bones by standard dry-ashing and instrumental neutron activation analysis (INAA). INAA of the continuously growing hypsodont incisor teeth from CFTR(−) mice revealed reduced Ca and normal P in the enamel layer—a finding consistent with changes in the deciduous teeth of CF children. Interestingly, enamel fluoride was increased in the CFTR(−) incisors and may associate with abnormal enamel crystallite formation. The iron content of the incisor enamel was reduced, explaining the loss of yellow pigmentation in CFTR(−) incisors. In contrast to the incisors, the mineral content of the slow-growing brachydont molar teeth was not different between CFTR(−) and CFTR(+) mice. It was concluded that CFTR does not play a direct role in the mineralization of bones or brachydont teeth in mice. Functional CFTR is apparently required for normal mineralization of the hypsodont incisors. However, multiple changes in the mineral composition of the CF incisors suggest an indirect role for CFTR, perhaps by maintaining a normal salivary environment for continuous tooth eruption. Preliminary reports published in Pediatric Pulmonology, 14, 253A (1997) and 15, 253A (1998).     

7-Oxo-24ξ(28)-dihydrocycloeucalenol,a potent inhibitor of plant sterol biosynthesis

Cycloeucalenol-obtusifoliol isomerase from higher plant cells catalyses the opening of the cyclopropane ring of cycloeucalenol yielding obtusifoliol. 7-Oxo-24ξ(28)-dihydrocycloeucalenol was not a substrate but behaved like a potent inhibitor of the isomerase. The inhibition was reversible and highly specific; the inhibitor needed the presence of the 7-oxo group, the cyclopropane ring and the absence of a 4β-methyl group to be active. Other enzymes involved in plant sterol biosynthesis such as 2, 3-oxidosqualene-cycloartenol cyclase and S-adenosyl methionine cycloartenol C-24 methyltransferase were not inhibited by 7-oxo-24ξ(28)-dihydrocycloeucalenol. In vivo treatment of a suspension of bramble cells growing in a liquid medium with 7-oxo-24ξ(28)-dihydrocycloeucalenol resulted in a strong accumulation of 9β 19-cyclopropyl sterols confirming that the main cellular target of the inhibitor is the cycloeucalenol-obtusifoliol isomerase.     

Effects of space environment on embryonic growth up to hatching of salamander eggs fertilized and developed during orbital flights.

In vertebrates, only few experiments have been performed in microgravity to study the embryonic development from fertilization. To date, these concern only amphibian and fish. We report here a study on the embryonic development of Pleurodeles waltl (urodele amphibian) eggs oviposited in microgravity. The experiment was performed twice on board the Mir space station and the data obtained included video recording and morphological, histological and immunocytological analyses. The data confirm that the microgravity conditions have effects during the embryonic period, particularly during cleavage and neurulation, inducing irregular segmentation and abnormal closure of the neural tube. Moreover, we observed several abnormalities hither to undescribed corresponding to cortical cytoplasm movements, a decrease of cell adhesion and a loss of cells. These abnormalities were temporary and subsequently reversible. The young larvae that hatched during the flight displayed normal morphology and swimming behavior after landing. The results obtained in the urodele Pleurodeles waltl are in accordance with those observed earlier in the anuran Xenopus laevis and in the fish Oryzias latipes.