Reference

Effect of L- and D-tetramisole on inorganic phosphorus-32 and calcium-45 uptake and mineralization by matrix vesicle-enriched fractions from chicken epiphyseal cartilage

Effect of L- and D-tetramisole on inorganic phosphorus-32 and calcium-45 uptake and mineralization by matrix vesicle-enriched fractions from chicken epiphyseal cartilage. Register, Thomas C.; Warner, Gregory P.; Wuthier, Roy E. (Dep. Chem., Univ. South Carolina, Columbia, SC 29208, USA). J. Biol. Chem., 259(2), 922-8 (English) 1984. CODEN: JBCHA3. ISSN: 0021-9258. DOCUMENT TYPE: Journal CA Section: 13 (Mammalian Biochemistry) The role of alk. phosphatase (I) in matrix vesicle-mediated calcification was clarified by studying the effect of L-tetramisole, a strong uncompetitive inhibitor of this enzyme, and D-tetramisole, its inactive isomer, on the uptake of inorg. [32P]phosphate (32Pi) and 45Ca2+ by matrix vesicle-enriched microsomes obtained from chicken epiphyseal cartilage. Uptake of both 32Pi and 45Ca2+ was inhibited in a dose-dependent manner by the L-isomer; however, 32Pi uptake was selectively inhibited at low drug concns. 1306-06-5 and 7440-70-2 are cas registry numbers of chemicals which are used as reagents here. and at early time periods. With increasing incubation time, inhibition of uptake of both ions was lost. Apatite crystal growth was only weakly inhibited by both the D- and L-isomers of tetramisole. The kinetics of ion uptake by the vesicles were complex. 45Ca2+/32Pi uptake ratios, taken with the selective inhibition of 32Pi uptake by L-tetramisole, indicated that early phases of vesicle ion uptake might be governed by I, a known Pi-binding protein. Later stages were clearly controlled by apatite formation. Although inhibition of vesicle uptake of 32Pi and 45Ca2+ by graded levels of L-tetramisole paralleled inhibition of I activity, surprisingly, D-tetramisole was almost as inhibitory of ion uptake as the L-isomer. This finding, coupled with the fact that I substrates were not required for vesicle ion uptake, indicates that I hydrolase activity is not directly involved in vesicle-mediated calcification under these exptl. conditions. .

The role of calcium ions in phytochrome-mediated germination of spores of Onoclea sensibilis L

The role of calcium ions in phytochrome-mediated germination of spores of Onoclea sensibilis L. Wayne, Randy; Hepler, Peter K. (Dep. Bot., Univ. Massachusetts, Amherst, MA 01003, USA). Planta, 160(1), 12-20 (English) 1984. CODEN: PLANAB. ISSN: 0032-0935. DOCUMENT TYPE: Journal CA Section: 11 (Plant Biochemistry) Phytochrome is confirmed to be the photoreceptor pigment in the germination response of O. sensibilis by demonstrating red-far-red (R-FR) photoreversibilty. External Ca2+ is required for this response, with a threshold at a submicromolar concn. EGTA, La3+, and Co2+ reversibly inhibit germination. La3+ only inhibits germination when applied before or during irradn. 10476-85-4 and 1306-06-5 which are cas registry numbers are also used here., indicating that the external Ca2+ requirement is transient, although in the absence of Ca2+ the R-stimulated system remains maximally poised to accept the ion for >4 h after irradn. The ability to respond to Ca2+, 4.1 h after R-irradn. is not reversed by FR-irradn., indicating that Ca2+ transport has been uncoupled from phytochrome. Ba2+ and Sr2+, but not Mg2+, can substitute for Ca2+. Artificially increasing the concn. of intracellular free Ca2+ with the ionophore A23187 stimulates germination in the dark. The Ca2+-calmodulin antagonists, trifluoperazine and chlorpromazine, reversibly inhibit germination. Ca2+ is required in phytochrome-mediated fern spore germination; it may be acting as a second messenger. .