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Bernat, M; Loubet, M; Baumer, A. |
Phosphates from the Nauru atoll lie on a karstic structure developed at the expenses of a coral reef. These formations are fluorapatites low in carbonate, with less fluorine than common marine carbonate-fluorapatites (CFA). At least one of the deposits is from the last interglacial era (Th-230-U-234 dating). Rare Earth spectra seems to be affected by the dissolution-precipitation reactions leading to the formation of the carbonate-fluorapatite. But U and Sr isotopic ratios support the marine origin of most of these formations, except for one result, which give a Nd-143/Nd-144 ratio indicating a slight volcanic influence. Our results and the literature reports favorise the hypothesis that these phosphates originate from the endo-upwelling of phosphorus rich... |
Tipo: Text |
Palavras-chave: PHOSPHATES ATOLLS ISOTOPES U; TH; SR. |
Ano: 1991 |
URL: http://archimer.ifremer.fr/doc/00102/21374/18974.pdf |
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MATTHEW,A; SHMYGOL,A; WRAY,SUSAN. |
Control of smooth muscle is vital for health. The major route to contraction is a rise in intracellular [Ca2+], determined by the entry and efflux of Ca2+ and release and re-uptake into the sarcoplasmic reticulum (SR). We review these processes in myometrium, to better understand excitation-contraction coupling and develop strategies for preventing problematic labours. The main mechanism of elevating [Ca2+] is voltage-gated L-type channels, due to pacemaker activity, which can be modulated by agonists. The rise of [Ca2+] produces Ca-calmodulin and activates MLCK. This phosphorylates myosin and force results. Without Ca2+ entry uterine contraction fails. The Na/Ca exchanger (NCX) and plasma membrane Ca-ATPase (PMCA) remove Ca2+, with contributions of 30%... |
Tipo: Journal article |
Palavras-chave: Uterus; SR; Signalling; Ca-ATPase. |
Ano: 2004 |
URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000400017 |
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