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Query: UMLS:C0694563 (eds)
 1,062 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Digital-imaging fluorescence microscopy with fura-2 allows the determination of intracellular calcium concentration ([Ca2+]i) in single cells. At a cell density of 10(5) cells/petri dish 44% of the chick embryo heart cells had a high [Ca2+]i of 99.4 +/- 7.1 nM and 56% of the cells a low [Ca2+]i of 27.8 +/- 4.4 nM (mean +/- SE). This laboratory previously reported that high-[Ca2+]i and low-[Ca2+]i cells from chick embryo hearts differ in their sensitivity to cardiac glycosides, as shown by measuring the increase in [Ca2+]i to reach a new steady state [Ahlemeyer, B., Weintraut, H., Seibold, G. & Schoner, W. (1991) in The sodium pump: recent developments (Kaplan, J. H. & De Weer, P., eds) pp. 653-656, Rockefeller University Press, New York]. This time we used N-hydroxysuccinimidyl digoxigenin-3-O-methylcarbonyl-epsilon-aminocaproate (HDMA) which binds irreversibly to amino groups of the Na+/K(+)-ATPase, and sheep anti-digoxigenin Fab fragments coupled with fluorescein isothiocyanate to identify different cardiac glycoside-binding sites. Half-maximal labelling of high-[Ca2+]i cells was obtained at 0.36 nM HDMA, and at 12.0 nM with the low-[Ca2+]i cells. Specific labelling of the cells by HDMA was 91% and 80% in high-[Ca2+]i and low-[Ca2+]i cells, respectively, as revealed by competition experiments with a 1000-fold excess of ouabain. HDMA half-maximally elevated the [Ca2+]i of high-[Ca2+]i cells at a concentration of 50 pM and that of low-[Ca2+]i cells at 8.0 nM. Concentrations higher than 0.1 microM produced signs of intoxication. When the labelled cells were subjected to a SDS/PAGE, a 100-kDa band was found to contain HDMA. The electrophoretic mobility of a protein labelled at 10 nM HDMA was slightly higher than that of a protein labelled at 1.0 microM. The data suggest that different isoforms of the alpha-subunit of Na+/K(+)-ATPase may exist in low-[Ca2+]i and high-[Ca2+]i cells of chick embryo heart.
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PMID:Chick heart cells with high intracellular calcium concentration have a higher affinity for cardiac glycosides than those with low intracellular calcium concentration, as revealed by affinity labelling with a digoxigenin derivative. 155 87

Leucine aminopeptidase (LAP) was purified from hog lenses by application of the Himmelhoch procedure for isolation of hog kidney LAP [S. R. Himmelhoch (1970) in Methods in Enzymology (Perlmann, G. E., and Lorand, L., eds.), Vol. 19, pp. 508-513, Academic Press, New York.] This involved treating crude hog lens homogenates with hexadecyltrimethylammonium bromide, DEAE-cellulose adsorption and elution, ammonium sulfate fractionation (53-84% of saturation), and gel filtration on a Bio-Gel A-1.5m column. Purifications ranging from 2080- to 4700-fold with activity yields from 28 to 100% were achieved. The hog lens LAP appeared homogeneous by native and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE). Bio-Gel chromatography of the native enzyme and SDS-PAGE of dimethylsuberimidate-crosslinked LAP indicated a molecular weight of 326,000. SDS-PAGE of untreated LAP showed a subunit weight of 54,000, consistent with a hexameric enzyme structure. By immunodiffusion, LAP from hog lens and kidney were identical while hog lens and beef lens enzymes demonstrated only partial identity. Electrophoresis of the native enzymes showed a slightly lower mobility for the hog lens LAP than for beef LAP at pH 8.7.
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PMID:Purification, preliminary characterization, and immunological comparison of hog lens leucine aminopeptidase (EC 3.4.11.1) with hog kidney and beef lens aminopeptidases. 392 44

Nacre organic matrix has been conventionally classified as both 'water-soluble' and 'water-insoluble', based on its solubility in aqueous solutions after decalcification with acid or EDTA. Some characteristics (aspartic acid-rich, silk-fibroin-like content) were specifically attributed to either one or the other. The comparative study on the technique of extraction (extraction with water alone vs. demineralization with EDTA) presented here, seems to reveal that this generally accepted classification may need to be reconsidered. Actually, the nondecalcified soluble organic matrix, extracted in ultra-pure water, displays many of the characteristics of what until now has been called 'insoluble matrix'. We present the results obtained on this extract and on a conventional EDTA-soluble matrix, with various characterization methods: fractionation by size-exclusion and anion-exchange HPLC, amino acid analysis, glycosaminoglycan and calcium quantification, SDS/PAGE and FTIR spectroscopy. We propose that the model for the interlamellar matrix sheets of nacre given by Nakahara [In: Biomineralization and Biological Metal Accumulation, Westbroek, P. & deJong, E.W., eds, (1983) pp. 225-230. Reidel, Dordrecht, Holland] and Weiner and Traub [Phil. Trans. R. Soc. Lond. B (1984) 304, 425-434] may no longer be valid. The most recent model, proposed by Levi-Kalisman et al. [J. Struct. Biol. (2001) 135, 8-17], seemed to be more in accordance with our findings.
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PMID:Soluble silk-like organic matrix in the nacreous layer of the bivalve Pinctada maxima. 1238 58