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591.
Armand Malnoë Jos A. Cox Eric A. Stein 《Biochimica et Biophysica Acta (BBA)/General Subjects》1982,714(1):84-92
The binding parameters of 125I-labeled calmodulin to bovine cerebellar membranes have been determined and correlted with the activation of adenylate cyclase by calmodulin. In the presence of saturating levels of free Ca2+, calmodulin binds to a finite number of specific membrane sites with a dissociation constant (Kd) of 1.2 nM. Furthermore, Scatchard analysis reveals a second population of binding sites with a 100-fold lower affinity for calmodulin. The Ca2+-dependence of calmodulin binding and of adenylate cyclase activation varies with the amount of calmodulin present, as can be infered from the model of sequential equilibrium reactions which describes the activation of calmodulin-dependent enzymes. On the basis of this model, a quantitative analysis of the effect of free Ca2+ and of free calmodulin concentration on both binding and activation of adenylate cyclase was carried out. This analysis shows that both processes take place only when calmodulin is complexed with at least three Ca2+ atoms. The concentration of the active calmodulin ·Ca2+ species required for half-maximal activation of adenylate cyclase is very similar to the Kd of the high affinity binding sites on brain membranes. A Hill coefficient of approx. 1 was found for both processes indicating an absence of cooperativity. Phenothiazines and thioxanthenes antipsychotic agents inhibit calmodulin binding to membranes and calmodulin-dependent activation of adenylate cyclase with a similar order of potency. These results suggest that the Ca2+-dependent binding of calmodulin to specific high affinity sites on brain membranes regulates the activation of adenylate cyclase by calmodulin. 相似文献
592.
Herzl Schwalb Linda Owers Narhi Armand J. Fulco 《Biochimica et Biophysica Acta (BBA)/General Subjects》1985,838(3):302-311
When Bacillus megaterium ATCC 14581 is grown in the presence of barbiturates, a cytochrome P-450-dependent fatty acid monooxygenase (Mr 120 000) is induced (Kim, B.-H. and Fulco, A.J. (1983) Biochem. Biophys. Res. Commun. 116, 843–850). Gel filtration chromatography of a crude monooxygenase preparation from pentobarbital-induced B. megaterium indicated that not all of the induced cytochrome P-450 present in the extract was accounted for by this high-molecular-weight component. Further purification revealed the presence of two additional but smaller cytochrome P-450 species. The minor component, designated cytochrome P-450BM-2, had a molecular mass of about 46 kDa, but has not yet been completely purified or further characterized. The major component, designated cytochrome P-450BM-1, was obtained in pure form, exhibited fatty acid monooxygenase activity in the presence of iodosylbenzenediacetate, and has been extensively characterized. Its Mr of 38 000 makes it the smallest cytochrome P-450 yet purified to homogeneity. Although it is a soluble protein, a complete amino acid analysis indicated that it contains 42% hydrophobic residues. By the dansyl chloride procedure the NH2-terminal amino acid is proline; the penultimate NH2-terminal residue is alanine. The absolute absorption spectra of cytochrome P-450BM-1 show maxima in the same general regions as do P-450 cytochromes from mammalian or other bacterial sources, but they differ in detail. The oxidized form of P-450BM-1 has absorption maxima at 414, 533 and 567 nm, while the reduced form has peaks at 410 and 540 nm. The absorption maxima for the CO-reduced form of P-450BM-1 are found at 415, 448 and 550 nm. Antisera from rabbits immunized with pure P-450BM-1 strongly reacted with and precipitated this P-450, but showed no detectable affinity for either the 46 kDa P-450 or the 120 kDa fatty acid monooxygenase. 相似文献
593.
Armand B. Glassman William H. Coles Carol E. Bennett 《In vitro cellular & developmental biology. Plant》1979,15(11):873-876
Summary A modified method for establishing cultures of rabbit corneal cells is described. The new technique utilized a Lucite disc
in combination with a Tygon ring for growth of pure cell cultures and was compared with an explant method for growing cells.
Each method provided adequate cell cultures for biochemical or ultrastructure studies of rabbit corneal cells, but the ring
and disc method described here allowed the isolation of specific cell types without the interference of stromal cell contamination. 相似文献
594.
Armand T. Whitehead 《Journal of morphology》1971,135(4):483-505
The salivary gland of Periplaneta americana (L.) is innervated from both the stomatogastric nervous system (SNS) and subesophageal ganglion (SEG). Methylene-blue preparations, histological sections and electron microscopy revealed a pair of nerves from the SEG, each of which contains two axons 5–7 μ in diameter, and these are accompanied by several smaller ones. The nerves going to the salivary glands from the SNS contain a dozen or more axons, each less than 2 μ thick. Axons from two sources innervate the efferent salivary ducts, the acini, the anterior ends of the salivary reservoirs, and the reservoir suspensory muscles. A nerve which has reached an acinus forms a plexus upon its surface. Electron micrographs disclose penetration of axons with or without glial wrappings, into the intercellular spaces between gland cells. Axons without glial wrappings have been observed in intimate contact with gland-cell membranes, and several areas which resemble synaptic junctions have been seen. 相似文献
595.
M. J. Kotze Rochelle Thiart Odell Loubser J. N. P. de Villiers Maria Santos Marco A. Vargas Armand V. Peeters 《Human genetics》1996,98(4):476-478
Mutation analysis of the low density lipoprotein receptor (LDLR) gene revealed a novel 8-bp duplication after nucleotide
681 in a Costa Rican patient with familial hypercholesterolaemia. The frameshift caused by this mutation results in a premature
termination codon in the EGF precursor homology domain of the mature LDLR, whereby a truncated protein of the first 206 residues
with an additional 39 abnormal residues would be created. The insertion overlaps with previously described duplications of
18 bp and 21 bp, thus revealing an insertional hotspot in exon 4 of the LDLR gene. We propose that the structural features
of this region of the LDLR gene contribute significantly to genetic instability and the subsequent DNA duplication via an
endogenous sequence-directed mechanism of mutagenesis.
Received: 10 November 1995 / Revised: 15 March 1996 相似文献
596.
Luke S Tain Encarnación Lozano Alberto G Sáez Armand M Leroi 《BMC developmental biology》2008,8(1):28
Background
Dietary restriction (DR) results in increased longevity, reduced fecundity and reduced growth in many organisms. Though many studies have examined the effects of DR on longevity and fecundity, few have investigated the effects on growth. 相似文献597.
598.
599.
The mouse major histocompatibility complex (MHC) contains many genes in addition to the classical immune response genes. We have screened overlapping cosmid clones covering 170 kb of the H-2K region for genes expressed in embryonal carcinoma (EC) cells. The Ke-3 gene (Abe et al. 1988) found in this region was further studied by Southern, Northern, and sequence analysis. It is an expressed, intron-containing locus encoding a mouse homolog of the bacterial ribosomal protein S13. This is the first nonorganelle S13 homolog identified in metazoans, and its genomic location has been determined precisely. 相似文献
600.
P Dejours J Armand H Beekenkamp 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1991,312(13):677-682
The effects of PCO2 and pH changes in the ambient water on the nitrogen catabolism and the proportions of the excreted nitrogenous end products, ammonia and urea, were studied in the clawed frog, Xenopus laevis, at 24 degrees C. In animals living in artificial fresh water, the exposure to a hypocapnic alkalosis (PCO2 = 0.7 Torr instead of 10 Torr) did not entail any change in the nitrogen catabolism. In animals who lived in a water loaded with NaCl and had therefore a higher oxygen consumption, an intense nitrogen catabolism and a marked ureotelism, the hypocapnic alkalosis seems to have increased the intensity of the nitrogen catabolism. In neither group were there signs of ammonia toxicity. 相似文献