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21.
22.
Michel Goldberg Jacqueline Feinberg Sylvie Lecolle Marcia A. Kaetzel Dominique Rainteau James L. Lessard John R. Dedman Serge Weinman 《Cell and tissue research》1991,263(1):81-89
Summary Annexin VI and actin were detected by immunoblot analysis in the enamel- and dentin-related portions of dental tissues. Annexin VI was found mainly in the particulate fraction whereas actin was detected in both the soluble and particulate fractions. By immunoelectron microscopy, annexin VI antibodies conjugated with colloidal gold were seen to label the mitochondria, the cytosol and the nucleus of secretory ameloblasts and odontoblasts of rat incisor. In the processes of these cell, the plasmalemmal undercoat was labeled. Antiactin antibodies labeled the desmosome-like junctions, the cytosol, and the mitochondria of the cell bodies. Extensive labeling was seen at the periphery of the Tomes' processes and odontoblast processes. These results suggest that annexin VI may play a role in Ca2+-regulation in the cell bodies, especially as a calcium receptor protein in the mitochondria. Moreover, annexin VI and actin seem to be co-distributed in secretory processes. Thus, these proteins might be both involved in exocytotic and endocytotic events. 相似文献
23.
Osteogenesis imperfecta due to recurrent point mutations at CpG dinucleotides in the COL1A1 gene of type I collagen 总被引:7,自引:3,他引:4
Charles J. Pruchno Daniel H. Cohn Gillian A. Wallis Marcia C. Willing Barbra J. Starman Xiaoming Zhang Peter H. Byers 《Human genetics》1991,87(1):33-40
Summary Most individuals with osteogenesis imperfecta (OI) are heterozygous for dominant mutations in one of the genes that encode the chains of type I collagen. Each of the more than 30 mutations characterized to date has been unique to the affected member (s) of the family. We have determined that two individuals with a progressive deforming variety of OI, OI type III, have the same new dominant mutation [1(I)gly154 to arg] and that two unrelated infants with perinatal lethal OI, OI type II, share a second new dominant muation [1(I)gly1003 to ser]. These mutations occurred at CpG dinucleotides, in a manner consistent with deamination of a methylated cytosine residue, and raise the possibility that CpG dinucleotides are common sites of recurrent mutations in collagen genes. Further, these findings confirm that the OI type-III phenotype, previously thought to be inherited in an autosomal recessive manner, can result from new dominant mutations in the COL1A1 gene of type-I collagen. 相似文献
24.
Influence of Calcium Ion on Ethanol Tolerance of Saccharomyces bayanus and Alcoholic Fermentation by Yeasts 总被引:1,自引:0,他引:1
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Regina C. Nabais Isabel S-Correia Cristina A. Viegas Júlio M. Novais 《Applied microbiology》1988,54(10):2439-2446
The addition of Ca2+ (as CaCl2) in optimal concentrations (0.75 to 2.0 mM) to a fermentation medium with a trace contaminating concentration of Ca2+ (0.025 mM) led to the rapid production of higher concentrations of ethanol by Saccharomyces cerevisiae, Saccharomyces bayanus, and Kluyveromyces marxianus. The positive effect of calcium supplementation (0.75 mM) on alcoholic fermentation by S. bayanus was explained by the increase in its ethanol tolerance. The ethanol inhibition of growth and fermentation followed the equation μxi = μoi [1 - (X/Xmi)]ni, where μoi and μxi are, respectively, the specific growth (i = g) and fermentation (i = f) rates in the absence or presence of a concentration (X) of added ethanol, and Xmi is the maximal concentration of ethanol which allows growth or fermentation. The toxic power is given by ni. In Ca2+ - supplemented medium (0.75 mM), ng = 0.42 for growth and nf = 0.43 for fermentation compared with 0.52 and 0.55, respectively, in unsupplemented medium; for both media, Xmg = 10% (vol/vol) and Xmf = 13% (vol/vol). For lethal concentrations of ethanol, the specific death rates were minimal for cells that were grown and incubated with ethanol in medium with an optimal concentration of Ca2+, maximal for cells grown and incubated with ethanol in unsupplemented medium, and intermediate for cells grown in unsupplemented medium and incubated with ethanol in calcium-supplemented medium. The effect of Ca2+ on the acidification curve of energized cells in the presence of ethanol was found to be closely associated with its protective effect on growth, fermentation, and viability. 相似文献
25.
Intramitochondrial Sr2+, similar to Ca2+, inhibits oxidative phosphorylation in intact rat-liver mitochondria. Both Ca2+ and Sr2+ also inhibit the hydrolytic activity of the ATPase in submitochondrial particles. Half-maximal inhibition of ATPase activity was attained at a concentration of 2.5 mM Ca2+ or 5.0 mM Sr2+ when the concentration of Mg2+ in the medium was 1.0 mM. The inhibition of ATPase activity by both cations was strongly decreased by increasing the Mg2+ concentration in the reaction medium. In addition, kinetical data and the determination of the concentration of MgATP, the substrate of the ATPase, in the presence of different concentrations of Ca2+ or Sr2+ strongly indicate that these cations inhibit ATP hydrolysis by competing with Mg2+ for the formation of MgATP. On the basis of a good agreement between these results with submitochondrial particles and the results of titrations of oxidative phosphorylation with carboxyatractyloside or oligomycin in mitochondria loaded with Sr2+ it can be concluded that intramitochondrial Ca2+ or Sr2+ inhibits oxidative phosphorylation in intact mitochondria by decreasing the availability of adenine nucleotides to both the ADP/ATP carrier and the ATP synthase. 相似文献
26.
Rajendra G. Mehta Leonard J. Schiff Steven J. Moore Ann Marie Buckley Marcia I. Dawson 《In vitro cellular & developmental biology. Plant》1986,22(3):164-168
Summary The mechanism of action of retinoid in reversing keratinization in hamster trachea is yet unknown. The purpose of this study
was to determine if cellular retinoic acid binding protein (CRABP) is present in tracheal epithelium following incubation
in serum-free, vitamin A-deficient culture medium for 10 days, and if the effectiveness of a retinoid in reversing keratinization
in organ culture is correlated with its ability to compete for CRABP sites. The cytosol prepared from tracheal cultures contained
CRABP at a concentration of 2.61 pmoles per mg protein. Of the four retinoids with carboxyl end group selected for the study,
two of the biological active retinoids competed for the CRABP sites. However, no correlation was observed between the biological
activity of the inactive retinoids and their ability to associate with the CRABP sites. These results indicate that even though
the action of retinoid may be mediated by retinoid binding protein, it cannot be used as a sole predicator of retinoid response
in hamster trachea.
This investigation was supported by Contract N01-CP-31012 and U. S. P. H. Grants CA30512 and CA32428, which were awarded by
the Division of Cancer Etiology, National Cancer Institute, DHHS.
Editor's Statement Tracheal organ cultures provide a useful model for the study of epithelial differentiation and carcinogenesis.
Much attention has been given to the action of retinoids in this process. Mehta et al. demonstrate a lack of correlation between
biological activity and specific cytosolic binding of members of this class of compounds, pointing out the need for a more
complete biochemical understanding of the mechanism of action and active forms of retinoids in this and other systems in vivo
and in vitro. David W. Barnes 相似文献
27.
28.
A conformational study of the opioid peptide dermorphin by one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy
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Dermorphin, a natural peptide opioid containing a D-Ala2 residue, has been studied in dimethyl sulfoxide (DMSO) solution by means of several one-dimensional and two-dimensional 1H nuclear magnetic resonance (NMR) methods at various fields from 80 to 600 MHz. The combined use of conventional NMR parameters and of nuclear Overhauser effect effects points to an essentially extended structure. This conformation may be, in part, the result of strong interaction of the amide groups with DMSO molecules. 相似文献
29.
Summary Southern Corn Leaf Blight is caused by a toxin produced by a virulent form ofHelminthosporium maydis (Race T). The toxin has been shown to uncouple oxidative phosphorylation and dissipate Ca2+ gradients in mitochondria isolated from susceptible, but not resistant, corn. The possibility that the toxin acted by increasing the permeability of membranes to ions was tested using a planar bilayer membrane system. Addition of the toxin to the bilayer system, under voltage-clamp conditions, resulted in stepwise increases in current across the phospholipid bilayer, a response characteristic for channel formers. Single-channel conductance in 1m KCl is 27 pS which corresponds to 1.7×107 ions sec–1 channel–1 at 100 mV applied potential. The toxin channels are: (i) fairly uniform in conductance, (ii) ideally selective for K+ over Cl–, and (iii) most conductive to H+. The channel showed the following selectivity for alkali metal cations: Rb+>K+>Cs+>Na+>Li+ (169731) based on the most frequently observed conductance in 1m chloride salts. The toxin showed no voltage dependence over the range of –100 to +100 mV. Channel formation was also a property of a synthetic analog (Cmpd IV) of the toxin. The ability of the native toxin to form channels may be a mode of toxin action on mitochondrial membranes from susceptible corn. 相似文献
30.
Prolactin releasing and luteinizing hormone inhibiting activity of dermorphin shorter homologues in the rat 总被引:1,自引:0,他引:1
D Cocchi E C Degli Uberti G Trasforini S Salvadori R Tomatis R Torpia R Perelli-Cippo 《Life sciences》1985,36(18):1707-1713
Dermorphin, a heptapeptide isolated from the skin of the frogs Phillomedusa sauvagei and Phillomedusa rhodei, is endowed with potent peripheral and central opioid-like activity. Intracerebroventricular (icv) injection of dermorphin (31.2, 62.5 and 125 pmol/100g) induced in ovariectomized (OVX) rats dose related rises and decreases in prolactin (PRL) and luteinizing hormone (LH) levels, respectively. The aim of this work was to evaluate the same endocrine responses after administration of shorter peptide amide homologues, related to the N-terminal sequence of dermorphin. These compounds retain a substantial analgesic activity although the latter decreases with the decrease in the number of amino acid residues. Icv administration of the hexapeptide homologue (dermorphin 1-6 amide) to OVX rats did not induce any PRL rise or LH inhibition, even at the high dose of 250 pmol/100g. The pentapeptide (dermorphin 1-5 amide), instead, increased PRL and decreased LH secretion, although the effect was significant only at the dose of 250 pmol/100g. Administration of the tetrapeptide (dermorphin 1-4 amide) induced a significant PRL rise and LH inhibition at both the doses of 125 and 250 pmol/100g. The tetrapeptide was the smallest fragment of the dermorphin moiety which caused endocrine responses while the tripeptide (dermorphin 1-3 amide) was completely ineffective in this context. These data indicate that a complete dissociation exists between the behavioral and endocrine effects of the dermorphin homologues examined. In fact, shorter dermorphins whose analgesic potency was directly related to the number of amino acids, exhibited an opposite pattern in evoking endocrine effects. 相似文献