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排序方式: 共有219条查询结果,搜索用时 15 毫秒
1.
G Schettini T Florio O Meucci E Landolfi M J Cronin R M MacLeod 《Life sciences》1987,41(22):2437-2444
The control of prolactin secretion by Ca calmodulin and cyclic AMP was studied. Ca++ ionophore A23187 stimulated both cyclic AMP accumulation and prolactin release by primary culture of anterior pituitary cells in vitro. The increase of cyclic AMP formation by A23187 preceded that of prolactin release. To test the calmodulin involvement in these processes we used either selective calmodulin antagonist, the naphthalene sulphonamide derivative W7, or calmodulin containing liposomes. W7 dose dependently inhibited both basal or A23187 stimulated cyclic AMP accumulation and prolactin secretion. Insertion of Ca calmodulin within the cells stimulated prolactin secretion without modifying cyclic AMP accumulation. W7 inhibited the Ca calmodulin containing liposomes stimulation of prolactin release. These results suggest that calmodulin participates to the process of prolactin release. 相似文献
2.
Indirect evidence suggests that legumes can adjust rapidly theresistance of their root nodules to O2 diffusion. Here we describeexperiments using O2 specific micro-electrodes and dark fieldmicroscopy to study directly the operation of this diffusionbarrier. The O2 concentration sensed by the electrode decreasedsharply in the region of the inner cortex and was less than1.0 mmol m3 throughout the infected tissue in nodulesof both pea (Pisum sativum) and french bean (Phaseolus vulgaris).In a number of experiments the ambient O2 concentration wasincreased to 40% while the electrode tip was just inside theinner cortex. In 13 out of 21 cases the O2 concentration atthis position either remained low and unchanged or increasedirreversibly to near ambient values. In the remaining casesthe O2 concentration increased after 1 to 2.5 min and then decreasedto its former value. These results are ascribed to an increasein resistance of the barrier in response to increased O2 fluxinto the nodule. It was shown microscopically that air spacesboth at the boundary between the infected zone and the innercortex, and within the infected zone started to disappear 3min after nodules were exposed to high ambient O2 concentrationsand had disappeared completely after 8 min. These spaces werenot changed by exposure of the nodule for 10 min to either N2or air. Key words: Oxygen, root nodules, air spaces 相似文献
3.
Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications 总被引:1,自引:0,他引:1
Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of
individuals representing 54 species of frogs, two species of salamanders, a
caecilian, and a lungfish. Eight of these sites were present in all species
examined, and two were found in all but one species. Alignment of these
conserved restriction sites revealed, among anuran 28S rRNA genes, five
regions of major length variation that correspond to four of 12 previously
identified divergent domains of this gene. One of the divergent domains
(DD8) consists of two regions of length variation separated by a short
segment that is conserved at least throughout tetrapods. Most of the
insertions, deletions, and restriction-site variations identified in the
28S gene will require sequence-level analysis for a detailed reconstruction
of their history. However, an insertion in DD9 that is coextensive with
frogs in the suborder Neobatrachia, a BstEII site that is limited to
representatives of two leptodactylid subfamilies, and a deletion in DD10
that is found only in three ranoid genera are probably synapomorphies.
相似文献
4.
Interleukin 1 beta inhibition of TRH-stimulated prolactin secretion and phosphoinositides metabolism
G Schettini E Landolfi M Grimaldi O Meucci A Postiglione T Florio C Ventra 《Biochemical and biophysical research communications》1989,165(1):496-505
The effect of interleukin 1 beta on prolactin secretion and on phosphoinositide turnover in anterior pituitary cells was evaluated. Interleukin 1 beta significantly inhibited TRH-stimulated prolactin secretion assessed by the reverse hemolytic plaque assay. In particular, the cytokine reduced the percentage of plaque forming cells, the plaque mean area, the large plaques percentage. TRH-stimulated inositol phosphate production was also significantly inhibited by interleukin 1 beta. This study shows that interleukin 1 beta reduces TRH-induced prolactin secretion through a direct action on pituitary cell, and attenuates the TRH-stimulated phosphoinositide breakdown. This latter effect may suggest that the reduced lactotropes sensitivity to TRH action may be partially due to interleukin 1 beta inhibition of phosphatidylinositol breakdown. 相似文献
5.
Aberrant protein phosphorylation at tyrosine is responsible for the growth-inhibitory action of pp60v-src expressed in the yeast Saccharomyces cerevisiae. 总被引:1,自引:1,他引:0 下载免费PDF全文
M Florio L K Wilson J B Trager J Thorner G S Martin 《Molecular biology of the cell》1994,5(3):283-296
Expression of pp60v-src, the transforming protein of Rous sarcoma virus, arrests the growth of the yeast Saccharomyces cerevisiae. To determine the basis of this growth arrest, yeast strains were constructed that expressed either wild-type v-src or various mutant v-src genes under the control of the galactose-inducible, glucose repressible GAL1 promoter. When shifted to galactose medium, cells expressing wild-type v-src ceased growth immediately and lost viability, whereas cells expressing a catalytically inactive mutant (K295M) continued to grow normally, indicating that the kinase activity of pp60v-src is required for its growth inhibitory effect. Mutants of v-src altered in the SH2/SH3 domain (XD4, XD6, SPX1, and SHX13) and a mutant lacking a functional N-terminal myristoylation signal (MM4) caused only a partial inhibition of growth, indicating that complete growth inhibition requires either targeting of the active kinase or binding of the kinase to phosphorylated substrates, or both. Cells arrested by v-src expression displayed aberrant microtubule structures, alterations in DNA content and elevated p34CDC28 kinase activity. Immunoblotting with antiphosphotyrosine antibody showed that many yeast proteins, including the p34CDC28 kinase, became phosphorylated at tyrosine in cells expressing v-src. Both the growth inhibition and the tyrosine-specific protein phosphorylation observed following v-src expression were reversed by co-expression of a mammalian phosphotyrosine-specific phosphoprotein phosphatase (PTP1B). However a v-src mutant with a small insertion in the catalytic domain (SRX5) had the same lethal effect as wild-type v-src, yet induced only very low levels of protein-tyrosine phosphorylation. These results indicate that inappropriate phosphorylation at tyrosine is the primary cause of the lethal effect of pp60v-src expression but suggest that only a limited subset of the phosphorylated proteins are involved in this effect. 相似文献
6.
G. Schettini O. Meucci M. Grimaldi T. Florio E. Landolfi A. Scorziello C. Ventra 《Journal of neurochemistry》1991,56(3):805-811
In this study, we report the effect of pertussis toxin pretreatment on dihydropyridine modulation of voltage-sensitive calcium channels in PC12 cells. The rise in intracellular calcium concentration caused by potassium depolarization is not affected significantly by pertussis toxin pretreatment. Nicardipine, a dihydropyridine derivative, added either before or after potassium-induced depolarization, reduces the resultant elevation in cytosolic calcium level both in control and in pertussis toxin-treated cells. The dihydropyridine agonist Bay K 8644, when added before potassium, is able to enhance the potassium-induced spike of cytosolic calcium levels, an effect significantly reduced by pertussis toxin pretreatment. Moreover, the addition of Bay K 8644 after potassium holds the intracellular calcium concentration at a cytosolic sustained level during the slow inactivating phase of depolarization. This effect of Bay K 8644 is inhibited by nicardipine. Pertussis toxin pretreatment slightly weakens the effect of Bay K 8644 when added after potassium-induced depolarization, whereas it significantly reduces the nicardipine inhibition of cytosolic calcium rise stimulated by potassium and Bay K 8644, but not by potassium alone. In conclusion, our findings suggest that a pertussis toxin-sensitive guanine nucleotide regulatory protein could be involved in the interaction between dihydropyridine derivatives and voltage-dependent calcium channels. 相似文献
7.
E I Rotman K S De Jongh V Florio Y Lai W A Catterall 《The Journal of biological chemistry》1992,267(23):16100-16105
The primary (alpha 1) subunit of purified skeletal muscle dihydropyridine-sensitive calcium channels is present in full-length (212 kDa) and truncated (190 kDa) forms which are both phosphorylated by cAMP-dependent protein kinase (cA-PK) in vitro. In the present study, phosphorylation of the purified calcium channel by cA-PK followed by immunoprecipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and two-dimensional phosphopeptide mapping revealed differential phosphorylation of the related 190- and 212-kDa forms. The 190-kDa form of the alpha 1 subunit was phosphorylated on three major and three minor tryptic phosphopeptides; the 212-kDa form was phosphorylated on all six of these phosphopeptides plus two that were unique. Time course experiments showed that a single site on the COOH-terminal portion of the full-length form of the alpha 1 subunit is most intensely and rapidly (within 10 s) phosphorylated. Phosphorylation occurs almost exclusively on this COOH-terminal site unless harsh conditions such as treatment with denaturing detergents are employed to expose phosphorylation sites within the 190-kDa segment of the molecule. Elution of phosphopeptides from the second dimension chromatograph followed by immunoprecipitation with an anti-peptide antibody (anti-CP1) directed against the COOH-terminal amino acid sequence enabled us to identify this major phosphorylation site as serine 1854. The nearby consensus sites for cA-PK phosphorylation at serines 1757 and 1772 were phosphorylated only after denaturation or proteolytic cleavage. Phosphorylation of serine 1854 may play a pivotal role in the regulation of calcium channel function by cA-PK. 相似文献
8.
M Grimaldi O Meucci A Scorziello T Florio C Ventra R De Mercato G Schettini 《Life sciences》1992,51(16):1243-1248
We investigated the effect of interleukin-6 (IL-6) on second messenger systems in anterior pituitary (AP) cells. The acute exposition of membranes derived from the pituitary gland to IL-6 did not modify basal and forskolin-stimulated adenylate cyclase (AC) activity, as well as inositol phosphate (IP) production and free [Ca(++)]i. Preincubation of AP cells with IL-6 for 20 min did not affect basal second messengers levels, while completely abolished the stimulation by VIP of AC activity, partially inhibited forskolin-stimulated cAMP formation and reduced TRH-stimulated IP production. Finally, the pretreatment of AP cells for 20 min with IL-6 also reduced the TRH-induced rise in free [Ca(++)]i. 相似文献
9.
10.