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101.
Various chimaeric promoter regions coupled to the uidA -glucuronidase gene were evaluated for transient expression strength following electroporation into sugar-cane (monocot) and carrot (dicot) protoplasts. Multiple enhancer elements increased expression in sugar-cane, by up to 400-fold for the artificial Emu promoter relative to the CaMV 35S promoter. The relative expression strengths of promoters varied substantially between the species. Sugar-cane also differed in some respects from previously tested species in the family Poaceae. For example, in sugar-cane the nopaline synthase and CaMV 35S promoters were of equivalent strength, and insertion of Adh1 intron 1 into the 5 transcribed region decreased expression strength. 相似文献
102.
Arthur M. Brown 《The Journal of membrane biology》1993,131(2):93-104
Summary Ion channels are signaling molecules and by them-selves perform no work. In this regard they are un like the usual membrane
enzyme effectors for G proteins. The pathways of G protein receptor, G protein and ion channels are, therefore, purely infor
mational in function. Because a single G protein may have several ion channels as effectors, the effects should be coordinated
and this seems to be the case. Inhibition of Ca2+ current and stimulation of K+ currents would have a greater impact than either alone. Additional flexibility is provided by spontane ous noise in the complexes
of G protein receptor, G protein, and ion channel. By having a non-zero setpoint, the range of control is extended and the
responses become bi-directional. 相似文献
103.
T. Mastrocola I. H. Lambert B. Kramhøft M. Rugolo E. K. Hoffmann 《The Journal of membrane biology》1993,136(1):55-62
Trypsinized human skin fibroblasts in suspension perform regulatory volume decrease (RVD) after cell swelling in hypotonic medium. During RVD, 36Cl– efflux is dramatically increased and the cell membrane is depolarized, indicating the activation of Cl– channels. This activation of Cl– channels depends on extracellular as well as on intracellular Ca2+. The swelling-induced Cl– efflux and the RVD response are inhibited by the 5-lipoxygenase inhibitor ETH 615-139. Finally, following hypotonic treatment, cellular pH decreases. The pH decrease does not involve the Cl–/HCO
3
–
exchange because it is independent of the external Cl– concentration.T. Mastrocola was recipient of a scientific fellowship from the Italian Consiglio Nazionale delle Ricerche (C.N.R.). This work was supported by Progetto Finalizzato Ingegneria Genetica, C.N.R., Roma, and by the Danish Natural Research Council. 相似文献
104.
105.
106.
107.
J. Féthière R. Graihle L. Larose K. Babinski H. Ong A. De Léan 《Molecular and cellular biochemistry》1993,124(1):11-16
The differential distribution of natriuretic peptide receptor subtypes and their distinct properties were assessed in mammalian cellular models which were screened for their ability to produce cGMP upon stimulation by different natriuretic peptides. The ANF-R1A receptor subtype was distinguished by its selective activation by atrial natriuretic factor (ANF) while the ANF-R1C was characterized by preferential stimulation by C-type natriuretic peptide (CNP). AT-t20 pituitary cells, bovine adrenal chromaffin cells, and NIH-3T3 fibroblasts mainly express the ANF-R1C receptor subtype. Other cell lines such as PC12, RASM and GH3 express significant but varying amounts of both ANF-R1A and ANF-R1C subtypes. A10 and NIH cells which express high density of ANF-R2 receptor subtype, also demonstrate a higher sensitivity to CNP over ANF suggesting that they express significant amounts of ANF-R1C. Studies of the regulation by ATP of guanylyl cyclase activity indicate that both ANF-R1A and ANF-R1C subtypes are modulated in the same manner. In the presence of Mn2+, ATP inhibits the CNP-stimulated guanylyl cyclase activity while in the presence of Mg2+ adenine nucleotides potentiate the stimulation by CNP. In addition, we show that like the ANF-R1A, the ANF-R1C guanylyl cyclase activity can be regulated by phosphorylation since preincubation with TPA or FKL attenuates the subsequent stimulation by CNP in cultured cells. The results presented demonstrate that specific cell types express distinct natriuretic peptide receptor subtypes and also that the newly characterized ANF-R1C subtype is regulated by ATP and serine/threonine kinases in the same way as the ANF-R1A subtype.Abbreviation ANF
atrial natriuretic factor
- BNP
brain natriuretic peptide
- CNP
C-type natriuretic peptide
- ATP
adenosine-5-triphosphate
- IBMX
3-isobutyl-1-methylxanthine
- TPA
12-O-tetradecanoyl-phorbol-13-acetate
- FKL
forskolin
- PKC
calcium-phospholipid-dependent protein kinase
- PKA
cAMP-dependent protein kinase
- PKG
cGMP-dependent protein kinase
- C-ANF
[Cys116]-ANF-(102-116)-NH2
- CC
chromaffin cells 相似文献
108.
109.
环境因子对荒漠沙蜥种群密度影响的研究 总被引:6,自引:1,他引:5
本文研究人类改造荒漠的活动,植被,潜在的可利用的食物资源,竞争种的密度,土壤理化性质等坏境因子对荒漠沙蜥种群密度的影响。结果说明:人类的活动对沙蜥种群密度没有显著影响;决定沙蜥种群密度的主导因子是潜在的可利用的食物资源,植被,土壤含水量,竞争种的密度。这些因子的任何改变都能改变沙蜥的种群密度,均具有调节种群的作用。 相似文献
110.
Derek LeRoith Vadim M. Kavsan Anatolii P. Koval Charles T. Roberts 《Molecular reproduction and development》1993,35(4):332-338
The IGFs (IGF-I and IGF-II) are essential for normal mammalian growth and development. Their actions are mediated primarily by their interactions with the type I IGF receptor (IGF-I receptor), a transmembrane tyrosine kinase. The ligands and the IGF-I receptor are structurally related to insulin and to the insulin receptor, respectively. Analysis of evolutionary conservation has often provided insights into essential regions of molecules such as hormones and their receptors. The genes for insulin and IGFs have been partially characterized in a number of vertebrate species extending evolutionarily from humans as far back as fish. The sequences of the exons encoding the mature insulin and IGF peptides are highly conserved among vertebrate species, and IGF-I-Iike molecules are found in species whose origins extend back as much as 550 million years. The insulin receptor is also highly conserved in vertebrate species, and an insulinreceptor-like molecule has been characterized in Drosophila. In contrast, IGF-I receptors have only been characterized in mammalian species and partially studied in Xenopus, in which the tyrosine kinase domain is highly conserved. Studies are presently being undertaken to analyze in more detail the regulation of the genes encoding this important family of growth factors and the structure/function relationships in the gene products themselves. © 1993 Wiley-Liss, Inc. 相似文献