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31.
Ilani T Fishburn CS Levavi-Sivan B Carmon S Raveh L Fuchs S 《Cellular and molecular neurobiology》2002,22(1):47-56
D2 and D3 dopamine receptors belong to the superfamily of G protein-coupled receptors; they share a high degree of homology and are structurally similar. However, they differ from each other in their second messenger coupling properties. Previously, we have studied the differential coupling of these receptors to G proteins and found that while D2 receptor couples only to inhibitory G proteins, D3 receptor couples also to a stimulatory G protein, Gs. We aimed to investigate the molecular basis of these differences and to determine which domains in the receptor control its coupling to G proteins. For this purpose four chimeras were constructed, each composed of different segments of the original D2 and D3 receptors. We have demonstrated that chimeras with a third cytoplasmic loop of D2 receptor couple to Gi protein in a pattern characteristic of D2 receptor. On the other hand chimeras containing a third cytoplasmic loop of D3 receptor have coupling characteristics like those of D3 receptor, and they couple also to Gs protein. These findings demonstrate that the third cytoplasmic loop determines and accounts for the coupling of dopamine receptors D2 and D3 to G proteins. 相似文献
32.
Carbon export from arbuscular mycorrhizal roots involves the translocation of carbohydrate as well as lipid 总被引:4,自引:0,他引:4
Bago B Pfeffer PE Abubaker J Jun J Allen JW Brouillette J Douds DD Lammers PJ Shachar-Hill Y 《Plant physiology》2003,131(3):1496-1507
Arbuscular mycorrhizal (AM) fungi take up photosynthetically fixed carbon from plant roots and translocate it to their external mycelium. Previous experiments have shown that fungal lipid synthesized from carbohydrate in the root is one form of exported carbon. In this study, an analysis of the labeling in storage and structural carbohydrates after (13)C(1) glucose was provided to AM roots shows that this is not the only pathway for the flow of carbon from the intraradical to the extraradical mycelium (ERM). Labeling patterns in glycogen, chitin, and trehalose during the development of the symbiosis are consistent with a significant flux of exported glycogen. The identification, among expressed genes, of putative sequences for glycogen synthase, glycogen branching enzyme, chitin synthase, and for the first enzyme in chitin synthesis (glutamine fructose-6-phosphate aminotransferase) is reported. The results of quantifying glycogen synthase gene expression within mycorrhizal roots, germinating spores, and ERM are consistent with labeling observations using (13)C-labeled acetate and glycerol, both of which indicate that glycogen is synthesized by the fungus in germinating spores and during symbiosis. Implications of the labeling analyses and gene sequences for the regulation of carbohydrate metabolism are discussed, and a 4-fold role for glycogen in the AM symbiosis is proposed: sequestration of hexose taken from the host, long-term storage in spores, translocation from intraradical mycelium to ERM, and buffering of intracellular hexose levels throughout the life cycle. 相似文献
33.
Díaz-Quintana A Navarro JA Hervás M Molina-Heredia FP De la Cerda B De la Rosa MA 《Photosynthesis research》2003,75(2):97-110
Plastocyanin and cytochrome c
6 are two soluble metalloproteins that act as alternative electron carriers between the membrane-embedded complexes cytochromes
b
6
f and Photosystem I. Despite plastocyanin and cytochrome c
6 differing in the nature of their redox center (one is a copper protein, the other is a heme protein) and folding pattern
(one is a β-barrel, the other consists of α-helices), they are exchangeable in green algae and cyanobacteria. In fact, the
two proteins share a number of structural similarities that allow them to interact with the same membrane complexes in a similar
way. The kinetic and thermodynamic analysis of Photosystem I reduction by plastocyanin and cytochrome c
6 reveals that the same factors govern the reaction mechanism within the same organism, but differ from one another. In cyanobacteria,
in particular, the electrostatic and hydrophobic interactions between Photosystem I and its electron donors have been analyzed
using the wild-type protein species and site-directed mutants. A number of residues similarly conserved in the two proteins
have been shown to be critical for the electron transfer reaction. Cytochrome c
6 does contain two functional areas that are equivalent to those previously described in plastocyanin: one is a hydrophobic
patch for electron transfer (site 1), and the other is an electrically charged area for complex formation (site 2). Each cyanobacterial
protein contains just one arginyl residue, similarly located between sites 1 and 2, that is essential for the redox interaction
with Photosystem I.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
34.
Zurita F Barrionuevo FJ Berta P Ortega E Burgos M Jiménez R 《The International journal of developmental biology》2003,47(6):451-458
We have performed a morphological, hormonal and molecular study of the development of the sex ducts in the mole Talpa occidentalis. Females develop bilateral ovotestes with a functional ovarian portion and disgenic testicular tissue. The Müllerian ducts develop normally in females and their regression is very fast in males, suggesting a powerful action of the anti-Müllerian hormone in the mole. RT-PCR demonstrated that the gene governing this hormone begins to be expressed in males coinciding with testis differentiation, and expression continues until shortly after birth. Immunohistochemical studies showed that expression occurs in the Sertoli cells of testes. No expression was detected in females. Wolffian duct development was normal in males and degenerate in prenatal females, but developmental recovery after birth gave rise to the formation of rudimentary epididymides. This event coincides in time with increasing serum testosterone levels and Leydig cell differentiation in the female gonad, thus suggesting that testosterone produced by the ovotestes is responsible for masculinisation of female moles. During postnatal development, serum testosterone concentrations decreased in males but increased in females, thus approaching the levels that adult males and females have during the non-breeding season. 相似文献
35.
Ponzo OJ Cresta MA Rondina D Szwarcfarb B Basabe JC Scacchi P 《Neuro endocrinology letters》2000,21(6):441-446
OBJECTIVE AND DESIGN: the objective of this study performed in adult male rats was to determine the alteration in glycemic, insulin and gonadotrophin luteinizing hormone secretion, and noradrenaline pancreatic concentration caused by fasting (F) and aproteic diet (Ap) during 7 and 21 days respectively, as well as the recovery after 24-hour refeeding with control diet (Co). RESULTS: a significant decrease in glycemic levels was only achieved through fasting (F: 86 +/- 5.1 mg %), when compared with controls (Co: 107 +/- 5 mg %). In spite of the high levels of carbohydrates (89%) present in the aproteic diet, the animals fed with this diet showed no differences in glycemic levels (Ap: 120.3 +/- 12.2 mg %), compared with controls. As a result of fasting and aproteic diet, there was a significant decrease in insulin (F: 8.67 +/- 1.36; Ap: 5.7 +/- 0.67; Co: 31 +/- 3.4 uU/ml) and LH levels (F: 10.175 +/- 1.74; Ap: 13.7 +/- 4; Co: 29.83 +/- 4.91 ng/ml). The refed recovered insulin (FR: 50.57 +/- 6.63; ApR: 43.5 +/- 6.85 uU/ml), but not LH levels (FR: 14.25 +/- 3.54; ApR: 13.03 +/- 4.25 ng/ml). A significant increase was observed in the pancreatic noradrenaline concentration (P<0.001) of rats receiving aproteic diet (889.9 +/- 34.65 ng/mg tissue) and fasting during 7 days (827.5 +/- 55.7 ng/mg tissue), compared with controls (531.1 +/- 48.6 ng/mg tissue). CONCLUSIONS: fasting and aproteic diets altered gonadal and metabolic control. When returning to a normal nutritional condition, only the metabolic control, not the reproductive function, could be recovered in the first 24 hours of refeeding. Malnutrition-induced hypoinsulinemia would be caused by an increase in a specific noradrenergic tone. 相似文献
36.
A. Fusconi A. M. Tagliasacchi G. Berta A. Trotta S. Brazzaventre F. Ruberti S. Scannerini 《Protoplasma》2000,214(3-4):219-226
Summary Arbuscular mycorrhizal (AM) fungi significantly improve plant growth in soils with low phosphorus availability and cause many changes in root morphology, similar to those produced by increased P nutrition, mainly depending on root apex size and activity. The aim of this work was to discriminate between the morphogenetic role of AM fungi and P in leek (Allium porrum L.) by feeding mycorrhizal and nonmycorrhizal plants with two nutrient solutions containing 3.2 or 96 M P and examining specific parameters related to adventitious root apices (apex size, mitotic cycle, and RNA synthesis). The results showed that AM fungi blocked meristem activity as indicated by the higher percentages of inactive apices and metaphases in the apical meristem of mycorrhizal plants, whereas the high P supply lengthened the mitotic cycle without blocking the apices, resulting in steady, slow root growth. The possible involvement of abscisic acid in the regulation of root apex activity is discussed.Abbreviations ABA
abscisic acid
- AM
arbuscular mycorrhizae
- CI and CII
nonmycorrhizal control plants grown with low or high phosphorus concentration
- MI and MII
mycorrhizal plants grown with low or high phosphorus concentration
- PGR
plant growth regulator 相似文献
37.
Navarro JA Hervás M Sun J De la Cerda B Chitnis PR De la Rosa MA 《Photosynthesis research》2000,65(1):63-68
Wild-type plastocyanin from the cyanobacterium Synechocystis sp. PCC 6803 does not form any kinetically detectable transient complex with Photosystem I (PS I) during electron transfer,
but the D44R/D47R double mutant of copper protein does [De la Cerda et al. (1997) Biochemistry 36: 10125–10130]. To identify
the PS I component that is involved in the complex formation with the D44R/D47R plastocyanin, the kinetic efficiency of several
PS I mutants, including a PsaF–PsaJ-less PS I and deletion mutants in the lumenal H and J loops of PsaB, were analyzed by
laser flash absorption spectroscopy. The experimental data herein suggest that some of the negative charges at the H loop
of PsaB are involved in electrostatic repulsions with mutant plastocyanin. Mutations in the J loop demonstrate that this region
of PsaB is also critical. The interaction site of PS I is thus not as defined as first expected but much broader, thereby
revealing how complex the evolution of intermolecular electron transfer mechanisms in photosynthesis has been.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
38.
Gerard H. Bode Karin E. Pickl Maria Sanchez-Purrà Berta Albaiges Salvador Borrós Andy J. G. P?tgens Christoph Schmitz Frank M. Sinner Mario Losen Harry W. M. Steinbusch Hans-Georg Frank Pilar Martinez-Martinez European NanoBioPharmaceutics Research Initiative 《PloS one》2015,10(5)
AimsThe aim of the current study was to develop a method to detect peptide-linked nanoparticles in blood plasma.ResultsThe ELISA based method for the detection of FITC labeled peptides had a detection limit of 1 ng/mL. We were able to accurately measure peptides bound to pentafluorophenyl methacrylate nanoparticles in blood plasma of rats, and similar results were obtained by LC/MS.ConclusionsWe detected FITC-labeled peptides on pentafluorophenyl methacrylate nanoparticles after injection in vivo. This method can be extended to detect nanoparticles with different chemical compositions. 相似文献
39.
Esther C. Maier Ankur Saxena Berta Alsina Marianne E. Bronner Tanya T. Whitfield 《Developmental biology》2014
For both the intricate morphogenetic layout of the sensory cells in the ear and the elegantly radial arrangement of the sensory neurons in the nose, numerous signaling molecules and genetic determinants are required in concert to generate these specialized neuronal populations that help connect us to our environment. In this review, we outline many of the proteins and pathways that play essential roles in the differentiation of otic and olfactory neurons and their integration into their non-neuronal support structures. In both cases, well-known signaling pathways together with region-specific factors transform thickened ectodermal placodes into complex sense organs containing numerous, diverse neuronal subtypes. Olfactory and otic placodes, in combination with migratory neural crest stem cells, generate highly specialized subtypes of neuronal cells that sense sound, position and movement in space, odors and pheromones throughout our lives. 相似文献
40.