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51.
Daniela Cocchi Angela Santagostino Irit Gil-Ad Sergio Ferri Eugenio E. Müller 《Life sciences》1977,20(12):2041-2046
The effect of Leu5-enkephalin on growth hormone (GH) and prolactin (PRL) release was studied in the infant rat and compared to that of morphine. In 10 day-old pups, intracerebroventricular injection of Leu5-enkephalin (50, 75 and 100 μg) resulted in a dose-related increase in plasma GH; morphine was active as GH releaser at the dose of 5 and 10 μg, but not at 2.5 μg. Pretreatment with naloxone (2 mg/kg ip) suppressed the GH-releasing effect of either Leu5-enkephalin (100 μg) or morphine (10 μg). Leu5-enkephalin (75 and 100 μg) induced a rise in plasma PRL which was neither dose-related nor antagonized by naloxone; morphine (5 and 10 μg) was active as PRL releaser and its effect was antagonized by naloxone. These results indicate that: 1) Leu5-enkephalin stimulates both GH and PRL release; 2) the release of GH by Leu5-enkephalin but likely not that of PRL involves specific opiate receptors; 3) morphine releases GH and PRL through specific opiate receptors. 相似文献
52.
The enzyme 2-keto-3-deoxygluconate-6-P aldolase of Pseudomonas putida is inactivated by one of the chiral forms of 2-keto-(3RS)-3-bromobutyric acid (bromoketobutyrate). The inactivation shows saturation kinetics and competition with pyruvate. The minimal inactivation half-time is 4 min and that concentration of bromoketobutyrate half-saturating the enzyme is 2 mM. (3RS)-[3-3H]bromoketobutyrate is catalytically detritiated during enzyme inactivation. A kinetic analysis of rates gave data consistent with both catalysis and inactivation occurring at a single protein site, the catalytic site. The enzyme only detritiates one of the two optical isomers of bromoketobutyrate, and that form which is detritiated also alkylates the catalytic site. The inactive isomer of reagent degrades, with inversion, to L-lactate so that the chiral form specific for the enzyme is 2-keto-(3S)-3-bromobutyrate. Thus, as is the case with bromopyruvate, the enzyme catalyzes protonation of the re face at C-3 of the enzyme-reagent eneamine. As a result, bromoketobutyrate could serve as a chiral probe for stereochemical constraints of selected pyruvate-specific lyase active sites. 相似文献
53.
Daniela Duca Doina Ioan P. Meilă M. Ionescu-Cerna Ligia Simionescu C. Maximilian 《Human genetics》1981,57(2):214-216
Summary A dysmorphic 5-year-old girl with severe growth and mental deficiency was studied. She presented a de novo interstitial 2p deletion. Karyotype: 46,XX,del(2)(p13p15). 相似文献
54.
Results from this study indicate that adult rat brain posesses guanylate cyclase activity sensitive to serotonin (5-HT) and localized in the synaptic plasma membrane. The enzyme appears to have multiple activation sites for 5-HT with specific activity maxima at the 5-HT concentrations of 5 × 10?10M and 7 × 10?8M respectively. The rates of guanosine-3′:5′-monophosphate (cyclic GMP) formation at these concentrations of 5-HT are, respectively, 170% and 307% above the endogenous or basal production rate of 2.7±0.3picomoles/minute/milligram of synaptosomal membrane protein. We have also been able to identify distinct types (Type #1, #2, #3, and #4) of high affinity, specific binding sites for 5-HT on isolated synaptosomal membranes from rat brain. Dissociation constants of 2.6 × 10?10M, 2.5 × 10?9M, 7.0 × 10?9M, and 4.6 × 10?8M, characterize the binding of 5-HT to our sites of Type #1 through Type #4 respectively. The specific, high affinity binding was saturated at 5-HT concentrations of 5 × 10?10M for the Type #1 sites, 5 × 10?9M for our Type #2 sites, 1 × 10?8M for our Type #3 sites, and 7 × 10?8M for our Type #4 sites. The 5-HT concentrations producing saturation of our specific binding sites of Type #1 and Type #4 are virtually identical to those that elicit the two maxima of 5-HT stimulated cyclic GMP production, indicating that a membrane-bound guanylase cyclase may be closely associated with certain 5-HT receptors and/or re-uptake sites. 相似文献
55.
56.
In vivo accumulation of sulfated glycoprotein 2 mRNA in rat thymocytes upon dexamethasone-induced cell death 总被引:3,自引:0,他引:3
S Bettuzzi L Troiano P Davalli F Tropea M C Ingletti E Grassilli D Monti A Corti C Franceschi 《Biochemical and biophysical research communications》1991,175(3):810-815
Two hours after a single intraperitoneal injection of dexamethasone (20 micrograms/Kg b.w.) into adult male rats, a typical ladder of DNA fragments was detectable upon separation on agarose gels of DNA from thymocytes. This became maximally evident at 4 hours. Accumulation of sulfated glycoprotein-2 (SGP-2) mRNA, whose rate of expression has been associated to the processes of programmed cell death, preceded the appearance of DNA degradation, starting to increase as early as 30 min after steroid injection, and maintained higher than controls until 8 hrs; a different time course was shown by changes in the levels of beta-actin mRNA. In the spleen, under the same conditions, the SGP-2 message also increased at 30 min, prior to DNA fragmentation, but decreased thereafter below the control value. 相似文献
57.
Arabidopsis thaliana tumors were induced by octopine strain ofAgrobacterium tumefaciens B6S3 and its derivatives with modified T-DNA. Flowering shoots appeared sponta-neously onin vitro cultivated tumors and set seeds. R1 and R2 progeny of octopine synthesizing plants segregated in opine synthesis activities 3:1 and 15:1. Octopine synthase activity
showed absolute linkage with agropine synthesis in most lines. In R3 and R4 progenies, the fraction of octopine synthase and agropine synthesis positive plants was lower than expected, but Mendelian
segregation was restored if plants were cultivated on medium with 5-azacytidine. The most probable mechanism of disapearance
of opine synthesis is cytosine methylation. The effect of 5-azacytidine lasted for at least next two generations. 相似文献
58.
Cation transport in erythrocytes of some uremic patients is impaired. Most studies have focused on the defect of the erythrocyte Na+/K+ pump in these diseased states. Herein, this cation transport defect was studied by using nuclear magnetic resonance spectroscopy (NMR) which is a non-invasive method permitting study on living erythrocytes. Firstly, we verified that the Na+ transport defect in uremic erythrocytes was not due to non-specific causes such as membrane alteration or a modification of the intracellular metabolism. The proton relaxation data, determined using a paramagnetic doping method, are consistent with a lack of erythrocytic membrane damage in uremic patients. Also, 31P-NMR results showed that in our experimental conditions, uremic and normal erythrocytes exhibit similar variations of ATP level over time. Lastly, the use of anionic paramagnetic shift reagent in 23Na-NMR revealed a defect in the Na+/K+ pump of erythrocytes from uremic patients with high Nain concentration. This defect seems to be due to a reduced number of pump units and to the presence of an endogenous inhibitor in uremic plasma. 相似文献
59.
60.
Remains of vertebrates of Villafranchian age have been found in the Nuraghe Su Casteddu (Nuoro, Sardinia) formation. The fossiliferous layer contain a rich fauna of continental molluscs. The composition of the vertebrate fauna is as follows: Rana sp., ? Coluber sp., Aves indet., Episoriculus aff. gibberodon PETENYI, Talpa sp., Chiroptera indet. and Rodentia indet. It is the first discovery of Villafranchian vetebrates in Sardinia. 相似文献