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91.
Fractions and subcellular structures were prepared from rat brain homogenate and their purity was assessed using enzyme markers, gamma-aminobutyric acid binding, DNA content, and electron microscopy. Insulin binding was highest on the plasma membrane preparations and approximately 50% less so on brain homogenate crude mitochondrial (P2), myelinated axon, and synaptosome preparations. Very low levels of binding were found on mitochondria and nuclei. Differences in binding between fractions were due to numbers of binding sites, and not variable binding affinity. There was a close relationship between insulin binding and the activity of Na/K ATPase (E.C. 3.6.1.4) in all fractions (r = 0.98). Insulin binding to the P2 was compared with plasma membrane fractions in seven brain regions, and the results demonstrated the same close relationship between insulin binding and plasma membrane content in all regions except hypothalamus. Plasma membrane insulin binding was well represented by the binding on P2 membranes in all regions except hypothalamus and brainstem. It was concluded that insulin binding is distributed evenly over the surface of brain cells and is not increased on nerve endings. 相似文献
92.
Characterization of Neurotensin Binding Sites in Intact and Solubilized Bovine Brain Membranes 总被引:1,自引:0,他引:1
Analysis of the equilibrium binding of [3H]-neurotensin(1-13) at 25 degrees C to its receptor sites in bovine cortex membranes indicated a single population of sites with an apparent equilibrium dissociation constant (KD) of 3.3 nM and a density (Bmax) of 350 fmol/mg protein (Hill coefficient nH = 0.97). Kinetic dissociation studies revealed the presence of a second class of sites comprising less than 10% of the total. KD values of 0.3 and 2.0 nM were obtained for the higher and lower affinity classes of sites, respectively, from association-dissociation kinetic studies. The binding of [3H]neurotensin was decreased by cations (monovalent and divalent) and by a nonhydrolysable guanine nucleotide analogue. Competition studies gave a potency ranking of [Gln4]neurotensin greater than neurotensin(8-13) greater than neurotensin(1-13). Smaller neurotensin analogues and neurotensin-like peptides were unable to compete with [3H]neurotensin. Stable binding activity for [3H]neurotensin in detergent solution (Kd = 5.5 nM, Bmax = 250 fmol/mg protein, nH = 1.0) was obtained in 2% digitonin/1 mM Mg2+ extracts of membranes which had been preincubated (25 degrees C, 1 h) with 1 mM Mg2+ prior to solubilization. Association-dissociation kinetic studies then revealed the presence of two classes of sites (KD1 = 0.5 nM, KD2 = 3.6 nM) in a similar proportion to that found in the membranes. The solubilized [3H]-neurotensin activity retained its sensitivity to cations and guanine nucleotide. 相似文献
93.
94.
95.
我们曾观察到大鼠经γ-射线照射后胰淀粉酶活性降低和分泌减少[1],为进一步探讨照射后胰酶分泌减少的机制,本研究制备出分散的大鼠胰腺腺泡悬液并以不同浓度的~3H-二苯羟乙酸-3-喹咛环酯(~3Hquinuclidinyll benzilatc,简称~3H-QNB)进行M受体结合测定,同时观察胆碱能介质氨甲酰胆碱刺激腺泡所引起的淀粉酶释放反应。结果表明,γ-射线10Gy照射后3天,大鼠分散的胰腺腺泡在氨甲酰胆碱刺激时淀粉酶释放量减少到对照的50%,腺泡M受体与~3H-QNB最大结合量(Bmax)减少到对照的38%,伋M受体与~3H-QNB结合的解离常数(K_D)无改变,说明胰腺腺泡细胞M受体数量的减少可能是照射后胰腺腺泡分泌淀粉酶减少的原因之一。 相似文献
96.
Heng Xu John S. Partilla Brian R. de Costa Kenner C. Rice Richard B. Rothman 《Peptides》1992,13(6):1207-1213
Recent pharmacological data strongly support the hypothesis of δ receptor subtypes as mediators of both supraspinal and spinal antinociception (δ1 and δ2 receptors). In vitro ligand binding data, which are fully supportive of the in vivo data, are still lacking. A previous study indicated that [3H][
-Ala2,
-Leu5]enkephalin labels two binding sites in membranes depleted of μ binding sites by pretreatment with the site-directed acylating agent, 2-(p-ethoxybenzyl)-1-diethylaminoethyl-5-isothiocyanatobenzimidazole-HCI (BIT). The main goal of the present study was to develop a ligand-selectivity profile of the two δncx binding sites. The data indicated that naltrindole and oxymorphindole were relatively selective for site 1 (20-fold). [
-Ser2,Thr6]Enkephalin and deltorphin-II were only 2.7-fold and 2.2-fold selective for site 1. [
-Pen2,
-Pen5]Enkephalin and deltorphin-I were 80-fold and 38-fold selective for site 2.3-Iodo-Tyr-
-Ala-Gly-Phe-
-Leu was 52-fold selective for site 1. Morphine had moderate affinity for site 1 (Ki = 16 nM), and was about 11-fold selective for site 1. Thus, of the 10 drugs studied, only DPDPE and DELT-I were selective for site 2. Viewed collectively with other data, it is likely that the δ1 receptor and the δncx binding site are synonymous. 相似文献
97.
The possibility of interaction of hepatocytes with the heparin binding domain of Fibronectin was examined. Rat hepatocytes
adhered to coverslips coated with the 33-kDa heparin binding fragment of the C-terminal region of plasma fibronectin. When
different concentrations of the heparin binding fragment were used to coat coverslips and used as substratum, cell attachment
showed saturation kinetics. Half the maximum attachment was observed at 30–40 min after seeding of cells. The cells became
flat after 2–3 h indicating that they spread on the heparin binding domain as they do on intact fibronectin. Among the different
glycosaminoglycans tested, maximum inhibition of attachment was observed for heparin. However it was not possible to completely
inhibit attachment even at high concentrations. These results indicate that hepatocytes interact with fibronectin not only
through the Arg-Gly-Asp-containing cell binding fragment, but also through the heparin binding domain of fibronectin and,
further, that there exist heparin-dependent and heparin-independent mechanisms of interaction of cells with the 33-kDa heparin
binding fragment of fibronectin 相似文献
98.
David K. Grandy Richard Leduc Haripriya Makam Thomas Flanagan Emanuel J. Diliberto Jr. Olivier Civelli O. Humberto Viveros 《Cellular and molecular neurobiology》1992,12(2):185-192
1. A novel 1745-dalton pyroglutamyl peptide (BAM-1745)6 was recently isolated and characterized from bovine adrenal medulla chromaffin granules. Its amino acid sequence was found to be 93% identical to residues 580-593 of human chromogranin B (secretogranin I). 2. Based on this sequence a degenerate oligonucleotide probe was synthesized and used to identify a 2.4-kb bovine adrenal medulla chromogranin B cDNA. 3. The deduced polypeptide is 647 amino acids long and begins with a putative signal sequence of 20 residues as in the human, rat, and mouse proteins. Also conserved in the bovine protein is a tyrosine residue which may be sulfated, two N-terminal cysteines, and many paired basic amino acids which may serve as sites of posttranslational processing. The peptide BAM-1745 is flanked by paired basic amino acids and therefore is most likely a product of posttranslational processing. Bovine chromogranin B is 67, 58, and 58% identical to the human, rat, and mouse chromogranin B proteins, respectively. 4. The carboxyl terminus of bovine chromogranin B, including BAM-1745, was found to be the most conserved region of the polypeptide and may identify it as an important functional domain. 相似文献
99.
The PTP-2 cDNA encoding an intracellular protein tyrosine phosphatase (PTPase-2) was isolated and sequenced from mouse testis and T-cell cDNA libraries. This PTP-2 cDNA was found to be homologous to human PTP-TC and rat PTP-S, and contained 1,551 nucleotides, including 1,146 nucleotides encoding 382 amino acids as well as 5 (61 nucleotides) and 3 (344 nucleotides) non-coding regions. Northern blot analysis indicated that PTP-2 mRNA of 1.9 Kb was most abundant in testis and kidney, although it was also present in spleen, muscle, liver, heart and brain.Abbreviations PTPase
Protein Tyrosine Phosphatase (EC3.1.3.48)
- PTKase
Protein Tyrosine Kinase (EC2.7.1.112) 相似文献
100.
Saraswati Manda Nicoll Lerner-Marmarosh Mazzaz Hashmi Leo G. Abood 《Neurochemical research》1992,17(12):1191-1194
The present study, utilizing thioglycolamido as the reactive group, describes the synthesis and pharmacology of a new opioid antagonist affinity ligand, 6-thioglycolamido-6-desoxynaltrexone (TAN) and compares TAN with a related known compound, 6-bromoacetamido-6-desoxynaltrexone (BAN). Both compounds were tested for their reversible and irreversible inhibition of [3H]naloxone binding to calf brain membranes. Reversible binding of BAN and TAN had Ki values of 1×10–9 and 1×10–10 M, respectively as determined by log probit plots. Irreversible binding was determined after extensive washing to remove all non-covalently bound ligand. At a concentration of 5×10–8 and 1×10–8 M for BAN and TAN irreversible binding was inhibited 50% of the maximum value. A study of the time course of irreversible inhibition of [3H]naloxone binding revealed that maximal inhibition occurred within 5 min with a concentration of 1×10–7 M of either agent. TAN but not BAN when administered systematically to mice produced an antinociceptive effect as measured by the writhing test. When administered intracerebraventricularly BAN did not block morphine-induced analgesia for more than 2 hr; whereas, with a single ED50 dose of 20 nmoles of TAN i.c.v. morphine-induced analgesia was almost completely blocked for a period of over 24 hr, as determined by the tail flick test. Although the SH group of TAN were required for the covalent interaction with opioid receptors, the site of TAN's interaction appears to involve other than protein SH groups. 相似文献