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A simple method was developed for estimating serum glycosylated protein levels using gel filtration with Bio-Gel P6 by determining the protein and sugar content in the void volume fraction. The glycosylated protein levels (GSP) correlated well with fasting blood sugar levels and glycosylated albumin level (G-ALB) determined by affinity chromatography with Blue Sepharose CL6B. The glycosylation level of heparin-citrate precipitable fraction of serum which predominantly contained low density lipoprotein (G-LDL) also correlated well with GSP and LDL-cholesterol levels. Significantly different values were obtained for GSP, G-ALB, and G-LDL between normals and diabetics. 相似文献
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Indu S. Ambudkar Timothy Lockwich Yukiharu Hiramatsu Bruce J. Baum 《Molecular and cellular biochemistry》1992,114(1-2):73-77
Conclusions While it is generally accepted that Ca2+ plays an important regulatory role in the physiology of a number of non-excitable cells, the mechanisms which regulate intracellular [Ca2+ are far from well established. Ca2+ transporting mechanisms which distribute Ca2+ intracellularly as well as those which allow influx of extracellular Ca2+ are involved in mediating intracellular Ca2+ homestasis. In this paper we have described recent studies on the regulation of the Ca2+ influx system in the data, it appears that the process of Ca2+ entry is extremely complex and may involve several levels of regulation. Understanding the molecular basis of these regulatory mechanisms presents a challeging problem for future studies. 相似文献
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Valerie J. Horn Paul A. Sheehy Miriam B. Goodman Indu S. Ambudkar 《Molecular and cellular biochemistry》1991,101(1):43-49
Intracellular Ca2+ mobilization events were assessed in mouse L cells, which contain native prostaglandin E1 receptors and transfected human 2 adrenergic receptors. Both Fura2 (single cell measurements) and Quin 2, (cuvette assays) were used to determine [Ca2+]i levels. Our results demonstrate that in the transfected cells there is a dose-dependent increase in [Ca2+]i in response to isoproterenol (0.1 nM–100 nM), which is inhibited by the -adrenergic antagonist, propranolol, and is a result of intracellular Ca2+ release. [Ca2+]1 in these cells was also increased by prostaglandin E1, 8 bromo cyclic AMP, and aluminum fluoride. Both 8 bromo cAMP and isoproterenol induced a rapid increase in the levels of IP1, IP2, and IP3. The data presented demonstrate that the elevation of intracellular cyclic AMP induces an increase in IP3 production which leads to an elevation in [Ca2+];. We propose that this cyclic AMP dependent activation of the IP3 generating system occurs at a post-receptor site.Abbreviations cAMP
Adenosine Cyclic 3-5-Monophosphate
- [Ca2+]i
intracellular [Ca2+]i
- 8 Br cAMP
8 Bromo Adenosine Cyclic 3-5-Monophosphate
- DAG
Diacylglycerol
- EGTA]
[Ethylene Bis (oxyethylenenitrilo)] Tetracetic acid
- BSA
Bovine Serum Albumin
- HBSS-H
Hanks' Balanced Salt Solution buffered with HEPES to pH 7.4
- HEPES
4-(2-Hydroxyethyl)-1-piperazineethanesulfonic acid
- PIP2
Phosphatidylinositol 4,5-bisphosphate
- IP2
Inositol 4 Phosphate
- IP2
Inositol 4,5 Bisphosphate
- IP3
Inositol Trisphosphate
- PGE1
Prostaglandin E1
- PBS
Phosphate Buffered Saline Solution 相似文献
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Isolation, characterization and metal-ion-binding properties of the alpha-subunit from S-100a protein. 总被引:2,自引:1,他引:1 下载免费PDF全文
The present experiments were undertaken to investigate the role of the phosphoinositides phosphatidylinositol 4-phosphate (PtdIns-4-P) and phosphatidylinositol 4,5-biphosphate (PtdIns-4,5-P2) in the alpha 1-adrenergic stimulation of respiration in isolated hamster brown adipocytes. Exposure of isolated brown adipocytes to the alpha-adrenergic-receptor agonist phenylephrine provoked a breakdown of 30-50% of the PtdIns-4-P and PtdIns-4,5-P2 after prelabelling of the cells with [32P]Pi. Coincident with the breakdown of phosphoinositides was an accumulation of labelled phosphatidic acid, which continued for the duration of the cell incubation. The time course of phosphoinositide breakdown was defined more precisely by pulse-chase experiments. Under these conditions, phenylephrine caused radioactivity in phosphatidylinositol, PtdIns-4-P and PtdIns-4,5-P2 to fall by more than 50% within 30 s and to remain at the depressed value for the duration of the incubation (10 min). This phospholipid response to alpha-adrenergic stimulation was blocked by exposure of the cells to phorbol 12-myristate 13-acetate (PMA); likewise phenylephrine stimulation of respiration was prevented by PMA. beta-Adrenergic stimulation of respiration and inhibition of respiration by 2-chloroadenosine and insulin were, however, unaffected by treatment with PMA. On the assumption that PMA is acting in these cells as an activator of protein kinase C, these results suggest the selective interruption of alpha-adrenergic actions in brown adipocytes by activated protein kinase C. These findings suggest that breakdown of phosphoinositides is an early event in alpha-adrenergic stimulation of brown adipocytes which may be important for the subsequent stimulation of respiration. The results from the pulse-chase studies also suggest, however, that phenylephrine-stimulated breakdown of inositol phospholipids is a short-lived event which does not appear to persist for the entire period of exposure to the alpha 1-adrenergic ligand. 相似文献
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Yukiharu Hiramatsu Indu S. Ambudkar Bruce J. Baum 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1991,1092(3):391-396
β-Adrenergic receptor stimulation of adenylyl cyclase involves the activation of a GTP-binding regulatory protein (G-protein, termed here Gs). Inactivation of this G-protein is associated with the hydrolysis of bound GTP by an intrinsic high affinity GTPase activity. In the present study, we have characterized the GTPase activity in a Gs-enriched rat parotid gland membrane fraction. Two GTPase activities were resolved; a high affinity GTPase activity displaying Michaelis-Menten kinetics with increasing concentrations of GTP, and a low affinity GTPase activity which increased linearly with GTP concentrations up to 10 mM. The β-adrenergic agonist isoproterenol (10 μM) increased the Vmax of the high affinity GTPase component approx. 50% from 90 to 140 pmol/mg protein per min, but did not change its Km value (≈ 450 nM). Isoproterenol also stimulated adenylyl cyclase activity in parotid membranes both in the absence or presence of GTP. In the presence of a non-hydrolyzable GTP analogue, guanosine 5′-(3-O-thio)triphosphate (GTPγS), isoproterenol increased cAMP formation to the same extent as that observed with AlF4?. Cholera toxin treatment of parotid membranes led to the ADP-ribosylation of two proteins (≈ 45 and 51 kDa). Cholera toxin also specifically decreased the high affinity GTPase activity in membranes and increased cAMP formation induced by GTP in the absence or the presence of isoproterenol. These data demonstrate that the high affinity GTPase characterized here is the ‘turn-off’ step for the adenylyl cyclase activation seen following β-adrenergic stimulation of rat parotid glands. 相似文献
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