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  • 1
    Electronic Resource
    Electronic Resource
    Role of Phospholipids in Coupling of Adenosine and Dopamine Receptors to Striatal Adenylate Cyclase (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 36 (1981), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Treatment of striatal washed particles with phospholipase A2 or C abolished the activation of adenylate cyclase by dopamine but not by N6-phenylisopropyl adenosine (PIA). The inhibition of dopamine-sensitive cyclase was dependent on Ca2+ and increased with time and phospholipase concentration. F--sensitive cyclase was not affected by phospholipase A2 treatment, but was enhanced by phospholipase C treatment. Phospholipase D did not affect basal, PIA, dopamine, or F--sensitive cyclase activities. The observed effects of phospholipase A2 were not due to either the detergent effect of lysophospholipids or to contaminating proteases. Ropamine-sensitive cyclase, inactivated by pretreatment with phospholipase A2, was restored by asolectin (a soybean mixed phospholipid), phosphatidylcholine, phosphatidylethanol-amine, or phosphatidylserine, but not by phosphatidylinositol. Phosphatidylserine and phosphatidylcholine were equipotent in restoring dopamine-sensitive activity. Lubrol-PX, a nonionic detergent, abolished completely the dopamine-sensitive cyclase activity, whereas PIA-sensitive activity was slightly inhibited. In contrast, digitonin inhibited dopamine- and PIA-sensitive cyclase activity in a parallel fashion. Lubrol-PX released some adenylate cyclase into a 16,000 ×g supernatant fraction that was stimulated by PIA but not by dopamine. Removal of most of the free detergent by Bio-bead SM 2 enhanced stimulation by PIA but did not restore sensitivity to dopamine. Asolectin also did not restore the activity of dopamine-sensitive cyclase. The data suggest that the requirement for phospholipids for the coupling of dopamine and adenosine receptors to the striatal adenylate cyclase may be different and that the adenosine receptors may be more tightly coupled to the enzyme than are dopamine receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1981.tb00436.x
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  • 2
    Electronic Resource
    Electronic Resource
    Regulation of Adenosine-Sensitive Adenylate Cyclase from Rat Brain Striatum (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 35 (1980), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: An adenosine-sensitive adenylate cyclase has been characterized from rat brain striatum. In whole homogenates as well as in particulate fractions, N6-phenylisopropyl adenosine (PIA), 2-chloroadenosine, and adenosine N′-oxide were equipotent in stimulating adenylate cyclase. Although GTP inhibited basal as well as PIA-stimulated activity of whole homogenates, the enzyme showed an absolute dependency on GTP for stimulation by PIA, dopamine, epinephrine, and norepinephrine in a particulate fraction derived from discontinuous sucrose gradient centrifugation. Adenosine exerts two effects on this adenylate cyclase, stimulation at low concentrations and inhibition at high concentrations, suggesting the presence of two adenosine binding sites. The stimulation of adenylate cyclase by PIA was dependent on the concentration of Mg2-. The degree of stimulation by PIA was greater at a low concentration of Mg2+, which suggests that stimulation by PIA was accompanied by increasing the apparent affinity for Mg2+. Activation of adenylate cyclase by PIA was blocked by theophylline or 3-isobutyl- 1-methylxanthine (IBMX). The pH optimum for basal or (PIA + GTP)-stimulated activities was broad, with a peak between 8.5 and 9.5. In the presence of GTP, stimulation by an optimal concentration of PIA was additive, with maximal stimulation by the catecholamines. Phospholipase A2 treatment at a concentration of 1 U/ml for 5 min completely abolished the stimulatory effect of dopamine, whereas PIA-stimulated activity remained unaltered. These data suggest that rat brain striatum either has a single adenylate cyclase, which is stimulated by catecholamines and adenosine by distinct mechanisms, or has different cyclase populations, stimulated by either adenosine or catecholamines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1980.tb07089.x
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  • 3
    Electronic Resource
    Electronic Resource
    Decreasing Ratios of Phosphocreatine to β-ATP Correlates to Progressive Acute Rejection in a Concordant Mouse Heart to Rat Xenotransplantation Model (2001)
    Oxford, UK : Blackwell Science Ltd
    Scandinavian journal of immunology 53 (2001), S. 0 
    Details
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Biopsies are difficult to perform in rodent heart transplant models without compromising the graft function and therefore other means to evaluate the grafts repeatedly and noninvasively are warranted. The goal of the present study was to measure changes in ratios of high energy phosphorus containing metabolites detected with in vivo31Phosphorous Magnetic Resonance Spectroscopy (31P MRS) in a xenotransplantation model and to investigate if these ratios correlated to histological signs of acute xenograft rejection. Thirty-five heart transplantations were performed (NMRI-mice to Lewis (RT11) rats). Thirteen heart transplants underwent repeated daily in vivo31P MRS measurements and 22 grafts were measured on any of 4 postoperative days and thereafter sacrificed for histology. A modified scoring system based on Billingham's criteria was used to stage the rejection process. The median graft survival was 3.0 ± 0.44 (median ± SD) days (n = 17). Significant differences, both overall and interday, could be calculated for the phosphocreatine (PCr)/β-adenosine triphosphate (β-ATP) ratios and for the rejection score. The decreases in PCr/β-ATP ratios correlated significantly to the progressive acute rejection process in the sacrificed grafts (P = 0.01). Further studies are indicated to establish the potential of 31P MRS in immunosuppressed recipients of vascularized xenotransplants with prolonged graft survival.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3083.2001.00849.x
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  • 4
    Electronic Resource
    Electronic Resource
    Spectroscopic studies on three mixed-ligand copper(II) complexes
    Amsterdam : Elsevier
    Polyhedron 6 (1987), S. 1053-1058 
    Details
    ISSN: 0277-5387
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0277-5387(00)80954-7
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  • 5
    Electronic Resource
    Electronic Resource
    Spectroscopic studies on Cu(3-aminoisoxazole)"nX"2.mH"2O complexes
    Amsterdam : Elsevier
    Polyhedron 8 (1989), S. 935-940 
    Details
    ISSN: 0277-5387
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0277-5387(00)86448-7
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  • 6
    Electronic Resource
    Electronic Resource
    Presence of Stimulatory Adenosine Receptors Coupled to Adenylate Cyclase in Cultured Mesenteric Artery Cells (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 463 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb21532.x
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  • 7
    Electronic Resource
    Electronic Resource
    Reversal of defective G-proteins and adenylyl cyclase/cAMP signal transduction in diabetic rats by vanadyl sulphate therapy (1995)
    Springer
    Molecular and cellular biochemistry 153 (1995), S. 113-119 
    Details
    ISSN: 1573-4919
    Keywords: Adenylyl cyclase ; G-proteins ; diabetes ; insulin ; vanadate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Vanadium salts exhibit a wide variety of insulinomimetic effects. In the present studies, we have examined the modulation of G-protein levels and adenylyl cyclase activity in the liver of streptozotocin-induced chronic diabetic rats (STZD) by vanadyl sulfate treatment and compared it with that of insulin. The basal enzyme activity, as well as the stimulatory effects of guanine nucleotides, glucagon, N-Ethylcarboxamideadenosine (NECA), isoproterenol, forskolin and sodium fluoride (NaF) on adenylyl cyclase were significantly increased in STZ-D rat liver as compared to control. In addition, the levels of stimulatory (Gsα) as well as inhibitory (Giα-2 and Giα-3) as determined by immunoblotting techniques were also significantly higher in the STZ-D rat liver, however, the inhibitory effects of oxotremorine and low concentration of GTPγS on adenylyl cyclase were not different in the two groups. Vanadyl sulfate and insulin treatments restored the augmented basal enzyme activity, the stimulations exerted by stimulatory inputs on adenylyl cyclase and the G-protein levels to various degrees, however, vanadyl sulfate was more effective than insulin. In addition, unlike vanadyl sulfate, insulin was unable to improve the stimulation exerted by glucagon and isoproterenol on adenylyl cyclase activity in STZD rats. These results suggest that vanadyl sulfate mimics the effects of insulin to restore the defective levels of G-proteins and adenylyl cyclase activity. From these results it may be suggested that one of the mechanisms by which vanadyl sulfate improves the glucose homeostasis in STZ-D rats may be through its ability to modulate the levels of G-proteins and adenylyl cyclase signal transduction system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01075925
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  • 8
    Electronic Resource
    Electronic Resource
    Defective ANF-R2/ANP-C receptor-mediated signalling in hypertension (1995)
    Springer
    Molecular and cellular biochemistry 149-150 (1995), S. 223-231 
    Details
    ISSN: 1573-4919
    Keywords: G-proteins ; adenylyl cyclase ; ANF receptors ; hypertensive rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In the present studies we have shown that atrial natriuretic factor (peptide) receptor of ANF-R2/ANP-C type is coupled to adenylyl cyclase/cAMP signal transduction system through Gi-regulatory protein and is implicated in mediating some of the physiological responses of atrial natriuretic factor or peptide (ANP). ANF-R2/ANP-C receptor-mediated adenylyl cyclase inhibition was altered in hypertension. This alteration was tissue specific. In heart, aorta, brain and adrenal, the extent of inhibition of adenylyl cyclase by ANP was enhanced in SHR as compared to age-matched WKY, whereas in platelets, the ANP-mediated inhibition was completely attenuated. The enhanced inhibition of adenylyl cyclase by ANP was also observed in heart and aorta from DOCA-salt hypertensive rats. In addition, the augmented inhibition of adenylyl cyclase by ANP was observed in 2 weeks and older ANP but not in 3–5 days old SHR. Similarly, in DOCA-salt hypertensive rats, the enhanced inhibition of adenylyl cyclase by ANP was observed after 2 weeks of DOCA-salt treatment when the blood pressure was also enhanced, however one week of DOCA-salt treatment did not result in an augmented blood pressure and augmented ANP-mediated inhibition of adenylyl cyclase, suggesting that blood pressure increase may be responsible for the enhanced responsiveness of ANP to adenylyl cyclase inhibition. However, in genetic model of hypertension, the increased inhibition of adenylyl cyclase by ANP at 2 weeks of age (when the blood pressure is normal) may be implicated in the pathogenesis of hypertension. The augmented inhibition of adenylyl cyclase in cardiovascular tissues from SHR and DOCA-salt hypertensive rats may be due to the upregulation of ANF-R2/ANP-C receptors or due to the amplification of post-receptor signalling mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01076581
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  • 9
    Electronic Resource
    Electronic Resource
    Differential regulation of G-protein expression by vasoactive peptides (1997)
    Springer
    Molecular and cellular biochemistry 176 (1997), S. 21-27 
    Details
    ISSN: 1573-4919
    Keywords: atrial natriuretic peptide ; angiotensin II ; G-proteins ; adenylyl cyclase ; vascular smooth muscle cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Vasoactive peptides such as angiotensin II (AII), atrial natriuretic peptide (ANP) and vasopressin play an important role in the regulation of blood pressure. We have recently shown an augmentation of Giα levels in heart and aorta from genetic and experimentally-induced hypertensive rats, which may be attributed to the increased levels of vasoactive peptides. We have therefore investigated the effect of AII and ANP on the expression of G-proteins (Giα and Gsα) in cultured vascular smooth muscle cells (VSMC) and their relationship with adenylyl cyclase activity. Exposure of VSMC with AII resulted in the augmentation of the levels of Giα-2 and Giα-3 proteins and Giα-2 and Giα-3 mRNA and not of Gsα as determined by immunoblotting and Northern blotting techniques respectively. However, the stimulatory effects of N-ethylcarboxamide adenosine (NECA) and isoproterenol on adenylyl cyclase was diminished by AII treatment, whereas the inhibitory effects of AII and C-ANP4-23 were completely attenuated. On the other hand, pretreatment of the cells with C-ANP4-23 resulted in the reduction of the levels of Giα-2 and Giα-3 and not of Gsα. The inhibitory responses of adenylyl cyclase to C-ANP4-23 and AII were also attenuated and the stimulatory effects of GTPgS and other agonists were significantly augmented. These data indicate that AII and ANP modulate the expression of Gia protein in a different manner. It may be suggested that the enhanced levels of Giα protein observed in hypertension may be attributed to the augmented levels of AII and not to ANP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006810508860
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  • 10
    Electronic Resource
    Electronic Resource
    Alterations in Ca2+/Mg2+ ATPase activity upon treatment of heart sarcolemma with phospholipases (1987)
    Springer
    Molecular and cellular biochemistry 77 (1987), S. 89-96 
    Details
    ISSN: 1573-4919
    Keywords: sarcolemmal Ca2+/Mg2+ ATPases ; sarcolemmal phospholipids ; membrane integrity ; membrane ATPases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In order to examine the role of phospholipids in the activation of membrane bound Ca2+/Mg2+ ATPase, the activities of Ca2+ ATPase and Mg2+ ATPase were studied in heart sarcolemma after treatments with phospholipases A, C and D. The Mg2+ ATPase activity was decreased upon treating the sarcolemmal membranes with phospholipases, A, C and D; phospholipase A produced the most dramatic effect. The reduction in Mg2, ATPase activity by each phospholipase treatment was associated with a decrease in the Vmax value without any changes in the Ka value. The depression of Mg2+ ATPase in the phospholipase treated preparations was not found to be due to release of fatty acids in the medium and was not restored upon reconstitution of these membranes by the addition of synthetic phospholipids such as lecithin, lysolecithin or phosphatidic acid. In contrast to the Mg2+ ATPase, the sarcolemmal Ca2+ ATPase was affected only slightly by phospholipase treatments. The greater sensitivity of Mg⦒- ATPase to phospholipase treatments was also apparent when deoxycholate-treated preparations were employed. These results indicate that glycerophospholipids are required for the sarcolemmal Mg2+ ATPase activity to a greater extent in comparison to that for the Ca2+ ATPase activity and the phospholipids associated with Mg2+ ATPase are predominantly exposed at the outer surface of the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230154
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