| 1. |
- Fu, Michael, 1963, et al.
(författare)
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Diabetes-induced changes in the Gi-modulated muscarinic receptor-adenylyl cyclase system in rat myocardium.
- 1994
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Ingår i: Pharmacology & toxicology. - 0901-9928. ; 75:3-4, s. 186-93
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Tidskriftsartikel (refereegranskat)abstract
- The inhibitory guanine nucleotide binding regulatory protein (Gi)-mediated muscarinic receptor-adenylyl cyclase system was studied in myocardium from adult male Wistar rats with 10 weeks of diabetes induced by a single intravenous injection of streptozotocin (60 mg/kg). Neither the messenger ribonucleic acid level nor the amount of Gi was changed in the streptozotocin diabetic group as compared to the control group. The activity of the adenylyl cyclase stimulated by guanyliminodiphosphate was decreased by 48% in the streptozotocin diabetic group whereas stimulated activities of adenylyl cyclase by sodium fluoride and forskolin remained unchanged. The inhibition of forskolin-stimulated adenylyl cyclase activity by carbachol was more potent in membranes from the streptozotocin diabetic group than that in membranes from the control group. The competition binding curve between (3H)- quinuclidinyl benzilate and carbachol obtained from the streptozotocin diabetic group was shifted to the left as compared to the control group. These results suggest that the myocardium of streptozotocin-induced diabetic rats exhibited an increase in Gi function as demonstrated by the increased inhibition of guanyliminodiphosphate-mediated adenylyl cyclase and the superhigh affinity for carbachol of the muscarinic receptors. As there were signs, similar to those seen in clinical heart failure, in the streptozotocin diabetic group, these results demonstrate that functional alteration of Gi might underlie, at least in part, the cardiac dysfunction that is associated with diabetes.
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| 2. |
- Fu, Michael, 1963, et al.
(författare)
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Effect of metoprolol on activity of beta-adrenoceptor coupled to guanine nucleotide binding regulatory proteins in adriamycin-induced cardiotoxicity.
- 1991
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Ingår i: Basic research in cardiology. - 0300-8428. ; 86:2, s. 117-26
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Tidskriftsartikel (refereegranskat)abstract
- Prevention of cardiotoxicity without interfering with the therapeutic efficacy of adriamycin is a very crucial question. We have investigated the activity of beta-adrenoceptor coupled to guanine nucleotide binding regulatory proteins (G-proteins) and Ca(2+)-ATPase activity in experimental adriamycin-induced cardiotoxicity and the influence of metoprolol treatment on these variables. Adriamycin was administered to rats intravenously as a single dose of 6 mg/kg, and metoprol was continuously given by means of implanted osmotic pumps. beta-Adrenoceptor characteristics were measured by radioligand-binding experiments and by basal and stimulated adenylyl cyclase activity. Northern blot and dot blot analysis was used to quantify G-protein mRNA. It was shown that adriamycin did not induce any change in the total beta-adrenoceptor density, nor did the high affinity agonist binding to beta-adrenoceptor change. Adriamycin did not induce any alteration in the amount of mRNA encoding for stimulatory (Gs) or inhibitory (Gi) G-proteins. Also, basal and stimulated adenylyl cyclase activities were identical in the different experimental groups. In contrast, the Ca(2+)-ATPase was shown to increase in adriamycin-treated rats compared to control rats (45 +/- 3.8 versus 23 +/- 1.2 mumol Pi/mg/h, P less than .01). Metoprolol was shown to normalize this increase (29 +/- 2.1 mumol Pi/mg/h). Thus, it may be concluded that in experimental adriamycin-induced cardiotoxicity, despite Ca(2+)-overloading, the beta-adrenoceptor-G protein-adenylyl cyclase system remains intact. Metoprolol seems to prevent Ca(2+)-overloading independently of the beta-adrenoceptors studied here.
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| 3. |
- Fu, Michael, 1963, et al.
(författare)
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Localization of a functional autoimmune epitope on the muscarinic acetylcholine receptor-2 in patients with idiopathic dilated cardiomyopathy.
- 1993
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Ingår i: The Journal of clinical investigation. - 0021-9738. ; 91:5, s. 1964-8
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Tidskriftsartikel (refereegranskat)abstract
- A peptide corresponding to the sequence 169-193 of the second extracellular loop of the human muscarinic acetylcholine receptor-2 was used as an antigen to screen sera from patients with idiopathic dilated cardiomyopathy (DCM, n = 36) and healthy blood donors (HBD, n = 40). The sera from 14 patients with DCM (38.8%) and 3 HBD (7.5%) recognized the muscarinic receptor peptide at dilutions varying from 1:20 to 1:160 in ELISA. A highly significant correlation (P = 0.006) was found between the presence of antimuscarinic receptor-2 autoantibodies and anti-beta-adrenoceptor-1 autoantibodies in the patients' sera. Affinity-purified autoantibodies from positive sera of patients with DCM recognized on the electrotransferred protein of rat ventricular membrane a major band of about 80 kD. Incubation of autoantibodies with membrane resulted not only in a decrease in the maximal binding sites (Bmax) but also in an increase in Kd of radioligand binding in a concentration-dependent manner. This suggests a mixed-type of inhibition. Moreover, preincubation with atropine abolished the inhibitory effect of autoantibodies on the receptor binding whereas carbachol appeared to have no effect on the activity of the autoantibodies. These data define a subgroup of patients with idiopathic DCM who have in their sera functionally active autoantibodies against muscarinic receptor-2.
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| 4. |
- Fu, Michael, 1963, et al.
(författare)
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Oxygen free radical injury and Gs mediated signal transduction in the stunned porcine myocardium.
- 1992
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Ingår i: Cardiovascular research. - 0008-6363. ; 26:5, s. 449-55
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The aim was to investigate involvement of oxygen free radicals and any changes in the Gs mediated beta adrenergic signalling system of stunned porcine myocardium. METHODS: Myocardial stunning was induced in eight pentobarbitone anaesthetised pigs by brief occlusions of the distal left anterior descending coronary artery for periods of up to 10 min. Segment length function was measured in the ischaemic region and in a control region supplied by the circumflex artery. Left ventricular biopsies were obtained from the two regions 1 h after the last occlusion for ultrastructural and biochemical studies. Timolol has been used to prevent arrhythmia during ischaemia. RESULTS: At the time when biopsies were obtained, percent systolic shortening was reduced to 58% in the region subjected to ischaemia and was only minimally reduced in the control region. In the biopsies from the stunned region: (1) electron microscopy showed mild and reversible intracellular changes in the stunned myocardium; (2) the activities of superoxide dismutase and glutathione peroxidase were decreased by 66% and 52%, respectively; (3) the content of malondialdehyde was increased by 49%; (4) neither density nor affinity of beta adrenoceptors showed any changes; (5) there were no alterations in messenger RNA encoding for the alpha subunit of the stimulatory guanine nucleotide binding protein (Gs), demonstrated by northern and dot-blot hybridisations; (6) ELISA technique utilising a specific antipeptide antibody showed no quantitative change in Gs; (7) the activity of adenyl cyclase was unchanged. CONCLUSIONS: Even though the stunned porcine myocardium showed substantial evidence of free radical injury, the beta adrenergic signalling system was intact.
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| 5. |
- Norberg, Torbjörn, et al.
(författare)
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Comparison between p53 protein measurements using the luminometric immunoassay and immunohistochemistry with detection of p53 gene mutations using cDNA sequencing in human breast tumors.
- 1998
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Ingår i: International Journal of Cancer. - 0020-7136 .- 1097-0215. ; 79:4, s. 376-383
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Tidskriftsartikel (refereegranskat)abstract
- The p53 mutational status of 226 representative primary breast cancer samples, derived from a population-based cohort, was analyzed using cDNA-based sequencing. The results were comparedwith those obtained with immunohistochemistry (IHC) on microwave-treated paraffin sections and the p53specific luminometric immunoassay (LIA) on cytosols, all from the same individuals. Thirty-sevenmutations were found using cDNA sequencing and were categorized into A) missense mutations in theevolutionarily conserved regions; B) missense mutations outside the evolutionarily regions; and C) deletions, insertions and nonsense mutations. Using optimal cut-off values, LIA detected 15 of 16 missense mutations in category A, in which IHC defected all 16. In category B, 10 of 13 and 7 of 13mutations were detected, respectively. Some of the samples in category A had a very high p53 proteincontent when measured with the LIA, the reason for this being discussed. IHC detected 0 of 5 stop codon and 0 of 3 deletions/insertions mutations, while the LIA method detected 2 of 5 stop codon mutations and Iof 3 deletion/insertion mutations. Compared with cDNA sequencing, protein analyses using optimal cut-off values resulted in an overall sensitivity and specificity of 64.9% and 89.9%, respectively, for the LIA method. Corresponding values were 72.2% and 92% for IHC. In addition, patients from whom p53mutations could be detected by cDNA sequencing had a statistically significant (p = 0.0137) shorter survival, which was not readily apparent using the alternative LIA or IHC approaches at optimal cut-off values.
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| 6. |
- Risenfors, M, et al.
(författare)
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Early treatment with thrombolysis and betablockade in suspected acute myocardial infarction : results from the TEAHAT Study
- 1991
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Ingår i: Journal of Internal Medicine. - : Wiley-Blackwell Publishing Ltd.. - 0954-6820 .- 1365-2796. ; 734:suppl 1, s. 35-42
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Tidskriftsartikel (refereegranskat)abstract
- Independent trials of early administration of beta-blockers and thrombolytic agents have shown beneficial effects on both short- and long-term prognoses in acute myocardial infarction (AMI). The effects of a combination of the two strategies have not been thoroughly documented. Three hundred and fifty-two patients, of less than 75 years of age, with chest pain indicative of AMI, and onset less than 2 h and 45 min before first examination, were randomized to treatment with rt-PA or placebo. All patients without contraindication were given intravenous metoprolol 15 mg acutely and then 200 mg orally daily. Treatment was started either at the prehospital stage or in hospital. Thirty-seven per cent of patients had contraindications to beta-blockade, the most frequent of which were heart rate less than 60 beats min-1 and hypotension. The remaining 63% were given intravenous beta-blockade. No side-effects of metoprolol, alone or in combination with rt-PA, were observed during the prehospital phase. Overall, toleration of the treatment was good. Reduction in enzymatically estimated infarct size by rt-PA was more pronounced in patients who were also treated with metoprolol (41%, P less than 0.001) than in those with contraindications to beta-blockade (15%, NS). Patients who were also treated with metoprolol also had a lower incidence of Q-wave infarctions, congestive heart failure and ventricular fibrillation than those who were not given intravenous beta-blockade. In conclusion, toleration of intravenous administration of rt-PA and metoprolol was good, and this was also the case in the prehospital phase.
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