A possible mode of cardiovascular actions of dopamine in dogs.
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A possible mode of cardiovascular actions of dopamine was studied using ephedrine. In the dog pretreated with repeated administrations of ephedrine (total dose, 40 or 80 mg/kg, i.v.) or with combined administrations of ephedrine (total dose, 90 mg/kg, s.c. and i.v.) and reserpine (2 mg/kg, s.c., 24 hr previously), pressor responses to dopamine were eliminated and reversed to depressor responses whereas depressor responses to dopamine were potentiated. Positive chronotropic effects of dopamine were almost eliminated. Pressor and positive chronotropic effects of tyramine were almost abolished. Sympathomimetic effect of noradrenaline and adrenaline were potentiated while those of isoprenaline were inhibited. In the heart-lung preparation of ephedrine-treated dogs (total dose, 40 mg/kg, i.v.), cardiac stimulating effects of dopamine and tyramine were strongly depressed, and those of noradrenaline, adrenaline and isoprenaline were reduced to some extent. In the open-chest dogs, after pretreatment of cocaine (4 mg/kg, i.v.), pressor, positive inotropic and chronotropic effects of noradrenaline were potentiated, whilst those of tyramine were inhibited. Those of dopamine were not visibly altered, but depressor, negative chronotropic and inotropic effects of dopamine appeared at small doses. In the ephedrine-pretreated dogs, these sympathomimetic effects of dopamine and tyramine after cocaine were strongly depressed and those of noradrenaline were inhibited to a certain degree. The results obtained with ephedrine suggest that dopamine differs from other catecholamines and tyramine in the mode of cardiovascular actions. (+info)
In situ identification of cyanobacteria with horseradish peroxidase-labeled, rRNA-targeted oligonucleotide probes.
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Individual cyanobacterial cells are normally identified in environmental samples only on the basis of their pigmentation and morphology. However, these criteria are often insufficient for the differentiation of species. Here, a whole-cell hybridization technique is presented that uses horseradish peroxidase (HRP)-labeled, rRNA-targeted oligonucleotides for in situ identification of cyanobacteria. This indirect method, in which the probe-conferred enzyme has to be visualized in an additional step, was necessary since fluorescently monolabeled oligonucleotides were insufficient to overstain the autofluorescence of the target cells. Initially, a nonfluorescent detection assay was developed and successfully applied to cyanobacterial mats. Later, it was demonstrated that tyramide signal amplification (TSA) resulted in fluorescent signals far above the level of autofluorescence. Furthermore, TSA-based detection of HRP was more sensitive than that based on nonfluorescent substrates. Critical points of the assay, such as cell fixation and permeabilization, specificity, and sensitivity, were systematically investigated by using four oligonucleotides newly designed to target groups of cyanobacteria. (+info)
Abnormal norepinephrine clearance and adrenergic receptor sensitivity in idiopathic orthostatic intolerance.
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BACKGROUND: Chronic orthostatic intolerance (OI) is characterized by symptoms of inadequate cerebral perfusion with standing, in the absence of significant orthostatic hypotension. A heart rate increase of >/=30 bpm is typical. Possible underlying pathophysiologies include hypovolemia, partial dysautonomia, or a primary hyperadrenergic state. We tested the hypothesis that patients with OI have functional abnormalities in autonomic neurons regulating cardiovascular responses. METHODS AND RESULTS: Thirteen patients with chronic OI and 10 control subjects underwent a battery of autonomic tests. Systemic norepinephrine (NE) kinetics were determined with the patients supine and standing before and after tyramine administration. In addition, baroreflex sensitivity, hemodynamic responses to bolus injections of adrenergic agonists, and intrinsic heart rate were determined. Resting supine NE spillover and clearance were similar in both groups. With standing, patients had a greater decrease in NE clearance than control subjects (55+/-5% versus 30+/-7%, P<0.02). After tyramine, NE spillover did not change significantly in patients but increased 50+/-10% in control subjects (P<0.001). The dose of isoproterenol required to increase heart rate 25 bpm was lower in patients than in control subjects (0.5+/-0.05 versus 1.0+/-0.1 microg, P<0.005), and the dose of phenylephrine required to increase systolic blood pressure 25 mm Hg was lower in patients than control subjects (105+/-11 versus 210+/-12 microg, P<0.001). Baroreflex sensitivity was lower in patients (12+/-1 versus 18+/-2 ms/mm Hg, P<0.02), but the intrinsic heart rate was similar in both groups. CONCLUSIONS: The decreased NE clearance with standing, resistance to the NE-releasing effect of tyramine, and increased sensitivity to adrenergic agonists demonstrate dramatically disordered sympathetic cardiovascular regulation in patients with chronic OI. (+info)
Antioxidant effects of dopamine and related compounds.
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The antioxidant and free radical scavenging effects of dopamine, noradrenaline, tyramine, and tyrosine were investigated and compared with alpha-tocopherol. The antioxidant effect of dopamine and its related compounds on peroxidation of linoleic acid were in the order of dopamine > alpha-tocopherol = tyramine > tyrosine > noradrenaline as measured by the thiocyanate method. These amine compounds had reducing power, and a scavenging effect on reactive oxygen species, i.e., superoxide anion and hydroxyl radical. The results for reducing power and scavenging effect of these amine compounds had a similar trend as their inhibition of linoleic acid peroxidation. The antioxidant activity of these amine compounds in soybean oil was also evaluated by the Rancimat method. The induction time to reach 100 meq/kg peroxide value (POV) of soybean oil for dopamine, alpha-tocopherol, tyramine, tyrosine, noradrenaline, and control were 9.0, 8.2, 8.0, 6.4, 4.6, and 4.3 h, respectively. The antioxidant efficacy of amine compounds seems to be correlated with the numbers of hydroxy groups and their position on the phenolic ring. (+info)
Isolation from beer and structural determination of a potent stimulant of gastrin release.
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Beer was subjected to five successive chromatographic procedures to isolate the gastrin release-inducing activity, guided by bioassay of the fractions in anaesthetized Donryu rats. The procedures were: (1) hydrophobic interaction chromatography (aqueous effluent with an HP20 column); (2) weak cation-exchange chromatography (1 M acetic acid eluate with a CM Sephadex C-25 column); (3) gel filtration (methanol eluate with a Sephadex LH-20 column); (4) same as (2); (5) high-performance liquid chromatography (YMC-Pack ODS-AM with 7% acetonitrile-0.01 M HCl). The active component finally isolated had a specific activity approximately 10000 times higher than that of beer. It was identified by means of mass, 1H- and 13C-nuclear magnetic resonance spectral analyses as N-methyltyramine (NMT). The dose of NMT giving maximal gastrin-releasing activity was 25 microg/kg, and the 50% effective dose was approximately 10 microg/kg on oral administration to rats. NMT was isolated and identified as a gastrin release inducer in beer. Its concentration in beer is sufficient to account for most of the activity of beer. (+info)
Effects of imipramine, an uptake inhibitor, on double-peaked constrictor responses to periarterial nerve stimulation in isolated, perfused canine splenic arteries.
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Using a cannula insertion method, periarterial nerve electrical stimulations were performed at 1 and 10 Hz in the isolated, perfused canine splenic artery. Electrical nerve stimulation readily caused double-peaked vasoconstrictions. The 1st-peak response at 1 Hz was not influenced by treatment with imipramine but the 2nd one was significantly enhanced by it. The 2nd-peak response was markedly blocked by prazosin. An additional treatment with alpha,beta-methylene ATP, a P2X-purinoceptor desensitizer, abolished electrical stimulation-induced vascular responses that remained. At 10 Hz, the responses to electrical stimulation were not significantly influenced by imipramine. On the other hand, the imipramine treatment inhibited the tyramine-induced vasoconstriction but potentiated the noradrenaline-induced one. ATP-induced responses were not modified by imipramine. From these results, it is concluded that 1) the 1st-peaked constriction is mainly due to a P2X-purinoceptor-dependent mechanism, 2) the 2nd one is mainly due to an alpha1-adrenoceptor-dependent mechanism, and 3) presynaptic uptake mechanisms may perform an important role in the regulation of vascular reactivity, especially at a low frequency. (+info)
Effects of prolonged cold storage on double peaked vasoconstrictor responses to periarterial nerve stimulation in isolated canine splenic arteries.
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1. P2X-Purinoceptors and alpha1-adrenoceptors have previously been shown to involve in the double peaked vasoconstrictor responses to periarterial electrical nerve stimulation in the isolated and perfused canine splenic artery. The present study made an attempt to investigate effects of prolonged cold storage (7 days at 4 degrees C) on vasoconstrictor responses to periarterial electrical nerve stimulation, tyramine, noradrenaline and adenosine 5'-triphosphate (ATP) in the isolated canine splenic artery. 2. The periarterial nerve stimulation (1-10 Hz) readily causes a double peaked vasoconstriction in the non-stored preparations. After cold stored for 7 days, the double peaked vasoconstriction was still recognized, although the response became significantly smaller. The first phase was decreased relatively greater than the second phase by the cold storage. 3. In the cold stored preparations, the dose-response curve for tyramine was shifted to the right in a parallel manner. Prazosin almost completely inhibited tyramine-induced vasoconstriction but alpha,beta-methylene ATP failed to influence the response to tyramine. 4. The vasoconstrictor responses to noradrenaline and ATP were not significantly modified by the prolonged cold storage. 5. From these results, it is concluded that the functions of sympathetic co-transmission of purinergic components might be influenced more than that of adrenergic components in the cold storage canine splenic artery. (+info)
Detection of immunoglobulin light chain mRNA by in situ hybridisation using biotinylated tyramine signal amplification.
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A highly sensitive method for the light microscopic in situ hybridisation of immunoglobulin light chain mRNA in formalin fixed, paraffin wax embedded sections is reported. This method is based on signal amplification using horseradish peroxidase catalysed deposition of biotinylated tyramine at the sites of hybridisation. kappa and lambda light chain immunoglobulin mRNA in situ hybridisation was performed with fluorescein isothiocyanate conjugated oligonucleotide probe cocktails. The hybridisation signal was detected using a biotinylated tyramine signal amplification procedure with streptavidinbiotin-horseradish peroxidase complex as the final layer. Peroxidase was demonstrated using 3,3'-diaminobenzidine. The biotinylated tyramine signal amplification method resulted in the sensitive detection of immunonoglobulin light chain mRNA, with the whole procedure being completed in one day. Moreover, the use of peroxidase as the final reporter molecule also allowed haemamatoxylin to be used as counterstain, thereby permitting the evaluation of cellular morphology. (+info)