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  • 1
    Electronic Resource
    Electronic Resource
    Plasma catecholamines and modes of delivery: the relation between catecholamine levels and in-vitro platelet aggregation and adrenoreceptor radioligand binding characteristics. (1985)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 92 (1985), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. Catecholamines were measured in maternal venous, and mixed umbilical cord blood. Maternal catecholamines were significantly (P〈0·01) reduced by epidural analgesia with a 36% reduction in nor-adrenaline and a 33% reduction in adrenaline. Fetal catecholamines were elevated at birth with a 3–8 fold increase in noradrenaline but not adrenaline during spontaneous vaginal delivery. The lowest fetal catecholamines were obtained in the group delivered under epidural analgesia; lower plasma catecholamines were not associated with adverse respiratory effects. Fetal platelets showed impaired a2-adrenoceptor function with absent aggregatory responses to adrenaline in vitro. The defect in platelet function was unlikely to be related to changes in the number of fetal platelet α-receptors or to changes in receptor affinity for adrenaline, as fetal platelets failed to aggregate to adrenaline from deliveries with high and low cord blood catecholamines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1985.tb01397.x
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  • 2
    Electronic Resource
    Electronic Resource
    Stable 1 volt programmable voltage standard (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1866-1868 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several fully functional programmable voltage standard chips, each having a total of 32 768 Nb–PdAu–Nb Josephson junctions, have been fabricated and tested. The chips are based on a new design that provides fast programmability (1 μs) between voltages and stable voltage operation from −1 to +1 V. A comparison of the new standard with a conventional Josephson voltage standard is in agreement to 0.5±1.1 parts in 109. We demonstrate the utility of this standard by measuring the linearity of a digital voltmeter. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120189
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  • 3
    Electronic Resource
    Electronic Resource
    A pulse-driven programmable Josephson voltage standard (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3171-3173 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A voltage standard based on a series array of pulse-biased, nonhysteretic Josephson junctions is proposed. The output voltage can be rapidly and continuously programmed over a wide range by changing the pulse repetition frequency. Simulations relate the circuit margins to pulse height, width, and frequency. Experimental results on a prototype circuit confirm the expected behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115814
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  • 4
    Electronic Resource
    Electronic Resource
    Imidazoline Receptors, Subclassification, and Drug-Induced Regulation (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 763 (1995), 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.1749-6632.1995.tb32390.x
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  • 5
    Electronic Resource
    Electronic Resource
    THE CARDIOVASCULAR EFFECTS OF TRIMAZOSIN AND PRAZOSIN IN THE RABBIT (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 13 (1986), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The cardiovascular effects of trimazosin, a quinazoline derivative similar in structure to prazosin, were investigated and compared with prazosin in the rabbit.2. Radioligand binding to cerebral membranes showed that trimazosin has roughly 100-fold less affinity for the α1-adrenoceptor. This was further supported by its lower pA2 derived from phenylephrine contractile responses in isolated thoracic aorta preparations.3. Trimazosin is less extensively distributed and has a lower clearance from whole blood than prazosin although their whole blood elimination half-lives are comparable. In addition, although it is a less potent α1-adrenoceptor antagonist in vivo, its peripheral vascular depressor effect tends to be greater than prazosin.4. Trimazosin at the dose used and under the conditions of study did not reverse the peripheral pressor effect of angiotensin II or B-HT920 but at higher concentrations, unlike prazosin, it relaxed the K+ contracted thoracic aorta. In addition, following pharmacological autonomie blockade and treatment with prazosin in vivo, trimazosin caused a further depressor response. A similar though shorter lasting non-α1-receptor mediated action was also observed with prazosin.5. 1-Hydroxytrimazosin (CP23445), the major metabolite of trimazosin in man, showed little affinity for either the α1- or α2-adrenoceptor from radioligand binding studies.6. In addition to α1-adrenoceptor antagonism, trimazosin may exert an additional direct vasodilator effect in rabbits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1986.tb00944.x
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  • 6
    Electronic Resource
    Electronic Resource
    THE EFFECTS OF CALCIUM ANTAGONISTS ON BLOOD PRESSURE AND RESPONSES TO α-ADRENOCEPTOR AGONISTS IN HYPERTENSIVE RABBITS (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 14 (1987), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: SUMMARY1. The effects of the calcium antagonists verapamil and nifedipine on mean arterial blood pressure, heart rate and pressor responses to a range of α-adrenoceptor agonists were examined in male normotensive New Zealand white rabbits and in rabbits with perinephritis hypertension.2. Verapamil and nifedipine caused a greater fall in mean arterial pressure in hypertensive compared to normotensive rabbits both when the fall was expressed as an absolute and as a percentage change. Effects on heart rate were similar in normotensive and hypertensive animals.3. Pressor responses to phenylephrine were attenuated by nifedipine and verapamil in normotensive and hypertensive rabbits. Pressor responses to alphamethyl noradrenaline were also attenuated by nifedipine, but pressor responses to BHT 920 were not significantly altered by either calcium antagonist in normotensive or hypertensive rabbits at the dose used. Thus the calcium antagonists had a greater effect on α1-than α2-adrenoceptor mediated responses in both normotensive and hypertensive rabbits.4. Hypertensive animals showed an increased responsiveness to phenylephrine and alphamethyl noradrenaline but not BHT 920 compared to normotensives. This difference remained after treatment with both the calcium antagonists.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1987.tb00960.x
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  • 7
    Electronic Resource
    Electronic Resource
    THE EFFECT OF AGING ON α-ADRENOCEPTORS AND THEIR RESPONSES IN RABBITS (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 12 (1985), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The effects of age on α-adrenoceptor responses, sensitivity and number were studied in rabbits aged from 1 to 36 months.2. Three types of investigation were carried out: conscious animal studies, isolated tissue studies and radioligand binding studies.3. Specific [3H]-prazosin binding decreased with age in both spleen and heart suggesting that the number of α1-receptors declined at least in the tissues studied. The specific binding of [3H]-clonidine to spleen membranes and [3H]-yohimbine to platelets was not affected by age.4. In vitro responsiveness to α-adrenoceptor agonists decreased with age in abdominal aorta and renal artery, while the affinity of adrenoceptors for prazosin (pA2) was not altered. The decrease may be non-specific as responses to potassium were also altered. No change in α2-adrenoceptor mediated platelet aggregation was observed.5. No change in pressor or depressor responses to full adrenoceptor agonists or to antagonists was observed in vivo. However, responses to clonidine, which is a partial agonist at α1-adrenoceptors, were decreased.6. While aging influenced α-adrenoceptor subtypes differently, there was no direct relation between functional changes and number of receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1985.tb00906.x
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  • 8
    Electronic Resource
    Electronic Resource
    NORADRENALINE SENSITIVITY AND CALCIUM FLUXES IN ARTERIES FROM RABBITS WITH PERINEPHRITIS HYPERTENSION (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 17 (1990), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Contractions of isolated vascular and cardiac preparations taken from rabbits with perinephritis (one kidney, one wrapped) hypertension were compared with those of preparations from control operated animals.2. Significantly increased sensitivity to noradrenaline, which acts on α1-adrenoceptors, was found in mesenteric arterial rings but not in aortic rings. The degree of hypersensitivity was the same in the presence and absence of cocaine, suggesting that there is no increase in uptake of noradrenaline into adrenergic nerves in this model of hypertension. In contrast to these agonist-induced contractions, no increased sensitivity was found to potassium chloride, suggesting that hypersensitivity is specific for receptor mediated rather than membrane potential mediated effects.3. No hypersensitivity to noradrenaline was found in the isolated left or right atria, which suggests that the hypertension is associated with changes in excitation–contraction coupling in blood vessels but not in cardiac muscle.4. Hypertension increased basal 45Ca uptake in the mesenteric artery but not in the aorta. However, there was no significant difference between preparations from normotensive and hypertensive rabbits in 45Ca uptake or efflux stimulated by noradrenaline or KCl.5. Increased basal 45Ca uptake could contribute to the increased sensitivity to noradrenaline found in the mesenteric artery in rabbit perinephritis hypertension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1990.tb01354.x
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  • 9
    Electronic Resource
    Electronic Resource
    RX781094, a new potent α2 adrenoceptor antagonist (1983)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 322 (1983), S. 221-227 
    Details
    ISSN: 1432-1912
    Keywords: Alpha2 adrenoceptors ; Specific antagonists ; Central actions ; Peripheral actions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. RX781094 [2-(2-(1,4-benzodioxanyl))-2-imidazoline HCl] is a new α2 adrenoceptor selective antagonist. Its effects on cardiovascular response “in vivo” before and after administration of α1 and α2 adrenoceptor agonists have been studied in conscious and anaesthetized rabbits. The affinity of RX781094 for α1 and α1 adrenoceptors has been investigated “in vitro” in radioligand binding studies. 2. Intravenous injection of RX781094 caused an immediate short lived pressor response which was attenuated by α1 and α2 adrenoceptor antagonists; it also caused a prolonged bradycardia. 3. Pretreatment with intravenous RX 781094 inhibited the hypotensive response to both intravenous and intracisternal clonidine in a dose dependent manner. 4. RX781094 also showed a dose dependent inhibition of the acute pressor response to the α2 adrenoceptor selective agonist guanabenz. 5. Pressor dose response curves to noradrenaline, a mixed α1/α2 adrenoceptor agonist were shifted to the right after RX781094 whereas those to the α1 adrenoceptor agonist phenylephrine were unchanged. 6. RX781094 was more effective at displacing specifically bound 3H clonidine than 3H prazosin in membrane preparations from rabbit brain. 7. These observations are consistent with a selective α2 adrenoceptor antagonist effect of RX781094 at central and peripheral adrenoceptors in the rabbit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500769
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  • 10
    Electronic Resource
    Electronic Resource
    Regulation of adrenergic receptor number following chronic noradrenaline infusion in the rabbit (1988)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 338 (1988), S. 517-522 
    Details
    ISSN: 1432-1912
    Keywords: Noradrenaline infusion ; Adrenergic receptors ; Regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to study noradrenaline-induced regulation of alpha- and beta-adrenoceptors, groups of male New Zealand White rabbits (n = 8) were treated with intravenous noradrenaline (0.09 μmol/kg × h) or ascorbate (0.1 %) for I0 days via osmotic minipumps implanted in the femoral vein, and the number of cardiac, lung and lymphocyte beta-adrenoceptors as well as renal and platelet alpha2-adrenoceptors were determined. 1. The mean arterial blood pressure, heart rate and catecholamine levels were measured before commencing, and after 24 h and 10 days infusion. Circulating noradrenaline concentrations were elevated approximately 6-fold at 24 h and were sustained at these levels after 10 days administration of noradrenaline. There were no significant alterations in the blood pressure while a significant decrease in the heart rate was observed at 24 h. 2. Alpha2-adrenoceptor density was assessed using [3H]-yohimbine. A significant decrease in the number of alpha2-adrenoceptors in the kidney was observed following the 10 days infusion with noradrenaline. This down-regulation was in marked contrast to the lack of alteration in platelet alpha2-adrenoceptor number and the platelet alpha2-adrenoceptor mediated aggregatory response. 3. The density of beta-adrenoceptors in lymphocytes, heart and lung were quantified using (−)[125I] iodocyanopindolol (ICYP). The noradrenaline infusions caused significant reductions in beta-adrenoceptor number in the heart and lung (containing predominantly β1-adrenoceptors) but not in lymphocytes (possessing mainly β2-adrenoceptors). The K D-values (pM) for ICYP binding to heart and lung were also significantly decreased in the present studies. 4. It is concluded that, in this model, a moderate increase in circulating noradrenaline resulted in substantial decreases in alpha- and beta-adrenoceptor number but in a tissue and/or subtype selective manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00179323
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