II—R. C. Alabaster

Alabaster, R. C.

doi:10.1017/s0373463300020312

Cited by 5 publications

(13 citation statements)

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“…Pimobendan is reported to elevate cmp and has all the characteristics of a P D E inhibitor but in addition prolongs the action potential duration which may be an additional mechanism of its inotropic me bradycardia produced by the quinazolines, buquineran and carbazeran, is an unusual (though attractive) feature of P D E inhibitors. Alabaster et al (1977) demonstrated that buquineran increased guineapig atrial force and reduced rate, thereby resembling their findings with ouabain. Buquineran was found to inhibit the P D E enzyme but since it did not affect Na+,K+-ATPase activity, then the mechanism of the bradycardia remains a mystery.…”

Section: Discussionmentioning

confidence: 62%

Lack of inotropic selectivity of phosphodiesterase enzyme inhibitors in-vitro

Smith

Hall

West

1987

Journal of Pharmacy and Pharmacology

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Phosphodiesterase enzyme (PDE) inhibitors form a diverse category of chemical structures which display positive inotropic activity, but it is unclear as to how force/rate selective these are on the heart. In this study several recently developed PDE inhibitors, almost all of which are selective for the cardiac PDE III isoenzyme, were compared with the xanthine PDE inhibitor IBMX and with ouabain and the direct and indirect adenylate cyclase activators, forskolin and isoprenaline, respectively. These compounds were active in increasing paced guinea-pig left atrial force, the order of potency being: isoprenaline greater than ouabain greater than forskolin greater than pimobendan greater than IBMX greater than sulmazole greater than buquineran greater than carbazeran greater than milrinone greater than piroximone greater than amrinone. Ro 13-6438 and enoximone were however, both inactive. With the exception of buquineran and carbazeran, which produced bradycardia and were therefore force specific, all of the recently discovered PDE inhibitors increased the rate of contraction of the right atria and they were rate selective to the same extent as IBMX, isoprenaline and forskolin. Sulmazole, the only force selective PDE inhibitor of the compounds studied, was intermediate between IBMX and ouabain in force/rate selectivity and pimobendan showed no selectivity. Since both these agents also possess other actions, then these results suggest that in general, PDE III inhibitors do not show advantageous force selectivity in guinea-pig atria.

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Section: Discussionmentioning

confidence: 62%

Lack of inotropic selectivity of phosphodiesterase enzyme inhibitors in-vitro

Smith

Hall

West

1987

Journal of Pharmacy and Pharmacology

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“…Paralaurionite, a dimorph of laurionite, has not been observed in any titration. This is of significance as the two minerals occur in association with one another in certain deposits, including the Wesley Mine, near Bristol (Alabaster, 1989) and in the Laurium slags (Palache, 1934). It is not absolutely certain whether laurionite is the thermodynamically stable phase at ambient temperatures; paralaurionite is known, for example, in comparatively large amounts in the Mammoth-St. Anthony Mine, Tiger, Arizona (Bideaux, 1980).…”

Section: Resultsmentioning

confidence: 99%

“…3 This illustrates the interrelationships between the various lead hydroxychloride phases. Under natural saline conditions, seawater for example, where approximate chloride concentrations are 0.5 M, and the pH is about 8, the preferred phase to crystallise would be laurionite or its dimorph paralaurionite (no distinction is made here between the two), and this is reflected by frequency of reports of its occurrence under such conditions (Russell, 1920;Palache, 1934;Palache etal., 1951;Kohlberger, 1976;Campbell and Mills, 1977;Symes and Embrey, 1977;Bideaux, 1980;Schnorrer-KOhler, 1986;Schnorrer-KOhler etal., 1988;Alabaster, 1989). Reduction of salinity or an increase of pH gives rise to conditions when blixite can form.…”

Section: Resultsmentioning

confidence: 99%

“…Mendipite, cotunnite and laurionite have been noted from these deposits, crystallising from solutions at temperatures of up to 65 ~ Mendipite is nearly always found associated with other lead hydroxychlorides. At the Wesley Mine it is invariably intergrown with laurionite and paralaurionite (Alabaster, 1989). This suggests that solution conditions during crystallisation fluctuated about the laurionite-mendipite phase boundary.…”

Section: Resultsmentioning

confidence: 99%

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Studies of secondary mineral formation in the PbO-H₂O-HC1 system

Edwards¹

1992

Mineral. mag.

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New stability constant data are presented for the minerals blixite, mendipite and the compound Pb706C12.2H20 at 298.2 K and P = 105 Pa. Mendipite is in fact a metastable phase at this temperature, being thermodynamically stable under the appropriate conditions at temperatures above about 29 ~ Kinetic influences are of some significance with respect to the sequence of formation of solid phases in the PbO-HCI-H20 system, and these have been elucidated for some important reactions. Penfieldite and fiedlerite appear to be metastable phases at all temperatures at 105 Pa. The results have been used to reassess the conditions of formation of the lead(II) oxy-and hydroxychloride phases that are known to form as minerals and as corrosion products of lead-containing artefacts. The effect of CO2 on the system is also described. K E V w O R D S : lead minerals, blixite, mendipite, stability, secondary minerals.

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“…For example the prejunctional C2-adrenoceptors in vas deferens of rat and rabbit had a different antagonist potency series, yohimbine being more potent than Wy26703 in the rabbit but less potent in the rat. It was subsequently found that the potency of each antagonist at postjunctional a2-adrenoceptors in the rabbit saphenous vein was similar to that found at the prejunctional M2-adrenoceptors in rabbit vas deferens (Alabaster et al, 1986).…”

Section: Introductionmentioning

confidence: 77%

Difference in the potency of α₂‐adrenoceptor agonists and antagonists between the pithed rabbit and rat

Bulloch

Docherty

Flavahan

et al. 1987

British J Pharmacology

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1 The subtypes ofa-adrenoceptors which mediate pressor responses to sympathomimetic agonists or to nerve stimulation in pithed rabbits have been classified according to the effects of 'selective' antagonists and a comparison has been made, for the xt2-subtype, with corresponding responses in the rat.2 In the rabbit the dose-response curve for phenylephrine was shifted to the right in parallel by prazosin (1 mg kg-') and was unaffected by rauwolscine (1 mg kg '). The dose-response curve for noradrenaline was shifted to the right by prazosin (I mg kg -') and was shifted to a smaller extent by rauwolscine (1 mg kg -') or imiloxan (1Omg kg-'). After rauwolscine, prazosin produced a rightward shift larger than when given alone. After prazosin, rauwolscine produced a rightward shift larger than when given alone. 3 The responses to pressor nerve stimulation at low frequencies (< 1 Hz) could be reduced by prazosin, rauwolscine or imiloxan but those at a higher frequency could be reduced only by prazosin. 4 These results indicate that the responses to noradrenaline or to nerve stimulation are mediated by both a,-and a2-adrenoceptors. Low doses or frequencies have a proportionately greater component which is M2 5 Responses to noradrenaline after prazosin (1 mg kg -'), were sufficiently sensitive to rauwolscine to be considered as predominantly a2. A comparison was therefore made of such responses in the rat and rabbit. They were produced by a lower dose per unit body weight in the rat whereas this was less marked for the M2-adrenoceptor agonist guanabenz. In the rabbit they were more susceptible to blockade by rauwolscine but were less sensitive to Wy 26703 than in the rat. This demonstrates that the ;c2-adrenoceptors mediating pressor responses in vivo, like those in other tissues in vitro, are different in rat and rabbit, with regard to antagonists.

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II—R. C. Alabaster

Cited by 5 publications

References 0 publications

Lack of inotropic selectivity of phosphodiesterase enzyme inhibitors in-vitro

Lack of inotropic selectivity of phosphodiesterase enzyme inhibitors in-vitro

Studies of secondary mineral formation in the PbO-H₂O-HC1 system

Difference in the potency of α₂‐adrenoceptor agonists and antagonists between the pithed rabbit and rat

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II—R. C. Alabaster

Cited by 5 publications

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Lack of inotropic selectivity of phosphodiesterase enzyme inhibitors in-vitro

Lack of inotropic selectivity of phosphodiesterase enzyme inhibitors in-vitro

Studies of secondary mineral formation in the PbO-H2O-HC1 system

Difference in the potency of α2‐adrenoceptor agonists and antagonists between the pithed rabbit and rat

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Studies of secondary mineral formation in the PbO-H₂O-HC1 system

Difference in the potency of α₂‐adrenoceptor agonists and antagonists between the pithed rabbit and rat