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O Parry

Publications and source records attributed to O Parry.

33 records · Page 2Linked to original sources
PubMed1994

Advances in electrodiagnosis in Zimbabwe. Part II: "Evoked potentials".

This paper is a short review of the electrodiagnostic technique of "evoked potentials", a technique recently introduced to Zimbabwe. The types of evoked potentials recorded, the method of recording and their clinical applications are discussed. Abnormal evoked potentials from a variety of neurological disorders are illustrated. "Advances in electrodiagnosis in Zimbabwe" Part I discussed peripheral nerve conduction measurements and electromyography. This paper (Part II) will review the physiological basis of "Evoked Potentials" and their clinical applications.

Electrodiagnosis↗
PubMed1993

The skeletal muscle relaxant action of Portulaca oleracea: role of potassium ions.

An aqueous extract of the stems and leaves of Portulaca oleracea abolishes the twitch contraction of the directly stimulated rat hemidiaphragm preparation. The effects of the extract mimic qualitatively the action of potassium oxalate--a known constituent of Portulaca oleracea--on the diaphragm. Removal of K+ ions from the methanol extract by passing it through a cation exchange resin reduced the inhibitory effect of the extract. There was a positive correlation between the concentration of K+ ions in the extract and the effects of potassium chloride of similar molarity. It is concluded that the K+ ion content of Portulaca oleracea is at least partly responsible for the relaxant effect observed on the isolated rat diaphragm.

Animals↗
PubMed1992

Some pharmacological actions of aloe extracts and Cassia abbreviata on rats and mice.

The effects of crude extracts (500 mg/kg IP and 500-1000 mg/kg PO) of three species of aloes and Cassia abbreviata in rats and mice were studied, particularly as regards their abortifacient actions. The LD50 values were as follows: A. globuligemma < 250 mg/kg IP; A.chabaudii 250-500 mg/kg IP; A. cryptopoda > 1500 mg/kg IP and C.abbreviata 500-750 mg/kg IP. Thus the most toxic was A.globuligemma. Their most visibly striking toxic effects in rats were CNS depression, and post mortem investigations showed widespread haemorrhagic lesions. Administration of the aloes and A.abbreviata to pregnant mice and rats did not cause expulsion or resorption of the foetuses. Several rats died within 36 hours of injection of A.chabaudii and A.globuligemma, but even in these rats there was no expulsion or resorption of the foetuses. Rats which survived the treatment delivered normal sized, healthy litters at term. It is suggested that neither the aloe species test nor C.abbreviata possess abortifacient activity at doses which are not toxic to the animals.

Aloe↗
PubMed1992

The effects of Cassia abbreviata on rat blood pressure.

The effects of a crude extract of the stem bark of Cassia abbreviata on mean arterial pressure in anaesthetized rats were investigated. Bolus injections of the stem bark elicited a transitory fall in blood pressure which was dose-dependent. The depressor response was not blocked by atropine nor propranolol thus indicating that muscarinic and beta 2 receptors are not involved. However it was partially blocked by diphenhydramine, and H1 antagonist. The latter also partially blocked the depressor response to histamine which is mediated partially through both H1 and H2 receptors. It is concluded that the stem bark of C. abbreviata contains histamine or a chemically related substance and that it is this component which is responsible for lowering the blood pressure.

Animals↗
PubMed1988

Effect of an aqueous extract of Portulaca oleracea leaves on smooth muscle and rat blood pressure.

An aqueous extract of Portulaca oleracea leaves and stems produced a dose-dependent relaxation of guinea pig fundus, taenia coli and rabbit jejunum and a dose-dependent contraction of the rabbit aorta. On spontaneously-beating rabbit right atria and electrically-paced left atria, the extract produced a dose-dependent negative inotropic and chronotropic effects. On rat blood pressure, the extract produced dose-dependent pressor responses. Phentolamine reduced the relaxant effect of the extract on gut smooth muscle and abolished the contractile response on the aorta as well as the pressor response on blood pressure. Guanethidine and tetrodotoxin had no effect on extract-induced relaxant or contractile responses. On rat blood pressure atropine and cyproheptadine had no effect on extract-induced pressor response, whereas propranolol slightly reduced the pressor response. An increase in extracellular calcium reversed the inhibitory effect of the extract on the rabbit atria. The extract may, therefore, act in part on postsynaptic alpha-adrenoceptors and by interference with transmembrane calcium influx.

Animals↗
PubMed1987

Skeletal muscle relaxant action of an aqueous extract of Portulaca oleracea in the rat.

The aqueous extract of Portulaca oleracea produced skeletal muscle relaxation in rats following i.p. or oral administration, as assessed by the prolongation of pull-up time. The i.p. route of administration was more effective. When compared with chlordiazepoxide (20 mg/kg, i.p.), diazepam (40 mg/kg, i.p.) and dantrolene sodium (30 mg/kg, oral), the extract (200-1000 mg/kg, i.p.) proved a more effective skeletal muscle relaxant. With 1000 mg/kg i.p., 80% lethality was seen. The LD50 in an acute toxicity test in mice was 1040 mg/kg i.p.

Animals↗
PubMed1987

Comparison of the skeletal muscle relaxant properties of Portulaca oleracea extracts with dantrolene sodium and methoxyverapamil.

The effects of aqueous (AEE), dialysable (DIF) and methanol (MEE) extracts of Portulaca oleracea stems and leaves were compared with those of dantrolene sodium and methoxyverapamil (D-600) with respect to inhibition of twitch tension on the rat phrenic nerve-hemidiaphragm and with respect to contracture induced by nicotinic agonists on the frog rectus abdominis preparations. The extracts, dantrolene and D-600 inhibited twitch tension due to indirect electrical stimulation via the phrenic nerve (NS) on hemidiaphragm muscle, whereas the extracts and dantrolene inhibited, in addition, twitch amplitude due to direct muscle stimulation (MS). The extracts, dantrolene and D-600 also attenuated K+- and caffeine-induced contractures with the extracts and D-600 also reducing the time taken for the K+-induced contracture to fall to basal tension. In addition, the tetanic tension due to NS and MS was attenuated with only the extracts and dantrolene reducing the twitch/tetanus ratio (MS). There was a non-significant but consistent tendency for mutual potentiation between the extracts and dantrolene with respect to their inhibitory effect on twitch amplitude (MS) resulting in a shift to the left of the concentration-response curves to the extracts or dantrolene. This was not evident with the extracts and D-600 or dantrolene and D-600. Simultaneous addition of the extracts and dantrolene resulted in an increase in the rate of twitch tension inhibition and a decrease in the time to maximum relaxation of twitch amplitude (MS). The extracts and D-600 proved more effective in attenuating nicotinic agonist (acetylcholine, carbachol and nicotine)-induced contractures on the rectus abdominis muscle than dantrolene. From these observations, it appears that the Portulaca oleracea extracts mimic, in part, the effect of D-600 and dantrolene on the rat hemidiaphragm and frog rectus abdominis muscles; therefore, the muscle relaxant properties of the extracts may be due, in part, to inhibition of trans-membrane Ca influx, interference with the Ca-induced Ca release process and/or inhibition of the release of intracellular Ca from stores in the sarcoplasmic reticulum.

Animals↗
PubMed1986

Effects of Olax gambecola methanol extract on smooth muscle and rat blood pressure.

A methanol extract of the roots of Olax gambecola induced a biphasic contractile response consisting of a transitory initial rapid contraction (Phase I), followed by a slowly developing sustained increase in basal tone (Phase II) on rat fundus, antrum, guinea pig taenia coli, rabbit jejunum and aorta. The Phase I contraction was abolished by atropine, attenuated significantly by indomethacin and potentiated by physostigmine while the Phase II response was unaffected. Hexamethonium, morphine, serotonin (5-HT) antagonists or desensitization of 5-HT receptors did not alter either the Phase I or the Phase II contractions. Calcium channel blockers and procedures affecting calcium translocation abolished the Phase I contraction while only reducing the Phase II contractions. Transmural electrical stimulation produced contractions of the fundus which were attenuated by the extract. Single bolus injections of extract produced a rapid fall in blood pressure in both normotensive and spontaneously hypertensive rats but intravenous infusion resulted in a sustained fall in blood pressure which was maintained throughout the infusion period. Chronic i.p. administration of extract to spontaneously hypertensive rats reduced blood pressure markedly but did not alter the blood pressure of normotensive animals. The hypotensive response to single bolus injections was abolished by atropine and potentiated by physostigmine. The activity profile of the extract suggests the presence of at least two active principles in the crude extract of Olax gambecola used in this study.

Animals↗
PubMed1986

Skeletal muscle relaxant properties of the aqueous extract of Portulaca oleracea.

The skeletal muscle relaxant properties of an aqueous extract of Portulaca oleracea were examined on the twitch and tetanus tension evoked by electrical stimulation using the rat phrenic nerve-hemidiaphragm and frog sciatic nerve-sartorius muscle preparations and on contractures induced by nicotinic agonists using the rat rectus abdominis muscle preparation. The extract (5-50 X 10(-4) g/ml) produced a dose-dependent initial enhancement, followed by a longer lasting depression of twitch tension as induced by indirect electrical stimulation (NS) as well as direct stimulation (MS) of the diaphragm and sartorius muscle preparations. The augmentation of twitch amplitude (MS) produced by the extract was not significantly antagonised or potentiated by d-tubocurarine (5-50 X 10(-8) M) or physostigmine (5-50 X 10(-8) M) at concentrations which blocked or potentiated NS-induced twitch contractions. Furthermore, tetrodotoxin (5 X 10(-7) g/ml) alone or in combination with d-tubocurarine did not significantly attenuate extract-induced augmentation of twitch contractions to MS. In addition, the depression of twitch tension due to NS was not antagonised by physostigmine but was reversed and/or abolished by Ca2+ (2-5 X 10(-3) M) or potassium thiocyanate (1 X 10(-3) M). Contractures induced by K+ (80 mM) or by tetanic stimulation (20-60 Hz) were significantly reduced by the extract whereas, contracture induced by caffeine (2.5-6.0 mM) was not affected. Ca2+-free Tyrode's solution and EDTA (1.25 X 10(-3) g/ml) potentiated extract-induced depression of twitch tension to MS. On the rectus abdominis, contractures induced by nicotinic agonists (acetylcholine, 3-500 X 10(-7) M; carbachol, 5-500 X 10(-7) M and nicotine, 5-500 X 10(-8) M) were significantly attenuated and/or abolished by the extract (5-10 X 10(-3) g/ml). These observations indicate that the aqueous extract possesses unique skeletal muscle relaxant properties which do not appear to involve interference with cholinoceptor mechanism(s). It appears that the mechanism of action of the extract may involve interference with Ca2+ mobilization in skeletal muscle.

Animals↗
PubMedDate not supplied

Effects of extracts of Portulaca oleracea on skeletal muscle in vitro.

Extracts of Portulaca oleracea inhibited twitch tension due to direct (MS) and indirect electrical stimulation via the phrenic nerve (NS) of the rat hemidiaphragm muscle. The rank order of potency was dialysable extract greater than or equal to methanol extract greater than diethylether extract, although all exhibited equal efficacy. The non-dialysable extract did not inhibit twitch tension due to MS or NS. The dialysable, methanol and diethylether extracts inhibited tetanus tension, and attenuated the area under the K+- and caffeine-induced contracture. The contracture induced by nicotinic agonists and K+ on the rectus abdominis muscle was significantly inhibited by these extracts.

Animals↗