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Biomedical subjects

R C Causon

Publications and source records attributed to R C Causon.

29 records · Page 2Linked to original sources
PubMed1984

Determination of d-isoproterenol sulphate by high-performance liquid chromatography with amperometric detection.

The application of reversed-phase high-performance liquid chromatography (HPLC) to the determination of isoproterenol sulphate in human plasma and urine was investigated. Sulphoconjugation of the inactive isomer of isoproterenol was chosen as an experimental model to study individual variations in the rate of sulphation of phenols in man. This approach allowed the ingestion of relatively large amounts of drug and detection of the conjugated material after acid hydrolysis, using alumina clean-up and HPLC with amperometric detection. This method was found to be rapid, sensitive, precise and suited to pharmacokinetic studies in man.

Adult↗
PubMed1984

Ascending brain-stem noradrenergic pathways modulate the renin response to haemorrhage.

Ventral noradrenergic projections (VNAB) from lateral tegmental (A1, A2) and dorsal noradrenergic projections (DNAB) from the coeruleal (A6) as well as A1 cell groups in the brain-stem of the rat were lesioned by intracerebral injection of 6-hydroxydopamine. A marked increase in plasma renin activity and adrenaline concentrations followed haemorrhage (0.5 ml/100 g body weight) in the sham-operated rats. VNAB-lesioned rats showed a similar response to the sham-operated controls, but in DNAB-lesioned animals the rise of plasma renin was markedly attenuated.

Animals↗
PubMed1983

High-performance liquid chromatography with amperometric detection of plasma L-3,4-dihydroxyphenylalanine in Parkinsonian patients.

An assay for the quantitative estimation of L-3,4-dihydroxyphenylalanine in human plasma has been developed, using alpha-methylnoradrenaline as internal standard and ion-pair reversed-phase (C8), isocratic high-performance liquid chromatography with amperometric detection. A citrate-phosphate buffer, pH 3.1, containing 2 mM EDTA disodium salt, 6.5 mM 1-octanesulphonic acid and 14% v/v methanol, provided good separation of the analytes from each other and from the carbidopa present in the plasma of Sinemet-treated Parkinsonian patients. The sensitivity, selectivity and precision of the method were found to be sufficient to enable its routine use for pharmacodynamic studies.

Chromatography, High Pressure Liquid↗
PubMed1983

The effect of selective and non-selective beta-adrenoceptor blockade, and of naloxone infusion, on the hormonal mechanisms of recovery from insulin-induced hypoglycaemia in man.

The rise in plasma adenosine-3',5'-monophosphate occurring in response to insulin induced hypoglycaemia in normal human subjects, was abolished by non-selective beta-adrenoceptor blockade but unaffected by selective beta 1-adrenoceptor blockade. This implies that the rise is secondary to beta 2-adrenoceptor stimulation. The abolition of this rise by non-selective beta-adrenoceptor blockade had no pronounced effect on the recovery from hypoglycaemia. Endogenous opiate receptor blockade with naloxone had no significant effect on the recovery from insulin induced hypoglycaemia, or the hormonal mechanisms involved.

Adrenergic beta-Antagonists↗
PubMed1983

The effects of pentolinium on sympathetic activity in hypertensives and normotensive controls.

The effects of pentolinium tartrate 2.5 mg i.v. on blood pressure, heart rate and plasma noradrenaline and adrenaline concentrations were studied in 21 hypertensives and in 20 normal controls. Mean basal catecholamine concentrations and the extent of their suppression by pentolinium were similar in both groups. The reductions in both plasma catecholamine levels correlated with the prepentolinium values. Supine systolic blood pressure was significantly reduced and there was a small increase in heart rate. These data support the use of plasma noradrenaline as an index of sympathetic activity but are inconsistent with the hypothesis that essential hypertension is associated with hyperactivity of the sympathetic nervous system.

Adult↗
PubMed1982

Measurement of catecholamines in biological fluids by high-performance liquid chromatography: a comparison of fluorimetric with electrochemical detection.

An improved method for the determination of catecholamines in biological fluids, by reversed-phase high-performance liquid chromatography (HPLC) with fluorimetric detection is presented. The pH titration previously employed in the alumina extraction was abandoned in favour of the use of a molar excess of PH 8.5 Tris--HCl buffer. A novel lyophilisation step serves to concentrate the catechols and by reconstituting in mobile phase, chromatography disturbances are minimised. The addition of 2 mM octanesulphonic acid to citrate--phosphate mobile phase at pH 6.0 gave optimal resolution and sensitivity. That HPLC separation can improve the specificity of the trihydroxyindole reaction, to the extent of providing a reliable analytical method, has been demonstrated and validated by the technique of HPLC with electrochemical detection. A correlation coefficient of 0.98 was obtained between the two techniques as applied to the measurement of urinary catecholamines. The HPLC--fluorimetric method was sensitive enough to measure 0.1 ng/ml of noradrenaline or adrenaline at a signal-to-noise ratio of 2.0. Application of the method to the quantitative determination of catecholamines in human urine, plasma and rat brain homogenates is demonstrated.

Brain↗
PubMed1982

Catecholamine measurements in phaeochromocytoma: a review.

The early diagnosis of phaeochromocytoma by measurement of catecholamines or their metabolites is important, since it brings the prospect of permanent cure to a small but significant proportion of the hypertensive population. The development of sensitive and specific methods for the analysis of catecholamines has led to the increased use of such measurements in the biochemical diagnosis and localisation of this rare tumour.

Adrenal Gland Neoplasms↗