Reduced imprecision of the radioenzymatic assay of plasma catecholamines by improving the stability of the internal standards

1986 ◽  
Vol 156 (2) ◽  
pp. 221-225 ◽  
Author(s):  
J.J.M.L. Hoffmann ◽  
J.J. Willemsen ◽  
J.W.M. Lenders ◽  
Th.J. Benraad
Keyword(s):  
Plasma Catecholamines ◽  
Internal Standards ◽  
Radioenzymatic Assay ◽  
The Stability

Kinetics of enzymatic O-methylation: its value in assays for catecholamines in plasma.

1984 ◽  
Vol 30 (1) ◽  
pp. 24-27 ◽  
Author(s):  
L Mason ◽  
C Weinkove
Keyword(s):  
Mathematical Analysis ◽  
Plasma Catecholamines ◽  
High Concentration ◽  
Internal Standards ◽  
Linear Approximations ◽  
Endogenous Catecholamine ◽  
Radioenzymatic Assay ◽  
Exponential Equations ◽  
Kinetics Of ◽  
Catecholamine Concentration

Abstract The kinetics of enzymatic O-methylation of catecholamines were studied under conditions like those used in the radioenzymatic assay of plasma catecholamines. Inappropriate Michaelis-Menten kinetics and linear approximations of exponential equations were not used. Mathematical analysis indicated the importance of the ratio of methyl donor (S-adenosylmethionine) to substrate (catecholamine) concentration. If the reaction is incomplete, only a large ratio will allow linear approximations between product formed and initial catecholamine concentration. The use of high-concentration internal standards to correct for plasma interference may give erroneous results by reducing this ratio. Accuracy will be improved by ensuring (a) that S-adenosylmethionine is always greatly in excess of catecholamine, (b) that concentrations of added standards are of the same order as for endogenous catecholamine, and (c) that a high activity of enzyme is used, to allow the reaction to reach completion even in the presence of some inhibition.

Plasma Catecholamines: Experience with a Single-Isotope Radioenzymatic Assay

1984 ◽  
Vol 21 (4) ◽  
pp. 239-245 ◽  
Author(s):  
R Neil Dalton
Keyword(s):  
Clinical Chemistry ◽  
Plasma Catecholamines ◽  
Tumour Markers ◽  
Chemistry Laboratory ◽  
Plasma Adrenaline ◽  
Tumour Localisation ◽  
Radioenzymatic Assay ◽  
Clinical Chemistry Laboratory

The performance of a rapid and sensitive single-isotope radioenzymatic assay for plasma catecholamines, in a routine clinical chemistry laboratory, is reported and discussed. The value of plasma adrenaline and noradrenaline as tumour markers in the diagnosis, tumour localisation, and post-operative follow-up of four patients with phaeochromocytoma is emphasised.

Hypercatecholaminemia in Reye's Syndrome

PEDIATRICS ◽  
1984 ◽  
Vol 73 (4) ◽  
pp. 481-488
Author(s):  
Bahjat A. Faraj ◽  
Daniel B. Caplan ◽  
Stephen L. Newman ◽  
Peter A. Ahmann ◽  
Vernon M. Camp ◽  
...  
Keyword(s):  
Liver Biopsy ◽  
Cerebral Edema ◽  
Plasma Catecholamines ◽  
Hospitalized Patients ◽  
Control Population ◽  
Reye's Syndrome ◽  
Positive Correlation ◽  
Radioenzymatic Assay ◽  
Csf Concentration

To evaluate the role of catecholamines in Reye's syndrome, a specific and sensitive radioenzymatic assay was used to study plasma and CSF concentration of dopamine, norepinephrine, and epinephrine in 14 patients with liver-biopsy-proven Reye's syndrome. The results (median and range) revealed significant (P < .04, P < .0024, and P < .030, respectively) elevation in plasma dopamine (131, 0 to 1,193 pg/mL), norepinephrine (1,455, 20 to 5,271 pg/mL), and epinephrine (345, 7.6 to 2,504 pg/mL) at the onset of the disease when compared with the level of these neurotransmitters in a group of hospitalized patients without hepatic disorders. There was a positive correlation between plasma catecholamines and stage of coma on admission (r = .54 to .86; P < .001 to .024). Furthermore, the concentration of dopamine, norepinephrine, and epinephrine in the CSF increased significantly during the development of cerebral edema in all patients with Reye's syndrome as compared with concentrations in a control population. Hypercatecholaminemia may contribute to the encephalopathy of Reye's syndrome.

Rapid fluctuations in plasma catecholamines in monkeys under undisturbed conditions

1982 ◽  
Vol 242 (1) ◽  
pp. E40-E46
Author(s):  
B. C. Hansen ◽  
G. P. Schielke ◽  
K. L. Jen ◽  
R. A. Wolfe ◽  
H. Movahed ◽  
...  
Keyword(s):  
Plasma Levels ◽  
Rhesus Monkeys ◽  
Cross Correlation ◽  
Plasma Catecholamines ◽  
Central Venous Catheters ◽  
Central Venous ◽  
Radioenzymatic Assay ◽  
Large Fluctuations ◽  
Periodic Fluctuations ◽  
Male Rhesus

We have demonstrated in monkeys and in man sustained synchronous oscillations in plasma levels of insulin, C-peptide, glucagon, and glucose that have periods ranging from 8 to 11 min. To identify the mechanisms of these oscillations, we studied plasma levels of catecholamines in search for periodic fluctuations. Blood was obtained at 2-min intervals from fasting, undisturbed, chair-adapted male rhesus monkeys via chronically implanted central venous catheters. Plasma levels of epinephrine, norepinephrine, and dopamine were measured by a radioenzymatic assay. Large fluctuations in plasma epinephrine were observed with an average peak-to-trough amplitude of 34 pg/ml at a mean level of 122 pg/ml. Similar fluctuations in norepinephrine and dopamine occurred and were correlated to those of epinephrine: r = 0.51 and 0.35, respectively. The most common periodicity in all three catecholamines was 6-13 min/cycle as determined by spectral analyses. Cross-correlation analyses indicated that fluctuations in the catecholamines were significantly negatively correlated with oscillations in insulin and were unrelated to fluctuations in glucagon. These fluctuations in plasma catecholamines may be related to mechanisms controlling the periodicity observed in plasma insulin and glucose.

Plasma catecholamines during hypoxemia in fetal lamb

1982 ◽  
Vol 243 (5) ◽  
pp. R520-R525 ◽  
Author(s):  
W. R. Cohen ◽  
G. J. Piasecki ◽  
B. T. Jackson
Keyword(s):  
Inferior Vena ◽  
Plasma Catecholamines ◽  
Vena Cava ◽  
Plasma Norepinephrine ◽  
Low Oxygen ◽  
Peripheral Plasma ◽  
Radioenzymatic Assay ◽  
Fetal Lamb ◽  
Very High ◽  
Catecholamine Levels

Changes in peripheral plasma catecholamines were studied during varying degrees of hypoxemia in fetal lambs of 95–140 days gestation. Epinephrine and norepinephrine concentrations were measured by radioenzymatic assay in plasma obtained simultaneously from the distal aorta and inferior vena cava in 15 chronically catheterized fetuses with the mother breathing 20, 10, or 8% oxygen mixtures. Levels of both epinephrine and norepinephrine increased significantly after 5 min of hypoxemia and showed a strong inverse exponential correlation with PO2 (P less than 0.001). Plasma norepinephrine always exceeded epinephrine concentrations (P less than 0.01). Resting arterial and venous catecholamine levels were not different, but during hypoxemia arterial levels of both epinephrine and norepinephrine exceeded venous levels significantly, suggesting the adrenal medulla as a major source of these substances. Hypoxemia led to fetal bradycardia, the degree of which moderated somewhat with extremely low oxygen tensions and associated very high catecholamine levels. Fetal blood pressure increased initially in proportion to norepinephrine levels but reached a plateau at concentrations higher than 10 ng/ml. Although concentrations of catecholamines were lower in the earlier gestation fetuses studied, similar qualitative relations between catecholamines and PO2 were evident at all gestational ages.

Effect of in vitro hemolysis on assay of plasma catecholamines and DOPA.

1980 ◽  
Vol 26 (9) ◽  
pp. 1354-1356 ◽  
Author(s):  
R T Smith
Keyword(s):  
Plasma Catecholamines ◽  
Human Erythrocytes ◽  
Treatment Groups ◽  
Plasma Pool ◽  
Radioenzymatic Assay ◽  
Significant Difference ◽  
Processing Techniques ◽  
Single Plasma ◽  
Plasma Control

Abstract I analyzed for free and sulfate-conjugated catecholamines and DOPA (3,4-dihydroxyphenylalanine) in four aliquots of a single plasma pool with use of Upjohn's "Cat-A-Kit" (catecholamines radioenzymatic assay kit [3H]. One aliquot was a clear plasma control; the others were supplemented with different concentrations of lysed human erythrocytes, to investigate possible interference by hemolysis with analysis for norepinephrine, epinephrine, dopamine, or DOPA in plasma. I observed no statistically significant difference that could be attributed to the degree of hemolysis between control and treatment groups for DOPA or any catecholamine fraction. Hemolysis in plasma from improper collection or processing techniques apparently does not preclude accurate and precise quantitation of free or sulfate-conjugated catecholamines or DOPA with the Cat-A-Kit.

The Stability of Geosmin and MIB and Their Deuterated Analogues in Surface Waters and Organic Solvents

1992 ◽  
Vol 25 (2) ◽  
pp. 115-122 ◽  
Author(s):  
W. Korth ◽  
J. Ellis ◽  
K. Bowmer
Keyword(s):  
Carbon Disulfide ◽  
Surface Waters ◽  
Carbonyl Compounds ◽  
Biological Processes ◽  
Sample Storage ◽  
Internal Standards ◽  
Physical Chemical ◽  
The Stability ◽  
Acetone Hexane

Deuterated geosmin [trans-l,10-[2H3]-dimethyl-9α-decalol] anddeuteratedmethylisoborneol [2-exo-hydroxy-2-[2H3]-methylbornane] were synthesised and evaluated as alternatives to 1-chloroalkanes as internal standards in the determination of geosmin and MIB in surface waters. Geosmin and MIB were stored as dilute solutions in methanol, ethanol, acetone, hexane or carbon disulfide for >6 months without deterioration. Dichloromethane caused substantial decomposition of MIB. When added at the time of sampling, the labelled standards compensated for losses of analyte by physical, chemical and biological processes during sample storage. The labelled compounds were effective internal standards for the determination of other odorous metabolites such as the carbonyl compounds β-cyclocitral, β-ionone, geranylacetone and 6-methylhept-5-en-2-one.

Open discussion

1982 ◽  
Vol 99 ◽  
pp. 605-613
Author(s):  
P. S. Conti
Keyword(s):  
Buenos Aires ◽  
Large Mass ◽  
List Type ◽  
Common Phenomenon ◽  
Open Discussion ◽  
The Stability ◽  
Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

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