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D W Seccombe

Publications and source records attributed to D W Seccombe.

34 records · Page 2Linked to original sources
PubMed1987

Minimizing analytical interferences from digoxin-like immunoreactive substances (DLIS) in cases of digoxin toxicity.

Recently, the value of therapeutic drug monitoring for digoxin has been called into question by the finding of endogenous digoxin-like immunoreactive substances (DLIS) in the serum of individuals, especially premature and full-term neonates, not being treated with digoxin. In some cases, values have been as high as 10 micrograms/L. Levels as high as 20 micrograms/L and 80 micrograms/g can be found in bile and meconium. Because of the magnitude of this interference, it is essential that methods be developed for measuring digoxin in the presence of DLIS. This is particularly important when such analyses are required in forensic science cases of suspected digoxin toxicity. This report outlines the high performance liquid chromatographic (HPLC) and radioimmunoassay (RIA) methods that we used in assessing the relative contribution made by digoxin, its metabolites, and DLIS to serum and tissue digoxin concentrations obtained by RIA in a forensic pediatric case of suspected digoxin toxicity.

Blood Proteins↗
PubMed1986

L-carnitine treatment in glutaric aciduria type I.

Patients with organic aciduria may have a higher than normal requirement for L-carnitine. In a patient with type I glutaric aciduria, serum total L-carnitine levels were 8.5 microM (normal, 54.4 +/- 14.2 [2 SD] microM). After treatment with L-carnitine for 1 month, serum levels of both free and total L-carnitine were normal with an acyl-to-total ratio of 0.18. The fractional clearance rates of free and acylcarnitine were increased fourfold by treatment. Acetylcarnitine accounted for a lower than normal percentage of acylcarnitine recovered in serum and urine. Data suggest that this patient may have been carnitine-deficient.

Carnitine↗
PubMed1985

Effect of assay conditions on cross reactivity of digoxin-like immunoreactive substance(s) with radioimmunoassay kits.

One or more digoxin-like immunoreactive substances (DLIS), most frequently present in serum of premature and full-term neonates. cross react to various extents with different digoxin immunoassay kit reagents. Mostly, this variation is attributed to the relative cross reactivity of DLIS with the antiserum in each kit. However, modification of standard assay procedures for digoxin can also greatly alter the relative cross reactivity of DLIS. Using sequential RIA kit methods for digoxin by 20 to 60% relative to the standard equilibrium RIA mode. Cross reactivity was decreased still more if the concentrations of antiserum (binding-site concentration) and tracer (125 l-labeled digoxin) were decreased, and conversely. Serum samples containing only digoxin, analyzed by the modified method, consistently yielded results well comparable with those obtained with the manufacturers' recommended procedures. We describe use of the different responses to digoxin and DLIS of standard and sequential radioimmunoassays and use of simultaneous equation to calculate the concentration of DLIS (in digoxin equivalents) in digoxin-containing samples.

Cross Reactions↗
PubMed1984

Perinatal changes in a digoxin-like immunoreactive substance.

An endogenous digoxin-like immunoreactive substance(s) (DLIS) exists in the serum of premature and full term infants not receiving digoxin. We followed serum changes in DLIS concentration sequentially over the first 14 postnatal days in 24 premature neonates who did not receive digoxin in the intensive care nursery. All infants had measurable levels (greater than 0.6 ng/ml) of DLIS in their serum. There was a distinct peak in DLIS concentration in 19 of 24 infants occurring at 4 +/- 1.6 (SD) days after birth (range, 1-8 days). No peak was found in five infants. The peak serum level of DLIS obtained in the first 8 days of life was negatively correlated with gestational age and birth weight. DLIS levels in amniotic fluid remained constant from 16 to 33 weeks of gestation but rose from 33 wk to term. DLIS concentrations in umbilical artery, umbilical vein, and maternal serum at normal full term delivery suggested that DLIS was of fetal origin. DLIS and digoxin concentrations are additive when present in the same serum sample if measured by standard radioimmunoassay methods.

Aging↗
PubMed1983

Seven different digoxin immunoassay kits compared with respect to interference by a digoxin-like immunoreactive substance in serum from premature and full-term infants.

Seven different digoxin immunoassay kits showed cross reactivity with an endogenous digoxin-like immunoreactive substance consistently present in serum of neonates, whether premature or full-term. The degree of interference, in decreasing order was: NML greater than New England Nuclear greater than Bio-Rad greater than Clinical Assays greater than Becton Dickinson greater than Serono greater than Syva (EMIT). More recently purchased NML kits showed less sensitivity to the substance, evidently reflecting lot-to-lot differences in antibody. A single baseline determination of the substance before digoxin is administered inadequately compensates for this interference, because the interferent concentrations can differ from day to day, with evidence that it may be most concentrated on the fourth to sixth postnatal day. Its concentration in the serum of neonates is unrelated to the concentration of dehydroepiandrostenedione sulfate, an indicator of fetal adrenal-cortical activity.

Cross Reactions↗
PubMed1980

Carnitine acetyltransferase in developing mammals.

Carnitine acetyltransferase (CAT) activity was determined in mitochondria and microsomes of liver and brown adipose tissue in fetal and postnatal rats, rabbits and guinea pigs. In rat liver and brown adipose tissue, mitochondrial CAT activity increased perinatally. Microsomal CAT activity also increased in brown adipose tissue. In liver, however, a rise was first noted after the 20th postnatal day. The ratio of mitochondrial to microsomal activity was higher in brown fat than liver throughout the period studied. Absolute values for both were always much higher in brown adipose tissue than in liver. Catalase activity (an enzyme localized in the peroxisomes) in rat liver increased after day 20 while in brown adipose tissue it attained a peak at 7 days after birth. At all times, hepatic activity exceeded activity in brown adipose tissue. The ratio on day 30 was 1 (brown adipose tissue) to 25 (liver). In both guinea pigs and rabbits, hepatic mitochondrial CAT activity was 10- to 20-fold higher than in the rat already prenatally. Microsomal activity, on the other hand, was approximately the same in all three species. It is concluded that probably only the mitochondrial CAT is directly related to fatty acid oxidation. The role of microsomal enzyme remains unclear.

Acetyltransferases↗
PubMed1978

Effect of fasting on free and esterified carnitine levels in human serum and urine: correlation with serum levels of free fatty acids and beta-hydroxybutyrate.

Serum levels of free L-carnitine, acylcarnitines, creatinine, beta-hydroxybutyrate, free fatty acids, cholesterol, triglycerides, and glucose were determined in healthy volunteers during a 24-36-hr fast. The effect of oral administration of free L-carnitine (1 g/person) on these parameters was studied. Urinary excretion of carnitine and creatinine was monitored throughout. Serum and urine levels of free carnitine and its renal clearance decreased during the fast. However, the serum concentration and urinary excretion of acylcarnitines increased during the same interval. Following the ingestion of free L-carnitine, both serum and urinary levels of free L-carnitine rose. Within 6 hr of ingestion, 10% of the administered dose could be accounted for by urinary excretion. No significant effect on the other serum constituents under study was seen following the oral L-carnitine dose. A significant negative correlation was found between serum levels of free L-carnitine and beta-hydroxybutyrate and free fatty acids (r equal -0.567, p less than 0.001 and r equal -0.607, p less than 0.001, respectively) during the fast.

Acetylcarnitine↗
PubMed1977

Fetal utilization of maternally derived ketone bodies for lipogenesis in the rat.

When D-beta-[3-14C]hydroxybutyrate was injected via the femoral vein into pregnant Sprague-Dawley rats at 21 days of gestation, D-beta-[3-14C]hydroxybutyrate was enzymatically detected in fetal plasma within 5 min. The time course of the incorporation of DL-beta-[3-14C]hydroxybutyrate into fetal lipids was studied. Lipid extracts of brown adipose tissue exhibited the greatest relative incorporation followed by pancreas, liver and lung. Less radioactivity was incorporated into brain and placenta. The incorporation into fetal lipids was several-fold greater than into maternal lipids. The labelling of the individual phospholipids was similar in the different tissues with phosphatidylcholine accounting for more than 50%. 75% of the radioactivity in brown adipose tissue was in the triacylglycerol fraction. In brain, liver and placenta, approximately half of the neutral lipid radioactivity was in cholesterol. Experiments in which D-beta-[3-14C]hydroxybutyrate was directly injected into fetuses in utero confirmed that this substrate was directly used by the fetuses without maternal intervention. These studies demonstrate that the rat placenta is permeable to beta-hydroxybutyrate and suggest that this ketone body is rapidly used by the fetus for the synthesis of fatty acids and cholesterol.

Adipose Tissue, Brown↗
PubMed1977

Fructose-1,6-diphosphatase activity in brown adipose tissue of the developing rat.

An enzyme activity capable of converting fructose-1,6-diphosphate to fructose-6-phosphate was demonstrated to present in crude tissue extracts from brown adipose tissue of the rat. Mg2+ was essential for the expression of activity. EDTA (0.5 mM) increased the activity by 30%. Fructose-1,6-diphosphate in concentrations of 1 and 10 mM inhibits activity by 30% and 60% respectively. A 65% inhibition was observed in the presence of 0.2 micrometer 5' AMP. The activity of the enzyme was measured in rat brown adipose tissue at different stages of development. It rises sharply between day 2 and day 6 and continues to increase reaching a maximum between 6 and 11 days. Thereafter the activity gradually declines to values observed prenatally. The normal developmental rise in activity could be prevented by chemical sympathectomy on day 2. This procedure had no effect when carried out on day 9. There was a significant increase in enzyme activity after cold adaptation. The possible physiological significance of this enzyme in brown adipose tissue is discussed.

Adaptation, Physiological↗
PubMed1977

Carnitine content of blood and amniotic fluid.

Free carnitine levels were determined in amniotic fluids between the 10th and 40th week of gestation. They were found to decrease significantly with gestational age. Blood levels of carnitine were lower in pregnant than in nonpregnant women. Levels were found to be higher in cord blood than in maternal blood and usually were higher in the umbilical artery than vein. Intra-arterial injection of L-carnitine into a pregnant ewe did not cause a rise in the fetal blood level of carnitine, which, in contrast to human fetal blood, contained less than half the level of carnitine in maternal blood.

Age Factors↗
PubMed1976

Automated method for L-carnitine determination.

Because of renewed interest in a possible connection between carnitine, lipid disorders, and myopathy, an automated method of analysis is desirable. Deproteinization of serum by use of membrane filter cones and automated assay with a bichromatic analyzer (the ABA-100) substantially increases efficiency without sacrificing the specificity and accuracy of the original manual enzymatic method. The described procedure allows for analysis of 80 speciments a day and is thus suitable for screening of selected populations. Normal values found in blood sera of adults were in the range of 25.0-73.8 mu mol/liter and the method has sufficient sensitivity to accurately measure concentrations as small as 10 mu mol/liter.

Adult↗