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Biomedical subjects

J J de Ridder

Publications and source records attributed to J J de Ridder.

9 recordsLinked to original sources
PubMed1977

The use of high-performance liquid chromatography for sample clean-up in mass fragmentographic assays.

A novel high-performance liquid chromatography (HPLC) sample clean-up procedure for use in mass fragmentographic assays of (sub)-nanogram amounts of drugs in human plasma is described and compared with a conventional extraction sequence for sample purificaiton. With the assay of the new antidepressant drug mianserin hydrochloride (Org GB 94) as an example, the HPLC procedure is discussed with respect to retention time, recovery, purification, colum deterioration and convenience. It is demonstrated that HPLC sample clean-up is a useful and time-saving procedure for routine clinical analyses.

Chromatography, High Pressure Liquid↗
PubMed1977

Mass fragmentographic assay of nanogram amounts of the antidepressant drug mianserin hydrochloride (Org GB 94) in human plasma.

For the assay of the antidepressant compound mianserin hydrochloride (Org GB 94) in human plasma, a mass fragmentographic method, using the deuterated analogue as internal standard and a high-performance liquid chromatographie sample clean-up procedure has been developed. The assay specifications obtained are a lower limit for reliable measurements of 1 ng/ml, and accuracy of ca. 0.01 ng/ml, a precision of 6--7% and a capacity of about 60 samples per day. The applicability of the assay method is illustrated by measurements of single-dose and steady-state plasma levels in clinical experiments, demonstrating the possibility of monitoring plasma levels during at least 24 h after a single dose of 15 mg of Org GB 94. The mean steady-state plasma levels after a daily dose of 3 X 20 mg of Org GB 94 appeared to be remarkably constant with time: 38, 36 and 34 ng/ml after 2, 4, and 6 weeks of treatment of 18 depressed patients.

Adult↗
PubMed1976

The uptake of choline by rat liver mitochondria.

1. Rat liver mitochondria can accumulate choline against a concentration gradient. Maximally about 30 nmol choline per mg mitochondrial protein are found in the matrix space. 2. The process of choline uptake is biphasic. After a rapid uptake of 1.5-15 nmol per mg protein, a slower uptake occurs if an energy supply is present. In the absence of energy, only the rapid uptake is found. 3. The inhibition of uncoupler-stimulated choline oxidation by cations is the result of an inhibition of choline uptake.

Adenosine Triphosphate↗
PubMed1976

Mianserin hydrochloride: a novel antidepressant.

The antidepressant activities of mianserin hydrochloride were investigated and compared with those of amitriptyline. The therapeutic efficacy of the two drugs appeared similar, but the incidence of side-effects was significantly higher with amitriptyline. Plasma levels of mianserin were determined during the trial and were not related to the therapeutic activity of the drug.

Adjustment Disorders↗
PubMed1975

Control of choline oxidation by rat-liver mitochondria.

The steady-state concentrations of choline and its reaction products in intact rat-liver mitochondria were determined under different conditions. From these measurements, it is concluded that in a sucrose medium choline dehydrogenation and betaine aldehyde dehydrogenation are the rate-limiting steps in overall choline oxidation under "State-3" or uncoupled conditions, respectively. Ageing of the mitochondria leads to changes in the mitochondrial membrane, resulting in a markedly different pattern of oxidation products. This finding explains why rotenone inhibits oxygen uptake with choline as substrate in fresh but not in aged mitochondria.

Acetoacetates↗