Georg R. Beilharz

Endogenous phospholipase and choline release in human erythrocytes: a study using 1H-NMR spectroscopy.

Abstract 1H spin-echo NMR spectroscopy has been used to show for the first time, to our knowledge, the presence of a phospholipase D activity in human erythrocytes. The enzyme is presumably intra-cellular and we have demonstrated that it is activated by a component of Krebs bicarbonate medium; most probably calcium ions. The existence of a phospholipase in human erythrocytes allows a simple explanation for the choline accumulation that occurs in these cells of manic-depressive and other patients receiving lithium carbonate therapy.

Studies of rat brain metabolism using proton nuclear magnetic resonance: spectral assignments and monitoring of prolidase, acetylcholinesterase, and glutaminase

The first application of inversion‐recovery spin‐echo proton nuclear magnetic resonance spectroscopy to the monitoring of reactions in rat brain preparations is presented. The initial report of the assignment of proton spin‐echo nuclear magnetic resonance spectra from rabbit brain homogenates (C. R. Middlehurst et al., J. Neurochem. 42, 878–879, 1984) was used to assist in the assignment of spectra acquired from rat brain homogenates that were obtained from animals killed by cervical fracture or focussed microwave irradiation. Microwave‐irradiated brains were divided into four major anatomical regions. Differences in metabolite levels were detected when spectra from fresh tissue and from various regions were compared. The in situ steady‐state kinetics of prolidase in whole brain homogenate was determined.

Lithium, Red Blood Cell Choline and Clinical State A Prospective Study in Manic-Depressive Patients

Red blood cell (RBC) choline and ergothioneine levels were measured after repeated sampling of bipolar manic-depressive patients over 11 months of lithium maintenance. In addition, blood levels were measured in healthy volunteers, newly hospitalised lithium-free patients and from patients prior to, and after, initiating lithium. RBC choline levels did not differ between normal volunteers and newly admitted lithium-free patients with either mania or depression. After 4 weeks of lithium treatment RBC choline levels increased 6-fold, whereas the levels of the closely related compound ergothioneine did not change. Significant changes in mood during lithium maintenance were not accompanied by changes in RBC choline levels. These data indicate that lithium produced a specific accumulation of choline in erythrocytes. However the increased levels appear to be unrelated to clinical state and do not distinguish lithium responders from non-responders

Proton Nuclear Magnetic Resonance Spectroscopy of Rabbit Brain Homogenate

Abstract: Proton nuclear magnetic resonance (1H NMR) spectroscopy in conjunction with the inversion‐recovery spin‐echo pulse sequence was used to obtain spectra from rabbit brain homogenate. The instrumental parameters required for the acquisition of spectra together with the assignment of major peaks are given. The rationale and prospectus for the use of this technique for the study of neurochemistry is outlined.

Determination of choline in erythrocytes using high-resolution proton nuclear magnetic resonance spectroscopy: comparison with a choline oxidase method

Detailed operating conditions are reported for the determination of choline in human erythrocytes using proton nuclear magnetic resonance spectroscopy in conjunction with the inversion-recovery spin-echo pulse sequence. The results of the NMR method were in excellent agreement with those obtained using an enzymatic (choline oxidase) assay; however, they were approximately three times higher than those reported using gas chromatography/mass spectrometry techniques. The differences may be partly due to the method of preparing or sampling cells since there is a distribution of choline in cells of different ages. However, choline levels were not affected by the methods used in the present study for storing or preparing cells.

Plasma and erythrocyte choline concentrations in rats following chronic treatment with lithium or choline

Rats were given daily injections of choline, lithium or lithium plus choline for either 11 or 18 days and red cell choline, glycine and glutathione levels were measured using proton nuclear magnetic resonance spectroscopy. In addition, plasma choline, plasma lithium and red cell lithium levels were measured 4 hr after the last dosage. Choline (1 mmol/kg) alone increased plasma but not red cell choline concentrations. Lithium (0.94 mmol/kg) elevated red cell choline levels but did not affect plasma choline concentrations. In contrast, red cell choline levels were not elevated in rats treated with a higher dose of lithium (1.88 mmol/kg). When choline was given in addition to the lower dose of lithium, a similar accumulation of red cell choline was observed suggesting that the lithium-induced choline accumulation was not enhanced by a greater availability of free choline. No differences were detected in red cell glycine or glutathione levels between any of the treatment groups. Therefore, lithium produced a specific (dose-dependent) accumulation of choline in rat erythrocytes. However, the 100% increase observed in rats was not as marked as the increased red cell choline levels reported in patients maintained on lithium (8 to 10-fold). This discrepancy supports the concept that species differences exist in red cell choline transport or metabolism.