Dose-related effects of nerve growth factor (NGF) on choline acetyltransferase (ChAT), acetylcholine (ACh) content and ACh turnover in the brain of newborn rats.

Dose-effect relations of ?-nerve growth factor (NGF) have been established on the induction of choline acetyltransferase (ChAT) in basal forebrain nuclei, striatum, cortex and hippocampus of newborn rats after single intracerebroventricular (i.c.v.) injections. Doses above 2 ?g were maximally effective in each of the four brain regions. With the same doses and in the same time course acetylcholine (ACh) concentrations were elevated in the same brain regions. ChAT activity was increased up to 220% in the septum, 200% in the striatum, 160% in the cortex and 120% in the hippocampus. The ACh concentration was elevated up to 175% in the septum, 140% in the striatum, 130% in the cortex and 117% in the hippocampus. The incorporation of labelled choline into ACh showed an increase in ACh turnover of about 60% after i.c.v. application of 5 ?g NGF. Unspecific effects of NGF on brain growth have been excluded. NGF may possibly be useful for the treatment of memory and cognitive impairment as in senile dementia of Alzheimer's type.

A suitable method to monitor inhibition of cholinesterase activities in tissues as induced by reversible enzyme inhibitors.

A radiometric method has been used to estimate in vivo activities of cholinesterases in various tissues in the presence of reversible inhibitors. Determination of the samples was performed with the lowest possible degree of dilution to avoid reactivation of the enzyme which would prevent reliable calculation. Dose-response curves and concentration-response curves were performed using physostigmine and tetrahydroacridine, two reversible anticholinesterases in clinical use. Specific inhibition of acetyl- and butyrylcholinesterase was performed using BW284C51 and iso-OMPA, respectively.

Estimation of cholinesterase activity (EC 3.1.1.7; 3.1.1.8) in undiluted plasma and erythrocytes as a tool for measuring in vivo effects of reversible inhibitors.

In vivo effects of reversible inhibitors of cholinesterase activity were determined radiometrically in undiluted samples of erythrocytes and plasma. [14C]acetylcholine at substrate saturation, 25 degrees C and pH 7.4 permitted rapid and precise determination of butyrylcholinesterase (EC 3.1.1.8) and acetylcholinesterase (EC 3.1.1.7) activities. Reference values for acetylcholinesterase and butyrylcholinesterase were estimated in the plasma and erythrocyte haemolysate of 102 healthy volunteers. The time course of in vitro inhibition was monitored, starting immediately after addition of 9-amino-1,2,3,4-tetrahydroacridine (tacrine), eserine or pyridostigmine to undiluted human plasma. Maximal inhibition (in vitro) was seen within 60 min with tacrine and eserine, in contrast to 180 min with pyridostigmine. The inhibition remained constant for more than 10 h except with eserine, from which enzyme activity showed an early recovery. Concentration response experiments were performed in undiluted human plasma and undiluted human erythrocyte haemolysate. Ki-values of tacrine, eserine and pyridostigmine were estimated. In contrast to pyridostigmine and eserine, tacrine was found to have a higher affinity for butyrylcholinesterase than for acetylcholinesterase. Tacrine at 2.5 mumol/l resulted in complete inhibition of butyrylcholinesterase and 70% inhibition of acetylcholinesterase activity. Dilution of these samples up to 100-fold was accompanied by almost complete recovery of acetylcholinesterase and by 50% recovery of butyrylcholinesterase.

Lithium therapy and the turnover of phosphatidylcholine in human erythrocytes.

In 17 lithium-treated patients with manic-depressive disorders and 11 healthy subjects the concentrations of choline, phosphorylcholine, cytidyldiphosphate choline, lipid bound choline, and glycerophosphorylcholine were measured in plasma and erythrocytes. Plasma levels of high density, low density, and very low density lipoproteins were also estimated as well as the concentrations of 4 free fatty acids. Free choline (more than 10-fold) and phosphorylcholine (2-fold) were significantly increased in erythrocytes of lithium-treated patients as compared to the healthy untreated controls. Differences in the other substrates were not significant. Osmotic resistance of the erythrocytes was not changed during lithium treatment. Inhibition of the choline flux across the erythrocyte membrane in vitro from lithium-treated patients was not abolished by equilibration of the concentration gradient. It is concluded that the accumulation of choline in erythrocytes from patients on lithium therapy may be due to trapping of lipid derived choline because of an alteration in membrane permeability and not to increased breakdown of phosphatidylcholine.

Lack of adaptive changes in human pancreatic amylase and lipase secretion in response to high-carbohydrate, low-fat diet applied by a 10-day continuous intraduodenal infusion.

In order to investigate whether the human exocrine pancreas is capable of adapting to a diet with a high-carbohydrate, low-fat, and normal protein content, 10 healthy subjects were given a continuous intraduodenal infusion of such a dietary composition (8760 kJ in 2400 ml/day) via a portable infusion pump over a period of 10 days. The diet consisted of 76% of calories as carbohydrates (80% oligosaccharides, 20% mono- and disaccharides), 10% as fat (more than 90% C18 fatty acids) and 14% as protein (oligo- and polypeptides; 11.8 g nitrogen per day). A complete pancreozymin-secretin test was carried out before and after the experimental period. The results show that the above dietary regimen leads to a significant (P less than 0.05) increase in the stimulated secretion rates of trypsin and chymotrypsin, whereas, in contrast to the findings in animal experiments, no change could be measured in the secretion rates of amylase and lipase.

[Quantitative mineral estimations in vertebral bodies by computer tomography (author's transl)]. / Quantitative Mineralsalzbestimmung im Wirbelkörper mittels Computertomographie.

The accuracy of computer tomographic bone density measurements in the axial skeleton was tested by comparing results obtained from the first lumbar body in abdominal phantoms. An almost linear relationship (r = 0.998) was found between increasing concentrations of a calcium chloride solution and CT absorption values. The sum of the CT values of sections through the vertebral body correlated well with their ash content (r = 0.90) as well as with the hydroxyl apatite values obtained by I125-absorption densitometry (r = 0.88). Reproducibility of CT measurements on the phantom was good (coefficient of variation = 1.2% in the spongiosa). Average CT values of separate measurements of the spongiosa and cortex could be correlated with the total spongiosa by a special programme (r = 0.95). In the practical application of this technique, possible sources of error must be considered, such as the effect of high energy polychromatic radiation, inhomogeneity of the object being investigated and difficulties in positioning the patients

Inhibition of choline incorporation into brain lipids in rats by urethane, a proposed mechanism of depression of the central nervous system.

Concentrations and specific radioactivities of choline, acetylcholine, phosphorylcholine, lipid choline, and sn-glycero-3-phosphorylcholine after i.v. injection of methyl-14C-choline were measured in the brain of untreated controls and of rats anesthesized with urethane. The specific activity was found to be decreased during deep anesthesia by 40% in acetylcholine, 20-30% in phosphorylcholine, 50-75% in lipid choline, and 30-40% in sn-glycero-3-phosphoryl-choline. No significant change was detected in the specific activity of choline. The brain concentration of acetylcholine was increased by 40%, the concentration of sn-glycero-3-phosphorylcholine, however, was diminished by 10% during anesthesia. No change was found in the concentration of the other choline containing compounds investigated. Measuring choline incorporation into 4 subcellular fractions of brain tissue specific activities were found to be decreased by the same percentage, although 2 fractions (nuclei and microsomes) were higher labelled than the 2 other fractions (crude mitochondria with synaptosomes and lysosomes). A correlation between the biochemical and the functional alterations is supported by the dose-effect relationships on both parameters. It is suggested that urethane reduces turnover of lipids and by that mechanism inhibits the exocytotic release of the transmitter from presynaptic nerve endings.

Mechanism of the enrichment of phosphatidylcholine in liver accompanying enzyme induction by phenobarbital.

The mechanism of the increase of phosphatidylcholine in liver, accompanying enzyme induction by phenobarbital, has been studied in rats. Using radioactively labeled precursors, the two main pathways of phosphatidylcholine biosynthesis--the CDP-choline pathway and the methylation of phosphatidylethanolamine--were analyzed after pretreatment with 4 doses of phenobarbital (80 mg/kg) on 3 consecutive days. After i.v. injection of choline [Me-3H], choline [Me-14C] or NaH2[32P]O4 the specific radioactivity (sp. act.) of phosphatidylcholine (dpm/nmol) was decreased by 60%, and after methionine [Me-3H] or ethanolamine [1.2-14C] by 40% compared to control rats. These changes are partly due to the increased concentration of phosphatidylcholine and phosphatidylethanolamine, causing the incorporated precursors to dilute, and partly to a secondary effect which leads to a reduction of the sp. act. of free choline in pretreated animals. The concentration of glycerylphosphorylcholine, one of the metabolites of phosphatidylcholine catabolism, was also diminished by almost 50%. From these results it may be concluded that the increase of phosphatidylcholine is due to a retardation of its breakdown rather than to an increase of its synthesis.

Synthesis of choline from ethanolamine in rat brain.

Specific radioactivities of choline, acetylcholine, phosphocholine, lecithin, lysolecithin, and glycerophosphorylcholine have been measured in brain, blood, liver, and muscle after the intravenous injection of three labeled precursors: choline, methyl-labeled methionine, and ethanolamine. In relation to the specific activity of free choline in blood there was significantly more radioactivity in the free choline of brain after administration of methyl-labeled methionine and labeled ethanolamine than after labeled choline. Since the choline moiety of lipids, which returns back to the choline pool, contained less radioactivity after methyl-labeled methionine and labeled ethanolamine than after labeled choline, it is the most likely interpretation of the finding that choline, in brain can be formed by methylation of free ethanolamine. Data from liver confirm that lecithin is formed in the liver by methylation of phosphatidylethanolamine. No indication was found for the synthesis of choline in muscle. Rates of transfer and transport of choline in brain have been calculated as nmol x g-1 x min-1 as follows: turnover rate of choline, 36.5; rate of synthesis of choline by methylation and net loss of choline into the bloodstream, 6.3; inflow from the blood 6.2; outflow into the blood, 12.5; transfer into lipids and vice versa, 20; transfer to acetylcholine and vice versa, 4.