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Biomedical subjects

H Woelk

Publications and source records attributed to H Woelk.

At least 19 recordsLinked to original sources
PubMed1979

Unusual features in a case diagnosed as subacute sclerosing panencephalitis (SSPE).

SSPE is characterised by progressive mental deterioration, myoclonic and similar motor disorders and final severe comatose states, increase of immunoglobuline G in the CSF, strongly elevated antibody titers to measles virus in serum and CSF and typical periodic K-complexes in the EEG. The disease appears commonly in childhood and has a fatal course. Cases with atypical signs have occasionally been reported. The case described in this paper shows a number of uncommon features: late onset, partial remission and stationary course, increased antibody titers to measles virus but relatively low in comparison to others, dissociation of cytoplasmic and nuclear fluorescent antibodies against SSPE brain tissue and an initial increase of antibodies against rubella virus. The patient was treated with isoprinosine. Improvement was observed before the start of this therapy and stabilized while treatment was being continued.

Adult↗
PubMed1979

Activity and subcellular distribution of phospholipase A1 from neuronal cell-enriched fractions of the rabbit cerebral cortex.

Glycerophosphatides, specifically labeled either in the 1 or in the 2 position, were used to measure the activity of neuronal phospholipase A1 and to investigate the subcellular distribution of the enzyme. The microsomes were found to possess the highest phospholipase activity, with a threefold increase as compared to the cell homogenate. A considerable enzymatic activity could still be observed in the plasma membranes isolated from the neuronal-enriched cell fraction. Microsomal phospholipase possessed the highest activity with phosphatidylcholine, whereas phosphatidylserine was cleaved at a much lower rate. The rate of release of labeled fatty acids from the substrates by the microsomal phospholipase decreased with increasing degree of unsaturation of the fatty acids at the 1 position. The presence of plasmalogens and of alkylacyl analogues in the incubation mixture caused an appreciable inhibition of the hydrolysis of the diacyl glycerophosphatides.

Animals↗
PubMed1979

Effects of piracetam on the incorporation of 32P into the phospholipids of neurons and glial cells isolated from rabbit cerebral cortex.

In the search for the biochemical basis of the action of Piracetam, the effects of this encephalotropic substance on the neuronal and glial phospholipid metabolism was investigated. Piracetam increases the incorporation of 32P into phosphatidylinositol and phosphatidyl choline of both glia and neuronal cell bodies (Figs. 1 and 2). When taking the important role of phosphatidylinositol in the processes of synaptic transmission and axonal conduction into consideration, the data obtained in the present work suggest that piracetam may stimulate excitatory neurons and may be involved in the process of synaptic transmission. The stimulatory effect of piracetam on the incorporation of 32P into phosphatidylinositol and phosphatidyl choline appears to be mediated by noerpinephrine or another neurotransmitter. Glial cells, isolated from the cerebral cortex of a rabbit, contained approximately one-third more phospholipids per uint protein than the neuronal cell bodies. The distribution and pattern of phospholipid relative to the total amount, was rather similar in both cell types. The incorporation of 32P into phosphatidylinositol and phosphatidyl choline was somewhat faster in neurons than in glial cells. Compared to glial cells the neuronal cell fraction had a higher phospholipid turnover.

Animals↗
PubMed1979

[Effect of piracetam on neuronal and synaptosomal phospholipase A2 activity].

In search of the biochemical mechanism of the action of 2-oxopyrrolidine-1-acetamide (piracetam, Normabrain, Nootrop) the influence of the encephalotropic substance on the hydrolysis of different glycerophosphatides by the neuronal and synaptosomal phospholipase A2 was investigated. Pure synaptosomes and neurons were prepared by a new method. The synaptosomal and neuronal phospholipase A2 plays an important role during the process of synaptic transmission. The administration of piracetam enhanced both the neuronal and synaptosomal phospholipase A2-activity by about 50%. The piracetam-induced stimulation of the enzyme activity was in the same order of magnitude for all substrates investigated. Thus piracetam stimulates the synaptic transmission. The stimulation of the phospholipase A2-activity by piracetam appears to be mediated by a neurotransmitter.

Animals↗
PubMed1978

Membrane-bound base-exchange reactions in animal tissues.

The calcium-stimulated incorporation of ethanolamine, L-serine and choline into rabbit synaptosomal phospholipids in vitro has been investigated. The synaptosomal membranes were prelabelled in vitro in their choline-, ethanolamine- or serine-phosphoglycerides by base-exchange and then chasing experiments were performed by displacing the lipid-bound base by ethanolamine, choline or L-serine labelled with a different isotope. The results indicate that membrane phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine are substrates for the exchange with all the three mentioned bases. A very small phospholipid pool (0.5-2% of the total available pool) is active in the calcium-dependent exchange between membrane phosphatidylcholine or phosphatidylethanolamine and free bases, whereas the pool of exchanging phosphatidylserine is sensibly larger (2-9%). In another series of experiments the effect of the base-exchange reaction upon the production of cyclic-AMP at the level of rat brain synaptic membranes has been examined. An exchange with ethanolamine produces a significant decrease of the NaF-stimulated production of the cyclic nucleotide, whereas it increases the noradrenaline-induced production. With some exceptions, the exchange with L-serine produces opposite effects. The possible physiological importance of phospholipid pool at the synaptosomal level is discussed.

Adenylyl Cyclases↗
PubMed1978

Enzymic studies on glial and neuronal cells during myelination.

The formation of ethanolamine plasmalogen from labelled 1-alkyl-2-acyl-sn-glycero-3-phosphorylethanolamine was studied in neurons and glial cells of the developing rat brain. It was found that the conversion of the ether to the enol-ether bond of the 1-alkyl moiety by the neuronal and glial desaturase system requires unsaturated fatty acids at the 2 position of the substrate. There is almost no difference between the activity of the neuronal and glial desaturase during the period of active myelination, whereas the neuronal cell fraction of the adult rats displays a threefold higher enzyme activity as compared to the glial cells. Evidence for the involvement of a microsomal electron transport system in the enzymic conversion of alkylacyl-glycero-3-phosphorylethanolamine to ethanolamine plasmalogen was obtained by using specific antibodies against NADH-cytochrome b5 reductase. Cytochrome b5 stimulated the biosynthesis of ethanolamine plasmalogen.

Animals↗
PubMed1978

The action of piracetam on the formation of ethanolamine-plasmalogen by neuronal microsomes of the developing rat brain.

In search of a common biochemical denominator of the action of the nootropic drug 2-oxo-pyrrolidine-1-acetamide (piracetam, Normabrain, Nootrop) the effects of the substance on the neuronal respiratory chain were investigated. The activity of the electron transport system of the respiratory chain was measured by the conversion of the ether to the enolether bond (plasmalogen) of ethanolamine containing glycerophosphatides. Piracetam enhances the formation of ethanolamine-plasmalogen from the corresponding ether lipid by neuronal microsomes and thus resembles the action of cytochrome b5. The addition of antibody against cytochrome b5 was able to inhibit the piracetam-dependent stimulation of the plasmalogen biosynthesis. Thus it appears that the stimulatory effect of piracetam on the formation of ethanolamine-plasmalogen is mediated by an increased synthesis or turnover of cytochrome b5.

Adenine Nucleotides↗
PubMed1977

Biosynthesis of rat brain phosphatidylethanolamines from intracerebrally injected ethanolamine.

[2-3H]Ethanolamine was injected intracerebrally into male rats and the brains of the animals immediately removed by particular procedures at regular intervals over the first 1200 sec. The incorporation of radioactivity into brain phosphorylethanolamine, cytidine-5'-diphosphate (CDP) ethanolamine and phosphatidylethanolamines was examined and quantitated. The nature of phosphatidylethanolamine molecular subspecies, which became labelled, was also investigated after isotope administration. Phosphorylethanolamine, CDP-ethanolamine and phosphatidylethanolamines were all labelled already 5 sec after the administration of labelled ethanolamine. The specific radioactivities of different phosphatidylethanolamine molecular subspecies varied according to the time elapsed from the injection to the sacrifice of the animals. This last result, together with the data on time course of labelling of ethanolamine phosphoglycerides and their precursors, provides indications that this base may be incorporated into lipids not only by net synthesis pathway, but also by base-exchange reaction.

Animals↗
PubMed1976

Relationships between base-exchange reaction and the microsomal phospholipid pool in the rat brain in vitro.

The calcium-stimulated incorporation of ethanolamine, choline and L-serine into rat brain microsomal phospholipids has been investigated. The membranes were prelabeled in vitro in their choline or serine phosphoglycerides by base-exchange and then chasing experiments were done by displacing the lipid-bound base by ethanolamine, choline, or L-serine labeled with a different isotope. The results indicate that membrane phosphatidylcholine is presumably a substrate for the exchange with all the three bases, whereas phosphatidylserine exchanges only with ethanolamine and L-serine but not with choline. A small phospholipid pool (3-7% of the total available pool) is active in the calcium-dependent exchange with choline, ethanolamine, and L-serine. When the microsomal membranes are prelabeled in vitro in their phosphatidylcholine moiety through the cytidine-dependent pathway and then chasing experiments are performed with the three nitrogenous bases, as above, the small phospholipid pool is hardly detectable. In view of these and other results (Gaiti et al., FEBS Letters 49:361 1975), it is suggested that at least two different pools of phosphatidylethanolamine, phosphatidylserine, and phosphatidylcholine might exist in rat brain microsomes.

Animals↗