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M F Diebler

Publications and source records attributed to M F Diebler.

34 records · Page 2Linked to original sources
PubMed1988

Calcium-independent release of acetylcholine from electric organ synaptosomes and its changes by depolarization and cholinergic drugs.

Chemiluminescent detection was applied to measure the continuous spontaneous Ca2+-independent liberation of acetylcholine (ACh) from Torpedo electric organ synaptosomes. Differentiation between the release of ACh and choline was achieved by inhibiting cholinesterases with phospholine, and a way to quantify the continuous release was devised. The method permitted measurements during short time intervals from minute amounts of tissue and without an accumulation of ACh in the medium. Synaptosomes continuously liberated small amounts of ACh during incubations in the presence of 3 mM K+ and in the absence of Ca2+. The spontaneous liberation of ACh was similar both quantitatively and qualitatively at pH values of 8.6 and 7.8. It was unaltered by MgCl2 (10.4 mM), 2-(4-phenylpiperidino)cyclohexanol (10 microM), ouabain (104 microM), atropine (10 microM), and valinomycin (102 nM). Carbamoylcholine brought about a decrease, which could be partially reversed by atropine. The Ca2+-independent output of ACh was increased considerably when the concentration of K+ ions was raised (eightfold at 103 and 35-fold at 203 mM K+). Carbamoylcholine (104 microM) blocked the increase in ACh release produced by high K+; this effect of carbamoylcholine was not reversed by atropine (10 microM). When Ca2+ was added to synaptosomes depolarized by a high concentration of K+, the amount of ACh released during the first 1-3 min after the addition of Ca2+ was at least 20 times higher than in the absence of Ca2+, but the release returned rapidly to predepolarization values. Similarly high values of ACh release could be achieved by adding Ca2+ plus the ionophore A23187 and even higher values by adding Ca2+ plus gramicidin.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1985

Mg-ATPase and Torpedo cholinergic synaptic vesicles.

The reported presence of Mg-ATPase activity in cholinergic synaptic vesicles from the electric organ of Torpedo marmorata was reinvestigated in view of possible contamination of vesicles by other subcellular fractions. After dilution in concentrated sucrose, the vesicular fraction isolated on a sedimentation sucrose gradient was purified further on a flotation density gradient. It appears that this treatment allows separation of the vesicles according to their content. The two vesicular content markers, acetylcholine and ATP, are recovered as sharp coincident peaks at a density close to 0.48 M sucrose. Empty vesicles are identified in denser regions by the protein pattern on gel electrophoresis which is identical to the pattern obtained for filled vesicles. Refractionation of vesicles depleted of their acetylcholine content by valinomycin leads to an extreme picture, with a massive shift of the vesicles toward denser regions. We have then shown that a ouabain-insensitive Mg-ATPase is indeed associated with the vesicle membrane, but the activity is fully apparent only when vesicles are permeabilized either as the result of the fractionation procedure or after detergent treatment. The relative insensitivity of the Mg-ATPase associated with the synaptic vesicles to oligomycin, N,N'-dicyclohexylcarbodiimide, and azide indicates that this enzyme differs from the classic F1F0 mitochondrial enzyme. The most striking finding is the sensitivity to vanadate of the vesicular Mg-ATPase, which suggests the involvement of a phosphorylated intermediate. On the basis of both the difference in inhibitor sensitivity between untreated and detergent-treated vesicles and of the pronase experiments, the possibility that the enzyme has an inward orientation is discussed.

Adenosine Triphosphatases↗
PubMed1984

Histochemical changes of the developing human cerebral neocortex. Studies on two enzymes of energy metabolism in three cortical areas.

Developmental changes of two mitochondrial enzymes, succinate- and menadione-dependent alpha-glycerophosphate dehydrogenases (SDH, M alpha GPDH) have been studied by histochemical techniques in early autopsy material in the following areas of human neocortex: area 4 (motor cortex), area 17 (visual cortex) and area 40 (associative cortex). Each area studied revealed a special enzymatic architecture. SDH - a marker of oxidative activity - develops for several years after birth and in some areas (4 and 40) reaches its adult pattern only after 11 years. Considerable modifications occur during development in the relative activities of the different cortical layers. SDH activity initially appears in layers which send projections to subcortical relays or receive specific thalamocortical afferents. Layers which receive cortico-cortical projections mature later on. In contrast to SDH activity that of M alpha GPDH is elevated already before birth, increases until one month of age and decreases afterwards. This enzyme present in neuroblasts disappears from mature cortical neurons, except from those of the VIth layer. The distribution of this enzyme in cortical layers of the child is opposite to that of SDH. The developmental evolution of these two enzymes has been confirmed by biochemical assays.

Adult↗
PubMed1982

Acetylcholine release from isolated synaptic vesicles related to ionic permeability changes: continuous detection with a chemiluminescent method.

The effect of ionic permeability changes on acetylcholine (ACh) release from isolated cholinergic synaptic vesicles of Torpedo was studied using a chemiluminescent method for continuous ACh detection. Vesicles rendered freely permeable to potassium by valinomycin lost most of their ACh content in K+ media, if the accompanying anion was permeant; it thus appeared that ACh leakage occurred as the result of internal osmotic changes. Upon addition of ionophores that catalyse monovalent cation/H+ exchange (gramicidin D or a mixture of valinomycin plus protonophore FCCP), a rapid but transient ACh release was observed. Surprisingly, nigericin which also catalyses K+/H+ exchange, had no effect on ACh release. The divalent cation ionophore A23187 promoted ACh release only when calcium (and not magnesium) was introduced into the external medium in a millimolar concentration range. As the simultaneous addition of the protonophore FCCP and A23187 decreased this calcium-dependent ACh leakage, a releasing effect of A23187 through Ca2+/H+ exchange is suspected. The present results emphasise the role of internal protons for ACh retention inside synaptic vesicles.

Acetylcholine↗
PubMed1981

Thermal inactivation of acetyl-CoA synthetase in the electric organ of Torpedo marmorata.

Using thermal inactivation, further characterization studies on acetyl-CoA synthetase found in isolated nerve endings and in mitochondria obtained from the electric organ of Torpedo marmorata were made. They confirm different properties of the two enzymatic forms. Moreover, the acetyl-CoA synthetase activity found in the cytosol of disrupted synaptosomes exhibits a homogeneous thermic inactivation curve which corresponds to a single enzymatic form. It has the same localization as choline acetyltransferase.

Acetate-CoA Ligase↗
PubMed1981

Acetylcholine incorporation by cholinergic synaptic vesicles from Torpedo marmorata.

The ability of cholinergic vesicles to incorporate acetylcholine (ACh) was studied using highly purified synaptic vesicles from Torpedo electric organ. Depleted vesicles were capable of rapidly taking up exogenous ACh. Evidence that this represented true incorporation was that labelled ACh comigrated with vesicular ATP on gel filtration and that vesicle-associated ACh was protected against enzymatic hydrolysis and was releasable under hypoosmotic conditions. The total amount of ACh incorporated depended on the ACh concentration up to 100 mM. A sudden fall in the external ACh concentration did not cause leakage of the ACh incorporated in vitro. Preliminary results indicated that retention of ACh inside the vesicle was pH-dependent. Choline was also taken up by vesicles, but the time pattern strongly suggested that it was not being retained. The magnitude of ach incorporation was estimated with respect to the intravesicular space.

Acetylcholine↗
PubMed1979

Subcellular localization and ionic properties of acetyl-coenzyme A synthetase in the electric organ of Torpedo marmorata.

Acetyl-CoA synthetase activity was shown to be present in pure cholinergic synaptosomes from electric organ of Torpedo marmorata. After osmotic disruption of synaptosomes a substantial part of the activity was recovered in the soluble fraction. The effects of varying pH and increasing K+ concentrations on the synaptosomal enzyme activity were shown to differ from those observed with the mitochondrial enzyme. Whereas this latter enzyme showed optimal activity above pH 8.5, and a maximal activation in the presence of 120 mM-K+, the synaptosomal enzyme exhibited an optimal activity at pH 7.9 and a moderate K+ stimulatory effect with an optimal concentration of 30 mM.

Acetate-CoA Ligase↗
PubMed1977

Biosynthesis of acetyl-coenzyme A in the electric organ of Torpedo marmorata in relation to acetylcholine metabolism.

Formation of acetyl-CoA through acetyl-CoA synthetase (forward reaction) and through choline acyltransferase (backward reaction) was investigated in tissue extract from the electric organ of Torpedo marmorata. When the tissue extract was submitted to gel filtration on Sephadex G-25, the formation of acetyl-CoA by acetyl-CoA synthetase appeared fully dependent on ATP and CoA and partially dependent on acetate (an endogenous supply of acetate is discussed). Choline acetyltransferase was a potent source of acetyl-CoA, only requiring acetylcholine and CoA, and was much more efficient than acetyl-CoA synthetase for concentrations of acetylcholine likely to be present in nerve endings.

Acetate-CoA Ligase↗
PubMed1977

[Histochemical, quantitative and ultrastructural maturation of human fetal muscle].

Histochemical studies of muscle specimens from human fetuses showed: (a) a uniform fiber type population having the properties of Type IIC fibres up to 19 weeks of development; (b) a progressive appearance of Type I fibres after that age; (c) a decrease in number of Type IIC fibres during the last 3 months of pregnancy, accompanied by the appearance of Type IIB and Type IIA fibres; (d) the presence after the myotube stage of fibers with a light peripheral halo in sections stained for mitochondrial dehydrogenases. Electron-microscopic examination of the muscle fibres confirmed the existence of a peripheral halo devoid of myofibrils and mitochondria and showed: (a) scarcity of myofibrils in comparison with mature muscle fibres and (b) irregularity in shape of the myofibrils. In addition, quantitative studies demonstrated an important variation of the fibre diameters up to 21 weeks and the increase of the mean diameter after this age. It is suggested that the persistence after birth of some features of immaturity identical to those described in this work may be considered as a pathological finding.

Adenosine Triphosphatases↗
PubMed1975

Vascular and neuroglial changes in experimental herpes simplex encephalitis enzyme histochemical study.

An enzyme histochemical study of experimental herpes simplex encephalitis of the mouse has revealed a decrease in the number of capillaries displaying alkaline phosphatase activity. Glial cells showed increased Inosine 5 diphosphatase and ATPase activity. These enzyme histochemical changes were distributed throughout the nervous parenchyma while the lesions, seen by light microscopy, are localized to well defined areas. Mice inoculated with a pure culture of irradiated HSV failed to show the above mentioned modifications.

Adenosine Triphosphatases↗
PubMedDate not supplied

The effects of apolipoprotein E deficiency on brain cholinergic neurons.

Previous studies utilizing apolipoprotein E (apoE)-deficient mice revealed distinct decreases in the levels of cholinergic synaptic markers of projecting basal forebrain cholinergic neurons and no such alterations in other brain cholinergic systems. In order to investigate the mechanisms underlying these neuron-specific cholinergic effects, primary neuronal cultures from apoE-deficient and control mice were prepared and characterized. These include basal forebrain cultures, which are enriched in projecting cholinergic neurons, and cortical cultures, which contain cholinergic interneurons. The levels of cholinergic nerve terminals in these cultures were assessed by ligand binding measurements of the levels of the vesicular acetylcholine transporter (VAChT). This revealed that basal forebrain cultures of apoE-deficient mice contain markedly lower VAChT levels (approximately 50%) than do control cultures, but that VAChT levels of the corresponding cortical cultures of the apoE-deficient and control mice were the same. Time course studies revealed that VAChT levels of the basal forebrain cultures increased with culture age, but that the relative reduction in VAChT levels of the apoE-deficient cholinergic neurons was unaltered and was the same for freshly prepared and for 96 h old cultures. These in vitro observations are in accordance with the in vivo findings and suggest that projecting basal forebrain cholinergic neurons, but not cholinergic interneurons, are markedly dependent on apoE and that similar mechanisms mediate the in vivo and in vitro effects of apoE deficiency on cholinergic function.

Acetylcholine↗
PubMedDate not supplied

Influence of retinoic acid and of cyclic AMP on the expression of choline acetyltransferase and of vesicular acetylcholine transporter in NG108-15 cells.

Treatment of the cholinergic cell line NG108-15 with retinoic acid or cAMP results in an increase of choline acetyltransferase activity (ChAT) whereas none of these agents influences the amount of the vesicular acetylcholine transporter (VAChT) as judged from vesamicol binding and immunoblot studies. We suggest that immaturity of posttranslational events controlling the expression of VAChT protein is responsible for the apparent absence of coregulation of ChAT and VAChT protein expression.

Animals↗
PubMedDate not supplied

Cortical organization of the postero-medial barrel-subfield in mice and its reorganization after destruction of vibrissal follicles after birth.

The postero-medial barrel-subfield (PMBSF) of the SI cortex of normal adult mice contains clusters of cells called "barrels". Each barrel histochemically shows increased activity of succinate, lactate, and glucose-6-phosphate dehydrogenase and also GABA-T activity. Some neuronal perikarya in the barrel walls show GABA-T activity. Mitochondrial alpha-GPDH and AChE show equal activities in the hollows and in the walls of the barrels. On this cortical vibrissa field, the contralateral and ipsilateral vibrissae project somatotopically in a way which coincides with the barrels. The mystacial vibrissae and the common fur of the muzzle project to different loci. The cortical surface area for the normal fur is 0.025 mm2, whereas the cortical vibrissal area is 1.0 mm2. In mice with lesioned whisker pads the succinate-dehydrogenase activity of the IVth layer in the vibrissal area becomes a continuous sheet similar to the adjacent IVth layer, the thickness of the cortex is relatively preserved, and the total enzyme activities, biochemically assayed, are unchanged. These features can be explained by a functional substitution. In mice with whisker pads lesioned since birth, the vibrissal area can still be identified by the projections from ipsilateral vibrissae (undamaged side). This vibrissal area, and this alone, is found to be invaded by projections from the contralateral common fur of the muzzle. Experimental data suggest that the compensatory process may result from an invasion of the vibrissal area by a new set of ascending fibers, and not merely from axonal sprouting either at the periphery or at the cortical level.

4-Aminobutyrate Transaminase↗