scholarly journals The biosynthesis of gangliosides. The incorporation of galactose, N-acetylgalactosamine and N-acetylneuraminic acid into endogenous acceptors of subcellular particles from rat brain in vitro

1971 ◽  
Vol 121 (3) ◽  
pp. 483-493 ◽  
Author(s):  
A. Arce ◽  
H. J. Maccioni ◽  
R. Caputto
Keyword(s):  
Rat Brain ◽  
Acetylneuraminic Acid

Gangliosides bound to subcellular particles from rat brain were labelled by incubation of the particles (i) with CMP-N[3H]-acetylneuraminic acid and (ii) simultaneously, with CMP-N[3H]-acetylneuraminic acid and UDP-N-acetyl-[14C1]galactosamine or with CMP-N[3H]-acetylneuraminic acid and UDP-[U-14C]-galactose. Analysis of the labelled gangliosides showed that in (i), (a) the labelling was mostly in the neuraminidase-labile sialyl groups, (b) rigid relationships exist between the enzymes and the sialyl acceptors; the enzymes are not free to interact with all the specific substrates present in the preparation and (c) the precursor of the trisialoganglioside was the major disialoganglioside with a sialyl 2→8 sialyl group. In (ii), (a) precursor–product relationships between the main pools of each ganglioside apparently do not exist, (b) for the labelling of Tay–Sachs ganglioside the amount formed from hematoside was at least 2.5 times that from aminoglycolipid and (c) the major monosialoganglioside was the precursor for the major disialoganglioside with a sialyl 2→8 sialyl group.

scholarly journals Rat brain microsomal gangliosides. Accessibility to a neuraminidase preparation and the possible existence of different pools in relation to their biosynthesis

1974 ◽  
Vol 138 (2) ◽  
pp. 291-298 ◽  
Author(s):  
H. J. F. Maccioni ◽  
A. Arce ◽  
C. Landa ◽  
R. Caputto
Keyword(s):  
Rat Brain ◽  
Chemical Structure ◽  
Proper Position ◽  
Neuraminidase Treatment ◽  
Acetylneuraminic Acid ◽  
Microsomal Membranes ◽  
Labelling Experiment ◽  
Labile N ◽  
The Right

1. Treatment of rat brain microsomal membranes with a neuraminidase preparation from Clostridium perfringens resulted in an almost complete conversion of polysialogangliosides into monosialogangliosides. 2. Neuraminidase treatment of the membranes did not increase the incorporation of N-[3H]acetylneuraminic acid from CMP-N-[3H]acetylneuraminic acid into the gangliosidic fraction, indicating that a monosialoganglioside is an acceptor of N-acetylneuraminic acid in these membranes only if, in addition to having the right chemical structure, it is in a proper position, probably in relation to the endogenous sialyltransferases. 3. These experiments also indicated that no independent turnover of the neuraminidase-labile N-acetylneuraminyl groups of gangliosides occurred in vitro. 4. N-[3H]Acetylneuraminic acid from endogenous polysialogangliosides labelled in vitro was released by neuraminidase at a slower rate than N-acetylneuraminic acid from unlabelled gangliosides of the same membranes. From this it was concluded that recently synthesized polysialogangliosides (completed in vitro) are in the membranes in a position less accessible to neuraminidase than are those synthesized earlier which were present in the membranes at the start of the labelling experiment.

scholarly journals The biosynthesis of brain gangliosides. Ganglioside-glycosylating activity in rat brain neuronal perikarya fraction

1978 ◽  
Vol 174 (3) ◽  
pp. 673-680 ◽  
Author(s):  
H J F Maccioni ◽  
S S Defilpo ◽  
C A Landa ◽  
R Caputto
Keyword(s):  
Rat Brain ◽  
Time Course ◽  
Brain Homogenate ◽  
Acetylneuraminic Acid ◽  
Synaptosomal Fraction ◽  
Old Rats ◽  
Brain Gangliosides

Rat brain homogenate and the synaptosmal and neuronal perikarya fractions from 17-day-old rats were compared for their activities in sialosylating endogenous gangliosides and transferring N-acetylneuraminic acid and galactose to several glycolipids in vitro. The sialosylation of endogenous gangliosides and the activities of sialosyltransferases acting either on lactosylceramide or haematoside as acceptors, as well as galactosyltransferase acting on Tay-Sachs ganglioside as acceptor, were between 3-and 12-fold higher in the neuronal perikarya fraction than in whole homgenate on a protein or ganglioside basis. The activities found in the synaptosomal fraction were negligible. No evidence was found to indicate that the low activities in this fraction were due to the presence of inhibitors of the transfer activities or to inacessibility of the substrates to their respective enzymes. These findings, and the time course of labelling of gangliosides of the neuronal perikarya and synaptosomes from rats that received an injection of N-[3H]acetylmannosamine, indicate that the main cellular site of glycosylation of neuronal gangliosides is in the neuronal perikarya.

scholarly journals High Glycogen Levels in Brains of Rats with Minimal Environmental Stimuli: Implications for Metabolic Contributions of Working Astrocytes

2002 ◽  
Vol 22 (12) ◽  
pp. 1476-1489 ◽  
Author(s):  
Nancy F. Cruz ◽  
Gerald A. Dienel
Keyword(s):  
Rat Brain ◽  
Sensory Stimulation ◽  
Enzyme Inactivation ◽  
Biologically Active ◽  
Metabolic Labeling ◽  
Tissue Sampling ◽  
Normal Rat ◽  
Sampling Procedures ◽  
Very High

The concentration of glycogen, the major brain energy reserve localized mainly in astrocytes, is generally reported as about 2 or 3 μmol/g, but sometimes as high as 3.9 to 8 μmol/g, in normal rat brain. The authors found high but very different glycogen levels in two recent studies in which glycogen was determined by the routine amyloglucosidase procedure in 0.03N HCl digests either of frozen powders (4.8 to 6 μmol/g) or of ethanol-insoluble fractions (8 to 12 μmol/g). To evaluate the basis for these discrepant results, glycogen was assayed in parallel extracts of the same samples. Glycogen levels in ethanol extracts were twice those in 0.03N HCl digests, suggesting incomplete enzyme inactivation even with very careful thawing. The very high glycogen levels were biologically active and responsive to physiologic and pharmacological challenge. Glycogen levels fell after brief sensory stimulation, and metabolic labeling indicated its turnover under resting conditions. About 95% of the glycogen was degraded under in vitro ischemic conditions, and its “carbon equivalents” recovered mainly as glc, glc-P, and lactate. Resting glycogen stores were reduced by about 50% by chronic inhibition of nitric oxide synthase. Because neurotransmitters are known to stimulate glycogenolysis, stress or sensory activation due to animal handling and tissue-sampling procedures may stimulate glycogenolysis during an experiment, and glycogen lability during tissue sampling and extraction can further reduce glycogen levels. The very high glycogen levels in normal rat brain suggest an unrecognized role for astrocytic energy metabolism during brain activation.

In vitro interaction of ACTH with rat brain muscarinic receptors

Peptides ◽  
1986 ◽  
Vol 7 (3) ◽  
pp. 425-429 ◽  
Author(s):  
Jeroen A.D.M. Tonnaer ◽  
Marianna Van Vugt ◽  
Joop S. De Graaf
Keyword(s):  
Rat Brain ◽  
Muscarinic Receptors ◽  
In Vitro Interaction

In vitro screen of inhibitors of rat brain serotonin synthesis

1969 ◽  
Vol 47 (5) ◽  
pp. 501-506 ◽  
Author(s):  
E. G. McGeer ◽  
D. A. V. Peters
Keyword(s):  
Rat Brain ◽  
Tryptophan Hydroxylase ◽  
Inhibitory Effect ◽  
Complexing Agents ◽  
Serotonin Synthesis ◽  
Structural Requirements ◽  
Class A ◽  
Numerous Data ◽  
Comparison Of The Results

Over 700 compounds were screened at 10−4 M concentration as inhibitors of the conversion of L-tryptophan-14C to serotonin-14C in crude rat brain homogenates. Most of the compounds had little or no inhibitory effect. Those with strong inhibitory properties were tested as inhibitors of 5-hydroxytryptophan decarboxylase and, if active on the decarboxylase, were assayed as tryptophan hydroxylase inhibitors. Except for a few oxidizing and complexing agents and for some substituted p-phenylenediamines, the compounds found to inhibit tryptophan hydroxylase by >50% belonged to the three types of inhibitors already known, i.e. catechols, phenylalanine and ring-substituted phenylalanines, and 6-substituted tryptophans. The numerous data in this screen make possible some comments as to the structural requirements for activity within each class. A comparison of the results on tryptophan hydroxylase with data on tyrosine hydroxylase inhibition in similar homogenates makes it clear that two separate, if somewhat similar, enzymes are involved.

scholarly journals Phosphorylation-dependent interaction of the synaptic vesicle proteins cysteine string protein and synaptotagmin I

2002 ◽  
Vol 364 (2) ◽  
pp. 343-347 ◽  
Author(s):  
Gareth J.O. EVANS ◽  
Alan MORGAN
Keyword(s):  
Rat Brain ◽  
Direct Interaction ◽  
Secretory Vesicle ◽  
Brain Membrane ◽  
Synaptotagmin I ◽  
Phosphorylated Form ◽  
Order Of Magnitude ◽  
And Function

The secretory vesicle cysteine string proteins (CSPs) are members of the DnaJ family of chaperones, and function at late stages of Ca2+-regulated exocytosis by an unknown mechanism. To determine novel binding partners of CSPs, we employed a pull-down strategy from purified rat brain membrane or cytosolic proteins using recombinant hexahistidine-tagged (His6-)CSP. Western blotting of the CSP-binding proteins identified synaptotagmin I to be a putative binding partner. Furthermore, pull-down assays using cAMP-dependent protein kinase (PKA)-phosphorylated CSP recovered significantly less synaptotagmin. Complexes containing CSP and synaptotagmin were immunoprecipitated from rat brain membranes, further suggesting that these proteins interact in vivo. Binding assays in vitro using recombinant proteins confirmed a direct interaction between the two proteins and demonstrated that the PKA-phosphorylated form of CSP binds synaptotagmin with approximately an order of magnitude lower affinity than the non-phosphorylated form. Genetic studies have implicated each of these proteins in the Ca2+-dependency of exocytosis and, since CSP does not bind Ca2+, this novel interaction might explain the Ca2+-dependent actions of CSP.

Effects of anesthetics on sodium uptake into rat brain cortex in vitro

1972 ◽  
Vol 21 (12) ◽  
pp. 1763-1773 ◽  
Author(s):  
R. Shankaran ◽  
J.H. Quastel
Keyword(s):  
Rat Brain ◽  
Brain Cortex ◽  
Sodium Uptake ◽  
Rat Brain Cortex
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