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Botulinum toxins: Pharmacology, immunology, and current developments
Published in Anthony V. Benedetto, Botulinum Toxins in Clinical Aesthetic Practice, 2017
Within the BoNT-A molecule, antibodies directed against certain peptides within amino acid residues 449–1296 of the heavy chain are neutralizing.152 Nearly all of the regions overlap or coincide with the regions on the protein that bind to synaptosomes in vitro.152 Similar results have been found for BoNT-B.153 The pattern of antibody recognition varies among patients with neutralizing antibodies, such that not all patients develop antibodies to the same portion of the BoNT molecule,152 underscoring the potential role of individual genetic factors in neutralizing antibody development.154
Glutamine
Published in Elling Kvamme, Glutamine and Glutamate in Mammals, 1988
J. Tyson Tildón, H. Ronald Zielke
The brain is heterogeneous and this complexity gives rise to metabolic compartmentation.74,80,81 Therefore, it is not unreasonable to conclude that one or more of these compartments may use glutamine as an energy source. Yu et al.23 determined the metabolic fate of glutamate in primary astrocytes and concluded that this amino acid can substitute for glucose as a metabolic substrate for astrocytes. Since glutaminase is present in these cells,21,82it seems reasonable that after its conversion to glutamate, glutamine could be oxidized via the TCA cycle in astrocytes. Similar results were obtained using GABAergic preparations of cerebral cortical neurons in primary culture even though a small portion of the glutamine was converted to GABA.75 Bradford et al.10 have also shown that glutamine can be the major substrate for isolated synaptosomes. Other workers22,25 provide additional evidence that glutamine can be metabolized via a variety of routes. The results have implications which must be considered in the overall homeostasis of the brain. In addition to its role as a major precursor for neurotransmitters such as glutamate and GABA,83 glutamine has the potential to be utilized as an energy source in this tissue. Although absolute proof is still required, the evidence strongly supports this conclusion.
Uptake and Release of Glutamate and Glutamine in Neurons and Astrocytes in Primary Cultures
Published in Elling Kvamme, Glutamine and Glutamate in Mammals, 1988
Arne Schousboe, Jørgen Drejer, Leif Hertz
Due to the dual role of glutamate as a neurotransmitter and as an intermediary metabolite, it is of importance to gain knowledge of the dynamic interplay between neurons and astrocytes concerning fluxes of this amino acid in and out of the cells. Since glutamine on one hand is a glutamate metabolite and on the other may serve as an important precursor for glutamate (see Chapter 17), it is equally relevant to discuss uptake and release processes for this amino acid in the different cells types. Such information has been obtained using different kinds of cellular and subcellular (e.g., synaptosome) preparations. A preparation for which detailed information is available is primary cultures of neurons and astrocytes, i.e., cultures obtained directly from the living animals, often at an immature state.1-2 Such cultures constitute reliable models for their in vivo counterparts and the transport studies can be performed in cells that are undamaged by any separation procedure.1-4 For this reason, the present review will be restricted to dealing with transport processes in primary cultures of neurons and astrocytes. Cell lines will not be included because of the risk of quantitative alterations in transport phenomena in these transformed cells.1-3 Initially, a brief description of the cultured cells will be given (Section II).
The neurosciences at the Max Planck Institute for Biophysical Chemistry in Göttingen
Published in Journal of the History of the Neurosciences, 2023
From 1959, Victor Whittaker carried out important and ground-breaking work on the function of the synaptic vesicles and on the role of acetylcholine as a neurotransmitter (Zimmermann and Fonnum 2016). Two technical innovations made this success possible: the availability of adequate centrifuges and introduction of electron microscopy (Zimmermann 2018). Whittaker managed to fractionate the brain tissue of mammals and to enrich different elements through centrifugation (Whittaker 1959). One of these fractions contained large quantities of organelles filled with synaptic vesicles. Under the electron microscope, it was shown that these were pinched off nerve terminals, and Whittaker named them synaptosomes (Gray and Whittaker 1962). The team was able to enrich vesicles from synaptosomes and to find that the neurotransmitter acetylcholine is stored in the vesicles.
Inhibition of protein phosphatase-1 and -2A by ellagitannins: structure-inhibitory potency relationships and influences on cellular systems
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2019
Zoltán Kónya, Bálint Bécsi, Andrea Kiss, Dániel Horváth, Mária Raics, Katalin E. Kövér, Beáta Lontay, Ferenc Erdődi
Preparation of synaptosomes from murine brain cortex was carried out as described previously24. Functional synaptosomes were kept in Krebs buffer (118 mM NaCl, 5 mM KCl, 25 mM NaHCO3, 1 mM MgCl2, 10 mM d-glucose, pH 7.4). After preparation, synaptosomes were treated with either tellimagrandin I or mahtabin A in 1, 10 or 100 µM final concentrations, or with 10 µM tautomycetin (TMC) for 45 min at 30 °C. After the treatments synaptosomes were applied for exocytosis assay or were lysed and the protein lysates were subjected to Western blot. For exocytosis assay an already established protocol25 was used. FM 2–10 water-soluble styryl dye was incorporated first into the outer leaflet of synaptosome membrane, then into the synaptosomes. Exocytosis was induced by addition of 30 mM KCl to the synaptosomes. The fluorescent intensity of FM 2–10 styryl dye negatively correlated with the extent of synatposomal exocytosis and was measured by Fluoroskan FL (excitation: 488 nm, emission: 540 nm). Western blot of synaptosome proteins was carried out as described previously24,25.
Chronic exposure to multi-metals on testicular toxicity in rats
Published in Toxicology Mechanisms and Methods, 2021
Amit Gupta, Anoop Kumar, Saba Naqvi, Swaran J. S. Flora
The testis synaptosomes were prepared by the method described by Gray and Whittaker (1962). The free intracellular calcium level was determined by Meder et al. 1997 with slight modifications using fluorescent calcium indicator dye Fura-2 AM (1(2-(5-carboxyoxazol-2-yl)-6-aminobenzofuran-5-oxy)-2-(2′-amino-5′-methylphenoxy)ethane N,N,N’,N’-tetraacetic acid pentaacetoxy methyl ester). The fluorescence (F) was taken at 340-380/510nm. Further, the calibration was done by lysing testis synaptosomes with Triton X-100 to obtain Fmax and 7.5mM EGTA for Fmin. The free intracellular calcium level was determined as follows- d for Ca2+ Fura-2 complex is 225nM.