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Khan AA, Allemailem KS, Almatroodi SA, Almatroudi A, Rahmani AH. Recent strategies towards the surface modification of liposomes: an innovative approach for different clinical applications. 3 Biotech 2020; 10:163. [PMID: 32206497 PMCID: PMC7062946 DOI: 10.1007/s13205-020-2144-3] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 02/16/2020] [Indexed: 01/02/2023] Open
Abstract
Liposomes are very useful biocompatible tools used in diverse scientific disciplines, employed for the vehiculation and delivery of lipophilic, ampiphilic or hydrophilic compounds. Liposomes have gained the importance as drug carriers, as the drugs alone have limited targets, higher toxicity and develop resistance when used in higher doses. Conventional liposomes suffer from several drawbacks like encapsulation inefficiencies and partially controlled particle size. The surface chemistry of liposome technology started from simple conventional vesicles to second generation liposomes by modulating their lipid composition and surface with different ligands. Introduction of polyethylene glycol to lipid anchor was the first innovative strategy which increased circulation time, delayed clearance and opsonin resistance. PEGylated liposomes have been found to possess higher drug loading capacity up to 90% or more and some drugs like CPX-1 encapsuled in such liposomes have increased the disease control up to 73% patients suffering from colorectal cancer. The surface of liposomes have been further liganded with small molecules, vitamins, carbohydrates, peptides, proteins, antibodies, aptamers and enzymes. These advanced liposomes exhibit greater solubility, higher stability, long-circulating time and specific drug targeting properties. The immense utility and demand of surface modified liposomes in different areas have led their way to the modern market. In addition to this, the multi-drug carrier approach of targeted liposomes is an innovative method to overcome drug resistance while treating ceratin tumors. Presently, several second-generation liposomal formulations of different anticancer drugs are at various stages of clinical trials. This review article summarizes briefly the preparation of liposomes, strategies of disease targeting and exclusively the surface modifications with different entities and their clinical applications especially as drug delivery system.
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Affiliation(s)
- Amjad Ali Khan
- Department of Basic Health Science, College of Applied Medical Sciences, Qassim University, P.O. Box 6699, Buraidah, 51452 Saudi Arabia
| | - Khaled S. Allemailem
- Department of Basic Health Science, College of Applied Medical Sciences, Qassim University, P.O. Box 6699, Buraidah, 51452 Saudi Arabia
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, P.O. Box 6699, Buraidah, 51452 Saudi Arabia
| | - Saleh A. Almatroodi
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, P.O. Box 6699, Buraidah, 51452 Saudi Arabia
| | - Ahmed Almatroudi
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, P.O. Box 6699, Buraidah, 51452 Saudi Arabia
| | - Arshad Husain Rahmani
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, P.O. Box 6699, Buraidah, 51452 Saudi Arabia
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2
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GABA Effects During Neuronal Differentiation of Stem Cells. Neurochem Res 2008; 33:1546-57. [DOI: 10.1007/s11064-008-9642-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 02/21/2008] [Indexed: 12/18/2022]
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3
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Plesner A, Hampe CS, Daniels TL, Hammerle LP, Lernmark A. Preservation of enzyme activity and antigenicity after mutagenesis of the membrane anchoring domain of GAD65. Autoimmunity 2002; 34:221-30. [PMID: 11905848 DOI: 10.3109/08916930109014691] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The smaller isoform of glutamic acid decarboxylase, GAD65, is an important autoantigen implicated in the pathogenesis of type 1 diabetes whereas the larger isoform, GAD67 appears to play no major role. The primary difference between the two isoforms resides in the N-terminal part of the molecule including the GAD65 membrane-anchoring domain. The aim of this study was to generate mutants of the membrane targeting domain spanning amino acids 24 to 31 of GAD65 to determine effects on enzyme activity and antibody recognition. Three GAD65 mutants were generated by substituting two, nine or eleven nucleotides coding for the membrane targeting with the corresponding bases of GAD67. SDS-PAGE and Western blotting wildtype (wt) and mutated GAD65 ascertained that they were of similar size and recognized GAD65-specific antibodies. No difference in enzymatic activity was found between the mutants and wt GAD65. GAD65 antibody positive sera from type 1 diabetes patients immunoprecipitated mutated GAD65 whether two, nine or eleven nucleotides were replaced. Mono-or polyclonal antibodies to the N-terminal region demonstrated that the mutated GAD65 with two or nine nucleotides replaced was immunoprecipitated markedly better than wt whereas no difference was detected using antibodies specific for the PLP-binding site in the middle part of GAD65 or the C-terminal region. Taken together, these data suggest that no major conformational changes have been introduced by mutating the membrane-anchoring domain of GAD65.
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Affiliation(s)
- A Plesner
- Department of Medicine, University of Washington, Seattle 98195-7710, USA.
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4
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Nathan B, Bao J, Hsu CC, Yarom M, Deupree DL, Lee YH, Tang XW, Kuo CY, Burghen GA, Wu JY. An integral membrane protein form of brain L-glutamate decarboxylase: purification, characterization and its relationship to insulin-dependent diabetes mellitus. Brain Res 1994; 642:297-302. [PMID: 8032892 DOI: 10.1016/0006-8993(94)90934-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A new and novel form of L-glutamate decarboxylase (GAD; EC 4.1.1.15) was purified from whole porcine brain to apparent homogeneity by a combination of column chromatographies on DE-52, ultragel AcA 34, hydroxylapatite and Sephadex G-200, and native gel electrophoresis. The purified GAD was established as an integral membrane protein based on hydrophobic interaction chromatography and membrane extraction studies. This membrane GAD (MGAD) has a native molecular weight of 120 +/- 5 kDa and is a homodimer of 60 +/- 2 kDa. Immunoprecipitation and immunoblotting tests using the sera from insulin-dependent diabetes mellitus (IDDM) patients revealed the presence of antibodies against this newly identified MGAD in IDDM. The role of MGAD in the pathogenesis of IDDM and related autoimmune disorders is also discussed.
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Affiliation(s)
- B Nathan
- Department of Physiology and Cell Biology, University of Kansas, Lawrence 66045
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Nathan B, Hsu C, Bao J, Wu R, Wu J. Purification and characterization of a novel form of brain L-glutamate decarboxylase. A Ca(2+)-dependent peripheral membrane protein. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37275-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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6
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Massieu L, Rivera A, Tapia R. Convulsions and inhibition of glutamate decarboxylase by pyridoxal phosphate-gamma-glutamyl hydrazone in the developing rat. Neurochem Res 1994; 19:183-7. [PMID: 8183428 DOI: 10.1007/bf00966814] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have previously shown that in the adult rat the inhibition of brain glutamate decarboxylase (GAD) activity by pyridoxal phosphate-gamma-glutamyl hydrazone (PLPGH) administration does not result in convulsions, whereas in the adult mouse intense convulsions invariably occur. In the present study we report that, surprisingly, immature rats from 2 to 20 days of age treated with PLPGH (80 mg/kg) showed generalized tonic-clonic convulsions, whereas no convulsions at all were present in 30 days-old or older rats. GAD activity, measured by enzymic determination of GABA formed in forebrain homogenates, was inhibited by about 60% at the time of convulsions in 15 days-old and younger rats, whereas the inhibition was between 40 and 50% in older animals. The addition of the coenzyme pyridoxal 5'-phosphate to the incubation medium completely reversed this inhibition. In all treated animals GABA levels were lower compared to controls. The results indicate that the susceptibility of GAD in vivo to a diminished cofactor concentration decreases with age. It seems possible that changes in the expression of enzyme forms are reflected in developmental variations in the susceptibility to seizures induced by vitamin B6 depletion, but alterations of other B6-dependent biochemical pathways cannot be discarded.
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Affiliation(s)
- L Massieu
- Departamento de Neurociencias, Universidad Nacional Autónoma de México, México, D.F
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7
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Nathan B, Bao J, Hsu CC, Aguilar P, Wu R, Yarom M, Kuo CY, Wu JY. A membrane form of brain L-glutamate decarboxylase: identification, isolation, and its relation to insulin-dependent mellitus. Proc Natl Acad Sci U S A 1994; 91:242-6. [PMID: 8278373 PMCID: PMC42923 DOI: 10.1073/pnas.91.1.242] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
A membrane form of L-glutamate decarboxylase (GAD) was identified and purified to apparent homogeneity from hog brain. The purified GAD was established as an integral membrane protein by phase-partitioning assay, charge-shift electrophoresis, and chromatography on a hydrophobic interaction column. This membrane GAD has a native molecular mass of 96 +/- 5 kDa and is a homodimer of 48 +/- 3-kDa subunits. Immunoprecipitation and immunoblotting tests revealed the presence of antibodies against this membrane GAD in sera from patients with insulin-dependent diabetes mellitus. Since this form of GAD appears to be an integral membrane protein and is presumed to have extracellular domains exposed, it seems reasonable to suggest that membrane GAD is more likely than soluble GAD to be involved in the pathogenesis of insulin-dependent diabetes and related autoimmune disorders such as stiff-man syndrome.
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Affiliation(s)
- B Nathan
- Department of Physiology and Cell Biology, University of Kansas, Lawrence 66045-2106
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Kugler P. Enzymes involved in glutamatergic and GABAergic neurotransmission. INTERNATIONAL REVIEW OF CYTOLOGY 1993; 147:285-336. [PMID: 7901176 DOI: 10.1016/s0074-7696(08)60771-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- P Kugler
- Department of Anatomy, University of Würzburg, Germany
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Balcar VJ, Zetzsche T, Wolff JR. Glutamate decarboxylase in developing rat neocortex: does it correlate with the differentiation of GABAergic neurons and synapses? Neurochem Res 1992; 17:253-60. [PMID: 1620269 DOI: 10.1007/bf00966667] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Postnatal development of glutamate decarboxylase was studied in the rat cerebral cortex. Two methods were used: estimation of the enzymatic activity of glutamate decarboxylase in homogenates of developing cortical tissue and visualization of structures containing glutamate decarboxylase-like immunoreactivity. Glutamate decarboxylase-like immunoreactivity appeared first in perikarya and dendrites and only later in axons and axon varicosities. The most rapid increase in the glutamate decarboxylase activity took place during the second postnatal week and this coincided with a rapid increase in the density of axon varicosities containing glutamate decarboxylase-like immunoreactivity but preceded the most rapid phase in the formation of GABAergic synapses by several days. However, there was a change in the characteristics of glutamate decarboxylase which correlated with GABA synaptogenesis: two fractions of glutamate decarboxylase with different sensitivities to the activating effects of Triton X-100 could be distinguished as from about the time when most of the GABAergic synapses are formed.
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Affiliation(s)
- V J Balcar
- Department of Anatomy, University of Sydney, Australia, N.S.W
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10
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Erlander MG, Tillakaratne NJ, Feldblum S, Patel N, Tobin AJ. Two genes encode distinct glutamate decarboxylases. Neuron 1991; 7:91-100. [PMID: 2069816 DOI: 10.1016/0896-6273(91)90077-d] [Citation(s) in RCA: 904] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
gamma-Aminobutyric acid (GABA) is the most widely distributed known inhibitory neurotransmitter in the vertebrate brain. GABA also serves regulatory and trophic roles in several other organs, including the pancreas. The brain contains two forms of the GABA synthetic enzyme glutamate decarboxylase (GAD), which differ in molecular size, amino acid sequence, antigenicity, cellular and subcellular location, and interaction with the GAD cofactor pyridoxal phosphate. These forms, GAD65 and GAD67, derive from two genes. The distinctive properties of the two GADs provide a substrate for understanding not only the multiple roles of GABA in the nervous system, but also the autoimmune response to GAD in insulin-dependent diabetes mellitus.
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Affiliation(s)
- M G Erlander
- Neuroscience Program, University of California Los Angeles 90024
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Erlander MG, Tobin AJ. The structural and functional heterogeneity of glutamic acid decarboxylase: a review. Neurochem Res 1991; 16:215-26. [PMID: 1780024 DOI: 10.1007/bf00966084] [Citation(s) in RCA: 340] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Studies of the GABA-synthetic enzyme glutamate decarboxylase (glutamic acid decarboxylase; GAD; E.C.4.1.1.15) began in 1951 with the work of Roberts and his colleagues. Since then, many investigators have demonstrated the structural and functional heterogeneity of brain GAD. At least part of this heterogeneity derives from the existence of two GAD genes.
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Affiliation(s)
- M G Erlander
- Neuroscience Program, University of California, Los Angeles 90024
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12
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Kaufman DL, Houser CR, Tobin AJ. Two forms of the gamma-aminobutyric acid synthetic enzyme glutamate decarboxylase have distinct intraneuronal distributions and cofactor interactions. J Neurochem 1991; 56:720-3. [PMID: 1988566 PMCID: PMC8194030 DOI: 10.1111/j.1471-4159.1991.tb08211.x] [Citation(s) in RCA: 623] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Glutamate decarboxylase (GAD) catalyzes the production of gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter. The mammalian brain contains two forms of GAD, with Mrs of 67,000 and 65,000 (GAD67 and GAD65). Using a new antiserum specific for GAD67 and a monoclonal antibody specific for GAD65, we show that the two forms of GAD differ in their intraneuronal distributions: GAD67 is widely distributed throughout the neuron, whereas GAD65 lies primarily in axon terminals. In brain extracts, almost all GAD67 is in an active holoenzyme form, saturated with its cofactor, pyridoxal phosphate. In contrast, only about half of GAD65 (which is found in synaptic terminals) exists as active holoenzyme. We suggest that the relative levels of apo-GAD65 and holo-GAD65 in synaptic terminals may couple GABA production to neuronal activity.
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Affiliation(s)
| | - Carolyn R. Houser
- Department of Anatomy and Cell Biology, University of California at Los Angeles,Brain Research Institute, University of California at Los Angeles,Veterans Administration Medical Center, West Los Angeles, Wadsworth Division, Los Angeles, California, U.S.A
| | - Allan J. Tobin
- Department of Biology, University of California at Los Angeles,Brain Research Institute, University of California at Los Angeles,Molecular Biology Institute, University of California at Los Angeles
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Toledo A, Rodriguez R, Sabriá J, Rodriguez J, Blanco I. Calcium effects on the solubilization of membrane-bound histidine decarboxylase in the rat brain. J Neurochem 1991; 56:380-4. [PMID: 1988545 DOI: 10.1111/j.1471-4159.1991.tb08162.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In a previous work we have shown that histidine decarboxylase (HD) activity is found in a soluble and a membrane-bound form. A major part (82%) of the membrane-bound HD activity in the crude mitochondrial fraction (P2) was present in the synaptic plasma membrane-containing subfraction. Physiological concentrations of Ca2+ had no direct effect on HD activity but caused a solubilization of approximately 50% of membrane-bound HD in the P2 fraction. Mg2+ had similar but lower effects (20% solubilization) than Ca2+. Incubation with depolarizing concentrations of K+ in the presence of 1 mM CaCl2 caused a significant (30%) solubilization of HD.
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Affiliation(s)
- A Toledo
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Autónoma de Barcelona, Spain
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14
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Affiliation(s)
- M Erecińska
- Department of Pharmacology, University of Pennsylvania, School of Medicine, Philadelphia 19104-6084
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15
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Hagel C, Fleissner A, Seifert R. A microassay for the determination of soluble and membrane-bound glutamate decarboxylase activity--influences of cations, lipid composition, and pyridoxal 5'-phosphate on the glutamate decarboxylase binding to liposomes. Anal Biochem 1989; 182:64-70. [PMID: 2574957 DOI: 10.1016/0003-2697(89)90719-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A radiochemical microassay for soluble and membrane-bound glutamate decarboxylase (GAD) is described. Up to 180 samples can be determined per day with a variation coefficient of 2%. The method detects newly synthesized gamma-amino-n-butyric acid in the picomole range and can easily be applied to other enzymes whose substrate and product differ by charge. In an aqueous homogenate of brain (1 + 10; w/v) about 15% of the total GAD activity are spun down by centrifugation (1 h, 100,000g) increasing to 35% of the total GAD activity in solutions with 8 mM calcium chloride or 100 mM potassium acetate. There is similar dependence on the cation concentration when GAD binds to phospholipid vesicles (liposomes) as well as dependence on lipid concentration and lipid composition. The coenzyme pyridoxal 5'-phosphate has no influence on GAD binding to liposomes.
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Affiliation(s)
- C Hagel
- Department of Neurochemistry, Psychiatric University Clinic, Hamburg, Federal Republic of Germany
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Toledo A, Sabriá J, Rodriguez R, Brandner R, Rodriguez J, Palacios JM, Blanco I. Properties and ontogenic development of membrane-bound histidine decarboxylase from rat brain. J Neurochem 1988; 51:1400-6. [PMID: 3171585 DOI: 10.1111/j.1471-4159.1988.tb01104.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Histidine decarboxylase (HD) activity was determined in high-speed fractions (100,000 g for 60 min) obtained from whole rat brain homogenates. Twenty-eight percent of the HD activity was associated with membranes, and the remaining was soluble. Several properties of the soluble and membrane-bound HD were compared. No significant differences in the values of Km for histidine and pyridoxal 5'-phosphate were observed. The solubilization of membrane-bound HD with Triton X-100 resulted in an increase of 60% over the nonsolubilized activity with no changes in the Km for substrate and cofactor. The proportion of free pyridoxal 5'-phosphate-independent activity was identical in both fractions. The soluble and membrane-bound forms of the enzyme differ slightly in their pH-activity profiles, although both enzymes showed an optimum pH near 6.5. The HD activities present in soluble and membrane fractions were determined at different postnatal ages. The soluble activity increased until day 90, whereas the membrane-bound activity became stabilized from day 20.
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Affiliation(s)
- A Toledo
- Departamento Bioquimica y Biologia Molecular, Facultad de Medicina, Universidad Autónoma de Barcelona, Spain
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Denner LA, Wei SC, Lin HS, Lin CT, Wu JY. Brain L-glutamate decarboxylase: purification and subunit structure. Proc Natl Acad Sci U S A 1987; 84:668-72. [PMID: 3468504 PMCID: PMC304276 DOI: 10.1073/pnas.84.3.668] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Glutamate decarboxylase (GDCase; L-glutamate-1-carboxy-lyase, EC 4.1.1.15) was purified from whole rat brain approximately equal to 1300-fold to apparent homogeneity with a specific activity of 2.4 units per mg of protein by a combination of column chromatographies on DEAE-cellulose, hydroxylapatite, and gel filtration, and preparative nondenaturing polyacrylamide gel electrophoresis. The purified preparation contained a single protein band that comigrated with GDCase activity in three diverse analyses: nondenaturing regular (5%) and gradient (3.6-25%) polyacrylamide gel electrophoresis and isoelectric focusing at pH 4-7. The native molecular mass was calculated to be 120 +/- 10 kDa from gradient polyacrylamide gel electrophoresis and 110 +/- 10 kDa from gel filtration. Under the treatment with NaDodSO4 and 2-mercaptoethanol, GDCase dissociated into two subunits of 40 +/- 2 and 80 +/- 4 kDa, as estimated from NaDodSO4 gel electrophoresis. However, only a 40-kDa subunit was detected when GDCase was treated with 4 M urea plus NaDodSO4 and 2-mercaptoethanol, suggesting that the 80-kDa subunit is the dimer of the 40-kDa subunit. In immunoblotting, polyclonal antibodies against GDCase reacted with both 40- and 80-kDa subunits, while monoclonal antibody reacted with only 80-kDa subunits. The isoelectric point of the native enzyme was 5.4. The Km for glutamate was 1.59 X 10(-3) M. In addition to L-glutamate, cysteine sulfinic acid was also decarboxylated at approximately equal to 10% of the rate of glutamate. The pH optimum was fairly broad, with a maximum at approximately equal to 7.3. The enzyme was strongly inhibited by carbonyl-trapping agents, sulfhydryl reagents, thiol compounds, and beta-methylene-DL-aspartate.
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Stelzer A, Laas R, Fleissner A. Subcellular distribution of glutamic acid decarboxylase in rat brain regions following electroconvulsive stimulation. J Neural Transm (Vienna) 1985; 62:99-106. [PMID: 4020383 DOI: 10.1007/bf01260419] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Electroconvulsive stimulation of rats evoked significant increases of glutamic acid decarboxylase (GAD) activity in the synaptosomal fractions of neocortex (including white matter) and hippocampal formation. The elevation of synaptosomal-bound GAD activity was not significant in cingulate cortex, striatum, caudal brainstem and thalamus. The electroconvulsive shocks had no effect on the GAD activity of the cytoplasmic fractions of any brain regions investigated. The highest physiological level of synaptosomal GAD activity was found in thalamus, followed (in decreasing order) by striatum, hippocampus, cingulate cortex, caudal brainstem and neocortex.
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Angel I, Fleissner A, Seifert R. Synaptic vesicles from hog brain—their isolation and the coupling between synthesis and uptake of γ-aminobutyrate by glutamate decarboxylase. Neurochem Int 1983; 5:697-712. [DOI: 10.1016/0197-0186(83)90095-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/1983] [Accepted: 03/30/1983] [Indexed: 11/16/2022]
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Itoh M, Ebadi M. The selective inhibition of hippocampal glutamic acid decarboxylase in zinc-induced epileptic seizures. Neurochem Res 1982; 7:1287-98. [PMID: 7155279 DOI: 10.1007/bf00965899] [Citation(s) in RCA: 68] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The intracerebroventricular administration of Zn2+ (0.3 mumol/10 microliters) causes epileptic seizures characterized by running fits, jumping, vocalization, fasiculation of facial muscles, myoclonic movements of the limbs and tonic-clonic convulsions. These episodes are blocked or reversed by gamma-aminobutyric acid (0.4 mumol/10 microliters). When assayed under conditions where pyridoxal phosphate was not added, the activity of glutamic acid decarboxylase decreased significantly in hippocampus from 18.9 to 15.3 and 9.7 mumols 14CO2 formed/gram proteins/20 min, 15 and 30 min following administration of Zn2+. The inhibition of glutamic acid decarboxylase by Zn2+ was selective occurring only in hippocampus and not in the hypothalamus, amygdala, caudate or thalamus. The inhibition of glutamic acid decarboxylase was not due to a reduction in the concentration of endogenous pyridoxal phosphate which remained unaltered in hippocampus following Zn2+ administration.
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Ebadi M, Itoh M, Bifano J, Wendt K, Earle A. The role of Zn2+ in pyridoxal phosphate mediated regulation of glutamic acid decarboxylase in brain. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1981; 13:1107-12. [PMID: 6271607 DOI: 10.1016/0020-711x(81)90174-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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