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G M Anlezark

Publications and source records attributed to G M Anlezark.

11 recordsLinked to original sources
PubMed1992

The bioactivation of 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954)--I. Purification and properties of a nitroreductase enzyme from Escherichia coli--a potential enzyme for antibody-directed enzyme prodrug therapy (ADEPT).

A nitroreductase enzyme has been isolated from Escherichia coli B. This enzyme is an FMN-containing flavoprotein with a molecular mass of 24 kDa and requires either NADH or NADPH as a cofactor. Partial protein sequence analysis showed extensive homology with the "classical nitroreductase" of Salmonella typhimurium and a nitroreductase induced in Enterobacter cloacae. In common with the Salmonella enzyme, the E. coli B enzyme is capable of reducing nitrofurazone. The E. coli nitroreductase is also capable of reducing the anti-tumour agent CB1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide], a property shared with the mammalian enzyme DT diaphorase [NAD(P)H dehydrogenase (quinone)] as isolated from Walker cells. The reduction of CB1954 by the E. coli enzyme results in the generation of cytotoxic species. Both enzymes also share the properties of being able to reduce quinones and are both inhibited by dicoumarol. The nitroreductase is a more active enzyme against CB1954 (kcat = 360 min-1) than Walker DT diaphorase (kcat = 4 min-1) and also has a lower Km for NADH (6 vs 75 microM).

Amino Acid Sequence↗
PubMed1992

The bioactivation of 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954)--II. A comparison of an Escherichia coli nitroreductase and Walker DT diaphorase.

A nitroreductase enzyme that has been isolated from Escherichia coli B is capable of bioactivating CB1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide] to a cytotoxic agent, a property shared with the mammalian enzyme Walker DT diaphorase [NAD(P)H dehydrogenase (quinone), EC 1.6.99.2] as isolated from Walker cells. In contrast to Walker DT diaphorase, which can only reduce the 4-nitro group of CB1954, the E. coli nitroreductase can reduce either (but not both) nitro groups of CB1954 to the corresponding hydroxylamino species. The two hydroxylamino species are formed in equal proportions and at the same rates. CB1954 is reduced much more rapidly by the E. coli nitroreductase than by Walker DT diaphorase. If the reduction of CB1954 was carried out in the presence of V79 cells (which are insensitive to CB1954) a large cytotoxic effect was evident. This cytotoxicity was only observed under conditions in which the E. coli nitroreductase or Walker DT diaphorase reduced the drug. It is proposed that E. coli B nitroreductase would be a suitable enzyme for antibody-directed enzyme prodrug therapy (ADEPT) in combination with CB1954.

Antibodies↗
PubMed1979

Convulsant and anticonvulsant actions in DBA/2 mice of compounds blocking the reuptake of GABA.

Compounds blocking the uptake of GABA into neurons or glia have been injected intracerebroventricularly (icv) or intraperitoneally (ip) in DBA/2 mice, age 21-28 days. Protection against audiogenic seizures was seen 30 min after the icv injection of (+)-2,4-diaminobutyric acid (0.5-2.0 mumoles), (+/-)-nipecotic acid (1.6-3.2 mumoles), (+)-ethyl nipecotate (0.4-0.8 mumoles), (-)-piperazic acid (4 mumoles) and putrescine (2 mumoles) or the ip injection of (+)-2,4-diaminobutyric acid (4-8 mmoles/kg and (+)-ethyl nipecotate (0.24-0.32 mmoles/kg). Of these ethyl nipecotate and nipecotic acid were the most effective anticonvulsants icv, but nipecotic acid was ineffective ip. Limb myoclonus and other epileptic manifestations (rearing, wild running, tonic clonic seizures) occurred in the absence of auditory stimulation after (+)-2,4-diaminobutyric acid (0.5-2.0 mumoles), (+/-)-cis-3-aminocyclohexane carboxylic acid (3.2-6.4 mumoles) and putrescine (2 mumoles). beta-Alanine (2-4 mumoles, icv) depressed respiration but did not protect against audiogenic seizures or induce myoclonus.

Alanine↗
PubMed1977

Monoamine and GABA metabolism and the anticonvulsant action of di-n-propylacetate and ethanolamine-O-sulphate.

The time course of changes in behaviour, seizure response and cerebral monoamine and gamma-aminobutyric acid (GABA) metabolism has been studied in relation to the anticonvulsant actions of di-n-propylacetic acid (DPA) and ethanolamine-O-sulphate (EOS) on sound-induced seizures in DBA/2 mice. Changes in cerebral monoamine metabolism after EOS (75 or 150 mug, intracerebroventricularly) were not related to its anticonvulsant action. The primary effect was GABA-transaminase inhibition (by 50-70%) leading to a 2-4 fold increase in cerebral GABA concentration. Increases in brain GABA concentration (maximally 36%), 5-hydroxyindoleacetic acid (5HIAA, maximally 134%) and homovanillic acid (HVA, maximally 183%) were seen after DPA (400-600 mg/kg, i.p.). The time course of the increases in HVA and 5HIAA did not correlate with the anticonvulsant effect. Elimination of these increases by the use of inhibitors of monoamine synthesis (alpha-methyl-p-tyrosine and p-chlorophenyl-alanine) did not alter the anticonvulsant effect of DPA. Experiments using probenecid suggested that the increases in 5HIAA and HVA after DPA result from inhibition of their active transport out of the brain.

Acoustic Stimulation↗
PubMed1977

Acute dystonia as an idiosyncratic response to neuroleptics in baboons.

Among 25 baboons, Papio papio, 2 consistently showed acute dystonic reactions, with mouthing, compulsive gnawing and limb and trunk dystonia, following the intravenous administration of neuroleptics and related drugs (haloperidol, 0-6-1-2 mg/kg; pimozide 0-5-2-5 mg/kg; chlorpromazine 5-25 mg/kg; metoclopramide 1-5-1-7 mg/kg; oxyperomide 0-25-1-0 mg/kg). The syndrome was not seen after thioridazine (3-7 mg/kg). The dystonic responses occurred within 1-2 h of drug injection and lasted for 2-24 h. They were abolished for 1-3 h within 1-2 min of the intravenous injection of acetylcholine antagonists (benztropine 0-2 mg/kg; hyoscine 0-02 mg/kg). Pre-treatment with a combination of reserpine (2 mg/kg) and alpha-methylparatyrosine (2 X 200 mg/kg) substantially reduced the dystonic response to haloperidol. A second larger dose of haloperidol (5 mg/kg), given 60-90 min after 0-5 mg/kg) initially reduced the intensity of the dystonic response, but after 29 min induced vomiting and generalized seizures in the idiosyncratic baboons. The hypothesis is advanced that the dystonic responses result from release of dopamine on to a sub-population of receptors in the striatum that are relatively insensitive to blockade by neuroleptics.

5-Hydroxytryptophan↗
PubMed1975

Effects of apomorphine, ergocornine and piribedil on audiogenic seizures in DBA/2 mice.

Audiogenic seizures in DBA/2 mice have been studied after administration of drugs believed to act as dopamine agonists. Apomorphine at 0.4 mg/kg delays all phases of the response, the tonic phase is absent after 2.0 mg/kg; the clonic phase is abolished by 10 mg/kg. Ergocornine (0.5-8.0 mg/kg) produces effects on the latency and occurrence of seizure stages similar to those of apomorphine. Piribedil, ET 495 (4-100 mg/kg) is less potent; even after 100 mg/kg clonic and tonic phases occurred in 50% of the mice.

Acoustic Stimulation↗