Studies on glutathione transferases belonging to class pi in cell lines with different capacities for conjugating (+)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene.

The glutathione transferases (GST) belonging to class pi are primarily responsible for the intracellular detoxification of the highly mutagenic and carcinogenic compound (+)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE). The aim of the present investigation was to study the nature and function of the GST pi gene in relation to the mutagenicity of BPDE in different cell lines. The studies were performed on three cell lines commonly used in toxicological studies, i.

Determination of the relative contributions of the diselenide and selenol forms of ebselen in the mechanism of its glutathione peroxidase-like activity.

The molecular basis of the glutathione peroxidase activity of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) was investigated by the use of synthesised, authentic intermediates identical to those formed by the reaction of ebselen with glutathione. The second order rate constants for the reaction of ebselen (0.29 mM-1 min-1), ebselen-glutathione selenosulfide (less than or equal to 0.

Characterisation and quantitation of a selenol intermediate in the reaction of ebselen with thiols.

The reaction of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) with thiols was investigated with particular attention to the formation of an ebselen selenol intermediate. The selenol intermediate could be trapped in a mixture of ebselen and thiols with 1-chloro-2,4-dinitrobenzene and the resulting product displayed unique spectral characteristics. The reaction of authentic, synthesised ebselen selenol with 1-chloro-2,4-dinitrobenzene (CDNB) was shown to give rise to the same compound (2,4-dinitrophenyl (N-phenyl-2-carboxamido phenyl) selenide as characterized by light spectroscopy, NMR, IR and elemental analysis.

The oligomeric structure of rat liver microsomal glutathione transferase studied by chemical cross-linking.

The oligomeric structure of rat liver microsomal glutathione transferase was investigated using four different chemical cross-linking reagents. Studies were performed with the isolated enzyme, with the enzyme incorporated into phosphatidyl choline liposomes and with rat liver microsomes. Cross-linking was analyzed by use of SDS-PAGE combined with Western blotting.

Mechanism of activation of rat liver microsomal glutathione transferase by noradrenaline and xanthine oxidase.

Activation of glutathione transferase activity in rat liver microsomes under a variety of conditions producing oxidative stress was investigated. Neither hydrogen peroxide (10 mM) (added or produced endogenously by glucose + glucose oxidase) nor duroquinone together with an NADPH-regenerating system (which generates the superoxide anion radical) had any significant effect on the glutathione transferase activity towards 1-chloro-2,4-dinitrobenzene. On the other hand, incubation of microsomes with 1 mM noradrenaline (which autooxidizes and generates superoxide anion radical) gave a 160% activation, as shown earlier (Aniya and Anders, J Biol Chem 264: 1998-2002, 1989).

N-acetyl-p-benzoquinone imine-induced protein thiol modification in isolated rat hepatocytes.

Incubation of isolated rat hepatocytes with N-acetyl-p-benzoquinone imine (NAPQI) or 3,5-dimethyl-N-acetyl-p-benzoquinone imine (3,5-Me2-NAPQI) resulted in a concentration-dependent decrease in the protein thiol content of the mitochondrial, cytosolic and microsomal fractions. On a concentration basis, 3,5-Me2-NAPQI induced a more marked depletion of protein thiols than did NAPQI. Sodium dodecyl sulphate-polyacrylamide gel electrophoretic separation of the proteins of each fraction showed that different proteins had different susceptibilities to modification of their cysteine residues by the quinone imines.

Studies on the activation of rat liver microsomal glutathione transferase in isolated hepatocytes.

The mechanism of activation of microsomal glutathione transferase in isolated liver cells by diisapropylidene acetone (phorone) was investigated. Phorone (1 mM) causes a time-dependent increase (up to 2.6-fold) in the glutathione transferase activity of microsomes isolated from treated hepatocytes.

The liver in typhoid fever: always affected, not just a complication.

The course of liver involvement during the first three weeks of typhoid fever was studied in 20 patients. Previous studies of liver involvement in typhoid fever have not considered the time course of changes. In this study, hepatomegaly was found during the 2nd or 3rd wk more often than in the 1st wk (36% vs.

CCK-8 modulates D2 receptor agonist-induced hypermotility in the nucleus accumbens.

The influence of CCK-8 on locomotor effects associated with independent D2 receptor stimulation was studied. To selectively stimulate mesolimbic D2 receptors LY 171555 was injected into the nucleus accumbens of awake rats. Locomotor activity was measured in the open-field test.

Studies on the activity and activation of rat liver microsomal glutathione transferase with a series of glutathione analogues.

The substrate specificity of rat liver microsomal glutathione transferase toward glutathione has been examined in a systematic manner. Out of a glycyl-modified and eight gamma-glutamyl-modified glutathione analogues, it was found that four (glutaryl-L-Cys-Gly, alpha-L-Glu-L-Cys-Gly, alpha-D-Glu-L-Cys-Gly, and gamma-L-Glu-L-Cys-beta-Ala) function as substrates. The kinetic parameters for three of these substrates (the alpha-D-Glu-L-Cys-Gly analogue gave very low activity) were compared with those of GSH with both unactivated and the N-ethylmaleimide-activated microsomal glutathione transferase.

2-Bromolisuride, an ergot derivative, with dopamine antagonistic and serotonin agonistic properties.

The open-field test was used to study the involvement of dopaminergic and serotonergic mechanisms in the effects of 2-bromolisuride on locomotor activity in the rat. 2-Bromolisuride produced a dose-dependent inhibition of spontaneous locomotor activity. This is most likely due to an antagonistic action at postsynaptic dopamine receptors.

Chemical modification of rat liver microsomal glutathione transferase defines residues of importance for catalytic function.

Amino acid residues that are essential for the activity of rat liver microsomal glutathione transferase have been identified using chemical modification with various group-selective reagents. The enzyme reconstituted into phosphatidylcholine liposomes does not require stabilization with glutathione for activity (in contrast with the purified enzyme in detergent) and can thus be used for modification of active-site residues. Protection by the product analogue and inhibitor S-hexylglutathione was used as a criterion for specificity.

The influence of tifluadom on cholecystokinin-induced antinociception.

The effects of tifluadom, a benzodiazepine-kappa-opioid-receptor agonist, on cholecystokinin-octapeptide (CCK-8)-induced antinociception were investigated in the mouse writhing test. When given alone, tifluadom produced pronounced, dose-dependent analgesia. The antinociceptive effect of intracerebroventricularly injected CCK-8 was potentiated by high doses of tifluadom.

Activation of microsomal glutathione transferase activity by reactive intermediates formed during the metabolism of phenol.

The activity of microsomal glutathione transferase was increased 1.7-fold in rat liver microsomes which carried out NADPH dependent metabolism of phenol. Known phenol metabolites were therefore tested for their ability to activate the microsomal glutathione transferase.

Inhibition studies on rat liver microsomal glutathione transferase.

A set of inhibitors for rat liver microsomal glutathione transferase have been characterized. These inhibitors (rose bengal, tributyltin acetate, S-hexylglutathione, indomethacin, cibacron blue and bromosulphophtalein) all have I50 values in the 1-100 microM range. Their effects on the unactivated enzyme were compared to those on the N-ethylmaleimide- and trypsin-activated microsomal glutathione transferase.

[Liver and spleen surgery using cavitating ultrasound].

Liver and spleen can be selectively skeletized by means of ultrasonosurgery (10-200 W/cm2, 20-40 kHz). These are technological solutions which have provided major prerequisites for low-risk oncosurgery. The technique (ultrasonic sealing) can as well be used in conjunction with monomeric tissue glues to safely and hermetically seal areas of resection of injuries in parenchymatous organs.

Atypical neuroleptics suppress dopaminergic behavioral supersensitivity.

Seven days after bilateral 6-OHDA denervation of the nucleus accumbens locomotor activity was recorded in rats. 6-OHDA lesion strongly enhanced hypermotility induced by apomorphine (1.0 mg/kg IP) as a sign of behavioral dopaminergic supersensitivity.

Activity of rat liver microsomal glutathione transferase toward products of lipid peroxidation and studies of the effect of inhibitors on glutathione-dependent protection against lipid peroxidation.

Rat liver microsomal glutathione transferase displays glutathione peroxidase activity with linoleic acid hydroperoxide, linoleic acid ethyl ester hydroperoxide, and dilinoleoyl phosphatidylcholine hydroperoxide, with rates of 0.2, 0.3, and 0.

Activation of rat liver microsomal glutathione transferase by limited proteolysis.

The activity of rat liver microsomal glutathione transferase is increased by limited tryptic proteolysis; the membrane-bound and purified forms of the enzyme are activated about 5- and 10-fold respectively. The cleavage sites that correlate with this activation were determined by amino acid sequence analysis to be located after Lys-4 and Lys-41. Differences in the relative extent of cleavage at these two sites did not consistently affect the degree of activation.