Liver Enzyme Activities after Multiple Administration of Nifedipine in Mice

Abstract: The effect of multiple nifedipine administration on hexobarbital sleeping time, liver monooxygenase and synthetase activities, lipid peroxidation and microsomal membrane fluidity were studied in male albino mice. The drug was administered orally at a dose of 25 mg/kg daily for 14 and 21 days. Nifedipine caused enzyme induction, demonstrated by shortened hexobarbital sleeping time, enhanced ethylmorphine N-demethylase, aniline 4-hydroxylase, ethoxycoumarine O-deethylase, UDP-glucuronyl transferase, glutathione S-transferase and NADPH-cytochrome c reductase activities and increased content of cytochrome P450 and cytochrome b₅. This effect persisted until the 7th day after the last dose of nifedipine. There were no changes in lipid peroxidation and fluidity of the microsomal membranes after 14-day nifedipine administration. The increased cytochrome P450 content and drug metabolizing enzyme activities could be not associated with changes in these liver microsomal membrane properties.     

Combined effect of sodium maleate and some thiol compounds on mercury excretion and redistribution in rats

1. (+)-Penicillamine in a dose of 193 μmoles/kg given subcutaneously twice a day on the sixth and seventh days after the administration of 100 μg mercury increased the urinary excretion of rats more than the equimolar dose of N-acetyl-(+)-penicillamine but less than 2,3-dimercaptopropanol 48.3 μmoles/kg.

2. Sodium maleate in a dose of 156 μmoles/kg given on the sixth and seventh days after the mercury did not influence mercury excretion or redistribution. Sodium maleate in the same dose increased considerably the effect of (+)-penicillamine on the urinary excretion and redistribution of mercury. It increased the effect of N-acetyl-(+)-penicillamine only slightly. There was a tendency to decrease the effect of 2,3-dimercaptopropanol.

3. All the complexing agents decreased the kidney content of mercury and increased the liver and blood concentration of mercury. These changes were highest with 2,3-dimercaptopropanol. The combination of sodium maleate with (+)-pencillamine caused higher mercury excretion and lower kidney content but a smaller increase in the liver and blood mercury contents than 2,3-dimercaptopropanol.

     

On the enzyme-inducing action of calcium antagonists

The effects of three calcium antagonists, nifedipine (NF), verapamil (V) and diltiazem (DL), on rat liver monooxygenases were studied. The drugs were administered in oral doses of 50, 40 and 30 mg/kg daily for 3 weeks in male Wistar rats. NF and V shortened the hexobarbital (HB) sleeping time and increased benzphetamin-N-demethylase (BND), ethylmorphine-N-demethylase (EMND), aniline hydroxylase (AH), ethoxycoumarineO-deethylase (ECOD), ethoxyresorufin-O-deethylase (EROD) and NADPH-cytochrome c reductase activities and the content of cytochrome P-450 and microsomal heme, but did not change the content of cytochrome b₅. The data suggest that these calcium antagonists exert an enzyme-inducing effect on the hepatic monooxygenases. DL significantly increased only the EROD and NADPH-cytochrome c reductase activities and shortened HB sleeping time to a lesser extent, suggesting a weaker enzymeinducing effect as compared to NF and V. The three drugs increased the -aminolevulinic acid (ALA) synthetase activity and decreased heme oxygenase (HO) activity. The increased cytochrome P-450 content is probably due to the increased synthesis and the decreased breakdown of this hemoprotein.     

Mechanisms of stabilization of biomembranes by alpha-tocopherol. The role of the hydrocarbon chain in the inhibition of lipid peroxidation

The effects of alpha-tocopherol and its homologues with different chain lengths (6-hydroxy-chromanes: C1, C6, C11) on lipid peroxidation in natural membranes (liver microsomes and mitochondria, brain synaptosomes) and liposomes were studied. It was shown that the antioxidant activity of alpha-tocopherol homologues decreased in the order: C1 greater than C6 greater than C11 greater than alpha-tocopherol (C16). Using fluorescent measurements, the possible reasons underlying these differences were investigated: (i) the distribution between the aqueous media and nonpolar phase of the membrane, which predetermines the binding of alpha-tocopherol homologues to membranes; (ii) the incorporation of alpha-tocopherol homologues into lipid bilayer; (iii) non-uniform distribution (formation of the clusters) of tocopherol homologues in the lipid bilayer; and (iv) transbilayer mobility of alpha-tocopherol homologues and accessibility of the inhibitors for radical-generating centres under enzymically and non-enzymically induced lipid peroxidation. It was demonstrated that: (i) binding of C1 with membranes was less efficient than that of longer-chain homologues (C6, C11, C16); (ii) the level of incorporation of alpha-tocopherol homologues into membranes decreased in a succession alpha-tocopherol C11 greater than C6 greater than C1; (iii) all alpha-tocopherol homologues existed in the lipid bilayer not only in a monomeric form but also associated in clusters thus decreasing the efficiency of radical scavenging; (iv) the short-chain alpha-tocopherol homologue, C1, exhibited a high transbilayer mobility whereas the long-chain one, C16, underwent no transbilayer migration within tens of minutes. The inhibiting effect of alpha-tocopherol esters and C1-acetate was predetermined by their hydrolysis in biomembranes; a strong correlation exists between the rate of the ester hydrolysis and their antioxidant activity in the membrane. In liposomes, in which the esterase activity was absent, alpha-tocopherol esters and C1-acetate exhibited very low lipid peroxidation inhibition.     

Hyperactive self-inactivating piggyBac for transposase-enhanced pronuclear microinjection transgenesis

We have developed a unique method for mouse transgenesis. The transposase-enhanced pronuclear microinjection (PNI) technique described herein uses the hyperactive piggyBac transposase to insert a large transgene into the mouse genome. This procedure increased transgene integration efficiency by fivefold compared with conventional PNI or intracytoplasmic sperm injection-mediated transgenesis. Our data indicate that the transposase-enhanced PNI technique additionally requires fewer embryos to be microinjected than traditional methods to obtain transgenic animals. This transposase-mediated approach is also very efficient for single-cell embryo cytoplasmic injections, offering an easy-to-implement transgenesis method to the scientific community.     

Epileptogenic effect of intracortically applied kainic acid in cats

The effect of two doses (5 micrograms/microliters) of kainic acid (KA) injected intracortically into the posterior lateral gyrus of cats was investigated. KA in a dose of 5 micrograms/microliters provoked cortical epileptogenic focus 8-12 min after its application, developing later into a focal seizure. Administration of 10 micrograms/microliters KA resulted after 15-20 sec in paroxysmal discharges of spikes and sharp-slow waves at the site of the application, which propagated ipsilaterally. Thereafter the paroxysmal activity spread contralaterally, became generalized and developed into an epileptic state. The effect of KA was considered to be a dose-dependent one. N-Aminomethylpiperazine-3, 3-diethyl-2, 4-pyridinedione (DKMP) in a dose of 100 mg/kg injected i.v. on the background of developed epileptic state exerted a rapid inhibitory effect of 60-100 min duration on the paroxysmal activity. employed as a model of secondary generalized focal epilepsy.     

Experimental study of the mechanical properties of human abdominal fascia

The aim of the study is to characterise mechanical properties of human abdominal fascia according to its direction of loading and localization. The one-dimensional tensile behaviour of human abdominal fascia and its orthotropy has been studied experimentally using human umbilical (UF) and transversalis fascia (FT). The specimens have been cut and stretched parallel and orthogonal to the main fibre bundles. 90 specimens 10 mm wide and up to 70 mm long have been tested. The following mechanical parameters, characterising tensile properties of human abdominal fascia, have been calculated from the obtained stress-stretch ratio curves: maximal stress T(L)(max), stretch ratio at maximal stress λ(T(max)), maximal stretch ratio at failure λ(max), and a secant modulus E(i). The tissue strips obtained from defined areas reveal break stress between 0.63 and 1.99 MPa for FT and 0.93-1.61 MPa for UF. The parameter estimation has shown that in the physiological strain range specimens from both type of fascia can be considered orthotropic material according to their secant module, maximum stress T(L)(max) and stretch at maximum stress. Anisotropy factor AF (ratio of the stress in longitudinal and transverse directions) has been used to establish the level of the orthotropy of material and its variations with the stretch ratio. The maximum AF is 4.3 for FT at 20% deformation and 3.3 for UF at 5% deformation. The differences between the mechanical properties of FT and UF according to localization are not statistically significant thus the mechanical properties of human abdominal fascia are not affected by the localization.     

Helper-independent piggyBac plasmids for gene delivery approaches: Strategies for avoiding potential genotoxic effects

Efficient integration of functional genes is an essential prerequisite for successful gene delivery such as cell transfection, animal transgenesis, and gene therapy. Gene delivery strategies based on viral vectors are currently the most efficient. However, limited cargo capacity, host immune response, and the risk of insertional mutagenesis are limiting factors and of concern. Recently, several groups have used transposon-based approaches to deliver genes to a variety of cells. The piggyBac (pB) transposase in particular has been shown to be well suited for cell transfection and gene therapy approaches because of its flexibility for molecular modification, large cargo capacity, and high transposition activity. However, safety considerations regarding transposase gene insertions into host genomes have rarely been addressed. Here we report our results on engineering helper-independent pB plasmids. The single-plasmid gene delivery system carries both the piggyBac transposase (pBt) expression cassette as well as the transposon cargo flanked by terminal repeat element sequences. Improvements to the helper-independent structure were achieved by developing new plasmids in which the pBt gene is rendered inactive after excision of the transposon from the plasmid. As a consequence, potentially negative effects that may develop by the persistence of an active pBt gene posttransposition are eliminated. The results presented herein demonstrate that our helper-independent plasmids represent an important step in the development of safe and efficient gene delivery methods that should prove valuable in gene therapy and transgenic approaches.