New method of lysophospholipid incorporation into biological membranes. Effect of lysophosphatidylcholine on the activity of membrane-bound enzymes

The incorporation of lysophosphatidylcholine into biological membranes and its effect on some membrane-bound enzymes of mitochondria and microsomes from rat liver and hepatoma were studied. It was shown that in the presence of lipid-exchange proteins of the liver a far greater amount of lysophosphatidylcholine is incorporated into the membranes than in the-iv absence. The increase of the lysophosphatidylcholine content in the membranes has no effect on the activity of mitochondrial monoamine oxidase, inhibits the activity of microsomal cytochrome P-450 and activates glucose-6-phosphatase.     

Effect of combined anesthetics on the activity of various myocardium enzymes

It is demonstrated by experiments with rabbits that the Ca2+-ATP-ase activity is stabilized when using combined anesthetics (diacetylcholine + halothane + N2O) as distinct from application of halothane. A decrease in the cholinesterase activity is less pronounced than under the halothane action but more than with the diacetylcholine application. A decrease in the Na+, K+-ATP-ase activity is observed with all types of anesthesia. A considerable inhibition of creatine kinase under the action of combined anesthesia and halothane and an increase of the lactate dehydrogenase activity under diacetylcholine application in mitochondria are shown. Reliable differences in the succinic dehydrogenase activity are not detected.     

The effect of nucleotides and mitochondrial chaperonin 10 on the structure and chaperone activity of mitochondrial chaperonin 60.

Mitochondrial chaperonins are necessary for the folding of newly imported and stress-denatured mitochondrial proteins. The goal of this study was to investigate the structure and function of the mammalian mitochondrial chaperonin system. We present evidence that the 60 kDa chaperonin (mt-cpn60) exists in solution in dynamic equilibrium between monomers, heptameric single rings and double-ringed tetradecamers. In the presence of ATP and the 10 kDa cochaperonin (mt-cpn10), the formation of a double ring is favored. ADP at very high concentrations does not inhibit malate dehydrogenase refolding or ATP hydrolysis by mt-cpn60 in the presence of mt-cpn10. We propose that the cis (mt-cpn60)14.nucleotide.(mt-cpn10)7 complex is not a stable species and does not bind ADP effectively at its trans binding site.     

The effect of SSB-protein from Ehrlich ascites carcinoma cells on activity of various enzymes of DNA replication and repair

The effect of a single-stranded DNA-binding protein (SSB-protein) form Ehrlich ascites tumour cells (EAT) on the activity of homologous purified DNA-polymerases alpha and beta, DNA-replicase, primase and DNA-polymerases from phage T4 and Bacillus stearothermophillus was studied. It was shown that the SSB-protein caused a 1.5-2.5-fold stimulation of the DNA-polymerase alpha activity on different templates (e.g., denaturated and activated DNA, poly(dA). The degree of stimulation depended on the template type, protein/template ratio and purity of DNA-polymerase alpha. The activity of DNA-polymerase was inhibited by the SSB-protein, when the activated DNA was used as a matrix and was unchanged on the denaturated DNA. The activity of some prokaryotic DNA-polymerases was increased under the influence of the SSB-protein. The protein enhanced the processivity of T4 DNA-polymerase and strongly inhibited the activity of replicase and primase. A conclusion about the complex effect of the SSB-protein on the activity of replicative and repair enzymes is drawn.     

The effect of antimycin A on mouse liver inner mitochondrial membrane channel activity.

In a patch-clamp study, we found antimycin A in low (1-2) microM concentrations decreased the open probability of the multiple conductance channel activity and the approximately 110 picosiemens channel of the inner mitochondrial membrane (for a review of mitochondrial channels see Kinnally, K. W., Antonenko, Yu. N., and Zorov, D. B. (1992) J. Bioenerg. Biomembr. 24, 99-110). Higher antimycin A concentrations (e.g. 10 microM) facilitated multiple conductance channel opening. These effects were reversible, and the binding site(s) are probably distinct from those responsible for the inhibition of the electron transport chain, since the latter are virtually irreversible. A model with two closed and two open states is presented for the approximately 110-picosiemens activity.     

The effect of various microelements on changes in the activity of certain enzymes in hydroponically cultivated barley during the first period of growth

The paper deals with the effect of the application of certain ions (Zn²⁺, B₄O₇ ^2- Mn²⁺, Cu²⁺, MoO₄ ^2-,) on the development of the activity displayed by amylase, urease, and glutamate-oxalacetate (GOT) in hydroponically cultivated barley during the first seven days of ontogenesis. The enzymes were studied separately in the overground and root parts of the plants. The following main conclusions can be drawn from the findings made: The amylase activity of the control plants in connection with their development diminished slightly in the overground part, while it was relatively constant in the roots. Due to the effect of certain elements tested, this activity increased pronouncedly (significant differences were confirmed in variants containing MoO₄ ^2-, Zn²⁺, and Co²⁺). The urease level in the overground part of the control plants remained low throughout the entire experimental period and was only little influenced by the individual microelements under study (with the exception of B⁴O₇ ^2-). On the other hand, the urease activity in the root system increased markedly, the B₄O₇ ^2- ions exhibiting a significantly stimulating effect. The activity of glutamate-oxalacetate transaminase (GOT) in the overground part of the control plants increased only slightly in the course of the initial development, while in the root system it grew relatively more pronouncedly. In the overground part of the plants all the microelements administered displayed a significantly depressive effect on the development of this enzyme activity; in the roots, the inhibitory action was maintained only in the last experimental period in variants with Zn²⁺ ions.     

The effect of perfluordecaline on the activity of phase III xenobiotic transformation enzymes

Injection of perfluorodecaline to rats caused an increase of the phase II xenobiotic biotransformation enzyme activities followed by cytochrome P-450 induction. The activities of liver microsomal UDP-glucuronosyl transferase and glutathione transferase increased by 130 and 40%, respectively, against the control level. The increase of the cytosolic glutathione transferase activity was insignificant In contrast, the activity of sulfotransferase decreased about 2-fold. The role of modification of xenobiotic biotransformation enzymes in the biological effect of perfluorodecaline is discussed.     

The effect of various culture conditions on the levels of ammonia assimilatory enzymes of Corynebacterium callunae

Corynebacterium callunae (NCIB 10338) grows faster on glutamate than ammonia when used as sole nitrogen sources. The levels of glutamine synthetase (GS; EC 6.3.1.2) and glutamate synthase (GOGAT; EC 1.4.1.13) of C. callunae were found to be influenced by the nitrogen source. Accordingly, the levels of GS and GOGAT activities were decreased markedly under conditions of ammonia excess and increased under low nitrogen conditions. In contrast, glutamate dehydrogenase (GDH; EC 1.4.1.4) activities were not significantly affected by the type or the concentration of the nitrogen source supplied. The carbon source in the growth medium could also affect GDH, GS and GOGAT levels. Of the carbon sources tested in the presence of 2 mM or 10 mM ammonium chloride as the nitrogen source pyruvate, acetate, fumarate and malate caused a decrease in the levels of all three enzymes as compared with glucose. GDH, GS and GOGAT levels were slightly influenced by aeration. Also, the enzyme levels varied with the growth phase. Methionine sulfoximine, an analogue of glutamine, markedly inhibited both the growth of C. callunae cells and the transferase activity of GS. The apparent K _m values of GDH for ammonia and glutamate were 17.2 mM and 69.1 mM, respectively. In the NADPH-dependent reaction of GOGAT, the apparent K _m values were 0.1 mM for -ketoglutarate and 0.22 mM for glutamine.Abbreviations GDH glutamate dehydrogenase - GS glutamine synthetase - GOGAT glutamate synthase     

The effect of age on mitochondrial ultrastructure.

The ultrastructure of perfused livers and of mitochondrial fractions from 6-month-old and 30-month-old C57/BL mice were studied. In old mice the liver cell mitochondria were enlarged and rounded with a light 'foamy', vacuolated matrix, short cristae and a loss of dense granules. Quantitative studies showed a 60% increase in the mean size and an increased proportion of larger mitochondria in intact 30-month-old perfused livers. Endothelial and Kupffer cell mitochondria were smaller than those of the parenchymal cells. Mitochondria in pellets prepared from 6- and 30-month-old livers were rounded and condensed, although there were a few larger and 'foamy' mitochondria in the preparations from old mice. Up to 47% of large mitochondria in the old livers were lost during cell fractionation.