[Hypothalamic peptide stimulating growth hormone release].
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Animals↗
Biomedical subjects
T E Novikova
Publications and source records attributed to T E Novikova.
[Phenylephrine synchromizes rhythm of protein synthesis in hepatocyte culture].
Published data indicate that 1-3 microM adrenomimetic phenylephrine increases the concentration of calcium ions in the cytoplasm of cultured hepatocytes. We studied low-density cultures exhibiting no protein synthesis rhythm in the fresh medium and demonstrated that a 2 min action of 2 microM phenylephrine induces protein synthesis rhythm, i.e., synchronizes the synthesis oscillations in hepatocytes. A similar effect was observed for a selective inhibitor of the reticulum calcium pump, di-tert-butyl-benzohydroquinone, that increases the cytoplasm concentration of calcium ions by a receptor-independent mechanism. A calcium antagonist imipramine obviated the synchronization effect of phenylephrine. We propose that short-term changes in the cytoplasm concentration of calcium ions covering the whole cell population are among intracellular mechanisms of protein synthesis synchronization in hepatocytes in vitro.
Adrenergic alpha-Agonists↗
[The adrenoreceptor blocker prazosin does not prevent synchronization of the protein biosynthesis rhythm by exogenous gangliosides in the hepatocyte culture].
We studied the effect of the alpha 1-adrenolytic prazosine on dense cultures of hepatocytes, which are normally characterized by the protein synthesis rhythm, and diluted cultures, in which such a rhythm is revealed after external synchronization. Exogenous gangliosides (a fraction of the total gangliosides of the bovine brain) then synchronize the rhythm in diluted cultures; this effect is also displayed in the presence of 10(-7) M prazosine. The synchronizing effect of the medium conditioned by dense cultures was also preserved in the presence of prazosine. In the dense cultures that don't normally require external synchronization, prazosine affected intensified the rhythmic patter of changes in the protein synthesis. After a total of 0.3 microM gangliosides were introduced in the medium with prazosine-pretreated dense cultures, the protein synthesis rhythm was visualized. We propose that, while blocking adrenoreceptors, prazosine does not prevent the action of exogenous synchronizing factors on the hepatocytes, but inhibits the release of such factors from the cell.
Adrenergic alpha-Antagonists↗
[Changes in the concentration of calcium ions and rhythm of protein synthesis in the culture of hepatocytes].
We studied the effects of the chelating agents of extra- and intracellular calcium ions, EGTA and BAPTA-AM, and of the inhibitor of Ca2+ release from the reticulum, TMB-8, in the kinetics of protein synthesis in hepatocyte cultures. We also studied dense cultures capable of self-synchronization of protein synthesis oscillations and diluted cultures, in which synchronization is induced by phenylephrine or gangliosides (standard preparation of total gangliosides from the bovine brain). Preincubation of the diluted or dense cultures in the presence of 2 mM EGTA for 1-2 h with subsequent protein assay in a medium with EGTA did not affect the kinetics of protein synthesis: no rhythm was found in the diluted cultures, while it was preserved in the dense cultures. When the diluted cultures preincubated in the presence of EGTA were placed in a medium with EGTA and 2 microM phenylephrine for 2 min, the rhythm was visualized. The treatment of diluted cultures with 100 microM TMB-8 for 5 or 10 min with subsequent washing and incubation in a medium with 3 microM gangliosides led to visualization of the protein synthesis rhythm, i.e., to the synchronization of oscillations, while no rhythm was found in the standard cultures. Preincubation of the diluted cultures in a medium with 10, 15, or 20 microM BAPTA-AM did not affect the kinetics of protein synthesis. When, after such preincubation, the diluted cultures were placed in the medium with gangliosides, the rhythm was visualized. In the dense cultures, normally capable of self-synchronization, no rhythm of protein synthesis was found after their treatment with 10-20 microM BAPTA-AM for 1 h. The transfer of such cultures in the medium with gangliosides led to visualization of the rhythm. Thus, calcium affects the kinetics of protein synthesis: after the rise of Ca2+ in the cytoplasm was blocked, the rhythm of protein synthesis was not visualized due, supposedly, to disturbed mechanisms of medium conditioning. However, exogenous gangliosides in the dense or diluted cultures preincubated in the presence of BAPTA-AM ore TMB-8 allowed the rhythm visualization, i.e., synchronization may not depend on changes in the intracellular calcium concentration.
Animals↗
[Disturbed cooperation of hepatocytes in the rhythm of protein synthesis by chelating agent of cytoplasmic calcium BAPTA-AM].
Previously we demonstrated synchronized oscillations of protein synthesis rate in the hepatocyte cultures upon accumulation of monosialognaglioside GM1 in the medium or after introduction of exogenous GM1 to the medium. The synchronized oscillations of the protein synthesis rate in dense hepatocyte cultures were blocked 30 min after their treatment with 10-20 microM BAPTA-AM--a chelating agent of cytoplasmic calcium. Enzyme immunoassay for GM1 demonstrated similar amounts of GM1 in the medium conditioned for 3 h by dense hepatocyte cultures pretreated with 20 microns]M BAPTA-AM for 1 h and in the medium of normal dense cultures--0.0060 +/- 0.0005 and 0.0055 +/- 0.0005 pmol/1000 cells, respectively. The content of GM1 was also similar in the normal and BAPTA-AM-pretreated hepatocytes--0.158 +/- 0.013 and 0.183 +/- 0.014 pmol/1000 cells, respectively. The synchronized rhythm of protein synthesis has been confirmed in the diluted cultures in the medium conditioned by the normal dense cultures. However, the medium conditioned by the dense cultures pretreated with BAPTA-AM induces no synchronization of the diluted cultures. Since GM1 concentration was normal in this medium, we propose the effect of physicochemical form of the gangliosides accumulated in the medium on their ability to synchronize the rhythm of protein synthesis.
Animals↗
[Cooperation of the hepatocytes in vitro in the rythm of the protein synthesis is intensified by GM1 ganglioside in vesicles and liposomes].
The medium conditioned by dense, self-synchronized hepatocyte cultures was centrifuged at 150,000 g to obtain two fractions. The light fraction (supernatant fluid) contained ganglioside monomers and micelles, and the heavy fraction (pellet) contained gangliosides in the vesicles shed from the cell membrane. In the test populations of hepatocytes, the rhythm of protein synthesis was used as an indicator of cell synchronization resulting from their cooperative activity. Low-density hepatocyte cultures with asynchronous fluctuations of protein synthesis proved to be synchronized by both the initial conditioned medium and its vesicular fraction. Our previous studies have shown that this occurs under the effect of GM1 monosialoganglioside, which is released from cultured cells and accumulates in the conditioned medium. Liposomes consisting of GM1 and phosphatidylcholine from egg yolk (1:19 mol%), compared to free exogenous GM1, synchronized the rhythm of protein synthesis more effectively: synchronization was observed at a GM1 concentration in liposome suspension of only 0.0003 microM, compared to 0.06 microM and higher in the case of free GM1. Thus, GM1 as a component of membranes and monolayer lipid structures proved to be much more effective than free GM1 in promoting hepatocyte cooperation with respect to the rhythm of protein synthesis.
Animals↗
[Age-related features of protein synthesis rhythm in hepatocytes. Effects of extracellular medium].
Cell interactions have been studied in cultures pf hepatocytes from young and old rats. The rhythm of protein synthesis is an index of cell interaction and synchronization in culture, while the amplitude of oscillations characterized cell cooperation in an aggregate rhythm. The mean rhythm amplitude in the culture of hepatocytes from old rats is twice lower than that from young rats. Gangliosides (mixture, bovine brain gangliosides) and alpha1-adrenomimetic phenylephrine enhanced synchronization of cultures of the cells from old rats and increased the amplitude of oscillations to the level of young animals. Addition of rat blood serum (10%) to the medium revealed the rhythm of protein synthesis in the culture, asynchronous in the control, i.e., led to their synchronization. In media with young and old rat blood sera, oscillations were intense, with high amplitudes, and low, respectively. Addition of bovine brain gangliosides to a medium with old rat blood serum increased the amplitudes of oscillations to a level of the rhythm stimulated by the young rat serum. Thus, the cells of old animals can fully perceive synchronizing factors and, in the case of their increased concentration, the rhythm of protein synthesis in old animals did not differ from that in young rats. Current data on biochemical mechanisms underlying intercellular cooperation in the formation of population rhythm of protein synthesis have been discussed.
Activity Cycles↗
[Rhythm of protein synthesis in cultures of hepatocytes from rats of different ages. Norm and effect of the peptide livagen].
The circumhoralian rhythm of protein synthesis was determined in a monolayer culture of hepatocytes from rats at the age of 1 to 24 months and weighing from 45 to 480 g, respectively. The peptide lyvagen (Lys-Glu-Asp-Ala) obtained by directed chemical synthesis on the basis of amino acid analysis of the liver polypeptide preparations increased the level of protein synthesis in the hepatocytes from rats of different ages; the highest effect was observed in the cells of old animals. In old rats, lyvagen increased the amplitude of protein synthesis fluctuations. The peptide epitalon (Ala-Glu-Asp-Gly) constructed on the basis of analysis of the epiphysis peptides did not change the intensity of protein synthesis in the cultured hepatocytes.
Age Factors↗
[Aftereffect of synchronizers of protein synthesis rhythm in hepatocytes in vitro].
The effect of gangliosides and phenylephrine synchronizing the protein synthesis rhythm was preserved in hepatocytes cultured in the normal serum-free medium for one-two days. Hence, the membrane signal triggers intracellular, as was shown by us earlier, calcium-dependent processes, which regulate the kinetics of protein synthesis for a certain time after the signal perception.
Animals↗
[Effect of synthetic somatostatin on basal and stimulated growth hormone and prolactin secretion in vitro].
The effect of synthetic somatostatin on the basal and stimulated secretion of growth hormone and prolactin under conditions of incubation of the adenohypophysis (ADH) tissue in vitro was studied. The labeled growth hormones (GH) and prolactin (Pl) secreted was assayed by the method of electrophoresis in polyacrylamide gel as modified by the authors. Synthetic somatostatin (10 and 100 nM) suppressed the basal and stimulated by 2--0-dibutyril AMP, theophylline, and prostaglandins of E series GH labeled secretion. In doses of 100 nM the inhibitor also suppressed the basal and the stimulated by 2--0-dibutyril AMP and theophylline release of labeled Pl. Apparently, the inhibitory action of somatostatin involves the reduction of the ADH activity of adenylatecyclase.
Animals↗
[Protein synthesis in a hepatocyte culture in the presence of exogenous adenylic and guanyl nucleotides].
Circahoral opposite-in phase fluctuations of protein syntheses and intracellular ATP content have been observed in monolayer hepatocyte cell culture. Peculiarities of protein synthesis in hepatocytes have been studied in vitro in presence of adenylic and guanylic nucleotides. Addition of exogenous ATP leads to the decrease in the level of protein synthesis and smoothing off of the fluctuations. The presence of exogenous ADP leads to the increase in protein synthesis and retaining of the amplitude of fluctuations of this process. Effect of exogenous GTP is similar to that of ATP. Different aspects of action of exogenous NTPs on the rhythms of protein synthesis have been considered.
Adenosine Diphosphate↗
[The possible connection of adenylic nucleotides to the rhythm of protein synthesis in hepatocytes in vitro].
Circahoral protein synthesis rhythms observed in hepatocytes in vitro differ in phase from the oscillations of intracellular amount of ATP. ATP added to culture medium interferes with the rhythms of protein synthesis and intracellular DNA content. Addition of ADP increases both the incorporation level of hepatocytes and ATP content. The data obtained has been discussed.
Adenine Nucleotides↗
[Determination of purine and pyrimidine derivatives in acid-soluble fractions of organs and tissues using high-performance reverse-phase ion-pair chromatography].
Simultaneous separation of the main ribonucleotides, nucleosides and bases was carried out using tetrabutyl ammonium phosphate (TBA) hetaerons with a reversed-phase (C18) packing material. Chromatographic properties of purine and pyrimidine metabolites in radially compressed NovaPak C18 system was studied at various concentrations of acetonitrile and TBA in the mobile phase. The optimal conditions for gradient separation of nucleotides, nucleosides and bases were evaluated. The procedure was used for analysis of blood from healthy persons and patients with acute myocardial infarction.
Animals↗
[Establishment of rhythmic protein synthesis in the developing parotid gland during postnatal ontogeny].
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Animals↗
[The rhythm of protein synthesis in denervated rat liver].
Using the radiochemical method, we found a circahoralian rhythm of protein synthesis in slices of rat liver two weeks after transection of the vagus nerve anterior stem or bilateral subphrenic vagotomy with simultaneous transection of the celiac plexus hepatic branches. The rhythm was similar to those found in slices of normal liver or in a monolayer culture of hepatocytes. The incorporation of leucine in proteins and the pool of free leucine were similar in the denervated and normal liver. The self-synchronization of individual cell oscillations in protein synthesis intensity was shown earlier in experiments performed on cell cultures. A study of protein synthesis in the denervated liver suggests that cell interactions are also the main mechanism underlying the synchronization of oscillating cellular functions in the organ in situ.
Animals↗
[Cellular self-synchronization in a hepatocyte culture with antiphase fluctuations in the intensity of protein synthesis].
A part of suspension with isolated hepatocytes was cooled and then warmed to normal temperature. In cultures formed with such cells, antiphase oscillations of the protein synthesis rate were detected concerning control cultures from another part the same hepatocyte suspension. Oscillations of protein synthesis were observed in the mixed cultures formed with equal parts of antiphase subpopulations of hepatocytes. The experiments established cell interactions in vitro resulted in synchronization of protein synthesis oscillations in different cells the same population.
Animals↗
[The distant interaction of the cells in a hepatocyte culture. The population rhythm of protein synthesis].
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Animals↗
[The effect of macromolecular adhesion factors isolated from the blood serum and liver of mammals on the intensity of protein synthesis and the ATP content in hepatocytes in vitro].
The influence of the extra-low dozes of the macromolecular adhesive factors (MAF) on the protein synthesis and on the ATP contents in the rat hepatocytes on different models in vitro has been investigated. The protein synthesis intensity, the cell penetrability for labelled 3H-leucine and the intracell ATP contents in the experiments with the hepatocyte monolayer in control cells has been showed to be the same as those in the cells treated by MAF-1 and MAF-2. In the liver cells the protein synthesis intensity was depressed essentially under the action of MAF-1 and MAF-2 with respect to the control cells. The penetrability of the liver cells has increased in 50% of experiments after MAF-1 and MAF-2 treatment. The data obtained show the necessity of preservation of morphological structure of organs for the realization of the biological activity of appropriate MAF.
Adenosine Triphosphate↗