Effect of nonachlazine on transmembrane ionic currents in the frog atrial trabeculae

The effect of the antianginal drug nonachlazine displaying antiarrhythmic properties on transmembrane ionic currents in the frog atrial fibers was studied in experiments on isolated trabeculae of the frog atria. The transmembrane ionic currents were measured by a voltage clamp technique based on a double sucrose gap arrangement. Nonachlazine (1.03 X 10(-5) mol/l) decreased the amplitude of the fast inward current whatever the magnitude of membrane potential. The drug inhibited the slow inward current and prevented the adrenaline-increased permeability of the slow sodium-calcium channel if external sodium ions were replaced by choline chloride. Nonachlazine (1.03 X 10(-5) mol/l) diminished the amplitude of the inward ionic current in a calcium-free medium as well. The stimulatory effect of prostacycline (2 X 10(-7) mol/l) on the fast inward ionic current was inhibited by nonachlazine. The data obtained suggest that the antiarrhythmic effect of nonachlazine might be linked with the inhibition of the fast sodium inward current and the slow calcium inward current.     

Biochemical basis for the spasmolytic effect of isoquinoline and phenothiazine derivatives

Experiments with isolated ring-like strips of pig heart veins and arteries and those with rat small intestinal strips made in the presence of hyperpotassium contracture have demonstrated that spasmolytic activity of papaverine, nospa, nonachlazine, and ethmozine is a consequence of the reduced respiratory intensity and phosphorylation in smooth muscle mitochondria. No changes in the anaerobic glycolysis rate have been found after drug administrations.     

The effect of psychotropic substances on synaptosomal uptake of gamma-aminobutyric H3-acid and the activity of Na,K-ATPase]

The centrally acting drugs belonging to different groups--fluphenazine, trifluperidol, phthoracyzine, imipramine, diazepam, apomorphine, fentanyl, diphneylhydantoin, nonachlazine displayed in vitro an inhibitory effect on the uptake of gamma-aminobutyric acid by rat brain synaptosomes. A decrease in the activity of synaptosomal Na,K-ATPase was found in most cases. Drugs that failed to alter GABA uptake were as a rule found to be ineffective in relation to the enzyme activity (carbidine, morphine). GABA uptake was not affected by certain drugs inhibiting the Na,K-ATPase activity (azabuperon, tetrabenazine). It is supposed that the drugs used had at least two possible sites of action - Na,K-ATPase itself and hypothetic GABA transmembrane carrier.     

Effects of phenothiazine and dibenzazepine derivatives on the muscarinic cholinergic system]

Interactions of some dialkylaminoalkyl (DAL) and dialkylaminoacyl (DAC) derivatives of phenothiazine and dibenzazepine with muscarinic cholinergic receptors (MR) of rabbit striatum and heart and rat brain were investigated. DAC derivatives were more active at brain and heart MR in some cases. The most active preparation was G-512, DA-analogue of chlorpromazine. Some cardiotropic properties of antianginal preparation nonachlazine may be connected with its central antimuscarinic activity.     

The mechanism of nonachlazine on cardiac activity and blood supply]

Nonachlazine (10 mg/kg intravenously) exerted a two-phase influence on the heart activity. The short phase of the weakening of the heart activity gave place to the intensive increase in the cardiac output and the contractility of the myocardium. An increase in the blood supply and heart activity coincided in time with the accumulation of the quantity of noradrenaline and with increase in the phosphorylase "a" activity. Beta-adrenoblockers prevented the development of the effect in question. It is assumed that the efficacy of nonachlazine during ischemic heart disease was connected with its capacity to activate the adrenergic mechanisms of the glycogenolysis regulation leading to the switching of the myocardial metabolism to the anaerobic route of energy release.     

Effect of phenothiazines on the viscosity and electrical stability of model phospholipid membranes

The effect of five phenothiazine derivatives on the viscosity of model phospholipid membranes (by eximerization of pyrene) and on their electrical stability has been studied All the phenothiazines tested (chlorpromazine, propazine, triftazin and nonachlazine), except for chloracyzine, considerably increase the viscosity of phospholipid liposome bilayer at a concentration of 10(-5)-10(-4) M. Phenothiazines have been also shown to decrease liposome break-down potential even at a concentration of 10(-7) M. No correlation between the magnitude of break-down potential and changes in liposome membrane viscosity has been revealed.     

Influence of nonakhlazin on adrenergic neurotransmission in the vas deferens of rats]

The effect of a new antianginal drug--nonachlazine on the adrenergic neurotransmission in the isolated rat vas deferens was studied by examining the vas deferens contractions in response to the transmural electric stimulation of the postganglionic sympathetic nerves and addition of noradrenaline (NA) or BaCl2. After the nonachlazine treatment the NA content in the vas deferens was also studied by the spectrofluorometric method. Besides, the effect of the drug on the uptake of the exogenous NA was investigated. Nonachlazine was found to possess some sympatholytic and spasmolytic effect and could block the uptake of the exogenous NA greatly.     

Identification of a deoxyribonuclease activity in the nuclei of the cervical carcinoma HeLa

A deoxyribonuclease activity has been identified in the nuclei of the human cervical carcinoma HeLa. This activity has the novel property of existing as a single strand specific endo- and exodeoxyribonuclease activity. These activities are ionic strength sensitive, with retardation of activity occurring at 50 mM NaCl and above, with the Mn++ ion preferred over the Mg++ ion as activating cation. This activity extensively damages DNA via its single strand nicking and gaping activity. The method used to solubilize this activity as well as the enzyme's characteristics are discussed.     

Biochemical studies on the origin of the ATPase of the avian myeloblastosis virus

The adenosine triphosphatase activity of the avian myeloblastosis virus obtained from the blood of the virus-infected chicken was compared with that of the host cell myeloblasts. The specific activity of the viral enzyme is unusually higher than that of the myeloblasts. A significant difference in inhibitor sensitivity was observed with quercetin. When the virus was grown in chicken embryonic fibroblasts in culture, the resulting virus showed very little adenosine triphosphatase activity, comparable to that of the fibroblasts and similar sensitivity to inhibitors. Antibody raised against the purified enzyme of avian myeloblastosis virus inhibits the enzyme activity of the myeloblasts while the activity of the fibroblasts enzyme as well as that of fibroblast-grown virus remains unaffected.     

Seasonal dependence of the activity of antioxidant defence enzymes in the ground squirrel (Citellus citellus): the effect of cold.

1. The activity of antioxidant defense enzymes (SOD, CAT, GSH-Px and GST) was analysed during the autumn and winter in the ground squirrel adapted to 30 degrees C and subsequently exposed to cold for 6 and 24 hr. 2. The liver CAT activity as well as the IBAT CAT and GSH-Px activities differed between animals adapted to 30 degrees C, studied in autumn, and those studied in winter. 3. MnSOD activity in the liver was increased in autumn but decreased in winter after 6 hr cold exposure reaching the control level 24 hr later. Cold exposure induced a decrease in CAT activity (except after 24 hr cold exposure in winter) and an increase in GSH-Px activity. Lower GST activity was found after 24 hr exposure to cold in winter. 4. The IBAT SOD activity decreased under the influence of cold during both seasons with a tendency to return to the control level only in winter. Cold exposure produced a decrease in GST in both seasons and CAT activity in autumn. GSH-Px activity was increased in winter only. 5. The results indicate a seasonal dependence of the activity of antioxidant defence enzymes in the ground squirrel. Seasonal influence was evidenced in animals exposed to cold as well.     

Regulation of the specificity of the 26S proteasome endoribonuclease activity in K562 cells under the action of differentiation and apoptosis inducers

The specificity of the 26S proteasome endoribonuclease activity in proerythroleukemic K562 cells has been shown to change under the effects of inducers of erythroid differentiation inducers led to specific stimulation of RNase activity for certain mRNAs and to reduction of proteasome RNase activity for other mRNAs. The studied enzymatic activity was shown to be specifically and selectively dependent on phosphorylation of the 26S proteasome subunits, as well as on Mg and Ca ions. It was shown that the specificity of the proteasome RNase activity is regulated during differentiation and apoptosis. Selective regulation of the proteasome via the activities of different nuclease centers was suggested. This regulation may be accomplished through changes in the phosphorylation state of the proteasome subunits as well as by cation homeostasis.     

The development of the acinar heterotopic pattern of phosphoenolpyruvate carboxykinase activity in the newborn rat

Summary The postnatal appearance of phosphoenolpyruvate carboxykinase activity (PEPCK) and acinar heterotopy was investigated in newborn rats aged 2 h, 12 h, 24 h and 3 days, as well as in juvenile rats aged 25 days. The livers showed an almost homogeneous distribution of activity along the sinusoidal length at the beginning of extrauterine life where energy needs are greatest. Compared to rats aged 2 h, the PEPCK activity was higher in the livers from rats aged 12 h. The increase in activity was most pronounced in the intermediary zone. After 24 h of extrauterine life the activity decreased again creating a homogeneous acinar activity pattern. By day 3 activity had increased in the periportal zone, while decreasing in the perivenous zone, resulting in a periportal to perivenous gradient. By day 25 total activity had reached highest values both in males and females, due to a relatively high perivenous activity. The more prominent acinar gradient corresponded approximately to the one seen in adult animals.     

The development of the acinar heterotopic pattern of phosphoenolpyruvate carboxykinase activity in the newborn rat

The postnatal appearance of phosphoenolpyruvate carboxykinase activity (PEPCK) and acinar heterotopy was investigated in newborn rats aged 2 h, 12 h, 24 h and 3 days, as well as in juvenile rats aged 25 days. The livers showed an almost homogeneous distribution of activity along the sinusoidal length at the beginning of extrauterine life where energy needs are greatest. Compared to rats aged 2 h, the PEPCK activity was higher in the livers from rats aged 12 h. The increase in activity was most pronounced in the intermediary zone. After 24 h of extrauterine life the activity decreased again creating a homogeneous acinar activity pattern. By day 3 activity had increased in the periportal zone, while decreasing in the perivenous zone, resulting in a periportal to perivenous gradient. By day 25 total activity had reached highest values both in males and females, due to a relatively high perivenous activity. The more prominent acinar gradient corresponded approximately to the one seen in adult animals.     

Subcellular distribution of adenosine system enzymes in the hypothalamus and hippocampus of the rat brain

The subcellular distribution of 5'-nucleotidase and adenosine deaminase in rat brain hypothalamus and hippocampus was studied. In the hippocampus the 5'-nucleotidase activity was shown to be much higher than in the hypothalamus, while the adenosine deaminase activity, contrariwise, is nearly two times as high as that in the hypothalamus. During the analysis of subcellular distribution 5'-nucleotidase and adenosine deaminase were detected in all fractions under study, i. e., in nuclear, soluble, myelin fractions as well as in synaptic membranes, synaptosomes and "pure" mitochondria. The highest 5'-nucleotidase activity was found in the myelinic and synaptic fractions both in the hypothalamus and in the hippocampus. The highest adenosine deaminase activity was detected in the soluble fraction of the above structures. The enzyme activity in synaptic membranes and synaptosomes was nearly two times as low.     

On the activities of glycogen phosphorylase and glycogen synthase in the liver of the rat

A procedure was developed for determination of glycogen synthase and phosphorylase activities in liver after various in vivo physiological treatments. Liver samples were obtained from anaesthetised rats by freeze-clamping in situ. Other procedures were shown to stimulate the activity of phosphorylase and depress the activity of glycogen in the liver. The direction of glycogen metabolism appears to be regulated by the relative proportions of the two enzymes, as shown by a strong positive correlation between total activities and active forms of phosphorylase and synthase. The enzyme activities responded as expected to stimuli such as insulin and glucose, which depressed phosphorylase and increased synthase activity, and glucagon, which increased phosphorylase and decreased synthase activity. In fasted animals approximately 50% of each enzyme was in the active form, which suggests the existence of a potential futile cycle for glycogen metabolism. The role for such a cycle in the regulation of glycogen synthesis and degradation is discussed.     

On the activities of glycogen phosphorylase and glycogen synthase in the liver of the rat.

A procedure was developed for determination of glycogen synthase and phosphorylase activities in liver after various in vivo physiological treatments. Liver samples were obtained from anaesthetised rats by freeze-clamping in situ. Other procedures were shown to stimulate the activity of phosphorylase and depress the activity of glycogen in the liver. The direction of glycogen metabolism appears to be regulated by the relative proportions of the two enzymes, as shown by a strong positive correlation between total activities and active forms of phosphorylase and synthase. The enzyme activities responded as expected to stimuli such as insulin and glucose, which depressed phosphorylase and increased synthase activity, and glucagon, which increased phosphorylase and decreased synthase activity. In fasted animals approximately 50% of each enzyme was in the active form, which suggests the existence of a potential futile cycle for glycogen metabolism. The role for such a cycle in the regulation of glycogen synthesis and degradation is discussed.     

The activity of acid and alkaline phosphatase during the development of the vaginal anlage in rat and mouse

Summary The authors have studied the activity of alkaline and acid phosphatase in the rat and the mouse vaginal anlage. The activity is high in the epithelium of the müllerian vagina and low or uncertain in that of the sinus vagina. When a lumen is formed in the latter, there appears in rat an activity of both phosphatases of the same intensity as seen in the müllerian vagina. In mouse, the epithelium of the müllerian vagina transitory loses its activity of alkaline phosphatase when the epithelium undergoes transformation. The whole vagina is then surrounded by a zone of high stromal activity of alkaline phosphatase. The epithelium lacks activity except in the fornix region where the activity remains in a zone close to the lumen Thereafter the activity disappears in the subepithelial strorna and instead apears in the basal layer of the epithelium. The activity of acid phosphatase increases in the mouse sinus vagina at the same time as lumen is formed, being of the same intensity here as in the müllerian vaginal part.     

Physiological implications of the contrasting modulation of the activities of the epsilon- and zeta-isoforms of diacylglycerol kinase

We have shown that the requirement of the epsilon-isoform of diacylglycerol kinase for diacylglycerols containing arachidonic acid is specific for this substrate and cannot be replaced by the presence of an arachidonoyl group in other places in the membrane; rather, it has to be present on the substrate itself. In addition, we demonstrate that the increased activity shown toward 1-stearoyl-2-arachidonoylglycerol by the epsilon-isoform of diacylglycerol kinase is not a consequence of altered membrane physical properties but is rather a specific interaction with the arachidonoyl group. We have also compared the modulation of the activity of the epsilon-isoform of diacylglycerol kinase with that of the zeta-isoform with regard to some of the intermediates involved in phosphatidylinositol cycling. One of the products of the hydrolysis of phosphatidylinositol diphosphate is diacylglycerol enriched in arachidonic acid. The activity of the epsilon-isoform is known to be specific for this form of diacylglycerol. We show that in contrast, the activity of the zeta-isoform is lower against 1-stearoyl-2-arachidonoylglycerol compared with dioleoylglycerol. We demonstrate that addition of phosphatidylserine, as well as other anionic phospholipids including L-alpha-phosphatidylinositol 4,5-bisphosphate, strongly inhibits the epsilon-isoform, but these anionic lipids increase the activity of the zeta-isoform. Addition of Ca(2+), which is released from internal stores as a consequence of phosphatidylinositol cycling, promotes the activity of the epsilon-isoform of this enzyme but has little effect on the zeta-isoform. The contrasting conditions required for maximal activity of these two isoforms of diacylglycerol kinase, as well as their different substrate specificity, suggest that they have different physiological roles in signal transduction.     

Role of sugar chains in the expression of the biological activity of human erythropoietin.

Various deglycosylated derivatives of recombinant human erythropoietin (hEPO) were prepared and used to determine the role of the sugar chains in the expression of its biological activity in vivo and in vitro. Three N-linked oligosaccharides of hEPO have been partially or fully removed to obtain N-glycan (NG) (2)-, NG(1)-, and NG(0)-hEPO carrying two, one, and no N-linked sugar chains, respectively. The preparation lacking only O-linked sugar chain O O-glycan (OG) (0)-hEPO was also used. As de-N-glycosylation proceeded, the in vivo activity of the hormone decreased drastically, and the activity of these derivatives was correlated with the number of sialic acids bound to them. On the contrary, the in vitro activity was increased by the de-N-glycosylation; NG(0)-hEPO showed a 3-fold higher specific activity than the intact hormone. This was confirmed by binding experiments of the derivatives to target cells. The in vitro activity and the affinity also correlated with the number of sialic acids bound to the deglycosylated hEPO preparations. On the other hand, OG(0)-hEPO was as active as the intact hormone in vivo and in vitro. In conclusion, the N-linked sugar chains are not required for in vitro activity but required for in vivo activity, acting as anchors for the essential terminal sialic acids. The O-linked sugar chain has no essential role in the biological activity of the hormone in vivo or in vitro.     

Differences in the reducing power along the rat GI tract: Lower antioxidant capacity of the colon

The ability of the gastrointestinal (GI) tract, as well as other tissues, to cope with reactive oxygen species (ROS) efflux in pathological events is determined partly by epithelial antioxidant levels. These levels are comprized of tissue antioxidant enzymes and low molecular weight antioxidants (LMWA). While glutathione levels and the activity of enzymatic antioxidants along the GI tract have been studied, the contribution of the overall LMWA to the total antioxidant capacity has not yet been determined. In this study the overall antioxidant activity in the mucosa/submucosa and muscularis/serosa of various sections along the small intestine and colon of the rat was evaluated by determining the reducing power, which reflects the total antioxidant activity derived from LMWA, using cyclic voltammetry. The activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase was also measured. The reducing power (total antioxidant activity) was higher in the mucosa/submucosa of the small intestine as compared to the mucosa/submucosa of the colon. Similarly, catalase and SOD activity in the mucosa/submucosa of the small intestine was significantly higher than in the mucosa/submucosa of the colon. Differences were also observed in the reducing power and SOD activity in the muscularis/serosa of the rat small intestine as compared to the colon. The low antioxidant capacity in the colon may facilitate reactive oxygen species (ROS)-mediated injury and lead to inflammatory diseases such as ulcerative colitis, specifically in the colon.