Development of the mesencephalic and diencephalic serotoninergic system in mice and the role of serotonin in this process

The development of functional activity of the serotoninergic system in the mesencephalon and diencephalon of mice is followed during ontogeny, and it is found that serotoninergic neural elements become capable of specific serotonin uptake and K⁺-stimulated serotonin release on day 17 of prenatal life. A single serotonin injection into a female mouse on day 8 of gestation resulted in a drastically reduced specific³H-serotonin uptake by the brain of its 18-day fetuses. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 8, pp. 167–169, August, 1996     

The calcium channel antagonist diltiazem effectively blocks two types of potassium channels in the neuronal membranes

Effect of the Ca²⁺-channel antagonist diltiazem on potential-operated Ca²⁺ and K⁺ currents was studied on isolated edible snail neurons by a two-microelectrode patch-clamp technique. Diltiazem in a concentration of 0.1 mM inhibits Ca²⁺ current, high-threshold Ca²⁺-dependent K⁺ current, and Ca²⁺-independent K⁺ current and has no effect on low-threshold K⁺ current and leakage current. It is suggested that therapeutic effect of diltiazem is mediated through blockade of Ca²⁺ and K⁺ channels. Tranlated fromByulleten' Eksperimental'noi biologii i Meditsiny, Vol. 124, No. 9, pp. 271–274. September, 1997     

Effect of sarcolemmal anion transport system blockers on the development of ischemia-induced myocardial edema and recovery of contractile function during reperfusion

Subtotal 30-min ischemia leads to myoglobin release and increases water content in the heart. Reperfusion partially restores the developed pressure. Addition of furosemide (a Na⁺, K⁺, 2Cl⁻-sumport blocker) or NMA (inhibitor of Na⁺/H⁺-exchange) to perfusate decreases myocardial water content, reduces myoglobin loss, and completely restores myocardial contractile function. The low-rate perfusion of isolated heart and its reperfusion with solutions containing DIOA (inhibitor of K⁺, Cl⁻-co-transport) or IAA-94 (Cl⁻ channel blocker) increases water accumulation and myoglobin release from the myocardium, and deteriorated its contractile function during reperfusion. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 4, pp. 400–403, April, 1999     

Effect of vinpocetine on various types of high-threshold potassium currents in snail neurons

A high-threshold (−20 mV) K⁺ current was recorded from isolated edible snail neurons by a two-microelectrode voltage clamp technique. This current consisted of three components: fast-inactivating K⁺ currents (I_A), noninactivating K⁺ current (I_KD), and Ca²⁺-dependent K⁺ current (I_K(Ca)). Different cells had one to three components of K⁺ current. Vinpocetine increased I_A, moderately inhibited I_KD (by 30–50%) and strongly suppressed I_K(Ca) (by 60–90%). Inhibition of I_K(Ca) was not related to the effect of vinpocetine on the inward Ca²⁺ current. When K⁺ current consisted of all three components, the effect of vinpocetine on the ionic current amplitude was opposite at different potentials. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 126, No. 10, pp. 408–411, October, 1998     

Oxytocin stimulates the apical K+ conductance in frog skin

We measured the effects of oxytocin (0.1 U/ml) on the current (I _sc) recorded through skins ofRana temporaria incubated with an isotonic K⁺ solution on the api al side while the transepithelial potential was clamped to zero. Under these conditions,I _sc is carried by inward K⁺ movements. Oxytocin markedly stimulated this inward K⁺ current. When the spontaneous fluctuations were analyzed we found that oxytocin increased the plateau (S _o ⁽¹⁾) of the spontaneous Lorentzian component without modifying the corner frequency (f _c ⁽¹⁾). Addition of Ba²⁺ to the mucosal solution blockedI _sc both in the presence and absence of oxytocin. Moreover, with mucosal Ba²⁺ a characteristic blocker-induced Lorentzian component appeared in the power spectrum. Analysis of this blocker-induced noise showed that oxytocin increased the number of active K⁺ channels in the apical membrane, while the changes in single channel current were in agreement with expected alterations of the electrochemical driving force.     

Effects of the nootropics piracetam and GVS-111 on voltage-dependent ion channels of neuronal membranes

The effect of two nootropics, piracetam and N-phenylacetyl-L-prolyglycine ethyl ester (GVS-111), is studied by measuring high-threshold K⁺ and Ca²⁺ currents in isolated snail neurons using a two-microelectrode patch-clamp technique. Piracetam and GVS-111 are shown to reduce the amplitude of both the K⁺ and the Ca²⁺ (to a lesser extent) current. The threshold concentrations for GVS-111 and piracetam are 10⁻⁹-10⁻⁸ M and 1–5×10⁻⁴ M, respectively. It is assumed that the antiamnestic effect of the nootropics is partially mediated by a blockade of ion channels of the neuronal membrane. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, N ^o 2, pp. 151–155, February, 1996 Presented by G. N. Kryzhanovskii, Member of the Russian Academy of Medical Sciences     

Potassium and sodium ions in the nerve tissue of emotionally overstrained rabbits

Measurement of K⁺ and Na⁺ concentrations in samples of individual brain nuclei and in ganglia of the autonomic nervous system from rabbits subjected to severe emotional stress (ES) through aperiodic stimulation of ventromedial hypothalamic nuclei and electrocutaneous stimulation revealed significantly altered levels of these ions in locus ceruleus samples from animals predisposed to ES-induced cardiovascular disorders and in samples of neurons of the caudal part of the brainstem from those resistant to such disorders. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, No 8, pp. 129–131, August, 1994 Presented by K. V. Sudakov, Member of the Russian Academy of Medical Sciences     

The development of the diencephalon in Xenopus

Summary The development of the diencephalon and the time of origin of neurons of thalamic nuclei were determined in Xenopus with 3H-thymidine autoradiography Isotope was administered into embryos, tadpoles and metamorphic animals and sacrificed after survival time between 24 hours and 5 months. The position and the number of heavily labeled cells, corresponding to terminal mitoses at the time of isotope injection were established on transverse and sagittal sections of the frog brain. Neurons in the diencephalon were distributed in a spatiotemporal manner such, that cells generated earliest were located in the caudo-ventro-lateral portion of the diencephalon followed in a rostro-dorso-medial sequence by cells formed at later stages. The waves of cell generation resulted in three apparent developmental gradients in the caudo-rostral, latero-medial and in the ventro-dorsal directions in the diencephalon. Consequently neurons generated latest were found in the rostro-dorso-medial portion of the diencephalon. the overall rostro-dorso-medial diencephalic growth and the spatiotemporal generation of its neurons are the reverse of the tectal growth and cell generation reported in Xenopus which occurs in a rostrolateral to caudomedial direction.The findings of the present observations appear to indicate that the mirror-image reversal of the retinotectal and retinodiencephalic projections along the temporo-nasal retinal axis is the consequence of the divergent growth of the diencephalon and the tectum from the common embryonic di-mesencephalic junction. These observations furthermore suggest that the orientation of the retinal maps is ensured by the differential maturity gradients in the tectum and diencephalon, respectively, presumably expressed in molecular terms.     

Changes in intracellular ion activities induced by adrenaline in human and rat skeletal muscle

To study the stimulating effect of adrenaline (ADR) on active Na⁺/K⁺ transport we used double-barrelled ion-sensitive micro-electrodes to measure the activities of extracellular K⁺ (aK_e) and intracellular Na⁺ (aNa_i) in isolated preparations of rat soleus muscle, normal human intercostal muscle and one case of hyperkalemic periodic paralysis (h.p.p.). In these preparations bath-application of ADR (10⁻⁶ M) resulted in a membrane hyperpolarization and transient decreasesaK_e andaNa_i which could be blocked by ouabain (3×10⁻⁴ M). In the h.p.p. muslce a continuous rise ofaNa_i induced by elevation ofaK_e to 5.2 mM could be stopped by ADR. In addition, the intracellular K⁺ activity (aK_i), the free intracellular Ca²⁺ concentration (pCa_i) and intracellular pH (pH_i) were monitored in rat soleus muscle. During ADRaK_i increased, pH_i remained constant and intracellular Ca²⁺ apparently decreased. In conclusion, our data show that ADR primarily stimulates the Na⁺/K⁺ pump in mammalian skeletal muscle. This stimulating action is not impaired in the h.p.p. muscle. Parts of the results have been presented to the German Physiological Society (Ballanyi and Grafe 1987)     

Potassium transport through the erythrocyte plasma membrane in patients with insulin-dependent diabetes mellitus: Effects of insulin therapy

Plasma membrane potential and function of Ca²⁺-activated K⁺ channels of erythrocytes are studied in patients with insulin-dependent diabetes mellitus. A significant increase in membrane potential and in the degree of opening of Ca²⁺-activated K⁺ channels is revealed in comparison with erythrocytes of healthy donors. The degree of channel opening is higher in patients with nephropathy than in those with retinopathy, in which this parameter is normal. Insulin therapy normalize the erythrocyte plasma membrane potential in the patients and has no effect on the degree of channel opening. Ion transport disturbances and modulations of Na⁺, K⁺, and Ca²⁺ levels in erythrocytes may impair their function in insulin-dependent diabetes mellitus. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 7, pp. 109–113, July, 1996     

Inhibition of potassium-induced release of histamine from mast cells by tetraethylammonium and tetramethylammonium

In accordance with our previous results, a marked release of histamine (HA) from rat peritoneal mast cells was initiated by 150 mM KCl in the absence of extracellular Ca²⁺. This release could be reduced by 20–60 mM tetraethylammonium (TEA) or tetramethylammonium (TMA), the non-selective K⁺-channel blockers, Ouabain, the general inhibitor of (Na⁺+K⁺) ATP-ase, failed to produce any changes in this release. The action of TEA discriminated between the initiation of HA release evoked by different agents, producing a blockade of the K⁺-induced but not the 48/80-stimulated HA release. In total, these data suggest the presence of TEA/TMA-sensitive K⁺-channels in the mast cell membrane and their involvement in one of the possible pathways for the initiation of HA release.     

Role of potassium ions in monocyte-regulating effects of chorionic gonadotropin

We studied the effects of chorionic gonadotropin on intracellular K⁺ content and phagocytic activity of human peripheral blood monocytes. Since the immunomodulating properties of chorionic gonadotropin are known to depend on female sex steroids, the phase of the menstrual cycle was taken into account. Chorionic gonadotropic modulated the content of intra-cellular K⁺ and phagocytic activity of monocytes. These changes were most pronounced under the effect of chorionic gonadotropin in high physiological doses (100 U/ml) and depended on the phase of the menstrual cycle. A direct correlation was found between elevation of K⁺ content in monocytes and activation of phagocytosis during the luteal phase. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 130, No. 11, pp. 566–569, November, 2000     

Effect of benzodiazepines on synaptosomal Ca2+ transport in mice with different phenotype of emotional stress reactions

The effects of 5 benzodiazepines on basal and K⁺-induced Ca²⁺ concentration in synaptoneurosomes from intact and stressed C57B1/6 and BALB/c mice were studiedin vitro. Membrane depolarization induced by low KCl concentrations produced different effects on Ca²⁺ accumulation by synaptoneurosomes from two mouse strains. Benzodiazepines appliedin vitro exerted no effects on Ca²⁺ influx. In synaptoneurosomes from both C57B1/6 and BALB/c mice exposed to emotional stress diazepam in a dose of 5 mg/kg reduced the basal and K⁺-induced Ca²⁺ accumulation. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 129, No. 3, pp. 304–305, March, 2000     

On the functional interaction between nicotinic acetylcholine receptor and Na+,K+-ATPase

Previous studies have shown that nanomolar acetylcholine (ACh) produces a 2 to 4-mV hyperpolarization of skeletal muscle fibers putatively due to Na⁺,K⁺-ATPase activation. The present study elucidates the involvement of the nicotinic ACh receptor (nAChR) and of Na⁺,K⁺-ATPase isoform(s) in ACh-induced hyperpolarization of rat diaphragm muscle fibers. A variety of ligands of specific binding sites of nAChR and Na⁺,K⁺-ATPase were used. Dose–response curves for ouabain, a specific Na⁺,K⁺-ATPase inhibitor, were obtained to ascertain which Na⁺,K⁺-ATPase isoform(s) is involved. The ACh dose–response relationship for the hyperpolarization was also determined. The functional relationship between these two proteins was also studied in a less complex system, a membrane preparation from Torpedo electric organ. The possibility of a direct ACh effect on Na⁺,K⁺-ATPase was studied in purified lamb kidney Na⁺,K⁺-ATPase and in rat red blood cells, systems where no nAChR is present. The results indicate that binding of nAChR agonists to their specific sites results in modulation of ouabain-sensitive (most probably α2) isoform of Na⁺,K⁺-ATPase, leading to muscle membrane hyperpolarization. In the Torpedo preparation, ouabain modulates dansyl-C6-choline binding to nAChR, and vice versa. These results provide the first evidence of a functional interaction between nAChR and Na⁺,K⁺-ATPase. Possible interaction mechanisms are discussed.     

Modulation of type A K+ current inDrosophila larval muscle by internal Ca2+; effects of the overexpression of frequenin

The calcium-dependent modulation of type A K⁺ current (I _A) has been investigated using a two-electrode voltage clamp on larval muscle cells ofDrosophila. It was found that the amplitude ofI _A increases when [Ca²⁺]₀ is changed from 0.2 mM to 2 mM. The increase inI _A amplitude is not due to overlap with the Ca²⁺-dependent fast K⁺ current,I _CF, since it is observed also inslo ¹ mutants, which are deficient for this current. This effect is not due to Ca²⁺-dependent shifts in the steady-state activation/inactivation kinetics. The phenomenon is probably due to elevations in internal calcium since it is abolished by Ca²⁺ channel blockers and promoted by caffeine (5 mM) if added in the absence of external calcium. This calcium effect was dose-dependent since it was not observed in the presence caffeine plus 2 mM calcium in the bath nor for values of [Ca²⁺]₀ above 4 mM. The Ca²⁺-dependent modulation ofI _A is absent inV7, a mutation that causes overexpression of frequenin, a recoverin-like Ca²⁺-binding protein which stimulates guanylyl cyclase [31]. One possible explanation for the loss ofI _A modulation in theV7 mutation is that the excess of frequenin alters intracellular cGMP-dependent metabolic pathways responsible for the internal calcium homeostasis.     

Transport of nitrullin,a new nitrosoalkylurea derivative,into tumor and normal cells

The interaction between the antitumor drug nitrullin and the system providing the transport ofl-lysine into P388 leukemic cells and murine enterocytes is studied. Two types of lysine carriers with low and high affinity for the substrate are identified. Nitrullin competitively inhibits the transport of³H-lysine and shows the same affinity for both carriers. It is similar to that of lysine for the low-affinity carrier and is 80-fold lower than lysine affinity for the high-affinity carrier. Kinetic characteristics of the low-affinity transport of³H-lysine and K_i of nitrullin are similar to those obtained at a reciprocal substrate-inhibitor ratio. Nitrullin does not inhibit active transport of³H-lysine into enterocytes against the background of considerable (70%) passive diffusion. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 12, pp. 648–650, December, 1996     

p-Aminohippurate/2-oxoglutarate exchange in bovine renal brush-border and basolateral membrane vesicles

The transport of the amphiphilic organic anion, P-aminohippurate (PAH), across the luminal (brush-border) and contraluminal (basolateral) membrane of renal proximal tubule cells was studied with membrane vesicles isolated from bovine kidney cortex. On the basis of the enrichment of specific activities of marker enzymes, leucine aminopeptidase and Na⁺/K⁺-ATPase, brush-border and basolateral membrane vesicles can be obtained from bovine kidneys in reasonably pure form. The uptake of [³H]PAH into both brush-border and basolateral membrane vesicles was trans-stimulated by intravesicular PAH and by 2-oxoglutarate. In the absence of Na⁺, [³H]PAH/2-oxoglutarate exchange was cis-inhibited by unlabelled 2-oxoglutarate in the medium. In the presence of an inward Na⁺ gradient, 10 M 2-oxoglutarate, but no other Krebs cycle derivative, cis-stimulated [³H]PAH uptake, indicating that a Na³-coupled dicarboxylate transporter and PAH/2-oxoglutarate exchanger cooperate in both membranes to enhance [³H]PAH uptake. [³H]PAH uptake showed a non-saturable and a saturable component with similar apparent K _m values in brush-border and basolateral membranes. Although one negatively charged PAH molecule exchanges with one doubly negatively charged 2-oxoglutarate molecule the exchange was electroneutral. Probenecid inhibited [³H]PAH/2-oxoglutarate exchange in brush-border and basolateral membrane vesicles with indistinguishable kinetics. We conclude that similar or identical PAH transporters are located in brush-border and basolateral membranes of bovine kidney proximal tubule cells. This arrangement seems species-specific since a Na⁺ gradient plus 2-oxoglutarate caused concentrative [³H]PAH uptake in brush-border membrane vesicles from bovine, but not from rat kidney.     

Identification of an ATP-sensitive K+ channel in rat cultured cortical neurons

To determine whether membranes of mammalian central neurons contain an ATP-sensitive K⁺ (K_ATP) channel similar to that present in pancreatic cells, the patch-clamp technique was applied to cultured neurons prepared from the neonatal rat cerebral cortex and hippocampus. In whole-cell experiments with hippocampal neurons, extracellular application of 0.5 mM diazoxide (a K_ATP channel activator) elicited a hyperpolarization concomitant with an increase in membrane conductance, whereas application of 0.5 mM tolbutamide (a K_ATP channel blocker) induced a depolarization with a decrease in conductance. Similar results were obtained with cortical neurons. In outside-out patch experiments with cortical neurons, a K⁺ channel sensitive to these drugs was found. The channel was completely blocked by 0.5 mM tolbutamide and activated by 0.5 mM diazoxide. The single-channel conductance was 65 pS under symmetrical 145 mM K⁺ conditions and 24 pS in a physiological K⁺ gradient. In inside-out patch experiments, this channel was demonstrated to be inhibited by an application of 0.2–1 mM ATP to the cytoplasmic surface of the patch membrane. These results indicate that the membranes of rat cortical neurons contain a K_ATP channel that is quite similar to that found in pancreatic cells. It is also suggested that the same or a similar K⁺ channel may exist in membranes of hippocampal neurons.     

Stimulation of proliferative activity of human natural killers (CD16+CD56+ cells) by recombinant interleukin-3in vitro

The proliferative activity of human natural killers (CD16⁺CD56⁺ cells) in the presence of 100 and 1000 IU/ml human recombinant interleukin-3 is investigatedin vitro. It is shown that recombinant interleukin-3 reliably enhances natural killer proliferation, causing a 9–15.2-fold increase of³H-thymidine uptake by CD16⁺CD56⁺ cells both in complete culture medium and in conditioned medium. The effect of the factor is 3.9–6.4 and 3.6–8.9-fold more potent than that of recombinant interleukin-2 and granulocyte-macrophage colony-stimulating factor, respectively, in the same doses. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 4, pp. 409–412, April, 1995 Presented by S. V. Prozorovskii, Member of the Russian Academy of Medical Sciences     

Bacterial phenotypes mediated bymviAand their relationship to the mouse virulence ofSalmonella typhimurium

The focus of this study was the phenotypic characterization ofSalmonella typhimuriummutants lacking the function of the response regulatormviA. The inactivation ofmviA⁺(mviA: :kan) is shown to induce a significant change in the growth of most virulent strains, as reflected in the size of the colonies formed on agar plates. The colony phenotype observed in these strains has been designated as the small colony morphology (Scm⁺) phenotype. Mutants exhibiting the Scm⁺phenotype are shown to be significantly attenuated for virulence in susceptible (Ity^s) mice. The Scm⁺phenotype therefore provides anin vitrophenotypic marker formviA⁺activity. Further examination of Scm⁺mutants has revealed that they lack expression of a 55 kDa periplasmic protein which is detected in isogenicmviA⁺strains. This protein has been designatedmviA⁺relatedprotein A (MrpA) and was expressed in direct correlation with virulence in allS. typhimuriumstrains examined.