Alpha calcium/calmodulin dependent protein kinase II in learning-dependent plasticity of mouse somatosensory cortex.

Calcium/calmodulin dependent protein kinase II (CaMKII), and more specifically its alpha subunit, is widely believed to be fundamental for hippocampal synaptic plasticity. In the cerebral cortex, deprivation-evoked plasticity was shown to depend on alphaCaMKII autophosphorylation abilities. Here we analyzed how learning-induced functional reorganization of cortical representations affected alphaCaMKII in adult Swiss mice. Mice were subjected to short-lasting sensory training in which stimulation of whiskers was paired with tail shock. The pairing results in enlargement of functional representation of vibrissae activated during the training. alphaCaMKII protein and its autophosphorylation level were determined by Western-blotting in somatosensory cortex crude synaptosomal fraction (P2) and postsynaptic protein-enriched, Triton X-100 insoluble fraction (TIF). The first training session resulted in an increase in alphaCaMKII autophosphorylation at autonomy site observed in TIF. A similar increase was also observed after the first session of just whiskers stimulation, which alone does not induce rearrangement of cortical representations. These data indicate that increased autophosphorylation of postsynaptic alphaCaMKII is not a correlate of induction phase of plasticity related reorganization of cortical representation of vibrissae. The increase observed in both experimental groups was transient and did not persist in the maintenance phase of the plastic change. Furthermore, we found that the training caused a delayed upregulation of alphaCaMKII protein level in crude synaptosomal fraction, but not in TIF, and the upregulation was not accompanied by an increase in autophosphorylation level of the kinase. The result indicates alphaCaMKII involvement in the late phase of plastic change and suggests the participation of a presynaptic pool of kinase rather than postsynaptic at this point.

Bioavailability of diazepam from aqueous-organic solution, submicron emulsion and solid lipid nanoparticles after rectal administration in rabbits.

The bioavailability of diazepam in rabbits after rectal administration of three formulations: organic-aqueous Relsed rectal solution (containing ethanol, benzyl alcohol and propylene glycol), submicron emulsion and solid lipid nanoparticles (SLN), was studied. Submicron emulsion contained MCT oil (20% w/w), egg lecithin and poloxamer; SLN were prepared with cetyl palmitate 10% w/v and non-ionic emulsifying agent, Plantacare. All formulations contained 4 mg/ml of diazepam and the dose administrated to rabbits was 2 mg/kg. In both submicron preparations nearly the same mean size of the dispersed particles (201-206 nm) and the fraction of the free drug in aqueous phase (0.9-1.5%) was determined. Besides very moderate prolongation of drug release, the submicron emulsion as a vehicle did not alter pharmacokinetics of diazepam when compared with the solution: the mean C(max) was 48.9+/-24.0 and 49.5+/-17.0 ng/ml, and area under the curve was 134.0+/-42.3 and 186.8+/-59.8 ng h/ml, for solution and emulsion, respectively. The low relative bioavailability, 47% compared to the solution, was observed after administration of SLN. Transmission electron microscopy pictures revealed that some of diazepam is present on the surface of the SLN and this fraction was immediately absorbed, while the diffusion of the drug in the solid core was not efficient enough to allow a complete release. It may be concluded that submicron emulsion may be a good choice of an ethanol-free drug formulation, but lipid matrix, which is solid at body temperature, is not advantageous system for diazepam rectal delivery, even if delivered as a submicron dispersion.

Comparative analysis of effects of imidazoline drugs on isolated rat heart atria.

Effects of cumulative concentrations of 16 known imidazoline and 2 imidazole drugs on amplitude and rate of spontaneously beating isolated rat heart atria were measured and related to the respective effects induced by norepinephrine. In addition, the effects of fixed concentrations of the agents on the responses evoked by cumulative concentrations of norepinephrine were determined. In general, imidazolines classified as alpha 1-adrenoceptor agonist showed positive inotropic activity providing evidence for involvement of the alpha 1-adrenoceptor in mediating cardiac contractility. Negative chronotropic effect was common for the imidazolines studied, including alpha 1-adrenoceptor agonists, alpha 2-adrenoceptor agonists, alpha 1/alpha 2-adrenoceptor antagonists and antazoline--an antihistaminergic imidazoline devoid of adrenoceptor affinity. On the other hand, the imidazole derivative, medetomidine, showed a weak positive chronotropic activity. Negative chronotropic properties appeared to be independent of the alpha-adrenoceptors and may result from the membrane stabilizing action, involving probably the sodium channel blockade.

Synthesis and pharmacological activity of 5-substituted-s-triazole-3-thiols.

Two subgroups of 5-substituted triazoles were synthesized: derivatives of 3(3-substituted-amino-2-hydroxypropylthio)-5-substituted-4H-1,2,4- triazole and derivatives of N-substituted amides of 5-substituted-s-(1,2,4-triazole-3)thioglycolic acid. Selected members of the two subseries were tested pharmacologically. The blood pressure lowering effect in anaesthetized normotensive rats was weak to moderate. More pronounced was the inhibitory effect against adrenaline induced human blood platelet aggregation. In experiments on isolated rat heart atria and on isolated rat tail artery the activity of the agents was much weaker than in the case of known beta or alpha adrenoceptor antagonists. Generally, the chance to find a potential antihypertensive agent within the group studied seems to be low. Antiaggregatory activity of the compounds deserves further studies.

Synthesis, structure and biological activity of 1,2,4-triazolo-1,3-thiazine derivatives.

A group of condensed triazole-thiazine derivatives (2a-i, 3b, 3j) was obtained in reaction of the corresponding 5-substituted 1,2,4-triazole-3-thiones (1a-j) with epichlorohydrin in alkaline medium. The structure of the compounds synthesized was confirmed by spectral and roentgenographic methods. Tuberculostatic and circulatory activities of the compounds were also studied.

Studies on quinoxaline derivatives. Synthesis of quinoxalylamino-1,3-diazacycloalkanes with potential hypotensive activity.

A series of quinoxalylamino-1,3-diazacycloalkanes was obtained by the reaction of the corresponding substituted aminoquinoxalines with alcohols and amines. The effect of selected compounds on the blood pressure of anaesthesized normotensive rats was studied.

Studies on pyrazine derivatives. XXX. Synthesis of pyrazinylamino-1,3-diazacycloalkanes of potential circulatory activity.

A series of pyrazinylamino-1,3-diazacycloalkanes was obtained by reaction of the corresponding substituted aminopyrazines with aliphatic amines. Selected compounds were studied with respect to their potential circulatory activity. The effect on the blood pressure, isolated rat tail artery and heart atria, and an influence on the human blood platelet aggregation were investigated.

Subcellular distribution and expression of cofilin and ezrin in human colon adenocarcinoma cell lines with different metastatic potential.

The dynamic reorganization of the actin cytoskeleton is regulated by a number of actin binding proteins (ABPs). Four human colon adenocarcinoma cell lines - parental and three selected sublines, which differ in motility and metastatic potential, were used to investigate the expression level and subcellular localization of selected ABPs. Our interest was focused on cofilin and ezrin. These proteins are essential for cell migration and adhesion. The data received for the three more motile adenocarcinoma sublines (EB3, 3LNLN, 5W) were compared with those obtained for the parental LS180 adenocarcinoma cells and fibroblastic NRK cells. Quantitative densitometric analysis and confocal fluorescence microscopy were used to examine the expression levels and subcellular distribution of the selected ABPs. Our data show distinct increase in the level of cofilin in adenocarcinoma cells accompanied by the reduction of inactive phosphorylated form of cofilin. In more motile cells, cofilin was accumulated at cellular periphery in co-localization with actin filaments. Furthemore, we indicated translocation of ezrin towards the cell periphery within more motile cells in comparison with NRK and parental adenocarcinoma cells. In summary, our data indicate the correlation between migration ability of selected human colon adenocarcinoma sublines and subcellular distribution as well as the level of cofilin and ezrin. Therefore these proteins might be essential for the higher migratory activity of invasive tumor cells.

Testing conception of engagement of imidazoline receptors in imidazoline drugs effects on isolated rat heart atria.

Recently, attention has been payed to the role of imidazolines in physiology of the heart. However, no systematic comparative studies were reported regarding the activity of a representative set of specific ligands towards imidazoline receptors in the heart preparations. The aim of this project was to test effects of a set of ligands on the pharmacological function of putative imidazoline receptors in isolated rat heart atria. Known imidazoline drugs with a postulated high affinity to imidazoline I(1) receptor: AGN192403, rilmenidine, moxonidine and clonidine were used. The specific ligands of imidazoline I(2) receptor: 2-BFI, BU239 and putative natural ligand for imidazoline I(1), I(2) and I(3) receptors, agmatine, were tested also. The spontaneously beating right and left atria, driven electrically, were studied. Dose-response curves for amplitude and rate of the contractions of the atria were produced by administration of increasing doses of the agents. Phentolamine as alpha(1)/alpha(2) adrenergic receptors blocker and idazoxan as I(2)/I(1)/alpha(2) receptors blocker were added in order to inhibit ino- and chronotropic effects of the compounds studied. The -log EC(50) parameters were calculated. The positive inotropic effect on left atria were evoked with the rank order of potency: agmatine >> clonidine > BU239 > rilmenidine > or = moxonidine and these effects were generally diminished by idazoxan. Moxonidine produced a weak positive inotropic effect potentiated by idazoxan. Rilmenidine and moxonidine were assumed to act as partial agonists of imidazoline I(1) receptor. AGN192403 did not change the amplitude of beating of left atria. The positive chronotropic effects on spontaneously beating right heart atria were with in the following order of potency: BU239 > or = agmatine >>> clonidine > AGN192403. Idazoxan markedly antagonized chronotropic effect of both BU239 and agmatine. 2-BFI weakly diminished the rate of beating of atria; moxonidine and rilmenidine had no effect. In conclusion, imidazoline receptors of the I(1) subtype may be involved in inotropic reaction of the agents studied, but this effect depends mainly on the alpha(2)/alpha(1) adrenergic receptors. Engagement of I(2) imidazoline receptors, along with the alpha(2) adrenergic ones, in chronotropic activity of isolated right atria of rat has been demonstrated.

Lumican inhibits B16F1 melanoma cell lung metastasis.

BACKGROUND: Lumican is a small leucine-rich proteoglycan (SLRP) of the extracellular matrix (ECM) involved in the control of melanoma growth and invasion. The aim of the present study was to analyse the role of lumican in the regulation of the development of lung metastasis. METHODS: B16F1 melanoma cells stably transfected with lumican expressing plasmid (Lum-B16F1) were injected to syngenic mice. The lung metastasis was compared to mice injected with mock-transfected B16F1 cells (Mock-B16F1). The expression of lumican, cyclin D1, apoptotic markers, vascular endothelium growth factor (VEGF) and Von Willebrand Factor (vWF) within lung metastasis nodules was investigated by immunohistochemistry. In parallel, cells cultured in presence of lumican were assayed for apoptosis and motility. RESULTS: We observed that the number and the size of lung metastasis nodules were significantly decreased in mice injected with Lum-B16F1 cells in comparison to Mock-B16F1 cells. This was associated with an increase of tumour cell apoptosis within metastasis nodules but the cell proliferation rate remained constant in the two mice groups. In contrast, the VEGF immunostaining and the number of blood vessels within the lung metastasis nodules were decreased in the lumican-expressing tumours. In vitro, a significant decrease of apoptotic markers in wild type B16F1 cells incubated with increasing amounts of lumican core protein was observed. In addition, pseudotubes formation on Matrigel(R) and the migratory capacity of endothelial cells was inhibited by lumican. Altogether, our results indicate that lumican decreases lung metastasis development not only by inducing tumour cell apoptosis but also by inhibiting angiogenesis.

Possible role of ascorbic acid in catecholamines-stimulated Na+-K+-adenosine triphosphatase activity of the central nervous tissues.

Using EDTA and illuminated bovine retinas homogenate it has been found that Na+-K+-ATPase was stimulated by noradrenaline (NA), dopamine (DA), cAMP and dibutyryl cAMP. Phentolamine, an alpha adrenergic antagonist and INPEA, a beta adrenergic antagonist used at the same concentrations as catecholamines (CA) depressed the stimulatory effect of NA. Phentolamine increased the stimulatory effect of DA but INPEA inhibited it. It is proposed, therefore, that DA acts on retina Na+-K+-ATPase by putative DA receptors regulated by adrenergic antagonists. Ascorbic acid (AA), 0.125-1.0 mM depressed Na+-K+-ATPase activity of retinas, rat brain cortex and cerebellum homogenates. The results are consistent with the hypothesis that CA and AA can exert their effects in the presence of EDTA. In the retina the effects of CA is mediated by cAMP and alpha receptor influencing process. AA is postulated as a factor regulating the stimulation of CA on Na+-K+-ATP-ase and thereby the turnover of neurotransmitters in the central nervous system tissues.

Chromatographic modelling of interactions between melanin and phenothiazine and dibenzazepine drugs.

Differences in drug-melanin interactions were determined for 13 phenothiazine neuroleptics and 2 dibenzazepine thymoleptics by means of high-performance liquid chromatography. The chromatographic column was packed with a stationary phase obtained by chemical immobilization of synthetic L-dopa melanin on silica particles. For six phenothiazines the melanin-binding parameters were also determined by an ultrafiltration method. Correlation between measures of drug-melanin interaction determined chromatographically and by the standard slow-equilibrium method was significant, however moderate. The chromatographic method of assessing interactions between drugs and melanin permitted reliable and quantitatively comparable data for representative series of solutes to be readily obtained. Such data were subjected to the analysis of quantitative structure-retention relationships (QSRR). It was found that retention of the agents on the immobilized melanin column could be described by two-parameter regression equations comprising the energy of the lowest unoccupied molecular orbital and either the water-accessible surface area of a drug molecule or its hydrophobicity parameter, determined chromatographically on an immobilized artificial membrane column. The QSRR equation derived allows for the estimation of melanin binding based on the structure of a compound candidate, and thus rationalizes predictions of potential toxicity of drugs or drug candidates.

Quantitative relationships between the structure of beta-adrenolytic and antihistamine drugs and their retention on an alpha 1-acid glycoprotein HPLC column.

Chromatographic retention parameters of a series of 7 beta-adrenolytics and of 12 antihistamine drugs were determined employing an alpha 1-acid glycoprotein (AGP) high-performance liquid chromatographic (HPLC) column. For the group of antihistamines capillary electrophoretic (CE) retention was additionally measured in the presence of either AGP or human serum albumin (HSA). Two series of solutes hydrophobicity parameters were obtained by reversed-phase HPLC on an immobilized artificial membrane (IAM) column. The solutes studied were subjected to molecular modelling and the structural descriptors obtained were applied in studies of quantitative structure-retention (protein binding) relationships (QSRR). It was found that retention on AGP correlates well with the literature on physiological protein binding data. This retention was demonstrated to depend on hydrophobicity: to a lesser extent in the case of beta-adrenolytics and strongly in the case of antihistamines. Hydrophobicity, along with molecular width and electron excess charge on aliphatic nitrogen was demonstrated to describe retention of antihistamines on AGP. The AGP column is recommended as a convenient reactor for studies of drug-protein interactions. Preliminary CE data do not correlate with the HPLC data.

A search for new antihypertensive agents. II. Circulatory activity and selection of structures among 2-methylbenzimidazole derivatives.

A series of twelve 2-methylbenzimidazole derivatives was prepared and their effect on the contraction of isolated rat tail artery, on beating rate and amplitude of isolated rat heart atria, on human blood platelet aggregation, and on blood pressure in urethane-anesthetized normotensive rats were tested. Numerical measures of pharmacodynamic activity were quantitatively related to the changes in chemical structure of the agents. Conclusions are drawn about the mechanism of pharmacodynamic action of 2-methylbenzimidazole derivatives, which is not executed directly through the adrenergic system. The further direction of synthesis is established basing on the results obtained.

Furosemide antagonizes the contractile response to noradrenaline on isolated rat tail artery.

To determine the effect of furosemide (FUR) on the noradrenaline (NA) contraction of arteries, experiments were performed on isolated rat tail arteries according to Nicholas. FUR (300 mumol/l, 3 mmol/l) as well as Ca2+ transport system inhibitor, verapamil (VER), decreased the NA contractile force and FUR (3 mmol/l) antagonized the effect of VER (10 and 100 nmol/l). Calculated dose ratios according to Stephenson indicated that FUR and VER compete not only with NA but with each other. FUR decreased Ca2+ concentration in rat arteries studied in vivo by atomic absorption spectrophotometric method as well. It could be assumed that FUR depresses the sensitivity to NA and antagonizes NA induced contraction of arteries acting on transmembrane Ca2+ transport system.

Structure and alpha-adrenergic activity of pyrazinimidazolines.

The effects of newly synthetized pyrazinimidazolines on the contraction of isolated rat tail artery and on the chronotropic action of rat atria as well as the effects on blood pressure in anaesthetized rats were determined. The structure-activity relationships were studied, including standard imidazoline drugs. Starting from practically inactive derivatives the step-by-step structural modifications have been made resulting in markedly active chemical congeners, which were designed, synthetized and tested pharmacologically.

A search for new antihypertensive agents. I. Alpha-adrenergic activity and selection of structures among pyrazine substituted imidazolines.

A group of new pyrazinylimidazolines was prepared and their effect on the contraction of isolated rat tail artery as well as their effect on blood pressure in urethane anesthetized normotensive rats were tested. The biological responses were compared to those elicited by standard imidazoline drugs and structure-activity relationships were analysed. The new chemical derivatives were subsequently synthetized and tested pharmacologically. Basing on the experimental results obtained and comparing these to the reported data on arylimidazolines the following suggestions have been put forward concerning the further modifications of alpha-adrenergically active pyrazinylimidazolines: 1) a distance of about 5 A should separate imidazoline nitrogen and pyrazine nucleus, 2) bond refractivity of the separating bridge should be above 5.33, 3) hydrophobicity of substituents in pyrazine ring must be possibly high.