Enhanced Hydrofobicity of Polymers for Personal Protective Equipment Achieved by Chemical and Physical Modification

The article presents significant results in research on creating superhydrophobic properties of materials which can be used as an interesting material for use in self-cleaning polymer protective gloves and similar applications where the superhydrophobicity plays a significant role. In this work the influence of laser surface modification of MVQ silicone rubber was investigated. The research was conducted using a nanosecond-pulsed laser at 1060 nm wavelength. After a process of laser ablation, the surface condition was examined using a SEM microscope and infrared spectroscopy. During the tests, the contact angle was checked both before and after the laser modification of samples pre-geometrised in the process of their production. The test results presented in the paper indicate that the chemical and physical modifications contribute to the change in the MVQ silicone rubber contact angle. A significant increase (by more than 30°) in the contact angle to 138° was observed. It was confirmed that surface geometrisation is not the only factor contributing to an increase in the contact angle of the analyzed material; other factors include a change in laser texturing parameters, such as mean beam power, pulse duration, scanning speed and pulse repetition frequency.

Analysis of resistance to bending of metal electroconductive layers deposited on textile composite substrates in PVD process

In the article a description of the behaviour of metallic layers created in the process of physical vacuum deposition on a composite textile substrates during their cyclical bending process is presented. Either the results of experimental research or the theoretical considerations of changes in the structure resistance as a function of the number of fatigue cycles are presented. It was confirmed mathematically that at the beginning of the bending process, in the case of a small number of bends, single cracks appear on the surface of the layer. After exceeding a certain number of bends, the nature of defects on the surface of the layer changes and the dominating mechanism of changes is the widening and elongation of already existing cracks. It has been confirmed mathematically that changes in resistance in these cases depend respectively on the number of bending cycles and next on quadratic value of number of cycles. A correspondence between the mathematical description and experimental results was obtained.

Laser Patterning a Graphene Layer on a Ceramic Substrate for Sensor Applications

This paper describes a method for patterning the graphene layer and gold electrodes on a ceramic substrate using a Nd:YAG nanosecond fiber laser. The technique enables the processing of both layers and trimming of the sensor parameters. The main aim was to develop a technique for the effective and efficient shaping of both the sensory layer and the metallic electrodes. The laser shaping method is characterized by high speed and very good shape mapping, regardless of the complexity of the processing. Importantly, the technique enables the simultaneous shaping of both the graphene layer and Au electrodes in a direct process that does not require a complex and expensive masking process, and without damaging the ceramic substrate. Our results confirmed the effectiveness of the developed laser technology for shaping a graphene layer and Au electrodes. The ceramic substrate can be used in the construction of various types of sensors operating in a wide temperature range, especially the cryogenic range.

Electrical and Thermal Properties of Heater-Sensor Microsystems Patterned in TCO Films for Wide-Range Temperature Applications from 15 K to 350 K

This paper presents an analysis of the electrical and thermal properties of miniature transparent heaters for use in a wide range of temperature applications, from 15 K to 350 K. The heater structures were produced in transparent conducting oxide (TCO) layers: indium tin oxide (ITO) and ITO/Ag/ITO on polymer substrates-polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), by direct laser patterning. Thermo-resistors for temperature measurement were created in the same process, with geometry corresponding to the shape of the heating path. The thermo-resistors integrated with the heating structure allowed easy control of the thermal state of the heaters. Laser patterning provided high precision and repeatability in terms of the geometry and electrical properties of the heater-sensor structures. Measurements at temperatures from 15 K to above room temperature (350 K) confirmed the excellent dynamics of the heating and cooling processes, due to current flow. The largest value for surface heating power was over 3 W/cm². A heater-sensor structure equipped with a small capacity chamber was successfully applied for controlled heating of small volumes of different liquids. Such structures have potential for use in research and measurements, where for various reasons controlled and accurate heating of small volumes of liquids is required.

A Fully Transparent Flexible Sensor for Cryogenic Temperatures Based on High Strength Metallurgical Graphene

Low-temperature electronics operating in below zero temperatures or even below the lower limit of the common -65 to 125 °C temperature range are essential in medical diagnostics, in space exploration and aviation, in processing and storage of food and mainly in scientific research, like superconducting materials engineering and their applications-superconducting magnets, superconducting energy storage, and magnetic levitation systems. Such electronic devices demand special approach to the materials used in passive elements and sensors. The main goal of this work was the implementation of a fully transparent, flexible cryogenic temperature sensor with graphene structures as sensing element. Electrodes were made of transparent ITO (Indium Tin Oxide) or ITO/Ag/ITO conductive layers by laser ablation and finally encapsulated in a polymer coating. A helium closed-cycle cryostat has been used in measurements of the electrical properties of these graphene-based temperature sensors under cryogenic conditions. The sensors were repeatedly cooled from room temperature to cryogenic temperature. Graphene structures were characterized using Raman spectroscopy. The observation of the resistance changes as a function of temperature indicates the potential use of graphene layers in the construction of temperature sensors. The temperature characteristics of the analyzed graphene sensors exhibit no clear anomalies or strong non-linearity in the entire studied temperature range (as compared to the typical carbon sensor).

Noncontact Atomic Force Microscope Dissipation Reveals a Central Peak of SrTiO_{3} Structural Phase Transition

The critical fluctuations at second order structural transitions in a bulk crystal may affect the dissipation of mechanical probes even if completely external to the crystal surface. Here, we show that noncontact force microscope dissipation bears clear evidence of the antiferrodistortive phase transition of SrTiO_{3}, known for a long time to exhibit a unique, extremely narrow neutron scattering "central peak." The noncontact geometry suggests a central peak linear response coupling connected with strain. The detailed temperature dependence reveals for the first time the intrinsic central peak width of order 80 kHz, 2 orders of magnitude below the established neutron upper bound.

A single gene defect causing claustrophobia

Claustrophobia, the well-known fear of being trapped in narrow/closed spaces, is often considered a conditioned response to traumatic experience. Surprisingly, we found that mutations affecting a single gene, encoding a stress-regulated neuronal protein, can cause claustrophobia. Gpm6a-deficient mice develop normally and lack obvious behavioral abnormalities. However, when mildly stressed by single-housing, these mice develop a striking claustrophobia-like phenotype, which is not inducible in wild-type controls, even by severe stress. The human GPM6A gene is located on chromosome 4q32-q34, a region linked to panic disorder. Sequence analysis of 115 claustrophobic and non-claustrophobic subjects identified nine variants in the noncoding region of the gene that are more frequent in affected individuals (P=0.028). One variant in the 3'untranslated region was linked to claustrophobia in two small pedigrees. This mutant mRNA is functional but cannot be silenced by neuronal miR124 derived itself from a stress-regulated transcript. We suggest that loosing dynamic regulation of neuronal GPM6A expression poses a genetic risk for claustrophobia.

β3 integrin is dispensable for conditioned fear and hebbian forms of plasticity in the hippocampus

Integrins play key roles in the developing and mature nervous system, from promoting neuronal process outgrowth to facilitating synaptic plasticity. Recently, in hippocampal pyramidal neurons, β3 integrin (ITGβ3) was shown to stabilise synaptic AMPA receptors (AMPARs) and to be required for homeostatic scaling of AMPARs elicited by chronic activity suppression. To probe the physiological function for ITGβ3-dependent processes in the brain, we examined whether the loss of ITGβ3 affected fear-related behaviours in mice. ITGβ3-knockout (KO) mice showed normal conditioned fear responses that were similar to those of control wild-type mice. However, anxiety-like behaviour appeared substantially compromised and could be reversed to control levels by lentivirus-mediated re-expression of ITGβ3 bilaterally in the ventral hippocampus. In hippocampal slices, the loss of ITGβ3 activity did not compromise hebbian forms of plasticity--neither acute pharmacological disruption of ITGβ3 ligand interactions nor genetic deletion of ITGβ3 altered long-term potentiation (LTP) or long-term depression (LTD). Moreover, we did not detect any changes in short-term synaptic plasticity upon loss of ITGβ3 activity. In contrast, acutely disrupting ITGβ1-ligand interactions or genetic deletion of ITGβ1 selectively interfered with LTP stabilisation whereas LTD remained unaltered. These findings indicate a lack of requirement for ITGβ3 in the two robust forms of hippocampal long-term synaptic plasticity, LTP and LTD, and suggest differential roles for ITGβ1 and ITGβ3 in supporting hippocampal circuit functions.

Inhomogeneous relaxation of a molecular layer on an insulator due to compressive stress

We discuss the inhomogeneous stress relaxation of a monolayer of hexahydroxytriphenylene (HHTP) which adopts the rare line-on-line (LOL) coincidence on KCl(001) and forms moiré patterns. The fact that the hexagonal HHTP layer is uniaxially compressed along the LOL makes this system an ideal candidate to discuss the influence of inhomogeneous stress relaxation. Our work is a combination of noncontact atomic force microscopy experiments, density functional theory and potential energy calculations, and a thorough interpretation by means of the Frenkel-Kontorova model. We show that the assumption of a homogeneous molecular layer is not valid for this organic-inorganic heteroepitaxial system since the best calculated energy configuration correlates with the experimental data only if inhomogeneous relaxations of the layer are taken into account.

High-resolution imaging of C60 molecules using tuning-fork-based non-contact atomic force microscopy

Recent advances in non-contact atomic force microscopy (nc-AFM) have led to the possibility of achieving unprecedented resolution within molecular structures, accomplished by probing short-range repulsive interaction forces. Here we investigate C(60) molecules adsorbed on KBr(111) and Cu(111) by tuning-fork-based nc-AFM. First, measurements of C(60) deposited on KBr(001) were conducted in cryogenic conditions revealing highly resolved nc-AFM images of the self-assembly. Using constant-frequency shift mode as well as three-dimensional spectroscopic measurements, we observe that the relatively weak molecule-substrate interaction generally leads to the disruption of molecular assembled structures when the tip is probing the short-range force regime. This particular issue hindered us in resolving the chemical structure of this molecule on the KBr surface. To obtain a better anchoring of C(60) molecules, nc-AFM measurements were performed on Cu(111). Sub-molecular resolutions within the molecules was achieved which allowed a direct and unambiguous visualization of their orientations on the supporting substrate. Furthermore, three-dimensional spectroscopic measurements of simultaneous force and current have been performed above the single molecules giving information of the C(60) molecular orientation as well as its local conductivity. We further discuss the different imaging modes in nc-AFM such as constant-frequency shift nc-AFM, constant-height nc-AFM and constant-current nc-AFM as well as three-dimensional spectroscopic measurement (3D-DFS) employed to achieve such resolution at the sub-molecular scale.

Three-dimensional dynamic force spectroscopy measurements on KBr(001): atomic deformations at small tip-sample separations

Three-dimensional dynamic force spectroscopy measurements were carried out above KBr(001) at low temperature in order to investigate the distance dependence of the tip-sample interactions. In particular, the recorded 3D frequency shift data as well as the extracted interaction force and potential energy fields were analysed with respect to influences of tip and/or sample deformations. We found that a postprocessing correction of the observed deformations significantly modifies the magnitude of the extracted interaction forces and also the image contrast.

Socio-demographic predictors and reasons for vitamin and/or mineral food supplement use in a group of outpatients in Skopje

BACKGROUND

Vitamins and/or mineral food supplements (VMS) are mono- or multi-component products prepared in different pharmaceutical forms and categorized as food supplements. Numerous researchers have investigated the epidemiological predictors of use of VMS in population. Data of this kind in our setting are limited.

AIMS

This survey aimed to gain information on the prevalence of use, certain sociodemographic predictors and reasons for VMS use in a group of 256 outpatients in Skopje.

MATERIALS AND METHODS

This study was designed as an open-ended, cross-sectional survey. Data on VMS use were collected by survey method with a specially designed questionnaire as an instrument for this research. Appropriate statistical tests were used to analyse the data.

RESULTS

Data from 256 outpatients from Skopje were analysed. Of them, one hundred and five (41.02%) reported using VMS. Female outpatients (p<0.01) and participants of Macedonian ethnicity (p<0.01), with a higher educational level (p<0.01) and those having their own income (p<0.05) reported significantly higher consumption of VMS. We found a statistically significant difference between the group of users and non-users of VMS regarding smoking status (p<0.05), alcohol consumption (p<0.05) and presence of a chronic disease (p<0.01). Physicians, magazines and friends were the most common source of information on VMS while maintaining good health and prevention of disease was the most common reasons for the use of these products. Only 63% of the users had disclosed the information on taking VMS to their physicians.

CONCLUSION

This research provided an insight into VMS in our setting. Predictors on the use of VMS are of interest since these products contribute to total intake of vitamins and minerals in the population and they represent a source of valuable information when planning public health activities.

Tissue plasminogen activator in the amygdala: a new role for an old protease

Evidence has accumulated that point to the tissue plasminogen activator (tPA), a serine protease historically associated with blood physiology, as an important regulator of the central nervous system functioning. tPA is highly expressed in the limbic system where it regulates neuronal viability and experience-induced plasticity. In the amygdala tPA is a critical mediator of stress-induced structural and functional rearrangements that ultimately shape up behavioral responses to stressful stimuli. The importance of tPA in the limbic system was confirmed using tPA-deficient mice; these animals do not show biochemical, structural and behavioral signatures normally associated with stress. tPA-mediated facilitation of experience-induced plasticity in the limbic system is mediated by a complex mechanism that may involve direct or indirect interactions of tPA with NMDA receptor, its binding to the LRP receptor or activation of brain-derived growth factor.

Stress-induced spine loss in the medial amygdala is mediated by tissue-plasminogen activator

The amygdala, which exerts a regulatory influence on the stress response, is itself affected by stress. It has been reported that the serine protease tissue-plasminogen activator (tPA), a key mediator of spine plasticity, is required for stress-induced facilitation of anxiety-like behavior. Importantly, tPA is also involved in stress-induced activation of molecular signals that have the potential to contribute to neuronal remodeling in the medial amygdala (MeA). However, little is known about the precise nature of, and specific role played by tPA in, stress-induced structural plasticity in the MeA. Hence, we compared the impact of chronic restraint stress on spine density of medium spiny stellate neurons in MeA in wild-type mice with mice in which the tPA gene is disrupted (tPA-/-). In wild-type mice, chronic stress caused significant reduction in MeA spine density, which was in contrast to enhanced spine density in the neighboring basolateral amygdala (BLA). Strikingly, tPA-/- mice exhibited significant attenuation of stress-induced spine retraction in the MeA, but BLA spinogenesis was not affected. Therefore, tPA-dependence of stress-induced modulation in spine density was restricted to the MeA. Further, MeA neurons in tPA-/- mice, even when challenged with repeated stress, were able to maintain levels of spine density that were comparable to that of wild-type mice without stress. Our findings provide novel evidence for a permissive role for tPA in amygdalar spine plasticity elicited by behavioral stress.

Tissue plasminogen activator in the bed nucleus of stria terminalis regulates acoustic startle

The bed nucleus of stria terminalis is a basal forebrain region involved in regulation of hormonal and behavioral responses to stress. In this report we demonstrate that bed nucleus of stria terminalis has a high and localized expression of tissue plasminogen activator, a serine protease with neuromodulatory properties and implicated in neuronal plasticity. Tissue plasminogen activator activity in the bed nucleus of stria terminalis is transiently increased in response to acute restraint stress or i.c.v. administration of a major stress mediator, corticotropin-releasing factor. We show that tissue plasminogen activator is important in bed nucleus of stria terminalis function using two criteria: 1, Neuronal activation in this region as measured by c-fos induction is reduced in tissue plasminogen activator-deficient mice; and 2, a bed nucleus of stria terminalis-dependent behavior, potentiation of acoustic startle by corticotropin-releasing factor, is attenuated in tissue plasminogen activator-deficient mice. These studies identify a novel site of tissue plasminogen activator expression in the mouse brain and demonstrate a functional role for this protease in the bed nucleus of stria terminalis.

Angiotensin-(1-7): an active member of the renin-angiotensin system

Angiotensin-(1-7) [Ang-(1-7)] is an active member of renin-angiotensin system (RAS). It counterbalances vasoconstriction, mitogenic, arrhythmogenic and prothrombotic actions of Ang II. Inducing natiuresis and diuresis opposes also the water and sodium retention produced by Ang II. Till now the specific receptor side for Ang-(1-7) has been not cloned, but the current data strongly suggest that an interaction (cross-talk) between angiotensin receptors may play a role in the effects of Ang-(1-7).

Rapid, specific and active site-catalyzed effect of tissue-plasminogen activator on hippocampus-dependent learning in mice

In the present study we trained tissue-plasminogen activator (tPA)-knockout (tPA -/-) and wild-type (tPA +/+) male mice in step-down inhibitory avoidance learning, a hippocampus-dependent task. tPA -/- displayed significantly shorter latencies to step down at 90 min, one, two and seven days after training indicating the learning deficit in these animals (P < 0.05 vs tPA +/+). The locomotor activity, the level of anxiety in an elevated-plus maze, as well as the pain threshold did not differ between the two strains of mice. The learning disability of tPA -/- was overcome by more intense training. The learning deficit was also partially restored by limited intrahippocampal delivery of tPA (infused for 2 h before training; P < 0.05 vs control), but not by the delivery of urokinase plasminogen activator, indicating the acute need for tPA in learning. The beneficial effect of tPA was abolished by co-infusion of its inhibitor tPA-STOP, indicating that the facilitatory effect of tPA on learning requires a proteolytic step. However, tPA activity in the hippocampus was not indispensable for effective memory retrieval in tPA-infused tPA -/- mice. Thus, rapid, specific and proteolytic action of tPA facilitates hippocampus-dependent learning, but not retrieval of previously acquired information.

Propranolol modifies platelet serotonergic mechanisms in rats

Though the mechanisms for the vascular actions of vasodilatory beta-blockers are mostly determined, some of their interactions with monoaminergic systems are not elucidated. Because there are evidences supporting a possible involvement of serotonin (5-HT) in the actions of beta-blockers, we studied the effect of propranolol on peripheral serotonergic mechanisms in normotensive and Goldblatt two-kidney - one clip (2K1C) hypertensive rats. In both groups of animals propranolol decreased systolic blood pressure, significantly increased whole blood serotonin concentration and at the same time it decreased platelet serotonin level. The uptake of the amine by platelets from hypertensive animals was lower than that of normotensive animals and it was decreased by propranolol only in the latter. In both groups propranolol inhibited potentiation of ADP-induced platelet aggregation by serotonin. In conclusion, this study provides evidence that propranolol modifies platelet serotonergic mechanisms in normotensive and renal hypertensive rats.

Studies on the antithrombotic action of AT1 receptor antagonists

BACKGROUND

In our previous experiments we showed that the prototype member of the AT1 receptor antagonists (AT1-As) family, losartan, prevented the development of arterial and venous thrombosis in rats. Recent studies have demonstrated that apart from blocking AT1 receptor, losartan is also a competitive antagonist to thromboxane A2/prostaglandin H2 receptor (TP receptor). Thus, we decided to assess if this feature could contribute to the antithrombotic action of losartan.

MATERIAL AND METHODS

We compared the influence losartan, its active metabolite EXP3174 and valsartan on rat platelet adhesion to fibrillar collagen and platelet aggregation in response to thromboxane A2 analogue, U46619. We also assessed the efficacy of these drugs in platelet-dependent pulmonary thrombosis in mice as well as preventive and therapeutic models of venous thrombosis in rats.

RESULTS

All the three compounds, given in a single dose, inhibited rat platelet adhesion to fibrillar collagen and platelet aggregation induced with U46619 in vitro and ex vivo, with the action of losartan being much more pronounced than that of EXP3174 or valsartan. Losartan also more effectively protected mice from death in response to the intravenous injection of collagen / epinephrine and it was the only compound which reduced mice mortality after the intravenous injection of U46619. In contrast, all the three AT1 receptor antagonists exerted a similar thrombolytic action and comparably decreased the thrombus weight in the therapeutic and preventive model of venous thrombosis, although in the latter case a high dose of losartan was slightly more effective than a corresponding dose of EXP3174 and valsartan.

CONCLUSIONS

Since losartan is endowed with a relatively low affinity towards the AT1 receptor, we conclude that its superiority over EXP 3174 and valsartan in inhibiting thrombocyte function and platelet-dependent thrombosis could result from its stronger action on the TP receptor. This feature seems to be less important in the thrombolytic effect of AT1-As and in the inhibition of the venous thrombosis development, in which platelets play only a minor role.

The differential effect of angiotensin II and angiotensin 1-7 on norepinephrine, epinephrine, and dopamine concentrations in rat hypothalamus: the involvement of angiotensin receptors

Angiotensin 1-7 has been recently claimed the active member of the angiotensins' family. In the present study we compared the effect of angiotensin II and angiotensin 1-7 on the concentration of dopamine, serotonin, epinephrine, and norepinephrine and some of their metabolites in the rat hypothalamus, where the levels of angiotensins are particularly high. Intracerebroventricular injection of angiotensin II, but not angiotensin 1-7, time-dependently elevated the levels of both epinephrine (p < 0.05) and norepinephrine (p < 0.05) in the hypothalamus and both effects could be prevented by intracerebroventricular injection of either AT(1) (candesartan), AT(2) (PD123319) or AT(1-7) (A-779) receptor antagonist. Neither angiotensin II nor angiotensin 1-7 produced any changes in the level of dopamine, dihydroxyphenylacetic acid, homovanilic acid, serotonin, 5-hydroxyindoleacetic acid, or tryptophan at any time point in comparison with the control groups. However, AT(1) but not AT(2) receptor blockade, unmasked the stimulatory effect of angiotensin 1-7 on dopamine concentration in the hypothalamus. Thus, angiotensin II and its active metabolite angiotensin 1-7 regulate selectively, albeit differentially, adrenergic, noradrenergic and dopaminergic systems in the hypothalamus, the effects that involve AT(1), AT(2) and AT(1-7) angiotensin receptors.

Propranolol prevents the development of venous thrombosis in rats by a platelet-dependent mechanism

To clarify if one of the most common antihypertensive drugs, propranolol, can prevent venous thrombotic process, rats were treated with propranolol (PRO; 5 mg/kg i.p.) in an acute or chronic (14 days) manner. Both regimens resulted in a marked reduction of the systolic blood pressure (p < 0.001) and, probably as a consequence, in the shortening of the bleeding time (p < 0.01). After ligation of the vena cava, the incidence of the venous thrombosis and the thrombus weight decreased significantly in both propranolol-treated groups (p < 0.01) when compared to control rats. The antithrombotic effect of PRO was not accompanied by any changes in activated partial thromboplastin time, prothrombin time or euglobulin clot lysis time. However, long-term administfation of PRO resulted in a reduction of the ADP-induced platelet aggregation.

Losartan inhibits the adhesion of rat platelets to fibrillar collagen--a potential role of nitric oxide and prostanoids

The aim of the study was to evaluate the effect of losartan on rat platelet adhesion to fibrillar collagen. Washed platelets were counted before and after 15 minutes incubation with collagen (50 microg/ml) and the percentage of adhering platelets was calculated as the index of their adhesion. When the platelets were incubated with collagen 40.8 +/- 0.3% of the platelets adhered. Losartan produced a dose dependent decrease in a number of adhering platelets both when the drug was administered to the animals ex vivo at doses of 3, 10 and 30 mg/kg (p < 0.01-0.001) or was added to the preparation of washed platelets in vitro in concentrations of 10(-8)-10(-5) M (p < 0.01-0.001). In the next step of the study we assessed the influence of L-NAME (10 mg/kg ex vivo, 30 microM in vitro) and indomethacin (2.5 mg/kg ex vivo, 30 microM in vitro) on the antiadhesive effect of losartan (10 mg/kg ex vivo, 10(-6) M in vitro). Blockade of nitric oxide synthase with L-NAME partially reversed the antiadhesive effect of losartan both ex vivo and in vitro. Indomethacin diminished the inhibitory effect of losartan on platelet adhesion when administered ex vivo, but it failed to modify this parameter when added to the suspension of platelets in vitro. In conclusion, losartan reduces platelet adhesion to fibrillar collagen in a dose-dependent manner. The observed action of losartan seems to be mediated mainly by endothelium- and platelet-derived nitric oxide.

Thiol repletion prevents venous thrombosis in rats by nitric oxide/prostacyclin-dependent mechanism: relation to the antithrombotic action of captopril

Clinical and experimental data have recently accumulated for antithrombotic action of angiotensin-converting enzyme inhibitors (ACE-1s). We have shown previously that captopril (which contains a thiol group in the moiety) exerts more pronounced antithrombotic activity than does an equipotent dose of enalapril (the drug devoid of the thiol group). To clarify the relative importance of the presence of the thiol group in the molecule versus angiotensin-converting enzyme (ACE) inhibitory properties in the antithrombotic action of captopril, rats were treated with captopril (5 mg/kg twice daily; CAP), epicaptopril (stereoisomer of captopril devoid of ACE-inhibitory properties; 5 mg/kg twice daily; EPI), N-acetylcysteine (3.75 mg/kg twice daily; ACC), enalapril (3 mg/kg once daily; ENA), or distilled water (VEH) for 10 days, per os. After ligation of the vena cava, the incidence of the venous thrombosis and/or the thrombus weight decreased significantly in all but the ENA-treated groups when compared with control rats. The effect of CAP, EPI, and ACC was accompanied by a marked reduction of euglobulin clot lysis time and, with the exception of ACC, by an increase in prothrombin time in the blood collected from the site of the thrombus formation. Antithrombotic activity of EPI was completely abolished by nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) or indomethacin, with the parallel reversal of fibrinolytic and coagulation parameters toward normal. Activated partial thromboplastin time, mean blood pressure, and bleeding time were not altered by either of the administered drugs. Thus, we demonstrated that thiol compounds exert antithrombotic activity by increasing fibrinolysis and/or suppression of the extrinsic pathway of the coagulation cascade in a nitric oxide/prostacyclin-dependent manner.

Attenuation of the acute amnestic effect of ethanol by ifenprodil: comparison with ondansetron and dizocilpine

The aim of the present study was to examine the influence of ifenprodil, a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist which also blocks 5-HT3 receptors, on the amnestic effect of ethanol in a passive avoidance task in mice. The anti-amnestic action of ifenprodil was compared with the effects of the 5-HT3 receptor antagonist ondansetron and the non-competitive NMDA-receptor antagonist dizocilpine (MK-801). Ethanol, 2 g/kg and dizocilpine 0.1 mg/kg significantly impaired the passive avoidance response. In contrast, ifenprodil (0.1-10 mg/kg), ondansetron (0.03-0.3 mg/kg) and dizocilpine (0.01 and 0.03 mg/kg) did not alter passive avoidance by themselves. Dizocilpine did not diminish the amnestic action of ethanol when administered at doses of 0.03-0.1 mg/kg. However, the amnestic effect of ethanol was partially restored towards normal by ifenprodil 0.3 mg/kg and by ondansetron 0.03 mg/kg (alone or together with dizocilpine 0.01 mg/kg) but it was not affected by other doses of ifenprodil (0.1, 1 and 10 mg/kg) and ondansetron (0.1 and 0.3 mg/kg). In conclusion, ifenprodil at an appropriate dose reduced ethanol-induced amnesia in a step-through passive avoidance task. The results are compatible with the assumption that the anti-amnestic action of ifenprodil may be (at least partially) due to an antagonism at 5-HT3 receptors.

Hypotensive effect of angiotensin II after AT1-receptor blockade with losartan

Recent data suggest that hypotensive effect of losartan may not be attributed solely to AT1-receptor blockade, but also to excessive AT2 or other receptors stimulation by elevated angiotensin II and its derivative peptides. Therefore in the present study we examined the effect of angiotensin II on mean blood pressure after AT -receptor blockade with losartan. Male Wistar rats were anaesthetised and received injection of either losartan (30 mg/kg, 1 ml/kg, i.v.) or saline (the same volume and route) followed by bolus injection of angiotensin II (100, 300 or 1,000 ng/kg; 1 ml/kg, i.v.) or 1-hour infusion of angiotensin II (200 ng/kg/min; 2.5 ml/kg/h, i.v.). Control animals received saline instead. Angiotensin II, given either as the injection or the infusion, caused an evident increase in mean blood pressure (p ranged from 0.05 to 0.001 depending on the experimental group). Losartan caused a rapid drop in mean blood pressure and blunted the hypertensive effect of angiotensin II (p < 0.01). Moreover, in the losartan-pretreated animals the hypotensive phase was enhanced by the infusion, but not single injection of angiotensin II, which was most evident from the 30 th minute of observation (p < 0.05 vs control). In conclusion, hypotensive effect of losartan may be amplified by simultaneous increase in angiotensin II level, the situation observed during chronic AT1-receptor blockade.

Differential effects of nicotine against stress-induced changes in dopaminergic system in rat striatum and hippocampus

A number of studies have shown an increase in nicotine self-administration among smokers when exposed to stress. Since it is well known that nicotine or stress alter the dopaminergic system, we examined the effect of chronic nicotine administration on the dopamine level and its metabolism in the striatum and the hippocampus during stressful conditions in rats. Nicotine (0.4 mg/kg, i.p. for 14 days) increased the dopamine level in the striatum (P<0. 05) and decreased it in the hippocampus (P<0.05) in comparison with the effect of saline. Three hours of water-immersion restraint stress sharply elevated the dopamine level (P<0.05) and reduced the 3-methoxytyramine level (P ranged from 0.05 to 0.001 depending on the area and time point) in both brain regions studied, while dihydroxyphenylacetic acid and homovanilic acid levels were not altered. Nicotine pretreatment attenuated some of these changes in a region- and time-dependent manner. However, stress induced a decrease in dopamine turnover in the hippocampus (P<0.05) but not in the striatum, and nicotine failed to prevent this effect. Stress-induced alterations gradually returned toward normal during the 48-h observation period, and in some cases this was facilitated by nicotine. Thus, we demonstrated differential, region- and time-dependent protective effects of chronic nicotine administration against stress-induced changes in dopamine levels and release in brain regions critically affected by stress.

Nicotine attenuates stress-induced changes in plasma amino acid concentrations and locomotor activity in rats

It is known that stressor stimuli (both systemic and processive) and nicotine activate central nervous system. Surprisingly, numerous studies have demonstrated an increase in nicotine self-administration among smokers when exposed to stress in order to reduce the stress-related tension. Therefore, in the present study, we decided to investigate the influence of nicotine on both behavioral (i.e., on locomotor activity) and metabolic (i.e., on the level of amino acids in the plasma) changes following water immersion restraint stress in rats. As expected, the stress produced evident decline in locomotor activity of the rats (p < 0.001) and in the levels of all plasma amino acids studied (p < 0.05). Nicotine alone also significantly reduced locomotor activity (p < 0.05) and the levels of some plasma amino acids. However, when administered to rats subjected to water immersion and restraint, nicotine attenuated both stress-induced decrease in locomotor activity (p < 0.05) and in some plasma amino acids. Thus, this study demonstrated that the mode of action of nicotine is strongly dependent on the level of initial brain activity, which provide new evidence for arousal-modulation model of nicotine action.

Ifenprodil influences changes in mouse behaviour related to acute and chronic ethanol administration

The aim of the present study was to examine the influence of ifenprodil (a non-competitive NMDA receptor antagonist which also blocks 5-HT3 receptors and alpha1-adrenoceptors) on the effects of ethanol in the mouse in vivo and to elucidate the role of various receptors in these actions. The ethanol (4 g/kg i.p.)-induced sleeping time was shortened by ifenprodil 1 mg/kg but was not affected by ifenprodil 0.3 mg/kg, the 5-HT3 receptor antagonist ondansetron 0.03 mg/kg and the non-competitive NMDA receptor antagonist MK-801 ((+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cycloheptan-5,10-imine maleate) 0.01 mg/kg. Ifenprodil 10 mg/kg mimicked the alpha1-adrenoceptor antagonist prazosin 1 mg/kg in that it prolonged the hypnotic response to ethanol (no additive effect when both drugs were given in combination); this is compatible with an involvement of alpha1-adrenoceptors in this effect of ifenprodil. Chronic exposure to ethanol (7%) induced physical dependence. The severity of ethanol withdrawal was suppressed by ifenprodil 1 and 10 mg/kg. In conclusion, ifenprodil influences ethanol-related changes in mouse behaviour and may prove to be useful in the treatment of alcoholism.

Antithrombotic activity of losartan in two kidney, one clip hypertensive rats. A study on the mechanism of action

The potential antithrombotic action of losartan, an AT1 receptor antagonist, administered to two-kidney, one-clip rats (2K1C) in an experimental model of venous thrombosis was evaluated. The involvement of nitric oxide (NO) in this effect was also studied. Venous stasis was induced by ligation of the vena cava. Losartan after single dose (10 mg/kg, p.o.) significantly reduced the venous thrombus growth. The antithrombotic action of losartan in 2K1C rats was abolished by N(G)-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg s.c.) and restored by L-arginine (1000 mg/kg s.c.). Platelet adhesion to fibrillar collagen significantly decreased after administration of losartan. No changes in primary hemostasis and platelet aggregation were observed. Moreover, coagulation parameters such as activated partial thromboplastin time, prothrombin time and euglobulin clot lysis time were found unchanged after losartan administration either in systemic circulation or at the place of thrombus formation. Our results indicate that antithrombotic activity of losartan in 2K1C rats is NO--dependent; observed inhibition of platelet adhesion could also play a role in this phenomenon.

Losartan inhibits experimental venous thrombosis in spontaneously hypertensive rats

The potential antithrombotic action of losartan, the AT1 receptor antagonist, in an experimental model of venous thrombosis in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) was tested. The involvement of nitric oxide and prostacyclin in this effect was also studied. Venous stasis was induced by ligation of the vena cava. Losartan, after administration of a single, hypotensive dose (10 mg/kg, p.o.), significantly reduced the thrombus weight in SHR but not in WKY. The antithrombotic activity of losartan in SHR was abolished by NG-nitro L-arginine methyl ester (L-NAME) (30 mg/kg s.c.) but not by indomethacin (2.5 mg/kg s.c.). No changes in primary hemostasis, platelet aggregation, coagulation parameters such as activated partial thromboplastin time, prothrombin time, euglobulin clot lysis time, and fibrinogen level, either in SHR or in WKY rats, were found. Our results indicate the NO-dependent mechanism in the antithrombotic effect of losartan on venous thrombosis in SHR.

The antithrombotic effect of captopril and losartan on experimental arterial thrombosis in rats

The mechanism by which ACE-Is (angiotensin converting enzyme inhibitors) reduces the rate of coronary thrombosis among patients with left ventricular dysfunction is not known. A potential interaction between the renin-angiotensin system (RAS) and the thrombotic process has been suggested. The goal of the present study was to evaluate the antithrombotic action of drugs which block the RAS by different mechanisms; captopril (50 mg/kg p.o.)-the angiotensin converting enzyme inhibitor and losartan (30 mg/kg p.o.)-the selective AT1 receptor antagonist. The normotensive rats were treated in acute or chronic manner (7 days) and then the arterial thrombosis was induced by insertion of a loop-shaped cannula into the abdominal aorta. The occlusion time (the period during which the loop was totally occluded by thrombus) was significantly prolonged in comparison with the control groups after chronic treatment with captopril (by 46%; p < 0.01) and losartan (by 42%; p < 0.05). Our results provide experimental evidence that the drugs blocking RAS exert an antithrombotic effect in the arterial thrombosis model in rats. This effect was independent from changes in blood pressure and primary hemostasis.

Nitric oxide and prostacyclin are involved in antithrombotic action of captopril in venous thrombosis in rats

The long-term administration of captopril to patients with a left ventricular dysfunction after myocardial infarction reduces the rate of recurrent coronary thrombosis. Thus, in the present study we investigated the influence of angiotensin-converting enzyme inhibitors (ACE-Is) on experimental venous thrombosis in normotensive rats and the involvement of NO and PGI2 in this effect. Animals were treated with captopril (1.5, 5 or 25 mg/kg twice daily, CAP), enalapril (15 mg/kg once daily, ENA) or distilled water for 10 days, per os. After ligation of the vena cava the thrombus weight decreased in both CAP and ENA treated rats. The effect was most pronounced in animals given the highest dose of CAP (p<0.0001 vs. control) and was significantly stronger than observed in ENA treated animals (CAP vs. ENA p<0.01). The mean blood pressure measured by the "tail cuff" method and platelet aggregation were not altered by either of the ACE-Is. The antithrombotic activity of CAP was reduced by indomethacin (2.5 mg/kg, s.c.) and independently by the NO-synthase inhibitor N(G)-nitro L-arginine methyl ester (3 mg/kg i.v. bolus + 3 mg/kg/h i.v. infusion, L-NAME). In the latter case CAP regained its antithrombotic properties in rats pretreated with L-Arginine (300 mg/kg i.v. + 300 mg/kg/h i.v.) before administration of L-NAME (p<0.05 vs. control). Moreover, the concomitant administration of indomethacin and L-NAME failed to completely abolish the antithrombotic action of captopril. Similar effects were observed in respect to the incidence of venous thrombosis. Our study documents a novel and important effect of ACE-Is on the vein thrombotic process and demonstrates the involvement of NO and PGI2 in this phenomenon.

Cyclosporine A affects serotonergic mechanisms in uremic rats

The aim of this study was to investigate the mechanism of cyclosporine-induced hypertension in respect to its action on blood serotonergic system. The experiment was carried out on healthy rats and animals with experimental chronic renal failure. Cyclosporine A (CsA) injected into the healthy and uremic rats caused an increase in systolic blood pressure. This effect was completely abolished by ketanserin, an antagonist of 5-HT2 receptors. Concomitantly a rise in blood and platelet serotonin concentration was observed. It is concluded that serotonin may play a role in the development of hypertension caused by CsA. Moreover, ketanserin may serve as a drug for pharmacological protection of CsA-induced rise of blood pressure in uremia.

Effects of drugs affecting the renin-angiotensin system on venous thrombosis in normotensive rats

The aim of this study was to compare the potential antithrombotic action of captopril (angiotensin converting enzyme inhibitor) and losartan (a selective AT1 receptor antagonist) after their chronic administration in a model of venous thrombosis in rats. Captopril significantly reduced the incidence of venous thrombosis (67% vs 14%; p < 0.05) and both drugs markedly reduced the weight of thrombus. At the same time the platelet aggregation was reduced only in rats treated with losartan (100 +/- 7% vs 52 +/- 11%; p < 0.001). The mean blood pressure dropped only after losartan administration. We observed no changes in "transection" bleeding time after both drugs administration. In conclusion, captopril and losartan exerted an antithrombotic effect in venous thrombosis model in rats. The precise mechanism of this action should be established.

Losartan does not influence the blood platelet aggregation in normotensive rats

Platelet aggregation was studied in PRP upon stimulation with ADP and collagen in normotensive rats treated with losartan (10 mg/kg). The acute and subchronic (5 days) losartan administration did not change the aggregating response of rat platelets. Similarly, in vitro study aggregation of platelets remained unaltered following incubation with losartan and its active metabolite EXP3174. In this study we presented the lack of influence of losartan and its main metabolite on rat platelet aggregation in normotensive rats.

Influence of captopril on some haemostatic parameters in rats with ongoing process of venous thrombosis

Recent laboratory findings strongly suggest that renin-angiotensin system plays an important role in regulation of haemostasis and fibrinolysis. In our previous study we showed that captopril exerts antithrombotic effect in venous thrombosis in rats. In this study we demonstrated that this effect is not a result of changes in platelet count, fibrinogen level alterations in blood coagulation pathways and fibrinolytic activity of the plasma. Further investigations are necessary to elucidate the mechanism of antithrombotic action of captopril.

Effect of endothelin-1 on some hemostatic parameters in normotensive rats

Some parameters of hemostasis and fibrinolysis were investigated in rats administered with endothelin-1 (ET-1). ET-1 (0.5, 1.0, 5.0 nmol/kg) dose-dependently shortened the bleeding time (BT). Concomitantly significant shortening of the clotting time (CT) was observed. ET-1 produced prolongation of the activated partial thromboplastin time (APTT), whereas prothrombin time (PT) remained unchanged. ET-1 did not influence in vitro platelet aggregation induced by ADP and collagen. The euglobulin clot lysis time (ECLT) was significantly shortened after ET-1 administration. Our results suggest that ET-1 modulates the process of hemostasis and fibrinolysis in the rat.

Antithrombotic effect of enalapril, an angiotensin-converting enzyme inhibitor, on venous thrombosis in rats

The aim of the study was to investigate the potential antithrombotic action of enalapril in comparison with captopril after their acute and chronic administration in an experimental model of venous thrombosis in rats. Chronic treatment with captopril but not enalapril significantly reduced the incidence of venous thrombosis (67% vs 11%; p < 0.05). Both drugs markedly reduced the weight of thrombus. At the same time the platelet aggregation was reduced in rats acutely treated with both captopril and enalapril to 50 +/- 13% and 53 +/- 18%, respectively. The mean blood pressure dropped only after acute ACE-Is administration. No changes were observed in "transection" bleeding time. In conclusion, captopril and enalapril were able to inhibit the growth of thrombus in rats. Their antithrombotic effect seems to be independent from hypotensive action and influence on platelet aggregation.