BK channel openers inhibit ROS production of isolated rat brain mitochondria

To delineate the potential mechanism of neuroprotective effects of potassium channel openers we have investigated, how Ca²⁺-activated large conductance potassium channel (BK_Ca channel) openers influence the production of reactive oxygen species (ROS) by rat brain mitochondria, since mitochondrial generation of ROS is known to have a crucial influence on neuronal survival. We studied the effects of BK_Ca channel openers CGS 7184 and NS 1619 on hydrogen peroxide production rate of isolated rat brain mitochondria. In K⁺-containing media 3 μM of both channel openers reduced the hydrogen peroxide production rates by approximately 20%. This effect was not observed in Na⁺-containing media. This potassium-dependent partial inhibition of hydrogen peroxide production was found to be sensitive to the selective blockers of BK_Ca channel iberiotoxin and charybdotoxin applied in nanomolar concentrations. Taken together, our data are compatible with the viewpoint that the opening of a Ca²⁺-activated large conductance potassium channel being localised in the inner membrane of brain mitochondria inhibits ROS production by respiratory chain complex I. This finding is suggested to explain the beneficial effects of BK potassium channel openers on neuronal survival.     

Impact of cladribine on soluble adhesion molecules in multiple sclerosis

Mitosek‐Szewczyk K, Stelmasiak Z, Bartosik‐Psujek H, Belniak E. Impact of cladribine on soluble adhesion molecules in multiple sclerosis.
Acta Neurol Scand: 2010: 122: 409–413.
© 2010 The Authors Journal compilation © 2010 Blackwell Munksgaard. Background – Soluble forms of vascular cell adhesion molecule‐1 (VCAM‐1), intracellular adhesion molecule‐1 (ICAM‐1) and E‐Selectin play a role in the regulation of blood–brain barrier damage and represent markers of the clinical course of multiple sclerosis (MS) and magnetic resonance imaging activity. We determined sICAM, sVCAM and sE‐Selectin concentrations in the cerebrospinal fluid (CSF) and serum of patients with remitting–relapsing multiple sclerosis before and after cladribine treatment as well as in a control group. Methods – We examined 17 patients diagnosed according to McDonald’s criteria. Thirteen healthy age‐matched subjects served as controls. The ELISA method was used to measure sICAM‐1, sVCAM‐1 and sE‐Selectin. Results – The concentration of sICAM and sE‐Selectin decreased in sera (difference between patients and controls was statistically significant, in the former P < 0.04, in the latter P < 0.0003) but not in the CSF of MS patients after cladribine treatment. Conclusions – The reduction in sICAM and sE‐Selectin concentrations after cladribine treatment indicates an immuno‐suppressive effect of the drug. The changes in levels of sICAM and sE‐Selectin after cladribine treatment reflect disease activity and indicate a reduction in the inflammatory reaction.     

Lipid metabolism as a target for potassium channel effectors

K(+) channel effectors are widely used in the treatment of various diseases, including diabetes mellitus type II, hypertension, and cardiac arrhythmia. In addition, a constantly growing body of literature reveals that some of these substances, despite their direct effect on K(+) channels, may influence cellular lipid metabolism. As a result, membrane lipid content and cellular concentrations of lipid messengers are changed. Due to the dependence of K(+) channel activity on membrane lipids, these observations seem to be of particular importance not only to characterize secondary effects of K(+) channel effectors but also to understand the long-term effects of these agents on K(+) channel activity.     

Antidepressant- and anxiolytic-like activity of magnesium in mice

The antidepressant- and anxiolytic-like effects of magnesium, an N-methyl-d-aspartate (NMDA) glutamate receptor inhibitor, were studied in mice using the forced swim test and elevated plus-maze test, respectively. The doses of 20 and 30 mg Mg/kg, reduced immobility time in the forced swim test exerting antidepressant-like activity. In the elevated plus-maze test, magnesium at the same doses produced anxiolytic-like effect. The doses of magnesium active in both tests did not affect locomotor activity. To evaluate the tolerance to these effects, we also performed experiments on the following acute/chronic magnesium treatment schedule: chronic saline and saline challenge at 0.5 h before behavioral experiments or serum magnesium determination (S+S), chronic saline and magnesium challenge (S+Mg), chronic magnesium and saline challenge (Mg+S), chronic magnesium and magnesium challenge (Mg+Mg). The antidepressant- and anxiolytic-like effect of magnesium was demonstrated in groups treated acutely and chronically with magnesium (Mg+Mg), but not in the Mg+S group. Moreover, these effects seem to be connected with at least 58% increase in serum magnesium concentration. The results indicate that magnesium induces the antidepressant- and anxiolytic-like effects without tolerance to these activities, which suggests a potential antidepressant and anxiolytic activity of magnesium in these disorders in humans.     

Computerized color-vision test based upon postreceptoral channel sensitivities

An automated, computerized color-vision test was designed to diagnose congenital red-green color-vision defects. The observer viewed a yellow appearing CRT screen. The principle was to measure increment thresholds for three different chromaticities, the background yellow, a red, and a green chromaticity. Spatial and temporal parameters were chosen to favor parvocellular pathway mediation of thresholds. Thresholds for the three test stimuli were estimated by four-alternative forced-choice (4AFC), randomly interleaved staircases. Four 1.5-deg, 4.2 cd/m2 square pedestals were arranged as a 2 x 2 matrix around the center of the display with 15-minute separations. A trial incremented all four squares by 1.0 cd/m2 for 133 ms. One randomly chosen square included an extra increment of a test chromaticity. The observer identified the different appearing square using the cursor. Administration time was approximately 5 minutes. Normal trichromats showed clear Sloan notch as defined by log (deltaY/deltaR), whereas red-green color defectives generally showed little or no Sloan notch, indicating that their thresholds were mediated by their luminance system, not by the chromatic system. Data from 107 normal trichromats showed a mean Sloan notch of 0.654 (SD = 0.123). Among 16 color-vision defectives tested (2 protanopes, 1 protanomal, 6 deuteranopes, & 7 deuteranomals), the Sloan notch was between -0.062 and 0.353 for deutans and was < -0.10 for protans. A sufficient number of color-defective observers have not yet been tested to determine whether the test can reliably discriminate between protans and deutans. Nevertheless, the current data show that the test can work as a quick diagnostic procedure (functional trichromatism or dichromatism) of red-green color-vision defect.     

Anxiolytic action of group II and III metabotropic glutamate receptors agonists involves neuropeptide Y in the amygdala

Several lines of evidence indicate that activation of group II and III metabotropic glutamate (mGlu) receptors produces anxiolytic-like effects in rodents. On the other hand neuropeptide Y (NPY) induces an anxiolytic effect in rats after intraventricular or intraamygdalar administration. Therefore, in the present study we investigated whether the anxiolytic action of (2S,3S,4S)-(carboxycyclopropyl)glycine (L-CCG-I), an mGlu2/3 receptor agonist, and (1S,3R,4S)-1-aminocyclopentane-1,3,4-tricarboxylic acid (ACPT-1), an mGluR4/6/7/8 receptor agonist, was mediated by a mechanism involving NPY receptor. In behavioral studies, the anxiolytic activity of L-CCG-I (10 microg/0.5 microl/site) and ACPT-1 (1.5 microg/0.5 microl/site) was examined using plus-maze tests. The Y1 receptor antagonist BIBO 3304 was given at a dose of 128 ng/0.5 microl/site. All the compounds tested were injected bilaterally into the amygdala, BIBO 40 min and mGluR agonists 30 min before the test. It was found that the anxiolytic effects of mGluR agonists were abolished by BIBO 3304 {((R)-N-[[4-(aminocarbonylaminomethyl) phenyl] methyl]-N2-(diphenylacetyl)-argininamide trifluoroacetate)3304} administration. Immunohistochemical studies showed a moderate density of mGlu2/3 receptor immunoreactivity (IR) in the amygdala. The effect of L-CCG-I and ACPT-1 on NPY expression in the amygdala was studied using immunohistochemistry (IH), while NPYmRNA expression was studied using in situ hybrydization. We showed a diminution in NPY-IR after L-CCG-I administration and decrease in NPYmRNA expression after both L-CCG-I and ACPT-1 treatment, to about 77% (IH) or 32-41% (mRNA) of the control level 18 h after injection of these mGluR agonists. Our results indicate that the anxiolytic action of both compounds is conveyed by NPY neurons with the involvement of Y1 receptors in the amygdala, and that NPY neurons seem to be regulated by the glutamatergic system.     

Characterization of changes in the short unique segment of pseudorabies virus BUK-TK900 (Suivac A) vaccine strain

Summary. Mutant strains of pseudorabies virus (PRV) of reduced virulence, such as Bartha or BUK-TK900, have been used for vaccination purposes for many years. In contrast to the Bartha strain, BUK-TK900 has not been well characterised at the molecular level. The detailed analysis of this vaccine strain was urged by the fact of the isolation in Poland of field strains which were suspected to originate from BUK-TK900.We characterised changes in the U_S region of this strain, focusing our attention on gE and gI genes. The only deletion, about 300bp, found in BamHI 7 fragment (covering most of the U_S region) was located in the 28K (US2) gene. BUK-TK 900 produced small plaques on all cell lines tested in our laboratory (SK6, Vero, MDBK, 3T3). The plaque size was restored to about 70% of wild type virus plaque size when growing BUK-TK900 virus on 3T3 complementing cell line expressing PRV gE and up to 100% when cell line producing gE and gI was used. Both gE and gI genes from BUK-TK900 and from some derivative field isolates have been amplified by PCR reaction but no deletions in these genes have been found. Molecular weight of gene products differed from wild type proteins: gE was bigger than wild type gE while gI was smaller. Both proteins were correctly recognised by all tested polyclonal and monoclonal antibodies. Radioimmunoprecipitation study showed that BUK-TK900 gE and gI interact forming a complex. The whole ORF of BUK-TK900 gE was sequenced and only few point mutations were found; only two of them led to changes of amino acids in the polypeptide chain. These were: methionine at position 124 replaced by threonine and glutamine at position 162 replaced by arginine. The introduction of first of these mutations (Met to Thr) to PRV wild type strain NIA-3 resulted in 22% reduction of plaque size. This result confirms the importance of this domain of gE for its function; it was found previously by others that deletion of amino acids 125 and 126 reduced virulence and neurotropism of PRV. More changes were found in BUK-TK900 gI sequence. Over 80% of these changes were located in the terminal 1/3rd of the sequence. Some of these mutations may have significant effect on the secondary structure of gI glycoprotein. The change of the secondary structure may be responsible for the decrease of gI stability and the observed reduction of gI molecular mass.Present address: Cedi-Diagnostics B.V., Lelystad, The Netherlands.Received May 4, 2001; accepted March 18, 2003 Published online June 11, 2003     

CCK1R agonists: a promising target for the pharmacological treatment of obesity

Almost 30 years have passed since Gibbs, Young, and Smith demonstrated the ability of exogenously administered cholecystokinin (CCK) to inhibit food intake in rats. This observation was the beginning of very extensive studies into the role CCK plays in the regulation of food intake in mammals. CCK is a brain-gut peptide, which exists in multiple forms. CCK peptides exert their action on two distinct receptor subtypes: CCK-A (Alimentary) now called the CCK1R, mostly expressed peripherally; and CCK-B (Brain), renamed the CCK2R, which is primarily present in the brain. Through the use of subtype-selective agonists and antagonists for the CCK receptor, it was determined that the effect of CCK on feeding was dependent on agonist induced activation of peripheral CCK1 receptors. This discovery was followed by intense research with the goal of identifying small molecule agonists on the CCK1 receptor as potentially useful agents for the treatment of obesity. This review will attempt to summarize the results of this research.     

Predominant staphylococci in the intensive care unit of a paediatric hospital

Coagulase-negative staphylococci cause a significant number of infections, especially in immunocompromised patients, including premature neonates. Nosocomial strains present in the environment create a special risk.We studied staphylococci isolated from the intensive care unit of a paediatric teaching hospital over the period of six months in 1997. Biotyping and species identification were performed; resistance to methicillin and other beta-lactam antibiotics and patterns of resistance to antimicrobial agents were determined.Staphylococcus cohnii was the predominant species of 147 isolates of staphylococci recovered from the ward environment. Strains were resistant to several antibiotics and 97% were resistant to methicillin. In isolates from infants (72) methicillin-resistant strains of Staphylococcus epidermidis were predominant. Susceptibility to beta-lactams (penicillin, amoxycillin, amoxycillin-clavulanic acid and cephalosporins: cephalothin, cefuroxime and cefotaxime) showed differences between the two species. Some S. cohnii were susceptible to penicillin and amoxycillin despite methicillin-resistance. S. epidermidis were relatively susceptible to amoxycillin-clavulanic acid and cephalosporins. All strains investigated were susceptible to vancomycin, but nearly 30% demonstrated high-level resistance to mupirocin. The search for strains of the same origin showed clones belonging to S. epidermidis, S. hominis and S. saprophyticus but not S. cohnii.A large number of multiresistant, phenotypically different S. cohnii strains surviving in the ward environment may provide a reservoir of antimicrobial resistance genes.