Schiff bases as potential fungicides and nitrification inhibitors

A number of substituted Schiff bases were synthesized and characterized by (1)H NMR and mass spectrometry. These compounds were screened for antifungal activity in vitro against pathogenic fungi, namely, Sclerotium rolfsii and Rhizoctonia bataticola, and for their effect on nitrification inhibition under laboratory conditions. Maximum antifungal activity was exhibited by (2,4-dichlorobenzylidene)-(2,4,5-trichlorophenyl)-amine and (3-nitrobenzylidene)-(2,4,5-trichlorophenyl)-amine against both fungi (ED(50) with range from 3 to 24 microg/mL). Maximum nitrification inhibition (NI) was exhibited by (2,4-dichlorobenzylidene)-(2-fluorophenyl)-amine, (4-fluorophenyl)-(3-nitrobenzylidene)-amine, (2,6-dichlorobenzylidene)-(4-fluorophenyl)-amine, and (2,6-dichlorobenzylidene)-(3 fluorophenyl)-amine (NI in the range 91-96%).

Alpha,beta-poly(L-aspartate-graft-PEI): A pseudo-branched PEI as a gene carrier with low toxicity and high transfection efficiency

The aim of this research is to develop a novel branched polyethylenimine (PEI)-like polycation as a potential gene carrier with high gene transfection efficiency and low toxicity. In particular, alpha,beta-poly(l-aspartate-graft-PEI) (Asp-g-PEI), a pseudo-branched PEI, was synthesized by the ring-opening reaction of poly(l-succinimide) (PSI) with low molecular weight branched PEI (LMW PEI, MW=600 and 1200). Good plasmid condensation and protection ability of Asp-g-PEI were confirmed by agarose gel electrophoresis assay. Asp-g-PEI/DNA complexes showed high positive zeta potential, narrow size distribution, good dispersity and a compact spherical shape with size below 250nm when the N/P ratio was above 5, suggesting that they can be endocytosed. Cytotoxicity of Asp-g-PEI/DNA complexes was rather lower than that of PEI25K/DNA complexes, especially at high N/P ratio. The most efficient gene transfection of Asp-g-PEI/DNA complexes was similar or a little higher than that of PEI25K in 293T, HeLa and HepG2 cell lines, while almost 4 and 6 times higher than that of parent PEI1200 and PEI600, respectively, in HeLa cell line; as the molecular weight of parent PEI in Asp-g-PEI was increased from 600 to 1200, the transfection efficiency showed a tendency to decrease. The mechanism of Asp-g-PEI-mediated gene transfection was attributed to the "proton sponge effect" due to PEI in the copolymer.

Influence of several fungicides on the antioxidant activity of red wines (var. Monastrell)

The antioxidant activity of wines obtained from grapes treated with six fungicides (famoxadone, fenhexamid, fluquinconazole, kresoxim-methyl, quinoxyfen and trifloxystrobin) was investigated. Two field trials in triplicate were carried out for each formulation of the fungicide at the recommended dose of the manufacturer. The first trial was carried out under good agricultural practices (GAP), following the recommended pre-harvest interval, and the second one under critical agricultural practices (CAP) that involves treating the same field just before the harvest. The residue levels were determined by gas and liquid chromatography coupled to mass detectors (GC-MS and LC-MS). The antioxidant activity was determined in the wines obtained from the thirteen trials including one control, six from treated grapes obeying the pre-harvest interval, and six from grapes treated at the day of harvest or at most unfavorable conditions. Elimination of 40-100% of the initial fungicide residues present in grapes was observed during the wine-making process. It can be inferred from the results that the use of these fungicides did not produce any decrease of the antioxidant activity in the wines (7.19 +/- 0.22 mmol Trolox/L for the blank wine versus a range of 6.45 +/- 0.82 mmol Trolox/L to 10.06 +/- 0.59 mmol Trolox/L for the treated wines) at the pre-harvest interval and most unfavorable conditions. Nevertheless, the presence of famoxadone, kresoxim-methyl and quinoxyfen increased the antioxidant activity and this was directly related to their residue levels in the grapes. Also, the wine phenolic composition was altered in variable intensity by the presence of the fungicide residues.

Pituitary adenylate cyclase-activating polypeptide induces somatolactin release from cultured goldfish pituitary cells

In the goldfish pituitary, nerve fibers containing pituitary adenylate cyclase-activating polypeptide (PACAP) are located in close proximity to somatolactin (SL)-producing cells, and PACAP enhances SL release from cultured pituitary cells. However, there is little information about the mechanism of PACAP-induced SL release. In order to elucidate this issue, we used the cell immunoblot method. Treatment with PACAP at 10(-8) and 10(-7)M, but not with vasoactive intestinal polypeptide (VIP) at the same concentrations, increased the immunoblot area for SL-like immunoreactivity from dispersed pituitary cells, and PACAP-induced SL release was blocked by treatment with the PACAP selective receptor (PAC(1)R) antagonist, PACAP(6-38), at 10(-6)M, but not with the PACAP/VIP receptor antagonist, VIP(6-28). PACAP-induced SL release was also attenuated by treatment with the calmodulin inhibitor, calmidazolium at 10(-6)M. This led us to explore the signal transduction mechanism up to SL release, and we examined whether PACAP-induced SL release is mediated by the adenylate cyclase (AC)/cAMP/protein kinase A (PKA)- or the phospholipase C (PLC)/inositol 1,4,5-trisphosphate (IP(3))/protein kinase C (PKC)-signaling pathway. PACAP-induced SL release was attenuated by treatment with the AC inhibitor, MDL-12330A, at 10(-5)M or with the PKA inhibitor, H-89, at 10(-5)M. PACAP-induced SL release was suppressed by treatment with the PLC inhibitor, U-73122, at 3 x 10(-6)M or with the PKC inhibitor, GF109203X, at 10(-6)M. These results suggest that PACAP can potentially function as a hypophysiotropic factor mediating SL release via the PAC(1)R and subsequently through perhaps the AC/cAMP/PKA- and the PLC/IP(3)/PKC-signaling pathways in goldfish pituitary cells.

A cellular model for screening neuronal nitric oxide synthase inhibitors

Nitric oxide synthase (NOS) inhibitors are potential drug candidates because it has been well demonstrated that excessive production of nitric oxide critically contributes to a range of diseases. Most inhibitors have been screened in vitro using recombinant enzymes, leading to the discovery of a variety of potent compounds. To make inhibition studies more physiologically relevant and bridge the gap between the in vitro assay and in vivo studies, we report here a cellular model for screening NOS inhibitors. Stable transformants were generated by overexpressing rat neuronal NOS in HEK 293T cells. The enzyme was activated by introducing calcium ions into cells, and its activity was assayed by determining the amount of nitrite that was formed in culture medium using the Griess reagent. We tested a few NOS inhibitors with this assay and found that the method is sensitive, versatile, and easy to use. The cell-based assay provides more information than in vitro assays regarding the bioavailability of NOS inhibitors, and it is suitable for high-throughput screening.

Antimicrobial evaluation of imines and thiazolidinones derived from 3-phenylpropane hydrazide

Methyl 3-phenylpropanoate (1), after hydrazination into 3-phenylpropanehydrazide (2), was converted into N-arylidene-3-phenylpropane hydrazides (3a-e), which on cyclization with thioglycolic acid yielded N-(4-oxo-2-arylthiazolidin-3-yl)-3-phenylpropanamides (4a-e). All the proposed structures of newly synthesized compounds were in full agreement with the spectral data. Due to para substitution, compound 3a, 4a and 4b were found to be the most potent when evaluated for antibacterial and antifungal activities.

Microwave assisted solvent-free synthesis and biological activities of novel imines (Schiff bases)

Twelve new ortho-Hydroxyketimines were synthesized by conventional as well as microwave method and evaluated for their antinemic activity against Meloidogyne incognita [(Kofoid and White) Chitwood]. Conventional methods for synthesis of Schiff bases require refluxing at 140 degrees C of the reactants in different solvents for at least 24 h or more, where as the microwave-assisted synthesis has brought down the reaction time from 24 h to 1 minute. The procedure reported is simple as it does not require any organic solvents and the time has been reduced to only 1 minute. Comparative yields of all compounds by different methods revealed that the yield was low in conventional method (79-87%) as compared to microwave assisted synthesis (94-97%). The bioassay revealed that all the test compounds exhibited promising nematicidal activity; N-propyl-2-hydroxypropiophenonimine being the most effective with LC(50) value of 74.46 mgL(-1) followed by N-hexyl-2-hydroxyacetophenonimine with LC(50) value of 99.60 mgL(-1) after 72 h of exposure. The results obtained from bioassay indicated that this class of compounds has not only given a lead with regard to potential of Schiff bases in pest control, but has suggested that a carbon chain length of 6 atoms in the side chain is optimum on the basis of structure activity relationship (SAR).

Synthesis, characterization and antimicrobial evaluation of novel imines and thiazolidinones

2-(4-Chloro-3-methylphenoxy)acetohydrazide (2) derived from ethyl 2-(4-chloro-3-methylphenoxy) acetate (1) was reacted with different aromatic aldehydes to yield N-(substituted benzylidiene)-2-(4-chloro-3-methylphenoxy)acetamide (3a-e). Cyclization of compound (3a-e) with thioglycolic acid yielded 2-(4-chloro-3-methylphenoxy)-N-(4-oxo-2-arylthiazolidin-3-yl) acetamide (4a-e). The newly synthesized compounds were characterized on the basis of spectral studies and evaluated for antibacterial and antifungal activities.

The drug transporter MgMfs1 can modulate sensitivity of field strains of the fungal wheat pathogen Mycosphaerella graminicola to the strobilurin fungicide trifloxystrobin

BACKGROUND

The major facilitator superfamily (MFS) drug transporter MgMfs1 of the wheat pathogen Mycosphaerella graminicola (Fuckel) J Schroeter is a potent multidrug transporter with high capacity to transport strobilurin fungicides in vitro. The data presented in this paper indicate that, in addition to the predominant cause of strobilurin resistance, cytochrome b G143A subsititution, MgMfs1 can play a role in sensitivity of field strains of this pathogen to trifloxystrobin.

RESULTS

In a major part of field strains of M. graminicola (collected in the Netherlands in 2004) containing the cytochrome b G143A substitution, the basal level of expression of MgMfs1 was elevated as compared with sensitive strains lacking the G143A substitution. Induction of MgMfs1 expression in wild-type isolates upon treatment with trifloxystrobin at sublethal concentrations proceeded rapidly. Furthermore, in disease control experiments on wheat seedlings, disruption mutants of MgMfs1 displayed an increased sensitivity to trifloxystrobin.

CONCLUSION

It is concluded that the drug transporter MgMfs1 is a determinant of strobilurin sensitivity of field strains of M. graminicola.

Dual action of nitric oxide in the pathogenesis of ischemia/reperfusion-induced mucosal injury in mouse stomach

AIM

We investigated the roles of NO/NOS isoforms in the pathogenesis of ischemia/reperfusion (I/R)-induced gastric injury in mouse stomachs.

METHODS

Under urethane anesthesia, the celiac artery was clamped, and then reperfusion was established 30 min later by removal of the clamp. After a 60-min reperfusion, the stomach was examined for macroscopic lesions.

RESULTS

Following I/R, hemorrhagic lesions were generated in the mucosa, although ischemia alone caused no visible damage. Prior administration of L-NAME (a nonselective NOS inhibitor) significantly aggravated these lesions, in a L-arginine-inhibitable manner. By contrast, the selective iNOS inhibitor 1400W significantly prevented the occurrence of I/R-induced gastric lesions. The mucosal MPO activity was increased after I/R, and this response was enhanced and attenuated by prior administration of L-NAME and 1400W, respectively. Interestingly, the later treatment with L-NAME, given 10 min before reperfusion, significantly reduced the severity of the I/R-induced gastric damage, in a L-arginine-dependent manner. The expression of iNOS mRNA was up-regulated in the stomach following I/R, with an increase of mucosal NO content, and the NO production was significantly inhibited by both L-NAME and 1400W.

CONCLUSION

Endogenous NO plays a dual role in the pathogenesis of IR-induced gastric damage; NO/cNOS is protective while NO/iNOS is proulcerogenic during I/R.

[No-synthase activity in primary cultured frog urinary bladder epithielial cells and no-dependent antimicrobial effect]

We have shown previously that endogenous NO modulates the effect of arginine-vasotocin on the increase in the osmotic water permeability of the frog urinary bladder epithelium. The aim of the present work was to develop a procedure of cultivation of epithelial cells from the frog urinary bladder as a primary culture in order to study in vitro the cellular production of NO and its regulation. Isolated cells were cultivated in modified L-15 medium with 10% FBS and gentamycin (40 microg/ml) at room temperature. Under these conditions, at least 50% cells kept their viability until 8 days of incubation. NO-synthase (NOS) activity was estimated as nitrite (NO2-) accumulation in culture medium; NO2- concentration in the presence of L-NAME, inhibitor of all NOS types, was considered as NOS-independent and was subtracted from each value. The nitrite accumulation was linear in time during 3 days of cultivation and was inhibited by 1400W, inducible NOS (iNOS) inhibitor, and 7-nitroindazole, constitutive NOS's inhibitor, at doses 5-50 and 10-200 microM, respectively. One-day incubation of he cells in the medium with low concentration of gentamycin (1 or 2 microg/ml) led to the significant increase in amount of bacterial in cultured fluid identified as E. coli and Acinetobacter sp. Addition of L-NAME (5 - 103 M) to the medium potentiated the bacteria growth 1.5- and 2.5-times in the presence of 2 and 1 microg gentamycin/ml, respectively. Thus, epithelial cells form the frog urinary bladder possess NO-dependent antibacterial effect which is probably provided by induction of iNOS expression. Taken together, these data demonstrate that the primary culture of the frog urinary bladder epithelial cells is a perspective experimental model for the study of regulation of NOS activity and NO production being of particular interest in relation to the defense effect of NO in epithelia.

Synthesis and in vitro evaluation of 5-arylidene-3-hydroxyalkyl-2-phenylimino-4-thiazolidinones with antidegenerative activity on human chondrocyte cultures

5-Arylidene-3-hydroxyalkyl-2-phenylimino-4-thiazolidinones (7,8) were synthesized and evaluated for their antidegenerative activity on human chondrocyte cultures stimulated by IL-1beta. This in vitro model has proven to be a useful experimental model to reproduce the mechanisms involved in arthritic diseases. The cell viability, the amount of GAGs, the production of NO and PGE(2) and the inhibition of MMP-3 were measured. Several thiazolidinones 7 and 8 exhibited the ability to block the production or action of the degenerative factors induced by IL-1beta.

Zwitterionic glycosidase inhibitors: salacinol and related analogues

Natural products with interesting biological properties and structural diversity have often served as valuable lead drug candidates for the treatment of human diseases. Salacinol, a naturally occurring alpha-glucosidase inhibitor, was shown to be one of the active principles of the aqueous extract of a medicinal plant that has been prescribed traditionally as an Ayurvedic treatment for type II diabetes. Salacinol contains an intriguing zwitterionic sulfonium-sulfate structure that comprises a 1,4-anhydro-4-thio-D-arabinitol core and a polyhydroxylated acyclic chain. Due to the unique structural features and its potential to become a lead drug candidate in the treatment of type II diabetes, a great deal of attention has been focused on salacinol and its analogues. Since the isolation of salacinol, several papers describing various synthetic routes to salacinol and its analogues have appeared in the literature. This review is aimed at highlighting the synthetic aspects of salacinol and related compounds as well as their structure-activity relationship studies.

Synthesis and biological evaluation of a small library of nojirimycin-derived bicyclic iminosugars

Novel nojirimycin-derived bicyclic structures, containing cyclic carbamate, urea and guanidine moieties have been synthesised starting from suitably protected alpha-C-vinylnojirimycin and alpha-C-allylnojirimycin, respectively, and their biological activity against different glycosidases and as antibacterial agents tested.

In vivo investigations on the cholinesterase-inhibiting effects of tricyclic quinazolinimines: Scopolamine-induced cognitive impairments in rats are attenuated at low dosage and reinforced at higher dosage

Tricyclic quinazolinimines as a novel class of potent inhibitors of cholinesterases in vitro are micro- and sub-micromolar inhibitors with activities at both acetyl- (AChE) and butyrylcholinesterase (BChE) or at BChE only. To further establish the antiamnesic properties of this class of compounds, an in vivo test system has been established. Cognitive impairment in rats was reversibly induced by scopolamine (0.05 mg/100 g body weight) and evaluated in an eight-arm radial maze. A representative quinazolinimine (MD212) showed attenuation of cognitive deficits at a low dosage (0.01 mg/100 g body weight), whereas at a high dosage (>0.1 mg/100 g body weight) the effect of scopolamine is markedly reinforced. As MD212 applied alone does not influence rat's cognition at all, the reinforcement of scopolamine effect has to be due to the amplification of scopolamine action possibly by (1) inhibition of scopolamine metabolism, (2) influence of scopolamine on MD212 metabolism or (3) allosteric modulation of mACh receptors. Receptor-binding studies proved hypothesis (3): MD212 stabilizes [3H]N-methylscopolamine binding to muscarinic receptors allosterically.

Cisplatinum and Transplatinum Complexes with Benzyliminoether Ligands; Synthesis, Characterization, Structure−Activity Relationships, and In Vitro and In Vivo Antitumor Efficacy

New benzyliminoether derivatives [PtCl2{N(H)=C(OMe)CH2Ph}2] of cis (1a, 1b) and trans (2a, 2b) geometry were prepared and characterized by means of elemental analysis, multinuclear NMR and FT-IR techniques, and X-ray crystallography; this latter was carried out for 1b. The cytotoxic properties of these new platinum(II) complexes were evaluated in terms of cell growth inhibition against a panel of different types of human cancer cell lines. cis-[PtCl2{E-N(H)=C(OMe)CH2Ph}2] (1a) was significantly more potent than cisplatin against all tumor cell lines tested, showing IC50 values from about 2- to 17-fold lower than the reference compound. Chemosensitivity tests performed on cisplatin-sensitive and -resistant cell lines have demonstrated that complex 1a is able to overcome cisplatin resistance. Analyzing the mechanism by which complex 1a led to cell death, we have found that it induced apoptosis in a dose-dependent manner, accompanied by the activation of caspase-3. The in vivo studies carried out using two transplantable tumor models (L1210 leukemia and Lewis lung carcinoma) showed that derivative 1a induced a remarkable antitumor activity in both tumor models, as measured by prolonged survival and reduced tumor mass compared to control groups.

Nitrosative Stress and Corneal Transplant Endothelial Cell Death During Acute Graft Rejection

BACKGROUND

Nitrosative stress takes place in endothelial cells (EC) during corneal acute graft rejection. The purpose of this study was to evaluate the potential role of peroxynitrite on corneal EC death.

METHODS

The effect of peroxynitrite was evaluated in vivo. Fifty, 250, and 500 microM in 1.5 microL of the natural or denatured peroxynitrite in 50 microM NaOH, 50 microM NaOH alone, or balanced salt solution were injected into the anterior chamber of rat eyes (n=3/group). Corneal toxic signs after injection were assessed by slit-lamp, in vivo confocal imaging, pachymetry, and EC count. The effect of peroxynitrite was also evaluated on nitrotyrosine and leucocyte elastase inhibitor/LDNase II immunohistochemistry. Human corneas were incubated with peroxynitrite and the effect on EC viability was evaluated. A specific inducible nitric oxide synthase inhibitor (iNOS) was administered systemically in rats undergoing allogeneic corneal graft rejection and the effect on EC was evaluated by EC count.

RESULTS

Rat eyes receiving as little as 50 microM peroxynitrite showed a specific dose-dependent toxicity on EC. We observed an intense nitrotyrosine staining of human and rat EC exposed to peroxynitrite associated with leucocyte elastase inhibitor nuclear translocation, a noncaspase dependent apoptosis reaction. Specific inhibition of iNOS generation prevented EC death and enhanced EC survival of the grafted corneas. However, inhibition of iNOS did not have a significant influence on the incidence of graft rejection.

CONCLUSION

Nitrosative stress during acute corneal graft rejection in rat eyes induces a noncaspase dependent apoptotic death in EC. Inhibition of nitric oxide production during the corneal graft rejection has protective effects on the corneal EC survival.

From Multifunctionalized Poly(ethylene imine)s toward Antimicrobial Coatings

Primary amine groups of branched poly(ethylene imine) (PEI) were functionalized with quaternary ammonium groups, alkyl chains of different length, allylic and benzylic groups in a one-step reaction, using a carbonate coupler. The structure of the obtained amphiphilic polymers was determined by means of 1H and 13C NMR spectroscopy. Depending on their hydrophilic/hydrophobic balance, the obtained polymers can be used as water-soluble disinfectants and for antimicrobial coating materials. The bactericidal properties of some of the amphiphilic polymers against Gram-negative and Gram-positive bacteria were investigated. Minimal inhibitory concentrations (log 4 reduction of bacterial growth) against Escherichia coli and Bacillus subtilis were determined in the range of 0.3-0.4 mg/mL and 0.03-0.04 mg/mL for water-soluble polymers. Glass slides coated with functionalized PEIs showed a reduction of colony forming units of at least 95%, at best 99.9%, against E. coli and B. subtilis.

Phosphatidylinositol 3-kinase is involved in prostaglandin E2-mediated murine duodenal bicarbonate secretion

Prostaglandin E(2) (PGE(2)) plays an important role in the regulation of duodenal bicarbonate (HCO(3)(-)) secretion, but its signaling pathway(s) are not fully understood. In the present study, we investigated the signaling pathways involved in PGE(2)-mediated duodenal HCO(3)(-) secretion. Murine duodenal mucosal HCO(3)(-) secretion was examined in vitro in Ussing chambers by pH-stat titration in the presence of a variety of signal transduction modulators. Phosphatidylinositol 3-kinase (PI3K) activity was measured by immunoprecipitation of PI3K and ELISA, and Akt phosphorylation was measured by Western analysis with anti-phospho-Akt and anti-Akt antibodies. PGE(2)-stimulated duodenal HCO(3)(-) secretion was reduced by the cAMP-dependent signaling pathway inhibitors MDL-12330A and KT-5720 by 23% and 20%, respectively; the Ca(2+)-influx inhibitor verapamil by 26%; and the calmodulin antagonist W-13 by 24%; whereas the PI3K inhibitors wortmannin and LY-294002 reduced PGE(2)-stimulated HCO(3)(-) secretion by 51% and 47%, respectively. Neither the MAPK inhibitor PD-98059 nor the tyrosine kinase inhibitor genistein altered PGE(2)-stimulated HCO(3)(-) secretion. PGE(2) application caused a rapid and concentration-dependent increase in duodenal mucosal PI3K activity and Akt phosphorylation. These results demonstrated that PGE(2) activates PI3K in duodenal mucosa and stimulates duodenal HCO(3)(-) secretion via cAMP-, Ca(2+)-, and PI3K-dependent signaling pathways.

Involvement of guanylate cyclase in the cardiovascular response induced by adenosine A2B receptor stimulation in the posterior hypothalamus of the anesthetized rats

Cardiovascular inhibitory effects induced by the posterior hypothalamic adenosine A(2) receptors were suggested by our previous reports. In this experiment, we examined the influence of the posterior hypothalamic adenosine A(2B) receptors on central cardiovascular regulation of blood pressure (BP) and heart rate (HR). Posterior hypothalamic injection of drugs was performed in anesthetized, artificially ventilated male Sprague-Dawley rats. Injection of 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA; 2 nmol), an adenosine A(2) receptor agonist, showed the decrease of arterial blood pressure and heart rate, and the alloxazine, an adenosine A(2B) receptor antagonist, partially blocked the depressor and bradycardiac effects of CPCA (2 nmol). To examine the role of adenosine A(2B) receptors among the adenosine A(2) subtypes, we applied the 5'-N-Ethylcarboxamidoadenosine (NECA), an adenosine A(2B) receptor agonist, to the posterior hypothalamus. Injection of NECA (1, 4 and 8 nmol) produced a dose-dependent decrease of arterial blood pressure and HR. Pretreatment with alloxazine (5 nmol) partially blocked the depressor and bradycardiac effects of NECA (4 nmol). Also, pretreatment with LY-83,583 (5 nmol), a soluble guanylate cyclase inhibitor, attenuated the depressor and bradycardiac effects of NECA (4 nmol). However, pretreatment with MDL-12,330 (10 nmol), an adenylate cyclase inhibitor, did not affect these effects of NECA (4 nmol). These results suggest that adenosine A(2B) receptor in the posterior hypothalamus plays an inhibitory role in central cardiovascular regulation, and that guanylate cyclase mediates the depressor and bradycardiac actions of adenosine A(2B) receptors.

A role for inflammatory mediators in the IL-18 mediated attenuation of LTP in the rat dentate gyrus

Pro-inflammatory cytokines are known to be elevated in several pathological conditions that are associated with deficits in cognition. We have previously demonstrated that interleukin-18 (IL-18) inhibits long-term potentiation (LTP) in the dentate gyrus in vitro. In this study we have examined the involvement of the inflammatory mediators COX-2 and iNOS in IL-18-mediated inhibition of LTP. The effect of an anti-inflammatory PPARgamma agonist was also investigated. We report that the impairment of LTP by IL-18 is significantly attenuated by prior application of the COX-2 inhibitor, SC-236 and the iNOS inhibitor 1400W. These agents had no effect on paired pulse depression in the dentate gyrus. Furthermore, application of the PPARgamma agonist ciglitazone also attenuated IL-18-mediated inhibition of LTP. We discuss a role for p38 MAP kinase in these effects. This study provides novel evidence for the involvement of inflammatory mediators in IL-18-mediated inhibition of LTP in the rat dentate gyrus in vitro.

Serotonin delays habituation of leech swim response to touch

Serotonin, acting through a cAMP-signaling pathway, delayed habituation to criterion of the leech's swim response to touch. This delay was reversed by crushing the connective between serotonin-exposed and serotonin-naive ganglia, and correlated with an increase in spontaneous impulse activity in this connective. We suggest that increased activity in intersegmental interneurons may play a role in maintaining swim responsiveness when concentrations of serotonin are elevated.

Acyclic Ribooxacarbenium Ion Mimics as Transition State Analogues of Human and Malarial Purine Nucleoside Phosphorylases

Transition state analogues of PNP, the Immucillins and DADMe-Immucillins, were designed to match transition state features of bovine and human PNPs, respectively. A third generation of inhibitors has been designed that contain an acyclic iminoalcohol to replace the cyclic mimic of the ribooxacarbenium ion at the transition states of PNPs. The best third generation inhibitor is equivalent to the best inhibitors found in the previous transition state analogues.