bluuebunny/crossref_metadata_2025 huggingface dataset:
Nupafant, a PAF‐antagonist prototype for suppression of ventricular fibrillation without liability for QT prolongation?
Authors: Baker K E , Wood L M , Whittaker M , Curtis M J
Published: August 2006

Background and purpose:

PAF antagonists inhibit ischaemia‐induced ventricular fibrillation (VF) in animals. However, unfavourable ancillary actions (on QT interval and coronary flow) have been reported with the PAF antagonist, BN‐50739. If these are class actions, they would preclude development of PAF antagonists as novel anti‐VF drugs. Our purpose was to examine this proposition using the hitherto untested PAF antagonist, nupafant.

Experimental approach:

Two rat heart preparations (Langendorff and ‘dual coronary’ perfusion) were used to assay nupafant's effects on ischaemia‐induced VF, coronary flow and QT interval, and to test for the site‐selectivity necessary if any effects on VF are caused by PAF antagonism.

Key results:

Global (whole‐heart) delivery of 10 μM nupafant, reduced the incidence of ischaemia‐induced VF and widened QT interval without affecting coronary flow. Importantly, lower concentrations (0.1 and 1 μM) had no effect on VF, yet widened QT almost identically to 10 μM nupafant. When nupafant was delivered selectively to (and entrapped within) the involved region it partially protected against VF (P<0.05). This occurred without change in QT interval. Selective nupafant delivery to the uninvolved region was without effect.

Conclusions and implications:

Nupafant protects against ischaemia‐induced VF primarily by site‐selective actions in the ischaemic region but, unlike BN‐50739, the effect is unrelated to its QT widening action, and is not compromised by any effect on coronary flow. This establishes proof of concept that VF suppression by PAF antagonism need not invariably be associated with QT prolongation or vasodilatation, justifying further development of this drug class.

British Journal of Pharmacology (2006) 149, 269–276. doi:10.1038/sj.bjp.0706846
Effect of a nitric oxide releasing derivative of paracetamol in a rat model of endotoxaemia
Authors: Marshall M , Keeble J , Moore P K
Published: August 2006

Background and purpose:

Nitroparacetamol is a nitric oxide‐releasing paracetamol with novel anti‐inflammatory properties compared to the parent compound. This study has investigated the anti‐inflammatory activity of nitroparacetamol in a model of endotoxaemia in rats to probe the mechanisms underlying this effect.

Experimental approach:

Nitroparacetamol (92 mg kg−1), paracetamol (50 mg kg−1) or vehicle were administered to male, Wistar rats 15 min prior to or 3 h after lipopolysaccharide (0.5 mg kg−1, serotype 0127:B8). Mean arterial pressure and heart rate were measured for 5 h and plasma and organs were then obtained to determine organ dysfunction, inducible nitric oxide synthase and cyclooxygenase‐2 expression (lung, liver and kidney tissue) and plasma nitrate/nitrite. In separate experiments, nitroparacetamol, paracetamol or vehicle was administered 1 h before acetylcholine (0.1 μg kg−1) or sodium nitroprusside (0.25 μg kg−1) to determine if nitroparacetamol desensitizes responses to exogenous/endogenous nitric oxide.

Key results:

Nitroparacetamol prevented but did not reverse the lipopolysaccharide‐induced hypotension. There was no effect on heart rate or plasma markers of organ dysfunction. Nitroparacetamol prevented the increased plasma nitrate/nitrite and expression of COX‐2 and iNOS, whereas paracetamol exerted partial inhibition of COX‐2 in lung alone. Nitroparacetamol also reduced responses to acetylcholine and sodium nitroprusside.

Conclusions and implications:

NO is the active component of nitroparacetamol in this model of endotoxaemia. Pro‐inflammatory processes targeted by nitroparacetamol have been shown to include iNOS/COX‐2 induction and possibly vascular soluble guanylyl cyclase. Precise mechanisms underlying the NO effect are unclear but inhbition of cytokine formation may be important.

British Journal of Pharmacology (2006) 149, 516–522. doi:10.1038/sj.bjp.0706855
KATPchannel openers of the benzopyran type reach their binding site via the cytosol
Authors: Stephan D , Salamon E , Weber H , Russ U , Lemoine H , Quast U
Published: August 2006

Background and purpose:

ATP‐sensitive K+(KATP) channels are composed of pore‐forming subunits (Kir6.x) and of sulphonylurea receptors (SUR). Both sulphonylureas and KATPchannel openers act by binding to SUR. Sulphonylureas reach their binding site from the cytosol but it remains unknown whether this holds for openers too.

Experimental approach:

A poorly membrane‐permeant sulphonic acid derivative of the benzopyran‐type opener, bimakalim, was synthesized, descyano‐bimakalim‐6‐sulphonic acid (BMSA). Binding of BMSA and bimakalim was compared in membranes and intact cells expressing the Kir6.2/SUR2B channel and channel opening was compared in inside‐out patches and whole cells.

Key results:

In membranes, bimakalim and BMSA bound to Kir6.2/SUR2B withKivalues of 61 nMand 4.3 μM, showing that the negative charge decreased affinity 69‐fold. In intact cells, however, binding of BMSA was much weaker than in membranes (75‐fold) whereas that of bimakalim was unchanged. TheKivalue of BMSA decreased with increasing incubation time. In inside‐out patches, bimakalim (1 μM) and BMSA (100 μM) opened the Kir6.2/SUR2B channel closed by MgATP to a similar degree whereas in whole‐cell experiments, only bimakalim was effective.

Conclusions and implications:

Despite its negative charge, BMSA is an effective channel opener. The fact that BMSA binds and acts more effectively when applied to the inner side of the cell membrane shows that benzopyran openers reach their binding site at SUR from the cytosol. This suggests that the binding pocket of SUR is only open on the cytoplasmic side.

British Journal of Pharmacology(2006)149, 199–205. doi:10.1038/sj.bjp.0706858
Rapid desensitization of somatodendritic 5‐HT1Areceptors by chronic administration of the high‐efficacy 5‐HT1Aagonist, F13714: a microdialysis study in the rat
Authors: Assié M‐B , Lomenech H , Ravailhe V , Faucillon V , Newman‐Tancredi A
Published: August 2006

Background and purpose:

Desensitization of somatodendritic 5‐HT1Areceptors is involved in the mechanism of action of several antidepressants, but the rapidity of this effect and the amount of agonist stimulation needed are unclear. We evaluated the capacity of the high‐efficacy 5‐HT1Aagonist, F13714 (3‐chloro‐4‐fluorophenyl‐(4‐fluoro‐4‐{[(5‐methyl‐6‐methylamino‐pyridin‐2‐ylmethyl)‐amino]‐methyl}‐piperidin‐1‐yl‐methanone) and of the partial agonist, flesinoxan, to desensitize somatodendritic 5‐HT1Areceptors involved in the control of 5‐HT release.

Experimental approach:

Intracerebral microdialysis in the hippocampus of freely moving rats was used to examine the acute and chronic effects of the two compounds (administered by osmotic pumps for 3, 7 or 14 days) on extracellular 5‐HT levels, measured by HPLC with electrochemical detection.

Key results:

When given acutely, F13714, flesinoxan and the low‐efficacy 5‐HT1Aagonist, buspirone, dose‐dependently decreased extracellular 5‐HT concentrations (ED50values: 0.04, 0.77 and 5.6 mg kg−1, respectively). The selective 5‐HT1Aantagonist WAY100635 inhibited the effects of the three compounds. F13714 (2.5 mg kg−1per day for 3, 7 or 14 days and 0.63 mg kg−1for 7 days) significantly attenuated the inhibition of 5‐HT release induced by buspirone (10 mg kg−1). In contrast, flesinoxan (10 mg kg−1per day) failed to alter the response to buspirone at any of the treatment durations.

Conclusions and implications:Rat somatodendritic 5‐HT1Areceptors controlling hippocampal 5‐HT release were rapidly desensitized by chronic activation with a high‐efficacy 5‐HT1Aagonist, but not by chronic activation with a partial agonist. Thus, rapid 5‐HT1Aautoreceptor desensitization by high‐efficacy agonists may accelerate the onset of the therapeutic effects of antidepressants.

British Journal of Pharmacology(2006)149, 170–178. doi:10.1038/sj.bjp.0706859
Comparative studies of AJG049, a novel Ca2+ channel antagonist, on voltage‐dependent L‐type Ca2+ currents in intestinal and vascular smooth muscle
Authors: Hashimoto M , Teramoto N , Zhu H‐L , Takahashi K , Ito Y
Published: August 2006

Background and purpose:

Antagonists of Ca2+ channels reduce contraction of intestinal smooth muscle but also affect vascular smooth muscle. We have therefore examined the effects of AJG049, a newly synthesized antagonist for regulation of gut motility, on voltage‐dependent L‐type Ca2+ channels, in vascular and intestinal smooth muscle, comparing AJG049 with two other Ca2+ channel antagonists, verapamil and diltiazem.

Experimental approach:

Affinities of AJG049 for various types of voltage‐dependent Ca2+ channels were examined by binding studies. Effects of AJG049 on voltage‐dependent inward Ca2+ (or Ba2+) currents (ICa or IBa) in dispersed smooth muscle cells from guinea‐pig ileum, colon and mesenteric artery were measured using conventional whole‐cell configurations.

Key results:

In binding studies, AJG049 showed a high affinity for the diltiazem‐binding site of L‐type Ca2+ channels. In whole‐cell configuration, AJG049 suppressed ICa in ileal myocytes, with concentration‐, voltage‐and use‐dependencies. AJG049 shifted the steady‐state inactivation curve of ICa to the left. The order of potency to inhibit ICa in ileal myocytes was AJG049>verapamil>diltiazem. AJG049 also suppressed IBa in guinea‐pig mesenteric arterial myocytes, showing concentration‐ and voltage‐dependencies and the potency order for this action was also AJG049>verapamil>diltiazem. For the relative ratio of Ki values between ileal and mesenteric arterial myocytes, the order was AJG049>diltiazem≫verapamil.

Conclusions and implications:

These results show that AJG049 inhibits L‐type Ca2+ channels mainly through the diltiazem‐binding site(s). From our results, AJG049 showed a little selectivity for these Ca2+ channels in intestinal smooth muscle.

British Journal of Pharmacology (2006) 149, 155–162. doi:10.1038/sj.bjp.0706861
Assays for enhanced activity of low efficacy partial agonists at the D2 dopamine receptor
Authors: Lin H , Saisch S G N , Strange P G
Published: August 2006

Background and purpose:

Low efficacy partial agonists at the D2 dopamine receptor may be useful for treating schizophrenia. In this report we describe a method for assessing the efficacy of these compounds based on stimulation of [35S]GTPγS binding.

Experimental approach:

Agonist efficacy was assessed from [35S]GTPγS binding to membranes of CHO cells expressing D2 dopamine receptors in buffers with and without Na+. Effects of Na+ on receptor/G protein coupling were assessed using agonist/[3H]spiperone competition binding assays.

Key results:

When [35S]GTPγS binding assays were performed in buffers containing Na+, some agonists (aripiprazole, AJ‐76, UH‐232) exhibited very low efficacy whereas other agonists exhibited measurable efficacy. When Na+ was substituted by N‐methyl D‐glucamine, the efficacy of all agonists increased (relative to that of dopamine) but particularly for aripiprazole, aplindore, AJ‐76, (−)‐3‐PPP and UH‐232. In ligand binding assays, substitution of Na+ by N‐methyl D‐glucamine increased receptor/G protein coupling for some agonists ‐. aplindore, dopamine and (−)‐3‐PPP – but for aripiprazole, AJ‐76 and UH‐232 there was little effect on receptor/G protein coupling.

Conclusions and implications:

Substitution of Na+ by NMDG increases sensitivity in [35S]GTPγS binding assays so that very low efficacy agonists were detected clearly. For some agonists the effect seems to be mediated via enhanced receptor/G protein coupling whereas for others the effect is mediated at another point in the G protein activation cycle. AJ‐76, aripiprazole and UH‐232 seem particularly sensitive to this change in assay conditions. This work provides a new method to discover these very low efficacy agonists.

British Journal of Pharmacology (2006) 149, 291–299. doi:10.1038/sj.bjp.0706866
BML‐241 fails to display selective antagonism at the sphingosine‐1‐phosphate receptor, S1P3
Authors: Jongsma M , Hendriks‐Balk M C , Michel M C , Peters S L M , Alewijnse A E
Published: August 2006

Background and purpose:

The thiazolidine carboxylic acid, BML‐241, has been proposed as a lead compound in development of selective antagonists at the sphingosine‐1‐phosphate receptor (S1P3), based on its inhibition of the rise in intracellular calcium concentrations ([Ca2+]i) in HeLa cells overexpressing S1P receptors. We have studied the antagonistic properties of BML‐241 for the S1P3 receptor in more detail.

Experimental approach:

Chinese hamster ovary (CHO) cells stably transfected with the S1P3, S1P2 or α1A‐adrenoceptors were used to investigate the effect of BML‐241 on increases in [Ca2+]i mediated via different receptors. CHO‐K1 cells were used to study ATP‐induced [Ca2+]i elevations. Effects on S1P3‐mediated inhibition of forskolin‐induced cAMP accumulation and on binding to α1A‐adrenoceptors were also investigated. In addition, the effect of BML‐241 on contractions of rat mesenteric artery induced by phenylephrine was studied in an organ bath.

Key results:

High concentrations of BML‐241 (10 μM) inhibited the rise in [Ca2+]i induced by S1P3 and S1P2 receptor stimulation; lower concentrations were ineffective. This high concentration of BML‐241 also inhibited [Ca2+]i increases via P2 (nucleotide) receptor or α1A‐adrenoceptor stimulation. Moreover, BML‐241 (10 μM) inhibited α1‐adrenoceptor‐mediated contraction of rat mesenteric artery but did not displace [3H]‐prazosin from α1A‐adrenoceptors in concentrations up to 100 μM. BML‐241 (10 μM) did not affect the S1P3‐mediated decrease of forskolin‐induced cAMP accumulation.

Conclusions and Implications:

We conclude that BML‐241 is a low potency, non‐selective inhibitor of increases in [Ca2+]i, rather than a specific antagonist at the S1P3 receptor.

British Journal of Pharmacology (2006) 149, 277–282. doi:10.1038/sj.bjp.0706872
Nonadiabatic effects in the photoelectron spectrum of the pyrazolide-d3 anion: Three-state interactions in the pyrazolyl-d3 radical
Authors: Ichino Takatoshi , Gianola Adam J. , Lineberger W. Carl , Stanton John F.
Published: August 2006

The 351.1nm photoelectron spectrum of the 1-pyrazolide-d3 anion has been measured. The photoelectron angular distributions indicate the presence of nearly degenerate electronic states of the 1-pyrazolyl-d3 radical. Equation-of-motion ionization potential coupled-cluster singles and doubles (EOMIP-CCSD) calculations have been performed to study the low-lying electronic states. The calculations strongly suggest that three electronic states, energetically close to each other, are accessed in the photodetachment process. Strong interactions of the pseudo-Jahn-Teller type in each pair of the three states are evident in the calculations for the radical at the anion geometry. Model diabatic potentials of the three states have been constructed around the anion geometry in terms of the anion reduced normal coordinates up to the second order. An analytic method to parametrize the quadratic vibronic coupling (QVC) model potentials has been introduced. Parameters of the QVC model potentials have been determined from the EOMIP-CCSD and CCSD(T) calculations. Simulations of the 1-pyrazolide-d3 spectrum have been performed with the model Hamiltonian, treating all vibronic interactions amongst the three states simultaneously. The simulation reproduces the fine structure of the observed spectrum very well, revealing complicated nonadiabatic effects in the low-lying states of the radical. The ground state of the 1-pyrazolyl-d3 radical is A22 and the electron affinity is 2.935±0.006eV. The first excited state is B12 with a term energy of 32±1meV. While the high-symmetry (C2v) stationary points of the X̃A22 and ÃB12 states are minima, that of the B̃B22 state is a saddle point as a result of the pseudo-Jahn-Teller interactions with the other two states. The topology of the adiabatic potential energy surfaces is discussed.
Low-temperature silicon wafer bonding based on Ti∕Si solid-state amorphization
Authors: Yu Jian , Wang Yinmin , Lu Jian-Qiang , Gutmann Ronald J.
Published: August 2006

Strong and nearly void-free bonding has been achieved using a low-temperature Ti∕Si-based wafer bonding technique. Bare Si wafers are bonded with oxidized Si wafers at temperatures from 300to450°C, using ∼30nm thick Ti as bonding intermediate. High-resolution transmission electron microscopy and electron energy-loss spectrometry elemental mapping indicate that the strong bonding is attributed to a solid-state amorphization between Ti and Si. Ti demonstrates particularly attractive capabilities to overcome kinetic barriers commonly associated with low-temperature silicon wafer bonding.
Luminescence enhancement of (Ca,Zn)TiO3:Pr3+ phosphor using nanosized silica powder
Authors: Haranath D. , Khan A. F. , Chander Harish
Published: August 2006

The results pertaining to luminescence enhancement due to high-temperature amalgamation of nanometer-sized silica powder and the oxide mixture of calcium, zinc, titanium, and praseodymium are presented. The (Ca,Zn)TiO3:Pr3+ phosphor showed an intense and narrow band emission at ∼614nm under ambient light/ultraviolet excitation, which is associated with the typical H43→D21 transition of Pr3+. The observed red emission is quite stable and long (∼60min) for a dark-adapted human eye and shows no appreciable degradation in the optical properties for prolonged exposure to surrounding/atmosphere. With the addition of nanosized silica powder, the photoluminescence was augmented nearly 1.6 times as that of unadded sample. The present results are entirely different from those reported previously for Pr3+ doped-(Ca,Zn)TiO3 phosphor and silica-based persistent phosphors.
Effect of the misorientation of the 4H-SiC substrate on the open volume defects in GaN grown by metal-organic chemical vapor deposition
Authors: Tengborn E. , Rummukainen M. , Tuomisto F. , Saarinen K. , Rudzinski M. , Hageman P. R. , Larsen P. K. , Nordlund A.
Published: August 2006

Positron annihilation spectroscopy has been used to study GaN grown by metal-organic chemical vapor deposition on misoriented 4H-SiC substrates. Two kinds of vacancy defects are observed: Ga vacancies and larger vacancy clusters in all the studied layers. In addition to vacancies, positrons annihilate at shallow traps that are likely to be dislocations. The results show that the vacancy concentration increases and the shallow positron trap concentration decreases with the increasing substrate misorientation.
A reaction surface Hamiltonian study of malonaldehyde
Authors: Tew David P. , Handy Nicholas C. , Carter Stuart
Published: August 2006

We report calculations using a reaction surface Hamiltonian for which the vibrations of a molecule are represented by 3N−8 normal coordinates, Q, and two large amplitude motions, s1 and s2. The exact form of the kinetic energy operator is derived in these coordinates. The potential surface is first represented as a quadratic in Q, the coefficients of which depend upon the values of s1,s2 and then extended to include up to Q6 diagonal anharmonic terms. The vibrational energy levels are evaluated by solving the variational secular equations, using a basis of products of Hermite polynomials and appropriate functions of s1,s2. Our selected example is malonaldehyde (N=9) and we choose as surface parameters two OH distances of the migrating H in the internal hydrogen transfer. The reaction surface Hamiltonian is ideally suited to the study of the kind of tunneling dynamics present in malonaldehyde. Our results are in good agreement with previous calculations of the zero point tunneling splitting and in general agreement with observed data. Interpretation of our two-dimensional reaction surface states suggests that the OH stretching fundamental is incorrectly assigned in the infrared spectrum. This mode appears at a much lower frequency in our calculations due to substantial transition state character.
Electron energy barriers at interfaces of GaAs(100) with LaAlO3 and Gd2O3
Authors: Afanas’ev V. V. , Stesmans A. , Droopad R. , Passlack M. , Edge L. F. , Schlom D. G.
Published: August 2006

Electron energy barriers at the interfaces of GaAs(100) with Gd2O3 appear to be insensitive to the Fermi level pinning indicating that charges at interface states are of marginal importance for the band alignment at semiconductor/insulator interfaces. The inferred conduction band offset of 1.6±0.1eV for GaAs(100)∕Gd2O3 is close to that measured at the GaAs(100)∕LaAlO3 interface which is consistent with the 5.8 and 5.7eV wide band gaps of these two insulators. However, the defects revealed by photoionization measurements exhibit a distinctly different in-depth distribution. In GaAs∕LaAlO3 most of the traps are located close to the semiconductor surface, while in GaAs∕Gd2O3 case they are found distributed across the entire oxide layer.
Mesa-size-dependent color contrast in flip-chip blue/green two-color InGaN∕GaN multi-quantum-well micro-light-emitting diodes
Authors: Chen Horng-Shyang , Yeh Dong-Ming , Lu Chih-Feng , Huang Chi-Feng , Lu Yen-Cheng , Chen Cheng-Yen , Huang Jian-Jang , Yang C. C.
Published: August 2006

The authors fabricate blue/green two-wavelength, InGaN∕GaN quantum-well (QW), flip-chip micro-light-emitting diodes (μ-LEDs) of different mesa sizes by stacking QWs of different indium contents. It is found that the blue/green contrast ratio of such a μ-LED increases with the mesa size. The relatively stronger blue intensity in a device of a larger mesa area is due to its higher operation junction temperature such that hole migration can be enhanced through thermally exciting holes to escape from the QW (green emitting) closest to the p-type layer and to be captured by the neighboring QWs (blue emitting). The higher junction temperature in such a μ-LED of a larger mesa area is due to its smaller ratio of the sidewall surface area over the active volume, leading to the less effective sidewall heat radiation and light extraction.
Whispering gallery modes in high quality ZnSe∕ZnMgSSe microdisks with CdSe quantum dots studied at room temperature
Authors: Renner J. , Worschech L. , Forchel A. , Mahapatra S. , Brunner K.
Published: August 2006

The authors observed whispering gallery modes with quality factors exceeding 2000 in ZnSe∕ZnMgSSe microdisks with self-assembled CdSe quantum dots at room temperature. The microdisks were realized by electron beam lithography and reactive ion etching and mounted on a glass plate. The far field emission of the microdisks exhibits a maximum in the direction parallel to the disk plane and couples efficiently into the glass plate. The microdisk spectra were analyzed in terms of mode separation for disk diameters ranging from 1.5to3.0μm. Transversal magnetic and transversal electric modes were identified.
Risk behaviour among Aboriginal and Torres Strait Islander gay men: comparisons with other gay men in Australia
Authors: Lawrence Chris G. , Rawstorne Patrick , Hull Peter , Grulich Andrew E. , Cameron Scott , Prestage Garrett P.
Published: August 2006

Objectives: To determine any differences in HIV-risk and drug-use behaviour among Aboriginal and Torres Strait Islander gay men and other gay men in Australia. Methods: The Gay Community Periodic Survey is a repeated cross-sectional prevalence study of the sexual and drug use behaviours of Australian gay men conducted since 1996. Responses from Aboriginal and Torres Strait Islander (ATSI) gay men were compared with those from non-ATSI gay men for the years 2000–2004. Results: Of 34 708 responses collected in major Australian cities over a 6-year period, 1208 identified as Aboriginal or Torres Strait Islander. There was little difference between ATSI and non-ATSI men in the reported prevalence of HIV, though ATSI gay men were more likely than non-ATSI gay men to engage in unprotected anal intercourse with casual partners and to inject illicit drugs but were more likely to have been recently tested for HIV. Conclusions: These ATSI gay men were at increased risk of HIV and other blood-borne viruses, though this may be due to differences in socio-economic status as much as cultural background. These findings indicate the continued need for targeted sexual and injecting-drug-use health interventions among this population.
Protein phosphatase 1 positively regulates stomatal opening in response to blue light in
Vicia faba
Authors: Takemiya Atsushi , Kinoshita Toshinori , Asanuma Miwako , Shimazaki Ken-ichiro
Published: August 2006

Phototropins, plant blue light receptors, mediate stomatal opening through the activation of the plasma membrane H
+
-ATPase by unknown mechanisms. Here we report that type 1 protein phosphatase (PP1) positively regulates the blue light signaling between phototropins and the H
+
-ATPase in guard cells of
Vicia faba
. We cloned the four catalytic subunits of PP1 (PP1c) from guard cells and determined the expression of the isoforms in various tissues. Transformation of
Vicia
guard cells with PP1c isoforms that had lost enzymatic activity by one amino acid mutation, or with human inhibitor-2, a specific inhibitor protein of PP1c, suppressed blue light-induced stomatal opening. Addition of fusicoccin, an activator of the plasma membrane H
+
-ATPase, to these transformed guard cells induced normal stomatal opening, suggesting that the transformations did not affect the basic mechanisms for stomatal opening. Tautomycin, an inhibitor of PP1, inhibited blue light-induced H
+
pumping, phosphorylation of the plasma membrane H
+
-ATPase in guard cell protoplasts, and stomatal opening. However, tautomycin did not inhibit the blue light-dependent phosphorylation of phototropins. We conclude that PP1 functions downstream of phototropins and upstream of the H
+
-ATPase in the blue light signaling pathway of guard cells.
Broad activation of the olfactory bulb produces long-lasting changes in odor perception
Authors: Mandairon Nathalie , Stack Conor , Kiselycznyk Carly , Linster Christiane
Published: August 2006

A number of electrophysiological experiments have shown that odor exposure alone, unaccompanied by behavioral training, changes the response patterns of neurons in the olfactory bulb. As a consequence of these changes, across mitral cells in the olfactory bulb, individual odors should be better discriminated because of previous exposure. We have previously shown that a daily 2-h exposure to odorants during 2 weeks enhances rats' ability to discriminate between chemically similar odorants. Here, we first show that the perception of test odorants is only modulated by enrichment with odorants that activate at least partially overlapping regions of the olfactory bulb. Second, we show that a broad activation of olfactory bulb neurons by daily local infusion of NMDA into both olfactory bulbs enhances the discrimination between chemically related odorants in a manner similar to the effect of daily exposure to odorants. Computational modeling of the olfactory bulb suggests that activity-dependent plasticity in the olfactory bulb can support the observed modulation in olfactory discrimination capability by enhancing contrast and synchronization in the olfactory bulb. Last, we show that blockade of NMDA receptors in the olfactory bulb impairs the effects of daily enrichment, suggesting that NMDA-dependent plasticity is involved in the changes in olfactory processing observed here.
Tcof1
/Treacle is required for neural crest cell formation and proliferation deficiencies that cause craniofacial abnormalities
Authors: Dixon Jill , Jones Natalie C. , Sandell Lisa L. , Jayasinghe Sachintha M. , Crane Jennifer , Rey Jean-Philippe , Dixon Michael J. , Trainor Paul A.
Published: August 2006

Neural crest cells are a migratory cell population that give rise to the majority of the cartilage, bone, connective tissue, and sensory ganglia in the head. Abnormalities in the formation, proliferation, migration, and differentiation phases of the neural crest cell life cycle can lead to craniofacial malformations, which constitute one-third of all congenital birth defects. Treacher Collins syndrome (TCS) is characterized by hypoplasia of the facial bones, cleft palate, and middle and external ear defects. Although TCS results from autosomal dominant mutations of the gene
TCOF1
, the mechanistic origins of the abnormalities observed in this condition are unknown, and the function of Treacle, the protein encoded by
TCOF1
, remains poorly understood. To investigate the developmental basis of TCS we generated a mouse model through germ-line mutation of
Tcof1
. Haploinsufficiency of
Tcof1
leads to a deficiency in migrating neural crest cells, which results in severe craniofacial malformations. We demonstrate that
Tcof1
/Treacle is required cell-autonomously for the formation and proliferation of neural crest cells.
Tcof1
/Treacle regulates proliferation by controlling the production of mature ribosomes. Therefore,
Tcof1
/Treacle is a unique spatiotemporal regulator of ribosome biogenesis, a deficiency that disrupts neural crest cell formation and proliferation, causing the hypoplasia characteristic of TCS craniofacial anomalies.
Coactivator-associated arginine methyltransferase 1 (CARM1) is a positive regulator of the
Cyclin E1
gene
Authors: El Messaoudi Selma , Fabbrizio Eric , Rodriguez Carmen , Chuchana Paul , Fauquier Lucas , Cheng Donghang , Theillet Charles , Vandel Laurence , Bedford Mark T. , Sardet Claude
Published: August 2006

The
Cyclin E1
gene (
CCNE1
) is an ideal model to explore the mechanisms that control the transcription of cell cycle-regulated genes whose expression rises transiently before entry into S phase. E2F-dependent regulation of the
CCNE1
promoter was shown to correlate with changes in the level of H3-K9 acetylation/methylation of nucleosomal histones positioned at the transcriptional start site region. Here we show that, upon growth stimulation, the same region is subject to variations of H3-R17 and H3-R26 methylation that correlate with the recruitment of coactivator-associated arginine methyltransferase 1 (CARM1) onto the
CCNE1
and
DHFR
promoters. Accordingly, CARM1-deficient cells lack these modifications and present lowered levels and altered kinetics of
CCNE1
and
DHFR
mRNA expression. Consistently, reporter gene assays demonstrate that CARM1 functions as a transcriptional coactivator for their E2F1/DP1-stimulated expression. CARM1 recruitment at the
CCNE1
gene requires activator E2Fs and ACTR, a member of the p160 coactivator family that is frequently overexpressed in human breast cancer. Finally, we show that grade-3 breast tumors present coelevated mRNA levels of
ACTR
and
CARM1
, along with their transcriptional target
CCNE1
. All together, our results indicate that CARM1 is an important regulator of the
CCNE1
gene.
Conformational transition pathway in the allosteric process of human glucokinase
Authors: Zhang Jian , Li Chenjing , Chen Kaixian , Zhu Weiliang , Shen Xu , Jiang Hualiang
Published: August 2006

Glucokinase (GK) is an important enzyme for regulating blood glucose levels and a potentially attractive target for diabetes of the young type 2 and persistent hyperinsulinemic hypoglycemia of infancy. To characterize the conformational transition of GK from the closed state to the superopen state, a series of conventional molecular dynamics (MD) and target MD (TMD) simulations were performed on both the wild-type enzyme and its mutants. Two 10-ns conventional MD simulations showed that, although the allosteric site of GK is ≈20 Å away from the active site, the activator is able to enhance the activity of the enzyme through conformational restriction. Fourteen TMD simulations on GK and five of its mutants revealed a reliably conformational transition pathway. The overall conformational transition includes three stages, and three likely stable intermediate states were identified by free energy scanning for the snapshots throughout the pathway. The conformational transition feature revealed by our TMD simulations rationalized several important mutagenesis and kinetic data. Remarkably, the TMD simulations predicted that Y61S, I159A, A201R, V203E, and V452S mutations, which have not been investigated so far, may facilitate the opening process of GK. These predictions also have been verified by mutagenesis and kinetic analyses in this study. These observations are beneficial to understanding the mechanism of GK regulation and designing the compounds for treating metabolic diseases.
RETRACTED: Characterization of capsaicin synthase and identification of its gene (
csy1
) for pungency factor capsaicin in pepper (
Capsicum
sp.)
Authors: Prasad B. C. Narasimha , Kumar Vinod , Gururaj H. B. , Parimalan R. , Giridhar P. , Ravishankar G. A.
Published: August 2006

Capsaicin is a unique alkaloid of the plant kingdom restricted to the genus
Capsicum
. Capsaicin is the pungency factor, a bioactive molecule of food and of medicinal importance. Capsaicin is useful as a counterirritant, antiarthritic, analgesic, antioxidant, and anticancer agent. Capsaicin biosynthesis involves condensation of vanillylamine and 8-methyl nonenoic acid, brought about by capsaicin synthase (CS). We found that CS activity correlated with genotype-specific capsaicin levels. We purified and characterized CS (≈35 kDa). Immunolocalization studies confirmed that CS is specifically localized to the placental tissues of
Capsicum
fruits. Western blot analysis revealed concomitant enhancement of CS levels and capsaicin accumulation during fruit development. We determined the N-terminal amino acid sequence of purified CS, cloned the CS gene (
csy1
) and sequenced full-length cDNA (981 bp). The deduced amino acid sequence of CS from full-length cDNA was 38 kDa. Functionality of
csy1
through heterologous expression in recombinant
Escherichia coli
was also demonstrated. Here we report the gene responsible for capsaicin biosynthesis, which is unique to
Capsicum
spp. With this information on the CS gene, speculation on the gene for pungency is unequivocally resolved. Our findings have implications in the regulation of capsaicin levels in
Capsicum
genotypes.
A
Drosophila
model of the rhabdomyosarcoma initiator PAX7-FKHR
Authors: Galindo Rene L. , Allport Jay A. , Olson Eric N.
Published: August 2006

Alveolar rhabdomyosarcoma (ARMS) is an aggressive myogenic-type tumor and a gain-of-function disease, caused by misexpression of the PAX3-FKHR or PAX7-FKHR fusion oncoprotein from structurally rearranged chromosomes. PAX3-FKHR misexpressed in terminally differentiating mouse myofibers can cause rhabdomyosarcoma at a low frequency, suggesting that skeletal muscle is an ARMS tissue of origin. Because patterned muscle is widely viewed as irreversibly syncytial, questions persist, however, regarding this potential pathogenetic mechanism for ARMS tumor initiation. To further explore this issue, we generated transgenic
Drosophila
lines that conditionally express human PAX-FKHR. Here we show that PAX7-FKHR causes nucleated cells to form and separate from syncytial myofibers, which then spread to nonmuscular tissue compartments, including the central nervous system, and that wild-type PAX3 demonstrates similar potential. We further show that Ras, which is known to interfere with the differentiation of myogenic cells, genetically interacts with PAX7-FKHR: constitutively activated Ras enhances
PAX7-FKHR
phenotypes, whereas loss-of-function
ras
alleles dominantly suppress PAX7-FKHR activity, including rescue of lethality. These results show that PAX-FKHR can drive the generation of discrete nucleated cells from differentiated myofibers
in vivo
, argue for syncytial muscle as an ARMS tissue of origin, and demonstrate that
Drosophila
provides a powerful system to screen for genetic modifiers of PAX-FKHR.
Dopamine targets cycling B cells independent of receptors/transporter for oxidative attack: Implications for non-Hodgkin’s lymphoma
Authors: Meredith Elizabeth J. , Holder Michelle J. , Rosén Anders , Lee Adrian Drake , Dyer Martin J. S. , Barnes Nicholas M. , Gordon John
Published: August 2006

Human B lymphocytes and derived lines from a spectrum of B cell malignancy were studied for expression of dopaminergic pathway components and for their cytostatic response to the catecholamine and related, potentially therapeutic compounds. Proliferating normal lymphocytes and dividing malignant clones rapidly arrested on exposure to dopamine in the low (≤10 μM) micromolar range. The antiparkinsonian drugs
l
-DOPA and apomorphine (particularly) were similarly antiproliferative. With the exception of D4, dopamine receptors D1–D5 were variably expressed among normal and neoplastic B cell populations, as was the dopamine transporter. Transcripts for D1 and D2 were frequently found, whereas D3 and D5 revealed restricted expression; dopamine transporter was detected in most cases. Nevertheless, pharmacological analysis disclosed that dopamine targeted cycling B cells independent of these structures. Rather, oxidative stress constituted the primary mechanism: the catecholamine’s actions being mimicked by hydrogen peroxide and reversed by exogenous catalase, and evidence for the intracellular redox protein thioredoxin contributing protection. Among proliferating clones, growth arrest was accompanied by cell death in populations deplete in antiapoptotic Bcl-2: resting lymphocytes escaping low micromolar dopamine toxicity. Dysregulated
bcl-2
expression, although preventing oxidative-induced caspase-dependent apoptosis, by itself conferred only minor protection against dopamine cytostasis. The selective impact of dopamine on lymphocytes that are in active cycle indicates an axis for therapeutic intervention not only in B cell neoplasia but also in lymphoproliferative disturbances generally. Rational tailoring of drug delivery systems already in development for Parkinson’s disease could provide ideal vehicles for carrying the oxidative hit directly to the target populations.
The PhoP/PhoQ two-component system stabilizes the alternative sigma factor RpoS in
Salmonella enterica
Authors: Tu Xuanlin , Latifi Tammy , Bougdour Alexandre , Gottesman Susan , Groisman Eduardo A.
Published: August 2006

The sigma factor RpoS regulates the expression of many stress response genes and is required for virulence in several bacterial species. We now report that RpoS accumulates when
Salmonella enterica
serovar Typhimurium is growing logarithmically in media with low Mg
2+
concentrations. This process requires the two-component regulatory system PhoP/PhoQ, which is specifically activated in low Mg
2+
. We show that PhoP controls RpoS protein turnover by serving as a transcriptional activator of the
iraP
(
yaiB
) gene, which encodes a product that enhances RpoS stability by interacting with RssB, the protein that normally delivers RpoS to the ClpXP protease for degradation. Mutation of the
phoP
gene rendered
Salmonella
as sensitive to hydrogen peroxide as an
rpoS
mutant after growth in low Mg
2+
. In
Escherichia coli
, low Mg
2+
leads to only modest RpoS stabilization, and
iraP
is not regulated by PhoP/PhoQ. These findings add the sigma factor RpoS to the regulatory proteins and two-component systems that are elevated in a PhoP/PhoQ-dependent fashion when
Salmonella
face low Mg
2+
environments. Our data also exemplify the critical differences in regulatory circuits that exist between the closely related enteric bacteria
Salmonella
and
E. coli
.
Evolution of cooperation among tumor cells
Authors: Axelrod Robert , Axelrod David E. , Pienta Kenneth J.
Published: August 2006

The evolution of cooperation has a well established theoretical framework based on game theory. This approach has made valuable contributions to a wide variety of disciplines, including political science, economics, and evolutionary biology. Existing cancer theory suggests that individual clones of cancer cells evolve independently from one another, acquiring all of the genetic traits or hallmarks necessary to form a malignant tumor. It is also now recognized that tumors are heterotypic, with cancer cells interacting with normal stromal cells within the tissue microenvironment, including endothelial, stromal, and nerve cells. This tumor cell–stromal cell interaction in itself is a form of commensalism, because it has been demonstrated that these nonmalignant cells support and even enable tumor growth. Here, we add to this theory by regarding tumor cells as game players whose interactions help to determine their Darwinian fitness. We marshal evidence that tumor cells overcome certain host defenses by means of diffusible products. Our original contribution is to raise the possibility that two nearby cells can protect each other from a set of host defenses that neither could survive alone. Cooperation can evolve as by-product mutualism among genetically diverse tumor cells. Our hypothesis supplements, but does not supplant, the traditional view of carcinogenesis in which one clonal population of cells develops all of the necessary genetic traits independently to form a tumor. Cooperation through the sharing of diffusible products raises new questions about tumorigenesis and has implications for understanding observed phenomena, designing new experiments, and developing new therapeutic approaches.
Surface molecular view of colloidal gelation
Authors: Roke Sylvie , Berg Otto , Buitenhuis Johan , van Blaaderen Alfons , Bonn Mischa
Published: August 2006

We investigate the phase behavior of surface-functionalized silica colloids at both the molecular and macroscopic levels. This investigation allows us to relate collective properties such as aggregation, gelation, and aging directly to molecular interfacial behavior. By using surface-specific vibrational spectroscopy, we reveal dramatic changes in the conformation of alkyl chains terminating submicrometer silica particles. In fluid suspension at high temperatures, the interfacial molecules are in a liquid-like state of conformational disorder. As the temperature is lowered, the onset of gelation is identified by macroscopic phenomena, including changes in turbidity, heat release, and diverging viscosity. At the molecular level, the onset of this transition coincides with straightening of the carbon–carbon backbones of the interfacial molecules. In later stages, their intermolecular crystalline packing improves. It is the increased density of this ordered boundary layer that increases the van der Waals attraction between particles, causing the colloidal gas to aggregate. The approach presented here can provide insights into phase transitions that occur through surface modifications in a variety of colloidal systems.
The plasminogen activator system modulates sympathetic nerve function
Authors: Schaefer Ulrich , Machida Takuji , Vorlova Sandra , Strickland Sidney , Levi Roberto
Published: August 2006

Sympathetic neurons synthesize and release tissue plasminogen activator (t-PA). We investigated whether t-PA modulates sympathetic activity. t-PA inhibition markedly reduced contraction of the guinea pig vas deferens to electrical field stimulation (EFS) and norepinephrine (NE) exocytosis from cardiac synaptosomes. Recombinant t-PA (rt-PA) induced exocytotic and carrier-mediated NE release from cardiac synaptosomes and cultured neuroblastoma cells; this was a plasmin-independent effect but was potentiated by a fibrinogen cleavage product. Notably, hearts from t-PA–null mice released much less NE upon EFS than their wild-type (WT) controls (i.e., a 76.5% decrease; P < 0.01), whereas hearts from plasminogen activator inhibitor-1 (PAI-1)–null mice released much more NE (i.e., a 275% increase; P < 0.05). Furthermore, vasa deferentia from t-PA–null mice were hyporesponsive to EFS (P < 0.0001) but were normalized by the addition of rt-PA. In contrast, vasa from PAI-1–null mice were much more responsive (P < 0.05). Coronary NE overflow from hearts subjected to ischemia/reperfusion was much smaller in t-PA–null than in WT control mice (P < 0.01). Furthermore, reperfusion arrhythmias were significantly reduced (P < 0.05) in t-PA–null hearts. Thus, t-PA enhances NE release from sympathetic nerves and contributes to cardiac arrhythmias in ischemia/reperfusion. Because the risk of arrhythmias and sudden cardiac death is increased in hyperadrenergic conditions, targeting the NE-releasing effect of t-PA may have valuable therapeutic potential.
Colloidal lithography and current fabrication techniques producing in-plane nanotopography for biological applications
Authors: Wood M.A
Published: August 2006

Substrate topography plays a vital role in cell and tissue structure and functionin situ, where nanometric features, for example, the detail on single collagen fibrils, influence cell behaviour and resultant tissue formation.In vitroinvestigations demonstrate that nanotopography can be used to control cell reactions to a material surface, indicating its potential application in tissue engineering and implant fabrication. Developments in the catalyst, optical, medical and electronics industries have resulted in the production of nanopatterned surfaces using a variety of methods. The general protocols for nanomanufacturing require high resolution and low cost for fabricating devices. With respect to biological investigations, nanotopographies should occur across a large surface area (ensuring repeatability of experiments and patterning of implant surfaces), be reproducible (allowing for consistency in experiments), and preferably, accessible (limiting the requirement for specialist equipment). Colloidal lithography techniques fit these criteria, where nanoparticles can be utilized in combination with a functionalized substrate to produce in-plane nanotopographies. Subsequent lithographic processing of colloidal substrates utilizing, for example, reactive ion etching allows the production of modified colloidal-derived nanotopographies. In addition to two-dimensional in-plane nanofabrication, functionalized structures can be dip coated in colloidal sols, imparting nanotopographical cues to cells within a three-dimensional environment.
Ecological correlates of population genetic structure: a comparative approach using a vertebrate metacommunity
Authors: Manier Mollie K , Arnold Stevan J
Published: August 2006

Identifying ecological factors associated with population genetic differentiation is important for understanding microevolutionary processes and guiding the management of threatened populations. We identified ecological correlates of several population genetic parameters for three interacting species (two garter snakes and an anuran) that occupy a common landscape. Using multiple regression analysis, we found that species interactions were more important in explaining variation in population genetic parameters than habitat and nearest-neighbour characteristics. Effective population size was best explained by census size, while migration was associated with differences in species abundance. In contrast, genetic distance was poorly explained by the ecological correlates that we tested, but geographical distance was prominent in models for all species. We found substantially different population dynamics for the prey species relative to the two predators, characterized by larger effective sizes, lower gene flow and a state of migration-drift equilibrium. We also identified an escarpment formed by a series of block faults that serves as a barrier to dispersal for the predators. Our results suggest that successful landscape-level management should incorporate genetic and ecological data for all relevant species, because even closely associated species can exhibit very different population genetic dynamics on the same landscape.