In vivo responses of cutaneous C-mechanosensitive neurons in mouse to punctate chemical stimuli that elicit itch and nociceptive sensations in humans

Native cowhage spicules, and heat-inactivated spicules containing histamine or capsaicin, evoke similar sensations of itch and nociceptive sensations in humans. In ongoing studies of the peripheral neural mechanisms of chemical itch and pain in the mouse, extracellular electrophysiological recordings were obtained, in vivo, from the cell bodies of mechanosensitive nociceptive neurons in response to spicule stimuli delivered to their cutaneous receptive fields (RFs) on the distal hindlimb. A total of 43 mechanosensitive, cutaneous, nociceptive neurons with axonal conduction velocities in the C-fiber range (C-nociceptors) were classified as CM if responsive to noxious mechanical stimuli, such as pinch, or CMH if responsive to noxious mechanical and heat stimuli (51°C, 5 s). The tips of native cowhage spicules, or heat-inactivated spicules containing histamine or capsaicin, were applied to the RF. Heat-inactivated spicules containing no chemical produced only a transient response occurring during insertion. Of the 43 mechanosensitive nociceptors recorded, 20 of the 25 CMHs responded to capsaicin, and of these, 13 also responded to cowhage and/or histamine. In contrast, none of the 18 CMs responded to any of the chemical stimuli. The time course of the mean discharge rate of CMHs was similar in response to each type of spicule and generally similar, although reaching a peak earlier, to the temporal profiles of itch and nociceptive sensations evoked by the same stimuli in humans. These findings are consistent with the hypothesis that the itch and nociceptive sensations evoked by these punctuate chemical stimuli are mediated at least in part by the activity of mechanoheat-sensitive C-nociceptors. In contrast, activity in mechanosensitive C-nociceptors that do not respond to heat or to pruritic chemicals is hypothesized as contributing to pain but not to itch.

Drift Mobility Measurements in Porous Silicon

Modulated electroluminescence (EL) measurements performed on a series of porous silicon (PSi) diodes are presented. The maximum response time of the devices scales with the square of the PSi layer thickness and inversely with the applied forward bias voltage. These scaling results indicate that the maximum response time is a carrier transit time from which a drift mobility μ of 10−4 cm2/Vs is deduced at room temperature. Time-of-flight transport measurements on PSi are in qualitative agreement with this value for μ in addition, they identify μ as the electron mobility and show that transport is dispersive, in contrast to the interpretation of the modulated EL experiments.

Prediction of G-protein-coupled receptor classes in low homology using Chou's pseudo amino acid composition with approximate entropy and hydrophobicity patterns

We use approximate entropy and hydrophobicity patterns to predict G-protein-coupled receptors. Adaboost classifier is adopted as the prediction engine. A low homology dataset is used to validate the proposed method. Compared with the results reported, the successful rate is encouraging. The source code is written by Matlab.

Homeobox gene IRX1 is a tumor suppressor gene in gastric carcinoma

The IRX1 tumor suppressor gene is located on 5p15.33, a cancer susceptibility locus. Loss of heterozygosity of 5p15.33 in gastric cancer was identified in our previous work. In this study, we analyzed the molecular features and function of IRX1. We found that IRX1 expression was lost or reduced in gastric cancer. However, no mutations were identified in IRX1-encoding regions. IRX1 transcription was suppressed by hypermethylation, and the expression of IRX1 mRNA was partially restored in gastric cancer cells after 5-Aza-dC treatment. Restoring IRX1 expression in SGC-7901 and NCI-N87 gastric cancer cells inhibited growth, invasion and tumorigenesis in vitro and in vivo. We identified a number of target genes by global microarray analysis after IRX1 transfection combined with real-time PCR and chromatin immunoprecipitation assay. BDKRB2, an angiogenesis-related gene, HIST2H2BE and FGF7, cell proliferation and invasion-related genes, were identified as direct IRX1 target genes. The hypermethylation of IRX1 was not only detected in primary gastric cancer tissues but also in the peripheral blood of gastric cancer patients, suggesting IRX1 could potentially serve as a biomarker for gastric cancer.

Effect of dietary probiotic, Bacillus coagulans, on growth performance, chemical composition, and meat quality of Guangxi Yellow chicken

The effect of Bacillus coagulans ZJU0616 with different concentrations supplemented as probiotic was evaluated on growth performance, feed conversion ratio, survival rate, breast chemical composition, and meat quality of Guangxi Yellow chicken. Birds were randomly segregated into 12 groups so that 3 replicates were available for each of the 3 treatments (T-1, T-2, and T-3) and control groups. The control groups were fed a basal diet without any probiotic and other groups were fed the diets that consisted of 3 probiotic levels at initial concentrations of 1.0 x 10(6) cfu.g(-1) (T-1), 2.0 x 10(6) cfu.g(-1) (T-2), and 5.0 x 10(6) cfu.g(-1) (T-3). The lowest final weight and daily weight gain were found in control groups (P < 0.05) and there were no significant differences among probiotic-treated groups. Significantly lower feed conversion ratio and higher survival rate were observed in T-2 and T-3 than that of the control. There were no significant differences (P > 0.05) in contents of breast chemical composition including moisture, CP, crude fat, and crude ash among all groups. For the meat quality parameter assays, the pH, shear force, and drip loss were used as indicators. As for pH values of breasts, no significant difference was found across all treatments. Higher shear force was observed (P < 0.05) in T-2 compared with T-1 and the control. Similar significant difference was also observed in T-1 compared with the control. However, there was no significant difference in shear force between T-3 and the other probiotic treatment groups (T-1 and T-2). As for probiotic-treated groups, there was significant difference (P < 0.05) in breast drip loss compared with that of the control (6.22 +/- 0.18%), with the lowest drip loss found in T-3 (5.38 +/- 0.25%). However, no significant difference was observed in drip loss between T-2 and T-3.

Indoor air pollution from solid biomass fuels combustion in rural agricultural area of Tibet, China

In this study, we are trying to investigate the indoor air pollution and to estimate the residents' pollution exposure reduction of energy altering in rural Tibet. Daily PM(2.5) monitoring was conducted in indoor microenvironments like kitchen, living-room, bedroom, and yard in rural Tibet from December 2006 to March 2007. For kitchen air pollution, impact of two fuel types, methane and solid biomass fuels (SBFs), were compared. Questionnaire survey on the domestic energy pattern and residents' daily activity pattern was performed in Zha-nang County. Daily average PM(2.5) concentrations in kitchen, living-room, bedroom, and yard were 134.91 microg/m(3) (mean, n = 45, 95%CI 84.02, 185.80), 103.61 microg/m(3) (mean, n = 21, 95%CI 85.77, 121.45), 76.13 microg/m(3) (mean, n = 18, 95%CI 57.22, 95.04), and 78.33 microg/m(3) (mean, n = 34, 95%CI 60.00, 96.65) respectively. Using SBFs in kitchen resulted in higher indoor pollution than using methane. PM(2.5) concentrations in kitchen with dung cake, fuel wood and methane use were 117.41 microg/m(3) (mean, n = 18, 95%CI 71.03, 163.79), 271.11 microg/m(3) (mean, n = 12, 95%CI 104.74, 437.48), and 46.96 microg/m(3) (mean, n = 15, 95%CI 28.10, 65.82) respectively. Family income has significant influence on cooking energy choice, while the lack of commercial energy supply affects the energy choice for heating more. The effects of two countermeasures to improve indoor air quality were estimated in this research. One is to replace SBFs by clean energy like methane, the other is to separate the cooking place from other rooms and by applying these countermeasures, residents' exposure to particulate matters would reduce by 25-50% (methane) or 20-30% (separation) compared to the present situation.

PRACTICAL IMPLICATIONS

Indoor air pollution caused by solid biomass fuels is one of the most important burdens of disease in the developing countries, which attracts the attention of environment and public health researchers, as well as policy makers. This paper gives a pilot research on the indoor air pollution and estimated the effects of some intervention policies in Tibet of China, where the living habits of the residents are quite different from other parts of the world. This work would be an important supply to the indoor air pollution studies, and would be helpful in policy making.

Cough sensors. IV. Nicotinic membrane receptors on cough sensors

Cigarette smoke is undoubtedly one of the most common inhaled irritants in the human respiratory tract, and invariably evokes coughing in both smokers and nonsmokers. Results obtained from the studies in human volunteers and from single-fiber recording of vagal bronchopulmonary afferents in animals clearly indicate that nicotine is primarily responsible for the airway irritation and coughing caused by inhalation of cigarette smoke. Furthermore, both nicotine and acetylcholine can evoke inward current, membrane depolarization, and action potentials in isolated pulmonary sensory neurons, and these responses are blocked by hexamethonium. Taken together, these findings suggest that the tussive effect of nicotine is probably mediated through an activation of nicotinic acetylcholine receptors (nAChRs) expressed on the sensory terminals of cough receptors located in the airway mucosa. Indeed, the expressions of alpha4-alpha7 and beta2-beta4 subunits of nAChR transcripts in pulmonary sensory neurons have lent further support to this conclusion. The specific subtypes of the neuronal nAChRs and their subunit compositions expressed on the cough sensors remain to be determined.

A novel electrospun polysulfone fiber membrane: application to advanced treatment of secondary bio-treatment sewage

Electrospun nanofibers and fine fibers have been used to remove submicron particles in air filtration. In this paper, direct-and polyaluminium chloride (PAC) pre-coagulation filtration of secondary bio-treatment sewage was studied using electrospun polysulfone fiber membrane (EPSFM). According to the results obtained, for direct filtration, suspended solids (SS), chemical oxygen demand (COD(Cr)) and NH3-N decreased 86.7, 71.2, 91.7% respectively, in filtrate of secondary bio-treatment sewage, while for PAC pre-coagulation filtration, the removal rate of SS, COD(Cr) and NH3-N reached 91.3, 85.3, 93.3 % respectively. EPSFM had a high efficiency in removing NH3-N, COD(Cr) and SS, especially for micron and submicron particles. EPSFM can reduce the content of some toxic metals, such as Cu, Zn and Ti, through interception and adsorption mechanism and can also remove dissolved organic matter such as humics and proteins through interception mechanism. EPSFM can remove some of volatile organic chemicals (VOCs) by adsorption and filtration, the removal rate of VOCs was in the range of 59-100 %. The number of VOCs in secondary bio-treatment sewage and its filtrate from direct filtration were 27 and 18 respectively, the major VOCs were benzene-, cyclohexane-, adamantine- and hydrocarbon derivates.

SAG/ROC2/RBX2 is a HIF-1 target gene that promotes HIF-1 alpha ubiquitination and degradation

SAG (sensitive to apoptosis gene) or ROC2/RBX2 is the second family member of ROC1/RBX1, a component of SCF (Skp1, Cullin, F-box protein) and VCB (von Hippel-Lindau (VHL), Cullin and Elongin B/C) E3 ubiquitin ligases. SAG protected cells from hypoxia-induced apoptosis when overexpressed. We report here that SAG was subjected to hypoxia induction at the levels of mRNA and protein. Hypoxia induction of SAG was largely HIF-1alpha dependent. A consensus HIF-1-binding site, GCGTG was identified in the first intron of the SAG gene. In response to hypoxia, HIF-1 bound to this site and transactivated SAG expression. SAG transactivation required both the intact binding site in cis and HIF-1alpha in trans. On the other hand, like its family member, ROC1, SAG promoted VHL-mediated HIF-1alpha ubiquitination and degradation, which was significantly inhibited upon small interfering RNA silencing of SAG or ROC1. Furthermore, the endogenous HIF-1alpha at both basal and hypoxia-induced levels was significantly increased upon SAG silencing. Finally, SAG forms in vivo complex with Cul-5 and VHL under hypoxia condition. These results suggest an HIF-1-SAG feedback loop in response to hypoxia, as follows: hypoxia induces HIF-1 to transactivate SAG. Induced SAG then promotes HIF-1alpha ubiquitination and degradation. This feedback loop may serve as a cellular defensive mechanism to reduce potential cytotoxic effects of prolonged HIF-1 activation under hypoxia.

Airway irritation and cough evoked by inhaled cigarette smoke: role of neuronal nicotinic acetylcholine receptors

In a series of studies carried out in different experimental models, we investigated the type(s) of lung afferents and mechanism(s) underlying the cigarette smoke-induced airway irritation and cough. In healthy non-smokers, the intensity of airway irritation and cough evoked by cigarette smoke was markedly reduced after premedication with hexamethonium. A similar pattern of responses was also triggered by inhalation of nicotine aerosol. These studies in human subjects suggested nicotine as the primary causative agent in cigarette smoke that evokes airway irritation. Indeed, single-fiber recording experiments performed in anesthetized dogs showed that both C-fibers and rapidly adapting receptors in the lungs and airways were stimulated by inhalation of one puff of cigarette smoke, and the intensity of this stimulatory effect was related to the nicotine content in the cigarette and abolished by hexamethonium. To further study the direct effect of nicotine on these sensory nerves, we measured the change in intracellular calcium concentration ([Ca(2+)](i)) of pulmonary sensory neurons isolated from the nodose and jugular ganglia of adult rats. Our results showed that nicotine evoked an abrupt and transient increase in [Ca(2+)](i) in approximately 34% of the 522 neurons tested, and 1,1-dimethyl-4-phenylpiperazinium, a selective agonist of the neuronal nicotinic acetylcholine receptors (NnAChRs), evoked a similar pattern of response as that of nicotine in these neurons. In conclusion, results of these studies show that nicotine exerts a direct stimulatory effect on vagal pulmonary sensory neurons. This stimulatory effect of nicotine is primarily responsible for the airway irritation and cough evoked by inhaled cigarette smoke, and is mediated through an activation of the NnAChRs.

Lansoprazole, levofloxacin and amoxicillin triple therapy vs. quadruple therapy as second-line treatment of resistant Helicobacter pylori infection

AIM

To test the efficacy of levofloxacin-based second-line therapy for resistant Helicobacter pylori infection.

METHODS

One hundred and six patients who failed H. pylori eradication were randomized to receive (i) lansoprazole 30 mg, amoxicillin 1 g, levofloxacin 500 mg, all given twice daily for 7 days (LAL); or (ii) lansoprazole 30 mg twice daily, metronidazole 400 mg thrice daily, bismuth subcitrate 120 mg and tetracycline 500 mg four times daily for 7 days (quadruple). Post-treatment H. pylori status was determined by (13)C-urea breath test.

RESULTS

Intention-to-treat and per-protocol H. pylori eradication rates were 57/60% for the LAL group and 71/76% for the quadruple group respectively. Metronidazole, clarithromycin, amoxicillin and levofloxacin resistance were found in 76%, 71%, 0% and 18% of patients, respectively. Levofloxacin resistance led to treatment failure in the LAL group. For patients with dual resistance to metronidazole and clarithromycin, the eradication rates were 79% in the LAL group (levofloxacin-sensitive) and 65% in the quadruple group (P=0.34).

CONCLUSION

Lansoprazole, amoxicillin plus levofloxacin second-line therapy is comparable with quadruple therapy in efficacy. Subjects, especially those with dual resistance to metronidazole and clarithromycin, may consider levofloxacin-based therapy for levofloxacin-sensitive strains.

Update on clarithromycin resistance in Helicobacter pylori in Hong Kong and its effect on clarithromycin-based triple therapy

AIM

To determine the antibiotic susceptibility of Helicobacter pylori and evaluate the efficacy of a clarithromycin-based triple therapy in relation to antibiotic resistance.

METHODS

Consecutive patients referred for upper endoscopy due to dyspeptic symptoms were recruited. Gastric biopsies were obtained for the CLO test, histology and culture. Antibiotic susceptibility was assessed by the E-test. Patients with H. pylori infection received rabeprazole 20 mg, clarithromycin 500 mg, and amoxicillin 1,000 mg, all twice daily for 7 days.

RESULTS

Of 234 patients recruited, 124 were H. pylori-positive and culture was successful in 102 patients. The updated prevalences of resistance to clarithromycin, amoxicillin and metronidazole were 7.8, 0 and 39.2%, respectively. A total of 86 patients received 1-week triple therapy with rabeprazole 20 mg, clarithromycin 500 mg, and amoxicillin 1,000 mg, all twice daily, and 81 patients attended the follow-up test. Eradication rates by per-protocol and intention-to-treat analysis were 92.6 and 87.2%, respectively. The eradication rate by per protocol was significantly higher in patients with clarithromycin-susceptible strains than in those with clarithromycin-resistant strains (98.6 vs. 28.6%, p < 0.001).

CONCLUSION

Clarithromycin resistance reduces the clinical efficacy of clarithromycin-based triple therapy. However, due to the low prevalence of clarithromycin resistance, clarithromycin-based therapy is still the first choice for clinical use.

Postnatal expression profile of OBCAM implies its involvement in visual cortex development and plasticity

This study examined the expression of a neuron-specific cell adhesion molecule, OBCAM (opioid-binding cell adhesion molecule), at both the mRNA and protein levels in the cat primary visual cortex at various postnatal ages, using cDNA array analysis and immunocytochemistry. Results obtained using both methods showed that the expression level of OBCAM was high in young and low in older and adult visual cortex. OBCAM-immunoreactivities were associated predominantly with perikarya and dendrites of pyramidal neurons, and OBCAM-immunopositive neurons were present in all cortical layers. Immunostaining of OBCAM in adult visual cortex showed a reduced number of immunopositive neurons and neurites and relatively lower staining intensities as compared with younger animals. In addition, the number of OBCAM-immunopositive neurons was significantly higher in the visual cortex of 4-month-old animals dark-reared from birth than those in age-matched normally reared animals. These results suggest that OBCAM may play an important role in visual cortex development and plasticity.

Standard treatment for Helicobacter pylori infection is suboptimal in non-ulcer dyspepsia compared with duodenal ulcer in Chinese

BACKGROUND

Recent studies suggest that the Helicobacter pylori eradication rate in patients with non-ulcer dyspepsia is lower when compared to patients with peptic ulcer diseases.

AIM

The aim of this study was to study the efficacy of triple therapy for H. pylori infection in patients with duodenal ulcer vs. patients with non-ulcer dyspepsia.

METHODS

A total of 582 Chinese patients with proven H. pylori infection were recruited to receive: omeprazole 20 mg, amoxicillin 1000 mg and clarithromycin 500 mg all given twice daily for 7 days (OCA regime). Endoscopy with rapid urease test, histology and culture were performed before treatment. Post-treatment H. pylori status was determined by (13)C-urea breath test. Metronidazole, clarithromycin and amoxicillin resistance was defined as minimum inhibitory concentration (MIC) of >8 microg/mL, >1 microg/mL and >1 microg/mL, respectively.

RESULTS

A significantly higher (intention-to-treat/per-protocol) eradication rate was found in patients with duodenal ulcer than those with non-ulcer dyspepsia (91/94% vs. 84/88% respectively, P = 0.011 and P = 0.016). Clarithromycin resistance rate was higher in patients with non-ulcer dyspepsia than those with duodenal ulcer (14% vs. 6%, P = 0.015). Clarithromycin resistance (40% vs. 5%, P < 0.001, OR 12, 95% CI: 5.7-24.3) and the diagnosis of non-ulcer dyspepsia (91% vs. 84%, P = 0.011, OR 2.0, 95% CI: 1.2-3.3) significantly affected the success of H. pylori eradication.

CONCLUSION

Clarithromycin resistance accounts for the significantly lower and suboptimal H. pylori eradication rate of OCA regimen in Chinese patients with non-ulcer dyspepsia compared to those with duodenal ulcer.

Effect of cyclo-oxygenase inhibitors on Helicobacter pylori susceptibility to metronidazole and clarithromycin

BACKGROUND

We previously reported that aspirin inhibited Helicobacter pylori growth and suppressed the mutagenic effect of metronidazole.

AIM

To determine the effects of a cyclo-oxygenase (COX)-2-specific inhibitor, SC-236, and a non-selective COX inhibitor, indometacin, on the growth, urease activity and antimicrobial susceptibility of H. pylori.

METHODS

Three H. pylori reference strains, and 18 clinical isolates were treated with SC-236 or indometacin for 24 and 48 h. Growth, urease activity and susceptibility to clarithromycin and metronidazole of the bacteria were assessed by viable colony counting, spectrophotometry and E-test respectively.

RESULTS

SC-236 and indometacin inhibited H. pylori growth in a dose-dependent manner with the lowest inhibitory concentrations of 0.03 and 0.1 mm, and the lethal concentrations of 0.09 and 0.3 mm, respectively. The numbers of CFU/mL in Brucella broth containing 0.09 mm SC-236 were 2 log lower at 24 h, and even 3 log lower at 48 h than that at 0 h (P = 0.035, compared with the vehicle control). Treatment of 0.3 mm indometacin reduced the number of CFU/mL by 1 log at 24 h compared with that at 0 h (P = 0.037 compared with the vehicle control). Helicobacter pylori urease activity began to decrease with 0.06 mm SC-236 at 24 h (P = 0.016), and 0.3 mm indometacin at 48 h (P = 0.025). MICs of metronidazole and clarithromycin against H. pylori were decreased significantly in the presence of 0.03 mm SC-236 or 0.1 mm indometacin (all P < 0.001).

CONCLUSION

Both SC-236 and indometacin suppressed the growth and urease activity of H. pylori in a dose-dependent manner, and increased its susceptibility to the antibiotics.

Aspirin inhibits the growth of Helicobacter pylori and enhances its susceptibility to antimicrobial agents

BACKGROUND AND AIM

The role of Helicobacter pylori and aspirin in peptic ulcer formation and recurrence remains an important clinical topic. The interaction between aspirin and H pylori in vitro is also not clear. We investigated the effect of aspirin on the growth of H pylori and on the susceptibility of H pylori to antimicrobials.

METHODS

Time killing studies of H pylori were performed with different concentrations of aspirin and salicylate. Growth of bacteria was assessed spectrophotometrically and by viable colony count. The effects of aspirin on the efficiency of colony formation and on metronidazole induced mutation to rifampicin resistance in H pylori were determined. Minimal inhibitory concentrations (MICs) of aspirin and metronidazole were tested by the standard agar dilution method. MICs of amoxycillin and clarithromycin were determined by the E test method.

RESULTS

Aspirin and salicylate inhibited the growth of H pylori in a dose dependent manner and bactericidal activity was due to cell lysis. Aspirin 400 micro g/ml caused a 2 logs decrease in colony forming units/ml at 48 hours, and suppressed the normal ability of metronidazole to induce new mutations to rifampicin. The IC(90) of aspirin was 512 micro g/ml. Increased susceptibility of amoxycillin, clarithromycin, and metronidazole to H pylori was observed at 1 mM (180 micro g/ml) aspirin.

CONCLUSIONS

Aspirin inhibited the growth of H pylori, suppressed the mutagenic effect of metronidazole, and enhanced the susceptibility of H pylori to antimicrobial agents. This mechanism is important in future drug development for effective clearing and overcoming resistance.

Randomized controlled study of rabeprazole, levofloxacin and rifabutin triple therapy vs. quadruple therapy as second-line treatment for Helicobacter pylori infection

AIM

To test the efficacy of rabeprazole, levofloxacin and rifabutin triple therapy vs. quadruple therapy for the second-line treatment of Helicobacter pylori infection.

METHODS

One hundred and nine patients who had failed previous H. pylori eradication were randomized to receive: (i) rabeprazole, 20 mg b.d., rifabutin, 300 mg once daily, and levofloxacin, 500 mg once daily, for 7 days (triple therapy); or (ii) rabeprazole, 20 mg b.d., metronidazole, 400 mg t.d.s., bismuth subcitrate, 120 mg q.d.s., and tetracycline, 500 mg q.d.s., for 7 days (quadruple therapy). Endoscopy and culture were performed before treatment.

RESULTS

The clarithromycin (79% vs. 21%, P < 0.001) and metronidazole (89% vs. 40%, P < 0.001) resistance rates were significantly higher in patients with previous exposure than in those with no previous exposure. The intention-to-treat and per protocol eradication rates were 91%/91% for the triple therapy group and 91%/92% for the quadruple therapy group. For patients with double resistance to metronidazole and clarithromycin, the eradication rates were 85% (17/20) in the triple therapy group and 87% (13/15) in the quadruple therapy group. Compliance was greater than 95% for both regimens.

CONCLUSION

Rabeprazole, levofloxacin and rifabutin-based triple therapy and quadruple therapy were equally effective as second-line treatments for H. pylori infection.

Neuromodulatory transmitter systems in the cortex and their role in cortical plasticity

Cortical neuromodulatory transmitter systems refer to those classical neurotransmitters such as acetylcholine and monoamines, which share a number of common features. For instance, their centers are located in subcortical regions and send long projection axons to innervate the cortex. The same transmitter can either excite or inhibit cortical neurons depending on the composition of postsynaptic transmitter receptor subtypes. The overall functions of these transmitters are believed to serve as chemical bases of arousal, attention and motivation. The anatomy and physiology of neuromodulatory transmitter systems and their innervations in the cerebral cortex have been well characterized. In addition, ample evidence is available indicating that neuromodulatory transmitters also play roles in development and plasticity of the cortex. In this article, the anatomical organization and physiological function of each of the following neuromodulatory transmitters, acetylcholine, noradrenaline, serotonin, dopamine, and histamine, in the cortex will be described. The involvement of these transmitters in cortical plasticity will then be discussed. Available data suggest that neuromodulatory transmitters can modulate the excitability of cortical neurons, enhance the signal-to-noise ratio of cortical responses, and modify the threshold for activity-dependent synaptic modifications. Synaptic transmissions of these neuromodulatory transmitters are mediated via numerous subtype receptors, which are linked to multiple signal transduction mechanisms. Among the neuromodulatory transmitter receptor subtypes, cholinergic M(1), noradrenergic beta(1) and serotonergic 5-HT(2C) receptors appear to be more important than other receptor subtypes for cortical plasticity. In general, the contribution of neuromodulatory transmitter systems to cortical plasticity may be made through a facilitation of NMDA receptor-gated processes.

Gene expression patterns during enhanced periods of visual cortex plasticity

During a critical period in its postnatal development the mammalian visual cortex displays susceptibility to experience-dependent alterations of neuronal response properties. Plasticity represents an integrated set of developmental processes controlled by a transcriptional hierarchy that coordinates the action of many genes. To illuminate the expression of these critical genes, we examined gene expression patterns of 18371 non-redundant cDNAs in the visual cortex of cats at birth, at eye opening, at the peak of the critical period of eye dominance plasticity and in the adult cat using filter-based cDNA arrays and software-based hierarchical cluster analysis. We identified a small set of genes that were selectively expressed during the peak of the critical period for plasticity. We further examined the patterns of expression of these genes by analyzing the gene expression pattern of dark-reared chronologically older animals that are known to retain this ocular dominance plasticity beyond the chronologically defined critical period. This additional cluster assessment allowed us to separate age-related changes in the patterns of gene expression from plasticity-related changes, thus identifying a subset of genes that we define as plasticity candidate genes. Those plasticity candidate genes that have previously characterized functions include participants in second messenger systems, in cell adhesion, in transmitter recycling and cytokines, among others. Comparison of cDNA array quantitation with reverse transcription-polymerase chain reaction showed almost identical expression profiles for three genes that we examined. The expression pattern of one identified gene, opioid binding cell adhesion molecule, from the cDNA array analysis, is also in agreement with immunocytochemical results. We conclude that the approach of high-density cDNA array hybridization can be used as a useful tool for examining a complex phenomenon of developmental plasticity since it is amenable to multiple developmental stage gene expression comparisons.

[Absolute configuration of the diastereoisomer of 2-amino-3-(1,2-dicarboxyethylthio) propanoic acid from Amanita pantherina]

Four stereoisomers of 2-amino-3-(1,2-dicarboxyethylthio) propanoic acid were prepared by reaction of L- and D-cysteine with fumaric acid. The absolute configuration of the diastereoisomer of 2-amino-3-(1,2-dicarboxyethylthio) propanoic acid from Amanita pantherina were assigned as (2R, 1'R) and (2R, 1'S) by analysis of the optical properties. Pharmacological tests showed that all of the four stereoisomers inhibited the depolarization of NMDA on spinal motorneurones in newborn rats, The inhibition intensity of L-A, D-A and D-B were higher than that of L-B.

One-week omeprazole, furazolidone and amoxicillin rescue therapy after failure of Helicobacter pylori eradication with standard triple therapies

AIM

To test the efficacy of omeprazole, furazolidone and amoxicillin triple therapy for the treatment of Helicobacter pylori infection after failure of standard first-line therapy recommended by the Asia-Pacific Consensus on the management of H. pylori infection.

METHODS

Patients with failed H. pylori eradication received omeprazole, 20 mg, furazolidone, 100 mg, and amoxicillin, 1 g, all twice daily for 1 week. Endoscopy (CLO test, histology and culture) was performed before treatment. Post-treatment H. pylori status was determined by 13C-urea breath test 6 weeks later.

RESULTS

Fifty patients were recruited. Resistance to metronidazole, clarithromycin and both drugs was in the range of 50-64%, 60-75% and 40-50%, respectively, after failure of first-line therapy. Amoxicillin resistance was not found. The intention-to-treat and per protocol H. pylori eradication rates were 52% and 53%, respectively. Patients with double resistance to metronidazole and clarithromycin showed the lowest eradication rate (38%), which was significantly lower than that of patients with sensitive strains (88%). Side-effects were minimal and compliance was excellent (98%).

CONCLUSIONS

One-week omeprazole, furazolidone and amoxicillin rescue therapy achieved a high eradication rate in strains sensitive to metronidazole and clarithromycin. This is a cheap and safe rescue regimen when guided by pre-treatment sensitivity testing.

Hypersensitivity of pulmonary C fibre afferents induced by cationic proteins in the rat

1. Airway administration of synthetic cationic proteins, poly-L-lysine (PLL) and poly-L-arginine (PLA), is known to induce bronchial hyper-responsiveness, and an involvement of bronchopulmonary C fibre activation has been suggested. In this study we investigated the effects of PLL and PLA on single-unit pulmonary vagal C fibre afferents in anaesthetized, open-chest rats. 2. Intratracheal (I.T.) instillation of PLL or PLA activated C fibre endings in a dose-dependent manner; for example, a high dose of PLL (50 microg in 0.1 ml) had a sporadic but intense stimulatory effect on these afferents. The augmented C fibre activity slowly declined but remained elevated even after 120 min. 3. Intratracheal instillation of PLL or PLA greatly enhanced the sensitivities of pulmonary C fibres to both lung inflation and chemical stimuli (e.g. capsaicin); for example, the change in fibre activity in response to constant-pressure lung inflation (tracheal pressure (P(t)) = 30 cmH(2)O; 10 s duration) increased by approximately 6-fold after PLL instillation. 4. When administered by intravenous injection or instilled into a different region of the lung, PLL or PLA, even at a higher dose, failed to have any effect on the C fibre endings. 5. The stimulatory and sensitizing effects of PLL or PLA were completely nullified when their cationic charges were neutralized with low molecule weight heparin. 6. In conclusion, I.T. instillation of synthetic cationic proteins causes an intense stimulatory effect on pulmonary C fibres and potentiates their sensitivities to both lung inflation and chemical stimuli. These effects are probably generated by an interaction between the cationic charges carried by these proteins and the airway mucosa.

Effects of human eosinophil granule-derived cationic proteins on C-fiber afferents in the rat lung

Experiments were performed to test the hypothesis that human eosinophil granule-derived cationic proteins stimulate vagal C-fiber afferents in the lungs and elicit pulmonary chemoreflex responses in anesthetized Sprague-Dawley rats. Intratracheal instillation of eosinophil cationic protein (ECP; 1-2 mg/ml, 0.1 ml) consistently induced an irregular breathing pattern, characterized by tachypnea (change in breathing frequency of 44.7%) and small unstable tidal volume (VT). The tachypnea, accompanied by decreased heart rate and arterial blood pressure, started within 30 s after the delivery of ECP and lasted for >30 min. These ECP-induced cardiorespiratory responses were completely prevented by perineural capsaicin treatment of both cervical vagi, which selectively blocked C-fiber conduction, suggesting the involvement of these afferents. Indeed, direct recording of single-unit activities of pulmonary C-fibers further demonstrated that the same dose of ECP evoked a pronounced and sustained (>30-min) stimulatory effect on pulmonary C-fibers. Furthermore, the sensitivity of these afferents to lung inflation was also markedly elevated after the ECP instillation, whereas the vehicle of ECP administered in the same manner had no effect. Other types of eosinophil granule cationic proteins, such as major basic protein and eosinophil peroxidase, induced very similar respiratory and cardiovascular reflex responses. In conclusion, these results show that eosinophil granule-derived cationic proteins induce a distinct stimulatory effect on vagal pulmonary C-fiber endings, which may play an important role in the airway hyperresponsiveness associated with eosinophil infiltration in the airways.

Sensitivity of vagal afferent endings to chemical irritants in the rat lung

This study was carried out to investigate the relationship between the conduction velocity of the vagal afferents arising from the rat lungs and their sensitivities to capsaicin, other chemical irritants, and lung inflation. We recorded single-unit activities of vagal pulmonary afferents (n = 205) in anesthetized, open-chest rats, and distinguished C fibers (conduction velocity < 2 m/sec) from myelinated afferents; the latter group was further classified into rapidly adapting pulmonary receptors (RARs) and slowly adapting pulmonary stretch receptors (SARs) on the basis of their adaptation indexes to lung inflation. Right-atrial injection of capsaicin (1 microg/kg) evoked an abrupt and intense stimulatory effect in 88.9% (64/72) of the pulmonary C fibers tested, but only a mild stimulation in 6.3% (3/48) of the RARs and none of the SARs. Other inhaled and injected chemical stimulants (e.g., cigarette smoke, lactic acid) activated 68.9% (42/61) of the pulmonary C fibers. The same chemical irritants exerted a mild stimulatory effect in only 14.5% (8/55) of the RARs; this subgroup of RARs exhibited a low or no baseline activity, and half of them were located near the hilum. Chemical stimulants had little or no effect on SARs. The response of pulmonary C fibers to lung inflation (tracheal pressure = 30 cm H2O) was not only extremely weak, but also showed a longer onset latency and an irregular pattern. In a sharp contrast, lung inflation evoked rapid and vigorous discharges in both RARs and SARs. In conclusion, C fibers are the primary type of chemosensitive vagal pulmonary afferents in rat lungs.

Identification of a novel truncated isoform of trkB in the kitten primary visual cortex

Neurotrophins have been shown to play important roles in development and plasticity of the visual cortex (VC). Since signal transduction of neurotrophins is mediated through neurotrophin receptors, we attempted to analyze neurotrophin receptors in the VC. In this study, we isolated cDNAs encoding the intracellular regions of truncated isoforms of the trkB receptor from 30-d-old kitten primary VC. Two distinct truncated isoforms of trkB were isolated and characterized by sequence analyses. One of the isoforms corresponds to the previously described truncated trkB in several mammalian species. The second isoform represents a novel truncated trkB variant form in the kitten VC. Sequence analysis revealed that this contains a sequence that has not yet been reported in any species. This novel isoform, designated trkB.T4, results from alternative splicing 189-bp (63 amino acids) downstream from the splice site giving rise to the first known truncated isoforms of trkB. In the context of recent hypotheses regarding the function of truncated trkB receptors, sequence analysis indicates that trkB.T4 may bear putative signaling/internalization sequences.

[Preparation of green fluorescent protein retrovirus and its application in mediating gene transfer into retinal pigment epithelial cells]

OBJECTIVE

To determine whether human retinal pigment epithelial (RPE) cells can be infected by retrovirus and modified by retrovirus-mediated gene transfer.

METHODS

Recombination retroviral vector pLNCX-GFP (green fluorescent protein, GFP) was generated by inserting 780 bp GFP cDNA fragment into the MCS site of pLNCX. pLNCX-GFP was transfected into ecotropic packaging cell line PhiX-Eco and amphotropic packaging cell line PhiX-Ampho and PA317. Retroviral titer was tested by counting GFP expression of NIH3T3 cells. Then RPE cells were infected by using GFP retrovirus-containing supernatant.

RESULTS

GFP was expressed and retrovirus was produced upon pLNCX-GFP being transfected into packaging cell line. The GFP retrovirus was able to infect primary cultured human RPE cells and immortalized RPE cell line.

CONCLUSION

The retrovirus can introduce a foreign gene into RPE cells efficiently, thereby it can be used as an important tool to deliver gene into RPE for therapy of fundus diseases.

Characterization of urocortin in human pregnancy

OBJECTIVE

To examine whether urocortin is produced locally to regulate utero-placental vascular tone during pregnancy.

METHODS

We examined the distribution of urocortin in human placenta, fetal membranes and uterine tissue at term in the presence and absence of labor using a urocortin antibody produced in our laboratory and the immunoperoxidase staining method. Subsequently, we tested urocortin secretion from chorio-decidual cells in vitro using an immunoblot technique. Then, we tested whether urocortin is present in maternal plasma throughout gestation using a radioimmunoassay. A Sephadex G-50 column was used to examine whether immunoreactive urocortin (IR-urocortin) in maternal plasma is the same as synthetic urocortin.

RESULTS

IR-urocortin was observed in vascular smooth muscle of myometrium decidual stromal cells, syncytiotrophoblast and amnion epithelium. No differences in staining intensity for urocortin were detected between tissues obtained in the absence or presence of labor. Staining intensity for IR-urocortin was greatest in the decidua, suggesting this may be the main site of urocortin production. Positive staining for urocortin was observed in 40% of chorio-decidual cells with 34% of these cells secreting urocortin under basal conditions. Urocortin was detectable in maternal plasma from 16 weeks gestation and concentrations did not change as gestation progressed. IR-urocortin in the maternal plasma eluted from a Sephadex G-50 column at the same site as synthetic urocortin and had a calculated retention co-efficient of 0.44.

CONCLUSION

This study indicates that urocortin is produced by the decidua during human pregnancy and is detectable in maternal plasma. These data are consistent with the hypothesis that urocortin is produced locally by the decidua and may act to regulate utero-placental blood flow.

Laminar distribution of cholinergic- and serotonergic-dependent plasticity within kitten visual cortex

Both cholinergic and serotonergic modulatory projections to mammalian striate cortex have been demonstrated to be involved in the regulation of postnatal plasticity, and a striking alteration in the number and intracortical distribution of cholinergic and serotonergic receptors takes place during the critical period for cortical plasticity. As well, agonists of cholinergic and serotonergic receptors have been demonstrated to facilitate induction of long-term synaptic plasticity in visual cortical slices supporting their involvement in the control of activity-dependent plasticity. We recorded field potentials from layers 4 and 2/3 in visual cortex slices of 60--80 day old kittens after white matter stimulation, before and after a period of high frequency stimulation (HFS), in the absence or presence of either cholinergic or serotonergic agonists. At these ages, the HFS protocol alone almost never induced long-term changes of synaptic plasticity in either layers 2/3 or 4. In layer 2/3, agonist stimulation of m1 receptors facilitated induction of long-term potentiation (LTP) with HFS stimulation, while the activation of serotonergic receptors had only a modest effect. By contrast, a strong serotonin-dependent LTP facilitation and insignificant muscarinic effects were observed after HFS within layer 4. The results show that receptor-dependent laminar stratification of synaptic modifiability occurs in the cortex at these ages. This plasticity may underly a control system gating the experience-dependent changes of synaptic organization within developing visual cortex.

[Using GFP retrovirus to label tumor cells and vascular endothelia cells]

BACKGROUND

To prepare retrovirus which carry GFP gene and are able to label living cells simply and rapidly.

METHODS

The recombinant retroviral vector pLNCX-GFP was constructed by inserting 780?bp GFP cDNA fragment into the MCS site of retroviral plasmid pLNCX. Both ecotropic packaging cell line ΦX-Eco and amphotropic packaging cell line ΦX-Ampho and PA317 were transfected by pLNCX-GFP with liposome. The supernate collected from transfected packaging cells was used to infect a variety of tumor cell lines and vascular endothelia cell lines.

RESULTS

When packaging cells were transfected by retroviral vector pLNCX-GFP, the GFP expression could be observed in 25%-40% of cells and GFP retrovirus then could be detected, however G418 resistant clones showed more stable GFP expression and higher retrovirus titer. The GFP retrovirus from different packaging cell line showed variant ability to infect tumor cell lines and vascular endothelia cell lines and the tumor cells infected by GFP retrovirus showed stable GFP expression in vitro. GFP transduced tumor cells could grow in syngenic animal and continue expressing GFP.

CONCLUSIONS

Using GFP retrovirus to label target cells represent an important advantage over conventional plasmid because they can efficiently transfer GFP gene into target cells and GFP can be stably expressed in target cells no matter in vitro or in vivo.

Localization and characterization of urocortin during human pregnancy

Urocortin, a recently identified peptide of the corticotropin releasing hormone (CRH) peptide family, has potent vasodilatory effects in the human fetal placental circulation in vitro, promoting us to hypothesize that urocortin is produced locally to regulate uteroplacental vascular tone during pregnancy. In the present study, we examined the distribution of urocortin in the human placenta, fetal membranes and uterine tissue at term in the presence and absence of labour, using a urocortin antibody produced in our laboratory and the immunoperoxidase staining method. Immunoreactive (IR)-urocortin was observed in the vascular smooth muscle of the myometrium (n=5), decidual stromal cells, syncytiotrophoblast and amnion epithelium (n=10). No differences in staining intensity for urocortin were detected between tissues obtained in the absence (n=5) or presence (n=5) of labour. Staining intensity for IR-urocortin was greatest in the decidua suggesting this may be a site of urocortin production during pregnancy. Subsequently, we tested urocortin secretion from chorio-decidual cells in vitro, using an immunoblot technique. Positive staining for urocortin was observed in 40 per cent of chorio-decidual cells with 34 per cent of these cells secreting urocortin under basal conditions. Since urocortin was secreted by decidual cells we questioned whether urocortin was present in maternal plasma throughout gestation, using radioimmunoassay. Urocortin was detectable in maternal plasma from 7 weeks of gestation and concentrations did not change as gestation progressed. IR-urocortin in the maternal plasma eluted from a Sephadex G-50 column at the same site as synthetic urocortin and had a calculated retention coefficient (Kd) of 0.44. In summary, this study indicates that urocortin is produced by the decidua during human pregnancy and is detectable in maternal plasma. These data are consistent with the hypothesis that urocortin is produced locally by the decidua and may act to regulate uteroplacental blood flow.

[Formation of stereocomplexes in atactic poly(methyl methacrylate) studied by FTIR]

The stereocomplexation of atactic poly(methyl methacrylate) (a-PMMA) films after isolated from acetone, benzene, and chloroform solution, respectively, was studied by Fourier transformation infrared (FTIR). The results of spectra showed that the stereocomplex was formed for the films cast from acetone and benzene solutions with the appearance of the characteristic bands for the stereocomplex. The population of trans-trans conformers for the i- and s-sequences increased and the side chain preferred to its energetically optimized conformation during the formation of stereocomplex. The stereocomplexes may be formed by the interactions between the i- and s-sequences in the same molecular chain. During the annealing process the self-aggregation of s-sequences played a role in the aggregation process of stereocomplex, which was a function of annealing temperature and annealing time.

First Report of Tobacco vein banding mosaic virus in China (Xian, Shaanxi Province) in Datura stramonium and Tobacco

Tobacco vein banding mosaic virus (TVBMV) has been reported in Taiwan (1), North America (Tennessee) (2), and Japan (3) and induces a severe disease of tobacco. During surveys on viruses of vegetables in China, TVBMV was isolated from a Datura stramonium weed plant in July 1998 in Shaanxi Province. It showed severe mosaic with blistering of the leaves. The plant was also infected by Cucumber mosaic virus (CMV). When sap from D. stramonium was frozen, thawed, and mechanically inoculated, only TVBMV was recovered. The 3'-end of the viral genome was amplified by reverse transcription-polymerase chain reaction (RT-PCR) using primers derived from the potyviridae primers (4) and cloned in pBlueScript. The sequence of 1,630 bp (GenBank AF274315) was determined on both DNA strands and found to have approximately 94% homology with other TVBMV sequences (L 28816 from Tennessee, X77637 from Taiwan, and AB020524 from Japan). The host range of the Chinese isolate was similar to that reported for the U.S. isolate. D. stramonium, Nicotiana benthamiana, N. clevelandii, N. glutinosa, N. tabacum Samsun, White Burley type and Xanthi, Lycopersicon esculentum cv. Marmande, and Petunia hybrida were systemically infected. A local infection developed in N. rustica, Chenopodium amaranticolor, C. quinoa, and Ocimum basilicum. The Chinese isolate did not infect Capsicum annuum cv. Quadrato d'Asti, Solanum melongena, or several Cucurbitaceae and Leguminosae species. Myzus persicae transmitted the Chinese TVBMV in a non-persistent mode from both D. stramonium and tobacco to the same plants and to tomato. No seed transmission occurred in experimentally infected D. stramonium (20 seedlings), tobacco White Burley type (200 seedlings), and tomato cv. Marmande (100 seedlings). The virus was found in the roots of D. stramonium and tobacco. Since the virus was not seed-transmissible, overwintering rootstocks may provide sites for winter survival of the virus. An antiserum was produced against the virus and an enzyme-linked immunosorbent assay survey was carried out in solanaceous crops including D. stramonium collected in July 1999 in Shaanxi, Shanxi, Henan, and Hebei provinces and Beijing surroundings. TVBMV was found only in the same field as in 1998 in four D. stramonium plants in association with CMV and in a tobacco plant 200 m from D. stramonium. TVBMV was not found in the closest tomato crops, where infection of CMV was severe. This is the first report of TVBMV in China, and Xian is the most northern location in which this virus has been found. References: (1) J. K. Chiang et al. Bull. Tobacco Res. Inst. 32:39, 1990. (2) B. B. Reddick et al. Plant Dis. 76:856, 1992. (3) H. Tochihara. Rev. Plant Prot. Res. 13:122, 1980. (4) A. Gibbs and A. Mackenzie. J. Virol. Meth. 63:9, 1997.

[The regulation of calcium in the movement of colonic smooth muscle in wrap restraint stress rats]

OBJECTIVE

To investigate the influence of contraction of isolated colonic smooth muscle and role of guanylin in colonic movement in wrap restraint stress rats.

METHODS

By using wrap restraint stress induced defecation rats, the tone of isolated longitudinal and circular colonic muscle strips and guanylin contents in colon and blood were measured by transducer and radioligand binding assay respectively.

RESULTS

There were similarities between the intestinal effects of wrap restraint stress in rats and irritable bowel syndrome (IBS) in human. Therefore, wrap restraint stress rat is an appropriate animal model to study stress related intestinal dysfunction. In wrap restraint stress rats, both the tone of smooth muscle and the reaction to K(+), Ca(2+) and acetycholine increased significantly; meanwhile guanylin contents in blood and colon increased also. Trimebutine can decrease the basic tone of smooth muscle and reaction to Ca(2+), K(+) and acetycholine.

CONCLUSIONS

The abnormality of colonic smooth muscle contraction is one of the mechanisms in IBS and regulation of colonic smooth muscle contraction is a new method to treat IBS.

Activity-dependent and use-dependent regulation of dopamine-receptor clustering

In this study, fluorescence-conjugated ligands were employed to label dopaminergic D1-like and D2-like receptors, respectively, in neurons derived from the frontal cortex of embryonic rats. The receptor binding sites were visualized and analyzed using confocal microscopy. Our results showed that fluorescently labeled receptors tended to form clusters with a diameter of about one micrometer and were distributed on both somata and dendrites. Chronic treatment with tetrodotoxin reduced the number of fluorescent clusters of both D1-like and D2-like receptors, while chronic treatment with a high concentration of potassium increased the number of fluorescent clusters of both D1-like and D2-like receptors. Further, chronic treatment with SCH23390 up-regulated the number of D1-like receptor clusters, whereas chronic treatment with bromocriptine down-regulated the number of D2-like receptor clusters. In addition, chronic treatment with spiperone down-regulated the number of D1-like receptor clusters. These results suggest that both neuronal activity and dopaminergic receptor occupancy are important factors that determine dopaminergic receptor clustering which is an essential step toward synaptogenesis during neuronal maturation process.

Development of antirotavirus agents in Asia

Human rotaviruses are the major etiologic agents of diarrhea in infants and young children under 2 years of age worldwide. Rotavirus diarrhea is a life-threatening disease for children; many efforts are made to reduce the morbidity and mortality in Asia. To date many natural compounds and some Western medicines have exhibited their antirotavirus effects in clinical studies, in animal experiments and in vitro. Compared with antirotavirus agents in the USA and Europe, natural compounds have been identified as ideal candidates for antirotaviral drugs in Asia because they are cheaper and effective, have no side-effect and no toxicity. We have attempted to reveal the antirotavirus mechanism of some natural compounds. We found that cacao pigment, tea extract and pine seed shell extract inhibit rotavirus adsorption to cells while cacao pigment may also inhibit rotavirus reproduction in vitro. The usage of antirotavirus agents in Asia demonstrated that additional effective approaches to control rotavirus infection, such as antirotavirus agents, are necessary, in particular for the children with rotavirus diarrhea who have severe complications.

Prostaglandin E(2) enhances chemical and mechanical sensitivities of pulmonary C fibers in the rat

It has been recently reported that pulmonary reflex responses to injection or inhalation challenge of capsaicin are enhanced by exogenous Prostaglandin E(2) (PGE(2)). The present study was carried out to determine whether PGE(2) enhances the stimulatory effects of chemical stimulants and lung inflation on vagal pulmonary C fibers, and if so, whether the excitabilities of other types of lung afferents are also augmented by PGE(2). In anesthetized, open-chest rats, administration of PGE(2) (1.5 microgram/kg/min for 2 min) did not significantly change the baseline activity of vagal pulmonary C fibers, but it markedly enhanced the stimulatory effects of both low (0.25 microgram/kg) and high doses (0.5 microgram/kg) of capsaicin on these fibers. Similarly, potentiating effects of PGE(2) were found on the pulmonary C-fiber responses to injections of lactic acid and adenosine, although considerable variability existed in the degrees of potentiation between the different stimulants. Furthermore, PGE(2) infusion also significantly enhanced the C-fiber response to constant-pressure lung inflation (tracheal pressure [Pt] = 30 cm H(2)O). In contrast, PGE(2) did not alter the responses of either slowly adapting pulmonary receptors or rapidly adapting pulmonary receptors to lung inflation. In summary, these results show that the sensitivity of pulmonary C-fiber afferents to both mechanical and chemical stimuli is enhanced by PGE(2), suggesting that endogenous release of this autocoid may play a part in the airway irritation and dyspneic sensation associated with airway inflammation.

Interaction of the tumor suppressor PTEN/MMAC with a PDZ domain of MAGI3, a novel membrane-associated guanylate kinase

PTEN/MMAC is a phosphatase that is mutated in multiple human tumors. PTEN/MMAC dephosphorylates 3-phosphorylated phosphatidylinositol phosphates that activate AKT/protein kinase B (PKB) kinase activity. AKT/PKB is implicated in the inhibition of apoptosis, and cell lines and tumors with mutated PTEN/MMAC show increased AKT/PKB kinase activity and resistance to apoptosis. PTEN/MMAC contains a PDZ domain-binding site, and we show here that the phosphatase binds to a PDZ domain of membrane-associated guanylate kinase with inverted orientation (MAGI) 3, a novel inverted membrane-associated guanylate kinase that localizes to epithelial cell tight junctions. Importantly, MAGI3 and PTEN/MMAC cooperate to modulate the kinase activity of AKT/PKB. These data suggest that MAGI3 allows for the juxtaposition of PTEN/MMAC to phospholipid signaling pathways involved with cell survival.

Confocal imaging of N-methyl-D-aspartate receptors in living cortical neurons

The fluorescence-conjugated N-methyl-D-aspartate receptor-selective antagonist, BODIPY-conantokin-G, was employed to label N-methyl-D-aspartate receptors in living neurons derived from the visual cortex of embryonic rats. The fluorescent labeling was visualized and analysed using confocal microscopy and digital imaging techniques. BODIPY-conantokin-G binding sites were homogeneously distributed across somata four days after neurons (E17-20) were placed in culture. In five-day-old cultures, BODIPY-conantokin-G binding sites became clusters of fluorescently labeled spots which were arranged irregularly on somata and proximal neurites. Distal neurites displayed fluorescent labeling after 10-15 days in culture. Displacement experiments showed that spermine and unlabeled conantokin-G compete with BODIPY-conantokin-G labeling at the N-methyl-D-aspartate receptor-associated polyamine site. The N-methyl-D-aspartate receptor antagonist 2-amino-5-phosphonovaleric acid also depressed the labeling but with a weaker effect, probably due to interactions occurring between the N-methyl-D-aspartate receptor agonist binding site and the polyamine modulatory site. The fluorescent dyes FM 1-43 and FM 4-64 were used in double-labeling studies to compare the distribution of nerve terminals with that of BODIPY-conantokin-G binding sites. BODIPY-conantokin-G binding clusters were associated with presynaptic nerve terminals while isolated BODIPY-conantokin-G binding sites were not always opposed to terminals. The aggregation of receptors to form clusters may lead to the functional formation of excitatory synapses. To investigate whether modulation of membrane potentials affected the formation of N-methyl-D-aspartate receptor clusters, cultured neurons were chronically treated for a week with either tetrodotoxin (to block membrane action potentials) or a high concentration of potassium to depolarize the membrane. While neurons in the tetrodotoxin-treated group showed a similar number of fluorescently labeled clusters compared with the control group, neurons in the high potassium group exhibited a higher number of fluorescently labeled receptor clusters. These results suggest that more active neurons may tend to form more N-methyl-D-aspartate synapses during early development.