Mechanisms of action of otilonium bromide (OB) in human cultured smooth muscle cells and rat colonic strips

BACKGROUND

The pharmacological properties of otilonium bromide (OB) have been investigated using different experimental models, techniques, and conditions, and consequently, the results are not always easy to compare. The aim of the present work was to investigate the pharmacological properties of OB in human cultured colonic smooth muscle cells (HCSMCs), which is the main target of the drug 'in vivo'. Rat colonic strips were used to confirm the pharmacological properties.

METHODS

Human cultured colonic smooth muscle cells were studied using the calcium imaging technique. Microelectrodes and muscle bath experiments were performed in rat colonic strips.

KEY RESULTS

Otilonium bromide (OB) concentration dependently inhibited nifedipine-sensitive calcium transients induced by KCl (EC50  = 3.6 μM) and BayK8644 (EC50  = 4.0 μM). All the following experiments were performed in the presence of nifedipine. In HCSMC, carbachol-induced calcium transients were inhibited by OB (EC50  = 8.4 μM). Carbachol evoked 1-a smooth muscle depolarization (10 mV) that was antagonized by 100 μM OB; and 2-a contraction that was inhibited by OB (EC50  = 13.0 μM). 'Non-nitrergic (L-NNA 1 mM) non-purinergic (MRS2500 1 μM)' conditions were used to elicit endogenous excitatory responses. Electrical field stimulation caused 1-an atropine-sensitive excitatory junction potential that was inhibited by OB (EC50  = 8.9 μM) and 2-an atropine-sensitive contraction that was inhibited by OB (EC50  = 7.3 μM). In HCSMC, neurokinin A (NKA) and CaCl2 induced calcium transients that were inhibited by OB (NKA: EC50  = 11.7 μM; CaCl2 : EC50  = 17.5 μM).

CONCLUSIONS & INFERENCES

Otilonium bromide causes inhibition of L-/T-type calcium channels, muscarinic, and tachykininergic responses that acting together explain the pharmacological properties of the compound.

P2Y(1) knockout mice lack purinergic neuromuscular transmission in the antrum and cecum

BACKGROUND

Pharmacological studies using selective P2Y(1) antagonists, such as MRS2500, and studies with P2Y(1)(-/-) knockout mice have demonstrated that purinergic neuromuscular transmission is mediated by P2Y(1) receptors in the colon. The aim of the present study was to test whether P2Y(1) receptors are involved in purinergic neurotransmission in the antrum and cecum.

METHODS

Microelectrode recordings were performed on strips from the antrum and cecum of wild type animals (WT) and P2Y(1)(-/-) mice.

KEY RESULTS

In the antrum, no differences in resting membrane potential and slow wave activity were observed between groups. In WT animals, electrical field stimulation elicited a MRS2500-sensitive inhibitory junction potential (IJP). In P2Y(1)(-/-) mice, a nitrergic IJP (N(ω) -nitro-l-arginine-sensitive), but not a purinergic IJP was recorded. This IJP was equivalent to the response obtained in strips from WT animals previously incubated with MRS2500. Similar results were obtained in the cecum: 1- the purinergic IJP (MRS2500-sensitive) recorded in WT animals was absent in P2Y(1)(-/-) mice 2- nitrergic neurotransmission was preserved in both groups. Moreover, 1- spontaneous IJP (MRS2500-sensitive) could be recorded in WT, but not in P2Y(1)(-/-) mice 2- MRS2365 a P2Y(1) agonist caused smooth muscle hyperpolarization in WT, but not in P2Y(1) (-/-) animals, and 3- β-NAD caused smooth muscle hyperpolarization both in WT and P2Y(1)(-/-) animals.

CONCLUSIONS & INFERENCES

1- P2Y(1) receptor is the general mechanism of purinergic inhibition in the gastrointestinal tract, 2- P2Y(1)(-/-) mouse is a useful animal model to study selective impairment of purinergic neurotransmission and 3- P2Y(1)(-/-) mouse might help in the identification of purinergic neurotransmitter(s).

[Analysis of the duration of and reasons for changing the first combination of antiretroviral therapy]

OBJECTIVE

To determine the duration of and reasons behind changing the various combinations of drugs used for the initiation of antiretroviral treatment in naïve patients.

METHODS

A retrospective observational study that included all patients with HIV infection who started antiretroviral therapy in a high-tech university reference hospital during the period from 1 January 2003 and 31 December 2005. Patients were followed until 31 December 2008. To estimate the cumulative probability of discontinuation the Kaplan-Meier method was used.

RESULTS

A total of 441 patients were included. The average duration of the first treatment was 384 (interquartile interval 84-1290) days. The regimen based on non-nucleoside reverse transcriptase inhibitors and those that included as nucleosides abacavir or tenofovir in combination with lamivudine or emtricitabine showed a significantly longer duration than the rest. The main reasons for termination were the side effects, although in a lesser percentage than that obtained in previous studies. No associations were found between the rest of the characteristics of the patients or of the treatment and the risk of termination.

DISCUSSION

Although the duration of the first antiretroviral treatment remains short, currently fewer changes are made due to side effects and due to loss to follow-up. The reasons may be better tolerance and less complexity. However, more studies are needed to determine the benefits of one regimen or another, and to be able to generalise the results.

Extracting features of Gaussian self-similar stochastic processes via the Bandt-Pompe approach

By recourse to appropriate information theory quantifiers (normalized Shannon entropy and Martín-Plastino-Rosso intensive statistical complexity measure), we revisit the characterization of Gaussian self-similar stochastic processes from a Bandt-Pompe viewpoint. We show that the ensuing approach exhibits considerable advantages with respect to other treatments. In particular, clear quantifiers gaps are found in the transition between the continuous processes and their associated noises.

Characterization of Gaussian self-similar stochastic processes using wavelet-based informational tools

Efficient tools to characterize stochastic processes are discussed. Quantifiers originally proposed within the framework of information theory, like entropy and statistical complexity, are translated into wavelet language, which renders the above quantifiers into tools that exhibit the important "localization" advantages provided by wavelet theory. Two important and popular stochastic processes, fractional Brownian motion and fractional Gaussian noise, are studied using these wavelet-based informational tools. Exact analytical expressions are obtained for the wavelet probability distribution. Finally, numerical simulations are used to validate our analytical results.

Trace analysis of tiamulin in honey by liquid chromatography–diode array–electrospray ionization mass spectrometry detection

A liquid chromatography with diode array or electrospray ionisation mass spectrometry detection (LC-DAD-ESI-MS) method for the determination of tiamulin residues in honey is presented. The procedure employs a solid-phase extraction (SPE) on polymeric cartridges for the isolation of tiamulin from honey samples diluted in aqueous solution of tartaric acid. Chromatographic separation of the tiamulin is performed, in isocratic mode, on a C18 column using methanol and ammonium carbonate 0.1% in water, in proportion (30:70, v/v). Average analyte recoveries were from 88 to 106% in replica sets of fortified honey samples. The LC-ESI-MS method detection limits differ from 0.5 microg kg(-1) for clear honeys to 1.2 microg kg(-1) for dark honeys. The developed method has been applied to the analysis of tiamulin residues in multifloral honey samples collected from veterinary treated beehives.

Cyclical upregulated iNOS and long-term downregulated nNOS are the bases for relapse and quiescent phases in a rat model of IBD

We previously reported that indomethacin induces a chronic intestinal inflammation in the rat where the cyclical characteristic phases of Crohn's disease are manifested with a few days' interval and lasting for several months: active phase (high inflammation, hypomotility, bacterial translocation) and reactive phase (low inflammation, hypermotility, no bacterial translocation). In this study, we investigated the possible role of both constitutive and inducible isoforms of nitric oxide (NO) synthase (NOS) and cyclooxygenase (COX) in the cyclicity of active and reactive phases in rats with chronic intestinal inflammation. Rats selected at either active or reactive phases and from 2 to 60 days after indomethacin treatment were used. mRNA expression of both constitutive and inducible NOS and COX isoforms in each phase was evaluated by RT-PCR and cellular enzyme localization by immunohistochemistry. The effects of different COX and NOS inhibitors on the intestinal motor activity were tested. mRNA expression of COX-1 was not modified by inflammation, whereas mRNA expression of neuronal NOS was reduced in all indomethacin-treated rats. In contrast, NOS and COX inducible forms showed a cyclical oscillation. mRNA expression and protein of both iNOS and COX-2 increased only during active phases. The intestinal hypomotility associated with active phases was turned into hypermotility after the administration of selective iNOS inhibitors. Sustained downregulation of constitutive NOS caused hypermotility, possibly as a defense mechanism. However, this reaction was masked during the active phases due to the inhibitory effects of NO resulting from the increased levels of the inducible NOS isoform.

LC-ESI-MSD fast determination of residual mitomycin C in hen aqueous humour after corneal refractive surgery

A simple, fast and reliable method has been developed for the assay of traces of mitomycin C (MMC) in hen aqueous humour samples. The determination was carried out by high-performance liquid chromatography with electrospray ionization mass spectrometric detection. In isocratic elution analysis, the mobile phase was a mixture of water-acetonitrile (78:22, v/v) and the chromatographic column was C(18) at 35 degrees C. The method has been validated over a range from 0.1 to 250 microg L(-1) in hen aqueous humour with correlation coefficients higher than 0.999. Limit of detection and limit of quantification for MMC based in signal to noise ratio of 3 and 10, respectively, were 20 and 71 ng L(-1). The developed method allows the analysis of MMC in hen aqueous humour samples obtained at different times and conditions in order to evaluate and compare the efficacy of the drug administration.

Ileal brake failure in streptozotocin-induced diabetic rat

BACKGROUND

Diabetes mellitus frequently alters gastrointestinal function, but the pathophysiology of the diabetic gut has not been fully elucidated. Our aim was to characterize the enterogastric modulation of gastric emptying in an experimental model of diabetic rat and to determine the putative consequences of impaired regulation on glycaemic control.

METHODS

Studies were performed in streptozotozin-induced diabetic and control groups of male Sprague-Dawley rats. In rats fitted with chronic ileal cannulae, gastric emptying of a peptide meal was measured during ileal infusion of either lipids (ileal brake) or saline. The influence of the ileal brake mechanism on blood glucose levels after oral administration of a glucose solution was also evaluated.

RESULTS

Diabetic rats exhibited a precipitous gastric emptying (80% +/- 3% versus 57% +/- 3% in controls; P < 0.05). Ileal lipids delayed gastric emptying in control (38 +/- 4%; P < 0.05 versus ileal saline) but not in diabetic animals (77 +/- 5%; N.S. versus ileal saline). As the ileal brake contributes to the management of postprandial blood glucose levels (114 +/- 4.9 mg/dL after ileal lipids versus 134 +/- 7.8 mg/dL after ileal saline in control rats; P < 0.05), the failure of this mechanism in diabetic rats worsens glycaemic control after feeding (455 +/- 20.4 mg/dL after ileal lipids versus 399 +/- 8.7 mg/dL after ileal saline; P < 0.05).

CONCLUSION

Experimental diabetes impairs the ileal brake mechanism and disturbs gastric emptying. These abnormalities may contribute to difficult glycaemic control.

Capillary gas chromatography with mass spectrometric and atomic emission detection for characterization and monitoring chlordimeform degradation in honey

Capillary gas chromatography-mass spectrometry and capillary gas chromatography-atomic emission detection have been successfully used to identify and monitor the main degradation products of chlordimeform when this compound is initially present in honey. The analysis of laboratory-spiked honey samples over 28 weeks revealed the occurrence of two degradation products: 4-chloro-o-toluidine (I) and N-formyl-4-chloro-o-toluidine (III). During this period the concentration of chlordimeform decreased to 7.5% of its initial value; the concentration of compound I increased gradually whereas compound III was present in a larger proportion and reached a maximum around the 14th week.

Validation of a liquid chromatographic method for the determination of ranitidine hydrochloride residues on surfaces in the manufacture of pharmaceuticals

A liquid chromatographic method for determination of the residues of ranitidine hydrochloride on various surfaces employed in drug manufacture is described. Cotton swabs, moistened with a methanol-water (1:1, v/v) mixture were used to remove any residues of drugs from glass, vinyl, and stainless steel surfaces, and gave recoveries of 85%, 78% and 90%, respectively. Residues were determined by high-performance liquid chromatography on a C18 column at 25 degrees C with methanol-ammonium acetate (40:60 v/v) pH 6.7 as the mobile phase and detection at 320 nm. The method was validated over a concentration range of 20-10 000 ng/ml and had a detection limit of 2 ng/ml.

High-performance liquid chromatographic determination of methyl anthranilate, hydroxymethylfurfural and related compounds in honey

A high-performance liquid chromatographic method for determining 5-hydroxymethyl-2-furaldehyde (hydroxymethylfurfural), 2-furaldehyde (furfural), furan-2-carboxylic acid (2-furoic acid), furan-3-carboxylic acid (3-furoic acid), furan-3-carboxaldehyde (3-furaldehyde) and 2-aminobenzoic acid methyl ester (methyl anthranilate) in honey and honeydew samples is described. To prevent matrix interference and to isolate the compounds, a clean-up step which implies a solid-phase extraction on polymeric cartridges and an elution with 0.5 ml methanol is recommended. The compounds are separated on a reversed-phase column with a gradient of (A) 1% aqueous acetic acid-acetonitrile (97:3, v/v) and (B) acetonitrile-water (50:50, v/v), with UV detection at 250 nm. The method is applied to the analysis of samples from different botanical origin.

[Clinical practice guidelines of the Spanish Society of Cardiology for pulmonary thromboembolism and hypertension]

Primary pulmonary hypertension is a progressive disease. Most affected patients are young and middle-aged women. Etiology is unknown, although a familial and genetic factor is present in up to 6% of cases. Endothelial dysfunction and abnormalities in calcium channels of smooth muscle fibers are the present pathogenetics theories. Diagnostic tests try to exclude secondary causes of pulmonary hypertension and to evaluate its severity. Acute vasodilatory test is vital in the selection of treatment. Oral anticoagulation is indicated in all patients. Lung transplant is performed when medical treatment is unsuccessful. Atrial septostomy is an alternative and palliative treatment for selected cases. Chronic thromboembolic pulmonary hypertension is a special form of secondary pulmonary hypertension, clinically undistinguishable from primary primary hypertension, is of mandatory diagnosis because it can be cured with thromboembolectomy. Pulmonary embolism is common in hospitalised patients. The mortality rate for pulmonary embolism continues to be high: up to 30% in untreated patients. The accurate detection of pulmonary embolism remains difficult, as pulmonary embolism can accompany as well as mimic other cardiopulmonary illnesses. Non-invasive diagnostic tests have poor specificity and sensitivity. The D-dimer level and the spiral CT angiography have also been employed as new alternatives and important tools for precise diagnosis of suspected pulmonary embolism. The standard therapy of pulmonary embolism is intravenous heparin for 5 to 10 days in conjunction with oral anticoagulants posteriorly for 3 to 6 months. The incidence of deep venous thrombosis, pulmonary embolism and death due to pulmonary embolism, can be reduced significantly and shown clear benefits only by adoption of a prophylactic strategy with low-molecular-weight-heparins or dextrans in patients at risk.

Use of a particle beam interface combined with mass spectrometry/negative chemical ionization to determine polar herbicide residues in soil by liquid chromatography

The use of mass spectrometry/negative chemical ionization (MS/NCI), in combination with selected-ion monitoring, allows sensitive and selective determination of polar and thermally unstable herbicide residues by liquid chromatography coupled to a particle beam interface. The method has been applied to the analysis of soil samples for herbicide residues, using various procedures for their extraction and employing matrix-standard calibration to avoid quantitative errors due to transfer of matter through the interface. Data for the fragment ions found in the MS/NCI procedure and chromatograms from analyses of real samples are also presented.

Validation of the removal of acetylsalicylic acid. Recovery and determination of residues on various surfaces by high performance liquid chromatographic

The validation of a procedure to clean glass, vinyl and stainless steel surfaces that have been exposed to acetylsalicylic acid during its manufacture is described. The cleaning procedure using two cotton swabs moistened with the mobile phase was validated using a wipe-test and a high-performance liquid chromatography (HPLC) method developed to determine low quantities of the acid. The HPLC method involves an octadecylsilane column at 55 degrees C, a mixture of water-acetonitrile-orthophosphoric acid (779:220:1, v/v) as mobile phase and detection at 226 nm. Recoveries of 86%, 90% and 94% were obtained from vinyl, glass and stainless steel plates respectively. The validation gave acceptable levels of sensitivity, recovery, precision and linearity.

[The prevalence of methicillin-resistant Staphylococcus aureus phagotype 95 in the Hospitales Vall d'Hebron of Barcelona]

BACKGROUND

In our hospital endemic methicillin resistant Staphylococcus aureus (MRSA) has been documented since 1971, with epidemic and interepidemic periods. During these years phage groups I, I-III, and non-typable were found by the international set of phages Phage group 95 (F95) was unusual between 1986 (when phage typing was first available) and 1991, with prevalence of 5.2% (mean), and 100% of sensibility to methicillin. In November 1991 appeared the first MRSA F95 strain, and its prevalence has been increasing until 1997.

MATERIAL AND METHODS

We have studied 133 strains of MRSA F95 isolated from 87 patients, 39 of them hospitalized in the General Hospital (HG), 38 in Traumatology Hospital (HT) and 8 in the Children's Hospital (HI). Two of these patients had successive stancies in HG and HT. Antimicrobial susceptibility was determined by the disk diffusion method and microdilution to check oxacillin resistance. Moreover these method we have maked: detection of mecA, phage typing with the international set of phages and study of the PGFE patterns by digestion of chromosomic DNA with Smal.

RESULTS

The percentage of methicillin resistance in F95 strains was increased since the appear of the first strain between 8.3% in 1991 to a maximum of 76.9% in 1995, we had a descens to 13.7% in 1996 but 1997 can back to augment it to 72.5%. MICs for oxacillin of these strains were low (< or = 64 mg/l to 87.4% of strains), and all of them were mecA positive, 78.1% of them were resistant to macrolides, 96.5% to tobramycin and 84.9% to quinolones, but only 10.5% to gentamicin, 4.7% were resistant to cotrimoxazol, 1.2% to fosfomycin and 2.5% to rifampin. All of them were sensible to doxycycline, and vancomycin. The pulse field gel electrophoresis showed 7 restriction patterns in MRSA F95, 73.8% of strains correspond to one of them (B), spreading from the spinal cord injury unit and prevalent in HT; and 10.8% to another (C), the first that appear, spreading from the neurosurgical unit and with high prevalence in HG. 6.9% has pattern J a B subtype that appear in broth HG and HT. Pattern E is prevalent in HI it was spread from neonatology unit.

CONCLUSIONS

The emergence in a Center with endemic resistance of new strains of MRSA, not all of them of the same clone, with characteristic resistance pattern to antibiotics and in convivence with other phage groups is one demonstration of genetic variability of SAMR in our entorn.

Chemical modification of lysine side chains of cyclodextrin glycosyltransferase from Thermoanaerobacter causes a shift from cyclodextrin glycosyltransferase to alpha-amylase specificity

Cyclodextrin glycosyltransferases and alpha-amylases are two groups of enzymes with related secondary structures. However, cyclodextrin glycosyltransferases display transferase activities not present in alpha-amylases, probably derived from the existence of two more domains and different amino acid sequences. The hydrolytic activity of cyclodextrin glycosyltransferases is generally quite low, except for two cyclodextrin glycosyltransferases from termophiles. In this work, we have carried out the chemical modification (with acetic anhydride) of the amino groups of cyclodextrin glycosyltransferase from Thermoanaerobacter to assess their contributions to protein function. The acetylated cyclodextrin glycosyltransferase showed a significant reduction of its cyclization, coupling and disproportionation activities. Surprisingly, the hydrolytic (saccharifying) activity was slightly enhanced. These results suggest the participation of one or more lysine side chains in the interactions contributing to the transferase activity, either in any of the S11 subsites or in the acceptor binding site.

Solid-phase microextraction applied to the analysis of pesticide residues in honey using gas chromatography with electron-capture detection

The possibilities of using solid-phase microextraction to determine residues of pesticides in honey have been examined. For this purpose, three types of fiber have been assayed: polyacrylate of 85 microns thickness, and polydimethylsiloxane of 7 and 100 microns thickness. They have been applied to the extraction of 21 pesticides of different chemical families. The effects of the temperature, extraction time and ionic strength on the microextraction have been studied, proposing the most adequate for each fiber. Under optimized conditions, precision, intervals of linearity and detection limits were evaluated.

Quantitation of active ingredients and excipients in nasal sprays by high-performance liquid chromatography, capillary electrophoresis and UV spectroscopy

A study on the use of different analytical methodologies to determine active ingredients and excipients found in commercial nasal sprays is presented. Two of the developed methodologies consisted of separation techniques, i.e. high-performance liquid chromatography and capillary electrophoresis, and the third one involved a UV-spectroscopic multicomponent procedure. The samples studied are characterized by a high viscosity and the existence of a large number of particles in suspension; therefore, special emphasis is paid on the sample preparation required by each methodology. Advantages and drawbacks of each analytical technique are also discussed in terms of speed of analysis, sensitivity and reproducibility. From this work it is observed that although the UV method needs the most laborious sample preparation, the total time required per analysis is the shortest one. The best reproducibility in terms of analysis time and quantitation of the analyzed compounds is obtained using HPLC. CE allows the determination of more components in the same sample.

Gas chromatography with electron-capture and nitrogen-phosphorus detection in the analysis of pesticides in honey after elution from a Florisil column. Influence of the honey matrix on the quantitative results

A modified procedure to extract pesticides from honey samples that involves loading the honey onto a Florisil packed column and subsequently eluting it with an n-hexane-dichloromethane mixture is proposed. Anomalous high gas chromatographic responses and subsequently very high recoveries for the pesticides in the extracts were obtained by a conventional calibration with pesticide solutions in organic solvent. This effect was attributed to the honey matrix and can be circumvented by using spiked honey extracts as calibration standards.

Contribution of inhibitory neurotransmitters to the CCK induced relaxation of the circular muscle of avian ileum

The sulphated form of cholecystokinin-octapeptide (CCK-OP) induces a concentration-dependent relaxation of the circular muscle of isolated chicken ileum which is unaffected by atropine or propranolol but abolished by tetrodotoxin (TTX). The aim of this study was to investigate whether purinergic (ATP), nitrergic (NO) and peptidergic (VIP) neurons are implicated in the response to CCK-OP. In preparations prerelaxed with ATP, CCK-OP caused a further relaxation (average 46%). In addition, suramin (a P2 purinoceptor antagonist) inhibited the response to both ATP and CCK-OP. L-N(G)-nitroarginine (L-NO-Arg) reduced the response to CCK-OP, an effect which was reversed by L-arginine (L-Arg). In the presence of trypsin, the response to CCK-OP was markedly decreased (to about 10% of the original response). Moreover, in preparations prerelaxed with chVIP, the response to CCK-OP consisted of a small additional relaxation (average 15,7%). The responses to chicken VIP (chVIP) or sodium nitroprusside (NaNP), a NO donor, are TTX resistant whereas that to ATP is blocked by TTX. L-NO-Arg significantly reduced the relaxation induced by ATP, but did not change that induced by chVIP. The response to ATP after exposure of the tissue to maximal chVIP concentration was significantly reduced (average 25%). Our results suggest that the effects of CCK-OP seem to be mediated through purinergic neurons, which in turn would stimulate the release of NO and a peptide (possibly chVIP). ChVIP and NO interact with receptors located on muscle cells causing the relaxation of the circular muscle coat of the ileum.

Effects of cholecystokinin on chicken cecal motility: mechanisms involved

The aims of this work are to characterize the effects of cholecystokinin (CCK) on chicken ceca and to study in vitro the mechanisms through which such actions are mediated. Longitudinal and circular cecal strips kept in vitro in organ baths were responsive to CCK sulphated octapeptide (CCK-8s). On longitudinal strips the response consisted of a fast phasic contraction followed by a sustained increase in tone which was dose dependent and decreased markedly in the presence of tetrodotoxin (TTX). Ketanserin (10(-5) M) also caused a decrease in the CCK-8s response. CCK tetrapeptide (CCK-4) and CCK unsulphated octapeptide (CCK-8ns) induced slightly less contractile effects at concentrations of 2 x 10(-6) M only. L365,260 and L364,718 decreased the response of longitudinal strips to CCK-8s with similar efficacy. On circular strips CCK-8s caused rhythmic phasic contractions of dose dependent amplitude and frequency, and both effects were resistant to TTX. The EC50 for the amplitude was about 4 times higher than that for the frequency. CCK-8ns (2x 10(-6) M) also caused phasic contractions, whereas the same concentrations of CCK-4 did not elicit any motor effects. L365,260 and L364,718 showed different efficacy in decreasing amplitude or frequency of contraction. These results suggest that 1) Both muscularly and neurally located CCK receptors are present on the longitudinal layer of chicken ceca whereas only muscular receptors are present on the circular muscle. 2) 5HT2 receptors seem to be involved in the neurally mediated CCK-8s response observed in the longitudinal layer. 3) The different potency of CCK-8s, CCK-8ns and CCK4 to induce contractile effects and of the CCK-A and CCK-B antagonists to block such effects suggests the existence of two different CCK receptors on the circular layer.

Mechanisms mediating the effects of cholecystokinin on avian small intestine longitudinal smooth muscle

The aims of this study were (1) to define the effects of CCK-8s and related peptides on chicken ileum longitudinal smooth muscle and (2) to explore the mechanisms by which such effects occur. The effects of CCK-8s were assayed in vitro on chicken longitudinal ileal strips. CCK-8s produced contraction of ileal strips (EC50 8.8.10(-9) M). CCK-8ns and CCK-4 did not have remarkable contractile effects even when added at concentrations 200-times higher than the EC50 for CCK-8s. L365,260 slightly inhibited the effects of CCK-8s whereas L364,718 was ineffective. Tetrodotoxin (10(-6) M) markedly decreased the effects of CCK-8s. Atropine (10(-6) M) did not modify the neurally mediated effects of CCK-8s, whereas ketanserin (10(-5) M) decreased the response to CCK-8s. Substance P-desensitized preparations exhibited reduced responses to CCK-8s. Our results indicate that CCK receptors present in chicken ileum behave similarly but not identically to the CCK-A receptor described in mammals. Most of these CCK receptors are neurally located but a minor proportion is also present on smooth muscle. The neurally mediated response to CCK-8s does not involve cholinergic mechanisms, but serotonin and substance P releasing neurons.

[Serological parameters for the diagnosis and follow-up of toxoplasmosis. Experimental models]

BACKGROUND

Toxoplasmosis is a disease of increasing incidence. Its laboratory diagnosis is difficult, specially in acute toxoplasmosis. The data obtained in experimental models attempting to distinguish between acute and chronic toxoplasmosis by the simultaneous study of four serological tests: IgM and IgG antibodies, circulating antigens (CA) and antigens present in immune complexes (IC) are reported.

METHODS

The evolution of IgM and IgG antibodies, CA and IC was followed in 3 murine models in acute, subacute and chronic toxoplasmosis, compared with the use of the ELISA technique.

RESULTS

Acute toxoplasmosis is characterized by the presence of CA and IC in 100% of the individuals at high concentrations with IgM and IgG only being detectable at low concentrations. In subacute and chronic toxoplasmosis the response to IgG antibodies (100% in animals) is prominent, with detection of IgM being variable and the detection of CA and IC being reduced to the phase considered as acute.

CONCLUSIONS

The detection of IgM and IgG antibodies, circulating antigens and immune complexes may be of great usefulness in the differentiation of acute, recently acquired or chronic toxoplasmosis.

Cecocolonic motility in the chicken. Effects of cholecystokinin

The aims of this work were 1) to define electromyographically the motility pattern of chicken ceca and colon; 2) to study the changes induced by photoperiod and food intake on the motility of this area and 3) to characterize the motor effects of intravenous (i.v.) cholecystokinin in vivo, measuring changes in electrical activity and intracecal pressure. Electromyographical studies show that in ceca, the spike burst frequency is higher during the day than during the night and in the fed than in the fasted state; about 90% of the bursts propagate towards the apex and corresponde to filling movements. In the colon the spike burst frequency during the day is 2.9 bursts/min in animals fed ad libitum. Nocturnal recordings in animals fed ad libitum and diurnal recordings in fasted animals show a significantly decreased electrical activity. Both CCK-8s and CCK-4 induce a dose-dependent decrease of colonic electrical activity and a dose-dependent increase in the number of colonic defecations. CCK-4 also causes a slight inhibition in the cecum, whereas CCK-8s induces an increase in cecal electrical activity. Intracecal pressure recordings performed in anaesthetized animals provide similar results. In conclusion, the cecocolonic motility of the chicken displays a circadian pattern and undergoes substantial modifications in the fed compared to the fasted state. CCK-8s is not mediating the increased colonic activity that follows food intake, as its effects on colonic motility are inhibitory. In contrast, i.v. CCK-8s induces defecation and a dose dependent increase in cecal electrical activity, intraluminal pressure and colonic defecation. Intravenous CCK-4 induces inhibitory effects both on ceca and colon.

Supercritical fluid extraction of fluvalinate residues in honey. Determination by high-performance liquid chromatography

A method for the analysis of fluvalinate residues in honey from beehives treated with this product to prevent varroatosis is described. The method involves supercritical fluid extraction with carbon dioxide and further analysis by high-performance liquid chromatography on a C18 reversed-phase column, acetonitrile-water (80:20) as mobile phase and detection at 254 nm. This method is simpler than the one in which extraction with organic solvents, thin-layer chromatography and gas chromatography is used.

3'-terminal sequence of the plum pox virus PS and ŏ6 isolates: evidence for RNA recombination within the potyvirus group

The sequence of the 3'-terminal 1768 nucleotides of the PS and ŏ6 isolates of plum pox virus (PPV) has been determined and compared with that of the equivalent regions of other PPV isolates sequenced previously. The sequenced region is part of the PPV open reading frame encoding the last 186 amino acids of the NIb protein and the coat protein (CP, 330 amino acids), followed by a non-coding region of 220 nucleotides and a poly(A) tail. PPV-PS and PPV(-)ŏ6, just like PPV-El Amar, show rather high levels of nucleotide diversity in the sequence encoding the C-terminal region of the NIb protein (19.4 to 31%) and the N terminus of CP (22.8 to 41.1%) when compared with PPV-Rankovic, PPV-D and PPV-NAT, whereas the level of diversity in the rest of the CP sequence and the 3' non-coding region is low (8 to 10.8% and 5.5 to 7.7%, respectively). However, the first 429 sequenced nucleotides of PPV(-)ŏ6 are very similar to those of the PPV-Rankovic, PPV-D and PPV-NAT isolates, whereas the rest of the sequence clearly resembles PPV-PS. Thus, PPV(-)ŏ6 seems to be the result of a natural recombination event between two wild strains of PPV. To our knowledge this is the first evidence of homologous RNA recombination (a process which could play an important role in the evolution of RNA viruses) within the potyvirus group.

Receptors implicated in the actions of serotonin on chicken ileum longitudinal smooth muscle

The presence of serotonin (5-HT) in the chicken gastrointestinal tract has been previously reported, but its motor effects have been poorly described. The aims of this work were: A) to define the effects of 5-HT on chicken longitudinal ileum; B) to explore the mechanisms by which such effects occur and C) to identify the subtype(s) of 5-HT-ergic receptors implicated. The motor responses to 5-HT were assayed in vitro using ileal strips taken from male White Leghorn chickens 7-9 week old. 5-HT elicited ileal contraction (EC50 9.6 x 10(-8) M), which was markedly decreased in the presence of tetrodotoxin (TTX). Repeated exposure of the tissue to supramaximal concentrations of 5-HT did not however lead to desensitization. Atropine (10(-6) M), ketanserin (10(-5) M), methysergide (10(-5) M) and methiothepine (10(-6) M) attenuated the response to 5-HT. Ketanserin was an effective inhibitor of the residual response to 5-HT obtained even in the presence of TTX. Several serotonergic agonists were assayed to further analyse the type of receptors involved in the response to 5-HT. 5-methoxytryptamine (5-MOT), a mixed 5-HT1, 5-HT2 and 5-HT4 agonist, reproduced all the effects of 5-HT. 8-OH-DPAT, a selective 5-HT1A agonist, trifluoromethylphenylpiperazine, a mixed 5-HT1B/C agonist, and m-chlorophenylbiguanide, a 5-HT3 agonist, did not induce any consistent contractile effects. Sumatriptan, a 5-HT1D agonist, exerted a slight agonistic effect which was blocked by methiothepine and decreased by TTX but not by atropine. Cisapride, a 5-HT4 partial agonist in mammals, decreased the effects of both 5-HT and 5-MOT. These results indicate that chicken ileum contains 5-HT1 receptors similar to the 5-HT1D mammalian subtype but not the 5-HT1A, 5-HT1B, 5-HT1C or 5-HT3 subtypes. 5-HT2 receptors are also present and would appear to be located on smooth muscle.

Proteolytic processing of the plum pox potyvirus polyprotein by the NIa protease at a novel cleavage site

The expression of potyvirus genomic RNA takes place through translation of its unique long and functional open reading frame into a large polyprotein that undergoes extensive proteolytic processing. Most of the cleavages are performed by the virus-encoded NIa protease, which cuts the polyprotein at defined sites that are characterized by conserved heptapeptide sequences. We have demonstrated in vitro cleavage activity by the plum pox potyvirus (PPV) NIa protease at a novel site, previously identified by sequence analysis, thus allowing a further refinement of the potyviral genetic map. This novel site is located 52 amino acids upstream from the site corresponding to the N-terminus of the CI protein (the NIa cleavage site previously considered the closest to the beginning of the polyprotein). The specificity of the processing was demonstrated by its abolishment when the Gln at position -1 of the cleavage site was changed to His. This novel NIa cleavage site was only partially processed, a characteristic that was not altered when its heptapeptide sequence was modified to become that of the efficiently cleaved NIb-CP junction. On the contrary, substitutions at the nonconserved position +3 had notable effects, positive or negative, on the efficiency of processing. These results show the relevance of sequence and/or conformational context outside the conserved heptapeptide for modulating the cleavage reaction catalyzed by the NIa protease.

Absorbability of oleic and palmitic acid in young chicks. Effect of yolk sac ablation

The aims of the present study were: 1) to describe the changes in the absorption of free oleic and palmitic acids in young chicks during the first two weeks after hatching; 2) to find out if yolk sac ablation induces any change in the absorbability of such fatty acids. The study was carried out in normal and yolk-sac-ablated broiler chicks aged 2, 8 and 13 days. 14C-labelled oleic and palmitic acids were given p.o. in suspension. Stools were collected for 48h and the recovery of radioactivity was determined and considered as an indicator of the extent of absorption. Our results indicate that the absorption of palmitic acid decreased with age (p less than 0.05) whereas the absorption of oleic acid increased significantly (p less than 0.005). The changes in the absorptive capacity for each fatty acid occurred during the first week. The absorption of both fatty acids was greater in yolk-sac-ablated chicks (p less than 0.05). The relative contents of different fatty acids in yolk lipids was investigated. The results clearly indicate that the ratio OA/PA linearly increased from hatching until the 4th day. Thus the possibility that yolk sac lipids passing to the intestine through the yolk stalk are able to modify the absorptive processes cannot be excluded.

Plum pox potyvirus RNA replication in a crude membrane fraction from infected Nicotiana clevelandii leaves

In vitro synthesis of plum pox potyvirus (PPV)-specific nucleic acid has been measured in a crude fraction prepared from leaves of PPV-infected Nicotiana clevelandii plants. Using alkali and DNase treatments, the synthesized nucleic acid was shown to be RNA. The electrophoretic mobility and the differing sensitivity to RNase at high and low salt concentrations allowed the identification of in vitro products probably corresponding to replicative form and replicative intermediate RNA, as well as to single-stranded RNA. Most of the PPV-specific RNA synthesized was shown to be of positive polarity. The in vitro RNA synthesis, performed in the presence of actinomycin D, required all four ribonucleoside triphosphates and Mg2+ ions. This enzyme extract contained about 6% of the leaf protein and most of the identified virus-encoded proteins. Altogether, the results presented in this paper suggest that in vitro RNA synthesis was carried out by the PPV replicase complex.

Novel catalytic activity associated with positive-strand RNA virus infection: nucleic acid-stimulated ATPase activity of the plum pox potyvirus helicaselike protein

The cylindrical inclusion protein of potyviruses contains the so-called nucleoside triphosphate binding motif, an amino acid sequence motif present in proteins encoded by most positive-strand RNA viruses, some double-strand RNA viruses, apparently all groups of double-strand DNA viruses, and also several single-strand DNA viruses. Further sequence analysis has allowed to include the cylindrical inclusion protein of potyviruses as a member of a superfamily of helicaselike proteins. In this paper we show that the purified cylindrical inclusion protein of plum pox potyvirus interacts with RNA and ATP and copurifies with a nucleic acid-stimulated ATPase activity. To our knowledge, this is the first time that this kind of enzymatic activity has been experimentally associated with a positive-strand RNA virus-encoded protein.

Mutational analysis of plum pox potyvirus polyprotein processing by the NIa protease in Escherichia coli

A binary Escherichia coli expression system has been used to study the pathway for proteolytic processing of the plum pox potyvirus (PPV) polyprotein. Trans cleavage at the carboxyl end of the cylindrical inclusion protein occurred, although with lower efficiency than that at the large nuclear inclusion protein-capsid protein junction. No trans cleavage at the carboxyl end of the small nuclear inclusion protein (NIa) was detected. The proteolytic activities at different cleavage sites of several deletion and point mutations of NIa protein have been analysed. The large delta SX deletion and two different point mutations at His 239 abolished proteolytic activity at all sites. The effect of other mutations, particularly a Glu substitution for Asp 274, depended on the particular cleavage site analysed. The results obtained with the PPV NIa protein mutants were similar to those reported for comparable mutations in the tobacco etch virus 49K protease, despite differences in the sequences recognized for processing. No evident competitive inhibition of the proteolytic activity of PPV NIa protease by the presence of an excess of the different protease mutants could be demonstrated.

Determination of polyprotein processing sites by amino terminal sequencing of nonstructural proteins encoded by plum pox potyvirus

Nonstructural proteins of plum pox potyvirus were partially purified following a procedure described for the isolation of tobacco etch virus nuclear inclusion proteins. Plum pox virus proteins with electrophoretic mobilities corresponding to 49, 59 and 68 kDa reacted with antibodies against the 49 kDa and 54 kDa components of the nuclear inclusions and the 70 kDa component of the cylindrical inclusions of tobacco etch virus, respectively. Further purification by size exclusion high performance liquid chromatography or SDS-polyacrylamide gel electrophoresis, and amino terminal amino acid sequencing permitted the location in the plum pox virus polyprotein of the cleavage sites from which the 49 kDa (NIa-type, protease), 59 kDa (NIb-type, putative RNA replicase), and 68 kDa (CI-type) proteins originate. A 110 kDa protein which copurified with the plum pox virus inclusion proteins reacted with both anti-NIa and anti-NIb sera and had the same amino terminus as the plum pox virus 49 kDa protein, indicating that it is a non-processed 49-59 kDa polypeptide.

Proteolytic activity of the plum pox potyvirus NIa-protein on excess of natural and artificial substrates in Escherichia coli

The plum pox potyvirus (PPV) NIa protease expressed from a medium copy number plasmid was able to process an excess of substrate expressed from a high copy number plasmid, in a binary Escherichia coli expression system. The delta B7 NIa protease mutant only partially processed the NIb-CP junction but its efficiency was independent of the amount of substrate. The delta B7 mutant essentially did not recognize an artificial cleavage site which was quite efficiently recognized by the wild-type protease. No competitive inhibition of the proteolytic activity by the presence of excess of different protease mutants was observed.

Homologous potyvirus and flavivirus proteins belonging to a superfamily of helicase-like proteins

Comparison of the nucleoside triphosphate-binding motif(NTBM)-containing proteins of two groups of apparently distantly related positive-strand RNA viruses (potyvirus and flavivirus), revealed significant sequence similarity. In addition, these two groups of viral proteins show amino acid motifs in common with those conserved in a group of five NTBM-containing proteins from prokaryotic and eukaryotic cells, some of which have been experimentally related to helicase activity. Here we propose that the proteins mentioned above constitute a superfamily of helicase-like proteins, distinct from the one previously described [Gorbalenya et al., FEBS Lett. 235 (1988) 16-24; Hodgman, Nature 333 (1988) 22-23; 578], which includes the NTBM-containing proteins from another group of positive-strand RNA viruses, the 'Sindbis-like' viruses.