Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ATR”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources
PubMed1993

Comparison of acyl-carrier protein and other protein structures in aqueous solutions by Fourier-transform infrared spectroscopy.

Protein solution structures were analyzed by horizontal attenuated total reflectance (ATR) FTIR spectroscopy. Secondary structure compositions determined from analyses of amide-I and II region and amide-III region difference spectra were compared. Data for proteins of known solution structure, cytochrome c, concanavalin A and lysozyme, were compared with those reported in the literature. Melittin, a peptide from bee venom whose secondary structural configuration varies depending upon solution conditions was also examined. Acyl-carrier protein (ACP) is a small protein of recognized dynamic structure that in its diverse physiologic roles interacts specifically with numerous different proteins. Horizontal ATR FTIR analysis of ACP's secondary structure indicated a predominantly helical structure best defined as a combination of ordered and disordered helices. The FTIR-derived structural composition agreed with those determined for ACP by other techniques. Comparison of independent analyses of the amide-I and III regions to determine protein configuration compositions was a useful method of verifying the internal consistency of the calculated structural compositions of dynamically-structured proteins.

Acyl Carrier Protein↗
PubMed1988

The activity of olfactory receptor cells is affected by acetylcholine and substance P.

The effects of acetylcholine (ACh) and substance P (SP) on the unit activity of receptor cells recorded from the superfused frog olfactory mucosa were studied. Single neurones were excited or, more rarely, depressed by the application of chemicals. Cholinergic antagonists were used to investigate the involvement of nicotinic and muscarinic receptors in the recorded responses. The ACh-evoked firing was antagonized by D-tubocurarine (D-TC), atropine (ATR) and SP. Responses to SP appeared to be D-TC resistant, but activation by the peptide was moderately antagonized by ATR. The results suggest that ACh and SP could affect the functioning of the olfactory receptor cells.

Acetylcholine↗
PubMed1994

Adaptive acid tolerance response by Salmonella typhi and candidate live oral typhoid vaccine strains.

The data presented here demonstrate that Salmonella typhi is capable of expressing an acid tolerance response (ATR) and that effective induction of this response (in nutrient-rich medium) occurs at pH 5.0 in anaerobic conditions. The candidate live oral S. typhi vaccine strains made by precise genetic methods and which carry auxotrophic mutations were CVD 906 (carries defined attenuating deletion mutations: delta aroC, delta aroD), CVD 908 (carries defined attenuating deletion mutations: delta aroC, delta aroD), 541Ty (carries attenuating deletion mutations: aroA, purA), and galE, Vi-negative (via) strain EX462. All generate an effective ATR. In contrast, nitrosoguanidine-derived live oral typhoid vaccine strain Ty21a only weakly expresses acid tolerance. This further demonstrates that the non-specific mutagenesis process used to produce Ty21a affects genetic loci outside the intended target genes for mutagenesis, galE and via, and further emphasizes the importance of using precise genetic techniques when developing live oral S. typhi vaccines.

Acids↗
PubMed1988

Efficacy of echo-Doppler examination for the evaluation of renovascular disease.

The accuracy of the diagnosis of renal artery stenosis using noninvasive echo-Doppler velocimetry was compared with that of angiography in 40 renal arteries. The duplex-Doppler signals were detected through the muscle of the back (the translumbar approach). Renal artery stenosis was diagnosed by three objectively defined Doppler parameters, the acceleration index (AI), the acceleration time (AT), and the acceleration time ratio (ATR). The normal range obtained on 11 control subjects was defined as AI greater than or equal to 3.78, AT less than or equal to 0.07 s, and ATR less than or equal to 1.35. High technological success (98%) was obtained using the translumbar approach. In comparison with angiography (cases of significant stenosis), the accuracy of the echo-Doppler method using the criteria of the AI was 95%, the sensitivity was 100%, and the specificity was 93%. This noninvasive method may be one of the most accurate screening methods for diagnosing significant renal artery stenosis.

Blood Flow Velocity↗
PubMed1988

Presynaptic alpha-adrenoceptor regulation of transmitter release in the conscious rat.

1. Blood pressure (BP) and heart rate (HR) were recorded in conscious, adrenal demedulated rats. The rats were subjected to a 1-min period of mild "stress", induced by jet-air directed into the experimental cage. The plasma content of noradrenaline (NA), dopamine (DA) and 3, 4-dihydroxy-phenylacetic acid (DOPAC) was determined 1 min after termination of "stress". 2. The presynaptic alpha 2-adrenoceptor antagonist yohimbine (YOH) (10(-7) - 10(-6) mol/kg, given 5 min prior to "stress") did not alter the increase in BP and HR, induced by "stress", when compared to control rats (receiving NaCl instead of YOH at the corresponding time). 3. Pre-treatment with atropine (ATR) (2.5 mg/kg) 5 min before YOH (10(-6) mol/kg) or NaCl increased HR but not BP significantly in both groups of rats. "Stress", as above, gave a significant prolongation of the increase in HR in rats receiving YOH, when compared to control rats. The increase in BP was not significantly altered, compared to controls. 4. The neuronal re-uptake inhibitor desmethylimipramine (DMI) (0.1 mg/kg) was given together with ATR (2.5 mg/kg) 5 min before YOH (10(-6) mol/kg) or NaCl in one group of rats. This treatment induced a significant increase in HR but did not affect BP. "Stress", induced as above, extended the duration of the increase in HR in the YOH-treated rats, compared to controls. The increase in BP was not significantly different between the YOH-treated rats and the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Medulla↗
PubMed2005

Plant uncoupling protein in mitochondria from aged-dehydrated slices of Jerusalem artichoke tubers becomes sensitive to superoxide and to hydrogen peroxide without increase in protein level.

We investigated the occurrence of the plant Uncoupling Protein (UCP) in mitochondria isolated from both fresh (f-JAM) and aged-dehydrated (a-d-JAM) slices of Jerusalem artichoke tubers (Helianthus tuberosus L.). The presence of UCP was shown by immunological analysis and its function was investigated by measuring the decrease of the mitochondrial membrane potential due to linoleic acid (LA) and its inhibition by purine nucleotides under conditions in which the adenine nucleotide translocator (ANT) was inhibited by atractyloside (Atr). f-JAM and a-d-JAM had the same protein content, but differed from one another with respect to purine nucleotide inhibition, substrate specificity, and sensitivity to ROS. Hydrogen peroxide and superoxide anion, generated in situ by xanthine plus xanthine oxidase, caused a significant increase in the UCP function in a-d-JAM, but not in f-JAM. This occurred in a manner sensitive to ATP, but not to Atr, thus showing that ANT has no role in the process. The dependence of the rate of membrane potential decrease on increasing LA concentrations, either in the absence or the presence of ROS, showed a sigmoidal saturation both in f-JAM and a-d-JAM. However, addition of ROS in a-d-JAM resulted in about 40% increase of the Vmax value, with no change in the K0.5 (about 20 microM), whereas in f-JAM no effect on either the Vmax or K0.5 (about 28 microM) was found. Furthermore, a decreased ROS production as a result of LA addition was found in both f-JAM and a-d-JAM, the effect being more marked in a-d-JAM.

Carrier Proteins↗
PubMed2004

Characterisation of bioactive and resorbable polylactide/Bioglass composites by FTIR spectroscopic imaging.

Formation, size and distribution of hydroxyapatite domains in resorbable composites made of poly(DL-lactide) foams and Bioglass particles after exposure to a solution of phosphate-buffer saline (PBS) for different periods of time have been analysed with FTIR imaging using the micro-ATR-IR approach. The spectral information of 4096 spectra measured simultaneously with the IR microscope equipped with a focal plane infrared array detector allowed us to obtain chemical images showing the distribution of Bioglass particles in the composites. FTIR imaging in micro-ATR mode allowed to obtain images with enhanced spatial resolution. A random distribution of hydroxyapatite domains with average size of ca. 10 microm on the surface of the composites was found after exposure to PBS for 14 and 28 days. The further growth of the hydroxyapatite domains after exposure to PBS for 63 days was detected. The spectroscopic imaging method introduced here promises to become a powerful method for characterisation of resorbable polymer composites containing bioactive inorganic phases developed for bone tissue engineering scaffolds. The accurate detection of hydroxyapatite domains and the imaging of their location in the scaffold structure is required to provide an assessment of the composites bioactivity.

Absorbable Implants↗
PubMed2004

Surface properties and biocompatibility of solvent-cast poly[-caprolactone] films.

Poly(epsilon-caprolactone) (PCL) was dissolved in four solvent systems, chloroform, tetrahydrofuran, acetone and ethyl acetate, and cast onto glass Petri dishes. The surface properties of the resulting films were investigated. The extent to which their properties were determined by the solvent used in each case was quantified in terms of contact angle, surface morphology, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), and the adhesion and proliferation of fibroblasts by direct contact. The surface of the PCL film in contact with glass was denoted the SG surface, and the other, which was exposed to the gas phase, a mixture of air and residual solvent vapour, was denoted the SA surface. In the case of hydrophobic solvent systems, the advancing contact angle of the SG surface was always lower than that of the SA surface. With hydrophilic solvent systems, on the other hand, the advancing contact angle of the SG film surface was higher when the contact angle of the Petri dish was higher than that of the gaseous mixture of the air and solvent vapour, otherwise it was lower or equal to that of the surface on which it was cast. The surface morphology was dictated by the solubility of PCL in the respective solvent systems: high dissolution solvents such as chloroform and tetrahydrofuran produced films that comprised PCL aggregates, the particles being larger in the case of chloroform, whereas the less efficient solvents (acetone and ethyl acetate) resulted in a filamentous structure. The ATR-FTIR results confirmed that the chemistry of the SA surfaces differed according to the solvent system used. Preliminary cell culture experiments carried out with the PCL films established that murine (L929) fibroblasts grew well on all surfaces regardless of the solvent used, although the rates of adhesion and proliferation were not as great as on tissue culture plastic controls. Of all the surfaces examined in this study, the cells favoured the SG aspect of ethyl acetate cast PCL films, the surface of which had the finest pore size and relatively low contact angle.

Animals↗
PubMed2006

The effect of PLGA doping of polycaprolactone films on the control of osteoblast adhesion and proliferation in vitro.

Poly(epsilon-caprolactone) (PCL) film was modified using specified amounts of poly(d,l-lactide-co-glycolide) (PLGA) to provide a means to control polymer degradation. The aim of the study was to determine the effects of doping PCL with PLGA on the materials degradation, morphology and cell adhesion, to determine the significant variables within the process that could provide further control of cell adhesion. PLGA-doped PCL films were aged in osteogenic medium at 37 degrees C for up to 28 days. The aged samples were analysed in terms of weight loss or weight gain, molecule deposition and surface morphology. Molecule deposition was determined using Fourier transform infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR) and morphology was determined using scanning electron microscopy and interferometric microscopy. The loss of the PLGA doping during degradation enhanced the formation of nano-porous structures in the remaining PCL domains, which attracted the deposition of substances from the osteogenic medium, which favoured the attachment and growth of human osteoblasts. The growth of osteoblasts was influenced by the controlled release of acidic products through polymer blending. Two pairs of FTIR-ATR absorption bands at 1090 and 1110 cm(-1), and at 1180 and 1190 cm(-1) were found to correlate to both PLGA and PCL, respectively. Changing the level of PLGA doping in PCL provided an approach to control the acidic products which can direct the growth of osteoblast cells.

Caproates↗
PubMed2005

Development of a fluid functionalized lipidic matrix applied to direct in situ polynucleotide detection.

This work presents a new approach for direct detection of polyelectrolytes at the air-water interface, based on the investigation of the interfacial properties of an active lipidic matrix especially designed for polynucleotide immobilization. A synthetic lipid with a cationic spermine headgroup, DiOctadecylamidoGlycylSpermine (DOGS), was spread at the interface to form a distortable film able to capture polynucleotides. The control of the organization state of this functionalized monolayer upon compression was achieved by recording surface pressure-area (pi-A) isotherm diagrams, presenting a specific shape with a typical liquid expanded-liquid condensed phase transition on a pure water subphase. In the presence of various dsDNA concentrations in the subphase, the isotherms were markedly modified in a time and concentration-dependent manner. The main modifications, corresponding to a large shift towards higher molecular areas and a clear fading of the phase transition, were corroborated by the fine analysis of the monolayer compressibility profile, thus suggesting a characteristic change in the monolayer fluidity as a function of both time and DNA concentration. Moreover, an ATR-Fourier transform infrared (ATR-FTIR) characterization showed evidences for the adsorption of DNA strands onto the lipidic matrix. The direct observation of the mixed monolayer morphology by Brewster angle microscopy (BAM) strongly suggests that DNA adsorption induces a reorganization of lipids at the interface, as evidenced by the change in the condensed lipidic domains morphology in the presence of DNA in the subphase. The immobilization of various polynucleotidic probes of 4000, 400 and 22 base length, confirmed by fluorescence microscopy, had similar effects on DOGS interfacial properties. Preliminary studies are finally presented to explore the possibility of using this system for the study of hybridization between complementary strands. Hence, this study demonstrates this functionalized matrix behaves as a fluid support where polynucleotide immobilization induces interfacial properties modifications, which could be further exploited through the experimental characterization of Faraday instabilities sensitive to visco-elasticity variations.

Adsorption↗
PubMed2006

The DNA damage machinery and homologous recombination pathway act consecutively to protect human telomeres.

Telomeres protect chromosome ends from being detected as lesions and from triggering DNA damage checkpoints. Paradoxically, telomere function depends on checkpoint proteins such as ATM and ATR, but a molecular model explaining this seemingly contradictory relationship has been missing so far. Here we show that the DNA damage machinery acts on telomeres in at least two independent steps. First, the ATR-dependent machinery is recruited to telomeres before telomere replication is completed, likely in response to single-stranded DNA resulting from replication fork stalling. Second, after replication, telomeres attract ATM and the homologous recombination (HR) machinery. In vivo and in vitro results suggest that the HR machinery is required for formation of a telomere-specific structure at chromosome ends after replication. Our results suggest that telomere ends need to be recognized as DNA damage to complete end replication and to acquire a structure that is essential for function.

Bromodeoxyuridine↗
PubMed2005

Biological and chemical transformation of atrazine in coastal aquatic sediments.

The degradation and distribution potential of atrazine, a persistent triazine herbicide, into three chemical fractions were measured in coastal aquatic sediments in the laboratory over time. Sediments with varying organic carbon contents were extracted with an organic solvent followed by an alkali hydrolysis reaction, and atrazine, deethylatrazine (DEA) and deisopropylatrazine (DIA) were quantified in the aqueous, solvent, and basic fractions using gas chromatography-mass spectrometry. The total amount of atrazine and its metabolites recovered after 95 days varied by site and ranged from 5% to 30% in which 95% was atrazine found primarily in the solvent fraction. Sediment organic carbon was positively correlated with the distribution of atrazine into the basic fraction and the decline in the total amount recovered. No DIA was detected in laboratory spiked sediments and transformation to DEA was limited in all sediments and made up less than 1% of the mass balance. The production and persistence of DEA were inversely correlated to organic carbon; sediments with less carbon and limited binding sites had increased formation and persistence of DEA. A secondary metabolite, methylated atrazine (M-ATR) not previously documented to be derived from atrazine, was chemically produced, detected in all sediments and time points, and concentrations were an order of magnitude higher than DEA. Based on results from spiked estuarine sediments, atrazine and M-ATR may have the potential to persist in the environment while DEA and DIA may not be an ecological threat due to their limited formation.

Atrazine↗
PubMed2005

High precision procedure for determination of selected herbicides and their degradation products in drinking water by solid-phase extraction and gas chromatography-mass spectrometry.

For target monitoring of selected herbicides in groundwater transport studies, a precise and accurate method for the determination of atrazine (ATR), desethylatrazine (DEAT) and 2,6-dichlorobenzamide (BAM) was developed. The method is based on solid-phase extraction and GC-MS analysis. Deuterated standards are used as surrogates for calibration by the overall procedure. For legal requirements the method described was validated and is regularly subject to external quality control. Typical limits of detection are 2 ng/l. Uncertainty contributions were evaluated using the GUM workbench modelling software. At the concentration level of interest (100 ng/l), an expanded uncertainty of no more than 10% was estimated. Accurate data on the distribution of ATR, DEAT and BAM in affected well fields enabled operational changes to be implemented to control the drinking water supply according to legal requirements.

Chromatography, Liquid↗
PubMed2004

In situ Fourier-transform infrared spectroscopy studies of inorganic ions adsorption on metal oxides and hydroxides.

In this work, the studies describing the use of attenuated total reflection-infrared spectroscopy to obtain information on the sorption mechanism of inorganic ions on metal oxy-hydroxides are reviewed. ATR-IR is amongst the rare techniques which allow to analyze the sorption phenomena in situ and led to several results about the speciation of sorbed anions (sulfate, carbonate, phosphate, perchlorate, ...) or ternary inorganic complexes since it is able to distinguish outer-sphere and inner-sphere complexes. The principles of this method are summarized, and the experimental protocols, the results and the limitations are elaborated. The sample deposition method, initially based on a paste or a concentrated suspension, has evolved towards the coating of the ATR crystal by a colloid layer, increasing the sensibility and the reproducibility of the measurements. Observed absorption frequencies of ions sorbed on metal oxy-hydroxides (goethite, hematite, alumina, silica, TiO2, ...) are reported to help the identification of peaks in new experimental works. This method, characterized by an in situ analysis performed with a special cell used in a widespread instrumentation (IR spectrometer), is very recent but its advantages suitable for the current problems in the sorption field should help its rapid development for the next years.

Journal Article↗
PubMed2004

Polyurethane vascular catheter surface grafted with zwitterionic sulfobetaine monomer activated by ozone.

Polyurethane (PU) is a conventional biomedical material with favorable biocompatibility and excellent mechanical properties and widely used in making vascular catheter, but its antithrombogenic property is not good enough to make it as a more demanding applicable biomaterial. Surface modification is an effective way to improve the hemocompatibility for biomaterials. The purpose of present study was to use ozonization method to modify the surface of PU vascular catheter slice to improve its antithrombogenicity by grafting N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium (DMMSA), a zwitterionic sulfobetaine monomer. PU vascular catheter (PUVC) grafted with DMMSA (PUVC-g-PDMMSA) was characterized by ATR-FTIR and XPS. ATR-FTIR and XPS investigation confirmed the graft polymerization. The blood compatibility of the grafted films was evaluated by platelet rich plasma (PRP) platelet adhesion study and scanning electron microscopy (SEM) was used to observe the morphology of platelet using PU vascular catheter (PUVC) as the reference. No platelet adhesion was observed for the grafted PUVC slice incubated with PRP at 37 degrees C for 120 min. It is significant that this new zwitterionic sulfobetaine grafted PUVC have improved antithrobogenicity. It is effective that the inner surface of vascular catheter with inner diameter in only 3mm can be grafted with PDMMSA by using ozonization method.

Betaine↗
PubMed2004

Platelet adhesive resistance of polyurethane surface grafted with zwitterions of sulfobetaine.

A possible approach to improve the blood compatibility of poly(etherurethane)s (PU) involves the covalent attachment of key molecular on its surface. Recently, polymer tailed with zwitterions was found having good blood compatibility. The purpose of present study was to design and synthesis a novel nonthrombogenic biomaterial by modifying the surface of poly(etherurethane) with zwitterions of sulfobetaine via HDI spacer. The films of polyurethane were grafted with sulfobetaine by a three-step procedure. In the first step, the film surfaces were treated with hexamethylene diisocyanate (HDI) in toluene at 50 degrees C in the presence of di-n-butyl tin dilaurate(DBTDL) as a catalyst. The extent of the reaction was measured by ATR-IR spectra; a maximum number of free NCO group was obtained after a reaction time of 2.5 h. In the second step, the primary amine group of N,N-diethylethylenediamine (DEA) or N,N-dimethylethylenediamine (DMA) was allowed to react in toluene with isocyanate groups bound on surface. In the third step, two kinds of sulfobetaines were formed in the surface through the ring-opening reaction between tertiary amine of DMA or DEA and 1,3- propanesultone (PS). The reaction process was monitored with ATR-IR spectra and XPS spectra. The wettability of films was investigated by water contact angle measurement. A platelet adhesion experiment was conducted as a preliminary test to confirm the improved blood compatibility of PU. The number of platelets adhering to PU decreased greatly compared to original after 1 h and 3 h of contact with human plate-rich plasma.

Betaine↗
PubMed2005

Bioconcentration of atrazine and chlorophenols into roots and shoots of rice seedlings.

Accumulation of o-chlorophenol (CP), 2,4-dichlorophenol (DCP), and atrazine (ATR), as single and mixed contaminants, from hydroponic solutions into roots and shoots of rice seedlings was studied following 48-h exposure of the plant roots. As single contaminants at low levels, the observed bioconcentration factors (BCFs) of CP and DCP with roots approximated the equilibrium values according to the partition-limited model. The BCF of atrazine with roots was about half the partition limit for unknown reasons. The BCFs of CP and ATR with shoots also approximated the partition limits, while the BCF for more lipophilic DCP with shoots was about half the estimated limit, due to insufficient water transport into plants for DCP. As mixed contaminants at low levels, the BCFs with both roots and shoots were comparable with those for the single contaminants; at high levels, the BCFs generally decreased because of the enhanced mixed-contaminant phytotoxicity, as manifested by the greatly reduced plant transpiration rate.

Anthelmintics↗
PubMed2004

Selenomethionine protects against adverse biological effects induced by space radiation.

Ionizing radiation-induced adverse biological effects impose serious challenges to astronauts during extended space travel. Of particular concern is the radiation from highly energetic, heavy, charged particles known as HZE particles. The objective of the present study was to characterize HZE particle radiation-induced adverse biological effects and evaluate the effect of D-selenomethionine (SeM) on the HZE particle radiation-induced adverse biological effects. The results showed that HZE particle radiation can increase oxidative stress, cytotoxicity, and cell transformation in vitro, and decrease the total antioxidant status in irradiated Sprague-Dawley rats. These adverse biological effects were all preventable by treatment with SeM, suggesting that SeM is potentially useful as a countermeasure against space radiation-induced adverse effects. Treatment with SeM was shown to enhance ATR and CHK2 gene expression in cultured human thyroid epithelial cells. As ionizing radiation is known to result in DNA damage and both ATR and CHK2 gene products are involved in DNA damage, it is possible that SeM may prevent HZE particle radiation-induced adverse biological effects by enhancing the DNA repair machinery in irradiated cells.

Aerospace Medicine↗