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PubMed2006

What we have learned from 5 cases of permanent capsule retention.

BACKGROUND: Capsule endoscopy allows the direct visualization of the entire small bowel. There is limited data on the clinical significance of permanent capsule retention. OBJECTIVE: Our purpose was to document the frequency, findings, risk factors, management, and outcomes of permanent capsule retention. DESIGN: Retrospective, case series. SETTING: Single tertiary referral center, outpatient. RESULTS: Permanent capsule retention occurred in 2% of our cases (5/245). The following pathologies caused insufficient capsule passage: adenocarcinoma in a patient with hereditary nonpolyposis colorectal cancer (1), idiopathic stenosis (1), stricturing Crohn's disease (2), and adhesions (1). Capsule retention lead to a symptomatic small-bowel obstruction in only 1 of these cases (0.4%). As a consequence, 2 cases had successful endoscopic retrieval; 3 cases required surgical intervention. Four of 5 patients had a clear clinical benefit resulting from the capsule findings or the secondary procedure. CONCLUSIONS: Permanent capsule retention is rare. Even though this event may lead to the necessity of an endoscopic or surgical intervention, a clear benefit for the patient in respect to the underlying disease resulted in 4 of 5 patients.

Aged↗
PubMed2006

New graduate nurse self-concept and retention: a longitudinal survey.

Graduate nurse attrition is an increasing phenomenon within a world of decreasing nursing numbers. The newly developed nursing self-concept of the graduate nurse may provide a key indicator for predicting graduate retention. This study explores the development of multiple dimensions of nursing self-concept and examines their relationship to graduate nurse retention plans. A descriptive survey design with repeated measures was utilised to assess nurse self-concept and retention plans. The key findings suggest that multiple dimensions of graduate nurse self-concepts rise significantly in the second half of their graduate year and that nurse general self-concept is a strong predictor of graduate nurse retention. The implications of this study are that monitoring of self-concept throughout the transitional period for new nurses can lead to early detection and appropriate intervention strategies thereby improving retention rates for new nurses.

Adult↗
PubMed2004

Cu(II) retention on a humic substance.

Humic substances (HS) are macromolecular products derived from a physical, chemical, and microbiological process called "humification." These substances play an important role in the mobility and bioavailability of nutrients and contaminants in the environment. Adsorption isotherms provide a macroscopic view of the retention phenomena. However, complementary techniques are needed in order to study the retention mechanism. The application of the classical models and some modern ones, based on humic substances chemistry, do not accurately describe these adsorption data. The aim of this paper is to model isotherms and combine adsorption data with spectroscopy and microscopy techniques to study the Cu(II) retention on a HS. The adsorption isotherms shape varies significantly with the solution pH from L-type (pH 2-6) to S-type (pH 8). FTIR shows that, when pH is 2 the retention of Cu(II), as [Cu(H(2)O)(6)](2+), is the preferred retention mechanism. The quantity of Cu(II) retained as [Cu(OH)(H(2)O)(6)](+) rises, as pH increases. At pH 4, Cu(II) begins to precipitate, which is the preferred mechanism at pH 8.02. The presence of HS has a great influence on the precipitation process of Cu(II), giving rise to amorphous precipitates. As it is shown by SEM-XRF, Cu(II) distributes heterogeneously on HS surface and accumulates on the humic phases. The presence of different anions (chloride and nitrate) slightly modifies the HS behavior as cation exchanger. When Cl(-) ions are present, part of the Cu(II) form [CuCl(4)](2-), which is stable in solution due to its negative charge; when the anion present is NO(3)(-) the formed complex, [CuNO(3)](+), is retained on the HS.

Adsorption↗
PubMed2005

Particle and surface characterization of a natural illite and study of its copper retention.

Illite clays are known to have a strong affinity for metallic pollutants in the environment and can be applied as low-cost adsorbents for industrial waste treatment. A crucial factor in the development of such applications, however, is the understanding of the chemical, mineralogical, and colloidal properties of these clays. It is also important to understand the mechanisms involved in the surface adsorption of metals by these adsorbants. In order to study the retention of transition metals on illite clays, we have applied surface characterization techniques such as FPIA, SEM-EDX, XRD, N2 (77 K) adsorption, and FTIR. In addition to these experimental techniques, we have also employed a theoretical model that accounts for the chemistry of transition metal ions, and considers the global retention process to be the sum of several single retention processes. This model adequately fits the experimental data and allows for the speciation of metal retention on illite surfaces. Between pH values of 2.53 and 3.01 the only adsorption processes are the electrostatic sorption of [Cu(H2O)6]2+, and the surface complexation of [Cu(H2O)6]2+ and [Cu(OH)(H2O)5]+ ions. Surface complexation of [Cu(OH)(H2O)5]+ ions increases with pH, overcoming [Cu(H2O)6]2+ retention, and thus contributing to the surface precipitation of Cu(OH)2.

Adsorption↗
PubMed2004

Comparison of cell uptake, biodistribution and tumor retention of folate-coated and PEG-coated gadolinium nanoparticles in tumor-bearing mice.

The purpose of these studies was to compare the cell uptake, biodistribution and tumor retention of folate-coated and PEG-coated gadolinium (Gd) nanoparticles. Gd is a potential agent for neutron capture therapy (NCT) of tumors. Gd nanoparticles were engineered from oil-in-water microemulsion templates. To obtain folate-coated nanoparticles, a folate ligand [folic acid chemically linked to distearoylphosphatidylethanolamine (DSPE) via a PEG spacer MW 3350] was included in nanoparticle preparations. Similarly, control nanoparticles were coated with DSPE-PEG-MW 3350 (PEG-coated). Nanoparticles were characterized based on size, size distribution, morphology, biocompatibility and tumor cell uptake. In vivo studies were carried out in KB (human nasopharyngeal carcinoma) tumor-bearing athymic mice. Biodistribution and tumor retention studies were carried out at pre-determined time intervals after injection of nanoparticles (10 mg/kg). Gd nanoparticles did not aggregate platelets or activate neutrophils. The retention of nanoparticles in the blood 8, 16 and 24 h post-injection was 60%, 13% and 11% of the injected dose (ID), respectively. A maximum Gd tumor localization of 33+/-7 microg Gd/g was achieved. Both folate-coated and PEG-coated nanoparticles had comparable tumor accumulation. However, the cell uptake and tumor retention of folate-coated nanoparticles was significantly enhanced over PEG-coated nanoparticles. Thus, the benefits of folate ligand coating were to facilitate tumor cell internalization and retention of Gd-nanoparticles in the tumor tissue. The engineered nanoparticles may have potential in tumor-targeted delivery of Gd thereby enhancing the therapeutic success of NCT.

Animals↗
PubMed2006

Quantitative structure and retention relationships for gas chromatographic data: application to alkyl pyridines on apolar and polar phases.

Quantitative structure and retention relationships (QSRR) have been developed to model gas chromatographic retention data of alkyl pyridines on apolar (branched alkane) and polar (primary alcohol) stationary phases. The retention properties analyzed are Kovats retention index, I; partial molar enthalpy, DeltaH; partial molar entropy, DeltaS and partition coefficient, log K. Using the seven valence molecular connectivity indices (chi) calculated for the 18 alkyl pyridines, regression models are generated to predict the retention properties. The best model (model A) obtained with the descriptors ((1)chi(P)(V), (3)chi(P)(V) and (6)chi(CH)(V) was unable to produce a satisfactory statistical performance and correct order of elution. The model has been modified (model B) by including steric parameter s, which has been empirically derived by considering the steric effects due to the presence of alkyl groups at the ortho and meta positions. The modified model predicts the correct order of elution for all the alkyl pyridines and good correlation coefficients, r. The r values obtained for I, DeltaH, DeltaS and log K are: r=0.955, 0.975, 0.984 and 0.955 (model A) become r=0.999, 0.996, 0.990 and 0.999 (model B) on the apolar stationary phase and r=0.931, 0.926, 0.911 and 0.931 (model A) become r=0.999, 0.992, 0.958 and 0.999 (model B) on the polar stationary phase.

Chromatography, Gas↗
PubMed2006

Absorption of zinc and retention of calcium: dose-dependent inhibition by phytate.

The dose-dependent inhibitory effect of sodium phytate (myo-inositol-hexaphosphate) on absorption of zinc and retention of calcium was studied in man. No systematic study of this dose-response effect has been reported to this time. Forty subjects were served meals containing white wheat rolls without/with additions of phytate. Ten subjects were given test meals containing one or two of the studied levels of phytate and in addition all subjects were served meals to which no phytate was added. The zinc content was 3.1 mg (47 micromol) and the calcium content 266 mg (6.6 mmol). The rolls were labelled extrinsically with radioisotopes, 65Zn and 47Ca, and whole-body retention of both minerals was measured. Totally 105 meals were served, 36 meals in which no phytate was added and 9-10 meals on each level of phytate. The zinc absorption in meals to which either 0, 25, 50, 75, 100, 140, 175 or 250 mg of phytate-P (0, 134, 269, 403, 538, 753, 941 or 1344 micromol phytate) had been added was 22%, 16%, 14%, 11%, 7%, 7%, 7% and 6%, respectively (mean values). The addition of 50 mg phytate-P or more significantly decreased zinc absorption (p=0.01) as compared to absorption from the test meals with no added phytate. The calcium retention at day 7 in the same meals was 31%, 28%, 27%, 26%, 22%, 19%, 14% and 11% (mean values). The addition of 100 mg phytate-P or more significantly decreased calcium retention (p=0.03) compared to the test meals with no added phytate. It was concluded that the inhibitory effect of phytate on the absorption of zinc and the retention of calcium was dose dependent.

Absorption↗
PubMed2006

Beneficial effects of galantamine on performance in the object recognition task in Swiss mice: deficits induced by scopolamine and by prolonging the retention interval.

Episodic memory has been found to be impaired in several neuropsychiatric disorders. The object recognition task (ORT), introduced by Ennaceur and Delacour [Ennaceur A., Delacour J. A new one-trial test for neurobiological studies of memory in rats: 1. Behavioral data. Behav Brain Res 1988; 31: 47-59.], is a method to measure a specific form of episodic memory in rats and mice. It is based on the spontaneous behavior of rodents and can be considered as a retention test completely free of reference memory components. Therefore, the ORT has been increasingly used as an experimental tool in assessing drug effects on memory and investigating the neural mechanisms underlying learning and memory. In the present study, the main goal was to evaluate the effects of galantamine in Swiss mice in the ORT on scopolamine-induced deficits and with different retention intervals. Mice had a good object recognition memory at the 15 min retention intertrial interval (ITI). Object discrimination was absent at the longer intervals (1 h, 4 h and 24 h). Galantamine (10 mg/kg, administered s.c., 30 min prior to acquisition) partially reversed effects of scopolamine (0.63 mg/kg, administered s.c., 30 min prior to acquisition) and normalized performance to control levels. A lower dose of galantamine (0.63 mg/kg) was also investigated when two different retention intervals (15 min and 1 h) were used. Galantamine (0.63 mg/kg) had no adverse effects. Solvent-treated mice in the 1 h ITI condition did not discriminate between the novel and the familiar object (discrimination index was equal to zero), while galantamine (0.63 mg/kg)-treated mice attained a good object recognition memory performance. In conclusion, galantamine was shown to possess memory-enhancing effects in two conditions that reduced object discrimination: scopolamine-induced deficits and when a longer retention interval was used.

Animals↗
PubMed1997

Does a hypertonic saline load predict fluid retention in pacing induced heart failure?

OBJECTIVE: We examined the response to hypertonic saline challenge (SC) as a potential predictor of fluid retention during heart failure induced by rapid ventricular pacing. METHODS: Twelve dogs (22 +/- 4 kg) were given an intra-arterial bolus of 30 ml of 20% saline after establishing baseline fluid intake and urine output (24 h). Dogs were classified according to whether they drank more (Group A) or less (Group B) than the amount required to dilute the s.c. to isotonicity. Fluid retention was then assessed during heart failure after rapid ventricular pacing according to a graded ordinal scale and correlated with the responses to s.c.. RESULTS: No difference was noted in baseline fluid intake (1112 +/- 236 ml in Group A vs. 809 +/- 129 ml in Group B). Five hours after s.c. cumulative water intake was significantly greater in Group A than in Group B (1018 +/- 136 vs. 591 +/- 17 ml) (P < 0.01). Urine sodium concentration was 113 +/- 11 and 124 +/- 28 mmol/l at baseline in Group A and B, respectively; increased to 190 +/- 21 and 295 +/- 59 mmol/l at 5 h and remained elevated 24 h after s.c., 177 +/- 60 and 274 +/- 55 mmol/l (both P < 0.01 for within-group comparisons vs. baseline). Urine sodium concentration was less in Group A than in Group B at 5 and 24 h (P < 0.05). The fluid retention score was greater in Group A (3.6 +/- 0.5) than in Group B (0.8 +/- 0.4) (P < 0.01). Fluid retention in heart failure correlated with water intake after the pre-pacing s.c. (r = 0.68, P < 0.025) and inversely with urine concentrating ability (r = -0.58, P < 0.05). Furthermore, water intake and urine concentrating ability following the s.c. were inversely related (r = -0.67, P < 0.02). CONCLUSIONS: We conclude that normal dogs may be classified according to their fluid intake after s.c.. Those dogs that drank excessively and produced a dilute urine were more likely to retain fluid during pacing-induced heart failure. Hence, fluid intake and the ability to excrete a concentrated urine after a saline challenge may be useful variables to predict fluid retention in pacing-induced heart failure.

Animals↗
PubMed1998

Super-normal 201Tl retention in hibernating myocardium: an ex-vivo study using the failing human heart.

OBJECTIVE: Although the relationship between delayed 201Tl distribution and blood flow in acutely ischemic and infarcted myocardium has been widely explored in the experimental setting, its behaviour in chronically hypoperfused dysfunctioning human myocardium has not yet been evaluated. METHODS: In tissue samples of excised failing hearts taken from ischemic (IHD) patients and idiopathic dilated cardiomyopathy (IDC) controls, we evaluated the relationship between delayed 201Tl retention (4 h redistribution), blood flow (assessed by means of 99mTc-labelled human albumin microspheres injected during transplantation) and biochemically-assessed fibrosis. 201Tl activity was expressed as the percent of the activity in the region with highest flow and the least fibrosis. RESULTS: Fibrosis and 201Tl activity were inversely related (r = -0.62, P = 0.0001). In IDC controls, low flows corresponded to uniformly preserved 201Tl retention. In IHD, 46 segments with flows < or = 0.60 ml.min-1.g-1 and 20 segments with flows > 0.60 ml.min-1.g1 showed matching delayed 201Tl retention and flow values; in the remaining 27, there was a disproportionately high tracer accumulation in comparison with flow (flow/201Tl mismatch). Despite significantly less fibrosis and lower flows, the mismatch segments showed significantly greater. 201Tl activity than the segments with concordantly high tracer retention and flow values. Conversely, at equivalent flow rates, the mismatch regions had less fibrosis than the areas with concordantly depressed 201Tl activity and perfusion. CONCLUSIONS: This super-normal 201Tl retention in hibernating myocardium may indicate a mechanism of cell adaptation to chronic hypoperfusion.

Adult↗
PubMed1997

The bradykinin B2 receptor antagonist Icatibant (HOE 140) corrects avid Na+ retention in rats with CCl4-induced liver cirrhosis: possible role of enhanced microvascular leakage.

Avid Na+ retention is a hallmark of liver cirrhosis. The aim of this study was to investigate whether and how bradykinin is involved in Na+ retention in rats with CCl4-induced liver cirrhosis. To this end the bradykinin B2 receptor antagonist Icatibant (HOE 140) was used. On one hand, bradykinin has a renal natriuretic action. On the other hand, bradykinin is a potent mediator of both vasodilation and microvascular leakage. Both vascular mechanisms, which are reported for cirrhosis, could cause vascular underfilling and Na+ retention by activating the renin-angiotensin-aldosterone system. Icatibant normalised Na+ retention and reduced the hyperactivity of the renin-angiotensin-aldosterone system, suggesting a bradykinin-induced vascular disturbance. Icatibant had no significant effect on the mild hypotension which developed with CCl4 treatment. However, there was indirect evidence for enhanced microvascular leakage that was strongly inhibited by Icatibant. Our experimental results demonstrate that bradykinin is a key mediator of Na+ retention in liver cirrhosis and suggest that a bradykinin-induced increase in microvascular leakage is mainly responsible.

Animals↗
PubMed2000

Pressure-induced retention of the lysozyme on reversed-phase liquid chromatography.

This study investigated the effect of pressure on the retention behavior of a model protein, lysozyme, on octadecylsilica (C18) stationary phase under various equilibrium conditions. It is demonstrated that the retention time of the lysozyme was increased by as much as two to three times as the absolute pressure on the viewing window was increased from 23 to 318 bar. This pressure-induced retention was likely to be reversible and the corresponding volume change (deltaV = Vsta - Vmob) was found to be on the order of minus tens to hundreds of mL/mol. Moreover, the pressure-induced retention was also observed for a homologous series of hydrophobic poly-L-phenylalanine, which do not have the secondary structure, and the volume change was determined to be around minus 10 mL/mol per phenylalanine. Perturbations in solute ionization and conformational change are predicted to have a minor impact under the investigated conditions. It is believed that the pressure-induced shift of the equilibria regarding hydrophobic ad-desorption is the major cause of the observed increase of protein retention. About ten phenylalanine-equivalent residues on the lysozyme surface were involved in the hydrophobic association with the chromatographic ligands.

Chromatography, Liquid↗
PubMed2001

Effect of the eluent pH and acidic modifiers in high-performance liquid chromatography retention of basic analytes.

The retention of ionogenic bases in liquid chromatography is strongly dependent upon the pH of the mobile phase. Chromatographic behavior of a series of substituted aniline and pyridine basic compounds has been studied on C18 bonded silica using acetonitrile-water (10:90) as the eluent with different pHs and at various concentrations of the acidic modifier counter anions. The effect of different acidic modifiers on solute retention over a pH range from 1.3 to 8.6 was studied. Ionized basic compounds showed increased retention with a decrease of the mobile phase pH. This increase in retention was attributed to the interaction with counter anions of the acidic modifiers. The increase in retention is dependent on the nature of the counter anion and its concentration in the mobile phase. It was shown that altering the concentration of counter anion of the acidic modifier allows the optimization of the selectivity between basic compounds as well as for neutral and acidic compounds.

Buffers↗
PubMed2001

Effect of counter-anion concentration on retention in high-performance liquid chromatography of protonated basic analytes.

The influence of acid and salt concentration in the mobile phase on the retention of basic analytes has been studied. An increase in the retention of fully protonated analytes with increasing the concentration of inorganic additives was found. The addition of salt, such as perchlorate, trifluoroacetate, and phosphate, leads to the increase of retention for fully protonated analytes while mobile phase pH remains constant. The observed effect was attributed to the interaction of protonated analytes with the counter-anion of acid or salt, which leads to the disruption of the analyte solvation shell and the increase of its hydrophobicity and corresponding increase of retention. A mathematical model for the description of the influence of counter-anion concentration on analyte retention is proposed.

Anions↗
PubMed2001

Characterisation of retention in micellar high-performance liquid chromatography, in micellar electrokinetic chromatography and in micellar electrokinetic chromatography with reduced flow.

The retention (migration) behaviour of various barbiturates, phenylurea and triazine herbicides in micellar electrokinetic chromatography (MEKC) with uncoated fused-silica capillaries was compared with the behaviour in micellar electrokinetic chromatography with reduced electroosmotic flow (RF-MEKC) using capillaries modified with linear polyacrylamide. The error in the values of the retention factors caused by the neglection of the contribution of the electroosmotic flow in RF-MEKC was investigated and a method for correcting this error was suggested. The retention was characterised using the lipophilic and polar indices to characterise and to predict the retention as a function of the concentration of the surfactant (sodium dodecylsulphate) in the running buffer in MEKC and in RF-MEKC. Homologous series of n-alkylbenzenes and of n-alkan-2-ones were compared as the standard sets for the calibration of the retention (migration) index scale. The values of the lipophilic indices of a given solute measured in reversed-phase HPLC, MEKC and RF-MEKC are close to each other. Under ideal MEKC conditions, the values of the polarity indices are close to one for various sample solutes. However, for partially ionised compounds such as weakly acidic barbiturates, where the contribution of the electrophoretic migration is significant, the values of the polarity indices are significantly lower than one. Optimum conditions for separations of mixtures of triazine and phenylurea herbicides and of barbiturates using various techniques tested were compared.

Chromatography, High Pressure Liquid↗
PubMed2001

Prediction of retention times for anions in linear gradient elution ion chromatography with hydroxide eluents using artificial neural networks.

The feasibility of using an artificial neural network (ANN) to predict the retention times of anions when eluted from a Dionex AS11 column with linear hydroxide gradients of varying slope was investigated. The purpose of this study was to determine whether an ANN could be used as the basis of a computer-assisted optimisation method for the selection of optimal gradient conditions for anion separations. Using an ANN with a (1, 10, 19) architecture and a training set comprising retention data obtained with three gradient slopes (1.67, 2.50 and 4.00 mM/min) between starting and finishing conditions of 0.5 and 40.0 mM hydroxide, respectively, retention times for 19 analyte anions were predicted for four different gradient slopes. Predicted and experimental retention times for 133 data points agreed to within 0.08 min and percentage normalised differences between the predicted and experimental data averaged 0.29% with a standard deviation of 0.29%. ANNs appear to be a rapid and accurate method for predicting retention times in ion chromatography using linear hydroxide gradients.

Anions↗
PubMed1981

Gas-liquid chromatographic retention indices of 1318 substances of toxicological interest on SE-30 or OV-1 stationary phase.

Retention indices associated with 1318 substances likely to be encountered in toxicological analyses are presented. They are listed in ascending order of retention index for identification purposes and also in alphabetical order of compound name. The 4586 values used in this collection have been extracted from 36 sources, many of which have not been previously published. In many cases, where the quoted retention index is the mean of several determinations, the reproducibility and reliability of this value may be assessed. A histogram of the 1742 values listed is provided to help in determining the usefulness of a retention index for identification purposes. The reproducibility of inter-laboratory retention index measurements for twenty compounds on both SE-30 and OV-17 are presented and show the former, on average, to give more reproducible results.

Chromatography, Gas↗
PubMed1988

Correlation of calcitonin structure with chromatographic retention in high-performance liquid chromatography.

Chromatographic selectivity and position specificity were examined by using deletion and substitution analogues of calcitonin (CT), a 32-amino acid polypeptide. The biological activity of CT has been shown to be related to structural features, including a regular spacing of hydrophobic and hydrophilic residues in positions 8-22. The effect of structure on retention behavior in hydrophobic interaction chromatography (HIC) and reversed-phase chromatography (RPC) of 19 CT analogues was examined. No simple correlation was found between chromatographic retention and amino acid composition. Deletion of one leucine residue reduced retention in both chromatographic systems, but the magnitude of the change depended upon the site at which the deletion occurred. For example, deletion analogues des(Leu16)-, des-(Leu12)-, des(Leu10)-, des(Leu9)-, des(Leu4)-, and salmon calcitonin had retention times of 5.22, 8.44, 11.64, 13.53, 15.45, and 20.28 min, respectively, in HIC in contrast to RPC retentions of 15.19, 15.84, 28.53, 27.57, 25.92 and 34.79 min, respectively. Serine deletion was also shown to be position-specific. Non-amphiphilic analogues were eluted before amphiphilic ones. Circular dichroic spectral studies showed that the CT analogues possessed little secondary structure in the HIC solvents in contrast to alpha-helix formation in RPC solvents. The HIC data provided indirect evidence of secondary structure, induced in the amphiphilic CT analogues at the HIC solvent-chromatographic surface interface. Solute-solvent interactions contributed to differences observed between the selectivity of RPC and HIC.

Amino Acid Sequence↗