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At least 883 records · Page 49Linked to original sources
PubMed1995

Analysis of metallothionein isoforms by capillary electrophoresis: optimisation of protein separation conditions using micellar electrokinetic capillary chromatography.

Capillary electrophoresis (CE) techniques have been successfully applied to the separation of metallothionein (MT) isoforms and have proved to be rapid, practical and economical. Study of a variety of different electrolytes and capillaries has shown that electrolyte buffer composition and capillary wall surface modifications can have considerable influence on isoform separation and resolution. Ionic surfactants such as sodium dodecyl sulphate (SDS) form micelles at elevated concentrations and the partitioning of molecules between the hydrophobic micelle phase and the aqueous phase and their resulting migration in an electric field is the basis of the technique known as micellar electrokinetic capillary chromatography (MECC). In the present work, we have used sheep and rabbit MT to optimise MECC conditions for analysis of MT isoforms. Capillaries of 57 cm gave much better separations than shorter columns although analysis times were increased to about 12 min. Changing the buffer and SDS concentration or the pH affected the selectivity of isoform separation and up to 5 isoforms in sheep MT and 6 in rabbit MT were completely or partially resolved. Comparing different diameter capillaries we conclude that 25 microns I.D. columns give better separations than 50 or 75 microns I.D. columns although sensitivity is reduced by a factor of about 3 and 5, respectively. Using our MECC conditions, columns coated with C1 or C18 hydrophobic material were not found to be useful in improving MT separation or resolution although further evaluation of these columns is in progress.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Comparison of micellar electrokinetic chromatography (MEKC) with capillary gas chromatography in the separation of phenols, anilines and polynuclear aromatics potential field-screening applications of MEKC.

Capillary electrophoresis (CE) is known to be complementary to liquid chromatography, but comparison of CE with capillary gas chromatography (GC) for applicable analytes has not been extensive. Capillary GC has been the preeminent separation technique for environmental analysis, but CE has yet to be applied systematically to the determination of environmental analytes. We present data on separations of three classes of semivolatile analytes of interest to environmental analysis: phenols, anilines and polynuclear aromatic hydrocarbons (PNAs). Standard GC conditions were used to illustrate typical separations observed on 30-m and 40-m columns. Rapid analyses were addressed using a high-temperature 15-m column of thinner film. CE separations employed borate buffer with sodium cholate as the micellar agent in micellar electrokinetic chromatography (MEKC). The effects of organic additives were studied using methanol, acetone and tetrahydrofuran. gamma-Cyclodextrin was also used in MEKC to enhance the separation of polynuclear aromatic hydrocarbons and to examine its effects on separations of phenols and anilines. Short capillaries effected very rapid (< 3 min) compound-class characterization, an approach which has potential use in site characterization/remediation (field-screening) studies.

Aniline Compounds↗
PubMed1994

Experimental basis for separation of membrane vesicles by preparative free-flow electrophoresis.

In practice it has been possible to separate membrane particles of different origins but of similar chemical composition by preparative free-flow electrophoresis. Examples include the vacuolar (tonoplast) and plasma membranes of plants and membranes derived from the cis and trans regions of the rat liver Golgi apparatus. Yet, when analyzed for intrinsic molecules that might contribute to significant differences in surface charge, the separated membranes were surprisingly similar. As more information was generated, it became apparent that the membranes with greatest electrophoretic mobility (i.e. lysosomes, rightside-out tonoplast vesicles and membranes from the trans region of the Golgi apparatus), where those membranes with an inherent ability to acidify their interiors. By so doing, the vesicles generate a membrane potential, negative outside, which might serve as a basis for enhanced electrophoretic mobility. To test the hypothesis, tonoplast membranes were incubated with ATP to drive proton import or with monensin to dissipate the ATP-supported proton gradient. With ATP, mobility was enhanced. Also, when ATP-treated vesicles were analyzed in the presence of monensin, the ATP effect on mobility was reversed. Similarly with Golgi apparatus, mobility of the most electrophoretically mobile portions of the separation was enhanced by ATP and the ATP effect was reversed with monensin. A trans origin of the vesicles was verified by assay of the trans Golgi apparatus marker, thiamine pyrophosphatase. Finally, incubation with ATP (and reversal by monensin) was employed as an aid to the free-flow electrophoretic separation of kidney endosomes from complex mixtures. These lysosomal derivatives also are capable of acidification of their interiors in an ATP-dependent process and of generating, at the same time, a negative (outside) membrane potential. The findings provide both an experimental basis to enhance membrane separations by preparative free-flow electrophoresis and, at the same time, a theoretical basis to help explain why certain membranes of very similar overall chemical composition may be separated by electrophoretic methods.

Adenosine Triphosphatases↗
PubMed1995

Sample dimensionality: a predictor of order-disorder in component peak distribution in multidimensional separation.

While the use of multiple dimensions in separation systems can create very high peak capacities, the effectiveness of the enhanced peak capacity in resolving large numbers of components depends strongly on whether the distribution of component peaks is ordered or disordered. Peak overlap is common in disordered distributions, even with a very high peak capacity. It is therefore of great importance to understand the origin of peak order/disorder in multidimensional separations and to address the question of whether any control can be exerted over observed levels of order and disorder and thus separation efficacy. It is postulated here that the underlying difference between ordered and disordered distributions of component peaks in separation systems is related to sample complexity as measured by a newly defined parameter, the sample dimensionality s, and by the derivative dimensionality s'. It is concluded that the type and degree of order and disorder is determined by the relationship of s (or s') to the dimensionality n of the separation system employed. Thus for some relatively simple samples (defined as having small s values), increased order and a consequent enhancement of resolution can be realized by increasing n. The resolution enhancement is in addition to the normal gain in resolving power resulting from the increased peak capacity of multidimensional systems. However, for other samples (having even smaller s values), an increase in n provides no additional benefit in enhancing component separability.

Chromatography↗
PubMed1996

Mixed micelles of short chain alkyl surfactants and bile salts in electrokinetic chromatography: enhanced separation of corticosteroids.

The separation of a complex mixture of 17 corticosteroids was investigated by mixed micellar electrokinetic chromatography (MMEKC) employing various bile salts and/or alkylsulfonates. In this study, influence of individual surfactants and mixed micelles of hydrocarbon-bile salt surfactants on retention behavior, selectivity and the size of the elution window is investigated. Retention behavior of corticosteroids in SDS and bile salt micelles is examined using linear solvation energy relationships (LSER). In addition, the effects of type of bile salt surfactant on elution patterns were investigated. It was found that separation patterns are mostly influenced by the number of hydroxyl functional groups on the steroidal backbone of the bile salts, while the type of ionic head group has little, if any, effect on the steroids separation. Comparisons between mixed micellar techniques and the inclusion of conventional modifiers to various single and binary surfactant systems were made. The addition of modifiers such as acetonitrile, urea and beta-cyclodextrin to SDS surfactant systems, as well as mixed bile salt systems of sodium taurocholate and sodium glycodeoxycholate, did not improve the separation of the steroids. On the other hand, the addition of the short-chain alkylsulfonate sodium butanesulfonate to the mixture of taurocholate and glycodeoxycholate greatly improved the separation of the 17 corticosteroids and provided a baseline separation of all solutes. The effects of carbon chain length and concentration of alkylsulfonate on capacity factor, selectivity, efficiency and the size of the elution window were investigated.

Adrenal Cortex Hormones↗
PubMed1985

Effects of spatial separation and retinal eccentricity on two-dot vernier acuity.

Experiments investigated how vernier acuity for dot targets is affected by dot spatial separation and retinal eccentricity. Beck and Schwartz [Vision Res. 19, 313-319, 1979] found that the vernier thresholds increased linearly with interdot separation from 7.5 to 30 min arc. Experiment 1 showed that the vernier thresholds increased linearly with interdot separation from 0.5 to 8 deg arc. Experiments 2 and 3 showed that moving the dots into the periphery while keeping the interdot separation constant increased the threshold little if at all. The results are interpreted as supporting the hypothesis that there is (1) an encoding of dot positions in retinal coordinates, and (2) that the relative positions of the dots are made explicit in terms of the slope of the virtual line joining them. The increase in threshold with dot separation indicates that the visual system is unable to directly access and compare the retinal positions of the dots. The constancy of the threshold with eccentricity indicates that the visual system encodes the retinal positions of two well-separated dots as accurately in the periphery as in the fovea.

Depth Perception↗
PubMed1991

The impact of jitter on separation discrimination: combination of monocular inputs.

The eyes are in continuous motion. A robust system required to make spatial separation judgments should be resistant to the positional noise produced by such movements. Two parallel lines have been jittered horizontally in order to assess the impact of stimulus movement on the retina. Jitter that maintains the separation between the two lines has minimal effect on separation discrimination thresholds, regardless of whether the targets in the two eyes jitter in a positively correlated, negatively correlated or uncorrelated manner. Presenting both eyes with line pairs but only altering the separation in one eye in the second interval yields poorer performance. However, if one eye receives a change in separation while the other views a dark screen then that monocular threshold is very similar to the binocular threshold. These results are most simply explained by procedures which average the monocular separation estimates.

Convergence, Ocular↗
PubMed1979

Influence of 48 hour calf separation on milk production and calf growth in range cows.

Hereford cows and their calves were either left together or separated for a 48-hr period between 50 and 80 days postpartum. Milk production and calf weights were determined 1 and 2 weeks prior to and 1 and 3 weeks after calf separation. Daily milk production of separated cows (5.6+/-.1 kg) was not different from that of control cows (5.3+/-.1 kg) at any sampling period. Similarly, calf growth was not affected (P > .10) by separation; both groups of calves gained .64 kg/day. Average 205-day adjusted weaning weights were also similar, for the control (173.5+/-4.6 kg) and separated calves (181.8+/-4.6 kg). These results indicate that 48-hr calf separation could be used in a treatment regime to decrease the postpartum anestrous interval in range cattle without detrimental effects on milk production, calf growth or 205-day adjusted weaning weight.

Journal Article↗
PubMed1989

The relationship of child abuse indicators to the assessment of perceived risk and to the court's decision to separate.

The most serious decision taken in child abuse cases is to formally separate the child and the family. There has been concern that the criteria for making these decisions should be made explicit. The consequences of the separation for the child, family, and society is one set of reasons for this concern. Another is that with the increasing number of cases being reported, there is a need for reliable, consistent, and efficient decisions across cases. This paper operationally defines a set of indicators for the separation decision. One hundred fifty-two cases of suspected child abuse from the Royal Children's Hospital were coded in terms of the indicators and the outcome of the case. The outcome was the court's decision to separate the child. The study investigated whether and in what way these indicators were related to the separation outcome. In addition the perceived risk to the child was operationally defined, and the relationship of the indicators and the court's decision to perceived risk was studied. Statistical analysis of the data showed that the indicators most associated with the separation outcome were severity of abuse, parenting, and the family social system. Two important implications for practice are that information on explicit indicators should be recorded for cases, and that they can provide a base for training of new child protection workers.

Australia↗
PubMed1994

Separation of viable and non-viable yeast using dielectrophoresis.

Dielectrophoresis, the movement of particles in non-uniform AC electric fields, was used to rapidly separate viable and non-viable yeast cells with good efficiency. Known mixtures of viable and heat-treated cells of Saccharomyces cerevisiae were separated and selectively isolated using positive and negative dielectrophoretic forces generated by microelectrodes in a small chamber. Good correlations with the initial known relative compositions were obtained by direct microscopic counting of cells at the electrodes after initial dielectrophoretic separation (r = 0.995), from methylene blue staining (r = 0.992) and by optical absorption measurements (r = 0.980) of the effluent after selectively flushing out the viable and non-viable cells from the chamber. Through measurement of cell viability by staining with methylene blue and plate counts, for an initial suspension of approx. 1.4 x 10(7) cells per ml containing 60% non-viable cells, the dielectrophoretically separated non-viable fraction contained 3% viable cells and the viable fraction 8% dead cells. The separation efficiency is increased by dilution of the initial suspension or by repeat operation(s). Cell viability was not affected by the separation procedure.

Electrophoresis↗
PubMed1993

Temporal and social factors influencing behavioral and hormonal responses to separation in mother and infant squirrel monkeys.

The behavioral and hormonal responses of mother and infant squirrel monkeys (Saimiri sciureus) were examined to assess temporal and environmental factors that influence the response to separation. In two experiments evaluating the effects of 1-, 3-, 6-, and 24-hr separations, it was found that signs of infant behavioral agitation decreased over time, whereas adrenocortical activation persisted or even increased. Moreover, two separation environments were shown to differentially affect behavioral and hormonal responses. Separated infants vocalized significantly more when their mothers were proximal than when isolated, but showed lower cortisol levels in the adjacent separation than in the total-isolation condition. These data indicate that the intensity of the infant's calling response cannot be used to predict internal state (as reflected by cortisol levels). Furthermore, vocalization rate is highly dependent upon contingent stimuli, such as the presence of maternal cues. Following separation, the mothers also showed elevated cortisol levels. However, both the magnitude and pattern of the response differed considerably from that of the infant.

Animals↗
PubMed1987

Separation of metalloporphyrins from metallation reactions by liquid chromatography and electrophoresis.

The analytical separation of the indium and manganese complexes of three synthetic, meso-substituted, water-soluble porphyrins from their respective free bases in metallation reaction mixtures is described. The ligands tetra-3N-methylpyridyl porphyrin, tetra-4N-methylpyridyl porphyrin and tetra-N,N,N-trimethylanilinium porphyrin are complexed with In (III) and Mn (III) and are separated from residual free base by high-performance liquid chromatography (HPLC) in acidic conditions with gradient elution on ODS bonded stationary phase. Electrophoretic separation is achieved on both cellulose polyacetate strips and polyacrylamide tube gels under basic conditions. Although analytical separations can be achieved by both HPLC and electrophoresis, only HPLC is suitable for the development of preparative scale separations. Column chromatography, ion-pairing and ion-suppression HPLC techniques fail to separate such highly charged and closely related aromatic compounds.

Chemical Phenomena↗
PubMed1993

Improved thin-layer chromatographic separation of 32P-postlabeled DNA adducts.

DNA adducts represent the putative initiating event in the chemical carcinogenesis process. 32P-Postlabeling is one of several assays which have been developed for the sensitive detection of DNA adducts. An integral part of the 32P-postlabeling assay is the separation of adducted nucleotides by multidirectional, multisolvent, anion-exchange polyethyleneimine-cellulose thin-layer chromatography. Standard since the introduction of this assay has been the use of high-salt, high-urea solvents for the resolution of adducts during the D3 and D4 phases of the chromatography. Urea solvents are able to separate adducts resulting from a number of chemicals, however, they are time-consuming, retain a lot of background noise, may push adducts into inadequately resolved diagonal radioactive zones, and may not separate adducts of similar structure. In this study we introduce the use of a dilute ammonium hydroxide solvent for D4 chromatography and compare it to other standard solvents such as lithium chloride-Tris.HCl-urea, sodium phosphate-Tris.HCl-urea, and isopropanol-4 M ammonium hydroxide for adduct separation, resolution, recovery, retention of background noise, and chromatography development time. We found that 0.2 M ammonium hydroxide worked well for the recovery, separation, and resolution of a wide array of adducts derived from highly lipophilic polycyclic aromatic hydrocarbons and aromatic amines. In addition, this solvent required much less time (< 1/4) as compared to the other solvents and more importantly allowed the separation of adducts which otherwise comigrated and were not visible when using the other three D4 solvents.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonium Hydroxide↗
PubMed1996

Separation of biologically active peptides by capillary electrophoresis and high-performance liquid chromatography.

HPLC and CE have been applied to the separation of some newly synthesized substances, including nonapeptides from the intrachinary region of insulin, insulin-like growth factors I and II (IGF I and II) and some penta- and hexapeptides. All the peptides are satisfactorily separated using a reversed-phase HPLC system with a C18 stationary phase and mobile phases of 20-40% acetonitrile (v/v) and 0.2% trifluoroacetic acid in water (v/v). The best CE separation of IGF I and II has been achieved in a 30 mM phosphate buffer (pH 4-5), whereas 150 mM phosphoric acid (pH 1.8) is optimal for the insulin nonapeptides. The latter electrolyte is also suitable for the CE separation of the hexapeptides, as is a micellar system containing 20 mM borate-50 mM sodium dodecyl sulfate (pH 9.0). Complete CE resolution of the D- and L-forms is possible in a 50 mM phosphate buffer (pH 2.5) containing 10 mM beta-cyclodextrin. UV spectrophotometric detection was used throughout, at wavelengths from 190 to 215 nm. The CE procedures are, in general, preferable to HPLC separations, as they exhibit better separation efficiencies, are faster and consume smaller amounts of analytes and reagents.

Amino Acid Sequence↗
PubMed2006

Separation of amnion from choriodecidua is an integral event to the rupture of normal term fetal membranes and constitutes a significant component of the work required.

OBJECTIVE: This study was undertaken to determine the sequence of events that occur during fetal membrane (FM) rupture and to compare the biophysical properties of intact FM with its separated individual components (amnion and choriodecidua). STUDY DESIGN: FM physical properties were determined with computerized, specially adapted, industrial, strength testing equipment and the rupture sequence (in vitro) video documented. Separated individual FM component properties were compared with those of reapproximated components, and of intact FMs. RESULTS: The sequence of FM rupture was (1) FM components stretch together under load; (2) amnion separates from choriodecidua; (3) choriodecidua ruptures; (4) amnion distends further, nonelastically; and (5) amnion ruptures. In all FMs tested, amnion was stronger, stiffer, and more ductile than choriodecidua. The sum of work required to rupture separated FM components (amnion + choriodecidua), or reapproximated components, was significantly less than that of intact FMs. CONCLUSION: Separation of amnion from choriodecidua occurs as part of normal term FM rupture. FMs become significantly weaker as a result of this separation.

Amnion↗
PubMed2004

Maternal separation has no effect on voluntary ethanol intake in female Wistar rats.

Adverse experiences, early in life or during adulthood, can increase the vulnerability for development of drug dependence. Investigators have shown that short and prolonged periods of maternal separation during the postnatal period can affect voluntary ethanol intake in male rats. Recent study findings have indicated sex-dependent effects of maternal separation, and, in the current study, the effects of maternal separation on acquisition of voluntary ethanol intake in female Wistar rats were investigated. Rat pups were subjected to daily maternal separation for 15 min (MS15) or 360 min (MS360) during the first 3 weeks of life or reared under normal animal facility rearing (AFR) conditions. During 25 days, starting at 10 weeks of age, the effects of maternal separation on acquisition of voluntary ethanol intake were investigated. In contrast with previous study results for male rats, neither MS15 nor MS360 affected acquisition of voluntary ethanol intake in female rats. A stressful situation in adulthood, restraint stress, resulted in a significant increase in ethanol intake during the restraint period compared with baseline levels in the animals reared under normal AFR conditions, an effect that persisted throughout the postrestraint period. In rats subjected to MS15 or MS360, a significant increase in ethanol intake was shown during the postrestraint period compared with baseline levels. The current study findings therefore give further evidence for sex differences in the consequences of maternal separation. Compared with previous findings in male rats, acquisition of ethanol intake was not affected, and restraint-induced effects were less pronounced but more prolonged, in female rats.

Alcohol Drinking↗
PubMed2005

TSE clearance during plasma products separation process by Gradiflow(TM).

BACKGROUND AND OBJECTIVES: Recent experimental evidence from rodent models suggests a potential risk for transmissible spongiform encephalopathy (TSE) transmission by blood. The emergence of a new variant Creutzfeldt-Jakob disease (vCJD) has raised increased concerns about the safety of blood components and plasma products derived from vCJD-infected donors. Recent risk-minimisation strategies have included a ban on the use of UK-sourced plasma for the preparation of licensed blood products and leukodepletion of blood donations for fear of possible transmission of the human TSE via blood or blood components. The aim of this study was to investigate the capability and efficacy of a preparative electrophoresis system (Gradiflow) in the removal of TSE contaminants during the separation of plasma products. MATERIALS AND METHODS: Using hamster adapted scrapie 263 K as a model for TSE agent, albumin and IgG separation from human plasma by Gradiflow were performed separately by spiking a 263 K scrapie microsomal fraction to the feed material at each process step. Samples from pre- and post-Gradiflow separation process were titrated to the end-point for the detection of the disease-associated, proteinase K resistant form of the pathogenic prion protein (PrP(Sc)) by Western blot. RESULTS: Under all conditions tested, a greater than 3 log(10) reduction was achieved with no PrP(Sc) detected in any of the pooled products for either of the IgG or albumin separations. These data show that Gradiflow processing has clear advantages for concurrent purification of plasma products and in-process TSE removal. CONCLUSIONS: Our findings suggest that Gradiflow process is a viable alternative to remove causative TSE agents during plasma products separation, potentially eliminating the risk of TSE agents transmission.

Animals↗
PubMed2006

Separation of phenols and furfural by pervaporation and reverse osmosis membranes from biomass--superheated steam pyrolysis-derived aqueous solution.

The separation of valuable chemicals from raw products, where a great number of chemicals coexist, is the key technology in biomass refinery. In this study, the applicability of membrane separation of valuable chemicals from our currently developed portable superheated steam (SHS) biomass pyrolysis process was demonstrated. Phenols (phenol, p-cresol, guaiacol, methyl guaiacol, and ethyl guaiacol), furfural, and acetone were successfully separated by pervaporation using the silicone rubber membrane from model solutions and an actual SHS derived aqueous solution. The solution was also concentrated effectively by reverse osmosis separation using a polyamide membrane. When a high concentration of SHS solution was fed to the pervaporation process, a phase-separated permeate was obtained, which indicated that the reverse osmosis concentration combined with pervaporation separation is useful for the superheated steam process.

Acetone↗