Coated capillaries and additives for the separation of proteins by capillary zone electrophoresis and capillary isoelectric focusing.

Strategies reported for the separation of proteins in capillary zone electrophoresis and capillary isoelectric focusing are reviewed. The strategies are grouped into two categories: coated capillaries and buffer/sample additives. Success attained with each case and also, more importantly, the limitations of the methodology are discussed. Recent results from our own laboratory in the area of capillary isoelectric focusing in uncoated, fused silica capillaries using additives are summarized. The advantages and disadvantages of coated columns vs. additives are delineated.

Attitudes of pediatricians toward maternal employment.

The largest number of women in history is employed outside the home including 55% of mothers with children less than 18 years of age. The attitudes of pediatricians toward employed mothers were assessed by a mail survey to the entire membership of the American Academy of Pediatrics. Usable responses were received from 5,758 pediatricians (31%). Adequacy of child care and economic necessity were ranked as the most important factors considered by responding pediatricians when advising a mother inquiring whether she should work outside the home. One third of the respondents stated the child can be any age when the mother becomes employed. The majority of respondents did not feel there was a difference between children of employed mothers and homemaker mothers. Special considerations for employed mothers were provided by half of the respondents, more frequently by female than male pediatricians. Most respondents are supportive of mothers working outside the home, but bias against employed mothers does exist. Pediatricians whose spouses do not work outside the home, those in older age groups, and male pediatricians tended to hold more traditional attitudes toward maternal employment.

Novel chiral surfactant for the separation of enantiomers by micellar electrokinetic capillary chromatography.

A novel chiral surfactant was prepared as both enantiomeric forms, (R)- and (S)-N-dodecoxycarbonylvaline, and employed for the separation of enantiomeric mixtures by micellar electrokinetic capillary chromatography (MECC). The enantioselectivities (alpha) obtained for twelve typical pharmaceutical amines using the (S)-surfactant were compared to those obtained with (S)-N-dodecanoylvaline, a chiral surfactant described in the literature. Higher enantioselectivities were seen for ten of the twelve compounds using (S)-N-dodecoxycarbonylvaline. Furthermore, (S)-N-dodecoxycarbonylvaline had significantly less background absorbance in the low UV. It is shown that exact enantiomer migration order reversal can be obtained by individually employing both enantiomeric forms of the surfactant. For ionizable compounds like the amines examined here, enantioselectivity can be optimized by changing the pH of the MECC buffer. Partitioning is optimized through surfactant concentration, organic additives and pH. The ability to achieve fast chiral separations is shown. A separation of ephedrine enantiomers in urine is shown, with the only sample preparation being filtration.

Radiologic total lung capacity measurement. Development and evaluation of a computer-based system.

The development of a computer-based radiologic total lung capacity (TLC) measurement system designed to be used by non-physician personnel is detailed. Four operators tested the reliability and validity of the system by measuring inspiratory PA and lateral pediatric chest radiographs with a Graf spark pen interfaced to a DEC VAX 11/780 computer. First results suggest that the ultimate goal of developing an accurate and easy to use TLC measurement system for non-physician personnel is attainable.

Determination of peptide 520 in human plasma using post-column photolysis with electrochemical detection in liquid chromatography.

A simple LC method for the determination of peptide 520 in human plasma was developed. Based on micellar chromatography, sodium octyl sulphate (SOS) was added into the mobile phase in order to separate the peptide from human plasma components. The procedure was fast and sensitive for the determination of the peptide in untreated human plasma. The electrochemical (EC) detection limit for peptide 520 in human plasma was 0.5 microgram ml-1. Linearity of the calibration plot for peptide 520 in human plasma was 0.999. This approach represents a direct injection technique for the potential detection and analysis of numerous peptides in biofluids, besides just plasma, with absolute quantification.

A phosphate binding assay for sevelamer hydrochloride by ion chromatography.

Sevelamer hydrochloride is a cross-linked polymeric amine; it is the active ingredient of Renagel capsules. Renagel is indicated for the control of hyperphosphatemia in patients with end-stage renal disease. An in vitro phosphate-binding assay is required to measure the drug's efficacy. The assay developed for this purpose involves mixing the drug (polymer) with a solution of known phosphate concentration, filtering off the polymer-phosphate complex, and quantitating the unbound phosphate concentration by ion chromatography. The binding capacity, reported as mmol of phosphate bound g of polymer(-1), is calculated from the calculated amount of bound phosphate and the weight of polymer used. The method has been validated for accuracy, precision, linearity, range, and ruggedness.

A general framework for evaluating the reliability of medical measurement systems.

Measurements of physical and social phenomena are often used in the decision-making process despite the error introduced by human and context variation. It would be advantageous to a decision maker to know the sources and magnitudes of such errors in using a measurement system or in choosing among alternative measurement systems. This paper describes an approach to determining the reliability of a measurement procedure called generalizability (G) theory. G theory uses the results of a random-effects analysis of variance to estimate the magnitude of error variability associated with each of several potential sources. These estimates can then be used to calculate a number of indices which typify the amount of precision provided by a measurement system in a particular context of usage. The major concepts of G theory are described and illustrated in the context of evaluating a radiologic total lung capacity measurement system.

Visual perspective taking in children: further ramifications of an information-processing model.

Forty children between ages 6 and 8 were administered a set of spatial perspective tasks. On half of the items, children responded by rotating a duplicate of the target display; on the remainder, children reconstructed the displays to correspond to a perspective view. The displays differed as to whether they contained marked or unmarked objects. On the basis of an information-processing analysis of these tasks, we predicted that the response-type variables and stimulus variables would interact in known ways. Analysis of variance results revealed a good fit with the hypothesized outcomes. Main effects were detected for age, which favored older children, and for display, which favored unmarked objects; the rotation task proved easier. Significant interactions revealed that task demands increasing task difficulty were more problematic in the construction task than in the rotation task, as predicted.

Children's solution strategies and mental rotation: evidence for a developmental shift.

We examined children's ability to anticipate the appearance of transformed multicomponents using visual stimuli with variations of a mental rotation task. We hypothesized that (a) performance would depend on the presence, location, and spatial relationship of specific stimulus features, and that (b) younger children would use a single component to make their predictions, whereas older children would be more likely to use multiple components. In Study 1, 40 first-, and fifth-grade subjects were presented with 32 rotation problems consisting of varied stimulus characteristics; subjects selected the correct option from a field where foils were indicative of the strategy used. Analyses of variance and log linear analyses revealed the hypothesized stimulus effect differentially associated with the children's ages. In Study 2, sixty 5-, 7-, and 9-year olds confronted 64 mental rotation problems with multicomponent stimuli and a construction task. Results and implications confirmed those of Study 1.

Non-invasive fetal electrocardiography.

The recording of a fetal electrocardiogram from abdominal surface electrodes is severely obscured by additive noise. There are several sources of interference. A two-step method was used to filter the interferences. The mother's electrocardiogram is removed first. The second stage of the filter eliminates the remaining noise by means of coherent averaging techniques. These require the detection of fetal heartbeats. A detection algorithm is suggested that shows high efficiency in this environment, where signal-to-noise ratio is extremely low.

Technology, power and the state.

Technical innovations may produce not only the changes they were intended to effect but also lead to consequences which are unexpected and sometimes destructive. There is an intimate relation between technological innovation and political power. Any great advances in reproductive technology are very likely to be controlled and commandeered by the state with all kinds of unforeseeable consequences.

Capillary electrophoresis: the promise and the practice.

The field of capillary electrophoresis has undergone rapid development over the past 10 years. Many advances have been made, but there are still some problems that must be addressed before the technique can reach its full potential.

Peptide mapping using EOF-driven capillary isoelectric focusing.

Capillary isoelectric focusing (CIEF) in uncoated and commercially available coated capillaries was applied to the separation of tryptic peptides from bovine and chicken cytochrome c. This is the first report of peptide mapping by CIEF. Before separation, the pIs of individual peptides expected to be formed during the digest were calculated, and then the separation pattern obtained was correlated with the calculated pIs. This correlation was reasonably good for some peptides, but not as good for others. However, differentiation of the two species digests was easily achieved based on the CIEF map. The major limitation of the method is the fact that uv detection at 280 nm must be employed, meaning that only tryptophan and tyrosine containing peptides will be detected, since the ampholytes used to generate the pH gradient absorb below 280 nm. Post-column derivatization of the peptides is one solution to this problem. Migration time reproducibility was on the order of 2%, and run times were less than 20 min for the entire pH gradient range in the uncoated capillary. In the coated capillary, superior resolution was obtained at the expense of longer run times.

Use of Ce(IV) oxidizing agent for the derivatization of polycyclic aromatic hydrocarbons for liquid chromatography-electrochemical detection.

Polycyclic aromatic hydrocarbons (PAHs) were oxidized with Ce(IV), and the resulting quinones were determined by reductive-mode liquid chromatography-electrochemical detection. This oxidation is a rapid, automatable step, involving of Ce(IV) reagent to the PAH sample and cleaning up the derivative with C18 solid-phase extraction. Using a C18 analytical column and a 2-propanol-phosphate buffer as the mobile phase, detection limits were in the ppb range for naphthalene, phenanthrene and anthracene, with linearity over 3-5 orders of magnitude. Method validation was performed by addition of the PAHs to tap water and determining the levels by reference to a calibration curve. The three PAHs can be simultaneously derivatized and determined under the same chromatographic conditions. Analysis of a motor-oil sample is also shown.

Evaluation of several solid phase extraction liquid chromatography/tandem mass spectrometry on-line configurations for high-throughput analysis of acidic and basic drugs in rat plasma.

Several configurations using 6- and 10-port switching valves were studied for high flow, on-line extraction of rat plasma coupled to an electrospray triple quadrupole mass spectrometer. Each plasma sample was diluted 1:1 with an aqueous internal standard solution. The sample was injected into a 2.1 x 20 mm cartridge column packed with 25 microm divinylbenzene/N-vinylpyrrolidone packing using 100% aqueous mobile phase at 4 mL/min. After sample loading and sample cleanup, the analytes were eluted from the extraction column with a 1.0-min gradient at 0.4 mL/min. The samples were either analyzed directly after elution from the extraction column or after additional separation using a short high performance liquid chromatography (HPLC) column. The different configurations were tested using an acidic drug (diflunisal) and a basic drug (clemastine) in rat plasma. On-line analysis was performed by injecting 200 microL of diluted plasma. The mass spectrometer was operated in the multiple reaction monitoring (MRM) mode. All calibration standards gave relative standard deviations (RSDs) below 5%. The total time per sample was 3 min.

Separation of amino acid enantiomers by micellar electrokinetic capillary chromatography using synthetic chiral surfactants.

A synthetic chiral surfactant was employed for the enantioselective micellar electrokinetic capillary chromatographic (MECC) separation of amino acid enantiomers derivatized with 6-aminoquinoyl-N-hydroxysuccinimidyl carbamate (AQC). The effect of surfactant concentration and buffer pH on resolution was studied, and the optimized conditions were used to evaluate the method in terms of sensitivity, reproducibility, and linearity. Resolution and alpha values for 12 ACQ-derivatized amino acids are reported. The ability to perform both achiral and chiral separations simultaneously is illustrated in a separation of a mixture of six amino acid enantiomeric pairs, all with baseline resolution. The direct reversal of enantiomer migration order, useful in quantitation and chiral identification, is also shown. Comparisons with other N-protected amino acid derivatives are made in terms of resolution and sensitivity, and the advantages of this chiral MECC technique used in conjunction with the inherent advantages of the AQC derivatizing reagent are discussed.

Comprehension of Euclidean space in young children: the early emergence of understanding and its limits.

In two studies Ss (N = 114) aged 3-5 years of age were assessed as to their ability to reconstruct or recognize spatial displays depicting Euclidean geometric features. The Ss responded either with the standard display present or in its absence, a memory condition. Items differed as to whether the objects located in the plane required attention to either one axis, the horizontal or vertical, or to both. In Study I Ss constructed their matches with an open-ended assessment device, while in Study II, they selected the match from a field of four distractors. Results from both studies were convergent despite differences in assessment technique and specifics of data analysis, and indicated an effect for age and condition, and that children do less well when dealing with double-axis displays in the memory condition. In addition, it appears that males were less attentive to display orientation cues than were females. Results are discussed in terms of Piagetian theoretical formulations about children's spatial development, their sensitivity to Euclidean spatial features, and the lack of synchrony between perceptual abilities and memory.

Nonlinear analyses of cell proliferation in the central nervous system reveal stochastic and deterministic components.

This paper analyzes the dynamics of cell proliferation in the developing central nervous system. Three different algorithms, Fano factor, Allan factor and detrended fluctuations analysis, are used to estimate de scaling exponent of space numerical series obtained by recording the number and position of proliferating cells along the cephalic-caudal axis of the system. It can be concluded that the dynamics of proliferation involves two component: (a) a random noncorrelated stochastic component representing a basal proliferating activity uniformly distributed along the cephalic-caudal axis and (b) a deterministic nonstationary component that imposes a defined global trend to the process. The deterministic nonstationary trend can be interpreted as the effect of a controlling influence operating along the cephalic-caudal axis. This result indicates that the proliferative activity is spatially organized along the cephalic-caudal axis of the system.