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PubMed2005

Electrokinetic transport in nanochannels. 2. Experiments.

We present an experimental study of nanoscale electrokinetic transport in custom-fabricated quartz nanochannels using quantitative epifluorescence imaging and current monitoring techniques. One aim is to yield insight into electrical double layer physics and study the applicability of continuum theory to nanoscale electrokinetic systems. A second aim is to explore a new separation modality offered by nanoscale electrophoretic separations. We perform parametric variations of applied electric field, channel depth, background buffer concentration, and species valence to impose variations on zeta potential, effective mobility, and Debye length among other parameters. These measurements were used to validate a continuum theory-based analytical model presented in the first of this two-paper series. Our results confirm the usefulness of continuum theory in predicting electrokinetic transport and electrophoretic separations in nanochannels. Our model leverages independent measurements of zeta potential performed in a microchannel system at electrolyte concentrations of interest. These data yield a zeta potential versus concentration relation that is used as a boundary condition for the nanochannel electrokinetic transport model. The data and model comparisons together show that the effective mobility governing electrophoretic transport of charged species in nanochannels depends not only on ion mobility values but also on the shape of the electric double layer and analyte ion valence. We demonstrate a method we term electrokinetic separation by ion valence, whereby both ion valence and mobility may be determined independently from a comparison of micro- and nanoscale transport measurements.

Electrochemistry↗

PubMed2000

Mobilization of peripheral blood stem cells in high-risk breast cancer patients using G-CSF after standard dose docetaxel.

Chemotherapy, in addition to recombinant growth factors, has been effective in mobilizing stem cells. Unfortunately, the use of chemotherapy for this purpose has resulted in profound myelosuppression and increased morbidity. Docetaxel, the single most active agent in the treatment of advanced breast cancer, was evaluated for its potential to mobilize stem cells when given at conventional doses followed by granulocyte colony-stimulating factor (G-CSF). Sixteen high-risk breast cancer patients were mobilized with a regimen consisting of docetaxel (100 mg/m2) followed by daily G-CSF (10 microg/kg), beginning 72 h after the docetaxel, and continuing until completion of the apheresis. The median white blood cell count (WBC) nadir was 1,000/microl (range 500 to 4000/microl ) occurring a median of 6 days (range 4 to 9 days) after the docetaxel. No patient experienced a neutropenic febrile episode due to the mobilization regimen. The median time interval for initiating the apheresis was 8 days (range 6 to 11 days) following the docetaxel. The median number of apheresis was 2 (range 1 to 3) in each patient. Stem cell recovery as measured by the CD34 cell count x 10(6)/kg was a median of 5.2 (range 1.4 to 15.1). A significant correlation was found between CFU-GM, BFU-E, and CFU-GEMM/kg and CD34 cells/kg (r = 0.891, 0.945, and 0.749, respectively, p < 0.001). When our results were compared to a matched cohort receiving G-CSF alone, the docetaxel group demonstrated a superior CD34 cells/kg yield (p = <0.001). Following myeloablative chemotherapy consisting of thiotepa and cyclophosphamide with or without carboplatinum, the hematopoetic recovery determined by an absolute neutrophil count (ANC) of greater than 500/microl and an unsupported platelet count of > or =20,000/microl for 48 h, was a median of 10 days (range 9 to 14 days) and 10 days (range 8 to 30 days), respectively. The results demonstrate that conventional dose docetaxel, combined with G-CSF, is an effective mobilization regimen with minimal toxicity in high-risk breast cancer patients.

Adult↗

PubMed1995

Protein-rejecting ability of surface-bound dextran in end-on and side-on configurations: comparison to PEG.

There is much interest in attaching polyethylene glycol (PEG) and other hydrophilic, neutral polymers to surfaces to reduce the extent of protein and cell adsorption. Interestingly, these same surface-bound polymers are effective in masking surface charge and reducing electrokinetic effects such as particle electrophoretic mobility, streaming potential, and electroosmosis. It is apparent that similar molecular properties are responsible for both protein and cell rejection and reduction of electrokinetic effects. In this work we compared the fibrinogen-rejecting ability and the effect on electrophoretic mobility of three polymer coatings bound to polystyrene. The three polymers were side-bound dextran, end-bound dextran, and end-bound PEG. The results of these measurements were used to elucidate the importance of polymer packing density and polymer layer thickness on protein adsorption and reduction of electrokinetic effects. Protein adsorption appears not to be sensitive to polymer layer thickness or the presence of dilute polymer tails in a surface coating, while electrokinetic effects are. Protein adsorption is, however, very sensitive to the availability of exposed surface. Finally, the unique effectiveness of PEG is apparent in this research as in previous studies.

Adsorption↗

PubMed2006

Influence of bacteria on Pb and Zn speciation, mobility and bioavailability in soil: A laboratory study.

A soil column experiment was carried out to investigate the effects of inoculation of bacteria on metal bioavailability, mobility and potential leachability through single chemical extraction, consequential extraction and in situ soil solution extraction technologies. Results showed that bacteria inoculated, including Azotobacter chroococcum, Bacillus megaterium and Bacillus mucilaginosus, may pose both positive and negative impacts on bioavailability and mobility of heavy metals in soil, depending on the chemical nature of the metals. The activities of bacteria led to an increase of water dissolved organic carbon (DOC) concentration and a decrease of pH value, which enhanced metal mobility and bioavailability (e.g. an increase of water-soluble and HOAc-soluble Zn). On the other hand, bacteria could immobilize metals (e.g. a great reduction of water-soluble Pb) due to the adsorption by bacterial cell walls and possible sedimentation reactions with phosphate or other anions produced through bacterial metabolism.

Adsorption↗

PubMed2000

No mutagenic or recombinogenic effects of mobile phone fields at 900 MHz detected in the yeast Saccharomyces cerevisiae.

Both actively growing and resting cells of the yeast Saccharomyces cerevisiae were exposed to 900-MHz fields that closely matched the Global System for Mobile Communication (GSM) pulsed modulation format signals for mobile phones at specific absorption rates (SAR) of 0.13 and 1.3 W/kg. Two identical anechoic test chambers were constructed to perform concurrent control and test experiments under well-controlled exposure conditions. Using specific test strains, we examined the genotoxic potential of mobile phone fields, alone and in combination, with a known genotoxic compound, the alkylating agent methyl methansulfonate. Mutation rates were monitored by two test systems, a widely used gene-specific forward mutation assay at CAN1 and a wide-range assay measuring the induction of respiration-deficient (petite) clones that have lost their mitochondrial function. In addition, two further assays measured the recombinogenic effect of mobile phone fields to detect possible effects on genomic stability: First, an intrachromosomal, deletion-formation assay previously developed for genotoxic screening; and second, an intragenic recombination assay in the ADE2 gene. Fluctuation tests failed to detect any significant effect of mobile phone fields on forward mutation rates at CAN1, on the frequency of petite formation, on rates of intrachromosomal deletion formation, or on rates of intragenic recombination in the absence or presence of the genotoxic agent methyl methansulfonate.

Humans↗

PubMed2005

Dynamic studies on the mobility of trace elements in soil and sediment samples influenced by dumping of residues of the flood in the Mulde River region in 2002.

In the analysis of soil samples, batch sequential extraction procedures are traditionally used for the fractionation of trace elements to access their mobility and potential risk for the contamination of groundwater. In the present work a continuous-flow technique has been used that enables not only the fast and efficient leaching of trace elements but as well as time-resolved studies on the mobilization of arsenic and selected heavy metals in different forms to be made. Rotating coiled columns (RCC) earlier used mainly in countercurrent chromatography have been successfully applied to the dynamic leaching of heavy metals from soils contaminated by flooding sludge's. The sample was retained in a PTFE rotating column as the stationary phase whereas aqueous solutions were continuously pumped through. The contents of elements were determined by on-line coupling of RCC and inductively coupled plasma atomic emission spectrometry (ICP-AES). This enables real-time data on the leaching process to be obtained. Dynamic and traditional batch procedures were compared. It has been shown that the aqueous elution under centrifugal forced conditions is much more effective for the mobilization of heavy metals. Hence, the dynamic leaching is characterized by a substantially more intensive interaction between solid and water and is besides substantially more time-saving than the conventional batch procedure. The RCC procedure was also employed for preliminary leaching studies with a simulated "acid rain". In comparison with the water leaching, the mobilization of heavy metals and arsenic from soil samples with employment of simulated acid rain as eluent was less effective.

Chemistry Techniques, Analytical↗

PubMed2004

Mobile phone interference with medical equipment and its clinical relevance: a systematic review.

OBJECTIVE: To conduct a systematic review of studies on clinically relevant digital mobile phone electromagnetic interference with medical equipment. DATA SOURCES: MEDLINE and SUMSEARCH were searched for the period 1966-2004. The Cochrane Library and Database of Abstracts of Reviews of Effects were also searched for systematic reviews. STUDY SELECTION: Studies were eligible if published in a peer-reviewed journal in English, and if they included testing of digital mobile phones for clinically relevant interference with medical equipment used to monitor or treat patients, but not implantable medical devices. DATA SYNTHESIS: As there was considerable heterogeneity in medical equipment studied and the conduct of testing, results were summarised rather than subjected to meta-analysis. RESULTS: Clinically relevant electromagnetic interference (EMI) secondary to mobile phones potentially endangering patients occurred in 45 of 479 devices tested at 900 MHz and 14 of 457 devices tested at 1800 MHz. However, in the largest studies, the prevalence of clinically relevant EMI was low. Most clinically relevant EMI occurred when mobile phones were used within 1 m of medical equipment. CONCLUSIONS: Although testing was not standardised between studies and equipment tested was not identical, it is of concern that at least 4% of devices tested in any study were susceptible to clinically relevant EMI. All studies recommend some type of restriction of mobile phone use in hospitals, with use greater than 1 m from equipment and restrictions in clinical areas being the most common.

Australia↗

PubMed2001

Temporal and spatial studies of autocatalyst-derived platinum, rhodium, and palladium and selected vehicle-derived trace elements in the environment.

The distribution of platinum, rhodium, and palladium (platinum-group elements; PGEs) adjacent to two major U.K. roads shows a rapid decrease (more than 1 order of magnitude) away from the road and reflects patterns shown by other traffic-derived trace elements such as Pb and Zn. However, ratios of Pt:Rh remain relatively constant from 0 to 10 m distance, suggesting that at least some of the PGEs are transported away from the source. A temporal study over a 12-month period, of road dust and surface samples, reveals elevated concentrations above background levels, with maximum values of Pt >500 ng g(-1), Rh 70 ng g(-1), and Pd 70 ng g(-1). Concentrations vary considerably throughout the year and show some tentative correlation with rainfall. Element speciation, an essential control on mobility and hence distribution, was investigated, and the results of solubility experiments show that up to 30% of the Pd present dissolves in acid solutions. This indicates that at least some of the Pd is present in a soluble form and is therefore potentially highly mobile.

Air Pollution↗

PubMed1989

Construct validity of an aspect of the coping process: potential adaptation to stress.

The focus of this study was to examine construct validity of the Adaptive Potential Assessment Model (APAM). Incorporated within a larger theory and paradigm entitled Modeling and Role-Modeling, APAM depicts three main states, arousal, equilibrium, and impoverishment; each state represents a different potential to mobilize coping resources. Arousal and impoverishment are considered stress states while equilibrium is considered a nonstress state. The sample was young, male students (N = 73) who were experiencing varying degrees of stress. Physiological and psychological data were gathered by utilizing several instruments and clinical assessment techniques. APAM was validated in a healthy population. Discriminant function analysis revealed motor-sensory behavior, fatigue-sadness, hope, and verbal anxiety as useful predictors in determining adaptive potential states. Misclassifications of subjects determined to be at risk by the investigator and not by the mathematical algorithm are considered. The benefits of holistically identifying clients' ability to mobilize coping resources is that nurses can plan intervention more effectively if these categorizations can be consistently verified.

Adaptation, Psychological↗

PubMed1983

Nursing diagnoses concurrent with multiple sclerosis.

Nursing Diagnoses which commonly occur in patients with MS was the focus of this descriptive study. Using a functional health pattern assessment format, nine inpatients and six outpatients were assessed. Five frequently occurring dysfunctional patterns were: Self-Care Deficit, Self-Esteem Disturbance, Potential for Ineffective Family Coping: Compromised, Sleep Disturbance, and Social Isolation. The four most frequently identified Nursing Diagnoses (dysfunctional patterns plus etiology) were: Self-Esteem Disturbance related to Altered Body Image, Self-Care Deficit: I Bathing related to Generalized Weakness, Social Isolation related to Impaired Mobility, and Potential Ineffective Family Coping: Compromised.

Activities of Daily Living↗

PubMed2005

Mobilization and activation of a signaling competent alpha6beta4integrin underlies its contribution to carcinoma progression.

This review examines the hypothesis that the function of the alpha 6beta 4 integrin is altered substantially as normal epithelia undergo malignant transformation and progress to invasive carcinoma and that the functions of this integrin contribute to the behavior of aggressive carcinoma cells. Specifically, alpha 6beta 4 functions primarily as an adhesion receptor in normal epithelia, often as a component of hemidesmosomes and associated with intermediate filaments. Factors in the host-tumor microenvironment have the potential to mobilize alpha 6beta 4 from hemidesmosomes and promote its association with F-actin in lamellae and filopodia, a process that is mediated by PKC-dependent phosphorylation of the beta 4 cytoplasmic domain. Importantly, this altered localization of alpha 6beta 4 appears to be coupled to an activation of its signaling potential, which may occur through its association with growth factor receptors or lipid rafts, possibilities that are not mutually exclusive. The primal signaling event triggered by alpha 6beta 4 appears to be activation of PI3-K and this activation has profound consequences on the migration, invasion and survival of carcinoma cells. Arguably, the ability of alpha 6beta 4 to stimulate the PI3-K-dependent translation of VEGF and possibly other growth factors may be the most significant contribution of this integrin to carcinoma because of the potential autocrine and paracrine effects of these factors.

Actins↗

PubMed2026

Global lessons from antibiotic resistance: Metformin-hydrolysing genes in transposable elements, a new threat for type II diabetic patients?

OBJECTIVES: To investigate the evolutionary origin, genomic mobility, and potential dissemination of metformin-hydrolysing genes (mfmAB), and to assess whether environmental selection by metformin pollution may drive the emergence of transferable pharmaceutical-degrading traits analogous to antibiotic resistance. METHODS: Large-scale comparative genomics was performed using publicly available bacterial genomes carrying mfmAB homologs. Phylogenomic reconstruction, average nucleotide identity analysis, genomic context comparison, plasmid characterization, and insertion sequence mapping were used to infer evolutionary history and identify mechanisms of horizontal gene transfer. RESULTS: mfmAB homologs were identified in twelve Aminobacter and three Pseudomonas genomes within a conserved ∼8.2 kb gene cluster. Phylogenomic analyses showed that metformin-degrading capacity emerged independently in multiple Aminobacter lineages across distinct continents, consistent with convergent evolution under anthropogenic selective pressure. Genomic comparisons indicated a chromosomal origin of mfmAB, followed by mobilization onto conjugative plasmids through IS1182-mediated transposition. In Pseudomonas, additional IS3/IS6-mediated transposition events integrated mfmAB into diverse plasmid backbones, frequently within composite transposons also encoding guanylurea and biguanide degradation pathways (guuH, bguH). These findings reveal a dynamic modular assembly of metabolic functions facilitating adaptation to pharmaceutical pollutants. CONCLUSIONS: Metformin pollution appears to promote the emergence and mobilization of pharmaceutical-degrading genes through mechanisms paralleling antibiotic resistance evolution. Although no clinical impact has yet been demonstrated, the potential spread of such genes into human-associated microbiomes and their possible co-selection with antibiotic resistance determinants represent an emerging One Health concern. Environmental surveillance of pharmaceutical-degrading genes is warranted to anticipate future threats to drug efficacy.

Convergent evolution↗

PubMed2004

Protein kinase A activation promotes plasma membrane insertion of DCC from an intracellular pool: A novel mechanism regulating commissural axon extension.

Protein kinase A (PKA) exerts a profound influence on axon extension during development and regeneration; however, the molecular mechanisms underlying these effects of PKA are not understood. Here, we show that DCC (deleted in colorectal cancer), a receptor for the axon guidance cue netrin-1, is distributed both at the plasma membrane and in a pre-existing intracellular vesicular pool in embryonic rat spinal commissural neurons. We hypothesized that the intracellular pool of DCC could be mobilized to the plasma membrane and enhance the response to netrin-1. Consistent with this, we show that application of netrin-1 causes a modest increase in cell surface DCC, without increasing the intracellular concentration of cAMP or activating PKA. Intriguingly, activation of PKA enhances the effect of netrin-1 on DCC mobilization and increases axon extension in response to netrin-1. PKA-dependent mobilization of DCC to the plasma membrane is selective, because the distributions of transient axonal glycoprotein-1, neural cell adhesion molecule, and trkB are not altered by PKA in these cells. Inhibiting adenylate cyclase, PKA, or exocytosis blocks DCC translocation on PKA activation. These findings indicate that netrin-1 increases the amount of cell surface DCC, that PKA potentiates the mobilization of DCC to the neuronal plasma membrane from an intracellular vesicular store, and that translocation of DCC to the cell surface increases axon outgrowth in response to netrin-1.

Adenylyl Cyclase Inhibitors↗

PubMed2006

Interaction of cationic vesicle with ribonucleotides (AMP, ADP, and ATP) and physicochemical characterization of DODAB/ribonucleotides complexes.

The interaction between ribonucleotides (AMP, ADP, and ATP) and cationic vesicles prepared from dioctadecyldimethylammonium bromide (DODAB) were investigated in detail. The physicochemical properties of ribonucleotides/cationic lipid complexes were present. Gel exclusion-UV spectroscopic results showed that all the charge ratios of DODAB/ribonucleotides (AMP, ADP, and ATP) are 2:1 when the maximal ribonucleotides were adsorbed onto DODAB, while the molar ratios were different, e.g., 2:1 for DODAB/AMP, 4:1 for DODAB/ADP and 6:1 for DODAB/ATP. These differences may be attributed to the different anion charges of AMP, ADP and ATP. The results demonstrated that ribonucleotides combined with DODAB vesicles with the electrostatic attraction in the complexation of DODAB and ribonucleotides. Transmission electron microscopic results revealed the different extents of aggregation of cationic vesicles in the complexation process of ribonucleotides with cationic lipid. The variation dependence of zeta-potentials or electrophoretic mobilities on vesicle size was also different. The zeta-potentials and electrophoretic mobilities of the DODAB vesicles (0.01 and 0.02 mM) gradually decreased when the ribonucleotide concentration increased. However, the mean diameters of the DODAB vesicles (0.1 and 0.5 mM) gradually increased when the ribonucleotide concentration increased.

Adenosine Diphosphate↗

PubMed1992

Migration and social mobility: South East England as an escalator region.

"This paper uses data from the OPCS [Office of Population Censuses and Surveys] Longitudinal Study and the National Health Service Central Register to examine the contention that the South East region of England acts as a kind of 'upward social class escalator' within the British urban and regional system. To establish that this is so it is shown firstly, that the South East attracts to itself through inter-regional migration a more than proportional share of the potentially upwardly mobile young adults; secondly, that it promotes these young people along with its own young adults at rates which are higher than elsewhere in the country; and finally, that a significant proportion of those who achieve these higher levels of status and pay then 'step off' the escalator. They do this by migrating away from the South East at later stages of their working lives and at or near to retirement." (SUMMARY IN FRE AND GER)

Demography↗

PubMed2001

Erythropoietin and iron: the role of ascorbic acid.

Provision of sufficient available iron is a prerequisite to ensure the optimal response to recombinant human erythropoietin (rHuEpo). Functional iron deficiency (a state when iron supply is reduced to meet the demands for increased erythropoiesis) is the common cause of rHuEpo hyporesponsiveness in dialysis patients who have normal iron status, even when they are iron-overloaded. Iron supplementation is not justified for this hyporesponsiveness in patients with iron overload due to the potential hazards of iron overload aggravated by intravenous iron therapy. Furthermore, in vivo studies indicated that the promising effect of intravenous iron medication to overcome iron-deficient erythropoiesis is not observed in iron-overloaded haemodialysis (HD) patients. Ascorbic acid, a water-soluble antioxidant as well as a reducing agent, has a number of associations with iron metabolism. Recent research highlights that ascorbic acid can potentiate the mobilization of iron from inert tissue stores and facilitates the incorporation of iron into protoporphyrin in iron-overloaded HD patients being treated with rHuEpo. Interest has turned towards the use of ascorbic acid as an adjuvant therapy in this field. This review focuses on the improvement of rHuEpo response by administration of ascorbic acid and discusses its clinical implications and potential issues for nephrologists.

Ascorbic Acid↗

PubMed2001

Electroacoustic and Potentiometric Studies of the Hematite/Water Interface.

The basic charging properties of nearly spherical hematite particles were studied by using potentiometric titration and the electroacoustic technique. Both the pH and the ionic strength dependence of the surface charge and the zeta-potential were studied in detail. For calculating the zeta-potential from mobility data a few different theories were used and obtained differences are discussed. At pH values higher than 7 and at high electrolyte concentrations (50 mM and 100 mM NaNO(3)), it was difficult to fit the mobility data by using the full mobility spectra including both magnitude and phase angle at several frequencies. In this regime the best fits were obtained by using a theory for aggregated complexes (porous particles). From potentiometric titrations in 0.01, 0.1, and 1.0 M NaNO(3), parameters for a 1-pK Basic Stern Model were determined. The model was used to examine the possibility of correlating the experimentally determined zeta-potentials to the model-calculated potentials at the Stern plane. Qualitatively, the model predicted the correct ionic strength dependence of the zeta-potentials, and there was also a rather good quantitative agreement at high ionic strengths (50 and 100 mM NaNO(3)). However, at lower ionic strengths the model predicted values up to 40% higher than those found from the electroacoustic study. Surface conduction behind the slip plane was discussed as a possible cause for this discrepancy. Copyright 2001 Academic Press.

Journal Article↗

PubMed2003

Central and total obesity in middle aged men and women in relation to lifetime socioeconomic status: evidence from a national birth cohort.

STUDY OBJECTIVE: To investigate the influence of social class in childhood, young adulthood and middle age, and intergenerational mobility, on adult central and total obesity. DESIGN: Prospective, population based, birth cohort study. PARTICIPANTS AND SETTING: 1472 men and 1563 women born in 1946 in England, Scotland, and Wales. OUTCOME MEASURES: Waist-hip ratio, waist-height ratio, waist circumference, and body mass index at age 53 years. MAIN RESULTS: Father's social class at participant's age 4 years was inversely associated with adult central and total obesity at age 53 years in men and women. For example, the mean difference of waist-hip ratio (95% confidence intervals) between father's professional social class I and unskilled manual social class V was 2.6% (0.7 to 4.6) for men and 2.5% (0.5 to 4.4) for women. The effect of father's social class remained after adjustment for participant's own social class in young adulthood and middle age. Both adult social classes were inversely related to obesity among women, but not men, after adjustment for childhood circumstances. Upwardly mobile men and women were less obese than participants remaining in their father's social class and their levels of obesity tended to be between the class they left and the class they joined. CONCLUSIONS: The effect of social class on adult obesity differed according to the stage in the life course at which social class was measured, and gender. Childhood circumstances had enduring influences on adult obesity, although our results on intergenerational mobility indicate potential reversibility of early life disadvantage.

Anthropometry↗