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PubMed1990

Exclusion of poly(ethylene glycol) from liposome surfaces.

The electrophoretic mobility of vesicles is measured for concentrations of poly(ethylene glycol) from 0 wt.% to 10 wt.%. Mixtures of phosphatidylcholines and phosphatidic acid are used. The zeta potential calculated from the electrophoretic mobility and the viscosity of the suspension becomes more negative for all vesicles studied. Binding of poly(ethylene glycol) to the phospholipid surface by addition of the poly(oxyethylene)-containing surfactant C12E8 has the opposite effect and a decrease of the zeta potential is observed. Independent measurements of the surface potential of the vesicles in the presence of PEG by use of a positively charged spin probe and ESR spectroscopy and a fluorescent pH indicator and fluorescence spectroscopy show that actually the surface potential is not changed. A theory of the electrophoretic behaviour of vesicles in the presence of PEG is given which explains the contradiction between the two methods. It is assumed that the polymer is excluded from the vesicle surface (depletion layer) and that the viscosity near the surface is lower than the viscosity in the bulk phase. The thickness of the depletion layer is calculated from the experiments. The decrease of the zeta potential in the presence of poly(oxyethylene) chains linked to the vesicle surface results from the friction increase.

Calcium↗
PubMed2003

Acute stress evokes selective mobilization of T cells that differ in chemokine receptor expression: a potential pathway linking immunologic reactivity to cardiovascular disease.

T lymphocytes and monocytes/macrophages are the most abundant cells found in the atherosclerotic plaque. These cells can migrate towards the activated endothelium through the local release of chemotactic cytokines, or chemokines. Given the important role of leukocyte migration in atherosclerosis and the role of stress in mediating leukocyte trafficking, the present study examined the effects of an acute stressor on the redistribution of T cells (CD3+) and monocytes that express the chemokine receptors CCR5, CCR6, CXCR1, CXCR2, CXCR3, and CXCR4. Forty-four undergraduate students underwent a public speaking task. The acute stressor induced sympathetic cardiac activation, parasympathetic cardiac withdrawal, lymphocytosis, and monocytosis (all p<.001). Although the total number of T lymphocytes did not change, there was a selective increase in the number of circulating T cells expressing CXCR2, CXCR3, and CCR5. The ligands of these receptors are chemokines known to be secreted by activated endothelial cells. Analyses of individual differences in stress-induced responses demonstrated a positive relationship between sympathetic cardiac reactivity and mobilization of the various T cell subsets (.35<r<.56;p<.05). For the monocytes, all sub-populations increased in parallel with total monocyte numbers, with no relation to changes in sympathetic cardiac drive. These results indicate that acute stress induces a mobilization of T cells that are primed to respond to inflamed endothelium. Acute stressors may thus promote the recruitment of circulating immune cells into the sub-endothelia, and therefore accelerate atherosclerotic plaque formation and potentially contribute to the complications that follow acute stressful events. This mechanism may help explain the link between stress, reactivity, and cardiovascular disease.

Acute Disease↗
PubMed2005

Using remote assessment to provide home modification services to underserved elders.

PURPOSE: Although remote home assessment would enable specialists to prescribe home modifications for anyone, anywhere, the strategy is dependent on the ability to provide specialists with the same information as an in-home assessment. The purpose of this paper is to document that remote assessment is feasible and concurs largely with traditional in-home assessment based on expert judgment. DESIGN AND METHODS: We compared two new remote assessments, a "zero-tech" paper-and-pencil protocol and a "high-tech" televideo protocol, to traditional in-home assessments to determine the equivalence of the remote and in-home assessments. We determined equivalence by comparing each of the remote assessments to a traditional in-home assessment in the same home. In-home assessments were conducted by home-modification specialists in all homes. Data collection for the remote protocols was conducted by individuals inexperienced in home modification. Assessment data from the remote protocols were analyzed by specialists to diagnose problems and prescribe solutions. RESULTS: The overall rates of correct problem identification (i.e., Sensitivity + Specificity) were significant (p =.000) for both the remote paper-and-pencil (96.4%) and remote televideo (87.1%) protocols. Similarly, rates of agreement in recommendations of solutions were significant (p =.000) for both remote assessments (78.8% and 77.4%, respectively). IMPLICATIONS: The need for home-modification services, particularly in rural areas, far exceeds the capacity of specialists to provide them. Our findings suggest that remote assessments can potentially be used to identify mobility and safety problems in the home as well as to recommend solutions to those problems. As a result, remote home assessment has the potential to provide underserved elders with access to home-modification services that have heretofore eluded them.

Aged↗
PubMed1997

Mobile thromboses of the aortic arch without aortic debris. A transesophageal echocardiographic finding associated with unexplained arterial embolism. The Filiale Echocardiographie de la Société Française de Cardiologie.

BACKGROUND: Atherosclerotic lesions of the aortic arch are potential sources of arterial embolism. Mobile thrombi in the aortic arch in young patients without diffuse atherosclerosis have been reported recently, but such cases remain exceptional. We describe a series of young patients with unexplained arterial embolism in whom transesophageal echocardiography detected mobile aortic arch thromboses. METHODS AND RESULTS: Transesophageal echocardiography files collected between 1991 and 1995 in French academic cardiology centers were reviewed to identify patients who fulfilled the following criteria: (1) an arterial embolic event in the preceding weeks; (2) a mobile pedunculated aortic arch thrombosis, defined as an echogenic mass protruding into the lumen of the aorta and inserted on the aortic arch; and (3) absence of obvious diffuse aortic atherosclerosis or of aortic debris on transesophageal echocardiography. Twenty-three cases were identified from 27 855 examinations. Thromboses were located on the horizontal aorta (n = 4), near the ostium of the left subclavian artery (n = 5), or on the concavity of the posterior segment of the aortic arch (in the isthmus) (n = 14). The insertion site was a small atherosclerotic plaque in 21 patients. The remaining aortic wall always appeared normal or mildly atherosclerotic. The mean age of the patients was 45 +/- 8.4 years (range, 26 to 61 years). All patients were treated with intravenous heparin after the diagnosis of aortic arch thrombosis, and surgical removal of the thrombosis was performed in 10 patients in whom histological examination confirmed an atherosclerotic process at the site of insertion of the thrombosis. The prognosis was mainly influenced by embolic events. CONCLUSIONS: Thromboses of the aortic arch appear to be a variant form of aortic atherosclerotic disease associated with arterial embolism in young patients.

Adult↗
PubMed1999

Human G-CSF-mobilized CD34-positive peripheral blood progenitor cells can stimulate allogeneic T-cell responses: implications for graft rejection in mismatched transplantation.

To investigate mechanisms of stem cell graft rejection we studied the allo-stimulatory potential of G-CSF mobilized peripheral blood progenitor cells (PBPC). CD34+ cells were purified (>95%) in a two-step procedure using immunoaffinity columns for CD34 selection and T-depletion. The capacity of CD34+ cells to stimulate allogeneic T-cell responses was compared with other cells from the same individual. CD34+ cells induced potent proliferative responses at stimulator:responder ratios of 1:20, but were approximately 50-fold less efficient compared to dendritic cells. Furthermore, CD34+ cells primed responses from partially matched allogeneic T cells in bulk cultures. Dual-colour flow cytometry showed that the co-stimulatory molecules B7.1, CD40 and ICAM-1 were absent on resting CD34-positive progenitor cells, but were induced during incubation with allogeneic lymphocytes due to a cytokine-mediated effect. Up-regulation of accessory molecules on CD34+ cells was reproduced by incubation with interferon-gamma or GM-CSF which enhanced the allo-stimulatory activity of CD34+ cells. Blocking studies with inhibitory antibodies suggested co-stimulatory functions for B7.2, ICAM-3, CD40 and LFA-3. CD34+ cells were more efficient in inducing allogeneic T-cell responses when compared to the unprocessed leukapheresis products. The reduced allo-stimulatory ability of G-CSF mobilized PBPC could be explained by the presence of CD3+ 4+ and CD3+ 8+ lymphocytes with suppressor activity. We conclude that current methods of stem cell selection for transplantation do not avoid allosensitization of the recipient and that further graft manipulation with add-back of lymphocytes or selection of subsets of CD34+ cells with reduced allo-stimulatory ability may reduce graft rejection.

Antibodies, Blocking↗
PubMed1999

Electrokinetic Phenomena in a Concentrated Dispersion of Charged Mercury Drops.

Equations are derived which govern the electrokinetic phenomena in a concentrated dispersion of charged spherical mercury drops in an electrolyte solution on the basis of Kuwabara's cell model. Expressions for the electrophoretic mobility and the sedimentation velocity are obtained. For the case in which the overlapping of the electrical double layers of adjacent drops is negligible, expressions for the electrical conductivity and the sedimentation potential are derived. An Onsager relation between electrophoretic mobility and sedimentation potential is also obtained. Copyright 1999 Academic Press.

Journal Article↗
PubMed2003

Short-term mobilization of processing resources is revealed in the event-related potential.

This study investigates whether an occasional effortful improvement of performance, as asked for by a precue, is reflected in event-related potential (ERP) changes. To estimate the limits of possible effort-induced behavioral and ERP changes, we manipulated the time between precue and imperative stimulus (IS; precue interval, PCI). The subjects could, in fact, improve their performance in the effort trials, with all but the shortest PCI. The postcue ERP revealed a fronto-central contingent negative variation (CNV), which was preceded by a frontal positive/occipital negative wave (P2/N2). Both the P2/N2 and the CNV were larger for effort than for standard trials for all PCIs. For the shortest PCI (300 ms), the CNV increase was seen after the IS. The CNV increase for PCIs 600 and 300 began at about 400 ms postcue. The results suggest that effortful performance improvement is associated with prior increase of a frontocentral CNV and a preceding P2/N2. The CNV increase is thought to reflect the activity of a frontal executive process by which additional processing resources can be mobilized on a trial-to-trial basis within less than 500 ms.

Adult↗
PubMed1992

Characteristics and regulation of ganglioside-induced elevation of free cytoplasmic Ca2+ in human blood platelets.

We have found that gangliosides GD3 and GM3 induced rapid, reversible elevation of free cytoplasmic Ca2+ in fura-2-loaded human blood platelets. The effect persisted in Ca(2+)-free medium, indicating that gangliosides stimulated mobilization of intracellular stores. The action of gangliosides was concentration-dependent with EC50 of about 1 microM. The Ca(2+)-mobilizing effects of gangliosides were potentiated by epinephrine and inhibited by substances inducing activation of protein kinase C and cAMP-dependent protein kinases. Acidic phospholipids partially mimicked the Ca(2+)-mobilizing effects of gangliosides indicating that lipid head charge is essential for this activity. While the elevation of [Ca2+]i produced by arachidonic acid was almost completely blocked by aspirin pretreatment, the effects of gangliosides were diminished only 2-fold, indicating that gangliosides activate both aspirin-sensitive and aspirin-insensitive mechanisms of [Ca2+]i elevation.

Arachidonic Acid↗
PubMed2005

Rapid mobilization of murine and human hematopoietic stem and progenitor cells with AMD3100, a CXCR4 antagonist.

Improving approaches for hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC) mobilization is clinically important because increased numbers of these cells are needed for enhanced transplantation. Chemokine stromal cell derived factor-1 (also known as CXCL12) is believed to be involved in retention of HSCs and HPCs in bone marrow. AMD3100, a selective antagonist of CXCL12 that binds to its receptor, CXCR4, was evaluated in murine and human systems for mobilizing capacity, alone and in combination with granulocyte colony-stimulating factor (G-CSF). AMD3100 induced rapid mobilization of mouse and human HPCs and synergistically augmented G-CSF-induced mobilization of HPCs. AMD3100 also mobilized murine long-term repopulating (LTR) cells that engrafted primary and secondary lethally-irradiated mice, and human CD34(+) cells that can repopulate nonobese diabetic-severe combined immunodeficiency (SCID) mice. AMD3100 synergized with G-CSF to mobilize murine LTR cells and human SCID repopulating cells (SRCs). Human CD34(+) cells isolated after treatment with G-CSF plus AMD3100 expressed a phenotype that was characteristic of highly engrafting mouse HSCs. Synergy of AMD3100 and G-CSF in mobilization was due to enhanced numbers and perhaps other characteristics of the mobilized cells. These results support the hypothesis that the CXCL12-CXCR4 axis is involved in marrow retention of HSCs and HPCs, and demonstrate the clinical potential of AMD3100 for HSC mobilization.

Animals↗
PubMed2002

Bioavailability of metals to the amphipod Monoporeia affinis: interactions with authigenic sulfides in urban brackish-water and freshwater sediments.

Could reduced eutrophication be a potential environmental threat because of increased mobility and bioavailability of trace metals? This question was addressed by oxygenating intact sediment cores, varying in redox potential and salinity, in a test system containing the amphipod Monoporeia affinis. Results show a low mobility of metals during oxygenation, and despite high concentrations of metals in sediments, only Pb showed a notable degree of bioaccumulation. Cadmium was bioaccumulated particularly in freshwater sediment, and body burden of Cd was related to salinity, porewater, and sediment concentrations. Despite high sediment and porewater concentrations of Cu and Zn, no relationship was recorded to body burden. For three of four tested metals, Cd, Pb, and Zn, metals in sediment were more important for body burdens in amphipods as compared to metals in porewater. Food, rather than interstitial water, therefore seems to be the main route of metal contaminants to these amphipods. Furthermore, this observed low release of metals from sediments and low body burden significance of porewater metals indicate that ameliorated oxygen conditions in contaminated sediments may be regarded as a minor environmental threat for one of the most important Baltic benthic organisms.

Amphipoda↗
PubMed2003

The ecology of arsenic.

Arsenic is a metalloid whose name conjures up images of murder. Nonetheless, certain prokaryotes use arsenic oxyanions for energy generation, either by oxidizing arsenite or by respiring arsenate. These microbes are phylogenetically diverse and occur in a wide range of habitats. Arsenic cycling may take place in the absence of oxygen and can contribute to organic matter oxidation. In aquifers, these microbial reactions may mobilize arsenic from the solid to the aqueous phase, resulting in contaminated drinking water. Here we review what is known about arsenic-metabolizing bacteria and their potential impact on speciation and mobilization of arsenic in nature.

Archaea↗
PubMed2007

Mobile phone ownership and use among school children in three Hungarian cities.

In spite of rapid worldwide increase in mobile phone use and public concerns about associated potential health effects, little is known about patterns of mobile phone ownership and use in the general population and among children. In April 2005, we conducted a survey of mobile phone ownership and use among fourth grade school children in three Hungarian cities. From 24 schools, 1301 student filled out a short, self-administered questionnaire on basic demographics, mobile phone ownership, pattern of mobile phone use, and after-school activities. Overall, 989 students (76%) owned a mobile phone. Three hundred thirteen students (24%) used a mobile phone daily to make phone calls, and an additional 427 students (33%) used mobile phones for phone calls at least several times per week. Sixty-six students (5%) sent text messages daily and an additional 308 students (24%) sent text messages at least several times per week. Girls, children with no siblings, children who were members of a sport club, and children who played computer games daily were more likely to own and use mobile phones regularly. A higher number of socially disadvantaged children in a class predicted lower likelihood of regular mobile phone use among children. Our results suggest that mobile phone ownership and regular use is highly prevalent among school children in Hungary. Due to rapid changes in ownership patterns follow up surveys will be required to obtain information on temporal trends and changes in mobile phone ownership and pattern of use among school children.

Cell Phone↗
PubMed2006

Osteoclasts degrade endosteal components and promote mobilization of hematopoietic progenitor cells.

Here we investigated the potential role of bone-resorbing osteoclasts in homeostasis and stress-induced mobilization of hematopoietic progenitors. Different stress situations induced activity of osteoclasts (OCLs) along the stem cell-rich endosteum region of bone, secretion of proteolytic enzymes and mobilization of progenitors. Specific stimulation of OCLs with RANKL recruited mainly immature progenitors to the circulation in a CXCR4- and MMP-9-dependent manner; however, RANKL did not induce mobilization in young female PTPepsilon-knockout mice with defective OCL bone adhesion and resorption. Inhibition of OCLs with calcitonin reduced progenitor egress in homeostasis, G-CSF mobilization and stress situations. RANKL-stimulated bone-resorbing OCLs also reduced the stem cell niche components SDF-1, stem cell factor (SCF) and osteopontin along the endosteum, which was associated with progenitor mobilization. Finally, the major bone-resorbing proteinase, cathepsin K, also cleaved SDF-1 and SCF. Our findings indicate involvement of OCLs in selective progenitor recruitment as part of homeostasis and host defense, linking bone remodeling with regulation of hematopoiesis.

Animals↗
PubMed2003

Mobile phones in the hospital--past, present and future.

The phenomenon of electromagnetic interference by mobile phones is real and potentially clinically significant. This has been recognised by the Department of Health and the Medical Devices Agency, leading to bans on phone use in hospitals. Current evidence suggests that mobile phones can cause malfunction of medical equipment, but only when used in close proximity. Allowing phone use in non-patient care areas and improving staff education may improve compliance with hospital policies.

Cell Phone↗
PubMedDate not supplied

Critical appraisal of transesophageal echocardiography: limitations, pitfalls, and complications.

Because transesophageal echocardiography is invasive, it has the potential for serious complications. Limitations occur because of the restricted transducer mobility within transducers for special situations. Pitfalls (potential erroneous diagnoses resulting from misinterpretation of normal and abnormal anatomy) are prevalent with this new technology. This report critically reviews transesophageal echocardiography and discusses and illustrates commonly encountered limitations, pitfalls, and complications.

Echocardiography↗
PubMed2004

Effect of blood reticulocyte concentration on electrophoretic mobility of erythrocytes in rats.

In intact rats electrokinetic characteristics of erythrocytes weakly depended on the intensity of erythropoiesis. This dependence became significant when the degree of erythropoiesis approached the upper limit of variations. Electrophoretic mobility of erythrocytes progressively decreased with increasing blood reticulocyte count. Subpopulations of erythrocytes with low mobility in electric field accumulated in the blood. Our results indicate that erythrocytes whose electrokinetic potential is similar to the mean mobility of circulating cells migrate from the bone marrow into the circulation under normal conditions.

Animals↗
PubMed1992

Regulation of prostacyclin production by [Ca2+]i and protein kinase C in aortic smooth muscle cells.

The respective roles of protein kinase C (PKC) and of cytosolic free Ca2+ concentration ([Ca2+]i) in prostacyclin synthesis were investigated in aortic smooth muscle cells by using A23187 and phorbol 12-myristate 13-acetate (PMA) to bypass the hormonal receptor. Exposure of the cells to A23187 markedly increased prostacyclin production, which was not affected by the PKC inhibitor staurosporine or by PKC depletion after prolonged incubation (48 h) of cells with PMA. The increase in [Ca2+]i induced by A23187 did not affect membranous or cytosolic PKC activity in control and PMA-stimulated cells. Activation of PKC by PMA, a weak stimulant of prostacyclin production by itself, strongly potentiated A23187-induced prostacyclin production, as well as that induced by the calcium-mobilizing hormone arginine vasopressin (AVP). The potentiating effect persisted for 30 min after the removal of PMA. However, this "memory" effect was not due to sustained levels of membranous PKC activity but probably to the prolonged influence of PKC-induced phosphorylation(s). Taken together, our results suggest that, although an increase in [Ca2+]i is sufficient for inducing prostacyclin production in rat aortic smooth muscle cells, activation of PKC is necessary for AVP-induced prostacyclin production in this same tissue.

Animals↗
PubMed2005

Psychological predictors of problem mobile phone use.

Mobile phone use is banned or illegal under certain circumstances and in some jurisdictions. Nevertheless, some people still use their mobile phones despite recognized safety concerns, legislation, and informal bans. Drawing potential predictors from the addiction literature, this study sought to predict usage and, specifically, problematic mobile phone use from extraversion, self-esteem, neuroticism, gender, and age. To measure problem use, the Mobile Phone Problem Use Scale was devised and validated as a reliable self-report instrument, against the Addiction Potential Scale and overall mobile phone usage levels. Problem use was a function of age, extraversion, and low self-esteem, but not neuroticism. As extraverts are more likely to take risks, and young drivers feature prominently in automobile accidents, this study supports community concerns about mobile phone use, and identifies groups that should be targeted in any intervention campaigns.

Accidents, Traffic↗