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PubMed2004

Migration from can coatings: part 2. Identification and quantification of migrating cyclic oligoesters below 1000 Da.

Metal cans for food use can be coated with lacquers based on polyester resins. Recent research has focussed on the identification and quantification of migrants released by coatings that are potentially absorbable (below 1000 Da). The presented method describes a procedure that was optimized to hydrolyse the polyester migrants into their monomers, polyvalent acids and polyols. The polyols were identified by gas chromatography with flame ionization detection GC-FID and the acids by high-performance liquid chromatography (HPLC) coupled with an ultraviolet and an electrospray ionization-mass selective detector (HPLC-ESI-MSD/UVD), respectively. With the knowledge of the polyester monomers, it was possible--at least tentatively--to identify the main components in the migrate as cyclic oligoesters by HPLC-ESI-MSD/UVD. A cyclic oligomer, CYCLO [3IPA (isophthalic acid) 3EG (ethylene glycol)] was synthesized and characterized by infrared, nuclear magnetic resonance and mass spectrometry as well as by elementary analysis for further confirmation. To determine the amount of migrating cyclic oligoesters, the response of the migrating substances was compared using different detectors, UVD, MSD and evaporative light scattering detector (ELSD). The response of the ELSD was dependent on the molecular weight of the analytes that reduced the accuracy of this detection type. The wavelength with the same absorption coefficient for IPA and terephthalic acid (TPA) was obtained at 232 nm. The UV(232nm) response of an oligoester is proportional to the number of its IPA/TPA moieties, which was verified for several TPA/IPA esters. The amount of the migrating oligoesters was determined using an UV(232nm) calibration of a commercially available TPA ester and the number of IPA/TPA moieties molecules gained from the ESI-MSD spectra. According to this method, the amount of migrating oligoesters below 1000 Da in the 95% ethanol migrate varied from 0.1 to 0.6 mg dm(-2) (0.6-3.6 mg kg(-1) food) in the examined coatings. The determined amounts account for about 50% of the total migrate below 1000 Da.

Chromatography, Gas↗
PubMed1996

Regulation of oligodendrocyte precursor migration by extracellular matrix: evidence for substrate-specific inhibition of migration by tenascin-C.

In order to analyse the role of the extracellular matrix (ECM) in the migration of oligodendrocyte precursor cells we have used a chemotaxis chamber assay in which the filter separating the wells is coated with different ECM molecules. Two molecules, fibronectin and the laminin family member merosin, promoted migration either alone or in combination with the chemotactic growth factor platelet-derived growth factor. The effects of the ECM molecules and growth factor were additive, and demonstrated that the migrating oligodendrocyte precursors respond both to haptotactic and chemotactic stimuli. A third extracellular molecule, tenascin-C, inhibited migration. This inhibition was substrate-specific; while migration on fibronectin was inhibited there was no effect on merosin-stimulated migration. This specificity confirms that tenascin-C inhibits migration by modulation of individual cell-ECM interactions rather than by a non-specific process of interference with substrate adhesion. An understanding of the role of tenascin-C in central nervous system development will therefore require characterisation of the different colocalising ECM molecules at different developmental stages.

Animals↗
PubMed2005

Developing a new resource on international nurse migration: the international centre on nurse migration.

A new collaborative project on nurse migration was recently launched by the International Council of Nurses and the Commission on Graduates of Foreign Nursing Schools. This collaboration, the International Centre on Nurse Migration, guided by the principles of ethical recruitment and equitable treatment of migrating nurses, focuses on promoting, collecting, creating, and disseminating data and information on nurse migration; acting as a resource center; tracking trends and patterns of global health care workforce migration; analyzing policy; generating policy options; advocating for sound policy concerning nurse migration; promoting, undertaking, and disseminating research; providing consultant and expert advice; and offering continuing education about migration.

Foreign Professional Personnel↗
PubMed2005

Nucleokinesis in tangentially migrating neurons comprises two alternating phases: forward migration of the Golgi/centrosome associated with centrosome splitting and myosin contraction at the rear.

During rodent cortex development, cells born in the medial ganglionic eminence (MGE) of the basal telencephalon reach the embryonic cortex by tangential migration and differentiate as interneurons. Migrating MGE cells exhibit a saltatory progression of the nucleus and continuously extend and retract branches in their neuritic arbor. We have analyzed the migration cycle of these neurons using in vitro models. We show that the nucleokinesis in MGE cells comprises two phases. First, cytoplasmic organelles migrate forward, and second, the nucleus translocates toward these organelles. During the first phase, a large swelling that contains the centrosome and the Golgi apparatus separates from the perinuclear compartment and moves rostrally into the leading neurite, up to 30 mum from the waiting nucleus. This long-distance migration is associated with a splitting of the centrioles that line up along a linear Golgi apparatus. It is followed by the second, dynamic phase of nuclear translocation toward the displaced centrosome and Golgi apparatus. The forward movement of the nucleus is blocked by blebbistatin, a specific inhibitor of nonmuscle myosin II. Because myosin II accumulates at the rear of migrating MGE cells, actomyosin contraction likely plays a prominent role to drive forward translocations of the nucleus toward the centrosome. During this phase of nuclear translocation, the leading growth cone either stops migrating or divides, showing a tight correlation between leading edge movements and nuclear movements.

Animals↗
PubMed1993

Oligodendrocyte precursor (O-2A progenitor cell) migration; a model system for the study of cell migration in the developing central nervous system.

Cell migration plays an important role in the development of complex multicellular organisms. The molecular mechanisms that regulate this migration are therefore of great interest. Unfortunately, however, analysis of cell migration in vertebrates is hampered by the inaccessibility of the cells and the difficulty of manipulating their environment within the embryo. This review focuses on one particular migratory cell population, the oligodendrocyte precursor cell or O-2A progenitor cell, that gives rise to the myelin-forming oligodendrocytes within the CNS. These cells migrate extensively during normal development. They can be purified and grown in large numbers in cell culture, so allowing the use of reductionist approaches using cell and molecular biology techniques. Moreover, cultured cells will migrate within the CNS following transplantation. As a result, the migration of these cells in vivo can be analysed following manipulation in vitro. Taken together, we believe that the different properties of these cells makes them excellent candidates for studies addressing the control of cell migration in the developing nervous system.

Animals↗
PubMed1993

Purification and characterization of an autocrine migration factor for vascular smooth muscle cells (SMC), SMC-derived migration factor.

Migration of medial smooth muscle cells (SMC) into the intima is a key step in intimal thickening of atherosclerotic tissues. We previously reported that cultured SMC secrete a potent migration factor for SMC, named SMC-derived migration factor (SDMF). We purified this factor to homogeneity from 20 liters of serum-free conditioned medium of cultured rat aortic SMC by sequential heparin-Sepharose column, red-Sepharose column, TSK-heparin high performance liquid chromatography (HPLC) column, and Superose 6 HPLC column chromatographies. SDMF was found to be a 58-kDa polypeptide by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Reduction by mercaptoethanol caused only a slight decrease in its molecular mass to 53 kDa. Preparative isoelectric focusing revealed that SDMF is a basic protein with a pI of approximately 10. Purified SDMF enhanced the migration of rat SMC dose dependently, its maximal activity being 4 times that of platelet-derived growth factor-BB. In contrast, SDMF did not enhance the migration of endothelial cells from either human umbilical cord vein or rabbit retinal tissue. SDMF had no effect on the proliferation of SMC. These findings suggest that SDMF enhances SMC migration in vascular walls and that the autocrine system of SMC migration contributes to the formation of intimal thickening in atheroma formation.

Animals↗
PubMed1987

Macrophage migration inhibition induced by MDP, LPS, PMA, and MIF/MAF: reversal by macrophage migration enhancement factor (MEF), L-fucose, L-fucosyl BSA, D-mannose, and D-mannosyl BSA.

Our data establish that migration inhibition factor (MIF) and migration enhancement factor (MEF) mutually neutralize the effect of each other in a concentration-dependent manner. The monosaccharides L-fucose and D-mannose were also shown to reverse MIF and additionally to stimulate alveolar macrophage (AM) migration in the absence of MIF. The specific activity of these sugars was increased 200-fold when conjugated to bovine serum albumin (BSA). Macrophage activation is usually observed concurrently with migration inhibition when macrophages are incubated with MIF preparations. Migration inhibition occurred also when AM were incubated in the presence of known metabolic activators (MDP, PMA, and LPS). It was found that L-fucose, D-mannose, L-fucosyl BSA, and D-mannosyl BSA could reverse migration inhibition caused by MIF as well as by these metabolic activators. These observations suggest that reversal of MIF by L-fucose is unexplained solely on the basis that L-fucose is functioning as a competitive inhibitor; instead, they suggest that MEF and the above sugars and their conjugates stimulate AM through a receptor system different from the MIF receptor. These observations support the concept that MEF is an important macrophage modulator in CMI responses.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1993

Migration history, migration behavior and selectivity.

"A series of proportional hazards models are used to study the relationship between migration history and migration behavior for a sample of young adults from the [U.S.] National Longitudinal Survey of Youth. The results support the argument that migration is a selective process. College educated young adults have a greater hazard rate of making an initial migration but a lower hazard rate of re-migration, suggesting they have less need of corrective geographic behavior. Individuals who have moved two or more times are less responsive to national unemployment conditions than first time migrants. Migration is related to the timing of unemployment within a sojourn. The findings suggest that migrant stock is an important determinant of how labor markets function."

Americas↗
PubMed1976

Assay of human lymphokines in vitro. Evidence for a migration stimulation factor (MStF) which interferes with the macrophage migration inhibition assay.

When cultured in vitro, human lymphocytes produced a range of materials which were able to reduce the migration inhibitory effect of human macrophage migration inhibition factor (MIF) and in some cases stimulated macrophage migration to greater than control levels. In addition, lymphocytes stimulated with antigen or mitogen produced a lymphokine-like migration stimulation "factor". Detectable production of this factor occurred 24--48 h after antigen stimulation. The migration stimulation factor (MStF) (MW 50-250,000; pI 6-5) was not chemotactic and could be separated from migration inhibition and chemotactic factors by chromatography and iso-electric focussing.

Cell Migration Inhibition↗
PubMed1996

[Return migrations in the Italian migration system: a reexamination].

The authors discuss trends in return migration in Italy, with a focus on regional differences. "On a regional level, the effects of return migration are very much connected with socio-economic structure. Only highly developed and autonomous regions can absorb productive investments and changes brought about by return migration. Several southern regions--especially those with greater migration experience--have shown in the last decades a very poor socio-economic development." The study is concerned with both internal and international migration. (SUMMARY IN ENG AND FRE)

Demography↗
PubMed1992

Lymphocyte migration in the mouse. II. Differential B and T-lymphocyte migration into a site of chronic inflammation.

Different patterns of B and T-lymphocyte migration were observed in normal mice and in animals with a site of chronic inflammation. The early migration of lymphocytes into a site of chronic inflammation, induced by sensitisation and challenge to Bordetella pertussis vaccine (BPV), comprised mainly B-cells. Subsequently, a greater influx of T-cells occurred as the inflammation progressed. The lymphocyte population in the inflammatory exudate was composed of equal numbers of B and T-cells throughout the 30 day time course. Preferential migration of B-cells to Peyer's patches (PP) and T-cells to peripheral lymph nodes (PLN) occurred in both normal mice and animals with a site of chronic inflammation. In contrast, B-cells migrated preferentially to the spleen in normal mice while in mice with chronic inflammation a greater migration of T-cell was observed. These findings indicate the presence of homing receptors for PP on B-cells and of PLN homing receptors on T-cells, with their distribution unaffected during the development of the inflammatory response. In contrast, the inflammatory process did alter the type of cell migrating into the spleen which may reflect an increase in antigen presentation in the mice challenged with BPV.

Animals↗
PubMed2004

Radioactive seed migration to the chest after transperineal interstitial prostate brachytherapy: extraprostatic seed placement correlates with migration.

PURPOSE: To examine the incidence of seed migration detected on chest X-ray and to identify the predictors associated with its occurrence. METHODS AND MATERIALS: Between May 1998 and April 2000, 102 patients underwent permanent prostate brachytherapy at our institution and 100 were eligible for the study. Chest X-rays obtained at follow-up were examined for the number and location of seeds. The patient and treatment variables potentially associated with the occurrence and number of seed migrations were analyzed. RESULTS: One or more seeds were identified on the chest X-rays of 55 (55%) of 100 patients. The mean number of intrathoracic seeds in patients with migration was 2.2 (range, 1-10), and the proportion of seeds that migrated to the thorax was 0.98%. The rate of extraprostatic seeds planned was 43.9%, and postimplant CT identified 37.9% in such a location. The number of seeds planned for extraprostatic placement and below the apex were statistically significant (alpha = 0.05) predictors in univariate logistic analysis. Multivariate analysis revealed the planned number of extraprostatic seeds as the only statistically significant predictor (p = 0.04). CONCLUSION: Extraprostatic placement of loose seeds is associated with an increased likelihood for, and frequency of, seed migration to the thorax. Nonetheless, the small proportion of implanted seeds that migrated (<or=1%) is highly unlikely to have significant dosimetric consequences.

Aged↗
PubMed1998

Leukocyte migration: a new triple migration chamber assay allows investigation of various cell interactions simultaneously.

Examination of the interactions between various cells of the vascular wall and blood components are essential for understanding different pathophysiological processes. Such investigations require appropriate techniques. Several groups have attempted to establish different methods. In all blood vessels except capillaries, endothelial cells (EC) and smooth muscle cells (SMC) coexist and interact very closely. The current study describes a new 3-dimensional triple chamber migration assay, studying leukocyte migration through human endothelial cell monolayers (ECM) towards human SMC layers simultaneously. To test the new assay, SMC-layers were prestimulated with different concentrations of tumor necrosis factor alpha (TNF-alpha, 1 ng/ml, 10 ng/ml, 100 ng/ml) over 6 hours. Then, two microporous membranes, a collecting membrane and a third membrane with cultured ECM, were inserted. Freshly isolated peripheral blood mononuclear cells (PBMNC) were seeded on the ECM and transmigrated cells were measured after further 3 hours incubation. The migration against non stimulated SMC-layers was used as control. Prestimulated SMC-layers led to a dose dependent increase of PBMNC migration into the subendothelial cell space. Antibodies against interleukin-1 reduced the PBMNC migration. In conclusion, this assay allows to study cell migration into the subendothelial space and interactions between different vascular cells. Moreover, this assay can also be used for studies on other cell-cell interactions in man.

Cell Migration Inhibition↗
PubMed2003

Migration versus apparent migration: importance of errors due to positioning variation in plain radiographic follow-up of aortic stent-grafts.

PURPOSE: To demonstrate the influence of radiographic positioning on the assessment of stent-graft migration using plain radiographs following endovascular abdominal aortic aneurysm repair. METHODS: Equations were derived to correct for artifactual stent-graft migration introduced by geometric distortion due to variations in positioning between radiographs acquired at different times. A phantom system was used to validate the equations. RESULTS: Errors in stent position increase with (1) the distance of the aortic stent-graft from the midline and (2) differences in radiographic centering points in the craniocaudal direction; other variables have little effect. For typical stent positions, errors are small if the centering changes by <8 cm. Consistent radiographic positioning to within 4 cm on successive imaging studies limits errors to 1.5 mm. Even if artifactual migration is large, the true migration can be reliably calculated to within 2 mm. CONCLUSIONS: Artifactual migration due to variation in radiographic centering is not usually clinically significant if care is taken to center radiographs consistently. Radiographs in which artifactual migration may be important are readily identified, and mathematical correction is straightforward.

Aortic Aneurysm, Abdominal↗
PubMed1975

Studies on leukocyte migration inhibiton: the role of E rosette-forming cells in specific antigen-induced inhibition of migration.

The role of E rosette-forming cells in leukocyte migration inhibition was investigated with human buffy coat cells fractionated by combined E rosette formation and Ficoll-Hypaque (FH) density gradient centrifugation. The migration of unfractionated dextran-sedimented leukocytes and FH-separated mononuclear cells (MN) were equally inhibited in the presence of Escherichia coli somatic antigen (E. coli), purified protein derivative of tuberculin (PPD) and influenza virus antigen (Flu). Polymorphonuclear leukocytes (PMN) separated from whole leukocytes by one FH density gradient fractionation contained greater than 1.0% E rosette-forming cells and were inhibited by E. coli and PPD. PMN submitted to three transits of FH (DF III) contained less than or equal to 0.02% E rosette forming cells and were unaffected by each of the three antigens. The migration of mixtures of 10% MN and 90DF III cells were inhibited in the presence of specific antigen, while MN depleted of E rosette-forming cells (less than or equal to 0.5%) pooled with equal numbers of DF III cells did not respond to any antigen by migration inhibition. These results show that PMN purified by three transits of FH are unable to respond to specific antigen by inhibition of migration from microcapillary tubes, and specific antigen-induced inhibition of migration of peripheral blood leukocytes does not occur in the absence of D rosette-forming cells in normal subjects.

Adolescent↗
PubMed1994

Does drought increase migration? A study of migration from rural Mali during the 1983-1985 drought.

"Using data from a longitudinal panel study conducted in 1982 and 1989 in...Mali, this article demonstrates that the level of migration did not rise during the drought of 1983-1985. However, there was a dramatic increase in the migration of women and children during the severe 1983-1985 drought. Along with this increase in migration by women and children, there was a shift to short-cycle circulation, with 64 percent of the migrants adopting circular patterns. The study describes the characteristics of these migrants and recommends changes to development and migration policies that will facilitate such migrations in subsequent droughts."

Africa↗
PubMed1998

Tangential migration of ameboid microglia in the developing quail retina: mechanism of migration and migratory behavior.

Long distance migration of microglial precursors within the central nervous system is essential for microglial colonization of the nervous parenchyma. We studied morphological features of ameboid microglial cells migrating tangentially in the developing quail retina to shed light on the mechanism of migration and migratory behavior of microglial precursors. Many microglial precursors remained attached on retinal sheets containing the inner limiting membrane covered by a carpet of Müller cell endfeet. This demonstrates that most ameboid microglial cells migrate tangentially on Müller cell endfeet. Many of these cells showed a central-to-peripheral polarized morphology, with extensive lamellipodia spreading through grooves flanked by Müller cell radial processes, to which they were frequently anchored. Low protuberances from the vitreal face of microglial precursors were firmly attached to the subjacent basal lamina, which was accessible through gaps in the carpet of Müller cell endfeet. These results suggest a mechanism of migration involving polarized extension of lamellipodia at the leading edge of the cell, strong cell-to-substrate attachment, translocation of the cell body forward, and retraction of the rear of the cell. Other ameboid cells were multipolar, with lamellipodial projections radiating in all directions from the cell body, suggesting that microglial precursors explore the surrounding environment to orient their movement. Central-to-peripheral migration of microglial precursors in the retina does not follow a straight path; instead, these cells perform forward, backward, and sideways movements, as suggested by the occurrence of (a) V-shaped bipolar ameboid cells with their vertex pointing toward either the center or the periphery of the retina, and (b) threadlike processes projecting from either the periphery-facing edge or the center-facing edge of ameboid microglial cells.

Animals↗