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PubMed1998

The role of leukocyte emigration and IL-8 on the development of lipopolysaccharide-induced lung injury in rabbits.

Leukocyte emigration and alveolar macrophage-derived cytokines may contribute to lung microvascular injury associated with adult respiratory distress syndrome. We have used mAbs against cell adhesion molecules on leukocytes (anti-CD18 and anti-CD49d) or against IL-8 to investigate these contributions. Intratracheal (i.t.) instillation of LPS (50 microg/kg) caused a significant increase in bronchoalveolar lavage polymorphonuclear leukocytes (PMNs) without an increase in mononuclear cells (MNCs) or an increase in lung permeability. Injection of LPS (10 microg/kg) i.v. at 24 h after i.t. LPS caused significant increases in bronchoalveolar lavage PMNs, MNCs, IL-8, and monocyte chemotactic protein-1, as well as increases in lung permeability. Rabbits that were administered i.t. LPS followed by i.v. LPS and treated with anti-CD18 mAb had a significantly lower lung permeability index and emigration of fewer PMNs but no change in MNC emigration compared with saline treatment. Anti-IL-8 mAb treatment resulted in a significantly lower lung permeability index with no change in PMN emigration compared with no treatment. These results suggest that PMN emigration is necessary but not sufficient for the development of LPS-induced lung injury, and that IL-8 plays a significant role in PMN-dependent lung injury, independent of PMN emigration.

Animals↗
PubMed1993

[Emigration from the Soviet Union during the past decades. Part 1].

"This article is an analysis of the extent and causes of the emigration from the [former] Soviet Union during [the] past decade.... Attention is paid not only to the total number of persons leaving the country to live permanently abroad but also to age and professional structure of the emigres, to the scope of emigration of not only the Soviet Union as an entity but also of individual union republics.... The article contains data on the number of emigres arriving in Israel during 1919 up to 1991, the data on age structure of immigrants to Israel as well as the structure of emigrants by original employment in the Soviet Union in 1991." (SUMMARY IN ENG AND RUS)

Age Distribution↗
PubMed1994

Brain drain or links to the world: views on emigrants from Singapore.

"This article will present a general picture of emigration and emigrants from Singapore, with specific references to Australia where the data permit. The first section presents some flow data on the magnitudes of emigration from Singapore.... It is necessary to place this outflow against the background of the constraints imposed by the country's small size. This is discussed in the second section, together with the economic policies and strategies adopted to overcome these constraints. The third section documents the public debate on emigration and the responses to the 'problem.' This is followed in the last section by a prognosis for the future, particularly with regard to the implications for Australia. The article ends with a discussion of the relationship between emigration and nation building, using Singapore as a case study."

Asia↗
PubMed1977

Emigration: psychopathologic reaction in the families left behind.

In order to investigate whether emigration acts as a psychic stress on the families left at home, two groups of families were compared: In group A the head of the family had emigrated, in group B the head of the family was a candidate for emigration. Compared to group B, group A showed a significantly higher rate of psychopathology related to the stress of emigration. Wives and children were mainly affected. The stress of emigration on the wives was corroborated by finding a high proportion of separated couples in group A in comparison with none in group B.

Child↗
PubMed1982

Estimating the emigration rates of legal immigrants using administrative and survey data: the 1971 cohort of immigrants to the United States.

Based on administrative and survey data as well as data-based assumptions about the bounds on alien address reporting, this study provides estimates of the lower and upper bounds for the cumulative net emigration rates, by country and area of origin, of the FY1971 cohort of legal immigrants to the United States as of January 1979. The merged data indicate that the cumulative net emigration rate for the entire cohort could have been as high as 50 percent. Canadian emigration was probably between 51 and 55 percent. Emigration rates for legal immigrants from Central America, the Caribbean (excluding Cuba), and South America were at least as high as 50 percent, and could have been as high as 70 percent. Emigration rates for Koreans and Chinese could not have exceeded 22 percent over the same period.

Demography↗
PubMed1994

Social Security and the emigration of immigrants.

Each year the Social Security Administration forecasts the financial status of the Old-Age, Survivors, and Disability Insurance (OASDI) programs by projecting trends in key variables such as the labor-force participation and earnings of the U. S. population. In the difficult task of projecting the long-term financial status of Social Security, assumptions are made concerning the relationship of immigrants to Social Security. An important aspect of that relationship is the emigration of immigrants. This article describes the general assumptions related to the level and timing of emigration that underlie projections of Social Security's financial status and examines how closely these assumptions fit research findings based on a variety of data sources. Previous trends in emigration and factors that may affect current and future levels of emigration are described. The article also presents theoretical expectations and empirical evidence concerning the timing of emigration.

Adult↗
PubMed1999

Ventrally emigrating neural tube cells contribute to the formation of Meckel's and quadrate cartilage.

A population of multipotential neuroepithelial cells originating in the ventral portion of the hindbrain neural tube has been shown recently to emigrate at the site of attachment of the trigeminal nerve. These ventrally emigrating neural tube cells populate the mesenchyme of the first pharyngeal (branchial) arch. Because the Meckel's and the quadrate cartilage develop from this mesenchyme, we sought to determine whether these ventrally emigrating neural tube cells contributed to their development. The ventral neural tube cells were tagged with a replication-deficient retroviral vector containing the LacZ gene. This method permanently labels the descendents of the neural tube cells; thus, they can be subsequently tracked during development. The viral concentrate was microinjected into the lumen of the rostral hindbrain of chick embryos, after the emigration of neural crest is finished, on embryonic day 2 (stage 14). In control embryos, the virus was placed on top of the neural tube. Embryos were killed on days 3, 4, and 7 and processed for the detection of LacZ-positive cells. By day 7, the Meckel's and the quadrate cartilage can be easily recognized. LacZ-positive cells were seen in both cartilages. They were located in perichondrium and in the cartilage. Immunostaining with the neural crest cell marker HNK-1 indicated that the LacZ-positive cells were HNK-1 negative. The HNK-1-positive neural crest-derived cells were located in the cartilage but not in the perichondrium. These results indicate that the chondrocytes in the Meckel's and the quadrate cartilage differentiate from two sources of cells; the ventrally emigrating neural tube cells and the neural crest. The developmental significance of differentiation of cartilage from the ventral neural tube cells and of the heterogeneous origin of chondrocytes in morphogenesis remains to be established. Dev Dyn 1999;216:37-44.

Animals↗
PubMed2003

Ventrally emigrating neural tube cells migrate into the developing vestibulocochlear nerve and otic vesicle.

Virtually all cell types in the inner ear develop from the cells of the otic vesicle. The otic vesicle is formed by the invagination of non-neural ectodermal cells known as the otic placode. We investigated whether a recently described cell population, originating from the ventral part of the hindbrain neural tube known as the ventrally emigrating neural tube (VENT) cells, also contributes cells to the otic vesicle. The ventral hindbrain neural tube cells were labeled with the fluorescent vital dye DiI or replication-deficient retroviruses containing the LacZ gene in chick embryos on embryonic day 2, after the emigration of neural crest from this region. One day later, the labeled cells were detected only in the hindbrain neural tube. Shortly thereafter, the labeled cells began to appear in the eighth (vestibulocochlear) cranial nerve and otic vesicle. From embryonic day 3.5-5, the labeled cells were detected in the major derivatives of the otic vesicle, i.e. the endolymphatic duct, semicircular canals, utricle, saccule, cochlea, and vestibulocochlear ganglion. That the emigrated cells originated from the ventral part of the hindbrain neural tube was confirmed by focal application of DiI impregnated filter paper and with quail chimeras. It is concluded that, in addition to the otic placode cells, the otic vesicle also contains the ventrally emigrating neural tube cells, and that both cell populations contribute to the structures and cell types in the inner ear. It is well known that inductive signals from the hindbrain are required for the morphogenesis of the inner ear. The migration of the hindbrain neural tube cells into the otic vesicle raises the possibility that the inductive effect of the hindbrain might be mediated, at least in part, by the ventrally emigrating neural tube cells and that, therefore, a mechanism exists that involves cells rather than diffusible molecules only.

Animals↗
PubMed1998

Emigration of neuroepithelial cells from the hindbrain neural tube in the chick embryo.

It is generally believed that after the emigration of neural crest, the neuroepithelial cells of the neural tube are committed to differentiate only as neurons and supporting cells of the central nervous system. Neural crest cells arise from the dorsal portion of the developing neural tube and contribute to the formation of the peripheral nervous system and a variety of non-neural structures. In contrast to this view we have recently shown, by focal application of the vital dye Dil in duck embryos, that an additional population of cells emigrates from the neural tube. By using an entirely different technique we confirm and extend these observations in the chick embryo. Replication-deficient retroviral vector LZ12 containing the gene LacZ was utilized to label the neural tube cells. The viral concentrate was microinjected into the lumen of the rostral hind-brain neural tube, considerably after the completion of emigration of neural crest cells. The labeled cells were monitored in whole mounts and histological sections. Initially, the labeled cells were restricted to the neuroepithelium of the hindbrain neural tube. Subsequently, they were seen in the neural tube and in the ganglion of the fifth cranial nerve (trigeminal ganglion). Later, they migrated beyond the trigeminal ganglion, i.e., into the mesenchyme of the first pharyngeal arch. Immunostaining with the neural crest cell marker, HNK-1, indicated that the emigrated neuroepithelial cells were HNK-1 negative. It is concluded that in the chick embryo some neuroepithelial cells emigrate at the site of attachment of the trigeminal nerve, migrate into the ganglion and then into the mesenchyme of the first arch. This cell population differs antigenically from the neural crest cells.

Animals↗
PubMed2002

Sexual differences for emigration behavior in natural populations of Drosophila melanogaster.

Evolutionary biology considers migration behavior as central in genetic structure of populations and speciation. Here we report on emigration patterns in Drosophila melanogaster behavior under laboratory conditions. For this study, a special apparatus was employed that includes a few important changes in its design and size compared with other known systems. The results presented in this paper were obtained on flies derived from natural populations of two contrasting climatic and geographical regions, from mesic northern and xeric southern parts of Israel. Highly significant difference between sexes in emigration activity was found for both localities. Emigration activity of females appeared to be higher than that of males. We also found that the flies' geographic origin affects emigration behavior (flies from a relatively closed natural system seem to display lower emigration ability than those from an open habitat), although broader sampling from various habitats is needed to confirm these results.

Animals↗
PubMed1999

A central role for thymic emigrants in peripheral T cell homeostasis.

After initial seeding by thymic emigrants, homeostatic regulation of the T cell pool has been thought to occur entirely within the periphery. Here we report that the degree of thymic emigration directly affects the number and the CD4/CD8 ratio of peripheral T cells. We demonstrate that the increase in T cell pool size caused by the engraftment of 2, 6, or 9 thymic lobes correlates almost exactly with the number of emigrants exported from those grafts in the previous 3 weeks, regardless of how long the graft has been in place. The extent of the increase supports the concept of a 3-week period after thymic export in which emigrant T cells are exempt from peripheral T cell homeostasis. This apparent exclusion of recent thymic emigrants from the niche-based regulation of peripheral T cell numbers ensures repertoire turnover throughout adult life and provides the basis of a direct and previously unrecognized role for the thymus in the regulation of peripheral T cell homeostasis.

Animals↗
PubMed1995

Both dendritic cells and memory T lymphocytes emigrate from organ cultures of human skin and form distinctive dendritic-T-cell conjugates.

Prior studies of mouse skin in organ culture have shown that dendritic cells selectively emigrate from the explants over 1-3 d. This emigration may model the movements of dendritic cells that can occur in situ, as in transplantation and contact sensitivity. In this study, we cultured explants of normal human skin that had been removed with a dermatome. Dendritic cells with characteristic morphology and mixed leukocyte response-stimulatory activity emigrated. The dendritic cells had the expected phenotype, e.g., rich in major histocompatibility complex class II and accessory molecules such as B7-1, intercellular adhesion molecule-1, and leukocyte function-associated antigen-3. Small lymphocytes also were present in the emigrated populations and proved to be T cells exclusively, almost entirely of the TcR alpha beta and memory type (CD45RAweak, CD45RO LFA-3/CD58+), with a CD4:CD8 subset ratio of about 2:1. Some of the T cells were bound tightly to the dendritic cells. These conjugates did not dissociate after exposure to trypsin or to calcium- and magnesium-free medium, or during cytofluorography. This made it possible to sort distinct populations of single dendritic cells, single T cells, and conjugates of the two cell types. Conjugates would continue to form from mixtures of separated dendritic cells and T cells in culture. Therefore, cutaneous dendritic cells and memory T lymphocytes emigrate from human skin explants, and some of these cells form distinctive conjugates that we hypothesize contribute to immunologic recall reactions.

Cell Communication↗
PubMed2001

Combining band recovery data and Pollock's robust design to model temporary and permanent emigration.

Capture-recapture models are widely used to estimate demographic parameters of marked populations. Recently, this statistical theory has been extended to modeling dispersal of open populations. Multistate models can be used to estimate movement probabilities among subdivided populations if multiple sites are sampled. Frequently, however, sampling is limited to a single site. Models described by Burnham (1993, in Marked Individuals in the Study of Bird Populations, 199-213), which combined open population capture-recapture and band-recovery models, can be used to estimate permanent emigration when sampling is limited to a single population. Similarly, Kendall, Nichols, and Hines (1997, Ecology 51, 563-578) developed models to estimate temporary emigration under Pollock's (1982, Journal of Wildlife Management 46, 757-760) robust design. We describe a likelihood-based approach to simultaneously estimate temporary and permanent emigration when sampling is limited to a single population. We use a sampling design that combines the robust design and recoveries of individuals obtained immediately following each sampling period. We present a general form for our model where temporary emigration is a first-order Markov process, and we discuss more restrictive models. We illustrate these models with analysis of data on marked Canvasback ducks. Our analysis indicates that probability of permanent emigration for adult female Canvasbacks was 0.193 (SE = 0.082) and that birds that were present at the study area in year i - 1 had a higher probability of presence in year i than birds that were not present in year i - 1.

Animals↗
PubMed1974

Immune-mediated emigration of neutrophils into the lumen of the small intestine.

By using pigs sensitized to bovine serum albumin (BSA), it was found that exposure of the intestinal mucosa to BSA induced, in 4 h, the emigration of large numbers of neutrophils into the intestinal lumen. This response was specific for the immunizing antigen and could be transferred to nonimmune animals with immune serum. The emigration of neutrophils through the intestinal mucosa was not accompanied by the edema, hemorrhage, and thrombosis which were apparent after intracutaneous inoculation of BSA into the same animals. Twenty-four hours after a 4-h mucosal exposure to BSA, the intestinal mucosa showed no evidence of neutrophil emigration nor any other abnormal features. These observations suggested that emigration of neutrophils into the intestinal lumen can be a specific, antibody-mediated immune response which occurs in the absence of intestinal injury. Possible relationships between immune-mediated enteroluminal emigration of neutrophils, neutrophil production, and a protective role for the neutrophil in the intestinal lumen were considered.

Animals↗
PubMed1996

Contribution of LFA-1 and Mac-1 to CD18-dependent neutrophil emigration in a neonatal rabbit model.

Human neonatal polymorphonuclear leukocytes (PMNs) exhibit decreased mobility, adherence, and transendothelial migration in vitro compared with adult PMNs. These deficits, in part, are due to functional and quantitative defects in neonatal Mac-1 (CD11b/CD18), whereas LFA-1 (CD11a/CD18) function is similar to that found in adults (D.C.Anderson, O.Abbassi, T.K.Kishimoto, J.M.Koenig, L.V.McIntire, and C.W.Smith, J.Immunol. 146: 3372-3379, 1991; C. W. Smith, T. K. Kishimoto, O. Abbassi, B.J.Hughes, R.Rothlein, L.V.McIntire, E.Butcher, and D.C. Anderson, J. Clin. Invest. 87: 609-618, 1991). We tested the hypothesis that the primary mechanism for the neonatal PMN CD18-dependent emigration in vivo is due to LFA-1. Neutrophils from 1-day-old rabbit pups had 32 and 60% of adult rabbit levels of CD11a and CD11b, respectively. Rabbit pups or adult rabbits received the monoclonal antibody (MAb) R7.1 (anti-CD11a) or R15.7 (anti-CD18) or the vehicle phosphate-buffered saline (PBS) before the instillation of intraperitoneal thioglycollate. Six hours later peritoneal exudate was collected. The administration of MAbs R7.1 and R15.7 in adult animals resulted in 60 and 83% inhibition of leukocyte emigration, respectively, compared with PBS-treated animals (P < 0.01). In neonatal animals, R7.1 and R15.7 inhibited leukocyte peritoneal accumulation to the same extent (50 and 60%, respectively) compared with PBS-treated animals (P < 0.01). Adult animals were also treated with the anti-CD11b MAb 198. MAb 198 decreased emigration by 25%, although this was not significant compared with PBS-treated animals. We conclude that although neonatal animals have significantly less neutrophil CD11a, the diminished levels did not contribute to a reduced ability to emigrate to the peritoneum and, like adult animals, neonatal animals primarily utilize LFA-1 for accumulation in this model. The contribution of Mac-1 to neonatal leukocyte emigration remains uncertain.

Age Factors↗
PubMedDate not supplied

Phagocytosis by emigrated, intra-abdominal neutrophils is depressed during human secondary peritonitis.

The phagocytic function of neutrophils is a crucial element in host defense against invading microorganisms. Patients with diffuse peritonitis depend on adequate reactivity of neutrophils, in particular locally in the peritoneal cavity as well as in the circulation. This study examined phagocytosis as well as numerical expression of Fcgamma I-III (CD16, CD32, CD64) and complement receptors (CD18, CD35) of emigrated, intra-abdominal and circulating neutrophils during human secondary peritonitis using fluorescence-activated cell analysis. Optimally opsonized E. coli bacteria were used independently of the well-known low level of opsonic molecules during peritonitis. Compared with controls (abdominal surgery without peritonitis), the percentage of emigrated neutrophils which engulfed E. coli bacteria was significantly depressed until 48 h after diagnosis of, and surgery for, peritonitis. When patients with complicated peritonitis (septic shock, multiple organ failure) were compared with patients without complications, phagocytosis was even more depressed in patients with complications. Numerical expression of CD64 (Fcgamma RI) and CD35 (CR1) increased significantly on emigrated polymorphonuclear leukocytes (PMNs) during peritonitis when compared to controls. There was no difference in CD18 and CD32 (Fcgamma RII) expression between the two groups. Numerical expression of CD16 (Fcgamma RIII) on emigrated PMNs decreased significantly in peritonitis. This was more pronounced in patients with complicated peritonitis. We conclude that there is a long-lasting depression of phagocytosis by emigrated PMNs during peritonitis, independent of the opsonic activity. Our data suggest that decreased phagocytosis might be correlated to the profound drop in CD16 on these cells.

Abdominal Cavity↗
PubMed1997

Emigrated rat neutrophils adhere to cardiac myocytes via alpha 4 integrin.

Previous work has shown that neutrophils isolated from whole blood adhere to cardiac-myocytes via CD18 (beta 2 integrin) to cause injury to the heart cells. In vitro, we have found that upon endothelial transmigration, neutrophils can also express alpha 4 beta 1; however, whether this contributes to neutrophil adhesion to parenchymal cells remains entirely unknown. Unstimulated and tumor necrosis factor-alpha-stimulated rat cardiac myocytes adherent to gelatin-coated coverslips supported N-formyl-Met-Leu-Phe (fMLP)-induced neutrophil (isolated from whole blood) adhesion entirely via CD18 (blocked with monoclonal antibody [mAb] WT-3). Emigrated neutrophils spontaneously adhered to cardiac myocytes also entirely via CD18. However, if fMLP was used to restimulate emigrated neutrophils, the adhesion to cardiac myocytes was entirely independent of CD18. Although an anti-alpha 4 integrin antibody (mAb TA-2) alone did not reduce the emigrated neutrophil-myocyte interaction, dual administration of TA-2 and WT-3 reduced adhesion by 81%. alpha 4 integrin was expressed in small amounts on the surface of circulating neutrophils, increased following transmigration, and then increased > 5-fold after restimulation of these emigrated neutrophils. In the presence of the anti-CD18 antibody, a fibronectin fragment (FN-40) but not a vascular cell adhesion molecule-1 antibody (mAb 5F10) inhibitied neutrophil-myocyte interactions by 80%. Similar results were seen when the rat chemokine CINC-gro was used instead of fMLP, suggesting that the alpha 4-dependent adhesion was not specific to fMLP. These data demonstrate that alpha 4 integrin can be physiologically induced to increase in number and avidity after neutrophil emigration and that this adhesion molecule can cause firm adhesion to fibronectin on parenchymal cells, including rat cardiac myocytes.

Animals↗
PubMed1992

Transforming growth factor-beta control of cell-substratum adhesion during avian neural crest cell emigration in vitro.

It has been proposed that, in higher vertebrates, the onset of neural crest cell migration from the neural tube involves spatially and temporally coordinated changes in cellular adhesiveness that are under the control of external signals released in the extracellular milieu by neighboring tissues. In the present study, we have analyzed the dynamics of changes in cell-substratum adhesiveness during crest cell emigration and searched for regulatory cues using an in vitro model system. This model is based on the fact that, in vivo, crest cell dispersion occurs gradually along a rostrocaudal wave, allowing us to explant portions of the neural axis, termed migratory and premigratory levels, that differ in the time in culture at which neural crest cells initiate migration and in the locomotory behavior of the cells. We found that neural crest cell emigration is not triggered by the main extracellular matrix molecules present in the migratory pathways, as none of these molecules could abolish the intrinsic difference in the timing of emigration between the different axial levels. Using an in vitro adhesion assay, we found that presumptive neural crest cells from premigratory level explants gradually acquired the ability to respond to extracellular matrix material with time in culture, suggesting that acquisition of appropriate, functional integrin receptors was a necessary step for migration. Finally, we showed that members of the transforming growth factor-beta family reduced in a dose-dependent manner the delay of neural crest cell emigration from premigratory level explants and were able to increase significantly the substratum-adhesion properties of crest cells. Our results suggest that acquisition of substratum adhesion by presumptive neural crest cells is a key event during their dispersion from the neural tube in vitro, and that members of the transforming growth factor-beta family may act as potent inducers of crest cell emigration, possibly by increasing the substratum adhesion of the cells.

Animals↗