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At least 595 records · Page 33Linked to original sources
PubMedDate not supplied

Kinship analysis of Pacific salmon: insights into mating, homing, and timing of reproduction.

Multilocus microsatellite genotypes were used to infer kinship and relatedness in two species of Pacific salmon from three populations in Washington State. Even in the absence of direct genetic data from parents, clustering of individuals according to allele sharing and reconstruction of parental genotypes allowed resolution of full- and half-sib relationships among 135 chinook salmon (Oncorhynchus tshawytscha) sampled as preemergent juveniles from 14 redds in the Dungeness River. Inferred reproductive behaviors included single-pair matings, polyandry in which females mated with two to three males at a single redd, polygyny in which males mated with two females at different redds, use of two redds by a single female, and use of one redd site by two females. Greater average relatedness (rxy) in the upper reach of the Dungeness River implied within-reach homing of returning adults. In steelhead trout (O. mykiss), the frequency of related pairs (dyads) of mature individuals that migrated up Snow Creek less than a week apart was greater than expected for randomly chosen dyads, as was the frequency of steelhead dyads that were spawned on the same day in the Forks Creek hatchery. These results imply a heritable basis for upstream migration date and maturation date in steelhead trout.

Animals↗
PubMedDate not supplied

Anatomic considerations for abdominally placed permanent left ventricular assist devices.

To determine anatomic parameters for a permanent, electrically actuated left ventricular assist device (LVAD), the effects of abdominal placement of pneumatic LVADs used as temporary support for patients awaiting heart transplantation was studied. Understanding the anatomic constraints imposed by the abdominal viscera in LVAD placement is crucial, because improper placement can result in compression or obstruction of adjacent structures. Anatomic compatibility was assessed in four men (age 22-48 years) who were supported by the LVAD for over 1 month (range 35-132 days). The pump was intraperitoneally placed in the left upper quadrant. Radiographic techniques were employed, including CT scanning (with patients supine) and contrast imaging (patients in anatomical position), and the pump and conduits appeared to be properly positioned, with minimal compression of the body of the stomach, and no obstruction of adjacent organs. Three patients returned to a solid food diet and exercised daily by stationary cycling and walking. No signs of migration or erosion of the pump were present at the time of LVAD removal and cardiac transplantation. Successful clinical experience with short-term use of the LVAD suggests that the electrically actuated device can be well tolerated in patients requiring permanent left ventricular assistance.

Abdomen↗
PubMed2002

Time-dependent reversal of sepsis-induced PMN uptake and lung vascular injury by expression of CD18 antagonist.

We determined the time-dependent effects of conditional expression of neutrophil inhibitory factor (NIF), a specific 41-kDa CD18 integrin antagonist, on the time course of NIF expression and lung PMN (polymorphonuclear leukocyte) infiltration and vascular injury in a model of Escherichia coli-induced sepsis in mice. Studies were made in mice transduced with the E-selectin (ES) promoter-NIF construct (using liposomes) in which the NIF cDNA was driven by the inflammation- and endothelial cell-specific ES promoter. We observed time-dependent expression of NIF in pulmonary vascular endothelium that paralleled the ES expression. Expression of both was evident at 1 h after E. coli challenge, peaked at 3-6 h, and returned to basal level within 48 h. We observed that increases in PMN uptake and transalveolar PMN migration induced by E. coli challenge were reversed in a time-dependent manner following NIF expression in mice. NIF expression also prevented the progression of lung vascular injury and edema formation following E. coli challenge. Thus the conditional expression of NIF using the ES promoter can reverse, in a time-dependent manner, lung PMN infiltration and vascular injury induced by gram-negative sepsis. The results support the model that initial engagement of CD18 integrins enables the further recruitment of additional PMN into lung tissues such that PMN continue to sequester and migrate after E. coli challenge.

Amino Acid Sequence↗
PubMed1975

Cholinesterase activity in the hypoglossal nucleus of the rat and the changes produced by axotomy: a light and electron microscopic study.

Within the hypoglossal nucleus large amounts of acetylcholinesterase (AChE) activity are present in all the neurons, whereas intracellular butyrylcholinesterase (BuChE) activity occurs only within a ventro-caudally situated cluster of cells. AChE activity within the neurons occurs mainly in the cisternae of the granular endoplasmic reticulum but there is some in the intermembranous space of the nuclear envelope and in the Golgi complexes. In the neuropil, reaction product is seen along some axonal and synaptic membranes. The distribution of BuChE in the ventro-caudal cells is identical with that of AChE except that BuChE activity is absent from the neuropil. The level of intraneuronal AChE activity falls rapidly during the first few days after axotomy. The fall is due partly to a dissolution and peripheral migration of the E.R. but also to a decrease in AChE content of the E.R. that remains. Return of staining begins in the 4th week and continues as the E.R. reassembles. Staining in the neuropil falls more slowly, but recovers less completely. The ventro-caudal group of cells shows the same kinds of change, but more dramatically. BuChE activity returns only erratically and never completely. The similarity in normal distribution, and in response to axotomy, of the two cholinesterases suggests that their functions are related.

Acetylcholinesterase↗
PubMed1978

[Dynamics of immunologic reactivity in the acute phase of virus hepatitis B].

In 15 patients with acute icteric viral hepatitis B the immunological reactivity was tested. The examinations were performed on the 1st, 7th, and 14th day of hospitalization. They consisted of the determination of the HBsAg and its antibodies in the serum, of the percentage of the B- and T-lymphocytes, of the lymphocyte transformation test under the influence of phytohaemagglutinin, of the lymphocyte migration inhibitory test when the HBsAg is present as well as of the determination of the IgG, IgA and the IgM-level. A decreased percentage of the T-lymphocytes, a decreased blastic transformation and an inhibition of the lymphocyte migration was proved. After a transient increase in the first and second examination the IgG-level returned to the normal in the third examination, whereas the IgM-level increased. Finally dynamics and importance of the cellular reactivity in the pathogenesis of viral hepatitis B are discussed.

Acute Disease↗
PubMed1996

Re-emergence of malaria in India.

Malaria was nearly eradicated from India in the early 1960s but the disease has re-emerged as a major public health problem. Early set backs in malaria eradication coincided with DDT shortages. Later in the 1960s and 1970s malaria resurgence was the result of technical, financial and operational problems. In the late 1960s malaria cases in urban areas started to multiply, and upsurge of malaria was widespread. As a result in 1976, 6.45 million cases were recorded by the National Malaria Eradication Programme (NMEP), highest since resurgence. The implementation of urban malaria scheme (UMS) in 1971-72 and the modified plan of operation (MPO) in 1977 improved the malaria situation for 5-6 yr. Malaria cases were reduced to about 2 million. The impact was mainly on vivax malaria. Easy availability of drugs under the MPO prevented deaths due to malaria and reduced morbidity, a peculiar feature of malaria during the resurgence. The Plasmodium falciparum containment programme (PfCP) launched in 1977 to contain the spread of falciparum malaria reduced falciparum malaria in the areas where the containment programme was operated but its general spread could not be contained. P. falciparum showed a steady upward trend during the 1970s and thereafter. Rising trend of malaria was facilitated by developments in various sectors to improve the national economy under successive 5 year plans. Malaria at one time a rural disease, diversified under the pressure of developments into various ecotypes. These ecotypes have been identified as forest malaria, urban malaria, rural malaria, industrial malaria, border malaria and migration malaria; the latter cutting across boundaries of various epidemiological types. Further, malaria in the 1990s has returned with new features not witnessed during the pre-eradication days. These are the vector resistance to insecticide(s); pronounced exophilic vector behaviour; extensive vector breeding grounds created principally by the water resource development projects, urbanization and industrialization; change in parasite formula in favour of P. falciparum; resistance in P. falciparum to chloroquine and other anti-malarial drugs; and human resistance to chemical control of vectors. Malaria control has become a complex enterprise, and its management requires decentralization and approaches based on local transmission involving multi-sectoral action and community participation.

Disease Outbreaks↗
PubMed1998

Military service and migration in nineteenth-century France: some evidence from Loir-et-Cher.

"Military service in France during the nineteenth century removed many young men from their own localities for long periods. The widely accepted claim that few conscripts returned home after completing their period of service is based on little evidence. The paper examines the conscription classes of 1856 and 1891 in two cantons in the departement of Loir-et-Cher. In those cases, there was not a significant relationship between conscription and migration, nor between literacy and migration. Instead, migration of youths in their twenties was linked partly to prior experiences of migration but principally to their occupations."

Adolescent↗
PubMed1989

Changes in plasma and pituitary levels of prolactin in the toad, Bufo japonicus, throughout the year with special reference to the breeding migration.

Monthly surveys of the plasma prolactin level in Bufo japonicus at two localities, one in Tokyo and the other in Saitama Prefecture, revealed that the level was highest during the month of breeding in early spring with an additional peak recognized in autumn. The level was lowest during the winter torpid period before breeding and during the spring torpid period after breeding. The pituitary prolactin content observed in Tokyo also showed an annual cycle similar to the plasma prolactin, except that the content in winter was higher than that in summer. A further precise survey of the plasma prolactin level before and during the breeding period revealed that the level in male toads migrating toward the pond for breeding was as low as the level in torpid toads, and also that the level was elevated in only about 50% of migrating female toads. In the pond, almost all female and male toads showed high plasma prolactin levels. Soon after the females finished breeding and returned to land, the level declined to the baseline without exception. In contrast, many males retained high levels on land. The present results indicate that prolactin is not a water drive factor, at least in B. japonicus. Prolactin may, however, play a role in toad osmoregulation in water. There is a possibility that the high prolactin level in some of the migrating female toads is related to oviductal secretion, as some female toads ovulate during migration.

Acclimatization↗
PubMedDate not supplied

The new brain drain from Eastern to Western Europe.

"The purpose of this article is to review major issues associated with the flow of expertise from Eastern to Western Europe.... Four interrelated areas are explored: (i) the levels and factors of current East-West skilled migration; (ii) the needs for future policy-oriented research on labour market trends in the countries of origin, and on the skill profile of recent East European migrants; (iii) the organization of the voluntary return of selected expatriate professionals, including the reintegration with capital of potential investors and entrepreneurs; [and] (iv) measures, in the field of training and economic cooperation/international trade, to prevent future significant levels of skilled migration."

Demography↗
PubMed1997

Transendothelial migration induces rapid expression on neutrophils of granule-release VLA6 used for tissue infiltration.

Little is known of the mechanisms allowing neutrophils to infiltrate tissue after transendothelial migration. We postulated that VLA6 might be involved in neutrophil infiltration because it revealed as the most expressed beta1 integrins among VLA5, VLA4, and VLA3, which also appeared to define subsets within the blood neutrophil population. Transendothelial migration up-regulated by threefold (5,000 to 15,000 receptors) VLA6 expression on neutrophils. VLA6 up-regulation was transient, peaking in 6 min and returning to baseline in 1 h when tested in response to N-formyl-methionyl-leucyl-phenylalanine. Neutrophil degranulation experiments revealed a steady correlation between expression of VLA6 and granule content release, notably beta-glucuronidase, indicating that VLA6 molecules were preformed and stored mostly in azurophilic granules. Migration across fibroblast monolayers of neutrophils preactivated for VLA6 up-regulation was blocked when they were preincubated with anti-VLA6. However, anti-VLA6 had no effect on transfibroblast migration of non-preactivated neutrophils. These results indicate that VLA6 was functional only on activated neutrophils that used their up-regulated VLA6 to cross fibroblasts. Activation of neutrophils by transendothelial migration induces rapid expression of granule release VLA6 that appears to be a key adhesion mechanism used by a subset of neutrophils to infiltrate tissue.

Cell Degranulation↗
PubMed1976

Somatic nuclear division in the sporidia of Ustilago violacea. IV. Microtubules and the spindle-pole body.

In unbudded cells of the anther smut fungus Ustilago violacea there is a dome-shaped spindle-pole body (SPB) consisting of a core 0.1 mum in diameter surrounded by a ribosome-free region 0.3-0.4 mum in diameter lying in a pocket of the nuclear membrane. After budding the nucleus moves towards the bud and begins to rotate rapidly. At about this stage the SPB divides into two parallel bars each about 0.1-0.15 mum in diameter and 0.3 mum long, separated by a distance of about 0.3 mum. Microtubules associated with the nuclear membrane but not with the SPB are present at the time of nuclear rotation. These microtubules disappear when rotation stops. Microtubules attached to the SPB are found during migration of the chromatinic portion of the nucleus into the bud cell. These microtubules disappear when migration stops and the nuclear membrand begins to break down. The twin SPB bars appear to move into the nucleus through a break in the membrane and begin to move apart forming a spindle about 1 mum long. Chromosomal microtubules (one per kinetochore) were found in several serial sections, and in addition there appeared to be several continuous microtubules present. The separation of the two chromatinic masses appeared to result from elongation of the continuous microtubules to about 3 mum long. Cytoplasmic microtubules and spindle microtubules were both found attached to the SPB as it elongated and one nucleus returned to the mother cell. The paper concludes with a discussion of the SPB as a multifuncitonal control center affecting nuclear migration, spindle formation, membrane breakdown and synthesis, karyogamy, conjugation, budding, chromosomal movement, replication, and disjunction.

Basidiomycota↗
PubMed2001

The effect of antigen stimulation on the migration of mature T cells from the peripheral lymphoid tissues to the thymus.

Although the maturation and export of T cells from the thymus has been extensively studied, the movement of cells in the opposite direction has been less well documented. In particular, the question of whether T cells which have been activated by antigen in the periphery are more likely to return to the thymus had been raised but not clearly answered. We examined this issue by activating T cells present in the periphery with their cognate antigen, and assessing migration to the thymus. TCR-transgenic cells from OT-I mice (Thy1.2+), which recognise the ovalbumin peptide OVA257-264 in the context of H-2Kb, were transferred into otherwise unmanipulated Thy1.1+ C57BL/6 mice. Recipient mice were injected i.v. with 5 microg peptide (SIINFEKL) approximately 24 hours later. The numbers of donor-derived (Thy1.2+) cells in the thymus and peripheral lymphoid tissue were determined. The results clearly show increased numbers of transgenic cells in the thymus 3 days after antigenic stimulation. However, since numbers of transgenic cells increased in the spleen and LN in about the same proportion, the data do not support the notion that there is highly increased selective migration of activated T cells to the thymus. Rather, they suggest that a sample of peripheral cells enters the thymus each day, and that the mature immigrants detected in the thymus merely reflect the contents of the peripheral T cell pool.

Animals↗
PubMed1984

Neutrophil alveolitis following endotoxemia. Enhancement by previous exposure to hyperoxia.

We injected Escherichia coli endotoxin, 2.5 mg/kg, intraperitoneally in rats, sequentially quantified alveolar inflammation during a 6-day period by several techniques, and observed the effect of previous exposure to hyperoxia on the intensity of alveolitis in this model. As noted in other models of endotoxemia, we found intravascular sequestration of leukocytes and an increase in the retention of 125I albumin in the lung 4 to 6 h after the injection of endotoxin. Bronchoalveolar lavage fluid (BALF) obtained at this time only slightly stimulated the migration of neutrophils in vitro, and the numbers and types of cells recovered by lavage were normal. Fifteen h after the injection of endotoxin, however, bronchoalveolar lavage fluid stimulated both random and directed migration of neutrophils in vitro, although recovery of neutrophils by lavage was increased only slightly. By 24 h, 125I albumin retention had returned to normal levels, but the chemotactic activity of BALF remained high, and the percentage and absolute number of neutrophils recovered by lung lavage were increased markedly. The recovery of neutrophils remained significantly elevated for 3 days but declined to control levels by 6 days, whereas the recovery of alveolar macrophages was increased at this time. Exposure to 100% O2 for 36 h prior to endotoxemia accelerated and intensified neutrophil influx into the lung and increased the stimulatory effect of BALF on neutrophil migration in vitro. We conclude that a single episode of endotoxemia in the rat causes a multi-phasic alveolar inflammatory response, and that this response is accelerated and intensified by prior, mild exposure to hyperoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Airway hyperresponsiveness after endotoxin inhalation depends on leukocyte infiltration.

We have investigated the relationship between acute airway hyperresponsiveness and polymorphonuclear cell (PMN) migration in airways following saline or endotoxin (ET) aerosol inhalation in 63 guinea pigs. In 20 of these animals, granulocytopenia was induced by prior treatment with hydroxyurea (HU). Airway responsiveness (AR) to inhaled methacholine, together with leukocyte counts in bronchoalveolar lavage fluid (BALF) and in tracheal epithelium, was also examined before and at 30 min, 1, 3 and 6 hr after saline or ET inhalation. In saline inhalation groups, AR and PMN counts in BALF and in tracheal epithelium did not differ from control animals at any time points. However, in ET inhalation groups AR increased significantly at 1 and 3 hr and returned to the pre-exposure level at 6 hr. This period of hyperresponsiveness was associated with an increment of PMN migration into tracheal epithelium. However, the increment of PMN counts in BALF was delayed to 3 and 6 hr after ET. In HU treated animals, AR and PMN counts in BALF and in tracheal epithelium did not change during 6 hr after ET inhalation. These results suggest that the hyperresponsiveness induced by ET inhalation either depends upon PMN migration into the tracheal epithelium.

Administration, Inhalation↗
PubMedDate not supplied

Unemployment of the educated and emigration of post-secondary graduates from the LDCs.

The author examines the emigration of educated individuals from developing countries and reviews selected approaches to the study of international human capital flows. Attention is then given to two policy issues: the financing of postsecondary education and an international brain drain tax. The following factors are identified as critical in their impact on educated worker migration: "(a) the rigidity or flexibility of the wage in the market for the services of educated labour; (b) the extent of government subsidy (explicit or implicit) of the cost of post-secondary education; (c) the extent of responsiveness of the investment in education to the private return on such investment or its being exogenously controlled by the government; and (d) the type of restrictions (if any) imposed by the receiving industrialized countries on the migration flows from the LDCs." Comments by M. Ali Khan on a previous article by Blomqvist on the subject are also included (pp. 655-6).

Demography↗
PubMed1996

Changes in beta 4 integrin expression and localization in vivo in response to corneal epithelial injury.

PURPOSE: To determine whether production and localization of beta 4 integrin is altered during in vivo corneal epithelial cell migration in response to debridement wounding. METHODS: Rat corneas were wounded and animals were killed at times ranging from 3 hours to 14 days. At various time points, corneal epithelial integrins were quantitated by gel electrophoresis and immunoblotting of epithelial extracts and then were localized by immunohistochemistry. RESULTS: As early as 6 hours after wounding, an increase in the amount of the beta 4 integrin subunit expressed per microgram of total protein was observed. The level of beta 4 continued to increase until wound closure. By 14 days after wounding, beta 4 expression returned to control levels. The level of expression of beta 1 and alpha (v) integrins were found not to change significantly throughout migration. Immunohistochemical analyses using antibodies against either the beta 4 integrin subunit or HD1, a hemidesmosomal plaque component, showed that in control sections, beta 4 integrin and HD1 codistributed in a linear staining pattern above the basement membrane. As early as 4 hours after wounding, beta 4 was present in both basal and suprabasal epithelial cells, and HD1 was retained at the basal aspect of the epithelial basal cells. CONCLUSIONS: These data show that changes in expression and localization of beta 4 integrin occur in the corneal epithelium in response to debridement wounding in vivo. Previously, we had shown that quantitative changes in beta 4 integrin expression do not occur in an in vitro organ culture model used for the study of corneal epithelial cell migration. Increased beta 4 expression may not be required for migration per se, but it may be play a role in either stabilizing cell:cell or cell:substrate adhesion in vivo or in preparing cells to undergo mitosis during restratification.

Animals↗
PubMedDate not supplied

Ovulation rate and embryonic migration in cross-bred gilts.

The object of the investigation was to compare the activity between left and right ovaries in gilts slaughtered after their 1st, 2nd, 3rd or 4th detected oestrus and to relate the incidence of embryonic migration to the total number of foetuses present. The study comprised 254 cross bred gilts (Swedish Landrace X Swedish Yorkshire) not returning to oestrus within 24 days after A.I. with frozen semen. The gilts were slaughtered 5-8 weeks after A.I. The genital tracts were examined within two hours after slaughter. The number of corpora lutea and the number of normally developed foetuses were recorded. The results indicated that the left ovary had a higher ovulation rate than the right (P less than 0.001). The left ovary was also heavier than the right (0.01 less than P less than 0.05). The number of corpora lutea increased from oestrous number 2 to 4 (2 vs 4, 3 vs 4, 0.01 less than p less than 0.05). The oestrous number did not significantly influence the fertilization rate. The incidence of embryonic migration increased with increasing number of foetuses (0.01 less than p less than 0.05). Migration from left to right and from right to left occurred with the same frequencies.

Animals↗
PubMed2005

Effects of density dependent migrations on the dynamics of a predator prey model.

We study the effects of density dependent migrations on the stability of a predator-prey model in a patchy environment which is composed with two sites connected by migration. The two patches are different. On the first patch, preys can find resource but can be captured by predators. The second patch is a refuge for the prey and thus predators do not have access to this patch. We assume a repulsive effect of predator on prey on the resource patch. Therefore, when the predator density is large on that patch, preys are more likely to leave it to return to the refuge. We consider two models. In the first model, preys leave the refuge to go to the resource patch at constant migration rates. In the second model, preys are assumed to be in competition for the resource and leave the refuge to the resource patch according to the prey density. We assume two different time scales, a fast time scale for migration and a slow time scale for population growth, mortality and predation. We take advantage of the two time scales to apply aggregation of variables methods and to obtain a reduced model governing the total prey and predator densities. In the case of the first model, we show that the repulsive effect of predator on prey has a stabilizing effect on the predator-prey community. In the case of the second model, we show that there exists a window for the prey proportion on the resource patch to ensure stability.

Animal Migration↗