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PubMed1991

A theoretical analysis of the beneficial effects of the brain-drain phenomenon.

"The primary objective of this paper is to examine the impact of migration, and ultimately remittances on economic development in an LDC [less-developed country] within the context of a two-sector development model. For this purpose we construct a two-period development model wherein the country loses professional workers in the first period, but receives foreign-exchange remittances in the second period. Then we derive the conditions under which the 'brain drain' phenomenon may promote social welfare gains over the two periods horizon." The results indicate that "emigration of skilled labor causes the real rate of return to capital to fall and the real wage to labor in the home country to rise. Emigration of skilled labor unambiguously causes a real income loss in less developed labor-exporting countries in the first period, but may cause a real income gain to the LDC in the long run. We also find that the per capita income in an LDC may rise as a consequence of emigration in the short-run, but in the long run capita income unambiguously rises." (SUMMARY IN FRE)

Demography↗
PubMed1983

The entry of T and B lymphocytes into rat popliteal lymph nodes undergoing a graft-versus-host reaction.

The entry of radiolabeled blood-borne T and B lymphocytes into resting popliteal lymph nodes and popliteal lymph nodes stimulated with semiallogeneic lymphocytes was investigated in rats. Thoracic duct lymphocytes separated into T- and B-lymphocyte populations on nylon-wool columns were radiolabeled with 51chromium and equal numbers of T or B lymphocytes were injected intravenously. While the ratio of T and B lymphocytes in the blood is approximately 3:1 it was found that the ratio of T to B lymphocytes migrating into lymph nodes was approximately 9 T to 1 B lymphocyte in both resting and antigenically stimulated lymph nodes. Since the ratio of T to B lymphocytes in thoracic duct lymph is similar to that of blood, there is a disparity between the number of T cells entering and leaving lymph nodes. These results suggest that some T lymphocytes may return to the blood directly and/or there is increased T lymphocyte death in lymph nodes.

Animals↗
PubMed2006

The wave speed of intergradation zone in two-species lattice Müllerian mimicry model.

A spatially explicit model is studied to analyse the movement of coupled clines in two-species Müllerian mimicry system as exemplified by the comimicking helicoiine butterflies in Central-South America Heliconius erato and Heliconius melpomene. In this system, a pair of comimicking wing patterns of two species (mimicry ring) is found in a geographical region but another pair of wing patterns is found in a different geographical region. The distribution of mimicry rings thus forms a spatial mosaic in a large geographical scale, and the mechanism responsible for their stable maintenance has been a long-standing question in evolutionary biology. We here examine the speed of the movement of boundaries that divide the regions inhabited by different mimetic morphs in each comimicking species, by assuming coupled two-state stochastic cellular automatons where the flipping rate of the site occupied by a mimetic morph depends on the local density of the same morph and of the comimicking morph in the other species. The speed of cline movement shows a complex dependence on the coupling parameter between mimetic species--greater coupling of comimicking morphs between species slows down the cline movement only when the reduction in predation rate exhibits diminishing return to the increase of local mimetic morph density. The analytical predictions are confirmed by the results of Monte Carlo simulations. The speed of advance is quite different from that predicted from the conventional reaction-diffusion model, indicating that demographic stochasticity plays a critical role in determining the speed of cline movement. We also examine if the spatial heterogeneity in migration rate can stably maintain clines.

Animals↗
PubMed1987

Microinjection of ubiquitin: changes in protein degradation in HeLa cells subjected to heat-shock.

Ubiquitin was radiolabeled by reaction with 125I-Bolton-Hunter reagent and introduced into HeLa cells using erythrocyte-mediated microinjection. The injected cells were then incubated at 45 degrees C for 5 min (reversible heat-shock) or for 30 min (lethal heat-shock). After either treatment, there were dramatic changes in the levels of ubiquitin conjugates. Under normal culture conditions, approximately 10% of the injected ubiquitin is linked to histones, 40% is found in conjugates with molecular weights greater than 25,000, and the rest is unconjugated. After heat-shock, the free ubiquitin pool and the level of histone-ubiquitin conjugates decreased rapidly, and high molecular weight conjugates predominated. Formation of large conjugates did not require protein synthesis; when analyzed by two-dimensional electrophoresis, the major conjugates did not co-migrate with heat-shock proteins before or after thermal stress. Concomitant with the loss of free ubiquitin, the degradation of endogenous proteins, injected hemoglobin, BSA, and ubiquitin was reduced in heat-shocked HeLa cells. After reversible heat-shock, the decrease in proteolysis was small, and both the rate of proteolysis and the size of the free ubiquitin pool returned to control levels upon incubation at 37 degrees C. In contrast, neither proteolysis nor free ubiquitin pools returned to control levels after lethal heat-shock. However, lethally heat-shocked cells degraded denatured hemoglobin more rapidly than native hemoglobin and ubiquitin-globin conjugates formed within them. Therefore, stabilization of proteins after heat-shock cannot be due to the loss of ubiquitin conjugation or inability to degrade proteins that form conjugates with ubiquitin.

Autoradiography↗
PubMed1993

Two-year follow up of bipolar hemiarthroplasty.

Forty-seven bipolar hemiarthroplasties were performed from January 1985 to December 1986. Twenty-three patients (24 hips) returned for a history, physical, and repeat radiographs. Ten primary press-fit and two cemented primary bipolar hemiarthroplasties were performed. Four patients underwent cemented and eight received press-fit revision bipolar hemiarthroplasties. Fourteen patients had simultaneous cancellous, reamed femoral head autograft, or allograft acetabular bone augmentation. Omitting one patient who had replacement for Lévi's pleonosteosis, the average acetabular migration among the remaining 23 patients was 4 mm of superior and 1.5 mm of medial progression. The mean modified d'Aubigne hip score was 33 for primary press-fit arthroplasty, 30 for primary cemented arthroplasty, 22 for press-fit revisions, and 32 for cemented bipolar revision arthroplasty. Morcellized bone graft tended to variably resorb with time. Among the press-fit stems, all but two patients complained of at least occasional thigh pain. All but one patient with primary press-fit hemiarthroplasty walked with a limp. We conclude that, although good early results can be obtained, significant number of patients will have groin and thigh pain. We have found no evidence either radiologically or clinically that nonstructural bone grafting with reamed femoral head will reliably incorporate or prevent further acetabular migration.

Acetabulum↗
PubMed2003

Case report: gnathostomiasis in two travelers to Zambia.

Gnathostomiasis is a systemic infection caused by migrating nematode larvae of the genus Gnathostoma. It is a zoonosis involving a wide variety of animals as intermediate and definitive hosts, and consumption of raw fish is the main risk factor. The condition is most commonly seen in southeastern Asia, but has been described in a number of other countries, all outside Africa. We report the infection in two travelers returning from southcentral Africa, who presented with non-specific symptoms and marked eosinophilia, and in whom schistosomiasis was initially suspected. The typical migratory skin lesions of gnathostomiasis appeared later. The infections responded well to albendazole. The patients acquired the infection in western Zambia; this region of Africa appears to be a newly identified risk area for gnathostomiasis in tourists who indulge in eating raw freshwater fish.

Aged↗
PubMed1991

Keratocyte activity in wound healing after epikeratophakia in rabbits.

Epikeratophakia is a refractive surgical procedure for the correction of aphakia, high myopia, or keratoconus. To solve clinical problems associated with epikeratophakia, a basic knowledge of its postoperative healing process is needed. The authors investigated keratocyte activities, particularly cell proliferation and collagen synthesis, during wound healing after epikeratophakia in rabbits. Epikeratophakia was done on rabbit corneas with a homologous cryolathed keratolens. Ten, 16, 28, 45, 63, 90, 254, and 360 days after the operation, the corneas were excised, labeled with either 3H-thymidine (10 microCi/ml) or 3H-proline (10 microCi/ml) for 4 hr and examined histologically and by autoradiography. Keratocytes in keratolenses were killed during the freezing process. On postoperative day 10, a few keratocytes migrated to the edge of the keratolens from the host stroma. On days 16 and 28, keratocytes in the keratolens and host stroma near the junction between the host and the keratolens incorporated 3H-thymidine, suggesting active proliferation. The proliferating activity was no longer seen after day 45. The repopulation of keratocytes was almost complete on day 90 and gradually returned to normal through day 360. Keratocytes in the keratolens and host stroma beneath the keratolens showed a higher 3H-proline incorporation than the control from days 16-254 with the highest activity at around 4-9 weeks after surgery. These results suggest that remodeling of collagen fibers continues for a long postoperative period after epikeratophakia.

Animals↗
PubMed1980

Ender nailing of intertrochanteric and subtrochanteric fractures of the femur.

Condylocephalic intramedullary Ender nailing of fractures of the proximal end of the femur offers four advantages. The operation is short and is minimally traumatic, with little blood loss. The patient returns to functional ambulatory status within a few days. Infection of the fracture site and at the nail portals is a negligible risk, and the risk of delayed union and non-union is greatly reduced. The method has also introduced a group of new complications such as irritation at the knee, decreased range of knee motion, and distal and proximal migration and penetration of the nails, yet these problems did not cause failures of the method. Osteoporosis was found to be a significant factor contributing to complications. External rotation deformity has not been a major problem in the present study and was improved by use of nails that had an anteversion bend. Delayed union was observed in only one patient with an intertrochanteric fracture which eventually healed. All subtrochanteric fractures healed within three months, which represents a favorable result in comparison with other methods.

Adult↗
PubMed1993

[Palliative treatment of esophageal neoplastic stenoses with self-expanding metallic stents].

Thirty Strecker nickel-titanium self-expanding metallic stents were implanted in 20 patients with esophageal strictures and inoperable neoplasms in the Departments of Radiology of the University School of Medicine of Ferrara, Genoa, Novara and Rome, from March 1992 to April 1993; follow-up ranged 1 to 13 months. Thanks to the stents, esophageal strictures could be dilated, significantly reducing dysphagia and allowing the patients to return on to a solid diet. Radiological and endoscopic exams proved the efficacy of the stents in all but 2 patients in whom the tumors had invaded the stent lumen and caused obstruction. In all cases the stents were highly biocompatible and well tolerated. Neither major complications, such as perforation or bleeding, were observed, nor minor ones, such as fever or migration from the site of implant, which may occur with plastic prostheses. To conclude, self-expanding metallic stents used in clinical trials for 13 months proved an effective method in the palliative treatment of malignant esophageal strictures.

Aged↗
PubMed1977

Interstate migrants in the United States: some social-economic differences by type of move;.

U.S. interstate migrants (over a five-year period) are separated into three groups: (a) those leaving state of birth; (b) those returning to state of birth; and (c) those outside state of birth at the beginning of the period and moving on to a third state by the end. Evidence is presented suggesting that the third group is particularly selective of persons with high social and economic status. The findings are linked to certain hypotheses about the changing role and function of migration in a highly developed country where the transition from a rural society based on agriculture has essentially been completed.

Adolescent↗
PubMed2007

Smelling home can prevent dispersal of reef fish larvae.

Many marine fish and invertebrates show a dual life history where settled adults produce dispersing larvae. The planktonic nature of the early larval stages suggests a passive dispersal model where ocean currents would quickly cause panmixis over large spatial scales and prevent isolation of populations, a prerequisite for speciation. However, high biodiversity and species abundance in coral reefs contradict this panmixis hypothesis. Although ocean currents are a major force in larval dispersal, recent studies show far greater retention than predicted by advection models. We investigated the role of animal behavior in retention and homing of coral reef fish larvae resulting in two important discoveries: (i) Settling larvae are capable of olfactory discrimination and prefer the odor of their home reef, thereby demonstrating to us that nearby reefs smell different. (ii) Whereas one species showed panmixis as predicted from our advection model, another species showed significant genetic population substructure suggestive of strong homing. Thus, the smell of reefs could allow larvae to choose currents that return them to reefs in general and natal reefs in particular. As a consequence, reef populations can develop genetic differences that might lead to reproductive isolation.

Animal Migration↗
PubMed2003

Growth factor, cytokine and protease interactions during corneal wound healing.

Healing of corneal injuries is an exceptionally complex process involving the integrated actions of multiple growth factors, cytokines, and proteases produced by epithelial cells, stromal keratocytes, inflammatory cells, and lacrimal gland cells. Following corneal injury, basal epithelial cells migrate and proliferate in response to chemotactic cytokines and mitogenic growth factors, including epidermal growth factor and keratinocyte growth factor. Simultaneously, keratocytes adjacent to the injured area undergo apoptosis under the Fas/Fas ligand system, while more distant keratocytes transform into activated fibroblasts and migrate into the wound, where they begin synthesizing new extracellular matrix components that form the scar tissue under the dominant influence of the TGFb/ CTGF system. Epithelial cells and activated stromal fibroblasts also secrete growth factors and cytokines that have paracrine and autocrine functions. Corneal repair proceeds for the next several weeks to months, during which time the gene expression profile slowly returns to the pre-injury pattern and the provisional scar matrix slowly remodels by actions of matrix metalloproteinases. While minor epithelial injuries heal by regeneration of normal architecture, large stromal injuries heal by repair with irregular scar tissue that impairs the optical properties of the cornea.Also, if the integrated regulation of the wound healing process is interrupted at any point, the wound fails to heal properly and a corneal ulcer develops. Better understanding of the cellular and molecular changes that occur during repair of corneal wounds will provide the opportunity to design agents that selectively modulate key phases of corneal wound healing, resulting in scars that more closely resemble normal corneal architecture.

Journal Article↗
PubMed1996

Biology of chemokine and classical chemoattractant receptors: differential requirements for adhesion-triggering versus chemotactic responses in lymphoid cells.

Several chemoattractant receptors can support agonist-induced, integrin-dependent arrest of rolling neutrophils in inflamed venules in vivo, as well as subsequent crawling into tissues. It has been hypothesized that receptors of the Galpha(i)-linked chemoattractant subfamilies, especially receptors for chemokines, may mediate parallel activation-dependent arrest of homing lymphocyte subsets. However, although several chemokines can attract subsets of B or T cells, robust chemoattractant triggering of resting lymphocyte adhesion to vascular ligands has not been observed. To study the biology of individual leukocyte chemoattractant receptors in a defined lymphoid environment, mouse L1/2 pre-B cells and/or human Jurkat T cells were transfected with alpha (IL-8 receptor A) or beta (MIP-1alpha/CC-CKR-1) chemokine receptors, or with the classical chemoattractant C5a (C5aR) or formyl peptide receptors (fPR). All receptors supported robust agonist-dependent alpha4beta1 integrin-mediated adhesion of lymphocytes to VCAM-1. L1/2 cells cotransfected with fPR and beta7 integrin were also induced to bind MAdCAM-1, suggesting common mechanisms coupling chemoattractant receptors to activation of distinct integrins. Adhesion was rapid but transient, with spontaneous reversion to unstimulated levels within 5 min after peak binding. When observed under flow conditions, alpha4beta1-mediated arrest occurred within seconds after initiation of contact and rolling of IL-8RA transfectants on VCAM-1/IL-8 co-coated surface; and arrest reversed spontaneously after a mean of 5 min with a return to rolling behavior. Each of the receptors also conferred agonist-specific chemotaxis; however, whereas strong adhesion required simultaneous occupancy of many receptors with maximal responses above the Kd, chemotaxis in each case was suppressed at high agonist concentrations. The findings indicate that alpha and beta chemokine as well as classical chemoattractant receptors can trigger robust adhesion as well as directed migration of lymphoid cells, but that the requirements for and kinetics of adhesion triggering and chemotaxis are distinct, thus permitting their independent regulation. They suggest that the discordance between proadhesive and chemoattractant responses of circulating lymphocytes to many chemokines may reflect quantitative aspects of receptor expression and/or coupling rather than qualitative differences in receptor signaling.

Animals↗
PubMed2005

De-activation of neutrophils in suspension by fluid shear stress: a requirement for erythrocytes.

Leukocyte de-activation in response to a mechanical stimulus may be an important mechanism to reduce inflammation in the circulation and cardiovascular complications. We examine here a specific form of leukocyte activation in the form of pseudopod projection, a process that is important during cell spreading and migration, but if it occurs in circulating leukocytes, may also lead to their entrapment in the microvascular network. Fresh neutrophils were activated with fMLP, suspended without adhesion to endothelium, and sheared in a cone-and-plate device while both shear stress and shear rate were measured. A fraction of the activated neutrophils retracted their pseudopods under the influence of fluid shear and returned to round shape. Pseudopod retraction was observed only in the presence of erythrocytes (at shear stresses up to approximately 25 dyn/cm(2)). At a constant hematocrit and increasing plasma viscosities with addition of macromolecules, the number of de-activated neutrophils scaled with shear stress and less so with shear rate. We examined a biochemical and rheological role of erythrocytes during shear de-activation of neutrophils. Addition of superoxide dismutase (SOD) in phosphate buffer served to enhance neutrophil de-activation by fluid shear. Replacement of erythrocytes by solid microspheres (5.4 mum) to simulate the particle properties of the erythrocytes, did not serve to enhance neutrophil de-activation unless in the presence of SOD. At higher shear stresses without erythrocytes (38-77 dyn/cm(2)), we also observed neutrophil de-activation but only in the presence of SOD. These results suggest that erythrocytes play an important role in neutrophil de-activation by reducing the superoxide level in plasma. Shear stress, rather than shear rate, is the key determinant that regulates neutrophil de-activation.

Animals↗
PubMed1992

Amplexus induces surge of luteinizing hormone in male toads, Bufo japonicus.

At mating time in the wild, male toads (Bufo japonicus) exhibit a surge in circulating luteinizing hormone (LH) that is thought to result in spermiation. Experiments were performed to identify proximate control of this gonadotropin surge. Male toads migrating to a breeding pond were captured and put in plastic containers either with equal numbers of females or without females. All the males placed with the females clasped them in amplexus that lasted for about 12 hr. During this period, plasma LH and follicle-stimulating hormone levels increased progressively to about 25 and 2 times the initial levels, respectively, and then returned to the initial levels. No significant increases in plasma gonadotropin levels were observed in the males kept without females. These results suggest that the amplexus directly induced the LH surge, but do not preclude control by pheromonal or visual stimuli. To isolate effects of these factors, solitary male toads were kept with dummies of the female. The dummy was a block of "konnyaku," Japanese food whose component is mannan extracted from the root of a plant. Konnyaku is highly elastic, white in color, and virtually odorless. Thus, these dummies felt, but did not look or smell, realistic. All the males clasped their dummy and formed amplexus for 12 hr or more; an LH surge indistinguishable from that with the females was observed. It is concluded that the amplexus itself is the stimulus that induces the LH surge, and subsequent spermiation, in male toads. A strongly male-biased sex ratio, combined with a need to time spermiation precisely with actual mating, may have resulted in the evolution of this neuroendocrine reflex in male Bufo.

Animals↗
PubMed1997

Ligament reconstruction arthroplasty for trapeziometacarpal arthrosis.

Twenty-eight patients (30 thumbs) were evaluated after ligament reconstruction arthroplasty for trapeziometacarpal arthrosis. The mean patient age was 60 years, 86% were women, and the average follow-up period was 38 months. Subjective results showed excellent (40%) or good (57%) pain relief in 97% of patients. Return to previous work or activity level was achieved in 98%. Eighty-six percent of patients expressed overall satisfaction with the surgical outcome, mostly because of pain relief. Functional improvement was reported for many activities, except jar opening, which continued to be the most difficult task to perform. Thumb mobility improved, while key pinch strength showed an overall decrease of 27%. Proximal migration of the thumb metacarpal measured 27%, and radial subluxation was negligible. Thumb metacarpophalangeal joint hyperextension was present to some degree in more than 50% of patients before surgery and in 7 of 30 thumbs (23%) after surgery. Hyperextension was prevalent among women on hormone-replacement therapy, including 3 patients in whom these deformities recurred in spite of attempts to stabilize their joints during surgery.

Aged↗
PubMed2003

Benzophenone in cartonboard packaging materials and the factors that influence its migration into food.

Benzophenone may be present in cartonboard food-packaging materials as a residue from UV-cured inks and lacquers used to print on the packaging. It may also be present if the cartonboard is made from recycled fibres recovered from printed materials. A method has been devised to test for benzophenone in cartonboard packaging materials and to test for migration levels in foodstuffs. Packaging is extracted with solvent containing d10-benzophenone as the internal standard. Foods are extracted with solvent containing d10-benzophenone and the extract defatted using hexane. The extracts are analysed by GC-MS. For analysis of food, the limit of detection was 0.01 mg x kg(-1) and the limit of quantification was 0.05 mg x kg(-1). The calibration was linear from 0.05 to 20 mg x kg(-1). The method for food analysis was validated in-house and it also returned satisfactory results in a blind check-sample exercise organized by an independent laboratory. The methods were applied to the analysis of 350 retail samples that used printed cartonboard packaging. A total of 207 (59%) packaging samples had no significant benzophenone (<0.05 mg x dm(-2)). Seven (2%) were in the range 0.05- 0.2 mg x dm(-2), 60 (17%) were from 0.2 to 0.8 mg x dm(-2) and 76 (22%) were from 0.8 to 3.3 mg x dm(-2). A total of 71 samples were then selected at random from the 143 packaging samples that contained benzophenone, and the food itself was analysed. Benzophenone was detected in 51 (72%) of the foods. Two food samples (3%) were in the range 0.01-0.05 mg kg(-1). A total of 29 (41%) were from 0.05 to 0.5 mg kg(-1), 17 (24%) were from 0.5 to 5 mg x kg(-1) and three (4%) food samples exceeded 5 mg x kg(-1). The highest level of benzophenone in food was 7.3 mg x kg(-1) for a high-fat chocolate confectionery product packaged in direct contact with cartonboard, with room temperature storage conditions and with a high contact area:food mass ratio. When the mass fraction of benzophenone migration was calculated for the different contact and storage regimes involved, the attenuation effects of indirect contact and of low temperature storage were cumulative. Thus, there was a sixfold reduction in migration for indirect contact compared with direct contact, a sixfold reduction for chilled/frozen storage compared with ambient storage, and 40-fold reduction for the two contact conditions combined.

Benzophenones↗
PubMed1997

2-Methoxyestradiol, an endogenous estrogen metabolite, induces apoptosis in endothelial cells and inhibits angiogenesis: possible role for stress-activated protein kinase signaling pathway and Fas expression.

2-Methoxyestradiol (2-ME) is an endogenous metabolite of estradiol-17beta and the oral contraceptive agent 17-ethylestradiol. 2-ME was recently reported to inhibit endothelial cell proliferation. The current study was undertaken to explore the mechanism of 2-ME effects on endothelial cells, especially whether 2-ME induces apoptosis, a prime mechanism in tissue remodeling and angiogenesis. Cultured bovine pulmonary artery endothelial cells (BPAEC) exposed to 2-ME showed morphological (including ultrastructural) features characteristic of apoptosis: cell shrinkage, cytoplasmic and nuclear condensation, and cell blebbing. 2-ME-induced apoptosis in BPAEC was a time- and concentration-dependent process (EC50 = 0.45 +/- 0.09 microM, n = 8). Nucleosomal DNA fragmentation in BPAEC treated with 2-ME was identified by agarose gel electrophoresis (DNA ladder) as well as in situ nick end labeling. Under the same experimental conditions, estradiol-17beta and two of its other metabolites, estriol and 2-methoxyestriol (< or =10 microM), did not have an apoptotic effect on BPAEC. 2-ME activated stress-activated protein kinase (SAPK)/c-Jun amino-terminal protein kinase in BPAEC in a concentration-dependent manner. The activity of SAPK was increased by 170 +/- 27% and 314 +/- 22% over the basal level in the presence of 0.4 and 2 microM 2-ME (n = 3-6), respectively. The activation of SAPK was detected at 10 min, peaked at 20 min, and returned to basal levels at 60 min after exposure to 2-ME. Inhibition of SAPK/c-Jun amino-terminal protein kinase activation by basic fibroblast growth factor, insulin-like growth factor, or forskolin reduced 2-ME-induced apoptosis. Immunohistochemical analysis of BPAEC indicated that 2-ME up-regulated expression of both Fas and Bcl-2. In addition, 2-ME inhibited BPAEC migration (IC50 = 0.71 +/- 0.11 microM, n = 4) and basic fibroblast growth factor-induced angiogenesis in the chick chorioallantoic membrane model. Taken together, these results suggest that promotion of endothelial cell apoptosis, thereby inhibiting endothelial cell proliferation and migration, may be a major mechanism by which 2-ME inhibits angiogenesis.

2-Methoxyestradiol↗