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PubMed1999

Y-Chromosome evidence for a northward migration of modern humans into Eastern Asia during the last Ice Age.

The timing and nature of the arrival and the subsequent expansion of modern humans into eastern Asia remains controversial. Using Y-chromosome biallelic markers, we investigated the ancient human-migration patterns in eastern Asia. Our data indicate that southern populations in eastern Asia are much more polymorphic than northern populations, which have only a subset of the southern haplotypes. This pattern indicates that the first settlement of modern humans in eastern Asia occurred in mainland Southeast Asia during the last Ice Age, coinciding with the absence of human fossils in eastern Asia, 50,000-100,000 years ago. After the initial peopling, a great northward migration extended into northern China and Siberia.

Africa↗
PubMed1983

Physicians who move and why: from residency to practice, 1974-1978.

As medical residents leave their residencies, a majority also move away from the locales in which they received their training. Data presented in this paper on physicians entering their first professional positions between 1974 and 1978 show that over 65 percent left the counties of their residencies. Following the national migration pattern of the civilian population, the medical residents left the northern "Frost Belt" and entered the southern "Sun Belt" of the United States. Physician "movers" typically were in nonprimary care medical specialties and moved into self-employment or office-based medical practices. These migrating physicians, compared with physician "stayers," were disproportionately male, more often resided in states other than those of their medical education, and moved into smaller urban or nonurban centers of the United States. Other characteristics that distinguish movers from stayers also are presented here.

Humans↗
PubMed1991

Patterns of immunoreactive pancreatic polypeptide in human plasma.

Pancreatic polypeptide (PP) is synthesized as an amino-terminal moiety of a precursor peptide and is released into plasma during stimulation as an amidated hormone (PP1-36). The purpose of this investigation was to ascertain the immunoreactive forms of PP in human plasma using HPLC chromatographic technique. Plasma was obtained from five normal volunteers under various postprandial intervals and from the Blood Bank. PP in each plasma sample was processed for HPLC analysis by immunoprecipitation and/or immunoaffinity extractions. Migration patterns of PP-forms were identified under isocratic elution. This study shows that human plasma contains four distinct immunoreactive (IR) forms of PP during stimulation by a protein-rich meal. These forms are PP1-36 (peak 4), PP3-36 (peak 3) and unidentified material migrating as peak 2 and peak 1. The corresponding migration constants were Kav 0.828 +/- 0.04, Kav 0.790 +/- 0.003, Kav 0.570 +/- 0.009 and Kav 0.409 +/- 0.007, respectively. The predominant fasting from of IR PP chromatographed as peak 1, while peaks 2 and 4 were reduced in amplitude. The 1 h and 3 h postprandial chromatograms of HPLC profiles of plasma PP were similar in shape but lower in relative magnitude and amplitude. The authenticity of peak 4 as the migration of native PP1-36 was confirmed using purified IR native PP1-36 extracted from human pancreas. Partial amino acid sequence analysis of PP peak 3 revealed deletions of two N-terminal amino acid residues. The chemical identities of peaks 1 and 2 are unknown but appear to differ from PP in peaks 3 and 4 by virtue of their migration profiles. It is concluded that there are at least four distinct IR forms of PP in human plasma. Native PP1-36 accounts for less than 1% of total PP after an overnight fast and is about 1/3 of total postprandial IR plasma PP. Discernment of the nature and etiology of forms of PP in plasma may provide a new understanding of the role of PP in mammalian physiology.

Adult↗
PubMed1992

DNA relatedness, karyotyping and gene probing of Candida tropicalis, Candida albicans and its synonyms Candida stellatoidea and Candida claussenii.

Isolates of Candida albicans with varied phenotypes, including sucrose-negative variants (C. stellatoidea, serotypes A and B) and avirulent germ tube-negative forms (C. claussenii) showed significant (greater than 90%) DNA relatedness to classical C. albicans, but insignificant relatedness to C. tropicalis and sucrose-negative C. tropicalis. A transverse alternating-field gel electrophoresis procedure (TAFE) showed discrete karyotype patterns among the phenotypic variants of C. albicans including the sucrose-negative C. stellatoidea. The number of chromosome-sized DNA bands for C. tropicalis (7 bands) were within the range of bands observed for C. albicans (5 to 10 bands). The general DNA-migration pattern for C. albicans appeared distinct from that of C. tropicalis. An aspartyl proteinase (PrA) gene probe from C. albicans hybridized with chromosomal DNA from C. albicans, C. claussenii and C. stellatoidea but not with that from C. tropicalis.

Aspartic Acid Endopeptidases↗
PubMedDate not supplied

Acute tubular necrosis: use of gadolinium-DTPA and fast MR imaging to evaluate renal function in the rabbit.

Sequential fast magnetic resonance (MR) images (repetition time = 33 ms, echo time = 7 ms, alpha = 22 degrees, one image every 12 s) were acquired using gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) (10 or 100 mumol/kg) to study perfusion and concentrating ability in normal rabbit kidneys and in kidneys with HgCl2-induced acute tubular necrosis (ATN). In normal rabbits receiving 100 mumol Gd-DTPA/kg a concentric region of decreased MR signal was observed. In sequential images the dark ring pattern migrated centripetally through the kidney moving from the corticomedullary junction to the inner medulla. The decrease in MR signal intensity occurred as a consequence of T2 relaxation (magnetic susceptibility) due to high concentration of Gd-DTPA within the tubules. This suggests that the dark ring pattern may serve as a qualitative feature indicative of the ability of the kidneys to concentrate. With the onset of HgCl2-induced ATN the pattern of enhancement due to Gd-DTPA administration changed markedly. Although the kidneys with ATN did continue to be perfused, the concentric dark ring pattern seen in normal kidneys receiving 100 mumol Gd-DTPA/kg was not observed. These results suggest that Gd-DTPA and fast imaging MR may provide a method of assessing perfusion and concentrating ability within the healthy or diseased kidney.

Acute Kidney Injury↗
PubMed1998

Posterior epidural migration of an extruded lumbar disc fragment causing cauda equina syndrome. Clinical and magnetic resonance imaging evaluation.

STUDY DESIGN: Retrospective case report. OBJECTIVES: To illustrate the rare occurrence of cauda equina syndrome resulting from posterior epidural disc fragment migration documented by magnetic resonance imaging. SUMMARY OF BACKGROUND DATA: Disc fragment migration patterns are generally limited by the attachments of the posterior longitudinal ligament and its associated "midline septum" and "peridural" or "lateral membrane." The majority of symptomatic lumbar disc herniations are noted to be in a lateral position with resultant nerve root irritation. Although caudal, rostral, and lateral migration of disc fragments are common, posterior epidural migration of an extruded disc fragment has been reported only rarely, and only once in association with cauda equina syndrome. METHODS: The patient described in this report presented with an acute cauda equina syndrome. Investigation with magnetic resonance imaging revealed a posterior epidural mass, which was hypointense on T1-weighted and T2-weighted images. Postgadolinium imaging showed rim enhancement of the lesion. The preoperative differential diagnosis included epidural abscess, hematoma, or neoplasm. An urgent decompressive lumbar laminectomy was performed. At surgery, the lesion proved to be a massive extruded disc fragment. RESULTS: At the 1-year follow-up examination, the patient had recovered full motor, sensory, urologic, and sexual function. CONCLUSIONS: Extruded disc fragments may migrate posterior to the thecal sac. Magnetic resonance images of a posterior disc fragment may mimic those of other more common posterior epidural lesions.

Cauda Equina↗
PubMed1998

Modelling inter-ward migration in Hereford and Worcester: the importance of housing growth and tenure.

"In this paper, we use the 1991 Special Migration Statistics to analyse inter-ward flows in the British county of Hereford and Worcester. New modelling techniques...based on the Poisson distribution are used in this research which partially overcome the under-dispersion problem resulting from modelling zero and very small flows.... Analysis at this scale provides the potential for more detailed generalization about migration processes such as suburbanization, counterurbanization, intra-urban mobility, rural depopulation and the relationship between housing and demographic change at the local level. Unlike migration flows over long distances, which are often employment related, these flows are primarily motivated by residential requirements and housing type and growth are identified as key variables in the interpretation of these migration patterns."

Demography↗
PubMed2002

Identification of a mutated fibronectin as a tumor antigen recognized by CD4+ T cells: its role in extracellular matrix formation and tumor metastasis.

CD4+ T cells play an important role in orchestrating host immune responses against cancer, particularly by providing critical help for priming and extending the survival of CD8+ T cells. However, relatively little is known about major histocompatibility complex class II-restricted human tumor antigens capable of activating CD4+ T cells. Here, we describe the identification of a mutated fibronectin (FN) as a tumor antigen recognized by human histocompatibility leukocyte antigen-DR2-restricted CD4+ T cells. Deoxyribonucleic acid (DNA) sequencing analysis indicated that this gene contains a mutation that results in the substitution of lysine for glutamic acid and gives rise to a new T cell epitope recognized by CD4+ T cells. Tumor cells harboring the mutant FN resulted in the loss of FN matrix formation and the gain of metastatic potential based on the migration pattern compared with that of tumor cells that express wild-type FN. Additional experiments using cell lines stably expressing the mutated FN cDNA demonstrated that the point mutation in FN was responsible for the loss of FN staining in extracellular matrices and the enhancement of tumor cell migration. These findings represent the first demonstration that a mutated gene product recognized by CD4+ T cells is directly involved in tumor metastasis, which indicates the importance of CD4+ T cells in controlling the spread of tumor cells to distant anatomic sites.

Antigens, Neoplasm↗
PubMed2001

Human endothelial cell-derived nuclear proteins that recognise polymorphic DNA elements in the von Willebrand factor gene promoter include YY1.

Four common base-change polymorphisms have been found in the von Willebrand factor gene promoter: (-1793 C/G, -1234 T/C, -1185 G/A and -1051 A/G). All four polymorphisms are in strong linkage disequilibrium and recent reports have indicated these polymorphisms are associated with plasma vWF:Ag levels suggesting that one or more of these elements influence regulation of the vWF gene. We report that human endothelial cell-derived trans-acting factors display allelic preferences in binding activity to each polymorphic site. The common A allele variant of the -1051 polymorphism and the rarer A allele variant of the -1185 polymorphism provided specific binding of nuclear proteins. The G allele counterpart of these two variants did not produce any complex formation indicating that the nucleotide substitution at these positions alters the DNA binding ability of nuclear factors. The two alleles of the -1234 polymorphism produced two complexes with a similar migration pattern however stronger binding was found to the common T variant of this allele. Two specific complexes associated with the rarer G allele of the -1793 polymorphism, but only one associated with the C allele. Supershift experiments revealed that the trans-acting factor YYI recognised the slower migrating complex formed on the -1234 T/C and the -1051 A polymorphic sites with a strong binding preference for the -1234 T allele variant. The identification of YY1 as a component of the factors that recognise these elements suggests that this ubiquitous nuclear protein may play a role in the regulation of the vWF promoter.

Base Sequence↗
PubMed2005

Gene-flow between populations of cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) is highly variable between years.

Both large and small scale migrations of Helicoverpa armigera Hübner in Australia were investigated using AMOVA analysis and genetic assignment tests. Five microsatellite loci were screened across 3142 individuals from 16 localities in eight major cotton and grain growing regions within Australia, over a 38-month period (November 1999 to January 2003). From November 1999 to March 2001 relatively low levels of migration were characterized between growing regions. Substantially higher than average gene-flow rates and limited differentiation between cropping regions characterized the period from April 2001 to March 2002. A reduced migration rate in the year from April 2002 to March 2003 resulted in significant genetic structuring between cropping regions. This differentiation was established within two or three generations. Genetic drift alone is unlikely to drive genetic differentiation over such a small number of generations, unless it is accompanied by extreme bottlenecks and/or selection. Helicoverpa armigera in Australia demonstrated isolation by distance, so immigration into cropping regions is more likely to come from nearby regions than from afar. This effect was most pronounced in years with limited migration. However, there is evidence of long distance dispersal events in periods of high migration (April 2001-March 2002). The implications of highly variable migration patterns for resistance management are considered.

Analysis of Variance↗
PubMed1988

Early return of Sri Lankan migrants in the Middle East.

The author examines early return migration patterns of labor migrants from Sri Lanka in the Middle East. "Attention [is given] to the reasons why a considerable number of migrants return to their country of origin prematurely.... Differentials in the duration of stay in the host country, as well as some of the consequences of early return migration for the migrant and his family [are discussed].... The data used for this article are based primarily on a random survey held among 899 return migrants, 858 family members of current migrants and 409 non-migrants...[for] the period December 1985 to July 1986." (SUMMARY IN FRE AND SPA)

Africa↗
PubMed1992

International migrations in Europe: Polish perspectives for the 1990s.

"This article presents estimates of the size of emigration from Poland during the 1980s as well as projections concerning the migration patterns in the 1990s. The author anticipates a contraction of the volume of population outflow by some 50 percent: from about 100,000 to about 50,000 per year, on the average. These projections are based upon the examination of the role of a number of incentives and barriers to migration, including economic, demographic and political factors. In the final section, prospects concerning immigration to Poland are briefly discussed."

Demography↗
PubMed2004

Recent range expansion and low levels of contemporary gene flow in Calomys musculinus: its relationship with the emergence and spread of Argentine haemorrhagic fever.

The geographic distribution of haplotype diversity in the rodent Calomys musculinus, sampled from 16 wild populations of Argentina, was analysed on two geographical scales. The species is the natural reservoir of the Junin virus, the etiological agent of the Argentine haemorrhagic fever (AHF). In all, 24 composite haplotypes were recognised in the mtDNA D-loop region. Haplotypes 1 and 2, internal in the network, were the most frequent and were present in almost all populations. The absence of large genetic gaps between widely distributed haplotypes, the existence of exclusive haplotypes in more than 50% of the sampled populations and the absence of isolation by distance at a macrogeographical scale are in support of the hypothesis of a recent range expansion of the populations of the Humid Pampa, with low to moderate current gene flow. The dispersal of this opportunistic species would have been favoured by the explosive increments in density after agriculture was introduced. When only nearby populations within the endemic area of AHF were considered, a pattern of isolation by distance was detected. At present, genetic drift appears to be the main force acting to randomly differentiate C. musculinus populations, which would also lead to random differentiation of Junin virus strains and a reduction in the virulence of the pathogen in 'historic' AHF areas. The knowledge of migration patterns of the reservoir populations facilitates reliable prediction of the potential spread of the human disease.

Animals↗
PubMed2003

Reduced expression of P2Y1 receptors in connexin43-null mice alters calcium signaling and migration of neural progenitor cells.

Glial calcium signals play important roles during CNS development. Calcium transients induced by ATP, acting on purinergic receptors, stimulate DNA synthesis, increase astrocytic and neural stem cell proliferation, and are prominent during the differentiation of radial glia. We have shown previously that expression of P2Y receptors in astrocytes is altered when connexin43 (Cx43) is downregulated. To evaluate the consequences of Cx43 deletion on calcium signaling during neural progenitor development, studies were performed on neurospheres derived from embryonic striatum. After adhesion, cells migrating from wild-type (WT) and Cx43-null neurospheres displayed spontaneous calcium oscillations. Such activity was blunted by apyrase, 2'-deoxy-N6-methyladenosine 3',5'-bisphosphate (MRS-2179), and suramin, suggesting that ATP released by neural cells acts on purinergic receptors to induce calcium oscillations. The amplitudes of Ca2+ transients induced by P2Y but not P2X receptor agonists were larger in WT than in Cx43-null progenitors, suggesting that these two cell populations express different P2 receptors. Suramin, a nonselective P2 receptor antagonist, and MRS-2179, a P2Y1 receptor-selective antagonist, reduced the proliferation rate and the migration of WT progenitor cells to levels similar to those of Cx43-null cells. Conversely, exogenous expression of P2Y1 receptors in Cx43-null cells restored their migration pattern to levels seen in WT progenitors. However, treatment with P2 receptor antagonists did not alter the ratio of nestin to GFAP expression in WT neural progenitors. These data show that altered autocrine-paracrine communication attributable to reduced levels of P2Y1 receptors in neural progenitor cells lacking Cx43 affects proliferation and migration but not cell differentiation during early CNS development.

Adenosine Triphosphate↗
PubMed2003

Birds, migration and emerging zoonoses: west nile virus, lyme disease, influenza A and enteropathogens.

Wild birds are important to public health because they carry emerging zoonotic pathogens, either as a reservoir host or by dispersing infected arthropod vectors. In addition, bird migration provides a mechanism for the establishment of new endemic foci of disease at great distances from where an infection was acquired. Birds are central to the epidemiology of West Nile virus (WNV) because they are the main amplifying host of the virus in nature. The initial spread of WNV in the U.S. along the eastern seaboard coincided with a major bird migration corridor. The subsequent rapid movement of the virus inland could have been facilitated by the elliptical migration routes used by many songbirds. A number of bird species can be infected with Borrelia burgdorferi, the etiologic agent of Lyme disease, but most are not competent to transmit the infection to Ixodes ticks. The major role birds play in the geographic expansion of Lyme disease is as dispersers of B. burgdorferi-infected ticks. Aquatic waterfowl are asymptomatic carriers of essentially all hemagglutinin and neuraminidase combinations of influenza A virus. Avian influenza strains do not usually replicate well in humans, but they can undergo genetic reassortment with human strains that co-infect pigs. This can result in new strains with a marked increase in virulence for humans. Wild birds can acquire enteropathogens, such as Salmonella and Campylobacter spp., by feeding on raw sewage and garbage, and can spread these agents to humans directly or by contaminating commercial poultry operations. Conversely, wild birds can acquire drug-resistant enteropathogens from farms and spread these strains along migration routes. Birds contribute to the global spread of emerging infectious diseases in a manner analogous to humans traveling on aircraft. A better understanding of avian migration patterns and infectious diseases of birds would be useful in helping to predict future outbreaks of infections due to emerging zoonotic pathogens.

Animal Migration↗
PubMed1977

Skin penetration of infective hookworm larvae. III. Comparative studies on the path of migration of the hookworms Ancylostoma braziliense, Ancylostoma ceylanicum, and Ancylostoma caninum.

The lateral skin areas of nine hookworm-free puppies were exposed to infective larvae of Ancylostoma braziliense, Ancylostoma ceylanicum and Ancylostoma caninum. Serial sections, stained with Harris' haematoxylin and eosin, showed that many similarities exist in the migration patterns of the hookworm species used. However, striking differences were observed between Ancylostoma braziliense on the one hand and Ancylostoma ceylanicum and Ancylostoma caninum on the other hand with regard to the speed with which the penetration occurred. Larvae of Ancylostoma braziliense may travel directly from the epidermis into the dermis--apart from migration via hair follicle systems--a path of migration we did not observe in infections with the other species used. Larvae of Ancylostoma braziliense seem to pass the skin more rapidly than those of Ancylostoma ceylanicum and Ancylostoma caninum. Many larvae of Ancylostoma ceylanicum managed to penetrate the skin 2--6 h after the onset of the exposure.

Ancylostoma↗
PubMed1980

Action of Corn and Rice-inactivating Proteins on a Purified Nitrate Reductase from Chlorella vulgaris.

When nitrate reductase (NR) purified from Chlorella was incubated with NR-inactivating proteins purified from corn roots and rice cell suspension cultures or with trypsin there was a loss in NADH-NR and NADH cytochrome c reductase (NADH-CR) activities with time whereas the reduced methylviologen NR (MV-NR) remained active. When NADH-NR and NADH-CR activities were inactivated completely by the incubation with corn protein, the major protein band obtained by polyacrylamide gel electrophoresis shifted from an R(F) value of 0.12 to an R(F) of 0.25 and reduced MV-NR activity moved to the new position on the gel. When NADH-NR and NADH-CR activities were partially inactivated by the corn protein, NADH-NR activity was detected in an intermediate position (R(F) value of 0.18). Incubation with trypsin also caused a change in the NR protein migration pattern (R(F) value of 0.20). This protein band also had reduced MV-NR activity. Thus, the corn inactivator degrades NR in a fashion similar to but not identical with trypsin. The incubation of NR with rice inactivating protein resulted in a loss of NADH-NR but had no effect on the migration of NR protein or on the reduced MV-NR activity or mobility suggesting that the rice protein binds to Chlorella NR.

Journal Article↗
PubMed1986

Electrophoretic separation of the plus and minus strands of rotavirus SA11 double-stranded RNAs.

The genome of the rotaviruses consists of eleven segments of completely double-stranded RNA (dsRNA). To provide a method for separating and identifying the complementary plus and minus strand RNAs within these segments, we have characterized their migration patterns under denaturing conditions on agarose-urea gels. Virion-derived 3H-labelled dsRNAs were resolved by electrophoresis on a polyacrylamide gel and the individual genome segments recovered by electroelution. Upon electrophoresis in a low pH 1.75% agarose gel containing 6 M urea, the dsRNAs were denatured with complementary plus and minus strands migrating at different rates. Our results showed that, like cytoplasmic polyhedrosis virus but unlike human reovirus (Smith et al., 1981), rotavirus plus strand RNA migrates faster than its complementary minus strand on agarose-urea gels.

Electrophoresis, Agar Gel↗