Showing papers on "Population published in 1989"
Journal Article•
TL;DR: It is suggested that the natural selection against large insertion/deletion is so weak that a large amount of variation is maintained in a population.
11,521 citations
TL;DR: The relationship between the two estimates of genetic variation at the DNA level, namely the number of segregating sites and the average number of nucleotide differences estimated from pairwise comparison, is investigated in this article.
Abstract: The relationship between the two estimates of genetic variation at the DNA level, namely the number of segregating sites and the average number of nucleotide differences estimated from pairwise comparison, is investigated. It is found that the correlation between these two estimates is large when the sample size is small, and decreases slowly as the sample size increases. Using the relationship obtained, a statistical method for testing the neutral mutation hypothesis is developed. This method needs only the data of DNA polymorphism, namely the genetic variation within population at the DNA level. A simple method of computer simulation, that was used in order to obtain the distribution of a new statistic developed, is also presented. Applying this statistical method to the five regions of DNA sequences in Drosophila melanogaster, it is found that large insertion/deletion (greater than 100 bp) is deleterious. It is suggested that the natural selection against large insertion/deletion is so weak that a large amount of variation is maintained in a population.
11,417 citations
TL;DR: Two types of cloned helper T cells are described, defined primarily by differences in the pattern of lymphokines ynthesized, and the different functions of the two types of cells and their lymphokine synthesis are discussed.
Abstract: Effector functions in the immune system are carried out by a variety of cell types, and as our understanding of the complexity of the system expands, the number of recognized subdivisions of cell types also continues to increase. B lymphocytes, producing antibody, were initially distinguished from T lymphocytes, which provide help for B cells (1, 2). The T-cell population was further divided when surface markers allowed separation of helper cells from cytotoxic cells (3). Although there were persistent reports of heterogeneity in the helper T-cell compartment (reviewed below), only relatively recently were distinct types of helper cells resolved. In this review we describe the differences between two types of cloned helper T cells, defined primarily by differences in the pattern of lymphokines ynthesized, and we also discuss the different functions of the two types of cells and their lymphokines. Patterns of lymphokine synthesis are convenient and explicit markers to describe T-cell subclass differences, and evidence increases that many of the functions of helper T cells are predicted by the functions of the lymphokines that they synthesize after activation by antigen and presenting cells. The separation of many mouse helper T-cell clones into these two distinct types is now well established, but their origin in normal T-cell populations is still not clear. Further divisions of helper T cells may have to be recognized before a complete picture of helper T-cell function can be obtained.
7,814 citations
Journal Article•
TL;DR: A preliminary demarcation of a type of Bourgeois public sphere can be found in this article, where the authors remark on the type representative publicness on the genesis of the Bourgois Public Sphere.
Abstract: Part 1 Introduction - preliminary demarcation of a type of Bourgeois Public Sphere: the initial question remarks on the type representative publicness on the genesis of the Bourgois Public Sphere. Part 2 Social structures of the Public Sphere: the basic blueprint institutions of the public sphere the Bourgois family and the institutionalization of a privateness oriented to an audience the public sphere in the world of letters in relation to the public sphere in the political realm. Part 3 Political functions of the public sphere: the model case of British development the continental variants civil society as the sphere of private autonomy: private law and a liberalized market the contradictory institutionalization of the public sphere in the Bourgeois constitutional state. Part 4 The bourgeois public sphere - idea and ideology: publicity as the bridging principle between politics and morality, Kant on the dialectic of the public sphere, Hegel and Marx the ambivalent view of the public sphere in the theory of liberalism, John Stuart Mill and Alexis de Tocqueville. Part 5 The social-structural transformation of the public sphere: the tendency toward a mutual infiltration of public and private spheres the polarization of the social sphere and the intimate sphere from a culture-debating (kulturrasonierend) public to a culture-consuming public the blurred blueprint - developmental pathways in the disintegration of the bourgeois public sphere. Part 6 the transformation of the public sphere's political function: from the journalism of private men of letters to the public consumer services of the mass media - the public sphere as a platform for advertising the transmitted function of the principle of publicity manufactured publicity and nonpublic opinions - the voting behaviour of the population the political public sphere and the transformation of the liberal constitutional state into a social-welfare state. Part 7 On the concept of public opinion: public opinion as a fiction of constitutional law-and the social-psychological liquidation of the concept a sociological attempt at clarification.
6,328 citations
TL;DR: In this paper, a simple spectral cloud ensemble was proposed to provide realistic values of the thermal forcing by convection under various synoptic conditions, such as tropical penetrative convection, tradewind cumuli, and extratropical organized convection.
Abstract: Observational studies indicate that a mass flux approach may provide a realistic framework for cumulus parameterization in large-scale models, but this approach, through the introduction of a spectral cloud ensemble, leads normally to rather complex schemes. In this paper the question is addressed whether much simpler schemes can already provide realistic values of the thermal forcing by convection under various synoptic conditions. This is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection (GATE, Marshall Islands), tradewind cumuli (ATEX, BOMEX) and extratropical organized convection (SESAME-79) and then in a NWP model. The scheme considers a population of clouds where the cloud ensemble is described by a one-dimensional bulk model as earlier applied by Yanai et al. in a diagnostic study of tropical convection. Cumulus scale downdrafts are included. Various types of convection are represented, i.e., penetrative convection in c...
3,296 citations
TL;DR: A new method is described for estimating genetic relatedness from genetic markers such as protein polymorphisms based on Grafen's (1985) relatedness coefficient, which eliminates a downward bias for small sample sizes and improves estimation of relatedness for subsets of population samples.
Abstract: A new method is described for estimating genetic relatedness from genetic markers such as protein polymorphisms. It is based on Grafen's (1985) relatedness coefficient and is most easily interpreted in terms of identity by descent rather than as a genetic regression. It has several advantages over methods currently in use: it eliminates a downward bias for small sample sizes; it improves estimation of relatedness for subsets of population samples; and it allows estimation of relatedness for a single group or for a single pair of individuals. Individual estimates of relatedness tend to be highly variable but, in aggregate, can still be very useful as data for nonparametric tests. Such tests allow testing for differences in relatedness between two samples or for correlating individual relatedness values with another variable.
2,858 citations
TL;DR: Evidence from this study and other trials suggest that consideration should be given to a national programme of FOB screening to reduce CRC mortality in the general population.
2,778 citations
Book•
09 Nov 1989
TL;DR: The diversity of teleost fishes defining the problem organization of the text adaptive response to the environmental change and ways of studying the use of time and space are described.
Abstract: The diversity of teleost fishes defining the problem organization of the text adaptive response to the environmental change. Environmental and organismic constraints: body form and locomotion, respiration and gill structure, sensory capacities. Feeding: trophic categories in fishes, morphological adaptions for feeding, diet composition, temporal changes in diet composition, factors that determine the rate of food consumption, flexibility in the feeding ecology of fishes. Bioenergetics: structure of an energy budget, effects of environmental factors on metabolism, examples of energy budgets. Use of time and space: methods of studying the use of time and space, temporal patterns of fish movement, patterns of movement and the use of space. Growth: definition and measurement of growth, patterns of growth, factors affecting growth rates, modelling the growth of fishes. Reproduction: timing of reproduction, the site of reproduction, allocation of resources to reproduction, allocation to individual progeny, unusual reproductive strategies. Biotic interactions 1 predation and parasitism: predation, pathogens. Biotic interactions 11 competition and mutualism. Dynamics of population abundance and production: defining the population, estimation of fish abundance, measures of the rate of population change, measurement of mortality rates, patterns of mortality in fish populations, regulation of fish populations and the stock recruitment relationship, models of population growth, concept of production, measurement of production, bioenergetic basis of production, magnitude of population production. Life-history strategies: evolution of life-history patterns, cost of reproduction and the consequences, bioenergetics of life-history patterns, phenotypic plasticity of life-history traits, life-history patterns and exploitation. Fish assemblages: general patterns of species diversity, historical factors in species diversity, contemporary determinants of species diversity, examples of fish assemblages, community-wide properties.
2,565 citations
TL;DR: In this paper, the discrimination problem is defined as follows: e random variable Z, of observed value z, is distributed over some space (say, p-dimensional) either according to distribution F, or according to Distribution G. The problem is to decide, on the basis of z, which of the two distributions Z has.
Abstract: : The discrimination problem (two population case) may be defined as follows: e random variable Z, of observed value z, is distributed over some space (say, p-dimensional) either according to distribution F, or according to distribution G. The problem is to decide, on the basis of z, which of the two distributions Z has.
2,520 citations
TL;DR: The polymerase chain reaction (PCR) process is used to show that several randomly chosen simple sequence loci with different nucleotide composition and from different species show extensive length polymorphisms.
Abstract: Short simple sequence stretches occur as highly repetitive elements in all eukaryotic genomes and partially also in prokaryotes and eubacteria. They are thought to arise by slippage like events working on randomly occurring internally repetitive sequence stretches. This predicts that they should be generally hypervariable in length. I have used the polymerase chain reaction (PCR) process to show that several randomly chosen simple sequence loci with different nucleotide composition and from different species show extensive length polymorphisms. These simple sequence length polymorphisms (SSLP) may be usefully exploited for identity testing, population studies, linkage analysis and genome mapping.
2,428 citations
TL;DR: This discussion finds that the genetic structure of a population, in particular the genetic variance-covariance matrix for a set of important life-history traits, reflects the very recent past, describes the present and predicts the near-term future.
Abstract: Trade-offs represent the costs paid in the currency of fitness when a beneficial change in one trait is linked to a detrimental change in another. If there were no trade-offs, then selection would drive all traits correlated with fitness to limits imposed by history and design. However, we find that many life-history traits are maintained well within those limits. Therefore, trade-offs must exist. Trade-offs have played a central role in the development of life-history theory, from Gadgil & Bossert (1970), Charnov & Krebs (1973), Schaffer (1972, 1974a, b) and Bell (1980) on to the present. They have been measured through field observations (e.g. Clutton-Brock, Guinness & Albon, 1982, 1983), through experimental manipulations in laboratory (e.g. Partridge & Farquhar, 1981) and field (e.g. Askenmo, 1979), through -phenotypic correlations in the laboratory (e.g. Bell, 1984a, b) and through genetic correlations (e.g. Rose & Charlesworth, 1981a, b), to mention only a few of the more prominent studies. They have been reviewed by Stearns (1976, 1977), Bell (1980), Charlesworth (1980), Warner (1984), Reznick (1985), Partridge & Harvey (1985, 1988) and most thoroughly by Bell & Koufopanou (1986). In addition, the methods used to measure trade-offs have been the subject of criticism (Tuomi, Hakala & Haukioja, 1983; Partridge, 1987) and controversy (Reznick, Perry & Travis, 1986; Bell, 1986). The most prominent life-history trade-off involves the cost of reproduction. It has two major components, costs paid in survival and costs paid in future reproduction. Two approaches to analysing those costs were suggested by Williams: genetic costs represented by antagonistic pleiotropy (Williams, 1957) and phenotypic costs represented by negative correlations between current reproductive effort and future survival and reproduction (Williams, 1966a, b). A third, physiological approach to trade-offs has been developed by Hirshfield & Tinkle (1974) and Calow (1979), among many others (cf. Townsend & Calow, 1981). In this extensive discussion, a few points have not always received the attention they deserve: (1) That trade-offs can be measured and analysed at the level of the genotype, the phenotype and what lies between (intermediate structure) is well known and uncontroversial but it has not always been emphasized that each of those levels makes an essential contribution to our understanding. It is not a question of either genetic correlations or phenotypic correlations or physiological trade-offs but of how such measurements combine to deliver information about potential evolutionary responses. A study conducted at just one of these levels is likely to be of as little use as the information on the nature of the elephant delivered by one blind man holding its tail. (2) One can draw a useful distinction between intraindividual trade-offs for example, between the reproductive effort made by a female in one season and the probability that she will survive to the next season and intergenerational trade-offs for example, between a female's reproductive effort and the probability that her offspring will survive to the next season. Intraindividual tradeoffs (and only some of them) have received most attention but intergenerational trade-offs, which are arguably just as important, have been relatively ignored. They deserve more attention. (3) The genetic structure of a population, in particular the genetic variance-covariance matrix for a set of important life-history traits, reflects the very recent past, describes the present and predicts the near-term future. There is no logical or direct way to use the current genetic structure of a population to infer the trade-offs that constrained the past approach to the current state even if they occurred as recently as a few tens of generations ago (J. Travis, personal communication). (4) Our understanding of a trade-off can be described as first order (slope known), second order (curvature known) or third order (all details, including interaction effects, known). In a few cases we have reliable information about firstorder effects. In no case known to me do we have reliable information on second-order effects, which are important in the theory (e.g. Schaffer, 1974a). Measurement of third-order effects, however desirable (Pease & Bull, 1988), remains a matter for future research.
TL;DR: The purpose is to document the ubiquity and importance of intraguild predation and to establish a theoretical framework for its analysis, which is the first synthesis of IGP into a general work.
Abstract: Interactions between species are usually categorized as either competition (-), predation/parasitism (+ -), mutualism (+ +), commensalism (+ 0), or amensalism (-0). Intraguild predation (IGP) is a combination of the first two, that is, the killing and eating of species that use similar, often limiting, resources and are thus potential competitors. Intraguild predation is distinguished from traditional concepts of competition by the immediate energetic gains for one participant (the predator). It differs from classical predation because the act reduces potential exploitation competition. Thus, its impact on population dynamics is more complex than either competition or predation alone (see below). Our purpose is to document the ubiquity and importance of intraguild predation and to establish a theoretical framework for its analysis. A taxonomically widespread interaction, IGP significantly affects the distribution, abundance, and evolution of many species. One intriguing conclusion is that IGP promotes the occurrence of alternative stable states in many circumstances. Although sometimes recognized by theoreticians and empirically oriented biologists, this is the first synthesis of IGP into a general work.
Posted Content•
TL;DR: In this paper, the authors examined the process of selection into self-employment over the life cycle and the determinants of self employment earnings using data from the National Longitudinal Survey of Young Men (NLS) for 1966-1981 and the Current Population Surveys for 1968-1987.
Abstract: About 4.2 million men and women operate businesses on a full-time basis. Comprising more than a tenth of all workers, they run most of our nation’s firms and employ about a tenth of all wage workers. The fraction of the labor force that is self-employed has increased since the mid-1970s after a long period of decline.1 This paper examines the process of selection into self-employment over the life cycle and the determinants of self-employment earnings using data from the National Longitudinal Survey of Young Men (NLS) for 1966–1981 and the Current Population Surveys for 1968–1987.
TL;DR: Findings confirm the homology between IPSID and low-grade B-cell "Western" lymphomas arising in mucosa-associated lymphoid tissue and suggest that the follicular pattern sometimes seen in these lymphomas is caused by selective colonization of reactive follicles by CCL tumor cells.
Abstract: We performed a detailed histological and immunohistological study on both fresh-frozen and paraffin-embedded tissue from full-thickness jejunal biopsy specimens taken from three patients with immunoproliferative small-intestinal disease (IPSID). In all three patients, the mucosal infiltrate consisted of "centrocyte-like" (CCL) cells forming lymphoepithelial lesions and plasma cells. In one patient, the mucosal infiltrate was strikingly follicular. Immunohistochemistry showed alpha 1 heavy chain, but no light chain, in the perinuclear space and cytoplasm of the CCL cells and in the plasma cells. In two patients, the plasma cells (but not the CCL cells) also contained alpha 2 heavy chain. In the case showing a follicular pattern, the extrafollicular CCL cells and most of the cells within the mucosal follicles expressed alpha 1 heavy chain, but a minor and variable population of cells expressed polytypic IgM. The dendritic reticulum cells stained for alpha 1 (but not alpha 2) heavy chain, mu chain, and both light chains. In all cases, the CCL cells did not stain for common acute lymphoblastic leukaemia antigen (CALLA); in the follicles, CALLA negative cells displaced a residual CALLA-positive population to the periphery and merged with the CALLA negative cells outside the follicles. These findings confirm the homology between IPSID and low-grade B-cell "Western" lymphomas arising in mucosa-associated lymphoid tissue; they suggest that the follicular pattern sometimes seen in these lymphomas is caused by selective colonization of reactive follicles by CCL tumor cells.
TL;DR: Comparison studies are needed of the validity, reliability, and responsiveness of generic and disease-specific measures in the same population and in minority and age-specific groups.
Abstract: Application of generic and specific measures of health status and quality of life to different diseases, conditions, states, and populations is increasing. Four strategies for using these measures are separate generic and specific measures, modified generic measures, disease-specific supplements, and batteries. The preferred strategy depends on project aims, methodological concerns, and practical constraints. Generic measures are necessary to compare outcomes across different populations and interventions, particularly for cost-effectiveness studies. Disease-specific measures assess the special states and concerns of diagnostic groups. Specific measures may be more sensitive for the detection and quantification of small changes that are important to clinicians or patients. Comparison studies are needed of the validity, reliability, and responsiveness of generic and disease-specific measures in the same population and in minority and age-specific groups.
TL;DR: In this article, the authors assessed clinically diagnosed Alzheimer's disease and other dementing illnesses in a geographically defined US community and found that the prevalence rate was strongly associated with the age of individuals.
Abstract: Clinically diagnosed Alzheimer's disease and other dementing illnesses were assessed in a geographically defined US community. Of 3623 persons (80.8% of all community residents over 65 years of age) who had brief memory testing in their homes, a stratified sample of 467 persons underwent neurological, neuropsychological, and laboratory examination. Prevalence rates of Alzheimer's disease were calculated for the community population from the sample undergoing clinical evaluation. Of those over the age of 65 years, an estimated 10.3% (95% confidence limits, 8.1% and 12.5%) had probable Alzheimer's disease. This prevalence rate was strongly associated with age. Of those 65 to 74 years old, 3.0% (95% confidence limits, 0.8 and 5.2) had probable Alzheimer's disease, compared with 18.7% (95% confidence limits, 13.2 and 24.2) of those 75 to 84 years old and 47.2% (95% confidence limits, 37.0 and 63.2) of those over 85 years. Other dementing conditions were uncommon. Of community residents with moderate or severe cognitive impairment, 84.1% had clinically diagnosed Alzheimer's disease as the only probable diagnosis. These data suggest that clinically diagnosed Alzheimer's disease is a common condition and that its public health impact will continue to increase with increasing longevity of the population. (JAMA. 1989;262:2551-2556)
TL;DR: An overview of research findings on the determinants and consequences of personal networks is presented and it calls for greater specification of the role of networks in migration research and for the inclusion of women in future research.
Abstract: Family, friendship and community networks underlie much of the recent migration to industrial nations Current interest in these networks accompany the development of a migration system perspective
TL;DR: The traditional model of industrial production is highly wasteful and ultimately unsustainable in contemporary society as mentioned in this paper and without change to a more integrated environmentally sound model of production waste pollution economic development and population growth will bury the earth.
Abstract: The traditional model of industrial production is highly wasteful and ultimately unsustainable in contemporary society. Without change to a more integrated environmentally sound model of production waste pollution economic development and population growth will bury the earth. While technology industrial advances and economic development have allowed significant improvements in the standard of living for segments of the worlds population unforeseen adverse side effects of global scale have also been borne. To allow sustained high standards of living among populations of more developed nations and foster development within developing nations traditional industrial activity must be reformed. All efforts should be made to optimize the consumption of energy and materials minimize the generation of waste and use processes effluents as the raw materials of others. Though challenging we must nonetheless strive toward rationalizing this goal. In discussing these issues and as support for this argument the authors cite examples of petroleum derivative conversion to plastics iron ore conversion to steel and platinum-group metals refinement for use as catalysts.
TL;DR: It is suggested that the strong excitatory drive brought about by the sharp wave-concurrent population bursts during consummatory behaviors, immobility, and slow wave sleep may be sufficient for the induction of long-term synaptic modification in the initiator neurons of the CA3 region and in their targets in CA1.
TL;DR: Changes in the senescent neutrophil that are associated with their recognition by macrophages are the subject of this investigation, and these processes may represent a mechanism for the removal of neutrophils during inflammation that also serves to limit the degree of tissue injury.
Abstract: Mechanisms governing the normal resolution processes of inflammation are poorly understood, yet their elucidation may lead to a greater understanding of the pathogenesis of chronic inflammation. The removal of neutrophils and their potentially histotoxic contents is one prerequisite of resolution. Engulfment by macrophages is an important disposal route, and changes in the senescent neutrophil that are associated with their recognition by macrophages are the subject of this investigation. Over 24 h in culture an increasing proportion of human neutrophils from peripheral blood or acutely inflamed joints underwent morphological changes characteristic of programmed cell death or apoptosis. Time-related chromatin cleavage in an internucleosomal pattern indicative of the endogenous endonuclease activation associated with programmed cell death was also demonstrated. A close correlation was observed between the increasing properties of apoptosis in neutrophils and the degree of macrophage recognition of the aging neutrophil population, and a direct relationship between these parameters was confirmed within aged neutrophil populations separated by counterflow centrifugation into fractions with varying proportions of apoptosis. Macrophages from acutely inflamed joints preferentially ingested apoptotic neutrophils and histological evidence was presented for occurrence of the process in situ. Programmed cell death is a phenomenon of widespread biological importance and has not previously been described in a cell of the myeloid line. Because it leads to recognition of intact senescent neutrophils that have not necessarily disgorged their granule contents, these processes may represent a mechanism for the removal of neutrophils during inflammation that also serves to limit the degree of tissue injury.
TL;DR: Targeted sampling provides a cohesive set of research methods that can help researchers study health or social problems that exist among populations that are difficult to reach because of their attributed social stigma, legal status, and consequent lack of visibility.
Abstract: This paper describes some of the efforts of an interdisciplinary research team investigating the transmission of human immunodeficiency virus (HIV), the causative pathogen associated with the acquired immunodeficiency syndrome (AIDS) and related conditions. The risk groups studied were injecting drug users and their sexual partners. Due to the clandestine nature of illicit drug use, we were faced with two interrelated problems: developing a scientific method to monitor the spread of the HIV infection among these drug users and their sexual partners, groups generally thought to be especially difficult to reach; and creating a health education intervention that would help stop the epidemic from spreading among this population and through them to other members of the community. The method we developed to sample injecting drug users is called targeted sampling. Although it incorporates some aspects of other well established sampling strategies, it is sufficiently different to be treated as a separate research method. Further, targeted sampling provides a cohesive set of research methods that can help researchers study health or social problems that exist among populations that are difficult to reach because of their attributed social stigma, legal status, and consequent lack of visibility.
TL;DR: The conclusion is that, although FST and rare‐alleles methods are expected to be equally effective in analyzing ideal data, practical problems in estimating the frequencies of rare alleles in electrophoretic studies suggest that FST is likely to be more useful under realistic conditions.
Abstract: Three methods for estimating the average level of gene flow in natural population are discussed and compared. The three methods are FST , rare alleles, and maximum likelihood. All three methods yield estimates of the combination of parameters (the number of migrants [Nm] in a demic model or the neighborhood size [4πDσ2 ] in a continuum model) that determines the relative importance of gene flow and genetic drift. We review the theory underlying these methods and derive new analytic results for the expectation of FST in stepping-stone and continuum models when small sets of samples are taken. We also compare the effectiveness of the different methods using a variety of simulated data. We found that the FST and rare-alleles methods yield comparable estimates under a wide variety of conditions when the population being sampled is demographically stable. They are roughly equally sensitive to selection and to variation in population structure, and they approach their equilibrium values at approximately the same rate. We found that two different maximum-likelihood methods tend to yield biased estimates when relatively small numbers of locations are sampled but more accurate estimates when larger numbers are sampled. Our conclusion is that, although FST and rare-alleles methods are expected to be equally effective in analyzing ideal data, practical problems in estimating the frequencies of rare alleles in electrophoretic studies suggest that FST is likely to be more useful under realistic conditions.
TL;DR: The theoretical and practical issues encountered in conducting the matching operation and the results of that operation are discussed.
Abstract: A test census of Tampa, Florida and an independent postenumeration survey (PES) were conducted by the U.S. Census Bureau in 1985. The PES was a stratified block sample with heavy emphasis placed on hard-to-count population groups. Matching the individuals in the census to the individuals in the PES is an important aspect of census coverage evaluation and consequently a very important process for any census adjustment operations that might be planned. For such an adjustment to be feasible, record-linkage software had to be developed that could perform matches with a high degree of accuracy and that was based on an underlying mathematical theory. A principal purpose of the PES was to provide an opportunity to evaluate the newly implemented record-linkage system and associated methodology. This article discusses the theoretical and practical issues encountered in conducting the matching operation and presents the results of that operation. A review of the theoretical background of the record-linkage...
TL;DR: The expected number of segregating sites and the expectation of the average number of nucleotide differences among DNA sequences randomly sampled from a population, which is not in equilibrium, have been developed and indicate that the number of segregation sites is influenced by the size of the current population more strongly than is theaverage number ofucleotide differences.
Abstract: The expected number of segregating sites and the expectation of the average number of nucleotide differences among DNA sequences randomly sampled from a population, which is not in equilibrium, have been developed. The results obtained indicate that, in the case where the population size has changed drastically, the number of segregating sites is influenced by the size of the current population more strongly than is the average number of nucleotide differences, while the average number of nucleotide differences is affected by the size of the original population more severely than is the number of segregating sites. The results also indicate that the average number of nucleotide differences is affected by a population bottleneck more strongly than is the number of segregating sites.
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TL;DR: In this article, the authors present an empirical analysis of the impact of the Mariel Boatlift on the Miami labor market, focusing on the effects on wages and unemployment rates of less-skilled workers.
Abstract: This paper presents an empirical analysis of the impact of the Mariel Boatlift on the Miami labor market, focusing on the effects on wages and unemployment rates of less-skilled workers. The Mariel immigrants increased the population and labor force of the Miami metropolitan area by 6-7 percent. Most of the immigrants were relatively unskilled: as a result, the proportional increase in labor supply to less-skilled occupations and industries was probably much greater. Nevertheless, an analysis of wages of non-Cuban workers in Miami over the 1979-85 period reveals virtually no effect of the Mariel influx. Likewise, there is no indication that the Boatlift lead to an increase in the unemployment rates of less-skilled blacks or other non-Cuban workers. Even among the Cuban population wages and unemployment rates of earlier immigrants were not substantially effected by the arrival of the Mariels.
TL;DR: It is suggested that the ratio-dependent form of the trophic function is a simple way of accounting for many types of heterogeneity that occur in large scale natural systems, while the prey- dependent form may be more appropriate for homogeneous systems like chemostats.
TL;DR: In neurones in which evoked GDPs were blocked by bicuculline, a NMDA‐mediated component was revealed by increasing the strength or the frequency of stimulation, and during the second week of postnatal life, superfusion with bicuciulline induced, as in adult slices, interictal discharges.
Abstract: 1. Intracellular recordings were made from rat CA3 hippocampal neurones in vitro during the first eighteen days of postnatal life. The cells had resting membrane potentials more negative than -51 mV, action potentials greater than 55 mV and membrane input resistances of 117 +/- 12 M omega. An unusual characteristic of these cells was the presence of spontaneous giant depolarizing potentials (GDPs) which were observed during the first eight postnatal (P) days in over 85% of neurones. They were less frequent between P9 and P12 (48%) and disappeared after P12. 2. The GDPs were synchronously generated by a population of neurones; they reversed polarity at -27 mV when recorded with KCl-containing electrodes and at -51 mV with potassium acetate- or potassium methylsulphate-filled electrodes. 3. The GDPs were blocked by bath application of bicuculline (10 microM) or picrotoxin (100-200 microM). Exogenously applied gamma-aminobutyric acid (GABA; 0.2-1 mM) induced at resting membrane potential a bicuculline-sensitive membrane depolarization which reversed polarity at -25 and -51 mV when recorded with KCl- or potassium methylsulphate-filled electrodes respectively. 4. The GDPs were reduced in frequency or blocked by the N-methyl-D-aspartate (NMDA) receptor antagonists DL-2-amino-7-phosphonoheptanoate (AP-7; 50 microM), D(-)2-amino-5-phosphonovalerate (AP-5, 10-50 microM) and (+-)3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP, 10-50 microM) or NMDA channel blockers phencyclidine (2 microM) and ketamine (20 microM). 5. Stimulation of the hilus during the first week of life evoked a GDP followed by a hyperpolarization. The GDPs were generated by a population of synchronized neurones and reversed polarity at -27 mV with KCl-filled electrodes and at -52 mV with potassium acetate- or potassium methylsulphate-containing electrodes. 6. Bath application of bicuculline (1-10 microM) or picrotoxin (100-200 microM) reversibly blocked the evoked GDPs in the majority of cells. The NMDA receptor antagonists AP-5 (50 microM), AP-7 (50 microM) and CPP (30 microM) usually reduced the amplitude and the duration of the evoked GDPs. In neurones in which evoked GDPs were blocked by bicuculline, a NMDA-mediated component was revealed by increasing the strength or the frequency of stimulation. 7. During the second week of postnatal life, when spontaneous GDPs were extremely rare or absent, superfusion with bicuculline (10 microM) induced, as in adult slices, interictal discharges. These reversed polarity near 0 mV with KCl- or potassium acetate-containing electrodes and were reduced in amplitude and duration by AP-5 (50 microM).(ABSTRACT TRUNCATED AT 400 WORDS)
TL;DR: In this article, minigene constructs representing the bcl-2-Ig fusion gene found at this chromosomal breakpoint were placed into the germ line of mice to assess the effects of the t(14;18) interchromosomal translocation during development.
TL;DR: In this article, a significant proportion of migration in low-income countries, particularly in rural areas, is composed of moves by women for the purpose of marriage, and the authors seek to explain these mobility patterns by examining marital arrangements among Indian households.
Abstract: A significant proportion of migration in low-income countries, particularly in rural areas, is composed of moves by women for the purpose of marriage. We seek to explain these mobility patterns by examining marital arrangements among Indian households. In particular, we hypothesize that the marriage of daughters to locationally distant, dispersed yet kinship-related households is a manifestation of implicit interhousehold contractual arrangements aimed at mitigating income risks and facilitating consumption smoothing in an environment characterized by information costs and spatially covariant risks. Analysis of longitudinal South Indian village data lends support to the hypothesis. Marriage cum migration contributes significantly to a reduction in the variability of household food consumption. Farm households afflicted with more variable profits tend to engage in longer-distance marriage cum migration. The hypothesized and observed marriage cum migration patterns are in dissonance with standard models of marriage or migration that are concerned primarily with search costs and static income gains.
TL;DR: In this paper, the authors developed an instrument that would permit the application of recent advances in self-esteem theory to the study of self-perception in the physical domain and developed four subdomain subscales designed to assess perceived bodily attractiveness, sports competence, physical strength, and physical conditioning.
Abstract: The purpose of this study was to develop an instrument that would permit the application of recent advances in self-esteem theory to the study of self-perception in the physical domain. Open-ended questionnaire responses were used to identify important contributors to the physical self-esteem of a college age population. Based on these data, four subdomain subscales designed to assess perceived bodily attractiveness, sports competence, physical strength, and physical conditioning were constructed along with a general physical self-worth subscale as the basis of the Physical Self-Perception Profile. The sensitivity, reliability, and stability of the subscales were supported for both genders across three independent samples. Exploratory and confirmatory factor analysis indicated the discriminant validity of the subdomain subscales, supporting the concept of multidimensionality within the physical domain. Zero-order correlation, partial correlation, and multiple regression analyses provided results consisten...