BMP signaling regulates Nkx2-5 activity during cardiomyogenesis.

Nkx2-5 regulates the transcription of muscle-specific genes during cardiomyogenesis. Nkx2-5 expression can induce cardiomyogenesis in aggregated P19 cells but not in monolayer cultures. In order to investigate the mechanism by which cellular aggregation regulates Nkx2-5 function, we examined the role of bone morphogenetic protein 4 (BMP4). We showed that the expression of the BMP inhibitor, noggin, was sufficient to inhibit the induction of cardiomyogenesis by Nkx2-5 during cellular aggregation. Furthermore, soluble BMP4 could activate Nkx2-5 function in monolayer cultures, resulting in the formation of cardiomyocytes. Therefore, BMP signaling is necessary and sufficient for the regulation of Nkx2-5 activity during cardiomyogenesis in P19 cells.

Nkx2-5 activity is essential for cardiomyogenesis.

The homeobox transcription factor tinman is essential for heart vessel formation in Drosophila. In contrast, mice lacking the murine homologue Nkx2-5 are defective in cardiac looping but not in cardiac myocyte development. The lack of an essential role for Nkx2-5 in cardiomyogenesis in mammalian systems is most likely the result of genetic redundancy with family members. In this study, we used a dominant negative mutant of Nkx2-5, created by fusing the repressor domain of engrailed 2 to the Nkx2-5 homeodomain, termed Nkx/EnR. Expression of Nkx/EnR inhibited Me(2)SO-induced cardiomyogenesis in P19 cells but not skeletal myogenesis. Nkx/EnR inhibited expression of cardiomyoblast markers, such as GATA-4 and MEF2C, but not of mesoderm markers, such as Brachyury T and Wnt5b, or of skeletal lineage markers, such as MyoD and Mox1. To identify the minimal region of Nkx2-5 that can trigger cardiomyogenesis, we analyzed the activity of various Nkx2-5 deletion mutants. The C-terminal domain was not necessary for the ability of Nkx2-5 to induce cardiomyogenesis and loss of this domain did not enhance myogenesis. Therefore, Nkx2-5 function is essential for commitment of mesoderm into the cardiac muscle lineage, and the N-terminal region, together with the homeodomain, is sufficient for cardiomyogenesis in P19 cells.

The dynamics of neighborhood age composition.

"In this paper we investigate the changing demography of [U.S.] neighborhoods. We focus upon the dynamics of the age structure of neighborhoods, paying particular attention to the roles of (a) the magnitude of mobility and (b) the age composition of in-migrants and out-migrants. A model for studying the changing age composition of neighborhoods is developed, and alternative scenarios characterized by the nature of in-movement and out-movement are examined to make statements about the age of householders in neighborhoods. We find that high rates of mobility may serve to bring about a relatively youthful equilibrium age structure quite rapidly, whereas low rates lead to a higher mean age and to damped harmonic fluctuations both in the mean age of householders and in the magnitude of the age heterogeneity of the neighborhood. In addition, we compare the evolutions of age structure in neighborhoods with age patterns of in-movement and out-movement that could typify areas of renters and areas of homeowners."

The geography of elderly minority populations in the United States.

"Because minority populations often have greater needs for health care and fewer resources to pay for it, it is important to assess the demand for services. This paper takes an initial step in that direction by focusing upon the geographic distribution of elderly minority populations in the United States. The study is carried out at several spatial scales, and it is concluded that elderly minority populations tend to be even more segregated than their non-elderly counterparts."

Surveillance systems for monitoring the development of spatial patterns.

Statistical methods concerned with the identification of temporal patterns may be classified into those that examine retrospectively a set of observations, and those that constitute surveillance systems that monitor changes as new observations become available. A similar distinction applies to the identification of geographical patterns in spatial data. There has been a notable lack of attention given to the surveillance of spatial pattern. This paper concerns development of a cumulative sum statistic and procedure for the monitoring of spatial pattern, and its application to both simulated data and to data on Burkitt's lymphoma in Uganda.

A generalization of Hewitt's test for seasonality.

BACKGROUND: Hewitt's statistic for seasonality in monthly data is the maximal rank sum among all possible rank sums derived using consecutive 6-month periods. In this paper, Hewitt's test is extended to include those instances where 3, 4 or 5-month pulses or periods of raised incidence are hypothesized. METHODS: Monte Carlo methods are used to drive the approximate distribution of the test statistic under the null hypothesis, when the length of the hypothesized period is k = 3, 4, or 5. A combinatorial method is used to derive exact levels for the test statistic. The test is applied to monthly data on adolescent suicide. Finally, the power of the test is compared with the chi2 statistic using Monte Carlo simulation. RESULTS: The distribution of the test statistic was found and used to test the null hypothesis of no seasonal variation in monthly adolescent suicides, using a period of k = 3 months. The null hypothesis was rejected, indicating seasonality in the data. Monte Carlo simulations show the test statistic to be more powerful than the chi2 statistic when sample sizes are small. CONCLUSIONS: This generalization of Hewitt's test should be most useful in those instances where the researcher wishes to carry out a quick and simple test of the null hypothesis of no seasonality against the alternative of a predetermined 3, 4, or 5 month period of raised incidence. When there is no a priori hypothesis about the appropriate length of period.

Geographic perspectives on elderly population growth.

"The proportion of a region's population that is elderly may change over time for many different reasons. The proportion may grow because of the net in-migration of elderly individuals, or it may grow because of the net out-migration of nonelderly residents. Furthermore, the proportion may grow if the number of nonmovers in the 'pre-elderly' cohort is relatively high. This paper discusses in detail the ways in which this proportion may change over time. This is complemented by a state-level empirical study of elderly population growth in the United States during the late 1980s. The spatial pattern of the rate of new entry into the elderly cohort among nonmovers is found to be particularly influential in determining changes in the proportion of a state's population that is elderly."

On the relationship between handedness and season of birth for men.

A sample of 8,929 male baseball players and a sample of 2,234 males from the U.S. National Health and Nutrition Examination Survey are used to assess the relation between handedness and season of birth. The results, when coupled with a further examination of the 1991 data of Dellatolas, Curt, and Lellouch, lead to the conclusion that those born during the spring and early summer are more likely to be left-handed than are those born during the fall and winter.

On the relationship between handedness and longevity.

During the past five years, there have been numerous studies of the relationship between handedness and longevity. In this report, I review previous contributions and use methods of survival analysis on a set of 4,448 males to determine the strength of the relationship between handedness and longevity. The results indicate that left-handers have small, yet significant, declines in survival probabilities between the ages of 65 and 85.

The effects of sex preselection on the sex ratio of families.

Advances in the potential for couples to predetermine the sex of their children will have significant consequences for many aspects of society. Among the likely demographic impacts are changes in both population size and the sex ratio. The aim of this article is to assess the effects of sex preselection on the sex ratio of families. The expected family sex ratio is derived and characterized for couples with particular preferences for the sex composition of their families. When couples desire k children of one sex and none of the other, the proportion of children in the completed family that are of the desired sex falls with increasing k. Constraints on total family size further reduce this proportion. When couples have a desire for a balanced composition of one boy and one girl, and when they have a preference for, say, a boy to be born first, they can expect a proportion of boys in the family that at first rises, and then falls, as sex preselection methods improve.

Buffon's needle and the estimation of migration distances.

"A procedure is suggested for estimating migration distances from data on the proportion of migrants crossing regional boundaries. The method makes use of Buffon's needle, a problem in geometrical probability from the eighteenth century.... The procedure is described for various scenarios that differ in their assumptions about region shape, the spatial distribution of population, and the distribution of migration distances. An application to migration distances in the United States is given, and additional attention is given to the estimation of intraregional migration distances." (SUMMARY IN FRE)

Feline haemobartonellosis: clinical, haematological and pathological studies in natural infections and the relationship to infection with feline leukaemia virus.

Haemobartonella felis infection was demonstrated in 38 cats which could be divided into four groups as follows: group A, feline leukaemia virus (FeLV) free cats with H felis infection alone; group B, FeLV free cats with H felis infection and other clinical conditions; group C, FeLV positive cats with H felis infection but no clinical manifestation of FeLV related or any other intercurrent disease; and group D, FeLV positive cats with H felis infection and clinical manifestations of FeLV related or other diseases. Cats in group A were healthy carriers of the infection and none was anaemic, whereas some in group B had clinical haemobartonellosis and anaemia. This anaemia was mainly mild, normocytic and normochromic. Most of the cats in group C and all in group D were more severely ill and anaemic, the anaemia usually being macrocytic and hypochromic. Splenomegaly occurred only in groups C and D. Treatment with tetracyclines did not eliminate H felis from any of the cats and blood transfusions were ineffective in promoting long term recovery from anaemia in cats with intercurrent H felis and FeLV infections. The findings in the cats in groups C and D were further compared with those in a fifth group of cats which were infected with FeLV but free of H felis.

Dynamic flow modeling with interregional dependency effects: an application to structural change in the U.S. migration system.

Causative matrix methods can be used to project levels of population change, to monitor changing migration trends, and to aid in forecasting movement during periods of consolidation and dissipation. They are appealing because they provide measures of the changing strengths of all interregional dependency effects. Separate competing destinations and competing origins perspectives on temporal change can be obtained. The column sums and the eigenvalues provide useful aggregate gauges of the relative strengths of regional shifts. Patterns of U.S. interregional migration from 1935 to 1982 are examined using the causative matrix approach. Trends in the gross migration streams underlying the dramatic increase in core-periphery net migration taking place in the 1970s are examined, as is a more recent shift in the major source area of core region net outflow.

Forecasting interstate migration with limited data: a demographic-economic approach.

"The limitations of available migration data preclude a time-series approach of modeling interstate migration [in the United States]. The method presented here combines aspects of the demographic and economic approaches to forecasting migration in a manner compatible with existing data. Migration rates are modeled to change in response to changes in economic conditions. When applied to resently constructed data on migration based on income tax returns and then compared to standard demographic projections, the demographic-economic approach has a 20% lower total error in forecasting net migration by state for cohorts of labor-force age."

Economic-demographic models for forecasting interregional migration.

"A class of spatial economic-demographic forecasting models is proposed. The models combine elements of traditional Markov and economic gravity models. A base-period probability structure is modified by the changing relative distribution of economic opportunity. Estimation issues are addressed, and an empirical application to US interstate migration during the late 1970s is described. It is contended that the framework represents a merger of past demographic and economic modeling traditions in a spatial interaction framework."

New directions in the modelling of interregional migration.

"This paper suggests two new approaches to modeling job-related migration. Both approaches are designed to simultaneously capture the inertia of past flows and information pertaining to economic conditions. One approach makes use of the incremental form of the logit model, and the other models the job application and competition process. Both techniques are illustrated using interregional migration flow data for the United States, and the results are compared with other migration models."

Wage distributions and spatial preferences in competitive job search and migration.

"Aggregate interstate migration data [for the United States] indicate that the majority of observed flows are from higher to lower wage states, quite contrary to the predictions of human capital theory. It is argued that a search theoretic framework may be used to complement and strengthen human capital theory. Such a framework may then include consideration of the flows of job information and aspects of job competition. A model is proposed for application to longitudinal micro-level data which overcomes a variety of theoretical and inferential problems and which remains within the bounds of empirical application." (summary in FRE, GER)

Interregional migration models with source and interaction information.

"Information flows in models of migration are emphasized. In particular, migrants are assumed to react to two types of information about job vacancies. 'Interaction information' may be defined as interpersonal communication between recent migrants and their former neighbors or friends, and 'source information' represents a direct flow of information from employers or agencies to individuals. Models are developed that investigate the effects of various communication rates and information retention levels on vacancy rates and labor-force population trajectories. It is found that attempts by planners to reduce regional inequities in vacancy rates through controlled advertising may be successful, but at the possible cost of increasing temporal fluctuations of regional vacancy rates."