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PubMed2003

High prevalence of overweight in a stable Spanish hemodialysis population: a cross sectional study.

OBJECTIVE: In the general population, the prevalence of overweight is high and is considered a mortality risk factor. In maintenance hemodialysis (MHD) patients reports regarding overweight and its predictors are scarce. Our aim was to evaluate the prevalence and predictors of overweight in MHD patients, supplemented with additional follow-up data on mortality. METHODS: Retrospective, observational, cross-sectional study of 190 white, noncomplicated patients on MHD recruited from 5 Spanish dialysis centers. Three anthropometric indexes were scored (relative body weight, skinfold thickness, and midarm muscle circumference), and body mass index (BMI) and dietary intake during a 5-day period were recorded. Patient survival was evaluated during a mean follow-up period of 25 +/- 20 months. RESULTS: Undernutrition (score < 7) was detected in only 15% of patients, and no patient had severe malnutrition (score < 4). The percentage of patients scored below 7, was similar in nondiabetics and type 2 diabetic patients, whereas it was significantly higher in type 1 diabetics (P =.002). Notably, 38% of patients (38% of nondiabetics, 50% of type 2 diabetics, and none of the type 1 diabetics) were overweight (BMI > or = 25 kg/m(2)). To evaluate the predictors of overweight, a stepwise logistic regression analysis was performed entering age, sex, time on dialysis, caloric intake normalized for ideal energy requirements, and protein intake. Overweight was independently influenced only by ageing (odds ratio [OR], 1.04; confidence interval [CI], 1.02-1.07; P =.0007) and female gender (OR, 2.05; CI, 1.09-3.86; P <.0001). By Cox proportional multivariate analysis, survival was positively influenced by BMI (RR, 0.88, CI, 0.79-0.97; P <.01). As expected, albumin also had a positive influence whereas age and diabetes had a negative influence on survival. This preliminary result suggests that a higher BMI may exert a protective role on survival. CONCLUSION: Overweight represents the predominant nutritional abnormality in our MHD population, especially in the elderly, women, and type 2 diabetics.

Age Factors↗
PubMed1996

A gradient from stable to cyclic populations of Clethrionomys rufocanus in Hokkaido, Japan.

A total of 31 years of abundance data from 90 populations of the grey-sided vole (Clethrionomys rufocanus) in northern Hokkaido (Japan) were analysed with respect to population dynamic characteristics. Both non-periodic and multi-annually periodic fluctuations occur among the studied populations. The length of the period varies from 2 to 5 years. The dynamics appear approximately linear on a logarithmic scale, and a log-linear stochastic difference model with one time-lag is found to recreate the periodograms of the time series. The deterministic (log-linear) component of these models determines the periodicity while stochasticity sustains the cycles. The dynamics of the Hokkaidian vole populations are found to vary clinally from the western coast eastwards and towards the interior of the study area. This gradient corresponds superficially to the latitudinal gradient seen in microtine populations in Fennoscandia. However, under close scrutiny, these gradients differ greatly: the Hokkaidian gradient is caused by a cline in delayed density dependence. Statistical delayed density dependence is more negative towards the east and the interior.

Animals↗
PubMed2005

Lineage restriction maintains a stable organizer cell population at the zebrafish midbrain-hindbrain boundary.

The vertebrate hindbrain is subdivided into segments, termed neuromeres, that are units of gene expression, cell differentiation and behavior. A key property of such segments is that cells show a restricted ability to mix across segment borders -- termed lineage restriction. In order to address segmentation in the midbrain-hindbrain boundary (mhb) region, we have analyzed single cell behavior in the living embryo by acquiring time-lapse movies of the developing mhb region in a transgenic zebrafish line. We traced the movement of hundreds of nuclei, and by matching their position with the expression of a midbrain marker, we demonstrate that midbrain and hindbrain cells arise from two distinct cell populations. Single cell labeling and analysis of the distribution of their progeny shows that lineage restriction is probably established during late gastrulation stages. Our findings suggest that segmentation as an organizing principle in early brain development can be extended to the mhb region. We argue that lineage restriction serves to constrain the position of the mhb organizer cell population.

Animals↗
PubMedDate not supplied

Trends in the economic status of the elderly, 1976-2000.

The economic well-being of elderly Americans (aged 65 or older) improved between 1976 and 2000. Overall, poverty rates fell during this period, median real income rose, and median income relative to the working-age population was relatively stable. Most population subgroups shared in the reduced poverty rates; however, the economic status of elderly Hispanics did not improve. This article attempts to explain those economic trends by identifying changes in five sources of income for the elderly and analyzing the changes in the context of demographic changes in the elderly populations over the past 25 years. As a result of increased longevity, for example, larger proportions of elderly men and women are now 80 or older, and smaller proportions are 65 to 69. Hispanics and Asian Americans make up a larger share of the elderly population and whites a smaller share. The fraction of women who are married has increased, the fraction who are widowed has fallen, and the fraction who are divorced has grown. Such demographic changes can greatly affect the economic status of subgroups as well as the overall elderly population. Of the five sources of income for the elderly, Social Security remains the most prevalent and important. While both the rate of receipt and the share of aggregate income from Social Security benefits stayed relatively steady over the past 25 years, the average real Social Security benefit increased because of rising wages. Income from assets, the second most important source of income for the elderly, fluctuated. Because the elderly are more likely to hold interest-bearing assets such as bonds rather than stocks, their asset income is responsive to changes in nominal interest rates and bond yields. Receipt of pension income increased during this period, although it leveled off during the 1990s. Factors contributing to this pattern include enactment of the Employee Retirement Income Security Act of 1974, which increased protections of pension benefits for spouses, and improved labor market opportunities for blacks and women. In recent years, defined contribution pension plans have become more prevalent than defined benefit plans, but the full effect of this change on pension income may not yet be apparent. After decades of decline, labor force participation rates of older men leveled out in the mid-1980s and then increased. For older women, the trend before the mid-1980s was flat, but since then rates have risen substantially. The increased use of part-time jobs or self-employment to ease the transition into retirement, the economic expansion of the 1990s, and the liberalization of the Social Security earnings test may all have contributed to those trends. Although the percentage of elderly people with earnings has increased only modestly in the past few years, the share of income from earnings has grown substantially--from 16 percent of income in 1984 to 23 percent in 2000. Finally, Supplemental Security Income (SSI) benefits are indexed for inflation but not for growth in real wages. As real incomes of the elderly rose, therefore, fewer elderly persons were eligible to receive SSI or, for those receiving SSI, were eligible for smaller benefits. The proportion of elderly persons receiving public assistance, primarily SSI, declined from 11 percent in 1976 to 5 percent in 2000.

Aged↗
PubMed1996

Scheduled sanitation to reduce stable fly (Diptera: Muscidae) populations in beef cattle feedlots.

Sanitation has been long recommended as a means of reducing stable fly, Stomoxys calcitrans (L.), populations at cattle feedlots, but there is little published research to support this recommendation. In each of the 2 yr of this study, 4 feedlots received complete sanitation and 4 feedlots received no cleaning. The objective was to have the initial cleaning done before 1 June and then to reclean as needed every 2 wk thereafter. The feedlots that were cleaned had significantly fewer flies than the uncleaned feedlots, with 50.9% fewer stable flies during the 1st yr and 36.2% fewer flies in the 2nd yr. These reductions were realized even though initial cleaning was not done by 1 June in either year: bad weather delayed completion until 20 June the 1st yr and 29 June the 2nd yr. Sanitation at cattle feedlots significantly reduces stable fly populations and sanitation may have been more effective if initial cleaning was done by 1 June.

Animals↗
PubMed1974

Biological populations with nonoverlapping generations: stable points, stable cycles, and chaos.

Some of the simplest nonlinear difference equations describing the growth of biological populations with nonoverlapping generations can exhibit a remarkable spectrum of dynamical behavior, from stable equilibrium points, to stable cyclic oscillations between 2 population points, to stable cycles with 4, 8, 16, . . . points, through to a chaotic regime in which (depending on the initial population value) cycles of any period, or even totally aperiodic but boundedpopulation fluctuations, can occur. This rich dynamical structure is overlooked in conventional linearized analyses; its existence in such fully deterministic nonlinear difference equations is a fact of considerable mathematical and ecological interest.

Ecology↗
PubMed1975

The inhibitory effects of MgCl2 on the inactivation kinetics of poliovirus by urea.

By analyzing the inhibitory effects of Mg-2+ on the three-stage urea inactivation curve of poliovirus, it was concluded that urea inactivates poliovirus via a two-step reaction as follows: urea initially converts the native virus into an intermediate state which is still infectious but is now highly sensitive to inactivation. This reaction is unaffected by Mg-2+ and is reversible. In the subsequent reaction, the sensitized virus is either irreversibly inactivated by urea or reversibly stablized by Mg-2+. In addition, the inactivation curve revealed that a fraction of relatively stable virus population was established in the presence of urea and that the size of this persistent virus population depended on the concentration of urea. It was not determined whether urea induced the formation of this stable fraction of virus or merely selected for a preexisting stable population of virus. However, evidence was presented that (1) the persistent virus population was not due to the depletion or inactivation of urea in the sample, (2) whatever stabilized the virus, it could not be removed or reversed by simple dilution as in the case of Mg-2+, (3) no excess stabilizing material was made to stabilize the addition of untreated virus and finally (4) the persistent virus population was resistant to that concentration of urea in which it was observed but could be further inactivated by a higher concentration of urea, only to result in a smaller fraction of persistent virus population.

Dose-Response Relationship, Drug↗
PubMed2005

Population dynamics with a stable efficient equilibrium.

We propose a game-theoretic dynamics of a population of replicating individuals. It consists of two parts: the standard replicator one and a migration between two different habitats. We consider symmetric two-player games with two evolutionarily stable strategies: the efficient one in which the population is in a state with a maximal payoff and the risk-dominant one where players are averse to risk. We show that for a large range of parameters of our dynamics, even if the initial conditions in both habitats are in the basin of attraction of the risk-dominant equilibrium (with respect to the standard replication dynamics without migration), in the long run most individuals play the efficient strategy.

Animals↗
PubMed2004

Stable association between strains of Mycobacterium tuberculosis and their human host populations.

Mycobacterium tuberculosis is an important human pathogen in virtually every part of the world. Here we investigate whether distinct strains of M. tuberculosis infect different human populations and whether associations between host and pathogen populations are stable despite global traffic and the convergence of diverse strains of the pathogen in cosmopolitan urban centers. The recent global movement and transmission history of 100 M. tuberculosis isolates was inferred from a molecular epidemiologic study of tuberculosis that spans 12 years. Genetic relationships among these isolates were deduced from the distribution of large genomic deletions, which were identified by DNA microarray and confirmed by PCR and sequence analysis. Phylogenetic analysis of these deletions indicates that they are unique event polymorphisms and that horizontal gene transfer is extremely rare in M. tuberculosis. In conjunction with the epidemiological data, phylogenies reveal three large phylogeographic regions. A host's region of origin is predictive of the strain of tuberculosis he or she carries, and this association remains strong even when transmission takes place in a cosmopolitan urban center outside of the region of origin. Approximate dating of the time since divergence of East Asian and Philippine clades of M. tuberculosis suggests that these lineages diverged centuries ago. Thus, associations between host and pathogen populations appear to be highly stable.

Humans↗