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PubMed2004

Estimating population density of the Formosan subterranean termite, Coptotermes formosanus(Isoptera: Rhinotermitidae) using the effective sampling area of in-ground monitoring stations.

The effective sampling area of a monitoring station, alpha, was calculated for several Coptotermes formosanus Shiraki colonies in Broward County, Florida, USA. A simple mark-recapture protocol provided data on termite station catch within a foraging range of a colony. Average recapture probability was 0.005 close to the release point (< 5 m) and declined to 0.0008 at a distance of 51 to 60 m. The relation between the log % termites recaptured was fitted with log distance, to determine P(x), the average proportion of captured termites that started at distance x from the release point. The effective sampling area was estimated by using P(x) and the equation, alpha 2 pi integral [ x P(x)] dx. Integrating this equation, an average estimate alpha that ranged from 0.607 to 14.5 m2 was obtained. Factors influencing the variation of alpha among the colonies are discussed. The effective sampling area estimated should be taken as a reliable estimator that translates subterranean termite catches into termite population density.

Animals↗
PubMed1997

Effect of population density on the early post-implantation mouse embryo growth in vitro.

OBJECTIVES: To investigate the relationship between embryo population density and embryo development in vitro. METHODS: Swiss Webster albino mice were used and blastocysts were flushed from the uterine horns. Various numbers of blastocysts were randomly assigned to separate 35 mm dishes and cultured for 9 days. RESULTS: The effect of duration of culture to the mean success rates was different as the number of embryos in the dish was changed. In early egg cylinder (EEC) stage, the mean success rate was a flat function of the number of embryos. But the mean success rate was a decreasing function in late egg cylinder (LEC) stage and the decreasing rate was faster in early somite (ES) stage. Interestingly, the mean success rate to ES stage was nearly constant when more than 10 embryos were cultured in one dish. CONCLUSION: The success rate to each developmental stage in vitro decreased as the number of embryos in the dish and the duration of cultured increased.

Animals↗
PubMed1998

[Apoptotic cell death of F9 mouse embryonal teratocarcinoma depends on cell population density].

Apoptosis, or programmed cell death, is an active process fundamental to the development and homeostasis of multicellular organisms. Mouse embryonal carcinoma F9 cell line was shown to express wild type p53 protein known to be one of the major regulators of apoptotic cell death. Herein we describe apoptosis-inducing conditions for F9 cells. The density reached by a cell population in culture is shown to be a factor of apoptotic death for both undifferentiated and induced to differentiation F9 cells. However, the relationships between population cell density and apoptosis induction are different in undifferentiated and differentiating cells.

Animals↗
PubMed1975

Some influences of population density on Hymenolepis diminuta in rats.

When measured 56 days postinfection the length, wet weight and dry weight of Hymenolepis diminuta were all found to decrease with increasing number of cysticercoids given up to 20. The mean position of the worms in 10, 12 and 20 worm infections is significantly posterior to that of 1, 2 and 5 worm infections and the worms are attached over a wider area of the intestine. Egg production by the worms was followed up to day 56 postinfection; the number of eggs produced per worm and even per rat decreased with increasing population density. Thus the best way to get most eggs and to maintain the parasite in the laboratory is to have rats infected with only one tapeworm. Rats given 1-20 cysticercoids showed a mean recovery of 100-65%, while rats given 40-200 cysticercoids showed a mean recovery ranging from 13 to 2%. In addition to 'normal' worms, defined as worms greater than 10 mm, small, most probably destrobilated, worms were found. In the 50 and 100 cysticercoid infections, worm recoveries were, respectively, 8% 'normal', 16% small, and 2% 'normal', 5% small. From the significantly lower recovery from heavy infections it is concluded that a deleterious factor is operating during the 8 weeks after the infection.

Animals↗
PubMedDate not supplied

Effect of climatic factors and population density on varicella zoster virus epidemiology within a tropical country.

Blood samples were collected from healthy subjects, aged 9 months-29 years in urban and rural communities from 4 distinct regions in Thailand, to determine the seroprevalence rate of varicella-zoster virus (VZV) antibody and its relationship with demographic, climatic, and socioeconomic factors. The overall seroprevalence rate was 52.8% and increased from 15.5% in the 9-month to 4-year-old group to 75.9% in the 20-29 year-olds. The age-adjusted seroprevalence was significantly higher in the cooler than in the warmer regions. In the warmer regions only, the age-specific seroprevalence was significantly higher in the urban population than in the rural population. In Thailand, climate is the main determinant of VZV seroprevalence. The delayed onset of natural immunity is more marked in warmer climate areas. Population density is a secondary determinant; in the warmer areas, the pattern of adolescent and adult susceptibility was greater in rural than in urban areas.

Adolescent↗
PubMed2004

The relationships of social participation and community ratings to health and health behaviors in areas with high and low population density.

Previous studies have linked social participation and community levels of trust with improved health status. We examined the associations between levels of community participation, self-reported community ratings (trust), and health within a public health surveillance survey conducted in Kansas (N=4601). Independent variables were individual ratings of their communities (excellent, very good, good/ fair, poor), and their involvement in community groups or organizations in the last 5 years (yes/no). Dependent variables were self-rated health status, depressive symptoms, physical activity, smoking, obesity, and binge drinking. After controlling for age, gender, race/ethnicity, education, and having a medical doctor, self-rated health status (p<0.001) and physical activity (PA) (p<0.001) were positively, and smoking (p<0.001) and depressive symptoms (p<0.001) were negatively associated with community ratings. Only PA (p<0.001) remained associated with community involvement in a multivariate analyses. Multilevel analysis using county-level data showed no significant interactions between population density and dependent variables. Individuals from rural areas had the highest community involvement but relatively low levels of community ratings. Our findings suggest that individuals in rural areas, especially in densely settled rural areas, may face increased risks of poor health.

Adolescent↗
PubMed1979

Mangabey(Cercocebus albigena). Social organization and population density in relation to food use and availability.

Data are presented on the feeding behavior and activities of mangabeys (Cercocebus albigena) in the Ngogo study area, Kibale Forest, Uganda. Mangabeys spend 47% of activity observations feeding, 27% moving, and the remainder of the activity observations is accounted for by grooming, playing, vocalizing, copulating, etc. Feeding on fruit constitutes 58% of feeding records, arthropods 25%, young leaves and flowers 10%, cambium 5% and rare and unidentified items 2%. 29 tree species are used as sources of vegetable food and 31 tree species are used as substrate for arthropod search. Mangabeys move an average distance of 1,299 m per day, and use an average of 28,50 X 50 m quadrats per day. The activity patterns, the types and number of food species, the daily distances traveled, and the number of quadrats used per day, are not significantly different from those found in the literature for mangabeys in the Kanyawara research area, Kibale Forest, Uganda. Mangabey population density in Ngogo is approximately 1.46 times that of the Kanyawara mangabeys. The difference in density is associated with Ngogo exhibiting a greater mangabey food tree density than is found at Kanyawara. The higher mangabey density in Ngogo is associated with an average group size similar to that at Kanyawara, and an increase in the number of groups per unit area. The greater number of groups is accommodated by the mangabey having smaller home ranges, and less home range overlap than do the Kanyawara mangabeys. I suggest that these results are compatible with an interpretation based on disease control via regulation of group size, and social and spatial isolation between groups. The role of food availability in regulation of group size, or determining land tenure systems remains uncertain.

Animals↗
PubMed1984

Models for mineralization kinetics with the variables of substrate concentration and population density.

The rates of mineralization of [14C]benzoate by an induced population of Pseudomonas sp. were measured at initial substrate concentrations ranging from 10 ng/ml to 100 micrograms/ml. Plots of the radioactivity remaining in the culture were fit by nonlinear regression to six kinetic models derived from the Monod equation. These models incorporate only the variables of substrate concentration and cell density. Plots of the mineralization kinetics in cultures containing low, intermediate, and high initial substrate concentrations were well fit by first-order, integrated Monod, and logarithmic kinetics, respectively. Parameters such as maximum specific growth rate, half-saturation constant, and initial population density divided by yield agreed between cultures to within a factor of 3.4. Benzoate mineralization by microorganisms in acclimated sewage was shown to fit logistic (sigmoidal), Monod, and logarithmic kinetics when the compound was added at initial concentrations of 0.1, 1.0, and 10 micrograms/ml, respectively. The mineralization of 10 micrograms of benzoate per ml in sewage also followed logarithmic kinetics in the absence of protozoa. It is concluded that much of the diversity in shapes of mineralization curves is a result of the interactions of substrate concentration and population density. Nonlinear regression with models incorporating these variables is a valuable means for analysis of microbial mineralization kinetics.

Benzoates↗
PubMed2005

[The effect of population density on the elimination dynamics of a recessive lethal mutation from experimental populations].

Dynamics of the elimination of the temperature-sensitive lethal mutation l(2)M167DTS from experimental populations of Drosophila melanogaster under permissive conditions (25 degrees C) was studied. We have shown a rapid elimination of the mutation from the populations, selection for fitness of heterozygous individuals, association of the selection with high larval density and with the direction of the cross that had produced the founder males of the l(2)M167DTS/+ population, and the effect of relative competitive ability of l(2)M167DTS/+ males on the efficiency of the mutation introduction. Modification systems were shown be involved in fitness selection under conditions of high larval density.

Animals↗
PubMed1994

The anti-proliferative action of transforming growth factor-beta 1 on a rat intestinal epithelial cell line (RIE-1) is dependent on cell population density and culture passage number.

1. The proliferation of RIE-1 rat intestinal epithelial cells was potently but reversibly inhibited by transforming growth factor-beta 1 (TGF-beta 1). In early-passage cultures, complete growth arrest was observed when sparse cultures were treated with TGF-beta 1 (1 ng/ml). 2. However, increasing the initial cell culture density resulted in decreased TGF-beta 1-mediated inhibition of cell proliferation. 3. Independent of this population density effect, RIE-1 cells also exhibit a marked phenotypic transition around passage-8 to -10, such that later-passage cells were less responsive to growth inhibition by TGF-beta 1.

Animals↗
PubMed2006

Population density methods for stochastic neurons with realistic synaptic kinetics: firing rate dynamics and fast computational methods.

An outstanding problem in computational neuroscience is how to use population density function (PDF) methods to model neural networks with realistic synaptic kinetics in a computationally efficient manner. We explore an application of two-dimensional (2-D) PDF methods to simulating electrical activity in networks of excitatory integrate-and-fire neurons. We formulate a pair of coupled partial differential-integral equations describing the evolution of PDFs for neurons in non-refractory and refractory pools. The population firing rate is given by the total flux of probability across the threshold voltage. We use an operator-splitting method to reduce computation time. We report on speed and accuracy of PDF results and compare them to those from direct, Monte-Carlo simulations. We compute temporal frequency response functions for the transduction from the rate of postsynaptic input to population firing rate, and examine its dependence on background synaptic input rate. The behaviors in the1-D and 2-D cases--corresponding to instantaneous and non-instantaneous synaptic kinetics, respectively--differ markedly from those for a somewhat different transduction: from injected current input to population firing rate output (Brunel et al. 2001; Fourcaud & Brunel 2002). We extend our method by adding inhibitory input, consider a 3-D to 2-D dimension reduction method, demonstrate its limitations, and suggest directions for future study.

Action Potentials↗
PubMed2001

Population densities of hydrogenlike ions in a non-Maxwellian plasma.

In this paper we examine the effects of non-Maxwellian electron energy distributions on the population densities of excited atomic levels for hydrogenlike ions. We model the electron energy distribution function by two Maxwellian finite elements, one approximating the bulk distribution with temperature T(b) and the other the tail distribution with temperature T(t). We present results for various T(b)/T(t) ratios for Si XIV.

Journal Article↗
PubMed1993

Effects of population density and cadmium toxicity on growth and survival of blowflies.

The blowfly Lucilia sericata has been reared on artificial diets containing from 0 to 200 mg Cd kg(-1) at population densities ranging from 8 larvae per 4-g diet to 8 larvae per 32-g diet. Peak larval weight, development period, pupal weight, adult-emergence weight, and fecundity were measured. Larvae of blowflies respond to food deprivation by a reduction in larval weight and subsequent pupal and adult size. Contaminating the food supply with cadmium produced similar additive effects, reduced the growth rate, and increased the age of pupation. The results are of importance in determining the effects of environmental pollutants on population dynamics.

Journal Article↗
PubMed1992

Observations on population density of Culex quinquefasciatus and transmission indices of Bancroftian filariasis during and after Integrated Vector Management strategy.

An Integrated Vector Management strategy, implemented as an alternative to the conventional control operations that include mainly chemical control in Pondicherry, South India, reduced very substantially the population density of Culex quinquefasciatus. This resulted in drastic decrease in the intensity of transmission of bancroftian filariasis transmitted by Culex quinquefasciatus and consequently the incidence of new infections in children of 0-5 age group was minimized. When the IVM strategy was withdrawn after five years of implementation and conventional control measures were re-adopted, resilience of Culex quinquefasciatus population was observed and human exposure to the risk of infection increased. The results suggest that maintenance of vector density at reduced levels for prolonged periods, is necessary to control infectious diseases like filariasis, which is difficult in the present day urban situations in developing countries. Hence the emphasis should be on chemotherapy to achieve control of lymphatic filariasis.

Animals↗
PubMed2003

Efficient use of strong light for high photosynthetic productivity: interrelationships between the optical path, the optimal population density and cell-growth inhibition.

The interrelationships between the optical path in flat plate reactors and photosynthetic productivity were elucidated. In preliminary works, a great surge in photosynthetic productivity was attained in flat plate photoreactors with an ultra short (e.g. 1.0 cm) optical path, in which extremely high culture density was facilitated by vigorous stirring and strong light. This surge in net photosynthetic efficiency was associated with a very significant increase in the optimal population density facilitated by the very short optical path (OP). A salient feature of these findings concerns the necessity to address growth inhibition (GI) which becomes increasingly manifested as cell concentration rises above a certain, species-specific, threshold (e.g. 1-2 billion cells of Nannochloropsis sp. ml(-1)). Indeed, ultrahigh cell density cultures may be established and sustained only if growth inhibition is continuously, or at least frequently, removed. Nannochloropsis culture from which GI was not removed, yielded 60 mg(-1) h(-1), yielding 260 mg l(-1) h(-1) when GI was removed. Two basic factors crucial for obtaining maximal photosynthetic productivity and efficiency in strong photon irradiance are defined: (1) areal cell density must be optimal, as high as possible (cell growth inhibition having been eliminated), insuring the average photon irradiance (I(av)) available per cell is falling at the end of the linear phase of the PI(av) curve, relating rate of photosynthesis to I(av), i.e. approximately photon irradiance per cell. (2) The light-dark (L-D) cycle period, which is determined by travel time of cells between the dark and the light volumes along the optical path, should be made as short as practically feasible, so as to approach, as much as possible the photosynthetic unit turnover time. This is obtainable in flat plate reactors by reducing the OP to as small a magnitude as is practically feasible.

Adaptation, Physiological↗