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At least 19 recordsLinked to original sources
PubMed1992

Blood chemistry and endoparasites of the mountain hare (Lepus timidus L.) in high and low density populations.

In order to study the effect of high population density on the condition, blood characteristics and helminth parasitism of mountain hares (Lepus timidus), 12 specimens were shot in December 1982 and 12 more in February 1983 on the west coast of central Finland (group 1, dense population). In addition 14 hares were shot in December 1982 about 100 km from group 1 (group 2, dense population). Group 3 consists of 15 hares from stable, rather low density populations shot in southern Finland during three previous winters. The hares in group 1 were the lightest, had the least fat and were the most seriously infected with Protostrongylus pulmonalis and Trichostrongylus retortaeformis, while those in group 2 were the heaviest and had the highest Ca, Mg, alkaline phosphatase and creatinine values. The group 3 hares had the most fat. The group 1 animals shot in February 1983 had higher Ca, Mg, triglyceride and cholesterol values than those shot in December 1982. It seems that high population density combined with a lack of suitable food leads to poor condition and high endoparasite abundances. The differences in Ca and Mg are probably due to diet. The higher creatinine values in group 2 and in the hares with little or no T. retortaeformis infection may be due to the greater muscle mass.

Adipose Tissue↗
PubMed1992

Effect of larval population density on dynamics of growth in Chrysomyia albiceps (Wiedemann). I. Effect of feeding behaviour and growth rate of larvae.

The feeding behaviour of uncrowded and crowded larvae differed as soon as feeding began. In case of high density populations, larvae tend to form dense clusters and this gregariousness is responsible for much of the injury and resulting predation. Larval growth rate had the same pattern up to 200 larvae per 20 grams meat, then this pattern greatly changed with the increase of densities. Larval survivorship remained high at densities up to 160 larvae per 20 gm meat, then decreased rapidly as larval density increased. The duration of larval development was extended and synchronization of larval pupal ecdysis was affected. Percentage of pupation and pupal weight were greatly decreased at high densities.

Animals↗
PubMed2025

Pervasive fitness trade-offs revealed by rapid adaptation to shifting population densities in large experimental populations of Drosophila melanogaster.

Trade-offs are an inherent feature of organismal biology that are expected play a fundamental role in the evolution of natural populations. Efforts to quantify trade-offs are largely confined to phenotypic measurements and the identification of negative genetic-correlations among fitness-relevant traits. Here, we use time-series genomic data collected during experimental evolution in large, genetically diverse populations of Drosophila melanogaster to directly measure the manifestation of trade-offs in response to fluctuating selection on ecological timescales. Specifically, we first conducted a lab-based selection experiment to quantify a genome-wide signal of antagonistic pleiotropy elicited in response to shifting population densities and associated with reproduction and stress tolerance selection. In doing so, we identified a putative role of two cosmopolitan inversions in these trade-offs. We then conducted an independent experiment to show that a simple manipulation of increasing population density under controlled lab-based conditions identified loci that are relevant to selection during population expansion and collapse in a complex, semi-natural setting. In concert, our results reveal how adaptation in complex, natural environments can be coarse-grained in such a manner to drive repeatable and predictable patterns of genomic variation, and further add credence to models positing a role of generic fitness trade-offs in the maintenance of variation in natural populations.

Drosophila melanogaster↗
PubMed1989

Effect of cage population density on plasma corticosterone and peripheral lymphocyte populations of laboratory mice.

The effect of different population densities of mice per cage on plasma corticosterone, peripheral lymphocytes and specific lymphocyte subpopulations was investigated. The animals were housed in groups of 2, 4 or 8 mice per cage and the blood samples were taken from each animal of these groups on days one, 7 and 14. A significant elevation (P less than 0.05) in plasma corticosterone concentration was observed in the group of 8 mice per cage on days one and 7 as compared with those of 2 or 4 mice per cage. The number of peripheral lymphocytes was significantly decreased in the groups of 2 (P less than 0.01) and 8 (P less than 0.05) mice per cage as compared with the group of 4 mice per cage on day one. A significantly decreased number of lymphocytes (P less than 0.01) in the group of 8 mice per cage continued to day 7. There were no significant differences in specific lymphocyte subpopulations observed among these groups. The results of this study suggest that a population density of 4 mice per cage induced minimal stress compared to that induced by the population densities of 2 or 8 mice per cage. Since stress is known to induce alteration in a variety of biological functions, the population density of mice per cage should be considered in the interpretation of research data.

Animals↗
PubMed1992

Demography of the Hadza, an increasing and high density population of Savanna foragers.

This is a report on the demography of the Hadza, a population of East African hunter-gatherers. In it, we describe the results of a census, and our estimation of age structure, survivorship, mean age of women at childbearing, number of live children, total population size and density, and rate of change since 1967. We show that relevant measures fit closely the stable population model North 6 chosen by Dyson to represent Hadza demography in the 1960s. We compare aspects of Hadza demography with surrounding non-Hadza and with the !Kung. Among other things, we find that the Hadza have a higher population density, higher fertility, and a faster population growth rate than do the !Kung. These demographic differences are consistent with our expectations, which were based on differences in the costs and benefits of foraging in the two regions. We also show that Hadza demographic parameters display remarkable consistency over the past 20 years. Since neighboring populations have been encroaching on the area used by the Hadza, and Hadza foragers have been subject to interludes of externally imposed settlement, this consistency is surprising. We discuss some of the implications.

Adolescent↗
PubMed1992

Population density and cancer incidence differentials in New York State, 1978-82.

Patterns of cancer incidence within five population density quintiles in New York State, exclusive of New York City, were investigated between 1978 and 1982. Sex-specific, standardized incidence ratios were calculated within each population density quintile for all cancer cases combined and for site-specific cancers based on cancer incidence patterns exhibited by the general population of New York State, exclusive of New York City. Areas with the highest population density demonstrated a 13 percent excess of cancer cases among males and a seven percent excess among females. In contrast, areas with the lowest population density exhibited lower cancer incidence, among both males (12 percent less) and females (12 percent less). Males demonstrated a significant, direct linear relationship between increasing population density and all cancer sites combined, and for cancers of the oral cavity and pharynx, esophagus, stomach, colon, rectum, liver, pancreas, larynx, lung, bladder, brain, and nervous system, and for Hodgkin's disease and multiple myelomas. Among females, a significant, direct linear relationship was observed between increasing population density and all cancer sites combined, and for cancers of the buccal cavity and pharynx, esophagus, stomach, lung, breast, and kidney. Malignant melanomas of the skin, and in situ and invasive cancers of the cervix exhibited unusual incidence patterns across the population density quintiles. These data are most useful in generating hypotheses for further studies to define specific etiologic factors operating within population density groupings. Population density, as measured in this investigation, may represent a surrogate measure for other factors which are related to cancer morbidity.

Female↗
PubMed1992

Broiler production under varying population densities.

The influence of population density on the growth performance and stress level of Hubbard x Hubbard chicks of equally mixed sex was studied. Six hundred and sixteen birds were housed under .05, .07, .09, or .11 m2 per bird (four replicates per density) from 0 to 7 wk. There were no treatment effects on feed conversion at 6 or 7 wk. Birds housed at .07, .09, and .11 m2 per bird had similar 7-wk BW and carcass weights, all significantly higher than birds housed at .05 m2 per bird. Under .05 m2 per bird, a higher percentage of breast blisters and ammonia burns (30%) was observed than at other densities. The 7-wk heterophil to lymphocyte ratios of birds raised at .09 and .11 m2 per bird (.42 and .45) were significantly higher than those at .05 and .07 m2 per bird (.28 and .30). Lowered BW and decreased carcass quality of birds raised at .05 m2 per bird suggested that these birds were stressed. However, decision analysis of economic potential indicated that the optimum profit potential per square meter was .05 m2 per bird for Maximax and Equally Likely decisions and .07 m2 per bird for the Maximin decision.

Animal Husbandry↗
PubMed1990

Population density and cancer mortality differentials in New York State, 1978-1982.

Patterns of cancer mortality within five population density quintiles in Upstate New York (New York State, exclusive of New York City), were investigated between 1978 and 1982. Sex-specific standardized mortality ratios (SMRs) were calculated within each population density quintile for all cancer deaths combined and for site-specific cancer deaths based on cancer mortality patterns exhibited by the general population of New York State, exclusive of New York City. Areas with the highest population density demonstrated a 12% excess of cancer deaths among males and a 6% excess among females. In contrast, areas with the lowest population density exhibited lower cancer mortality, among both males (9% less) and females (7% less). Males demonstrated a significant linear relationship between increasing population density and deaths for all cancer sites combined and for cancers of the oral cavity and pharynx, oesophagus, stomach, colon, gallbladder, pancreas, lung, prostate, and kidney. Among females, a significant linear relationship was observed between increasing population density and deaths for all cancer sites combined and for deaths due to cancers of the stomach, colon, liver and breast. Deaths due to cancers of the rectum, malignant melanomas of the skin, and cervix also exhibited unusual patterns of mortality across the population density quintiles. These data are most useful in generating hypotheses for further studies to define specific aetiological factors operating within population density groupings. Population density, as measured in this investigation, may represent a surrogate measure for other factors which are related to cancer morbidity and cancer mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1978

A graph analysis of the relationship between population density and social pathology.

This article deals with systematic variables--population density and pathological effects--at the level of a community or organizational system. Existing studies of the relationship between population density and social pathology (e.g., mortality, mental illness) in humans have failed to determine a strictly causal relationship between density and pathology in a linear model. They have not established a direct link between density and pathology in a simple two-variable, linear causal approach. Eliminating other variables by statistical control has obscured the conditions of a complex phenomenon. By incorporating socioeconomic variables into a general system model, this paper suggests that the total configuration of social organization, adaptation, previous group experience, and environment determine the effects of population density. Using a method of graph analysis, a model is presented of the relationship between population density and social pathology which has a high degree of isomorphism with the empirical situation.

Adrenocorticotropic Hormone↗
PubMed1989

[Tuberculosis morbidity in regions with a low population density].

Tuberculosis incidence was studied in the northern areas of Irkutsk Province with low population density. In the areas slower lowering of pulmonary tuberculosis incidence was noted. The main contingent of the new cases included persons with the disease detected during fluorographic examinations. In the areas with low population density, the percentage of the new cases with tubercle bacilli isolation and late diagnosis of tuberculosis was higher than in the areas with high population density. The influence of migration on the epidemiological status with respect to tuberculosis in the areas with low population density was less significant as compared to that in the areas with high population density.

Age Factors↗
PubMed1991

Population density alters the responsiveness of GH4C1 pituitary tumor cells to 17 beta-estradiol.

In this study we have examined the effect of population density on the ability of 17 beta-estradiol (E2) to induce PRL mRNA, DNA synthesis, and progesterone receptor in GH4C1 pituitary tumor cells. These parameters were examined at three subconfluent population densities that varied over a 4-fold range. The culture medium was changed daily in these experiments to reduce the possibility of nutrient depletion, medium toxification, or E2 metabolism. At the low population density, a 5-day treatment with E2 at a concentration of 1.0 nM resulted in an 8.1-fold increase in the level of PRL mRNA, as measured by the cytosolic dot blot procedure. At the intermediate density, E2 induced PRL mRNA 2.4-fold. At the high density, the level of PRL mRNA was reduced by 50% in response to 5 days of treatment with E2. The cytosolic dot blot procedure would reflect changes in the level of PRL mRNA per cell as well as changes in the number of cells per culture. Therefore, the level of beta-actin mRNA was also measured, assuming that it would remain constant on a per cell basis. When the level of PRL mRNA was normalized to the level of beta-actin mRNA in the same cytosols, E2 increased PRL mRNA 2.6-fold in the low density cultures and 1.9-fold in the intermediate density cultures, and had no effect on the level of PRL mRNA in the high density cultures. The effect of population density on the induction of GH4C1 cell proliferation by E2 was examined directly by measuring cellular DNA, thymidine incorporation by whole cells, and deoxythymidine triphosphate (dTTP) incorporation by isolated nuclei. At the low density, E2 initially stimulated GH4C1 cell proliferation, as evidenced by an increased rate of dTTP incorporation. However, this stimulatory effect was lost by day 5 of treatment, as the population density of the E2-treated low density cultures increased. At the high density, the inhibitory effect of E2 on dTTP incorporation was observed by day 2 of treatment and thereafter become more pronounced. These stimulatory and inhibitory effects of E2 were also revealed when the level of cellular DNA was measured. In contrast to the effects of population density on the induction of PRL mRNA and cell proliferation, an increase in density had no observable effect on the induction of progesterone receptor by E2. These data illustrate the critical importance of the culture environment in studies examining estrogen action in vitro.

Actins↗
PubMed1972

Relative population densities of Aedes albopictus and A. guamensis on Guam.

Aedes guamensis Farner & Bohart is indigenous to Guam but A. albopictus is known to have arrived in 1944. The larval ecology of the two species is very similar; both species breed in tree holes, coconut shells, and other natural and man-made water containers. The purpose of the study was to compare the relative densities of larval populations of the two species with those determined in a survey made in 1948-49. The results suggest that as the population density of A. albopictus increased, that of A. guamensis decreased by as much as about 95% in artificial containers, and by 30% or more in natural breeding habitats. Since there seems to be no environmental factor involved in rendering the breeding places unsuitable for A. guamensis, the reduction in A. guamensis populations may be, in part, the result of competition from A. albopictus.

Aedes↗
PubMed1986

The relationship of cancer incidence to terrestrial radiation and population density in Connecticut, 1935-1974.

The relationship of cancer incidence to terrestrial radiation and population density was investigated. Cancer incidence was obtained using 40 years of age-standardized data from the Connecticut Tumor Registry, and environmental radiation was estimated using data from an airborne gamma radiation survey of the entire state. These variables were examined ecologically, using the 169 towns of the state as the analytic units in a weighted regression analysis. The study design involves a large population base in a state having relatively high terrestrial radiation exposure levels overall and reasonable variation in exposure between towns. For all cancer combined, only one of the eight sex-specific analyses by decade yielded a significant radiation regression coefficient, and this was negative. In the sex- and site-specific analyses, almost all the coefficients for radiation were not significantly different from zero. In contrast, significant positive relationships of cancer incidence with population density were found for all cancer, for cancer of the lung for both sexes, for stomach, colonic, and prostatic cancer for males, and for lymphomas, thyroid, breast, and ovarian cancer for females. Both the radiation and population density relationships were adjusted for socioeconomic status. Socioeconomic status was significantly negatively associated with stomach and lung cancer in males and with cervical cancer in females; it was also positively associated with lymphomas and breast cancer in females. A power calculation revealed that, despite the relatively large size of this study, there was only a small probability of detecting a radiation effect of the strength anticipated from previous estimates.

Air Pollution, Radioactive↗
PubMed1989

[Population density as a regulation factor of genetic structure and size of animal populations. Phenotypic variability of reaction to increase in density in Drosophila populations].

The presence of considerable level of phenotypic variability for the nature of fertility change in conditions of imago density increase has been shown in Drosophila natural populations. Genetic peculiarities of insects play the main role in its determination. The genotype groups sensitive and stable to density increase exist in the populations. The former have relatively high fertility at low density and low fertility at overcrowding. The latter are of contrary nature of fertility at given density conditions.

Analysis of Variance↗
PubMedDate not supplied

[Method of mathematical description of the dynamics of cell population density].

The paper presents a method of building a mathematical model of the time dynamics of the cell population density and mitotic index which allows the prediction of the population growth as related to the cultivation conditions. The process of mammalian cell division has been shown to delay noticeably with a decrease of the cultivation temperature from 36 to 30 degrees C and an increase of the initial population density. The curve of the population density has a typical sigmoidal pattern.

Cell Division↗
PubMed1976

[Effects of the population density on growth of SD-JCL rats (author's transl)].

The effects of the population density on growth and life span of 21 to 26 months in SD-JCL-rats were investigated. The mean life spans of males and females were 23 and 24 months, respectively. The population density had no definite influence on increase in body weight of females, whereas a most accelerated growth of males was seen with 2 rats per cage. The total amounts of food intake of each animal throughout its life were about 15 and 11 kg for males and females, respectively, and those of water intake were about twice the food. No correlation was observed between the population density and the weights of the liver, kidney, heart and femur, though mals reared at 5 animals per cage had lightest adrenals among all the animals.

Adrenal Glands↗
PubMed1977

The association of population density, reduced space, and uncomfortable temperatures with misconduct in a prison community.

This study investigated the relation of population size, amount of personal space, and population density to the incidence of disruptive behavior over a 3-year period in a correctional institution for male youthful offenders. Population size was significantly correlated with the number but not the rate of disciplinary violations. The total amount of personal space and the index of population density were significantly correlated with both the number and the rate of violations. A post hoc analysis showed that the incidence of uncomfortably hot days had no relation to disruptive behavior. These results are contrasted with laboratory data on human crowding reporting no relation between population density and behavior pathology. It is suggested that the chronic high density explored in the present field study differs from temporarily crowded conditions produced in laboratory research on human crowding.

Adolescent↗