Population Growth Curves Research Articles

Autoregressive growth curves and Kalman filtering.

The first part of this paper describes how a Kalman filter can be used to construct maximum likelihood (ML) estimates of autoregressive (AR) and polynomial parameters in polynomial growth curves with AR-1 errors and irregularly-spaced data. The second part introduces a disturbed highest derivative polynomial (DHDP) as a model for growth curves. This model does not depend on regression coefficients. Variances of the highest derivative disturbance and the observation error are estimated (by ML) using a Kalman filter. The estimated DHDP growth curve is obtained by optimally smoothing the output of the filter. Equally spaced data is not required. The DHDP model and analysis are developed for an individual and extended to a population growth curve using data from many individuals with covariates.

Demographic Comments on the HANIHARA's Estimation of the Overseas Migrants to Ancient Japan

HANIHARA estimated the number of overseas migrants to ancient Japan during the 1, 000 years from the third century B. C. to the seventh century A. D. by employing a population growth model in conjunction with a morphological change model (J. Anthrop. Soc. Nippon, 95(3) : 391-403). Demographic comments in this article regard 1) the consistency in the equation for population simulation, 2) adequacy in hypothesizing annual migrants in the equation, 3) ways of evaluating the probable range of population growth rate during the thousand years, 4) the smooth connection of the population growth curve for the period concerned, in terms of the preceeding neolithic Jomon, and the succeeding historic times, and 5) others.

SEASONAL DISPERSAL AND HOST PREFERENCE BY ADULT SHARPNOSED LEAFHOPPERS (HOMOPTERA: CICADELLIDAE) IN NORTH CAROLINA WOODLANDS1

Scaphytopius spp. were sweep-sampled weekly from 20 April to 20 November 1984 in creeping blueberry, Vaccinium crassifolium Andrews, near a commercial blueberry field in North Carolina to establish migration patterns. Population growth curves of adults were compared to those of 5th-instar nymphs. Differences in curve patterns indicated adult dispersal from creeping blueberry during the first two generations and return in the 3rd generation. Adults were sampled in wild highbush blueberry, V. corymbosum L.; sheepkill, Kalmia angustifolic (Small); huckleberry, Gaylussacia frondosa (L.) Torrey & Gray; and creeping blueberry to determine inter-host dispersal and host preference. Analysis of variance on numbers of captured males showed significant differences between host species for S. magdalensis (Provancher), but none for S. verecundus (Van Duzee). The former species preferred sheepkill, highbush blueberry and huckleberry, while the latter was uniformly distributed among all four host species. It was recommended that sampling programs for wild S. magdalensis be conducted in huckleberry due to abundance of this host and ease of sampling.

Apoptosis induced by cold shock [formula omitted] is dependent on cell growth phase

Chinese hamster V79 fibroblast cells were exposed to brief periods of cold but non-freezing temperatures at different points on the population growth curve. Upon rewarming, cells at the transition from loarithmic to stationary growth exhibited apoptosis (programmed cell death). Cells in other stages of growth, or after reentry into logarithmic growth by refeeding, did not exhibit apoptosis. Apoptosis was expressed by marked cytoplasmic blebbing, by a characteristic non-random fragmentation of DNA into nucleosomal-sized pieces, and by loss of colony-forming ability. The data suggest that cold shock served as a stimulus for susceptible cells to undergo apoptosis. Thus, the experiments decribe a new in vitro system for studying the mechanisms of apoptosis.

Growth of Japanese Fetuses ‐Analysis from the Viewpoint of Population and Biological Growth Curves‐

AbstractIn 1984, Peter Dunn postulated that infants from 28 weeks ‘gestation till 18 weeks’ postnatal age who grow normally have almost identical potential growth velocities, regardless of racial and geographic differences. He suggested that the straight line growth curve in this period could be used as a perinatal growth chart for international reference. We composed biological growth curves for Japanese fetuses by eliminating data with risk factors for fetal growth, and compared them with the curves of Dunn. Our conclusions are as follows:1) Japanese population fetal growth curves correspond with the curve of Dunn between 28 and 38 weeks' gestation.2) Even in ideal conditions, flattening of fetal growth after 38 weeks' gestation always occurs.3) In the early postnatal period, infants grow with the same straight line velocity as during fetal growth between 28–38 weeks' gestation. Infants from 28 weeks' gestation to 18 weeks' postnatal age have an almost identical growth potential in spite of some degree of growth constraint in utero after 38 weeks' gestation.

Palynological Light on Tropical Rainforest Dynamics

Although there are more than a hundred Quaternary pollen diagrams from the non-arid tropics, very few are from strictly lowland ever-wet rainforest. Nevertheless, those from more upland or seasonal sites imply major changes of size and location of all tropical forests which must have had repercussions on the composition of and niche realization in the lowland ever-wet forest. Among the ecologically most important implications are that these features of the forest have been constantly changing at varying rates for at least a million years and still are changing. While it is no longer possible necessarily to associate diversity with changelessness, the alternative extreme view that diversity is the outcome of Quaternary environmental change has yet to be demonstrated palynologically. The courses of expansions of some trees in the early stages of establishment of an Australian rainforest in the Holocene are fitted to standard population growth curves and the significance of fine resolution pollen analysis for the study of rainforest ecology is demonstrated.

Palynological light on tropical rainforest dynamics

Although there are more than a hundred Quaternary pollen diagrams from the non-arid tropics, very few are from strictly lowland ever-wet rainforest. Nevertheless, those from more upland or seasonal sites imply major changes of size and location of all tropical forests which must have had repercussions on the composition of and niche realization in the lowland ever-wet forest. Among the ecologically most important implications are that these features of the forest have been constantly changing at varying rates for at least a million years and still are changing. While it is no longer possible necessarily to associate diversity with changelessness, the alternative extreme view that diversity is the outcome of Quaternary environmental change has yet to be demonstrated palynologically. The courses of expansions of some trees in the early stages of establishment of an Australian rainforest in the Holocene are fitted to standard population growth curves and the significance of fine resolution pollen analysis for the study of rainforest ecology is demonstrated.

A simulation model for the management of vicuña populations

The population dynamics of the vicuña was modelled based on field data from the Central Galeras Sector, Perú. Rains were simulated in order to obtain net primary productivity and grass availability which act upon density-dependent fecundity and mortality. The model produces a population growth curve that tends to stabilize at densities around 100 vicuñas per km 2. Harvest and shearing processes were simulated as part of the vicuña population management model. Harvest was based upon a fixed threshold density D e below which no harvest occurs; for densities above D e harvesting is applied at a rate proportional to the difference between D e and the current population density (fixed escapement or ‘bang-bang’ harvest rule). Management optimization was analyzed by determining the optimal escapement density D e, which maximized either net profits or the number of animals harvested. Analyzing the results as cumulative totals over 20 years of simulation, an optimum harvest production was obtained for a D e of about 40 vicuñas per km 2, and maximum profit was obtained for a D e around 70 vicuñas per km 2. Analyzing the results of 20 years of simulation as annual averages with an original population density of 40 vicuñas per km 2, the harvest production and profits were maximized for a D e of 40 and 60 vicuñas per km 2, respectively. The model was validated using data from the Reserva Nacional San Guillermo, Argentina, where vicuña and guanaco populations coexist (although their interaction was not modelled). The sensitivity analysis was performed with three different techniques: (a) stepwise multiple linear regression, (b) visual graphic analysis based on a polar coordinates system, and (c) direct evaluation of the effect on management decisions. The curve shape parameters of the fecundity and mortality functions proved to be the most important ones in determining the outcome of the model.

DIAGNOSIS OF LESCH-NYHAN HETEROZYGOTES USING PERIPHERAL BLOOD: 97

Although carriers of deficient genes for Lesch-Nyhan syndrome are detectable using cultured fibroblasts or hair roots, peripheral blood has been insufficient specimen for the diagnosis. We have established a method using peripheral T-cells for the diagnosis of the heterozygotes. Mononuclear cells from five mothers of Lesch-Nyhan boys were stimulated with phytohemagglutinin and then maintained in the medium containing T-cell growth factor. The growing viable T-cells were then exposed to 6-thioguanine. Most of the cells were killed by the treatment, but after 2-4 days, rapid growth of 6-thioguanine resistant cells was observed. T-cells from Lesch-Nyhan boys were totally resistant to 6-thioguanine and normal T-cells were sensitive. We estimated the percentages of HGPRT negative cells among T-cell growth factor-responsive T-cells from each heterozygote by comparing the growth curves for these cell populations with those for mixed cell populations containing enzyme-negative (Lesch-Nyhan's cells) cells and positive (normal) cells in various ratios. The Lesch-Nyhan mothers were estimated to contain 5-40% enzyme negative T-cells, indicating that mosaicism is present in T-cell populations in heterozygotes and the carrier state for Lesch-Nyhan syndrome is detectable using peripheral blood.

Biologic bases for international fetal growth curves.

A simple, inexpensive method for assessing maternal nutritional status during pregnancy was sought to control for nutrition in the development of fetal growth curves for diverse populations. Triceps skinfold thickness was measured at intervals throughout pregnancy in 60 Ethiopian women. In normally nourished pregnancies this measurement increases in the first two trimesters and decreases in the third, reflecting early pregnancy storage of fat and its release in late gestation to meet the increasing energy needs of the fetus. Ethiopian women who had skinfold thickness increases and decreases as great as those in the United Kingdom (UK) had neonates as heavy as those in the UK. This may mean that Ethiopian fetuses have the same growth potential as those in the UK and that the same growth curves can be used for the two populations. Skinfold thickness measurements may be the means by which nutrition can be controlled as a growth factor in determining the intrinsic fetal growth potentials of diverse populations.

Modelling individual growth of the Antarctic krill Euphausia superba Dana

Growth of the Antarctic krill, Euphausia superba, is not easily determined from net catches nor from laboratory experiments. Therefore, in support of these methods, a phenomenological model was constructed which in its present state describes the growth of a single krill specimen under periodically limiting food conditions with summer seasons of variable lengths. Published data of krill body length vs. age and of the annual cycle of primary production of algae in the Drake Passage were used to formulate equations and to calculate growth curves. At 1,000 days after hatching, the model predicts a body length of 63 mm, growth being delayed by 380 days compared with constant, optimal feeding conditions. Final length, weight and time delay are related to the amount of food supplied and compared with published population growth curves.

Role of female behavior in controlling population growth in mice

Sex ratio does not appear to be a factor in generating the characteristic population growth curve. Freely growing populations of house mice, consisting of all females and one male, stopped their growth at approximately the same densities as normal sexratio populations used as references. The mechanism(s) of female control of population dynamics may be related to female aggressive behavior. As the all-female/one-male populations approached their maximum size, the females began to show wounding patterns and social hierarchies in much the same manner as males in populations with normal sex ratios. The male in each of the populations was severely wounded in the posterior region, and each lost its tail as a result of injuries which could have been inflicted only by the females. The female social hierarchy can be seen only when there has been reproduction and population growth. Assembled populations of all females rarely exhibit aggressive behavior. Female aggression becomes apparent only when the population approaches its maximum size and thereafter. These data are consistent with the hypothesis that males are competitive among themselves for territory and social rank, and ultimately to mate with the females. Other investigators have indicated that females respond to population size, which may reflect increased competition between the females with the establishment of territories. Thus female agression may control population growth, a role previously ascribed to male aggression.

12. The Population Growth Curve by E. C. Rhodes and Its Application to the Population of Japan(General Session,The 1982 Meeting of the Population Association of Japan,Meeting Reports)

12. The Population Growth Curve by E. C. Rhodes and Its Application to the Population of Japan(General Session,The 1982 Meeting of the Population Association of Japan,Meeting Reports)

A comparison of 3-parameter, single-species population models, in relation to the management of brushtail possums in New Zealand.

A range of published 3-parameter, single-species models are compared using possums in New Zealand as an example. Most models yield similar population growth curves and similar estimates of maximum sustainable yield (MSY). A new model of competition for refuges, and interactive models of competition for food, both yield growth curves peaked to the right. In the second case, the relationship between the shape of the curve and the parameters of the interactive model is described. Three management consequences of asymmetric (rightward-peaked) growth as opposed to logistic growth are discussed. First, where the animal is a pest a greater control effort is required to reduce density. Second, for sustained yield harvesting the best policy is an adaptive one which initially requires no knowledge of the shape of the growth curve. Third, sustainable yields may be 50% higher than those predicted by the simple logistic model.

Intrinsic resistance to the lethal effects of x-irradiation in insect and arachnid cells

Twelve cell lines representing 10 genera of three orders (Diptera, Lepidoptera, and Orthoptera) of the class Insecta and one cell line (Acarina) from the class Arachnida were examined to discern their sensitivity to the lethal effects of x-irradiation. Radiosensitivity was measured by a combination of colony formation and population growth curve techniques. Each of these arthropod cell lines is significantly more radioresistant than mammalian cells, though the degree of resistance varies greatly with order. Dipteran cells are 3 to 9 times and lepidopteran cells 52 to 104 times more radioresistant than mammalian cells. Orthopteran and acarine cells are intermediate in radiosensitivity between dipteran and lepidopteran cells. These cells, especially the lepidopteran, should be valuable in determining the molecular nature of repair mechanisms that result in resistance to ionizing radiation.

Longitudinal studies of fetal growth with the use of dynamic image ultrasonography

To characterize the growth of individual fetuses, serial measurements of the crown-rump length (CRL), biparietal diameter (BPD), head circumference (HC), and abdominal circumference (AC) were made at specified intervals of 2 to 3 weeks (between 6 to 8 weeks [conceptual age] and delivery) in 20 normal fetuses with known dates of conception. Values for the HC-AC ratio and the estimated fetal weight were also obtained from these data. Measurements of CRL were similar to those reported previously, except in those cases in which the follicular phase was prolonged or the fetal growth potential was reduced. Mathematical modeling demonstrated that the linear-cubic model was optimal for the BPD and HC growth curves, the linear model for the AC, and the linear-quadratic model for fetal weight. The HC-AC ratio could not be modeled adequately because of significant individual variability. Optimal models for average longitudinal growth curves were determined for the BPD, HC, AC, and fetal weight from individual growth curves. These average longitudinal curves were similar in shape, mean values, and variability to those obtained in previous cross-sectional studies. Statistical analysis indicated that the coefficients of the average longitudinal curves are not likely to change by more than 5% to 15% if the size of the sample is increased very significantly. These results indicate that the average longitudinal growth curves are good estimators of the true population growth curves.

Fitting and using growth curves.

A technique is presented for fitting and analyzing growth patterns using Gompertz, power, and exponential curves. Data collection involves measuring growth rate as a function of size. This is useful because growth rates at many different sizes can be measured at the same time, which removes the effect of environmental change from the observed growth pattern. Using size instead of age as the independent variable is important because size is usually more closely related to growth rate than is age. The particular technique presented here yields estimates of the variance of the curve parameters so that growth curves for different populations can be compared.

The Relationship of Human Behavior to Population Growth Curves

The Relationship of Human Behavior to Population Growth Curves

Prolonged "Ultra" Low-Dose-Rate Irradiation: Effects on Chinese Hamster Cell Population Growth, Survival, and Radiation Sensitivity

The apparent clinical efficacy of125 I implants of solid tumors and32 P as an intraperitoneal adjuvant in patients with early ovarian carcinoma has raised clinical interest in the radiobiology of continuous radiation at dose rates in the range of 10 rad/hr. Cell population growth, survival, and radiation survival curve characteristics were examined for two Chinese hamster lines, CHO and V-79. Nonconfluent monolayers of these cells were passed serially and maintained at 37°C in226 Ra fields with dose rates of 9.5 or 12.5 rad/hr. Cell population growth continued with an increased doubling time (T2) for long (4-12 weeks) intervals during which the surviving fraction (S.F.) initially decreased to the range 0.10-0.05 for prolonged periods (23-103 days) until an abrupt drop to less than 0.00001 occurred. During the prolonged stable period (re T2 and S.F.) no change in sensitivity to acute doses of X irradiation was observed in the asynchronous populations surviving the continuous radiations at 9.5 or 12.5 rad/hr.

Seasonality and Patterns of Natural Selection for Life Histories

I present a model to investigate the effects of density-dependent resource availability on per capita population growth rate. By considering a continuous time model of inclusive fitness, population losses as well as growth are essential determinants of phenotypic fitness. The outcome of natural selection for various life-history characteristics is dependent upon not only the shape of the life history-specific population growth curves, but also upon the form of the seasonality function. As the magnitude and length of a resource shortage period increases, the rate of decrease becomes a more important component of fitness. Seasonality is often characterized by (1) a period of population decrease, when natural selection favors functions which minimize somatic or embryonic mortality, and (2) a period of high resource availability when high somatic and gametic productivity are favored. Assuming that mean resource availability remains constant, seasonally deterministic and/or random variation in the availability...