Creating our Future — Some Concerns of an Environmentalist

1994 ◽  
Vol 1 (1) ◽  
pp. 83-86
Author(s):  
George Lewis
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Rapid Growth ◽  
Human Population ◽  
Doubling Time ◽  
Gold Coast ◽  
Population Doubling ◽  
Western World ◽  
Population Doubling Time ◽  
The Media

Australia is often described as having the fastest human population growth in the western world at 1.4 per cent per annum (ABS 1993). Queensland's growth rate in comparison is 2.52 per cent while the Gold Coast is currently experiencing 6.1 per cent which is equivalent to a population doubling time of 11 years. While such rapid growth is lauded in the media and discussed in glowing terms by economists, engineers and entrepreneurs, there are many others who in recent years have queried the wisdom of such rapidly increasing growth. In 1992 a group calling themselves The Union of Concerned Scientists, ‘comprising 1575 scientists from 69 countries, including a majority of Nobel laureates’ (Caswell 1) issued a ‘Warning to Humanity’ regarding the accelerating damage threatening humanity's global support systems. According to this group, ‘no more than one or a few decades remain before the chance to avert the threats we now confront will be lost and the prospects for humanity immeasurably diminished’. They refer specifically to over-consumption, poverty and spiralling populations: all of which we have in south-east Queensland.

scholarly journals Development and population growth of Hydra viridissima Pallas, 1766 (Cnidaria, Hydrozoa) in the laboratory

2008 ◽  
Vol 68 (2) ◽  
pp. 379-383 ◽  
Author(s):  
FC. Massaro ◽  
O. Rocha
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Generation Time ◽  
Doubling Time ◽  
Test Organism ◽  
Laboratory Culture ◽  
Individual Growth ◽  
Population Doubling ◽  
Population Doubling Time ◽  
The Individual

Hydras, the most representative freshwater Cnidaria, are of common occurrence in bodies of water in every continent except Antarctica. This study was planned with the aim of maintaining a population of Hydra viridissima in laboratory culture to enable the determination of the individual and population growth-rates of this species, as well as its population doubling time and generation time, with a view to employing these common animals as test-organisms in ecotoxicological assays. The organisms were maintained in reconstituted water at 20 ± 2 °C, illuminated at 800 lux with a photoperiod of 12 hours light: 12 hours dark, and were fed on neonates of the cladoceran Ceriodaphnia silvestrii (3 or 4 neonates per hydra, 3 times a week). The individual growth-rate (k) of the species was 0.43, the maximum length of the column 2.53 mm and the generation time 6.6 ± 1.5 days on average. The hydra population showed an intrinsic growth-rate (r) of 0.0468, according to the fitted curve, and a doubling time of 14.8 ± 2.63 days. Hydra viridissima is easy to grow in the laboratory and performs well in the conditions used in this study. It is thus a promising candidate test-organism for ecotoxicological studies.

scholarly journals Morphological and functional characteristics of cell culture derived from the mouse nail unit

2017 ◽  
Vol 5 (1) ◽  
pp. 62-66
Author(s):  
O. Kalmukova ◽  
A. Ustymenko ◽  
T. Lutsenko ◽  
P. Klymenko ◽  
V. Kyryk
Keyword(s):  
Cell Culture ◽  
Growth Rate ◽  
Doubling Time ◽  
Cultured Cells ◽  
Primary Cultures ◽  
Population Doubling ◽  
Synthetic Activity ◽  
Population Doubling Time ◽  
Proliferative Potential

Nail unit is a complex anatomical structure that is capable of rapid growth and regeneration throughout the life. Such significant reparative potential is associated with the presence different types of stem and progenitor cells, whose biology remains one of the fundamental issues today. Taking into account the active search for new stem cell sources for cell therapy, the view of the nail unit as a potential site for the localization of undifferentiated cells with stem potency is topical problem.Purpose. The study was conducted with an objective to establish the morphological, morphometric and proliferative characteristics of cultured cells isolated from the mouse nail unit.Materials and methods. Primary cultures of cells were obtained from tissue sampling, which included areas of the proximal nail fold, nail matrix and onychodermis of the FVB mouse nail organ. Cells were cultured in DMEM:F12 medium with 15 % fetal bovine serum during 6 passages. We determined the colony-forming activity, the population growth rate and doubling time, measured the area of cells, nuclei, and calculated the nuclear-cytoplasmic ratio. For cell morphology analysis, we used staining with Bemer’s hematoxylin and eosin, Heidenhain’s iron hematoxylin and May-Grünwald stain.Results. According to the morphological analysis in vitro the cells from mouse nail unit are heterogeneous with high synthetic activity and a low nuclear-cytoplasmic ratio – the features characteristic of the low-differentiated cells. The population doubling time of the culture was 80 ± 6.5 hours on average, the fastest growing cells were at the 4th passage (63 ± 7 hours). The specific growth rate for cell culture is low (0.01 ± 0.0007).The colony forming efficiency at the 5th passage was only 4 %. A significant number of colonies was small with large poorly proliferative cells, which may indicate a production of large numbers of transitional progenitor cells.Conclusion. The obtained cell culture from the mouse nail unit according to the analysis of their morphology, morphometry and proliferative potential is heterogeneous and requires the further development of pure culture technologies for the detailed characterization of separate subpopulations of cells.

scholarly journals Linking lineage and population observables in biological branching processes

2019 ◽  
Author(s):  
Reinaldo García-García ◽  
Arthur Genthon ◽  
David Lacoste
Keyword(s):  
Population Dynamics ◽  
Generation Time ◽  
Doubling Time ◽  
Branching Processes ◽  
Underlying Mechanism ◽  
Population Doubling ◽  
Population Doubling Time ◽  
Division Rate ◽  
Fluctuation Theorems ◽  
The Mean

Using a population dynamics inspired by an ensemble of growing cells, a set of fluctuation theorems linking observables measured at the lineage and population levels are derived. One of these relations implies inequalities comparing the population doubling time with the mean generation time at the lineage or population levels. We argue that testing these inequalities provides useful insights into the underlying mechanism controlling the division rate in such branching processes.

Paradoxically slow preadipocyte replication and differentiation in corpulent rats

1990 ◽  
Vol 258 (2) ◽  
pp. E368-E376 ◽  
Author(s):  
G. Shillabeer ◽  
J. M. Forden ◽  
J. C. Russell ◽  
D. C. Lau
Keyword(s):  
Adipose Tissue ◽  
Doubling Time ◽  
Tissue Growth ◽  
Population Doubling ◽  
Population Doubling Time ◽  
Sprague Dawley ◽  
Induced Differentiation ◽  
Sd Rats

We have investigated the in vitro rate of replication and differentiation of preadipocytes derived from lean (+/+) and obese (cp/cp) male JCR:LA-corpulent (cp) rats in an attempt to identify mechanisms that regulate adipose tissue growth. Cp/cp rats were twofold heavier than age-matched lean rats by 9-10 mo. Cp/cp-derived preadipocytes demonstrated an inherently slower rate of replication than +/+ preadipocytes (population doubling time: cp/cp 52.3 +/- 9.6 h vs. +/+ 19.7 +/- 1.6 h), although the preadipocyte pool in the cp/cp was significantly greater. Cp/cp preadipocytes were resistant to hormonally induced differentiation (19.9 +/- 9.4% of cells accumulated lipid) but differentiated when cocultured with mature adipocytes to the same extent as preadipocytes derived from Sprague-Dawley (SD) rats (cp/cp 48.4 +/- 15.2% vs. SD 52.2 +/- 11.9%). In contrast, SD preadipocytes did not differentiate in response to mature adipocytes from +/+ rats (13.8 +/- 5.2%). Our observations suggest that preadipocyte replication and maturation may not be controlled in a coordinated manner.

Impact of temperature and dissolved oxygen level on the population dynamics of naidids and their reproduction in biological activated carbon filters: a life table demographic study

2019 ◽  
Vol 19 (5) ◽  
pp. 1363-1370
Author(s):  
Xiao-Bao Nie ◽  
Yu-Qing Wu ◽  
Yuan-Nan Long ◽  
Chang-Bo Jiang ◽  
Li Kong
Keyword(s):  
Population Dynamics ◽  
Drinking Water ◽  
Activated Carbon ◽  
Life Table ◽  
Doubling Time ◽  
Population Doubling ◽  
Population Doubling Time ◽  
Biological Activated Carbon ◽  
Water Plant ◽  
Water Plants

Abstract Aquatic macro-organisms, such as naidids, propagate excessively in biological activated carbon (BAC) filters. This has become a troublesome problem for drinking water plants. For successful control of naidid contamination risk, it is necessary to determine the population dynamics under different environmental conditions within drinking water plants, with special emphasis on BAC filters. In this study, field studies of naidid distribution in a drinking water plant were conducted, and the effects of temperature and dissolved oxygen (DO) on naidid population dynamics were investigated using the life table method. The results indicated that naidid pollution in the water plant occurred seasonally and was induced by the excessive propagation of naidids in the BAC filters. Increased temperature and DO increased the naidid intrinsic rate of natural increase and decreased the naidid population doubling time. The life table method was also used to acquire the reproductive parameters of naidids in BAC filters based on simulative experiments. These results indicated that naidids can reproduce asexually in BAC filters, and the population doubling time was 12.60 days.

Adult human aortic smooth muscle cells in culture produce active TGF-beta

1993 ◽  
Vol 265 (2) ◽  
pp. C571-C576 ◽  
Author(s):  
H. L. Kirschenlohr ◽  
J. C. Metcalfe ◽  
P. L. Weissberg ◽  
D. J. Grainger
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Dna Synthesis ◽  
Doubling Time ◽  
Muscle Cells ◽  
Lung Epithelial Cells ◽  
Population Doubling ◽  
Population Doubling Time ◽  
Tgf Beta ◽  
Adult Human

Vascular smooth muscle cells (VSMC) from adult human aortas proliferated in culture in response to fetal calf serum (FCS) with a population doubling time of 70-85 h compared with 35 +/- 5 h for VSMC derived from adult rat aortas. Medium conditioned on cultures prepared from aortas from three different donors and mixed 1:1 with fresh Dulbecco's modified Eagle's medium plus 20% FCS [human conditioned medium (HCM)] reduced the rate of proliferation of rat VSMC by 46 +/- 6% (n = 3) after 48 h compared with cells in fresh medium. HCM did not reduce the proportion (> 65%) of rat VSMC that entered DNA synthesis but delayed entry into mitosis by at least 18 h. This effect was similar to previous observations of the action of transforming growth factor-beta (TGF-beta) on rat VSMC (G. K. Owens, A. A. Geisterfer, Y. W. Yang, and A. Komoriya. J. Cell Biol. 107: 771-780, 1988). A TGF-beta assay using DNA synthesis in mink lung epithelial cells confirmed that human, but not rat, VSMC in culture secrete active TGF-beta. Addition of a neutralizing antibody to TGF-beta to human VSMC in the presence of 20% FCS decreased the population doubling time from 74 +/- 3 to 46 +/- 6 h (n = 3). These observations demonstrate that the long population doubling time of human VSMC is due to the production of active TGF-beta and to an inhibitory autocrine loop.

scholarly journals Influences of Temperature on Development and Survival, Reproduction and Growth of a Calanoid Copepod (Pseudodiaptomus dubia)

2009 ◽  
Vol 9 ◽  
pp. 866-879 ◽  
Author(s):  
Changling Li ◽  
Xiaoxia Luo ◽  
Xianghu Huang ◽  
Binhe Gu
Keyword(s):  
Growth Rate ◽  
Water Temperature ◽  
Larval Development ◽  
Calanoid Copepod ◽  
Southern China ◽  
Larval Survival ◽  
Population Doubling ◽  
Population Doubling Time ◽  
Reproduction Rate ◽  
Egg Hatching

Pseudodiaptomus dubiais a calanoid copepod that is distributed widely in the estuarine-coastal waters of Asia and is a dominant copepod in the shrimp grow-out ponds in southern China. A laboratory culture experiment was conducted to evaluate the influences of water temperature on larval development, survival, and reproduction. Results indicate that within a temperature range from 15 to 35°C, larval development increases as the temperature increases. The water temperature for optimal larval survival rate ranges from 20 to 35°C. Longevity and egg hatching time decrease as the temperature increases from 20 to 35°C. Total fecundity and reproduction frequency increase as the water temperature increases, with the maximum at 30°C. Fecundity and reproduction frequency decrease when the temperature exceeds 30°C. Intrinsic growth rate (rm) ranges from 0.168 to 0.195 at 25 to 30°C; net reproduction rate (R0) and finite growth rate (?) are 163 to 264 and 1.183 to 1.215, respectively, when the temperature is greater than 20 and 35°C; population doubling time (t) varies from 3.556 to 4.128 days at temperatures less than 20 and 35°C. Population generation time (T) is negatively correlated with temperature, with the optimal population growth rate at 25 to 30°C.

scholarly journals Salinity and Population Parameters of Bald Eagles (Haliaeetus Leucocephalus) in the Lower Chesapeake Bay

The Auk ◽  
2006 ◽  
Vol 123 (2) ◽  
pp. 393-404 ◽  
Author(s):  
Bryan D. Watts ◽  
A. Catherine Markham ◽  
Mitchell A. Byrd
Keyword(s):  
Chesapeake Bay ◽  
Carrying Capacity ◽  
Doubling Time ◽  
Salinity Gradient ◽  
Bald Eagle ◽  
Population Doubling ◽  
Haliaeetus Leucocephalus ◽  
Population Doubling Time ◽  
Population Parameters ◽  
Nesting Density

Abstract We evaluated the relationship between salinity and Bald Eagle (Haliaeetus leucocephalus) population parameters using 26 years of survey data for the lower Chesapeake Bay. Tidal tributaries within the study area were stratified according to the Chesapeake Bay Program's segmentation scheme, and segments with the same salinity classification were considered spatial replicates. Salinity categories included tidal fresh, oligohaline, mesohaline, and polyhaline. Four parameters— colonization rate, nesting density, projected carrying capacity, and productivity— were derived from nesting data within each shoreline segment and compared across the salinity gradient. The study-wide Bald Eagle population is exhibiting exponential growth, with an average doubling time of 7.9 years. All population parameters showed significant directional variation with salinity. Average population doubling time for tidal fresh reaches was <6 years, compared with >16 years for polyhaline areas. Current Bald Eagle nesting density is negatively related to salinity and varies by a factor of 4 across the gradient. Comparison of current densities with projected carrying capacity suggests that these differences will be stable or increasing as the geographic areas approach equilibrium densities. We suggest that fisheries within lower saline reaches, including spring spawning runs of anadromous Clupeidae (shad and herring), are the most likely explanation for salinity effects. Observed distribution patterns suggest that lands along low-salinity waters are the core of the Bald Eagle nesting population within the lower Chesapeake Bay and should be the focus of long-term programs designed to benefit nesting eagles. Salinidad y Parámetros Poblacionales de Haliaeetus leucocephalus en la Bahia de Chesapeake

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