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At least 451 records · Page 25Linked to original sources
PubMed1989

Planarians in toxicology. I. Physiology of sexual-only Dugesia dorotocephala: effects of diet and population density on adult weight and cocoon production.

A rare sexual-only race of Dugesia dorotocephala produces offspring from cocoons rather than by fissioning, allowing individuals to be accurately aged. Because each animal possesses fully developed male and female reproductive systems and a true brain with synapses, many types of toxicological studies which normally use vertebrates are possible with these animals. Prior to using this race for toxicological studies, a 3(3) factorial study was carried out to determine the effects of environmental conditions on reproduction and growth. The factors studied were crowding (2, 4, or 8 animals/50 ml medium), age (17, 19, 21 months), and type of dietary protein (soy, liver, cooked egg yolk). Protein composition dramatically affected the numbers of cocoons deposited per planarian, mean weight, and temporal patterns of weight changes. During 65 days of observation, planarians fed liver deposited an average of 3.28 cocoons/planarian while those fed soya or egg yolk deposited an average of 0.24 cocoon/planarian. Crowding, but not age, affected the numbers of cocoons deposited. Statistical analysis showed that protein composition, age, and crowding, alone and in factorial combinations, affected both the absolute weight changes and the temporal patterns in weight changes in each group.

Animals↗
PubMed2004

[Influence of rearrangement and cleaning of the peridomiciliary area and building disinsectization on sandfly population density in the municipality of Doutor Camargo, Paraná State, Brazil].

Phlebotomine sandfly captures were performed in the domicile, domestic animal shelters, and peridomicile before and after rearrangement, cleaning, and disinsectization. Phlebotomine sandflies were captured with Falcão traps from October 1998 to April 2000 in the Recanto Marista district, Doutor Camargo municipality, Paraná State. The results were compared with those from October 1996 to September 1997. In this survey, 122,616 phlebotomine sandflies were captured using 10 traps, as compared to 157,983 in the previous period, with 6 traps. Lutzomyia neivai predominated in both periods. During the former period an hourly average of 1,641.9 phlebotomine sandflies were captured as compared to 806.7 in the latter. The results with four traps installed in the same locations shows that the hourly average was 1,318.8 in the former period and 156.0 in the latter. The large reduction in the number of phlebotomine sandflies captured in the second period may be due to the impact of alterations in the environment and the disinsectization of the buildings after the first period.

Animals↗
PubMed1991

Effect of diet and population density on male turkeys under various environmental conditions. 2. Body composition and meat yield.

Large White Nicholas male turkeys were reared at two stocking densities (.21 or .46 m2 per bird) and fed one of four diets: 1) control corn and soybean (mash) with 1% fat (CSM); 2) as Diet 1, pelleted (CSP); 3) as Diet 1 with supplemental fat increasing from 1 through 8% with age (CSF); and 4) as Diet 1 with barley at 0, 20, 35, 50, and 65% during successive 4-wk periods (CSB). The turkeys were reared in four environments: (A) intermittent light schedule [4(2 h light (L):4 h dark D))] with temperature at 7 or 21 C during light and dark photoperiod, respectively; (B) and (D) with intermittent light (2L:4D) with a constant 21 and 7 C temperatures, respectively; (C) continuous light cycle (18L:6D) with temperatures as in Environment A. At 20 wk of age, two turkeys per replicate pen, were killed for determination of body composition and meat yield. Compared with turkeys fed CSM diet, those on CSF and CSP diet had increased percentage carcass fat. Meat yield per bird and percentage carcass fat were greater for turkeys reared at .46 m2 per bird compared with rearing at .21 m2 per bird. Pelleting and fat supplementation resulted in significantly increased amounts of breast meat and leg compared with CSM. Breast meat yield (percentage) and amount were greater at 7 C (Environment D) than at 21 C (Environment B) and the cycling regimen (Environment A). Percentage abdominal fat was greatest at 7 C. Interactions of environment and diet were detected for breast meat yield percentage (P less than .023) and weight (P less than .036). Diet type had no effect on percentage breast meat or weight in Environment C. An increased amount of breast meat was obtained by feeding CSP in Environments A, B, and D, and dietary fat supplementation increased breast meat yield in Environments A and D over CSM treatment.

Adipose Tissue↗
PubMed1983

Host availability limits population density of Panstrongylus megistus.

In order to determine whether host availability limits triatomine population growth, 5th-stage Panstrongylus megistus were maintained in feeding chambers containing 0, 1, 2, or 3 mice. During the 5-day feeding period, triatomines exposed to two or three mice gained significantly more weight than did bugs exposed to one mouse. In addition, half of the bugs exposed to two or three mice molted, as compared to one-fifth of the P. megistus exposed to one mouse. Thus, weight gain and molting were related to host density. In contrast, bug mortality was related to the triatomine-mouse ratio, being greatest among bugs exposed to one mouse. Twenty-nine nonplastered mud-stick houses in a Chagas' disease endemic area were censused and examined for triatomines. About 70% of houses with greater than or equal to 4 persons contained dense bug populations, while only 20% of houses with 1-3 persons were densely infested. Moreover, blood-meal identifications demonstrated that two-thirds of the P. megistus collected from these houses fed on man. The density of triatomines present in infested houses is related to the number of persons available as hosts.

Animals↗
PubMed1989

Estimates of Egyptian culcine longevity in nature altered by fluctuations in biting population density.

Estimates of vectorial capacity (VC) depend upon longevity of mosquito field populations, and expected longevity is estimated from the parity rate of the population. Seasonal variation in parity rates confound estimates of longevity which may not reflect actual population survival but are induced by changes in the rate of emergence of female mosquitoes. By comparing parity rates and biting activity in natural population of 2 Culicine mosquitoes, Culex pipiens and Cx. antennatus, we found that parity rate was low in the beginning of the season and high at the end. Parity rate appeared least affected during the weeks with maximal daily biting activity. We conclude that estimates of VC are most accurately determined for the two vector species studied when mosquito biting activity is maximal.

Animals↗
PubMedDate not supplied

Statistical sensitivity for detection of spatial and temporal patterns in rodent population densities.

A long-term monitoring program begun 1 year after the epidemic of hantavirus pulmonary syndrome in the U.S. Southwest tracked rodent density changes through time and among sites and related these changes to hantavirus infection rates in various small-mammal reservoir species and human disease outbreaks. We assessed the statistical sensitivity of the program's field design and tested for potential biases in population estimates due to unintended deaths of rodents. Analyzing data from two sites in New Mexico from 1994 to 1998, we found that for many species of Peromyscus, Reithrodontomys, Neotoma, Dipodomys, and Perognathus, the monitoring program detected species-specific spatial and temporal differences in rodent densities; trap-related deaths did not significantly affect long-term population estimates. The program also detected a short-term increase in rodent densities in the winter of 1997-98, demonstrating its usefulness in identifying conditions conducive to increased risk for human disease.

Analysis of Variance↗
PubMed1982

[Effect of population density during raising on amino acid levels in the serum and various organs of broilers].

Experiments were carried out on a productional premise of controlled microclimate. Broilers were raised under one and the same conditions of keeping and feeding at two density values - 14 and 22 birds per 1 m2 of the flooring area. The level of amino acids was followed up in the blood serum, liver, and the red and white muscles of the broilers of the two groups. It was found that at higher rates of population (22 birds per 1 m2) the biotic-ecologic factors were influenced the integral effect being the activation of catabolism of proteins in the body of birds. At higher density the amount of amino acids in these organs was found to drop, changes being observed also in the amino acid profile. Nitrogen in the feed was also influenced positively in terms of its conversion into amine nitrogen.

Amino Acids↗
PubMed2003

Population densities of cockroaches from human dwellings in urban areas in the Republic of Korea.

Studies on the population and infestation rates of domestic cockroaches were conducted from September 1999 to October 2000 in 154 residences in 21 districts (dong) in Busan and 170 residences in 12 districts in Seoul, Republic of Korea, using sticky traps. Blattella germanica, Periplaneta americana and Periplaneta fuliginosa were collected from three different types of houses, apartments, single dwelling houses and multi-union houses (villa). B. germanica was the dominant species collected from all residences. P. fuliginosa was collected more frequently (0.2 and 0.7/trap) than P. americana (0.1 and 0.2/trap) in Busan and Seoul, respectively. Population indices for B. germanica in Busan were nearly twice as high (mean 6.4/trap) when compared to Seoul (mean 3.6/trap). Mean numbers of B. germanica (6.4/trap), P. americana (0.1/trap) and P. fuliginosa (0.2/trap) in Busan were not significantly different among the three residential types sampled. In Seoul, mean numbers of P. americana (0.2/trap) and P. fuliginosa (0.7/trap) were not significantly different among the residential types whereas B. germanica (3.6/trap) indices were significantly greater for houses (11.4/trap) than for apartments (2.0/trap). Except for single dwelling houses in Seoul, seasonal mean indices for B. germanica were not significantly different for these cities. Residential infestation rates of P. americana (8.2% and 0.6%) and P. fuliginosa (13.7% and 2.8%) were very low compared to the infestation rates of B. germanica (56.9% and 76.2%) throughout the study period in Busan and Seoul, respectively. Houses were most commonly infested with B. germanica (72.9% in Busan and 93.8% in Seoul), followed by apartments (54.2% in Busan and 68.3% in Seoul) and villas (43.6% in Busan and avg. 66.4% in Seoul). The infestation rates of the cockroaches were related to the residential types (P < 0.05).

Animals↗
PubMed2001

Effect of bacterial population density on germination wheat seeds and dynamics of simple artificial ecosystems.

Effect of the size of rhizospheric bacterial populations on germination of seeds and development of simple terrestrial "wheat plants--rhizospheric microorganisms--artificial soil" and "wheat plants-artificial soil" systems has been studied. Experiments demonstrated that within specify ranges in the inoculate, the rhizospheric bacteria are capable of increasing the yield of germinated seeds and stimulate the growth of plantlets. Germination of seeds inoculated with bacteria was either stimulated, or inhibited or remained at control levels depending on the amount of bacteria. Plant biomass growth and total photoassimilation has been found to depend on the amount of bacteria on the plant roots: the higher the amount of bacteria on plant roots, the smaller is the biomass of plants but the total photoassimilation is, higher. Thus, depending on the amount of bacteria on the roots of plants the system either increases the biomass of plants or increases the total photoassimilation, i.e. "pumps" carbon through itself involving bacteria. Grant numbers: N99-04-96017, N15.

Ecosystem↗
PubMed1976

Population density and regulation of cell division in 3T3 cells. I. Inorganic phosphate levels, uptake and release.

Triggering mechanisms for initiating density dependent inhibition of cell division in 3T3 cell monolayers are activated approximately two to three population doublings prior to cessation of cell division at monolayer confluency. This activation occurs at a critical contact cell density of approximately 8 X 10(3) cells/cm2. During this period there are selective controls on transport and storage of required low molecular weight nutrients. A possible correlation between orthophosphate and rates of cell division has been investigated. We have demonstrated a relationship between cellular concentrations of orthophosphate and initiation of density dependent inhibition of cell division. Prior to critical intercellular contact, the [Pi] in 3T3 is 10 mM. During critical contact, this concentration is quickly reduced to approximately 2 mM and remains at this concentration to confluency. Similar alterations do not occur in Py 3T3 cells, which maintain a concentration of approximately 2 mM Pi regardless of cell density. After confluent 3T3 cells are released from inhibition of cell division the [Pi] must increase several-fold before DNA synthesis commences. These are physiological changes in 3T3 cellular [Pi] as a function of cell density, and cannot be attributed to nutrient depletion, altered transport of Pi into the cell, increased [ATP], or increased [PPi] levels. The controlled modulation of [Pi] may regulate glycolysis and coordinate counter-ion changes (Ca++) may regulate mitochondrial activity.

Adenosine Triphosphate↗