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FEMS Microbiology Ecology Apr 2020Larval crowding represents a complex stressful situation arising from inter-individual competition for time- and space-limited resources. The foraging of a large number...
Larval crowding represents a complex stressful situation arising from inter-individual competition for time- and space-limited resources. The foraging of a large number of individuals may alter the chemical and bacterial composition of food and in turn affect individual's traits. Here we used Drosophila melanogaster to explore these assumptions. First, we used a wide larval density gradient to investigate the impact of crowding on phenotypical traits. We confirmed that high densities increased development time and pupation height, and decreased viability and body mass. Next, we measured concentrations of common metabolic wastes (ammonia, uric acid) and characterized bacterial communities, both in food and in larvae, for three contrasting larval densities (low, medium and high). Ammonia concentration increased in food from medium and high larval densities, but remained low in larvae regardless of the larval density. Uric acid did not accumulate in food but was detected in larvae. Surprisingly, bacterial composition remained stable in guts of larvae whatever their rearing density, although it drastically changed in the food. Overall, these results indicate that crowding deeply affects individuals, and also their abiotic and biotic surroundings. Environmental bacterial communities likely adapt to altered nutritional situations resulting from crowding, putatively acting as scavengers of larval metabolic wastes.
Topics: Animals; Drosophila melanogaster; Gastrointestinal Microbiome; Humans; Larva; Phenotype; Population Density
PubMed: 32221589
DOI: 10.1093/femsec/fiaa055 -
PloS One 2017Mast cells and basophils depend on aggregation of the high-affinity IgE receptor, FceRI, to initiate secretion. A variety of studies have shown that FceRI densities vary...
Mast cells and basophils depend on aggregation of the high-affinity IgE receptor, FceRI, to initiate secretion. A variety of studies have shown that FceRI densities vary 100 fold among subjects' basophils and it has been speculated that high densities might be responsible for unusual behaviors of the cells, notably sensitivity to certain monomeric IgE antibodies or spontaneous release. These studies experimentally examined the density dependence of spontaneous release and signaling element expression in subjects' basophils with FceRI densities ranging from approximately 6000 to 600,000 per cell. Through the use of numerical simulation, this study examined the expectations for spontaneous receptor aggregation and aggregate persistence at densities of FceRI ranging from 5000 to 500,000. Experimentally, FceRI density was not associated with greater spontaneous histamine release even when secretion was enhanced by the inclusion of deuterium oxide in the buffers. There was also no association of 15 activating or de-activating signaling elements with FceRI density. The numerical simulations demonstrated that at densities of ≈500,000 receptors, 13% of receptors were involved in transient aggregates at any given moment but that these aggregates rarely persisted for greater than 10 milliseconds. In contrast, a weak linear antigen aggregator, with ligand affinities known to induce secretion, would generate aggregates persisting for an average of ≈60 milliseconds. These results suggest that although a high density of FceRI likely produces a large number of transient aggregates, these aggregates do not persist long enough to induce signaling that results in secretion and do not induce the cells to alter their expression of several signaling elements known to be important in regulating secretion from human basophils. The results set some boundaries on the aggregation requirements for inducing histamine release from human basophils.
Topics: Basophils; Humans; Immunoglobulin E; Nuclear Proteins
PubMed: 28671980
DOI: 10.1371/journal.pone.0179734 -
Frontiers in Integrative Neuroscience 2022We report in a companion paper that in the mouse brain, in contrast to the 1,000-fold variation in local neuronal densities across sites, capillary density (measured...
We report in a companion paper that in the mouse brain, in contrast to the 1,000-fold variation in local neuronal densities across sites, capillary density (measured both as capillary volume fraction and as density of endothelial cells) show very little variation, of the order of only fourfold. Here we confirm that finding in the rat brain and, using published rates of local blood flow and glucose use at rest, proceed to show that what small variation exists in capillary density across sites in the rat brain is strongly and linearly correlated to variations in local rates of brain metabolism at rest. Crucially, we show that such variations in local capillary density and brain metabolism are not correlated with local variations in neuronal density, which contradicts expectations that use-dependent self-organization would cause brain sites with more neurons to have higher capillary densities due to higher energetic demands. In fact, we show that the ratio of endothelial cells per neuron serves as a linear indicator of average blood flow and glucose use per neuron at rest, and both increase as neuronal density decreases across sites. In other words, because of the relatively tiny variation in capillary densities compared to the large variation in neuronal densities, the anatomical infrastructure of the brain is such that those sites with fewer neurons have more energy supplied per neuron, which matches a higher average rate of energy use per neuron, compared to sites with more neurons. Taken together, our data support the interpretation that resting brain metabolism is not demand-based, but rather limited by its capillary supply, and raise multiple implications for the differential vulnerability of diverse brain areas to disease and aging.
PubMed: 35757100
DOI: 10.3389/fnint.2022.821850 -
Poultry Science Sep 2017Free-range laying hen systems are increasing in number within Australia. Variation in outdoor stocking densities has led to development of a national information...
Free-range laying hen systems are increasing in number within Australia. Variation in outdoor stocking densities has led to development of a national information standard on free-range egg labeling, including setting a maximum density of 10,000 hens per hectare. However, there are few data on the impacts of differing outdoor densities on production and egg quality. ISA Brown hens in small (150 hens) flocks were housed in identical indoor pens, each with access (from 21 weeks) to different sized ranges simulating one of three outdoor stocking densities (2 replicates each: 2,000 hens/hectare (ha), 10,000 hens/ha, 20,000 hens/ha). Hen-day production was tracked from 21 through 35 weeks with eggs visually graded daily for external deformities. All eggs laid on one day were weighed each week. Eggs were collected from each pen at 25, 30, and 36 weeks and analyzed for egg quality. There were no effects of outdoor stocking density on average hen-day percentage production (P = 0.67), egg weight (P = 0.09), percentages of deformed eggs (P = 0.30), shell reflectivity (P = 0.74), shell breaking strength (P = 0.07), shell deformation (P = 0.83), or shell thickness (P = 0.24). Eggs from hens in the highest density had the highest percentage shell weight (P = 0.004) and eggs from the lowest density had the highest yolk color score (P < 0.001). The amount of cuticle present did not differ between densities (P = 0.95) but some aspects of shell colors (P ≤ 0.01) and location of protoporphyrin IX (P = 0.046) varied. Hen age affected the majority of measurements. Stocking density differences may be related to hen diet as previous radio-frequency identification tracking of individual hens in these flocks showed birds used the range for longer in the lowest density and the least in the highest density, including depleting the range of vegetation sooner in the smaller ranges. An additional study assessing the relationship between individual hen range use, nutrition, and egg quality is warranted.
Topics: Animal Husbandry; Animals; Chickens; Egg Shell; Female; Housing, Animal; New South Wales; Ovum; Population Density; Protoporphyrins; Reproduction
PubMed: 28431098
DOI: 10.3382/ps/pex107 -
Journal of Oral Biology and... 2020Limited statistically and clinically significant studies have been down on connective tissue factors in the odontogenic tumors. Therefore, the aim of this study was to...
BACKGROUND
Limited statistically and clinically significant studies have been down on connective tissue factors in the odontogenic tumors. Therefore, the aim of this study was to determine the biological behavior of two selected epithelial odontogenic tumors (Ameloblastoma and Adenomatoid odontogenic tumor) by detecting CD34, VEGFR3 and eosinophil densities.
METHODS
In this cross-sectional study, paraffin blocks including 20 cases of ameloblastoma and 20 (AOT), were selected. Totally, 4 sections were prepared for hematoxylin-eosin, Congo red staining, immunohistochemistry with CD34 and VEGFR3. Expression of VEGFR3, CD34 and lymphatic, blood vessels and eosinophil densities was examined.
RESULTS
The mean of blood, lymphatic vessels and eosinophils densities in ameloblastoma were 14.9 ± 6.4, 4.4 ± 2 and 3.2 ± 2.7, respectively; and in AOT, they were 8.9 ± 3.4, 3.6 ± 1.3 and 1.2 ± 07, respectively. There was a significant difference in eosinophils and blood vessels densities between the two lesions (p = 0.005; p = 0.003). By increasing the density of eosinophils, the density of the blood vessels increased in both lesions (r = 0.539, P = 0.001) There was no positive relationship between eosinophils and lymphatic vessels densities in the two above mentioned odontogenic lesions (p = 0.288, R = 0.191).
CONCLUSION
It can be suggested that tumor angiogenesis and eosinophil densities may play a more effective role than lymphangiogenesis in local invasive behavior of ameloblastoma rather than AOT.
PubMed: 31687323
DOI: 10.1016/j.jobcr.2019.09.003 -
Zhongguo Xiu Fu Chong Jian Wai Ke Za... Apr 2022To review the research progress of different cell seeding densities and cell ratios in cartilage tissue engineering. (Review)
Review
OBJECTIVE
To review the research progress of different cell seeding densities and cell ratios in cartilage tissue engineering.
METHODS
The literature about tissue engineered cartilage constructed with three-dimensional scaffold was extensively reviewed, and the seeding densities and ratios of most commonly used seed cells were summarized.
RESULTS
Articular chondrocytes (ACHs) and bone marrow mesenchymal stem cells (BMSCs) are the most commonly used seed cells, and they can induce hyaline cartilage formation and . Cell seeding density and cell ratio both play important roles in cartilage formation. Tissue engineered cartilage with good quality can be produced when the cell seeding density of ACHs or BMSCs reaches or exceeds that in normal articular cartilage. Under the same culture conditions, the ability of pure BMSCs to build hyaline cartilage is weeker than that of pure ACHs or co-culture of both.
CONCLUSION
Due to the effect of scaffold materials, growth factors, and cell passages, optimal cell seeding density and cell ratio need further study.
Topics: Bone Marrow Cells; Cartilage, Articular; Cells, Cultured; Chondrocytes; Chondrogenesis; Tissue Engineering; Tissue Scaffolds
PubMed: 35426288
DOI: 10.7507/1002-1892.202110091 -
BMC Genetics Nov 2020Due to the diversity of rice varieties and cropping systems in China, the limitation of seeding density and seedling quality makes it hard to improve...
BACKGROUND
Due to the diversity of rice varieties and cropping systems in China, the limitation of seeding density and seedling quality makes it hard to improve machine-transplanted efficiency. Previous studies have shown that indica and japonica varieties varied in machine transplanting efficiency and optimal seeding density. In this study, a RIL population derived from '9311' and 'Nipponbare' were performed to explore the seedling traits variations and the genetic mechanism under three seeding densities.
RESULTS
The parents and RIL population exhibited similar trends as the seeding density increased, including seedling height and first leaf sheath length increases, shoot dry weight and root dry weight decreases. Among the 37 QTLs for six traits detected under the three seeding densities, 12 QTLs were detected in both three seeding densities. Five QTL hotspots identified clustered within genomic regions on chromosomes 1, 2, 4, 6 and 11. Specific QTLs such as qRDW and qFLSL were detected under low and high seeding densities, respectively. Detailed analysis the QTL regions identified under specific seeding densities revealed several candidate genes involved in phytohormones signals and abiotic stress responses. Whole-genome additive effects showed that '9311' contributed more loci enhancing trait performances than 'Nipponbare', indicating '9311' was more sensitive to the seeding density than 'Nipponbare'. The prevalence of negative epistasis effects indicated that the complementary two-locus homozygotes may not have marginal advantages over the means of the two parental genotypes.
CONCLUSIONS
Our results revealed the differences between indica rice and japonica rice seedling traits in response to seeding density. Several QTL hotspots involved in different traits and specific QTLs (such as qRDW and qFLSL) in diverse seeding densities had been detected. Genome-wide additive and two-locus epistasis suggested a dynamic of the genetic control underlying different seeding densities. It was concluded that novel QTLs, additive and epistasis effects under specific seeding density would provide adequate information for rice seedling improvement during machine transplanting.
Topics: Agriculture; China; Epistasis, Genetic; Genotype; Oryza; Phenotype; Quantitative Trait Loci; Seedlings
PubMed: 33243137
DOI: 10.1186/s12863-020-00952-1 -
3D Printing in Medicine Apr 2020Fill density is a critical parameter affecting the functional performance of 3D printed porous constructs in the biomedical and pharmaceutical domain. Numerous studies...
Understanding the relationship between slicing and measured fill density in material extrusion 3D printing towards precision porosity constructs for biomedical and pharmaceutical applications.
BACKGROUND
Fill density is a critical parameter affecting the functional performance of 3D printed porous constructs in the biomedical and pharmaceutical domain. Numerous studies have reported the impact of fill density on the mechanical properties, diffusion characteristics and content release rates of constructs. However, due to the way in which slicing toolpath calculations are performed, there is substantial deviation between the measured and slicing fill density for relatively small sized constructs printed at low fill densities (high porosities). The purpose of the current study was to investigate this discrepancy using a combination of mathematical modeling and experimental validation.
METHODS
The open source slicer Slic3r was used to 3D print 20 mm × 20 mm × 5 mm constructs at three identified slicing fill density values, 9.58%, 20.36% and 32.33% (exact values entered into software), in triplicates. A mathematical model was proposed to accurately predict fill density, and the measured fill density was compared to both the predicted as well as the slicing fill density. The model was further validated at two additional slicing fill densities of 15% and 40%. The total material within the construct was analyzed from the perspective of material extruded within the beads as well as the bead to bead interconnects using the predictive model.
RESULTS
The slicing fill density deviated substantially from measured fill density at low fill densities with absolute errors larger than 26% in certain instances. The proposed model was able to predict fill density to within 5% of the measured fill density in all cases. The average absolute error between predicted vs. measured fill density was 3.5%, whereas that between slicing vs. measured fill density was 13%. The material extruded in the beads varied from 86.5% to 95.9%, whereas that extruded in the interconnects varied from 13.5% to 4.1%.
CONCLUSIONS
The proposed model and approach was able to predict fill density to a reasonable degree of accuracy. Findings from the study could prove useful in applications where controlling construct fill density in relatively small sized constructs is important for achieving targeted levels of functional criteria such as mechanical strength, weight loss and content release rate.
PubMed: 32335739
DOI: 10.1186/s41205-020-00063-8 -
The American Journal of Tropical... Jan 2022Facility births and antenatal care (ANC) are key to improving maternal health. This study evaluates the relationship between physician and nurse/midwife densities and...
Facility births and antenatal care (ANC) are key to improving maternal health. This study evaluates the relationship between physician and nurse/midwife densities and the use of key maternal health services in sub-Saharan Africa (SSA). We matched individual-level maternal health service indicators from Demographic and Health Surveys between 2008 and 2017, to country-level physician and nurse/midwife per-capita densities, across 35 SSA countries. We performed univariate and multivariate probit regression analyses to evaluate the association between healthcare worker (HCW) densities and facility births as our primary outcome and additional ANC services as secondary outcomes. We controlled for established maternal health predictors, including literacy, child marriage, reported problems accessing healthcare, GDP per capita, political instability, and government effectiveness scores. HCW density across SSA was low at 0.13 physicians and 0.91 nurses/midwives per 1,000 people, compared with 2010 worldwide mean densities of 1.33 and 3.07, respectively. The probability of facility birth increased by 9.8% (95% CI: 2.1-17.5%) for every additional physician per 1,000 people and 8.9% (95% CI: 7.1-9.7%) for every additional nurse/midwife per 1,000 people. HCW densities were also associated with increased likelihood of ANC by the respective provider type, and with antenatal testing for preeclampsia (urine and blood pressure checks). Other ANC services demonstrated variable relationships with HCW densities based on provider type. In 35 SSA countries, HCW density was positively associated with many key measures of maternal health service utilization including facility birth and ANC testing for preeclampsia.
Topics: Africa South of the Sahara; Child; Female; Health Personnel; Humans; Maternal Health Services; Pre-Eclampsia; Pregnancy; Prenatal Care
PubMed: 35026729
DOI: 10.4269/ajtmh.21-0727 -
Plant Biotechnology (Tokyo, Japan) 2016Plant growth promotion and inhibition under low- and high-density conditions (referred to as the density effect) has been studied extensively. Here, we show that such...
Plant growth promotion and inhibition under low- and high-density conditions (referred to as the density effect) has been studied extensively. Here, we show that such density effects were unaffected by the position of wild-type (WT) and () strains of (Arabidopsis) within pots. Additionally, () and were newly discovered alleles of the () and () genes that are involved in brassinosteroid biosynthesis. Unlike , the semi-dwarf mutants of and exhibited normal flowering times and a shortening of rosette leaves at high densities. Moreover, the and variants suppressed flowering stem shortening at high densities. , but not suppressed the reduction in silique number at intermediate densities. SPINDLY (SPY) is a negative regulator of GA signaling, while PHYTOCHROME B (PHYB) is a red-light photoreceptor. High-density growth did not reduce the flowering time of mutants, but did affect that of mutants. Neither nor suppressed the shortening of rosette leaves at high densities; however, suppressed flowering stem shortening. Moreover, suppressed the reduction of silique number at high densities, while and promoted the decrease. These data suggest that GA, BR, and light signaling pathways play important roles in the density effect.
PubMed: 31274995
DOI: 10.5511/plantbiotechnology.16.0912a