EFFECTIVENESS OF SELECTION IN REDUCING THE GENETIC LOAD IN POPULATIONS OF PEROMYSCUS POLIONOTUS DURING GENERATIONS OF INBREEDING

It has been hypothesized that natural selection reduces the “genetic load” of deleterious alleles from populations that inbreed during bottlenecks, thereby ameliorating impacts of future inbreeding. We tested the efficiency with which natural selection purges deleterious alleles from three subspecies of Peromyscus polionotus during 10 generations of laboratory inbreeding by monitoring pairing success, litter size, viability, and growth in 3604 litters produced from 3058 pairs. In P. p. subgriseus, there was no reduction across generations in inbreeding depression in any of the fitness components. Strongly deleterious recessive alleles may have been removed previously during episodes of local inbreeding in the wild, and the residual genetic load in this population was not further reduced by selection in the lab. In P. p. rhoadsi, four of seven fitness components did show a reduction of the genetic load with continued inbreeding. The average reduction in the genetic load was as expected if inbreeding depression in this population is caused by highly deleterious recessive alleles that are efficiently removed by selection. For P. p. leucocephalus a population that experiences periodic bottlenecks in the wild, the effect of further inbreeding in the laboratory was to exacerbate rather than reduce the genetic load. Recessive deleterious alleles may have been removed from this population during repeated bottlenecks in the wild; the population may be close to a threshold level of heterozygosity below which fitness declines rapidly. Thus, the effects of selection on inbreeding depression varied substantially among populations, perhaps due to different histories of inbreeding and selection.     

On the failure of two butterfly species to respond to the presence of conspecific eggs prior to oviposition

Abstract. 1. The eggs of Euptychiine butterflies are laid singly, but their distributions tend to be contagious. However, these insects do not discriminate between egg-laden and egg-free plants.
2. Response to conspecific eggs is not part of the mechanism responsible for clumped egg distribution.     

TRAINING LOAD,IMMUNE SYSTEM,UPPER RESPIRATORY SYMPTOMS AND PERFORMANCE IN WELL-TRAINED CYCLISTS THROUGHOUT A COMPETITIVE SEASON

This study aimed to evaluate the leukocyte subset counts, serum immunoglobulin A, performance and upper respiratory symptoms (URS), as well as their interrelationships, of well-trained cyclists for a 29-week training season using monitored loads. The season was divided into three phases: preparatory (nine weeks), first competitive phase (nine weeks) and second competitive phase (11 weeks). The sample consisted of eight well-trained cyclists, aged 18 ± 2 years. Immunological parameters and performance were evaluated during weeks 1 (baseline), 10 (early first competitive phase), 19 (early second competitive phase) and 29 (end of the second competitive phase). The training loads (volume x rating of perceived exertion) were monitored daily while the monitoring of URS was performed every 15 days using the WURSS-44 questionnaire. The data were analyzed using a one-way ANOVA and a Pearson correlation test with the significance level set at p ≤ 0.05. No significant differences were found for training load, leukocyte subset counts or serum immunoglobulin A among the three phases. However, serum immunoglobulin A was 50.9% below the control group values. URS were significantly higher during the preparatory period, and there were significant correlations between URS and training load (strain) in the preparatory period (r = 0.72, p = 0.032) and second competitive phase (r = 0.73, p = 0.036). In conclusion, indicators of training load without a significant change throughout the season did not significantly affect immune parameters measured; however, the increase of strain can cause an increase of upper respiratory symptoms throughout the season, but without loss of performance.     

Computational method for the real-time calculation of the full-body muscle load distribution

A method is described for minimising a quadratic function subject to equality and inequality constraints. This approach is applicable to solving the full-body muscle load distribution problem and calculating joint contact loads. It has been found that this approach can provide the solution on modest computing facilities and in significantly less time than using active set and interior point quadratic programming techniques. Hence the approach is suitable for providing real-time feedback to subjects undergoing biomechanical analysis of muscle, skeletal and joint loadings.     

High prevalence of Sarcocystis spp. infections in cattle (Bos taurus) from central China

Myocardium and diaphragm samples of cattle (n?=?521) from HeNan Province (China) were screened for Sarcocystis sarcocysts by histological examination, pepsin digestion, and molecular assays. Morphology and molecular assays were used for identification. The prevalence of Sarcocystis infection in cattle was 41.5% (216/521). Histological examination identified sarcocysts in the myocardium (49.4%, 200/405) and diaphragm (13.8%, 16/116) of cattle. Two species were identified, namely S. cruzi (41.3%, 215/521) and S. hominis (0.2%, 1/521). The findings of the present study indicate a high prevalence of S. cruzi infection in cattle from central China.     

A dynamic analysis of viral load, T lymphocyte subsets and main biochemical indexes before and after prevention of mother to child transmission (PMTCT) in HIV/AIDS

This study aims to investigate changes in viral load, T lymphocyte subsets and other main biochemical indexes of HIV/AIDS in the prevention of mother to child transmission (PMTCT). In this study, 152 pregnant women with HIV/AIDS enrolled into our hospital from January 2013 to June 2015 were chosen as objects. Changes in viral load, T lymphocyte subsets and other main biochemical indexes of HIV/AIDS were tested and compared before and after 3 months of PMTCT and in neonatals one week after birth. The CD4/CD8 examination result, and difference in CD4 before and after prevention (in the newborns after a week) was statistically significant (P < 0.05), and the rest showed no statistical significance. For the dynamic analysis of main biochemical test results: K⁺, Na⁺, Cl^-, BG, OS, BUN, BUN/Cr, UA,TDIL, DBIL, TP, ALB, CK, LDH, HDL, LDL and other indexes before and after prevention attained statistical significances (P < 0.05 or above). The same sample in the three groups was detected by repeated analysis of variance, K⁺, Na⁺, Cl^-, BG, OS, BUN/Cr, UA, DBI L, ALB, CK, LDH, HDL, LDL and other indexes also showing P at less than 0.05 or above, among which K⁺, Cl^-, CK, LDL showed homogeneity of variance, while Na⁺, BG, OS, BUN/Cr, UA, DBIL, ALB, LDH, HDL showed unequal homogeneity of variance. The study suggests that the dynamic analysis of viral load, T lymphocyte subsets and main biochemical indexes before and after PMTCT in HIV/AIDS are important means to evaluate the dose and treatment of antiretroviral drugs. Monitoring of above indexes is helpful to judge and analyze the condition of the maternal body at various stages, so antiviral drug treatment can be adjusted.     

Invasion theory and biological control

Recent advances in the mathematical theory of invasion dynamics have much to offer to biological control. Here we synthesize several results concerning the spatiotemporal dynamics that occur when a biocontrol agent spreads into a population of an invading pest species. We outline conditions under which specialist and generalist predators can influence the density and rate of spatial spread of the pest, including the rather stringent conditions under which a specialist predator can successfully reverse a pest invasion. We next discuss the connections between long distance dispersal and invasive spread, emphasizing the different consequences of fast spreading pests and predators. Recent theory has considered the effects of population stage-structure on invasion dynamics, and we discuss how population demography affects the biological control of invading pests. Because low population densities generally characterize early stages of an invasion, we discuss the lessons invasion theory teaches concerning the detectability of invasions. Stochasticity and density-dependent dynamics are common features of many real invasions, influencing both the spatial character (e.g. patchiness) of pest invasions and the success of biocontrol agents. We conclude by outlining theoretical results delineating how stochastic effects and complex dynamics generated by density dependence can facilitate or impede biological pest control.     

A human health risk assessment of soil and crops contaminated by heavy metals in industrial regions,central Iran

In this study, the concentrations of heavy metal (Cd, Pb, Fe, and Ni) in contaminated soils adjacent to two steel mill companies and in three crops (i.e., wheat, rice, and onion) grown in these regions were compared with a non-industrial site in Isfahan province, central Iran. The results were manifold. The heavy metal concentrations of both the soil and crops within the two industrial regions turned out to be more significant than the nonindustrial counterpart. In addition, the soils surrounding the companies were demonstrated to be contaminated by Cd, Pb, and Ni according to the limits provided by the international standards (i.e., USEPA and European Union standards). As for the crops from the investigated contaminated sites, the mean concentrations of Cd, Ni, and Pb exceeded the maximum permissible levels for human consumption stipulated by FAO/WHO standards. Furthermore, the values gained from the target hazard quotient were above one, meaning that the crops are contaminated. Given the results gained from a comparison made between estimated daily intake and tolerable daily intake, it can be concluded that the inhabitants of the two investigated contaminated sites are at a potentially serious health risk caused by exposure to the crops contaminated with the heavy metal.     

Estimation of genetic purging under competitive conditions

Inbreeding depression for fitness traits is a key issue in evolutionary biology and conservation genetics. The magnitude of inbreeding depression, though, may critically depend on the efficiency of genetic purging, the elimination or recessive deleterious mutations by natural selection after they are exposed by inbreeding. However, the detection and quantification of genetic purging for nonlethal mutations is a rather difficult task. Here, we present two comprehensive sets of experiments with Drosophila aimed at detecting genetic purging in competitive conditions and quantifying its magnitude. We obtain, for the first time in competitive conditions, an estimate for the predictive parameter, the purging coefficient (d), that quantifies the magnitude of genetic purging, either against overall inbreeding depression (d ≈ 0.3), or against the component ascribed to nonlethal alleles (d_NL ≈ 0.2). We find that competitive fitness declines at a high rate when inbreeding increases in the absence of purging. However, in moderate size populations under competitive conditions, inbreeding depression need not be too dramatic in the medium to short term, as the efficiency of purging is also very high. Furthermore, we find that purging occurred under competitive conditions also reduced the inbreeding depression that is expressed in the absence of competition.     

Mechanical Load Enhances Procollagen Processing in Dermal Fibroblasts by Regulating Levels of Procollagen C-Proteinase

Mechanical forces are emerging as key regulators of cell function. We hypothesize that mechanical load may influence dermal fibroblast activity. We assessed the direct effects of mechanical load on human dermal fibroblast procollagen synthesis and processing in vitro. Cells were loaded in a biaxial loading system (Flexercell 3000). Hydroxyproline levels were measured in the medium and cell layer as an estimate of procollagen synthesis and processing to insoluble collagen. Mechanical load (in the presence of serum or TGF-beta) enhanced procollagen synthesis by 45 +/- 3% (P < 0.001), and 38 +/- 4% (P < 0.001), respectively, over unloaded growth factor controls after 48 h. Insoluble collagen deposition was enhanced in the same cultures by 115 +/- 8% (P < 0.01) and 72% +/- 9% (P < 0.01), respectively. This effect was inhibited using l-arginine suggesting that procollagen C-proteinase, the enzyme which directly cleaves the C-terminal propeptide of procollagen to form insoluble collagen, is required for the fiber formation observed. Procollagen mRNA levels in loaded samples increased by more than two-fold in both serum and TGF-beta-treated cultures at 48 h. Procollagen C-proteinase mRNA levels were also enhanced by a similar magnitude, although the increase was observed at 24 h. Procollagen C-proteinase protein levels were also increased at this time. Protein and mRNA levels of the procollagen C-proteinase enhancer protein, which binds the C-terminal propeptide of procollagen to enhance the rate of peptide cleavage, were unaffected by mechanical load. This study demonstrates that mechanical load promotes procollagen synthesis in dermal fibroblasts by enhancing gene expression and posttranslational processing of procollagen.