Distribution of male yellow dungflies around ovipasition sites: the effect of body size

Abstract.

• 1 Spatial and temporal variation in body size of yellow dungflies, Scatophaga stercoraria, gathering on and around cow droppings was studied in an Icelandic population in order to elucidate the effect of male and female size on male mating tactics.
• 2 Males copulating on droppings were on average larger than males copulating in the grass, but of similar size to males guarding ovipositing females. Males searching on droppings were smaller than males copulating or guarding females on droppings but larger than males copulating in the grass. No such differences were found in female size.
• 3 Resource-holding power of males (RHP, i.e. male: female size ratio) differed between the three mating groups and was highest for males on the droppings. Size and RHP clearly affect the tactics of copulating males. Males with low RHP tend to copulate in the grass in spite of the cost of longer copulation duration. We argue that this is caused by risk of takeovers from large searching males.
• 4 There was no change in male size with the age of individual droppings. Contrary to what might be expected, large searching males are not predominantly found at fresh droppings when the probability of catching unpaired females is highest. We suggest instead that good prospects in taking females over from other males must make the strategy to search for females on older droppings profitable.
• 5 RHP did not change with age of dropping in the three mating groups. The size of ovipositing females increased with age of dropping, probably reflecting longer copulation and egg-laying times of large females.
• 6 We found an overall positive relationship between sizes of male and female partners. This correlation was highly significant for copulating pairs in the grass. This is probably a consequence of males with low RHP copulating in the grass and fights in which larger males take over females from smaller males. A weaker, but significant, correlation was found amongst ovipositing pairs. This must be due to take-over effects. No size correlation was found for pairs copulating on droppings.

     

Signal amplification of microarray-based immunoassay by optimization of nanoliposome formulations

The use of microarray-based immunoassay is often limited by its sensitivity. To increase the sensitivities of such an immunoassay, liposome encapsulation was explored. Two different liposome formations and several preparation methods were examined to optimize encapsulation and signal-enhancing efficacy for enzyme-linked immunosorbent assay (ELISA) and antibody array. The signal amplification by liposome encapsulation was demonstrated through a detection for foodborne pathogenic Listeria. In plate-trapped antigen (PTA) ELISA, horseradish peroxidase (HRP)-loaded liposome increased signal 9-fold more than the control. Limits of detection (LODs) of HRP-encapsulated liposome were 6.4×10(5) and 5.5×10(6)CFU/ml in sandwich ELISA and antibody array, respectively. Furthermore, when chromogenic 4-chloro-1-naphthol (4-CN) substrate was used for signal development in the antibody array, the signal could be detected with the naked eye. These results suggest that the liposome encapsulation technique can have great potential for signal amplification and, therefore, for increasing assay sensitivity for various formats of immunoassay, especially microarray-based format.     

Nanostructured Lipid Carriers (NLC) for Parenteral Delivery of an Anticancer Drug

The purpose of this research was to formulate nanostructured lipid carriers (NLC) for the parenteral delivery of an anticancer drug, all-trans retinoic acid (ATRA). The ATRA was incorporated into NLC by the de novo emulsification method. The effect of the formulation factor, i.e., type and oil ratio, initial ATRA concentration on physicochemical properties was determined. The anticancer efficacy of ATRA-loaded NLC on HL-60 and HepG2 cells was also studied. NLC was formulated using a blend of solid lipids (cetyl palmitate) and liquid lipids (soybean oil (S), medium-chain triglyceride (M), S/oleic acid (O; 3:1) and M/O (3:1)) at a weight ratio of 1:1. ATRA-loaded NLC had an average size of less than 200 nm (141.80 to 172.95 nm) with a narrow PDI and negative zeta potential that was within an acceptable range for intravenous injection. The results indicated that oleic acid enhanced the ATRA-loading capacity of NLC. In vitro ATRA release was only approximately 4.06% to 4.34% for 48 h, and no significant difference in ATRA release rate from all NLC formulations in accordance with the composition of the oil phase. Moreover, no burst release of the drug was observed, indicating that NLC could prolong the release of ATRA. The initial drug concentration affected the photodegradation rate but did not affect the release rate. All ATRA-loaded NLC formulations exhibited the photoprotective property. The cytotoxicity results showed that all ATRA-loaded NLC had higher cytotoxicity than the free drug and HL-60 cells were more sensitive to ATRA than HepG2 cells.     

Methylated N-(4-N,N-Dimethylaminobenzyl) Chitosan, a Novel Chitosan Derivative, Enhances Paracellular Permeability Across Intestinal Epithelial Cells (Caco-2)

The aim of this study was to investigate the effect of methylated N-(4-N,N-dimethylaminobenzyl) chitosan, TM-Bz-CS, on the paracellular permeability of Caco-2 cell monolayers and its toxicity towards the cell lines. The factors affecting epithelial permeability, e.g., degree of quaternization (DQ) and extent of dimethylaminobenzyl substitution (ES), were evaluated in intestinal cell monolayers of Caco-2 cells using the transepithelial electrical resistance and permeability of Caco-2 cell monolayers, with fluorescein isothiocyanate dextran 4,400 (FD-4) as a model compound for paracellular tight-junction transport. Cytotoxicity was evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide viability assay. The results revealed that, at pH 7.4, TM-Bz-CS appeared to increase cell permeability in a concentration-dependent manner, and this effect was relatively reversible at lower doses of 0.05–0.5 mM. Higher DQ and the ES caused the permeability of FD-4 to be higher. The cytotoxicity of TM-Bz-CS depended on concentration, %DQ, and %ES. These studies demonstrated that this novel modified chitosan has potential as an absorption enhancer.     

Secondary metabolite from Nostoc XPORK14A inhibits photosynthesis and growth of Synechocystis PCC 6803

Screening of 55 different cyanobacterial strains revealed that an extract from Nostoc XPORK14A drastically modifies the amplitude and kinetics of chlorophyll a fluorescence induction of Synechocystis PCC 6803 cells. After 2 d exposure to the Nostoc XPORK14A extract, Synechocystis PCC 6803 cells displayed reduced net photosynthetic activity and significantly modified electron transport properties of photosystem II under both light and dark conditions. However, the maximum oxidizable amount of P700 was not strongly affected. The extract also induced strong oxidative stress in Synechocystis PCC 6803 cells in both light and darkness. We identified the secondary metabolite of Nostoc XPORK14A causing these pronounced effects on Synechocystis cells. Mass spectrometry and nuclear magnetic resonance analyses revealed that this compound, designated as M22, has a non‐peptide structure. We propose that M22 possesses a dual‐action mechanism: firstly, by photogeneration of reactive oxygen species in the presence of light, which in turn affects the photosynthetic machinery of Synechocystis PCC 6803; and secondly, by altering the in vivo redox status of cells, possibly through inhibition of protein kinases.     

Chitosan and its quaternized derivative as effective long dsRNA carriers targeting shrimp virus in Spodoptera frugiperda 9 cells

RNA interference (RNAi) is a promising strategy to combat shrimp viral pathogens at lab-scale experiments. Development of effective orally delivered agents for double-stranded (ds)RNA is necessary for RNAi application at farm level. Since continuous shrimp cell lines have not been established, we are developing a dsRNA-delivery system in Spodoptera frugiperda (Sf9) cells for studying in vitro RNAi-mediated gene silencing of shrimp virus. Sf9 cells challenged with yellow head virus (YHV) were used for validating nanoparticles as effective dsRNA carriers. Inexpensive and biodegradable polymers, chitosan and its quarternized derivative (QCH4), were formulated with long dsRNA (>100 bp) targeting YHV. Their morphology and physicochemical properties were examined. When treated with chitosan- and QCH4-dsRNA complexes, at least 50% reduction in YHV infection in Sf9 cells relative to the untreated control was evident at 24h post infection with low cytoxicity. Inhibitory effects of chitosan- and QCH4-dsRNA complexes were comparable to that of dsRNA formulated with Cellfectin(?), a commercial lipid-based transfection reagent. The natural and quaternized chitosan prepared in this study can be used for shrimp virus-specific dsRNA delivery in insect cultures, and have potential for future development of dsRNA carriers in shrimp feed.     

Parallels,nonparallels, and plasticity in population differentiation of threespine stickleback within a lake

The frequent occurrence of parallel phenotypic divergence in similar habitats is often evoked when emphasizing the role of ecology in adaptive radiation and speciation. However, because phenotypic plasticity can contribute to the observed pattern of divergence, confirmation of divergence at loci underlying phenotypic traits is important for confirming adaptive divergence. In the present study, we examine parallel morphological, neutral, and potentially adaptive genetic divergence of threespine stickleback inhabiting different habitats within a lake. Three genetic clusters best explained the neutral genetic structure within the lake; however, morphological differences were only weakly connected to genetic clusters and there was considerable phenotypic variation within clusters. Among the factors that could contribute to the observed pattern of morphological and genetic divergence are phenotypic plasticity, selective mortality of hybrids, and habitat choice based on morphology. Several loci are identified as outliers indicating divergent selection between the morphs and some parallels in morphological and adaptive genetic divergence are found in stickleback spawning at two lava sites. However, neutral genetic structure indicates considerable genetic connectivity among the two lava sites, and the parallels in morphology may therefore represent selective distribution of phenotypes rather than parallel divergence. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 803–813.     

Mucoadhesive property and biocompatibility of methylated N-aryl chitosan derivatives

The methylated N-aryl chitosan derivatives, methylated N-(4-N,N-dimethylaminocinnamyl) chitosan chloride (MDMCMCh) and methylated N-(4-pyridylmethyl) chitosan chloride (MPyMeCh), were synthesized by two steps, the reductive amination and the methylation. The physicochemical properties of chitosan derivatives were determined by ATR-FTIR, NMR, X-ray diffraction (XRD) and thermogravimetric (TG) techniques. The XRD analysis showed that the crystallinity and thermal stability of methylated chitosan derivatives were lower than those of chitosan. The effects of degree of quaternization (DQ), polymer structure and positive charge location on mucoadhesive property and cytotoxicity were investigated by using a mucin particle method and MTT assay compared to N,N,N-trimethylammonium chitosan chloride (TMChC). It was found that the mucoadhesive property and cytotoxicity increased with increasing DQ. At the DQ of 65%, the mucoadhesive property of the MDMCMCh was twofold lower than that of the TMChC. However, this phenomenon did not affect the mucoadhesive property when the DQ was higher than 65%. Surprisingly, the MPyMeCh showed the lowest toxicity even with the high DQ. These could be due to the resonance effect of the positive charge in the pyridine ring and the molecular weight after methylation. Finally, our result revealed that the mucoadhesive property was dependent on the DQ and polymer structure whereas the cytotoxicity was dependent on the combination of the polymer structure, positive charge location and molecular weight after methylation.     

Place-Based Attributes Predict Community Membership in a Mobile Phone Communication Network

Social networks can be organized into communities of closely connected nodes, a property known as modularity. Because diseases, information, and behaviors spread faster within communities than between communities, understanding modularity has broad implications for public policy, epidemiology and the social sciences. Explanations for community formation in social networks often incorporate the attributes of individual people, such as gender, ethnicity or shared activities. High modularity is also a property of large-scale social networks, where each node represents a population of individuals at a location, such as call flow between mobile phone towers. However, whether or not place-based attributes, including land cover and economic activity, can predict community membership for network nodes in large-scale networks remains unknown. We describe the pattern of modularity in a mobile phone communication network in the Dominican Republic, and use a linear discriminant analysis (LDA) to determine whether geographic context can explain community membership. Our results demonstrate that place-based attributes, including sugar cane production, urbanization, distance to the nearest airport, and wealth, correctly predicted community membership for over 70% of mobile phone towers. We observed a strongly positive correlation (r = 0.97) between the modularity score and the predictive ability of the LDA, suggesting that place-based attributes can accurately represent the processes driving modularity. In the absence of social network data, the methods we present can be used to predict community membership over large scales using solely place-based attributes.