Search

We discuss the genetic, demographic, and selective forces that are likely to be at play in restricting observed levels of DNA sequence variation in natural populations to a much smaller range of values than would be expected from the distribution of census population sizes alone—Lewontin's Paradox. While several processes that have previously been strongly emphasized must be involved, including the effects of direct selection and genetic hitchhiking, it seems unlikely that they are sufficient to explain this observation without contributions from other factors. We highlight a potentially important role for the less-appreciated contribution of population size change; specifically, the likelihood that many species and populations may be quite far from reaching the relatively high equilibrium diversity values that would be expected given their current census sizes. [ABSTRACT FROM AUTHOR]

Many phoretic relationships between arthropods are understudied because of taxonomic impediments. We here illustrate for avian lice riding on hippoboscid flies how new natural history data on phoretic relationships can be acquired quickly with modern and cost‐effective barcoding techniques. Most avian lice are host‐specific, but some can arrive on new hosts by hitchhiking on hippoboscid flies that feed on bird blood. Our summary of the literature yielded 254 published records which we here show to belong to two large and 13 small interaction networks for birds, flies, and lice. In order to generate new records, we developed a protocol based on screening bird carcasses sourced with the help of citizen scientists. The inspection of 131 carcasses from Singapore led to the first record of a Guimaraesiella Eichler (Ischnocera: Philopteridae) louse species riding on Ornithoica momiyamai Kishida flies collected from a pitta carcass. Phoresy may explain why this louse species is now known from three phylogenetically disparate hosts (Pitta moluccensis (Müller), Ficedula zanthopygia (Hay); Pardaliparus elegans Lesson). A second new case of phoresy enhanced a large interaction network dominated by Ornithophila metallica (Schiner), a cosmopolitan and polyphagous hippoboscid fly species. Overall, we argue that many two‐ and three‐way phoretic relationships between arthropods (e.g., mites, pseudoscorpions, beetles, flies) can be resolved with cost‐effective large‐scale NGS barcoding, which can be used to partially overcome taxonomic impediments by pre‐sorting specimens for taxonomic revision. [ABSTRACT FROM AUTHOR]

The flagellum is a complex molecular nanomachine crucial for cell motility. Its assembly requires coordinated expression of over 50 flagellar genes, regulated by the transcription activator FleQ. Phylogenomic analyses suggest that many non-flagellated bacterial species have evolved from flagellated ancestors by losing specific flagellar components, though the evolutionary mechanisms driving this process remain unclear. In this study, we examined the evolutionary dynamics of Pseudomonas syringae DC3000 under standard laboratory conditions using quantitative proteomics. We observed a notable reduction in flagellar gene expression following prolonged serial passages. Whole-genome sequencing revealed multiple adaptive mutations in fleQ , dksA , and glnE , all of which are associated with flagellar biosynthesis. Furthermore, our findings demonstrate that nonmotile Δ fleQ cells can hitchhike onto wild-type cells, potentially facilitated by increased production of the surfactant syringafactin. Our study suggests that the high metabolic costs associated with flagella biosynthesis, coupled with advantageous hitchhiking properties, contribute to the degenerative evolution of flagella. [ABSTRACT FROM AUTHOR]

The long-range movement of organelles, vesicles, and macromolecular complexes by microtubule-based transport is crucial for cell growth and survival. The canonical view of intracellular transport is that each cargo directly recruits molecular motors via cargo-specific adaptor molecules. Recently, a new paradigm called 'hitchhiking' has emerged: some cargos can achieve motility by interacting with other cargos that have already recruited molecular motors. In this way, cargos are co-transported together and their movements are directly coupled. Cargo hitchhiking was discovered in fungi. However, the observation that organelle dynamics are coupled in mammalian cells suggests that this paradigm may be evolutionarily conserved. We review here the data for hitchhiking and discuss the biological significance of this non-canonical mode of microtubule-based transport.

ABSTRACT Interactions between different bacterial species shape bacterial communities and their environments. The opportunistic pathogens Pseudomonas aeruginosa and Burkholderia cenocepacia both can colonize the lungs of individuals affected by cystic fibrosis. Using the social surface behavior called swarming motility as a study model, we noticed intricate interactions between B. cenocepacia K56-2 and P. aeruginosa PA14. While strain K56-2 does not swarm under P. aeruginosa favorable swarming conditions, co-inoculation with a nonmotile PA14 flagellum-less ΔfliC mutant restored spreading for both strains. We show that P. aeruginosa provides the wetting agent rhamnolipids allowing K56-2 to perform swarming motility, while aflagellated PA14 appears to “hitchhike” along with K56-2 cells in the swarming colony. IMPORTANCE Pseudomonas aeruginosa and Burkholderia cenocepacia are important opportunistic pathogens often found together in the airways of persons with cystic fibrosis. Laboratory cocultures of both species often ends with one taking over the other. We used a surface motility assay to study the social interactions between populations of these bacterial species. Under our conditions, B. cenocepacia cannot swarm without supplementation of the wetting agent produced by P. aeruginosa. In a mixed colony of both species, an aflagellated mutant of P. aeruginosa provides the necessary wetting agent to B. cenocepacia, allowing both bacteria to swarm and colonize a surface. We highlight this peculiar interaction where both bacteria set aside their antagonistic tendencies to travel together.

Cell-mediated drug delivery system (CDDS) has shown great potential for cancer therapy. However, a single cell-mediated drug delivery mechanism has not generally been successful, particularly for systemic administration. To augment the antitumor therapy efficacy, herein, we propose a strategy of cell relay-delivery for the use of artificially damaging/aging erythrocytes to hitchhike on circulating monocytes/macrophages for intratumoral accumulation of anticancer drugs. This biomimetic relay-delivery strategy was derived from the manner in which circulating monocytes/macrophages in body specifically engulf damaged/senescent erythrocytes and actively transmigrate into the tumor bulk. The strategy elegantly combines the natural functions of both cells, which therefore provides a new perspective to challenge current obstacles in drug delivery. According to the strategy, we developed biotinylated erythrocyte-poly (lactic-co-glycolic acid) (PLGA) nanoparticle hybrid DDSs (bE-NPs) using avidin-biotin coupling. In such a system, biotinylated erythrocytes can mimic the natural property of damaged/senescent erythrocytes, while PLGA NPs are capable of encapsulating anticancer drugs and promoting sustained drug release. Anticancer drugs can effectively target tumor sites by two steps. First, by using biotinylated erythrocytes as the carrier, the drug-loaded PLGA NPs could be specifically phagocytized by monocytes/macrophages. Second, by taking advantage of the tumor-tropic property of monocytes/macrophages, the drug-loaded PLGA NPs could be efficiently transported into the tumor bulk. After encapsulating vincristine (VIN) as the model drug, bE-NPs exhibited the most favorable antitumor effects in vitro and in vivo by the cell relay-delivery effect. These results demonstrate that the cell relay-delivery provides a potential method for improving tumor treatment efficacy.

Rheumatoid arthritis (RA) is a common chronic inflammatory disease capable of causing the disability. Although various antioxidant strategies have been attempted for prevention and treatment of RA through scavenging the free radicals, the therapeutic effect is limited. Recently, it is reported that the unremitting course of RA intensely correlates with the persistence of immunologic memory, in which the imbalance of T helper 17 (Th17) cells/regulatory T (Treg) cells plays an important role. Herein, we constructed Janus mesenchymal stem cell (MSC)-hitchhiked melanin nanoparticles (MSCFM) for RA therapy, where one half of MSC kept intact for chemotactically migrating towards the RA inflammatory sites and efficiently restoring the Th17/Treg balance based on the property of MSCs, while the other half hitchhiked the iron-doped melanin (FM) nanoparticles (NPs) and release them to scavenge free radicals for maintaining the durability of Th17/Treg balance. In vitro studies indicated MSCFM could migrate towards CXCL12 inflammatory cytokine, scavenge reactive oxygen and nitrogen species, inhibit Th17 cell proliferation and induce Treg cell production. Further in vivo studies corroborated that intravenously injected MSCFM could target the RA site of collagen-induced arthritis mouse model and alleviate the pathological progression of RA. MSCFM holds great potential as an anti-inflammatory agent for RA management. [Display omitted] ● Th17/Treg imbalance plays a vital role in causing rheumatoid arthritis (RA) ● Janus mesenchymal stem cell (MSCFM) was constructed for RA therapy ● One half of MSCFM targets RA sites and restores the Th17/Treg balance ● The other half of MSCFM releases the hitchhiked nanoparticles to clear free radical ● MSCFM repairs and maintains the Th17/Treg balance for improvement of RA therapy [ABSTRACT FROM AUTHOR]

Summary: Seed morphology and quality of cultivated soybean (Glycine max) have changed dramatically during domestication from their wild relatives, but their relationship to selection is poorly understood. Here, we describe a semi‐dominant locus, ST1 (Seed Thickness 1), affecting seed thickness and encoding a UDP‐D‐glucuronate 4‐epimerase, which catalyses UDP‐galacturonic acid production and promotes pectin biosynthesis. Interestingly, this morphological change concurrently boosted seed oil content, which, along with up‐regulation of glycolysis biosynthesis modulated by ST1, enabled soybean to become a staple oil crop. Strikingly, ST1 and an inversion controlling seed coat colour formed part of a single selective sweep. Structural variation analysis of the region surrounding ST1 shows that the critical mutation in ST1 existed in earlier wild relatives of soybean and the region containing ST1 subsequently underwent an inversion, which was followed by successive selection for both traits through hitchhiking during selection for seed coat colour. Together, these results provide direct evidence that simultaneously variation for seed morphology and quality occurred earlier than variation for seed coat colour during soybean domestication. The identification of ST1 thus sheds light on a crucial phase of human empirical selection in soybeans and provides evidence that our ancestors improved soybean based on taste. [ABSTRACT FROM AUTHOR]

Salt marshes are a type of coastal wetland that are affected by dynamic coastal processes. Ice blocks and wrack (mats of plant debris) regularly float onto northern marshes and become stranded, affecting vegetation and soil accretion. There is little research regarding the capacity of ice and wrack to transport viable plant propagules onto marshes where they can colonize, which may be particularly important at barren new salt marsh restoration sites. Contributions of sediment by ice may also be important to raise the marsh platform to elevations appropriate for plant colonization. We collected ice (n = 27) and wrack (n = 18) samples at marshes in the Bay of Fundy, ran germination trials with the contents, and measured the quantity of sediment in the ice. We found viable propagules from halophytic and non-halophytic species in wrack, and viable propagules of Sporobolus pumilus in ice. Additionally, we found sediment densities between 0.01 and 4.75 g/cm3 in ice blocks that translated to 26.61–21,483.59 kg of total sediment per block, representing a large source of sediment. We found that the number of germinating propagules could not be predicted by wrack size, and that pH, sediment density, sediment weight in ice blocks were variable across the marsh surface, while ice salinity was negatively correlated with elevation and distance from creek. Our results indicate that ice and wrack represent a potential source for vegetation colonization at salt marsh sites and highlights their contributions to facilitating vegetation colonization through building marsh soils. [ABSTRACT FROM AUTHOR]

The free 1st toe hemi-pulp transfer for finger pulp reconstruction was acknowledged as the optimal one. However, the treatment of the 1st toe donor defect, owning to the impossibility of primary closure, was frequently oversimplified. This study presented a "hitchhiking" approach to resurface finger pulp and the subsequent 1st toe donor site defect in a one-stage procedure. From 2014 to 2019, finger pulp amputations (13 digits in 12 patients) were reconstructed with free 1st toe pulp flaps, and the donor site was resurfaced by the 2nd toe pedicled flap with the 2nd toe's primary closure. Therapeutic evaluation of repaired fingers and toes was based on cold intolerance, two-point discrimination (2PD), and gait disturbance. All finger and toe pulp flaps survived uneventfully. The average size of free 1st toe and pedicled 2nd toe flap was 3.1 cm × 2.0 cm (3.5 cm × 1.4 cm to 4.2 cm × 2.5 cm) and 3.0 cm × 1.1 cm (2.0 cm × 0.9 cm to 3.8 cm × 1.5 cm), respectively. The regained average static 2PD on the finger and 1st toe pulps was 6 mm (ranged 5–10 mm) and 4 mm (ranged 2–6 mm), respectively. All reconstructed 1st toe pulps were qualified for normal gait. One patient complained the mild cold intolerance, and hammer-toe deformities were involved in two cases. To fulfill donor site care and cost-effective rule, the toe-to-finger pulp reconstruction can't underestimate the morbidity on 1st toe donor site due to inappropriate intervention. Equally importantly, the hitchhiking pedicled 2nd toe flap should be recruited in the reconstructive scheme. [ABSTRACT FROM AUTHOR]

Microorganisms have long been isolated from soils to develop microbial inoculants, with the goal of spiking them into new soils to augment target functions. However, establishment can be sporadic, and we assume that inoculants simply arrive at their destination. Here, we posit a need for integrating dispersal into inoculant development and deployment. We argue that consideration for an inoculant's dispersal ability, whether via active (e.g., chemotaxis) or passive (e.g., attachment to other organisms) means, and including methods of deployment that allow multiple establishment attempts could help increase the predictability of inoculant success. Dispersal can influence many key aspects of in-field survival, including the ability to escape stressors, seek favorable colonization sites, facilitate multiple establishment attempts, and engage in multikingdom interactions. Introducing microbial inoculants to augment target functions in soil, particularly in agricultural settings, has recently increased in interest by farmers and agrotech companies, but inoculant establishment in-field has been unpredictable. Dispersal is an underexplored avenue for improving inoculant establishment and persistence in-field. The inoculant's ability to disperse in-field can impact whether it reaches sites of interest (e.g., plant roots or systemic field infiltration), and can provide avenues to escape stressors and allow inoculants to continually improve their living situation in sites of interest. We posit a need for incorporating dispersal in the inoculant development pipeline and for inoculant deployment in-field. We provide examples for selecting superior dispersers, deploying inoculants in ways that facilitate multiple introductions, and leveraging the dispersal abilities of other organisms. [ABSTRACT FROM AUTHOR]

"Trust is the most joyous kind of bond with another living being. But isn't it true that whenever we enjoy being with someone, there is [both] a factor of risk there, and also a factor of trust, which gives our enjoyment an edge of rapture?" (Lingis (2004),x). Trust is akin to a permeable border, solid but skin-thin, that makes possible connections between Other and self, self and world. A hitchhiker exercises trust when surrendering to another but, as a prerequisite to a successful journey, also submits to indeterminacies and ambiguities of chance encounters. Trust is openness, but also an acceptance of risk. Whilst on the road, it is impossible to know who you will travel with next. Trust guides and draws lines and dots on the map. Trust determines the length of waiting times at petrol pumps; it regulates feelings of safety; and shapes geographic contours. Trust is an emotion that welcomes becoming. In contrast, a lack of trust impedes the friendship necessary to move the hitchhiker's body; provokes feelings of danger; and, inevitably, will hamper the fluency of lines on the map. Trust is the fundamental stuff of hitchhiking. But, what is trust? How does it look like, feel like, how is it evoked, and where is it located? Does it have a color, a gender? Drawing insights from the phenomenological work of Alphonso Lingis and my own personal experiences being-on-the-road, this contribution analyses geographies, feelings and the sensing of trust associated with and experienced in hitchhiking. [ABSTRACT FROM AUTHOR]

Human behavior has a major impact on the spread of the disease during an epidemic. At the same time, the spread of disease has an impact on human behavior. In this paper, we propose a coupled model of human behavior and disease transmission, take into account both individual-based risk assessment and neighbor-based replicator dynamics. The transmission threshold of epidemic disease and the stability of disease-free equilibrium point are analyzed. Some numerical simulations are carried out for the system. Three kinds of return matrices are considered and analyzed one by one. The simulation results show that the change of human behavior can effectively inhibit the spread of the disease, individual-based risk assessments had a stronger effect on disease suppression, but also more hitchhikers. This work contributes to the study of the relationship between human behavior and disease epidemics.

Recently, the selection–recombination equation with a single selected site and an arbitrary number of neutral sites was solved by Alberti and Baake (2021) by means of the ancestral selection–recombination graph. Here, we introduce a more accessible approach, namely the ancestral initiation graph. The construction is based on a discretisation of the selection–recombination equation. We apply our method to systematically explain a long-standing observation concerning the dynamics of linkage disequilibrium between two neutral loci hitchhiking along with a selected one. In particular, this clarifies the nontrivial dependence on the position of the selected site. [ABSTRACT FROM AUTHOR]

Dispersal shapes the dynamics of populations, their genetic structure and species distribution; therefore, knowledge of an organisms' dispersal abilities is crucial, especially in economically important and invasive species. In this study, we investigated dispersal strategies of two phytophagous eriophyoid mite species: Aceria tosichella (wheat curl mite, WCM) and Abacarus hystrix (cereal rust mite, CRM). Both species are obligatory plant parasites that infest cereals and are of economic significance. We investigated their dispersal success using different dispersal agents: wind and vectors. We hypothesised that in both mite species the main mode of dispersal is moving via wind, whereas phoretic dispersal is rather accidental, as the majority of eriophyoid mite species do not possess clear morphological or behavioural adaptations for phoresy. Results confirmed our predictions that both species dispersed mainly with wind currents. Additionally, WCM was found to have a higher dispersal success than CRM. Thus, this study contributes to our understanding of the high invasive potential of WCM. [ABSTRACT FROM AUTHOR]

Detecting selective sweeps driven by strong positive selection and localizing the targets of selection in the genome play a major role in modern population genetics and genomics. Most of these analyses are based on the classical model of genetic hitchhiking proposed by Maynard Smith and Haigh (1974, Genetical Research, 23, 23). Here, we consider extensions of the classical two-locus model. Introducing mutation at the strongly selected site, we analyze the conditions under which soft sweeps may arise. We identify a new parameter (the ratio of the beneficial mutation rate to the selection coefficient) that characterizes the occurrence of multiple-origin soft sweeps. Furthermore, we quantify the hitchhiking effect when the polymorphism at the linked locus is not neutral but maintained in a mutation-selection balance. In this case, we find a smaller relative reduction of heterozygosity at the linked site than for a neutral polymorphism. In our analysis, we use a semi-deterministic approach; i.e., we analyze the frequency process of the beneficial allele in an infinitely large population when its frequency is above a certain threshold; however, for very small frequencies in the initial phase after the onset of selection we rely on diffusion theory. [ABSTRACT FROM AUTHOR]

Patterns of variation and evolution at a given site in a genome can be strongly influenced by the effects of selection at genetically linked sites. In particular, the recombination rates of genomic regions correlate with their amount of within-population genetic variability, the degree to which the frequency distributions of DNA sequence variants differ from their neutral expectations, and the levels of adaptation of their functional components. We review the major population genetic processes that are thought to lead to these patterns, focusing on their effects on patterns of variability: selective sweeps, background selection, associative overdominance, and Hill–Robertson interference among deleterious mutations. We emphasize the difficulties in distinguishing among the footprints of these processes and disentangling them from the effects of purely demographic factors such as population size changes. We also discuss how interactions between selective and demographic processes can significantly affect patterns of variability within genomes. [ABSTRACT FROM AUTHOR]

Herein, an unprecedented synergistic strategy for the development of high-performance NIR-II fluorophore is proposed and validated. Based on an unsymmetrical cyanine dye design strategy, the NIR-II emissive dye NIC was successfully developed by replacing only one of the indoline donors of symmetrical cyanine dye ICG with a fully conjugated benz[c,d]indole donor. This minor structural change maximally maintains the high extinction coefficient advantage of cyanine dyes. NIC-ER with endogenous albumin-hitchhiking capability was constructed to further enhance its in vivo fluorescence brightness. In the presence of HSA (Human serum albumin), NIC-ER spontaneously resides in the albumin pocket, and a brilliant ~89-fold increase in fluorescence was observed. Due to its high molar absorptivity and moderate quantum yield, NIC-ER in HSA exhibits bright NIR-II emission with high photostability and significant Stokes shift (>110 nm). Moreover, NIC-ER was successfully employed for tumor-targeted NIR-II/PA imaging and efficient photothermal tumor elimination. Overall, our strategy may open up a new avenue for designing and constructing high-performance NIR-II fluorophores. [ABSTRACT FROM AUTHOR]

After a decrease in its practice, the interest in hitchhiking is currently renewed. However, so far, very little is known about the personality characteristics of hitchhikers. Consequently, the aim of this study was to investigate the associations between hitchhiking and personality traits, with the Big Five and emotional competences. Five hundred and seventy-eight travellers (452 hitchhikers, M age = 28.4 years old; and 126 non-hitchhikers, M age = 27.7 years old) took part in the study. Participants completed an online survey including hitchhiking behaviour, the Big Five Inventory, and the Profile for Emotional Competences. After controlling for sociodemographic factors, hitchhiking was found to be positively associated with openness, and negatively associated with neuroticism. No associations were found with emotional competences. These findings improve our understanding of the personality characteristics associated with hitchhiking, however longitudinal studies are required to understand how hitchhiking is related to personality. [ABSTRACT FROM AUTHOR]

Solar energy, the use and importance of which is increasing day by day, stands out among renewable energy sources with many applications. In this study, the application of solar powered orthopedic back support backpack has been presented with a special photovoltaic module structure. The 2x12W photovoltaic panel system has been mounted on the backpack with a rail arrangement and optional use is provided according to the user's preference. Since there will be additional equipment in the solar self-energized backpack compared to a normal bag, the sections where the items should be put in the bag according to their weight should be specified to the user. Considering the center of gravity of the backpack, pockets have been made in the parts where heavy components will be fixed, and a 12V 7Ah lead acid battery is mounted in this section. There is a 5V - 1A USB output at the system output and a modified sinus inverter for AC loads. In addition, prototype production was carried out for the realized design, and a backpack was produced, which can be used for charging mobile phones and feeding simple AC loads such as heaters, coolers and shavers. It is thought that this bag will be an attractive product for camping applications and travellers traveling by hitchhiking. [ABSTRACT FROM AUTHOR]

Abstract The Sally lightfoot crab, Grapsus grapsus (Linnaeus, 1758), is distributed along the Eastern Pacific coast and along the Western Atlantic coast, from the Gulf of Mexico to the Southwestern Atlantic. In Brazil, the only established populations are found on the Brazilian oceanic islands, although two previous records (1901 and 1966) reported the presence of individuals on the continental coast. Here, we report new records of the Sally lightfoot crab on the coast of the states of Espírito Santo and Rio Grande do Norte, southeastern and northeastern Brazil, respectively. We also discuss three main hypotheses that could explain occasional records (1901, 1966, 2005, and 2020) of single individuals on the mainland: rafting events associated with flotsam and debris carried by oceanic currents; hitchhiking on vessels and fishing boats navigating routes from the Brazilian oceanic islands to the mainland; and stochastic settlement through larval dispersal.

Background: The endosymbiont Wolbachia can manipulate arthropod reproduction and invade host populations by inducing cytoplasmic incompatibility (CI). Some host species are coinfected with multiple Wolbachia strains which may have sequentially invaded host populations by expressing different types of modular CI factor (cif) genes. The tephritid fruit fly Rhagoletis cerasi is a model for CI and Wolbachia population dynamics. It is associated with at least four Wolbachia strains in various combinations, with demonstrated (wCer2, wCer4), predicted (wCer1) or unknown (wCer5) CI phenotypes. Results: We sequenced and assembled the draft genomes of the Wolbachia strains wCer1, wCer4 and wCer5, and compared these with the previously sequenced genome of wCer2 which currently invades R. cerasi populations. We found complete cif gene pairs in all strains: four pairs in wCer2 (three Type I; one Type V), two pairs in wCer1 (both Type I) and wCer4 (one Type I; one Type V), and one pair in wCer5 (Type IV). Wolbachia genome variant analyses across geographically and genetically distant host populations revealed the largest diversity of single nucleotide polymorphisms (SNPs) in wCer5, followed by wCer1 and then wCer2, indicative of their different lengths of host associations. Furthermore, mitogenome analyses of the Wolbachia genome-sequenced individuals in combination with SNP data from six European countries revealed polymorphic mitogenome sites that displayed reduced diversity in individuals infected with wCer2 compared to those without. Conclusions: Coinfections with Wolbachia are common in arthropods and affect options for Wolbachia-based management strategies of pest and vector species already infected by Wolbachia. Our analyses of Wolbachia genomes of a host naturally coinfected by several strains unravelled signatures of the evolutionary dynamics in both Wolbachia and host mitochondrial genomes as a consequence of repeated invasions. Invasion of already infected populations by new Wolbachia strains requires new sets of functionally different cif genes and thereby may select for a cumulative modularity of cif gene diversity in invading strains. Furthermore, we demonstrated at the mitogenomic scale that repeated CI-driven Wolbachia invasions of hosts result in reduced mitochondrial diversity and hitchhiking effects. Already resident Wolbachia strains may experience similar cytoplasmic hitchhiking effects caused by the invading Wolbachia strain. [ABSTRACT FROM AUTHOR]

Complement is an enzymatic humoral pattern-recognition defence system of the body. Non-specific deposition of blood biomolecules on nanomedicines triggers complement activation through the alternative pathway, but complement-triggering mechanisms of nanomaterials with dimensions comparable to or smaller than many globular blood proteins are unknown. Here we study this using a library of <6 nm poly(amido amine) dendrimers bearing different end-terminal functional groups. Dendrimers are not sensed by C1q and mannan-binding lectin, and hence do not trigger complement activation through these pattern-recognition molecules. While, pyrrolidone- and carboxylic acid-terminated dendrimers fully evade complement response, and independent of factor H modulation, binding of amine-terminated dendrimers to a subset of natural IgM glycoforms triggers complement activation through lectin pathway-IgM axis. These findings contribute to mechanistic understanding of complement surveillance of dendrimeric materials, and provide opportunities for dendrimer-driven engineering of complement-safe nanomedicines and medical devices. Understanding nanomaterials interactions with complement is important for a number of applications. Here, the authors study the interaction of sub 6 nm dendrimers with complement and show the small dendrimers escape complement activation but do interact with IgM to trigger lectin-pathway complement activation. [ABSTRACT FROM AUTHOR]

Active‐targeting nanomedicine formulations have an intricate in vivo behavior. Nanomedicines developed to target endothelial αvβ3‐integrin are recently demonstrated to display extensive uptake by circulating phagocytes. These phagocytes show inherent tumor‐homing capacities and therefore are capable of actively delivering the endocytosed nanomaterial in lesions. Here, the targeting kinetics and mechanisms of cyclic arginine–glycine–aspartate (cRGD)‐decorated lipid nanoparticles (NPs) toward activated vasculature in inflamed lesions during wound healing are studied. The cRGD‐NP targeting toward inflamed lesions is identified to be mechanistically similar to the NP accumulation in cancerous lesions. Through a complementary experimental approach, it is observed that circulating phagocytes engage cRGD‐NPs and are subsequently homed to the inflamed endothelium. The inflammation‐associated phagocytes remain static among endothelial cells upon targeting, resulting in the extensive presence of cRGD‐NP‐positive phagocytes in the angiogenic vessels. Hence, phagocytic immune cells contribute to cRGD‐NP targeting toward angiogenesis. This mechanistic study underlines the need for detailed investigations of NP in vivo behavior. This is critically important for the realization of NPs potential as advanced (immunological) therapeutic agents. [ABSTRACT FROM AUTHOR]

The effort to draw boundaries between public and private space in contemporary cities, is articulated through reflections on the State's action to intervene and regulate the common use of space in the face of the interests and demands of for the private use by individuals, social groups, and/or corporations. If the collective ownership of spaces refers to the domains of action of various agents monitored by the State due to its power of governance (Foucault, 2012), private appropriation of spaces tends to be associated with the figure of the individual and the sphere of his/her actions. The purpose of this text arises from the dialogue between two ethnographic researches: one about the practice of hitchhiking in the city of Florianópolis (SC, Brazil) and the other about the practices of formation and construction of permacultural housing in Porto Alegre and Pelotas (RS, Brazil). We are interested in thinking about how these activities can blur and destabilize imagined/constructed boundaries between what is public and private departing from the concept of infrastructures (Star, 1999; Larkin, 2013). [ABSTRACT FROM AUTHOR]

Hitchhiking bistatic radar system takes the direct wave signal that is transmitted by the non-cooperative radar emitter as the reference to detect and analyze the target echo signal, so as to realize the positioning and tracking of the target. This radar system has the advantages of low cost and strong survivability. Aiming at the problem of passive radar to covert the detection of maritime targets, this paper develops a hitchhiking bistatic radar system for maritime target detection, which uses the shore-based radar as the non-cooperative radar emitter. By continuously collecting the direct wave and target echo data of the non-cooperative radar, the direct wave reference signal reconstruction, pulse compression, interference suppression and synchronization processing, non-coherent integration, MTI (moving target indication), clutter map processing, and adaptive CFAR (constant false alarm rate) detection are completed to obtain the azimuth, bistatic range, and Doppler frequency of the target, and finally realize the positioning of non-cooperative maritime targets. This paper first introduces and demonstrates the composition principle of the system, introduces the signal processing implementation method of the system in detail, and tests and analyzes the key algorithms. The experimental results show that the system can realize the passive coherent detection of maritime moving targets and locate multiple targets at the same time. The experiment obtains a very clear PPI (plane position indicator) display picture of the hitchhiking bistatic radar system, and the radar detection data of the experimental system is in good agreement with the AIS (automatic identification system) data.

In 2019 the RV Meteor cruised from Guadalupe in April/May to Cape Verde in June/July and to Namibia in August/September. The distance is about 10,000 km. The ship has a moon pool for installation of instruments. In Cape Verde we had a first glimpse of the already sparsely populated moon pool. We reached Namibian waters in mid-August. In mid-September, 47 days later and 6000 km south, the ship's moon pool was sampled in the port of Walvis Bay. 13 different taxa could be identified belonging to two phyla, four classes, six orders and 10 families. Most of these species have not yet been observed in the port or in the adjacent areas and are new records for the entire Namibian coast. The goose barnacles Conchoderma auritum (Linnaeus, 1767), Conchoderma virgatum Spengler, 1789 and Lepas anatifera Linnaeus, 1758 were particularly noticeable. They were only surpassed by the large number of amphipods. The species Ericthonius brasiliensis (Dana, 1853), Jassa marmorata Holmes, 1905, Stenothoe senegalensis Krapp-Schickel, 2015 and Paracaprella pusilla Mayer, 1890 are particularly noteworthy here. In addition, the pycnogonid species Endeis straughani Clark, 1970 and the titan acorn barnacle Megabalanus coccopoma (Darwin, 1854) should be mentioned, which occurred very frequently as well. The present study shows, on the one hand, an example of the transatlantic spread of bioinvasive species by ships as vectors and, on the other hand, a convenient method for sampling ship hulls. [ABSTRACT FROM AUTHOR]

Red blood cell (RBC) hitchhiking is a method of drug delivery that can increase drug concentration in target organs by orders of magnitude. In RBC hitchhiking, drug-loaded nanoparticles (NPs) are adsorbed onto red blood cells and then injected intravascularly, which causes the NPs to transfer to cells of the capillaries in the downstream organ. RBC hitchhiking has been demonstrated in multiple species and multiple organs. For example, RBC-hitchhiking NPs localized at unprecedented levels in the brain when using intra-arterial catheters, such as those in place immediately after mechanical thrombectomy for acute ischemic stroke. RBC hitchhiking has been successfully employed in numerous preclinical models of disease, ranging from pulmonary embolism to cancer metastasis. In addition to summarizing the versatility of RBC hitchhiking, we also describe studies into the surprisingly complex mechanisms of RBC hitchhiking as well as outline future studies to further improve RBC hitchhiking's clinical utility. [ABSTRACT FROM AUTHOR]

Motility allows many microbes to traverse their environment to find nutrient sources or escape unfavorable environments. However, some microbes are nonmotile and are restricted to their immediate conditions. Intriguingly, sporadic reports have demonstrated that many nonmotile microbes can utilize the motility machinery of other microbes in their vicinity. This form of transportation, called hitchhiking, has been observed with both prokaryotic and eukaryotic microbes. Importantly, many hitchhiking microbes are pathogenic to humans or plants. Here, we discuss reports of intermicrobial hitchhiking to generate a comprehensive view of hitchhiking mechanisms and how such interactions may influence human and plant health. We hypothesize that microbial hitchhiking is ubiquitous in nature and may become the subject of an independent subfield of research in microbiology. Sporadic reports demonstrate that some nonmotile microbes utilize trans-species hitchhiking to traverse their environment. Hitchhiking has been observed with eukaryotic and prokaryotic microbes. Four general hitchhiking mechanisms have been elucidated thus far: mechanical pushing by motile cells, direct attachment to cell bodies, direct attachment to bacterial flagella, and internal transport by cells. Several immotile human and plant pathogens hitchhike motile microbes that are natively found in their vicinity. In some instances, hitchhiking is implicated in infectivity mechanisms of microbial pathogens. [ABSTRACT FROM AUTHOR]

Hitchhikers (phoretic organisms) identify their vehicles using species‐specific visual, chemical and vibrational cues. However, what factors influence their choice between vehicles of the same species has rarely been investigated.Hitchhikers must not only avoid overcrowded vehicles but may also need to travel with conspecifics to ensure mates at their destination. Hence, a trade‐off between overcrowding and presence of conspecifics likely determines the choice of a vehicle especially when destination sites are distant, ephemeral and unique.Here, we investigate whether a trade‐off between the presence of conspecifics versus overcrowding by conspecifics or heterospecifics on a vehicle affects hitchhiker choice. We also investigate the sensory modality responsible for this choice. We experimentally examine these questions using a phoretic nematode community (containing plant‐ and animal‐parasitic taxa) obligately associated with a brood‐site pollination mutualism. In this model system, nematodes co‐travel with conspecifics and heterospecifics on pollinators as vehicles, between ephemeral plant brood sites to complete their developmental life cycle. In this system, hitchhiker overcrowding has proven negative impacts on vehicle and plant fitness. We expected nematodes to respond to conspecifics and heterospecific density on offered vehicles when making their choice.We found that animal‐parasitic nematodes preferred vehicles containing some conspecifics within a certain density range. However, plant‐parasitic nematodes preferentially boarded vehicles that were devoid of conspecifics or had few conspecifics. Plant parasites that preferred empty vehicles likely hitchhiked in pairs. Both nematode types employed volatile cues to discriminate between vehicles with different conspecific nematode densities. Our results suggest that vehicle overcrowding by conspecifics, most likely, guaranteed access to mates at the destination determined hitchhiker choice. Surprisingly, and contrary to our expectations, plant‐ and animal‐parasitic nematodes did not respond to heterospecific crowding on vehicles and did not discriminate between vehicles with different heterospecific nematode densities. The reason for this lack of response to heterospecific presence is unknown.This study not only shows that phoretic organisms use different strategies while choosing a vehicle but also confirms that density‐dependent effects can ensure the stability and persistence of phoretic interactions in a mutualism by balancing overcrowding against reproductive assurance. [ABSTRACT FROM AUTHOR]

Symbionts of ant colonies can hitchhike on winged ant reproductives (alates) during colony nuptial flights. Attaphila fungicola Wheeler, a miniature cockroach that lives in the nests of Texas leaf-cutter ants (Atta texana Buckley), hitchhikes on female alates (winged queens). Hitchhiking roaches are presumably vertically transmitted from leaf-cutter parent colonies to daughter colonies, remaining with female alates as they transition into foundresses (workerless queens); however, foundresses have limited resources and high mortality rates. Rather than remaining with foundresses likely to die (vertical transmission), roaches might abandon them during dispersal to infect higher-quality later stages of colony development (female alate–vectored transmission). In field experiments, I find evidence for female alate–vectored transmission and discover that roaches use a second hitchhiking step (riding foraged plant material) to infect established colonies. This work reveals a novel relationship between host dispersal and symbiont transmission and shows that colony development can be an important selection pressure on transmission. [ABSTRACT FROM AUTHOR]

Copyright of Revista Inovação, Projetos e Tecnologia is the property of Revista Inovacao, Projetos e Tecnologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Title: Slab City StoriesAuthor: Jessica Lum "Slab City Stories" is a multimedia visual journalism project documenting the people and residents of Slab City, a squatter community in southern California. The project can be viewed online at http://slabcitystories.com  Slab City, located about two miles east of Niland, California, is home to a few dozen during blistering summers, but draws thousands during the temperate winter season. These migrating snowbirds seek the sun and warmth of the California desert, as well as the alternative lifestyle that flourishes here. Slab City is named for the remains of concrete foundations that dot the area, once part of the military naval reservation, Camp Dunlap. The site was decommissioned in 1956 and deeded to the state of California in 1961. Residents of “The Slabs,” as it is called, are squatters living in trailers and recreational vehicles in various stages of upkeep: broken-down or brand new "land yachts" worth several hundred thousands. Many people also build their own structures, tents and shacks. Most subsist off of food stamps or social security benefits: usually for retirement or disability. Some support themselves through barter, trade and odd jobs from other Slabbers, or Slab City residents. Slab City is a vibrant community, home to artists and musicians who create and display their work in places like East Jesus' art garden or Builder Bill's stage, The Range, which hosts a weekly open mic show every Saturday night. Residents join social clubs like the Oasis Club or Loners on Wheels where they meet for morning coffee, meals and happy hours. Others prefer to live on the edge of it all, because even in the desert, quiet can be hard to find.

Recent studies have demonstrated that phages can be co-transported with motile non-host bacteria, thereby enabling their invasion of biofilms and control of biofilm composition. Here, we developed a novel approach to isolate non-host bacteria able to co-transport phages from soil. It is based on the capability of phage-carrying non-host bacteria to move along mycelia out of soil and form colonies in plaques of their co-transported phages. The approach was tested using two model phages of differing surface hydrophobicity, i.e., hydrophobic Escherichia virus T4 (T4) and hydrophilic Pseudoalteromonas phage HS2 (HS2). The phages were mixed into soil and allowed to be transported by soil bacteria along the mycelia of Pythium ultimum. Five phage-carrying bacterial species were isolated (Viridibacillus sp., Enterobacter sp., Serratia sp., Bacillus sp., Janthinobacterium sp.). These bacteria exhibited phage adsorption efficiencies of ≈90–95% for hydrophobic T4 and 30–95% for hydrophilic HS2. The phage adsorption efficiency of Viridibacillus sp. was ≈95% for both phages and twofold higher than T4-or HS2-adsorption to their respective hosts, qualifying Viridibacillus sp. as a potential super carrier for phages. Our approach offers an effective and target-specific way to identify and isolate phage-carrying bacteria in natural and man-made environments.

Abstract Background Upon the detection of imminent peril, pea aphids (Acyrthosiphon pisum) often drop off their host plant. Dropping in response to insect enemies is intermittent in nature, but when a mammalian herbivore feeds on their host plant, a large mixed-age group of aphids usually drops off the plant at once. Aphids that reach the ground are confronted with new, hostile environmental conditions and must therefore quickly walk toward a suitable host plant. The longer it takes an aphid to reach a host plant, the more it is exposed to the risks of starvation, desiccation and predation. Results We found that young nymphs, which have limited mobility and high mortality on the ground, quickly climb on conspecific (not necessarily parental) adults and cling to them before the latter start walking in search of a plant. This “riding” behavior is likely to be adaptive for the nymphs, for it shortens their journey and the time they spend off a host plant. Adults however, seem to be irritated by the riding nymphs, as they often actively try to remove them. Conclusions After dropping from the host plant, young aphid nymphs travel at least part of the way back to a plant on the backs of adults. For the riding behavior to take place, nymphs need to successfully find adults and withstand removal attempts.

Central to proteopathies and leading to most age‐related neurodegenerative disorders is a failure in protein quality control (PQC). To harness the toxicity of misfolded and damaged disease proteins, such proteins are either refolded, degraded by temporal PQC, or sequestered by spatial PQC into specific, organelle‐associated, compartments within the cell. Here, we discuss the impact of vesicle trafficking pathways in general, and syntaxin 5 in particular, as key players in spatial PQC directing misfolded proteins to the surface of vacuole and mitochondria, which facilitates their clearance and detoxification. Since boosting vesicle trafficking genetically can positively impact on spatial PQC and make cells less sensitive to misfolded disease proteins, we speculate that regulators of such trafficking might serve as therapeutic targets for age‐related neurological disorders. [ABSTRACT FROM AUTHOR]

The lymphatic system plays an integral role in the development and progression of a range of disease conditions, which has impelled medical researchers and clinicians to design, develop and utilize advanced lymphatic drug delivery systems. Following interstitial administration, most therapeutics and molecules are cleared from tissues via the draining blood capillaries. Macromolecules and delivery systems >20 kDa in size or 10–100 nm in diameter are, however, transported from the interstitium via draining lymphatic vessels as they are too large to cross the blood capillary endothelium. Lymphatic uptake of small molecules can be promoted by two general approaches: administration in association with synthetic macromolecular constructs, or through hitchhiking on endogenous cells or macromolecular carriers that are transported from tissues via the lymphatics. In this paper we review the latter approach where molecules are targeted to lymph by hitchhiking on endogenous albumin transport pathways after subcutaneous, intramuscular or intradermal injection. We describe the properties of the lymphatic system and albumin that are relevant to lymphatic targeting, the characteristics of drugs and delivery systems designed to hitchhike on albumin trafficking pathways and how to further optimise these properties, and finally the current applications and potential future directions for albumin-hitchhiking approaches to target the lymphatics. Unlabelled Image • Explains the general principles that guide therapeutic delivery to the lymphatics. • Reviews the properties of albumin relevant to lymphatic targeting. • Outlines characteristics of systems designed to target lymphatics by albumin-hitchhiking. • Proposes mechanisms to optimise albumin-hitchhiking to target lymphatics. • Critically appraises current and future clinical applications of albumin hitchhiking. [ABSTRACT FROM AUTHOR]

Bacteria typically reside in heterogeneous environments with various chemogradients where motile cells can gain an advantage over nonmotile cells. Since motility is energetically costly, cells must optimize their swimming speed and behaviour to maximize their fitness. Here, we investigate how cheating strategies might evolve where slow or nonmotile microbes exploit faster ones by sticking together and hitching a ride. Starting with physical and biological first principles, we computationally study the effects of sticking on the evolution of motility in a controlled chemostat environment. We find that stickiness allows for slow cheaters to dominate when chemoattractants are dispersed at intermediate distances. In this case, slow microbes exploit faster ones until they consume the population, leading to a tragedy of commons. For long races, slow microbes do gain an initial advantage from sticking, but eventually fall behind. Here, fast microbes are more likely to stick to other fast microbes and co‐operate to increase their own population. We therefore conclude that whether the nature of the hitchhiking interaction is parasitic or mutualistic, depends on the chemoattractant distribution. [ABSTRACT FROM AUTHOR]

It is increasingly evident that natural selection plays a prominent role in shaping patterns of diversity across the genome. The most commonly studied modes of natural selection are positive selection and negative selection, which refer to directional selection for and against derived mutations, respectively. Positive selection can result in hitchhiking events, in which a beneficial allele rapidly replaces all others in the population, creating a valley of diversity around the selected site along with characteristic skews in allele frequencies and linkage disequilibrium among linked neutral polymorphisms. Similarly, negative selection reduces variation not only at selected sites but also at linked sites, a phenomenon called background selection (BGS). Thus, discriminating between these two forces may be difficult, and one might expect efforts to detect hitchhiking to produce an excess of false positives in regions affected by BGS. Here, we examine the similarity between BGS and hitchhiking models via simulation. First, we show that BGS may somewhat resemble hitchhiking in simplistic scenarios in which a region constrained by negative selection is flanked by large stretches of unconstrained sites, echoing previous results. However, this scenario does not mirror the actual spatial arrangement of selected sites across the genome. By performing forward simulations under more realistic scenarios of BGS, modeling the locations of protein-coding and conserved noncoding DNA in real genomes, we show that the spatial patterns of variation produced by BGS rarely mimic those of hitchhiking events. Indeed, BGS is not substantially more likely than neutrality to produce false signatures of hitchhiking. This holds for simulations modeled after both humans and Drosophila, and for several different demographic histories. These results demonstrate that appropriately designed scans for hitchhiking need not consider BGS's impact on false-positive rates. However, we do find evidence that BGS increases the false-negative rate for hitchhiking, an observation that demands further investigation. [ABSTRACT FROM AUTHOR]

DNA barcoding based on mitochondrial (mt) nucleotide sequences is an enigma. Neutral models of mt evolution predict DNA barcoding cannot work for recently diverged taxa, and yet, mt DNA barcoding accurately delimits species for many bilaterian animals. Meanwhile, mt DNA barcoding often fails for plants and fungi. I propose that because mt gene products must cofunction with nuclear gene products, the evolution of mt genomes is best understood with full consideration of the two environments that impose selective pressure on mt genes: the external environment and the internal genomic environment. Moreover, it is critical to fully consider the potential for adaptive evolution of not just protein products of mt genes but also of mt transfer RNAs and mt ribosomal RNAs. The tight linkage of genes on mt genomes that do not engage in recombination could facilitate selective sweeps whenever there is positive selection on any element in the mt genome, leading to the purging of mt genetic diversity within a population and to the rapid fixation of novel mt DNA sequences. Accordingly, the most important factor determining whether or not mt DNA sequences diagnose species boundaries may be the extent to which the mt chromosomes engage in recombination. [ABSTRACT FROM AUTHOR]

Hitchhiking is a travel mode characterised by unpredictable travel times involving several possible combinations of lifts on roads. In this paper, we formulate a hitchhiker's problem and develop a time-dependent stochastic route planning algorithm for hitchhikers. Namely, we introduce a concept of the stochastic time-dependent hitchhiking graph to find hitchhiking strategies with the least expected travel time or maximised reliability. We introduce various heuristics to prune the original hitchhiking graph to improve computational efficiency. We provide a complexity analysis of the problem and evaluate the proposed solution on real-world networks of several countries. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Traffic & Transportation Research / Trafik ve Ulaşım Araştırmaları Dergisi is the property of Journal of Traffic & Transportation Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Neo-sex chromosomes are found in many taxa, but the forces driving their emergence and spread are poorly understood. The female-specific neo-W chromosome of the African monarch (or queen) butterfly Danaus chrysippus presents an intriguing case study because it is restricted to a single 'contact zone' population, involves a putative colour patterning supergene, and co-occurs with infection by the male-killing endosymbiont Spiroplasma. We investigated the origin and evolution of this system using whole genome sequencing. We first identify the 'BC supergene', a broad region of suppressed recombination across nearly half a chromosome, which links two colour patterning loci. Association analysis suggests that the genes yellow and arrow in this region control the forewing colour pattern differences between D. chrysippus subspecies. We then show that the same chromosome has recently formed a neo-W that has spread through the contact zone within approximately 2,200 years. We also assembled the genome of the male-killing Spiroplasma, and find that it shows perfect genealogical congruence with the neo-W, suggesting that the neo-W has hitchhiked to high frequency as the male-killer has spread through the population. The complete absence of female crossing-over in the Lepidoptera causes whole-chromosome hitchhiking of a single neo-W haplotype, carrying a single allele of the BC supergene and dragging multiple non-synonymous mutations to high frequency. This has created a population of infected females that all carry the same recessive colour patterning allele, making the phenotypes of each successive generation highly dependent on uninfected male immigrants. Our findings show how hitchhiking can occur between the physically unlinked genomes of host and endosymbiont, with dramatic consequences. A chromosome carrying a colour patterning supergene has spread rapidly through a population of African monarch butterflies (Danaus chrysippus) by hitchhiking with a male-killing endosymbiont, Spiroplasma, showing how hitchhiking can occur between the unlinked genomes of host and endosymbiont, with dramatic consequences. [ABSTRACT FROM AUTHOR]

The recurrent fixation of newly arising, beneficial mutations in a species reduces levels of linked neutral variability. Models positing frequent weakly beneficial substitutions or, alternatively, rare, strongly selected substitutions predict similar average effects on linked neutral variability, if the product of the rate and strength of selection is held constant. We propose an approximate Bayesian (ABC) polymorphism-based estimator that can be used to distinguish between these models, and apply it to multi-locus data from Drosophila melanogaster. We investigate the extent to which inference about the strength of selection is sensitive to assumptions about the underlying distributions of the rates of substitution and recombination, the strength of selection, heterogeneity in mutation rate, as well as the population's demographic history. We show that assuming fixed values of selection parameters in estimation leads to overestimates of the strength of selection and underestimates of the rate. We estimate parameters for an African population of D. melanogaster ((s) over cap similar to 2E-03, 2N (lambda) over cap similar to 2E-04) and compare these to previous estimates. Finally, we show that surveying larger genomic regions is expected to lend much more discriminatory power to the approach. It will thus be of great interest to apply this method to emerging whole-genome polymorphism data sets in many taxa.