Faster growth with shorter antigens can explain a VSG hierarchy during African trypanosome infections:a feint attack by parasites

The parasitic African trypanosome, Trypanosoma brucei, evades the adaptive host immune response by a process of antigenic variation that involves the clonal switching of variant surface glycoproteins (VSGs). The VSGs that come to dominate in vivo during an infection are not entirely random, but display a hierarchical order. How this arises is not fully understood. Combining available genetic data with mathematical modelling, we report a VSG-length-dependent hierarchical timing of clonal VSG dominance in a mouse model, consistent with an inverse correlation between VSG length and trypanosome growth-rate. Our analyses indicate that, among parasites switching to new VSGs, those expressing shorter VSGs preferentially accumulate to a detectable level that is sufficient to trigger a targeted immune response. This may be due to the increased metabolic cost of producing longer VSGs. Subsequent elimination of faster-growing parasites then allows slower-growing parasites with longer VSGs to accumulate. This interaction between the host and parasite is able to explain the temporal distribution of VSGs observed in vivo. Thus, our findings reveal a length-dependent hierarchy that operates during T. brucei infection. This represents a ‘feint attack’ diversion tactic utilised by these persistent parasites to out-maneuver the host adaptive immune system

Bolus ingestion of whey protein immediately post-exercise does not influence rehydration compared to energy-matched carbohydrate ingestion

Whey protein is a commonly ingested nutritional supplement amongst athletes and regular exercisers; however, its role in post-exercise rehydration remains unclear. Eight healthy male and female participants completed two experimental trials involving the ingestion of 35 g of whey protein (WP) or maltodextrin (MD) at the onset of a rehydration period, followed by ingestion of water to a volume equivalent to 150% of the amount of body mass lost during exercise in the heat. The gastric emptying rates of the solutions were measured using 13C breath tests. Recovery was monitored for a further 3 h by the collection of blood and urine samples. The time taken to empty half of the initial solution (T1/2) was different between the trials (WP = 65.5 ± 11.4 min; MD = 56.7 ± 6.3 min; p = 0.05); however, there was no difference in cumulative urine volume throughout the recovery period (WP = 1306 ± 306 mL; MD = 1428 ± 443 mL; p = 0.314). Participants returned to net negative fluid balance 2 h after the recovery period with MD and 3 h with WP. The results of this study suggest that whey protein empties from the stomach at a slower rate than MD; however, this does not seem to exert any positive or negative effects on the maintenance of fluid balance in the post-exercise period

Infection with cerebral metacercariae of microphallid trematode parasites reduces reproductive output in the gammarid amphipod Gammarus insensibilis (Stock 1966) in UK saline lagoons

Saline lagoons are priority habitats in the United Kingdom supporting several protected specialist species. One specialist, the amphipod Gammarus insensibilis, is infected with behaviour-altering microphallid trematodes such as Microphallus papillorobustus. In saline lagoons around the coast of England (Gilkicker and Lymington–Keyhaven on the Hampshire coast and Moulton Marsh in Lincolnshire) there is variation in the prevalence of this parasite in the gammarid populations (0 at Salterns in the Lymington–Keyhaven lagoon system to 98% at Gilkicker). Infection intensity ranged from 0 to 20 metacercariae in individual amphipods. Higher infection intensity can alter the shape of the amphipod's head. Under experimental conditions respiration rate is significantly reduced in infected animals and reproductive output (expressed as early stage embryos mg g dry weight−1) is significantly lower in infected females. It is important to consider the role of host–parasite interactions in order to understand the ecology of specialist lagoon species such as G. insensibilis and their lagoon habitats

Infection with cerebral metacercariae of microphallid trematode parasites reduces reproductive output in the gammarid amphipod Gammarus insensibilis (Stock 1966) in UK saline lagoons

Saline lagoons are priority habitats in the United Kingdom supporting several protected specialist species. One specialist, the amphipod Gammarus insensibilis, is infected with behaviour-altering microphallid trematodes such as Microphallus papillorobustus. In saline lagoons around the coast of England (Gilkicker and Lymington–Keyhaven on the Hampshire coast and Moulton Marsh in Lincolnshire) there is variation in the prevalence of this parasite in the gammarid populations (0 at Salterns in the Lymington–Keyhaven lagoon system to 98% at Gilkicker). Infection intensity ranged from 0 to 20 metacercariae in individual amphipods. Higher infection intensity can alter the shape of the amphipod's head. Under experimental conditions respiration rate is significantly reduced in infected animals and reproductive output (expressed as early stage embryos mg g dry weight−1) is significantly lower in infected females. It is important to consider the role of host–parasite interactions in order to understand the ecology of specialist lagoon species such as G. insensibilis and their lagoon habitats

Interstitial boron atoms in the palladium lattice of an industrial type of nanocatalyst: properties and structural modifications

It is well-established that the inclusion of small atomic species such as boron (B) in powder metal catalysts can subtly modify catalytic properties, and the associated changes in the metal lattice imply that the B atoms are located in the interstitial sites. However, there is no compelling evidence for the occurrence of interstitial B atoms, and there is a concomitant lack of detailed structural information describing the nature of this occupancy and its effects on the metal host. In this work, we use an innovative combination of high-resolution 11B magic-angle-spinning (MAS) and 105Pd static solid-state NMR nuclear magnetic resonance (NMR), synchrotron X-ray diffraction (SXRD), in situ X-ray pair distribution function (XPDF), scanning transmission electron microscopy-annular dark field imaging (STEM-ADF), electron ptychography, and electron energy loss spectroscopy (EELS) to investigate the B atom positions, properties, and structural modifications to the palladium lattice of an industrial type interstitial boron doped palladium nanoparticle catalyst system (Pd-intB/C NPs). In this study, we report that upon B incorporation into the Pd lattice, the overall face centered cubic (FCC) lattice is maintained; however, short-range disorder is introduced. The 105Pd static solid-state NMR illustrates how different types (and levels) of structural strain and disorder are introduced in the nanoparticle history. These structural distortions can lead to the appearance of small amounts of local hexagonal close packed (HCP) structured material in localized regions. The short-range lattice tailoring of the Pd framework to accommodate interstitial B dopants in the octahedral sites of the distorted FCC structure can be imaged by electron ptychography. This study describes new toolsets that enable the characterization of industrial metal nanocatalysts across length scales from macro- to microanalysis, which gives important guidance to the structure-activity relationship of the system

Bolus Ingestion of Whey Protein Immediately Post-Exercise Does Not Influence Rehydration Compared to Energy-Matched Carbohydrate Ingestion

Whey protein is a commonly ingested nutritional supplement amongst athletes and regular exercisers; however, its role in post-exercise rehydration remains unclear. Eight healthy male and female participants completed two experimental trials involving the ingestion of 35 g of whey protein (WP) or maltodextrin (MD) at the onset of a rehydration period, followed by ingestion of water to a volume equivalent to 150% of the amount of body mass lost during exercise in the heat. The gastric emptying rates of the solutions were measured using 13C breath tests. Recovery was monitored for a further 3 h by the collection of blood and urine samples. The time taken to empty half of the initial solution (T1/2) was different between the trials (WP = 65.5 ± 11.4 min; MD = 56.7 ± 6.3 min; p = 0.05); however, there was no difference in cumulative urine volume throughout the recovery period (WP = 1306 ± 306 mL; MD = 1428 ± 443 mL; p = 0.314). Participants returned to net negative fluid balance 2 h after the recovery period with MD and 3 h with WP. The results of this study suggest that whey protein empties from the stomach at a slower rate than MD; however, this does not seem to exert any positive or negative effects on the maintenance of fluid balance in the post-exercise period

Major Surface Glycoproteins of Insect Forms of Trypanosoma brucei Are Not Essential for Cyclical Transmission by Tsetse

Procyclic forms of Trypanosoma brucei reside in the midgut of tsetse flies where they are covered by several million copies of glycosylphosphatidylinositol-anchored proteins known as procyclins. It has been proposed that procyclins protect parasites against proteases and/or participate in tropism, directing them from the midgut to the salivary glands. There are four different procyclin genes, each subject to elaborate levels of regulation. To determine if procyclins are essential for survival and transmission of T. brucei, all four genes were deleted and parasite fitness was compared in vitro and in vivo. When co-cultured in vitro, the null mutant and wild type trypanosomes (tagged with cyan fluorescent protein) maintained a near-constant equilibrium. In contrast, when flies were infected with the same mixture, the null mutant was rapidly overgrown in the midgut, reflecting a reduction in fitness in vivo. Although the null mutant is patently defective in competition with procyclin-positive parasites, on its own it can complete the life cycle and generate infectious metacyclic forms. The procyclic form of T. brucei thus differs strikingly from the bloodstream form, which does not tolerate any perturbation of its variant surface glycoprotein coat, and from other parasites such as Plasmodium berghei, which requires the circumsporozoite protein for successful transmission to a new host

Environmental sensing and response genes in cnidaria : the chemical defensome in the sea anemone Nematostella vectensis

Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Cell Biology and Toxicology 24 (2008): 483-502, doi:10.1007/s10565-008-9107-5.The starlet sea anemone Nematostella vectensis has been recently established as a new model system for the study of the evolution of developmental processes, as cnidaria occupy a key evolutionary position at the base of the bilateria. Cnidaria play important roles in estuarine and reef communities, but are exposed to many environmental stressors. Here I describe the genetic components of a ‘chemical defensome’ in the genome of N. vectensis, and review cnidarian molecular toxicology. Gene families that defend against chemical stressors and the transcription factors that regulate these genes have been termed a ‘chemical defensome,’ and include the cytochromes P450 and other oxidases, various conjugating enyzymes, the ATP-dependent efflux transporters, oxidative detoxification proteins, as well as various transcription factors. These genes account for about 1% (266/27200) of the predicted genes in the sea anemone genome, similar to the proportion observed in tunicates and humans, but lower than that observed in sea urchins. While there are comparable numbers of stress-response genes, the stress sensor genes appear to be reduced in N. vectensis relative to many model protostomes and deuterostomes. Cnidarian toxicology is understudied, especially given the important ecological roles of many cnidarian species. New genomic resources should stimulate the study of chemical stress sensing and response mechanisms in cnidaria, and allow us to further illuminate the evolution of chemical defense gene networks.WHOI Ocean Life Institute and NIH R01-ES01591