Factors affecting transmission of trypanosomes through tsetse flies

The maintenance of human sleeping sickness and nagana across sub-Saharan Africa depends on cyclical transmission of trypanosomes through tsetse flies. Infection rates in tsetse are normally very low as most parasites ingested with a bloodmeal die in the fly gut. Infections which successfully establish in the fly midgut may subsequently mature into mammalian infective trypanosomes in the salivary glands. However, these processes are not automatic and involve tsetse, symbiont, trypanosome and environmental factors.Previous work showed that the symbiotic bacterium Sodalis glossinidius was involved in susceptibility to trypanosome infection. Streptozotocin (a toxic analogue of the bacterium's main food source) has been recently shown to decrease trypanosome infection rates in the offspring of treated tsetse. In the present work streptozotocin did remove S. glossinidius from the offspring of treated flies but it was not possible to generate a line of tsetse free from 5. glossinidius infection.Other potential factors involved in acquisition of trypanosome infection were then examined. A range of antioxidants or cyclic GMP were shown to prevent trypanosome death in the tsetse midgut. The process was shown to be independent of protein synthesis as D-cysteine (an unphysiological isomer of L-cysteine) also enhanced midgut infection rates. Further experiments showed that cGMP could significantly inhibit trypanosome death when fed up to 96 h post-infection, whereas antioxidants only functioned for 48 h post-infection. Moreover it was found that maturation of established midgut infections could be regulated by environmental stimuli as well as by antioxidants. Cold shock of infected flies as well as addition of L-cysteine but not D-cysteine to the bloodmeal resulted in significant increases in maturation rates, while nitric oxide synthase inhibitors reduced maturation rates.It is concluded that reactive oxygen species play a major role in killing trypanosomes entering the tsetse midgut and that cysteine containing proteins and/or nitric oxide are essential for differentiation of established midgut infections into mammalian infective salivary gland infections

Influence of reheating on the trispectrum and its scale dependence

We study the evolution of the non-linear curvature perturbation during perturbative reheating, and hence how observables evolve to their final values which we may compare against observations. Our study includes the evolution of the two trispectrum parameters, \gnl and \taunl, as well as the scale dependence of both \fnl and \taunl. In general the evolution is significant and must be taken into account, which means that models of multifield inflation cannot be compared to observations without specifying how the subsequent reheating takes place. If the trispectrum is large at the end of inflation, it normally remains large at the end of reheating. In the classes of models we study, it is very hard to generate \taunl\gg\fnl^2, regardless of the decay rates of the fields. Similarly, for the classes of models in which \gnl\simeq\taunl during slow--roll inflation, we find the relation typically remains valid during reheating. Therefore it is possible to observationally test such classes of models without specifying the parameters of reheating, even though the individual observables are sensitive to the details of reheating. It is hard to generate an observably large \gnl however. The runnings, \nfnl and \ntaunl, tend to satisfy a consistency relation \ntaunl=(3/2)\nfnl, but are in general too small to be observed for the class of models considered regardless of reheating timescale

Hard ticks (Acari: Ixodidae) and tick-borne diseases of sheep and goats in Africa: A Review

Ticks are leading vectors of economically important pathogens that affect small ruminants due to favourable climatic conditions across different regions of the African continent. They are responsible for both direct and indirect economic losses in the livestock industry. This review focuses on the species diversity of hard ticks, their biology, tick-borne diseases of sheep and goats including non-infectious disease, and risk factors to tick infestation in Africa. Furthermore, our review provides recent updates on distribution of ticks and tick-borne pathogens of small ruminants in Africa. It was observed that several species and subspecies of hard ticks belonging to the genera Hyalomma (Hy), Rhipicephalus (Rh), Ixodes (I) and Amblyomma (Am) were found infesting small ruminants across the different regions of the continent. Of these genera, Rhipicephalus ticks accounts for the majority of the registered species, with exactly 27 different species infesting small ruminant stocks comprising of different developmental instars and adults of the tick. Rhipicephalus decolaratus, Rh. e. evertsi and Rh. appendiculatus were the three most common Rhipicephalus species reported. Both protozoal (Babesia and Theileria) and bacterial (Anaplasma, Rickettsia, Ehrlichia, Coxiella and Mycoplasma) pathogens have being reported to be amplified in several hard tick species and/or small ruminant hosts. Furthermore, tick paralysis and lameness were non-infectious conditions attributed to tick infestations. Amblyomma hebraeum and Rh. glabroscutatum may cause lameness in goats, while Hy. rufipes is responsible for the same condition in Merino sheep. Host paralysis due to a neurotoxin released by female Rh. e. evertsi and I. rubicundus has been documented within the continent. We therefore advocate for the need of integrated control measures against tick-borne pathogens (TBPs) including their arthropod vectors, to be performed simultaneously to ease the burden of vector-borne diseases in small ruminant production.<br/

The consequence of natural selection on genetic variation in the mouse

AbstractLaboratory mouse strains are known to have emerged from recent interbreeding between individuals of Mus musculus isolated populations. As a result of this breeding history, the collection of polymorphisms observed between laboratory mouse strains is likely to harbor the effects of natural selection between reproductively isolated populations. Until now no study has systematically investigated the consequences of this breeding history on gene evolution. Here we have used a novel, unbiased evolutionary approach to predict the founder origin of laboratory mouse strains and to assess the balance between ancient and newly emerged mutations in the founder subspecies. Our results confirm a contribution from at least four distinct subspecies. Additionally, our method allowed us to identify regions of relaxed selective constraint among laboratory mouse strains. This unique structure of variation is likely to have significant consequences on the use of mouse to find genes underlying phenotypic variation

Time-domain THz spectroscopy reveals coupled protein-hydration dielectric response in solutions of native and fibrils of human lyso-zyme

Here we reveal details of the interaction between human lysozyme proteins, both native and fibrils, and their water environment by intense terahertz time domain spectroscopy. With the aid of a rigorous dielectric model, we determine the amplitude and phase of the oscillating dipole induced by the THz field in the volume containing the protein and its hydration water. At low concentrations, the amplitude of this induced dipolar response decreases with increasing concentration. Beyond a certain threshold, marking the onset of the interactions between the extended hydration shells, the amplitude remains fixed but the phase of the induced dipolar response, which is initially in phase with the applied THz field, begins to change. The changes observed in the THz response reveal protein-protein interactions me-diated by extended hydration layers, which may control fibril formation and may have an important role in chemical recognition phenomena

Effects of cyclic nucleotides on midgut infections and maturation of T. b. brucei in G. m. morsitans

Cyclic nucleotide signalling through cyclic adenosine monophosphate (cAMP) is thought to play an important role in the transformation of the long slender (dividing) form to the short-stumpy (arrested) form in the mammalian bloodstream but the role of cyclic nucleotides in the tsetse-based part of the trypanosome life cycle is unknown. In a series of in vivo experiments, it was found that cyclic guanosine monophosphate (cGMP) but not cAMP could induce significantly higher rates of midgut infection in tsetse. Continuous feeding of either cGMP or cAMP to tsetse had no effect on rates of maturation of established midgut infections suggesting that these two parts of the life cycle in tsetse are not linked

Optically-ambidextrous circularly-polarised reflection from the chiral cuticle of the scarab beetle Chrysina resplendens

This is the author accepted manuscript. The final version is available from Royal Society via the DOI in this record.The evolution of structural colour mechanisms in biological systems has given rise to many interesting optical effects in animals and plants. The instance of the scarab beetle Chrysina resplendens is particularly distinctive. Its exoskeleton has a bright, golden appearance and reflects both right-handed and left-handed circularly-polarized light concurrently. The chiral nanostructure responsible for these properties is a helicoid, in which birefringent dielectric planes are assembled with an incremental rotation. This study correlates details of the beetle’s circularly-polarized reflectance spectra directly with physical aspects of its structural morphology. Electron micrography is used to identify and measure the physical dimensions of the key constituent components. These include a chiral multilayer configuration comprising two chirped, lefthanded helicoids that are separated by a birefringent retarder. A scattering matrix technique is used to simulate the system’s optical behaviour in which the roles of each component of the morphological substructure are elucidated by calculation of the fields throughout its depth.This work was supported by AFOSR grant number FA9550-10-1- 0020

Effect of Gestational Folic Acid Supplementation of Sows on Offspring Muscle Development and Postnatal Growth Response

Pairs of littermate, primiparous sows were penned individually and fed daily 1.9 kg of a low folic acid (FA) (.28 mg/kg) basal diet supplemented with 0 or 8 mg of FA from mating through parturition. All sows were fed the basal diet for 112 days prior to breeding to minimize the sows initial body folic acid stores. FA supplementation in sows during gestation resulted in elevated concentrations of serum FA. However, FA supplementation did not affect litter birth weight, litter muscle, fat, or bone weights, or litter DNA and protein content of three individual muscles at birth. FA supplementation of the sow also did not affect the offspring’s body weight gain, feed intake, and gain:feed ratio from body weights of 13 to 107 kg. Based on these data, a dietary folic acid regimen of .3 ppm (.53 mg/day) during pregnancy supports normal muscle growth in pigs pre- and postnatall

Tensor Product Decomposition Networks: Uncovering Representations of Structure Learned by Neural Networks

We introduce an analysis technique for understanding compositional structure present in the vector representations used by neural networks. The inner workings of neural networks are notoriously difficult to understand, and in particular it is far from clear how they manage to perform remarkably well on tasks that depend on compositional structure even though they use continuous vector representations with no obvious compositional structure. Using our analysis technique, we show that the representations of these models can be closely approximated by Tensor Product Representations, a type of interpretable structure that lends significant insight into the workings of these hard-to-interpret models