Aedes Mosquito Saliva Modulates Rift Valley Fever Virus Pathogenicity

Background

Rift Valley fever (RVF) is a severe mosquito-borne disease affecting humans and domestic ruminants. Mosquito saliva contains compounds that counteract the hemostatic, inflammatory, and immune responses of the host. Modulation of these defensive responses may facilitate virus infection. Indeed, Aedes mosquito saliva played a crucial role in the vector''s capacity to effectively transfer arboviruses such as the Cache Valley and West Nile viruses. The role of mosquito saliva in the transmission of Rift Valley fever virus (RVFV) has not been investigated.

Objective

Using a murine model, we explored the potential for mosquitoes to impact the course of RVF disease by determining whether differences in pathogenesis occurred in the presence or absence of mosquito saliva and salivary gland extract.

Methods

C57BL/6NRJ male mice were infected with the ZH548 strain of RVFV via intraperitoneal or intradermal route, or via bites from RVFV-exposed mosquitoes. The virus titers in mosquitoes and mouse organs were determined by plaque assays.

Findings

After intraperitoneal injection, RVFV infection primarily resulted in liver damage. In contrast, RVFV infection via intradermal injection caused both liver and neurological symptoms and this route best mimicked the natural infection by mosquitoes. Co-injections of RVFV with salivary gland extract or saliva via intradermal route increased the mortality rates of mice, as well as the virus titers measured in several organs and in the blood. Furthermore, the blood cell counts of infected mice were altered compared to those of uninfected mice.

Interpretation

Different routes of infection determine the pattern in which the virus spreads and the organs it targets. Aedes saliva significantly increases the pathogenicity of RVFV.     

Effect of nifedipine on anorectal sensorimotor functions in health and fecal incontinence

The mechanisms of increased rectal stiffness in women with fecal incontinence (FI) and rectal urgency are not understood. Our hypothesis was that distention-induced activation of mechanosensitive L-type calcium channels in smooth muscle contributes to increased rectal stiffness in FI. Anal pressures, rectal distensibility (compliance, capacity, and contractile response to sinusoidal oscillation), and rectal sensation were assessed before and after oral nifedipine (30 + 10 mg) or placebo in 16 women with FI and 16 asymptomatic women. At baseline, FI patients had a lower anal pressure increment during squeeze (health, 66.9 ± 7.6: FI, 28.6 ± 5.9, mean ± SE, P ≤ 0.01), lower rectal capacity (P = 0.052), and higher rectal pressures during sinusoidal oscillation (health, 13.7 ± 3.2: FI, 21.7 ± 1.4, mean ± SE, P = 0.02) than the healthy women, which suggests an exaggerated rectal contractile response to distention. Nifedipine decreased mean BP, increased heart rate (P = 0.01 vs. placebo), and reduced anal resting pressure (P ≤ 0.01) but did not significantly modify rectal distensibility in health or FI. Plasma nifedipine concentrations (health, 103 ± 21 ng/ml: FI, 162 ± 34 ng/ml) were correlated with increased rectal compliance (r = 0.6, P = 0.02) in all study participants and, in healthy subjects, with decreased rectal pressures during sinusoidal oscillation (r = 0.86, P = 0.01), indicative of reduced stiffness. No consistent effects on rectal perception were observed. These observations confirm that FI is associated with anal weakness and increased rectal stiffness. At therapeutic plasma concentrations, nifedipine reduced anal resting pressure but did not improve rectal distensibility in FI, outcomes that argue against a predominant contribution of myogenic L-type calcium channels to reduced rectal distensibility in FI.     

Octopamine and serotonin have opposite effects on antipredator behavior in the orb-weaving spider, <Emphasis Type="Italic">Larinioides cornutus</Emphasis>

In this study, we experimentally elevated levels of octopamine and serotonin in an orb-weaving spider, and observed the effects on the antipredator behavior thanatosis (death feigning), activity level, and running speed. We found that octopamine significantly shortened the duration of thanatosis, and its effect wore off over 24 h. We also found that serotonin significantly lengthened thanatosis, but in this case, the effect persisted for over 24 h. Neither octopamine nor serotonin affected the general activity or running speed of the spiders. To our knowledge, this is the first study to directly explore the role of biogenic amines on a specific antipredator behavior in spiders. Given that spiders must be both aggressive toward prey, yet wary of predators, we believe that this system will be an outstanding model to explore connections between behavioral ecology and neurochemistry.     

Spatial structure and the effects of host and soil environments on communities of ectomycorrhizal fungi in wooded savannas and rain forests of Continental Africa and Madagascar

Mycorrhizal fungi play a key role in mineral nutrition of terrestrial plants, but the factors affecting natural distribution, diversity and community composition of particularly tropical fungi remain poorly understood. This study addresses shifts in community structure and species frequency of ectomycorrhizal (EcM) fungi in relation to host taxa, soil depth and spatial structure in four contrasting African ecosystems. We used the rDNA and plastid trnL intron sequence analysis for identification of fungi and host plants, respectively. By partitioning out spatial autocorrelation in plant and fungal distribution, we suggest that African EcM fungal communities are little structured by soil horizon and host at the plant species and family levels. These findings contrast with patterns of vegetation in these forests and EcM fungal communities in other tropical and temperate ecosystems. The low level of host preference indirectly supports an earlier hypothesis that pioneer Phyllanthaceae may facilitate the establishment of late successional Fabaceae and potentially other EcM host trees by providing compatible fungal inoculum in deforested and naturally disturbed ecosystems of tropical Africa.     

Cyclic release of carbon dioxide accompanied by abdominal telescoping movements in forager ants of Formica polyctena (Hymenoptera, Formicidae)

Abstract.  Discontinuous gas exchange and abdominal telescoping movements were investigated in intact forager ants of Formica polyctena Förster. For simultaneous recording of discontinuous gas exchange and abdominal movements, an electrolytic differential microrespirometer was combined with an infrared-optical device using an infrared-sensor diode commonly applied as a cardiograph in insect studies. The air in the insect chamber was saturated with water vapour, and an ant was contacted with a sliver of wet filter paper. Accordingly, the ants used in the experiments were regarded as being hydrated. The enforced immobility of the ant in the respirometry chamber (0.15 mL volume) induced continuous struggling during the first hours of measurement but, after 3–4 h, the activity periods alternated with quiescent periods when regular cycles of discontinuous gas exchange (8.97 mHz) were displayed. After remaining in the chamber for a day, the ants showed such cycles (8.15 mHz) without any interruption by periods of activity. The cyclic release of carbon dioxide (burst) was accompanied by a bout of telescoping movements of the abdominal segments (rapid contractions and slow relaxations), which were interpreted as active ventilation. The irregular and rare abdominal contractions, recorded during the interburst periods on the first day of measurements, were regarded as a symptom of stress because these disappeared on the second day. In approximately 20% of foragers, the telescoping movements during the interburst periods were characterized by very rapid (0.09 s) protractions and slow retractions of the abdominal segments, obviously acting as inspiration movements. The results do not support the hypothesis that discontinuous gas exchange is an adaptation for conserving water in ants.     

Occurrence of virulence and antimicrobial resistance genes in Escherichia coli isolates from different aquatic ecosystems within the St. Clair River and Detroit River areas

Although the number of Escherichia coli bacteria in surface waters can differ greatly between locations, relatively little is known about the distribution of E. coli pathotypes in surface waters used as sources for drinking or recreation. DNA microarray technology is a suitable tool for this type of study due to its ability to detect high numbers of virulence and antimicrobial resistance genes simultaneously. Pathotype, phylogenetic group, and antimicrobial resistance gene profiles were determined for 308 E. coli isolates from surface water samples collected from diverse aquatic ecosystems at six different sites in the St. Clair River and Detroit River areas. A higher frequency (48%) of E. coli isolates possessing virulence and antimicrobial resistance genes was observed in an urban site located downstream of wastewater effluent outfalls than in the other examined sites (average of 24%). Most E. coli pathotypes were extraintestinal pathogenic E. coli (ExPEC) pathotypes and belonged to phylogenetic groups B2 and D. The ExPEC pathotypes were found to occur across all aquatic ecosystems investigated, including riverine, estuarine, and offshore lake locations. The results of this environmental study using DNA microarrays highlight the widespread distribution of E. coli pathotypes in aquatic ecosystems and the potential public health threat of E. coli pathotypes originating from municipal wastewater sources.     

Use of High Throughput Sequencing and Light Microscopy Show Contrasting Results in a Study of Phytoplankton Occurrence in a Freshwater Environment

Assessing phytoplankton diversity is of primary importance for both basic and applied ecological studies. Following the advances in molecular methods, phytoplankton studies are switching from using classical microscopy to high throughput sequencing approaches. However, methodological comparisons of these approaches have rarely been reported. In this study, we compared the two methods, using a unique dataset of multiple water samples taken from a natural freshwater environment. Environmental DNA was extracted from 300 water samples collected weekly during 20 years, followed by high throughput sequencing of amplicons from the 16S and 18S rRNA hypervariable regions. For each water sample, phytoplankton diversity was also estimated using light microscopy. Our study indicates that species compositions detected by light microscopy and 454 high throughput sequencing do not always match. High throughput sequencing detected more rare species and picoplankton than light microscopy, and thus gave a better assessment of phytoplankton diversity. However, when compared to light microscopy, high throughput sequencing of 16S and 18S rRNA amplicons did not adequately identify phytoplankton at the species level. In summary, our study recommends a combined strategy using both morphological and molecular techniques.     

HS1, a Lyn kinase substrate, is abnormally expressed in B-chronic lymphocytic leukemia and correlates with response to fludarabine-based regimen

In B-Chronic Lymphocytic Leukemia (B-CLL) kinase Lyn is overexpressed, active, abnormally distributed, and part of a cytosolic complex involving hematopoietic lineage cell-specific protein 1 (HS1). These aberrant properties of Lyn could partially explain leukemic cells' defective apoptosis, directly or through its substrates, for example, HS1 that has been associated to apoptosis in different cell types. To verify the hypothesis of HS1 involvement in Lyn-mediated leukemic cell survival, we investigated HS1 protein in 71 untreated B-CLL patients and 26 healthy controls. We found HS1 overexpressed in leukemic as compared to normal B lymphocytes (1.38±0.54 vs 0.86±0.29, p<0.01), and when HS1 levels were correlated to clinical parameters we found a higher expression of HS1 in poor-prognosis patients. Moreover, HS1 levels significantly decreased in ex vivo leukemic cells of patients responding to a fludarabine-containing regimen. We also observed that HS1 is partially localized in the nucleus of neoplastic B cells. All these data add new information on HS1 study, hypothesizing a pivotal role of HS1 in Lyn-mediated modulation of leukemic cells' survival and focusing, one more time, the attention on the BCR-Lyn axis as a putative target for new therapeutic strategies in this disorder.     

Engraftment and differentiation of embryonic stem cell-derived neural progenitor cells in the cochlear nerve trunk: growth of processes into the organ of Corti

Hearing loss in mammals is irreversible because cochlear neurons and hair cells do not regenerate. To determine whether we could replace neurons lost to primary neuronal degeneration, we injected EYFP-expressing embryonic stem cell-derived mouse neural progenitor cells into the cochlear nerve trunk in immunosuppressed animals 1 week after destroying the cochlear nerve (spiral ganglion) cells while leaving hair cells intact by ouabain application to the round window at the base of the cochlea in gerbils. At 3 days post transplantation, small grafts were seen that expressed endogenous EYFP and could be immunolabeled for neuron-specific markers. Twelve days after transplantation, the grafts had neurons that extended processes from the nerve core toward the denervated organ of Corti. By 64-98 days, the grafts had sent out abundant processes that occupied a significant portion of the space formerly occupied by the cochlear nerve. The neurites grew in fasciculating bundles projecting through Rosenthal's canal, the former site of spiral ganglion cells, into the osseous spiral lamina and ultimately into the organ of Corti, where they contacted hair cells. Neuronal counts showed a significant increase in neuronal processes near the sensory epithelium, compared to animals that were denervated without subsequent stem cell transplantation. The regeneration of these neurons shows that neurons differentiated from stem cells have the capacity to grow to a specific target in an animal model of neuronal degeneration.     

Discovery of imidazole vinyl pyrimidines as a novel class of kinase inhibitors which inhibit Tie-2 and are orally bioavailable

Tie-2 is a receptor tyrosine kinase which is involved in angiogenesis and thereby growth of human tumours. The discovery and SAR of a novel class of imidazole-vinyl-pyrimidine kinase inhibitors, which inhibit Tie-2 in vitro is reported. Their synthesis was carried out by condensation of imidazole aldehydes with methyl pyrimidines. These compounds are lead-like, with low molecular weight, good physical properties and oral bioavailability.