Insulin-Like Peptides and the Target of Rapamycin Pathway Coordinately Regulate Blood Digestion and Egg Maturation in the Mosquito Aedes aegypti

Mosquitoes are insects that vector many serious pathogens to humans and other vertebrates. Most mosquitoes must feed on the blood of a vertebrate host to produce eggs. In turn, multiple cycles of blood feeding promote frequent contacts with hosts and make mosquitoes ideal disease vectors. Both hormonal and nutritional factors are involved in regulating egg development in the mosquito, Aedes aegypti. However, the processes that regulate digestion of the blood meal remain unclear.Here we report that insulin peptide 3 (ILP3) directly stimulated late phase trypsin-like gene expression in blood fed females. In vivo knockdown of the mosquito insulin receptor (MIR) by RNA interference (RNAi) delayed but did not fully inhibit trypsin-like gene expression in the midgut, ecdysteroid (ECD) production by ovaries, and vitellogenin (Vg) expression by the fat body. In contrast, in vivo treatment with double-stranded MIR RNA and rapamycin completely blocked egg production. In vitro experiments showed that amino acids did not simulate late phase trypsin-like gene expression in the midgut or ECD production by the ovaries. However, amino acids did enhance ILP3-mediated stimulation of trypsin-like gene expression and ECD production.Overall, our results indicate that ILPs from the brain synchronize blood meal digestion and amino acid availability with ovarian ECD production to maximize Vg expression by the fat body. The activation of digestion by ILPs may also underlie the growth promoting effects of insulin and TOR signaling in other species

Fast synaptic transmission in the goldfish CNS mediated by multiple nicotinic receptors

In this study, fast synaptic transmission at vertebrate CNS connections mediated by several different nicotinic ACh receptors (nAChRs) was investigated with paired recordings from pre- and postsynaptic neurons. Analysis of the response kinetics at the axo-axonic connections between the Mauthner (M-) axon and cranial relay neurons (CRN) indicates up to three main components are present and can be characterized by fast, ∼1.5 ms, intermediate, ∼6 ms and slow, ∼15 ms, decay time constants. Further analysis indicates most responses have multiexponential decays and each response falls into one of six classes dependent on the weight and combination of kinetic components. Pharmacological results suggest that up to three nAChRs, α7*, α3β2* and α3β4*, mediate the postsynaptic responses and correspond to the fast, intermediate and slow decay components, respectively. The fast decay component is blocked by ∼35 nm methyllycaconitine (MLA), 100 nmα-bungarotoxin (α-Btx) or 150 nmα-conotoxin (α-Ctx) ArIB. The intermediate decay component is blocked by 2 μm dihydro-beta-erythroidine (DHβE) or 200 nmα-Ctx GIC. The slow decay component is blocked by 10 μmα-Ctx AuIB, but not by 7.25 μm DHβE. Intriguingly, the mEPSPs (minis) at connections with evoked EPSPs best fitted by multiple exponentials, were not composite; rather, there were multiple populations of minis, each with single exponential decay times corresponding to those of the different evoked EPSP components. This indicates that the different receptors are topographically segregated at the connection between the M-axon and CRN axon. These results suggest that, as with glutamate, fast nicotinic synaptic transmission in the CNS can be mediated by multiple receptors in the same postsynaptic neuron. The coexistence of EPSPs of different durations may have implications for network function and plasticity

Environmental Chemical Exposures and Autism Spectrum Disorders: A Review of the Epidemiological Evidence

In the past decade, the number of epidemiological publications addressing environmental chemical exposures and autism has grown tremendously. These studies are important because it is now understood that environmental factors play a larger role in causing autism than previously thought and because they address modifiable risk factors that may open up avenues for the primary prevention of the disability associated with autism. In this review, we covered studies of autism and estimates of exposure to tobacco, air pollutants, volatile organic compounds and solvents, metals (from air, occupation, diet, dental amalgams, and thimerosal-containing vaccines), pesticides, and organic endocrine-disrupting compounds such as flame retardants, non-stick chemicals, phthalates, and bisphenol A. We included studies that had individual-level data on autism, exposure measures pertaining to pregnancy or the 1st year of life, valid comparison groups, control for confounders, and adequate sample sizes. Despite the inherent error in the measurement of many of these environmental exposures, which is likely to attenuate observed associations, some environmental exposures showed associations with autism, especially traffic-related air pollutants, some metals, and several pesticides, with suggestive trends for some volatile organic compounds (e.g., methylene chloride, trichloroethylene, and styrene) and phthalates. Whether any of these play a causal role requires further study. Given the limited scope of these publications, other environmental chemicals cannot be ruled out, but have not yet been adequately studied. Future research that addresses these and additional environmental chemicals, including their most common routes of exposures, with accurate exposure measurement pertaining to several developmental windows, is essential to guide efforts for the prevention of the neurodevelopmental damage that manifests in autism symptoms