In a laboratory setting, chlorantraniliprole was harmless to Orius laevigatusfor residues aged 1-14 d, in contrast to abamectin, which resulted in nearly 100% mortality up to 14 d . In a field setting, the half-life of chlorantraniliprole on rice straw was 3.5 d , and in sugarcane, was 8 d at both 1x and 2x the recommended field rate . Hence, the relatively short half-life of chlorantraniliprole compared to that of lambdacyhalothrin, further suggests that it had minimal effect on the acute mortality of H. convergens mortality in our study, which was still substantial by day 8 . The persistence of the toxicity effects of pyrethroid residues in the field appears to vary considerably among natural enemy species and active ingredients. For example, field-aged residues of esfenvalerate remained highly toxic to adult Trichogramma platneri Nagarkatti after 21 days, but were harmless after 7 days for Colpoclypeus florus. In addition, residues of permethrin and esfenvalerate on almond twigs were sufficient to cause 50% acute mortality of G. occidentalis even after 7 months of aging in the field . Nonetheless, pyrethroids are subject to photodegradation under field conditions. When exposed to UV light, lambda-cyhalothrin can degrade to 5% of the initial amount applied after 20 min . Similarly, when applied to a rice paddy, the half-lives of both components of the combination insecticide were determined to be 5 days . Thus rates of degradation of lambda-cyhalothrin under field conditions may vary with formulation, UV exposure within the canopy of the crop, and with residue substrate. Despite the potential for degradation of lambda-cyhalothrin under field conditions, the high level of sensitivity of the voltage-gated sodium channels of insects to disruption by pyrethroids resulted in the persistence of acute effects on H. convergens larvae in a walnut orchard after 38 days. From this study we have been able to show that acute mortality response of H. convergens to the insecticide combination of chlorantraniliprole and lambda-cyhalothrin was affected by residue age, setting, and life stage.
Adults and larvae both experienced high levels mortality when exposed to fresh residues of the combination insecticide. Chlorantraniliprole is frequently not toxic, whereas lambda-cyhalothrin is highly toxic,low round pots to a number of natural enemy species, and therefore the latter active ingredient was likely responsible for the high mortality of H. convergens. Larvae were more susceptible to the insecticide residues than adults, and aging had a greater effect for field-aged residues that were exposed to UV from natural daylight than for laboratory-aged residues that were exposed to fluorescent lighting. Thus, traditional laboratory bio-assays can yield greater estimates of the persistence of acute mortality responses among natural enemies than bio-assays based on field-aged residues. However, the acute mortality responses of H. convergens to fresh residues of the combination insecticide were similar for insects exposed to field-aged or laboratory-aged residues. This indicates that traditional laboratory bio-assays remain a useful tool for assessing acute toxicity for fresh residues, while bio-assays with field-aged residues are needed to accurately assess the persistence of toxic effects on natural enemy mortality. Integration of chemical signals at the peripheral sensory system remains one of the least understood mechanisms of insect olfaction, particularly in mosquitoes. Despite the great progress made in the last 2 decades in understanding how receptors form the basis of chemosensory perception in insects, how olfactory signals integrate at the periphery remains an enigma . ‘‘It is as if a new continent has been discovered but only the coastline has been mapped’’ . In the largest majority of reported cases , antennal neurons of Cx. quinquefasciatus displayed excitatory responses , but evidence for inhibitory responses , already known for Ae. aegypti , is now emerging for Cx. quinquefasciatus . It has been observed in moths , beetles , the fruit fly , and mosquitoes that activation of one neuron interferes with signaling of other olfactory receptor neurons . It has also been reported that a single compound caused reduction of nerve impulse followed by a transient post-stimulus excitation . Although Carlson and collaborators elegantly demonstrated that in the fruit fly lateral inhibition is most likely mediated by ephaptic coupling , the complete ensemble of the molecular mechanism of inhibition at the peripheral olfactory system of mosquitoes remains terra incognita.
A simple explanation of the ephaptic coupling is that, upon stimulation of an ORN, the potential declines. Consequently, per channel current generated by a cocompart mentalized neuron is reduced . This scenario argues that the firing of a neuron causes reduced spike frequency by a colocated neuron because of the close apposition of their neuronal processes. Although ephaptic coupling could explain lateral inhibition, other mechanisms of intraneuron inhibition may exist. While de-orphanizing odorant receptors expressed predominantly in Cx. quinquefasciatus female antennae, we serendipitously recorded currents from an OR that generate inhibition in response to certain odorants. Further studies unraveled a hitherto unknown mechanism of peripheral, intrareceptor inhibition in mosquito olfaction.To test whether the inhibitory responses were manifested in vivo at the periphery of the olfactory system, we generated transgenic flies, with CquiOR32 expression driven by DmelOrco promoter, and recorded electroantennogram responses by using a standard method . Not surprisingly, control flies gave strong response to -2-hexenal and weak response to methyl salicylate , whereas Orco-Gal4/UAS-CqOR32 flies gave robust response to methyl salicylate, with the strong response to -2-hexenal unchanged . w1118 flies gave very weak responses to eucalyptol at high doses, but interestingly Orco-Gal4/UAS-CqOR32 flies generated dose-dependent, inverse EAG responses . To further scrutinize this unusual reverse EAG responses, we used gas chromatography with electroantennographic detection . In GC-EAD analyses, injected mixtures are separated by GC and subjected to antennal preparations under the same condition thus ruling out any possibility of mechanical interference and minor sample contamination. Here, methyl salicylate responded with regular EAG responses, i.e., with the first phase , which is referred to as rise of the receptor potential, and the second phase starting at the end of the stimulus, commonly referred to as the decline of the receptor potential . This is analogous to the depolarization, repolarization, and hyperpolarization of a nervous impulse. As opposed to methyl salicylate, eucalyptol consistently gave inverse EAD responses thus corroborating what we observed in EAG analyses . Next, we recorded EAG responses when flies were challenged with odorants and an inhibitor. First, we compared the response of w1118 and Orco-Gal4/UAS-CqOR32 flies to -2-hexenal when it was delivered alone or in combination with eucalyptol. EAG responses from w1118 flies to 0.1% -2-hexenal alone or in combination with 10% eucalyptol did not differ significantly . By contrast, EAG responses from Orco-Gal4/UAS-CqOR32 flies to 0.1% -2-hexenal plus 10% eucalyptol were significantly lower than those elicited by 0.1% -2-hexenal alone . We then examined the dose-dependent effect of this inhibition by using Orco-Gal4/UAS-CqOR32 flies. Robust responses to 0.1% methyl salicylate were reduced in a dose-dependent manner with the addition of eucalyptol but remained unchanged at the end of the tests. Likewise, EAG responses to 0.01% -2-hexenal were reduced when coapplied with eucalyptol . Of note, -2-hexenal does not activate CquiOR32 .
Such inhibition presumably results from CquiOR32 indirectly inhibiting responses of the fly endogenous receptors to -2-hexenal. In these continuous experiments, a small difference between EAG responses before and after costimulus tests may be due to loss of this volatile semiochemical from the cartridge rather than adaptation. Taken together, these results further suggest that intrareceptor inhibition occurs in vivo as indicated by the inhibitory effect of eucalyptol on methyl salicylate responses. Additionally, the effect of eucalyptol on the response to -2-hexenal suggests that intraneuronal inhibition occurred. A few lines of evidence support this hypothesis. First and foremost,plastic pots 30 liters eucalyptol does not cause inhibition in control flies and -2-hexenal does not activate CquiOR32 . The simplest explanation is that, in Orco-Gal4/UAS-CqOR32 flies, all endogenous receptors are coexpressed with CquiOR32. Thus, CquiOR32 response to eucalyptol interferes with the response of DmelOR7a to -2-hexenal. In short, inhibitor and agonist are likely to be acting on different receptors in the same neurons, thus an intraneuron inhibition. To further test the notion of intraneuronal inhibition, we turned to single sensillum recordings .The best ligand for ab4A, the neuron in ab4 sensilla with a large spike amplitude, is -2-hexenal , although ab4A is also very sensitive to other ligands, including hexanal . Contrary to ab4B, ab4A houses only one OR, namely, DmelOr7a . Because expression of CquiOR32 was driven by DmelOrco, ab4A neurons in our transgenic flies house both DmelOr7a and CquiOR32. Coexpression was confirmed by a significantly stronger response to methyl salicylate recorded from Orco-Gal4/UAS-CquiOR32 than from WT flies , while retaining response to hexanal . It is known that methyl salicylate is the best ligand for DmelOr10a in ab1D but elicits only very low response in ab4A . The low response of WT flies to methyl salicylate did not differ significantly when the odorant was delivered alone or codelivered with eucalyptol . By contrast, responses recorded from Orco-Gal4/UAS-CquiOR32 flies were significantly lower when the two stimuli were delivered simultaneously from two different cartridges . Next, we tested whether CquiOR32 response to eucalyptol would affect DmelOR7a response to a cognate ligand, hexanal. Responses of WT flies to hexanal did not differ significantly when comparing hexanal alone with hexanal plus eucalyptol . Recordings from ab4 sensilla in the Orco-Gal4/UAS-CquiOR32 flies showed a slight, albeit not significant, increase in response to hexanal. This is unlikely to be due to hexanal activation of CquiOR32 . When hexanal and eucalyptol were delivered simultaneously firing of DmelOR7a was completely abolished . We also recorded from ab7 sensilla, which expresses DmelOR98a, in ab7A and for which butyl acetate is one of the best ligands . Eucalyptol elicited inhibitory response in ab7A neurons of Orco-Gal4/UASCquiOR32 flies . In the transgenic flies both methyl salicylate and butyl acetate generated excitatory responses , which were inhibited by eucalyptol . Because methyl salicylate and eucalyptol elicit inward and reverse currents in CquiOR32, this in vivo inhibition is not surprising. However, the consistent observation that eucalyptol inhibits the response of an endogenous receptor to a cognate ligand supports the notion that intraneuronal inhibition occurs when receptors are colocated in a neuron. Specifically, the inhibitory responses of CquiOR32 interferes with the activation of a collocated receptor by a cognate ligand.
For example, activation of DmelOR7a in ab4A neuron by hexanal and activation of DmelOR98a in ab7A neuron by butyl acetate were both inhibited by eucalyptol upon interaction with CquiOR32. Contrary to the fruit fly, which expresses only one receptor per neuron , mosquitoes can coexpress multiple ORs in the same neuron .Tissue fibrosis and cancer are two major causes of high human morbidity and mortality worldwide. Although there are multiple therapies for cancer, including chemotherapy, oncologic surgery, and radiation therapy, an effective therapeutic strategy is needed.1 Among these therapeutic strategies, chemotherapy is the main tool for curing various cancers. The therapeutic resistance of anticancer drugs, such as 5‐fluorouracil, gemcitabine, gefitinib, and trastuzumab, has been widely observed in the clinic.2 However, due to the lack of effective therapeutic drugs, tissue fibrosis still threatens human health. Although some drugs exhibit anti-fibrotic effects, including angiotensin‐ converting enzyme inhibitors, aldosterone inhibitors, statins, angiotensin II type 1 receptor blockers, endothelin receptors, β‐blockers, acetylsalicylic acid, and matrix metalloproteinase inhibitors, none of them are specifically designed to target fibrosis, and the related side effects limit their clinical use for treating fibrosis.Thus, anti-fibrotic and anticancer treatments are extremely urgent, and new therapeutic drugs should be designed based on specific targets that contribute to the progression of fibrosis and tumors. Epithelial‐mesenchymal transition is a reversible terminal differentiation process in which epithelial cells shed their properties and acquire a more mesenchymal phenotype.EMT is a fundamental process widely involved in the development and the progression of various diseases, and there are mainly three types of EMT. Type I EMT is involved in embryonic development and organ formation. Type II EMT is critical for wound healing and fibrosis. Type III EMT contributes to the progression and metastasis of tumors.Extensive studies revealed that EMT profoundly contributed to the production of myofibroblasts, which are the major cells producing massive amounts of collagen that leads to the deposition of collagen in the development of fibrosisIn addition, EMT confers increased motility and invasiveness in epithelial‐derived tumor cells and promotes tumor metastasis. Therefore, fibrosis and tumors share the common process of EMT, and drugs that specifically target EMT may exhibit both anti-fibrosis and antitumor effects, which will provide an effective strategy against fibrosis and tumors.