Neuronal architecture of the mosquito deutocerebrum

Abstract

Mosquito behavior is heavily dependent on olfactory and mechanosensory cues, which are detected by receptor neurons on the antenna and on the palps. Recent progress in mosquito sensory genomics highlights the need for an up-to-date understanding of the neural architecture of the mosquito brain. Here we present a detailed description of the neural structure of the primary target of the majority of these neurons, the deutocerebrum, in the African malaria (Anopheles gambiae) and yellow fever (Aedes aegypti) mosquitoes. Special focus is made on the olfactory system, the antennal lobe (AL), where we present high-resolution three-dimensional models of the ALs of male and female Ae. aegypti. These models reveal a sexual dimorphism in the number of glomeruli, 49 and 50 glomeruli in male and female mosquitoes, respectively, and in the size of several of the identified glomeruli. The fine structure of receptor neuron terminations in the AL and the rest of the deutocerebrum is described, as are the arborizations of intrinsic deutocerebral neurons and neurons providing output to higher brain areas. In the AL a specific and very large center receiving input from the mechanosensory Johnston's organ is revealed as a multilobed structure receiving peripheral input according to a somatotopic pattern. Within the antennal nerve a specific neuropil containing early, bouton-like ramifications of receptor neurons is described. Within the glomerular array of the AL, neurons providing a possible feedback circuit to antennal receptor neurons are shown. With these results we provide a new resolution in mosquito deutocerebral architecture.

Current topics in the epidemiology of oral cavity and oropharyngeal cancers

“…For example, oral infection by oncogenic HPV types strongly elevated risk for oropharyngeal cancer (OR 230, 95% CI, 44-1200), after adjustment for alcohol and tobacco in a study conducted in Sweden. 101,102 Furthermore, HPV16 seropositivity conferred an estimated 14-fold increase in risk for subsequent oropharyngeal cancer in a nested, case-control study that provided important evidence that exposure preceded development of disease. 99 Although evidence suggests that HPV is associated with cancers in nonsmokers and nondrinkers, 89 the degree to which oral HPV infection may combine with tobacco use or alcohol use or both to increase risk of oral cancer is currently unclear, with some studies suggesting a synergistic effect with tobacco 92 or alcohol, 97 while others have found no such synergy.…”

Neuronal projections from the Haller's organ and palp sensilla to the synganglion of Amblyomma americanum§

“…This may explain the lack of macroglomeruli in tick olfactory lobes. The absence of increased glomeruli was also observed in A. aegypti (IGNELL et al, 2005) and R. prolixus (BARROZO et al, 2009). …”

“…Assuming that the number of olfactory receptors in A. americanum is similar to that observed in A. variegatum, and considering we counted 16 to 21 glomeruli, it can be hypothesized that each glomerulus is innervated by approximately four afferent neurons. This number is considerably lower than that observed in insects (ANTON & HOMBERG, 1999;IGNELL et al, 2005), but higher than that observed in the predatory mite P. persimilis in which the number of sensory receptor neurons is the same as the number of glomeruli ( VAN WIJK et al, 2006).…”

“…Further, A. americanum nymphs have 10 sensilla, nine of which contain two mechanoreceptor dendrites plus several (4 to 12) chemosensory receptors dendrites (FOELIX & WANG, 1972). In contrast, maxillary palp neurons in mosquitoes project to the antennal lobe, and there are odorant receptors present in this organ (ANTON & ROSPARS, 2004;IGNELL et al, 2005).…”

“…Particularly with medically important insects, three-dimensional maps of glomeruli within the antennal lobes were established using various models (IGNELL et al, 2005;GHANINIA et al, 2007;BARROZO et al, 2009).…”