The carotid body is a major peripheral chemoreceptor that senses changes in arterial blood oxygen, carbon dioxide, and pH, what is important for regulation of breathing and cardiovascular function. The mechanisms by which the carotid body senses O2 and CO2 are well known; conversely, the mechanisms by which it senses pH variations are almost unknown. Here we used immunohistochemistry to investigate how the human carotid body contributes to the detection acidosis analyzing whether it expresses acid-sensing ion channels (ASIC) ion channels, and to know if these channels are in the cells chemosensory glomic cells or in the afferent nerves. ASIC1, ASIC2 and ASIC3, and to a much lesser extent ASIC4, immunoreactivity was detected in subpopulations of type I glomus cells, as well as in the nerves of the carotid body. In addition, immunoreactivity was found for all ASIC subunits in neurons of the petrosal and superior cervical sympathetic ganglia, where afferent and efferent neurons are located, respectively, innervating the carotid body. This study reports for the fist time the occurrence of ASIC proteins in the human carotid body, demonstrating that they are present in glomus chemosensory cells (ASIC1 < ASIC2 > ASIC3 > ASIC4) and nerves, presumably both afferent an efferent supplying the organ. These results suggest that the detection of acidosis by the carotid body can be mediated by ASIC ion channels present in the type I glomus cells or directly by sensory nerve fibers.

Morphological and phylogenetic (45S nrDNA+RPB1 gene) analyses of three glomoid spore-producing arbuscular mycorrhizal fungi revealed the presence of two new species be-longing to the genus Glomus in the family Glomeraceae. In the field, Glomus highlandensis sp. nov. was found in a saltmarsh of the Scottish Highlands and in maritime sand dunes of the Baltic Sea in Poland, both saline environments, while G. mongioie sp. nov. originates from the Italian Alps. Phylogenetic placement analysis using environmental sequences indicated that G. highlandensis could have likely worldwide distribution while G. mongioie seems to be a rare species in the world. The molecular and phylogenetic analysis provided important insights about the presence of ribosomal variants in Glomus, with potential negative implication in phylogeny and species recognition.