The Microvascular Anatomy of the Trachea in Adult Xenopus laevis Daudin (Lissamphibia; Anura): Scanning Electron Microscopy of Vascular Corrosion Casts and Correlative Light Microscopy

Studies on the amphibian respiratory tract microvascular anatomy are few and contradictory. Using scanning electron microscopy of vascular corrosion casts, correlative light microscopy of paraplast‐embedded Goldner‐stained serial tissue sections, and three‐dimensional morphometry, we studied the topographic microvascular anatomy in the trachea of the adult South African Clawed Toad, Xenopus laevis Daudin. Histomorphology showed that the cartilaginous portion of the trachea contained irregularly shaped hyaline cartilage plates in its cranial and caudal portions and C‐shaped hyaline cartilage rings in the middle portion. Tracheal cartilages formed large continuous plates on the ventral circumference, numerous small discontinuous plates on the dorsal circumference, and large vertical plates on the caudolateral circumference. The muscular portion of the trachea consisted of bands of smooth muscle that joined the free ends of cartilage plates. The supply of the trachea was via pulmonal artery—tracheobronchial trunk artery—tracheobronchial artery—tracheal artery. The subepithelial capillary network consisted of rectangular meshes which are in the area of the tracheal cartilages located between the cartilages and the respiratory epithelium. Small tracheal veins merged into a single tracheal vein that emptied into the pulmonary vein. Because of its dense subepithelial capillary network and its drainage into the pulmonal vein, the trachea could actively take part in respiration. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.     

Novel NCC mutants and functional analysis in a new cohort of patients with Gitelman syndrome

Gitelman syndrome (GS) is an autosomal recessive disorder characterized by hypokalemic metabolic alkalosis in conjunction with significant hypomagnesemia and hypocalciuria. The GS phenotype is caused by mutations in the solute carrier family 12, member 3 (SLC12A3) gene that encodes the thiazide-sensitive NaCl cotransporter (NCC). We analyzed DNA samples of 163 patients with a clinical suspicion of GS by direct sequencing of all 26 exons of the SLC12A3 gene. In total, 114 different mutations were identified, 31 of which have not been reported before. These novel variants include 3 deletions, 18 missense, 6 splice site and 4 nonsense mutations. We selected seven missense mutations to investigate their effect on NCC activity and plasma membrane localization by using the Xenopus laevis oocyte expression system. The Thr392Ile mutant did not display transport activity (probably class 2 mutation), while the Asn442Ser and Gln1030Arg NCC mutants showed decreased plasma membrane localization and consequently function, likely due to impaired trafficking (class 3 mutation). Even though the NaCl uptake was hampered for NCC mutants Glu121Asp, Pro751Leu, Ser475Cys and Tyr489His, the transporters reached the plasma membrane (class 4 mutation), suggesting an effect on NCC regulation or ion affinity. The present study shows the identification of 38 novel mutations in the SLC12A3 gene and provides insight into the mechanisms that regulate NCC.     

Effects of ZnO nanomaterials on Xenopus laevis growth and development

The objectives of this study were to quantify uptake and developmental effects of zinc oxide nanomaterials (nano-ZnO) on Xenopus laevis throughout the metomormosis process. To accomplish this, X. laevis were exposed to aqueous suspensions of 40-100 nm nano-ZnO beginning in-ovo and proceeding through metamorphosis. Nanomaterials were dispersed via sonication methods into reconstituted moderately hard water test solutions. A flow-through system was utilized to decrease the likelihood of depletion in ZnO concentration. Exposure to 2 mg/L nano-ZnO significantly increased mortality incidence to 40% and negatively affected metamorphosis of X. laevis. Tadpoles exposed to 2 mg/L nano-ZnO developed slower as indicated by tadpoles with an average stage of 56 at the conclusion of the study which was significantly lower than the control tadpole stages. No tadpoles exposed to 2 mg/L of nano-ZnO completed metamorphosis by the conclusion of the study. Tadpoles exposed to 0.125 mg/L nano-ZnO experienced faster development along with larger body measurements indicating that low dose exposure to nano-ZnO can stimulate growth and metamorphosis of X. laevis.     

Effects of atrazine, agricultural runoff, and selected effluents on antimicrobial activity of skin peptides in Xenopus laevis

Atrazine (technical and formulation), agricultural runoff containing atrazine, and treated sewage and landfill effluents were evaluated for their potential to modulate antimicrobial activity of Xenopus laevis skin secretions against the chytrid fungus, Batrachochytrium dendrobatidis. This chytrid fungus is implicated in several localized mass mortality events, yet the cause of the susceptibility of amphibians to this newly emergent pathogen is unknown. Antimicrobial peptides secreted from dermal glands are thought to provide critical protection against this pathogen. Chronic exposure of X. laevis larvae to agricultural runoff decreased protein content of collected secretions, while treated wastewater effluents increased protein content. However, the in vitro bioactivity was decreased in treatments with both increased and decreased protein. No differences were observed in protein or bioactivity following laboratory exposures of technical atrazine or a typical atrazine formulation (AAtrex^® 4L/Top Surf^®). These findings demonstrate that exposure of an amphibian model to agricultural runoff or effluent from municipal sewage treatment plants and landfills alters peptide production and in vitro activity of protective peptides. Although evidence suggests peptide production and bioactivity is a critical part of amphibian resistance to pathogens such as the chytrid fungus, the implications of observed effects for immunity and infection are not clear.     

Narrow tuning of an odorant receptor to plant volatiles in Spodoptera exigua (Hübner)

Olfaction plays an important role in insects in recognizing volatile compounds, which are used to find food and mates, as well as avoid danger, predators and pathogens. The key players in the detection of volatile compounds are olfactory receptor (OR) proteins, which are located within the dendritic membrane of sensory neurons and extend into the lymph of sensilla on insect antennae. In the present study, we identify an OR gene, named SexiOR3, which is expressed in adult antenna in both sexes, but with female bias, in the beet armyworm moth Spodoptera exigua. Further in situ hybridization analysis revealed that SexiOR3 was mainly located in short trichoid sensilla. In in vitro heterologous expression experiments, SexiOR3 was narrowly tuned to E‐β‐farnesene and several compounds of related structure, among 62 different compounds tested in this study. Furthermore, SexiOR3 responds to E‐β‐farnesene at a low concentration of 10^?9 M, comparable to that of pheromone receptors (PRs) responding to the pheromones. This is a very interesting finding for a general OR, indicating that high specificity is a feature of at least one general OR and not only the PRs. The results suggest that the OR3 gene may play an important role in the moth olfactory system, and underpins important insect behaviour.     

Functional characterization of sex pheromone receptors in the purple stem borer,Sesamia inferens (Walker)

The sex pheromone communication system in moths is highly species‐specific and extremely sensitive, and pheromone receptors (PRs) are thought to be the most important factors in males. In the present study, three full‐length cDNAs encoding PRs were characterized from Sesamia inferens antennae. These three PRs were all male‐specific in expression, but their relative expression levels were very different; SinfOR29 was 17‐ to 23‐fold higher than the other two PRs. Phylogenetic and motif pattern analyses showed that these three PRs were allocated to different PR subfamilies with different motif patterns. Functional analysis using the heterologous expression system of Xenopus oocytes demonstrated that SinfOR29 specifically and sensitively responded to the major pheromone component, Z11‐16:OAc [concentration for 50% of maximal effect (EC₅₀) = 3.431 × 10^?7 M], while SinfOR21 responded robustly to a minor pheromone component Z11‐16:OH (EC₅₀ = 1.087 × 10^?6 M). SinfOR27, however, displayed no response to any of the three pheromone components, but, interestingly, it was sensitive to a non‐sex pheromone component Z9,E12‐14:OAc (EC₅₀ = 1.522 × 10^?6 M). Our results provide insight into the molecular mechanisms of specificity and sensitivity of the sex pheromone communication system in moths.