Histological Architecture of the Nasal Region in Rana chensinensis

The nasal region of Rana chensinensis is divided into the nasal capsules and nasal cavities. In this study, we investigated the adult histological structure of the nasal capsules and nasal cavities in the frog R. chensinensis under the microscope. We found that an eminentia olfactoria is present in this frog and the presence of the eminentia olfactoria may be connected to a terrestrial life style. The double staining method using alcian blue and alizarin red showed that the septomaxilla, the most important bone associated with the olfactory capsules, is an intramembranous bone in R. chensinensis. The opening of the nasolacrimal duct showed a close proximity to the apertura nasalis externa. The presence of the nasolacrimal duct in the olfactory region may be an adaptation to a terrestrial environment. The function of the vomeronasal and olfactory organs is discussed in the paper.     

Morphological evidence for two types of Mammalian vomeronasal system

The vomeronasal (VN) systems of rodents and opossums are of the segregated type, i.e alpha-subtype G protein Gi2- or Go-expressing VN neurons, which are sensory cells, project discretely to the rostral or caudal region of the accessory olfactory bulb (AOB). Although this zone-specific projection is believed to be a common feature for processing pheromones in mammals, we previously found a uniform-type VN system in goat in which only Gi2-expressing VN axons terminate at the AOB. In most mammals, it remains unclear whether their VN systems are of the segregated or uniform type. Therefore, we investigated morphologically the VN systems of different mammalian species (dog, horse, musk shrew and common marmoset). Consequently, all VN axons of the examined animals were positively stained with immunohistochemistry for Gi2 in the same way as that in the goat. On the other hand, we observed immunoreactivities against Go in the olfactory axons, but not in the VN axons. These results suggest that many mammals have uniform-type VN systems, and at least two types of VN systems exist in terrestrial mammals. This morphological evidence will help us determine the processing function of VN systems.     

Type-specific inositol 1,4,5-trisphosphate receptor localization in the vomeronasal organ and its interaction with a transient receptor potential channel,TRPC2

The vomeronasal organ (VNO) is the receptor portion of the accessory olfactory system and transduces chemical cues that identify social hierarchy, reproductive status, conspecifics and prey. Signal transduction in VNO neurons is apparently accomplished via an inositol 1,4,5-trisphosphate (IP3)-activated calcium conductance that includes a different set of G proteins than those identified in vertebrate olfactory sensory neurons. We used immunohistochemical (IHC) and SDS-PAGE/western analysis to localize three IP3 receptors (IP3R) in the rat VNO epithelium. Type-I IP3R expression was weak or absent. Antisera for type-II and -III IP3R recognized appropriate molecular weight proteins by SDS-PAGE, and labeled protein could be abolished by pre-adsorption of the respective antibody with antigenic peptide. In tissue sections, type-II IP3R immunoreactivity was present in the supporting cell zone but not in the sensory cell zone. Type-III IP3R immunoreactivity was present throughout the sensory zone and overlapped that of transient receptor potential channel 2 (TRPC2) in the microvillar layer of sensory epithelium. Co-immunoprecipitation of type-III IP3R and TRPC2 from VNO lysates confirmed the overlapping immunoreactivity patterns. The protein-protein interaction complex between type-III IP3R and TRPC2 could initiate calcium signaling leading to electrical signal production in VNO neurons.     

微塑料与蝌蚪健康的关系研究进展

微塑料(MPs), 尤其是纳米级可通过生物毒性效应影响蝌蚪健康, 是继气候变化、紫外线辐射和致病菌外, 导致两栖动物种群数量衰退的另一潜在致危因素。本文介绍了MPs的定义、赋存方式及其尺度效应, 总结了MPs在蝌蚪体内的摄入、积累和清除情况, 从形态表型、行为特征和组织病理学变化的角度概述了MPs对蝌蚪健康的危害。在水陆转换的生态学背景下和特定年龄阶段的生活史背景下, 围绕免疫功能的可塑性和可供蝌蚪研究使用的免疫学参数, 提出了未来值得关注的研究方向。     

A new species of Telmatobius (Amphibia,Anura, Telmatobiidae) from the Pacific slopes of the Andes,Peru

We describe a new species of Telmatobius from the Pacific slopes of the Andes in central Peru. Specimens were collected at 3900 m elevation near Huaytará, Huancavelica, in the upper drainage of the Pisco river. The new species has a snout–vent length of 52.5 ± 1.1 mm (49.3–55.7 mm, n = 6) in adult females, and 48.5 mm in the single adult male. The new species has bright yellow and orange coloration ventrally and is readily distinguished from all other central Peruvian Andean species of Telmatobius but Telmatobius intermedius by having vomerine teeth but lacking premaxillary and maxillary teeth, and by its slender body shape and long legs. The new species differs from Telmatobius intermedius by its larger size, flatter head, and the absence of cutaneous keratinized spicules (present even in immature females of Telmatobius intermedius), and in males by the presence of minute, densely packed nuptial spines on dorsal and medial surfaces of thumbs (large, sparsely packed nuptial spines in Telmatobius intermedius). The hyper-arid coastal valleys of Peru generally support low species richness, particularly for groups such as aquatic breeding amphibians. The discovery of a new species in this environment, and along a major highway crossing the Andes, shows that much remains to be done to document amphibian diversity in Peru.     

Olfactory receptors and signalling elements in the Grueneberg ganglion

The Grueneberg ganglion (GG) is a cluster of neurones present in the vestibule of the anterior nasal cavity. Although its function is still elusive, recent studies have shown that cells of the GG transcribe the gene encoding the olfactory marker protein (OMP) and project their axons to glomeruli of the olfactory bulb, suggesting that they may have a chemosensory function. Chemosensory responsiveness of olfactory neurones in the main olfactory epithelium (MOE) and the vomeronasal organ (VNO) is based on the expression of either odorant receptors or vomeronasal putative pheromone receptors. To scrutinize its presumptive olfactory nature, the GG was assessed for receptor expression by extensive RT-PCR analyses, leading to the identification of a distinct vomeronasal receptor which was expressed in the majority of OMP-positive GG neurones. Along with this receptor, these cells expressed the G proteins Go and Gi, both of which are also present in sensory neurones of the vomeronasal organ. Odorant receptors were expressed by very few cells during prenatal and perinatal stages; a similar number of cells expressed adenylyl cyclase type III and G(olf/s), characteristic signalling elements of the main olfactory system. The findings of the study support the notion that the GG is in fact a subunit of the complex olfactory system, comprising cells with either a VNO-like or a MOE-like phenotype. Moreover, expression of a vomeronasal receptor indicates that the GG might serve to detect pheromones.     

Crystallization and preliminary X-ray investigation of the recombinant Trypanosoma brucei rhodesiense calmodulin

Bipyramidal crystals of the recombinant calmodulin from Trypanosoma brucei rhodesiense were obtained by vapor diffusion against 55% (v/v) 2-methyl-2,4-pentanediol in 0.05 M cacodylate buffer, pH 5.6. When few nucleation events occurred, crystals grew to 0.25 × 0.25 × 1.20 mm. The space group of the crystal is I4₁22, with unit cell dimensions a = b = 56.88 Å, c = 230.11 Å, α = β = γ = 90°, z = 16. The molecular mass and volume of the unit cell suggest that there is one molecule in the asymmetric unit. The I/σ(I) ratio for data at 3.0 Å resolution was 3.67, indicating that the final structure can be refined at higher resolution. Molecular replacement methods and the PC-refinement technique have not yet yielded the structure under a variety of search conditions. We are currently investigating the multiple isomorphous replacement approach to determine this crystal structure. © 1995 Wiley-Liss, Inc.     

Chiropteran vomeronasal complex and the interfamilial relationships of bats

Within the extant orders of living mammals, the distribution of the vomeronasal organ (VNO) and associated structures is very stable, being universally present in the vast majority or universally absent in cetaceans and sirenians. Chiroptera is the most noteworthy exception, with variation in the absence or presence of the vomeronasal complex occurring even at the species level in some instances. The VNO and/or its component structures, such as the accessory olfactory bulb, were studied in serially sectioned snouts and brains from 114 genera and 292 species representing all extant chiropteran families except Myzopodidae and Antrozoidae. Taxa were scored for the following characters: (1) degree of formation of the vomeronasal epithelial tube, (2) shape of the vomeronasal cartilage, (3) occurrence of the nasopalatine duct, and (4) occurrence of the accessory olfactory bulb. To reconstruct the evolutionary history of the bat vomeronasal complex, the distributions of these four characters were mapped, using the computer program MacClade, onto chiropteran phylogenies in the literature derived from other data sets. In all phylogenies, these four characters exhibit a high degree of homoplasy, only part of which is accounted for by several polymorphic taxa. However, perhaps the most remarkable result is that in the most parsimonious solutions the absence of the vomeronasal epithelial tube and accessory olfactory bulb is identified as primitive for Chiroptera, with both structures reevolving numerous times: such a scenario would be unique to bats among mammals. An alternative, though less parsimonious interpretation, which does not require reevolution of this very complex system, is that a well-developed vomeronasal epithelial tube is primitive for Chiroptera, as in nearly all other orders of mammals, but has been reduced or lost in the majority of families. Explication of the peculiar evolutionary history of the vomeronasal system in bats awaits studies on the adult morphology in the more than 630 species not yet examined and, in particular, on ontogeny, which to date is known for only a handful of taxa.A preliminary account of this research was presented at the Tenth International Bat Research Conference and Twenty-Fifth North American Bat Research Symposium held at Boston University, Massachusetts, on 6–11 August 1995.