Zebrafish hox paralogue group 2 genes function redundantly as selector genes to pattern the second pharyngeal arch

The pharyngeal arches are one of the defining features of the vertebrates, with the first arch forming the mandibles of the jaw and the second forming jaw support structures. The cartilaginous elements of each arch are formed from separate migratory neural crest cell streams, which derive from the dorsal aspect of the neural tube. The second and more posterior crest streams are characterized by specific Hox gene expression. The zebrafish has a larger overall number of Hox genes than the tetrapod vertebrates, as the result of a duplication event in its lineage. However, in both zebrafish and mouse, there are just two members of Hox paralogue group 2 (PG2): Hoxa2 and Hoxb2. Here, we show that morpholino-mediated "knock-down" of both zebrafish Hox PG2 genes results in major defects in second pharyngeal arch cartilages, involving replacement of ventral elements with a mirror-image duplication of first arch structures, and accompanying changes to pharyngeal musculature. In the mouse, null mutants of Hoxa2 have revealed that this single Hox gene is required for normal second arch patterning. By contrast, loss-of-function of either zebrafish Hox PG2 gene individually has no phenotypic consequence, showing that these two genes function redundantly to confer proper pattern to the second pharyngeal arch. We have also used hoxb1a mis-expression to induce localized ectopic expression of zebrafish Hox PG2 genes in the first arch; using this strategy, we find that ectopic expression of either Hox PG2 gene can confer second arch identity onto first arch structures, suggesting that the zebrafish Hox PG2 genes act as "selector genes."     

On-line combination of capillary isoelectric focusing and capillary non-gel sieving electrophoresis using a hollow-fiber membrane interface: a novel two-dimensional separation system for proteins

A novel two-dimensional (2D) separation system for proteins was reported. In the system, a piece of dialysis hollow-fiber membrane was employed as the interface for on-line combination of capillary isoelectric focusing (CIEF) and capillary non-gel sieving electrophoresis (CNGSE). The system is similar equivalent to two-dimensional polyacrylamide gel electrophoresis (2D PAGE), by transferring the principal of 2D PAGE separation to the capillary format. Proteins were focused and separated in first dimension CIEF based on their differences in isoelectric points (pIs). Focused protein zones was transferred to the dialysis hollow-fiber interface, where proteins hydrophobically complexed with sodium dodecyl sulfate (SDS). The negatively charged proteins were electromigrated and further resolved by their differences in size in the second dimension CNGSE, in which dextran solution, a replaceable sieving matrix instead of cross-linked polyacrylamide gel was employed for size-dependent separation of proteins. The combination of the two techniques was attributed to high efficiency of the dialysis membrane interface. The feasibility and the orthogonality of the combined CIEF-CNGSE separation technique, an important factor for maximizing peak capacity or resolution elements, were demonstrated by examining each technique independently for the separation of hemoglobin and protein mixtures excreting from lung cancer cells of rat. The 2D separation strategy was found to greatly increase the resolving power and overall peak capacity over those obtained for either dimension alone.     

Molecular investigation of genetic assimilation during the rapid adaptive radiations of East African cichlid fishes

Adaptive radiations are characterized by adaptive diversification intertwined with rapid speciation within a lineage resulting in many ecologically specialized, phenotypically diverse species. It has been proposed that adaptive radiations can originate from ancestral lineages with pronounced phenotypic plasticity in adaptive traits, facilitating ecologically driven phenotypic diversification that is ultimately fixed through genetic assimilation of gene regulatory regions. This study aimed to investigate how phenotypic plasticity is reflected in gene expression patterns in the trophic apparatus of several lineages of East African cichlid fishes, and whether the observed patterns support genetic assimilation. This investigation used a split brood experimental design to compare adaptive plasticity in species from within and outside of adaptive radiations. The plastic response was induced in the crushing pharyngeal jaws through feeding individuals either a hard or soft diet. We find that nonradiating, basal lineages show higher levels of adaptive morphological plasticity than the derived, radiated lineages, suggesting that these differences have become partially genetically fixed during the formation of the adaptive radiations. Two candidate genes that may have undergone genetic assimilation, gif and alas1, were identified, in addition to alterations in the wiring of LPJ patterning networks. Taken together, our results suggest that genetic assimilation may have dampened the inducibility of plasticity related genes during the adaptive radiations of East African cichlids, flattening the reaction norms and canalizing their feeding phenotypes, driving adaptation to progressively more narrow ecological niches.     

锦鲤咽齿替换及齿胚的解剖学观察,前插1

从鱼类解剖学和口腔医学的角度,观察和讨论了锦鲤咽齿、齿胚的形态结构和咽齿的替换,并对咽齿和咬合板做了扫描电镜观察.发现锦鲤咽齿替换与齿胚有密切关系;咽齿替换分为两侧不同名齿同时替换、同侧两枚不同名齿同时替换和单侧一枚齿自主替换3种类型;咽齿替换是终生发生的,遵循着"被替换咽齿的骨性支持从基骨骨孔开始吸收-同名齿胚的移行与就位-旧齿脱落与新齿支持组织改建为骨性"的过程.认为齿胚的发育是启动咽齿替换的起始因素;锦鲤与野生鲤有近缘关系.     

Imprint cytology in laryngeal and pharyngeal tumours

OBJECTIVE: The aim of this study was to evaluate the role of cytology in providing a reliable diagnosis upon which the clinician can base further investigative or treatment strategies in patients with laryngeal and pharyngeal tumours. METHODS: Imprint cytology diagnoses from 174 patients were correlated with the histological result of a corresponding biopsy. RESULTS: We found that the imprint cytology proved to be a useful, quick and reliable method with complete diagnostic accuracy, sensitivity, specificity, positive predictive value and negative predictive values of 97%, 96%, 100%, 100% and 92% respectively. CONCLUSION: Imprint cytology allows diagnostic statements in a shorter time than is possible with histological sections and proves a useful adjunct in evaluating laryngeal and pharyngeal lesions. The validity of the method depends on the care with which the specimen is sampled and on the experience of the investigator.     

The Immunofluorescent Localization of Subventral Pharyngeal Gland Epitopes of Preparasitic Juveniles of Heterodera glycines Using Laser Scanning Confocal Microscopy

Laser scanning confocal microscopy (LSCM) was used to localize the reactivity of a monoclonal antibody (Sv2) that binds to the subventral pharyngeal glands of preparasitic juveniles of Heterodera glycines. The greater resolution, magnification, and image analysis of LSCM compared with conventional epifluorescent microscopy enabled Sv2 binding to be localized much more precisely to the periphery of the secretory granules. A linear increase of about 55% in fluorescent intensity was found over a 23-μm length of subventral pharyngeal gland just distal to the terminal ampullae. LSCM is a rapid and effective technique for precise immunolocalization of epitopes.     

Freshwater larval trematodes: Cercaria ghaziaporzanae n. sp., of the pharyngeal longifurcate distome group,parasitic in ancylid molluscs

A new species of a pharyngeal longifurcate distome furcocercous cercaria characterized, chiefly, by two pairs of penetration glands located pre- and post-acetabulum, well-developed oesophagus and intestinal caeca, 20 flame cells, and by the absence of a transverse excretory commissures, is described from an ancylid mollusc, Gundlachia sp., abundant in Laguna de Los Patos, near Universidad de Oriente, Cumaná, Venezuela. A review of larval trematodes parasitic in ancylid molluscs, with information on their life histories, is given.     

Development of the pharyngeal arch skeleton in Catostomus commersonii (Teleostei: Cypriniformes)

Skeletal elements of the gill arches of adult cypriniform fishes vary widely in number, size, and shape and are important characters in morphologically based phylogenetic studies. Understanding the developmental basis for this variation is thus phylogenetically significant but also important in relation to the many developmental genetic and molecularly based studies of the early developing and hence experimentally tractable gill arches in the zebrafish, a cyprinid cypriniform. We describe the sequence of the chondrification and ossification of the pharyngeal arches and associated dermal bones from Catostomus commersonii (Catostomidae, Cypriniformes) and make selected comparisons to other similarly described pharyngeal arches. We noted shared spatial trends in arch development including the formation of ventral cartilages before dorsal and anterior cartilages before posterior. Qualitatively variable gill arch elements in Cypriniformes including pharyngobranchial 1, pharyngobranchial 4, and the sublingual are the last such elements to chondrify in C. commersonii. We show that the sublingual bone in C. commersonii has two cartilaginous precursors that fuse and ossify to form the single bone in adults. This indicates homology of the sublingual in catostomids to the two sublingual bones in the adults of cobitids and balitorids. Intriguing patterns of fusion and segmentation of the cartilages in the pharyngeal arches were discovered. These include the individuation of the basihyal and anterior copula through segmentation of a single cartilage rod, fusion of cartilaginous basibranchials 4 and 5, and fusion of hypobranchial 4 with ceratobranchial 4. Such “fluidity” in cartilage patterning may be widespread in fishes and requires further comparative developmental studies. J. Morphol., 2009. © 2008 Wiley‐Liss, Inc.