Morphological variation of the palatal organ and chewing pad of catostomidae (Teleostei: Cypriniformes)

We studied the morphology and shape variation of the palatal organ and chewing pad of sucker fishes, family Catostomidae. The palatal organ is a muscularized structure that forms a large mass on the roof of the posterior part of the buccopharyngeal cavity in cypriniform fishes. It functions in coordination with the branchial arches to separate food items from inorganic debris during feeding. The palatal organ exhibits considerable variability in morphology among catostomids. It is shorter, narrower, and thinner in species of the subfamily Cycleptinae (e.g., Cycleptus elongatus) than in other catostomid subfamilies. The thickest and widest palatal organ is seen in species of the subfamily Ictiobinae (e.g., Ictiobus cyprinellus). The shape and size of the palatal organ generally varies between these extremes in species of subfamily Catostominae (e.g., Catostomus and Moxostoma species). Principal components analysis and analysis of variance has differentiated means of various palatal organ measurements for each monophyletic subfamily and tribe of Catostomidae with statistical significance. These results corroborate previously established typological classification of catostomids based on pharyngeal tooth count, pharyngeal tooth morphology, and diet. A keratinized chewing pad forms on the posterior surface of the palatal organ in catostomids or on a skeletal process in cyprinids and serves as an occlusion surface for pharyngeal teeth. The chewing pad is lunate in catostomids and generally ovoid in cyprinids. It is absent from the species of loaches (e.g., botiids, cobitids, and nemacheilids) and gyrinocheilids examined. A synonymy of terms used in the past to describe the palatal organ and chewing pad of Cypriniformes is provided. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

A comparison of sampling methods for bibionid larvae (Diptera: Bibionidae) in grassland

Three extraction methods were compared for the recovery of bibionid larvae from grassland soil samples. Only wet-sieving followed by flotation in a saturated salt solution yielded bibionids. No larvae were recovered either with modified Tullgren funnels or by slow immersion of soil cores into a saturated salt solution. The efficiency with which larval bibionid populations can be estimated is poor. Generally, smaller cores yielded more larvae per volume of soil. Most bibionids were found in the top 4 cm of soil. It is concluded that 10 cm diameter and 6–8 cm deep soil cores are an acceptable compromise between efficiency and sampling effort but sample size will largely be determined by the resources available for processing of samples.     

Hexapeptide library as a universal tool for sample preparation in protein glycosylation analysis

Recent analytical advancements allow for large-scale glycomics and glycan-biomarker research with N-glycans released from complex protein mixtures of e.g. plasma with a wide range of protein concentrations. Protein enrichment techniques to obtain samples with a better representation of low-abundance proteins are hardy applied. In this study, hexapeptide ligands previously described for enrichment of low-abundance proteins in proteomics are evaluated for glycan analysis. A repeatable on-bead glycan release strategy was developed, and glycans were analyzed using capillary sieving electrophoresis on a DNA analyzer. Binding of proteins to the hexapeptide library occurred via the protein backbone. At neutral pH no discrimination between protein glycoforms was observed. Interestingly, glycan profiles of plasma with and without hexapeptide library enrichment revealed very similar patterns, despite the vast changes in protein concentrations in the samples. The most significant differences in glycosylation profiles were ascribed to a reduction in immunoglobulin-derived glycans. These results suggest that specific and sensitive biomarkers will be hard to access on the full plasma level using protein enrichment in combination with glycan analysis. Instead, fractionation techniques or profiling strategies on the glycopeptide level after enrichment are proposed for in-depth glycoproteomics research.     

Evolutionary developmental biology and vertebrate head segmentation: A perspective from developmental constraint

Summary The question of vertebrate head segmentation has become one of the central issues in Evolutionary Developmental Biology. Beginning as a theory based in comparative anatomy, a segmental theory of the head has been adopted and further developed by comparative embryologists. With the use of molecular and cellular biology, and in particular analyses of the Hox gene complex, the question has been addressed at new levels, but it remains unresolved. In this review, vertebrate head segmentation is reevaluated, by introducing findings from experimental embryology and evolutionary biology. Developmental biology has shown that pattern is generated through hierarchically organized and causally linked series of events. The question of head segmentation can be viewed as a question of generative constraint, that is whether segmentation in the head is imposed by underlying segmental patterns, as it is in the trunk. In this respect, amphioxus appears to be segmented along the entire anteroposterior axis, with myotomes and peripheral nerves repeating with the same rhythm (somitomerism). Similarly, in the vertebrate trunk, the segmental patterns shared by myotomes, peripheral nerves and vertebrae are derived from the somites. However, in the head of vertebrates there is no such mesodermal pattern, although neuromerism and branchiomerism do indicate the presence of constraints derived from rhombomeres and pharyngeal pouches, respectively. These data fit better the concept of dual metamerism of the vertebrate body proposed by Romer (1972), than the traditional head cavity-based segmental model by Goodrich (1930).     

Retinoic acid given at late embryonic stage depresses sonic hedgehog and Hoxd-4 expression in the pharyngeal area and induces skeletal malformation in flounder (Paralichthys olivaceus) embryos

During the development of pharyngeal cartilages, signal molecules, including sonic hedgehog (shh) and various growth factors, as well as Hox genes are expressed in the pharyngeal area. To elucidate whether shh and Hoxd-4 function in pharyngeal cartilage formation in teleost jaw and gill primordia, spatial and temporal patterns of shh expression in flounder (Paralichthys olivaceus) embryonic pharynx were examined. The effects of retinoic acid (RA) on shh and Hoxd-4 expression and the patterning of pharyngeal cartilages were analyzed. At the prim-5 stage, when cartilage precursor cells aggregate in the pharyngeal primordia, pharyngeal endoderm expressed shh in two domains, in portions of the mandibular and hyoid primordia and in the gill primordia. After a further 40 h, shh domains expanded at the posterior edge of the endoderm of each mandibular, hyoid and gill primordium, concurrent with the growth of the primordia. A new shh expression domain appeared at the endodermal border of the mouth. Retinoic acid treatment depressed shh and Hoxd-4 expression, and also reduced the amount of expansion of the shh expression domains. Pharyngeal cartilages that formed in these embryos were malformed; their growth direction was shifted posteriorly and size was reduced. This provides the possibility that shh and Hoxd-4 regulate the growth and direction of pharyngeal cartilage precursor cells and that RA disturbs their expression, causing skeletal malformation.     

Overlapping origins of pharyngeal arch crest cells on the postotic hind-brain

The developing hind-brain of vertebrates consists of segmental units called rhombomeres. Although crest cells emigrate from the hind-brain, they are subsequently subdivided into several cell populations that are attached to restricted regions of the hind-brain. At the preotic level, only even-numbered rhombomeres are accompanied by crest cells, while the odd-numbered ones are not. At the postotic level, such the birhombomeric repetition becomes obscure. In order to map the origins and distributions of postotic crest cells, focal injections of Dil were made into various axial levels of the postotic neural tube. Cephalic crest cells at the postotic level first form a single cell population deposited by cells along the dorsolateral pathway. They are called the circumpharyngeal crest cells (CP cells) and are secondarily subdivided into each pharyngeal arch ectomesenchyme. The neural tube extending from r5 to the somite 3/4 boundary gave rise to CP cells. The neuraxial origins of each pharyngeal ectomesenchyme extended for more than three somite lengths, most of which overlapped with the other. Unlike in the preotic region, there is no segmental registration between neuraxial levels and pharyngeal arches. Caudal portions of the CP cell population show a characteristic distribution pattern that circumscribes the postotic pharyngeal arches caudally. Heterotopic transplantation of the Dil-labeled neural crest into the somite 3 level resulted in a distribution of labeled cells similar to that of CP cells, suggesting that the pattern of distribution depends upon dynamic modification of the body wall associated with pharyngeal arch formation.     

Cellular succession in the epithelium lining the pharyngeal cavity of planarians

Regardin cell renewal of planarian epithelial tissue, little is known at present except for the epidermis (Tyler, 1984). According to Skaer (1965), the definitive epidermal cells in planarian embryos originate in the parenchyma where they develop as precursor cells which then migrate into the epidermis. This process of development is also reported in regenerating planarians (Spiegelman & Dudley, 1973; Morita & Best, 1974; Hori, 1978). Recently the validity of Skaer's conclusion has clearly been confirmed by Ishii & Sakurai (1998) using SEM and TEM.The present study deals with the origin and renewal of cells of another epithelium — that lining the pharyngeal cavity of a freshwater planarian Dugesia japonica. This epithelium is known to consist of cells with secretory granduls of fingerprint-like structure (Ishii, 1966; Bowen & Ryder, 1973; Gamo & Garcia-Corrales, 1988; Asai, 1991). The characteristic feature of these specific granules, as well as epitheliosomes (Tyler, 1984) of the epidermis, is very useful as a cell marker for distinguishing cell types and following cell differentiation. Gamo & Garcia-Corrales (1988) claimed the cell populations of the pharyngeal epithelium of Dugesia gonocephala is morphologically and functionally heterogeneous. The sequence of morphological alteration offers the oppurtunity to distinguish at least three functional stages. These represent different adaptive forms of a single cell type, and indicate transformation from one to the next induced by cell renewal. It suggests a beta cell (noeblast) origin of the epithelial cells.In the present study SEM observations revealed theat there are morphologically three distinct cell types which are considered to be juvenile, mature, and senile cells respectively, judging from the differences in cells and the many transitional forms among them (Fig. 1). When observed by TEM, the cytoplasmic patterns of these cell types are correspondingly different from one another, similarly the surface specializations of the plasma membranes of each cell type which facilitate their identification by TEM also vary. Apparently alterations of cell morphology are involved in ageing in a single cell type. Morphological features of each cell type are summarized. Juveniles (R) rarely occur, are small cells provided with prominent apical ruffles and considered to be phagocytic because the cells often contain newly formed phagosomes. Mature cells (F) predominate, are large, polygonal, flat cells, presumably with an intense secretory activity. The cells contain many profiles of granular ER and a small number of specific (secretory) granules. Senile cells (M) are intermittently distributed, irregularly contoured cells with heavy surface microvilli. The specific granules are dense in the apical cytoplasm, and profiles of granular ER decease in number.The precursor epithial cells that are seen in the parenchyma exhibit a considerable degree of differentiation before their translocation into the lining. The primordial cells observed are neoblast-like, with several cohromatoid bodies and many free ribosomes (Morita et al., 1969). These results obtain thus support the evidence and prediction of Gamo & Garcia-Corrales (1988). The observed mode of cell replacement appears to be the same as found in the epidermis (Lentz, 1967).     

TCAV-1, a monoclonal antibody specific to epithelial pharyngeal cells in the planarian Dugesia (Girardia) tigrina. Application to pattern formation of the pharynx during regeneration

During regeneration in planarians, anterior (head and prepharyngeal) and posterior (postpharyngeal and tail) fragments rebuild one of the most peculiar structures of planarians: the pharynx and the pharynx cavity. Previous studies (see Brønsted, 1969, for a general review, and Asai, 1990, 1991, for anterior regeneration) have shown that within postpharyngeal pieces both structures appear in the old stump from clusters of undifferentiated cells. However, the lineage and differentiation of their elements (inner and outer epithelial cells, muscle layers, gland cells, nerve rings) and the overall pattern of growth and differentiation is not clear.     

Physicochemical Properties of Serotonin 5-HT3 Binding Sites Solubilized from Membranes of NG 108-15 Neuroblastoma-Glioma Cells

Specific binding sites with pharmacological properties typical of serotonin 5-HT3 receptors were identified in membranes of the murine hybridoma cell line NG 108-15, using [3H]zacopride as a ligand. Optimal solubilization of these sites (yield, 50%) could be achieved using the detergent 3-[3-(cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS) at 24 mM plus 0.5 M NaCl in 25 mM Tris-HCl, pH 7.4. Specific [3H]zacopride binding to soluble sites in the 100,000-g CHAPS extract was saturable and showed characteristics (Bmax = 425 +/- 81 fmol/mg of protein; KD = 0.19 +/- 0.02 nM) closely related to those of membrane-bound sites (Bmax = 932 +/- 183 fmol/mg of protein; KD = 0.60 +/- 0.03 nM). Determination of association (k+1 = 0.17 nM min-1) and dissociation (k-1 = 0.02 min-1) rate constants for the soluble sites gave a KD value of 0.12 nM, a result consistent with that calculated from saturation studies. As assessed from the displacement potencies (IC50) of 10 different drugs, the pharmacological profile of [3H]zacopride specific binding sites was essentially the same (r = 0.99) in the CHAPS-soluble extract and in cell membranes, although some increase in the affinity for 5-HT3 antagonists (zacopride, ICS 205-930, and MDL 72222) and decrease in the affinity for 5-HT3 agonists (2-methyl-5-hydroxytryptamine and phenylbiguanide) were noted for the soluble sites. Sucrose density gradient sedimentation of the CHAPS-soluble extract gave a Svedberg coefficient of 12S for the material with [3H]zacopride specific binding capacity. Chromatographic analyses using Sephacryl S-400 and wheat germ agglutinin-agarose columns indicated marked enrichment (by 2.5- and 10-fold, respectively) in [3H]zacopride specific binding activity in the corresponding eluates compared with the starting soluble extract, a finding suggesting that both steps are of potential interest for the partial purification of solubilized 5-HT3 receptors. Two soluble materials with apparent molecular masses of approximately 600 and approximately 36 kDa were found to bind [3H]zacopride specifically in the Sephacryl S-400 eluate. Interestingly, molecular mass determination by radiation inactivation of [3H]zacopride binding sites in frozen NG 108-15 cells gave a value of approximately 35 kDa.