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Single Row (single + row)
Selected AbstractsBrachyury -downstream notochord genes and convergent extension in Ciona intestinalis embryosDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 5 2007Kohji Hotta Formation of the chordate body is accomplished by a complex set of morphogenetic movements including convergent extension of notochord cells. In the ascidian Ciona intestinalis, Brachyury plays a key role in the formation of the notochord, and more than 30 Bra-downstream notochord genes have been identified. In the present study, we examined the effects of functional suppression of nine Bra -downstream notochord genes, which include Ci-PTP, Ci-ACL, Ci-prickle, Ci-netrin, Ci-trop, Ci-Noto3, Ci-ASAK, Ci-ERM and Ci-pellino. When the function of the first two genes (Ci-PTP and Ci-ACL) was suppressed with specific morpholinos, the notochord cells failed to converge, while functional suppression of Ci-prickle resulted in a failure of intercalation, and therefore the cells in these three types of embryo remained in the mid-dorsal region of the embryo. Functional suppression of the next four genes (Ci-netrin, Ci-trop, Ci-Noto3 and Ci-ASAK) resulted in the partial defect of intercalation, and the notochord did not consist of a single row. In addition, when the function of the last two genes (Ci-ERM and Ci-pellino) was suppressed, notochord cells failed to elongate in the embryo, even though convergence/extension took place normally. These results indicate that many Bra -downstream notochord genes are involved in convergence/extension of the embryo. [source] Ultrastructure of the spermatozoon of Apus apus (Linnaeus 1758), the common swift (Aves; Apodiformes; Apodidae), with phylogenetic implicationsACTA ZOOLOGICA, Issue 4 2005Barrie G. M. Jamieson Abstract The spermatozoon of Apus apus is typical of non-passerines in many respects. Features shared with palaeognaths and the Galloanserae are the conical acrosome, shorter than the nucleus; the presence of a proximal as well as distal centriole; the elongate midpiece with mitochondria grouped around an elongate distal centriole; and the presence of a fibrous or amorphous sheath around the principal piece of the axoneme. The perforatorium and endonuclear canal are lost in A. apus as in some other non-passerines. All non-passerines differ from palaeognaths in that the latter have a transversely ribbed fibrous sheath whereas in non-passerines it is amorphous, as in Apus, or absent. The absence of an annulus is an apomorphic but homoplastic feature of swift, psittaciform, gruiform and passerine spermatozoa. The long distal centriole, penetrating the entire midpiece, is a remarkably plesiomorphic feature of the swift spermatozoa, known elsewhere only in palaeognaths. The long centriole of Apus, if not a reversal, would be inconsistent with the former placement of the Apodiformes above the Psittaciformes from DNA,DNA hybridization. In contrast to passerines, in A. apus the microtubules in the spermatid are restricted to a transient single row encircling the cell. The form of the spermatozoon fully justifies the exclusion of swifts from the passerine family Hirundinidae. [source] Dentition and tooth replacement pattern in Chalcides (Squamata; Scincidae)JOURNAL OF MORPHOLOGY, Issue 2 2003Sidney Delgado Abstract This study was undertaken as a prerequisite to investigations on tooth differentiation in a squamate, the Canarian scincid Chalcides. Our main goal was to determine whether the pattern of tooth replacement, known to be regular in lizards, could be helpful to predict accurately any stage of tooth development. A growth series of 20 laboratory-reared specimens, aged from 0.5 month after birth to about 6 years, was used. The dentition (functional and replacement teeth) was studied from radiographs of jaw quadrants. The number of tooth positions, the tooth number in relation to age and to seasons, and the size of the replacement teeth were recorded. In Chalcides, a single row of pleurodont functional teeth lies at the labial margin of the dentary, premaxillary, and maxillary. Whatever the age of the specimens, 16 tooth positions were recorded, on average, in each quadrant, suggesting that positions are maintained throughout life. Replacement teeth were numerous whatever the age and season, while the number of functional teeth was subject to variation. Symmetry of tooth development was evaluated by comparing teeth two by two from the opposite side in the four jaw quadrants of several specimens. Although the relative size of some replacement teeth fitted perfectly, the symmetry criterion was not reliable to predict the developmental stage of the opposite tooth, whether the pair of teeth compared was left,right or upper,lower. The best fit was found when comparing the size of successive replacement teeth from the front to the back of the jaw. Every replacement tooth that is 40,80% of its definitive size is followed, in the next position on the arcade, by a tooth that is, on average, 20% less developed. Considering teeth in alternate positions (even and odd series), each replacement tooth was a little more developed than the previous, more anterior, one (0.5,20% when the teeth are from 10,40% of their final size). The latter pattern showed that tooth replacement occurred in alternate positions from back to front, forming more or less regular rows (i.e., "Zahnreihen"). In Chalcides, the developmental stage of a replacement tooth in a position p can be accurately predicted provided the developmental stage of the replacement tooth in position p-1 or, to a lesser degree, in position p-2 is known. This finding will be particularly helpful when starting our structural and ultrastructural studies of tooth differentiation in this lizard. J. Morphol. 256:146,159, 2003. © 2003 Wiley-Liss, Inc. [source] A Reappraisal Of Coletta Seca, A Basal Procolophonoid Reptile From The Lower Triassic Of South AfricaPALAEONTOLOGY, Issue 5 2002Sean P. Modesto The skeletal structure of Coletta seca, a small procolophonoid reptile from the Lower Triassic Lystrosaurus Assemblage Zone of South Africa, is reconsidered in light of descriptions of other procolophonoids. The presence of a single row of relatively large, fang,like vomerine teeth, identified originally as the single autapomorphy of this taxon, is reinterpreted as two rows of parachoanal vomerine teeth that are similar in organization to those of coeval procolophonids from Russia. Coletta is distinguished from other procolophonoids by a complex tongue,and,groove suture between the anterolateral margin of the parietal and the posterolateral edge of the postfrontal, and by a transversely broad interpterygoid vacuity. The postfrontal in Coletta retains contact with the postorbital, as in basal taxa such as Owenetta, but it is restricted to the orbital margin, as in Procolophon and all other procolophonids. A phylogenetic analysis identifies Coletta as the sister taxon of the clade Procolophonidae. This phylogenetic position suggests that Procolophonoidea originated and diversified initially in Gondwana during the Permian, prior to Procolophonidae achieving a cosmopolitan distribution in the succeeding Triassic. [source] Silicification in sorghum (Sorghum bicolor) cultivars with different drought tolerancePHYSIOLOGIA PLANTARUM, Issue 1 2002Alexander Lux Sorghum belongs to a group of economically important, silicon accumulating plants. X-ray microanalysis coupled with environmental scanning electron microscopy (ESEM) of fresh root endodermal and leaf epidermal samples confirms histological and cultivar specificity of silicification. In sorghum roots, silicon is accumulated mostly in endodermal cells. Specialized silica aggregates are formed predominantly in a single row in the form of wall outgrowths on the inner tangential endodermal walls. The density of silica aggregates per square mm of inner tangential endodermal cell wall is around 2700 and there is no significant difference in the cultivars with different content of silicon in roots. In the leaf epidermis, silicon deposits were present in the outer walls of all cells, with the highest concentration in specialized idioblasts termed ,silica cells'. These cells are dumb-bell shaped in sorghum. In both the root endodermis and leaf epidermis, silicification was higher in a drought tolerant cultivar Gadambalia compared with drought sensitive cultivar Tabat. Silicon content per dry mass was higher in leaves than in roots in both cultivars. The values for cv. Gadambalia in roots and leaves are 3.5 and 4.1% Si, respectively, and for cv. Tabat 2.2 and 3.3%. However, based on X-ray microanalysis the amount of Si deposited in endodermal cell walls in drought tolerant cultivar (unlike the drought susceptible cultivar) is higher than that deposited in the leaf epidermis. The high root endodermal silicification might be related to a higher drought resistance. [source] Low-resolution remotely sensed images of winegrape vineyards map spatial variability in planimetric canopy area instead of leaf area indexAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2008A. HALL Abstract Background and Aims:, Knowledge of the spatial variability of grapevine canopy density is useful in managing the variability of grape composition and yield. Rapid assessment of the characteristics of vineyards by remote sensing offers distinct advantages over ground-based measurements. In an effort to capture such advantages, this study aimed to assess the relative contribution to LAI of grapevine canopy density and grapevine canopy area derived from high-spatial-resolution airborne digital imagery. Methods and Results:, High-spatial-resolution airborne NDVI imagery of minimally pruned, unconfined (i.e. not confined by trellising) grapevines was used to partition image pixels into grapevine-only and non-grapevine groupings. An evaluation of the relative contributions of grapevine planimetric area (number of grapevine pixels across a single row) and leaf layers (NDVI of grapevine-only pixels) found that the variability observed across the vineyard was dominated by changes in canopy area rather than grapevine-only NDVI. Conclusion:, The primary predictive variable of grapevine LAI is canopy area. Low-spatial-resolution NDVI imagery of minimally pruned, unconfined vineyards is therefore effective in mapping spatial variability in planimetric canopy area, rather than LAI. Significance of the Study:, The process of estimating grapevine LAI from mixed pixels has incorrectly assumed that both components of LAI within a pixel's footprint, namely the number of leaf layers and planimetric canopy area, produce a consistent response in NDVI. Correlations between NDVI and LAI reported in previous studies based on low-resolution imagery most likely relied on the proxy relationship between NDVI and canopy area. [source] Effects of ethephon, methanol, ethanol and girdling treatments on berry maturity and colour development in Cardinal table grapesAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2003NIKOLAOS NIKOLAOU Abstract To hasten berry maturity and improve skin colour, the early-season table grape variety Cardinal was treated (post veraison) with a bunch + foliar spray using either 240 or 480 mg/L ethephon, as well as with 30% methanol, 30% ethanol (v/v); or by girdling. Treatment effects were evaluated in a randomised experimental design, with 10 replications of one plant per plot, down a single row. Ethephon at 480 mg/L applied twice, on July 2 when 5% of the berries showed colouring and on July 9 when 20% of the berries developed partial colour, increased total soluble solids, °Brix/titratable acidity and skin colour. Girdling, methanol and ethanol also increased total soluble solids and berry colouration and caused faster ripening. Ethephon at 480 mg/L was generally the most effective means of hastening ripening and improving colour. [source] Comparative anatomy and systematics of Catasetinae (Orchidaceae)BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2001WILLIAM LOUIS STERN FLS Catasetinae consist of five genera of pseudobulbous Orchidaceae of the Neotropics. Anatomy is characterized by sunken, three-celled foliar hairs, mostly tetracytic stomatal apparatuses, superficial stomata, homogeneous mesophyll, foliar fibre bundles, collateral vascular bundles in a single row, xylem and phloem sclerenchyma associated with vascular bundles in leaves, conical, and rough-surfaced silica bodies adjacent to vascular bundle sclerenchyma; epidermal cells of pseudobulbs with heavily thickened outer walls, pseudobulb ground tissue of assimilatory and water-storage cells, scattered vascular bundles in pseudobulbs, and sclerenchyma and stegmata associated only with phloem of pseudobulbs; roots with thin-walled velamen cells and tenuous spirals of cell wall material, distinctive epivelamen cells, thin-walled exodermal cells and vascular tissue embedded in parenchyma. Except for mucilaginous idioblasts that occur in Mormodes and Cycnoches, there are few outstanding anatomical differences among the five genera. Thus, there are few anatomical characteristics of phylogenetic value. The monophyly of Catasetinae is supported by the presence of sunken foliar hairs. Our results support a close relationship between Clowesia and Catasetum, and between Mormodes and Cycnoches. Among the outgroups Pteroglossaspis is especially distinctive. [source] | ||||||||||