Ventral Chord Research Articles

A Novel Cyclophilin from Parasitic and Free-living Nematodes with a Unique Substrate- and Drug-binding Domain

A highly diversified member of the cyclophilin family of peptidyl-prolyl cis-trans isomerases has been isolated from the human parasite Onchocerca volvulus (OvCYP-16). This 25-kDa cyclophilin shares 43-46% similarity to other filarial cyclophilins but does not belong to any of the groups previously defined in invertebrates or vertebrates. A homolog was also isolated from Caenorhabditis elegans (CeCYP-16). Both recombinant O. volvulus and C. elegans cyclophilins were found to possess an enzyme activity with similar substrate preference and insensitivity to cyclosporin A. They represent novel cyclophilins with important differences in the composition of the drug-binding site in particular, namely, a Glu(124) (C. elegans) or Asp(123) (O. volvulus) residue present in a critical position. Site-directed mutagenesis studies and kinetic characterization demonstrated that the single residue dictates the degree of binding to substrate and cyclosporin A. CeCYP-16::GFP-expressing lines were generated with expression in the anterior and posterior distal portions of the intestine, in all larval stages and adults. An exception was found in the dauer stage, where fluorescence was observed in both the cell bodies and processes of the ventral chord motor neurons but was absent from the intestine. These studies highlight the extensive diversification of cyclophilins in an important human parasite and a closely related model organism.

FTZ-F1β, a novel member of the Drosophila nuclear receptor family

The Drosophila melanogaster gene FTZ-F1 beta, encoding a novel member of the steroid/thyroid hormone receptor gene superfamily, was isolated by cross-hybridization with a complementary DNA for the Drosophila nuclear receptor, FTZ-F1 (Lavorgna et al., 1991). The cDNA deduced protein sequence for FTZ-F1 beta displays significant amino acid identity with other vertebrate and invertebrate nuclear receptors, most notably with FTZ-F1. Also, bacterially expressed FTZ-F1 beta protein binds to a FTZ-F1 binding site found in the zebra stripe promoter element of the segmentation gene fushi tarazu (ftz). Northern blot analysis detected FTZ-F1 beta expression at all stages of the Drosophila life cycle including a possible maternal component. In situ hybridization in whole-mounted embryos localized transcripts for FTZ-F1 beta evenly expressed throughout the blastodermal layer in early embryos. At later stages of development strong FTZ-F1 beta expression is observed in both the brain and ventral chord structures as well as in the hindgut. Temporal and spatial expression patterns of the FTZ-F1 beta gene suggest that it may have multiple roles in early embryogenesis, neurogenesis, and in the adult. Furthermore, the identification of FTZ-F1 beta as a nuclear receptor family member suggests that an as yet undiscovered FTZ-F1 beta specific ligand is involved in Drosophila development.

Sem Observations and Developmental Biology of Tobrilus Paludicola Micoletzky, 1925 (Nematoda: Enoplida)

Detailed SEM observations were made on Tobrilus paludicola Micoletzky, 1925 and on its developmental biology. The cuticle is marked with fine transverse striations. The lip region is continuous and lips are broadly triangular in shape. The labial papillae are in a 6+6+4 arrangement. Amphids are small, ovoid, post-labial apertures. Embryonic development is completed 18-26 h after egg laying. The gonad in males and females develops from a single primordium. The supplement formation in third stage male juveniles is marked by the formation of numerous ventral chord supplement nuclei and finally their aggregation in groups at definite distances at a later stage.

The Life Cycle of Mononchoides Fortidens (Nematoda: Diplogasteroidea) With Emphasis On Gonad Development

Mononchoides fortidens reproduced by amphimixis. Smooth, elongate eggs measuring 60-80 x 35-45 μm were laid in single-cell stage. Embryonic and post-embryonic development lasted for 16-20 h and 3-6 days respectively. Sexes were first distinguished during second moulting by the anterior elongation of primordium in males and anterior as well as posterior elongation in females. The aggregation of cells dorsal to the rectum in males represented the site of spicule formation. In females specialized ventral chord nuclei on the mid-ventral side of genital primordium formed the vagina. A flexure developed first in the third stage male, and later in fourth stage females. The life cycle from egg to adult was completed in 4-7 days.

Rachis vascularization and leaflet venation in developing leaves of Fraxinus pennsylvanica

Leaves of Fraxinus pennsylvanica are served by a double trace that exits the stem vasculature through a single gap. During embryonic leaf development, the leaf traces subdivide in the node to produce subsidiary bundles that differentiate acropetally in the leaf base and basipetally in the stem. The acropetal bundles converge distally in the node to form a rachis vasculature consisting of a semicircular arc joined by a ventral chord. Each lateral leaflet is vascularized by bundles contributed by both the semicircular arc and the ventral chord of the rachis. One rachis ridge bundle divides to form two leaflet ridge bundles and a new rachis ridge bundle diverges from the ventral chord. The leaflet ridge bundles diverge as basal veins and subsequent secondary veins diverge from the midvein in an approximate right–left sequence. Green ash has odd pinnate leaves; the terminal leaflet is vascularized by the rachis residual following departure of the last leaflet pair. Secondary veins extend to the lamina margins and then curve upward to initiate the marginal loops of the brochidodromous venation. Periclinal divisions occur in close association with secondary veins in the prospective plate meristem region. Anticlinal divisions occur in subepidermal layers of the internal ridge points in the prospective palisade mesophyll region.The latter divisions probably contribute both to lamina extension and to spreading of the conduplicately folded lamina wings.

VASCULARIZATION OF DEVELOPING LEAVES OF GLEDITSIA TRIACANTHOS L. I. THE NODE, RACHIS, AND RACHILLAE

Leaves of Gleditsia triacanthos L. are served by three leaf traces that subdivide in the node to produce subsidiary bundles. The subsidiary bundles differentiate basipetally in the stem and acropetally in the petiole using the original leaf trace bundles (those that developed acropetally) as templates for their development. Within the pulvinus, the acropetal bundle components merge to form the rachis vasculature consisting of a semicircular arc and a ventral chord; several small bundles diverge to form ventral ridge bundles. Mixing of bundles occurs during vascularization of the lateral rachillae axes. Each diverging rachilla axis receives bundles from the semicircular arc, the ventral chord, and a ridge bundle in a relatively reproducible and predictable pattern. During this process the main rachis vasculature is gradually depleted, but the ridge bundles are reconstituted following divergence of each rachilla pair. The distal rachilla pair is vascularized by a bilateral partitioning of the entire rachis vasculature; a remnant of the central leaf trace terminates in a subulate terminal appendage. Vascularization of the bipinnate G. triacanthos leaf is compared to that of the simple Populus deltoides leaf.

Embryonic and Post-Embryonic Development of Cylindrocorpus Longis'Toma (Nematoda: Cylindrocorporidae)

Embryonic development in C. longistoma follows the general pattern of other nematode species. Embryonic development lasts 30-34 hours. The relationship between larval movement and the hatching mechanism is discussed. The proportional changes which occur in gross body form during postembryogenesis are studied through a biometrical analysis of morphometric and allometric characters. The greatest increase in body length occurs during the third stage, coinciding with the greatest increase in gonad length. Due to lack of allometry between pairs of morphometric characters, 'a', 'b', and 'c' ratios are unacceptable for taxonomic purposes pertaining to this species. Growth of the reproductive system is relatively stable and the use of 'V' and 'T' for taxonomic purposes is acceptable. The genital primordium of first- and second-stage larvae consists of two germinal and two somatic cells. Sexual differences are discernible during the second molt by the presence or absence of specialized ventral chord nuclei and differential development of the genital primordium. Specialized ventral chord nuclei take part in the formation of the vagina. A specialized somatic nucleus separates from the uterine wall and initiates the vaginal primordium. Specialized ventral chord nuclei are absent in male larvae. During the third molt the anterior portion of the male gonad turns posteriad and grows along the ventral side of the body. Primordia of spicules and gubernaculum begin development during the third molt and male accessory structures are completed during the final molt. Nuclear divisions in the reproductive system occur throughout molts and stages.

Culturing, Embryology and Life History Studies On the Lance Nematode, Hoplolaimus Indicus

Two populations of Hoplolaimus indicus were cultured monoxenically on excised roots of Sorghum vulgare var. CSH 1 (jowar) in nutrient agar. Prior feeding was necessary for oviposition and development of successive postembryonic stages. The first molt occurred within the egg and the development outside the egg consisted of three larval stages and an adult stage with the three usual molts. The life cycle at a temperature of 28°-32°C from egg to egg stage was completed at 27-36 days and from egg stage to male at 25-27 days. Sex differentiation was indicated in the second molt by the presence of four specialized ventral chord nuclei present only in female larvae.

Mode of Reproduction and Development of the Reproductive System of Helicotylenchus Dihystera

The morphology of the adult female reproductive system was studied in Helicolylenchus dibystera and H. digonicus. In both species, it was found to comprise the following parts: Ovary (8.7 to 21.2 oogonia and oocytes in anterior gonad, 7.6 to 18.3 in posterior gonad of H. dihystera), narrow .constriction (four cells), tubular oviduct (sixteen cells), constriction (eight cells), dorsally bulging, nonfunctional spermatotheca (twelve cells), glandular tricolumella (twelve cells) and uterus proper. The final number of cells making up the spermatotheca is determined during the last molt, no cell divisions take place later in the adult. No spermatozoa could be demonstrated in the spermatotheca or in any other part of the gonoducts and reproduction was by mitotic parthenogenesis. The cells of the tricolumella have a secretory function and the material they produce appears to be deposited on the surface of the eggs. The post-embryonic development of H. dihystera comprises four larval stages and the adult. The first molt takes place within the egg. The three larval stages outside the egg can be recognized on the basis of the degree of development of the reproductive system. The reproductive system of each larval stage has a constant number of nuclei. Nuclear divisions in the reproductive system occur only during molting, whereas cell enlargement takes place mainly during the larval stages. The reproductive system consists of four nuclei in the second larval stage, fourteen nuclei in the third and 108 nuclei in the fourth larval stage. The final differentiation of the various gonadal parts takes place during the fourth molt. Specialized ventral chord nuclei and some other nuclei outside the gonad whose origin could not be determined take part in the formation of the vagina. One of the central nuclei of the gonad proper appears to function as vaginal organizer (I nucleus).