Home About us Contact
|
Home About us Contact | ||
|
|
||
Anterior Pole (anterior + pole)
Selected AbstractsSpecific developmental gene silencing in the honey bee using a homeobox motifINSECT MOLECULAR BIOLOGY, Issue 6 2002M. Beye Abstract Manipulating the expression of genes in species that are not currently used as genetic models will provide comparative insights into the evolution of gene functions. However the experimental tools in doing so are limited in species that have not served as models for genetic studies. We have examined the effects of double stranded RNA (dsRNA) in the honey bee, an insect with considerably basic scientific interest. dsRNA derived from a 300 bp stretch of the E30 homeobox motif was injected into honey bee embryos at the anterior pole in the preblastoderm stage. We found that the dsRNA fragment successfully disrupted the protein expression of the target gene throughout the whole embryo. The disruption caused deficient phenotypes similar to known loss of function mutants of Drosophila engrailed, whereas embryos injected with nonsense dsRNA showed no abnormalities. We show that the large size of the honey bee egg (D: 0.3 mm, L: 1.6 mm) and the long preblastoderm stage (11,12 h) can be exploited to generate embryos with partial disruption of gene function, which may provide an elegant alternative to classical chimeric analyses. This is the first report of targeted disruption of gene function in the honey bee, and the results prove that the chosen target gene is a functional ortholog to engrailed in Drosophila. [source] Larval development in the Homoscleromorpha (Porifera, Demospongiae)INVERTEBRATE BIOLOGY, Issue 3 2003Nicole Boury-Esnault Abstract. Embryonic development from coeloblastula to fully developed larva was investigated in 8 Mediterranean homoscleromorph species: Oscarella lobularis, O. tuberculata, O. microlobata, O. imperialis, Plakina trilopha, P. jani, Corticium candelabrum, and Pseudocorticium jarrei. Morphogenesis of the larva is similar in all these species; however, cell proliferation is more active in species of Oscarella than in Plakina and C. candelabrum. The result of cell division is a wrinkled, flagellated larva, called a cinctoblastula. It is composed of a columnar epithelium of polarized, monoflagellated cells among which are scattered a few non-flagellated ovoid cells. The central cavity always contains symbiotic bacteria. Maternal cells are also present in O. lobularis, O. imperialis, and P. jarrei. In the fully developed larva, cell shape and dimensions are constant for each species. The cells of the anterior pole have large vacuoles with heterogeneous material; those of the postero-lateral zone have an intranuclear paracrystalline inclusion; and the flagellated cells of the posterior pole have large osmiophilic inclusions. Intercellular junctions join the apical parts of the cells, beneath which are other specialized cell junctions. A basement membrane underlying the flagellated cells lines the larval cavity. This is the first observation of a basement membrane in a poriferan larva. The basal apparatus of flagellated cells is characterized by an accessory centriole located exactly beneath the basal body. The single basal rootlet is cross striated. The presence of a basement membrane and a true epithelium in the larva of Homoscleromorpha,unique among poriferan clades and shared with Eumetazoa,suggests that Demospongiae could be paraphyletic. [source] Embryogenesis and metamorphosis in a haplosclerid demosponge: gastrulation and transdifferentiation of larval ciliated cells to choanocytesINVERTEBRATE BIOLOGY, Issue 3 2002Sally P. Leys Abstract. Early development and metamorphosis of Reniera sp., a haplosclerid demosponge, have been examined to determine how gastrulation occurs in this species, and whether there is an inversion of the primary germ layers at metamorphosis. Embryogenesis occurs by unequal cleavage of blastomeres to form a solid blastula consisting micro- and macromeres; multipolar migration of the micromeres to the surface of the embryo results in a bi-layered embryo and is interpreted as gastrulation. Polarity of the embryo is determined by the movement of pigment-containing micromeres to one pole of the embryo; this pole later becomes the posterior pole of the swimming larva. The bi-layered larva has a fully differentiated monociliated outer cell layer, and a solid interior of various cell types surrounded by dense collagen. The pigmented cells at the posterior pole give rise to long cilia that are capable of responding to environmental stimuli. Larvae settle on their anterior pole. Fluorescent labeling of the monociliated outer cell layer with a cell-lineage marker (CMFDA) demonstrates that the monociliated cells resorb their cilia, migrate inwards, and transdifferentiate into the choanocytes of the juvenile sponge, and into other amoeboid cells. The development of the flagellated choanocytes and other cells in the juvenile from the monociliated outer layer of this sponge's larva is interpreted as the dedifferentiation of fully differentiated larval cells,a process seen during the metamorphosis of other ciliated invertebrate larvae,not as inversion of the primary germ layers. These results suggest that the sequences of development in this haplosclerid demosponge are not very different than those observed in many cnidarians. [source] Contributions of Mouse Genetic Background and Age on Anterior Lens Capsule ThicknessTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 12 2008Brian P. Danysh Abstract Accurate lens capsule thickness measurements are necessary for studies investigating mechanical characteristics of the capsule. Confocal Z -axis imaging was used to measure the anterior lens capsule thickness of living intact lenses with minimal tissue manipulation. Measurements of the anterior capsule thickness is reported for the first time in young and old mice from four inbred strains, BALB/c, FVB/N, C57BL/6, and 129X1, and the outbred strain ICR. Our data demonstrates that the mouse anterior lens capsule continues to grow postnatally similar to that described in other mammals. It is also shown there is a significant difference in anterior lens capsule thickness between unrelated mouse strains, suggesting that capsule thickness is a quantitative trait shared by strains with common ancestry. Measurements, taken from other regions of FVB/N capsules revealed the anterior pole to be the thickest, followed by the equatorial region and posterior pole. In addition to mouse, anterior capsule measurements taken from intact cattle, rabbit, rat lenses, and human capsulotomy specimens correlated with the overall size of the animal. Anat Rec, 2008. © 2008 Wiley-Liss, Inc. [source] Characterization of a Cryptosporidium parvum Gene Encoding a Protein with Homology to Long Chain Fatty Acid SynthetaseTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2003Leonardo Camero ABSTRACT: We describe here the cloning, sequencing, and characterization of a novel Cryptosporidium parvum gene, encoding a protein with significant homology to the long-chain fatty acyl-CoA synthetase (LCFA, EC 6.2.13). The gene has an open reading frame of 2,301 bp, coding for a 766 amino acid polypeptide, and with an estimated MW of 86.1 kDa. By indirect immunofluorescence assay, monoclonal antibodies C3CE7 and ESD labeled the anterior pole of fixed C. parvum sporozoites and developmental stages in C. parvum-infected cultures at 24, 48, and 72 h post-infection. These monoclonal antibodies inhibited more than 3.5% of parasite growth in vitro. The effect of triacsin C, a potent selective inhibitor of LCFA synthetase, on parasite growth was assessed in cell culture; complete inhibition of parasite growth at 2.5 ug/inl was obtained with little evidence of drug-associated cytotoxicity. These results suggest that the fatty acyl-CoA synthetase may be a useful target in the development of selective inhibitors and immunologic interventions against C. parvum [source] Tibial Bone KPro technique and long term resultsACTA OPHTHALMOLOGICA, Issue 2009J TEMPRANO The operation is performed in three stages. The first stage consists in preparing the eye to receive and maintain the keratoprosthesis. For this purpose the anterior surface of the eye is cleaned and regularized, eliminating fibrous tissue and the entire epithelium. Subsequently we obtain a 2 x 3 cm graft of buccal mucosa from the inferior lip comprising the entire mucosal and submucosal thickness. The graft is sutured to cover the anterior pole of the eye to promote revitalization. The second stage consists in preparing the keratoprosthesis. A 10 mm disk of tibial bone from the superior part of the medial face of the tibia is obtained using a crown drill. The posterior part of the piece of bone obtained is then cut with a chisel to obtain a thickness of 3 mm. Subsequently the obtained disk of bone is cleaned and a central opening of 3.5 mm is performed to introduce in this opening a PMMA optic cylinder, 9 mm in length, 3.5 mm in diameter in its narrow portion, 4 mm in the wider portion. Fixation is achieved with cyanoacrylate. This is left to dry and then it is introduced into a palpebral pocket of the inferior lid of the patient. The pocket is closed with sutures and the piece is left in place for three months. For the third stage we remove the keratoprosthesis device from the palpebral pocket and if it is found to be in perfect conditions we dissect the buccal mucous membrane which is covering the cornea and perform a central window with a 4.5 mm trephine to remove the transparent or cataractous lens and perform a total iridectomy. The posterior portion of the optic cylinder is introduced into the anterior chamber. The prosthesis is sutured to the anterior pole of the eye with non-absorbible sutures. Finally the buccal mucosa is replaced, covering the entire area. One point of blepharorraphy is applied. Long term results. We started to use this technique in 1988 and after 21 years of experience we have 80% of anatomically perfect results. In 20 % of the cases the prosthesis extruded due to total or partial resorption of the bone. It has to be emphasized that these were cases without any other possibility of treatment. We did 143 cases during these years. The longest follow-up of a prosthesis "in situ" is 19 years. The earliest extrusion was after one year. The complications are the same as for OOKP (glaucoma, retinal detachment, vitritis, extrusion) The functional results depend on the conditions of the retina and the optic nerve. There were many cases with 20/20 vision. The mean value of retention of the prosthesis is 15 years. [source] | ||||||||||