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Posterior Pole (posterior + pole)
Selected AbstractsEarly lens development in the zebrafish: A three-dimensional time-lapse analysisDEVELOPMENTAL DYNAMICS, Issue 9 2009Teri M.S. Greiling Abstract In vivo, high-resolution, time-lapse imaging characterized lens development in the zebrafish from 16 to 96 hr postfertilization (hpf). In zebrafish, the lens placode appeared in the head ectoderm, similar to mammals. Delamination of the surface ectoderm resulted in the formation of the lens mass, which progressed to a solid sphere of cells separating from the developing cornea at approximately 24 hpf. A lens vesicle was not observed and apoptosis was not a major factor in separation of the lens from the future cornea. Differentiation of primary fibers began in the lens mass followed by formation of the anterior epithelium after delamination was complete. Secondary fibers differentiated from elongating epithelial cells near the posterior pole. Quantification characterized three stages of lens growth. The study confirmed the advantages of live-cell imaging for three-dimensional quantitative structural characterization of the mechanism(s) responsible for cell differentiation in formation of a transparent, symmetric, and refractile lens. Developmental Dynamics 238:2254,2265, 2009. © 2009 Wiley-Liss, Inc. [source] Postplasmic/PEM RNAs: A class of localized maternal mRNAs with multiple roles in cell polarity and development in ascidian embryosDEVELOPMENTAL DYNAMICS, Issue 7 2007François Prodon Abstract Ascidian is a good model to understand the cellular and molecular mechanisms responsible for mRNA localization with the discovery of a large family of localized maternal mRNAs, called postplasmic/PEM RNAs, which includes more than 40 members in three different ascidian species (Halocynthia roretzi, Ciona intestinalis, and C. savignyi). Among these mRNAs, two types (Type I and Type II) have been identified and show two different localization patterns from fertilization to the eight-cell stage. At the eight-cell stage, both types concentrate to a macromolecular cortical structure called CAB (for Centrosome Attracting Body) in the posterior-vegetal B4.1 blastomeres. The CAB is responsible for unequal cleavages and the partitioning of postplasmic/PEM RNAs at the posterior pole of embryos during cleavage stages. It has also been suggested that the CAB region could contain putative germ granules. In this review, we discuss recent data obtained on the distribution of Type I postplasmic/PEM RNAs from oogenesis to late development, in relation to their localization and translational control. We have first regrouped localization patterns for Type I and Type II into a comparative diagram and included all important definitions in the field. We also have made an exhaustive classification of their embryonic expression profiles (Type I or Type II), and analyzed their functions after knockdown and/or overexpression experiments and the role of the 3,-untranslated region (3,UTR) controlling both their localization and translation. Finally, we propose a speculative model integrating recent data, and we also discuss the relationship between postplasmic/PEM RNAs, posterior specification, and germ cell formation in ascidians. Developmental Dynamics 236:1698,1715, 2007. © 2007 Wiley-Liss, Inc. [source] Three types of cilia including a novel 9+4 axoneme on the notochordal plate of the rabbit embryoDEVELOPMENTAL DYNAMICS, Issue 12 2006Kerstin Feistel Abstract Motile monocilia play a pivotal role in left-right axis determination in mouse and zebrafish embryos. Cilia with 9+0 axonemes localize to the distal indentation of the mouse egg cylinder ("node"), while Kupffer's vesicle cilia in zebrafish show 9+2 arrangements. Here we studied cilia in a prototype mammalian embryo, the rabbit, which develops via a flat blastodisc. Transcription of ciliary marker genes Foxj1, Rfx3, lrd, polaris, and Kif3a initiated in Hensen's node and persisted in the nascent notochord. Cilia emerged on cells leaving Hensen's node anteriorly to form the notochordal plate. Cilia lengthened to about 5 ,m and polarized from an initially central position to the posterior pole of cells. Electron-microscopic analysis revealed 9+0 and 9+2 cilia and a novel 9+4 axoneme intermingled in a salt-and-pepper-like fashion. Our data suggest that despite a highly conserved ciliogenic program, which initiates in the organizer, axonemal structures may vary widely within the vertebrates. Developmental Dynamics 235:3348,3358, 2006. © 2006 Wiley-Liss, Inc. [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] Morphology and ultrastructure of the swimming larvae of Crambe crambe (Demospongiae, Poecilosclerida)INVERTEBRATE BIOLOGY, Issue 4 2001María J. Uriz Abstract. We describe the morphology and ultrastructure of the free-swimming larvae of the sponge Crambe crambe, one of the most abundant encrusting sponges on shallow rocky bottoms of the western Mediterranean. Larvae of C. crambe are released in July and August. The larva is uniformly flagellated except at the posterior zone. Flagellated cells are extraordinarily slender, elongate, and sinuous and form a pseudo-stratified layer. Their distal zone contains abundant mitochondria, some small vesicles, a Golgi complex, and the basal apparatus of the flagellum. Abundant lipid droplets are present throughout the cell. The nucleus is most often in a basal position. The flagellum projects from the bottom of an asymmetrical socket formed by cytoplasmic expansions. The basal body extends in a conical tuft and a laminar rootlet in close association with the Golgi system. The cells at the posterior pole are flat and polygonal on the surface, with long overlapping pseudopodia in the typical shape of a pinacoderm. Sparse collagen is present throughout the whole larva including the flagellated layer. Archeocytes and sclerocytes are abundant in the posterior region. Typical collencytes and spherulous cells seem to be absent. Intracellular and extracellular rod-like bacteria with conspicuous fimbria occur exclusively in the posterior region of the larva. The asymmetrical cytoplasmic prolongations, which surround the flagellum, and the basal apparatus of the flagellum are suggested as the sites of stimulus reception and triggering of locomotor responses, respectively. This ultrastructural study of the larva of C. crambe has shown features directly linked to its behavior and ecology. [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] 4366: Treatment of choroidal neovascularization associated with choroidal nevusACTA OPHTHALMOLOGICA, Issue 2010E PILOTTO Purpose Purpose:To evaluate safety and efficacy of different treatments of choroidal neovascularization (CNV) associated with choroidal nevus at the posterior pole. Methods Methods: Six patients affected by choriodal nevus complicated by CNV were treated with photodynamic therapy with verteporfin (PDT; 50 J/cm2, 83 seconds) (five cases), or intravitreal anti-VEGF (bevacizumab, 1.25 mg) (one case). All patients underwent an ophthalmologic evaluation, including fluorescein and indocyanine green angiography, A-and B scan ultrasonography and OCT at presentation and at each follow-up examination. CNV was extrafoveal in all PDT treated cases, and a foveal serous detachment was detectable. CNV was subfoveal in the eye treated with anti-VEGF. Results Results: Mean follow-up was 15.5 months (range: 6 , 24). Visual acuity improved in four of the PDT treated cases and in the anti-VEGF treated eye, while it remained unchanged in the remaining PDT treated lesion. In all eyes resolution of the foveal serous detachment was detectable. In all PDT treated eyes a single treatment was performed with no recurrence during follow-up. Meanwhile anti-VEGF was repeated after three months for CNV recurrence. Conclusion Conclusions: PDT and anti-VEGF seem both effective in the treatment of CNV secondary to choroidal nevus but a larger study is required to evaluate long-term efficacy and safety expecially of anti-VEGF therapy. [source] 2334: The challenge of interpreting the histomorphology of human fetal lensesACTA OPHTHALMOLOGICA, Issue 2010KU LOEFFLER Purpose On histology, the crystalline lens is , especially in fetal and infant eyes - an organ susceptible to numerous artifacts. Nevertheless, evaluation of the lens is often of paramount importance in the classification of fetal syndromes or forensic questions. Thus, the aim of our study is to evaluate various factors that might have an impact on lens histomorphology. Methods Our collection of eyes by now comprises more than 500 specimens from fetuses with a gestational age between 8 and 38 weeks, including a variety of syndroms. Apart from induced fetocid, death occured due to spontaneous abortion or post-natally. Specimens were fixed in formalin, and in selected cases one eye was put into Karnovsky's solution for comparison. All systemic findings as well as data related to the termination procedure were recorded. - Some individual cases shall be presented to demonstrate the variability of histopathologic findings. Results Most of the eyes revealed lens features different from the descriptions available in textbooks. At all ages, there were various morphologic changes particularly of the subcapsular cortex, compatible with cataractous lenses in the adult, while the well-known phenomenon of an indentation at the posterior pole was seen especially in older fetuses. The difference in fixatives had only a moderate impact on structural alterations. Conclusion Alterations in fetal lens morphology are extremely frequent and variable. These can be due to delayed fixation, cutting artifacts and other variables and have to be carefully taken into account particularly when interpreting post-mortem findings. The diagnosis of a fetal cataract should therefore only be made with great caution and not without a careful macroscopic evaluation. [source] Combined intravitreal anti-vascular endothelial growth factor (Avastin®) and photodynamic therapy to treat retinal juxtapapillary capillary haemangiomaACTA OPHTHALMOLOGICA, Issue 5 2010Stefan Mennel Abstract. Objective:, Retinal capillary haemangioma complications are characterized by progressive exudation with consecutive intraretinal and subretinal leakage. A successful therapy without side-effects has not been found. We report a case of retinal juxtapapillary capillary haemangioma causing consecutive leakage with macular involvement. The tumour was treated with a combination of anti-vascular endothelial growth factor (VEGF) and photodynamic therapy (PDT) and was followed for 1 year. Methods:, A 44-year-old woman with retinal juxtapapillary capillary haemangioma in the right eye experienced a decrease of visual acuity from 20/20 to 20/60 because of a severe leakage from the tumour involving the macula with lipid depositions. Two sessions of PDT (sparing the part of the haemangioma located within the optic disc) and five injections of bevacizumab were applied in a period of 5 months. Visual acuity, visual field testing, retinal thickness measurements, fundus photography and fluorescein angiography were performed to evaluate the treatment effect. Results:, One year after the last injection, visual acuity increased to 20/40. All lipid exudates at the posterior pole resolved. Retinal thickness decreased from 490 to 150 ,m with the restoration of normal central macular architecture. Leakage in fluorescence angiography reduced significantly, but hyperfluorescence of the tumour was still evident. Visual field testing and angiography did not show any treatment-related vaso-occlusive side-effects. Conclusion:, In this single case, the combination of anti-VEGF and PDT appeared to be an effective strategy for the treatment of retinal juxtapapillary capillary haemangioma without side-effects. Further studies with a greater number of eyes and adequate follow-up are necessary to support these first clinical results. [source] Prophylactic laser treatment of soft drusen maculopathy: a prospective, randomized Nordic studyACTA OPHTHALMOLOGICA, Issue 7 2009Christina I. Frennesson Abstract. Purpose:, This study aimed to investigate whether mild laser treatment of soft drusen maculopathy might reduce the incidence of choroidal neovascularization (CNV) and/or significantly reduce loss of visual acuity compared with outcomes in a control group. Methods:, A total of 135 patients (mean age 70.4 years) were randomized into a treatment group of 67 subjects and a control group of 68 subjects. The treatment group was subdivided into a group of 54 subjects with bilateral soft drusen and a group of 13 subjects with unilateral soft drusen in the study eye and advanced AMD in the fellow eye. The control group was subdivided into a bilateral group of 54 subjects and a unilateral group of 14 subjects. Sub-threshold or barely visible laser spots were scattered on and between drusen in the posterior pole. Inclusion of patients was stopped prematurely as other studies did not show any benefit from the treatment. Mean follow-up time was 3.7 years. Results:, More CNVs developed in the treated group (4/54 eyes in the bilateral group, 3/13 eyes in the unilateral group; 7/67 eyes in total) than in the control group (3/54 eyes in the bilateral group, 2/14 eyes in the unilateral group; 5/68 eyes in total) but these differences were not statistically significant for either the bilateral or unilateral groups (p = 0.20,0.32). No CNV developed in the bilateral treated group before 4 years of follow-up. Visual acuity was significantly reduced from baseline to the last follow-up in all groups (p < 0.0001,0.02) except the unilateral control group (p = 0.08), but there were no significant differences between the treated and control groups for either the bilateral or unilateral groups (p = 0.17,0.97). Conclusions:, Mild prophylactic laser treatment of soft drusen maculopathy was neither beneficial nor harmful and cannot be recommended. [source] Impact of medication on ocular blood flowACTA OPHTHALMOLOGICA, Issue 2009L SCHMETTERER Purpose Reduced ocular blood flow appears to play a role in the pathophysiology of glaucoma. Hence, there is considerable interest in drugs that are capable of improving ocular perfusion. Methods A large numer of clinical trials have been performed investigating the ocular hemodynamic effects of topical and systemic medications. Such trials used a variety of different methods to assess ocular blood flow parameters. Results When adminsitered systemically most vasodilators decrease systemic blood pressure thereby reducing ocular perfusion pressure (OPP). Only few classes of drugs have been reported to increase ocular blood flow with no or minimal effect on OPP. Among these carbonic anhydrase inhibitors and endothelin receptor anatgonists show the most prononced ocular vasodilator effects. The ocular hemodynamoic effects of topical medications is generally considered small. Conclusion When drugs are given systemically the effects on OPP have to be considered. In addition, the potentially positive effects on ocular perfusion need to be carefully weighed against the side effects. With topically administered drugs the ocular hemodynamic effects will be generally small, because the drugs reach the posterior pole of the eye in small concentrations only. [source] Screening for retinal detachment using a wide field scanning laser ophthalmoscopeACTA OPHTHALMOLOGICA, Issue 2009G BONNAY Purpose The development of non-mydriatic retinal photography has changed the clinical practice, allowing detection of abnormalities in the posterior pole without clinical examination in mydriasis. However the field of view does not exceed 60° and peripheral retinal detachments are likely to be missed on these images. The purpose of this study was to evaluate a wide field (200°) imaging system (Optos, UK ) using a scanning laser ophthalmoscope (SLO) for screening purposes in retinal detachment. Methods All patients referred for retinal detachment from November 2007 to April 2008 were examined by one retinal surgeon who also performed the fundus drawing. An SLO image was taken by an orthoptist in training. A masked image lecture of the entire data base was performed by a resident. Both were unaware of the details of the retinal examination. The number of breaks and the extent of the detachment on the drawing were compared with the findings detected on the SLO image. Results 56 eyes with retinal detachment were documented. In 40 out of 56 eyes the retinal breaks could be detected on the SLO images obtained. The retinal breaks situated superiorly between 11 and 1o'clock or inferiorly between 5 and 7 o'clock and two retinal detachments, one superior and one inferior, were not detected on the SLO images. SLO image analysis enabled correct diagnosis of retinal breaks in more than 7/10 cases. Retinal detachments were detected in more than 9/10 cases. Conclusion Although the wide field SLO imaging system is not suitable as a diagnostic tool of retinal breaks and retinal detachment replacing the fundus examination by a retinal specialist, it represents a reliable screening method. Commercial interest [source] Investigation of particular surgical steps in epiretinal prostheses implantation procedure in pigsACTA OPHTHALMOLOGICA, Issue 2009D IVASTINOVIC Purpose Proliferative vitreoretinopathy (PVR) is known a known complication of implantation of epiretinal prostheses in porcine eyes using our combined surgical procedure of vitrectomy, lensectomy, large scleral incision and retinal tack insertion. The aim of the present experimental study is to investigate the intraocular reaction to particular parts of the epiretinal prostheses implantation procedure in pigs. Methods 15 pigs were divided into 3 groups. Group 1 (n=6) underwent vitrectomy, lensectomy, insertion of inactive epiretinal prosthesis through a scleral incision and fixation to the posterior pole with a retinal tack. In group 2 (n=5) vitrectomy, scleral incision and retinal tack insertion were performed. Group 3 (n=4) received vitrectomy, scleral incision and insertion of a shortened prosthesis into the vitreous cavity. The follow up was 4 weeks. Results PVR was observed in all eyes of group 1 and in one eye of the group 3 with unintentional perforation of the lens capsule by the shortened implant. In all other eyes funduscopy revealed no clinical pathology. Conclusion Our results indicate that lensectomy is the key stimulus for PVR in porcine eyes while other steps of the implantation procedure are well tolerated. Though pigs do not seem to be a reactive animal model, lens manipulation should be avoided in the surgical procedure for the implantation of retinal prostheses. [source] Incidence and clinical characteristics of symptomatic choroidal metastasis from lung cancerACTA OPHTHALMOLOGICA, Issue 5 2008Klaus-Martin Kreusel Abstract. Purpose:, To determine the clinical characteristics of symptomatic choroidal metastasis (CM) resulting from metastatic lung cancer. Methods:, Twenty-two consecutive patients with symptomatic CM resulting from lung cancer were retrospectively reviewed for ocular findings, medical history and systemic disease. All patients underwent a complete screening for further organ metastasis by computed tomography (CT) and bone scintigraphy. Annual frequency of CM was determined and compared with the incidence predicted from ocular screening studies. Results:, In eight of 22 (36%; 95% confidence interval [CI] 17,59) patients, lung cancer had been diagnosed before occurrence of CM, with a median interval of 13 months. In 14 patients lung cancer was detected after diagnosis of CM, with a median interval of 1 month. Choroidal metastasis was unilateral, solitary and located close to or at the posterior pole in the majority of patients. Further organ metastasis with a median number of three affected organ systems was present in 19 (86%; 95% CI 65,97) patients. Median survival after diagnosis of symptomatic CM was 13 months, by contrast with 2 months in lung cancer patients with CM identified in an ocular screening study. The mean number of patients in Berlin diagnosed with symptomatic CM was 1.4 per year, which was two orders of magnitude less than predicted from screening studies. Conclusions:, Symptomatic choroidal lung cancer metastasis in the majority of patients presents as a solitary tumour before diagnosis of lung cancer in patients with multiple organ systems affected by metastatic disease. Contrary to predictions from ocular screening studies, it is a rare clinical entity. [source] | ||||||||||