Search results for "Retina"
showing 10 items of 864 documents
A surface hopping algorithm for nonadiabatic minimum energy path calculations
2015
The article introduces a robust algorithm for the computation of minimum energy paths transiting along regions of near-to or degeneracy of adiabatic states. The method facilitates studies of excited state reactivity involving weakly avoided crossings and conical intersections. Based on the analysis of the change in the multiconfigurational wave function the algorithm takes the decision whether the optimization should continue following the same electronic state or switch to a different state. This algorithm helps to overcome convergence difficulties near degeneracies. The implementation in the MOLCAS quantum chemistry package is discussed. To demonstrate the utility of the proposed procedur…
Electroretinographic oscillatory potentials in insulin-dependent diabetes patients: A long-term follow-up.
2002
Purpose: The aim of this research was to study the relevance of long-term follow-up of electroretinographic oscillatory potentials (OPs) in predicting the onset of minimal non-proliferative diabetic retinopathy in insulin-dependent diabetes patients. Methods: A total of 80 insulin-dependent diabetics, with normal fundi and normal OPs at first examination, were followed prospectively for 10 years. Oscillatory potentials were measured and fundus examinations performed once or twice per year. Results: During follow-up, 35% of patients developed diabetic retinopathy after a mean disease duration of 12 ± 2 years. A decrease in OP amplitudes was seen in 46% of this group, but reductions were also…
Plasticity of retinal ribbon synapses.
1996
Ribbon synapses differ from conventional chemical synapses in that they contain, within the cloud of synaptic vesicles (SV's), a specialized synaptic body, most often termed synaptic ribbon (SR). This body assumes various forms. Reconstructions reveal that what appear as rod- or ribbon-like profiles in sections are in fact rectangular or horseshoe-shaped plates. Moreover, spherical, T-shaped, table-shaped, and highly pleomorphic bodies may be present. In mammals, ribbon synapses are present in afferent synapses of photoreceptors, bipolar nerve cells, and hair cells of both the organ of Corti and the vestibular organ. Synaptic ribbons (SR's) are also found in the intrinsic cells of the third…
Changes in the Three Dimensional Structure of Synaptic Ribbons in the Pineal Gland of the Guinea-Pig Caused by Constant Light
1997
Synaptic bodies (SBs) are dynamic synaptic organelles of afferent synapses of the retina, inner ear, lateral line organ and pineal gland in vertebrates. When investigated in a transmission electron microscope, their electron-dense rod-like, round or irregular profiles are surrounded by electron-lucent vesicles. The three-dimensional structure of pineal SBs is not precisely known. Pineal glands of two guinea-pigs (one kept under an LD cycle of 12:12 h; one kept in constant light for 8 weeks) were investigated. SBs were reconstructed in three dimensions to visualise morphological changes in constant light. Transmission electron microscope micrographs from up to 18 serial sections with a known…
A Transition Zone Complex Regulates Mammalian Ciliogenesis and Ciliary Membrane Composition
2011
Mutations in genes encoding ciliary components cause ciliopathies, but how many of these mutations disrupt ciliary function is unclear. We investigated Tectonic1 (Tctn1), a regulator of mouse Hedgehog signaling, and found that it is essential for ciliogenesis in some, but not all, tissues. Cell types that do not require Tctn1 for ciliogenesis require it to localize select membrane-associated proteins to the cilium, including Arl13b, AC3, Smoothened and Pkd2. Tctn1 forms a complex with multiple ciliopathy proteins associated with Meckel (MKS) and Joubert (JBTS) syndromes, including Mks1, Tmem216, Tmem67, Cep290, B9d1, Tctn2, and Cc2d2a. Components of the Tectonic ciliopathy complex colocaliz…
Taurine in the interphotoreceptor matrix
2014
TAURINE IN THE INTERPHOTORECEPTOR MATRIX Gueli Maria Concetta Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche (BioNEC), Università degli Studi di Palermo Taurine (Tau) is the most abundant amino compound free in the retina. It is concentrated in the photoreceptor inner segment, in the outer nuclear layer and in the synapses. The retina synthesizes and receives Tau from choroidal blood via the pigment epithelium (PE). The high content in the retina suggest the possibily of verifying whether it was present in the interphotoreceptor matrix (IPM), which occupies the subretinal space. In this study we have determined the Tau level in the IPM, separating it from other soluble ami…
The inhibitory effect of D-glucosamine on thymidine kinase in chick embryo retinas and HeLa cells
1984
D-Glucosamine markedly inhibits thymidine incorporation into the TCA-insoluble fraction and thymidine kinase activity in HeLa cells. Both the inhibitory effects are also observed in isolated retinas of chick embryos. In this case the inhibitory effects are age-dependent and the magnitude of the responses decreases with embryonic development. In addition the time of exposure to D-glucosamine which is necessary to reveal the inhibitory effect on thymidine kinase increases with the age of the embryos.
Towards the new spectral-domain optical coherence tomography based classification of age-related macular degeneration
2012
Introducción: La degeneración macular asociada a la edad (DMAE) es un problema sociosanitario de primer orden en las sociedades industrializadas. La aportación de las nuevas técnicas diagnósticas, fundamentalmente la tomografía de coherencia óptica de dominio espectral (SD-OCT), ha ayudado a comprender mejor esta enfermedad. Objetivo: Recordar la clasificación clínica vigente de la DMAE, exponer la nueva clasificación tomográfica de la DMAE exudativa, y revisar los nuevos nuevos hallazgos tomográficos de la degeneración macular seca. Desarrollo: Clásicamente se distinguen dos formas de DMAE: seca y exudativa; asimismo existen tres estadios progresivos de severidad: precoz, intermedio y tard…
Systemische fibrinolytische Therapie mit Urokinase bei Zentralarterienverschluss der Netzhaut
2005
BACKGROUND AND OBJECTIVE Systemic fibrinolysis has become an important therapeutical option in patients with thrombotic occlusion of coronary or pulmonary arteries. In view of the hemorrhagic risk systemic fibrinolytic therapy for retinal vessel occlusion has been discussed controversial. In the present case study results and complications of systemic fibrinolysis should be investigated in patients with central retinal artery occlusion. PATIENTS AND METHODS From 1995 to 2002 a case series of 19 consecutive patients (8 female, 11 male, age: 63.2+/-14,3 years) with central retinal artery occlusion were treated by systemic application of urokinase using a standardized scheme. The latency from …
Integrin-dependent and -independent functions of astrocytic fibronectin in retinal angiogenesis
2011
Fibronectin (FN) is a major component of the extracellular matrix and functions in cell adhesion, cell spreading and cell migration. In the retina, FN is transiently expressed and assembled on astrocytes (ACs), which guide sprouting tip cells and deposit a provisional matrix for sprouting angiogenesis. The precise function of FN in retinal angiogenesis is largely unknown. Using genetic tools, we show that astrocytes are the major source of cellular FN during angiogenesis in the mouse retina. Deletion of astrocytic FN reduces radial endothelial migration during vascular plexus formation in a gene dose-dependent manner. This effect correlates with reduced VEGF receptor 2 and PI3K/AKT signalli…