Retinal pigmented epithelium does not transdifferentiate in adult goldfish

The neural retina of adult goldfish can regenerate from an intrinsic source of proliferative neuronal progenitor cells, but it is not known whether the retina can regenerate by transdifferentiation of the retinal pigmented epithelium (RPE), a phenomenon demonstrated in adult newts. In this study, we asked whether following surgical removal of the neural retina in adult goldfish the RPE was capable of autonomously transdifferentiating and generating new neural retina. The retina was prelabeled by injecting the fluorescent dye Fluoro-Gold (FG) into the eye prior to surgical removal; this procedure ensured that residual retina was labeled with FG and could therefore be distinguished from unlabeled, regenerated retina. To examine the time course of retinal regeneration, and to identify regenerated retinal neurons, the thymidine analogue bromodeoxyuridine was injected intraocularly, and retinas were examined up to 2 months later. We found that the RPE did not transdifferentiate; instead, retinas regenerated only when pieces of residual neural retina were left intact. Under these circumstances, newly regenerated cells derived from proliferating cells intrinsic to the residual neural retina. When retinas were completely removed, as was evident from a lack of FG labeling, there was no retinal regeneration. © 1995 John Wiley & Sons, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50086/1/480270402_ftp.pd

The unique origin of rod photoreceptors in the teleost retina

A population of mitotic cells that produce new neurons has recently been discovered in the layer of photoreceptors in retinas of several species of larval and adult fish. These cells generate new rods which are inserted into the photoreceptor mosaic at locations scattered across the entire expanse of the differentiated retina. Subsequently these new rods establish synaptic connections with retinal neurons already present. The continued production of rods in the fish is apparently needed to maintain visual sensitivity during postembryonic growth of the eye.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25790/1/0000352.pd

Information flow among developing cells : Cellular communication during ocular development. Cell and developmental biology of the eye (proceedings series). Edited by J. B. Sheffield and S. R. Hilfer. New York: Springer-Verlag. (1982). 196 pp. $32.50

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25261/1/0000704.pd

Developmental patterning of rod and cone photoreceptors in embryonic zebrafish

Cone photoreceptors in the zebrafish retina are arranged in a crystalline lattice, with each spectral subtype at a specific position in the array: rod photoreceptors are inserted around the cones. Patterning events and developmental mechanisms that lead to the formation of the cone mosaic are not known. To begin investigating this issue, we examined the initial stages of opsin expression in zebrafish embryos by in situ hybridization with goldfish opsin cRNA probes to determine how and when the cone mosaic pattern arises. We found both differences and similarities in the spatiotemporal patterns of rod and cone development, which suggest the following: (1) Expression of opsin message (including rod opsin, blue and red cone opsins) was initiated at 50–52 hours postfertilization by a few photoreceptors which were consistently found in a ventral patch of retina located nasal to the choroid fissure. (2) The cone mosaic pattern was generated by a crystallization-like process initiated in the precocial ventral patch and secondarily in nasal retina, which then swept like a wave into dorsotemporal retina. (3) The pattern of differentiation of rods in the ventronasal patch differed substantially from that in the remainder of the retina, suggesting that these precocial rods might differ from typical rods. (4) Developmental maturation of rods in zebrafish, as reflected by expression of opsin, may be accelerated compared to cones, which are thought to become postmitotic before rods. These data are consistent with a model in which lateral inductive interactions among differentiating photoreceptors lead to patterning of the array. © 1995 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50066/1/903590403_ftp.pd

Introduction

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41832/1/18-57-2-183_00570183.pd

Autocrine Down-Regulation of Basic Fibroblast Growth Factor Receptors Causes Mitotoxin Resistance in a Human Melanoma Cell Line

The ability of melanoma to develop resistance to mitotoxins, growth-factor- directed anti-neoplastic agents that offer potential for the treatment of this highly refractory disease, may limit therapeutic efficacy. To address this problem, we developed a subcloned human melanoma cell line that is resistant to the mitotoxin composed of basic fibroblast growth factor conjugated to the ribosome-inactivating protein saporin. Resistance was caused by autocrine FGF ligands, which down-regulate bFGF receptors and reduce bFGF-saporin binding. Inhibiting the autocrine loop with suramin or with neutralizing antibodies to FGF up-regulated receptors and decreased resistance in vitro. Furthermore, suramin restored sensitivity in resistant tumor xenografts. These results suggest the potential of therapeutic modalities combining agents that neutralize growth factors with receptor-directed mitotoxins for targeting malignant melanoma either to prevent emergence of resistance or to circumvent resistance once it occurs

Neuronal cell proliferation and ocular enlargement in black moor goldfish

The mechanisms that control cell proliferation in the developing nervous system are not well understood. In larval and adult goldfish addition of new retinal neurons continues as the eye grows, but the factors that modulate the rate of cell proliferation are unknown. The eyes of Black Moors grow excessively during postembryonic life, probably as a direct result of abnormally elevated intraocular pressure. Ocular growth must be partly autonomous in Black Moors because in some individuals the two eyes are very different in size. To determine whether cell proliferation and neuronal cell number in the retina were correlated with size of the eye, we counted dividing neuronal progenitor cells (rod precursors) and mature retinal neurons (ganglion cells) in the retinas of ocularly asymmetric fish. Rod Precursors, which are scattered across the retina in the outer nuclear layer, were labeled with 3 H-thymidine and counted on histological sections processed for autoradiography. Ganglion cells were counted in retinal whole mounts. We found that the total population of dividing rod precursors and the total number of ganglion cells were systematically greater in the large eye compared to the small eye of individual fish. We conclude that control of the rate of neuronal proliferation in the teleost retina is intrinsic to the eye and is probably regulated by the same factors that control ocular growth.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50040/1/902760207_ftp.pd

Avaliar a validade da avaliação das carteiras de acreditação

This study examines one part of a validity argument for portfolio assessments of teaching practice used as an indicator of teaching quality to inform a licensure decision.  We investigate the relationship among portfolio assessment scores, a test of teacher knowledge (ETS’s Praxis I and II),  and changes in student achievement (on Touchstone’s Degrees of Reading Power Test [DRP]).  Key questions are the extent to which the assessment of teaching practice (a) predict gains in students’ achievement and (b) contribute unique information to this prediction beyond what is contributed by the tests of teacher knowledge.  The venue for our study is Connecticut State Department of Education’s (CSDE) support and licensure system for beginning teachers, the Beginning Educator Support and Training (BEST) program (as it was implemented at the time of our study). We investigated whether elementary teachers’ mean effects on their students’ reading achievement support the use of BEST elementary literacy portfolio scores as a measure of teaching quality for licensure, using a data set gathered from both State and two urban school district sources.  The HLM findings indicate that BEST portfolio scores do indeed distinguish among teachers who were more and less successful in enhancing their students’ achievement. An additional analysis indicated that the BEST portfolios add information that is not contained in the Praxis tests, and are more powerful predictors of teachers’ contributions to student achievement gains.Este estudio examina una parte de un argumento de validez para las evaluaciones de los cartera de la práctica docente utilizados como un indicador de la calidad docente para informar una decisión licencia. Investigamos la relación entre los resultados de la evaluación de cartera , una prueba de conocimientos del profesorado ( Praxis I del ETS y II), y los cambios en los logros del estudiante ( en grados de piedra de toque de la prueba eléctrica de la lectura [ DRP ] ) . Las cuestiones clave son la medida en que la evaluación de la práctica docente ( a) predecir las ganancias en el rendimiento de los estudiantes y ( b ) contribuir información única a esta predicción más allá de lo aportado por las pruebas de conocimiento de los maestros . El lugar elegido para nuestro estudio es el Departamento de apoyo y otorgamiento de licencias ( CSDE ) Sistema de Educación para los maestros principiantes del Estado de Connecticut , el Principio Educador , y la programa (BEST ) (como se implementó en el momento de nuestro estudio ) Adiestramiento. Hemos investigado si los "efectos medias en sus alumnos los profesores elementales logros en lectura apoyan el uso de las mejores puntuaciones de la cartera de alfabetización primaria como una medida de calidad de la enseñanza para obtener la licencia , el uso de un conjunto de datos recogidos de Estado y de dos fuentes distrito escolar urbano . Los hallazgos indican que las puntuaciones HLM mejor cartera de hecho distinguen entre los profesores que se encontraban cada vez menos éxito en la mejora de los logros de sus alumnos. Un análisis adicional indicó que los mejores carteras añadir información que no está contenida en las pruebas Praxis , y son más potentes predictores de las contribuciones de los profesores a las ganancias de rendimiento de los estudiantes .O presente estudo analisa uma parte de um argumento de validade para avaliação da carteira de prática de ensino utilizadas como um indicador da qualidade do ensino para informar a decisão de licença. Nós investigamos a relação entre os resultados do portfólio de avaliação, um teste de conhecimentos e competências ( ETS Praxis I e II) , e as mudanças no desempenho do aluno (em graus pedra de toque de teste elétrico leitura [ DRP ] ) . As questões-chave são a medida em que a avaliação da prática docente ( a) prever ganhos no desempenho dos alunos e ( b) contribuir com informações exclusivas para a predição além da evidência fornecida pelo conhecimento dos professores. O local escolhido para o nosso estudo é o suporte Departamento e licenciamento ( CSDE ) Sistema de Educação para professores iniciantes do Estado de Connecticut, o Educador Começando , eo programa (BEST ) (como implementado no momento do nosso estudo ) Treinamento. Nós investigamos se os "efeitos médios em seus professores elementares de leitura os alunos realização apoiar o uso das melhores pontuações da carteira de alfabetização primária como uma medida da qualidade da educação para o licenciamento , o uso de um conjunto de dados coletados fontes do Estado e dois distrito escolar urbano . os resultados indicam que as pontuações melhor portfolio HLM realmente distinguir entre os professores que estavam menos bem sucedido de sempre na melhoria da realização dos seus alunos. Uma análise indicou ainda que os melhores portfolios adicionar informações não contidas nos testes Praxis , e são preditores mais poderosos de contribuições dos professores para os ganhos de desempenho dos alunos

Molecular characterization of retinal stem cells and their niches in adult zebrafish

BACKGROUND: The persistence in adult teleost fish of retinal stem cells that exhibit all of the features of true 'adult stem cells' – self-renewal, multipotency, and the capacity to respond to injury by mitotic activation with the ability to regenerate differentiated tissues – has been known for several decades. However, the specialized cellular and molecular characteristics of these adult retinal stem cells and the microenvironmental niches that support their maintenance in the differentiated retina and regulate their activity during growth and regeneration have not yet been elucidated. RESULTS: Our data show that the zebrafish retina has two kinds of specialized niches that sustain retinal stem cells: 1) a neuroepithelial germinal zone at the interface between neural retina and ciliary epithelium, called the ciliary marginal zone (CMZ), a continuous annulus around the retinal circumference, and 2) the microenvironment around some Müller glia in the differentiated retina. In the uninjured retina, scattered Müller glia (more frequently those in peripheral retina) are associated with clusters of proliferating retinal progenitors that are restricted to the rod photoreceptor lineage, but following injury, the Müller-associated retinal progenitors can function as multipotent retinal stem cells to regenerate other types of retinal neurons. The CMZ has several features in common with the neurogenic niches in the adult mammalian brain, including access to the apical epithelial surface and a close association with blood vessels. Müller glia in the teleost retina have a complex response to local injury that includes some features of reactive gliosis (up-regulation of glial fibrillary acidic protein, GFAP, and re-entry into the cell cycle) together with dedifferentiation and re-acquisition of phenotypic and molecular characteristics of multipotent retinal progenitors in the CMZ (diffuse distribution of N-cadherin, activation of Notch-Delta signaling, and expression of rx1, vsx2/Chx10, and pax6a) along with characteristics associated with radial glia (expression of brain lipid binding protein, BLBP). We also describe a novel specific marker for Müller glia, apoE. CONCLUSION: The stem cell niches that support multi-lineage retinal progenitors in the intact, growing and regenerating teleost retina have properties characteristic of neuroepithelia and neurogenic radial glia. The regenerative capacity of the adult zebrafish retina with its ability to replace lost retinal neurons provides an opportunity to discover the molecular regulators that lead to functional repair of damaged neural tissue

Use of osmium tetroxide-potassium ferricyanide in reconstructing cells from serial ultrathin sections

We describe a technique, modified from Langford and Coggeshall [Anat. Rec., 197 (1980) 297-303; J. Comp. Neurol., 203 (1981) 745-750], for enhancing membrane contrast and defining cellular boundaries, that is useful for reconstructing individual cells from serial ultrathin sections. The cells of interest in our study were neuronal germinal cells and their differentiated progeny in the retinas of young goldfish. These cells were labeled by pulse injections of [3H]thymidine, and they were subsequently identified in EM autoradiographs by the presence of silver grains overlying their nuclei. In tissue prepared by traditional procedures (fixation in mixed aldehydes, postfixation in osmium tetroxide) it was difficult to follow the processes of these cells through the complex, dense network of cells in the differentiated retina. However, in tissue postfixed with a mixture of osmium tetroxide and potassium ferricyanide, the contrast of the cell membranes was improved and, in favorable preparations, a dense precipitate was formed in the extracellular spaces, serving to outline individual cells. This greatly faciliated the preparation of reconstructions from serial ultrathin sections.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26703/1/0000253.pd