The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Jerry F. Butler - One of the best experts on this subject based on the ideXlab platform.
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Ultrastructure of the Tabanidae compound eye: Unusual features for Diptera
Journal of Insect Physiology, 1991Co-Authors: W. Clay Smith, Jerry F. ButlerAbstract:Abstract The ultrastructure of non-Muscamorpha Diptera is poorly defined. This study is an ultrastructural investigation of the Tabanidae (Diptera) retina, covering 14 species in five genera. The purpose is to identify differences in ultrastructure between tabanids (suborder Brachycera) and the well-known anatomy of muscamorph flies (suborder Cyclorrhapha). Tabanids are observed to have the following features: (i) corneal nipples; (ii) corneal layers; (iii) axial seven-lobed formations in each Ommatidium; (iv) closely apposed rhabdomeres distally; (v) rhabdomere twisting only in the proximal Ommatidium and (vi) large tracheal air sacs surrounding each Ommatidium. Each of these features is described ultrastructurally and discussed with respect to their proposed function.
Mia Horowitz - One of the best experts on this subject based on the ideXlab platform.
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Past1 mutant flies contain an abnormal number of photoreceptors in their eyes.
2017Co-Authors: Orly Dorot, Hermann Steller, Daniel Segal, Mia HorowitzAbstract:(A) Schematic representation of the apical section of an Ommatidium. (B) Schematic representation of a cross-section of an Ommatidium. (C) Scanning electron microscopy images of eyes of wild type or homozygous null Past1 mutant (Past1110-1) three-days-old adult flies. Upper panels x240, lower panels x1500. (D) Transmission electron microscopy images of eyes of wild type or Past1110-1 three-days-old adult flies. Orange frame delineates an example of an Ommatidium with fewer photoreceptors than in the wild type. Blue frame delineates an example of an Ommatidium with two potential R7 photoreceptors.
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Specification of cone and inter-ommatidial cells in Past1 mutant eyes.
2017Co-Authors: Orly Dorot, Hermann Steller, Daniel Segal, Mia HorowitzAbstract:(A) Elav (grey, or red in the merge) and cut (grey, or green in the merge) staining of wild type and Past1110-1 homozygous mutant early-mid pupal eyes (42-48h after puparium formation). Shown are Z-projections of confocal sections. The enlarged images on the right of each frame show an Ommatidium with four cone cells in wild type and an Ommatidium with five cone cells in Past1110-1mutant eyes. (B) Quantification of four or five cone cells in wild type (n = 189) and Past1110-1mutant (n = 186) ommatidia; P < 0.001. (C) Dlg (green) staining of wild type and Past1110-1mutant early-mid pupal eyes (42-48h after puparium formation). Shown are Z-projections of confocal sections. The enlarged images on the right of each frame show an Ommatidium with nine inter-ommatidial pigment cells and four cone cells in wild type and an Ommatidium with nine inter-ommatidial pigment cells and five cone cells in Past1110-1mutant eyes. (D) Dlg (green) and phalloidin (red) staining of wild type and Past1110-1mutant late pupal eyes (85-96h after puparium formation). Different focal planes of the same Ommatidium, presenting: upper sections of the ommatidia for Dlg and lower sections for phalloidin.
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A model for Ommatidium development.
2017Co-Authors: Orly Dorot, Hermann Steller, Daniel Segal, Mia HorowitzAbstract:(A) According to Tomlinson et al. 2011, expression of Notch in R1 or R6 leads to their development into R7 or cone cells. (B) A model for Ommatidium development, presenting the impact of Past1 mutation (Past1null) on development of R1/R6/R7 and the cone cells. We assume that when overexpressed there is PAST1-mediated downregulation of endocytic processes, as shown in Fig 10, and therefore it behaves like a mutant Past1, that leads to Notch overexpression.
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Ommatidial defects in Past1 mutant flies.
2017Co-Authors: Orly Dorot, Hermann Steller, Daniel Segal, Mia HorowitzAbstract:(A) Phalloidin staining of wild type or Past1110-1 homozygous mutant late pupa eyes. Dotted squares mark ommatidia with less than seven rhabdomeres. (B) Quantification of abnormal ommatidia (with less than seven rhabdomeres) in late pupal eyes of wild type (n = 229) and of Past1110-1 mutants (n = 222) ommatidia; P < 0.001. (C) Elav (red) and chapotin (green) staining of wild type and Past1110-1mutant early-mid pupa eyes (42-48h after puparium formation). The dotted square outlines an Ommatidium with eight normal photoreceptors in wild type and an Ommatidium with abnormal seven photoreceptors in Past1110-1mutant eyes. (D) Quantification of abnormal number of photoreceptors in early-mid pupa eyes of wild type (n = 198) and of Past1110-1 mutant (n = 123) ommatidia; P < 0.001.
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Specification of R7, cone and inter-ommatidial pigment cells in GFP-PAST1B transgenic flies.
2017Co-Authors: Orly Dorot, Hermann Steller, Daniel Segal, Mia HorowitzAbstract:(A) Staining of GMRGal4>UAS-GFP-PAST1B (GFP appears as grey, or green in the merge, in all the panels) (line 1), early-mid pupa eyes (42-48h after puparium formation) with Elav (grey, or red in the merge) and pros (grey, or purple in the merge). The dotted circle represents an Ommatidium with two R7 photoreceptors (B) Quantification of the number of R7 photoreceptors in early-mid pupa eyes of wild type (n = 249) and overexpressing transgenic PAST1B (line 1) (n = 145) Ommatidium; P < 0.001. (C) Phalloidin (grey, or red in the merge) and cut (grey or purple in the merge) staining of mirrGal4>UAS-GFP-PAST1B (line 1) early-mid pupa eyes (42-48h after puparium formation). The dotted circles represent ommatidia with five cone cells and the dotted square represents an Ommatidium with three cone cells. Shown are Z-projections of confocal sections. (D) Quantification of the number of cone cells in early-mid pupal eyes of wild type (n = 189) and transgenic PAST1B (line 1) (n = 138) ommatidia; P < 0.002. (E) Phalloidin (grey, or red in the merge) and Dlg (grey, or purple in the merge) staining of mirrGal4>UAS-GFP-PAST1B (line 1) early-mid pupa eyes (42-48h after puparium formation). The arrowhead marks an extra inter-ommatidial pigment cell.
Nicholas E Baker - One of the best experts on this subject based on the ideXlab platform.
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Cell proliferation, survival, and death in the Drosophila eye.
Seminars in cell & developmental biology, 2001Co-Authors: Nicholas E BakerAbstract:The Drosophila retina has a precise repeating structure based on the unit eye, or Ommatidium. This review summarizes studies of the cell proliferation and survival episodes that affect the number of cells available to make each Ommatidium. Late in larval development, as differentiation and patterning begin, the retinal epithelium exhibits striking regulation of the cell cycle including a transient G1 arrest of all cells, followed by a "Second Mitotic Wave" cell cycle that is regulated at the G2/M transition by local intercellular signals. Reiterated episodes of cell death also contribute to precise regulation of retinal cell number. The EGF receptor homolog has multiple roles in retinal proliferation and survival.
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ellipse mutations in the drosophila homologue of the egf receptor affect pattern formation cell division and cell death in eye imaginal discs
Developmental Biology, 1992Co-Authors: Nicholas E Baker, Gerald M. RubinAbstract:Ellipse alleles are mutations of the EGF-receptor homologue that reduce the number of ommatidia in the eye imaginal disc. Cobalt sulfide staining, expression of hairy and scabrous proteins, and mosaic analysis indicated that Elp mutations affect ommatidial precluster formation in the morphogenetic furrow. BrdU incorporation studies suggest that cells diverted from precluster formation instead enter S-phase after the morphogenetic furrow. Genetic studies suggest that the DER has multiple functions during eye development and that several recessive hypomorphic alleles affect another aspect of DER function that is required after precluster formation. Elp mutations show genetic interactions with the neurogenic mutations Notch and Delta. The small number of ommatidia that differentiate in Elp/Elp are separated more than in wildtype and have been studied to investigate what aspects of Ommatidium development are intrinsic to the Ommatidium itself. It appears that each developing Ommatidium cues the determination of photoreceptors, cone cells, and primary pigment cells, but that the secondary and tertiary pigment cells, and the mechanosensory bristles, can form independently. The normal rotation of ommatidia in the dorsal-ventral axis does not require the presence of the ommatidial array. A short-range signal from a nearby Ommatidium is important for mitosis. Cells not close to an Ommatidium do not go through mitosis and many die.
Steven C. Chamberlain - One of the best experts on this subject based on the ideXlab platform.
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The morphology and physiology of a “mini-Ommatidium” in the median optic nerve of Limulus polyphemus
Visual neuroscience, 1995Co-Authors: Faramarz H. Samie, Robert N. Jinks, William W. Weiner, Steven C. ChamberlainAbstract:Examination of the Limulus median optic nerve with low-magnification light microscopy allows clear visualization of an ultraviolet-sensitive mini-Ommatidium enshrouded by pigment cells, glial cells, and guanophores. Serial 1-μm sections of median optic nerves containing mini-ommatidia revealed the presence of a single, heavily pigmented photoreceptor (retinular) cell and a single, unpigmented arhabdomeric cell. Computer-assisted serial reconstructions from 1-μm sections confirmed the presence of two cells, each bearing a nucleus, and two axons leaving the mini-Ommatidium. The retinular cell is morphologically similar to retinular cells from the median and lateral eyes. Its rhabdomere appears to be a continuous sheet of microvilli with much infolding. The structure of the arhabdomeric cell is nearly identical to those found in the median ocellus. As in other photoreceptors in Limulus , the retinular cell of the mini-Ommatidium is innervated by efferent fibers from the brain. Each mini-Ommatidium generates a single train of nerve impulses in response to light, presumably from the arhabdomeric cell. Measurement of the spectral sensitivity of the mini-Ommatidium based upon a constant-response criterion indicated that the retinular cell is maximally sensitive to near ultraviolet light with λ max = 380 nm. Comparison of intensity-response functions revealed that those of the mini-Ommatidium are significantly steeper than those of the ocellus almost certainly as the result of neural processing in the ocellus which is absent in the mini-Ommatidium.
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the morphology and physiology of a mini Ommatidium in the median optic nerve of limulus polyphemus
Visual Neuroscience, 1995Co-Authors: Faramarz H. Samie, Robert N. Jinks, William W. Weiner, Steven C. ChamberlainAbstract:Examination of the Limulus median optic nerve with low-magnification light microscopy allows clear visualization of an ultraviolet-sensitive mini-Ommatidium enshrouded by pigment cells, glial cells, and guanophores. Serial 1-μm sections of median optic nerves containing mini-ommatidia revealed the presence of a single, heavily pigmented photoreceptor (retinular) cell and a single, unpigmented arhabdomeric cell. Computer-assisted serial reconstructions from 1-μm sections confirmed the presence of two cells, each bearing a nucleus, and two axons leaving the mini-Ommatidium. The retinular cell is morphologically similar to retinular cells from the median and lateral eyes. Its rhabdomere appears to be a continuous sheet of microvilli with much infolding. The structure of the arhabdomeric cell is nearly identical to those found in the median ocellus. As in other photoreceptors in Limulus , the retinular cell of the mini-Ommatidium is innervated by efferent fibers from the brain. Each mini-Ommatidium generates a single train of nerve impulses in response to light, presumably from the arhabdomeric cell. Measurement of the spectral sensitivity of the mini-Ommatidium based upon a constant-response criterion indicated that the retinular cell is maximally sensitive to near ultraviolet light with λ max = 380 nm. Comparison of intensity-response functions revealed that those of the mini-Ommatidium are significantly steeper than those of the ocellus almost certainly as the result of neural processing in the ocellus which is absent in the mini-Ommatidium.
W. Clay Smith - One of the best experts on this subject based on the ideXlab platform.
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Ultrastructure of the Tabanidae compound eye: Unusual features for Diptera
Journal of Insect Physiology, 1991Co-Authors: W. Clay Smith, Jerry F. ButlerAbstract:Abstract The ultrastructure of non-Muscamorpha Diptera is poorly defined. This study is an ultrastructural investigation of the Tabanidae (Diptera) retina, covering 14 species in five genera. The purpose is to identify differences in ultrastructure between tabanids (suborder Brachycera) and the well-known anatomy of muscamorph flies (suborder Cyclorrhapha). Tabanids are observed to have the following features: (i) corneal nipples; (ii) corneal layers; (iii) axial seven-lobed formations in each Ommatidium; (iv) closely apposed rhabdomeres distally; (v) rhabdomere twisting only in the proximal Ommatidium and (vi) large tracheal air sacs surrounding each Ommatidium. Each of these features is described ultrastructurally and discussed with respect to their proposed function.
