STRUCTURAL BASIS FOR WAVELENGTH DISCRIMINATION IN THE BANKED RETINA OF THE FIREFLY SQUID WATASENIA SCINTILLANS

There is a greatly thickened region of retina in the ventral part of the eye of the firefly squid Watasenia scintillans, with an outer segment (OS) layer around 600 µm thick. The distal two-thirds of this OS layer is yellow and contains a visual pigment, based on 4-hydroxyretinal (A4), with an absorbance maximum at 470 nm. The proximal third is pink and contains a visual pigment, based on dehydroretinal (A2), with an absorbance maximum at 500 nm. Light and electron microscopic investigations demonstrate the presence of four types of photoreceptor cell. In the pink layer, three of the four types (alpha, ß and gamma) produce no microvilli and are columnar in structure. These cells form square microvillous rhabdoms only in the distal yellow layer. The fourth cell type (delta) produces microvilli in the pink layer only. These observations led us to propose that the A2-based visual pigment is contained in the pink-layer cells and that the A4-based visual pigment is contained in the three types of yellow-layer cells. The absorbance of fresh retina was determined by microspectrophotometry. The yellow OS layer, with an absorbance of 0.7 per 100 µm thickness at 470 nm, is expected to act as a short-wavelength cut-off filter to the underlying pink OS cells, shifting their photosensitivity peak by an estimated 50 nm to 550 nm. Possible wavelength discrimination by this squid is discussed.

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Co-expression of xenopsin and rhabdomeric opsin in photoreceptors bearing microvilli and cilia

eLife ◽

10.7554/elife.23435 ◽

2017 ◽

Vol 6 ◽

Cited By ~ 22

Author(s):

Oliver Vöcking ◽

Ioannis Kourtesis ◽

Sharat Chandra Tumu ◽

Harald Hausen

Keyword(s):

Visual Pigment ◽

Photoreceptor Cell ◽

Gene Loss ◽

Photoreceptor Cells ◽

Common Origin ◽

Opsin Gene ◽

Cell Type ◽

Rods And Cones ◽

Gene Structures ◽

And Function

Ciliary and rhabdomeric opsins are employed by different kinds of photoreceptor cells, such as ciliary vertebrate rods and cones or protostome microvillar eye photoreceptors, that have specialized structures and molecular physiologies. We report unprecedented cellular co-expression of rhabdomeric opsin and a visual pigment of the recently described xenopsins in larval eyes of a mollusk. The photoreceptors bear both microvilli and cilia and express proteins that are orthologous to transporters in microvillar and ciliary opsin trafficking. Highly conserved but distinct gene structures suggest that xenopsins and ciliary opsins are of independent origin, irrespective of their mutually exclusive distribution in animals. Furthermore, we propose that frequent opsin gene loss had a large influence on the evolution, organization and function of brain and eye photoreceptor cells in bilaterian animals. The presence of xenopsin in eyes of even different design might be due to a common origin and initial employment of this protein in a highly plastic photoreceptor cell type of mixed microvillar/ciliary organization.

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Convergent Beam Electron Diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100070072 ◽

1978 ◽

Vol 36 (3) ◽

pp. 304-315

Author(s):

G. Lehmpfuhl

Keyword(s):

Electron Diffraction ◽

Diffraction Pattern ◽

Crystal Surface ◽

Diffraction Spot ◽

Crystal Thickness ◽

Large Area ◽

Electron Microscopic ◽

Additional Information ◽

Microscopic Investigations

Introduction In electron microscopic investigations of crystalline specimens the direct observation of the electron diffraction pattern gives additional information about the specimen. The quality of this information depends on the quality of the crystals or the crystal area contributing to the diffraction pattern. By selected area diffraction in a conventional electron microscope, specimen areas as small as 1 µ in diameter can be investigated. It is well known that crystal areas of that size which must be thin enough (in the order of 1000 Å) for electron microscopic investigations are normally somewhat distorted by bending, or they are not homogeneous. Furthermore, the crystal surface is not well defined over such a large area. These are facts which cause reduction of information in the diffraction pattern. The intensity of a diffraction spot, for example, depends on the crystal thickness. If the thickness is not uniform over the investigated area, one observes an averaged intensity, so that the intensity distribution in the diffraction pattern cannot be used for an analysis unless additional information is available.

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Dendritic cells of the human epidermis: immuno-electron microscopic studies of la antigen reactivity

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100084090 ◽

1978 ◽

Vol 36 (2) ◽

pp. 644-645

Author(s):

G. Rowden ◽

M. G. Lewis ◽

T. M. Phillips

Keyword(s):

Dendritic Cells ◽

Langerhans Cells ◽

Cell Types ◽

Cell Type ◽

Electron Microscopic ◽

La Antigen ◽

Microscopic Studies ◽

A Cell ◽

C3 Receptors ◽

Antigen Reactivity

Langerhans cells of mammalian stratified squamous epithelial have proven to be an enigma since their discovery in 1868. These dendritic suprabasal cells have been considered as related to melanocytes either as effete cells, or as post divisional products. Although grafting experiments seemed to demonstrate the independence of the cell types, much confusion still exists. The presence in the epidermis of a cell type with morphological features seemingly shared by melanocytes and Langerhans cells has been especially troublesome. This so called "indeterminate", or " -dendritic cell" lacks both Langerhans cells granules and melanosomes, yet it is clearly not a keratinocyte. Suggestions have been made that it is related to either Langerhans cells or melanocyte. Recent studies have unequivocally demonstrated that Langerhans cells are independent cells with immune function. They display Fc and C3 receptors on their surface as well as la (immune region associated) antigens.

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Determination of the phase structure of polymerblends by electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109604 ◽

1978 ◽

Vol 36 (1) ◽

pp. 492-493

Author(s):

Dr. G. Kaemof

Keyword(s):

Screw Extruder ◽

Electron Microscopic ◽

Thin Sections ◽

Single Screw Extruder ◽

Transmission Electron ◽

The Matrix ◽

Twin Screw ◽

Special Case ◽

Microscopic Investigations

A mixture of polycarbonate (PC) and styrene-acrylonitrile-copolymer (SAN) represents a very good example for the efficiency of electron microscopic investigations concerning the determination of optimum production procedures for high grade product properties.The following parameters have been varied:components of charge (PC : SAN 50 : 50, 60 : 40, 70 : 30), kind of compounding machine (single screw extruder, twin screw extruder, discontinuous kneader), mass-temperature (lowest and highest possible temperature).The transmission electron microscopic investigations (TEM) were carried out on ultra thin sections, the PC-phase of which was selectively etched by triethylamine.The phase transition (matrix to disperse phase) does not occur - as might be expected - at a PC to SAN ratio of 50 : 50, but at a ratio of 65 : 35. Our results show that the matrix is preferably formed by the components with the lower melting viscosity (in this special case SAN), even at concentrations of less than 50 %.

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Mutations in calphotin, the gene encoding a Drosophila photoreceptor cell-specific calcium-binding protein, reveal roles in cellular morphogenesis and survival.

Genetics ◽

10.1093/genetics/138.2.413 ◽

1994 ◽

Vol 138 (2) ◽

pp. 413-421 ◽

Cited By ~ 1

Author(s):

Y Yang ◽

D Ballinger

Keyword(s):

Calcium Binding ◽

Photoreceptor Cell ◽

Cell Structure ◽

Specific Protein ◽

Cell Organelle ◽

Cell Type ◽

Gene Encoding ◽

Cellular Morphogenesis ◽

Transgenic Flies ◽

Drosophila Photoreceptor

Abstract Calphotin is a Drosophila photoreceptor cell-specific protein expressed very early in eye development, at the time when cell-type decisions are being made. Calphotin is a very hydrophobic and proline-rich protein which lacks obvious transmembrane domains. The cDNA encoding Calphotin was mapped to a region removed by a set of existing chromosomal deletions. Mutations that alter photoreceptor cell structure and development were isolated that fail to complement these deletions. These mutations fall into two classes. Class I mutations alter the structure of the rhabdomere, a photoreceptor cell organelle specialized for phototransduction. Class II mutations have rough eyes, due to misorientation of the rhabdomeres and photoreceptor cell death. Transformation rescue of these phenotypes in transgenic flies bearing calphotin genomic DNA indicates that both classes of mutations are in the calphotin gene. Analysis of these mutations suggest that Calphotin plays important roles in both rhabdomere development and in photoreceptor cell survival.

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New insights into the structural basis of integrin activation

Blood ◽

10.1182/blood-2003-01-0334 ◽

2003 ◽

Vol 102 (4) ◽

pp. 1155-1159 ◽

Cited By ~ 133

Author(s):

Jian-Ping Xiong ◽

Thilo Stehle ◽

Simon L. Goodman ◽

M. Amin Arnaout

Keyword(s):

Conformational Changes ◽

Structural Changes ◽

Structural Basis ◽

Integrin Activation ◽

Cellular Functions ◽

Electron Microscopic ◽

The Past ◽

Intracellular Signals ◽

Bidirectional Signaling ◽

New Hypothesis

Abstract Integrins are cell adhesion receptors that communicate biochemical and mechanical signals in a bidirectional manner across the plasma membrane and thus influence most cellular functions. Intracellular signals switch integrins into a ligand-competent state as a result of elicited conformational changes in the integrin ectodomain. Binding of extracellular ligands induces, in turn, structural changes that convey distinct signals to the cell interior. The structural basis of this bidirectional signaling has been the focus of intensive study for the past 3 decades. In this perspective, we develop a new hypothesis for integrin activation based on recent crystallographic, electron microscopic, and biochemical studies.

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IR spectroscopic and electron microscopic investigations of colored lead silicate glasses

Russian Journal of Applied Chemistry ◽

10.1134/s107042721012027x ◽

2010 ◽

Vol 83 (12) ◽

pp. 2205-2209

Author(s):

Kh. A. Adinaev ◽

A. A. Ismatov

Keyword(s):

Silicate Glasses ◽

Lead Silicate ◽

Electron Microscopic ◽

Ir Spectroscopic ◽

Microscopic Investigations

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Pathobioogy of intracranial germ-cell tumors: Immunochemical, immunohistochemical, and electron microscopic investigations

Journal of Neuro-Oncology ◽

10.1007/bf02571298 ◽

1987 ◽

Vol 5 (2) ◽

pp. 105-115 ◽

Cited By ~ 20

Author(s):

Hiroshi K. Inoue ◽

Hirofumi Naganuma ◽

Nobuo Ono

Keyword(s):

Germ Cell ◽

Germ Cell Tumors ◽

Electron Microscopic ◽

Intracranial Germ Cell Tumors ◽

Microscopic Investigations

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Light and electron microscopic investigations in the Dictyonemataceae (Basidiolichens)

Canadian Journal of Botany ◽

10.1139/b77-294 ◽

1977 ◽

Vol 55 (20) ◽

pp. 2565-2573 ◽

Cited By ~ 10

Author(s):

Robert D. Slocum ◽

Gary L. Floyd

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Cellular Level ◽

Fungal Symbiont ◽

Electron Microscopic ◽

Basidiomycetous Fungus ◽

Transmission Electron ◽

Fungal Symbiosis ◽

Algal Host ◽

Microscopic Investigations

The nature of the association between the basidiomycetous mycobiont and the blue-green phycobiont in two species of the tropical basidiolichen Dictyonema was investigated using Nomarski light optics and scanning and transmission electron microscopy. Although members of this family may exhibit either a homoiomerous or heteromerous type of thallus organization, the fungus–alga relationship at the cellular level is remarkably consistent. Scytonema filaments are intimately associated with appressorial hyphae of the mycobiont and with extensive intracellular hyphae, which appear to be unrelated to the basidiomycetous fungal symbiont. This is the first report of a lichen displaying an apparent dual fungal symbiosis with the algal host. Association with the intracellular fungus produces no discernible damage to the phycobiont and apparently does not interfere with the symbiosis involving the basidiomycetous fungus.

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